Abstract
The novel mechanism CVT (Shaft Drive CVT, S-CVT) was developed by the authors. It transmits power by a traction drive same as the Half Toroidal CVT. S-CVT has parallel input/output shafts with conical disks and the idler shaft having conical rollers at both ends, which is placed perpendicularly to the input/output shafts. All disks and rollers can move along each axis directions, and these movements produce the ratio changing by the changes of the rotational radii of disks and rollers. The efficiency is the key evaluation function of CVT, but that of first prototype S-CVT was less than 90%. To improve the efficiency, the backup roller mechanism was devised. Its effectiveness was confirmed by the theoretical calculation and the experiment, and the efficiency of 95% was obtained by modified prototype S-CVT. The improvement of power to weight ratio, namely the increase of transmitted power with downsizing and lightening, is also important to apply the S-CVT to automobiles. To achieve this objective, the new concave disk, named the zero-spin disk, was devised. Because of the decreasing the spin angular velocity ratio and the contact pressure, this disk decreases the slip ratio and increases the torque capacity with downsizing. In this report, the efficiency of the zero-spin disk and roller was estimated by the calculation and the experiment. The theoretical efficiency of S-CVT using the zero-spin disk was calculated by considering the power transmission of the backup roller based on the traction curve. The calculated efficiency and speed efficiency were 87.7 to 92.7% and 99.0 to 99.4%, respectively. These efficiencies were also measured by the experiment using the prototype S-CVT equipped with the zero-spin disk and backup roller. The results of 79.6% to 95.2% and 99.0 to 99.1%, respectively, showed agreement with the calculated results.
