GB2310705A

GB2310705A - Coupling of a steering wheel to a steering shaft

Info

Publication number: GB2310705A
Application number: GB9604543A
Authority: GB
Inventors: Ricardo Antonio Pastor
Original assignee: Delphi Automotive Systems France
Current assignee: Delphi Automotive Systems France
Priority date: 1996-03-02
Filing date: 1996-03-02
Publication date: 1997-09-03
Anticipated expiration: 2016-03-02
Also published as: GB9604543D0; GB2310705B

Abstract

A tubular steering shaft (16) has a splined portion (22) adjacent its free end, a portion (26) having a tapered external surface (28), and a portion (30) having a screw-threaded external surface (32). A tubular hub (48) on which a steering wheel (14) is securable has a tapered portion (52) positioned around the tapered portion of the tubular shaft, and a splined portion (56) engageable with the splined portion (22) of on the tubular shaft. A nut (62) cooperates with the screw-threaded surface (32) of the steering shaft and engages the hub (48) such that it can rotate about the hub but is axially fixed to it. The screwing of the nut (62) along the shaft pulls the hub along the splines and brings the tapered surfaces into mutual engagement to hold the steering wheel (14) on the shaft (16). The arrangement avoids the need to reach a retaining nut through the front central portion of the steering wheel.

Description

STEERING SYSTEM FOR A MOTOR VEHICLE This invention relates to a steering system for a motor vehicle.

It is known to provide a steering system in a motor vehicle in which a steering wheel hub is secured to a shaft of the steering column. The shaft has a externally splined portion which engages with an internally splined portion on the hub. The shaft has a threaded portion which extends through a bore in the hub, and a nut is threaded on the threaded portion to secure the steering wheel to the shaft. As a consequence of this design, access is required through the front central portion of the steering wheel in order to have access to the nut. This arrangement has a disadvantage in terms of mounting an air bag module and/or a warning horn switch on the steering wheel.

It is an object of the present invention to overcome the above mentioned disadvantage.

To this end, a steering system in accordance with the present invention for a motor vehicle, comprises a tubular shaft which is rotatable about its longitudinal axis, the tubular shaft having a free end, a first portion adjacent the free end having splines on its external surface, a second portion adjacent the first portion having a tapered external surface, and a third portion adjacent the second portion having a threaded external surface, the third portion having a larger external diameter than the first portion; a tubular hub on which a steering wheel is securable, the tubular hub having a longitudinal axis substantially aligned with the longitudinal axis of the tubular shaft, a free end positioned around the second portion of the tubular shaft, a first portion adjacent the free end of the tubular hub having a tapered internal surface substantially corresponding to and engageable with the tapered surface on the tubular shaft, and a second portion adjacent the first portion of the tubular hub having splines on its internal surface substantially corresponding to and engageable with the splined surface on the tubular shaft; and a nut rotatable relative to the tubular shaft and the tubular hub about the longitudinal axis, the nut having means engageable with corresponding means on the tubular hub, and an internal threaded surface adjacent the external threaded surface on the tubular shaft, rotation of the nut relative to the tubular shaft moving the tubular hub in an axial direction relative to the tubular shaft.

In the present invention, there is no need to provide access through the central front portion of the steering wheel in order to attach/detach the steering wheel from the steering column. As a consequence, an air bag module and/or warning horn switch may be integrally mounted on the steering wheel prior to attachment of the steering wheel on the steering column, which has assembly advantages.

The present invention will now be described, by way of example, with reference to the accompanying drawing, in which: Figure 1 is a cross-sectional view of a steering system in accordance with the present invention; Figure 2 is a partial cross-sectional view of a first modification to the steering system of Figure 1 in accordance with the present invention; Figure 3 is a partial cross-sectional view of a second modification to the steering system of Figure 1 in accordance with the present invention; and Figure 4 is a partial cross-sectional view of a third modification to the steering system of Figure 1 in accordance with the present invention.

