Patent ID: 8182397

Claim:
A hydraulic control apparatus for an automatic transmission, comprising: a first solenoid valve capable of supplying a first working fluid pressure to a hydraulic servo of a first friction engagement element; a second solenoid valve capable of supplying a second working fluid pressure to a hydraulic servo of a second friction engagement element; and a third solenoid valve capable of supplying a third working fluid pressure to a hydraulic servo of a third friction engagement element, wherein the second friction engagement element is engaged at higher shift speeds, and the hydraulic control apparatus attains a low shift speed, which is one of lower shift speeds, by engaging the first friction engagement element and the third friction engagement element, and attains a high shift speed, which is one of the higher shift speeds, by engaging the second friction engagement element and the third friction engagement element, wherein the first, second, and third solenoid valves are formed by normally closed type solenoid valves that do not output the first, second, and third working fluid pressures when being de-energized, and the hydraulic control apparatus further comprises: a preliminary shift speed switch valve, which is switched between a lower shift speed-side position where a first preliminary oil pressure for the hydraulic servo of the first friction engagement element is output, and a higher shift speed-side position where a second preliminary oil pressure for the hydraulic servo of the second friction engagement element is output, based on an engagement state of the second friction engagement element; and an oil pressure supply switch valve, which is switched between a normal-state position where the first, second, and third working fluid pressures can be supplied to the hydraulic servos of the first, second, and third friction engagement elements, respectively, and a failure-state position where the first and second preliminary oil pressures can be supplied to the hydraulic servos of the first and second friction engagement elements, respectively, and a line pressure can be supplied to the hydraulic servo of the third friction engagement element, during a failure that causes de-energization.