EP2336532A2 - Method for detecting the readiness of a lambda probe for functions in selected operating phases - Google Patents
Method for detecting the readiness of a lambda probe for functions in selected operating phases Download PDFInfo
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- EP2336532A2 EP2336532A2 EP10193702A EP10193702A EP2336532A2 EP 2336532 A2 EP2336532 A2 EP 2336532A2 EP 10193702 A EP10193702 A EP 10193702A EP 10193702 A EP10193702 A EP 10193702A EP 2336532 A2 EP2336532 A2 EP 2336532A2
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- functions
- combustion engine
- lambda
- internal combustion
- lambda probe
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Classifications
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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
- F02D41/00—Electrical control of supply of combustible mixture or its constituents
- F02D41/02—Circuit arrangements for generating control signals
- F02D41/14—Introducing closed-loop corrections
- F02D41/1438—Introducing closed-loop corrections using means for determining characteristics of the combustion gases; Sensors therefor
- F02D41/1493—Details
- F02D41/1495—Detection of abnormalities in the air/fuel ratio feedback system
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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
- F02D41/00—Electrical control of supply of combustible mixture or its constituents
- F02D41/02—Circuit arrangements for generating control signals
- F02D41/04—Introducing corrections for particular operating conditions
- F02D41/12—Introducing corrections for particular operating conditions for deceleration
- F02D41/123—Introducing corrections for particular operating conditions for deceleration the fuel injection being cut-off
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
- F02D—CONTROLLING COMBUSTION ENGINES
- F02D41/00—Electrical control of supply of combustible mixture or its constituents
- F02D41/24—Electrical control of supply of combustible mixture or its constituents characterised by the use of digital means
- F02D41/2406—Electrical control of supply of combustible mixture or its constituents characterised by the use of digital means using essentially read only memories
- F02D41/2425—Particular ways of programming the data
- F02D41/2429—Methods of calibrating or learning
- F02D41/2441—Methods of calibrating or learning characterised by the learning conditions
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
- F02D—CONTROLLING COMBUSTION ENGINES
- F02D41/00—Electrical control of supply of combustible mixture or its constituents
- F02D41/24—Electrical control of supply of combustible mixture or its constituents characterised by the use of digital means
- F02D41/2406—Electrical control of supply of combustible mixture or its constituents characterised by the use of digital means using essentially read only memories
- F02D41/2425—Particular ways of programming the data
- F02D41/2429—Methods of calibrating or learning
- F02D41/2451—Methods of calibrating or learning characterised by what is learned or calibrated
- F02D41/2454—Learning of the air-fuel ratio control
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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
- F02D41/00—Electrical control of supply of combustible mixture or its constituents
- F02D41/02—Circuit arrangements for generating control signals
- F02D41/14—Introducing closed-loop corrections
- F02D41/1438—Introducing closed-loop corrections using means for determining characteristics of the combustion gases; Sensors therefor
- F02D41/1444—Introducing closed-loop corrections using means for determining characteristics of the combustion gases; Sensors therefor characterised by the characteristics of the combustion gases
- F02D41/1454—Introducing closed-loop corrections using means for determining characteristics of the combustion gases; Sensors therefor characterised by the characteristics of the combustion gases the characteristics being an oxygen content or concentration or the air-fuel ratio
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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
- F02D41/00—Electrical control of supply of combustible mixture or its constituents
- F02D41/24—Electrical control of supply of combustible mixture or its constituents characterised by the use of digital means
- F02D41/2406—Electrical control of supply of combustible mixture or its constituents characterised by the use of digital means using essentially read only memories
- F02D41/2425—Particular ways of programming the data
- F02D41/2429—Methods of calibrating or learning
- F02D41/2451—Methods of calibrating or learning characterised by what is learned or calibrated
- F02D41/2474—Characteristics of sensors
Definitions
- the invention relates to a method for detecting the operational readiness of a lambda probe for functions in selected operating phases of an internal combustion engine.
- the invention also provides a computer program and a computer program product which are suitable for carrying out the method.
- broadband lambda probes during a coasting phase, i. a phase in which a vehicle without drive moves in the thrust and the fuel supply is interrupted, for example, carried out a calibration of the signal of the probe. Since the oxygen concentration in the exhaust gas is known with sufficient accuracy during the thrust, it is possible to detect the deviation of the measured oxygen concentration from the expected and known oxygen concentration and to use it to calibrate the probe signal by ascertaining and correcting multiplicative sensor errors. Such functions will hereinafter be referred to as "lambda push functions" for short.
