JPH09240503A - Four-wheel steered tractor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent side slip of a four-wheel steered tractor in traveling on the slope by optionally adjusting only the turning angle of rear wheels by an operator. SOLUTION: A full hydraulic controller 6 is controlled by the rotation of a steering wheel 5, pressure oil is supplied to steering cylinders 1, 3 through directional control valves 10, 11, and front wheels 2 and rear wheels 4 are turned. In the case of the same phase steering mode, both the directional control valve 10 and the directional control valve 11 are made in the position B. A manual switch 23 is provided on the way of wiring for connecting solenoids 21, 22 of a solenoid valve 14 for correcting the angle of the rear wheels to a four-wheel steering controller 20. When an operator operates the manual switch 23 either right or left, the solenoid 21 or 22 is turned on, the solenoid valve 14 is switched to the position B or C, discharge oil of a hydraulic pump 7 is supplied to the steering cylinder 3, and the rear wheels 4 are further turned.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a four-wheel steering tractor capable of steering front and rear wheels, and more particularly to a steering control device in the in-phase steering mode in which both front and rear wheels turn in the same direction. is there.

[0002]

2. Description of the Related Art FIG. 3 shows a hydraulic circuit of a steering device in a conventional four-wheel steering tractor of this type. Reference numeral 1 is a steering cylinder that turns the front wheels 2, and reference numeral 3 is a rear wheel 4.
It is a steering cylinder that turns the. The rotation of the steering wheel 5 controls the full hydraulic controller 6,
The pressure oil of the hydraulic pump 7 driven by an engine (not shown) is led from the P port of the full hydraulic controller 6 to the oil passage 8 or 9 via the A port or the B port.

In the four-wheel steering mode, the directional control valve 10 is switched to the position (b), pressure oil is supplied to the steering cylinder 1 to turn the front wheels 2 left or right, and
The directional control valve 11 is switched to the (b) or (c) position, pressure oil is supplied to the steering cylinder 3, and the rear wheel 4 turns left or right. The pressure oil discharged from the steering cylinder 1 or 3 is returned to the tank 12 from the T port of the total hydraulic controller 6.

Here, when the directional control valve 11 is switched to the position (b), the front and rear wheels 2 and 4 are in the same phase steering mode in which the directional control valve 11 turns in the same direction, and the directional control valve 11 is (c).
When the position is switched to the position of 1, the front wheel 2 and the rear wheel 4 are in the opposite phase steering mode in which they turn in opposite directions. Further, when switching from the four-wheel steering mode to the front-wheel steering mode or the rear-wheel steering mode, it is necessary to turn the front wheels 2 or the rear wheels 4 to the neutral state or to a predetermined angle. By switching one of the solenoid valves 14 and 15 for angle correction connected to the discharge oil passage 13, the hydraulic pump 7
Supply the discharged oil to the steering cylinder 3 or the steering cylinder 1 through the oil passages 16, 17 or 18, 19.
The turning angle of the front wheel 2 or the rear wheel 4 is forcibly corrected.

[0005]

When the four-wheel steering tractor travels along a contour line on a slope, the airframe tends to skid to the valley side. Therefore, as shown in FIG. 3, the in-phase steering mode is set. The control valves 10 and 11 are switched to the respective positions (b), and the front wheels 2 and the rear wheels 4 travel in a state in which the front wheels 2 and the rear wheels 4 are slightly turned toward the mountain side, as indicated by a chain double-dashed line. Since the working machine is connected to the rear part of the machine body, the rear wheel 4 may float up. At this time, the rear wheel 4 slides down to the valley side, and the machine body cannot return to its original posture.

However, the conventional solenoid valve 14 for angle correction,
Reference numeral 15 automatically operates when the steering mode is switched to correct the angles of the front and rear wheels 2 and 4, but the operator cannot arbitrarily adjust the turning angle.

Therefore, there arises a technical problem to be solved in order to allow the operator to arbitrarily adjust only the turning angle of the rear wheels to prevent the skid of the four-wheel steering tractor when traveling on a slope. The present invention aims to solve this problem.

[0008]

SUMMARY OF THE INVENTION The present invention has been proposed in order to achieve the above object, and controls all hydraulic controllers by rotation of a steering wheel, and steers front and rear wheels by switching directional control valves. In a four-wheel steering tractor having an electromagnetic valve for angle correction that connects each port of the steering cylinder to a tank, the front and rear wheels are in the same direction. A four-wheel steering tractor provided with a manual switch capable of switching only a solenoid valve for angle correction of a rear wheel during a turning in-phase steering mode.

[0009]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 shows a hydraulic circuit of a steering device of a four-wheel steering tractor. The same components as those of the conventional hydraulic circuit are designated by the same reference numerals and the description thereof will be omitted.

Direction control valves 10 for the front and rear steering cylinders,
11, and the solenoid valves 14 and 15 for angle correction are controlled by command signals from the four-wheel steering controller 20. In particular, the solenoids 21 and 22 of the solenoid valve 14 for the rear wheels are controlled.
A manual switch 23 is provided in the middle of the wiring connecting the four-wheel steering controller 20 with the.

The manual switch 23 is a normally open type, and when the operator manually operates it to the left side, the solenoid 21
Is turned on, and when operated to the right, the solenoid 22 is turned on. When the operator releases the hand, the manual switch 23 returns to the neutral position and the solenoid 2
Both 1 and 22 are formed to be turned off.

