Work vehicles

Abstract

To provide a work vehicle capable of preventing a turning radius from swelling large and of appropriately progressing to the next step.SOLUTION: A riding type rice transplanter P is configured to perform automatic steering control controlling a steering device 9 on the basis of location information on a traveling machine body 1 acquired by a location information acquisition system 41. When the automatic steering control is on and an indicated steering angle for the steering device 9 is over a prescribed turning determined angle from a detection angle of the steering angle sensor 21 or a control part 50, front wheels 10 are steered up to a mechanical limit angle, and a detected angle of the steering angle sensor 21 when the limit angle is reached is set as an indicated steering angle for turning.SELECTED DRAWING: Figure 9

Description

[Technical field]

[0001] The present invention relates to a work vehicle capable of performing automatic steering control. [Background technology]

[0002] There is known a work vehicle capable of performing automatic steering control that controls a steering device based on position information of a traveling vehicle body acquired by a position information acquisition system (see, for example, Patent Document 1). This type of work vehicle is equipped with a steering angle sensor that detects the steering angle of the front wheels, and automatic steering control is performed so that a target steering angle (a steering angle commanded by a control unit) and an angle detected by the steering angle sensor match. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2020-195285 A Summary of the Invention [Problem to be solved by the invention]

[0004] However, in this type of work vehicle, due to the characteristics of the steering angle sensor and the surrounding mechanical configuration, there is a risk that errors such as hysteresis will occur between the angle detected by the steering angle sensor and the actual steering angle of the front wheels, which may reduce the accuracy of the automatic steering control. In particular, when the vehicle is turning, the effect of the errors becomes greater, which may cause the turning radius to increase significantly, making it impossible to properly proceed to the next step. [Means for solving the problem]

[0005] The present invention has been created in consideration of the above-mentioned actual situation and with the aim of solving these problems. The invention of claim 1 is a work vehicle comprising a running body having front and rear wheels, a position information acquisition system that acquires position information of the running body, a steering device that steers the front wheels by driving an actuator, a steering angle sensor that detects the steering angle of the front wheels, and a control unit that is configured to be able to execute automatic steering control that controls the steering device based on the position information of the running body acquired by the position information acquisition system, wherein the control unit is characterized in that when the automatic steering control is on and the detected angle of the steering angle sensor or the instructed steering angle from the control unit to the steering device exceeds a predetermined turning judgment angle, the control unit is equipped with a turning instruction steering angle setting means that steers the front wheels to a mechanical limit angle and sets the detected angle of the steering angle sensor at the time when the limit angle is reached as a turning instruction steering angle. The invention of claim 2 is the work vehicle described in claim 1, wherein the turning command steering angle setting means, when the automatic steering control is on and the detection angle of the steering angle sensor or the command steering angle exceeds the predetermined turning judgment angle, steers the front wheels to a mechanical limit angle, and then steers the front wheels in the opposite direction by a predetermined return angle, and sets the detection angle of the steering angle sensor at that point in time as the turning command steering angle. The invention of claim 3 is the work vehicle described in claim 1, wherein the turning command steering angle setting means, when the automatic steering control is on and the detection angle of the steering angle sensor or the command steering angle exceeds the predetermined turning judgment angle, steers the front wheels to a mechanical limit angle, and sets the angle obtained by subtracting a predetermined return angle from the detection angle of the steering angle sensor at the time when the limit angle is reached as the turning command steering angle. The invention of claim 4 is a work vehicle described in any one of claims 1 to 3, characterized in that the control unit resets the turning instruction steering angle to an initial value when the automatic steering control is off, or when the detection angle of the steering angle sensor or the instruction steering angle becomes less than the predetermined turning judgment angle. Effect of the Invention

