Patent Grant
10947699
The present invention relates to a hydraulic system for a construction machine, and particularly to a hydraulic system for a construction machine that uses a hydraulic closed circuit in which a hydraulic actuator is driven directly by a hydraulic pump.
In recent years, energy saving is an important development item in a construction machine such as a hydraulic excavator or a wheel loader. For energy saving of a construction machine, energy saving of a hydraulic system itself is important, and application of a hydraulic system that uses a hydraulic closed circuit in which a hydraulic pump and a hydraulic actuator are directly connected to each other such that hydraulic fluid is delivered and discharged between each other (such hydraulic system is hereinafter referred to as “hydraulic closed circuit system”) is investigated. The hydraulic closed circuit is free from pressure loss by a control valve and is free also from flow rate loss because only a necessary flow rate is delivered by a pump. Also it is possible to regenerate position energy and energy upon deceleration of the hydraulic actuator. Therefore, by applying the hydraulic closed circuit system, energy saving of a construction machine can be implemented.
A hydraulic closed circuit system applied to a construction machine is disclosed, for example, in Patent Document 1 that describes a configuration that each of a plurality of hydraulic pumps is selectively connected to one of a plurality of hydraulic actuators by closed circuit connection through a selector valve to make composite operation and high-speed operation of the hydraulic actuator possible.
Meanwhile, Patent Document 2 discloses a technology that, in a hydraulic system for which a hydraulic open circuit in which a plurality of hydraulic actuators are connected to one hydraulic pump through a directional control valve (such hydraulic system is hereinafter referred to as “hydraulic open circuit system”), in the case where an abnormal state that a solenoid proportional valve is closed by a failure or another abnormal state that a controller is stopped occurs, it is made possible to drive the hydraulic actuator at a speed equal to or lower than that in a normal state by setting the delivery pressure of a hydraulic pressure source (pilot primary pressure) lower than a predetermined pressure by a variable relief valve and suppressing the stroke of a directional control valve.
Patent Document 1: JP-2015-048899-A
Patent Document 2: JP-2016-114129-A
In the hydraulic closed circuit system disclosed in Patent Document 1, a plurality of switching valves are open-close controlled by a controller (machine body controller) such that one of hydraulic actuators is coupled to one hydraulic pump through a line in response to a lever operation by a driver. Here, in the case where such a situation that a selector valve or a controller fails and two or more switching valves connected to a same hydraulic pump are opened simultaneously occurs, two or more actuators connected to the two or more switching valves that are opened simultaneously are connected to each other through the line. Here, in a hydraulic closed circuit, because hydraulic operating fluid is permitted to flow bidirectionally in a line, a check valve cannot be inserted in the line. Therefore, there is a subject that, if two or more switching valves are opened simultaneously, then since the hydraulic operating fluid flows from an actuator having a high pressure to another actuator having a low pressure, operation of the hydraulic actuator, which is not intended by the operator possibly occurs.
On the other hand, in the hydraulic open circuit system disclosed in Patent Document 2, in the case where a controller for controlling a solenoid proportional valve (machine body controller) fails, since the failure detection function of the solenoid proportional valve and the controlling function of the variable relief valve are lost, the directional control vale cannot be controlled to a closed state. Accordingly, even if the technology disclosed in Patent Document 2 is applied to the hydraulic closed circuit system disclosed in Patent Document 2, operation of the hydraulic actuator, which is not intended by the operator, cannot be suppressed.
The present invention has been made in view of such a subject as described above, and it is an object of the present invention to provide a construction machine that incorporates a hydraulic closed circuit system in which, even in the case where a selector valve is sticked in an open state by a failure of the selector valve or a control system therefor, unintended operation of the hydraulic actuator is suppressed and operation of the machine can be continued.
In order to attain the subject described above, according to the present invention, there is provided a construction machine including a plurality of closed circuit pumps, a plurality of hydraulic actuators, a plurality of operation levers corresponding to the plurality of hydraulic actuators, a plurality of switching valves capable of connecting each of the plurality of closed circuit pumps to one of the plurality of hydraulic actuators by closed circuit connection, and a machine body controller that performs open-close control of the plurality of switching valves and flow-rate control of the plurality of closed circuit pumps in response to an operation of the plurality of operation levers. The construction machine includes a first sensor that detects open-closed states of the plurality of switching valves, a first compulsory valve closing device that changes over the plurality of switching valves to a closed position irrespective of the open-close control by the machine body controller, and a valve device controller that is configured to, when detecting based on the open-closed states of the plurality of switching valves that one selector valve of the plurality of switching valves is sticked at an open position against a command by the machine body controller, control the first compulsory valve closing device such that other switching valves except the one selector valve, the other switching valves being connected to one closed circuit pump of the plurality of closed circuit pumps, the one closed circuit pump being connected to the one selector valve, are closed.
With the present invention configured in such a manner as described above, in the case where one of the plurality of switching valves is sticked in an open state by a failure of the selector valve or a control system therefor, the other switching valves connected to one closed circuit pump to which the selector valve sticking in an open state is connected are closed compulsorily such that the two hydraulic actuators are not connected to each other through a line, and therefore, unintended operation of the hydraulic actuators can be suppressed and operation of the machine body can be continued.
With the present invention, also where a selector valve is sticked in an open state by a failure of a selector valve or a control system therefor, unintended operation of the hydraulic actuators can be suppressed and operation of the machine body can be continued.
In the following, embodiments of the present invention are described with reference to the drawings taking a large hydraulic excavator as an example of a construction machine. It is to be noted that, in the figures, like members are denoted by like reference characters and overlapping description is omitted suitably.
Referring to
On the front side of the upper swing structure 102, a front work implement 104 that is an operating device for performing, for example, an excavating work is attached pivotably at a proximal end section thereof. Here, the front side signifies a direction in which an operator who boards the cab 101 is directed (leftward direction in FIG.
