Work vehicle

Abstract

To provide a work vehicle that is able to hold a horizontal position of a loading portion properly.SOLUTION: A work vehicle comprises: a vehicle body having a loading portion on which a load can be loaded; a plurality of traveling wheels located at front and rear positions on both left and right sides of the vehicle body; a support mechanism which is supported by the vehicle body and supports the plurality of traveling wheels so that their positions can be changed with respect to the vehicle body; an inclination detection unit which detects an inclined state of the vehicle body; and a control device which, based on the inclined state of the vehicle body, can control an operation of the support mechanism so that the loading portion is brought into a horizontal position. The control device is configured to calculate an inclination angle of a ground with which the plurality of traveling wheels are in contact. The work vehicle is configured not to control the operation of the support mechanism when the ground is inclined within a range of a preset inclination angle with the plurality of traveling wheels kept stopped and is configured to continue to control the operation of the support mechanism when the ground is inclined at the preset inclination angle or more with the plurality of traveling wheels kept stopped.SELECTED DRAWING: Figure 8

Description

Technical Field

[0001] The present invention relates to a work vehicle having a plurality of traveling wheels that can be steered separately.

Background Art

[0002] For example, in the work vehicle disclosed in Patent Document 1, a vehicle body having a loading portion on which luggage can be loaded, a plurality of traveling wheels respectively located at the front and rear on both the left and right sides of the vehicle body, and a support mechanism (referred to as a "refraction link mechanism" in the document) for supporting the plurality of traveling wheels so that their positions can be changed with respect to the vehicle body are provided. By the control device controlling the support mechanism, the loading portion is held in a horizontal posture.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] By the way, when the work vehicle stops, the operation of the traveling device stops, and the operation of the support mechanism also stops. At this time, if the stop position of the work vehicle is on a sloping ground, there is a possibility that the horizontal posture of the mounting portion may not be appropriately maintained due to the stop of the operation of the support mechanism. For this reason, a configuration in which the support mechanism is always operated can be considered, but if the support mechanism is always operated, it is disadvantageous in terms of running cost.

[0005] An object of the present invention is to provide a work vehicle capable of appropriately maintaining the horizontal posture of the mounting portion.

Means for Solving the Problems

[0006] The work vehicle of the present invention comprises a vehicle body having a loading section capable of loading cargo, a plurality of running wheels located at the front and rear on both the left and right sides of the vehicle body, a support mechanism supported by the vehicle body and capable of supporting the plurality of running wheels so as to be able to change their position relative to the vehicle body, a tilt detection unit for detecting the tilt state of the vehicle body, and a control device capable of controlling the operation of the support mechanism so that the loading section is in a horizontal position based on the tilt state of the vehicle body. , a drive source that supplies driving energy to operate the support mechanism, The control device is configured to calculate the inclination angle of the ground to which the plurality of running wheels make contact, and to not control the operation of the support mechanism when the ground is inclined within a preset range of inclination angles while the plurality of running wheels are stopped, and to continue controlling the operation of the support mechanism when the ground is inclined at or above the preset inclination angle while the plurality of running wheels are stopped. The system is configured to allow the drive source to stop when the ground is inclined within the range of the set inclination angle while the multiple wheels are stopped, and to prohibit the drive source from stopping when the ground is inclined at or above the set inclination angle while the multiple wheels are stopped. It is characterized by having this feature.

[0007] According to the present invention, if the ground is inclined at an angle greater than the set inclination angle, the control device continues to control the operation of the support mechanism. Therefore, compared to a configuration in which the support mechanism stops operating, the horizontal position of the mounting part is properly maintained. Also, if the ground is inclined within the range of the set inclination angle, the ground is generally horizontal, so the mounting part is easily maintained in a horizontal position compared to when the ground is inclined. Therefore, if the ground is inclined within the range of the set inclination angle, the control device does not control the operation of the support mechanism. This reduces running costs compared to a configuration in which the control device continues to control the operation of the support mechanism on flat ground. Thus, the present invention realizes a work vehicle that can properly maintain the horizontal position of the mounting part. In this invention, "within the range of the set inclination angle" may include the set inclination angle or exclude it. If "within the range of the set inclination angle" includes the set inclination angle, then "greater than or equal to the set inclination angle" in this invention may mean "an inclination angle greater than the set inclination angle" without including the set inclination angle. Furthermore, if "within the range of the set tilt angle" does not include the set tilt angle, then "greater than or equal to the set tilt angle" may include the set tilt angle.

