JP2024077989A - Work vehicle - Google Patents

Abstract

To provide a work vehicle which can keep a stop position of the work vehicle for a long time in a simple structure.SOLUTION: A work vehicle comprises: a vehicle body 1 with a loading part that can load a cargo; a plurality of traveling wheels 2 which are respectively arranged at a front and rear sides in both right and left sides of the vehicle body 1 to be operable respectively; a steering angle detection part which respectively detects directions of the plurality of the traveling wheels 2; and a controller which can perform drive control respectively driving the plurality of the traveling wheels 2 and direction control respectively changing directions of the plurality of the traveling wheels 2. The controller differentiates, when stopping the drive control, the direction of a first traveling wheel positioned at one side of right and left sides of the vehicle body among the plurality of the traveling wheels 2 from the direction of a second traveling wheel positioned at the other side of the right and left sides of the vehicle body among the plurality of the traveling wheels 2.SELECTED DRAWING: Figure 7

Description

The present invention relates to a work vehicle having multiple running wheels that can be steered separately.

For example, the work vehicle disclosed in Patent Document 1 is equipped with multiple running wheels, which are driven and controlled by a control device. In addition, the multiple running wheels are configured so that they can be steered separately by a turning mechanism.

JP 2020-1443 A

When a work vehicle stops, it is important that the vehicle maintains its stopped position. For this reason, the running wheels are generally equipped with a braking mechanism. However, if the work vehicle remains stopped for an extended period of time, the braking force of the brakes will decrease over time, and the vehicle may not maintain its stopped position for an extended period of time. For this reason, if the work vehicle is stopped for an extended period of time on a slope, for example, it is possible that the work vehicle will gradually move down the slope over time. One way to avoid this inconvenience is to install a mechanical parking brake on the work vehicle. However, installing such a parking brake would increase costs due to the increased number of parts.

The object of the present invention is to provide a work vehicle that can maintain its stopped position for a long period of time with a simple configuration.

The work vehicle of the present invention is equipped with a vehicle body having a loading section capable of loading cargo, a plurality of running wheels located at the front and rear of both the left and right sides of the vehicle body and capable of steering independently, a steering angle detection unit that detects the orientation of each of the plurality of running wheels, and a control device capable of controlling the drive control of each of the plurality of running wheels and the control of changing the orientation of each of the plurality of running wheels independently, and when the drive control is stopped, the control device changes the orientation of each of the plurality of running wheels, the first running wheel located on one side of the vehicle body and the second running wheel located on the other side of the vehicle body, to be different from each other.

According to the present invention, the control device makes the orientation of the first running wheel located on one of the left and right running wheels and the second running wheel located on the other of the left and right running wheels different from each other. When the orientations of the left and right running wheels are different from each other, the rolling direction of one of the left and right running wheels and the rolling direction of the other of the left and right running wheels are different. As a result, the left and right running wheels act on each other in directions different from the rotation direction, and receive a reaction force in the lateral slip direction from the ground. In other words, when the running wheels try to roll, friction occurs between the running wheels and the ground. As a result, the left and right running wheels do not rotate. As a result, 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 without the need for a dedicated parking brake. As a result, a work vehicle that can maintain the stopping position of the work vehicle for a long period of time with a simple configuration is realized.

In the present invention, when the control device stops the drive control, it is preferable that the direction of each of the first running wheel and the second running wheel is made to be different so that they are opposite to each other with respect to the neutral direction in which the vehicle body moves straight or approximately straight.

With this configuration, the left and right running wheels exert forces in opposite directions on each other with respect to the straight-ahead direction of the vehicle body. As a result, each of the left and right running wheels receives a reaction force from the ground in the direction of skidding, and stops rotating.

In the present invention, it is preferable that the control device causes the orientations of all of the plurality of running wheels to differ from one another when the drive control is stopped.

This configuration ensures that the work vehicle's stopped position is maintained reliably every time the control device stops drive control. In addition, the configuration in which all of the multiple running wheels are oriented in different directions creates strong friction between the running wheels and the ground. This ensures that the work vehicle's stopped position is firmly maintained.

