EP1034416B1 - Method for evaluating the march of pressure in a combustion chamber - Google Patents

Method for evaluating the march of pressure in a combustion chamber Download PDF

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Publication number
EP1034416B1
EP1034416B1 EP98958153A EP98958153A EP1034416B1 EP 1034416 B1 EP1034416 B1 EP 1034416B1 EP 98958153 A EP98958153 A EP 98958153A EP 98958153 A EP98958153 A EP 98958153A EP 1034416 B1 EP1034416 B1 EP 1034416B1
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EP
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Prior art keywords
pressure
cycles
engine
pressure profile
specific manner
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EP98958153A
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German (de)
French (fr)
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EP1034416B2 (en
EP1034416A2 (en
Inventor
Klaus Walter
Holger Bellmann
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Robert Bosch GmbH
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Robert Bosch GmbH
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Classifications

    • 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
    • F02D41/009—Electrical control of supply of combustible mixture or its constituents using means for generating position or synchronisation signals
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01L—CYCLICALLY OPERATING VALVES FOR MACHINES OR ENGINES
    • F01L1/00—Valve-gear or valve arrangements, e.g. lift-valve gear
    • F01L1/34—Valve-gear or valve arrangements, e.g. lift-valve gear characterised by the provision of means for changing the timing of the valves without changing the duration of opening and without affecting the magnitude of the valve lift
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02D—CONTROLLING COMBUSTION ENGINES
    • F02D35/00—Controlling engines, dependent on conditions exterior or interior to engines, not otherwise provided for
    • F02D35/02—Controlling engines, dependent on conditions exterior or interior to engines, not otherwise provided for on interior conditions
    • F02D35/023—Controlling engines, dependent on conditions exterior or interior to engines, not otherwise provided for on interior conditions by determining the cylinder pressure
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01L—CYCLICALLY OPERATING VALVES FOR MACHINES OR ENGINES
    • F01L2201/00—Electronic control systems; Apparatus or methods therefor
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02D—CONTROLLING COMBUSTION ENGINES
    • F02D13/00—Controlling the engine output power by varying inlet or exhaust valve operating characteristics, e.g. timing
    • F02D13/02—Controlling the engine output power by varying inlet or exhaust valve operating characteristics, e.g. timing during engine operation
    • F02D13/0203—Variable control of intake and exhaust valves
    • F02D13/0215—Variable control of intake and exhaust valves changing the valve timing only
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02D—CONTROLLING COMBUSTION ENGINES
    • F02D13/00—Controlling the engine output power by varying inlet or exhaust valve operating characteristics, e.g. timing
    • F02D13/02—Controlling the engine output power by varying inlet or exhaust valve operating characteristics, e.g. timing during engine operation
    • F02D13/0261—Controlling the valve overlap
    • 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
    • F02D41/0002—Controlling intake air
    • F02D2041/001—Controlling intake air for engines with variable valve actuation

