Design Optimization of Input and Output Coupled Power Split Infinitely Variable Transmissions

The authors present an optimization procedure in designing infinitely variable transmission architectures, which allows them to achieve a significant reduction in power recirculation and, hence, an increase in mechanical efficiency. The focus of this paper is on infinitely variable transmissions used in off-highway vehicles and, in particular, on input and output coupled architectures. The optimized solutions have been analyzed in depth, with particular attention to the power flowing through the infinitely variable unit, which strongly influences the overall efficiency of the transmission. The major result of this study is that the so far neglected output coupled solution, if properly optimized, guarantees very good performance over the entire range of vehicle speed. The analysis then shows that the particular choice of either input or output coupled architecture by itself, or of a mixed solution, strictly depends on the specific application under consideration and that none of them should be discarded a priori.