Work machine and method for controlling a work machine

Abstract

To provide a work machine which can be moved in a target direction even when an articulate angle is changed during automatic steering control.SOLUTION: A work machine includes a vehicle body, a steered road wheel, an actuator, and a controller. The vehicle body includes a rear frame, and a front frame connected to the rear frame so as to turn with respect to the rear frame. The steered road wheel is supported by the front frame. The actuator changes a steering angle of the steered road wheel. The controller controls the actuator. The controller determines a target direction in which the vehicle body travels. The controller acquires an articulate angle of the front frame with respect to the rear frame. The controller sets the steering angle so that the vehicle body moves in the target direction by controlling the actuator in correspondence with the articulate angle.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The present invention relates to a work machine and a method for controlling a work machine. [Background technology]

[0002] Some conventional work machines have a rear frame, a front frame that rotates relative to the rear frame, and steering wheels supported by the front frame (see Patent Document 1). In this type of work machine, the direction of travel of the work machine is determined by rotating the front frame relative to the rear frame and changing the steering angle of the steering wheels.

[0003] While traveling, work machines are prone to deviating from their intended direction due to loads of soil and sand or uneven road surfaces. Therefore, operators must simultaneously operate the steering components to maintain the machine's course while operating the work equipment, such as the blade. Such operations are difficult and place a heavy burden on the operator.

[0004] Therefore, Patent Document 1 discloses an automatic steering control that automatically controls the steering angle so that the working machine maintains the traveling direction in a target direction. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent Publication No. 2021-054269 Summary of the Invention [Problem to be solved by the invention]

[0006] In the conventional work machine described above, the work machine moves in a target direction through automatic steering control. For example, in a conventional work machine, automatic steering control is executed when the articulation angle, which is the rotation angle of the front frame relative to the rear frame, is zero. In this case, while automatic steering control is being executed, the controller determines whether the work machine is moving in the target direction. Here, if the traveling direction of the work machine deviates from the target direction, the controller controls the steering angle to move the work machine in the target direction.

[0007] An object of the present invention is to provide a work machine that can be moved in a target direction even if the articulation angle changes. [Means for solving the problem]

[0008] A work machine according to one aspect of the present invention includes a vehicle body, steerable wheels, an actuator, and a controller. The vehicle body includes a rear frame and a front frame connected to the rear frame so as to be rotatable relative to the rear frame. The steerable wheels are supported by the front frame. The actuator changes the steering angle of the steerable wheels. The controller controls the actuator.

[0009] The controller determines a target direction in which the vehicle body will travel. The controller obtains an articulation angle of the front frame relative to the rear frame. The controller controls the actuators according to the articulation angle to set a steering angle so that the vehicle body moves in the target direction.

[0010] A method according to another aspect of the present invention is a method for controlling a work machine. The work machine includes a vehicle body, a steering wheel, and an actuator. The vehicle body includes a rear frame and a front frame connected to the rear frame so as to be rotatable relative to the rear frame. The steering wheel is supported by the front frame.

[0011] The method according to this aspect includes determining a target direction in which the vehicle body will travel, obtaining an articulation angle of the front frame relative to the rear frame, and setting a steering angle by controlling an actuator in accordance with the articulation angle so that the vehicle body moves in the target direction. [Effects of the Invention]

[0012] According to the present invention, when the target direction of the vehicle body is acquired, the actuator is controlled in accordance with the articulation angle. By controlling this actuator, the steering angle is set so that the vehicle body moves in the target direction. As a result, the work machine can be moved in the target direction even if the articulation angle changes. [Brief explanation of the drawings]

[0013] [Figure 1] 1 is a perspective view of a work machine according to an embodiment. [Figure 2] FIG. 1 is a side view of a work machine. [Figure 3] FIG. 1 is a schematic diagram showing the configuration of a work machine. [Figure 4A] FIG. 2 is a top view showing the front of the work machine. [Figure 4B] FIG. 2 is a top view showing the front of the work machine. [Figure 5] 10 is a flowchart showing a process for setting a steering angle according to an articulation angle during automatic control. [Figure 6A] FIG. 2 is a top view showing the front of the work machine. [Figure 6B] FIG. 2 is a top view showing the front of the work machine. DETAILED DESCRIPTION OF THE INVENTION

