5 Engine Management

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Engine management sy stems

Scuola di Dottorato di Ricerca 2010 - Road vehicle and engine engineering science 1

THE ENGINE MANAGEMENT SYSTEM FORGASOL INE AND DIESEL ENGINES

References

Automot ive Handbook – R. Bos ch/SAE

Gasoline-engin e management – R. Bos ch/SAE

Diesel-engin e management – R.Bos ch/SAE




Scuola di Dottorato di Ricerca 2010 - Road vehicle and engine engineering science

The engine management system ensures that the driver request is implemented;

for example, i t converts the accelerat ion/decelerat ion requests into a

correspon ding engine outpu t .

During its evolution electronic engine control progressively increases the number

of engine subsystems it manages and kind of tasks it performs. This development

is necessary to provide the needed accuracy and adaptability in order to minimise

exhaust emiss ions and fue l consumpt ion , provide opt im al dr iveabi l i ty for alloperating condition, minimise evaporat ive emission (gasoline engines) and

provide system diagnos is when malfunctions occur.

In order to meet these objectives the control system has been organised in

different functions. Each function manages a specific engine activity and is in

charge to accomplish some definite target. The engine operating conditions are

supervised by a finite state machine that defines the engine states and manages

the transition between these states.In the next slides a brief description of objectives, functions, components and

engine modes of the controls, both for Spark ignition engines and for Diesel

engine, is performed.

The engine m anagement s ystem





Exhaust EmissionsThe engine exhaust consists of products from the combustion of the air and fuel mixture. Under perfect

combustion conditions the hydrocarbons would combine in a thermal reaction with oxygen in the air to form

carbon dioxide (CO2) and water (H2O). Unfortunately perfect combustion does not occur and in addition toCO2 and water, carbon mon oxide (CO), oxides of nit rogen (NOX) and hydrocarbon (HC) occur in the

exhaust as a result of combustion reaction. Additives and impurities in the fuel also generate minute

quantities of pollutants such as lead oxides, lead halogenides and sulphur oxides. In diesel engines there

is also an appreciable amount of soot created. In Europe and United States the level of pollution, in terms

of HC, CO, NOX and, for diesel engines, particulates emitted in a vehicle’s exhaust, is regulated by law.

Fuel consumption A lot of different factors are working in partnership to make of central importance fuel economy:

The need of a better and more rational use of energetic resources to reach a sustainable growth

The fuel price increase and its market consequence

the legislation requirements both in Europe and in USA

The electronic engine control system provides the fuel metering and ignition timing precision required to

minimise fuel consumption.

Driveability Another requirement of the electronic engine control system is to provide acceptable driv eabil i ty under

al l operat ing co ndit ions . No stalls, hesitations or other objectionable roughness should occur under

vehicle operation. Driveability is influenced by almost every operation of the control system and, unlike

exhaust emissions or fuel economy, is not easily measured. Other factors that influence driveability are

the idle speed control, EGR control and evaporative emissions control.





Evaporative Emissions (Gasoline engine only)Hydrocarbon (HC) emissions in the form of fuel vapours escaping from the v ehicle are closely regulated.

The prime source of these emissions is the fuel tank. Due to ambient heating of the fuel and the return ofunused hot fuel from the engine, fuel vapours are generated in the tank. The evaporative emission control

system (EECS) is used to control the evaporative HC emissions. The fuel vapours are rotated to the

intake manifold via the EECS and they are burned in the combustion process. The quantity of fuel vapours

delivered to the intake manifold must be metered such that exhaust emissions and driveability are not

adversely effected. The metering is provide by a purge control whose function is controlled by the

electronic control unit.

System DiagnosticsThe purpose of system diagnostics is to provide a warning to the driver when the contro l sy stem

determines a malfunct ion of a component or a system and to assist the service technician in identify

and correct the failure. To the driver the engine may appear to be operating correctly, but excessive

amounts of pollutants may be emitted. The ECU determines a malfunction has occurred when a sensor

signal, received during normal engine operation or during a system test, indicates there is a problem. For

critical operations such as fuel metering and ignition control, if a required sensor input is faulty, a substitute

value may be used by the ECU so that the engine will continue to operate.Starting from 2001 (Euro3) the European On Bord Diagnosis (EOBD) statutes require that, when a failure

occur in a system critical for exhaust emissions, the malfunctioning indicator lamp (MIL), visible to the

driver, must be illumined. Information on the failure is stored in the ECU. A service technician can retrieve

the information on the failure on the ECU and correct the problem.





