Diesel Distributor Fuel-Injection Pumps VE

Diesel-engine management Diesel distributor fuel-injection pumps

Technical Instruction Published by: © Robert Bosch GmbH, 1999 Postfach 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 the responsible technical departments of Robert Bosch GmbH.

Presentation: Dipl.-Ing. (FH) Ulrich Adler, Berthold Gauder, Leinfelden-Echterdingen.

Translation: Peter Girling.

Photographs: Audi AG, Ingolstadt and Volkswagen AG, Wolfsburg.

Technical graphics: Bauer & Partner, Stuttgart.

Unless otherwise specified, the above persons are employees of Robert Bosch GmbH, Stuttgart.

Reproduction, copying, or translation of this publication, wholly or in part, only with our previous written permission and with source credit. Illustrations, descriptions, schematic drawings, and other particulars only serve to explain and illustrate the text. They are not to be used as the basis for design, installation, or delivery conditions. We assume no responsibility for agreement of the contents with local laws and regulations. Robert Bosch GmbH is exempt from liability, and reserves the right to make changes at any time.

Printed in Germany. Imprimé en Allemagne.

4th Edition, April 1999. English translation of the German edition dated: November 1998. Diesel distributor fuel-injection pumps VE

The reasons behind the diesel-powered Combustion in the diesel engine vehicle’s continuing success can be The diesel engine 2 reduced to one common denominator: Diesels use considerably less fuel than their gasoline-powered counterparts. Diesel fuel-injection systems: And in the meantime the diesel has An overview practically caught up with the gasoline Fields of application 4 engine when it comes to starting and Technical requirements 4 running refinement. Regarding exhaust- Injection-pump designs 6 gas emissions, the diesel engine is just as good as a gasoline engine with Mechanically-controlled (governed) catalytic converter. In some cases, it is axial-piston distributor fuel-injection even better. The diesel engine’s emis- pumps VE sions of CO2, which is responsible for the “green-house effect”, are also lower Fuel-injection systems 8 than for the gasoline engine, although Fuel-injection techniques 9 this is a direct result of the diesel Fuel supply and delivery 12 engine’s better fuel economy. It was Mechanical engine-speed control also possible during the past few years (governing) 22 to considerably lower the particulate Injection timing 29 emissions which are typical for the Add-on modules and diesel engine. shutoff devices 32 The popularity of the high-speed diesel engine in the passenger car though, Testing and calibration 45 would have been impossible without Nozzles and nozzle holders 46 the diesel fuel-injection systems from Bosch. The very high level of precision Electronically-controlled axial- inherent in the distributor pump means piston distributor fuel-injection that it is possible to precisely meter pumps VE-EDC 54 extremely small injection quantities to the engine. And thanks to the special Solenoid-valve-controlled governor installed with the VE-pump in passenger-car applications, the engine axial-piston distributor fuel-injection responds immediately to even the finest pumps VE-MV 60 change in accelerator-pedal setting. All points which contribute to the sophisti- Start-assist systems 62 cated handling qualities of a modern- day automobile. The Electronic Diesel Control (EDC) also plays a decisive role in the overall improvement of the diesel-engined passenger car. The following pages will deal with the design and construction of the VE distributor pump, and how it adapts injected fuel quantity, start-of-injection, and duration of injection to the different engine operating conditions. Combustion in the diesel Combustion in the diesel engine engine

Power stroke The diesel engine Following the ignition delay, at the begin- ning of the third stroke the finely atom- Diesel combustion principle ized fuel ignites as a result of auto-igni- The diesel engine is a compression- tion and burns almost completely. The ignition (CI) engine which draws in air cylinder charge heats up even further and compresses it to a very high level. and the cylinder pressure increases With its overall efficiency figure, the diesel again. The energy released by the igni- engine rates as the most efficient com- tion is applied to the piston. bustion engine (CE). Large, slow-running The piston is forced downwards and the models can have efficiency figures of as combustion energy is transformed into much as 50% or even more. mechanical energy. The resulting low fuel consumption, coupled with the low level of pollutants in Exhaust stroke the exhaust gas, all serve to underline In the fourth stroke, the piston moves up the diesel engine’s significance. again and drives out the burnt gases The diesel engine can utilise either the through the open exhaust valve. 4- or 2-stroke principle. In automotive A fresh charge of air is then drawn in applications though, diesels are practi- again and the working cycle repeated. cally always of the 4-stroke type (Figs. 1 and 2). Combustion chambers, Working cycle (4-stroke) turbocharging and In the case of 4-stroke diesel engines, supercharging gas-exchange valves are used to control Both divided and undivided combustion the gas exchange process by opening chambers are used in diesel engines and closing the inlet and exhaust ports. Fig. 1 Principle of the reciprocating piston engine Induction stroke During the first stroke, the downward TDC Top Dead Center, BDC Bottom Dead Center. Vh Stroke volume, VC Compression volume, movement of the piston draws in un- s Piston stroke. throttled air through the open intake valve. VC TDC

Compression stroke s During the second stroke, the so-called Vh compression stroke, the air trapped in the BDC cylinder is compressed by the piston which is now moving upwards. Com- pression ratios are between 14:1 and 24:1. In the process, the air heats up to TDC temperatures around 900¡C. At the end of the compression stroke the nozzle injects fuel into the heated air at pressures BDC 2 of up to 2,000 bar. UMM0001E (prechamber engines and direct-injec- Diesel-engine exhaust The diesel tion engines respectively). emissions engine Direct-injection (DI) engines are more ef- A variety of different combustion deposits ficient and more economical than their are formed when diesel fuel is burnt. prechamber counterparts. For this rea- These reaction products are dependent son, DI engines are used in all commer- upon engine design, engine power out- cial-vehicles and trucks. On the other put, and working load. hand, due to their lower noise level, The complete combustion of the fuel prechamber engines are fitted in passen- leads to major reductions in the forma- ger cars where comfort plays a more im- tion of toxic substances. Complete com- portant role than it does in the commer- bustion is supported by the careful cial-vehicle sector. In addition, the matching of the air-fuel mixture, abso- prechamber diesel engine features con- lute precision in the injection process, siderably lower toxic emissions (HC and and optimum air-fuel mixture turbulence. NOX), and is less costly to produce than In the first place, water (H2O) and carbon the DI engine. The fact though that the dioxide (CO2) are generated. And in rela- prechamber engine uses slightly more tively low concentrations, the following fuel than the DI engine (10...15 %) is substances are also produced: leading to the DI engine coming more and more to the forefront. Compared to Ð Carbon monoxide (CO), the gasoline engine, both diesel versions Ð Unburnt hydrocarbons (HC), are more economical especially in the Ð Nitrogen oxides (NOX), part-load range. Ð Sulphur dioxide (SO2) and sulphuric acid (H2SO4), as well as Diesel engines are particularly suitable Ð Soot particles. for use with exhaust-gas turbochargers or mechanical superchargers. Using an When the engine is cold, the exhaust-gas exhaust-gas turbocharger with the diesel constituents which are immediately engine increases not only the power noticeable are the non-oxidized or only yield, and with it the efficiency, but also partly oxidized hydrocarbons which are reduces the combustion noise and the directly visible in the form of white or blue toxic content of the exhaust gas. smoke, and the strongly smelling alde- hydes.

Fig. 2 4-stroke diesel engine 1 Induction stroke, 2 Compression stroke, 3 Power stroke, 4 Exhaust stroke. 1234

UMM0013Y 3 Diesel fuel- injection Diesel fuel-injection systems: systems: An overview An overview

Fields of application Technical

Diesel engines are characterized by their requirements high levels of economic efficiency. This is of particular importance in commercial More and more demands are being made applications. Diesel engines are em- on the diesel engine’s injection system as ployed in a wide range of different ver- a result of the severe regulations govern- sions (Fig. 1 and Table 1), for example as: ing exhaust and noise emissions, and Ð The drive for mobile electric generators the demand for lower fuel-consumption. (up to approx. 10 kW/cylinder), Basically speaking, depending on the Ð High-speed engines for passenger particular diesel combustion process cars and light commercial vehicles (up (direct or indirect injection), in order to to approx. 50 kW/cylinder), ensure efficient air/fuel mixture formation, Ð Engines for construction, agricultural, the injection system must inject the fuel and forestry machinery (up to approx. into the combustion chamber at a pres- 50 kW/cylinder), sure between 350 and 2,050 bar, and the Ð Engines for heavy trucks, buses, and injected fuel quantity must be metered tractors (up to approx. 80 kW/cylinder), with extreme accuracy. With the diesel Ð Stationary engines, for instance as engine, load and speed control must take used in emergency generating sets (up place using the injected fuel quantity with- to approx. 160 kW/cylinder), out intake-air throttling taking place. Ð Engines for locomotives and ships (up The mechanical (flyweight) governing to approx. 1,000 kW/cylinder). principle for diesel injection systems is in- Fig. 1 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 unit pump system; UIS unit injector system; CR Common Rail system.

PF VE VE VE VE ZWM ZWM

VR MW MW VR CW CW

M A A MW PF PF

MW P P P CR CR

CR CR UPS UPS

UIS UPS

UIS

4 UMK1563-1Y creasingly being superseded by the Elec- According to the latest state-of-the-art, Fields of tronic Diesel Control (EDC). In the pas- it is mainly the high-pressure injection application, senger-car and commercial-vehicle sec- systems listed below which are used for Technical tor, new diesel fuel-injection systems are motor-vehicle diesel engines. requirements all EDC-controlled.

Table 1 Diesel fuel-injection systems: Properties and characteristic data

Fuel-injection Injection Engine-related data system Type No. of cylinders Max. speed Max. power per cylinder Solenoid valve Mechanical Electromechanical Max. nozzle pressure Electronic Direct injection Indirect injection Injected fuel quantity per stroke Pilot injection Post injection

mm3 bar minÐ1 kW m e em MV DI IDI VE NE

In-line injection pumps M 111,60 1,550 m, e IDI Ð 4…6 5,000 1,120 A 11,120 1,750 m DI / IDI Ð 2…12 2,800 1,127 MW 11,150 1,100 m DI Ð 4…8 2,600 1,136 P 3000 11,250 1,950 m, e DI Ð 4…12 2,600 1,145 P 7100 11,250 1,200 m, e DI Ð 4…12 2,500 1,155 P 8000 11,250 1,300 m, e DI Ð 6…12 2,500 1,155 P 8500 11,250 1,300 m, e DI Ð 4…12 2,500 1,155 H 1 11,240 1,300 e DI Ð 6…8 2,400 1,155 H 1000 11,250 1,350 e DI Ð 5…8 2,200 1,170

Axial-piston distributor injection pumps VE 11,120 1,200/350 m DI / IDI Ð 4…6 4,500 1,125 VE…EDC 1) 11,170 1,200/350 e, em DI / IDI Ð 3…6 4,200 1,125 VE…MV 11,170 1,400/350 e, MV DI / IDI Ð 3…6 4,500 1,125

Radial-piston distributor injection pump VR…MV 1,1135 1,700 e, MV DI Ð 4.6 4,500 1,150

Single-plunger injection pumps PF(R)… 150… 800… m, em DI / IDI Ð arbitrary 300… 75… 18,000 1,500 2,000 1,000 UIS 30 2) 11,160 1,600 e, MV DI VE 8 3a) 3,000 1,145 UIS 31 2) 11,300 1,600 e, MV DI VE 8 3a) 3,000 1,175 UIS 32 2) 11,400 1,800 e, MV DI VE 8 3a) 3,000 1,180 UIS-P1 3) 111,62 2,050 e, MV DI VE 6 3a) 5,000 1,125 UPS 12 4) 11,150 1,600 e, MV DI VE 8 3a) 2,600 1,135 UPS 20 4) 11,400 1,800 e, MV DI VE 8 3a) 2,600 1,180 UPS (PF[R]) 13,000 1,400 e, MV DI Ð 6…20 1,500 1,500

Common Rail accumulator injection system CR 5) 1,100 1,350 e, MV DI VE 5a)/NE 3…8 5,000 5b)30 CR 6) 1,400 1,400 e, MV DI VE 6a)/NE 6…16 2,800 200 1) EDC Electronic Diesel Control; 2) UIS unit injector system for comm. vehs. 3) UIS unit injector system for pass. 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 90û crankshaft BTDC, freely selectable; 5b) Up to 5,500 minÐ1 during overrun; 6) CR for comm. vehs., buses, and diesel-powered locomotives; 6a) Up to 30û crankshaft BTDC. 5 Diesel fuel- Injection-pump and with it the start of delivery and the start injection of injection. The control sleeve’s position systems: designs is varied as a function of a variety of dif- An overview ferent influencing variables. Compared In-line fuel-injection pumps to the standard PE in-line injection pump therefore, the control-sleeve version fea- All in-line fuel-injection pumps have a tures an additional degree of freedom. plunger-and-barrel assembly for each cylinder. As the name implies, this com- Distributor fuel-injection prises the pump barrel and the corre- pumps sponding plunger. The pump camshaft integrated in the pump and driven by the Distributor pumps have a mechanical engine, forces the pump plunger in (flyweight) governor, or an electronic the delivery direction. The plunger is re- control with integrated timing device. The turned by its spring. distributor pump has only one plunger- The plunger-and-barrel assemblies are and-barrel asembly for all the engine’s arranged in-line, and plunger lift cannot cylinders. be varied. In order to permit changes in the delivery quantity, slots have been Axial-piston distributor pump machined into the plunger, the diagonal In the case of the axial-piston distributor edges of which are known as helixes. pump, fuel is supplied by a vane-type When the plunger is rotated by the mov- pump. Pressure generation, and distribu- able control rack, the helixes permit the tion to the individual engine cylinders, is selection of the required effective stroke. the job of a central piston which runs on Depending upon the fuel-injection con- a cam plate. For one revolution of the ditions, delivery valves are installed be- driveshaft, the piston performs as many tween the pump’s pressure chamber and strokes as there are engine cylinders. the fuel-injection lines. These not only The rotating-reciprocating movement is precisely terminate the injection process imparted to the plunger by the cams on and prevent secondary injection (dribble) the underside of the cam plate which ride at the nozzle, but also ensure a family on the rollers of the roller ring. of uniform pump characteristic curves On the conventional VE axial-piston dis- (pump map). tributor pump with mechanical (flyweight) governor, or electronically controlled PE standard in-line fuel-injection pump actuator, a control collar defines the Start of fuel delivery is defined by an inlet effective stroke and with it the injected port which is closed by the plunger’s top fuel quantity. The pump’s start of delivery edge. The delivery quantity is determined can be adjusted by the roller ring (timing by the second inlet port being opened by device). On the conventional solenoid- the helix which is diagonally machined valve-controlled axial-piston distributor into the plunger. pump, instead of a control collar an The control rack’s setting is determined electronically controlled high-pressure by a mechanical (flyweight) governor or solenoid valve controls the injected fuel by an electric actuator (EDC). quantity. The open and closed-loop control signals are processed in two ECU’s. Control-sleeve in-line fuel-injection Speed is controlled by appropriate trig- pump gering of the actuator. The control-sleeve in-line fuel-injection pump differs from a conventional in-line Radial-piston distributor pump injection pump by having a “control In the case of the radial-piston distributor sleeve” which slides up and down the pump, fuel is supplied by a vane-type pump plunger. By way of an actuator shaft, pump. A radial-piston pump with cam ring 6 this can vary the plunger lift to port closing, and two to four radial pistons is responsible for generation of the high pressure and for come possible due to the omission of the Injection-pump fuel delivery. The injected fuel quantity is high-pressure lines. Such high injection designs metered by a high-pressure solenoid pressures coupled with the electronic valve. The timing device rotates the cam map-based control of duration of injection ring in order to adjust the start of delivery. (or injected fuel quantity), mean that a As is the case with the solenoid-valve- considerable reduction of the diesel en- controlled axial-piston pump, all open and gine’s toxic emissions has become possi- closed-loop control signals are processed ble together with good shaping of the in two ECU’s. Speed is controlled by rate-of-discharge curve. appropriate triggering of the actuator. Electronic control concepts permit a variety of additional functions. Single-plunger fuel-injection pumps Unit-pump system (UPS) The principle of the UPS unit-pump sys- PF single-plunger pumps tem is the same as that of the UIS unit PF single-plunger injection pumps are injector. It is a modular high-pressure in- used for small engines, diesel locomo- jection system. Similar to the UIS, the tives, marine engines, and construction UPS system features one UPS single- machinery. They have no camshaft of plunger injection pump for each engine their own, although they correspond to cylinder. Each UP pump is driven by the the PE in-line injection pumps regarding engine’s camshaft. Connection to the no- their method of operation. In the case of zzle-and-holder assembly is through a large engines, the mechanical-hydraulic short high-pressure delivery line preci- governor or electronic controller is at- sely matched to the pump-system com- tached directly to the engine block. The ponents. fuel-quantity adjustment as defined by Electronic map-based control of the start the governor (or controller) is transferred of injection and injection duration (in by a rack integrated in the engine. other words, of injected fuel quantity) The actuating cams for the individual PF leads to a pronounced reduction in the single-plunger pumps are located on the diesel engine’s toxic emissions. The use engine camshaft. This means that injec- of a high-speed electronically triggered tion timing cannot be implemented by solenoid valve enables the character- rotating the camshaft. Here, by adjusting istic of the individual injection process, an intermediate element (for instance, a the so-called rate-of-discharge curve, to rocker between camshaft and roller tap- be precisely defined. pet) an advance angle of several angular degrees can be obtained. Accumulator injection Single-plunger injection pumps are also system suitable for operation with viscous heavy oils. Common-Rail system (CR) Pressure generation and the actual injec- Unit-injector system (UIS) tion process have been decoupled from With the unit-injector system, injection each other in the Common Rail accumu- pump and injection nozzle form a unit. lator injection system. The injection pres- One of these units is installed in the ensure is generated independent of engine gine’s cylinder head for each engine cyl- speed and injected fuel quantity, and is inder, and driven directly by a tappet or stored, ready for each injection process, indirectly from the engine’s camshaft in the rail (fuel accumulator). The start of through a valve lifter. injection and the injected fuel quantity are calculated in the ECU and, via the in- Compared with in-line and distributor injection unit, implemented at each cylin- jection pumps, considerably higher injec- der through a triggered solenoid valve. tion pressures (up to 2050 bar) have be- 7 Axial-piston distributor Mechanically-controlled pumps (governed) axial-piston distributor fuel-Injection pumps VE