Definitions

  • the invention relates to a method for evaluating the combustion chamber pressure in an internal combustion engine.
  • a combustion chamber pressure sensor is usually assigned to each cylinder of the internal combustion engine.
  • a crankshaft sensor is used that delivers an output signal that is representative of the crankshaft position. Both signals are evaluated together in the control unit of the internal combustion engine.
  • a camshaft sensor is no longer required, since the crank and camshaft position can be synchronized, especially after starting, by linking the combustion chamber pressure curve and the crankshaft sensor signal.
  • the cylinder detection and the detection of the crankshaft revolution of a combustion cycle of the internal combustion engine is carried out in the known method, for example by evaluating and differentiating the pressure increase in a specific cylinder, between pressure increase in the compression stroke and pressure increase when combustion has taken place. Since these values are different, it can be determined in which crankshaft revolution the internal combustion engine is located. Based on this knowledge, control signals for the internal combustion engine can be generated.
  • an evaluation of the combustion chamber pressure curve is not carried out in order to recognize the valve timing, that is to say whether the exhaust valve opens, whether the exhaust valve closes, whether the intake valve opens or whether the intake valve closes.
  • the method according to the invention with the features of the main claim has the advantage that an exact analysis of the combustion chamber pressure curve is carried out so that the valve timing with respect to the crankshaft position can be determined. For this purpose, characteristic events are evaluated, from which certain valve timing can be clearly identified. For the valve control times outlet opens, outlet closes, inlet opens, inlet closes, characteristic pressure curves result which, according to the invention, are advantageously extracted from the combustion chamber pressure curve.
  • valve timing can be determined by recognizing the various associated characteristic events. Some valve timing can also be recognized by evaluating the combustion chamber pressure curve in the same way. A comparison with stored characteristic values typical of internal combustion engines enables engine-specific determinations of valve timing.
  • Further processing of the combustion chamber pressure signal before further evaluation advantageously enables further valve timing determinations.
  • additional operating conditions of the internal combustion engine such as taking into account the occurrence of knocking combustion and the resulting additional signal processing, for example averaging, can also advantageously determine valve timing when difficult conditions or operating states of the internal combustion engine occur.
  • FIG. 1 shows a device, known per se, for detecting the pressure curve in the cylinders of an internal combustion engine. Relevant parts of the internal combustion engine are shown in FIG. 1a.
  • Figure 2 shows a characteristic combustion chamber pressure curve over the crankshaft angle.
  • Figure 3 is a flow diagram of an inventive Shown evaluation method and Figures 4, 5 and 6 show different relationships between combustion chamber pressure, combustion chamber volume and crankshaft angle.
  • Cylinder pressure sensors 14, 15, 16 and 17 are arranged in the cylinders 10, 11, 12 and 13 of a four-cylinder internal combustion engine, which determine the pressure profiles P1, P2, P3 and P4.
  • crankshaft sensor 18 which emits an output signal S1 which is characteristic of the crankshaft position ⁇ .
  • Both the output signals of the cylinder pressure sensors 14, 15, 16 and 17 and the output signal of the crankshaft sensor 18 are fed to the control unit 19 of the internal combustion engine, which processes these signals. Further signals (e.g. a temperature T, a load L, etc.) can be fed to the control unit via inputs 20, which signals can also be further processed in the control unit.
  • Further signals e.g. a temperature T, a load L, etc.
  • the control unit 19 comprises a multiplexer 21, via which the output signal of the cylinder pressure sensors can optionally be led to an analog / digital converter 22.
  • the switching of the multiplexer 21 is dependent on the crankshaft angle and is triggered by the control unit 19 by means of appropriate controls.
  • the actual evaluation of the signals takes place in a microprocessor 23 of the control device 19, which can output control signals S2 and S3 to various components of the internal combustion engine, for example ignition or injection signals, via an output unit 23a depending on the quantities determined.
  • the signal processing takes place, on the basis of which the valve timing can be deduced, or on the basis of which the valve timing can be determined.
  • FIG. 3 shows an evaluation scheme in which the pressure is calculated from the sensor signal in step SCH1.
  • the crankshaft angle ⁇ is read in step SCH2, so that the reference P ( ⁇ ) is present in step SCH3.
  • the pressure curve is evaluated in step SCH4, possibly taking into account stored data, and in step SCH5 the relevant valve control unit is inferred.
  • the fuel air mixture is supplied to the cylinder of an internal combustion engine, for example the cylinder 10 (FIG. 1a), by opening the intake valve 24.
  • the fuel is injected from the injection valve 25 upstream of the inlet valve 24 into the intake manifold 26 and ignited via the spark plug 27.
  • the gas generated in the cylinder can be discharged via an outlet valve 28.
  • the intake valve and the exhaust valve are actuated in a known manner with the aid of the camshaft or camshafts, not shown.
  • the camshaft or the camshafts are driven in a known manner by the crankshaft.
  • the position of the camshaft or camshafts in relation to the crankshaft can be changed by the control unit 19 as a function of the speed by means of corresponding control signals S3.
  • the assignment between the camshaft position and the crankshaft position can be determined by the inventive detection of the valve timing as a function of the crankshaft angle.
  • the combustion chamber pressure curve shown schematically in FIG. 2 is evaluated according to the invention according to various criteria in order to infer events that are characteristic of the camshaft position in relation to the crankshaft position and thus of the valve seat control times. Such an event can be, for example, the crankshaft position at which the intake valve closes.
  • Other valve timings include the exhaust timings. Inlet opens, outlet closes. For each valve timing there are characteristic or characterizing features in the pressure curve, the evaluation of which is described in more detail below.
  • the expansion line of the combustion chamber pressure curve can be evaluated in order to detect the valve control time "outlet opens".
  • the processes in the cylinder are a thermodynamically closed system, so that the processes can be calculated according to thermodynamic laws.
  • With increasing volume there is a decrease in pressure, which occurs similar to a polytropic expansion. It is characteristic of this that the amount of the pressure gradient decreases with increasing volume. If the outlet valve is opened, gas flows out of the cylinder due to the pressure, which is still higher than the environment.
  • the evaluation of the pressure gradient for the outlet opening that has taken place can thus be used as a characteristic or characteristic behavior of the pressure curve. If the pressure gradient exhibits a behavior which is characterized by a decreasing decrease and a sudden increase in the amount of the pressure gradient, it can be concluded that the outlet opening has taken place.
  • the evaluation can be carried out mathematically, for example by checking a sign change in the second derivative of the pressure according to the volume. If such a change of sign occurs in the second derivative of the pressure after the crank angle, it can be concluded that the outlet has been opened.
  • FIG. 4 which shows the relationship between pressure P and volume V between top dead center OT and bottom dead center UT
  • point A1 would indicate the outlet opening that has taken place.
  • the second derivative of pressure is by volume d 2 P dv has a change of sign. This also applies to the context d 2 P d.alpha 2 ,
  • the volume or crank angle is detected at which the compression line passes a known, fixed level. In the simplest case, this comparison level is obtained from the pressure curve during the extension. The position of the intersection A2 between the compression pressure curve and the pressure curve during extension in the crank angle pattern or in the volume curve can be seen in FIG. 5. Although it is not a direct measure of the valve timing "intake closes", it shifts when the intake valve closes. A setpoint for the position of point A2 can thus be applied depending on the load and the speed of the motor become. The deviation of the actual value of point A2 from the target value is then used for diagnosis.
  • the engine-specific data can be recorded, for example, in a test bench before commissioning. The data obtained in this way are stored in memories of, for example, the control unit, which can access this data at any time.
  • the evaluation of the combustion chamber pressure curve is not only limited to the pressure-volume relationship, but an evaluation based on the pressure-crank angle relationship is also possible.
  • the combustion chamber pressure P is plotted against the crankshaft angle ⁇ .
  • the combustion chamber pressure curve can also be evaluated as a substitute by comparison with the ambient pressure. For example, to detect the valve timing "intake valve closes intake valve" the volume or the crankshaft angle at which the Compression pressure is equal to the ambient pressure. In this case, point A3 is defined as the point of intersection of the compression pressure curve with the ambient pressure.
  • the course of the combustion chamber pressure can also be evaluated on the basis of a fixed pressure value. In this case, however, special diagnostic strategies are required which prevent incorrect diagnosis due to a strong change in the ambient pressure, for example when driving at high altitude. If the control device detects such a high travel, for example in connection with other evaluations for regulating the internal combustion engine, the detection of valve timing can be prevented at least temporarily.
  • valve timing is changed, for example by a corresponding change in the camshaft positions, this also leads to a change in the course of the combustion chamber pressure during the compression phase, during the combustion phase and during the expansion phase.
  • the valve timing is changed by changing the camshaft position so that the residual gas content of the cylinder charge changes in a characteristic manner.
  • a higher residual gas content which may be caused, for example, by late closing of the exhaust valve or early opening of the intake valve, in each case based on the crankshaft angle, increases both the absolute pressure and the pressure gradient during the compression phase, assuming the same Fresh air mass intake. Assuming the same ignition point, the combustion will start late, with the corresponding effects on the characteristic values describing the combustion and the expansion.
  • engine-specific parameters or maps are stored in the memory of the control unit, these parameters or maps can be accessed at any time.
  • a comparison with the measured cylinder pressure curve reveals, based on knowledge of the engine-specific relationships, for example also with determined mathematical relationships, which valve control times are available. Characteristic values can be adapted during engine operation. The current valve timing can also be deduced from the adapted characteristic values. Another variation of the combustion pressure curve can also be shown, as the residual gas content increases with increasing residual gas content. This provides the possibility of inferring the valve timing from the scatter of the characteristic values via engine-specific maps or characteristic curves, engine-specific mathematical relationships or parameters adapted during engine operation.
  • a combination of the evaluation options mentioned above is possible at any time. Furthermore, it is possible both to evaluate the pressure gradients and to evaluate the pressure maximum, the position of the pressure maximum and generally when evaluating individual pressure profiles, for example to carry out an averaging, for example over several engine cycles, and to assign the characteristic values of the combustion chamber pressure curve to specific parameters investigate. Again, engine-specific and to consider relationships or mathematical relationships stored as a map or characteristic curve.
  • a defined combustion chamber pressure integral or a differential combustion chamber pressure integral can also first be formed, the integration limits being selected appropriately and in particular being set in such a way that that phases typical of valve timing are combined.
  • valve timing Another possibility for detecting the valve timing is to derive characteristic quantities for certain valve timing from the occurrence of vibrations in the combustion chamber pressure curve as a result of knocking combustion or from the need for countermeasures to avoid knocking combustion, which in turn are taken due to pressure fluctuations in the combustion chamber pressure curve. An additional averaging can be carried out.
  • the invention can be used in internal combustion engines with any number of cylinders, the number of cylinder pressure sensors corresponding, for example, to the number of cylinders or half the number. In a simplified version, at least one sensor can be used. Knock sensors or any combustion sequence sensors from whose output signal for valve timing characteristic features can be obtained can also be used as sensors.

Description

Die Erfindung betrifft ein Verfahren zur Auswertung des Brennraumdrucks bei einer Brennkraftmaschine.The invention relates to a method for evaluating the combustion chamber pressure in an internal combustion engine.

