GB1593398A

GB1593398A - Rack and pinion assemblies

Info

Publication number: GB1593398A
Application number: GB4506976A
Authority: GB
Original assignee: TRW Steering Systems Ltd
Current assignee: TRW Steering Systems Ltd
Priority date: 1976-10-29
Filing date: 1976-10-29
Publication date: 1981-07-15
Also published as: DE2748011A1; FR2369467A1; IT1088615B

Description

(54) IMPROVEMENTS IN OR RELATING TO RACK AND PINION ASSEMBLIES (71) We, CAM GEARS LIMITED, a British Company, of 45 Wilbury Way, Hitchin, Hertfordshire SG4 OTU, do hereby declare the invention for which we pray that a Patent may be granted to us and the method by which it is to be performed to be particularly described in and by the following statement: The present invention relates to a rack and pinion assembly, and is particularly concerned with such an assembly which is suitable for use in a vehicle steering gear.

A rack and pinion assembly of the kind with which the present invention is concerned (hereinafter referred to as "the kind specified") includes a pinion rotatably mounted in a pinion housing, a rack bar movable in a longitudinal direction through the pinion housing, and a rack on the rack bar operably connected with the pinion so that rotation of the pinion effects movement of the rack bar longitudinally through the pinion housing.

The pinion is generally supported in its housing in a pair of axially spaced bearings which are located one at each end of the pinion teeth. Hitherto the bearings have been provided by balls or rollers located in races of the appropriate construction, and the inclusion of these bearings adds considerably to the cost of a rack and pinion assembly. Attempts have been made to devise a pinion bearing which can provide both radial and axial supports for the pinion, and which is less expensive than the conventional ball or roller bearings. One such less expensive bearing comprises cooperating spigot and socket parts which are coaxial with the pinion, in which one part is carried by the pinion housing and the other part by the pinion. With this less expensive bearing, the problem arises that if the spigot should collapse or break up then the pinion is no longer supported at the region of the collapsed bearing, and the resultant side movement of the pinion may mean that the steering control is lost and that broken pieces of the spigot may jam between the teeth of the rack and pinion.

It is an aim of the invention to alleviate the above problem, and accordingly there is provided a rack and pinion assembly of the kind specified comprising a pinion bearing shaft which is mounted at one end on pinion bearings comprising cooperating projection and socket parts located in a recessed portion of the pinion housing, to provide radial support and axial location of the pinion in the pinion housing with one part supported at least partly by the pinion housing and the other part carried by the pinion bearing shaft for rotation therewith, in which the pinion bearing shaft and the pinion housing recessed portion are dimensioned and arranged so that the pinion bearing shaft will be radially supported by the recessed portion on failure of the projection and socket parts.

One assembly of the invention may include a generally cup-shaped retainer located in the recessed portion of the pinion housing, and the said projection part can be a ball-bearing cooperating with a socket in said one end of the pinion bearing shaft.

This ball-bearing may also cooperate with a socket in the retainer end.

In an alternative construction, the said projection part may be a suitably shaped part of the retainer end, and may cooperate with a socket in the said one end of the pinion bearing shaft. The retainer may seal the recessed portion of the pinion housing, and the retainer may have an outwardly extending rim which either engages an inner wall of the pinion housing or cooperates with a complementary part of the pinion housing.

Another assembly of the invention may include adjustment means operable to adjust the position of the retainer in the recessed portion so as to provide the required degree of tightness of the pinion bearings. Preferably, this adjustment means may comprise a screw and lock nut mounted on the pinion housing to bear on the retainer end.

In a further assembly of the invention, said one part is located on a bearing plate which is movably located in the said recessed portion. This further assembly may also include adjustment means operable to adjust the position of the bearing plate in the recessed portion to provide a required degree of tightness of the pinion bearings, and this adjustment means may comprise a screw and lock nut mounted on the pinion housing to bear on the bearing plate.

The retainer may be made of pressed steel and may either be a press fit in the pinion housing or may be movably located in the recessed portion in response to the adjustment means.

