Work vehicle

Abstract

To solve the problem that, as the inventor has noticed, when straight advancing assist is over and a vehicle body is being moved for next straight advancing assist, it is not easy to appropriately acquire a straight line path reference point.SOLUTION: A work vehicle includes: a controller for performing straight advancing assist that causes a vehicle body to advance straight along a straight line path; and a straight advancing assist start instruction member for giving a straight advancing assist start instruction to the controller in accordance with a user's manual operation. When the straight advancing assist is over and the vehicle body is being moved for coming straight advancing assist, the controller repeatedly determines whether or not a straight line path reference point acquisition condition is satisfied, acquires as a straight line path reference point a location of the vehicle body and stores the straight line path reference point when it determines that the straight line path reference point acquisition condition is satisfied, and can start straight advancing assist in the case that a straight advancing assist start instruction is given by the start instruction member after storing the straight line path reference point.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a work vehicle such as a rice transplanter.

Background Art

[0002] There is known a work vehicle such as an agricultural work vehicle that includes a GPS device and teaching path generation means, generates a teaching path by the teaching path generation means based on position information measured by the GPS device, further generates a target path parallel to the teaching path by the teaching path generation means, and automatically turns toward the next target path when an operator operates an automatic turning operation tool and autonomously travels on the next target path after the turning operation is completed (see, for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] By the way, the inventor of the present invention considers various needs of work vehicle users and believes that the trend of continuously implementing convenient functions on work vehicles such as rice transplanters is accelerating more and more.

[0005] However, the inventor has noticed that the usability when using convenient functions is not always good for conventional work vehicles.

[0006] More specifically, for example, the inventor has noticed that it is not easy to appropriately acquire a straight line path reference point when the straight-ahead assist ends and the vehicle body is being moved for the next straight-ahead assist.

[0007] The present invention aims to provide a work vehicle that can improve usability in consideration of the above-described conventional problems.

Means for Solving the Problems

[0008] A first aspect of the present invention is a work vehicle that travels along a straight path, a controller (110) that performs straight-ahead assist for causing the vehicle body (100) to travel straight along the straight path, a straight-ahead assist start instruction member (120) that gives an instruction to start the straight-ahead assist in response to a manual operation by the user to the controller (110), and is provided with when the straight-ahead assist ends and the vehicle body (100) is being moved for the next straight-ahead assist, the controller (110) repeatedly determines whether a straight-path reference point acquisition condition is satisfied, and when it is determined that the straight-path reference point acquisition condition is satisfied, the position of the vehicle body (100) is acquired as a straight-path reference point and the straight-path reference point is stored, and after storing the straight-path reference point, when a straight-ahead assist start instruction is given by the start instruction member (120), the straight-ahead assist can be started. The work vehicle is characterized by this.

[0009] A second aspect of the present invention is that the controller (110) continues to determine whether the straight-path reference point acquisition condition is satisfied even after storing the straight-path reference point, and when it is determined that the straight-path reference point acquisition condition is no longer satisfied while the straight-ahead assist start instruction is not given, the stored straight-path reference point is discarded. This is the work vehicle of the first aspect of the present invention, which is characterized by this.

[0010] A third aspect of the present invention is that the controller (110) does not acquire the straight-path reference point again until the time when it is determined that a straight-path reference point re-acquisition condition is satisfied after discarding the straight-path reference point, The straight-line path reference point reacquisition condition is a condition related to the steering angle, and the steering angle is an approximate angle corresponding to the steering position for straight-ahead driving of the vehicle body (100), and the approximate angles are stably consistent. This is the first or second working vehicle of the present invention.

Advantages of the Invention

[0011] According to the first aspect of the present invention, it is possible to improve usability.

[0012] According to the second aspect of the present invention, in addition to the effects of the first aspect of the present invention, it is possible to improve convenience.

[0013] According to the third aspect of the present invention, in addition to the effects of the first or second aspect of the present invention, it is possible to further improve convenience.

Brief Description of the Drawings

[0014]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Mode for Carrying Out the Invention

[0015] While referring to the drawings, embodiments of the present invention will be described in detail.

[0016] The same applies hereinafter, but some components may not be shown in the drawings, and may be shown perspectively or omitted.

[0017] While explaining the operation of the rice transplanter of the present embodiment, the operation vehicle operation control method of the invention related to the present invention, which is realized by the controller 110 and the like, will also be explained.