[0008]

[0009] Also, The drive source supplies the driving energy necessary to operate the support mechanism. Therefore, if the drive source stops, the support mechanism becomes inoperable, and the control device can no longer continue to control the operation of the support mechanism. In this configuration, if the ground is tilted at an angle greater than the set inclination angle, the control device prevents the drive source from stopping. Therefore, the control device can reliably control the operation of the support mechanism.

[0010] In the present invention, the drive source is configured to supply the driving energy to the plurality of running wheels, and the control device preferably does not supply the driving energy to the plurality of running wheels when the plurality of running wheels are stopped.

[0011] In this configuration, no driving energy is supplied to the wheels when the work vehicle is stationary. Therefore, if the ground is tilted beyond the set inclination angle, the control device can be configured to stop supplying driving energy to the wheels and continue to control the operation based on the driving energy of the support mechanism. This allows for both reduced running costs and proper maintenance of the horizontal position of the mounting section.

[0012] In the present invention, it is preferable that the device includes a hydraulic motor that drives each of the plurality of travel wheels by supplying and discharging hydraulic fluid that has received the driving energy, and a control valve that can change the amount of hydraulic fluid supplied and discharged to the hydraulic motor, and that the control device is configured to stop the plurality of travel wheels by closing the control valve and blocking the supply and discharge of hydraulic fluid to the hydraulic motor.

[0013] In this configuration, multiple wheels are driven by hydraulics. Therefore, if the supply and discharge of hydraulic fluid to the hydraulic motor is cut off, the wheels stop, and if the hydraulic fluid inside the hydraulic motor does not flow, the rotation of the hydraulic motor is locked. At this time, the hydraulic motor functions as a brake on the wheels.

[0014] In the present invention, the support mechanism is provided with a plurality of telescopic actuators for changing the position of the running wheels relative to the vehicle body, and a telescopic amount detection unit for detecting the amount of telescopic extension of each of the plurality of telescopic actuators, and the control device is configured to control the operation of each of the plurality of telescopic actuators so that the loading section is in a horizontal position based on the inclination state of the vehicle body and the amount of telescopic extension of each of the plurality of telescopic actuators, and it is preferable that the control device is configured not to control the operation of each of the plurality of telescopic actuators when the ground is inclined within the range of the set inclination angle when the plurality of running wheels are stopped, and to continue to control the operation of each of the plurality of telescopic actuators when the ground is inclined at or above the set inclination angle when the plurality of running wheels are stopped.

[0015] In this configuration, if the ground is sloped beyond the set inclination angle, the control device continues to control the operation of the telescopic actuator. Therefore, the horizontal position of the mounting section is properly maintained compared to a configuration in which the telescopic actuator stops operating. Also, if the ground slope is within the set inclination angle range, the ground is generally horizontal, so the mounting section is easily maintained in a horizontal position compared to when the ground is sloped. Therefore, if the ground is sloped within the set inclination angle range, the control device does not control the operation of the telescopic actuator. This reduces running costs compared to a configuration in which the control device continues to control the operation of the telescopic actuator on flat ground. [Brief explanation of the drawing]

[0016] [Figure 1] Side view of the work vehicle. [Figure 2] Rear view of the work vehicle. [Figure 3] This is a plan view of the work vehicle. [Figure 4] This is a plan view of the support mechanism. [Figure 5] This is a side view of the support mechanism. [Figure 6] This is a control block diagram. [Figure 7]It is a plan view of a work vehicle in a state where the directions of the traveling wheels are different from each other. [Figure 8] It is a flowchart showing control when stopped.

Embodiments for Carrying Out the Invention

[0017] Embodiments of the present invention will be described based on the drawings. In the following description, the direction of the arrow "FW" shown in the figure is "front", the direction of the arrow "BK" is "rear", the direction of the arrow "RH" is "right", the direction of the arrow "LH" is "left", the direction of the arrow "UP" is "up", and the direction of the arrow "DW" is "down".

[0018] As shown in FIGS. 1 to 3, the work vehicle includes a vehicle body 1 having a substantially rectangular shape in plan view, four traveling wheels 2, four auxiliary wheels 3, a support mechanism A, and four hydraulic motors 4. The vehicle body 1 supports the entire vehicle. The four traveling wheels 2 support the vehicle body 1. The four auxiliary wheels 3 are provided corresponding to each of the four traveling wheels 2. The support mechanism A supports the four traveling wheels 2 so that their positions can be changed with respect to the vehicle body 1. The hydraulic motor 4 drives the traveling wheel 2. The hydraulic motor 4 uses the supply and discharge of hydraulic oil as driving energy. By the four hydraulic motors 4, each of the four traveling wheels 2 is driven independently.

