GB2282574A

GB2282574A - Fitting a steering wheel with airbag to a steering column

Info

Publication number: GB2282574A
Application number: GB9320507A
Authority: GB
Inventors: Dan Persson; Lars-Gunnar Skoette
Original assignee: Autoliv Development AB
Current assignee: Autoliv Development AB
Priority date: 1993-10-05
Filing date: 1993-10-05
Publication date: 1995-04-12
Anticipated expiration: 2013-10-05
Also published as: DE4497497B4; JPH09506569A; DE4497497T1; AU688388B2; AU7866594A; FR2710891B1; FR2710891A1; WO1995009756A1; GB2282574B; GB9320507D0

Abstract

A steering wheel for a motor vehicle comprises a hub (3) incorporating an air-bag unit (5, fig. 3). Means for mounting the wheel upon an elongate steering column are provided in a lower region of the hub, the mounting means comprising a connecting element which is movable in a direction substantially perpendicular to the longitudinal axis of the column in order to mount the wheel upon or release the wheel from the column, the connecting element being accessible from the exterior of the hub without the need to remove the air-bag unit from the wheel. Electrical connections are made automatically as the wheel is fitted (figs. 3 and 4). In a first embodiment, connecting element 19 is secured to a column (14, fig. 3) with a bolt 26; chamfered locking surfaces 20 to 23 (fig. 2) prevent axial movement of the wheel. In a second embodiment, a bolt with a tapered end (54, fig. 4) locates in a tapered bore 56 in the steering column. <IMAGE>

Description

DESCRIPTION OF INVENTION "A STEERING WHEEL" THE PRESENT INVENTION relates to a steering wheel and more particularly to a steering wheel for a motor vehicle where the steering wheel is intended to incorporate an air-bag safety device.

Air-bag safety devices are becoming increasingly common in motor vehicle and it is a well established practice to mount a driver's air-bag safety device in the hub of the steering wheel of a vehicle. However, the mounting of the air-bag within the hub of the steering wheel is not without problems.

A conventional and simple method of mounting the vehicle steering wheel upon the steering column in the motor vehicle involves forming the hub of the steering wheel with a bore by way of which the steering wheel can be mounted over the free end of the steering column with a threaded nut then being located upon a threaded portion adjacent the end of the steering column. The bore in the hub of the steering wheel is typically formed with splines or the like which co-operate with corresponding formations on tr steering column so that rotation of the steering wheel is imparted to the steering column.

If an air-bag is to be mounted within the hub of the steering wheel then it must be located above the nut which would normally secure the steering wheel upon the steering column and this usually means that the air-bag must be mounted within the steering wheel after the steering wheel has been mounted upon the steering column because otherwise it would not be possible to locate the nut upon the threaded portion at the end of the steering column. The mounting of the air-bag upon the steering wheel after the wheel has been mounted upon the steering column is inconvenient from a manufacturing point of view where it is desirable to pre-assemble as many components as possible before they are finally assembled into the body of the vehicle on a production line. Thus, it is desirable to pre-assemble the steering wheel and the air-bag unit before this sub-assembly is located upon the steering column.

DE-OS 3,630,685 discloses one way of tackling this particular problem which involves providing an annularshaped air-bag within the steering wheel, the annular shape of the air-bag permitting access for connecting a nut on to the end of the steering column through the centre of the air-bag. The annular shape of the air-bag is, however, far from ideal and in addition it is necessary, following the mounting of the steering wheel and air-bag sub-assembly on to the steering column to locate a plug or the like into the central region of the hub of the steering wheel in order to cover the nut at the end of the steering column.

Thus even adopting this particular approach involves a further assembly step during the final stages of assembly on the production line.

The present invention seeks to provide an improved steering wheel assembly which addresses the problems outlined above.

