Work machine control system and control method

Abstract

To provide a control system and a control method for a work machine enabling a bucket swinging operation and capable of reducing a load applied to a vehicle body.SOLUTION: A control system for a work machine comprises: a rear frame; a front frame connected to the rear frame so as to be bent; a bucket operable with respect to the front frame; an actuator for driving the bucket; a sensor detecting a relative position of the rear frame and the front frame; and a work machine controller 10 controlling the actuator. The work machine controller 10 receives an input of the detection result of the sensor and controls the operation of the actuator based on the detection result of the sensor.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present disclosure relates to a control system and method for a work machine. [Background technology]

[0002] In a work machine equipped with a work implement including a bucket at the front of the vehicle body, mud and other debris may adhere to the bucket during work using the bucket. In order to remove the debris from the bucket, the work machine may perform an operation to quickly vibrate the bucket (hereinafter referred to as "bucket swing" in this specification). U.S. Patent No. 10,597,845 (Patent Document 1) discloses a work implement vibration system for a vehicle equipped with a work implement. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] U.S. Patent No. 10,597,845 Summary of the Invention [Problem to be solved by the invention]

[0004] In a work machine, if the bucket is swung while the vehicle body is unstable, the load on the vehicle body may increase.

[0005] The present disclosure proposes a control system and a control method for a work machine that enables a bucket swinging operation and reduces the load on the vehicle body. [Means for solving the problem]

[0006] A control system for a work machine according to one aspect of the present disclosure includes a rear frame, a front frame connected to the rear frame so as to be able to flex, a bucket movable relative to the front frame, an actuator for driving the bucket, a sensor for detecting the relative position of the rear frame and the front frame, and a controller for controlling the actuator, wherein the controller receives input of detection results from the sensor and controls operation of the actuator based on the detection results from the sensor. [Effects of the Invention]

[0007] The work machine control system and control method disclosed herein enable the bucket swinging operation and reduce the load on the vehicle body. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a side view of a wheel loader as an example of a work machine based on an embodiment. FIG. [Figure 2] FIG. 1 is a schematic block diagram showing the configuration of an entire system including a wheel loader. [Figure 3] FIG. 1 is a schematic plan view of a wheel loader in an articulated state. [Figure 4] FIG. 2 is a block diagram showing the functional configuration of a work machine controller. [Figure 5] FIG. 10 is a diagram illustrating a conventional bucket swing operation control. [Figure 6] 10A and 10B are diagrams illustrating control of a bucket swinging operation according to an embodiment. [Figure 7] FIG. 10 is a diagram showing the rate of change of the flow rate of hydraulic oil supplied to the bucket cylinder with respect to the articulation angle. [Figure 8] FIG. 10 is a diagram showing the flow rate of hydraulic oil supplied to the bucket cylinder during the bucket swing operation. [Figure 9] FIG. 10 is a diagram showing the flow rate of hydraulic oil supplied to the bucket cylinder during an operation of vibrating the bucket at a low speed. [Figure 10]FIG. 10 is a block diagram showing the functional configuration of a work machine controller according to a second embodiment. [Figure 11] FIG. 11 is a diagram showing the maximum allowable flow rate of hydraulic oil supplied to a bucket cylinder relative to the articulation angle in the third embodiment. [Figure 12] FIG. 11 is a diagram showing the flow rate of hydraulic oil supplied to the bucket cylinder during a bucket swinging operation in the third embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, an embodiment will be described with reference to the drawings. In the following description, the same components are denoted by the same reference numerals. The names and functions of the components are also the same. Therefore, detailed description thereof will not be repeated.

[0010] [First embodiment] <Overall configuration of wheel loader 1> In the embodiment, a wheel loader 1 will be described as an example of a work machine. Fig. 1 is a side view of a wheel loader 1 as an example of a work machine based on the embodiment.

[0011] As shown in Fig. 1, the wheel loader 1 comprises a body frame 2, a work implement 3, a traveling device 7, and a cab 5. The body frame 2, the cab 5, etc. make up the body (work machine body) of the wheel loader 1. The work implement 3 and the traveling device 7 are attached to the body of the wheel loader 1.

[0012] The traveling device 7 allows the body of the wheel loader 1 to travel, and includes traveling wheels 7A, 7B. The wheel loader 1 is a wheeled vehicle equipped with traveling wheels 7A, 7B on both the left and right sides of the body as rotating bodies for traveling. The wheel loader 1 is self-propelled by driving the traveling wheels 7A, 7B to rotate, and can perform desired work using the work implement 3.

[0013] In this specification, the direction in which the wheel loader 1 travels straight ahead is referred to as the fore-and-aft direction of the wheel loader 1. In the fore-and-aft direction of the wheel loader 1, the side on which the work implement 3 is arranged relative to the body frame 2 is referred to as the front direction, and the side opposite the front direction is referred to as the rear direction. The left-and-right direction of the wheel loader 1 is the direction perpendicular to the fore-and-aft direction when the wheel loader 1 is viewed from above on flat ground. Looking forward, the right and left sides of the left-and-right direction are the right direction and the left direction, respectively. The up-and-down direction of the wheel loader 1 is the direction perpendicular to the plane defined by the fore-and-aft direction and the left-and-right direction. In the up-and-down direction, the side with the ground is the bottom side, and the side with sky is the top side.

[0014] The vehicle body frame 2 includes a front frame 2A and a rear frame 2B. The front frame 2A is located in front of the rear frame 2B. The front frame 2A is connected to the rear frame 2B so that it can be bent. The front frame 2A and rear frame 2B make up the vehicle body frame 2 with an articulated structure. The wheel loader 1 is an articulated work machine in which the front frame 2A and rear frame 2B are connected.

[0015] A work implement 3 and a pair of left and right running wheels (front wheels) 7A are attached to the front frame 2A. The work implement 3 is disposed at the front of the vehicle body and is supported by the vehicle body of the wheel loader 1. The work implement 3 includes a boom 32 and a bucket 31. The bucket 31 is disposed at the tip of the work implement 3. The bucket 31 is a working tool for excavating and loading.

