DE102017211442B4 - Method for determining the ambient air humidity of a motor vehicle - Google Patents
Method for determining the ambient air humidity of a motor vehicle Download PDFInfo
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- 238000000034 method Methods 0.000 title claims abstract description 25
- 239000012080 ambient air Substances 0.000 title claims abstract description 9
- 239000003570 air Substances 0.000 claims abstract description 29
- 238000002485 combustion reaction Methods 0.000 claims abstract description 18
- 238000005259 measurement Methods 0.000 claims abstract description 10
- 239000000446 fuel Substances 0.000 claims abstract description 5
- 238000011144 upstream manufacturing Methods 0.000 claims abstract description 4
- 239000007789 gas Substances 0.000 claims description 75
- MWUXSHHQAYIFBG-UHFFFAOYSA-N Nitric oxide Chemical compound O=[N] MWUXSHHQAYIFBG-UHFFFAOYSA-N 0.000 claims description 39
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 claims description 20
- 239000001301 oxygen Substances 0.000 claims description 20
- 229910052760 oxygen Inorganic materials 0.000 claims description 20
- 238000012937 correction Methods 0.000 claims description 2
- 239000000523 sample Substances 0.000 description 11
- CURLTUGMZLYLDI-UHFFFAOYSA-N Carbon dioxide Chemical compound O=C=O CURLTUGMZLYLDI-UHFFFAOYSA-N 0.000 description 2
- 238000010586 diagram Methods 0.000 description 2
- 238000004519 manufacturing process Methods 0.000 description 2
- 239000000203 mixture Substances 0.000 description 2
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Chemical compound O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 2
- 230000015572 biosynthetic process Effects 0.000 description 1
- 238000009530 blood pressure measurement Methods 0.000 description 1
- 229910002092 carbon dioxide Inorganic materials 0.000 description 1
- 239000001569 carbon dioxide Substances 0.000 description 1
- 239000003054 catalyst Substances 0.000 description 1
- 230000003197 catalytic effect Effects 0.000 description 1
- 238000006243 chemical reaction Methods 0.000 description 1
- 238000009833 condensation Methods 0.000 description 1
- 230000005494 condensation Effects 0.000 description 1
- 238000001816 cooling Methods 0.000 description 1
- 230000003111 delayed effect Effects 0.000 description 1
- 230000001419 dependent effect Effects 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- 230000018109 developmental process Effects 0.000 description 1
- 238000009826 distribution Methods 0.000 description 1
- 239000011261 inert gas Substances 0.000 description 1
- VUZPPFZMUPKLLV-UHFFFAOYSA-N methane;hydrate Chemical compound C.O VUZPPFZMUPKLLV-UHFFFAOYSA-N 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 230000035945 sensitivity Effects 0.000 description 1
- 238000003860 storage Methods 0.000 description 1
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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
- F02D41/0025—Controlling engines characterised by use of non-liquid fuels, pluralities of fuels, or non-fuel substances added to the combustible mixtures
- F02D41/0047—Controlling exhaust gas recirculation [EGR]
- F02D41/0065—Specific aspects of external EGR control
- F02D41/0072—Estimating, calculating or determining the EGR rate, amount or flow
-
- 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
- F01N11/00—Monitoring or diagnostic devices for exhaust-gas treatment apparatus, e.g. for catalytic activity
-
- 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
- F02D41/0025—Controlling engines characterised by use of non-liquid fuels, pluralities of fuels, or non-fuel substances added to the combustible mixtures
- F02D41/0047—Controlling exhaust gas recirculation [EGR]
- F02D41/005—Controlling exhaust gas recirculation [EGR] according to engine operating conditions
- F02D41/0055—Special engine operating conditions, e.g. for regeneration of exhaust gas treatment apparatus
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
- F02D—CONTROLLING COMBUSTION ENGINES
- F02D41/00—Electrical control of supply of combustible mixture or its constituents
- F02D41/02—Circuit arrangements for generating control signals
- F02D41/04—Introducing corrections for particular operating conditions
- F02D41/12—Introducing corrections for particular operating conditions for deceleration
- F02D41/123—Introducing corrections for particular operating conditions for deceleration the fuel injection being cut-off
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
- F02D—CONTROLLING COMBUSTION ENGINES
- F02D41/00—Electrical control of supply of combustible mixture or its constituents
