Diesel distributor fuel-injection ?· Diesel distributor fuel-injection pumps ... the diesel fuel-injection systems from Bosch. The very high level of precision inherent in the distributor pump means
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Dieseldistributor fuel-injection pumps
Robert Bosch GmbH, 1999Postfach 3002 20,D-70442 Stuttgart.Automotive Equipment Business Sector,Department for Automotive Services,Technical Publications (KH/PDI2).
Editor-in-Chief:Dipl.-Ing. (FH) Horst Bauer.
Editors:Dipl.-Ing. Karl-Heinz Dietsche,Dipl.-Ing. (BA) Jrgen Crepin,Dipl.-Holzw. Folkhart Dinkler,Dipl.-Ing. (FH) Anton Beer.
Author:Dr.-Ing. Helmut Tschke, assisted by theresponsible technical departments of Robert Bosch GmbH.
Presentation:Dipl.-Ing. (FH) Ulrich Adler,Berthold Gauder, Leinfelden-Echterdingen.
Photographs:Audi AG, Ingolstadt andVolkswagen AG, Wolfsburg.
Technical graphics:Bauer & Partner, Stuttgart.
Unless otherwise specified, the above persons areemployees of Robert Bosch GmbH, Stuttgart.
Reproduction, copying, or translation of thispublication, wholly or in part, only with our previous written permission and with source credit.Illustrations, descriptions, schematic drawings, andother particulars only serve to explain and illustratethe text. They are not to be used as the basis fordesign, installation, or delivery conditions. Weassume no responsibility for agreement of thecontents with local laws and regulations.Robert Bosch GmbH is exempt from liability,and reserves the right to makechanges at any time.
Printed in Germany.Imprim en Allemagne.
4th Edition, April 1999.English translation of the German edition dated:November 1998.
Combustion in the diesel engineThe diesel engine 2
Diesel fuel-injection systems: An overviewFields of application 4Technical requirements 4Injection-pump designs 6
Mechanically-controlled (governed)axial-piston distributor fuel-injectionpumps VEFuel-injection systems 8Fuel-injection techniques 9Fuel supply and delivery 12Mechanical engine-speed control (governing) 22Injection timing 29Add-on modules and shutoff devices 32Testing and calibration 45Nozzles and nozzle holders 46
Electronically-controlled axial-piston distributor fuel-injectionpumps VE-EDC 54
Solenoid-valve-controlled axial-piston distributor fuel-injectionpumps VE-MV 60
Start-assist systems 62
Dieseldistributor fuel-injection pumps VE
The reasons behind the diesel-poweredvehicles continuing success can bereduced to one common denominator:Diesels use considerably less fuel thantheir gasoline-powered counterparts.And in the meantime the diesel haspractically caught up with the gasolineengine when it comes to starting andrunning refinement. Regarding exhaust-gas emissions, the diesel engine is justas good as a gasoline engine withcatalytic converter. In some cases, it iseven better. The diesel engines emis-sions of CO2, which is responsible forthe green-house effect, are also lowerthan for the gasoline engine, althoughthis is a direct result of the dieselengines better fuel economy. It was also possible during the past few yearsto considerably lower the particulateemissions which are typical for thediesel engine. The popularity of the high-speed dieselengine in the passenger car though,would have been impossible without the diesel fuel-injection systems fromBosch. The very high level of precisioninherent in the distributor pump meansthat it is possible to precisely meterextremely small injection quantities tothe engine. And thanks to the specialgovernor installed with the VE-pump inpassenger-car applications, the engineresponds immediately to even the finestchange in accelerator-pedal setting. Allpoints which contribute to the sophisti-cated handling qualities of a modern-day automobile.The Electronic Diesel Control (EDC)also plays a decisive role in the overallimprovement of the diesel-enginedpassenger car.The following pages will deal with thedesign and construction of the VE distri-butor pump, and how it adapts injectedfuel quantity, start-of-injection, andduration of injection to the differentengine operating conditions.
The diesel engine
Diesel combustion principleThe diesel engine is a compression-ignition (CI) engine which draws in air and compresses it to a very high level.With its overall efficiency figure, the dieselengine rates as the most efficient com-bustion engine (CE). Large, slow-runningmodels can have efficiency figures of asmuch as 50% or even more. The resulting low fuel consumption,coupled with the low level of pollutants inthe exhaust gas, all serve to underlinethe diesel engines significance. The diesel engine can utilise either the 4- or 2-stroke principle. In automotiveapplications though, diesels are practi-cally always of the 4-stroke type (Figs. 1and 2).
Working cycle (4-stroke)In the case of 4-stroke diesel engines,gas-exchange valves are used to controlthe gas exchange process by openingand closing the inlet and exhaust ports.
Induction strokeDuring the first stroke, the downwardmovement of the piston draws in un-throttled air through the open intake valve.
