Optimized parameters sizing between EVT and THS used for hybrid electric vehicles

Both of the electric variable transmission (EVT) and Toyota Hybrid System (THS) can be used as an power split device in the hybrid electric vehicles (HEVs). They can make the internal combustion engine (ICE) independent of the road loads and run in the high efficiency area to reduce the fuel consumption as well as emissions. However, the planetary gears of THS make serious vibration and noise, limiting the further application of THS in HEVs. This paper studies the parameters sizing between EVT and THS to make the EVT instead of THS. In order to obtain the better driving properties of EVT, an optimized parameters sizing is established by placing a speed-increase gear and a deceleration gear in the system. Finally, the simulation comparison of fuel consumption and dynamic properties between THS and EVT are built, which shows the rationality of the optimized parameters sizing method.