In the present invention, it is preferable that a tilt detection unit is provided that detects the tilt state of the vehicle body, and the control device differentiates the orientation of the first running wheel located on the low ground side on one of the left and right sides among the plurality of running wheels, and the second running wheel located on the low ground side on the other of the left and right sides among the plurality of running wheels, based on the tilt state of the vehicle body.

With this configuration, the first and second running wheels are both positioned on the low ground side, so they each firmly support the weight of the vehicle body. This increases the friction between the running wheels and the ground, and the work vehicle is firmly held in its stopped position.

In the present invention, an operation detection unit is provided that detects manual operation of the plurality of running wheels, and the control device preferably causes the respective orientations of the first running wheel and the second running wheel to differ from each other when a preset time has elapsed since the operation detection unit stopped detecting the manual operation.

This configuration ensures that the vehicle remains in the stopped position whenever the operation detection unit no longer detects manual operation.

In the present invention, a support mechanism that is supported by the vehicle body and supports the multiple running wheels in a position changeable manner relative to the vehicle body, a hydraulic motor that uses the supply and discharge of hydraulic oil as driving energy to drive each of the multiple running wheels, a control valve that can change the amount of hydraulic oil supplied and discharged to the hydraulic motor, and a tilt detection unit that detects the tilt state of the loading unit are provided, and the control device is preferably configured to be able to control the operation of the support mechanism so that the loading unit is in a horizontal position based on the tilt state of the loading unit, and is configured to close the control valve when the vehicle is stopped to stop the drive control by cutting off the supply and discharge of the hydraulic oil to the hydraulic motor.

According to this configuration, the loading section is configured to be able to maintain a horizontal position based on the operation of the support mechanism. In addition, the multiple traveling wheels are driven by hydraulic pressure. Therefore, when the supply and discharge of hydraulic oil to the hydraulic motor is cut off, the traveling wheels stop, and when hydraulic oil 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 for the traveling wheels. However, there may be cases where hydraulic oil leaks from the hydraulic motor, in which case the hydraulic motor will no longer function as a brake. Even in such a case, the stopped position of the work vehicle is firmly maintained by a configuration in which the first traveling wheel and the second traveling wheel are oriented in different directions.

FIG. FIG. FIG. FIG. FIG. FIG. FIG. 2 is a plan view of a work vehicle with traveling wheels facing in different directions. FIG. 11 is a flowchart showing control when the vehicle is stopped.

An embodiment of the present invention will be described with reference to the drawings. In the following description, the direction of the arrow "FW" shown in the drawings will be defined as "forward", the direction of the arrow "BK" as "backward", the direction of the arrow "RH" as "right", the direction of the arrow "LH" as "left", the direction of the arrow "UP" as "up", and the direction of the arrow "DW" as "down".

As shown in Figures 1 to 3, the work vehicle is equipped with a vehicle body 1 having a substantially rectangular shape in a 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 motor 4 drives the running wheels 2. The hydraulic motor 4 uses the supply and discharge of hydraulic oil as driving energy. Each of the four running wheels 2 is independently driven by the four hydraulic motors 4. The running wheel 2 located on either the left or right side corresponds to the "first running wheel" of the present invention. The running wheel 2 located on either the left or right side corresponds to the "second running wheel" of the present invention.

The running wheels 2 are located at the front and rear of both the left and right sides of the vehicle body 1. In this embodiment, the work vehicle has four running wheels 2, located at the left front, right front, left rear, and right rear. The work vehicle also has four support mechanisms A, located at the left front, right front, left rear, and right rear. The support mechanisms A include 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 expandable actuator for changing the position of the running wheels 2 relative to the vehicle body 1, and is configured to be able to individually change the attitude of the bending link mechanism 5.

The top surface of the vehicle body 1 is provided with a flat loading section 8 on which luggage can be loaded. The loading section 8 is a roughly rectangular section in a plan view, and extends from the right end to the left end of the vehicle body 1. Luggage can be placed on the loading section 8. Examples of luggage that can be placed on the loading section 8 include agricultural equipment, agricultural supplies such as fertilizer and chemicals, harvested crops and harvest baskets, and pallets on which these are placed.

