DE19644407C2 - Process for reducing the emissions of an internal combustion engine - Google Patents
Process for reducing the emissions of an internal combustion engineInfo
- Publication number
- DE19644407C2 DE19644407C2 DE19644407A DE19644407A DE19644407C2 DE 19644407 C2 DE19644407 C2 DE 19644407C2 DE 19644407 A DE19644407 A DE 19644407A DE 19644407 A DE19644407 A DE 19644407A DE 19644407 C2 DE19644407 C2 DE 19644407C2
- Authority
- DE
- Germany
- Prior art keywords
- internal combustion
- fuel
- combustion engine
- exhaust
- exhaust gas
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Fee Related
Links
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
- F02D41/30—Controlling fuel injection
- F02D41/38—Controlling fuel injection of the high pressure type
- F02D41/40—Controlling fuel injection of the high pressure type with means for controlling injection timing or duration
- F02D41/402—Multiple injections
- F02D41/405—Multiple injections with post injections
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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
- F01N13/011—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 purifying devices arranged in parallel
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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
- 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
- F01N3/0871—Regulation of absorbents or adsorbents, e.g. purging
- F01N3/0878—Bypassing absorbents or adsorbents
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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
- F01N3/10—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust
- F01N3/18—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust characterised by methods of operation; Control
- F01N3/20—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust characterised by methods of operation; Control specially adapted for catalytic conversion ; Methods of operation or control of catalytic converters
- F01N3/2006—Periodically heating or cooling catalytic reactors, e.g. at cold starting or overheating
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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
- F02D41/024—Introducing corrections for particular conditions exterior to the engine in relation with the state of the exhaust gas treating apparatus to increase temperature of the exhaust gas treating 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
- 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
- F01N2250/00—Combinations of different methods of purification
- F01N2250/12—Combinations of different methods of purification absorption or adsorption, and catalytic conversion
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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
- F01N2410/00—By-passing, at least partially, exhaust from inlet to outlet of apparatus, to atmosphere or to other device
- F01N2410/12—By-passing, at least partially, exhaust from inlet to outlet of apparatus, to atmosphere or to other device in case of absorption, adsorption or desorption of exhaust gas constituents
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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
- F01N2430/00—Influencing exhaust purification, e.g. starting of catalytic reaction, filter regeneration, or the like, by controlling engine operating characteristics
- F01N2430/06—Influencing exhaust purification, e.g. starting of catalytic reaction, filter regeneration, or the like, by controlling engine operating characteristics by varying fuel-air ratio, e.g. by enriching fuel-air mixture
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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
- F01N2610/00—Adding substances to exhaust gases
- F01N2610/03—Adding substances to exhaust gases the substance being hydrocarbons, e.g. engine fuel
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
- F02B—INTERNAL-COMBUSTION PISTON ENGINES; COMBUSTION ENGINES IN GENERAL
- F02B75/00—Other engines
- F02B75/12—Other methods of operation
- F02B2075/125—Direct injection in the combustion chamber for spark ignition engines, i.e. not in pre-combustion chamber
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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
- F02D2250/00—Engine control related to specific problems or objectives
- F02D2250/18—Control of the engine output torque
- F02D2250/21—Control of the engine output torque during a transition between engine operation modes or states
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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
- F02D41/30—Controlling fuel injection
- F02D41/38—Controlling fuel injection of the high pressure type
- F02D41/40—Controlling fuel injection of the high pressure type with means for controlling injection timing or duration
- F02D41/402—Multiple injections
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
- Y02T10/00—Road transport of goods or passengers
- Y02T10/10—Internal combustion engine [ICE] based vehicles
- Y02T10/12—Improving ICE efficiencies
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
- Y02T10/00—Road transport of goods or passengers
- Y02T10/10—Internal combustion engine [ICE] based vehicles
- Y02T10/40—Engine management systems
Landscapes
- Engineering & Computer Science (AREA)
- Chemical & Material Sciences (AREA)
- Combustion & Propulsion (AREA)
- Mechanical Engineering (AREA)
- General Engineering & Computer Science (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Health & Medical Sciences (AREA)
- Toxicology (AREA)
- Exhaust Gas After Treatment (AREA)
- Electrical Control Of Air Or Fuel Supplied To Internal-Combustion Engine (AREA)
Description
Die Erfindung betrifft ein Verfahren zur Reduzierung der Emis sionen einer Brennkraftmaschine der im Oberbegriff des An spruchs 1 angegebenen Gattung.The invention relates to a method for reducing the emissions sions of an internal combustion engine in the preamble of the An say 1 specified genus.
