Construction machine and method for controlling construction machine

Abstract

This construction machine is provided with traveling wheels, a steering actuator, and a controller. The steering actuator changes the steering angle of the traveling wheels from a neutral angle to the left and right. The controller controls the steering actuator. The controller performs automatic steering control for controlling the steering angle by the steering actuator so that the construction machine travels along a prescribed target travel route. The controller determines a travel direction state indicating a forward / backward travel direction of the construction machine. The controller sets the steering angle to a neutral angle when it is determined that the traveling direction state is unknown during the automatic steering control.

Description

Technical Field

[0001] The present disclosure relates to controlling a construction machine and a method for a construction machine. Background Art

[0002] In construction machinery, there is a type of automatic steering control in which the construction machinery moves along a predetermined target travel route. For example, in Patent Document 1, a travel path is generated based on the position and orientation of a motor grader and the travel direction of the motor grader. Then, a steering mechanism is controlled in such a way that the motor grader travels along the travel path.

[0003] Prior art literature

[0004] Patent Literature

[0005] Patent Document 1: (Japan) Patent Publication No. 2021-54269 Summary of the invention

[0006] Technical problem to be solved by the invention

[0007] In the above-mentioned automatic steering control, when the construction machine deviates to the right from the travel path, the controller steers the front wheels to the left when moving forward and to the right when moving backward, thereby correcting the direction of the construction machine. When the construction machine deviates to the left from the travel path, the controller steers the front wheels to the right when moving forward and to the left when moving backward, thereby correcting the direction of the construction machine. In this way, the construction machine is automatically controlled to travel along the travel path.

[0008] The front and rear travel direction of the construction machine is determined, for example, by a command signal indicating the front and rear travel direction of the construction machine. For example, the construction machine has a shift lever that is operated to switch the forward and reverse directions of the construction machine. The controller detects the position of the shift lever and determines the front and rear travel direction of the construction machine based on the position of the shift lever.

[0009] However, in a construction machine, even if the shift lever is switched from the forward position to the reverse position, the construction machine may continue to move forward due to inertia. In this case, even if the controller determines that the direction of travel of the construction machine is reverse based on the position of the shift lever, the construction machine actually moves forward. Therefore, during the automatic steering control, the running wheels are turned in the direction opposite to the correct direction, causing the construction machine to shake. The purpose of the present disclosure is to suppress the shaking of the construction machine when the forward and reverse directions of the construction machine are switched during the automatic steering control.

[0010] Technical solutions for solving technical problems

[0011] The engineering machinery disclosed in one aspect includes a travel wheel, a steering actuator, and a controller. The steering actuator changes the steering angle of the travel wheel from a neutral angle to the left or right. The controller controls the steering actuator. The controller performs automatic steering control by controlling the steering angle through the steering actuator so that the engineering machinery travels along a specified target travel route. The controller determines a travel direction state indicating the front and rear travel direction of the engineering machinery. When the controller determines that the travel direction state is unclear during the automatic steering control, the controller sets the steering angle to a neutral angle.

[0012] Other aspects of the method for controlling construction machinery disclosed herein include the following steps: executing automatic steering control for controlling the steering angle of the construction machinery in such a manner that the construction machinery travels along a specified target route; determining a travel direction state indicating the front and rear travel directions of the construction machinery; and setting the steering angle to a neutral angle when it is determined in the automatic steering control that the travel direction state is unclear.

[0013] Another aspect of the present disclosure is a method for controlling construction machinery, which comprises the following steps: executing automatic steering control for controlling the steering angle of the construction machinery in such a manner that the construction machinery travels along a specified target travel route; determining a travel direction state indicating the front and rear travel directions of the construction machinery; and setting the steering angle to a neutral angle when the front and rear travel directions of the construction machinery are switched in the automatic steering control.

[0014] Effects of the Invention

[0015] According to the present disclosure, when it is determined that the state of the traveling direction indicating the front and rear traveling direction of the construction machine is unclear during the automatic steering control, the steering angle is set to a neutral angle. Thus, the construction machine is prevented from turning in a direction opposite to the appropriate direction. Therefore, when the forward and reverse directions of the construction machine are switched during the automatic steering control, the shaking of the construction machine can be suppressed. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 It is a perspective view of the construction machine according to the embodiment.