Stand der TechnikState of the art

Es ist bekannt, den Verlauf des Brennraumdrucks in den Zylindern einer Brennkraftmaschine mit Hilfe geeigneter Sensoren zu ermitteln und aus diesem Verlauf Betriebszustände der Brennkraftmaschine zu erkennen und Ansteuersignale zur Steuerung der Brennkraftmaschine zu gewinnen. Dabei ist üblicherweise jedem Zylinder der Brennkraftmaschine ein Brennraumdrucksensor zugeordnet. Zusätzlich wird ein Kurbelwellensensor eingesetzt, der ein Ausgangssignal liefert, das repräsentativ ist für die Kurbelwellenstellung. Beide Signale werden gemeinsam im Steuergerät der Brennkraftmaschine ausgewertet. Ein Nockenwellensensor wird dabei nicht mehr benötigt, da die Synchronisation von Kurbel- und Nockenwellenstellung insbesonders nach dem Start aus der Verknüpfung des Brennraumdruckverlaufs und des Kurbelwellensensorsignals möglich ist. Ein Verfahren, bei dem der Brennraumdruckverlauf in Abhängigkeit von der Kurbelwellenstellung ausgewertet wird, zur Zylindererkennung und zur Erzeugung von für die Zündung erforderlichen Signalen ist bekannt. Die Zylindererkennung und die Erkennung, in welcher Kurbelwellenumdrehung eines Verbrennungszyklusses sich die Brennkraftmaschine befindet, wird bei dem bekannten Verfahren durchgeführt, indem beispielsweise der Druckanstieg in einem bestimmten Zylinder ausgewertet wird und unterschieden wird, zwischen Druckanstieg im Kompressionshub und Druckanstieg bei erfolgter Verbrennung. Da diese Werte unterschiedlich sind, läßt sich feststellen, in welcher Kurbelwellenumdrehung sich die Brennkraftmaschine befindet. Ausgehend von dieser Erkenntnis können Steuersignale für die Brennkraftmaschine erzeugt werden.It is known to determine the course of the combustion chamber pressure in the cylinders of an internal combustion engine with the aid of suitable sensors and to identify operating states of the internal combustion engine from this course and to obtain control signals for controlling the internal combustion engine. A combustion chamber pressure sensor is usually assigned to each cylinder of the internal combustion engine. In addition, a crankshaft sensor is used that delivers an output signal that is representative of the crankshaft position. Both signals are evaluated together in the control unit of the internal combustion engine. A camshaft sensor is no longer required, since the crank and camshaft position can be synchronized, especially after starting, by linking the combustion chamber pressure curve and the crankshaft sensor signal. A method in which the combustion chamber pressure curve is evaluated as a function of the crankshaft position for cylinder detection and for generating signals necessary for the ignition is known. The cylinder detection and the detection of the crankshaft revolution of a combustion cycle of the internal combustion engine is carried out in the known method, for example by evaluating and differentiating the pressure increase in a specific cylinder, between pressure increase in the compression stroke and pressure increase when combustion has taken place. Since these values are different, it can be determined in which crankshaft revolution the internal combustion engine is located. Based on this knowledge, control signals for the internal combustion engine can be generated.

Bei dem bekannten Verfahren wird eine Auswertung des Brennraumdruckverlaufs zur Erkennung der Ventilsteuerzeiten, also zur Erkennung, ob das Auslaßventil sich öffnet, ob das Auslaßventil schließt, ob das Einlaßventil öffnet oder ob das Einlaßventil sich schließt, nicht durchgeführt.In the known method, an evaluation of the combustion chamber pressure curve is not carried out in order to recognize the valve timing, that is to say whether the exhaust valve opens, whether the exhaust valve closes, whether the intake valve opens or whether the intake valve closes.

In der US-A-4633707 ist eine Ermittlung der Zeitpunkte 'Einlass schliesst' und 'Auslass öffnet' über eine Druckmessung im Kalt antrieb der Brennkraftmaschine angedeutet.In US-A-4633707 a determination of the times "inlet closes" and "outlet opens" is indicated by a pressure measurement in the cold drive of the internal combustion engine.

Vorteile der ErfindungAdvantages of the invention

Das erfindungsgemäße Verfahren mit den Merkmalen des Hauptanspruchs hat demgegenüber den Vorteil, daß eine genaue Analyse des Brennraumdruckverlaufs durchgeführt wird, so daß die Ventilsteuerzeiten in Bezug auf die Kurbelwellenstellung ermittelbar sind. Dazu werden kennzeichnende Ereignisse ausgewertet, aus denen eindeutig bestimmte Ventilsteuerzeiten erkannt werden können. Für die Ventilsteuerzeiten Auslaß öffnet, Auslaß schließt, Einlaß öffnet, Einlaß schließt, ergeben sich charakteristische Druckverläufe, die erfindungsgemäß in vorteilhafter Weise aus dem Brennraumdruckverlauf extrahiert werden.The method according to the invention with the features of the main claim has the advantage that an exact analysis of the combustion chamber pressure curve is carried out so that the valve timing with respect to the crankshaft position can be determined. For this purpose, characteristic events are evaluated, from which certain valve timing can be clearly identified. For the valve control times outlet opens, outlet closes, inlet opens, inlet closes, characteristic pressure curves result which, according to the invention, are advantageously extracted from the combustion chamber pressure curve.

Weitere Vorteile der Erfindung werden durch die in den Unteransprüchen angegebenen Maßnahmen erzielt. Dabei ist besonders vorteilhaft, daß verschiedene Ventilsteuerzeiten durch Erkennung der verschiedenen zugehörigen kennzeichnenden Ereignisse ermittelbar sind. Einige Ventilsteuerzeiten können auch durch eine gleichartige Auswertung des Brennraumdruckverlaufs erkannt werden. Ein Vergleich mit brennkraftmaschinentypischen abgespeicherten Kenngrößen ermöglicht motorspezifische Bestimmungen von Ventilsteuerzeiten.Further advantages of the invention are achieved by the measures specified in the subclaims. It is particularly advantageous that different valve timing can be determined by recognizing the various associated characteristic events. Some valve timing can also be recognized by evaluating the combustion chamber pressure curve in the same way. A comparison with stored characteristic values typical of internal combustion engines enables engine-specific determinations of valve timing.

Eine Weiterverarbeitung des Brennraumdrucksignales vor der weiteren Auswertung, also beispielsweise eine Differentiation oder eine Integration des Brennraumdruckverlaufs ermöglicht in vorteilhafter Weise weitere Ventilsteuerzeitermittlungen. Die Berücksichtigung zusätzlicher Betriebsbedingungen der Brennkraftmaschine wie beispielsweise die Berücksichtigung des Auftretens von klopfender Verbrennung und die daraus folgende zusätzliche Signalverarbeitung, beispielsweise eine Mittelwertbildung, lassen in vorteilhafter Weise auch dann noch Ventilsteuerzeiten ermitteln, wenn schwierige Bedingungen bzw. Betriebszustände der Brennkraftmaschine auftreten.Further processing of the combustion chamber pressure signal before further evaluation, that is to say, for example, differentiation or integration of the combustion chamber pressure curve, advantageously enables further valve timing determinations. Taking into account additional operating conditions of the internal combustion engine, such as taking into account the occurrence of knocking combustion and the resulting additional signal processing, for example averaging, can also advantageously determine valve timing when difficult conditions or operating states of the internal combustion engine occur.

