Abstract: Metal belt CVT uses planetary gear train (PGT) to fulfill the shifting between forward gear and reverse gear. Due to adding one row of planetary gear set, the degree-of-freedom of double-row PGT increases, leading to the intensification of excitation and the whine noise of CVT in reverse gear. In view of these, a metal-belt CVT is studied in this paper, and it can be inferred through noise measurement and order analysis that gear whine in reverse gear stems from PGT. In order to lower the gear whine in reverse gear, a kinetic analysis is conducted on double-row PGT. A nonlinear model for pure torsional vibration is developed with consideration of gear backlash, and an optimization on the magnitude of gear modification is performed using genetic algorithm with the vibration acceleration variance of planetary gears as objective function. The gears optimized are verified by tests with a result showing that the gear modification optimized enhances the sound quality of the CVT

Key words: CVT, double-row PGT, nonlinear kinetic analysis, gear whine, gear modification, GA optimization