Diesel Distributor Fuel-injection Pumps - BOSCH

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Diesel-engine managementDieseldistributor fuel-injection pumpsTechnical Instruction

Published by: Robert Bosch GmbH, 1999Postfach 30 02 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) Jürgen Crepin,Dipl.-Holzw. Folkhart Dinkler,Dipl.-Ing. (FH) Anton Beer.Author:Dr.-Ing. Helmut Tschöke, assisted by theresponsible technical departments ofRobert Bosch GmbH.Presentation:Dipl.-Ing. (FH) Ulrich Adler,Berthold Gauder, Leinfelden-Echterdingen.Translation:Peter Girling.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 previouswritten 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.Imprimé en Allemagne.4th Edition, April 1999.English translation of the German edition dated:November 1998.

Dieseldistributor fuel-injection pumps VEThe reasons behind the diesel-poweredvehicle’s 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 exhaustgas emissions, the diesel engine is justas good as a gasoline engine withcatalytic converter. In some cases, it iseven better. The diesel engine’s emissions of CO2, which is responsible forthe “green-house effect”, are also lowerthan for the gasoline engine, althoughthis is a direct result of the dieselengine’s better fuel economy. It wasalso 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 withoutthe 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 sophisticated handling qualities of a modernday 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 distributor pump, and how it adapts injectedfuel quantity, start-of-injection, andduration of injection to the differentengine operating conditions.Combustion in the diesel engineThe diesel engine2Diesel fuel-injection systems:An overviewFields of applicationTechnical requirementsInjection-pump designs446Mechanically-controlled (governed)axial-piston distributor fuel-injectionpumps VEFuel-injection systems8Fuel-injection techniques9Fuel supply and delivery12Mechanical engine-speed control(governing)22Injection timing29Add-on modules andshutoff devices32Testing and calibration45Nozzles and nozzle holders46Electronically-controlled axialpiston distributor fuel-injectionpumps VE-EDC54Solenoid-valve-controlledaxial-piston distributor fuel-injectionpumps VE-MV60Start-assist systems62

Combustion in the dieselengineThe diesel engineDiesel combustion principleThe diesel engine is a compressionignition (CI) engine which draws in airand compresses it to a very high level.With its overall efficiency figure, the dieselengine rates as the most efficient combustion 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 engine’s significance.The diesel engine can utilise either the4- or 2-stroke principle. In automotiveapplications though, diesels are practically 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 unthrottled air through the open intake valve.2Compression strokeDuring the second stroke, the so-calledcompression stroke, the air trapped in thecylinder is compressed by the pistonwhich is now moving upwards. Compression ratios are between 14:1 and24:1. In the process, the air heats up totemperatures around 900 C. At the endof the compression stroke the nozzle injects fuel into the heated air at pressuresof up to 2,000 bar.Power strokeFollowing the ignition delay, at the beginning of the third stroke the finely atomized fuel ignites as a result of auto-ignition and burns almost completely. Thecylinder charge heats up even furtherand the cylinder pressure increasesagain. The energy released by the ignition 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 andsuperchargingBoth divided and undivided combustionchambers are used in diesel enginesFig. 1Principle of the reciprocating piston engineTDC Top Dead Center, BDC Bottom Dead Center.Vh Stroke volume, VC Compression volume,s Piston stroke.VCTDCsVhBDCTDCBDCUMM0001ECombustionin the dieselengine

(prechamber engines and direct-injection engines respectively).Diesel-engine exhaustemissionsDirect-injection (DI) engines are more efficient and more economical than theirprechamber counterparts. For this reason, DI engines are used in all commercial-vehicles and trucks. On the otherhand, due to their lower noise level,prechamber engines are fitted in passenger cars where comfort plays a more important role than it does in the commercial-vehicle sector. In addition, theprechamber diesel engine features considerably 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.A variety of different combustion depositsare formed when diesel fuel is burnt.These reaction products are dependentupon engine design, engine power output, and working load.The complete combustion of the fuelleads to major reductions in the formation of toxic substances. Complete combustion is supported by the carefulmatching of the air-fuel mixture, absolute precision in the injection process,and optimum air-fuel mixture turbulence.In the first place, water (H2O) and carbondioxide (CO2) are generated. And in relatively low concentrations, the followingsubstances are also produced: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.The dieselengine––––Carbon monoxide (CO),Unburnt hydrocarbons (HC),Nitrogen oxides (NOX),Sulphur dioxide (SO2) and sulphuricacid (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 aldehydes.Fig. 24-stroke diesel engine1 Induction stroke, 2 Compression stroke, 3 Power stroke, 4 Exhaust stroke.234UMM0013Y13

