EP2214948A1

EP2214948A1 - A steering wheel arrangement

Info

Publication number: EP2214948A1
Application number: EP07852212A
Authority: EP
Inventors: Laurent Groleau
Original assignee: Autoliv Development AB
Current assignee: Autoliv Development AB
Priority date: 2007-12-05
Filing date: 2007-12-05
Publication date: 2010-08-11
Also published as: EP2214948A4; WO2009072943A1

Abstract

A steering wheel arrangement is disclosed which comprises a steering wheei frame (32) secured to a steering column (16) for co-rotation with the steering coiumn (16). The arrangement has a centra! non-rotating hub (43) provided within the periphery of the steering whee! frame and the steering coiumn (16) is rotatably mounted about a column axis (A) within a steering column housing (18). The housing (18) has a first fixed gear (27), and the hub (43) has a second fixed gear (40). The arrangement has a planetary gear arrangement (46) provided on the steering wheel frame (32) and which comprises a first planetary gear (47) in mesh with the first fixed gear (27) and a second planetary gear (52) arranged in mesh with the second fixed gear (40). The planetary gears are arranged for rotation relative to the steering wheel frame (32) about an axis of rotation which is inclined at an angle to the coiumn axis (24). The planetary gear arrangement (46) is configured such that rotation of one of the planetary gears imparts rotational movement to the other planetary gear. In a preferred embodiment, the two planetary gears (47, 52) are fixed to one another for co-rotation about a common axis of rotation.

Description

Title: A STEERING WHEEL ARRANGEMENT Description of invention

This invention relates to a steering wheel arrangement, and in particular concerns a steering wheel arrangement in which the steering whee! has a central, non-rotating hub, around which an outer peripheral part of the steering wheei may be rotated.

St has been proposed previously to provide a steering wheel unit for use in a motor vehicle in which the central hub of the arrangement remains stationary during rotation of the steering wheel. Arrangements of this type are particularly advantageous when used with a steering wheel-mounted air-bag module of the type generally known as a "Driver's Air-Bag" (DAB) module because deployment of the air-bag can be more closely controlled if the air- bag is always in the same orientation relative to the cabin of the motor vehicle when it is activated. This sort of arrangement also facilitates the mounting of controi buttons or the like on the upper surface of the air-bag unit in positions where they are always easily operable by the driver.

With reference to Figure 1 of known steering whee! arrangement having a centra! non-rotating hub as described above are shown. A fixed element 2 is generally in the disc, having an off-centre substantially circular aperture 3 therethrough, with a diverging skirt portion 2a extending away from the edges of the disc to allow the fixed element to be mounted to other components. A steering wheel element 4 is mounted to the outer surface of the fixed element 2 by means of a first ring-bearing 6. An engagement portion of the steering wheel element 4 extends away from the plane of the disc of the fixed element 2, and has a sυbstantiaiiy circular, inward-facing, toothed surface 7 provided thereon, forming a ring gear.

A steering coiumn eSement 8 is mounted to the inner surface of the aperture 3 which is provided in the fixed eiement 2 by means of a second ring bearing 9. The steering coiumn element 8 also extends away from the plane of the disc of the fixed eiement 2, in the same direction as does the engagement portion of the steering wheel element 4, and is provided with a pinion gear 11 which lies paraiie! with the plane of the fixed element 2 and has a toothed outer periphery 12, The arrangement is such that a part of the toothed periphery 12 of the pinion gear 11 engages with a part of the toothed inner surface 7 of the ring gear, so that rotation of the steering wheel eSement causes rotation of the steering column 8 in the same sense.

A support etement 13 protrudes from the fixed eiement 2 through a space between the ring gear and the pinion gear 11 , passing through the ring gear close to the side of the ring gear furthest from the point at which the pinion gear 11 engages with the ring gear.

The support eSement 13 that supports the non-rotating central hub of the steering wheei is the only support therefor. The support eSement 13 must therefore necessarily be strong and have a large diameter. Because this relatively heavy-gauge support element 13 must pass through the ring gear, the amount of space within the ring gear that can be occupied by the pinion gear 11 is relatively small, to leave a sufficiently large gap within the ring gear for this occur, indeed, in some known designs, two bolts are provided to support the central hub, both of which pass through the space determined by the ring gear. This means that the ratio between the diameters of the ring gear and the pinion gear 11 must be relatively large, and in the case of the known steering wheel arrangement 1 illustrated, the ratio between these diameters is around 1/1.3. A steering ratio of this order is not always advantageous, and in many applications it is desirabie to achieve a steering ratio closer to, or preferably equal to, 1/1.

