Patent ID: 7419452

Claim:
A hydraulic control apparatus of a vehiclular automatic transmission which has two friction engagement devices belonging to a first group and a plurality of friction engagement devices belonging to a second group, and which is caused to establish a plurality of speed change stages of different speed change ratios by either one of an event of simultaneous engagements of the two friction engagement devices belonging to the first group and an event of simultaneous engagements of one of the friction engagement devices belonging to the first group and one of the friction engagement devices belonging to the second group, and which is caused to establish one of low vehicle speed-side speed change stages having greater speed change ratios than a predetermined speed change stage by engaging one of the friction engagement devices belonging to the first group and selectively engaging one of the friction engagement devices belonging to the second group, or is caused to establish one of high vehicle speed-side speed change stages having smaller speed change ratios than the predetermined speed change stage by engaging another one of the friction engagement devices belonging to the first group and selectively engaging one of the friction engagement devices belonging to the second group, the hydraulic control apparatus comprising: a fail-safe device to which oil pressures for engaging the friction engagement devices belonging to the second group are input, and which, if there occurs a failure where an oil pressure that causes simultaneous engagements of friction engagement devices belonging to the second group is output, stops supply of an oil pressure to a friction engagement device other than a priority-given friction engagement device belonging to the second group so that an oil pressure is output to the priority-given friction engagement device in accordance with predetermined degrees of priority, so as to establish one of the low vehicle speed-side speed change stages provided that a low vehicle speed-side speed change stage was established prior to the failure, and so as to establish one of the high vehicle speed-side speed change stages provided that a high vehicle speed-side speed change stage was established prior to the failure; and a switching device that changes a manner of input of the oil pressures to the fail-safe device and thereby change the degrees of priority based on a state of engagement of at least one friction engagement device belonging to the first group.