[0019] The traveling wheels 2 are located at the front and rear on both the left and right sides of the vehicle body 1. In the present embodiment, the work vehicle includes four traveling wheels 2 at the left front, right front, left rear, and right rear. The work vehicle also includes four support mechanisms A at the left front, right front, left rear, and right rear. The support mechanism A includes a folding link mechanism 5, four first hydraulic cylinders 6, and four second hydraulic cylinders 7. Each of the four first hydraulic cylinders 6 and the four second hydraulic cylinders 7 is a telescopic actuator for changing the position of the traveling wheel 2 with respect to the vehicle body 1, and is configured to be able to individually change the posture of the folding link mechanism 5.

[0020] The upper surface of the vehicle body 1 is provided with a flat loading area 8 on which cargo can be loaded. The loading area 8 is a roughly rectangular section in plan view and extends from the right end to the left end of the vehicle body 1. Cargo can be placed on the loading section 8. 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 items are placed.

[0021] The vehicle body 1, specifically the lower side of the loading section 8, is equipped with a hydraulic power source 9, multiple hydraulic control valves 12, an ECU 13 (Electronic Control Unit), a battery 11 for power supply, and the like. The hydraulic power source 9 supplies hydraulic fluid to the first hydraulic cylinder 6, the second hydraulic cylinder 7, and the hydraulic motor 4. Thus, the hydraulic power source 9 is configured to supply the driving energy necessary to operate the support mechanism A and the driving energy necessary to drive the four running wheels 2. The multiple hydraulic control valves 12 adjust the supply state of hydraulic fluid from the hydraulic power 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. The hydraulic power source 9 corresponds to the "drive source" of the present invention. The first hydraulic cylinder 6 and the second hydraulic cylinder 7 correspond to the "extension actuators" of the present invention. The hydraulic control valves 12 correspond to the "control valves" of the present invention.

[0022] The hydraulic power source 9 is supported by the underframe 10. The hydraulic power source 9 is equipped with an engine 9a, a hydraulic pump 9b, a hydraulic oil tank 9c, a radiator 9d, a fuel tank 9e, and the like. The hydraulic pump 9b is driven by the engine 9a. The fuel tank 9e is located at the rear of the vehicle body 1.

[0023] The ECU13 is equipped with a microcomputer and can perform various controls according to a control program. In this embodiment, the control device C is composed of a plurality of hydraulic control valves 12 and the ECU13. The engine 9a drives a generator (not shown). The electricity generated by the generator is then used to charge the battery 11.

[0024] A control unit 21 is provided at the rear of the loading section 8 in the vehicle body 1. The control unit 21 can be manually operated by an operator from outside the vehicle. The vehicle can be operated by the operator using the control unit 21. In addition to operation with the control unit 21, the vehicle can also be operated remotely using a wireless remote control device RC. The remote control device RC may be, for example, a proportional wireless transmitter, a smartphone, or a tablet computer. The control unit 21 and the remote control device RC are configured to output signals such as driving commands for the driving wheels 2, turning commands, and lifting commands for the articulating link mechanism 5, based on the operator's manual operation.

[0025] [Support mechanism] As described above, the support mechanism A comprises a bending link mechanism 5, a plurality of first hydraulic cylinders 6, and a plurality of second hydraulic cylinders 7. As shown in Figure 1, the four running wheels 2 are individually supported relative to the vehicle body 1 via the bending link mechanism 5 so as to be able to move up and down. In other words, the support mechanism A is supported by the vehicle body 1 and supports the four running wheels 2 so as to be able to change their position relative to the vehicle body 1.

[0026] As shown in Figures 4 and 5, the articulated link mechanism 5 is equipped with a base end 14, a first link 15, and a second link 16. The base end 14 is supported by the vehicle body 1. The upper end of the first link 15 is supported at the lower part of the base end 14 so as to be rotatable around the horizontal axis X1. One end of the second link 16 is supported at the lower end of the first link 15 so as to be rotatable around the horizontal axis X2. A support bracket 17 is connected to the other end of the second link 16. The running wheels 2 are supported by the support bracket 17.

[0027] A boss portion 18 is provided at the pivoting end of the second link 16. The support bracket 17 is supported by the boss portion 18 so as to be able to pivot around the vertical axis Y. A bracket 19 is provided at one end of the second link 16. An arm portion 17a is provided on the support bracket 17. A hydraulically driven slewing cylinder 20 is provided extending from the bracket 19 to the arm portion 17a.