[0014] An embodiment of the present invention will now be described with reference to the drawings. Fig. 1 is a perspective view of a work machine 1 according to the embodiment. Fig. 2 is a side view of the work machine 1. As shown in Fig. 1, the work machine 1 includes a body 2, front wheels 3A, 3B, rear wheels 4A-4D, and a work implement 5. The body 2 includes a front frame 11, a rear frame 12, a cab 13, and a power compartment 14.

[0015] The rear frame 12 is connected to the front frame 11. The front frame 11 is connected to the rear frame 12 so as to be rotatable relative to the rear frame 12. For example, the front frame 11 can articulate left and right relative to the rear frame 12.

[0016] In the following description, the front, rear, left and right directions of the vehicle body 2 are defined when the articulation angle of the front frame 11 relative to the rear frame 12 is zero, i.e., when the front frame 11 and the rear frame 12 are straight.

[0017] The cab 13 and the power compartment 14 are disposed on the rear frame 12. A driver's seat (not shown) is disposed in the cab 13. The power compartment 14 is disposed behind the cab 13. The front frame 11 extends forward from the rear frame 12. The front wheels 3A, 3B are attached to the front frame 11. The front wheels 3A, 3B are disposed spaced apart in the left-right direction. The front wheels 3A, 3B are rotatably supported by the front frame 11. The rear wheels 4A-4D are attached to the rear frame 12.

[0018] The work implement 5 is movably connected to the vehicle body 2. The work implement 5 includes a support member 15 and a blade 16. The support member 15 is movably connected to the vehicle body 2. The support member 15 supports the blade 16. The support member 15 includes a draw bar 17 and a circle 18. The draw bar 17 is disposed below the front frame 11.

[0019] The drawbar 17 is connected to a front portion 19 of the front frame 11. The drawbar 17 extends rearward from the front portion 19 of the front frame 11. The drawbar 17 is supported relative to the front frame 11 so as to be swingable at least in the up-down direction and the left-right direction of the vehicle body 2. For example, the front portion 19 includes a ball joint. The drawbar 17 is rotatably connected to the front frame 11 via the ball joint.

[0020] The circle 18 is connected to the rear of the drawbar 17. The circle 18 is supported rotatably relative to the drawbar 17. The blade 16 is connected to the circle 18. The blade 16 is supported by the drawbar 17 via the circle 18. As shown in FIG. 2 , the blade 16 is supported by the circle 18 rotatably around a tilt shaft 21. The tilt shaft 21 extends in the left-right direction.

[0021] As shown in FIG. 2, the work machine 1 is equipped with a plurality of steering actuators 41A, 41B and a plurality of articulating actuators 27, .

[0022] The multiple steering actuators 41A, 41B are used to steer the front wheels 3A, 3B. For example, the multiple steering actuators 41A, 41B are hydraulic cylinders. The multiple steering actuators 41A, 41B are connected to the front wheels 3A, 3B, respectively. The multiple steering actuators 41A, 41B extend and retract using hydraulic pressure. In the following description, the extension and contraction of the multiple steering actuators 41A, 41B, for example, the extension and contraction of a hydraulic cylinder, is referred to as a "stroke operation."

[0023] The plurality of steering actuators 41A, 41B include a left steering actuator 41A and a right steering actuator 41B. The left steering actuator 41A and the right steering actuator 41B are arranged apart from each other in the left-right direction.

[0024] The left steering actuator 41A is connected to the front frame 11 and the front wheel 3A. The right steering actuator 41B is connected to the front frame 11 and the front wheel 3B. The front wheels 3A and 3B are steered by the stroke operations of the left steering actuator 41A and the right steering actuator 41B.

[0025] In Fig. 2, the left steering actuator 41A is shown, but the right steering actuator 41B is not shown. Since the left steering actuator 41A and the right steering actuator 41B are paired members, in Fig. 2, the members not shown are indicated by reference numerals in parentheses.