[0017] Figure 2 It is a side view of the construction machinery.

[0018] Figure 3 It is a schematic diagram showing the structure of construction machinery.

[0019] Figure 4 It is a top view showing the front part of the construction machine.

[0020] Figure 5 This is a diagram showing an example of the travel of the construction machine based on the operation of the steering operating member.

[0021] Figure 61 is a diagram showing automatic control of the steering angle in the straight-line maintaining mode.

[0022] Figure 7 This is a flowchart showing a process for determining a target angle according to a traveling direction state.

[0023] Figure 8 It is a block diagram showing the decision logic of the traveling direction state. DETAILED DESCRIPTION

[0024] Hereinafter, embodiments of the present invention will be described with reference to the drawings. Figure 1 It is a perspective view of the construction machine 1 according to the embodiment. Figure 2 is a side view of the construction machinery 1. Figure 1 As shown, the construction machine 1 includes a vehicle body 2, running wheels 3A, 3B, 4A-4D, and a working device 5. The vehicle body 2 includes a front frame 11, a rear frame 12, a cab 13, and a power room 14. The running wheels 3A, 3B, 4A-4D include front wheels 3A, 3B and rear wheels 4A-4D. The construction machine 1 turns left or right by turning the front wheels 3A, 3B to the left or right.

[0025] The rear frame 12 is connected to the front frame 11. The front frame 11 can be hinged to the left and right relative to the rear frame 12. In the following description, the front, rear, left, and right directions mean the front, rear, left, and right directions of the vehicle body 2 when the hinge angle is zero, that is, the front frame 11 and the rear frame 12 are straight.

[0026] The cab 13 and the engine room 14 are arranged on the rear frame 12. A driver's seat (not shown) is arranged in the cab 13. The engine room 14 is arranged behind the cab 13. The front frame 11 extends forward from the rear frame 12. The front wheels 3A and 3B are mounted on the front frame 11. The rear wheels 4A to 4D are mounted on the rear frame 12.

[0027] The working device 5 is movably connected to the vehicle body 2. The working device 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 traction rod 17 and an arc member 18. The traction rod 17 is arranged below the front frame 11.

[0028] The drawbar 17 is connected to the 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.

[0029] The arc member 18 is connected to the rear of the traction rod 17. The arc member 18 is supported rotatably relative to the traction rod 17. The blade 16 is connected to the arc member 18. The blade 16 is supported on the traction rod 17 via the arc member 18. Figure 2 As shown, the blade 16 is supported by the arc member 18 so as to be rotatable around the tilting shaft 21. The tilting shaft 21 extends in the left-right direction.

[0030] The construction machine 1 includes a plurality of actuators 22-26 for changing the posture of the working device 5. The plurality of actuators 22-26 include a plurality of hydraulic cylinders 22-25. The plurality of hydraulic cylinders 22-25 are connected to the working device 5. The plurality of hydraulic cylinders 22-25 are extended and retracted by hydraulic pressure. The plurality of hydraulic cylinders 22-25 change the posture of the working device 5 relative to the vehicle body 2 by extending and retracting. In the following description, the extension and retraction of the hydraulic cylinders is referred to as "stroke action".

[0031] In detail, the plurality of hydraulic cylinders 22-25 include a left lift cylinder 22, a right lift cylinder 23, a traction rod shift cylinder 24, and a blade tilt cylinder 25. The left lift cylinder 22 and the right lift cylinder 23 are disposed separately from each other in the left-right direction. The left lift cylinder 22 and the right lift cylinder 23 are connected to the traction rod 17. The left lift cylinder 22 and the right lift cylinder 23 are connected to the front frame 11 via a lifting bracket 29. The traction rod 17 swings up and down by the stroke action of the left lift cylinder 22 and the right lift cylinder 23. As a result, the blade 16 moves up and down.

