Development of a Generalized Model to Predict Efficiency of Electrified Power Transmission Considering Optimal Driving Efficiency

Over the last decade the electrified powertrain has been expanded due to strict fuel efficiency regulations, which leads to the development of various powertrain systems. It is recent trend to improve the overall system efficiency in which various power sources such as ICE and motor are combined with a simple gearbox. Accordingly, it is becoming indispensable to analyze the efficiency of the entire system from the initial stage of system development. In this study, a generalized numerical model is developed to predict the loss of gearbox under various power sources and power flows. This numerical model newly applied generalized equations for additional various power transmissions, including the previously verified power loss equation of gearbox components. In addition, for a reasonable and objective efficiency comparison between gearboxes, the optimal operating points are calculated in consideration of the overall powertrain system efficiency covering the total vehicle load. The average efficiency at the optimal operating points is introduced as the efficiency index of the gearbox. The developed model is employed to predict the efficiency of a HEV system and a EV system. The results are discussed from various perspectives.