The front work implement 104 includes a boom 2 connected at a proximal end section thereof for elevation/depression movement to the front side of the upper swing structure 102. The boom 2 operates through a boom cylinder 1 that is a single rod type hydraulic cylinder. A cylinder rod 1b of the boom cylinder 1 is connected at a distal end section thereof to the upper swing structure 102, and a cylinder head 1a of the boom cylinder 1 is connected at a proximal end section thereof to the boom 2. To a distal end section of the boom 2, the arm 4 is connected at a proximal end section thereof pivotably in the upward and downward direction. The arm 4 operates through an arm cylinder 3 as a hydraulic actuator that is a single rod type hydraulic cylinder. A cylinder rod 3b of the arm cylinder 3 is connected at a distal end section thereof to the arm 4, and a cylinder head 3a of the arm cylinder 3 is connected at a proximal end section thereof to the boom 2. To a distal end section of the arm 4, a bucket 6 is connected at a base end section thereof pivotably in the upward and downward direction. The bucket 6 operates through a bucket cylinder 5 that is a single rod type hydraulic cylinder. A cylinder rod 5b of the bucket cylinder 5 is connected at a distal end section thereof to the bucket 6, and a cylinder head 5a of the bucket cylinder 5 is connected at a proximal end section thereof to the arm 4.
In the cab 101, a boom lever 34a (depicted in
Referring to
The closed circuit pumps 35 and 36 are driven by power received from an engine 9 through a transmission device 10. The closed circuit pumps 35 and 36 include a tilting swash plate mechanism (not depicted) having a pair of input/output ports as flow rate adjustment means, and regulators 35a and 36a that adjust the tilting angle of the swash plates to adjust the displacement volume. The regulators 35a and 36a control the delivery flow rate and the delivery direction of the closed circuit pumps 35 and 36 on the basis of pump delivery flow rate command values received from the machine body controller 11.
The switching valves 37 to 40 open or close in response to a control signal received from the machine body controller 11 to connect the closed circuit pumps 35 and 36 to the boom cylinder 1 or the arm cylinder 3 by closed circuit connect, respectively.
When the selector valve 37 is open, the other selector valve 38 connected to the same closed circuit pump 35 is closed, and one of delivery ports of the closed circuit pump 35 is connected to the cylinder rod 1b of the boom cylinder 1 through the lines 20 and 21 while the other delivery port is connected to the cylinder head 1a of the boom cylinder 1 through the lines 22 and 23, and the lines 10, 21, 23 and 24 form a closed circuit thereby. On the other hand, when the selector valve 38 is open, the other selector valve 37 connected to the same closed circuit pump 35 is closed, and one of the delivery ports of the closed circuit pump 35 is connected to the cylinder head 3a of the arm cylinder 3 through the lines 20, 28 and 25 while the other delivery port is connected to the cylinder rod 3b of the arm cylinder 3 through the lines 22, 29 and 27, and the lines 20, 28, 25, 27, 29 and 22 form a closed circuit.
Similarly, when the selector valve 40 is open, the other selector valve 39 connected to the same closed circuit pump 36 is closed, and one of delivery ports of the closed circuit pump 36 is connected to the cylinder head 3a of the arm cylinder 3 through the lines 24 and 25 while the other delivery port is connected to the cylinder rod 3b of the arm cylinder 3 through the lines 26 and 27, and the lines 24, 25, 27 and 26 form a closed circuit thereby. On the other hand, when the selector valve 39 is open, the other selector valve 40 connected to the same closed circuit pump 36 is closed, and one of the delivery ports of the closed circuit pump 36 is connected to the cylinder rod 1b of the arm cylinder 3 through the lines 24, 30 and 21 while the other delivery port is connected to the cylinder head 1a of the boom cylinder 1 through the lines 26, 31 and 23, and the lines 24, 30, 21, 23, 31 and 26 form a closed circuit.
The selector valve 37 includes a solenoid valve 37a and poppet valves 37b and 37c. The solenoid valve 37a is biased toward the closing side by spring force, and is opened or closed in response to a control signal (opening signal or closing signal) received from the machine body controller 11 to connect the pilot chamber of the poppet valves 37b and 37c to a pilot hydraulic fluid source 41 or a tank 32. In the case where a closing signal is inputted to the solenoid valve 37a, the pilot chamber of the poppet valves 37b and 37c is connected to the tank 32 and the pressure thereof becomes low, whereupon the poppet valves 37b and 37c are driven to the closing side by the spring force and the lines 20 and 21 and the lines 22 and 23 are disconnected from each other. In the case where an opening signal is inputted to the solenoid valve 37a, the pilot chamber of the poppet valves 37b and 37c is connected to the pilot hydraulic fluid source 41 and the pressure thereof becomes high, whereupon the poppet valves 37b and 37c are driven to the open side and the lines 20 and 21 and the lines 22 and 23 are placed into a communication state with each other. Since the switching valves 38 to 40 are similar to the selector valve 37, description of the same is mitted. It is to be noted that, while, in the present embodiment, a selector valve that drives a poppet valve using a pilot hydraulic source and a solenoid valve is used as an example, only a solenoid valve that opens and closes a line in accordance with an electric signal may be used for the configuration.
The machine body controller 11 is connected to the boom lever 34a and the arm lever 34b as operation levers through signal lines and is connected to the solenoid valves 37a to 40a of the switching valves 37 to 40 through control signal lines.
The machine body controller 11 includes an information acquisition section 11a, a machine body controlling calculation section 11b, a valve signal outputting section 11c and a pump signal outputting section 11d. The information acquisition section 11a detects an operation amount of the boom lever 34a and the arm lever 34b.
The machine body controlling calculation section 11b determines connection between the closed circuit pumps 35 and 36 and the boom cylinder 1 and arm cylinder 3 on the basis of an operation amount of the boom lever 34a and the arm lever 34b. In this state, for example, in the case where the operation amount of the boom lever 34a is equal to or smaller than one half a maximum operation amount, the machine body controlling calculation section 11b determines to open the selector valve 37 and close the selector valve 38 such that only the closed circuit pump 35 is connected to the boom cylinder 1 and sets the pump delivery flow rate command value for the closed circuit pump 35 to a value according to the operation amount of the boom lever 34a. On the other hand, in the case where the operation amount of the boom lever 34a exceeds one half the maximum operation amount, the machine body controlling calculation section 11b determines to open the switching valves 37 and 39 such that the closed circuit pumps 35 and 36 are connected to the boom cylinder 1 and sets the pump delivery flow rate command values for the closed circuit pumps 35 and 36 to a value according to the operation amount of the boom lever 34a. In the case where the boom lever 34a and the arm lever 34b are operated, the machine body controlling calculation section 11b determines to open the switching valves 37 and 40 and close the switching valves 38 and 39 such that the closed circuit pump 35 is connected to the boom cylinder 1 and besides the closed circuit pump 36 is connected to the arm cylinder 3 and sets the pump delivery flow rate command values for the closed circuit pumps 35 and 36 according to the operation amounts of the boom lever 34a and of the arm lever 34b, respectively. The delivery directions of the closed circuit pumps 35 and 36 are determined by the operation directions of the boom lever 34a and the arm lever 34b.
