Abstract:

As the existing continuously variable transmissions ( CVTs) cannot transmit high torque,first,a design scheme with input coupled type for transmitting high torque is put forward. Then,the connection modes of the 2K-H type differential gear train and the double-row differential gear train with the fixed-axis gear train and with the input axis are analyzed. By using the input power-distributing ratio as an evaluation index,it is found that,as compared with the 2K-H type differential gear train,the double-row differential gear train is of larger interval of input power-distributing ratio and more compact structure. According to these findings,a novel CVT mechanism is designed,which is composed of a dual-cavity half-toroidal continuously variable unit,a fixed-axis gear train and a double-row differential gear train in a closed loop. Moreover,the performance indexes describing the torque transmission of the novel CVT,namely the split ratio of input torque and the ratio of output torque to input torque,are derived,and the variation trends of the transmission ratios of the fixed-axis gear train and the shifting mechanism of the double-row differential gear train,which benefit the high torque output of the novel CVT,are discussed. Finally,the correctness of the variation trends of the two transmission ratios is confirmed by numerical examples.

Key words: continuously variable transmission, input coupled type, performance index, transmission ratio