JP2020104726A - Work vehicle - Google Patents

Abstract

To provide a work vehicle designed such that the height of a vehicle body from the ground can be appropriately set in accordance with a difference in work situation and the position of the vehicle body can be stabilized regardless of a change in the condition of a road surface.SOLUTION: A plurality of travel wheels S are supported by a vehicle body frame via a telescopic, cylindrical support member 19. Each of the plurality of travel wheels S is provided with a vehicle height adjustment mechanism 40 of hydraulic operation system, which allows the relative height of each travel wheel S with respect to the vehicle body frame to be switched in the range of a predetermined length by telescopically operating each support member 19 by means of a hydraulic cylinder 41. This mechanism comprises: a hydraulic control valve capable of individually controlling supply of hydraulic oil to the plurality of hydraulic cylinders 41; a control unit that controls actuation of each hydraulic control valve so that the vehicle body has a target state through vehicle height adjustment by the hydraulic cylinders with respect to a change in the position of the vehicle; and a plurality of accumulators connected to the respective hydraulic chambers of the plurality of hydraulic cylinders.SELECTED DRAWING: Figure 3

Description

TECHNICAL FIELD The present invention relates to a work vehicle having a plurality of traveling wheels, and more particularly, for working while traveling across a planting plant, or while traveling on the ground where irregularities and slopes exist. Regarding a suitable work vehicle.

In this type of work vehicle, conventionally, there is a vertically-oriented case that supports traveling wheels in the up-down direction and has a high clearance to increase the ground clearance of the vehicle body. The length has been set to a predetermined constant length (for example, see Patent Document 1).

With this configuration, for example, a fertilizer application device or a chemical spraying device is attached to the rear part of the vehicle body, and the left and right traveling wheels cross the ridges and travel in the field while supplying chemicals such as fertilizers and herbicides to the crops. When performing work, the ground clearance of the vehicle body can be increased to allow the vehicle to travel without contacting the crops planted in the field.

JP, 2003-94907, A

In the above conventional configuration, the vertical length of the vertically oriented case is fixed and the ground height of the vehicle body is constant when the traveling wheels are in contact with the ground. As a result, there is a disadvantage that the ground clearance of the vehicle body may become excessive or insufficient. For example, if the ground height of the car body is set according to the height of the crop, when the crop is short, the vertical distance between the car body and the crop becomes too wide, and fertilizer or There was a risk that the work could not be performed satisfactorily because the chemicals were scattered and could not be supplied to the crops in an appropriate state.

In addition, when working while traveling on uneven ground, traveling wheels may get into concave parts or climb convex parts, which may cause the body to lean and make the posture unstable. In this case, the vehicle body will continue to travel with the vehicle body largely inclined, and the posture of the vehicle body may become unstable.

Therefore, there has been a demand for a work vehicle capable of setting the ground clearance of the vehicle body to an appropriate height according to the difference in the working situation and stabilizing the posture of the vehicle body regardless of the change in the road surface situation.

A feature configuration of a work vehicle according to the present invention is that a plurality of traveling wheels are supported by a vehicle body frame via a tubular support member that is capable of extending and contracting, and a hydraulic cylinder extends and retracts the supporting member to perform the vehicle body of the traveling wheels. A hydraulically operated vehicle height adjusting mechanism capable of switching a relative height with respect to the frame within a predetermined length range is provided for each of the plurality of traveling wheels, and hydraulic oil is separately provided for each of the plurality of hydraulic cylinders. A hydraulic control valve that can control the supply state of the vehicle, a control unit that controls the operation of the hydraulic control valve so that the vehicle body reaches a target state by adjusting the vehicle height by the hydraulic cylinder in response to a posture change of the vehicle body, A plurality of accumulators connected to the oil chambers of the hydraulic cylinders are provided.

According to the present invention, the relative height of the traveling wheels with respect to the vehicle body frame can be changed and adjusted when the support member expands and contracts due to the operation of the vehicle height adjustment mechanism. By adjusting the height of each of the plurality of traveling wheels, it is possible to change the ground clearance of the vehicle body while maintaining the vehicle body in a desired posture.

The vehicle height adjusting mechanism expands and contracts the support member by the operation of the hydraulic cylinder, and the control unit controls the operation of the hydraulic control valve for the hydraulic cylinder so that the vehicle body reaches a target state. As a result, for example, when the road surface on which the vehicle body travels is a sloping ground, or when the vehicle crosses over the ridge to enter the work site, the vehicle body may cross over the ridge from the work site and exit on the ridge road. By controlling the operation of the plurality of hydraulic cylinders so that the vehicle has a target attitude (for example, a horizontal attitude), the attitude of the vehicle body can be maintained at the target attitude.

Also, if the road surface on which the vehicle body travels is a generally flat surface, but there are small irregularities, the traveling wheels may enter the recesses or ride on the protrusions, The vehicle body may vibrate. In such a case, the traveling wheels tend to move up or down slightly relative to the vehicle body. However, since the accumulator is connected to the oil chamber of the hydraulic cylinder, the working oil is absorbed or discharged by the accumulator, and the relative rise of the traveling wheels with respect to the vehicle body can be allowed. As a result, it is possible to suppress the vibration of the vehicle body by allowing the relative vertical movement of the traveling wheels due to the small unevenness, and to maintain the vehicle body posture at the target posture.

