EP2574760B1 - Method and control device for a combustion engine - Google Patents

Method and control device for a combustion engine Download PDF

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Publication number
EP2574760B1
EP2574760B1 EP12002810.5A EP12002810A EP2574760B1 EP 2574760 B1 EP2574760 B1 EP 2574760B1 EP 12002810 A EP12002810 A EP 12002810A EP 2574760 B1 EP2574760 B1 EP 2574760B1
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EP
European Patent Office
Prior art keywords
ion current
cylinder
air
cylinders
fuel mixture
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EP12002810.5A
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German (de)
French (fr)
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EP2574760A1 (en
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Gerald Rämisch
Gerd Hammer
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Volkswagen AG
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Volkswagen AG
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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
    • F02D35/021—Controlling engines, dependent on conditions exterior or interior to engines, not otherwise provided for on interior conditions using an ionic current sensor
    • 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
    • F02D41/008—Controlling each cylinder individually
    • F02D41/0085—Balancing of cylinder outputs, e.g. speed, torque or air-fuel ratio

Definitions

  • the present invention relates to methods for an internal combustion engine, in particular to methods for detecting and correcting cylinder unequal distributions in the air-fuel mixture, and to corresponding control devices.
  • a so-called cylinder equalization is sought.
  • cylinder equalization means that each cylinder contributes the same power contribution to the overall performance of the engine and, moreover, that the combustion process in each cylinder is as similar as possible under the same operating conditions.
  • One parameter is the lambda value of each cylinder. In gasoline engines, a lambda value of approximately 1 is usually desired and set via one or more lambda probes in the exhaust gas tract of the engine via a corresponding air-fuel mixture setting.
  • the DE 2 944 834 A1 relates to a method for controlling the air ratio lambda in a self-igniting internal combustion engine.
  • Gas constituents emerging from the combustion chambers of the internal combustion engine are detected in the form of an ion current by an ion current probe arranged in the immediate vicinity of an exhaust valve of the internal combustion engine.
  • the ion current serves as a control variable in a control device which influences the composition of the operating mixture with respect to the air ratio.
  • the ionic current is integrated or averaged over a working cycle because the afterburning occurring at very different times each has its maximum and also over the course of a work cycle has greatly varying increases in the reactions and the resulting ion currents.
  • the DE 101 15 902 C1 relates to a lambda cylinder equalization method for lambda equalization with a lambda equal to 1 regulated, a catalyst in the exhaust system having multi-cylinder internal combustion engine.
  • an exhaust gas parameter is continuously detected in the exhaust tract of the internal combustion engine downstream of the catalytic converter, which shows a local minimum when the combustion in all cylinders takes place at lambda equal to 1.
  • the fuel supply at each two cylinders is depressed by simultaneous enrichment of the mixture for the one and emaciation for the other cylinder, wherein the trimming is selected so that the combined exhaust of both cylinders corresponds to an exhaust gas of averaged Lambda combustion equal to 1 and the trimming so is set, that the exhaust gas parameter is minimized.
  • the exhaust parameter may include, for example, the exhaust gas temperature or the catalyst temperature or a NO x concentration.
  • the DE 10 2004 041 230 A1 relates to a cylinder equalization by means of ion current measurement.
  • cylinders assigned to a same exhaust gas collector form a cylinder group.
  • maximum cylinder pressures in a single cylinder are determined by means of ion current measurement and the cylinder-specific average values of the maximum pressures are formed.
  • cylinder-group-specific average values are formed by averaging.
  • Each of the cylinder-specific average values is compared with the associated cylinder-group-specific mean value and, depending on these comparisons, at least one cylinder is identified which is to be influenced in its operating behavior.
  • From the DE 10 2007 030 527 A1 is a method for cylinder equalization in a supercharged spark-ignition internal combustion engine known.
  • a relationship between the balance of a cylinder and the smoothness of the cylinder is determined and based on this relationship on the deviation of the mixture composition of the cylinder with each other and finally corrected based on the deviations of the mixture composition of each cylinder.
  • the DE 10 2009 026 839 A1 relates to a method for operating an internal combustion engine, in which the cylinders are equated by an evaluation of smoothness in cylinder-individual leaning of the mixture.
  • the DE 199 16204 C1 a method for Verbrennungskenn Anlagennbetician an internal combustion engine ready.
  • an ion current curve is measured by an ion current probe during successive cycles. From the successively measured ion current curves is determined a combustion characteristic variable specific ion current characteristic and from this the combustion characteristic.
  • the air / fuel ratio, ie the lambda value of the air / fuel mixture to be combusted in the combustion chamber and the exhaust gas recirculation rate can be determined with this method as a combustion parameter.
  • the instantaneous composition of the air-fuel mixture can be determined.
  • the lambda value can be determined from the slope of the flank of the first ion current maximum in the course of an ion current analysis.
  • the US 2008/053406 A1 relates to a method and apparatus for compensating for the influence of varying fuel and air components on an ion current signal.
  • the device additionally comprises an ion reference sensor module with a reference combustion chamber, an ion sensor and a reference burner.
  • the reference module is operated with fuel and air having the same characteristics as the fuel and the air of the internal combustion engine. In this case, the air-fuel ratio and the quantity of the reference combustion chamber supplied gas or fuel are kept constant.
  • a calibration module periodically detects a reference ion current signal from the ion sensor of the reference module and determines how the reference ion current signal has changed. Based on the change, a scaling factor is determined. This is used to scale an ion current signal from a spark plug of the internal combustion engine to compensate for the changes without having to know the causes of the changes.
  • the WO 00/61932 A1 provides a method for determining combustion characteristics of an internal combustion engine.
  • an ion current curve is measured by an ion current probe.
  • the air-fuel ratio of the air-fuel mixture to be combusted in the combustion chamber is determined from the ion current curves measured on the following.
  • an instantaneous, provisional lambda value is determined from a measured ion current curve.
  • the lambda values obtained from the ion current signal are averaged over several consecutive cycles.
  • the averaging depth is chosen as a function of the operating state, with the averaging depth being selected smaller than in stationary operating phases in the event of a sudden change in the operating state of the internal combustion engine.
  • a diagnosis of cylinder unevenness in the air-fuel mixture (lambda) based on an ion current signal is very sensitive to cross-dependence and undesirable side effects.
  • a lateral dependence between the individual cylinders can in particular by a variation of the residual gas due to a change of STEU Times of intake and exhaust valves occur.
  • Even with engines with several groups of cylinders in V or W arrangement and asymmetric firing order accurate determination of the air-fuel mixture of individual cylinders is problematic.
  • different fuel qualities, as further undesirable side effects may adversely affect a diagnosis of cylinder inequality based on an ion current signal.
  • the object of the present invention is therefore to provide improved methods for determining and correcting a cylinder inequality distribution in the air-fuel mixture.
  • a method for an internal combustion engine having at least one cylinder is provided.
  • a first ionic current is detected for the cylinder while the internal combustion engine is operating with a first air-fuel mixture.
  • a second ionic current for the at least one cylinder is detected, while the internal combustion engine is operated with a second air-fuel mixture.
  • the first air-fuel mixture and the second air-fuel mixture are different.
  • an ion current difference is determined for the cylinder.
  • Changing the air-fuel mixture during operation of the internal combustion engine is also referred to as fuel trim.
  • a change in the ionic current is determined depending on the fuel trim.
  • the ionic flow difference can be determined individually for each cylinder of the internal combustion engine.
  • the ion current difference that occurs due to fuel trim is substantially independent of the absolute value of the ion current.
  • a cylinder unevenness distribution in the air-fuel mixture between a plurality of cylinders of the internal combustion engine is thus determined depending on the ionic flow differences of the plurality of cylinders by operating the internal combustion engine first with the first air-fuel mixture, the first ionic current being detected for each of the cylinders, and thereafter with the second air-fuel mixture is operated, wherein the second ionic current is determined for each cylinder. Since all cylinders were operated with the same fuel trim, different ion current differences indicate corresponding cylinder inequalities. For equivalent cylinders, the ion flow differences of the individual cylinders are substantially the same with the same fuel trim, regardless of lateral dependencies and fuel quality.
  • a method for a multi-cylinder engine in which an ion flow for each cylinder is detected by at least two cylinders of the plurality of cylinders during operation of the engine. Depending on the detected ion currents of the at least two cylinders, a lonenstromffenwert is determined. For each of the at least two cylinders, a deviation of the ionic current from the ionic mean value is determined and a cylinder inequality distribution in the air-fuel mixture between the at least two cylinders is determined as a function of the deviations of the at least two cylinders.
  • a cylinder inequality distribution in particular a lambda inequality distribution, can be determined with simple means from the ionic currents.
  • the ion currents can be determined from an integration of a respective ion current profile or an integration of a plurality of averaged ion current profiles.
  • an injection amount for each cylinder of the plurality of cylinders of the internal combustion engine may be adjusted depending on the ion current differences of the plurality of cylinders so as to reduce a difference between the ion current differences of the plurality of cylinders. This achieves a robust correction of the injection quantity and thus a robust cylinder equalization on the basis of an ion current measurement.
  • the ion stream can be detected, for example, in the combustion chamber of the respective cylinder, in particular by means of a spark plug arranged in the combustion chamber of the respective cylinder.