- F02D41/02—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
- F02D41/1441—Plural sensors
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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
- F02D41/1456—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 with sensor output signal being linear or quasi-linear with the concentration of oxygen
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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
- F01N2560/00—Exhaust systems with means for detecting or measuring exhaust gas components or characteristics
- F01N2560/02—Exhaust systems with means for detecting or measuring exhaust gas components or characteristics the means being an exhaust gas sensor
- F01N2560/028—Exhaust systems with means for detecting or measuring exhaust gas components or characteristics the means being an exhaust gas sensor for measuring or detecting humidity or water
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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
- F01N2560/00—Exhaust systems with means for detecting or measuring exhaust gas components or characteristics
- F01N2560/07—Exhaust systems with means for detecting or measuring exhaust gas components or characteristics the means being an exhaust gas flow rate or velocity meter or sensor, intake flow meters only when exclusively used to determine exhaust gas parameters
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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
- F01N2900/00—Details of electrical control or of the monitoring of the exhaust gas treating apparatus
- F01N2900/06—Parameters used for exhaust control or diagnosing
- F01N2900/12—Parameters used for exhaust control or diagnosing said parameters being related to the vehicle exterior
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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
- F01N2900/00—Details of electrical control or of the monitoring of the exhaust gas treating apparatus
- F01N2900/06—Parameters used for exhaust control or diagnosing
- F01N2900/14—Parameters used for exhaust control or diagnosing said parameters being related to the exhaust gas
- F01N2900/1411—Exhaust gas flow rate, e.g. mass flow rate or volumetric flow rate
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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
- F01N2900/00—Details of electrical control or of the monitoring of the exhaust gas treating apparatus
- F01N2900/06—Parameters used for exhaust control or diagnosing
- F01N2900/16—Parameters used for exhaust control or diagnosing said parameters being related to the exhaust apparatus, e.g. particulate filter or catalyst
- F01N2900/1628—Moisture amount in exhaust 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
- F02D2200/04—Engine intake system parameters
- F02D2200/0418—Air humidity
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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
- F02D41/144—Sensor in intake manifold
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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
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- Engineering & Computer Science (AREA)
- Chemical & Material Sciences (AREA)
- Combustion & Propulsion (AREA)
- Mechanical Engineering (AREA)
- General Engineering & Computer Science (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Exhaust-Gas Circulating Devices (AREA)
- Combined Controls Of Internal Combustion Engines (AREA)
Abstract
Verfahren zum Ermitteln der Feuchte der Umgebungsluft in einem Kraftfahrzeug mit Verbrennungsmotor (1) und Abgasrückführung (LP-EGR, HP-EGR) bei abgeschalteter Kraftstoffzufuhr unter Verwendung eines stromaufwärts einer Abgasnachbehandlungseinrichtung (4) angeordneten Abgassensors (5), dadurch gekennzeichnet, dass die Umgebungsluftfeuchte unter Verwendung eines weiteren, stromabwärts der Abgasnachbehandlungseinrichtung (4) angeordneten Abgassensors (6) ermittelt wird und zur Korrektur einer Messung des Luftmassenstroms und zur Korrektur einer Schätzung der Abgasrückführungsrate verwendet wird.Method for determining the humidity of the ambient air in a motor vehicle with an internal combustion engine (1) and exhaust gas recirculation (LP-EGR, HP-EGR) with the fuel supply switched off using an exhaust gas sensor (5) arranged upstream of an exhaust gas aftertreatment device (4), characterized in that the ambient air humidity is determined using a further exhaust gas sensor (6) arranged downstream of the exhaust gas aftertreatment device (4) and is used to correct a measurement of the air mass flow and to correct an estimate of the exhaust gas recirculation rate.
