Transient dynamics of metal V-belt CVT: Effects of band pack slip and friction characteristic

A continuously variable transmission (CVT) offers a continuum of gear ratios between desired limits. The present research reports a detailed continuous one-dimensional transient-dynamic model of a metal V-belt CVT that accurately captures the various transient dynamic interactions occurring in the CVT system. Since a sundry of models mentioned in the literature ignore the influence of slip between the band pack and the belt element on the CVT performance, a unique model is outlined in this paper that aptly captures the slip-dynamics between the band-pack and the belt element. A considerable amount of effort in this paper is also dedicated towards modeling the inertial coupling between the belt and the pulley and studying its influence on the dynamic performance of a CVT. A metal V-belt CVT falls under the category of friction-limited drives as its performance and torque capacity rely significantly on the friction characteristic of the contact patch between the belt element and the pulley. A unique friction characteristic is also embedded into the CVT model to capture the effects of friction under dry and lubricated contact conditions. Simple trigonometric functions are introduced to capture the effects of pulley flexibility on the thrust ratio and slip behavior of the CVT. The results discuss the influence of band pack slip, friction characteristic, and pulley flexibility on the dynamic performance, the axial force requirements, and the torque transmitting capacity of a metal V-belt CVT drive.