In the vehicle body 1, below the loading section 8, there are provided a hydraulic supply source 9, multiple hydraulic control valves 12, an ECU 13 (Electronic Control Unit), a battery 11 for power supply, and the like. The hydraulic supply source 9 sends hydraulic oil toward the first hydraulic cylinder 6, the second hydraulic cylinder 7, and the hydraulic motor 4. Thus, the hydraulic supply source 9 is configured to be able to supply driving energy for operating the support mechanism A and driving energy for driving the four traveling wheels 2. The multiple hydraulic control valves 12 adjust the supply state of hydraulic oil from the hydraulic supply source 9. The hydraulic control valve 12 may be a proportional valve or a solenoid valve of a PWM control type. The ECU 13 controls the operation of the hydraulic control valve 12. The hydraulic control valve 12 corresponds to the "control valve" of the present invention.

The hydraulic supply source 9 is supported by the underframe 10. The hydraulic supply source 9 is equipped with an engine 9a, a hydraulic pump 9b, a hydraulic oil tank 9c, a radiator 9d, a fuel tank 9e, etc. 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 is capable of executing various controls according to a control program. In this embodiment, the control device C is composed of multiple hydraulic control valves 12 and the ECU 13. A generator (not shown) is driven by the power of the engine 9a. The electricity generated by the generator is then charged into the battery 11.

The driving operation unit 21 is provided behind the loading section 8 of the vehicle body 1. The driving operation unit 21 can be manually operated by an operator from outside the vehicle. The vehicle can be driven by the operator operating the driving operation unit 21. In addition to operating the driving operation unit 21, the vehicle can also be driven by remote control using a wireless remote control device RC. The remote control device RC can be, for example, a proportional wireless transmitter, a smartphone, or a tablet computer. Each of the driving operation unit 21 and the remote control device RC is configured to be able to output driving command signals and turning command signals for the traveling wheels 2, lifting and lowering command signals for the bending link mechanism 5, etc., based on the operator's manual operation.

[Support mechanism]
As described above, the support mechanism A includes the bending link mechanism 5, a plurality of first hydraulic cylinders 6, and a plurality of second hydraulic cylinders 7. As shown in Fig. 1, the four traveling wheels 2 are supported so as to be able to rise and fall individually with respect to the vehicle body 1 via the bending link mechanism 5. In other words, the support mechanism A is supported by the vehicle body 1 and supports the four traveling wheels 2 so as to be able to change their positions with respect to the vehicle body 1.

As shown in Figures 4 and 5, the bending link mechanism 5 is provided 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 about 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 about the horizontal axis X2. In addition, a support bracket 17 is connected to the other end of the second link 16. The running wheel 2 is supported by the support bracket 17.

A boss portion 18 is provided at the swing end of the second link 16. The support bracket 17 is supported by the boss portion 18 so that it can swing 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 swivel cylinder 20 is provided between the bracket 19 and the arm portion 17a.

The first hydraulic cylinder 6 is configured to be able to change the swinging position of the first link 15 relative to the vehicle body 1. The second hydraulic cylinder 7 is configured to be able to change the swinging position of the second link 16 relative to the first link 15.

When the first hydraulic cylinder 6 expands and contracts with the second hydraulic cylinder 7 stopped operating, the first link 15, the second link 16, and the running wheel 2 all swing together around the horizontal axis X1 while maintaining a constant relative posture. When the second hydraulic cylinder 7 expands and contracts with the first hydraulic cylinder 6 stopped operating, the second link 16 and the running wheel 2 all swing together around the horizontal axis X2 while maintaining a constant posture of the first link 15.

The auxiliary wheels 3 are rotatably supported at the intermediate bent portions of each of the multiple bent link mechanisms 5. The auxiliary wheels 3 are wheels with 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. The support shaft protrudes outward in the vehicle body width direction. The auxiliary wheels 3 are rotatably supported at the protruding portion of the support shaft.

