Steering assembly for a vehicle

1 . A steering assembly for a steer-by-wire vehicle, comprising:

a rotatably mounted elongate steering column configured for attachment of a steering member at one end, the steering column being rotatable about its longitudinal axis in either direction from a straight ahead position;

a damper comprising:

a housing defining a volume for receipt of damping fluid;

a rotor within the housing, the rotor being coupled with the steering column and rotatable therewith;

a stator mounted within the housing, the stator being moveable within the housing within a defined range of movement; and

a biasing member acting on the stator;

wherein each of the stator and rotor comprises a shear surface, the shear surfaces of the stator and the rotor being positioned adjacent one another to generate a resistance to rotation of the rotor when the housing contains damping fluid; and

a total surface area of the shear surfaces of the stator and the rotor positioned adjacent one another which generates the resistance to rotation of the rotor varies as the steering column is rotated from the straight ahead position by virtue of displacement of the stator relative to the rotor.

2 . The steering assembly according to claim 1 , wherein the total surface area of the shear surfaces of the stator and the rotor positioned adjacent one another is increased or decreased as the steering column is rotated from the straight ahead position.

3 . The steering assembly according to claim 1 , wherein the stator is rotatable about the longitudinal axis of the steering column and is configured to be displaced against the biasing member axially towards the rotor as it is rotated.

4 . The steering assembly according to claim 1 , wherein stator is rotatable within the housing, and the stator and rotor are coupled by the damping fluid, such that the stator is rotated relative to the housing when the steering column is rotated at a speed greater than a predetermined threshold.

5 . The steering assembly according to claim 1 , wherein the stator comprises a cam, and the steering assembly comprises a cam follower fixed relative to the housing, and wherein the cam and cam follower are arranged so as to displace the stator axially towards the rotor against the biasing member as the cam follower is moved along the cam.

6 . The steering assembly according to claim 5 , wherein the cam is configured to rotate with the stator and comprises a cam surface, wherein a position of the cam surface along the longitudinal axis varies along the length of the cam.

7 . The steering assembly according to claim 5 , wherein the cam is arcuate or part-annular.

8 . The steering assembly according to claim 7 , wherein the cam is coaxial with the longitudinal axis of the steering column.

9 . The steering assembly according to any one of claim 5 , wherein the cam and cam follower are arranged such that the cam follower is moved along the cam and the stator is displaced axially towards the rotor against the biasing member as the stator is rotated relative to the housing.

10 . The steering assembly according to any one of claim 5 , wherein the biasing member is located between the stator and the rotor and is arranged so as to bias the cam into contact with the cam follower.

11 . The steering assembly according to claim 1 , wherein the biasing member comprises a compression spring configured to bias the stator away from the rotor.

12 . The steering assembly according to claim 10 , wherein the biasing force increases as the stator is displaced axially towards the rotor.

13 . The steering assembly according claim 5 , wherein the cam and the cam follower are arranged so as to displace the stator axially towards the rotor against the biasing member when the rotational speed of the steering column exceeds a predetermined threshold.

14 . The steering assembly according to claim 1 , wherein the biasing member is located between the stator and the housing.

15 . The steering assembly according to claim 1 , wherein the stator and the rotor each comprise a respective elongate projection extending therefrom, and wherein each elongate projection comprises a respective shear surface.

16 . The steering assembly according to claim 15 , wherein the elongate projection of the stator extends towards the rotor and the elongate projection of the rotor extends towards the stator.

17 . The steering assembly according to claim 15 , wherein each elongate projection is arcuate and at least one shear surface of each elongate projection comprises an annular shear surface, and the total area of annular shear surfaces positioned adjacent one another is increased as the steering column is rotated from the straight ahead position.

18 . The steering assembly according to claim 17 , wherein the total area of annular shear surfaces positioned adjacent one another is increased as the stator is displaced against the biasing member axially towards the rotor.

19 . A steering assembly according to claim 1 , wherein the stator and the rotor each comprise a plurality of radially spaced elongate projections and one or more passages described between adjacent elongate projections, wherein an elongate projection of the stator is configured to be received within a passage of the rotor and an elongate projection of the rotor is configured to be received within a passage of the stator.

20 . The steering assembly according to claim 19 , wherein the amount by which the elongate projections of the stator axially overlap the elongate projections of the rotor is increased as the stator is displaced against the biasing member axially towards the rotor, thereby increasing the total surface area of the shear surfaces positioned adjacent one another.

21 . The steering assembly according to claim 1 , wherein the shear surface of each of the stator and the rotor are planar.

22 . The steering assembly according to claim 21 , wherein the shear surface of the stator is spaced from the shear surface of the rotor along the longitudinal axis of the steering column.

23 . The steering assembly according to claim 22 , wherein the shear surface of the stator is configured to be displaced axially against the biasing member towards the shear surface of the rotor.

24 . The steering assembly according to claim 21 , wherein the shear surfaces overlap when viewed along the longitudinal axis of the steering assembly.

25 . The steering assembly according to claim 1 , wherein the stator is rotatable within the housing and mounted eccentrically.

26 . A steering assembly according to claim 15 , wherein the stator is rotatable within the housing and mounted eccentrically and the rotor is arranged such that spacing between the shear surface of the elongate projection of the stator and the shear surface of the elongate projection of the rotor varies as the steering column is rotated from the straight ahead position.

27 . The steering assembly according to claim 26 , wherein stator is rotatable within the housing, and the stator and rotor are coupled by the damping fluid, such that the stator is rotated when the steering column is rotated at a speed greater than a predetermined threshold.

28 . The steering assembly according to claim 27 , wherein the spacing between the shear surfaces is reduced as the stator is rotated thereby increasing the total surface area of the shear surfaces positioned adjacent one another.

29 . The steering assembly according to claim 25 , wherein the biasing member is configured to bias the stator towards the straight ahead position.

30 . The steering assembly according to claim 1 , comprising a pair of circumferentially spaced end stops configured to limit the extent of rotation of the stator, wherein the stops are positioned either side of the straight ahead position.

31 . A steering column assembly comprising the steering assembly as claimed in claim 1 .

32 . A vehicle comprising the steering assembly as claimed in claim 1 .