JPS62221971A - Four-wheel steering gear - Google Patents

Abstract

PURPOSE:To make spring force adjustable, by installing a pair of air pistons in a rear-wheel steering drive cylinder and interposing a spring between these pistons. CONSTITUTION:When a hydraulic fluid is fed to one side hydraulic chamber 53 for a drive cylinder of a rear-wheel steering gear, another hydraulic fluid in the other hydraulic chamber 54 is restored. In consequence, one side movable piston 34 moves a drive shaft 33 in the right direction, thereby steering rear wheels. At this time, if air is led into a first air chamber 45 and pressure is made to go up, neutral position holding force of the drive shaft 33 becomes strengthened in cooperation with the pressure and spring force of a spring 42. Reversely, if air is led into each of second air chambers 46 and 47, it acts on a direction weakening the spring force of the spring 42.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a four-wheel steering device that power assists the steering force of rear wheels in response to front wheel steering.

(Prior Art) The conventional device shown in FIG. 4 steers the front wheels 2, 3 by turning the handle 1, switches the pulp 4 in connection with the front wheel steering, and controls the drive cylinder 5 on the rear wheel side. is operated to steer the rear wheels 6.7.

In the drive cylinder 5 as described above, springs 11 and 12 are provided in the pressure chambers 9 and 10 defined by the piston 8, and the spring force keeps the piston 8 in the neutral position.

(Problems to be Solved by the Invention) In this type of device, it is desirable that the spring force of the springs 11 and 12 be large for large vehicles and small for small vehicles; The problem with this device is that the spring force cannot be freely selected. for example,
the spring 11.1 to increase the spring force;
If an attempt is made to increase the thickness of the cylinder 2 and the number of turns thereof, the drive cylinder 5 will become larger. However, in the case of rear-wheel drive vehicles and four-wheel drive vehicles, the propeller shaft and differential gear are located on the rear wheels, so if the drive cylinder becomes larger, it becomes impossible to install it, and in the end,
There was a problem in that the spring force of the springs 11 and 12 could not be increased.

Further, in the conventional device, since the spring force of the spring cannot be freely adjusted, there is a problem in that it is difficult to make subtle control adjustments or changes between the operating pressure and the differential displacement amount.

(Means for Solving the Problems) In order to achieve the above object, the present invention has the following configuration.

That is, in conjunction with front wheel steering, the steering direction of the rear wheels is controlled by M, and a drive cylinder is provided to power assist the steering force of the rear wheels, and the rear wheels are steered by moving the drive shaft of this drive cylinder. In the four-wheel steering device, a pair of air pistons are provided in the drive cylinder, a spring is interposed between them, and the space between the air pistons with the spring interposed is a first one.
an air chamber, an air supply/discharge port is formed in this first air chamber, a second air chamber is further defined outside the air piston, and a supply/discharge port is formed in each of these second air chambers. Further, the working force of the air piston is applied to the drive shaft, and the driving force of the movable piston is applied to the drive shaft, so that the pressure action of the first air chamber is applied to the driving force of the movable piston. The pressure acting on the second air chamber acts as an assisting force against the driving force of the movable piston.

(Operation of the present invention) With the above configuration, when air is supplied to the first air chamber, the spring force of the spring is substantially increased, and air is supplied to the second air chamber. In some cases, the same effect occurs as if the spring force of the spring described above was weakened.

(Effects of the present invention) According to the device of the present invention, even if the size of the drive cylinder is constant, the spring force of the spring can be adjusted substantially, so that the drive cylinder can be installed within the permissible limit. It is possible to correspond to the size of the vehicle while maintaining the size within the range, and it is also possible to easily make delicate control adjustments between the operating pressure and the operating displacement amount of the drive cylinder.

(Embodiment of the present invention) A first embodiment showing an embodiment of the present invention has a front wheel steering device a and a rear wheel steering device a. Then, the input shaft 14 rotates while twisting the torsion bar 15, and the rotary valve 16 is switched depending on the direction of rotation of the input shaft 14. Moreover, the chambers 18 and 19 partitioned by the piston 17 communicate with either the pump P or the tank T, depending on the switching position of the rotary valve 16, and control the moving direction of the piston 17. A rack portion 17a is formed on the piston 17 thus constructed, and a sector gear 20 is formed on this rack portion 17a.
are interlocking.

Therefore, when one chamber 18 communicates with the pump P and the other chamber 18 communicates with the tank T, the piston 17 moves to the right in FIG. Rotate it. Further, one chamber 18 communicates with the tank T.

When the other chamber 19 communicates with the pump P, the piston 17 moves to the left in the drawing and rotates the sector gear 20 counterclockwise. When the sector gear 20 rotates in this manner, the pitman arm 21 is rotated and power assists the steering force of the front wheels.

A gear portion 20a is formed on the L sector gear 20, and this gear portion 20a is located on the opposite side of the engaging portion with the rack portion 17a. It engages with the rack portion 22a of the S rack piston 22.

The metering cylinder S also has a passageway 25.24 in an oil chamber 23.24 defined by the rack piston 22.
As shown in FIG. 1, these passages 25 and 26 are connected to the drive cylinder d of the rear wheel steering system via a one-phase switching solenoid valve 27. Then, on the upstream side of the solenoid valve 27, a solenoid valve 28 is connected to connect one passage 25, 28 and to cut off the communication, and a suction solenoid valve 29 is connected to one passage 25. .

When the front wheel steering device a is driven with the electromagnetic valve 28 set in the closed position, the sector gear 20 rotates as the piston 17 moves, and the rack piston 22 of the metering cylinder S also moves. let For example, when the rack piston 22 moves to the left in the drawing, the hydraulic oil in one oil chamber 23 flows out and is supplied to the drive cylinder d, and the return oil from the drive cylinder d flows into the other oil chamber 22. Inflow. In other words, the drive cylinder d is driven using the hydraulic oil discharged from the metering cylinder S as a hydraulic source, and power assists the steering force of the rear wheel steering system.

