GB2621988A

GB2621988A - Steering column assembly

Info

Publication number: GB2621988A
Application number: GB2212386.3A
Authority: GB
Inventors: Harvey Philip
Original assignee: ZF Automotive UK Ltd
Current assignee: ZF Automotive UK Ltd
Priority date: 2022-08-25
Filing date: 2022-08-25
Publication date: 2024-03-06
Also published as: GB202212386D0

Abstract

A steering column assembly includes first and second column tubes 2, 3 telescopically mounted so as to be movable relative to one another along an adjustment axis. A magnetorheological material 5 is provided between column tubes 2,3. A magnetic field can be selectively applied, for example using an electromagnet, to magnetorheological material 5 to releasably secure column tubes 2, 3. First tube 2 may comprise one or more projections and second tube 3 one or more corresponding guideways, with material 5 between the projections and the guideways. Magnetorheological material may be an elastomer and may comprise a planar strip. A vehicle with such a steering column assembly is also provided.

Description

STEERING COLUMN ASSEMBLY

This invention relates generally to steering column assemblies and, in particular, to steering column assemblies for motor vehicles and motor vehicles comprising such steering column assemblies. More specifically, although not exclusively, this invention relates to retractable steering column assemblies for autonomous vehicles.

Autonomous vehicles are intended to be used primarily in autonomous mode, in which control of the vehicle is carried out without manual intervention. However, it is desirable for to autonomous vehicles to be controllable manually if necessary or desired, and for that reason vehicle controls such as a steering wheel (typically having a "steer-by-wire" operation) must be provided. It is desirable for the steering wheel of such autonomous vehicles to be moved into a stowed condition during autonomous control of the vehicle in order to maximise the space available within the vehicle cabin, and for the steering wheel to be moved into an extended deployed condition for manual control.

When in the deployed condition, the steering wheel must be locked in position such that, when in use, movement along the axis of the steering column is prevented. Further, in the deployed condition it is desirable for the position of the steering wheel to be adjustable along the axis of the steering column for the comfort of the driver. However, in the event of an accident, it is advantageous for the lock to be removed such that the steering wheel provides minimal resistance to impact by an occupant of the vehicle.

In accordance with the present invention, a steering column assembly comprises: a first column tube and a second column tube telescopically mounted so as to be movable relative to one another along an adjustment axis; a magnetorheological material between the first and second column tubes; and means for selectively applying a magnetic field to the magnetorheological material to releasably secure the first column tube relative to the second column tube.

The steering column assembly in accordance with the present invention has a simpler construction and a lower cost as compared with prior art steering column assemblies that are to provide similar functionality.

The steering column assembly in accordance with the present invention allows the first column tube and second column tube to be locked or secured relative to one another along the adjustment axis when the assembly is in a deployed condition, i.e. when an autonomous vehicle within which the assembly is installed is operated in a manual mode.

Due to the presence of the magnetorheological material the lock is removed when the magnetic field is removed. In the event of an accident, the steering column assembly (to which a steering wheel may be mounted) provides minimal resistance to impact due to the removal of the lock.

Therefore, the first column tube and second column tube can be secured relative to one io another when required whilst also providing a safe condition in the event of an accident through the use of a magnetorheological material.

In an embodiment, the first column tube comprises an elongate projection whose longitudinal axis extends parallel to the adjustment axis. The elongate projection may comprise or define a guide.

The second column tube may comprise a corresponding elongate guideway.

The magnetorheological material may be located between the elongate projection and the guideway.

The magnetorheological material may be located or received in an interface between the elongate projection and the guideway.

In one embodiment, the elongate projection comprises a planar face.

The magnetorheological material may be provided between the planar face and the guideway.

The elongate projection may comprise a web.

The elongate projection may extend from the inner one of the first and second column tubes.

The elongate projection may extend outwardly with respect to the adjustment axis.

In one embodiment, the extent to which the elongate projection extends outwardly is constant along the length of the projection.

