JSAE 20119184 SAE 2011-01-2021 Study of Diesel Engine System for Hybrid Vehicles Tomomi Yamada, Hiroyuki Haga, Isao Matsumoto, and Terutoshi Tomoda Toyota Motor Corporation ABSTRACT In this study, we combined a diesel engine with the Toyota Hybrid System (THS). Utilizing the functions of the THS, reducing engine friction, lowering the compression ratio, and adopting a low pressure loop exhaust gas recirculation system (LPL-EGR) were examined to achieve both low fuel consumption and low nitrogen oxides (NOx) emissions over a wide operating range. After applying this system to a test vehicle it was verified that the fuel economy greatly surpassed that of a conventional diesel engine vehicle and that NOx emissions could be reduced below the value specified in the Euro 6 regulations without DeNOx catalysts. 1. BACKGROUND OF RESEARCH Recent years have seen growing demand for lower fuel consumption and cleaner exhaust emissions to help address environmental problems such as global warming and air pollution, and energy resource problems. Regulations concerning NOx and other components of exhaust gas emissions are becoming even more stringent, and there are also plans in the near future to enforce strict controls on CO 2 as well in the world. This research combined a diesel engine, which has greater potential for good fuel economy, with the THS. The synergy effect of fuel economy improvement in the diesel engine itself wa s examined. The aim was to achieve the low CO 2 emissions, not only during driving in urban areas, but also during highway driving at high speeds. Furthermore, the THS was utilized to reduce the level of exhaust gas emissions, which are an issue for diesel engines, as well as to reduce the cost of exhaust gas after treatment devices. Figure 1 shows the trends for CO 2 emissions that are produced depending on vehicle weight. The specific targets for the diesel engine were an average thermal efficiency of 42 %, which is equivalent to 90 g of CO 2/km and top of the D-segment class shown in the figure, and also to achieve the Euro 6 levels for exhaust gas emissions without DeNOx catalysts in the New European Driving Cycle (NEDC). 2. CONCEPT OF DIESEL ENGINE FOR USE WITH THS 2.1. ISSUES FOR COMBINING DIESEL ENGINE WITH THS The base diesel engine was a 2.2 liter, 4-cylinder shown in Fig. 2 and Table 1. A diagram of the power train system configuration is shown in Fig. 3. The THS has the following three functions to enhance engine efficiency: (1) automatic stopping of the engine during electric vehicle (EV) running and when the Common rail HPL-EGR systemPiezo injectorVariable nozzleturbocharger DOHC 4 valve Aluminum die-cast cylinder block4 cylinder2.2 L Diesel Common rail HPL-EGR systemPiezo injectorVariable nozzleturbocharger DOHC 4 valve Aluminum die-cast cylinder block4 cylinder2.2 L Diesel Fig. 2 3D drawing of base engineFig. 1 Target of this study NEDC300 200 100CO2(g/km) 1000 Vehicle weight (kg)1500 2000 2500 0Target: 90 g/kmAverage /g75e= 42% with modified THSGasolineD-segment DieselGasoline- HEV NEDC300 200100CO2(g/km) 1000 Vehicle weight (kg)1500 2000 2500 0Target: 90 g/kmAverage /g75e= 42% with modified THSGasolineD-segment DieselGasoline- HEVCopyright © 2011 Society of Automotive Engineers of Japan, Inc. and Copyright © 2011 SAE International SAE Int. J. Alt. Power. | Volume 1 | Issue 2 (December 2012) 560Downloaded from SAE International by Univ of California, Sunday, July 29, 2018 vehicle is stopped and idling, (2) recovery of kinetic energy during de celeration, and (3) control of the operating range of the engine (this is referred to as the electric CVT function) [1]. The electric CVT is a function that selects the most efficient operating range by controlling the engine speed with electric motor. However, a conventional diesel engine has high NOx emissions in the high load range where fuel economy is good. In addition, since di