JPH05105097A - Rack-and-pinion type hydraulic power steering system for four-wheel steered vehicle - Google Patents

Abstract

PURPOSE:To simplify the structure and improve a sealing function by installing an elastic member in space between a housing and a rack so as to make a tubular member displaceable in the radial direction, setting up a sealing member lying between the rack and the tubular member in an interval between both first and second rack gears and forming an interspace between the sealing member and a piston into an oil chamber. CONSTITUTION:A cylindrical part 40 is inserted into an interspace between both inner and outer circumferences of a rack 5 and a rack housing 6, and an interval between the inner circumference and an outer circumference of the rack 5 is sealed up by a sealing member 30. With flection in the rack 5, the sealing member 30 is pressed to an inner circumferential surface of the cylindrical member 40 in space between a first rack gear 5a and a second rack gear 5b. If so, the cylindrical member 40 supported by the rack housing 6 via two elastic members 41, 42 is elastically shifted in the radial direction. In consequence, pressing force is reduced to some extent. In addition, an interspace between the sealing member 30 and a piston 25 is set down to an oil chamber 28, and the second rack gear 5b is set up in this oil chamber 28. Therefore such a possibility that both symmetrical width sizes in the system might be enlarged is thus preventable.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rack and pinion type hydraulic power steering system for a four-wheel steering vehicle.

[0002]

2. Description of the Related Art A pinion that rotates by a steering operation input, a rack having first rack teeth that mesh with the pinion, a rear wheel steering pinion that meshes with second rack teeth formed on the rack, and 2. Description of the Related Art A rack-and-pinion steering device for a four-wheel steering vehicle, which has a housing that covers a rack and is configured to steer the front wheels and the rear wheels by left and right movement of the rack, has been conventionally used.

In such a steering device, there is a steering device in which a hydraulic cylinder is integrated outside the housing covering the rack in order to apply a steering force assisting force by hydraulic pressure (see Japanese Patent Publication No. 2-3752).

[0004]

SUMMARY OF THE INVENTION In the above conventional configuration,
Since the hydraulic cylinder is provided outside the housing, there is a problem that the structure is complicated and a large space is required.

As a solution to such a problem, there is a rack and pinion type hydraulic power steering device for a four-wheel steering vehicle previously proposed by the present applicant (Japanese Patent Application No. 2-429).
No. 61). In this, a piston is provided on the outer periphery of the rack, a pair of left and right oil chambers partitioned by the pistons are formed inside the housing, and high-pressure oil is supplied to the oil chambers to give a steering operation assisting force. It was done like this. As a result, it is not necessary to provide a hydraulic cylinder outside the housing, and the structure is simplified. Further, a seal member is attached to the rack between the first rack tooth and the second rack tooth, and the left and right oil chambers are provided between the seal member and the piston. Thus, by disposing one rack tooth inside the one oil chamber, it is possible to prevent the lateral dimension of the device from increasing.

However, when both the first rack teeth and the second rack teeth are formed on the rack, the section modulus of the rack becomes small, so that the rack is easily bent by an external force acting from the road surface through the steering wheel. Therefore, as described above, the seal member attached to the rack between the first rack tooth and the second rack tooth is pressed against the inner circumference of the housing with a large force due to the bending of the rack, and is plastically deformed,
There is a problem that the sealing function cannot be achieved. For example, as shown in FIG. 6, a seal member 102 attached to the rack 101 is provided with a ring-shaped packing 102a made of rubber having high elasticity and the ring-shaped packing 102a.
Teflon backup ring that is more rigid than 1
02b and the peripheral groove 101a of the rack 101.
May be fitted to. The packing 102a ensures oil tightness, and the backup ring 102
By b, the packing 102a is prevented from coming off from the circumferential groove 101a of the rack 101 due to the frictional force with the housing 103 and the hydraulic pressure. In this case, the rack 101
When the seal member 102 is pressed against the inner peripheral surface of the housing 103 due to the bending of, the frictional force with the housing 103 increases and the packing 102a easily separates from the peripheral groove 101a. Particularly, when the backup ring 102b is plastically deformed by the pressing force, the packing 102a cannot be backed up when the rack 101 is moved, and the packing 102a easily separates from the circumferential groove 101a. As a result, there is a problem that the sealing function cannot be achieved.

