JP4478538B2 - Capacity control method and capacity control device of hydraulic pump for work machine of work vehicle - Google Patents

Description

  The present invention relates to a capacity control method and a capacity control apparatus for a hydraulic pump for a work machine of a work vehicle.

  2. Description of the Related Art Conventionally, as disclosed in, for example, Patent Document 1, a technique for improving fuel efficiency by detecting a working state in a wheel loader and changing a flow rate of a variable displacement hydraulic pump for work implements according to the working state. It has been known.

  FIG. 6 shows a side view of the wheel loader 11. In FIG. 6, the wheel loader 11 includes a work machine 20 at the front portion of the vehicle body. The work machine 20 includes a lift arm 21 that moves up and down by the expansion and contraction of the lift cylinder 23. At the front end of the lift arm 21, a bucket 22 is attached that swings through the tilt arm 24 by the expansion and contraction of the tilt cylinder 25.

  In the prior art disclosed in Patent Document 1, the wheel loader 11 detects the bottom pressure of the lift cylinder 23 or the tilt cylinder 25 and detects the working state based on these bottom pressures. For example, when shifting from non-excavation work to excavation work, the capacity of the working machine hydraulic pump is immediately reduced. This is called the first prior art.

  Moreover, when raising the bucket 22 at the time of loading work, the technique of reducing the capacity | capacitance of the hydraulic pump for working machines is known if the bucket 22 becomes predetermined height. When the lift cylinder 23 is extended at the same speed, the rising speed of the bucket 22 increases as the height of the bucket 22 increases. In order to avoid this, the capacity of the working machine hydraulic pump is immediately reduced when the bucket 22 reaches a predetermined height. This is called the second prior art. Similar to the first prior art, the second prior art also has an effect of improving fuel efficiency.

JP 2003-184134 A

  However, if the capacity of the work implement hydraulic pump is immediately reduced, the operation speed of the work implement is suddenly reduced, a deceleration shock occurs, and the operator feels uncomfortable with the operation of the work implement. is there.

At this time, for example, when switching between the non-excavation work and the excavation work as in the first prior art, the vehicle body originally vibrates vigorously because the bucket excavates the load, and even if a deceleration shock occurs, the operator There is less to feel it. Therefore, the operator does not feel a sense of incongruity in the operation of the work machine.
However, as the second conventional technique suddenly lowers the rising speed while the bucket 22 is rising, the operator feels a decelerating shock and feels that the ascending operation has stopped for a moment. As a result, for example, when loading into a dump truck, he or she may hesitate to approach the dump truck.

  The present invention has been made paying attention to the above-described problem, and a capacity control method for a hydraulic pump for a work machine of a work vehicle, in which a deceleration shock is small even when the bucket is raised, and an operator feels uncomfortable with respect to the operation of the work machine, and The object is to provide a capacity control device.

In order to achieve the above object, the first invention provides:
In a capacity control method of a hydraulic pump for a work machine of a work vehicle having a work machine equipped with a bucket,
Determine whether the bucket is in a loaded state,
When the loaded bucket exceeds a predetermined height when it rises, the capacity of the hydraulic pump for the work machine that drives the work machine is gradually reduced to the predetermined capacity, and after the capacity of the hydraulic pump is reduced to the predetermined capacity Has fixed the capacity of the hydraulic pump to the predetermined capacity to raise the bucket .
Further, the second invention is the first invention,
When the loaded bucket exceeds the horizontal height when it rises, the capacity of the hydraulic pump is reduced.
On the other hand, the third invention
In a capacity control device for a hydraulic pump for a work machine of a work vehicle having a work machine with a bucket mounted on the tip of a liftable lift arm,
A pump controller that controls the capacity of the hydraulic pump for the work machine that drives the work machine;
A capacity changing device for changing the capacity of the hydraulic pump for the work machine based on an instruction from the pump controller;
A lift angle detector for detecting the angle of the lift arm with respect to the ground;
A load detector for detecting whether the bucket is in a loaded state,
The pump controller is based on the outputs of the lift angle detector and the load detector,
When bucket load state exceeds a predetermined height when raised, gradually reduced to a predetermined volume capacity of the hydraulic pump for a working machine, after the capacity of the hydraulic pump is reduced to the predetermined capacity of the hydraulic pump control is performed Ru raise the bucket to secure the capacity to the predetermined volume.
The fourth invention is the third invention, wherein
The load detector detects at least an angle of the bucket with respect to the ground.
Furthermore, the fifth invention is the third invention or the fourth invention,
The pump controller reduces the capacity of the hydraulic pump when the loaded bucket exceeds the horizontal height when it rises.

