| 摘要 |
PURPOSE:To prevent any local abrasion on the rolling element in the caption by locally providing ring-shaped grooves inside the rolling contact surface of a rolling element for reducing concentration of contact stress in a contact portion. CONSTITUTION:At both axial end portions of the contact portion of a rolling element 21 to a rotor 11, ring-shaped grooves 22 which are concentric with a rolling contact surface are engraved respectively from the end face inside the rolling contact surface of the rolling element 21. When the rolling element 21 and the rotor 11 are brought in contact with each other so as to be pressed and rotated together, contact stress is concentrated at both axial end portions 23 of the contact portion of the rolling element 21. But the rigidity is reduced by the grooves 22 so that both end portions 23 of the rolling element 21 may be easily subjected to elastic deformation. Accordingly, the stress concentration generated at the end portions by said local elastic deformation is relaxed, and therefore local abrasion can be prevented.
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