Compression strokeDuring the second stroke, the so-calledcompression stroke, the air trapped in thecylinder is compressed by the pistonwhich is now moving upwards. Com-pression ratios are between 14:1 and24:1. In the process, the air heats up totemperatures around 900C. At the endof the compression stroke the nozzle in-jects fuel into the heated air at pressuresof up to 2,000 bar.
Power strokeFollowing the ignition delay, at the begin-ning of the third stroke the finely atom-ized fuel ignites as a result of auto-igni-tion and burns almost completely. Thecylinder charge heats up even furtherand the cylinder pressure increasesagain. The energy released by the igni-tion is applied to the piston.The piston is forced downwards and thecombustion energy is transformed intomechanical energy.
Exhaust strokeIn the fourth stroke, the piston moves upagain and drives out the burnt gasesthrough the open exhaust valve. A fresh charge of air is then drawn inagain and the working cycle repeated.
Combustion chambers,turbocharging and superchargingBoth divided and undivided combustionchambers are used in diesel engines
Combustion in the diesel
Combustion in the dieselengine
Principle of the reciprocating piston engine
TDC Top Dead Center, BDC Bottom Dead Center.Vh Stroke volume, VC Compression volume,s Piston stroke.
(prechamber engines and direct-injec-tion engines respectively).
Direct-injection (DI) engines are more ef-ficient and more economical than theirprechamber counterparts. For this rea-son, DI engines are used in all commer-cial-vehicles and trucks. On the otherhand, due to their lower noise level,prechamber engines are fitted in passen-ger cars where comfort plays a more im-portant role than it does in the commer-cial-vehicle sector. In addition, theprechamber diesel engine features con-siderably lower toxic emissions (HC andNOX), and is less costly to produce thanthe DI engine. The fact though that theprechamber engine uses slightly morefuel than the DI engine (10...15%) isleading to the DI engine coming moreand more to the forefront. Compared tothe gasoline engine, both diesel versionsare more economical especially in thepart-load range.
Diesel engines are particularly suitablefor use with exhaust-gas turbochargersor mechanical superchargers. Using anexhaust-gas turbocharger with the dieselengine increases not only the poweryield, and with it the efficiency, but alsoreduces the combustion noise and thetoxic content of the exhaust gas.
Diesel-engine exhaustemissionsA variety of different combustion depositsare formed when diesel fuel is burnt.These reaction products are dependentupon engine design, engine power out-put, and working load.The complete combustion of the fuelleads to major reductions in the forma-tion of toxic substances. Complete com-bustion is supported by the carefulmatching of the air-fuel mixture, abso-lute precision in the injection process,and optimum air-fuel mixture turbulence.In the first place, water (H2O) and carbondioxide (CO2) are generated. And in rela-tively low concentrations, the followingsubstances are also produced:
Carbon monoxide (CO), Unburnt hydrocarbons (HC), Nitrogen oxides (NOX), Sulphur dioxide (SO2) and sulphuric
acid (H2SO4), as well as Soot particles.
When the engine is cold, the exhaust-gasconstituents which are immediatelynoticeable are the non-oxidized or onlypartly oxidized hydrocarbons which aredirectly visible in the form of white or bluesmoke, and the strongly smelling alde-hydes.
4-stroke diesel engine
1 Induction stroke, 2 Compression stroke, 3 Power stroke, 4 Exhaust stroke.
1 2 3 4
Fields of applicationDiesel engines are characterized by theirhigh levels of economic efficiency. This isof particular importance in commercialapplications. Diesel engines are em-ployed in a wide range of different ver-sions (Fig. 1 and Table 1), for example as: The drive for mobile electric generators
(up to approx. 10 kW/cylinder), High-speed engines for passenger
cars and light commercial vehicles (upto approx. 50 kW/cylinder),
Engines for construction, agricultural,and forestry machinery (up to approx.50 kW/cylinder),
Engines for heavy trucks, buses, andtractors (up to approx. 80 kW/cylinder),
Stationary engines, for instance asused in emergency generating sets (upto approx. 160 kW/cylinder),
Engines for locomotives and ships (upto approx. 1,000 kW/cylinder).
More and more demands are being madeon the diesel engines injection system asa result of the severe regulations govern-ing exhaust and noise emissions, and the demand for lower fuel-consumption.Basically speaking, depending on theparticular diesel combustion process(direct or indirect injection), in order toensure efficient air/fuel mixture formation,the injection system must inject the fuelinto the combustion chamber at a pres-sure between 350 and 2,050 bar, and theinjected fuel quantity must be meteredwith extreme accuracy. With the dieselengine, load and speed control must takeplace using the injected fuel quantity with-out intake-air throttling taking place. The mechanical (flyweight) governingprinciple for diesel injection systems is in-
Diesel fuel-injection systems:An overview
Overview of the Bosch diesel fuel-injection systems
M, MW, A, P, ZWM, CW in-line injection pumps in order of increasing size; PF single-plunger injection pumps; VE axial-piston distributor injection pumps; VR radial-piston distributor injection pumps; UPS unitpump system; UIS unit injector system; CR Common Rail system.
creasingly being superseded by the Elec-tronic Diesel Control (EDC). In the pas-senger-car and commercial-vehicle sec-tor, new diesel fuel-injection systems areall EDC-controlled.
