Work vehicle

Abstract

To provide a work vehicle that enables a user, etc., to freely change a correspondence relation between a machine body state and a steering mode.SOLUTION: A work vehicle includes: a machine body; a forward travelling device which is supported by the machine body, and which can be steered; a backward travelling device which is supported by the machine body, and which can be steered; a steering operation tool that receives a steering operation; a steering device which can change a mode to multiple steering modes, and which steers, in accordance with the received steering operation by the steering operation tool, at least either one of the forward travelling device or the backward steering device; a state obtaining unit that obtains a machine body state; a storing unit that stores a correspondence relation between the machine body state and the steering mode suitably applied so as to correspond to the machine body state; a steering mode changing unit that changes, based on the correspondence relation, the mode of the steering device to the steering mode corresponding to the obtained machine body state; and a changing unit that changes, based on a received manipulation, the correspondence relation stored in the storing unit.SELECTED DRAWING: Figure 6

Description

Technical Field

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

Background Art

[0002] For example, in the work vehicle (referred to as "work vehicle" in the document) disclosed in Patent Document 1, each of the front traveling device (referred to as "front wheels" in the document) and the rear traveling device (referred to as "rear wheels" in the document) is configured to be steerable. According to the body state (referred to as "working machine height" in the document), the steering mode is switched between a steering mode for steering only the front traveling device (referred to as "front wheel steering mode" in the document) and a steering mode for steering both the front traveling device and the rear traveling device (referred to as "four-wheel steering mode" in the document).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] By the way, in a conventional work vehicle with four-wheel steering as exemplified in Patent Document 1, even though a plurality of steering modes can be switched according to the body state, the correspondence relationship between the body state and the steering mode to be used according to the body state was fixed. For this reason, even if a user or the like wanted to change the correspondence relationship between the body state and the steering mode, the correspondence relationship was a configuration that could not be changed.

[0005] An object of the present invention is to provide a work vehicle in which a user or the like can freely change the correspondence relationship between the body state and the steering mode.

Means for Solving the Problems

[0006] The work vehicle of the present invention is characterized by comprising: a machine body; a forward travel device supported by the machine body and capable of steering; a rear travel device supported by the machine body and capable of steering; a steering control device that receives steering operations; a steering device that can change modes to a plurality of steering modes and steers at least one of the forward travel device and the rear travel device in response to the steering operations received by the steering control device; a state acquisition unit that acquires the state of the machine body; a storage unit that stores the correspondence between the state of the machine body and the steering mode to be used in accordance with the state of the machine body; a steering mode change unit that changes the mode of the steering device to the steering mode corresponding to the acquired state of the machine body based on the correspondence; and a change unit that changes the correspondence stored in the storage unit based on the received human operation.

[0007] According to the present invention, a correspondence between the machine state and the steering mode to be used according to the machine state is stored in the memory unit. The modification unit can change this correspondence based on human operation. The memory unit can then store the changed correspondence. As a result, users can freely change the correspondence between the machine state and the steering mode. This realizes a work vehicle in which users can freely change the correspondence between the machine state and the steering mode.

[0008] In the present invention, it is preferable that the aircraft state includes a forward state in which the aircraft can move forward and a reverse state in which the aircraft can move backward.

[0009] This configuration allows users to select their desired steering mode depending on whether the vehicle is moving forward or backward.

[0010] In the present invention, it is preferable that the modification unit can change the steering mode to be used in response to the reverse state to an RWS mode in which only the rear-running device is steered.

[0011] With this configuration, when the operator or other personnel perform reverse driving, the steering mode automatically switches to RWS mode. This allows the operator or other personnel to steer while reversing with intuitive operation, making reverse driving even easier.

[0012] In the present invention, it is preferable that the modification unit can change the steering mode to be used in response to the reverse state to an FWS mode in which only the forward travel device is steered.

[0013] With this configuration, when the operator or other personnel perform reverse driving, the steering mode automatically switches to FWS mode. This allows the operator or other personnel to steer while reversing with intuitive operation, making reverse driving even easier.

[0014] In the present invention, it is preferable that the modification unit can change the steering mode to be used in response to the reverse state to a 4WS mode that steers the forward and reverse driving devices.

[0015] With this configuration, the steering mode automatically switches to 4WS mode when the operator or other personnel perform reverse driving. This allows for tighter turning radius steering, making reverse driving even easier.

[0016] In the present invention, it is preferable that the machine body is equipped with a work device for performing work on a field, and that the machine body state includes a working state in which the work device is performing work and a non-working state in which the work device is not performing work.

[0017] This configuration allows users to select the steering mode they wish to use, depending on whether they are working or not.

[0018] In the present invention, it is preferable that the modification unit can change the steering mode to be used in response to the non-working state to an RWS mode in which only the rear-wheel drive device is steered.

[0019] With this configuration, when an operator or the like stops the working device, the steering mode is automatically switched to the RWS mode. Therefore, for example, when performing reverse travel after the forward travel involving the operation of the working device has ended, the operator or the like can perform intuitive steering during reverse travel, making the reverse travel easier.

[0020] In the present invention, it is preferable that the changing unit can change the steering mode to be used corresponding to the non-working state to the FWS mode for steering only the front traveling device.

[0021] With this configuration, when an operator or the like stops the working device, the steering mode is automatically switched to the FWS mode. Therefore, for example, when traveling after the forward travel involving the operation of the working device has ended, the operator or the like can perform intuitive steering in the non-working state, making the travel in the non-working state easier.

[0022] In the present invention, it is preferable that the changing unit can change the steering mode to be used corresponding to the non-working state to the 4WS mode for steering the front traveling device and the rear traveling device.

[0023] With this configuration, when an operator or the like stops the working device, the steering mode is automatically switched to the 4WS mode. Therefore, for example, when traveling after the forward travel involving the operation of the working device has ended, it is possible to perform steering with good turning performance, making the travel in the non-working state easier.

[0024] In the present invention, it is preferable that an engine, a starting operation tool for receiving a manual operation for starting the engine, and a selection operation tool for receiving a manual operation for changing the correspondence relationship by the changing unit are provided, and the changing unit can change the correspondence relationship in response to both the starting operation tool and the selection operation tool being operated.

[0025] With this configuration, by operating both the start operation tool and the selection operation tool, it becomes possible to change the correspondence relationship by the change unit. The start operation tool is used when an operator or the like starts the prime mover. For example, if an operator operates only the selection operation tool, there is a possibility that the correspondence relationship may be changed unintentionally. However, when an operator or the like changes the correspondence relationship, operations of both the start operation tool and the selection operation tool are required. This avoids the possibility that an operator or the like may unintentionally change the correspondence relationship.

[0026] In the present invention, it is preferable that a selection operation tool for receiving a manual operation for changing the correspondence relationship by the change unit is provided, a plurality of the correspondence relationships are stored in the storage unit, and the selection operation tool is provided with a first operation unit for changing the correspondence relationship to be used and a second operation unit for determining the change of the correspondence relationship to be used.

[0027] With this configuration, an operator or the like can select a steering mode to be used corresponding to the aircraft state with the first operation unit, and can determine the selected steering mode with the second operation unit.

