Work vehicles

Abstract

To provide a work vehicle that can improve operability by allowing switching between automated and manual operation in handling irregular situations. [Solution] A work vehicle according to one embodiment comprises a vehicle body on which a worker rides and a control device for automatically driving the vehicle body, wherein the vehicle body has an operating device for switching the mode of the vehicle body and a differential mechanism that rotates the left and right front wheels of the vehicle body at different rotational speeds when turning, and the modes of the vehicle body include a 4WD auto mode and a normal mode, and in the 4WD auto mode, the control device cuts off the drive to the inner rear wheel of the vehicle body when turning and activates the differential mechanism, and when it detects wheel slippage of the vehicle body while the drive to the inner rear wheel of the vehicle body is cut off and the differential mechanism is activated, it activates a differential lock mechanism to lock the differential mechanism.

Description

Technical Field

[0001] The present invention relates to a work vehicle.

Background Art

[0002] Conventionally, in a manned monitoring type robot seedling transplanter (work vehicle), since an operator does not ride on the work vehicle, in order to prevent the work by the stack from being interrupted, when slipping to a certain extent, an auto deflock mechanism operates, and when the slip is not eliminated even if the auto deflock mechanism operates, the running performance is enhanced by forcibly driving all four wheels (for example, see Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] Even in a work vehicle in which an operator rides (for example, a ride-on type robot seedling transplanter), mainly the work vehicle performs work by automatic driving, and irregularity corresponding such as slipping can also be automatically performed. However, since an operator rides on the work vehicle, there may be a case where the operator desires to perform irregularity corresponding manually. That is, there may be a case where it is better to operate all of the above auto deflock mechanism and four-wheel drive automatically, and a case where it is better for the operator to operate manually. Therefore, there has been a demand for a work vehicle that can improve the operability by making it possible to switch between automatic response and manual operation in irregularity corresponding.

[0005] The present invention has been made in view of the above, and an object thereof is to provide a work vehicle that can improve the operability by making it possible to switch between automatic response and manual operation in irregularity corresponding.

Means for Solving the Problems

[0006] To solve the above-mentioned problems and achieve the objective, a work vehicle (1) according to one embodiment comprises a vehicle body (2) on which a worker rides, and a control device (100) that makes the vehicle body (2) move automatically, wherein the vehicle body (2) has an operating device (45) for switching the mode of the vehicle body (2), and a differential mechanism that rotates the left and right front wheels (10) of the vehicle body (2) at different rotational speeds when turning, and the modes of the vehicle body (2) include a 4WD auto mode and a normal mode, and in the 4WD auto mode, the control device (100) cuts off the drive to the inner rear wheel of the vehicle body (2) when turning, activates the differential mechanism, and cuts off the drive to the inner rear wheel of the vehicle body (2) when turning When the differential mechanism is operating and wheel slippage of the vehicle body (2) is detected, the differential lock mechanism (97) is activated to lock the differential mechanism. If a stronger propulsion force is to be generated after detecting wheel slippage of the vehicle body (2), the four-wheel drive is activated. Detection of wheel slippage of the vehicle body (2) is performed based on the difference in rotation between the left and right wheels of the vehicle body (2), or the vehicle speed of the vehicle body (2) measured by the vehicle body (2) position acquisition device (150). When the differential lock mechanism (97) or four-wheel drive is activated due to wheel slippage of the vehicle body (2), the control device (100) sets the target vehicle speed of the vehicle body (2) below a certain level. [Effects of the Invention]

[0007] According to one embodiment, the work vehicle can improve operability by allowing switching between automatic response and manual operation in response to irregular situations. [Brief explanation of the drawing]

[0008] [Figure 1] Figure 1 is a side view showing a work vehicle. [Figure 2] Figure 2 is a plan view showing the work vehicle. [Figure 3]Figure 3 is a block diagram showing the control system, centered around the control device of the seedling transplanter. [Figure 4] Figure 4 shows the mode selector switch. [Figure 5] Figure 5 is an explanatory diagram of the autonomous operation of a seedling transplanter in a field. [Figure 6] Figure 6 shows the display on the monitor. [Modes for carrying out the invention]

[0009] (Overview of work vehicles) First, an overview of the work vehicle 1 according to the first embodiment will be described with reference to Figures 1 and 2. Figure 1 is a side view of the work vehicle 1. Figure 2 is a top view of the work vehicle 1.

[0010] In the following explanation, the forward and backward directions refer to the direction of travel when the work vehicle 1 is moving straight, with the front side of the direction of travel defined as "forward" and the rear side as "rear." The direction of travel of the work vehicle 1 is the direction from the driver's seat 41 toward the steering wheel 35 when moving straight (see Figures 1 and 2).

[0011] The left-right direction is the direction perpendicular to the front-back direction, and left and right are defined with respect to the "front" side. That is, with the operator (also called the worker) seated in the cockpit 41 and facing forward, the left side is "left" and the right side is "right".

[0012] The vertical direction refers to the vertical direction. The front-back, left-right, and up-down directions are orthogonal to each other. These directions are defined for the sake of explanation, and the present invention is not limited by these directions.

[0013] In this embodiment, the work vehicle 1 is described as a ride-on seedling transplanter 1 equipped with a seedling planting unit 4 as a field work device, which receives seedlings in the field. As shown in Figures 1 and 2, the seedling transplanter 1 is equipped with a liftable seedling planting unit 4 on the rear side of the traveling vehicle body 2 via a lifting link mechanism 3 for planting seedlings in the field.

[0014] The main body of the fertilizer applicator 5 is arranged on the upper rear part of the traveling vehicle body 2. In addition, when the work vehicle 1 is not the seedling transplanter 1, it may be equipped with a seeding device for supplying seeds as a work device.

[0015] The traveling vehicle body 2 is a four-wheel drive vehicle equipped with left and right front wheels 10 and rear wheels 11, which are wheels and driving wheels. On the front side of the main frame 15 that constitutes the vehicle body skeleton of the traveling vehicle body 2, there is a transmission case 13 that transmits driving force to the seedling planting part 4 and a hydraulic continuously variable transmission device 14 that outputs the driving force supplied from the engine 30, that is, the rotation generated by the engine 30, to the transmission case 13.

[0016] The continuously variable transmission device 14 is a hydrostatic continuously variable transmission called a so-called HST (Hydro Static Transmission). Hereinafter, the case where the continuously variable transmission device is the HST 14 will be described.