[0028] The first hydraulic cylinder 6 is configured to change the swinging position of the first link 15 relative to the vehicle body 1. The second hydraulic cylinder 7 is also configured to change the swinging position of the second link 16 relative to the first link 15.

[0029] 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 running wheels 2 each oscillate together around the horizontal axis X1 while maintaining a constant relative posture. When the second hydraulic cylinder 7 extends or retracts while the first hydraulic cylinder 6 is stopped, the second link 16 and the running wheels 2 oscillate together around the horizontal axis X2 while maintaining a constant posture of the first link 15.

[0030] Auxiliary wheels 3 are rotatably supported at the intermediate bending sections of each of the multiple bending link mechanisms 5. The auxiliary wheels 3 have approximately the same outer diameter as the running wheels 2. The first link 15 and the second link 16 are pivotally connected by a support shaft. This support shaft protrudes outward in the width direction of the vehicle body. The auxiliary wheels 3 are rotatably supported at the protruding portion of this support shaft.

[0031] The direction of the running wheels 2 is changed by the extension and retraction of the swivel cylinder 20. In other words, the running wheels 2 are driven to rotate by the extension and retraction of the swivel cylinder 20. The swivel cylinder 20 is located on the left-right center side of the vehicle body 1 relative to the running wheels 2 that are to be rotated. When the swivel cylinder 20 extends and retracts, the running wheels 2 rotate around the vertical axis Y relative to the articulating link mechanism 5. This makes it possible to rotate the running wheels 2.

[0032] The running wheel 2 located lower on the front right side of the vehicle body 1 rotates clockwise when the slewing cylinder 20 extends and counterclockwise when the slewing cylinder 20 retracts. The running wheel 2 located lower on the front left side of the vehicle body 1 rotates counterclockwise when the slewing cylinder 20 extends and clockwise when the slewing cylinder 20 retracts. The running wheel 2 located lower on the rear right side of the vehicle body 1 rotates counterclockwise when the slewing cylinder 20 extends and clockwise when the slewing cylinder 20 retracts. The running wheel 2 located lower on the rear left side of the vehicle body 1 rotates clockwise when the slewing cylinder 20 extends and counterclockwise when the slewing cylinder 20 retracts. When the vehicle body 1 is moving straight or nearly straight, the stroke position of each of the four slewing cylinders 20 is set to a neutral stroke position between the extension stroke end and the retraction stroke end.

[0033] [Regarding the control configuration] The control configuration of this embodiment will be explained with reference to Figure 6. The ECU 13 controls the flow rate of hydraulic fluid in the hydraulic control valve 12. The hydraulic control valve 12 is configured to adjust the supply and discharge amounts of hydraulic fluid to each of the four hydraulic motors 4, four first hydraulic cylinders 6, four second hydraulic cylinders 7, and four slewing cylinders 20. As a result, the ECU 13 can control the rotational speed of the hydraulic motors 4, that is, the rotational speed of the running wheels 2.

[0034] This work vehicle is equipped with various sensors. Each of the four first hydraulic cylinders 6 and the four second hydraulic cylinders 7 is equipped with a stroke sensor S1. In addition, each of the four slewing cylinders 20 is equipped with a stroke sensor S2 capable of detecting the stroke position. The vehicle body 1 is equipped with a tilt sensor S3 capable of detecting its tilt state. Furthermore, a rotation sensor S4 capable of detecting the rotational speed of the running wheels 2 is provided near the running wheels 2. In addition, the hydraulic motor 4 is equipped with a pressure sensor S5 capable of detecting the pressure of the hydraulic fluid. The stroke sensor S1 corresponds to the "extension amount detection unit" of the present invention.

[0035] The stroke sensor S1 can detect the stroke positions of the four first hydraulic cylinders 6 and the four second hydraulic cylinders 7. The stroke position of the first hydraulic cylinders 6 corresponds to the detected value corresponding to the oscillation position of the first link 15. The stroke position of the second hydraulic cylinders 7 corresponds to the detected value corresponding 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.

[0036] The tilt sensor S3 is equipped with an inertial measuring device (IMU) with a well-known configuration. The IMU has a three-axis accelerometer and a gyro sensor, and can detect changes in the attitude of the vehicle body 1, specifically, tilt in the longitudinal and lateral directions. The tilt sensor S3 is configured to detect the tilt state of the loading section 8. The tilt sensor S3 corresponds to the "tilt detection unit" of the present invention.

