Patent Application
20250109573
This application claims the benefit of priority to Japanese Patent Application No. 2023-170306 filed on Sep. 29, 2023. The entire contents of this application are hereby incorporated herein by reference.
The present invention relates to working machines such as skid-steer loaders and compact track loaders.
A working machine such as a skid-steer loader or a compact track loader performs various types of work with a working unit including a working device provided on a machine body and one of various attachments such as a bucket attached to the working device, while being caused to travel by traveling device(s) supporting the machine body. If the prime mover of such a working machine is subjected to a load of a predetermined amount or higher, the prime mover may stop unintendedly. Such a phenomenon is, in the case where the prime mover is an engine, called an engine stall.
In order to prevent the prime mover of a working machine from stopping unintendedly due to a load, for example, with the technique disclosed in
For example, as disclosed in Japanese Unexamined Patent Application Publication No. 2019-65999, there is a known technique in which a plurality of solenoid-operated variable throttles are provided specifically to reduce the pilot pressure on a first control valve for boom cylinder(s) and reduce the pilot pressure on a second control valve for bucket cylinder(s), and the flow rate of hydraulic fluid from the first control valve to the boom cylinder and the flow rate of hydraulic fluid from the second control valve to the bucket cylinder are limited individually. As described above, with the techniques disclosed in Japanese Patent No. 6629282 and Japanese Unexamined Patent Application Publication No. 2019-65999, the flow rate(s) of hydraulic fluid to specific actuator(s) is/are limited so that other hydraulic pressure device(s) are not subjected to adverse effects.
Some types of work performed by the working unit of a working machine entail a load of a predetermined amount or higher on the prime mover. For example, in cases where an attachment including a high-power actuator which requires hydraulic fluid at a high flow rate to operate is used, where a great external force is applied on a working device, or the like cases, the prime mover is subjected to a load of a predetermined amount or higher. In the case where the work that applies a load of a predetermined amount or higher on the prime mover is performed using the working unit, more of the power from the prime mover is consumed by hydraulic pump(s) for work, the rotation speed of the prime mover drops, and the prime mover unintentionally stops more easily. However, the reality is that such cases in which a load of a predetermined amount or higher is imposed on the prime mover are not taken into consideration.
One or more example embodiments of the present invention provide working machines each of which makes it possible to eliminate or reduce the likelihood that the prime mover will stop unintentionally due to a load of a predetermined amount or higher.
One or more example embodiments of the present invention include the following feature(s). A working machine according to an example embodiment of the present invention includes a main pump to be actuated by power from a prime mover in or on a machine body to deliver hydraulic fluid, a working unit including a working device and an attachment attached to the working device and operable to perform work via the working device and the attachment upon actuation, by the hydraulic fluid, of at least one actuator included in at least one of the working device or the attachment, a solenoid valve to change a flow rate of the hydraulic fluid to the at least one actuator based on a control signal inputted thereto, a controller configured or programmed to input the control signal into the solenoid valve, an accelerator to be used to input a target rotation speed of the prime mover, and a rotation speed sensor to detect an actual rotation speed of the prime mover. The controller is configured or programmed to, while the working unit is performing specific work that imposes a load of a predetermined amount or higher on the prime mover, if a drop which is a decrease in the actual rotation speed of the prime mover relative to the target rotation speed reaches a first threshold or greater, change the control signal based on the actual rotation speed to limit the flow rate of the hydraulic fluid to the at least one actuator.
In an example embodiment of the present invention, the working machine may further include an auxiliary (AUX) port to allow the hydraulic fluid to flow to and from an auxiliary actuator which is the at least one actuator included in the attachment, a pilot pump to be actuated by power from the prime mover to deliver pilot fluid, and an AUX control valve including at least one AUX pressure receiver and operable to control the flow rate of the hydraulic fluid supplied via the AUX port to the auxiliary actuator based on a pilot pressure which is a pressure of the pilot fluid acting on the at least one AUX pressure receiver. The solenoid valve may include an AUX solenoid valve to, based on the control signal inputted thereto from the controller, change the pilot pressure acting on the at least one AUX pressure receiver to change the flow rate of the hydraulic fluid from the AUX control valve to the auxiliary actuator. The controller may be configured or programmed to, while the specific work is being performed by the attachment which is a specific attachment including the auxiliary actuator, when the drop reaches the first threshold or greater, change the control signal based on the actual rotation speed of the prime mover to reduce the pilot pressure acting on the at least one AUX pressure receiver to limit the flow rate of the hydraulic fluid from the AUX control valve to the auxiliary actuator.
In an example embodiment of the present invention, the controller may be configured or programmed to control an electric current value of the control signal to the AUX solenoid valve at a predetermined value when another work differing from the specific work is being performed by the attachment which is another attachment differing from the specific attachment and when the specific work is being performed by the specific attachment but the drop is not equal to or greater than the first threshold, and, while the specific work is being performed by the specific attachment, if the drop reaches the first threshold or greater, reduce the electric current value of the control signal to the AUX solenoid valve such that the electric current value is smaller than when the other work is being performed by the other attachment and than when the drop during the specific work is not equal to or greater than the first threshold, to reduce the flow rate of the hydraulic fluid to the auxiliary actuator.
In an example embodiment of the present invention, the working machine may further include a pilot pump to be actuated by power from the prime mover to deliver pilot fluid, and a work control valve including at least one work pressure receiver and operable to control the flow rate of the hydraulic fluid supplied to at least one work actuator included in the working device based on a pilot pressure which is a pressure of the pilot fluid acting on the at least one work pressure receiver. The solenoid valve may include a work solenoid valve to, based on the control signal inputted thereto from the controller, change the pilot pressure acting on the at least one work pressure receiver to change the flow rate of the hydraulic fluid from the work control valve to the at least one work actuator. The controller may be configured or programmed to, while the specific work is being performed by the working device and the attachment, if the drop reaches the first threshold or greater, change the control signal based on the actual rotation speed of the prime mover to reduce the pilot pressure acting on the at least one work pressure receiver to limit the flow rate of the hydraulic fluid from the work control valve to the at least one work actuator.
In an example embodiment of the present invention, the controller may be configured or programmed to control an electric current value of the control signal to the work solenoid valve at a predetermined value when another work differing from the specific work that does not impose a load of a predetermined amount or higher is being performed and when the specific work is being performed but the drop is not equal to or greater than the first threshold, and, while the specific work is being performed, if the drop reaches the first threshold or greater, reduce the electric current value of the control signal to the work solenoid valve such that the electric current value is smaller than when the other work is being performed and than when the drop during the specific work is not equal to or greater than the first threshold, to reduce the flow rate of the hydraulic fluid to the at least one work actuator.
In an example embodiment of the present invention, the working machine may further include an input interface to receive input of information indicating the attachment attached to the working device. The controller may be configured or programmed to, based on the information indicating the attachment, determine whether or not work to be performed by the working unit is the specific work that imposes a load of a predetermined amount or higher.
In an example embodiment of the present invention, the controller may be configured or programmed to, until a predetermined period of time has passed since a start of the specific work, change the control signal inputted into the solenoid valve based on the actual rotation speed of the prime mover to limit the flow rate of the hydraulic fluid to the actuator if the drop reaches a second threshold greater than the first threshold.
In an example embodiment of the present invention, the working machine may further include a variable displacement travel pump to be actuated by power from the prime mover, the travel pump including at least one pump pressure receiver and operable to vary a delivery flow rate of the hydraulic fluid based on a pilot pressure which is a pressure of pilot fluid acting on the at least one pump pressure receiver, a travel motor to be actuated by the hydraulic fluid delivered by the travel pump, a traveling device to be actuated by power from the travel motor to cause the machine body to travel, and a travel solenoid valve to change the pilot pressure acting on the at least one pump pressure receiver based on a control signal inputted thereto from the controller. The controller may be configured or programmed to, while the traveling device is causing the machine body to travel, if the drop reaches a third threshold or greater, change the control signal inputted into the travel solenoid valve based on the actual rotation speed of the prime mover to limit the delivery flow rate of the hydraulic fluid from the travel pump, the third threshold differing from the first threshold.
In an example embodiment of the present invention, the working machine may further include a memory and/or a storage to store a control-under-high-load graph indicating an electric current value of the control signal to the solenoid valve for use when the drop reaches the first threshold or greater during the specific work. The control-under-high-load graph may indicate that the electric current value of the control signal decreases in proportion to a decrease in rotation speed of the prime mover. The controller may be configured or programmed to determine the electric current value of the control signal based on the control-under-high-load graph and the actual rotation speed of the prime mover, and input the control signal having the determined electric current value into the solenoid valve to limit the flow rate of the hydraulic fluid to the at least one actuator such that the flow rate decreases.
In an example embodiment of the present invention, the controller may be configured or programmed to change, gradually at a predetermined rate, the electric current value of the control signal inputted into the solenoid valve such that the electric current value matches the electric current value determined based on the control-under-high-load graph and the actual rotation speed of the prime mover.
In an example embodiment of the present invention, the control-under-high-load graph may indicate that a slope is steeper in a second range of the electric current value of the control signal than in a first range of the electric current value of the control signal, the slope being a ratio of an increase in electric current value of the control signal to an increase in rotation speed of the prime mover, the second range being below the first range. The controller may be configured or programmed to, if the drop during the specific work reaches the first threshold or greater, change, based on the control-under-high-load graph, the electric current value of the control signal based on the actual rotation speed to a greater extent when the electric current value of the control signal is in the second range than when the electric current value of the control signal is in the first range.
In an example embodiment of the present invention, the working machine may further include an input interface to receive input of an instruction to change the flow rate of the hydraulic fluid to the at least one actuator. The memory and/or the storage may store at least one control-not-under-high-load graph indicating a constant electric current value of the control signal to the solenoid valve. The controller may be configured or programmed to, when another work differing from the specific work is being performed and when the specific work is being performed but the drop is not equal to or greater than the first threshold, input the control signal having the constant electric current value indicated by one of the at least one control-not-under-high-load graph that corresponds to the at least one actuator into the solenoid valve, and, based on the instruction inputted via the input interface, shift the corresponding control-not-under-high-load graph in a direction in which the electric current value of the control signal changes.
In an example embodiment of the present invention, the memory and/or the storage may store a control-during-normal-time graph indicating a constant electric current value of the control signal to the solenoid valve for use when the drop is not equal to or greater than the first threshold during the specific work. The control-under-high-load graph may indicate that the electric current value of the control signal decreases in proportion to a decrease in rotation speed of the prime mover. The control-under-high-load graph and the control-during-normal-time graph may have a common point indicating the same electric current value of the control signal at the same rotation speed of the prime mover. The controller may be configured or programmed to, if the drop reaches the first threshold or greater during the specific work, shift the control-under-high-load graph in a direction in which the rotation speed of the prime mover changes such that the rotation speed at the common point matches the actual rotation speed of the prime mover.
In an example embodiment of the present invention, the controller may be configured or programmed to correct the control-under-high-load graph based on at least one of a state of the working machine, a state of the working device, a state of the hydraulic fluid, the attachment, or input information.
In an example embodiment of the present invention, the controller may be configured or programmed to, if the at least one of the state of the working machine, the state of the working device, the state of the hydraulic fluid, the attachment, or the input information matches a predetermined condition a satisfaction of which leads to a further increase in the load of a predetermined amount or higher on the prime mover, correct the control-under-high-load graph such that the flow rate of the hydraulic fluid to the at least one actuator is reduced to a greater extent than when the control-under-high-load graph is not corrected.
In an example embodiment of the present invention, the controller may be configured or programmed to, if the at least one of the state of the working machine, the state of the working device, the state of the hydraulic fluid, the attachment, or the input information matches a predetermined condition a satisfaction of which necessitates ensuring work performance of the working machine, correct the control-under-high-load graph such that the flow rate of the hydraulic fluid to the at least one actuator is reduced to a lesser extent than when the control-under-high-load graph is not corrected.
In an example embodiment of the present invention, the working machine may further include a swash plate angle sensor to detect an angle of a swash plate of the main pump which is a variable displacement pump, an AUX port to allow the hydraulic fluid to flow to and from an auxiliary actuator which is the at least one actuator included in the attachment, and an AUX pressure sensor to detect a pressure of the hydraulic fluid acting on the AUX port. The controller may be configured or programmed to calculate a horsepower consumed by the auxiliary actuator based on a detected value detected by the swash plate angle sensor and a detected value detected by the AUX pressure sensor, and correct the control-under-high-load graph based on the calculated horsepower.
In an example embodiment of the present invention, the working machine may further include an AUX port to allow the hydraulic fluid to flow to and from an auxiliary actuator which is the at least one actuator included in the attachment, and an AUX pressure sensor to detect a pressure of the hydraulic fluid acting on the AUX port. The controller may be configured or programmed to correct the control-under-high-load graph based on the pressure of the hydraulic fluid flowing between the AUX port and the auxiliary actuator detected by the AUX pressure sensor.
In an example embodiment of the present invention, the working machine may further include an AUX port to allow the hydraulic fluid to flow to and from an auxiliary actuator which is the at least one actuator included in the attachment. The controller may be configured or programmed to detect a flow rate of the hydraulic fluid flowing between the AUX port and the auxiliary actuator and correct the control-under-high-load graph based on the detected flow rate.
In an example embodiment of the present invention, the working machine may further include an input interface to receive input of information indicating the attachment attached to the working device. The controller may be configured or programmed to correct the control-under-high-load graph based on the information indicating the attachment.
In an example embodiment of the present invention, the working machine may further include a variable displacement travel pump to be actuated by power from the prime mover, the travel pump including at least one pump pressure receiver and operable to vary a delivery flow rate of the hydraulic fluid based on a pilot pressure which is a pressure of pilot fluid acting on the at least one pump pressure receiver, a travel motor to be actuated by the hydraulic fluid delivered by the travel pump, a traveling device to be actuated by power from the travel motor to cause the machine body to travel, a travel solenoid valve to change the pilot pressure acting on the at least one pump pressure receiver based on a control signal inputted thereto from the controller to limit the delivery flow rate of the hydraulic fluid from the travel pump, and an input interface to receive input of priority information indicating that one of (i) limiting the delivery flow rate of the travel pump using the travel solenoid valve and (ii) limiting the flow rate of the hydraulic fluid to the at least one actuator using the solenoid valve is prioritized over the other. The controller may be configured or programmed to correct the control-under-high-load graph based on the priority information.
In an example embodiment of the present invention, the working machine may further include an AUX port to allow the hydraulic fluid to flow to and from an auxiliary actuator which is the actuator included in the attachment, a pilot pump to be actuated by power from the prime mover to deliver pilot fluid, and an AUX control valve including at least one AUX pressure receiver and operable to control the flow rate of the hydraulic fluid supplied via the AUX port to the auxiliary actuator based on a pilot pressure which is a pressure of the pilot fluid acting on the at least one AUX pressure receiver, a work control valve including at least one work pressure receiver and operable to control the flow rate of the hydraulic fluid supplied to a work actuator included in the working device based on a pilot pressure which is a pressure of the pilot fluid acting on the at least one work pressure receiver, and an input interface. A plurality of the solenoid valves may include an AUX solenoid valve to, based on the control signal inputted thereto from the controller, change the pilot pressure acting on the at least one AUX pressure receiver of the AUX control valve to limit the flow rate of the hydraulic fluid from the AUX control valve to the auxiliary actuator, and a work solenoid valve to, based on the control signal inputted thereto from the controller, change the pilot pressure acting on the at least one work pressure receiver of the work control valve to limit the flow rate of the hydraulic fluid from the work control valve to the work actuator. The input interface may be operable to receive input of priority information indicating that one of (i) limiting the flow rate of the hydraulic fluid using the AUX solenoid valve and (ii) limiting the flow rate of the hydraulic fluid using the work solenoid valve is prioritized over the other. The controller may be configured or programmed to correct the control-under-high-load graph based on the priority information.
In an example embodiment of the present invention, the working machine may further include a travel pump to be actuated by power from the prime mover to deliver hydraulic fluid, a travel motor including an output shaft to be actuated by the hydraulic fluid delivered by the travel pump to rotate the output shaft, and a travel switching valve to switch between a first state in which a rotation speed of the output shaft of the travel motor is brought into a first speed stage and a second state in which the rotation speed of the output shaft of the travel motor is brought into a second speed stage which is higher than the first speed stage. The controller may be configured or programmed to correct the control-under-high-load graph based on whether the travel switching valve is in the first state or the second state.
In an example embodiment of the present invention, the working machine may further include a temperature sensor to detect a temperature of the hydraulic fluid. The controller may be configured or programmed to correct the control-under-high-load graph based on the temperature detected by the temperature sensor.
In an example embodiment of the present invention, the working machine may further include a pair of traveling devices at a left side and a right side of the machine body, and a travel operator including a position for forward travel, a position for rearward travel, and a turning position to be operated to any of the positions to cause the pair of traveling devices to cause the machine body to travel forward, travel rearward, or turn. The controller may be configured or programmed to correct the control-under-high-load graph based on an operation state of the travel operator.
In an example embodiment of the present invention, the working machine may further include a work operator to be operated to actuate the working device. The controller may be configured or programmed to correct the control-under-high-load graph based on an operation state of the work operator.
In an example embodiment of the present invention, the controller may be configured or programmed to produce a quasi accelerator signal which changes at a predetermined rate based on an accelerator signal inputted thereto via the accelerator, determine a quasi rotation speed of the prime mover based on the quasi accelerator signal, and change the control signal based on the quasi rotation speed instead of the actual rotation speed.
In an example embodiment of the present invention, the controller may be configured or programmed to, while the specific work is being performed by the working unit, if the target rotation speed is suddenly changed by the accelerator by a predetermined value or more, calculate a decrease in the actual rotation speed relative to the target rotation speed a plurality of times within a predetermined period of time to obtain a plurality of the decreases, and calculate, as the drop, an average of the plurality of calculated decreases.
The above and other elements, features, steps, characteristics and advantages of the present invention will become more apparent from the following detailed description of the example embodiments with reference to the attached drawings.
A more complete appreciation of example embodiments of the present invention and many of the attendant advantages thereof will be readily obtained as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings described below.
Example embodiments will now be described with reference to the accompanying drawings, wherein like reference numerals designate corresponding or identical elements throughout the various drawings. The drawings are to be viewed in an orientation in which the reference numerals are viewed correctly.
Example embodiments of the present invention will now be described with reference to the drawings.
As shown in
The traveling devices 5 are provided at the left and right of the machine body 2, respectively. That is, a pair of left and right traveling devices 5 are provided. The pair of left and right traveling devices 5 support the machine body 2 such that the machine body 2 is allowed to travel. In the present example embodiment, crawler traveling devices are shown as an example of the traveling devices 5. However, instead of the crawler traveling devices, the traveling devices 5 may be wheeled traveling device(s) including front wheel(s) and rear wheel(s), or may be semi-crawler traveling device(s). The traveling device 5 provided at the left of the machine body 2 may be referred to as a first traveling device 5, and the traveling device 5 provided at the right of the machine body 2 may be referred to as a second traveling device 5.
