WO2011064266A1 - Reducing agent tank having a tank extraction system - Google Patents

Reducing agent tank having a tank extraction system Download PDF

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Publication number
WO2011064266A1
WO2011064266A1 PCT/EP2010/068148 EP2010068148W WO2011064266A1 WO 2011064266 A1 WO2011064266 A1 WO 2011064266A1 EP 2010068148 W EP2010068148 W EP 2010068148W WO 2011064266 A1 WO2011064266 A1 WO 2011064266A1
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WO
WIPO (PCT)
Prior art keywords
reducing agent
tank
quality
scr
sensor
Prior art date
Application number
PCT/EP2010/068148
Other languages
German (de)
French (fr)
Inventor
Philippe Grass
Original Assignee
Continental Automotive Gmbh
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Filing date
Publication date
Application filed by Continental Automotive Gmbh filed Critical Continental Automotive Gmbh
Publication of WO2011064266A1 publication Critical patent/WO2011064266A1/en

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Classifications

    • 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
    • F01N3/2066—Selective catalytic reduction [SCR]
    • 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
    • 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
    • F01N3/2066—Selective catalytic reduction [SCR]
    • F01N3/208—Control of selective catalytic reduction [SCR], e.g. dosing of reducing agent
    • 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
    • F01N9/00—Electrical control of exhaust gas treating apparatus
    • 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
    • F01N2550/00—Monitoring or diagnosing the deterioration of exhaust systems
    • F01N2550/05—Systems for adding substances into exhaust
    • 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
    • F01N2560/026—Exhaust systems with means for detecting or measuring exhaust gas components or characteristics the means being an exhaust gas sensor for measuring or detecting NOx
    • 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
    • F01N2560/06—Exhaust systems with means for detecting or measuring exhaust gas components or characteristics the means being a temperature sensor
    • 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
    • F01N2560/12—Other sensor principles, e.g. using electro conductivity of substrate or radio frequency
    • 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
    • F01N2610/02—Adding substances to exhaust gases the substance being ammonia or urea
    • 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
    • F01N2610/14—Arrangements for the supply of substances, e.g. conduits
    • 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
    • F01N2610/14—Arrangements for the supply of substances, e.g. conduits
    • F01N2610/1406—Storage means for substances, e.g. tanks or reservoirs
    • 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
    • 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

Definitions

  • the present invention relates to a reducing agent tank having a tank removal system for taking a reducing agent from the reducing agent tank and for conveying the reducing agent to an SCR catalyst in an exhaust line.
  • exhaust gas treatment units are known from the prior art, in which a reducing agent (urea water solution) stored in a reducing agent tank is fed to the exhaust gas line of an internal combustion engine.
  • Cars powered by diesel fuel in particular cause an increased nitrogen oxide (NOx) immission, which can be reduced by means of reducing agent injection into the exhaust gas system.
  • NOx nitrogen oxide
  • SCR selective catalytic reduction
  • Urea water solutions of a certain quality d. H. a certain mixing ratio between urea and water.
  • These urea water solutions are known under the trade names AdBlue, Urea, Denoxium and AUS 32.
  • a sufficient reduction of nitrogen oxide is therefore only possible if the reducing agent solution has a sufficiently high quality. having quality.
  • a reduction of the nitrogen oxides in the exhaust gas of the internal combustion engine is not sufficiently ensured.
  • Due to legal regulations, vehicles of modern design must have an on-board diagnostic unit that monitors all the vehicle's emission-related systems (OBD2).
  • OBD2 emission-related systems
  • the senor is designed as a sensor for measuring the conductivity of the reducing agent.
  • the conductivity of the reducing agent is relatively high and can be detected easily and inexpensively.
  • oil has a completely different conductivity that would be immediately recognized by the conductivity sensor located in the tank sampling system. This ensures that only high-quality reducing agent is injected into the SCR catalytic converter.
  • a conductivity sensor arranged in the reducing agent tank would most probably not detect contamination of the reducing agent by an oil accumulation, because the overall conductivity of the reducing agent would not be significantly affected by the oil accumulation.
  • the signals of the sensor are evaluated by a control unit, wherein the control device on detection of a lower reducing agent quality, the promotion of the reducing agent to the SCR catalyst interrupts. This ensures that only high-quality reducing agents are injected into the SCR catalyst.
  • FIG. 1 shows an internal combustion engine 6 with fuel injection nozzles 29 and with an exhaust gas system 7.
  • Internal combustion engines in particular diesel engines, generate a not inconsiderable amount of environmentally harmful nitrogen oxides NO x.
  • the discharged from the engine 6 nitrogen oxides NOx are discharged with the exhaust gas 23 via the exhaust line 7 to the environment, if not suitable measures to reduce the nitrogen oxides NOx are taken in the exhaust system.
  • the exhaust system shows a system of catalysts.
  • an oxidation catalyst 8 is provided, which is followed by a so-called SCR catalyst for reducing the nitrogen oxides NOx contained in the exhaust gas.
  • SCR stands here as abbreviation Selective Catalytic Reduction.
  • the SCR catalyst 9 the conversion of the nitrogen oxides NOx into harmless nitrogen N 2 and water H 2 0 takes place.
  • a urea-water solution which is also referred to as reducing agent 2
  • the reducing agent 2 then reacts with the nitrogen oxides NOx in the harmless components H 2 0 and N 2 .
  • a quantity of urea adapted to the NOx concentration in the exhaust gas 23 has to be injected into the SCR catalytic converter 9 via the nozzle 10.
  • any contaminants, such as oil be drawn in from the sampling tube 4 and injected into the SCR catalytic converter.