In der DE-OS 22 54 895 ist ein Verfahren zur Behandlung von Mo torabgasen beschrieben, wobei in den Abgasstrang einer Brenn kraftmaschine während des Motor-Anfangsbetriebs stromauf eines ersten Katalysators zusätzlich Brennstoff eingespritzt wird. Durch das Zusetzen einer Kraftstoffmenge in das Abgas unmittel bar vor dem vordersten Katalysator wird sichergestellt, daß der Katalysator rascher auf eine Temperatur gebracht wird, die zur Einleitung und Aufrechterhaltung der Oxidation von Kohlen monoxid und Kohlenwasserstoffen im Abgas führt.DE-OS 22 54 895 describes a method for the treatment of Mo Torabgasen described, with a burner in the exhaust line Engine upstream of one during initial engine operation fuel is injected in the first catalyst. By adding a quantity of fuel to the exhaust gas immediately bar in front of the front catalytic converter ensures that the Catalyst is brought to a temperature more quickly, which leads to Initiation and maintenance of coal oxidation leads to monoxide and hydrocarbons in the exhaust gas.
In der DE 43 38 883 A1 ist eine Katalysatoranordnung zur Reduk tion von in sauerstoffhaltigen Abgasen enthaltenen Stickoxiden beschrieben. Diese Katalysatoranordnung enthält mehrere in Ab gasströmungsrichtung mit Abstand aufeinanderfolgende Katalysa toren gleichen Aufbaus, die sowohl reduzierend als auch oxidie rend wirken. Mittels einer Dosiereinrichtung, der Signale für die Abgastemperatur zugeführt werden, erfolgt eine Kraftstoff zufuhr von Abgas vor dem jeweiligen Katalysator. Diese Anord nung ist für das Abgas von Dieselmaschinen oder Ottomaschinen, die mit magerem Kraftstoff/Luft-Gemisch betrieben werden, vor gesehen. DE 43 38 883 A1 describes a catalyst arrangement for reduc tion of nitrogen oxides contained in oxygen-containing exhaust gases described. This catalyst arrangement contains several in Ab gas flow direction with successive catalytic converters gates of the same structure, which are both reducing and oxidizing act. By means of a dosing device, the signals for the exhaust gas temperature is supplied, a fuel takes place supply of exhaust gas upstream of the respective catalytic converter. This arrangement is for the exhaust gas from diesel engines or petrol engines, which are operated with a lean fuel / air mixture seen.
Die bekannten Anordnungen erfordern einen zusätzlichen Bauaufwand, um die zusätzliche Kraftstoffmenge in die Ab gasleitung einzubringen und entsprechend zu dosieren.The known arrangements require an additional one Construction effort to the additional amount of fuel in the Ab insert the gas line and dose accordingly.
