GB2310026A

GB2310026A - Steering wheel assembly

Info

Publication number: GB2310026A
Application number: GB9602228A
Authority: GB
Inventors: Eric R Bellamy
Original assignee: Camloc UK Ltd
Current assignee: Camloc UK Ltd
Priority date: 1996-02-05
Filing date: 1996-02-05
Publication date: 1997-08-13
Anticipated expiration: 2016-02-05
Also published as: GB2310026B; GB9602228D0

Abstract

A steering wheel comprising a central hub 3 and an air bag assembly 4 engages a steering shaft 5 by means of tapered region 6 and splines 8 on the hub 3 which mate with corresponding tapered region 7 and splines 9 on the shaft 5. A split collet 11 is maintained in a radially expanded condition by a plug (23, Fig 2) until, upon mounting the steering wheel on the shaft 5, the plug 23 is displaced and the force of spring 22 against tapered sleeve 19 collapses the collet around the tapered end region 15 of the shaft 5 through a snap-fit arrangement to prevent subsequent removal of the steering wheel assembly 2.

Description

STEERING WHEEL ASSEMBLY This invention relates to a steering wheel assembly, and in the preferred embodiment provides a steering wheel assembly which can quickly and easily be mounted on a steering shaft of a motor vehicle by a simple push-fit movement.

The conventional means of securing a steering wheel to the steering column shaft of a motor vehicle comprises providing mating tapers and/or splines on the steering wheel hub and shaft respectively, locating the steering wheel on the taper and/or splines of the shaft by an axial movement of the steering wheel relative to the shaft, and securing the steering wheel in position by means of a nut which engages mating threads on the end of the shaft and holds the steering wheel in position by means of an interposed washer.

Conventionally, the nut is tightened to a predetermined torque and is secured in place by appropriate restraining means.

Whilst the above describes system provides for satisfactory retention of the steering wheel on the shaft, it suffers from the disadvantage that access to the central region of the steering wheel, on the drivers side thereof, is required to secure the fixing nut. As a result, any components which, in the final vehicle, are to overlie the central nut must be secured in position after the steering wheel itself is secured in position. Such components, for example an air bag assembly, cannot accordingly be preassembled with the steering wheel prior to mounting the steering wheel on the steering column shaft. Such components can be difficult to secure in position after the steering wheel has been mounted because of the orientation and limited clearance behind the steering wheel when it is in its final use position.

It is accordingly the object of the present invention to provide a steering wheel mounting arrangement in which the steering wheel can be pre-assembled with any components (such as air bag assemblies) which are required in the final configuration of the steering wheel assembly, before the steering wheel assembly is secured to the steering column shaft.

Accordingly, one aspect of the present invention provides a steering wheel assembly for securing to the shaft of a steering column, wherein the steering wheel has a central hub provided with means for preventing relative rotation of the steering wheel and the shaft and wherein the hub is provided with a snap-fit detaining device which, when the steering wheel assembly is pushed onto the shaft, will permit passage of a portion of the shaft therethrough and will then snap-fit into engagement with a surface on the shaft to prevent subsequent removal of the steering wheel assembly from the shaft by means of an axial pull applied to the steering wheel assembly.

Preferably, means are provided for biasing the steering wheel onto the shaft after the snap-fit detaining device has engaged the corresponding surface on the shaft. The biasing means preferably provides a continuous bias on the steering wheel throughout the life of the vehicle to ensure that any movement which may tend to develop between the shaft and the steering wheel hub will result in the steering wheel being biased further onto the shaft by the biasing means.

Accordingly, any tendency for the steering wheel to become loose on the shaft will be prevented.

Preferably, the biasing means is provided by means of mating tapers on the detaining device and on the shaft, the tapers being orientated such that a circumferentially inward force applied to the detaining device will tend to draw the steering wheel assembly further onto the shaft. Means are accordingly provided for applying a circumferentially inward force on the detaining device. Such means may, for example, comprise a spring which applies the force in the axial direction to a sleeve which has a tapered surface which acts on a corresponding tapered surface of the detaining device such that axial load applied to the sleeve by the spring tends to collapse the detaining device.

Preferably, the detaining device can be released to permit removable of the steering wheel assembly from the shaft. In the preferred embodiment of the invention where the force tending to bias the steering wheel onto the shaft is provided by an axially operating spring, means are preferably provided for compressing the spring so as to permit the detaining device to expand and release the mating surface on the shaft.

