| 摘要 |
PROBLEM TO BE SOLVED: To provide a piston having a spring holding protrusion in a shape matched with a spring to be held so as not to damage the spring. SOLUTION: Seal members 3, 4 are formed on inner and outer peripheral portions of a piston body 1. The piston body 1 is provided with an urging protrusion 6 for urging a friction member such as a clutch plate when the piston body 1 moves inwardly in the axial direction by action of a hydraulic pressure, and with a spring holding protrusion 7 for holding the spring for returning the piston body outwardly in the axial direction when the hydraulic pressure is released. The spring holding protrusion 7 comprises a metal reinforcing portion 10 integrally formed with the piston body 1, and an elastomer coat portion 11 coating an outer surface of the metal reinforcing portion 10.
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