  • the ionic current can be detected, for example, in a predetermined crankshaft angle range, for example in a crankshaft angle range of -20 ° to + 30 ° with respect to the top dead center of the respective cylinder.
  • the crankshaft angle range should be selected such that the ignition timing of the respective cylinder is not included in the crankshaft angle range.
  • a crankshaft angle range from the ignition point to + 30 ° with respect to the top dead center of the respective cylinder comprises a working range of the cylinder, in which the ion current indicates a characteristic statement about the air-fuel mixture to be combusted. Therefore, this crankshaft angle range is particularly suitable.
  • the first and / or second ion current are detected as follows: over the predetermined crankshaft angle range, for example from the ignition timing to + 30 ° with respect to the top dead center of the respective cylinder, an ion current profile is detected and integrated over the crankshaft angle. The detected ionic current thus represents the integral of the ionic current profile over the predetermined crankshaft angle range.
  • the formation of the ion current integral over the predetermined crankshaft angle range may have a characteristic value of the ion current signal, which is independent of the actual ion current waveform and thus independent of the type of combustion (normal, lean or rich).
  • the ion current waveform by integrating the ion current waveform, fluctuations in the ion current waveform due to measurement errors can be compensated.
  • multiple ion current waveforms may be acquired at multiple cycles of the respective cylinder and an average ion current waveform may be formed by averaging the multiple ion current waveforms, which is then integrated over the crankshaft angle to determine an ion current value.
  • an average ion current waveform may be formed by averaging the multiple ion current waveforms, which is then integrated over the crankshaft angle to determine an ion current value.
  • a plurality of second ion streams may be detected at different second air-fuel mixtures for each cylinder.
  • a plurality of second ion streams can be determined with different fuel trim and a relationship between the fuel trim and the second ion streams determined.
  • a range of the air-fuel mixture may be determined in which a fuel trim causes a characteristic change in the ion current. This range is usually close to 1 in lambda and therefore particularly suitable for cylinder equalization.
  • the first air-fuel mixture and the second air-fuel mixture differ by different amounts of fuel.
  • the amount of fuel in the second air-fuel mixture may be varied in a range of -40% to + 40% to the amount of fuel of the first air-fuel mixture.
  • the engine can be operated in a range including both lean and rich combustion.
  • lambda values of below and above 1 can be approached reliably.
  • a reliable operation of the internal combustion engine is ensured in this area, so that the method during operation of the internal combustion engine can be performed without unpleasant effects on the operation of the internal combustion engine and thus on the operation of a vehicle in which the internal combustion engine is housed can occur.
  • the internal combustion engine is switched abruptly between an operation with the first air-fuel mixture and an operation with the second air-fuel mixture.
  • jumping means, for example, first of all determining the first ionic current for each cylinder during operation with the first air-fuel mixture and then operating the internal combustion engine with the second air-fuel mixture during the next filling of a cylinder.
  • the sudden change between the first and second air-fuel mixture also causes a sudden change in the ion current difference. Since the remaining parameters of the vehicle, such as Fresh air temperature, boost pressure of a turbocharger, engine temperature or oxygen content do not or only slightly change, boundary conditions when determining the ion current difference can be kept substantially constant.
  • the cylinder unevenness distribution in the air-fuel mixture which has been determined according to one of the methods described above, can be provided as on-board diagnostic information.
  • This on-board diagnostic information can be stored, for example, in a memory of an engine controller for documentation of the monitoring of the lambda inequality and, when exceeding a predetermined cylinder inequality, used to control, for example, a warning light in the vehicle.
  • an ion current signal can be used, which is determined, for example, at the electrodes of a spark plug in each cylinder of the internal combustion engine.
  • Such a diagnosis may be required, for example, due to legal requirements, such as the California On-Board Diagnostic Act (OBD).
  • OBD California On-Board Diagnostic Act
  • the ion current signal can be detected over a predetermined crankshaft angle range as an ion current signal profile and integrated over the predetermined crankshaft angle range. As a result, a characteristic ion current value can be obtained.
  • both the ion current signal and the integrated ion current signal are affected by lateral dependencies resulting, for example, from different amounts of residual gas.
  • fuel quality can affect the ion current signal as well as the integrated ion current signal.
  • FIG. 12 shows a variation of an integrated ion current signal due to a change in intake camshaft angle for various cylinders of an internal combustion engine. In the in Fig.
  • the diagram shows the integrated ion current signals (int ion current) for different cylinders (cyl.) at different camshaft angles to which the respective intake valves are opened.
  • the integrated ion current signals of the individual cylinders differ considerably. Therefore, consideration of the absolute values of the integrated ion current signals is unsuitable for detection of lambda inequality.
  • Fig. 2 shows therefore method steps of an improved method 200 for determining a lambda unequal distribution.
  • a first step 201 ion current signals are measured for each cylinder in a speed-synchronous measuring grid.
  • additional engine information for example, an ignition angle, read by, for example, an engine electronics.
  • the ion current signals for each cylinder are defined in one Crankshaft angle window, which can be dependent on ignition, integrated.
  • Fig. 3 shows by way of example three ion current signals 301, 302 and 303, which can occur in a cylinder at different burns.
  • Curve 301 shows, for example, the course of the ion current signal in a normal combustion, ie in combustion with approximately lambda equal to 1, whereas the curve 302 combustion with a rich mixture, ie with an increased fuel fraction, and the curve 303 lean combustion, ie a combustion with a reduced fuel content, shows.
  • the corresponding ion curves 301-303 are compared with the crankshaft angle, which in Fig. 3 is shown integrated on the x-axis. Since the ion current can be detected, for example, by means of a spark plug in the corresponding cylinder of the internal combustion engine, the integration range is selected such that the influence of the spark does not fall within the integration range. In the in Fig.
  • the influence of the spark in the range of -20 ° to approximately -16 ° can be clearly seen. Therefore, the ion current is integrated, for example, in the range of -16 ° to approximately + 28 ° with respect to the top dead center of the corresponding cylinder.
  • the integration area is in Fig. 3 indicated by the arrow 304.
  • the cylinder-selective integral values are averaged over a predetermined number of working cycles and yield a first ion current value, a so-called reference value (step 203).
  • the ion current signals for the respective reference values of the respective cylinders are detected before trimming the amount of fuel, that is, the reference values are averaged ion current integral values in an operation of the internal combustion engine with a first air-fuel mixture.
  • the fuel amount is de-rated for all cylinders, i. the internal combustion engine is subsequently operated with a second air-fuel mixture which is different from the first air-fuel mixture.
  • the second air-fuel mixture may be, for example, a richer or a leaner air-fuel mixture.
  • step 205 an average ion current integral value for each cylinder over a defined number of operating cycles is determined for each cylinder from correspondingly detected ion current signals during operation with the second air-fuel mixture.
  • a second averaged ion current integral value is determined, a so-called trim value.
  • Fig. 4 exemplifies the effect of fuel trim on the integrated ion current.
  • the diagram shows the percentage of fuel added. Negative fuel trim indicates a corresponding decrease in fuel fraction in the air-fuel mixture and positive fuel trim indicates an increase in fuel fraction in the air-fuel mixture.
  • the integrated ion current is averaged across all cylinders (Graph 401). In addition, the ion current for fuel trim was normalized from 0% to zero. The at the fuel trim -30%, -25%, -15%, -5%, 10%, 20%, and 30% ranges 402-408 indicate a range of integrated cylinder ion streams at the respective fuel trim.
  • the integrated ion current varies in the range of approximately -7.5 to -9.5.
  • This bandwidth results from the above-mentioned transverse dependencies between the cylinders.
  • a change in the lonenstromintegrals is characteristic of a corresponding fuel trim, ie for a corresponding change in the amount of fuel. Therefore, in step 206, the absolute value of the integrated ion currents is not considered, but a difference between the reference value and the reference value is formed for each cylinder. Since the difference is independent of the abovementioned transverse dependencies, a lambda inequality can be determined on the basis of the differences in the ion current signals. In Fig.
  • a defined fuel trim 409 between -30% and -20% and a corresponding change in the ion current integral 410 is shown. Since the fuel trim was performed equally for all cylinders, a corresponding lambda unequal distribution of the individual cylinders can be determined from different differences between the trim value and the reference value of the individual cylinders. This lambda unequal distribution can be stored, for example, as on-board diagnostic information in an engine control or displayed to a driver of the vehicle via a corresponding display.
  • step 207 on the basis of the lambda unevenness distribution thus determined, a correction of the injection quantity for each cylinder can be carried out and thus an equalization of the lambda for all cylinders can be achieved.
  • the correction of the injection quantities causes a lambda change of the individual cylinders of the engine 208 and can be determined again as described above with the steps 201-206.
  • FIG. 10 shows a vehicle 500 having an internal combustion engine 208 with four cylinders 501-504.
  • a spark plug 505-508 is respectively disposed, which are coupled to a control device 509.
  • the control device 509 is capable of detecting an ion current with the aid of the spark plugs 505-508 in the combustion chambers of the cylinders 501-504, respectively.
  • the control device 509 determines, as previously described in connection with the flowchart 200 of FIG Fig. 2 has been described, a lambda inequality.
  • the controller 509 drives a warning light 510 of the vehicle 500 to indicate to the driver that the lambda bias has exceeded the predetermined threshold.
  • the controller 509 may drive an engine controller (not shown) of the engine 208 to achieve lambda equalization, as in step 207 of FIG Fig. 2 has been described.

