The main drivers for powertrain electrification of two-wheelers, motorcycles and ATVs are increasingly stringent emission and noise limitations as well as the upcoming demand for carbon neutrality. Two-wheeler applications face significantly different constraints, such as packaging and mass targets, limited charging infrastructure in urban areas and demanding cost targets.
Battery electric two wheelers are the optimal choice for transient city driving with limited range requirements. Hybridization provides considerable advantages and extended operation limits. Beside efficiency improvement, silent and zero emission modes with solutions allowing fully electric driving, combined boosting enhances performance and transient response.
In general, there are two different two-wheeler base categories for hybrid powertrains: motorcycles featuring frame-integrated internal combustion engine (ICE) and transmission units, coupled with secondary drives via chain or belt; and scooters equipped with integral single-sided swingarm power units, featuring an internal combustion engine with a continuously variable transmission (CVT).
A promising hybrid scooter powertrain concept allows combining efficiency improvement with additional benefits of electric driving – utilizing a power-split electrified continuously variable transmission (e-CVT) with a planetary gearset. In this hybrid concept, the planetary gearset seamlessly manages the modulation of the transmission ratio interacting with the e-motor’s operation modes. A hybrid strategy, considering the power demand and battery state of charge was developed concurrently with the implementation of all driving modes.
The paper explains the e-CVT-layout, the selection criteria of ICE and e-motor-performance, while addressing the applicable hybrid operation modes. The evaluation of performance and efficiency had been conducted in the relevant drive cycle sections.