TORQUE-CONVERTER LOCK-UP CLUTCH CONTROL

摘要

A direct-coupling control system for a fluid gear in an automatic vehicular transmission, having a fluid gear provided with input and output members; a direct-coupling mechanism capable of connecting the input and output members of the fluid gear mechanically and directly by a locking force which is determined on the basis of a function of a difference between a working pressure and an internal pressure in the fluid gear; and a control valves provided between a pressure supply source and the direct-coupling mechanism and adapted to control the working pressure. The direct-coupling control system includes a pressure retainer valve for controlling the internal pressure in the fluid gear so as to reduce the same in accordance with an increase in a vehicle speed or an engine output.