Description
Die Erfindung betrifft ein Verfahren zum Ermitteln der Feuchte der Umgebungsluft in einem Kraftfahrzeug mit Verbrennungsmotor und Abgasrückführung sowie ein zur Durchführung des Verfahrens eingerichtetes Kraftfahrzeug gemäß den Oberbegriffen der unabhängigen Patentansprüche.The invention relates to a method for determining the humidity of the ambient air in a motor vehicle with an internal combustion engine and exhaust gas recirculation, and to a motor vehicle set up to carry out the method according to the preambles of the independent claims.
Ein derartiges Verfahren ist aus der
Die US 2014 / 0 014 079 A1 offenbart ein Verfahren zur Messung der Umgebungsluftfeuchte in einem Lufteinlass eines Kraftfahrzeug-Verbrennungsmotor mit Abgasrückführung unter Verwendung eines im Einlass angeordneten Sauerstoffsensors. Außerdem sind zwei Abgassensoren stromaufwärts bzw. stromabwärts einer Abgasnachbehandlungseinrichtung angeordnet.US 2014/0 014 079 A1 discloses a method for measuring the ambient air humidity in an air inlet of a motor vehicle internal combustion engine with exhaust gas recirculation using an oxygen sensor arranged in the inlet. In addition, two exhaust gas sensors are arranged upstream or downstream of an exhaust gas aftertreatment device.
Die
Die
Die
Bei Verbrennungsmotoren hat Feuchte einen Einfluss auf Kondensation im Einlass sowie auf die Schätzung des aktuellen Stickoxid-Ausstoßes, die zur Steuerung von Abgasnachbehandlungseinrichtungen verwendet wird.In the case of internal combustion engines, moisture has an influence on condensation in the intake and on the estimate of the current nitrogen oxide emissions, which is used to control exhaust gas aftertreatment devices.
Es gibt zwei verschiedene Methoden, den Stickoxid-Ausstoß eines Verbrennungsmotors zu schätzen.There are two different methods for estimating the nitrogen oxide emissions of an internal combustion engine.
Die erste Methode bedient sich recht komplizierter Schätzungen, welche die Verbrennung und die chemischen Reaktionen im Zylinder zu modellieren versuchen. Eine derartige Schätzung der Ausbildung von Stickoxiden (NO und NO2) kann zum Beispiel bei jedem von vielen verschiedenen Kurbelwellenwinkeln aktualisiert werden. Alternativ kann die Gesamt-Stickoxidproduktion auf Basis von Informationen über Spitzendrücke und Spitzentemperaturen geschätzt werden.The first method uses quite complicated estimates that attempt to model combustion and chemical reactions in the cylinder. Such an estimate of the formation of nitrogen oxides (NO and NO 2 ) can be updated, for example, at any of many different crankshaft angles. Alternatively, total nitrogen oxide production can be estimated based on information about peak pressures and temperatures.
Für die erste Methode ist typischerweise relevant, dass bereits kleine Abweichungen in den Informationen über den Druck im Zylinder zu signifikanten Fehlern bei der Stickoxid-Schätzung führen können. Daher müssen Zylinderdruckmessungen über die Lebensdauer des Verbrennungsmotors präzise und robust sein.For the first method, it is typically relevant that even small deviations in the information about the pressure in the cylinder can lead to significant errors in the nitrogen oxide estimate. Therefore, cylinder pressure measurements must be precise and robust over the life of the internal combustion engine.
Eine Schwierigkeit ist auch, dass die Inhomogenität der Gasmischung und von deren Temperaturverteilung die Produktion von Stickoxiden wesentlich beeinflusst.Another difficulty is that the inhomogeneity of the gas mixture and its temperature distribution have a significant influence on the production of nitrogen oxides.
Für Motorsteuerungen wird häufig eine zweite Methode mit einfacheren und robusteren Modellen verwendet. Typischerweise wird der Stickoxid-Ausstoß eines Verbrennungsmotors auf Basis des Anteils der verbrannten Gasmasse im Einlasskrümmer oder der Sauerstoffkonzentration im Einlasskrümmer wie folgt geschätzt:
Der Anteil der verbrannten Gasmasse kann kostensparend geschätzt werden, oder dieser kann mit einem sog. Fman-Sensor im Einlasskrümmer direkt gemessen werden.The proportion of the burned gas mass can be estimated in a cost-saving manner, or this can be measured directly with a so-called Fman sensor in the intake manifold.
