| 摘要 |
Provided is a hydraulic control system (20) comprising a manual shift valve (23) for outputting a forward range pressure (PD) or a reverse range pressure (PR), and a linear solenoid valve (SL4) for outputting an apply pressure to a hydraulic servo (54) of a fourth clutch (C-4) to be applied at a reverse time. The hydraulic control system (20) further comprises a C-4 relay valve (45) interposed between the linear solenoid valve (SL4) and the hydraulic servo (54). The C-4 relay valve (45) is locked, when it inputs a signal pressure of a solenoid valve (SL), at a normal position thereby to provide the communication of the apply pressure from the linear solenoid valve (SL4), with the hydraulic servo (54), and is switched, when deenergized in failure, to a fail position by the reverse range pressure (PR) thereby to provide the communication of the reverse range pressure (PR) with the hydraulic servo (54). As a result, a reverse gear can be established, even in failure when the solenoid valve (SL) to be energized for the reverse gear at a normal time is deenergized. |
