EP1209332B1 - Method and device for regenerating a NOx catalytic converter - Google Patents
Method and device for regenerating a NOx catalytic converter Download PDFInfo
- Publication number
- EP1209332B1 EP1209332B1 EP20010250407 EP01250407A EP1209332B1 EP 1209332 B1 EP1209332 B1 EP 1209332B1 EP 20010250407 EP20010250407 EP 20010250407 EP 01250407 A EP01250407 A EP 01250407A EP 1209332 B1 EP1209332 B1 EP 1209332B1
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- Prior art keywords
- regeneration
- signal
- exhaust gas
- internal combustion
- combustion engine
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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
- F02D41/1439—Introducing closed-loop corrections using means for determining characteristics of the combustion gases; Sensors therefor characterised by the position of the sensor
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
- F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
- F01N13/00—Exhaust or silencing apparatus characterised by constructional features ; Exhaust or silencing apparatus, or parts thereof, having pertinent characteristics not provided for in, or of interest apart from, groups F01N1/00 - F01N5/00, F01N9/00, F01N11/00
- F01N13/009—Exhaust or silencing apparatus characterised by constructional features ; Exhaust or silencing apparatus, or parts thereof, having pertinent characteristics not provided for in, or of interest apart from, groups F01N1/00 - F01N5/00, F01N9/00, F01N11/00 having two or more separate purifying devices arranged in series
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
- F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
- F01N3/00—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust
- F01N3/08—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous
- F01N3/0807—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by using absorbents or adsorbents
- F01N3/0814—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by using absorbents or adsorbents combined with catalytic converters, e.g. NOx absorption/storage reduction catalysts
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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
- F02D41/021—Introducing corrections for particular conditions exterior to the engine
- F02D41/0235—Introducing corrections for particular conditions exterior to the engine in relation with the state of the exhaust gas treating apparatus
- F02D41/027—Introducing corrections for particular conditions exterior to the engine in relation with the state of the exhaust gas treating apparatus to purge or regenerate the exhaust gas treating apparatus
- F02D41/0275—Introducing corrections for particular conditions exterior to the engine in relation with the state of the exhaust gas treating apparatus to purge or regenerate the exhaust gas treating apparatus the exhaust gas treating apparatus being a NOx trap or adsorbent
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
- F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
- F01N3/00—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust
- F01N3/08—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous
- F01N3/0807—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by using absorbents or adsorbents
- F01N3/0828—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by using absorbents or adsorbents characterised by the absorbed or adsorbed substances
- F01N3/0842—Nitrogen oxides
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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
- F02D2200/00—Input parameters for engine control
- F02D2200/02—Input parameters for engine control the parameters being related to the engine
- F02D2200/08—Exhaust gas treatment apparatus parameters
- F02D2200/0802—Temperature of the exhaust gas treatment apparatus
- F02D2200/0804—Estimation of the temperature of the exhaust gas treatment apparatus
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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
- F02D2200/00—Input parameters for engine control
- F02D2200/02—Input parameters for engine control the parameters being related to the engine
- F02D2200/08—Exhaust gas treatment apparatus parameters
- F02D2200/0806—NOx storage amount, i.e. amount of NOx stored on NOx trap
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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
- F02D2200/00—Input parameters for engine control
- F02D2200/02—Input parameters for engine control the parameters being related to the engine
- F02D2200/08—Exhaust gas treatment apparatus parameters
- F02D2200/0814—Oxygen storage amount
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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
- F02D2200/00—Input parameters for engine control
- F02D2200/02—Input parameters for engine control the parameters being related to the engine
- F02D2200/08—Exhaust gas treatment apparatus parameters
- F02D2200/0816—Oxygen storage capacity
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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
Definitions
- the invention relates to methods for carrying out a regeneration of a NO x storage catalytic converter in an exhaust line of an internal combustion engine and to devices for carrying out the regeneration with the features mentioned in the preambles of the independent claims 1 to 3 or 20 or 21.
- the internal combustion engine is temporarily switched to a rich or stoichiometric working mode ( ⁇ ⁇ 1).
- a reducing agent mass flow of the exhaust gas increases, the nitrate incorporated nitrogen oxides are desorbed and catalytically reacted on the NO x storage catalyst with simultaneous oxidation of CO and HC.
- the invention is therefore based on the object to provide a method for NO x regeneration of a NO x storage catalyst available, which is optimized in terms of the lowest possible reducing agent emission and at the same time ensures complete regeneration of the storage catalyst.
- the fastest possible procedure of the method ie short regeneration periods, should be ensured. It is further intended to provide a device which is suitable and advantageous for carrying out the method.
- the achievement of the predetermined signal threshold value can be determined in advance with sufficient reliability.
- This makes it possible to take into account the time span corresponding to the exhaust gas running time between the internal combustion engine and the NO x storage catalytic converter - hereinafter referred to simply as the exhaust gas flow time - so that the NO x regeneration can be stopped in good time, that is to say before the occurrence of a reductant breakthrough.
- the method thus allows a reduction of CO and HC emission and minimization of a need for NO x regeneration additional fuel consumption.
- the extrapolation of the oxygen-dependent signal of the measuring device is carried out according to an advantageous embodiment of the method based on current operating parameters of the internal combustion engine and / or the exhaust system. These may include, for example, a current air-fuel mixture (combustion lambda) supplied to the internal combustion engine and / or an exhaust gas mass flow and / or an exhaust gas temperature and / or a catalyst temperature.
- a current air-fuel mixture combustion lambda
- the accuracy of the extrapolation can be further increased by taking into account a behavioral model of the NO x storage catalytic converter.
- a behavioral model can be, for example, the course of a regeneration rate as a function of the current reducing agent mass flow and / or the catalyst temperature include.
- the behavioral model can also take into account the waveform measured during the current regeneration.
- An advantageous further development of the method can also be achieved by extrapolating the signal taking into account a behavioral model of the oxygen-sensitive measuring device.
- a behavioral model of the oxygen-sensitive measuring device ie a time delay, with which the measuring device displays changed exhaust gas conditions, but also a current, measured about an internal resistance, temperature of the measuring device can be considered.
- the exhaust gas flow time is preferably provided to calculate these using current operating parameters of the internal combustion engine. It can be used on known operating parameters such as engine load, speed or exhaust gas temperature or other suitable data.
- a preferred embodiment of the method provides for setting limits for different operating conditions of the internal combustion engine and / or the exhaust system and suppressing the extrapolation if these limits are not met.
- limit values for the exhaust gas mass flow and / or for the temperature of the NO x storage catalytic converter are expedient, since the regeneration rates are too unstable if the exhaust gas mass flows are too high or the catalyst temperatures are too low to be able to be extrapolated with sufficient reliability.
- the signal extrapolation can advantageously also be suppressed if there are operating point-dependent disturbing influences which influence an irregular NO x regeneration. This is the case, for example, with a fuel cut of the internal combustion engine.
- the extrapolation is not carried out during the entire regeneration period of the storage catalytic converter, but only after elapse of a predetermined time after the beginning of the regeneration and / or flow rate of a given exhaust gas mass and / or after exceeding a predetermined minimum threshold of the signal of the measuring device.
- the extrapolation according to the invention makes it possible, in this aspect of the invention, to take into account the exhaust gas flow time during the change of the combustion lambda during the regeneration, so that it is possible to react to an expected signal height to a certain extent with foresight.