Eine Schätzung des Anteils der verbrannten Gasmasse im Einlass (oder der Sauerstoffkonzentration im Einlass) hängt von dem Luftmassenstrom, der Temperatur im Einlasskrümmer, dem sensorisch gemessenen Ladedruck und dem (häufig stromabwärts der Turbine eines Turboladers gemessenen) Abgas-Lambda-Wert ab. An estimate of the proportion of burned gas mass in the inlet (or the oxygen concentration in the inlet) depends on the air mass flow, the temperature in the intake manifold, the sensor-measured boost pressure and the exhaust gas lambda value (often measured downstream of the turbine of a turbocharger).
Den Abgas-Lambda-Wert, d. h. den Anteil der verbrannten Gasmasse in den Abgasen, erhält man durch Lambda-Messung im Auslass. Insbesondere ist Fman = Fexh x egr, worin Fexh der Anteil der verbrannten Gasmasse im Auslass ist und egr die Abgasrückführungsrate ist, die auf Basis einer Messung des Luftmassenstroms ermittelt wird.The exhaust lambda value, i.e. H. the proportion of the burned gas mass in the exhaust gases is obtained by measuring the lambda in the outlet. In particular, Fman = Fexh x egr, where Fexh is the proportion of the burned gas mass in the outlet and egr is the exhaust gas recirculation rate, which is determined on the basis of a measurement of the air mass flow.
Die Messung des Luftmassenstroms hängt jedoch von der Feuchte ab. Das Prinzip von Luftmassensensoren basiert auf der Kühlung eines Sensorelements durch die vorbei strömende Luft. Der Wärmeaustausch mit Wasserdampf ist jedoch anders als mit einem reinen Luftstrom, weshalb die Luftmassenmessung je nach Feuchtekonzentration schlechter werden kann.However, the measurement of the air mass flow depends on the humidity. The principle of air mass sensors is based on the cooling of a sensor element by the air flowing past. However, the heat exchange with water vapor is different than with a pure air flow, which is why the air mass measurement can become worse depending on the moisture concentration.
Während es für die Stickoxid-Schätzung nicht sehr darauf anzukommen scheint, ob der Anteil der verbrannten Gasmasse im Einlass eher Kohlendioxid oder eher Wasser ist, bedeutet eine Zunahme der Feuchte im Luftstrom einfach, dass sich bei gleicher Position des Abgasrückführungsventils mehr Inertgas (oder weniger Sauerstoff) im Einlass befindet.While it does not seem to matter much for the nitrogen oxide estimate whether the proportion of the gas mass burned in the inlet is more carbon dioxide or water, an increase in the humidity in the air flow simply means that with the same position of the exhaust gas recirculation valve more inert gas (or less oxygen) ) is in the inlet.
Während der Anteil der verbrannten Gasmasse im Einlass direkt mittels einer Lambdasonde gemessen werden kann, beruht die Abgasrückführungsrate auf Schätzungen und ist entsprechend unzuverlässig.While the proportion of the burned gas mass in the inlet can be measured directly using a lambda probe, the exhaust gas recirculation rate is based on estimates and is accordingly unreliable.
Der Erfindung liegt die Aufgabe zu Grunde, das gattungsgemäße Verfahren derart weiterzuentwickeln, dass mit besonders einfachen Mitteln zuverlässige Werte für wichtige Motorbetriebsparameter erhalten werden.The invention is based on the object of further developing the generic method in such a way that reliable values for important engine operating parameters are obtained with particularly simple means.
Diese Aufgabe wird gemäß der Erfindung durch ein Verfahren und ein Kraftfahrzeug mit den Merkmalen der unabhängigen Patentansprüche gelöst. Vorteilhafte Weiterbildungen der Erfindung sind in den abhängigen Patentansprüchen angegeben.This object is achieved according to the invention by a method and a motor vehicle with the features of the independent claims. Advantageous developments of the invention are specified in the dependent claims.