The working unit 4U includes a working device 4 provided on the machine body 2, and an attachment 11 attached to the working device 4. The working device 4 includes boom(s) 10, first link(s) 12, second link(s) 13, lift cylinder(s) 14, and tilt cylinder(s) 15.
The booms 10 are provided on the left and right sides of the cabin 3 swingably up and down. A front-end portion 10a of the left boom 10 and a front-end portion 10a of the right boom 10 are connected via an irregular shaped connection pipe. A rear-end portion 10b of the left boom 10 and a rear-end portion 10b of the right boom 10 are connected via a circular connection pipe. The first links 12, the second links 13, the lift cylinders 14, and the tilt cylinders 15 are provided on the left and right sides of the machine body 2 such that they correspond to the left boom 10 and the right boom 10. The first links 12 and the second links 13 support the rear-end portions 10b of the booms 10 swingably up and down.
Specifically, each first link 12 is positioned vertically at the rear-end portion 10b of the corresponding boom 10. A top-end portion 12a of the first link 12 is pivotally supported on the rear-end portion 10b of the boom 10 via pivot shaft 16 rotatably about a horizontal axis. The pivot shaft 16 passes through a rear portion of a bracket 10k attached to a rear-end portion of the boom 10. A bottom-end portion 12b of the first link 12 is pivotally supported at the rear of the machine body 2 via pivot shaft 17 rotatably about a horizontal axis. The pivot shaft 17 is provided at an upper rear portion of the machine body 2.
Each second link 13 is provided in front of the corresponding first link 12. A front-end portion 13a of the second link 13 is pivotally supported by a pivot shaft 20 rotatably about a horizontal axis. The pivot shaft 20 is supported by a bracket 2d secured to the machine body 2. A rear-end portion 13b of the second link 13 is pivotally supported by a pivot shaft 21 rotatably about a horizontal axis. The pivot shaft 21 is located forward of and higher than the pivot shaft 17, and supported on a bottom portion of the corresponding bracket 10k.
A top-end portion 14a of each lift cylinder 14 is pivotally supported by a pivot shaft 18 rotatably about a horizontal axis. The pivot shaft 18 is provided at an intermediate portion of the corresponding boom 10 and passes through a front portion of the corresponding bracket 10k. A bottom-end portion 14b of the lift cylinder 14 is pivotally supported by a pivot shaft 19 rotatably about a horizontal axis. The pivot shaft 19 is provided at a lower rear portion of the machine body 2.
As the lift cylinder 14 extends or retracts, the boom 10 swings up or down about the pivot shaft 16. Specifically, the front-end portion 10a of the boom 10 moves up or down. As the boom 10 swings up or down, the second link 13 swings up or down about the pivot shaft 20. As the second link 13 swings up or down, the first link 12 swings forward or rearward about the pivot shaft 17. Specifically, the boom 10 is movable forward and rearward. The front-end portion 10a of the boom 10 is pivotally supported by a pivot shaft 23a provided at a lower portion of a hitch 24 rotatably about a horizontal axis.
The tilt cylinders 15 are located forward of the respective left and right booms 10. A top-end portion 15a of each tilt cylinder 15 is pivotally supported via pivot shaft 22 rotatably about a horizontal axis. The pivot shaft 22 is provided in a bracket 10j secured to a curve portion 10c of the corresponding boom 10. A bottom-end portion 15b of the tilt cylinder 15 is pivotally supported by a pivot shaft 23b provided at an upper portion of the hitch 24 rotatably about a horizontal axis.
The attachment 11 is attached to a front surface of the hitch 24. The hitch 24 is a linkage to attach and detach the attachment 11 thereto and therefrom. As the tilt cylinders 15 extend or retract, the hitch 24 swings about the pivot shaft 23a, and the attachment 11 attached to the hitch 24 swings up, down, forward, and/or rearward. That is, the attachment 11 is attached swingably (tiltably) to the front-end portions 10a of the booms 10 via the hitch 24.
The attachment 11 is a working tool to perform work.
Instead of the bucket 11a, for example, as shown in
In the case where the bucket 11a is a standard attachment 11 attached to the working machine 1, attachments 11 and 11b other than the bucket 11a may be referred to as auxiliary attachments. Some of the auxiliary attachments 11 and 11b include actuator(s) 27 such as a hydraulic motor, a hydraulic cylinder, and/or the like. For example, the mulcher 11b includes a hydraulic motor as the actuator 27. The actuator 27 provided on or in the auxiliary attachment 11, 11b may be referred to as an auxiliary actuator.
The auxiliary actuator 27 is actuated by hydraulic fluid supplied from the working machine 1. The working machine 1 includes AUX port(s) 25. The AUX port(s) 25 allow(s) hydraulic fluid to be introduced into and discharged from the auxiliary actuator 27. The AUX port(s) 25 include(s) a first AUX port 25a and a second AUX port 25b. The booms 10 and the machine body 2 include a plurality of fluid passages connected to the first AUX port 25a and the second AUX port 25b.
For example, a user or the like (or may be the user of the working machine 1), as shown in
As described earlier, the working unit 4U performs work via the working device 4 and the attachment 11 upon actuation by hydraulic fluid of the actuator(s) 14, 15 and/or 27 included in at least one of the working device 4 or the attachment 11.
The main pump P2 is actuated by power from the prime mover 6 to deliver hydraulic fluid from the hydraulic fluid tank T to a main fluid passage 45. The hydraulic fluid delivered by the main pump P2 is used to actuate hydraulic actuators of the working unit 4U, i.e., the lift cylinders 14 and the tilt cylinders 15 of the working device 4 as well as the auxiliary actuator 27 of the auxiliary attachment 11, 11b. The lift cylinders 14 and the tilt cylinders 15 of the working device 4 may be referred to collectively as work actuators.
The working machine 1 includes a plurality of control valves 60. The plurality of control valves 60 include a lift control valve 60A, a tilt control valve 60B, and an AUX control valve 60C. The plurality of control valves 60 are configured to control the operation of the actuators 14, 15 and 27 of the working unit 4U. The plurality of control valves 60 are each connected to the main fluid passage 45. The plurality of control valves 60 are configured to change the flow rate (output) and the direction of supply of hydraulic fluid supplied from the main fluid passage 45 to the corresponding actuators 14, 15 and 27 to control the operation of the corresponding actuators 14, 15 and 27.
The lift control valve 60A is connected via a plurality of fluid passages to the lift cylinders 14 to move the booms 10 up and down. The lift control valve 60A is a pilot-operated direct spool three-way switching valve. The lift control valve 60A includes a plurality of work pressure receivers 61a and 61b and, in response to the pilot pressure acting on the work pressure receivers 61a and 61b, switches to a third position (neutral position), a first position different from the third position, or a second position different from the third position and the first position. When the lift control valve 60A is in the third position, hydraulic fluid is not supplied from the main fluid passage 45 to the lift cylinders 14.
Upon switching of the lift control valve 60A to the first position or the second position, hydraulic fluid is supplied from the main fluid passage 45 to the lift cylinders 14 and the direction of supply of hydraulic fluid changes. When the lift control valve 60A is in the first position or the second position, as the opening of the lift control valve 60A changes with the pilot pressure, the flow rate of the hydraulic fluid supplied from the main fluid passage 45 to the lift cylinders 14 changes. Thus, the lift control valve 60A controls, according to the pilot pressure acting on the work pressure receivers 61a and 61b, the flow rate and the direction of supply of hydraulic fluid from the main fluid passage 45 to the lift cylinders 14 to cause the lift cylinders 14 to extend or retract.
The tilt control valve 60B is connected via plurality of fluid passages to the tilt cylinders 15 to cause the attachment 11 to swing. The tilt control valve 60B is a pilot-operated direct spool three-way switching valve. The tilt control valve 60B includes a plurality of work pressure receivers 62a and 62b and, in response to the pilot pressure acting on the work pressure receivers 62a and 62b, switches to a third position (neutral position), a first position different from the third position, or a second position different from the third position and the first position. When the tilt control valve 60B is in the third position, hydraulic fluid is not supplied from the main fluid passage 45 to the tilt cylinders 15.
Upon switching of the tilt control valve 60B to the first position or the second position, hydraulic fluid is supplied from the main fluid passage 45 to the tilt cylinders 15 and the direction of supply of the hydraulic fluid changes. When the tilt control valve 60B is in the first position or the second position, as the opening of the tilt control valve 60B changes with the pilot pressure, the flow rate of the hydraulic fluid supplied from the main fluid passage 45 to the tilt cylinders 15 changes. Thus, the tilt control valve 60B controls, according to the pilot pressure acting on the work pressure receivers 62a and 62b, the flow rate and the direction of supply of hydraulic fluid from the main fluid passage 45 to the tilt cylinders 15 to cause the tilt cylinders 15 to extend or retract. Since the lift control valve 60A and the tilt control valve 60B are configured to control the operation of the actuators 14 and 15 of the working device 4, the lift control valve 60A and the tilt control valve 60B may be referred to collectively as work control valves.
The AUX control valve 60C is connected to the AUX ports 25 by a plurality of fluid passages 64. Specifically, a first port of the AUX control valve 60C and the first AUX port 25a are connected via a fluid passage 64a, and a second port of the AUX control valve 60C and the second AUX port 25b are connected via a fluid passage 64b. The AUX control valve 60C is a pilot-operated direct spool three-way switching valve. The AUX control valve 60C includes a plurality of AUX pressure receivers 63a and 63b and, in response to the pilot pressure acting on the AUX pressure receivers 63a and 63b, switches to a third position (neutral position) 60d, a first position 60a different from the third position 60d, or a second position 60b different from the third position 60d and the first position 60a.
When the AUX control valve 60C is in the third position 60d, hydraulic fluid is not supplied from the main fluid passage 45 to the auxiliary actuator 27 via the fluid passage(s) 64 and the AUX port(s) 25. When the AUX control valve 60C is switched to the first position 60a or the second position 60b, hydraulic fluid is supplied from the main fluid passage 45 to the auxiliary actuator 27 via the fluid passage(s) 64 and the AUX port(s) 25 and the direction of supply of the hydraulic fluid changes.
Specifically, upon switching of the AUX control valve 60C to the first position 60a, hydraulic fluid is supplied from the main fluid passage 45 to the auxiliary actuator 27 via the fluid passage 64a and the first AUX port 25a, and hydraulic fluid returns to the AUX control valve 60c from the auxiliary actuator 27 via the fluid passage 64b and the second AUX port 25b and is drained from the AUX control valve 60C. When the AUX control valve 60C switches to the second position 60b, hydraulic fluid is supplied from the main fluid passage 45 to the auxiliary actuator 27 via the fluid passage 64b and the second AUX port 25b, and hydraulic fluid returns to the AUX control valve 60C from the auxiliary actuator 27 via the fluid passage 64a and the first AUX port 25a and is drained from the AUX control valve 60C.
When the AUX control valve 60C is in the first position 60a or the second position 60b, as the opening of the AUX control valve 60C changes with the pilot pressure, the flow rate of the hydraulic fluid supplied from the main fluid passage 45 to the auxiliary actuator 27 via the AUX port(s) 25 changes. Thus, the AUX control valve 60C controls, according to the pilot pressure acting on the AUX pressure receivers 63a and 63b, the flow rate and the direction of supply of hydraulic fluid from the main fluid passage 45 to the auxiliary actuator 27 via the fluid passage(s) 64 and the AUX port(s) 25 to actuate the auxiliary actuator 27.
The working machine 1 includes a plurality of AUX solenoid valves 65. The plurality of AUX solenoid valves 65 are configured to operate the AUX control valve 60C. The plurality of AUX solenoid valves 65 are each a proportional valve to have its solenoid energized and its opening changed according to a control signal (electric current signal) inputted thereto. The plurality of AUX solenoid valves 65 are provided on a branch fluid passage 40c branched from the fluid discharge passage 40, and change the pilot pressure of pilot fluid supplied from the fluid discharge passage 40 by having the opening changed. As the electric current value of the control signal inputted into each of the plurality of AUX solenoid valves 65 increases, the opening of each of the plurality of AUX solenoid valves 65 increases and the pilot pressure outputted from each of the plurality of AUX solenoid valves 65 increases.
The plurality of AUX solenoid valves 65 include a first AUX solenoid valve 65A and a second AUX solenoid valve 65B. The first AUX solenoid valve 65A and the second AUX solenoid valve 65B are respectively connected to the AUX pressure receivers 63a and 63b of the AUX control valve 60c by control fluid passages 66. Specifically, the fluid passages 66 include a first control fluid passage 66a to connect the first AUX solenoid valve 65A and the AUX pressure receiver 63a of the AUX control valve 60C, and a second control fluid passage 66b to connect the second AUX solenoid valve 65B and the AUX pressure receiver 63b of the AUX control valve 60C.
When the opening of the first AUX solenoid valve 65A is greater than 0 (zero), pilot fluid from the fluid discharge passage 40 acts on the AUX pressure receiver 63a of the AUX control valve 60C via the first AUX solenoid valve 65A and the first control fluid passage 66a. In so doing, the pilot pressure corresponding to the opening of the first AUX solenoid valve 65A acts on the AUX pressure receiver 63a. When the pilot pressure acting on the AUX pressure receiver 63a is equal to or more than a predetermined value, the spool of the AUX control valve 60C moves, and the AUX control valve 60C switches from the third position 60d to the first position 60a, allowing hydraulic fluid to be supplied from the AUX control valve 60C to the auxiliary actuator 27 via the fluid passage 64a and the first AUX port 25a.
As the opening of the first AUX solenoid valve 65A changes and the pilot pressure acting on the AUX pressure receiver 63a changes, the opening of the AUX control valve 60C in the first position 60a also changes. As the opening of the AUX control valve 60C in the first position 60a changes, the flow rate and the pressure of hydraulic fluid supplied from the AUX control valve 60C to the auxiliary actuator 27 via the fluid passage 64a and the first AUX port 25a change.
When the opening of the second AUX solenoid valve 65B is greater than 0 (zero), the pilot fluid from the fluid discharge passage 40 acts on the AUX pressure receiver 63b of the AUX control valve 60C via the second AUX solenoid valve 65B and the second control fluid passage 66b. In so doing, the pilot pressure corresponding to the opening of the second AUX solenoid valve 65B acts on the AUX pressure receiver 63b. When the pilot pressure acting on the AUX pressure receiver 63b is equal to or more than a predetermined value, the spool of the AUX control valve 60C moves, the AUX control valve 60C switches from the third position 60d to the second position 60b, allowing hydraulic fluid to be supplied from the AUX control valve 60C to the auxiliary actuator 27 via the fluid passage 64b and the second AUX port 25b.
As the opening of the second AUX solenoid valve 65B changes and the pilot pressure acting on the AUX pressure receiver 63b changes, the opening of the AUX control valve 60C in the second position 60b also changes. As the opening of the AUX control valve 60C in the second position 60b changes, the flow rate and the pressure of hydraulic fluid supplied to the auxiliary actuator 27 from the AUX control valve 60C via the fluid passage 64b and the second AUX port 25b change.
As described above, the plurality of AUX solenoid valves 65 (the first AUX solenoid valve 65A and the second AUX solenoid valve 65B), by changing the pilot pressures acting on the respective AUX pressure receivers 63a and 63b of the AUX control valve 60C according to the control signals inputted thereto, change the flow rate of hydraulic fluid from the AUX control valve 60C to the auxiliary actuator 27.
The working machine 1 includes work operating equipment 67. The work operating equipment 67 is configured to operate the lift cylinders 14 and the tilt cylinders 15 of the working device 4. The work operating equipment 67 is configured to, by changing the pilot pressure acting on the work pressure receiver(s) 61, 61b, 62a and/or 62b of the work control valve(s) 60A and/or 60B, change the flow rate and the direction of supply of hydraulic fluid to the lift cylinders 14 and/or the tilt cylinders 15. The work operating equipment 67 includes a work operator 68 and a plurality of operating valves 69.
The work operator 68 is an operating lever pivotable along the left-and-right direction (machine body width direction) and the front-rear direction. The work operator 68 is supported by the plurality of work operating valves 69. The work operator 68 can be moved from a neutral position in the forward direction (direction of arrow A1) and in the rearward direction (direction of arrow A2), as well as from the neutral position in the leftward direction (direction of arrow A3) and the rightward direction (direction of arrow A4). In other words, the work operator 68 can be pivoted from the neutral position (base position) in at least four directions.
The plurality of work operating valves 69 are configured to be actuated according to the operation of the common work operator 68. Specifically, the plurality of work operating valves 69 are connected to the fluid discharge passage 40, and change the pilot pressure of pilot fluid supplied from the fluid discharge passage 40. The plurality of work operating valves 69 are operated by the work operator 68. The plurality of work operating valves 69 include a first pilot valve 69A, a second pilot valve 69B, a third pilot valve 69C, and a fourth pilot valve 69D.
The first pilot valve 69A is a pilot value to achieve lowering movement of lift cylinders. When the work operator 68 is pivoted in the forward direction (direction of A1) (operated forward), the first pilot valve 69A changes its outputting pilot pressure according to the operation amount (degree of pivoting) (i.e., according to the operation) of the work operator 68. The second pilot valve 69B is a pilot valve to achieve raising movement of lift cylinders. When the work operator 68 is pivoted in the rearward direction (direction of A2) (operated rearward), the second pilot valve 69A changes its outputting pilot pressure according to the operation amount of the work operator 68. The third pilot valve 69C is a pilot valve to achieve upward tilting. When the work operator 68 is pivoted in the leftward direction (operated leftward), the third pilot valve 69C changes its outputting pilot pressure according to the operation amount of the work operator 68. The fourth pilot valve 69D is a pilot valve to achieve downward tilting. When the work operator 68 is pivoted in the rightward direction (operated rightward), the fourth pilot valve 69D changes its outputting pilot pressure according to the operation amount of the work operator 68.
The plurality of work operating valves 69 are connected to a plurality of control valves 60 by work fluid passages 46. The work fluid passages 46 include a first work fluid passage 46a, a second work fluid passage 46b, a third work fluid passage 46c, and a fourth work fluid passage 46d. The first work fluid passage 46a connects the first pilot valve 69 and the work pressure receiver 61a of the lift control valve 60A. The second work fluid passage 46b connects the second pilot valve 69B and the work pressure receiver 61b of the lift control valve 60A. The third work fluid passage 46c connects the third pilot valve 69C and the work pressure receiver 62a of the tilt control valve 60B. The fourth work fluid passage 46d connects the fourth pilot valve 69D and the work pressure receiver 62b of the tilt control valve 60B.