WO2007/080357 discloses a modified steering wheel arrangement of a type similar to that described above which seeks to address the above-mentioned technical probiems. However, the resulting arrangement is nevertheless similar to that described above, in the sense that the central non-rotating hub, to which an air-bag module can be secured, is fixed directly to the steering column, thus requiring a particular interface to mount the steering wheel to the resulting structure. This means that different interfaces are required for different motor vehicles and this can result in unnecessarily high manufacturing costs and Sow fiexibility.

US 4,729,254 discloses an arrangement in which there is no direct connection between the central non-rotating hub and the steering column housing, and uses a pair of interconnected satellite gears arranged for co-rotation about an axis substantially parallel to the axis of rotation of the steering column.

It is an object of the present invention to provide an improved steering wheel arrangement,

Accordingly, the present invention provides a steering wheel arrangement comprising: a steering wheel frame secured to a steering column for co- rotation with the steering column, and a central non-rotating hub provided within the periphery of the steering wheel frame, the steering column being rotatably mounted about a column-axis within a steering column housing; the housing having a first fixed gear, and the hub having a second fixed gear, the arrangement being characterised by a planetary gear arrangement provided on the steering wheel frame and comprising a first planetary gear arranged in mesh with the first fixed gear, and a second planetary gear arranged in mesh with the second fixed gear, wherein said planetary gears are each arranged for rotation relative to said frame about an axis of rotation which is incϋned at an ang!e to the column-axis, the planetary gear arrangement being configured such that rotation of one of said planetary gears imparts rotational movement to the other planetary gear.

Preferably, said pianetary gears are arranged for rotation at the same speed as one another during movement of the steering wheel frame.

Advantageously, said planetary gears are fixed to one-another for co-rotation about a common axis of

Conveniently, said planetary gears are releasabiy fixed to one another via breakable element.

Preferably, said second pianetary gear is biased in to mesh fixed gear.

Advantageously, said pianetary gears are arranged for roi respective axes of rotation, and are in mesh with one another.

Conveniently, each said axis of rotation is inclined at a different angle to the column-axis.

Preferably, said first pianetary gear is biased into mesh with said first fixed gear.

Advantageously, the or each said axis of rotation intersects said column axis at a point beyond the end of said steering column.

Conveniently, the or each said axis of rotation intersects said column axis at a point along the length of said steering column. Preferably, said first fixed gear is biased into mesh with said first planetary gear.

Advantageously, each said gear is a bevel gear.

Conveniently, each said gear is an external bevel gear.

Preferably, the central non-rotating hub comprises a support element configured to support an airbag module.

So that the invention may be more readily understood, and so that further features thereof may be appreciated, embodiments of the invention will now be described, by way of example, with reference to the accompanying drawings, in which :-

Figure 1 shows components of a known steering wheel arrangement;

Figure 2 shows components of a steering wheel arrangement in accordance with a first embodiment of the present invention; Figure 3 is an exploded perspective view showing part of the arrangement illustrated in Figure 2;

Figure 4 is a perspective view illustrating part of the arrangement illustrated in

Figure 2;

Figure 5 is a transverse cross-sectiona! view through a steering wheel arrangement in accordance with a second embodiment of the present invention;

Figure 6 is a view corresponding generally to that of Figure 5, but showing a section radially offset relative to the section illustrated in Figure 5; and

Figure 6 is a perspective view illustrating part of the assembled arrangement of the second embodiment. Referring snstiaSfy to Figure 2, a steering whee! arrangement 15, in accordance with a first embodiment of the present invention, is illustrated.

A generally elongate steering column 16 is provided which narrows at its free end so as to have a substantially frusto-conical end region 17, the outer surface of which is provided with a plurality of serrations or splines in a manner known perse. The steering coiumn 16 is mounted for rotation within a steering column housing 18 which comprises a generally cylindrical steering tube 19 provided with one or more bearings 20 (only one illustrated in Figure 2) in order to rotatabiy receive the steering column 16. As can be seen from Figure

2, the steering column 16 projects beyond the end of the steering tube 19.

An annular damp 21 is fitted around the steering tube 19, in the region of its free end, and is tightened around the steering tube in a clamping manner (for example, by tightening a clamping screw 22) so as to be fixed in position around the steering tube 19.