[0017] A sub-shifting mechanism 16 for switching the traveling mode of the traveling vehicle body 2 during road travel in the high-speed mode or during seedling planting in the low-speed mode is provided in the transmission case 13. Front wheel final cases 10a are provided on the left and right sides of the transmission case 13, and the front wheels 10 are attached to the left and right front axles 10b that project outward from the front wheel support parts that can change the steering direction of the left and right front wheel final cases 10a.

[0018] In addition, on the rear part side of the main frame 15, rear wheel gear cases 11a are attached to both the left and right sides of the rear frame 22 provided in the lateral direction (see FIG. 2), and the rear wheels 11 are respectively attached to the left and right rear axles 11b that project outward from the rear wheel gear cases 11a.

[0019] In addition, on the upper part of the rear frame 22, left and right link support frames 23 that support the lifting link mechanism 3 project upward. On the lower side of the left and right link support frames 23 and between the left and right, a pair of left and right lower link arms 24 are provided. A lifting cylinder 25 that operates by hydraulic pressure is provided between the left and right of the left and right lower link arms 24.

[0020] Above the lifting cylinder 25, an upper link arm 26 is provided, and a lifting link mechanism 3, which is a parallel link mechanism, is formed. Note that the left and right lower link arms 24, each having one end connected to the traveling vehicle body 2 side, the lifting cylinder 25, and the other end side of the upper link arm 26 are attached to the front part of the seedling planting part 4.

[0021] Also, an engine 30 is mounted on the main frame 15. The rotational power of the engine 30 is transmitted to the transmission case 13 via the belt transmission device 21 and the HST 14. The rotational power transmitted to the transmission case 13 is shifted by a sub-shifting mechanism 16 in the transmission case 13 and then divided into traveling power and externally extracted power.

[0022] Also, the rotational power of the engine 30 is transmitted to a hydraulic pump (not shown). The hydraulic pressure generated by the hydraulic pump is supplied to the HST 14, the power steering mechanism 88 (see FIG. 3) of the steering 35, the lifting cylinder 25, etc.

[0023] The externally extracted power taken out from the rotational power transmitted to the transmission case 13 is transmitted to a planting clutch case 27 provided at the rear part of the traveling vehicle body 2, and is transmitted from the planting clutch case 27 to the seedling planting part 4 by the planting transmission shaft 67.

[0024] On the other hand, left and right drive shafts 42 are provided at the rear part of the transmission case 13. The rotational power from the engine 30 is transmitted to the left and right rear wheel gear cases 11a via the transmission case 13 and the drive shafts 42.

[0025] Furthermore, a side clutch 44 (see Figure 3) for switching power transmission to the left and right drive shafts 42 is located upstream of the left and right drive shafts 42 in the transmission direction. As shown in Figure 1, a side clutch pedal 43a for engaging and disengaging the left and right side clutches 44 is provided on one side of the front lower part of the driver's seat 41. Below the driver's seat 41 are brake pedals for operating the left and right brake mechanisms and an accelerator pedal 32 (see Figure 3) for operating the engine speed. The engine speed increases while the accelerator pedal 32 is pressed down.

[0026] By depressing the side clutch pedal 43a on the inside of the turn, disengaging the side clutch 44, and then operating the steering wheel 35 to turn, the drive rotation of the inner rear wheel 11 can be completely shut off.

[0027] A bonnet 39 is provided on the upper front of the vehicle body 2, with a control panel 38 for operating various parts positioned on top. The control panel 38 is equipped with a monitor 86 (see Figure 3), etc.

[0028] The bonnet 39 is also equipped with a steering wheel 35 for steering the vehicle body 2, an HST lever 36 for operating the HST 14 and seedling planting unit 4, and a sub-transmission lever 37 for operating the sub-transmission mechanism 16.

[0029] Furthermore, a front cover 40 that can be opened and closed is provided on the front side of the bonnet 39. Inside the front cover 40 are the fuel tank, battery, and an interlocking mechanism that rotates the left and right front wheels 10 and the lower parts of the left and right front wheel final cases 10a in response to the steering of the steering 35. The front wheels 10 are, for example, steering wheels that turn in response to the steering of the steering 35.

[0030] An engine cover 30a is provided behind the bonnet 39 and above the engine 30, covering the top and sides of the engine 30, and a cockpit 41 where the driver sits is provided on top of the engine cover 30a.

[0031] A fertilizer application device 5 is provided behind the cockpit 41, at the rear end of the main frame 15. The driving force for the fertilizer application device 5 is transmitted by a fertilizer transmission mechanism, which is provided so as to face the fertilizer application device 5 from one side of the left and right rear wheel gear cases 11a.

[0032] On both the left and right sides of the lower part of the engine cover 30a and bonnet 39, a roughly horizontal floor step 33 is formed. As shown in Figure 2, the floor step 33 is partially lattice-shaped, so that, for example, if mud from the driver's shoes falls onto the floor step 33, the fallen mud will fall onto the field.

[0033] Furthermore, a rear step 330 is connected to the rear of the floor step 33, as shown in Figure 2. It is preferable that the surface of the rear step 330 be treated with an anti-slip finish, for example, by forming multiple protrusion patterns, to prevent feet from slipping during work.

[0034] Furthermore, on the front side of the vehicle body 2, and on both the left and right sides, there are spare seedling frames 50 on seedling frame support posts 51, each with multiple spare seedling trays 52 arranged at vertical intervals, allowing for the placement of seedlings to be replenished in the seedling planting section 4, as well as work materials such as fertilizer bags.

[0035] Furthermore, a seedling tank 53 for loading seedlings to be planted in the field is attached to the rear end of the lifting link mechanism 3, along with a sliding mechanism for sliding it in the left-right direction. Long seedling partition fences 54 are arranged on the seedling tank 53 at predetermined intervals in the left-right direction. Below the seedling tank 53, a seedling planting device 55 is positioned to scoop up the loaded seedlings and plant them in the field.

[0036] The seedling planting device 55 plants the same number of rows as the number of planting work rows separated by the seedling partition fence 54, i.e., 8 rows simultaneously. Four planting transmission cases 56 are arranged at intervals below the seedling tank 53, and planting rotary tools 57 are attached to both the left and right sides of the planting transmission cases 56, which rotate and pick up seedlings with planting rods 58 to plant in the field.

