Needle bearing and method for grinding bearing parts thereof

Abstract

It is an object of the invention to provide a needle bearing which can prevent occurrence of flake and seizure in the bearing parts even under such severe lubricating condition as provided by a compressor for a car air conditioner or a planetary unit for an automatic transmission. The needle bearing is structured by barrel grinding the raceway surface of a ring and the surface of a rolling body without using a ceramic-related abrasive such as alumina or silicon carbide.

1 . A needle bearing comprising: 
 a retainer having a plurality of pockets;    rings; and    a plurality of rolling bodies rollably incorporated in the respective pockets of the retainer and rolling on raceway surfaces of the rings,    wherein at least one of the retainer, the rolling bodies and the rings is free from a foreign substance having hardness equal to or higher than the hardness of the base material of the rolling bodies.    
   
   
       2 . (canceled)  
   
   
       3 . A needle bearing comprising: 
 a retainer having a plurality of pockets;    rings; and    a plurality of rolling bodies rollably incorporated in the respective pockets of the retainer and rolling on raceway surfaces of the rings,    wherein at least one of the retainer, the rolling bodies and the rings is free from, on the surface thereof, a foreign substance having a mean diameter of larger than 30 μm.    
   
   
       4 . A needle bearing comprising: 
 a retainer having a plurality of pockets;    rings; and    a plurality of rolling bodies rollably incorporated in the respective pockets of the retainer and rolling on raceway surfaces of the rings,    wherein, in case where 0.01 mm 2  of the surface of at least one of the bearing parts, that is, the retainer, the rolling bodies and the ring is set as a unit area, the rate per unit area of existence of hard foreign substances having hardness equal to or higher than the hardness of the base material of the rolling bodies and sticking to the surfaces of the bearing parts is set equal to or less than 10%.    
   
   
       5 . A needle bearing comprising: 
 a retainer having a plurality of pockets;    rings; and    a plurality of rolling bodies rollably incorporated in the respective pockets of the retainer and rolling on raceway surfaces of the rings,    wherein, in case where 0.01 mm 2  of the surface of at least one of the bearing parts, that is, the retainer, the rolling bodies and the ring is set as a unit area, the number per unit area of hard foreign substances having hardness equal to or higher than the hardness of the base material of the rolling bodies and sticking to the surfaces of the bearing parts is set equal to or less than 300.