Various embodiments of the invention will now be described by way of example with reference to the accompanying illustrative drawings, in which: Figure I is a side elevation partly in section of one rack and pinion assembly of the invention Figure 2 is a side elevation partly in section of a modification to part of the assembly of Figure 1; Figure 3 is a side elevation partly in section of another assembly of the invention; and Figures 4 to 7 are side elevations partly in section of parts of further assemblies of the invention; Referring to Figure 1, one rack and pinion assembly of the invention includes a pinion 2 rotatably mounted on a pair of axially spaced bearings shown generally at 4 and 6 in a pinion housing 8. The pinion 2 can be rotatably driven by a shaft 10 and engages with a rack on a bar 12 so that rotation of the pinion 2 effects longitudinal movement of the rack bar 12 through the pinion housing 8. The teeth of the pinion 2 and the rack are maintained in meshing engagement by means of a conventional spring loaded yoke 14.

A pinion bearing shaft 16 is secured to one end of the pinion 2 to extend into a tubular recess 18 in the pinion housing 8.

This recess 18 is sealed by a cup shaped pressed steel retainer 20 having an outwardly extending rim 22 to engage the inner wall of the pinion housing 8 adjacent to the recess 18. The bearing 6 comprises a ball bearing 24 retained in position between cooperating sockets in the base of the retainer 20 and the end of the pinion bearing shaft 16.

The assembly includes a screw operated adjustment device 26 to adjust the degree of compression exerted upon the bearings 4 and 6.

It will be appreciated that the ball bearing 24 provides both radial support and axial location for the pinion 2 at the right hand end of the assembly as illustrated.

The clearance between the pinion bearing shaft 16 and the tubular wall of the retainer 20 is sufficiently small so that in the event of collapse of the bearing 6, the pinion bearing shaft and hence the pinion 2 will still be supported in the recess 18. Although this support of the pinion will be comparatively loose it will still enable at least some degree of steering control to be maintained, and will prevent or at least reduce the risk of broken bearing parts entering and jamming the meshing teeth of the rack and pinion.

Figure 2 is a modification to the assembly of Figure 1, in which the ball bearing 24 has been replaced by an inwardly extending hemispherical projection 30 on the base of the retainer 20.

Figure 3 illustrates another assembly of the invention, and for clarity corresponding components of Figures 1 and 3 have been given the same reference numerals.

Referring to Figure 3, a recessed portion 32 of the pinion housing 8 has an end wall 34. A pressed steel retainer 36 is slidably located inside the recessed portion 32 under the control of a screw and lock nut adjustment mechanism 38. As with the assembly of Figure 1, the bearing 6 comprises a ball bearing 24 located between cooperating recesses in the pinion bearing shaft 16 and the base of the retainer 36. The adjustment mechanism 38 is operated to provide the required degree of tightness on the bearings 4 and 6.

Figure 4 illustrates a modification to the assembly of Figure 3. Referring to Figure 4, the retainer 36 of Figure 3 is replaced by a bearing plate 46 which makes a sliding fit in the recessed portion 32. The bearing 6 comprises an inwardly extending hemispherical projection 48 of the plate 46 which cooperates with a recess on the end of the pinion bearing shaft 16.

The bearing plate may, for example, be made of sintered material or case hardened cold-formed steel.

Figure 5 illustrates another assembly of the invention in which a pressed steel cup-shaped retainer 50 is retained in the recessed portion 32 by an inwardly extending rim of the pinion housing 8. The bearing 6 comprises a hemispherical projection 54 on the base of the retainer 50 which cooperates with a socket on the end of the pinion bearing shaft 16.

Figure 6 illustrates a modification in which a cup-shaped retainer 56 makes a press fit in the recessed portion 32, and is retained in the portion 32 by an outwardly extending rim 58 on the retainer 56 which cooperates with a suitably shaped recess in the pinion housing 8. As with the assembly of Figure 6, the bearing 6 comprises a hemispherical projection 54 which cooperates with a socket on the end of the pinion bearing shaft 16.

Figure 7 illustrates an assembly having a cup-shaped retainer 62 retained in the recessed portion 32 by an inwardly extending rim 52 of the pinion housing 8. The bearing 6 comprises a ball bearing 64 retained in position between cooperating sockets on the base of the retainer 62 and the end of the pinion bearing shaft 16.

