The Control Theory and Implementation Method of Clamping Force on Metal Belt CVT

The model of speed ratio and clamping force upon driving and driven belt wheel in continuously variable transmission (CVT) system is built in this paper, which is based on the structure of CVT and electro-hydraulic control scheme; according to the method of single-pressure hydraulic control circuit, the relationship between the pressure of driving and driven cylinder and the speed ratio of CVT when unit torque is transferred will be derived, and thus the PID control model of clamping force upon driving and driven belt wheel is to be established. It is proved by test-bed experiment that better working stability and longer-time reliable working performance will be provided by the electro-hydraulic control system of CVT, and the model of clamping force and control scheme based on PID theory can follow the variation of target speed ratio and target clamping force better, which will certainly guarantee vehicle´s starting and running and implementation of engine´s ideal speed and be able to satisfy the necessities of actual control.