The valve signal outputting section 11c outputs control signals to the switching valves 37 to 40 on the basis of the opening/closing information for the switching valves 37 to 40 determined by the machine body controlling calculation section 11b to control opening/closing of the selector values 37 to 40. The pump signal outputting section 11d outputs control signals to the regulators 35a and 36a on the basis of the pump delivery flow rate command values set by the machine body controlling calculation section 11b to control the delivery flow rate and the delivery direction of the closed circuit pumps 35 and 36.
A flushing valve 46a is connected to the lines 21 and 23 and connects one of the lines 21 and 23 having a lower pressure to the tank 32. Meanwhile, another flushing valve 46b is connected to the lines 25 and 27 and connects one of the lines 25 and 27 having a lower pressure to the tank 32. Each of the flushing valves 46a and 46b has a function for discharging surplus hydraulic operating fluid of the respective closed circuit and a function for sucking insufficient hydraulic operating fluid of the closed circuit from the tank 32.
Now, a configuration relating to the present invention in the present embodiment is described.
In the switching valves 37 to 40, first to fourth pilot pressure sensors 37d to 40d are provided as first open-close sensor for detecting respective open-closed states. The first to fourth pilot pressure sensors 37d to 40d are connected to the valve device controller 33 by signal lines. For example, if description is given taking the selector valve 37 as an example, the pilot pressure sensor 37d is provided in a line that connects the solenoid valve 37a and the poppet valves 37b and 37c and detects a pilot pressure outputted from the solenoid valve 37a. When a closing signal is inputted to the solenoid valve 37a, since the pilot pressure sensor 37d is connected to the tank 32, a low pressure of the pilot pressure sensor 37d is detected. On the other hand, when an opening signal is inputted to the solenoid valve 37a, since the pilot pressure sensor 37d is connected to the pilot hydraulic fluid source 41, a high pressure of the pilot pressure sensor 37d is detected. Also in the switching valves 38 to 40, the second to fourth pilot pressure sensors 38d to 40d are provided in similar lines, respectively. It is to be noted that, although, in the present embodiment, the first sensor is configured from the first to fourth pilot pressure sensors 37d to 40d, for example, in the case where each selector valve is a solenoid valve, the first sensor may be configured from a stroke sensor or the like that measures the amount of movement of the valve body of the solenoid valve.
The boom lever 34a and the arm lever 34b have first and second neutral detection switches 62a and 62b provided therefor, respectively. The first and second neutral detection switches 62a and 62b detect a non-operational state (neutral) or an operational state (non-neutral) of the boom lever 34a and the arm lever 34b. In the case where each of the boom lever 34a and the arm lever 34b is neutral, the first and second neutral detection switches 62a and 62b output 0. On the other hand, in the case where each of the boom lever 34a and the arm lever 34b is non-neutral, the first and second neutral detection switches 62a and 62b output 1.
The valve device controller 33 is connected to the first and second neutral detection switches 62a and 62b and the first to fourth pilot pressure sensors 37d to 40d through signal lines and is connected to the first and second valve fully closing switches 50 and 51 through control signals. The valve device controller 33 includes an operation amount detection section 33a, a valve state detection section 33b, a failure decision section 33c and a signal generation section 33d.
Referring to
Referring to
Now, a case in which at least one of the boom lever 34a and the arm lever 34b is operated is described. In the case where at least one of outputs of the first and second neutral detection switches 62a and 62b is 1 and only one of the switching valves 37 and 38 is open, the failure decision section 33c decides that the switching valves 37 and 38 are normal and sets the control command value for the first valve fully closing switch 50 to opening. On the other hand, in the case where one of outputs of the first and second neutral detection switches 62a and 62b is 1 and both of the switching valves 37 and 38 are open, the failure decision section 33c decides that at least one of the switching valves 37 and 38 is in failure and sets the control command value for the first valve fully closing switch 50 to closing. Further, in the case where at least one of outputs of the first and second neutral detection switches 62a and 62b is 1 and both of the switching valves 37 and 38 are closed, the failure decision section 33c decides that at least one of the switching valves 37 and 38 is in failure. However, if both of the switching valves 37 and 38 are closed, then since unintended operation of the hydraulic actuators 1 and 3 does not occur, the failure decision section 33c sets the control command value for the first valve fully closing switch 50 to opening.
Referring to
In the case where it is decided at step S2 that both of the pressures of the first and second pilot pressure sensors 37d and 38d are higher than a pressure threshold value (predetermined pressure) Pth (Yes), since the switching valves 37 and 38 are open simultaneously and unintended operation of the hydraulic actuators 1 and 3 possibly occurs, the control command value for the first valve fully closing switch 50 is set to closing at step S4. On the other hand, in the case where at least one of the pressures of the first and second pilot pressure sensors 37d and 38d is lower than the pressure threshold value Pth set in advance (No), since at least one of the switching valves 37 and 38 is closed and no unintended operation of the hydraulic actuators 1 and 3 occurs, the control command value for the first valve fully closing switch 50 is set to opening at step S5. Here, it is sufficient if the pressure threshold value Pth at step S2 is set to a value between the highest pressure (pressure of the pilot hydraulic fluid source 41 depicted in
In the case where it is decided at step S3 that both of the pressures of the first and second pilot pressure sensors 37d and 38d are lower than the pressure threshold value Pth (Yes), since both of the switching valves 37 and 38 are closed and unintended operation of the hydraulic actuators 1 and 3 does not occur, the control command value for the first valve fully closing switch 50 is set to opening at step S5. On the other hand, in the case where it is decided that at least one of the pressures of the first and second pilot pressure sensors 37d and 38d is higher than the pressure threshold value Pth set in advance (No), since, although none of the boom lever 34a and the arm lever 34b is operated, one of the switching valves 37 and 38 is open and unintended operation of the hydraulic actuators 1 and 3 possibly occurs, the control command value for the first valve fully closing switch 50 is set to closing at step S6.
