Study on the transmission efficiency of electro-mechanical continuously variable transmission with adjustable clamping force

The purpose of this study is to analyze the EMCVT transmission efficiency. Power loss of a continuously variable transmission (CVT) consists of the energy consumed by an actuator and frictional energy loss in a CVT variator. The objective of studying electro-mechanical continuously variable transmission (EMCVT) is reducing the energy consumed by a CVT actuator. However, power loss resulting from frictional loss may increase owing to increases in the driven pulley clamping force. And then a simplified transmission efficiency model of an EMCVT was established to analyze the energy consumed by an electro-mechanical actuator and frictional energy loss. Under ECE (Economic Commission for Europe) and EUDC (Extra Urban Driving Cycle) driving cycles, the energy consumed by an EMCVT is compared with that consumed by an electro-hydraulic CVT (EHCVT). Comparison results indicate that the EMCVT transmission efficiency is lower than that of an EHCVT. Thus, an EMCVT with two actuator motors is proposed to reduce the frictional energy loss in the variator. Simulation results indicate that the transmission efficiency of the proposed EMCVT exceeds that of an EHCVT. The frictional energy loss is reduced by controlling the driven pulley clamping force, and this improves the EMCVT transmission efficiency.