According to one aspect of this invention there is provided a steering wheel for a motor vehicle, the steering wheel comprising a rim, a hub accommodating an air-bag unit and at least one spoke extending between the hub and the rim, the steering wheel further comprising mounting means in a lower region of the hub for mounting the steering wheel upon an elongato steering column within a motor vehicle, the mounting means comprising a connecting element located within the hub, the connecting element being movable in a direction substantially perpendicular to the longitudinal axis of the steering column in order to mount the steering wheel upon or release the steering wheel from the steering column, the connecting element being accessible from the exterior of the hub without having to remove the air-bag unit from the hub of the steering wheel.

Preferably movement of the connecting element in a direction substantially perpendicular to the longitudinal axis of the steering column is effected by rotating a threaded bolt which passes through a threaded bore in a component fixed to the steering wheel.

Conveniently the component fixed to the steering wheel which defines said threaded bore through which the threaded bolt passes also defines a bore designed to receive a free end of the steering column upon which the steering wheel is designed to be mounted.

Advantageously the hub of the steering wheel is provided with a housing having side walls, there being an opening or a movable panel formed in one of the side walls by way of which access is provided to the connecting element.

The connecting element may comprise a threaded bolt, the free end of which is adapted to be received within a bore formed in the steering column in order to mount the steering wheel upon the steering column. T h e free end of the threaded bolt and the bore in the steering column may be of conical form such that the insertion of the free end of the bolt into the bore in the steering column secures the steering wheel upon the steering column at a predetermined position axially of the steering column.

Alternatively the connecting element may comprise a bifurcated member having arms adapted to extend into under-cut regions formed in the steering column and prevent axial movement of the steering wheel relative to the steering column when the steering wheel is mounted thereon.

The arms of the bifurcated member may define chamfered surfaces adapted to engage corresponding surfaces defining the under-cut regions in the steering column.

Preferably the hub of the steering wheel is provided with means for establishing an electrical connection with an electrical supply in a motor vehicle when the steering wheel is mounted upon a steering column in the motor vehicle.

Conveniently said electrical connection is established automatically when the steering wheel is located upon the steering column.

Advantageously the electrical connection comprises co-operating male and female connectors which are automatically inter-connected upon locating the steering wheel upon the steering column.

Preferably the hub of the steering wheel further comprises a two-part housing for an electrical supply coil, a first part of the housing hazing fixed relative to the hub so that it cannot rotate about the axis of the steering column when the steering wheel is mounted thereon and a second part of the housing which is movable relative to the first part of the housing.

Conveniently housing is provided with means for preventing relative movement between the first part and the second part of the housing when the steering wheel is not located upon a steering column, said preventing means being automatically released upon the mounting of the steering wheel upon the steering column so as to permit relative angular movement between the first part and the second part of the housing.

Advantageously the hub of the steering wheel is provided with means for establishing a mechanical connection with a component connected to the chassis of a vehicle when the steering wheel is mounted upon a steering column mounted in the vehicle.

Preferably said mechanical connection comprises a snap-fitting connection which is automatically established when the steering wheel is located upon the steering column.

According to another aspect, this invention provides a method of mounting a steering wheel upon a steering column in a motor vehicle, the steering wheel comprising a rim, a hub incorporating an air-bag unit and at least one spoke extending between the rim and the hub, the method comprising the steps of initially mounting the air-bag unit within an upper region of the hub of the steering wheel and subsequently mounting the steering wheel incorporating the air-bag unit on to the end of the steering column, the steering wheel being mounted upon the steering column by way of mounting means comprising a connecting element which is moved in a direction substantially perpendicular to the longitudinal axis of the steering column in order to locate the steering wheel thereon.

In order that the present invention may be more readily understood and so that further features thereof may be appreciated, the invention will now be described by way of example with reference to the accompanying drawings in which: FIGURE 1 is a plan view of a steering wheel in accordance with this invention with parts of the wheel removed for the purposes of illustration; FIGURE 2 is a cross-sectional view taken on the line II-II of Figure 1 showing the steering wheel prior to mounting upon a steering column; FIGURE 3 is a cross-sectional view taken on the line III-III of Figure 1 showing the steering wheel when mounted upon a steering column; and FIGURE 4 is a cross-sectional view through an alternative embodiment of a steering wheel in accordance with the present invention when mounted on a steering column.

