Work vehicle

Abstract

To provide a work vehicle that is easy to balance and drive smoothly. [Solution] The work vehicle is a work vehicle that can travel on a travel surface G and comprises a machine body 1 to which an attachment IM can be attached to the front or rear, a posture changing mechanism 5 that supports the machine body 1 and can change the posture of the machine body 1, and a travel device 2 that supports the posture changing mechanism 5 and can travel on the travel surface G. When the attachment IM is attached to the machine body 1, the posture change by the posture changing mechanism 5 causes the front-rear center point CP of the machine body 1 to move to the side opposite to the attachment IM.

Description

Technical Field

[0001] The present invention relates to a work vehicle capable of traveling on a traveling surface.

Background Art

[0002] For example, the work vehicle disclosed in Patent Document 1 includes a vehicle body, a plurality of traveling wheels respectively located at the front and rear on both left and right sides of the vehicle body, and a support mechanism that supports the plurality of traveling wheels so that their positions can be changed with respect to the vehicle body.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] It is conceivable to attach a work device for performing agricultural work or the like to the conventional work vehicle described above, or to connect and tow a carriage or the like. When such a mounted object is mounted on the front or rear of the vehicle body (corresponding to the fuselage of the present application), the load on the traveling wheels on the side where the mounted object is mounted increases, and the load on the traveling wheels on the other side decreases. As a result of such load imbalance, problems may occur during traveling (for example, stalling of the hydraulic motor of the traveling wheel, slipping of the traveling wheel, or lifting of the traveling wheel).

[0005] In order to correct the load imbalance, it is conceivable to attach a balance weight to the side with a small load, as is generally done with tractors and the like. In this case, disadvantages such as an increase in the weight of the work vehicle and a decrease in the loadable weight of the work vehicle occur, which is not preferable.

[0006] An object of the present invention is to provide a work vehicle in which the balance of the fuselage is easily stabilized and stable traveling is easily performed.

Means for Solving the Problems

[0007] The present invention relates to a work vehicle capable of traveling on a running surface, comprising: a machine body capable of attaching an attachment to its front or rear; a posture changing mechanism that supports the machine body and can change the posture of the machine body; and a running device that supports the posture changing mechanism and can travel on the running surface, wherein when the attachment is attached to the machine body, the posture change by the posture changing mechanism causes the front-rear center point of the machine body to move to the side opposite to the attachment.

[0008] According to the present invention, a change in attitude causes the front-to-rear center point of the aircraft to move to the opposite side of the attached object. As a result, the aircraft's center of gravity moves to the opposite side of the attached object. This prevents the center of gravity from being biased to one side of the aircraft's front or rear, which would increase the load on the front or rear running gear during operation. Therefore, even when an attachment is mounted on the front or rear of the aircraft, the aircraft's balance becomes more stable, and the running gear becomes easier to operate.

[0009] In the present invention, the traveling device comprises a front traveling device that supports the front of the machine body and a rear traveling device that is located behind the front traveling device and supports the rear of the machine body, and when the attachment is attached to the machine body, it is preferable that the front-to-rear center point of the machine body is located on the opposite side from the attachment with respect to the midpoint between the ground contact point of the front traveling device and the ground contact point of the rear traveling device.

[0010] In this configuration, changing the aircraft's attitude causes the aircraft's front-to-rear center point to be positioned on the opposite side of the attachment from the midpoint between the contact points of the front and rear running gears. This results in an attitude that makes it easier to stabilize the aircraft's balance. Furthermore, it suppresses the excessive load on one of the aircraft's running gears during operation.

[0011] In the present invention, the machine body has a first end which is the end on the side of the front or rear where the attached object is located, and a second end which is the end opposite to the first end. When the attached object is attached to the machine body, it is preferable that the distance from the second end to the running surface becomes smaller and the distance from the first end to the running surface becomes larger when the attitude is changed by the attitude changing mechanism.

[0012] In this configuration, changing the orientation reduces the distance from the second end opposite the attached object to the running surface. This makes it less likely for the running device on the second end side to move away from the running surface. Therefore, the increase in the load on the running device on the first end side due to the running device on the second end side moving away from the running surface is suppressed.

[0013] In the present invention, the attitude changing mechanism has a plurality of extendable and retractable mechanisms, and when the attachment is attached to the aircraft, it is preferable that the attitude change by the attitude changing mechanism causes the extendable and retractable mechanism located on the second end side of the plurality of extendable and retractable mechanisms to contract, and the extendable and retractable mechanism located on the first end side of the plurality of extendable and retractable mechanisms to extend.

[0014] In this configuration, the extension and retraction of the telescopic mechanism reduces the distance from the second end opposite the mounted object to the running surface. This makes it less likely for the running device on the second end side to move away from the running surface. Therefore, the increase in load on the running device on the first end side due to the running device on the second end side moving away from the running surface is suppressed.

[0015] In the present invention, the running gear is switchable between a two-wheel steering state and a four-wheel steering state, and when a towed carriage towed by the work vehicle is attached to the rear of the machine body as the attachment, it is preferable that the running gear be in the two-wheel steering state.

[0016] When the working vehicle turns, if there is a large difference between the turning radius of the traveling device and the turning radius of the towed cart, the body will be pulled outward in the turning direction by the towed cart. Due to the force generated toward the towed cart side, the traveling device on the side opposite to the towed cart may leave the traveling surface. In this case, the load on the traveling device on the towed cart side will increase. According to this configuration, when the working vehicle turns, it is difficult for a large difference to occur between the turning radius of the traveling device and the turning radius of the towed cart. As a result, when the working vehicle turns, the body is not easily pulled by the towed cart, and the traveling device on the side opposite to the towed cart is not easily separated from the traveling surface. Therefore, an increase in the load on the traveling device on the towed cart side is suppressed.