Further, whether the steering direction of the rear wheels is in the same phase or in opposite phase to the steering direction of the front wheels can be selected by switching the phase switching solenoid valve 27.

The specific structure of the drive cylinder d is as shown in FIG. 3.

That is, the drive cylinder d has covers 31 and 32 attached to both sides of its tube 30, and the drive shaft 33 passing through the drive cylinder d is attached to the cover 3.
1.32 and is slidably supported.

Further, a space is provided between the cover 31, 32 and the drive shaft 33, and the movable piston 34 is provided within this space.
．． 35 inside so that it can slide freely. The movable pistons 34, 35 thus constructed also function as bearings for the drive shaft 33.

Furthermore, air pistons 3B and 37 are slidably fitted onto the outer peripheries of the movable pistons 34 and 35, and the outer peripheries of the air pistons 3B and 37 are brought into sliding contact with the inner periphery of the tube 30. .

Spring seats 38, 39 are fixed to the inner sides of these air pistons 36, 37 with ports 40, 41, and these spring seats 38, 39
A spring 42 is interposed between them.

And by the spring force of this spring 42.

The spring seat 38.39 or the air piston 36.37 is held in the position shown in contact with the cover 31.32, in which case the flange 43.44 formed on the drive shaft 33 is in contact with the spring seat 38.37. I am trying to make contact with 38.

Also, the space formed between the two air pistons 36 and 37 is the first air chamber 45, and this air piston 38
．． The chambers partitioned outward from the air chamber 37 are designated as second air chambers 48 and 47. The first air chamber 46 is connected to the tube 3
The supply/discharge boat formed on the 4th day has been connected to the compressor 50 via the valve mechanism 48. Furthermore, Book L 2
The air chambers 46, 47 are connected to the compressor 50 via the valve mechanism 49 from supply/discharge boats 51, 52 formed on the covers 31, 32.

Note that one end of the movable piston 34, 35 is connected to the hydraulic chamber 53.
．． The hydraulic chambers 53 and 54 are connected to the metering cylinder S via the phase switching solenoid valve 27.
is connected to.

When no pressure is applied to the hydraulic chambers 53 and 54, the air piston 3 is moved by the spring force of the spring 42.
6.37 maintains the normal position shown in contact with the cover 31.32. In the illustrated state where the air piston 38.37 maintains its normal position, the spring seat 38.38
is in pressure contact with the 7 flange 43, 44, so that the drive shaft 33 is kept in a neutral position.

With the air pistons 38 and 37 kept in the normal position as described above, the front wheel steering bag W1a is driven to operate the metering cylinder S.
When the hydraulic oil discharged from the metering cylinder S is supplied to one hydraulic chamber 53, for example, the hydraulic oil in the other hydraulic chamber 54 is returned to the metering cylinder S. As a result, one movable piston 34 moves to the right in FIG. 3 and pushes the 7-lunge 43, moving the drive shaft 33 to the right and steering the rear wheels 6.7.

When hydraulic oil is supplied to the other hydraulic chamber 54, the movable piston 35 moves to the left in FIG.
to steer.

At this time, air is introduced into the first air chamber 45, and the first
When the pressure in the air chamber 45 is increased, the pressure and the spring force of the spring 42 combine to strengthen the force for holding the drive shaft 33 in the neutral position, and the air piston 34.
35 and the reaction force against the movement of the movable piston 34.35 also increases. In other words, it is the same as if the spring force of the spring 42 was substantially increased.

On the contrary, when air is introduced into the second air chambers 4B and 47,
The force acts in a direction that weakens the spring force of the spring 42.

Therefore, in this embodiment, the spring force of the spring 45 can be substantially adjusted depending on whether air is introduced into the first air chamber 45 or the second air chamber 46,47. In this way, the spring force of the spring 45 can be adjusted simply by controlling the direction of air introduction, so while keeping the size of the drive cylinder d constant,
The spring force of the spring can be substantially adjusted, and the same drive cylinder d can be used for large and small cars.

Further, it becomes easier to control and adjust the displacement amount of the drive shaft 33 with respect to the operating pressure from the metering cylinder S.

[Brief explanation of drawings]

Drawings 1 to 3 show embodiments of this invention.
2 is a sectional view of a front wheel steering device, FIG. 3 is a sectional view of a rear wheel steering device, and FIG. 4 is a circuit diagram of a conventional device. 2.3... Front wheel, 6,7... Rear wheel, d... Drive cylinder, 34.35... Movable piston, 36.37.
...Air piston, 42...Spring, 45...
1st air chamber, 46.47... 2nd air chamber, 48.51
．． 52... Supply and discharge boat.

Claims (1)

[Claims] A four-wheel system that controls the steering direction of the rear wheels in relation to front wheel steering, and is provided with a drive cylinder that power assists the steering force of the rear wheels, and that steers the rear wheels by moving the drive shaft of the drive cylinder. In the steering system,
A pair of air pistons is provided in the drive cylinder, a spring is interposed between them, and a space between the air pistons with the spring interposed therebetween is defined as a first air chamber;
An air supply/discharge port is formed in the first air chamber, a second air chamber is further defined outside the air piston, and an air supply/discharge port is formed in each of the second air chambers,
Further, the structure is such that the acting force of the air piston is applied to the drive shaft and the driving force of the movable piston is applied to the drive shaft, so that the pressure action of the first air chamber is in reaction to the driving force of the movable piston. A four-wheel drive device in which the pressure action of the second air chamber becomes an assist force for the driving force of the movable piston.