[0026] The multiple articulating actuators 27, 28 are used to rotate the front frame 11 relative to the rear frame 12. For example, the multiple articulating actuators 27, 28 are hydraulic cylinders. The multiple articulating actuators 27, 28 are connected to the front frame 11 and the rear frame 12. The multiple articulating actuators 27, 28 extend and retract using hydraulic pressure.

[0027] The multiple articulate actuators 27, 28 include a left articulate cylinder 27 and a right articulate cylinder 28. The left articulate cylinder 27 and the right articulate cylinder 28 are arranged spaced apart from each other in the left-right direction.

[0028] The left articulate cylinder 27 is connected to the front frame 11 and the rear frame 12 on the left side of the vehicle body 2. The right articulate cylinder 28 is connected to the front frame 11 and the rear frame 12 on the right side of the vehicle body 2. The stroke operations of the left articulate cylinder 27 and the right articulate cylinder 28 cause the front frame 11 to rotate left and right relative to the rear frame 12.

[0029] In Fig. 1, the right articulate cylinder 28 is shown, but the left articulate cylinder 27 is not shown. In Fig. 2, the left articulate cylinder 27 is shown, but the right articulate cylinder 28 is not shown. Because the left articulate cylinder 27 and the right articulate cylinder 28 are paired members, in Figs. 1 and 2, the members not shown are indicated by reference numerals in parentheses.

[0030] As shown in FIG. 2, the work machine 1 is equipped with a plurality of actuators 22-26 for changing the attitude of the work implement 5. For example, the plurality of actuators 22-25 are hydraulic cylinders. The actuator 26 is a rotary actuator. In this embodiment, the actuator 26 is a hydraulic motor. The actuator 26 may also be an electric motor.

[0031] The plurality of actuators 22-25 are connected to the work implement 5. The plurality of actuators 22-25 are hydraulically extended and retracted. The plurality of actuators 22-25 change the attitude of the work implement 5 relative to the vehicle body 2 by extending and retracting.

[0032] In particular, the plurality of actuators 22 - 25 include a left lift cylinder 22 , a right lift cylinder 23 , a drawbar shift cylinder 24 , and a blade tilt cylinder 25 .

[0033] The left lift cylinder 22 and the right lift cylinder 23 are disposed apart from each other in the left-right direction. The left lift cylinder 22 and the right lift cylinder 23 are connected to the draw bar 17. The left lift cylinder 22 and the right lift cylinder 23 are connected to the front frame 11 via a lifter bracket 29. The stroke movement of the left lift cylinder 22 and the right lift cylinder 23 causes the draw bar 17 to swing up and down. This causes the blade 16 to move up and down.

[0034] The drawbar shift cylinder 24 is connected to the drawbar 17 and the front frame 11. The drawbar shift cylinder 24 is connected to the front frame 11 via a lifter bracket 29. The drawbar shift cylinder 24 extends obliquely downward from the front frame 11 toward the drawbar 17. The stroke movement of the drawbar shift cylinder 24 causes the drawbar 17 to swing left and right.

[0035] The blade tilt cylinder 25 is connected to the circle 18 and the blade 16. The stroke movement of the blade tilt cylinder 25 causes the blade 16 to rotate around the tilt axis 21.

[0036] The actuator 26 is connected to the drawbar 17 and the circle 18. The actuator 26 rotates the circle 18 relative to the drawbar 17. This causes the blade 16 to rotate around a rotation axis that extends in the vertical direction.

[0037] Figure 3 is a schematic diagram showing the configuration of the work machine 1. As shown in Figure 3, the work machine 1 includes a drive source 31, a first hydraulic pump 32, a second hydraulic pump 48, a first pilot valve 49, and a second pilot valve 50. The work machine 1 also includes a steering valve 42A, an articulating valve 42B, and a work implement valve 34. The work machine 1 also includes a power transmission device 33.

[0038] The driving source 31 is, for example, an internal combustion engine, or may be an electric motor or a hybrid of an internal combustion engine and an electric motor.

