EP0698208A1 - Sensor to determine the gas component concentration in gas mixtures - Google Patents

Sensor to determine the gas component concentration in gas mixtures

Info

Publication number
EP0698208A1
EP0698208A1 EP95910421A EP95910421A EP0698208A1 EP 0698208 A1 EP0698208 A1 EP 0698208A1 EP 95910421 A EP95910421 A EP 95910421A EP 95910421 A EP95910421 A EP 95910421A EP 0698208 A1 EP0698208 A1 EP 0698208A1
Authority
EP
European Patent Office
Prior art keywords
measuring electrode
electrode
sensor according
sensor
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.)
Ceased
Application number
EP95910421A
Other languages
German (de)
French (fr)
Inventor
Gerhard Hoetzel
Harald Neumann
Johann Riegel
Frank Stanglmeier
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Robert Bosch GmbH
Original Assignee
Robert Bosch GmbH
Priority date (The priority date 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 date listed.)
Filing date
Publication date
Application filed by Robert Bosch GmbH filed Critical Robert Bosch GmbH
Publication of EP0698208A1 publication Critical patent/EP0698208A1/en
Ceased legal-status Critical Current

Links

Classifications

    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
    • G01N27/26—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating electrochemical variables; by using electrolysis or electrophoresis
    • G01N27/403—Cells and electrode assemblies
    • G01N27/406—Cells and probes with solid electrolytes
    • G01N27/407—Cells and probes with solid electrolytes for investigating or analysing gases
    • G01N27/4075—Composition or fabrication of the electrodes and coatings thereon, e.g. catalysts
    • 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
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
    • G01N27/26—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating electrochemical variables; by using electrolysis or electrophoresis
    • G01N27/403—Cells and electrode assemblies
    • G01N27/406—Cells and probes with solid electrolytes
    • G01N27/4067—Means for heating or controlling the temperature of the solid electrolyte
    • 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
    • F01N2550/02—Catalytic activity of catalytic converters
    • 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 invention relates to a sensor for determining the concentration of gas components in gas mixtures according to the preamble of the main claim.
  • the sensor is particularly suitable for monitoring the functionality of catalysts in exhaust gas detoxification systems of internal combustion engines.
  • EP-A2-466 020 discloses a sensor for determining the proportion of oxidizable gases, in particular hydrogen, in which an electrode catalyzes the equilibrium adjustment of the exhaust gas (equilibrium electrode) and an electrode which does not catalyze the equilibrium setting of the exhaust gas (mixed potential electrode) is arranged on an oxygen ion-conducting solid electrolyte and is exposed to the exhaust gas.
  • an electrode catalyzes the equilibrium adjustment of the exhaust gas
  • an electrode which does not catalyze the equilibrium setting of the exhaust gas mixed potential electrode
  • Reference gas in combination whose oxygen content is known.
  • a voltage resulting from the difference between the mixed potential at the mixed potential electrode and the oxygen potential at the equilibrium electrode provides information about the hydrogen concentration in the exhaust gas.
  • a sensor for monitoring the function of catalysts in exhaust gas detoxification systems of internal combustion engines is known from DE-OS 23 04 464, in which an oxygen ion-conducting solid electrolyte with a catalytically active electrode that catalyzes the equilibrium of the exhaust gas and a catalytically inactive, the equilibrium setting of the exhaust gas is not catalyzing electrode is provided.
  • the catalytically inactive electrode consists of gold or silver, the catalytically active electrode made of platinum or a platinum alloy. In a first embodiment, both electrodes are exposed to the exhaust gas. In a further embodiment, the catalytically active electrode is exposed to a reference gas with a costly oxygen partial pressure.
  • the catalytic activity of the measuring electrodes is determined exclusively by material constants. A setting to a desired activity is no longer possible with these sensors after the electrodes have been produced.
  • the sensor according to the invention with the characterizing features of the main claim has the advantage that the measuring electrodes of the sensor can be set to a desired activity in a defined manner during operation. This is particularly advantageous if sensors of the same type are to be used for different applications.
  • the second measuring electrode is brought to a temperature which ensures a mixed potential for the corresponding task. With increasing temperature, the catalytic activity increases with the second measuring electrode and at the same time the mixed potential effect decreases.
  • different measuring electrodes that do not catalyze or only slightly catalyze the equilibrium of the gas mixture can be used to set a mixing potential.
  • a measuring electrode which is particularly suitable for measuring the free oxygen in the exhaust gas is present if the electrode has no or only a low catalytic activity. For example, platinum mixed with bismuth is suitable as the electrode material. Another
  • Measuring electrode material which has a competitive reaction between O 2 and CO or HC is present, for example, with gold and / or silver or with a platinum alloy with gold and / or silver.
  • An additional increase in Measuring signal can be achieved if two or more measuring electrodes connected in series are arranged.
  • FIG. 1 shows a cross section of a sensor according to the invention
  • FIG. 2 shows the characteristic curve of the sensor according to FIG. 1 with a measuring electrode indicating the free oxygen of the exhaust gas
  • FIG. 3 shows the characteristic curve of the sensor according to FIG. 1 with a measuring electrode, the catalytic activity of which is due to a competitive reaction between oxygen and other gas components
  • FIG. 4 shows a cross section of the sensor according to FIG
  • FIG. 5 shows a top view of a sensor according to the invention in accordance with a second exemplary embodiment
  • FIG. 6 shows a characteristic curve of the sensor according to FIG. 4 with a measuring electrode indicating the free oxygen of the exhaust gas
  • FIG. 7 shows a characteristic curve of the sensor according to FIG. 4 with a measuring electrode whose catalytic activity is determined by a competitive reaction between oxygen and other gas components.
  • the sensor according to FIG. 1 consists of an oxygen-ion-conducting solid electrolyte 10, for example of ZrO 2 stabilized with Y 2 O 3 , onto which a first, catalytically active measuring electrode 11 (equilibrium electrode ) catalyzing the equilibrium of the exhaust gas and a second, catalytically inactive one that hot, the equilibrium setting of the exhaust gas is not applied or only to a small extent catalyzing measuring electrode 12 (mixed potential electrode).
  • the equilibrium electrode 11 contains, for example, platinum or a platinum alloy with additions of rhodium or palladium.
  • a first porous ceramic protective layer 13 is over the equilibrium electrode 11 and over the
  • the protective layers 13, 14 consist, for example, of Al 2 O 3 , the first protective layer 13 being able to be active by adding catalyst substances and promoters and acting as an upstream catalyst with respect to the equilibrium electrode 11.
  • the diffusion inhibition caused by the protective layer 13 additionally limits the amount of gas reaching the equilibrium electrode 11, as a result of which the
  • the mixed potential electrode 12 consists of a material which is suitable for producing no or only a low catalytic activity with regard to the oxidizable gas components, but which is preferably able to adsorb oxygen. Such properties have, for example, an electrode containing platinum and bismuth.
  • the mixed potential electrode 12 contains gold and / or silver or a platinum alloy with gold and / or silver. Such a material has the effect that the catalytic conversion is at least inhibited by oxidation of CO and / or HC and reduction of N0 X.
  • the oxidizable gas components adsorb, for example, on the mixed potential electrode 12, so that that in the gas mixture existing oxygen does not reach the mixed potential electrode 12 or only with difficulty.
  • the free oxygen present in the gas mixture reacts, for example, with CO to form CO 2. This means that no or only a few oxygen ions can be formed at the three-phase boundary.
  • the sensor according to FIG. 1 also has a heating device 16 integrated in the solid electrolyte 10 and embedded in an electrical insulation 15.
  • the heating device 16 consists of a first one
  • the heating circuits of the two resistance heaters 17, 18 are arranged in the solid electrolyte 10 that the
  • Temperature field of the first resistance heater 17 influences the equilibrium electrode 11 and the temperature field of the second resistance heater 18 influences the mixed potential electrode 12. This can be realized in that the first resistance heater 17 below the
  • Equilibrium electrode 11 and the second resistance heater 18 is arranged below the mixed potential electrode 12.
  • a targeted temperature setting for each of the measuring electrodes 11, 12 is possible when using a plurality of separate heaters, the temperature of the areas being controllable separately or in combination by a control device (not shown) via the heater voltage UJJI and U jj2 .
  • the potential difference between the equilibrium electrode 11 and the mixed potential electrode 12 is tapped as the measurement signal U.
  • U G potential or equilibrium electrode 11
  • U M potential or mixed potential electrode 12.
  • an inactive catalyst there is a high potential difference with lambda values ⁇ 1. As the activity of the catalyst increases, the potential difference decreases to approximately 0. The situation is similar when using a mixed potential electrode 12 of type B.
  • a high potential difference is found in a non-active catalyst with lambda values> 1, the measurement signal U from U jj - UR is formed. With increasing activity of the
  • the catalyst difference also decreases here, the potential difference becoming approximately 0 in the case of a fully active catalyst.
  • the senor in addition to the equilibrium electrode 11 and the mixed potential electrode 12, the sensor has a reference electrode 24 which is exposed to a reference gas in a reference channel 23 and which is advantageously also made of a material which catalyzes the equilibrium setting of the gas mixture.
  • the reference channel 23 is connected to the atmosphere, for example, so that air is used as the reference gas.
  • the heating device 16 is designed as in the embodiment shown in Figure 1. Since the distance between the resistance heaters 17, 18 and the equilibrium electrode 11 and the mixed potential electrode 12 is greater as a result of the reference channel 23 introduced in the solid electrolyte 10, it is conceivable that the heating power must be increased compared to the sensor according to FIG. 1 in order to form the corresponding temperature gradients.
  • the EMF occurring between the equilibrium electrode 11 and the reference electrode 24 are measured signal U Q and those between the Mixed potential electrode 12 and the reference electrode 24 appearing EMF recorded as measurement signal U M.
  • FIG. 3 A further embodiment of the sensor according to the invention can be seen in FIG. 3, in which the heating device 16 is formed from a common resistance heater 19.
  • the equilibrium electrode 11 and the mixed potential electrode 12 are arranged on the solid electrolyte 10 such that both are located in different temperature zones of the resistance heater 19.
  • the temperature gradient formed in the solid electrolyte 10 is used, the temperature directly above the heating conductor track 20 being higher than above the feed line 21.
  • the equilibrium electrode 11 is immediately above the
  • Heating conductor track 20 arranged.
  • the mixed potential electrode 12 is located on the solid electrolyte 10 at the edge of the heating conductor track 20 and / or above the feed line 21 in the region of a lower temperature.
  • Equilibrium electrode 11 and the mixed potential electrode 12 can also be realized by a special heater geometry or by a special heater design, as a result of which different differential heating outputs are used along the heating conductor path of a resistance heater.
  • the catalytic activity of the measuring electrodes 11, 12 can be set in a defined manner via the temperature.
  • a characteristic curve of the sensor according to FIG. 2 with a mixed potential electrode 12 of type A is shown in FIG. 6 forth.
  • the characteristic curve shows the signal curve of the measurement signal U G1 of the equilibrium electrode 11 and the signal curve of the measurement signals U M1 ⁇ ⁇ U M1 'of the mixed potential electrode 12.
  • the measurement signals O Q J_ and U ⁇ i were not shown with a downstream in the flow direction of the exhaust gas
  • Catalyst arranged sensor measured. With a sensor arranged upstream of the catalytic converter in the flow direction of the exhaust gas, the EMF of the mixed potential electrode 12 was recorded as the measurement signal U M1 '.
  • the measurement signal U ⁇ i 'recorded upstream from the catalytic converter characterizes the characteristic curve of a catalytic converter with an efficiency of 0%, that is to say it indicates a total catalytic converter failure. Due to the oxygen adsorbed on the mixed potential electrode 12, there is a small potential difference at ⁇ ⁇ 1 between the reference electrode 24 and the mixed potential electrode 12.
  • the oxygen partial pressure is always vanishingly small, regardless of the state of the catalyst used for the afterburning.
  • the oxygen partial pressure corresponds to the thermodynamic equilibrium partial pressure, because the electrode material of the equilibrium electrode 11 ensures a complete conversion of the gas mixture.
  • the oxygen partial pressure in the exhaust gas increases. Almost nothing changes at the three-phase boundary of the equilibrium electrode 11.
  • the oxygen partial pressure depends on the catalytic activity of the catalyst. If the catalytic converter is fully effective, the oxygen partial pressure at this electrode is also relatively small, so that in this case the characteristic curve the mixed potential electrode at least approximately assumes the course of the measurement signal U G1 of the equilibrium electrode 11.
  • the characteristic of the measurement signal U ⁇ i becomes flatter.
  • the characteristic curve shown in dashed lines in FIG. 6 corresponds to the course of the measurement signal U ⁇ i with an efficiency of the catalyst of, for example, 90%.
  • Equilibrium electrode 11 applies here what has already been said in the curve discussion for FIG.
  • the measurement signal U .2 'of the mixed potential electrode 12 picked up by a sensor arranged upstream of the catalytic converter in the flow direction of the exhaust gas has a profile at a potential which corresponds approximately to the voltage of a lambda probe in the rich exhaust gas ( ⁇ ⁇ 1). This curve decreases only slightly with higher lambda values because the relatively high potential difference is approximately retained due to the competition reactions occurring at the mixed potential electrode 12.
  • the oxygen partial pressure is also low at the mixed potential electrode 12 downstream of the catalytic converter.
  • a measurement signal of the mixed potential electrode 12 is recorded which corresponds approximately to the measurement signal U 2 of the equilibrium electrode 11.
  • the potential of the mixed potential electrode 12 increases in the range ⁇ > 1.
  • the dashed curve indicates the measurement signal U M2 with an efficiency of the catalyst of, for example, 90%.
  • the measurement signals U G ⁇ and U ⁇ i or U G2 and U ⁇ 2 are fed to an evaluation circuit, not shown, and compared there with one another.
  • the efficiency of the catalytic converter is inferred from the comparison of the two measurement signals, the efficiency decreasing with increasing deviation of the measurement signals from one another.