An object of the present invention is to provide a rack and pinion type hydraulic power steering system for a four-wheel steering vehicle which can solve the above technical problems.

[0008]

A feature of the present invention is that a pinion rotated by a steering operation input and a rack having first rack teeth meshing with the pinion are formed.
The rear wheel steering pinion that meshes with the second rack teeth formed on the rack, a housing that covers the rack, a piston provided on the rack, and a pair of left and right oil chambers partitioned by the piston are provided. A rack-and-pinion hydraulic power steering device for a four-wheel steering vehicle, in which a high-pressure oil is supplied to a chamber to provide an assisting force for a steering operation, wherein the left and right sides of the piston are between the housing and the inner and outer circumferences of the rack. A tubular member is inserted, the tubular member is supported by a housing via an elastic member so as to be displaceable in the radial direction, and the outer periphery of the rack and the inner periphery of the tubular member are provided between the first rack tooth and the second rack tooth. A seal member that seals between the seal members is attached to the rack, and the space between each seal member and the piston is one of the left and right oil chambers.

[0009]

According to the structure of the present invention, due to the flexing of the rack,
The seal member attached to the rack between the first rack tooth and the second rack tooth is pressed against the inner peripheral surface of the tubular member. Then, the tubular member supported by the housing via the elastic member is elastically displaced in the radial direction. The radial displacement of the tubular member reduces the force pressing the seal member against the inner peripheral surface of the tubular member.

[0010]

Embodiments of the present invention will be described below with reference to the drawings.

The rack-and-pinion hydraulic power steering system 1 for a four-wheel steering vehicle shown in FIGS. 1 to 3 has an input shaft 2 connected to a steering wheel (not shown) of the vehicle and a torsion bar 3 attached to the input shaft 2. A pinion 4 connected through
A rack 5 having a first rack tooth 5a that meshes with the pinion 4, a rear wheel steering pinion 12 that meshes with a second rack tooth 5b formed on the rack 5, and a rack housing 6 that covers the rack 5. I have it. The first
The rack tooth 5a and the second rack tooth 5b are adjacent to each other, the first rack tooth 5a is formed on the side surface of the rack 5, and the second rack tooth 5a
b is formed on the lower surface of the rack 5.

The rack 5 includes a first support yoke 7
Is supported by the second support yoke 18 and the bush 8 fitted to the end portion of the rack housing 6, and front wheels (not shown) are connected to both ends via ball joints, tie rods, knuckle arms, and the like.

The first support yoke 7 is inserted into an insertion hole 9 formed in the rack housing 6 so as to be movable in the left-right direction in FIG. This first support yoke 7
Presses the first rack tooth 5a against the pinion 4 by the elastic force of the spring 10, so that the pinion 4 and the first rack tooth 5a
The smooth engagement with the gear is achieved. The insertion hole 9
An adjusting member 11 is screwed into the screw, and the pressing force of the spring 10 can be adjusted by adjusting the screwing amount.

As shown in FIG. 4, an output shaft 16 is integrated with the rear wheel steering pinion 12, and the output shaft 16 is a bearing for the rack housing 6 and a support case 21 integrated with the rack housing 6. It is supported via 13, 14. The output shaft 16 is projected rearward from the support case 21 via the seal member 15. A rear wheel steering device (not shown) is connected to the output shaft 16, and the rear wheel (not shown) is steered according to the rotation of the output shaft 16.
As the rear wheel steering device, a known device can be used.

The second support yoke 18 is inserted in an insertion hole 17 formed in the rack housing 6 so as to be vertically movable. The second support yoke 18 presses the second rack teeth 5b against the rear wheel steering pinion 12 by the elastic force of the spring 19, so that the meshing between the second rack teeth 5b and the pinion 12 is smoothed. An adjusting member 20 is screwed into the insertion hole 17, and the pressing force of the spring 19 can be adjusted by adjusting the screwing amount.

Thus, when the input shaft 2 is rotated by operating the handle, this rotation is transmitted from the pinion 4 to the first rack teeth 5a, and the rack 5 reciprocates in the left-right direction to steer the front wheels. Further, the rear wheel steering pinion 12 is rotated by the lateral movement of the rack 5, and the rotation of the pinion 12 is transmitted to the rear wheel steering device via the output shaft 16 to steer the rear wheels.

