Patent ID: 8075448

Claim:
An oil pressure control apparatus for an automatic transmission, wherein an oil pressure servo that engages and disengages one friction engagement element includes first and second hydraulic oil chambers to engage the friction engagement element with a low torque capacity when an oil pressure is supplied to the first hydraulic oil chamber or the second hydraulic oil chamber and with a torque capacity higher than the low torque capacity when an oil pressure is supplied to both the first and second hydraulic oil chambers, and the oil pressure control apparatus includes a failure solenoid valve that can output a failure signal pressure when a failure occurs and a failure switching valve that is switched from a normal position to a failure position on the basis of the failure signal pressure, and is constructed to secure supply of the oil pressure to an oil pressure servo for the friction engagement element which has been engaged before the failure switching valve is switched when the failure switching valve is switched, the oil pressure control apparatus comprising: a first switching valve that changes whether an oil pressure is supplied to or discharged from the first hydraulic oil chamber; a second switching valve that changes whether an oil pressure is supplied to or discharged from the second hydraulic oil chamber; and a switching solenoid valve that can output a switching signal pressure that switches the first switching valve, wherein the second switching valve is switched on the basis of the failure signal pressure, and an oil pressure can be individually supplied to and discharged from the first and second hydraulic oil chambers on the basis of the switching signal pressure from the switching solenoid valve and the failure signal pressure from the failure solenoid valve.