Abstract
The purpose of this study is to show the mechanism of power loss of the V-rubber CVT for motor scooters in which one surface of the pair in the driving pulley is free in rotation to the revolution of the shaft. The allowable transmittable torque was compared with that of traditional CVT where the power was transmitted though the both sides of surfaces of the driving pulley. Temperature change was observed around the drive and driven pulley with thermographic camera to investigate the effective traction area. In transmission, the change of shear strain on the rubber V-belt was also measured. In the test, the thrust force onto driven pulley was constant. Test results showed that the allowable transmittable torque of the CVT with free pulley was almost equal to that of the traditional one at the reduction ratio of low (i=0.6).In opposite, such result was not seen at the reduction ratio of high (i=1.7), in which the allowable transmittable torque of the CVT with free pulley was lower than that of the traditional one. Allowable transmittable torque agreed with the mechanism of the change of pitch radius according to the reduction ratio. Transmitting efficiency of CVT with free pulley (rotationally free pulley) was reduced 1.5％ at most compared with that that of traditional one when the applied torque was 12.5Nm. When the CVT was driven with free pulley, significantly elevated temperature was seen on the driving pulleys compared with that on traditional one. It was suggested that the remarkable slip was accompanied between belt and pulleys when the CVT was driven by rotationally free and fixed pulley on the driving shaft. The belt partly worked as like applied break near the surface contacted with free pulley. Comparatively large hysteresis loss due to shear deformation of the V-belt was consumed the transmitted power in driving pulley and decreased the transmitting efficiency of the CVT, when the CVT was driven by one rotationally free pulley.
Keywords: CVT, Rubber V-belt, Motor scooter, Transmitting efficiency, Power loss, Shear strain