[0032] The traction rod shift cylinder 24 is connected to the traction rod 17 and the front frame 11. The traction rod shift cylinder 24 is connected to the front frame 11 via the lifting bracket 29. The traction rod shift cylinder 24 extends obliquely downward from the front frame 11 toward the traction rod 17. The traction rod 17 swings left and right by the stroke action of the traction rod shift cylinder 24. The blade tilt cylinder 25 is connected to the arc member 18 and the blade 16. The blade 16 rotates around the tilt shaft 21 by the stroke action of the blade tilt cylinder 25.

[0033] The plurality of actuators 22-26 include a rotary actuator 26. The rotary actuator 26 is connected to the traction rod 17 and the arc member 18. The rotary actuator 26 rotates the arc member 18 relative to the traction rod 17. Thus, the blade 16 rotates around a rotation axis extending in the up-down direction.

[0034] Figure 3 Schematic diagram showing the structure of the construction machine 1. Figure 3 As shown, the construction machine 1 includes a driving source 31, a hydraulic pump 32, a power transmission device 33 and a working device valve 34. The driving source 31 is, for example, an internal combustion engine. Alternatively, the driving source 31 may also be an electric motor, or a hybrid power of an internal combustion engine and an electric motor. The hydraulic pump 32 is driven by the driving source 31 to discharge hydraulic oil.

[0035] The working device valve 34 is connected to the hydraulic pump 32 and the plurality of hydraulic cylinders 22-25 via a hydraulic circuit. The working device valve 34 includes a plurality of valves respectively connected to the plurality of hydraulic cylinders 22-25. The working device valve 34 controls the flow rate of the hydraulic oil supplied from the hydraulic pump 32 to the plurality of hydraulic cylinders 22-25. The working device valve 34 is, for example, an electromagnetic proportional control valve. Alternatively, the working device valve 34 may also be a hydraulic pilot proportional control valve.

[0036] In the present embodiment, the swing actuator 26 is a hydraulic motor. The working device valve 34 is connected to the hydraulic pump 32 and the swing actuator 26 via a hydraulic circuit. The working device valve 34 controls the flow rate of the hydraulic oil supplied from the hydraulic pump 32 to the swing actuator 26. In addition, the swing actuator 26 may also be an electric motor.

[0037] The power transmission device 33 transmits the driving force from the driving source 31 to the rear wheels 4A-4D. The power transmission device 33 may also include a torque converter and / or a plurality of speed change gears. Alternatively, the power transmission device 33 may also be a transmission such as an HST (Hydraulic Static Transmission) or an HMT (Hydraulic Mechanical Transmission).

[0038] The construction machine 1 includes a working device operating component 35, a shift operating component 53, a throttle operating component 36, a brake operating component 47, and a controller 37. The working device operating component 35 can be operated by an operator to change the posture of the working device 5. The working device operating component 35 includes, for example, a plurality of operating levers. Alternatively, the working device operating component 35 may also be other components such as a switch or a touch panel. The working device operating component 35 outputs a signal indicating the operator's operation on the working device operating component 35.

[0039] The shift operating component 53 can be operated by the operator to indicate the front and rear travel direction of the construction machine 1. The shift operating component 53 includes, for example, a shift lever. Alternatively, the shift operating component 53 can also be other components such as a switch or a touch panel. The shift operating component 53 can be operated between a forward position (F), a reverse position (R), and a neutral position (N1). The shift operating component 53 outputs a signal indicating the operating position of the shift operating component 53.

[0040] The throttle operating component 36 can be operated by the operator to make the construction machine 1 travel. The throttle operating component 36 includes, for example, an accelerator pedal. Alternatively, the throttle operating component 36 can also be other components such as a switch or a touch panel. The throttle operating component 36 outputs a signal indicating the operator's operation of the throttle operating component 36. The brake operating component 47 can be operated by the operator to brake the construction machine 1. The brake operating component 47 includes, for example, a brake pedal.

[0041] The controller 37 controls the power transmission device 33 according to the operation of the shift operating member 53, thereby switching the forward and reverse directions of the construction machine 1. Alternatively, the shift operating member 53 may be mechanically connected to the power transmission device 33. The forward and reverse gears of the power transmission device 33 may also be switched by mechanically transmitting the operation of the shift operating member 53 to the power transmission device 33.

