JP2558131Y2 - Power steering device - Google Patents

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 power steering device.

[0002]

2. Description of the Related Art A rack and pinion type power steering apparatus for steering an automobile is provided with a piston on a rack shaft meshing with a pinion connected to a steering wheel, and a rack shaft and a cylindrical rack shaft for accommodating the rack shaft. An oil chamber is formed between the casing and the case, and pressure oil corresponding to the steering force acting on the steered wheels is supplied to the oil chamber to move the rack shaft, thereby assisting the force required for operating the steered wheels. It has become.

The rack shaft meshes with a pinion in a pinion case connected to one end of a rack shaft case, and the meshing portion is pressed by a support yoke to maintain a constant meshing state. It has become. In such a rack and pinion type power steering mechanism, a rack shaft is supported by the support yoke and a rack bush which is a support member provided at the other end of the rack shaft case. Was. Also,
The oil chamber, in a rack shaft, and a sealing member provided on the rack bush side was supposed to be sealed by the two sealing members of the sealing member provided on the support yoke side.

However, in the power steering device as described above,
When a reverse input is given to the rack shaft from the vehicle side, the rack shaft is bent. Since the rack shaft is supported by the support yoke and the rack bush, the bending becomes large near the sealing member provided on the support yoke side, which is present in the middle of the rack shaft. There is a problem that an eccentric force acts, and the sealing member is deteriorated by the eccentric force to shorten its life.

In order to solve such a problem, conventionally, in order to support the rack shaft only when the rack shaft is bent, a sealing member provided on the support yoke side is provided on the support yoke side with the rack shaft. On the other hand, there has been proposed a power steering device including an intermediate bush having a small clearance, and suppressing the eccentricity of the rack shaft by the intermediate bush.

[0006]

However, in the power steering device having the intermediate bush as described above, if the clearance is too large, the eccentricity of the rack shaft cannot be sufficiently suppressed. If the clearance is excessively small, the rack shaft collides with the intermediate bush even when the rack shaft is slightly eccentric, so that it is difficult to set an appropriate clearance, for example, a striking sound at the time of the collision easily occurs. Was not practical.

The present invention has been made in view of such circumstances, and provides a power steering apparatus that sufficiently suppresses eccentricity of a rack shaft and suppresses a hitting sound when the rack shaft is eccentric. With the goal.

[0008]

A power steering apparatus according to the present invention is housed in a cylindrical body, and has a rack shaft, one end of which is meshed with a pinion shaft, a rack shaft inside the cylindrical body. A piston fixed in the middle of the rack shaft to a cylinder formed by sealing between the two support members with a sealing member, respectively, while supporting with the support members arranged at the other end and the middle part of the rack shaft. In the power steering apparatus having a hydraulic cylinder for assisting steering, the supporting member for supporting the intermediate portion is an endless cylinder which is internally fitted so that an outer peripheral cylindrical surface thereof is brought into contact with the cylindrical body. A cylindrical member whose inner peripheral cylindrical surface is brought into contact with the outer periphery of the rack shaft and whose outer peripheral cylindrical surface is
The first recess extending over substantially the entire length of the
Over the entire length of the inner peripheral cylindrical surface in the axial direction.
Extending second concave portion at a circumferentially intermediate position of the first concave portion
Provided at multiple locations so that both recesses are staggered in the circumferential direction,
As a result between the first recess and the second recess respectively
A projection is formed over substantially the entire length in the axial direction.
It is characterized by having.

[0009]

When the rack shaft is bent, especially the middle portion of the rack shaft is largely eccentric. At this time, the supporting members for supporting the middle portion of the rack shaft are formed at a plurality of positions in the inner and outer circumferential directions. hand
Among the protrusions of the recesses formed as a result of over substantially the entire length in the axial direction in which, by elastically deforming in the radial direction in the gap range of the outer peripheral side, a predetermined amount or more of eccentricity of rack shaft is surely suppressed, polarized The possibility that the cored rack shaft collides with another portion of the support member is small, and the hitting sound caused by the collision is suppressed.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be specifically described below with reference to the drawings showing embodiments thereof. FIG. 1 is a longitudinal sectional view showing a power steering device according to the present invention.