[0016] The work implement 3 includes boom cylinders 36. The front frame 2A and the boom 32 are connected by a pair of boom cylinders 36. The base ends of the boom cylinders 36 are attached to the front frame 2A. The tip ends of the boom cylinders 36 are attached to the boom 32. The boom cylinders 36 are hydraulic actuators that move the boom 32 up and down relative to the front frame 2A. As the boom 32 moves up and down, the bucket 31 attached to the tip of the boom 32 also moves up and down.

[0017] The work implement 3 further includes a bell crank 33, a connecting link 34, and a bucket cylinder 35. The bell crank 33 is rotatably supported on the boom 32 at approximately the center of the boom 32. The bucket cylinder 35 connects the bell crank 33 to the front frame 2A. The connecting link 34 is connected to the tip of the bell crank 33. The connecting link 34 connects the bell crank 33 to the bucket 31.

[0018] The base end of the bucket cylinder 35 is attached to the front frame 2A. The tip end of the bucket cylinder 35 is attached to the base end of the bell crank 33. The bucket cylinder 35 is a hydraulic actuator that rotates the bucket 31 up and down relative to the boom 32. The bucket cylinder 35 is an implement cylinder that drives the bucket 31. The bucket 31 is configured to be movable relative to the boom 32. The bucket 31 is configured to be movable relative to the front frame 2A.

[0019] A cab 5 in which an operator sits and a pair of left and right running wheels (rear wheels) 7B are attached to the rear frame 2B. The box-shaped cab 5 is disposed behind the boom 32. The cab 5 is mounted on the body frame 2. A seat in which the operator sits, operating devices described below, and the like are disposed within the cab 5. The cab 5 may be mounted on the front frame 2A.

[0020] <System configuration> 2 is a schematic block diagram showing the configuration of an entire system including a wheel loader 1 according to an embodiment. The wheel loader 1 includes a work machine controller 10, an engine 11, and a power take-off (PTO) 12.

[0021] The engine 11 is a drive source, such as a diesel engine, that generates drive power for driving the work implement 3. The output of the engine 11 is controlled by adjusting the amount of fuel injected into the cylinder of the engine 11. The PTO 12 distributes the output of the engine 11 to a traveling system that drives the traveling device 7 and a hydraulic system that drives the work implement 3. The engine 11, PTO 12, and hydraulic system are mounted on the rear frame 2B behind the cab 5.

[0022] The hydraulic system is a mechanism for mainly driving the work implement 3 (for example, the boom 32 and bucket 31). The hydraulic system includes a hydraulic pump 21 for the work implement driven by the PTO 12, a hydraulic pilot type bucket operation valve 22 and a boom operation valve 23 provided in the discharge circuit of the hydraulic pump 21, electromagnetic proportional control valves 24 and 25 for the bucket connected to the respective pilot pressure receiving portions of the bucket operation valve 22, and electromagnetic proportional control valves 26 and 27 for the boom connected to the respective pilot pressure receiving portions of the boom operation valve 23.

[0023] The work implement 3 is driven by hydraulic oil from the hydraulic pump 21. The hydraulic pump 21 is driven by the engine 11 and operates the work implement 3 by the hydraulic oil it discharges. The boom cylinder 36 receives a supply of hydraulic oil from the hydraulic pump 21 and extends and contracts, causing the boom 32 to rise and fall. The bucket cylinder 35 receives a supply of hydraulic oil from the hydraulic pump 21 and extends and contracts, causing the bucket 31 to rotate up and down.

[0024] The electromagnetic proportional control valves 24 to 27 are connected to a pilot pump (not shown) and control the supply of hydraulic oil from the pilot pump to each pilot pressure receiving part of the boom operating valve 23 and the bucket operating valve 22 in response to a control signal from the work machine controller 10.

[0025] Specifically, the electromagnetic proportional control valve 24 contracts the bucket cylinder 35 and switches the bucket operating valve 22 so that the bucket 31 moves in the dump direction (the direction in which the cutting edge of the bucket 31 moves down). In addition, the electromagnetic proportional control valve 25 expands the bucket cylinder 35 and switches the bucket operating valve 22 so that the bucket 31 moves in the tilt direction (the direction in which the cutting edge of the bucket 31 moves up).

[0026] The electromagnetic proportional control valve 26 switches the boom operation valve 23 so that the boom cylinder 36 is retracted and the boom 32 is lowered. In addition, the electromagnetic proportional control valve 27 switches the boom operation valve 23 so that the boom cylinder 36 is extended and the boom 32 is raised.

[0027] The work machine controller 10 is connected to an operation device, a boom angle sensor 44, a bucket angle sensor 45, a boom bottom pressure sensor 46, and a frame angle sensor 47. The operation device is provided in the cab 5. The operation device includes a boom operation lever 41 and a bucket operation lever 42. The operation device also includes a steering handle, a steering lever, an accelerator pedal, etc., which are not shown.

[0028] The boom operation lever 41 is disposed, for example, on the right side of the seat inside the cab 5. The boom operation lever 41 incorporates a lever angle sensor that detects the lever angle. The boom operation lever 41 can be manually operated by the operator to operate the boom 32. When the operator operates the boom operation lever 41, the lever angle sensor detects the lever angle corresponding to the amount of operation and outputs the detected lever angle to the work machine controller 10 as a boom lever signal.

[0029] Bucket operation lever 42 is disposed, for example, on the right side of the seat inside cab 5. Bucket operation lever 42 has a built-in lever angle sensor that detects the lever angle. Bucket operation lever 42 can be manually operated by the operator to operate bucket 31. When the operator operates bucket operation lever 42, the lever angle sensor detects the lever angle corresponding to the amount of operation and outputs the detected lever angle to work machine controller 10 as a bucket lever signal.

[0030] The boom operation lever 41 and the bucket operation lever 42 may be configured as separate levers. Alternatively, one lever may have the functions of both the boom operation lever 41 and the bucket operation lever 42. For example, operation of the lever in the forward and backward directions may be set to operate to move the boom 32 up and down, and operation of the lever in the left and right directions may be set to operate to rotate the bucket 31.