Diesel fuelinjectionsystems:An overviewDiesel fuel-injection systems:An overviewFields of applicationDiesel engines are characterized by theirhigh levels of economic efficiency. This isof particular importance in commercialapplications. Diesel engines are employed in a wide range of different versions (Fig. 1 and Table 1), for example as:– The drive for mobile electric generators(up to approx. 10 kW/cylinder),– High-speed engines for passengercars 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).TechnicalrequirementsMore and more demands are being madeon the diesel engine’s injection system asa result of the severe regulations governing exhaust and noise emissions, andthe 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 pressure 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 without intake-air throttling taking place.The mechanical (flyweight) governingprinciple for diesel injection systems is in-Fig. 1Overview of the Bosch diesel fuel-injection RCRCRCRUPSUPSUISUPSUIS4UMK1563-1YM, MW, A, P, ZWM, CW in-line injection pumps in order of increasing size; PF single-plunger injectionpumps; 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 Electronic Diesel Control (EDC). In the passenger-car and commercial-vehicle sector, new diesel fuel-injection systems areall EDC-controlled.According to the latest state-of-the-art,it is mainly the high-pressure injectionsystems listed below which are used formotor-vehicle diesel engines.Fields ofapplication,TechnicalrequirementsTable 1Diesel fuel-injection systems: Properties and characteristic ��––––––––4 62 124 84 124 126 124 126 85 ton distributor injection pumpsVE11,1201,200/350 m11,1701,200/350 e, emVE EDC 1)VE MV11,1701,400/350 e, MVDI / IDIDI / IDIDI / IDI–––4 63 63 64,5004,2004,5001,1251,1251,125Radial-piston distributor injection pumpVR MV1,11351,700e, MVDI–4.64,5001,150m, emDI / IDI–arbitrarye, MVe, MVe, MVe, MVe, MVe, MVe, MVDIDIDIDIDIDIDIVEVEVEVEVEVE–8 3a)8 3a)8 3a)6 3a)8 3a)8 3a)6 20300 2,0003,0003,0003,0005,0002,6002,6001,50075 1,0001,1451,1751,1801,1251,1351,1801,500Common Rail accumulator injection system1,1001,350e, MVCR 5)1,4001,400e, MVCR 6)DIDIVE 5a)/NE 3 8VE 6a)/NE 6 165,000 5b)2,80030200Single-plunger injection pumpsPF(R) 150 800 18,0001,50011,1601,600UIS 30 2)11,3001,600UIS 31 2)11,4001,800UIS 32 2)111,622,050UIS-P1 3)11,1501,600UPS 12 4)11,4001,800UPS 20 4)UPS (PF[R])13,0001,400Max. powerper cylinderIDIDI / IDIDIDIDIDIDIDIDIMax. speedm, emmm, em, em, em, eeeIn-line injection pumpsM111,60A11,120MW11,150P 300011,250P 710011,250P 800011,250P 850011,250H111,240H 100011,250No. of cylindersVE Pilot injectionNE Post injectionbarDI Direct injectionIDI Indirect nicalSolenoid valveEngine-related dataMax. nozzlepressureInjectionInjected fuelquantity per strokeFuel-injectionsystemTypemin–1kW1)EDC Electronic Diesel Control; 2) UIS unit injector system for comm. vehs. 3) UIS unit injector system forpass. cars; 3a) With two ECU’s 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 min–1 during overrun; 6) CR for comm. vehs., buses, and diesel-poweredlocomotives; 6a) Up to 30 crankshaft BTDC.5