[0039] The first hydraulic pump 32 is driven by the drive source 31 to discharge hydraulic oil. The first hydraulic pump 32 supplies hydraulic oil to a steering valve 42A, an articulate valve 42B, and a work implement valve 34. The hydraulic oil supplied via these valves operates the multiple steering actuators 41A, 41B, the multiple articulate actuators 27, 28, and the multiple actuators 22-26.

[0040] The second hydraulic pump 48 is driven by the drive source 31 to discharge hydraulic oil. The first pilot valve 49 is connected to the second hydraulic pump 48 and the steering valve 42A via a hydraulic circuit. The first pilot valve 49 controls the pressure of the hydraulic oil supplied from the second hydraulic pump 48 to the pilot port of the steering valve 42A. The first pilot valve 49 is an electromagnetic proportional control valve.

[0041] The second pilot valve 50 is connected to the second hydraulic pump 48 and a steering valve 42A (described later) via a hydraulic circuit. The second pilot valve 50 is connected to the second steering member 46. The second pilot valve 50 controls the pressure of hydraulic oil (hereinafter referred to as "pilot hydraulic pressure") supplied from the second hydraulic pump 48 to a pilot port of the steering valve 42A in accordance with the operation of the second steering member 46. Note that the second pilot valve 50, like the first pilot valve 49, may be an electromagnetic proportional control valve.

[0042] The steering valve 42A is connected to the first hydraulic pump 32 and the multiple steering actuators 41A, 41B via a hydraulic circuit. The steering valve 42A controls the flow rate of hydraulic oil supplied from the first hydraulic pump 32 to the multiple steering actuators 41A, 41B. For example, the steering valve 42A is a hydraulic pilot type control valve. When the hydraulic oil from the first hydraulic pump 32 is supplied to the steering valve 42A, the multiple steering actuators 41A, 41B perform stroke operations.

[0043] The articulate valve 42B is connected to the first hydraulic pump 32 and the multiple articulate actuators 27, 28 via a hydraulic circuit. The articulate valve 42B controls the flow rate of hydraulic oil supplied from the first hydraulic pump 32 to the multiple articulate actuators 27, 28. For example, the articulate valve 42B is a hydraulic pilot type control valve. When the hydraulic oil from the first hydraulic pump 32 is supplied to the articulate valve 42B, the multiple articulate actuators 27, 28 perform stroke operations.

[0044] The work implement valve 34 is connected to the first hydraulic pump 32 and the multiple actuators 22-26 via a hydraulic circuit. The work implement valve 34 includes multiple valves connected to the multiple actuators 22-26, respectively. The work implement valve 34 controls the flow rate of hydraulic oil supplied from the first hydraulic pump 32 to the multiple actuators 22-26. The work implement valve 34 is, for example, an electromagnetic proportional control valve. Alternatively, the work implement valve 34 may be a hydraulic pilot type proportional control valve.

[0045] The power transmission device 33 transmits driving force from the drive source 31 to the rear wheels 4A-4D. The power transmission device 33 may include a torque converter and / or a plurality of speed change gears. Alternatively, the power transmission device 33 may be a transmission such as an HST (Hydraulic Static Transmission) or an HMT (Hydraulic Mechanical Transmission).

[0046] As shown in FIG. 3, the work machine 1 includes a first steering member 45, a second steering member 46, an articulating lever 55, a work implement operating member 35, a shift member 53, and an accelerator operating member 36.

[0047] The first steering member 45 and the second steering member 46 can be operated by an operator to steer the front wheels 3A, 3B. The first steering member 45 is a lever such as a joystick. Alternatively, the first steering member 45 may be a member other than a lever.

[0048] The first steering member 45 can be tilted to the left or right from a neutral position N1. The first steering member 45 is connected to a first operation sensor 51. The first operation sensor 51 is included in the work machine 1. The first operation sensor 51 outputs a first operation signal that indicates an operation of the first steering member 45 by the operator. For example, the first operation sensor 51 detects the tilt angle of the first steering member 45, and outputs a first operation signal that corresponds to the tilt angle of the first steering member 45.