[0018] The rice transplanter of the present embodiment is a specific example of the work vehicle in the present invention that travels along a plurality of parallel straight paths.

[0019] (1) First, with reference to FIGS. 1 to 4, the configuration and operation of the rice transplanter of the present embodiment will be specifically described.

[0020] Here, FIG. 1 is a left side view of the rice transplanter of the embodiment in the present invention, FIG. 2 is an explanatory diagram of obtaining a straight path reference point and starting an instruction for straight-ahead assist of the rice transplanter of the embodiment in the present invention, FIG. 3 is an explanatory diagram of the work vehicle operation control method of the rice transplanter of the embodiment in the present invention, and FIG. 4 is an explanatory diagram near the straight-ahead assist sensor 1006 of the rice transplanter of the embodiment in the present invention.

[0021] The work vehicle operation control method of the present embodiment is a control method performed based on a flowchart having steps S1 to S7.

[0022] The straight-ahead assist start instruction member 120 is a member that gives an instruction to start straight-ahead assist to the controller 110 that performs straight-ahead assist for causing the vehicle body 100 to travel straight along a straight path in response to a manual operation by the user.

[0023] In the present embodiment, when the straight-line path reference point acquisition condition is satisfied and the lever raising operation of the finger lever as the straight-ahead assist start instruction member 120 is manually performed, the straight-ahead assist is started.

[0024] When the straight-ahead assist ends and the vehicle body 100 is being moved for the next straight-ahead assist, when the controller 110 determines that the straight-line path reference point acquisition condition is satisfied, the controller 110 acquires the position of the vehicle body 100 as the straight-line path reference point and stores the straight-line path reference point. After storing the straight-line path reference point, when a straight-ahead assist start instruction is given, the straight-ahead assist is started.

[0025] For the transition from a straight line path to a straight line path, the turning is typically performed manually, but it may be performed automatically by using a method aiming at a predetermined target straight line path or the like. In any case, when the vehicle body 100 is being turned, if the straight-line path reference point P is automatically acquired and stored, a straight line path R passing through the straight-line path reference point P is set as a straight line path parallel to the straight line path immediately before the turning.

[0026] When a turning travel following an arc-shaped turning path is performed, when the vehicle body 100 is being turned in the normal sense, the position of the vehicle body 100 may be acquired as the straight-line path reference point. On the other hand, after such a turning travel ends, the position of the vehicle body 100 may also be acquired as the straight-line path reference point. More specifically, after the turning travel ends, depending on the user's steering skill level, the timing when so-called row alignment for adjusting the interval between adjacent seedling planting rows is performed and the timing when the planting rod is rotated and the straight-ahead travel for planting is started, at a point in time between them, the steering angle stably coincides with an approximately zero angle corresponding to the straight-ahead steering position and the straight-line path reference point acquisition condition is often satisfied, and the position of the vehicle body 100 may be acquired as the straight-line path reference point.

[0027] In the present embodiment, when the straight-line path reference point acquisition conditions defined by the following (Claim 1) to (Claim 9) are completely satisfied, the straight-line path reference point P of an agricultural machine such as a rice transplanter equipped with an automatic steering function by straight-ahead assist is acquired.

[0028] (Claim 1) The so-called Point A and Point B, which are the first and second reference points for determining the directions of a plurality of parallel straight-line paths, are acquired in advance prior to straight-ahead assist.

[0029] (Claim 2) The tilling rotor 1001 is turned on at a height of less than 450 millimeters.

[0030] (Claim 3) GPS (Global Positioning System) radio waves can be acquired by the GPS device 1002.

[0031] (Claim 4) The vehicle body azimuth deviation, which is the deviation between the vehicle body azimuth of the turning vehicle body 100 and the straight-ahead azimuth given by the direction of the straight-line path, is 3 degrees or less.

[0032] (Claim 5) The inclination of the vehicle body 100 from the horizontal plane, which is important for grasping the vehicle body posture, is less than 10 degrees.

[0033] (Claim 6) The vehicle speed of the vehicle body 100 is not the so-called road running speed.

[0034] (Claim 7) The trunnion angle of the HST (Hydro Static Transmission) device 1003 is not the angle on the reverse side.

[0035] (Claim 8) The GPS vehicle speed measured by the GPS device 1002 is 0.5 kilometers per hour or more, that is, approximately 0.14 meters per second or more.