Aus der US 5,207,058 geht ein Verfahren zur Reduzierung der Emissionen einer Otto-Brennkraftmaschine hervor, wel ches durch Zugabe von Kraftstoff in die Verbrennungsab gase mittels nachträglicher Einspritzungen in eine Brenn kammer während des Auslaßtaktes des betreffenden Zylin ders eine Erwärmung des Katalysators im Abgastrakt vor sieht. Die Oxidationsreaktion der zusätzlichen Kraft stoffmenge verursacht die gewünschte Abgaserwärmung vor dem Katalysator, um diesen auf die angestrebte Zieltem peratur aufzuheizen. Das bekannte Verfahren sieht den Einsatz eines Dreiwegekatalysators zur Behandlung der Abgase vor, welcher jedoch bekanntlich zum Erreichen einer effektiven Schadstoffumwandlung stöchiometrische Abgaszusammensetzungen erforderlich macht. Direktein spritzende Otto-Brennkraftmaschinen können jedoch vor teilhaft mit Luftüberschuß bei der Verbrennung betrieben werden, wodurch beispielsweise der Kraftstoffverbrauch gesenkt werden kann. Bei Lambda - Werten außerhalb des stöchiometrischen Fensters und insbesondere bei Lambda < 1 kann ein Dreiwege-Katalysator nicht effektiv arbeiten und mindestens einer der zu reduzierenden Schadstoffe wird unbehandelt in die Umwelt ausgestoßen. Mit der zustätz lichen Nacheinspritzung wird bei dem bekannten Verfahren das Abgas angefettet zwecks Schaffung stöchiometrischer Luftverhältnisse. Die Menge des nachträglich einzu spritzenden Kraftstoffes muß jedoch klein sein, um eine schädliche Überhitzung des Katalysators zu vermeiden, so daß auch der Betriebsbereich möglicher Lambda-Werte des zu verbrennenden Frischgases eng begrenzt ist, da offen bar nur eine solche Luftüberschußmenge im Abgas enthalten sein darf, welche an der Oxidationsreaktion der Nacheinspritzmenge beteiligt ist.A reduction method is known from US Pat. No. 5,207,058 the emissions of an Otto engine, wel by adding fuel to the combustion chamber gases by means of subsequent injections into a combustion chamber during the exhaust stroke of the relevant cylinder before heating the catalyst in the exhaust tract sees. The oxidation reaction of the additional force The amount of substance causes the desired exhaust gas heating the catalyst to get this to the desired goal heat up temperature. The known method sees that Use of a three-way catalyst for the treatment of Exhaust gases before, which, however, is known to reach an effective pollutant conversion stoichiometric Requires exhaust gas compositions. Direct one splashing Otto internal combustion engines can, however, be used partly operated with excess air during combustion be, for example, the fuel consumption can be lowered. For lambda values outside the stoichiometric window and especially when lambda <1 a three-way catalytic converter cannot work effectively and at least one of the pollutants to be reduced released into the environment untreated. With the addition Lichen post-injection is in the known method the exhaust gas is greased to create stoichiometric Air conditions. The amount to be added later splashing fuel must be small, however, in order to to avoid harmful overheating of the catalyst, so that the operating range of possible lambda values of the fresh gas to be burned is narrowly limited since it is open bar only such excess air in the exhaust gas May be included, which is part of the oxidation reaction of the Post injection quantity is involved.
Der vorliegenden Erfindung liegt die Aufgabe zugrunde, ein Verfahren zur Reduzierung der Emissionen einer Brenn kraftmaschine der im Oberbegriff des Anspruchs 1 angege benen Gattung zu schaffen, das bei einem verminderten Bauaufwand sicher durchführbar ist und das einen Betrieb der Brennkraftmaschine mit beliebigen λ-Werten zuläßt.The present invention is based on the object a method of reducing the emissions of a burning Engine specified in the preamble of claim 1 to create the same genre, which in a diminished Construction effort can be carried out safely and that operation allows the internal combustion engine with any λ values.
Diese Aufgabe wird durch ein Verfahren mit den Merkmalen des Anspruchs 1 gelöst.This task is accomplished by a method with the characteristics of claim 1 solved.
