Development of a Simulation Technique for CVT Metal Pushing V-Belt with Feedback Control 2004-01-1326

A pushing metal V-belt is the core part of a Continuously Variable Transmission (CVT). Knowing its behavior and internal forces is key to defining the operational conditions of the transmission. To maintain the steady-state speed ratio, an optimal pulley thrust is required. If the force is too large, the transmission efficiency is affected; if too small, the belt slips. Because so far the optimal value of the pulley thrusts had been derived from physical test, analytical understanding of this effect was lacking.

In the physical test, controlled thrust is applied to one of the pulleys, further complicating the simulation process. This article describes a new simulation technique developed to resolve this problem. To predict the motion of the belt, a simulation was created, using a multi-body analysis code with a feedback control applied to the pulley thrust. The analysis model consisted of numerous elements, a multi-layer ring, and a pulley set. The ring was modeled as customized state equations, including elongation and bending effects, as well as block-ring normal and friction forces. Contact elements were used to simulate contact and friction at predefined locations. Rigid pulleys were used, but pulley conical stiffnesses were considered. With this technique, not only was the ratio of thrust between the pulleys in the transmission successfully predicted, but the variation of the internal forces during the transient phase of a speed ratio change was also made possible. Vector visualization of the forces acting on both pulleys made clear the influence of the pulley conical stiffnesses.