Sliding performance of toroidal type CVT transmissions

Abstract

Toroidal Continuously Variable Transmissions (T-CVT) are mechanisms where torque is transferred through traction forces over heavily loaded lubricated elliptical contacts [1]. Lubricated traction is governed by the shear stresses of the lubricating film, which is directly related with the sliding (SRR) motion between disc and rollers. Therefore, it may be assumed that sliding is essential for the torque transmission. However, sliding is a power loss source, which means that a balance has to be found between traction and power loss as a function of sliding. Moreover, an additional power loss source appears in this kind of transmission at low sliding values known as spinning, which increases sliding on the contact area. The sliding motion control is carried out by means of clamping mechanisms in order to adapt the normal load as a function of the working conditions [2]. In this work, the sliding performance of a T-CVT is studied as a function of different variables such as torque and clamping force.