Transient Mechanics of V-Belt Variators

A new theoretical approach to the unsteady mechanics of rubber V-belts provides an efficient tool for modeling the CVT behavior during the speed ratio shift. The analysis develops from a substantial reformulation of the mass conservation condition for the traveling belt, with reference to an elementary control dihedral between two planes intersecting on the pulley axis. The tension force and the elastic penetration of the belt are calculated along the arc of contact numerically, showing very different distributions in comparison with the steady state and indicating the possible presence of partial adhesive regions where the belt winds along arcs of spirals of Archimedes. Simple closed-form approximations are proposed, with the purpose of speeding up the calculation of the variator operative characteristics. The experimental comparison with some results by other authors is also carried out, showing an acceptable agreement as a whole.