A hydraulic cylinder 23 is provided for giving an assisting force for the steering operation. The cylinder tube of the hydraulic cylinder 23 is constituted by the rack housing 6, and the piston 25 is fixed to the rack 5. A pair of left and right oil chambers 27 partitioned by the piston 25,
A control valve 31 is formed on the outer periphery of the input shaft 2 in order to supply high pressure oil to the valve 28 according to the steering direction and the reaction force acting on the rack 5 from the road surface. The control valve 31 includes a valve housing 32 integrated with the rack housing 6 and a valve housing 3
2 has a tubular valve member 33 surrounding the input shaft 2. The valve member 33 is connected to the pinion 4 so as to rotate together. Also, the valve housing 3
2 is an inlet port 34 connected to a pump (not shown)
And an outlet port 37 connected to a tank (not shown)
And a pipe 35 in one oil chamber 27 of the hydraulic cylinder 23.
It is provided with a first cylinder port 38 connected via the above, and a second cylinder port 39 connected to the other oil chamber 28 via a pipe 36. Each port 34, 37, 38, 39
Communicate with each other via a flow path opened and closed by relative rotation of the input shaft 2 and the valve member 33. That is, when the steering is not performed, the inlet port 34 and the outlet port 37 communicate with each other, the high-pressure oil supplied from the pump flows back to the tank, and the steering assisting force does not act. When the steering operation is performed by rotating the handle, the torsion bar 3 is twisted according to the reaction force acting on the rack 5 from the road surface via the steering wheel, and the valve member 33 integrated with the pinion 4 is connected to the input shaft. Two
Rotate relative to. Then, the oil passage between the inlet port 34 and the outlet port 37 is closed, high pressure oil is supplied from the inlet port 34 to one of the oil chambers 27 and 28 of the hydraulic cylinder 23 in accordance with the steering direction, and the oil is also supplied. Oil from the other of the chambers 27, 28 flows back through the outlet port 37 to the tank. As a result, the hydraulic cylinder 23 applies a steering assist force according to the steering direction and the reaction force that acts on the rack 5 from the road surface via the steering wheels.

A pair of left and right oil chambers 2 of the hydraulic cylinder 23.
Between 7 and 28, a ring-shaped seal member 45 attached to the outer circumference of the piston 25 is partitioned by sealing the piston 25 and the inner and outer circumferences of the rack housing 6 in an oil-tight manner.

In FIG. 2, the left end of the left oil chamber 27 is oil-tightly sealed by an oil seal 46. The oil seal 46 is press-fitted on the inner circumference of the rack housing 6 and abuts on the outer circumference of the rack 5.

In FIG. 2, the right end of the oil chamber 28 on the right side is oil-tightly sealed by a ring-shaped sealing member 30. That is, as shown in FIG. 1, the tubular member 40 is inserted between the inner and outer peripheries of the rack 5 and the rack housing 6, and the tubular member 4
The seal member 30 seals between the inner circumference of 0 and the outer circumference of the rack 5. As shown in FIG. 5, the sealing member 30 includes a rubber ring-shaped packing 30a and a packing 30a.
Stiffer Teflon backup ring 3
0b and is fitted in a circumferential groove 45 formed on the outer circumference of the rack 5. This seal member 30 and piston 2
An oil chamber 28 on the right side is formed between 5 and 5. The packing 30
The oil-tightness is ensured by a, and the backup ring 30b prevents the packing 30a from coming off from the circumferential groove 45 of the rack 5 due to the frictional force between the inner circumferential surface of the tubular member 40 and the hydraulic pressure. ing.

The tubular member 40 is supported by the rack housing 6 via elastic members 41 and 42 so as to be displaceable in the radial direction. Thereby, as shown in FIG. 5, a space δ is formed between the inner and outer circumferences of the tubular member 40 and the rack housing 6. In this embodiment, O-rings are used as the elastic members 41 and 42, and the outer circumference of the tubular member 40 and the inner circumference of the rack housing 6 are oil-tightly sealed. As a result, due to the bending of the rack 5, the seal member 30 attached to the rack 5 between the first rack tooth 5a and the second rack tooth 5b is pressed against the inner peripheral surface of the tubular member 40.
Then, the tubular member 40 supported by the rack housing 6 via the elastic members 41 and 42 elastically shifts in the radial direction. The radial displacement of the tubular member 40 reduces the force pressing the seal member 30 against the inner peripheral surface of the tubular member 40. As a result, the frictional force does not increase between the packing 30a and the tubular member 40, and the packing 30a can be prevented from coming off the circumferential groove 45. Further, since the backup ring 30b of the packing 30a is prevented from being plastically deformed, the packing 30a is reliably prevented from being separated from the circumferential groove 45. The rightward movement of the tubular member 40 in FIG. 2 is prevented by the step formed on the inner circumference of the rack housing 6, and the leftward movement thereof is prevented by the second support yoke 18.
Blocked by.