The clamp arrangement is illustrated in perspective view in Figure 4, from which it can be seen that a plurality of elongate spring elements 23 extend from the annular clamp 21 , at respective positions spaced radially around its periphery, so as to extend generally parallel to the axis of rotation A of the steering coiumn 16. Each spring element 23 is secured to the annular clamp 21 by a pair of screws 24.

At a position spaced above the annular clamp 21 , the opposite ends of the spring elements 23 are secured, in a similar manner, to a depending skirt 25 of an annular gear element 26 (illustrated more clearly in Figure 2).

As can be seen from Figure 2, the gear element 26 fits around the steering column 16, to allow significant clearance between the steering column and the gear element. At its uppermost region, the gear element 26 takes the form of an annular external beve! gear 27 having a series of peripheral gear teeth provided around a conical pitch surface 28.

The spring elements 23 are configured to allow for deflection in an axial direction (relative to the steering column axis A)₁ but are configured to resist torsional movement around the steering column axis A. The spring elements

23 thus provide a degree of bias to the gear element 26, in an axiai direction away from the annular damp 21. However, by virtue of their torsional rigidity, the spring elements 23 form a substantially rigid connection between the annular clamp 21 and the gear element 26 in a rotational sense and so the bevel gear 27 is effectively a fixed gear in the sense that it is not allowed to rotate relative to the other components of the steering column housing 18.

The gear element 26 defines an inner circular bearing surface 29 having a diameter slightly larger than the aperture 30 provided through the uppermost part of the gear element 26. An inwardiy-directed lip 31 is thus formed adjacent the bearing surface 29.

The steering wheel arrangement 15 further comprises a steering wheel having a substantially rigid steering wheel frame 32 which defines a number of spokes

33 of the steering wheel in a manner known per se. The spokes 33 can either be formed integrally with the rim of the steering wheel frame, or can be formed seperately and secured to the rim. The steering wheel frame 32 is provided with a central mounting aperture 34 which is provided with a plurality of serrations or splines on its inner surface which are complimentary to those provided on the outer surface of the frusto-conical end region 17 of the steering column 16. The steering wheel frame 32 can thus be mounted on the steering column 16 in a substantially conventional manner by engagement between the respective splines on the frusto-conical end regions 17 of the steering column 16 and on the inner surface of the mounting aperture 34. The steering wheel frame 32 is secured to the end of the steering column 16 by a fixing bolt 35 in a substantially conventional manner. !n this way, the steering wheel frame is secured to the steering coiumn 16 for co-rotation with the steering coiumn, the connection being rigid.

The steering wheel frame 32 has a depending skirt 36 which is received within the end aperture 30 of the gear element 26, with clearance between the two. The lower region of the steering whee! skirt 36 is supported for rotation relative to the fixed gear element 26 by an annular bearing 37 which bears against the bearing surface 29 of the fixed gear element 26. It should therefore be appreciated that as the steering wheel frame 32 is rotated in order to rotate the steering column 16, the lower region of the steering wheel skirt 36 is supported for rotation relative to the fixed gear element 26, the fixed gear element 26 remaining in a stationary position in a rotational sense, by virtue of the torsional rigidity of the spring elements 23.

An annular wave-spring (also sometimes called a wave-washer in the art) is provided in a space between the bearing 37 and the lip 31. The wave-spring 38 serves to impart a degree of axial bias to the fixed gear element 26, in a direction towards the end of the steering column 16.

The centra! region of the steering wheel frame 32 supports a second annular bearing 39 around the free end of the steering column 16, and this bearing provides rotational support between the steering wheel frame 32 and a second gear element 40. The second gear element 40 also takes the form of a bevel gear having a plurality of peripheral gear teeth provided around a conical pitch surface 41. As can be seen from Figure 1 , the second gear element 40 has a smaller diameter than the first gear element 26 provided on the steering coiumn housing 18, but both of these gear elements have their conical pitch surfaces inclined in the same direction relative to the axis A of the steering column, with both of the conical pitch surfaces 28, 41 narrowing with movement along the axis A in a direction towards the end of the steering column 16,

The second gear element 40 is formed integraiiy with, or is securely attached to, an annular skirt 42 which forms part of a central hub 43 of the steering wheel. As illustrated in Figure 2, the annular skirt 42 carries a generally annular support plate 44 at its uppermost end, and it is intended support plate 44 serves as a support for an air-bag module 45 mounted the hub 43 in a manner known perse.

