Patent ID: 7090614
Filing Date: 2006-08-15
Classification: F16H,Y10T

Abstract:
1. An automatic transmission comprising: a plurality of frictional engagement elements for constructing plural shift stages with combinations of engagement and disengagement thereof; a control portion for controlling the engagement and the disengagement of the frictional engagement elements by controlling supplied hydraulic pressure; a switching means for switching a mode to a learning mode for learning a precharge time; and a precharge time determination means activated by switching to the learning mode, the precharge time determination means determining the precharge time based on an input value including at least turbine rotational speed; wherein the precharge time determination means change the frictional engagement elements into an engagement side by maintaining the hydraulic pressure at the frictional engagement elements for determining the precharge time at a first precharge pressure by controlling the control portion while maintaining input shaft rotational speed of the automatic transmission when the automatic transmission is switched to the learning mode at a vehicle stop state; a first precharge time defined from a start of maintaining the first precharge pressure until variation of an input value deriving from a decline of the turbine rotational speed assumes significant is obtained; and wherein a second precharge time at a second precharge pressure is obtained to be set for learning by a predetermined formula.