[0006] According to the invention of claim 1, when the vehicle turns, the front wheels are steered to the mechanical limit angle, so that the turning radius is prevented from increasing too much and the vehicle can proceed to the next stroke appropriately. Also, the angle detected by the steering angle sensor at the time when the limit angle is reached is set as the command steering angle for turning, so that the front wheels can be maintained at the mechanical limit angle while the vehicle is turning. In addition, according to the invention of claim 2, after the front wheels are steered to the mechanical limit angle, the front wheels are steered in the opposite direction by a predetermined return angle, and the angle detected by the steering angle sensor at that point is set as the command steering angle for turning, thereby suppressing the operation of the relief valve that occurs at the limit angle and reducing the load on the hydraulic equipment. In addition, according to the invention of claim 3, the angle obtained by subtracting a predetermined return angle from the detection angle of the steering angle sensor at the time when the limit angle is reached is set as the command steering angle for turning. Therefore, after the front wheels reach the limit angle, the front wheels can be steered in the opposite direction by the predetermined return angle based on the command steering angle for turning thus subtracted. In addition, according to the invention of claim 4, the control unit resets the turning instruction steering angle to its initial value when the automatic steering control is off or when the detected angle or the indicated steering angle of the steering angle sensor becomes equal to or less than a predetermined turning judgment angle, thereby suppressing the influence on the automatic steering control other than when the aircraft is turning, and by resetting a new turning instruction steering angle each time the aircraft is turned, it is possible to appropriately respond to error fluctuations in the steering angle sensor during work. [Brief description of the drawings]

[0007] [Figure 1] FIG. 1 is a left side view of a riding rice transplanter according to an embodiment of the present invention. [Diagram 2] FIG. [Diagram 3] FIG. [Figure 4] FIG. [Diagram 5] FIG. [Figure 6]FIG. 2 is a perspective view of the steering device as viewed from the right front. [Figure 7] 5A and 5B are diagrams illustrating the steering angle, in which FIG. 5A is a plan view of a steering device, and FIG. 5B is a diagram illustrating the relationship between the mechanical steering angle and the steering angle detected by a steering angle sensor. [Figure 8] 1A is a perspective view of the automatic steering unit, FIG. 1B is a front view showing an operation panel of the automatic steering unit, and FIG. 1C is a front view showing another example of the operation panel. [Figure 9] FIG. 2 is a block diagram showing the control configuration of the riding rice transplanter. [Figure 10] FIG. 2 is an explanatory diagram showing the working travel path of the riding rice transplanter. [Figure 11] FIG. 1 is an explanatory diagram showing the turning path of a riding rice transplanter. [Figure 12] 5 is a flowchart showing a main routine of limit angle forced steering control. [Figure 13] 10 is a flowchart showing a flag control which is a subroutine of the limit angle forced steering control. [Figure 14] 10 is a flowchart showing an execution / stop control which is a subroutine of the limit angle forced steering control. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In Fig. 1 to Fig. 3, reference numeral 1 denotes a running machine body of a riding rice transplanter P (work vehicle), and a planting work machine 3 is connected to the rear of the running machine body 1 via a lifting link mechanism 2 so as to be liftable and lowerable.

[0009] The planting machine 3 is equipped with a seedling carrier 4 on which the mat seedlings are placed, and a planting mechanism 5 that picks up the seedlings from the lower end of the seedling carrier 4 and plants them in the field. The planting machine 3 of this embodiment is a six-row planting model that can plant six rows of seedlings at the same time, and six planting mechanisms 5 are arranged side by side at predetermined intervals in the vehicle width direction.

[0010] The running body 1 comprises an engine mounting section 6 on which an engine (not shown) is mounted, an HST 7 (see Figure 4) that continuously changes the speed of the engine power, a transmission case 8 (see Figures 4 and 5) that further changes the speed of the power input from the HST 7 and outputs it as running power and working power, front wheels 10 that are driven by the running power output by the transmission case 8 and steered by a steering device 9 described later, rear wheels 11 that are driven by the running power output by the transmission case 8, and a control section 12 on which the operator rides.

[0011] The operating section 12 is equipped with operating tools such as a steering handle 13 for steering the front wheels 10, a main speed change lever 14 for changing the speed of the HST 7, and a work machine lifting / lowering lever (not shown) that also serves as a lifting / lowering tool for the planting work machine 3 and a planting clutch operating tool.