ECU

SENSORS ACTUATORS

From and towards other vehicle system’s cont ro l

The engine control system includes: sensors for the detection of the engine operating modes

electronic co ntro l uni t (ECU) which elaborates the signal values supplied by the

sensor, according to defined control strategies and algorithms, and defines the actions to

be delivered to the actuators

actuators which have the task to actuate the defined commands

System layout





The key s ensors

Load sensor (Mass Flowmeters) – Mass flowmeters operate according to the hot-wire or

hot-film principle without any moving mechanical part inside the unit. The closed-loopcont ro l c i rcu i t in the meter’s hou sing mainta ins a cons tant temp erature di f ferent ia l

between a f ine plat inum wire or th in - fi lm resistor and the passing air stream. The

current required for heating provides an extremely precise, albeit nonlinear, index of air-mass

flow rate; the ECU converts the signal into linear form. Due to its closed-loop design, this air-

mass meter can monitor flow variations in the millisecond range.

Oxygen sensor – The fuel metering system of spark ignition engine employs the

exhaust-gas residual-oxy gen content as measured by the lamb da oxygen senso r to

regulate very precisely the air /fuel mixtu re for com bus t ion to the value lambd a = 1

(stoichiometric combustion). The oxygen sensor is a solid electrolyte made of ZrO ceramic

material that becomes electrically conductive for oxygen ions at temperature higher than

300°C. A galvanic charge is generated at the sensor terminals, which are design as porous

platinum thick-film electrodes and coated with a ceramic spinel layer: the voltage varies tothe greatest extend at the lambda value of 1.

Engine speed sensor – Generally a Magnet ic Speed Senso r detects wh en r ing g ear

teeth, or other ferrous p roject ions, pass the t ip of the senso r. Electrical impulses are

produced by the sensor’s internal coil and sent to the speed control unit. The signal from the

magnetic speed sensor, teeth per second (Hz.), is directly proportional to engine speed.





Hot-wire Air Flow Meter

Last g enerat ion

Bosch Source





Plug-in sensor

housing

Hybrid-section

cover

Measuring

channel cover

Sensor chip

(CMF)

Carrier plate

Hybrid SHF

O-ring

Temperature

sensor

Hot-wire Air Flow Meter

Bosch Source





Nernst Type Oxygen Sensors

Thimble type Planar type

Exhaust gas

P O2

P O2 Air

Exhaust gas

P O2

Sensingcell

Referenceair duct

Heater

ZrO2 - CeramicElectrodesPorous protective layerInsulation

U S In4 F RT

P O2

P O2

U reg

Sensor characteristic curve

0.9

0.6

0.3

0

0.98 1.0 1.02

Normalized A / F ratio

S e n s o

r v o l t a g e

=

Bosch Source





Thimble type ZrO2 oxygen sensor LSH25

Oxygen content sensor (Lambda sensor)

Bosch Source





Gasol ine injector – The fuel injector essentially consis t of a valve housing wi th

solenoid c oi l and electr ic co nnect ions , a valve seat with s pray- or i f ice disk and a

mo ving valve needle with solenoid armature. When the coil is de-energized, the spring

and the force resulting from the fuel pressure press the valve needle against the valve seat

to seal the fuel supply system from the intake manifold. When the coil is energized, it

generates a magnetic field which pulls in the armature and lifts the valve needle off of itsseat to allow fuel to flow through the fuel injector.

The igni t ion coi l – It is a energy-charged high-vol tage source simi lar to a

transformer . Energy is supplied by the vehicle electrical system during the dwell period or

charging time. At the moment of ignition, which at the same time is the end of the charging

time, the energy is then transferred with the required high voltage and sparking energy to

the spark plug. The ignition coil comprises two coils that are magnetically linked by an ironcore.