Brief Description of the Drawings

[0017] [Figure 1] It is a left side view of the working vehicle. [Figure 2] It is a plan view of the working vehicle. [Figure 3] It is a front view of the working vehicle. [Figure 4] It is a left side view of the posture changing mechanism. [Figure 5] It is a control block diagram. [Figure 6] It is a diagram showing an example of posture change by the posture changing mechanism. [Figure 7] It is a diagram showing an example of posture change by the posture changing mechanism. [Figure 8] It is a flowchart diagram showing an example of posture change by the posture changing mechanism. [Figure 9] It is a diagram showing the turning of the working vehicle in a four-wheel steering state. ​​​​​​​​​​​​Embodiments of the present invention will be described based on the drawings. In the following description, the direction of the arrow "FR" shown in the drawings is defined as "front", the direction of the arrow "BK" is defined as "rear", the direction of the arrow "RT" is defined as "right", the direction of the arrow "LT" is defined as "left", the direction of the arrow "UP" is defined as "up", and the direction of the arrow "DW" is defined as "down".

[0019] The work vehicle can travel on a traveling surface G such as an uneven surface. The uneven surface refers to a ground with irregularities or a sloping ground.

[0020] As shown in FIGS. 1, 2, and 3, the work vehicle includes a rectangular body 1 in plan view, a posture changing mechanism 5 that supports the body 1 and can change the posture of the body 1, a traveling device 2 that supports the posture changing mechanism 5 and can travel on the traveling surface G, a plurality of auxiliary wheels 3, a hydraulic motor 4 that drives the traveling device 2, a flat loading portion 8 on which luggage can be loaded, and an operation device 23. The traveling device 2 has a plurality of wheels 21. Specifically, the work vehicle has four wheels 21 at the left front, right front, left rear, and right rear of the body 1.

[0021] In FIGS. 1 and 3, a front-rear center line C1 extending in the vertical direction through the front-rear center point CP of the body 1 is shown by a two-dot chain line. Also, in FIG. 2, a left-right center line C2 extending in the front-rear direction through the front-rear center point CP of the body 1 is shown by a two-dot chain line. That is, the front-rear center point CP is located at the front-rear center and the left-right center of the body 1. Note that the "front part of the body 1" refers to the part of the body 1 located on the front side of the front-rear center line C1. Also, the "rear part of the body 1" refers to the part of the body 1 located on the rear side of the front-rear center line C1.

[0022] The body 1 can be equipped with a mounted object IM (see FIGS. 6 and 7) at the front part or the rear part. Also, the body 1 has a front end portion 1a that is the front end of one of the front and rear, and a rear end portion 1b that is the rear end of one of the front and rear and is on the opposite side of the front end portion 1a.

[0023] 〔Posture Changing Mechanism〕 As shown in Figure 1, the attitude change mechanism 5 can change the distance D from the front contact point FG or rear contact point RG of the wheel 21 to the axis X1 at the upper end of the first link 15. In this embodiment, the work vehicle is equipped with four attitude change mechanisms 5 on the left front, right front, left rear, and right rear of the machine body 1. Each of the four attitude change mechanisms 5 is supported by one of the four wheels 21.

[0024] As shown in Figures 1 and 4, the attitude change mechanism 5 includes a bending link mechanism 51, a retractable first hydraulic cylinder 6 (corresponding to a retractable mechanism), and a retractable second hydraulic cylinder 7 (corresponding to a retractable mechanism). In this embodiment, the first hydraulic cylinder 6 and the second hydraulic cylinder 7 are actuators capable of changing the distance D from the running surface G to the machine body 1. The first hydraulic cylinder 6 and the second hydraulic cylinder 7 individually change the attitude of the attitude change mechanism 5.

[0025] As shown in Figures 1, 2, and 3, the running gear 2 has left and right front wheels 21a (corresponding to the front running gear) that support the front of the machine body 1 as wheels 21, and left and right rear wheels 21b (corresponding to the rear running gear) that are located behind the left and right front wheels 21a and support the rear of the machine body 1 as wheels 21. In other words, the running gear 2 is located at the front and rear on both the left and right sides of the machine body 1. The running gear 2 can be switched between a two-wheel steering state and a four-wheel steering state.

[0026] Multiple auxiliary wheels 3 are provided, corresponding to each of the four wheels 21.

[0027] The hydraulic motor 4 is driven by the supply and discharge of hydraulic fluid. Each of the four wheels 21 is driven independently by four hydraulic motors 4, one for each wheel 21.

[0028] The loading section 8 is a rectangular area in plan view and constitutes the upper surface of the machine body 1. The loading section 8 extends from the right end to the left end of the machine body 1. It also extends from the front end 1a to the rear end 1b of the machine body 1. The loading section 8 is capable of carrying cargo. The cargo placed on the loading section 8 may include, for example, agricultural machinery, agricultural materials such as fertilizers and chemicals, harvested produce and harvesting baskets, and pallets on which these are placed.

[0029] The operating control device 23 is located at the rear of the machine body 1. The operating control device 23 can be manually operated by an operator. In other words, the work vehicle moves by manual operation of the operating control device 23. The work vehicle also moves by remote control using a wireless remote control device RC (see Figure 5). The remote control device RC is, for example, a proportional wireless transmitter, a smartphone, or a tablet computer. The operating control device 23 and the remote control device RC can output signals such as travel commands to the travel device 2, turning commands, and lifting commands to the attitude change mechanism 5, based on manual operation by the operator. However, the work vehicle may also operate autonomously.

[0030] As shown in Figures 1, 2, and 3, the work vehicle includes a hydraulic power source 9, a control device C that controls the work vehicle, and a battery 11 that supplies power to the control device C.

[0031] The hydraulic power source 9 supplies hydraulic fluid to the first hydraulic cylinder 6, the second hydraulic cylinder 7, and the hydraulic motor 4. In other words, the hydraulic power source 9 supplies hydraulic fluid for operating the attitude change mechanism 5 and hydraulic fluid for driving the travel device 2.