- the method thus allows a reduction in CO and HC emission and minimization of a need for the NO x regeneration additional fuel consumption.
- the (theoretical) achievement of the signal threshold value prescribed for a regeneration interruption is determined in advance.
- the regeneration can be stopped in time, that is, before the occurrence of a Reduktionsstoff bebruches.
- the increase can take place after the expiry of a predefinable portion of a total regeneration duration determined by the extrapolation. It is even more advantageous to increase the combustion lambda on reaching a second predetermined signal threshold value by the projected sensor signal taking into account the exhaust gas flow time, the second signal threshold is usefully smaller than the first signal threshold, if it is a probe voltage.
- the increase of the combustion lambda before the regeneration end causes a reduction of a reducing agent mass flow at a time at which only small amounts of stored nitrogen oxides in the storage catalyst are available for the conversion of the reducing agent.
- the risk of reducing agent breakthrough at the end of the regeneration is thus further reduced. It has proven particularly useful to increase the lambda Lambda values of 0.94 to 0.99, in particular 0.95 to 0.98.
- the combustion lambda of the internal combustion engine is lowered below a previous lambda value until the projected sensor signal, taking into account the exhaust gas running time, reaches a third predetermined signal threshold value.
- combustion lambda values of 0.6 to 0.9, in particular 0.7 to 0.8 have proven particularly useful.
- the NO x storage catalytic converter thus becomes with a comparatively very rich exhaust gas atmosphere acted as long as the memory still has a marked by the third signal threshold minimum loading of nitrogen oxides.
- an efficiency of the NO x conversion is increased, the regeneration duration is shortened and, ultimately, the additional fuel consumption to be expended for the regeneration is minimized.
- threshold values whose exceeding-triggered by the extrapolated sensor signal further variations of the combustion lambda. Additional threshold values may, for example, take into account an otherwise determined aging state of the storage catalytic converter. The various increases and / or reductions of the internal combustion engine to be supplied air-fuel mixture can also be done gradually or even continuously.
- the devices according to the invention comprise means with which the described method steps can be carried out.
- the means comprise a control unit in which an algorithm for controlling the method steps is stored in digital form.
- This control unit can advantageously also be integrated in an engine control unit of the vehicle.
- the oxygen-sensitive measuring device may be a lambda probe arranged downstream of the NO x storage catalytic converter, in particular a broadband or a step response lambda probe, or an NO x sensor having a lambda output signal.
- the Indian FIG. 1 shown internal combustion engine 10 is associated with a generally designated 12 exhaust system.
- the exhaust system 12 includes an exhaust passage 14, in which a arranged in a near-engine position precatalyst 16 and a large-volume NO x storage 18 is arranged.
- the exhaust duct 14 usually houses various gas and / or temperature sensors (not shown) for controlling the internal combustion engine 10.
- Shown here is merely an oxygen-sensitive measuring device 20, which is arranged downstream of the NO x storage 18.
- the measuring device 20 may be, for example, a lambda probe or an NO x sensor, which is equipped with a Lambdamessfunktion. In any case, the measuring device 20 provides a dependent of an oxygen content of the exhaust gas signal U ⁇ .
- This signal U ⁇ is transmitted to an engine control unit 22, in which it is digitized and further processed. Further, the operating state of the internal combustion engine 10 information concerning also found in the engine control unit 22.
- a control unit 24 is integrated, in which an algorithm for performing the method for NO x regeneration of the NO x storage 18 is stored.
- the engine control unit 22 and the control unit 24 are capable of influencing at least one operating parameter of the internal combustion engine 10, in particular an air-fuel mixture (combustion lambda) to be supplied, as a function of the signal U ⁇ of the measuring device in a manner to be explained.
- FIG. 2 shows the time course of various parameters of the internal combustion engine 10 and the exhaust system 12 during a NO x regeneration of the NO x storage catalytic converter 18, which is carried out according to a conventional method.
- the internal combustion engine 10 is in a lean mode of operation in which it is supplied with an oxygen-rich air-fuel mixture with ⁇ M >> 1 (graph 100).
- the exhaust gas contains an excess of nitrogen oxides NO x , which is not complete by the precatalyst 16 can be converted.
- NO x is therefore stored in the NO x storage 18, the NO x load continuously increases (Graph 102). Based on a suitable criterion, a NO x regeneration need is recognized at a time t A.
- the internal combustion engine Consequently, 10 is switched by influencing the engine control unit 22 in a rich operating mode with ⁇ F ⁇ 1.
- ⁇ F ⁇ 1 As a result of the now increased mass flow of reducing agents CO and HC in the exhaust is - the x desorbed NO x storing catalyst 18 embedded NO and nitrogen reduced.
- a decrease in the NO x charge (graph 102) of the storage catalytic converter 18 is only noticeable after a certain time delay after switching the internal combustion engine 10, since at the time t A the exhaust duct 14 is still filled with lean exhaust gas, which initially still the storage catalytic converter 18 must happen before the reducing agents reach it.
- the course of the NO x regeneration is meanwhile tracked with the aid of the signal U ⁇ provided by the measuring device 20, generally a voltage.
- the probe voltage U ⁇ (graph 104) behaves inversely proportional to an oxygen concentration of the exhaust gas downstream of the storage catalytic converter 18. Since the reducing agent is consumed to a lesser and greater extent as regeneration progresses, the signal U ⁇ of the measuring device 20 rises slowly. At a time t E , the signal U ⁇ reaches a predetermined threshold value U SE , whereupon the internal combustion engine 10 is generally switched back into a lean operating mode with ⁇ M >> 1.
- FIG. 3 shows - this time during regeneration according to a first typical embodiment of the method according to the invention.
- the signal U ⁇ of the measuring device 20 (graph 104) is first measured and recorded in a known manner.
- the control unit 24 begins at a time t AH with a projection of the signal U ⁇ .
- the control unit 24 further calculates a period .DELTA.t, which corresponds to the current exhaust gas running time, which requires the exhaust gas until reaching the storage catalytic converter.
- the time of the actual regeneration end t E is then determined by subtracting the exhaust gas flow time ⁇ t from the time t S.
- the projection and thus the regeneration end t E is constantly updated on the basis of current operating parameters and on the basis of the actual signal profile U ⁇ .
- the projected sensor signal U ⁇ a second, not shown for reasons of clarity signal threshold U S2 , which is located between U S1 and U SE .
- the achievement of the signal threshold value U S2 signals that the NO x charge of the storage catalytic converter 18 is almost exhausted.
- the combustion lambda is further raised to a value of ⁇ F4 near 1. ⁇ F4 is then typically 0.95 to 0.98.
- the time t S determined at which the predetermined signal threshold U SE is achieved theoretically.
- the time of the (actual) regeneration end t E is then determined.
- the internal combustion engine 10 is switched back to the lean operating mode with ⁇ M in order to prevent pollutant breakdown (graph 106).
- the small amount of NO X (graph 102) still present in the storage catalytic converter 18 at this point in time ensures that the small amount of reducing agent still contained in the exhaust gas is largely converted.
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Description
Die Erfindung betrifft Verfahren zur Durchführung einer Regeneration eines NOx-Speicherkatalysators in einem Abgasstrang einer Verbrennungskraftmaschine sowie Vorrichtungen zur Durchführung der Regeneration mit den in den Oberbegriffen der unabhängigen Ansprüche 1 bis 3 beziehungsweise 20 oder 21 genannten Merkmalen.The invention relates to methods for carrying out a regeneration of a NO x storage catalytic converter in an exhaust line of an internal combustion engine and to devices for carrying out the regeneration with the features mentioned in the preambles of the independent claims 1 to 3 or 20 or 21.
