Design considerations for improving transmission efficiency of the rubber V-belt CVT

This paper proposes design considerations for increasing transmission effic iency of rubber V-belt continuously variable transmissions (CVT). Herein, p ower loss is categorized into speed and torque losses. Since speed loss con tributes less than 4% of the total power loss in most operating conditions for the CVT used in motorcycles, only torque loss is considered in this stu dy. The mechanisms resulting in torque loss may be attributed to the hyster esis of belt bending, compression and shear as well as friction due to radi al motion of the belt. These loss mechanisms are studied on the basis of be lt motion characteristics. Design variables are then analyzed to identify t heir relationship with respect to transmission efficiency. These variables include external load, rotating speed and wedge angle of the pulley, speed ratio, pre tension, and thickness and tooth profile of the belt. In additio n, an experimental study is performed for verification of the proposed anal ytical approach.