[0042] The controller 37 controls the drive source 31 and the power transmission device 33 according to the operation of the accelerator operating member 36 to drive the construction machine 1. In addition, the controller 37 controls the hydraulic pump 32 and the working implement valve 34 according to the operation of the working implement operating member 35 to operate the working implement 5.

[0043] The controller 37 includes a storage device 38 and a processor 39. The processor 39 is, for example, a CPU, and executes a program for controlling the construction machine 1. The storage device 38 includes a memory such as a RAM and a ROM, and an auxiliary storage device such as an SSD or a HDD. The storage device 38 stores a program and data for controlling the construction machine 1.

[0044] The construction machine 1 is provided with a vehicle speed sensor 51. The vehicle speed sensor 51 detects the vehicle speed of the construction machine 1. The vehicle speed sensor 51 outputs a signal indicating the vehicle speed of the construction machine 1. The vehicle speed sensor 51 detects, for example, the output rotation speed of the power transmission device 33. The output rotation speed of the power transmission device 33 is equivalent to the vehicle speed of the construction machine 1. Alternatively, the vehicle speed sensor 51 may also be a GNSS (Global Navigation Satellite System) receiver such as a GPS (Global Positioning System).

[0045] The construction machine 1 is provided with a direction sensor 52. The direction sensor 52 detects the direction of travel of the vehicle body 2. The direction sensor 52 outputs a direction signal indicating the direction of travel of the vehicle body 2. The controller 37 obtains the direction of travel of the vehicle body 2 based on the direction signal from the direction sensor 52. The direction of travel of the vehicle body 2 is indicated by, for example, the yaw angle of the vehicle body 2. The direction sensor 52 is, for example, an IMU (inertial measurement unit). The controller 37 calculates the direction of travel of the vehicle body 2 based on the acceleration and angular velocity of the vehicle body 2. Alternatively, the direction sensor 52 may also be a GNSS receiver. The controller 37 may also obtain the direction of travel of the vehicle body 2 based on the change in the position of the construction machine 1 detected by the direction sensor 52.

[0046] like Figure 3 As shown, the construction machine 1 includes a steering angle sensor 40, a steering actuator 41, and a steering valve 42. The steering actuator 41 is a hydraulic cylinder. The steering actuator 41 is extended and retracted by hydraulic oil from a hydraulic pump 32. The steering actuator 41 steers the front wheels 3A and 3B by extending and retracting.

[0047] Figure 4 1 is a top view showing the front part of the construction machine 1. Figure 4 As shown, the front wheels 3A and 3B include a first front wheel 3A and a second front wheel 3B. The first front wheel 3A and the second front wheel 3B are separated in the left-right direction. The first front wheel 3A is supported on the front frame 11 in a manner that allows rotation around a first steering shaft 43. The second front wheel 3B is supported on the front frame 11 in a manner that allows rotation around a second steering shaft 44. The first steering shaft 43 and the second steering shaft 44 extend in the up-down direction.

[0048] The steering actuator 41 is connected to the front wheels 3A, 3B and the front frame 11. The steering actuator 41 changes the steering angle θ1 of the front wheels 3A, 3B from a predetermined neutral angle to the left or right. Figure 4 As shown, the steering angle θ1 is the angle of the front wheels 3A, 3B relative to the front-rear direction of the construction machine 1. The front-rear direction of the construction machine 1 refers to the front-rear direction of the front frame 11. However, the front-rear direction of the construction machine 1 may also refer to the front-rear direction of the rear frame 12.

[0049] The neutral angle is the steering angle θ1 of 0 degrees. Therefore, the steering angle θ1 being the neutral angle means that the front wheels 3A and 3B are facing the front of the construction machine 1. Figure 4 In FIG. 3A, 3A' indicates the first front wheel 3A which has turned from the neutral angle to the left by a steering angle θ1. 3B' indicates the second front wheel 3B which has turned from the neutral angle to the left by a steering angle θ1.

[0050] The steering valve 42 is connected to the hydraulic pump 32 and the steering actuator 41 via a hydraulic circuit. The steering valve 42 controls the flow rate of hydraulic oil supplied from the hydraulic pump 32 to the steering actuator 41 .