According to the first invention and the third invention which is an apparatus invention thereof, the lifting speed of the bucket changes smoothly, the deceleration shock is reduced, and the operator can work without feeling uncomfortable with the operation of the work machine. . Further, fuel consumption can be reduced by reducing the capacity of the working machine hydraulic pump when the bucket is above a predetermined height.
Further, according to the fourth aspect of the invention, it is possible to more accurately determine the work state of whether or not the bucket is in a loaded state.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 1 shows a side view of the wheel loader 11. In FIG. 1, the wheel loader 11 includes a front vehicle body 17 and a rear vehicle body 15 that articulate each other. The rear vehicle body 15 is provided with an engine room 18. A cab 12 is mounted on the front body 17.

  A work machine 20 is attached to the front end portion of the front body 17. The work machine 20 includes a lift arm 21 whose base end is attached to the front vehicle body 17 via an arm pin 28 so as to be swingable. The front vehicle body 17 and the lift arm 21 are connected by a pair of left and right lift cylinders 23 and 23. By expanding and contracting the lift cylinders 23, the lift arm 21 swings up and down around the arm pin 28.

  A bucket 22 is swingably attached to the tip of the lift arm 21 via a bucket pin 27. An intermediate portion of the tilt arm 24 is attached to the intermediate portion of the lift arm 21 so as to be swingable.

  One end of the tilt arm 24 and the front vehicle body 17 are connected by a tilt cylinder 25. The other end of the tilt arm 24 and the bucket 22 are connected by a tilt rod 26. By expanding and contracting the tilt cylinder 25, the bucket 22 swings up and down around the bucket pin 27.

  An engine 13 is housed in the engine room 18 of the rear body 15. The engine 13 drives a variable displacement working machine hydraulic pump (hereinafter referred to as a working machine hydraulic pump 29) via the torque converter 19. The work machine hydraulic pump 29 supplies pressure oil to the lift cylinder 23 and the tilt cylinder 25 via a hydraulic pipe (not shown).

  FIG. 2 shows the movement of the bucket 22 when the wheel loader 11 performs the loading operation. When performing the loading operation, the load 40 is lifted upward while being loaded on the bucket 22 as shown in FIG. At this time, the cutting edge 22A of the bucket 22 faces upward with respect to the ground 41 so that the load 40 does not spill.

  In the following description, the height of the bucket 22 is represented by the height of the center of the bucket pin 27. The height of the bucket 22 such that the straight line L connecting the center of the bucket pin 27 and the center of the arm pin 28 substantially coincides with the horizontal is referred to as the horizontal height of the bucket 22. The angle of the bucket 22 refers to an angle α formed by the blade edge 22A of the bucket 22 with respect to the ground 41.

  FIG. 3 shows an example of a system diagram of a capacity control device 30 that controls the capacity of the working machine hydraulic pump 29. The capacity control device 30 includes work machine operating means 34 such as a lever for operating the lift cylinder 23 and the tilt cylinder 25, a pump controller 31 for controlling the capacity of the work machine hydraulic pump 29, and the capacity of the work machine hydraulic pump 29. A capacity changing device 38 for changing the lift arm 21, a lift angle detector 32 for detecting the angle of the lift arm 21 with respect to the ground 41, and a load detector 33 for detecting the load amount of the bucket 22.

  The work machine operation means 34 and the pump controller 31 are installed inside the cab 12, for example. As the lift angle detector 32, for example, a potentiometer or the like that is provided in the vicinity of the arm pin 28 and detects its rotation angle is suitable. Alternatively, a stroke sensor that detects the length of the lift cylinder 23 may be provided, and the lift angle may be calculated from the length of the lift cylinder 23.

