| 摘要 |
PURPOSE:To eliminate the capacity deficiency or the like of a highest speed stage selecting friction element by connecting a signal pressure circuit to open a control valve feeding the engine brake operating pressure to the highest speed stage selection pressure releasing circuit of a highest speed stage selecting shift valve. CONSTITUTION:When a driver performs the engine brake request operation, the engine brake command pressure is generated, a highest speed stage selecting shift valve is set to the down-shift position to release the highest speed stage selection pressure, and an automatic transmission is set to a shift stage other than the highest speed stage. On the other hand, the engine brake operating pressure reaches a control valve 38, the fourth speed releasing pressure is inputted from a circuit 101 as soon as the release of the highest speed stage selection pressure is started, a spool 152 is moved to the left when pressure change to the third speed is completed, and the engine brake operating pressure is fed to an overrun clutch POR/C. The control valve does not participate in the pressure loss of the highest speed selection pressure, and the capacity deficiency of a highest speed stage selecting friction element fastened by this pressure and the increase of a pump drive load can be prevented. |
