Plastic bearing, particularly for use in MacPherson strut

1. A ring bearing, comprising:

an upper casing;

a lower casing; and

a plastic ring engaged between the upper and lower casings, thereby forming said ring bearing;

said upper and lower casings respectively defining upper and lower annular facing surfaces for engaging said plastic ring therebetween;

said upper and lower facing surfaces each having radially inner and outer portions;

said upper and lower facing surfaces each being substantially curved in a direction between said inner and outer portions thereof;

said plastic ring having upper and lower spacing portions, each being centrally located between said inner and outer portions of said upper and lower facing surfaces, thereby defining respective spaces oriented longitudinally of said ring between said plastic ring and said upper and lower facing surfaces which reduce contact friction with the respective facing surfaces.

2. A MacPherson strut having an upper spring seat, a spring, a strut tube, and a ring bearing disposed for engaging the spring seat, the spring and the strut tube; wherein the ring bearing comprises the ring bearing of claim 1 .

3. The MacPherson strut of claim 2 , further comprising additional grooves or recesses in the upper and/or lower surfaces of the plastic ring which further reduce contact friction with the respective facing surfaces of the upper and lower casings.

4. The MacPherson strut of claim 2 , wherein said respective facing surfaces of said ring have at least in part a smaller radius of curvature than said facing surfaces of said casings.

5. The MacPherson strut of claim 2 , wherein said respective facing surfaces of said ring have at least in part the same radius of curvature as said facing surfaces of said casings.

6. The MacPherson strut of claim 2 , wherein said respective facing surfaces of said casings and said ring are engaged primarily at said inner and outer portions thereof.

7. The ring bearing of claim 1 , further comprising additional grooves or recesses in the upper and/or lower surfaces of the plastic ring which further reduce contact friction with the respective facing surfaces of the upper and lower casings.

8. The ring bearing of claim 1 , wherein said respective facing surfaces of said ring have at least in part a smaller radius of curvature than said facing surfaces of said casings.

9. The ring bearing of claim 1 , wherein said respective facing surfaces of said ring have at least in part the same radius of curvature as said facing surfaces of said casings.

10. The ring bearing of claim 1 , wherein said respective facing surfaces of said casings and said ring are engaged primarily at said inner and outer portions thereof.

11. The ring bearing of claim 1 , wherein said spacing portion is defined by a flattened portion of said ring facing the corresponding said upper or lower facing surface.

12. The ring bearing of claim 1 , wherein said spacing portion is defined by a groove formed in said ring facing the corresponding said upper or lower facing surface.

13. The ring bearing of claim 12 , wherein one of said upper and lower facing surfaces has a respective projection which projects into the corresponding groove formed in the ring.

14. The ring bearing of claim 1 , wherein said spacing portion is defined by a recess formed in said ring facing the corresponding said upper or lower facing surface.

15. A ring bearing, comprising:

an upper casing;

a lower casing; and

a plastic ring engaged between the upper and lower casings, thereby forming said ring bearing;

said upper and lower casings respectively defining upper and lower annular facing surfaces for engaging said plastic ring therebetween;

said upper and lower facing surfaces each having radially inner and outer portions;

wherein said ring has radially outer and inner portions which are relatively enlarged, in a direction between said upper and lower facing surfaces, with respect to a radially central portion thereof;

said plastic ring having a spacing portion, centrally located between said inner and outer portions of one of said upper and lower facing surfaces, thereby defining a respective space oriented longitudinally of said ring between said plastic ring and said one of said upper and lower facing surfaces which reduces contact friction with the respective facing surface.

16. The ring bearing of claim 15 , wherein said spacing portion is defined by a flattened portion of said ring facing the corresponding said upper or lower facing surface.

17. The ring bearing of claim 15 , wherein said spacing portion is defined by a groove formed in said ring facing the corresponding said upper or lower facing surface.

