EP0938667A1 - Gas sensor - Google Patents

Gas sensor

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Publication number
EP0938667A1
EP0938667A1 EP98950029A EP98950029A EP0938667A1 EP 0938667 A1 EP0938667 A1 EP 0938667A1 EP 98950029 A EP98950029 A EP 98950029A EP 98950029 A EP98950029 A EP 98950029A EP 0938667 A1 EP0938667 A1 EP 0938667A1
Authority
EP
European Patent Office
Prior art keywords
measuring
gas
electrodes
oxygen
gas sensor
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.)
Withdrawn
Application number
EP98950029A
Other languages
German (de)
French (fr)
Inventor
Susanne Brosda
Ulrich Guth
Silvia Lenaerts
Götz REINHARDT
Ulrich SCHÖNAUER
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.)
Heraeus Electro Nite International NV
Original Assignee
Heraeus Electro Nite International NV
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
Priority claimed from DE19757112A external-priority patent/DE19757112C2/en
Application filed by Heraeus Electro Nite International NV filed Critical Heraeus Electro Nite International NV
Publication of EP0938667A1 publication Critical patent/EP0938667A1/en
Withdrawn legal-status Critical Current

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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

Definitions

  • the invention relates to a gas sensor according to claims 1 and 2 as well as its use and a measuring method.
  • a generic gas sensor is known for example from DE 195 34 918 A1.
  • two electrodes are arranged with an interdigitated comb structure (see FIG. 1), opposite them, on the reference air side there is a reference electrode.
  • This invention focuses on reliable sealing, so that no information is given on the functions and advantages of the two electrodes (sensor contacts) on the measuring gas side of the solid electrolyte.
  • the design enables voltammetric measurement of two gas components in a gas mixture.
  • a generic gas sensor is known from DE 36 10 366 A1, in which several electrochemical measuring cells are arranged on a tubular support. Only gaseous pollutants can be measured there (not oxygen). The measurement signals are evaluated by calculating the characteristic curves of the pollutant concentrations.
  • Such a gas sensor is also known from DE 41 09 516 C2.
  • the solid electrolyte is in the form of a plate on which an electrode serving as a reference is applied on one side and at least two measuring electrodes are applied to the opposite side, which interact with different constituents in a gas mixture.
  • the plate-shaped sensor is installed in a housing in order to then be installed as a gas probe in the exhaust line of motor vehicles, perpendicular to the flow direction of the exhaust gas.
  • This probe works without a reference gas, which requires an electrode potential that is independent of the environment.
  • electrodes of this type are not stable with regard to their electrochemical potential, in particular when changing from lean to rich mixture compositions.
  • the realization of a stable and homogeneous temperature distribution on the entire surface is very difficult.
  • a similar, relatively complicated sensor is also known from DE 42 43 734 A1.
  • the invention has for its object to provide a gas sensor with which at least two gaseous components can be reliably detected simultaneously over a wide range of the gas mixture composition and which also ensures a stable reference signal with the aid of ambient air, which additionally and if necessary influences the oxygen content made possible by supplying or removing oxygen to the respective measuring electrodes.
  • the solid electrolyte generally a solid electrolyte body with almost any geometric shape, is designed as a tube closed on one side, on which a reference electrode is arranged on its inner wall, as close as possible to the closed end, and a plurality of electrodes are arranged on its outside, facing the measurement gas.
  • the solid electrolyte consists, for example, of partially or fully stabilized ZrO 2 or CeO 2 .
  • the arrangement of the at least two independent measuring electrodes on the solid electrolyte ensures the simultaneous detection of at least two measuring signals which correspond to at least two different gas components.
  • the heating element can also be applied in the form of a heating conductor on the outside of the solid electrolyte, but in order to To avoid shunts, an electrically insulating layer is arranged between the heating conductor and the solid electrolyte.
  • At least one of the electrodes as a measuring electrode on the outside of the solid electrolyte tube closed on one side consists of a catalytically active material, different measuring electrodes can have different catalytically active materials, and is therefore particularly suitable for potentiometric oxygen measurement according to the principle of a Nemst probe.
  • the second measuring electrode consists of a catalytically inactive material. Hydrocarbons are preferably detected at these electrodes.
  • the surfaces of the measuring electrodes facing the measuring gas are covered with a preferably porous diffusion layer, which can be made of aluminum oxide, spinel or magnesium oxide, for example, and which can have a different layer thickness on the measuring electrodes in order to specifically target the residence time of the oxygen in them to be able to influence.
  • a porous diffusion layer which can be made of aluminum oxide, spinel or magnesium oxide, for example, and which can have a different layer thickness on the measuring electrodes in order to specifically target the residence time of the oxygen in them to be able to influence.
  • the reference electrode assigned to each other and spaced apart from one another can be divided into partial reference electrodes spaced apart from one another.
  • a gas-symmetrical differential measurement can be carried out between two measuring electrodes, the selectivity to hydrocarbons being improved, for example, by the choice of the oxygen pressure on these electrodes.
  • cross influences arising from changing lambda are avoided.
  • the catalytically inactive metal oxides include, for example, mixed-conducting, perovskite compounds of the general formula Ln ⁇ -A ⁇ B, ⁇ , where Ln is a lanthanide cation, A is an element from the group Mn, Cr, Co, Fe, Ti or Ni (in particular Cr or Ti) and B is an element from the group Ga, Al, Sc, Mg or Ca.
  • the gas sensor according to the invention is therefore particularly suitable for use in the simultaneous measurement of oxygen or lambda and hydrocarbons or carbon monoxide in a gas mixture.
  • the measurement of oxygen is preferably carried out on the catalytically active measuring electrode, the potential arising depending on the oxygen concentration in the measuring gas being measured against the air reference electrode.
  • This measuring electrode equilibrates the measuring gas and the voltage determined on it gives a signal corresponding to the known lambda probes.
  • a voltage can also be determined against the (air) reference, which depends on the concentration of unburned constituents, i.e. is determined by the concentration of hydrocarbons or carbon monoxide in the exhaust gas.
  • oxygen is pumped from the reference gas side to the measuring gas side, an excess of oxygen being formed on the measuring gas side and a difference signal being measured between two different measuring electrodes.
  • FIG. 1 shows a family of characteristics of the measurement signals of the gas sensor from FIG. 3 in the case of a propane / oxygen / measurement gas mixture
  • Figure 2 shows a section through a tubular gas sensor for amperometric oxygen and potentiometric hydrocarbon determination
  • FIG. 3 shows a section through another possible tubular gas sensor for determining oxygen and hydrocarbons
  • Figure 4 shows a section through a tubular gas sensor for potentiometric oxygen and amperometric oxygen and hydrocarbon determination.