- Procedures for correcting the characteristic of a linear lambda probe go from DE 198 42 425 C2 or DE 10 2005 056 152 A1 out.
- the invention is therefore based on the object of specifying a method which provides a criterion for starting the lambda thrust functions.
- the basic idea of the invention is to make the release criterion of the lambda push function dependent on a dynamic diagnosis of the lambda probe.
- load-shear transition here e.g. the increase in measured oxygen concentration was evaluated to detect and evaluate the dynamic properties of the broadband lambda probe.
- this time gradient goes to zero, is on the presence of the operational readiness of the lambda probe for functions in the operating phase of the internal combustion engine, so closed, for example, for the presence of the operational readiness for the aforementioned lambda push functions.
- the rise time is a measure of the cutoff frequency of the probe. Their suitability for certain user functions depends on this. This rise time correlates e.g. directly with the permeability or sooting of the mentioned protective tube.
- the lambda push functions are therefore only released when the rise has reached its final value to a very good approximation, i. when the time gradient approaches zero. In this case, the acquired measured value corresponds to the oxygen concentration of fresh air in overrun mode.
- a particularly advantageous embodiment of the method can be used when the operating phase is the overrun operation of the internal combustion engine.
- the lambda push functions can be of different types. These are particularly advantageously calibration functions for calibrating the probe signal.
- the invention also provides a method for detecting the gas permeability of a protective tube surrounding a lambda probe.
- the time gradient of the signal of the lambda probe can likewise be used.
- the time gradient of the signal of the lambda probe is detected during a change of an operating phase of the internal combustion engine and closed due to a comparison of the time gradient of the lambda probe with a time gradient, which characterizes a gas-permeable protective tube on the permeability of the protective tube. If an impermeable protective tube is detected or a partially permeable protective tube, an error message can be output, for example.
- the computer program may be present as a computer program product with a program code stored on a machine-readable medium.
- This machine-readable carrier may be, for example, a DVD, CD or a flash memory or the like. In this way it is possible to "retrofit" the procedure for existing vehicles.
- Fig. 1 schematically an internal combustion engine 110 is shown, in the exhaust line 112, a catalyst 120 is arranged. Downstream of the catalyst, a lambda probe 130, for example, a known broadband lambda probe is arranged, the signal of which is supplied to a control unit 140.
- the control unit 140 controls, depending on this signal, the composition of the engine 110 supplied fuel air mixture, which in Fig. 1 schematically represented by an arrow 141.
- the shear phase plays a special role. During this coasting phase, the fuel supply is interrupted. Since the oxygen concentration in the exhaust gas is known with sufficient accuracy during the thrust, corresponding functions can evaluate the deviation of the measured oxygen concentration from the expected one.
- lambda push functions may be, for example, a push calibration.
- multiplicative sensor errors are determined and corrected by a comparison between the measured oxygen concentration and the known oxygen concentration of fresh air.
- the thrust functions are not released immediately after a change of the operating phase, thus for example during a load-thrust transition. Rather, the fresh air mass flow flowing through the internal combustion engine is first integrated and this integral compared with a predetermined empirically determined minimum value. Only when the minimum value is reached, the lambda push functions are released. This feature is a sort of "purge criterion" for the exhaust gas system.
- the invention now makes it possible to detect the operational readiness of a lambda probe for such functions in selected operating phases, for example in the overrun phase.
- it is proposed to make the release criterion of the probe dependent on a dynamic diagnosis. For example, in a transition from load operation to overrun, ie in a load-shear transition, for example, the time increase of the measured oxygen concentration is evaluated to detect and evaluate the dynamic properties of the broadband lambda probe.
- the signal S which characterizes the oxygen concentration
- curve 210 a sensor with gas-permeable exhaust pipe
- curve 240 partially fumed exhaust pipe
- the time t which elapses until the probe signal S no longer changes, the rise time, is in Fig. 2 for a probe with a free exhaust pipe with t1 and for a probe with partially fumed exhaust pipe with t2. These times respectively correspond to the point in which the time gradient of the probe signal tends to zero, ie in other words, the probe signal no longer changes over time.
- the presence of the operational readiness of the lambda probe for functions, in particular lambda push functions can be signaled.