Landscapes

  • Chemical & Material Sciences (AREA)
  • Health & Medical Sciences (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Engineering & Computer Science (AREA)
  • Biochemistry (AREA)
  • Molecular Biology (AREA)
  • Electrochemistry (AREA)
  • Physics & Mathematics (AREA)
  • Analytical Chemistry (AREA)
  • General Health & Medical Sciences (AREA)
  • General Physics & Mathematics (AREA)
  • Immunology (AREA)
  • Pathology (AREA)
  • General Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Combustion & Propulsion (AREA)
  • Measuring Oxygen Concentration In Cells (AREA)

Abstract

The proposal is for a sensor for determining the gas component concentration in gas mixtures. The sensor has a solid oxygen-ion-conducting electrolyte (10) having a first measuring electrode (11) which catalyses the equilibrium setting of the gas mixture and a second measuring electrode (12) which does not catalyse or only slightly catalyses the equilibrium setting of the exhaust gas, and a heating device (16) to control the temperature of the measuring electrodes (11, 12). The first (11) and second (12) measuring electrodes are arranged in different temperature regions of the solid electrolyte (10) in such a way that the catalytic activity of the measuring electrodes (11, 12) can be adjusted via the temperature. The sensor is particularly suitable for monitoring the function ability of catalysts in exhaust gas purification devices of internal combustion engines.