  • FIG. 1 shows an example of a family of curves of measurement signals determined using a gas sensor.
  • the sensor voltage is plotted in millivolts compared to the Propane gas concentration in volume%. Air is used as the reference gas.
  • Curve 1 shows the measurement signal of the catalytically active platinum electrode.
  • Curve 2 the measurement signal of the catalytically inactive electrode (for example gold) and curve 3 the difference signal between the two electrodes in a gas-symmetrical arrangement.
  • FIG. 2 shows a cross section through a sensor according to the invention.
  • a catalytically active electrode 2 ′′ is arranged on a tubular solid electrolyte 1 made of ZrO 2 , opposite the reference electrode 9 ′ in the reference air channel 4.
  • an insulating layer 8 made of Al 2 O 3 is arranged on the outside of the ZrO 2 tube 1 one heating element 5 is arranged symmetrically for faster heating of this gas sensor.
  • two differently catalytically active measuring electrodes 2, 2a made of platinum or a platinum alloy, which are assigned to the reference electrode 9, are applied to the solid electrolyte 1.
  • the two measuring electrodes 2, 2a are in turn covered by a protective layer or a porous diffusion layer 11 made of aluminum oxide.
  • the gas sensor allows, in an oxygen excess, which is created by applying a voltage U P1 between the electrodes 9 and 2a or Up 2 between the electrodes 9 and 2 and thereby pumping oxygen into the measuring gas space, gas symmetrically and potentiometrically on two outer Electrodes 2.2a to determine the hydrocarbon concentration or carbon monoxide concentration.
  • the electrode pairs 9.2 and 9.2a can be optimally matched to one another.
  • the high sensitivity achieved in this way can be specifically influenced by the heating elements 5 separately assigned to the electrodes 2, 2 a. If the reference electrode 9 is formed separately as two partial reference electrodes, the sensitivity can be increased further.
  • the solid electrolyte tube 1 is, for example, held in a housing in a manner well known to a person skilled in the art from the prior art, it being possible for the individual layers and electrodes to be electrically contacted in a likewise known manner, for example at one end of the solid electrolyte tube 1.
  • hydrocarbon gas-symmetrically is measured as the difference signal U_, while the voltage U-is measured as an oxygen signal against reference between the electrodes 9 'and 2 ".
  • FIG. 3 also shows a section through a tubular solid electrolyte 1 made of ZrO 2 .
  • a catalytically inactive electrode 3 made of perovskite material and catalytically active electrodes 2, 2a made of platinum or a platinum alloy are attached to the outside. The latter will be covered by a porous diffusion layer 11 made of A ⁇ O 3 .
  • This porous diffusion layer can have a different thickness over the two electrodes 2, 2 a.
  • a reference electrode 9, 9 'or counter electrode 9' is arranged in the interior of the tube 1.
  • the gas sensor is provided with a heating element 5.
  • the oxygen is determined amperometrically by means of a pump current between the measuring electrode 2 and the reference electrode 9, which acts here as a counter electrode.
  • the hydrocarbon is determined potentiometrically by measuring the voltage U 3 at the electrodes 9 'and 3 or by measuring the difference U 2 between the electrodes 2 and 2a.
  • FIG. 4 shows a sensor structure similar to that in FIG. 2, but additional measuring electrodes 2 ', 2a' are additionally arranged above the diffusion layer 11.
  • the diffusion layer is also designed here as a solid electrolyte, so that an amperometric measurement by means of pump currents can take place between the measuring electrodes 2 and 9 or 2a and 9.
  • the hydrocarbon is determined as a difference measurement U 2 between the electrodes 2 'and 2a'.
  • the oxygen signal (potentiometric lambda determination) U- is measured between the electrodes 9 'and 2 ".
  • the two outer electrodes 2' and 2a ' are covered with a porous, oxygen ion-conducting material 13, which is also in the space between these two electrodes 2'"2a. At least laterally, down to the insulating layer 8, the material 13 is covered by a gas-tight seal 14 in order to rule out leakages of the measuring gas or oxygen.

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

Abstract

The invention relates to a gas sensor for measuring oxygen and/or the air/fuel lambda ratio and the hydrocarbon and/or the carbon monoxide in gas mixtures. The aim of the invention is to provide a sensor which can measure several gaseous constituents reliably. To this end, the inventive sensor is provided with a reference electrode representing a constant oxygen partial pressure, a solid electrolyte which conducts oxygen ions, and at least two measuring electrodes. The measuring electrodes and the reference electrode are located directly on the solid electrolyte. The sensor is also provided with electrical lines for the purposes of connection and picking off, for the electrical measuring signals. The solid electrolyte (1) is configured with one side facing the gas being measured and with one reference gas side separate from the gas being measured. The arrangement of the electrodes with the reference electrode (9; 9') on the reference gas side and the at least two measuring electrodes (2; 2'; 2"; 3) on the measured gas side is such that at least one measuring electrode (2) is allocated to one of the reference electrodes (9), said measuring electrode forming the anode of this electrode pair (2, 9), and the electrode pair (2, 9) being configured for applying a voltage or a current for pumping oxygen. The arrangement delivers at least two measuring signals representing different gaseous constituents at the same time.

Description

Gas-Sensor Gas sensor
Die Erfindung betrifft einen Gassensor gemäß Anspruch 1 und 2 sowie seine Verwendung und ein Meßverfahren.The invention relates to a gas sensor according to claims 1 and 2 as well as its use and a measuring method.
Ein gattungsgemäßer Gassensor ist beispielsweise aus DE 195 34 918 A1 bekannt. Hierbei sind auf der dem Meßgas zugewandten Seite des Festelektrolyten zwei Elektroden mit einer ineinander greifenden Kammstruktur (siehe Fig.1) angeordnet, ihnen gegenüber, auf der Refe- renzluftseite befindet sich eine Referenzelektrode. Diese Erfindung ist schwerpunktmäßig auf eine zuverlässige Abdichtung gerichtet, so daß zu den Funktionsweisen und Vorteilen der zwei Elektroden (Sensorkontakte) auf der Meßgasseite des Festelektrolyten keine Angaben gemacht werden. Die Bauweise ermöglicht eine voltammetrische Messung zweier Gaskomponenten in einem Gasgemisch.A generic gas sensor is known for example from DE 195 34 918 A1. Here, on the side of the solid electrolyte facing the measuring gas, two electrodes are arranged with an interdigitated comb structure (see FIG. 1), opposite them, on the reference air side there is a reference electrode. This invention focuses on reliable sealing, so that no information is given on the functions and advantages of the two electrodes (sensor contacts) on the measuring gas side of the solid electrolyte. The design enables voltammetric measurement of two gas components in a gas mixture.