[0037] The fertilizer application device 5 has a fertilizer hopper 70 where fertilizer is stored, which is divided into the same number of sections as the number of work rows in the seedling planting section 4 (eight sections in the example shown in Figure 2). However, since an eight-section fertilizer hopper 70 is long in the left-right direction, it reduces the convenience of loading and unloading fertilizer. Therefore, a so-called side fertilizer application structure may be used, where sections divided into four sections are arranged on the left and right sides.

[0038] At the bottom of the fertilizer hopper 70, a dispensing device 71 is provided for each row to supply a set amount of fertilizer. Below the dispensing device 71, a ventilation duct 72 is provided in the left-right direction through which the airflow that moves the fertilizer passes. Below the dispensing device 71, a fertilizer hose 73 is provided to guide the fertilizer to the vicinity of the seedling planting position in the seedling planting section 4. In addition, a blower 74 is provided at one end of the ventilation duct 72, which is operated by an electric motor 76 to generate the airflow for conveying the fertilizer.

[0039] As shown in Figures 1 and 2, below the seedling planting section 4, a center float 62C that makes contact with and slides on the field surface, and two side floats 62L and 62R on each side are provided so as to be rotatable around an axis. Note that the center float 62C and the left and right side floats 62L and 62R are sometimes collectively referred to as float 62.

[0040] Furthermore, below the seedling planting section 4, in front of the float 62, a leveling rotor 63 is provided to level the unevenness of the field surface. The leveling rotor 63 receives driving force from the rear wheel gear cases 11a on the left and right sides via rotor transmission shafts 63a.

[0041] Furthermore, as shown in Figure 1, line markers 65 are provided on both the left and right sides of the seedling planting unit 4. One of these markers touches the field surface, forming a groove that serves as a guide for travel in the next work row (next process). When one side of the line markers 65 touches the ground, the other side moves upward and apart. When the seedling planting unit 4 is raised during a turn, both sides move upward and apart. After the turn, when the seedling planting unit 4 is lowered, one side moves upward and the other side touches the ground.

[0042] Furthermore, as shown in Figures 1 and 2, a vertically elongated center mascot 66 is provided in the left-right center of the vehicle body 2 and in front of the bonnet 39. By aligning the center mascot 66 with the grooves formed in the field using the left and right line markers 65, it becomes possible to travel in accordance with the working position of the immediately preceding work row, thereby improving work accuracy and preventing the occurrence of non-work.

[0043] Depending on the soil type of the field, the guide lines formed by the left and right line markers 65 may quickly become buried, causing the indicator for moving straight to disappear. In such cases, it is advisable to use the left and right side markers 19, which are positioned in front of the left and right line markers 65. That is, by moving the left and right side markers 19 outwards and positioning them above the planted seedlings, it becomes possible to perform planting work in line with the planting of seedlings in the previous work row.

[0044] Furthermore, as shown in Figure 1, the seedling transplanter 1 is equipped with a position acquisition device 150. The position acquisition device 150 acquires the current position and orientation of the seedling transplanter 1. The position acquisition device 150 includes, for example, an orientation sensor and positioning means such as GPS (Global Positioning System) or GNSS (Global Navigation Satellite System). The position acquisition device 150 may be composed of multiple devices. The position acquisition device 150 may also include a camera and an ultrasonic sensor, which may acquire the turning position in the field and detect the distance to the turning position.

[0045] For example, the position acquisition device 150 receives positioning information from the positioning means, creates current position information and direction information of the vehicle body 2 based on the received positioning information, and acquires the current position and direction. The position acquisition device 150 is, for example, mounted on the mounting bracket 59 and positioned above the vehicle body 2.

[0046] The straight-line control program and the turning control program, created based on position information from the position acquisition device 150, are stored in separate locations. The straight-line control program is stored, for example, in the straight-line control ECU (Electronic Control Unit) 100a within the position acquisition device 150, and the turning control program is stored, for example, in the turning control ECU 100b housed in the bonnet 39. The straight-line control ECU 100a and the turning control ECU 100b are included in the control device 100 (see Figure 3), which will be described later. The straight-line control ECU 100a and the turning control ECU 100b may be stored in the same ECU.

[0047] (Control system for seedling transplanter) Next, the control system of the seedling transplanter 1 will be described with reference to Figures 3 and 4. Figure 3 is a block diagram showing the control system of the seedling transplanter 1, centered on the control device 100. Figure 4 is a diagram showing the mode switching switch 45. The seedling transplanter 1 is capable of controlling each part by electronic control and is equipped with a control device 100 that controls each part.

[0048] The control device 100 includes a processing unit with a CPU (Central Processing Unit), a storage unit with ROM (Read Only Memory) and RAM (Random Access Memory), and an input / output unit, all of which are connected to each other and can exchange signals. The storage unit stores computer programs for controlling the seedling transplanter 1. The control device 100 performs its various functions by reading the computer programs stored in the storage unit.

[0049] The control device 100 is connected to actuators such as a throttle motor 80, hydraulic control valves 81 and 82, a planting clutch operating solenoid 83, a side clutch operating solenoid 84, an HST motor 85, a line drawing marker lifting motor 87, a steering motor 95, and a differential lock switching motor 96.

[0050] The throttle motor 80 increases or decreases the rotational speed of the engine 30's output shaft by operating a throttle that adjusts the intake volume of the engine 30. The hydraulic control valve 81 controls the extension and retraction of the lifting cylinder 25. The hydraulic control valve 82 controls the power steering mechanism 88. The planting clutch operating solenoid 83 operates the planting clutch 27a.

[0051] The side clutch operating solenoid 84 operates the side clutch 44, which switches the power transmission state to the rear wheels 11 (see Figure 1). Note that a side clutch 44 is provided for each of the left and right rear wheels 11, and two side clutch operating solenoids 84 are provided, one for each side clutch 44.

[0052] The HST motor 85 changes the tilt angle of the swash plate of the HST14 by changing the rotation angle of the trunnion of the HST14. The steering motor 95 is a motor that drives the steering 35, which is a steering device that adjusts the amount of steering (steering angle) of the front wheels 10 (see Figure 1) when automatic turning control is performed. The steering motor 95 rotates the steering 35. The line marking marker lifting motor 87 lifts and lowers the line marking marker 65.

[0053] The differential lock switching motor 96 is a motor that switches the operation and deactivation of the differential lock mechanism 97 (hereinafter referred to as the differential lock mechanism (same-speed rotation mechanism)). The differential lock mechanism 97 locks the differential mechanism, which rotates the left and right front wheels 10 at different rotational speeds when turning. In other words, when the differential lock mechanism 97 is engaged, the differential mechanism is locked, and the left and right wheels rotate at the same rotational speed.

