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EP0474711B1 - Process for determining the combustion air mass in the cylinders of an internal combustion engine - Google Patents

Process for determining the combustion air mass in the cylinders of an internal combustion engine Download PDF

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Publication number
EP0474711B1
EP0474711B1 EP90908491A EP90908491A EP0474711B1 EP 0474711 B1 EP0474711 B1 EP 0474711B1 EP 90908491 A EP90908491 A EP 90908491A EP 90908491 A EP90908491 A EP 90908491A EP 0474711 B1 EP0474711 B1 EP 0474711B1
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EP
European Patent Office
Prior art keywords
air mass
combustion
cylinder
determined
combustion air
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
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EP90908491A
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German (de)
French (fr)
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EP0474711A1 (en
Inventor
Siegfried Ellmann
Manfred Wier
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Siemens AG
Siemens Corp
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Siemens AG
Siemens Corp
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    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02D—CONTROLLING COMBUSTION ENGINES
    • F02D35/00—Controlling engines, dependent on conditions exterior or interior to engines, not otherwise provided for
    • F02D35/02—Controlling engines, dependent on conditions exterior or interior to engines, not otherwise provided for on interior conditions
    • F02D35/023—Controlling engines, dependent on conditions exterior or interior to engines, not otherwise provided for on interior conditions by determining the cylinder pressure
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02D—CONTROLLING COMBUSTION ENGINES
    • F02D41/00—Electrical control of supply of combustible mixture or its constituents
    • F02D41/02—Circuit arrangements for generating control signals
    • F02D41/18—Circuit arrangements for generating control signals by measuring intake air flow
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02D—CONTROLLING COMBUSTION ENGINES
    • F02D41/00—Electrical control of supply of combustible mixture or its constituents
    • F02D41/24—Electrical control of supply of combustible mixture or its constituents characterised by the use of digital means
    • F02D41/2406—Electrical control of supply of combustible mixture or its constituents characterised by the use of digital means using essentially read only memories
    • F02D41/2425—Particular ways of programming the data
    • F02D41/2429—Methods of calibrating or learning
    • F02D41/2451—Methods of calibrating or learning characterised by what is learned or calibrated
    • F02D41/2474—Characteristics of sensors
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02D—CONTROLLING COMBUSTION ENGINES
    • F02D2200/00—Input parameters for engine control
    • F02D2200/02—Input parameters for engine control the parameters being related to the engine
    • F02D2200/04—Engine intake system parameters
    • F02D2200/0402—Engine intake system parameters the parameter being determined by using a model of the engine intake or its components
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02D—CONTROLLING COMBUSTION ENGINES
    • F02D41/00—Electrical control of supply of combustible mixture or its constituents
    • F02D41/24—Electrical control of supply of combustible mixture or its constituents characterised by the use of digital means
    • F02D41/2406—Electrical control of supply of combustible mixture or its constituents characterised by the use of digital means using essentially read only memories
    • F02D41/2409—Addressing techniques specially adapted therefor

