Innovative hybridization of CVT drivetrains

Sales of hybrid vehicles are becoming more significant every year. The introduction of the Toyota Prius almost 10 years ago, changed the spectrum in the automotive powertrain market importantly. The Toyota Prius operates using an electric CVT principle, whereas the Honda Civic IMA uses a mechanical pulley-type CVT in parallel with an electric motor. The CVT principle in the Prius excels in driving agility and fuel economy but is relatively costly particularly as of dual electric machines and high power electronics and battery pack. This is one of the reasons why this hybrid system is now introduced in the higher class vehicles (D, E and F segment). The Honda IMA system uses mature and low cost pulley-CVT technology in combination with a much smaller electric machine. This saves cost though overall performance is penalized especially when combined with a down-sized engine. Drivetrain Innovations is developing a hybrid drivetrain module that can be fitted in a pulley-type CVT transmission housing and combines the benefits of both the Prius and IMA hybrids, i.e. highperformance and low cost. This makes cost-effective hybridization of B and C segment vehicles possible. The new hybrid module integrates a novel "mechanical motor/generator" with an "electric motor/generator," inside a standard pulley-CVT, see Figure 1. When fitted to state-of-the-art CVT technology the drivetrain is estimated to achieve a fuel economy close to 3L/100km for B and C segment vehicles on the JP 10-15 cycle. The mechanical M/G ensures high power engine boosting and the small electric M/G enables electric driving at low speeds. This paper describes the developments concerning the hybrid application for CVTs as they are particularly suited for the Japanese automotive market.