[0036] (Claim 9) The steering wheel angle of the steering device 1004 that gives the steering angle is -20 degrees or more and +20 degrees or less.

[0037] Therefore, the acquisition of the straight-line travel reference point P is separated from the start and disconnection of the straight-ahead assist.

[0038] For example, in the steering straight-ahead determination according to the above-described (Claim 9), a mode in which the instantaneous value of the steering angle is not used and the average value of the steering angle for an average movement of 500 milliseconds is used is also conceivable. Even if a fine steering wheel operation is performed for the transition to an adjacent planting row and the steering angle deviates from the straight-ahead angle range for a short period, the acquisition of the straight-line travel reference point P can be performed without problems, so the start of the straight-ahead assist is less likely to be hindered.

[0039] The above-described value of 500 milliseconds that gives the average movement time can be rewritten with a value from 100 to 3000 milliseconds, and the above-described value of 20 degrees that gives the steering wheel angle range can be rewritten with a value from 10 to 100 degrees. For the straight-ahead assist sensor 1006 that detects the rotation angle of the steering wheel shaft 1005 driven by the steering motor with the start of the straight-ahead assist, the detection range corresponds to a steering angle range of -150 degrees to 150 degrees, and the resolution is approximately 0.3 degrees.

[0040] For example, a mode in which the following (Claim 10) is added to the straight-line travel reference point acquisition conditions is also conceivable.

[0041] (Claim 10) The steering angular velocity is 90 degrees per second or less.

[0042] If the vehicle body orientation deviation is less than 3 degrees and the straight-ahead steering state continues, the straight-line path reference point acquisition conditions defined by (Claim 1) to (Claim 9) are often satisfied, and the stored straight-line path reference point P is retained. However, in such a case, if the straight-ahead assist start instruction is not given and the driving distance increases, the straight-ahead assist start position is likely to deviate significantly from the straight-line path R passing through the straight-line path reference point P, so large serpentine driving of the vehicle body 100 toward the straight-line path R is likely to occur. By adding (Claim 10), when a rapid steering operation for alignment is performed at a large steering angular velocity, the straight-line path reference point P is appropriately discarded, and the occurrence of serpentine driving is suppressed.

[0043] An alert regarding whether the straight-line path reference point is stored is output to the user.

[0044] Such an alert is given by using the on or off state of an alert lamp, etc. An event such as the occurrence of a lateral deviation amount exceeding an allowed level, which will be described later, may be given by using the blinking of the on and off states of a general-purpose alert lamp at short time intervals, or may be given by using the on state of a dedicated lamp.

[0045] Since the user can recognize whether the straight-line path reference point is stored through the alert, it is almost never the case that a straight-ahead assist start instruction is given even though the straight-line path reference point is not stored.

[0046] However, in the case where a straight-ahead assist start instruction is given due to the user's carelessness or the like even though the straight-line path reference point is not stored, it is conceivable that the reception of the straight-ahead assist start instruction is not performed and the straight-ahead assist is not started, or that a provisional reception of the straight-ahead assist start instruction is performed and the start of the straight-ahead assist itself is suspended, and when the straight-line path reference point is acquired, the straight-ahead assist is immediately started.

[0047] After the controller 110 stores the straight-line route reference point, if a straight-ahead assist start instruction has not been given before the point in time when it is determined that the straight-line route reference point acquisition conditions are not satisfied, the stored straight-line route reference point is discarded. However, if a straight-ahead assist start instruction has been given, the stored straight-line route reference point is not discarded.

[0048] For example, after the straight-line route reference point P is stored, if a straight-ahead assist start instruction has not been given before the point in time when it is determined that the straight-line route reference point acquisition conditions defined by (Requirements 1) to (Requirements 10) are not satisfied, it is conceivable that the stored straight-line route reference point P will be discarded.

[0049] Note that after the controller 110 stores the straight-line route reference point, if a straight-ahead assist start instruction has not been given before the point in time when it is determined that the straight-ahead assist start conditions are not satisfied, the stored straight-line route reference point is discarded. However, if a straight-ahead assist start instruction has been given, it is not necessary to discard the stored straight-line route reference point.