The orientation 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 turn by the extension and retraction of the swivel cylinder 20. The swivel cylinder 20 is disposed on the left-right central side of the vehicle body 1 relative to the running wheels 2 to be turned. When the swivel cylinder 20 extends and retracts, the running wheels 2 rotate around the vertical axis Y relative to the bending link mechanism 5. This allows the running wheels 2 to be turned.

The running wheels 2 located at the lower front right part of the vehicle body 1 rotate clockwise by the extension of the swivel cylinder 20, and rotate counterclockwise by the contraction of the swivel cylinder 20. The running wheels 2 located at the lower front left part of the vehicle body 1 rotate counterclockwise by the extension of the swivel cylinder 20, and rotate clockwise by the contraction of the swivel cylinder 20. The running wheels 2 located at the lower rear right part of the vehicle body 1 rotate counterclockwise by the extension of the swivel cylinder 20, and rotate clockwise by the contraction of the swivel cylinder 20. The running wheels 2 located at the lower rear left part of the vehicle body 1 rotate clockwise by the extension of the swivel cylinder 20, and rotate counterclockwise by the contraction of the swivel cylinder 20. When the vehicle body 1 moves straight or approximately straight, the stroke positions of each of the four swivel cylinders 20 are located at a neutral stroke position preset between the stroke end on the extension side and the stroke end on the contraction side.

[Regarding control configuration]
The control configuration of this embodiment will be described with reference to Fig. 6. The ECU 13 controls the adjustment of the flow rate of hydraulic oil in the hydraulic control valve 12. The hydraulic control valve 12 is configured to be able to adjust the supply and discharge amount of hydraulic oil to each of the four hydraulic motors 4, the four first hydraulic cylinders 6, the four second hydraulic cylinders 7, and the four swing cylinders 20. This allows the ECU 13 to control the rotation speed of the hydraulic motors 4, i.e., the rotation speed of the traveling 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. Each of the four slewing cylinders 20 is equipped with a stroke sensor S2 capable of detecting the stroke position. A tilt sensor S3 capable of detecting the tilt state of the vehicle body 1 is equipped. Furthermore, a rotation sensor S4 capable of detecting the rotation speed of the running wheels 2 is equipped 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 oil. The stroke sensor S2 corresponds to the "steering angle detection unit" of this 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 is a detection value corresponding to the swing position of the first link 15. The stroke position of the second hydraulic cylinders 7 is a detection value corresponding to the swing position of the second link 16. In other words, the stroke sensor S1 detects the amount of expansion and contraction of each of the first hydraulic cylinders 6 and the second hydraulic cylinders 7.

The tilt sensor S3 is equipped with an inertial measurement unit (IMU) of well-known configuration. The IMU has a three-axis acceleration sensor and a gyro sensor, and can detect changes in the attitude of the vehicle body 1, specifically, tilt in the front-rear and left-right directions. The tilt sensor S3 is configured to be able to detect the tilt state of the loading section 8. The tilt sensor S3 corresponds to the "tilt detection section" of the present invention.

The ECU 13 is connected to the operation detection unit 22. The operation detection unit 22 receives both a signal from the driving operation unit 21 and a wireless signal from a remote control device RC that uses wireless communication. The operation detection unit 22 is configured to detect manual operation of the four running wheels 2 and the bending link mechanism 5.

The ECU 13 includes a non-volatile memory (not shown) that stores programs corresponding to the functional units described below, and a CPU (not shown) that executes the programs. The functions of each functional unit are realized by the CPU executing the programs. The ECU 13 includes, as functional units, an attitude control unit 100, a driving control unit 101, and a tilt angle calculation unit 102, etc.

The inclination angle calculation unit 102 calculates the inclination angle of the ground on which each of the four running wheels 2 comes into contact, based on the detection information of the inclination sensor S3, the stroke positions of each 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 be able to calculate the inclination angle of the ground on which the four running wheels 2 come into contact. The inclination angle calculation unit 102 corresponds to the "inclination detection unit" of the present invention.

