EP2130025A2 - Sensor element of a gas sensor - Google Patents

Sensor element of a gas sensor

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Publication number
EP2130025A2
EP2130025A2 EP08708915A EP08708915A EP2130025A2 EP 2130025 A2 EP2130025 A2 EP 2130025A2 EP 08708915 A EP08708915 A EP 08708915A EP 08708915 A EP08708915 A EP 08708915A EP 2130025 A2 EP2130025 A2 EP 2130025A2
Authority
EP
European Patent Office
Prior art keywords
sensor element
measuring
electrode
electrodes
branches
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Withdrawn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
EP08708915A
Other languages
German (de)
French (fr)
Inventor
Peer Kruse
Enno Baars
Alexander Hetznecker
Lothar Diehl
Henrik Schittenhelm
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 EP2130025A2 publication Critical patent/EP2130025A2/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Withdrawn legal-status Critical Current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
    • G01N15/00—Investigating characteristics of particles; Investigating permeability, pore-volume or surface-area of porous materials
    • G01N15/06—Investigating concentration of particle suspensions
    • G01N15/0656—Investigating concentration of particle suspensions using electric, e.g. electrostatic methods or magnetic methods
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N33/00—Investigating or analysing materials by specific methods not covered by groups G01N1/00 - G01N31/00
    • G01N33/0004—Gaseous mixtures, e.g. polluted air
    • G01N33/0009—General constructional details of gas analysers, e.g. portable test equipment
    • G01N33/0027—General constructional details of gas analysers, e.g. portable test equipment concerning the detector
    • 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
    • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
    • Y10T29/00—Metal working
    • Y10T29/49—Method of mechanical manufacture
    • Y10T29/49002—Electrical device making
    • Y10T29/49117—Conductor or circuit manufacturing
    • Y10T29/49124—On flat or curved insulated base, e.g., printed circuit, etc.
    • Y10T29/49155—Manufacturing circuit on or in base
    • Y10T29/49156—Manufacturing circuit on or in base with selective destruction of conductive paths

Definitions

  • the present invention relates to a sensor element for determining a gas component or of particles in a sample gas, and to a method for its production and its use according to the preamble of the independent claims.
  • DE 10 2004 046 882 A1 discloses a sensor for detecting soot in a fluid flow, which sensor is designed on the basis of a ceramic substrate. It comprises two spaced-apart, designed as interdigital electrodes measuring electrodes which are exposed to the investigated combustion exhaust gas. If soot deposits between the measuring electrodes, the insulation resistance of the ceramic material is reduced. This is detected and assigned to a soot concentration in the fluid stream.
  • a heating element of the sensor makes it possible to free the electrodes or their surroundings thermally from deposited soot particles.
  • the object of the present invention is to provide a sensor element for sensors for determining a gas component or of particles in a measurement gas or a method for the production thereof, the sensor functionality of which is essentially independent of manufacturing tolerances during the singulation of the sensor elements.
  • the measuring electrodes of the sensor element are positioned on a surface of the sensor element such that they can be severed during the singulation process of the sensor elements without being impaired in their function. For this reason, it is possible to deliberately guide the measuring electrodes of the sensor element to the outer edge of the sensor element. In this way, on the one hand a copy scattering by the singulation process is avoided and on the other the sensor sensitivity increases disproportionately, since an increase of the sensitive area is achieved and, moreover, the sensitivity of electrodes in the area of the outer edge of a sensor element due to the favorable Ansröm argue for a metered sample gas is particularly pronounced.
  • the measuring electrodes are designed as interdigital electrodes whose branches have a spacing of between 40 and 200 ⁇ m. This way is reliable ensures that even low particle concentrations can be detected in a manageable time period.
  • the sensor element has a heating element or a temperature sensor. In this way, a temporary heating and regeneration of the sensor element is possible as well as a temperature compensation of the measurement signals determined with the sensor element.
  • the sensor element described can be used advantageously for determining soot in exhaust gases of internal combustion engines or stationary incinerators.
