Patent ID: 7524267
Filing Date: 2009-04-28
Classification: F16H,Y10T

Abstract:
1. A hydraulic control apparatus for a vehicular automatic transmission in which a plurality of shift speeds having different speed ratios are achieved by selectively engaging and disengaging a plurality of hydraulic frictional engagement devices, the hydraulic control apparatus comprising: a plurality of solenoid valves which respectively correspond to respective hydraulic frictional engagement devices of the plurality of hydraulic frictional engagement devices, which output hydraulic pressure directly to the respective hydraulic frictional engagement devices, and which are controlled to achieve any one of a plurality of shift speeds; and a switching valve device which includes wherein the plurality of hydraulic frictional engagement devices include a first hydraulic frictional engagement device that is engaged when a shift speed of the automatic transmission is lower than or equal to a predetermined shift speed, and is disengaged when the shift speed is higher than the predetermined shift speed, and wherein the hydraulic frictional engagement device that is disengaged when there is a failure that may cause tie-up includes the first hydraulic frictional engagement device.