Rolling bearing for rocker arm

1. A rolling bearing for a rocker arm comprising:

an outer ring in rolling contact with a camshaft of an engine;

an inner ring placed inside said outer ring and fixed to the rocker arm; and

a plurality of rolling elements provided between said outer ring and said inner ring, wherein

at least one of said outer ring, said inner ring and said rolling elements has a nitrogen-rich layer, an austenite crystal grain size number in a range exceeding 10, a surface hardness Hv of at least 653, and said nitrogen-rich layer has an area ratio of a spherical carbide of at least 10%.

2. The rolling bearing for the rocker arm according to claim 1 , wherein

said surface hardness Hv is at least 720 and at most 800.

3. The rolling bearing for the rocker arm according to claim 1 , wherein

said rocker arm is pivotably attached to a pivot shaft placed between one end and the other end of said rocker arm, an end portion of an open/close valve of said engine abuts on said one end, said rocker arm has, at said other end, a bifurcated inner-ring support portion, and said inner ring is fixed to said bifurcated inner-ring support portion.

4. The rolling bearing for the rocker arm according to claim 1 , wherein

said rolling bearing is provided between one end and the other end of said rocker arm,

said inner ring is fixed in an inner-ring hole extending between two sidewalls of said rocker arm, an end portion of an open/close valve of said engine abuts on said one end of said rocker arm, and a pivot abuts on the other end of said rocker arm.

5. The rolling bearing for the rocker arm according to claim 1 , wherein

said rocker arm has a rocker arm body and an interlocking rod transmitting a stress from said camshaft, said rocker arm body is pivotably attached to a pivot shaft placed between one end and the other end of said rocker arm body, an end portion of an open/close valve of said engine abuts on said one end of said rocker arm body, one end portion of said interlocking rod abuts on said other end of said rocker arm body, and said inner ring is fixed to the other end portion of said interlocking rod.

6. The rolling bearing for the rocker arm according to claim 1 , wherein

said rolling bearing is a full-type needle bearing.

7. A rolling bearing for a rocker arm comprising:

an inner ring fixed to the rocker arm provided between a valve and a cam of an engine to adjust intake air and exhaust air;

an outer ring placed outside said inner ring and contacting said cam; and

a plurality of rolling elements placed between said outer ring and said inner ring, wherein

at least one of said outer ring, said inner ring and said rolling elements has a nitrogen-rich layer, an austenite crystal grain size number of said nitrogen-rich layer is in a range exceeding 10, an amount of retained austenite of said nitrogen-rich layer is, in a surface layer portion of a rolling surface after grinding, in a range of 11% by volume to 25% by volume, and said nitrogen-rich layer has an area ratio of a spherical carbide of at least 10%.

8. The rolling bearing for the rocker arm according to claim 7 , wherein

nitrogen content of said nitrogen-rich layer is, in the surface layer portion of the rolling surface after grinding, in a range of 0.1% by weight to 0.7% by weight.

9. The rolling bearing for the rocker arm according to claim 7 , wherein

said rocker arm is pivotably attached to a pivot shaft placed between one end and the other end of said rocker arm, said one end has a bifurcated inner-ring support portion, said inner ring is fixed to said bifurcated inner-ring support portion, and an end portion of a valve of said engine abuts on said other end.

10. The rolling bearing for the rocker arm according to claim 7 , wherein

an end portion of a valve of said engine abuts on one end of said rocker arm, a pivot is fitted to the other end thereof, and said inner ring is fixed in an inner-ring hole of two opposing sidewalls between said one end and said other end of said rocker arm.

11. The rolling bearing for the rocker arm according to claim 7 , wherein

said rocker arm is pivotably supported on a pivot shaft placed between one end and the other end of said rocker arm, an end portion of a valve of said engine abuts on said one end, one end portion of an interlocking rod transmitting a stress from said camshaft abuts on said other end, said inner ring of said rolling bearing for the rocker arm is fixed to the other end portion of said interlocking rod, and said outer ring contacts said cam.

12. The rolling bearing for the rocker arm according to claim 7 , wherein

said rolling bearing for the rocker arm is a full-type needle bearing.

13. A rolling bearing for a rocker arm comprising:

an outer ring in rolling contact with a camshaft of an engine;

an inner ring placed inside said outer ring and fixed to the rocker arm; and

a plurality of rolling elements provided between said outer ring and said inner ring, wherein

all of said outer ring, said inner ring and said rolling elements have a nitrogen-rich layer,

said nitrogen-rich layer of at least one of said inner ring and said rolling elements has an austenite crystal grain size number in a range exceeding 10, an amount of retained austenite of said at least one of said inner ring and said rolling elements is at least 11% by volume and at most 25% by volume, nitrogen content of said at least one of said inner ring and said rolling elements is at least 0.1% by mass and at most 0.7% by mass, and said nitrogen-rich layer has an area ratio of a spherical carbide of at least 10%.

14. The rolling bearing for the rocker arm according to claim 13 , wherein

said rocker arm is attached to a rocker arm shaft placed between one end and the other end of said rocker arm, an end portion of a valve of said engine abuts on said one end, said rocker arm has, at said other end, a bifurcated inner-ring support portion, and said inner ring is fixed to said bifurcated inner-ring support portion.

15. The rolling bearing for the rocker arm according to claim 13 , wherein

said rolling bearing is provided between one end and the other end of said rocker arm,

said inner ring is fixed in an inner-ring hole extending between two sidewalls of said rocker arm, an end portion of an open/close valve of said engine abuts on said one end of said rocker arm, and a pivot abuts on the other end of said rocker arm.