As described above, the posture of the vehicle body can be maintained at the target posture not only when the posture of the vehicle body changes greatly but also when the posture of the vehicle body vibrates due to the fine irregularities.

Therefore, according to the present invention, it becomes possible to set the ground clearance of the vehicle body to an appropriate height according to the difference in the working situation, and to stabilize the posture of the vehicle body regardless of the change in the road surface situation. ..

In the present invention, it is preferable that an inclination sensor that measures the inclination angle of the vehicle body and a plurality of stroke sensors that measure the expansion/contraction operation amounts of the hydraulic cylinders are provided.

According to this configuration, by measuring the actual inclination angle of the vehicle body with the inclination sensor, the degree of the actual inclination of the vehicle body is measured, and the stroke sensor measures the expansion/contraction operation amount of the hydraulic cylinder. By doing so, it is possible to accurately determine how far the posture of the vehicle body is from the target posture, and it is possible to perform control for maintaining the posture of the vehicle body at the target posture with high accuracy.

In the present invention, it is preferable that a pressure sensor for measuring the pressure in the oil chamber of each of the plurality of hydraulic cylinders is provided.

According to this configuration, by measuring the pressure in the oil chamber of the hydraulic cylinder with the pressure sensor, it is possible to estimate the ground contact state of the traveling wheels with respect to the road surface based on, for example, fluctuations in pressure during traveling. To add the explanation, when a plurality of traveling wheels are traveling while they are in contact with the road surface and one of the traveling wheels enters a recess formed in the road surface, the contact pressure of the traveling wheel decreases. As a result, the pressure in the oil chamber of the corresponding hydraulic cylinder decreases. At this time, since it can be inferred from the measurement result of the pressure sensor, for example, the hydraulic cylinder is adjusted so that the pressure of the oil chamber of the hydraulic cylinder becomes a value equivalent to the pressure of the hydraulic cylinder for the other traveling wheels. By performing the extension operation, it becomes possible to travel with all the traveling wheels in contact with the ground at an appropriate ground pressure. When one of the traveling wheels rides on the convex portion formed on the road surface, the pressure becomes high.Therefore, by retracting the hydraulic cylinder, all traveling wheels should be grounded at an appropriate ground pressure with respect to the ground. Can drive.

In this way, the information on the pressure in the oil chamber allows all the traveling wheels to travel in a state where they are in contact with the ground at an appropriate ground pressure, and there is no disadvantage such as idling due to lifting of the traveling wheels. It is possible to maintain the state.

In the present invention, the hydraulic cylinder is a double-acting cylinder, the accumulator is provided separately for each of the bottom side oil chamber and the rod side oil chamber in the hydraulic cylinder, the hydraulic control valve, It is preferable that the flow control valve is capable of changing and adjusting the flow rate of the hydraulic oil supplied to the hydraulic cylinder.

According to this configuration, since the double-acting hydraulic cylinder is used for the actuation, it is possible to promptly actuate each of the extending operation and the retracting operation. An accumulator is provided in each of the bottom side oil chamber and the rod side oil chamber, so the accumulator can properly absorb and discharge the hydraulic oil in both the expanding and contracting directions of the hydraulic cylinder. The vibration of the vehicle body can be suppressed.

When operating the hydraulic cylinder, if the deviation between the target operation amount and the current operation amount is large, while operating quickly by supplying a large flow rate of hydraulic oil, the deviation is small. In some cases, by supplying a small amount of hydraulic oil, the posture can be changed smoothly without causing hunting or the like.

In the present invention, it is preferable that the vehicle includes a driver's seat on which a driver sits and an operation member arranged in front of the driver's seat.

According to this configuration, the driver can comfortably drive while sitting in the driver's seat. As described above, even when the driver is seated, the posture of the vehicle body is stabilized, which facilitates the driving operation.

It is the whole work vehicle side view. It is a top view which shows the wheel support structure of a working vehicle. It is a front view showing a wheel support structure. It is a perspective view of a part of wheel support structure. It is a perspective view of a part of wheel support structure. It is a cross-sectional front view of the vehicle height adjustment mechanism in the maximum extension state. It is a cross-sectional front view of the vehicle height adjustment mechanism in the shortest state. It is sectional drawing which shows the structure of a stroke sensor. It is a control block diagram. It is a hydraulic circuit diagram. It is a flow chart of control operation. It is operation|movement explanatory drawing. It is a flow chart of control operation. It is a flow chart of control operation.

[First Embodiment]
Hereinafter, a work vehicle according to a first embodiment of the present invention will be described with reference to the drawings.

〔overall structure〕
FIG. 1 shows a passenger management machine as a work vehicle according to the present embodiment. This passenger management machine is equipped with a chemical spraying device 2 as a working device at the rear part of a four-wheel traveling type vehicle body 1. This riding management machine performs a work of spraying a chemical to a crop while traveling across a planting strip of the crop in a field where the crop has already been planted. In the present embodiment, an example in which the present invention is applied to a passenger management machine (passenger type worker) will be described, but the application target of the present invention is not limited to this.

