To prevent grease leakage from a double row ball bearing 5a consisting of a rotation support device for a pulley.
The shortest distance between respective balls 15, 15 of one side ball row and another side ball row with respect to the axial direction of the outer race 11 and the inner race 13, is set to S. The shortest distance between the inner surface of the one side seal plate 17 of respective seal plates 17, 17 and respective balls 15 of the one side ball row with respect to the axial direction is set to a. The shortest distance between the inner surface of another seal plate 17 and respective balls 15 of another side ball row with respect to the axial direction is set to b. The outer diameter of the respective balls 15, 15 is set to D. The above purpose is attained by setting to be a≥b>S, (a/D)≥(b/D)=0.2 to 0.4 and S/D≥0.12.
Nakai Shun
Kinzo Koyama
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