Work machine and method for controlling work machine

Abstract

The present invention suppresses vibration of a vehicle body. This work machine comprises: a vehicle body; a work machine that is attached to the vehicle body so as to be able to operate and has an attachment at a tip thereof; an operation device that outputs an operation command for operating the attachment; a vibration sensor that detects the vibration of the vehicle body; and a controller that, on the basis of the detection result of the vibration of the vehicle body generated by the work performed by the attachment, limits the operation of the attachment for the operation command.

Description

Work machine and work machine control method

[0001] The present disclosure relates to a work machine and a method for controlling a work machine.

[0002] An example of prior art is the work machine described in Japanese Patent Laid-Open No. 2021-43804 (Patent Document 1). In this work machine, an applying unit that applies force to an operating lever that operates the work equipment is controlled based on the acceleration of the vehicle body, and the magnitude of the force applied to the operating lever is automatically adjusted.

[0003] Japanese Patent Application Laid-Open No. 2021-43804

[0004] If the operating lever is shaken due to vibration of the work machine body, the input of the operating lever may be unintentionally applied to the work equipment, causing the work equipment to shake and further increasing the vibration of the body.

[0005] The present disclosure proposes a work machine and a method for controlling a work machine that can suppress vibrations of the vehicle body.

[0006] A work machine according to the present disclosure comprises a vehicle body, a work implement operably attached to the vehicle body and having an attachment at its tip, an operating device that outputs operation commands to operate the attachment, a vibration sensor that detects vibrations of the vehicle body, and a controller that sets limits on the operation of the attachment in response to the operation commands based on the detection results of vibrations of the vehicle body generated during work by the attachment.

[0007] A method for controlling a work machine according to the present disclosure includes receiving input of an operation command to operate an attachment at the tip of a work machine operably attached to a vehicle body, detecting vibrations of the vehicle body caused by work by the attachment, and setting restrictions on the operation of the attachment in response to the operation command based on the detection results of the vibrations of the vehicle body.

[0008] According to the work machine and the control method for the work machine of the present disclosure, vibrations of the vehicle body can be suppressed.

[0009] Fig. 1 is a side view of a wheel loader as an example of a work machine. Fig. 2 is a schematic block diagram showing the configuration of an entire system including the wheel loader. Fig. 3 is a schematic diagram of an operation lever. Fig. 4 is a block diagram showing the functional configuration of a work machine controller. Fig. 5 is a flowchart showing an example of bucket operation control. Fig. 6 is a first diagram showing the flow rate of hydraulic oil supplied to a bucket cylinder. Fig. 7 is a second diagram showing the flow rate of hydraulic oil supplied to a bucket cylinder.

[0010] Hereinafter, the embodiments will be described with reference to the drawings. In the following description, the same parts and components are denoted by the same reference numerals. Their names and functions are also the same. Therefore, detailed descriptions thereof will not be repeated. In the drawings, configurations may be omitted or simplified for the sake of convenience. It is also intended from the beginning that any configurations may be extracted from the embodiments and arbitrarily combined.

[0011] <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.

[0012] 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 main 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.

[0013] 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 that has 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.

[0014] 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. The right and left sides of the left-and-right direction when looking forward 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 ground is the bottom side, and the side with sky is the top side.

[0015] The vehicle body frame 2 includes a front frame 2A and a rear frame 2B. The front frame 2A is disposed in front of the rear frame 2B. The front frame 2A is connected to the rear frame 2B so as to be able to bend. The front frame 2A and rear frame 2B form 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.

[0016] 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 work tool for excavating and loading. The bucket 31 is an example of an attachment that is detachably mounted to the tip of the boom 32. Depending on the type of work, the attachment can be changed to a grapple, fork, plow, or the like.

[0017] 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. The work implement 3 is operably attached to the front frame 2A.

[0018] 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.

[0019] 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.

[0020] 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.

[0021] 2 is a schematic block diagram showing the configuration of an overall system including the wheel loader 1 according to the embodiment. The wheel loader 1 includes a work machine controller 10, an engine 11, and a power take-off (PTO) device 12.

[0022] 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.

[0023] The hydraulic system is a mechanism mainly for driving the work implement 3 (for example, the boom 32 and the 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.

[0024] The work implement 3 is driven by hydraulic oil from a 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, thereby raising and lowering the boom 32. The bucket cylinder 35 receives a supply of hydraulic oil from the hydraulic pump 21 and extends and contracts, thereby rotating the bucket 31 up and down.

