JP7829468B2 - Work vehicle - Google Patents

Description

This invention relates to a work vehicle having multiple independently steerable wheels.

For example, the work vehicle disclosed in Patent Document 1 includes a vehicle body having a loading section capable of carrying cargo, multiple running wheels 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 "bending link mechanism" in the document) that supports the multiple running wheels so as to be able to change their position relative to the vehicle body. The control device controls the support mechanism to maintain the loading section in a horizontal position.

Japanese Patent Publication No. 2020-1443

Incidentally, when the work vehicle stops, the operation of the running gear also stops, and the operation of the support mechanism also stops. At this time, if the work vehicle stops on a slope, there is a risk that the horizontal position of the mounting section may not be properly maintained due to the stopping of the support mechanism. Therefore, a configuration that keeps the support mechanism constantly operating could be considered, but keeping the support mechanism constantly operating is disadvantageous in terms of running costs.

The objective of this invention is to provide a work vehicle capable of appropriately maintaining the horizontal position of the mounting section.

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 changing the position of the plurality of running wheels 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 tilt state of the vehicle body, and a drive source for supplying driving energy to operate the support mechanism , wherein the control device is configured to calculate the tilt angle of the ground to which the plurality of running wheels make contact. Furthermore, the system is configured such that the operation of the support mechanism is not controlled when the ground is inclined within a preset range of inclination angles while the plurality of running wheels are stopped, and the operation of the support mechanism is continuously controlled when the ground is inclined at or above the preset inclination angle while the plurality of running wheels are stopped, and the system is configured such that the deactivation of the drive source is permitted when the ground is inclined within the preset range of inclination angles while the plurality of running wheels are stopped, and the deactivation of the drive source is prohibited when the ground is inclined at or above the preset inclination angle while the plurality of running wheels are stopped .

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" excludes the set tilt angle, then "greater than or equal to the set tilt angle" may include the set tilt angle.

Furthermore, 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 will no longer be able to continue controlling 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 will prevent the drive source from stopping. Therefore, the control device can reliably control the operation of the support mechanism.

In this invention, the drive source is configured to supply the driving energy to the plurality of wheels, and the control device preferably refrains from supplying the driving energy to the plurality of wheels when they are stopped.

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.

In this invention, the system preferably includes a hydraulic motor that drives each of the plurality of travel wheels by supplying and discharging hydraulic fluid that receives the driving energy, and a control valve capable of changing the amount of hydraulic fluid supplied and discharged to the hydraulic motor. The control device is preferably configured to stop the plurality of travel wheels by closing the control valve and interrupting the supply and discharge of hydraulic fluid to the hydraulic motor.

In this configuration, multiple wheels are driven by hydraulics. Therefore, if the supply and discharge of hydraulic fluid to the hydraulic motor is interrupted, the wheels stop, and if the hydraulic fluid inside the hydraulic motor stops flowing, the rotation of the hydraulic motor locks. At this time, the hydraulic motor functions as a brake on the wheels.

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. 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. Preferably, 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 while 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 beyond the set inclination angle while the plurality of running wheels are stopped.

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, compared to a configuration where the telescopic actuator stops operating, the horizontal position of the mounting section is properly maintained. Furthermore, if the ground slope is within the set inclination angle range, the ground is generally horizontal, making it easier to maintain a horizontal position compared to when the ground is sloped. Therefore, when 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 where the control device continues to control the operation of the telescopic actuator on flat ground.

Side view of the work vehicle. Rear view of the work vehicle. This is a plan view of the work vehicle. This is a plan view of the support mechanism. This is a side view of the support mechanism. This is a control block diagram. This is a plan view of a work vehicle with its wheels facing opposite directions. This is a flowchart illustrating the control system when the vehicle is stopped.

Embodiments of the present invention will be described based on the drawings. In the following description, the direction of the arrow "FW" in the drawings will be considered "forward," the direction of the arrow "BK" will be considered "backward," the direction of the arrow "RH" will be considered "right," the direction of the arrow "LH" will be considered "left," the direction of the arrow "UP" will be considered "up," and the direction of the arrow "DW" will be considered "down."

As shown in Figures 1 to 3, the work vehicle is equipped with a vehicle body 1 that is roughly rectangular in plan view, four running 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 running wheels 2 support the vehicle body 1. The four auxiliary wheels 3 are provided corresponding to each of the four running wheels 2. The support mechanism A supports the four running wheels 2 so that their positions can be changed relative to the vehicle body 1. The hydraulic motors 4 drive the running wheels 2. The hydraulic motors 4 use the supply and discharge of hydraulic fluid as driving energy. Each of the four running wheels 2 is driven independently by the four hydraulic motors 4.