tubing, the governor, and the timing Fuel-injection device (if required). systems The combustion processes in the diesel engine depend to a large degree upon Assignments the quantity of fuel which is injected and upon the method of introducing this fuel The fuel-injection system is responsible to the combustion chamber. for supplying the diesel engine with fuel. The most important criteria in this re- To do so, the injection pump generates spect are the fuel-injection timing and the the pressure required for fuel injection. duration of injection, the fuel’s distribution The fuel under pressure is forced through in the combustion chamber, the moment the high-pressure fuel-injection tubing to in time when combustion starts, the the injection nozzle which then injects it amount of fuel metered to the engine per into the combustion chamber. degree crankshaft, and the total injected The fuel-injection system (Fig. 1) in- fuel quantity in accordance with the cludes the following components and engine loading. The optimum interplay of assemblies: The fuel tank, the fuel filter, all these parameters is decisive for the the fuel-supply pump, the injection faultless functioning of the diesel engine nozzles, the high-pressure injection and of the fuel-injection system. Fig. 1 Fuel-injection system with mechanically-controlled (governed) distributor injection pump 1 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 (GZS).

5 1

6 2

7 8

8 UMK1199Y Types Fuel-injection Fuel-injection techniques The increasing demands placed upon techniques the diesel fuel-injection system made it necessary to continually develop and improve the fuel-injection pump. Fields of application Following systems comply with the Small high-speed diesel engines present state-of-the-art: demand a lightweight and compact fuel- Ð In-line fuel-injection pump (PE) with injection installation. The VE distributor mechanical (flyweight) governor or fuel-injection pump (Fig. 2) fulfills these Electronic Diesel Control (EDC) and, if stipulations by combining required, attached timing device, Ð Fuel-supply pump, Ð Control-sleeve in-line fuel-injection Ð High-pressure pump, pump (PE), with Electronic Diesel Ð Governor, and Control (EDC) and infinitely variable Ð Timing device, start of delivery (without attached in a small, compact unit. The diesel timing device), engine’s rated speed, its power output, Ð Single-plunger fuel-injection pump (PF), and its configuration determine the Ð Distributor fuel-injection pump (VE) parameters for the particular distributor with mechanical (flyweight) governor pump. or Electronic Diesel Control (EDC). Distributor pumps are used in passenger With integral timing device, cars, commercial vehicles, agricultural Ð Radial-piston distributor injection tractors and stationary engines. pump (VR), Ð Common Rail accumulator injection system (CRS), Ð Unit-injector system (UIS), Fig. 2: VE distributor pump fitted to a 4-cylinder Ð Unit-pump system (UPS). diesel engine

UMK0318Y 9 Axial-piston Subassemblies facilitate adaptation to the specific distributor requirements of the diesel engine in pumps In contrast to the in-line injection pump, question. the VE distributor pump has only one pump cylinder and one plunger, even for multi-cylinder engines. The fuel deliv- Design and construction ered by the pump plunger is apportioned The distributor pump’s drive shaft runs by a distributor groove to the outlet ports in bearings in the pump housing and as determined by the engine’s number of drives the vane-type fuel-supply pump. cylinders. The distributor pump’s closed The roller ring is located inside the housing contains the following functional pump at the end of the drive shaft al- groups: though it is not connected to it. A rotating-reciprocating movement is imparted Ð High-pressure pump with distributor, to the distributor plunger by way of the Ð Mechanical (flyweight) governor, cam plate which is driven by the input Ð Hydraulic timing device, shaft and rides on the rollers of the Ð Vane-type fuel-supply pump, roller ring. The plunger moves inside Ð Shutoff device, and the distributor head which is bolted to the Ð Engine-specific add-on modules. pump housing. Installed in the distributor head are the electrical fuel Fig. 3 shows the functional groups and shutoff device, the screw plug with vent their assignments. The add-on modules screw, and the delivery valves with their Fig. 3 The subassemblies and their functions 1 Vane-type fuel-supply pump with pressure regulating valve: Draws in fuel and generates pressure inside 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 within the 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 and in part as a function of the load.

10 UMK0317Y holders. If the distributor pump is also also contains the full-load adjusting Fuel-injection equipped with a mechanical fuel shutoff screw, the overflow restriction or the techniques device this is mounted in the governor overflow valve, and the engine-speed cover. adjusting screw. The hydraulic injection The governor assembly comprising the timing device is located at the bottom of flyweights and the control sleeve is the pump at right angles to the pump’s driven by the drive shaft (gear with longitudinal axis. Its operation is in- rubber damper) via a gear pair. The fluenced by the pump’s internal pressure governor linkage mechanism which which in turn is defined by the vane-type consists of the control, starting, and fuel-supply pump and by the pres- tensioning levers, can pivot in the sure-regulating valve. The timing device housing. is closed off by a cover on each side The governor shifts the position of the of the pump (Fig. 4). control collar on the pump plunger. On the governor mechanism’s top side is the governor spring which engages with the external control lever through the control-lever shaft which is held in bearings in the governor cover. The control lever is used to control pump function. The governor cover forms the top of the distributor pump, and Fig. 4 The subassemblies and their configuration 1 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.

1 4

6 7

UMK0319Y 11 Axial-piston Pump drive Fuel supply and distributor pumps The distributor injection pump is driven delivery by the diesel engine through a special drive unit. For 4-stroke engines, the Considering an injection system with pump is driven at exactly half the engine distributor injection pump, fuel supply crankshaft speed, in other words and delivery is divided into low-pressure at camshaft speed. The VE pump must and high-pressure delivery (Fig. 1). be positively driven so that it’s drive shaft is synchronized to the engine’s piston movement. Low-pressure stage This positive drive is implemented by Low-pressure delivery means of either toothed belts, pinion, The low-pressure stage of a distributor- gear wheel or chain. Distributor pumps pump fuel-injection installation com- are available for clockwise and for prises the fuel tank, fuel lines, fuel filter, counter-clockwise rotation, whereby the vane-type fuel-supply pump, pressure- injection sequence differs depending control valve, and overflow restriction. upon the direction of rotation. The vane-type fuel-supply pump draws The fuel outlets though are always fuel from the fuel tank. It delivers a supplied with fuel in their geometric virtually constant flow of fuel per sequence, and are identified with the revolution to the interior of the injection letters A, B, C etc. to avoid confusion pump. A pressure-control valve is fitted with the engine-cylinder numbering. to ensure that a defined injection-pump Distributor pumps are suitable for en- interior pressure is maintained as a gines with up to max. 6 cylinders. function of supply-pump speed. Using this valve, it is possible to set a defined pressure for a given speed. The pump’s Fig. 1 Fuel supply and delivery in a distributor-pump fuel-injection system 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 plug.

1 7

5 6 4

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12 UMK0316Y

¯°¾¿ÀÎÏÐß interior pressure then increases in injection pump is powerful enough to draw Fuel-injection proportion to the speed (in other words, the fuel out of the fuel tank and to build up techniques the higher the pump speed the higher sufficient pressure in the interior of the in- the pump interior pressure). Some of the jection pump. fuel flows through the pressure- In those cases in which the difference regulating valve and returns to the in height between fuel tank and injection suction side. Some fuel also flows pump is excessive and (or) the fuel line through the overflow restriction and between tank and pump is too long, a back to the fuel tank in order to pro- pre-supply pump must be installed. This vide cooling and self-venting for the overcomes the resistances in the fuel injection pump (Fig. 2). An overflow valve line and the fuel filter. Gravity-feed can be fitted instead of the overflow tanks are mainly used on stationary restriction. engines.

Fuel-line configuration Fuel tank For the injection pump to function ef- The fuel tank must be of noncorroding ficiently it is necessary that its high- material, and must remain free of leaks pressure stage is continually provided at double the operating pressure and in with pressurized fuel which is free of any case at 0.3 bar. Suitable openings or vapor bubbles. Normally, in the case of safety valves must be provided, or passenger cars and light commercial similar measures taken, in order to vehicles, the difference in height between permit excess pressure to escape of the fuel tank and the fuel-injection its own accord. Fuel must not leak past equipment is negligible. Furthermore, the the filler cap or through pressure- fuel lines are not too long and they have compensation devices. This applies adequate internal diameters. As a result, when the vehicle is subjected to minor the vane-type supply pump in the mechanical shocks, as well as when Fig. 2 Interaction of the fuel-supply pump, pressure-control valve, and overflow restriction 1 Drive shaft, 2 Pressure-control valve, 3 Eccentric ring, 4 Support ring, 5 Governor drive, 6 Drive-shaft dogs, 7 Overflow restriction, 8 Pump housing. 1 2 3 4 5 6 78

UMK0321Y 13 Axial-piston cornering, and when standing or driving Vane-type fuel-supply pump for low- distributor on an incline. The fuel tank and the pressure delivery pumps engine must be so far apart from each 1 Inlet, 2 Outlet. other that in case of an accident there is no danger of fire. In addition, special regulations concerning the height of the fuel tank and its protective shielding apply to vehicles with open cabins, as well as to tractors and buses

Fuel lines As an alternative to steel pipes, flame- inhibiting, steel-braid-armored flexible 2 fuel lines can be used for the low- pressure stage. These must be routed to ensure that they cannot be damaged mechanically, and fuel which has dripped or evaporated must not be able to accumulate nor must it be able to ignite.

Fuel filter The injection pump’s high-pressure stage and the injection nozzle are manufactured with accuracies of several thousandths of a millimeter. As a result, 1

Fig. 3: Vane-type fuel-supply pump with impeller on the drive shaft UMK0324Y Fig. 4

14 UMK0320Y contaminants in the fuel can lead to force pushes the impeller’s four vanes Fuel-injection malfunctions, and inefficient filtering can outward against the inside of the techniques cause damage to the pump com- eccentric ring. The fuel between the ponents, delivery valves, and injector vanes’ undersides and the impeller nozzles. This means that a fuel filter serves to support the outward movement specifically aligned to the requirements of the vanes.The fuel enters through the of the fuel-injection system is absolutely inlet passage and a kidney-shaped imperative if trouble-free operation and recess in the pump’s housing, and fills a long service life are to be achieved. the space formed by the impeller, the Fuel can contain water in bound form vane, and the inside of the eccentric ring. (emulsion) or unbound form (e.g., The rotary motion causes the fuel condensation due to temperature between adjacent vanes to be forced into changes). If this water gets into the the upper (outlet) kidney-shaped recess injection pump, corrosion damage can be and through a passage into the interior of the result. Distributor pumps must the pump. At the same time, some of the therefore be equipped with a fuel filter fuel flows through a second passage to incorporating a water accumulator from the pressure-control valve. which the water must be drained off at regular intervals. The increasing Pressure-control valve popularity of the diesel engine in the The pressure-control valve (Fig. 5) is passenger car has led to the connected through a passage to the development of an automatic water- upper (outlet) kidney-shaped recess, and warning device which indicates by is mounted in the immediate vicinity of means of a warning lamp when water the fuel-supply pump. It is a spring- must be drained. loaded spool-type valve with which the pump’s internal pressure can be varied Vane-type fuel supply pump as a function of the quantity of fuel being The vane-type pump (Figs. 3 and 4) is delivered. If fuel pressure increases located around the injection pump’s drive beyond a given value, the valve spool shaft. Its impeller is concentric with the opens the return passage so that the fuel shaft and connected to it with a Woodruff can flow back to the supply pump’s key and runs inside an eccentric ring suction side. If the fuel pressure is too mounted in the pump housing. low, the return passage is closed by the When the drive shaft rotates, centrifugal spring. Fig. 5 Fig. 6 Pressure-control valve Overflow restriction UMK0323Y UMK0322Y 15 Axial-piston The spring’s initial tension can be High-pressure stage distributor adjusted to set the valve opening pumps pressure. The fuel pressure needed for fuel injection is generated in the injection Overflow restriction pump’s high-pressure stage. The The overflow restriction (Figure 6) is pressurized fuel then travels to the screwed into the injection pump’s injection nozzles through the delivery governor cover and connected to the valves and the fuel-injection tubing. pump’s interior. It permits a variable amount of fuel to return to the fuel tank Distributor-plunger drive through a narrow passage. For this The rotary movement of the drive shaft fuel, the restriction represents a flow is transferred to the distributor plunger resistance that assists in maintaining via a coupling unit (Fig. 7), whereby the the pressure inside the injection pump. dogs on cam plate and drive shaft Being as inside the pump a precisely engage with the recesses in the yoke, defined pressure is required as a function which is located between the end of the of pump speed, the overflow restriction drive shaft and the cam plate. The cam and the flow-control valve are pre- plate is forced against the roller ring by cisely matched to each other. a spring, and when it rotates the cam lobes riding on the ring’s rollers convert the purely rotational movement of the drive shaft into a rotating-reciprocating movement of the cam plate. The distributor plunger is held in the cam plate by its cylindrical fitting piece and is locked into position relative to the cam Fig. 7 Pump assembly for generation and delivery of high pressure in the distributor-pump interior

16 UMK0326Y Pump assembly with distributor head Fuel-injection Generates the high pressure and distributes the fuel to the respective fuel injector. techniques 1 Yo ke, 2 Roller ring, 3 Cam plate, 4 Distributor-plunger foot, 5 Distributor plunger, 6 Link element, 7 Control collar, 8 Distributor-head flange, 9 Delivery-valve holder, 10 Plunger-return spring, 4...8 Distributor head.