[0032] The hydraulic power source 9 comprises an engine 9a, a hydraulic pump (not shown), a cooling fan 9b, an oil cooler 9c, a hydraulic oil tank 9d, and a fuel tank 9e. The engine 9a, hydraulic pump, cooling fan 9b, oil cooler 9c, and hydraulic oil tank 9d are supported by a lower frame 10 that extends downward from the body 1. Power from the engine 9a is transmitted to the hydraulic pump and cooling fan 9b via a pulley (not shown) and a belt (not shown) wound around the pulley.

[0033] As shown in Figure 1, in this embodiment, the fuel tank 9e and engine 9a are located at the front of the aircraft 1. The cooling fan 9b, oil cooler 9c, hydraulic oil tank 9d, and battery 11 are located at the rear of the aircraft 1. In other words, these components are distributed between the front and rear of the aircraft 1. As a result, the center of gravity of the aircraft 1 coincides with the front-to-rear center point CP of the aircraft 1 in a plan view, thus stabilizing the balance of the aircraft 1.

[0034] As shown in Figures 2 and 5, the control device C comprises a plurality of ECUs (Electronic Control Units) 13 and a plurality of hydraulic control valves 12. Each ECU 13 has a memory unit and a CPU (Central Processing Unit) that executes programs. The memory unit is composed of, for example, an HDD, ROM, or non-volatile memory. The plurality of hydraulic control valves 12 adjust the supply state of hydraulic fluid from the hydraulic supply source 9. The hydraulic control valves 12 may be proportional valves or PWM-controlled solenoid valves. The ECU 13 controls the operation of the hydraulic control valves 12.

[0035] The generator is driven by power from engine 9a. The electricity generated by the generator is then used to charge battery 11.

[0036] [Refracting link mechanism] As shown in Figure 4, the articulated link mechanism 51 comprises a base end 14, a first link 15, and a second link 16. Although Figure 4 shows the articulated link mechanism 51 and front wheel 21a located on the right front of the aircraft body 1, the other three articulated link mechanisms 51 and the three wheels 21 have a similar configuration. The base end 14 is fixed to the aircraft body 1. The upper end of the first link 15 is connected to the lower part of the base end 14. The upper end of the first link 15 is rotatable around an axis X1 extending in the left-right direction. One end of the second link 16 is connected to the lower end of the first link 15. One end of the second link 16 is rotatable around an axis X2 extending in the left-right direction. A support bracket 17 is connected to the other end of the second link 16. The front wheel 21a or rear wheel 21b is held by the support bracket 17.

[0037] A boss portion 18 is provided at the other end of the second link 16. The support bracket 17 is connected to the boss portion 18. The support bracket 17 is pivotable around an axis Y that extends in the vertical direction. A hydraulically driven slewing cylinder 20 is provided at one end of the second link 16.

[0038] The first hydraulic cylinder 6 can change the attitude of the first link 15 relative to the aircraft body 1. The second hydraulic cylinder 7 can also change the attitude of the second link 16 relative to the first link 15.

[0039] When the first hydraulic cylinder 6 extends or retracts while the second hydraulic cylinder 7 is stopped, the first link 15, the second link 16, and the wheel 21 oscillate together around the axis X1. When the second hydraulic cylinder 7 extends or retracts while the first hydraulic cylinder 6 is stopped, the second link 16 and the wheel 21 oscillate together around the axis X2 while the posture of the first link 15 is maintained.

[0040] An auxiliary wheel 3 is rotatably supported at the connection point between the first link 15 and the second link 16. The auxiliary wheel 3 is a wheel with a smaller outer diameter than either the front wheel 21a or the rear wheel 21b.

[0041] The front wheel 21a or rear wheel 21b is steered by the extension and retraction of the slewing cylinder 20. The slewing cylinder 20 is located on the left and right center side of the aircraft body 1 relative to the front wheel 21a or rear wheel 21b. When the slewing cylinder 20 extends and retracts, the front wheel 21a or rear wheel 21b rotates around the axis Y relative to the attitude change mechanism 5.

[0042] When the running gear 2 is in a two-wheel steering state, the two slewing cylinders 20 that steer the left and right front wheels 21a extend and retract during turning. Also, when the running gear 2 is in a four-wheel steering state, the four slewing cylinders 20 that steer the left and right front wheels 21a and the left and right rear wheels 21b extend and retract during turning.

[0043] Specifically, the right front wheel 21a, located on the front right side of the aircraft 1, rotates clockwise by the extension of the slewing cylinder 20. Conversely, the right front wheel 21a rotates counterclockwise by the contraction of the slewing cylinder 20. On the other hand, the left front wheel 21a, located on the front left side of the aircraft 1, rotates counterclockwise by the extension of the slewing cylinder 20. Conversely, the left front wheel 21a rotates clockwise by the contraction of the slewing cylinder 20.

[0044] The right rear wheel 21b, located on the rear right side of the aircraft 1, rotates clockwise by the extension of the slewing cylinder 20. The right rear wheel 21b also rotates counterclockwise by the contraction of the slewing cylinder 20. On the other hand, the left rear wheel 21b, located on the rear left side of the aircraft 1, rotates counterclockwise by the extension of the slewing cylinder 20. The left rear wheel 21b also rotates clockwise by the contraction of the slewing cylinder 20. When the aircraft 1 is moving in a straight line, the stroke positions of the four slewing cylinders 20 are set to a neutral stroke position between the extension stroke end and the contraction stroke end.

[0045] As shown in Figure 5, the ECU 13 controls the flow rate of hydraulic fluid in the hydraulic control valve 12. The hydraulic control valve 12 adjusts the supply and discharge amounts of hydraulic fluid to the four hydraulic motors 4, the four first hydraulic cylinders 6, the four second hydraulic cylinders 7, and the four slewing cylinders 20, respectively. In this way, the ECU 13 controls the rotational speed of the hydraulic motors 4, i.e., the travel speed of the travel device 2. The ECU 13 also controls the extension and retraction speed of the slewing cylinders 20, i.e., the steering speed of the travel device 2.

