Torsion device

1. A torsion device comprising:

a first part comprising a first resilient torsion member including:

a first support end;

a first free end spaced from the first support end; and

a first engagement region;

a second part comprising a second resilient torsion member including:

a second support end;

a second free end spaced from the second support end; and

a second engagement region;

wherein the second part is rotatable relative to the first part about an axis of rotation between a first angular position and a second angular position, and the first and second torsion members are configured to urge the first and second engagement regions together to cause flexure of at least one of the first and second resilient torsion members as the second part rotates relative to the first part from the first angular position to the second angular position.

2. A torsion device according to claim 1 , wherein the first and second torsion members are configured to urge the first and second engagement regions together as angular spacing between the first and second support ends increases as the second part rotates relative to the first part from the first angular position to the second angular position.

3. A torsion device according to claim 1 , wherein the first and second torsion members are configured to urge the first and second engagement regions together as angular spacing between the first and second support ends decreases as the second part rotates relative to the first part from the first angular position to the second angular position.

4. A torsion device according to claim 1 , wherein at least one of the first and second engagement region comprises a curved surface.

5. A torsion device according to claim 4 , wherein the first and second engagement regions are configured to roll over one another as the second part rotates relative to the first part.

6. A torsion device according to claim 5 , wherein the curved surfaces are of substantially equal curvature.

7. A torsion device according to claim 1 , wherein the first and second parts comprise third and fourth engagement regions respectively configured to abut one another when the second torsion member approaches the first angular position as the second part rotates relative to the first part from the second angular position to the first angular position.

8. A torsion device according to claim 1 , wherein the first and second torsion members are configured to provide a progressive increase in torsional resistance with increased displacement angle as the second part moves from the first angular position to the second angular position.

9. A torsion device according to claim 1 , wherein the first and second torsion members are provided in a sealed housing filled with fluid.

10. A torsion device according to claim 9 , wherein the sealed housing defines a passageway structure configured to allow fluid to flow around at least one of the first and second torsion members as the second torsion member moves between the first and second angular position.

11. A torsion device according to claim 10 , wherein the passageway structure provides a resistance to fluid flow around at least one of the first and second torsion members that varies as the second part moves relative to the first part.

12. A torsion device according to claim 9 , wherein the fluid is a smart fluid.

13. A torsion device according to claim 1 and further comprising a sensor for monitoring an angular position of the second part relative to the first part.

14. A trailing arm suspension assembly for a vehicle comprising the torsion device of claim 1 , wherein the torsion device is configured to oppose movement of a trailing arm.

15. A vehicle wheel comprising a bearing arrangement including the torsion device of claim 1 , wherein the vehicle wheel is rotatable about a rotary suspension axis that is offset from a primary rotation axis of the wheel and the torsion device is configured to oppose rotation about the rotary suspension axis.