The first column tube may comprise a plurality of elongate projections and the second column tube may comprise a corresponding elongate guideway for each of the elongate projections.

In one embodiment. the steering column assembly comprises magnetorheological material to located between each of the elongate projections of the first column tube and the corresponding guideways in the second column tube.

The magnetorheological material may be attached to the first column tube.

In one embodiment, the steering column assembly comprises a third column tube telescopically mounted so as to be moveable relative to the second column tube along the adjustment axis.

A magnetorheological material may be located between the second and third column tubes.

The steering column assembly may comprise means for selectively applying a magnetic field to the magnetorheological material between the second and third column tubes, e.g. to releasably secure the second column tube relative to the third column tube The second column tube may comprise a further elongate projection whose longitudinal axis extends parallel to the adjustment axis. The further elongate projection may comprise or define a further guide.

The third column tube may comprise a further corresponding guideway, wherein the magnetorheological material is located between the further elongate projection and the further guideway.

The magnetorheological material may be located or received in an interface between the further elongate projection and the further guideway.

In one embodiment, the further elongate projection extends from the inner one of the second and third column tubes.

The further elongate projection may extend outwardly with respect to the adjustment axis.

In one embodiment, the extent to which the further elongate projection extends outwardly is constant along the length of the further projection.

The second column tube may comprise a plurality of further elongate projections and the io third elongate tube may comprise a corresponding further guideway for each of the further elongate projections.

In one embodiment, the steering column assembly may comprise magnetorheological material located between each of the further elongate projections of the second column tube and the corresponding further guideways in the third column tube.

The magnetorheological material may be attached to the third column tube.

In one embodiment, the means for selectively applying a magnetic field to the magnetorheological material between the first and second column tubes also comprises means for selectively applying a magnetic field to the magnetorheological material between the second and third column tubes.

The first column tube may be mounted within the second column tube and the second column tube may be mounted within the third column tube.

The magnetorheological material may be planar.

The magnetorheological material may be an elongate strip The magnetorheological material may extend lengthwise, substantially parallel to the adjustment axis.

The magnetorheological material may comprise a planar strip.

The planar strip or elongate strip may comprise one or more mounting projections.

In one embodiment, the magnetorheological material comprises an elastomer.

In one embodiment, the position of the means for selectively applying a magnetic field to the magnetorheological material is fixed with respect to the outermost column tube.

The means for selectively applying a magnetic field to the magnetorheological material may comprise an electromagnet.

The steering column assembly may comprise a magnetic field guide configured to guide

io the magnetic field from the electromagnet.

The steering column assembly may comprise means for securing the outermost column tube to a vehicle.

In one embodiment, one or a plurality of column tubes comprises a metal extrusion. The first column tube, second column tube and/or third column tube may comprise a metal extrusion.

The first column tube, second column tube and/or third column tube may be formed of steel.

The first column tube, second column tube and/or third column tube may be formed of aluminium. One or more of the first column tube, second column tube and third column tube may be formed of steel and the remaining column tubes may be formed of aluminium. The first column tube and second column tube may each be formed of steel and the third column tube may be formed of aluminium.

The first column tube, second column tube and/or third column tube may be an extruded metallic tube.

The present invention also includes a vehicle comprising a steering column assembly as described above.

For the avoidance of doubt, any of the features described herein apply equally to any aspect of the invention.

Another aspect of the invention provides a computer program element comprising and/or describing and/or defining a three-dimensional design for use with a simulation means or a three-dimensional additive or subtractive manufacturing means or device, e.g. a three-dimensional printer or CNC machine, the three-dimensional design comprising an embodiment of the steering column assembly described above.