  • Figure 1 is a schematic representation of a sensor element for determining
  • Figure 2 is a schematic representation of a sensor element for determining
  • FIG. 1 shows a basic structure of a first embodiment of the present invention.
  • a ceramic sensor element which serves to determine a particle concentration, such as the soot concentration, in a gas mixture surrounding the sensor element.
  • the sensor element 10 comprises, for example, a plurality of ceramic layers 11a and 11b, which form a planar ceramic body. They are preferably made of an electrically insulating material such as alumina, barium-containing alumina or ceria.
  • the ceramic layers of an oxygen-ion-conducting solid electrolyte material such as with Y 2 O 3 stabilized or partially stabilized ZrÜ 2 executed, in which case all electrically conductive leads for measuring electrodes or optionally heating element or temperature sensor by insulating layers, not shown from a electrically insulating ceramic material relative to the surrounding solid electrolyte material are isolated.
  • LTCC Low Temperature Cof ⁇ red Ceramics
  • the integrated shape of the planar ceramic body of the sensor element 10 is produced by laminating together the functional films printed with ceramic films and then sintering the laminated structure in a conventional manner.
  • two measuring electrodes 15, 16 are applied, which are preferably formed as interdigitated interdigital electrodes.
  • the use of interdigital electrodes as measuring electrodes 15, 16 enables a particularly accurate determination of the electrical resistance or the electrical conductivity of the surface material located between the measuring electrodes 15, 16.
  • contact surfaces 18, 20 are provided in the region of an end of the sensor element facing away from the gas mixture, which are connected to the measuring electrodes 15, 16 by electrode feed lines 22, 24.
  • a voltage is applied to the measuring electrodes 15, 16. Since the measuring electrodes 15, 16 are for example applied to the surface of the electrically insulating ceramic layer 11a, substantially no current flow initially occurs between the measuring electrodes 15, 16. If a measuring gas flowing around the sensor element 10 contains electrically conductive particles, in particular soot, so they are deposited on the surface of the ceramic layer 1 Ia. Since soot has a certain electrical conductivity, sufficient loading of the surface of the ceramic layer 11a with carbon black leads to an increasing current flow between the measuring electrodes 15, 16, which correlates with the extent of the loading.
  • a preferably constant direct or alternating voltage is applied to the measuring electrodes 15, 16 and the current flow occurring between the measuring electrodes 15, 16 is determined, an impedance or capacitance change can be detected and the loading of the sensor element with soot can be detected. Furthermore, it can be concluded from the integral of the current flow over time on the deposited particle mass or on the current particle mass flow, in particular soot mass flow, and on the particle concentration in the gas mixture. With this measurement method, the concentration of all those particles in a gas mixture is detected, which influence the electrical conductivity of the located between the measuring electrodes 15, 16 ceramic material positive or negative.
  • the application of the electrode structures of the measuring electrodes 15,16 on the ceramic layer I Ia can be done directly by screen printing in Cofiretechnik or in the wake of the production of the ceramic base support by subsequent baking of the structure by Postfiring.
  • the advantage of Postf ⁇ ring lies in the additional usability of other materials that would not survive a sintering in the context of Cofiring at about 1400 0 C.
  • For applying the measuring electrodes 15,16 by means of post fi ring coating processes offer that work without contact, such as Inkj et techniques.
  • the sensor element 10 furthermore preferably has a ceramic heating element, not shown, which is designed in the form of an electrical resistance conductor and serves to heat the sensor element 10 in particular to the temperature of the gas mixture to be determined or to burn off the soot particles deposited on the large areas of the sensor element.
  • the resistance conductor track is preferably designed in the form of a meander. By applying a corresponding heating voltage to the resistance track, the heating power of the heating element can be regulated accordingly.
  • the sensor element 10 may include a temperature sensor, not shown, which is preferably designed in the form of an electrical resistance track or alternatively as a thermocouple, NTC or PTC resistor.
