GB2397861A

GB2397861A - A rack and pinion guide

Info

Publication number: GB2397861A
Application number: GB0326571A
Authority: GB
Inventors: Giorgio Bersini
Original assignee: TRW Automotive Italia SRL
Current assignee: ZF Automotive Italia SRL
Priority date: 2003-01-29
Filing date: 2003-11-14
Publication date: 2004-08-04
Anticipated expiration: 2023-11-14
Also published as: ES2246666B1; ES2246666A1; FR2850345B1; ITBS20030011U1; GB0326571D0; DE10349787A1; GB2397861B; FR2850345A1

Abstract

A guide for the rack 15 of a rack 15 and pinion 14 steering box, comprising a yoke 17 over which the rack 15 moves, a rack adjuster 18 immobilizing the yoke 17 within a corresponding seat provided in the body 13 of the steering box, an elastic member 19 located between the said rack adjuster 18 and the yoke 17 to keep the latter in contact with the rack 15, characterized in that the guide also comprises a noise-preventing member 20 located between the yoke 17 and the rack adjuster 18 to attenuate the axial vibrations induced by the guide when the vehicle is in use. The elastic member 19 may be a helical spring 19, while the noise-preventing member 20 is a ring which could be bonded to the yoke 17 or the rack adjuster 18. The noise preventing ring 20 is preferably made of a plurality of layers of steel and rubber.

Description

239786 1

RACK GUIDE FOR STEERING SYSTEMS

This invention relates to steering systems for motor vehicles comprising rack and pinion steering and relates in particular to the rack guides.

As is known, a steering system substantially comprises steering column, an intermediate shaft and a steering box into which a rack and pinion mechanism is inserted. Rotation of the wheel, assisted by the steering column, is converted into lateral movement of the rack and pinion mechanism within the steering box, which moves the wheels to permit steering. In its lateral movements the rack is supported by a guide which needs an appropriate amount of play for correct functioning of the mechanism.

Generally guides comprise a member supporting the movement proper, known as a yoke, housed in a seat provided in the steering box and configured to enclose the rack, a rack adjuster immobilising the yoke in its respective seat and a helical spring located between the yoke and the rack 2 0 adjuster to provide the necessary axial play for the guide and to compensate for inevitable wear of the yoke.

Because of the aforesaid play, however, axial vibrations are set up in the guide which are substantial, especially when the vehicle is used on rough ground, and gives rise to an irksome noise on account of the metallic nature of the components.

The purpose of this invention is to overcome such a disadvantage by providing a guide which envisages the use of a noise-preventing ring of suitable material and thickness between the yoke and the corresponding rack adjuster designed to attenuate the axial vibration induced in the yoke, especially in the range of frequencies which can be perceived by the human ear.

The invention will be described, by way of example, with reference to theaccompanying drawings, in which: Figure 1 shows a rack and pinion steering box in perspective view, Figure 2 shows the elements of the guide in an exploded perspective view, and - 2 Figure 3 shows a cross- section of the steering box corresponding to a guide.

With reference to Figure 1, a steering box 11 of a mechanical or hydraulic type for conversion of the rotational movement of steering column 12 into a lateral movement controlling the wheels is illustrated. Steering box 11 comprises, in a known manner, a body 13 containing a pinion 14 and a rack 15 meshing therewith. The rack 15, which moves within the body of the steering box, is supported by a bush - not shown - and a guide 16 housed in a corresponding seat provided in the said body 13.

The guide 16 comprises a yoke 17 over which the rack 15 moves, a rack adjuster 18 locking the yoke in the corresponding seat, a helical spring 19 located between the rack adjuster and the yoke to keep the latter in contact with rack 15, and a noise-preventing ring 20 also provided between the yoke and the rack adjuster coaxially with spring 19.

Yoke 17 and rack adjuster 18 have corresponding opposing axial seats to support the ends of helical spring 19 and corresponding opposing 2 0 annular surfaces 17', 18' between which noise-preventing ring 20 is located. The latter may also be bonded to one of the said annular surfaces.

Advantageously ring 20 is a multilayer ring made of sheets of stainless steel and rubber, the thickness of which is selected according to the frequency range in which it is intended that the vibration should be 2 5 attenuated.

In practice the axial vibrations induced in the guide through use of the vehicle, in particular on rough ground, are damped by the noise preventing ring, particularly in the range of frequencies which can be perceived by the human ear. Such a damping function is appreciable both when the vehicle is new and after a high mileage, because wear of the yoke increases the play in the rack. - 3

Claims

1. Guide for the rack of a rack and pinion steering box in a steering system, comprising a yoke (17) over which the rack (15) moves, a rack adjuster (18) immobilizing the yoke within a corresponding seat provided in the body of the steering box and open towards the rack, and an elastic member (19) located between the said rack adjuster and the yoke to keep the latter in contact with the rack, characterized in that it also comprises a noise-preventing member (20) located between the yoke and the rack adjuster to attenuate the axial vibrations induced by the guide when the vehicle is in use.

2. Guide according to claim 1, in which the elastic member is a helical spring restrained between two axial seats made opposite each other in the yoke and the rack adjuster, in which the noise-preventing member is a ring located between two facing annular surfaces bounding the said spring seats.

3. Guide according to claim 2, in which the noise-preventing ring is bonded to one of the said annular surfaces of the yoke and the rack adjuster.

4. Guide according to according to any one of the preceding claims, in which the noise-preventing ring comprises a plurality of layers or sheets of steel and rubber, the thickness of which is selected to attenuate vibrations in a desired frequency range.

5. Guide for the rack of a rack and pinion steering box in a steering system, substantially as herein desribed with reference to the accompanying drawings.