Within the scope of this application it is expressly intended that the various aspects, embodiments, examples and alternatives set out in the preceding paragraphs, in the claims and/or in the following description and drawings, and in particular the individual features thereof, may be taken independently or in any combination. That is, all embodiments and/or features of any embodiment can be combined in any way and/or combination, unless such features are incompatible. For the avoidance of doubt, the terms "may", "and/or", "e.g.", "for example" and any similar term as used herein should be interpreted as non-limiting such that any feature so-described need not be present. Indeed, any combination of optional features is expressly envisaged without departing from the scope of the invention, whether or not these are expressly claimed. The applicant reserves the right to change any originally filed claim or file any new claim accordingly, including the right to amend any originally filed claim to depend from and/or incorporate any feature of any other claim although not originally claimed in that manner.

Embodiments of the invention will now be described by way of example only with reference to the accompanying drawings in which: Figure 1 is a perspective view of a steering column for a vehicle incorporating a steering column assembly in accordance with the present invention, shown in a partially retracted condition; Figure 2 is a perspective view of the steering column assembly of Figure 1, shown in a partially retracted condition; Figure 3 is a perspective view of a first column tube of the steering column assembly of Figures 1 and 2; Figure 4 is an exploded perspective view of the first column tube of Figure 3 including planar strips of magnetorheological material; Figure 5 is a perspective view of a planar strip of magnetorheological material; Figure 6 is a perspective view of a second column tube of the steering column assembly of Figures 1 and 2; Figure 7 is a perspective view of a third column tube of the steering column assembly of Figures 1 and 2; lo Figure 8 is a perspective view of an electromagnet of the steering column assembly of Figures 1 and 2; Figure 9 is a perspective view of the third column tube of Figure 7 having the electromagnet of Figure 8 mounted thereto; Figure 10 is a cross-section through the steering column assembly of Figures 1 and 2; and Figure 11 is a sectional view through the steering column assembly of Figures 1 and 2.

Referring now to Figures 1 and 2, there is shown a steering column assembly 1 for a vehicle in accordance with the invention. The steering column assembly 1 is telescopically adjustable along a longitudinal axis A-A which is coincident with the rotational axis of elongate steering column 10, the outer end 10a of which a steering wheel (omitted from the drawings for clarity) is attached in use. The steering column assembly 1 is mounted to a vehicle (not shown) via mounting plate 11.

The steering column assembly 1 comprises an innermost, first column tube 2 which is slidably and telescopically received within an intermediate, second column tube 3 which, in turn, is slidably and telescopically received within an outer, third column tube 4. In use, the third column tube 4 is secured to a vehicle (not shown) into which the steering column assembly 1 is to be installed. The relative positions of the first column tube 2, second column tube 3 and third column tube 4, and therefore the position of a steering wheel attached thereto, can be adjusted by displacing the tubes relative to one another along the axis A-A by virtue of an adjustment mechanism 7.

The adjustment mechanism 7 includes a first leadscrew 70 rotatably mounted in a securing lug 71 at a first of its ends and also received within an internally threaded bore of a gearbox housing 72. The securing lug 71 is fixedly secured to a vehicle via the mounting plate 11 and the gearbox housing 72 is secured to the intermediate, second tube 3. The adjustment mechanism 7 further includes a second leadscrew 73 rotatably mounted at a first of its ends in the gearbox housing 72 and threadedly received within an internally threaded io displacement member 74 at a second of its ends. The displacement member 74 includes a connector plate 75 to connect the adjustment mechanism 7 to the first column tube 2 through an elongate access slot 34 in the second column tube 3. The gearbox housing 72 includes an electric motor 76 secured thereto, and arranged to move the inner, intermediate and outer tubes 2, 3, 4 relative to one another along the adjustment axis A-A by driving the is first leadscrew 70 and second leadscrew 73.

Planar strips of magnetorheological material 5 are attached to the first column tube 2 and located between the first column tube 2 and the second column tube 3. Similarly, further planar strips of magnetorheological material 5 are attached to the third column tube 4 and located between the second column tube 3 and the third column tube 4. The magnetorheological material 5 includes an elastomeric matrix having magnetic particles dispersed throughout.