Definitions

  • the invention relates to a method for determining the combustion air mass that is available in the cylinders of an internal combustion engine for a specific combustion, according to the preamble of claim 1.
  • the combustion air mass available for this must be known exactly.
  • the air mass flowing through the intake manifold is measured using an air mass measurement, e.g. via the opening angle of the throttle valve, the negative pressure or via hot wire air mass meter.
  • this measured air mass does not yet correspond to the combustion air mass.
  • Different gas running times at different speeds, dead times under transient operating conditions, different environmental conditions etc. cause a temporal and a quantitative difference in the measured air mass with respect to the combustion air mass available for a specific combustion cycle.
  • the measured air mass is corrected using correction factors so that it corresponds to the combustion air mass.
  • the correction factors are determined on the engine test bench and in driving tests and are usually stored in a map.
  • the present invention is therefore based on the object of specifying a method in which the correction factors can be optimally adapted again and again during operation of the internal combustion engine.
  • the invention is based on the consideration that the combustion air mass can be determined precisely by measuring the compression pressure curve in the cylinders. This compression pressure is therefore continuously measured by a combustion chamber pressure sensor during each compression stroke in each cylinder. Since the pressure increase during the compression stroke is a polytropic change in state, the combustion air mass can be calculated from the crank mechanism kinematics and the thermodynamic state equations. This combustion air mass is then compared with the combustion air mass determined via the air mass measurement. If there is a deviation, the usual correction is adjusted in the further determination of the air mass so that the deviation disappears.
  • the correction is only changed if deviations have occurred several times in succession. Interference that occurs for a short time is thereby filtered out.
  • An ignition plug 7 in each cylinder is controlled by an ignition system 6.
  • a microcomputer 5 with corresponding input and output interfaces controls the fuel injection and ignition. For this purpose, as input variables it receives a position signal corresponding to the position of the throttle valve 2 and the combustion chamber pressure p via a combustion chamber pressure sensor 4 for each cylinder. Further input variables are the values derived from the corresponding sensors for the speed n, the intake air temperature TAL and the crankshaft position KW.
  • the microcomputer 5 executes the method shown in FIG. 2 before each fuel injection into one of the cylinders.
  • step S1 the position ⁇ of the throttle valve and the speed n of the internal combustion engine are read.
  • An air mass ⁇ L is then determined in step S2 from a map stored in the microcomputer 5.
  • step S4 the air mass correction factor LK is then subtracted from the air mass ⁇ L and the combustion air mass ⁇ LV is thus obtained.
  • step S5 the microcomputer 5 then determines an injection time ti from this combustion air mass ⁇ LV and the speed n and opens the fuel injector 3 assigned to the corresponding cylinder for this injection time ti. As a result, the amount of fuel corresponding to the combustion air mass ⁇ LV enters the cylinder via the fuel injection valve 3 supplied with constant pressure, so that an arbitrarily adjustable, e.g. B. stoichiometric, mixture is present.
  • an arbitrarily adjustable e.g. B. stoichiometric
  • steps S6 to S10 check the combustion air mass ⁇ LV determined by means of the air mass measurement using the combustion chamber pressure p measured by the combustion chamber pressure sensor 4.
  • step S6 the pressure curve during the compression stroke of the cylinder is recorded by means of ongoing individual measurements of the combustion chamber pressure p1 to pm.
  • the crankshaft position KW determines the beginning and end of the compression stroke.
  • the combustion air mass ⁇ LVp resulting from the pressure measurement is then calculated from the crank mechanism kinematics and the thermodynamic gas equations in step S9.
  • step S10 the combustion air masses determined via the air mass measurement (steps S1 to S4) and the combustion air masses determined via the pressure measurement (steps S6 to S9) now follow. If there is no discrepancy in the comparison, the program run is ended.
  • step S11 If, on the other hand, there is a deviation, it is checked in step S11 whether this exceeds a limit value G. If this is not the case, the program run is ended again, since only slight deviations in the combustion air masses determined are irrelevant. Step S12 follows for larger deviations. To rule out temporary, short-term deviations, a check is made to determine whether there have been ten deviations.
  • step S13 one or both characteristic fields of steps S2 and S3 are adapted in step S13.
  • individual map points or entire map areas are modified so that the combustion air mass determined via the air mass measurement becomes the same as that determined via the pressure measurement.
  • Corresponding methods for map adaptation are described, for example, in SAE PAPER 865080.
  • the determination of the polytropic exponent ⁇ in step S8 also offers a simple diagnostic option for the state of the cylinder in question.
  • air loss (blowby) occurs in the cylinders, which is caused by the wear of the piston rings and the resulting deterioration of the seal. Without this loss of air - i.e. with the cylinder intact - the polytropic exponent ⁇ has a certain constant value.
  • the change in the polytropic exponent is therefore used for diagnosis.
  • the amount of the change is then a measure of the air loss and thus of the condition of the cylinder.
  • the changes that occur are therefore saved and can be queried by an appropriate diagnostic device during the next engine diagnosis.
  • the changes can also be evaluated by a diagnostic system in the vehicle, which means e.g. the driver can be warned in time of impending defects.

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  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Combustion & Propulsion (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Analytical Chemistry (AREA)
  • Combined Controls Of Internal Combustion Engines (AREA)

Abstract

In this process, the combustion air mass in the cylinders of an internal combustion engine is determined by measuring the air mass and the pressure in the combustion chamber. The combustion air mass determined by measuring the pressure in the combustion chamber is compared with the combustion air mass determined by measuring the air mass, and is used to correct the results of the latter measurement.

