A Variable-Speed Traction Drive with Internal Spherical Disks : Mechanism of Traction Drive and Method for Calculating Power Transmission Efliciency

The mechanism of a continuously variable speed traction drive (CVT) with two internal spherical disks was introduced. Equations were derived for calculating changes in speed ratio and power losses caused by the spinning motion at the contact surface. The effective traction force between contact surfaces with an elliptical shape was calculated using the traction coefficient curves obtained by two roller tests and the resulting empirical equations. In this calculation, the effective pressure was utilized instead of a Hertzian mean pressure. The spinning loss was divided into torque and speed losses at the contact surface. Numerical calculations were performed to estimate the losses produced in a trial CVT with a capacity of about 5 kW at 1800 rpm. The equations developed are aplicable to any other type of CVT after certain modifications.