Verbrennungskraftmaschinen, die aus Gründen einer Verbrauchsoptimierung wenigstens zeitweise in einem mageren Betriebsmodus, das heißt mit einem sauerstoffreichen Abgas mit λ > 1, betrieben werden, produzieren Stickoxide NOx in einem stöchiometrischen Überschuss. Dies hat zur Folge, dass bei einer katalytischen oxidativen Umsetzung von unverbrannten Kohlenwasserstoffen HC und Kohlenmonoxid CO Stickoxide NOx nicht vollständig zu umweltneutralem Stickstoff umgesetzt werden. Zur Abhilfe ist bekannt, NOx-Speicherkatalysatoren in den Abgaskanälen von Verbrennungskraftmaschinen anzuordnen, die in mageren Betriebsphasen das NOx als Nitrat einlagern. Um NOx-Durchbrüche aufgrund eines vollbeladenen NOx-Speicherkatalysators zu vermeiden, muss der NOx-Speicherkatalysator in wiederkehrenden Abständen regeneriert werden. Zu diesem Zweck wird die Verbrennungskraftmaschine kurzfristig in einen fetten oder stöchiometrischen Arbeitsmodus (λ ≤ 1) umgeschaltet. Infolgedessen steigt ein Reduktionsmittelmassenstrom des Abgases an, die als Nitrat eingelagerten Stickoxide werden desorbiert und katalytisch am NOx-Speicherkatalysator unter gleichzeitiger Oxidation von CO und HC umgesetzt.Internal combustion engines, which are operated for reasons of consumption optimization at least temporarily in a lean operating mode, that is, with an oxygen-rich exhaust gas with λ> 1, produce nitrogen oxides NO x in a stoichiometric excess. This has the consequence that in a catalytic oxidative conversion of unburned hydrocarbons HC and carbon monoxide CO nitrogen oxides NO x are not completely converted to environmentally neutral nitrogen. As a remedy, it is known to arrange NO x storage catalysts in the exhaust ducts of internal combustion engines, which store the NO x as nitrate in lean phases of operation. To avoid NO x breakthroughs due to a fully loaded NO x storage catalytic converter, the NO x storage catalytic converter must be regenerated at recurring intervals. For this purpose, the internal combustion engine is temporarily switched to a rich or stoichiometric working mode (λ ≦ 1). As a result, a reducing agent mass flow of the exhaust gas increases, the nitrate incorporated nitrogen oxides are desorbed and catalytically reacted on the NO x storage catalyst with simultaneous oxidation of CO and HC.
In einfachen Verfahren wird eine Regenerationsdauer, während der der Speicherkatalysator mit der fetten Abgasatmosphäre beaufschlagt wird, fest vorgegeben. Nachteilig hieran ist, dass ein tatsächlicher Beladungszustand des NOx-Speicherkatalysators und eine aktuelle Regenerationsrate desselben nicht berücksichtigt wird. Eine solche Vorgehensweise birgt die Gefahr, dass die Regenerationsdauer zu kurz oder zu lang gewählt wird, wobei im ersteren Fall eine unvollständige Regeneration des Speichers und im zweiten Fall ein unnötiger Kraftstoffmehrverbrauch sowie eine Emission umweltschädlicher Reduktionsmittel (HC und CO) in Kauf genommen wird. Verfeinerte Verfahren versuchen einen tatsächlichen Beladungszustand des NOx-Speicherkatalysators anhand bestimmter Betriebsparameter während der letzten Magerphase abzuschätzen und leiten hieraus eine erforderliche Regenerationsdauer ab. Jedoch ist auch dieses Verfahren mit erheblichen Ungenauigkeiten behaftet, so dass sich auch hier unzweckmäßige NOx-Regenerationsdauern mit den genannten Folgen ergeben können.In simple methods, a regeneration duration, during which the storage catalytic converter is exposed to the rich exhaust gas atmosphere, is fixed. The disadvantage of this is that an actual loading state of the NO x storage catalytic converter and a current regeneration rate of the same is not taken into account. Such an approach involves the risk that the regeneration period is too short or too long, in the former case, an incomplete regeneration of the memory and in the second case an unnecessary fuel consumption and a Emission of environmentally harmful reducing agents (HC and CO) is accepted. Refined methods attempt to estimate an actual state of charge of the NO x storage catalyst based on certain operating parameters during the last lean phase and deduce therefrom a required regeneration duration. However, this method is also subject to considerable inaccuracies, so that here too inappropriate NO x regeneration periods can result with the mentioned consequences.
Des Weiteren sind Verfahren bekannt, wie zum Beispiel in
Der Erfindung liegt daher die Aufgabe zugrunde, ein Verfahren zur NOx-Regeneration eines NOx-Speicherkatalysators zur Verfügung zu stellen, welches hinsichtlich einer möglichst geringen Reduktionsmittelemission optimiert ist und gleichzeitig eine vollständige Regeneration des Speicherkatalysators gewährleistet. In einem weiteren Aspekt soll ein möglichst schneller Ablauf des Verfahrens, das heißt kurze Regenerationsdauern, sichergestellt werden. Es soll ferner eine zur Durchführung des Verfahrens geeignete und vorteilhafte Vorrichtung bereitgestellt werden.The invention is therefore based on the object to provide a method for NO x regeneration of a NO x storage catalyst available, which is optimized in terms of the lowest possible reducing agent emission and at the same time ensures complete regeneration of the storage catalyst. In a further aspect, the fastest possible procedure of the method, ie short regeneration periods, should be ensured. It is further intended to provide a device which is suitable and advantageous for carrying out the method.
Diese Aufgabe wird durch ein Verfahren mit den in dem unabhängigen Anspruch 1 genannten Merkmalen gelöst. Eine geeignete Vorrichtung ist durch die in dem unabhängigen Anspruch 18 genannten Merkmale gekennzeichnet.This object is achieved by a method having the features mentioned in the independent claim 1. A suitable device is characterized by the features mentioned in
Gemäß einem ersten erfindungsgemäßen Verfahren ist vorgesehen, dass
- (a) während der NOX-Regeneration das sauerstoffabhängige Signal der stromab des NOX-Speicherkatalysators angeordneten Messeinrichtung hochgerechnet wird,
- (b) auf Basis des hochgerechneten Signals ein theoretischer Zeitpunkt bestimmt wird, an dem ein vorgegebener Signalschwellenwert voraussichtlich überschritten wird, und
- (c) das Regenerationsende bestimmt wird, indem eine im Wesentlichen einer Abgaslaufzeit zwischen Verbrennungskraftmaschine und NOX-Speicherkatalysator entsprechende Zeitspanne von dem theoretischen Zeitpunkt subtrahiert wird.
- (a) during the NO x regeneration, the oxygen-dependent signal of the measuring device arranged downstream of the NO x storage catalytic converter is extrapolated,
- (b) determining, based on the extrapolated signal, a theoretical time at which a predetermined signal threshold is likely to be exceeded, and
- (c) determining the regeneration end by subtracting an amount of time substantially corresponding to an exhaust running time between the internal combustion engine and the NO x storage catalyst from the theoretical time.
