Development of Supercharged Direct-injection Two Stroke Engine with Intake and Exhaust Valve for Series Hybrid (2nd Report)　- To Realize Lean Burn -

The two-stroke engine has a small displacement and high performance, and therefore saves space when the engine is installed in a vehicle. Thus, the application of two-stroke engines to HEVs is a very effective means of reducing vehicle weight and securing engine space. On the other hand, the unfired element increases in the exhaust gas with a two-stroke engine because the air-fuel mixture is blown through to the exhaust system during the scavenging process inside the cylinder. Moreover, combustion becomes unstable due to the large amount of residual burnt gas in the cylinder. To solve these problems, we propose a two-stroke engine that has intake and exhaust valves that injects fuel directly into the cylinder. We previously reported the engine shape and the method that can provide high scavenging efficiency and stable combustion in such a two-stroke engine as the first report. In this second report, we report on the results of our research to improve fuel efficiency and realize low emission while achieving high performance suitable for two-stroke engine. In order to improve fuel efficiency, the amount of burned gas was set to an appropriate amount by optimizing the timing of the intake and exhaust valves and the lift amount, and lean combustion was realized by utilizing the excellent ignitability associated with the high temperature in the cylinder. In addition, it is reported that THC emission, which is a particular problem in two-stroke engines, is reduced by preventing unburned gas from blowing into the exhaust pipe by adopting the in-cylinder direct injection.