Brief Description of the Drawings

[0028] [Figure 1] It is a left side view showing the whole riding work machine. <00001​​​​​​​​​​​​​​​​​​​​​​This is a flowchart illustrating the process in orientation correction mode. [Modes for carrying out the invention]

[0029] In Figures 1 to 3, the arrow labeled "F" indicates the forward direction, the arrow labeled "B" indicates the backward direction, the arrow labeled "U" indicates the upward direction, the arrow labeled "D" indicates the downward direction, the arrow labeled "R" indicates the right direction, and the arrow labeled "L" indicates the left direction.

[0030] [Overall configuration of the tractor] As shown in Figures 1 to 3, the machine body 3 is supported by the left and right front wheels 1 and the left and right rear wheels 2. An operating unit 4 is provided on the machine body 3. A steering handle 20 is provided on the operating unit 4. The front wheels 1 are the "front running device" as described in the claims. The rear wheels 2 are the "rear running device" as described in the claims. The steering handle 20 is the "steering control device" as described in the claims.

[0031] As shown in Figures 1 to 3, the aircraft body 3 is equipped with a front transmission case 5, a rear transmission case 6, a hydrostatic continuously variable transmission 7, an aircraft frame 8, an aircraft frame 9, and an engine 10. The continuously variable transmission 7 is connected to the front of the rear transmission case 6, and the channel-shaped aircraft frame 8 is connected across the front transmission case 5 and the continuously variable transmission 7. The left and right aircraft frames 9 are connected to the front transmission case 5 and are arranged along the front-to-rear direction. The left and right front wheels 1 are supported by the aircraft frame 9. The left and right rear wheels 2 are supported by the rear transmission case 6. The engine 10 is the "prime mover" as described in the claims.

[0032] The engine 10 is connected to the front of the front transmission case 5 and the upper part of the aircraft frame 9. The engine 10 is covered by a bonnet 11. Power from the engine 10 is transmitted to a transmission shaft (not shown) and transmission gears (not shown) inside the front transmission case 5. A transmission shaft (not shown) is connected between the front transmission case 5 and the continuously variable transmission 7, and power from the engine 10 is transmitted from the front transmission case 5 to the continuously variable transmission 7 via this transmission shaft.

[0033] The front transmission case 5 has a PTO shaft 17 that shifts the power from the engine 10. The PTO shaft 17 extends from the front transmission case 5 to the rear end of the aircraft 3. The power shifted by the front transmission case 5 is distributed to the continuously variable transmission 7 and the PTO shaft 17.

[0034] The continuously variable transmission 7 is configured to allow stepless shifting between forward and reverse. Power from the continuously variable transmission 7 is transmitted to the left and right rear wheels 2 via a sub-transmission (not shown) and a rear differential (not shown) inside the rear transmission case 6. Power branched off just before the rear differential is transmitted from the front differential (not shown) via a transmission shaft (not shown) connected across the rear transmission case 6 and the front transmission case 5, through a transmission shaft (not shown) for front wheel transmission in the front transmission case 5, to the front differential (not shown), and then transmitted to the left and right front wheels 1.

[0035] Left and right rear transmission cases 18 are provided on the left and right sides of the rear transmission case 6. In the rear view of Figure 3, the left and right rear transmission cases 18 are shown enclosed by thick lines and colored gray. In other words, the rear view of Figure 3 clearly shows the left and right rear transmission cases 18. On both the left and right sides of the rear transmission case 6, there are rear drive output units 6A that output power to the left and right rear wheels 2. The lateral inner ends 18A of each of the left and right rear transmission cases 18 are connected to the rear drive output units 6A of the rear transmission case 6. The lateral outer ends 18B of each of the left and right rear transmission cases 18 extend downward, and the lateral outer ends 18B of the rear transmission cases 18 are connected to the rear wheels 2. In this way, each of the left and right rear transmission cases 18 transmits the power output from the rear transmission case 6 to the left and right rear wheels 2. Power output from the rear transmission case 6 is transmitted from the rear drive output unit 6A to the rear wheels 2 via a transmission shaft (not shown) inside the rear transmission case 18. As a result, the left and right rear wheels 2 rotate. The rear transmission case 18 is configured such that the upper connecting part connected to the rear drive output unit 6A is positioned higher than the lower connecting part connected to the rear wheels 2.

[0036] A first front transmission case 19A is located in front of the front mission case 5, and the first front transmission case 19A extends along the side of the aircraft. Second front transmission cases 19B are located on the left and right sides of the first front transmission case 19A, respectively. In the front view of Figure 2, the first front transmission case 19A is clearly shown with a thick line, with other components located in front of it visible through it. Also in the front view of Figure 2, the left and right second front transmission cases 19B are shown enclosed by thick lines and colored gray.

[0037] The inner lateral ends of the left and right second front transmission cases 19B are connected to the outer lateral ends of the first front transmission case 19A. The outer lateral ends of the left and right second front transmission cases 19B extend downward, and the outer lateral ends of the second front transmission cases 19B are connected to the front wheels 1. Power for front wheel transmission from the front transmission case 5 is transmitted to the front wheels 1 via the front wheel differential device (not shown) and transmission shaft (not shown) inside the first front transmission case 19A, and the transmission gear (not shown) inside the second front transmission case 19B. As a result, the left and right front wheels 1 rotate. The second front transmission case 19B is configured such that the portion connected to the outer lateral end of the first front transmission case 19A is located higher than the portion connected to the front wheels 1.

[0038] As described above, the tractor shown in this embodiment is a tractor with a configuration known as "high clearance." As shown in Figures 2 and 3, the left and right rear transmission cases 18 extend downward from both sides of the rear transmission case 6, and the second front transmission case 19B extends downward from both sides of the first front transmission case 19A. In other words, the running gear of the present invention is formed in a roughly gate-like shape when viewed from the front and rear of the machine. As a result, there is space below the machine body 3 in which growing crops can be planted directly. In addition, the left and right front wheels 1 swing around the vertical axis of the first front transmission case 19A, and the left and right rear wheels 2 swing around the vertical axis of the rear transmission case 18. The tractor of this embodiment is capable of four-wheel steering. The tractor of this embodiment is particularly suitable for inter-row cultivation work in fields.

[0039] As shown in Figures 1 to 3, a switching device 50 that accepts human operation is provided on the side of the operating unit 4. The switching device 50 is the "selection device" described in the claims.

[0040] A three-point linkage mechanism 12 is connected to the rear end of the machine body 3 (the rear lower part of the rear transmission case 6) so as to be able to swing up and down, and the three-point linkage mechanism 12 raises and lowers the working device. The working device attached to the tractor may be, for example, a cultivator, disc harrow, power harrow, inter-row cultivator and weeding machine, seeding device, planter, fertilizer applicator, leaf cutter, pinching device, spraying device, ridging device, mulcher, rotary rake, tedder, and grass cutting device.

[0041] The three-point linkage mechanism 12 is equipped with a single top link 13, left and right lower links 14, and left and right lift arms 15 that can be swung up and down. The lower links 14 are connected to the rear end of the machine body 3 so as to be able to swing up and down. A connecting rod 16 is connected between the right lift arm 15 and the right lower link 14. When the left and right lift arms 15 are swung up and down, the left and right lower links 14 swing up and down, and the work device is raised and lowered.

