EP1792154A1 - Method for correcting a measured cylinder pressure of an internal combustion engine - Google Patents

Method for correcting a measured cylinder pressure of an internal combustion engine

Info

Publication number
EP1792154A1
EP1792154A1 EP05769867A EP05769867A EP1792154A1 EP 1792154 A1 EP1792154 A1 EP 1792154A1 EP 05769867 A EP05769867 A EP 05769867A EP 05769867 A EP05769867 A EP 05769867A EP 1792154 A1 EP1792154 A1 EP 1792154A1
Authority
EP
European Patent Office
Prior art keywords
cylinder pressure
combustion chamber
internal combustion
combustion engine
measured
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.)
Withdrawn
Application number
EP05769867A
Other languages
German (de)
French (fr)
Inventor
Uwe Kassner
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Robert Bosch GmbH
Original Assignee
Robert Bosch GmbH
Priority date (The priority date 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 date listed.)
Filing date
Publication date
Application filed by Robert Bosch GmbH filed Critical Robert Bosch GmbH
Publication of EP1792154A1 publication Critical patent/EP1792154A1/en
Withdrawn legal-status Critical Current

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Classifications

    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01L—MEASURING FORCE, STRESS, TORQUE, WORK, MECHANICAL POWER, MECHANICAL EFFICIENCY, OR FLUID PRESSURE
    • G01L23/00—Devices or apparatus for measuring or indicating or recording rapid changes, such as oscillations, in the pressure of steam, gas, or liquid; Indicators for determining work or energy of steam, internal-combustion, or other fluid-pressure engines from the condition of the working fluid
    • G01L23/08—Devices or apparatus for measuring or indicating or recording rapid changes, such as oscillations, in the pressure of steam, gas, or liquid; Indicators for determining work or energy of steam, internal-combustion, or other fluid-pressure engines from the condition of the working fluid operated electrically
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01L—MEASURING FORCE, STRESS, TORQUE, WORK, MECHANICAL POWER, MECHANICAL EFFICIENCY, OR FLUID PRESSURE
    • G01L27/00—Testing or calibrating of apparatus for measuring fluid pressure
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01M—TESTING STATIC OR DYNAMIC BALANCE OF MACHINES OR STRUCTURES; TESTING OF STRUCTURES OR APPARATUS, NOT OTHERWISE PROVIDED FOR
    • G01M15/00—Testing of engines
    • G01M15/04—Testing internal-combustion engines
    • G01M15/08—Testing internal-combustion engines by monitoring pressure in cylinders