When the work operator 68 is pivoted in the forward direction (direction of A1), the first pilot valve 69A is operated, and pilot fluid is supplied from the first pilot valve 69A to the first work fluid passage 46a. The pilot pressure of the pilot fluid supplied from the first pilot valve 69A acts on the work pressure receiver 61a of the lift control valve 60A via the first work fluid passage 46a. With this, the lift control valve 60A changes the flow rate and the direction of supply of hydraulic fluid supplied to the lift cylinders 14, and therefore the lift cylinders 14 retract and the booms 10 move down.
When the work operator 68 is pivoted in the rearward direction (direction of A2), the second pilot valve 69B is operated, and pilot fluid is supplied from the second pilot valve 69B to the second work fluid passage 46b. The pilot pressure of the pilot fluid supplied from the second pilot valve 69B acts on the work pressure receiver 61b of the lift control valve 60A via the second work fluid passage 46b. With this, the lift control valve 60A changes the flow rate and the direction of supply of the hydraulic fluid supplied to the lift cylinders 14, and therefore the lift cylinders 14 extend and the booms 10 move up.
When the work operator 68 is pivoted in the leftward direction (direction of A3), the third pilot valve 69C is operated, and pilot fluid is supplied from the third pilot valve 69C to the third work fluid passage 46c. The pilot pressure of the pilot fluid supplied from the third pilot valve 69C acts on the work pressure receiver 62a of the tilt control valve 60B via the third work fluid passage 46c. With this, the tilt control valve 60B changes the flow rate and the direction of supply of the hydraulic fluid supplied to the tilt cylinders 15, and therefore the tilt cylinders 15 retract and the attachment 11 swings upward. In so doing, in the case where the attachment 11 is a bucket 11a, the bucket 11a performs shoveling movement.
When the work operator 68 is pivoted in the rightward direction (direction of A4), the fourth pilot valve 69D is operated, and pilot fluid is supplied from the fourth pilot valve 69D to the fourth work fluid passage 46d. The pilot pressure of the pilot fluid supplied from the fourth pilot valve 69D acts on the work pressure receiver 62b of the tilt control valve 60B via the fourth work fluid passage 46d. With this, the tilt control valve 60B changes the flow rate and the direction of supply of the hydraulic fluid supplied from the tilt control valve 60B to the tilt cylinders 15, and therefore the tilt cylinders 15 extend and the attachment 11 swings downward. In so doing, in the case where the attachment 11 is a bucket 11a, the bucket 11a performs dumping movement.
The working machine 1 includes a load sensing (LS) system 80. The LS system 80 controls the flow rate of hydraulic fluid delivered by the main pump P2 such that a differential pressure (which is obtained by subtracting, from the delivery pressure of hydraulic fluid from the variable displacement main pump P2, the highest of the load pressures on the actuators 14, 15, and 27 actuated by hydraulic fluid delivered by the main pump P2) is constant.
The LS system 80 includes a swash plate change cylinder 81, a flow rate compensation valve 82, and an opening change cylinder 83. The swash plate change cylinder 81 adjusts the angle of the swash plate of the main pump P2. The flow rate compensation valve 82 allows the hydraulic pressure to act on the swash plate change cylinder 81 to actuate the swash plate change cylinder 81. The opening change cylinder 83 is actuated by the pilot pressure of pilot fluid from the pilot pump P1 to change the opening of the flow rate compensation valve 82.
A PLS fluid passage 84 and a PPS fluid passage 85 are connected to the flow rate compensation valve 82. The PLS fluid passage 84 is a fluid passage to transmit a PLS pressure, which is the highest of the load pressures on the plurality of actuators 14, 15 and 27 (actuator's highest load pressure). The PPS fluid passage 85 is a fluid passage to transmit a PPS pressure, which is the delivery pressure of the main pump P2. The flow rate compensation valve 82 actuates the swash plate change cylinder 81 to adjust the angle of the swash plate of the main pump P2 such that the differential pressure, which is obtained by subtracting the PLS pressure from the PPS pressure, is constant. With this, the delivery flow rate of hydraulic fluid from the main pump P2 is controlled, and hydraulic power corresponding to the load applied on the working device 4 and on the auxiliary attachment 11, 11b is outputted from the main pump P2.
In the present example embodiment, the LS system 80 is configured such that the swash plate of the main pump P2 is pressed in the direction that increases the delivery flow rate of hydraulic fluid from the main pump P2 by the self pressure of the main pump P2. The swash plate change cylinder 81 is configured such that the swash plate change cylinder 81 causes the force against the self pressure of the main pump P2 to act on the swash plate. The flow rate compensation valve 82 is configured such that the flow rate compensation valve 82 controls the delivery flow rate of the main pump P2 by adjusting the hydraulic pressure acting on the swash plate change cylinder 81. Thus, when the hydraulic pressure acting on the swash plate change cylinder 81 drops (reaches zero), the angle of the swash plate of the main pump P2 becomes maximum, and the flow rate of the hydraulic fluid delivered by the main pump P2 becomes maximum.
Each travel pump 50 is actuated by power from the prime mover 6. The travel pump 50 is a swash-plate variable displacement axial pump, and includes pump pressure receivers 50 and 50b to receive pilot pressure. The pump pressure receivers 50 and 50b include a forward-travel pump pressure receiver 50a and a rearward-travel pump pressure receiver 50b. The travel pump 50 is configured such that the angle of the swash plate is changed according to the pilot pressure acting on the pump pressure receivers 50a and 50b. As the angle of the swash plate of the travel pump 50 is changed, the flow rate and the direction of hydraulic fluid delivered by the travel pump 50 change. The travel pumps 50 include a first travel pump 50L corresponding to the first traveling device 5, and a second travel pump 50R corresponding to the second traveling device 5.
Each travel motor 51 is a hydraulic motor to be actuated by hydraulic fluid delivered by the corresponding travel pump 50. The travel motors 51 include a first travel motor 51L corresponding to the first traveling device 5 and the first travel pump 50L, and a second travel motor 51R corresponding to the second traveling device 5 and the second travel pump 50R.
The first travel motor 51L is connected to the first travel pump 50L by a closed loop circulating fluid passage 53a. The first travel motor 51L is actuated by hydraulic fluid supplied from the first travel pump 50L. The first travel motor 51L includes an output shaft 51Lj, and changes the rotation speed of the output shaft 51Lj according to the flow rate of hydraulic fluid supplied from the first travel pump 50L. Power from the first travel motor 51L is transmitted from the output shaft 51Lj to the drive shaft of the first traveling device 5 via transmission, so that the first traveling device 5 is driven.
The first travel motor 51L includes a swash plate, and is configured such that, when the angle of the swash plate is changed by a swash plate switching cylinder 52L, the rotation speed stage of the output shaft 51Lj is switched between a first speed stage (low speed stage) and a second speed stage (high speed stage) higher than the first speed stage. Specifically, when the swash plate switching cylinder 52L retracts, the rotation speed of the output shaft 51Lj of the first travel motor 51L is set to the first speed stage. When the swash plate switching cylinder 52L extends, the rotation speed of the output shaft 51Lj of the first travel motor 51L is set to the second speed stage.
The second travel motor 51R is connected to the second travel pump 50R by a closed loop circulating fluid passage 53b. The second travel motor 51R is actuated by hydraulic fluid supplied from the second travel pump 50R to drive the second traveling device 5 via an output shaft 51Rj and the like. The second travel motor 51R is configured such that, when the angle of the swash plate is changed by a swash plate switching cylinder 52R, the rotation speed stage of the output shaft 51Rj is switched between the first speed stage and the second speed stage. The configuration of the second travel motor 51R, the second travel pump 50R, the second traveling device 5, and the swash plate switching cylinder 52R is the same as the configuration of the first travel motor 51L, the first travel pump 50L, the first traveling device 5, and the swash plate switching cylinder 52L, and therefore details are omitted.
The working machine 1 includes travel operating equipment 54. The travel operating equipment 54 is configured to operate the travel pumps 50, the travel motors 51, and the traveling devices 5. The travel operating equipment 54 is configured to, by changing the pilot pressure acting on the pump pressure receivers 50a and 50b of the travel pumps 50, change the angle of the swash plates of the travel pumps 50 to change the delivery flow rate and the direction of hydraulic fluid delivered by the travel pumps 50, the rotation speed and the rotation direction of the output shafts 51Lj and 51Rj of the travel motors 51, as well as the actuation speed and the actuation direction of the traveling devices 5. The travel operating equipment 54 includes a travel operator 55 and a plurality of travel operating valves 56.
The travel operator 55 is an operating lever pivotable along to the left-and-right direction (machine body width direction) and the front-rear direction. The travel operator 55 is supported by a plurality of travel operating valves 56. The travel operator 55 can be moved from a neutral position in the forward direction (direction of arrow A1) and the rearward direction (direction of arrow A2), as well as from the neutral position in the leftward direction (direction of arrow A3) and the rightward direction (direction of arrow A4). In other words, the travel operator 55 can be pivoted from the neutral position (base position) in at least four directions.
The plurality of travel operating valves 56 are configured to be actuated according to the operation of the common travel operator 55. Specifically, the plurality of travel operating valves 56 are connected to the fluid discharge passage 40, and change the pilot pressure of pilot fluid supplied from the fluid discharge passage 40. The plurality of travel operating valves 56 are operated by the travel operator 55. The plurality of travel operating valves 56 include a first operating valve 56A, a second operating valve 56B, a third operating valve 56C, and a fourth operating valve 56D.
When the travel operator 55 is pivoted in the forward direction (direction of A1) (operated forward), the first operating valve 56A changes its outputting pilot pressure according to the operation amount (operation). When the travel operator 55 is pivoted in the rearward direction (direction of A2) (operated rearward), the second operating valve 56B changes its outputting pilot pressure according to the operation amount. When the travel operator 55 is pivoted in the leftward direction (direction of A3) (operated leftward), the third operating valve 56C changes its outputting pilot pressure according to the operation amount. When the travel operator 55 is pivoted in the rightward direction (direction of A4) (operate rightward), the fourth operating valve 56D changes its outputting pilot pressure according to the operation amount.
The plurality of travel operating valves 56 are connected to the corresponding travel pumps 50 by travel fluid passages 42. The travel fluid passages 42 include a first travel fluid passage 42a, a second travel fluid passage 42b, a third travel fluid passage 42c, a fourth travel fluid passage 42d, and a fifth travel fluid passage 42e. The first travel fluid passage 42a is connected to the forward-travel pump pressure receiver 50a of the first travel pump 50L. The second travel fluid passage 42b is connected to the rearward-travel pump pressure receiver 50b of the first travel pump 50L. The third travel fluid passage 42c is connected to the forward-travel pump pressure receiver 50a of the second travel pump 50R. The fourth travel fluid passage 42d is connected to the rearward-travel pump pressure receiver 50b of the second travel pump 50R.
The fifth travel fluid passage 42e is connected to the plurality of travel operating valves 56 and the plurality of travel fluid passages 42. Specifically, the fifth travel fluid passage 42e includes a bridge fluid passage 42e1 and a plurality of coupling fluid passages 42e2. The bridge fluid passage 42e1 has connected thereto a plurality of shuttle valves 43 and first ends of the plurality of coupling fluid passages 42e2 which are arranged alternately. Second ends of the plurality of the coupling fluid passages 42e2 are connected to the respective plurality of travel operating valves 56. The plurality of shuttle valves 43 have connected thereto the respective plurality of travel fluid passages 42.
When the travel operator 55 is pivoted in the forward direction (direction A1), the first operating valve 56A is operated, and pilot fluid is supplied from the first operating valve 56A to the fifth travel fluid passage 42e. The pilot pressure of the pilot fluid supplied from the first operating valve 56A acts on the forward-travel pump pressure receiver 50a of the first travel pump 50L via the fifth travel fluid passage 42e and the first travel fluid passage 42a. The pilot pressure of pilot fluid from the first operating valve 56A acts on the forward-travel pump pressure receiver 50a of the second travel pump 50R via the fifth travel fluid passage 42e and the third travel fluid passage 42c. With this, the angle of the swash plate of the first travel pump 50L and the angle of the swash plate of the second travel pump 50R are changed, the output shafts 51Lj and 51Rj of the first travel motor 51L and the second travel motor 51R rotate in a normal direction (rotate to achieve forward travel), the first traveling device 5 and the second traveling device 5 are driven to travel forward, and the working machine 1 travels straight in the forward direction.
When the travel operator 55 is pivoted in the rearward direction (direction of A2), the second operating valve 56B is operated, and pilot fluid is supplied from the second operating valve 56B to the fifth travel fluid passage 42e. The pilot pressure of the pilot fluid supplied from the second operating valve 56B acts on the rearward-travel pump pressure receiver 50b of the first travel pump 50L via the fifth travel fluid passage 42e and the second travel fluid passage 42b. The pilot pressure of pilot fluid from the second operating valve 56B acts on the rearward-travel pump pressure receiver 50b of the second travel pump 50R via the fifth travel fluid passage 42e and the fourth travel fluid passage 42d. With this, the angle of the swash plate of the first travel pump 50L and the angle of the swash plate of the second travel pump 50R are changed, the output shafts 51Lj and 51Rj of the first travel motor 51L and the second travel motor 51R rotate in a reverse direction (rotates to achieve rearward travel), the first traveling device 5 and the second traveling device 5 are driven to travel rearward, and the working machine 1 travels straight in the rearward direction.
When the travel operator 55 is pivoted in the leftward direction (direction of A3), the third operating valve 56C is operated, and pilot fluid is supplied from the third operating valve 56C to the fifth travel fluid passage 42e. The pilot pressure of the pilot fluid supplied from the third operating valve 56C acts on the forward-travel pump pressure receiver 50a of the second travel pump 50R via the fifth travel fluid passage 42e and the third travel fluid passage 42c. The pilot pressure of pilot fluid from the third operating valve 56C acts on the rearward-travel pump pressure receiver 50b of the first travel pump 50L via the fifth travel fluid passage 42e and the second travel fluid passage 42b. With this, the angle of the swash plate of the first travel pump 50L and the angle of the swash plate of the travel pump 50R are changed, the output shaft 51Lj of the first travel motor 51L rotates in the reverse direction, the first traveling device 5 is driven to travel rearward, as well as the output shaft 51Rj of the second travel motor 51R rotates in the normal direction, and the second traveling device 5 is driven to travel forward, causing the working machine 1 to turn left.
When the travel operator 55 is pivoted in the rightward direction (direction of A4), the fourth operating valve 56D is operated, and pilot fluid is supplied from the fourth operating valve 56D to the fifth travel fluid passage 42e. The pilot pressure of the pilot fluid supplied from the fourth operating valve 56D acts on the forward-travel pump pressure receiver 50a of the first travel pump 50L via the fifth travel fluid passage 42e and the first travel fluid passage 42a. The pilot pressure of pilot fluid from the fourth operating valve 56D acts on the rearward-travel pump pressure receiver 50b of the second travel pump 50R via the fifth travel fluid passage 42e and the fourth travel fluid passage 42d. With this, the angle of the swash plate of the first travel pump 50L and the angle of the swash plate of the second travel pump 50R are changed, the output shaft 51Lj of the first travel motor 51L rotates in the normal direction, the first traveling device 5 is driven to travel forward, as well as the output shaft 51Rj of the second travel motor 51R rotates in the reverse direction and the second traveling device 5 is driven to travel rearward, causing the working machine 1 to turn right.
When the travel operator 55 is pivoted in a diagonal direction, the rotation direction and the rotation speed of the output shafts 51Lj and 51Rj of the first travel motor 51L and the second travel motor 51R are determined by the difference between the pilot pressure acting on each forward-travel pump pressure receiver 50a and the pilot pressure acting on each rearward-travel pump pressure receiver 50b, so that the working machine 1 turns right or left while traveling forward or rearward.
Specifically, when the travel operator 55 is pivoted diagonally leftward and forward, the working machine 1 turns left while traveling forward at a speed corresponding to the pivot angle of the travel operator 55. When the travel operator 55 is pivoted diagonally rightward and forward, the working machine 1 turns right while traveling forward at a speed corresponding to the pivot angle of the travel operator 55. When the travel operator 55 is pivoted diagonally leftward and rearward, the working machine 1 turns left while traveling rearward at a speed corresponding to the pivot angle of the travel operator 55. When the travel operator 55 is pivoted diagonally rightward and rearward, the working machine 1 turns right while traveling rearward at a speed corresponding to the pivot angle of the travel operator 55.
The working machine 1 includes travel switching valves 57. Each travel switching valve 57 is switchable between a first state in which the rotation speed of the output shafts 51Lj and 51Rj of the travel motor 51 is the first speed stage and a second state in which the rotation speed of the output shafts 51Lj and 51Rj of the travel motor 51 is the second speed stage. The travel switching valves 57 include first switching valves 58L and 58R, and a second switching valve 59.
The first switching valve 58L is a two-way switching valve switchable between a first position 58L1 and a second position 58L2. The first switching valve 58L is connected to the swash plate switching cylinder 52L via fluid passage. When the first switching valve 58L is in the first position 58L1, the first switching valve 58L stops the supply of hydraulic fluid to the swash plate switching cylinder 52L. With this, the swash plate switching cylinder 52L retracts under the elastic force of a spring. When the first switching valve 58L is in the second position 58L2, the first switching valve 58L allows hydraulic fluid to be supplied to the swash plate switching cylinder 52L. With this, the swash plate switching cylinder 52L extends in response to hydraulic pressure.
The second switching valve 59 is configured to switch the switching position of the first switching valve 58L and the switching position of the first switching valve 58R. Specifically, the second switching valve 59 is a two-way switching valve configured such that its solenoid is energized in response to a control signal inputted thereto to switch the second switching valve 59 to a first position 59a or a second position 59b. The second switching valve 59 is connected to the first switching valve 58L and the first switching valve 58R via the fluid passage 41.
When the second switching valve 59 is in the first position 59a, the second switching valve 59 allows hydraulic fluid to be supplied to a pressure receiver of the first switching valve 58L and a pressure receiver of the first switching valve 58R. With this, the first switching valve 58L switches to the first position 58L1, and the first switching valve 58R switches to the first position 58R1. That is, when the second switching valve 59 is in the first position 59a, the travel switching valves 57 are in the first state, the swash plate switching cylinders 52L and 52R retract, and the rotation speed of the output shafts 51Lj and 51Rj of the travel motors 51 (the first travel motor 51L and the second travel motor 51R) switches to the first speed stage.
When the second switching valve 59 is in the second position 59b, the second switching valve 59 does not allow hydraulic fluid to be supplied to the pressure receiver of the first switching valve 58L or the pressure receiver of the first switching valve 58R. With this, the first switching valve 58L switches to the second position 58L2, and the first switching valve 58R switches to the second position 58R2. That is, when the second switching valve 59 is in the second position 59b, the travel switching valves 57 are in the second state, the swash plate switching cylinders 52L and 52R extend and the rotation speed of the output shafts 51Lj and 51Rj of the travel motors 51 (the first travel motor 51L and the second travel motor 51R) switches to the second speed stage. Thus, the travel switching valves 57 switch the travel motors 51 (the first travel motor 51L and the second travel motor 51R) to the first speed stage or the second speed stage.
