Theoretical Model of Metal V-Belt Drives During Rapid Ratio Changing

Today the use of metal V-belt (MVB) on C.V.T. (continuously variable transmission) based systems is the rule in automotive applications. The great advantage of this kind of belt is the capability to resist the moving half-pulley’s high axial thrust necessary to transmit the large torque involved. This paper suggest a theoretical model of belt’s behavior during rapid ratio speed changes with the aim to represent the dynamical response of the system during the transient condition. The paper proposes a relation which correlates some easily measurable macroscopic quantities: axial thrust, torque transmitted and belt’s tensions on the slack and tight side. The metal V-belt consists of wedge-shaped plates that are supported by a flexible band, of which there are two types: the metal V-belt without clearance and the metal V-belt with clearance between plates. Our investigation is carried out for the first type of belt and under the hypothesis that there is a rapid variation of speed ratio. The result, that has been reached, allows to predict the behavior of the system and simplifies the planning of continuously variable transmission with metal V-belt.