18. The ring bearing of claim 17 , wherein said one of said upper and lower facing surfaces has a respective projection which projects into the corresponding groove formed in the ring.

19. The ring bearing of claim 15 , wherein said spacing portion is defined by a recess formed in said ring facing the corresponding said upper or lower facing surface.

20. The ring bearing of claim 15 , wherein said ring is generally dumbbell-shaped when seen in cross-section.

21. The ring bearing of claim 15 , wherein said plastic ring has another spacing portion, centrally located between said inner and outer portions of the other one of said upper and lower facing surfaces, thereby defining a respective space oriented longitudinally of said ring between said plastic ring and said other one of said upper and lower facing surfaces which reduces contact friction with the respective central facing surface.

22. The ring bearing of claim 21 , wherein the other one of said upper and lower facing surfaces has a respective projection which projects into the corresponding space between the facing surface and the ring.

23. A MacPherson strut having an upper spring seat, a spring, a strut tube, and a ring bearing disposed for engaging the spring seat, the spring and the strut tube; wherein the ring bearing comprises the ring bearing of claim 15 .

24. A ring bearing, comprising:

an upper casing;

a lower casing; and

a plastic ring engaged between the upper and lower casings, thereby forming said ring bearing;

said upper and lower casings respectively defining upper and lower annular facing surfaces for engaging said plastic ring therebetween;

said upper and lower facing surfaces of said casings each having radially inner and outer portions;

wherein said inner and outer portions of each of said upper and lower facing surfaces have respective radially extending flat surfaces which together define a cross-sectional V-shape, and said plastic ring has a corresponding cross-sectional V-shape.

25. A MacPherson strut having an upper spring seat, a spring, a strut tube, and a ring bearing disposed for engaging the spring seat, the spring and the strut tube; wherein the ring bearing comprises the ring bearing of claim 24 .

26. The ring bearing of claim 24 , further comprising a friction-reducing recess formed extending longitudinally in said ring opposite a respective one of said inner and outer portions of said upper and lower facing surfaces.

27. The ring bearing of claim 26 , wherein respective friction-reducing recesses are formed extending longitudinally in said ring opposite each of said inner and outer portions of said upper and lower facing surfaces.

28. A ring bearing, comprising:

an upper casing;

a lower casing; and

a plastic ring engaged between the upper and lower casings, thereby forming said ring bearing;

said upper and lower casings respectively defining upper and lower annular facing surfaces for engaging said plastic ring therebetween;

said upper and lower facing surfaces each having radially inner and outer portions;

wherein said inner and outer portions of each of said upper and lower facing surfaces have respective flat portions which together define a general V-shape when seen in cross-section, and said plastic ring has a corresponding cross-sectional V-shape;

said plastic ring having upper and lower spacing portions, each being centrally located between said inner and outer portions of said upper and lower facing surfaces, thereby defining respective spaces oriented longitudinally of said ring between said plastic ring and said upper and lower facing surfaces which reduce contact friction with the respective facing surfaces.

29. The ring bearing of claim 28 , further comprising upper and lower spacing portions formed in said upper and lower facing surfaces, opposite said corresponding spacing portions formed in said ring.

30. A ring bearing, comprising:

an upper casing;

a lower casing; and

a plastic ring engaged between the upper and lower casings, thereby forming said ring bearing;

said upper and lower casings respectively defining upper and lower annular facing surfaces for engaging said plastic ring therebetween;

said upper and lower facing surfaces each having radially inner and outer portions;

wherein said inner and outer portions of each of said upper and lower facing surfaces have respective flat portions which together define a general V-shape when seen in cross-section, and said plastic ring has a corresponding cross-sectional V-shape;

wherein said upper and lower facing surfaces have respective upper and lower spacing portions, each being centrally located between said inner and outer portions of said upper and lower facing surfaces, thereby defining respective spaces oriented longitudinally of said ring between said plastic ring and said upper and lower facing surfaces which reduce contact friction with the respective facing surfaces.