Diesel fuelinjectionsystems:An overviewInjection-pumpdesignsIn-line fuel-injection pumpsAll in-line fuel-injection pumps have aplunger-and-barrel assembly for eachcylinder. As the name implies, this comprises the pump barrel and the corresponding plunger. The pump camshaftintegrated in the pump and driven by theengine, forces the pump plunger inthe delivery direction. The plunger is returned 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 movable control rack, the helixes permit theselection of the required effective stroke.Depending upon the fuel-injection conditions, delivery valves are installed between the pump’s pressure chamber andthe fuel-injection lines. These not onlyprecisely terminate the injection processand prevent secondary injection (dribble)at the nozzle, but also ensure a familyof 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 plunger’s topedge. The delivery quantity is determinedby the second inlet port being opened bythe helix which is diagonally machinedinto the plunger.The control rack’s setting is determinedby a mechanical (flyweight) governor orby an electric actuator (EDC).6Control-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 the start of delivery and the startof injection. The control sleeve’s positionis varied as a function of a variety of different influencing variables. Comparedto the standard PE in-line injection pumptherefore, the control-sleeve version features an additional degree of freedom.Distributor fuel-injectionpumpsDistributor pumps have a mechanical(flyweight) governor, or an electroniccontrol with integrated timing device. Thedistributor pump has only one plungerand-barrel asembly for all the engine’scylinders.Axial-piston distributor pumpIn the case of the axial-piston distributorpump, fuel is supplied by a vane-typepump. Pressure generation, and distribution to the individual engine cylinders, isthe job of a central piston which runs ona cam plate. For one revolution of thedriveshaft, the piston performs as manystrokes as there are engine cylinders.The rotating-reciprocating movement isimparted to the plunger by the cams onthe underside of the cam plate which rideon the rollers of the roller ring.On the conventional VE axial-piston distributor pump with mechanical (flyweight)governor, or electronically controlledactuator, a control collar defines theeffective stroke and with it the injectedfuel quantity. The pump’s start of deliverycan be adjusted by the roller ring (timingdevice). On the conventional solenoidvalve-controlled axial-piston distributorpump, instead of a control collar anelectronically controlled high-pressuresolenoid valve controls the injected fuelquantity. The open and closed-loop control signals are processed in two ECU’s.Speed is controlled by appropriate triggering of the actuator.Radial-piston distributor pumpIn the case of the radial-piston distributorpump, fuel is supplied by a vane-typepump. A radial-piston pump with cam ringand two to four radial pistons is responsible

for generation of the high pressure and forfuel delivery. The injected fuel quantity ismetered by a high-pressure solenoidvalve. The timing device rotates the camring in order to adjust the start of delivery.As is the case with the solenoid-valvecontrolled axial-piston pump, all open andclosed-loop control signals are processedin two ECU’s. Speed is controlled byappropriate triggering of the actuator.Single-plunger fuel-injectionpumpsPF single-plunger pumpsPF single-plunger injection pumps areused for small engines, diesel locomotives, marine engines, and constructionmachinery. They have no camshaft oftheir own, although they correspond tothe PE in-line injection pumps regardingtheir method of operation. In the case oflarge engines, the mechanical-hydraulicgovernor or electronic controller is attached directly to the engine block. Thefuel-quantity adjustment as defined bythe governor (or controller) is transferredby a rack integrated in the engine.The actuating cams for the individual PFsingle-plunger pumps are located on theengine camshaft. This means that injection timing cannot be implemented byrotating the camshaft. Here, by adjustingan intermediate element (for instance, arocker between camshaft and roller tappet) an advance angle of several angulardegrees can be obtained.Single-plunger injection pumps are alsosuitable for operation with viscous heavyoils.Unit-injector system (UIS)With the unit-injector system, injectionpump and injection nozzle form a unit.One of these units is installed in the engine’s cylinder head for each engine cylinder, and driven directly by a tappet orindirectly from the engine’s camshaftthrough a valve lifter.Compared with in-line and distributor injection pumps, considerably higher injection pressures (up to 2050 bar) have be-come possible due to the omission of thehigh-pressure lines. Such high injectionpressures coupled with the electronicmap-based control of duration of injection(or injected fuel quantity), mean that aconsiderable reduction of the diesel engine’s toxic emissions has become possible together with good shaping of therate-of-discharge curve.Electronic control concepts permit a variety of additional functions.Injection-pumpdesignsUnit-pump system (UPS)The principle of the UPS unit-pump system is the same as that of the UIS unitinjector. It is a modular high-pressure injection system. Similar to the UIS, theUPS system features one UPS singleplunger injection pump for each enginecylinder. Each UP pump is driven by theengine’s camshaft. Connection to the nozzle-and-holder assembly is through ashort high-pressure delivery line precisely matched to the pump-system components.Electronic map-based control of the startof injection and injection duration (inother words, of injected fuel quantity)leads to a pronounced reduction in thediesel engine’s toxic emissions. The useof a high-speed electronically triggeredsolenoid valve enables the characteristic of the individual injection process,the so-called rate-of-discharge curve, tobe precisely defined.Accumulator injectionsystemCommon-Rail system (CR)Pressure generation and the actual injection process have been decoupled fromeach other in the Common Rail accumulator injection system. The injection pressure is generated independent of enginespeed and injected fuel quantity, and isstored, ready for each injection process,in the rail (fuel accumulator). The start ofinjection and the injected fuel quantityare calculated in the ECU and, via the injection unit, implemented at each cylinder through a triggered solenoid valve.7