  As the load detector 33, a bottom pressure detector that detects the bottom pressure of the lift cylinder 23 is suitable. Based on the output of the load detector 33, the pump controller 31 can load the bucket 22 with a load larger than a predetermined load (hereinafter referred to as a loaded state) or not (hereinafter referred to as an unloaded state). Call)

  The capacity changing device 38 includes a swash plate angle cylinder 35 that changes the angle of the swash plate of the working machine hydraulic pump 29 by expansion and contraction, a swash plate angle detector 36 that detects the angle of the swash plate, and an output signal of the pump controller 31. And a driver 37 for driving the swash plate angle cylinder 35. The capacity changing device 38 moves the swash plate of the working machine hydraulic pump 29 based on an instruction from the pump controller 31 to change the capacity of the working machine hydraulic pump 29.

  FIG. 4 is a flowchart showing an example of a procedure for controlling the capacity of the work machine hydraulic pump 29 when the bucket 22 is raised. First, the pump controller 31 determines whether the bucket 22 is in a loaded state or an empty state based on the output of the load detector 33 (step S11). The capacity of the working machine hydraulic pump 29 at this time is referred to as a pre-control capacity. The capacity before control may be, for example, the rated capacity of the working machine hydraulic pump 29, or may be a capacity smaller than that.

  In the case of a loaded state in step S11, the pump controller 31 determines whether or not the bucket 22 is rising based on the change in the output of the lift angle detector 32 (step S12). In step S12, it may be determined by detecting whether or not the work implement operating means 34 is operated to determine whether or not the bucket 22 is being raised.

  If the bucket 22 is not rising in step S12, the process returns to step S11. When the bucket 22 is rising in step S12, the pump controller 31 determines whether the bucket 22 is above the horizontal height based on the output of the lift angle detector 32 (step S13). If it is not above horizontal in step S13, it returns to step S11.

  If the bucket 22 is above the horizontal height in step S13, the pump controller 31 outputs a signal to the capacity changing device 38, and gradually changes the angle of the swash plate to thereby change the hydraulic pump 29 for work implement. Is gradually reduced (step S14).

  The pump controller 31 detects the capacity of the working machine hydraulic pump 29 based on the output of the swash plate angle detector 36, and determines whether or not the capacity has become a predetermined capacity (hereinafter referred to as a reduced capacity) ( Step S15). The reduced capacity is determined by, for example, a ratio to the pre-control capacity.

  In step S15, when the capacity of the working machine hydraulic pump 29 becomes the reduced capacity, the pump controller 31 outputs a signal to the capacity changing device 38, and the angle at which the capacity of the working machine hydraulic pump 29 becomes the reduced capacity. (Step S16).

  And the pump controller 31 determines whether the raising of the bucket 22 stopped based on the change of the output of the lift angle detector 32 (step S17). If it is determined to be stopped in step S17, the capacity of the working machine hydraulic pump 29 is returned to the original capacity before control (step S18), and the process returns to step S11.

Next, the procedure for gradually reducing the capacity of the working machine hydraulic pump 29 in steps S14 to S16 will be described in detail.
FIG. 5 shows a change in the consumption torque of the engine 13 when the bucket 22 is raised. The horizontal axis is the height of the bucket 22, and the vertical axis is the consumed torque. On the horizontal axis, “ground” indicates that the bucket 22 is grounded, “horizontal” indicates that the bucket 22 is at a horizontal height, and “top” indicates that the bucket 22 is raised highest. ing.

  In FIG. 5, the bucket 22 loaded with the load 40 rises at a constant flow rate from the ground contact position. At this time, when the capacity of the working machine hydraulic pump 29 does not change, the consumption torque increases in a quadratic curve as shown by the solid line A.

