Designing a Super-Fast Prius: Systematic Design of Multispeed eCVT via Virtual Design Space

Abstract

Despite its excellent fuel economy (FE), the Toyota Prius has a poor acceleration performance (AP). Its performance is improved by using bigger propulsion components and a multi-speed transmission for SUVs and high-performance models. Nevertheless, this performance improvement is limited as the input-split architecture cannot use its small motor/generator for motoring. To overcome this shortcoming, this paper suggests adding fixed gear (FG) modes to the Prius system. FG modes can boost the AP thanks to the power amplification resulting from using both motor/generators as motors. With a focus on the architectural design of FG modes, all potential placements of clutches and gears are enumerated. The analysis of candidate physical FG modes revealed a redundancy as one transmission ratio (ω <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><i>E</i></sub> /ω <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><i>O</i></sub> ) can be created by different clutch and gear pairs. To omit this redundancy, this paper conducts the architecture search within the concise virtual design space. The virtual design space consists of all different combinations of candidate input-split and virtual FG architectures. The performance is evaluated within the virtual design space and virtual designs with good FE and AP and feasible gradeability are selected. An optimal virtual design that is drastically faster (67.82 % faster) than the single-mode Prius and with a better FE (5.56 % higher) is selected and converted into fifty physical multi-speed architectures.