[0050] For example, the straight-ahead assist start conditions defined by the requirement that the lateral deviation amount from the straight-line route R does not exceed 10 centimeters are adopted. After the straight-line route reference point P is stored, even in the straight-ahead assist standby state where the straight-line route reference point acquisition conditions are satisfied, if a straight-ahead assist start instruction has not been given before the point in time when it is determined that the lateral deviation amount calculated based on the CAN (Controller Area Network) data received from the straight-ahead assist unit exceeds 10 centimeters, it is conceivable that the stored straight-line route reference point P will be discarded.

[0051] Of course, along with the discarding of the straight-line route reference point P, the acceptance of the straight-ahead assist start instruction is rejected, so the start of inappropriate straight-ahead assist is suppressed.

[0052] When a straight-ahead assist start instruction is given, it can be said that the formal adoption of the straight-line path reference point that was provisionally acquired is determined.

[0053] Also, after the controller 110 discards the straight-line path reference point, it may not need to acquire the straight-line path reference point again until it determines that the straight-line path reference point reacquisition condition is satisfied.

[0054] Even immediately after the straight-line path reference point P is discarded, the straight-line path reference point acquisition condition is often satisfied. Considering the possibility that a user who recognizes the occurrence of a lateral displacement amount exceeding the allowed level by an alert or the like may perform an appropriate steering operation, the acquisition of a new straight-line path reference point is suppressed.

[0055] The straight-line path reference point reacquisition condition is a condition related to the elapsed time since the straight-line path reference point was discarded.

[0056] For example, after the straight-line path reference point P is discarded due to the lateral displacement amount exceeding the allowed level, a mode can be considered in which the straight-line path reference point is not newly acquired until approximately 1 second of observation time has elapsed. The acquisition of a new straight-line path reference point is suppressed until the lateral displacement amount becomes small and the timing at which an ideal straight-ahead assist start is expected.

[0057] Note that the straight-line path reference point reacquisition condition may be a condition related to the steering angle since the straight-line path reference point was discarded.

[0058] For example, after the straight-line path reference point P is discarded due to the lateral displacement amount exceeding the allowed level, a mode can be considered in which the straight-line path reference point is not newly acquired until the steering wheel angle of the steering device 1004 that gives the steering angle enters an angle range of -1 degree or more and +1 degree or less. When a steering operation according to a stricter requirement for the steering angle compared to (Claim 9) is performed so as to cross the steering wheel center position, a new straight-line path reference point is smoothly acquired regardless of the elapse of the above-described observation time, and thus an ideal straight-ahead assist start is expected.

[0059] (2) Next, with reference mainly to FIGS. 5 to 7, the configuration and operation of the rice transplanter of the present embodiment will be described in more detail.

[0060] Here, FIGS. 5 to 7 are explanatory views (Parts 1 to 3) of the vicinity of the fertilizer applicator 220 of the rice transplanter according to the embodiment of the present invention.

[0061] In FIG. 5, the output direction of the rear wheel rotation axis in the front view is described. In FIG. 6, the output direction of the rear wheel rotation axis in the side view is described. In FIG. 7, a so-called electric HMT (Hydro Mechanical Transmission) fertilizer application mechanism is described.

[0062] Regarding the configuration of the fertilizer applicator 220 that uses the HMT mechanism, in which the rear wheel rotation output is taken out as the fertilizer application output to the fertilizer application drive shaft via the universal joint 2002, the electric unit 2003, and the roller clutch 2007, it is as follows.

[0063] The driving speed of the fertilizer applicator 220 driven by using the driving force of the rear wheel 210 can be adjusted according to the rotation speed of the motor 240 output via the planetary gear mechanism 230.

[0064] In a rice transplanter with a fertilizer applicator, a configuration is conceivable in which the rotational output is obtained from the rear wheel 210, the fertilizer applicator 220 which is an electric fertilizer applicator is driven, and the driving speed of the fertilizer applicator is adjusted according to the motor rotation speed by a mechanism using the planetary gear 2006 and the motor 240. By obtaining torque from the rear wheel rotation of the rear wheel 210, the mechanical start delay caused by the large starting torque required by the fertilizer applicator 220 is suppressed, and a configuration that does not require a large torque of the motor 240 is realized.

[0065] In the above-described configuration, a configuration in which the fertilizer application drive output is performed upward from the vehicle body from the rear wheel case 2001, which is also called the rear wheel rear case, is conceivable.

[0066] In the above-described configuration, a configuration may be considered in which the output from the rear wheel case 2001 is transmitted from the planetary gear 2006 to the ring gear 2004 and output to the fertilizer drive shaft by a unit.