1 2 3

4 5 6 7 10 8 9 UMK0327Y

Fig. 8 plate by a pin. The distributor plunger Cam plates and cam contours is forced upwards to its TDC position The cam plate and its cam contour in- by the cams on the cam plate, and the fluence the fuel-injection pressure and two symmetrically arranged plunger- the injection duration, whereby cam return springs force it back down again to stroke and plunger-lift velocity are the its BDC position. decisive criteria. Considering the different The plunger-return springs abut at one combustion-chamber configurations and end against the distributor head and at combustion systems used in the various the other their force is directed to the engine types, it becomes imperative that plunger through a link element. These the fuel-injection factors are individually springs also prevent the cam plate tailored to each other. For this reason, a jumping off the rollers during harsh special cam-plate surface is generated for acceleration. The lengths of the return each engine type and machined into the springs are carefully matched to each cam-plate face. This defined cam plate is other so that the plunger is not displaced then assembled in the corresponding from its centered position (Fig. 8). distributor pump. Since the cam-plate surface is specific to a given engine type, the cam plates are not interchangeable between the different VE-pump variants. 17 Axial-piston Distributor head these movements within 60¡ of plunger distributor The distributor plunger, the distributor- rotation. pumps head bushing and the control collar are As the distributor plunger moves from so precisely fitted (lapped) into the TDC to BDC, fuel flows through the open distributor head (Fig. 8), that they seal inlet passage and into the high-pressure even at very high pressures. Small chamber above the plunger. At BDC, the leakage losses are nevertheless un- plunger’s rotating movement then closes avoidable, as well as being desirable for the inlet passage and opens the distribu- plunger lubrication. For this reason, the tor slot for a given outlet port (Fig. 10a). distributor head is only to be replaced The plunger now reverses its direction as a complete assembly, and never the of movement and moves upwards, the plunger, control collar, or distributor working stroke begins. The pressure flange alone. that builds up in the high-pressure chamber above the plunger and in the Fuel metering outlet-port passage suffices to open the The fuel delivery from a fuel-injection delivery valve in question and the fuel pump is a dynamic process comprising is forced through the high-pressure line several stroke phases (Fig. 9). The to the injector nozzle (Fig. 10b). The pressure required for the actual fuel working stroke is completed as soon as injection is generated by the high-pres- the plunger’s transverse cutoff bore sure pump. The distributor plunger’s reaches the control edge of the control stroke and delivery phases (Fig. 10) collar and pressure collapses. From show the metering of fuel to an engine this point on, no more fuel is delivered cylinder. For a 4-cylinder engine the to the injector and the delivery valve distributor plunger rotates through 90¡ closes the high-pressure line. for a stroke from BDC to TDC and back Fig. 9: The cam plate rotates against the roller ring, again. In the case of a 6-cylinder en- whereby its cam track follows the rollers causing gine, the plunger must have completed it to lift (for TDC) and drop back again (for BDC)

18 UMK0328Y Fig. 10 Distributor plunger with stroke and delivery phases Fuel-injection techniques

a Inlet passage UT 1 closes. At BDC, the metering slot (1) closes the inlet passage, and the distributor slot (2) opens the outlet port.

b Fuel delivery. UT 4 2 3 During the plunger stroke towards TDC (working stroke), the plunger pressurizes the fuel in the high- pressure chamber (3). The fuel travels through the outlet-port passage (4) to the injection nozzle.

c End of delivery. UT OT Fuel delivery ceases as soon as the 5 6 control collar (5) opens the transverse cutoff bore (6).

d Entry of fuel. UT OT Shortly before TDC, the inlet passage is opened. During the plunger’s return stroke to BDC, the high-pressure chamber is filled with fuel and the transverse cutoff bore is closed again. The outlet-port passage is also closed at this point.

OT = TDC UT = BDC

UMK0329Y 19 Axial-piston During the plunger’s continued move- The delivery valve is a plunger-type distributor ment to TDC, fuel returns through the valve. It is opened by the injection pres- pumps cutoff bore to the pump interior. During sure and closed by its return spring. this phase, the inlet passage is opened Between the plunger’s individual delivery again for the plunger’s next working cycle strokes for a given cylinder, the (Fig. 10c). delivery valve in question remains During the plunger’s return stroke, its closed. This separates the high-pres- transverse cutoff bore is closed by the sure line and the distributor head’s plunger’s rotating stroke movement, outlet-port passage. During delivery, and the high-pressure chamber above the the pressure generated in the high- plunger is again filled with fuel through pressure chamber above the plunger the open inlet passage (Fig. 10d). causes the delivery valve to open. Fuel then flows via longitudinal slots, into a Delivery valve ring-shaped groove and through the The delivery valve closes off the high- delivery-valve holder, the high-pressure pressure line from the pump. It has the line and the nozzle holder to the injection job of relieving the pressure in the line nozzle. by removing a defined volume of fuel As soon as delivery ceases (transverse upon completion of the delivery phase. cutoff bore opened), the pressure in This ensures precise closing of the in- the high-pressure chamber above the jection nozzle at the end of the injection plunger and in the highpressure lines process. At the same time, stable drops to that of the pump interior, and the pressure conditions between injection delivery-valve spring together with the pulses are created in the high-pressure static pressure in the line force the de- lines, regardless of the quantity of fuel livery-valve plunger back onto its being injected at a particular time. seat again (Fig. 11). Fig. 11 Distributor head with high-pressure chamber 1 Control collar, 2 Distributor head, 3 Distributor plunger, 4 Delivery-valve holder, 5 Delivery-valve.

1 2 3

4 5

20 UMK0335Y Delivery valve with return-flow “retraction volume” resulting from the Fuel-injection restriction retraction piston on the delivery-valve techniques Precise pressure relief in the lines is plunger does not suffice to reliably necessary at the end of injection. This prevent cavitation, secondary injection, though generates pressure waves and combustion-gas blowback into which are reflected at the delivery the nozzle-and-holder assembly. Here, valve. These cause the delivery valve constant-pressure valves are fitted to open again, or cause vacuum phases which relieve the high-pressure system in the high-pressure line. These pro- (injection line and nozzle-and-holder cesses result in post-injection of fuel with assembly) by means of a single-acting attendant increases in exhaust emis- non-return valve which can be set to a sions or cavitation and wear in the injec- given pressure, e.g., 60 bar (Fig. 13). tion line or at the nozzle. To prevent such harmful reflections, the delivery valve is High-pressure lines provided with a restriction bore which is The pressure lines installed in the fuel- only effective in the direction of return injection system have been matched flow. This return-flow restriction com- precisely to the rate-of-discharge curve prises a valve plate and a pressure and must not be tampered with during spring so arranged that the restriction service and repair work. The high-pres- is ineffective in the delivery direction, sure lines connect the injection pump whereas in the return direction damping to the injection nozzles and are routed comes into effect (Fig. 12). so that they have no sharp bends. In automotive applications, the high- Constant-pressure valve pressure lines are normally secured with With high-speed direct-injection (Dl) special clamps at specific intervals, and engines, it is often the case that the are made of seamless steel tubing. Fig. 12 Fig. 13 Delivery valve with return-flow restriction Constant-pressure valve 1 Delivery-valve holder, 2 Return-flow restriction, 1 Delivery-valve holder, 2 Filler piece with spring 3 Delivery-valve spring, 4 Valve holder, locator, 3 Delivery-valve spring, 4 Delivery-valve 5 Piston shaft, 6 Retraction piston. plunger, 5 Constant-pressure valve, 6 Spring seat, 7 Valve spring (constant-pressure valve), 8 Setting sleeve, 9 Valve holder, 10 Shims.

1 1

2 10 2 3

3 4

9 6 6 8 5 7 4 UMK1184Y UMK1183Y 21 Axial-piston Mechanical engine- mechanical (flyweight) governor and the distributor lever assembly. It is a sensitive control pumps speed control device which determines the position of the control collar, thereby defining (governing) the delivery stroke and with it the injected fuel quantity. It is possible to adapt Application the governor’s response to setpoint changes by varying the design of the The driveability of a diesel-powered lever assembly (Fig. 1). vehicle can be said to be satisfactory when its engine immediately responds Governor functions to driver inputs from the accelerator The basic function of all governors is pedal. Apart from this, upon driving off the limitation of the engine’s maximum the engine must not tend to stall. The speed. Depending upon type, the gov- engine must respond to accelerator- ernor is also responsible for keeping pedal changes by accelerating or decel- certain engine speeds constant, such erating smoothly and without hesitation. as idle speed, or the minimum and On the flat, or on a constant gradient, maximum engine speeds of a stipulated with the accelerator pedal held in a given engine-speed range, or of the complete position, the vehicle speed should also speed range, between idle and maxi- remain constant. When the pedal is mum speed. The different governor released the engine must brake the types are a direct result of the variety of vehicle. On the diesel engine, it is the governor assignments (Fig. 2): injection pump’s governor that ensures Ð Low-idle-speed governing: The diesel that these stipulations are complied with. engine’s low-idle speed is controlled by The governor assembly comprises the the injection-pump governor. Fig. 1 Distributor injection pump with governor assembly, comprising flyweight governor and lever assembly

22 UMK0343Y Ð Maximum-speed governing: With the function of engine speed (torque control). Mechanical accelerator pedal fully depressed, the In some cases, add-on modules are governing maximum full-load speed must not necessary for these extra assignments. increase to more than high idle speed (maximum speed) when the load is Speed-control (governing) accuracy removed. Here, the governor responds The parameter used as the measure for by shifting the control collar back towards the governor’s accuracy in controlling the “Stop” position, and the supply of fuel engine speed when load is removed is to the engine is reduced. the so-called speed droop (P-degree). Ð Intermediate-speed governing: Vari- This is the engine-speed increase, able-speed governors incorporate in- expressed as a percentage, that occurs termediate-speed governing. Within when the diesel engine’s load is re- certain limits, these governors can also moved with the control-lever (accelera- maintain the engine speeds between tor) position unchanged. Within the idle and maximum constant. This speed-control range, the increase in means that depending upon load, the engine speed is not to exceed a given engine speed n varies inside the en- figure. This is stipulated as the high idle gine’s power range only between nVT speed. This is the engine speed which (a given speed on the full-load curve) results when the diesel engine, starting and nLT (with no load on the engine). at its maximum speed under full load, is Other control functions are performed relieved of all load. The speed increase is by the governor in addition to its gov- proportional to the change in load, erning responsibilities: and increases along with it. Ð Releasing or blocking of the extra fuel required for starting, n Ð n δ = lo vo Ð Changing the full-load delivery as a nvo Fig. 2 or expressed in %: Governor characteristics n Ð n a Minimum-maximum-speed governor, δ = lo vo .100% b Variable-speed governor. nvo 1 Start quantity, 2 Full-load delivery, 3 Torque control (positive), 4 Full-load speed regulation, 5 Idle. where δ = Speed droop a mm 1 nlo = High idle (maximum) speed n = Maximum full-load speed 23 4 vo The required speed droop depends on engine application. For instance, on an engine used to power an electrical gen- erator set, a small speed droop is re-

Control-collar travel quired so that load changes result in 5 only minor speed changes and there- b mm fore minimal frequency changes. On the 1 other hand, for automotive applications large speed droops are preferable 23 4 because these result in more stable control in case of only slight load changes (acceleration or deceleration) and lead to better driveability. A low-value speed droop would lead to rough, jerking Control-collar travel 5 operation when the load changes. 0 Engine speed minÐ1 UMK0344E 23 Axial-piston Variable-speed governor governor housing, and is free to rotate distributor around it. When the flyweights rotate pumps The variable-speed governor controls they pivot outwards due to centrifugal all engine speeds between start and force and their radial movement is high idle (maximum). The variable-speed converted to an axial movement of the governor also controls the idle speed and sliding sleeve. The sliding-sleeve travel the maximum full-load speed, as well as and the force developed by the sleeve the engine-speed range in between. influence the governor lever assembly. Here, any engine speed can be selected This comprises the starting lever, ten- by the accelerator pedal and, depending sioning lever, and adjusting lever (not upon the speed droop, maintained shown). The interaction of spring forces practically constant (Fig. 4). and sliding-sleeve force defines the This is necessary for instance when setting of the governor lever assembly, ancillary units (winches, fire-fighting variations of which are transferred to pumps, cranes etc.) are mounted on the the control collar and result in adjust- vehicle. The variable-speed governor ments to the injected fuel quantity. is also often fitted in commercial and agricultural vehicles (tractors and Starting combine harvesters). With the engine at standstill, the flyweights and the sliding sleeve are in their Design and construction initial position (Fig. 3a). The start- The governor assembly is driven by the ing lever has been pushed to the start drive shaft and comprises the flyweight position by the starting spring and has housing complete with flyweights. pivoted around its fulcrum M2. At the The governor assembly is attached to same time the control collar on the dis- the governor shaft which is fixed in the tributor plunger has been shifted to its Fig. 3 Variable-speed governor. Start and idle positions a Start position, b Idle position. 1 Flyweights, 2 Sliding sleeve, 3 Tensioning lever, 4 Starting lever, 5 Starting spring, 6 Control collar, 7 Distributor-plunger cutoff port, 8 Distributor plunger, 9 Idle-speed adjusting screw, 10 Engine-speed control lever, 11 Control lever, 12 Control-lever shaft, 13 Governor spring, 14 Retaining pin, 15 Idle spring. a Starting-spring travel, c Idle-spring travel, h1 max. working stroke (start); h2 min. working stroke (idle): M2 fulcrum for 4 and 5.