[0046] The work vehicle is equipped with various sensors. Stroke sensors S1 are provided on each of the four first hydraulic cylinders 6 and the four second hydraulic cylinders 7. In addition, stroke sensors S2 capable of detecting stroke position are provided on each of the four slewing cylinders 20. Furthermore, the machine body 1 is equipped with a tilt sensor S3 capable of detecting the tilt state of the machine body 1. In addition, the running gear 2 is equipped with a rotation sensor S4 capable of detecting the rotation speed of the wheels 21. Moreover, the hydraulic motor 4 is equipped with a pressure sensor S5 capable of detecting the pressure of the hydraulic fluid.

[0047] The stroke sensor S1 can detect the stroke positions of the four first hydraulic cylinders 6 and the four second hydraulic cylinders 7, respectively. The stroke position of the first hydraulic cylinders 6 corresponds to the oscillation position of the first link 15. Similarly, the stroke position of the second hydraulic cylinders 7 corresponds to the oscillation position of the second link 16. In other words, the stroke sensor S1 detects the amount of extension and retraction of the first hydraulic cylinders 6 and the second hydraulic cylinders 7, respectively.

[0048] The tilt sensor S3 is equipped with an inertial measurement unit (IMU). The IMU has a three-axis accelerometer and a gyroscope, and detects the attitude of the aircraft 1, specifically the tilt of the aircraft 1 in the front-rear and left-right directions.

[0049] The ECU13 is connected to the operation detection unit 22. The operation detection unit 22 receives signals from the driving control device 23 and signals from the wireless communication remote control device RC.

[0050] As shown in Figure 5, the ECU 13 includes, as functional units, an attitude control unit 100, a driving control unit 101, an inclination angle calculation unit 102, a steering control unit 103, and a center of gravity position calculation unit 104.

[0051] The attitude control unit 100 can detect the swinging attitude of the first link 15 relative to the aircraft body 1 and the swinging attitude of the second link 16 relative to the first link 15, based on the values ​​detected by the stroke sensor S1. Furthermore, as shown in Figure 1, the attitude control unit 100 can calculate the aircraft height H (see Figure 1) from the line segment L1 connecting the front contact point FG, which is the contact point of the front wheel 21a, and the rear contact point RG, which is the contact point of the rear wheel 21b, to the upper end of the aircraft body 1, and the distance D (see Figure 1) from the front contact point FG or rear contact point RG of the wheel 21 to the axis X1 at the upper end of the first link 15.

[0052] When the work vehicle is moving, the attitude control unit 100 performs horizontal control, controlling the attitude change mechanism 5 so that the loading section 8 of the machine body 1 is in a horizontal position, based on the detection information of the tilt sensor S3. In horizontal control, the attitude control unit 100 controls the extension and retraction of the four first hydraulic cylinders 6 and the four second hydraulic cylinders 7 so that the tilt angle in the front-rear direction and the tilt angle in the left-right direction from the horizontal position of the machine body 1 are values ​​corresponding to the horizontal position, based on the detected values ​​of the tilt sensor S3 and the stroke sensor S1.

[0053] The travel control unit 101 controls the supply and discharge of hydraulic fluid to the hydraulic motor 4 so that the rotational speed of the wheel 21 reaches a target value, based on the rotational speed of the wheel 21 detected by the rotation sensor S4. The travel control unit 101 also controls the supply (pressure) of hydraulic fluid to the hydraulic motor 4 so that the driving torque of the wheel 21 reaches a target value, based on the hydraulic fluid pressure detected by the pressure sensor S5. The hydraulic control valve 12 can change the amount of hydraulic fluid supplied to and discharged from the hydraulic motor 4. The travel control unit 101 performs a switching operation of the hydraulic control valve 12 that supplies and discharges hydraulic fluid to the hydraulic motor 4.

[0054] When the work vehicle stops, the travel control unit 101 shuts off the supply and discharge of hydraulic fluid to the four hydraulic motors 4 via the hydraulic control valve 12. When the supply and discharge of hydraulic fluid to the hydraulic motors 4 is shut off, the hydraulic motors 4 stop. As a result, the rotation of each of the four wheels 21 stops.

[0055] The inclination angle calculation unit 102 calculates the inclination angle of the running surface G on which the four wheels 21 make contact with the ground, based on the detected value of the inclination sensor S3, the extension and contraction amounts of the four first hydraulic cylinders 6, and the extension and contraction amounts of the four second hydraulic cylinders 7.

[0056] The steering control unit 103 can steer the wheels 21 based on the values ​​detected by the stroke sensor S2. Specifically, the steering control unit 103 performs a switching operation of the hydraulic control valve 12 that supplies and discharges hydraulic fluid to the slewing cylinder 20. The steering control unit 103 changes the direction of each of the four wheels 21.

[0057] When the work vehicle is in a four-wheel steering state, the steering control unit 103 does not shut off the supply and discharge of hydraulic fluid to the four slewing cylinders 20 via the hydraulic control valve 12. On the other hand, when the work vehicle is in a two-wheel steering state, the steering control unit 103 shuts off the supply and discharge of hydraulic fluid to the slewing cylinders 20 corresponding to the left and right rear wheels 21b via the hydraulic control valve 12, and does not shut off the supply and discharge of hydraulic fluid to the slewing cylinders 20 corresponding to the left and right front wheels 21a via the hydraulic control valve 12. Specifically, the hydraulic control valve 12 shuts off the supply and discharge of hydraulic fluid to the slewing cylinder 20 located at the right rear of the machine body 1 and the slewing cylinder 20 located at the left rear of the machine body 1. Also, the hydraulic control valve 12 does not shut off the supply and discharge of hydraulic fluid to the slewing cylinder 20 located at the right front of the machine body 1 and the slewing cylinder 20 located at the left front of the machine body 1.