Description

Sensor zur Bestimmung der Konzentration von Gaskomponen gn in GasgemischenSensor for determining the concentration of gas components gn in gas mixtures
Stand der TechnikState of the art
Die Erfindung geht aus von einem Sensor zur Bestimmung der Konzentration von Gaskomponenten in Gasgemischen nach der Gattung des Hauptanspruchs. Der Sensor ist besonders geeignet zur Überwachung der Funktionsfähigkeit von Katalysatoren in Abgasentgiftungsanlagen von Brennkraftmaschinen.The invention relates to a sensor for determining the concentration of gas components in gas mixtures according to the preamble of the main claim. The sensor is particularly suitable for monitoring the functionality of catalysts in exhaust gas detoxification systems of internal combustion engines.
Brennkraftmaschinen erzeugen in ihrem Abgas unter anderem Kohlenmonoxid, Stickoxide sowie unverbrannte oder teilweise verbrannte Kohlenwasserstoffe. Die mit herkömmlichen Lambda-Sonden durchgeführte Messung des Sauerstoffgehalts in Abgasen allein liefert nicht immer ausreichende Informationen über die Qualität der Verbrennung des Kraftstoffgemisches. Für verschiedene Anwendungsfälle ist es besonders wichtig, den Anteil der bei unvollständigen Verbrennungen auftretenden oxidierbaren Gaskomponenten kontrollieren zu können. Neben der Herabsetzung der Grenzwerte der Abgasemission gewinnnt die Überwachung des Katalysators in Abgasanlagen hinsichtlich seiner Funktion, beispielsweise bei der On-board-Diagnose zunehmend an Bedeutung.Internal combustion engines produce carbon monoxide, nitrogen oxides and unburned or partially burned hydrocarbons in their exhaust gas. The measurement of the oxygen content in exhaust gases using conventional lambda probes alone does not always provide sufficient information about the quality of the combustion of the fuel mixture. For various applications, it is particularly important to be able to control the proportion of oxidizable gas components that occur during incomplete combustion. In addition to reducing the exhaust gas limit values, monitoring the catalytic converter in exhaust systems with regard to its function, for example in on-board diagnostics, is becoming increasingly important.
Aus der EP-A2-466 020 ist ein Sensor zur Bestimmung des Anteils an oxidierbaren Gasen, insbesondere von Wasserstoff bekannt, bei dem eine die Gleichgewichtseinstellung des Abgases katalysierende Elektrode (Gleichgewichtselektrode) und eine die Gleichgewichtseinstellung des Abgases nicht katalysierende Elektrode (Mischpotentialelektrode) angeordnet auf einem Sauerstoffionenleitenden Festelektrolyt dem Abgas ausgesetzt sind. Eine für beide Elektroden wirkende Gegen- bzw. Referenzelektrode steht mit einemEP-A2-466 020 discloses a sensor for determining the proportion of oxidizable gases, in particular hydrogen, in which an electrode catalyzes the equilibrium adjustment of the exhaust gas (equilibrium electrode) and an electrode which does not catalyze the equilibrium setting of the exhaust gas (mixed potential electrode) is arranged on an oxygen ion-conducting solid electrolyte and is exposed to the exhaust gas. A counter or reference electrode acting for both electrodes stands with one
Referenzgas in Verbindung, dessen Sauerstoffgehalt bekannt ist. Eine aus der Differenz zwischen dem Mischpotential an der Mischpotentialelektrode und dem Sauerstoffpotential an der Gleichgewichtselektrode resultierende Spannung gibt Aufschluß auf die Wasserstoffkonzentration im Abgas.Reference gas in combination, whose oxygen content is known. A voltage resulting from the difference between the mixed potential at the mixed potential electrode and the oxygen potential at the equilibrium electrode provides information about the hydrogen concentration in the exhaust gas.
Ein Sensor für die Überwachung der Funktion von Katalysatoren in Abgasentgiftungsanlagen von Brennkraftmaschinen ist aus der DE-OS 23 04 464 bekannt, bei dem ein Sauerstoffionenleitender Festelektrolyt mit einer katalytisch aktiven, die Gleichgewichtseinstellung des Abgases katalysierenden Elektrode und einer katalytisch inaktiven, die Gleichgewichtseinstellung des Abgases nicht katalyisierenden Elektrode versehen ist. Die katalytisch inaktive Elektrode besteht dabei aus Gold oder Silber, die katalytisch aktive Elektrode aus Platin oder einer Platinlegierung. Bei einer ersten Ausführungsform werden beide Elektroden dem Abgas ausgesetzt. Bei einer weiteren Ausführungsform ist die katalytisch aktive Elektrode einem Referenzgas mit einem kostantem Sauerstoffpartialdruck ausgesetzt.A sensor for monitoring the function of catalysts in exhaust gas detoxification systems of internal combustion engines is known from DE-OS 23 04 464, in which an oxygen ion-conducting solid electrolyte with a catalytically active electrode that catalyzes the equilibrium of the exhaust gas and a catalytically inactive, the equilibrium setting of the exhaust gas is not catalyzing electrode is provided. The catalytically inactive electrode consists of gold or silver, the catalytically active electrode made of platinum or a platinum alloy. In a first embodiment, both electrodes are exposed to the exhaust gas. In a further embodiment, the catalytically active electrode is exposed to a reference gas with a costly oxygen partial pressure.
Die katalytische Aktivität der Meßelektroden wird bei den bekannten Sensoren ausschließlich durch Materialkonstanten bestimmt. Eine Einstellung auf eine gewünschte Aktivität ist bei diesen Sensoren nach der Herstellung der Elektroden nicht mehr möglich. Vorteile der ErfindungIn the known sensors, the catalytic activity of the measuring electrodes is determined exclusively by material constants. A setting to a desired activity is no longer possible with these sensors after the electrodes have been produced. Advantages of the invention
Der erfindungsgemäße Sensor mit den kennzeichnenden Merkmalen des Hauptanspruchs hat den Vorteil, daß die Meßelektroden des Sensors beim Betreiben definiert auf eine gewünschte Aktivität einstellbar sind. Dies ist besonders von Vorteil, wenn gleichartige Sensoren für unterschiedliche Anwendungsfälle eingesetzt werden sollen.The sensor according to the invention with the characterizing features of the main claim has the advantage that the measuring electrodes of the sensor can be set to a desired activity in a defined manner during operation. This is particularly advantageous if sensors of the same type are to be used for different applications.
Mit den in den Unteransprüchen aufgeführten Maßnahmen sind vorteilhafte Weiterbildungen und Verbesserungen des erfindungsgemäßen Sensors möglich. Besonders vorteilhaft ist es, die Temperatur an den Meßelektroden über die Heizleistung der Heizeinrichtung einzustellen. Die erste Meßelektrode wird vorteilhafterweise auf einer höherenWith the measures listed in the subclaims, advantageous developments and improvements of the sensor according to the invention are possible. It is particularly advantageous to set the temperature at the measuring electrodes via the heating power of the heating device. The first measuring electrode is advantageously on a higher one
Temperatur gehalten, damit eine ausreichende katalytische Aktivität erhalten bleibt. Die zweite Meßelektrode hingegen wird auf eine Temperatur gebracht, die ein Mischpotential für die entsprechende Aufgabenstellung sicherstellt. Mit zunehmender Temperatur steigt bei der zweiten Meßelektrode die katalytische Aktivität und gleichzeitig sinkt die Mischpotentialwirkung. Zur Einstellung eines Mischpotentials sind in Abhängigkeit von der AbgasZusammensetzung verschiedene, die Gleichgewichtseinstellung des Gasgemisches nicht oder nur wenig katalysierende Meßelektroden verwendbar. Eine zur Messung des freien Sauerstoffs im Abgas besonders geeignete Meßelektrode liegt vor, wenn die Elektrode keine oder nur eine geringe katalytische Aktivität besitzt. Als Elektrodenmaterial eignet sich beispielweise mit Wismut versetztes Platin. Ein anderesTemperature maintained so that sufficient catalytic activity is maintained. The second measuring electrode, on the other hand, is brought to a temperature which ensures a mixed potential for the corresponding task. With increasing temperature, the catalytic activity increases with the second measuring electrode and at the same time the mixed potential effect decreases. Depending on the exhaust gas composition, different measuring electrodes that do not catalyze or only slightly catalyze the equilibrium of the gas mixture can be used to set a mixing potential. A measuring electrode which is particularly suitable for measuring the free oxygen in the exhaust gas is present if the electrode has no or only a low catalytic activity. For example, platinum mixed with bismuth is suitable as the electrode material. Another
