GB2071225A - Self-adjusting bearing - Google Patents

Abstract

A ball 10 for mounting a rotatable shaft 16 (e.g. an accelerator linkage of a motor vehicle) is captive in a housing 17 consisting of a shell 20 providing a bearing surface 20b and an axially opposite shell 18. A compressible element (e.g. rubber O- ring 24) is pressed between the ball 10 and the shell 18. The dimensions are such that on assembling the shells 18, 20 about the ball 10 and O-ring 24, the ring 24 is compressed. Manufacturing tolerances affect the degree of compression, but within expected limits thereof the ring 24 will be moderately compressed, and hence the ball 10 abuts surface 20b with moderate force, so as to be slidable relative thereto in response to a torque exceeding a threshold value, thus adjusting the axis of the bearing. <IMAGE>

Description

SPECIFICATION Self-adjusting bearing The present invention relates to a self-adjusting bearing.

Many mechanical systems employ rotatable shafts journalled in one or more bearings. For a shaft to be smoothly rotatable it must be coaxial with its bearing(s). In a standard manufacturing process, accurate alignment of components cannot be guaranteed, especially if the process is of some complexity, e.g. car assembly. To provide greater manufacturing tolerances, self-adjusting bearings may be used. These are bearings whose axes can pivot in response to forces caused by misalignment. A known form employs a generally ball-shaped plastics element which is held fairly tightly in a spherical seating, so as to be swivellable if sufficient torque is applied. The ball has a diametrical bore for receiving a shaft which is rotatable therein. In use the shaft rotates in the bore and the bail is generally immobile relative to the seating.During assembly of the bearing and shaft, if they are not initially aligned a sufficient force will pivot the ball in its seating. This pivoting is generally intended to occur only during assembly, and possibly also if the assembled device is subsequently subject to distortion.

For proper functioning, the firmness with which the ball is held in the seating is important. If it is held too tightly, the bearing will not be selfadjusting under the influence of moderate forces.

If it is held too loosely, the ball will tend to rotate with the shaft. For a low-cost bearing, the seating may be made from mild steel castings or pressings, so that the bearing surface thereof is relatively rough. Consequently the rubbing of the ball on the seating during such rotation tends to wear it away. This will further reduce the grip of the sealing on the ball, which may soon be entirely worn away, leaving the shaft threaded loosely through the seating. In a bearing intended for a shaft of the accelerator control of a motor vehicle, the ball may have a diameter of the order of 2-3 cm. To attain a proper grip, the ball and seating should be manufactured to tolerances of the order of 25 ,um (1 thou). This is difficult to achieve.Either the cheapness, which is a major reason for using this type of bearing, must be lost (or lessened), or a substantial proportion of low quality bearings must be accepted.

According to the invention there is provided a self-adjusting ball and socket type bearing, including a socket having two opposed internal surface portions and a ball elements located therebetween, one of said surface portions being a concave bearing surface for the ball element; the bearing further including a compressible element located between the ball element and the second of said surface portions, the dimensions of the components being such that during assembly of the bearing the compressible element is compressed, and in the assembled bearing remains compressed between the second surface portion and the ball element, which abuts the concave bearing surface.

It will usually be convenient for the ball element to be substantially spherical. However, other shapes are possible, so long as there is a suitable surface for sliding relative to a bearing surface.

Such bearings may be of particular use in motor vehicles, e.g. in the accelerator linkages thereof. In another aspect the invention provides a vehicle having an accelerator linkage including such a bearing.

A preferred embodiment of the invention will now be described with reference to the accompanying drawing, whidh the sole figure is an axial section of a self-adjusting ball and socket type bearing.

A captive ball-member 10 is generally spherical, with a diametrical bore 12, and two flat parallel end-faces 14 in respective axial planes. A shaft 1 6 is insertable through the bore 12 so as to be freely rotatable therein.

The ball-member 10 is held in a housing 1 7 formed of two cup-form shells 1 8, 20. These shells have respective peripheral flanges 1 8a, 20a by means of which they are secured together (e.g.

by spot welds) about the ball-member 10. One of the shells (20) includes a part-spherical inner surface 20b which is dimensional so that the ballmember 10 can fit flush against it. The cup of the other shell 18 has an inner surface 1 Ob which diverges outwardly from the spherical surface of the ball-member 10, so that there is an annular chamber 22 defined between them. This holds an O-ring gasket 24 of compressible resilient material, e.g. natural or synthetic rubber. (The gasket 24 is put in place before the shells 1 8, 20 are secured together to form the housing 17.) The parts are dimensioned so that, when the ballmember 10, gasket 24 and housing 17 are assembled, the gasket 24 is somewhat compressed, and urges the ball-member against the spherical surface 20b.The thickness of the gasket 24 is such that, allowing for the expected variations in the dimensions of manufactured components, it will always be at least slightly compressed on assembly. Its material is such that the expected range of compression (as determined by the manufacturing tolerances) will cause the force with which the ball-member 10 is urged against the surface 20b to be within an acceptable range, such that the bearing is self-adjusting but the ball does not rotate with the shaft 1 6.

The bearing can be made extremely cheaply.

The shells (18,20) may be formed by stamping mild steel sheet. The use of a compressible gasket 24 means that manufacturing tolerances are high, so that cheap and simple manufacturing processes are suitable. The inner surface 20b of such a shell will be fairly rough, so that the coefficient of function between it and a ballmember 10 (which may be of a rigid plastics material, e.g. an acetal copolymer) will be quite high, so that slippage is unlikely to occur during normal rotation of the shaft 1 6 within the bore 12.

Claims (8)

1. A self-adjusting ball and socket type bearing including a socket having two opposed internal surface portions and a ball element located therebetween, one of said surface portions being a concave bearing surface for the ball element; the bearing further including a compressible element located between the ball element and the second of said surface portions, the dimensions of the components being such that during assembly of the bearing the compressible element is compressed, and in the assembled bearing remains compressed between the second surface portion and the ball element, which abuts the concave bearing surface.

2. A bearing according to claim 1, wherein said compressible element is resiliently compressible.

3. A bearing according to claim 1 or claim 2, wherein said socket comprises two opposed cupform elements which provide respective ones of said surface portions.

4. A bearing according to claim 3, wherein said cup-form elements have mutually abutting peripheral flanges by means of which they are secured together.

5. A bearing according to any one of the preceding claims, wherein the compressible elements is an O-ring.

6. A bearing according to any one of the preceding claims, wherein said ball element has a central bore for receiving rotatably a shaft.

7. A self-adjusting ball and socket bearing substantially as described herein with reference to and as illustrated in the accompanying drawing.

8. A motor vehicle having an accelerator linkage including at least one bearing according to any one of the preceding claims.