Based on the detection value of the stroke sensor S1, the posture control unit 100 can determine the swing posture of the first link 15 relative to the vehicle body 1, the swing posture of the second link 16 relative to the first link 15, etc. As a result, it is possible to calculate the height from the ground contact portion of the running wheel 2 to the vehicle body 1. When the vehicle body is moving, the posture control unit 100 executes horizontal control to control the operation of the support mechanism A so that the loading section 8 of the vehicle body 1 is in a horizontal posture based on the detection information of the inclination sensor S3. In the horizontal control, the posture 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 posture of the vehicle body 1 become values corresponding to the horizontal posture based on the detection information of the inclination sensor S3 and the detection information of the stroke sensor S1. In this way, the posture control unit 100 of the control device C is configured to be able to control the operation of each of the first hydraulic cylinder 6 and the second hydraulic cylinder 7 in the support mechanism A so that the loading section 8 is in a horizontal position based on the inclination state of the vehicle body 1 (loading section 8) and the respective expansion and contraction amounts of the first hydraulic cylinder 6 and the second hydraulic cylinder 7.

The travel control unit 101 controls the supply and discharge of hydraulic oil to the hydraulic motor 4 based on the rotation speed of the traveling wheels 2 detected by the rotation sensor S4 so that the rotation speed of the traveling wheels 2 becomes a target value. The travel control unit 101 also controls the supply (pressure) of hydraulic oil to the hydraulic motor 4 based on the pressure of the hydraulic oil detected by the pressure sensor S5 so that the drive torque of the traveling wheels 2 becomes a target value. The hydraulic control valve 12 is configured to be able to change the amount of hydraulic oil supplied and discharged to the hydraulic motor 4. The travel control unit 101 executes a switching operation of the hydraulic control valve 12 that supplies and discharges hydraulic oil to the hydraulic motor 4.

The travel control unit 101 is also configured to be able to change the orientation of the travelling wheels 2 based on the detection value of the stroke sensor S2. Specifically, the travel control unit 101 executes a switching operation of the hydraulic control valve 12 that supplies and discharges hydraulic oil to the turning cylinder 20. The travel control unit 101 is configured to be able to control the changing of the orientation of each of the four travelling wheels 2 individually.

[Control when the vehicle is stopped]
When the vehicle body 1 stops, the travel control unit 101 controls the hydraulic control valve 12 to cut off the supply and discharge of hydraulic oil to the hydraulic motor 4. When the supply and discharge of hydraulic oil to the hydraulic motor 4 is cut off, the hydraulic motor 4 stops. At this time, the hydraulic oil inside the hydraulic motor 4 stops flowing. Therefore, the hydraulic motor 4 cannot rotate, and the rotation of each of the four traveling 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 therefore to the four traveling wheels 2, when the four traveling wheels 2 are stopped. Since the hydraulic control valve 12 is cut off, the hydraulic oil inside the hydraulic motor 4 cannot enter or leave. As a result, each of the four traveling wheels 2 is locked by the hydraulic oil inside the hydraulic motor 4, and the vehicle body 1 can be maintained in a stopped state. In this way, 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 to cut off the supply and discharge of hydraulic oil to the hydraulic motor 4 when the vehicle stops.

However, the hydraulic oil inside the hydraulic motor 4 may leak little by little from the hydraulic control valve 12 over time. In this case, the hydraulic oil inside the hydraulic motor 4 may not be able to keep each of the four running wheels 2 locked. Particularly on slopes, if the hydraulic oil 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 vehicle body 1 may not be able to maintain its stopped position. To avoid such inconveniences, in this embodiment, the travel control unit 101 is configured to rotate each of the four running wheels 2 in a different direction when the vehicle body 1 is stopped.

Specifically, as shown in FIG. 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 the orientations of all four running wheels 2 different from each other.