Direkteinspritzende Ottomotoren können gegenüber solchen mit Saugrohreinspritzung in der Warmlaufphase deutlich magerer betrieben werden. Diese Maßnahme senkt die Koh lenwasserstoffemission deutlich ab. Zusätzlich zu dieser bekannten Maßnahme bietet die vorliegende Erfindung den Vorteil, daß die direkteinspritzende Brennkraftmaschine mit einem Luftüberschuß betrieben werden kann, wobei der Wert λ < 2 betragen kann. Als besonders bevorzugt wird ein Betrieb der Brennkraftmaschine mit Luftüberschuß von λ 1,1 bis 1,4 angesehen. Mittels des vorhandenen Injek tors wird nach der eigentlichen Verbrennung des Luft- Kraftstoff-Gemisches während des Auslaßtaktes in den je weiligen Zylinder eine definierte Menge Otto-Kraftstoff nachträglich eingespritzt. Dabei ist die Kraftstoffmenge so bemessen, daß die nicht verbrannte Luftmasse aufoxi diert werden kann. Direct-injection gasoline engines can be compared to such with intake manifold injection clearly in the warm-up phase run lean. This measure lowers the Koh hydrogen emissions significantly. In addition to this known measure, the present invention provides the Advantage that the direct injection internal combustion engine can be operated with an excess of air, the Value λ <2 can be. Is particularly preferred an operation of the internal combustion engine with excess air from λ 1.1 to 1.4 viewed. Using the existing injection after the actual combustion of the air Fuel mixture during the exhaust stroke in each cylinder a defined amount of petrol injected subsequently. Here is the amount of fuel dimensioned so that the unburned air mass is exposed can be dated.
Der nacheingespritzte Kraftstoff und die unverbrannten Kohlenwasserstoffe verbrennen mit dem Restsauerstoff in einer exothermen Reaktion. Dies führt zu einer umgehenden starken Erhöhung der Abgastemperatur, wodurch der Katalysator rasch auf Betriebstemperatur gebracht wird.The post-injected fuel and the unburned Hydrocarbons burn in with the residual oxygen an exothermic reaction. This leads to an immediate strong increase in exhaust gas temperature, causing the Catalyst is quickly brought to operating temperature.
Mit dem erfindungsgemäße Verfahren sind Brennkraftma schinen, die mit einem NOx-Speicherkatalysator ausge rüstet sind, mit beliebigen λ-Werten betreibbar, da im Betrieb mit λ-Werten < 1 das Abgas einem Speicherkata lysator zugeführt und im Betrieb mit einem Wert λ = 1 eine Abgasklappe geöffnet wird, so daß das Abgas durch einen den Speicherkatalysator umgehenden Bypass strömt. Während bei den bekannten Anordnungen mit NOx-Speicher katalysator zum kurzzeitigen Umstellen auf ein fettes oder stöchiometrisches Gemisch üblicherweise eine rasche Änderung des Luft- oder Kraftstoffliefergrades erfolgt, wodurch in der Regel Drehmomentsprünge auftreten, hat die vorliegende Erfindung den Vorteil, daß die Brennkraftma schine unabhängig von der zusätzlichen Kraftstoff nacheinspritzung weiterhin mit dem λ-Wert aus dem Kenn feld betrieben wird. Der zum sogenannten Ausräumen des Katalysators notwendige Kraftstoff wird durch die Nach einspritzung dem heißen Abgas im Brennraum zugeführt und verdampft sofort. Auf diese Weise steht dem Speicherkata lysator das zur Regeneration notwendige fette Gemisch ohne Veränderung der Motoreinstellung zur Verfügung. With the inventive method are internal combustion machinen out with a NOx storage catalyst are equipped, can be operated with any λ values, since in Operation with λ values <1 the exhaust gas a storage data lysator supplied and in operation with a value λ = 1 an exhaust flap is opened so that the exhaust gas through a bypass flowing around the storage catalytic converter flows. While in the known arrangements with NOx storage catalyst for a short changeover to a rich one or stoichiometric mixture usually a rapid Change in air or fuel delivery level, which usually causes torque jumps has the present invention the advantage that the Brennma shine regardless of the additional fuel post-injection continues with the λ value from the characteristic field is operated. The for the so-called clearing the The catalyst necessary fuel is provided by the post injection to the hot exhaust gas in the combustion chamber and evaporates immediately. In this way, the storage data analyzer the fat mixture necessary for regeneration available without changing the engine setting.