[0054] The control device 100 is connected to detection devices such as a rotation speed sensor 90, a steering amount sensor 91 (steering angle sensor), and a tilt sensor 92. Four rotation speed sensors 90 are provided, one for each of the left and right front wheels 10 and rear wheels 11, and they detect the rotation speed of the left and right front wheels 10 and rear wheels 11, respectively.

[0055] The steering amount sensor 91 detects the amount of operation of the steering device, which is the steering 35, that is, the amount of steering (steering angle) of the front wheels 10. The steering amount sensor 91 is mounted, for example, on an axis connected to the pitman arm. The steering amount is detected in both the left and right directions, with the value when the steering 35 is in a preset straight-ahead position as the reference value. The tilt sensor 92 detects the tilt angle, which is the inclination of the vehicle body 2.

[0056] Furthermore, the control device 100 receives signals as operation signals from the accelerator pedal 32, HST lever 36, sub-transmission operation lever 37, mode selector switch 45, autonomous driving selector switch 46, planting unit lifting switch 47, automatic turning selector switch 48, line marking marker automatic lifting switch 49, and others.

[0057] The HST lever 36 is operated to change the forward / reverse movement and travel speed of the vehicle body 2. The sub-transmission lever 37 is operated to switch the travel speed of the vehicle body 2 to a speed appropriate for the location (field or road) in which it is traveling.

[0058] The autonomous driving selector switch 46 is a switch that switches whether or not to perform autonomous driving. Specifically, the autonomous driving selector switch 46 is a switch that switches the driving mode between autonomous driving mode and manual driving mode.

[0059] The planting unit lifting switch 47 is a switch that toggles whether or not to raise or lower the seedling planting unit 4. The planting unit lifting switch 47 can be changed to the "up" and "down" positions.

[0060] When the planting unit lifting switch 47 is in the "up" position, the seedling planting unit 4 rises to a predetermined non-working position, and the seedling planting device 55 stops, resulting in a non-working state. When the planting unit lifting switch 47 is in the "down" position, the seedling planting unit 4 lowers to a predetermined working position, and the seedling planting device 55 operates, resulting in a working state. In other words, the planting unit lifting switch 47 is a switch that detects the working state of the seedling planting unit 4. Note that a separate switch may be provided to detect the working state of the seedling planting unit 4.

[0061] The automatic line marking marker lifting switch 49 is a switch that toggles whether or not to automatically raise and lower the line marking marker 65 in conjunction with the amount of steering 35 operation, that is, the amount of steering of the front wheels 10. When the automatic line marking marker lifting switch 49 is "ON", control is performed to automatically raise and lower the line marking marker 65 in conjunction with the amount of steering. On the other hand, when the automatic line marking marker lifting switch 49 is "OFF", control is not performed to automatically raise and lower the line marking marker 65 in conjunction with the amount of steering.

[0062] The automatic rotation switch 48 is a switch that toggles whether or not automatic rotation is enabled. When the automatic rotation switch 48 is set to "ON", automatic rotation is enabled. When the automatic rotation switch 48 is set to "OFF", automatic rotation is disabled. When the automatic rotation switch 48 is set to "OFF", automatic rotation will not be performed even if the conditions for automatic rotation are met.

[0063] The mode selector switch 45 shown in Figure 4 is a switch that switches the mode of the vehicle body 2. For example, the mode selector switch 45 is a switch that can be operated in three positions. When switch position 45a is pressed and the mode selector switch 45 is set to "4DWAUTO", the mode of the vehicle body 2 is 4WD auto mode. When the mode selector switch 45 is set to "normal mode" (when neither switch position 45a nor switch position 45b is pressed), the mode of the vehicle body 2 is normal mode. When switch position 45b is pressed and the mode selector switch 45 is set to "4WDLOCK", the mode of the vehicle body 2 is 4WD lock mode. The modes of the vehicle body 2 will be described later.

[0064] Here, we will describe the functional configuration of the control device 100.

[0065] The control device 100 detects the rotational speeds of the front wheels 10 and rear wheels 11 in 4WD auto mode during a turn, based on the detection results of the rotational speed sensor 90. In 4WD auto mode, the control device 100 also cuts off the drive to the rear wheel 11 on the inside of the turning vehicle body 2 and activates the differential mechanism of the front wheels 10.

[0066] The control device 100 detects slippage of the front wheels 10 based on the rotational difference between the left and right front wheels 10. Specifically, the control device 100 calculates the ratio of the rotational speed of the right front wheel 10 to the rotational speed of the left front wheel 10 as the rotational difference. Alternatively, the control device 100 calculates the ratio of the rotational speed of the left front wheel 10 to the rotational speed of the right front wheel 10 as the rotational difference. The control device 100 may also calculate the difference between the rotational speed of the left front wheel 10 and the rotational speed of the right front wheel 10 as the left-right difference.

[0067] The control device 100 detects wheel slippage of the front wheels 10 when the ratio of rotational speeds, which is the difference in rotational speed, deviates from a first reference value by a first predetermined value or more. The first reference value is set to a value corresponding to the steering angle of the front wheels 10. In other words, the control device 100 detects that the vehicle is turning normally due to the differential mechanism when the ratio of rotational speeds is less than the first predetermined value from the first reference value, and detects that either the left or right front wheels 10 are slipping when the ratio of rotational speeds deviates from a first predetermined value or more from the first reference value.

[0068] Furthermore, the control device 100 detects wheel slippage of the rear wheels 11 based on the rotational difference between the left and right rear wheels 11. Specifically, the control device 100 calculates the ratio of the rotational speed of the right rear wheel 11 to the rotational speed of the left rear wheel 11 as the rotational difference. Alternatively, the control device 100 calculates the ratio of the rotational speed of the left rear wheel 11 to the rotational speed of the right rear wheel 11 as the rotational difference. The control device 100 may also calculate the difference between the rotational speed of the left rear wheel 11 and the rotational speed of the right rear wheel 11 as the left-right difference.

[0069] The control device 100 detects wheel slippage of the rear wheels 11 when the ratio of rotational speeds, which is the rotational difference, deviates from the second reference value by a second predetermined value or more. The second reference value is set to a value corresponding to the steering angle of the front wheels 10. In other words, if the ratio of rotational speeds is less than the second predetermined value from the second reference value, the control device 100 detects that the vehicle is turning normally with the drive of the inner rear wheel 11 disengaged, and if the ratio of rotational speeds deviates from the second reference value by a second predetermined value or more, it detects that either the left or right rear wheel 11 is slipping.

