| 摘要 |
PURPOSE:To positively prohibit the establishment of reverse speed under a forward speed running condition by permitting oil pressure to the hold port of a reserve speed prohibiting valve to be oil pressure for an oil chamber which is exclusively used for reverse speed, wherein oil pressure is supplied only at the time of reverse speed out of a friction engagement device for the establishment of reverse speed. CONSTITUTION:At the time of forward speed running, line oil pressure is applied to the hold port 118 of a reverse speed prohibiting valve 100, so that a valve body 102 and a plug 104 are held at permissible positions when switch-over is made from the condition to reverse speed, they are energized by a spring 120 to the permissible positions. And if vehicle speeds are less than a specified one, an electromagnetic drain valve 150 is opened so as to permit line oil pressure to be applied to the oil chamber 42a of the third clutch 42, and the outside oil chamber 48b and the inside oil chamber 48a of the second brake 48 so that a reverse speed condition is established. In this case, the same oil pressure as that of the oil chamber 42a is applied to a hold port 116 so as to force the valve body and the plug to be energized to the permissible positions by pressing force owing to oil pressure in addition to the force of the spring 120. Even when line oil pressure is applied to an inhibit port 114 because of the erroneous operation of the electromagnetic drain valve 150, the movement to a prohibited position is thereby prevented. |