[0037] The ECU 13 is connected to the operation detection unit 22. The operation detection unit 22 receives signals from the driving operation unit 21 and wireless signals from the wireless communication remote control device RC. The operation detection unit 22 is configured to detect human operation of the four running wheels 2 and the articulating link mechanism 5.

[0038] The ECU13 includes a non-volatile memory (not shown) for storing programs corresponding to the functional units described later, and a CPU (not shown) for executing said programs. The functions of each functional unit are realized when the program is executed by the CPU. The ECU13 includes, as functional units, an attitude control unit 100, a driving control unit 101, an inclination angle calculation unit 102, and the like.

[0039] The inclination angle calculation unit 102 calculates the inclination angle of the ground to which each of the four running wheels 2 makes contact, based on the detection information from the inclination sensor S3, the stroke positions of the four first hydraulic cylinders 6, and the stroke positions of the four second hydraulic cylinders 7. In other words, the control device C is configured to calculate the inclination angle of the ground to which the four running wheels 2 make contact.

[0040] The attitude control unit 100 can determine the swinging posture of the first link 15 relative to the vehicle body 1, the swinging posture of the second link 16 relative to the first link 15, etc., based on the values ​​detected by the stroke sensor S1. As a result, it is possible to calculate the height from the contact point of the running wheels 2 to the vehicle body 1. When the vehicle body is moving, the attitude control unit 100 performs horizontal control, controlling the operation of the support mechanism A so that the loading section 8 of the vehicle 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 operation of the four first hydraulic cylinders 6 and the four second hydraulic cylinders 7 so that the tilt angle in the longitudinal direction and the tilt angle in the lateral direction from the horizontal position of the vehicle body 1 are values ​​corresponding to the horizontal position, based on the detection information of the tilt sensor S3 and the detection information of the stroke sensor S1. In this way, the attitude control unit 100 of the control device C is configured to control the operation of the first hydraulic cylinders 6 and the second hydraulic cylinders 7 in the support mechanism A so that the loading section 8 is in a horizontal position, based on the tilt state of the vehicle body 1 (loading section 8) and the respective extension and contraction amounts of the first hydraulic cylinders 6 and the second hydraulic cylinders 7.

[0041] 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 travel wheels 2 reaches a target value, based on the rotational speed of the travel wheels 2 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 travel wheels 2 reaches a target value, based on the hydraulic fluid pressure detected by the pressure sensor S5. The hydraulic control valve 12 is configured to 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.

[0042] Furthermore, the travel control unit 101 is configured to change the direction of the travel wheels 2 based on the detected value of the stroke sensor S2. Specifically, the travel control unit 101 performs a switching operation of the hydraulic control valve 12 that supplies and discharges hydraulic fluid to the slewing cylinder 20. The travel control unit 101 is configured to control the direction of each of the four travel wheels 2 individually.

[0043] [Regarding control when the vehicle is stopped] When the vehicle body 1 comes to a stop, the travel control unit 101 controls the hydraulic control valve 12 to shut off the supply and discharge of hydraulic fluid to the hydraulic motor 4. When the supply and discharge of hydraulic fluid to the hydraulic motor 4 is shut off, the hydraulic motor 4 stops. At this time, the hydraulic fluid inside the hydraulic motor 4 stops flowing. As a result, the hydraulic motor 4 becomes unable to rotate, and the rotation of each of the four travel wheels 2 stops. In other words, the travel control unit 101 of the control device C does not supply driving energy to the four hydraulic motors 4, and consequently to the four travel wheels 2, while the four travel wheels 2 are stopped. Because the hydraulic control valve 12 is shut off, the inflow and outflow of hydraulic fluid inside the hydraulic motor 4 is impossible. As a result, each of the four travel wheels 2 is locked by the hydraulic fluid inside the hydraulic motor 4, and the vehicle body 1 can maintain its stopped state. Thus, the travel control unit 101 of the control device C is configured to stop the drive control of the hydraulic motor 4 by closing the hydraulic control valve 12 when the vehicle comes to a stop, thereby shutting off the supply and discharge of hydraulic fluid to the hydraulic motor 4.