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  • Chemical & Material Sciences (AREA)
  • Combustion & Propulsion (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Combined Controls Of Internal Combustion Engines (AREA)
  • Electrical Control Of Air Or Fuel Supplied To Internal-Combustion Engine (AREA)

Description

Die vorliegende Erfindung betrifft Verfahren für einen Verbrennungsmotor, insbesondere Verfahren zur Erkennung und Korrektur von Zylinderungleichverteilungen im Luft-Kraftstoffgemisch, sowie entsprechende Steuervorrichtungen.
Im Rahmen einer sauberen und effizienten Verbrennung von Kraftstoff in einem Verbrennungsmotor von Fahrzeugen, beispielsweise Personenkraftwagen oder Lastkraftwagen, wird eine sogenannte Zylindergleichstellung angestrebt. Unter der Zylindergleichstellung fällt beispielsweise, dass jeder Zylinder einen gleichen Leistungsbeitrag zur Gesamtleistung des Motors beiträgt und darüber hinaus in jedem Zylinder bei gleichen Betriebsbedingungen der Verbrennungsvorgang möglichst gleich ist. Eine Kenngröße ist dabei der Lambda-Wert eines jeden Zylinders. Bei Ottomotoren wird üblicherweise ein Lambda-Wert von näherungsweise 1 angestrebt und über eine oder mehrere Lambda-Sonden im Abgastrakt des Motors über eine entsprechende Luft-Kraftstoff-Gemischeinstellung eingestellt. Auch wenn im Abgastrakt im Wesentlichen der Wert Lambda gleich 1 erreicht wird, können die einzelnen Zylinder systembedingt oder aufgrund von Fertigungstoleranzen der Einspritzventile unterschiedliche Lambdawerte ungleich 1 aufweisen. Dies kann zu einer Verschlechterung von Emissionswerten, einer Erhöhung des Kraftstoffverbrauchs oder einer Laufunruhe führen. Weiterhin kann es aufgrund gesetzlicher Anforderungen, beispielsweise gemäß dem Kalifornischen On-Board-Diagnose-Gesetz (OBD-Gesetz) erforderlich sein, eine derartige Lambda-Ungleichverteilung zwischen den einzelnen Zylindern zu erkennen. In dem Stand der Technik sind daher verschiedene Verfahren und Vorrichtungen zur Erkennung von ungleich eingestellten Zylindern bekannt.
Die DE 2 944 834 A1 betrifft ein Verfahren zur Regelung der Luftzahl Lambda bei einer selbstzündenden Brennkraftmaschine. Aus den Brennräumen der Brennkraftmaschine austretende Gasbestandteile werden durch eine in unmittelbarer Nähe eines Auslassventils der Brennkraftmaschine angeordnete lonenstromsonde in Form eines lonenstroms erfasst. Der lonenstrom dient als Regelgröße in einer Regeleinrichtung, welche die Zusammensetzung des Betriebsgemisches bezüglich der Luftzahl beeinflusst. Der lonenstrom wird über ein Arbeitsspiel integriert bzw. gemittelt, weil die auftretende Nachverbrennung zu sehr unterschiedlichen Zeitpunkten jeweils ihr Maximum hat und auch über den Verlauf eines Arbeitsspiels stark wechselnde Anstiege der Reaktionen und der resultierenden lonenströme aufweist.The present invention relates to methods for an internal combustion engine, in particular to methods for detecting and correcting cylinder unequal distributions in the air-fuel mixture, and to corresponding control devices.
As part of a clean and efficient combustion of fuel in an internal combustion engine of vehicles, such as passenger cars or trucks, a so-called cylinder equalization is sought. For example, cylinder equalization means that each cylinder contributes the same power contribution to the overall performance of the engine and, moreover, that the combustion process in each cylinder is as similar as possible under the same operating conditions. One parameter is the lambda value of each cylinder. In gasoline engines, a lambda value of approximately 1 is usually desired and set via one or more lambda probes in the exhaust gas tract of the engine via a corresponding air-fuel mixture setting. Even if the lambda value is essentially equal to 1 in the exhaust tract, the individual cylinders may have different lambda values not equal to 1 due to the system or due to manufacturing tolerances of the injection valves. This can lead to a deterioration of emission values, an increase in fuel consumption or a rough running. Furthermore, due to legal requirements, such as the California On-Board Diagnostic Act (OBD Law), it may be necessary to detect such a lambda unequal distribution between the individual cylinders. In the prior art, therefore, various methods and devices for detecting unequal set cylinders are known.
The DE 2 944 834 A1 relates to a method for controlling the air ratio lambda in a self-igniting internal combustion engine. Gas constituents emerging from the combustion chambers of the internal combustion engine are detected in the form of an ion current by an ion current probe arranged in the immediate vicinity of an exhaust valve of the internal combustion engine. The ion current serves as a control variable in a control device which influences the composition of the operating mixture with respect to the air ratio. The ionic current is integrated or averaged over a working cycle because the afterburning occurring at very different times each has its maximum and also over the course of a work cycle has greatly varying increases in the reactions and the resulting ion currents.

Die DE 101 15 902 C1 betrifft ein Lambda-Zylindergleichstellungsverfahren zur Lambda-Gleichstellung bei einer auf Lambda gleich 1 geregelten, einen Katalysator im Abgastrakt aufweisende Mehrzylinder-Brennkraftmaschine. Bei dem Verfahren wird fortlaufend im Abgastrakt der Brennkraftmaschine stromabwärts des Katalysators ein Abgasparameter erfasst, der ein lokales Minimum zeigt, wenn die Verbrennung in allen Zylindern bei Lambda gleich 1 erfolgt. Die Kraftstoffversorgung bei jeweils zwei Zylindern wird durch gleichzeitige Anreicherung des Gemisches für den einen und Abmagerung für den anderen Zylinder vertrimmt, wobei die Vertrimmung so gewählt ist, dass das zusammengeführte Abgas beider Zylinder einem Abgas einer Verbrennung von gemittelt Lambda gleich 1 entspricht und die Vertrimmung so eingestellt wird, dass der Abgasparameter minimiert wird. Der Abgasparameter kann beispielsweise die Abgastemperatur oder die Katalysatortemperatur oder eine NOx-Konzentration umfassen.The DE 101 15 902 C1 relates to a lambda cylinder equalization method for lambda equalization with a lambda equal to 1 regulated, a catalyst in the exhaust system having multi-cylinder internal combustion engine. In the method, an exhaust gas parameter is continuously detected in the exhaust tract of the internal combustion engine downstream of the catalytic converter, which shows a local minimum when the combustion in all cylinders takes place at lambda equal to 1. The fuel supply at each two cylinders is depressed by simultaneous enrichment of the mixture for the one and emaciation for the other cylinder, wherein the trimming is selected so that the combined exhaust of both cylinders corresponds to an exhaust gas of averaged Lambda combustion equal to 1 and the trimming so is set, that the exhaust gas parameter is minimized. The exhaust parameter may include, for example, the exhaust gas temperature or the catalyst temperature or a NO x concentration.

Die DE 10 2004 041 230 A1 betrifft eine Zylindergleichstellung mittels lonenstrommessung. Bei einem Verbrennungsmotor mit mehreren Zylindern und mindestens einem Abgassammler bilden Zylinder, die einem gleichen Abgassammler zugeordnet sind, eine Zylindergruppe. Für ein Zeitintervall werden maximale Zylinderdrücke in einem einzelnen Zylinder mittels lonenstrommessung ermittelt und die zylinderspezifischen Mittelwerte der maximalen Drücke gebildet. Aus den zylinderspezifischen Mittelwerten jeder Zylindergruppe werden durch Mittelung zylindergruppenspezifische Mittelwerte gebildet. Jeder der zylinderspezifischen Mittelwerte wird mit dem zugehörigen zylindergruppenspezifischen Mittelwert verglichen und in Abhängigkeit dieser Vergleiche mindestens ein Zylinder identifiziert, welcher in seinem Betriebsverhalten zu beeinflussen ist.The DE 10 2004 041 230 A1 relates to a cylinder equalization by means of ion current measurement. In an internal combustion engine having a plurality of cylinders and at least one exhaust gas collector, cylinders assigned to a same exhaust gas collector form a cylinder group. For a time interval maximum cylinder pressures in a single cylinder are determined by means of ion current measurement and the cylinder-specific average values of the maximum pressures are formed. From the cylinder-specific average values of each cylinder group, cylinder-group-specific average values are formed by averaging. Each of the cylinder-specific average values is compared with the associated cylinder-group-specific mean value and, depending on these comparisons, at least one cylinder is identified which is to be influenced in its operating behavior.

Aus der DE 10 2007 030 527 A1 ist ein Verfahren zur Zylindergleichstellung bei einer aufgeladenen fremdgezündeten Brennkraftmaschine bekannt. Bei dem Verfahren wird ein Zusammenhang zwischen der Vertrimmung eines Zylinders und der Laufruhe des Zylinders ermittelt und auf Basis dieses Zusammenhangs auf die Abweichung der Gemischzusammensetzung der Zylinder untereinander geschlossen und schließlich auf Basis der Abweichungen die Gemischzusammensetzung jedes Zylinders korrigiert.From the DE 10 2007 030 527 A1 is a method for cylinder equalization in a supercharged spark-ignition internal combustion engine known. In the method, a relationship between the balance of a cylinder and the smoothness of the cylinder is determined and based on this relationship on the deviation of the mixture composition of the cylinder with each other and finally corrected based on the deviations of the mixture composition of each cylinder.

Die DE 10 2009 026 839 A1 betrifft ein Verfahren zum Betreiben einer Brennkraftmaschine, bei dem die Zylinder durch eine Auswertung der Laufruhe bei zylinderindividueller Abmagerung des Gemischs gleichgestellt werden.The DE 10 2009 026 839 A1 relates to a method for operating an internal combustion engine, in which the cylinders are equated by an evaluation of smoothness in cylinder-individual leaning of the mixture.

Schließlich stellt die DE 199 16204 C1 ein Verfahren zur Verbrennungskenngrößenbestimmung einer Brennkraftmaschine bereit. Bei dem Verfahren wird während aufeinanderfolgender Arbeitsspiele jeweils eine lonenstromkurve durch einen lonenstromsonde gemessen. Aus den aufeinanderfolgend gemessenen lonenstromkurven wird eine verbrennungskenngrößenspezifische lonenstromkenngröße und aus dieser die Verbrennungskenngröße bestimmt. Insbesondere kann mit diesem Verfahren als Verbrennungskenngröße das Luft/Kraftstoff-Verhältnis, d.h. der Lambda-Wert des im Brennraum zu verbrennenden Luft-Kraftstoff-Gemischs und die Abgasrückführrate ermittelt werden. Durch Messung des lonenstroms an einer Zündkerze in jedem einzelnen Zylinder kann die momentane Zusammensetzung des Luft-Kraftstoff-Gemischs bestimmt werden. Dazu kann der Lambda-Wert aus der Steigung der Flanke des ersten lonenstrommaximums im Rahmen einer lonenstromanalyse bestimmt werden.Finally, the DE 199 16204 C1 a method for Verbrennungskenngrößenbestimmung an internal combustion engine ready. In the method, an ion current curve is measured by an ion current probe during successive cycles. From the successively measured ion current curves is determined a combustion characteristic variable specific ion current characteristic and from this the combustion characteristic. In particular, the air / fuel ratio, ie the lambda value of the air / fuel mixture to be combusted in the combustion chamber and the exhaust gas recirculation rate can be determined with this method as a combustion parameter. By measuring the ion current at a spark plug in each individual cylinder, the instantaneous composition of the air-fuel mixture can be determined. For this purpose, the lambda value can be determined from the slope of the flank of the first ion current maximum in the course of an ion current analysis.