It will be appreciated that all the above described assemblies have the important common feature that on collapse of the bearing 6, the pinion shaft 16 and hence the pinion 2 would still be supported by the recessed portion 32 of the pinion housing 8, and would continue to provide steering control.

In the assemblies of Figures 1, 2, 5, 6 and 7, the retainer makes a press fit in the pinion housing to seal the recessed portion.

WHAT WE CLAIM IS: 1. A rack and pinion assembly of the kind specified comprising a pinion bearing shaft which is mounted at one end on pinion bearings comprising cooperating projection and socket parts located in a recessed portion of the pinion housing to provide radial support and axial location of the pinion in the pinion housing, with one part supported at least partly by the pinion housing and the other part carried by the pinion bearing shaft for rotation therewith, in which the pinion bearing shaft and the pinion housing recessed portion are dimensioned and arranged so that the pinion bearing shaft will be radially supported by the recessed portion on failure of the projection and socket parts.

2. An assembly as claimed in Claim 1, including a generally cup-shaped retainer located in the recessed portion of the pinion housing.

3. An assembly as claimed in Claim 2, in which the said projection part is a ballbearing cooperating with a socket in said one end of the pinion bearing shaft.

4. An assembly as claimed in Claim 3, in which the ball-bearing also cooperates with a socket in the retainer end.

5. An assembly as claimed in Claim 2, in which the said projection part is a shaped part of the retainer end.

6. An assembly as claimed in Claim 5, in which the said shaped part of the retainer end cooperates with a socket in said one end of the pinion bearing shaft.

7. An assembly as claimed in any one of Claims 2 to 6, in which the retainer seals the recessed portion of the pinion housing.

8. An assembly as claimed in Claim 7, in which the retainer has an outwardly extending rim which engages an inner wall of the pinion housing.

9. An assembly as claimed in Claim 7, in which the retainer has an outwardly extending rim which cooperates with a complementary part of the pinion housing.

10. An assembly as claimed in any of Claims 2 to 6 including adjustment means operable to adjust the position of the retainer in the recessed portion to provide the required degree of tightness of the pinion bearings.

11. An assembly as claimed in Claim 10, in which the adjustment means comprises a screw and lock nut mounted on the pinion housing to bear on the retainer end.

12. An assembly as claimed in Claim 1, in which said one part is located on a bearing plate movably located in the said recessed portion; said assembly including adjustment means operable to adjust the position of the bearing plate in the recessed portion to provide a required degree of tightness of the pinion bearings.

13. An assembly as claimed in Claim 12, in which said adjustment means comprises a screw and lock nut mounted on the pinion housing to bear on the bearing plate.

14. A rack and pinion assembly substantially as herein described and shown in the accompanying drawings.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. extending rim 58 on the retainer 56 which cooperates with a suitably shaped recess in the pinion housing 8. As with the assembly of Figure 6, the bearing 6 comprises a hemispherical projection 54 which cooperates with a socket on the end of the pinion bearing shaft 16. Figure 7 illustrates an assembly having a cup-shaped retainer 62 retained in the recessed portion 32 by an inwardly extending rim 52 of the pinion housing 8. The bearing 6 comprises a ball bearing 64 retained in position between cooperating sockets on the base of the retainer 62 and the end of the pinion bearing shaft 16. It will be appreciated that all the above described assemblies have the important common feature that on collapse of the bearing 6, the pinion shaft 16 and hence the pinion 2 would still be supported by the recessed portion 32 of the pinion housing 8, and would continue to provide steering control. In the assemblies of Figures 1, 2, 5, 6 and 7, the retainer makes a press fit in the pinion housing to seal the recessed portion. WHAT WE CLAIM IS:

1. A rack and pinion assembly of the kind specified comprising a pinion bearing shaft which is mounted at one end on pinion bearings comprising cooperating projection and socket parts located in a recessed portion of the pinion housing to provide radial support and axial location of the pinion in the pinion housing, with one part supported at least partly by the pinion housing and the other part carried by the pinion bearing shaft for rotation therewith, in which the pinion bearing shaft and the pinion housing recessed portion are dimensioned and arranged so that the pinion bearing shaft will be radially supported by the recessed portion on failure of the projection and socket parts.