[0025] The electromagnetic proportional control valves 24 to 27 are connected to a pilot pump (not shown) and control the supply of pilot oil from the pilot pump to each pilot pressure receiving portion of the boom operation valve 23 and the bucket operation valve 22 in accordance with a control signal from the work machine controller 10.

[0026] Specifically, the electromagnetic proportional control valve 24 contracts the bucket cylinder 35 and switches the bucket operation 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 operation 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).

[0027] 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.

[0028] 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 an IMU (Inertial Measurement Unit) 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.

[0029] The boom operation lever 41 is disposed, for example, on the right side of the seat in 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. The lever angle sensor generates a boom lever signal. The boom lever signal is an operation command for operating the boom 32 according to the lever angle. The lever angle sensor outputs the boom lever signal to the work machine controller 10.

[0030] The bucket operation lever 42 is disposed, for example, on the right side of the seat inside the cab 5. The bucket operation lever 42 has a built-in lever angle sensor that detects the lever angle. The bucket operation lever 42 can be manually operated by the operator to operate the bucket 31. When the operator operates the bucket operation lever 42, the lever angle sensor detects the lever angle according to the amount of operation. The lever angle sensor generates a bucket lever signal. The bucket lever signal is an operation command for operating the bucket 31 according to the lever angle. The lever angle sensor outputs the bucket lever signal to the work machine controller 10.

[0031] The boom angle sensor 44 is configured, for example, by a rotary encoder provided at an attachment portion (support shaft) of the boom 32 to the body frame 2. The boom angle sensor 44 detects the boom angle between the center line of the boom 32 and the horizontal line, and outputs a boom angle detection signal to the work machine controller 10.

[0032] Here, the center line of the boom 32 is line YY in Figure 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 Figure 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, it outputs a negative value.

[0033] Bucket angle sensor 45 is configured, for example, by a rotary encoder provided on the rotation shaft of bell crank 33. Bucket angle sensor 45 detects the bucket angle and outputs a bucket angle detection signal to work machine controller 10. Bucket angle sensor 45 outputs a bucket angle of 0 degrees when the bucket 31 is in a state where the cutting edge of the bucket 31 is horizontal to the ground with the bucket 31 in a state where the bucket 31 is in contact with the ground. Bucket angle sensor 45 outputs a positive value when the bucket 31 is moved in the tilt direction (upward), and outputs a negative value when the bucket 31 is moved in the dump direction (downward).

[0034] The boom bottom pressure sensor 46 detects the pressure on the bottom side of the boom cylinder 36 (boom bottom pressure) and outputs a boom bottom pressure detection signal to the work machine controller 10. The boom bottom pressure increases when the bucket 31 is loaded and decreases when the bucket 31 is empty.

[0035] The IMU 47 is mounted on the vehicle body of the wheel loader 1. The IMU 47 is attached to the vehicle body frame 2, for example, and detects the attitude of the vehicle body frame 2. The IMU 47 detects the acceleration and angular velocity of the vehicle body frame 2 in the front-rear, left-right, and up-down directions. The IMU 47 corresponds to an example of an acceleration sensor that detects the acceleration of the vehicle body. Since the acceleration of the vehicle body is an example of a physical quantity that represents the vibration of the vehicle body, the IMU 47 can be said to correspond to an example of a vibration sensor that detects the vibration of the vehicle body. The IMU 47 outputs a detection signal of the acceleration of the vehicle body to the work machine controller 10.

[0036] 3 is a schematic diagram of the control lever 43. The control device has the control lever 43 that can be manually operated by the operator. The control lever 43 is a multi-function lever that has the functions of both the boom control lever 41 and the bucket control lever 42. Tilting the control lever 43 in the forward / backward direction is set to operate the boom 32 up and down, and tilting the control lever 43 in the left / right direction is set to operate the bucket 31. The boom angle and bucket angle described above are set according to the angle of tilt of the control lever 43 from the neutral state.

[0037] The operating lever 43 has a base portion 52, a shaft portion 53, and an expanded diameter portion 54. The base portion 52 is attached to, for example, a right console located to the right of the seat inside the cab 5. The shaft portion 53 and the expanded diameter portion 54 can integrally move and tilt in the front-to-rear and left-to-right directions relative to the base portion 52. The expanded diameter portion 54 forms the tip of the operating lever 43. The operating lever 43 has the expanded diameter portion 54 at its tip. The shaft portion 53 has a rod-like shape. The expanded diameter portion 54 is formed with a larger diameter than the shaft portion 53. In a cross section perpendicular to the longitudinal direction of the shaft portion 53, the expanded diameter portion 54 has a larger cross-sectional area than the shaft portion 53. The weight of the tip of the operating lever 43 is relatively large. The center of gravity of the operating lever 43 is located closer to the tip than the center in the longitudinal direction.