A pair of front wheels 3 as traveling wheels S that can be turned are provided on the left and right sides of the front part of the traveling body 1, and a pair of rear wheels 4 as traveling wheels S that can be turned on the left and right sides of the rear part of the traveling body 1. Is provided. In this way, all four wheels are capable of turning, for example, a two-wheel steering state in which only two front wheels 3 are turned, and four wheels in which the front wheels 3 and the rear wheels 4 are turned in opposite directions and travel with a small turning radius. It is possible to switch to the steering state.

The front wheels 3 and the rear wheels 4 are provided so as to be able to travel between rows located between crop rows. An engine 5 is mounted on the front portion of the traveling vehicle body 1, and a driving unit 6 is provided on the rear portion of the traveling vehicle body 1. Below the traveling vehicle body 1, there is provided a mission case 7 in which a transmission (not shown) for shifting the power of the engine 5 is installed. The mission case 7 is provided so as to extend in the front-rear direction from the lower rear portion of the engine 5 to a position corresponding to the rear wheel 4 in a side view. A front side frame body 8 is provided on the lower side of the engine 5 so as to cover the outer peripheral portion. The mission case 7 and the front-side frame body 8 are integrally connected, and a vehicle body frame F that supports the entire vehicle body is configured by these. The driver 6 is provided with a driver's seat 9 on which a driver is seated, and a steering wheel (operating member) 10 positioned in front of the driver's seat 9 for steering operation. In addition to the above, the operation unit 6 is also provided with an elevating lever 11 and a gear shift lever 12 for elevating the drug spraying device 2.

In the traveling vehicle body 1, the power of the engine 5 is transmitted to the left and right front wheels 3 and the left and right rear wheels 4 after being shifted by the transmission in the mission case 7. Therefore, the traveling vehicle body 1 is configured as a four-wheel drive type in which four traveling wheels S are driven. As shown in FIG. 2, a lateral transmission shaft 14 is provided inside a cylindrical rear lateral transmission case 13 connected to the left and right sides of the transmission case 7, and the power after shifting is transmitted to the left and right sides via the lateral transmission shaft 14. It is transmitted to the rear wheel 4. The rear lateral transmission case 13 is supported by the mission case 7, that is, the vehicle body frame F.

As shown in FIG. 2, a cylindrical front side lateral transmission case 15 is provided at the left and right intermediate portions of the left and right front wheels 3, and the power from the transmission case 7 is stored in the front and rear intermediate shaft 16 and the lateral transmission case 15. It is transmitted to the left and right front wheels 3 via a differential mechanism (not shown) provided and a lateral transmission shaft 18. The front lateral transmission case 15 is supported on the vehicle body frame F so as to be capable of rolling (rotating) around a front-rear axis X that is the same axis as the intermediate shaft 16.

As shown in FIG. 3, a vertical transmission case 19 as a supporting member is connected to both lateral ends of the front horizontal transmission case 15. As shown in FIG. 6, a vertically oriented transmission shaft 20 is provided in the vertically oriented transmission case 19. A shaft end portion of a horizontal transmission shaft 18 provided in the front horizontal transmission case 15 and an upper end portion of a vertical transmission shaft 20 are interlockingly connected via an upper bevel gear mechanism 21. The lower end of the vertical transmission shaft 20 and the rotary shaft 3a of the front wheel 3 are interlockingly connected via a lower bevel gear mechanism 22.

The traveling wheel S is supported on the vehicle body frame F so as to be capable of changing its orientation around the rotation axis Y of the vertically-oriented transmission shaft 20. Since the support structure of the wheel having the vertical transmission case 19 and the vertical transmission shaft 20 has the same configuration for each of the four traveling wheels S, the support structure for one of the front wheels 3, which is one of them, will be described below. Explained.

[Wheel support structure]
As shown in FIG. 6, an end portion of the front lateral transmission case 15 is bent in a curved shape in a front view in a state of covering the upper bevel gear mechanism 21, and an opening that opens downward is formed. .. An upper connecting body 23, which is integrally connected to an upper end portion of the vertical transmission case 19, rotates around the rotation axis Y of the vertical transmission shaft 20 at the end of the front horizontal transmission case 15 so as to cover the opening. It is movably fitted and connected. A wheel support case 24, which covers the lower bevel gear mechanism 22 and supports the rotating shaft 3a of the front wheel 3, is connected to a lower end portion of the vertical transmission case 19.

As shown in FIG. 5, a retaining member 25 is provided to prevent the upper connecting body 23 from coming off in a fitted and connected state. As shown in FIG. 5, the retainer 25 is made of a strip-shaped member, one end of which is bolted to the outer periphery of the upper connector 23 and the other end of which is connected to the end of the front lateral transmission case 15. It engages with the formed stepped portion 26 to prevent coming off.