Definitions

  • the present invention relates to a method for correcting a measured cylinder pressure of an internal combustion engine.
  • Cylinder pressure transducers are known which, if possible, are integrated in an already existing component of the internal combustion engine. Typical embodiments are the integration of a suitable pressure transducer into a spark plug, a high-pressure injection valve or a glow plug. On the one hand, the front part of the component is already assigned to the main purpose of the component and offers no installation space for the pressure transducer, on the other hand, the pressure transducers are often provided with integrated electronic circuits which can not be exposed to the high temperatures near the combustion chamber. The cylinder pressure is then transmitted via suitable channels in the component from the combustion chamber to the pressure converter.
  • the problem underlying the present invention is therefore to be able to measure the temporal pressure curve more accurately even without combustion-flush placement of the pressure transducer and to suppress disturbance components resulting from pipe vibrations.
  • a method for correcting a measured cylinder pressure of an internal combustion engine in which a cylinder pressure sensor is connected to a combustion chamber via a duct, wherein a vibration frequency of a gas oscillation caused in the duct during a power stroke is determined and the measured values of ZylinderdruckaufNeille ⁇ is be filtered by means of a band-stop filter with the previously determined Schwingungsfre ⁇ frequency.
  • the gas oscillation is a so-called pipe vibration and manifests itself, from the viewpoint of the cylinder pressure transducer, as pressure oscillation over time, which is superimposed on the actual pressure curve in the combustion chamber.
  • the bandstop filter is preferably a digital filter.
  • the oscillation frequency is the resonance frequency or natural frequency of the gas column in the gas channel from the combustion chamber to the cylinder pressure transducer.
  • the oscillation frequency can be determined from a gas temperature in the combustion chamber, which is calculated from measured pressure values.
  • the temperature of the gas is determined from the combustion chamber pressure by means of a suitable, known per se Model calculated.
  • the oscillation frequency can be determined by a spectral analysis of the pressure profile in the combustion chamber.
  • the pipe vibration has a considerably higher frequency than the fundamental vibration of the pressure curve, which has the frequency of the crankshaft speed.
  • the pipe vibration has a frequency in the kHz range. Since the fundamental oscillation is known from the crankshaft speed, harmonics (the spark oscillation) can be easily identified.
  • a first method step the cylinder pressure profile is measured and stored for a complete working cycle.
  • the pressure trace is then stored as a time series in a memory, e.g. a programmable logic controller before.
  • the gas temperature is determined and from this the pipe vibration frequency is calculated.
  • the gas temperature is calculated using an isentropic equation for an (ideal or real) gas.
  • the band-stop filter is implemented as a program of the programmable controller, in which case, in particular, a blocking frequency and a damping factor are determined as parameters of the filter.
  • the cylinder pressure profile is filtered with the band-stop filter.
  • the time series is thereby subjected to the filter, whereby the filtered values can be written back to the same memory cells.
  • Fig. 2 pressure curve in a combustion chamber with superimposed pipe vibration.
  • An internal combustion engine 1 according to FIG. 1 of a motor vehicle which as such is not shown in detail, comprises a piston, t.-2, which can be reciprocated in a cylinder 3.
  • Conventional internal combustion engines 1 comprise a plurality of pistons 2 and cylinders 3. Subsequently, only one cylinder is shown in order to clarify the terms used.
  • the internal combustion engine 1 will comprise a plurality of cylinders.
  • the cylinder 3 comprises a combustion chamber 4 which is delimited inter alia by the piston 2, an inlet valve 5 and an outlet valve 6. With the inlet valve 5 is an intake pipe 7 and the outlet valve 6 is an exhaust pipe 8 is coupled.
  • an injection valve 9 and a spark plug 10 protrude into the combustion chamber 4 (in a gasoline engine with direct gasoline injection).
  • a diesel engine only one or more injection valves 9 will be present, in a gasoline engine only one or more Spark plugs 10 to be available.
  • Fuel can be injected into the combustion chamber 4 via the injection valve 9. With the spark plug 10, the fuel in the combustion chamber 4 ignited the was ⁇ .
  • a rotatable throttle valve 11 is housed, via which the intake pipe 7 air can be supplied. Upstream or downstream of the throttle valve 11, an air mass sensor 15 is arranged. The amount of supplied air is dependent on the angular position of the throttle valve 11.
  • a lambda probe 13 for measuring the ⁇ value of the fuel combustion in the combustion chamber 4 is arranged in a gasoline engine. Downstream of the lambda probe 13, a catalyst 12 is housed, which serves the further chemical conversion of pollutants contained in the exhaust gases.
  • the piston 2 is connected via a connecting rod 14 shown schematically with a Kurbelwel ⁇ le of the internal combustion engine, not shown here.
  • the piston 2 is set in motion by the combustion of the fuel / air mixture in the combustion chamber 4 during a power stroke, this movement is converted by means of the connecting rod 14 and the crankshaft in a known manner in a rotational movement.
  • a control unit 18 is acted upon by input signals 19, which represent operating variables of the internal combustion engine 1 measured by means of sensors. For example, that is
  • Control unit 18 with the air mass sensor 15, the Lambda sensor 13, a tachometer, an air temperature sensor and the like connected. Furthermore, the control unit 18 is connected to an accelerator pedal sensor which generates a signal which indicates the position of an accelerator pedal actuatable by a driver and thus the requested torque.
  • the control unit 18 generates output signals 20 with which the behavior of the internal combustion engine 1 can be influenced via actuators or actuators. For example, the control unit 18 with the injection valve 9, the Spark plug 10 and the throttle valve 11 and the like ver ⁇ connected and generates the signals required for their control.
  • control unit 18 is provided to control or regulate the operating variables of the internal combustion engine 1.
  • the fuel mass injected from the injection valve 9 into the combustion chamber 4 is controlled or regulated by the control unit 18, in particular with regard to low fuel consumption and / or low pollutant development.
  • the control unit 18 is provided with a microprocessor which is stored in a storage medium such.
  • a read-only memory (ROM) has stored a program that controls the aforementioned method steps.
  • a cylinder pressure sensor 16 is angeord ⁇ net, which is connected to an electrical supply line 17 with the Steuerge ⁇ device 18. Between Zylinderdruckaufsacrificing 16 and combustion chamber 4, a channel 21 of length 1 is arranged.
  • the installation position of the cylinder pressure transducer 16 is shown here only schematically, this can vary depending on the available space and other requirements.
  • the course of the cylinder pressure provided by the cylinder pressure sensor 16 and variables derived therefrom are used as input signal for various control functions.
  • Output signals of the control are, for example, control signals for measuring the fuel and controlling the ignition of the mixture.
  • the cylin derdruckaufêt 16 provides a signal according to FIG. 2, the actual pressure curve pipe vibrations are superimposed by the Ka ⁇ 21. Shown in FIG.
  • the method is based on a modeling of the Pfeifenschwin ⁇ supply, so that a suitable filtering of the measured Zy ⁇ cylinder pressure curve can be done before the actual thermodynamic features are calculated from the cylinder pressure.
  • the basic idea is to suppress the singular frequency of the Pfeifen ⁇ oscillation with a filter that blocks this frequency (so-called band-stop characteristic). With a numerical method, a digital filter, this is possible for the measured pressure curve after complete detection of the work cycle.
  • An embodiment is the storage of the once determined filter coefficients in the controller for the different frequencies of the pipe vibration or the calculation of the respective coefficients in dependence on the operating point of the internal combustion engine.
  • the frequency f can be determined.
  • Main variable variable This parameter can be determined once during calibration of the control and stored in maps. Another possibility is the calculation via a suitable thermodynamic model.
  • one possible embodiment is the spectral analysis of the cylinder pressure signal.
  • the pipe vibration can thus be determined in frequency depending on the operating point.
  • the spectral analysis can be done offline during calibration for various engine operating points or online for each duty cycle. Then the suitable filter can again be selected in order to sufficiently suppress this frequency.
  • a particular advantage of initially complete storage of a working cycle is the possibility of compensating for the undesired phase shift of the cylinder pressure signal by passing through the filter twice (zero-phase filtering). The important relationships between the crank angle and cylinder pressure curve are thus not distorted.

