CVT behaviour in "Slip mode" and "Creep mode" phases

This paper is concerned with the shifting dynamics of the Van Doorne type metal V-belt CVT transmission. A one-dimensional continuous model of the belt is proposed, the effect of band-belt interaction is discussed and two different friction models are considered: the Coulomb friction model and a visco-plastic friction model. The authors point out that the Coulomb friction model cannot explain correctly the shifting behavior of the variator during "creep-mode" phases (slow shifting maneuvers), but it could rather foresee the limiting traction capability of the belt or its behavior in "slip-mode" (rapid shifting maneuvers). Therefore a visco-plastic frÏction model is proposed to describe the CVT shifting dynamics also in "creep-mode". The model is able to detect the transition front "creep-mode" to "slip-mode". Moreover a simple relation is obtained to link the shift speed with the clamping forces ratio, the drive pulley rotating velocity, the torque load and the ictual value of the speed ratio.