[0038] The enlarged diameter portion 54 has at least one switch 55. The switch 55 can be operated by an operator. For example, an operator seated on the seat can operate the switch 55 with his / her right thumb while holding the shaft portion 53 with his / her right palm. The operating lever 43 is a joystick in which the lever and the switch 55 are integrated.

[0039] The switch 55 includes push button switches 56 and 57 and a rocker switch 58. The switch 55 may include other types of switches, such as a slide switch. The switch 55 may include a switch for operating a turn signal. The switch 55 may include a forward / reverse switch, a switch for operating the work implement 3, a traction control release switch, or a switch having another function. The switch 55 may be provided on the back surface of the enlarged diameter portion 54.

[0040] The operating lever 43 has an electric wire 59. The electric wire 59 extends from the inside to the outside of the operating lever 43. The electric wire 59 is disposed to pass through the shaft portion 53 and the base portion 52. One end of the electric wire 59 is electrically connected to the switch 55. The electric wire 59 transmits an electric signal generated by operating the switch 55. The electric wire 59 has a portion that is disposed inside the right console.

[0041] <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 vibration detection unit 101, a command calculation unit 102, a storage unit 108, and a timer 109.

[0042] The vibration detection unit 101 receives input of the detection result of the acceleration of the vehicle body from the acceleration sensor (IMU 47). The vibration detection unit 101 calculates the vibration of the vehicle body using the acceleration of the vehicle body. The vibration detection unit 101 calculates the vibration of the vehicle body caused by work using the bucket 31. One example of work using the bucket 31 is bucket swinging work. Bucket swinging work is work in which the bucket 31 is repeatedly moved in the dump direction and in the tilt direction, causing the bucket 31 to quickly vibrate. Bucket swinging work is performed to remove dirt and other adhering matter from the bucket 31. The vibration detection unit 101 detects that the bucket swinging work is causing large vibrations in the vehicle body that are greater than a threshold value. The vibration detection unit 101 outputs the detection result of the vibration of the vehicle body to the command calculation unit 102.

[0043] The command calculation unit 102 receives an input of an operation command for operating the bucket 31 from the operation lever 43 (bucket operation lever 42). The command calculation unit 102 basically outputs a control signal (EPC current) according to the operation command to the bucket electromagnetic proportional control valves 24, 25 connected to the bucket operation valve 22.

[0044] The command calculation unit 102 checks the vehicle body vibration detected by the vibration detection unit 101. When the command calculation unit 102 detects large vehicle body vibration, it outputs a control signal that corrects the input operation command to the electromagnetic proportional control valves 24, 25. The command calculation unit 102 determines a command flow rate of hydraulic oil to be supplied to the bucket cylinder 35 according to the magnitude of the vehicle body vibration, and outputs an EPC current according to the command flow rate to the electromagnetic proportional control valves 24, 25. The command calculation unit 102 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 vehicle body vibration. The command calculation unit 102 changes the limit value for the movement of the bucket 31 according to the magnitude of the vehicle body vibration. When the vehicle body vibration reaches a certain threshold or greater, the command calculation unit 102 imposes a limit on the movement of the bucket 31 in response to the operation command.

[0045] The command calculation unit 102 sets a limit on the amplitude of the bucket swinging operation that quickly vibrates the bucket 31. For example, the command calculation unit 102 limits the maximum flow rate of hydraulic oil supplied to the bucket cylinder 35. Alternatively, the command calculation unit 102 reduces the allowable number of bucket swings per unit time. The command calculation unit 102 changes the maximum frequency at which the operator can operate the bucket operating lever 42 to perform the bucket swing operation, depending on the magnitude of the vibration of the vehicle body.

[0046] The memory unit 108 is a non-volatile memory, and is provided as an area for storing necessary data. The memory unit 108 stores programs for controlling the various operations of the wheel loader 1, and various data required for executing those programs. The memory unit 108 also temporarily stores working data that is generated in conjunction with the operation of the wheel loader 1. The work machine controller 10 executes various processes for controlling the operation of the wheel loader 1 based on the programs stored in the memory unit 108. The timer 109 keeps track of time.

