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

In recent years there has been an increased interest in the continuously variable split power transmissions as these drive units are capable of vehicle launches and directional changes without using clutches. These tasks are accomplished by appropriately splitting power between the fixed mechanical and variable ratio branches. The power is recombined at the transmission output. A properly designed split power transmission arrangement will improve vehicular agility and reduce variator size.

This paper provides characteristics of six single stage input coupled continuously variable toroidal split power transmission arrangements. Mathematical equations are derived for speed, torque and power. A computer program that utilizes the capabilities of Matlab is developed. The program calculates the required fixed and variable branch gear ratios for the predefined variator, planetary and overall transmission ratios. Further, the program produces numerical results and visual plots of relationships between transmission ratio, variator ratio, planetary ratio, and the power flow through the transmission branches. Characteristics of the transmission arrangements are analyzed and compared and documented. Suggestions for practical use of the split power transmissions are given and methods to reduce the recirculated power through the variable and fixed branches are provided.