  • FIG. 1 shows a multiplicity of sensors.
  • a temperature sensor 17 and a level sensor 21 can be seen.
  • the temperature sensor 17 the temperature of the reducing agent 2 present in the reducing agent tank 1 can be continuously detected.
  • it can be determined with the temperature sensor 17 whether the reducing agent 2 is present in the reduction medium tank 1 is frozen or is in a liquid state.
  • the level sensor 21 makes it possible to measure the level of the reducing agent 2 in the reducing agent tank 1 over the entire service life of the internal combustion engine 6. All recorded data on the state of the reducing agent 2 are stored in an electrical memory 25.
  • an ultrasound transmitter / receiver can be recognized on the reducing agent tank 1 with which the speed of sound of an ultrasound wave of a specific frequency of the reducing agent 2 located in the reducing agent tank 1 can be determined.
  • the ultrasonic velocity of an ultrasonic pulse with a certain frequency in pure water differs significantly from the ultrasonic velocity of an ultrasonic wave with a certain frequency in a twenty, fifty or ninety percent reductant solution.
  • certain quality deficits of the reducing agent 2 can not or only insufficiently be detected with the sensors described so far.
  • the oil accumulation 30 shown in the reducing agent tank 1 can not be detected by the previously described sensors. If this oil 30 were to be sucked by the tank removal system without this oil suction being detected, fatal damage to the SCR catalyst 9 would be unavoidable.
  • a removal tube 4 can be seen in the reducing agent tank 1, which leads with a pipe 24 to a filter 14 and a pump 13, the reducing agent.
  • the SCR valve 11 is electrically connected to the SCR control unit 15.
  • the SCR control unit 15 thus controls the SCR valve 11.
  • the SCR control unit 15 holds a plurality of signals from the following sensors:
  • NOx sensors 18 which are arranged in the exhaust gas line 7 directly behind the internal combustion engine 6 or between the oxidation catalytic converter 8 and the SCR catalytic converter 9 and / or behind the SCR catalytic converter 9 at the outlet of the exhaust line 7;
  • Temperature sensors 17, which in turn are arranged directly behind the internal combustion engine 6 and / or behind the oxidation catalytic converter 8 and / or in the SCR catalytic converter 9 and / or behind the SCR catalytic converter 9,
  • Ultrasonic transmitter and receiver 20 arranged in or on the reducing agent tank 1,
  • All of these sensors deliver their signals to the SCR control unit 15, which in turn contains an electronic memory 25 in which all the signals supplied are recorded over the entire service life of the internal combustion engine.
  • the conductivity sensors 22, which are arranged in the extraction tube 4 and / or in the tube 24, are of particular importance. With these conductivity sensors 22, the suction of contaminants, such as the suction of oil 30, can be effectively detected. If such a soiling suction is detected, the controller 15 may protectively intervene. For this purpose, for example, the SCR valve 11 is closed and / or the return valve 12 is adjusted such that the dirt sucked in by the pump 13 through the removal tube 4 (eg oil 30) returns via the return pipe 28 back to the reducing agent tank 1 is transported.
  • control unit 16 of the internal combustion engine also receives information from the SCR control unit 15 with which the internal combustion engine can be controlled in accordance with the quality of the reducing agent and the soiling detected in the reducing agent 2. It is Z. B. conceivable that after refilling of pure water in the reducing agent tank 1, the quality of the reducing agent 2 has dropped such that an exhaust aftertreatment and the corresponding reduction of NOx can no longer be sufficiently ensured. In such a case, on the one hand, an entry is made in an error memory of the on-board diagnostic unit of the vehicle and, on the other hand, the
  • Internal combustion engine 6 are driven via the control unit 16 of the internal combustion engine in an operating state in which as little NOx is produced. This may be at the expense of the maximum performance of the internal combustion engine 6, would be a possible deliberate consequence, since the driver would be forced due to the power loss of the internal combustion engine to visit a corresponding repair workshop, which ensures that in the reducing agent tank 1, a reducing agent 2 with sufficient Qua - Quality is available. Even if a contamination of the reducing agent 2 has been detected by oil 30, the internal combustion engine can be driven by the control unit 16 in a state in which as little NOx is generated. This would ensure an environmentally sound after-treatment of the exhaust gas 23 in the exhaust line 7 at all times.

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  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Combustion & Propulsion (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Health & Medical Sciences (AREA)
  • Toxicology (AREA)
  • Exhaust Gas After Treatment (AREA)

Abstract

The invention relates to a reducing agent tank (1) having a tank extraction system for extracting a reducing agent (2) from the reducing agent tank and for feeding the reducing agent to an SCR catalyst (9) in an exhaust gas line (7). In order to be able to simply and reliably make a determination about the quality of the reducing agent (2) used for purifying exhaust gas, a sensor (22) monitoring the quality of the reducing agent (2) is disposed in the tank extraction system.

Description

Beschreibung description
Reduktionsmitteltank mit einem Tankentnahmesystem Die vorliegende Erfindung betrifft einen Reduktionsmitteltank mit einem Tankentnahmesystem zur Entnahme eines Reduktionsmittels aus dem Reduktionsmitteltank und zur Beförderung des Reduktionsmittels zu einem SCR Katalysator in einem Abgasstrang . Reducing agent tank with a tank removal system The present invention relates to a reducing agent tank having a tank removal system for taking a reducing agent from the reducing agent tank and for conveying the reducing agent to an SCR catalyst in an exhaust line.