As shown in FIGS. 3 and 4, a double-acting hydraulic cylinder 27 for steering operation (hereinafter referred to as steering wheel) is provided in front of the front lateral transmission case 15 and in a posture parallel to the front lateral transmission case 15. (Referred to as a cylinder). A cylinder tube 28 of the steering cylinder 27 is connected to the front lateral transmission case 15 via a bracket 29. The piston rod 30 of the steering cylinder 27 is interlocked with one end of a tie rod 32 via a ball joint 31, and the other end of the tie rod 32 is interlocked with a knuckle arm 34 provided in the upper connecting body 23 via a ball joint 33. It is connected.

When the steering cylinder 27 is operated, the vertical transmission case 19, the wheel support case 24, and the front wheel 3 are integrally integrated with each other through the knuckle arm 34 and the upper connecting body 23 to form the rotation axis Y of the vertical transmission shaft 20. The front wheel 3 is turned around and the direction of the front wheel 3 is changed. The steering cylinder 27 is switched according to the operation of the steering handle 10 and is hydraulically slid leftward or rightward from the neutral position for straight traveling. A rotation angle detection device 35 for detecting the rotation angle of the upper connecting body 23, that is, the rotation angle of the front wheel 3 is provided on the upper portion of the end portion of the front lateral transmission case 15.

By operating the steering cylinder 27, the upper connecting body 23, that is, the vertically-oriented transmission case 19 and the front wheel 3 can be rotated within a predetermined operating range. The turning operation angle of the upper connecting body 23 is detected by the turning angle detection device 35, and is fed back to the control device 80 (see FIG. 9) described later, so that the turning angle corresponding to the operation of the steering wheel 10 becomes the steering angle. The cylinder 27 is controlled. Incidentally, in FIG. 9, the description of the steering control system is omitted.

[Vehicle height adjustment mechanism]
Each of the vertical transmission shaft 20 and the vertical transmission case 19 has an inner/outer double structure that is capable of expanding and contracting while sliding in the axial direction of the vertical transmission shaft 20. As shown in FIGS. 6 and 7, the vertical transmission case 19 has an outer cylinder member 19A and an inner cylinder member 19B, and is configured to be expandable and contractable while sliding. The vertical transmission case 19 is provided with the outer cylinder member 19A positioned on the lower side and the inner cylinder member 19B positioned on the upper side, and the lower end portion of the outer cylinder member 19A is integrally connected to the wheel support case 24. The upper end of the inner tubular member 19B is integrally connected to the upper connecting body 23.

The vertical transmission shaft 20 has a cylindrical shaft 20A and an inner shaft 20B slidable in the axial direction while maintaining a state of integrally rotating by spline fitting inside the cylindrical shaft 20A. The upper end of the inner shaft 20B is integrally rotatably connected to the upper bevel gear mechanism 21. The lower end of the cylinder shaft 20A is integrally rotatably connected to the lower bevel gear mechanism 22.

A hydraulic operation type in which the vertical transmission shaft 20 and the vertical transmission case 19 are extended/contracted in the rotation axis Y direction of the vertical transmission shaft 20 to switch the relative height of the front wheel 3 with respect to the vehicle body frame F in a plurality of steps. The vehicle height adjusting mechanism 40 is provided. As shown in FIG. 3, the vehicle height adjusting mechanism 40 is provided with a hydraulic cylinder 41 extending along the axial direction of the vertically-oriented transmission shaft 20.

The hydraulic cylinder 41 is provided across the upper connection body 23 and the support bracket 42 provided at the lower portion of the wheel support case 24. The upper end of the cylinder tube 41A of the hydraulic cylinder 41 is integrally connected to the upper connecting body 23, and the lower end of the piston rod 41B of the hydraulic cylinder 41 is connected to the wheel support case 24. Therefore, the upper connection body 23 and the wheel support case 24 are integrally connected via the hydraulic cylinder 41, and when the steering cylinder 27 operates, those members integrally rotate and the front wheel 3 moves. It is turned.

By extending and contracting the hydraulic cylinder 41, the vehicle height is changed and adjusted within a long range (for example, about several tens of cm) between the most extended state as shown in FIG. 6 and the most retracted state as shown in FIG. can do. The outer peripheral side of the overlapping portion 50 where the outer tubular member 19A and the inner tubular member 19B overlap each other is supported by the base member 45 in a state where the vertical transmission case 19 is most extended. As described above, even if the vertical width of the overlapping portion 50 is narrow due to the extension of the vertically-oriented transmission case 19, the outer peripheral side is supported by the base member 45 to prevent the reduction of the supporting strength.

At the end of the lateral transmission case 15 to which the upper connecting body 23 is rotatably connected, a support boss 51 that rotatably supports the inside of the vertical transmission case 19 is provided in the radial direction of the vertical transmission case 19. It is located on the one side and is provided in a state of extending downward along the direction of the rotation axis Y. That is, at the end of the lateral transmission case 15, the support boss 51 that rotatably supports the inner peripheral side of the upper connection body 23 via the bearing 52 is integrated along the axial direction of the vertical transmission shaft 20. The extension is formed so as to extend downward. The support boss portion 51 rotatably supports the vertical transmission shaft 20 located on the inner peripheral side via a bearing 53.

