Dynamics of CVT chain drives

The dynamics of continuously variable transmissions (CVT) is characterized by the discrete structure of the chain, which causes the polygonal action. Hence the mechanical model contains each chain link and pulley as a separate body. While a chain link is part of a strand, only joint forces act on the chain links, whereas, in the contact situation, additional impulsive and frictional forces in the contact zones, between the chain link's rocker pins and the tapered surfaces of the pulleys, have to be taken into account. In order to calculate the contact forces, Coulomb's friction law as well as a time saving continuous approximation are applied. Due to the fact that the deformation of the pulleys has a decisive influence on the dynamics of the complete chain drive, the pulleys are described as an elastic multibody system. Simulation results show the influence of the cone pulley's deformation on the power transmission. A comparison of calculated and measured results verifies the model presented.