| 摘要 |
The annular contact surface (1b1) of the bottom portion of an outer ring is formed with an uneven pattern comprising a number of projections (A) (regions A1, A2, A3) and recesses (regions B1, B2). Each projection (A) is a substantially Y-shaped region having a given level above the bottom surface of the regions (B1, B2). The regions (A1) and (A2), forming the Y's heads of the projection (A), lead to the outer diameter of the annular contact surface (1b1), while the region (A3) forming the Y's leg leads to the inner diameter of the annular contact surface (1b1).
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