Zur Reduzierung von Stickoxidemissionen von Kraftfahrzeugen sind aus dem Stand der Technik Abgasbehandlungseinheiten bekannt, bei denen ein Reduktionsmittel (Harnstoffwasserlösung) , das in einem Reduktionsmitteltank gespeichert ist, dem Abgasstrang einer Brennkraftmaschine zugeführt wird. Gerade mit Dieselkraftstoff betriebene Kraftfahrzeuge verursachen eine erhöhte Stickoxid (NOx) Immission, die mit Hilfe der Reduktionsmitteleinspritzung in den Abgasstrang reduziert werden kann. Zur Verringerung der Stickoxidemission wird hierbei das sogenannte Selektiv-Catalytic-Reduction (SCR) Verfahren eingesetzt. Da das Reduktionsmittel durch das Eindüsen in den Abgasstrang der Brennkraftmaschine im Bereich eines SCR- Katalysators über längere Sicht verbraucht wird, muss von Zeit zu Zeit frisches Reduktionsmittel in den Reduktionsmit- teltank nachgefüllt werde. Die Reduktion von StickoxidenTo reduce nitrogen oxide emissions from motor vehicles, exhaust gas treatment units are known from the prior art, in which a reducing agent (urea water solution) stored in a reducing agent tank is fed to the exhaust gas line of an internal combustion engine. Cars powered by diesel fuel in particular cause an increased nitrogen oxide (NOx) immission, which can be reduced by means of reducing agent injection into the exhaust gas system. To reduce the nitrogen oxide emission in this case, the so-called selective catalytic reduction (SCR) method is used. Since the reducing agent is consumed by spraying into the exhaust gas line of the internal combustion engine in the region of an SCR catalytic converter over a longer period of time, from time to time fresh reducing agent must be replenished into the reducing medium tank. The reduction of nitrogen oxides
(NOx) ist dabei nur möglich, wenn die Harnstoff-Lösung eine genügend hohe Qualität aufweist und nicht verunreinigt ist. Verunreinigungen können zum Beispiel durch den Eintrag von Öl oder Dieselkraftstoff in den Reduktionsmitteltank entstehen. Reduktionsmittel sind in diesem Zusammenhang in der Regel(NOx) is only possible if the urea solution has a sufficiently high quality and is not contaminated. Impurities can be created, for example, by introducing oil or diesel fuel into the reducing agent tank. Reducing agents are usually in this context
Harnstoff-Was serlösungen mit einer bestimmten Qualität, d. h. einem bestimmten Mischungsverhältnis zwischen Harnstoff und Wasser. Diese Harnstoff-Wasserlösungen sind unter dem Handelsnamen AdBlue, Urea, Denoxium und AUS 32 bekannt. Urea water solutions of a certain quality, d. H. a certain mixing ratio between urea and water. These urea water solutions are known under the trade names AdBlue, Urea, Denoxium and AUS 32.
Eine ausreichende Reduktion von Stickoxid ist also nur möglich, wenn die Reduktionsmittellösung eine genügend hohe Qua- lität aufweist. Bei der Befüllung des Reduktionsmitteltankes mit einer Reduktionsmittellösung minderer Qualität ist dagegen eine Reduktion der Stickoxide im Abgas der Brennkraftmaschine nicht ausreichend sichergestellt. Auf Grund gesetzli- eher Vorschriften müssen Fahrzeuge moderner Bauart eine On- Board-Diagnoseeinheit aufweisen, die sämtliche abgasrelevanten Systeme des Fahrzeuges überwacht (OBD2). Bei Befüllung des Reduktionsmitteltankes mit einer Reduktionsmittellösung minderer Qualität oder bei Verunreinigungen der Reduktions- mittels wird durch eine On-Board-Diagnoseeinheit ein allgemeiner Fehler der Abgasbehandlungseinheit erfasst. A sufficient reduction of nitrogen oxide is therefore only possible if the reducing agent solution has a sufficiently high quality. having quality. When filling the reducing agent tank with a reducing agent solution of lower quality, however, a reduction of the nitrogen oxides in the exhaust gas of the internal combustion engine is not sufficiently ensured. Due to legal regulations, vehicles of modern design must have an on-board diagnostic unit that monitors all the vehicle's emission-related systems (OBD2). When the reducing agent tank is filled with a reducing agent solution of inferior quality or when the reducing agent is contaminated, a general fault of the exhaust gas treatment unit is detected by an on-board diagnostic unit.
Es ist die Aufgabe der vorliegenden Erfindung, ein einen Reduktionsmitteltank mit einem Tankentnahmesystem anzugeben, mit dem auf einfache und sichere Art eine Aussage über dieIt is the object of the present invention to provide a reducing agent tank with a tank removal system, with the simple and secure way a statement about the
Qualität des zur Abgasreinigung verwendeten Reduktionsmittels getroffen werden kann. Quality of the reducing agent used for the exhaust gas purification can be made.
Gemäß der Erfindung wird diese Aufgabe durch den Gegenstand des unabhängigen Patentanspruchs 1 gelöst. Vorteilhafte Ausgestaltungen finden sich in den abhängigen Ansprüchen sowie in der Beschreibung und der Zeichnung. According to the invention, this object is solved by the subject matter of independent claim 1. Advantageous embodiments can be found in the dependent claims and in the description and the drawing.
