JP2000072005A - Rack shaft bearing structure in power steering - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent generation of noise by dissolving looseness of a rack shaft caused by a clearance between the rack shaft and a bearing metal bush in a rack shaft bearing structure in a power steering used in a vehicle steering system. SOLUTION: A metal bush 8 and a resin bush 9 disposed adjacently to the metal bush 8 and having a smaller diameter than the metal bush 8 are fittingly fixed to bearing parts 2c, 2d in a rack shaft storage part 2a of a gear box 2 housing a rack shaft 3. The rack shaft 3 is supported by these metal bush 8 and resin bush 9.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a bearing structure of a rack shaft in a power steering device used for a steering device of a vehicle, and more particularly, to a clearance between a rack shaft and a metal bush bearing the rack shaft. The present invention relates to a bearing structure of a rack shaft in a power steering device which eliminates backlash caused by the above and prevents generation of abnormal noise.

[0002]

2. Description of the Related Art A bearing structure of a rack shaft in a conventional power steering apparatus is shown in FIG.
A metal bush 08 is mounted on a bearing portion 02c in a rack shaft housing portion 02a of a gear box for housing the rack shaft 03.
Is fitted, and one end side of the rack shaft 03 (the opposite side to the rack) is supported by the metal bush 08.

[0003]

In such a bearing structure, there is a clearance between the rack shaft 03 and the metal bush 08, so that when the rack shaft 03 moves left and right, backlash occurs in the rack shaft 03. Generates abnormal noise. In order to prevent such play, the metal bush 08 and the rack shaft 03
It is necessary to improve the accuracy of.

According to the present invention, the metal bush 08 and the rack shaft 03 need not be improved in accuracy,
An object of the present invention is to provide a bearing structure of a rack shaft in a power steering device that absorbs backlash of a rack shaft 03 and prevents generation of abnormal noise.

[0005]

SUMMARY OF THE INVENTION The present invention relates to a bearing structure for a rack shaft in a power steering apparatus which solves the above-mentioned problems. A metal bush and a resin bush disposed adjacent to the metal bush and having an inner diameter smaller than the metal bush are fitted to a bearing portion in the gear box to be accommodated, and a rack is formed by the metal bush and the resin bush. A bearing structure for a rack shaft in a power steering device, wherein the shaft is made to bear.

According to the first aspect of the present invention, the bearing of the rack shaft has a metal bush fitted to a bearing portion in a gear box and a metal bush adjacent to the metal bush. And a resin bush having a smaller inside diameter than the metal bush.

As a result, the play (micro vibration) of the rack shaft caused by the clearance between the rack shaft and the metal bush is absorbed by the resin bush.
No abnormal noise is generated. Further, since the heavy load of the rack shaft can be received by the metal bush, there is no hindrance to the operation of the rack shaft. Furthermore, in order to eliminate backlash of the rack shaft, there is no need to specially improve the accuracy of the metal bush and the rack shaft.
These precisions can be made appropriate.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the invention described in claim 1 of the present application shown in FIGS. 1 to 6 will be described below. FIG. 1 is a partially cutaway view showing a power steering device to which a bearing structure of a rack shaft according to the present embodiment is applied. FIG. 2 is an enlarged view of a main part of FIG.
FIG. 3 is an enlarged vertical sectional view of a resin bush used in the bearing structure of the rack shaft in FIG.
FIG. 4 is a right side view of FIG. 3, FIG.
6 is an enlarged vertical sectional view of a metal bush used in the bearing structure of the rack shaft in FIG.
6 is a right side view of FIG. 5.

In FIG. 1 and FIG. 2, a power steering device 1 to which a bearing structure of a rack shaft 3 according to the present embodiment is applied is a center take-off type electric power steering device, in which a gear box 2 accommodates a rack shaft. A mounting portion for mounting the inner ends of a pair of left and right tie rods (not shown) to the rack shaft 3 is provided substantially at the center in the length direction of the portion 2a.

The rack shaft 3 has a rack (not shown) near one end thereof (right end in FIG. 1), and is slidably received in the rack shaft receiving portion 2a of the gear box 2 in FIG. ing.

In the sensor housing portion 2b of the gear box 2, a torsion bar connecting the input shaft 4 connected to the steering wheel of the vehicle (not shown) to the output shaft, the output shaft and the amount of distortion of the torsion bar are stored. A sensor to be detected is housed therein, and the rack of the rack shaft 3 meshes with a pinion formed on the output shaft, and outputs a manual input by steering the steering wheel and a steering assist force according to the sensor output by the electric motor 5, Rack shaft 3
And a tie rod (not shown) for transmission to the wheel side.

An impact absorbing member 6 made of an elastic material such as rubber is embedded in both end surfaces of the rack shaft 3.
Both ends of the rack shaft accommodating portion 2a of the gear box 2 are opened, and the cap 7 is firmly fitted into the opening.