[0070] Thus, according to the control device 100 of this embodiment, wheel slippage can be detected by the rotation speed of the left and right wheels (front wheels 10 or rear wheels 11).

[0071] When the control device 100 detects wheel slippage, it drives the differential lock switching motor 96 to activate the differential lock mechanism 97 of the front wheels 10. By activating the differential lock mechanism 97 when either the front wheels 10 or the rear wheels 11 are slipping, the left and right front wheels 10 rotate at the same speed, allowing for highly accurate elimination of wheel slippage.

[0072] If the front wheels 10 continue to spin after the differential lock mechanism 97 of the front wheels 10 has been activated, the control device 100 engages a clutch with the drive shaft 42 of the inner rear wheel 11 to drive the inner rear wheel 11. In other words, if the front wheels 10 continue to spin despite the differential lock mechanism 97 being activated, the control device 100 can forcibly drive all four wheels to eliminate the spin with high precision.

[0073] Next, with reference to Figures 5 and 6, the control of the mode switching of the vehicle body 2 by the seedling transplanter 1 will be explained. Figure 5 is an explanatory diagram of the autonomous driving of the seedling transplanter 1 in the field. Figure 6 is a diagram showing the display of the monitor 86 (see Figure 3). Figure 6(a) shows the display of normal straight-ahead driving. Figure 6(b) shows the display of normal left-turn driving. Figure 6(c) shows the display of normal right-turn driving. Figure 6(d) shows the display of right-turn driving with the differential lock mechanism 97 activated. Figure 6(e) shows the display of left-turn driving with the differential lock mechanism 97 activated. Figure 6(f) shows the display of left-turn driving before activating the differential lock mechanism 97. Figure 6(g) shows the display of right-turn driving before activating the differential lock mechanism 97. Figure 6(h) shows the display of driving with four-wheel drive activated. Figure 6(i) shows the display of left-turn driving before activating four-wheel drive. Figure 6(j) shows the display for right-turn driving before activating the four-wheel drive.

[0074] In Figure 6, the white areas indicate the off state, the shaded areas without radial lines indicate the on state, and the shaded areas with radial lines indicate the blinking state.

[0075] The control device 100 has an autonomous driving mode in which it controls the steering motor 95 (see Figure 3) while feeding back the steering amount of the front wheels 10 to operate the steering 35 (see Figure 3). The autonomous driving mode includes an automatic straight-line mode and an automatic turning mode.

[0076] As shown in Figure 5, in autonomous driving mode, the seedling transplanter 1 automatically performs seedling planting work in the field, with an operator riding in the vehicle body 2, while repeatedly moving straight and turning along the planned driving route. The control device 100 acquires the current position information and turning position information of the seedling transplanter 1 using the position acquisition device 150 located above the vehicle body 2, as described above.

[0077] The seedling transplanter 1 plants seedlings while moving back and forth within a designated work area in the field. In this case, for straight-line travel, the control device 100 executes an automatic straight-line mode, allowing the machine to automatically travel along the set straight-line travel path L1. For turning travel, the control device 100 executes an automatic turning mode, allowing the machine to automatically turn along the turning travel path L2.

[0078] The straight-line travel path L1 is parallel to the reference line L0, which serves as the travel reference. The reference line L0 is set in the field according to the direction in which seedlings are planted. The control device 100 acquires the start and end positions of the straight-line travel as the reference start point (point A) and reference end point (point B), respectively, and stores the line segment connecting points A and B as the reference line L0.

[0079] The control device 100 controls the steering motor 95 so that the steering amount of the steering 35 becomes a predetermined amount while the seedling transplanter 1 is turning. In this case, the control device 100 executes the process regardless of the position information acquired by the position acquisition device 150. The predetermined steering amount is a preset value. The predetermined steering amount is set according to the type of seedling transplanter 1, etc. The predetermined steering amount is set so that the transition from automatic turning to automatic straight driving is performed smoothly.

[0080] Here, we will explain in detail the control of each mode of the vehicle body 2 during turning.

[0081] (4WD Auto Mode) When the mode is switched to 4WD auto mode by the mode selector switch 45, the control device 100 disengages the side clutch 44 on the inside of the turn, thereby cutting off the drive to the inner rear wheel 11 of the vehicle body 2 and activating the differential mechanism of the front wheel 10. The seedling transplanter 1 can turn while suppressing damage to the field by decelerating the inner front wheel 10 and rear wheel 11.

[0082] When the drive to the inner rear wheel 11 of the vehicle body 2 is deactivated and the differential mechanism of the front wheels 10 is activated, the vehicle body 2 may become unable to move due to slippage or getting stuck. In order to move the vehicle body 2, the control device 100 activates the differential lock mechanism 97 when it detects slippage of the wheels of the vehicle body 2 (for example, the front wheels 10).

[0083] Even if the differential lock mechanism 97 that locks the differential mechanism is activated, the vehicle body 2 may not be able to move. In order to move the vehicle body 2, the control device 100 generates a stronger thrust. When the control device 100 generates a stronger thrust, it forcibly activates the four-wheel drive. A stronger thrust is generated when the detection of slippage of the rear wheels 11 of the vehicle body 2 continues for a predetermined period of time, for example, when the rear wheel 11 on the inside of a turn continues not to rotate.

[0084] As described above, the detection of wheel slippage of the vehicle body 2 is performed based on the difference in rotation between the left and right wheels of the vehicle body 2. Alternatively, the detection of wheel slippage of the vehicle body 2 is performed based on the vehicle speed of the vehicle body 2 measured by the position acquisition device 150. For example, wheel slippage of the vehicle body 2 is detected when the vehicle speed of the vehicle body 2 measured by the position acquisition device 150 is below a predetermined speed.

[0085] The control device 100 then reduces the target speed of the vehicle body 2 to below a certain level when it activates the differential lock mechanism 97 or the four-wheel drive due to the wheels of the vehicle body 2 slipping. This prevents the drive torque from rapidly recovering when the differential lock mechanism 97 and the four-wheel drive are activated in the seedling transplanter 1, thereby improving the safety of the worker riding in the vehicle body 2. The target speed of the vehicle body 2 is the target speed at which the wheels of the vehicle body 2 rotate.

