| 摘要 |
PROBLEM TO BE SOLVED: To solve a problem of a contact ellipse running onto an outer circumferential shoulder part and to elongate the service life of a thrust ball bearing by setting a groove bottom reference height in the outer circumferential end of a groove recess forming a raceway groove larger than the groove bottom reference height of the internal circumferential end. SOLUTION: A flat part 17 is formed higher than a central projection 16 by (c) and the groove bottom reference height (b) of the outer circumferential end 14 is set higher than the groove bottom reference height (a) of the internal circumferential end 14'. Practically, the groove bottom reference height (b) of the outer circumferential end 14 is set to such a dimension that a contact ellipse A of a ball 5 in loading is not deviated to the outer circumferential end 14 of the groove recess 13. In loading, the ball 5 rolls outside the groove bottom pitch circle at the diameter of an eccentric quantity (e). However, the groove bottom reference height (b) of the outer circumferential end 14 of the groove recess 13 is formed into relatively large so that the contact ellipse A is prevented from deviating to the outside of the outer circumferential end 14. This constitution can miniaturize the thrust ball bearing and at the same time elongate its service life.
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