[0044] However, the hydraulic fluid inside the hydraulic motor 4 may leak little by little from the hydraulic control valve 12 over time. In this case, each of the four running wheels 2 will no longer be able to maintain its locked state with the hydraulic fluid inside the hydraulic motor 4. Especially on slopes, if the hydraulic fluid inside the hydraulic motor 4 leaks, the weight of the work vehicle may cause each of the four running wheels 2 to gradually rotate, and the stopping position of the vehicle body 1 may not be maintained. To avoid such problems, in this embodiment, when the vehicle body 1 is stopped, the running control unit 101 is configured to make the orientation of each of the four running wheels 2 different from each other.

[0045] Specifically, as shown in Figure 7, when the vehicle body 1 is stopped, the orientation of each of the four running wheels 2 is changed. In other words, when the driving control unit 101 in the control device C stops the drive control of the running wheels 2, it makes all four running wheels 2 face different directions from each other.

[0046] In the example shown in Figure 7, of the two running wheels 2 located below the front of the vehicle body 1, the right running wheel 2 rotates counterclockwise, and the left running wheel 2 rotates clockwise. As a result, the front of each of the left and right running wheels 2 located below the front of the vehicle body 1 is positioned closer to the left-right center of the vehicle body 1 than the rear of each of the left and right running wheels 2.

[0047] Furthermore, of the two running wheels 2 located below the rear of the vehicle body 1, the right running wheel 2 rotates clockwise, and the left running wheel 2 rotates counterclockwise. As a result, the rear of each of the two running wheels 2 located below the rear of the vehicle body 1 is positioned closer to the left-right center of the vehicle body 1 than the front of each of the two running wheels 2.

[0048] The orientation of each of the four running wheels 2 is changed by the contraction of the slewing cylinder 20. The cap-side end of the slewing cylinder 20 is located towards the front-to-rear center of the vehicle body 1 relative to the rod-side end of the slewing cylinder 20. Therefore, when the driving control unit 101 stops the drive control of the driving wheels 2, it controls each of the four slewing cylinders 20 to operate toward the contracted side from the neutral stroke position. By this method, the driving control unit 101 of the control device C causes the orientation of each of the four driving wheels 2 to differ from that of the other, such that the ends of the driving wheels 2 that are located on the front-to-rear outer side relative to the vehicle body 1 are located closer to the left-to-right center of the vehicle body 1 than the ends of the driving wheels 2 that are located on the front-to-rear inner side relative to the vehicle body 1.

[0049] Thus, when the driving control unit 101 in the control device C stops the drive control of the driving wheels 2, it causes the direction of the driving wheels 2 located on one side and the driving wheels 2 located on the other side to be opposite to each other with respect to the neutral direction that allows the vehicle body 1 to move straight or nearly straight. Furthermore, when the driving control unit 101 in the control device C stops the drive control of the driving wheels 2, it causes the direction of the front and rear driving wheels 2 located on one side and the other side to be different from each other.

[0050] As a result, each of the four running wheels 2 acts a force on the other in a direction different from the direction of rotation, receiving a sideways sliding reaction force from the ground. In other words, when the four running wheels 2 try to roll, friction is generated between each of the running wheels 2 and the ground. This prevents each of the four running wheels 2 from rotating. This ensures that the stopping position of the work vehicle is maintained, for example, even when the work vehicle is stopped for a long period of time on a slope. Furthermore, when the vehicle body 1 performs a pivot turn, the running control unit 101 can quickly change the orientation of each of the four running wheels 2 to be aligned with the tangential direction on the same arc of a circle with the center of the vehicle body 1 as its core.

[0051] Based on the flowchart in Figure 8, the control when the vehicle body 1 stops will be explained. First, the ECU 13 determines whether the four driving wheels 2 have stopped (step #01). If the four driving wheels 2 have stopped (step #01: Yes), the ECU 13 determines whether the operation detection unit 22 has detected human operation from the driving operation unit 21 or the remote control device RC (step #02). If the operation detection unit 22 has not detected human operation (step #02: No), the ECU 13 counts on the timer and determines whether a preset time has elapsed since the operation detection unit 22 stopped detecting human operation (step #03). The determination in step #03 is repeated until the timer count time has elapsed to the preset time. Then, when the timer count time has elapsed to the preset time (step #03: Yes), the driving control unit 101 makes the direction of each of the four driving wheels 2 different from each other (step #04). In other words, the driving control unit 101 of the control device C, after a predetermined time has elapsed since the operation detection unit 22 stopped detecting human operation, causes one of the driving wheels 2 on the left and right sides to face different directions from the other driving wheel 2 on the left and right sides.