[0058] The center of gravity position calculation unit 104 calculates the position coordinates of the four wheels 21 relative to the aircraft body 1 based on the detection value of the stroke sensor S1. The center of gravity position calculation unit 104 also calculates the load on the four wheels 21 based on the detection value of the pressure sensor S5. Based on the position coordinates of the wheels 21 relative to the aircraft body 1 and the load on the four wheels 21, the center of gravity position vector of each wheel 21 is calculated over time. From these center of gravity position vectors of each wheel 21 and the preset dimensions of the aircraft body 1, the position of the center of gravity of the aircraft body 1 (three-dimensional coordinates) is uniquely determined.

[0059] [Regarding the attachment of equipment to the aircraft] As shown in Figure 6, the attachment IM is, for example, a towed trolley TR attached to the rear of the machine body 1 and towed by a work vehicle. The towed trolley TR has multiple wheels. Also, as shown in Figure 7, the attachment IM is, for example, a bucket BT attached to the front of the machine body 1 that is capable of scooping up and lifting objects. However, the attachment IM is not limited to these, and may be other devices. Here, the hydraulic fluid pressure (differential pressure of the hydraulic motor 4) detected by the pressure sensor S5 changes when the work vehicle is running, depending on whether the attachment IM is attached to the machine body 1 or not. The control device C determines whether the attachment IM is attached to the machine body 1 or not based on the hydraulic fluid pressure detected by the pressure sensor S5.

[0060] In the example shown in Figure 6, the towed carriage TR (equipment IM) is mounted on the rear of the machine body 1, and when the work vehicle is in motion, a greater load is likely to be generated on the left and right rear wheels 21b than on the left and right front wheels 21a. In other words, the differential pressure between the two hydraulic motors 4 that drive the left and right rear wheels 21b is greater than the differential pressure between the two hydraulic motors 4 that drive the left and right front wheels 21a. In this case, the control device C determines that the towed carriage TR is mounted on the rear of the machine body 1.

[0061] In the example shown in Figure 7, the bucket BT (attachment IM) is mounted on the front of the machine 1, and when the work vehicle is in motion, a greater load is likely to be generated on the left and right front wheels 21a than on the left and right rear wheels 21b. In other words, the differential pressure between the two hydraulic motors 4 that drive the left and right front wheels 21a is greater than the differential pressure between the two hydraulic motors 4 that drive the left and right rear wheels 21b. In this case, the control device C determines that the bucket BT is mounted on the front of the machine 1. In other words, the control device C determines the position where the attachment IM is mounted on the machine 1 by comparing the differential pressure between the multiple hydraulic motors 4.

[0062] [Regarding changes in the aircraft's attitude] Next, the attitude change of aircraft 1 will be explained based on the flowcharts shown in Figures 6, 7, and 8. Note that the steps described below may be performed in any order, and multiple steps may be performed simultaneously, as long as there are no inconsistencies.

[0063] The control device C determines whether or not the attachment IM is attached to the aircraft body 1 (step #01). If the attachment IM is not attached to the aircraft body 1 (step #01: No), the process completes normally. If the attachment IM is attached to the aircraft body 1 (step #01: Yes), the control device C determines whether or not the attachment IM is attached to the rear of the aircraft body 1 (step #02).

[0064] As shown in Figure 6, when the towed trolley TR is attached to the rear of the machine body 1 (Step #02: Yes), the travel control unit 101 shuts off the supply and discharge of hydraulic fluid to the four hydraulic motors 4 by the hydraulic control valve 12. The control device C determines whether the wheels 21 have stopped based on the rotational speed of the wheels 21 detected by the rotation sensor S4 (Step #03).

[0065] The process in step #03 is repeated until it is determined that wheel 21 has stopped (step #03: No). If it is determined that wheel 21 has stopped (step #03: Yes), the attitude of the aircraft 1 is changed so that the front-to-rear center point CP moves forward (step #04).

[0066] Specifically, as shown in Figure 6, the attitude control unit 100 extends the first hydraulic cylinder 6 and the second hydraulic cylinder 7 located on the right rear (rear end 1b side) of the aircraft body 1. The attitude control unit 100 also extends the first hydraulic cylinder 6 and the second hydraulic cylinder 7 located on the left rear (rear end 1b side) of the aircraft body 1.

[0067] Furthermore, as shown in Figure 6, the attitude control unit 100 retracts the first hydraulic cylinder 6 and the second hydraulic cylinder 7 located on the right front (front end 1a side) of the aircraft body 1. The attitude control unit 100 also retracts the first hydraulic cylinder 6 and the second hydraulic cylinder 7 located on the left front (front end 1a side) of the aircraft body 1. As a result, of the multiple first hydraulic cylinders 6 and second hydraulic cylinders 7, the first hydraulic cylinder 6 and the second hydraulic cylinder 7 located on the front end 1a side of the aircraft body 1 are retracted, and of the multiple first hydraulic cylinders 6 and second hydraulic cylinders 7, the first hydraulic cylinder 6 and the second hydraulic cylinder 7 located on the rear end 1b side of the aircraft body 1 are extended.

[0068] In Figure 6, the rear end 1b of the machine body 1, which is the end on the towed trolley TR side, corresponds to the "first end" in the claims. The front end 1a of the machine body 1, which is the end opposite to the towed trolley TR, corresponds to the "second end" in the claims.