[0042] The PTO shaft 17 is located at the rear end of the machine body 3. The PTO shaft 17 transmits rotational force from the engine 10 to the work device via a universal joint (not shown). The PTO shaft 17 is positioned higher than the lower link 14 in its lowest position and outputs rotational power.

[0043] [Explanation of the four-wheel steering mechanism] Based on Figure 4, the hydraulic circuit of the steering mechanism in this embodiment will be described. This hydraulic circuit is a schematic circuit of the hydraulic fluid used for steering operations of the front wheels 1 and rear wheels 2 shown in Figures 1 to 3.

[0044] The hydraulic fluid is stored in the hydraulic fluid reservoir 21. The hydraulic fluid pump 22 is configured to draw the hydraulic fluid from the hydraulic fluid reservoir 21. When the suction force of the hydraulic fluid pump 22 acts on the hydraulic fluid, impurities contained in the hydraulic fluid are removed by the oil filter 21A. The hydraulic fluid is then drawn into the hydraulic fluid pump 22 via the suction oil passage 22i and discharged to the power steering unit 23 via the discharge oil passage 22f.

[0045] The power steering unit 23 is connected to a discharge oil passage 22f and a return oil passage 23a. Since the discharge oil passage 22f is directly connected to the discharge port of the hydraulic oil pump 22, when the hydraulic oil pump 22 is operating, the hydraulic oil pressure in the discharge oil passage 22f is higher than the hydraulic oil pressure in the return oil passage 23a. For this reason, the discharge oil passage 22f is the inlet oil passage, and the return oil passage 23a is the return oil passage.

[0046] Based on the amount of movement of the steering wheel 20, hydraulic fluid is supplied from the power steering unit 23 to the front wheel steering actuator 27 and the rear wheel steering actuator 28, respectively. The power steering unit 23 is connected to the front wheel steering valve 24 and the rear wheel steering valve 25.

[0047] A first intermediate oil passage 26a is connected to both the power steering unit 23 and the front wheel steering valve 24. A second intermediate oil passage 26b is connected to both the power steering unit 23 and the rear wheel steering valve 25. Furthermore, a third intermediate oil passage 26c is connected to both the front wheel steering valve 24 and the rear wheel steering valve 25. In other words, when at least one of the front wheels 1 and the rear wheels 2 is steered, the hydraulic fluid flows through the first intermediate oil passage 26a, the third intermediate oil passage 26c, and the second intermediate oil passage 26b, or the second intermediate oil passage 26b, the third intermediate oil passage 26c, and the first intermediate oil passage 26a.

[0048] The front wheel steering valve 24 is connected to the first front wheel oil passage 27a and the second front wheel oil passage 27b. The first front wheel oil passage 27a is connected to one end of the front wheel steering actuator 27, and the second front wheel oil passage 27b is connected to the other end of the front wheel steering actuator 27.

[0049] The front wheel steering valve 24 is, for example, a solenoid valve. The front wheel steering valve 24 is configured to switch between a connected state in which the first front wheel oil passage 27a and the first intermediate oil passage 26a are connected and the second front wheel oil passage 27b and the third intermediate oil passage 26c are connected, and a blocked state in which the first front wheel oil passage 27a and the first intermediate oil passage 26a are blocked and the second front wheel oil passage 27b and the third intermediate oil passage 26c are blocked. When the front wheel steering valve 24 is in the blocked state, the first intermediate oil passage 26a and the third intermediate oil passage 26c are connected.

[0050] When the front wheel steering valve 24 is connected, the rod of the front wheel steering actuator 27 can slide left and right due to the pressure of the hydraulic fluid. This allows the front wheels 1 to be steered left and right. When the front wheel steering valve 24 is closed, the rod of the front wheel steering actuator 27 cannot slide. This results in the front wheels 1 being unsteered.

[0051] When the front wheel 1 is steered to one side, either the first front wheel oil passage 27a or the second front wheel oil passage 27b becomes the supply oil passage, and the other becomes the return oil passage. The rod of the front wheel steering actuator 27 then slides to one side (the side where the return oil passage is located), and the direction of the front wheel 1 changes.

[0052] The rear wheel steering valve 25 is connected to the first rear wheel oil passage 28a and the second rear wheel oil passage 28b. The first rear wheel oil passage 28a is connected to one end of the rear wheel steering actuator 28, and the second rear wheel oil passage 28b is connected to the other end of the rear wheel steering actuator 28.

[0053] The rear wheel steering valve 25 is, for example, a solenoid valve. The rear wheel steering valve 25 is configured to be switchable between the following straight connection state, the following cross connection state, and the following shut-off state. The straight connection state of the rear wheel steering valve 25 is a state in which the first rear wheel oil passage 28a and the second intermediate oil passage 26b are connected in communication, and the second rear wheel oil passage 28b and the third intermediate oil passage 26c are connected in communication. The cross connection state of the rear wheel steering valve 25 is a state in which the first rear wheel oil passage 28a and the third intermediate oil passage 26c are connected in communication, and the second rear wheel oil passage 28b and the second intermediate oil passage 26b are connected in communication. The closed state of the rear wheel steering valve 25 is when the first rear wheel oil passage 28a is blocked from both the second intermediate oil passage 26b and the third intermediate oil passage 26c, and the second rear wheel oil passage 28b is blocked from both the second intermediate oil passage 26b and the third intermediate oil passage 26c. When the rear wheel steering valve 25 is in the closed state, it connects the second intermediate oil passage 26b and the third intermediate oil passage 26c.

[0054] When the rear wheel steering valve 25 is connected, the rod of the rear wheel steering actuator 28 can slide left and right due to the pressure of the hydraulic fluid. This allows the rear wheels 2 to be steered left and right. When the rear wheel steering valve 25 is closed, the rod of the rear wheel steering actuator 28 cannot slide. This results in the rear wheels 2 being unsteered.

[0055] When the rear wheel 2 is steered to one side, one of the first rear wheel oil passage 28a and the second rear wheel oil passage 28b becomes the supply oil passage, and the other becomes the return oil passage. Then, the rod of the rear wheel steering actuator 28 slides to one side (the side where the return oil passage is located), and the direction of the rear wheel 2 changes.

[0056] Thus, the power steering unit 23 is configured to supply hydraulic fluid to the left and right cylinder chambers of the front wheel steering actuator 27 via the first front wheel oil passage 27a and the second front wheel oil passage 27b. Similarly, the power steering unit 23 is configured to supply hydraulic fluid to the left and right cylinder chambers of the rear wheel steering actuator 28 via the first rear wheel oil passage 28a and the second rear wheel oil passage 28b.

[0057] By switching the spool (not shown) in the power steering unit 23 and the spool in the front wheel steering valve 24, the first front wheel oil passage 27a is connected to one of the discharge oil passage 22f and the return oil passage 23a, and the second front wheel oil passage 27b is connected to the other of the discharge oil passage 22f and the return oil passage 23a.

[0058] By switching the spool (not shown) in the power steering unit 23 and the spool in the rear wheel steering valve 25, the first rear wheel oil passage 28a is connected to one of the discharge oil passage 22f and the return oil passage 23a, and the second rear wheel oil passage 28b is connected to the other of the discharge oil passage 22f and the return oil passage 23a.