[0086] (Normal mode) When the mode is switched to normal mode by the mode selector switch 45, the control device 100 cuts off the drive to the inner rear wheel 11 of the vehicle body 2 during turns and activates the differential mechanism of the front wheels 10. The seedling transplanter 1 can turn while suppressing damage to the field by decelerating the inner front wheel 10 and rear wheel 11 during turns. If the vehicle body 2 becomes unable to move due to slipping or getting stuck, the operator can manually operate the vehicle body 2 to make it move. For example, the operator can make the vehicle body 2 move by activating the differential lock mechanism 97 and four-wheel drive, operating the steering 35, or decelerating the target speed of the vehicle body 2.

[0087] In 4WD auto mode and normal mode, the control device 100 determines slip based on the vehicle speed of the vehicle 2 measured by the position acquisition device 150. If the slip is resolved, the control device 100 gradually increases the target vehicle speed of the vehicle 2; if the slip is not resolved, it maintains or decelerates the target vehicle speed of the vehicle 2. If the slip is not resolved, the control device 100 increases the engine speed. Here, slip is determined by whether the vehicle speed of the vehicle 2 measured by the position acquisition device 150 is below a predetermined speed.

[0088] The only way to determine if the slip has been completely resolved is through the position acquisition device 150. Furthermore, increasing the speed of the vehicle 2 while the slip has not been resolved can cause it to get stuck, damaging the field. With the seedling transplanter 1 of the present invention, by keeping the speed of the vehicle 2 low and increasing the engine speed, the ability to traverse obstacles can be improved through high-torque turning.

[0089] The control device 100 may maintain the increased engine speed (maximum speed) even after the slip is resolved. The control device 100 terminates the increased engine speed when the turn is completely finished and the vehicle body 2 reaches the work start position after the turn (when the planting clutch 27a is engaged). This prevents the seedling transplanter 1 from repeatedly raising and lowering the engine speed.

[0090] As mentioned above, the modes of the vehicle body 2 may include a 4WD lock mode.

[0091] (4WD Lock Mode) When the mode selector switch 45 is set to 4WD lock mode, the differential lock mechanism 97 is constantly activated during turns, and the four-wheel drive is constantly engaged. This allows the seedling transplanter 1 to always be in a state of high off-road capability.

[0092] Even in 4WD lock mode, the control device 100 determines slip based on the vehicle speed of the vehicle 2 measured by the position acquisition device 150. If the slip is resolved, the control device 100 gradually increases the target vehicle speed of the vehicle 2. If the slip is not resolved, it maintains or decelerates the target vehicle speed of the vehicle 2 and increases the engine speed. In this way, the control device 100 can perform the same functions in 4WD lock mode as in 4WD auto mode and normal mode.

[0093] As configured above, the seedling transplanter 1 is a so-called ride-on robotic rice transplanter, and therefore primarily operates by automatic driving, and can also automatically handle irregular situations such as slipping. Since an operator is riding on the seedling transplanter 1, there are times when the operator wants to handle irregular situations manually, or when it is better for the operator to handle irregular situations manually. Therefore, making it possible to switch between automatic and manual operation improves operability.

[0094] Next, we will explain other features and effects of the control of the seedling transplanter 1 during turning.

[0095] The control device 100 may maintain the target speed of the vehicle body 2 after activating the differential lock mechanism 97 or the four-wheel drive. For example, if the control device 100 has reduced the target speed of the vehicle body 2 to below a certain level after activating the differential lock mechanism 97 or the four-wheel drive, it may drive the vehicle body 2 to maintain that target speed. This allows the seedling transplanter 1 to turn with stable behavior.

[0096] Alternatively, the control device 100 may increase the target speed of the vehicle body 2 to the speed it was at before the vehicle body 2's wheels began to slip. For example, if the control device 100 has reduced the target speed of the vehicle body 2 to below a certain level after activating the differential lock mechanism 97 or the four-wheel drive, it may increase the target speed and drive the vehicle body 2. This helps to suppress the time it takes for the seedling transplanter 1 to turn. Note that the vehicle speed before the wheels began to slip refers to the vehicle speed during the turn before the vehicle speed decreases due to slipping or getting stuck.

[0097] When the steering wheel 35 or HST lever 36 is operated, the control device 100 prioritizes control based on the operation of the steering wheel 35 or HST lever 36 over control of the target vehicle speed and engine speed of the vehicle body 2. In other words, when the steering wheel 35 or HST lever 36 is operated, the control that automatically adjusts the vehicle speed and engine speed of the vehicle body 2 is stopped, and control is performed in accordance with the operation of the steering wheel 35 or HST lever 36.

[0098] When the accelerator pedal 32 is operated, the control device 100 prioritizes the control of the target vehicle speed and engine speed of the vehicle 2 over the control based on the operation of the accelerator pedal 32. In other words, when the accelerator pedal 32 is operated, the engine speed is not changed in response to the operation of the accelerator pedal 32, and the control that automatically adjusts the vehicle speed and engine speed of the vehicle 2 continues.

[0099] This allows the operator to perform the desired operation when the target speed and engine speed of the vehicle body 2 are being controlled and an operation is performed to change the direction of travel of the vehicle body 2.

[0100] The control device 100 maintains the operation of the differential lock mechanism 97 or four-wheel drive when the steering wheel 35, HST lever 36, or accelerator pedal 32 is operated, as long as the vehicle is in 4WD auto mode or 4WD lock mode and the differential lock mechanism 97 or four-wheel drive is engaged. To stop the operation of the differential lock mechanism 97 or four-wheel drive, it is necessary to switch to normal mode using the mode selector switch 45. For example, the operation of the differential lock mechanism 97 or four-wheel drive may be stopped when the vehicle is switched to normal mode and the steering wheel 35, HST lever 36, or accelerator pedal 32 is operated.

[0101] As a result, when the vehicle is in 4WD auto mode or 4WD lock mode and the differential lock mechanism 97 or four-wheel drive is engaged, a state of high off-road capability is maintained even when the steering wheel 35, HST lever 36, or accelerator pedal 32 is operated.

[0102] As shown in Figure 6, the control device 100 may display a warning on the monitor 86 (see Figure 3) when the differential lock mechanism 97 or four-wheel drive is activated during turning. The control device 100 may also display various drive states in each mode of the vehicle body 2. Since the worker riding in the vehicle body 2 may feel that the recovery of drive torque or the engagement of the clutch has occurred suddenly, safety must be considered. With the seedling transplanter 1, safety can be ensured by providing a warning via the monitor 86.