Durch die Anordnung eines Sensors, der die Qualität des Re- duktionsmittels überprüft, in dem Tankentnahmesystem, ist durchgehend gewährleistet, dass die Verunreinigungen weitgehend homogen im entnommenen Reduktionsmittel verteilet sind. Bei der Lagerung des Reduktionsmittels im Tank kann es nämlich vorkommen, dass zum Beispiel eine Ölansammlung auf dem Reduktionsmittel schwimmt, was dazu führen würde, dass im Reduktionsmitteltank angeordnete Sensoren zur Überprüfung der Qualität des Reduktionsmittels eine ausreichend hohe Reduktionsmittelqualität feststellen, weil sich zum Beispiel die Leitfähigkeit des Reduktionsmittels im Reduktionsmitteltank durch die konzentrierte Ölansammlung kaum oder gar nicht verändert hat. Dennoch besteht die Gefahr, dass das Tankentnahmesystem früher oder später die unerkannte Ölansammlung an- saugt und zum SCR Katalysator transportiert. Wenn dann das Öl in den SCR Katalysator eingedüst wird, würde es zur Zerstörung des SCR Katalysators kommen, was teure Reparaturmaßnahmen an der Abgasanlage des Fahrzeuges zur Folge hätte. Mit der erfindungsgemäßen Anordnung eines Sensors, der die Qualität des Reduktionsmittels überprüft und der in dem Tankentnahmesystem angeordnet ist, wird sichergestellt, dass fortwährend das gerade entnommene Reduktionsmittel auf seine Qualität hin überprüft wird und damit wird der SCR Katalysator effektiv vor Beschädigungen durch Eindüsungen falscher Substanzen geschützt. Aus der Erfindung ergibt sich ein nicht unwesentlicher Beitrag zum Schutze unserer Umwelt. By arranging a sensor that checks the quality of the reducing agent in the tank removal system, it is ensured throughout that the impurities are largely distributed homogeneously in the removed reducing agent. When storing the reducing agent in the tank, it may happen that, for example, an accumulation of oil floats on the reducing agent, which would cause sensors arranged in the reducing agent tank to check the quality of the reducing agent to determine a sufficiently high reducing agent quality, because, for example, the conductivity of the reducing agent in the reducing agent tank has hardly or not at all changed by the concentrated oil accumulation. Nevertheless, there is a risk that the tank removal system will sooner or later cause unrecognized oil accumulation. sucks and transported to the SCR catalyst. If the oil is then injected into the SCR catalyst, it would lead to the destruction of the SCR catalyst, which would result in expensive repair measures on the vehicle exhaust system. With the arrangement according to the invention of a sensor which checks the quality of the reducing agent and which is arranged in the tank removal system, it is ensured that the just taken reducing agent is continuously checked for its quality and thus the SCR catalyst is effectively protected against damage by injections of wrong substances , From the invention results in a not insignificant contribution to the protection of our environment.
Gemäß einer Ausgestaltung ist der Sensor als Sensor zur Mes- sung der Leitfähigkeit des Reduktionsmittels ausgebildet. Die Leitfähigkeit des Reduktionsmittels ist relativ hoch und kann einfach und kostengünstig erfasst werden. Öl zum Beispiel hat eine völlig andere Leitfähigkeit, die sofort von dem in dem Tankentnahmesystem angeordneten Leitfähigkeitsensor erkannt werden würde. Damit kann sichergestellt werden, dass ausschließlich qualitativ hochwertiges Reduktionsmittel in den SCR Katalysator eingedüst wird. Zur Unterscheidung der Erfindung vom Stand der Technik sei hier deutlich darauf hingewiesen, dass ein im Reduktionsmitteltank angeordneter Leitfähig- keitssensor höchstwahrscheinlich eine Verunreinigung des Reduktionsmittels durch eine Olansammlung gar nicht erkennen würde, weil die Gesamtleitfähigkeit des Reduktionsmittels durch die Olansammlung nicht wesentlich beeinflusst werden würde. Das Extrahieren der Olansammlung aus dem Reduktions- mitteltank und das Eindüsen des Öls in den SCR Katalysator hätte aber fatale Folgen für den SCR Katalysator. Dies kann nur der erfindungsgemäß angeordnete Sensor und insbesondere der erfindungsgemäß angeordnete Sensor zur Messung der Leitfähigkeit des Reduktionsmittels verhindern. According to one embodiment, the sensor is designed as a sensor for measuring the conductivity of the reducing agent. The conductivity of the reducing agent is relatively high and can be detected easily and inexpensively. For example, oil has a completely different conductivity that would be immediately recognized by the conductivity sensor located in the tank sampling system. This ensures that only high-quality reducing agent is injected into the SCR catalytic converter. To distinguish the invention from the prior art, it should be clearly pointed out that a conductivity sensor arranged in the reducing agent tank would most probably not detect contamination of the reducing agent by an oil accumulation, because the overall conductivity of the reducing agent would not be significantly affected by the oil accumulation. However, extracting the oil accumulation from the reducing agent tank and injecting the oil into the SCR catalyst would have fatal consequences for the SCR catalyst. This can be prevented only by the sensor arranged according to the invention and in particular the sensor arranged according to the invention for measuring the conductivity of the reducing agent.
Gemäß einer weiteren Ausgestaltung werden die Signale des Sensors von einem Steuergerät ausgewertet, wobei das Steuer- gerät beim Erkennen einer minderen Reduktionsmittelqualität die Beförderung des Reduktionsmittels zu dem SCR Katalysator unterbricht. Hiermit wird sichergestellt, dass in den SCR Katalysator ausschließlich Reduktionsmittel von hoher Qualität eingedüst wird. According to a further embodiment, the signals of the sensor are evaluated by a control unit, wherein the control device on detection of a lower reducing agent quality, the promotion of the reducing agent to the SCR catalyst interrupts. This ensures that only high-quality reducing agents are injected into the SCR catalyst.