  • the temperature sensor is used to measure the temperature of the gas mixture and is u.a. for correcting the temperature-dependent measured resistance of the ceramic material located between the measuring electrodes 15, 16 or for correcting the diffusion bonding.
  • the sensor element is used in a sensor for determining the soot concentration in an exhaust gas system and if a separate exhaust gas temperature sensor or alternatively a control device with a temperature model stored as a map exists, then a temperature measuring sensor integrated in the sensor element can be dispensed with.
  • the production of the sensor element 10 takes place by first producing a plurality of ceramic sensor elements on a common ceramic substrate and subsequently separating them. Due to manufacturing tolerances in the production of the sensor elements, for example.
  • the measuring electrodes 15, 16 by screen printing is in conventional sensor elements, only a limited range of the sensor surface available because exceeding this range there is a risk that the conductive paths of the measuring electrodes be damaged in the subsequent separation of the sensor elements and there is a total failure of the sensor element.
  • the arrangement of the measuring electrodes 15, 16 or the electrode leads 22 or 24 in a sensor element according to the invention in such a way that it does not affect the functionality of the measuring electrodes 15, 16 when the conductive paths of one of the measuring electrodes 15, 16 comes.
  • the measuring electrodes 15, 16 are preferably designed as interdigital electrodes, the interdigital electrodes having a series of intermeshing branches 15a, 16a, and a main strand 15b, 16b, respectively, to which the branches 15a, 16a are electrically connected, and the branches of the interdigital electrodes 15a, 16a are aligned substantially parallel to a longitudinal axis of the sensor element 10.
  • the main strands 15b, 16b are preferably guided up to the outer edge of the ceramic layer 11a parallel to a longitudinal axis of the sensor element 10 and thus positioned over the entire width of the sensor element 10, so that they are severed when the sensor element 10 is singulated.
  • the particular advantage of this electrode arrangement is that the sensitive area of the sensor element 10 formed by the interdigitated measuring electrodes 15, 16 is maximized and that the sensitive area is extended, in particular, into the area of the outer edges of the ceramic layer 11a, which is responsible for the sensitivity of the sensor element 10 is of great importance.
  • At least one of the electrode leads 22, 24 is guided in another layer plane of the sensor element 10, for example in the layer plane of the ceramic layer 11b.
  • the contacting of the electrode feed line 22 guided in another layer plane of the ceramic sensor element 10 takes place by means of plated-through holes in order to ensure the electrical connection of the electrode feed line 22 to the contact point 20 or the measuring electrode 15.
  • the electrode leads 22, 24 are preferably applied with a safety margin to the outer edges of the sensor element 10 on the ceramic layer I Ia, I Ib, as in a separation of the same, the associated measuring electrode 15,16 would be inoperative.
  • the branches 15 a, 16 a at least in regions a greater distance from a longitudinal axis of symmetry of the sensor element 10 than the electrode leads 22, 24th
  • one of the two measuring electrodes 15, 16 is preferably designed in the form of two partial electrodes 151, 1511.
  • Both sub-electrodes 151, 1511 have a common electrode lead 22, which branches, for example, in the region of the measuring electrode 15, wherein each sub-electrode 151, 1511 is contacted by a branch.
  • the two sub-electrodes 151, 1511 are positioned on the surface of the ceramic layer 11a in such a way that the electrode lead 24 of the second measuring electrode 16 can be guided centrally between the two sub-electrodes 151, 1511 in particular without causing electrical contact with one of the electrodes two partial electrodes 151, 1511 comes.
  • each of the sub-electrodes 151, 1511 has a separate electrode lead and thus three contact points for contacting the measuring electrodes 151, 1511, 16 are provided.
  • the sensor element according to the present invention is particularly suitable for determining the soot concentration in exhaust gases of internal combustion engines or stationary combustion devices such as heating systems, turbines or power plants. However, it is also suitable for determining the particle concentration in fluids, as used for example in the chemical industry.