[0051] The steering angle sensor 40 detects the steering angle θ1. The steering angle sensor 40 outputs an angle signal indicating the steering angle θ1. The controller 37 obtains the current steering angle θ1 based on the angle signal from the steering angle sensor 40. The steering angle sensor 40 detects, for example, the stroke amount of the steering actuator 41. The steering angle θ1 is calculated based on the stroke amount of the steering actuator 41. Alternatively, the steering angle sensor 40 may also directly detect the steering angle θ1.

[0052] like Figure 3 As shown, the engineering machine 1 includes a steering operating component 45. The steering operating component 45 can be operated by an operator to change the steering angle θ1 of the front wheels 3A and 3B to the left and right. The steering operating component 45 can be operated from a neutral position (N2) to a left steering range (L) and a right steering range (R). The steering operating component 45 is, for example, a lever. Alternatively, the steering operating component 45 may also be other components such as a steering wheel or a switch. The steering operating component 45 outputs a signal indicating the operator's operation on the steering operating component 45.

[0053] The controller 37 controls the steering valve 42 according to the operation of the steering operating member 45 to operate the steering actuator 41. As a result, the steering angle θ1 of the front wheels 3A, 3B changes to the left and right, and the construction machine 1 turns to the left and right.

[0054] Next, the automatic steering control for automatically controlling the steering angle θ1 will be described. In the automatic steering control, the controller 37 controls the steering actuator 41 so that the steering angle θ1 becomes a predetermined target angle. The automatic control includes a center return mode and a straight-moving maintenance mode.

[0055] In the center return mode, the controller 37 controls the steering actuator 41 to automatically return the steering angle θ1 to the neutral angle when the steering operating member 45 returns to the neutral position (N2) from the left steering range (L) or returns to the neutral position (N2) from the right steering range (R).

[0056] For example, when the steering angle θ1 is a predetermined angle to the left, if the steering operating member 45 returns to the neutral position (N2), the controller 37 controls the steering actuator 41 so that the steering angle θ1 returns from the predetermined angle to the left to the neutral angle. When the steering angle θ1 is a predetermined angle to the right, if the steering operating member 45 returns to the neutral position (N2), the controller 37 controls the steering actuator 41 so that the steering angle θ1 returns from the predetermined angle to the right to the neutral angle.

[0057] Figure 5 4 is a diagram showing an example of the travel of the construction machine 1 based on the operation of the steering operating member 45. Figure 5As shown, when the construction machine 1 is at the location P1, the steering operating member 45 is at the neutral position (N2). The steering angle θ1 is the neutral angle, and the construction machine 1 is moving straight. At the location P2, if the operator operates the steering operating member 45 by the operation amount L1 within the left operation range, the steering angle θ1 of the front wheels 3A and 3B changes from the neutral angle to the left. As a result, the construction machine 1 turns to the left.

[0058] When the operator keeps the steering operation member 45 at the operation amount L1 from the point P2 to the point P3, the steering angle θ1 of the front wheels 3A, 3B continues to increase to the maximum steering angle θmax to the left, thereby causing the construction machine 1 to continue turning to the left.

[0059] Furthermore, at point P3, when the operator returns the steering member 45 to the neutral position (N2), the steering angle θ1 of the front wheels 3A, 3B decreases from the maximum steering angle θmax to the neutral angle in the center return mode. Then, at point P5, the steering angle θ1 of the front wheels 3A, 3B returns to the neutral angle.

[0060] In the straight-line maintenance mode, the controller 37 controls the steering angle θ1 so that the construction machine 1 travels along a straight target travel route. Specifically, the controller 37 controls the steering angle θ1 so that the travel direction of the vehicle body 2 is maintained in the target direction. Figure 5 As shown, the controller 37 determines the travel direction (H1) of the vehicle body 2 when the steering angle θ1 returns to the neutral angle at the point P5 as the target direction. Furthermore, the controller 37 controls the steering actuator 41 to maintain the travel direction of the vehicle body 2 in the target direction H1. As a result, the construction machine 1 moves along a linear target travel route R1 extending in the target direction H1.

