Continuously improved

摘要

The continuously variable transmission (CVT) raises a tantalising prospect for hybrid powertrains. It provides a smooth, uninterrupted supply of drive, with some intriguing packaging options and almost infinite adjustment of the engine and electric machine across a wide range of ratios. The drawback with conventional belt and pulley-type CVTs is their efficiency. While dual-clutch transmissions (DCTs) are around 95% efficient and conventional automatics are in the low 90s, traditional CVTs are typically in the region of 85%.That's enough to knock a significant hole in the efficiency gains of a hybrid system. Fully toroidal CVTs, such as those developed by theTorotrak Group, may hold the answer, though.