[0049] The second steering member 46 is a steering wheel. Alternatively, the second steering member 46 may be a member other than a steering wheel. When the second steering member 46 is not operated by the operator, it is held in the position where it was last operated. When the first steering member 45 and the second steering member 46 are operated simultaneously, the operation of the second steering member 46 takes priority.

[0050] The second steering member 46 is rotatable about the rotation axis Ax1. A second operation sensor 47 is attached to the second steering member 46. The second operation sensor 47 is included in the work machine 1. The second operation sensor 47 outputs a second operation signal that indicates an operation of the second steering member 46 by the operator. For example, the second operation sensor 47 detects an angular displacement of the second steering member 46 about the rotation axis Ax1, and outputs a second operation signal that corresponds to the angular displacement of the second steering member 46.

[0051] The articulation lever 55 can be operated by an operator to rotate the front frame 11 relative to the rear frame 12. The articulation lever 55 is a lever such as a joystick. Alternatively, the articulation lever 55 may be a member other than a lever.

[0052] The articulate lever 55 can be tilted to the left or right from a neutral position N2. The articulate lever 55 is connected to a third operation sensor 60. The third operation sensor 60 is included in the work machine 1. The third operation sensor 60 outputs a third operation signal that indicates the operation of the articulate lever 55 by the operator. For example, the third operation sensor 60 detects the amount of operation of the articulate, and outputs a third operation signal that corresponds to the amount of operation of the articulate.

[0053] The work implement operation member 35 can be operated by the operator to change the attitude of the work implement 5. The work implement operation member 35 includes, for example, a plurality of operation levers. Alternatively, the work implement operation member 35 may be another member such as a switch or a touch panel. The work implement operation member 35 outputs a signal indicating an operation of the work implement operation member 35 by the operator.

[0054] The shift member 53 can be operated by an operator to switch between forward and reverse travel of the work machine 1. The shift member 53 includes, for example, a shift lever. Alternatively, the shift member 53 may be another member such as a switch or a touch panel. The shift member 53 outputs a signal indicating an operation of the shift member 53 by the operator.

[0055] The accelerator operating member 36 can be operated by the operator to drive the work machine 1. The accelerator operating member 36 includes, for example, an accelerator pedal. Alternatively, the accelerator operating member 36 may be another member such as a switch or a touch panel. The accelerator operating member 36 outputs a signal indicating operation of the accelerator operating member 36 by the operator.

[0056] The work machine 1 is equipped with a direction sensor 52, a steering angle sensor 40, and an articulation angle sensor 30. The direction sensor 52 detects the traveling direction of the vehicle body 2. The direction sensor 52 outputs a direction signal indicating the traveling direction of the vehicle body 2. The direction sensor 52 is, for example, an IMU (Inertial Measurement Unit). Alternatively, the direction sensor 52 may be a GNSS (Global Navigation Satellite System) receiver such as a GPS (Global Positioning System).

[0057] The steering angle sensor 40 is used to detect the steering angle θ1 of the front wheels 3A, 3B. The steering angle sensor 40 detects the stroke amounts of the multiple steering actuators 41A, 41B. The steering angle sensor 40 outputs a stroke signal indicating these stroke amounts. Note that the steering angle sensor 40 may also directly detect the steering angle θ1. In this case, the steering angle sensor 40 outputs an angle signal indicating the steering angle θ1.

[0058] Here, the steering angle θ1 is defined as follows: As shown in Fig. 4A, the work machine 1 includes a first steering shaft 43A and a second steering shaft 43B. The first steering shaft 43A and the second steering shaft 43B are rotation shafts for the front wheels 3A, 3B.

[0059] The first steering shaft 43A and the second steering shaft 43B are provided on the front frame 11. The first steering shaft 43A and the second steering shaft 43B extend in the vertical direction. The first steering shaft 43A and the second steering shaft 43B support the front wheels 3A, 3B so that they can rotate independently.

