Patent ID: 6085136
Filing Date: 2000-07-04
Classification: F16H,Y10T

Abstract:
A lockup control system for a vehicle power train including an internal combustion engine; an automatic transmission; a torque converter interposed between the engine and the transmission; a torque converter lockup clutch interposed between the engine and transmission and having a complete engagement lockup mode for vehicle operation during deceleration wherein the lockup clutch is completely engaged to prevent the torque converter from slipping, and a slip lockup mode wherein the lockup clutch is incompletely engaged to restrain the torque converter from slipping; sensors providing input signals indicative of vehicle power train operating parameters; a controller receiving the input signals and processing the same in accordance with predetermined logic rules to issue an output command signal; and a lockup actuator operative responsive to the output command signal to adjust lockup clutch engagement force with which the lockup clutch is engaged to a commanded value, wherein:the controller determines the commanded value as a function of a deviation between a current value of slip speed within the torque converter and a desired value thereof;the controller sets a limit to the determined commanded value during operation of the lockup clutch in the slip lockup mode;wherein said controller defines said limit by a lower limit value of a range of values of lockup clutch engagement force predetermined for operation of the lockup clutch in the slip lockup mode.