Abstract
This paper proposes a theoretical approach to the transient behaviour of metal belt CVTs during the speed ratio change. The mass conservation relationship is formulated considering an elementary control volume and balancing the inside mass increase with the total mass flux through the control surface. The plate deflection is calculated by a variational approach, based on the principle of virtual work, where the restoring effect of the centrifugal forces is also taken into account. The mechanical behavior of the belt-pulley coupling is strongly dependent on both the belt deformation and the pulley bending wall. Two different modes can be recognized in the CVT behavior, depending on the shift velocity: a "slip" mode for rapid shift, where the belt sliding along the radial direction is prevalent, and an "adhesive" mode for slow shift, where sticking belt trajectories develop with spiral shapes.
Keywords: Metal Belt CVT, Pulley Bending, Belt Deformation, Speed Ratio Shift