[0059] When the second front wheel oil passage 27b and the return oil passage 23a are connected, the first front wheel oil passage 27a and the discharge oil passage 22f are connected. In this case, hydraulic fluid is supplied to the left chamber of the cylinder in the front wheel steering actuator 27, and the piston rod slides toward the right side of the machine. Also, when the second front wheel oil passage 27b and the discharge oil passage 22f are connected, the first front wheel oil passage 27a and the return oil passage 23a are connected. In this case, hydraulic fluid is supplied to the right chamber of the cylinder in the front wheel steering actuator 27, and the piston rod slides toward the left side of the machine.

[0060] When the second rear wheel oil passage 28b and the return oil passage 23a are connected, the first rear wheel oil passage 28a and the discharge oil passage 22f are connected. In this case, hydraulic fluid is supplied to the left chamber of the cylinder in the rear wheel steering actuator 28, and the piston rod slides toward the right side of the machine. Also, when the second rear wheel oil passage 28b and the discharge oil passage 22f are connected, the first rear wheel oil passage 28a and the return oil passage 23a are connected. In this case, hydraulic fluid is supplied to the right chamber of the cylinder in the rear wheel steering actuator 28, and the piston rod slides toward the left side of the machine.

[0061] The piston rods in these cylinders slide from side to side, allowing the front wheel 1 and the rear wheel 2 to each swing up and down around their respective axes.

[0062] The hydraulic fluid discharged from the power steering unit 23 into the return oil passage 23a has impurities removed by the oil filter 29 and is then returned to the hydraulic fluid reservoir 21.

[0063] [Regarding the control system] Based on Figure 5, the control system of the work vehicle of this embodiment will be described. This control system includes a steering device 40, a front wheel angle detection unit 41, a rear wheel angle detection unit 42, a work state detection unit 43, a gear change state detection unit 44, a storage unit 45, a change unit 46, a steering mode change unit 47, a determination unit 48, and a notification unit 49. The work state detection unit 43 and the gear change state detection unit 44 are the "state acquisition units" described in the claims.

[0064] The steering device 40 controls the power steering unit 23, the front wheel steering valve 24, and the rear wheel steering valve 25, respectively, based on the amount of movement of the steering handle 20 and the steering mode selected by the operator using the switching device 50. As a result, the steering device 40 is able to steer the front wheels 1 and the rear wheels 2, respectively.

[0065] The steering device 40 is equipped with an electronic control unit 40A. The electronic control unit 40A can be composed of a microprocessor, a DSP (digital signal processor), software, and logic circuits. This electronic control unit 40A manages multiple steering modes. In other words, the steering device 40 is capable of steering control for both the front wheels 1 and the rear wheels 2, and has multiple steering modes with different steering control characteristics. The steering device 40 may also include a power steering unit 23, a front wheel steering valve 24, and a rear wheel steering valve 25.

[0066] The steering modes include FWS mode (front wheel steering mode), RWS mode (rear wheel steering mode), 4WS mode (four-wheel steering mode), CWS mode (claw steering mode), and direction correction mode. The steering device 40 is configured to be switchable between these steering modes. The steering device 40 is configured to be switchable depending on each steering mode, including whether or not to steer the front wheels 1, whether or not to steer the rear wheels 2, and whether or not to steer the rear wheels 2 to the left or right relative to the direction in which the steering wheel 20 turns when steering the rear wheels 2.

[0067] The following explains FWS mode, RWS mode, 4WS mode, and CWS mode. Direction correction mode will be discussed later.

[0068] The switching device 50 is equipped with an automatic button 50A, an FWS button 50B, an RWS button 50C, a 4WS button 50D, and a CWS button 50E. The switching device 50 is configured to accept operations to switch the steering mode of the steering device 40 between FWS mode, RWS mode, 4WS mode, and CWS mode. The automatic button 50A will be described later.

[0069] FWS mode is a steering mode in which only the front wheel 1 is steered. In other words, FWS mode is a steering mode in which the front wheel 1 is set to a steerable state and the rear wheel 2 is set to a non-steered state. When the operator presses the FWS button 50B, the steering mode of the steering device 40 is set to FWS mode. When the steering mode of the steering device 40 is FWS mode, the electronic control unit 40A switches the front wheel steering valve 24 to the connected state and switches the rear wheel steering valve 25 to the closed state. In other words, the steering device 40 enables steering control for the front wheel 1 and sets the rear wheel 2 to a non-steered state. This makes it possible to steer the front wheels of the tractor.

[0070] RWS mode is a steering mode in which only the rear wheels 2 are steered. In other words, RWS mode is a steering mode in which the front wheels 1 are set to a non-steered state and the rear wheels 2 are set to a steerable state. When the operator presses the RWS button 50C, the steering mode of the steering device 40 is set to RWS mode. When the steering mode of the steering device 40 is RWS mode, the electronic control unit 40A switches the front wheel steering valve 24 to the shut-off state and switches the rear wheel steering valve 25 to the cross-connected state. In other words, the steering device 40 enables steering control for the rear wheels 2 and sets the front wheels 1 to a non-steered state. This makes rear-wheel steering of the tractor possible.

[0071] The 4WS mode is a steering mode that sets the front wheels 1 and rear wheels 2 into a steerable state. When the operator presses the 4WS button 50D, the steering mode of the steering device 40 is set to 4WS mode. When the steering mode of the steering device 40 is set to 4WS mode, the electronic control unit 40A switches the front wheel steering valve 24 to the connected state and switches the rear wheel steering valve 25 to the cross-connected state. In other words, the steering device 40 enables steering control for both the front wheels 1 and rear wheels 2. This makes four-wheel steering of the tractor possible.

[0072] CWS mode is a steering mode in which the front wheels 1 and rear wheels 2 are set to a steerable state, and the rear wheels 2 are steered in the opposite direction to the direction in 4WS mode. In other words, CWS mode is a steering mode in which the front wheels 1 and rear wheels 2 are steered in the same direction. When the operator presses the CWS button 50E, the steering mode of the steering device 40 is set to CWS mode. When the steering mode of the steering device 40 is CWS mode, the electronic control unit 40A switches the front wheel steering valve 24 to the connected state and switches the rear wheel steering valve 25 to the straight connected state. In other words, the steering device 40 enables steering control for the front wheels 1 and rear wheels 2. This makes claw steering of the tractor possible.

[0073] Thus, the steering device 40 can switch between multiple steering modes and steers at least one of the front wheels 1 and rear wheels 2 in response to the steering operation received by the steering handle 20. Specifically, the steering device 40 changes modes by switching the state of the front wheel steering valve 24 and the rear wheel steering valve 25. Then, the power steering unit 23 supplies hydraulic fluid to the first intermediate oil passage 26a or the second intermediate oil passage 26b, thereby steering the front wheels 1 and rear wheels 2.

[0074] Furthermore, when the steering mode of the steering device 40 is RWS mode or 4WS mode, the electronic control unit 40A may be configured to switch the rear wheel steering valve 25 to a straight connection state. Also, when the steering mode of the steering device 40 is CWS mode, the electronic control unit 40A may be configured to switch the rear wheel steering valve 25 to a cross connection state. This configuration can be appropriately changed depending on whether the rear wheel steering actuator 28 is positioned in front of or behind the rear transmission case 18.