Referring initially to Figure 1 of the accompanying drawings a steering wheel comprises a rim 1 connected by way of a plurality of spokes 2 to a hub 3.

The hub 3 has an upper portion 4 incorporating an air-bag unit 5 in a conventional manner. Thus, the upper portion 4 defines an enclosure 6 for receiving an inflatable bag, and carries a gas generator 7 to inflate the bag in an accident situation. The upper portion of the hub also has an igniter 8 to initiate operation of the gas generator, an electrical connection 9 extending from the igniter to connect with the electrical system in a motor vehicle in which the steering wheel is eventually fitted.

The complete air-bag unit 5 is fixed, by means of screws 10 or the like, to the hub 3 via an intermediate frame or support 11, as shown in part only in dotted outline in Figure 2.

The air-bag unit itself and the housing and cover therefore are of a conventional design and will therefore not be described in any detail.

The lower portion of the hub 3 has an external housing 12. The spokes 2 extend downwardly within the housing 12 to support a mounting block 13 which forms part of the means for connecting the steering wheel to a steering column 14 located in a motor vehicle in which the steering wheel is provided.

The mounting block 13 defines a bore 15 having a shoulder 16 at its lower end. The bore 15 is designed to receive the upper end of the steering column 14, with the internal surface of the bore and the external surface of the steering column carrying co-operating splines or the like so that rotational movement of the steering wheel is transmitted to the steering column.

The steering column 14 is formed with a shoulder or step 17 which engages with the shoulder 16 at the end of the bore 15 in the mounting block 13 and therefore forms a seat for the location of the steering wheel upon the steering column. The free end of the steering column 14 has a centrally located circular projection 18 which increases in diameter as it extends away from the end of the column. Thus, the projection 18 may be considered to be of dovetail cross-section (see Figure 3). The projection 18 on the free end of the steering column cooperates with a connecting element located on the top of the mounting block 13.

The connecting element comprises a bifurcated member 19 having two arms 20,21 each defining a chamfered surface 22,23. The chamfered surfaces lie opposite each other on either side of the gap defined between the arms 20,21. The arms 20,21 are designed to be slid beneath the tapered external surface of the projection 18 at the free end of the steering column so that the chamfered surfaces 22,23 lie immediately adjacent the tapered external surface of the projection and prevent axial movement of the steering wheel relative to the steering column.

It is to be noted that the chamfered surfaces 22,23 will accommodate or transmit axial forces acting to lift the steering wheel away from the steering column whilst under-surfaces 24,25 of the arms 20,21 will accommodate or transmit forces in the opposite axial direction. Thus the connection between the steering wheel and the steering column can, of course, accommodate axial forces in either direction with respect to the longitudinal axis of the steering column, there being two surfaces 22,23 and 24,25 for accommodating the axial forces in each direction.

The bifurcated member 19 is connected to one end of a threaded bolt 26 which passes through a threaded bore formed in an upstandinq wall 27 on the upper surface of the mounting block 13. The free end of the bolt 26 carries an enlarged head 28 by way of which the bolt may be rotated.

Access to the head of the bolt is obtained through an access hatch or opening 29 formed in the housing 12.

Rotation of the bolt 26 causes it and the bifurcated member 19 carried thereby, to move perpendicularly with respect to the longitudinal axis of the steering column 14.

This rotation of the bolt 26 is used to move the bifurcated member 19 between a lockiny position in which the arms 20,21 are positioned directly beneath and engage the projection 18 at the free end of the steering column 14 and lock the steering wheel thereon, and a release position in which the bifurcated member is withdrawn radially outwardly and in which the arms 20,21 are outside of the radial extent of the projection 18 thereby permitting removal of the steering wheel from the end of the steering column.

It is to be appreciated that rotation of the bolt 26 and radial movement of the bifurcated member 19 which forms the connecting element between the steering wheel and the steering column can be effected from one side of the housing for the hub of the steering wheel and without the need to remove or in any way adjust the air-bag unit 5. Thus, the complete air-bag unit 5 may be mounted upon the steering wheel before the steering wheel is mounted upon the steering column during the final assembly of a motor vehicle on a production line. The installation and testing of the air-bag unit in situ on the steering wheel may be undertaken remote from the factory production line for the motor vehicle in which the steering wheel is eventually to be incorporated.