The key actuators





The gasol ine injector

The gasol ine enginecontro l system

Fuel rai lECU

Servo throt t le body

Pressure regulator

InjectorKnock sensor

Bosch Source





ME 7 Motronic Components

(Evoluted gasoline management system )

Bosch Source





MOTRONIC - Torqu e Guid ed Engin e Managemen t Systems

M7 System Overv iew with OBD and RLFS

Bosch Source





The modern gasoline engine management system integrates both engine andignition control: the microprocessor continuously monitors the engine and vehicle

parameters measured by the sensors and calcu lates in real t ime :

the torque requested by the dr iver through the accelerator pedal,

the necessary f resh air ch arge to be introduced into the cylinders by actuating

a proper throttle angle,

the corresponding fuel delivery amoun t to guarantee a stoichiometric mixtureratio by actuating a definite opening time of the injectors

the adequate ign i t ion t iming (ignition angle in respect to the TDC) by

interrupting the primary winding of the ignition coil

In th e ECU there are loaded two necessary inform at ion packages :

the con tro l strategies for every engine operation mode, that are engineered

according to project targets,

and the cal ibrat ion data , mapped vs engine load and speed, temperatures,

and others parameters, that are specific value for any engine –vehicle application.

The contro l strategies





Cranking - During engine cranking, the goals are

to get the engine started with the minimal amount or delay

and to minimize the exhaust emissions (during crank the catalyst is cold and its efficiency is very low).

To accomplish a rapid and robust start fuel must be delivered that meets the requirements for starting

for any com binat ions of engine coolant and amb ient temp eratures . For a cold engine, an increase

in the commanded A/F ratio is required due to poor fuel vaporization and “wall wetting” , which decrease

the amount of usable fuel. Wall wetting is the condensation of some of the vaporized fuel on the cold

metal surfaces in the intake port and combustion chamber. It is critical that fuel does not wet the spark

plugs, which can reduce the effectiveness of the spark plug and prevent the plug from firing.

Warm-Up - During the warm-up phase, there are three conflicting objectives:

keep the engine operating smoothly (i.e. no stalls or driveability problems),

increase exhaust temperature to quickly achieve operational temperature for catalyst (light-off) andlambda sensor so that close-loop control can begin operating,

and keep exhaust emissions and fuel consumption to a minimum.

The best method for achieving these objectives is very dependent on the specific application.

If the engine is still cold, fuel enrichment will be required to keep the engine running smoothly due,

again, to poor fuel vaporization and wall welling effects. The amount of enrichment is dependent on

engine temperature and is a correction factor to the injector pulse width.


E i





Cut-off - During deceleration, such as coasting or braking, there is no torque

requirement. Therefore, the fuel may be shut off until either an increase in throttle angle isdetected or the engine speed falls to a speed slightly above idle rpm. During the

development of the fuel cut-off strategy, the advantage of reduced emission and fuel

consumption must be balanced against driveability requirements. The use of fuel cut off

may change the perceived amount of engine braking felt by the driver. In addition, care

must be taken to avoid a “bump” feel when entering and when exiting the fuel cut off mode,

due to change in torque.

Idling - The objectives of the engine control system during idle are:

Provide a balance between the engine torque produced and the changing engine loads,

thus achieving a consistent idle speed even with various load changes due to accessories

(i.e. air conditioning, power steering, and electric loads) being turned on and off and during

engagement of the automatic transmission. In addition, the idle control must be able tocompensate for long-term changes in engine load, such as the reduction in engine friction

that occurs with engine break-in.

Provide the lowest idle speed that allows smooth running to achieve the lowest exhaust

emissions and fuel consumption (up to 30 percent of a vehicle fuel consumption in city

driving occurs during idling).


E i t t





Normal - This mode practically cover the greatest part of engine operative range. When

the engine work in steady state condi t ion (i.e. without sensible variation of load and

speed) the learning phase of the auto-adaptative strategies is activated. During transition

such as acceleration or deceleration, the objective of the engine control system is to

provide a smooth transition from one engine operating condition to another (i.e., no

hesitations, stalls, bumps, or other objectionable driveability concerns), and keep exhaust

emissions and fuel consumption to a minimum.

Accelerat ion Enr ichment: When an increase in engine load and throttle angle occurs, a

corresponding increase in fuel mixture richness is required to compensate for increasedwell wetting. The sudden increase in air results in a lean mixture that must be corrected

swiftly to obtain good transitional response. The rate of change of engine load and throttle

angle are used to determine the quantity of fuel during acceleration enrichment. The

amount of fuel must be enough to provide desired performance, but not so much as to

degrade exhaust emission and fuel economy. During acceleration enrichment, the ignition

timing is set to the maximum torque without knocking.