In the preferred embodiment of the invention the snapfit detaining device is preferably held in an expanded condition prior to offering up of the steering wheel to the shaft such that the end portion of the shaft may readily enter the snap-fit detaining device. Preferably, the snapfit detaining device is held in the expanded position by a plug which is displaced from its operative position by the shaft as the steering wheel is pushed onto the shaft, thereby enabling the snap-fit detaining device to come into operation. Preferably, the shaft is provided with means for retaining the plug after it has been removed from its operative position.

The invention will be better understood from the following description of a preferred embodiment thereof, given by way of example only, reference being had to the accompanying drawings wherein: Figure 1 illustrates schematically in transverse cross section a preferred embodiment of the invention; Figures 2A and 2B illustrate the sequence of mounting the steering wheel of the preferred embodiment on a shaft; Figures 3A, 3B and 3C illustrate respectively the configuration of the components of the system at nominal tolerances and its two possible variations from nominal tolerances; and Figure 4 illustrates the method by which the steering wheel assembly of the preferred embodiment may be removed from its associated shaft.

Referring firstly to Figure 1 there is shown schematically in cross section the central region 1 of a steering wheel assembly 2 which comprises a conventional steering wheel having a central hub 3 and an air bag assembly 4 which is secured to the steering wheel 2 by conventional means. The steering wheel 2 is shown mounted on a steering column shaft 5. The hub 3 of the steering wheel engages the shaft 5 by means of a tapered region 6 which mates with a corresponding tapered region 7 on the shaft and a splined region 8 which mates with a corresponding splined region 9 on the shaft. The spline and tapered arrangement is a standard arrangement for securing steering wheels in position and will be well understood by those skilled in the art.

Removal of the steering wheel by application of an axial force to the steering wheel in the direction of the arrow A is prevented by a detaining device 10.

The detaining device 10 comprises a collet 11 which includes a tapered portion 12 and a flange 13. The collet 11 is split by a slot 14 so that it is radially expandable and contractible. The taper on the interior of the tapered portion 12 mates with a corresponding taper provided on a distal portion 15 of the shaft 5. The flange 13 of the collet 11 bears against a face 16 provided on the steering wheel hub 3.

The collet 11 is surrounded by a retainer 17 which is secured to the steering wheel 3 by suitable fixing devices 18. A sleeve 19 is located between the tapered portion 12 of the collet and the retainer 17. The radially outermost surface 20 of the sleeve 19 is cylindrical and is a free sliding fit within the retainer 17. The radially inner surface 21 of the sleeve 19 is tapered to mate with the external taper of the tapered portion 12. A spring, for example a 5 turn crest-to-crest SPIRAWAVE (registered trade mark) spring, acts between the flange 13 and the sleeve 19 to bias the sleeve away from the flange. By virtue of the mating tapers on the interior of the sleeve 19 and on the tapered portion 12, the action of the spring on the sleeve 19 produces a radially inward force tending to collapse the collet 11.

It will be noted that the spring 22 will drive the sleeve 19 to a position where the sleeve resists radial expansion of the collet. Any tendency of the sleeve to slip towards the flange 13 under the influence of radially outwardly directed forces from the collet will be resisted by the spring 22. Accordingly, in addition to providing a radially inward force on the collet tending to collapse the collet the sleeve 19 prevents any radial expansion of the collet. It will be appreciated from Figure 1 that any attempt to remove the steering wheel from the shaft 5 by exsertion of a force in the direction of the arrow A on the steering wheel will be prevented by the detaining device 10 since in order to move the steering wheel in a direction of the arrow A the collet must be expanded, and expansion of the collet is prevented by the sleeve 19. It will further be appreciated that, in the event of "bedding in" or other action tending to slacken the mating engagement of the tapered portion 6 of the hub and the tapered portion 7 of the shaft, the action of the radially inwardly directed force on the collet produced by the sleeve 19 of spring 22 will tend to drive the steering wheel further onto the taper 7. Thus, even some slack tends to develop in use between the steering wheel hub 3 and the shaft 5, the action of the detaining device will tend to eliminate such slack.

Referring now to Figures 2A and 2B, the method by which the steering wheel assembly 2 is mounted on the shaft 5 is illustrated. In the as manufactured configuration of the steering wheel assembly 2 (Figure 2A) the spring 22 is fully compressed and the sleeve 19 is as close as it can get to the flange 13. In this configuration the internal diameter of the collet is at its maximum available value. The components are held in this configuration by a plug 23 located within the collet at a point where the interior surface of the collet is substantially cylindrical. The air bag assembly 4 and all other components associated with the steering wheel assembly have been pre-assembled onto the steering wheel.

The entire as manufactured steering wheel assembly is offered up to the shaft 5 in the direction of the arrow B.