[0012] The steering device 9 is a device that steers the front wheels 10 in response to manual operation of the steering wheel 13 or operation of an automatic steering unit 15 (see Figure 8) described later, and as shown in Figures 4 to 7, it is equipped with a pair of left and right front axles 16 that support the pair of left and right front wheels 10 in a steerable manner, a torque generator 18 that swings a pitman arm 17 left and right in response to manual operation of the steering wheel 13 or operation of the automatic steering unit 15 described later, and a pair of left and right steering rods 19 that connect the pitman arm 17 to the left and right front axles 16.

[0013] 4 to 7, the steering device 9 is provided with a steering angle sensor 21 that detects the steering angle of the front wheels 10 via a sensor interlocking mechanism 20. The steering angle sensor 21 is, for example, a potentiometer, and is attached to a sensor bracket 22.

[0014] The sensor interlocking mechanism 20 comprises a first interlocking arm 24 and a second interlocking arm 25 which rotate together around a first support shaft 23 as a fulcrum, a third interlocking arm 27 which rotates around a second support shaft 26 provided on the sensor bracket 22 as a fulcrum, a first interlocking rod 28 which connects the first interlocking arm 24 and the pitman arm 17, and a second interlocking rod 29 which connects the second interlocking arm 25 and the third interlocking arm 27.

[0015] When the front wheels 10 are steered, the third interlocking arm 27 rotates via the pitman arm 17, the first interlocking rod 28, the first interlocking arm 24, the second interlocking arm 25, and the second interlocking rod 29. The third interlocking arm 27 has a pin 27a that engages with the sensor arm 21a of the steering angle sensor 21, and inputs a rotation angle corresponding to the steering angle of the front wheels 10 to the steering angle sensor 21.

[0016] As shown in Fig. 7(a), the steering device 9 can steer the front wheels 10 up to a mechanical limit angle of ±α2, and the detection range of the steering angle sensor 21 includes the mechanical limit angle range of -α2 to +α2 of the front wheels 10. However, as shown in Fig. 7(b), there is a possibility that errors such as hysteresis and offset may occur between the angle detected by the steering angle sensor 21 and the actual steering angle of the front wheels 10 due to the characteristics of the steering angle sensor 21 and the mechanical configuration surrounding it.

[0017] As shown in (a) of Fig. 8, an automatic steering unit 15 is connected to the steering wheel 13. The automatic steering unit 15 includes a steering motor 30 (see Fig. 9) that rotates the steering wheel 13 with motor power instead of manual operation of the steering wheel 13, and an operation panel 31 on which operating tools and monitor lamps related to automatic steering control, which will be described later, are arranged. The automatic steering unit 15 also includes a current value sensor 32 (see Fig. 9) that detects the value of a current flowing through the steering motor 30, and has a manual operation priority function that detects manual operation of the steering wheel 13 based on the detection value of the current value sensor 32 and automatically stops driving the steering motor 30.

[0018] As shown in (b) of Fig. 8, the operation panel 31 is equipped with a power switch 33, an automatic steering switch 34 that allows switching of automatic steering control from an automatic steering OFF state in which automatic steering is not performed to an automatic steering ON state in which automatic steering is performed and from the automatic steering ON state to the automatic steering OFF state, a start point A registration switch 35 that registers a start point A described later, an end point B registration switch 36 that registers an end point B described later, a reset switch 37 disposed near the automatic steering switch 34, and a notification display unit 38 that issues a notification by displaying a lamp. Note that (c) of Fig. 8 shows an operation panel 31B that is used when automatic steering is performed based on a camera image.

[0019] 1 to 3, a positioning frame 40 shaped like a square when viewed from the front is erected on the control unit 12. The positioning frame 40 has a pair of left and right vertical frame sections 40a extending upward, and a horizontal frame section 40b connecting the upper ends of the left and right vertical frame sections 40a. Two GNSS antennas 42, 43, which are components of a position information acquisition system 41 described below, are attached to the horizontal frame section 40b, and a tablet 44 that displays navigation information and the like is attached to one of the left and right vertical frames 40a.