Meßelektrodenmaterial, welches eine Konkurrenzreaktion zwischen O2 und CO oder HC aufweist liegt beispielsweise mit Gold und/oder Silber oder aber mit einer Platinlegierung mit Gold und/oder Silber vor. Eine zusätzliche Erhöhung des Meßsignals ist dadurch erzielbar, wenn zwei oder mehr in Reihe geschaltete Meßelektroden angeordnet werden.Measuring electrode material which has a competitive reaction between O 2 and CO or HC is present, for example, with gold and / or silver or with a platinum alloy with gold and / or silver. An additional increase in Measuring signal can be achieved if two or more measuring electrodes connected in series are arranged.
Zeichnungdrawing
Zwei Ausführungsbeispiele der Erfindung sind in der Zeichnung dargestellt und in der nachfolgenden Beschreibung näher erläutert. Es zeigen Figur 1 einen Querschnitt eines erfindungsgemäßen Sensors, Figur 2 die Kennlinie des Sensors gemäß Figur 1 mit einer den freien Sauerstoff des Abgases anzeigenden Meßelektrode, Figur 3 die Kennlinie des Sensors gemäß Figur 1 mit einer Meßelektrode, deren katalytische Aktivität durch eine Konkurrenzreaktion zwischen Sauerstoff und anderen Gaskomponenten bestimmt ist, Figur 4 einen Querschnitt des Sensors gemäß Figur 1 mit einerTwo embodiments of the invention are shown in the drawing and explained in more detail in the following description. 1 shows a cross section of a sensor according to the invention, FIG. 2 shows the characteristic curve of the sensor according to FIG. 1 with a measuring electrode indicating the free oxygen of the exhaust gas, FIG. 3 shows the characteristic curve of the sensor according to FIG. 1 with a measuring electrode, the catalytic activity of which is due to a competitive reaction between oxygen and other gas components, FIG. 4 shows a cross section of the sensor according to FIG
Referenzelektrode, Figur 5 eine Draufsicht auf einen erfindungsgemäßen Sensor gemäß einem zweiten Ausführungsbeispiel, Figur 6 eine Kennlinie des Sensors gemäß Figur 4 mit einer den freien Sauerstoff des Abgases anzeigenden Meßelektrode und Figur 7 eine Kennlinie des Sensors gemäß Figur 4 mit einer Meßelektrode, deren katalytische Aktivität durch eine Konkurrenzreaktion zwischen Sauerstoff und anderen Gaskomponenten bestimmt ist.5 shows a top view of a sensor according to the invention in accordance with a second exemplary embodiment, FIG. 6 shows a characteristic curve of the sensor according to FIG. 4 with a measuring electrode indicating the free oxygen of the exhaust gas and FIG. 7 shows a characteristic curve of the sensor according to FIG. 4 with a measuring electrode whose catalytic activity is determined by a competitive reaction between oxygen and other gas components.
Ausführungsbeispieleembodiments
Der Sensor gemäß Figur 1 besteht aus einem sauerstoffionenleitendem Festelektrolyt 10 beispielsweise aus mit Y2O3-stabilisiertem Zrθ2, auf den eine erste, katalytisch aktive, das heißt, die Gleichgewichtseinstellung des Abgases katalysierende Meßelektrode 11 (Gleichgewichtselektrode) und eine zweite, katalytisch inaktive, das heiß, die Gleichgewichtseinstellung des Abgases nicht oder nur in geringem Maße katalysierende Meßelektrode 12 (Mischpotentialelektrode) aufgebracht sind. Die Gleichgewichtselektrode 11 enthält beispielsweise Platin oder eine Platinlegierung mit Zusätzen von Rhodium oder Palladium.The sensor according to FIG. 1 consists of an oxygen-ion-conducting solid electrolyte 10, for example of ZrO 2 stabilized with Y 2 O 3 , onto which a first, catalytically active measuring electrode 11 (equilibrium electrode ) catalyzing the equilibrium of the exhaust gas and a second, catalytically inactive one that hot, the equilibrium setting of the exhaust gas is not applied or only to a small extent catalyzing measuring electrode 12 (mixed potential electrode). The equilibrium electrode 11 contains, for example, platinum or a platinum alloy with additions of rhodium or palladium.
Über die Gleichgewichtselektrode 11 ist eine erste poröse keramische Schutzschicht 13 und über dieA first porous ceramic protective layer 13 is over the equilibrium electrode 11 and over the
Mischpotentialelektrode 12 eine zweite poröse keramische Schutzschicht 14 gelegt. Die Schutzschichten 13, 14 bestehen beispielsweise aus AI2O3, wobei die erste Schutzschicht 13 durch Zusätze von Katalysatorstoffen und Promotoren aktiv sein kann und gegenüber der Gleichgewichtselektrode 11 als vorgeschalteter Katalysator wirkt. Die durch die Schutzschicht 13 hervorgerufene Diffusionshemmung bewirkt zusätzlich eine Begrenzung der zur Gleichgewichtselektrode 11 gelangenden Gasmenge, wodurch dieMixed potential electrode 12 placed a second porous ceramic protective layer 14. The protective layers 13, 14 consist, for example, of Al 2 O 3 , the first protective layer 13 being able to be active by adding catalyst substances and promoters and acting as an upstream catalyst with respect to the equilibrium electrode 11. The diffusion inhibition caused by the protective layer 13 additionally limits the amount of gas reaching the equilibrium electrode 11, as a result of which the
Gleichgewichtseinstellung gefördert wird.Balance is encouraged.
Zwei Ausführungen von Mischpotentialelektroden 12 sind möglich:Two versions of mixed potential electrodes 12 are possible:
Typ A) Die Mischpotentialelektrode 12 besteht aus einem Material, das geeignet ist, keine, beziehungsweise nur eine geringe katalytische Aktivität bezüglich der oxidierbaren Gaskomponeten auszubilden, den Sauerstoff jedoch bevorzugt zu adsorbieren vermag. Derartige Eigenschaften weist beispielsweise eine Platin und Wismut enthaltende Elektrode auf.Type A) The mixed potential electrode 12 consists of a material which is suitable for producing no or only a low catalytic activity with regard to the oxidizable gas components, but which is preferably able to adsorb oxygen. Such properties have, for example, an electrode containing platinum and bismuth.
Typ B) Die Mischpotentialelektrode 12 enthält Gold und/oder Silber oder eine Platinlegierung mit Gold und/oder Silber. Ein derartiges Material bewirkt, daß die katalytische Umsetzung durch Oxidation von CO und/oder HC und Reduktion von N0X zumindest gehemmt wird. Die oxidierbaren Gaskomponenten adsorbieren beispielsweise an der Mischpotentialelektrode 12, so daß der im Gasgemisch vorhandene Sauerstoff nicht oder nur schwer an die Mischpotentialelektrode 12 gelangt. Zusätzlich reagiert der im Gasgemisch vorhandene freie Sauerstoff zum Beispiel mit CO zu CO2 • Somit können an der Dreiphasengrenze auch keine oder nur wenige Sauerstoffionen gebildet werden.Type B) The mixed potential electrode 12 contains gold and / or silver or a platinum alloy with gold and / or silver. Such a material has the effect that the catalytic conversion is at least inhibited by oxidation of CO and / or HC and reduction of N0 X. The oxidizable gas components adsorb, for example, on the mixed potential electrode 12, so that that in the gas mixture existing oxygen does not reach the mixed potential electrode 12 or only with difficulty. In addition, the free oxygen present in the gas mixture reacts, for example, with CO to form CO 2. This means that no or only a few oxygen ions can be formed at the three-phase boundary.
Der Sensor gemäß Figur 1 besitzt ferner eine in den Festelektrolyt 10 integrierten und in eine elektrische Isolation 15 eingebettete Heizeinrichtung 16. Die Heizeinrichtung 16 besteht aus einem erstenThe sensor according to FIG. 1 also has a heating device 16 integrated in the solid electrolyte 10 and embedded in an electrical insulation 15. The heating device 16 consists of a first one
Widerstandsheizer 17 und einem zweiten Widerstandsheizer 18, die getrennt voneinander mittels einer ersten Heizerspannung Ujj]_ und einer zweiten Heizerspannung Ujj2 betrieben werden. Die Heizkreise der beiden Widerstandsheizer 17, 18 sind derart im Festelektrolyt 10 angeordnet, daß dasResistance heater 17 and a second resistance heater 18, which are operated separately from one another by means of a first heater voltage U jj] _ and a second heater voltage U jj2 . The heating circuits of the two resistance heaters 17, 18 are arranged in the solid electrolyte 10 that the