According to the above structure, since the hydraulic cylinder 23 for applying the steering assisting force is provided inside the rack housing 6, the structure is simplified and the space is effectively used as compared with the hydraulic cylinder 23 provided outside. be able to. In addition, the oil chamber 28 on one side is provided between the piston 25 and the seal member 30 mounted between the first rack tooth 5a and the second rack tooth 5b.
Since the second rack teeth 5b are arranged in the oil chamber 28, the lateral width of the device can be prevented from increasing.
Even if the seal member 30 is pressed against the inner periphery of the tubular member 40 due to the bending of the rack 5, the tubular member 40 is displaced in the radial direction and the pressing force acting on the seal member 30 is reduced. It does not separate from the circumferential groove 45, and the sealing function is not impaired.

The present invention is not limited to the above embodiment. For example, in the above-mentioned embodiment, the seal member between the first rack tooth and the second rack tooth is composed of the rubber packing and the backup ring in the above-mentioned embodiment, but any structure can be used as long as it can perform the sealing function. Is not limited. Further, in the above embodiment, the elastic member 4 interposed between the inner and outer circumferences of the tubular member 40 and the rack housing 6.
Although the ones also serving as the sealing means were used as 1, 42,
The elastic member and the dedicated sealing means may be provided separately, without being necessarily used in common.

[0024]

According to the rack and pinion type hydraulic power steering system for a four-wheel steering vehicle according to the present invention, a hydraulic cylinder for applying a steering assist force is provided inside the housing to simplify the structure and effectively utilize the space. Can be planned. Further, between the first rack tooth and the second rack tooth, between the seal member attached to the rack and the piston is one oil chamber, and the one rack tooth is arranged in this oil chamber. It is possible to prevent the directional dimension from increasing. Moreover, the pressing force acting on the seal member is reduced by the elastic displacement in the radial direction of the tubular member inserted between the housing and the inner and outer peripheries of the rack, and a highly reliable sealing function can be achieved.

[Brief description of drawings]

FIG. 1 is a sectional view of a main part of a steering device according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view of the steering device according to the embodiment of the present invention.

FIG. 3 is a vertical cross-sectional view of a steering device according to an embodiment of the present invention.

4 is a sectional view taken along line IV-IV of FIG.

FIG. 5 is a sectional view of a main part of a steering device according to an embodiment of the present invention.

FIG. 6 is a partial cross-sectional view of a steering device according to a conventional example.

[Explanation of symbols]

 4 Pinion 5 Rack 5a 1st rack tooth 5b 2nd rack tooth 6 Rack housing 12 Rear wheel steering pinion 25 Piston 27, 28 Oil chamber 30 Seal member 40 Cylindrical member 41, 42 Elastic member

Claims (1)

[Claims] 1. A pinion that rotates by a steering operation input, a rack having first rack teeth that mesh with the pinion, a rear wheel steering pinion that meshes with second rack teeth formed on the rack, and A housing that covers the rack, a piston provided in the rack, and a pair of left and right oil chambers that are partitioned by the pistons are provided, and by supplying high-pressure oil to the oil chamber, a steering operation assisting force is applied. A rack and pinion type hydraulic power steering device for a four-wheel steering vehicle, wherein a tubular member is inserted between the housing and the inner and outer peripheries of the rack on one of the left and right sides of the piston, and the tubular member is an elastic member that can be displaced in the radial direction. And a seal member that is supported by the housing via the seal and seals between the outer periphery of the rack and the inner periphery of the tubular member between the first rack tooth and the second rack tooth. Is attached to a rack, and a left and right oil chamber is provided between a seal member and a piston, and a rack and pinion hydraulic power steering device for a four-wheel steering vehicle.