ab 12 9 13 14 c 15 10 11 a 3 1 4 1 5 2

M2 M2

8 h1 h2

24 UMK0346Y start-quantity position by the ball pin on Characteristic curves of the variable- Mechanical the starting lever. This means that speed governor governing when the engine is cranked the A: Start position of the control collar, distributor plunger must travel through a S: Engine starts with start quantity, SÐL: Start quantity reduces to idle quantity, complete working stroke (= maximum L: Idle speed nLN following engine start-up delivery quantity) before the cutoff bore (no-load), is opened and delivery ceases. Thus LÐB: Engine acceleration phase after shifting the engine-speed control lever from idle to a given the start quantity (= maximum delivery required speed nc, quantity) is automatically made available BÐB': The control collar remains briefly in the when the engine is cranked. full-load position and causes a rapid increase in engine speed, The adjusting lever is held in the pump B'ÐC: Control collar moves back (less injected housing so that it can rotate. It can be fuel quantity, higher engine speed). In accordance shifted by the fuel-delivery adjusting with the speed droop, the vehicle maintains the required speed or speed nc in the part-load screw (not shown in Figure 3). Similarly, range, the start lever and tensioning lever are E: Engine speed nLT , after removal of load also able to rotate in the adjusting lever. from the engine with the position of the engine- A ball pin which engages in the control speed control-lever remaining unchanged. collar is attached to the underside of the start lever, and the start spring to mm its upper section. The idle spring is A S attached to a retaining pin at the top end of the tensioning lever. Also attached to this pin is the governor s spring. The connection to the engine- BB' Full load speed control lever is through a lever and C the control-lever shaft. It only needs a very low speed for the sliding sleeve to shift against the soft L E No-load start spring by the amount a. In the Control-collar travel process, the start lever pivots around 0 500 1,000 1,500 2,000 minÐ1 n n n n fulcrum M2 and the start quantity is auto- A C LT VH n matically reduced to the idle quantity. Engine speed n LO UMK0348E Low-idle-speed control Fig. 4 With the engine running, and the this means that idle speed can be accelerator pedal released, the engine- adjusted independent of the accelerator- speed control lever shifts to the idle pedal setting, and can be increased or position (Figure 3b) up against the idle- decreased as a function of temperature speed adjusting screw. The idle speed or load. is selected so that the engine still runs reliably and smoothly when unloaded or Operation under load only slightly loaded. The actual control During actual operation, depending is by means of the idle spring on the upon the required engine speed or retaining pin which counteracts the force vehicle speed, the engine-speed control generated by the flyweights. lever is in a given position within its This balance of forces determines the pivot range. This is stipulated by the sliding-sleeve’s position relative to the driver through a given setting of the distributor plunger’s cutoff bore, and accelerator pedal. At engine speeds with it the working stroke. At speeds above idle, start spring and idle spring above idle, the spring has been have been compressed completely and compressed by the amount c and is no have no further effect on governor longer effective. Using the special idle action. This is taken over by the spring attached to the governor housing, governor spring. 25 Axial-piston Example (Fig. 5): and as a result the start and tensioning distributor Using the accelerator pedal, the driver levers pivot around M2 and push the pumps sets the engine-speed control lever to a control collar in the “Stop” direction so specific position corresponding to a that the control port is opened sooner. desired (higher) speed. As a result of It is possible to reduce the delivery this adjustment of the control-lever quantity to “zero” which ensures that position, the governor spring is ten- engine-speed limitation takes place. This sioned by a given amount, with the means that during operation, and as long result that the governor-spring force as the engine is not overloaded, every exceeds the centrifugal force of the position of the engine-speed control lever flyweights and causes the start lever and is allocated to a specific speed range the tensioning lever to pivot around between full-load and zero. The fulcrum M2. Due to the mechanical result is that within the limits set by its transmission ratio designed into the speed droop, the governor maintains the system, the control collar shifts in the desired speed (Fig. 4). “Full-load” direction. As a result, the If the load increases to such an extent delivery quantity is increased and the (for instance on a gradient) that even engine speed rises. This causes the though the control collar is in the full- flyweights to generate more force which, load position the engine speed con- through the sliding sleeve, opposes the tinues to drop, this indicates that it is governor-spring force. impossible to increase fuel delivery any The control collar remains in the “Full- further. This means that the engine is load” position until a torque balance overloaded and the driver must change occurs. If the engine speed continues to down to a lower gear. increase, the flyweights separate even further, the sliding-sleeve force prevails, Fig. 5 Fig. 5: Variable-speed governor, operation under load a Governor function with increasing engine speed, b with falling engine speed. 1 Flyweights, 2 Engine-speed control lever, 3 Idle-speed adjusting screw, 4 Governor spring, 5 Idle spring, 6 Start lever, 7 Tensioning lever, 8 Tensioning-lever stop, 9 Starting spring, 10 Control collar, 11 Adjusting screw for high idle (maximum) speed, 12 Sliding sleeve, 13 Distributor-plunger cutoff bore, 14 Distributor plunger. h1 Working stroke, idle, h2 Working stroke, full-load, M2 fulcrum for 6 and 7.

3 4 11 5 2

1 6 7 8 9 12 1

M2 M2

h1 14 h2 26 UMK0349Y Overrun (engine braking) Minimum-maximum-speed Mechanical During downhill operation the engine is governor governing “driven” by the vehicle, and engine speed tends to increase. This causes The minimum-maximum-speed gover- the flyweights to move outwards so that nor controls (governs) only the idle the sliding sleeve presses against the (minimum) speed and the maximum tensioning and start levers. Both levers speed. The speed range between these change their position and push the points is directly controlled by the ac- control collar in the direction of less fuel celerator pedal (Fig. 6). delivery until a reduced fuel-delivery figure is reached which corresponds to Design and construction the new loading level. At the extreme, The governor assembly with flyweights, the delivery figure is zero. Basically, and the lever configuration, are com- with the variable-speed governor, this parable with those of the variable-speed process applies for all settings of the governor already dealt with. The main engine-speed control lever, when the difference lies in the governor spring and engine load or engine speed changes its installation. It is in the form of to such an extent that the control a compression spring and is held in a collar shifts to either its full-load or stop guide element. Tensioning lever and position. governor spring are connected by a retaining pin.

Starting With the engine at standstill, the flyweights are also stationary and the sliding sleeve is in its initial position. This Fig. 6 enables the starting spring to push the Characteristic curves of the minimum- flyweights to their inner position through maximum-speed governor with idle spring the starting lever and the sliding sleeve. and intermediate spring On the distributor plunger, the control a Starting-spring range, collar is in the start-quantity position. b Range of starting and idle spring, d Intermediate-spring range, f Governor-spring range. Idle control Once the engine is running and the accelerator pedal has been released, the mm engine-speed control lever is pulled back a b d Uncontrolled f to the idle position by its return spring. The centrifugal force generated by the flyweights increases along with engine speed (Fig. 7a) and the inner flyweight

s legs push the sliding sleeve up against the start lever. The idle spring on the tensioning lever is responsible for the Full load controlling action. The control collar is shifted in the direction of “less delivery” by the pivoting action of the start lever, its

Control-collar travel position being determined by interaction between centrifugal force and spring No-load force.

Engine speed n minÐ1 UMK0351E 27 Axial-piston Operation under load fuel quantity is directly determined by the distributor If the driver depresses the accelerator accelerator pedal. To accelerate, or climb pumps pedal, the engine-speed control lever a hill, the driver must “give gas”, or ease is pivoted through a given angle. The off on the accelerator if less engine starting and idle springs are no longer power is needed. effective and the intermediate spring If engine load is now reduced, with comes into effect. The intermediate the engine-speed control lever position spring on the minimum-maximum-speed unchanged, engine speed increases governor provides a “soft” transition to without an increase in fuel delivery. The the uncontrolled range. If the engine- flyweights’ centrifugal force also in- speed control lever is pressed even creases and pushes the sliding sleeve further in the full-load direction, the even harder against the start and intermediate spring is compressed until tensioning levers. Full-load speed control the tensioning lever abuts against the does not set in, at or near the engine’s retaining pin (Fig. 7b). The intermediate rated speed, until the governor-spring spring is now ineffective and the pre-tension has been overcome by the uncontrolled range has been entered. effect of the sliding-sleeve force. This uncontrolled range is a function of If the engine is relieved of all load, speed the governor-spring pretension, and in increases to the high idle speed, and the this range the spring can be regarded as engine is thus protected against over- a solid element. The accelerator-pedal revving. position (engine-speed control lever) is Passenger cars are usually equipped now transferred directly through the with a combination of variable-speed governor lever mechanism to the control governor and minimum-maximum-speed collar, which means that the injected governor. Fig. 7 Minimum-maximum-speed governor a Idle setting, b Full-load setting. 1 Flyweights, 2 Engine-speed control lever, 3 Idle-speed adjusting screw, 4 Governor spring, 5 Intermediate spring, 6 Retaining pin, 7 Idle spring, 8 Start lever, 9 Tensioning lever, 10 Tensioning-lever stop, 11 Starting spring, 12 Control collar, 13 Full-load speed control, 14 Sliding sleeve, 15 Distributor plunger cutoff bore, 16 Distributor plunger. a Start and idle-spring travel, b Intermediate-spring travel, h1 Idle working stroke, h2 Full-load working stroke, M2 fulcrum for 8 and 9.

4 b 3 13 5 2 6 a 1 7 8 9 10 14 1 11

M2 M2

16 15

h1 h2

28 UMK0352Y Fig. 1 Curve of a working stroke at full load Injection Injection timing and at low speed (not drawn to scale). timing In order to compensate for the injection FB Start of delivery, SB Start of injection, lag and the ignition lag, as engine SV Injection lag, VB Start of combustion, ZV Ignition lag, SE End of injection, speed increases the timing device VE End of combustion. advances the distributor pump’s start 1 Combustion pressure, of delivery referred to the engine’s 2 Compression pressure, UT BDC, crankshaft. Example (Fig. 1): OT TDC. Start of delivery (FB) takes place after Plunger position h the inlet port is closed. The high pres- bar sure then builds up in the pump which, ZV as soon as the nozzle-opening pres- SV sure has been reached leads to the start of injection (SB). The period 1 between FB and SB is referred to as the injection lag (SV). The increasing VB SE SB VE compression of the air-fuel mixture in the FB combustion chamber then initiates the ignition (VB). The period between SB Combustion-chamber pressure 2 and VB is the ignition lag (ZV). As soon as the cutoff port is opened again the BDC TDC BDC pump pressure collapses (end of pump delivery), and the nozzle needle closes FB SB SE again (end of injection, SE). This is bar p followed by the end of combustion (VE). 400

300 Assignment 200 During the fuel-delivery process, the injection nozzle is opened by a pressure 100 Pump high pressure wave which propagates in the high- 0 pressure line at the speed of sound. TDC Basically speaking, the time required for mm this process is independent of engine D speed, although with increasing engine n 0.3 speed the crankshaft angle between start of delivery and start of injection 0.2 SV also increases. This must be 0.1 compensated for by advancing the start of delivery. The pressure wave’s Nozzle-needle lift 0 propagation time is determined by the TDC length of the high-pressure line and the speed of sound which is approx. mm3 1,500 m/s in diesel fuel. The interval °cms Q represented by this propagation time is termed the injection lag. In other words, 6 the start of injection lags behind the start 4 of delivery. This phenomena is the 2 reason for the injector opening later Rate of injection (referred to the engine’s piston position) 0 -16 -12 -8 -4-2TDC 2841216 at higher engine speeds than at low °cms BTDC °cms ATDC engine speeds. Following injection, the Degrees camshaft injected fuel needs a certain time in UMK0357E 29 Axial-piston order to atomize and mix with the air to piston position, this means that the in- distributor form an ignitable mixture. jection pump’s start of delivery must be pumps This is termed the air-fuel mixture advanced along with increasing engine preparation time and is independent of speed in order to compensate for the engine speed. In a diesel engine, the overall delay caused by ignition lag time required between start of injection and injection lag. This start-of-delivery and start of combustion is termed the advance is carried out by the engine- ignition lag. speed-dependent timing device. The ignition lag is influenced by the diesel fuel’s ignition quality (defined by the Cetane Number), the compression Timing device ratio, the intake-air temperature, and the quality of fuel atomization. As a Design and construction rule, the ignition lag is in the order The hydraulically controlled timing de- of 1 millisecond. This means that pre- vice is located in the bottom of the suming a constant start of injection, the distributor pump’s housing, at right crankshaft angle between start of angles to the pump’s longitudinal axis injection and start of combustion (Fig. 2), whereby its piston is free to increases along with increasing engine move in the pump housing. The housing speed. The result is that combustion can is closed with a cover on each side. no longer start at the correct point There is a passage in one end of the (referred to the engine-piston position). timing device plunger through which the Being as the diesel engine’s most fuel can enter, while at the other end the efficient combustion and power can only plunger is held by a compression spring. be developed at a given crankshaft or The piston is connected to the roller ring Fig. 2 Distributor injection pump with timing device 1 Roller ring, 2 Roller-ring rollers, 3 Sliding block, 4 Pin, 5 Timing-device piston, 6 Cam plate, 7 Distributor plunger.

1234567 30 UMK0354Y Fig. 3 through a sliding block and a pin so that Timing device, method of operation Injection piston movement can be converted to a Initial position, timing rotational movement of the roller ring. b Operating position. 1 Pump housing, 2 Roller ring, 3 Roller-ring rollers, 4 Pin, Method of operation 5 Passage in timing-device piston, The timing-device piston is held in its 6 Cover, 7 Timing-device piston, initial position by the timing-device spring 8 Sliding block, 9 Timing-device spring. (Fig. 3a). During operation, the pressure- control valve regulates the fuel pressure inside the pump so that it is proportional to engine speed. As a result, the engine- a speed-dependent fuel pressure is applied to the end of the timing-device 1 piston opposite to the spring. As from about 300 minÐ1, the fuel pressure inside the pump overcomes the 2 spring preload and shifts the timing- device piston to the left and with it the 3 sliding block and the pin which engages in the roller ring (Fig. 3b). The roller ring is rotated by movement of the pin, and 4 the relative position of the roller ring to the cam plate changes with the result 5 that the rollers lift the rotating cam plate at an earlier moment in time. In other 6 words, the roller ring has been rotated through a defined angle with respect to the cam plate and the distributor 9 8 7 plunger. Normally, the maximum angle is 12 degrees camshaft (24 degrees crankshaft). b

UMK0355Y 31 Axial-piston Add-on modules the add-on modules and their effects distributor upon the diesel engine. The schematic pumps and shutoff devices (Fig. 2) shows the interaction of the basic distributor pump and the various Application add-on modules.

The distributor injection pump is built Torque control according to modular construction Torque control is defined as varying principles, and can be equipped with a fuel delivery as a function of engine variety of supplementary (add-on) units speed in order to match it to the (Fig. 1). These enable the implemen- engine’s fuel-requirement characteristic. tation of a wide range of adaptation If there are special stipulations with possibilities with regard to optimization regard to the full-load characteristic of engine torque, power output, fuel (optimization of exhaust-gas compo- economy, and exhaust-gas composition. sition, of torque characteristic curve, and The overview provides a summary of of fuel economy), it may be necessary Fig. 1 Distributor injection pump with add-on modules 1 Cold-start accelerator, 2 Manifold-pressure compensator.

32 UMK0358Y Fig. 2 Schematic of the VE distributor pump with mechanical/hydraulic full-load torque control Add-on modules LDA Manifold-pressure compensator. and shutoff Controls the delivery quantity as a function of the charge-air pressure. devices HBA Hydraulically controlled torque control. Controls the delivery quantity as a function of the engine speed (not for pressure-charged engines with LDA).

LFB Load-dependent start of delivery. Adaptation of pump delivery to load. For reduction of noise and exhaust-gas emissions.

ADA Altitude-pressure compensator. Controls the delivery quantity as a function of atmospheric pressure.

KSB Cold-start accelerator. Improves cold-start behavior by changing the start of delivery.

GST Graded (or variable) start quantity. Prevents excessive start quantity during warm start.

TLA Temperature-controlled idle-speed increase. Improves engine warm-up and smooth running when the engine is cold.

ELAB Electrical shutoff device.

A Cutoff port, nactual Actual engine speed (controlled variable), nsetpoint Desired engine speed (reference variable), QF Delivery quantity, tM Engine temperature, tLU Ambient-air temperature, pL Charge-air pressure, pA Atmospheric pressure, pi Pump interior pressure.