Temperaturfeld des ersten Widerstandsheizers 17 die Gleichgewichtselektrode 11 und das Temperaturfeld des zweiten Widerstandsheizers 18 die Mischpotentialelektrode 12 beeinflußt. Dies läßt sich dadurch realisieren, daß der erste Widerstandsheizer 17 unterhalb derTemperature field of the first resistance heater 17 influences the equilibrium electrode 11 and the temperature field of the second resistance heater 18 influences the mixed potential electrode 12. This can be realized in that the first resistance heater 17 below the
Gleichgewichtselektrode 11 und der zweite Widerstandsheizer 18 unterhalb der Mischpotentialelektrode 12 angeordnet ist. Eine gezielte Temperatureinstellung für jeweils eine der Meßelektroden 11, 12 ist bei der Verwendung mehrerer separater Heizer möglich, wobei die Temperatur der Bereiche gesondert oder kombiniert von einer nicht dargestellten Regeleinrichtung über die Heizerspannung UJJI und Ujj2 regelbar ist.Equilibrium electrode 11 and the second resistance heater 18 is arranged below the mixed potential electrode 12. A targeted temperature setting for each of the measuring electrodes 11, 12 is possible when using a plurality of separate heaters, the temperature of the areas being controllable separately or in combination by a control device (not shown) via the heater voltage UJJI and U jj2 .
Beim Sensor gemäß Figur 1 wird die Potentialdifferenz zwischen der Gleichgewichtselektrode 11 und der Mischpotentialelektrode 12 als Meßsignal U abgegriffen. Bei einer Mischpotentialelektrode 12 vom Typ A besitzt das Meßsignal U den in Figur 2 dargestellten Verlauf, wobei das Meßsignal U aus UG - UM gebildet wird, mit UG = Potential oder Gleichgewichtselektrode 11 und UM = Potential oder Mischpotentialelektrode 12. Bei einem nicht aktiven Katalysator liegt eine hohe Potentialdifferenz bei Lambdawerten < 1 vor. Mit zunehmender Aktivität des Katalysators verringert sich die Potentialdifferenz bis annähernd 0. Ähnlich ist die Situation bei Verwendung einer Mischpotentialelektrode 12 vom Typ B. Gemäß Figur 2 ist eine hohe Potentialdifferenz bei einem nicht aktiven Katalysator bei Lambdawerten > 1 anzutreffen, wobei das Meßsignal U aus Ujj - UR gebildet wird. Mit zunehmender Aktivität desIn the sensor according to FIG. 1, the potential difference between the equilibrium electrode 11 and the mixed potential electrode 12 is tapped as the measurement signal U. In the case of a mixed potential electrode 12 of type A, the measurement signal U has the profile shown in FIG. 2, the measurement signal U being formed from U G - U M , with U G = potential or equilibrium electrode 11 and U M = potential or mixed potential electrode 12. In the case of an inactive catalyst, there is a high potential difference with lambda values <1. As the activity of the catalyst increases, the potential difference decreases to approximately 0. The situation is similar when using a mixed potential electrode 12 of type B. According to FIG. 2, a high potential difference is found in a non-active catalyst with lambda values> 1, the measurement signal U from U jj - UR is formed. With increasing activity of the
Katalysators nimmt auch hier die Potentialdifferenz ab, wobei bei einem voll wirksamen Katalysator die Potentialdifferenz annähernd 0 wird.The catalyst difference also decreases here, the potential difference becoming approximately 0 in the case of a fully active catalyst.
Beim Ausführungsbeispiel gemäß Figur 2 besitzt der Sensor zusätzlich zu der Gleichgewichtselektrode 11 und der Mischpotentialelektrode 12 eine in einem Referenzkanal 23 einem Referenzgas ausgesetzte Referenzelektrode 24, welche zweckmäßigerweise ebenfalls aus einem die Gleichgewichtseinstellung des Gasgemisches katalysierenden Material ausgeführt ist. Der Referenzkanal 23 ist beispielsweise mit der Atmosphäre verbunden, so daß als Referenzgas Luft verwendet wird. Die Heizeinrichtung 16 ist wie bei dem in Figur 1 dargestellten Ausführungsbeispiel ausgeführt. Da durch den im Festelektrolyt 10 eingebrachten Referenzkanal 23 der Abstand zwischen den Widerstandsheizern 17, 18 und der Gleichgewichtselektrode 11 sowie der Mischpotentialelektrode 12 größer ist, ist es denkbar, daß zur Ausbildung der entsprechenden Temperaturgradienten die Heizleistung gegenüber dem Sensor gemäß Figur 1 erhöht werden muß.In the exemplary embodiment according to FIG. 2, in addition to the equilibrium electrode 11 and the mixed potential electrode 12, the sensor has a reference electrode 24 which is exposed to a reference gas in a reference channel 23 and which is advantageously also made of a material which catalyzes the equilibrium setting of the gas mixture. The reference channel 23 is connected to the atmosphere, for example, so that air is used as the reference gas. The heating device 16 is designed as in the embodiment shown in Figure 1. Since the distance between the resistance heaters 17, 18 and the equilibrium electrode 11 and the mixed potential electrode 12 is greater as a result of the reference channel 23 introduced in the solid electrolyte 10, it is conceivable that the heating power must be increased compared to the sensor according to FIG. 1 in order to form the corresponding temperature gradients.
Beim Sensor gemäß Figur 2 werden die zwischen der Gleichgewichtselektrode 11 und der Referenzelektrode 24 auftretenden EMK als Meßsignal UQ und die zwischen der Mischpotentialelektrode 12 und der Referenzelektrode 24 auftretende EMK als Meßsiganal UM aufgenommen.In the sensor according to FIG. 2, the EMF occurring between the equilibrium electrode 11 and the reference electrode 24 are measured signal U Q and those between the Mixed potential electrode 12 and the reference electrode 24 appearing EMF recorded as measurement signal U M.
Eine weitere Ausführungsform des erfindungsgemäßen Sensors geht aus Figur 3 hervor, bei der die Heizeinrichtung 16 aus einem gemeinsamen Widerstandsheizer 19 gebildet ist. Bei dieser Ausführungsform ist die Gleichgewichtselektrode 11 und die Mischpotentialelektrode 12 derart auf dem Festelektrolyt 10 angeordnet, daß sich beide in unterschiedlichen Temperaturzonen des Widerstandsheizers 19 befinden. Bei dieser Ausführungform wird der sich im Festelektrolyt 10 ausbildende Temperaturgradient ausgenutzt, wobei unmittelbar über der Heizleiterbahn 20 die Temperatur höher ist als über der Zuleitung 21. Die Gleichgewichtselektrode 11 ist dabei unmittelbar über derA further embodiment of the sensor according to the invention can be seen in FIG. 3, in which the heating device 16 is formed from a common resistance heater 19. In this embodiment, the equilibrium electrode 11 and the mixed potential electrode 12 are arranged on the solid electrolyte 10 such that both are located in different temperature zones of the resistance heater 19. In this embodiment, the temperature gradient formed in the solid electrolyte 10 is used, the temperature directly above the heating conductor track 20 being higher than above the feed line 21. The equilibrium electrode 11 is immediately above the
Heizleiterbahn 20 angeordnet. Die Mischpotentialelektrode 12 befindet sich auf dem Festelektrolyt 10 am Rande der Heizleiterbahn 20 und/oder über der Zuleitung 21 im Bereich geringerer Temperatur. Eine gezielte Temperaturverteilung im oder auf dem Festelektrolyt 10 in Bezug auf dieHeating conductor track 20 arranged. The mixed potential electrode 12 is located on the solid electrolyte 10 at the edge of the heating conductor track 20 and / or above the feed line 21 in the region of a lower temperature. A targeted temperature distribution in or on the solid electrolyte 10 in relation to the
Gleichgewichtselektrode 11 und die Mischpotentialelektrode 12 läßt sich ferner durch eine spezielle Heizergeometrie beziehungsweise durch ein spezielles Heizerdesign realisieren, wodurch unterschiedliche differenzielle Heizleistungen entlang der Heizleiterbahn eines Widerstandsheizers genutzt werden.Equilibrium electrode 11 and the mixed potential electrode 12 can also be realized by a special heater geometry or by a special heater design, as a result of which different differential heating outputs are used along the heating conductor path of a resistance heater.
Durch die Anordnung der Gleichgewichtselektrode 11 und der Mischpotentialelektrode 12 in unterschiedlichen Temperaturbereichen des Festelektrolyten 10 läßt sich die katalytische Aktivität der Meßelektroden 11, 12 über die Temperatur definiert einstellen.By arranging the equilibrium electrode 11 and the mixed potential electrode 12 in different temperature ranges of the solid electrolyte 10, the catalytic activity of the measuring electrodes 11, 12 can be set in a defined manner via the temperature.
