System and method for controlling working hydraulic pressure for

Abstract

A system and method for controlling a working hydraulic pressure supplied to a mechanical power transmission applicable to an automative vehicle, the power transmission having a fluid power transmitting device such as a torque converter, in which a target duration of time during which a shifting operation occurs is retrieved from a table map according to an operating state of the fluid power transmitting device and is compared with an actual duration of time during which the shifting operation occurs. A characteristic value of the fluid power transmitting device is retrieved according to a speed ratio between input and output revolutional speeds of the fluid power transmitting device and is corrected and rewritten according to a magnitude relationship between the target and actual durations of times. An input torque of the mechanical power transmission can, thus, accurately be estimated using the learned characteristic value of the fluid power transmitting device without influence of environmental changes such as a change of altitude and/or variations of the characteristics of the transmission. Consequently, the setting accuracy of the working hydraulic pressure can be improved on the basis of the estimated input torque, thereby the control accuracy of the shifting operation can be improved.