According to the latest state-of-the-art, it is mainly the high-pressure injection systems listed below which are used formotor-vehicle diesel engines.
Fields ofapplication, Technicalrequirements
Fuel-injection Injection Engine-related datasystemType
mm3 bar min1 kW
In-line injection pumpsM 111,60 1,550 m, e IDI 46 5,000 1,120A 11,120 1,750 m DI / IDI 212 2,800 1,127MW 11,150 1,100 m DI 48 2,600 1,136P 3000 11,250 1,950 m, e DI 412 2,600 1,145P 7100 11,250 1,200 m, e DI 412 2,500 1,155P 8000 11,250 1,300 m, e DI 612 2,500 1,155P 8500 11,250 1,300 m, e DI 412 2,500 1,155H 1 11,240 1,300 e DI 68 2,400 1,155H 1000 11,250 1,350 e DI 58 2,200 1,170
Axial-piston distributor injection pumpsVE 11,120 1,200/350 m DI / IDI 46 4,500 1,125VEEDC 1) 11,170 1,200/350 e, em DI / IDI 36 4,200 1,125VEMV 11,170 1,400/350 e, MV DI / IDI 36 4,500 1,125
Radial-piston distributor injection pumpVRMV 1,1135 1,700 e, MV DI 4.6 4,500 1,150
Single-plunger injection pumpsPF(R) 150 800 m, em DI / IDI arbitrary 300 75
18,000 1,500 2,000 1,000UIS 30 2) 11,160 1,600 e, MV DI VE 8 3a) 3,000 1,145UIS 31 2) 11,300 1,600 e, MV DI VE 8 3a) 3,000 1,175UIS 32 2) 11,400 1,800 e, MV DI VE 8 3a) 3,000 1,180UIS-P1 3) 111,62 2,050 e, MV DI VE 6 3a) 5,000 1,125UPS 12 4) 11,150 1,600 e, MV DI VE 8 3a) 2,600 1,135UPS 20 4) 11,400 1,800 e, MV DI VE 8 3a) 2,600 1,180UPS (PF[R]) 13,000 1,400 e, MV DI 620 1,500 1,500
Common Rail accumulator injection systemCR 5) 1,100 1,350 e, MV DI VE 5a)/NE 38 5,000 5b) 30CR 6) 1,400 1,400 e, MV DI VE 6a)/NE 616 2,800 200
Table 1Diesel fuel-injection systems: Properties and characteristic data
1) EDC Electronic Diesel Control; 2) UIS unit injector system for comm. vehs. 3) UIS unit injector system for pass. cars; 3a) With two ECUs large numbers of cylinders are possible; 4) UPS unit pump system for comm. vehs. and buses; 5) CR 1st generation for pass. cars and light comm. vehs.; 5a) Up to 90 crankshaft BTDC, freely selectable; 5b) Up to 5,500 min1 during overrun; 6) CR for comm. vehs., buses, and diesel-powered locomotives; 6a) Up to 30 crankshaft BTDC.
In-line fuel-injection pumps
All in-line fuel-injection pumps have aplunger-and-barrel assembly for eachcylinder. As the name implies, this com-prises the pump barrel and the corre-sponding plunger. The pump camshaftintegrated in the pump and driven by theengine, forces the pump plunger in the delivery direction. The plunger is re-turned by its spring. The plunger-and-barrel assemblies arearranged in-line, and plunger lift cannotbe varied. In order to permit changes inthe delivery quantity, slots have beenmachined into the plunger, the diagonaledges of which are known as helixes.When the plunger is rotated by the mov-able control rack, the helixes permit theselection of the required effective stroke.Depending upon the fuel-injection con-ditions, delivery valves are installed be-tween the pumps pressure chamber andthe fuel-injection lines. These not onlyprecisely terminate the injection processand prevent secondary injection (dribble)at the nozzle, but also ensure a family of uniform pump characteristic curves(pump map).
PE standard in-line fuel-injection pumpStart of fuel delivery is defined by an inletport which is closed by the plungers topedge. The delivery quantity is determinedby the second inlet port being opened bythe helix which is diagonally machinedinto the plunger.The control racks setting is determinedby a mechanical (flyweight) governor orby an electric actuator (EDC).
Control-sleeve in-line fuel-injectionpumpThe control-sleeve in-line fuel-injectionpump differs from a conventional in-lineinjection pump by having a controlsleeve which slides up and down thepump plunger. By way of an actuator shaft,this can vary the plunger lift to port closing,
and with it...