[0052] Once the processing in step #04 is complete, the ECU 13 determines whether the current location of the vehicle body 1 is on a slope or not based on the detection information from the tilt sensor S3 (step #05). Specifically, the ECU 13 determines whether the slope angle of the ground calculated by the slope angle calculation unit 102 is equal to or greater than a preset set slope angle. If the slope angle of the ground is equal to or greater than the set slope angle, the ECU 13 determines that the current location of the vehicle body 1 is on a slope. If the slope angle of the ground is less than the set slope angle, the ECU 13 determines that the current location of the vehicle body 1 is on flat land.

[0053] If the vehicle body 1 is currently on an incline (Step #05: Yes), the ECU 13 continues to control the attitude control unit 100 (Step #06) and prohibits stopping the drive of the hydraulic power source 9 (Step #07). When the control of the attitude control unit 100 stops on an incline, the hydraulic control valves 12 for the first hydraulic cylinder 6 and the second hydraulic cylinder 7 are closed, and the stroke positions of the first hydraulic cylinder 6 and the second hydraulic cylinder 7 are maintained. Therefore, immediately after the control of the attitude control unit 100 stops, the horizontal state of the loading section 8 is maintained. However, as time passes, the hydraulic fluid inside the first hydraulic cylinder 6 and the second hydraulic cylinder 7 leaks from the hydraulic control valves 12. When this happens, the bending link mechanism 5 gradually descends due to the weight of the loading section 8, and the loading section 8 gradually tilts along the incline, and the horizontal state of the loading section 8 is no longer maintained. To avoid such inconveniences, if the vehicle body 1 is currently on an incline, the control of the attitude control unit 100 is continued, and the drive of the hydraulic power source 9 is also continued. In other words, the attitude control unit 100 of the control device C is configured to continue controlling the operation of the first hydraulic cylinder 6 and the second hydraulic cylinder 7 when the ground is inclined at or above a set incline angle while the four running wheels 2 are stopped. As a result, even if the running wheels 2 stop on an incline, the horizontal state of the loading section 8 is maintained.

[0054] If the current location of the vehicle body 1 is not on a slope (Step #05: No), then the current location of the vehicle body 1 is on flat ground. Therefore, the ECU 13 stops controlling the attitude control unit 100 (Step #08) and allows the hydraulic power source 9 to stop driving (Step #09). As described above, over time, the hydraulic fluid inside the first hydraulic cylinder 6 and the second hydraulic cylinder 7 leaks from the hydraulic control valve 12. Nevertheless, because the ground is flat, each of the multiple bending link mechanisms 5 descends almost evenly, and the horizontal state of the loading section 8 is maintained. Therefore, if the current location of the vehicle body 1 is on flat ground, stopping the control of the attitude control unit 100 and stopping the driving of the hydraulic power source 9 is permitted. This makes it possible to reduce running costs compared to a configuration in which the attitude control unit 100 of the control device C continues to control the operation of the support mechanism A on flat ground. In other words, the attitude control unit 100 of the control device C is configured not to control the operation of the first hydraulic cylinder 6 and the second hydraulic cylinder 7 when the four running wheels 2 are stopped and the ground is inclined within the range of the set inclination angle.

[0055] Thus, the control device C is configured not to control the operation of the support mechanism A and to allow the hydraulic power source 9 to stop when the ground is inclined within a preset range of inclination angles while the four travel wheels 2 are stopped. On the other hand, the control device C is configured to continue controlling the operation of the support mechanism A and to prohibit the stopping of the hydraulic power source 9 when the ground is inclined beyond the set inclination angle while the four travel wheels 2 are stopped.

[0056] [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.

[0057] (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 11, or an electric motor driven by the battery 11.

[0058] (2) In the above-described embodiment, the first hydraulic cylinder 6 and the second hydraulic cylinder 7 were shown as the telescopic actuators. The embodiment is not limited to this, and for example, the telescopic actuator may be a pneumatic actuator or an electric actuator.

[0059] (3) Support mechanism A may be a mechanism comprising one link or three or more links. For example, support mechanism A may be equipped with an electric actuator as a device for changing the posture.

[0060] (4) The running wheels 2 may be driven by an electric motor instead of a hydraulic motor 4, or they may be driven by an engine or the like via a drive mechanism.

[0061] (5) In the above-described embodiment, the support mechanism A is provided with a bending link mechanism 5. The embodiment is not limited to this one, and for example, the support mechanism A may be provided with a sliding mechanism that can move up and down instead of the bending link mechanism 5.