Therefore, the rack shaft 3 is moved to the end of the rack shaft receiving portion 2a by receiving the manual input by the steering of the steering wheel, the steering assist force output by the electric motor 5, and the inertia force of the electric motor 5. Sometimes, the shock absorbing member 6 buried in the end face of the rack shaft 3 collides with the inner wall surface of one of the right and left caps 7 to reduce its size. In this manner, the inner wall surface of the cap 7 functions as a stopper for the rack shaft 3 and the shock absorbing member 6 reduces the impact force due to the collision.

The bearing 2c in the rack shaft receiving portion 2a of the gear box 2 that receives the end of the rack shaft 3 on the side opposite to the side on which the rack is formed, as shown better in FIG. , Cylindrical metal bush 8
Is fitted. 5 and 6 show the structure of the metal bush 8 in an enlarged manner.

Further, a bearing portion 2d adjacent to the bearing portion 2c
Is fitted with a resin bush 9. Bearing 2d
Has a larger diameter than the bearing portion 2c, and has at one end an annular shape for receiving a plurality of projections 9a (see FIGS. 3 and 4) protruding from the outer peripheral surface at one end side of the resin bush 9. Grooves are drilled.

The minimum inner diameter of the resin bush 9 is slightly smaller than the inner diameter of the metal bush 8, and the inner peripheral surface of the resin bush 9 is directly connected to the rack shaft 3 as shown in FIGS. A plurality of raised surfaces 9b are formed at equal intervals in the circumferential direction. Serrations 9c are formed on the outer peripheral surface of the resin bush 9 to prevent the contact surfaces of the resin bush 9 from sticking to each other after the resin bush 9 is fitted to the bearing portion 2d.

The fitting of the resin bush 9 to the bearing 2d is as follows.
Before the rack shaft 3 is accommodated in the rack shaft accommodating portion 2a, the resin bush 9 can be easily contracted by elastic deformation and inserted through the end opening of the gear box 2. In addition, 10 is an air vent hole.

Therefore, the end of the rack shaft 3 on the side opposite to the side on which the rack is formed is the metal bush 8.
And a resin bush 9 which is arranged adjacent to the metal bush 8 and has a minimum inner diameter slightly smaller than the inner diameter of the metal bush 8.

Since the present embodiment is configured as described above, the following effects can be obtained. The bearing of the rack shaft 3 is fitted to a metal bush 8 fitted to a bearing portion 2c in a rack shaft accommodating portion 2a of the gear box 2 and to a bearing portion 2d adjacent to the metal bush 8, so that the metal bush 8 This is performed by a resin bush 9 having a smaller inner diameter.

As a result, since the play (small vibration) of the rack shaft 3 caused by the clearance between the rack shaft 3 and the metal bush 8 is absorbed by the resin bush 9, no abnormal noise is generated. In addition, since the heavy load of the rack shaft 3 can be handled by the metal bush 8, the operation of the rack shaft 3 is not hindered.

Furthermore, it is not necessary to particularly improve the precision of the metal bush 8 and the rack shaft 3 in order to eliminate the play of the rack shaft 3, and these precisions can be made appropriate and the cost increases. Can be suppressed.

Furthermore, the protrusion 9a of the resin bush 9
Is fitted in the annular groove of the bearing portion 2d, so that the resin bush 9 and the metal bush 8 are prevented from falling off.

[Brief description of the drawings]

FIG. 1 is a partially cutaway view of a power steering apparatus to which a bearing structure of a rack shaft according to an embodiment of the present invention described in claim 1 of the present application is applied.

FIG. 2 is an enlarged view of a main part of FIG.

FIG. 3 is an enlarged vertical sectional view of a resin bush used in the bearing structure of the rack shaft of FIG. 1;
FIG. 3 is a sectional view taken along line II-III.

FIG. 4 is a right side view of FIG.

5 is an enlarged longitudinal sectional view of a metal bush used in the bearing structure of the rack shaft of FIG. 1, and is a sectional view taken along line VV of FIG. 6;

FIG. 6 is a right side view of FIG.

FIG. 7 is a diagram showing a conventional example.

[Explanation of symbols]

1. Power steering device 2. Gear box 2a
… Rack shaft housing part, 2b… Sensor housing part,
2c, 2d ... bearing part, 3 ... rack shaft, 4 ... input shaft, 5 ... electric motor, 6 ... shock absorbing member, 7 ... cap, 8
... metal bush, 9 ... resin bush, 9a ... projection, 9
b ... raised surface, 9c ... serration, 10 ... air vent hole.

Claims (1)

[Claims] 1. A metal bush and a resin bush disposed adjacent to the metal bush and having an inner diameter smaller than the metal bush are fitted to a bearing portion in a gear box accommodating the rack shaft. A bearing structure for a rack shaft in a power steering device, wherein the rack shaft is supported by a metal bush and a resin bush.