JPH0948362A - Steering hydraulic circuit of tractor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To simplify a conversion of a steering mode of a tractor, and to simplify the structure of a solenoid valve. SOLUTION: To an autobit roll 2 converted by a steering handle 1, and to a power steering hydraulic circuit 5 between a double acting type front wheel steering cylinder 3 and a rear wheel steering cylinder 4, a switch solenoid valve 6 to open and close circuits to the front and the rear wheel steering cylinders 3 and 4, and front and rear main solenoid valves 7 and 8 to open and close the circuits to the both steering cylinders 3 and 4 separately, are provided in the two-position converting valve type of opening and closing. Furthermore, between the switch solenoid valve 6, and the front and the rear main solenoid valves 7 and 8 to open and close the circuits to the front and the rear steering cylinders 3 and 4 separately, a subsolenoid valve 9 in the three-position converting valve type of the opening, the closing, and the direction conversion, is provided, and a feeding circuit 10 to feed an oil from a hydraulic pump P side is also connected, so as to compose this steering hydraulic circuit of a tractor.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a steering hydraulic circuit for a tractor. Front-wheel steering mode (FW)
S) and rear wheel steering mode (RWS) by rear wheel steering,
When switching the steering mode between the four-wheel steering mode (four-WS) and the front-rear wheel steering, it is intended to easily determine the angular positions of the front and rear wheels when switching between the modes.

[0002]

2. Description of the Related Art The steering mode of a tractor is roughly classified into the FWS as described above.
, RWS, and 4WS, each time the steering mode is switched, the steering wheel is operated to direct the front wheels or the rear wheels to the neutral position (straight ahead position), and then the steering mode is switched. , Restart the steering wheel operation. Therefore, the operation is troublesome in switching the steering mode.

[0003]

The present invention provides a power steering hydraulic circuit 5 between an orbit roll 2 which is switched by a steering wheel 1 and a front-wheel steering cylinder 3 and a rear-wheel steering cylinder 4 in a double-acting form. Open / close solenoid valve 6 for opening / closing the circuit to these front / rear wheel steering cylinders 3, 4.
And front and rear main solenoid valves 7 and 8 for separately opening and closing the circuits to the steering cylinders 3 and 4, respectively, are provided in the form of a two-position switching valve for opening and closing. Front / rear main solenoid valves 7, 8 for opening / closing the circuits to the rear wheel steering cylinders 3, 4 separately
Between the and, a sub-solenoid valve 9 in the form of a three-position switching valve for opening and closing and switching the direction is provided, and a supply circuit 10 for supplying oil from the hydraulic pump P side is connected in series. The configuration.

[0004]

By the steering operation of the steering handle 1, the front wheel steering cylinder 3 or the rear wheel steering cylinder 4 is hydraulically operated by the orbit roll 2 through the power steering hydraulic circuit 5, and the front wheels or the rear wheels are operated. The steering is done. When the steering mode designation is changed, the open / close solenoid valve 6 is controlled by the output from the controller.
Alternatively, the front and rear main solenoid valves 7, 8 and the sub solenoid valve are switched and controlled to control the steering wheel 1.
The front-wheel steering cylinder 3 or the rear-wheel steering cylinder 4 on the non-steering side is returned to the neutral position or is corrected to match the steering cylinder 3 or 4 on the side already steered by the steering wheel 1. .

At this time, the front and rear main solenoid valves 7 and 8 are for operating the front and rear wheel steering cylinders 3 and 4 to the neutral position or the correction position in accordance with the designation of the steering mode, At this time, the sub solenoid valve 9
The steering valve is switched to the right, and the open / close solenoid valve 6 operates when operating the front / rear wheel steering cylinders 3 and 4 in the power steering hydraulic circuit 5 to the neutral position or the correction position. It is intended to eliminate the influence on the steering wheel 1.

In this way, when the front and rear wheel steering cylinders 3 and 4 operate at the steering start positions corresponding to the respective steering modes, the opening / closing solenoid valve 6 opens the power steering hydraulic circuit 5 and the orbit roll. Steering is performed by operating the steering wheel 1 of 2. Further, the sub-solenoid valve 9 is in the neutral position and the hydraulic pressure supply to the supply circuit 10 is stopped to supply the hydraulic pressure of the hydraulic pump P only to the orbit roll 2 side.