Indem also das Signal der Messeinrichtung hochgerechnet wird, kann mit einer ausreichenden Zuverlässigkeit das Erreichen des vorgegebenen Signalschwellenwertes im Voraus ermittelt werden. Dies ermöglicht die Berücksichtigung der der Abgaslaufzeit zwischen Verbrennungskraftmaschine und NOX-Speicherkatalysator entsprechenden Zeitspanne - nachfolgend einfachheitshalber als Abgaslaufzeit bezeichnet -, so dass die NOx-Regeneration rechtzeitig, das heißt vor dem Auftreten eines Reduktionsmitteldurchbruches, abgebrochen werden kann. Insgesamt ermöglicht das Verfahren damit eine Verminderung der CO- und HC-Emission und eine Minimierung eines für die NOx-Regeneration notwendigen Kraftstoffmehrverbrauchs.Thus, by extrapolating the signal of the measuring device, the achievement of the predetermined signal threshold value can be determined in advance with sufficient reliability. This makes it possible to take into account the time span corresponding to the exhaust gas running time between the internal combustion engine and the NO x storage catalytic converter - hereinafter referred to simply as the exhaust gas flow time - so that the NO x regeneration can be stopped in good time, that is to say before the occurrence of a reductant breakthrough. Overall, the method thus allows a reduction of CO and HC emission and minimization of a need for NO x regeneration additional fuel consumption.
Die Hochrechnung des sauerstoffabhängigen Signals der Messeinrichtung erfolgt gemäß einer vorteilhaften Ausgestaltung des Verfahrens anhand aktueller Betriebsparameter der Verbrennungskraftmaschine und/oder der Abgasanlage. Diese können etwa ein aktuelles, der Verbrennungskraftmaschine zugeführtes Luft-Kraftstoff-Gemisch (Verbrennungslambda) und/oder ein Abgasmassenstrom und/oder eine Abgastemperatur und/oder eine Katalysatortemperatur umfassen. Die Genauigkeit der Hochrechnung kann weiterhin dadurch erhöht werden, dass sie unter Berücksichtigung eines Verhaltensmodells des NOX-Speicherkatalysators erfolgt. Ein solches Verhaltensmodell kann etwa den Verlauf einer Regenerationsrate in Abhängigkeit von dem aktuellen Reduktionsmittelmassenstrom und/oder der Katalysatortemperatur beinhalten. Das Verhaltensmodell kann zudem den während der aktuellen Regeneration gemessenen Signalverlauf berücksichtigen. Eine vorteilhafte Weiterentwicklung des Verfahrens kann ferner erzielt werden, indem das Signal unter Berücksichtigung eines Verhaltensmodells der sauerstoffempfindlichen Messeinrichtung hochgerechnet wird. Dabei kann insbesondere eine Trägheit, also eine Zeitverzögerung, mit der die Messeinrichtung veränderte Abgasbedingungen anzeigt, aber auch eine aktuelle, etwa über einen Innenwiderstand gemessene, Temperatur der Messeinrichtung berücksichtigt werden.The extrapolation of the oxygen-dependent signal of the measuring device is carried out according to an advantageous embodiment of the method based on current operating parameters of the internal combustion engine and / or the exhaust system. These may include, for example, a current air-fuel mixture (combustion lambda) supplied to the internal combustion engine and / or an exhaust gas mass flow and / or an exhaust gas temperature and / or a catalyst temperature. The accuracy of the extrapolation can be further increased by taking into account a behavioral model of the NO x storage catalytic converter. Such a behavioral model can be, for example, the course of a regeneration rate as a function of the current reducing agent mass flow and / or the catalyst temperature include. The behavioral model can also take into account the waveform measured during the current regeneration. An advantageous further development of the method can also be achieved by extrapolating the signal taking into account a behavioral model of the oxygen-sensitive measuring device. In particular, an inertia, ie a time delay, with which the measuring device displays changed exhaust gas conditions, but also a current, measured about an internal resistance, temperature of the measuring device can be considered.
Obwohl es prinzipiell möglich ist, die Abgaslaufzeit als Festwert vorzugeben, ist bevorzugt vorgesehen, diese anhand aktueller Betriebsparameter der Verbrennungskraftmaschine zu berechnen. Dabei kann auf bekannte Betriebsparameter wie Motorlast, Drehzahl oder Abgastemperatur oder auch andere geeignete Daten zurückgegriffen werden.Although it is in principle possible to specify the exhaust gas flow time as a fixed value, it is preferably provided to calculate these using current operating parameters of the internal combustion engine. It can be used on known operating parameters such as engine load, speed or exhaust gas temperature or other suitable data.
Da die Zuverlässigkeit der Hochrechnung des Signalverlaufes unter bestimmten extremen Randbedingungen vermindert sein kann, sieht eine bevorzugte Ausführung des Verfahrens vor, Grenzwerte für verschiedene Betriebsbedingungen der Verbrennungskraftmaschine und/oder der Abgasanlage vorzugeben und die Hochrechnung zu unterdrücken, wenn diese Grenzwerte nicht eingehalten werden. Dabei sind insbesondere Grenzwerte für den Abgasmassenstrom und/oder für die Temperatur des NOx-Speicherkatalysators sinnvoll, da bei zu hohen Abgasmassenströmen oder zu niedrigen Katalysatortemperaturen die Regenerationsraten zu unstetig sind, um mit ausreichender Zuverlässigkeit hochgerechnet werden zu können. Die Signalhochrechnung kann vorteilhafterweise auch dann unterdrückt werden, wenn betriebspunktabhängige Störeinflüsse vorliegen, die eine irreguläre NOx-Regeneration beeinflussen. Dies ist beispielsweise bei einer Schubabschaltung der Verbrennungskraftmaschine der Fall.Since the reliability of the extrapolation of the signal curve can be reduced under certain extreme boundary conditions, a preferred embodiment of the method provides for setting limits for different operating conditions of the internal combustion engine and / or the exhaust system and suppressing the extrapolation if these limits are not met. In particular, limit values for the exhaust gas mass flow and / or for the temperature of the NO x storage catalytic converter are expedient, since the regeneration rates are too unstable if the exhaust gas mass flows are too high or the catalyst temperatures are too low to be able to be extrapolated with sufficient reliability. The signal extrapolation can advantageously also be suppressed if there are operating point-dependent disturbing influences which influence an irregular NO x regeneration. This is the case, for example, with a fuel cut of the internal combustion engine.
Gemäß einer weiteren vorteilhaften Ausgestaltung des Verfahrens erfolgt die Hochrechnung nicht während der gesamten Regenerationsdauer des Speicherkatalysators, sondern erst nach Verstreichen einer vorgegebenen Zeit nach Beginn der Regeneration und/oder nach Durchsatz einer vorgegebenen Abgasmasse und/oder nach Überschreiten einer vorgegebenen Mindestschwelle des Signals der Messeinrichtung. Durch diese Maßnahmen wird gewährleistet, dass der Signalverlauf bereits über eine gewisse Mindestdauer bekannt ist und somit zuverlässiger extrapoliert werden kann. Nach Beginn der Hochrechnung sollte der Signalverlauf weiterhin verfolgt werden, so dass die Hochrechnung ständig aktualisiert werden kann.According to a further advantageous embodiment of the method, the extrapolation is not carried out during the entire regeneration period of the storage catalytic converter, but only after elapse of a predetermined time after the beginning of the regeneration and / or flow rate of a given exhaust gas mass and / or after exceeding a predetermined minimum threshold of the signal of the measuring device. These measures ensure that the signal profile is already known for a certain minimum duration and thus extrapolated more reliably can be. After the start of extrapolation, the waveform should continue to be tracked, so that the extrapolation can be constantly updated.
