Hybrid System and Emission Control System Development for the Lexus GS450h

Authors

Y. Sonoda, S. Abe, Toyota Motor Corporation, Toyota-shi

Year

2006

Print Info

Fortschritt-Berichte VDI, Reihe 12, Nr. 622

Summary

The original Toyota Hybrid System (THS) was first installed in the Prius and was introduced in 1997 as the world’s first mass-produced hybrid passenger car. THS has been continuously improved. In 2003, THS-II (marketed as Hybrid Synergy Drive ), was installed in a new larger Prius. In 2005, the Hybrid Synergy Drive was installed in two SUV’s: the Lexus RX400h and the Toyota Highlander Hybrid. With this hybrid system, both V8 engine power performance and family car class fuel economy with outstanding emission performance were achieved. In 2006, the Hybrid Synergy Drive line-up is expanded to a rear-wheel-drive system in the Lexus GS450h. This paper will explain the hybrid system of the GS450h, which achieves both 4.5-liter class power performance and compact class fuel economy, while meeting the most stringent SULEV emission standard. The GS450h uses a new V-6 3.5-liter gasoline engine (2GR-FSE), which adopted the D-4S (Direct injection 4-stroke gasoline engine system Superior version) system. This new stoichiometric direct injection system uses two fuel injectors (direct injection injector and port injector) for each cylinder. It is known that retarding the ignition timing during warm-up for reduction of cold-start emissions is limited by the engine torque fluctuation. We solved this engine torque fluctuation problem by formation of the optimal weak stratified air-fuel mixture with the D-4S system. Furthermore, by adopting Dual VVT-i (Variable intake and exhaust Valve Timing intelligence), the internal EGR gas was utilized to atomize the fuel spray, and the increase expansion ratio has made it possible to promote combustion of HC in the cylinders. As a result, cold-start emissions have been improved.

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