Ein Ausführungsbeispiel der Erfindung wird nachfolgend anhand einer Zeichnung näher erläutert. Figur 1 zeigt eine Brennkraftmaschine 6 mit Kraftstoffein- spritzdüsen 29 und mit einem Abgasstrang 7. Brennkraftmaschinen, insbesondere Dieselmotoren, erzeugen eine nicht unerhebliche Menge von umweltschädlichen Stickoxyden NOx. Die von der Brennkraftmaschine 6 abgegebenen Stickoxyde NOx werden mit dem Abgas 23 über den Abgasstrang 7 an die Umwelt abgegeben, wenn nicht geeignete Maßnahmen zur Reduktion der Stickoxyde NOx im Abgasstrang getroffen werden. An embodiment of the invention will be explained in more detail with reference to a drawing. FIG. 1 shows an internal combustion engine 6 with fuel injection nozzles 29 and with an exhaust gas system 7. Internal combustion engines, in particular diesel engines, generate a not inconsiderable amount of environmentally harmful nitrogen oxides NO x. The discharged from the engine 6 nitrogen oxides NOx are discharged with the exhaust gas 23 via the exhaust line 7 to the environment, if not suitable measures to reduce the nitrogen oxides NOx are taken in the exhaust system.
Zur Abgasreinigung zeigt der Abgasstrang ein System aus Kata- lysatoren. Zunächst ist ein Oxidationskatalysator 8 vorgesehen, der von einem sogenannten SCR-Katalysator zum Abbau der im Abgas enthaltenen Stickoxyde NOx gefolgt wird. SCR steht hier als Abkürzung Selective Catalytic Reduction. Im SCR- Katalysator 9 findet die Umwandlung der Stickoxyde NOx in harmlosen Stickstoff N2 und Wasser H20 statt. Dazu wird über die Düse 10 eine Harnstoffwasserlösung, die auch als Reduktionsmittel 2 bezeichnet wird, in den SCR-Katalysator 9 eingespritzt. Das Reduktionsmittel 2 reagiert dann mit den Stickoxyden NOx in die harmlosen Bestandteile H20 und N2. For exhaust gas purification, the exhaust system shows a system of catalysts. First, an oxidation catalyst 8 is provided, which is followed by a so-called SCR catalyst for reducing the nitrogen oxides NOx contained in the exhaust gas. SCR stands here as abbreviation Selective Catalytic Reduction. In the SCR catalyst 9, the conversion of the nitrogen oxides NOx into harmless nitrogen N 2 and water H 2 0 takes place. For this purpose, a urea-water solution, which is also referred to as reducing agent 2, is injected into the SCR catalytic converter 9 via the nozzle 10. The reducing agent 2 then reacts with the nitrogen oxides NOx in the harmless components H 2 0 and N 2 .
Zur optimalen Reaktion zwischen NOx und der Harnstofflösung muss eine der NOx-Konzentration im Abgas 23 angepasste Harnstoffmenge über die Düse 10 in den SCR-Katalysator 9 eingedüst werden. Keinesfalls dürfen Verunreinigungen wie zum Bei- spiel Öl von dem Entnahmerohr 4 angesaugt werden und in den SCR Katalysator eingedüst werden. Dazu ist es wichtig, die genaue Zusammensetzung des Reduktionsmittels 2 aus Wasser und Harnstoff zu kennen. Da nur geringe Mengen Reduktionsmittel 2 in den SCR-Katalysator eingedüst werden müssen, und eine häufige Betankung eines Kraftfahrzeuges mit Reduktionsmittel 2 vermieden werden soll, verbleibt eine bestimmte Menge des Re- duktionsmittels 2 über einen langen Zeitraum im Reduktionsmitteltank 1. Im Reduktionsmitteltank 1 kann das Reduktionsmittel 2 mit der Zeit altern, wobei sich beispielsweise organische Substanzen im Reduktionsmittel 2 niederschlagen oder das Reduktionsmittel auf Grund niedriger Temperaturen (unter -11°C) zeitweise einfriert und eventuell dadurch seine Zusammensetzung und Qualität verliert. Darüber hinaus ist es denkbar, dass der Reduktionsmitteltank 1 vorsätzlich oder fahrlässig mit einem minderwertigen Reduktionsmittel 2 oder gar mit anderen Medien, zum Beispiel Öl, betankt wird. Wenn die Qualität des Reduktionsmittels 2 auf Grund solcher Ereignisse vermindert wird, muss dies festgestellt werden, um weiterhin für eine optimale Reinigung des Abgases 23 sorgen zu können und den SCR Katalysator 9 zu schützen. Bei einer verringerten Harnstoffkonzentration im Reduktionsmittel 2 müsste bei- spielsweise eine erhöhte Menge Reduktionsmittel 2 in den SCR- Katalysator 9 eingedüst werden. Wenn auf Grund einer kompletten Fehlbetankung des Reduktionsmitteltanks 1 überhaupt keine sinnvolle Reinigung des Abgases 3 von NOx mehr möglich ist, muss ein entsprechendes Fehlersignal im Cockpit des Fahr- zeugsführers erscheinen und/oder ein entsprechender Eintrag muss im FehlerSpeicher der On-Board-Diagnoseeinheit (OBD) niedergelegt werden. Darüber hinaus ist in Figur 1 der Einfüllstutzen 3 des Reduktionsmitteltanks 1 zu erkennen, der mit einem Tankdeckel 5 verschlossen ist. For optimum reaction between NOx and the urea solution, a quantity of urea adapted to the NOx concentration in the exhaust gas 23 has to be injected into the SCR catalytic converter 9 via the nozzle 10. Under no circumstances should any contaminants, such as oil, be drawn in from the sampling tube 4 and injected into the SCR catalytic converter. For this purpose, it is important to know the exact composition of the reducing agent 2 from water and To know urea. Since only small amounts of reducing agent 2 must be injected into the SCR catalyst, and frequent fueling of a motor vehicle with reducing agent 2 is to be avoided, a certain amount of the reducing agent 2 remains in the reducing agent tank 1 over a long period of time Reduce reducing agent 2 over time, with, for example, organic substances precipitate in the reducing agent 2 or the reducing agent due to low temperatures (below -11 ° C) temporarily freezes and possibly loses its composition and quality. In addition, it is conceivable that the reducing agent tank 1 intentionally or negligently with an inferior reducing agent 2 or even with other media, for example, oil refueled. If the quality of the reducing agent 2 is reduced as a result of such events, this must be determined in order to be able to continue to ensure optimal cleaning of the exhaust gas 23 and to protect the SCR catalytic converter 9. At a reduced urea concentration in the reducing agent 2, for example, an increased amount of reducing agent 2 would have to be injected into the SCR catalytic converter 9. If due to a complete misfuelling of the reducing agent tank 1 at all no meaningful cleaning of the exhaust gas 3 of NOx is possible, a corresponding error signal must appear in the cockpit of the vehicle driver and / or a corresponding entry must in the error memory of the on-board diagnostic unit (OBD ). In addition, in Figure 1, the filler neck 3 of the reducing agent tank 1 can be seen, which is closed with a fuel cap 5.
