Patent ID: 6860830
Filing Date: 2005-03-01
Classification: F15B,F16H,Y10S,Y10T

Abstract:
1. A hydraulic control device for an automatic transmission that comprises a plurality of rotational elements and a plurality of hydraulically actuated friction elements to achieve a plurality of gear positions by engaging or disengaging the friction elements in predetermined combinations, and comprises oil pressure switches, which output signals indicating the level of oil pressure, in oil supply channels of predetermined friction elements to which is supplied a line pressure via regulating valves, said hydraulic control device comprising: an engagement state determining section that determines whether respective ones of the friction elements are being controlled to be engaged; and a protection control section that brings the corresponding regulating valves into a pressure regulating state such that an output from the regulating valves of the friction elements determined as being controlled to be engaged among the predetermined friction elements having the oil pressure switches is kept lower than the line pressure.