| 摘要 |
PROBLEM TO BE SOLVED: To prevent a large surface pressure based on an edge load from acting on the rolling surface of each ball by setting the curvature radiuses of the sectional forms of inner and outer ring raceway tracks to specified ratios to the diameter of the ball. SOLUTION: In an alternator ball bearing where the ratio D/d of the pitch circle diameter D of a plurality of balls 14 to the diameter (d) of each ball 14 is within the range of 3.0-5.0, the curvature radius r9a of an inner ring raceway track 9a is regulated within the range of 50.9-51.2% of the outer diameter (d) of the ball 14. Further, the curvature radius r11 of an outer ring raceway track 11 is regulated within the range of 53.0-53.7% of the outer diameter (d) of the ball 14 as in the past. The curvature radius r9a of the inner ring raceway track 9 is limited to a relatively larger value than in the past in this way, whereby the rolling surface of each ball 14 never runs out from the inner ring raceway track 9a even if each ball 14 is slightly displaced. Accordingly, the rolling fatigue life can be improved even in the use under a sever condition as a large vibration acts thereon with high rotation. |