[0069] As a result of the attitude change by the attitude change mechanism 5 described above, the front-to-rear center point CP of the machine body 1 moves to the opposite side (front side) from the towed trolley TR, as shown in Figure 6. The distance D3 (an example of distance D) from the rear contact point RG of the rear wheel 21b to the axis X1 of the right rear of the machine body 1 or the axis X1 of the left rear of the machine body 1 becomes larger than the distance D2 (an example of distance D) from the front contact point FG of the front wheel 21a to the axis X1 of the right front of the machine body 1 or the axis X1 of the left front of the machine body 1. In other words, the attitude change by the attitude change mechanism 5 increases the distance D3 from the rear end 1b of the machine body 1 to the running surface G, and decreases the distance D2 from the front end 1a of the machine body 1 to the running surface G. In short, the work vehicle adopts a downward-sloping posture as a result of the attitude change by the attitude change mechanism 5.

[0070] The control device C determines whether the front-rear center point CP of the machine body 1 is located on the opposite side (front side) from the towed trolley TR relative to the midpoint CG between the front contact point FG of the front wheel 21a and the rear contact point RG of the rear wheel 21b (step #05). In this embodiment, the position of the center of gravity of the machine body 1 is in a position that overlaps with the front-rear center point CP of the machine body 1 in a plan view. Therefore, the control device C determines whether the front-rear center point CP of the machine body 1 is located in front of the midpoint CG based on the position of the center of gravity of the machine body 1 calculated by the center of gravity position calculation unit 104. Not limited to this, the control device C may calculate the position of the front-rear center point CP of the machine body 1 over time based on the dimensions of the machine body 1 set in advance and the detected value of the stroke sensor S1. In this case, the control device C determines whether the front-rear center point CP of the machine body 1 is located in front of the midpoint CG based on the calculated position of the front-rear center point CP of the machine body 1.

[0071] If the front-to-rear center point CP of the aircraft 1 is located in front of the midpoint CG (Step #05: Yes), the attitude control unit 100 stops the attitude change (Step #06) and completes the process normally. In this embodiment, based on the detection value of the stroke sensor S1, the attitude control unit 100 stops the extension and retraction of the first hydraulic cylinder 6 and the second hydraulic cylinder 7 when the left and right first links 15 and left and right second links 16 located at the rear of the aircraft 1 are in an attitude where they extend in a straight line diagonally downward and rear of the aircraft 1.

[0072] Furthermore, based on the values ​​detected by the stroke sensor S1, the attitude control unit 100 stops the extension and retraction of the first hydraulic cylinder 6 and the second hydraulic cylinder 7 when the left and right first links 15 located at the front of the aircraft body 1 extend diagonally downward and rearward, and the left and right second links 16 located at the front of the aircraft body 1 extend diagonally downward and forward. The process in step #05 is repeated until it is determined that the front-to-rear center point CP of the aircraft body 1 is located in front of the midpoint CG (step #05: No).

[0073] As shown in Figure 7, when the bucket BT is mounted on the front of the machine body 1 (step #02: No), the travel control unit 101 shuts off the supply and discharge of hydraulic fluid to the four hydraulic motors 4 by the hydraulic control valve 12. The control device C determines whether the wheels 21 have stopped based on the rotational speed of the wheels 21 detected by the rotation sensor S4 (step #07).

[0074] The process in step #07 is repeated until it is determined that wheel 21 has stopped (step #07: No). If it is determined that wheel 21 has stopped (step #07: Yes), the attitude of the aircraft 1 is changed so that the front-to-rear center point CP moves backward (step #08).

[0075] Specifically, as shown in Figure 7, the attitude control unit 100 extends the first hydraulic cylinder 6 and the second hydraulic cylinder 7 located on the right front (front end 1a side) of the aircraft body 1. The attitude control unit 100 also extends the first hydraulic cylinder 6 and the second hydraulic cylinder 7 located on the left front (front end 1a side) of the aircraft body 1.

[0076] Furthermore, as shown in Figure 7, the attitude control unit 100 retracts the first hydraulic cylinder 6 and the second hydraulic cylinder 7 located on the right rear (rear end 1b side) of the aircraft body 1. The attitude control unit 100 also retracts the first hydraulic cylinder 6 and the second hydraulic cylinder 7 located on the left rear (rear end 1b side) of the aircraft body 1. In other words, of the multiple first hydraulic cylinders 6 and second hydraulic cylinders 7, the first hydraulic cylinder 6 and the second hydraulic cylinder 7 located on the rear end 1b side of the aircraft body 1 are retracted, and of the multiple first hydraulic cylinders 6 and second hydraulic cylinders 7, the first hydraulic cylinder 6 and the second hydraulic cylinder 7 located on the front end 1a side of the aircraft body 1 are extended.

[0077] In Figure 7, the front end 1a of the machine body 1, which is the end on the bucket BT side, corresponds to the "first end" in the claims. The rear end 1b of the machine body 1, which is the end opposite to the bucket BT, corresponds to the "second end" in the claims.

[0078] As a result of the attitude change by the attitude change mechanism 5 described above, the front-to-rear center point CP of the machine body 1 moves to the opposite side (rear side) from the bucket BT, as shown in Figure 7. Also, the distance D2 from the front contact point FG of the front wheel 21a to the axis X1 of the right front of the machine body 1 or the axis X1 of the left front of the machine body 1 becomes larger than the distance D3 from the rear contact point RG of the rear wheel 21b to the axis X1 of the right rear of the machine body 1 or the axis X1 of the left rear of the machine body 1. In other words, as a result of the attitude change by the attitude change mechanism 5, the distance D2 from the front end 1a of the machine body 1 to the running surface G becomes larger, and the distance D3 from the rear end 1b of the machine body 1 to the running surface G becomes smaller. In short, the work vehicle adopts a rearward-sloping posture as a result of the attitude change by the attitude change mechanism 5.

[0079] The control device C determines, based on the position of the center of gravity of the aircraft 1, whether the front-to-rear center point CP of the aircraft 1 is located on the opposite side (rear side) from the bucket BT relative to the midpoint CG (step #09).