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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Combustion & Propulsion (AREA)
  • Combined Controls Of Internal Combustion Engines (AREA)

Abstract

Disclosed is a method for correcting a measured cylinder pressure of an internal combustion engine in which a cylinder pressure sensor (16) is connected to a combustion chamber (4) via a duct (21). According to the inventive method, interference portions resulting from whistling vibrations are suppressed by determining a frequency of a gas column vibration generated in the duct (21) during a working stroke and filtering the measured values of the cylinder pressure sensor (16) at the previously determined oscillation frequency by means of a band elimination filter.

Description

Verfahren zur Korrektur eines gemessenen Zylinderdruckes einer BrennkraftmaschineMethod for correcting a measured cylinder pressure of an internal combustion engine
Stand der TechnikState of the art
Die vorliegende Erfindung betrifft ein Verfahren zur Kor¬ rektur eines gemessenen Zylinderdruckes einer Brennkraft¬ maschine.The present invention relates to a method for correcting a measured cylinder pressure of an internal combustion engine.
Es sind Zylinderdruckaufnehmer bekannt, die möglichst in ei¬ ne bereits vorhandene Komponente der Brennkraftmaschine in¬ tegriert sind. Typische Ausführungsformen sind die Integra¬ tion eines geeigneten Druckwandlers in eine Zündkerze, ein Hochdruckeinspritzventil oder eine Glühkerze. Der Druck- wandler ist dabei meist deutlich vom Brennraum entfernt: zum einen ist der vordere Teil der Komponente bereits dem Haupt-f zweck der Komponente zugeordnet und bietet keinen Bauraum für den Druckwandler, zum anderen sind die Druckwandler häu¬ fig mit integrierten elektronischen Schaltungen versehen, die den hohen Temperaturen nahe dem Brennraum nicht ausge¬ setzt werden können. Der Zylinderdruck wird dann über ge¬ eignete Kanäle in der Komponente vom Brennraum zum Druck¬ wandler übertragen.Cylinder pressure transducers are known which, if possible, are integrated in an already existing component of the internal combustion engine. Typical embodiments are the integration of a suitable pressure transducer into a spark plug, a high-pressure injection valve or a glow plug. On the one hand, the front part of the component is already assigned to the main purpose of the component and offers no installation space for the pressure transducer, on the other hand, the pressure transducers are often provided with integrated electronic circuits which can not be exposed to the high temperatures near the combustion chamber. The cylinder pressure is then transmitted via suitable channels in the component from the combustion chamber to the pressure converter.
Probleme des Standes der TechnikProblems of the prior art
Es ist bekannt, dass diese Kanäle zu deutlichen Verfälschun¬ gen des Zylinderdrucksignals führen können. Sie wirken als Resonator und sog. Pfeifenschwingungen verfälschen das Sig- nal. Fig. 2 zeigt einen Druckverlauf mit überlagerter Pfei- fenschwingung. Eine detaillierte Analyse des Zylinderdrucks und die Berechnung geeigneter Merkmale ist somit nicht mehr möglich. Hochwertige Zylinderdruckaufnehmer umgehen diese Verfälschung durch brennraumbündige Unterbringung des Druck- wandlers.It is known that these channels can lead to significant distortions of the cylinder pressure signal. They act as resonators and so-called pipe vibrations distort the signal. 2 shows a pressure curve with overlaid arrows. fenschwingung. A detailed analysis of the cylinder pressure and the calculation of suitable features is therefore no longer possible. High-quality cylinder pressure transducers avoid this adulteration by accommodating the pressure transducer flush with the combustion chamber.
Das der vorliegenden Erfindung zu Grunde liegende Problem ist es daher, den zeitlichen Druckverlauf auch ohne brenn¬ raumbündige Unterbringung des Druckwandlers genauer messen zu können und aus Pfeifenschwingungen resultierende Störan¬ teile zu unterdrücken.The problem underlying the present invention is therefore to be able to measure the temporal pressure curve more accurately even without combustion-flush placement of the pressure transducer and to suppress disturbance components resulting from pipe vibrations.
Vorteile der ErfindungAdvantages of the invention
Dieses Problem wird gelöst durch ein Verfahren zur Korrek¬ tur eines gemessenen Zylinderdruckes einer Brennkraftma¬ schine, bei der ein Zylinderdruckaufnehmer über einen Ka¬ nal mit einem Brennraum verbunden ist, wobei eine Schwin¬ gungsfrequenz einer in dem Kanal hervorgerufenen Gas- Schwingung während eines Arbeitstaktes bestimmt wird und die Messwerte des Zylinderdruckaufnehme∑is mittels eines Bandsperrfilters mit der zuvor bestimmten Schwingungsfre¬ quenz gefiltert werden. Die Gasschwingung ist eine so ge¬ nannte Pfeifenschwingung und äußert sich aus Sicht des Zy- linderdruckaufnehmers als Druckschwingung über der Zeit, die dem eigentlichen Druckverlauf in dem Brennraum überla¬ gert ist. Das Bandsperrfilter ist vorzugsweise ein digita¬ les Filter. Die Schwingungsfrequenz ist die Resonanzfre¬ quenz bzw. Eigenfrequenz der