Ein weiteres erfindungsgemäßes Verfahren sieht vor, dass
- (a) während der NOX-Regeneration das sauerstoffabhängige Signal der stromab des NOX-Speicherkatalysators angeordneten Messeinrichtung hochgerechnet wird und
- (b) ein der Verbrennungskraftmaschine während der Regeneration zugeführtes Luft-Kraftstoff-Gemisch (Verbrennungslambda) in Abhängigkeit von dem hochgerechneten Signal unter Berücksichtigung einer im Wesentlichen der Abgaslaufzeit zwischen Verbrennungskraftmaschine und NOX-Speicherkatalysator entsprechenden Zeitspanne variiert wird.
- (A) during the NO x regeneration, the oxygen-dependent signal of the arranged downstream of the NO x storage catalytic converter measuring device is extrapolated, and
- (b) an air-fuel mixture (combustion lambda) supplied to the internal combustion engine during the regeneration is varied as a function of the projected signal, taking into account a time span substantially corresponding to the exhaust gas running time between the internal combustion engine and the NO x storage catalytic converter.
Die erfindungsgemäße Hochrechnung ermöglicht in diesem Aspekt der Erfindung die Berücksichtigung der Abgaslaufzeit bei der Veränderung des Verbrennungslambdas während der Regeneration, so dass auf eine zu erwartende Signalhöhe gewissermaßen vorausschauend reagiert werden kann. So ist es beispielsweise möglich, das Verbrennungslambda anzuheben, bevor ein durch die Hochrechnung prognostizierter, unerwünschter Reduktionsmitteldurchbruch auftritt, und diesen letztlich durch diese Maßnahme zu verringern oder sogar vollständig zu unterdrücken. Insgesamt ermöglicht das Verfahren damit eine Verminderung der CO- und HC-Emission und eine Minimierung eines für die NOX-Regeneration notwendigen Kraftstoffmehrverbrauchs.The extrapolation according to the invention makes it possible, in this aspect of the invention, to take into account the exhaust gas flow time during the change of the combustion lambda during the regeneration, so that it is possible to react to an expected signal height to a certain extent with foresight. Thus, for example, it is possible to raise the combustion lambda before an undesired reductant breakdown predicted by the projection occurs, and ultimately to reduce or even completely suppress this by this measure. Overall, the method thus allows a reduction in CO and HC emission and minimization of a need for the NO x regeneration additional fuel consumption.
Die genannten Vorteile ergeben sich in noch stärkerem Ausmaß durch ein weiteres erfindungsgemäßes Verfahren, das im Wesentlichen eine Kombination der beiden erstgenannten Verfahren darstellt und nach welchem
- (a) während der NOX-Regeneration das sauerstoffabhängige Signal der Messeinrichtung hochgerechnet wird,
- (b) auf Basis des hochgerechneten Signals ein theoretischer Zeitpunkt bestimmt wird, an dem ein vorgegebener erster Signalschwellenwert überschritten wird, und
- (c) ein der Verbrennungskraftmaschine während der Regeneration zugeführtes Luft-Kraftstoff-Gemisch in Abhängigkeit von dem hochgerechneten Signal und/oder dem Zeitpunkt unter Berücksichtigung einer im Wesentlichen einer Abgaslaufzeit zwischen Verbrennungskraftmaschine und NOX-Speicherkatalysator entsprechenden Zeitspanne variiert wird, wobei insbesondere das Regenerationsende bestimmt wird, indem die im Wesentlichen der Abgaslaufzeit entsprechende Zeitspanne von dem theoretischen Zeitpunkt subtrahiert wird.
- (a) during the NO x regeneration, the oxygen-dependent signal of the measuring device is extrapolated,
- (b) determining on the basis of the extrapolated signal a theoretical time at which a predetermined first signal threshold is exceeded, and
- (C) an air-fuel mixture supplied to the internal combustion engine during the regeneration as a function of the extrapolated signal and / or the time taking into account a substantially exhaust gas flow time between the internal combustion engine and NO x storage catalytic converter corresponding time period is varied, in particular the regeneration end is determined by the time substantially corresponding to the exhaust gas time is subtracted from the theoretical time.
Zusätzlich zu den Maßnahmen des vorausgenannten Verfahrens wird demnach das (theoretische) Erreichen des für einen Regenerationsabbruch vorgegebenen Signalschwellenwertes im Voraus ermittelt. Somit kann die Regeneration rechtzeitig, das heißt vor dem Auftreten eines Reduktionsmitteldurchbruches, abgebrochen werden.Accordingly, in addition to the measures of the aforementioned method, the (theoretical) achievement of the signal threshold value prescribed for a regeneration interruption is determined in advance. Thus, the regeneration can be stopped in time, that is, before the occurrence of a Reduktionsmitteldurchbruches.
Nach einer besonders vorteilhaften Ausgestaltung der Verfahren wird das Verbrennungslambda der Verbrennungskraftmaschine dem Regenerationsende vorausgehend auf einen Wert nahe λ = 1 angehoben, wobei dieser Wert größer, das heißt magerer, als ein vorausgegangener Lambdawert und gleichzeitig < oder = 1 ist. Erfindungsgemäß ergeben sich mehrere Alternativen, um einen Zeitpunkt dieser Anhebung zu bestimmen. Beispielsweise kann die Anhebung nach Ablauf eines vorgebbaren Anteils einer durch die Hochrechnung ermittelten Regenerationsgesamtdauer erfolgen. Noch vorteilhafter ist es, das Verbrennungslambda bei Erreichen eines zweiten vorgegebenen Signalschwellenwertes durch das hochgerechnete Sensorsignal unter Berücksichtigung der Abgaslaufzeit anzuheben, wobei der zweite Signalschwellenwert sinnvollerweise kleiner ist als der erste Signalschwellenwert, sofern es sich um eine Sondenspannung handelt. Die Anhebung des Verbrennungslambdas vor dem Regenerationsende bewirkt eine Verminderung eines Reduktionsmittelmassenstroms zu einem Zeitpunkt, an dem nur noch geringe Mengen eingelagerter Stickoxide im Speicherkatalysator zur Konvertierung der Reduktionsmittel zur Verfügung stehen. Durch diese Maßnahme wird somit die Gefahr eines Reduktionsmitteldurchbruchs am Ende der Regeneration zusätzlich vermindert. Dabei hat es sich besonders bewährt, das Verbrennungslambda auf Lambdawerte von 0,94 bis 0,99, insbesondere auf 0,95 bis 0,98, anzuheben.According to a particularly advantageous embodiment of the method, the combustion lambda of the internal combustion engine is raised to the regeneration end to a value near λ = 1, which value is greater, that is leaner than a previous lambda value and at the same time <or = 1. According to the invention, there are several alternatives to determine a time of this increase. For example, the increase can take place after the expiry of a predefinable portion of a total regeneration duration determined by the extrapolation. It is even more advantageous to increase the combustion lambda on reaching a second predetermined signal threshold value by the projected sensor signal taking into account the exhaust gas flow time, the second signal threshold is usefully smaller than the first signal threshold, if it is a probe voltage. The increase of the combustion lambda before the regeneration end causes a reduction of a reducing agent mass flow at a time at which only small amounts of stored nitrogen oxides in the storage catalyst are available for the conversion of the reducing agent. By this measure, the risk of reducing agent breakthrough at the end of the regeneration is thus further reduced. It has proven particularly useful to increase the lambda Lambda values of 0.94 to 0.99, in particular 0.95 to 0.98.