1 Full-load torque control with governor lever assembly, 2 Hydraulic full-load torque control.

Basic pump Add-on module

tLU /tM nsetpoint Uon /Uoff pL /pA

TLA GST

Engine-speed Control of injected LDA control fuel quantity ADA

ELAB HBA 12 A

nactual Injection Drive Vane-type fuel- High-pressure Delivery-valve nozzles QF supply pump pump with distributor assembly Fuel

LFB

pi p

tM Timing device KSB

UMK0359E 33 Axial-piston to install torque control. In other words, actual fuel requirements. This is known distributor the engine should receive precisely the as “torque control”, and in the case of pumps amount of fuel it needs. The engine’s the distributor injection pump can be fuel requirement first of all climbs as a implemented using the delivery valve, the function of engine speed and then levels cutoff port, or an extended governor- off somewhat at higher speeds. The lever assembly, or the hydraulically fuel-delivery curve of an injection pump controlled torque control (HBA). Full-load without torque control is shown in Fig. 3. torque control using the governor lever As can be seen, with the same setting of assembly is applied in those cases in the control collar on the distributor which the positive full-load torque control plunger, the injection pump delivers with the delivery valve no longer suffices, slightly more fuel at high speeds than it or a negative full-load torque control has does at lower speeds. This is due to the become necessary. throttling effect at the distributor plunger’s cutoff port. This means that if the Positive torque control injection pump’s delivery quantity is Positive torque control is required on specified so that maximum-possible those injection pumps which deliver too torque is developed at low engine much fuel at higher engine revs. The speeds, this would lead to the engine delivery quantity must be reduced as being unable to completely combust the engine speed increases. excess fuel injected at higher speeds and smoke would be the result together Positive torque control using with engine overheat. On the other the delivery valve hand, if the maximum delivery quantity Within certain limits, positive torque is specified so that it corresponds to control can be achieved by means of the the engine’s requirements at maximum delivery valve, for instance by fitting a speed and full-load, the engine will not be softer delivery-valve spring. able to develop full power at low engine speeds due to the delivery quantity Positive torque control using dropping along with reductions in engine the cutoff port speed. Performance would be below Optimization of the cutoff port’s dimen- optimum. The injected fuel quantity must sions and shape permit its throttling effect therefore be adjusted to the engine’s to be utilized for reducing the delivery Fig. 3 quantity at higher engine speeds. Fuel-delivery characteristics, with and without torque control Positive torque control using the a Negative, b Positive torque control. governor lever assembly (Fig. 4a) 1 Excess injected fuel, The decisive engine speed for start of 2 Engine fuel requirement, 3 Full-load delivery with torque control, torque control is set by preloading the Shaded area: torque-control springs. When this speed Full-load delivery without torque control. is reached, the sliding-sleeve force (FM) and the spring preload must be in equilibrium, whereby the torque-control mm3 lever (6) abuts against the stop lug (5) stroke 123 of the tensioning lever (4). The free end F

Q of the torque-control lever (6) abuts b a against the torque-control pin (7). If engine speed now increases, the sliding-sleeve force acting against the starting lever (1) increases and the common pivot point (M ) of starting Delivery quantity minÐ1 4 Engine speed n lever and torque-control lever (6) 34 UMK0360E changes its position. At the same time, the torque-control lever tilts around the presses against the preloaded torque- Add-on stop pin (5) and forces the torque- control spring. As soon as the slid- modules control pin (7) in the direction of the ing-sleeve force exceeds the torque- and shutoff stop, while the starting lever (1) swivels control spring force, the torque-control devices around the pivot point (M2) and forces the lever (6) is forced in the direction of the control collar (8) in the direction of re- torque-control-pin collar. As a result, the duced fuel delivery. Torque control ceases common pivot point (M4) of the starting as soon as the torque-control-pin collar lever and torque-control lever changes its (10) abuts against the starting lever (1). position. At the same time the starting lever swivels around its pivot point Negative torque control (M2) and pushes the control collar (8) Negative torque control may be in the direction of increased delivery. necessary in the case of engines which Torque control ceases as soon as the have black-smoke problems in the torque-control lever abuts against the pin lower speed range, or which must collar. generate specific torque characteristics. Similarly, turbocharged engines also Negative torque control using hydrauli- need negative torque control when the cally controlled torque control HBA manifold-pressure compensator (LDA) In the case of naturally aspirated diesel has ceased to be effective. In this case, engines, in order to give a special shape the fuel delivery is increased along with to the full-load delivery characteristic engine speed (Fig. 3). as a function of engine speed, a form of torque control can be applied which Negative torque control using the is similar to the LDA (manifold-pressure governor lever assembly (Fig. 4b) compensator). Once the starting spring (9) has been Here, the shift force developed by the compressed, the torque-control lever hydraulic piston is generated by the (6) applies pressure to the tensioning pressure in the pump interior, which in lever (4) through the stop lug (5). The turn depends upon pump speed. In torque-control pin (7) also abuts against contrast to spring-type torque control, the tensioning lever (4). If the sliding- within limits the shape of the full-load sleeve force (FM) increases due to rising characteristic can be determined by a engine speed, the torque-control lever cam on a sliding pin. Fig. 4 Torque control using the governor-lever assembly a Positive torque control, b Negative torque control. 1 Starting lever, 2 Torque-control spring, a b 3 Governor spring, 4 Tensioning lever, 34 4 5 Stop lug, 6 Torque-control lever, 7 Torque-control pin, 8 Control collar, M4 M4 9 Starting spring, 5 5 9 10 Pin collar, FM FM 10 6 11 Stop point, 11 M2 Pivot point for 1 and 4, 7 1 M Pivot point for 1 and 6, M 4 2 2 7 M2 Sliding-sleeve force, FM 1 2 ∆ s Control-collar travel. 8 6 8

∆ s ∆ s

UMK0362Y 35 Axial-piston Manifold-pressure With an exhaust turbocharger, the distributor compensation engine’s exhaust gas, instead of simply pumps being discharged into the atmosphere, Exhaust-gas turbocharging is used to drive the turbocharger’s Because it increases the mass of air turbine at speeds which can exceed inducted by the engine, exhaust turbo- 100,000 minÐ1. Turbine and turbocharger charging boosts a diesel engine’s power compressor are connected through a output considerably over that of a nat- shaft. The compressor draws in air, urally aspirated diesel engine, with little compresses it, and supplies it to the increase in dimensions and engine engine’s combustion chambers under speeds. This means that the brake pressure, whereby not only the air horsepower can be increased corre- pressure rises but also the air sponding to the increase in air mass temperature. If temperatures become (Figure 6). In addition, it is often possible excessive, some form of air cooling to also reduce the specific fuel con- (intercooling) is needed between the sumption. An exhaust-gas turbocharger turbocharger and the engine intake. is used to pressure-charge the diesel engine (Fig. 5). Fig. 5: Diesel engine with exhaust-gas turbocharger

36 UMK0365Y Power and torque comparison, naturally aspi- Manifold-pressure compensator Add-on rated and pressure-charged engines (LDA) modules The manifold-pressure compensator and shutoff kW Naturally aspirated engine Nm (LDA) reacts to the charge-air pressure devices Pressure-charged engine generated by the exhaust-gas turbocharger, or the (mechanical) super- charger, and adapts the full-load deliv- Pe

d ery to the charge-air pressure (Figs. 6 e M

and 7). Torque Power Assignment

Md The manifold-pressure compensator (LDA) is used on pressure-charged diesel engines. On these engines the injected fuel quantity is adapted to minÐ1 the engine’s increased air charge (due to Engine speed n pressure-charging). If the pressure- UMK0367E charged diesel engine operates with a Fig. 6 Fig. 7 reduced cylinder air charge, the in- Distributor injection pump with manifold-pressure compensator (LDA) 1 Governor spring, 2 Governor cover, 3 Reverse lever, 4 Guide pin, 5 Adjusting nut, 6 Diaphragm, 7 Compression spring, 8 Sliding pin, 9 Control cone, 10 Full-load adjusting screw, 11 Adjusting lever, 12 Tensioning lever, 13 Starting lever, 14 Connection for the charge-air, 15 Vent bore. M1 pivot for 3.

14 5 6

4 7 M1 15 8 9

3 10 2 1 11 12 13

UMK0364Y 37 Axial-piston jected fuel quantity must be adapted starting lever and tensioning lever to distributor to the lower air mass. This is performed swivel around their common pivot point pumps by the manifold-pressure compensator thus shifting the control collar in the which, below a given (selectable) direction of increased fuel delivery. Fuel charge-air pressure, reduces the full-load delivery is adapted in response to the quantity. increased air mass in the combustion chamber (Fig. 8). On the other hand, Design and construction when the charge-air pressure drops, The LDA is mounted on the top of the the spring underneath the diaphragm distributor pump (Fig. 7). In turn, the top pushes the diaphragm upwards, and with of the LDA incorporates the connection it the sliding pin. The compensation for the charge-air and the vent bore. The action of the governor lever mechanism interior of the LDA is divided into two now takes place in the reverse direction separate airtight chambers by a dia- and the injected fuel quantity is adapted phragm to which pressure is applied by to the change in charge pressure. Should a spring. At its opposite end, the spring the turbocharger fail, the LDA reverts to is held by an adjusting nut with which its initial position and the engine operates the spring’s preload is set. This serves normally without developing smoke. The to match the LDA’s response point to full-load delivery with charge-air pressure the charge pressure of the exhaust is adjusted by the full-load stop screw turbocharger. The diaphragm is con- fitted in the governor cover. nected to the LDA’s sliding pin which has a taper in the form of a control cone. This is contacted by a guide pin which transfers the sliding-pin movements to the reverse lever which in turn changes the setting of the full-load stop. The initial Fig. 8 setting of the diaphragm and the sliding Charge-air pressure: Operative range pin is set by the adjusting screw in the top a Turbocharger operation, of the LDA. b Normally aspirated operation. p1 Lower charge-air pressure, Method of operation p2 Upper charge-air pressure. In the lower engine-speed range the charge-air pressure generated by the exhaust turbocharger and applied to the diaphragm is insufficient to overcome the mm3/ stroke LDA operative pressure of the spring. The diaphragm range remains in its initial position. As soon as the charge-air pressure applied to the diaphragm becomes effective, the diaphragm, and with it the sliding pin and control cone, shift against the force of the e a spring. The guide pin changes its Q position as a result of the control cone’s vertical movement and causes the reverse lever to swivel around its pivot Injected fuel quantity point M1 (Fig. 7). Due to the force exerted b by the governor spring, there is a non- positive connection between tensioning lever, reverse lever, guide pin, and p p mbar sliding-pin control cone. As a result, the 1 2 tensioning lever follows the reverse Charge-air pressure p 38 lever’s swivelling movement, causing the UMK0368E Load-dependent Design and construction Add-on compensation For load-dependent injection timing, modules modifications must be made to the gov- and shutoff Depending upon the diesel engine’s load, ernor shaft, sliding sleeve, and pump devices the injection timing (start of delivery) housing. The sliding sleeve is provided must be adjusted either in the “advance” with an additional cutoff port, and or “retard” direction. the governor shaft with a ring-shaped groove, a longitudinal passage and two Load-dependent start of delivery transverse passages (Fig. 9). The pump (LFB) housing is provided with a bore so that a connection is established from the Assignment interior of the pump to the suction side of Load-dependent start of delivery is de- the vane-type supply pump. signed so that with decreasing load (e.g., change from full-load to part- Method of operation load), with the control-lever position un- As a result of the rise in the supply- changed, the start of delivery is shifted pump pressure when the engine speed in the “retard” direction. And when en- increases, the timing device adjusts the gine load increases, the start of delivery start of delivery in the “advance” direc- (or start of injection) is shifted in the tion. On the other hand, with the drop in “advance” direction. These adjustments the pump’s interior pressure caused by lead to “softer” engine operation, and the LFB it is possible to implement a cleaner exhaust gas at part- and full- (relative) shift in the “retard” direction. load. This is controlled by the ring-shaped groove in the governor shaft and the sliding-sleeve’s control port. The control Fig. 9 Design and construction of the governor assembly with load-dependent start of delivery (LFB) 1 Governor spring, 2 Sliding sleeve, 3 Tensioning lever, 4 Start lever, 5 Control collar, 6 Distributor plunger, 7 Governor shaft, 8 Flyweights. M2 Pivot point for 3 and 4.

1 2

M2 7 8 5

UMK0369Y 39 Axial-piston lever is used to input a given full-load port is closed again. The fuel in the pump distributor speed. If this speed is reached and the interior can now no longer flow through pumps load is less than full load, the speed the governor shaft to the suction side, increases even further, because with a and the pump interior pressure increases rise in speed the flyweights swivel again. The timing-device piston shifts outwards and shift the sliding sleeve. On against the force of the timing- the one hand, this reduces the delivery device spring and adjusts the roller ring quantity in line with the conventional so that start of delivery is shifted in the governing process. On the other, the “advance” direction (Fig. 10). sliding sleeve’s control port is opened by the control edge of the governor-shaft Atmospheric-pressure groove. The result is that a portion of the compensation fuel now flows to the suction side through the governor shaft’s longitudinal and At high altitudes, the lower air density transverse passages and causes a reduces the mass of the inducted air, pressure drop in the pump’s interior. and the injected full-load fuel quantity This pressure drop results in the timing- cannot burn completely. Smoke results device piston moving to a new position. and engine temperature rises. To pre- This leads to the roller ring being turned vent this, an altitude-pressure compen- in the direction of pump rotation so that sator is used to adjust the full-load start of delivery is shifted in the “retard” quantity as a function of atmospheric direction. If the position of the control pressure. lever remains unchanged and the load increases again, the engine speed drops. Altitude-pressure compensator The flyweights move inwards and the (ADA) sliding sleeve is shifted so that its control Fig. 10 Design and construction Sliding-sleeve positions in the load- The construction of the ADA is identical dependent injection timing (LFB) to that of the LDA. The only difference a Start position (initial position), being that the ADA is equipped with an b Full-load position shortly before the control aneroid capsule which is connected to port is opened, c Control port opened, pressure reduction in a vacuum system somewhere in the pump interior. vehicle (e.g., the power-assisted brake 1 Longitudinal bore in the governor shaft, system). The aneroid provides a con- 2 Governor shaft, 3 Sliding-sleeve control port, 4 Sliding-sleeve, 5 Governor-shaft transverse stant reference pressure of 700 mbar passage, 6 Control edge of the groove in the (absolute). governor shaft, 7 Governor-shaft transverse passage. 1 2 3 4 Method of operation Atmospheric pressure is applied to the a upper side of the ADA diaphragm. The reference pressure (held constant by the aneroid capsule) is applied to the 5 6 7 diaphragm’s underside. If the atmospheric pressure drops (for instance when the vehicle is driven in the b mountains), the sliding bolt shifts verti- cally away from the lower stop and, similar to the LDA, the reverse lever causes the injected fuel quantity to be c reduced.

40 UMK0370Y Cold-start compensation Mechanical cold-start accelerator (KSB) Add-on engaging in roller ring (cold-start position) modules The diesel engine’s cold-start charac- 1 Lever, 2 Access window, 3 Ball pin, and shutoff teristics are improved by fitting a cold- 4 Longitudinal slot, 5 Pump housing, 6 Roller ring, devices 7 Roller in the roller ring, 8 Timing-device piston, start compensation module which shifts 9 Torque-control pin, 10 Sliding block. 11 Timing- the start of injection in the “advance” device spring, 12 Shaft, 13 Coil spring. direction. Operation is triggered either by the driver using a bowden cable in 1 2 3 4 the cab, or automatically by means of a temperature-sensitive advance mechanism (Fig. 11). 5 Mechanical cold-start accelerator (KSB) on the roller ring 6

Design and construction 7 The KSB is attached to the pump housing, the stop lever being connected 13 12 through a shaft to the inner lever on which a ball pin is eccentrically 8 mounted. The ball pin’s head extends into the roller ring (a version is available in which the advance mechanism en- 11 10 9 gages in the timing-device piston). The UMK0373Y stop lever’s initial position is defined Fig. 12 by the stop itself and by the helical Method of operation coiled spring. Attached to the top of Automatically and manually operated the stop lever is a bowden cable which cold-start accelerators (KSB) differ only serves as the connection to the manual with regard to their external advance or to the automatic advance mechanism. mechanisms. The method of operation is The automatic advance mechanism is identical. With the bowden cable not mounted on the distributor pump, where- pulled, the coil spring pushes the stop as the manual operating mechanism is lever up against the stop. Ball pin and in the driver’s cab (Fig. 12). roller ring are in their initial position. The force applied by the bowden cable Fig. 11 Mechanical cold-start accelerator (KSB), advance mechanism with automatic operation (cold-start position) 12 1 Clamp, 2 Bowden cable, 3 Stop lever, 4 Coil spring, 5 KSB advance lever, 6 Control device sensitive to the temperature of the coolant and the surroundings.