- the lambda push functions should ideally be released and started only when the increase has reached its final value to a very good approximation.
- the then determined measured value corresponds in this case with the oxygen concentration of fresh air.
- the threshold for the integral will now be the fresh air mass flow is made dependent on the measured rise time.
- this rise time is t1
- this time is the time t2.
- This correlation between the threshold value of the integral of the fresh air mass flow and the measured rise time is advantageously realized as a characteristic element, ie the relationship is stored in a characteristic field whose input signal is a rise time and whose output signal is a fresh air mass.
- a characteristic element can also be provided in duplicate. This is useful, for example, when the internal combustion engine is operated at least temporarily with an exhaust gas recirculation open in the thrust. Since the exhaust gas recirculation has a significant influence on the dynamics of the oxygen concentration, it is expedient to provide different characteristics for the two cases, ie for the case with and for the case without exhaust gas recirculation.
- lambda sensors are installed in the exhaust system, e.g. one upstream and one downstream of the catalytic converter, or the internal combustion engine has a plurality of exhaust gas lines, correspondingly many characteristic elements are provided.
- a corresponding adjustment of the threshold would also be useful in an extension of the gas running time, for example, if a lambda probe is retrofitted downstream, for example, in the case of retrofitting exhaust aftertreatment components. Even if the increased gas running time were to be a fault sequence, it could be prevented by the method according to the invention that the emission deterioration exceeds a legally impermissible level.
- the method according to the invention has been explained above with reference to the pushing operation. However, the method is not limited to this. In principle, other operating phases can be provided outside of the thrust, for example, the release of functions that use the lambda signal and either expect a certain lambda value, or require a steady signal. Also in this case, the operational readiness can be delayed until a time gradient tends towards the value zero, ie be delayed in response to a dynamics monitoring.
- the invention also provides a method for detecting the gas permeability of a protective tube surrounding a lambda probe.
- the time gradient of the signal of the lambda probe is detected during a change of an operating phase of the internal combustion engine into a different, different operating phase, thus, for example, during a load-shear transition and due to a comparison of the time gradient of the lambda probe with a time gradient, which characterizes a gas-permeable protective tube. closed to the permeability of the protective tube.
- a time gradient 242 may be determined that is compared to a time gradient 212. Based on this comparison, the permeability of the thermowell can be deduced.
- the above method is advantageously implemented as a computer program on a computing device, in particular the control unit 140 of the internal combustion engine 110.
- the program code may be stored on a machine-readable carrier which the controller 140 may read. In this way, retrofits are possible.
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- Engineering & Computer Science (AREA)
- Chemical & Material Sciences (AREA)
- Combustion & Propulsion (AREA)
- Mechanical Engineering (AREA)
- General Engineering & Computer Science (AREA)
- Measuring Oxygen Concentration In Cells (AREA)
- Combined Controls Of Internal Combustion Engines (AREA)
- Electrical Control Of Air Or Fuel Supplied To Internal-Combustion Engine (AREA)
Abstract
Description
Die Erfindung betrifft ein Verfahren zur Erkennung der Betriebsbereitschaft einer Lambda-Sonde für Funktionen in ausgewählten Betriebsphasen einer Brennkraftmaschine.The invention relates to a method for detecting the operational readiness of a lambda probe for functions in selected operating phases of an internal combustion engine.
Gegenstand der Erfindung sind auch ein Computerprogramm und ein Computerprogrammprodukt, welche zur Durchführung des Verfahrens geeignet sind.The invention also provides a computer program and a computer program product which are suitable for carrying out the method.
Bei sogenannten Breitbandlambdasonden wird während einer Schubphase, d.h. einer Phase, in der sich ein Fahrzeug ohne Antrieb im Schub bewegt und die Kraftstoffzufuhr unterbrochen ist, beispielsweise eine Kalibrierung des Signals der Sonde vorgenommen. Da nämlich während des Schubs die Sauerstoffkonzentration im Abgas hinreichend genau bekannt ist, ist es möglich, die Abweichung der gemessenen Sauerstoffkonzentration von der erwarteten und bekannten Sauerstoffkonzentration zu erfassen und zur Kalibrierung des Sondensignals durch Ermittlung und Korrektur multiplikativer Sensorfehler heranzuziehen. Derartige Funktionen werden nachfolgend kurz als "Lambda-Schubfunktionen" bezeichnet.In so-called broadband lambda probes, during a coasting phase, i. a phase in which a vehicle without drive moves in the thrust and the fuel supply is interrupted, for example, carried out a calibration of the signal of the probe. Since the oxygen concentration in the exhaust gas is known with sufficient accuracy during the thrust, it is possible to detect the deviation of the measured oxygen concentration from the expected and known oxygen concentration and to use it to calibrate the probe signal by ascertaining and correcting multiplicative sensor errors. Such functions will hereinafter be referred to as "lambda push functions" for short.