Zeichnungdrawing

Ein Ausführungsbeispiel der Erfindung ist in den Figuren der Zeichnung dargestellt und wird in der nachfolgenden Beschreibung näher erläutert. Im einzelnen zeigt Figur 1 eine an sich schon bekannte Einrichtung zur Erfassung des Druckverlaufs in den Zylindern einer Brennkraftmaschine. In Figur 1a sind relevante Teile der Brennkraftmaschine dargestellt. Figur 2 zeigt einen charakteristischen Brennraumdruckverlauf über dem Kurbelwellenwinkel. In Figur 3 ist ein Flußdiagramm eines erfindungsgemäßen Auswerteverfahrens dargestellt und die Figuren 4, 5 und 6 zeigen verschiedene Zusammenhänge zwischen Brennraumdruck, Brennraumvolumen und Kurbelwellenwinkel.An embodiment of the invention is shown in the figures of the drawing and is explained in more detail in the following description. In detail, FIG. 1 shows a device, known per se, for detecting the pressure curve in the cylinders of an internal combustion engine. Relevant parts of the internal combustion engine are shown in FIG. 1a. Figure 2 shows a characteristic combustion chamber pressure curve over the crankshaft angle. In Figure 3 is a flow diagram of an inventive Shown evaluation method and Figures 4, 5 and 6 show different relationships between combustion chamber pressure, combustion chamber volume and crankshaft angle.

In Figur 1 sind die wesentlichsten Bestandteile einer Einrichtung zur Erfassung des Brennraumdrucks in jedem Zylinder einer Brennkraftmaschine dargestellt. Dabei sind in den Zylindern 10, 11, 12 und 13 einer Vierzylinderbrennkraftmaschine jeweils Zylinderdrucksensoren 14, 15, 16 und 17 angeordnet, die die Druckverläufe P1, P2, P3 und P4 ermitteln. Zusätzlich ist ein Kurbelwellensensor 18 vorhanden, der ein für die Kurbelwellenstellung α charakteristisches Ausgangssignal S1 abgibt.1 shows the most important components of a device for detecting the combustion chamber pressure in each cylinder of an internal combustion engine. Cylinder pressure sensors 14, 15, 16 and 17 are arranged in the cylinders 10, 11, 12 and 13 of a four-cylinder internal combustion engine, which determine the pressure profiles P1, P2, P3 and P4. In addition, there is a crankshaft sensor 18 which emits an output signal S1 which is characteristic of the crankshaft position α.

Sowohl die Ausgangssignale der Zylinderdrucksensoren 14, 15, 16 und 17 als auch das Ausgangssignal des Kurbelwellensensors 18 werden dem Steuergerät 19 der Brennkraftmaschine zugeführt, das diese Signale verarbeitet. Über Eingänge 20 können dem Steuergerät weitere Signale (z.B. eine Temperatur T, eine Last L usw.)zugeführt werden, die im Steuergerät ebenfalls weiterverarbeitet werden können.Both the output signals of the cylinder pressure sensors 14, 15, 16 and 17 and the output signal of the crankshaft sensor 18 are fed to the control unit 19 of the internal combustion engine, which processes these signals. Further signals (e.g. a temperature T, a load L, etc.) can be fed to the control unit via inputs 20, which signals can also be further processed in the control unit.

Das Steuergerät 19 umfaßt einen Multiplexer 21, über den wahlweise das Ausgangssignal der Zylinderdrucksensoren zu einem Analog/Digitalwandler 22 geführt werden. Die Umschaltung des Multiplexers 21 erfolgt kurbelwellenwinkelabhängig und wird durch entsprechende Ansteuerungen vom Steuergerät 19 ausgelöst. Die eigentliche Auswertung der Signale erfolgt in einem Mikroprozessor 23 des Steuergerätes 19, der über eine Ausgabeeinheit 23a in Abhängigkeit von den ermittelten Größen Steuersignale S2 und S3 an verschiedene Komponenten der Brennkraftmaschine, beispielsweise Zünd-/ oder Einspritzsignale abgeben kann.The control unit 19 comprises a multiplexer 21, via which the output signal of the cylinder pressure sensors can optionally be led to an analog / digital converter 22. The switching of the multiplexer 21 is dependent on the crankshaft angle and is triggered by the control unit 19 by means of appropriate controls. The actual evaluation of the signals takes place in a microprocessor 23 of the control device 19, which can output control signals S2 and S3 to various components of the internal combustion engine, for example ignition or injection signals, via an output unit 23a depending on the quantities determined.

Im Mikroprozessor 23 des Steuergerätes 19 erfolgt die Signalverarbeitung, anhand derer auf die Ventilsteuerzeiten geschlossen werden kann, bzw. anhand derer die Ventilsteuerzeiten ermittelt werden.In the microprocessor 23 of the control unit 19, the signal processing takes place, on the basis of which the valve timing can be deduced, or on the basis of which the valve timing can be determined.

In Figur 3 ist ein Auswerteschema dargestellt, bei dem jeweils im Schritt SCH1 der Druck aus dem Sensorsignal berechnet wird. Im Schritt SCH2 wird der Kurbelwellenwinkel α eingelesen, sodaß im Schritt SCH3 der Bezug P(α) vorliegt. Im Schritt SCH4 wird der Druckverlauf ausgewertet, eventuell unter Berücksichtigung abgespeicherter Daten und im Schritt SCH5 wird auf die betreffende Ventilsteuereinheit geschlossen.FIG. 3 shows an evaluation scheme in which the pressure is calculated from the sensor signal in step SCH1. The crankshaft angle α is read in step SCH2, so that the reference P (α) is present in step SCH3. The pressure curve is evaluated in step SCH4, possibly taking into account stored data, and in step SCH5 the relevant valve control unit is inferred.

Dem Zylinder einer Brennkraftmaschine, beispielsweise dem Zylinder 10 (Fig. 1a) wird das Kraftstoff Luftgemisch durch Öffnen des Einlaßventils 24 zugeführt. Dabei wird bekanntermaßen der Kraftstoff vom Einspritzventil 25 vor das Einlaßventil 24 in das Saugrohr 26 eingespritzt und über die Zündkerze 27 gezündet. Über ein Auslaßventil 28 kann das im Zylinder erzeugte Gas ausgelassen werden. Die Ansteuerung des Einlaßventils und des Auslaßventils erfolgt in bekannter Weise mit Hilfe der nicht dargestellten Nockenwelle bzw. der Nockenwellen. Die Nockenwelle bzw. die Nockenwellen werden von der Kurbelwelle in bekannter Weise angetrieben. Die Lage der Nockenwelle bzw. der Nockenwellen bezogen auf die Kurbelwelle kann durch entsprechende Ansteuersignale S3 vom Steuergerät 19 drehzahlabhängig verändert werden. Durch die erfindungsgemäße Erfassung der Ventilsteuerzeiten in Abhängigkeit vom Kurbelwellenwinkel kann die Zuordnung zwischen Nockenwellenlage und Kurbelwellenlage bestimmt werden.The fuel air mixture is supplied to the cylinder of an internal combustion engine, for example the cylinder 10 (FIG. 1a), by opening the intake valve 24. As is known, the fuel is injected from the injection valve 25 upstream of the inlet valve 24 into the intake manifold 26 and ignited via the spark plug 27. The gas generated in the cylinder can be discharged via an outlet valve 28. The intake valve and the exhaust valve are actuated in a known manner with the aid of the camshaft or camshafts, not shown. The camshaft or the camshafts are driven in a known manner by the crankshaft. The position of the camshaft or camshafts in relation to the crankshaft can be changed by the control unit 19 as a function of the speed by means of corresponding control signals S3. The assignment between the camshaft position and the crankshaft position can be determined by the inventive detection of the valve timing as a function of the crankshaft angle.