Description

Die Erfindung betrifft ein Verfahren zum Bestimmen der Verbrennungsluftmasse die in den Zylindern einer Brennkraftmaschine für eine bestimmte Verbrennung zur Verfügung steht, gemäß Oberbegriff von Anspruch 1.The invention relates to a method for determining the combustion air mass that is available in the cylinders of an internal combustion engine for a specific combustion, according to the preamble of claim 1.

Um bei einer Brennkraftmaschine für jeden Verbrennungstakt die richtige Kraftstoffmenge zuweisen zu können, muß die dafür zur Verfügung stehende Verbrennungsluftmasse genau bekannt sein. Bei modernen Brennkraftmaschinen wird dazu die durchströmende Luftmasse im Saugrohr über eine Luftmassenmessung, wie z.B. über den Öffnungswinkel der Drosselklappe, den Unterdruck oder über Hitzdrahtluftmassenmesser erfaßt. Diese gemessene Luftmasse entspricht aber noch nicht der Verbrennungsluftmasse. Verschiedene Gaslaufzeiten bei unterschiedlichen Drehzahlen, Totzeiten bei instationären Betriebszuständen, verschiedene Umgebungsbedingungen usw. bewirken einen zeitlichen und einen mengenmäßigen Unterschied der gemessenen Luftmasse bezüglich der für einen bestimmten Verbrennungstakt zur Verfügung stehenden Verbrennungsluftmasse.In order to be able to assign the correct amount of fuel to an internal combustion engine for each combustion cycle, the combustion air mass available for this must be known exactly. In modern internal combustion engines, the air mass flowing through the intake manifold is measured using an air mass measurement, e.g. via the opening angle of the throttle valve, the negative pressure or via hot wire air mass meter. However, this measured air mass does not yet correspond to the combustion air mass. Different gas running times at different speeds, dead times under transient operating conditions, different environmental conditions etc. cause a temporal and a quantitative difference in the measured air mass with respect to the combustion air mass available for a specific combustion cycle.

Zur Kompensation dieser Einflüsse wird die gemessene Luftmasse mittels Korrekturfaktoren korrigiert, so daß sie der Verbrennungsluftmasse entspricht. Die Korrekturfaktoren werden auf dem Motorprüfstand und in Fahrversuchen ermittelt und sind üblicherweise in einem Kennfeld abgelegt.To compensate for these influences, the measured air mass is corrected using correction factors so that it corresponds to the combustion air mass. The correction factors are determined on the engine test bench and in driving tests and are usually stored in a map.

Diese gefundenen Korrekturfaktoren führen bei der neuen Brennkraftmaschine zu einer optimalen Zuordnung der gemessen Luftmasse zur Verbrennungsluftmasse. Durch auftretende Defekte oder Alterung wird diese Zuordnung jedoch mehr und mehr verfälscht.These correction factors found in the new internal combustion engine lead to an optimal allocation of the measured air mass to the combustion air mass. However, due to defects or aging, this assignment is increasingly falsified.

Der vorliegenden Erfindung liegt daher die Aufgabe zugrunde, ein Verfahren anzugeben, bei dem die Korrekturfaktoren im Betrieb der Brennkraftnaschine immer wieder optimal angepaßt werden können.The present invention is therefore based on the object of specifying a method in which the correction factors can be optimally adapted again and again during operation of the internal combustion engine.

Die erfindungsgemäße Lösung ist im Anspruch 1 gekennzeichnet. Vorteilhafte Weiterbildungen der Erfindung finden sich in den Unteransprüchen.The solution according to the invention is characterized in claim 1. Advantageous developments of the invention can be found in the subclaims.

Bei der Erfindung wird von der Überlegung ausgegangen, daß über eine Messung des Kompressionsdruckverlaufs in den Zylindern die Verbrennungsluftmasse genau bestimmt werden kann. Dieser Kompressionsdruck wird daher über einen Brennraumdrucksensor während jedes Kompressionstakts in jedem Zylinder laufend gemessen. Da der Druckanstieg während des Kompressionstakts eine Polytrope Zustandsänderung ist, kann die Verbrennungsluftmasse aus der Kurbeltriebkinematik und den thermodynamischen Zustandsgleichungen berechnet werden. Diese Verbrennungsluftmasse wird dann mit der über die Luftmassenmessung ermittelten Verbrennungsluftmasse verglichen. Ergibt sich dabei eine Abweichung so wird bei der weiteren Luftmassenbestimmung die übliche Korrektur so angepaßt, daß die Abweichung verschwindet.The invention is based on the consideration that the combustion air mass can be determined precisely by measuring the compression pressure curve in the cylinders. This compression pressure is therefore continuously measured by a combustion chamber pressure sensor during each compression stroke in each cylinder. Since the pressure increase during the compression stroke is a polytropic change in state, the combustion air mass can be calculated from the crank mechanism kinematics and the thermodynamic state equations. This combustion air mass is then compared with the combustion air mass determined via the air mass measurement. If there is a deviation, the usual correction is adjusted in the further determination of the air mass so that the deviation disappears.