The support boss portion 51 is provided in a state of extending downwardly to a lower side than an intermediate portion in the vertical direction of the inner tubular member 19B. In this way, by supporting the vertical transmission case 19 from the inner peripheral side by the support boss portion 51 which is long in the vertical direction, the reduction of the supporting strength of the vertical transmission case 19 is prevented.

[Stroke sensor]
The hydraulic cylinder 41 has a built-in stroke sensor, and as shown in FIG. 8, is provided with a stroke sensor 60 as an operation amount detecting means in a state of extending in the cylinder tube along the longitudinal direction. The stroke sensor 60 is provided across the upper connection body 23 and the support bracket 42 provided at the lower portion of the wheel support case 24.

The outer cylinder 62 is provided with an outer cylinder 62 as a first member that relatively moves as the hydraulic cylinder 41 expands and contracts, and an inner cylinder 63 as a second member slidably fitted in the outer cylinder 62. Also, a cylindrical sliding member 64 having a cylinder structure is provided, in which the end portion of the inner cylinder 63 facing the outside is closed and a closed space is formed inside. In the tubular sliding member 64, the upper end of the outer cylinder 62 is connected to the upper connecting body 23, and the lower end of the inner cylinder 63 is connected to the support bracket 42.

The stroke sensor 60 is housed inside the tubular sliding member 64. The stroke sensor 60 is provided in a state in which it moves integrally with the outer cylinder 62 and has a screw shaft 66 integrally formed with a spiral blade 65 on the outer peripheral portion, and the inner cylinder 63 and the screw shaft 66. A sliding contact member 67 that guides the screw shaft 66 to rotate by slidingly acting on the spiral blade 65 along with the relative movement with the cylinder 62, and an electromagnetic wave serving as a rotation detection sensor capable of detecting the rotation speed of the screw shaft 66. And a pickup sensor 68 of a type.

The screw shaft 66 is supported by a support portion 69 provided at an upper end portion of the outer cylinder 62 in a state of integrally moving along the axial direction and rotatably in the circumferential direction. The screw shaft 66 extends along the inside of the inner cylinder 63. At the upper end of the inner cylinder 63, a sliding contact member 67, which is externally inserted on the screw shaft 66 and slides on the spiral blade 65, is provided. A detection gear 70 is provided on the screw shaft 66 at a position extending above the sliding contact member 67. The outer cylinder 62 is provided with an electromagnetic pickup sensor 68 having a well-known structure at a position corresponding to the outer peripheral portion of the detection gear 70. The pickup sensor 68 is widely used, for example, in agricultural machines and other devices, and can accurately detect the rotation speed.

When the outer cylinder 62 and the inner cylinder 63 relatively move in the axial direction with the expansion and contraction operation of the hydraulic cylinder 41, the spiral blade 65 of the screw shaft 66 receives the sliding contact action of the sliding contact member 67 and corresponds to the moving amount. The screw shaft 66 rotates by the rotation amount. The pickup sensor 68 can detect the rotation speed of the screw shaft 66 based on the waveform of the current generated when the teeth of the detection gear 70 pass by the rotation of the screw shaft 66. Then, by counting the number of rotations of the screw shaft 66 from the start of rotation to the stop, the amount of movement of the screw shaft 66 in the axial direction (the amount of expansion/contraction operation of the hydraulic cylinder 41) can be obtained.

[Hydraulic circuit configuration]
The vehicle height adjusting mechanism 40 is provided in four sets corresponding to each of the four traveling wheels S. Next, a hydraulic circuit configuration for controlling the operation of the four hydraulic cylinders 41 included in the four vehicle height adjustment mechanisms 40 will be described.

FIG. 10 shows a hydraulic circuit for each hydraulic cylinder 41. A hydraulic control that includes a hydraulic pump 72 that is driven by the engine 5 and that can control the supply state of the hydraulic oil separately to the four hydraulic cylinders 41 in the four branch paths to which the hydraulic oil from the hydraulic pump 72 is branched and supplied. Each valve 73 is provided. Each hydraulic cylinder 41 is a double-acting cylinder.

The hydraulic control valve 73 can be switched between an ascending position where the hydraulic cylinder 41 is extended, a descending position where the hydraulic cylinder 41 is retracted, and a neutral position where the operation is stopped by sliding the spool with an electromagnetic operation force. is there. The hydraulic control valve is configured by an electromagnetic proportional flow control valve capable of changing and adjusting the flow rate of the hydraulic oil supplied to the hydraulic cylinder 41 in each of the extension operation and the contraction operation by changing the electromagnetic operation force. ..

When the hydraulic control valve 73 is switched to the raised position, the hydraulic oil from the hydraulic control valve 73 is supplied to the bottom side oil chamber 41a, the hydraulic oil is discharged from the rod side oil chamber 41b to the drain tank 74, and the hydraulic cylinder 41 Is expanded. When the hydraulic control valve 73 is switched to the lowered position, the hydraulic oil from the hydraulic control valve 73 is supplied to the rod side oil chamber 41b, the hydraulic oil is discharged from the bottom side oil chamber 41a to the drain tank 74, and the hydraulic cylinder 41 Is degenerated.