In the example shown in FIG. 7, of the left and right running wheels 2 located under the front of the vehicle body 1, the right running wheel 2 turns counterclockwise, and the left running wheel 2 turns clockwise. Therefore, for each of the left and right running wheels 2 located under the front of the vehicle body 1, the front part of each of the left and right running wheels 2 is located closer to the left and right center of the vehicle body 1 than the rear part of each of the left and right running wheels 2.

Of the left and right running wheels 2 located under the rear of the vehicle body 1, the right running wheel 2 rotates clockwise, and the left running wheel 2 rotates counterclockwise. Therefore, for each of the left and right running wheels 2 located under the rear of the vehicle body 1, the rear part of each of the left and right running wheels 2 is located closer to the left and right center of the vehicle body 1 than the front part of each of the left and right running wheels 2.

The orientation of each of the four running wheels 2 is changed by the contraction operation of the swivel cylinder 20. The cap side end of the swivel cylinder 20 is located toward the front-rear center of the vehicle body 1 relative to the rod side end of the swivel cylinder 20. For this reason, when the travel control unit 101 stops the drive control of the running wheels 2, it controls each of the four swivel cylinders 20 to operate toward the contraction side from the neutral stroke position. With this method, the travel control unit 101 of the control device C makes the orientation of each of the four running wheels 2 different from each other so that the end of the running wheel 2 located on the outer side of the vehicle body 1 is located closer to the left-right center of the vehicle body 1 than the end of the running wheel 2 located on the inner side of the vehicle body 1.

In this way, when the driving control unit 101 in the control device C stops the drive control of the running wheels 2, it makes the respective orientations of the running wheels 2 located on one side of the left or right side and the running wheels 2 located on the other side of the left or right side different from each other so that they are opposite to the neutral orientation in which the vehicle body 1 moves straight or approximately straight. Also, when the driving control unit 101 in the control device C stops the drive control of the running wheels 2, it makes the respective orientations of the running wheels 2 located on one side of the left or right side and the other side of the left or right side different from each other for the front and rear running wheels 2.

As a result, each of the four running wheels 2 exerts a force on each other in a direction different from the direction of rotation, and receives a reaction force from the ground in the direction of skid. In other words, when the four running wheels 2 try to roll, friction occurs between each of the running wheels 2 and the ground. This causes each of the four running wheels 2 to stop rotating. This allows the work vehicle to maintain its stopped position even when it is stopped for a long period of time on a slope, for example. Also, when the vehicle body 1 makes a pivot turn, the travel control unit 101 can quickly change the direction of each of the four running wheels 2 to a direction along the tangent on the same arc of a circle whose center is the center of the vehicle body 1.

Based on the flowchart of FIG. 8, the control when the vehicle body 1 stops will be described. First, the ECU 13 determines whether the four running wheels 2 have stopped (step #01). When the four running wheels 2 have stopped (step #01: Yes), the ECU 13 determines whether the operation detection unit 22 has detected a manual operation from the driving operation unit 21 or the remote control device RC (step #02). If the operation detection unit 22 has not detected a manual 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 a manual operation (step #03). The determination of step #03 is repeated until the timer count time has elapsed the preset time. Then, when the timer count time has elapsed the preset time (step #03: Yes), the driving control unit 101 causes the directions of the four running wheels 2 to differ from each other (step #04). In other words, when a preset time has elapsed since the operation detection unit 22 stopped detecting manual operation, the driving control unit 101 of the control device C causes the directions of one of the left and right running wheels 2 and the other of the left and right running wheels 2 to differ from each other.

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

If the current location of the vehicle body 1 is on a slope (step #05: Yes), the ECU 13 continues to control the attitude control unit 100 (step #06) and prohibits the hydraulic supply source 9 from being stopped (step #07). When the control of the attitude control unit 100 is stopped on a slope, 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, the horizontal state of the loading unit 8 is maintained immediately after the control of the attitude control unit 100 is stopped. However, as time passes, the hydraulic oil inside each of the first hydraulic cylinder 6 and the second hydraulic cylinder 7 leaks from the hydraulic control valve 12. When this happens, the bending link mechanism 5 gradually descends due to the weight of the loading unit 8, the loading unit 8 gradually tilts along the slope, and the horizontal state of the loading unit 8 is no longer maintained. In order to avoid such inconveniences, when the current location of the vehicle body 1 is on a slope, the control of the attitude control unit 100 is continued and the drive of the hydraulic supply source 9 is also continued. In other words, the attitude control unit 100 of the control device C is configured to continue to control the operation of each 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 at a set inclination angle or more. This allows the loading unit 8 to remain horizontal even if the running wheels 2 are stopped on a slope.