[0060] The steering angle θ1 is the angle at which the front wheels 3A, 3B rotate about the first steering axis 43A and the second steering axis 43B relative to the front frame 11. For example, the steering angle θ1 is the rotation angle of the front wheels 3A, 3B relative to the fore-and-aft direction of the front frame 11.

[0061] Specifically, a first center line L1 is defined on the front frame 11. The first center line L1 is the center line of the front frame 11 that extends in the fore-and-aft direction of the front frame 11. The first center line L1 passes through an articulated shaft 44, which will be described later, when viewed from above the work machine 1. The steering angle θ1 is the rotation angle of the front wheels 3A, 3B relative to the first center line L1.

[0062] The steering angle θ1 varies left and right from the neutral position due to the stroke operation of the multiple steering actuators 41A, 41B. The steering angle θ1 at the neutral position is zero degrees. At the neutral position, the front wheels 3A, 3B are arranged parallel to the first center line L1 of the front frame 11. In FIG. 4A, 3A' and 3B' indicate the front wheels in a state where they are steered by the steering angle θ1 from the neutral position.

[0063] The articulation angle sensor 30 is used to detect the articulation angle θ2 of the front frame 11 relative to the rear frame 12. The articulation angle sensor 30 detects the stroke amounts of the left articulation cylinder 27 and the right articulation cylinder 28. The articulation angle sensor 30 outputs a stroke signal indicating these stroke amounts. Note that the articulation angle sensor 30 may also directly detect the articulation angle θ2. In this case, the articulation angle sensor 30 outputs an angle signal indicating the articulation angle θ2.

[0064] Here, the articulation angle θ2 is defined as follows: As shown in FIG. 4B, the work machine 1 includes an articulation shaft 44. The articulation shaft 44 is provided on the front frame 11 and the rear frame 12. The articulation shaft 44 extends in the vertical direction. The articulation shaft 44 rotatably supports the front frame 11.

[0065] The articulation angle θ2 is the angle at which the front frame 11 rotates relative to the rear frame 12 around the articulation shaft 44. For example, a second center line L2 is defined on the rear frame 12. The second center line L2 is the center line of the rear frame 12 that extends in the fore-and-aft direction of the rear frame 12. The second center line L2 passes through the articulation shaft 44 when the work machine 1 is viewed from above.

[0066] The articulation angle θ2 is the angle between the first center line L1 and the second center line L2. When the articulation angle θ2 is zero, the direction of the second center line L2 coincides with the direction of the first center line L1, as shown in Fig. 4A. Note that Fig. 4B shows a state in which the first center line L1 has rotated by the articulation angle θ2 relative to the second center line L2 with respect to the articulation shaft 44.

[0067] As shown in Fig. 3, the work machine 1 includes a controller 37. The controller 37 includes a storage device 38 and a processor 39. The processor 39 is, for example, a CPU, and executes programs for controlling the work machine 1. The storage device 38 includes memory such as RAM and ROM, and an auxiliary storage device such as an SSD or HDD. The storage device 38 stores programs and data for controlling the work machine 1.

[0068] The controller 37 obtains the amount of operation of the first steering member 45 from a first operation signal from the first operation sensor 51. The controller 37 obtains the amount of operation of the second steering member 46 from a second operation signal from the second operation sensor 47. When the controller 37 obtains the first operation signal and the second operation signal simultaneously, the controller 37 gives priority to the second operation signal.

[0069] When the first steering member 45 is operated, the controller 37 controls the pilot oil pressure to the steering valve 42A by controlling the first pilot valve 49 in response to the first operation signal. This controls the hydraulic oil supplied from the steering valve 42A to the multiple steering actuators 41A, 41B, causing the multiple steering actuators 41A, 41B to expand and contract. As a result, the steering angle θ1 of the front wheels 3A, 3B is changed.