[0061] Specifically, the controller 37 determines the target angle of the steering angle θ1 based on the difference between the current traveling direction of the vehicle body 2 and the target direction H1. The controller 37 controls the steering actuator 41 so that the steering angle θ1 becomes the target angle. For example, the controller 37 determines the target angle of the steering angle θ1 by multiplying the difference between the current traveling direction of the vehicle body 2 and the target direction H1 by a predetermined gain. The controller 37 controls the steering actuator 41 through feedback control so that the steering angle θ1 is maintained at the target angle.

[0062] In the straight-line maintenance mode, the controller 37 makes the target angle of the steering angle θ1 opposite to that when the vehicle body 2 moves forward when the vehicle body 2 moves backward. Figure 6As shown in FIG. 1 , when the orientation of the construction machine 1 is deviated to the right from the target travel route R1, as shown by arrow mark A1, when the construction machine 1 is moving forward, the controller 37 determines the target angle to be an angle to the left of the neutral angle. When the orientation of the construction machine 1 is deviated to the right from the target travel route R1, as shown by arrow mark A2, when the construction machine 1 is moving backward, the controller 37 determines the target angle to be an angle to the right of the neutral angle.

[0063] On the contrary, when the direction of the construction machine 1 is deviated to the left from the target travel route R1, the controller 37 determines the target angle to be an angle to the right of the neutral angle when the construction machine 1 is moving forward. When the direction of the construction machine 1 is deviated to the left from the target travel route R1, the controller 37 determines the target angle to be an angle to the left of the neutral angle when the construction machine 1 is moving backward. That is, the controller 37 determines the travel direction state of the vehicle body 2 and determines the target angle according to the travel direction state. The travel direction state indicates the front and rear travel directions of the construction machine 1.

[0064] Figure 7 FIG. 4 is a flowchart showing a process for determining a target angle according to a traveling direction state. Figure 7 As shown, in step S101, the controller 37 obtains the vehicle speed. The controller 37 obtains the vehicle speed based on the signal from the vehicle speed sensor 51. In step S102, the controller 37 obtains the shift operation position. The shift operation position is the operation position of the shift operation member 53. The controller 37 obtains the shift operation position based on the signal from the shift operation member 53. The controller 37 obtains any one of the forward position (F), the reverse position (R), and the neutral position (N2) as the shift operation position.

[0065] In step S103, the controller 37 determines the traveling direction state. The controller 37 determines the traveling direction state based on the vehicle speed and the shift operation position. Figure 8 is a block diagram showing the decision logic of the traveling direction state. Figure 8 As shown, the travel direction states include "stop", "forward", "backward" and "unknown".

[0066] like Figure 8 As shown, in the initial state, the travel direction state is "stop". When the travel direction state is "stop", the controller 37 determines that the travel direction state is "forward" when the forward condition is satisfied. The forward condition includes the case where the shift operation position is the forward position (F).

[0067] When the reverse condition is satisfied when the traveling direction state is “stopped,” the controller 37 determines that the traveling direction state is “reverse.” The reverse condition includes a condition that the shift operation position is the reverse position (R).

[0068] The controller 37 determines that the traveling direction state is "unknown" when the first unknown condition is satisfied when the traveling direction state is "forward". The first unknown condition includes a condition that the shift operation position is a position other than the forward position (F) and the vehicle speed is less than a first threshold. That is, the first unknown condition includes a condition that the shift operation position is a reverse position (R) or a neutral position (N2) and the vehicle speed is less than the first threshold. The first threshold, for example, indicates a slow speed to the extent that the front and rear traveling directions of the construction machine 1 cannot be accurately determined.

[0069] When the second unknown condition is satisfied when the traveling direction state is "reverse", the controller 37 determines that the traveling direction state is "unknown". The second unknown condition includes the condition that the shift operation position is a position other than the reverse position (R) and the vehicle speed is less than the second threshold. That is, the second unknown condition includes the condition that the shift operation position is the forward position (F) or the neutral position (N2) and the vehicle speed is less than the second threshold. The second threshold may be the same as the first threshold. The second threshold may also be different from the first threshold. The second threshold, for example, represents a slow speed to the extent that the front and rear traveling directions of the construction machine 1 cannot be accurately determined.