When a four-wheel steering tractor travels along a contour line on a slope, the vehicle body tends to skid to the valley side. Therefore, as shown in FIG. 11 are switched to the respective positions (b), and the front wheels 2 and the rear wheels 4 are driven with the front wheels 2 and the rear wheels 4 being slightly turned to the mountain side, as indicated by a chain double-dashed line. However, since the working machine is connected to the rear part of the machine body, the rear wheel 4 may float up, and the rear wheel 4 slides to the valley side.

At that time, the operator manually switches 23
Is operated to the mountain side (left side in the figure), the solenoid 21
Is turned on and the solenoid valve 14 is switched to the position (b). Therefore, the oil discharged from the hydraulic pump 7 is supplied to the steering cylinder 3 via the oil passage 16, the rear wheel 4 is further turned to the mountain side, and the rear wheel 4 is prevented from sliding to the valley side.

Then, when the operator releases the manual switch 23 when the correction of the turning angle of the rear wheel 4 is completed, the manual switch 23 returns to the neutral position and the solenoid 21 is turned off, whereby the electromagnetic field is reduced. The valve 14 returns to the position (a) and the vehicle travels in the original in-phase steering mode.

Here, when traveling on the sloping ground in the in-phase steering mode, when the angle of inclination of the field is gentle and the turning angles of the front and rear wheels 2 and 4 are small, the traveling is continued in the in-phase steering mode. There is a problem that the wheel 4 starts to climb to the mountain side.

In order to prevent this, an angle sensor (not shown) for detecting the turning angle of the front wheel 2 is provided, and the turning angle of the front wheel 2 is detected by the angle sensor to a predetermined value (for example, 5).
If it is less than 10 degrees, the directional control valve 11 is forcibly switched to the neutral position (a) even in the in-phase steering mode, and the front wheels 2 are changed to be steered. And
When the turning angle of the front wheels 2 exceeds a predetermined value, the directional control valve 11 is switched to the position (b) again to automatically restore the state in which both the front wheels 2 and the rear wheels 4 are steered. .

Further, a sensor for detecting the inclination may be provided instead of the manual switch 23. FIG. 2 shows the furrow working machine 3.
0, indicating that the arm 3
2 and 33 are attached so that they can swing up and down, and each arm 3
Rollers 34, 35 are pivotally attached to 2, 33. Further, the ridge sensors 36 and 37 are mounted inside the arms 32 and 33 so that the upward rotation of the arms 32 and 33 can be detected.

Now, when the ridge working machine 30 is traveling and the inclination angle of the field changes midway, the ridge working machine 30 is inclined toward the lower slope. At this time, of the left and right rollers 34, 35, the roller located on the valley side comes into contact with the ridge 38 or 39, the roller is pressed and the arm 32 or 33 is rotated upward, and the ridge sensor 36 or 37 is When turned on, the inclination of the furrow working machine 30 is detected.

For example, when the ridge working machine 30 inclines to the left in the figure, the ridge sensor 36 is turned on and the rear wheel 4
In order to correct the turning angle of the
Switch to the position. When the ridge working machine 30 is tilted to the right, the ridge sensor 37 is turned on, and the solenoid valve 14 is switched to the position (b) so as to correct the turning angle of the rear wheel 4 to the left.

As described above, even in the case where the left and right inclination angles change every moment in a wavy field, the ridge sensors 36 and 37 are provided.
The rotation angle of the rear wheel 4 can be automatically corrected by the detection of, and the sideslip of the rear wheel 4 can be prevented.

The present invention can be variously modified without departing from the spirit of the present invention, and it goes without saying that the present invention extends to the modified ones.

[0022]

As described above, according to the present invention, the operator can adjust the turning angle of the rear wheel by operating the manual switch. Therefore, for example, when a four-wheel steering tractor travels along a contour line on a slope, by adjusting only the turning angle of the rear wheels at any time, skidding on slopes can be prevented and the stability of travel can be improved. .

[Brief description of drawings]

FIG. 1 is a hydraulic circuit diagram of a steering device showing an embodiment of the present invention.

FIG. 2 is a rear view of the furrow working machine according to another embodiment.

FIG. 3 is a hydraulic circuit diagram showing a conventional technique.

[Explanation of symbols]

 1,3 Steering cylinder 2 Front wheel 4 Rear wheel 5 Steering wheel 6 Full hydraulic controller 10,11 Directional control valve 12 Tank 14,15 Solenoid valve (for angle correction) 20 Four-wheel steering controller 23 Manual switch

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Masato Nagai No. 1 Hachikura, Tobe-cho, Iyo-gun, Ehime Prefecture

Claims (1)

[Claims] 1. A full hydraulic controller is controlled by rotation of a steering wheel, and steering cylinders for front wheels and rear wheels are arbitrarily selected to be operable by switching directional control valves, and each of the steering cylinders is formed. In a four-wheel steering tractor equipped with a solenoid valve for correcting the angle that connects the port to the tank, only the solenoid valve for correcting the angle of the rear wheels is operated during the same-phase steering mode in which the front and rear wheels turn in the same direction. A four-wheel steering tractor having a switchable manual switch.