Patent ID: 6625532
Filing Date: 2003-09-23
Classification: F16H,Y10T

Abstract:
A solenoid control method for an automatic transmission, comprising:causing a current signal varied in a stepwise manner to pass through a filter having a predetermined transfer function, the current signal being inputted to a solenoid to drive a control valve which a working oil pressure on at least one frictional element of the automatic transmission is controlled to perform a predetermined shift operation by r educing the working oil pressure to release the frictional element; and inputting the filter passed current signal to the solenoid to drive the control valve, wherein the frictional element comprises a plurality of frictional elements and wherein the automatic transmission performs such a change-over shift operation that, while a first frictional element is clutched in response to a rise in the working oil pressure thereon, a second frictional element is released in response to a reduction in the working oil pressure thereon and wherein, when a down-shift operation is carried out with the first frictional element clutched, the current signal is caused to pass through the filter and, thereafter, is inputted to each solenoid to drive the corresponding control valves for the first and second frictional elements at a phase after a gear ratio has reached a desired value.