An electromagnet 6 is mounted to the exterior of the third column tube 4 for selectively applying a magnetic field to the magnetorheological material 5. The electromagnet 6 includes a core 6a having a wire coil 6b wrapped therearound. A power supply (not shown) provides a supply of current to the wire coil 6b, in use.

In use, in the absence of a magnetic field provided by the electromagnet 6, the first column tube 2, second column tube 3 and third column tube 4 are moveable relative to one another along longitudinal axis A-A. In order to releasably secure the tubes relative to one another a current is supplied to the wire coil 6b causing the electromagnet 6 to apply a magnetic field to the magnetorheological material 5. In the presence of a magnetic field, the magnetorheological material provides a field-dependent physical change. In the present embodiment, the presence of a magnetic field causes the magnetorheological material 5 to provide interference between the first column tube 2 and the second column tube 3 and the magnetorheological material 5 to provide interference between the second column tube 3 and the third column tube 4, thereby securing the tubes relative to one another.

In order to move the inner, intermediate and outer tubes 2, 3, 4 relative to one another, in the absence of an applied magnetic field, the motor 76 drives the first lead screw 70 and/or second lead screw 73. As the first lead screw 70 is fixed to the securing lug 71, the gearbox housing 72 moves along the first lead screw 70 as it is driven. As the second lead screw 73 is rotatably mounted, the gearbox housing 72 is moved relative to the displacement member 74 as the second lead screw 73 is driven. In either case, the displacement member 74 and connector plate 75 are moved relative to the securing lug 71 upon operation of the electric motor 76.

In order to deploy the steering column assembly 1 from a fully retracted condition (not shown), movement of the connector plate 75 causes the first column tube 2 to move relative to the third column tube 3 and causes the second column tube 3 to move relative to the third column tube 4 until either a sensor detects that a fully deployed condition is achieved or a mechanical stop is reached.

In order to withdraw the steering column assembly 1 from a fully deployed condition (not shown), the motor is operated in the reverse direction, which causes the first column tube 2 to be drawn into the second column tube 3 and causes the second column tube 3 to be drawn into the third column tube 4 until either a sensor detects that a fully retracted condition is achieved or a mechanical stop is reached.

Referring now to Figure 3, there is shown the first column tube 2 isolated from the remaining features of the steering column assembly 1.

The first, innermost, column tube 2 includes substantially cylindrical body 20 having a pair of elongate projections 21 extending therefrom. The first column tube 2 is formed from steel in this embodiment. Each of the elongate projections 21 has a longitudinal axis that extends parallel to longitudinal axis A-A and extends outwardly with respect to axis A-A. The elongate projections 21 are spaced from one another around the circumference of the body 20 and, as will be explained, are received in a respective one of two identical complementarily-shaped elongate recesses 35 in the second, intermediate tube 3 to provide a guide for movement of the first, innermost column tube 2 and second, intermediate column tube 3 relative to one another.

The elongate projections 21 are formed by folding or crimping the wall of the first column tube 2. The folded or crimped portion is cut and welded to provide a clearance zone 22 to accommodate one or more components of the assembled steering column assembly 1. The elongate projections 21 each have a tapered, welded lead-in 23 extending from the clearance zone.

io Each of the elongate projections 21 has a pair of opposed planar faces 24 and a series of mounting holes 25 for attaching the magnetorheological material 5. The mounting holes 25 are arranged in pairs with each elongate projection 21 having two pairs 25a, 25b spaced along its longitudinal axis.

Referring now to Figures 4 and 5, there is shown the first column tube 2 having the magnetorheological material 5 attached thereto and the planar strip of magnetorheological material 5 in isolation, respectively.

As described above, the magnetorheological material 5 is formed from a moulded silicone elastomer having magnetic particles dispersed throughout and is moulded into the planar strips 5. In this embodiment, each planar strip 5 is identical and has opposed planar faces 50, 51. A pair of spaced clearance apertures 52 extend through the thickness of the planar strip. Adjacent each respective clearance aperture 52 and extending from one of the planar faces 50, 51 is an integrally moulded mounting projection in the form of a push-fit rivet 53 head. Each push-fit rivet head 53 is split centrally to allow the two halves of the rivet head to be deformed towards each other when pushed through an aperture and to allow the two halves to spring back into their normal positions to retain the strip when the rivet head has been pushed fully through the aperture.