[0075] The front wheel angle detection unit 41 detects the orientation of the front wheel 1 relative to the left and right, based on the neutral orientation of the front wheel 1. The neutral orientation of the front wheel 1 is the orientation in which the aircraft 3 is moving straight or nearly straight.

[0076] The rear wheel angle detection unit 42 detects the left-right orientation of the rear wheel 2, based on the neutral orientation of the rear wheel 2. The neutral orientation of the rear wheel 2 is the direction in which the aircraft 3 moves straight or nearly straight.

[0077] The work status detection unit 43 detects whether or not the work device is performing work on the field. The work status detection unit 43 may be a sensor connected to the work device, a sensor that detects the rotation of the PTO shaft 17, or a sensor that detects the raising and lowering of the three-point linkage mechanism 12.

[0078] The gear shift state detection unit 44 is configured to detect the gear shift state in the continuously variable transmission 7. The gear shift states in the continuously variable transmission 7 include a forward state in which the machine 3 moves forward, a reverse state in which the machine 3 moves backward, and a neutral state in which the power of the engine 10 is not transmitted to either the front wheel 1 or the rear wheel 2. Therefore, the gear shift state detection unit 44 can detect whether the machine 3 is moving forward, backward, or stopped. The gear shift state detection unit 44 may also be configured to detect the state of the main gear shift lever provided in the driver's unit 4, for example.

[0079] Alternatively, the gear shift state detection unit 44 may be configured to detect the gear shift state in the auxiliary transmission (not shown) inside the rear transmission case 6. The gear shift states of the auxiliary transmission include a low-speed state in which the machine 3 moves forward with work performed by the work device, a high-speed state in which the machine 3 moves forward without work performed by the work device, a neutral state in which the power of the engine 10 is not transmitted to either the front wheel 1 or the rear wheel 2, and a reverse state in which the machine 3 moves backward. Even with this configuration, the gear shift state detection unit 44 can detect whether the machine 3 is moving forward, backward, or stopped. The gear shift state detection unit 44 may also be configured to detect the state of the auxiliary transmission lever provided in the driver's unit 4, for example.

[0080] The memory unit 45, the modification unit 46, and the steering mode modification unit 47 will be described later, along with the automatic steering mode modification function based on the automatic button 50A.

[0081] The determination unit 48 acquires information regarding the orientation of the front wheel 1 and rear wheel 2 from the front wheel angle detection unit 41 and the rear wheel angle detection unit 42. The determination unit 48 then determines that a neutral misalignment has occurred if the orientation of either the front wheel 1 or the rear wheel 2, which is set to a non-steering state, deviates from the neutral orientation by more than a preset threshold. As will be described in detail later, when the determination unit 48 determines that a neutral misalignment has occurred, it sends a notification signal to the electronic control unit 40A. A neutral misalignment is a state in which the orientation of one of the front wheel 1 and rear wheel 2, which is set to a non-steering state, deviates from the neutral orientation by more than a preset threshold.

[0082] The notification unit 49 issues an alert when the determination unit 48 determines that a neutral misalignment has occurred. In other words, the notification unit 49 issues an alert when, based on the detection results of the front wheel angle detection unit 41 and the rear wheel angle detection unit 42, a neutral misalignment has occurred in which the direction of one of the front wheels 1 and rear wheels 2, which is set to a non-steering state, deviates from the neutral direction by more than a preset threshold.

[0083] [Regarding the automatic steering mode change function based on the automatic button] When the operator presses the automatic button 50A, the electronic control unit 40A is configured to receive a mode change signal from the steering mode change unit 47 and change the steering mode.

[0084] The memory unit 45 (an example of memory) is a device for storing data and is composed of storage devices such as EEPROM and non-volatile RAM (flash memory, FeRAM, etc.). The memory unit 45 stores the correspondence between the aircraft state and the steering mode to be used in accordance with that aircraft state.

[0085] Figure 6 shows an example of the correspondence between the aircraft state and the steering mode. In Figure 6, the aircraft state is shown as the gear shift state and the working device state. The gear shift state is the detection result of the gear shift state detection unit 44 and shows the forward state, neutral state and reverse state. In other words, the aircraft state includes the forward state in which the aircraft 3 can move forward and the reverse state in which the aircraft 3 can move backward. The working device state is the detection result of the work state detection unit 43 and shows the working state and non-working state. In other words, the aircraft state includes the working state in which the working device is performing work and the non-working state in which the working device is not performing work. Figure 6 shows the first correspondence relationship, the second correspondence relationship and the third correspondence relationship. These correspondence relationships are stored in the storage unit 45.

[0086] In the first, second, and third correspondences, when the gear shift state is forward and the working device state is working, the steering mode of the steering device 40 becomes FWS mode. In the first, second, and third correspondences, when the gear shift state is forward and the working device state is not working, the steering mode of the steering device 40 becomes 4WS mode. In the first correspondence, when the gear shift state is reverse, the steering mode of the steering device 40 becomes FWS mode regardless of the working device state. In the second correspondence, when the gear shift state is reverse, the steering mode of the steering device 40 becomes RWS mode regardless of the working device state. In the third correspondence, when the gear shift state is reverse, the steering mode of the steering device 40 becomes 4WS mode regardless of the working device state. When the operator presses the automatic button 50A, the steering mode of the steering device 40 is changed based on the selected and set correspondence among these three correspondences. As will be described in detail later, in this embodiment, the correspondence used in the automatic steering mode change function based on the automatic button 50A is configured to be changeable.

[0087] The steering mode change unit 47 acquires the machine state based on the detection results of the work state detection unit 43 and the detection results of the gear change state detection unit 44. The steering mode change unit 47 then reads the steering mode corresponding to the machine state from the storage unit 45 and causes the steering device 40 to change the steering mode. In other words, the steering mode change unit 47 changes the steering device 40 to the steering mode corresponding to the acquired machine state based on the correspondence between the machine state and the steering mode that should be used in accordance with the machine state.

[0088] As will be explained in more detail later, the modification unit 46 changes the correspondence stored in the memory unit 45 based on the human operation received by the switching device 50. In other words, the modification unit 46 can change the correspondence between the aircraft state and the steering mode to be used in accordance with that aircraft state.

[0089] [Regarding the function to change the steering mode corresponding to the aircraft's state] As described above, when the operator presses the automatic button 50A, the steering device 40 changes the steering mode according to the aircraft state. The correspondence between the aircraft state and the steering mode is stored in the memory unit 45. In this embodiment, the modification unit 46 is configured to change the correspondence between the aircraft state and the steering mode (Figure 6) stored in the memory unit 45.

[0090] Based on Figure 7, the function for changing the correspondence between the machine state and the steering mode will be explained. Although not described in detail, the tractor is equipped with a starting device 30 that accepts manual operation to start the engine 10. First, with the engine 10 stopped, when the operator presses the automatic button 50A and uses the starting device 30 to start the engine 10, the flowchart in Figure 7 is initiated. In other words, the system is configured so that the correspondence can be changed by the modification unit 46 in response to both the engine 10 starting device 30 and the switching device 50 being operated.

[0091] First, after the engine 10 starts, the modification unit 46 determines whether the pressing of the automatic button 50A has ended (step #01). In other words, step #01 determines whether the operator has released the automatic button 50A after the engine 10 has started, while the operator has pressed the automatic button 50A during the engine starting operation. As long as the automatic button 50A is pressed (step #01: No), the modification unit 46 repeats the determination in step #01.