Außerdem ist ein gattungsgemäßer Gassensor aus DE 36 10 366 A1 bekannt, bei dem mehrere elektrochemische Meßzellen auf einem rohrförmigen Träger angeordnet sind. Dort können nur gasförmige Schadstoffe gemessen werden (nicht Sauerstoff). Die Auswertung der Meßsignale erfolgt über das Verrechnen der Kennlinien der Schadstoffkonzentrationen.In addition, a generic gas sensor is known from DE 36 10 366 A1, in which several electrochemical measuring cells are arranged on a tubular support. Only gaseous pollutants can be measured there (not oxygen). The measurement signals are evaluated by calculating the characteristic curves of the pollutant concentrations.
Weiterhin ist ein derartiger Gassensor aus DE 41 09 516 C2 bekannt. Der Festelektrolyt ist hierbei in Form eines Plättchens ausgebildet, auf dem auf einer Seite eine als Referenz dienende Elektrode und auf der gegenüberliegenden Seite mindestens zwei Meßelektroden aufgebracht sind, die mit verschiedenen Bestandteilen in einem Gasgemisch wechselwirken. Der plättchen- förmige Sensor wird in ein Gehäuse eingebaut um dann als Gassonde in den Abgasstrang von Kraftfahrzeugen installiert zu werden, und zwar senkrecht zur Strömungsrichtung des Abgases. Diese Sonde arbeitet ohne ein Referenzgas, was ein von der Umgebung unabhängiges Elektrodenpotential voraussetzt. Derartige Elektroden sind jedoch bezüglich ihres elektrochemischen Potentials, insbesondere beim Übergang von mageren zu fettem Gemischzusammensetzungen nicht stabil. Außerdem ist bei nicht rotationssymmetrischen Ausgestaltungen des Sensoraufbaus die Realisierung einer stabilen und an der gesamten Oberfläche homogenen Temperaturverteilung sehr schwierig. Auch aus DE 42 43 734 A1 ist ein ähnlicher, relativ komplizierter Sensor bekannt.Such a gas sensor is also known from DE 41 09 516 C2. The solid electrolyte is in the form of a plate on which an electrode serving as a reference is applied on one side and at least two measuring electrodes are applied to the opposite side, which interact with different constituents in a gas mixture. The plate-shaped sensor is installed in a housing in order to then be installed as a gas probe in the exhaust line of motor vehicles, perpendicular to the flow direction of the exhaust gas. This probe works without a reference gas, which requires an electrode potential that is independent of the environment. However, electrodes of this type are not stable with regard to their electrochemical potential, in particular when changing from lean to rich mixture compositions. In addition, in the case of non-rotationally symmetrical configurations of the sensor structure, the realization of a stable and homogeneous temperature distribution on the entire surface is very difficult. A similar, relatively complicated sensor is also known from DE 42 43 734 A1.
Demgegenüber liegt der Erfindung die Aufgabe zugrunde, einen Gassensor anzugeben, mit dem über einen weiten Bereich der Gasgemischzusammensetzung gleichzeitig mindestens zwei gasförmige Bestandteile zuverlässig detektiert werden können und der zudem ein stabiles Referenzsignal mit Hilfe von Umgebungsluft gewährleistet, das ergänzend und falls erforderlich die Beeinflussung des Sauerstoffgehaltes durch Zu- oder Abführung von Sauerstoff an den jeweiligen Meßelektroden ermöglicht.In contrast, the invention has for its object to provide a gas sensor with which at least two gaseous components can be reliably detected simultaneously over a wide range of the gas mixture composition and which also ensures a stable reference signal with the aid of ambient air, which additionally and if necessary influences the oxygen content made possible by supplying or removing oxygen to the respective measuring electrodes.
Diese Aufgabe wird erfindungsgemäß durch die Merkmale der Ansprüche 1 , 2 und 18 gelöst. Vorteilhafte Weiterbildungen der Erfindung sowie die Verwendung des erfindungsgemäßen Gassensors sind in den weiteren Ansprüchen ausgeführt.This object is achieved by the features of claims 1, 2 and 18. Advantageous developments of the invention and the use of the gas sensor according to the invention are set out in the further claims.
Vorteilhafterweise ist der Festelektrolyt, im allgemeinen ein Festelektrolytkörper mit nahezu beliebiger geometrischer Form, als einseitig geschlossenes Röhrchen ausgebildet, auf dem an seiner Innenwand, möglichst nahe am geschlossenen Ende, eine Referenzelektrode und an seiner Außenseite, dem Meßgas zugewandt, mehrere Elektroden angeordnet sind. Der Festelektrolyt besteht beispielsweise aus teil- oder vollstabilisierten ZrO2oder aus CeO2. Die Anordnung der mindestens zwei unabhängigen Meßelektroden auf dem Festelektrolyten gewährleistet die gleichzeitige Erfassung von mindestens zwei Meßsignalen, die mindestens zwei unterschiedlichen Gasbestandteilen entsprechen. Dadurch, daß ein rohrförmiger Festelektrolyt mit kreisrundem Querschnitt eingesetzt wird, werden die Störungen bei einer Einbaulage senkrecht zum Abgasstrom minimiert, so daß der Sensor relativ gleichmäßig vom Meßgas umspült wird. Die zu messenden Gaskomponenten gelangen auf diese Art praktisch ohne Verzögerung an die Meßelektroden, störende Turbulenzen werden vermieden.Advantageously, the solid electrolyte, generally a solid electrolyte body with almost any geometric shape, is designed as a tube closed on one side, on which a reference electrode is arranged on its inner wall, as close as possible to the closed end, and a plurality of electrodes are arranged on its outside, facing the measurement gas. The solid electrolyte consists, for example, of partially or fully stabilized ZrO 2 or CeO 2 . The arrangement of the at least two independent measuring electrodes on the solid electrolyte ensures the simultaneous detection of at least two measuring signals which correspond to at least two different gas components. Due to the fact that a tubular solid electrolyte with a circular cross section is used, the interference in an installation position perpendicular to the exhaust gas flow is minimized, so that the sensor is flushed relatively evenly by the measurement gas. In this way, the gas components to be measured reach the measuring electrodes practically without delay, and disturbing turbulence is avoided.
Wird der Gassensor bei Temperaturen unterhalb 400°C betrieben, so ist es vorteilhaft ein Heizelement für den Sensor vorzusehen. Das Heizelement kann dafür in Form eines Heizleiters ebenfalls auf der Außenseite des Festelektrolyten aufgebracht sein, wobei jedoch, um Nebenschlüsse zu vermeiden, zwischen Heizleiter und Festelektrolyt eine elektrisch isolierende Schicht angeordnet ist.If the gas sensor is operated at temperatures below 400 ° C, it is advantageous to provide a heating element for the sensor. For this purpose, the heating element can also be applied in the form of a heating conductor on the outside of the solid electrolyte, but in order to To avoid shunts, an electrically insulating layer is arranged between the heating conductor and the solid electrolyte.