In the case it is decided at step S7 after one of steps S4 to S6 is executed that one of the outputs of the first and second neutral detection switches 62a and 62b is greater than 0 (namely, the boom lever 34a or the arm lever 34b is operated) (Yes), the processing advances to step S8, but in the case where both of the outputs of the first and second neutral detection switches 62a and 62b are equal to or smaller than 0 (namely, none of the boom lever 34a and the arm lever 34b is operated) (No), then the processing advances to step S9.
In the case where it is decided at step S8 that the pressures of third and fourth pilot pressure sensors 39d and 40d are higher than the pressure threshold value Pth set in advance (Yes), since the switching valves 39 and 40 are open simultaneously and unintended operation of the hydraulic actuators 1 and 3 can possibly occur, the control command value for the second valve fully closing switch 51 is set to closing at step S10. On the other hand, in the case where it is decided that at least one of the pressures of the third and fourth pilot pressure sensors 39d and 40d is lower than the pressure threshold value Pth set in advance (No), since at least one of the switching valves 39 and 40 is closed and unintended operation of the hydraulic actuators 1 and 3 does not occur, the control command value for the second valve fully closing switch 51 is set to opening at step S11.
In the case where it is decided at step S9 that the pressures of the third and fourth pilot pressure sensors 39d and 40d are lower than the pressure threshold value Pth set in advance (Yes), since both of the switching valves 39 and 40 are closed and unintended operation of the hydraulic actuators 1 and 3 does not occur, the control command value for the second valve fully closing switch 51 is set to opening at step S11. On the other hand, in the case where it is decided that at least one of the pressures of the third and fourth pilot pressure sensors 39d and 40d is higher than the pressure threshold value Pth set in advance (No), since, although none of the boom lever 34a and the arm lever 34b is operated, one of the switching valves 39 and 40 is open and unintended operation of the hydraulic actuators 1 and 3 can possibly occur, the control command value of the second valve fully closing switch 51 is set to closing at step S12.
After one of steps S10 to S12 is executed, the processing returns to step S1 and the processes at the steps beginning with step S1 are executed repetitively.
Referring to
The first valve fully closing switch 50 connects the control signal lines from the solenoid valves 37a and 38a to the open side contact 50a or the ground side contact 50b in response to a control signal from the valve device controller 33. Meanwhile, the second valve fully closing switch 51 connects the control signal lines from the solenoid valves 39a and 40a to the open side contact 51a or the ground side contact 51b in response to a control signal from the valve device controller 33. In particular, when an opening signal from the valve device controller 33 is received, the first and second valve fully closing switches 50 and 51 connect the control signal lines from the solenoid valves 37a to 40a to the ground side contacts 50b and 51b, respectively, but when a closing signal is received, the first and second valve fully closing switches 50 and 51 connect the control signal lines to the open side contacts 50a and 51a, respectively. For example, if, in a state in which an opening signal is outputted from the machine body controller 11 to the solenoid valve 37a, the first valve fully closing switch 50 is connected to the ground side contact 50b in response to an opening signal from the valve device controller 33, then the control signal is transmitted from the machine body controller 11 to the solenoid valve 37a. Consequently, the solenoid valve 37a is driven to the open side and is opened to open the selector valve 37 (poppet valves 37b and 37c). On the other hand, if the first valve fully closing switch 50 is connected to the open side contact 50a in response to a closing signal from the valve device controller 33, then the control signal from the machine body controller 11 is not transmitted to the solenoid valve 37a. Consequently, the solenoid valve 37a is not driven to the open side but is closed by the spring force to close the selector valve 37 (poppet valves 37b and 37c). In this manner, the first and second valve fully closing switches 50 and 51 configure a first compulsory valve closing device for switching the switching valves 37 to 40 to their closed position irrespective of open-close control of the machine body controller 11.
Now, operation of the hydraulic system 200 is described.
First, operation of the hydraulic system 200 in the case where the switching valves 37 to 40 and the machine body controller 11 function normally is described.
Referring to
The valve signal outputting section 11c outputs, on the basis of the control command values for the switching valves 37 to 40 from the machine body controlling calculation section 11b, an opening signal to the switching valves 37 and 39 and outputs a closing signal to the switching valves 38 to 40. The pump signal outputting section 11d outputs a control signal to the regulators 35a and 36a of the closed circuit pumps 35 and 36 on the basis of the pump delivery flow rate command values from the machine body controlling calculation section 11b.
The closed circuit pumps 35 and 36 deliver hydraulic operating fluid at delivery flow rates set by the regulators 35a and 36a to the lines 20 and 24, respectively. Further, since the solenoid valves 37a and 39a of the switching valves 37 and 39 are opened in accordance with the opening signal, the poppet valves 37b, 37c, 39b and 39c are opened. On the other hand, since the solenoid valves 38a and 40a of the switching valves 38 and 40 are closed in response to the closing signal, the poppet valves 38b, 38c, 40b and 40c are closed. The hydraulic operating fluid delivered from the closed circuit pump 35 flows to the line 21 through the line 20 and the poppet valve 37b of the selector valve 37. Meanwhile, the hydraulic operating fluid delivered from the closed circuit pump 36 flows to the line 21 through the line 24, selector valve 39 (poppet valve 39b) and line 30. The hydraulic operating fluid from the closed circuit pump 35 and the hydraulic operating fluid from the closed circuit pump 36 merge in the line 21 and flow into the cylinder head 1a of the boom cylinder 1 to extend the boom cylinder 1. Part of the hydraulic operating fluid discharged from the cylinder rod 1b of the boom cylinder 1 is sucked into the closed circuit pump 35 through the line 23, selector valve (poppet valve 37b) and line 22. Meanwhile, the remaining part of the hydraulic operating fluid discharged from the cylinder rod 1b of the boom cylinder 1 is sucked into the closed circuit pump 36 through the line 31 selector valve 39 (poppet valve 39b) and line 24. At this time, an excess or deficient amount of the hydraulic operating fluid, which appears in each closed circuit, is supplied to or discharged from the tank 32 through the flushing valve 46a.