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  • Life Sciences & Earth Sciences (AREA)
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  • Combustion & Propulsion (AREA)
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  • Investigating Or Analyzing Materials By The Use Of Electric Means (AREA)
  • Investigating Or Analyzing Materials By The Use Of Fluid Adsorption Or Reactions (AREA)

Abstract

The invention relates to a sensor element for the determination of a gas component or particles in a measuring gas, having a first and a second measurement electrode (15, 16), wherein the measurement electrodes (15, 16) are embodied as interdigital electrodes having a series of engaging branches (15a, 16a) and each having a main line (15b, 16b) to which the branches (15a, 16a) are connected in an electrically conductive manner, and wherein the branches (15a, 16a) of the interdigital electrodes have a substantially parallel orientation to a longitudinal axis of the sensor element (10).

Description

Beschreibung description
Titeltitle
Sensorelement eines GassensorsSensor element of a gas sensor
Die vorliegende Erfindung betrifft ein Sensorelement zur Bestimmung einer Gaskomponente oder von Partikeln in einem Messgas sowie ein Verfahren zu dessen Herstellung und dessen Verwendung nach dem Oberbegriff der unabhängigen Ansprüche.The present invention relates to a sensor element for determining a gas component or of particles in a sample gas, and to a method for its production and its use according to the preamble of the independent claims.
Stand der TechnikState of the art
Der effektive Einsatz von Abgasnachbehandlungssystemen setzt deren Kontrolle hinsichtlich ihrer Funktionstüchtigkeit im Dauereinsatz voraus. Dazu werden Sensoren benötigt, mit denen auch im Langzeitbetrieb eine bspw. genaue Ermittlung der aktuell in einem Verbrennungsabgas vorliegenden Partikelkonzentration ermöglicht werden kann. Darüber hinaus soll mittels derartiger Sensoren eine Beladungsprognose beispielsweise eines in einem Abgassystem vorgesehenen Dieselpartikelfilter ermöglicht werden, um eine hohe Systemsicherheit zu erreichen und dadurch kostengünstigere Filtermaterialien einsetzen zu können. Für diese Anwendung sind insbesondere resistive Rußsensoren geeignet, die die Widerstandsänderung einer interdigitalen Elektrodenstruktur aufgrund von Rußanlagerungen zur Detektion des Rußes heranziehen.The effective use of exhaust aftertreatment systems requires their control in terms of their functionality in continuous use. For this purpose, sensors are needed with which even in long-term operation, for example, an accurate determination of the currently present in a combustion exhaust gas particle concentration can be made possible. In addition to be made possible by means of such sensors, a load prediction, for example, provided in an exhaust system diesel particulate filter in order to achieve a high system security and thereby be able to use more cost-effective filter materials. In particular resistive soot sensors are suitable for this application, which use the change in resistance of an interdigital electrode structure due to soot deposits for the detection of the soot.
So ist aus der DE 10 2004 046 882 Al ein Sensor zur Detektion von Ruß in einem Fluidstrom bekannt, der auf der Basis eines keramischen Substrats ausgeführt ist. Er umfasst zwei voneinander beabstandete, als Interdigitalelektroden ausgeführte Messelektroden, die dem zu untersuchenden Verbrennungsabgas ausgesetzt sind. Lagert sich zwischen den Messelektroden Ruß ab, so kommt es zu einer Reduzierung des Isolationswiderstandes des keramischen Materials. Dies wird detektiert und einer Rußkonzentration im Fluidstrom zugeordnet. Ein Heizelement des Sensors ermöglicht es, die Elektroden bzw. deren Umgebung auf thermischem Wege von abgelagerten Rußpartikeln zu befreien.For example, DE 10 2004 046 882 A1 discloses a sensor for detecting soot in a fluid flow, which sensor is designed on the basis of a ceramic substrate. It comprises two spaced-apart, designed as interdigital electrodes measuring electrodes which are exposed to the investigated combustion exhaust gas. If soot deposits between the measuring electrodes, the insulation resistance of the ceramic material is reduced. This is detected and assigned to a soot concentration in the fluid stream. A heating element of the sensor makes it possible to free the electrodes or their surroundings thermally from deposited soot particles.
