CVT Split Power Transmissions, A Configuration Versus Performance Study with an Emphasis on the Hydromechanical Type

Split power transmissions are often a viable power path for continuously variable powertrains. The planetary gear set is the central mechanism of these powerpaths which creates the possibility for numerous configurations. Determining the right configuration for a specific application can thus be complicated if the designer does not have an easy way to evaluate each configuration. This paper will address this issue. The different split power configurations are explored. Speed ratio and torque ratio formulas for the different configurations are introduced. An efficient and simple method to determine positive and negative power flow is also demonstrated. The development of tractive effort curves is discussed as a methodology to determine the theoretical performance of any configuration with an emphasis on the use of hydraulics as the variator.