The memory and/or the storage 110 includes a nonvolatile memory and/or the like. The memory and/or the storage 110 also stores data for use in controlling elements of the working machine 1. The input/output interface 111 is a user interface such as a touchscreen or a tablet terminal device. The controller 100 causes the input/output interface 111 to display (output) various information relating to the working machine 1 stored in the internal memory and/or the memory and/or the storage 110 to the user or the like (which may be some other user).
The user of the working machine 1 or the like inputs various information via the input/output interface 111. For example, information indicating the attachment 11 attached to the working device 4 is inputted via the input/output interface 111. The controller 100 causes the internal memory and/or the memory and/or the storage 110 to store the information inputted via the input/output interface 111. The input/output interface 111 includes an input interface and an output interface. The input/output interface 111 may include a least one manual operator which is at least one of button(s), switch(es), dial(s) slider(s), or the like.
The working machine 1 includes an accelerator 101, a speed operator 102, and an auxiliary operator 103. These devices 101 to 103 are connected to the controller 100. These devices 101 to 103 are located in the vicinity of the seat 8 inside the cabin 3, and are operated by the user of the working machine 1.
The accelerator 101 is a device to input (receive input of) the target rotation speed of the prime mover 6, and includes an acceleration operator and an acceleration sensor. The acceleration operator may be a manual operator such as a lever, a pedal, a dial, a slider, and/or the like. The accelerator sensor outputs a signal corresponding to the operating position of the acceleration operator. The controller 100 determines the target rotation speed of the prime mover 6 based on an accelerator signal outputted from the acceleration sensor of the accelerator 101.
The speed operator 102 is an input interface to input (receive input of) an instruction to switch the travel motor(s) 51 (the first travel motor 51L and/or the second travel motor 51R) to the first speed stage or the second speed stage, and includes a speed-change operator and a speed-change-instruction detector. The speed-change operator is, for example, a manual operator such as an operating switch, a dial, a slider, and/or the like, and includes a position corresponding to the first speed stage and a position corresponding to the second speed stage. The speed-change-instruction detector outputs a signal corresponding to the operating position of the speed-change operator.
The controller 100 determines whether or not there is an instruction to switch to the first speed stage or the second speed stage corresponding to the operating position of the speed-change operator, based on the signal outputted from the speed-change-instruction detector of the speed operator 102. If the controller 100 determines that there is an instruction to switch to the first speed stage, the controller 100 switches the travel motor(s) 51 (the first travel motor 51L and/or the second travel motor 51R) to the first speed stage via the travel switching valves 57 (the first switching valves 58L and/or 58R, and the second switching valve 59). With this, the rotation speed of the output shafts 51Lj and/or 51Rj of the travel motor(s) 51, the actuation speed of the traveling device(s) 5 (the first traveling device 5 and/or the second traveling device 5), and the vehicle speed of the working machine 1 decrease.
If the controller 100 determines that there is an instruction to switch to the second speed stage, the controller 100 switches the travel motor(s) 51 to the second speed stage via the travel switching valves 57. With this, the rotation speed of the output shafts 51Lj and/or 51Rj of the travel motor(s) 51, the actuation speed of the traveling device(s) 5, and the vehicle speed of the working machine 1 increase.
The auxiliary operator 103 is an input interface to input (receive input of) (i) an AUX output start instruction which is an instruction to allow, via the AUX ports 25, hydraulic fluid to be introduced into and discharged from the auxiliary actuator 27 provided on or in the auxiliary attachment 11, 11b, and (ii) an AUX output stop instruction which is an instruction to stop the hydraulic fluid from being introduced and discharged. The auxiliary operator 103 includes an auxiliary output operator and an output instruction detector. The auxiliary output operator is a manual operator such as an operating switch, a dial, a slider, and/or the like, and includes a start position corresponding to the AUX output start instruction and a stop position corresponding to the AUX output stop instruction. The detector outputs a signal corresponding to the operating position of the auxiliary output operator.
If the controller 100 determines that there is an AUX output start instruction (instruction to start output from an AUX port 25) based on the output signal from the detector of the auxiliary operator 103, the controller 100 switches the AUX control valve 60C to the first position 60a or the second position 60b via the AUX solenoid valves 65 (the first AUX solenoid valve 65A and the second AUX solenoid valve 65B), to allow hydraulic fluid to be introduced into and discharged from to the auxiliary actuator 27 from and into the AUX control valve 60C via the fluid passage 64 and the AUX ports 25. With this, the auxiliary actuator 27 is actuated, making it possible to perform work with the auxiliary attachment 11, 11b.
If the controller 100 determines that there is an AUX output stop instruction (instruction to stop output from an AUX port 25) based on the output signal from the detector of the auxiliary operator 103, the controller 100 switches the AUX control valve 60C to the third position 60d via the AUX solenoid valves 65 to stop hydraulic fluid from being introduced into and discharge from the auxiliary actuator 27. With this, the auxiliary actuator 27 stops.
The amount of hydraulic fluid introduced into and discharged from the auxiliary actuator 27 via the AUX ports 25 is controlled by the controller 100. For example, attachment information relating to the attachment 11 usable on the working machine 1 is stored in advance in the memory and/or the storage 110. The attachment information includes identification information of the attachment 11 and information indicating specifications and/or the like of the attachment 11. The specifications of the attachment 11 include information indicating whether there is an auxiliary actuator 27 or not and, in the case where there is an auxiliary actuator 27, also include information indicating the specifications of the auxiliary actuator 27. The specifications of the auxiliary actuator 27 include the type the auxiliary actuator 27, the power of the auxiliary actuator 27, the flow rate of hydraulic fluid used to actuate the auxiliary actuator 27, control data for the AUX solenoid valves 65 to actuate the auxiliary actuator 27, and/or the like.
When information indicating the attachment 11 attached to the working device 4 is inputted via the input/output interface 111, the controller 100 reads attachment information corresponding to the attached attachment 11 from the memory and/or the storage 110 based on the inputted information. The controller 100 determines whether or not the attachment 11 attached to the working device 4 includes an auxiliary actuator 27 based on the read attachment information, and if the working device 4 includes an auxiliary actuator 27, the controller 100 additionally reads the specifications of the auxiliary actuator 27 from the attachment information.
Then, when the controller 100 determines that there is an AUX output start instruction based on the output signal from the detector of the auxiliary operator 103, the controller 100 controls, based on the control data included in the specifications of the auxiliary actuator 27, the electric current value of a control signal inputted into the first AUX solenoid valve 65A and the second AUX solenoid valve 65B to adjust the opening of the first AUX solenoid valve 65A and the opening of the second AUX solenoid valve 65B. With this, according to the auxiliary actuator 27, the AUX control valve 60C switches to the first position 60a or the second position 60b, and the opening of the AUX control valve 60C is adjusted, so that hydraulic fluid is introduced into and discharged from the auxiliary actuator 27 from and to the AUX control valve 60C via the AUX ports 25 and the like in directions corresponding to the auxiliary actuator 27 and at a flow rate corresponding to the auxiliary actuator 27.
The auxiliary operator 103 also functions as an input interface to input (receive input of) an instruction to change the flow rate of hydraulic fluid supplied to the auxiliary actuator 27. The auxiliary operator 103 includes an auxiliary flow rate operator and a flow rate instruction detector. The auxiliary flow rate operator is a manual operator such as an operating switch, a dial, a slider and/or the like. The flow rate instruction detector outputs a signal corresponding to the operating position of the auxiliary flow rate operator.
The controller 100 receives a flow rate change instruction which is an instruction to change the flow rate of hydraulic fluid supplied to the auxiliary actuator 27 based on the output signal from the flow rate instruction detector of the auxiliary operator 103. Then, the controller 100 controls, based on the control data for the auxiliary actuator 27 and the flow rate change instruction, the electric current value of a control signal inputted into the first AUX solenoid valve 65A and the second AUX solenoid valve 65B to adjust the opening of the first AUX solenoid valve 65A and the opening of the second AUX solenoid valve 65B. With this, according to the auxiliary actuator 27, the AUX control valve 60C switches to the first position 60a or the second position 60b and the opening of the AUX control valve 60C is adjusted, so that the flow rate of hydraulic fluid introduced into and discharged from the auxiliary actuator 27 from and to the AUX control valve 60C is changed from the flow rate corresponding to the control data (default value) to the flow rate corresponding to the flow rate change instruction (user input value).
The operation of the auxiliary attachment 11, 11b (e.g., switching between driving (turning ON) and stopping (turning OFF) the auxiliary attachment 11, 11b, the drive state of the auxiliary attachment 11, 11b, and/or the like) may be controlled by a dedicated attachment operator. Alternatively, the operation of the auxiliary attachment 11, 11b may be controlled using the input/output interface 111, by application program(s) for operation stored in advance in the memory and/or the storage 110 being executed by the controller 100. In such a case, the controller 100 may change the position and the opening of the AUX control valve 60C via the AUX solenoid valves 65 according to the operation state of the attachment operator or the input/output interface 111 to start, adjust (adjust the amount of introduced/discharged fluid and the flow direction of fluid), or stop the introduction and discharge of hydraulic fluid into and from the auxiliary actuator 27. The auxiliary operator 103 may be omitted and the input/output interface 111 may include the foregoing configuration of the auxiliary operator 103.
The working machine 1 includes a rotation speed sensor 104, a swash plate angle sensor 105, pressure sensor(s) 106, and a temperature sensor 107. The sensors 104 to 107 are connected to the controller 100.
The rotation speed sensor 104 detects the actual rotation speed of the prime mover 6. The controller 100 controls the driving of the prime mover 6 such that the actual rotation speed of the prime mover 6 matches the target rotation speed inputted via the accelerator 101. As another example, a controller different from the controller 100 of the working machine 1 (for example, an engine controller unit) may control the driving of the prime mover 6 such that the actual rotation speed of the prime mover 6 matches the target rotation speed.
The controller 100 may automatically switch the travel motor(s) 51 to the first speed stage or the second speed stage based on the actual rotation speed of the prime mover 6 detected by the rotation speed sensor 104. For example, when the travel motors 51 are in the second speed stage, if the actual rotation speed of the prime mover 6 decreases below a predetermined value, the controller 100 switches the travel motors 51 to the first speed stage via the travel switching valves 57 (automatic deceleration). The controller 100 may automatically switch the travel motors 51 to the first speed stage or the second speed stage based on other parameter(s) such as the vehicle speed of the working machine 1 detected via sensor and/or the like. Thus, there are cases where the switching of the travel motor(s) 51 to the first speed stage or the second speed stage is not only performed via manual operation of the speed operator 102, but also automatically performed by the controller 100.
The swash plate angle sensor 105 detects the angle of the swash plate of the main pump P2. The temperature sensor 107 detects the temperature of hydraulic fluid and pilot fluid. A plurality of the pressure sensors 106 are provided at various portions of the hydraulic circuit of the work system of
As shown in
The load pressure sensor 106k is connected to the PLS fluid passage 84, and detects the highest load pressure (PLS pressure) of the load pressures on the actuators 14, 15 and 27. As shown in
The controller 100 reads input information indicating the attachment 11 inputted via the input/output interface 111 and stored in the internal memory or in the memory and/or the storage 110, and reads the attachment information corresponding to the attachment 11 indicated by the input information (S1 of
In the case where, for example, the attachment 11 attached to the working device 4 is an attachment including no auxiliary actuators 27 such as the bucket 11a, the controller 100 determines that the attachment 11 includes no auxiliary actuators 27 based on the attachment information about the attachment 11 (NO at S2). In such a case, even if work (such as excavation) is performed by the working device 4 and the attachment 11, since the load on the prime mover 6 is low and the work is low-load work, the controller 100 fully closes the AUX solenoid valve 65 and keeps the AUX control valve 60C in the neutral position (third position) 60d according to the low-load work (S3). With this, hydraulic fluid is not introduced or discharged to or from the AUX ports 25 from or to the AUX control valve 60C, and the AUX ports 25 are not in use.
On the other hand, in the case where the attachment 11 attached to the working device 4 is an auxiliary attachment including an auxiliary actuator 27, the controller 100 determines that there is an auxiliary actuator 27 based on the attachment information corresponding to the auxiliary attachment 11 (YES at S2).
In the case where the attachment 11 attached to the working device 4 is, for example, an auxiliary attachment including a low-power or medium-power auxiliary actuator 27 such as a broom, when work (cleaning with a brush) is performed by the working device 4 and the auxiliary attachment 11, the load on the prime mover 6 is low or medium. That is, the work performed by the working device 4 and the auxiliary attachment 11 is low-load work or medium-load work. In such a case, the controller 100 determines that the auxiliary actuator 27 of the auxiliary attachment 11 is not a high-power auxiliary actuator based on the attachment information corresponding to the auxiliary attachment 11 (NO at S4). Then, since the work performed by the working device 4 and the auxiliary attachment 11 is low-load work or medium-load work, the controller 100 performs a low-load/medium-load output process to control the output (the amount of hydraulic fluid supplied) from the AUX ports 25 to the auxiliary actuator 27 according to the work (S5).
In the case where, for example, the attachment 11 attached to the working device 4 is an auxiliary attachment including a high-power auxiliary actuator 27 such as the mulcher 11b, when work (such as fallen tree crushing work) is performed by the working device 4 and the auxiliary attachment 11, the load on the prime mover 6 is high. That is, the work performed by the working device 4 and the auxiliary attachment 11 is high-load work. In such a case, the controller 100 determines that the auxiliary actuator 27 of the auxiliary attachment 11 is a high-power auxiliary actuator based on the attachment information corresponding to the attachment 11 (YES at S4). Then, since the work performed by the working device 4 and the auxiliary attachment 11 is high-load work, the controller 100 performs a high-load output process to control the output from the AUX ports 25 to the auxiliary actuator 27 according to the high-load work (S6).
In the low-load/medium-load output process, an AUX output start instruction is inputted from the auxiliary operator 103 in response to the operation of the auxiliary output operator of the auxiliary operator 103 to a start position by the user of the working machine 1 (S11 of
The control data read at step S12 includes a control graph L1 (
In the case where the user does not operate the auxiliary flow rate operator of the auxiliary operator 103 (NO at S14 of
In the case where the user operates the auxiliary flow rate operator of the auxiliary operator 103 to input a flow rate change instruction to change the flow rate of hydraulic fluid to the auxiliary actuator 27 (YES at S14), the controller 100 shifts the control graph L1 according to the flow rate change instruction (S15). Specifically, the controller 100 determines a changed value of the control signal for the actuated AUX solenoid valve based on the flow rate change instruction, and shifts the control graph L1 along the direction of the vertical axis in which the electric current value of the control signal of
In the example shown in
After the controller 100 shifts the control graph L1, the controller 100 inputs a control signal into the actuated AUX solenoid valve based on the shifted control graph L1s. That is, the controller 100 inputs, into the actuated AUX solenoid valve, a control signal having the electric current value indicated by the shifted control graph L1s according to the instruction from the user. With this, hydraulic fluid at a flow rate intended by the user is outputted (supplied) to the auxiliary actuator 27 of the auxiliary attachment 11 from the AUX control valve 60C via the AUX port 25 and the like (S16).
Specifically, at step S16, the controller 100 inputs a control signal having the electric current value according to the control graph L1 or the shifted control graph L1s into one of the first AUX solenoid valve 65A and the second AUX solenoid valve 65B that has been determined as being the actuated AUX solenoid valve. With this, the actuated AUX solenoid valve opens, and the opening of the actuated AUX solenoid valve is adjusted. In so doing, the other of the first AUX solenoid valve 65A and the second AUX solenoid valve 65B that has not been determined as being the actuated AUX solenoid valve does not receive input of a control signal, and the AUX solenoid valve remains closed. Thus, the pilot pressure from the actuated AUX solenoid valve acts on the corresponding AUX pressure receiver 63a or 63b of the AUX control valve 60C, and the AUX control valve 60C switches to the first position 60a or the second position 60b. Furthermore, the opening of the AUX control valve 60C is adjusted.
Then, hydraulic fluid is supplied from the AUX control valve 60C to the auxiliary actuator 27 via corresponding fluid passage 64 and a corresponding AUX port 25 in a direction corresponding to the auxiliary attachment 11 (auxiliary actuator 27) at a flow rate corresponding to the auxiliary attachment 11 (auxiliary actuator 27) (or a flow rate intended by the user). The hydraulic fluid from the auxiliary actuator 27 is introduced into the AUX control valve 60C via corresponding AUX port 25 and a corresponding fluid passage 64 in a direction corresponding to the auxiliary attachment 11 at a flow rate corresponding to the auxiliary attachment 11 (or a flow rate intended by the user), and is drained from the AUX control valve 60C. With this, the auxiliary actuator 27 is actuated, making it possible to perform corresponding low-load or medium-load work via the auxiliary actuator 27 and the working device 4. Note that the working machine 1 may perform low-load or medium-load work using the auxiliary attachment 11 and the working device 4 while being caused to travel by the traveling devices 5 (the same applies to high-load work).
After that, while low-load or medium-load work is being performed, even if the rotation speed of the prime mover 6 changes, provided that the rotation speed is within the under-work rotation speed range E1, the controller 100 controls the electric current value of the control signal inputted into the actuated AUX solenoid valve at a constant value based on the control graph L1, and maintains the opening of the actuated AUX solenoid valve. With this, hydraulic fluid continues to be introduced via the AUX port 25 and the like into the auxiliary actuator 27 in a direction corresponding to the auxiliary actuator 27 at a flow rate according to the auxiliary actuator 27.
After that, when an AUX output stop instruction is inputted from the auxiliary operator 103 in response to the user operating the auxiliary output operator to a stop position (YES at S17 of
The control data read at step S22 of
The control-under-high-load graph L3 indicates the electric current value of the control signal which, when the actual rotation speed of the prime mover 6 detected by the rotation speed sensor 104 has decreased relative to the target rotation speed of the prime mover 6 inputted via the accelerator 101 and the decrease (i.e., drop) has reached a predetermined threshold or greater (i.e., when dropping has occurred), is to be inputted into the actuated AUX solenoid valve according to the rotation speed of the prime mover 6.