Durch die vorliegende Erfindung ergibt sich eine deutli che Reduzierung der Warmlaufemission und zwar durch den Magerbetrieb im Warmlauf, die Sekundärrektionen im Aus laßkanal und das schnelle Anspringen des Katalysators. Da keine zusätzlichen Systeme zur Kraftstoff und/oder Luft einbringung in der Abgasleitung erforderlich sind, ergibt sich gegenüber den bekannten Systemen auch ein deutlicher Kostenvorteil. Da bei direkteinspritzenden Brennkraftma schinen für jeden Zylinder ein Injektor vorgesehen ist, erfordert es hardwareseitig keinen zusätzlichen Bauauf wand, um die Nacheinspritzung in allen Zylindern der Brennkraftmaschine durchzuführen.The present invention results in a clear che reduction of the warm-up emission by the Lean operation in warm-up, the secondary reactions in off let channel and the quick start of the catalyst. There no additional fuel and / or air systems introduction in the exhaust pipe are required compared to the known systems Cost advantage. As with direct injection internal combustion an injector is provided for each cylinder, it does not require any additional construction on the hardware side turned to the post-injection in all cylinders of the Perform internal combustion engine.
Gemäß einer besonderen Weiterbildung des Verfahrens wird aus dem gemessenen λ-Wert ein Signal gebildet, das einer Steuereinheit zuführbar ist. In dieser Steuereinheit wird ein Ausgangssignal zum Ansteuern des Injektors berechnet, so daß mit Hilfe der Nacheinspritzung lediglich die tat sächlich benötigte Kraftstoffmenge eingespritzt wird.According to a special development of the method a signal is formed from the measured λ value, which one Control unit can be fed. In this control unit calculates an output signal to control the injector, so that with the help of post-injection only did that Actually required amount of fuel is injected.
Das erfindungsgemäße Verfahren ist nachstehend anhand der Zeichnung, die eine schematische Darstellung eines Zylin ders einer Brennkraftmaschine mit einer Abgasanlage zeigt, näher er läutert.The method according to the invention is based on the Drawing showing a schematic representation of a zylin otherwise shows an internal combustion engine with an exhaust system, closer purifies.
In der einzigen Zeichnungsfigur ist ein Teil einer Brenn kraftmaschine gezeigt mit einem Zylinder 1, in dem ein Brenn raum 2 gebildet ist, der von einem Zylinderkopf 3 und einem in dem Zylinder 1 geführten Kolben 4 begrenzt ist. In dem Zylin derkopf 3 befindet sich ein Einlaßkanal 5 mit einem steuerbaren Einlaßventil 7 sowie ein Auslaßkanal 6 mit einem steuerbaren Auslaßventil 8. In dem Zylinderkopf 3 ist außerdem ein Injektor 9 angeordnet, der an eine Kraftstoffleitung 10 angeschlossen ist und zum Einspritzen des Kraftstoffs in den Brennraum 2 dient. Der Injektor 9 wird von einer Steuereinheit 20 angesteu ert, um die jeweils benötigte Kraftstoffmenge in den Brennraum 2 einzuspritzen.In the single drawing figure, part of an internal combustion engine is shown with a cylinder 1 , in which a combustion chamber 2 is formed, which is limited by a cylinder head 3 and a piston 4 guided in the cylinder 1 . In the cylin derkopf 3 there is an inlet channel 5 with a controllable inlet valve 7 and an outlet channel 6 with a controllable outlet valve 8 . In addition, an injector 9 is arranged in the cylinder head 3 , which is connected to a fuel line 10 and serves to inject the fuel into the combustion chamber 2 . The injector 9 is actuated by a control unit 20 in order to inject the required amount of fuel into the combustion chamber 2 .