[0020] As shown in FIG. 9, the traveling vehicle 1 includes a position information acquisition system 41 and a control unit 50 as a control configuration for performing automatic steering control. For example, an RTK-GNSS positioning system capable of highly accurate positioning with an error of several centimeters is adopted as the position information acquisition system 41. The RTK-GNSS positioning system performs GNSS positioning such as GPS at a fixed base station and a moving mobile station, and corrects the positioning data in real time with a correction signal transmitted from the base station to the mobile station, thereby achieving highly accurate positioning with an error of several centimeters. In addition, if two GNSS antennas are installed at a predetermined interval on the mobile station, it becomes possible to detect not only the absolute position of the mobile station but also the traveling direction (azimuth) of the mobile station with high accuracy based on the two positioning results.

[0021] Specifically, as shown in Fig. 9, the position information acquisition system 41 of this embodiment includes a GNSS unit 45 which is a control unit that executes RTK-GNSS positioning, a reference GNSS antenna 42 and an orientation GNSS antenna 43 which are attached to the horizontal frame portion 40b of the positioning frame 40 at a predetermined interval in the vehicle width direction, and a correction signal receiving device 47 which receives a correction signal from a fixedly installed RTK base station 46. The GNSS unit 45 transmits positioning data (absolute position data and traveling direction data) obtained by RTK-GNSS positioning to the control unit 50 via wired communication means such as CAN, and transmits it to the tablet 44 via wireless communication means such as Bluetooth (registered trademark).

[0022] The control unit 50 is a control unit (including a CPU, a memory unit, a timer, etc.) that executes automatic steering control, and as shown in FIG. 9, the input side of the control unit 50 is connected to the above-mentioned steering angle sensor 21, current value sensor 32, automatic steering switch 34, start point A registration switch 35, end point B registration switch 36 and reset switch 37, and the output side of the control unit 50 is connected to the above-mentioned steering motor 30 and notification display unit 38, as well as an alarm buzzer 39 that outputs an alarm sound.

[0023] The automatic steering control is an automatic control function that automatically steers the front wheels 10 so that the traveling body 1 automatically moves straight along a virtual target driving line (L1, L2, ... Ln) based on the position information of the traveling body 1 acquired by the position information acquisition system 41, and when it reaches the end of the virtual target driving line, automatically turns and transitions to the virtual target driving line of the next stroke.

[0024] In normal rice planting work using 6-row planting specifications, a first work stroke (shown by circled number 1 in FIG. 10) in which planting travel is performed leaving a headland that serves as turning space for the traveling body 1, a second work stroke (shown by circled number 2 in FIG. 10) in which planting travel is performed on the outer periphery of the headland, and a third work stroke (shown by circled number 3 in FIG. 10) in which planting travel is performed on the inner periphery of the headland. The automatic steering control in this embodiment includes automatic straight-line control and automatic turning control in the first work stroke, but automatic steering control may also be executed in the second and third work strokes.

[0025] As shown in Figure 10, at the start of work, the start point A registration switch 35 is operated at the start position of the reference travel line (L0), which is the first planting work process, to register the positioning data of the start point A, and the end point B registration switch 36 is operated at the end position of the reference travel line (L0) to register the positioning data of the end point B. This causes the subsequent virtual target travel lines (L1, L2, ... Ln) to be automatically calculated based on the reference travel line (L0).

[0026] As shown in FIG. 11, in the automatic steering control, when the traveling machine body 1 (the planting position of the planting machine 3) reaches the end of the virtual target traveling line (the rear end of the traveling machine body 1 is at position T0), the planting machine 3 is automatically raised and the front wheels 10 are automatically steered to the turning instruction steering angle, and the traveling machine body 1 is turned at the headland. In the automatic steering control, when the rear end of the traveling machine body 1 reaches the turning end position T1, the front wheels 10 are returned to the straight direction and the traveling machine body 1 enters the virtual target traveling line of the next process. In addition, in the automatic steering control, when the traveling machine body 1 (the planting position of the planting machine 3) reaches the start of the virtual target traveling line of the next process (the rear end of the traveling machine body 1 is at position T2), the planting machine 3 is automatically lowered and the planting traveling of the next process is started.