Nach einer weiteren vorteilhaften Ausgestaltung wird das Verbrennungslambda der Verbrennungskraftmaschine so lange unterhalb eines vorausgegangenen Lambdawertes abgesenkt, bis das hochgerechnete Sensorsignal unter Berücksichtigung der Abgaslaufzeit einen dritten vorgegebenen Signalschwellenwert erreicht. In diesem Zusammenhang haben sich Verbrennungslambdawerte von 0,6 bis 0,9, insbesondere von 0,7 bis 0,8, besonders bewährt. Durch diese Ausgestaltung des Verfahrens wird der NOX-Speicherkatalysator folglich mit einer vergleichsweise sehr fetten Abgasatmosphäre beaufschlagt, solange der Speicher noch einen durch die dritte Signalschwelle markierte Mindestbeladung an Stickoxiden aufweist. Durch diese zumindest zeitweise sehr fette Beaufschlagung des Speicherkatalysators wird eine Effizienz der NOX-Umsetzung erhöht, die Regenerationsdauer verkürzt und letztendlich der für die Regeneration aufzuwendende Kraftstoffmehrverbrauch minimiert.According to a further advantageous embodiment, the combustion lambda of the internal combustion engine is lowered below a previous lambda value until the projected sensor signal, taking into account the exhaust gas running time, reaches a third predetermined signal threshold value. In this context, combustion lambda values of 0.6 to 0.9, in particular 0.7 to 0.8, have proven particularly useful. As a result of this embodiment of the method, the NO x storage catalytic converter thus becomes with a comparatively very rich exhaust gas atmosphere acted as long as the memory still has a marked by the third signal threshold minimum loading of nitrogen oxides. As a result of this, at least temporarily, very powerful admission of the storage catalytic converter, an efficiency of the NO x conversion is increased, the regeneration duration is shortened and, ultimately, the additional fuel consumption to be expended for the regeneration is minimized.
Es ist selbstverständlich denkbar, weitere Schwellenwerte vorzugeben, deren Überschreitung -durch das hochgerechnete Sensorsignal weitere Variationen des Verbrennungslambdas auslöst. Zusätzliche Schwellenwerte können beispielsweise einen anderweitig ermittelten Alterungszustand des Speicherkatalysators berücksichtigen. Die verschiedenen Anhebungen und/oder Absenkungen des der Verbrennungskraftmaschine zuzuführenden Luft-Kraftstoff-Gemisches können auch stufenweise oder sogar kontinuierlich erfolgen.It is, of course, conceivable to specify further threshold values whose exceeding-triggered by the extrapolated sensor signal further variations of the combustion lambda. Additional threshold values may, for example, take into account an otherwise determined aging state of the storage catalytic converter. The various increases and / or reductions of the internal combustion engine to be supplied air-fuel mixture can also be done gradually or even continuously.
Die erfindungsgemäßen Vorrichtungen umfassen Mittel, mit denen die geschilderten Verfahrensschritte ausführbar sind. Die Mittel umfassen eine Steuereinheit, in der ein Algorithmus zur Steuerung der Verfahrensschritte in digitaler Form hinterlegt ist. Diese Steuereinheit kann vorteilhaft auch in ein Motorsteuergerät des Fahrzeuges integriert sein.The devices according to the invention comprise means with which the described method steps can be carried out. The means comprise a control unit in which an algorithm for controlling the method steps is stored in digital form. This control unit can advantageously also be integrated in an engine control unit of the vehicle.
Die sauerstoffsensitive Messeinrichtung kann eine stromab des NOx-Speicherkatalysators angeordnete Lambdasonde, insbesondere eine Breitband- oder eine Sprungantwort-Lambdasonde, sein oder ein NOx-Sensor, der über ein Lambdaausgangssignal verfügt.The oxygen-sensitive measuring device may be a lambda probe arranged downstream of the NO x storage catalytic converter, in particular a broadband or a step response lambda probe, or an NO x sensor having a lambda output signal.
Weitere bevorzugte Ausgestaltungen der Erfindung ergeben sich aus den übrigen, in den Unteransprüchen genannten Merkmalen.Further preferred embodiments of the invention will become apparent from the remaining, mentioned in the dependent claims characteristics.
Die Erfindung wird nachfolgend in Ausführungsbeispielen anhand der zugehörigen Zeichnungen näher erläutert. Es zeigen:
- Figur 1
- eine Prinzipdarstellung einer Verbrennungskraftmaschine mit einer Abgasanlage;
Figur 2- zeitliche Verläufe verschiedener Abgasparameter während einer herkömmlichen NOx-Regeneration;
- Figur 3
- zeitliche Verläufe verschiedener Abgasparameter während einer NOx Regeneration gemäß einer ersten Ausführung der vorliegenden Erfindung; und
- Figur 4
- zeitliche Verläufe verschiedener Abgasparameter während einer NOx-Regeneration gemäß einer zweiten Ausführung der vorliegenden Erfindung.
- FIG. 1
- a schematic diagram of an internal combustion engine with an exhaust system;
- FIG. 2
- time histories of different exhaust gas parameters during a conventional NO x regeneration;
- FIG. 3
- time histories of various exhaust parameters during NO x regeneration according to a first embodiment of the present invention; and
- FIG. 4
- Timing of various emission parameters during a NO x regeneration according to a second embodiment of the present invention.