According to the present invention, as described above, the power steering hydraulic circuit 5 is provided with the front / rear main solenoid valves 7 and 8 and the opening / closing solenoid valve 6 in the form of a two-position switching valve for opening / closing. Since the supply circuit 10 having the sub-solenoid valve 9 in the form of a three-position switching valve for switching is connected in series, the solenoid valves 6 to 9 are connected.
With a simple structure, the reference positions of the front and rear wheel steering cylinders 3 and 4 can be determined by electronic output from the controller according to the steering mode, and the switching operation of each steering mode is easy. Can be facilitated. Moreover, since the opening / closing solenoid valve 6 closes the power steering hydraulic circuit 5 when switching the steering mode, it is possible to eliminate the influence of the sub solenoid valve 9 on the orbit roll 2. The operation of the rear steering cylinders 3 and 4 can be performed quickly and accurately.

[0008]

[Example] Wheels 11 and 12 are provided at the front and rear of a tractor vehicle body so as to be a four-wheel traveling mode, and front and rear wheel steering cylinders 3 and 3, respectively.
By the hydraulic operation of No. 4, double-acting type pistons 13, 14,
The rods 15 and 16, the steering arms 17 and 18, the tie rods 19 and 20, and the like can be interlocked and steered. Each of the front wheels 11 and the rear wheels 12 includes steering pins 21 on both left and right ends of the front axle housing and the rear axle housing.
The front and rear steering cylinders 3 and 4 are rotatable around 22 and are provided on the corresponding axle housing portions or vehicle bodies.

The hydraulic circuits for each of the front and rear steering cylinders 3 and 4 are a power steering hydraulic circuit 5 which is switched and controlled by an orbit roll 2 and a supply circuit 1 which connects the power steering hydraulic circuit 5 and the power steering hydraulic circuit 5.
It consists of 0. The orbit roll 2 flows the amount of oil according to the steering direction and the operation angle in the power steering hydraulic circuit 5 by the steering operation of the steering handle 1.
This hydraulic pressure operates the front and rear wheel steering cylinders 3 and 4. The open / close solenoid valve 6 opens / closes a portion of the power steering hydraulic circuit 5 with the orbit roll 2 side, and communicates with the front / rear main solenoid valves 7, 8 in the closed position. In addition, front and rear main solenoid valves 7,
The power steering hydraulic circuit 5 is provided on the front-wheel steering cylinder 3 side and the rear-wheel steering cylinder 4 side of the power steering hydraulic circuit 5, and opens and closes the circuits on the front-rear-wheel steering cylinders 3 and 4 side. The open / close solenoid valves 6 and the front / rear main solenoid valves 7 and 8 are two-position switching valves that open / close the circuit 5.

The sub-solenoid valve 9 is provided in a supply circuit 10 which is connected between the open / close solenoid valve 6 of the power steering hydraulic circuit 5 and the front / rear main solenoid valves 7 and 8, and controls the hydraulic pressure of the hydraulic pump P to a neutral position. From the left side steering to the right side steering, and a circuit 23 for supplying oil to the orbit roll 2 is continuously provided at the neutral position. T is a tank port.

The controller CPU has a microcomputer, and on the input side, a steering sensor 24 for detecting the steering direction and angle of the steering handle 1, the FW.
It has a changeover switch 25 for switching the steering mode such as S, RWS, and 4WS, front and rear wheel steering sensors 26 and 27 for detecting the steering angles of the front wheels 11 and the rear wheels 12, and the like. The solenoids A, B, C, L and R of the solenoid valves 6 to 9 can be output.

FIG. 1 shows the state of the front wheel steering mode FWS in which the solenoids A, B, C, L and R of the valves 6 to 9 are all in the OFF state. The control when the steering mode FWS is switched to, for example, the four-wheel steering mode 4WS will be described. The rear wheel 12 is aligned with the steering position of the front wheel 11 and then switched. Set the steering mode switch 25 to the front wheel steering mode FW.
When the mode is switched from S to the four-wheel steering mode 4WS, the solenoids A, B, C and L or R are first turned ON, the open / close solenoid valve 6 and the front main solenoid valve B are both closed, and the rear main solenoid valve 8 is closed. Is open,
The hydraulic pressure supplied from the supply circuit 10 is supplied to the rear wheel steering cylinder 4 via the valve 8 in a state where the sub solenoid valve 9 is controlled to be opened to the left or right. As a result, the steering angle of the rear wheel 12 is corrected to match the steering angle of the front wheel 11.