16. The rolling bearing for the rocker arm according to claim 13 , wherein

said rocker arm has a rocker arm body and an interlocking rod transmitting a stress from said camshaft, said rocker arm body is attached to a rocker arm shaft placed between one end and the other end of said rocker arm body, an end portion of an open/close valve of said engine abuts on said one end of said rocker arm body, one end portion of said interlocking rod abuts on the other end of said rocker arm body, and said inner ring is fixed to the other end portion of said interlocking rod.

17. A rolling bearing for a rocker arm comprising:

an outer ring in rolling contact with a camshaft of an engine;

an inner ring placed inside said outer ring and fixed to the rocker arm; and

a plurality of rolling elements provided between said outer ring and said inner ring, wherein

at least one member of members that are said outer ring, said inner ring and said rolling elements has a nitrogen-rich layer, said member having said nitrogen-rich layer has an austenite crystal grain size number in a range exceeding 10, and said member having said nitrogen-rich layer has an area ratio of a spherical carbide of at least 10%.

18. The rolling bearing for the rocker arm according to claim 17 , wherein

the area ratio of the spherical carbide of said member having said nitrogen-rich layer is at least 10% and at most 25%.

19. The rolling bearing for the rocker arm according to claim 17 , wherein

said rocker arm is pivotably attached to a pivot shaft placed between one end and the other end of said rocker arm, an end portion of an open/close valve of said engine abuts on said one end, said rocker arm has, at said other end, a bifurcated inner-ring support portion, and said inner ring is fixed to said bifurcated inner-ring support portion.

20. The rolling bearing for the rocker arm according to claim 17 , wherein

said rolling bearing is provided between one end and the other end of said rocker arm,

said inner ring is fixed in an inner-ring hole extending between two sidewalls of said rocker arm, an end portion of an open/close valve of said engine abuts on said one end of said rocker arm, and a pivot abuts on the other end of said rocker arm.

21. The rolling bearing for the rocker arm according to claim 17 , wherein

said rocker arm has a rocker arm body and an interlocking rod transmitting a stress from said camshaft, said rocker arm body is pivotably attached to a pivot shaft placed between one end and the other end of said rocker arm body, an end portion of an open/close valve of said engine abuts on said one end of said rocker arm body, one end portion of said interlocking rod abuts on said other end of said rocker arm body, and said inner ring is fixed to the other end portion of said interlocking rod.

22. The rolling bearing for the rocker arm according to claim 17 , wherein

said rolling bearing is a full-type needle bearing.

23. A rolling bearing for a rocker arm comprising:

an outer ring in rolling contact with a camshaft of an engine;

an inner ring placed inside said outer ring; and

a plurality of rolling elements provided between said outer ring and said inner ring, wherein

said inner ring is made of a steel containing at least 0.50% by mass of carbon, has a hollow cylindrical shape, has an end surface with a hardness of at least HV 200 and at most HV 300, has a hardened layer extending entirely in the radial direction from a rolling surface of said inner ring where said rolling elements roll to an inner circumferential surface of said inner ring, a surface layer portion of the rolling surface of said inner ring contains a nitrogen-rich layer, and the nitrogen-rich layer has an area of spherical carbides of at least 10%.

24. The rolling bearing for the rocker arm according to claim 23 , wherein

a surface layer portion of the rolling surface of said inner ring has an austenite crystal grain size number in a range exceeding 10, and said austenite crystal grain size number is a value in a surface layer of 50 μm of the rolling surface after grinding.

25. The rolling bearing for the rocker arm according to claim 23 , wherein

the surface layer portion of the rolling surface of said inner ring has an amount of retained austenite of at least 11% by volume and at most 40% by volume, and said amount of retained austenite is a value in a surface layer of 50 μm of the rolling surface after grinding.

26. The rolling bearing for the rocker arm according to claim 23 , wherein

said nitrogen-rich layer has a nitrogen content in a range of at least 0.1% by mass and at most 0.7% by mass, and said nitrogen content is a value in a surface layer of 50 μm of the rolling surface after grinding.

27. The rolling bearing for the rocker arm according to claim 23 , wherein

the rolling surface of said inner ring has a surface hardness of at least HV 653.

28. The rolling bearing for the rocker arm according to claim 23 , wherein

the nitrogen-rich layer of the surface layer portion of the rolling surface of said inner ring has an area ratio of a spherical carbide of at least 10%, and said area ratio of the spherical carbide is a value in a surface layer of 50 μm of the rolling surface after grinding.

29. The rolling bearing for the rocker arm according to claim 23 , wherein

said rocker arm is attached to a rocker arm shaft placed between one end and the other end of said rocker arm, a bifurcated inner-ring support portion is provided at said one end of said rocker arm, an end portion of an open/close valve of said engine abuts on said other end, and said inner ring is fixed to said bifurcated inner-ring support portion.

30. The rolling bearing for the rocker arm according to claim 23 , wherein

a pivot abuts on one end of said rocker arm, said rolling bearing is provided between said one end and the other end of said rocker arm, and an end portion of an open/close valve of said engine abuts on said other end.

31. The rolling bearing for the rocker arm according to claim 23 , wherein

said rocker arm is attached to a rocker arm shaft placed between one end and the other end of said rocker arm, one end portion of an interlocking rod transmitting a stress from said camshaft abuts on said one end of said rocker arm, an end portion of an open/close valve of said engine abuts on said other end, and said rolling bearing is provided at the other end portion of said interlocking rod.

32. The rolling bearing for the rocker arm according to claim 23 , wherein

said rolling bearing is a full-type needle bearing.