Electro-mechanical Transmission Ratio Shifter of Rubber Belt Continuously Variable Transmission for Motorcycle Applications

Abstract

This paper introduces an electro-mechanical transmission ratio shifter of rubber belt continuously variable transmission (CVT). The CVT basic system consists of primary pulley (input), secondary pulley (output) and a rubber belt. This belt connects the primary pulley to the secondary pulley and tranfers the speed and torque from the input to output by means of belt-pulley contact friction. Each pulley set has one fixed and one sliding pulley sheaves. The axial movement of primary sliding pulley sheave is actuated by an electro-mechanical system consisting of the DC servomotor, actuator gears and cam mechanism, while the secondary sliding pulley sheave is constantly pushed by contra spring to mantain the overall belt tension and to prevent belt slip. By controlling the DC motor revolution, the axial position of the primary sliding pulley sheave can be adjusted to vary the primary belt-pulley contact radius, which in turn mechanically changing the secondary belt-pulley contact radius and finally changing the transmission ratio. The relationship between motor revolution, primary belt-pulley contact radius, secondary belt-pulley contact radius and transmission ratio can be determined based on mathematical equations of variator geometry, the total gear ratio of the actuator gears and cam mechanism