The running wheels 2 are located at the front and rear on both the left and right sides of the vehicle body 1. In this embodiment, the work vehicle has four running wheels 2: left front, right front, left rear, and right rear. The work vehicle also has four support mechanisms A: left front, right front, left rear, and right rear. Each support mechanism A comprises a bending 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 an extendable/retractable actuator for changing the position of the running wheels 2 relative to the vehicle body 1, and is configured to allow individual changes in the posture of the bending link mechanism 5.

The upper surface of the vehicle body 1 is provided with a flat loading area 8 on which luggage 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.

The vehicle body 1, located below the loading section 8, is equipped with a hydraulic supply source 9, multiple hydraulic control valves 12, an ECU 13 (Electronic Control Unit), a battery 11 for power supply, and other components. The hydraulic supply source 9 supplies hydraulic fluid to the first hydraulic cylinder 6, the second hydraulic cylinder 7, and the hydraulic motor 4. Thus, the hydraulic supply 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 wheels 2. The multiple 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. The hydraulic supply source 9 corresponds to the "drive source" in this invention. The first hydraulic cylinder 6 and the second hydraulic cylinder 7 correspond to the "extension actuators" in this invention. The hydraulic control valves 12 correspond to the "control valves" in this invention.

The hydraulic power source 9 is supported by the underframe 10. The hydraulic power source 9 includes an engine 9a, a hydraulic pump 9b, a hydraulic oil tank 9c, a radiator 9d, a fuel tank 9e, and other components. The hydraulic pump 9b is driven by the engine 9a. The fuel tank 9e is located at the rear of the vehicle body 1.

The ECU 13 is equipped with a microcomputer and can perform various controls according to the control program. In this embodiment, the control device C is composed of multiple hydraulic control valves 12 and the ECU 13. The engine 9a drives a generator (not shown). The electricity generated by the generator is then used to charge the battery 11.

A control unit 21 is located at the rear of the loading section 8 on the vehicle body 1. The control unit 21 can be manually operated by an operator from outside the vehicle. Vehicle operation can be performed by the operator's control of the control unit 21. In addition to operation of the control unit 21, vehicle operation can also be performed 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. Both 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.

[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.

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.

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 pivotable 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.

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.

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 integrally around the horizontal axis X1 while maintaining a constant relative position. 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 integrally around the horizontal axis X2 while maintaining a constant position for the first link 15.

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.

The direction of the running wheel 2 is changed by the extension and retraction of the swivel cylinder 20. In other words, the running wheel 2 is driven to rotate by the extension and retraction of the swivel cylinder 20. The swivel cylinder 20 is positioned on the left-right center side of the vehicle body 1 relative to the running wheel 2 that is to be rotated. When the swivel cylinder 20 extends and retracts, the running wheel 2 rotates around the vertical axis Y relative to the articulating link mechanism 5. This enables the rotation of the running wheel 2.

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

[Regarding the control configuration]
The control configuration of this embodiment will be explained based on 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 amount 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 travel wheels 2.

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.

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 of the oscillation position of the first link 15. The stroke position of the second hydraulic cylinders 7 corresponds to the detected value of the oscillation position of the second link 16. In other words, the stroke sensor S1 detects the extension and contraction amounts of the first hydraulic cylinders 6 and the second hydraulic cylinders 7, respectively.

The tilt sensor S3 is equipped with an inertial measurement unit (IMU) with a well-known configuration. The IMU has a three-axis accelerometer and a gyro sensor, and can detect changes in the vehicle body 1's attitude, 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.

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 intervention on the four running wheels 2 and the articulating link mechanism 5.

The ECU 13 includes a non-volatile memory (not shown) for storing programs corresponding to the functional units described later, and a CPU (not shown) for executing those programs. The functions of each functional unit are realized when the program is executed by the CPU. The ECU 13 includes, as functional units, an attitude control unit 100, a driving control unit 101, an inclination angle calculation unit 102, and the like.

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.

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 front-rear direction and the tilt angle in the left-right 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.

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. Furthermore, the travel control unit 101 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.

Furthermore, the travel control unit 101 is configured to change the direction of the travel wheels 2 based on the detection 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 swivel cylinder 20. The travel control unit 101 is configured to control the direction of each of the four travel wheels 2 individually.