[0031] The boom angle sensor 44 is configured, for example, by a rotary encoder provided at the attachment portion (support shaft) of the boom 32 to the body frame 2, and detects the boom angle between the center line of the boom 32 and the horizontal line and outputs a detection signal. Here, the center line of the boom 32 is line YY in FIG. 2, which is a line connecting the attachment portion (center of the support shaft) of the boom 32 to the body frame 2 and the attachment portion (center of the bucket support shaft) of the bucket 31. When line YY in FIG. 2 is along the horizontal line, the boom angle sensor 44 outputs a boom angle of 0 degrees. When the tip of the boom 32 is raised from a boom angle of 0 degrees, the boom angle sensor 44 outputs a positive value, and when the tip of the boom 32 is lowered, the boom angle sensor 44 outputs a negative value.

[0032] Bucket angle sensor 45 is composed of, for example, a rotary encoder provided on the rotation shaft of bell crank 33, and outputs 0 degrees when the cutting edge of bucket 31 is horizontal to the ground with bucket 31 in place, outputs a positive value when bucket 31 is moved in the tilt direction (upward), and outputs a negative value when bucket 31 is moved in the dump direction (downward).

[0033] The boom bottom pressure sensor 46 detects the pressure (boom bottom pressure) on the bottom side of the boom cylinder 36. The boom bottom pressure increases when the bucket 31 is loaded and decreases when the bucket 31 is empty.

[0034] The frame angle sensor 47 is provided in a bending mechanism that bends the front frame 2A relative to the rear frame 2B. The frame angle sensor 47 detects the relative position between the rear frame 2B and the front frame 2A. The front frame 2A is bent relative to the rear frame 2B by extending and contracting an articulation cylinder connected to the front frame 2A and the rear frame 2B. The articulation cylinder is a hydraulic actuator that is hydraulically driven and changes the angle at which the front frame 2A is bent relative to the rear frame 2B.

[0035] Figure 3 is a schematic plan view of the wheel loader 1 in an articulated state. The frame angle sensor 47 detects the articulation angle shown in Figure 3, which is the angle at which the front frame 2A is bent relative to the rear frame 2B, and outputs a detection signal to the work machine controller 10. When the wheel loader 1 is in a straight-ahead state, the frame angle sensor 47 outputs an articulation angle of 0 degrees.

[0036] <Configuration of work machine controller 10> Fig. 4 is a block diagram showing the functional configuration of the work machine controller 10. As shown in Fig. 4, the work machine controller 10 mainly includes a bucket cylinder target flow rate calculation unit 51, a bucket swing frequency limiting unit 52, a bending angle reading unit 53, and an EPC current determination unit 54.

[0037] The bucket cylinder target flow rate calculation unit 51 receives as input a bucket lever signal indicating the detection result of the operation amount of the bucket operation lever 42 from the lever angle sensor of the bucket operation lever 42. Based on the bucket lever signal, the bucket cylinder target flow rate calculation unit 51 calculates the target flow rate of hydraulic oil to be supplied to the bucket cylinder 35 for driving the bucket 31. The bucket cylinder target flow rate calculation unit 51 outputs the calculated target flow rate of hydraulic oil to the bucket swing frequency limiting unit 52.

[0038] The bending angle reading unit 53 receives an input of a signal indicating the detection result of the articulation angle, which is the angle at which the front frame 2A bends with respect to the rear frame 2B, from the frame angle sensor 47. The bending angle reading unit 53 reads the articulation angle based on the signal input from the frame angle sensor 47. The bending angle reading unit 53 outputs the detection result of the articulation angle to the bucket swing frequency limiting unit 52.

[0039] The bucket swing frequency limiting unit 52 controls the operation of the bucket cylinder 35 in response to the operation of the bucket operating lever 42 based on the detection result of the articulation angle. Specifically, the bucket swing frequency limiting unit 52 changes the limit value for the movement of the bucket 31 in accordance with the magnitude of the articulation angle. More specifically, the bucket swing frequency limiting unit 52 reduces the allowable number of bucket swing operations per unit time, which cause the bucket 31 to vibrate more quickly, the larger the articulation angle. The bucket swing frequency limiting unit 52 changes the maximum frequency at which the operator can operate the bucket operating lever 42 to perform the bucket swing operation, in accordance with the articulation angle. The bucket swing frequency limiting unit 52 determines a command flow rate of hydraulic oil supplied to the bucket cylinder 35 in accordance with the magnitude of the articulation angle, and outputs the command flow rate to the EPC current determining unit 54.

[0040] The EPC current determination unit 54 determines a control signal (EPC current) according to the command flow rate of hydraulic oil to be supplied to the bucket cylinder 35. The EPC current determination unit 54 outputs an EPC current to the bucket electromagnetic proportional control valves 24, 25 connected to the bucket operation valve 22.

[0041] <Bucket swing operation control> Fig. 5 is a diagram showing conventional bucket swing operation control, in which the horizontal axis represents the articulation angle and the vertical axis represents the frequency (number of operations per second) at which the operator operates bucket operating lever 42.

[0042] The dashed line in Figure 5 indicates the limit frequency at which swinging the bucket causes the body of the wheel loader 1 to resonate in the roll direction. When the bucket is swung while the front frame 2A is bent relative to the rear frame 2B, a reaction force in the roll direction is applied to the rear frame 2B from the bucket 31 through the boom 32, bucket cylinder 35, and front frame 2A, causing the rear frame 2B to swing in the roll direction.

[0043] In the wheel loader 1, the vehicle body is long in the front-to-rear direction, so the impact of vibration in the pitch direction is small, but the width of the vehicle body in the left-to-right direction is short, so the impact of vibration in the roll direction is large. For this reason, the wheel loader 1 generally has a higher natural frequency for vibration in the roll direction than in the pitch direction. Because the vibration in the roll direction of the wheel loader 1 vehicle body is close to the frequency of the vibration of the bucket 31, the vehicle body is more likely to resonate with the vibration of the bucket 31. As a result, the vibration in the roll direction of the wheel loader 1 vehicle body is more likely to be larger than that in the pitch direction. As shown in Figure 5, the greater the articulation angle, the smaller the limit frequency at which the vehicle body of the wheel loader 1 resonates in the roll direction in response to bucket swing.