Referring to
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Now, operation of the hydraulic system 200 in the case where the selector valve 38 is sticked in an open state is described principally with reference to
Referring to
The valve signal outputting section 11c outputs an opening signal to the switching valves 37 and 39 and outputs a closing signal to the switching valves 38 and 40 on the basis of the control command values for the switching valves 37 to 40 from the machine body controlling calculation section 11b. The pump signal outputting section 11d outputs control signals to the regulators 35a and 36a of the closed circuit pumps 35 and 36 on the basis of the delivery flow rate command value from the machine body controlling calculation section 11b.
The closed circuit pumps 35 and 36 deliver hydraulic operating fluid to the lines 20 and 24 at delivery flow rates controlled by the regulators 35a and 36a, respectively. It is assumed that, at this time, the selector valve 38 fails and is sticked in an open state. In other words, it is assumed that, although a closing signal is inputted from the machine body controlling calculation section 11b, the solenoid valve 38a does not close and the poppet valves 38b and 38c remain open. Here, since the selector valve 37 is open in accordance with the opening signal from the machine body controller 11, as a result of the sticking in an open state of the selector valve 38, the switching valves 37 and (poppet valves 37b, 37c, 38b, 38c) are opened simultaneously. Consequently, the cylinder head 1a of the boom cylinder 1 is connected to the cylinder head 3a of the arm cylinder 3 through the lines 21, 20, 28 and 25 and the cylinder rod 1b of the boom cylinder 1 is connected to the cylinder rod 3b of the arm cylinder 3 through the lines 23, 22, 29 and 27. If, in this state, a load, for example, in the contracting direction acts upon the boom cylinder 1, then the hydraulic operating fluid of the cylinder head 1a of the boom cylinder 1 flows out due to the load and flows into the cylinder head 3a of the arm cylinder 3 through the lines 21, 20, 28 and 25. As a result, although the arm lever 34b is not operated, the arm cylinder 3 extends.
In
Referring to
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In
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According to the present embodiment configured in such a manner as described above, in the case where one of the switching valves 37 to 40 is sticked in an open state by failure of the switching valves 37 to 40 or control systems therefor, by compulsorily closing the other switching valves connected to one closed circuit pump to which the selector valve that is sticked in an open state is connected, the two hydraulic actuators 1 and 3 are not connected to each other through any line. Consequently, operation of the hydraulic actuators 1 and 3, which is not intended by the operator, is suppressed, and operation of the machine body can be continued.
A second embodiment of the present invention is described principally in regard to differences from the first embodiment.
The present embodiment further includes an open circuit pump, a proportional valve and an assist valve, and the open circuit pump and the proportional valve are connected to the cylinder head of a single rod hydraulic cylinder through an assist line in which the assist valve is provided, such that hydraulic operating fluid of the closed circuit pump and hydraulic operating fluid of the open circuit pump are merged and supplied to the cylinder head to improve the extension speed of the cylinder while part of the hydraulic operating fluid discharged from the cylinder head is sucked by the closed circuit pump while part of the remaining part of the hydraulic operating fluid is discharged to the tank through the proportional valve to improve the contraction speed.
Referring to
The open circuit pumps 12 and 13 are driven by power received from the engine 9 through the transmission device 10. The open circuit pumps 12 and 13 include tiling swash plate mechanisms (not depicted) each having an output port as flow rate adjustment means, and regulators 12a and 13a that adjust the tilt angle of the swash plates to adjust the pump displacement volume. The regulators 12a and 13a control the delivery flow rate of the open circuit pumps 12 and 13 on the basis of delivery flow rate command values received from the machine body controller 11. The open circuit pumps 12 and 13 suck hydraulic operating fluid from the tank 32 and deliver the hydraulic operating fluid to the assist lines 70 and 72, respectively.
The assist valve 80 includes a solenoid valve 80a and a poppet valve 80b. The solenoid valve 80a opens or closes in response to a control signal received from the machine body controller 11 to connect a pilot pressure receiving section of the poppet valve 80b to the pilot hydraulic fluid source 41 or the tank 32. In the case where a closing signal is inputted to the solenoid valve 80a, the pilot pressure receiving section of the poppet valve 80b is connected to the tank 32 and changes to a low pressure state, whereupon the poppet valve 80b is driven to the closing side by the spring force to disconnect the assist line 70 and the assist line 71 from each other. In the case where an opening signal is inputted to the solenoid valve 80a, the pilot chamber of the poppet valve 80b is connected to the pilot hydraulic fluid source 41 and the poppet valve 80b is driven to the open side by the pilot pressure to place the assist line 70 and the assist line 71 into a communication state with each other. It is to be noted that, although the present embodiment uses an assist valve that drives a poppet value using a pilot hydraulic pressure source and a solenoid valve as an example, only a solenoid valve that opens and closes an assist line by an electric signal may be used for the configuration. It is to be noted that, since the assist valves 81 to 83 are similar to the assist valve 80, description of them is omitted.
The proportional valves 54 and 55 open and close the poppet valves 54b and 55b by opening and closing of the solenoid valves 54a and 55a in response to control signals received from the machine body controller 11 similarly to the assist valves 80 to 83. However, since the valve opening of the solenoid valves 54a and 55a can be controlled continuously with respect to control command values from the machine body controller 11, also the proportional valves 54 and 55 are different from the assist valves 80 to 83 in that also the opening of the poppet valves 54b and 55b can be controlled continuously.
Now, the configuration relating to the present invention in the present embodiment is described.
In the assist valves 80 to 83, fifth to sixth pilot pressure sensors 80c to 83c are provided as a second sensor that detects open-closed states of the assist valves 80 to 83, respectively. The pilot pressure sensors 80c to 83c are connected to a valve device controller 33A through signal lines. For example, taking the assist valve 80 as an example, the pilot pressure sensor 80c is provided in a line that connects the solenoid valve 80a and the poppet valve 80b to each other. When a closing signal is inputted to the solenoid valve 80a, since the pilot pressure sensor 80c is connected to the tank 32, a low pressure is detected from the pilot pressure sensor 80c. On the other hand, when an opening signal is inputted to the solenoid valve 80a, since the pilot pressure sensor 80c is connected to the pilot hydraulic fluid source 41, a high pressure is detected from the pilot pressure sensor 80c. Also in the assist valves 80 to 83, the pilot pressure sensors 81c to 83c are provided individually in similar lines. It is to be noted that, although, in the present embodiment, the second sensor that detects open-closed states of the assist valves 80 to 83 is configured from the first to fourth pilot pressure sensors 37d to 40d, respectively, for example, where the assist valves are solenoid valves, the second sensor may be configured from stroke sensors for measuring the amount of movement of the valve body of the solenoid valves.