In this way, the rear wheels 12 are replaced by the front wheels 11.
The solenoid C remains ON, but the solenoids A and B are turned OFF, so that the power steering hydraulic circuit 5 by the orbit roll 2 can be steered according to the steering angle of the front main solenoid valve 7 Front wheel steering cylinder 3 and rear main solenoid valve 8
The rear wheel steering cylinder 4 is in a four-wheel steering mode 4WS state in which both can be steered. This steering handle 1
During the steering by, the sub-solenoid valve 9 is in the neutral position, and oil is sent from the circuit 23 to the orbit roll 2 side.

Next, the case of switching the front wheel steering mode FWS to the rear wheel steering mode RWS will be described. The front wheels 11 are switched after returning to the neutral position of the straight traveling posture. By switching the steering mode switch 25 from the front-wheel steering mode FWS to the rear-wheel steering mode RWS, the solenoids B and C remain off first, but the solenoid A and
L or R is turned on, and the front wheel steering cylinder 3 is steered to the neutral position by the hydraulic pressure by the operation of the sub solenoid valve 9 passing through the front main solenoid valve 7.

When the front wheel 11 is returned to the neutral position, the solenoid A is turned off, the solenoid C is turned on, the solenoid B is kept on, and the solenoid L or R is kept off. Then, the sub-solenoid valve 9 closes the supply circuit 10, and the opening / closing solenoid valve 6 and the rear main solenoid valve 8 open to steer the rear wheel 12 by the orbit roll 2.

In switching the steering mode as described above,
At the time of switching, the sub-solenoid valve 9 is switched between left L and right R to supply hydraulic pressure from the supply circuit 10 to the power steering hydraulic circuit 5, and by closing the opening / closing solenoid valve 6, the orbit roll 2 and this power steering hydraulic circuit 5 are closed. The circuit 5 is disconnected from the circuit 5, and the hydraulic pressure in the power steering hydraulic circuit 5 does not reversely move the orbit roll 2 so that the correction operation of the front and rear wheel steering cylinders 3 and 4 is quickly and accurately performed. . When the control by the sub-solenoid valve 9 is finished and the neutral position is reached, the hydraulic pressure can be sent from the circuit 23 to the orbit roll 2 side for steering by the steering wheel 1. At this time, the open / close solenoid valve 6 is in the open position.

3 is different from the above example in that the front wheel steering cylinder 3 and the rear wheel steering cylinder 4 have poppet solenoid valves 28 to 30 and 31 in the four-wheel steering hydraulic control circuit of FIG. To 33 are configured in a bridge form, one ends of both bridge circuits 28 to 30 and 31 to 33 are connected, and the A and B ports of the orbit roll 2 are connected. As a result, it is possible to reduce the amount of leak when the steering cylinders 3 and 4 are closed, to prevent contamination, and to improve responsiveness.

In the normal front wheel steering mode FWS, all poppet solenoid valves are turned off as shown in the figure. or,
In the rear wheel steering mode RWS, all poppet solenoid valves are turned on. In the four-wheel steering mode 4WS, the poppet solenoid valves 31 to 33 on the rear-wheel steering cylinder 4 side.
Is switched on and the poppet solenoid valves 28 to 30 on the front wheel steering cylinder 3 side are switched off.

4 to 6 are different from the above example in that
Piston 1 in the front and rear wheel steering cylinders 3 and 4
By separating 3 and 14 in the cylinder direction and hydraulically expanding and contracting the interval between these pistons 13 and 14, the steering modes of the steering arms 17 and 18, the front wheels 11 and the rear wheels 12 are changed and controlled. is there. The front / rear main solenoid valves 34, 35 in the power steering hydraulic circuit 5 are in the three-position switching mode, and the pistons 13 of the steering cylinders 3, 4 are controlled.
Circuits 5S, 5M capable of supplying / discharging hydraulic pressure are provided respectively on the outer side S of L, 13R, 14L, 14R and the interval M between the left and right pistons 13L, 13R. Each of the front and rear wheel steering cylinders 3 and 4 is attached to the vehicle body side so as not to move in the left-right direction. The front-wheel steering cylinder 3 is configured to be longer than the rear-wheel steering cylinder 4, and the left and right pistons 1 in a straight running state.
The interval M between 3L and 13R is set to be larger than the interval M between the pistons 14L and 14R on the rear wheel steering cylinder 4 side.