[0092] When the automatic button 50A is not pressed (Step #01: Yes), the modification unit 46 determines whether the automatic button 50A has been pressed again (Step #02). The determination of whether the automatic button 50A has been pressed in Step #02 uses an edge-sensitive method. The modification unit 46 detects the rising edge when the automatic button 50A is pressed. Therefore, the determination in Step #02 becomes Yes at the moment the automatic button 50A is first pressed. Alternatively, the configuration may be such that the determination in Step #02 becomes No if the automatic button 50A is being held down.

[0093] When the automatic button 50A is pressed (step #02: Yes), the correspondence between the steering modes used in accordance with the aircraft state is changed (step #03). Therefore, in this embodiment, each time the operator presses the automatic button 50A based on step #02, the modification unit 46 changes the correspondence between the steering modes used in accordance with the aircraft state in the order of first correspondence → second correspondence → third correspondence. If the automatic button 50A is pressed while the third correspondence is selected, the modification unit 46 sets the correspondence back to the first correspondence. In other words, each time the automatic button 50A is pressed, the processing of steps #02 and #03 loops, and the correspondence is changed in a loop in the order of first correspondence → second correspondence → third correspondence.

[0094] Thus, the switching device 50 accepts manual operation for changing the correspondence relationship by the modification unit 46. The automatic button 50A is used to change the correspondence relationship of the steering mode used in accordance with the aircraft state. The automatic button 50A is the "first operation unit" described in the claims.

[0095] If the automatic button 50A is not pressed (Step #02: No), the modification unit 46 determines whether the CWS button 50E has been pressed for a period of time longer than a preset time (Step #04). The preset time can be changed as appropriate, for example, within the range of 1 to 5 seconds. If the CWS button 50E has not been pressed for a period of time longer than the preset time (Step #04: No), the process returns to Step #02. If the CWS button 50E has been pressed for a period of time longer than the preset time (Step #04: Yes), the flowchart in Figure 7 ends.

[0096] Thus, the CWS button 50E is used to determine a change in the correspondence. The CWS button 50E is the "second operating unit" as described in the claims.

[0097] [About the orientation correction mode function] When the front wheel steering valve 24 is closed, the rod of the front wheel steering actuator 27 becomes immobile, and the front wheel 1 is in a non-steering state. Similarly, when the rear wheel steering valve 25 is closed, the rod of the rear wheel steering actuator 28 becomes immobile, and the rear wheel 2 is in a non-steering state. However, even if the rear wheel 2 is set to a non-steering state, if the rear wheel 2 is subjected to an impact from an uneven surface in the field, or if the hydraulic fluid of the rear wheel steering actuator 28 leaks, there is a risk that a "neutral deviation" may occur, where the rear wheel 2 deviates from the neutral direction to the left or right.

[0098] The direction correction mode is a steering mode used to change the direction of either front wheel 1 or rear wheel 2, which is set to a non-steering state, to a neutral direction.

[0099] The orientation of the front wheel 1 is detected by the front wheel angle detection unit 41, and the orientation of the rear wheel 2 is detected by the rear wheel angle detection unit 42. The determination unit 48 obtains the orientation of the front wheel 1 or rear wheel 2, which is set to a non-steering state, from the front wheel angle detection unit 41 or the rear wheel angle detection unit 42. The determination unit 48 then determines that a neutral deviation state has occurred if the obtained orientation deviates from the neutral orientation by a preset threshold or more.

[0100] The notification unit 49 then issues an alert when it determines that the neutral misalignment has occurred. In other words, the notification unit 49 issues an alert when it determines, based on the detection results of the front wheel angle detection unit 41 and the rear wheel angle detection unit 42, that a neutral misalignment has occurred in which the direction of one of the front wheels 1 and rear wheels 2, which is set to a non-steering state, is deviated from the neutral direction by a preset threshold or more.

[0101] Each of the buttons on the switching device 50, the automatic button 50A, the FWS button 50B, the RWS button 50C, the 4WS button 50D, and the CWS button 50E, is equipped with an indicator light, such as an LED. In other words, the notification unit 49 includes the indicator lights attached to the switching device 50, and the indicator lights are configured to emit an alert by flashing. The notification unit 49 also includes voice notification by a buzzer or speaker.

[0102] Based on Figure 8, the processing of the direction correction mode when a neutral misalignment occurs in the rear wheel 2 will be explained. First, the timing after a preset time has elapsed since the neutral misalignment occurred is the starting point of the flowchart shown in Figure 8. The notification unit 49 is configured to emit an alarm at this timing. In other words, the notification unit 49 is configured to emit an alarm after a preset time has elapsed since the neutral misalignment occurred in one of the front wheel 1 or rear wheel 2 which is set to a non-steering state (step #11). Specifically, the notification unit 49 flashes the indicator light of the FWS button 50B and outputs an audio alarm from a buzzer or speaker in the driver's unit 4.

[0103] In step #12, it is determined whether the aircraft 3 has stopped. The stopping of the aircraft 3 is determined based on the detection result of the gear change state detection unit 44. In other words, if the gear change state detection unit 44 detects a neutral state in which the power of the engine 10 is not transmitted to either the front wheel 1 or the rear wheel 2, the electronic control unit 40A determines that the aircraft 3 has stopped (step #12: Yes). If the aircraft 3 has not stopped (step #12: No), the processing in steps #11 and #12 is repeated. In other words, the condition for the steering device 40 to switch the steering mode to the direction correction mode includes the aircraft 3 being in a stopped state.

[0104] In step #13, it is determined whether or not the FWS button 50B has been pressed. If the FWS button 50B has not been pressed (step #13: No), the process from steps #11 to #13 is repeated. In other words, the FWS button 50B of the switching device 50 accepts an operation to switch the steering mode of the steering device 40 to the direction correction mode.

[0105] When the operator presses the FWS button 50B (Step #13: Yes), the steering mode of the steering device 40 is switched to the direction correction mode (Step #14). The steering device 40 is configured to switch the steering mode to the direction correction mode even if the direction of the front wheels 1, which are set to the steerable state, is not the neutral direction. The steering device 40 then sets the rear wheels 2, which were set to the non-steerable state, to the steerable state, and sets the front wheels 1, which were set to the steerable state, to the non-steered state. Specifically, the electronic control unit 40A switches the front wheel steering valve 24 to the shut-off state and switches the rear wheel steering valve 25 to the cross-connection state (or straight-connection state). Then, by operating the steering handle 20, steering control becomes possible for only the rear wheels 2.

[0106] In other words, when the steering device 40 is in FWS mode, if the direction of the rear wheels 2 deviates from the neutral direction by more than a preset threshold, and the FWS button 50B of the switching device 50 is operated, the steering mode is switched to the direction correction mode.

[0107] In step #15, it is determined whether the orientation of the rear wheel 2 has returned to the neutral position. This determination may be performed by the determination unit 48 or by the electronic control unit 40A. As long as the orientation of the rear wheel 2 does not return to the neutral position (step #15: No), the process in step #15 is repeated.