Der in der
Um die Emission von Schadstoffen zu verringern, wird gemäß der vorliegenden Erfindung ein anderer Ansatz verfolgt, um das Regenerationsende tE zu bestimmen. Der zeitliche Verlauf der gleichen Parameter wie in
Anhand ausgewählter Betriebsparameter berechnet die Steuereinheit 24 ferner eine Zeitspanne Δt, die der aktuellen Abgaslaufzeit, die das Abgas bis zum Erreichen des Speicherkatalysators benötigt, entspricht. Gemäß einem ersten Aspekt der Erfindung wird dann der Zeitpunkt des tatsächlichen Regenerationsendes tE durch Subtraktion der Abgaslaufzeit Δt von dem Zeitpunkt tS bestimmt. Während des Zeitraumes TH wird anhand aktueller Betriebsparameter und anhand des tatsächlichen Signalverlaufes Uλ die Hochrechnung und damit das Regenerationsende tE ständig aktualisiert. Ist das so bestimmte Regenerationsende tE erreicht, wird die Verbrennungskraftmaschine 10 wieder in den mageren Betriebsmodus mit λM umgeschaltet. Zu diesem Zeitpunkt liegt in dem Speicherkatalysator 18 noch eine geringe Menge eingelagertes NOx vor (Graph 102), welches ausreicht, um die restlichen, im Abgas enthaltenen Reduktionsmittel zu konvertieren. Folglich werden stromab des Speicherkatalysators 18 nach dem Regenerationsende tE nur noch sehr geringe Anteile an Schadstoffen gemessen (Graph 106).Based on selected operating parameters, the
Die zeitlichen Verläufe der Parameter gemäß einer vorteilhaften Ausgestaltung eines weiteren erfindungsgemäßen Verfahrens, bei dem ein vorgegebenes Verbrennungslambda unter Berücksichtigung des hochgerechneten Sensorsignals Uλ und der Abgaslaufzeit variiert wird, zeigt
Unmittelbar nach Beginn der Hochrechnung des Sensorsignals Uλ zum Zeitpunkt tAH wird zunächst überprüft, ob zum aktuellen Zeitpunkt und nach Ablauf der ermittelten Abgaslaufzeit Δt das hochgerechnete Sensorsignal Uλ sich noch unterhalb eines vorgegebenen ersten Schwellenwertes US1 befindet. Nur bei Bejahung dieser Überprüfung kann - wie im dargestellten Beispiel - ein der Verbrennungskraftmaschine 10 zugeführtes Luft-Kraftstoff-Gemisch auf einen von einem anfänglich eingestellten Lambdawert λF1 abweichenden Lambdawert λF2 geändert werden. (Graph 100). Bei Absenkung des Lambdawertes auf einen gegenüber dem Lambdawert λF1 niedrigeren Lambdawert λF2 steigt der Reduktionsmittelmassenstrom des Abgases weiter an und damit die Regenerationsrate, was sich in einem steileren Abfall der NOX-Beladung des Speicherkatalysators 18 niederschlägt (Graph 102). λF2 wird so lange beibehalten, bis das hochgerechnete Signal Uλ unter Berücksichtigung von Δt den Schwellenwert US1 erreicht. Dies ist zum Zeitpunkt t1 der Fall, an dem das Verbrennungslambda wieder auf einen weniger fetten Lambdawert λF3 angehoben wird (Graph 100).Immediately after the start of the extrapolation of the sensor signal U λ at the time t AH , it is first checked whether the projected sensor signal U λ is still below a predetermined first threshold value U S1 at the current time and after expiry of the determined exhaust gas flow time Δt. Only if affirmative Verification can - as in the example shown - a the
Kurze Zeit später erreicht im vorliegenden Beispiel das hochgerechnete Sensorsignal Uλ einen zweiten, aus Gründen der Übersichtlichkeit nicht dargestellten Signalschwellenwert US2, der zwischen US1 und USE angesiedelt ist. Das Erreichen des Signalschwellenwertes US2 signalisiert, dass die NOX-Beladung des Speicherkatalysators 18 nahezu erschöpft ist. Um einen drohenden Schadstoffdurchbruch durch das fette Abgas zu vermeiden, wird das Verbrennungslambda weiter auf einen Wert von λF4 nahe 1 angehoben. λF4 beträgt dann typischerweise 0,95 bis 0,98.A short time later reached in the present example, the projected sensor signal U λ a second, not shown for reasons of clarity signal threshold U S2 , which is located between U S1 and U SE . The achievement of the signal threshold value U S2 signals that the NO x charge of the storage
Auf Basis des hochgerechneten Signalverlaufes wird ferner gemäß dem in
Der Vergleich der durch die Graphen 106 in den
- 1010
- VerbrennungskraftmaschineInternal combustion engine
- 1212
- Abgasanlageexhaust system
- 1414
- Abgaskanalexhaust duct
- 1616
- Vorkatalysatorprecatalyzer
- 1818
- NOX-SpeicherkatalysatorNO X storage catalyst
- 2020
- sauerstoffempfindliche Messeinrichtungoxygen-sensitive measuring device
- 2222
- MotorsteuergerätEngine control unit
- 2424
- Steuereinheitcontrol unit
- 100100
- Verbrennungslambdacombustion lambda
- 102102
- NOX-Beladung des NOX-SpeicherkatalysatorsNO x charge of the NO x storage catalyst
- 104104
- Signalverlauf (Uλ) der MesseinrichtungSignal curve (U λ ) of the measuring device
- 106106
- Reduktionsmittelgehalt im AbgasReducing agent content in the exhaust gas
- tA t A
- Regenerationsbeginnregeneration start
- tE t E
- Regenerationsenderegeneration end
- tS t s
- Zeitpunkt der Überschreitung von USE Time of exceeding of U SE
- tAH t AH
- HochrechnungsbeginnExtrapolation beginning
- TH T H
- HochrechnungsdauerExtrapolation time
- Δt.delta.t
- AbgaslaufzeitExhaust maturity
- Uλ U λ
- Signal der MesseinrichtungSignal of the measuring device
- USE U SE
- Schwellenwert zur Beendigung der NOX-RegenerationThreshold to stop the NO X regeneration
- USi U Si
- Schwellenwerte zur Anhebung oder Absenkung des VerbrennungslambdasThresholds for raising or lowering the combustion lambda
- λM λ M
- LambdamagerwertLambda lean value
- λF λ F
- LambdafettwertLambda fat value
Claims (21)
- Method for the NOX regeneration of an NOX storage catalytic converter (18) which is arranged in an exhaust duct of an internal combustion engine (10) which is capable of lean running, wherein a rich to stoichiometric exhaust gas atmosphere with λ ≤ 1 is applied to the NOX storage catalytic converter (18) until an end of the regeneration process is reached, and a regeneration course is pursued by means of an oxygen-dependent signal which is made available by an oxygen-sensitive measuring device (20) which is arranged downstream of the NOX storage catalytic converter (18), characterized in that(a) the oxygen-dependent signal (Uλ) of the measuring device (20) is projected forward during the NOX regeneration,
and at least one of the following measures is carried out:(b) an air/fuel mixture (combustion lambda) which is supplied to the internal combustion engine (10) during the regeneration is varied as a function of the projected signal (Uλ) taking into account a time period (Δt) essentially corresponding to an exhaust gas transit time between the internal combustion engine (10) and NOX storage catalytic converter (18), and(c) a theoretical time (tS) at which a predefined signal threshold value (USE) is exceeded is determined on the basis of the projected signal (Uλ) and the end (tE) of the regeneration is defined by subtracting the time period (Δt) from the theoretical time (tS). - Method according to Claim 1, characterized in that the air/fuel mixture (combustion lambda) which is supplied to the internal combustion engine (10) during the regeneration is varied as a function of the projected signal (Uλ) and the time (tS) taking into account the time period (Δt).
- Method according to one of the preceding claims, characterized in that the oxygen-dependent signal (Uλ) is projected forward by means of current operating parameters of the internal combustion engine (10) and/or of the exhaust gas system (12).
- Method according to Claim 3, characterized in that the oxygen-dependent signal (Uλ) is projected forward as a function of an air/fuel mixture which is supplied to the internal combustion engine (10) and/or an exhaust gas mass flow and/or an exhaust temperature and/or a catalytic converter temperature.
- Method according to Claim 3 or 4, characterized in that the oxygen-dependent signal (Uλ) is projected forward taking into account a behaviour model of the NOX storage catalytic converter (18).
- Method according to one of Claims 3 to 5, characterized in that the oxygen-dependent signal (Uλ) is projected forward taking into account a behaviour model of the oxygen-sensitive measuring device (20), in particular an inertia of the measuring device (20).
- Method according to one of the preceding claims, characterized in that the projection starts after the end of a predefined time after the start of the regeneration and/or after a predefined mass of exhaust gas has passed through and/or after a predefined threshold of the signal (Uλ) has been exceeded.
- Method according to one of the preceding claims, characterized in that the exhaust gas transit time (Δt) is calculated by means of current operating parameters of the internal combustion engine (10) or is predefined.
