FAIL SAFE MECHANISM OF AUTOMATIC TRANSMISSION AND FAIL SAFE VALVE IN FAIL SAFE MECHANISM

摘要

PROBLEM TO BE SOLVED: To provide a fail safe mechanism of an automatic transmission and a fail safe valve provided in the fail safe mechanism capable of discharging foreign matter by operating a valve element with prescribed timing without increasing the number of components while maintaining a fail safe function in failure of the automatic transmission.

SOLUTION: A reverse range pressure PR is supplied to an oil chamber 59 between a valve body 60 of a clutch apply control valve 50 and a plunger 70 on formation of a reverse stage of the automatic transmission. A pressure receiving area on one end side of the plunger 70 to which the reverse range pressure PR is actuated is set to be larger than a pressure receiving area on the other end side of the plunger 70 to which a line pressure PL is actuated, and the plunger 70 is moved to discharge foreign matter only when the reverse range pressure PR is actuated.

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