Kinematic considerations for reducing the circulating power effects in gear-type continuously variable transmissions

The present study deals with the kinematic analysis and design considerations of a continuously variable transmission (CVT) utilizing non-circular gear (NCG) sets with phase shift and summing differentials. The kinematic relationships are developed with emphasis on the effect of the different design parameters on reducing the circulating power inherent in this type of system. The study shows that a compromise has to be made between the number of non-circular gear sets to be used and the circulating power generated in the system. For the illustrative example of a 200 hp (149 kW) system it is shown that, for a gear ratio range from 1 to 4 and the considered characteristic curve on the non-circular gears, four sets of summing differentials are estimated to be required and the maximum instantaneous circulating power at the worst condition would be approximately 6 times the output power. The circulating power changes from its minimum of 1.5 to its maximum value with an average circulating power of 2.8 times the output power.