In the present example, magnetorheological material 5 is attached to each of the opposed planar faces 24 of the elongate projections 21 of the innermost tube 2. To attach the magnetorheological material 5 to a first of the opposed planar faces 24, each of the clearance apertures 52 are aligned with a respective mounting hole 25; one with a mounting hole 25 from a first of the pairs 25a and the other with a mounting hole from the other of the pairs 25b. Each push-fit rivet head 53 is pushed manually through a respective mounting hole 25; one with the other mounting hole from the first of the pairs 25a and the other from the other mounting hole from the second of the pairs 25b.

To attach a strip of the magnetorheological material 5 to the other of the opposed planar faces 24 it is rotated 180 degrees relative to the material attached to the first planar face 24 and attached in the manner described above. In such a case, each of the mounting holes 25 receive a respective push-fit rivet 53. Further, each of the clearance apertures 52 accommodate the free end of the head of a respective push-fit rivet 53.

io Referring now to Figure 6, there is shown the second, intermediate column tube 3 isolated from the remaining features of the steering column assembly 1.

The second column tube 3 is an extruded metallic tube in this embodiment and includes substantially cylindrical body 30 having a pair of elongate projections 31 extending is therefrom. The second column tube 3 is formed from steel in this embodiment. Each of the elongate projections 31 has a longitudinal axis that extends parallel to longitudinal axis AA and extend outwardly with respect to axis A-A. The elongate projections 31 are spaced from one another around the circumference of the body 30. Each elongate projection 31 defines an elongate guideway 35 arranged to receive a respective elongate projection 21 of the first, innermost column tube 2 so as to guide movement of the first column tube 2 and second column tube 3 relative to one another.

As will be explained, each of the elongate projections 31 of the intermediate column tube 3 is received in a complementarily-shaped elongate recess 41 in the third, outermost tube 4.

Each of the elongate projections 31 has a pair of opposed internal faces 32 arranged to lie adjacent to, but spaced from, the planar faces 24 of the first column tube 2. Further, each of the elongate projections 31 has a pair of external faces 33 arranged to lie adjacent to, but spaced from, one or more faces 42 of the recesses 41 of the third column tube 4, as described in greater detail below.

As described above, the cylindrical body 30 includes an elongate access slot 34 to allow access to the first column tube 2, and connection between the first column tube 2 and adjustment mechanism 7.

Referring now to Figure 7, there is shown the third, outermost column tube 4 isolated from the remaining features of the steering column assembly 1.

The third column tube 4 is an extruded metallic channel section 40 having a substantially U-shaped cross-sectional profile and two upwardly and outwardly extending elongate flanges 40a whose longitudinal axes are aligned with the adjustment axis A-A. The third column tube 4 is formed from aluminium or steel and includes a pair of elongate guideways 41 for receipt of the intermediate projections 31 of the second, intermediate tube 2. Each of the pair of elongate guideways 41 is defined by a pair of opposed internal faces 42 and io is arranged to receive a respective elongate projection 31 of the second column tube 3. In use, each of the external faces 33 of the elongate projections 31 is arranged to lie adjacent to, but spaced from, a respective internal face 42 of the elongate guideways 41.

An external surface of each of the elongate guideways 41 is provided with an elongate recess 43 extending along the length of the tube 4. The base of each recess 43 has a pair of spaced mounting holes 44 extending through the thickness of the third column tube 4 to the internal faces 42. The front end of each of the elongate flanges 40a extending outwardly from the exterior of the third column tube 4 is cut away as shown at 45 to allow the electromagnet 6 to be mounted. Further, an elongate enclosed tube section 46 extends along the length of the third column tube 4 between the elongate guideways 41.

