Control system and strategies of a double acting secondary sheave servo of a continuously variable transmission

摘要

A system and several strategies for controlling a continuously variable transmission with an improved secondary servo arrangement in order to efficiently provide sufficient clamping forces under high torque conditions. The valving means allowing for the relative movement of the second variable pulley's movable sheave includes a valving arrangement operative to regulate the secondary apply pressure at or below the hydraulic source pressure and distinct from the primary line pressure. Control signals are developed to prevent belt slip and to efficiently launch a vehicle, maintain the necessary primary to secondary clamping force ratio in overdrive conditions, and avoid overpressurization of the secondary servo for many vehicle operating conditions.