An accumulator 75 is provided for each of the bottom side oil chamber 41a and the rod side oil chamber 41b in each hydraulic cylinder 41. Specifically, the accumulator 75 includes a bottom-side hydraulic oil supply passage 76 through which hydraulic oil is supplied from the hydraulic control valve 73 to the bottom-side oil chamber 41 a of the hydraulic cylinder 41, and the hydraulic control valve 73 to the hydraulic cylinder 41. The rod-side oil chamber 41b is connected to each of the rod-side hydraulic oil supply paths 77 through which hydraulic oil is supplied. Therefore, a total of eight accumulators 75 are provided, two for each hydraulic cylinder 41.

The accumulator 75 sucks and accumulates excess hydraulic oil when the oil chamber of the hydraulic cylinder 41 has a sudden pressure increase, or accumulates the hydraulic oil when there is a sudden pressure drop in the oil chamber. It is possible to absorb a sudden pressure change caused by an external load such as the traveling wheel S vibrating up and down due to the fine unevenness of the ground surface by an operation such as discharging. As a result, the accumulation and discharge of the hydraulic oil by the accumulator 75 allows the relative stroke variation of the hydraulic cylinder 41 along the fine unevenness of the ground surface to prevent the vibration of the vehicle body.

A pressure sensor 78 capable of measuring the internal pressure is provided in each of the bottom-side hydraulic oil supply passage 76 and the rod-side hydraulic oil supply passage 77. The internal pressure of these hydraulic oil supply paths is the same as the pressure of the oil chamber of the hydraulic cylinder 41. Therefore, the pressure sensor 78 can measure the pressure in the oil chamber of the hydraulic cylinder 41 (bottom side oil chamber 41a or rod side oil chamber 41b). Similar to the accumulator 75, two pressure sensors 78 are provided for each hydraulic cylinder 41, two in total.

A relief valve 79 is connected to the hydraulic oil supply passage 77 on the rod side. When the internal pressure of the rod-side hydraulic oil supply passage 77 (rod-side oil chamber 41b) exceeds a permissible value, the relief valve 79 causes the hydraulic oil to flow to the drain tank 74, so that the pressure becomes equal to or higher than the permissible value. Trying to avoid. The hydraulic oil is supplied to the rod-side oil chamber 41b when the hydraulic cylinder 41 is contracted (the vehicle body is lowered), and when the hydraulic cylinder 41 is operated so as to be lowered, the vehicle body is The biasing force due to the weight may be added and the pressure in the oil chamber may become excessive. Therefore, by discharging the hydraulic oil by the relief valve 79, it is possible to prevent the pressure from becoming excessive.

[Control configuration]
Next, a control configuration for controlling the operation of the hydraulic cylinder 41 will be described.
As shown in FIG. 9, in addition to the above-described four hydraulic control valves 73, four stroke sensors 60, and eight pressure sensors 78, a control for controlling the operation of each hydraulic control valve 73. A control device 80 as a unit and an inertial measurement unit (IMU: Internal Measurement Unit) 81 capable of measuring a posture change state of a vehicle body are provided. The detection information of the stroke sensor 60, the pressure sensor 78, and the inertial measurement device 81 is input to the control device 80. The control device 80 includes a microcomputer and can execute various control operations.

The inertial measurement device 81 is generally used to measure the behavior of a moving body, and has a three-axis gyro and a three-direction acceleration sensor (not shown), and has a three-dimensional angular velocity and Acceleration can be calculated. Then, by a calculation process such as integrating the detection information, it is possible to obtain the variation state of the vehicle body, specifically, the left and right inclination angle and the front and rear inclination angle from the horizontal posture of the vehicle body. Therefore, the inertial measurement device 81 functions as an inclination sensor that measures the inclination state of the vehicle body.

The control device 80 controls the operation of each hydraulic control valve 73 so that the vehicle body is brought into a target state by adjusting the vehicle height by the hydraulic cylinder 41 with respect to the posture variation of the vehicle body. That is, the control device 80 obtains the target pressure of each hydraulic cylinder 41 required to bring the vehicle body to the target ground height and the target posture, based on the detection results of the inertial measurement device 81 and each stroke sensor 60. The pressure adjustment control for controlling the operation of the hydraulic control valve 73 is executed so that the detection value of the pressure sensor 78 becomes the target pressure.

As shown in FIG. 11, the control device 80 obtains a horizontal tilt angle and a front-back tilt angle from the horizontal posture of the vehicle body based on the detection result of the inertial measurement device 81, and the detected tilt angle detection information and four The value of the force of the hydraulic cylinder 41 required to control the vehicle center of gravity position G to the target position (target ground clearance), which corresponds to the operating pressure, based on the information of the detection result (detected stroke amount) of the stroke sensor 60 of FIG. It is determined as (first operation pressure) (step #1). Next, the force (second operation pressure) of the hydraulic cylinder 41 required to make the posture (front-back direction and left-right direction) of the vehicle body horizontal when the vehicle center of gravity position G is at the target position is calculated ( Step #2).

The first operating pressure and the second operating pressure correspond to the force (thrust) required to operate the necessary stroke amount for operating the hydraulic cylinder 41. Then, the first operation pressure and the second operation pressure are added, and the added value is converted into the contact force of each traveling wheel S with the road surface to obtain the target operation pressure (step #3). The operation of each hydraulic control valve 73 is controlled so that the pressure detected by the pressure sensor 78 corresponds to the target operating pressure (step #4).

