The present invention is directed to a work machine. The work machine comprises a chassis, a ground drive, a prime mover, a platform, and a control system. The ground drive translates the chassis across a ground surface. The prime mover is disposed on the chassis and configured to provide power to the ground drive. The platform is disposed on the chassis and movable from a first position to a second position. The control system comprises a signal generator, a throttle input, and a controller. The signal generator is configured to send a first signal. The throttle input is configured to send a throttle signal.
The controller is configured to receive the first signal and the throttle signal and provide an output throttle condition to the ground drive. A first condition is defined when the controller does not receive the first signal from the signal generator. In the first condition, the controller is configured to allow the throttle signal to determine the output throttle condition. A second condition is defined when the controller receives the first signal from the signal generator. In the second condition, the controller is configured to limit output throttle condition to a predetermined maximum.
In another aspect the invention is directed to a work machine. The work machine comprises a frame, a ground drive, a work attachment, a platform, a sensor, and a controller. The ground drive is supported on the frame. The work attachment is supported on the frame at a first end. The platform is supported on the frame at the second end and has a first position and a second position. The sensor is configured to determine the position of the platform and send a first signal when the platform is in the first position. The controller is in communication with the sensor and configured to limit the speed of the ground drive when the first signal is received.
In another aspect the invention is directed to a system for limiting hydraulic flow to a ground drive. The system comprises a signal generator, a controller, and a hydraulic circuit. The signal generator is configured to send a signal. The controller is in communication with the signal generator. The hydraulic circuit comprises a hydraulic pump and a ground drive motor. The ground drive motor powers a ground drive of a work machine. The controller is configured to limit flow from the hydraulic pump to the ground drive motor when the signal is received by the controller.
Turning now to the figures,
The work machine10 depicted comprises a chassis 12 and an attachment 14. The chassis supports an engine 15 to act as a prime mover for powering operative elements of the work machine 10. For illustrative purposes, the attachment 14 is a trenching chain on a trenching boom attached to loader arms 17. Other attachments, such as vibratory plows, buckets, microtrenching assemblies, or excavator arms may be utilized in conjunction with the chassis 12.
An operator 16 of the work machine 10 stands on a platform 18 located at a first end of the machine 10. A control panel 20 is positioned near and above the level of the platform 18 for the operator 16 to use. The control panel 20 comprises controls which operate the machine and control its associated attachment (
The chassis 12 shown utilizes two powered tracks as a ground drive 22 system, but other ground engagement systems such as wheels, steerable track assemblies, or a combination of both could be employed based on the demands of the application.
With reference now to
It is beneficial to provide a system to detect operator presence on the platform to ensure the safety of the operator 16 during operation. For example, when a trencher attachment 14 is active, a set of blades are rotated about the trencher boom to uncover a trench. The trencher attachment 14 may be configured to disengage upon the operator 16 dismounting the platform 18, thereby preventing the operator from approaching the active trencher. An operator presence system is provided in U.S. Pat. No. 10,582,652, issued to Kukuk, et al. (“Kukuk”), and is incorporated herein by reference.
In Kukuk, a platform switch, such as switch 40 (
With reference to
With reference again to
The operator input 46 may be buttons, a touchscreen display, switch, or lever, such as the control levers 26. Various controls are shown on
In some cases the operator 16 may prefer to operate the ground drive 22 of the machine 10 without standing on the platform 18. For example, the operator 16 may wish to stand to the side of the machine 10 and operate the controls while loading the machine onto a trailer. When the platform 18 is unoccupied in and the first position, the ECU 42 may limit the maximum speed of the ground drive 22 through limiting the power supplied by the engine 15.
Once the operator 16 steps back on the platform 18, the platform 18 will move from the first position to the second position. The controller 44 may then instruct the ECU 42 to allow full range of throttle. The controller 44 may also be configured to detect and store in memory the throttle level setpoint at the point in time that the platform moves from the second position to the first position. The controller 44 may then instruct the ECU 42 to return the engine throttle level to the recorded setpoint upon the operator 16 stepping back on the platform 18. In this case, the ECU 42 may slowly increase the throttle level to prevent a sudden or unexpected jump in the operation of the work machine 10.
As shown in
Ordinarily, the pilot steering valve 52 is directly actuated by an operator input, such as control lever 26 (
When the platform 18 is in the first position, indicating the operator 16 has stepped off the platform, the PPR valve 50 is activated by the controller 44. The PPR valve 50 then reduces the hydraulic flow provided to the pilot steering valve 52 to a lower value. This may occur by diverting hydraulic flow exceeding the maximum value back to a fluid reservoir 54.
As a result, the valve assembly 50 provides the hydraulic motors controlling the tracks or other ground engagement system 22 with a lower maximum fluid flow, even as the lever 26 controlling the pilot steering valve 52 (and thus the ground speed) is moved fully forward or aft.
For example, if the controller 44 is set to limit the PPR valve 50 to twenty percent of maximum throttle upon the platform moving to the first position, the lever 26 is able to increase the hydraulic flow at lever positions corresponding to zero through twenty percent power. However, after exceeding twenty percent, excess hydraulic flow through the PPR valve 50 is diverted to the reservoir 54. In this example, only twenty percent of the maximum power can ever be indicated by the PPR valve 50 (as actuated by the lever 26), and the hydraulic flow to the ground drive 22 does not increase further.