[0047] <Control of Bucket Operation> Figure 5 is a flowchart showing an example of control of bucket operation in this embodiment. As shown in Figure 5, in step S1, work machine controller 10 acquires the acceleration of the vehicle body. Vibration detection unit 101 receives an input of a detection signal of the acceleration of the vehicle body from IMU 47.

[0048] When the vehicle body vibrates, it repeatedly displaces upward and downward. Differentiating displacement with respect to time results in velocity, and differentiating velocity with respect to time results in acceleration. When the vehicle body vibrates, upward acceleration and downward acceleration act alternately on the vehicle body, and there is a moment when acceleration becomes zero. The vibration detection unit 101 converts the vehicle body acceleration input from the IMU 47 into time-series data arranged in chronological order. The vibration detection unit 101 obtains the peak value of the vehicle body acceleration from the time-series data of the vehicle body acceleration.

[0049] In step S2, the work machine controller 10 determines whether the acceleration of the vehicle body is equal to or greater than a predetermined threshold. The command calculation unit 102 reads out the threshold value of the vehicle body acceleration from the storage unit 108. The threshold value of the vehicle body acceleration is set, for example, as a value at which autonomous vibration of the vehicle body does not occur, and is stored in advance in the storage unit 108. The command calculation unit 102 compares the peak value of the vehicle body acceleration acquired in step S1 with the threshold value read out from the storage unit 108.

[0050] If the peak value of the acceleration of the vehicle body is equal to or greater than the threshold value (YES in step S2), in step S3, the work machine controller 10 determines whether or not the bucket swing state determination time t1 has elapsed. The command calculation unit 102 reads the time from the timer 109. The command calculation unit 102 starts counting time, starting from the time when it was determined in step S2 that the peak value of the acceleration of the vehicle body is equal to or greater than the threshold value and the process proceeded to step S3. The command calculation unit 102 calculates the elapsed time up to the current time. The command calculation unit 102 reads the time t1 from the memory unit 108. The command calculation unit 102 compares the elapsed time up to the current time with the time t1. The command calculation unit 102 determines whether or not the state in which the peak value of the acceleration of the vehicle body is equal to or greater than the threshold value has continued for the time t1.

[0051] If the state in which the peak value of the acceleration of the vehicle body is equal to or greater than the threshold value has not continued for the time t1 at the time of the determination in step S3 (NO in step S3), the processes in steps S1 to S3 are executed again. If it is determined in step S2 that the peak value of the acceleration of the vehicle body is equal to or greater than the threshold value, the process proceeds to step S3, where it is repeatedly determined whether the state in which the peak value of the acceleration of the vehicle body is equal to or greater than the threshold value has continued for the time t1.

[0052] If it is determined in step S3 that the peak value of the vehicle body acceleration has remained equal to or greater than the threshold value for time t1 (YES in step S3), then in step S4, work machine controller 10 corrects the input value from the operation device. Command calculation unit 102 corrects the input value of the bucket lever signal from bucket operation lever 42.

[0053] Fig. 6 is a first diagram showing the flow rate of hydraulic oil supplied to the bucket cylinder 35. The horizontal axis of Fig. 6 represents time, and the vertical axis of Fig. 6 represents the flow rate of hydraulic oil supplied to the bucket cylinder 35. "0%" in Fig. 6 indicates a state in which the bucket operation lever 42 is in the neutral position, the bucket 31 is stopped, and the supply of hydraulic oil to the bucket cylinder 35 is stopped.

[0054] The positive direction of the vertical axis in Fig. 6 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. 6 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. 6 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. 6 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. 6 indicates the target flow rate of hydraulic oil determined in accordance with the operation command output from the bucket operating lever 42. The solid line in Fig. 6 indicates the command flow rate of hydraulic oil after the flow rate of hydraulic oil has been restricted. A control signal based on the command flow rate shown in Fig. 6 is output from the command calculation unit 102 to the electromagnetic proportional control valves 24, 25.

[0056] At time T1, the bucket operation lever 42, which is in the neutral position, begins to tilt in a direction that moves the bucket 31 in the tilt direction. At time T2, the tilt of the bucket operation lever 42 reaches its maximum. After time T2, the tilt of the bucket operation lever 42 decreases. When the bucket operation lever 42 reaches the neutral state at time T3, the bucket operation lever 42 continues to tilt in that direction, moving the bucket 31 in the dump direction. At time T4, the tilt of the bucket operation lever 42 reaches its maximum. After time T4, the tilt of the bucket operation lever 42 decreases.