Zur Überwachung des Reduktionsmittels zeigt Figur 1 eine Vielzahl von Sensoren. Im Reduktionsmitteltank 1 ist ein Temperatursensor 17 und ein Füllstandssensor 21 zu erkennen. Mit dem Temperatursensor 17 kann ständig die Temperatur des im Reduktionsmitteltank 1 vorhandenen Reduktionsmittels 2 er- fasst werden. Insbesondere kann mit dem Temperatursensor 17 festgestellt werden, ob das Reduktionsmittel 2 im Reduktions- mitteltank 1 eingefroren ist oder in flüssigem Zustand vorliegt. Der Füllstandssensor 21 ermöglicht es, über die gesamte Lebensdauer der Brennkraftmaschine 6 den Füllstand des Reduktionsmittels 2 im Reduktionsmitteltank 1 zu messen. Alle erfassten Daten zum Zustand des Reduktionsmittels 2 werden in einem elektrischen Speicher 25 zu hinterlegen. Zudem ist am Reduktionsmitteltank 1 ein Ultraschallsender/-empfänger zu erkennen, mit dem die Schallgeschwindigkeit einer Ultraschallwelle einer bestimmten Frequenz des im Reduktionsmit- teltank 1 befindlichen Reduktionsmittels 2 bestimmt werden kann. Dazu ist es vorteilhaft, eine Reflektorfläche 27 in einem vorbestimmten Abstand d vor dem Ultraschallsender 20 zu montieren. Da der Abstand d zwischen dem Ultraschallsender/- empfänger 20 bekannt ist, und die Wellenlänge des vom Ultra- schallsender 20 ausgesendeten Ultraschallpulses auch bekannt ist, kann die Schallgeschwindigkeit des Ultraschallpulses im Reduktionsmittel 2 bestimmt werden. Mit dieser Ultraschallgeschwindigkeit im Reduktionsmittel 2 können Informationen über die Qualität und die Zusammensetzung des Reduktionsmittels 2 im Reduktionsmitteltank 1 gewonnen werden. Die Ultraschallgeschwindigkeit eines Ultraschallpulses mit einer bestimmten Frequenz in reinem Wasser unterscheidet sich dabei deutlich von der Ultraschallgeschwindigkeit einer Ultraschallwelle mit einer bestimmten Frequenz in einer zwanzig, fünfzig oder neunzig prozentigen Reduktionsmittellösung. Bestimmte Qualitätsdefizite des Reduktionsmittels 2 können jedoch mit den bisher beschriebenen Sensoren nicht oder nur unzureichend er- fasst werden. Die in dem Reduktionsmitteltank 1 dargestellte Ölansammlung 30 kann zum Beispiel nicht von den bisher be- schriebenen Sensoren festgestellt werden. Würde dieses Öl 30 von dem Tankentnahmesystem angesaugt werden, ohne dass diese Ölansaugung erkannte werden würde, wäre ein fataler Schaden am SCR Katalysator 9 unvermeidbar. Um dies zu verhindern ist im Reduktionsmitteltank 1 ein Entnahmerohr 4 zu erkennen, das mit einem Rohr 24 zu einem Filter 14 und einer Pumpe 13 führt, die das Reduktionsmittel 2 aus dem Reduktionsmitteltank; 1 über ein SCR-Ventil 11 zur SCR-Düse 10 im SCR-Katalysator pumpt. Die Einheit aus dem Entnahmerohr 4, dem Rohr 24, dem Filter 14, der Pumpe 13, dem Rücklauf entil 12, dem SCR Ventil 11 und dem Rücklaufrohr 28 bildet das Tankentnahmesystem. Mit dem SCR-Ventil 11 kann die Menge des eingespritzten Reduktionsmittels 2 reguliert werden. Dazu ist das SCR-Ventil 11 elektrisch mit der SCR- Steuereinheit 15 verbunden. Die SCR-Steuereinheit 15 steuert damit das SCR-Ventil 11 an. Dazu hält die SCR-Steuereinheit 15 eine Vielzahl von Signalen von den folgenden Sensoren: For monitoring the reducing agent, FIG. 1 shows a multiplicity of sensors. In the reducing agent tank 1, a temperature sensor 17 and a level sensor 21 can be seen. With the temperature sensor 17, the temperature of the reducing agent 2 present in the reducing agent tank 1 can be continuously detected. In particular, it can be determined with the temperature sensor 17 whether the reducing agent 2 is present in the reduction medium tank 1 is frozen or is in a liquid state. The level sensor 21 makes it possible to measure the level of the reducing agent 2 in the reducing agent tank 1 over the entire service life of the internal combustion engine 6. All recorded data on the state of the reducing agent 2 are stored in an electrical memory 25. In addition, an ultrasound transmitter / receiver can be recognized on the reducing agent tank 1 with which the speed of sound of an ultrasound wave of a specific frequency of the reducing agent 2 located in the reducing agent tank 1 can be determined. For this purpose, it is advantageous to mount a reflector surface 27 at a predetermined distance d in front of the ultrasonic transmitter 20. Since the distance d between the ultrasonic transmitter / receiver 20 is known, and the wavelength of the ultrasonic pulse emitted by the ultrasonic transmitter 20 is also known, the speed of sound of the ultrasonic pulse in the reducing agent 2 can be determined. With this ultrasonic speed in the reducing agent 2, information about the quality and the composition of the reducing agent 2 in the reducing