Performance simulation and verification of a continuously variable planetary (CVP) transmission

Abstract

Traction drive mechanisms and their fluids have been the subject of test, research and modeling for more than half a century. However, it cannot be said that traction drives have been in common use until the more recent commercialization of continuously variable transmissions (CVTs) in the automotive industry. Today the fruit from decades of development are seen by the introduction of toroidal and belt type CVTs in both conventional drivetrain and hybrid drivetrain vehicles. These up and coming applications require valid modeling and simulation methods which represent component interaction at the traction interface. The focus of this thesis is the implementation of a dynamic system simulation of a continuously variable planetary (CVP) transmission. Modeling of the traction interface is developed using rigid-plastic and elastic-plastic assumptions of traction fluid behavior. This general model is correlated with published fluid traction data at steady state operating conditions. The general traction model is further implemented within a dynamic system model and compared with test stand data from a CVP transmission. It is shown that the traction model correlates adequately with power transmission but poorly with secondary forces, specifically shift forces.