[0044] The solid line in Figure 5 shows the conventional limit value for the frequency at which the operator operates the bucket operation lever 42. Conventionally, the allowable number of bucket vibration operations per unit time was set constant, regardless of the magnitude of the articulation angle. Even when the articulation angle was sufficiently small and the possibility of resonance was low, the movement of the bucket 31 was restricted, making it difficult to remove deposits from the bucket 31 by swinging the bucket, reducing workability. Furthermore, when the articulation angle was large, operation at a frequency higher than the limit frequency at which resonance occurred was permitted, which could cause the vehicle body to vibrate significantly in the roll direction.

[0045] Figure 6 is a diagram showing control of the bucket swing operation in an embodiment. As in Figure 5, the horizontal axis of Figure 6 represents the articulation angle, and the vertical axis of Figure 6 represents the frequency (number of operations per second) at which the operator operates the bucket operating lever 42. As in Figure 5, the dashed line in Figure 6 represents the limit frequency at which the body of the wheel loader 1 resonates in the roll direction due to bucket swinging.

[0046] The solid line in FIG. 6 indicates the limit value of the frequency at which the operator operates the bucket operation lever 42 in this embodiment. As shown in FIG. 6, in this embodiment, the limit value of the movement of the bucket 31 is changed according to the magnitude of the articulation angle. The maximum frequency at which the bucket operation lever 42 can be operated to swing the bucket is changed according to the articulation angle. Specifically, the larger the articulation angle, the smaller the allowable number of bucket swings per unit time. To avoid resonance, the allowable number of bucket swings is set smaller than the resonating frequency shown by the dashed line in FIG. 6, with a margin for error.

[0047] When the wheel loader 1 is traveling straight, resonance is unlikely to occur, so high-frequency bucket swing is permitted. This makes it possible to efficiently remove deposits from the bucket 31. If the bucket is swung while the front frame 2A is bent relative to the rear frame 2B, there is a possibility that the rear frame 2B will resonate in the roll direction at a lower frequency, so the frequency at which the bucket can swing is lowered according to the angle of the vehicle frame. By limiting the movement of the bucket 31 when the articulation angle is large, it is possible to suppress resonance in the vehicle body, thereby reducing the load on the vehicle body.

[0048] The relationship diagram between the articulation angle and the bucket swing frequency shown in Fig. 6 is stored in advance in the work machine controller 10 (Figs. 2 and 4). The bending angle reading unit 53 receives as input the detection result of the frame angle sensor 47 from the frame angle sensor 47. The bucket cylinder target flow rate calculation unit 51 receives as input the detection result of the operation amount of the bucket operating lever 42 from the bucket operating lever 42. The bucket swing frequency limiting unit 52 reads out the allowable number of bucket swings per unit time based on the articulation angle from the pre-stored relationship diagram shown in Fig. 6. When the number of bucket swings per unit time in accordance with the operation of the bucket operating lever 42 is greater than the allowable number based on the articulation angle, the bucket swing frequency limiting unit 52 limits the operation of the bucket cylinder 35 so that the amplitude of vibration of the bucket 31 is smaller than the operation of the bucket operating lever 42.

[0049] 7 is a diagram showing the rate of change of the flow rate of hydraulic oil supplied to the bucket cylinder 35 relative to the articulation angle. Changing the upper limit of the swing frequency of the bucket 31 in accordance with the articulation angle can be achieved, for example, by limiting the rate of change of the flow rate of hydraulic oil supplied to the bucket cylinder 35.

[0050] For example, a table shown in FIG. 7 showing the possible bucket swing frequencies and the allowable values ​​of the rate of change of the flow rate of hydraulic oil supplied to the bucket cylinder 35 when the articulation angle is 0 degrees, 20 degrees, and 40 degrees is stored in advance in the work machine controller 10.

[0051] The larger the articulation angle, the smaller the rate of change of the flow rate of hydraulic oil supplied to the bucket cylinder 35. When the articulation angle is 0 degrees, in a straight-ahead state, the bucket swing frequency is set to a relatively large value of "large," and the allowable value for the rate of change of the flow rate of hydraulic oil is also set to a relatively large value of "large." When the articulation angle is an intermediate value of 20 degrees, the bucket swing frequency is set to an intermediate value of "medium," and the allowable value for the rate of change of the flow rate of hydraulic oil is also set to a relatively small value of "medium." When the articulation angle is the maximum of 40 degrees, the bucket swing frequency is set to a relatively small value of "small," and the allowable value for the rate of change of the flow rate of hydraulic oil is also set to a relatively small value of "small."

[0052] In practice, specific values ​​of the bucket swing frequency and the allowable flow rate change rate for articulation angles of 0 degrees, 20 degrees, and 40 degrees are stored in advance in the work machine controller 10. When the articulation angle is greater than 0 degrees and less than 20 degrees, and greater than 20 degrees and less than 40 degrees, specific values ​​of the bucket swing frequency and the allowable flow rate change rate are determined by linear interpolation. Note that the bucket swing frequency is a setting value related to the operation of the bucket operating lever 42 by the operator, and is therefore set to a value of about several hertz.

[0053] Fig. 8 is a diagram showing the flow rate of hydraulic oil supplied to the bucket cylinder 35 during the bucket swing operation. The horizontal axis of Fig. 8 represents time, and the vertical axis of Fig. 8 represents the flow rate of hydraulic oil supplied to the bucket cylinder 35. "0%" in Fig. 8 indicates a state in which the bucket operating lever 42 is in the neutral position, the bucket 31 is stopped, and the supply of hydraulic oil to the bucket cylinder 35 has stopped.

[0054] The positive direction of the vertical axis in FIG. 8 indicates the flow rate of hydraulic oil supplied to the bottom-side oil chamber of the bucket cylinder 35 to move the bucket 31 in the tilt direction. "+100%" in FIG. 8 is the maximum value of the flow rate of hydraulic oil supplied to the bucket cylinder 35 to move the bucket 31 in the tilt direction. The negative direction of the vertical axis in FIG. 8 indicates the flow rate of hydraulic oil supplied to the head-side oil chamber of the bucket cylinder 35 to move the bucket 31 in the dump direction. "-100%" in FIG. 8 is the maximum value of the flow rate of hydraulic oil supplied to the bucket cylinder 35 to move the bucket 31 in the dump direction.