[0070] When the forward condition is satisfied when the traveling direction state is "unclear", the controller 37 determines that the traveling direction state is "forward". When the backward condition is satisfied when the traveling direction state is "unclear", the controller 37 determines that the traveling direction state is "backward". When the stop condition is satisfied when the traveling direction state is "unclear", the controller 37 determines that the traveling direction state is "stop". The stop condition includes a condition that the vehicle speed is less than a third threshold value for more than a specified time. The third threshold value, for example, represents a slow speed that is considered to be a degree of stop of the construction machinery 1. As described above, the controller 37 determines whether the traveling direction state is "stop", "forward", "backward" or "unclear".

[0071] like Figure 7 As shown, in the case where the state of the traveling direction in the straight-line maintaining mode is forward, in step S104, the controller 37 determines the target angle of the steering angle θ1 as the forward target angle. The forward target angle is the target angle of the steering angle θ1 when the vehicle is moving forward. In the case where the state of the traveling direction in the straight-line maintaining mode is reverse, in step S105, the controller 37 determines the target angle of the steering angle θ1 as the reverse target angle. The reverse target angle is an angle that is opposite to the forward target angle on the left and right.

[0072] In the case where the state of the traveling direction is unknown in the straight-moving maintaining mode, the controller 37 determines the target angle of the steering angle θ1 as the neutral angle in step S106. In the execution of the straight-moving maintaining mode, the controller 37 repeatedly executes the above-mentioned processing. Therefore, when the controller 37 determines that the state of the traveling direction is unknown, the controller 37 sets the steering angle to the neutral angle, and then maintains the steering angle at the neutral angle until the state of the traveling direction is determined to be forward or reverse.

[0073] When the traveling direction state changes from unknown to forward, the controller 37 changes the steering angle from the neutral angle to the forward target angle. When the traveling direction state changes from unknown to reverse, the controller 37 changes the steering angle from the neutral angle to the reverse target angle.

[0074] In the construction machine 1 of the present embodiment described above, when it is determined that the traveling direction state is unclear during the automatic steering control, the steering angle is set to a neutral angle. This prevents the construction machine 1 from turning in a direction opposite to the correct direction. This prevents the construction machine 1 from shaking when the forward and reverse directions of the construction machine 1 are switched during the automatic steering control.

[0075] As mentioned above, although one embodiment of the present invention has been described, the present invention is not limited to the above-mentioned embodiment, and various modifications can be made without departing from the gist of the invention.

[0076] The construction machine 1 is not limited to a grader, but may be other construction machines such as a wheel loader, a dump truck, or a forklift. The number of the steering actuator 41 is not limited to one, but may be two or more. The steering actuator 41 is not limited to a hydraulic cylinder, but may be a hydraulic motor or an electric motor. In the above-mentioned embodiment, the construction machine 1 turns left or right by turning the front wheels left or right. However, the construction machine 1 may also turn left or right by turning the rear wheels left or right.

[0077] The processing of the automatic steering control is not limited to the above-mentioned embodiment, and may also be changed. For example, when the controller 37 determines that the state of the traveling direction is unclear, the steering angle may be maintained at a neutral angle until a predetermined time has passed. The controller 37 may also set the steering angle to a neutral angle when the front and rear traveling directions of the construction machine 1 are switched, regardless of whether the state of the traveling direction is unclear. The controller 37 may also maintain the steering angle at a neutral angle when the front and rear traveling directions of the construction machine 1 are switched, until a predetermined time has passed.

[0078] The target direction H1 is not limited to the direction of travel of the vehicle body 2 when the steering angle θ1 returns to the neutral angle, and may be determined by other methods. For example, the target direction H1 may be the direction of travel of the vehicle body 2 when the steering operating member returns to the neutral position (N2). Alternatively, the target direction H1 may be input by an operator. The target direction H1 may also be input from an external computer.

[0079] In the above-mentioned embodiment, the command signal indicating the front and rear travel direction of the construction machine 1 is a signal indicating the shift operation position from the shift operation member 53. However, the command signal indicating the front and rear travel direction of the construction machine 1 may also be other signals. For example, in the case where the controller 37 automatically controls the travel of the construction machine 1, the command signal indicating the front and rear travel direction of the construction machine 1 may also be generated by the controller 37.