An den Auslaßkanal 6 ist eine Abgasleitung 12 angeschlossen, wobei am Beginn der Abgasleitung 12, das heißt unmittelbar nach einem am Zylinderkopf 3 anageflanschten Abgaskrümmer, eine Lambda-Sonde 11 angeordnet ist, die ein dem jeweiligen Meßwert entsprechendes Signal an die Steuereinheit 20 liefert. Die Ab gasleitung 12 umfaßt einen Leitungsabschnitt 12*, in dem eine mittels eines Antriebs 19 bewegbare Abgasklappe 18 angeordnet ist. An den Leitungsabschnitt 12* schließen sich zwei parallele Zweigleitungen 12' und 12" an, wobei in jeder der Zweigleitun gen 12', 12" ein Drei-Wege-Katalysator 15 bzw. 16 angeordnet ist. In einem sich an die Zweigleitungen 12', 12" an schließenden gemeinsamen Endabschnitt 12''' ist eine Füh rungssonde 17 angeordnet, die ein entsprechendes Signal der Steuereinheit 20 zuführt. Die Abgasleitung 12 umfaßt außerdem einen Leitungsabschnitt 13, der vor dem Leitungsabschnitt 12* abzweigt und stromab der Abgasklappe 18 vor der Verzweigung der Zweigleitungen 12' und 12" wieder in die Abgasleitung 12 mün det. In dem Leitungsabschnitt 13 ist ein NOx- Speicherkatalysator 14 vorgesehen. An exhaust pipe 12 is connected to the exhaust port 6 , a lambda probe 11 being arranged at the beginning of the exhaust pipe 12 , that is to say immediately after an exhaust manifold flanged onto the cylinder head 3 , which delivers a signal corresponding to the respective measured value to the control unit 20 . From the gas line 12 comprises a line section 12 *, in which a movable by means of a drive 19 exhaust valve 18 is arranged. At the line section 12 * there are two parallel branch lines 12 'and 12 ", with a three-way catalyst 15 and 16 being arranged in each of the branch lines 12 ', 12 ". A guide probe 17 , which feeds a corresponding signal to the control unit 20, is arranged in a common end section 12 '''adjoining the branch lines 12 ', 12 ". The exhaust gas line 12 also comprises a line section 13 , which is in front of the line section 12 * and branches off downstream of the exhaust flap 18 prior to the branch of the branch lines 12 'and 12 "Coin det again into the exhaust pipe 12th A NOx storage catalytic converter 14 is provided in the line section 13 .
Das Verfahren zur Reduzierung der Emissionen der Brenn kraftmaschine wird im wesentlichen in Abhängigkeit der mittels der λ-Sonde 11 und der Führungssonde 17 erfaßten Luft- bzw. Ab gaswerte in Verbindung mit einem in dem Steuergerät 20 abgeleg ten Kennfeld betrieben. Liegt der an der λ-Sonde 11 gemessene Wert für λ < 1, so erzeugt das Steuergerät 20 ein Signal, durch das der Antrieb 19 die Abgasklappe 18 in die Schließstellung bringt. Dadurch ist der als Bypass zu dem NOx-Speicherkatalysator 14 wirkende Leitungsabschnitt 12* geschlossen und das gesamte Abgasvolumen wird durch den Leitungsabschnitt 13 und somit den Speicherkatalysator 14 geleitet. Da in diesem Betriebsfall ein Luftüberschuß im Abgas vorhanden ist, wird der Injektor 9 von der Steuereinheit 20 derart angesteuert, daß im Auslaßhub des Kolbens 4 in den Brennraum 2 des Zylinders 1 eine Kraftstoff menge, deren Dosierung in der Steuereinheit 20 berechnet wird, eingespritzt wird, wodurch die unverbrannten Kohlenwasserstoffe mit dem Restsauerstoff in einer exothermen Reaktion verbrennen. Dadurch erhöht sich die Abgastemperatur unmittelbar sehr stark, so daß sich der Katalysator rasch auf die Betriebstemperatur erwärmt. Bei einer Betriebsweise des Motors mit λ-Werten = 1, das entspricht der Teillast im oberen Bereich bzw. der Vollast, wird durch ein von der Steuereinheit 20 erzeugtes Signal der Antrieb 19 derart angesteuert, daß ein vollständiges öffnen der Abgasklappe 18 erfolgt. Somit strömt das Abgasvolumen durch den als Bypass dienenden Leitungsabschnitt 12* unmittelbar zu den in den Zweigleitungen 12' und 12" angeordneten Drei-Wege- Katalysatoren 15 und 16. Da in dieser Betriebsweise der Brenn kraftmaschine sehr heißes Abgas den Brennraum verläßt und durch den Leitungsabschnitt 12* das Abgas unmittelbar den Drei-Wege- Katalysatoren 15 und 16 zugeleitet wird, liegt der Speicherka talysator 14 nicht im Abgasstrom und wird