In Figur 2 ist der Verlauf des Brennraumdruckes P1 des Zylinders 10 über dem Kurbelwellenwinkel α aufgetragen. Der Zylinderdruck erreicht zwei Maximalwerte, die ein Arbeitsspiel oder 720°KW auseinander liegen. Das Maximum des Brennraumdrucks ist in dem Bereich, in dem eine Verbrennung stattfindet, höher als in dem Bereich, in dem ausschließlich eine Kompression auftritt. Eine Verbrennung findet im Beispiel nach Figur 2 in der Phase Ve statt. In der Phase Ko tritt lediglich eine Kompression auf.In Figure 2, the course of the combustion chamber pressure P1 of the cylinder 10 is plotted against the crankshaft angle α. The cylinder pressure reaches two maximum values that are one working cycle or 720 ° KW apart. The maximum of the combustion chamber pressure is higher in the area in which combustion takes place than in the area in which only compression occurs. In the example according to FIG. 2, combustion takes place in phase Ve. In phase Ko only compression occurs.

Der in Figur 2 schematisch dargestellte Brennraumdruckverlauf wird erfindungsgemäß nach verschiedenen Kriterien ausgewertet, um daraus auf Ereignisse zu schließen, die kennzeichnend für die Nockenwellenlage in Bezug auf die Kurbelwellenlage und damit für die Ventilsitzsteuerzeiten sind. Ein solches Ereignis kann beispielsweise die Kurbelwellenlage, bei der das Einlaßventil schließt, sein. Andere Ventilsteuerzeiten sind die Steuerzeiten Auslaß öffnet. Einlaß öffnet, Auslaß schließt. Für jede Ventilsteuerzeit gibt es im Druckverlauf charakteristische bzw. kennzeichnende Merkmale, deren Auswertung im folgenden näher beschrieben wird.The combustion chamber pressure curve shown schematically in FIG. 2 is evaluated according to the invention according to various criteria in order to infer events that are characteristic of the camshaft position in relation to the crankshaft position and thus of the valve seat control times. Such an event can be, for example, the crankshaft position at which the intake valve closes. Other valve timings include the exhaust timings. Inlet opens, outlet closes. For each valve timing there are characteristic or characterizing features in the pressure curve, the evaluation of which is described in more detail below.

Zur Detektierung der Ventilsteuerzeit "Auslaß öffnet" kann die Expansionslinie des Brennraumdruckverlaufs ausgewertet werden. Solange das Auslaßventil geschlossen ist, handelt es sich bei den Vorgängen im Zylinder um ein thermodynamisch geschlossenes System, so daß die Vorgänge nach thermodynamischen Gesetzmäßigkeiten berechnet werden können. Bei zunehmendem Volumen tritt eine Druckabnahme auf, die sich ähnlich einer polytropen Expansion einstellt. Charakteristisch dafür ist, daß der Betrag des Druckgradienten mit zunehmendem Volumen abnimmt. Wird das Auslaßventil geöffnet, so strömt bedingt durch den gegenüber der Umgebung noch erhöhten Druck Gas aus dem Zylinder aus.The expansion line of the combustion chamber pressure curve can be evaluated in order to detect the valve control time "outlet opens". As long as the exhaust valve is closed, the processes in the cylinder are a thermodynamically closed system, so that the processes can be calculated according to thermodynamic laws. With increasing volume, there is a decrease in pressure, which occurs similar to a polytropic expansion. It is characteristic of this that the amount of the pressure gradient decreases with increasing volume. If the outlet valve is opened, gas flows out of the cylinder due to the pressure, which is still higher than the environment.

Dadurch nimmt der Betrag des Druckgradienten zu. Als Kennzeichen bzw. charakteristisches Verhalten des Druckverlaufs kann somit die Auswertung des Druckgradienten für die erfolgte Auslaßöffnung herangezogen werden. Weist der Druckgradient ein Verhalten auf, das sich auszeichnet durch eine geringerwerdende Abnahme und eine plötzliche Vergrößerung des Betrages des Druckgradienten, kann auf die erfolgte Auslaßöffnung geschlossen werden. Mathematisch kann die Auswertung erfolgen, indem beispielsweise ein Vorzeichenwechsel in der zweiten Ableitung des Drucks nach dem Volumen abgeprüft wird. Tritt ein solcher Vorzeichenwechsel in der zweiten Ableitung des Drucks nach dem Kurbelwinkel auf, kann auf eine erfolgte Auslaßöffnung geschlossen werden. In Figur 4, die den Zusammenhang zwischen Druck P und Volumen V zwischen dem oberen Totpunkt OT und dem unteren Totpunkt UT wiedergibt, würde der Punkt A1 die erfolgte Auslaßöffnung bezeichnen. An dieser Stelle gilt, daß die zweite Ableitung des Drucks nach dem Volumen d 2 P dν einen Vorzeichenwechsel aufweist. Dies gilt auch für den Zusammenhang d 2 P dα 2 .This increases the amount of the pressure gradient. The evaluation of the pressure gradient for the outlet opening that has taken place can thus be used as a characteristic or characteristic behavior of the pressure curve. If the pressure gradient exhibits a behavior which is characterized by a decreasing decrease and a sudden increase in the amount of the pressure gradient, it can be concluded that the outlet opening has taken place. The evaluation can be carried out mathematically, for example by checking a sign change in the second derivative of the pressure according to the volume. If such a change of sign occurs in the second derivative of the pressure after the crank angle, it can be concluded that the outlet has been opened. In FIG. 4, which shows the relationship between pressure P and volume V between top dead center OT and bottom dead center UT, point A1 would indicate the outlet opening that has taken place. At this point, the second derivative of pressure is by volume d 2 P dv has a change of sign. This also applies to the context d 2 P d.alpha 2 ,