If the current location of the vehicle body 1 is not on a slope (step #05: No), the current location of the vehicle body 1 is flat land. Therefore, the ECU 13 stops the control of the attitude control unit 100 (step #08) and allows the hydraulic supply source 9 to stop driving (step #09). As described above, over time, the hydraulic oil inside each of the first hydraulic cylinder 6 and the second hydraulic cylinder 7 leaks from the hydraulic control valve 12. However, since the land is flat, each of the multiple bending link mechanisms 5 descends approximately evenly, and the horizontal state of the loading unit 8 is maintained. Therefore, if the current location of the vehicle body 1 is flat land, the control of the attitude control unit 100 is stopped and the driving of the hydraulic supply source 9 is allowed to stop. 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 land. 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.

In this way, the control device C is configured not to control the operation of the support mechanism A when the four running wheels 2 are stopped and the ground is inclined within a preset range of inclination angles, and is configured to permit the drive of the hydraulic supply source 9 to be stopped. On the other hand, the control device C is configured to continue to control the operation of the support mechanism A and prohibit the drive of the hydraulic supply source 9 from being stopped when the four running wheels 2 are stopped and the ground is inclined to an angle equal to or greater than the set inclination angle.

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

(1) In the above embodiment, when the control device C stops the drive control of the running wheels 2, it changes the orientation of all four running wheels 2 separately. This embodiment is not limited to the above, and the control device C may be configured to change the orientation of one to three of the four running wheels 2 separately. For example, the control device C may be configured to change the orientation of two running wheels 2 (first running wheel and second running wheel) located on the low ground side of the four running wheels 2, based on the inclination state of the vehicle body 1. For example, the control device C may be configured to change the orientation of the running wheel 2 (first running wheel) located on the low ground side of one of the front and rear on the left and right sides and the running wheel 2 (second running wheel) located on the low ground side of one of the front and rear on the other left and right sides, based on the inclination state of the vehicle body 1.

(2) The support mechanism A may be a mechanism having one link or three or more links. For example, the support mechanism A may be a mechanism having an electric actuator as a device for changing the posture.

(3) The running wheels 2 may be driven by an electric motor instead of the hydraulic motor 4, or may be driven via a drive mechanism by an engine 9a or the like.

(4) The running wheels 2 may be configured to be rotated by a hydraulic motor, an electric motor, or the like instead of the rotating cylinder 20.

(5) In the above embodiment, the driving operation unit 21 is provided behind the loading section 8 in the vehicle body 1. For example, the driving operation unit 21 may not be provided. In this case, the operation detection unit 22 may be configured to only accept wireless signals from a remote control device RC that uses a wireless communication method. Alternatively, the operation detection unit 22 may be configured to only accept signals from the driving operation unit 21.

(6) The support mechanism A of this embodiment may not be provided. In this case, the loading section 8 is not maintained in a horizontal position on a slope. However, if the first running wheel and the second running wheel are configured to be oriented in different directions on a slope, the risk of the work vehicle gradually descending the slope due to its own weight is avoided.

(7) In the above embodiment, the control device C causes the respective orientations of the first running wheel and the second running wheel to differ from each other when a preset time has elapsed since the operation detection unit 22 no longer detects manual operation. This is not limited to the embodiment, and for example, the control device C may be configured to immediately cause the respective orientations of the first running wheel and the second running wheel to differ from each other when the operation detection unit 22 no longer detects manual operation.

(8) In the above embodiment, the support mechanism A is provided with a bending link mechanism 5. This is not limiting, and for example, the support mechanism A may be configured to be provided with a sliding mechanism that can be raised and lowered instead of the bending link mechanism 5.