Normal front wheel steering mode, rear wheel steering mode,
Further, in the four-wheel steering mode, a certain amount of oil is fed into the space M between the pistons 13L and 13R on the front wheel 11 side as shown in FIG. As a result, both pistons 13L and 13R are integrally moved to the left and right to steer the front wheels. Further, on the rear wheel 12 side, the steering is performed in a state where the distance between the pistons 14L and 14R is shortened by discharging the oil from 5M.

When making a small turn on the spot, as shown in FIG. 6, the interval M between the pistons 13L and 13R on the front wheel 11 side is shortened and the interval M between the pistons 14L and 14R on the rear wheel 12 side is expanded. By doing so, the wheels 11, 12 can be steered along the turning circle locus line Y of the turning center X. At this time, the left and right front wheels 11 and rear wheels 1
The wheels 11 and 12 on either one of the two sides are turned off to bring them into a free rotation state. Also, this may be driven in reverse rotation. The center of the vehicle body is on the turning center X, and the turning can be performed on the spot with almost no movement.

In FIG. 7, the difference from the above example is that the return circuit 37 of the power steering circuit 36 is provided with a bubble removing device 38 for removing bubbles mixed in the oil, and the oil after removing the bubbles is supplied to the hydraulic pump P. It is configured to return to the suction side,
Prevent abnormal noise, prevent aeration of oil in the mission, and reduce suction negative pressure. The oil returned from the return circuit 37 flows down while swirling in the cyclone hopper 39 of the bubble removing device 38, passes through the throttle 40 of the circuit 41, and is returned to the suction side of the hydraulic pump P. An air vent pipe 42 is provided at the center of the cyclone hopper 39, and by applying an appropriate back pressure to the outlet side of the cyclone hopper 39 by a throttle 40 or the like, air bubbles mixed in the return oil can be removed from this air vent pipe. Can be removed from 42. 43 is an oil filter.

[Brief description of drawings]

FIG. 1 is a steering hydraulic circuit diagram.

FIG. 2 is a control block diagram.

FIG. 3 is a steering hydraulic circuit diagram showing a partially different embodiment.

FIG. 4 is a steering hydraulic circuit diagram showing a partially different embodiment.

FIG. 5 is a plan view showing a part of the operation thereof.

FIG. 6 is a plan view showing the operation of a part thereof.

FIG. 7 is a hydraulic circuit diagram showing a partially different embodiment.

[Explanation of symbols]

 1 Steering handle 2 Orbit roll 3 Front wheel steering cylinder 4 Rear wheel steering cylinder 5 Power steering hydraulic circuit 6 Open / close solenoid valve 7 Front main solenoid valve 8 Rear main solenoid valve 9 Sub main solenoid valve 10 Supply circuit P Hydraulic pump

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Koji Otsuka 1 Yakura, Tobe-cho, Iyo-gun, Ehime Prefecture Izeki Agricultural Machinery Co., Ltd.

Claims (1)

[Claims] 1. An orbit roll 2 which can be switched by a steering wheel 1 and a front-wheel steering cylinder 3 of a double-acting type.
And a power steering hydraulic circuit 5 between the rear wheel steering cylinder 4 and
An open / close solenoid valve 6 for opening / closing a circuit to these front and rear wheel steering cylinders 3, 4 and each steering cylinder 3, 4
The front and rear main solenoid valves 7 and 8 for separately opening and closing the circuit are provided in the form of two-position switching valves for opening and closing, respectively, and further, these opening and closing solenoid valves 6 and the front and rear wheel steering cylinders 3 and 4 are connected. A sub-solenoid valve 9 in the form of a three-position switching valve for opening and closing and switching the direction is provided between the front and rear main solenoid valves 7 and 8 for separately opening and closing the circuit of FIG. Supply circuit 1
Steering hydraulic circuit for tractors consisting of 0s.