[0057] When the operator operates the bucket operation lever 42 to perform bucket swing work, the operator typically alternates between operating the bucket operation lever 42 to the maximum extent to move the bucket 31 in the tilt direction and operating the bucket operation lever 42 to the maximum extent to move the bucket 31 in the dump direction. In FIG. 6 , the operator starts operating the bucket operation lever 42 in the tilt direction from the neutral position 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 operation lever 42 is in the neutral state, the operator starts operating the bucket 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] In the example shown in FIG. 6 , 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 an operation command from 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 the commanded flow rate is still 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 commanded 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 the commanded flow rate is still limited to the maximum allowable flow rate.

[0059] By controlling the command flow rate in this manner, the amplitude A of the command flow rate shown in Figure 6 is smaller than the amplitude of the target flow rate calculated in accordance with the operation command input from the bucket operation lever 42. The input value of the bucket lever signal from the bucket operation lever 42 is corrected, reducing the amount of movement of the bucket 31. The amplitude of movement of the bucket 31 in the dump direction and tilt direction is reduced. The control signals output to the electromagnetic proportional control valves 24, 25 are corrected in response to the operation command output from the bucket operation lever 42, and limits are placed on the movement of the bucket 31. A limit is placed on the amplitude of the bucket swing operation.

[0060] Fig. 7 is a second diagram showing the flow rate of hydraulic oil supplied to the bucket cylinder 35. As in Fig. 6, the horizontal axis of Fig. 7 represents time, and the vertical axis of Fig. 7 represents the flow rate of hydraulic oil supplied to the bucket cylinder 35. "0%" in Fig. 7 indicates a state in which the supply of hydraulic oil to the bucket cylinder 35 is stopped. The positive direction of the vertical axis of Fig. 7 represents the flow rate of hydraulic oil that moves the bucket 31 in the tilt direction. The negative direction of the vertical axis of Fig. 7 represents the flow rate of hydraulic oil that moves the bucket 31 in the dump direction.

[0061] The dashed line in Fig. 7 indicates the target flow rate of hydraulic oil determined in accordance with the operation command output from the bucket operating lever 42. The solid line in Fig. 7 indicates the command flow rate of hydraulic oil after the rate of change of the flow rate of hydraulic oil has been limited. A control signal based on the command flow rate shown in Fig. 7 is output from the command calculation unit 102 to the electromagnetic proportional control valves 24, 25.

[0062] In the example shown in Fig. 7, 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. 7 is limited. The command flow rate of hydraulic oil shown by the solid line in Fig. 7 is controlled so as to approach the target flow rate shown by the dashed line.

[0063] At time T1, the bucket operation lever 42, which is in the neutral position, begins to tilt in a direction that moves the bucket 31 in the tilt direction. At time T1, the commanded flow rate of hydraulic oil in the tilt direction also begins to increase, but the commanded flow rate is smaller than the target flow rate. Even when the tilt of the bucket operation lever 42 begins to decrease at time T2, the commanded flow rate continues to increase because it 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 T5. After time T5, the target flow rate becomes smaller than the commanded flow rate, so the commanded flow rate decreases to approach the target flow rate.

[0064] At time T3, the bucket operation lever 42 becomes neutral. 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 tilted in a direction that moves the bucket 31 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 tilt of the bucket operation lever 42 begins to decrease at time T4, the commanded flow rate continues to increase because it 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.

[0065] By controlling the command flow rate in this manner, the amplitude A of the command flow rate shown in Figure 7 is smaller than the amplitude of the target flow rate calculated in accordance with the operation command input from the bucket operation lever 42. The input value of the bucket lever signal from the bucket operation lever 42 is corrected, reducing the amount of movement of the bucket 31. The amplitude of the movement of the bucket 31 in the dump direction and tilt direction is reduced. A limit is placed on the movement of the bucket 31 in response to the operation command output from the bucket operation lever 42. A limit is placed on the amplitude of the bucket swing operation.

[0066] Returning to FIG. 5 , in step S5, the work machine controller 10 determines whether the work machine lever filtering duration time t2 has elapsed. The command calculation unit 102 reads the time from the timer 109. The command calculation unit 102 starts counting time, starting from the time when the input value from the operating device was corrected in step S4. The command calculation unit 102 calculates the elapsed time up to the current time. The command calculation unit 102 reads the time t2 from the memory unit 108. The command calculation unit 102 compares the elapsed time up to the current time with the time t2. The command calculation unit 102 determines whether the time t2 has elapsed since the input value from the operating device was corrected.

