Patent ID: 6368249
Filing Date: 2002-04-09
Classification: F16H,Y10S,Y10T

Abstract:
A method of controlling on-coming and off-going pressures supplied to on-coming and off-going clutches in a vehicle automatic transmission to downshift the transmission from a current speed ratio to a target speed ratio in response to a driver demand indication, the transmission having an input shaft coupled to receive engine output torque, the method comprising the steps of:monitoring a rate of change of the driver demand indication, and when the monitored rate of change exceeds a reference rate of change, indicating a high rate condition and storing the driver demand indication; setting and clearing a high demand indication based on said high rate indication and comparison of said driver demand indication to said stored indication; determining a downshift acceleration trajectory in dependence on said high demand indication, the downshift acceleration trajectory being set to a first calibrated value for achieving a smooth downshift when said high demand indication is cleared, and to a second calibrated value for achieving a quick and firm downshift when said high demand indication is set; and when a downshift is desired, controllably releasing the off-going clutch to allow the engine output torque to increase a speed of the input shaft toward a synchronous speed of the target speed ratio in accordance with the determined acceleration trajectory.