345 6 UMK0372Y 41 Axial-piston causes the stop lever, the shaft, the inner Temperature-controlled idle-speed distributor lever and the ball pin, to swivel and increase (TLA) pumps change the roller ring’s setting so that the The TLA is also operated by the control start of delivery is advanced. The ball pin device and is combined with the KSB. engages in a slot in the roller ring, which Here, when the engine is cold, the ball means that the timing-device piston pin at the end of the elongated KSB cannot rotate the roller ring any further in advance lever presses against the en- the “advance” direction until a given gine-speed control lever and lifts it away engine speed has been exceeded. from the idle-speed stop screw. The idle In those cases in which the KSB is speed increases as a result, and rough triggered by the driver from the cab running is avoided. When the engine has (timing-device KSB), independent of the warmed up, the KSB advance lever abuts advance defined by the timing device (a), against its stop and, as a result, the an advance of approx. 2.5¡ camshaft is engine-speed control lever is also up maintained (b), as shown in Fig. 13. With against its stop and the TLA is no longer the automatically operated KSB, this effective (Fig. 14). advance depends upon the engine temperature or ambient temperature. Hydraulic cold-start accelerator The automatic advance mechanism uses Advancing the start of injection by a control device in which a temperature- shifting the timing-device piston has sensitive expansion element converts the only limited applications. In the case of engine temperature into a stroke move- the hydraulic start-of-injection advance, ment. The advantage of this method is the speed-dependent pump interior that for a given temperature, the optimum pressure is applied to the timing-device start of delivery (or start of injection) is piston. In order to implement a start- always selected. of-injection advance, referred to the There are a number of different lever conventional timing-device curve, the configurations and operating mecha- pump interior pressure is increased nisms in use depending upon the automatically. To do so, the automatic direction of rotation, and on which side control of pump interior pressure is the KSB is mounted. modified through a bypass in the pressure-holding valve.

Fig. 13 Fig. 14 Effect of the mechanical cold-start Mechanical cold-start accelerator accelerator (KSB) (automatically controlled) with temperature- a Timing-device advance, dependent idle-speed increase b Minimum advance (approx. 2.5¡ camshaft). 1 Engine-speed control lever, 2 Ball pin, °cms 3 KSB advance lever, 4 Stop.

1 2

a 3 4 b

2.5° Injection-timing advance 0 0 minÐ1 Pump speed p UMK0374E 42 UMK0377Y Design and construction Effect of the hydraulic cold-start Add-on The hydraulic cold-start accelerator accelerator (KSB) modules comprises a modified pressure-control 1 Injection-timing advance. and shutoff valve, a KSB ball valve, a KSB control °cms devices valve, and an electrically heated expansion element.

Method of operation The fuel delivered by the fuel-supply pump is applied to one of the timing 1 device piston’s end faces via the injection pump’s interior. In accordance with the injection pump’s interior pressure, the piston is shifted against the force Injection-timing advance of its spring and changes the start- Ð1 of-injection timing. Pump interior min Pump speed p pressure is determined by a pressure- UMK0379E control valve which increases pump Fig. 16 interior pressure along with increasing adjusting screw in the integrated KSB pump speed and the resulting rise in control valve, the KSB function can be pump delivery (Fig. 15). set to a given engine speed. The fuel There is a restriction passage in the supply pump pressure shifts the KSB pressure-control valve’s plunger in order control valve’s plunger against the to achieve the pressure increase force of a spring. A damping restriction is needed for the KSB function, and the used to reduce the pressure fluctu- resulting advance curve shown as a ations at the control plunger. The KSB dotted line in Fig. 16. This ensures that pressure characteristic is controlled by the same pressure is effective at the its plunger’s control edge and the section spring side of the pressure-control at the valve holder. The KSB function valve. The KSB ball-type valve has a is adapted by correct selection of the correspondingly higher pressure level KSB control valve’s spring rate and its and is used in conjunction with the control section. When the warm engine thermo-element both for switching-on is started, the expansion element has and switching-off the KSB function, as already opened the ball valve due to the well as for safety switchoff. Using an prevailing temperature. Fig. 15 Hydraulic cold-start accelerator (KSB) 11 Pressure-control valve, 1 12 Valve plunger, 13 Restriction passage, 2 14 Internal pressure, 3 15 Fuel-supply pump, 4 16 Electrically heated expansion element, 17 KSB ball valve, 6 18 Pressureless fuel return, 5 7 19 KSB control valve, adjustable, 10 Timing device. 8

10 9

UMK1195Y 43

Axial-piston Engine shutoff stop lever pushes against the start lever distributor of the governor-lever mechanism. This pumps swivels around its pivot point M2 and Assignment shifts the control collar to the shutoff The principle of auto-ignition as applied position. The distributor plunger’s cutoff to the diesel engine means that the port remains open and the plunger engine can only be switched off by delivers no fuel. interrupting its supply of fuel. Normally, the mechanically governed Fig. 17 distributor pump is switched off by a Electrical shutoff device solenoid-operated shutoff (ELAB). Only (pull solenoid) in special cases is it equipped with a 1 Inlet passage, 2 Distributor plunger, mechanical shutoff device. 3 Distributor head, 4 Push or pull solenoid, 5 High-pressure chamber. Electrical shutoff device (ELAB) 4 The electrical shutoff (Fig. 17) using the vehicle’s key-operated starting switch is 1 coming more and more to the forefront due to its convenience for the driver. 5 On the distributor pump, the solenoid valve for interrupting the fuel supply is 2 installed in the top of the distributor head. When the engine is running, the 3 solenoid is energized and the valve keeps the passage into the injection UMK0382Y pump’s high-pressure chamber open Fig. 18 (armature with sealing cone has pulled Mechanical shutoff device in). When the driving switch is turned 1 Outer stop lever, 2 Start lever, to “OFF”, the current to the solenoid 3 Control collar, 4 Distributor plunger, winding is also cut, the magnetic field 5 Inner stop lever, 6 Tensioning lever, 7 Cutoff port. collapses, and the spring forces the M2 Pivot point for 2 and 6. armature and sealing cone back onto the valve seat again. This closes the inlet passage to the high-pressure chamber, the distributor-pump plunger ceases to deliver fuel, and the engine 1 5 stops. From the circuitry point of view, there are a variety of different possibilities for implementing the electrical shutoff (pull or push solenoid). 6 Mechanical shutoff device On the injection pump, the mechanical shutoff device is in the form of a lever assembly (Fig. 18). This is located in M2 2 the governor cover and comprises an outer and an inner stop lever. The outer 3 7 lever is operated by the driver from inside 4 the vehicle (for instance by means of bowden cable). When the cable is pulled, both levers swivel around their 44 common pivot point, whereby the inner UMK0380Y coupling, or with direct frequency control). Testing and Testing and calibration The pump is connected to the bench’s calibration calibrating-oil supply via oil inlet and outlet, and to its delivery measuring device via high-pressure lines. The Injection-pump test measuring device comprises calibrating benches nozzles with precisely set opening Precisely tested and calibrated injection pressures which inject into the bench’s pumps and governors are the prerequisite measuring system via spray dampers. Oil for achieving the optimum fuel-con- temperature and pressure is adjusted in sumption/performance ratio and compli- accordance with test specifications. ance with the increasingly stringent There are two methods for fuel-delivery exhaust-gas legislation. And it is at this measurement. One is the so-called point that the injection-pump test bench continuous method. Here, a precision becomes imperative. The most important gear pump delivers per cylinder and unit of framework conditions for the test bench time, the same quantity of calibrating-oil and for the testing itself are defined in as the quantity of injected fuel. The gear ISO-Standards which, in particular, place pump’s delivery is therefore a measure of very high demands upon the rigidity and delivery quantity per unit of time. A com- uniformity of the pump drive. puter then evaluates the measurement The injection pump under test is results and displays them as a bar chart clamped to the test-bench bed and con- on the screen. This measuring method nected at its drive end to the test-bench is very accurate, and features good coupling. Drive is through an electric reproducibility (Fig. 1). motor (via hydrostatic or manually- The other method for fuel-delivery mea- switched transmission to flywheel and surement uses glass measuring gradu- Fig. 18 ates. The fuel to be measured is at first Continuous injected-fuel-quantity directed past the graduates and back to measuring system the tank with a slide. When the specified 1 Calibrating-oil tank, 2 Injection pump, number of strokes has been set on the 3 Calibrating nozzle, 4 Measuring cell, stroke-counting mechanism the mea- 5 Pulse counter, 6 Display monitor. surement starts, and the slide opens and the graduates fill with oil. When the set number of strokes has been completed, the slider cuts off the flow of oil 2 6 again. The injected quantity can be read off directly from the graduates.

3 Engine tester for diesel 4 engines

5 The diesel-engine tester is necessary for the precise timing of the injection pump to the engine. Without opening the high-pressure lines, this tester measures M the start of pump delivery, injection timing, and engine speeds. A sensor is clamped over the high-pressure line 1 to cylinder 1, and with the stroboscopic timing light or the TDC sensor for detect- ing crankshaft position, the tester calculates start of delivery and injection UWT0059Y timing. 45

Axial-piston Nozzles and The following types of pintle nozzle are distributor available: pumps nozzle holders Ð Standard pintle nozzles (Fig. 1), Ð Throttling pintle nozzles, and The injection nozzles and their respec- Ð Flat-cut pintle nozzles (Fig. 2). tive nozzle holders are vitally important components situated between the in-line Design and construction injection pump and the diesel engine. All pintle nozzles are of practically identi- Their assignments are as follows: cal design, the only difference being in Ð Metering the injection of fuel, the pintle’s geometry: Ð Management of the fuel, Ð Defining the rate-of-discharge curve, Standard pintle nozzle Ð Sealing-off against the combustion On the standard pintle nozzle, the nozzle chamber. needle is provided with a pintle which Considering the wide variety of com- extends into the injection orifice of the bustion processes and the different forms nozzle body in which it is free to move of combustion chamber, it is necessary with a minimum of play. The injection that the shape, “penetration force”, and spray can be matched to the engine’s atomization of the fuel spray injected by requirements by appropriate choice of the nozzle are adapted to the prevailing dimensions and pintle designs. conditions. This also applies to the injection time, and the injected fuel quantity per degree camshaft. Since the design of the nozzle-holder combination makes maximum use of standardized components and assem- Fig. 1 blies, this means that the required flexi- Standard pintle nozzle bility can be achieved with a minimum of 1 Lift stop surface, 2 Ring groove, 3 Needle guide, components. The following nozzles and 4 Nozzle-body shaft, 5 Pressure chamber, nozzle holders are used with in-line injec- 6 Pressure shoulder, 7 Seat lead-in, 8 Inlet port, 9 Nozzle-body shoulder, 10 Nozzle-body collar, tion pumps: 11 Sealing surface, 12 Pressure shaft, Ð Pintle nozzles (DN..) for indirect-injec- 13 Pressure-pin contact surface. tion (IDI) engines, and 13 Ð Hole-type nozzles (DLL../DLSA..) for 12

direct-injection (DI) engines, 1 11 Ð Standard nozzle holders (single- spring nozzle holders), with and with- 2 out needle-motion sensor, and Ð Two-spring nozzle holders, with and 3 10 without needle-motion sensor. 9 Pintle nozzles

4 Application Pintle nozzles are used with in-line injection pumps on indirect-injection engines (pre-chamber and whirl-chamber engines). In this type of diesel engine, the air/fuel 5 8 mixture is for the most part formed by the air’s vortex work. The injected fuel spray serves to support this mixture-formation 6 7 46 process. UMK1390Y Throttling pintle nozzle Flat-cut pintle nozzle Nozzles The throttling pintle nozzle is a pintle This nozzle’s pintle has a ground surface and nozzle nozzle with special pintle dimensions. which opens a flow cross-section in addi- holders The special pintle design serves to define tion to the annular gap when the pintle the shape of the rate-of-discharge curve. opens (only slight needle lift). The result- When the nozzle needle lifts it first of all ing increased flow volume prevents de- opens a small annular gap so that only a posits forming in this flow channel. This is small amount of fuel is injected (throttling the reason why flat-cut pintle nozzles effect). coke-up far less, and any coking which As needle lift increases (due to pressure does take place is more uniform. The rise), the spray orifice is opened increas- annular gap between spray orifice and ingly until the major portion of the injec- throttling pintle is very small (less than tion (main injection) takes place towards 10 µm). Very often, the flat-cut pintle sur- the end of needle lift. Since the pressure face is parallel to the nozzle-needle axis. in the combustion chamber rises less Referring to Fig. 3, with an additional sharply, this shaping of the rate-of-injec- inclined cut on the pintle, the gradient of tion curve leads to “softer” combustion. the injected-fuel-quantity curve’s flat por- This results in quieter combustion in the tion can be increased so that the tran- part-load range. In other words, it is sition to full nozzle opening is less possible to shape the required rate-of- abrupt. Specially shaped pintles, such as discharge curve by means of the pintle the “radius” or “profile surface” types, can shape, the characteristic of the nozzle be applied to match the flow curve to needle’s spring, and the throttling gap. engine-specific requirements. Part-load noise and vehicle driveability are both improved as a result. Fig. 2 Fig. 3 Flat-cut pintle nozzle Flow quantity as a function of needle lift and a Side view, b Front view. nozzle version 1 Needle seat, 2 Nozzle-body floor, 1 Throttling pintle nozzle, 3 Throttling pintle, 4 Flat cut, 5 Injection orifice, 2 Throttling pintle nozzle with inclined cut on 6 Profiled pintle, 7 Total overlap, pintle (flat-cut pintle nozzle) 8 Cylindrical overlap, 9 Nozzle-body seat. a l/h

1 9

300 8

2 7 3 4 5 6 200

b Flow quantity

100 21

0 0 0.2 0.4 0.6 0.8 mm Needle lift UMK1397E UMK1391Y 47 Axial-piston Hole-type nozzles At those points where high flow rates distributor occur (spray-hole entrance), the abrasive pumps Application particles in the hydro-erosive (HE) me- Hole-type nozzles are used with in-line dium cause material loss. injection pumps on direct-injection en- This so-called HE-rounding process can gines. be applied to both sac-hole and seat-hole One differentiates between: nozzles, whereby the target is: Ð Sac-hole, and Ð Prevent in advance the edge wear Ð Seat-hole nozzles. caused by abrasive particles in the fuel and/or The hole-type nozzles also vary accord- Ð Reduce the flow tolerance. ing to their size: ÐType P with 4 mm needle diameter, For low hydrocarbon emissions, it is and highly important that the volume filled ÐType S with 5 and 6 mm needle dia- with fuel (residual volume) below the meters. edge of the nozzle-needle seat is kept to a minimum. Seat-hole nozzles are there- Design and construction fore used. The spray holes are located on the en- velope of a spray cone (Fig. 4). The number of spray holes and their diameter de- Designs pend upon: Ð The injected fuel quantity, Sac-hole nozzle Ð The combustion-chamber shape, and The spray holes of the sac-hole nozzle Ð The air swirl in the combustion cham- (Fig. 5) are arranged in the sac hole. ber. In the case of a round nozzle tip (Fig. 6a), depending upon design the spray holes The input edges of the spray holes can are drilled mechanically or by means of be rounded by hydro-erosive (HE) ma- electrochemical machining (e.c.m.). chining. Sac-hole nozzles with conical tip (Figs. 6b and 6c) are always drilled using e.c.m. Fig. 4 Sac-hole nozzles are available Spray cone Ð With cylindrical, and γ Spray-cone offset angle, d Spray cone. Ð Conical sac holes in a variety of different dimensions.

γ Sac-hole nozzle with cylindrical sac hole and round tip (Fig. 6a): This nozzle’s sac hole has a cylindrical and a semispherical portion, and permits a high level of design freedom with respect to Ð Number of spray holes, Ð Spray-hole length, and Ð Injection angle.

The nozzle tip is semispherical, and together with the shape of the sac hole, ensures that the spray holes are of identical length. δ

48 UMK1402Y Sac-hole nozzle with cylindrical sac hole Sac-hole nozzle with conical sac hole Nozzles and conical tip (6b): and conical tip (Fig. 6c): and nozzle This type of nozzle is used exclusively Due to the conical shape of this nozzle’s holders with spray-hole lengths of 0.6 mm. The sac hole, its volume is less than that of a tip’s conical shape enables the wall nozzle with cylindrical sac hole. The thickness to be increased between the volume is between that for a seat-hole throat radius and the nozzle-body seat nozzle and a sac-hole nozzle with cylin- with an attending improvement of nozzle- drical sac hole. In order to achieve uni- tip strength. form tip-wall thickness, the tip’s conical design corresponds to that of the sac hole.