Decelerat ion Enleanment : During deceleration the problem with well wetting is inversethan in acceleration; this means that at the end of the deceleration is possible to have a rich

mixture. If the deceleration is such that where is no torque requirement the mode becomes

cut-off.


E i t t





Elektronische Zündungssteuerung mit Klopfregelung

Motronic

Klopfsensor-Signal ohne Klopfen Klopfsensor-Signal mit Klopfen

Kno ck (accelerat ion) senso r

Bosch Source

E i t t





Engine and vehicle speed limitation

Using the inputs of engine rpm and vehicle speed to the electronic control unit thresholds

can be establish for limiting these variables with fuel cut-off. When the maximum speed is

achieved the fuel injectors are shut off. When the speed decreases below the threshold

fuel injection resumes. These operation must be done with some caution in order to avoid

poor driveability. The rpm limitation function is used to protect the engine from overrun.

The rpm limitation is obtained through fuel modulation

Evaporative emission control system

A vapour ventilation line exits the fuel tank and enters the fuel vapour canister. The

canister consist of an active charcoal element which absorbs the vapour and allows only

air to escape to the atmosphere. Only a certain volume of fuel vapour can be contained

by the canister. The vapours in the canister must therefore be purged from and burned by

the engine so that the canister can continue to store vapours as they are generated. Toaccomplish these, another line leads from the charcoal canister to the intake manifold.

Included in this line is the canister purge solenoid valve.


E i t t





Knock cont ro l (Gasoline Engines)

Engine knock occurs when the ignition timing is advanced too far the operating condition

and causes, during the flames propagation, uncontrolled spontaneously combustion in the

end-gas that can lead to engine damage, depending on the severity and frequency.

Unfortunately, the igni t ion t iming for opt im isat ion of torque, fuel economy and

exhaust emiss ions is in c lose p rox imi ty to the ign i t ion t iming that resu l ts in eng ine

knock . As the ignition timing that results in engine knock depends from a lot of factors,such as air/fuel ratio, fuel quality, engine load, and variation in compression ratio, is not

possible to put in the ignition timing table values that are safe with respect to the knock

without penalise the engine performance. To avoid this, knock sensor (one or more) is

installed on the engine block to detect knocking. Knock sensors are usua l ly

accelerat ion sensors that provide an electr ic signal , proport ion al to the engine

vibrat ion, to the electronic co ntro l un i t . From this signal, the ECU control algorithmdetermines which cylinder or cylinders are knocking. Ignition time is retarded for those

cylinder until the knock is no longer detected. The ignition timing is then advanced again

until knocking is detected







Turbocharger boost pressure control - The exhaust turbocharger consists of a

compressor and an exhaust turbine arranged on a common shaft. Energy from the exhaust

gas is converted to rotational energy by the exhaust turbine, which then drives the

compressor. The compressed air leaves the compressor and passes through the air cooler,

throttle valve, intake manifold, and into the cylinders. In o rder to ach ieve near co nstant air

charge pressure over a wide rpm range, the turboch arger uses a circui t that al lows

for the bypass of the exhaust gas away from the exhaust turbine throug h a valve

(wastegate) opening at a specif ied air charge press ure.

In the most modern turbocharged engines, by controlling the wastegate with a pulse-wide

modulated solenoid valve, di f ferent w astegate opening pressure can be sp eci f ied,depending o n the engine operat ive cond i t ions. Therefore, only the level of air charged

pressure required is developed. The electronic control unit uses information on engine load

from either manifold pressure or the air meter and rpm and throttle position. From these

information, a data table is referenced and the proper boost pressure (actually a duty cycle

of the control valve) is determined. On systems using manifold pressure sensor, a close-

loop control system can be developed to compare the specified value with the measured

value.

The boost p ressure cont ro l sys tem is u sua l ly used in c omb ination w i th the knock

contro l for turbocharged engines. When the ignition timing is retarded due to knock, an

increase in already high exhaust temperatures of turbocharged engines occurs. To

counteract the temperature increase, the boost pressure is reduced when the ignition timing

is retarded past a predetermined threshold.







