Bearing for Rocker Arm

Abstract

A bearing for a rocker arm includes a shaft corresponding to an inner race fixed to a rocker arm interposed between an engine valve and a cam to adjust intake and exhaust, an outer race 4 in contact with the cam, located outer to the inner race, and a plurality of needle rollers located between the outer race and the inner race. The outer race includes a nitrogen-enriched layer. The grain size number of austenite crystal grains in the nitrogen-enriched layer is in a range exceeding No. 10. The outer race outside cylindrical surface has random small concave pits.

1 . A rocker arm bearing including a shaft corresponding to an inner race fixed to a rocker arm interposed between an engine valve and a cam to adjust intake and exhaust, an outer race located outer to said inner race and in contact with said cam, and a plurality of rolling elements located between said outer race and inner race, 
 wherein said outer race includes a nitrogen-enriched layer, a grain size number of austenite crystal grains in the nitrogen-enriched layer being in a range exceeding No. 10, and including small concave pits randomly on a surface of an outside cylindrical perimeter of the outer race.    
   
   
       2 . The rocker arm bearing according to  claim 1 , wherein the surface of said outside cylindrical perimeter of the outer race having said small concave pits randomly formed has, when a surface roughness is represented by a parameter value of R qni  (ISO International Standard), a ratio of R qni  (L)/R qni  (C), identified as the ratio of an axial surface roughness R qni  (L) to circumferential surface roughness R qni  (C), that is at most 1.0, and a surface roughness parameter value of Sk that is at most −1.6.  
   
   
       3 . The rocker arm bearing according to  claim 1 , wherein said rocker arm is supported rotatably on a rotation shaft located between one end and another end of the rocker arm, said one end including a bifurcated inner race support to which said inner race is fixed, and said another end abutting against an end of said engine valve.  
   
   
       4 . The rocker arm bearing according to  claim 1 , wherein said rocker arm has first end portion fitted with a pivot and second end portion abut against an end of said engine valve, and said inner race is fixed through an inner race bore at two opposite sidewalls between said first end portion and said second end portion of said rocker arm.  
   
   
       5 . The rocker arm bearing according to  claim 1 , wherein the rocker arm is supported rotatably on a rotation shaft located between first end portion second end portion of the rocker arm, an end of said engine valve abutting against the second end portion, and one end of an interlock rod transmitting stress from said cam abutting against said first end portion, the inner race of said rocker arm rolling bearing being fixed to the other end of said interlock rod and the outer race forming contact with said cam.  
   
   
       6 . The rocker arm bearing according to  claim 1 , wherein said rocker arm bearing is a full complement type needle bearing.  
   
   
       7 . A rocker arm bearing including a shaft corresponding to an inner race fixed to a rocker arm interposed between an engine valve and a cam to adjust intake and exhaust, and an outer race located outer to said inner race and in contact with said cam, 
 wherein said outer race includes a nitrogen-enriched layer, a grain size number of austenite crystal grains in the nitrogen-enriched layer being in a range exceeding No. 10, and including small concave pits randomly on a surface of an outside cylindrical perimeter of the outer race.    
   
   
       8 . The rocker arm bearing according to  claim 7 , wherein the surface of said outside cylindrical perimeter of the outer race having said small concave pits randomly formed has, when a surface roughness is represented by a parameter value of R qni  (ISO International Standard), a ratio of R qni  (L)/R qni  (C), identified as the ratio of an axial surface roughness R qni  (L) to circumferential surface roughness R qni  (C), that is at most 1.0, and a surface roughness parameter value of Sk that is at most −1.6.  
   
   
       9 . The rocker arm bearing according to  claim 7 , wherein said rocker arm is supported rotatably on a rotation shaft located between one end and another end of the rocker arm, said one end including a bifurcated inner race support to which said inner race is fixed, and said another end abutting against an end of said engine valve.  
   
   
       10 . The rocker arm bearing  3  according to  claim 7 , wherein said rocker arm has first end portion fitted with a pivot, and second end portion abut against an end of said engine valve, and said inner race is fixed through an inner race bore at two opposite sidewalls between said first end portion and said second end portion of said rocker arm.  
   
   
       11 . The rocker arm bearing according to  claim 7 , wherein the rocker arm is supported rotatably on a rotation shaft located between first end portion and second end portion of the rocker arm, an end of said engine valve abutting against the second end portion, and one end of an interlock rod transmitting stress from said cam abutting against said first end portion, the inner race of said rocker arm bearing being fixed to the other end of said interlock rod, and the outer race forming contact with said cam.