Study of power loss in chain continuously variable transmissions (CVT) with a geometric model

Abstract

CVT chains are widely used in vehicles because the slip between parts is small, which enables efficient power transmission. However, the intermittent motion of CVT chain pins entering and leaving the pulleys causes undesirable vibration in the whole chain, and affects the basic performance of the CVT. Therefore, it is important to investigate the influence of the geometrical specifications of the chain on this vibratory motion. This study focused on the pin-pulley slip length when the pins enter and leave the pulleys, and a mathematical model for the power loss of a CVT chain was developed. The validity of this model was verified and confirmed experimentally. In addition, the influence of the shape of chain components on power loss was also investigated. In particular, the influence of the position of the contact point between the pins and pulleys on power loss was investigated both theoretically and experimentally, and geometric parameters were optimized. As a result, the model formulated in this paper can be used to investigate measures for reducing CVT power loss.