Bosch VE Pumps
Bosch VE Pumps
Bosch VE Pumps
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.
Printed in Germany.
Imprimé en Allemagne.
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
TDC Top Dead Center, BDC Bottom Dead Center.
During the first stroke, the downward 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
TDC
24:1. In the process, the air heats up to
temperatures around 900°C. At the end
UMM0001E
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 – Carbon monoxide (CO),
the gasoline engine, both diesel versions – Unburnt hydrocarbons (HC),
are more economical especially in the – Nitrogen oxides (NOX),
part-load range. – Sulphur dioxide (SO2) and sulphuric
acid (H2SO4), as well as
Diesel engines are particularly suitable – 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.
1 2 3 4
UMM0013Y
3
Diese
l f el-
injecutio
system
n
Diesel fuel-injection systems:
An ov
er view
s:
An overview
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
UMK1563-1Y
UIS
4
creasingly being superseded by the Elec- According to the latest state-of-the-art, Fields
o
tronic Diesel Control (EDC). In the pas- it is mainly the high-pressure injection applic f
ation,
senger-car and commercial-vehicle sec- systems listed below which are used for Techn
ic
tor, new diesel fuel-injection systems are motor-vehicle diesel engines. requir al
emen
all EDC-controlled. ts
Table 1
Diesel fuel-injection systems: Properties and characteristic data
Electromechanical
Type
No. of cylinders
DI Direct injection
Solenoid valve
NE Post injection
VE Pilot injection
Injected fuel
Max. nozzle
Max. power
per cylinder
Max. speed
Mechanical
Electronic
pressure
MV
em
5
1
6
2
7 8
UMK1199Y
8
Types Fuel-injection Fuel-i
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techni ection
ques
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-
– 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, – Fuel-supply pump,
– Control-sleeve in-line fuel-injection – High-pressure pump,
pump (PE), with Electronic Diesel – Governor, and
Control (EDC) and infinitely variable – Timing device,
start of delivery (without attached in a small, compact unit. The diesel
timing device), engine’s rated speed, its power output,
– Single-plunger fuel-injection pump (PF), and its configuration determine the
– 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
– Radial-piston distributor injection tractors and stationary engines.
pump (VR),
– Common Rail accumulator injection
system (CRS),
– Unit-injector system (UIS), Fig. 2: VE distributor pump fitted to a 4-cylinder
– Unit-pump system (UPS). diesel engine
UMK0318Y
9
Axial-
pi Subassemblies facilitate adaptation to the specific
distr ibston requirements of the diesel engine in
ut
pumpor In contrast to the in-line injection pump, question.
s
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 rotat-
ing-reciprocating movement is imparted
– High-pressure pump with distributor, to the distributor plunger by way of the
– Mechanical (flyweight) governor, cam plate which is driven by the input
– Hydraulic timing device, shaft and rides on the rollers of the
– Vane-type fuel-supply pump, roller ring. The plunger moves inside
– Shutoff device, and the distributor head which is bolted to the
– Engine-specific add-on modules. pump housing. Installed in the dis-
tributor 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.
1
UMK0317Y
5 2
10
holders. If the distributor pump is also also contains the full-load adjusting Fuel-i
nj
equipped with a mechanical fuel shutoff screw, the overflow restriction or the techni ection
ques
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-
pi
distr ibston
Pump drive Fuel supply and
ut
pumpor
s
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
8
UMK0316Y
12
interior pressure then increases in injection pump is powerful enough to draw Fuel-i
nj
proportion to the speed (in other words, the fuel out of the fuel tank and to build up techni ection
ques
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.
13
Axial- cornering, and when standing or driving Vane-type fuel-supply pump for low-
pi
distr ibston on an incline. The fuel tank and the pressure delivery
ut
pumpor engine must be so far apart from each 1 Inlet, 2 Outlet.
s
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
1
thousandths of a millimeter. As a result,
UMK0324Y
Fig. 3: Vane-type fuel-supply pump with impeller
on the drive shaft
Fig. 4
UMK0320Y
14
contaminants in the fuel can lead to force pushes the impeller’s four vanes Fuel-i
nj
malfunctions, and inefficient filtering can outward against the inside of the techni ection
ques
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
UMK0322Y
UMK0323Y
15
Axial-
pi
The spring’s initial tension can be High-pressure stage
distr ibston adjusted to set the valve opening
ut
pumpor pressure. The fuel pressure needed for fuel
s
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
UMK0326Y
16
Pump assembly with distributor head Fuel-i
nj
Generates the high pressure and distributes the fuel to the respective fuel injector. techni ection
ques
1 Yoke, 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
UMK0327Y
4 5 6 7 10 8 9
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- Distributor head these movements within 60° of plunger
pi
distr ibston The distributor plunger, the distributor- rotation.