Torque based contro l

The torque of common S.I. engines is pr imari ly inf luenced b y the throt t le , contro l l ing the

mass air f low and therefore also the amoun t of fresh air f lowing into the comb ust ion c hamber.In addition to this, other variables are influencing the relative variation of the engine torque: ignition

timing, air/fuel ratio, deactivation of injection of certain cylinders, boost pressure control for

turbocharged engines, EGR, variable valve timing/lift and variable manifold. But there are other

torque-influencing control functions that affect engine torque as idle speed control, cruise control,

traction control, transmission control, etc.: all these additional functions drastically increased the

complexity of the complete system over the past years.

Since many “torque” interactions occur simultaneously, priorities must be established. However,

since the interactions take place in the individual functions, it’s not easy to observe the effects on theoverall system. If torque-relevant control values are directly called up by one of the systems or

subsystems, the various interactions influence each other. This requires a complex data calibration

of the various ECU’s installed in the vehicle. Between the subsystems themselves there are also

strong interdependencies of the parameters to be calibrated.

The most new strategy that introduced the clutch torque as central intermediate value became the

decisive step for solving this situation. Based on these physical values, all demands can be

coordinated, before the optimal conversion to the respective engine control values takes place(criteria such as emissions, fuel economy and protection of components).

With the torque based approach to a sys tem architecture of an engine contro l system, al l

demands whic h can be formu lated as torque or eff ic iency are def ined, based o n these

phys ical v alues. This means that interfaces within single functions as well as between (sub)

systems, are defined as torques or efficiencies, enabling a transparent and simplified system

architecture.

In the next figure a Bosch example of the torque based system is represented.







MOTRONIC - Torque Guided Engine Management Systems

Torque Based System Structure for PFI Systems w/o ETC

Ind. fuelcut-off

Torque

demandcoordinator

Idle speed

actuator

Ignition

timing

Injectiontime

Waste gatecontrol

Coordination

of torque and

efficiency

demands

Realization

of desired

torque

Torque

conversion

Torque T o r q u e

External Torque

Demands

• Vehicle dynamic

control

• Driveability

Internal Torque

Demands

• Engine start-up

• Idle speed control

• Engine speed limitation

• Engine protection

Efficiency Demands • Engine start-up

• Catalyst heating

• Idle speed control

Efficiency

Engine

Driver

Throttle angle

Calculation of

driver‘s request

Current cylinder charge & engine speedCurrent cylinder charge & engine speed

Calculation of

driver‘s request

Current cylinder charge & engine speed

Calculation of

driver‘s request


Calculation of

driver‘s request


Calculation of

driver‘s request

Bosch Source






UNIJET 2000 ECU

Electronic Control Unit with

Advanced Injector Drivers

From Pilot Injection...

TDC +60°-60°

PILOT MAIN

COMBUSTIO

N

RATE

FUELLING

… to Sequential Multiple Injections

TDC +60°-60°

PILOT PRE MAIN AFTER

COMBUSTIO

N

RATE

FUELLING

POST

Mul t ipl e Injection : From UNIJET to MULTIJET

CRF Source






MOTRONIC - Torque Guided Eng ine Management Systems

Fuel Inject ion Concepts fo r S.I. Eng ines

Port Fuel Injection Gasoline Direct Injection

Mixture transport over theintake stroke

Mixture transport by chargemotion and piston geometry

Bosch Source






BMW 3.0l twin tu rbo d irect inject ion

gasol in e engine






Diesel engine management system - Comm on rai l

In the Diesel engine the combust ion torque is generated in the power cycle and is

determin ed by the fol lowing var iables if the excess air is sufficient:

the supp l ied fuel mas s, the start of combustion determined by the start of injection

the injection/combustion process

In addition, the maximum speed torque is limited by:

smoke emission

the cylinder pressure the temperature load of different components and

the mechanical load of the drive train

The primary function of engine management is to adjust the torque generated by the

engine or, in some applications, to adjust a specific engine speed within the permitted

operating range (i.e. idling). The control of exhaust emission and noise is performed by

engine management by changing the following varaibles: cylinder charge

exhaust gas recirculation rate (charge dilution)

charge motion (intake swirl)

start of injection

injection pressure

rate of discharge curve control (pilot injection, divided fuel injection, etc)






Diesel engine management system - Comm on rai l

The common ra i l system's principal feature is that injection pressure is independent ofengine speed and injected fuel quantity, this is not the case of the previous Diesel fuel

systems.