Die US 2008/053406 A1 betrifft ein Verfahren und eine Vorrichtung zur Kompensation des Einflusses variierender Kraftstoff- und Luft-Bestandteile auf ein lonenstrom-Signal. Die Vorrichtung umfasst neben einem Verbrennungsmotor zusätzlich ein lonen-Referenz-Sensor-Modul mit einer Referenzbrennkammer, einem lonensensor und einem Referenzbrenner. Das Referenz-Modul wird mit Kraftstoff und Luft betrieben, welche dieselben Charakteristiken wie der Kraftstoff und die Luft des Verbrennungsmotors aufweisen. Dabei werden das Luft-Kraftstoffverhältnis und die Quantität des der Referenzbrennkammer zugeführten Gases beziehungsweise Kraftstoffes konstant gehalten. Ein Kalibrierungsmodul erfasst periodisch ein Referenz-lonenstromsignal vom lonensensor des Referenzmoduls und bestimmt, wie sich das Referenz-lonenstromsignal geändert hat. Anhand der Änderung wird ein Skalierungsfaktor bestimmt. Mit diesem wird ein lonenstromsignal einer Zündkerze des Verbrennungsmotors skaliert, um die Änderungen zu kompensieren, ohne Kenntnisse über die Ursachen der Änderungen haben zu müssen.The US 2008/053406 A1 relates to a method and apparatus for compensating for the influence of varying fuel and air components on an ion current signal. In addition to an internal combustion engine, the device additionally comprises an ion reference sensor module with a reference combustion chamber, an ion sensor and a reference burner. The reference module is operated with fuel and air having the same characteristics as the fuel and the air of the internal combustion engine. In this case, the air-fuel ratio and the quantity of the reference combustion chamber supplied gas or fuel are kept constant. A calibration module periodically detects a reference ion current signal from the ion sensor of the reference module and determines how the reference ion current signal has changed. Based on the change, a scaling factor is determined. This is used to scale an ion current signal from a spark plug of the internal combustion engine to compensate for the changes without having to know the causes of the changes.

Die WO 00/61932 A1 stellt ein Verfahren zur Bestimmung von Verbrennungskenngröße einer Brennkraftmaschine bereit. Während aufeinander folgender Arbeitsspiele wird jeweils eine lonenstromkurve durch eine lonenstromsonde gemessen. Aus den aufeinder folgend gemessenen lonenstromkurven wird das Luft-Kraftstoffverhältnis des im Brennraum zu verbrennenden Luft-Kraftstoff-Gemischs ermittelt. Dazu wird aus einer gemessenen lonenstromkurve ein momentaner, vorläufiger Lambdawert bestimmt. Die aus dem lonenstromsondensignal gewonnenen Lambdawerte werden über mehrere aufeinander folgende Arbeitsspiele gemittelt. Die Mittelungstiefe wird betriebszustandsabhängig gewählt, wobei bei einer plötzlichen Änderung des Betriebszustands der Brennkraftmaschine die Mittelungstiefe kleiner als in stationären Betriebsphasen gewählt wird.The WO 00/61932 A1 provides a method for determining combustion characteristics of an internal combustion engine. During successive cycles, an ion current curve is measured by an ion current probe. The air-fuel ratio of the air-fuel mixture to be combusted in the combustion chamber is determined from the ion current curves measured on the following. For this purpose, an instantaneous, provisional lambda value is determined from a measured ion current curve. The lambda values obtained from the ion current signal are averaged over several consecutive cycles. The averaging depth is chosen as a function of the operating state, with the averaging depth being selected smaller than in stationary operating phases in the event of a sudden change in the operating state of the internal combustion engine.

Eine Diagnose einer Zylinderungleichverteilung im Luft-Kraftstoffgemisch (Lambda) auf der Grundlage eines lonenstromsignals ist jedoch sehr empfindlich gegenüber Querabhängigkeiten und unerwünschten Nebeneffekten. Eine Querabhängigkeit zwischen den einzelnen Zylindern kann insbesondere durch eine Variation des Restgases aufgrund einer Veränderung von Steu erzeiten der Ein- und Auslassventile auftreten. Auch bei Motoren mit mehreren Zylindergruppen in V- oder W-Anordnung und asymmetrischer Zündfolge ist eine genaue Bestimmung des Luft-Kraftstoffgemischs einzelner Zylinder problematisch. Darüber hinaus können beispielsweise unterschiedliche Kraftstoffqualitäten als weitere unerwünschte Nebeneffekte eine Diagnose einer Zylinderungleichverteilung auf der Grundlage eines lonenstromsignals negativ beeinflussen.
Aufgabe der vorliegenden Erfindung ist es daher, verbesserte Verfahren zur Bestimmung und Korrektur einer Zylinderungleichverteilung im Luft-Kraftstoffgemisch bereitzustellen.
Gemäß der vorliegenden Erfindung wird diese Aufgabe durch ein Verfahren für einen Verbrennungsmotor nach Anspruch 1 und eine Steuervorrichtung für einen Verbrennungsmotor nach Anspruch 14 gelöst. Die abhängigen Ansprüche definieren bevorzugte und vorteilhafte Ausführungsformen der Erfindung.
Gemäß der vorliegenden Erfindung wird ein Verfahren für einen Verbrennungsmotor mit mindestens einem Zylinder bereitgestellt. Bei dem Verfahren wir ein erster lonenstrom für den Zylinder erfasst, während der Verbrennungsmotor mit einem ersten Luft-Kraftstoffgemisch betrieben wird. Weiterhin wird ein zweiter lonenstrom für den mindestens einen Zylinder erfasst, während der Verbrennungsmotor mit einem zweiten Luft-Kraftstoffgemisch betrieben wird. Das erste Luft-Kraftstoffgemisch und das zweite Luft-Kraftstoffgemisch sind unterschiedlich. In Abhängigkeit von dem ersten lonenstrom und dem zweiten lonenstrom wird für den Zylinder eine lonenstromdifferenz bestimmt. Das Verändern des Luft-Kraftstoffgemischs im Betrieb des Verbrennungsmotors wird auch als Kraftstoffvertrimmung bezeichnet. Mit dem zuvor beschriebenen Verfahren wird daher eine Veränderung des lonenstroms in Abhängigkeit der Kraftstoffvertrimmung bestimmt. Die lonenstromdifferenz kann für jeden Zylinder des Verbrennungsmotors individuell bestimmt werden. Die lonenstromdifferenz, welche aufgrund der Kraftstoffvertrimmung auftritt, ist im Wesentlichen unabhängig von dem Absolutwert des lonenstroms. Dadurch können die oben genannten Querabhängigkeiten und Nebeneffekte, welche im Wesentlichen den Absolutwert des lonenstroms beeinflussen, wirksam eliminiert werden. Eine Zylinderungleichverteilung im Luft-Kraftstoffgemisch zwischen mehreren Zylindern des Verbrennungsmotors wird somit in Abhängigkeit von den lonenstromdifferenzen der mehreren Zylinder bestimmt, indem der Verbrennungsmotor zunächst mit dem ersten Luft-Kraftstoffgemisch betrieben wird, wobei der erste lonenstrom für jeden der Zylinder erfasst wird, und danach mit dem zweiten Luft-Kraftstoffgemisch betrieben wird, wobei der zweite lonenstrom für jeden Zylinder bestimmt wird. Da alle Zylinder mit der gleichen Kraftstoffvertrimmung betrieben wurden, zeigen unterschiedliche lonenstromdifferenzen entsprechende Zylinderungleichverteilungen an. Bei gleichgestellten Zylindern sind die lonenstromdifferenzen der einzelnen Zylinder bei gleicher Kraftstoffvertrimmung im Wesentlichen gleich, unabhängig von Querabhängigkeiten und der Kraftstoffqualität.
Gemäß der vorliegenden Erfindung wird weiterhin ein Verfahren für einen Verbrennungsmotor mit mehreren Zylindern bereitgestellt, bei welchem ein lonenstrom für jeden Zylinder von mindestens zwei Zylindern der mehreren Zylinder während eines Betriebs des Verbrennungsmotors erfasst wird. In Abhängigkeit von den erfassten lonenströmen der mindestens zwei Zylinder wird ein lonenstrommittelwert bestimmt. Für jeden der mindestens zwei Zylinder wird eine Abweichung des lonenstroms von dem lonenstrommittelwert bestimmt und eine Zylinderungleichverteilung im Luft-Kraftstoffgemisch zwischen den mindestens zwei Zylindern in Abhängigkeit von den Abweichungen der mindestens zwei Zylinder untereinander bestimmt. Da der lonenstrom im Wesentlichen von der Zusammensetzung des Luft-Kraftstoffgemischs in dem jeweiligen Zylinder abhängt, kann eine Zylinderungleichverteilung, insbesondere eine Lambda-Ungleichverteilung, mit einfachen Mitteln aus den lonenströmen bestimmt werden. Die lonenströme können insbesondere, wie zuvor beschrieben wurde, aus einer Integration eines jeweiligen lonenstromverlaufs oder einer Integration mehrerer gemittelter lonenstromverläufe bestimmt werden.However, a diagnosis of cylinder unevenness in the air-fuel mixture (lambda) based on an ion current signal is very sensitive to cross-dependence and undesirable side effects. A lateral dependence between the individual cylinders can in particular by a variation of the residual gas due to a change of STEU Times of intake and exhaust valves occur. Even with engines with several groups of cylinders in V or W arrangement and asymmetric firing order accurate determination of the air-fuel mixture of individual cylinders is problematic. In addition, for example, different fuel qualities, as further undesirable side effects, may adversely affect a diagnosis of cylinder inequality based on an ion current signal.
The object of the present invention is therefore to provide improved methods for determining and correcting a cylinder inequality distribution in the air-fuel mixture.
According to the present invention, this object is achieved by a method for an internal combustion engine according to claim 1 and a control device for an internal combustion engine according to claim 14. The dependent claims define preferred and advantageous embodiments of the invention.
According to the present invention, a method for an internal combustion engine having at least one cylinder is provided. In the method, a first ionic current is detected for the cylinder while the internal combustion engine is operating with a first air-fuel mixture. Furthermore, a second ionic current for the at least one cylinder is detected, while the internal combustion engine is operated with a second air-fuel mixture. The first air-fuel mixture and the second air-fuel mixture are different. Depending on the first ion current and the second ion current, an ion current difference is determined for the cylinder. Changing the air-fuel mixture during operation of the internal combustion engine is also referred to as fuel trim. With the previously described Method, therefore, a change in the ionic current is determined depending on the fuel trim. The ionic flow difference can be determined individually for each cylinder of the internal combustion engine. The ion current difference that occurs due to fuel trim is substantially independent of the absolute value of the ion current. Thereby, the above-mentioned lateral dependencies and side effects, which substantially affect the absolute value of the ion current, can be effectively eliminated. A cylinder unevenness distribution in the air-fuel mixture between a plurality of cylinders of the internal combustion engine is thus determined depending on the ionic flow differences of the plurality of cylinders by operating the internal combustion engine first with the first air-fuel mixture, the first ionic current being detected for each of the cylinders, and thereafter with the second air-fuel mixture is operated, wherein the second ionic current is determined for each cylinder. Since all cylinders were operated with the same fuel trim, different ion current differences indicate corresponding cylinder inequalities. For equivalent cylinders, the ion flow differences of the individual cylinders are substantially the same with the same fuel trim, regardless of lateral dependencies and fuel quality.
According to the present invention, there is further provided a method for a multi-cylinder engine in which an ion flow for each cylinder is detected by at least two cylinders of the plurality of cylinders during operation of the engine. Depending on the detected ion currents of the at least two cylinders, a lonenstrommittelwert is determined. For each of the at least two cylinders, a deviation of the ionic current from the ionic mean value is determined and a cylinder inequality distribution in the air-fuel mixture between the at least two cylinders is determined as a function of the deviations of the at least two cylinders. Since the ionic current essentially depends on the composition of the air-fuel mixture in the respective cylinder, a cylinder inequality distribution, in particular a lambda inequality distribution, can be determined with simple means from the ionic currents. In particular, as described above, the ion currents can be determined from an integration of a respective ion current profile or an integration of a plurality of averaged ion current profiles.