Eine Kennlinie des Sensors gemäß Figur 2 mit einer Mischpotentialelektrode 12 vom Typ A geht aus Figur 6 hervor. Die Kennlinie zeigt den Signalverlauf des Meßsignals UG1 der Gleichgewichtselektrode 11 und den Signalverlauf der Meßsignale UM1 ^ ά U M1' der Mischpotentialelektrode 12. Die Meßsignale OQJ_ und U^i wurden mit einem in Strömungsrichtung des Abgases stromab von einem nicht dargestelltenA characteristic curve of the sensor according to FIG. 2 with a mixed potential electrode 12 of type A is shown in FIG. 6 forth. The characteristic curve shows the signal curve of the measurement signal U G1 of the equilibrium electrode 11 and the signal curve of the measurement signals U M1 ^ ά U M1 'of the mixed potential electrode 12. The measurement signals O Q J_ and U ^ i were not shown with a downstream in the flow direction of the exhaust gas
Katalysator angeordneten Sensor gemessen. Mit einem in Strömungsrichtung des Abgases stromauf vom Katalysator angeordneten Sensor wurde die EMK der Mischpotentialelektrode 12 als Meßsignal UM1'aufgenommen. Das stromauf vom Katalysator aufgenommene Meßsignal U^i' charakterisiert die Kennlinie eines Katalysators mit einem Wirkungsgrad von 0 %, das heißt, es zeigt einen totalen Katalysatorausfall an. Aufgrund des an der Mischpotentialelektrode 12 adsorbierten Sauerstoffs liegt zwischen Referenzelektrode 24 und Mischpotentialelektrode 12 ein geringer Potentialunterschied bei λ < 1 vor. Das von der Gleichgewichtselektrode 11 aufgenommene Meßsignal UG1 hat den Lairtbda-Sprung im Gleichgewichtszustand bei Lambda = 1. An der katalytisch aktiven Gleichgewichtselektrode 11 ist der Sauerstoffpartialdruck unabhängig vom Zustand des für die Nachverbrennung verwendeten Katalysators immer verschwindend klein. Der Sauerstoffpartialdruck entspricht hierbei dem thermodynamischen Gleichgewichtspartialdruck, weil das Elektrodenmaterial der Gleichgewichtselektrode 11 eine vollständige Umsetzung des Gasgemischs gewährleistet.Catalyst arranged sensor measured. With a sensor arranged upstream of the catalytic converter in the flow direction of the exhaust gas, the EMF of the mixed potential electrode 12 was recorded as the measurement signal U M1 '. The measurement signal U ^ i 'recorded upstream from the catalytic converter characterizes the characteristic curve of a catalytic converter with an efficiency of 0%, that is to say it indicates a total catalytic converter failure. Due to the oxygen adsorbed on the mixed potential electrode 12, there is a small potential difference at λ <1 between the reference electrode 24 and the mixed potential electrode 12. The measurement signal U G1 picked up by the equilibrium electrode 11 has the Lairtbda jump in the equilibrium state at lambda = 1. At the catalytically active equilibrium electrode 11, the oxygen partial pressure is always vanishingly small, regardless of the state of the catalyst used for the afterburning. The oxygen partial pressure corresponds to the thermodynamic equilibrium partial pressure, because the electrode material of the equilibrium electrode 11 ensures a complete conversion of the gas mixture.
Ist der Katalysator nicht mehr wirksam, so steigt der Sauerstoffpartialdruck im Abgas an. An der Dreiphasengrenze der Gleichgewichtselektrode 11 ändert sich dabei nahezu nichts. An der Mischpotentialelektrode 12 dagegen hängt der Sauerstoffpartialdruck von der katalytischen Aktivität des Katalysators ab. Ist der Katalysator voll wirksam, so ist der Sauerstoffpartialdruck auch an dieser Elektrode verhältnismäßig klein, so daß in diesem Fall die Kennlinie der Mischpotentialelektrode zumindest annähernd den Verlauf des Meßsignals UG1 der Gleichgewichtselektrode 11 annimmt.If the catalytic converter is no longer effective, the oxygen partial pressure in the exhaust gas increases. Almost nothing changes at the three-phase boundary of the equilibrium electrode 11. At the mixed potential electrode 12, however, the oxygen partial pressure depends on the catalytic activity of the catalyst. If the catalytic converter is fully effective, the oxygen partial pressure at this electrode is also relatively small, so that in this case the characteristic curve the mixed potential electrode at least approximately assumes the course of the measurement signal U G1 of the equilibrium electrode 11.
Bei nachlassender katalytischer Aktivität des Katalysators steigt der Sauerstoffpartialdruck im Abgas hinter dem Katalysator an, so daß an der Dreiphasengrenze der Mischpotentialelektrode 12 vom Typ A die Potentialdifferenz abnimmt. Die Kennlinie des Meßsignals U^i wird flacher. Die in Figur 6 gestrichelt gezeichnete Kennlinie entspricht dem Verlauf des Meßsignals U^i bei einem Wirkungsgrad des Katalysators von zum Beispiel 90 %.When the catalytic activity of the catalyst decreases, the oxygen partial pressure in the exhaust gas behind the catalyst rises, so that the potential difference decreases at the three-phase boundary of the mixed potential electrode 12 of type A. The characteristic of the measurement signal U ^ i becomes flatter. The characteristic curve shown in dashed lines in FIG. 6 corresponds to the course of the measurement signal U ^ i with an efficiency of the catalyst of, for example, 90%.
Die Kennlinien eines Sensors mit einer Mischpotentialelektrode 12 vom Typ B geht aus Figur 7 hervor. Für den Verlauf des Meßsignals UG2 derThe characteristics of a sensor with a mixed potential electrode 12 of type B can be seen in FIG. 7. For the course of the measurement signal U G2
Gleichgewichtselektrode 11 gilt hierbei das bereits in der Kurvendiskussion zu Figur 4 Gesagte. Das von einem in Strömungsrichtung des Abgases stromauf vor dem Katalysator angeordneten Sensor aufgenommene Meßsignal U .2 ' der Mischpotentialelektrode 12 hat hierbei einen Verlauf bei einem Potential, welches in etwa der Spannung einer Lambda- Sonde im fetten Abgas (λ < 1) entspricht. Dieser Verlauf nimmt mit höheren Lambda-Werten nur wenig ab, weil aufgrund der an der Mischpotentialelektrode 12 vorkommenden Konkurrenzreaktionen die relativ hohe Potentialdifferenz annähernd erhalten bleibt.Equilibrium electrode 11 applies here what has already been said in the curve discussion for FIG. The measurement signal U .2 'of the mixed potential electrode 12 picked up by a sensor arranged upstream of the catalytic converter in the flow direction of the exhaust gas has a profile at a potential which corresponds approximately to the voltage of a lambda probe in the rich exhaust gas (λ <1). This curve decreases only slightly with higher lambda values because the relatively high potential difference is approximately retained due to the competition reactions occurring at the mixed potential electrode 12.
Ist der Katalysator voll wirksam, ist der Sauerstoffpartialdruck auch an der Mischpotentialelektrode 12 stromab hinter dem Katalysator klein. Es wird also bei Verwendung einer Mischpotentialelektrode 12 vom Typ B bei einem voll wirksamen Katalysator ein Meßsignal der Mischpotentialelektrode 12 aufgenommen, welches in etwa dem Meßsignal U 2 der Gleichgewichtselektrode 11 entspricht. Bei abnehmender katalytischer Wirksamkeit des Katalysators steigt das Potential der Mischpotentialelektrode 12 im Bereich λ > 1 an. Die gestrichelte Kennlinie gibt das Meßsignal UM2 bei einem Wirkungsgrad des Katalysators von zum Beispiel 90 % an.If the catalytic converter is fully effective, the oxygen partial pressure is also low at the mixed potential electrode 12 downstream of the catalytic converter. Thus, when using a mixed potential electrode 12 of type B with a fully effective catalyst, a measurement signal of the mixed potential electrode 12 is recorded which corresponds approximately to the measurement signal U 2 of the equilibrium electrode 11. With decreasing catalytic effectiveness of the catalyst the potential of the mixed potential electrode 12 increases in the range λ> 1. The dashed curve indicates the measurement signal U M2 with an efficiency of the catalyst of, for example, 90%.
Die Meßsignale UG^ und U^i beziehungsweise UG2 und U^2 werden einer nicht dargestellten Auswerteschaltung zugeführt und dort miteinander verglichen. Anhand des Vergleichs der beiden Meßsignale wird auf den Wirkungsgrad des Katalysators geschlossen, wobei mit zunehmender Abweichung der Meßsignale voneinander der Wirkungsgrad abnimmt. The measurement signals U G ^ and U ^ i or U G2 and U ^ 2 are fed to an evaluation circuit, not shown, and compared there with one another. The efficiency of the catalytic converter is inferred from the comparison of the two measurement signals, the efficiency decreasing with increasing deviation of the measurement signals from one another.

