Hydraulic pressure control system for hydraulically operated vehicle transmission

A system for controlling hydraulic pressure of a hydraulically operated vehicle transmission, comprising:

• vehicle operating condition detecting means for detecting parameters indicative of operating conditions of the vehicle;
• gearshift command output means for determining a gear ratio to be shifted to based on the detected parameters, to output a gearshift command;
• a plurality of frictional engaging elements for selectively establishing one gear stage in the transmission;
• and
• hydraulic pressure regulating means for regulating a supply of hydraulic pressure to at least one of said frictional engaging elements in response to the gearshift command, such that the determined gear ratio is established to transmit engine power to a vehicle wheel, said hydraulic pressure regulating means regulating the supply of hydraulic pressure to the at least one of said frictional engaging elements to decrease a time lag between an output of the gearshift command and a start of engagement of the frictional engaging element;
• wherein said hydraulic pressure regulating means includes:
• power transmission capacity detecting means for detecting a capacity of power transmitted from an input side to an output side of the frictional engaging element;
• and
• control means for controlling operation of said hydraulic pressure regulating means in response to the detected capacity of power detected by said power transmission capacity detecting means.