Verfahren zur Korrektur der Kennlinie einer linearen Lambdasonde gehen beispielsweise aus der
Weitere Lambda-Schubfunktionen gehen beispielsweise aus der
Um die vorgenannten Lambda-Schubfunktionen durchführen zu können, muss sichergestellt sein, dass sich während der Schubphase, bei der die Kraftstoffzufuhr unterbrochen ist, kein Restabgas am Einbauort der Lambdasonde vorhanden ist. Aus diesem Grunde werden bei einem Übergang von einer Lastphase in eine Schubphase, bei einem sogenannten Last-Schub-Übergang, die vorgenannten Lambda-Schubfunktionen nicht sofort gestartet. Vielmehr wird zunächst der durch den Motor strömende Frischluftmassenstrom integriert und dieses Integral mit einem Mindestwert verglichen. Erst wenn dieser Schwellenwert erreicht wird, werden die Lambda-Schubfunktionen freigegeben. Dieses Funktionsmerkmal stellt gewissermaßen ein Spülkriterium für den Abgasstrang dar.In order to perform the aforementioned lambda thrust functions, it must be ensured that no residual exhaust gas is present at the installation location of the lambda probe during the overrun phase, in which the fuel supply is interrupted. For this reason, in a transition from a load phase to a boost phase, in a so-called load-thrust transition, the aforementioned lambda thrust functions are not started immediately. Rather, first of all the fresh air mass flow flowing through the engine is integrated and this integral is compared with a minimum value. Only when this threshold is reached, the lambda push functions are released. This feature is a kind of flushing criterion for the exhaust system.
Nun kann speziell beim Betrieb einer Lambdasonde in einem Dieselmotor der Fall eintreten, dass ein Schutzrohr, welches das Sensorelement umgibt, verrußt. Durch eine Rußablagerung wird der Gasaustausch im Schutzrohr erschwert. Es kann also der Fall eintreten, dass die Lambdasonde bereits von reiner Frischluft umgeben ist, jedoch im Schutzrohr noch eine gewisse Abgasmenge vorhanden ist. Das Sensorelement wird dann noch nicht mit der erwarteten und geforderten Sauerstoffkonzentration von Frischluft beaufschlagt. Wird eine Lambda-Schubfunktion in einer solchen Situation gestartet, ist die Genauigkeit dieser Funktion beeinträchtigt. Beispielsweise können Funktionen, die den Lambdawert und damit die erfasste Sauerstoffkonzentration verwenden, gestört sein, was wiederum zu einer Verschlechterung der Emissionen führen kann.Now, especially when operating a lambda probe in a diesel engine, it may happen that a protective tube surrounding the sensor element becomes sooty. By soot deposition of the gas exchange in the protective tube is difficult. It may thus happen that the lambda probe is already surrounded by pure fresh air, but in the protective tube still a certain amount of exhaust gas is present. The sensor element is then not yet subjected to the expected and required oxygen concentration of fresh air. If a lambda push function is started in such a situation, the accuracy of this function is impaired. For example, functions that use the lambda value and thus the detected oxygen concentration may be disturbed, which in turn may lead to a deterioration of emissions.
Der Erfindung liegt daher die Aufgabe zugrunde, ein Verfahren anzugeben, welches ein Kriterium für einen Start der Lambda-Schubfunktionen bereitstellt.The invention is therefore based on the object of specifying a method which provides a criterion for starting the lambda thrust functions.