Durch die laufende Adaption der Luftmassenermittlung wird eine jedem Zylinder individuell richtige Kraftstoffmenge zugewiesen und so eine Zylindergleichstellung erreicht.Due to the ongoing adaptation of the air mass determination, an individually correct amount of fuel is assigned to each cylinder, thus achieving cylinder equality.

Gemäß einer Weiterbildung der Erfindung wird die Korrektur nur dann verändert, wenn mehrmals hintereinander Abweichungen aufgetreten sind. Dadurch werden kurzzeitig auftretende Störeinflüsse ausgefiltert.According to a development of the invention, the correction is only changed if deviations have occurred several times in succession. Interference that occurs for a short time is thereby filtered out.

Die Erfindung wird anhand der Zeichnungen näher erläutert. Dabei Zeigen

Figur 1
ein Übersichtsschaltbild mit den relevanten Teilen einer Brennkraftmaschine zur Durchführung des erfindungsgemäßen Verfahrens,
Figur 2, 3
ein Flußdiagramm zur Durchführung des Verfahrens, und
Figur 4
den Druckverlauf im einem Zylinder während des Kompressionstakts
In Figur 1 ist schematisch das Saugrohr 1 einer Brennkraftmaschine dargestellt, über das den einzelnen Zylindern Luft zugeführt wird. Zur Steuerung der Luftmasse ist eine Drosselklappe 2 vorgesehen, die vom Fahrer betätigt wird. Jedem Zylinder mit Einlaß- und Auslaßventil ist ein Kraftstoffeinspritzventil 3 zugeordnet, dem Kraftstoff mit konstantem Druck von einer nicht dargestellten Kraftstoffversorgungsanlage zugeführt wird.The invention is explained in more detail with reference to the drawings. Show
Figure 1
2 shows an overview circuit diagram with the relevant parts of an internal combustion engine for carrying out the method according to the invention,
Figure 2, 3
a flow chart for performing the method, and
Figure 4
the pressure curve in a cylinder during the compression stroke
In Figure 1, the intake manifold 1 of an internal combustion engine is shown schematically, through which air is supplied to the individual cylinders. To control the air mass, a throttle valve 2 is provided which is operated by the driver. A fuel injection valve 3 is assigned to each cylinder with intake and exhaust valve, to which fuel is supplied at a constant pressure from a fuel supply system, not shown.

Eine Zündkerze 7 in jedem Zylinder wird von einem Zündsystem 6 angesteuert.An ignition plug 7 in each cylinder is controlled by an ignition system 6.

Die Steuerung von Kraftstoffeinspritzung und Zündung übernimmt ein Mikrocomputer 5 mit entsprechenden Eingangs- und Ausgangsschnittstellen. Als Eingangsgrößen erhält er dazu ein Stellungssignal entsprechend der Stellung der Drosselklappe 2 sowie den Brennraumdruck p über jeweils einen Brennraumdrucksensor 4 für jeden Zylinder. Weitere Eingangsgrößen sind die von entsprechenden Sensoren abgeleiteten Werte für die Drehzahl n, die Ansauglufttemperatur TAL und die Kurbelwellenposition KW.A microcomputer 5 with corresponding input and output interfaces controls the fuel injection and ignition. For this purpose, as input variables it receives a position signal corresponding to the position of the throttle valve 2 and the combustion chamber pressure p via a combustion chamber pressure sensor 4 for each cylinder. Further input variables are the values derived from the corresponding sensors for the speed n, the intake air temperature TAL and the crankshaft position KW.

Der Mikrocomputer 5 führt vor jeder Kraftstoffeinspitzung in einen der Zylinder das in Figur 2 dargestellte Verfahren aus.The microcomputer 5 executes the method shown in FIG. 2 before each fuel injection into one of the cylinders.