The process of controlling the hydraulic control valve 73 by obtaining such a target operating pressure is repeatedly performed every set unit time in accordance with the change of the posture of the vehicle body, and as a result, the vehicle body is kept at the target ground level and the target height. It becomes possible to maintain the posture.

According to the above configuration, for example, when the road surface on which the vehicle body travels is a sloping ground, or when overcoming the ridge to enter the work site, when overcoming the ridge from the work site and exiting the ridge road, By executing the pressure adjustment control as described above, it is possible to maintain the vehicle body at the target ground height and the target posture.

Then, when the road surface on which the vehicle body travels is a roughly flat surface with small irregularities, the relative vertical movement of the traveling wheels S is allowed by the action of the accumulator 75. Thus, it becomes possible to suppress the vibration of the vehicle body and maintain the vehicle body posture at the target posture.

Further, since the control device 80 executes the pressure adjustment control for controlling the operation of the hydraulic control valve 73 based on the detection value of the pressure sensor 78, the relative up and down of the traveling wheel S by the action of the accumulator 75 is performed. Even if there is a motion, this makes it possible to perform a smooth posture control with less risk of hunting during the control operation.

In the passenger work vehicle having the above structure, it is possible to vertically move the vehicle body above ground over a wide range. For example, as shown in FIGS. 12A and 12B, it is possible to switch between a low posture state in which the four hydraulic cylinders 41 are shortened and a high posture state in which the four hydraulic cylinders 41 are respectively lengthened. .. Therefore, when working across crops, when the crop is short, it is possible to switch to the low-profile state and spray the drug at a low position. When the crop grows and is tall, the crop is not damaged by switching to a high posture. Further, as shown in FIG. 12C, when the road surface is greatly inclined in the left-right direction and the vehicle travels along the inclined surface, the hydraulic cylinder 41 on the lower side of the inclination is elongated and By shortening the hydraulic cylinder 41 on the upper side of the inclination, the vehicle body can travel in a horizontal posture or a posture approaching the horizontal posture.

[Second Embodiment]
Next, a second embodiment of the work vehicle according to the present invention will be described with reference to the drawings.
In this embodiment, the configuration of the control device 80 is different from that of the first embodiment, but other configurations are the same as those of the first embodiment. Hereinafter, only the points different from the first embodiment will be described, and description of the same configurations will be omitted.

In this embodiment, the control device 80, based on the detection results of the inertial measurement device 81 (inclination sensor) and the stroke sensor 60, the target operation amount of the hydraulic cylinder 41 for bringing the vehicle body to the target ground height and the target posture. The vehicle height attitude control for controlling the operation of the hydraulic control valve 73 is executed so that the detection value of the stroke sensor 60 becomes the target operation amount, and when the vehicle height attitude control is executed, A correction process is executed to correct the target operation amount according to the change in pressure measured by the sensor 78.

As shown in FIG. 13, the control device 80 obtains a lateral inclination angle and a longitudinal inclination angle from the horizontal posture of the vehicle body based on the detection result of the inertial measurement device 81, and the detection information of the detected inclination angle and four pieces Based on the information of the detection result (detected stroke amount) of the stroke sensor 60, the road surface inclination degree is obtained (step #11). Next, the target stroke amount required to set the vehicle body in a horizontal posture and to set the vehicle center of gravity position to the target height is obtained (step #12), and the actual stroke amount of the hydraulic cylinder 41 is set to the target stroke amount. The operation of the hydraulic control valve 73 is controlled (step #13). This control corresponds to the vehicle height attitude control.

Specifically, depending on the deviation between the actual stroke amount and the target stroke amount, the hydraulic oil flow rate for the hydraulic cylinder is set so that the operating speed increases as the deviation increases, and the operation of the hydraulic control valve is controlled. To do. In actual operation, a dead zone within a predetermined range with respect to the target stroke amount is set. As a result, even when the amount of expansion and contraction to be operated is large and the operation is performed quickly, overshoot or the like does not occur and hunting operation does not occur. The smaller the deviation is, the smaller the expansion/contraction amount to be operated is.

Then, while the vehicle height attitude control is being executed, the external force applied to one of the hydraulic cylinders 41 is obtained from the detection result of the pressure sensor 78 (step #14). There is a large convex portion or concave portion on the traveling road surface, and when any traveling wheel rides on the convex portion, the ground pressure increases and the pressure in the oil chamber of the hydraulic cylinder 41 becomes higher than that of the other hydraulic cylinders 41. Get higher On the contrary, when it enters the concave portion, the ground pressure decreases and the pressure of the oil chamber of the hydraulic cylinder 41 decreases.

Therefore, the target stroke amount for the hydraulic cylinder 41 whose pressure has changed is corrected by adding such an external force (step #15). This process corresponds to the correction process. For example, when the pressure increases, the target stroke amount is corrected to be shorter, and when the pressure decreases, the target stroke amount is corrected to be longer. Then, the operation of the hydraulic control valve 73 is controlled to operate the hydraulic cylinder 41 so that the target stroke amount thus corrected is obtained (step #16).