[0055] The dashed line in Fig. 8 indicates the target flow rate of hydraulic oil that is determined by the operator's operation of bucket operation lever 42. The target flow rate of hydraulic oil indicated by the dashed line in Fig. 8 is the flow rate of hydraulic oil that is calculated by bucket cylinder target flow rate calculation unit 51 and input from bucket cylinder target flow rate calculation unit 51 to bucket swing frequency limiting unit 52.

[0056] The solid line in Fig. 8 indicates the command flow rate of hydraulic oil after the rate of change of the flow rate of hydraulic oil has been limited. The command flow rate of hydraulic oil indicated by the solid line in Fig. 8 is the flow rate of hydraulic oil that is limited by bucket swing frequency limiting unit 52 and input from bucket swing frequency limiting unit 52 to EPC current determining unit 54. A control signal based on the command flow rate shown in Fig. 8 is output from EPC current determining unit 54 to electromagnetic proportional control valves 24, 25.

[0057] When swinging the bucket, the operator typically alternates between operating the bucket operating lever 42 to the maximum amount to move the bucket 31 in the tilt direction and operating the bucket operating lever 42 to the maximum amount to move the bucket 31 in the dump direction. In FIG. 8 , the operator starts operating the bucket operating lever 42, which is in the neutral position, in the tilt direction at time T1. When the operator reaches the maximum amount of operation in the tilt direction at time T2, he immediately reduces the amount of operation in the tilt direction. When the amount of operation in the tilt direction reaches zero at time T3 and the bucket operating lever 42 enters the neutral state, the operator starts operating it in the dump direction. When the operator reaches the maximum amount of operation in the dump direction at time T4, he immediately reduces the amount of operation in the dump direction.

[0058] The command flow rate of hydraulic oil, shown by the solid line in FIG. 8, is controlled so as to approach the target flow rate, shown by the dashed line. The rate of change of the flow rate of hydraulic oil supplied to the bucket cylinder 35 is limited, and the slope of the graph of the command flow rate, shown by the solid line in FIG. 8, is limited. At time T1, operation of the bucket operation lever 42 begins, and the command flow rate of hydraulic oil also begins to increase, but the command flow rate is smaller than the target flow rate. Even when the operation amount of the bucket operation lever 42 begins to decrease at time T2, the command flow rate continues to increase because it is still smaller than the target flow rate. The command flow rate continues to increase until the target flow rate and the command flow rate match at time T5. After time T5, the target flow rate becomes smaller than the command flow rate, so the command flow rate decreases to approach the target flow rate.

[0059] At time T3, the amount of operation in the tilt direction by the operator becomes zero, and the commanded flow rate continues to decrease after time T3. When the commanded flow rate in the tilt direction becomes zero at time T6, the bucket operation lever 42 is being operated in the dump direction and the target flow rate in the dump direction has been calculated, so the commanded flow rate of hydraulic oil also begins to increase in the dump direction. Even when the amount of operation of the bucket operation lever 42 begins to decrease at time T4, the commanded flow rate continues to increase because the commanded flow rate is still smaller than the target flow rate. The commanded flow rate continues to increase until the target flow rate and the commanded flow rate match at time T7. After time T7, the target flow rate becomes smaller than the commanded flow rate, so the commanded flow rate decreases to approach the target flow rate.

[0060] By controlling the command flow rate in this way, the amplitude A of the command flow rate shown in FIG. 8 is smaller than the amplitude of the target flow rate calculated based on the operation of the bucket operating lever 42 by the operator. Therefore, the amount of movement of the bucket 31 is reduced. The operator notices that the amplitude of the movement of the bucket 31 is small, and the operation of the bucket operating lever 42 Too fast You can recognize this.

[0061] Fig. 9 is a diagram showing the flow rate of hydraulic oil supplied to the bucket cylinder 35 during the operation of vibrating the bucket at a low speed. As in Fig. 8, the horizontal axis of Fig. 9 indicates time, and the vertical axis of Fig. 9 indicates the flow rate of hydraulic oil supplied to the bucket cylinder 35. The dashed line in Fig. 9 indicates the target flow rate of hydraulic oil determined by the operation of the bucket operating lever 42 by the operator, and 9 The solid line in the middle indicates the commanded hydraulic oil flow rate after limiting the rate of change of the hydraulic oil flow rate.

[0062] In the example shown in Fig. 8, the limit on the rate of change of the hydraulic oil flow rate caused a deviation between the target flow rate of the hydraulic oil and the command flow rate, and the amplitude of the command flow rate decreased, but this does not necessarily mean that a deviation will occur between the target flow rate and the command flow rate. The limit on the rate of change of the hydraulic oil flow rate sets an upper limit on the rate of change, so a rate of change smaller than the limit is allowed.

[0063] In the example shown in FIG. 9, the operator operates bucket operation lever 42 slowly, and the rate of change of the target flow rate of hydraulic oil calculated based on the operation of bucket operation lever 42 is smaller than the limit on the rate of change of the commanded flow rate. In this case, the commanded flow rate after the flow rate change rate limit is set equal to the target flow rate. The amplitude A0 of the commanded flow rate shown in FIG. 9 is equal to the amplitude of the target flow rate. In this way, if the operator operates bucket operation lever 42 slowly, it is possible to reciprocate bucket 31 in accordance with the operator's operation. This prevents the control that limits the rate of change of the flow rate of hydraulic oil from interfering with excavation work.

[0064] <Action and effect> The characteristic configurations and effects of the above-described embodiment will be summarized as follows.

[0065] 4, the work machine controller 10 receives input of the detection result from a frame angle sensor 47 that detects the relative position between the rear frame 2B and the front frame 2A. The work machine controller 10 controls the operation of the bucket cylinder 35 based on the detection result of the relative position between the rear frame 2B and the front frame 2A. The work machine controller 10 sets limits on the operation of the bucket cylinder 35 based on the detection result of the relative position between the rear frame 2B and the front frame 2A.

