| 摘要 |
PROBLEM TO BE SOLVED: To prevent the surface roughening of inner and outer rings with the lapse of time to stably keep the low vibration and reduced noise over a long period. SOLUTION: The surface roughness of a rolling surface 2 of an inner ring 1 and a rolling surface 4 of an outer ring 3 is reduced to below 18 nm, preferably below 10 nm to smoothen the rolling of balls 5, whereby the advancing of the surface roughening can be inhibited, and the increase of the rotating vibration and noise can be inhibited.
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