Abgassensoren in Form von Abgaslambdasonden und/oder Stickoxid-Sensoren sind bei modernen Kraftfahrzeugen weit verbreitet, so dass die Erfindung bei derartigen Kraftfahrzeugen ohne Änderungen an der Hardware realisiert werden kann.Exhaust gas sensors in the form of exhaust gas lambda sensors and / or nitrogen oxide sensors are widely used in modern motor vehicles, so that the invention can be implemented in such motor vehicles without changes to the hardware.
Das erfindungsgemäße Verfahren braucht nur relativ selten durchgeführt zu werden, und dies geschieht vorzugsweise in irgendeiner Phase, in der das Kraftfahrzeug ohne Kraftstoffzufuhr zu den Zylindern des Verbrennungsmotors verzögert. The method according to the invention only needs to be carried out relatively rarely, and this is preferably done in any phase in which the motor vehicle decelerates without supplying fuel to the cylinders of the internal combustion engine.
Die Feuchtigkeitskonzentration (Feuchte [Vol%]) wird vorzugsweise wie folgt aus Messwerten für die Sauerstoffkonzentration (O2_measured) und dem Sauerstoffgehalt von Frischluft bei einer vorgegebenen Referenzfeuchte worin O2_fresh_air_reference_humidity) berechnet:
Bevor die Sauerstoffkonzentration im Auslass mit den Abgassensoren gemessen wird, sollten ein oder mehrere Abgasrückführungsventile geschlossen werden und sollte einige Kurbelwellenzyklen gewartet werden.Before measuring the oxygen concentration in the exhaust with the exhaust gas sensors, one or more exhaust gas recirculation valves should be closed and a few crankshaft cycles should be maintained.
In einer bevorzugten Ausführungsform wird die Korrektur der Messung des Luftmassenstroms und der Schätzung der Abgasrückführungsrate nur auf Basis der Messwerte eines der beiden Abgassensoren durchgeführt, wobei die Messwerte des anderen der beiden Abgassensoren bzw. die daraus erhaltenen Werte für Luftmassenstrom und/oder Abgasrückführungsrate für eine Redundanzprüfung verwendet werden.In a preferred embodiment, the correction of the measurement of the air mass flow and the estimation of the exhaust gas recirculation rate is carried out only on the basis of the measured values of one of the two exhaust gas sensors, the measured values of the other of the two exhaust gas sensors or the values for air mass flow and / or exhaust gas recirculation rate obtained therefrom for a redundancy check be used.
Die Abgassensoren können Lambdasonden oder Stickoxid-Sensoren sein, wobei einer der beiden Abgassensoren stromaufwärts einer Abgasnachbehandlungseinrichtung und der andere stromabwärts davon angeordnet ist.The exhaust gas sensors can be lambda sensors or nitrogen oxide sensors, one of the two exhaust gas sensors being arranged upstream of an exhaust gas aftertreatment device and the other downstream of it.
Es folgt eine Beschreibung von Ausführungsbeispielen anhand der Zeichnungen. Darin zeigen:
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1 eine Prinzipskizze eines Verbrennungsmotors mit Niederdruck-Abgasrückführung; und -
2 eine Prinzipskizze eines Verbrennungsmotors mit Hochdruck-Abgasrückführung.
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1 a schematic diagram of an internal combustion engine with low-pressure exhaust gas recirculation; and -
2nd a schematic diagram of an internal combustion engine with high pressure exhaust gas recirculation.