The base of the hub housing 12 is formed with a downwardly projecting cylindrical portion 30 which carries a two-part housing for a coil 31 of electrical wire which is an extension of the wire 9 from the igniter 8 for the gas generator 7 and which surrounds the steering column 14 when the steering wheel is located thereon.

The two-part housing for the wire coil comprises a first, upper part 32 in the form of an annular ring 33 having a depending cylindrical flange 34 at its inner edge, the lower end of the cylindrical flange carrying an outwardly directed foot or rim 35 upon which the second or lower part 36 of the housing rests. The depending cylindrical flange 34 lies adjacent the steering column 14 when the steering wheel is mounted thereon. The annular ring 33 has an opening 37 through which the electrical wire passes before it then passes through the mounting block 13 and to the igniter 8 for the gas generator 7. The outer edge of the annular ring 33 carries a short depending flange 38 by way of which it is fixed within the housing 12 against a stop in the form of an inwardly directed projection 39 formed on the internal surface of the housing.

The second or lower part 36 of the housing for the wire coil 31 has a generally cylindrical body 40 having an inwardly directed flange 41 at a position approximately mid-way between its upper and lower edges. The inwardly directed edge of the flange 41 rests freely upon the foot or rim 35 defined by the first part 32 of the housing for the wire coil. The lower part 36 of the housing defines a downwardly projecting electrical connection or wire outlet 42. An electrical connection is established between the coil of wire 31 and electrical wiring 43 which is connected to a vehicle component 44 which is fixed to the vehicle chassis via the outlet 42. Thus, the outlet 42 and the component 44 may be formed with co-operating male and female slide-in connections, i.e. a pin and socket type connection in order to establish an electrical connection.

The steering column 14 passes through the component 44 via the intermediary of a bearing 45.

In addition to there being an electrical connection between the lower part 36 of the wire housing and the component 44 there is also a snap-action mechanical connection which is established when the steering wheel is mounted upon the end of the steering column 14. This mechanical connection is formed by means of co-operating tooth-like projections 46 which are provided around the lower-most edge of the cylindrical body 40 and on the component 44 as well as on the lower-most edge of the outlet 42 and that part of the component 44 with which the outlet connects. It is to be noted that upon locating the steering wheel on the end of the steering column 14 both the mechanical connection and the electrical connection are established automatically by way of the snap-action cooperating teeth 46 and the slide-in electrical connection.

Before the steering wheel has been mounted upon the steering column 14 it is desirable to hold the upper part 32 and a lower part 36 of the housing for the wire coil 31 in position relative to each other because these two parts are not directly connected to each other. For this purpose a spring 47 is mounted upon the lower end of the flange 34 of the first part 32 of the housing, this spring 47 effectively being pivotable about its point of connection on the end of the flange 34. One end of the spring 47 projects into a recess formed in the flange 41 of the second part 36 of the housing and thereby serves to prevent movement of the second part of the housing relative to the first part of the housing.

The opposite end of the spring 47 projects radially inwardly into the space defined within the cylindrical flange 34. As the steering wheel is located upon the end of the steering column 14 however, the steering column engages the inwardly projecting end of the spring 47 and pushes it radially outwardly into a small recess 48 formed in the surface of the cylindrical flange 34 (see Figure 2).

This causes pivotal movement of the spring 47 about its mounting point on the lower end of the cylindrical flange 34 which results in the outer-most end of the spring being released from the recess in the flange 41 of the second part 36 of the housing so that the second part may now move relative to the first part 32 of the housing (see Figure 3). In practise of course, it is the first part 32 of the housing which is fixed to the hub-housing 12 and which will therefore move upon rotation of the steering wheel. It is to be appreciated that the spring 47 would not normally be visible in Figure 3 of the drawings but is shown for the purposes of illustration at a position displaced through 900 around the steering column as compared with its actual position.