Gassäule im Gaskanal vom Brennraum zum Zylinderdruckaufnehmer.This problem is solved by a method for correcting a measured cylinder pressure of an internal combustion engine, in which a cylinder pressure sensor is connected to a combustion chamber via a duct, wherein a vibration frequency of a gas oscillation caused in the duct during a power stroke is determined and the measured values of ZylinderdruckaufnehmeΣis be filtered by means of a band-stop filter with the previously determined Schwingungsfre¬ frequency. The gas oscillation is a so-called pipe vibration and manifests itself, from the viewpoint of the cylinder pressure transducer, as pressure oscillation over time, which is superimposed on the actual pressure curve in the combustion chamber. The bandstop filter is preferably a digital filter. The oscillation frequency is the resonance frequency or natural frequency of the gas column in the gas channel from the combustion chamber to the cylinder pressure transducer.
Die Schwingungsfrequenz kann aus einer Gastemperatur in dem Brennraum, die aus gemessenen Druckwerten errechnet wird, bestimmt werden. Die Temperatur des Gases wird aus dem Brennraumdruck mittels eines geeigneten, an sich bekannten Modells errechnet. Alternativ kann die Schwingungsfrequenz durch eine Spektralanalyse des Druckverlaufs in dem Brenn¬ raum bestimmt werden. Die Pfeifenschwingung hat eine we¬ sentlich höhere Frequenz als die Grundschwingung des Druckverlaufes, die die Frequenz der Kurbelwellendrehzahl hat. Die Pfeifenschwingung hat eine Frequenz im kHz- Bereich. Da die Grundschwingung aus der Kurbelwellendreh¬ zahl bekannt ist, lassen sich Oberschwingungen (die Pfei¬ fenschwingung) leicht identifizieren.The oscillation frequency can be determined from a gas temperature in the combustion chamber, which is calculated from measured pressure values. The temperature of the gas is determined from the combustion chamber pressure by means of a suitable, known per se Model calculated. Alternatively, the oscillation frequency can be determined by a spectral analysis of the pressure profile in the combustion chamber. The pipe vibration has a considerably higher frequency than the fundamental vibration of the pressure curve, which has the frequency of the crankshaft speed. The pipe vibration has a frequency in the kHz range. Since the fundamental oscillation is known from the crankshaft speed, harmonics (the spark oscillation) can be easily identified.
In einer Weiterbildung des Verfahrens ist vorgesehen, dass in einem ersten Verfahrensschritt der Zylinderdruckverlauf für ein komplettes Arbeitsspiel gemessen und gespeichert wird. Der Druckverlauf liegt dann als Zeitreihe in einem Speicher, z.B. eines speicherprogrammierbaren Steuergerätes vor.In a development of the method, it is provided that in a first method step the cylinder pressure profile is measured and stored for a complete working cycle. The pressure trace is then stored as a time series in a memory, e.g. a programmable logic controller before.
In einer Weiterbildung des Verfahrens ist vorgesehen, dass in einem zweiten Verfahrensschritt die Gastemperatur be- stimmt und daraus die Pfeifenschwingungsfrequenz errechnet wird. Die Gastemperatur wir,d mittels einer Isentropenglei- chung für ein (ideales oder reales) Gas errechnet.In a development of the method, it is provided that in a second method step the gas temperature is determined and from this the pipe vibration frequency is calculated. The gas temperature is calculated using an isentropic equation for an (ideal or real) gas.
In einem dritten Verfahrensschritt werden in einer bevor- zugten Ausführungsform die Filterkoeffizienten für einIn a third method step, in a preferred embodiment, the filter coefficients for
Bandsperr-Filter errechnet. Das Bandsperr-Filter ist als Programm der speicherprogammierbaren Steuerung implemen¬ tiert, wobei hier insbesondere eine Sperrfrequenz und ein Dämpfungsmaß als Parameter des Filters bestimmt werden.Bandsperr filter calculated. The band-stop filter is implemented as a program of the programmable controller, in which case, in particular, a blocking frequency and a damping factor are determined as parameters of the filter.
In einem vierten Verfahrensschritt wird in der bevorzugten Ausführungsform der Zylinderdruckverlauf mit dem Bandsperr-Filter gefiltert. Die Zeitreihe wird dabei dem Filter unterzogen, wobei die gefilterten Werte in die gleichen Speicherzellen zurückgeschrieben werden können. Das eingangs genannte Problem wird auch durch ein Steuer¬ gerät für eine Brennkraftmaschine gelöst, das ein Verfah¬ ren nach, einem der vorhergehenden Ansprüche ausführen kann.In a fourth method step, in the preferred embodiment, the cylinder pressure profile is filtered with the band-stop filter. The time series is thereby subjected to the filter, whereby the filtered values can be written back to the same memory cells. The problem mentioned at the outset is also solved by a control unit for an internal combustion engine, which can carry out a method according to one of the preceding claims.
Zeichnungendrawings
Nachfolgend wird ein Ausführungsbeispiel der vorliegenden Erfindung anhand der beiliegenden Zeichnung näher erläu¬ tert. Dabei zeigen:Hereinafter, an embodiment of the present invention with reference to the accompanying drawings erläu¬ tert. Showing:
Fig. 1 eine Skizze eines Zylinders einer Brennkraftma¬ schine;1 is a sketch of a cylinder of a Brennkraftma¬ machine;
Fig. 2 Druckverlauf in einem Brennraum mit überlagerter Pfeifenschwingung.Fig. 2 pressure curve in a combustion chamber with superimposed pipe vibration.
Eine Brennkraftmaschine 1 gemäß Fig. 1 eines Kraftfahrzeu- ges, das als solches nicht näher dargestellt ist, umfasst einen Kolben;t.-2, der in einem Zylinder 3 hin- und herbeweg¬ bar ist. Übliche Brennkraftmaschinen 1 umfassen eine Mehr¬ zahl an Kolben 2 und Zylindern 3. nachfolgend wird nur ein Zylinder dargestellt um die verwendeten Begriffe zu ver- deutlichen. In der Regel wird die Brennkraftmaschine 1 mehrere Zylinder umfassen. Der Zylinder 3 umfasst einen Brennraum 4, der unter anderem durch den Kolben 2, ein Einlassventil 5 und ein Auslassventil 6 begrenzt ist. Mit dem Einlassventil 5 ist ein Ansaugrohr 7 und mit dem Aus- lassventil 6 ist ein Abgasrohr 8 gekoppelt. Im Bereich des Einlassventils 5 und des Auslassventils 6 ragen (bei einem Ottomotor mit Benzindirekteinspritzung)ein Einspritzventil 9 und eine Zündkerze 10 in den Brennraum 4. Bei einem Die¬ selmotor wird hier nur ein oder mehrere Einspritzventile 9, bei einem Ottomotor nur eine oder mehrere Zündkerzen 10 vorhanden sein. Über das Einspritzventil 9 kann Kraftstoff in den Brennraum 4 eingespritzt werden. Mit der Zündkerze 10 kann der Kraftstoff in dem Brennraum 4 entzündet wer¬ den. In dem Ansaugrohr 7 ist eine drehbare Drosselklappe 11 untergebracht, über die dem Ansaugrohr 7 Luft zuführbar ist. Stromauf oder auch stromab der Drosselklappe 11 ist ein Luftmassensensor 15 angeordnet. Die Menge der zuge¬ führten Luft ist abhängig von der Winkelstellung der Dros¬ selklappe 11. In dem Abgasrohr 8 ist bei einem Ottomotor eine Lambda-Sonde 13 zur Messung des λ-Wertes der Kraft- stoffverbrennung in dem Brennraum 4 angeordnet. Stromab der Lambda-Sonde 13 ist ein Katalysator 12 untergebracht, der der weiteren chemischen Umsetzung von in den Abgasen enthaltenen Schadstoffen dient.An internal combustion engine 1 according to FIG. 1 of a motor vehicle, which as such is not shown in detail, comprises a piston, t.-2, which can be reciprocated in a cylinder 3. Conventional internal combustion engines 1 comprise a plurality of pistons 2 and cylinders 3. Subsequently, only one cylinder is shown in order to clarify the terms used. As a rule, the internal combustion engine 1 will comprise a plurality of cylinders. The cylinder 3 comprises a combustion chamber 4 which is delimited inter alia by the piston 2, an inlet valve 5 and an outlet valve 6. With the inlet valve 5 is an intake pipe 7 and the outlet valve 6 is an exhaust pipe 8 is coupled. In the region of the intake valve 5 and the exhaust valve 6, an injection valve 9 and a spark plug 10 protrude into the combustion chamber 4 (in a gasoline engine with direct gasoline injection). In a diesel engine, only one or more injection valves 9 will be present, in a gasoline engine only one or more Spark plugs 10 to be available. Fuel can be injected into the combustion chamber 4 via the injection valve 9. With the spark plug 10, the fuel in the combustion chamber 4 ignited the wer¬. In the intake pipe 7, a rotatable throttle valve 11 is housed, via which the intake pipe 7 air can be supplied. Upstream or downstream of the throttle valve 11, an air mass sensor 15 is arranged. The amount of supplied air is dependent on the angular position of the throttle valve 11. In the exhaust pipe 8, a lambda probe 13 for measuring the λ value of the fuel combustion in the combustion chamber 4 is arranged in a gasoline engine. Downstream of the lambda probe 13, a catalyst 12 is housed, which serves the further chemical conversion of pollutants contained in the exhaust gases.
Der Kolben 2 ist über ein schematisch dargestelltes Pleuel 14 verbunden mit einer hier nicht dargestellten Kurbelwel¬ le des Verbrennungsmotors. Der Kolben 2 wird durch die Verbrennung des Kraftstoff/Luft-Gemisches in dem Brennraum 4 während eines Arbeitstaktes in Bewegung versetzt, diese Bewegung wird mittels des Pleuels 14 und der Kurbelwelle in bekannter Art und Weise in eine Drehbewegung umgesetzt. Ein Steuergerät 18 ist von Eingangssignalen 19 beauf¬ schlagt, die mittels Sensoren gemessene Betriebsgrößen der Brennkraftmaschine 1 darstellen. Beispielsweise ist dasThe piston 2 is connected via a connecting rod 14 shown schematically with a Kurbelwel¬ le of the internal combustion engine, not shown here. The piston 2 is set in motion by the combustion of the fuel / air mixture in the combustion chamber 4 during a power stroke, this movement is converted by means of the connecting rod 14 and the crankshaft in a known manner in a rotational movement. A control unit 18 is acted upon by input signals 19, which represent operating variables of the internal combustion engine 1 measured by means of sensors. For example, that is