[0103] For example, Figures 6(f) and 6(g) provide a warning about the recovery of drive torque by activating the differential lock mechanism 97. For example, Figures 6(i) and 6(j) provide a warning about the recovery of drive torque by activating the four-wheel drive system.

[0104] Next, a modified seedling transplanter 1 will be described.

[0105] The seedling transplanter 1, as a GNSS sensor, has a function to switch the reception method between RTK-GNSS (RTK positioning method) and D-GNSS (differential positioning method). Even when the reception method is switched between RTK-GNSS and D-GNSS, if the transplanter 1 cannot receive radio waves with the switched reception method, it controls the display to show the switched reception method differently from the display when reception is possible (for example, grayed out). This allows the user to know which reception method is currently being used, even when radio waves are not being received with the switched reception method.

[0106] The seedling transplanter 1 has the ability to select from one of the following modes: robot mode, straight-line assist mode, straight-line assist mode, turning assist mode, or manual mode. When robot mode is selected, the seedling transplanter 1 is controlled to use RTK-GNSS for satellite reception. The seedling transplanter 1 is equipped with a switch for switching robot mode and has an indicator unit that lights up a lamp or otherwise notifies the operator when robot mode is selected. As a result, when robot mode requires precision, the seedling transplanter 1 can perform work using highly accurate RTK-GNSS. In addition, the operator can check the current mode.

[0107] The seedling transplanter 1 is equipped with a notification unit that changes the display depending on the status: a lamp flashes when automatic movement is not possible in robot mode, and the lamp remains lit when automatic movement is possible. This allows the operator to confirm whether automatic movement is possible in robot mode.

[0108] The seedling transplanter 1 is equipped with a control system that maintains safety functions in robot mode, regardless of whether it is capable of autonomous driving or not. This ensures the safety of the seedling transplanter 1.

[0109] The seedling transplanter 1 has an area generation unit that generates an automatic travel area by traveling along three sides of the outer perimeter of the field, and switches to area generation mode by selecting teaching mode via mode switching. When teaching mode is selected, if the seedling transplanter 1 is not set to RTK-GNSS, it displays a warning message "Teaching is not possible because the receiving method is not set to RTK-GNSS." This allows the operator to understand that the RTK-GNSS correction signal is not available due to a poor connection of the VRS receiver, etc.

[0110] The seedling transplanter 1 can start teaching if the receiving method is set to RTK-GNSS when teaching mode is selected and the direction is determined. This allows the operator to understand that if only RTK-GNSS data acquisition is performed and the machine is not moving, teaching cannot be started because the direction is not determined.

[0111] When the seedling transplanter 1 is in teaching mode, if the receiving method is set to RTK-GNSS and the direction has not been determined, it displays a warning message that says, "Teaching is not possible because the direction has not been acquired." This allows the operator to understand that if only RTK-GNSS acquisition is performed and the machine is not moving, teaching cannot be started because the direction has not been determined.

[0112] The seedling transplanter 1 is equipped with a display unit that shows how to acquire the direction, in addition to a warning that the direction has not been acquired. This allows the operator to know how to acquire the direction.

[0113] The seedling transplanter 1 has a mode that allows only D-GNSS to be used, which can be configured on the monitor 86. This means that if the RTK-GNSS correction signal cannot be obtained due to a faulty connection of the VRS receiver or the like, the seedling transplanter 1 can be used with D-GNSS by switching modes.

[0114] The seedling transplanter 1 has a mode that allows only RTK-GNSS to be used, which can be configured on the monitor 86. This allows the seedling transplanter 1 to use RTK-GNSS for positioning even when only straight-line assist and turning assist are used.

[0115] The seedling transplanter 1, in a configuration that allows only RTK-GNSS to be used via settings on the monitor 86, has a function to stop automatic travel if RTK-GNSS malfunctions, and also has a function to select whether or not to switch to D-GNSS. As a result, the seedling transplanter 1 can choose whether or not to reacquire the route, since the route acquired by RTK-GNSS cannot be used with D-GNSS.

[0116] The seedling transplanter 1 is an automated work machine that has a mode-changing mechanism (for example, a rotary switch) that allows the operator to select from one of four modes: turning assist mode, straight-line assist mode, automated driving area teaching mode, or robot automated driving mode. This allows the operator to visually recognize which mode is currently being used by using the rotary switch.

[0117] Furthermore, in the seedling transplanter 1, the turning assist mode and straight-line assist mode are arranged side-by-side in the mode changing mechanism, with the teaching mode and automatic driving mode located next to them. This allows the seedling transplanter 1 to reduce the frequency of changes when changing the receiving method depending on the mode.

[0118] When teaching mode or automatic driving mode is selected, the seedling transplanter 1 automatically switches to RTK-GNSS as its receiving method. This allows the seedling transplanter 1 to automatically achieve high accuracy when used in robotic mode.

[0119] When the turning assist mode or straight-line assist mode is selected, the seedling transplanter 1 automatically switches to D-GNSS as its receiving method. This allows the seedling transplanter 1 to be used even when the RTK-GNSS correction signal is not connected.

[0120] The seedling transplanter 1 has a function that allows switching to use only RTK-GNSS via the monitor 86 settings. When set to RTK-GNSS only, the receiving method remains RTK-GNSS even when switching to turning assist mode or straight-line assist mode. This allows the seedling transplanter 1 to select a more accurate receiving method.

[0121] The seedling transplanter 1 is an autonomous working machine equipped with a first memory device that stores reference points acquired by D-GNSS, and a second memory device that stores reference points and routes acquired by RTK-GNSS. This allows for the storage of location information, even if discrepancies occur due to differences in reception methods.

[0122] Reference points stored in the first memory device become unusable when the reception method is changed from D-GNSS to RTK-GNSS, but they are not erased until planting is performed with a deviation of more than a specified amount relative to the direction of the straight line connecting the reference points. As a result, reference points stored in the first memory device cannot be used with other reception methods, but they are not erased for reuse within the same field.

[0123] The reference points stored in the first memory device are controlled to remain usable even if the reception method is changed from D-GNSS to RTK-GNSS, as long as it is changed back to D-GNSS. This configuration ensures that the reference points stored in the first memory device cannot be used with other reception methods, but they can be reused.

