CVT dynamics : theory and experiments

We present a detailed experimental study of the pushing V-belt CVT dynamics and compare the experimental data withthe theoretical predictions of the Carbone, Mangialardi, Mantriota (CMM) model [G. Carbone, L. Mangialardi, G.Mantriota, The influence of pulley deformations on the shifting mechanisms of MVB-CVT, ASME Journal of MechanicalDesign 127 (2005) 103–113]. A very good agreement between theory and experiments is found. In particular it is shownthat, during creep-mode (slow) shifting, the rate of change of the speed ratio is a linear function of the logarithm ofthe ratio between the axial clamping forces acting on the two movable pulleys. The shifting speed is also shown to be proportionalto the angular velocity of the primary pulley, and to increase as the clamping force on the secondary pulley isincreased. Indeed, a growth of the clamping force increases the pulley bending and, therefore, in agreement with the CMMmodel, increases the shifting speed. The authors also propose a relatively simple differential equation to describe the creepmodeevolution of the variator. Few parameters appear in the formula, which may be calculated either experimentally ortheoretically. The results of this study are of utmost importance for the design of advanced CVT control systems and theimprovement of the CVT efficiency, cars’ drivability and fuel economy.