Referring to
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Referring to
The first and second valve fully closing switches 50 and 51 are opened or closed in response to a control signal from the valve device controller 33A such that the control signal lines from the machine body controller 11 to the solenoid valves 37a to 40a and 80a to 83a are rendered conducting or non-conducting to open or close the solenoid valves 37a to 40a and 80a to 83a.
Now, operation of the hydraulic system 200A is described.
First, operation of the hydraulic system 200A in the case where the switching valves 37 to 40, assist valves 80 to 83 and machine body controller 11 operate normally is described.
Referring to
The valve signal outputting section 11c outputs an opening signal to the switching valves 37 and 39 and the assist valves 80 and 82 on the basis of the control command values of the switching valves 37 to 40, assist valves 80 to 83 and proportional valves 54 and 55 from the machine body controlling calculation section 11b; outputs a closing signal to the switching valves 38 and 40 and the assist valves 81 and 84; and outputs a closing signal to the proportional valves 54 and 55. The pump signal outputting section 11d outputs control signals to the regulators 35a and 36a of the closed circuit pumps 35 and 36 and the regulators 12a and 13a of the open circuit pumps 12 and 13 on the basis of pump delivery flow rate command values from the machine body controlling calculation section 11b.
The closed circuit pumps 35 and 36 deliver hydraulic operating fluid to the lines 20 and 24 with delivery flow rates controlled by the regulators 35a and 36a, respectively. Meanwhile, the open circuit pumps 12 and 13 deliver hydraulic operating fluid to the assist lines 70 and 72 with delivery flow rates controlled by the regulators 12a and 13a, respectively.
In response to the control signals from the machine body controller 11, the switching valves 37 and 39 and the assist valves 80 and 82 are opened while the switching valves 38 and 40 and the assist valves 81 and 83 are closed and the proportional valves 54 and 55 are closed.
The hydraulic operating fluid delivered from the closed circuit pump 35 flows to the line 21 through the line 20 and the selector valve 37. The hydraulic operating fluid delivered from the closed circuit pump 36 flows to the line 21 through the line 24, selector valve 39 and line 30. Further, the hydraulic operating fluid delivered from the open circuit pump 12 flows to the line 21 through the assist valve 80 (poppet valve 80b) and the assist line 71a. The hydraulic operating fluid delivered from the open circuit pump 13 flows to the line 21 through the assist line 72, the assist valve 82 (poppet valve 82b) and the assist line 71. The hydraulic operating fluid from the closed circuit pumps 35 and 36 and the hydraulic operating fluid from the open circuit pumps 12 and 13 merge at the line 21 and flow into the cylinder head 1a of the boom cylinder 1 to extend the boom cylinder 1. Part of the hydraulic operating fluid discharged from the cylinder rod 1b of the boom cylinder 1 is sucked into the closed circuit pump 35 through the line 23, poppet valve 37b of the selector valve 37 and line 22. The part of the remaining part of the hydraulic operating fluid discharged from the cylinder rod 1b of the boom cylinder 1 is sucked into the closed circuit pump 36 through the line 31, selector valve 39 (poppet valve 39b) and line 24.
Referring to
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Now, operation of the hydraulic system 200A in the case where the assist valve 81 is sticked in an open state is described principally with reference to
Referring to
The valve signal outputting section 11c outputs an opening signal to the selector valve 37 and the assist valve 80 and outputs a closing signal to the switching valves 38 to 40 and the assist valves 81 to 83 on the basis of the control command values for the switching valves 37 to 40 from the machine body controlling calculation section 11b, and outputs a closing signal to the switching valves 38 to 40 and the assist valves 81 and 84. Meanwhile, the machine body controlling calculation section 11b outputs a closing signal to the proportional valve 54. The pump signal outputting section 11d outputs control signals to the regulator 35a of the closed circuit pump 35 and the regulator 12a of the open circuit pump 12 on the basis of a pump delivery flow rate command value from the machine body controlling calculation section 11b.
The closed circuit pump 35 and the open circuit pump 12 deliver hydraulic operating fluid to the line 20 and the assist line 70 with delivery flow rates controlled by the regulators 35a and 12a, respectively. The selector valve 37 and the assist valve 80 are opened in response to an opening signal, and the switching valves 38 to 40 and the assist valves 81 to 83 are closed in response to a closing signal. It is assumed that, at this time, the assist valve 81 fails and is sticked in an open state. In other words, it is assumed that, although a closing signal is inputted from the machine body controlling calculation section 11b, the solenoid valve 81a is not closed and the poppet valve 81b remains open. Here, since the assist valve 80 is open in accordance with the opening signal from the machine body controller 11, by the sticking in an open state of the assist valve 81, the assist valves 80 and 81 (poppet valves 80b and 81b) are opened simultaneously, and the cylinder head 1a of the boom cylinder 1 is connected to the cylinder head 3a of the arm cylinder 3 through the line 21, the assist lines 71a, 70 and 71b and the line 25. If, in this state, a load acts in the contraction direction upon the boom cylinder 1, then the hydraulic operating fluid of the cylinder head 1a of the boom cylinder 1 flows out due to the load and flows into the cylinder head 3a of the arm cylinder 3 through the line 21, assist lines 71a, 70 and 71b and line 25. As a result, although the arm lever 34b is not operated, the arm cylinder 3 is extended.
Since, in
Referring to
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According to the present embodiment configured in such a manner as described above, the following advantageous effects are achieved in addition to advantageous effects similar to those of the first embodiment.