Referring to Figure 1 of the drawings, the steering system 10 includes a steering column 12 and a steering wheel 14. The steering column 12 comprises a tubular shaft 16 which is rotatable about a longitudinal axis A relative to an external sleeve 18 which is fixed to a body portion (not shown) of a motor vehicle. The shaft 16 has a free end 20, a first portion 22 adjacent the free end having splines 24 on its external surface, a second portion 26 adjacent the first portion having a tapered (conical) external surface 28, and a third portion 30 adjacent the second portion having a threaded external surface 32. The third portion 30 has a larger external diameter than the external diameter of the first portion 22. The shaft 16 preferably has a fourth portion 34 adjacent the third portion 30 which has an external diameter greater than the external diameter of the third portion, and a fifth portion 36 connected to the fourth portion by a tapered shoulder 38 with an external diameter greater than the external diameter of the fourth portion. The shaft 16 is rotatably mounted within the sleeve 18 by way of a bearing 40 which is retained between the tapered shoulder 38 and annular clips 42 mounted on the fourth portion 34 of the shaft 16. The bearing 40 is retained in the sleeve 18 between an inwardly directed circumferential groove 44 formed in the sleeve and tabs 46 punched inwardly in the sleeve.

The steering wheel 14 is secured (preferably by welding) to a tubular hub 48 which has a longitudinal axis substantially aligned with axis A. The hub 48 has a free end 50 which, when in position, surrounds the second portion 26 of the shaft 16. The hub 48 also has a first portion 52 adjacent the free end 50 which has a tapered (conical) internal surface 54, and a second portion 56 adjacent the first portion 52 which has splines 58 formed on its internal surface. The tapered internal surface 54 substantially corresponds to the tapered external surface 28 on the shaft 16 and is engageable therewith when the hub 48 is assembled on the shaft 16. The splined internal surface 58 substantially corresponds to the splined external surface 24 on the shaft .16 and is engageable therewith when the hub 48 is assembled on the shaft 16. The hub 48 also has an external shoulder 60 formed thereon which is directed away from the free end 50 of the hub and towards the steering wheel 14.

A locking nut 62 is used to secure the hub 48 to the shaft 16. The nut 62 has an internal shoulder 64 which, when assembled on the hub 48, engages the external shoulder 60 on the hub. The nut 62 also has an threaded internal surface 66 which engages the threaded external surface 32 on the shaft 16. The nut 62 is preferably attached to the hub 48 by coining or crimping to form the shoulder 64 adjacent the shoulder 60 on the hub.

The steering system 10 is assembled by sliding the hub 48 onto the shaft 16 such that the splined surfaces 24,58 interengage. The nut 62 is then rotated about axis A relative to the shaft 16 such that the threaded surfaces 32,66 interengage. This screw-threading action is continued to bring the shoulders 60,64 into engagement and the tapered surfaces 28,54 into engagement due to axial movement of the hub 48 relative to the shaft 16. The tightening action is preferably continued to a predetermined level of torque. Such an arrangement provides a frictional engagement between the tapered surfaces 28,54 which helps to enhance the interlock between the hub 48 and the shaft 16 provided by the engaged splined surfaces 24,58.

With the above described arrangement there is no need to provide access through the central front portion of the steering wheel in order to attach/detach the steering wheel from the steering column. The steering wheel 14 is secured to the shaft 16 of the steering column 12 by way of the nut 62 which is accessible from outside the steering wheel. Such an arrangement allows an air bag module and/or a warning horn switch (not shown) to be integrally mounted on the steering wheel 14 and hub 48 in a sub-assembly which is subsequently secured on the steering column 12.

Relative to previously known designs, the torque on the nut 48 can be set at a level which provides an increase in the frictional grip between the hub 48 and the shaft 16. Also, the use of a hollow shaft 16 and hub 48 provides an enclosed conduit or housing which may be used for enclosing an air bag firing system, and/or for enclosing remote control devices having actuation switches associated with the steering wheel 14, and/or for bringing electrical wiring, etc. to the steering wheel 14. Radial apertures 68 in the second portion 56 of the hub 48 can be used for bringing the electrical wiring out of the shaft 16 and hub 48 to the steering wheel 14. Still further, the diameter of the shaft 16 can be made larger than previously known solid shafts. This reduces the risk of the steering column 12 and steering wheel 14 reaching its first natural frequency (due to vibrations generated on driving the motor vehicle). Further still, the engaged splined surfaces 24,58 are used to provide alignment of the steering wheel 14 with the wheels of the motor vehicle.