[0070] Furthermore, when the second steering member 46 is operated, the second pilot valve 50 controls the pilot oil pressure to the steering valve 42A in response to the operation of the second steering member 46. This controls the hydraulic oil supplied from the steering valve 42A to the multiple steering actuators 41A, 41B, causing the multiple steering actuators 41A, 41B to expand and contract. As a result, the steering angle θ1 of the front wheels 3A, 3B is changed. Note that the controller 37 may adjust the pilot pressure output to the steering valve 42A by controlling the first pilot valve 49 in response to the second operation signal. This may change the steering angle θ1 of the front wheels 3A, 3B. In this case, the second pilot valve 50 may be omitted.

[0071] The controller 37 obtains the operation amount of the articulate lever 55 from the third operation signal from the articulate lever 55. The controller 37 controls the articulate valve 42B. For example, the controller 37 extends and retracts the left articulate cylinder 27 and the right articulate cylinder 28 by controlling the articulate valve 42B in accordance with the third operation signal. As a result, the controller 37 changes the articulate angle θ2.

[0072] The controller 37 controls the power transmission device 33 in accordance with the operation of the shift member 53. In this way, the traveling direction of the work machine 1 is switched between forward and reverse. Alternatively, the shift member 53 may be mechanically connected to the power transmission device 33. The operation of the shift member 53 may be mechanically transmitted to the power transmission device 33, thereby switching the gear of the power transmission device 33 between forward and reverse.

[0073] The controller 37 controls the drive source 31 and the power transmission device 33 in response to operation of the accelerator operating member 36. This causes the work machine 1 to travel. The controller 37 also controls the first hydraulic pump 32 and the work machine valve 34 in response to operation of the work machine operating member 35. This causes the work machine 5 to operate.

[0074] Next, a description will be given of automatic steering control executed by the controller 37. In automatic steering control, the controller 37 controls the steering angle θ1 in accordance with the articulation angle θ2 so as to maintain the traveling direction of the work machine 1 in a target direction. Figure 5 is a flowchart showing the processing of automatic steering control.

[0075] In step S101, the controller 37 acquires a target direction. For example, the controller 37 determines the traveling direction of the vehicle body 2 after the work machine 1 has turned by operating the first steering member 45 as the target direction. Alternatively, the controller 37 may determine the target direction so that the work machine 1 moves along a preset target route. For example, the target route may be input to the controller 37 by an operator. The target route may also be input to the controller 37 from an external computer. Alternatively, the controller 37 may automatically generate the target route.

[0076] In step S102, the controller 37 acquires the current traveling direction of the vehicle body 2. The controller 37 acquires the current traveling direction of the vehicle body 2 based on the direction signal from the direction sensor 52.

[0077] In step S103, the controller 37 acquires an initial value of the target steering angle. The initial value of the target steering angle is the target steering angle when the articulation angle θ2 is assumed to be zero. The controller 37 determines the initial value of the target steering angle so that the current traveling direction of the work machine 1 coincides with the target direction. For example, the controller 37 determines the value obtained by multiplying the difference between the current traveling direction and the target direction by a predetermined gain as the initial value of the target steering angle. The controller 37 may decrease the gain as the vehicle speed increases.

[0078] In step S104, the controller 37 acquires the articulation angle θ2. The controller 37 acquires the articulation angle θ2 based on the angle signal from the articulation angle sensor 30.

[0079] In step S105, the controller 37 calculates a correction value of the target steering angle. The controller 37 calculates the correction value of the target steering angle by correcting the initial value of the target steering angle in accordance with the articulation angle θ2. For example, the controller 37 calculates the correction value of the target steering angle using the following equation (1). A1=A0-θ2 (1) A1 is the correction value of the target steering angle. A0 is the initial value of the target steering angle. Note that in equation (1), the positive and negative values ​​of the correction value and initial value of the target steering angle and the articulation angle are the same if the rotation direction is the same. For example, the correction value and initial value of the target steering angle and the articulation angle may have positive values ​​for angles to the left from the neutral position and negative values ​​for angles to the right. Alternatively, the correction value and initial value of the target steering angle and the articulation angle may have negative values ​​for angles to the left from the neutral position and positive values ​​for angles to the right.