[0080] In the above embodiment, the target route R1 is defined by the target direction H1 in the straight-moving maintaining mode, but the target route R1 may be set by other methods. For example, the target route R1 may be any path input by the operator. The target route R1 may be any path input from an external computer.

[0081] Industrial Applicability

[0082] According to the present disclosure, when the forward and reverse directions of the construction machine are switched during automatic steering control, the shaking of the construction machine is suppressed.

[0083] Description of Reference Numerals

[0084] 1: Construction machinery

[0085] 3A, 3B: Driving wheels

[0086] 37: Controller

[0087] 41: Steering actuator

Claims

1. A construction machine, characterized in that: have: Traveling wheels; A steering actuator that changes the steering angle of the travel wheels from a neutral angle to the left or right; a controller that controls the steering actuator, The controller performs automatic steering control by controlling the steering angle through the steering actuator so that the construction machine travels along a prescribed target travel route. determining a traveling direction state indicating a front-rear traveling direction of the construction machine, When it is determined that the traveling direction state is unclear during the automatic steering control, the steering angle is set to the neutral angle.

2. The construction machinery according to claim 1, characterized in that: The controller acquires a command signal indicating a front and rear traveling direction of the construction machine, acquires a vehicle speed of the construction machine, and determines the traveling direction state based on the command signal and the vehicle speed.

3. The construction machinery according to claim 2, characterized in that: When the traveling direction state is forward, the controller determines that the traveling direction state is unclear when the command signal indicates an instruction other than forward and the vehicle speed is less than a predetermined threshold.

4. The construction machinery according to claim 2, characterized in that: When the traveling direction state is reverse, the controller determines that the traveling direction state is unclear when the command signal indicates an instruction other than reverse and the vehicle speed is less than a predetermined threshold.

5. The construction machine according to claim 1, characterized in that: The controller maintains the steering angle at the neutral angle until the traveling direction state is determined to be forward or reverse.

6. The construction machine according to claim 1, characterized in that: The controller acquires a command signal indicating the front and rear travel direction of the construction machine, When the switching of the traveling direction is instructed by the command signal, if it is determined that the traveling direction state is unclear, the steering angle is maintained at the neutral angle until a predetermined time has elapsed.

7. A method for controlling a construction machine, characterized in that: The following steps are required: performing automatic steering control to control a steering angle of the engineering machine so that the engineering machine travels along a specified target travel route; determining a traveling direction state indicating a front and rear traveling direction of the construction machine; When it is determined that the traveling direction state is unclear during the automatic steering control, the steering angle is set to a neutral angle.

8. The method according to claim 7, characterized in that The following steps are required: Acquiring a command signal indicating the front and rear travel direction of the engineering machinery; Obtaining the speed of the engineering machinery; The traveling direction state is determined based on the command signal and the vehicle speed.

9. The method according to claim 8, characterized in that The following steps are required: When the traveling direction state is forward, and when the command signal indicates an instruction other than forward and the vehicle speed is less than a predetermined threshold, it is determined that the traveling direction state is unclear.

10. The method according to claim 8, characterized in that The following steps are required: When the traveling direction state is reverse, and when the command signal indicates an instruction other than reverse and the vehicle speed is less than a predetermined threshold, it is determined that the traveling direction state is unclear.

11. The method according to claim 7, characterized in that The following steps are required: The steering angle is maintained at the neutral angle until it is determined that the traveling direction state is forward or reverse.

12. The method according to claim 7, characterized in that The following steps are required: Acquiring a command signal indicating the front and rear travel direction of the engineering machinery; When the switching of the traveling direction is instructed by the command signal, if it is determined that the traveling direction state is unclear, the steering angle is maintained at the neutral angle until a predetermined time has elapsed.

13. A method for controlling a construction machine, characterized in that: The following steps are required: performing automatic steering control to control a steering angle of the engineering machine so that the engineering machine travels along a specified target travel route; determining a traveling direction state indicating a front and rear traveling direction of the construction machine; When the front and rear traveling directions of the construction machine are switched during automatic steering control, the steering angle is set to a neutral angle.

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