[0027] However, as mentioned above, if there is an error such as hysteresis or offset between the angle detected by the steering angle sensor 21 and the actual steering angle of the front wheel 10, the effect of the error will be large when the aircraft is turning, and the turning radius may increase significantly, making it impossible to properly enter the next stroke.

[0028] Therefore, the control unit 50 of this embodiment includes a limit angle forced steering control means (turn command steering angle setting means) capable of solving the above-mentioned problems. When the automatic steering control is on and the detected angle of the steering angle sensor 21 or the command steering angle from the control unit 50 to the automatic steering unit 15 exceeds a predetermined turning judgment angle, the limit angle forced steering control means steers the front wheels 10 to a mechanical limit angle and sets the detected angle of the steering angle sensor 21 at the time when the limit angle is reached as the turning command steering angle. The reaching of the mechanical limit angle of the front wheels 10 can be determined based on whether or not the detection value of the above-mentioned current value sensor 32 exceeds a predetermined threshold value and the duration of this (hereinafter, may be referred to as a steering load counter) exceeds a predetermined time.

[0029] According to such limit angle forced steering control means, when the vehicle turns, the front wheel 10 is steered to the mechanical limit angle, so that the turning radius is prevented from increasing too much and the vehicle can proceed to the next stroke appropriately. Also, the angle detected by the steering angle sensor 21 at the time when the limit angle is reached is set as the command steering angle for turning, so that the front wheel 10 can be maintained at the mechanical limit angle while the vehicle is turning.

[0030] Furthermore, when the automatic steering control is on and the detected angle or commanded steering angle of the steering angle sensor 21 exceeds a predetermined turning judgment angle, the limit angle forced steering control means of this embodiment steers the front wheels 10 to a mechanical limit angle and sets an angle obtained by subtracting a predetermined return angle from the detected angle of the steering angle sensor 21 at the time when the limit angle is reached as a turning command steering angle. As a result, after the front wheels 10 reach the limit angle, the front wheels 10 can be steered in the opposite direction by the predetermined return angle based on the subtracted turning command steering angle. As a result, the operation of the relief valve generated at the mechanical limit angle can be suppressed, reducing the load on the hydraulic equipment.

[0031] In this embodiment, when the automatic steering control is turned off or when the detected angle or the commanded steering angle of the steering angle sensor 21 becomes equal to or smaller than a predetermined turning judgment angle, the commanded steering angle for turning is reset to the initial value. In this way, it is possible to suppress the influence on the automatic steering control except when the vehicle is turning, and also to appropriately deal with error fluctuations of the steering angle sensor 21 during work by resetting a new commanded steering angle for turning every time the vehicle turns.

[0032] Next, a processing procedure of the limit angle forced steering control for realizing the above-mentioned control function will be described with reference to Figs.

[0033] As shown in Fig. 12, the limit angle forced steering control includes subroutines, flag control (S1) and execution / stop control (S2). As shown in Fig. 13, in the flag control, the control unit 50 judges whether the automatic steering control is ON and the detected angle and the command steering angle of the steering angle sensor 21 exceed a predetermined threshold value (turning judgment angle) (S101), and if the judgment result is YES, the limit angle forced steering control flag is set (S102), and if the judgment result is NO, the limit angle forced steering control flag is reset (S103). In this embodiment, when the limit angle forced steering control flag is reset, the command steering angle for turning is also reset.

[0034] As shown in FIG. 14, in the execution / stop control, the control unit 50 smoothes the steering load counter (S201), and then judges the state of the limit angle forced steering control flag (S202). If it is judged that the limit angle forced steering control flag is in the reset state, the control unit 50 resets the limit angle reach flag and the front wheel angle return flag (S203, S204), and then returns to a higher-level routine.