Zweckmäßigerweise besteht mindestens eine der Elektroden als Meßelektrode auf der Außenseite des einseitig geschlossenen Festelektrolytrohres aus einem katalytisch aktiven Material, wobei unterschiedliche Meßelektroden unterschiedliche katalytisch aktive Materialien aufweisen können, und ist damit insbesondere für die potentiometrische Sauerstoffmessung nach dem Prinzip einer Nemst-Sonde geeignet. Die zweite Meßelektrode besteht dagegen aus einem katalytisch inaktiven Material. An diesen Elektroden werden vorzugsweise Kohlenwasserstoffe detektiert.Advantageously, at least one of the electrodes as a measuring electrode on the outside of the solid electrolyte tube closed on one side consists of a catalytically active material, different measuring electrodes can have different catalytically active materials, and is therefore particularly suitable for potentiometric oxygen measurement according to the principle of a Nemst probe. In contrast, the second measuring electrode consists of a catalytically inactive material. Hydrocarbons are preferably detected at these electrodes.
Es ist vorteilhaft, daß die dem Meßgas zugewandten Oberflächen der Meßelektroden mit einer vorzugsweise porösen Diffusionsschicht bedeckt sind, die beispielsweise aus Aiuminiumoxid, Spinell oder Magnesiumoxid sein kann und die auf den Meßelektroden jeweils eine unterschiedliche Schichtdicke aufweisen kann, um die Verweilzeit des Sauerstoffs in ihnen gezielt beeinflussen zu können.It is advantageous that the surfaces of the measuring electrodes facing the measuring gas are covered with a preferably porous diffusion layer, which can be made of aluminum oxide, spinel or magnesium oxide, for example, and which can have a different layer thickness on the measuring electrodes in order to specifically target the residence time of the oxygen in them to be able to influence.
Die zueinander beabstandeten Meßelektroden zugeordnete Referenzelektrode kann in zueinander beabstandete Teilreferenzelektroden aufgeteilt werden.The reference electrode assigned to each other and spaced apart from one another can be divided into partial reference electrodes spaced apart from one another.
Bei Verwendung unterschiedlicher katalytisch aktiver Elektrodenmaterialien an benachbarten, der gleichen Referenzelektrode zugeordneten Meßelektroden kann eine gassymmetrische Differenzmessung zwischen zwei Meßelektroden erfolgen.wobei sich durch beispielsweise die Wahl des Sauerstoffdrucks an diesen Elektroden die Selektivität gegenüber Kohlenwasserstoffen verbessern läßt. Gleichzeitig werden durch wechselndes Lambda entstehende Quereinflüsse vermieden. Durch die Schaltung einer Meßelektrode als Anode gegenüber der ihr zugeordneten Referenzelektrode kann durch Anlegen einer Spannung oder eines Stromes gezielt Sauerstoff von der Referenzgasseite zur Meßgasseite gepumpt werden.If different catalytically active electrode materials are used on adjacent measuring electrodes assigned to the same reference electrode, a gas-symmetrical differential measurement can be carried out between two measuring electrodes, the selectivity to hydrocarbons being improved, for example, by the choice of the oxygen pressure on these electrodes. At the same time, cross influences arising from changing lambda are avoided. By connecting a measuring electrode as an anode to the reference electrode assigned to it, oxygen can be pumped from the reference gas side to the measuring gas side in a targeted manner by applying a voltage or a current.
Als katalytisch aktive Materialien haben sich Platin oder Platinlegierungen bewährt. Weiterhin sind auch Rhodium oder Palladium als katalytisch aktive Elektroden Materialien geeignet. Unter den katalytisch inaktiven Materialien, die für die zweite Meßelektrode eingesetzt werden sollen, haben sich Gold und Goldlegierungen, sowie Metalloxide bewährt. Zu den katalytisch inaktiven Metalloxiden zählen beispielsweise gemischtleitende, perowskitische Verbindungen der allgemeinen Formel Ln^-A^B,^ , wobei Ln ein Lanthanoidkation ist, A ein Element der Gruppe Mn, Cr, Co, Fe, Ti oder Ni (insbesondere Cr oder Ti) und B ein Element der Gruppe Ga, AI, Sc, Mg oder Ca ist.Platinum or platinum alloys have proven themselves as catalytically active materials. Rhodium or palladium are also suitable as catalytically active electrode materials. Gold and gold alloys as well as metal oxides have proven themselves among the catalytically inactive materials that are to be used for the second measuring electrode. The catalytically inactive metal oxides include, for example, mixed-conducting, perovskite compounds of the general formula Ln ^ -A ^ B, ^, where Ln is a lanthanide cation, A is an element from the group Mn, Cr, Co, Fe, Ti or Ni (in particular Cr or Ti) and B is an element from the group Ga, Al, Sc, Mg or Ca.
Durch die unterschiedliche Zusammensetzung der Meßelektroden vermag man unterschiedliche Gasbestandteile an den Elektroden zur Wechselwirkung zu bringen. Der erfindungsgemäße Gassensor ist daher besonders geeignet, bei der Simuitanmessung von Sauerstoff bzw. Lambda und Kohlenwasserstoffen oder Kohlenmonoxid in einem Gasgemisch Verwendung zu finden.Due to the different composition of the measuring electrodes, different gas components on the electrodes can interact. The gas sensor according to the invention is therefore particularly suitable for use in the simultaneous measurement of oxygen or lambda and hydrocarbons or carbon monoxide in a gas mixture.
Die Messung von Sauerstoff erfolgt vorzugsweise an der katalytisch aktiven Meßelektrode, wobei das je nach Sauerstoffkonzentration im Meßgas sich einstellende Potential gegen die Luft- Referenzelektrode gemessen wird. Diese Meßelektrode setzt das Meßgas ins Gleichgewicht und die an ihr ermittelte Spannung gibt ein Signal entsprechend dem bekannter Lambda- Sonden.The measurement of oxygen is preferably carried out on the catalytically active measuring electrode, the potential arising depending on the oxygen concentration in the measuring gas being measured against the air reference electrode. This measuring electrode equilibrates the measuring gas and the voltage determined on it gives a signal corresponding to the known lambda probes.