[0066] In the articulated state where the front frame 2A bends relative to the rear frame 2B, the movement of the bucket 31 is restricted. The limit value of the bucket 31 movement is changed according to the magnitude of the articulation angle, thereby reducing the amplitude of the bucket 31. This reduces the reaction force acting on the rear frame 2B, thereby reducing the rolling vibration of the rear frame 2B and suppressing resonance between the vibration of the bucket 31 and the vibration of the rear frame 2B. This reduces the load on the structure, including the body frame and exterior, and extends the life of the structure.

[0067] The cab 5 is mounted on the rear frame 2B, and the operator sits in the cab 5 to operate the wheel loader 1. Reducing the rolling motion of the rear frame 2B prevents the body of the operator inside the cab 5 from being swayed from side to side, thereby reducing operator fatigue.

[0068] On the other hand, when an operator remotely operates the wheel loader 1, it is difficult for the operator to feel how much the vehicle body is shaking because the operator is not inside the cab 5. Even in the case of a work machine with remote operation specifications, it is possible to limit rapid bucket swings that would place a load on the vehicle body structures, thereby improving the lifespan of the structures.

[0069] The operating device includes a steering lever for bending the front frame 2A relative to the rear frame 2B. When the operator tilts the steering lever left or right to bend the front frame 2A, lateral acceleration is applied to the steering lever as the rear frame 2B sways left or right. This can cause unintended changes in the bending of the front frame 2A relative to the rear frame 2B. Furthermore, when the operator tilts the lever left or right to operate the bucket 31, lateral acceleration is applied to the lever as the rear frame 2B sways left or right, which can cause the bucket 31 to continue vibrating against the operator's intention. Reducing the roll sway of the rear frame 2B can suppress left-right sway of the lever, thereby preventing the wheel loader 1 from operating in a way that is different from the operator's intention.

[0070] As shown in Fig. 6, the work machine controller 10 may limit the allowable number of times per unit time that the bucket 31 can be vibrated, decreasing the allowable number of times per unit time as the articulation angle at which the front frame 2A bends relative to the rear frame 2B increases. This allows the bucket to swing when the articulation angle is small and the vehicle is traveling straight, making it possible to quickly remove deposits from the bucket 31. By changing the maximum frequency at which the bucket operating lever 42 can be operated to swing the bucket in accordance with the articulation angle and limiting bucket swing when the articulation angle is large, it is possible to reduce the sway of the vehicle body in the roll direction and reduce the load on the vehicle body.

[0071] 7, as a method for limiting the allowable number of operations per unit time that cause the bucket 31 to vibrate, the work machine controller 10 may limit the rate of change in the flow rate of hydraulic oil supplied to the bucket cylinder 35. By limiting the rate of change in the flow rate of hydraulic oil that extends and retracts the bucket cylinder 35, the acceleration of the bucket 31 can be limited, and therefore bucket swing can be reliably limited.

[0072] 7, the work machine controller 10 may decrease the rate of change in the flow rate of hydraulic oil supplied to the bucket cylinder 35 as the articulation angle increases. In this way, the bucket swinging motion can be limited when the articulation angle is large, and the shaking of the vehicle body in the roll direction can be reliably reduced.

[0073] As shown in Fig. 2, the work machine controller 10 receives input of the operation of the bucket operation lever 42 by the operator to operate the bucket 31. As shown in Fig. 8, the work machine controller 10 may impose restrictions on the operation of the bucket cylinder 35 in response to the operation of the bucket operation lever 42. When the operator suddenly operates the bucket 31 to vibrate in an articulated state, the bucket 31 is prevented from moving in accordance with the operation of the bucket operation lever 42. This makes it possible to limit bucket swing and reduce the amplitude of the bucket 31.

[0074] 8, the work machine controller 10 may set the command flow rate of hydraulic oil actually supplied to the bucket cylinder 35 to be smaller than the target flow rate of hydraulic oil to the bucket cylinder 35 calculated based on the operation of the bucket operation lever 42. By controlling the command flow rate so that it follows the target flow rate of hydraulic oil and setting a limit on the rate of change of the command flow rate, it is possible to reduce the amplitude of the bucket 31 when the bucket swings.

[0075] <Other variations> In the description of the embodiment, the rate of change of the hydraulic oil flow rate is equally limited in four cases: an increase and a decrease in the hydraulic oil flow rate in the tilt direction, and an increase and a decrease in the hydraulic oil flow rate in the dump direction. However, the limit on the rate of change of the flow rate may be different. For example, the allowable value of the rate of change of the flow rate when the hydraulic oil flow rate increases in the tilt direction and the dump direction may be smaller than the allowable value of the rate of change of the flow rate when the hydraulic oil flow rate decreases in the tilt direction and the dump direction. The rate of change of the flow rate may be limited when the hydraulic oil flow rate increases in the tilt direction and the dump direction, while the rate of change of the flow rate may not be limited when the hydraulic oil flow rate decreases in the tilt direction and the dump direction, and the hydraulic oil flow rate may be reduced in accordance with the operation of the bucket control lever 42 by the operator.

[0076] In the description of the embodiment, an example has been shown in which the work machine controller 10 limits the rate of change of the flow rate of hydraulic oil supplied to the bucket cylinder 35 as a method for limiting the allowable number of operations that vibrate the bucket 31 per unit time, but the present invention is not limited to this example. A low-pass filter may be applied to the operation of the bucket operating lever 42 instead of the bucket swing frequency limiting unit 52 shown in FIG. 4. By changing the cutoff frequency of the low-pass filter in accordance with the articulation angle, more specifically, by lowering the cutoff frequency as the articulation angle increases, it is possible to limit the bucket swing operation when the articulation angle is large and reliably reduce shaking of the vehicle body in the roll direction.

[0077] Alternatively, the cycle of operation of bucket operating lever 42 may be measured, and control may be exercised to stop bucket 31 when operation at a frequency above a certain level is detected. The frequency of operation of bucket operating lever 42, which serves as a threshold for stopping bucket 31, may be varied according to the articulation angle. By limiting the maximum frequency at which bucket 31 can be operated when the articulation angle is large, it is possible to reliably reduce shaking of the vehicle body in the roll direction.