[0035] When the control unit 50 determines that the limit angle forced steering control flag is set, it compares the steering angle sensor value with the command steering angle and compares the steering load counter value with a predetermined threshold value (limit angle reaching determination value) (S205 to S208). Here, if the steering angle sensor value is less than the commanded steering angle and the steering load counter value is less than a predetermined threshold value, the control unit 50 determines that the front wheels 10 have not reached the mechanical limit angle (YES in S205). Also, if the steering angle sensor value is less than the commanded steering angle and the steering load counter value is equal to or greater than the predetermined threshold value, the control unit 50 determines that the front wheels 10 have reached the mechanical limit angle even if the steering angle sensor value is less than the commanded steering angle (YES in S206). Also, if the steering angle sensor value is equal to or greater than the commanded steering angle and the steering load counter value is less than the predetermined threshold value, the control unit 50 determines that the front wheels 10 have not reached the mechanical limit angle even if the steering angle sensor value is equal to or greater than the commanded steering angle (YES in S207). Also, if the steering angle sensor value is equal to or greater than the commanded steering angle and the steering load counter value is equal to or greater than the predetermined threshold value, the control unit 50 determines that the front wheels 10 have reached the mechanical limit angle (YES in S208).

[0036] If the determination result in step S205 is YES, the control unit 50 continues steering the front wheels 10 in the limit angle direction, and if the determination result in step S207 is YES, the control unit 50 continues steering the front wheels 10 in the limit angle direction by gradually adding an additional angle to the value of the command steering angle (S209).

[0037] On the other hand, when the result of the determination in step S206 or step S208 is YES, the control unit 50 assigns the steering angle sensor value to the value of the command steering angle (turning command steering angle) (S210, S212), and then sets the limit angle arrival flag (S211, S213). After that, the control unit 50 subtracts a predetermined return angle from the command steering angle in accordance with the set determination of the limit angle arrival flag (S214) (S215). As a result, after the front wheels 10 reach the limit angle, the front wheels 10 can be steered in the opposite direction by the predetermined return angle based on the subtracted command steering angle. The subtraction process in step S215 is executed only once after the limit angle arrival flag is set, and after the subtraction process is executed, a skip process for skipping step S215 is executed based on the setting of the front wheel angle return flag (S216) (S217).

[0038] According to the present embodiment configured as described above, the riding rice transplanter P includes a traveling body 1 having front wheels 10 and rear wheels 11, a position information acquisition system 41 that acquires position information of the traveling body 1, a steering device 9 (automatic steering unit 15) that steers the front wheels 10 by driving an actuator, a steering angle sensor 21 that detects the steering angle of the front wheels 10, and a control unit 50 that is configured to be able to execute automatic steering control that controls the steering device 9 based on the position information of the traveling body 1 acquired by the position information acquisition system 41. The control unit 50 is configured to perform automatic steering. When the control is on and the angle detected by the steering angle sensor 21 or the command steering angle from the control unit 50 to the steering device 9 exceeds a predetermined turning judgment angle, the front wheels 10 are steered to the mechanical limit angle, and the angle detected by the steering angle sensor 21 at the time the limit angle is reached is set as the command steering angle for turning. Therefore, when the vehicle turns, the front wheels 10 can be steered to the mechanical limit angle, and as a result, the turning radius is prevented from increasing significantly, and the vehicle can enter the next process appropriately. Also, since the angle detected by the steering angle sensor 21 at the time the limit angle is reached is set as the command steering angle for turning, the front wheels 10 can be maintained at the mechanical limit angle while the vehicle is turning.

[0039] In addition, when the automatic steering control is on and the detected angle or the instructed steering angle of the steering angle sensor 21 exceeds a predetermined turning judgment angle, the limit angle forced steering control means steers the front wheels 10 to a mechanical limit angle and sets an angle obtained by subtracting a predetermined return angle from the detected angle of the steering angle sensor 21 at the time when the limit angle is reached as the instructed steering angle for turning.Therefore, after the front wheels 10 reach the limit angle, the front wheels 10 are steered in the opposite direction by the predetermined return angle based on the subtracted instructed steering angle for turning, thereby suppressing the relief operation of the hydraulic equipment.