auf diese Weise vor extremen hohen Temperaturen geschützt.The method for reducing the emissions of the internal combustion engine is operated essentially as a function of the air or exhaust gas values detected by means of the λ probe 11 and the guide probe 17 in conjunction with a map stored in the control unit 20 . If the value for λ <1 measured on the λ probe 11 , the control unit 20 generates a signal by means of which the drive 19 brings the exhaust flap 18 into the closed position. As a result, the line section 12 * acting as a bypass to the NOx storage catalytic converter 14 is closed and the entire exhaust gas volume is passed through the line section 13 and thus the storage catalytic converter 14 . Since there is an excess of air in the exhaust gas in this operating case, the injector 9 is controlled by the control unit 20 such that a quantity of fuel, the metering of which is calculated in the control unit 20 , is injected into the exhaust stroke of the piston 4 in the combustion chamber 2 of the cylinder 1 , causing the unburned hydrocarbons to burn with the residual oxygen in an exothermic reaction. As a result, the exhaust gas temperature increases very rapidly, so that the catalytic converter warms up quickly to the operating temperature. When the engine is operating with λ values = 1, which corresponds to the partial load in the upper range or the full load, the drive 19 is controlled by a signal generated by the control unit 20 such that the exhaust flap 18 is completely opened. Thus, the exhaust gas volume flows through the line section 12 * serving as a bypass directly to the three-way catalytic converters 15 and 16 arranged in the branch lines 12 'and 12 ". In this mode of operation of the internal combustion engine, very hot exhaust gas leaves the combustion chamber and through the line section 12 * the exhaust gas is fed directly to the three-way catalysts 15 and 16 , the storage catalyst 14 is not in the exhaust gas flow and is thus protected from extremely high temperatures.
Wie aus der vorstehenden Beschreibung deutlich wird, betrifft das Verfahren nicht nur die Start- und Warmlaufphase der Brenn kraftmaschine, obwohl ein wesentlicher Vorteil in der Emissi onsreduzierung speziell in der Startphase zu sehen ist. Bei Verwendung eines NOx-Speicherkatalysators ist es jedoch notwen dig, in Abhängigkeit der Betriebszustände, nämlich im Magerbe trieb, dem Speicherkatalysator kurzzeitig fette Kraftstoff- Luft-Verhältnisse zuzuführen. Dies wird bei der Erfindung durch die Direkteinspritzung in den Zylinder innerhalb des Auslaßhubs durch eine zweite, nämlich die Nacheinspritzung erreicht. Da durch ist es möglich, das Verbrennungsluftverhältnis unverän dert zu lassen, so daß keine Momentensprünge an der Kurbelwelle der Brennkraftmaschine auftreten.As is clear from the above description, concerns the process not only the start and warm-up phase of the burning engine, although a major advantage in the Emissi ons reduction can be seen especially in the start-up phase. At However, it is necessary to use a NOx storage catalytic converter dig, depending on the operating conditions, namely in the lean area drove the storage catalytic converter briefly rich fuel To supply air conditions. This is achieved with the invention direct injection into the cylinder within the exhaust stroke achieved by a second, namely the post-injection. There it is possible to keep the combustion air ratio unchanged to leave so that no torque jumps on the crankshaft the internal combustion engine occur.
Im Rahmen der Erfindung wäre auch die Anordnung einer zweiten Klappe 18a im Leitungsstrang 13 denkbar. Schließlich wäre auch ein Abgassystem ohne jegliche Klappe vor stellbar, sofern ein temperaturfester NOx-Speicher-Katalysator eingesetzt würde.Within the scope of the invention, the arrangement of a second flap 18 a in the wiring harness 13 would also be conceivable. Finally, an exhaust system without any flap would be conceivable if a temperature-resistant NOx storage catalytic converter was used.
Claims (4)
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