  When the bucket 22 reaches the horizontal height, the pump controller 31 gradually reduces the capacity of the working machine hydraulic pump 29 as shown in step S14. At this time, by reducing the capacity of the working machine hydraulic pump 29 linearly, the consumed torque slowly decreases while drawing a curve as shown by a solid line B. Therefore, the rising speed of the bucket 22 also gradually decreases.

  Then, as shown in steps S15 to S16, when the capacity of the working machine hydraulic pump 29 reaches the reduced capacity, the pump controller 31 fixes the capacity of the working machine hydraulic pump 29 (the “capacity fixing” position on the horizontal axis). ). As a result, the torque consumption increases while drawing a quadratic curve as shown by the solid line C. A broken line D in FIG. 5 indicates the consumption torque when the capacity of the working machine hydraulic pump 29 is not reduced.

  As a result, as compared with the case where the capacity of the work machine hydraulic pump 29 is switched immediately, the ascending speed is gradually reduced, so that the deceleration shock is reduced and the operator feels uncomfortable with the operation of the work machine. Few. Moreover, the consumption torque T1 when the bucket 22 reaches the top position is lower than the consumption torque T2 when the capacity of the working machine hydraulic pump 29 is not reduced, and fuel consumption is reduced.

  The reduced capacity of the working machine hydraulic pump 29 is preferably about 60 to 80% of the pre-control capacity, for example. As a result, when the bucket 22 reaches the vicinity of the top position, the rising speed is such that it is neither too fast nor too slow for the operator.

  For example, if it takes about n seconds to raise the bucket 22 from the horizontal height to the top position, the time from the horizontal height at which the capacity reduction is started to the “capacity fixed” position is (1/10). ) · N seconds to (6/10) · n seconds. Thereby, the ascending speed of the bucket 22 does not decelerate rapidly, and work without a sense of incongruity is possible.

  In step S13, the capacity of the working machine hydraulic pump 29 is changed by detecting that the bucket 22 has reached the horizontal height. However, the present invention is not limited to this. That is, it may be detected that the bucket 22 has reached a predetermined height that is not limited to the horizontal height, and the capacity control of the working machine hydraulic pump 29 may be started as a trigger. Steps S11 to S13 are not limited to this order, and the order may be changed.

  As described above, according to the above-described embodiment, the capacity of the working machine hydraulic pump 29 is gradually reduced when the bucket 22 is loaded and lifted. Thereby, the raising speed of the bucket 22 changes smoothly, the deceleration shock is reduced, and the operator can work without being confused by the operation of the work implement. Further, by reducing the capacity of the working machine hydraulic pump 29 when the bucket 22 is above the horizontal height, the consumption torque is reduced and the fuel consumption is reduced.

  In the above embodiment, the load state or the empty state is determined only by the bottom pressure of the lift cylinder 23. However, in addition to the bottom pressure of the lift cylinder 23, the angle α of the bucket 22 is considered. Thus, it may be determined whether the loaded state or the empty state.

  In detecting the angle α of the bucket 22, for example, a potentiometer (not shown) may be provided in the vicinity of the bucket pin 27. The pump controller 31 can detect the rotation angle of the bucket 22 relative to the lift arm 21 based on the output of the potentiometer. The pump controller 31 can detect the angle of the lift arm 21 with respect to the ground 41 based on the output of the lift angle detector 32.

  Thus, the pump controller 31 can detect the angle α of the bucket 22 from the rotation angle of the bucket 22 with respect to the lift arm 21 and the angle of the lift arm 21 with respect to the ground 41. Alternatively, instead of the potentiometer, a stroke sensor that detects the length of the tilt cylinder 25 may be provided, and the rotation angle of the bucket 22 relative to the lift arm 21 may be calculated from the length of the tilt cylinder 25.

  As described above, when the load 40 is loaded, the cutting edge 22A of the bucket 22 faces upward (see FIG. 2). Therefore, only when the output of the bottom pressure detector is larger than a predetermined value and the cutting edge 22A of the bucket 22 faces upward with respect to the ground 41 by a predetermined angle or more than the horizontal in step S11 of FIG. It is determined that the bucket 22 is in a loaded state.