[0080] If the front-rear center point CP of the aircraft 1 is located behind the midpoint CG (Step #09: Yes), the process proceeds to Step #06. In this embodiment, the attitude control unit 100 stops the extension and retraction of the four first hydraulic cylinders 6 and second hydraulic cylinders 7 when the distance D3 from the rear end 1b of the aircraft 1 to the running surface G becomes smaller than the distance D2 from the front end 1a of the aircraft 1 to the running surface G, based on the detected values ​​of the stroke sensor S1. The process in Step #09 is repeated until it is determined that the front-rear center point CP of the aircraft 1 is located behind the midpoint CG (Step #09: No).

[0081] As described above, in the example of Figure 6, the control device C determines that the towed carriage TR is attached to the rear of the machine body 1 and instructs the attitude change mechanism 5 to change the attitude so that the front-rear center point CP of the machine body 1 moves forward. On the other hand, in the example of Figure 7, the control device C determines that the bucket BT is attached to the front of the machine body 1 and instructs the attitude change mechanism 5 to change the attitude so that the front-rear center point CP of the machine body 1 moves backward. Next, the work vehicle travels with the attachment IM attached to the machine body 1. In the example of Figure 6, the work vehicle travels while towing the towed carriage TR. In the example of Figure 7, the work vehicle travels with the bucket BT attached.

[0082] [Regarding switching the steering state of the running gear] In Figures 9 and 10, a towed trolley TR is attached to the rear of the machine body 1. In Figure 9, the work vehicle is rotating, and the running gear 2 is in a four-wheel steering state. In Figure 10, the work vehicle is rotating, and the running gear 2 is in a two-wheel steering state.

[0083] As shown in Figure 9, if there is a large difference between the turning radius RD1 of the work vehicle from the turning center RC1 to the work vehicle and the turning radius RD2 of the towed trolley TR from the turning center RC2 to the towed trolley TR, the work vehicle will be pulled outward in the turning direction by the towed trolley TR when turning. In particular, when the work vehicle is traveling on sandy ground, the left and right front wheels 21a will slip due to being pulled outward in the turning direction by the towed trolley TR. This will place a large load on the left and right rear wheels 21b, and the rotation of the hydraulic motor 4 that drives the rear wheels 21b may stop (stall). Therefore, as shown in Figure 10, when a towed trolley TR is attached to the rear of the machine body 1, the travel control unit 101 automatically switches the travel device 2 to a two-wheel steering state.

[0084] Next, the switching of the steering state of the running gear 2 will be explained based on the flowcharts shown in Figures 9, 10, and 11. Note that the steps described below may be performed in any order, and multiple steps may be performed simultaneously, as long as no inconsistencies arise.

[0085] The control device C determines whether or not the attachment IM is attached to the aircraft body 1 (step #11). If the attachment IM is not attached to the aircraft body 1 (step #11: No), the process completes normally. If the attachment IM is attached to the aircraft body 1 (step #11: Yes), the control device C determines whether or not the attachment IM is attached to the rear of the aircraft body 1 (step #12).

[0086] If the attachment IM is not attached to the rear of the machine 1 (Step #12: No), the process completes normally. If the towed carriage TR is attached to the rear of the machine 1 (Step #12: Yes), the travel control unit 101 determines whether the steering state is a two-wheel steering state or not (Step #13).

[0087] If the steering state is two-wheel steering (Step #13: Yes), the process is completed successfully. If the steering state is four-wheel steering (Step #13: No), the travel control unit 101 switches the travel device 2 from four-wheel steering to two-wheel steering (Step #14) and completes the process successfully. Specifically, when the steering control unit 103 switches to two-wheel steering, it shuts off the supply and discharge of hydraulic fluid to the slewing cylinder 20 corresponding to the rear wheel 21b using the hydraulic control valve 12, and does not shut off the supply and discharge of hydraulic fluid to the slewing cylinder 20 corresponding to the front wheel 21a using the hydraulic control valve 12.

[0088] As shown in Figure 10, the automatic switching of the running gear 2 to a two-wheel steering state makes it less likely for a large difference to occur between the turning radius RD1 of the work vehicle and the turning radius RD2 of the towed carriage TR. In other words, even when the towed carriage TR is attached to the rear of the machine body 1, it is less likely for a large load to be placed on the left and right rear wheels 21b during turning.

[0089] [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.

[0090] (1) In the above-described embodiment, the hydraulic supply source 9 is shown as the drive source. The embodiment is not limited to this, and for example, the drive source may be an engine 9a, a battery, or an electric motor driven by a battery.

[0091] (2) In the above-described embodiment, the first hydraulic cylinder 6 and the second hydraulic cylinder 7 were shown as extension actuators. The embodiment is not limited to this, and for example, the extension actuator may be a pneumatic actuator or an electric actuator.

[0092] (3) The bending link mechanism 51 may be a mechanism comprising one link or three or more links.

[0093] (4) The wheels 21 may be driven by an electric motor instead of a hydraulic motor 4, or by an engine or the like via a drive mechanism.

[0094] (5) In the above embodiment, the work vehicle is equipped with four wheels 21. However, the number of wheels 21 may be less than four or five or more. The running gear 2 may also be a crawler type device.

[0095] (6) In the above-described embodiment, the posture changing mechanism 5 is provided with a bending link mechanism 51. The embodiment is not limited to this one, and for example, the posture changing mechanism 5 may be provided with a sliding mechanism that can move up and down instead of the bending link mechanism 51.

[0096] (7) In the above-described embodiment, a tilt sensor S3 is provided. The embodiment is not limited to this, and for example, a mechanical pendulum type sensor or a magnetic sensor may also be used.

[0097] (8) In the above embodiment, after the wheels 21 have stopped, the attitude of the aircraft body 1 is changed so that the front-rear center point CP moves (steps #04, #08). However, the process of steps #04 and #08 in Figure 8 may be performed while the running gear 2 is in motion.