As represented by a solid line in
In the case where the user operates the auxiliary flow rate operator of the auxiliary operator 103 to input a flow rate change instruction to change the flow rate of hydraulic fluid supplied to the auxiliary actuator 27 (YES at S24), the controller 100 shifts the control-during-normal-time graph L2 according to the flow rate change instruction (S25). Specifically, as with the case of the foregoing control graph L1, the controller 100 determines a changed value of the control signal for the actuated AUX solenoid valve based on the flow rate change instruction, and shifts the control-during-normal-time graph L2 in the direction of the vertical axis direction in which the electric current value of the control signal changes in
In the example shown in
In the case where the user does not operate the auxiliary flow rate operator of the auxiliary operator 103 (NO at S24 of
Next, the controller 100 acquires the actual rotation speed and the target rotation speed of the prime mover 6, and compares the actual rotation speed and the target rotation speed. In so doing, if the actual rotation speed of the prime mover 6 has not decreased relative to the target rotation speed (NO at S26), the controller 100 inputs the control signal having the electric current value which is based on the control-during-normal-time graph L2 or L2s into the actuated AUX solenoid valve.
In so doing, if the control-during-normal-time graph L2 has not been shifted, the controller 100 inputs the control signal having the constant electric current value (predetermined value) indicated by the control-during-normal-time graph L2 corresponding to the auxiliary attachment 11 (auxiliary actuator 27) into the actuated AUX solenoid valve. If the control-during-normal-time graph L2 has been shifted, the controller 100 inputs, into the actuated AUX solenoid valve, the control signal having the constant electric current value indicated by the shifted control-during-normal-time graph L2s corresponding to the user's instruction. With this, hydraulic fluid is outputted (supplied) from the AUX control valve 60C to the auxiliary actuator 27 of the auxiliary attachment 11 via the AUX port 25 and the like (S32 of
Specifically, at step S32 of
With this, the actuated AUX solenoid valve opens, the opening of the actuated AUX solenoid valve is adjusted according to the auxiliary attachment 11, and hydraulic fluid is introduced into the auxiliary actuator 27 via the AUX control valve 60C, the fluid passage 64 and the AUX port 25 in a direction corresponding to the auxiliary attachment 11 (auxiliary actuator 27) at a flow rate corresponding to the auxiliary attachment 11 (auxiliary actuator 27). Then, the auxiliary actuator 27 is actuated, making it possible to perform corresponding high-load work using the auxiliary actuator 27 and the working device 4.
After step S32 of
If the actual rotation speed of the prime mover 6 has decreased relative to the target rotation speed (YES at S26 of
If the actuated AUX solenoid valve is receiving input of a control signal (YES at S28), the controller 100 determines whether or not a predetermined time has passed since the start of the input of control signal into the actuated AUX solenoid valve. In so doing, if a predetermined time has not passed (NO at S29), the auxiliary actuator 27 is being activated or has just been activated, and therefore the controller 100 determines whether or not the drop is equal to or greater than the second threshold. If the drop is less than the second threshold (NO at S30 of
On the other hand, if the drop is equal to or greater than the second threshold (YES at S30), the controller 100 shifts the control-under-high-load graph L3 included in the control data read at step S22, according to the actual rotation speed of the prime mover 6 (S33). In so doing, if the control-during-normal-time graph L2 has not been shifted, for example, as shown in
If the control-during-normal-time graph L2 has been shifted, for example, as shown in
The controller 100 then changes the electric current value of the control signal being inputted into the actuated AUX solenoid valve according to the shifted control-under-high-load graph L3s and the actual rotation speed (the rotation speed at or after the drop reaches the second threshold or greater) of the prime mover 6 to limit the output of hydraulic fluid to the auxiliary actuator 27 (S34 of
At step S34, the controller 100 determines the restricted electric current value corresponding to the actual rotation speed of the prime mover 6 based on the shifted control-under-high-load graph L3s, and changes the electric current value of the control signal being inputted into the actuated AUX solenoid valve to the restricted electric current value which is smaller than the electric current value of the control signal being inputted. With this, the pilot pressure acting on the AUX pressure receiver 63a or 63b of the AUX control valve 60C decreases, the opening of the AUX control valve 60C decreases, and the flow rate of the hydraulic fluid flowing from AUX control valve 60C to the auxiliary actuator 27 via the AUX port 25 and the like is limited (reduced). That is, the controller 100 performs an anti-stall control to eliminate or reduce the likelihood that the prime mover 6 will stop unintentionally, by limiting the output from the AUX port 25. This anti-stall control may be referred to as AUX anti-stall control.
After step S34, if no AUX output stop instructions are inputted from the auxiliary operator 103 (NO at S35), the controller 100 again acquires the actual rotation speed and the target rotation speed of the prime mover 6. Then, if the actual rotation speed of the prime mover 6 has decreased relative to the target rotation speed (YES at S26 of
If a predetermined time has passed since the start of the input of control signal into the actuated AUX solenoid valve (YES at S28, YES at S29), the drive state of the auxiliary actuator 27 is stable, and therefore the controller 100 determines whether or not the drop is equal to or greater than the first threshold. The first threshold is a threshold used when the auxiliary actuator 27 is being driven, and is set to have a smaller value (for example, about 200 rpm) than the foregoing second threshold for use when the auxiliary actuator 27 is being activated or has just been activated. If the drop is less than the first threshold (NO at S31 of 7B), the controller 100 inputs, into the actuated AUX solenoid valve, the control signal having the constant electric current value indicated by the control-during-normal-time graph L2 or the shifted control-during-normal-time graph L2s (S32).
On the other hand, if the drop is equal to or more than the first threshold (YES at S31), the controller 100 shifts the control-under-high-load graph L3 according to the actual rotation speed of the prime mover 6 as described earlier (S33). Then, according to the shifted control-under-high-load graph L3s and the actual rotation speed of the prime mover 6 (the rotation speed at or after the drop reaches the first threshold or greater), the controller 100 changes the electric current value of the control signal being inputted into the actuated AUX solenoid valve to limit the output to the auxiliary actuator 27 (S34). That is, the controller 100 performs the AUX anti-stall control.
At step S34, for example, the controller 100 may suddenly change (suddenly reduce) the electric current value of the control signal being inputted into the actuated AUX solenoid valve to cause the electric current value to match the restricted electric current value (target electric current value) determined based on the control-under-high-load graph L3s and the actual rotation speed of the prime mover 6. Alternatively, since the controller 100 inputs a control signal into the actuated AUX solenoid valve via pulse width modulation (PWM), the controller 100 may gradually reduce the duty ratio of the PWM signal to gradually change (gently reduce) the electric current value Ac of the control signal being inputted to the actuated AUX solenoid valve at a predetermined rate (for example, about 10 mA/sec.) to cause that electric current value to match the restricted electric current value Ar over a predetermined time T1 (see
Even if, because step S34 of
In such a case, the controller 100 again changes the electric current value of the control signal for the actuated AUX solenoid valve based on the control-under-high-load graph L3s and the actual rotation speed of the prime mover 6 to limit the output to the auxiliary actuator 27 (S34 of
After limiting the output to the auxiliary actuator 27 at step S34 of
With this, the output of hydraulic fluid toward the auxiliary actuator 27 is not limited anymore, and the AUX anti-stall control stops. In so doing, the controller 100 may suddenly change (increase) the electric current value of the control signal inputted into the actuated AUX solenoid valve or gradually change (increase) the electric current value of the control signal inputted into the actuated AUX solenoid valve at a predetermined rate (for example, 10 mA/sec.) to cause the electric current value of the control signal inputted into the actuated AUX solenoid valve to match the electric current value indicated by the control-during-normal-time graph L2 or the shifted control-during-normal-time graph L2s.
Ater that, when an AUX output stop instruction is inputted from the auxiliary operator 103 (YES at S35 of
The above description of example embodiments discusses examples in which the threshold to be compared with the drop differs between when a predetermined time has passed since the start of supply of hydraulic fluid to the auxiliary actuator 27 and when a predetermined time has not passed since the start of supply of hydraulic fluid to the auxiliary actuator 27. However, the threshold may be the same between when a predetermined time has passed since the start of supply of hydraulic fluid to the auxiliary actuator 27 and when a predetermined time has not passed since the start of supply of hydraulic fluid to the auxiliary actuator 27.
While the prime mover 6 is being driven, the controller 100 or another electronic controller (ECU) controls the prime mover 6 such that the actual rotation speed matches the target rotation speed. However, in the case where the acceleration operator of the accelerator 101 is suddenly operated to a great extent, for example, as shown in
It may follow that the control of the prime mover 6 is delayed, the actual rotation speed Rc of the prime mover 6 temporarily departs greatly from the target rotation speed Rt (greatly decreases relative to the target rotation speed Rt), and the drop temporarily increases to the first threshold or greater (YES at S31 of
To address this, the controller 100 may generate a quasi accelerator signal Jf based on the accelerator signal Ja inputted from the accelerator 101 as shown in
After generating the quasi accelerator signal Jf as shown in
In the case where, as shown in
Then, the controller 100 changes the electric current value of the control signal being inputted into the actuated AUX solenoid valve to limit the output of hydraulic fluid to the auxiliary actuator 27, based on the shifted control-under-high-load graph L3s and the quasi rotation speed Rf (the quasi rotation speed Rf at or after the point in time at which the drop reaches the first threshold or more or the second threshold or more). Alternatively, the controller 100 may reduce the electric current value of the control signal for the actuated AUX solenoid valve to limit the flow rate of hydraulic fluid toward the auxiliary actuator 27 based on the shifted control-under-high-load graph L3s and the actual rotation speed Rc of the prime mover 6 (S34 of
With this, even if the acceleration operator is suddenly operated to a great extent with no load of a predetermined amount or higher on the prime mover 6 and therefore the target rotation speed Rt of the prime mover 6 suddenly increases and the target rotation speed Rt and the actual rotation speed Rc temporarily depart from each other greatly (even if the actual rotation speed Rc suddenly decreases relative to the target rotation speed Rt), the control-under-high-load graph L3 is not shifted unnecessarily. Thus, the AUX anti-stall control is appropriately performed according to the drop caused by a high-load on the prime mover 6, and a decrease in work performance of the auxiliary attachment 11 is prevented or reduced.
The rate of change of the quasi accelerator signal Jf generated by the controller 100 in the case where the accelerator 101 is operated suddenly to a great extent to achieve a decrease may differ from the rate of change of the quasi accelerator signal Jf generated by the controller 10 in the case where the accelerator 101 is operated suddenly to a great extent to achieve an increase. The rate of change of the quasi accelerator signal Jf generated by the controller 100 in the case where the accelerator 101 is operated suddenly to a great extent to achieve a decrease may be faster than the rate of change of the quasi accelerator signal Jf generated by the controller 100 in the case where the accelerator 101 is operated suddenly to a great extent to achieve an increase. The controller 100 may generate a quasi accelerator signal Jf by smoothing the accelerator signal Ja by a moving average with a predetermined period of time.
In the case where high-load work is being performed by the working unit 4U (auxiliary attachment 11), the controller 100 and/or the like, after generating a quasi accelerator signal Jf as shown
In view of this, in the case where high-load work is performed by the working unit 4U, if the target rotation speed Rt of the prime mover 6 suddenly decreases because of the accelerator 101 being suddenly operated to a great extent to achieve a decrease, the controller 100 may calculate a decrease in the actual rotation speed Rc relative to the target rotation speed Rt a plurality of times during a predetermined period of time, and calculate, as the drop, the average of the decreases determined through the calculations. With this, the AUX anti-stall control is appropriately continued, unintended stop of the prime mover 6 is prevented or reduced, and a decrease in work performance of the auxiliary attachment 11 is prevented or reduced.
Also in the case where the target rotation speed Rt of the prime mover 6 suddenly increases because of the accelerator 101 being suddenly operated to a great extent to achieve an increase when high-load work is performed by the working unit 4U, the controller 100 may calculate a decrease in the actual rotation speed Rc relative to the target rotation speed Rt a plurality of times during a predetermined period of time, and calculate, as the drop, the average of the decreases determined through the calculations. That is, the controller 100 may calculate the drop by subjecting the decreases of the actual rotation speed Rc relative to the target rotation speed Rt to a moving average.
In the example embodiments as has been described, the working machine 1 is configured such that, when high-load work is being performed by the working unit 4U, the controller 100 performs the AUX anti-stall control to limit the output from the AUX control valve 60C toward the auxiliary actuator 27 of the auxiliary attachment 11, 11b. However, alternatively or additionally, the controller 100 may perform an anti-stall control to limit the output from the work control valves 60A and 60B toward the actuators 14 and 15 using the solenoid valve 71 as shown in
The work solenoid valve 71 is provided in a branch fluid passage 40b branching from the fluid discharge passage 40. The branch fluid passage 40b is divided into a plurality of passages which are connected to a respective plurality of work operating valves 69 of the work operation equipment 67. The opening of the work solenoid valve 71 changes depending on the electric current value of a control signal inputted into the work solenoid valve 71, so that the pilot pressure of pilot fluid supplied from the fluid discharge passage 40 changes. Specifically, as the electric current value of the control signal inputted into the work solenoid valve 71 increases, the opening of the work solenoid valve 71 increases and the pilot pressure outputted from the work solenoid valve 71 to the plurality of work operating valves 69 (i.e., primary pressure on the work operating valves 69) increases.
As the primary pressure of the work operating valves 69 changes, the secondary pressure of the work operating valves 69 (i.e., the pilot pressure which acts on the work pressure receivers 61a, 61b, 62a, 62b of the work control valves 60A, 60B via work fluid passages 46a, 46b, 46c, 46d from the work operating valves 69) changes. Then, as the secondary pressure of the work operating valves 69 changes, the opening of the work control valves 60A, 60B changes and the output from the work control valves 60A, 60B to corresponding work actuators 14 and 15 (the amount of hydraulic fluid supplied) also changes. Specifically, as the primary pressure of the work operating valves 69 increases, the secondary pressure of the work operating valves 69 also increases, resulting in an increase in the opening of the work control valves 60A, 60B and an increase in the output from the work control valves 60A, 60B to the corresponding work actuators 14, 15.
With the above configuration, the work solenoid valve 71 changes the pilot pressure which acts on the work pressure receivers 61a, 61b, 62a, 62b of the work control valves 60A, 60B in accordance with a control signal inputted thereto to change the flow rate of hydraulic fluid supplied from the work control valves 60A, 60B to the work actuators 14, 15. The controller 100 changes the electric current value of the control signal inputted into the work solenoid valve 71 to change the opening of the work solenoid valve 71, thus adjusting the primary pressure and the secondary pressure of the work operating valves 69 to control the output to the work actuators 14, 15.
In the case where the controller 100 performs a low-load/medium-load output process via the procedure indicated in
For example, in the case where the user operates an input/output interface 111 to input a flow rate change instruction which is an instruction to change the flow rate of hydraulic fluid supplied to the work actuators 14 and/or 15 of the working device 4 (YES at S42 in
In the case where the user does not input a flow rate change instruction to change the flow rate of hydraulic fluid supplied to the work actuators 14 and/or 15 via the input/output interface 111 (NO at S42), the controller 100 does not shift the control-during-normal-time graph L4 and inputs, into the work solenoid valve 71, a control signal having an electric current value indicated by the control-during-normal-time graph L4 (S44).
Upon input of a control signal having an electric current value indicated by the control-during-normal-time graph L4 or the shifted control-during-normal-time graph L4s into the work solenoid valve 71, the work solenoid valve 71 opens to a predetermined extent, thus setting the primary pressure of the work operating valves 69 to a predetermined, unrestricted pressure. Under such circumstances, if the work operator 68 is operated in any direction, one or more of the work operating valves 69 that correspond to the direction in which the work operator 68 is operated are actuated, thus allowing a pilot pressure to act on the work pressure receiver(s) 61a, 61b, 62a, 62b of the work control valve(s) 60A and/or 60B corresponding to the actuated work operating valve(s) 69.
With this, the position and/or the opening of the corresponding work control valve(s) 60A and/or 60B is/are changed, so that hydraulic fluid is supplied, without limitation, to the corresponding work actuators 14 and/or 15 of the working device 4 from the work control valves 60A and/or 60B to actuate the work actuators (lift cylinders) 14 to raise or lower the booms 10 and/or actuate the work actuators (tilt cylinders) 15 to swing (tilt) the attachment 11 attached to the working device 4 (hitch 24). That is, a condition is achieved in which low-load work or medium-load work can be performed by the working device 4 and the attachment 11.
On the contrary, in the case where the controller 100 performs a high-load output process in the manner indicated in
Next, the controller 100 acquires the actual rotation speed and the target rotation speed of the prime mover 6, and, if the actual rotation speed of the prime mover 6 has not decreased relative to the target rotation speed of the prime mover 6 (NO at S47 in
In so doing, if the control-during-normal-time graph L4 has not been shifted, the controller 100 inputs, into the work solenoid valve 71, a control signal having a constant electric current value (predetermined value) indicated by the control-during-normal-time graph L4. If the control-during-normal-time graph L4 has been shifted, the controller 100 inputs, into the work solenoid valve 71, a control signal having a constant electric current value indicated by the shifted control-during-normal-time graph L4s corresponding to the user's instruction. With this, the work actuators 14 and/or 15 are actuated based on the operation of the work operator 68, allowing high-load work to be performed by the working device 4 and the auxiliary attachment 11, 11b. After step S50, the controller 100 performs step S41 again.
Next, if the actual rotation speed of the prime mover 6 decreases relative to the target rotation speed (YES at S47 in
If the drop is less than the first threshold (NO at S49 in
The controller 100 shifts the control-under-high-load graph L5 based on the actual rotation speed of the prime mover 6 at the time the drop reached the first threshold or greater (S51 in
The controller 100 then changes the electric current value of the control signal inputted into the work solenoid valve 71 based on the shifted control-under-high-load graph L5s and the actual rotation speed of the prime mover 6 (the rotation speed at or after the drop reaches the first threshold or greater) to limit the output to the work actuators 14 and/or 15 (S52). Specifically, the controller 100 determines a restricted electric current value corresponding to the actual rotation speed of the prime mover 6 from the control-under-high-load graph L5 or the shifted control-under-high-load graph L5s, and changes the electric current value of the control signal inputted into the work solenoid valve 71 to the restricted electric current value which is smaller than the currently inputted electric current value.
With this, the pilot pressure acting on the work pressure receiver(s) 61a, 61b, 62a, 62b of the work control valve(s) 60A, 60B decreases, the opening of the work control valve(s) 60A, 60B decreases, and the amount of hydraulic fluid supplied from the work control valve(s) 60A, 60B to the work actuators 14 and/or 15 is limited (reduced). That is, the controller 100 performs an anti-stall control in which the controller 100 limits the output from the work control valve(s) 60A, 60B to the work actuators 14 and/or 15 to eliminate or reduce the likelihood that the prime mover 6 will stop unintentionally. This anti-stall control may be referred to as work anti-stall control.