ut
pumpor head bushing and the control collar are As the distributor plunger moves from
s
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)
UMK0328Y
18
Fig. 10
Distributor plunger with stroke and delivery phases Fuel-i
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techni ection
ques
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 42 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- During the plunger’s continued move- The delivery valve is a plunger-type
pi
distr ibston ment to TDC, fuel returns through the valve. It is opened by the injection pres-
ut
pumpor cutoff bore to the pump interior. During sure and closed by its return spring.
s
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
UMK0335Y
20
Delivery valve with return-flow “retraction volume” resulting from the Fuel-i
nj
restriction retraction piston on the delivery-valve techni ection
ques
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
UMK1183Y
UMK1184Y
7
4
21
Axial-
pi
distr ibston
Mechanical engine- mechanical (flyweight) governor and the
lever assembly. It is a sensitive control
ut
pumpor
s 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 – 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
UMK0343Y
22
– Maximum-speed governing: With the function of engine speed (torque control). Mecha
n
accelerator pedal fully depressed, the In some cases, add-on modules are gover ical
ning
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).
– 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.
– Releasing or blocking of the extra fuel
required for starting, n –n
= lon vo
– Changing the full-load delivery as a vo
Fig. 2 or expressed in %:
Governor characteristics
a Minimum-maximum-speed governor, nlo – nvo .
= 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
a mm
= Speed droop
1
nlo = High idle (maximum) speed
nvo = Maximum full-load speed
2 3 4
Control-collar travel
2 3 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
UMK0344E
a b
12
9 13 14 c
15
10
11
a
3
1
4
1 5
2
M2 M2
7
UMK0346Y
8 h1 h2
24
start-quantity position by the ball pin on Characteristic curves of the variable- Mecha
n
the starting lever. This means that speed governor gover ical
ning
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,
S–L: 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 L–B: 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 B–B': 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'–C: 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-
speed control-lever remaining unchanged.
A ball pin which engages in the control
collar is attached to the underside of
the start lever, and the start spring to mm
its upper section. The idle spring is AS
attached to a retaining pin at the top
end of the tensioning lever. Also
Control-collar travel s
UMK0348E
fulcrum M2 and the start quantity is auto- nA nC nLT nVH
Engine speed n nLO
matically reduced to the idle quantity.
Fig. 4
Low-idle-speed control
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- Example (Fig. 5): and as a result the start and tensioning
pi
distr ibston Using the accelerator pedal, the driver levers pivot around M2 and push the
ut
pumpor sets the engine-speed control lever to a control collar in the “Stop” direction so
s
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.
a b
3 4 11
5
2
1 6
7
8
9 12
1
M2 M2
10
UMK0349Y
13
h1 14 h2
26
Overrun (engine braking) Minimum-maximum-speed Mecha
n
During downhill operation the engine is governor gover ical
ning
“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 fly-
weights 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
legs push the sliding sleeve up against
Control-collar travel s
a b
4 b
3 13
5
2
6
a
1 7
8
9
10 14
1 11
M2 M2
12
16 15
UMK0352Y
h1 h2
28
Fig. 1
Injecti
Injection timing Curve of a working stroke at full load
and at low speed (not drawn to scale). timing
on
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 Combustion pressure,
of delivery referred to the engine’s 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
ZV
sure then builds up in the pump which,
as soon as the nozzle-opening pres- SV
Combustion-chamber
start of injection (SB). The period 1
between FB and SB is referred to as the
VB SE
injection lag (SV). The increasing
SB VE
pressure
compression of the air-fuel mixture in the
FB
combustion chamber then initiates the
ignition (VB). The period between SB 2
and VB is the ignition lag (ZV). As soon
BDC TDC BDC
as the cutoff port is opened again the
pump pressure collapses (end of pump
delivery), and the nozzle needle closes FB SB SE
again (end of injection, SE). This is bar
Pump high pressure p
300
Assignment
200
During the fuel-delivery process, the
injection nozzle is opened by a pressure 100
0.3
speed, although with increasing engine
speed the crankshaft angle between
0.2 SV
start of delivery and start of injection
also increases. This must be
0.1
compensated for by advancing the
start of delivery. The pressure wave’s
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
Rate of injection Q
UMK0354Y
1 2 3 4 5 6 7
30
Fig. 3
through a sliding block and a pin so that Timing device, method of operation Injecti
on
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 ap-
1
plied to the end of the timing-device
piston opposite to the spring.