An den Meßelektroden, die vorzugsweise aus katalytisch inaktiven Material bestehen, wie etwa einem gemischtleitenden Metalloxid (Mischoxid), kann ebenfalls gegen die (Luft-)Referenz eine Spannung ermittelt werden, die von der Konzentration unverbrannter Bestandteile, d.h. von der Konzentration der Kohlenwasserstoffe oder des Kohlenmonoxids im Abgas bestimmt wird.At the measuring electrodes, which preferably consist of catalytically inactive material, such as a mixed conducting metal oxide (mixed oxide), a voltage can also be determined against the (air) reference, which depends on the concentration of unburned constituents, i.e. is determined by the concentration of hydrocarbons or carbon monoxide in the exhaust gas.
Nach dem erfindungsgemäßen Verfahren wird von der Referenzgasseite zur Meßgasseite Sauerstoff gepumpt, wobei auf der Meßgasseite ein Sauerstoffüberschuß gebildet wird und wobei ein Differenzsignal zwischen zwei unterschiedlichen Meßelektroden gemessen wird.According to the method of the invention, oxygen is pumped from the reference gas side to the measuring gas side, an excess of oxygen being formed on the measuring gas side and a difference signal being measured between two different measuring electrodes.
Ausführungsbeispiele werden im folgenden anhand der Zeichnungen erläutert. Dabei zeigtExemplary embodiments are explained below with reference to the drawings. It shows
Figur 1 eine Kennlinienschar der Meßsignale des Gassensors aus Figur 3 bei einem Pro- pan/ Sauerstoff-Meßgasgemisch;FIG. 1 shows a family of characteristics of the measurement signals of the gas sensor from FIG. 3 in the case of a propane / oxygen / measurement gas mixture;
Figur 2 einen Schnitt durch einen rohrförmigen Gassensor zur amperometrischen Sauerstoff- und potentiometrischen Kohlenwasserstoffbestimmung;Figure 2 shows a section through a tubular gas sensor for amperometric oxygen and potentiometric hydrocarbon determination;
Figur 3 einen Schnitt durch einen weiteren möglichen rohrförmigen Gassensor zur Sauerstoff- und Kohlenwasserstoffbestimmung;FIG. 3 shows a section through another possible tubular gas sensor for determining oxygen and hydrocarbons;
Figur 4 einen Schnitt durch einen rohrförmigen Gassensor zur potentiometrischen Sauerstoff- und amperometrischen Sauerstoff- und Kohlenwasserstoffbestimmung.Figure 4 shows a section through a tubular gas sensor for potentiometric oxygen and amperometric oxygen and hydrocarbon determination.
Figur 1 zeigt exemplarisch eine mit Hilfe eines Gassensors ermittelte Kurvenschar von Meßsignalen. Aufgetragen ist die Sensor-Spannung in Millivolt gegenüber der Propangaskonzentration in Volumen- %. Als Referenzgas dient Luft. Kurve 1 zeigt das Meßsignal der katalytisch aktiven Platin-Elektrode. Kurve 2 das Meßsignal der katalytisch inaktiven Elektrode (beispielsweise Gold) und Kurve 3 das Differenzsignal zwischen beiden Elektroden in gassymmetrischer Anordnung.FIG. 1 shows an example of a family of curves of measurement signals determined using a gas sensor. The sensor voltage is plotted in millivolts compared to the Propane gas concentration in volume%. Air is used as the reference gas. Curve 1 shows the measurement signal of the catalytically active platinum electrode. Curve 2 the measurement signal of the catalytically inactive electrode (for example gold) and curve 3 the difference signal between the two electrodes in a gas-symmetrical arrangement.
In Figur 2 ist ein Querschnitt durch einen erfindungsgemäßen Sensor dargestellt. Auf einem rohrförmigen Festelektrolyten 1 aus ZrO2ist eine katalytisch aktive Elektrode 2" angeordnet, ihr gegenüber, im Referenzluftkanal 4 die Referenzelektrode 9'. Weiterhin ist auf der Außenseite des ZrO2-Röhrchen 1 eine Isolierschicht 8 aus AI2O3 angeordnet, auf der ein Heizelement 5 zur schnelleren Aufheizung dieses Gassensors symmetrisch angeordnet ist. Gegenüber der Meßelektrode 2" sind auf dem Festelektrolyten 1 zwei unterschiedlich katalytisch aktive Meßelektroden 2, 2a aus Platin beziehungsweise einer Platinlegierung aufgebracht, die der Referenzelektrode 9 zugeordnet sind. Die beiden Meßelektroden 2, 2a werden ihrerseits von einer Schutzschicht beziehungsweise einer porösen Diffusionsschicht 11 aus Aluminiumoxid überdeckt. Zwischen den Meßelektroden 2 und 2a ist als isolierendes Material 12 Aluminiumoxid angeordnet. Dieser Aufbau des Gassensors erlaubt es, in einem Sauerstoffüberschuß, der durch Anlegen einer Spannung UP1 zwischen den Elektroden 9 und 2a oder Up2 zwischen den Elektroden 9 und 2 und dadurch erzeugtes Pumpen von Sauerstoff in den Meßgasraum entsteht, gassymmetrisch und potentiometrisch an zwei äußeren Elektroden 2,2a die Kohlenwasserstoff-Konzentration oder Kohlenmonoxid-Konzentration zu bestimmen. Dabei können die Elektrodenpaare 9,2 und 9,2a optimal aufeinander abgestimmt werden. Die dadurch erzielte hohe Sensitivität läßt sich durch den Elektroden 2,2a separat zugeordnete Heizelemente 5 gezielt beeinflussen. Im Falle einer getrennten Ausbildung der Referenzelektrode 9 als zwei Teilreferenzelektroden läßt sich die Sensivität weiter steigern. Das Festelektrolytrohr 1 ist beispielsweise in einer dem Fachmann aus dem Stand der Technik hinreichend bekannten Weise in einem Gehäuse gehaltert, wobei die einzelnen Schichten und Elektroden in ebenfalls bekannter Weise, beispielsweise an einem Ende des Festelektrolytrohrs 1 , elektrisch kontaktiert werden können.FIG. 2 shows a cross section through a sensor according to the invention. A catalytically active electrode 2 ″ is arranged on a tubular solid electrolyte 1 made of ZrO 2 , opposite the reference electrode 9 ′ in the reference air channel 4. Furthermore, an insulating layer 8 made of Al 2 O 3 is arranged on the outside of the ZrO 2 tube 1 one heating element 5 is arranged symmetrically for faster heating of this gas sensor. Compared to the measuring electrode 2 ″, two differently catalytically active measuring electrodes 2, 2a made of platinum or a platinum alloy, which are assigned to the reference electrode 9, are applied to the solid electrolyte 1. The two measuring electrodes 2, 2a are in turn covered by a protective layer or a porous diffusion layer 11 made of aluminum oxide. Between the measuring electrodes 2 and 2a 12 aluminum oxide is arranged as the insulating material. This construction of the gas sensor allows, in an oxygen excess, which is created by applying a voltage U P1 between the electrodes 9 and 2a or Up 2 between the electrodes 9 and 2 and thereby pumping oxygen into the measuring gas space, gas symmetrically and potentiometrically on two outer Electrodes 2.2a to determine the hydrocarbon concentration or carbon monoxide concentration. The electrode pairs 9.2 and 9.2a can be optimally matched to one another. The high sensitivity achieved in this way can be specifically influenced by the heating elements 5 separately assigned to the electrodes 2, 2 a. If the reference electrode 9 is formed separately as two partial reference electrodes, the sensitivity can be increased further. The solid electrolyte tube 1 is, for example, held in a housing in a manner well known to a person skilled in the art from the prior art, it being possible for the individual layers and electrodes to be electrically contacted in a likewise known manner, for example at one end of the solid electrolyte tube 1.