Die Herstellung derartiger resistiver keramischer Partikelsensoren erfolgt zunächst auf einem gemeinsamen keramischen Substrat. Abschließend erfolgt eine Vereinzelung der entsprechenden Sensorelemente. Bedingt durch Fertigungstoleranzen, bspw. bei Aufbringung der Messelektroden des Sensorelementes mittels Siebdruck, werden diese nur in einem begrenzten Bereich der Sensoroberfläche appliziert, um zu verhindern, dass bei der Vereinzelung der Sensorelemente die Leiterbahnen der Elektroden durchtrennt werden und der Sensor betriebsunfähig wird. Aufgrund dieser Toleranzen werden die Elektroden je nach Positionierung innerhalb des Toleranzbereichs mehr oder weniger zentriert auf dem Sensorelement angeordnet. Es hat sich jedoch gezeigt, dass die Sensorfunktionalität eines Sensorelementes eine deutliche Abhängigkeit von der Positionierung der Elektroden auf dem Sensorelements zeigt. Die Fertigungstoleranzen beim Vereinzeln der Sensorelementes führen daher zu einer Exemplarstreuung der resultierenden Sensorelemente.The production of such resistive ceramic particle sensors initially takes place on a common ceramic substrate. Finally, a separation of the corresponding Sensor elements. Due to manufacturing tolerances, for example when applying the measuring electrodes of the sensor element by means of screen printing, they are applied only in a limited area of the sensor surface to prevent that in the separation of the sensor elements, the tracks of the electrodes are severed and the sensor is disabled. Due to these tolerances, depending on the positioning within the tolerance range, the electrodes are arranged more or less centered on the sensor element. However, it has been shown that the sensor functionality of a sensor element shows a clear dependence on the positioning of the electrodes on the sensor element. The manufacturing tolerances during singulation of the sensor element therefore lead to a specimen scattering of the resulting sensor elements.
Aufgabe und Vorteile der ErfindungPurpose and advantages of the invention
Aufgabe der vorliegenden Erfindung ist es, ein Sensorelement für Sensoren zur Bestimmung einer Gaskomponente oder von Partikeln in einem Messgas bzw. ein Verfahren zu dessen Herstellung bereitzustellen, dessen Sensorfunktionalität im wesentlichen unabhängig von Fertigungstoleranzen während der Vereinzelung der Sensorelemente ist.The object of the present invention is to provide a sensor element for sensors for determining a gas component or of particles in a measurement gas or a method for the production thereof, the sensor functionality of which is essentially independent of manufacturing tolerances during the singulation of the sensor elements.
Diese Aufgabe wird durch ein Sensorelement bzw. ein Verfahren mit den kennzeichnenden Merkmalen der unabhängigen Ansprüche in vorteilhafter Weise gelöst.This object is solved by a sensor element or a method having the characterizing features of the independent claims in an advantageous manner.
Dies beruht insbesondere darauf, dass die Messelektroden des Sensorelementes so auf einer Oberfläche des Sensorelementes positioniert sind, dass diese während des Vereinzelungsprozesses der Sensorelemente gezielt durchtrennt werden können, ohne in ihrer Funktion beeinträchtigt zu werden. Aus diesem Grund ist es möglich, die Messelektroden des Sensorelementes bewusst bis zur Außenkante des Sensorelementes zu führen. Auf diese Weise wird zum einen eine Exemplarstreuung durch den Vereinzelungsprozess vermieden und zum zweiten steigt die Sensorempfindlichkeit überproportional an, da eine Vergrößerung des sensitiven Bereichs erreicht wird und darüber hinaus die Sensitivität von Elektroden im Bereich der Außenkante eines Sensorelementes aufgrund der günstigen Ansrömbedingungen für ein zutretendes Messgas besonders ausgeprägt ist.This is based, in particular, on the fact that the measuring electrodes of the sensor element are positioned on a surface of the sensor element such that they can be severed during the singulation process of the sensor elements without being impaired in their function. For this reason, it is possible to deliberately guide the measuring electrodes of the sensor element to the outer edge of the sensor element. In this way, on the one hand a copy scattering by the singulation process is avoided and on the other the sensor sensitivity increases disproportionately, since an increase of the sensitive area is achieved and, moreover, the sensitivity of electrodes in the area of the outer edge of a sensor element due to the favorable Ansrömbedingungen for a metered sample gas is particularly pronounced.