(9) In the above embodiment, the tilt sensor S3 is provided as the tilt detection unit. This is not limited to the embodiment, and the tilt detection unit may be, for example, a mechanical pendulum sensor or a magnetic sensor.

(10) In the above embodiment, the ECU 13 determines whether the inclination angle of the ground calculated by the inclination angle calculation unit 102 is equal to or greater than a preset inclination angle. If the inclination angle of the ground is equal to or greater than the preset inclination angle, the ECU 13 determines that the current location of the vehicle body 1 is on a slope. This is not limited to the embodiment, and "equal to or greater than the set inclination angle" may mean an inclination angle above the set inclination angle but not including the set inclination angle, and the ECU 13 may be configured to determine that the current location of the vehicle body 1 is flat land rather than on a slope when the inclination angle of the ground is equal to the set inclination angle.

The configurations disclosed in the above-mentioned embodiments (including other embodiments, the same applies below) can be applied in combination with configurations disclosed in other embodiments, so long as no contradiction occurs. Furthermore, the embodiments disclosed in this specification are merely examples, and the present invention is not limited to these embodiments, and can be modified as appropriate within the scope of the purpose of the present invention.

The present invention is applicable to work vehicles that have multiple running wheels that can be steered separately.

1: Vehicle body 2: Running wheels (first running wheel, second running wheel)
4: Hydraulic motor 8: Loading section 12: Hydraulic control valve (control valve)
22: Operation detection unit 102: Tilt angle calculation unit (tilt detection unit)
A: Support mechanism C: Control device S2: Stroke sensor (steering angle detection unit)
S3: Tilt sensor (tilt detection unit)

Claims (6)

A vehicle body having a loading section capable of loading luggage;
A plurality of running wheels located at the front and rear of each of the left and right sides of the vehicle body and capable of being steered separately;
A steering angle detection unit that detects the direction of each of the plurality of running wheels;
A control device capable of controlling the driving of each of the plurality of running wheels and controlling the changing of the orientation of each of the plurality of running wheels individually,
When the control device stops the drive control, it causes the directions of a first running wheel located on one side of the vehicle body among the plurality of running wheels, and a second running wheel located on the other side of the vehicle body among the plurality of running wheels, to differ from each other. The work vehicle according to claim 1, wherein when the control device stops the drive control, the control device changes the orientation of each of the first running wheel and the second running wheel so that they are opposite to each other with respect to the neutral orientation in which the vehicle body travels straight or approximately straight. The work vehicle according to claim 1, wherein the control device causes all of the plurality of running wheels to have different orientations when the drive control is stopped. A tilt detection unit is provided to detect a tilt state of the vehicle body,
The work vehicle described in claim 1, wherein the control device changes the orientation of the first running wheel located on the low ground side on one of the left and right sides of the plurality of running wheels, and the second running wheel located on the low ground side on the other of the left and right sides, based on the inclination state of the vehicle body. An operation detection unit is provided that detects a human operation on the plurality of running wheels,
A work vehicle as described in any one of claims 1 to 4, wherein the control device makes the respective orientations of the first running wheel and the second running wheel different from each other when a predetermined time has elapsed since the operation detection unit no longer detects the manual operation. a support mechanism that is supported by the vehicle body and supports the plurality of running wheels in a position changeable manner with respect to the vehicle body;
a hydraulic motor that uses the supply and discharge of hydraulic oil as driving energy to drive each of the plurality of traveling wheels;
a control valve capable of changing the amount of hydraulic oil supplied to and discharged from the hydraulic motor;
An inclination detection unit that detects an inclination state of the loading unit is provided,
5. The work vehicle according to claim 1, wherein the control device is configured to be able to control the operation of the support mechanism so that the loading section is in a horizontal position based on the inclined state of the loading section, and is configured to stop the drive control by closing the control valve when the vehicle is stopped to cut off the supply and discharge of the hydraulic oil to the hydraulic motor.

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