Zwischen den Elektroden 2 und 2a wird als Differenzsignal U_ gassymmetrisch Kohlenwasserstoff gemessen, während zwischen den Elektroden 9' und 2" die Spannung U-als Sauerstoffsi- gnal gegen Referenz gemessen wird.Between the electrodes 2 and 2a, hydrocarbon gas-symmetrically is measured as the difference signal U_, while the voltage U-is measured as an oxygen signal against reference between the electrodes 9 'and 2 ".
Figur 3 zeigt ebenfalls einen Schnitt durch einen rohrförmigen Festelektrolyt 1 aus ZrO2. Auf der Außenseite ist eine katalytisch inaktive Elektrode 3 aus perowskitischem Material und katalytisch aktive Elektroden 2,2a aus Platin oder einer Platinlegierung angebracht. Letztere werden von einer porösen Diffusionsschicht 11 aus A^O3 überdeckt. Diese poröse Diffusionsschicht kann über den beiden Elektroden 2,2a eine unterschiedliche Stärke aufweisen. Gegenüber den beiden Meßelektroden 2, 3 ist im Innern des Röhrchens 1 je eine Referenzelektrode 9, 9' oder Gegenelektrode 9' angeordnet. Analog Figur 2 ist der Gassensor mit einem Heizelement 5 versehen. Die Sauerstoffbestimmung erfolgt nach diesem Beispiel amperometrisch mittels eines Pumpstroms zwischen der Meßelektrode 2 und der Referenzelektrode 9, die hier als Gegenelektrode fungiert. Die Kohlenwasserstoffbestimung erfolgt potentiometrisch durch Messen der Spannung U3 an den Elektroden 9' und 3 beziehungsweise durch Differenzmessung U2 zwischen den Elektroden 2 und 2a.FIG. 3 also shows a section through a tubular solid electrolyte 1 made of ZrO 2 . A catalytically inactive electrode 3 made of perovskite material and catalytically active electrodes 2, 2a made of platinum or a platinum alloy are attached to the outside. The latter will be covered by a porous diffusion layer 11 made of A ^ O 3 . This porous diffusion layer can have a different thickness over the two electrodes 2, 2 a. Opposite the two measuring electrodes 2, 3, a reference electrode 9, 9 'or counter electrode 9' is arranged in the interior of the tube 1. Analogously to FIG. 2, the gas sensor is provided with a heating element 5. According to this example, the oxygen is determined amperometrically by means of a pump current between the measuring electrode 2 and the reference electrode 9, which acts here as a counter electrode. The hydrocarbon is determined potentiometrically by measuring the voltage U 3 at the electrodes 9 'and 3 or by measuring the difference U 2 between the electrodes 2 and 2a.
Figur 4 zeigt einen ähnlichen Sensoraufbau wie in Figur 2, zusätzlich sind jedoch über der Diffusionsschicht 11 weitere Meßelektroden 2', 2a' angeordnet. Die Diffusionsschicht ist hier auch als Festelektrolyt ausgebildet, so daß zwischen den Meßelektroden 2 und 9 beziehungsweie 2a und 9 eine amperometrische Messung mittels Pumpströmen erfolgen kann. Die Kohlenwasserstoffbestimmung erfolgt als Differenzmessung U2 zwischen den Elektroden 2' und 2a'. Das Sauerstoffsignal ( potentiometrische Lambdabestimmung) U- wird zwischen den Elektroden 9' und 2" gemessen. Die beiden äußeren Elektroden 2' und 2a' sind mit einem porösen, sauerstoffionenleitenden Material 13 abgedeckt, der sich auch in dem Zwischenraum zwischen diesen beiden Elektroden 2', 2a' erstreckt. Zumindest seitlich, bis auf die Isolierschicht 8 hinab, ist das Material 13 von einer gasdichten Versiegelung 14 abgedeckt, um Leckagen des Meßgases oder des Sauerstoffs auszuschließen. FIG. 4 shows a sensor structure similar to that in FIG. 2, but additional measuring electrodes 2 ', 2a' are additionally arranged above the diffusion layer 11. The diffusion layer is also designed here as a solid electrolyte, so that an amperometric measurement by means of pump currents can take place between the measuring electrodes 2 and 9 or 2a and 9. The hydrocarbon is determined as a difference measurement U 2 between the electrodes 2 'and 2a'. The oxygen signal (potentiometric lambda determination) U- is measured between the electrodes 9 'and 2 ". The two outer electrodes 2' and 2a 'are covered with a porous, oxygen ion-conducting material 13, which is also in the space between these two electrodes 2'"2a. At least laterally, down to the insulating layer 8, the material 13 is covered by a gas-tight seal 14 in order to rule out leakages of the measuring gas or oxygen.