Dementsprechend kann gemäß einer Ausführungsform eine Einspritzmenge für einen jeweiligen Zylinder der mehreren Zylinder des Verbrennungsmotors in Abhängigkeit der lonenstromdifferenzen der mehreren Zylinder derart eingestellt werden, dass ein Unterschied zwischen den lonenstromdifferenzen der mehreren Zylinder verringert wird. Dadurch wird eine robuste Korrektur der Einspritzmenge und somit eine robuste Zylindergleichstellung auf der Grundlage einer lonenstrommessung erreicht.Accordingly, according to an embodiment, an injection amount for each cylinder of the plurality of cylinders of the internal combustion engine may be adjusted depending on the ion current differences of the plurality of cylinders so as to reduce a difference between the ion current differences of the plurality of cylinders. This achieves a robust correction of the injection quantity and thus a robust cylinder equalization on the basis of an ion current measurement.

Der lonenstrom kann beispielsweise im Brennraum des jeweiligen Zylinders erfasst werden, insbesondere mittels einer in dem Brennraum des jeweiligen Zylinders angeordneten Zündkerze. Der lonenstrom kann beispielsweise in einem vorbestimmten Kurbelwellenwinkelbereich erfasst werden, beispielsweise in einem Kurbelwellenwinkelbereich von -20° bis +30° in Bezug auf den oberen Totpunkt des jeweiligen Zylinders. Um die lonenstrommessung unabhängig von dem Zündfunken der Zündkerze zu erfassen, sollte der Kurbelwellenwinkelbereich derart gewählt werden, dass der Zündzeitpunkt des jeweiligen Zylinders nicht in dem Kurbelwellenwinkelbereich enthalten ist. Ein Kurbelwellenwinkelbereich vom Zündzeitpunkt bis +30° in Bezug auf den oberen Totpunkt des jeweiligen Zylinders umfasst einen Arbeitsbereich des Zylinders, in welchem der lonenstrom eine charakteristische Aussage über das zu verbrennende Luft-Kraftstoffgemisch anzeigt. Daher ist dieser Kurbelwellenwinkelbereich besonders geeignet.
Gemäß einer Ausführungsform werden der erste und/oder zweite lonenstrom folgendermaßen erfasst: Über dem vorbestimmten Kurbelwellenwinkelbereich, beispielsweise vom Zündzeit-punkt bis +30° in Bezug auf den oberen Totpunkt des jeweiligen Zylinders, wird ein lonenstromverlauf erfasst und über den Kurbelwellenwinkel integriert. Der erfasste lonenstrom stellt somit das Integral des lonenstromverlaufs über dem vorbestimmten Kurbelwellenwinkelbereich dar. Da sich der Verlauf des lonenstromsignals über dem Kurbelwellenwinkel in Abhängigkeit einer normalen, mageren und fetten Verbrennung erheblich unterscheiden kann, kann durch die Bildung des lonenstromintegrals über dem vorbestimmten Kurbelwellenwinkelbereich ein charakteristischer Wert des Ionenstromsignals bestimmt werden, welcher unabhängig von dem tatsächlichen lonenstromsignalverlauf und somit unabhängig von der Art der Verbrennung (normal, mager oder fett) ist. Darüber hinaus können durch die Integration des lonenstromverlaufs Schwankungen im lonenstromverlauf aufgrund von Messfehlern ausgeglichen werden.The ion stream can be detected, for example, in the combustion chamber of the respective cylinder, in particular by means of a spark plug arranged in the combustion chamber of the respective cylinder. The ionic current can be detected, for example, in a predetermined crankshaft angle range, for example in a crankshaft angle range of -20 ° to + 30 ° with respect to the top dead center of the respective cylinder. In order to detect the ion current measurement independently of the spark of the spark plug, the crankshaft angle range should be selected such that the ignition timing of the respective cylinder is not included in the crankshaft angle range. A crankshaft angle range from the ignition point to + 30 ° with respect to the top dead center of the respective cylinder comprises a working range of the cylinder, in which the ion current indicates a characteristic statement about the air-fuel mixture to be combusted. Therefore, this crankshaft angle range is particularly suitable.
According to one embodiment, the first and / or second ion current are detected as follows: over the predetermined crankshaft angle range, for example from the ignition timing to + 30 ° with respect to the top dead center of the respective cylinder, an ion current profile is detected and integrated over the crankshaft angle. The detected ionic current thus represents the integral of the ionic current profile over the predetermined crankshaft angle range. Since the variation of the ionic current signal over the crankshaft angle may vary significantly depending on normal, lean and rich combustion, the formation of the ion current integral over the predetermined crankshaft angle range may have a characteristic value of the ion current signal, which is independent of the actual ion current waveform and thus independent of the type of combustion (normal, lean or rich). In addition, by integrating the ion current waveform, fluctuations in the ion current waveform due to measurement errors can be compensated.

Weiterhin können mehrere lonenstromverläufe bei mehreren Arbeitsspielen des jeweiligen Zylinders erfasst werden und ein Mittelwertionenstromverlauf durch Mitteln der mehreren lonenstromverläufe gebildet werden, welcher dann über den Kurbelwellenwinkel integriert wird, um einen lonenstromwert zu bestimmen. Durch das Mitteln der lonenstromverläufe über mehrere Arbeitsspiele des jeweiligen Zylinders können Messungenauigkeiten und punktuell auftretende Störungen ausgemittelt werden, so dass der integrierte lonenstrom einen zuverlässigen charakteristischen Wert des Zylinders darstellt.Furthermore, multiple ion current waveforms may be acquired at multiple cycles of the respective cylinder and an average ion current waveform may be formed by averaging the multiple ion current waveforms, which is then integrated over the crankshaft angle to determine an ion current value. By averaging the lonenstromverläufe over several cycles of the respective cylinder measurement inaccuracies and punctually occurring disturbances can be averaged, so that the integrated ion current represents a reliable characteristic value of the cylinder.

Gemäß einer weiteren Ausführungsform können für jeden Zylinder mehrere zweite lonenströme bei unterschiedlichen zweiten Luft-Kraftstoffgemischen erfasst werden. Somit können mehrere zweite lonenströme bei unterschiedlicher Kraftstoffvertrimmung bestimmt werden und ein Zusammenhang zwischen der Kraftstoffvertrimmung und den zweiten lonenströmen bestimmt werden. Aus dem Verlauf des Zusammenhangs zwischen den zweiten lonenströmen und der Kraftstoffvertrimmung kann ein Bereich des Luft-Kraftstoffgemischs bestimmt werden, in welchem eine Kraftstoffvertrimmung eine charakteristische Änderung des lonenstroms bewirkt. Dieser Bereich ist üblicherweise in der Nähe von Lambda gleich 1 und daher für die Zylindergleichstellung besonders geeignet.According to a further embodiment, a plurality of second ion streams may be detected at different second air-fuel mixtures for each cylinder. Thus, a plurality of second ion streams can be determined with different fuel trim and a relationship between the fuel trim and the second ion streams determined. From the course of the relationship between the second ion streams and the fuel trim, a range of the air-fuel mixture may be determined in which a fuel trim causes a characteristic change in the ion current. This range is usually close to 1 in lambda and therefore particularly suitable for cylinder equalization.

