Patent attributes
There is provided a hydraulic pressure control device for an automatic transmission having a fail-safe mechanism to cope with an operation malfunction of electromagnetic valves. A first changeover valve that can be switched between a normal state where a drain port EX of each electromagnetic valve communicates with a predetermined drain destination and a failure state where the drain port EX and a predetermined hydraulic oil supply passage is disposed in a drain oil passage of clutches C1 and C2, and a second changeover valve that can be switched between a normal state where a supply port IN of each electromagnetic valve communicates with a predetermined hydraulic oil supply passage and a failure state where the supply port IN communicates with a predetermined drain destination is disposed in a supply oil passage of the other engaging elements. Even when an operation malfunction is caused in any of the electromagnetic valves, the corresponding changeover valve is operated to establish engagement of the clutches C1 and C2, thereby forming a given shift stage.