[0080] For example, as shown in Fig. 6A, when the articulation angle θ2 is zero degrees, the initial value A0 of the target steering angle is +30 degrees. In that case, as shown in Fig. 6B, when the articulation angle θ2 is +15 degrees, the corrected value A1 of the target steering angle is +15 degrees. Note that these numerical values ​​are merely examples for ease of understanding and do not limit the scope of the present invention in any way.

[0081] In step S106, the controller 37 controls the steering actuators 41A and 41B so that the actual steering angle θ1 becomes the target steering angle. If the articulation angle θ2 is zero, the target steering angle is the initial value A0. If the articulation angle θ2 is less than zero or greater than zero, the target steering angle is the corrected value A1.

[0082] During automatic steering control, the controller 37 repeatedly executes the above-described processing, thereby automatically controlling the steering angle θ1 so that the work machine 1 travels in the target direction.

[0083] In the work machine 1 according to the present embodiment described above, the controller 37 determines the target direction in which the vehicle body 2 will travel. The controller 37 acquires the articulation angle θ2 of the front frame 11 relative to the rear frame 12. The controller 37 controls the multiple steering actuators 41A, 41B in accordance with the articulation angle θ2. In this way, the steering angle θ1 is set so that the vehicle body 2 moves in the target direction.

[0084] By configuring the work machine 1 in this manner, the multiple steering actuators 41A, 41B are controlled in accordance with the articulation angle θ2 when the target direction of the vehicle body 2 has been acquired. By controlling the multiple steering actuators 41A, 41B, the steering angle θ1 is set so that the vehicle body 2 moves in the target direction. As a result, the work machine 1 can be moved in the target direction even if the articulation angle θ2 changes.

[0085] Although one embodiment of the present invention has been described above, the present invention is not limited to the above embodiment, and various modifications are possible without departing from the gist of the invention.

[0086] The process of controlling the multiple steering actuators 41A, 41B in accordance with the current articulation angle θ2 may be applied not only when the vehicle body 2 moves forward as in the above embodiment, but also when the vehicle body 2 moves backward. In this case, the controller 37 may multiply the steering angle θ1 in the above embodiment by "-1".

[0087] The number of the multiple steering actuators 41A, 41B is not limited to that in the above embodiment, and may be one or three or more. The multiple steering actuators 41A, 41B are not limited to hydraulic cylinders, and may be hydraulic motors or electric motors. [Industrial Applicability]

[0088] According to the present invention, the work machine can be moved in the target direction even if the articulation angle changes. [Explanation of symbols]

[0089] 1. Work machinery 2. Body 3A,3B Front wheel 11 Front frame 12 Rear frame 37 Controller 41A, 41B Steering actuator 52 Direction Sensor θ1 steering angle θ2 articulation angle

Claims

1. a vehicle body including a rear frame and a front frame connected to the rear frame so as to be rotatable relative to the rear frame; a steering wheel supported by the front frame; an actuator for changing the steering angle of the steered wheels; a controller for controlling the actuator; Equipped with The controller determining a target direction in which the vehicle body will travel; obtaining an articulation angle of the front frame relative to the rear frame; By controlling the actuator in accordance with the articulation angle, the steering angle is set so that the vehicle body moves in the target direction. Work machinery.

2. The controller Obtaining a current traveling direction of the vehicle body; setting the steering angle in accordance with the articulation angle so that the current traveling direction coincides with the target direction; 2. The work machine according to claim 1.

3. The vehicle body further includes a direction sensor provided on the rear frame, The controller obtains the current heading from the direction sensor.

3. The work machine according to claim 2.

4. A method for controlling a work machine including a vehicle body including a rear frame and a front frame connected to the rear frame so as to be rotatable relative to the rear frame, steerable wheels supported by the front frame, and an actuator that changes the steering angle of the steerable wheels, determining a target direction in which the vehicle body will travel; Obtaining an articulation angle of the front frame relative to the rear frame; setting the steering angle so that the vehicle body moves in the target direction by controlling the actuator in accordance with the articulation angle; A method for providing the above.

5. Obtaining a current heading of the vehicle body; setting the steering angle in accordance with the articulation angle so that the current traveling direction coincides with the target direction; The method of claim 4 further comprising:

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