agent tank 1 can be obtained. The ultrasonic velocity of an ultrasonic pulse with a certain frequency in pure water differs significantly from the ultrasonic velocity of an ultrasonic wave with a certain frequency in a twenty, fifty or ninety percent reductant solution. However, certain quality deficits of the reducing agent 2 can not or only insufficiently be detected with the sensors described so far. For example, the oil accumulation 30 shown in the reducing agent tank 1 can not be detected by the previously described sensors. If this oil 30 were to be sucked by the tank removal system without this oil suction being detected, fatal damage to the SCR catalyst 9 would be unavoidable. To prevent this, a removal tube 4 can be seen in the reducing agent tank 1, which leads with a pipe 24 to a filter 14 and a pump 13, the reducing agent. 2 from the reducing agent tank; 1 via an SCR valve 11 to the SCR nozzle 10 in the SCR catalyst pumps. The unit from the sampling tube 4, the tube 24, the filter 14, the pump 13, the return valve 12, the SCR valve 11 and the return pipe 28 forms the tank removal system. With the SCR valve 11, the amount of the injected reducing agent 2 can be regulated. For this purpose, the SCR valve 11 is electrically connected to the SCR control unit 15. The SCR control unit 15 thus controls the SCR valve 11. For this purpose, the SCR control unit 15 holds a plurality of signals from the following sensors:
- NOx-Sensoren 18, die im Abgasstrang 7 direkt hinter der Brennkraftmaschine 6 oder zwischen dem Oxidationskataly- sator 8 und dem SCR-Katalysator 9 und/oder hinter dem SCR-Katalysator 9 am Ausgang des Abgasstranges 7 angeordnet sind, NOx sensors 18 which are arranged in the exhaust gas line 7 directly behind the internal combustion engine 6 or between the oxidation catalytic converter 8 and the SCR catalytic converter 9 and / or behind the SCR catalytic converter 9 at the outlet of the exhaust line 7;
- Temperatursensoren 17, die ihrerseits direkt hinter der Brennkraftmaschine 6 und/oder hinter dem Oxidationskata- lysator 8 und/oder im SCR-Katalysator 9 und/oder hinter dem SCR-Katalysator 9 angeordnet sind,  Temperature sensors 17, which in turn are arranged directly behind the internal combustion engine 6 and / or behind the oxidation catalytic converter 8 and / or in the SCR catalytic converter 9 and / or behind the SCR catalytic converter 9,
- Leitfähigkeitsensoren 22, die im Entnahmerohr 4 und/oder im Rohr 24 angeordnet sind,  Conductivity sensors 22 arranged in the extraction tube 4 and / or in the tube 24,
- Ultraschallsender und -empfänger 20, die im oder am Reduktionsmitteltank 1 angeordnet sind,  Ultrasonic transmitter and receiver 20 arranged in or on the reducing agent tank 1,
- Füllstandssensor (en) 21, der (die) im Reduktionsmitteltank 1 angeordnet ist (sind) .  - Level sensor (s) 21, which (is) arranged in the reducing agent tank 1 (are).
All diese Sensoren liefern ihre Signale der SCR-Steuereinheit 15, die ihrerseits einen elektronischen Speicher 25 beinhal- tet, in dem all die gelieferten Signale über die gesamte Lebensdauer der Brennkraftmaschine aufgezeichnet werden. All of these sensors deliver their signals to the SCR control unit 15, which in turn contains an electronic memory 25 in which all the signals supplied are recorded over the entire service life of the internal combustion engine.
Zum Schutze des SCR Katalysators 9 sind die Leitfähigkeitsensoren 22, die im Entnahmerohr 4 und/oder im Rohr 24 angeord- net sind, von besonderer Bedeutung. Mit diesen Leitfähigkeitsensoren 22 kann das Ansaugen von Verschmutzungen, wie zum Beispiel das Ansaugen von Öl 30, effektiv erkannt werden. Wenn eine solche Verschmutzungsansaugung erkannt wird, kann das Steuergerät 15 schützend eingreifen. Dazu wird zum Beispiel das SCR-Ventil 11 geschlossen und/oder das Rücklaufventil 12 so eingestellt, dass die von der von der Pumpe 13 durch das Entnahmerohr 4 angesaugte Verschmutzung (z. B. Öl 30) über das Rücklaufrohr 28 zurück in den Reduktionsmitteltank 1 befördert wird. To protect the SCR catalyst 9, the conductivity sensors 22, which are arranged in the extraction tube 4 and / or in the tube 24, are of particular importance. With these conductivity sensors 22, the suction of contaminants, such as the suction of oil 30, can be effectively detected. If such a soiling suction is detected, the controller 15 may protectively intervene. For this purpose, for example, the SCR valve 11 is closed and / or the return valve 12 is adjusted such that the dirt sucked in by the pump 13 through the removal tube 4 (eg oil 30) returns via the return pipe 28 back to the reducing agent tank 1 is transported.
