Patent ID: 8430794

Claim:
A hydraulic control apparatus of an automatic transmission which can supply a hydraulic oil pressure to at least one of hydraulic servos of a plurality of frictional engagement elements at a failure time when a de-energized condition is attained, comprising: a normally closed type first solenoid valve which can generate the hydraulic oil pressure; a normally open type second solenoid valve which outputs a first signal pressure for adjusting and controlling an oil pressure generated by an oil pump to a line pressure; a signal output device which outputs the line pressure or a modulator pressure, wherein the line pressure is reduced to a certain pressure, as a second signal pressure at a normal time, and causes the second signal pressure not to be output at the failure time; and an oil pressure switching device which, being switchable between a normal time position in which the hydraulic oil pressure from the first solenoid valve can be supplied to the hydraulic servo, and a failure time position in which the line pressure is supplied to the hydraulic servo, is switched to the normal time position by the first signal pressure and second signal pressure, which are input opposed to each other, being input, and switched to the failure time position by the first signal pressure being input and the second signal pressure not being input.