As described in greater detail below, a planar strip of magnetorheological material 5 is attached to each of the internal faces 42 by virtue of mounting holes 44. The planar strip of magnetorheological material 5 is attached in a similar manner to that described above in respect of the elongate projection 21 by inserting each push-fit rivet head 53 through a respective mounting hole 44.

Figure 8 shows the electromagnet core 6a isolated from the remaining features of the steering column assembly 1 and Figure 8 shows the electromagnet core 6a mounted to the exterior of the third column tube 4.

The electromagnet core 6a is provided in two parts, a main core 60a and a core bridge 61a. Each of the main core 60a and core bridge 61a are formed as a lamination of steel sheets in this embodiment. The main core 60a is substantially U-shaped, and its inner face is complementarily shaped to the general exterior shape of the outer tube 3, and the core 60a has a pair of opposed mounting lugs 62a at its free ends. The core bridge 61a has a substantially trapezium or trapezoid shaped cross-section in this example.

Figure 9 shows the electromagnet core 6a mounted to the third column tube 4. The core bridge 61a is interference fit into the elongate tube section 46 and retained therein. The inner face of the main core 60a is complementarily shaped to the general exterior shape of the outer tube 3. Each of the mounting lugs 62a of the main core 60a is interference fit into a respective elongate recess 43 of the third column tube 4 with the ends of the mounting lugs 62a abutting the base of the recesses 43, whereby the main core 60a is retained on io the exterior of the outer tube at one end.

Figures 10 and 11 show two cross-sectional views through the assembled steering column assembly 1.

The planar faces 24 of the first column tube 2, opposed internal faces 32 of the second column tube 3 and internal faces 42 of the third column tube 4 lie parallel and adjacent to one another.

Of particular relevance is the arrangement of magnetorheological material 5 between the first column tube 2, second column tube 3 and third column tube 4. The planar strips of magnetorheological material 5 lie adjacent and extend parallel to one another to create a pair of clamping zones C. The clamping zones C are regions in which interference is provided between the tubes upon the application of a magnetic field to the magnetorheological material 5.

Each of the planar strips of magnetorheological material 5 of each respective clamping zone C lies in a plane orthogonal to the planar faces 24 of the first column tube 2, opposed internal faces 32 of the second column tube 3 and internal faces 42 of the third column tube 4 The planar strips of magnetorheological material 5 are configured so that their thickness increases when they are subjected to a magnetic field of sufficient strength. Therefore, if it is desired to change the effective length of the steering column (for example to allow the steering column to be telescoped to a stowed position for autonomous driving, to allow the steering column to be adjusted to the desired position for manual driving or to allow the steering column to be collapsed quickly in the event of a collision), the electromagnet 6 is switched off, which allows the strips 5 to assume their minimum thickness, which allows the inner, intermediate and outer tubes 2, 3, 4 to be moved relative to one another along the adjustment axis A-A.

When it is desired to lock the steering column in a desired configuration (for example to lock it in a stowed condition for autonomous driving or in an extended position for manual driving) the electromagnet 6 is actuated, which causes the strips 5 to assume their maximum thickness, which locks the inner, intermediate and outer tubes 2, 3, 4 relative to ic one another along the adjustment axis A-A.

It will be appreciated by those skilled in the art that several variations to the aforementioned embodiments are envisaged without departing from the scope of the invention.

It will also be appreciated by those skilled in the art that any number of combinations of the aforementioned features and/or those shown in the appended drawings provide clear advantages over the prior art and are therefore within the scope of the invention described herein.

