Improvement of Efficiency of Shaft Drive CVT by Backup Roller

The authors developed the novel mechanism of CVT, the Shaft Drive CVT. The input shaft and output shaft with conical disks are parallel and an idler shaft having conical rollers at both ends is placed perpendicular to the input/output shafts. This idler shaft transmits torque from the input shaft to the output shaft and its linear motion produces the speed variation by changing the contact point between the input/output disk and the idler roller. To improve the efficiency of the Shaft Drive CVT, the backup conical roller mechanism was devised. It is mounted to the opposite side of the idler roller, and contact with the input/output disk and the backup disk as well as the idler roller. It transmits torque from the input/output disk to the idler roller through the backup disk, and the amount of transmitted torque is enlarged. Moreover, it reduces the bearing loss of the input/output shaft because it supports the axial force of idler roller at the opposite side. The result of theoretical calculation shows the improvement of the power-transmitted efficiency up to 6 points at e = 1. The effectiveness of the backup rollers was confirmed by the experiment, and the efficiency of 98.4% was obtained at e = 2. The magnitude of transmitted torque has increased 1.6 to 1.9 times compared with the case without the backup roller.Copyright © 2005 by ASME