| 摘要 |
PURPOSE:To improve the durability of an oil seal by forming a liquid sealing cylinder, which is separated from the inner surface of the cylinder of a hydraulic cylinder portion, between the first and the second relay pistons so as not to apply hydraulic pressure to the oil seal arranged on the outer circumferences of the relay pistons. CONSTITUTION:When a power piston 27 moves forward a shut-off valve is closed and a liquid sealing cylinder portion 36 comes in a tightly closed state. Under this state, the first and the second relay pistons 35, 37 are pushed by the power piston 27 to move forward so that a clutch is disengaged. At this time, the pressure (hydraulic pressure) in the liquid sealing cylinder portion 36 is applied to the first and the second relay pistons 35, 37 but not applied to the inner circumference of the cylinder of a hydraulic cylinder portion 23 which is separated from this liquid sealing cylinder portion 36. As the result, completely no hydraulic pressure is applied to an oil seal 33 arranged between the first relay piston 35 and the inner circumference of the cylinder of the hydraulic cylinder portion 23 so that the durability of the oil seal 33 is improved.
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