In so doing, the controller 100 may suddenly change (suddenly reduce) or gradually change at a predetermined rate (gradually reduce at a predetermined rate) the electric current value of the control signal inputted into the work solenoid valve 71 such that the electric current value matches the restricted electric current value. After step S52 in
As another example, a plurality of work solenoid valves, instead of the work solenoid valve 71 in
The description of example embodiments described above discusses examples in which the controller 100 determines whether the work performed by the working device 4 and the auxiliary attachment 11 is high-load work or work under other load (low-load work, medium-load work) based on input information relating to the attachment 11 inputted via the input/output interface 111 and based on attachment information corresponding to the input information. However, additionally or alternatively, for example, the controller 100 may determine whether the work performed by the working device 4 and the auxiliary attachment 11 is high-load work or work under other load based on the comparison between a predetermined pressure and the pressure of hydraulic fluid acting on the AUX port(s) 25 detected by the AUX pressure sensor(s) 106a, 106b when hydraulic fluid is being introduced and discharged via the AUX ports 25.
Alternatively, the controller 100 may determine whether the work performed by the working device 4 and the auxiliary attachment 11 is high-load work or work under other load based on the comparison between a predetermined pressure and the highest of the load pressures (PLS pressure) on the actuators 14, 15, and 27 detected by the load pressure sensor 106k.
Also when work is being performed by an attachment 11 including no auxiliary actuators 27 such as a bucket 11a, the prime mover 6 may be subjected to a load of a predetermined amount or higher if an excessively large external force acts on the attachment 11. To address this, also when work is being performed by an attachment 11 including no auxiliary actuators 27, for example, the controller 100 may detect that high-load work is being performed based on the pressure detected by at least one of the AUX pressure sensor(s) 106a, 106b or the load pressure sensor 106k and perform at least one of the AUX anti-stall control or the work anti-stall control.
The controller 100 may, instead of or in addition to at least one of the AUX anti-stall control or the work anti-stall control, perform an anti-stall control in which the controller 100 changes the pilot pressure applied from the travel operating valve(s) 56 to the travel pump(s) 50 using a solenoid valve 72 illustrated in
The travel solenoid valve 72 is provided in a branch fluid passage 40a branching from the fluid discharge passage 40. The branch fluid passage 40a is divided, at a position downstream of the travel solenoid valve 72, into a plurality of passages which are connected to the respective travel operating valves 56 of the travel operating equipment 54. The opening of the travel solenoid valve 72 changes depending on the electric current value of a control signal inputted into the travel solenoid valve 72, so that the pilot pressure of pilot fluid supplied from the fluid discharge passage 40 changes. Specifically, as the electric current value of the control signal inputted into the travel solenoid valve 72 increases, the opening of the travel solenoid valve 72 increases and the pilot pressure outputted from the travel solenoid valve 72 to the travel operating valves 56 (i.e., primary pressure of the travel operating valves 56) increases.
As the primary pressure of the travel operating valve(s) 56 changes, the secondary pressure of the travel operating valves(s) 56 (i.e., the pilot pressure which acts on the pump pressure receiver(s) 50a, 50b of the travel pump(s) 50 (the first travel pump 50L and/or the second travel pump 50R) from the travel operating valve(s) 56 via the travel fluid passage(s) 42a, 42b, 42c, 42d) changes. Then, as the secondary pressure of the travel operating valve(s) 56 changes, the angle of the swash plate(s) of the travel pump(s) 50 (the first travel pump 50L and/or the second travel pump 50R) changes and the output (the amount of hydraulic fluid supplied) from the travel pump(s) 50 to the travel motor(s) 51 (the first travel motor 51L and/or the travel motor 51R) changes. Specifically, as the primary pressure of the travel operating valves 56 increases, the secondary pressure of the travel operating valves 56 increases, so that the angle of the swash plates of the travel pumps 50 increases and the output from the travel pumps 50 to the travel motors 51 increases.
With the above configuration, the travel solenoid valve 72 changes the pilot pressure which acts on the pump pressure receivers 50a, 50b of the travel pumps 50 in accordance with a control signal inputted thereto to change the flow rate of hydraulic fluid supplied from the travel pumps 50 to the travel motors 51. The controller 100 changes the electric current value of the control signal inputted into the travel solenoid valve 72, thus adjusting the primary pressure and the secondary pressure of the travel operating valves 56 to control the output from the travel pumps 50 to the travel motors 51.
While the working machine 1 is being caused to travel by the traveling devices 5, if the actual rotation speed of the prime mover 6 has not decreased relative to the target rotation speed, the controller 100 determines the electric current value of the control signal for the travel solenoid valve 72 based on the actual rotation speed of the prime mover 6 and a control-during-normal-time graph L6 represented by a dot-dot-dash line in
Under such conditions, when the travel operator 55 is operated in any direction, one or more of the travel operating valves 56 that correspond to the direction in which the travel operator 55 is operated are actuated, so that the pilot pressure acts on the pump pressure receiver(s) 50a, 50b of the corresponding travel pump(s) 50 (the first travel pump 50L and/or the second travel pump 50R) corresponding to the actuated travel operating valve(s) 56. With this, hydraulic fluid is supplied from the corresponding travel pump(s) 50 to the travel motor(s) 51, the travel motor(s) 51 is/are actuated, the traveling device(s) 5 is/are actuated, and the working machine 1 travels.
On the contrary, if the actual rotation speed of the prime mover 6 decreases relative to the target rotation speed and the drop reaches the third threshold or greater, the controller 100 determines the electric current value of the control signal for the travel solenoid valve 72 based on the actual rotation speed of the prime mover 6 and based on a for-dropping control graph L7 (control graph for cases where the dropping occurs) represented by a solid line in
Therefore, when the controller 100 inputs into the travel solenoid valve 72 a control signal having the electric current value determined based on the for-dropping control graph L7 and the actual rotation speed of the prime mover 6, the opening of the travel solenoid valve 72 decreases and the primary pressure of the travel operating valves 56 becomes smaller than the normal time and limited to a predetermined pressure. Then, even when the travel operating valves 56 are actuated according to the operation of the travel operator 55, the pilot pressure (secondary pressure) applied from the travel operating valves 56 to the pump pressure receiver(s) 50a, 50b of the corresponding travel pump(s) 50 is limited (reduced) as compared to the normal time, and the output (the delivery flow rate of hydraulic fluid) of the travel pump(s) 50 is also limited (reduced). The output of the travel motor(s) 51 is also limited.
That is, the controller 100 performs an anti-stall control in which the controller 100 limits the output from the travel pumps 50 to the travel motors 51 to eliminate or reduce the likelihood that the prime mover 6 will unintentionally stop. This anti-stall control may be referred to as a travel anti-stall control.
In the case where the travel anti-stall control and at least one of the AUX anti-stall control or the work anti-stall control are performed concurrently by the controller 100, the third threshold for the drop for the travel anti-stall control and the first threshold and/or the second threshold for the drop for at least one of the AUX anti-stall control or the work anti-stall control have different values. With this, the point in time at which the travel anti-stall control is started differs from the point in time at which at least one of the AUX anti-stall control or the work anti-stall control is started.
The third threshold may be smaller than the first threshold (for example, the third threshold is 50 rpm, the first threshold is 200 rpm, etc.) With this, if the actual rotation speed of the prime mover 6 decreases relative to the target rotation speed due to a load on the prime mover 6 and the decrease (drop) reaches the third threshold or greater, the travel anti-stall control is started, and then, if the actual rotation speed of the prime mover 6 decreases further relative to the target rotation speed and the drop reaches the first threshold or greater, at least one of the AUX anti-stall control or the work anti-stall control is started.
As another example, a plurality of travel solenoid valves, instead of the travel solenoid valve 72 in
As another example, a solenoid valve 73 may be provided in the fluid discharge passage 40 at a position upstream of the junction at which the fluid discharge passage 40 is divided into the branch fluid passages 40a and 40b (on the same side of the junction as the pilot pump P1) as illustrated in
As another example, a solenoid valve 74 may be provided in the fluid discharge passage 40 at a position upstream of the junction at which the branch fluid passage 40a branches, the junction at which the branch fluid passage 40b branches, and the junction at which the branch fluid passage 40c branches, as illustrated in
In such a case, the controller 100 may control the electric current value of a control signal inputted into the solenoid valve 74 based on the control graphs L4, L5 and/or based on the control graphs L6, L7. The controller 100 may control the electric current value of a control signal inputted into the AUX solenoid valves 65 based on the control graphs L1, L2, L3 shown in
The load on the prime mover 6 changes in magnitude depending on the state of at least one of the working machine 1, the working device 4, or hydraulic fluid. The load on the prime mover 6 changes in magnitude also depending on the attachment 11 attached to the working device 4. The load on the prime mover 6 changes in magnitude also when the controller 100 controls element(s) of the working machine 1 based on input information.
In view of the above, the controller 100 may correct the control-under-high-load graph(s) L3, L5 based on at least one of the state of the working machine 1, the state of the working device 4, the state of hydraulic fluid, the attachment 11, or input information. The controller 100 may correct the control-under-high-load graph L3, L5 after determining that the drop is equal to or more than the first threshold (YES at step S31 in
The controller 100 may, for example, if at least one of the state of the working machine 1, the state of the working device 4, the state of hydraulic fluid, the attachment 11, or input information matches a predetermined condition the satisfaction of which leads to a further increase in a load of a predetermined amount or higher on the prime mover 6, correct the control-under-high-load graph(s) L3, L5 such that the flow rate of hydraulic fluid supplied to the actuator(s) 27, 14, 15 is further reduced.
The controller 100 may, for example, if at least one of the state of the working machine 1, the state of the working device 4, the state of hydraulic fluid, the attachment 11, or input information matches a predetermined condition the satisfaction of which necessitates ensuring the work performance of the working machine 1, correct the control-under-high-load graph(s) L3, L5 such that the flow rate of hydraulic fluid supplied to the actuator(s) 27, 14, 15 is less likely to be reduced (reduced to a lesser extent than when the graph(s) is/are not corrected). The following description discusses a specific example of correction of the control-under-high-load graph(s) L3, L5.
For example, the controller 100 calculates the horsepower and output of the main pump P2 and the output from the AUX ports 25 to the auxiliary actuator 27 of the auxiliary attachment 11, based on the angle of the swash plate of the main pump P2 detected by the swash plate angle sensor 105 and based on the pressure of hydraulic fluid acting on the AUX ports 25 detected by the AUX pressure sensors 106a, 106b. Next, the controller 100 calculates the horsepower consumed by the auxiliary actuator 27 based on the horsepower and output of the main pump P2 and based on the output to the auxiliary actuator 27.
The controller 100 may then correct the control-under-high-load graph L3 based on the horsepower consumed by the auxiliary actuator 27. In such a case, if, for example, the consumed horsepower is equal to or more than a predetermined value, the controller 100 corrects the slope of the control-under-high-load graph L3 (the ratio of an increase in electric current value of a control signal for the actuated AUX solenoid valve to an increase in rotation speed of the prime mover 6) by multiplying the control-under-high-load graph L3 by a correction coefficient corresponding to the consumed horsepower. As the consumed horsepower increases, the load on the prime mover 6 increases. Therefore, in so doing, the controller 100 may, for example, multiply the control-under-high-load graph L3 by a larger correction coefficient (a value equal to or more than 1) as the consumed horsepower increases, to increase the slope of the control-under-high-load graph L3.
Alternatively, for example, if the consumed horsepower is equal to or more than a predetermined value, the controller 100 shifts the control-under-high-load graph L3 in at least one of the direction of the horizontal axis or the direction of the vertical axis, as shown in
The controller 100 may correct the control-under-high-load graph L3 based on the pressure of hydraulic fluid supplied from the AUX ports 25 to the auxiliary actuator 27 detected by the AUX pressure sensor(s) 106a, 106b. In such a case, for example, if the supply pressure is equal to or more than a predetermined value, the controller 100 corrects the slope of the control-under-high-load graph L3 by multiplying the control-under-high-load graph L3 by a correction coefficient corresponding to the supply pressure (see
The controller 100 may correct the control-under-high-load graph L3 based on the amount of hydraulic fluid supplied from the AUX ports 25 to the auxiliary actuator 27. In such a case, for example, as illustrated in
Alternatively, the controller 100 calculates the delivery pressure of hydraulic fluid from the main pump P2 based on the value detected by the rotation speed sensor 104 (the actual rotation speed of the prime mover 6) and the detected value detected by the swash plate angle sensor 105 (the angle of the swash plate of the main pump P2), and calculates the pressure difference between the delivery pressure of hydraulic fluid from the main pump P2 and the pressure of hydraulic fluid acting on the AUX ports 25 based on the calculated delivery pressure and the detected value detected by the AUX pressure sensor(s) 106a, 106b. The controller 100 may then calculate (detect) the amount of hydraulic fluid supplied from the AUX ports 25 to the auxiliary actuator 27 based on the pressure difference, the cross-sectional area of the opening of the AUX ports 25, a predetermined flow rate coefficient, and the density of hydraulic fluid.
The controller 100 may then, if, for example, the supply amount is equal to or more than a predetermined value, correct the slope of the control-under-high-load graph L3 by multiplying the control-under-high-load graph L3 by a correction coefficient corresponding to the supply amount (see
The controller 100 may correct the control-under-high-load graph L3 based on input information indicating the attachment 11 (the attachment 11 attached to the working device 4) inputted via the input/output interface 111. For example, if the input information inputted via the input/output interface 111 indicates that the attachment 11 is a specific attachment subjected to a load of a predetermined amount or higher such as a mulcher 11b, for example, the controller 100 increases the slope of the control-under-high-load graph L3 by multiplying the control-under-high-load graph L3 by a predetermined correction coefficient corresponding to the specific attachment (see
The controller 100 may cause the input/output interface 111 to display an anti-stall priority settings screen G1 as illustrated in, for example,
On the anti-stall priority settings screen G1, when an AUX anti-stall key K1 is selected (operated) by the user of the working machine 1 or the like, the priority information indicating that the AUX anti-stall control is prioritized over the travel anti-stall control is inputted via the input/output interface 111 into the controller 100. If a travel anti-stall key K2 is selected by the user or the like, the priority information indicating that the travel anti-stall control is prioritized over the AUX anti-stall control is inputted via the input/output interface 111 into the controller 100.
The AUX anti-stall key K1 and the travel anti-stall key K2 are each displayed in different manners when selected and when not selected. In the example in
The controller 100 may correct the control-under-high-load graph L3 based on the priority information inputted via the input/output interface 111. Specifically, in the case where the priority information inputted via the input/output interface 111 indicates that the AUX anti-stall control is prioritized over the travel anti-stall control, the controller 100 multiplies the control-under-high-load graph L3 by a predetermined correction coefficient to increase the slope of the control-under-high-load graph L3 (see
In the case where the priority information inputted via the input/output interface 111 indicates that the travel anti-stall control is prioritized over the AUX anti-stall control, the controller 100 multiplies the control-under-high-load graph L3 by a predetermined correction coefficient (a value more than 0 and less than 1) to reduce the slope of the control-under-high-load graph L3.
Alternatively, if the travel anti-stall control is prioritized over the AUX anti-stall control, the controller 100 shifts the control-under-high-load graph L3 in at least one of the direction of the horizontal axis or the direction of the vertical axis by a predetermined shift amount.
The controller 100 may correct the control-under-high-load graph L3 depending on whether the travel switching valve(s) 57 (see
The controller 100 may correct the control-under-high-load graph L3 based on the temperature of hydraulic fluid detected by the temperature sensor 107. In such a case, if the temperature hydraulic fluid is equal to or less than a predetermined value, the viscous resistance of the hydraulic fluid increases, resulting in a further increase in load on the prime mover 6, and therefore, for example, the controller 100 multiplies the control-under-high-load graph L3 by a predetermined correction coefficient to increase the slope of the control-under-high-load graph L3 (see
The controller 100 may determine the operation state of the travel operator 55 (the direction in which the travel operator 55 is operated) based on the pilot pressure of pilot fluid flowing through the travel fluid passages 42a, 42b, 42c, 42d detected by the travel pressure sensors 106g, 106h, 106i, 106j and correct the control-under-high-load graph L3 based on the operation state.
For example, the controller 100 determines whether the working machine 1 is traveling forward, traveling rearward, or turning based on the direction in which the travel operator 55 is operated, and corrects the control-under-high-load graph L3 based on such a travel state of the working machine 1. In such a case, if the working machine 1 is turning, the load on the prime mover 6 is greater than when the working machine 1 is traveling straight, and therefore, for example, the controller 100 multiplies the control-under-high-load graph L3 by a predetermined correction coefficient to increase the slope of the control-under-high-load graph L3 (
The controller 100 may determine the operation state of the work operator 68 (the direction in which the work operator 68 is operated and the operation amount of the work operator 68) based on the pilot pressure of pilot fluid flowing through the work fluid passages 46a, 46b, 46c, 46d detected by the work pressure sensors 106c, 106d, 106e, 106f and correct the control-under-high-load graph L3 based on the operation state.
For example, the controller 100 determines how high the working device 4 (booms 10) is raised or lowered based on, for example, the operation direction and the operation amount of the work operator 68, and corrects the control-under-high-load graph L3 based on such a height. In such a case, when the working device 4 (the front-end portions 10a of the booms 10) is raised to a higher position, a larger load is imposed on the prime mover 6, and therefore, for example, the controller 100 multiplies the control-under-high-load graph L3 by a large correction coefficient to increase the slope of the control-under-high-load graph L3 (see
Additionally or alternatively, the working machine 1 may correct the control-under-high-load graph L3 based on, for example, the travel speed of the working machine 1, the rotation speed of the prime mover 6, the specifications (such as size) of the attachment 11, the specifications (such as rated power) of the auxiliary actuator 27, the specifications of the working machine 1, and/or the like.
The controller 100 may correct the control-under-high-load graph L5 for the work anti-stall control similarly to the control-under-high-load graph L3.
The controller 100 may cause the input/output interface 111 to display an anti-stall priority settings screen G2 as illustrated in, for example,
On the anti-stall priority settings screen G2, when a work anti-stall key K3 is selected, the priority information indicating that the work anti-stall control is prioritized over the travel anti-stall control is inputted via the input/output interface 111 into the controller 100. If the travel anti-stall key K2 is selected by the user or the like, the priority information indicating that the travel anti-stall control is prioritized over the work anti-stall control is inputted via the input/output interface 111 into the controller 100. The manner in which the control-under-high-load graph L5 is corrected by the controller 100 when such priority information is inputted is the same as the foregoing manner in which the control-under-high-load graph L3 is corrected based on the priority information inputted via the anti-stall priority settings screen G1, and the description therefor is omitted here (see
The controller 100 may cause the input/output interface 111 to display an anti-stall priority settings screen G3 as illustrated in, for example,
On the anti-stall priority settings screen G3, when the AUX anti-stall key K1 is selected, the priority information indicating that the AUX anti-stall control is prioritized over the work anti-stall control is inputted via the input/output interface 111 into the controller 100. In such a case, the controller 100 increases the slope of the control-under-high-load graph L3 as described earlier (see
When the work anti-stall key K3 is selected, the priority information indicating that the work anti-stall control is prioritized over the AUX anti-stall control is inputted via the input/output interface 111 into the controller 100. In such a case, the controller 100 increases the slope of the control-under-high-load graph L5 (see
The controller 100 may cause the input/output interface 111 to display an anti-stall settings screen G4 as illustrated in, for example,
When the ON key K1a of the above-listed keys is selected, the controller 100 performs the AUX anti-stall control during high-load work as described earlier, and, when the OFF key K1b is selected, the controller 100 does not perform the AUX anti-stall control even if the drop reaches the first threshold or greater or the second threshold or greater during high-load work. When the ON key K2a is selected, the controller 100 performs the work anti-stall control during high-load work as described earlier, and when the OFF key K2b is selected, the controller 100 does not perform the work anti-stall control even if the drop reaches the first threshold or greater during high-load work. When the ON key K3a is selected, the controller 100 performs the travel anti-stall control as described earlier, and when the OFF key K3b is selected, the controller 100 does not perform the travel anti-stall control even if the drop reaches the third threshold or greater.