[0108] When the operator steers the rear wheels 2 with the steering handle 20 and the direction of the rear wheels 2 is set to the neutral direction (Step #15: Yes), the steering mode of the steering device 40 is switched to FWS mode (Step #16). In other words, once the steering device 40 has finished changing the direction of the rear wheels 2 to the neutral direction using the direction correction mode, it returns to FWS mode. To put it another way, once the steering device 40 has finished changing the direction of the running gear to the neutral direction using the direction correction mode, it returns from direction correction mode to the original steering mode.

[0109] When the steering mode of the steering device 40 returns to FWS mode, the electronic control unit 40A switches the front wheel steering valve 24 to the connected state and switches the rear wheel steering valve 25 to the closed state. As a result, the rear wheels 2 are set to a non-steered state and the front wheels 1 are set to a steerable state.

[0110] Based on Figure 9, the processing of the direction correction mode when a neutral misalignment occurs in the front wheel 1 will be explained. First, the start point of the flowchart shown in Figure 9 is the timing after a preset time has elapsed since the neutral misalignment occurred. The notification unit 49 is configured to emit an alarm at this timing. In other words, the notification unit 49 is configured to emit an alarm after a preset time has elapsed since the neutral misalignment occurred in one of the front wheel 1 or rear wheel 2 which is set to a non-steering state (step #21). Specifically, the notification unit 49 flashes the indicator light of the RWS button 50C and outputs an audio alarm from a buzzer or speaker in the driver's unit 4.

[0111] In step #22, it is determined whether the aircraft 3 has stopped. The stopping of the aircraft 3 is determined based on the detection result of the gear shift state detection unit 44. In other words, if the gear shift state detection unit 44 detects a neutral state in which the power of the engine 10 is not transmitted to either the front wheel 1 or the rear wheel 2, the electronic control unit 40A determines that the aircraft 3 has stopped (step #22: Yes). If the aircraft 3 has not stopped (step #22: No), the processing in steps #21 and #22 is repeated. In other words, the condition for the steering device 40 to switch the steering mode to the direction correction mode includes the aircraft 3 being in a stopped state.

[0112] In step #23, it is determined whether or not the RWS button 50C has been pressed. If the RWS button 50C has not been pressed (step #23: No), the process from steps #21 to #23 is repeated. In other words, the RWS button 50C of the switching device 50 accepts an operation to switch the steering mode of the steering device 40 to the direction correction mode.

[0113] When the operator presses the RWS button 50C (Step #23: Yes), the steering mode of the steering device 40 is switched to the direction correction mode (Step #24). The steering device 40 is configured to switch the steering mode to the direction correction mode even if the direction of the rear wheels 2, which are set to the steerable state, is not the neutral direction. The steering device 40 then sets the front wheels 1, which were set to the non-steerable state, to the steerable state, and sets the rear wheels 2, which were set to the steerable state, to the non-steered state. Specifically, the electronic control unit 40A switches the rear wheel steering valve 25 to the shut-off state and switches the front wheel steering valve 24 to the connected state. Then, by operating the steering handle 20, steering control becomes possible for only the front wheels 1.

[0114] In other words, when the steering device 40 is in RWS mode, if the direction of the front wheels 1 deviates from the neutral direction by more than a preset threshold, and the RWS button 50C of the switching device 50 is operated, the steering mode is switched to the direction correction mode.

[0115] In step #25, it is determined whether the orientation of the front wheel 1 has been corrected to the neutral position. This determination may be performed by the determination unit 48 or by the electronic control unit 40A. As long as the orientation of the front wheel 1 has not been corrected to the neutral position (step #25: No), the process in step #25 is repeated.

[0116] When the operator steers the front wheels 1 with the steering wheel 20 and the direction of the front wheels 1 is set to the neutral direction (Step #25: Yes), the steering mode of the steering device 40 is switched to RWS mode (Step #26). In other words, once the change of the front wheels 1 to the neutral direction by the direction correction mode is complete, the steering device 40 returns to RWS mode. To put it another way, once the change of the running gear to the neutral direction by the direction correction mode is complete, the steering device 40 returns from direction correction mode to the original steering mode.

[0117] When the steering mode of the steering device 40 returns to RWS mode, the electronic control unit 40A switches the rear wheel steering valve 25 to a cross connection state (or straight connection state) and switches the front wheel steering valve 24 to a shut-off state. As a result, the front wheels 1 are set to a non-steering state and the rear wheels 2 are set to a steering-enabled state.

[0118] The notification unit 49 may be configured to change the notification pattern depending on the degree of deviation from the neutral position of the front wheel 1 or rear wheel 2, which is set to a non-steering state. For example, the greater the degree of deviation from the neutral position of the front wheel 1 or rear wheel 2, the shorter the blinking interval of the indicator light of the RWS button 50C or FWS button 50B, or the louder the volume of the buzzer or speaker. Alternatively, the notification unit 49 may be configured to emit a notification uniformly regardless of the degree of deviation from the neutral position of the front wheel 1 or rear wheel 2, which is set to a non-steering state.

[0119] The notification unit 49 may be configured to guide the direction of operation of the steering handle 20 to change the direction of the front wheel 1 or rear wheel 2 that is deviating from the neutral position when the front wheel 1 or rear wheel 2 is set to a non-steering state. For example, the meter panel of the driver's unit 4 may be equipped with a liquid crystal or OLED display panel, and the direction of operation of the steering handle 20 may be displayed on that display panel.

[0120] [Another embodiment] The present invention is not limited to the configurations exemplified in the embodiments described above, and other representative embodiments of the present invention are described below.

[0121] (1) The switching device 50 is the "selection device" described in the claims. The switching device 50 may be a lever type instead of a button type. In this case, it may be configured to be switchable by a lever to positions corresponding to the automatic button 50A, the FWS button 50B, the RWS button 50C, the 4WS button 50D, and the CWS button 50E.

[0122] (2) The front wheel 1 is the "front running device" as described in the claims, and the rear wheel 2 is the "rear running device" as described in the claims. The invention is not limited to this embodiment, and the front running device may be a crawler, and the rear running device may be a crawler.

[0123] (3) The steering handle 20 is the "steering control device" as described in the claims. The steering control device is not limited to this embodiment, and may be, for example, a stick lever.

[0124] (4) The configuration may not include the power steering unit 23, the front wheel steering valve 24, and the rear wheel steering valve 25 described above. In this case, a transmission mechanism capable of transmitting steering operations from the steering wheel 20 to the front wheels 1 and the rear wheels 2 may be provided. This transmission mechanism may include a clutch, chain, belt, gears, etc. This transmission mechanism may also be included in the steering device described in the claims.

[0125] (5) Figure 6 illustrates the first, second, and third correspondence relationships. In the above embodiment, three sets of correspondence relationships between four types of aircraft states and steering modes are preset, and the correspondence relationship to be used is selected (changed) from the presets. The embodiment is not limited to this one, and for example, a correspondence relationship in which the CWS mode is used in response to the reverse state may be stored in the memory unit 45. Also, a correspondence relationship in which the FWS mode, RWS mode, 4WS mode, and CWS mode are used in response to the forward state may be stored in the memory unit 45, and the change unit 46 may be configured to change these correspondence relationships as well. In addition, the correspondence relationship of the steering mode to be used in response to the reverse state may be set separately for the working state and the non-working state of the working device. That is, the change unit 46 may be configured to allow individual changes to the steering mode corresponding to a single aircraft state. For example, the change unit 46 may be able to change the steering mode to be used in response to the reverse state to the FWS mode or to the 4WS mode. Furthermore, for example, the modification unit 46 may be capable of changing the steering mode to be used in response to the non-working state of the work device to FWS mode or to 4WS mode.