Diese Aufgabe wird durch ein Verfahren mit den Merkmalen des Anspruchs 1 gelöst. Grundidee der Erfindung ist es, das Freigabekriterium der Lambda-Schubfunktion von einer Dynamikdiagnose der Lambdasonde abhängig zu machen. Bei einem beispielsweisen Last-Schubübergang wird hier z.B. der Anstieg der gemessenen Sauerstoffkonzentration ausgewertet, um die dynamischen Eigenschaften der Breitbandlambdasonde zu erfassen und zu bewerten. Ganz allgemein wird bei einem Übergang der Brennkraftmaschine von einer Betriebsphase in eine weitere ausgewählte, von der ersten unterschiedlichen Betriebsphase der Zeitgradient des die Sauerstoffkonzentration charakterisierenden Sondensignals erfasst und dann, wenn dieser Zeitgradient gegen null geht, wird auf das Vorliegen der Betriebsbereitschaft der Lambdasonde für Funktionen in der Betriebsphase der Brennkraftmaschine, also beispielsweise für das Vorliegen der Betriebsbereitschaft für die vorgenannten Lambda-Schubfunktionen geschlossen. Bei einem Last-Schubübergang, bei dem der Anstieg der gemessenen Sauerstoffkonzentration ausgewertet wird, um die dynamischen Eigenschaften der Breitbandlambdasonde zu erfassen und zu bewerten, ist beispielsweise die Anstiegszeit ein Maß für die Grenzfrequenz der Sonde. Ihre Eignung für bestimmte Anwenderfunktionen hängt hiervon ab. Diese Anstiegszeit korreliert z.B. unmittelbar mit der Durchlässigkeit bzw. Verrußung des erwähnten Schutzrohrs. Die Lambda-Schubfunktionen werden daher erst dann freigegeben, wenn der Anstieg in sehr guter Näherung seinen Endwert erreicht hat, d.h. wenn der Zeitgradient gegen Null geht. In diesem Falle korrespondiert der erfasste Messwert mit der Sauerstoffkonzentration von Frischluft im Schubbetrieb.This object is achieved by a method having the features of claim 1. The basic idea of the invention is to make the release criterion of the lambda push function dependent on a dynamic diagnosis of the lambda probe. In an example load-shear transition, here e.g. the increase in measured oxygen concentration was evaluated to detect and evaluate the dynamic properties of the broadband lambda probe. In general, during a transition of the internal combustion engine from one operating phase to another selected, from the first different operating phase of the time gradient of the oxygen concentration characterizing probe signal is detected and then when this time gradient goes to zero, is on the presence of the operational readiness of the lambda probe for functions in the operating phase of the internal combustion engine, so closed, for example, for the presence of the operational readiness for the aforementioned lambda push functions. For example, in a load-shear transition in which the increase in measured oxygen concentration is evaluated to detect and evaluate the dynamic characteristics of the broadband lambda probe, the rise time is a measure of the cutoff frequency of the probe. Their suitability for certain user functions depends on this. This rise time correlates e.g. directly with the permeability or sooting of the mentioned protective tube. The lambda push functions are therefore only released when the rise has reached its final value to a very good approximation, i. when the time gradient approaches zero. In this case, the acquired measured value corresponds to the oxygen concentration of fresh air in overrun mode.
Durch die in den abhängigen Ansprüchen aufgeführten Maßnahmen sind vorteilhafte Weiterbildungen und Verbesserungen des in dem unabhängigen Anspruch angegebenen Verfahrens möglich. Rein prinzipiell ist es möglich, das Verfahren auf Betriebsbereiche außerhalb des Schubs zu erweitern. In diesem Falle kann die Freigabe von Funktionen, die das Lambdasignal verwenden und die entweder einen bestimmten Lambdawert erwarten oder die ein eingeschwungenes Signal benötigen, ebenfalls verzögert werden in Abhängigkeit von der Anstiegszeit des Signals einer vorbeschriebenen Dynamiküberwachung.The measures listed in the dependent claims advantageous refinements and improvements of the method specified in the independent claim are possible. In principle, it is possible to extend the method to operating ranges outside the thrust. In this case, the release of functions that use the lambda signal and that either expect a certain lambda value or require a steady signal, may also be delayed depending on the rise time of the signal of a dynamic monitoring as described above.
Eine besonders vorteilhafte Ausgestaltung des Verfahrens kann zur Anwendung kommen, wenn die Betriebsphase der Schubbetrieb der Brennkraftmaschine ist. Die Lambda-Schubfunktionen können unterschiedlicher Art sein. Besonders vorteilhaft handelt es sich hierbei um Kalibrierungsfunktionen zur Kalibrierung des Sondensignals.A particularly advantageous embodiment of the method can be used when the operating phase is the overrun operation of the internal combustion engine. The lambda push functions can be of different types. These are particularly advantageously calibration functions for calibrating the probe signal.