[0067] In the above-described configuration, a configuration may be considered in which the sun gear 2005 is rotated by the motor 240. The motor is normally in a stopped state, but when the vehicle speed increases and the fertilizer application amount decreases, the motor 240 rotates at a higher speed.

[0068] In the above-described configuration, a configuration may be considered in which the rotation speed of the fertilizer drive shaft in the stopped state of the motor 240 is maximum and the fertilizer application amount takes the maximum amount of 80 kg / 10a.

[0069] In the above-described configuration, a configuration may be considered in which a sensor for detecting the rotation speed of the rear wheel 210 of the rear wheels and a sensor for detecting the output rotation speed of the fertilizer output to the fertilizer drive shaft are used.

[0070] In the above-described configuration, when fertilization is not performed, control may be performed to adjust the rotation speed of the motor 240 so that the output rotation speed to the fertilizer drive shaft becomes zero.

[0071] In the above-described configuration, when the fertilizer application amount is set between zero and the maximum amount, a configuration may be considered in which the fertilizer application amount is adjusted by controlling the ratio of the rotation speed of the rear wheel 210 of the rear wheels to the rotation speed of the fertilizer drive shaft by the rotation of the motor 240. Any fertilizer application amount between zero and 80 kg can be set, and in the case of fertilizer spreading with a fertilizer application amount of 40 kg / 10a, motor control is performed at a rotation speed ratio of 2:1.

[0072] In the above-described configuration, a configuration may be considered in which the so-called electric trial feeding is performed by rotating the motor 240 in a rotation direction opposite to the fertilizer rotation direction.

[0073] In the above-described configuration, when the parking brake pedal is locked and the vehicle body is in a parked state, and the engine is on but the rear wheels 210 are not rotating, a configuration can be considered in which, when the electric test feed button is pressed, the motor 240 rotates in the reverse direction.

[0074] In the above-described configuration, in a rice transplanter equipped with a GNSS (Global Navigation Satellite System) antenna, a configuration can be considered in which the ratio of the rotational speed of the rear wheels 210 and the rotational speed of the fertilizer application drive shaft is corrected according to the slip ratio calculated from the antenna vehicle speed and the rear wheel rotational vehicle speed. By performing correction based on the slip ratio, the adverse effect of inaccuracy in the fertilizer application amount due to wheel wear or the like is reduced.

[0075] (3) Next, with reference mainly to FIGS. 8 and 9, the configuration and operation of the rice transplanter of the present embodiment will be described in more detail.

[0076] Here, FIGS. 8 and 9 are explanatory views (one and two) of the vicinity of the distance sensor 320 of the rice transplanter according to the embodiment of the present invention.

[0077] In FIG. 8, the location of the distance sensor in a side view is described, and in FIG. 9, the location of the distance sensor in a front view is described.

[0078] More specifically, the position of the distance sensor 320 of the variable fertilizer application rice transplanter is as follows.

[0079] The amount of field material input can be adjusted according to the field depth calculated based on the distance to the water surface of the field.

[0080] A configuration of a rice transplanter can be considered in which the field depth is calculated by measuring the distance from the position of the distance sensor 320, which is an ultrasonic sensor, to the water surface of the field, and the amount of field material input can be changed.

[0081] A distance sensor 320 that measures the distance to the water surface of the field is positioned rearward compared to the foremost surface of a bumper 310 provided at the front side of the vehicle body when viewed from the side of the vehicle body.

[0082] In the above-described configuration, a configuration can be considered in which the distance sensor 320 is arranged on the rear side of the vehicle body 100 compared to the foremost surface of the bumper 310 on the front side of the rice transplanter. By arranging it inside the bumper 310, the distance sensor 320 can be guarded.

[0083] In the above-described configuration, a configuration can be considered in which the distance sensor 320 is arranged at a position overlapping the bumper 310 on the front side of the rice transplanter when viewed from the front of the vehicle body.

[0084] In the above-described configuration, a configuration can be considered in which the distance sensor 320 is arranged at a position overlapping the bumper 310 on the front side of the rice transplanter when viewed from the side of the vehicle body.

[0085] In the above-described configuration, a configuration of a type specification with an antenna that measures and corrects the vehicle body roll angle of the vehicle body 100 using GNSS and IMU (Inertial Measurement Unit) antenna sensors can be considered.