Zur Detektierung der Ventilsteuerzeit "Einlaß schließt" wird das Volumen bzw. der Kurbelwinkel detektiert, an dem die Kompressionslinie ein bekanntes, festes Niveau durchläuft. Im einfachsten Fall wird dieses Vergleichsniveau aus dem Druckverlauf während des Ausschiebens gewonnen. Die Lage des Schnittpunkts A2 zwischen Kompressionsdruckverlauf und Druckverlauf während des Ausschiebens im Kurbelwinkelmuster bzw. im Volumenverlauf läßt sich Figur 5 entnehmen. Sie ist zwar kein direktes Maß für die Ventilsteuerzeit "Einlaß schließt" , verschiebt sich jedoch bei einer Änderung des Schließens des Einlaßventils. Somit kann ein Sollwert für die Lage des Punktes A2 in Abhängigkeit von Last und Drehzahl motorabhängig appliziert werden. Zur Diagnose wird dann die Abweichung des Istwertes des Punktes A2 vom Sollwert herangezogen. Die Aufnahme der motorspezifischen Daten kann vor einer Inbetriebnahme beispielsweise in einem Prüfstand erfolgen. Die dabei gewonnen Daten werden in Speichern beispielsweise des Steuergerätes abgelegt, das jederzeit auf diese Daten zurückgreifen kann.To detect the valve timing "inlet closes", the volume or crank angle is detected at which the compression line passes a known, fixed level. In the simplest case, this comparison level is obtained from the pressure curve during the extension. The position of the intersection A2 between the compression pressure curve and the pressure curve during extension in the crank angle pattern or in the volume curve can be seen in FIG. 5. Although it is not a direct measure of the valve timing "intake closes", it shifts when the intake valve closes. A setpoint for the position of point A2 can thus be applied depending on the load and the speed of the motor become. The deviation of the actual value of point A2 from the target value is then used for diagnosis. The engine-specific data can be recorded, for example, in a test bench before commissioning. The data obtained in this way are stored in memories of, for example, the control unit, which can access this data at any time.

Die Auswertung des Brennraumdruckverlaufs ist nicht nur auf den Druck-Volumen-Zusammenhang beschränkt, sondern es ist auch eine Auswertung anhand des Druck-Kurbelwinkel-Zusammenhangs möglich. Durch Auswertung der Lage der Punkte A3 und A4 nach Figur 6 lassen sich entsprechende Rückschlüsse ziehen. In Figur 6 ist im übrigen der Brennraumdruck P über dem Kurbelwellenwinkel α aufgetragen. Zusätzlich sind die Lastwechsel OT-Punkte LWOT, ein Zünd-OT-Punkt ZOT, untere Totpunkte UT sowie Winkeln α3, β3 sowie α4, β4 eingetragen, wobei der Winkel α3 bzw. α4 jeweils den Abstand zwischen dem unteren Totpunkt UT und dem Punkt A3 bzw. A4 definiert, der Winkel β3 den Abstand zwischen A3 und ZOT und der Winkel β4 den Abstand zwischen A4 und LWOT definiert. Wenn der Druck an der Stelle A3 gleich dem Druck an der Stelle A4 ist, gilt für die Winkel α3=α4 und β3=β4.The evaluation of the combustion chamber pressure curve is not only limited to the pressure-volume relationship, but an evaluation based on the pressure-crank angle relationship is also possible. By evaluating the position of points A3 and A4 according to FIG. 6, appropriate conclusions can be drawn. 6, the combustion chamber pressure P is plotted against the crankshaft angle α. In addition, the load change TDC points LWOT, an ignition TDC point ZOT, bottom dead center UT and angles α3, β3 and α4, β4 are entered, the angle α3 and α4 in each case the distance between bottom dead center UT and point A3 or A4 defines, the angle β3 defines the distance between A3 and ZOT and the angle β4 defines the distance between A4 and LWOT. If the pressure at point A3 is equal to the pressure at point A4, the angles α3 = α4 and β3 = β4 apply.

Falls eine Auswertung des Brennraumdruckverlaufs während des Ausschiebens der im Zylinder befindlichen Verbrennungsgase nicht möglich ist, beispielsweise wenn der Brennraumdrucksensor infolge der hohen Verbrennungstemperatur durch thermoschockbedingte Kurzzeitdrift nur ungenaue Signale liefert, kann die Auswertung des Brennraumdruckverlaufs auch ersatzweise durch Vergleich mit dem Umgebungsdruck durchgeführt werden. Beispielsweise kann zur Erkennung der Ventilsteuerzeit "Einlaßventil schließt Einlaßventil" das Volumen bzw. der Kurbelwellenwinkel detektiert werden, bei dem der Kompressionsdruck gleich dem Umgebungsdruck ist. In diesem Fall wird der Punkt A3 als Schnittpunkt des Kompressionsdruckverlaufs mit dem Umgebungsdruck definiert. Damit wird jedoch eine Nullniveaukorrektur des Druckverlaufs notwendig, dies erhöht den Rechenaufwand und kann unter Umständen zu Fehlmessungen führen.If it is not possible to evaluate the combustion chamber pressure curve while the combustion gases in the cylinder are being pushed out, for example if the combustion chamber pressure sensor only provides inaccurate signals due to the high combustion temperature due to thermal shock-related short-term drift, the combustion chamber pressure curve can also be evaluated as a substitute by comparison with the ambient pressure. For example, to detect the valve timing "intake valve closes intake valve" the volume or the crankshaft angle at which the Compression pressure is equal to the ambient pressure. In this case, point A3 is defined as the point of intersection of the compression pressure curve with the ambient pressure. However, this means that a zero level correction of the pressure curve is necessary, this increases the computational effort and can under certain circumstances lead to incorrect measurements.

Falls Meßwerte des Umgebungsdrucks nicht zur Verfügung stehen oder falls es keinen Schnittpunkt zwischen dem Umgebungsdruck und der Kompressionslinie gibt, beispielsweise ist dies bei aufgeladenen Motoren der Fall, kann eine Auswertung des Brennraumdruckverlaufs auch noch anhand eines Druckfestwertes erfolgen. In diesem Fall sind jedoch spezielle Diagnosestrategien erforderlich, die eine Fehldiagnose bedingt durch eine starke Änderung des Umgebungsdrucks, beispielsweise bei einer Höhenfahrt verhindert. Falls vom Steuergerät eine solche Höhenfahrt, beispielsweise im Zusammenhang mit anderen Auswertungen zur Regelung der Brennkraftmaschine erkannt wird, kann eine Erkennung von Ventilsteuerzeiten zumindest zeitweise unterbunden werden.If measured values of the ambient pressure are not available or if there is no point of intersection between the ambient pressure and the compression line, for example in the case of supercharged engines, the course of the combustion chamber pressure can also be evaluated on the basis of a fixed pressure value. In this case, however, special diagnostic strategies are required which prevent incorrect diagnosis due to a strong change in the ambient pressure, for example when driving at high altitude. If the control device detects such a high travel, for example in connection with other evaluations for regulating the internal combustion engine, the detection of valve timing can be prevented at least temporarily.