It will be appreciated from the above description that with a steering wheel in accordance with this invention, the hub of the steering wheel may incorporate a conventional air-bag which can be built into the steering wheel prior to the steering wheel being mounted upon the steering column in a motor vehicle. This is made possible by virtue of the fact that the steering wheel is mounted upon the steering column by simply locating it over the free end of the column, whereupon an electrical connection and a mechanical connection are automatically established with a component connected to the vehicle chassis and then the bolt 26 can be accessed via the hub housing in order to move the bifurcated connecting member 19 into position in order to secure the steering wheel upon the end of the steering column. This greatly facilitates the manufacturing processes because only relatively quick and simple operations need to be performed in order to mount the steering wheel upon the steering column, these operations normally being performed as a vehicle is assembled on a factory production line. The somewhat more intricate mounting of the air-bag unit within the steering wheel can be performed beforehand in a remote location, such as at the site of production of the steering wheel itself.

Figure 4 of the drawings illustrates a slightly modified embodiment of this invention where the steering wheel may have only a single spoke 2 extending between the rim 1 and the hub 3. The upper region of the hub is very similar to that described above in relation to Figures 1 to 3 and incorporates a conventional air-bag unit having the same components as described above. No further description of this arrangement will therefore be given. Those parts which are common to the embodiment shown in Figure 4 and the previously described embodiments are identified by the references numerals used in relation to the embodiment of Figures 1 to 3. Thus the hub has a housing 12, the base of which is formed with a downwardly directed cylindrical projection 30 which again carries the same design of twopart housing for the wire coil 31 which extends from the wire 9 connected to the igniter 8 for the gas generator 7 in the air-bag unit 5. The two-part housing for the wire coil 31 is again mounted within the cylindrical projection 30 at the base of the hub housing in the same way as described above and mechanical and electrical connections are made with the component which is fixed to the vehicle chassis in the same way as described above.

In this modified embodiment of Figure 4 the spoke 2 carries, at its lower end, a plate 49 which in turn carries a circular tube 50 designed to surround a modified steering column 51 mounted in a motor vehicle. It can clearly be seen in Figure 4 that the plate 49 defines an opening 52 through which the wire 9 can extend from the coil 31 to the igniter 8 for the gas generator 7. The circular tube 50 is formed with an internally threaded boss 53 which receives a threaded bolt 54 having an enlarged head 55. The free end of the threaded bolt 54 is of conical form. The steering column 51 is formed with a tapered bore 56 corresponding in shape to the conical free end of the bolt 54. The bolt is designed to be received within the conical bore in the steering column in order to secure the steering wheel thereon. Access to the bolt 54 is gained through an opening 57 in the cylindrical projection 30 at the base of the hub housing 12.

The procedure for mounting the steering wheel of Figure 4 upon the steering column therefore involves initially locating the steering wheel in position so that the steering column passes up within the tube 50 whilst the bolt 57 is in a retracted or withdrawn position. When the bore 56 in the steering column is aligned with the bolt 54 the bolt is screwed in so that its conical free end engages the conical surface of the bore 56 in the steering column and the steering wheel is secured in position relative to the steering column. It will be appreciated that the conical surfaces at the free end of the bolt 54 and in the bore 56 in the steering column can accommodate axial forces in either direction along the axis of the steering column.

Once the steering wheel has been mounted upon the steering column in this way it therefore will not move in either direction axially with respect to the steering column.

It is to be understood that the embodiments described above merely represent examples of particular embodiments of this invention, and modifications may be made thereto without departing from the scope of the invention.

Claims

CLAIMS:

1. A steering wheel for a motor vehicle, the steering wheel comprising a rim, a hub accommodating an air-bag unit and at least one spoke extending between the hub and the rim, the steering wheel further comprising mounting means in a lower region of the hub for mounting the steering wheel upon an elongate steering column within a motor vehicle, the mounting means comprising a connecting element located within the hub, the connecting element being movable in a direction substantially perpendicular to the longitudinal axis of the steering column in order to mount the steering wheel upon or release the steering wheel from the steering column, the connecting element being accessible from the exterior of the hub without having to remove the air-bag unit from the hub of the steering wheel.

