| 摘要 |
PURPOSE:To enable a travel by selecting a shift valve to a high-speed select friction element operation mode in the advance travel range of a multi-stage automatic transmission, and to a low-speed select friction element operation mode in the backward travel range, respectively when a shift solenoid is turned off. CONSTITUTION:A conventional spring is removed from the chamber 46d of the third shift valve 46, and a spring 46g is housed in the chamber 46c. This chamber 46c is made open to the atmosphere. When solenoid pressure PSL is not generated by the third shift solenoid due to a trouble, therefore, backward travel select pressure PR is not supplied from a manual operation valve either, during an advance travel. Consequently, a shuttle valve 154 makes the chamber 46d free from pressure, and a spool 46b is lowered with the spring 46g. A direct clutch D/C is thereby turned on with line pressure PL and a sub-transmission is kept in a high-speed select mode. On the other hand, during a backward travel, rear motion select pressure PR is introduced to the chamber 46d via the shuttle valve 154 and the spool 46b is moved up. A reduction brake RD/B is thereby connected with the line pressure PL and a low-speed select mode is thereby maintained. |
