JPH09221055A - Four wheel steering device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To facilitate the turning of two wheels and two rear wheels in the same direction and in the same amount, in a traveling vehicle provided with a single rod type front wheel steering cylinder and a rear wheel cylinder. SOLUTION: A hydraulic circuit which activates the front steering cylinder 18 and the rear steering cylinder 23 comprises; a main circuit having a four wheel steering changeover valve for changing the mode of operation among three modes, a front steering mode wherein only the cylinder 18 is activated for turning the front wheels 2, 2, a rear steering mode wherein only the cylinder 23 is activated for turning the rear wheels, four wheel steering mode wherein both of the cylinders 18, 23 are activated to turn the front wheels and rear wheels 3, 3 symmetrically with respect the longitudinal axis of a vehicle; a subordinate circuit having a changeover valve 43 for activating rear setting cylinder 23; and a changeover switch 47 for changing the changeover valve 43 so as to activate the cylinders 18, 23 in an interlocked manner and thereby turn the front wheels and the rear wheels in the same direction.

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 system such as a tractor.

[0002]

2. Description of the Related Art As a four-wheel steering system for a power agricultural machine such as a tractor, for example, a front rod and a rear wheel are provided with single rod type steering cylinders, and the front and rear steering cylinders are expanded and contracted. A configuration for steering a vehicle is known. This conventional four-wheel steering system has a mode in which only the front wheels are steered by expanding and contracting the front wheel steering cylinder, and a mode in which only the rear wheels are operated by expanding and contracting the rear wheel steering cylinder,
The front-wheel steering cylinder and the rear-wheel steering cylinder can be expanded and contracted to switch to a mode in which the front wheels and the rear wheels are steered in opposite directions, and the mode is switched according to the situation.

[0003]

When the tractor travels along a contour line on a sloping ground, the action of the body sliding down to the valley side works. In such a situation, it is preferable to steer the front wheels and the rear wheels to a slightly mountain side, but the conventional four-wheel steering system described above cannot do this, so that traveling on a slope is not stable. Therefore, it is an object of the present invention to make it possible to steer the front wheels and the rear wheels in the same direction and to stabilize traveling on a slope.

[0004]

In order to solve the above-mentioned problems, the present invention has the following constitution. That is, a four-wheel steering system according to the present invention includes a single rod type front wheel steering cylinder and a rear wheel steering cylinder, and a hydraulic circuit for operating these steering cylinders is provided by expanding and contracting the front wheel steering cylinder. Steering mode, a mode in which the rear wheel steering cylinder is expanded and contracted to steer only the rear wheels, and a mode in which the front wheel steering cylinder and the rear wheel steering cylinder are expanded and contracted to steer the front and rear wheels in opposite directions. It consists of a main circuit equipped with a four-wheel steering switching valve for switching to the front wheel and a sub-circuit equipped with a rear-wheel steering switching valve that expands and contracts the rear-wheel steering cylinder. A switch for switching the rear wheel steering switching valve is provided so that the wheels are steered in the same direction by the same amount.

[0005]

DETAILED DESCRIPTION OF THE INVENTION A four-wheel steering system for a tractor illustrated in the drawings will be described below. The tractor 1 shown in FIGS. 1 and 2 includes a pair of left and right front wheels 2, 2 and a rear wheel 3,
A four-wheeled vehicle equipped with a steering wheel 5 having a hood 4 at the front of the vehicle body, and a steering handle 5 for steering the front wheels 2, 2 and the rear wheels 3, 3 individually or simultaneously at the front thereof. Further, a cockpit 6 is installed behind the steering wheel 5.

Lift arms 8 and 8 are provided at the rear part of the machine body for pivoting up and down, and a working machine (a rotary tiller in the illustrated example) is attached to a hitch 9 fixed to the rear ends of the lift arms 8 and 8.
10 are connected. Piston rods of lift cylinders 11 and 11 are connected to the lift arms 8 and 11a, 11a, and the working machine 10 is moved up and down by expanding and contracting the lift cylinders. Further, a rolling cylinder 12 is attached to one side of the hitch 9, and the hitch 9 is rotated around the PTO shaft 13 by extending and contracting the rolling cylinder to change the lateral inclination of the working machine 10. It has become.

As shown in FIG. 3, the front wheels 2 and 2 are pivotally supported by front wheel support cases 15 and 15 which are provided so as to be able to be deflected in a horizontal plane. The left and right knuckle arms 16 and 16 projecting from the front wheel support cases 15 and 15 are connected by a tie rod 17, and one of the knuckle arms 16 and 16 is connected.
A front wheel steering cylinder 18 is provided so as to rotate. Further, the rear wheels 3 and 3 are pivotally supported by rear wheel support cases 20 and 20 that are provided so as to be able to change directions in a horizontal plane. The left and right knuckle arms 21 and 21 projecting from the rear wheel support cases 20 and 20 are connected by a tie rod 22, and a rear wheel steering cylinder 23 is provided so that either one of the knuckle arms 21 can be rotated. Has been.