Gegenstand der Erfindung ist auch ein Verfahren zur Erkennung der Gasdurchlässigkeit eines eine Lambdasonde umgebenden Schutzrohrs. Hierfür kann ebenfalls der Zeitgradient des Signals der Lambdasonde herangezogen werden. Erfindungsgemäß wird hierzu bei einem Wechsel einer Betriebsphase der Brennkraftmaschine in eine andere unterschiedliche Betriebsphase der Brennkraftmaschine der Zeitgradient des Signals der Lambdasonde erfasst und aufgrund eines Vergleichs des Zeitgradienten der Lambdasonde mit einem Zeitgradienten, der ein gasdurchlässiges Schutzrohr charakterisiert, auf die Durchlässigkeit des Schutzrohrs geschlossen. Wird ein undurchlässiges Schutzrohr erkannt oder ein nur partial durchlässiges Schutzrohr, kann beispielsweise eine Fehlermeldung ausgegeben werden.The invention also provides a method for detecting the gas permeability of a protective tube surrounding a lambda probe. For this purpose, the time gradient of the signal of the lambda probe can likewise be used. According to the invention, the time gradient of the signal of the lambda probe is detected during a change of an operating phase of the internal combustion engine and closed due to a comparison of the time gradient of the lambda probe with a time gradient, which characterizes a gas-permeable protective tube on the permeability of the protective tube. If an impermeable protective tube is detected or a partially permeable protective tube, an error message can be output, for example.
Da für die Durchführung des Verfahrens in Kraftfahrzeugen heute übliche Hardware verwendet wird und insoweit keine zusätzliche Hardware erforderlich ist, kann es sehr vorteilhaft als Computerprogramm ausgeführt sein, das in einem Steuergerät der Brennkraftmaschine implementiert ist. Das Computerprogramm kann als Computerprogrammprodukt mit einem Programmcode vorliegen, der auf einem maschinenlesbaren Träger gespeichert ist. Dieser maschinenlesbare Träger kann beispielsweise eine DVD, CD oder ein Flash-Speicher oder dergleichen sein. Auf diese Weise ist es möglich, das Verfahren bei bestehenden Fahrzeugen gewissermaßen "nachzurüsten".Since customary hardware is used today for carrying out the method in motor vehicles and so far no additional hardware is required, it can be implemented very advantageously as a computer program that is implemented in a control unit of the internal combustion engine. The computer program may be present as a computer program product with a program code stored on a machine-readable medium. This machine-readable carrier may be, for example, a DVD, CD or a flash memory or the like. In this way it is possible to "retrofit" the procedure for existing vehicles.
Ausführungsbeispiele der Erfindung werden nachfolgend in Verbindung mit den Zeichnungen näher erläutert.Embodiments of the invention will be explained in more detail below in conjunction with the drawings.
Es zeigen:
- Fig. 1
- schematisch die Anordnung einer Breitbandlambdasonde im Abgasstrang einer Brennkraftmaschine und
- Fig. 2
- den Signalverlauf einer Breitbandlambdasonde mit gasdurchlässigem Schutzrohr und einer Breitbandlambdasonde mit nur teilweise gasdurchlässigem Schutzrohr über der Zeit.
- Fig. 1
- schematically the arrangement of a broadband lambda probe in the exhaust system of an internal combustion engine and
- Fig. 2
- the waveform of a broadband lambda probe with gas-permeable protective tube and a broadband lambda probe with only partially gas-permeable protective tube over time.