The steering wheel frame 32 carries a planetary gear arrangement indicated generally at 46 which extends generally through one of the spokes 33. The planetary gear arrangement 46 comprises a pair of planetary gears which are mounted for co-rotation with one another. A first planetary gear 47 is provided for rotation about an axis which is inclined at an angle α relative to the axis of rotation A of the steering coiumn 16. The first planetary gear 47 takes the form of a bevel gear having a conical pitch surface 49 which is provided with a plurality of gear teeth in mesh with the gear teeth of the fixed bevel gear 27. As will now be appreciated, the wave-spring 38 thus serves to bias the first fixed gear 27 in to mesh with the first planetary gear 47.

The first planetary gear 47 is provided with a recess 50 within which an elongated neck portion 51 of the second planetary gear 52 is received. The two planetary gears 57, 52 are secured to one another by a bolt 53 for co- rotation with one another, and are supported relative to the steering wheel frame 32 by a pair of annular bearings 54 (although it should be appreciated that the pair of bearings could be replaced with a single bearing).

The second planetary gear 52 also takes the form, at its uppermost end, of a bevel gear having a plurality of peripheral gear teeth provided around a conical pitch surface 55. The periphera! gear teeth of the second planetary gear 52 mesh with the peripheral gear teeth of the second fixed gear 40 around the uppermost end of the steering column 16.

in order to further reduce backlash between the gears in the mechanism, the first and second planetary gears 47, 52 are preferably biased in a direction aiong the inclined axis 48, towards the centra! axis A, under the action of the wave-spring 58. in this manner, the wave-spring 56 serves to bias the first planetary gear 47 in to mesh with the first fixed gear 27, and also serves to bias the second planetary gear 52 in to mesh with the second fixed gear 40.

!t should be noted that the relative sizes of the two fixed gears 27, 40, and the two planetary gears 47, 52 are chosen carefully so that the ratio of the number of gear teeth provided around the periphery of the first fixed gear 27 relative to the number of gear teeth provided around the second fixed gear 40 is equal to the ratio between the number of peripheral gear teeth provided around the first planetary gear 47 relative to the number of peripheral gear teeth provided around the secondary planetary gear 52. This means that the effective gear ratio between the first planetary gear 47 and the first fixed gear 27 is equal to the gear ratio between the second planetary gear 52 and the second fixed gear 40.

As will be appreciated, as the steering wheel frame 32 is rotated, in order to rotate the steering column 16 and hence steer the vehicle, the first fixed gear 27 remains stationary whilst the entire planetary gear arrangement 46 is moved around the steering column axis A. Due to the meshing engagement between the first planetary gear 47 and the first fixed gear 27, then this rotational movement of the steering wheel frame 32 causes the first and second planetary gears 47, 52 to rotate with one another around the inclined axis 48. Because the gear ratios between the two planetary gears and their respective fixed gears are equal, this rotational movement of the second planetary gear 52 is effective to cause rotation between the second fixed gear 40 and the steering wheel frame 42 which is exactly opposite in direction and speed to the rotation between the steering wheel frame 32 and the first fixed gear 27. This means that during rotation of the steering wheel frame 32, the second fixed gear 40 remains stationary relative to the first fixed gear 27 which means that the central hub 43 remains stationary during rotation of the steering wheel 32 and hence is a non-rotating central hub.

As an optional safety feature, the steering wheel arrangement described above can be provided with a mechanism effective to break the meshing engagement between the above-mentioned gears, and hence allow the hub to rotate relative to the steering wheel frame, in the event that the gear mechanism becomes jammed, for example by debris falling between the gear teeth. One such mechanism incorporates a breakable pin 57 extending between the two planetary gears 47, 52 and which, when intact, serves to prevent rotation between the two planetary gears. With the pin 57 intact, operation of the arrangement is thus exactly as described above. However, should any of the gears become blocked or jammed, rotational movement of the steering wheel 32 will be effective to break the pin 57, thereby allowing relative rotation between the two planetary gears 47, 52, and thereby releasing the gear arrangement and allowing rotation of the hub 43 relative to the steering column housing 18.

Reference wili now be made to Figures 5 to 6 which illustrate an aiternative embodiment of the present invention. The same reference numerals have been used to identify components similar to those described above in the first embodiment.

