Hydraulic pressure control device for automatic transmission

摘要

There is provided a circuit configuration which does not require an additional fail-safe mechanism caused by the addition of a changeover valve in a hydraulic pressure control device for an automatic transmission having a function to directly supply a line pressure and hold (lock) an engaging pressure by combinations of electromagnetic valves and changeover valves. A changeover valve 20 is disposed between an output port 12 and a feedback port 13 of a linear solenoid valve 10 of the hydraulic pressure control device for an automatic transmission. The changeover valve 20 operates depending on at least an output pressure from the output port, and is switched between (1) a first state (control mode) in which a pressure Pc corresponding to an indicator current is outputted through the linear solenoid valve 10 by bringing the output port into communication with the feedback port, and (2) a second state (lock mode) in which a line pressure PL is outputted through the linear solenoid valve 10 by bringing the feedback port 13 into communication with a drain passage EX and discharging oil from the feedback port.