Control system for a continuously variable v-belt transmission

Abstract

A continuously variable transmission, having a first pair of conical disks including an axially moveable disk and an axially non-movable disk whereby a running radius of the first pair of disks is changeable, a second pair of conical disks including an axially movable disk and an axially non-movable disk whereby a running radius of the second pair of disks is changeable, and an endless transmission element arranged to couple the first pair of disks with the second pair of disks. A first hydraulic actuator in operative connection with the movable disk of the first pair of disks for axially moving the disk, the first actuator having an inlet port, and a second hydraulic actuator is in operative connection with the movable disk of the second pair of disks for axially moving the disk, the second actuator having an inlet port. A first, four-quadrant controllable pump-motor has a first port connected to the inlet port of the first actuator, and a second port connected to the inlet port of the second actuator. The first pump-motor is operative to control a pressure ratio between the inlet ports of the actuators. A second, two-quadrant controllable pump-motor has an inlet port connected to a hydraulic medium source, and an outlet port connected to the inlet port of one of the actuators. The second pump-motor is operative to control tension in the endless transmission element. The output of the pump-motors is controlled and varied based on demand.