Die Figuren zeigen jeweils einen Verbrennungsmotor
In der Abgasleitung von der Turbine
Es wird vorgeschlagen, in Phasen, in denen das Kraftfahrzeug ohne Kraftstoffzufuhr zu den Zylindern des Verbrennungsmotors
- i. das Abgasrückführungsventil zu schließen, wenn der Verbrennungsmotor entweder Niederdruck- oder Hochdruck-Abgasrückführung aufweist, oder beide Abgasrückführungsventile zu schließen, wenn der Verbrennungsmotor sowohl Niederdruck- als auch Hochdruck-Abgasrückführung aufweist;
- ii. einige Kurbelwellenzyklen zu warten, um sicherzustellen, dass der Auslass ausschließlich Frischluft enthält;
- iii. die Sauerstoffkonzentration im Auslass mit der
Abgaslambdasonde 5 oder6 zu messen; - iv. die Feuchtigkeitskonzentration (Feuchte [Vol%]) wie folgt aus den Messwerten für die Sauerstoffkonzentration (O2_measured) zu berechnen:
- i. close the exhaust gas recirculation valve when the engine has either low pressure or high pressure exhaust gas recirculation, or close both exhaust gas recirculation valves when the engine has both low pressure and high pressure exhaust gas recirculation;
- ii. wait a few crankshaft cycles to ensure that the outlet contains only fresh air;
- iii. the oxygen concentration in the outlet with the exhaust
gas lambda probe 5 or6 to eat; - iv. calculate the moisture concentration (moisture [vol%]) as follows from the measured values for the oxygen concentration (O 2 _measured):
Es gilt: O2_measured = O2_fresh_air_reference_humidity / (1 + Feuchte [Vol%])
worin O2_fresh_air_reference_humidity der Sauerstoffgehalt von Frischluft bei einer vorgegebenen Referenzfeuchte ist, also ein bekannter Wert von 21 % oder etwas weniger.The following applies: O 2 _measured = O 2 _fresh_air_reference_humidity / (1 + moisture [vol%])
where O 2 _fresh_air_reference_humidity is the oxygen content of fresh air at a given reference humidity, i.e. a known value of 21% or slightly less.
Daraus ergibt sich:
Die Abgaslambdasonden
Die Feuchte kann zum Beispiel aus Mittelwerten oder gewichteten Mittelwerten der Messwerte der Abgaslambdasonden
Die Kenntnis der Luftfeuchte ermöglicht es nun, die Messung des Luftmassenstroms und daher die Schätzung der Abgasrückführungsrate zu korrigieren.Knowing the air humidity now makes it possible to correct the measurement of the air mass flow and therefore the estimate of the exhaust gas recirculation rate.
Alternativ zu den vorgenannten Mittelwertbildungen ist es auch möglich, die Korrektur der Messung des Luftmassenstroms und der Schätzung der Abgasrückführungsrate nur auf Basis der Messwerte einer der beiden Abgaslambdasonden
Falls ein Fman-Sensor vorhanden ist, der einen Sensorwert liefert, der für den Sauerstoffanteil im Einlasskrümmer bzw. umgekehrt für den Anteil der verbrannten Gasmasse im Einlasskrümmer charakteristisch ist, können die mittels der Abgaslambdasonden
Falls die Abgasnachbehandlungseinrichtung
Auch bei Dieselmotoren, die mehrere Stickoxid-Sensoren im Auslass aufweisen, ist das Verfahren ohne konstruktive Umrüstungen durchführbar. Stickoxid-Sensoren verfügen über eine Quer-Empfindlichkeit hinsichtlich Sauerstoffs, so dass sie auch zur Ermittlung der Luftfeuchte genutzt werden können.Even with diesel engines that have several nitrogen oxide sensors in the outlet, the process can be carried out without any structural modifications. Nitrogen oxide sensors have a cross sensitivity to oxygen, so that they can also be used to determine the air humidity.
Da die Umgebungsluftfeuchte ein Parameter ist, der sich nicht sehr dynamisch verändert, genügt es, das oben beschriebene Verfahren nur einmal pro Fahrzyklus durchzuführen, oder alternativ alle paar hundert Kilometer oder alle paar Stunden, wenn größere Strecken am Stück zurückgelegt werden.Since the ambient air humidity is a parameter that does not change very dynamically, it is sufficient to carry out the method described above only once per driving cycle, or alternatively every few hundred kilometers or every few hours if larger distances are covered in one go.
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