Strategic Future: Powertrain Vision for Tomorrow

Authors

Toshihiro Hirai, Alliance Global Director, Corporate Vice President, Nissan Motor Co., Ltd., Kanagawa, Japan

Year

2017

Print Info

Fortschritt-Berichte VDI, Series 12, No 802

Summary

In order to realize a sustainable society, the mobility solution promoted by Nissan is based on two pillars. The first one is the widespread use of “Zero Emission” vehicles that produce no CO₂ emissions, and the second one is the thorough improvement of efficiency of vehicles equipped with internal combustion engines. Regarding the widespread use of “Zero Emission” vehicles, Nissan aims for 25% sales ratio by 2025. However, simple manufacture and sale of the zero-emission vehicles is only a first step towards the widespread use of “Zero Emission” vehicles. The key factors to spread “Zero Emission” vehicles are the innovation in technology and the comprehensive effort in the construction of social infrastructure, including development and installation of quick-charging stations. Nissan focuses on promoting zero-emission mobility through these activities. On the other hand, regarding the improvement of vehicles equipped with internal combustion engines, thermal efficiency of almost 40% will be achieved by generation change before 2020, but this is just a passing point. Due to the progress in lean-burn technologies, such as turbocharging EGR, turbocharging Lean, the roadmap to the 45% thermal efficiency of internal combustion engines has already been seen. In order to have the internal combustion engines as valuable power source in the future, continuous effort to improve thermal efficiency is expected. The key for further continuous improvement of thermal efficiency is supposed to be the reduction of cooling loss and implementation of high compression ratio. However high compression ratio needs a long stroke that requires a geometrically unreasonable shape for an automobile internal combustion engine. This is a major physical obstacle on the path to the high compression ratio engine. The link mechanism adopted by the new VC-T (Variable Compression-Turbo) engine developed by Nissan, in addition to enabling variable compression ratio functionality has the effect of changing the motion of piston link. Because of this effect, the physical obstacle on the path to high compression ratio can be overcome, and long stroke can be implemented geometrically and reasonably. In a sense, it can be said that by acquiring this link mechanism technology, internal combustion engines gain the evolution potential for another 100 years. Although it seems a big challenge to aim for further significant improvement after thermal efficiency of internal combustion engines exceeds 45%, there are already cases of such high thermal efficiency being achieved in marine engines, power plants, etc. One of the key points is how the internal combustion engines is used. By narrowing down operating conditions, such as constant load operation, limiting rotation speed, etc. further improvement can be expected. In autumn 2016, Nissan launched a new electric powertrain “e-POWER”, a new power unit combining a gasoline engine and a Battery Electric Vehicle (BEV) motor. The “e-POWER” has the potential to acquire a higher level of economic efficiency, because engine and tires are not directly connected mechanically; even when the internal combustion engine is used as engine for power generation it can operate with most effective rotation speed and load.