With the anti-stall settings screen G4 as described above, the user such as the driver is able to freely make settings to limit or ensure the work performance of the working unit 4U, the work performance of the auxiliary attachment 11, 11b, and the travel performance of the working machine 1, thus improving convenience.
The controller 100 may be configured or programmed to automatically turn ON (enable) and turn OFF (disable) the AUX anti-stall control, the work anti-stall control, and the travel anti-stall control independently. Specifically, for example, the controller 100 selects one or more anti-stall controls that would be effective in preventing the prime mover 6 from unintentionally stopping from the AUX anti-stall control, the work anti-stall control, and the travel anti-stall control, based on information about at least one of the travel state of the working machine 1, the drive state of the working device 4, the state of the output to the auxiliary actuator 27, the type of the attachment 11 attached to the working machine 1, or the like. The controller 100 may then perform (turn ON, or enable) only the selected anti-stall control(s). Alternatively, the controller 100 may select one or more types of performance to be ensured from the work performance of he auxiliary attachment 11, 11b, the work performance of the working device 4, and the travel performance based on the at least one information described above, and perform only anti-stall control(s) not corresponding to the selected type(s) of performance.
The description of the above example embodiments discusses an example in which the solenoid valves 65 and 71 to 74 for anti-stall control are proportional valves. Additionally or alternatively, other solenoid valves such as solenoid throttle valves and/or solenoid switching valves may be used as solenoid valves for anti-stall control (AUX solenoid valve(s), work solenoid valve(s), travel solenoid valve(s), etc.) Electric work operation equipment and electric travel operating equipment each including a manual operator such as a joystick may be used instead of the hydraulic work operation equipment 67 and the hydraulic travel operating equipment 54. Solenoid work operating valves and travel operating valves may be used instead of the hydraulic work operating valves 69 and the hydraulic travel operating valves 56.
The description of the above example embodiments discusses an example in which the information indicating the attachment 11 and the priority information about anti-stall controls are inputted via the input/output interface 111. Additionally or alternatively, for example, the information indicating the attachment 11, the priority information about anti-stall controls, information about the ON or OFF state of each anti-stall control, and/or the like may be inputted into the controller 100 via communication interface to communicate with a computer external to the working machine 1 or via manual operator such as an operating switch which is hardware.
The description of the above example embodiments discusses an example which uses the control-under-high-load graphs L3 and L5 in each of which the electric current value of the control signal for the solenoid valve 65, 71 changes in proportion to a change in the rotation speed of the prime mover 6 and the slope thereof changes once, and the control-not-under-high-load graphs L1, L2, and L4 in each of which the electric current value of the control signal for the solenoid valve 65, 71 is constant. However, a control-under-high-load graph in which the electric current value of the control signal for the solenoid valve 65, 71 versus the rotation speed of the prime mover 6 changes in a curved manner or a control-under-high-load graph in which the slope is constant or changes a plurality of times may be used. A control-not-under-high-load graph in which the electric current value of the control signal for the solenoid valve 65, 71 versus the rotation speed of the prime mover 6 changes in a regular manner or irregular manner may be used.
The controller 100 may perform not only the AUX anti-stall control but also the work anti-stall control and/or the travel anti-stall control based on the quasi accelerator signal as shown as an example in each of
Working machines 1 according to one or more example embodiments described so far include features described in the following item(s) and achieve the following effect(s).
[Item 1]A working machine 1 includes a main pump P2 to be actuated by power from a prime mover 6 in or on a machine body 2 to deliver hydraulic fluid, a working unit 4U including a working device 4 and an attachment 11 attached to the working device 4 and operable to perform work via the working device 4 and the attachment 11 upon actuation, by the hydraulic fluid, of at least one actuator included in at least one of the working device 4 or the attachment 11, a solenoid valve 65, 71, 73, 74 to change a flow rate of the hydraulic fluid to the at least one actuator based on a control signal inputted thereto, a controller 100 configured or programmed to input the control signal into the solenoid valve 65, 71, 73, 74, an accelerator 101 to be used to input a target rotation speed of the prime mover 6, and a rotation speed sensor 104 to detect an actual rotation speed of the prime mover 6. The controller 100 is configured or programmed to, while the working unit 4U is performing specific work that imposes a load of a predetermined amount or higher on the prime mover 6, if a drop which is a decrease in the actual rotation speed of the prime mover 6 relative to the target rotation speed reaches a first threshold or greater, change the control signal based on the actual rotation speed to limit the flow rate of the hydraulic fluid to at least one the actuator.
With the configuration of item 1, while the working machine 1 is performing specific work that imposes a load of a predetermined amount or higher on the prime mover 6, if the drop of the rotation speed of the prime mover 6 reaches the first threshold or greater, the flow rate of hydraulic fluid supplied to actuator(s) of the working unit 4U is limited, making it possible to reduce the load on the prime mover 6 and eliminate or reduce the likelihood that the prime mover 6 will stop unintentionally due to the load of a predetermined amount or higher. Furthermore, while work that does not impose a load of a predetermined amount or higher on the prime mover 6 is being performed, the flow rate of hydraulic fluid supplied to actuator(s) of the working unit 4U is not limited, making it possible to ensure work performance.
[Item 2] The working machine 1 according to item 1 further includes an auxiliary (AUX) port 25 to allow the hydraulic fluid to flow to and from an auxiliary actuator 27 which is the at least one actuator included in the attachment 11, a pilot pump P1 to be actuated by power from the prime mover 6 to deliver pilot fluid, and an AUX control valve 60C including at least one AUX pressure receiver 63a, 63b and operable to control the flow rate of the hydraulic fluid supplied via the AUX port 25 to the auxiliary actuator 27 based on a pilot pressure which is a pressure of the pilot fluid acting on the at least one AUX pressure receiver 63a, 63b. The solenoid valve 65, 71, 73, 74 includes an AUX solenoid valve 65 (first AUX solenoid valve 65A, second AUX solenoid valve 65B) to, based on the control signal inputted thereto from the controller 100, change the pilot pressure acting on the at least one AUX pressure receiver 63a, 63b to change the flow rate of the hydraulic fluid from the AUX control valve 60C to the auxiliary actuator 27, and the controller 100 is configured or programmed to, while the specific work is being performed by the attachment (auxiliary attachment) 11 which is a specific attachment including the auxiliary actuator 27, when the drop relative to the target rotation speed reaches the first threshold or greater, change the control signal based on the actual rotation speed of the prime mover 6 to reduce the pilot pressure acting on the at least one AUX pressure receiver 63a, 63b to limit the flow rate of the hydraulic fluid from the AUX control valve 60C to the auxiliary actuator 27.
With the configuration of item 2, while specific work that imposes a load of a predetermined amount or higher on the prime mover 6 is being performed, if the drop reaches the first threshold or greater, the flow rate of hydraulic fluid supplied to the auxiliary actuator 27 is limited, making it possible to eliminate or reduce the likelihood that the prime mover 6 will stop unintentionally due to the load of a predetermined amount or higher. Furthermore, while work that does not impose a load of a predetermined amount or higher on the prime mover 6 is being performed, the flow rate of hydraulic fluid supplied to the auxiliary actuator 27 is not limited, making it possible to ensure work performance of the auxiliary attachment 11, 11b and the like.
[Item 3] The working machine 1 according to item 2, wherein the controller 100 is configured or programmed to control an electric current value of the control signal to the AUX solenoid valve 65 at a predetermined value when another work (low-load work or medium-load work that does not impose a load of a predetermined amount or higher on the prime mover 6) differing from the specific work is being performed by the attachment 11 which is another attachment differing from the specific attachment 11, 11b and when the specific work is being performed by the specific attachment 11, 11b but the drop is not equal to or greater than the first threshold. The controller 100 is configured or programmed to, while the specific work is being performed by the specific attachment 11, 11b, if the drop reaches the first threshold or greater, reduce the electric current value of the control signal to the AUX solenoid valve 65 such that the electric current value is smaller than when the other work is being performed by the other attachment 11 and than when the drop during the specific work is not equal to or greater than the first threshold, to reduce the flow rate of the hydraulic fluid to the auxiliary actuator 27.
With the configuration of item 3, the flow rate of hydraulic fluid supplied to the auxiliary actuator 27 is not limited when other work that does not impose a load of a predetermined amount or higher on the prime mover 6 is being performed and when the specific work that imposes a load of a predetermined amount or higher on the prime mover 6 is being performed but the drop is not equal to or greater than the first threshold, making it possible to ensure the work performance of the auxiliary attachment 11, 11b and the like. Furthermore, if the drop reaches the first threshold or greater during the specific work, the flow rate of hydraulic fluid supplied to the auxiliary actuator 27 is reduced, making it possible to eliminate or reduce the likelihood that the prime mover 6 will stop unintentionally from the load of a predetermined amount or higher.
[Item 4] The working machine 1 according to any one of items 1 to 3 further includes a pilot pump P1, and a work control valve 60A, 60B (lift control valve 60A, tilt control valve 60B) including at least one work pressure receiver 61a, 61b, 62a, 62b and operable to control the flow rate of the hydraulic fluid supplied to at least one work actuator 14, 15 (lift cylinder(s) 14, tilt cylinder(s) 15) included in the working device 4 based on a pilot pressure which is a pressure of pilot fluid acting on the at least one work pressure receiver 61a, 61b, 62a, 62b. The solenoid valve 65, 71, 73, 74 includes a work solenoid valve 71 to, based on the control signal inputted thereto from the controller 100, change the pilot pressure acting on the at least one work pressure receiver 61a, 61b, 62a, 62b to change the flow rate of the hydraulic fluid from the work control valve 60A, 60B to the at least one work actuator 14, 15, and the controller 100 is configured or programmed to, while the specific work is being performed by the working device 4 and the attachment 11, if the drop reaches the first threshold or greater, change the control signal based on the actual rotation speed of the prime mover 6 to reduce the pilot pressure acting on the at least one work pressure receiver 61a, 61b, 62a, 62b to limit the flow rate of the hydraulic fluid from the work control valve 60A, 60B to the at least one work actuator 14, 15.
With the configuration of item 4, the flow rate of hydraulic fluid supplied to the work actuators 14 and/or 15 is limited if the drop reaches the first threshold or greater while the specific work that imposes a load of a predetermined amount or higher on the prime mover 6 is being performed, making it possible to eliminate or reduce the likelihood that the prime mover 6 will stop unintentionally from the load of a predetermined amount or higher. Furthermore, when work that does not impose a load of a predetermined amount or higher on the prime mover 6 is being performed, the flow rate of hydraulic fluid supplied to the work actuators 14 and/or 15 is not limited, making it possible to achieve work performance of the working device 4 and the like.
[Item 5] The working machine 1 according to item 4, wherein the controller 100 is configured or programmed to control an electric current value of the control signal to the work solenoid valve 60A, 60B at a predetermined value when another work differing from the specific work that does not impose a load of a predetermined amount or higher is being performed and when the specific work is being performed but the drop is not equal to or greater than the first threshold. The controller 100 is configured or programmed to, while the specific work is being performed, if the drop reaches the first threshold or greater, reduce the electric current value of the control signal to the work solenoid valve 60A, 60B such that the electric current value is smaller than when the other work is being performed and than when the drop during the specific work is not equal to or greater than the first threshold, to reduce the flow rate of the hydraulic fluid to the at least one work actuator 14, 15.
With the configuration of item 5, the flow rate of hydraulic fluid supplied to the work actuators 14 and/or 15 is not limited when other work that does not impose a load of a predetermined amount or higher on the prime mover 6 is being performed and when the specific work that imposes a load of a predetermined amount or higher on the prime mover 6 is being performed but the drop is not equal to or greater than the first threshold, making it possible to ensure the work performance of the working device 4 and the like. Furthermore, if the drop reaches the first threshold or greater during the specific work, the flow rate of hydraulic fluid supplied to the work actuators 14 and/or 15 is reduced, making it possible to eliminate or reduce the likelihood that the prime mover 6 will stop unintentionally from the load of a predetermined amount or higher.
[Item 6] The working machine 1 according to any one of items 1 to 5, further including an input (input/output interface) 111 to receive input of information indicating the attachment 11 attached to the working device 4, wherein the controller 100 is configured or programmed to, based on the information indicating the attachment, determine whether or not work to be performed by the working unit 4U is the specific work that imposes a load of a predetermined amount or higher.
With the configuration of item 6, while specific work that imposes a load of a predetermined amount or higher on the prime mover 6 is being performed, if the decrease of the actual rotation speed of the prime mover 6 relative to the target rotation speed reaches the first threshold or greater, the flow rate of hydraulic fluid supplied to the actuator(s) 27, 14, 15 is reliably limited, making it possible to eliminate or reduce the likelihood that the prime mover 6 will stop unintentionally. Furthermore, while work that does not impose a load of a predetermined amount or higher on the prime mover 6 is being performed, the flow rate of hydraulic fluid supplied to the actuator(s) 27, 14, 15 is reliably not limited, making it possible to ensure work performance.
[Item 7] The working machine 1 according to item 2 or 3, wherein the controller 100 is configured or programmed to, until a predetermined period of time has passed since a start of the specific work, change the control signal inputted into the solenoid valve 65, 71, 73, 74 based on the actual rotation speed of the prime mover 6 to limit the flow rate of the hydraulic fluid to the at least one actuator 27, 14, 15 if the drop reaches a second threshold (activation threshold) or greater, the second threshold being greater than the first threshold.
With the configuration of item 7, the flow rate of hydraulic fluid supplied to the actuator(s) 27, 14, 15 is not limited during or immediately after the activation of the actuator(s) 27, 14, 15, making it possible to stably activate the actuator(s) 27, 14, 15 to start work.
[Item 8] The working machine 1 according to any one of items 1 to 7 includes a variable displacement travel pump 50 to be actuated by power from the prime mover 6, the travel pump 50 including at least one pump pressure receiver 50a, 50b (forward-travel pump pressure receiver 50a, rearward-travel pump pressure receiver 50b) and operable to vary a delivery flow rate of the hydraulic fluid based on a pilot pressure which is a pressure of pilot fluid acting on the at least one pump pressure receiver 50a, 50b, a travel motor 51 to be actuated by the hydraulic fluid delivered by the travel pump 50, a traveling device 5 to be actuated by power from the travel motor 51 to cause the machine body 2 to travel, and a travel solenoid valve 72 to change the pilot pressure acting on the at least one pump pressure receiver 50a, 50b based on a control signal inputted thereto from the controller 100. The controller 100 is configured or programmed to, while the traveling device 5 is causing the machine body 2 to travel, if the drop reaches a third threshold or greater, change the control signal inputted into the travel solenoid valve 72 based on the actual rotation speed of the prime mover 6 to limit the delivery flow rate of the hydraulic fluid from the travel pump 50, the third threshold differing from the first threshold.
With the configuration of item 8, the delivery flow rate of hydraulic fluid from the travel pump(s) 50 is limited if the drop reaches the third threshold or greater due to the load of a predetermined amount or higher on the prime mover 6 while the working machine 1 is traveling or is traveling and working. This also limits the output from the travel pump(s) 50 to the travel motor(s) 51 and reduces the load on the prime mover 6, making it possible to eliminate or reduce the likelihood that the prime mover 6 will stop unintentionally. Furthermore, since the third threshold differs from the first threshold, the point in time at which the delivery flow rate of hydraulic fluid from the travel pump(s) 50 starts being limited differs from the point in time at which the flow rate of hydraulic fluid supplied to the actuator(s) 27, 14, 15 starts being limited. With this, the load on the prime mover 6 is not reduced abruptly, making it possible to prevent or reduce the occurrence of, for example, hunting in which the drive state of the prime mover 6 becomes unstable.
[Item 9] The working machine 1 according to any one of items 1 to 7 further includes a memory and/or a storage 110 to store a control-under-high-load graph L3, L5 indicating an electric current value of the control signal to the solenoid valve 65, 71, 73, 74 for use when the drop reaches the first threshold or greater during the specific work. The control-under-high-load graph L3, L5 indicates that the electric current value of the control signal decreases in proportion to a decrease in rotation speed of the prime mover 6, and the controller 100 is configured or programmed to determine the electric current value of the control signal based on the control-under-high-load graph L3, L5 and the actual rotation speed of the prime mover 6, and input the control signal having the determined electric current value into the solenoid valve 65, 71, 73, 74 to limit the flow rate of the hydraulic fluid to the at least one actuator 27, 14, 15 such that the flow rate decreases.
With the configuration of item 9, when the drop reaches the first threshold or greater during the specific work, a control signal is inputted into the solenoid valve(s) 65, 71, 73, 74 according to the control-under-high-load graph(s) L3, L5, making it possible to appropriately and easily reduce the flow rate of hydraulic fluid supplied to the actuator(s) 27, 14, 15 and possible to eliminate or reduce the likelihood that the prime mover 6 will stop unintentionally. Furthermore, the flow rate of hydraulic fluid supplied to the actuator(s) 27, 14, 15 is not reduced excessively, making it possible to eliminate or reduce the likelihood that the work performance and operability (operational feeling) of the working unit 4U, etc., of the working machine 1 will decrease.
[Item 10] The working machine 1 according to item 9, wherein the controller 100 is configured or programmed to change, gradually at a predetermined rate, the electric current value of the control signal inputted into the solenoid valve 65, 71, 73, 74 such that the electric current value matches the electric current value determined based on the control-under-high-load graph L3, L5 and the actual rotation speed of the prime mover 6.
With the configuration of item 10, the flow rate of hydraulic fluid supplied to the actuator(s) 27, 14, 15 is not limited (reduced) abruptly, making it possible to further reduce or eliminate the likelihood that the work performance and operability of the working unit 4U, etc., will decrease.