The principal differences between the second embodiment illustrated in

Figures 5 to 7 and the first embodiment illustrated in Figure 2 to 4 is that in the second embodiment, the first and second fixed gears 27, 40 are of equal diameter and hence have an equal number of peripheral gear teeth; the planetary gear arrangement 46 comprises first and second planetary gears 47, 52 which are of equal size and hence have an equal number of peripheral gear teeth; and the first and second planetary gears 47, 52 are arranged in meshing relation to one another rather than for co-rotation with one another about the same axis. As can be seen from Figure 5, the first gear element 26 has a substantially identical form to the first gear element of the embodiment iliustrated in Figures 2 to 4, and is formed as a fixed beve! gear 27 around the steering column 16. Sn the arrangement of Figures 5 to 7, the steering wheel frame 32 is again mounted to the top of the steering column 18 in the same, generally conventional, manner by the fixing bolt 35, and again has a downwardly-depending skirt 36 which is received for rotation within the aperture 30 formed through the top of the first fixed gear 27. The first fixed gear is again provided with a similar annular bearing 37 and wave-spring 38.

However, as can be seen from Figure 5, in the arrangement of the second embodiment, the second fixed gear element 40 is larger than the second fixed gear element of the first embodiment. In the arrangement of Figures 5 to 7, the second fixed gear element 40 has a diameter substantially equal to that of the first fixed gear element 27, the two fixed gear elements having an equal number of peripheral teeth around their conical pitch surfaces 28, 41. It should also be noted that in the arrangement of Figures 5 to 7, the conical pitch surface 41 of the second fixed gear 40 is inverted relative to that of the first embodiment such that the conical pitch surfaces of the two fixed gears 27, 40 are arranged to face one another. Nevertheless, the second fixed gear element 40 is again supported for rotation relative to the steering wheel frame 32 by a bearing 39 in a generally similar manner as in the arrangement of Figures 2 to 4.

in the embodiment of Figures 5 to 7, the planetary gear arrangement 46 comprises a pair of planetary gears of substantially identical form to one another. Figure 5 illustrates the first planetary gear 47 which again takes the form of a bevel gear having a conical pitch surface 49. The first planetary gear 47 is mounted for rotation about an axis 57 which makes an angie β with the central axis of rotation A of the steering column 16. The first planetary gear 47 is supported for rotation about a spigot 58 on a pair of bearings 59 although the pair of bearings can be replaced with a single bearing), and is biased along the axis 57, towards the central axis A₁ under the action of an annular wave- spring 60.

it should therefore be appreciated that the first planetary gear 47 illustrated in Figure 5 meshes with the first fixed gear 27, and is biased in to mesh with the fixed gear under the action of the annular wave-spring 60.

Figure 6 is a view similar to that of Figure 5, but is taken through a different section line, rotated relative to the section Sine of Figure 5, about the central axis 24. Figure 6 illustrates the second planetary gear 52 and it can be seen that the second planetary gear 52 is substantially identical in form to the first planetary gear 47 illustrated in Figure 5. The second planetary gear 52 is mounted for rotation relative to the steering wheel frame 32 about an axis 61 which makes an angle y to the steering column axis A, and which intersects the steering column axis A at the same point as the axis 57 about which the first planetary gear 47 rotates, where angie y equals (180° - β).

The second planetary gear 52 is mounted for rotation in exactly the same manner as the first planetary gear 47 and hence is also mounted on a spigot 62 via a pair of bearings 63 (although a single bearing can be used instead) and is provided with a biasing wave-spring 64 effective to bias the second planetary gear 52 along its axis of rotation 61 , towards the central axis A of the steering column.

As can be seen from Figure 6, the second planetary gear 52 is provided in mesh with the second fixed gear 40, and the annular wave-spring 64 serves to bias the second planetary gear 52 in to firm mesh with the second fixed gear 40.

As illustrated in Figure 47, the two planetary gears 47, 52 are provided in mesh with one another.