Werden Ventilsteuerzeiten verändert, beispielsweise durch entsprechende Veränderung der Nockenwellenstellungen, führt dies auch zu einer Änderung des Brennraumdruckverlaufs während der Kompressionsphase, während der Verbrennungsphase und während der Expansionsphase. Beispielsweise werden durch Veränderung der Nockenwellenstellung die Ventilsteuerzeiten so verändert, daß sich der Restgasgehalt der Zylinderladung in charakteristische Weise ändert. Ein höherer Restgasgehalt, der beispielsweise durch spätes Schließen des Auslaßventils oder frühes Öffnen des Einlaßventils, jeweils bezogen auf den Kurbelwellenwinkel, bedingt sein kann, erhöht sowohl den Absolutdruck als auch den Druckgradienten während der Kompressionsphase bei angenommener gleicher Frischluftmassenzufuhr. Bei angenommenem gleichen Zündzeitpunkt wird die Verbrennung verspätet beginnen, mit den entsprechenden Auswirkungen auf die die Verbrennung und die Expansion beschreibenden Kennwerte. Sind verschiedene motorspezifische Kennwerte bzw. Kennfelder in Speichern des Steuergerätes abgelegt, kann jederzeit auf diese Kennwerte bzw. Kennfelder zurückgegriffen werden. Ein Vergleich mit dem gemessenen Zylinderdruckverlauf ergibt bei Kenntnis der motorspezifisch vorhandenen Zusammenhänge, beispielsweise auch mit ermittelten mathematischen Zusammenhängen, ein Rückschließen, welche der Ventilsteuerzeiten vorliegen. Während des Motorbetriebs können Kennwerte adaptiert werden. Aus den adaptierten Kennwerten läßt sich ebenfalls auf die aktuellen Ventilsteuerzeiten rückschließen. Auch die Streuung der die Verbrennung kennzeichnenden Größen von Zyklus zu Zyklus bei fremdgezündeten Motoren mit steigendem Restgasgehalt zunimmt, läßt sich eine weitere Auswertemöglichkeit für den Verbrennungsdruckverlauf darstellen. Damit ist die Möglichkeit gegeben, aus der Streuung der Kennwerte über motorspezifisch ermittelte Kennfelder bzw. Kennlinien, motorspezifisch ermittelte mathematische Zusammenhänge oder während des Motorbetriebs adaptierte Kennwerte auf die Ventilsteuerzeiten rückzuschließen.If valve timing is changed, for example by a corresponding change in the camshaft positions, this also leads to a change in the course of the combustion chamber pressure during the compression phase, during the combustion phase and during the expansion phase. For example, the valve timing is changed by changing the camshaft position so that the residual gas content of the cylinder charge changes in a characteristic manner. A higher residual gas content, which may be caused, for example, by late closing of the exhaust valve or early opening of the intake valve, in each case based on the crankshaft angle, increases both the absolute pressure and the pressure gradient during the compression phase, assuming the same Fresh air mass intake. Assuming the same ignition point, the combustion will start late, with the corresponding effects on the characteristic values describing the combustion and the expansion. If various engine-specific parameters or maps are stored in the memory of the control unit, these parameters or maps can be accessed at any time. A comparison with the measured cylinder pressure curve reveals, based on knowledge of the engine-specific relationships, for example also with determined mathematical relationships, which valve control times are available. Characteristic values can be adapted during engine operation. The current valve timing can also be deduced from the adapted characteristic values. Another variation of the combustion pressure curve can also be shown, as the residual gas content increases with increasing residual gas content. This provides the possibility of inferring the valve timing from the scatter of the characteristic values via engine-specific maps or characteristic curves, engine-specific mathematical relationships or parameters adapted during engine operation.

Eine Kombination der vorstehend erwähnten Auswertemöglichkeiten ist jederzeit möglich. Weiterhin ist es möglich, sowohl bei der Auswertung der Druckgradienten als auch bei der Auswertung des Druckmaximums, der Lage des Druckmaximums sowie generell bei der Auswertung einzelner Druckverläufe zunächst eine Mittelwertbildung, beispielsweise über mehrere Motorzyklen durchzuführen und die Mittelwerte des Brennraumdruckverlaufs auf bestimmte Ventilsteuerzeiten kennzeichnende Größen zu untersuchen. Dabei sind wiederum jeweils motorspezifisch ermittelte und als Kennfeld oder Kennlinie abgelegte Zusammenhänge oder mathematische Zusammenhänge zu berücksichtigen. Zur Detektierung wenigstens einer der Ventilsteuerzeiten "Auslaß öffnet" , "Auslaß schließt" , "Einlaß schließt" oder "Einlaß öffnet" kann auch zunächst ein definiertes Brennraumdruckintegral oder ein Differenzbrennraumdruckintegral gebildet werden, wobei die Integrationsgrenzen geeignet zu wählen sind und insbesonders so gelegt werden, daß ventilsteuerzeittypische Phasen zusammengefaßt werden.A combination of the evaluation options mentioned above is possible at any time. Furthermore, it is possible both to evaluate the pressure gradients and to evaluate the pressure maximum, the position of the pressure maximum and generally when evaluating individual pressure profiles, for example to carry out an averaging, for example over several engine cycles, and to assign the characteristic values of the combustion chamber pressure curve to specific parameters investigate. Again, engine-specific and to consider relationships or mathematical relationships stored as a map or characteristic curve. In order to detect at least one of the valve control times "outlet opens", "outlet closes", "inlet closes" or "inlet opens", a defined combustion chamber pressure integral or a differential combustion chamber pressure integral can also first be formed, the integration limits being selected appropriately and in particular being set in such a way that that phases typical of valve timing are combined.

Eine weitere Möglichkeit zur Detektierung der Ventilsteuerzeiten besteht darin, aus dem Auftreten von Schwingungen im Brennraumdruckverlauf in Folge klopfender Verbrennung oder aus der Notwendigkeit von Gegenmaßnahmen zur Vermeidung klopfender Verbrennung, welche wiederum aufgrund von Druckschwingungen im Brennraumdruckverlauf ergriffen werden, kennzeichnende Größen für bestimmte Ventilsteuerzeiten abzuleiten. Dabei kann wiederum eine zusätzliche Mittelwertbildung durchgeführt werden.Another possibility for detecting the valve timing is to derive characteristic quantities for certain valve timing from the occurrence of vibrations in the combustion chamber pressure curve as a result of knocking combustion or from the need for countermeasures to avoid knocking combustion, which in turn are taken due to pressure fluctuations in the combustion chamber pressure curve. An additional averaging can be carried out.

Die Erfindung läßt sich bei Brennkraftmaschinen mit beliebiger Zylinderzahl einsetzen, wobei die zahl der Zylinderdrucksensoren beispielsweise der Zahl der Zylinder oder der halben Zahl entspricht. In einer vereinfachten Version kann wenigstens ein Sensor eingesetzt werden. Als Sensoren können auch Klopfsensoren eingesetzt werden bzw. beliebige Verbrennungsablaufsensoren, aus deren Ausgangssignal für Ventilsteuerzeiten charakteristische Merkmale gewonnen werden können.The invention can be used in internal combustion engines with any number of cylinders, the number of cylinder pressure sensors corresponding, for example, to the number of cylinders or half the number. In a simplified version, at least one sensor can be used. Knock sensors or any combustion sequence sensors from whose output signal for valve timing characteristic features can be obtained can also be used as sensors.