FIG. 5 is a hydraulic circuit diagram of the four-wheel steering system for the tractor 1. The main circuit A is supplied with hydraulic oil by the hydraulic pump 25 and the sub-circuit B is supplied with hydraulic oil by the hydraulic pump 26. Consists of. Both hydraulic pumps 25, 2
6 is driven by the engine E.

The main circuit A is provided with four-wheel steering switching valves 28 and 29. The switching valve 28 is connected to the front wheel steering cylinder 18 via oil passages 30 and 31, and the switching valve 29 is connected to the oil passages 32 and 31.
It is connected to the rear wheel steering cylinder 23 at 33. Reference numeral 35 is an orbic roll, and hydraulic fluid sent from the hydraulic pump 25 is connected to the switching valve 28 in accordance with the steering direction of the steering wheel 5 and the amount of rotation.
Alternatively, the oil is supplied to the oil passage 37 connected to the switching valve 29. By switching the valve positions of the four-wheel steering switching valves 28 and 29, the front-wheel steering cylinder 18 is expanded and contracted to steer only the front wheels 2 and 2, and a "front-wheel steering mode" is provided.
The “rear wheel steering mode” in which the rear wheel steering cylinder 23 is expanded and contracted to steer only the rear wheels 3 and 3, and the front wheel steering cylinder 1
8 and the rear wheel steering cylinder 23 are simultaneously expanded and contracted to become one of the "four-wheel antiphase steering mode" in which the front wheels 2, 2 and the rear wheels 3, 3 are steered in opposite directions.

In the sub-circuit B, the lift cylinder 11,
An elevation control valve 40 for controlling 11 and a rolling control valve 41 for controlling the rolling cylinder 12 are provided, and hydraulic fluid sent from the hydraulic pump 26 is divided by the flow dividing valve 42 into both the elevation control valve 40 and the rolling control valve 41. It is designed to be supplied by flushing. Further, there is provided a rear wheel steering switching valve 43 to which hydraulic oil is supplied via the rolling control valve when the rolling control valve 41 is in the neutral position, and the oil discharge side of the rear wheel steering switching valve 43 is an oil passage 44, Four
It is connected to the oil passages 32 and 33 via 5.

The rear wheel steering switching valve 43 is an electromagnetic valve, and as shown in FIG. 3, the expansion solenoid 43a and the contraction solenoid 43b are located at a position where neither solenoid is energized and the expansion solenoid 43a. It is connected to a three-point position limit switch 47 having a position for energizing and a position for energizing the contracting solenoid 43b. The limit switch 47 is attached to the piston rod 23a of the rear wheel steering cylinder 23, and its switch lever 47a is interlocked with the movement of the piston rod 18a of the front wheel steering cylinder 18 via push-pull wires 48, 48, etc. It is designed to switch to one of three positions. A four-wheel in-phase steering switch 49 that is manually turned on and off is provided in the wiring connecting the limit switch 47 and the power supply.

When the four-wheel in-phase steering switch 49 is turned on, the front wheel steering cylinder 18 and the rear wheel steering cylinder 23 are turned on.
Limit switch 47 is turned off when the
When the rear wheel steering cylinder 23 becomes longer than the front wheel steering cylinder 18, the limit switch 47 switches to the side that excites the contraction solenoid 43b, and the rear wheel steering cylinder 23 becomes shorter than the front wheel steering cylinder 18. The limit switch 47 is switched to the side that excites the expansion solenoid 43a. That is, the front wheel steering cylinder 18 and the rear wheel steering cylinder 23 are controlled so as to always have the same length, whereby the front wheels 2, 2 and the rear wheels 3, 3 are controlled in accordance with the operation amount of the steering wheel 5. It is in the "four-wheel in-phase steering mode" in which the aircraft is steered in the same direction by the same amount and the aircraft moves diagonally in parallel like a crab.

The rear wheel steering switching valve 43 is the rolling control valve 4
1, the hydraulic oil is supplied only when the rolling control valve 41 is in the neutral position, so that the amount of hydraulic oil flowing through the oil passages 44, 45 is constant and the rear wheels 3, 3 Steering angle correction is stable.

Further, as shown in FIG. 4, the limit switch 47 is rotatably mounted on a mounting plate 50 fixed to the piston rod 23a of the rear wheel steering cylinder 23, and is integrated with the limit switch 47. A pair of neutral springs 52, 5 provided on both sides of the tip of the rotating arm 51.
It is supported by 3 so that it can always be kept in the neutral position. Then, one end of the push-pull wire 54 is connected to the arm 51, and the other end of the push-pull wire 54 is connected to the correction lever 55. Therefore, when the correction lever 55 is operated, the limit switch 47 is forcibly rotated, and the expansion solenoid 43a or the contraction solenoid 43b is energized.