As from about 300 min–1, 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-
pi
distr ibston
Add-on modules the add-on modules and their effects
upon the diesel engine. The schematic
ut
pumpor
s and shutoff devices (Fig. 2) shows the interaction of the
basic distributor pump and the various
add-on modules.
Application
1 2
UMK0358Y
32
Fig. 2
Schematic of the VE distributor pump with mechanical/hydraulic full-load torque control Add-o
n
modu
LDA Manifold-pressure compensator. les
and sh
Controls the delivery quantity as a function of the charge-air pressure. u
device toff
s
HBA Hydraulically controlled torque control.
Controls the delivery quantity as a function of the engine speed (not for pressure-charged engines
with LDA).
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.
Full-load torque control with governor lever assembly, Hydraulic full-load torque control.
Basic
pump
Add-
on m
odule
tLU /tM nsetpoint Uon /Uoff pL /pA
TLA GST
ELAB HBA 1 2
A
n actual 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- to install torque control. In other words, actual fuel requirements. This is known
pi
distr ibston the engine should receive precisely the as “torque control”, and in the case of
ut
pumpor amount of fuel it needs. The engine’s the distributor injection pump can be
s
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 1 2 3 of the tensioning lever (4). The free end
Delivery quantity QF
b
of the torque-control lever (6) abuts
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
UMK0360E
min –1
common pivot point (M4) of starting
Engine speed n lever and torque-control lever (6)
34 changes its position. At the same time,
the torque-control lever tilts around the presses against the preloaded torque- Add-o
n
stop pin (5) and forces the torque- control spring. As soon as the slid- modu
les
control pin (7) in the direction of the ing-sleeve force exceeds the torque- and sh
u
stop, while the starting lever (1) swivels control spring force, the torque-control device toff
s
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, 3 4
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
11 Stop point, 6
11
M2 Pivot point for 1 and 4, 7 1
M4 Pivot point for 1 and 6, 2 M2 7 M2
FM Sliding-sleeve force, 1 2
s Control-collar travel. 8 6 8
UMK0362Y
s s
35
Axial-
pi Manifold-pressure With an exhaust turbocharger, the
distr ibston compensation engine’s exhaust gas, instead of simply
ut
pumpor being discharged into the atmosphere,
s
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 min–1. 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 turbo-
charger
UMK0365Y
36
Power and torque comparison, naturally aspi- Manifold-pressure compensator Add-o
n
rated and pressure-charged engines (LDA) modu
les
The manifold-pressure compensator and sh
u
kW Naturally aspirated engine Nm (LDA) reacts to the charge-air pressure device toff
s
Pressure-charged engine generated by the exhaust-gas turbo-
charger, or the (mechanical) super-
Pe
charger, and adapts the full-load deliv-
ery to the charge-air pressure (Figs. 6
Torque Md
Power Pe
and 7).
Assignment
Md The manifold-pressure compensator
(LDA) is used on pressure-charged
diesel engines. On these engines the
UMK0367E injected fuel quantity is adapted to
min–1 the engine’s increased air charge (due to
Engine speed n pressure-charging). If the pressure-
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- jected fuel quantity must be adapted starting lever and tensioning lever to
pi
distr ibston to the lower air mass. This is performed swivel around their common pivot point
ut
pumpor by the manifold-pressure compensator thus shifting the control collar in the
s
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,
p2 Upper charge-air pressure.
Method of operation
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 dia-
phragm, and with it the sliding pin and
control cone, shift against the force of the
Injected fuel
quantity Qe
1 2
M2
7 8
5
UMK0369Y
39
Axial- lever is used to input a given full-load port is closed again. The fuel in the pump
pi
distr ibston speed. If this speed is reached and the interior can now no longer flow through
ut
pumpor load is less than full load, the speed the governor shaft to the suction side,
s
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
5 6 7
the aneroid capsule) is applied to the
diaphragm’s underside. If the atmo-
spheric 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.