2. A steering wheel according to Claim 1 wherein movement of the connecting element in a direction substantially perpendicular to the longitudinal axis of the steering column is effected by rotating a threaded bolt which passes through a threaded bore in a component fixed to the steering wheel.

3. A steering wheel according to Claim 2 wherein the component fixed to the steering wheel which defines said threaded bore through which the threaded bolt passes also defines a bore designed to receive a free end of the steering column upon which the steering wheel is aesigned to be mounted.

4. A steering wheel according to Claim 1, Claim 2 or Claim 3 wherein the hub of the steering wheel is provided with a housing having side walls, there being an opening or a movable panel formed in one of the side walls by way of which access is provided to the connecting element.

5. A steering wheel according to any one of Claims 1 to 4 wherein the connecting element comprises a threaded bolt, the free end of which is adapted to be received within a bore formed in the steering column in order to mount the steering wheel upon the steering column.

6. A steering wheel according to Claim 5 wherein the free end of the threaded bolt and the bore in the steering column are of conical form such that the insertion of the free end of the bolt into the bore in the steering column secures the steering wheel upon the steering column at a predetermined position axially of the steering column.

7. A steering wheel according to any one of Claims 1 to 4 wherein the connecting elemnt comprises a bifurcated member having arms adapted to extend into under-cut regions formed in the steering column and prevent axial movement of the steering wheel relative to the steering column when the steering wheel is mounted thereon.

8. A steering wheel according to Claim 7 wherein the arms of the bifurcated member define chamfered surfaces adapted to engage corresponding surfaces defining the under-cut regions in the steering column.

9. A steering wheel according to any one of the preceding Claims wherein the hub of the steering wheel is provided with means for establishing an electrical connection with an electrical supply in a motor vehicle when the steering wheel is mounted upon a steering column in the motor vehicle.

10. A steering wheel according to Claim 9 wherein said electrical connection is established automatically when the steering wheel is located upon the steering column.

11. A steering wheel according to Claim 9 or Claim 10 wherein the electrical connection comprises co-operating male and female connectors which are automatically interconnected upon locating the steering wheel upon the steering column.

12. A steering wheel according to Claims 9, 10 or 11 wherein the hub of the steering wheel further comprises a two-part housing for an electrical supply coil, a first part of the housing being fixed relative to the hub so that it cannot rotate about the axis of the steering column when the steering wheel is mounted thereon and a second part of the housing which is movable relative to the first part of the housing.

13. A steering wheel according to Claim 12 wherein said housing is provided with means for preventing relative movement between the first part and the second part of the housing when the steering wheel is not located upon a steering column, said preventing means being automatically released upon the mounting of the steering wheel upon the steering column so as to permit relative angular movement between the first part and the second part of the housing.

14. A steering wheel according any one of the preceding Claims wherein the hub of the steering wheel is provided with means for establishing a mechanical connection with a component connected to the chassis of a vehicle when the steering wheel is mounted upon a steering column mounted in the vehicle.

15. A steering wheel according to Claim 14 wherein said mechanical connection comprises a snap-fitting connection which is automatically established when the steering wheel is located upon the steering column.

16. A method of mounting a steering wheel upon a steering column in a motor vehicle, the steering wheel comprising a rim, a hub incorporating an air-bag unit and at least one spoke extending between the rim and the hub, the method comprising the steps of initially mounting the air-bag unit within an upper region of the hub of the steering wheel and subsequently mounting the steering wheel incorporating the air-bag unit on to the end of the steering column, the steering wheel being mounted upon the steering column by way of mounting means comprising a connecting element which is moved in a direction substantially perpendicular to the longitudinal axis of the steering column in order to locate the steering wheel thereon.

17. A steering wheel substantially as herein described with reference to and as shown in Figures 1 to 3 of the accompanying drawings.

18. A steering wheel substantially as herein described with reference to and as shown in Figure 4 of the accompanying drawings.

19. A method of mounting a steering wheel upon a steering column in a motor vehicle substantially as herein described.

20. Any novel feature or combination of features disclosed her in.