Beim Schritt S1 wird die Stellung α der Drosselklappe sowie die Drehzahl n der Brennkraftmaschine eingelesen. Aus einem im Mikrocomputer 5 abgespeicherten Kennfeld wird dann beim Schritt S2 eine Luftmasse ṁL bestimmt.In step S1, the position α of the throttle valve and the speed n of the internal combustion engine are read. An air mass ṁL is then determined in step S2 from a map stored in the microcomputer 5.

Diese Luftmasse ṁL entspricht nun noch nicht der Verbrennungsluftmasse ṁLV, die in den im Verbrennungsablauf nächstfolgenden Zylinder gelangt. Dementsprechend wird für die Luftmasse ṁL beim Schritt S3 ein Luftmassenkorrekturfaktor LK ermittelt. Dieser ist in einem Kennfeld abhängig von der beim vorhergehenden Schritt ermittelten Luftmasse ṁL und der Drehzahl n abgelegt. Die Werte für den Luftmassenkorrekturfaktor LK sind experimentell ermittelt und berücksichtigen insbesondere folgende Einflüsse:

  • Den Phasenfehler durch die Speicherwirkung des Saugrohrvolumens des Saugrohrs 1, insbesondere bei dynamischen Übergängen;
  • den Restgasgehalt durch interne Abgasrückführung bedingt durch die Ventilüberschneidungen;
  • die Wandfilmeinflüsse, insbesondere bei dynamischen Übergängen;
  • die zylinderselektive Luftzumessung bedingt durch Ventilüberschneidungen;
  • die Rechenzeiten des Mikrocomputers 5;
Der Luftmassenkorrekturfaktor LK kann auch über eine Echtzeitberechnung bestimmt werden, die die genannten Einflüsse formelmäßig erfaßt.This air mass ṁL does not yet correspond to the combustion air mass ṁLV that reaches the next cylinder in the combustion process. Accordingly, an air mass correction factor LK is determined for the air mass ṁL in step S3. This is stored in a map depending on the air mass ṁL determined in the previous step and the speed n. The values for the air mass correction factor LK have been determined experimentally and take into account the following influences in particular:
  • The phase error due to the storage effect of the intake manifold volume of the intake manifold 1, particularly in the case of dynamic transitions;
  • the residual gas content due to internal exhaust gas recirculation due to the valve overlap;
  • the wall film influences, especially with dynamic transitions;
  • cylinder-selective air metering due to valve overlap;
  • the computing times of the microcomputer 5;
The air mass correction factor LK can also be determined via a real-time calculation, which records the influences mentioned in terms of the formula.

Beim Schritt S4 wird dann der Luftmassenkorrekturfaktor LK von der Luftmasse ṁL abgezogen und so die Verbrennungsluftmasse ṁLV erhalten. Beim Schritt S5 ermittelt der Mikrocomputer 5 dann aus dieser Verbrennungsluftmasse ṁLV und der Drehzahl n eine Einspritzzeit ti und öffnet das dem entsprechenden Zylinder zugeordnete Kraftstoffeinspritzventil 3 für diese Einspritzzeit ti. Dadurch gelangt über das mit konstantem Druck versorgte Kraftstoffeinspritzventil 3 die der Verbrennungsluftmasse ṁLV entsprechende Kraftstoffmenge in den Zylinder, so daß ein beliebig einstellbares, z. B. stöchiometrisches, Gemisch vorliegt.In step S4, the air mass correction factor LK is then subtracted from the air mass ṁL and the combustion air mass ṁLV is thus obtained. In step S5, the microcomputer 5 then determines an injection time ti from this combustion air mass ṁLV and the speed n and opens the fuel injector 3 assigned to the corresponding cylinder for this injection time ti. As a result, the amount of fuel corresponding to the combustion air mass ṁLV enters the cylinder via the fuel injection valve 3 supplied with constant pressure, so that an arbitrarily adjustable, e.g. B. stoichiometric, mixture is present.