[0098] (9) In the above embodiment, the control device C identifies the position where the attachment IM is attached based on the differential pressure of the hydraulic motor 4 that drives the rear wheel 21b and the differential pressure of the hydraulic motor 4 that drives the front wheel 21a (step #02). Not limited to this, in step #02, the control device C may determine whether or not the hydraulic motor 4 that drives the wheel 21 is stalled. The determination of whether or not a stall has occurred is made based on the differential pressure of the hydraulic motor 4 (output of pressure sensor S5), the rotational speed of the hydraulic motor 4 (output of rotation sensor S4), the control instruction value of the hydraulic motor 4, etc. In this case, in step #04, the attitude of the aircraft 1 may be changed so that the front-rear center point CP or center of gravity moves to the opposite side from the wheel 21 that is stalled.

[0099] Furthermore, in this embodiment, during the process of step #05 in Figure 8, the control device C may determine whether or not the hydraulic motor 4 is stalled. In this case, if it is determined that all hydraulic motors 4 are not stalled (step #05: No), the attitude control unit 100 may stop the attitude change (step #06). Also, if it is determined that at least one hydraulic motor 4 is stalled (step #05: Yes), the process of step #05 is repeated until it is determined that all hydraulic motors 4 are not stalled. In other words, until it is determined that all hydraulic motors 4 are not stalled, the attitude change is performed so that the front-to-rear center point CP or center of gravity of the aircraft 1 moves to the opposite side of the wheel 21 that is stalled.

[0100] (10) In the above embodiment, the control device C determines the position where the attachment IM is attached based on the differential pressure of the hydraulic motor 4 that drives the rear wheel 21b and the differential pressure of the hydraulic motor 4 that drives the front wheel 21a (step #02). The work vehicle is not limited to this, and may be equipped with a sensor that detects whether or not the attachment IM is attached to the machine body 1. In this case, the control device C may determine the position where the attachment IM is attached based on the input of a signal from the sensor. Alternatively, when the attachment IM is attached to the machine body 1, a switch or the like may be manually operated, and the control device C may determine that the attachment IM is attached when a signal from this switch is input to the control device C.

[0101] (11) The position of the center of gravity of the aircraft 1 does not have to coincide with the front-to-rear center point CP of the aircraft 1 in a plan view. For example, if the center of gravity of the aircraft 1 is located on the side of the attached object IM rather than the front-to-rear center point CP of the aircraft 1, the center of gravity of the aircraft 1 will move to the opposite side of the attached object IM when the attitude is changed. As a result, the front-to-rear center point CP of the aircraft 1 will be located on the opposite side of the attached object IM with respect to the midpoint CG.

[0102] (12) In the above embodiment, in step #05, the attitude control unit 100 stops the extension and retraction of the first hydraulic cylinder 6 and the second hydraulic cylinder 7 when the first link 15 and the second link 16, which are supported by the rear wheel 21b, are in an attitude where they extend in a straight line diagonally downward and rear of the aircraft body 1. However, the attitude of the first link 15 and the second link 16 when extension and retraction is stopped may be any other attitude, as long as the front-to-rear center point CP of the aircraft body 1 is located in front of the midpoint point CG.

[0103] (13) The work vehicle may be, for example, a combine harvester, tractor, rice transplanter, paddy field direct seeder, corn harvester, potato harvester, carrot harvester, construction work machine, etc.

[0104] 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. Furthermore, 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]

[0105] This invention is applicable to work vehicles. [Explanation of Symbols]

[0106] 1: Aircraft 1a: Front end (first end, second end) 1b: Rear end (first end, second end) 2: Running gear 21a: Front wheels (front running gear) 21b: Rear wheels (rear running gear) 5: Posture change mechanism 6: First hydraulic cylinder (extension mechanism) 7: Second hydraulic cylinder (extension mechanism) CP: Anteroposterior center point D2 :Distance D3: Distance CG: Midway point FG: Front grounding point (grounding point) RG: Rear grounding point (grounding point) G: Running surface BT: Bucket (attached item) TR: Towed trolley (equipped object) IM: Wearable item

Claims

1. A work vehicle capable of traveling on a running surface, An aircraft capable of attaching equipment to the front or rear, A posture changing mechanism that supports the aircraft and can change the attitude of the aircraft, The vehicle comprises a vehicle that supports the attitude changing mechanism and is capable of traveling on the travel surface, When the aforementioned attachment is mounted on the machine, the machine's attitude is changed by the attitude changing mechanism, causing the front-to-rear center point to move to the side opposite to the aforementioned attachment.

2. The aforementioned traveling device comprises a front traveling device that supports the front of the machine body, and a rear traveling device that is located behind the front traveling device and supports the rear of the machine body. The work vehicle according to claim 1, wherein, when the attachment is mounted on the machine body, the front-rear center point of the machine body is located on the opposite side from the attachment with respect to the midpoint between the contact point of the front running gear and the contact point of the rear running gear.

3. The aforementioned aircraft has a first end, which is the end on the side of the front or rear that is on the side of the attached object, and a second end, which is on the opposite side of the first end. The work vehicle according to claim 2, wherein, when the attachment is mounted on the machine body, the change in attitude by the attitude changing mechanism reduces the distance from the second end to the running surface and increases the distance from the first end to the running surface.

4. The attitude changing mechanism has a plurality of extendable and retractable mechanisms, The work vehicle according to claim 3, wherein, when the attachment is mounted on the machine body, the posture change by the posture changing mechanism causes the telescopic mechanism located at the second end of the plurality of telescopic mechanisms to contract, and the telescopic mechanism located at the first end of the plurality of telescopic mechanisms to extend.

5. The aforementioned driving device is switchable between a two-wheel steering state and a four-wheel steering state. The work vehicle according to claim 1, wherein, when a towed carriage to be pulled by the work vehicle is attached to the rear of the machine body as the aforementioned attachment, the running gear becomes the two-wheel steering state.

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