As described above, this four-wheel steering system is a "front wheel steering mode" in which only the front wheels 2 and 2 are steered by switching the four-wheel steering switching valves 28 and 29 provided in the main circuit A. And one of the "rear wheel steering mode" for steering only the rear wheels 3, 3 and the "four-wheel anti-phase steering mode" for steering the front wheels 2, 2 and the rear wheels 3, 3 in opposite directions. When the four-wheel in-phase steering switch 48 is turned on in the "front wheel steering mode" when selected, the steering amount of the front wheels 2 and 2 is fed back to the rear wheel steering switching valve 43 provided in the sub-circuit B, This is the "four-wheel in-phase steering mode" in which the front wheels 2 and 2 and the rear wheels 3 and 3 are steered in the same direction by the same amount.

When working or traveling on a flat ground, the "front wheel steering mode" or "rear wheel steering mode" is usually used depending on the field conditions.
Select an appropriate steering mode from "four-wheel reverse-phase steering mode". Also, when working or traveling along contour lines on sloping ground, in order to prevent the aircraft from sliding down to the valley side,
The "four-wheel in-phase steering mode" is selected and the front wheels 2, 2 and the rear wheels 3, 3 are steered to the mountain side. In particular, when working on a sloping ground with a heavy work machine (for example, a rotary tiller) 10, the rear wheels 3 and 3 largely slide down to the valley side due to the weight of the work machine. Therefore, the correction lever 55 is operated to operate the rear wheel. Three
Steering 3 to the mountain side more than the front wheels 2 and 2 corrects the course of the airframe. When the correction lever 55 is released, the steering amounts of the rear wheels 3 and 3 return to the same as the steering amounts of the front wheels 2 and 2.

FIG. 6 shows a different four-wheel steering mechanism. This four-wheel steering mechanism is provided on a tractor having a ridge former 60 mounted on the rear side of the rotary tiller 10, and the ridge former 60 rolls the groove of an already formed ridge adjacent to the ridge currently being formed. It has rolling wheels 61 that move. This rolling wheel 61
Is a scanning sensor for running the machine body along the preformed ridges, and is supported so as to be swingable left and right about a shaft 62 as a fulcrum, and pulled by springs 64 and 65 to the left and right sides. Then, one end of the push-pull wire 54 is connected to the tip of an arm 66 that rotates integrally with the ridge former 60. That is, instead of manually switching the limit switch 47 by the correction lever 55 in the four-wheel steering mechanism shown in FIG. 3, the four-wheel steering mechanism shown in FIG. 6 automatically limits the limit based on the movement of the rolling wheels 61 which are copy sensors. The switch 47 is switched. In addition,
Since the work on the sloping ground is generally performed from the mountain side to the valley side, the rolling wheels 61 are provided on the mountain side of the rotary tiller 10.

When the course of the machine body is deviated during the ridge forming operation, the rolling wheels 61 hit the slope of the ridge and rotate left and right, whereby the limit switch 47 is switched via the push-pull wire 54. For example, when the rear wheels 3, 3 of the vehicle body slide down to the valley side on a sloping ground, the steering angle of the rear wheels is corrected to be large. As a result, the machine body can be run parallel to the already formed ridges.

[0019]

As described above, the four-wheel steering system according to the present invention uses an expensive directional control valve in a four-wheel steering mechanism including a single rod type front wheel steering cylinder and a rear wheel steering cylinder. It is possible to steer the front wheels and the rear wheels in the same direction and by the same amount with a simple hydraulic circuit configuration.

[Brief description of drawings]

FIG. 1 is a side view of a tractor.

FIG. 2 is a plan view of a tractor.

FIG. 3 is a diagram showing a four-wheel steering mechanism.

FIG. 4 is an enlarged view showing a main part of a four-wheel steering mechanism.

FIG. 5 is a hydraulic circuit diagram of a four-wheel steering system.

FIG. 6 is a hydraulic circuit diagram of a different four-wheel steering system.

[Explanation of symbols]

 1 tractor 2 front wheel 3 rear wheel 5 steering wheel 18 front wheel steering cylinder 23 rear wheel steering cylinder 28, 29 four wheel steering switching valve 43 rear wheel steering switching valve 47 limit switch 48 four wheel in-phase steering switch

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Masato Nagai, No. 1 Yakura, Tobe-cho, Iyo-gun, Ehime Prefecture, Technical Department, Iseki Agricultural Machinery Co., Ltd. Department

Claims (1)

[Claims] 1. A single-rod type front wheel steering cylinder and a rear wheel steering cylinder are provided, and a hydraulic circuit for operating these steering cylinders has a mode in which the front wheel steering cylinder is expanded and contracted to steer only the front wheels, and a rear wheel steering cylinder. A four-wheel steering switching valve that switches between a mode in which the wheel steering cylinder is expanded and contracted to steer only the rear wheels, and a mode in which the front wheel steering cylinder and the rear wheel steering cylinder are expanded and contracted to steer the front and rear wheels in opposite directions. And a sub-circuit with a rear-wheel steering switching valve that expands and contracts the rear-wheel steering cylinder.The front and rear wheels move in the same direction in the same direction in conjunction with the movement of the front-wheel steering cylinder. A four-wheel steering system comprising a switch for switching the rear-wheel steering switching valve so that the steering wheel is steered only.