UMK0370Y
40
Cold-start compensation Mechanical cold-start accelerator (KSB) Add-o
n
engaging in roller ring (cold-start position) modu
les
The diesel engine’s cold-start charac- 1 Lever, 2 Access window, 3 Ball pin, and sh
u
teristics are improved by fitting a cold- 4 Longitudinal slot, 5 Pump housing, 6 Roller ring, device toff
7 Roller in the roller ring, 8 Timing-device piston, s
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 12 3 4
the cab, or automatically by means of
a temperature-sensitive advance mech-
anism (Fig. 11).
5
Mechanical cold-start accelerator
(KSB) on the roller ring 6
UMK0373Y
into the roller ring (a version is available
in which the advance mechanism en- 11 10 9
gages in the timing-device piston). The
Fig. 12
stop lever’s initial position is defined
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)
1 2
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.
UMK0372Y
3 4 5 6
41
Axial- causes the stop lever, the shaft, the inner Temperature-controlled idle-speed
pi
distr ibston lever and the ball pin, to swivel and increase (TLA)
ut
pumpor change the roller ring’s setting so that the The TLA is also operated by the control
s
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
Injection-timing advance
a 3
4
b
2.5
UMK0374E
UMK0377Y
0
0 min–1
Pump speed p
42
Design and construction Effect of the hydraulic cold-start Add-o
n
The hydraulic cold-start accelerator accelerator (KSB) modu
les
comprises a modified pressure-control 1 Injection-timing advance. and sh
u
valve, a KSB ball valve, a KSB control cms device toff
s
valve, and an electrically heated ex-
pansion element.
Injection-timing advance
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
UMK0379E
of its spring and changes the start-
min–1
of-injection timing. Pump interior Pump speed p
pressure is determined by a pressure-
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- Engine shutoff stop lever pushes against the start lever
pi
distr ibston of the governor-lever mechanism. This
ut
pumpor swivels around its pivot point M2 and
s
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.
UMK0382Y
head. When the engine is running, the
3
solenoid is energized and the valve
keeps the passage into the injection
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 possi-
bilities 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
UMK0380Y
1 9
300
8
2 7
3
Flow quantity
4
5 6 200
100
2 1
0
UMK1391Y
UMK1397E
48
Sac-hole nozzle with cylindrical sac hole Sac-hole nozzle with conical sac hole Nozzle
s
and conical tip (6b): and conical tip (Fig. 6c): and n
ozzle
This type of nozzle is used exclusively Due to the conical shape of this nozzle’s holder
s
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
UMK1403Y
UMK1650Y
49
Axial-
pi
Seat-hole nozzle Standard nozzle holders
distr ibston In order to minimise the residual volume
ut
pumpor – and therefore the HC emissions – the Assignments and designs
s
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 – 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- – 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:
– Cylindrical external shape with diame-
Fig. 7 ters between 17 and 21 mm,
Seat-hole nozzle – Bottom-mounted springs (leads to low
moving masses),
– Pin-located nozzles for direct-injection
engines, and
– 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 follow-
ing components (Fig. 9):
– Nozzle-holder body,
– Intermediate element,
– Nozzle-retaining nut,
– Pressure pin,
– Spring,
UMK1407Y
– Shim, and
– Locating pins.
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 pas-
sage, 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.
3
Two-spring nozzle holders
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.
UMK1413Y
0.2
Nozzle-needle lift
b
mm
0.4
h2
h1 0.2
h2
UMK1423-1Y
0
UMK1422E
0 1 2 ms
h1
Time
52
This necessitates a nozzle holder with Two-spring nozzle holder with needle-motion Nozzle
s
needle-motion sensor (Fig. 13) which sensor for direct-injection (DI) engines and n
ozzle
outputs a signal as soon as the nozzle 1 Nozzle-holder body, 2 Needle-motion sensor, holder
3 Spring 1, 4 Guide element, 5 Spring 2, s
needle opens.
6 Pressure pin, 7 Nozzle-retaining nut.
Design
1
When it moves, the extended pressure
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
2
The magnetic flux in the coil changes as
a result of nozzle-needle movement and
induces a signal voltage which is propor-
tional to the needle’s speed of movement 3
but not to the distance it has travelled.