  That is, by providing a bottom pressure detector, a lift angle detector 32, and a potentiometer as the load detector 33, the pump controller 31 can more accurately determine whether or not the bucket 22 is in a load state. it can. The subsequent procedure is the same as steps S12 to S18 in the flowchart of FIG.

  Although the above description has been given by taking the wheel loader 11 as an example, the present invention can be similarly applied to other loader system work vehicles such as a skid steer loader in which the vehicle body does not articulate. In other words, when the bucket 22 is lifted by the hydraulic cylinder, it is effective for a work vehicle having a link structure in which the lifting speed of the bucket 22 increases as the extension length of the hydraulic cylinder increases.

The side view of a wheel loader (1st Embodiment). Explanatory drawing of a motion of a bucket (1st Embodiment). 1 is a system diagram of a work machine control device (first embodiment). The flowchart which shows the control procedure of the hydraulic pump for working machines (1st Embodiment). The graph which shows the consumption torque at the time of a bucket raise. (First embodiment). Side view of wheel loader (prior art).

Explanation of symbols

  11: Wheel loader, 12: Cab, 13: Engine, 15: Rear vehicle body, 17: Front vehicle body, 18: Engine room, 19: Torque converter, 20: Work machine, 21: Lift arm, 22: Bucket, 22A : Cutting edge, 23: Lift cylinder, 24: Tilt arm, 25: Tilt cylinder, 26: Tilt rod, 27: Bucket pin, 28: Arm pin, 29: Hydraulic pump for work machine, 30: Work machine control device, 31: Pump Controller: 32: Lift angle detector, 33: Load detector, 34: Working machine operating means, 35: Swash plate angle cylinder, 36: Swash plate angle detector, 37: Driver, 38: Capacity changing device, 39: Bucket Angle detector, 40: cargo, 41: ground.

Claims (5)

In a capacity control method of a hydraulic pump for a work machine of a work vehicle having a work machine equipped with a bucket,
Determine whether the bucket is in a loaded state,
When the loaded bucket exceeds a predetermined height when it rises, the capacity of the hydraulic pump for the work machine that drives the work machine is gradually reduced to the predetermined capacity, and after the capacity of the hydraulic pump is reduced to the predetermined capacity working capacity control method of a hydraulic pump for a working machine of a vehicle, characterized in Rukoto raise the bucket to secure the capacity to the predetermined capacity of said hydraulic pump.   In the capacity | capacitance control method of the hydraulic pump for working machines of the working vehicle of Claim 1,
  A capacity control method for a hydraulic pump for a working machine of a work vehicle, wherein the capacity of the hydraulic pump is reduced when a loaded bucket exceeds a horizontal height when the bucket is raised. In a capacity control device for a hydraulic pump for a work machine of a work vehicle having a work machine with a bucket mounted on the tip of a liftable lift arm,
A pump controller that controls the capacity of the hydraulic pump for the work machine that drives the work machine;
A capacity changing device for changing the capacity of the hydraulic pump for the work machine based on an instruction from the pump controller;
A lift angle detector for detecting the angle of the lift arm with respect to the ground;
A load detector for detecting whether the bucket is in a loaded state,
The pump controller is based on the outputs of the lift angle detector and the load detector,
When bucket load state exceeds a predetermined height when raised, gradually reduced to a predetermined volume capacity of the hydraulic pump for a working machine, after the capacity of the hydraulic pump is reduced to the predetermined capacity of the hydraulic pump capacity control device for a hydraulic pump for a working machine for a working vehicle and performs control for Ru raise the bucket to secure the capacity to the predetermined volume. In the capacity control apparatus of the working machine hydraulic pump for a work vehicle according to claim 3 ,
The load detector detects at least an angle of the bucket with respect to the ground, and a capacity control device for a hydraulic pump for a work machine of a work vehicle. In the capacity | capacitance control apparatus of the working machine hydraulic pump of the work vehicle of Claim 3 or Claim 4,
  The capacity controller of a hydraulic pump for a work machine of a work vehicle, wherein the pump controller reduces the capacity of the hydraulic pump when a loaded bucket exceeds a horizontal height when it rises.

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