[0124] The reference points and routes stored in the second memory device become unusable when the reception method is changed from RTK-GNSS to D-GNSS, but they are not erased until the next teaching is performed. This configuration ensures that the reference points and routes stored in the second memory device cannot be used with other reception methods, but are not erased for reuse within the same field.

[0125] The reference points and routes stored in the second memory device are controlled to be usable even if the reception method is changed from RTK-GNSS to D-GNSS, as long as it reverts back to RTK-GNSS. As a result, the reference points and routes stored in the second memory device cannot be used with other reception methods, but they can be reused.

[0126] The seedling transplanter 1 has a setting function that allows the user to arbitrarily select between D-GNSS and RTK-GNSS as the receiving method via the monitor 86 on the machine side. The seedling transplanter 1 has a function that prevents the receiving method from being changed to D-GNSS when robot mode is selected. This ensures that the seedling transplanter 1 maintains accuracy in robot mode.

[0127] The seedling transplanter 1 is equipped with a restriction release function that allows the receiving method to be changed when the vehicle body 2 is stopped. This allows the seedling transplanter 1 to change the receiving method to straight-line assist or other modes when it stops due to a malfunction or other reason.

[0128] The seedling transplanter 1 is configured such that if the operator's seating position cannot be detected when transitioning to automatic mode, it will not switch to automatic mode even if the 3-position selector switch is operated, and will not accept forward or backward movement commands. This ensures that the seedling transplanter 1 is configured to reliably have an operator seated when transitioning to automatic mode.

[0129] The 3-position selector switch is configured to switch modes for a function that only provides steering assistance during driving when not in robot mode. Therefore, when not in robot mode, the 3-position selector switch functions as a turning assist selector switch.

[0130] The seedling transplanter 1 is configured to prevent switching to automatic mode and to notify the monitor 86 or other device that mode switching is not possible if the machine is detected to be tilted at an angle greater than a certain angle relative to the horizontal plane while in robot mode and manual mode. As a result, the seedling transplanter 1 is configured not to enter automatic mode and mode switching is prohibited when tilt is detected.

[0131] The seedling transplanter 1 is configured to classify the GNSS reception status into multiple modes, allowing transition to robot mode when the position accuracy is high, enabling steering assist during travel when the position accuracy is medium, and prohibiting transition to robot mode and steering assist control when the accuracy is low. As a result, the seedling transplanter 1 is configured to allow robot mode when RTK-GNSS is enabled, allow straight-line assist and turning assist when D-GNSS is enabled, and disable robot and assist functions when TK-GNSS and D-GNSS are not enabled.

[0132] The seedling transplanter 1 is configured to switch a 3-position selector switch to manual mode using a motor or other power source when an abnormality is detected during operation in robot mode and automatic mode. This ensures that the physical switch can also be switched to manual mode in the event of an emergency stop.

[0133] When the motor that switches the 3-position selector switch is operating, the motor's operating part interferes with the 3-position selector switch, causing it to be fixed in the manual mode position. As a result, the motor that switches the 3-position selector switch directly interferes with the switch's knob, fixing it in manual mode.

[0134] The configuration is such that when the motor that switches the 3-position selector switch is operating, the 3-position selector switch unit is activated and switched to the manual mode position. As a result, the seedling transplanter 1 has a configuration in which the knob of the 3-position selector switch can be switched in both manual and electric modes.

[0135] In hydraulic rolling, the horizontal position of the planting unit is controlled according to the horizontal sensor (slope sensor) value, but it is assumed that operation will not be performed if the horizontal sensor malfunctions. In hydraulic rolling, by turning off the rolling on / off setting, the control switches from the horizontal sensor (slope sensor) to the rolling rotation sensor (potentiometer), and the planting unit is raised to return to a parallel position. (Pressure relief will operate.) In the seedling quantity correction function, when the input item is the number of seedlings to use k [seedlings / tan], the maximum and minimum values ​​for the number of seedlings to use k [seedlings / tan] are set from the range of seedling quantities that are mechanically possible.

[0136] If you know the size of your field in ares, you can input the field dimensions and the desired number of seedling trays, and the system will suggest a pre-calculated number of seedling trays.

[0137] Further effects and modifications can be readily derived by those skilled in the art. Therefore, broader aspects of the present invention are not limited to the specific details and representative embodiments expressed and described above. Accordingly, various modifications are possible without departing from the spirit or scope of the overall concept of the invention as defined by the appended claims and their equivalents. [Explanation of symbols]

[0138] 1. Seedling transplanter (work vehicle) 2. Running vehicle 10 Front wheels 11 Rear wheel (wheel) 32 Accelerator pedal 35 Steering 36 HST lever 45 Mode selector switch 97 Differential lock mechanism 100 Control device 150 Location acquisition device

Claims

1. The vehicle body on which the workers ride, A work vehicle comprising a control device for automatically driving the aforementioned vehicle body, The aforementioned vehicle body is An operating device for switching the mode of the aforementioned vehicle body, It has a differential mechanism that rotates the left and right front wheels of the vehicle body at different rotational speeds when turning, The modes of the aforementioned vehicle include 4WD auto mode and normal mode. In the 4WD auto mode, the control device is During a turn, the drive to the inner rear wheel of the vehicle body is cut off, and the differential mechanism is activated. When the drive to the inner rear wheel of the vehicle body is cut off and the differential mechanism is operating, if slippage of the vehicle body's wheels is detected, the differential lock mechanism is activated to lock the differential mechanism. If a stronger propulsion force is to be generated after detecting wheel slippage of the aforementioned vehicle body, the four-wheel drive system is activated. The detection of wheel slippage of the aforementioned vehicle body is performed based on the difference in rotation between the left and right wheels of the vehicle body, or the vehicle speed of the vehicle body measured by a vehicle body position acquisition device. The control device is a work vehicle that, when the differential lock mechanism or four-wheel drive is activated due to the wheels of the vehicle body slipping, sets the target vehicle speed of the vehicle body to below a certain level.

2. The work vehicle according to claim 1, wherein the control device, after activating the differential lock mechanism or four-wheel drive, maintains the target vehicle speed of the vehicle body, or increases the target vehicle speed of the vehicle body to the speed at which wheel slippage was detected.

3. The control device is Based on the vehicle speed of the traveling vehicle measured by the position acquisition device, slippage is determined. The work vehicle according to claim 2, wherein if the slip is eliminated, the target speed of the vehicle body is gradually increased, and if the slip is not eliminated, the target speed of the vehicle body is maintained or reduced and the engine speed is increased.

Images