[0067] If the time t2 has not elapsed (NO in step S5), the determination in step S5 is repeated, and the process waits until the time t2 has elapsed.

[0068] When time t2 has elapsed (YES in step S5), in step S6, work machine controller 10 acquires the acceleration of the vehicle body. In step S7, work machine controller 10 determines whether the peak value of the acceleration of the vehicle body is equal to or greater than a predetermined threshold. The processing in steps S6 and S7 is performed in the same manner as the processing in steps S1 and S2.

[0069] If it is determined in step S7 that the peak value of the acceleration of the vehicle body is equal to or greater than the threshold value (YES in step S7), the process returns to step S4, and steps S4 to S7 are repeated. In step S4, the input value from the operating device is further corrected, and the amplitude A shown in Figures 6 and 7 is further reduced. In step S7, it is determined whether the peak value of the acceleration of the vehicle body is still equal to or greater than the predetermined threshold value. The correction of the input value continues until the peak value of the acceleration of the vehicle body becomes smaller than the threshold value.

[0070] When the peak value of the vehicle body acceleration becomes smaller than the threshold value (NO in step S7), in step S8, work machine controller 10 changes the correction of the input value from the operation device back to the initial state. Command calculation unit 102 releases the restriction on the movement of bucket 31 in response to the operation command output by bucket operation lever 42. The movement of bucket 31 in response to the operation command is no longer restricted. Command calculation unit 102 outputs a control signal to electromagnetic proportional control valves 24, 25 in accordance with the operation command input from operation lever 43 (bucket operation lever 42). Then, the process returns.

[0071] If it is determined in step S2 that the peak value of the vehicle body acceleration is smaller than the threshold value (NO in step S2), the process of correcting the input value from the operation device is not performed. The command calculation unit 102 outputs a control signal to the electromagnetic proportional control valves 24, 25 in accordance with the operation command input from the operation lever 43 (bucket operation lever 42). The process then returns.

[0072] <Functions and Effects> Although some of the description overlaps with the above description, the characteristic configurations and functions and effects of the embodiment can be summarized as follows.

[0073] 5 to 7 , work machine controller 10 limits the movement of bucket 31 in response to an operation command to operate bucket 31 based on the detection results of vehicle body vibrations generated by work using bucket 31. The vibration sensor detects vehicle body vibrations, and when the magnitude of the vehicle body vibrations exceeds a threshold, the sensitivity of the operation of bucket 31 to the operation command output by the operating device is reduced to prevent resonance. By intervening in the operation command in accordance with the vehicle body vibration state, the vehicle body vibrations can be suppressed, thereby stabilizing the vehicle body.

[0074] The operation command output by the operating device for operating the bucket 31 may be a bucket lever signal generated by the operator's operation of the bucket operation lever 42. For example, the operation command may be a bucket lever signal generated when an operator intending to perform bucket swinging operation tilts the operation lever 43 alternately to the left and right. The operation command may also be a bucket lever signal generated when the bucket operation lever 42 is swung due to vibrations of the vehicle body. For example, the operation command may be a bucket lever signal generated when the bucket operation lever 42 is swung due to vibrations of the vehicle body caused by the bucket swinging operation after the operator has finished swinging the bucket and released the bucket operation lever 42.

[0075] In addition to detecting vibrations of the vehicle body using a vibration sensor, the period of vibration of the vehicle body may also be acquired. By detecting the period of vibration, it can be determined that the vehicle body has vibrated due to bucket swinging. It can also be determined that bucket swinging has been performed from the operation of the bucket operating lever 42.

[0076] As shown in Figures 2 and 5, the vibration sensor may be an acceleration sensor that detects the acceleration of the vehicle body. Since the acceleration of the vehicle body is an example of a physical quantity that represents the vibration of the vehicle body, the vibration of the vehicle body can be detected by detecting the acceleration of the vehicle body with an acceleration sensor. In addition to acceleration, physical quantities that represent vibration include displacement and velocity. The vibration sensor may include a displacement sensor and / or a velocity sensor instead of or in addition to the acceleration sensor.

[0077] 5, when the acceleration of the vehicle body remains at or above a threshold for time t1 or longer, work machine controller 10 may impose a restriction on the operation of bucket 31 in response to an operation command to operate bucket 31. When large vehicle body vibrations continue for a predetermined time, work machine controller 10 may intervene in the operation command output by the operating device to restrict the operation of bucket 31, thereby reducing the vehicle body vibrations and reliably stabilizing the vehicle body.