[Item 11] The working machine 1 according to item 9 or 10, wherein the control-under-high-load graph L3, L5 indicates that a slope is steeper in a second range C2 of the electric current value of the control signal than in a first range C1 of the electric current value of the control signal, the slope being a ratio of an increase in electric current value of the control signal to an increase in rotation speed of the prime mover 6, the second range C2 being below the first range C1, and the controller 100 is configured or programmed to, if the drop during the specific work reaches the first threshold or greater, change, based on the control-under-high-load graph L3, L5, the electric current value of the control signal based on the actual rotation speed to a greater extent when the electric current value is in the second range C2 than when the electric current value is in the first range C1.
With the configuration of item 11, it is possible to reduce the extent to which the flow rate of hydraulic fluid supplied to the actuator(s) 27, 14, 15 is limited when the actual rotation speed of the prime mover 6 starts dropping (decreasing) due to a load of a predetermined amount or higher, making it possible to prevent or reduce the likelihood that work performance will decrease. It is also possible, when the actual rotation speed of the prime mover 6 has dropped to a great extent due to a load of a predetermined amount or higher, to increase the extent to which the flow rate of hydraulic fluid supplied to the actuator(s) 27, 14, 15 is limited, making it possible to further reduce or eliminate the likelihood that the prime mover 6 will stop unintentionally.
[Item 12] The working machine 1 according to any one of items 9 to 11, further including an input interface 103, 111 (auxiliary operator 103, input/output interface 111) to receive input of an instruction to change the flow rate of the hydraulic fluid to the at least one actuator 27, 14, 15, wherein the memory and/or the storage 110 stores at least one control-not-under-high-load graph L1, L2, L4 (control graph L1, control-during-normal-time graph L2, L4) indicating a constant electric current value of the control signal to the solenoid valve 65, 71, 73, 74, and the controller 100 is configured or programmed to, when another work differing from the specific work is being performed and when the specific work is being performed but the drop is not equal to or greater than the first threshold, input the control signal having the constant electric current value indicated by one of the at least one control-not-under-high-load graph L1, L2, L4 that corresponds to the at least one actuator 27, 14, 15 into the solenoid valve 65, 71, 73, 74, and, based on the instruction inputted via the input interface 103, 111, shift the corresponding control-not-under-high-load graph L1, L2, L4 in a direction in which the electric current value of the control signal changes.
With the configuration of item 12, when some other work that does not impose a load of a predetermined amount or higher on the prime mover 6 is being performed by the working unit 4U and when specific work that imposes a load of a predetermined amount or higher on the prime mover 6 is being performed by the working unit 4U but the drop is not equal to or greater than the first threshold, the control signal is inputted into the solenoid valve(s) 65, 71, 73, 74 according to the control-not-under-high-load graph(s) L1, L2, L4, making it possible to appropriately and easily set the flow rate of hydraulic fluid supplied to the actuator(s) 27, 14, 15 and stably perform the specific work or the other work. Furthermore, since the user of the working machine 1 or the like is able to change the flow rate of hydraulic fluid supplied to the actuator(s) 27, 14, 15 using the input(s) 103, 111, it is possible to improve convenience.
[Item 13] The working machine 1 according to any one of items 9 to 12, wherein the memory and/or the storage 110 stores a control-during-normal-time graph L2, L4 indicating a constant electric current value of the control signal to the solenoid valve 65, 71, 73, 74 for use when the drop is not equal to or greater than the first threshold during the specific work, the control-under-high-load graph L3, L5 indicates that the electric current value of the control signal decreases in proportion to a decrease in rotation speed of the prime mover 6, the control-under-high-load graph L3, L5 and the control-during-normal-time graph L2, L4 have a common point indicating the same electric current value of the control signal at the same rotation speed of the prime mover 6, and the controller 100 is configured or programmed to, if the drop reaches the first threshold or greater during the specific work, shift the control-under-high-load graph L3, L5 in a direction in which the rotation speed of the prime mover 6 changes such that the rotation speed at the common point matches the actual rotation speed of the prime mover 6.
With the configuration of item 13, even if specific work is being performed, as long as the drop is not equal to or greater than the first threshold, the control signal is inputted into the solenoid valve(s) 65, 71, 73, 74 according to the control-during-normal-time graph L2, L4, making it possible to appropriately and easily set the flow rate of hydraulic fluid supplied to the actuator(s) 27, 14, 15 and possible to stably perform the specific work. Furthermore, it is possible, if the drop reaches the first threshold or greater during the specific work, to reduce the electric current value of the control signal supplied to the solenoid valve(s) 65, 71, 73, 74 while keeping the decrease in the electric current value small, according to the control-under-high-load graph L3s, L5s having been shifted based on the actual rotation speed of the prime mover 6 at the time the drop reached the first threshold or greater. This makes it possible to eliminate or reduce the likelihood that the flow rate of hydraulic fluid supplied to the actuator(s) 27, 14, 15 will decrease abruptly, and possible to eliminate or reduce the likelihood that the operation of the actuator(s) 27, 14, 15 will be unstable and that work performance will decrease.
[Item 14] The working machine 1 according to any one of items 9 to 13, wherein the controller 100 is configured or programmed to correct the control-under-high-load graph L3, L5 based on at least one of a state of the working machine 1, a state of the working device 4, a state of the hydraulic fluid, the attachment 11, or input information.
With the configuration of item 14, it is possible to appropriately limit the flow rate of hydraulic fluid supplied to the actuator(s) 27, 14, 15 based on at least one of the state of the working machine 1, the state of the working device 4, the state of the hydraulic fluid, the attachment 11, or the input information, and thus possible to eliminate or reduce the likelihood that the prime mover 6 will stop unintentionally and that the work performance of the working machine 1 will decrease.
[Item 15] The working machine 1 according to item 14, wherein the controller 100 is configured or programmed to, if the at least one of the state of the working machine 1, the state of the working device 4, the state of the hydraulic fluid, the attachment 11, or the input information matches a predetermined condition a satisfaction of which leads to an increase in the load of a predetermined amount or higher on the prime mover 6, correct the control-under-high-load graph L3, L5 such that the flow rate of the hydraulic fluid to the at least one actuator 27, 14, 15 is reduced to a greater extent than when the control-under-high-load graph is not corrected.
With the configuration of item 15, it is possible to appropriately limit the flow rate of hydraulic fluid supplied to the actuator(s) 27, 14, 15 according to the corrected control-under-high-load graph(s) L3t, L3u, L3v, L3w, L5t, L5u, L5v, L5w, and thus possible to further reduce or eliminate the likelihood that the prime mover 6 will stop unintentionally due to a load of a predetermined amount or higher.
[Item 16] The working machine 1 according to item 14, wherein the controller 100 is configured or programmed to, if the at least one of the state of the working machine 1, the state of the working device 4, the state of the hydraulic fluid, the attachment 11, or the input information matches a predetermined condition a satisfaction of which necessitates ensuring work performance of the working machine 1, correct the control-under-high-load graph L3, L5 such that the flow rate of the hydraulic fluid to the at least one actuator 27, 14, 15 is reduced to a lesser extent than when the control-under-high-load graph is not corrected.
With the configuration of item 16, it is possible to appropriately limit the flow rate of hydraulic fluid supplied to the actuator(s) 27, 14, 15 according to the corrected control-under-high-load graph(s) L3r, L3x, L3y, L3z, L5r, L5x, L5y, L5z, and thus possible to eliminate or reduce the likelihood that the prime mover 6 will stop unintentionally due to a load of a predetermined amount or higher while further reducing or eliminating the likelihood that the work performance of the working machine 1 will decrease.
[Item 17] The working machine 1 according to any one of items 14 to 16, further including a swash plate angle sensor 105 to detect an angle of a swash plate of the main pump P2 which is a variable displacement pump, an AUX port 25 to allow the hydraulic fluid to flow to and from an auxiliary actuator 27 which is the at least one actuator included in the attachment 11, 11b, and an AUX pressure sensor 106a, 106b to detect a pressure of the hydraulic fluid acting on the AUX port 25, wherein the controller 100 is configured or programmed to calculate a horsepower consumed by the auxiliary actuator 27 based on a detected value detected by the swash plate angle sensor 105 and a detected value detected by the AUX pressure sensor 106a, 106b, and correct the control-under-high-load graph L3, L5 based on the calculated horsepower.
With the configuration of item 17, it is possible, based on the horsepower consumed by the auxiliary actuator 27, to appropriately limit the flow rate of hydraulic fluid supplied to the actuator 27, 14, 15 and thus possible to eliminate or reduce the likelihood that the prime mover 6 will stop unintentionally due to a load of a predetermined amount or higher and that the work performance of the working machine 1 will decrease.
[Item 18] The working machine 1 according to any one of items 14 to 17, further including an AUX port 25, and an AUX pressure sensor 106a, 106b, wherein the controller 100 is configured or programmed to correct the control-under-high-load graph L3, L5 based on the pressure of the hydraulic fluid flowing between the AUX port 25 and the auxiliary actuator 27 detected by the AUX pressure sensor 106a, 106b.
With the configuration of item 18, it is possible, based on the pressure of hydraulic fluid discharged to the auxiliary actuator 27, to appropriately limit the flow rate of hydraulic fluid supplied to the actuator 27, 14, 15 and thus possible to eliminate or reduce the likelihood that the prime mover 6 will stop unintentionally due to a load of a predetermined amount or higher and that the work performance of the working machine 1 will decrease.
[Item 19] The working machine 1 according to any one of items 14 to 18, further including an AUX port 25, wherein the controller 100 is configured or programmed to detect a flow rate of the hydraulic fluid flowing between the AUX port 25 and the auxiliary actuator 27 and correct the control-under-high-load graph L3, L5 based on the detected flow rate.
With the configuration of item 19, it is possible, based on the amount of hydraulic fluid supplied to the auxiliary actuator 27, to appropriately limit the flow rate of hydraulic fluid supplied to the actuator 27, 14, 15 and thus possible to eliminate or reduce the likelihood that the prime mover 6 will stop unintentionally due to a load of a predetermined amount or higher and that the work performance of the working machine 1 will decrease.
[Item 20] The working machine 1 according to any one of items 14 to 19, further including an input 111 to receive input of information indicating the attachment 11 attached to the working device 4, wherein the controller 100 is configured or programmed to correct the control-under-high-load graph L3, L5 based on the information indicating the attachment 11 inputted via the input 111.
With the configuration of item 20, it is possible, depending on the attachment 11 attached to the working device 4, to appropriately limit the flow rate of hydraulic fluid supplied to the actuator(s) 27, 14, 15 and thus possible to eliminate or reduce the likelihood that the prime mover 6 will stop unintentionally due to a load of a predetermined amount or higher and that the work performance of the working machine 1 will decrease.
[Item 21] The working machine 1 according to any one of items 14 to 20, further including a variable displacement travel pump 50, a travel motor 51, a traveling device 5, a travel solenoid valve 72 to change the pilot pressure acting on the at least one pump pressure receiver 50a, 50b based on a control signal inputted thereto from the controller 100 to limit the delivery flow rate of the hydraulic fluid from the travel pump 50, and an input 111 to receive input of priority information indicating that one of (i) limiting the delivery flow rate of the travel pump 50 using the travel solenoid valve 72 and (ii) limiting the flow rate of the hydraulic fluid to the at least one actuator 27, 14, 15 using the solenoid valve 65, 71, 73, 74 is prioritized over the other, wherein the controller 100 is configured or programmed to correct the control-under-high-load graph L3, L5 based on the priority information.
With the configuration of item 21, it is possible, according to the demand of the user or the like regarding whether a work-related anti-stall control (AUX anti-stall control, work anti-stall control) is to be prioritized over a travel anti-stall control, to appropriately limit the flow rate of hydraulic fluid supplied to the actuator(s) 27, 14, 15 and thus possible to eliminate or reduce the likelihood that the prime mover 6 will stop unintentionally due to a load of a predetermined amount or higher and that the work performance of the working machine 1 will decrease.
[Item 22] The working machine 1 according to any one of items 14 to 21, further including an AUX port 25, a pilot pump P1, an AUX control valve 60C, a work control valve 60A, 60B, and an input 111, wherein a plurality of the solenoid valves 65, 71, 73, 74 include an AUX solenoid valve 65 to, based on the control signal inputted thereto from the controller 100, change the pilot pressure acting on the at least one AUX pressure receiver 63a, 63b of the AUX control valve 60C to limit the flow rate of the hydraulic fluid from the AUX control valve 60C to the auxiliary actuator 27, and a work solenoid valve 71, 73 to, based on the control signal inputted thereto from the controller 100, change the pilot pressure acting on the at least one work pressure receiver 61a, 61b, 62a, 62 of the work control valve 60A, 60B to limit the flow rate of the hydraulic fluid from the work control valve 60A, 60B to the work actuator 14, 15. The input 111 is operable to receive input of priority information indicating that one of (i) limiting the flow rate of the hydraulic fluid using the AUX solenoid valve 65 and (ii) limiting the flow rate of the hydraulic fluid using the work solenoid valve 71, 73 is prioritized over the other, and the controller 100 is configured or programmed to correct the control-under-high-load graph L3, L5 based on the priority information.
With the configuration of item 22, it is possible, according to the demand of the user or the like that one of the AUX anti-stall control and the work anti-stall control be prioritized over the other, to appropriately limit the flow rate of hydraulic fluid supplied to the actuator(s) 27, 14, 15 and thus possible to eliminate or reduce the likelihood that the prime mover 6 will stop unintentionally due to a load of a predetermined amount or higher and that the work performance of the working machine 1 will decrease.
[Item 23] The working machine 1 according to any one of items 14 to 22, further including a travel pump 50, a travel motor 51, and a travel switching valve 57 to switch between a first state in which a rotation speed of the output shaft 51Lj, 51Rj of the travel motor 51 is brought into a first speed stage and a second state in which the rotation speed of the output shaft 51Lj, 51Rj of the travel motor 51 is brought into a second speed stage which is higher than the first speed stage, wherein the controller 100 is configured or programmed to correct the control-under-high-load graph L3, L5 based on whether the travel switching valve 57 is in the first state or the second state.
With the configuration of item 23, during specific work that imposes a load of a predetermined amount or higher on the prime mover 6, it is possible, depending on the speed stage of the travel motor(s) 51 that is associated with a change in load, to appropriately limit the flow rate of hydraulic fluid supplied to the actuator(s) 27, 14, 15 and thus possible to eliminate or reduce the likelihood that the prime mover 6 will stop unintentionally and that the work performance of the working machine 1 will decrease.
[Item 24] The working machine 1 according to any one of items 14 to 23, further including a temperature sensor 107 to detect a temperature of the hydraulic fluid, wherein the controller 100 is configured or programmed to correct the control-under-high-load graph L3, L5 based on the temperature detected by the temperature sensor 107.
With the configuration of item 24, it is possible, based on viscous resistance that depends on the temperature of hydraulic fluid and/or the like, to appropriately limit the flow rate of hydraulic fluid supplied to the actuator(s) 27, 14, 15 and thus possible to eliminate or reduce the likelihood that the prime mover 6 will stop unintentionally and that the work performance of the working machine 1 will decrease.
[Item 25] The working machine 1 according to any one of items 14 to 24, further including a pair of traveling devices 5 (first traveling device 5, second traveling device 5) at a left side and a right side of the machine body 2, and a travel operator 55 including a position for forward travel, a position for rearward travel, and a position for turning to be operated to any of the positions to cause the pair of traveling devices 5 to cause the machine body 2 to travel forward, travel rearward, or turn, wherein the controller 100 is configured or programmed to correct the control-under-high-load graph L3, L5 based on an operation state of the travel operator 55.
With the configuration of item 25, it is possible, depending on the manner in which the working machine 1 is traveling (the position for forward travel, the position for rearward travel, the position for turning) that is associated with a change in load on the prime mover 6, to appropriately limit the flow rate of hydraulic fluid supplied to the actuator(s) 27, 14, 15 and thus possible to eliminate or reduce the likelihood that the prime mover 6 will stop unintentionally and that the work performance of the working machine 1 will decrease.
[Item 26] The working machine 1 according to any one of items 14 to 25, further including a work operator 68 to be operated to actuate the working device 4, wherein the controller 100 is configured or programmed to correct the control-under-high-load graph L3, L5 based on an operation state of the work operator 68.
With the configuration of item 26, it is possible, depending on the manner in which the working device 4 is operating (raised, lowered, tilted) that is associated with a change in load on the prime mover 6, to appropriately limit the flow rate of hydraulic fluid supplied to the actuator(s) 27, 14, 15 and thus possible to eliminate or reduce the likelihood that the prime mover 6 will stop unintentionally and that the work performance of the working machine 1 will decrease.
[Item 27] The working machine 1 according to any one of items 1 to 26, wherein the controller 100 is configured or programmed to produce a quasi accelerator signal Jf which changes at a predetermined rate based on an accelerator signal Ja inputted thereto via the accelerator 101, determine a quasi rotation speed of the prime mover 6 based on the quasi accelerator signal Jf, and change the control signal to the solenoid valve 65, 71, 73, 74 based on the quasi rotation speed instead of the actual rotation speed of the prime mover 6.
With the configuration of item 27, even if the acceleration operator of the accelerator 101 is operated abruptly and greatly while the prime mover 6 is being driven but is not subjected to a load of a predetermined amount or higher and the actual rotation speed and the target rotation speed of the prime mover 6 greatly depart from each other temporarily, it is possible to appropriately perform the AUX anti-stall control and/or the work anti-stall control and possible to eliminate or reduce the likelihood that the work performance of the working machine 1 will decrease.
[Item 28] The working machine 1 according to any one of items 1 to 27, wherein the controller 100 is configured or programmed to, while the specific work is being performed by the working unit 4U, if the target rotation speed is suddenly changed by the accelerator 101 by a predetermined value or more, calculate a decrease in the actual rotation speed relative to the target rotation speed a plurality of times within a predetermined period of time to obtain a plurality of the decreases and calculate, as the drop, an average of the plurality of calculated decreases.
With the configuration of item 28, even if the accelerator is operated abruptly and greatly and therefore the target rotation speed of the prime mover 6 increases abruptly and the actual rotation speed decreases greatly relative to the target rotation speed temporarily or the target rotation speed decreases abruptly and the actual rotation speed increases greatly relative to the target rotation speed temporarily, it is possible to appropriately perform or continue the AUX anti-stall control and/or the work anti-stall control and possible to eliminate or reduce the likelihood that the prime mover 6 will stop unintentionally and that work performance will decrease. In cases where at least one of the configurations of items 27 and 28 is applied to changing the control signal supplied to the solenoid valve 72, it is possible to appropriately perform or continue the travel anti-stall control and possible to eliminate or reduce the likelihood that the prime mover 6 will stop unintentionally and that the travel performance of the working machine 1 will decrease.
While example embodiments of the present invention have been described above, it is to be understood that variations and modifications will be apparent to those skilled in the art without departing from the scope and spirit of the present invention. The scope of the present invention, therefore, is to be determined solely by the following claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2023-170306 | Sep 2023 | JP | national |