d(governed) axial-piston distributorfuel-Injection pumps VEFuel-injectionsystemsAssignmentsThe fuel-injection system is responsiblefor supplying the diesel engine with fuel.To do so, the injection pump generatesthe pressure required for fuel injection.The fuel under pressure is forced throughthe high-pressure fuel-injection tubing tothe injection nozzle which then injects itinto the combustion chamber.The fuel-injection system (Fig. 1) includes the following components andassemblies: The fuel tank, the fuel filter,the fuel-supply pump, the injectionnozzles, the high-pressure injectiontubing, the governor, and the timingdevice (if required).The combustion processes in the dieselengine depend to a large degree uponthe quantity of fuel which is injected andupon the method of introducing this fuelto the combustion chamber.The most important criteria in this respect are the fuel-injection timing and theduration of injection, the fuel’s distributionin the combustion chamber, the momentin time when combustion starts, theamount of fuel metered to the engine perdegree crankshaft, and the total injectedfuel quantity in accordance with theengine loading. The optimum interplay ofall these parameters is decisive for thefaultless functioning of the diesel engineand of the fuel-injection system.Fig. 1Fuel-injection system with mechanically-controlled (governed) distributor injection pump1 Fuel tank, 2 Fuel filter, 3 Distributor fuel-injection pump, 4 Nozzle holder with nozzle, 5 Fuel return line,6 Sheathed-element glow plug (GSK) 7 Battery, 8 Glow-plug and starter switch, 9 Glow control unit ,,,,988UMK1199Y7

The increasing demands placed uponthe diesel fuel-injection system made itnecessary to continually develop andimprove the fuel-injection pump.Following systems comply with thepresent state-of-the-art:– In-line fuel-injection pump (PE) withmechanical (flyweight) governor orElectronic Diesel Control (EDC) and, ifrequired, attached timing device,– Control-sleeve in-line fuel-injectionpump (PE), with Electronic DieselControl (EDC) and infinitely variablestart of delivery (without attachedtiming device),– Single-plunger fuel-injection pump (PF),– Distributor fuel-injection pump (VE)with mechanical (flyweight) governoror Electronic Diesel Control (EDC).With integral timing device,– Radial-piston distributor injectionpump (VR),– Common Rail accumulator injectionsystem (CRS),– Unit-injector system (UIS),– Unit-pump system quesFields of applicationSmall high-speed diesel enginesdemand a lightweight and compact fuelinjection installation. The VE distributorfuel-injection pump (Fig. 2) fulfills thesestipulations by combining– Fuel-supply pump,– High-pressure pump,– Governor, and– Timing device,in a small, compact unit. The dieselengine’s rated speed, its power output,and its configuration determine theparameters for the particular distributorpump.Distributor pumps are used in passengercars, commercial vehicles, agriculturaltractors and stationary engines.Fig. 2: VE distributor pump fitted to a 4-cylinderdiesel engineUMK0318YTypes9

Axial-pistondistributorpumpsSubassembliesIn contrast to the in-line injection pump,the VE distributor pump has only onepump cylinder and one plunger, even formulti-cylinder engines. The fuel delivered by the pump plunger is apportionedby a distributor groove to the outlet portsas determined by the engine’s number ofcylinders. The distributor pump’s closedhousing contains the following functionalgroups:––––––High-pressure pump with distributor,Mechanical (flyweight) governor,Hydraulic timing device,Vane-type fuel-supply pump,Shutoff device, andEngine-specific add-on modules.Fig. 3 shows the functional groups andtheir assignments. The add-on modulesfacilitate adaptation to the specificrequirements of the diesel engine inquestion.Design and constructionThe distributor pump’s drive shaft runsin bearings in the pump housing anddrives the vane-type fuel-supply pump.The roller ring is located inside thepump at the end of the drive shaft although it is not connected to it. A rotating-reciprocating movement is impartedto the distributor plunger by way of thecam plate which is driven by the inputshaft and rides on the rollers of theroller ring. The plunger moves insidethe distributor head which is bolted to thepump housing. Installed in the distributor head are the electrical fuelshutoff device, the screw plug with ventscrew, and the delivery valves with theirFig. 3The subassemblies and their functions1 Vane-type fuel-supply pump with pressure regulating valve: Draws in fuel and generates pressureinside the pump.2 High-pressure pump with distributor: Generates injection pressure, delivers and distributes fuel.3 Mechanical (flyweight) governor: Controls the pump speed and varies the delivery quantity withinthe control range.4 Electromagnetic fuel shutoff valve: Interrupts the fuel supply.5 Timing device: Adjusts the start of delivery (port closing) as a function of the pump speed andin part as a function of the load.345102UMK0317Y1