[0078] As shown in Fig. 5, work machine controller 10 may release the restriction on the movement of bucket 31 when the acceleration of the vehicle body becomes smaller than a threshold value. When the vibration of the vehicle body decreases and the vehicle body stabilizes as a result of restricting the movement of bucket 31, control is performed to move bucket 31 in accordance with an operation command from the operation device. The operator operates bucket operation lever 42, and bucket 31 is moved in accordance with the operation of bucket operation lever 42. In this manner, responsiveness to the operation of the operator can be improved.

[0079] As shown in Figures 1 to 3, the operating device may be located inside the cab 5 in which the operator sits. Because the cab 5 is mounted on the vehicle body, when the vehicle body vibrates, the vibrations are transmitted to the operating device inside the cab 5. When the operating device is shaken by the vibration of the vehicle body, the movement of the operating device may become an operation command to operate the bucket 31. The vibration of the bucket 31 may increase the vibration of the vehicle body. By configuring the system to limit the movement of the bucket 31 when large vibrations of the vehicle body are detected, it is possible to prevent the vibration of the vehicle body from increasing and stabilize the vehicle body.

[0080] As shown in Figure 3, operating lever 43 may have an expanded diameter portion 54 at its tip. Operating lever 43 having expanded diameter portion 54 at its tip is prone to shaking when vibrations of the vehicle body are transmitted to it. By setting a limit on the movement of bucket 31 in response to an operation command for operating bucket 31 output from operating lever 43 when large vibrations of the vehicle body are detected, it is possible to prevent an increase in vibrations of the vehicle body and stabilize the vehicle body.

[0081] 3, expanded diameter section 54 may have a switch 55 that can be operated by the operator. If expanded diameter section 54 at the tip of operation lever 43 has switch 55, operation lever 43 will have a top-heavy structure with a large weight at the tip end, and will be prone to shaking when vibrations from the vehicle body are transmitted. By setting limits on the movement of bucket 31 in response to an operation command for operating bucket 31 output from operation lever 43 when large vibrations of the vehicle body are detected, it is possible to avoid an increase in vibrations of the vehicle body and stabilize the vehicle body.

[0082] 6 and 7 , the work performed by bucket 31 when vehicle body vibration occurs may be bucket swinging, which involves repeatedly moving bucket 31 in the dump direction and tilt direction. When the operator performs bucket swinging, vibration is more likely to occur in the vehicle body. When vehicle body vibration becomes large, an increase in vehicle body vibration can be prevented and the vehicle body can be stabilized by placing a limit on the movement of bucket 31 in response to an operation command for moving bucket 31 output from operating lever 43.

[0083] 6 and 7, the work machine controller 10 may set a limit on the amplitude A of the bucket swinging operation. By doing so, an increase in vibration of the vehicle body can be reliably avoided, and the vehicle body can be stabilized.

[0084] In the embodiment, an example has been described in which the operation device has the operation lever 43, and the operation lever 43 has the functions of both the boom operation lever 41 and the bucket operation lever 42. The boom operation lever 41 and the bucket operation lever 42 may be configured as separate levers. The operation of tilting the boom operation lever 41 in the forward / backward direction may be set as the operation for moving the boom 32 up and down, and the operation of tilting the bucket operation lever 42 in the forward / backward direction may be set as the operation for rotating the bucket 31.

[0085] The operating device does not necessarily have to be arranged inside the cab 5. The operating device may be arranged outside the wheel loader 1. The operator may operate the operating device inside the cab 5, or may operate the operating device outside the wheel loader 1.

[0086] In the embodiment, an example has been described in which the acceleration of the vehicle body in the up-down direction is detected by the IMU 47. The IMU 47 can detect the acceleration of the vehicle body in the front-rear and left-right directions. The detected values ​​of the acceleration of the vehicle body in the front-rear and left-right directions may be used to control the bucket operation.

[0087] The attachment at the tip of the work implement 3 is not limited to the bucket 31, but may be another type of attachment. The work machine is not limited to the wheel loader 1, but may be another type of work machine capable of performing excavation work.

[0088] <Additional Notes> The above description includes the following additional features.

[0089] (Supplementary Note 1) A work machine comprising: a vehicle body; a work implement operably attached to the vehicle body and having an attachment at its tip; an operating device that outputs an operation command to operate the attachment; a vibration sensor that detects vibrations of the vehicle body; and a controller that sets limits on the operation of the attachment in response to the operation command based on the detection results of vibrations of the vehicle body generated during work performed by the attachment.