[0062] (6) In the above-described embodiment, a tilt sensor S3 is provided as the tilt detection unit. The embodiment is not limited to this, and for example, the tilt detection unit may be a mechanical pendulum type sensor or a magnetic sensor.

[0063] (7) In the above-described embodiment, the control device C permits the hydraulic power source 9 to stop driving when the ground is inclined within the range of the set inclination angle while the multiple driving wheels 2 are stopped. Even in this case, the hydraulic power source 9 may be configured not to stop.

[0064] (8) In the above-described embodiment, the control device C does not supply driving energy to the multiple running wheels 2 when the multiple running wheels 2 are stopped. The embodiment is not limited to this, and for example, the control device C may be configured to supply driving energy to each of the hydraulic motors 4 that drive the multiple running wheels 2 in order to maintain the stopping torque when the multiple running wheels 2 are stopped.

[0065] (9) In the above embodiment, the ECU 13 determines whether the angle of inclination of the ground calculated by the inclination angle calculation unit 102 is equal to or greater than a preset set inclination angle. If the angle of inclination of the ground is equal to or greater than the set inclination angle, the ECU 13 determines that the current location of the vehicle body 1 is on a slope. The embodiment is not limited to this one, and "equal to or greater than the set inclination angle" means an inclination angle greater than the set inclination angle, excluding the set inclination angle itself. The ECU 13 may also be configured to determine that the current location of the vehicle body 1 is on flat land rather than on a slope if the angle of inclination of the ground is equal to the set inclination angle.

[0066] 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]

[0067] The present invention is applicable to a work vehicle having multiple independently steerable wheels. [Explanation of symbols]

[0068] 1: Vehicle body 2: Running wheels 4: Hydraulic motor 6: First hydraulic cylinder (extension actuator) 7: Second hydraulic cylinder (extension actuator) 8: Loading section 9: Hydraulic power source (drive source) 12: Hydraulic control valve (control valve) A: Support mechanism C: Control device S1: Stroke sensor (extension amount detection unit) S3: Tilt sensor (tilt detection unit)

Claims

1. A vehicle body having a loading section capable of loading cargo, Multiple running wheels located at the front and rear on both the left and right sides of the vehicle body, A support mechanism that is supported by the vehicle body and supports the plurality of running wheels so that their positions can be changed relative to the vehicle body, A tilt detection unit for detecting the tilt state of the vehicle body, A control device capable of controlling the operation of the support mechanism so that the loading section is in a horizontal position based on the inclination state of the vehicle body, The system includes a drive source that supplies driving energy to operate the support mechanism, The control device is The system is configured to calculate the inclination angle of the ground in which the plurality of running wheels make contact, and to not control the operation of the support mechanism when the ground is inclined within a preset range of inclination angles while the plurality of running wheels are stopped, and to continue controlling the operation of the support mechanism when the ground is inclined at or above the preset inclination angle while the plurality of running wheels are stopped. A work vehicle configured to allow the deactivation of the drive source when the ground is inclined within the range of the set inclination angle while the plurality of running wheels are stopped, and to prohibit the deactivation of the drive source when the ground is inclined at or above the set inclination angle while the plurality of running wheels are stopped.

2. The drive source is configured to supply the drive energy to the plurality of wheels, The work vehicle according to claim 1, wherein the control device does not supply the driving energy to the plurality of driving wheels when the plurality of driving wheels are stopped.

3. A hydraulic motor drives each of the plurality of travel wheels by supplying and discharging the hydraulic fluid that receives the aforementioned driving energy, The system is equipped with a control valve capable of changing the amount of hydraulic fluid supplied to and discharged from the hydraulic motor, The work vehicle according to claim 2, wherein the control device is configured to stop the plurality of running wheels by closing the control valve and blocking the supply and discharge of the hydraulic fluid to the hydraulic motor.

4. The support mechanism includes a plurality of telescopic actuators for changing the position of the running wheels relative to the vehicle body, The system includes an extension amount detection unit that detects the extension amount of each of the plurality of extension actuators, The control device is configured to control the operation of each of the multiple telescopic actuators so that the loading section is in a horizontal position, based on the inclination state of the vehicle body and the amount of extension or retraction of each of the multiple telescopic actuators. The work vehicle according to any one of claims 1 to 3, wherein the control device is configured to not control the operation of each of the multiple telescopic actuators when the ground is inclined within the range of the set inclination angle while the multiple travel wheels are stopped, and to continue controlling the operation of each of the multiple telescopic actuators when the ground is inclined at or above the set inclination angle while the multiple travel wheels are stopped.

Images