Darüber hinaus erhält das Steuergerät 16 der Brennkraftma- schine auch Informationen von der SCR-Steuereinheit 15, mit denen die Brennkraftmaschine entsprechend der Reduktionsmittelqualität und der im Reduktionsmittel 2 erkannten Verschmutzungen angesteuert werden kann. Es ist z. B. denkbar, dass nach dem Nachfüllen von reinem Wasser in den Reduktions- mitteltank 1 die Qualität des Reduktionsmittels 2 derart abgesunken ist, dass eine Abgasnachbehandlung und die entsprechende Reduktion des NOx nicht mehr ausreichend sichergestellt werden kann. In einem solchen Fall erfolgt zum einen ein Eintrag in einem FehlerSpeicher der On-Board- Diagnoseeinheit des Fahrzeuges und zum anderen kann dieIn addition, the control unit 16 of the internal combustion engine also receives information from the SCR control unit 15 with which the internal combustion engine can be controlled in accordance with the quality of the reducing agent and the soiling detected in the reducing agent 2. It is Z. B. conceivable that after refilling of pure water in the reducing agent tank 1, the quality of the reducing agent 2 has dropped such that an exhaust aftertreatment and the corresponding reduction of NOx can no longer be sufficiently ensured. In such a case, on the one hand, an entry is made in an error memory of the on-board diagnostic unit of the vehicle and, on the other hand, the
Brennkraftmaschine 6 über die Steuereinheit 16 der Brennkraftmaschine in einem Betriebszustand gefahren werden, in dem möglichst wenig NOx produziert wird. Das dies zu Lasten der maximalen Leistungsfähigkeit der Brennkraftmaschine 6 führen kann, wäre eine möglicherweise gewollte Konsequenz, da der Fahrzeugführer auf Grund des Leistungsverlustes der Brennkraftmaschine gezwungen wäre, eine entsprechende Reparaturwerkstatt aufzusuchen, die dafür sorgt, dass im Reduktionsmitteltank 1 ein Reduktionsmittel 2 mit ausreichender Qua- lität zur Verfügung steht. Auch wenn eine Verschmutzung des Reduktionsmittels 2 durch Öl 30 erkannt wurde, kann die Brennkraftmaschine von der Steuereinheit 16 in einen Zustand gefahren werden, in dem möglichst wenig NOx erzeugt wird. Damit wäre eine umweltgerechte Nachbehandlung des Abgases 23 im Abgasstrang 7 zu jederzeit sichergestellt. Internal combustion engine 6 are driven via the control unit 16 of the internal combustion engine in an operating state in which as little NOx is produced. This may be at the expense of the maximum performance of the internal combustion engine 6, would be a possible deliberate consequence, since the driver would be forced due to the power loss of the internal combustion engine to visit a corresponding repair workshop, which ensures that in the reducing agent tank 1, a reducing agent 2 with sufficient Qua - Quality is available. Even if a contamination of the reducing agent 2 has been detected by oil 30, the internal combustion engine can be driven by the control unit 16 in a state in which as little NOx is generated. This would ensure an environmentally sound after-treatment of the exhaust gas 23 in the exhaust line 7 at all times.

Claims

Patentansprüche claims
1. Reduktionsmitteltank mit einem Tankentnahmesystem zur Entnahme eines Reduktionsmittels aus dem Reduktionsmit- teltank und zur Beförderung des Reduktionsmittels zu einem SCR Katalysator in einem Abgasstrang, dadurch gekennzeichnet, dass in dem Tankentnahmesystem ein Sensor angeordnet ist, der die Qualität des Reduktionsmittels überprüft. 1. reducing agent tank with a tank removal system for taking a reducing agent from the Reduktionsmit- teltank and for conveying the reducing agent to an SCR catalyst in an exhaust line, characterized in that in the tank removal system, a sensor is arranged, which checks the quality of the reducing agent.
2. Reduktionsmitteltank mit einem Tankentnahmesystem nach Anspruch 1, dadurch gekennzeichnet, dass der Sensor als Sensor zur Messung der Leitfähigkeit des Reduktionsmittels ausgebildet ist. 2. reducing agent tank with a tank removal system according to claim 1, characterized in that the sensor is designed as a sensor for measuring the conductivity of the reducing agent.
3. Reduktionsmitteltank mit einem Tankentnahmesystem nach Anspruch 1 oder 3, dadurch gekennzeichnet, dass die Signale des Sensors von einem Steuergerät ausgewertet werden, wobei das Steuergerät beim Erkennen ei- ner minderen Reduktionsmittelqualität die Beförderung des Reduktionsmittels zu dem SCR Katalysator unterbricht . 3. reducing agent tank with a tank removal system according to claim 1 or 3, characterized in that the signals of the sensor are evaluated by a control unit, wherein the control unit interrupts the transport of the reducing agent to the SCR catalyst upon detection of a lower reducing agent quality.
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