Gemäß einer Ausführungsform unterscheiden sich das erste Luft-Kraftstoffgemisch und das zweite Luft-Kraftstoffgemisch durch unterschiedliche Kraftstoffmengen. Beispielsweise kann die Kraftstoffmenge in dem zweiten Luft-Kraftstoffgemisch in einem Bereich von -40 % bis +40 % gegenüber der Kraftstoffmenge des ersten Luft-Kraftstoffgemischs verändert werden. Durch eine Veränderung der Kraftstoffmenge in dem vorgenannten Bereich kann der Verbrennungsmotor in einem Bereich betrieben, welcher sowohl eine magere Verbrennung als auch eine fette Verbrennung umfasst. Somit können Lambda-Werte von unter und über 1 zuverlässig angefahren werden. Trotzdem bleibt ein zuverlässiger Betrieb des Verbrennungsmotors in diesem Bereich gewährleistet, so dass das Verfahren im laufenden Betrieb des Verbrennungsmotors durchgeführt werden kann, ohne dass unangenehme Auswirkungen auf den Betrieb des Verbrennungsmotors und somit auf den Betrieb eines Fahrzeugs, in welchem der Verbrennungsmotor untergebracht ist, auftreten können.According to one embodiment, the first air-fuel mixture and the second air-fuel mixture differ by different amounts of fuel. For example, the amount of fuel in the second air-fuel mixture may be varied in a range of -40% to + 40% to the amount of fuel of the first air-fuel mixture. By changing the fuel amount in the aforementioned range, the engine can be operated in a range including both lean and rich combustion. Thus lambda values of below and above 1 can be approached reliably. Nevertheless, a reliable operation of the internal combustion engine is ensured in this area, so that the method during operation of the internal combustion engine can be performed without unpleasant effects on the operation of the internal combustion engine and thus on the operation of a vehicle in which the internal combustion engine is housed can occur.

Gemäß einer weiteren Ausführungsform wird der Verbrennungsmotor sprunghaft zwischen einem Betrieb mit dem ersten Luft-Kraftstoffgemisch und einem Betrieb mit dem zweiten Luft-Kraftstoffgemisch umgestellt. Sprunghaft bedeutet in diesem Zusammenhang, dass beispielsweise zunächst für jeden Zylinder der erste lonenstrom bei einem Betrieb mit dem ersten Luft-Kraftstoffgemisch bestimmt wird und dann bei der nächsten Füllung eines Zylinders der Verbrennungsmotor mit dem zweiten Luft-Kraftstoffgemisch betrieben wird. Durch den sprunghaften Wechsel zwischen dem ersten und zweiten Luft-Kraftstoffgemisch findet auch eine sprunghafte Änderung der lonenstromdifferenz statt. Da sich die übrigen Parameter des Fahrzeugs, wie z.B. Frischlufttemperatur, Ladedruck eines Turboladers, Motortemperatur oder Sauerstoffgehalt nicht oder nur geringfügig ändern, können Randbedingungen beim Bestimmen der lonenstromdifferenz im Wesentlichen konstant gehalten werden.According to a further embodiment, the internal combustion engine is switched abruptly between an operation with the first air-fuel mixture and an operation with the second air-fuel mixture. In this context, jumping means, for example, first of all determining the first ionic current for each cylinder during operation with the first air-fuel mixture and then operating the internal combustion engine with the second air-fuel mixture during the next filling of a cylinder. The sudden change between the first and second air-fuel mixture also causes a sudden change in the ion current difference. Since the remaining parameters of the vehicle, such as Fresh air temperature, boost pressure of a turbocharger, engine temperature or oxygen content do not or only slightly change, boundary conditions when determining the ion current difference can be kept substantially constant.

Gemäß einer weiteren Ausführungsform kann die Zylinderungleichverteilung im Luft-Kraftstoffgemisch, welche nach einem der zuvor beschriebenen Verfahren bestimmt wurde, als On-Board-Diagnose-Information bereitgestellt werden. Diese On-Board-Diagnose-Information (OBD-Information) kann beispielsweise in einem Speicher einer Motorsteuerung zur Dokumentation der Überwachung der Lambda-Ungleichverteilung gespeichert werden und, beim Überschreiten einer vorbestimmten Zylinderungleichverteilung, dazu verwendet werden, beispielsweise eine Kontrollleuchte im Fahrzeug anzusteuern.According to a further embodiment, the cylinder unevenness distribution in the air-fuel mixture, which has been determined according to one of the methods described above, can be provided as on-board diagnostic information. This on-board diagnostic information (OBD information) can be stored, for example, in a memory of an engine controller for documentation of the monitoring of the lambda inequality and, when exceeding a predetermined cylinder inequality, used to control, for example, a warning light in the vehicle.

Gemäß der vorliegenden Erfindung wird weiterhin eine Steuervorrichtung für einen Verbrennungsmotor mit mehreren Zylinder bereitgestellt. Der Verbrennungsmotor weist in mindestens einen Zylinder ein lonenstromerfassungsmittel auf. Die Steuervorrichtung ist mit dem lonenstromerfassungsmittel koppelbar und ausgestaltet, einen ersten lonenstrom für den mindestens einen Zylinder zu erfassen, während der Verbrennungsmotor mit einem ersten Luft-Kraftstoffgemisch betrieben wird. Weiterhin ist die Steuervorrichtung ausgestaltet, einen zweiten lonenstrom für den mindestens einen Zylinder zu erfassen, während der Verbrennungsmotor mit einem zweiten Luft-Kraftstoffgemisch betrieben wird. Das erste Luft-Kraftstoffgemisch und das zweite Luft-Kraftstoffgemisch sind unterschiedlich. Aus dem ersten lonenstrom und dem zweiten lonenstrom des Zylinders bestimmt die Steuervorrichtung eine lonenstromdifferenz für den Zylinder. Die Steuervorrichtung ist somit zur Durchführung des zuvor beschriebenen Verfahrens geeignet und umfasst daher auch die zuvor beschriebenen Vorteile. Schließlich wird gemäß der vorliegenden Erfindung ein Fahrzeug bereitgestellt, welches einen Verbrennungsmotor und eine der zuvor beschriebenen Steuervorrichtungen umfasst. Der Verbrennungsmotor umfasst mindestens einen Zylinder, in welchem ein lonenstromerfassungsmittel angeordnet ist.
Die vorliegende Erfindung wird nachfolgend unter Bezugnahme auf die Zeichnungen im Detail beschrieben werden.

  • Fig. 1 zeigt lonenstromintegralwerte verschiedener Zylinder eines Verbrennungsmotors bei Variation der Einlassventilansteuerung.
  • Fig. 2 zeigt ein Ablaufdiagramm zur Zylindergleichstellung gemäß einer Ausführungsform der vorliegenden Erfindung.
  • Fig. 3 zeigt lonenstromsignalverläufe bei Variation einer Einspritzmenge.
  • Fig. 4 zeigt lonenstromintegralwerte in Abhängigkeit einer Kraftstoffvertrimmung.
  • Fig. 5 zeigt ein Fahrzeug gemäß einer Ausführungsform der vorliegenden Erfindung.
According to the present invention, there is further provided a control apparatus for a multi-cylinder internal combustion engine. The internal combustion engine has an ion current detection means in at least one cylinder. The controller is coupleable to the ion current sensing means and configured to detect a first ionic current for the at least one cylinder while operating the internal combustion engine with a first air-fuel mixture. Furthermore, the control device is configured to detect a second ion current for the at least one cylinder while the internal combustion engine is operated with a second air-fuel mixture. The first air-fuel mixture and the second air-fuel mixture are different. From the first ion stream and the second ion stream of the cylinder, the controller determines an ion stream difference for the cylinder. The control device is therefore suitable for carrying out the method described above and therefore also comprises the advantages described above. Finally, according to the present invention, a vehicle is provided which comprises an internal combustion engine and one of the previously described control devices. The internal combustion engine comprises at least one cylinder, in which an ion current detection means is arranged.
The present invention will be described below in detail with reference to the drawings.
  • Fig. 1 shows ion current integral values of various cylinders of an internal combustion engine with variation of the intake valve control.
  • Fig. 2 shows a flow chart for cylinder equalization according to an embodiment of the present invention.
  • Fig. 3 shows ion current waveforms with variation of an injection amount.
  • Fig. 4 shows ion current integral values as a function of fuel trim.
  • Fig. 5 shows a vehicle according to an embodiment of the present invention.

Zur Bestimmung und Diagnose einer Zylinderungleichverteilung im Luft-Kraftstoffgemisch, einer sogenannten Lambda-Ungleichverteilung, zwischen den einzelnen Zylindern kann beispielsweise ein lonenstromsignal verwendet werden, welches beispielsweise an den Elektroden einer Zündkerze in einem jeden Zylinder des Verbrennungsmotors bestimmt wird. Eine derartige Diagnose kann beispielsweise aufgrund von gesetzlichen Anforderungen, wie z.B. dem Kalifornischen On-Board-Diagnose-Gesetz (OBD-Gesetz) erforderlich sein. Zur Bestimmung des lonenstromsignals kann das lonenstromsignal über einem vorbestimmten Kurbelwellenwinkelbereich als lonenstromsignalverlauf erfasst werden und über den vorbestimmten Kurbelwellenwinkelbereich integriert werden. Dadurch kann ein charakteristischer lonenstromwert gewonnen werden. Insbesondere bei Motoren mit einer Vielzahl von Zylindern in beispielsweise einer V- oder W-Anordnung und asymmetrischer Zündfolge oder bei Motoren mit veränderlicher Ventilsteuerung werden jedoch sowohl das lonenstromsignal als auch das integrierte lonenstromsignal von Querabhängigkeiten, welche beispielsweise aus unterschiedlichen Restgasmengen resultieren, beeinflusst. Darüber hinaus kann eine Kraftstoffqualität das lonenstromsignal als auch das integrierte lonenstromsignal beeinflussen. Fig. 1 zeigt beispielsweise eine Veränderung eines integrierten lonenstromsignals aufgrund einer Veränderung eines Einlassventilnockenwellenwinkels für verschiedene Zylinder eines Verbrennungsmotors. In dem in Fig. 1 gezeigten Diagramm sind die integrierten lonenstromsignale (int. lonenstromsig.) für verschiedene Zylinder (Zyl.) bei verschiedenen Nockenwellenwinkeln, zu denen die entsprechenden Einlassventile geöffnet werden, dargestellt. Insbesondere durch Querabhängigkeiten zwischen den Zylindern in Bezug auf das Restgas unterscheiden sich die integrierten lonenstromsignale der einzelnen Zylinder erheblich. Daher ist eine Betrachtung der Absolutwerte der integrierten lonenstromsignale für eine Erkennung einer Lambda-Ungleichverteilung ungeeignet.For the determination and diagnosis of a cylinder inequality distribution in the air-fuel mixture, a so-called lambda unequal distribution, between the individual cylinders, for example, an ion current signal can be used, which is determined, for example, at the electrodes of a spark plug in each cylinder of the internal combustion engine. Such a diagnosis may be required, for example, due to legal requirements, such as the California On-Board Diagnostic Act (OBD). To determine the ion current signal, the ion current signal can be detected over a predetermined crankshaft angle range as an ion current signal profile and integrated over the predetermined crankshaft angle range. As a result, a characteristic ion current value can be obtained. However, especially in engines having a plurality of cylinders in, for example, a V or W arrangement and asymmetric firing order or variable valve timing motors, both the ion current signal and the integrated ion current signal are affected by lateral dependencies resulting, for example, from different amounts of residual gas. In addition, fuel quality can affect the ion current signal as well as the integrated ion current signal. Fig. 1 For example, FIG. 12 shows a variation of an integrated ion current signal due to a change in intake camshaft angle for various cylinders of an internal combustion engine. In the in Fig. 1 The diagram shows the integrated ion current signals (int ion current) for different cylinders (cyl.) at different camshaft angles to which the respective intake valves are opened. In particular, due to transverse dependencies between the cylinders with respect to the residual gas, the integrated ion current signals of the individual cylinders differ considerably. Therefore, consideration of the absolute values of the integrated ion current signals is unsuitable for detection of lambda inequality.