Claims

Ansprüche Expectations
1. Sensor zur Bestimmung der Konzentration von Gaskomponenten in Gasgemischen mit einem sauerstoffionenleitenden Festelektrolyt, welcher eine die Gleichgewichtseinstellung des Gasgemisches katalysierende ersten Meßelektrode und eine die Gleichgewichtseinstellung des Gasgemisches nicht oder nur wenig katalysierende zweiten Meßelektrode aufweist, wobei die erste Meßelektrode und die zweite Meßelektrode dem Gasgemisch ausgesetzt sind, und mit einer Heizeinrichtung zur Temperierung der Meßelektroden, dadurch gekennzeichnet, daß die erste Meßelektrode (11) und die zweite Meßelektrode (12) in unterschiedlichen Temperaturbereichen des Festelektrolyten (10) angeordnet sind, derart, daß die katalytische Aktivität der Meßelektroden (11, 12) mittels der Temperatur einstellbar ist.1. Sensor for determining the concentration of gas components in gas mixtures with an oxygen-ion-conducting solid electrolyte, which has a first measuring electrode that catalyzes the equilibrium of the gas mixture and a second measuring electrode that does not or only slightly catalyzes the equilibrium of the gas mixture, the first measuring electrode and the second measuring electrode of the gas mixture are exposed, and with a heating device for tempering the measuring electrodes, characterized in that the first measuring electrode (11) and the second measuring electrode (12) are arranged in different temperature ranges of the solid electrolyte (10) in such a way that the catalytic activity of the measuring electrodes (11 , 12) is adjustable by means of the temperature.
2. Sensor nach Anspruch 1, dadurch gekennzeichnet, daß die2. Sensor according to claim 1, characterized in that the
Temperatur der Meßelektrode (12) derart einstellbar ist, daß eine gewünschte Mischpotentialwirkung an der Meßelektrode (12) ausbildbar ist.The temperature of the measuring electrode (12) can be adjusted such that a desired mixed potential effect can be formed on the measuring electrode (12).
3. Sensor nach Anspruch 1, dadurch gekennzeichnet, daß die Meßelektrode (11) sich in Bereichen mit einer höheren Temperatur befindet und daß die Meßelektrode (12) sich in Bereichen mit einer niedrigeren Temperatur befindet.3. Sensor according to claim 1, characterized in that the measuring electrode (11) is in areas with a higher temperature and that the measuring electrode (12) is in areas with a lower temperature.
4. Sensor nach Anspruch 1, dadurch gekennzeichnet, daß für die Meßelektrode (11) und die Meßelektrode (12) jeweils ein Heizelement (18, 19) vorgesehen ist, mit welchen jeweils unterschiedliche Heizleistungen realisierbar sind. 4. Sensor according to claim 1, characterized in that a heating element (18, 19) is provided for the measuring electrode (11) and the measuring electrode (12), with each of which different heating powers can be realized.
5. Sensor nach Anspruch 1, dadurch gekennzeichnet, daß die Meßelektrode (11) und die Meßelektrode (12) unter Ausnutzung des sich im Festelektrolyten (10) ausbildenden Temperaturgradienten in verschiedenen Temperaturbereichen des Festelektrolyten (10) angeordnet sind.5. Sensor according to claim 1, characterized in that the measuring electrode (11) and the measuring electrode (12) using the temperature gradient formed in the solid electrolyte (10) are arranged in different temperature ranges of the solid electrolyte (10).
6. Sensor nach Anspruch 1, dadurch gekennzeichnet, daß die Heizleiterbahn der Heizeinrichtung (16) eine Heizergeometrie derart aufweist, daß unterschiedliche differenzielle ' Heizleistungen entlang der Heizleiterbahn vorgesehen sind.6. Sensor according to claim 1, characterized in that the heating conductor track of the heating device (16) has a heater geometry such that different differential 'heating powers are provided along the heating conductor track.
7. Sensor nach Anspruch 1, dadurch gekennzeichnet, daß die erste Meßelektrode (11) Platin oder eine Platinlegierung mit Rhodium und/oder Palladium enthält.7. Sensor according to claim 1, characterized in that the first measuring electrode (11) contains platinum or a platinum alloy with rhodium and / or palladium.
8. Sensor nach Anspruch 1, dadurch gekennzeichnet, daß die zweite Meßelektrode (12) Gold und/oder Silber oder eine Platinlegierung mit Gold und/oder Silber enthält.8. Sensor according to claim 1, characterized in that the second measuring electrode (12) contains gold and / or silver or a platinum alloy with gold and / or silver.
9. Sensor nach Anspruch 1, dadurch gekennzeichnet, daß die zweite Meßelektrode (12) Platin und Wismut enthält.9. Sensor according to claim 1, characterized in that the second measuring electrode (12) contains platinum and bismuth.
10. Verwendung des Sensors nach einem der Ansprüche 1 bis 9 zur Überwachung der Funk ionsfähigkeit eines Katalysators in Abgasentgiftungsanlagen von Brennkraftmaschine, wobei der Sensor in der Abgasanlage in Strömungsrichtung des Abgases stromab vom Katalysator angeordnet ist. 10. Use of the sensor according to one of claims 1 to 9 for monitoring the func tionality of a catalyst in exhaust gas detoxification systems of internal combustion engines, the sensor being arranged downstream of the catalyst in the exhaust gas system in the flow direction of the exhaust gas.
EP95910421A 1994-03-14 1995-02-28 Sensor to determine the gas component concentration in gas mixtures Ceased EP0698208A1 (en)

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
DE4408504A DE4408504A1 (en) 1994-03-14 1994-03-14 Sensor for determining the concentration of gas components in gas mixtures
DE4408504 1994-03-14
PCT/DE1995/000255 WO1995025277A1 (en) 1994-03-14 1995-02-28 Sensor to determine the gas component concentration in gas mixtures

Publications (1)

Publication Number Publication Date
EP0698208A1 true EP0698208A1 (en) 1996-02-28

Family

ID=6512680

Family Applications (1)

Application Number Title Priority Date Filing Date
EP95910421A Ceased EP0698208A1 (en) 1994-03-14 1995-02-28 Sensor to determine the gas component concentration in gas mixtures

Country Status (6)

Country Link
EP (1) EP0698208A1 (en)
JP (1) JP3553073B2 (en)
CN (1) CN1124522A (en)
AU (1) AU1754295A (en)
DE (1) DE4408504A1 (en)
WO (1) WO1995025277A1 (en)

