| 摘要 |
PURPOSE:To ensure efficient gear change control by changing over a shift solenoid to a solenoid pressure drain mode when a sub-transmission is selected to a high-speed select mode, and turning a shift valve to a high-speed select friction element operation mode. CONSTITUTION:When a driving condition requires the selection of the fourth gear, the third shift solenoid C is changed over to be off (pressure drain mode) while the first and second shift solenoids A and B are being kept off, or a main transmission is kept unchanged. The spool 46b of the third shift valve 46 is thereby lowered and a brake RD/B is released. Also, a high-speed select clutch D/C is coupled. Consequently, a sub-transmission is changed over from a speed reduction mode to a direct coupling mode, and the gear is shifted up. In this case, the rise of the working pressure of the clutch D/C is gradually reduced via a one-way orifice 158 and an accumulator 70, thereby alleviating a coupling shock. According to the aforesaid construction, an oil amount balance comes to have a margin, thereby enabling gear change control with little drive loss with an oil pump and with good efficiency. |
