Synchronization and Stability of Speed-Ratio Control Servomechanism of A Double Cavity Half Toroidal CVT

Abstract

A double cavity half toroidal continuously variable power transmission transmits input torque through a pair of variable units and changes its speed ratio by controlling attitude angels of four power rollers. One power roller among them is controlled by a hydraulic servomechanism and the others are followed it under the control principle of equal force transmission. Synchronization of four power rollers is guaranteed by safety wires, however nonlinearities of friction force on the control pistons or pressure delay in hydraulic lines due to air mix or pipe length cause instability of the speed ratio servomechanism through the safety wires. This paper focuses the relation between the synchronization and stability of the CVT by making bond graph analyses and experiments, and shows design guidelines on the stabilization of the double cavity half toroidal CVT. © 1999, The Japan Society of Mechanical Engineers. All rights reserved.