Steuergerät 18 mit dem Luftmassensensor 15, dem Lambdasen- sor 13, einem Drehzahlmesser, einem Lufttemperatursensor und dergleichen verbunden. Des Weiteren ist das Steuerge¬ rät 18 mit einem Fahrpedalsensor verbunden, der ein Signal erzeugt, das die Stellung eines von einem Fahrer betätig¬ baren Fahrpedals und damit das angeforderte Drehmoment an¬ gibt. Das Steuergerät 18 erzeugt Ausgangssignale 20, mit denen über Aktoren bzw. Steller das Verhalten der Brenn¬ kraftmaschine 1 beeinflusst werden kann. Beispielsweise ist das Steuergerät 18 mit dem Einspritzventil 9, der Zündkerze 10 und der Drosselklappe 11 und dergleichen ver¬ bunden und erzeugt die zu deren Ansteuerung erforderlichen Signale.Control unit 18 with the air mass sensor 15, the Lambda sensor 13, a tachometer, an air temperature sensor and the like connected. Furthermore, the control unit 18 is connected to an accelerator pedal sensor which generates a signal which indicates the position of an accelerator pedal actuatable by a driver and thus the requested torque. The control unit 18 generates output signals 20 with which the behavior of the internal combustion engine 1 can be influenced via actuators or actuators. For example, the control unit 18 with the injection valve 9, the Spark plug 10 and the throttle valve 11 and the like ver¬ connected and generates the signals required for their control.
Unter anderem ist das Steuergerät 18 dazu vorgesehen, die Betriebsgrößen der Brennkraftmaschine 1 zu steuern bzw. zu regeln. Beispielsweise wird die von dem Einspritzventil 9 in den Brennraum 4 eingespritzte Kraftstoffmasse von dem Steuergerät 18 insbesondere im Hinblick auf einen geringen Kraftstoffverbrauch und/oder eine geringe Schadstoffent¬ wicklung gesteuert bzw. geregelt. Zu diesem Zweck ist das Steuergerät 18 mit einem Mikroprozessor versehen, der in einem Speichermedium wie z. B. einem Read-Only-Memory (ROM) ein Programm abgespeichert hat, das die zuvor ge- nannten Verfahrensschritte steuert.Among other things, the control unit 18 is provided to control or regulate the operating variables of the internal combustion engine 1. For example, the fuel mass injected from the injection valve 9 into the combustion chamber 4 is controlled or regulated by the control unit 18, in particular with regard to low fuel consumption and / or low pollutant development. For this purpose, the control unit 18 is provided with a microprocessor which is stored in a storage medium such. B. a read-only memory (ROM) has stored a program that controls the aforementioned method steps.
An dem Brennraum 4 ist ein Zylinderdruckaufnehmer 16 angeord¬ net, der mit einer elektrischen Zuleitung 17 mit dem Steuerge¬ rät 18 verbunden ist. Zwischen Zylinderdruckaufnehmer 16 und Brennraum 4 ist ein Kanal 21 der Länge 1 angeordnet. Die Ein¬ baulage des Zylinderdruckaufnehmers 16 ist hier nur schema¬ tisch dargestellt, diese kann je nach vorhandenem Bauraum und sonstigen Anforderungen variieren. Der durch den Zylinder¬ druckaufnehmer 16 bereitgestellte Verlauf des Zylinderdrucks und davon abgeleitete Größen werden als Eingangssignal für verschiedene Steuerungsfunktionen verwendet. Ausgangssignale der Steuerung sind z.B. Ansteuersignale für die Kraftstoffzu¬ messung und die Steuerung der Zündung des Gemischs. Der Zylin¬ derdruckaufnehmer 16 liefert ein Signal gemäß Fig. 2, dem ei- gentlichen Druckverlauf sind Pfeifenschwingungen durch den Ka¬ nal 21 überlagert. Dargestellt in Fig. 2 ist der Brennraum¬ druck Pz in Pascal über den Kurbelwellenwinkel KW in Grad; ü- ber die Drehzahl kann KW in eine Zeitreihe umgerechnet werden. Das Verfahren geht von einer Modellierung der Pfeifenschwin¬ gung aus, sodass eine geeignete Filterung des gemessenen Zy¬ linderdruckverlaufs erfolgen kann, bevor die eigentlichen thermodynamisehen Merkmale aus dem Zylinderdruck berechnet werden. Grundgedanke ist, die singuläre Frequenz der Pfeifen¬ schwingung mit einem Filter, das diese Frequenz sperrt (sog. Bandsperr-Charakteristik) zu unterdrücken. Mit einem numeri¬ schen Verfahren, einem digitalen Filter, ist das für den ge¬ messenen Druckverlauf nach der kompletten Erfassung des Ar- beitsspiels möglich.On the combustion chamber 4, a cylinder pressure sensor 16 is angeord¬ net, which is connected to an electrical supply line 17 with the Steuerge¬ device 18. Between Zylinderdruckaufnehmer 16 and combustion chamber 4, a channel 21 of length 1 is arranged. The installation position of the cylinder pressure transducer 16 is shown here only schematically, this can vary depending on the available space and other requirements. The course of the cylinder pressure provided by the cylinder pressure sensor 16 and variables derived therefrom are used as input signal for various control functions. Output signals of the control are, for example, control signals for measuring the fuel and controlling the ignition of the mixture. The cylin derdruckaufnehmer 16 provides a signal according to FIG. 2, the actual pressure curve pipe vibrations are superimposed by the Ka¬ 21. Shown in FIG. 2 is the combustion chamber pressure P z in Pascal via the crankshaft angle KW in degrees; KW can be converted into a time series via the speed. The method is based on a modeling of the Pfeifenschwin¬ supply, so that a suitable filtering of the measured Zy¬ cylinder pressure curve can be done before the actual thermodynamic features are calculated from the cylinder pressure. The basic idea is to suppress the singular frequency of the Pfeifen¬ oscillation with a filter that blocks this frequency (so-called band-stop characteristic). With a numerical method, a digital filter, this is possible for the measured pressure curve after complete detection of the work cycle.