Gemäß dem Flußdiagramm der Figur 3 findet bei den Schritten S6 bis S10 eine Überprüfung der über die Luftmassenmessung ermittelten Verbrennungsluftmasse ṁLV mit Hilfe des über den Brennraumdrucksensor 4 gemessenen Brennraumdrucks p statt. Beim Schritt S6 wird der Druckverlauf während des Kompressionstakts des Zylinders über laufende Einzelmessungen des Brennraumdrucks p1 bis pm erfaßt. Anfang und Ende des Kompressionstakts bestimmt dabei die Kurbelwellenposition KW.According to the flow chart in FIG. 3, steps S6 to S10 check the combustion air mass ṁLV determined by means of the air mass measurement using the combustion chamber pressure p measured by the combustion chamber pressure sensor 4. In step S6, the pressure curve during the compression stroke of the cylinder is recorded by means of ongoing individual measurements of the combustion chamber pressure p1 to pm. The crankshaft position KW determines the beginning and end of the compression stroke.

Dieser Vorgang ist in Figur 4 gezeigt. Darin ist der Druckverlauf in dem Zylinder während des Kompressionstakts zwischen den Kurbelwellenpositionen KW1 bis KW2 gezeigt. Da der Druckverlauf während des Kompressionstakts eine polytrope Zustandsänderung ist, bleibt dabei der Polytropenexponent χ konstant. Dieser wird bei den Schritten S7 und S8 bestimmt. Δ ist dabei die Summe der Druckunterschiede von jeweils zwei aufeinanderfolgenden Einzelmessungen. Der Polytropenexponent χ ergibt sich aus Δ dividiert durch die Zahl der Einzelmessungen m.This process is shown in Figure 4. It shows the pressure curve in the cylinder during the compression stroke between the Crankshaft positions KW1 to KW2 shown. Since the pressure curve during the compression stroke is a polytropic change of state, the polytropic exponent χ remains constant. This is determined in steps S7 and S8. Δ is the sum of the pressure differences between two successive individual measurements. The polytropic exponent χ results from Δ divided by the number of individual measurements m.

Mit dem Polytropenexponenten χ und den bekannten Abmessungen des Zylinders wird dann beim Schritt S9 die sich aus der Druckmessung ergebende Verbrennungsluftmasse ṁLVp aus der Kurbeltriebkinematik und den thermodynamischen Gasgleichungen berechnet.With the polytropic exponent χ and the known dimensions of the cylinder, the combustion air mass ṁLVp resulting from the pressure measurement is then calculated from the crank mechanism kinematics and the thermodynamic gas equations in step S9.

Beim Schritt S10 folgt nun der Vergleich der über die Luftmassenmessung (Schritte S1 bis S4) und der über die Druckmessung (Schritte S6 bis S9) ermittelten Verbrennungsluftmassen. Ergibt der Vergleich keine Abweichung, so wird der Programmlauf beendet.At step S10, the combustion air masses determined via the air mass measurement (steps S1 to S4) and the combustion air masses determined via the pressure measurement (steps S6 to S9) now follow. If there is no discrepancy in the comparison, the program run is ended.

Ist dagegen eine Abweichung vorhanden, so wird beim Schritt S11 geprüft, ob diese einen Grenzwert G übersteigt. Ist dies nicht der Fall, so wird wiederum der Programmlauf beendet, da nur geringfügige Abweichungen der ermittelten Verbrennungsluftmassen keine Rolle spielen. Bei größeren Abweichungen folgt der Schritt S12. Um vorübergehende kurzzeitige Abweichungen auszuschließen, wird dabei geprüft, ob zehnmal eine Abweichung aufgetreten ist.If, on the other hand, there is a deviation, it is checked in step S11 whether this exceeds a limit value G. If this is not the case, the program run is ended again, since only slight deviations in the combustion air masses determined are irrelevant. Step S12 follows for larger deviations. To rule out temporary, short-term deviations, a check is made to determine whether there have been ten deviations.

Ist dies der Fall, wird beim Schritt S13 eines oder beide Kenn-Felder der Schritte S2 und S3 adaptiert. Je nach Größe und Höhe der Abweichung werden dabei einzelne Kennfeldpunkte oder auch ganze Kennfeldbereiche so abgeändert, daß die über die Luftmassenmessung ermittelte Verbrennungsluftmasse der über die Druckmessung ermittelten gleich wird. Entsprechende Verfahren zur Kennfeldadaption sind z.B. im SAE PAPER 865080 beschrieben.If this is the case, one or both characteristic fields of steps S2 and S3 are adapted in step S13. Depending on the size and magnitude of the deviation, individual map points or entire map areas are modified so that the combustion air mass determined via the air mass measurement becomes the same as that determined via the pressure measurement. Corresponding methods for map adaptation are described, for example, in SAE PAPER 865080.