In the case where one assist valve among the assist valves 80 to 83 is sticked in an open state by a failure of any of the assist valves 80 to 83 or a control system therefor, by compulsorily closing the other assist valves connected to one open circuit pump to which the assist valve sticking in an open state is connected, connection of the two hydraulic actuators 1 and 3 to each other is avoided, and consequently, operation of the hydraulic actuators 1 and 3, which is not intended by the operator, can be suppressed and operation of the machine body can be continued.
It is to be noted that the first and second valve fully closing switches 50 and 51 in the present embodiment configure a first compulsory valve closing device that switches the switching valves 37 to 40 to their closed position irrespective of the open-close control by the machine body controller 11 and a second compulsory valve closing device that switches the assist valves 80 to 83 to their closed position irrespective of the open-close control by the machine body controller 11. Further, the valve fully closing switches as the second compulsory valve closing device may be provided separately from the first and second valve fully closing switches 50 and 51.
A third embodiment of the present invention is described principally in regard to differences from the first embodiment.
In the present embodiment, the arm cylinder 3 (depicted in
Referring to
A swinging stopping switch 53 is provided on a control signal line that connects the machine body controller 11 and the swing brake 7b to each other. The swinging stopping switch 53 is connected to a valve device controller 33B through a control signal line and switchably has a connection side contact 53a and an open side contact 53b. The swinging stopping switch 53 is switched to the connection side contact 53a or the open side contact 53b in accordance with a control signal from the valve device controller 33B to conduct or interrupt a control signal from the machine body controller 11 to the swing brake 7b. Consequently, the swinging stopping switch 53 configures a compulsory operation device for operating the swing brake 7b irrespective of control by the machine body controller 11. In the present embodiment, it is assumed that, as an example, in the case where a control signal from the valve device controller 33B is not inputted to the swinging stopping switch 53, the swinging stopping switch 53 is connected to the connection side contact 53a as an initial state thereof. Further, in the present embodiment, although the swinging stopping switch 53 is configured from an electric relay, this is not restrictive.
Now, operation of the hydraulic system 200B in the case where the selector valve 38 is sticked in an open state is described.
Referring to
The valve signal outputting section 11c outputs an opening signal to the selector valve 37 and outputs a closing signal to the switching valves 38 to 40 on the basis of the control command values for the switching valves 37 to 40 from the machine body controlling calculation section 11b. Further, the valve signal outputting section 11c outputs a closing signal to the swinging stopping switch 53 such that the swing brake 7b is cancelled. The pump signal outputting section 11d outputs a control signal to the regulator 35a of the closed circuit pump 35 on the basis of the pump delivery flow rate command value from the machine body controlling calculation section 11b.
The swinging stopping switch 53 is connected, in its initial state, to the connection side contact 53a, and since the control signal line that connects the machine body controller 11 and the swing brake 7b to each other is in a conducting state, the swing brake 7b is cancelled by the cancelling signal from the machine body controller 11 and the swing shaft 7a is in a rotatable condition.
The closed circuit pump 35 delivers hydraulic operating fluid to the line 20 with the delivery flow rate controlled by the regulator 35a. It is assumed that the selector valve 38 fails and is sticked in an open state at this time. Here, since the selector valve 37 is open in accordance with the opening signal from the machine body controller 11, by the sticking in an open state of the solenoid valve 38a, the switching valves 37 and 38 (poppet valves 37b, 37c, 38b and 38c) are opened simultaneously, and the boom cylinder 1 and the swing motor 7 are connected to each other through the lines 21, 20, 28 and 25 and the lines 23, 22, 29 and 27. If it is assumed that, in this state, for example, a load in the contraction direction acts upon the boom cylinder 1, then the hydraulic operating fluid of the cylinder head 1a of the boom cylinder 1 flows out due to the load and flows into the swing motor 7 through the lines 21, 20, 28 and 25. As a result, although the swing lever 34c is not operated, the swing motor 7 rotates and the upper swing structure 102 (depicted in
Referring to
Referring to
Referring to
Referring to
Referring to
Also in the present embodiment configured in such a manner as described above, advantageous effects similar to those of the first embodiment are achieved. Further, in the case where one of the switching valves 37 to 40 is sticked in an open state by a failure of one of the switching valves 37 to 40 or a control system therefor, it is possible to operate the swing brake 7b to stop the swing motor 7 with certainty.
A fourth embodiment of the present invention is described principally in regard to differences thereof from the first embodiment.
According to the present embodiment, a first sensor is configured from a pump pressure sensor for detecting a pump pressure of a closed circuit pump and a load pressure sensor for detecting a load pressure of a hydraulic actuator in place of the first to fourth pilot pressure sensors 37d to 40d (depicted in
Referring to
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ΔP1=|pressure of pump pressure sensor 90−pressure of cylinder pressure sensor 94| [Expression 1]
ΔP2=|pressure of pump pressure sensor 91−pressure of cylinder pressure sensor 95| [Expression 2]
ΔP3=|pressure of pump pressure sensor 90−pressure of cylinder pressure sensor 96| [Expression 3]
ΔP4=|pressure of pump pressure sensor 91−pressure of cylinder pressure sensor 97| [Expression 4]
ΔP5=|pressure of pump pressure sensor 92−pressure of cylinder pressure sensor 94| [Expression 5]
ΔP6=|pressure of pump pressure sensor 93−pressure of cylinder pressure sensor 95| [Expression 6]
ΔP7=|pressure of pump pressure sensor 92−pressure of cylinder pressure sensor 96| [Expression 7]
ΔP8=|pressure of pump pressure sensor 93−pressure of cylinder pressure sensor 97| [Expression 8]
Subsequently, operation of the hydraulic system 200C in the case where the selector valve 38 is sticked in an open state is described.
Referring to
The valve signal outputting section 11c outputs an opening signal to the selector valve 37 and outputs closing signals to the switching valves 38 to 40 on the basis of the control command values for the switching valves 37 to 40 from the machine body controlling calculation section 11b. The pump signal outputting section 11d outputs a control signal to the regulator 35a of the closed circuit pump 35 on the basis of the pump delivery flow rate command value from the machine body controlling calculation section 11b.