[0086] In the above-described configuration, a configuration of a type specification with an antenna that measures and corrects the vehicle body pitch angle of the vehicle body 100 using GNSS and IMU antenna sensors can be considered.

[0087] In the above-described configuration, a configuration of a type specification without an antenna that measures and corrects the vehicle body pitch angle of the vehicle body 100 using a horizontal sensor arranged on the main frame of the machine can be considered.

[0088] In the above-described configuration, a configuration can be considered in which the horizontal sensor is arranged at the central position in the left-right direction of the machine within the range between the front wheel axle and the rear wheel axle when viewed from the side of the water.

[0089] Note that the program of the invention related to the present invention is a program for causing a computer to execute the operations of all or part of the steps (or processes, operations, actions, etc.) of the work vehicle operation control method of the invention related to the present invention described above, and is a program that operates in cooperation with the computer.

[0090] In addition, the recording medium of the invention related to the present invention is a recording medium that records a program for causing a computer to execute all or part of the operations of all or part of the steps (or processes, operations, actions, etc.) of the work vehicle operation control method of the invention related to the present invention described above, and is a computer-readable recording medium in which the read program is used in cooperation with the computer.

[0091] Note that the above-mentioned "part of the steps (or processes, operations, actions, etc.)" means one or some of those multiple steps.

[0092] In addition, the above-mentioned "operation of the steps (or processes, operations, actions, etc.)" means all or part of the operations of the above-mentioned steps.

[0093] In addition, one usage form of the program of the invention related to the present invention may be a form in which it is transmitted through a transmission medium such as the Internet, light, radio waves, or sound waves, read by a computer, and operates in cooperation with the computer.

[0094] In addition, as the recording medium, ROM (Read Only Memory), etc. are included.

[0095] In addition, the computer is not limited to pure hardware such as a CPU (Central Processing Unit), and may include firmware, an OS (Operating System), and further peripheral devices.

[0096] Note that, as described above, the configuration of the present invention may be realized either software-wise or hardware-wise.

Industrial Applicability

[0097] The work vehicle according to the present invention can improve usability and is useful for the purpose of being used in work vehicles such as rice transplanters.

Explanation of Signs

[0098] 100 Vehicle body 110 Controller 120 Straight-ahead assist start instruction member 210 Rear wheels 220 Fertilizer applicator 230 Planetary gear mechanism 240 Motor 310 Bumper 320 Distance sensor 1001 Cultivating rotor 1002 GPS device 1003 HST device 1004 Steering device 1005 Steering handle shaft 1006 Straight-ahead assist sensor 2001 Rear wheel case 2002 Universal joint 2003 Electric unit 2004 Ring gear 2005 Sun gear 2006 Planet gear 2007 Roller clutch P Straight-line route reference point R Straight-line route

Claims

1. A work vehicle that travels along a straight path, a controller (110) that performs straight-ahead assist for causing the vehicle body (100) to travel straight along the straight path, a straight-ahead assist start instruction member (120) that gives an instruction to start straight-ahead assist to the controller (110) according to a manual operation by the user, and is provided with, when the straight-ahead assist ends and the vehicle body (100) is being moved for the next straight-ahead assist, the controller (110) repeatedly determines whether a straight-path reference point acquisition condition is satisfied, and when it is determined that the straight-path reference point acquisition condition is satisfied, acquires the position of the vehicle body (100) as a straight-path reference point and stores the straight-path reference point, and after storing the straight-path reference point, when a straight-ahead assist start instruction is given by the start instruction member (120), the work vehicle is characterized in that the straight-ahead assist can be started.

2. After storing the straight-path reference point, the controller (110) continues to determine whether the straight-path reference point acquisition condition is satisfied, and when it is determined that the straight-path reference point acquisition condition is no longer satisfied while the straight-ahead assist start instruction is not given, the work vehicle according to claim 1, characterized in that the stored straight-path reference point is discarded.

3. After discarding the straight-path reference point, the controller (110) does not acquire the straight-path reference point again until it is determined that a straight-path reference point re-acquisition condition is satisfied. The straight-path reference point re-acquisition condition is a condition related to the steering angle, and the steering angle is approximately the angle corresponding to the steering position for straight-ahead travel of the vehicle body (100), and the work vehicle according to claim 1 or 2, characterized in that the approximate angles are stably the same.

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