[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.

However, the hydraulic fluid inside the hydraulic motor 4 may leak gradually 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, potentially preventing the vehicle body 1 from maintaining its stopping position. To avoid this problem, 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.

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 causes all four running wheels 2 to have different orientations from each other.

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, while the left running wheel 2 rotates clockwise. Therefore, the front of each of the two running wheels 2 located below the front of the vehicle body 1 is positioned closer to the center of the vehicle body 1 than the rear of each of the two running wheels 2.

Furthermore, of the two running wheels 2 located below the rear of the vehicle body 1, the right running wheel 2 rotates clockwise, while the left running wheel 2 rotates counterclockwise. Therefore, the rear of each of the two running wheels 2 located below the rear of the vehicle body 1 is positioned closer to the center of the vehicle body 1 than the front of each running wheel 2.

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.

Thus, when the driving control unit 101 in the control device C stops the drive control of the driving wheels 2, it causes the orientation 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 orientation 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 orientation of the front and rear driving wheels 2 located on one side and the other side to be different from each other.

As a result, each of the four running wheels 2 acts on the other in a direction opposite to its rotational direction, receiving a sideways sliding reaction force from the ground. In other words, when the four running wheels 2 attempt to roll, friction is generated between each wheel 2 and the ground. This prevents each of the four running wheels 2 from rotating. Therefore, even if the work vehicle is stopped for a long period of time on a slope, for example, the stopping position of the work vehicle is maintained. 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 align with the tangential direction of the same arc of a circle with the center of the vehicle body 1 as its core.

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 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 control unit 101 of the control device C, after a predetermined time has elapsed since the operation detection unit 22 stopped detecting human operation, will cause one of the left and right running wheels 2 to face a different direction from the other.

Once step #04 is complete, the ECU 13 determines, based on the detection information from the tilt sensor S3, whether the vehicle body 1 is currently located on a slope (step #05). Specifically, the ECU 13 determines whether the slope angle of the ground calculated by the tilt angle calculation unit 102 is greater than or equal to a preset set slope angle. If the slope angle of the ground is greater than or equal to the set slope angle, the ECU 13 determines that the vehicle body 1 is currently located on a slope. If the slope angle of the ground is less than the set slope angle, the ECU 13 determines that the vehicle body 1 is currently located on flat land.

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 supply 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 and the operation of the hydraulic power source 9 are 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. This ensures that the loading section 8 remains horizontal even when the running wheels 2 are stopped on an incline.

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 supply 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. However, since the ground is flat, each of the multiple articulated link mechanisms 5 descends approximately 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 supply 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 set inclination angle range.

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 inclination angle range 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 preset inclination angle while the four travel wheels 2 are stopped.

[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.

(1) In the above-described embodiment, the hydraulic supply source 9 is shown as the drive source. However, the embodiment is not limited to this one; for example, the drive source may be an engine 9a, a battery 11, or an electric motor driven by the battery 11.

(2) In the above-described embodiment, the first hydraulic cylinder 6 and the second hydraulic cylinder 7 were shown as the telescopic actuators. However, the embodiment is not limited to this one; for example, the telescopic actuators may be pneumatic actuators or electric actuators.

(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.

(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.

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

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

(7) In the above-described embodiment, the control device C permits the deactivation of the hydraulic power supply 9 when the ground is inclined within the set inclination angle range while the multiple travel wheels 2 are stopped. Even in this case, the hydraulic power supply 9 may not be deactivated.

(8) In the above-described embodiment, the control device C does not supply driving energy to the multiple travel wheels 2 when they are stopped. This embodiment is not limited to this one; for example, the control device C may be configured to supply driving energy to each of the hydraulic motors 4 that drive the multiple travel wheels 2 to maintain the stopping torque when the multiple travel wheels 2 are stopped.

(9) In the above embodiment, the ECU 13 determines whether the ground inclination angle calculated by the inclination angle calculation unit 102 is equal to or greater than a preset set inclination angle. If the ground inclination angle 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. This embodiment is not limited to this one; "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. Furthermore, if the ground inclination angle is equal to the set inclination angle, the ECU 13 may determine that the current location of the vehicle body 1 is on flat land rather than on a slope.

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.

This invention is applicable to work vehicles having multiple independently steerable wheels.

1: Vehicle body 2: Driving 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 (4)

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 . 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. 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. 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.