In
Nun ist es bei einem Betrieb der Lambdasonde in einem Dieselmotor nachteilig, dass das Schutzrohr, welches das Sensorelement umgibt, verrußen kann. Durch eine Rußablagerung wird der Gasaustausch im Schutzrohr erschwert. Es kann damit der Fall eintreten, dass die Lambdasonde bereits von reiner Frischluft umgeben ist, aber im Schutzrohr noch eine gewisse Abgasmenge vorhanden ist. Das Sensorelement wird dann noch nicht mit der erwarteten und geforderten Sauerstoffkonzentration von Frischluft beaufschlagt. Wird eine Lambda-Schubfunktion in einer solchen Situation freigegeben und gestartet, dann ist die Genauigkeit der Funktion beeinträchtigt. Beispielsweise sind Anwenderfunktionen, die auf der Kenntnis des Lambdasignals, d.h. die auf dem Lambdawert oder der Sauerstoffkonzentration als Grundlagensignal aufbauen, nicht mit der erforderlichen Genauigkeit durchzuführen. Dies wiederum kann zu einer Verschlechterung der Emissionswerte der Brennkraftmaschine führen.Now it is disadvantageous in an operation of the lambda probe in a diesel engine, that the protective tube surrounding the sensor element, can roughen. By soot deposition of the gas exchange in the protective tube is difficult. It can so that the case occur that the lambda probe is already surrounded by pure fresh air, but in the protective tube still a certain amount of exhaust gas is present. The sensor element is then not yet subjected to the expected and required oxygen concentration of fresh air. If a lambda push function is enabled and started in such a situation, the accuracy of the function is impaired. For example, user functions which are based on the knowledge of the lambda signal, that is to say those based on the lambda value or the oxygen concentration as base signal, can not be carried out with the required accuracy. This in turn can lead to a deterioration of the emission values of the internal combustion engine.
Die Erfindung ermöglicht nun die Erkennung der Betriebsbereitschaft einer Lambdasonde für derartige Funktionen in ausgewählten Betriebsphasen, beispielsweise in der Schubphase. Erfindungsgemäß wird vorgeschlagen, das Freigabekriterium der Sonde von einer Dynamikdiagnose abhängig zu machen. Bei beispielsweise einem Übergang vom Lastbetrieb in den Schubbetrieb, d.h. bei einem Last-Schubübergang wird z.B. der zeitliche Anstieg der gemessenen Sauerstoffkonzentration ausgewertet, um die dynamischen Eigenschaften der Breitbandlambdasonde zu erfassen und zu bewerten. Dies ist schematisch in
Wie vorstehend erwähnt, wird ein Integral des Frischluftmassenstroms erfasst. Gemäß der vorliegenden Erfindung wird nun der Schwellenwert für das Integral des Frischluftmassenstroms von der gemessenen Anstiegszeit abhängig gemacht. Im Falle einer neuen Sonde ist diese Anstiegszeit t1, im Falle einer Sonde mit verrußtem Schutzrohr ist diese Zeit die Zeit t2. Diese Korrelation zwischen Schwellenwert des Integrals des Frischluftmassenstroms und der gemessenen Anstiegszeit wird vorteilhafterweise als Kennlinienglied realisiert, d.h. der Zusammenhang ist in einem Kennlinienfeld gespeichert, dessen Eingangssignal eine Anstiegszeit ist und dessen Ausgangssignal eine Frischluftmasse ist. Rein prinzipiell kann ein solches Kennlinienglied auch in zweifacher Ausführung vorgesehen sein. Dies ist beispielsweise dann sinnvoll, wenn die Brennkraftmaschine zumindest zeitweise mit einer im Schub offenen Abgasrückführung betrieben wird. Da die Abgasrückführung signifikanten Einfluss auf die Dynamik der Sauerstoffkonzentration hat, ist sinnvollerweise vorgesehen, für die beiden Fälle, d.h. für den Fall mit und für den Fall ohne Abgasrückführung verschiedene Kennlinien vorzusehen.As mentioned above, an integral of the fresh air mass flow is detected. According to the present invention, the threshold for the integral will now be the fresh air mass flow is made dependent on the measured rise time. In the case of a new probe, this rise time is t1, in the case of a probe with a fouled tube, this time is the time t2. This correlation between the threshold value of the integral of the fresh air mass flow and the measured rise time is advantageously realized as a characteristic element, ie the relationship is stored in a characteristic field whose input signal is a rise time and whose output signal is a fresh air mass. In principle, such a characteristic element can also be provided in duplicate. This is useful, for example, when the internal combustion engine is operated at least temporarily with an exhaust gas recirculation open in the thrust. Since the exhaust gas recirculation has a significant influence on the dynamics of the oxygen concentration, it is expedient to provide different characteristics for the two cases, ie for the case with and for the case without exhaust gas recirculation.