[0126] (6) In the embodiment described above based on Figure 7, when an operator operates the starting device 30 for starting the engine 10 and the automatic button 50A, the corresponding relationship can be changed by the modification unit 46. The embodiment is not limited to this one, and for example, when an operator operates the starting device 30 and any button on the switching device 50, the corresponding relationship can be changed by the modification unit 46. Alternatively, when an operator operates a dedicated device other than the starting device 30 and any button on the switching device 50, the corresponding relationship can be changed by the modification unit 46. Furthermore, when an operator operates both buttons on the switching device 50, the corresponding relationship can be changed by the modification unit 46.

[0127] (7) In the embodiment described above based on Figure 7, the automatic button 50A is the "first operating unit" as described in the claims, and the CWS button 50E is the "second operating unit" as described in the claims. The embodiment is not limited to this one, and the first operating unit may be any one button on the switching device 50, and the second operating unit may be any one button on the switching device 50 other than the button assigned as the first operating unit.

[0128] (8) In the embodiments described above, the engine 10 is the "prime mover" as described in the claims. The invention is not limited to this embodiment, and an electric motor may be provided instead of the engine 10. In other words, the work vehicle described in the claims may be an electric work vehicle that is not equipped with an internal combustion engine. In this case, for example, the machine state may include the remaining battery charge.

[0129] (9) The gear shift state detection unit 44 is the "state acquisition unit" described in the claims. The gear shift state detection unit 44 may be configured to detect vehicle speed, for example. In this case, the forward state and the reverse state may not be gear shift states, but rather the rotation direction of at least one of the front wheels 1 and the rear wheels 2 and the vehicle speed.

[0130] (10) In the embodiments described above, the “state acquisition unit” in the claims includes the gear shift state (forward state, neutral state, reverse state) and the state of the work device (working state, non-working state). The state acquisition unit may acquire either the gear shift state or the state of the work device, but is not limited to these embodiments.

[0131] (11) In the above-described embodiment, the notification unit 49 is configured to emit an alarm after a preset time has elapsed since a neutral misalignment occurred in the front wheel 1 or the rear wheel 2. The embodiment is not limited to this one, and the notification unit 49 may be configured to emit an alarm immediately when a neutral misalignment occurs in the front wheel 1 or the rear wheel 2. The notification unit 49 may also be configured to emit an alarm when a neutral misalignment occurs and the machine 3 is stationary. Furthermore, the notification unit 49 may be configured to emit an alarm when a neutral misalignment occurs and the work device is in a non-working state and not performing any work.

[0132] (12) In the above-described embodiment, when the engine 10 is stopped, the operator presses the automatic button 50A and uses the starting device 30 to start the engine 10, and the flowchart in Figure 7 is initiated. The embodiment is not limited to this one, and for example, if the operator presses the automatic button 50A and operates the starting device 30 to turn on the power to the electronic control unit 40A, the flowchart in Figure 7 is initiated even when the engine 10 is stopped. It's okay to have it.

[0133] Furthermore, the configurations disclosed in the above-described embodiments (including other embodiments, the same applies hereinafter) can be applied in combination with configurations disclosed in other embodiments, as long as no inconsistencies arise. In addition, the embodiments disclosed herein are illustrative, and the embodiments of the present invention are not limited thereto, and can be modified as appropriate without departing from the object of the present invention. [Industrial applicability]

[0134] The present invention is applicable to work vehicles. Therefore, it is not limited to the tractor exemplified in this embodiment, but is applicable to various harvesting machines (e.g., combine harvesters, corn harvesters, sugarcane harvesters, potato harvesters, beet harvesters, carrot harvesters, etc.), rice transplanters, fertilizer managers, self-propelled spreaders, self-propelled mowers, etc. [Explanation of Symbols]

[0135] 1: Front wheels (front running gear) 2: Rear wheels (rear running gear) 3: Aircraft 10: Engine (prime mover) 20: Steering handle (steering operation tool) 40: Steering device 43: Working condition, damaged area (condition acquisition area) 44: Gear shift status detection unit (status acquisition unit) 45: Storage section 46: Changes 47: Steering mode change unit 50: Switching device (selection device) 50A: Automatic button (first control unit) 50E: CWS button (second control panel)

Claims

1. The aircraft and, A forward-traveling device supported by the aforementioned aircraft and capable of steering, A rear-travel device supported by the aforementioned aircraft and capable of steering, A steering control device that accepts steering inputs, A steering device that can switch between multiple steering modes and steers at least one of the forward travel device and the rear travel device in response to the steering operation received by the steering control device, A status acquisition unit that acquires the aircraft status, A storage unit that stores the correspondence between the aircraft state and the steering mode to be used in accordance with the aircraft state, A steering mode changing unit that changes the steering device to the steering mode corresponding to the acquired aircraft state based on the aforementioned correspondence relationship, A work vehicle equipped with a modification unit that modifies the correspondence stored in the memory unit based on the received human operation.

2. The work vehicle according to claim 1, wherein the machine state includes a forward state in which the machine can move forward and a reverse state in which the machine can move backward.

3. The work vehicle according to claim 2, wherein the modification unit is capable of changing the steering mode to be used in response to the reverse state to an RWS mode in which only the rear travel device is steered.

4. The work vehicle according to claim 2, wherein the modification unit is capable of changing the steering mode to be used in response to the reverse state to an FWS mode in which only the forward travel device is steered.

5. The work vehicle according to claim 2, wherein the modification unit is capable of changing the steering mode to be used in response to the reverse state to a 4WS mode that steers the forward and reverse travel devices.

6. The aforementioned machine is equipped with a work device for performing work on the field. The work vehicle according to claim 1, wherein the machine state includes a working state in which the work device is performing work and a non-working state in which the work device is not performing work.

7. The work vehicle according to claim 6, wherein the modification unit is capable of changing the steering mode to be used in the non-working state to an RWS mode in which only the rear-travel device is steered.

8. The work vehicle according to claim 6, wherein the modification unit is capable of changing the steering mode to be used in the non-working state to an FWS mode in which only the forward travel device is steered.

9. The work vehicle according to claim 6, wherein the modification unit is capable of changing the steering mode to be used in the non-working state to a 4WS mode that steers the front travel device and the rear travel device.

10. The prime mover and A starting device that accepts manual operation to start the aforementioned prime mover, A selection tool is provided to accept manual operation for changing the correspondence relationship by the modification unit, The work vehicle according to any one of claims 1 to 9, configured such that the corresponding relationship can be changed by the modification unit in response to both the starting device and the selection device being operated.

11. A selection operating device is provided to accept manual operation for changing the correspondence relationship by the aforementioned modification unit. Multiple such correspondences are stored in the aforementioned storage unit. The work vehicle according to any one of claims 1 to 9, wherein the selection operating device is provided with a first operating unit for changing the correspondence relationship to be used, and a second operating unit for determining the change in the correspondence relationship to be used.

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