Claims

Gas-SensorPatentansprüche Gas sensor patent claims
Gassensor zur Messung von Sauerstoff und/oder der Luft/Kraftstoff Verhältniszahl Lambda und Kohlenwasserstoff und/oder Kohlenmonoxid in Gasgemischen mit einer einen konstanten Sauerstoffpartialdruck repräsentierenden Referenzelektrode, einem sauerstoffionenleitenden Festelektrolyten und mindestens zwei Meßelektroden, wobei die Meßelektroden und die Referenzelektrode unmittelbar auf dem Festelektrolyten angeordnet sind, und mit elektrischen Leitungen zum Anschluß und zum Abgriff für die elektrischen Meßsignale, wobei der Festelektrolyt (1) mit einer dem Meßgas zugewandten Seite und einer vom Meßgas getrennten Referenzgasseite ausgebildet ist, wobei die Anordnung der Elektroden mit der Referenzelektrode (9; 9') auf der Referenzgasseite und den mindestens zwei Meßelektroden (2; 2'; 2"; 3) auf der Meßgasseite derart ausgebildet ist, daß einer der Referenzelektroden (9) mindestens eine Meßelektrode (2) zugeordnet ist, die die Anode dieses Elektrodenpaares (2,9) bildet, wobei das Elektrodenpaar (2,9) zum Anlegen einer Spannung oder eines Stromes zum Pumpen von Sauerstoff ausgebildet ist, wobei die Anordnung gleichzeitig mindestens zwei Meßsignale liefert, denen unterschiedliche gasförmige Bestandteile zugrundeliegen.Gas sensor for measuring oxygen and / or the air / fuel ratio lambda and hydrocarbon and / or carbon monoxide in gas mixtures with a reference electrode representing a constant oxygen partial pressure, an oxygen ion-conducting solid electrolyte and at least two measuring electrodes, the measuring electrodes and the reference electrode being arranged directly on the solid electrolyte , and with electrical lines for connection and tapping for the electrical measurement signals, the solid electrolyte (1) being formed with a side facing the measurement gas and a reference gas side separated from the measurement gas, the arrangement of the electrodes with the reference electrode (9; 9 ') on the reference gas side and the at least two measuring electrodes (2; 2 '; 2 "; 3) on the measuring gas side is designed in such a way that one of the reference electrodes (9) is assigned at least one measuring electrode (2), which is the anode of this pair of electrodes (2, 9) forms, where there s pair of electrodes (2,9) is designed to apply a voltage or a current for pumping oxygen, the arrangement simultaneously delivering at least two measurement signals which are based on different gaseous components.
Gassensor zur Messung von Sauerstoff und/oder der Luft/Kraftstoff Verhältniszahl Lambda und Kohlenwasserstoff und/oder Kohlenmonoxid in Gasgemischen mit einer einen konstanten Sauerstoffpartialdruck repräsentierenden Referenzelektrode, einem sauerstoffionenleitenden Festelektrolyten und mindestens zwei Meßelektroden, wobei die Meßelektroden und die Referenzelektrode unmittelbar auf dem Festelektrolyten angeordnet sind, und mit elektrischen Leitungen zum Anschluß und zum Abgriff für die elektrischen Meßsignale, wobei der Festelektrolyt (1) mit einer dem Meßgas zugewandten Seite und einer vom Meßgas getrennten Referenzgasseite ausgebildet ist, wobei die Anordnung der Elektroden mit der Referenzelektrode (9; 9') auf der Referenzgasseite und den mindestens zwei Meßelektroden (2; 2'; 2"; 3) auf der Meßgasseite derart ausgebildet ist, daß mindestens einer der Referenzelektroden (9) mindestens zwei Meßelektroden (2,2a) zugeordnet sind, die auf dem gleichen Festelektrolyten (1) beabstandet zueinander angeordnet sind, wobei die Anordnung gleichzeitig mindestens zwei Meßsignale liefert, denen unterschiedliche gasförmige Bestandteile zugrundeliegen.Gas sensor for measuring oxygen and / or the air / fuel ratio lambda and hydrocarbon and / or carbon monoxide in gas mixtures with a a reference electrode representing a constant oxygen partial pressure, an oxygen-ion-conducting solid electrolyte and at least two measuring electrodes, the measuring electrodes and the reference electrode being arranged directly on the solid electrolyte, and with electrical lines for connection and tapping for the electrical measuring signals, the solid electrolyte (1) having one of the The side facing the measuring gas and a reference gas side separated from the measuring gas is formed, the arrangement of the electrodes with the reference electrode (9; 9 ') on the reference gas side and the at least two measuring electrodes (2; 2'; 2 "; 3) on the measuring gas side being designed in this way is that at least one of the reference electrodes (9) are assigned to at least two measuring electrodes (2,2a) which are spaced apart on the same solid electrolyte (1), the arrangement simultaneously providing at least two measuring signals to which different gaseous components are added undel lie.
3. Gassensor nach Anspruch 1 , dadurch gekennzeichnet, daß mindestens einer der Referenzelektroden (9) mindestens zwei Meßelektroden (2,2a) zugeordnet sind, die auf dem gleichen Festelektrolyten (1) beabstandet zueinander angeordnet sind.3. Gas sensor according to claim 1, characterized in that at least one of the reference electrodes (9) are associated with at least two measuring electrodes (2,2a) which are arranged on the same solid electrolyte (1) spaced apart.
4. Gassensor nach Anspruch 2, dadurch gekennzeichnet, daß einer der Referenzelektroden (9) mindestens eine Meßelektrode (2) zugeordnet ist, die die Anode dieses Elektrodenpaares (2,9) bildet, wobei das Elektrodenpaar (2,9) zum Anlegen einer Spannung oder eines Stromes zum Pumpen von Sauerstoff ausgebildet ist.4. Gas sensor according to claim 2, characterized in that one of the reference electrodes (9) is assigned at least one measuring electrode (2) which forms the anode of this pair of electrodes (2,9), the pair of electrodes (2,9) for applying a voltage or a current for pumping oxygen.
5. Gassensor nach Anspruch 2 oder 3, dadurch gekennzeichnet, daß die dem Meßgas zugewandten Oberflächen der Meßelektroden (2,2a) mit einer Diffusionsschicht (11 ) bedeckt sind.5. Gas sensor according to claim 2 or 3, characterized in that the measuring gas facing surfaces of the measuring electrodes (2,2a) are covered with a diffusion layer (11).
6. Gassensor nach Anspruch 5, dadurch gekennzeichnet, daß die Diffusionsschicht (11) porös ist.6. Gas sensor according to claim 5, characterized in that the diffusion layer (11) is porous.
7. Gassensor nach Anspruch 5, dadurch gekennzeichnet, daß die Diffusionsschicht (11) aus Aluminiumoxid, Spinell oder Magnesiumoxid gebildet ist.7. Gas sensor according to claim 5, characterized in that the diffusion layer (11) is formed from aluminum oxide, spinel or magnesium oxide.
8. Gassensor nach Anspruch 5, dadurch gekennzeichnet, daß die Diffusionsschicht (11) auf den Meßelektroden (2,2a) jeweils eine unterschiedliche Stärke aufweist. 8. Gas sensor according to claim 5, characterized in that the diffusion layer (11) on the measuring electrodes (2,2a) each have a different thickness.