Fig. 2 zeigt daher Verfahrensschritte eines verbesserten Verfahrens 200 zur Bestimmung einer Lambda-Ungleichverteilung. In einem ersten Schritt 201 werden für jeden Zylinder in einem drehzahlsynchronen Messraster lonenstromsignale gemessen. Weiterhin werden zusätzliche Motorinformationen, beispielsweise ein Zündwinkel, von beispielsweise einer Motorelektronik eingelesen. Im Schritt 202 werden die lonenstromsignale für jeden Zylinder in einem definierten Kurbelwellenwinkelfenster, welcher zündwinkelabhängig sein kann, integriert. Fig. 3 zeigt beispielhaft drei lonenstromsignale 301, 302 und 303, welche in einem Zylinder bei unterschiedlichen Verbrennungen auftreten können. Die Kurve 301 zeigt beispielsweise den Verlauf des lonenstromsignals bei einer normalen Verbrennung, d.h. bei einer Verbrennung mit näherungsweise Lambda gleich 1, wohingegen die Kurve 302 eine Verbrennung mit einem fetten Gemisch, d.h. mit einem erhöhten Kraftstoffanteil, und die Kurve 303 eine magere Verbrennung, d.h. eine Verbrennung mit einem verminderten Kraftstoffanteil, zeigt. Zur Bestimmung des lonenstromintegralwerts werden die entsprechenden lonenkurven 301-303 über dem Kurbelwel-lenwinkel, welcher in Fig. 3 auf der x-Achse gezeigt ist, integriert. Da der lonenstrom beispielsweise mit Hilfe einer Zündkerze in dem entsprechenden Zylinder des Verbrennungsmotors erfasst werden kann, wird der Integrationsbereich derart gewählt, dass der Einfluss des Zündfunkens nicht in den Integrationsbereich fällt. In dem in Fig. 3 gezeigten Beispiel ist der Einfluss des Zündfunkens im Bereich von -20° bis näherungsweise -16° deutlich zu erkennen. Daher wird der lonenstrom beispielsweise im Bereich von -16° bis näherungsweise +28° bezogen auf den oberen Totpunkt des entsprechenden Zylinders integriert. Der Integrationsbereich ist in Fig. 3 durch den Pfeil 304 gekennzeichnet. Fig. 2 shows therefore method steps of an improved method 200 for determining a lambda unequal distribution. In a first step 201, ion current signals are measured for each cylinder in a speed-synchronous measuring grid. Furthermore, additional engine information, for example, an ignition angle, read by, for example, an engine electronics. In step 202, the ion current signals for each cylinder are defined in one Crankshaft angle window, which can be dependent on ignition, integrated. Fig. 3 shows by way of example three ion current signals 301, 302 and 303, which can occur in a cylinder at different burns. Curve 301 shows, for example, the course of the ion current signal in a normal combustion, ie in combustion with approximately lambda equal to 1, whereas the curve 302 combustion with a rich mixture, ie with an increased fuel fraction, and the curve 303 lean combustion, ie a combustion with a reduced fuel content, shows. To determine the ion current integral value, the corresponding ion curves 301-303 are compared with the crankshaft angle, which in Fig. 3 is shown integrated on the x-axis. Since the ion current can be detected, for example, by means of a spark plug in the corresponding cylinder of the internal combustion engine, the integration range is selected such that the influence of the spark does not fall within the integration range. In the in Fig. 3 In the example shown, the influence of the spark in the range of -20 ° to approximately -16 ° can be clearly seen. Therefore, the ion current is integrated, for example, in the range of -16 ° to approximately + 28 ° with respect to the top dead center of the corresponding cylinder. The integration area is in Fig. 3 indicated by the arrow 304.

Die zylinderselektiven Integralwerte werden über eine vorbestimmte Anzahl von Arbeitsspielen gemittelt und ergeben einen ersten lonenstromwert, einen sogenannten Referenzwert (Schritt 203). Die lonenstromsignale für die jeweiligen Referenzwerte der jeweiligen Zylinder werden vor einer Vertrimmung der Kraftstoffmenge erfasst, d.h., die Referenzwerte sind gemittelte lonenstromintegralwerte bei einem Betrieb des Verbrennungsmotors mit einem ersten Luft-Kraftstoffgemisch. Im Schritt 204 wird die Kraftstoffmenge für alle Zylinder vertrimmt, d.h. der Verbrennungsmotor wird nachfolgend mit einem zweiten Luft-Kraftstoffgemisch betrieben, welches unterschiedlich zu dem ersten Luft-Kraftstoffgemisch ist. Das zweite Luft-Kraftstoffgemisch kann beispielsweise ein fetteres oder ein magereres Luft-Kraftstoffgemisch sein. Im Schritt 205 werden aus entsprechend erfassten lonenstromsignalen beim Betrieb mit dem zweiten Luft-Kraftstoffgemisch für jeden Zylinder jeweils ein mittlerer lonenstromintegralwert über eine definierte Anzahl von Arbeitsspielen bestimmt. Somit wird für jeden Zylinder ein zweiter gemittelter lonenstromintegralwert bestimmt, ein sogenannter Vertrimmwert.The cylinder-selective integral values are averaged over a predetermined number of working cycles and yield a first ion current value, a so-called reference value (step 203). The ion current signals for the respective reference values of the respective cylinders are detected before trimming the amount of fuel, that is, the reference values are averaged ion current integral values in an operation of the internal combustion engine with a first air-fuel mixture. In step 204, the fuel amount is de-rated for all cylinders, i. the internal combustion engine is subsequently operated with a second air-fuel mixture which is different from the first air-fuel mixture. The second air-fuel mixture may be, for example, a richer or a leaner air-fuel mixture. In step 205, an average ion current integral value for each cylinder over a defined number of operating cycles is determined for each cylinder from correspondingly detected ion current signals during operation with the second air-fuel mixture. Thus, for each cylinder a second averaged ion current integral value is determined, a so-called trim value.

Fig. 4 zeigt beispielhaft die Auswirkung der Kraftstoffvertrimmung auf den integrierten lonenstrom. Auf der x-Achse des in Fig. 4 gezeigten Diagramms ist die Kraftstoffvertrimmung in Prozent aufgetragen. Eine negative Kraftstoffvertrimmung gibt eine entsprechende Verringerung des Kraftstoffanteils in dem Luft-Kraftstoffgemisch an und eine positive Kraftstoffvertrimmung eine Erhöhung des Kraftstoffanteils in dem Luft-Kraftstoffgemisch. Auf der y-Achse ist der integrierte lonenstrom über alle Zylinder gemittelt aufgetragen (Graph 401). Zusätzlich wurde der lonenstrom für die Kraftstoffvertrimmung von 0 % auf 0 normiert. Die bei den Kraftstoffvertrimmungen -30 %, -25 %, -15 %, -5 %, 10 %, 20 % und 30 % dargestellten Bereiche 402-408 zeigen eine Bandbreite der integrierten lonenströme der einzelnen Zylinder bei den entsprechenden Kraftstoffvertrimmungen an. So variiert der integrierte lonenstrom bei einer Kraftstoffvertrimmung von beispielsweise -30 % zwischen den einzelnen Zylindern eines Verbrennungsmotors im Bereich von näherungsweise -7,5 bis -9,5. Diese Bandbreite resultiert aus den oben genannten Querabhängigkeiten zwischen den Zylindern. Eine Änderung des lonenstromintegrals ist jedoch charakteristisch für eine entsprechende Kraftstoffvertrimmung, d.h. für eine entsprechende Änderung der Kraftstoffmenge. Daher wird im Schritt 206 nicht der Absolutwert der integrierten lonenströme betrachtet, sondern für jeden Zylinder eine Differenz aus Vertrimmwert minus Referenzwert gebildet. Da die Differenz unabhängig von den oben genannten Querabhängigkeiten ist, kann anhand der Differenzen der lonenstromsignale eine Lambda-Ungleichstellung bestimmt werden. In Fig. 4 ist beispielsweise eine definierte Kraftstoffvertrimmung 409 zwischen -30 % und -20 % und eine entsprechende Änderung des lonenstromintegrals 410 dargestellt. Da die Kraftstoffvertrimmung für alle Zylinder gleichermaßen durchgeführt wurde, kann aus unterschiedlichen Differenzen aus Vertrimmwert und Referenzwert der einzelnen Zylinder eine entsprechende Lambda-Ungleichverteilung der einzelnen Zylinder bestimmt werden. Diese Lambda-Ungleichverteilung kann beispielsweise als On-Board-Diagnose-Information in einer Motorsteuerung abgelegt werden oder über eine entsprechende Anzeige einem Fahrer des Fahrzeugs angezeigt werden. Fig. 4 exemplifies the effect of fuel trim on the integrated ion current. On the x-axis of the in Fig. 4 The diagram shows the percentage of fuel added. Negative fuel trim indicates a corresponding decrease in fuel fraction in the air-fuel mixture and positive fuel trim indicates an increase in fuel fraction in the air-fuel mixture. On the y-axis, the integrated ion current is averaged across all cylinders (Graph 401). In addition, the ion current for fuel trim was normalized from 0% to zero. The at the fuel trim -30%, -25%, -15%, -5%, 10%, 20%, and 30% ranges 402-408 indicate a range of integrated cylinder ion streams at the respective fuel trim. Thus, with fuel trim of, for example, -30% between the individual cylinders of an internal combustion engine, the integrated ion current varies in the range of approximately -7.5 to -9.5. This bandwidth results from the above-mentioned transverse dependencies between the cylinders. However, a change in the lonenstromintegrals is characteristic of a corresponding fuel trim, ie for a corresponding change in the amount of fuel. Therefore, in step 206, the absolute value of the integrated ion currents is not considered, but a difference between the reference value and the reference value is formed for each cylinder. Since the difference is independent of the abovementioned transverse dependencies, a lambda inequality can be determined on the basis of the differences in the ion current signals. In Fig. 4 For example, a defined fuel trim 409 between -30% and -20% and a corresponding change in the ion current integral 410 is shown. Since the fuel trim was performed equally for all cylinders, a corresponding lambda unequal distribution of the individual cylinders can be determined from different differences between the trim value and the reference value of the individual cylinders. This lambda unequal distribution can be stored, for example, as on-board diagnostic information in an engine control or displayed to a driver of the vehicle via a corresponding display.