Die Ermittlung des Polytropenexponenten χ beim Schritt S8 bietet zusätzlich eine einfache Diagnosemöglichkeit für den Zustand des betreffenden Zylinders. Mit zunehmender Alterung tritt in den Zylindern ein Luftverlust (Blowby) auf, der durch den Verschleiß der Kolbenringe und der dadurch verursachten Verschlechterung der Abdichtung bedingt ist. Ohne diesen Luftverlust - also bei vollkommen intaktem Zylinder - hat der Polytropenexponent χ einen bestimmten konstanten Wert. Zur Diagnose wird daher die Änderung der Polytropenexponenten herangezogen. Die Höhe der Änderung ist dann ein Maß für den Luftverlust und damit für den Zustand des Zylinders. Die auftretenden Änderungen werden daher abgespeichert und können bei der nächsten Motordiagnose von einem entsprechenden Diagnosegerät abgefragt werden. Ebenso können die Änderungen von einem im Fahrzeug befindlichen Diagnosesystem ausgewertet werden, wodurch z.B. der Fahrer rechtzeitig vor sich anbahnenden Defekten gewarnt werden kann.The determination of the polytropic exponent χ in step S8 also offers a simple diagnostic option for the state of the cylinder in question. With increasing aging, air loss (blowby) occurs in the cylinders, which is caused by the wear of the piston rings and the resulting deterioration of the seal. Without this loss of air - i.e. with the cylinder intact - the polytropic exponent χ has a certain constant value. The change in the polytropic exponent is therefore used for diagnosis. The amount of the change is then a measure of the air loss and thus of the condition of the cylinder. The changes that occur are therefore saved and can be queried by an appropriate diagnostic device during the next engine diagnosis. The changes can also be evaluated by a diagnostic system in the vehicle, which means e.g. the driver can be warned in time of impending defects.

Claims (6)

  1. Method for determining the combustion air mass which is available for a certain combustion in one cylinder or a plurality of cylinders of an internal combustion engine, the induced air mass being continuously measured by means of an air mass measurement in the induction pipe and this measured air mass being subject to a correction so that it corresponds to the combustion air mass, characterized in that the pressure in each cylinder is measured by means of a combustion space pressure measurement, in that the combustion air mass for each cylinder is determined from the variation of pressure during a compression stroke and in that compensation is provided for the difference between the combustion air masses determined by means of the air mass measurement and the combustion space pressure measurement by means of an adaptation of the correction.
  2. Method according to Claim 1, characterized in that the adaptation is only carried out when differences in the combustion air masses determined have appeared several times.
  3. Method according to Claim 1, characterized in that the correction takes place by means of a real-time calculation.
  4. Method according to one of Claims 1 to 3, characterized in that the correction takes place by means of at least one characteristic diagram.
  5. Method according to Claim 1, characterized in that the air loss ("blowby") is determined, by means of the polytropic equation, from the variation of pressure during a compression stroke by using the deviations between the polytropic constant χ found and the polytropic constant χ for an intact cylinder.
  6. Method according to Claim 5, characterized in that information is derived from the amount of the air loss and this information permits a conclusion with respect to an ageing effect or a defect in the internal combustion engine and is used for a diagnosis system.
EP90908491A 1989-06-01 1990-06-01 Process for determining the combustion air mass in the cylinders of an internal combustion engine Expired - Lifetime EP0474711B1 (en)

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
DE3917908A DE3917908A1 (en) 1989-06-01 1989-06-01 METHOD FOR DETERMINING THE AIR FILLING OF THE WORKING VOLUME OF A COMBINED PISTON INTERNAL COMBUSTION ENGINE AND FOR DETERMINING THE FUEL INJECTION LEVEL
DE3917908 1989-06-01
PCT/DE1990/000422 WO1990015236A1 (en) 1989-06-01 1990-06-01 Process for determining the combustion air mass in the cylinders of an internal combustion engine

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EP0474711A1 EP0474711A1 (en) 1992-03-18
EP0474711B1 true EP0474711B1 (en) 1994-10-26

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DE59007576D1 (en) 1994-12-01
DE3917908A1 (en) 1990-12-06
US5140850A (en) 1992-08-25
WO1990015236A1 (en) 1990-12-13
ES2063357T3 (en) 1995-01-01
JPH04506100A (en) 1992-10-22
EP0474711A1 (en) 1992-03-18

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