The closed circuit pump 35 delivers hydraulic operating fluid to the line 20 with the delivery flow rate controlled by the regulator 35a. It is assumed that the selector valve 38 fails and is sticked in an open state at this time. Here, since the selector valve 37 is open in accordance with the opening signal from the machine body controller 11, by the sticking in an open state of the selector valve 38, the switching valves 37 and 38 (poppet valves 37b, 37c, 38b and 38c) are open simultaneously, and the cylinder head 1a of the boom cylinder 1 is connected to the cylinder head 3a of the arm cylinder 3 through the lines 21, 20, 28 and 25, and the cylinder rod 1b of the boom cylinder 1 is connected to the cylinder rod 3b of the arm cylinder 3 through the lines 23, 22, 29 and 27. If it is assumed that, in this state, for example, a load in the contraction direction acts upon the boom cylinder 1, then the hydraulic operating fluid of the cylinder head 1a of the boom cylinder 1 flows out due to the load and flows into the cylinder head 3a of the arm cylinder 3 through the lines 21, 20, 28 and 25. As a result, although the arm lever 34b is not operated, the arm cylinder 3 extends.
Referring to
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According to the present embodiment configured in such a manner as described above, the following advantageous effects are achieved in addition to the advantageous effects of the first embodiment.
In the first embodiment, a first sensor (pilot pressure sensor) is provided for each selector valve. Here, the number of switching valves increases in proportion to the number of closed circuit pumps and the number of hydraulic actuators. Therefore, if the number of closed circuit pumps or hydraulic actuators increases, then the number of first sensor increases significantly and the cost increases. In contrast, in the present embodiment, since it is configured such that a first sensor is provided for each closed circuit pump and each hydraulic actuator, the increasing number of first sensor when the number of closed circuit pumps or hydraulic actuators increases is suppressed, and therefore, the cost can be reduced.
A fifth embodiment of the present invention is described principally in regard to differences thereof from the first embodiment.
In the present embodiment, the first and second valve fully closing switches 50 and 51 are controlled only on the basis of pressures of the first to fourth pilot pressure sensors 37d to 40d the switching valves 37 to 40 have without using the first and second neutral detection switches 62a and 62b (depicted in
Referring to
Referring to
Referring to
Now, operation of the hydraulic system 200D in the case where the selector valve 38 is sticked in an open state is described.
Referring to
On the basis of the operation amount of the boom lever 34a, the machine body controlling calculation section 11b sets the controlling command value for the selector valve 37 to opening and sets the controlling command value for the switching valves 38 and 40 to closing such that only the closed circuit pump 35 is connected to the boom cylinder 1, and sets the pump delivery flow rate command value for the closed circuit pump 35 to a value corresponding to the operation amount of the boom lever 34a.
On the basis of the controlling command values for the switching valves 37 to 40 from the machine body controlling calculation section 11b, the valve signal outputting section 11c outputs an opening signal to the selector valve 37 and outputs a closing signal to the switching valves 37 to 40. On the basis of the pump delivery flow rate command value from the machine body controlling calculation section 11b, the pump signal outputting section 11d outputs a control signal to the regulator 35a of the closed circuit pump 35.
The closed circuit pump 35 delivers hydraulic operating fluid to the line 20 in accordance with the delivery flow rate controlled by the regulator 35a. At this time, it is assumed that the selector valve 38 fails and is sticked in an open state. Here, since the selector valve 37 is open by the opening signal from the machine body controller 11, the switching valves 37 and 38 (poppet valves 37b and 38b) are open simultaneously from the sticking in an open state of the solenoid valve 38a and the cylinder head 1a of the boom cylinder 1 is connected to the cylinder head 3a of the arm cylinder 3 through the lines 21, 20, 28 and 25 and the cylinder rod 1b of the boom cylinder 1 is connected to the cylinder rod 3b of the arm cylinder 3 through the lines 23, 22, 29 and 27. If, for example, in this state, a load in the contraction direction acts upon the boom cylinder 1, then hydraulic operating fluid of the cylinder head 1a of the boom cylinder 1 flows out due to the load and flows into the cylinder head 3a of the arm cylinder 3 through the lines 21, 20, 28 and 25. As a result, although the arm lever 34b is in a non-operation state, the arm cylinder 3 extends.
Referring to
Referring to
Referring to
Referring to
Also in the present embodiment configured in such a manner as described above, advantageous effects similar to those in the first embodiment are achieved. Further, by the omission of the first and second neutral detection switches 62a and 62b (depicted in
While the embodiments of the present invention are described in detail above, the present invention is not limited to the embodiments described above but includes various modifications. For example, while, in the embodiments described above, the present invention is applied to a hydraulic excavator, the present invention is not limited to this and can be applied to general construction machinery in which a plurality of hydraulic actuators are driven by a hydraulic closed circuit. Further, the embodiments described above are described particularly in order to facilitate understandings of the present invention, and the present invention is not necessarily limited to the embodiments that include all components described hereinabove. Further, it is possible to add part of the components of a certain embodiment to the configuration of a different embodiment and also it is possible to delete some of the components of a certain embodiment or replace some of the components of an embodiment with some components of a different embodiment.
| Number | Date | Country | Kind |
|---|---|---|---|
| JP2017-068540 | Mar 2017 | JP | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/JP2018/004049 | 2/6/2018 | WO | 00 |
| Publishing Document | Publishing Date | Country | Kind |
|---|---|---|---|
| WO2018/179863 | 10/4/2018 | WO | A |
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| 20160032565 | Shimizu et al. | Feb 2016 | A1 |
| Number | Date | Country |
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| 2015-48899 | Mar 2015 | JP |
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| 2017-53386 | Mar 2017 | JP |
| Entry |
|---|
| International Preliminary Report on Patentability (PCT/IB/338 & PCT/IB/373) issued in PCT Application No. PCT/JP2018/004049 dated Oct. 10, 2019, including English translation of document C2 (Japanese-language Written Opinion (PCT/ISA/237) previously filed on May 16, 2019) six pages. |
| International Search Report (PCT/ISA/210) issued in PCT Application No. PCT/JP2018/004049 dated Apr. 17, 2018 with English translation (two (2) pages). |
| Japanese-language Written Opinion (PCT/ISA/237) issued in PCT Application No. PCT/JP2018/004049 dated Apr. 17, 2018 (four (4) pages). |
| Number | Date | Country | |
|---|---|---|---|
| 20190345692 A1 | Nov 2019 | US |