[0090] (Supplementary Note 2) The work machine according to Supplementary Note 1, wherein the vibration sensor includes an acceleration sensor that detects acceleration of the vehicle body.

[0091] (Supplementary Note 3) The work machine according to Supplementary Note 2, wherein the controller imposes a limit on the operation of the attachment in response to the operation command when a state in which the acceleration is equal to or greater than a threshold value continues for a predetermined time.

[0092] (Supplementary Note 4) The work machine according to Supplementary Note 2 or Supplementary Note 3, wherein the controller releases restrictions on movement of the attachment when the acceleration becomes smaller than the threshold value.

[0093] (Supplementary Note 5) The work machine according to any one of Supplementary Note 1 to Supplementary Note 4, wherein the work machine is mounted on the vehicle body and includes a cab in which an operator can ride, and the operating device is located inside the cab.

[0094] (Supplementary Note 6) The work machine according to Supplementary Note 5, wherein the operating device has an operating lever, and the operating lever has an expanded diameter portion at a tip end.

[0095] (Supplementary Note 7) The work machine according to Supplementary Note 6, wherein the enlarged diameter portion has a switch that can be operated by the operator.

[0096] (Supplementary Note 8) The work machine according to any one of Supplementary Note 1 to Supplementary Note 7, wherein the attachment has a bucket, and the work is a bucket swing work that repeats movement of the bucket in a dump direction and movement of the bucket in a tilt direction.

[0097] (Supplementary Note 9) The work machine according to Supplementary Note 8, wherein the controller sets a limit on the amplitude of the bucket swinging operation.

[0098] The embodiments disclosed herein are to be considered in all respects as illustrative 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.

[0099] 1 Wheel loader, 2 Body frame, 3 Work machine, 5 Cab, 7 Traveling device, 10 Work machine controller, 11 Engine, 21 Hydraulic pump, 22 Bucket operation valve, 23 Boom operation valve, 24 to 27 Electromagnetic proportional control valve, 31 Bucket, 32 Boom, 35 Bucket cylinder, 36 Boom cylinder, 41 Boom operation lever, 42 Bucket operation lever, 43 Operation lever, 44 Boom angle sensor, 45 Bucket angle sensor, 46 Boom bottom pressure sensor, 47 IMU, 52 Base portion, 53 Shaft portion, 54 Expanded diameter portion, 55 Switch, 56, 57 Push button switch, 58 Rocker switch, 59 Electric wire, 101 Vibration detection unit, 102 Command calculation unit, 108 Memory unit, 109 Timer, A Amplitude, t1, t2 Time.

Claims

1. A work machine comprising: a vehicle body; a work implement operably attached to the vehicle body and having an attachment at its tip; an operating device that outputs operation commands to operate the attachment; a vibration sensor that detects vibrations of the vehicle body; and a controller that sets limits on the operation of the attachment in response to the operation commands based on the detection results of vibrations of the vehicle body generated during work performed by the attachment.

2. A work machine according to claim 1, wherein the vibration sensor includes an acceleration sensor for detecting the acceleration of the vehicle body.

3. A work machine according to claim 2, wherein the controller imposes a limit on the movement of the attachment in response to the movement command when the acceleration remains equal to or greater than a threshold value for a predetermined period of time.

4. The work machine according to claim 3, wherein the controller releases the restriction on the movement of the attachment when the acceleration becomes smaller than the threshold value.

5. The work machine according to claim 1, wherein the work machine is mounted on the vehicle body and has a cab in which an operator can sit, and the operating device is disposed within the cab.

6. A work machine as set forth in claim 5, wherein the operating device has an operating lever, and the operating lever has an enlarged portion at its tip.

7. The work machine according to claim 6, wherein the enlarged portion has a switch operable by the operator.

8. A work machine according to claim 1, wherein the attachment has a bucket, and the work is a bucket swinging work in which the movement of the bucket in the dump direction and the movement of the bucket in the tilt direction are repeated.

9. The work machine according to claim 8, wherein the controller sets a limit on the amplitude of the bucket swinging operation.

10. A method for controlling a work machine, comprising: receiving an input of an operation command to operate an attachment at the tip of a work machine operably attached to a vehicle body; detecting vibrations of the vehicle body generated by work performed by the attachment; and setting restrictions on the operation of the attachment in response to the operation command based on the detection results of the vibrations of the vehicle body.

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