In FIG. 1, reference numeral 1 denotes a rack shaft having a circular cross section formed with rack teeth 10 on one side in the axial direction. The rack shaft 1 has a cylindrical shape, with a longitudinal direction being a left-right direction, a rack shaft case 2 fixed to a part of the vehicle body, and a cylindrical shape coaxially connected to one end of the rack shaft case 2. Inside the pinion case 3, the rack teeth 10 are inserted coaxially with the pinion case 3 in such a manner as to be located in the pinion case 3.

The rack teeth 10 of the rack shaft 1 mesh with pinion teeth 40 of a pinion shaft 4 which is interlocked with steering wheels (not shown) in the pinion case 3. The steering wheel moves in the axial direction. A guide hole 31 is formed in the pinion case 3 on the back surface of the meshing point between the rack shaft 1 and the pinion shaft 4 in a direction perpendicular to the rack shaft 1.
The guide hole 31 is provided with a support yoke 5 for pressing the rack shaft 1 toward the pinion shaft so as to securely mesh the rack teeth 10 and the pinion teeth 40. On the other hand, a rack bush 22 for supporting the other end of the rack shaft 1 is provided inside the other end of the rack shaft case 2. A rack stopper 23 for preventing the rack bush 22 from moving outward in the axial direction is provided.

An oil chamber is formed in the rack shaft case 2 between the rack shaft case 2 and the rack shaft 1, and the oil chamber is provided with an oil seal provided on an inner peripheral portion of the rack bush 22. A piston sealed around the rack shaft 1 by a first sealing member 24 and a second sealing member 25 formed of an oil seal provided at an intermediate portion in the axial direction of the rack shaft case 2. It is divided into oil chambers 20a and 20b via 21. To these oil chambers 20a and 20b, hydraulic oil for steering assistance is selectively supplied from a hydraulic pump (not shown).
In the axial direction is assisted.

On the support yoke 5 side of the second sealing member 25, as a support member for supporting a middle portion of the rack shaft 1 ,
An intermediate bush 26 is provided. One end of the rack shaft 1 is supported by the support yoke 5, the other end is supported by the rack bush 22, and an intermediate portion in the axial direction is supported by the intermediate bush 26. . The rack shaft 1 is connected to left and right wheels (not shown) via ball joints, link members, and the like (both not shown) disposed at both ends of the rack shaft 1. The wheels are steered by moving in the axial direction along with the rotation of the steered wheels.

FIG. 2 is a schematic longitudinal sectional view of the vicinity of the intermediate bush 26, and FIG. 3 is a sectional view taken along line III-III in FIG. As shown in FIG. 2, the second sealing member 25 is arranged in a first reduced diameter portion 2a which is reduced in diameter by one step from a portion of the rack shaft case 2 where the oil chamber 20a is formed. And
The intermediate bush 26 is connected to the first reduced diameter portion 2a, and the second reduced diameter portion 2 is reduced in diameter by one step.
b. Due to such a shape of the rack shaft case 2, the second sealing member 25 is prevented from moving in the axial direction at the end of the second reduced diameter portion 2b. Further, the intermediate bush 26 is arranged at a small distance from the second sealing member 25 in the axial direction.

The intermediate bush 26 is provided inside the rack shaft case 2.
A cylindrical member fitted and held, as shown in FIG.
At several places in the circumferential direction (eight places in the figure),
Contact the outer periphery of the rack shaft 1 and
A predetermined gap is formed with the inner circumference of the
Projection made elastically deformable in the radial direction within the gap of
.. Are provided. In the intermediate bush 26 having such a structure, when the rack shaft 1 is bent, the rack bush 26 responds to the bending.
Protrusions 260 and 260 Te, ... are elastically deformed radially outward. This elastic deformation is caused by the outer circumference of the protrusions 260, 260,.
2 is deformed with the gap formed between the inner circumference of the rack 2 and the inner circumference of the rack shaft 2 as the maximum value, and the bending of the rack shaft 1 is limited to the gap dimension or less.

FIG. 4 is a schematic longitudinal sectional view showing the vicinity of the intermediate bush 26 showing another embodiment of the present invention. In the figure, reference numeral 27 denotes a cylindrical intermediate bush case provided around the intermediate bush 26 and the rack shaft case 2. The intermediate bush case 27 has a ridge 271 projecting radially inward on the inner peripheral surface of the end on the second sealing member 25 side, and the inner peripheral surface of the end on the second sealing member 25 side. On the surface, it is substantially the same diameter as the inner diameter of the first reduced diameter portion 2a, and has a shape in which a flange portion 272 projecting outward in the radial direction is provided around the inner peripheral portion other than the portion where the protrusion 271 is formed. , The intermediate bush 26 is externally fitted. This intermediate bush case 27 has a flange portion
272 is arranged in the rack shaft case 2 so as to be located within the end of the first reduced diameter portion 2a on the second reduced diameter portion 2b side. Protrusions 27 in intermediate bush case 27 arranged in this way
1 and the end face on which the flange portion 272 is formed is in contact with the end face of the second sealing member 25, and the ridge 27
The first and flange portions 272 limit the movement of the second sealing member 25 to the support yoke 5 side.