Eine Ausführung ist die Speicherung der einmal ermittelten Filterkoeffizienten in der Steuerung für die verschiedenen Frequenzen der Pfeifenschwingung oder aber die Berechnung der jeweiligen Koeffizienten in Abhängigkeit vom Betriebspunkt der Brennkraftmaschine.An embodiment is the storage of the once determined filter coefficients in the controller for the different frequencies of the pipe vibration or the calculation of the respective coefficients in dependence on the operating point of the internal combustion engine.
Aus der Literatur ist der Zusammenhang zwischen der Frequenz der angeregten Pfeifenschwingung f und der Schallgeschwindig- keit c bekannt, c wird bestimmt aus der Länge 1 des Kanals 21 zwischen Brennraum 4 und Zylinderdruckaufnehmer 16 sowie der Gastemperatur T, der Gaskonstanten R und dem Isentropenexpo- nenten χ:The relationship between the frequency of the excited pipe vibration f and the sound velocity c is known from the literature, c is determined from the length 1 of the channel 21 between the combustion chamber 4 and the cylinder pressure transducer 16 and the gas temperature T, the gas constant R and the isentropic exponent χ:
/=c/(4*/)/ = C / (4 * /)
mitWith
Das heißt, für die Betriebspunkte der Brennkraftmaschine (z.B. beschrieben durch Drehzahl, Last, Kraftstoff/Luft-Verhältnis) kann die Frequenz f bestimmt werden. Wichtigster variabler Pa- rameter ist dabei die Gastemperatur T. Diese kann während der Kalibrierung der Steuerung einmal ermittelt und in Kennfeldern gespeichert werden. Eine weitere Möglichkeit ist die Berech¬ nung über ein geeignetes thermodynamisches Modell.That is, for the operating points of the internal combustion engine (eg described by speed, load, fuel / air ratio), the frequency f can be determined. Main variable variable This parameter can be determined once during calibration of the control and stored in maps. Another possibility is the calculation via a suitable thermodynamic model.
Weiterhin ist eine mögliche Ausführung die spektrale Analyse des Zylinderdrucksignals. Die Pfeifenschwingung kann damit in ihrer Frequenz abhängig vom Betriebspunkt bestimmt werden. Die spektrale Analyse kann offline während der Kalibrierung für verschiedene Betriebspunkte der Brennkraftmaschine oder online für jeden Arbeitszyklus erfolgen. Dann kann wieder das geeig¬ nete Filter ausgewählt werden, um diese Frequenz ausreichend zu unterdrücken.Furthermore, one possible embodiment is the spectral analysis of the cylinder pressure signal. The pipe vibration can thus be determined in frequency depending on the operating point. The spectral analysis can be done offline during calibration for various engine operating points or online for each duty cycle. Then the suitable filter can again be selected in order to sufficiently suppress this frequency.
Ein besonderer Vorteil der zunächst kompletten Speicherung ei¬ nes Arbeitsspiels ist die Möglichkeit, durch zweimaliges Durchlaufen des Filters die unerwünschte Phasenverschiebung des Zylinderdrucksignals zu kompensieren (Nullphasen- Filterung) . Die wichtigen Zusammenhänge zwischen Kurbelwinkel und Zylinderdruckverlauf werden somit nicht verfälscht.A particular advantage of initially complete storage of a working cycle is the possibility of compensating for the undesired phase shift of the cylinder pressure signal by passing through the filter twice (zero-phase filtering). The important relationships between the crank angle and cylinder pressure curve are thus not distorted.
Zusammengefasst ist der Ablauf des Korrekturverfahrens nach¬ folgend beschrieben:In summary, the sequence of the correction method is described below:
- Abtastung des Zylinderdruckverlaufs für ein komplettes Ar¬ beitspiel mit ausreichender Abtastfrequenz und Speicherung des Signals- Sampling of the cylinder pressure curve for a complete Ar¬ beitspiel with sufficient sampling frequency and storage of the signal
- Bestimmung der Gastemperatur und Berechnung der Pfeifen¬ schwingungsfrequenz - Bestimmung der Filterkoeffizienten für ein Bandsperr-Filter- Determination of the gas temperature and calculation of the Pfeifen¬ vibration frequency - Determination of the filter coefficients for a band-stop filter
- Filterung des Zylinderdruckverlaufs- Filtering of the cylinder pressure curve
Für Motorsteuerungssysteme kann mit diesem Verfahren der grundsätzliche Nachteil der brennraumfernen Anordnung des Zy- linderdruckwandlers wirkungsvoll kompensiert werden. Die Vor¬ teile der Anordnung, nämlich günstige Platzierung in einer Komponente und geringe thermische Belastung des Druckwandlers, bleiben erhalten. For engine control systems, with this method, the fundamental disadvantage of the combustion chamber remote arrangement of the Zy- low pressure transducer can be effectively compensated. The Vor¬ parts of the arrangement, namely favorable placement in a component and low thermal load of the pressure transducer, are retained.

