| 摘要 |
PURPOSE:To surely keep off any internal lock of a planetary gear type shift mechanism by installing a selector valve being operated according to a hydraulic feeding state to first and second actuators for both first and second friction elements when they are clamped together and releasing a third friction element. CONSTITUTION:A 3-4 clutch 27 is clamped, and at time of four gear speed when a 2-4 brake 23 is clamped, pressure in a release side oil chamber 23d of this 2-4 brake actuator 23A is opened, so that coast control valve 50 (selector valve) receives clamping pressure of the 3-4 clutch 27 and thereby it opens clamping hydraulic pressure of a coast clutch 21. This operation is performed for preventing an internal lock from occurring because if the 3-4 clutch 27 and the 2-4 brake 23 are clamped, a planetary gear unit 14 has caused this internal lock. Thus, as pilot pressure of the valve 50, hydraulic pressure showing a clamping state between the clutch 27 and the brake 23 is used, so that at time of fourth gear speed, the internal lock occurrence is prevented.
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