Line pressure control system for automatic transmission

Abstract

A line pressure control system for an automatic transmission wherein a shift range is determined by selectively engaging friction elements by means of a line pressure controlled according to an input torque of said automatic transmission. In the present invention, an engine output torque at the front stage of the automatic transmission is estimated from the operating condition. The input torque of the automatic transmission is calculated from the estimated engine output torque and the operation state of a torque converter. The calculated input torque of the automatic transmission is decreased during a predetermined time corresponding to an estimation response delay of the engine output torque after the engine is made in a no-load state, so as to properly control the line pressure.

Dependencies are inferred from the claim text.