As indicated above, the two planetary gears 47, 52 have an equal number of peripheral gear teeth, and the two fixed gears 27, 40 also have ar number of peripheral gear teeth. This means that the gear ratio between first planetary gear 47 and the first fixed gear 27 is equal to the gear ratio between the second planetary gear 52 and the second fixed gear 40. Thus, as the steering wheel frame 32 is rotated about the axis A, in order to rotate the steering column and hence steer the motor vehicle, the first fixed gear 27 remains stationary which means that the first planetary gear 47 is caused to rotate about its axis 57, with the axis 57 itself rotating around the main central axis A. Because the two planetary gears 47, 52 are provided in mesh with one another, this rotational movement of the first planetary gear 47 about its axis of rotation 57 imparts a complimentary rotational movement to the second planetary gear 52 about its respective axis of rotation 61. In turn, the second planetary gear 57 imparts rotational movement to the gear 40 of the centra! hub 43, relative to the steering wheel frame 32. Because the gear ratios between the two planetary gears and their respective fixed gears are equal, the second fixed gear 40 remains stationary as the steering wheel frame 32 is rotated around the central axis A. This means that the central hub 43 again remains in a fixed position relative to the steering column housing during rotation of the steering wheel.

As wiii be appreciated, both of the embodiments d conventional form of connection between the steering wheel frame 32 and the steering column 16. Both arrangements also avoid the need for direction connection between the air-bag support p!ate 44 and the steering column housing, but aiso provide gear arrangements where backlash is minimised.

As will be noted, in the arrangement of the first embodiment shown in Figures 2 to 4, the axis 48 about which the two planetary gears rotate intersect the centra! axis A of the steering column 16 at a point beyond the end of the steering column. In the arrangement of the second embodiment illustrated in

Figures 5 to 7, the axes 57, 61 about which the two planetary gears rotate, intersect the central axis A at a column.

When used in this specification and claims, the terms "comprises" and

"comprising" and variations thereof mean that the specified features, steps or integers are included. The terms are not to be ir presence of other features, steps or componer

The features disclosed in g claims, or the accompanying drawings, in ific forms or means for performing the disc attaining the disclosed result, as y, or in any combination of such features, be for realising the invention in diverse forms thereof.

Claims

CSaims

1. A steering whee! arrangement (15) is provided comprising: a steering wheel frame (32) secured to a steering column (16) for co-rotation with the steering column (16), and a central non-rotating hub (43) provided within the periphery of the steering wheel frame, the steering column (16) being rotatably mounted about a column-axis (A) within a steering column housing (18); the housing having a first fixed gear (27), and the hub (43) having a second fixed gear (40), the arrangement being characterised by a planetary gear arrangement (46) provided on the steering wheel frame (32) and comprising a first planetary gear (47) arranged in mesh with the first fixed gear (27), and a second planetary gear (52) arranged in mesh with the second fixed gear (40), wherein said planetary gears are each arranged for rotation relative to said frame (32) about an axis of rotation (48,57,61) which is inclined at an angle to the column-axis (A), the planetary gear arrangement (46) being configured such that rotation of one of said planetary gears (47) imparts rotational movement to the other planetary gear (52).

2. A steering wheel arrangement according to claim 1 , wherein said planetary gears (47,52) are arranged for rotation at the same speed as one another during movement of the steering wheel frame (32).

3. A steering wheel arrangement according to claim 1 or claim 2, wherein said planetary gears (47,52) are fixed to one-another for co-rotation about a common axis of rotation (48).

4. A steering wheel arrangement according to claim 3, wherein said planetary gears (47,52) are reieasably fixed to one another via a breakable element (57).

5. A steering whee! arrangement according to claim 1or ciaim 2, wherein said planetary gears (47,52) are arranged for rotation about respective axes of rotation (57,61), and are in mesh with one another.

6. A steering wheel arrangement according to ciaim 5, wherein each said axis of rotation (57,61) is inciined at a different angle to the column-axis (A).

7. A steering wheel arrangement according to ciaim 5 or claim 6, wherein said first planetary gear (47) is biased into mesh with said first fixed gear (27).

8. A steering wheel arrangement according to any one of claims 3 to 7, wherein said second planetary (52) gear is biased into mesh with said second fixed gear (40).

9. A steering whee! arrangement according to any one of claims 1 to 4, wherein the or each said axis of rotation (48) intersects said column axis (A) at a point beyond the end of said steering column (16).

10. A steering whee! arrangement according to any one of claims 1 to 8, wherein the or each said axis of rotation (58,61) intersects said column axis (A) at a point along the length of said steering column (16).

11. A steering wheei arrangement according to any preceding ciaim, wherein said first fixed gear (27) is biased into mesh with said first planetary gear (47).

12. A steering wheel arrangement according to any preceding claim, wherein each said gear (27,40,47,52) is a bevel gear.

13. A steering wheel arrangement according to any preceding claim, wherein the central non-rotating hub (43) comprises a support element (44) configured to support an airbag module (45).