The funct ion of pressu re generat ion and fuel in ject ion are separated b y an

accumula tor vo lum e. This volume is essential to the correct operation of the system

and is made up of the common fuel rail, the fuel lines and the injectors themselves.

The pressure is generated by a high p ressure plung er pump . For passenger cars

application, the desired rail pressure is regulated by a pressure-control valve mounted

on the high pressure side of the pump or the rail.

The system pressure generated by the high-pressure pump and regulated by a

pressure-control circuit is applied to the injector.

The injector is th e core of the system b y ensurin g correct fuel del ivery into the

combust ion chamber . At a precisely defined instant the control unit transmits an

activation signal to the injector solenoid to initiate fuel delivery. The injected fuel

quant i ty is def ined by the in jector opening t im e and the sys tem pressure.

Engine management sy stemsDi l S




Scuola di Dottorato di Ricerca 2010 - Road vehicle and engine engineering scienceStrictly confidential | DS/SGF | 07/04/2005 | © Robert Bosch GmbH reserves all rights even in the event of industrial property rights.

We reserve all rights of disposal such as copying and passing on to third parties.

System overview Common Rail

Source: DS/EAC5 Sr 492 12781e

© R o b e r t B o s c h G m b H r e s e r v e s a l l r i g h t s e v e n i n e v e n t o f i n d u s t r i a l r i g h t s . W e r e s e r v e a l l r i g h t s

o f d i s p o s a l s u c h a s c o p y i n g a n d p a s s i n g o n t h i r d p a r t i e s

other

sensors

Tank

Control unit

High

pressure

pumpCPx

other

actuators

Prefilter

Fuel filter

high pressure

backflow

pressure

Pressure regulating valve

DRV

Tank

Electrical

presupply

pump

EKP

Injector

(1...n)

Metering

unit

ZME

Rail pressure

sensor RDS4

EKP pressure

Rail (LWR)

electrical lines

Engine speed

(crank)

Engine speed

(cam)

Accelerator

pedal

return linepressure

Throttle (1x)

0.85

Throttle (1x/injector)

0.85 mm

Throttle

Diesel Systems

Bosch Source

Engine management sy stemsDi l S





Laser Welded Rail

Low pressure fitting

• connection to system backflow

ECU

RDS4

ECU

Engine Fixation

Rail Body

Throttles (optional)

High pressure fitting

• pipe connection to injectors

• pipe connection to pump

DRV

Rail Pressure sensor

Pressure Regulator Valve

Diesel Systems

Bosch Source

Engine management sy stemsDi l S t





CRS2.2 - High Pressure Pump (1600 bar)

CP1H CP3

Diesel Systems

Bosch Source




g e a age e sy s e s


Comm on rai l Diesel in jector (solenoid-valve type)

Start of injection and injected fuel quantity are set by electrical activation.

The injection point is set by the angle/time system of electronic Diesel control.

The fuel is sent from the high-pressure port via an inlet passage to the nozzle and via the

inlet restrictor into the valve control chamber.

The valve control chamber is connected by the outlet restrictor, which can be opened bya solenoid valve, to the fuel return.

When closed, the outlet restrictor overcomes the hydraulic force acting on the valve plunger

opposing the force acting on the pressure shoulder of the nozzle needle. As a result, the

nozzle needle is pressed into its seat and seal off the high pressure passage to engine

chamber tight. The nozzle spring closes the injector when the engine is not running and

there is no pressure in the rail. The outlet restrictor is opened when the solenoid valve isactivated. The inlet restrictor prevents a complete pressure compensation in such a way

that the pressure in valve control chamber and thus the hydraulic force acting on the valve

control plunger decrease. The nozzle needle opens as soon as hydraulic force drops below

that acting on the pressure shoulder of the nozzle needle. Fuel is now admitted through the

injection orifices into the engine combustion chambers

The key actuators




g g y

L’INIETTORE DEL COMMON RAIL

Bosch Source

5 Engine Management

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