This embodiment has the advantage of limiting the work machine's maximum speed without affecting the engine throttle level, if so desired. Such a system has practical implications. For example, an operator 16 may wish to use the attachment 14, for example, a bucket, to lift heavy material. In order to fine-tune this placement, it may be advantageous to step off the platform 18 and to the side of the work machine 10. In this scenario, the engine 15 fully powers the attachment 14 to keep a load elevated, while the PPR valve 50 limits hydraulic flow to the ground drive, and thus ground drive speed, when the platform is in the first position.
There may be scenarios in which an override of the platform switch 40 is necessary. For example, in extreme conditions the work machine 10 may become stuck in mud, such that the platform 18 is lifted to the first position even when an operator 16 is standing on the platform. In this case, an override is needed to communicate to the controller 44 to allow the full range of throttle or speed. Preferably, a button or switch is provided which, when initiated, instructs the controller 44 to override the normal operational parameters. The override may be configured such that it would not be available to actuate unless the operator is standing on the platform.
The work machine 10 shown comprises a loader lever 27 (
The attachment switch 28 is biased to an idle position. Therefore, the operator 16 must keep constant contact with the switch 28 to maintain an increased throttle level while in override mode. While in override mode, the loader lever 27 will continue to operate the control loader arms 17 as normal. The control levers 26 are also biased to a neutral position, requiring the operator to maintain continuous force on the control levers to move the machine. If the control levers 26 comprise a cruise control, the controller will not allow cruise mode to be activated if the platform 18 is in the first position regardless of whether the override mode is activated.
It may be preferable to implement throttle control for limiting hydraulic flow to the ground drive system 22 for other purposes. For example, if the platform 18 moves from the second position to the first position, the controller 44 may instruct the ECU 42 to idle the engine. Simultaneously, the controller 44 may instruct the PPR valve 50 to limit hydraulic flow to the pilot steering valve to a specified reduced pressure.
The ECU 42 continuously monitors the rpm of the engine, which in turn may communicate this information to the controller 44. The controller 44 may instruct the ECU 42 to increase the throttle level to maintain rpm within a specified range, for example, 1100 to 1300 rpm, while limiting the pressure available to the pilot steering valve 52. The speed of the ground drive 22 will therefore continue to be limited to within the specified range safe for pedestrian use while preventing the engine from stalling. Alternatively, the controller may instruct the PPR valve 50 to reduce flow to the pilot steering valve 52 in response to the rpm level in the engine dropping below a specified level.
The described system may also be used to provide engine anti-stall regardless of the mode of operation. When the platform 16 is in the second position, the controller 44 may utilize a variety of inputs to control the pilot steering valve 52 pressure via the PPR valve 50. Inputs may include engine load, ground drive speed and engine speed. These inputs act as a signal generator, to instruct the controller as to adverse conditions. The controller 44 can determine the maximum hydraulic pressure to allocate to the pilot steering valve 52 without stalling the engine.
If the engine is undergoing excessive engine load above a predetermined setpoint, the controller 44 will instruct the PPR valve 50 to restrict flow to the pilot steering valve 52 to a lower level to reduce the load. Flow is restricted by starting from the current maximum allowed flow and decreasing flow until engine load decreases. Once engine load decreases to an acceptable level, flow to the pilot steering valve will stabilize and may thereafter increase.
A threshold value may be assigned representing the engine load with respect to a particular ground drive 22 speed and engine speed. The controller 44 may continuously monitor and adjust the threshold value. So long as the engine load is below the threshold value assigned, the controller will instruct the PPR valve 50 to direct a maximum allowed flow to the pilot steering valve 52. If the engine 15 load is at or above the threshold value, the PPR valve 50 redirects flow away from the pilot steering valve 52 as described.
The disclosed engine anti-stall system may be particularly beneficial while traversing a steep incline. While traversing the incline the ground drive 22 speed would be limited. The anti-stall system would also be beneficial at the minimum engine speed while loading the machine 10 on a trailer for transport. There are some conditions at low engine speed and high load that could cause the machine to stall at a critical loading point.
The anti-stall system could also be used in conjunction with a ground drive speed sensor to prevent track or wheel slippage. The controller 44 monitors the ground drive 22 speed in conjunction with the engine load and engine speed to determine slippage. For example, a sudden spike in ground drive speed coupled with a decrease in engine load may indicate track slippage. To prevent further slippage, the controller may instruct the PPR valve 50 to progressively divert flow away from the steering valve 52 until slippage is no longer sensed. Once traction is regained, an increase in flow to the pilot steering valve 52 may be reintroduced.
Changes may be made in the construction, operation and arrangement of the various parts, elements, steps and procedures described herein without departing from the spirit and scope of the invention as described in the following claims.
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Number | Date | Country | |
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Number | Date | Country | |
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Parent | 16999246 | Aug 2020 | US |
Child | 18179175 | US |