In the power steering device configured as described above,
When a reverse input from the vehicle side is given to the rack shaft 1, the rack shaft 1 is bent and the rack shaft 1 is eccentric, and the amount of eccentricity is determined by the amount of the intermediate bush 26 that supports the middle part of the rack shaft 1 . becomes particularly large in the vicinity, the intermediate bush 26, the above-mentioned
, The eccentric amount of the rack shaft 1 at the support position of the intermediate bush 26 is provided.
Is limited to the range of the gap on the outer peripheral side of the protrusions 260, 260,.
Is done. Also, the inner circumferences of the protruding portions 260 are constantly in contact with the rack shaft 1 , and the eccentricity of the rack shaft 1
Is absorbed by the elastic deformation of the protruding portions 260, 260,.
The eccentric rack shaft 1 that is generated while being set
Collision with other parts of, that is, parts other than protrusions 260, 260, ...
Possibility is small that, hitting sound due to collision of this is suppressed.

[0019]

As described in detail [devised effect above with power steering apparatus according to the present invention, the support member for supporting the intermediate portion of the rack shaft, and the inner, the inner circumference of the outer periphery and the tubular casing of the rack shaft on the outer periphery Cylinder as a result of forming a concave part with a predetermined gap formed between
The protruding parts with surfaces are placed in multiple locations in the circumferential direction
The rack shaft protrudes from its periphery because
Parts are evenly supported by the
When a large supporting force is obtained, the rack shaft bends, and the middle part is going to be largely eccentric, the protruding part is elastically deformed in the radial direction, and the amount of eccentricity is reliably suppressed within the gap on the outer peripheral side. it is possible to <br/> control. Further, the inner periphery of the protruding portion is in contact with the outer periphery of the rack shaft, the eccentric force of the rack shaft is absorbed by the elastic deformation of the protruding portion, and the eccentric rack shaft is in contact with other portions of the support member. The present invention has an excellent effect such that the possibility of a strong collision is small and the hitting sound caused by the collision can be suppressed.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view showing a power steering device according to the present invention.

FIG. 2 is a schematic longitudinal sectional view near an intermediate bush.

FIG. 3 is a sectional view taken along line III-III in FIG. 2;

FIG. 4 is a schematic longitudinal sectional view of the vicinity of an intermediate bush showing another embodiment of the present invention.

[Explanation of symbols]

 Reference Signs List 1 rack shaft 2 rack shaft case 4 pinion shaft 5 support yoke 21 piston 22 rack bush 24 first sealing member 25 second sealing member 26 intermediate bush

Claims (1)

(57) [Scope of request for utility model registration] 1. A rack shaft housed in a cylindrical body, one end of which meshes with a pinion shaft, a meshing portion thereof, and a bearing member disposed at the other end and the middle of the rack shaft inside the cylindrical body, respectively. On the other hand, a piston fixed in the middle of the rack shaft is fitted inside a cylinder formed by sealing between the two support members with a sealing member, thereby forming a hydraulic cylinder for steering assistance. In the power steering device, a support member for supporting the intermediate portion is provided on the outer periphery of the cylindrical body.
An endless cylindrical member internally fitted so as to abut the cylindrical surface , the inner circumferential cylindrical surface of which is in contact with the outer periphery of the rack shaft, and extends over substantially the entire length of the outer circumferential cylindrical surface in the axial direction.
First concave portions are provided at a plurality of locations in the circumferential direction, and the inner peripheral cylindrical surface thereof is provided.
The second concave portion extending over substantially the entire length in the axial direction
The two recesses are staggered in the circumferential direction at the middle position in the circumferential direction of the recess
Provided at a plurality of locations, between the first concave portion and the second concave portion.
The protrusions between the recesses result in approximately the entire axial length, respectively.
Power steering apparatus characterized by being adapted to but is formed.