By such control, regardless of the unevenness of the road surface, the four traveling wheels S can travel in a state of being grounded along the ground, slipping, or the other traveling wheels S floating from the ground and spinning. It is possible to avoid disadvantages such as doing.

[Third Embodiment]
Next, a third embodiment of the work vehicle according to the present invention will be described with reference to the drawings.
In this embodiment, the configuration of the control device 80 is different from that of the first embodiment, but other configurations are the same as those of the first embodiment. Hereinafter, only the points different from the first embodiment will be described, and description of the same configurations will be omitted.

In this embodiment, as shown in FIG. 14, the control device 80 obtains a horizontal tilt angle and a front-back tilt angle from the horizontal posture of the vehicle body based on the detection result of the inertial measurement device 81, and detects the detected tilt angle. Based on the information and the detection results (detected stroke amounts) of the four stroke sensors, the road surface inclination degree is obtained (step #21). Next, the target stroke amount required to set the vehicle body in a horizontal posture and to set the vehicle center of gravity position to the target height is obtained (step #22), and the actual stroke amount of the hydraulic cylinder 41 is set to the target stroke amount. The operation of hydraulic control valve 73 is controlled (step #23). This control corresponds to the vehicle height attitude control, and the same control as that described in the second embodiment is performed.

In this embodiment, the vehicle height attitude control is executed only on the basis of the vehicle body inclination information and the stroke amount information. In this embodiment, the pressure sensor 78 is unnecessary, the control configuration is simplified, and Cost reduction can be achieved.

[Another embodiment]
(1) In the above-described embodiment, the accumulator 75 is provided for each of the bottom side oil chamber 41a and the rod side oil chamber 41b in each hydraulic cylinder 41, but instead of this configuration, the bottom side oil chamber 41a is used. It may be configured to be provided in either one of the rod side oil chamber 41b and the rod side oil chamber 41b, or may be configured not to include such an accumulator 75.

(2) In the above embodiment, the pressure sensor 78 is provided for each of the bottom side oil chamber 41a and the rod side oil chamber 41b in each hydraulic cylinder 41, but instead of this configuration, the bottom side oil chamber It may be configured to be provided in either one of the chamber 41a and the rod-side oil chamber 41b.

(3) In the above-described embodiment, the stroke sensor 60 is configured to be built in the hydraulic cylinder 41, but instead of this configuration, the stroke sensor 60 may be separately provided outside the hydraulic cylinder 41.

(4) In the above-described embodiment, the inertial measurement unit (IMU) is used as the tilt sensor, but instead of this configuration, various types such as a weight-type tilt sensor and a liquid level detection-type tilt sensor may be used. A tilt sensor can be used.

(5) In the above-described embodiment, the chemical spraying device 2 is provided in the rear part of the traveling vehicle body as the working device, but the working device may be provided with a fertilizer applying device or another type of working device. Further, the work device may be provided in a state in which it is located at an intermediate position between the front wheels 3 and the rear wheels 4 in the traveling vehicle body.

The present invention can be applied to a work vehicle including a plurality of traveling wheels.

19 Support Member 40 Vehicle Height Adjustment Mechanism 41 Hydraulic Cylinder 41a Bottom Side Oil Chamber 41b Rod Side Oil Chamber 73 Hydraulic Control Valve 75 Accumulator 78 Pressure Sensor F Body Frame S Running Wheels

Claims (5)

A plurality of traveling wheels are supported by the vehicle body frame via a tubular support member that can expand and contract,
A hydraulically operated vehicle height adjusting mechanism capable of expanding and contracting the support member by a hydraulic cylinder to switch the relative height of the traveling wheels with respect to the vehicle body frame within a predetermined length range is provided to each of the traveling wheels. Prepared for
A hydraulic control valve capable of controlling the supply state of hydraulic oil separately for each of the plurality of hydraulic cylinders,
A control unit that controls the operation of the hydraulic control valve so that the vehicle body is brought into a target state by adjusting the vehicle height by the hydraulic cylinder with respect to the attitude variation of the vehicle body;
A work vehicle provided with a plurality of accumulators connected to the oil chambers of the plurality of hydraulic cylinders, respectively. The work vehicle according to claim 1, further comprising: a tilt sensor that measures a tilt angle of a vehicle body; and a plurality of stroke sensors that measure an expansion/contraction operation amount of each of the plurality of hydraulic cylinders. The work vehicle according to claim 2, further comprising a pressure sensor that measures a pressure in an oil chamber of each of the plurality of hydraulic cylinders. The hydraulic cylinder is a double-acting cylinder,
The accumulator is separately provided for each of the bottom side oil chamber and the rod side oil chamber in the hydraulic cylinder,
The work vehicle according to any one of claims 1 to 3, wherein the hydraulic control valve is a flow control valve capable of changing and adjusting a supply flow rate of hydraulic oil to the hydraulic cylinder. The work vehicle according to any one of claims 1 to 4, comprising a driver's seat on which a driver sits, and an operating member arranged in front of the driver's seat.

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