[0040] In addition, when the automatic steering control is turned off or when the detected angle or indicated steering angle of the steering angle sensor 21 becomes equal to or less than a predetermined turning judgment angle, the control unit 50 resets the turning indicated steering angle to its initial value, thereby suppressing the effect on the automatic steering control other than when the aircraft is turning, and by resetting a new turning indicated steering angle each time the aircraft is turned, it is possible to appropriately respond to error fluctuations in the steering angle sensor 21 during work.

[0041] The present invention is not limited to the above embodiment, and various modifications and changes are possible within the scope of the gist of the present invention described in the claims. For example, the limit angle forced steering control means may steer the front wheels 10 to a mechanical limit angle and then steer the front wheels 10 in the opposite direction by a predetermined return angle when the automatic steering control is on and the detected angle or the commanded steering angle of the steering angle sensor 21 exceeds a predetermined turning judgment angle, and set the detected angle of the steering angle sensor 21 at that time as the commanded steering angle for turning. [Explanation of symbols]

[0042] 1 Running vehicle 2 Lifting link mechanism 3 Planting machine 4 Seedling stand 5 Planting mechanism 6 Engine mounting section 7 HST 8. Transmission Case 9. Steering Gear 10 Front wheel 11 Rear wheel 12 Control Unit 13 Steering handle 14 Main gear shift lever 15 Autopilot Unit 16 Front axle 17 Pitman Arm 18 Torque generator 19 Steering rod 20 Sensor interlocking mechanism 21 Steering angle sensor 21a Sensor arm 22 Sensor bracket 23 1st spindle 24 First interlocking arm 25 Second interlocking arm 26 2nd support shaft 27 3rd interlocking arm 27a Pin 28 First connecting rod 29 Second connecting rod 30 Steering motor 31, 31B Operation Panel 32 Current sensor 33 Power Switch 34 Automatic steering switch 35 Start point A registration switch 36 End point B registration switch 37 Reset Switch 38 Notification display section 39 Notification buzzer 40 Positioning Frame 40a Vertical frame section 40b Horizontal frame section 41 Location Information Acquisition System 42 Reference GNSS antenna 43 GNSS antenna for azimuth 44 Tablets 45 GNSS unit 46 RTK base stations 47 Correction signal receiving device 50 Control section

Claims

1. A running body having front and rear wheels; A position information acquisition system for acquiring position information of the traveling machine body; a steering device that steers the front wheels by driving an actuator; a steering angle sensor for detecting a steering angle of the front wheels; A control unit configured to be able to execute automatic steering control that controls the steering device based on the position information of the traveling machine body acquired by the position information acquisition system. a control unit that, when the automatic steering control is on and the detected angle of the steering angle sensor or the instructed steering angle from the control unit to the steering device exceeds a predetermined turning judgment angle, steers the front wheels to a mechanical limit angle, and sets the detected angle of the steering angle sensor at the time when the limit angle is reached as a turning instructed steering angle.

2. 2. The work vehicle according to claim 1, characterized in that, when the automatic steering control is on and the detected angle of the steering angle sensor or the instructed steering angle exceeds the predetermined turning judgment angle, the turning command steering angle setting means steers the front wheels to a mechanical limit angle, and then steers the front wheels in the opposite direction by a predetermined return angle, and sets the detected angle of the steering angle sensor at that point in time as the turning command steering angle.

3. 2. The work vehicle according to claim 1, wherein the turning command steering angle setting means, when the automatic steering control is on and the detected angle of the steering angle sensor or the command steering angle exceeds the predetermined turning judgment angle, steers the front wheels to a mechanical limit angle, and sets the turning command steering angle to an angle obtained by subtracting a predetermined return angle from the detected angle of the steering angle sensor at the time when the limit angle is reached.

4. The work vehicle according to any one of claims 1 to 3, characterized in that the control unit resets the turning instruction steering angle to an initial value when the automatic steering control is turned off, or when the detection angle of the steering angle sensor or the instruction steering angle becomes equal to or less than the predetermined turning judgment angle.

Images