Wenn darüber hinaus im Abgasstrang mehrere Lambdasonden verbaut sind, z.B. eine stromaufwärts und eine stromabwärts des Katalysators, oder die Brennkraftmaschine mehrere Abgasstränge aufweist, werden entsprechend viele Kennlinienglieder vorgesehen.In addition, if several lambda sensors are installed in the exhaust system, e.g. one upstream and one downstream of the catalytic converter, or the internal combustion engine has a plurality of exhaust gas lines, correspondingly many characteristic elements are provided.
Eine entsprechende Anpassung des Schwellenwerts wäre auch sinnvoll bei einer Verlängerung der Gaslaufzeit, wenn beispielsweise eine Lambdasonde nachträglich stromabwärts eingebaut wird, beispielsweise im Falle der Nachrüstung von Abgasnachbehandlungskomponenten. Auch wenn die erhöhte Gaslaufzeit eine Fehlerfolge sein sollte, könnte durch das erfindungsgemäße Verfahren verhindert werden, dass die Emissionsverschlechterung ein gesetzlich unzulässiges Maß überschreitet.A corresponding adjustment of the threshold would also be useful in an extension of the gas running time, for example, if a lambda probe is retrofitted downstream, for example, in the case of retrofitting exhaust aftertreatment components. Even if the increased gas running time were to be a fault sequence, it could be prevented by the method according to the invention that the emission deterioration exceeds a legally impermissible level.
Das erfindungsgemäße Verfahren wurde vorstehend anhand des Schubbetriebs erläutert. Das Verfahren ist hierauf jedoch nicht beschränkt. Rein prinzipiell können auch andere Betriebsphasen außerhalb des Schubs vorgesehen sein, beispielsweise die Freigabe von Funktionen, die das Lambdasignal verwenden und die entweder einen bestimmten Lambdawert erwarten, oder die ein eingeschwungenes Signal benötigen. Auch in diesem Falle kann die Betriebsbereitschaft so lange verzögert werden, bis ein Zeitgradient gegen den Wert Null strebt, d.h. verzögert werden in Abhängigkeit von einer Dynamiküberwachung. Die Erfindung sieht auch ein Verfahren zur Erkennung der Gasdurchlässigkeit eines eine Lambdasonde umgebenden Schutzrohrs vor. Bei diesem Verfahren wird bei einem Wechsel einer Betriebsphase der Brennkraftmaschine in eine andere, unterschiedliche Betriebsphase, also beispielsweise bei einem Last-Schubübergang der Zeitgradient des Signals der Lambdasonde erfasst und aufgrund eines Vergleichs des Zeitgradienten der Lambdasonde mit einem Zeitgradienten, der ein gasdurchlässiges Schutzrohr charakterisiert, auf die Durchlässigkeit des Schutzrohrs geschlossen. In
Das vorstehende Verfahren wird vorteilhafterweise als Computerprogramm auf einem Rechengerät, insbesondere dem Steuergerät 140 der Brennkraftmaschine 110 implementiert. Der Programmcode kann auf einem maschinenlesbaren Träger gespeichert sein, den das Steuergerät 140 lesen kann. Auf diese Weise sind auch Nachrüstungen möglich.The above method is advantageously implemented as a computer program on a computing device, in particular the
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DE102009054751.7A DE102009054751B4 (en) | 2009-12-16 | 2009-12-16 | Procedure for detecting the readiness for operation of a lambda probe for functions in selected operating phases |
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WO2013087262A1 (en) * | 2011-12-12 | 2013-06-20 | Robert Bosch Gmbh | Method and device for the dynamic monitoring of gas sensors |
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FR3062167A1 (en) * | 2017-01-26 | 2018-07-27 | Renault S.A.S | METHOD AND DEVICE FOR CALIBRATING AN OXYGEN SENSOR. |
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CN106837569B (en) * | 2017-02-17 | 2019-08-20 | 中国第一汽车股份有限公司 | A kind of automobile-used broad domain oxygen sensor ageing failure diagnosis method |
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EP0603543A1 (en) | 1992-12-22 | 1994-06-29 | Robert Bosch Gmbh | Method and apparatus to monitor a control apparatus in a combustion engine |
DE19842425C2 (en) | 1998-09-16 | 2003-10-02 | Siemens Ag | Method for correcting the characteristic of a linear lambda probe |
DE102005056152A1 (en) | 2005-11-23 | 2007-05-24 | Robert Bosch Gmbh | Method for calibrating the signal provided by a broadband lambda sensor and apparatus for carrying out the method |
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DE102009054751A1 (en) | 2011-06-22 |
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