电装第四代共轨SAE介绍2013-01-1590

ABSTRACTDiesel injection equipment is required to be more accurateand higher in pressure to meet the increasingly strictemission, fuel consumption regulations and higher engineperformance. It also needs to achieve a number ofrequirements such as robustness against diversified marketfuels, easy installation to engine, etc. DENSO has beenworking to develop 4th Generation Common Rail System(G4CRS) according to the following four concepts which areseemingly conflicting, since several years.

1. Increase injection pressure from 200 MPa to 250 MPaaiming at better spray characteristics

2. Develop a new control valve for injector to achieve zeroclearance leakage and minimized switching leakage aiming athigher fuel robustness, higher fuel efficiency, smaller pumpsize.

3. Locate the injector actuator and control valve near thenozzle to reduce the mass of movement aiming at higherinjection responsiveness accuracy.

4. Develop a new pump with pre-stroke control valve aimingat higher response for pressure control and less fueldeterioration.

This paper reports the G4CRS concepts, structure andperformance combining high pressure up to 250 MPa as wellas excellent fuel robustness and reliability. NOx and PMemission were reduced drastically and Fuel consumption wasimproved.

1. INTRODUCTIONVarious countermeasures against global warming have beenpromoted worldwide based on Kyoto Protocol in 1997.Further improvement of diesel engine efficiency as well asincreased bio fuel content is required to limit global warmingby less carbon dioxide (CO2) emissions. In this context thedevelopment of the injection equipment in combination withthe combustion process is a landmark in significantlyimproving the diesel engine capabilities. Presently thanks toits flexibility and multi injection capability the Common Rail

4th Generation Diesel Common Rail System:Realizing Ideal Structure Function for Diesel Engine2013-01-1590

Published04/08/2013

Shuichi MatsumotoDENSO Corp

Charles KloseDeere & Company

Jason SchneiderJohn Deere & Co

Noriaki NakaneDENSO Corp

Daiji UedaDENSO International America, Inc.

Shigeyuki KondoDENSO Corp

Copyright © 2013 SAE Internationaldoi:10.4271/2013-01-1590

THIS DOCUMENT IS PROTECTED BY U.S. AND INTERNATIONAL COPYRIGHTIt may not be reproduced, stored in a retrieval system, distributed or transmitted, in whole or in part, in any form or by any means.Downloaded from SAE International by Univ of Southern Queensland, Monday, April 08, 2013 05:13:58 AMSystem (CRS) has become the mainstream of fuel injectionequipment.

As emission and fuel consumption regulations on dieselvehicles are getting harder and harder, diesel fuel injectionequipment is required to be more accurate and allow forhigher injection pressure, creating a tendency of developingmore complex and more accurate CRS. Figure 1 shows theroadmap of DENSO common rail system.

Figure 1. DENSO CRS Development RoadmapIn order to meet these market demands, there are variousrequirements the CRS needs to fulfill. As the injection hasdirect effects on the engine combustion characteristicsincreasingly degree of injection flexibility, injectionaccuracy, fine atomization spray need to be realized whileproviding excellent ageing stability, fuel robustness, reducedenergy loss, pressure preservation in ISS and easy installationon engine.

DENSO launched the world's first serially producedelectronically controlled CRS in 1995 and since then hasbeen actively involved in developing advanced diesel enginetechnologies. In the year 2005, 10 years after launch, weestablished a completely new CRS concept to meet apparentand potential customer needs in the field. In the followingsections, the design concept leading to DENSO's new CRSgeneration are described.

2. INJECTOR DEVELOPMENTInjector is required to meet many different needs asmentioned above. First of all, the development target value ofinjection pressure is important in terms of compliance withemissions regulations and engine performance - actually anincrease from 200MPa to 300MPa is considered.[3,4]Increased pressure allows spray droplets to be finer so as torespond to emissions regulations in the future. The biggestchallenge to launch the injector which is capable of highpressure injection into the markets around the world in thefuture will be improvement in fuel robustness. That's one ofthe main driver deciding the following design targets andconstraints.

2.1. Improvement in Fuel Robustness byZero Clearance Leakage and MinimizedSwitching LeakagePossible concerns about ultra high pressure CRS can bederived from the properties of diversified fuels. Based on theextracted world fuel information and the injector designtargets shown in the table 1 were identified. As various kindsof fuels are available, some fuels may have bad properties. Ifbad fuels are used, “deposit are formed and adhere to theinjector”, “wear and seizure occur in the sliding portions”,“rust is formed”, resulting in injector functional failure. As astrategy of designing fuel robust injector against bad fuels,zero clearance leakage and minimized switching leakage willbe effective to lower fuel temperature and reduce the flowrate.