Fig. 5 Fig. 6 Sac-hole nozzle Sac-hole shapes 1 Pressure shaft, 2 Needle-lift stop face, a Cylindrical sac hole with round tip, 3 Inlet passage, 4 Pressure shoulder, b Cylindrical sac hole with conical tip, 5 Needle shaft, 6 Nozzle tip, c Conical sac hole with conical tip. 7 Nozzle-body shaft, 8 Nozzle-body shoulder, 1 Shoulder, 2 Seat entrance, 3 Needle seat, 9 Pressure chamber, 10 Needle guide, 4 Needle tip, 5 Injection orifice, 11 Nozzle-body collar, 12 Locating hole, 6 Injection-orifice entrance, 7 Sac hole, 13 Sealing surface, 8 Throat radius, 9 Nozzle-tip cone, 14 Pressure-pin contact surface. 10 Nozzle-body seat, 11 Damping cone.

1 11 2 10 3 9 4 8 7 5 6

c UMK1650Y UMK1403Y 49 Axial-piston Seat-hole nozzle Standard nozzle holders distributor In order to minimise the residual volume pumps Ð and therefore the HC emissions Ð the Assignments and designs start of the spray hole is located in the Nozzle holders with hole-type nozzles in seat taper, and with the nozzle closed it is combination with a radial-piston distrib- covered almost completely by the nozzle utor injection pump are used on DI needle. This means that there is no direct engines. connection between the sac hole and the With regard to the nozzle holders, one combustion chamber (Figs. 7 and 8). The differentiates between sac-hole volume here is much lower than Ð Standard nozzle holders (single- that of the sac-hole nozzle. Compared to spring nozzle holders) with and with- sac-hole nozzles, seat-hole nozzles have out needle-motion sensor, and a much lower loading limit and are there- Ð Two-spring nozzle holders, with and fore only manufactured as Size P with a without needle-motion sensor. spray-hole length of 1 mm. For reasons of strength, the nozzle tip is Application conically shaped. The spray holes are The nozzle holders described here have always formed using e.c.m. methods. the following characteristics: Ð Cylindrical external shape with diame- Fig. 7 ters between 17 and 21 mm, Seat-hole nozzle Ð Bottom-mounted springs (leads to low moving masses), Ð Pin-located nozzles for direct-injection engines, and Ð Standardised components (springs, pressure pin, nozzle-retaining nut) make combinations an easy matter.

Design The nozzle-and-holder assembly is com- posed of the injection nozzle and the nozzle holder. The nozzle holder comprises the following components (Fig. 9): Ð Nozzle-holder body, Ð Intermediate element, Ð Nozzle-retaining nut, Ð Pressure pin, Ð Spring, Ð Shim, and Ð Locating pins.

Fig. 8 The nozzle is centered in the nozzle body Seat-hole nozzle: Tip shape and fastened using the nozzle-retaining nut. When nozzle body and retaining nut are screwed together, the intermediate element is forced up against the sealing surfaces of nozzle body and retaining nut. The intermediate element serves as the needle-lift stop and with its locating pins centers the nozzle in the nozzle- holder body. 50 UMK1408Y UMK1407Y Fig. 9 The nozzle-holder body contains the Standard nozzle holder Nozzles Ð Pressure pin, 1 Edge-type filter, 2 Inlet passage, and nozzle Ð Spring, and 3 Pressure pin, 4 Intermediate element, holders Ð Shim. 5 Nozzle-retaining nut, 6 Wall thickness, 7 Nozzle, 8 Locating pins, 9 Spring, 10 Shim, 11 Leak-fuel passage, The spring is centered in position by the 12 Leak-fuel connection thread, pressure pin, whereby the pressure pin is 13 Nozzle-holder body, 14 Connection thread, 15 Sealing cone. guided by the nozzle-needle’s pressure shaft. 15 The nozzle is connected to the injection pump’s high-pressure line via the nozzle- 14 holder feed passage, the intermediate element, and the nozzle-body feed passage. If required, an edge-type filter can be installed in the nozzle holder. 1 13 Method of operation The nozzle-holder spring applies pres- 12 sure to the nozzle needle through the pressure pin. The spring’s initial tension defines the nozzle’s opening pressure which can be adjusted using a shim. On its way to the nozzle seat, the fuel pas- 11 ses through the nozzle-holder inlet passage, the intermediate element, and the 10 nozzle nody. When injection takes place, the nozzle needle is lifted by the injection 2 pressure and fuel is injected through the injection orifices into the combustion chamber. Injection terminates as soon as the injection pressure drops far enough for 9 the nozzle spring to force the nozzle needle back onto its seat.

Two-spring nozzle holders 3 4 Application 8 The two-spring nozzle holder is a fur- 5 ther development of the standard nozzle holder, and serves to reduce combustion 7 noise particularly in the idle and part-load ranges. 6 Design The two-spring nozzle holder features two springs located one behind the other. At first, only one of these springs has an influence on the nozzle needle and as such defines the initial opening pressure. The second spring is in contact with a stop sleeve which limits the needle’s initial stroke. UMK1413Y 51 Fig. 10 Axial-piston Two-spring nozzle holder for direct-injection When strokes take place in excess of the distributor (DI) engines initial stroke, the stop sleeve lifts and both pumps 1 Nozzle-holder body, 2 Shim, springs have an effect upon the nozzle 3 Spring 1, 4 Pressure pin, needle (Fig. 10). 5 Guide element, 6 Spring 2, 7 Pressure pin, 8 Spring seat, 9 Shim, 10 Intermediate element, Method of operation 11 Stop sleeve, During the actual injection process, the 12 Nozzle needle, 13 Nozzle-retaining nut, nozzle needle first of all opens an initial 14 Nozzle body. amount so that only a small volume of h1 Initial stroke, fuel is injected into the combustion h2 Main stroke. 1 chamber. Along with increasing injection pressure in the nozzle holder though, the nozzle needle opens completely and the main quantity is injected (Fig. 11). This 2-stage

2 rate-of-discharge curve leads to “softer” 3 combustion and to a reduction in noise.

Nozzle holders with needle- motion sensor

4 Application

5 The start-of-injection point is an important parameter for optimum diesel-engine 6 operation. For instance, its evaluation 7 permits load and speed-dependent injection timing, and/or control of the exhaust- 8 gas recirculation (EGR) rate. 9 10 11 12 Fig. 11 Comparison of needle-lift curves a Standard nozzle holder (single-spring nozzle holder), 13 b Two-spring nozzle holder. h1 Initial stroke, h2 Main stroke. a mm 14 0.4

0.2

b mm Nozzle-needle lift 0.4 h2 h 0.2 1 2 h 0

011 2 ms h Time UMK1423-1Y 52 UMK1422E This necessitates a nozzle holder with Two-spring nozzle holder with needle-motion Nozzles needle-motion sensor (Fig. 13) which sensor for direct-injection (DI) engines and nozzle outputs a signal as soon as the nozzle 1 Nozzle-holder body, 2 Needle-motion sensor, holders needle opens. 3 Spring 1, 4 Guide element, 5 Spring 2, 6 Pressure pin, 7 Nozzle-retaining nut. Design When it moves, the extended pressure 1 pin enters the current coil. The degree to which it enters the coil (overlap length “X” in Fig. 14) determines the strength of the magnetic flux.

Method of operation The magnetic flux in the coil changes as 2 a result of nozzle-needle movement and induces a signal voltage which is proportional to the needle’s speed of movement 3 but not to the distance it has travelled. This signal is processed directly in an 4 evaluation circuit (Fig. 12). When a given threshold voltage is ex- 5 ceeded, this serves as the signal to 6 the evaluation circuit for the start of injection.

7 UMK1588Y UMK1588D Fig. 13 Fig. 12 Fig. 14 Comparison between a needle-lift curve and Needle-motion sensor in a two-spring nozzle the corresponding signal-voltage curve of the holder for direct-injection (DI) engines needle-motion sensor 1 Adjusting pin, 2 Terminal, 3 Current coil, 4 Pressure pin, 5 Spring seat. a X Overlap length. Needle-lift- sensor signal

1 Needle lift

b Needle- motion- sensor signal Theshold 2 voltage

X 3 Start-of-injection signal

Signal voltage 4 5

°cks UMK1529Y UMK1427E 53 Axial-piston distributor Electronically-controlled pumps, VE-EDC axial-piston distributor fuel- injection pumps VE-EDC

Mechanical diesel-engine speed control vehicle (for instance, traction control (mechanical governing) registers a wide system (TCS), and electronic transmis- variety of different operating statuses sion-shift control). In other words, it can and permits high-quality A/F mixture be integrated completely into the overall formation. vehicle system. The Electronic Diesel Control (EDC) takes additional requirements into account. By applying electronic measure- System blocks ment, highly-flexible electronic data pro- The electronic control is divided into cessing, and closed control loops with three system blocks (Fig. 1): electric actuators, it is able to process 1. Sensors for registering operating mechanical influencing variables which it conditions. A wide variety of physical was impossible to take into account with quantities are converted into electrical the previous purely mechanical control signals. (governing) system. The EDC permits data to be exchanged 2. Electronic control unit (ECU) with with other electronic systems in the microprocessors which processes the in- Fig. 1 Electronic Diesel Control (EDC): System blocks

Sensors ECU Actuators Injected Needle-motion sensor fuel quantity

Temperature sensors Engine Fuel-injection pump (water, air, fuel) shutoff

Sensor for Start of control-collar position injection Micro- Air-flow sensor pro- EGR Transducer with cessor EGR valve Starting Engine-speed sensor Glow control unit control

Vehicle-speed sensor

Atmospheric-pressure sensor

Setpoint generators Diagnosis

Accelerator-pedal sensor Diagnosis display Maps Speed-selection lever

54 UMK0467E formation in accordance with specific Electronic control unit (ECU) Electronic control algorithms, and outputs corre- The ECU employs digital technology. The control for sponding electrical signals. microprocessors with their input and distributor 3. Actuators which convert the ECU’s output interface circuits form the heart pumps electrical output signals into mechanical of the ECU. The circuitry is completed quantities. by the memory units and devices for the conversion of the sensor signals into computer-compatible quantities. The Components ECU is installed in the passenger com- Sensors partment to protect it from external in- The positions of the accelerator and the fluences. control collar in the injection pump are There are a number of different maps registered by the angle sensors. These stored in the ECU, and these come into use contacting and non-contacting effect as a function of such parameters methods respectively. Engine speed and as: Load, engine speed, coolant tem- TDC are registered by inductive sensors. perature, air quantity etc. Exacting de- Sensors with high measuring accuracy mands are made upon interference and long-term stability are used for pres- immunity. Inputs and outputs are short- sure and temperature measurements. circuit-proof and protected against spu- The start of injection is registered by a rious pulses from the vehicle electrical sensor which is directly integrated in the system. Protective circuitry and me- nozzle holder and which detects the start chanical shielding provide a high level of injection by sensing the needle move- of EMC (Electro-Magnetic Compatibility) ment (Figs. 2 and 3). against outside interference.

Fig. 2 Fig. 3 Sensor signals Nozzle-and-holder assembly with 1 Untreated signal from the needle-motion sensor needle-motion sensor (NBF) (NBF), 1 Setting pin, 2 Sensor winding, 3 Pressure pin, 2 Signal derived from the NBF signal, 4 Cable, 5 Plug. 3 Untreated signal from the engine-speed signal, 4 Signal derived from untreated engine-speed signal, 5 Evaluated start-of-injection signal.

1 4

2 2 5

5 UMK0466Y UMK0468Y 55 Axial-piston Solenoid actuator for injected- Solenoid valve for distributor fuel quantity control start-of-injection control pumps, The solenoid actuator (rotary actuator) The pump interior pressure is depen- VE-EDC engages with the control collar through dent upon pump speed. Similar to the a shaft (Fig. 4). Similar to the mechani- mechanical timing device, this pressure cally governed fuel-injection pump, the is applied to the timing-device piston cutoff ports are opened or closed de- (Fig. 4). This pressure on the timing- pending upon the control collar’s posi- device pressure side is modulated by a tion. The injected fuel quantity can be clocked solenoid valve. infinitely varied between zero and With the solenoid valve permanently maximum (e.g., for cold starting). Using opened (pressure reduction), start of an angle sensor (e.g., potentiometer), injection is retarded, and with it fully the rotary actuator’s angle of rotation, closed (pressure increase), start of in- and thus the position of the control col- jection is advanced. In the intermediate lar, are reported back to the ECU and range, the on/off ratio (the ratio of used to determine the injected fuel solenoid valve open to solenoid valve quantity as a function of engine speed. closed) can be infinitely varied by the When no voltage is applied to the ac- ECU. tuator, its return springs reduce the injected fuel quantity to zero. Fig. 4 Distributor injection pump for electronic diesel control 1 Control-collar position sensor, 2 Solenoid actuator for the injected fuel quantity, 3 Electromagnetic shutoff valve, 4 Delivery plunger, 5 Solenoid valve for start-of-injection timing, 6 Control collar.

3 4

6 5

56 UMK0464Y Closed control loops (Fig. 5) with a check-back signalling unit and Electronic ensures that the control collar is cor- control for Injected fuel quantity rectly set. distributor The injected fuel quantity has a decisive pumps influence upon the vehicle’s starting, Start of injection idling, power output and driveability The start of injection has a decisive in- characteristics, as well as upon its par- fluence upon starting, noise, fuel con- ticulate emissions. For this reason, the sumption, and exhaust emissions. Start- corresponding maps for start quantity, of-injection maps programmed into the idle, full load, accelerator-pedal charac- ECU take these interdependencies into teristic, smoke limitation, and pump account. A closed control loop is used characteristic, are programmed into the to guarantee the high accuracy of the ECU. The driver inputs his or her re- start-of-injection point. A needle-motion quirements regarding torque or engine sensor (NBF) registers the actual start of speed through the accelerator sensor. injection directly at the nozzle and Taking into account the stored map compares it with the programmed start data, and the actual input values from of injection (Figs. 2 and 3). Deviations the sensors, a setpoint is calculated for result in a change to the on/off ratio of the setting of the rotary actuator in the the timing-device solenoid valve, which pump. This rotary actuator is equipped continues until deviation reaches zero. Fig. 5 Closed control loop of the electronic diesel control (EDC)

Q Air-flow quantity, nact Engine speed (actual), pA Atmospheric pressure, sset Control-collar signal (setpoint), sact Control-collar position (actual), sv set Timing-device signal (setpoint), tK Fuel temperature, tL Intake-air temperature, tM Engine temperature, ti act Start of injection (actual). Fuel Accelerator Operator’s Air pedal panel

ELAB ECU On/Off Cruise control

ssetpoint VE- pump

t Start- K quantity control EGR pA control sactual

t L s Start-of- Injected- v setpoint injection fuel-quan- control tity control Ql Vehicle speed sensor