The distal portion 15 of the shaft passes through the tapered region 6 of the hub and through the splined region 8 and enters the collet. A lead-in taper 24 is preferably provided on the end of the shaft 5 to assist entry of the shaft into the collet 19. At this stage, the components have reached the configuration shown in Figure 2B. Further force applied to the steering wheel assembly will cause a clip portion 25 provided on the plug 23 to enter a clip receiving counter bore 26 provided in the end of the shaft 5 and, thereafter, will cause displacement of the plug 23 from the parallel portion of the interior of the collet. When this occurs, the collet will be released and can snap radially inwardly to bring the mating tapers of the collet interior and of the distal region 15 into engagement with each other. Collapse of the collet about the distal region 15 will be accompanied by movement of the sleeve 19 to the right as viewed in Figures 2A and 2B and corresponding relaxation of the spring 22. This will result in the components arriving at the configuration shown in Figure 1.

Figures 3A, 3B and 3C illustrate the ability of the invention to accommodate variations in components due to manufacturing tolerances. Figure 3A illustrates the relative configuration of the various components when all components of the system are manufactured to nominal size.

Figure 3B illustrates the configuration of the various components if the tapered region 7 of the shaft is oversize and/or the tapered region 6 of the hub 3 is undersized.

Figure 3C illustrates the relative configuration of the components if the tapered region 7 is undersized and/or the tapered region 6 of the hub 3 is oversized. It will be noted that the invention is capable of accommodating a range of tolerances in the mating tapers of the shaft and steering wheel hub.

Referring now to Figure 4, if it is necessary to remove the steering wheel the air bag assembly and any other components overlying the central region of the wheel must first be removed. A removal tool 27 is then screwed into screw threads 28 provided on the retainer 17. Screwing the removal tool 27 into position causes the front 28 of the tool to act on the sleeve 19 forcing the sleeve towards the flange 13 and compressing the spring 22. The removal tool 27 is designed to enable the sleeve 19 to be returned to the position in which the spring 22 is almost fully compressed.

In this configuration, as illustrated in Figure 4, the collet 11 is free to expand, and accordingly will not prevent removal of the steering wheel. Preferably, the removal tool 27 includes a central bore 29 to enable an appropriate puller to be used which will apply a force between the steering wheel 2 and the shaft 5 in order to break the engagement between the tapered portions 6 and 7.

On removal of the steering wheel, the plug 23 being of slightly larger diameter than the distal of the shaft 5 will normally remain in the bore of the collet 11 and hold it in it's expanded condition ready for re-fitting the steering wheel to the shaft.

The removal tool can be disengaged and the air bag and other overlying equipment re-attached to the wheel, prior to re-fitting in the manner described previously.

In the event of the plug 23 remaining in the end of the shaft 5 on disassembly, it should be relocated in the cylindrical portion of the collet 11 prior to removing the removal tool.

Claims

CLAIMS:

1. A steering wheel assembly for securing to the shaft of a steering column, wherein the steering wheel has a central hub provided with means for preventing relative rotation of the steering wheel and the shaft and wherein the hub is provided with a snap-fit detaining device which, when the steering wheel assembly is pushed onto the shaft, will permit passage of a portion of the shaft therethrough and will then snap-fit into engagement with a surface on the shaft to prevent subsequent removal of the steering wheel assembly from the shaft by means of an axial pull applied to the steering wheel assembly.

2. A steering wheel assembly according to Claim l wherein means are provided for biasing the steering wheel onto the shaft after the snap-fit detaining device has engaged the corresponding surface on the shaft.

3. A steering wheel assembly according to Claim 2 wherein the biasing means provides a continuous bias on the steering wheel throughout the life of the vehicle to ensure that any movement which may tend to develop between the shaft and the steering wheel hub will result in the steering wheel being biased further onto the shaft by the biasing means.

4. A steering wheel assembly according to Claim 2 or Claim 3 wherein the biasing means is provided by means of mating tapers on the detaining device and on the shaft, the tapers being orientated such that a circumferentially inward force applied to the detaining device will tend to draw the steering wheel assembly further onto the shaft.

5. A steering wheel assembly according to any preceding claim including means for applying a circumferentially inward force on the detaining device.

6. A steering wheel assembly according to Claim 5 wherein the means for applying a circumferentially inward force comprise a spring which applies the force in the axial direction to a sleeve which has a tapered surface which acts on a corresponding tapered surface of the detaining device such that axial load applied to the sleeve by the spring tends to collapse the detaining device.

7. A steering wheel assembly according to any preceding claim wherein the detaining device is releasable to permit removable of the steering wheel assembly from the shaft.