[0078] The work machines to which the concepts of the present disclosure can be applied are not limited to wheel loaders, but may also be other types of work machines, such as hydraulic excavators with offset booms or swing booms in which the bucket can move left and right relative to the rotating frame.

[0079] [Second embodiment] In the first embodiment, an example has been described in which the operator operates the bucket operation lever 42 to perform the bucket swing operation. To facilitate the removal of deposits from the bucket 31 by the bucket swing operation, control is provided to perform the bucket swing operation automatically. When the operator inputs an operation to perform automatic bucket swing, the work machine controller 10 determines a command flow rate for the bucket cylinder 35 so that the bucket swing operation is achieved at a "predetermined automatic bucket swing frequency," and determines an EPC current based on the command flow rate. In this way, the work machine controller 10 automatically achieves the bucket swing operation without the operator operating the bucket operation lever 42.

[0080] In the second embodiment, a control for determining this "predetermined automatic bucket swing frequency" in accordance with the articulation angle will be described. Fig. 10 is a block diagram showing the functional configuration of a work machine controller 10 in the second embodiment. The work machine controller 10 in the second embodiment includes an automatic bucket swing frequency determiner 152, a bucket cylinder command flow rate determiner 153, a bending angle reader 53, and an EPC current determiner 54.

[0081] 10 is configured by, for example, a switch or a touch panel, etc. The operator operates the automatic bucket swing input unit 142 to input an operation to execute the automatic bucket swing operation.

[0082] As in the first embodiment, the bending angle reading unit 53 receives an input of a signal indicating the detection result of the articulation angle from the frame angle sensor 47. The bending angle reading unit 53 outputs the detection result of the articulation angle to the automatic bucket swing frequency determination unit 152.

[0083] When the automatic bucket swing frequency determiner 152 receives an input of an operation to execute the automatic bucket swing operation from the automatic bucket swing input unit 142, it determines the frequency of vibration of the bucket 31 when performing the automatic bucket swing operation based on the detection result of the articulation angle. Specifically, the automatic bucket swing frequency determiner 152 changes the limit value of the movement of the bucket 31 depending on the magnitude of the articulation angle. More specifically, the larger the articulation angle, the smaller the number of times the bucket 31 vibrates per unit time.

[0084] For example, a plurality of combinations of articulation angles and values ​​of the automatic bucket swing frequency corresponding to those articulation angles are stored in advance as a table in the work machine controller 10. Based on that table, the automatic bucket swing frequency determination unit 152 determines the automatic bucket swing frequency corresponding to the articulation angle read by the bending angle reading unit 53. If the articulation angle differs from the value defined in the table, a specific numerical value of the automatic bucket swing frequency is determined by linear interpolation.

[0085] The bucket cylinder command flow rate determination unit 153 determines a command flow rate of hydraulic oil to be supplied to the bucket cylinder 35 according to the magnitude of the articulation angle, and outputs the determined flow rate to the EPC current determination unit 54. The EPC current determination unit 54 determines a control signal (EPC current) according to the command flow rate of hydraulic oil to be supplied to the bucket cylinder 35, and outputs the EPC current to the electromagnetic proportional control valves 24, 25 for the bucket.

[0086] [Third embodiment] In the first embodiment, an example of control that substantially prevents a fast bucket swing operation when the articulation angle is large has been described, in which the rate of change of the flow rate of hydraulic oil supplied to the bucket cylinder 35 is limited. In the third embodiment, an example of limiting the maximum flow rate of hydraulic oil supplied to the bucket cylinder 35 will be described as another form.

[0087] FIG. 11 is a diagram showing the maximum allowable flow rate of hydraulic oil supplied to the bucket cylinder 35 versus the articulation angle in the third embodiment. A table of the maximum allowable flow rate of hydraulic oil supplied to the bucket cylinder 35 when the articulation angle is 0 degrees, 20 degrees, and 40 degrees, as shown in FIG. 11, is stored in advance in the work machine controller 10. The larger the articulation angle, the smaller the maximum allowable flow rate of hydraulic oil supplied to the bucket cylinder 35. When the articulation angle is 0 degrees, in the straight-ahead state, the maximum allowable flow rate of hydraulic oil is set to a relatively large value, "large." When the articulation angle is an intermediate value of 20 degrees, the maximum allowable flow rate of hydraulic oil is set to an intermediate value, "medium." When the articulation angle is the maximum of 40 degrees, the maximum allowable flow rate of hydraulic oil is set to a relatively small value, "small."

[0088] In practice, specific values ​​of the maximum allowable flow rate of hydraulic oil for articulation angles of 0 degrees, 20 degrees, and 40 degrees are stored in advance in the work machine controller 10. When the articulation angle is greater than 0 degrees and less than 20 degrees, and greater than 20 degrees and less than 40 degrees, the specific value of the maximum allowable flow rate of hydraulic oil is determined by linear interpolation.

[0089] 12 is a diagram showing the flow rate of hydraulic oil supplied to the bucket cylinder 35 during the bucket swinging operation in the third embodiment. As with FIG. 8 described in the first embodiment, FIG. 12 The horizontal axis of Fig. 12 The vertical axis of the figure indicates the flow rate of hydraulic oil supplied to the bucket cylinder 35. 12 The "0%" in the figure indicates that the supply of hydraulic oil to the bucket cylinder 35 is stopped. 12 The positive direction of the vertical axis indicates the flow rate of hydraulic oil that moves the bucket 31 in the tilt direction. 12 The negative direction of the vertical axis indicates the flow rate of hydraulic oil that moves the bucket 31 in the dump direction.

[0090] figure 12 The dashed line in the figure indicates the target flow rate of hydraulic oil determined by the operation of the bucket operation lever 42 by the operator. 12The solid line in the figure shows the command flow rate of the hydraulic oil after the flow rate of the hydraulic oil is restricted. 12 A control signal based on the command flow rate shown in is output from the EPC current determination unit 54 to the electromagnetic proportional control valves 24 and 25.

[0091] At time T1, the operator begins operating bucket operation lever 42, which is in the neutral position, in the tilt direction. When the operator reaches the maximum amount of operation in the tilt direction at time T2, he immediately reduces the amount of operation in the tilt direction. When the amount of operation in the tilt direction reaches zero at time T3 and bucket operation lever 42 enters the neutral state, the operator begins operating the lever in the dump direction. When the operator reaches the maximum amount of operation in the dump direction at time T4, he immediately reduces the amount of operation in the dump direction.