Claims

CLAIMSA steering column assembly comprising: a first column tube and a second column tube telescopically mounted so as to be movable relative to one another along an adjustment axis; a magnetorheological material between the first and second column tubes; and means for selectively applying a magnetic field to the magnetorheological material to releasably secure the first column tube relative to the second column tube.
2. A steering column assembly according to claim 1, wherein the first column tube comprises an elongate projection whose longitudinal axis extends parallel to the adjustment axis, and the second column tube comprises a corresponding elongate guideway, wherein the magnetorheological material is located between the elongate projection and the guideway.
A steering column assembly according to claim 2, wherein the elongate projection comprises a planar face, and the magnetorheological material is provided between the planar face and the guideway.
4. A steering column assembly as claimed in claim 2 or claim 3, wherein the elongate projection extends from the inner one of the first and second column tubes.
A steering column assembly as claimed in any of claims 2 to 4, wherein the elongate projection extends outwardly with respect to the adjustment axis.
A steering column assembly as claimed in any of claims 2 to 5, wherein the extent to which the elongate projection extends outwardly is constant along the length of the projection.
7. A steering column assembly as claimed in any of claims 2 to 6, wherein the first column tube comprises a plurality of elongate projections and the second column tube comprises a corresponding elongate guideway for each of the elongate projections and, optionally, comprising magnetorheological material located between each of the elongate projections of the first column tube and the corresponding guideways in the second column tube.
8. A steering column assembly as claimed in any preceding claim, comprising magnetorheological material attached to the first column tube.
9. A steering column assembly as claimed in any preceding claim, comprising a third column tube telescopically mounted so as to be moveable relative to the second io column tube along the adjustment axis and a magnetorheological material between the second and third column tubes, and means for selectively applying a magnetic field to the magnetorheological material between the second and third column tubes to releasably secure the second column tube relative to the third column tube.
10. A steering column assembly as claimed in claim 9, wherein the second column tube comprises a further elongate projection whose longitudinal axis extends parallel to the adjustment axis and the third column tube comprises a further corresponding guideway, wherein the magnetorheological material is located between the further elongate projection and the further guideway.
11 A steering column assembly as claimed in claim 9 or claim 10, wherein the further elongate projection extends from the inner one of the second and third column tubes.
12. A steering column assembly as claimed in any of claims 9 to 11, wherein the further elongate projection extends outwardly with respect to the adjustment axis.
13. A steering column assembly as claimed in any of claims 9 to 12, wherein the extent to which the further elongate projection extends outwardly is constant along the length of the further projection.
14. A steering column assembly as claimed in any of claims 9 to 13, wherein the second column tube comprises a plurality of further elongate projections and the third elongate tube comprises a corresponding further guideway for each of the further elongate projections and, optionally, comprising magnetorheological material located between each of the further elongate projections of the second column tube and the corresponding further guideways in the third column tube.
15. A steering column assembly as claimed in any of claims 9 to 14, comprising magnetorheological material attached to the third column tube.
16. A steering column assembly as claimed in any of claims 9 to 15, wherein the means for selectively applying a magnetic field to the magnetorheological material between io the first and second column tubes also comprises means for selectively applying a magnetic field to the magnetorheological material between the second and third column tubes. 17. 18. 19. 20. 22.
A steering column assembly as claimed in any of claims 9 to 16, wherein the first column tube is mounted within the second column tube and the second column tube is mounted within the third column tube.
A steering column assembly as claimed in any preceding claim, wherein the magnetorheological material is planar and, optionally, wherein the magnetorheological material comprises a planar strip.
A steering column assembly as claimed in claim 18, wherein the planar strip comprises one or more mounting projections.
A steering column assembly as claimed in any preceding claim, wherein the magnetorheological material comprises an elastomer.
A steering column assembly as claimed in any preceding claim, wherein the position of the means for selectively applying a magnetic field to the magnetorheological material is fixed with respect to the outermost column tube.
A steering column assembly as claimed in any preceding claim, wherein the means for selectively applying a magnetic field to the magnetorheological material comprises an electromagnet.
23. A steering column assembly as claimed in claim 22, further comprising a magnetic field guide configured to guide the magnetic field from the electromagnet.
24. A steering column assembly as claimed in any preceding claim, comprising means for securing the outermost column tube to a vehicle.
25. A vehicle comprising a steering column assembly as claimed in any preceding claim.