Dynamic and tribological analysis of a toroidal continuously variable transmissions

Abstract

The continuously variable transmission investigated in this paper works with contacts in the elastohydrodynamic regime of lubrication, thus the tangential forces between elements are transmitted through the shearing the lubricant film. The behaviour of the lubricant film when subjected to shear depends of the nature of the lubricant and the relative motion between the contacting surfaces. In this paper, a non-Newtonian behaviour is assumed for the lubricant while the relative motion is determined for every point on the contact area by kinematic methods. The net tractive force in the sliding direction and the spin torque are evaluated and from these the power losses in the contacts are calculated. The dynamic behaviour of the device is evaluated taking into account the behaviour of the lubricant as extracted from traction measurements. A simplified method for the evaluation of the dynamic response of the device to a rapid variation of the resistive torque is presented. The results show the importance of the rheological behaviour of the lubricant, measured by the slope of the linear region of lubricant traction curves.