Im Schritt 207 kann auf der Grundlage der so festgestellten Lambda-Ungleichverteilung eine Korrektur der Einspritzmenge für jeden Zylinder durchgeführt werden und somit eine Gleichstellung des Lambda für alle Zylinder erreicht werden. Die Korrektur der Einspritzmengen bewirkt eine Lambda-Änderung der einzelnen Zylinder des Motors 208 und kann wie zuvor beschrieben mit den Schritten 201-206 erneut bestimmt werden.In step 207, on the basis of the lambda unevenness distribution thus determined, a correction of the injection quantity for each cylinder can be carried out and thus an equalization of the lambda for all cylinders can be achieved. The correction of the injection quantities causes a lambda change of the individual cylinders of the engine 208 and can be determined again as described above with the steps 201-206.

Fig. 5 zeigt ein Fahrzeug 500 mit einem Verbrennungsmotor 208 mit vier Zylindern 501-504. In jedem der vier Zylinder 501-504 ist jeweils eine Zündkerze 505-508 angeordnet, welche mit einer Steuervorrichtung 509 gekoppelt sind. Die Steuervorrichtung 509 ist in der Lage, mit Hilfe der Zündkerzen 505-508 in den Brennräumen der Zylinder 501-504 jeweils einen lonenstrom zu erfassen. In Abhängigkeit der erfassten lonenströme bestimmt die Steuervorrichtung 509, wie zuvor in Zusammenhang mit dem Ablaufdiagramm 200 der Fig. 2 beschrieben wurde, eine Lambda-Ungleichverteilung. Wenn die Lambda-Ungleichverteilung einen vorbestimmten Schwellenwert überschreitet, steuert die Steuervorrichtung 509 eine Kontrollleuchte 510 des Fahrzeugs 500 an, um dem Fahrer anzuzeigen, dass die Lambda-Ungleichverteilung den vorbestimmten Schwellenwert überschritten hat. Darüber hinaus kann die Steuervorrichtung 509 eine (nicht gezeigte) Motorsteuerung des Verbrennungsmotors 208 derart ansteuern, dass eine Lambda-Gleichstellung erreicht wird, wie im Schritt 207 der Fig. 2 beschrieben wurde. Fig. 5 FIG. 10 shows a vehicle 500 having an internal combustion engine 208 with four cylinders 501-504. In each of the four cylinders 501-504, a spark plug 505-508 is respectively disposed, which are coupled to a control device 509. The control device 509 is capable of detecting an ion current with the aid of the spark plugs 505-508 in the combustion chambers of the cylinders 501-504, respectively. Depending on the detected ion currents, the control device 509 determines, as previously described in connection with the flowchart 200 of FIG Fig. 2 has been described, a lambda inequality. If the lambda inequality exceeds a predetermined threshold, the controller 509 drives a warning light 510 of the vehicle 500 to indicate to the driver that the lambda bias has exceeded the predetermined threshold. In addition, the controller 509 may drive an engine controller (not shown) of the engine 208 to achieve lambda equalization, as in step 207 of FIG Fig. 2 has been described.

Claims (15)

  1. Method for an internal combustion engine, wherein the internal combustion engine (208) comprises multiple cylinders (501-504), comprising:
    - detecting a first ion current (301-303) for each cylinder of at least two cylinders of the multiple cylinders (501-504) while the internal combustion engine (208) is being operated with a first air-fuel mixture,
    - detecting a second ion current (301-303) for each cylinder of at least two cylinders of the multiple cylinders (501-504) while the internal combustion engine (208) is being operated with a second air-fuel mixture, wherein the first air-fuel mixture and the second air-fuel mixture differ,
    - determining in each case one ion current difference for each cylinder of at least two cylinders of the multiple cylinders (501-504) from the first and second ion current (301-303) of the respective cylinder (501-504), and
    - determining a cylinder uneven distribution in the air-fuel mixture between the at least two cylinders in a manner dependent on the ion current differences of the at least two cylinders.
  2. Method according to Claim 1, wherein the method furthermore comprises, for each of the at least two cylinders:
    - correcting an injection quantity for the respective cylinder (501-504) in a manner dependent on the ion current differences of the at least two cylinders, such that a difference between the ion current differences of the at least two cylinders is reduced.
  3. Method according to one of the preceding claims, wherein the first and/or second ion current (301-303) is detected in the combustion chamber of the respective cylinder (501-504).
  4. Method according to Claim 3, wherein the first and/or second ion current (301-303) is detected by means of an ignition plug (505-508) arranged in the combustion chamber of the respective cylinder.
  5. Method according to one of the preceding claims, wherein the first and/or second ion current (301-303) is detected in a predetermined crank angle range (304).
  6. Method according to Claim 5, wherein the predetermined crank angle range (304) comprises a crank angle range from -20° to +30° in relation to a top dead centre of the respective cylinder.
  7. Method according to Claim 5 or 6, wherein the detection of the first and/or second ion current (301-303) comprises:
    - detecting and ion current profile over the predetermined crank angle range (304), and
    - integrating the ion current profile over the crank angle range (304).
  8. Method according to Claim 7, wherein the step of detecting the ion current profile comprises:
    - detecting multiple ion current profiles during multiple working cycles of the respective cylinder, and
    - forming an average ion current profile by averaging the multiple ion current profiles.
  9. Method according to one of the preceding claims, wherein the step of detecting the second ion current (301-303) for the respective cylinder (501-504) comprises:
    - detecting multiple second ion currents with different second air-fuel mixtures.
  10. Method according to one of the preceding claims, wherein the first air-fuel mixture and the second air-fuel mixture have different fuel quantities.
  11. Method according to Claim 10, wherein the fuel quantity in the second air-fuel mixture is changed in a range from -40% to +40% in relation to the fuel quantity of the first air-fuel mixture.
  12. Method according to one of the preceding claims, wherein the internal combustion engine (208) is switched abruptly between operation with the first air-fuel mixture and operation with the second air-fuel mixture.
  13. Method according to Claim 1, furthermore comprising:
    - providing an item of on-board diagnosis information in a manner dependent on the determined cylinder uneven distribution in the air-fuel mixture.
  14. Control device for an internal combustion engine having multiple cylinders, wherein the internal combustion engine (208) has an ion current detecting means (505-508) in the at least one cylinder (501-504), wherein the control device (509) is coupled to the ion current detecting means (505-508) and carries out a method according to one of Claims 1 to 12.
  15. Vehicle comprising:
    - an internal combustion engine (208) having at least one cylinder (501-504), wherein the internal combustion engine (208) has an ion current detecting means (505-508) in the at least one cylinder (501-504), and
    - a control device (509) according to Claim 14.
EP12002810.5A 2011-05-27 2012-04-21 Method and control device for a combustion engine Not-in-force EP2574760B1 (en)

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DE19816641C1 (en) * 1998-04-15 1999-10-07 Daimler Chrysler Ag Procedure for determining the smooth running of a gasoline engine
DE19916204C1 (en) 1999-04-10 2000-11-16 Daimler Chrysler Ag Method for determining combustion parameters of an internal combustion engine
DE10008552B4 (en) * 2000-02-24 2007-01-04 Robert Bosch Gmbh Method and device for evaluating a signal of an ion current sensor of an internal combustion engine
DE10115902C1 (en) 2001-03-30 2002-07-04 Siemens Ag Lambda cylinder adjustment method for multi-cylinder IC engine with exhaust gas catalyzer corrects fuel mixture for each 2 cylinders until detected exhaust gas parameter exhibits extreme value
DE10147171B4 (en) * 2001-09-25 2007-11-29 Siemens Ag Method for direct injection of fuel in the form of two injections with different injection angles and a control device for injection
DE102004041230A1 (en) 2004-08-26 2006-03-02 Volkswagen Ag Cylinder equalization method using ionic flow measurement for combustion engine, involves comparing determined average values of specific cylinders and average values of specific cylinder groups to identify cylinder and its operation mode
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DE102007030527A1 (en) 2007-06-30 2009-01-08 Daimler Ag Method for synchronizing cylinder in turbocharged spark-ignition, port-injection or particularly direct-injection internal combustion engine for vehicle, involves carrying out running smoothness measurement of internal combustion engine
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