Exhaust emissions Injection nozzle ti actual tM n actual EGR valve

Engine and vehicle

UMK0465E 57 Axial-piston This clocked solenoid valve is used to Idle-speed control distributor modulate the positioning pressure at the The idle-speed control avoids engine pumps, timing-device piston, and this results in “shake” at idle by metering the appro- VE-EDC the dynamic behavior being comparable priate amount of fuel to each individual to that obtained with the mechanical cylinder. start-of-injection timing. Because during engine overrun (with injection suppressed) and engine start- Safety measures ing there are either no start-of-injection signals available, or they are inadequate, Self-monitoring the controller is switched off and an The safety concept comprises the open-loop-control mode is selected. The ECU’s monitoring of sensors, actuators, on/off ratio for controlling the solenoid and microprocessors, as well as of the valve is then taken from a control map in limp-home and emergency functions the ECU. provided in case a component fails. If malfunctions occur on important com- Exhaust-gas recirculation (EGR) ponents, the diagnostic system not only EGR is applied to reduce the engine’s warns the driver by means of a lamp in toxic emissions. A defined portion of the the instrument panel but also provides a exhaust gas is tapped-off and mixed facility for detailed trouble-shooting in with the fresh intake air. The engine’s the workshop. intake-air quantity (which is proportional to the EGR rate) is measured by an air- Limp-home and emergency flow sensor and compared in the ECU functions with the programmed value for the EGR There are a large number of sophisti- map, whereby additional engine and cated limp-home and emergency func- injection data for every operating point tions integrated in the system. For in- are taken into account. stance if the engine-speed sensor fails, In case of deviation, the ECU modifies a substitute engine-speed signal is the triggering signal applied to an generated using the interval between electropneumatic transducer. This then the start-of-injection signals from the adjusts the EGR valve to the correct needle-motion sensor (NBF). And if the EGR rate. injected-fuel quantity actuator fails, a separate electrical shutoff device Cruise control (ELAB) switches off the engine. The An evaluated vehicle-speed signal is warning lamp only lights up if important compared with the setpoint signal input- sensors fail. The Table below shows the ted by the driver at the cruise-control ECU’s reaction should certain faults panel. The injected fuel quantity is then occur. adjusted to maintain the speed selected by the driver. Diagnostic output A diagnostic output can be made by Supplementary functions means of diagnostic equipment, which The electronic diesel control (EDC) can be used on all Bosch electronic provides for supplementary functions automotive systems. By applying a which considerably improve the ve- special test sequence, it is possible to hicle’s driveability compared to the systematically check all the sensors mechanically governed injection pump. and their connectors, as well as the correct functioning of the ECU’s. Active anti-buck damping With the active anti-buck damping (ARD) facility, the vehicle’s unpleasant 58 longitudinal oscillations can be avoided. Table 1. ECU reactions Electronic control for Failure Monitoring Reaction Warning Diagnostic distributor of lamp output pumps Correction Signal range Reduce injected ● sensors fuel quantity System- Signal range Limp-home sensors or emergency ●● function (graded) Computer Program runtime Limp-home (self-test) or emergency ●● function Fuel-quantity Permanent Engine shutoff ●● actuator deviation Advantages Engine shutoff

Ð Flexible adaptation enables optimi- As already stated on Page 40, the prin- zation of engine behavior and emission ciple of auto-ignition as applied to the control. diesel engine means that the engine Ð Clear-cut delineation of individual func- can only be switched off by interrupting tions: The curve of full-load injected fuel its supply of fuel. quantity is independent of governor When equipped with Electronic Diesel characteristic and hydraulic configuration. Control (EDC), the engine is switched Ð Processing of parameters which pre- off by the injected-fuel quantity actuator viously could not be performed me- (Input from the ECU: Injected fuel chanically (e.g., temperature-correction quantity = Zero). As already dealt with, of the injected fuel quantity characteris- the separate electrical engine shutoff tic, load-independent idle control). device serves as a standby shutoff in Ð High degree of accuracy throughout case the actuator should fail. complete service life due to closed control loops which reduce the effects of Electrical shutoff device tolerances. The electrical shutoff device is operated Ð Improved driveability: Map storage with the “ignition key” and is above all enables ideal control characteristics and used to provide the driver with a higher control parameters to be established level of sophistication and comfort. independent of hydraulic effects. These On the distributor fuel-injection pump, are then precisely adjusted during the the solenoid valve for interrupting the optimisation of the complete engine/ supply of fuel is fitted in the top of the vehicle system. Bucking and idle shake distributor head. With the diesel engine no longer occur. running, the inlet opening to the high- Ð Interlinking with other electronic sys- pressure chamber is held open by the en- tems in the vehicle leads the way ergized solenoid valve (the armature with towards making the vehicle safer, more sealing cone is pulled in). When the “igni- comfortable, and more economical, as tion switch” is turned to “Off”, the power well as increasing its level of environ- supply to the solenoid is interrupted and mental compatibility (e.g., glow systems the solenoid de-energized. The spring or electronic transmission-shift control). can now push the armature with sealing The fact that mechanical add-on units no cone onto the valve seat and close off the longer need to be accomodated, leads inlet opening to the high-pressure cham- to marked reductions in the amount of ber so that the distributor plunger can no space required for the fuel-injection longer deliver fuel. pump. 59 Axial-piston distributor Solenoid-valve-controlled pumps, VE-MV axial-piston distributor fuel-injection pumps VE-MV

Prospects Components On the electronically-controlled distrib- Angle-of-rotation sensor utor pumps of the future, the electrical Angle-of-rotation detection uses the actuator mechanism with control collar following components: Sensor, sensor for fuel metering will be superseded by a retaining ring on the driveshaft, and the high-pressure solenoid valve. This will trigger wheel with a given tooth pitch. permit an even higher degree of flexibility Detection is based upon the signals in the fuel metering and in the variability generated by the sensor. of the start of injection. The pulses generated by the sensor are inputted to the ECU where they are processed by an evaluation circuit. The fact Design and construction that the sensor is coupled to the pump’s This pump is of modular design. The field- roller ring ensures the correct assign- proven distributor injection pump can thus ment of the angular increment to the be combined with a new electronically position of the cam when the roller ring is controlled fuel-metering system (Fig. 1). rotated by the timing device. Basically speaking, the solenoid-valve- controlled distributor pump’s dimensions, Pump ECU installation conditions, and drivetrain in- The pump ECU is mounted on the upper cluding the pump’s cam drive, are identi- side of the pump and uses hybrid tech- cal to those of the conventional distributor niques. In addition to the mechanical pump. The most important new compo- loading with which it is confronted in nents are: the vehicle's under-hood environment, Ð Angle-of-rotation sensor (in the form the pump must also fulfill the following of an incremental angle/time system assignments: [IWZ]) which is located in the injection Ð Data exchange with the separately pump on the driveshaft between the mounted engine ECU via the serial vane-type supply pump and the roller bus system, ring, Ð Evaluation of the signal from the Ð Electronic pump ECU, which is mount- angle-of-rotation sensor (IWZ), ed as a compact unit on the top side of Ð Triggering of the high-pressure sol- the pump and connected to the engine enoid valve, ECU, Ð Triggering of the timing device. Ð High-pressure solenoid valve, installed in the center of the distributor head. Maps are stored in the pump ECU which not only take into account the setting With regard to its installation and hydrau- points for the particular vehicle applica- lic control, the timing device with pulse tion and certain engine characteristics, valve is identical to the one in the pre- but also permit the plausibility of the re- vious electronically-controlled distributor ceived signals to be checked. In addition, pump. they form the basis for defining a number of different computational values. 60 High-pressure solenoid valve Fuel supply and delivery Electronic The high-pressure solenoid valve must Via the distributor head and the opened control for fulfill the following assignments: high-pressure solenoid valve, the vane- distributor Ð Large valve cross-section for efficient type supply pump delivers fuel to the pumps filling of the high-pressure chamber, high-pressure chamber at a pressure of even at very high rotational speeds, approx. 12 bar. Ð Low weight (low moving masses), to No fuel is delivered when the high-pres- keep the loading of the parts to a mini- sure solenoid valve is de-energized mum, (open). The valve’s instant of closing Ð Short switching times to guarantee defines the injection pump’s start of high-precision fuel metering, and delivery. This can be located at the Ð Magnetic forces which are powerful bottom dead center (BDC) of the cam or enough to cope with the high pressures. on the rise portion of the cam slope. The high-pressure solenoid valve is com- Similarly, the valve’s instant of opening prised of: defines the pump’s end of delivery. The Ð The valve body, length of time the valve is closed deter- Ð The valve needle, and mines the injected fuel quantity. Ð The electromagnet with electrical The high pressure generated in the high- connection to the pump ECU. pressure chamber (the fuel from the The magnetic circuit is concentric to the supply pump is compressed by the axial valve. This fact permits a compact as- piston when this is forced up by the cam sembly comprising high-pressure sol- plate riding over the rollers of the roller enoid valve and distributor head. ring) opens the delivery valve and the fuel is forced through the pressure line to the injection nozzle in the nozzle Method of operation holder. Injection pressure at the nozzle is 1400 bar. Excess fuel is directed back Principle to the tank through return lines. Pressure generation in the solenoid- Since there are no additional intake ports valve-controlled distributor injection available, if the high-pressure solenoid pump is based on the same principle as valve should fail, fuel injection stops. that in the conventional electronically- This prevents uncontrolled “racing” of the controlled VE pump. engine. Fig. 1 Solenoid-valve-controlled axial-piston distributor fuel-injection pump (section)

UMK1205Y 61 Start-assist systems Start-assist systems

Since leakage and heat losses reduce the formed. The element is a metal tube which pressure and the temperature of the A/F is resistant to both corrosion and hot gases, mixture at the end of the compression and which contains a heater (glow) element stroke, the cold diesel engine is more diffi- embedded in magnesium-oxide powder cult to start and the mixture more difficult to (Fig. 1). This heater element comprises ignite than it is when hot. These facts make two series-connected resistors: the heater it particularly important that start-assist filament in the glow-tube tip, and the con- systems are used. The minimum starting trol filament. Whereas the heater filament temperature depends upon the engine maintains virtually constant electrical type. Pre-chamber and swirl-chamber resistance regardless of temperature, the engines are equipped with a sheathed- control filament is made of material with a element glow plug (GSK) in the auxiliary positive temperature coefficient (PTC). On combustion chamber which functions as a newer-generation glow plugs (GSK2), its “hot spot”. On small direct-injection (DI) resistance increases even more rapidly engines, this “hot spot” is located on the with rising temperature than was the case combustion chamber’s periphery. Large DI with the conventional S-RSK glow plug. truck engines on the other hand have the This means that the newer GSK2 glow alternative of using air preheating in the plugs are characterized by reaching the intake manifold (flame start) or special, temperature needed for ignition far more easily ignitable fuel (Start Pilot) which is quickly (850 ¡C in 4s). They also feature a sprayed into the intake air. Today, the start- lower steady-state temperature (Fig. 2) assist systems use sheathed-element which means that the glow plug’s tem- glow plugs practically without exception. perature is limited to a non-critical level. The result is that the GSK2 glow plug Sheathed-element can remain on for up to 3 minutes glow plug following engine start. This post-glow feature improves both the warm-up and The sheathed-element glow plug’s tubular run-up phases with considerable im- heating element is so firmly pressed into provements in noise and exhaust-gas the glow-plug shell that a gas-tight seal is emissions. Fig. 1 Sheathed-element glow plug GSK2 1 Electrical connector terminal, 2 Insulating washer, 3 Double gasket, 4 Terminal pin, 5 Glow-plug shell, 6 Heater seal, 7 Heater and control filament, 8 Glow tube, 9 Filling powder.

162 3 4 5 7 8 9

62 UMS0685-1Y Sheathed-element glow plugs: Functional sequence Sheathed- Temperature-time diagram element 1 S-RSK, 2 GSK2. The diesel engine’s glow plug and starter glow plugs, switch, which controls the preheat Flame °C and starting sequence, functions in a glow plugs similar manner to the ignition and 1,150 1 starting switch on the spark-ignition (SI) 1,050 engine. Switching to the “Ignition on” 2 position starts the preheating process 950 and the glow-plug indicator lamp lights Temperature up. This extinguishes to indicate that 850 the glow plugs are hot enough for the 750 engine to start, and cranking can begin. In the following starting phase, the drop- 650 01020304050s lets of injected fuel ignite in the hot, com- Time t pressed air. The heat released as a result UMS0688E leads to the initiation of the combustion Fig. 2 process (Fig. 3). Flame glow plug In the warm-up phase following a suc- cessful start, post-heating contributes The flame glow plug burns fuel to heat to faultless engine running (no misfiring) the intake air. Normally, the injection and therefore to practically smokeless system’s supply pump delivers fuel to the engine run-up and idle. At the same flame plug through a solenoid valve. The time, when the engine is cold, pre- flame plug’s connection fitting is pro- heating reduces combustion noise. A vided with a filter, and a metering device glow-plug safety switchoff prevents which permits passage of precisely battery discharge in case the engine the correct amount of fuel appropriate cannot be started. to the particular engine. This fuel then The glow-control unit can be coupled evaporates in an evaporator tube sur- to the ECU of the Electronic Diesel rounding the tubular heating element Control (EDC) so that information and mixes with the intake air. The resulting available in the EDC control unit can be mixture ignites on the 1,000 ¡C heating applied for optimum control of the glow element at the flame-plug tip. plugs in accordance with the particular operating conditions. This is yet another Glow control unit possibility for reducing the levels of blue smoke and noise. For triggering the glow plugs, the glow control unit (GZS) is provided with a power relay and a number of electronic Fig. 3 switching blocks. These, for instance, Typical preheating sequence control the glow duration of the glow 1 Glow-plug and starter switch, 2 Starter, plugs, or have safety and monitoring 3 Glow-plug indicator lamp, 4 Load switch, functions. Using their diagnosis func- 5 Glow plugs, 6 Self-sustained engine operation, tions, more sophisticated glow control tv Pre-heating time, tS Ready to start, tN Post-heating time. units are also able to recognise the 1 failure of individual glow plugs and inform the driver accordingly. Multiple 2 plugs are used as the control inputs 3 to the ECU. In order to avoid voltage drops, the power supply to the glow 4 tV tS tN plugs is through suitable threaded pins 5 or plugs. 6 Time t UMS0667-1E 63 The Program Order Number Gasoline-engine management Emission Control (for Gasoline Engines) 1 987 722 102

Engine management for spark-ignition engines Gasoline Fuel-Injection System K-Jetronic 1 987 722 159 Gasoline-engine management ME-Motronic Emission Control Gasoline Fuel-Injection System KE-Jetronic 1 987 722 101 Engine Management Gasoline Fuel-Injection System L-Jetronic 1 987 722 160 Gasoline Fuel-Injection System Mono-Jetronic 1 987 722 105 Ignition 1 987 722 154 Spark Plugs 1 987 722 155 M-Motronic Engine Management 1 987 722 161 ME-Motronic Engine Management 1 987 722 178 Diesel-engine management Diesel Fuel-Injection: An Overview 1 987 722 104 Technical Instruction Diesel Accumulator Fuel-Injection System Technical Instruction Common Rail CR 1 987 722 175 Diesel Fuel-Injection Systems Unit Injector System / Unit Pump System 1 987 722 179 æ æ Radial-Piston Distributor Fuel-Injection Pumps Type VR 1 987 722 174 Diesel Distributor Fuel-Injection Pumps VE 1 987 722 164 Æ Æ Electronic engine management for diesel engines Diesel In-Line Fuel-Injection Pumps PE 1 987 722 162 Engine management for spark-ignition engines Spark Plugs Diesel Acumulator Fuel-Injection Governors for Diesel In-Line Fuel-Injection Pumps 1 987 722 163 System Common Rail Automotive electrics/Automotive electronics Alternators 1 987 722 156 Batteries 1 987 722 153 Starting Systems 1 987 722 170 Electrical Symbols and Circuit Diagrams 1 987 722 169 Lighting Technology 1 987 722 176

Safety, Comfort and Convenience Systems 1 987 722 150 Technical Instruction Technical Instruction Driving and road-safety systems Compressed-Air Systems for Commercial Vehicles (1): Systems and Schematic Diagrams 1 987 722 165 Compressed-Air Systems for Commercial Vehicles (2): Equipment 1 987 722 166 æ æ Brake Systems for Passenger Cars 1 987 722 103 ESP Electronic Stability Program 1 987 722 177 Æ Æ

Vehicle safety systems for passenger cars Automotive electric/electronic systems ESP Electronic Stability Program Safety, Comfort and Convenience Systems

Engine management for diesel engines Radial-Piston Distributor Fuel-injection Pumps Type VR

Automotive Electric/Electronic Systems Lighting Technology Brake systems for passenger cars Technical Instruction Technical Instruction Brake Systems

Technical Instruction

æ æ æ ÆTechnical Instruction Æ Technical Instruction Æ

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1 987 722 164 KH/PDI-04.99-En (4.0)