This signal is processed directly in an 4
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
Needle lift
b Needle-
motion-
sensor signal
Theshold 2
voltage
Signal voltage
X
3
Start-of-injection
signal
4
UMK1427E
UMK1529Y
cks
53
Axial-
pi
distr ibston
ut
pumpor
Electronically-controlled
VE-ED
s,
C 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 ac-
count. 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
Vehicle-speed sensor
Atmospheric-pressure
sensor
Speed-selection lever
54
formation in accordance with specific Electronic control unit (ECU) Electr
on
control algorithms, and outputs corre- The ECU employs digital technology. The contro ic
lf
sponding electrical signals. microprocessors with their input and distrib or
u
3. Actuators which convert the ECU’s output interface circuits form the heart pump tor
s
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
4
UMK0466Y
UMK0468Y
5
55
Axial- Solenoid actuator for injected- Solenoid valve for
pi
distr ibston fuel quantity control start-of-injection control
ut
pumpor The solenoid actuator (rotary actuator) The pump interior pressure is depen-
s,
VE-ED engages with the control collar through dent upon pump speed. Similar to the
C
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 in-
jected 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
UMK0464Y
6 5
56
Closed control loops (Fig. 5) with a check-back signalling unit and Electr
on
ensures that the control collar is cor- contro ic
lf
Injected fuel quantity rectly set. distrib or
u
The injected fuel quantity has a decisive pump tor
s
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
tK Start-
quantity
control EGR pA
sactual control
tL
sv setpoint Start-of- Injected-
injection fuel-quan-
control tity control Ql Vehicle
speed
sensor
Exhaust
emissions
Injection
nozzle t i actual
tM n actual EGR valve
UMK0465E
57
Axial- This clocked solenoid valve is used to Idle-speed control
pi
distr ibston modulate the positioning pressure at the The idle-speed control avoids engine
ut
pumpor timing-device piston, and this results in “shake” at idle by metering the appro-
s,
VE-ED the dynamic behavior being comparable priate amount of fuel to each individual
C
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 Electr
on
contro ic
lf
Failure Monitoring Reaction Warning Diagnostic distrib or
u
of lamp output pump tor
Correction Signal range Reduce injected s
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
61
Star t-
as ist
systesm
s
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.
UMS0685-1Y
1 2 3 4 5 6 7 8 9
62
Sheathed-element glow plugs: Functional sequence Sheat
he
Temperature-time diagram eleme d-
nt
1 S-RSK, 2 GSK2. The diesel engine’s glow plug and starter glow p
lu
switch, which controls the preheat Flame gs,
C and starting sequence, functions in a glow p
lugs
1,150
similar manner to the ignition and
1 starting switch on the spark-ignition (SI)
Temperature
1,050
2
engine. Switching to the “Ignition on”
position starts the preheating process
950
and the glow-plug indicator lamp lights
850
up. This extinguishes to indicate that
the glow plugs are hot enough for the
750 engine to start, and cranking can begin.
650
In the following starting phase, the drop-
0 10 20 30 40 50 s UMS0688E lets of injected fuel ignite in the hot, com-
Time t pressed air. The heat released as a result
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,
tv Pre-heating time, tS Ready to start,
tions, more sophisticated glow control tN Post-heating time.
units are also able to recognise the 1
failure of individual glow plugs and
2
inform the driver accordingly. Multiple
plugs are used as the control inputs 3
to the ECU. In order to avoid voltage
UMS0667-1E
4
drops, the power supply to the glow
tV tS tN
plugs is through suitable threaded pins 5
or plugs. 6 Time t 63
The Program Order Number
Gasoline-engine management
Emission Control (for Gasoline Engines) 1 987 722 102
Gasoline Fuel-Injection System K-Jetronic 1 987 722 159
Gasoline Fuel-Injection System KE-Jetronic 1 987 722 101
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
Diesel Accumulator Fuel-Injection System
Common Rail CR 1 987 722 175
Diesel Fuel-Injection Systems
Unit Injector System / Unit Pump System 1 987 722 179
Radial-Piston Distributor Fuel-Injection
Pumps Type VR 1 987 722 174
Diesel Distributor Fuel-Injection Pumps VE 1 987 722 164
Diesel In-Line Fuel-Injection Pumps PE 1 987 722 162
Governors for Diesel In-Line Fuel-Injection Pumps 1 987 722 163
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
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
Brake Systems for Passenger Cars 1 987 722 103
ESP Electronic Stability Program 1 987 722 177