With the possibility of increasing the diameter of the hollow shaft 16 and the hub 48, the number of splines on the splined surfaces 24,58 can be increased compared to known arrangements. This provides an increase in the number of potential positions for the steering wheel 16 relative to the steering column 14, thereby increasing the adjustment capability.

Various modifications can be made to the arrangement shown in Figure 1 without departing from the scope of the present invention. Examples of some of these modifications can be seen in Figures 2 to 4.

In these figures, like parts have been given the same reference numeral. In the arrangement of Figure 2, the external diameter of the third portion 30' of the shaft 16 is greater than the maximum external diameter of the hub 48. With this arrangement, the nut 62' can be separately formed with its internal shoulder 64 and then slid into position on the hub 48 prior to securing the steering wheel 14 on the hub. In the arrangement of Figure 3, the shaft 16 is substantially identical to the shaft 16 of Figure 1, and the nut 62' is substantially identical to the nut 62' of Figure 2. In this case, an annular spacer 70 is positioned between the threaded external surface 32 on the third portion 30 of the shaft 16 and the threaded internal surface 66 on the nut 62'. The annular spacer 70 has a threaded internal surface 72 which makes a screw threaded engagement with the threaded external surface 32 of the third portion 30 of the shaft 16, and a threaded external surface 74 which makes a screw threaded engagement with the threaded internal surface 66 on the nut 62'. The arrangement shown in Figure 4 is similar to that shown in Figure 2 except that the shoulders on the hub 48' and the nut 62" are omitted. In this case, the hub 48' has a threaded external surface 76 which makes a screw threaded engagement with an additional threaded internal surface 78 on the nut 62" to provide the engagement between the hub and the nut. The screw threads of the surfaces 76,78 are of opposite hand to the screw threads of the surfaces 32,66.

Claims

Claims:-

1. A steering system for a motor vehicle comprising a tubular shaft which is rotatable about its longitudinal axis, the tubular shaft having a free end, a first portion adjacent the free end having splines on its external surface, a.second portion adjacent the first portion having a tapered external surface, and a third portion adjacent the second portion having a threaded external surface, the third portion having a larger external diameter than the first portion; a tubular hub on which a steering wheel is securable, the tubular hub having a longitudinal axis substantially aligned with the longitudinal axis of the tubular shaft, a free end positioned around the second portion of the tubular shaft, a first portion adjacent the free end of the tubular hub having a tapered internal surface substantially corresponding to and engageable with the tapered surface on the tubular shaft, and a second portion adjacent the first portion of the tubular hub having splines on its internal surface substantially corresponding to and engageable with the splined surface on the tubular shaft; and a nut rotatable relative to the tubular shaft and the tubular hub about the longitudinal axis, the nut having means engageable with corresponding means on the tubular hub, and an internal threaded surface adjacent the external threaded surface on the tubular shaft, rotation of the nut relative to the tubular shaft moving the tubular hub in an axial direction relative to the tubular shaft.

2. A steering system as claimed in Claim 1, wherein the internal threaded surface on the nut is directly engageable with the external threaded surface on the tubular shaft.

3. A steering system as claimed in Claim 1, wherein an annular spacer is positioned between the internal threaded surface on the nut and the external threaded surface on the tubular shaft, the annular spacer having an internal threaded surface and an external threaded surface directly engageable with the external threaded surface on the tubular shaft and the internal threaded surface on the nut, respectively.

4. A steering system as claimed in any one of Claims 1 to 3, wherein the means on the tubular hub is an external shoulder directed away from the free end of the tubular hub, and the means on the nut is an internal shoulder.

5. A steering system as claimed in Claim 2, wherein the means on the tubular hub is a threaded external surface, and the means on the nut is a threaded internal surface, the threads being of opposite hand to the threaded surfaces engageable between the nut and the tubular shaft.

6. A steering system as claimed in any one of Claims 1 to 5, wherein the shaft has a fourth portion adjacent the third portion which has an external diameter greater than the external diameter of the third portion, the fourth portion providing an external surface on which a bearing can be mounted.

7. A steering system as claimed in any one of Claims 1 to 6, wherein the hub has one or more radial apertures through the second portion thereof for the passage of electrical wiring.

8. A steering system substantially as herein described with reference to, and as shown in, the accompanying drawings.