Pressure-responsive control for a power train of the type having a torque converter equipped with a lockup clutch

摘要

A vehicle power train of the type including a torque converter for coupling an internal combustion engine to a transmission, and a hydraulically actuated lockup clutch for bypassing the torque converter and mechanically coupling the engine to the transmission. The transmission is of the type having a plurality of hydraulically actuated shift clutches for selecting a desired speed ratio and a desired direction of vehicle travel. During each shift of the transmission a pressure control valve arrangement acts to temporarily drop and then gradually increase the pressurized fluid delivered to the transmission and to the lockup clutch. Interposed between the pressure control valve arrangement and the lockup clutch, a delay valve automatically closes to place the lockup clutch in communication with a fluid drain when the output pressure of the pressure control valve arrangement drops upon shifting of the transmission, and reopens when the output pressure rises to a predetermined level. Thus is the lockup clutch disengaged at the time of each shift of the transmission and reengaged only after engagement of the selected transmission shift clutch.