Self-lubricating bearings

1. A self-lubricating bearing for use in low pressure, high frequency, small amplitude applications, the bearing having a self-lubricating liner and a counterface surface in close sliding contact therewith, the counterface surface having a surface finish of less than 20 nm and a hardness of less than in the region of 1000 VPN.

2. A self-lubricating bearing according to claim 1 , wherein the surface finish of the counterface surface is in the range of 5 nm to 20 nm.

3. A self-lubricating bearing according to claim 1 , wherein the counterface surface comprises a coating on a curved surface, the curved surface having an electrolytically ground finish.

4. A self-lubricating bearing according to claim 3 , wherein the coating over the electrolytically ground finish has a thickness of between 1-5 μm.

5. A self-lubricating bearing according to claim 3 , wherein the coating is a chemical deposition coating, a physical vapour deposition coating or an ion plating coating.

6. A self-lubricating bearing according to claim 1 , wherein the bearing is a spherical bearing.

7. A self-lubricating bearing according to claim 6 , wherein the spherical bearing includes a ball, the ball providing the counterface surface.

8. A self-lubricating bearing according to claim 1 , wherein the operating conditions, in use, are at stresses of less than 35 MPa, at a frequency of at least 0.1 Hz and with amplitudes comprising small angular motions of less than ±12° rotation.

9. A method of constructing a self-lubricating bearing comprising the steps of:

providing a self-lubricating liner with a curved surface;

providing a counterface having a curved surface, wherein the curved surface of the counterface has a surface finish of less than 20 nm and a hardness of less than 1000 VPN; and

placing the curved surfaces of the liner and the counterface surface in sliding contact with one another.

10. A method according to claim 9 , wherein the curved surfaces are correspondingly curved surfaces.

11. A method according to claim 9 , wherein the bearing is a spherical bearing comprising a ball, and the counterface is a surface of the ball.

12. A method according to claim 9 , further comprising forming a coating on the curved surface of the counterface, wherein the coating provides the counterface surface in sliding contact with the liner.

13. A method according to claim 12 , wherein the coating has a thickness in the range of about 1-5 μm.

14. A method according to claim 12 , wherein the coating is a chemical deposition coating, a physical vapour deposition coating or an ion plating coating.

15. A method according to claim 9 , wherein the counterface surface has a hardness of less than 750 VPN.

16. A method according to claim 9 , wherein providing a counterface having a curved surface further comprises electrolytically grinding the curved surface.

17. A method of operating a self-lubricating bearing having a self-lubricating liner and a counterface surface in close sliding contact therewith, the counterface surface having a surface finish of less than 20 nm and a hardness of less than 1000 VPN, wherein the operating conditions are at stresses of less than 35 MPa, at a frequency of at least 0.1 Hz and with amplitudes comprising small angular motions of less than ±12° rotation.

18. A method according to claim 17 , wherein the bearing is a spherical bearing comprising a ball, and the counterface surface is a surface of the ball.

19. A method according to claim 18 , wherein the ball is a heat treated metal ball.

20. A method according to claim 19 , wherein the ball has a physical vapour deposition coating providing the counterface surface in sliding contact with the liner.