holders. If the distributor pump is alsoequipped with a mechanical fuel shutoffdevice this is mounted in the governorcover.The governor assembly comprising theflyweights and the control sleeve isdriven by the drive shaft (gear withrubber damper) via a gear pair. Thegovernor linkage mechanism whichconsists of the control, starting, andtensioning levers, can pivot in thehousing.The governor shifts the position of thecontrol collar on the pump plunger. Onthe governor mechanism’s top side isthe governor spring which engageswith the external control lever throughthe control-lever shaft which is held inbearings in the governor cover.The control lever is used to controlpump function. The governor coverforms the top of the distributor pump, andalso contains the full-load adjustingscrew, the overflow restriction or theoverflow valve, and the engine-speedadjusting screw. The hydraulic injectiontiming device is located at the bottom ofthe pump at right angles to the pump’slongitudinal axis. Its operation is influenced by the pump’s internal pressurewhich in turn is defined by the vane-typefuel-supply pump and by the pressure-regulating valve. The timing deviceis closed off by a cover on each sideof the pump (Fig. 4).Fuel-injectiontechniquesFig. 4The subassemblies and their configuration1 Pressure-control valve, 2 Governor assembly, 3 Overflow restriction,4 Distributor head with high-pressure pump, 5 Vane-type fuel-supply pump, 6 Timing device,7 Cam plate, 8 Electromagnetic shutoff valve.3281467UMK0319Y511

Axial-pistondistributorpumpsPump driveThe distributor injection pump is drivenby the diesel engine through a specialdrive unit. For 4-stroke engines, thepump is driven at exactly half the enginecrankshaft speed, in other wordsat camshaft speed. The VE pump mustbe positively driven so that it’s driveshaft is synchronized to the engine’spiston movement.This positive drive is implemented bymeans of either toothed belts, pinion,gear wheel or chain. Distributor pumpsare available for clockwise and forcounter-clockwise rotation, whereby theinjection sequence differs dependingupon the direction of rotation.The fuel outlets though are alwayssupplied with fuel in their geometricsequence, and are identified with theletters A, B, C etc. to avoid confusionwith the engine-cylinder numbering.Distributor pumps are suitable for engines with up to max. 6 cylinders.Fuel supply anddeliveryConsidering an injection system withdistributor injection pump, fuel supplyand delivery is divided into low-pressureand high-pressure delivery (Fig. 1).Low-pressure stageLow-pressure deliveryThe low-pressure stage of a distributorpump fuel-injection installation comprises the fuel tank, fuel lines, fuel filter,vane-type fuel-supply pump, pressurecontrol valve, and overflow restriction.The vane-type fuel-supply pump drawsfuel from the fuel tank. It delivers avirtually constant flow of fuel perrevolution to the interior of the injectionpump. A pressure-control valve is fittedto ensure that a defined injection-pumpinterior pressure is maintained as afunction of supply-pump speed. Usingthis valve, it is possible to set a definedpressure for a given speed. The pump’sFig. 1Fuel supply and delivery in a distributor-pump fuel-injection systemÀ ÐÁ ²rs ¡ 1 Fuel tank, 2 Fuel line (suction pressure), 3 Fuel filter, 4 Distributor injection pump,5 High-pressure fuel-injection line, 6 Injection nozzle, 7 Fuel-return line (pressureless),8 Sheathed-element glow ,,,,,,,,,,,,UMK0316Y4

interior pressure then increases inproportion to the speed (in other words,the higher the pump speed the higherthe pump interior pressure). Some of thefuel flows through the pressureregulating valve and returns to thesuction side. Some fuel also flowsthrough the overflow restriction andback to the fuel tank in order to provide cooling and self-venting for theinjection pump (Fig. 2). An overflow valvecan be fitted instead of the overflowrestriction.injection pump is powerful enough to drawthe fuel out of the fuel tank and to build upsufficient pressure in the interior of the injection pump.In those cases in which the differencein height between fuel tank and injectionpump is excessive and (or) the fuel linebetween tank and pump is too long, apre-supply pump must be installed. Thisovercomes the resistances in the fuelline and the fuel filter. Gravity-feedtanks are mainly used on stationaryengines.Fuel-line configurationFor the injection pump to function efficiently it is necessary that its highpressure stage is continually providedwith pressurized fuel which is free ofvapor bubbles. Normally, in the case ofpassenger cars and light commercialvehicles, the

Diesel fuel-injection systems: An overview Fields of application 4 Technical requirements 4 Injection-pump designs 6 Mechanically-controlled (governed) axial-piston distributor fuel-injection pumps VE Fuel-injection systems 8 Fuel-injection techniques 9 Fuel supply and delivery 12 Mechanical engine-speed control (governing) 22 Injection timing 29

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