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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.

Prediction of power efficiency of gear boxes has become an increasingly important research topic since fuel economy requirements for passenger vehicles are more stringent, due to not only fuel cost but also environmental regulations. Under this circumstance, the automotive industry is dedicatedly focusing on developing a highly efficient gear box. Thus, the analysis of power efficiency of gear box should be performed to have a transmission that is highly efficient as much as possible at the beginning of design stage. In this study, a program is developed to analyze the efficiency of an entire gearbox, considering all components’ losses such as gear mesh, wet clutches, bearings, oil pump and so on. The analytical models are based on the formulations of each component power loss model which has been developed and published in many existing papers. The program includes power flow analysis of both a parallel gear-train and a planetary gear-train.

Shift feeling is one of the most important factors in developing a manual transmission. When drivers operate a manual transmission vehicle, they experience shift feeling which is classified into several factors such as shift smoothness, clarity, comfortability, sportiness, and so on. In the factors, shift smoothness characterized by double bump force is regarded as one of the most important things in experiencing shift feeling in Europe. The double bump force is reduced by attaching a constant mass damper which creates larger inertia of shift lever in control system of manual transmissions. However, it is possible to have side effects such as vibration of shift lever and clonk noise when employing the constant mass damper. In this research, a new control system with a variable inertia mechanism is designed and investigated to improve shift feeling while minimizing the side effects.