Families Citing this family (44)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE4437507C1 (en) * 1994-10-20 1995-11-30 Bosch Gmbh Robert Sensor element resistant to thermal shock, e.g. vehicle exhaust gas sensor
JP3481344B2 (en) * 1995-04-19 2003-12-22 日本碍子株式会社 Method for detecting deterioration of exhaust gas purifying catalyst and system therefor
DE19623434A1 (en) * 1996-06-12 1997-12-18 Bosch Gmbh Robert Sensor for determining the concentration of oxidizable components in a gas mixture
DE19636416B4 (en) * 1996-08-02 2007-04-26 Robert Bosch Gmbh Method and device for determining the sensitivity of a hydrocarbon sensor for an internal combustion engine
JP3802168B2 (en) * 1996-12-10 2006-07-26 日本碍子株式会社 Gas sensor and deterioration diagnosis method of exhaust gas purification apparatus using the same
DE69739309D1 (en) * 1996-12-29 2009-04-30 Ngk Spark Plug Co Exhaust gas sensor system
DE19731900A1 (en) * 1997-07-24 1999-02-11 Heraeus Electro Nite Int Conductive layer with variable electrical resistance, process for its manufacture and use
DE19815700B4 (en) * 1998-04-08 2004-01-29 Robert Bosch Gmbh Electrochemical sensor element with porous reference gas storage
JP2000028573A (en) * 1998-07-13 2000-01-28 Riken Corp Hydrocarbon gas sensor
DE19833087A1 (en) * 1998-07-23 2000-01-27 Bosch Gmbh Robert Gas sensor for vehicle engine; has measuring electrode comprising platinum base with sintered porous layer and noble metal covering layer, applied in galvanic bath
KR20010049489A (en) 1999-06-10 2001-06-15 오카무라 가네오 Device for Measuring Combustible-Gas Concentration and Method for Measuring Combustible-Gas Concentration by Use of the Same, and Device for Measuring Hydrocarbon-Gas Concentration and Method for Measuring Hydrocarbon-Gas Concentration by Use of the Same
DE19932048A1 (en) * 1999-07-09 2001-01-11 Bosch Gmbh Robert Sensor for determining a concentration of gas components in gas mixtures
DE19944181A1 (en) * 1999-09-15 2001-04-12 Bosch Gmbh Robert Sensor for determining the concentration of gas components in gas mixtures
US6849239B2 (en) 2000-10-16 2005-02-01 E. I. Du Pont De Nemours And Company Method and apparatus for analyzing mixtures of gases
BR0114823A (en) 2000-10-16 2004-02-25 Du Pont Apparatus and method for analyzing at least one individual gas component, apparatus and method for calculating the concentration of at least two individual gas components
EP1351762B1 (en) 2000-10-16 2006-11-29 E.I. Du Pont De Nemours And Company Infrared thermographic screening technique for semiconductor-based chemical sensors
DE10051833C2 (en) * 2000-10-19 2002-12-19 Bosch Gmbh Robert Planar gas sensor element
US20020100688A1 (en) * 2000-11-20 2002-08-01 Detwiler Eric J. Gas sensor with selective reference electrode and method of making and using the same
JP3801011B2 (en) * 2000-12-07 2006-07-26 株式会社デンソー Gas sensor element
FR2819314B1 (en) * 2001-01-08 2003-06-13 Alstom METHOD FOR THE NON-INTRUSIVE CONTROL OF A MIXTURE RATE OF A GAS MIXTURE WITH AT LEAST TWO COMPONENTS
DE10151328B4 (en) 2001-10-17 2005-05-04 Robert Bosch Gmbh Gas sensor
US7153412B2 (en) 2001-12-28 2006-12-26 Kabushiki Kaisha Toyota Chuo Kenkyusho Electrodes, electrochemical elements, gas sensors, and gas measurement methods
US20040126286A1 (en) 2002-06-19 2004-07-01 Deruyter John C. Method and apparatus for reducing a nitrogen oxide
DE10249466B4 (en) * 2002-10-24 2006-03-09 Robert Bosch Gmbh sensor element
DE10310953B4 (en) * 2003-03-13 2006-03-09 Robert Bosch Gmbh Unheated, planar sensor element for determining the concentration of a gas component in a gas mixture
US7228725B2 (en) * 2004-01-27 2007-06-12 H2Scan Llc Thin film gas sensor configuration
US7460958B2 (en) 2004-10-07 2008-12-02 E.I. Du Pont De Nemours And Company Computer-implemented system and method for analyzing mixtures of gases
US8236246B2 (en) 2004-10-07 2012-08-07 E I Du Pont De Nemours And Company Gas sensitive apparatus
US8075752B2 (en) * 2005-02-15 2011-12-13 Perkinelmer Health Sciences, Inc. Method and apparatus for providing an electrochemical sensor at an elevated temperature
JP4830525B2 (en) * 2005-04-14 2011-12-07 株式会社豊田中央研究所 Limit current type gas sensor and its use
US7611612B2 (en) * 2005-07-14 2009-11-03 Ceramatec, Inc. Multilayer ceramic NOx gas sensor device
DE102006062051A1 (en) * 2006-12-29 2008-07-03 Robert Bosch Gmbh Gas component measuring method for motor vehicle, involves fastening pump fixture in amperemetric measuring condition, such that pumping electricity is detected, and detecting voltage between electrodes in potentiometric measuring condition
CA2701942C (en) * 2007-10-09 2016-09-06 University Of Florida Research Foundation, Inc. Multifunctional potentiometric gas sensor array with an integrated temperature control and temperature sensors
DE102007059653A1 (en) * 2007-12-10 2009-06-18 Siemens Ag gas sensor
DE102013210903A1 (en) 2013-06-11 2014-12-11 Heraeus Sensor Technology Gmbh Gas sensor for measuring different gases and related manufacturing process
EP2884065B1 (en) * 2013-12-11 2019-09-11 Hirtenberger Holding GmbH Method for automated decontamination of a contaminated object and device for performing the method
DE102014214368A1 (en) * 2014-07-23 2016-01-28 Siemens Aktiengesellschaft Gas sensor for detecting NO and / or NO2 and operating method for such a gas sensor
DE102014214371A1 (en) * 2014-07-23 2016-01-28 Siemens Aktiengesellschaft Gas sensor for detection of NO and NO2 and operating method for the gas sensor
CN104374818A (en) * 2014-08-08 2015-02-25 杭州纳瑙新材料科技有限公司 Planar oxygen sensor
JP6406237B2 (en) * 2015-12-17 2018-10-17 株式会社デンソー Sensor element
CN106770581A (en) * 2016-11-29 2017-05-31 深圳万发创新进出口贸易有限公司 One kind is capable of identify that NO2The detection device of hazardous gas
WO2018135100A1 (en) * 2017-01-19 2018-07-26 Tdk株式会社 Gas sensor
JP6998802B2 (en) * 2018-03-12 2022-02-04 日本碍子株式会社 Gas sensor
JP6998801B2 (en) * 2018-03-12 2022-02-04 日本碍子株式会社 Gas sensor

Family Cites Families (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE2304464C2 (en) * 1973-01-31 1983-03-10 Robert Bosch Gmbh, 7000 Stuttgart Sensor for monitoring the functionality of catalytic converters in exhaust gas
US4005001A (en) * 1973-03-27 1977-01-25 Westinghouse Electric Corporation Combustibles sensor
JPS60259951A (en) * 1984-06-06 1985-12-23 Ngk Insulators Ltd Electrochemical element
DE4021929C2 (en) * 1990-07-10 1998-04-30 Abb Patent Gmbh sensor
EP0480076B1 (en) * 1990-09-13 1994-02-02 Honeywell B.V. Method and sensor for measuring oxygen partial pressure

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
See references of WO9525277A1 *

Also Published As

Publication number Publication date
AU1754295A (en) 1995-10-03
JP3553073B2 (en) 2004-08-11
CN1124522A (en) 1996-06-12
WO1995025277A1 (en) 1995-09-21
JPH08510840A (en) 1996-11-12
DE4408504A1 (en) 1995-09-21

Similar Documents

Publication Publication Date Title
EP0698208A1 (en) Sensor to determine the gas component concentration in gas mixtures
DE2517798C2 (en) Device for controlling a lean combustion mixture for an internal combustion engine of motor vehicles
DE4408361C2 (en) Electrochemical sensor for determining the oxygen concentration in gas mixtures
EP2220483B1 (en) Gas sensor
DE19861198B4 (en) Exhaust gas sensor and test method
DE2907106A1 (en) CATALYST FOR PURIFYING THE EXHAUST GAS FROM COMBUSTION ENGINES
EP0801740B1 (en) Electrochemical measuring probe and process for its production
DE3813930A1 (en) ELECTRODE STRUCTURE OF AN OXYGEN MEASUREMENT ELEMENT
DE2937802A1 (en) IMPROVED PROBE FOR MEASURING THE OXYGEN CONTENT IN THE EXHAUST GAS FROM COMBUSTION ENGINES
DE19623212A1 (en) Sensor for determining the concentration of oxidizable components in a gas mixture
EP1110079B1 (en) Electrochemical gas sensor and method for determining gas components
DE19702570C2 (en) Limit current type oxygen sensor
EP0843813A1 (en) Sensor for determining the concentration of oxidisable elements in a gas compound
DE19963008B4 (en) Sensor element of a gas sensor for the determination of gas components
EP0781993A1 (en) Gas sensor
WO2008080730A1 (en) Sensor element with additional diagnosis function
EP1196681B1 (en) Method for controlling a rich/lean combustion mixture in a defined manner
DE112016000301B4 (en) NOx sensor
DE19745328C2 (en) Structure for NO¶x¶ sensors
EP1112491A1 (en) Measuring sensor for the determination of a concentration of gas constituents in gaseous mixtures
DE2817873C2 (en) Sensor for detecting certain components of exhaust gases from a combustion device
DE10023062B4 (en) Measuring device for determining the concentration of gas components in the exhaust gas of an internal combustion engine and method for controlling an operation of the measuring device
EP1217361A2 (en) Multi-stage gas sensor, operating and manufacturing method
DE19818474A1 (en) Gas sensor and use
DE10040505A1 (en) Gas sensor, especially Lambada probe

Legal Events

Date Code Title Description
PUAI Public reference made under article 153(3) epc to a published international application that has entered the european phase

Free format text: ORIGINAL CODE: 0009012

AK Designated contracting states

Kind code of ref document: A1

Designated state(s): DE FR GB IT SE

17P Request for examination filed

Effective date: 19960321

17Q First examination report despatched

Effective date: 20011210

APBT Appeal procedure closed

Free format text: ORIGINAL CODE: EPIDOSNNOA9E

STAA Information on the status of an ep patent application or granted ep patent

Free format text: STATUS: THE APPLICATION HAS BEEN REFUSED

18R Application refused

Effective date: 20050211

APAF Appeal reference modified

Free format text: ORIGINAL CODE: EPIDOSCREFNE