[0092] In the third embodiment, the maximum allowable flow rate of hydraulic oil supplied to the bucket cylinder 35 is limited. At time T11, the target flow rate of hydraulic oil determined by input to the bucket operation lever 42 increases to the maximum allowable flow rate in the tilt direction. After time T11, the target flow rate becomes greater than the maximum allowable flow rate, but even in this case, the command flow rate is limited to the maximum allowable flow rate. At time T12, the target flow rate decreases to the maximum allowable flow rate, and therefore, after time T12, the command flow rate is made equal to the target flow rate. At time T13, the target flow rate increases to the maximum allowable flow rate in the dump direction. Between time T13 and time T14, the target flow rate becomes greater than the maximum allowable flow rate, but even in this case, the command flow rate is limited to the maximum allowable flow rate.

[0093] By controlling the command flow rate in this way, 12 The amplitude A of the command flow rate shown in is smaller than the amplitude of the target flow rate calculated based on the operation of the bucket operation lever 42 by the operator.

[0094] When the articulation angle is large, the maximum speed of the bucket 31 can be reduced by limiting the maximum allowable flow rate of the hydraulic oil and thereby limiting the amplitude of the operation that vibrates the bucket 31. This makes it possible to limit the bucket swing operation at high speeds.

[0095] The embodiments disclosed herein should be considered to be illustrative in all respects and not restrictive. The scope of the present invention is defined by the claims, not by the above description, and is intended to include all modifications within the meaning and scope of the claims. [Explanation of symbols]

[0096] 1 wheel loader, 2 body frame, 2A front frame, 2B rear frame, 3 work implement, 5 cab, 7 traveling device, 7A, 7B traveling wheels, 10 work implement controller, 11 engine, 21 hydraulic pump, 22 bucket operation valve, 23 boom operation valve, 24, 25, 26, 27 electromagnetic proportional control valve, 31 bucket, 32 boom, 33 bell crank, 34 connecting link, 35 bucket cylinder, 36 boom cylinder, 41 boom operation lever, 42 bucket operation lever, 44 boom angle sensor, 45 bucket angle sensor, 46 boom bottom pressure sensor, 47 frame angle sensor, 51 bucket cylinder target flow rate calculation unit, 52 bucket swing frequency limiting unit, 53 bending angle reading unit, 54 EPC current determination unit, 142 automatic bucket swing input unit, 152 automatic bucket swing frequency determination unit, 153 bucket cylinder command flow rate determination unit.

Claims

1. The rear frame and a front frame connected to the rear frame in a flexibly movable manner; a bucket movable relative to the front frame; an actuator that drives the bucket; a sensor for detecting a relative position between the rear frame and the front frame; a controller for controlling the actuator, The controller receives input of the detection results of the sensor, and controls the operation of the actuator that vibrates the bucket based on the detection results.

2. The control system for a work machine according to claim 1 , wherein the controller sets a limit on the operation of the actuator based on the detection result.

3. A rear frame, a front frame connected to the rear frame in a flexibly movable manner; a bucket movable relative to the front frame; an actuator that drives the bucket; a sensor for detecting a relative position between the rear frame and the front frame; a controller for controlling the actuator, The controller receives input of the detection results of the sensor, and sets a limit on the allowable number of times per unit time that the bucket can be vibrated, based on the detection results.

4. 4. The control system for a work machine according to claim 3, wherein the controller reduces the allowable number of operations per unit time that cause the bucket to vibrate as the angle at which the front frame bends relative to the rear frame increases.

5. A rear frame, a front frame connected to the rear frame in a flexibly movable manner; a bucket movable relative to the front frame; an actuator that drives the bucket; a sensor for detecting a relative position between the rear frame and the front frame; a controller for controlling the actuator, the actuator includes a bucket cylinder that receives a supply of hydraulic oil to drive the bucket, The controller receives input of the detection result of the sensor, and limits the rate of change of the flow rate of hydraulic oil supplied to the bucket cylinder based on the detection result.

6. 6. The control system for a work machine according to claim 5, wherein the controller reduces a rate of change in the flow rate of hydraulic oil supplied to the bucket cylinder as the angle at which the front frame bends relative to the rear frame increases.

7. A rear frame; a front frame connected to the rear frame in a flexibly movable manner; a bucket movable relative to the front frame; an actuator that drives the bucket; a sensor for detecting a relative position between the rear frame and the front frame; a controller for controlling the actuator, The controller receives input of the detection results of the sensor, and sets a limit on the amplitude of the operation that vibrates the bucket based on the detection results.

8. Further, an operating device that can be manually operated to operate the bucket is provided, The control system for a work machine according to any one of claims 2 to 7, wherein the controller imposes a limit on the operation of the actuator in response to the operation of the operating device.

9. A rear frame; a front frame connected to the rear frame in a flexibly movable manner; a bucket movable relative to the front frame; an operating device that can be manually operated to operate the bucket; an actuator that drives the bucket; a sensor for detecting a relative position between the rear frame and the front frame; a controller for controlling the actuator, the actuator includes a bucket cylinder that receives a supply of hydraulic oil to drive the bucket, The controller receives input of the detection results of the sensor, and, based on the detection results, reduces the flow rate of hydraulic oil supplied to the bucket cylinder to be less than the flow rate of hydraulic oil calculated based on the operation content of the operating device.

10. the work machine is mounted on the rear frame or the front frame and includes a cab in which an operator sits, The control system for a work machine according to claim 8 or claim 9, wherein the operating device is disposed within the cab.

11. The control system for a work machine according to any one of claims 1 to 10, wherein the work machine has rear wheels attached to the rear frame and front wheels attached to the front frame.

12. A control method for a work machine including a rear frame, a front frame connected to the rear frame so as to be able to flex, a bucket movable relative to the front frame, an actuator that drives the bucket, and a sensor that detects a relative position between the rear frame and the front frame, receiving an input of a detection result of the sensor; and controlling operation of the actuator that vibrates the bucket based on the detection result.

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