| 摘要 |
A radially inner surface of a sealing lip of an oil seal, is irradiated to induce a chemical reaction in the material of the sealing lip, to form hard helical portions. The hard helical portions act like a helical groove or rib to pump oil back to an oil-side for excellent sealing properties when there is a relative rotational movement between the sealing lip and a shaft to sealed, as well as a static sealing ability at the time there is no relative rotation movement.
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