Claims

Ansprüche claims
1. Verfahren zur Korrektur eines gemessenen Zylinderdru- ckes einer Brennkraftmaschine, bei der ein Zylinderdruck¬ aufnehmer (16) über einen Kanal (21) mit einem Brennraum (4) verbunden ist, dadurch gekennzeichnet, dass eine Schwingungsfrequenz einer in dem Kanal (21) hervorgerufe¬ nen Gasschwingung während eines Arbeitstaktes bestimmt wird und die Messwerte des Zylinderdruckaufnehmers (16) mittels eines Bandsperrfilters mit der zuvor bestimmten Schwingungsfrequenz gefiltert werden.1. Method for correcting a measured cylinder pressure of an internal combustion engine, in which a cylinder pressure transducer (16) is connected via a channel (21) to a combustion chamber (4), characterized in that a vibration frequency of one in the channel (21) caused gas oscillation during a power stroke is determined and the measured values of the cylinder pressure transducer (16) are filtered by means of a band-stop filter with the previously determined oscillation frequency.
2. Verfahren nach Anspruch 1, dadurch gekennzeichnet, dass die Schwingungsfrequenz aus einer Gastemperatur in dem2. The method according to claim 1, characterized in that the oscillation frequency from a gas temperature in the
Brennraum (4), die aus gemessenen Druckwerten errechnet wird, bestimmt wird.Combustion chamber (4), which is calculated from measured pressure values is determined.
3. Verfahren nach Anspruch 1 oder 2, dadurch gekennzeichnet, dass die Schwingungsfrequenz durch eine Spektralanalyse des3. The method according to claim 1 or 2, characterized in that the oscillation frequency by a spectral analysis of
Druckverlaufs in dem Brennraum bestimmt wird.Pressure curve is determined in the combustion chamber.
4. Verfahren nach einem der vorhergehenden Ansprüche, da¬ durch gekennzeichnet, dass in einem ersten Verfahrensschritt der Zylinderdruckverlauf für ein komplettes Arbeitsspiel ge¬ messen und gespeichert wird.4. The method according to any one of the preceding claims, da¬ characterized in that ge measured and stored ge in a first step, the cylinder pressure profile for a complete cycle.
5. Verfahren nach einem der vorhergehenden Ansprüche, da¬ durch gekennzeichnet, dass in einem zweiten Verfahrens- schritt die Gastemperatur bestimmt und daraus die Pfeifen¬ schwingungsfrequenz errechnet wird.5. The method according to any one of the preceding claims, da¬ characterized in that in a second process step determines the gas temperature and from this the Pfeifen¬ vibration frequency is calculated.
6. Verfahren nach einem der vorhergehenden Ansprüche, dadurch gekennzeichnet, dass in einem dritten Verfahrensschritt die Filterkoeffizienten für ein Bandsperr-Filter errechnet werden. 6. The method according to any one of the preceding claims, characterized in that the filter coefficients are calculated for a band-stop filter in a third method step.
7. Verfahren nach einem der vorhergehenden Ansprüche, dadurch gekennzeichnet, dass in einem vierten Verfahrensschritt der Zy¬ linderdruckverlauf mit dem Bandsperr-Filter gefiltert wird.7. The method according to any one of the preceding claims, characterized in that filtered in a fourth process step of Zy¬ cylinder pressure gradient with the band-stop filter.
8. Steuergerät für eine Brennkraftmaschine, das ein Verfahren nach einem der vorhergehenden Ansprüche ausführen kann. 8. Control device for an internal combustion engine, which can perform a method according to any one of the preceding claims.
EP05769867A 2004-09-09 2005-07-11 Method for correcting a measured cylinder pressure of an internal combustion engine Withdrawn EP1792154A1 (en)

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