Claims (15)

  1. Method of evaluating the combustion-chamber pressure in an internal combustion engine, having at least one cylinder pressure sensor which measures the cylinder pressure, and a crankshaft angle sensor which delivers a signal representative of the crankshaft position, and an evaluating arrangement which comprises at least one microprocessor and to which the signals of the sensors are fed, the microprocessor, from the combustion-chamber pressure profile as a function of the crankshaft angular position, inferring the occurrence of at least one of the valve control times "exhaust opening", "exhaust closing", "inlet opening", "inlet closing" with regard to the crankshaft angular position, characterized in that the measurements are taken during the normal operation of the internal combustion engine and combustion-chamber pressure profiles occurring in the process or events which depend on the combustion-chamber pressure profile and characterize the valve control times are evaluated.
  2. Method according to Claim 1, characterized in that the valve control time "exhaust opening" is inferred if the expansion line of the combustion-chamber pressure profile changes in such a way that the change in the pressure gradient with increasing volume or with increasing crankshaft angle changes the mathematical sign.
  3. Method according to Claim 1, characterized in that, to identify "inlet closing", the volume or the crankshaft angle at which the compression pressure is equal to the pressure which was present during the exhaust at the same distance from the top dead centre is detected.
  4. Method according to Claim 1 or 2, characterized in that, to determine the valve control time "inlet closing", the volume or the crankshaft angle at which the compression pressure is equal to the ambient pressure is detected.
  5. Method according to Claim 1 or 2, characterized in that, to identify the valve control time "inlet closing", the volume or the crankshaft angle at which the compression pressure is equal to a predeterminable fixed pressure is detected.
  6. Method according to Claim 1, characterized in that, to determine the valve control times "exhaust closing", "inlet closing" or "inlet opening", the absolute pressure level during the compression before the start of the combustion is evaluated, and the valve control times are inferred either from an individual pressure profile or from a pressure profile averaged over a plurality of cycles, by comparison with data determined in an engine-specific manner and filed as a characteristic map or as a characteristic curve, or with mathematical relationships determined in an engine-specific manner, or with adapted conversion factors.
  7. Method according to Claim 1, characterized in that, to identify at least one valve control time, the combustion pressure gradient during the compression before the start of the combustion or a polytropic exponent calculated therefrom is evaluated, the valve control time being inferred from the individual pressure profile or from a pressure profile averaged over a plurality of cycles, via conversions determined in an engine-specific manner and filed as a characteristic map or as a characteristic curve, or via mathematical relationships determined in an engine-specific manner, or via adapted conversion factors.
  8. Method according to Claim 1, characterized in that the valve control times "exhaust closing", "inlet opening" or "inlet closing" are inferred from the absolute pressure level or from the pressure gradient during the expansion before the opening of the exhaust valve, or from a polytropic exponent calculated from the pressure gradient, either from an individual pressure profile or from a pressure profile averaged over a plurality of cycles, via conversions determined in an engine-specific manner and filed as a characteristic map or as a characteristic curve, via mathematical relationships determined in an engine-specific manner, or via adapted conversion factors.
  9. Method according to Claim 1, characterized in that the valve control times "exhaust closing", "inlet opening" or "inlet closing" are inferred from the position of the maximum pressure increase, either from an individual pressure profile or from a pressure profile averaged over a plurality of cycles, via conversions determined in an engine-specific manner and filed as a characteristic map or as a characteristic curve, via mathematical relationships determined in an engine-specific manner, or via adapted conversion factors.
  10. Method according to Claim 1, characterized in that, to detect the valve control times, at least one of the following variables is used:
    spread of the position of the maximum pressure increase over a plurality of cycles,
    maximum pressure gradient which occurs from an individual pressure profile or from a pressure profile averaged over a plurality of cycles,
    spread of the maximum pressure gradient which occurs over a plurality of cycles,
    position of the maximum pressure from an individual pressure profile or from a pressure profile averaged over a plurality of cycles,
    spread of the position of the maximum pressure over a plurality of cycles,
    level of the maximum pressure from an individual pressure profile or from a pressure profile averaged over a plurality of cycles,
    in which case conversions determined in an engine-specific manner and filed as a characteristic map or as a characteristic curve, mathematical relationships determined in an engine-specific manner, or adapted conversion factors are also taken into account for determining the valve control times.
  11. Method according to Claim 1, characterized in that the valve control times are inferred from one of the variables:
    spread of the position of certain sections of the energy transformation over a plurality of cycles,
    position of the maximum of the energy transformation from an individual pressure profile or from a pressure profile averaged over a plurality of cycles,
    spread of the position of the maximum of the energy transformation over a plurality of cycles,
    maximum gradient of the energy transformation from an individual pressure profile or from a pressure profile averaged over a plurality of cycles,
    and while taking into account conversions determined in an engine-specific manner and filed as a characteristic map or as a characteristic curve, mathematical relationships determined in an engine-specific manner, or adapted conversion factors.
  12. Method according to Claim 1, characterized in that one of the following variables is evaluated:
    indicated work from an individual pressure profile or from a pressure profile averaged over a plurality of cycles,
    spread of the indicated work over a plurality of cycles,
    indicated high-pressure work from an individual pressure profile or from a pressure profile averaged over a plurality of cycles,
    spread of the indicated high-pressure work over a plurality of cycles,
    indicated low-pressure work from an individual pressure profile or from a pressure profile averaged over a plurality of cycles,
    spread of the indicated low-pressure work over a plurality of cycles and via conversions determined in an engine-specific manner and filed as a characteristic map or as a characteristic curve, via mathematical relationships determined in an engine-specific manner, or via adapted conversion factors.
  13. Method according to Claim 1, characterized in that the combustion-chamber pressure is integrated over a predeterminable range or in that the combustion-chamber pressure difference is integrated over a predeterminable range, and either the integrals are formed from an individual pressure profile or from a pressure profile averaged over a plurality of cycles, and the valve control times are inferred via conversions determined in an engine-specific manner and filed as a characteristic map or as a characteristic curve, via mathematical relationships determined in an engine-specific manner, or via adapted conversion factors.
  14. Method according to Claim 13, characterized in that the valve control times are inferred from the spread of the integral or integrals over a plurality of cycles.
  15. Method according to Claim 1, characterized in that the valve control times are inferred from the occurrence of oscillations in the combustion-chamber pressure profile as a result of knocking combustion or from the need for countermeasures for avoiding knocking combustion, these countermeasures in turn being taken on account of pressure oscillations in the combustion-chamber profile, either from an individual pressure profile or from a pressure profile averaged over a plurality of cycles, via conversions determined in an engine-specific manner and filed as a characteristic map or as a characteristic curve, via mathematical relationships determined in an engine-specific manner, or via adapted conversion factors.
EP98958153A 1997-09-23 1998-09-22 Method for evaluating the march of pressure in a combustion chamber Expired - Lifetime EP1034416B2 (en)

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
DE19741820 1997-09-23
DE19741820A DE19741820B4 (en) 1997-09-23 1997-09-23 Method for evaluating the combustion chamber pressure profile
PCT/DE1998/002809 WO1999015872A2 (en) 1997-09-23 1998-09-22 Method for evaluating the march of pressure in a combustion chamber

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JP4392987B2 (en) 2010-01-06
US20010002587A1 (en) 2001-06-07
DE19741820A1 (en) 1999-03-25
WO1999015872A3 (en) 1999-06-03
WO1999015872A2 (en) 1999-04-01
US6276319B2 (en) 2001-08-21
JP2001517786A (en) 2001-10-09
EP1034416B2 (en) 2007-03-14
EP1034416A2 (en) 2000-09-13
DE59803230D1 (en) 2002-04-04
DE19741820B4 (en) 2009-02-12

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