Patent ID: 6345548
Filing Date: 2002-02-12
Classification: F16H,Y10S,Y10T

Abstract:
A control system for an automatic transmission which comprises a power transmission mechanism incorporating a plurality of power transmission paths and a plurality of hydraulically operated frictionally engaging means for selecting said power transmission paths individually, a plurality of shift control valves for controlling supply of a hydraulic pressure to said hydraulically operated frictionally engaging means, and a forward/reverse hydraulic servomechanism for selecting either said power transmission paths which belong to a forward drive range or said power transmission paths which belong to a reverse drive range;wherein: said control system comprises a plurality of solenoid valves for supplying and draining a line pressure which is used to actuate said shift control valves and said forward/reverse hydraulic servomechanism for selecting said power transmission paths in a speed change control; said hydraulic pressure supplied to one of said hydraulically operated frictionally engaging means which establishes a certain speed ratio for said forward drive range is generated from the hydraulic pressure which is supplied into a forward drive servo-oil chamber of said forward/reverse hydraulic servomechanism; said control system further comprises first pressure detecting means and second pressure detecting means, said first pressure detecting means detecting the hydraulic pressure which is supplied to said forward drive servo-oil chamber for selecting said power transmission paths belonging to said forward drive range, and said second pressure detecting means detecting said hydraulic pressure which is supplied to said one of said hydraulically operated frictionally engaging means; and said control system determines whether said forward drive range is set correctly or not, based on a result of pressure detection by said first and second pressure detecting means.