- Method according to one of the preceding claims, characterized in that the projection of the signal (Uλ) does not take place if predefined limiting values for operating conditions of the internal combustion engine (10) and/or of the exhaust gas system (12) are not complied with.
- Method according to Claim 9, characterized in that limiting values are predefined for the exhaust gas mass flow and/or for the temperature of the NOX storage catalytic converter (18).
- Method according to Claim 9 or 10, characterized in that the projection of the signal (Uλ) does not take place in the event of an overrun shutoff during the NOX regeneration.
- Method according to one of the preceding claims, characterized in that the combustion lambda is raised if the projected sensor signal (Uλ) reaches a second predefined signal threshold value (US2) taking into account the exhaust gas transit time (Δt) or after the expiry of a predefinable portion of a regeneration period which is acquired by means of the projection.
- Method according to Claim 12, characterized in that the combustion lambda of the internal combustion engine (10) is raised, in advance of the end (tE) of the regeneration, to a value (λF4) which is higher than a preceding combustion lambda value and is ≤ 1.
- Method according to Claim 13, characterized in that the combustion lambda is raised to λF4 = 0.94 to 0.99, in particular to 0.95 to 0.98.
- Method according to one of the preceding claims, characterized in that the combustion lambda of the internal combustion engine (10) is lowered to a value (λF2) below a preceding lambda value ( (λF1) until the projected sensor signal (Uλ) reaches a third predefined signal threshold value (US1) taking into account the exhaust gas transit time (Δt).
- Method according to Claim 15, characterized in that the combustion lambda is lowered to λF2 = 0.6 to 0.9, in particular to 0.7 to 0.8.
- Method according to one of the preceding claims, characterized in that the raising and/or lowering of the combustion lambda is carried out incrementally.
- Device for carrying out a regeneration of an NOX storage catalytic converter (18) which is arranged in an exhaust duct of an internal combustion engine (10) which is capable of lean running, wherein a rich to stoichiometric exhaust gas atmosphere with λ ≤ 1 is applied to the NOx storage catalytic converter (18) until an end of the regeneration process is reached, and a regeneration sequence is pursued by means of an oxygen-dependent signal which is made available by an oxygen-sensitive measuring device (20) which is arranged downstream of the NOx storage catalytic converter (18), characterized by means with which the method steps(a) projecting forward of the oxygen-dependent signal (Uλ) of the measuring device (20) during the NOX regeneration,
and at least one of the following measures can be carried out:(b) an air/fuel mixture (combustion lambda) which is supplied to the internal combustion engine (10) during the regeneration is varied as a function of the projected signal (Uλ) taking into account a time period (Δt) essentially corresponding to an exhaust gas transit time between the internal combustion engine (10) and NOX storage catalytic converter (18), and(c) a theoretical time (tS) at which a predefined signal threshold value (USE) is exceeded is determined on the basis of the projected signal (Uλ) and the end (tE) of the regeneration is defined by subtracting the time period (Δt) from the theoretical time (tS). - Device according to Claim 18, characterized in that the means comprise a control unit (24) in which an algorithm for controlling the method steps is stored in a digital form.
- Device according to Claim 19, characterized in that the control unit (24) is integrated into an engine control device (22).
- Device according to one of Claims 18 to 20, characterized in that the oxygen-sensitive measuring device (20) comprises a broadband or step response lambda probe or an NOX sensor.
Applications Claiming Priority (4)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
DE10057936 | 2000-11-22 | ||
DE10057938 | 2000-11-22 | ||
DE2000157938 DE10057938A1 (en) | 2000-11-22 | 2000-11-22 | Regenerating nitrogen oxides storage catalyst in I.C. engine involves extrapolating oxygen-dependent signal from oxygen-sensitive measuring device |
DE2000157936 DE10057936A1 (en) | 2000-11-22 | 2000-11-22 | Regenerating nitrogen oxides storage catalyst in exhaust gas channel of lean-burn I.C. engine involves using extrapolated oxygen-dependent signal |
Publications (4)
Publication Number | Publication Date |
---|---|
EP1209332A2 EP1209332A2 (en) | 2002-05-29 |
EP1209332A3 EP1209332A3 (en) | 2004-06-09 |
EP1209332B1 true EP1209332B1 (en) | 2008-06-25 |
EP1209332B8 EP1209332B8 (en) | 2008-08-13 |
Family
ID=26007746
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
EP20010250407 Expired - Lifetime EP1209332B8 (en) | 2000-11-22 | 2001-11-21 | Method and device for regenerating an NOx storage catalytic converter |
Country Status (2)
Country | Link |
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EP (1) | EP1209332B8 (en) |
DE (1) | DE50114044D1 (en) |
Families Citing this family (6)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
DE10361286B4 (en) | 2003-12-24 | 2013-09-19 | Daimler Ag | Process for the regeneration of a nitrogen oxide storage catalyst |
GB2424197B (en) * | 2005-03-15 | 2009-01-14 | Ford Global Tech Llc | A method for adaptively controlling the regeneration of a lean nox trap |
US8006480B2 (en) | 2007-07-25 | 2011-08-30 | Eaton Corporation | Physical based LNT regeneration strategy |
GB2504975A (en) * | 2012-08-15 | 2014-02-19 | Gm Global Tech Operations Inc | Method of controlling a DeSOx regeneration process of a Lean NOx Trap |
FR3030620B1 (en) * | 2014-12-22 | 2018-03-09 | Renault S.A.S | METHOD FOR PURGING A NITROGEN OXIDE TRAP AND ASSOCIATED MOTORIZATION DEVICE |
US9631565B2 (en) * | 2015-09-15 | 2017-04-25 | Hyundai Motor Company | Control method for improving nitrogen oxide purification performance |
Family Cites Families (6)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JPH0814031A (en) * | 1994-06-24 | 1996-01-16 | Hitachi Ltd | Judgement on reduction and absorption performance of nox reduction catalyst in internal combustion engine, and reduction of nox |
EP0940570B1 (en) * | 1998-01-09 | 2001-08-22 | Ford Global Technologies, Inc. | Method for regenerating a nitrogen oxide trap in the exhaust system of an internal combustion engine taking into account the exhaust gas mass flow |
DE19808382A1 (en) * | 1998-02-27 | 1999-09-02 | Volkswagen Ag | Control of a NOx absorber catalytic converter |
DE19844082C1 (en) * | 1998-09-25 | 1999-10-14 | Siemens Ag | Regeneration of a nitrogen oxides storage catalyst used with lean burn engine |
FR2785331B1 (en) * | 1998-10-28 | 2000-12-22 | Renault | METHOD FOR CONTROLLING THE PURGE OF NITROGEN OXIDES FROM A CATALYTIC EXHAUST TREATMENT POT OF AN INTERNAL COMBUSTION ENGINE |
DE19915793A1 (en) * | 1999-04-08 | 2000-10-19 | Daimler Chrysler Ag | Process for the desorption of a nitrogen oxide adsorber of an exhaust gas cleaning system |
-
2001
- 2001-11-21 DE DE50114044T patent/DE50114044D1/en not_active Expired - Lifetime
- 2001-11-21 EP EP20010250407 patent/EP1209332B8/en not_active Expired - Lifetime
Also Published As
Publication number | Publication date |
---|---|
EP1209332A2 (en) | 2002-05-29 |
EP1209332B8 (en) | 2008-08-13 |
DE50114044D1 (en) | 2008-08-07 |
EP1209332A3 (en) | 2004-06-09 |
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