Development of Dual Stage Input Coupled Split Power Transmission Arrangements and their Characteristics

Continuously variable split power transmissions can offer a clutchless transition from reverse through neutral and into the forward driving mode. This is accomplished by splitting the input power between fixed ratio and variable ratio branches and recombining the power with a planetary set. Further, these transmissions offer seamless ratio changes throughout their range.

In contrast to these benefits, single stage designs can suffer from recirculated power, which increases the power level through the variator. This results in the need for a larger variator, which reduces efficiency and increases weight and inertia. In addition, single stage designs can experience high planetary member speeds as a result of a wide transmission ratio range.

Seven dual stage input coupled transmission models are developed in an effort to reduce the recirculated power and high planetary member speeds found in the single stage designs. Speed, torque and power models are developed in Matlab and Excel. Comparisons between the single and dual stage designs are presented Selection of the shift point between stages is discussed.