Fail-safe solenoid valve apparatus for controlling oil pressure for vehicular automatic transmission

An apparatus for controlling an oil pressure for a vehicular automatic transmission, said apparatus comprising:

• an accumulator connected to an oil passage which is in communication with each of hydraulic engaging elements for power transmission or speed changing;
• a regulator valve for regulating an oil pressure to be supplied to said hydraulic engaging elements;
• a first pressure control valve of electromagnetic type for controlling an output oil pressure of said regulator valve by causing an oil pressure to act thereupon;
• a second pressure control valve of electromagnetic type for controlling a back pressure of said accumulator;
• wherein a drain port of one of said first and second pressure control valves is connected to an oil passage on an output side of the other of said pressure control valves.