9. Gassensor nach Anspruch 2 oder 3, dadurch gekennzeichnet, daß zwischen den auf dem gleichen Festelektrolyten (1 ) beabstandet zueinander angeordneten Meßelektroden (2,2a) ein Isolationsmaterial (12), vorzugsweise Aluminiumoxid, Spinell oder Magnesiumoxid oder ein Hohlraum angeordnet ist.9. Gas sensor according to claim 2 or 3, characterized in that an insulating material (12), preferably aluminum oxide, spinel or magnesium oxide or a cavity is arranged between the measuring electrodes (2, 2a) spaced apart from one another on the same solid electrolyte (1).
10. Gassensor nach Anspruch 2 oder 3, dadurch gekennzeichnet, daß die Referenzelektrode (9), die den zueinander beabstandeten Meßelektroden (2,2a) zugeordnet ist, in beabstandet zueinander angeordnete Teilreferenzelektroden aufgeteilt ist.10. Gas sensor according to claim 2 or 3, characterized in that the reference electrode (9), which is assigned to the spaced measuring electrodes (2,2a), is divided into spaced-apart partial reference electrodes.
11. Gassensor nach Anspruch 1 oder 2, dadurch gekennzeichnet, daß auf einer auf dem Festelektrolyten aufgebrachten Isolierschicht (8) ein Heizelement (5) angeordnet ist.11. Gas sensor according to claim 1 or 2, characterized in that a heating element (5) is arranged on an insulating layer (8) applied to the solid electrolyte.
12. Gassensor nach Anspruch 1 oder 2, dadurch gekennzeichnet, daß mindestens eine Meßelektrode aus einem katalytisch aktiven Material besteht, wobei unterschiedliche Meßelektroden aus unterschiedlichen katalytisch aktiven Materialien gebildet sein können, während mindestens eine zweite Meßelektrode aus einem katalytisch inaktiven Material gebildet ist.12. Gas sensor according to claim 1 or 2, characterized in that at least one measuring electrode consists of a catalytically active material, wherein different measuring electrodes can be formed from different catalytically active materials, while at least one second measuring electrode is formed from a catalytically inactive material.
13. Gassensor nach Anspruch 12, dadurch gekennzeichnet, daß das katalytisch inaktive Material im Wesentlichen Gold, eine Goldlegierung oder ein Metalloxid enthält.13. Gas sensor according to claim 12, characterized in that the catalytically inactive material contains essentially gold, a gold alloy or a metal oxide.
14. Gassensor nach Anspruch 12, dadurch gekennzeichnet, daß das katalytisch aktive Material Platin oder eine Platinlegierung ist.14. Gas sensor according to claim 12, characterized in that the catalytically active material is platinum or a platinum alloy.
15. Gassensor nach Anspruch 1oder 2, dadurch gekennzeichnet, daß der Sauerstoff- und/ oder Lambda-Sensor ein potentiometrischer oder amperometrischer Sensor mit jeweils katalytisch aktiven Meßelektroden (2; 2'; 2") ist.15. Gas sensor according to claim 1 or 2, characterized in that the oxygen and / or lambda sensor is a potentiometric or amperometric sensor, each with catalytically active measuring electrodes (2; 2 '; 2 ").
16. Gassensor nach Anspruch 1 oder 2, dadurch gekennzeichnet, daß der Kohlenwasserstoff- Sensor ein potentiometrischer Sensor ist.16. Gas sensor according to claim 1 or 2, characterized in that the hydrocarbon sensor is a potentiometric sensor.
17. Gassensor nach Anspruch 1 oder 2, dadurch gekennzeichnet, daß der Festelektrolyt (1) als ein einseitig geschlossenes Röhrchen ausgebildet ist, wobei die Referenzelektrode17. Gas sensor according to claim 1 or 2, characterized in that the solid electrolyte (1) is designed as a tube closed on one side, the reference electrode
(9; 9') im Inneren des Röhrchens und die mindestens zwei Meßelektroden (2; 2'; 2"; 3) auf der Außenseite des Röhrchens angeordnet sind. (9; 9 ') inside the tube and the at least two measuring electrodes (2; 2'; 2 "; 3) are arranged on the outside of the tube.
18. Verfahren zum Messen mit einem Gassensor nach Anspruch 2 oder 3, dadurch gekennzeichnet, daß von der Referenzgasseite zur Meßgasseite Sauerstoff gepumpt wird, wobei auf der Meßgasseite ein Sauerstoffüberschuß gebildet wird, und daß ein Differenzsignal zwischen zwei unterschiedlichen Meßelektroden gemessen wird.18. A method for measuring with a gas sensor according to claim 2 or 3, characterized in that oxygen is pumped from the reference gas side to the measuring gas side, an excess of oxygen being formed on the measuring gas side, and in that a difference signal is measured between two different measuring electrodes.
19. Verwendung eines Gassensors nach Anspruch 1 oder 2, dadurch gekennzeichnet, daß das Signal des Sauerstoff- und/oder Lambda-Sensors, eingebaut als Sensor nach dem Katalysator für Kalibration des Lambda-Sensors vor dem Katalysator verwendet wird.19. Use of a gas sensor according to claim 1 or 2, characterized in that the signal of the oxygen and / or lambda sensor, installed as a sensor after the catalyst for calibration of the lambda sensor is used before the catalyst.
20. Verwendung eines Gassensors nach Anspruch 1 oder 2, dadurch gekennzeichnet, daß mit dem Meßsignal des Sauerstoff- und/oder Lambda-Sensors eine Korrektur des Kohlenwasserstoff-Sensors oder des Kohlenmonoxid-Sensors vorgenommen wird.20. Use of a gas sensor according to claim 1 or 2, characterized in that a correction of the hydrocarbon sensor or the carbon monoxide sensor is carried out with the measurement signal of the oxygen and / or lambda sensor.
21. Verwendung eines Gassensors nach Anspruch 1 oder 2, dadurch gekennzeichnet, daß mit dem Meßsignal des Sauerstoff- und/oder Lambda-Sensors eine Kalibrierung des Kohlenwasserstoff-Sensors oder des Kohlenmonoxid-Sensors vorgenommen wird. 21. Use of a gas sensor according to claim 1 or 2, characterized in that a calibration of the hydrocarbon sensor or the carbon monoxide sensor is carried out with the measurement signal of the oxygen and / or lambda sensor.
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EP0938666A1 (en) 1999-09-01
WO1999014584A1 (en) 1999-03-25
EP0938668A1 (en) 1999-09-01
WO1999014586A1 (en) 1999-03-25
US6342151B1 (en) 2002-01-29
JP2001505315A (en) 2001-04-17
BR9806177A (en) 1999-10-19
JP2001505311A (en) 2001-04-17
BR9806176A (en) 1999-10-19
BR9806178A (en) 1999-10-19
WO1999014585A1 (en) 1999-03-25
US6355151B1 (en) 2002-03-12
JP2001505316A (en) 2001-04-17

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