Weitere vorteilhafte Ausführungsformen des vorliegenden Sensorelements bzw. Verfahrens zum Herstellen desselben ergeben sich aus den Unteransprüchen.Further advantageous embodiments of the present sensor element or method for producing the same result from the subclaims.
So ist von Vorteil, wenn die Messelektroden als Interdigitalelektroden ausgeführt sind, deren Verzweigungen einen Abstand zwischen 40 und 200 μm aufweisen. Auf diese Weise ist zuverlässig gewährleistet, dass auch geringe Partikelkonzentrationen in einem überschaubaren Zeitraum detektiert werden können.It is advantageous if the measuring electrodes are designed as interdigital electrodes whose branches have a spacing of between 40 and 200 μm. This way is reliable ensures that even low particle concentrations can be detected in a manageable time period.
Weiterhin ist von Vorteil, wenn das Sensorelement ein Heizelement bzw. einen Temperaturmessfühler aufweist. Auf diese Weise ist eine zeitweilige Beheizung und Regenerierung des Sensorelementes möglich sowie eine Temperaturkompensation der mit dem Sensorelement ermittelten Messsignale.Furthermore, it is advantageous if the sensor element has a heating element or a temperature sensor. In this way, a temporary heating and regeneration of the sensor element is possible as well as a temperature compensation of the measurement signals determined with the sensor element.
Das beschriebene Sensorelement ist vorteilhaft einsetzbar zur Bestimmung von Ruß in Abgasen von Verbrennungsmotoren oder von stationären Verbrennungsanlagen.The sensor element described can be used advantageously for determining soot in exhaust gases of internal combustion engines or stationary incinerators.
Ausführungsbeispieleembodiments
Die Erfindung wird anhand der Zeichnungen und der nachfolgenden, darauf Bezug nehmenden Beschreibung näher erläutert. Es zeigenThe invention will be explained in more detail with reference to the drawings and the following description taken in conjunction therewith. Show it
Figur 1 die schematische Darstellung eines Sensorelementes zur Bestimmung vonFigure 1 is a schematic representation of a sensor element for determining
Partikeln gemäß einem ersten Ausführungsbeispiel in einer Explosionsdarstellung undParticles according to a first embodiment in an exploded view and
Figur 2 die schematische Darstellung eines Sensorelementes zur Bestimmung vonFigure 2 is a schematic representation of a sensor element for determining
Partikeln gemäß einem zweiten Ausführungsbeispiel in einer Aufsicht.Particles according to a second embodiment in a plan view.
Die in den Figuren 1 und 2 verwendeten Bezugszeichen bezeichnen, soweit nicht anders angegeben, stets funktionsgleiche Bau- und Systemkomponenten.The reference numbers used in FIGS. 1 and 2, unless otherwise stated, always refer to functionally identical building and system components.
In Figur 1 ist ein prinzipieller Aufbau einer ersten Ausführungsform der vorliegenden Erfindung dargestellt. Mit 10 ist ein keramisches Sensorelement bezeichnet, das der Bestimmung einer Partikelkonzentration, wie beispielsweise der Rußkonzentration, in einem das Sensorelement umgebenden Gasgemisch dient. Das Sensorelement 10 umfasst beispielsweise eine Mehrzahl von keramischen Schichten 1 Ia und I Ib, die einen planaren keramischen Körper bilden. Sie bestehen vorzugsweise aus einem elektrisch isolierenden Material wie beispielsweise Aluminiumoxid, bariumhaltigem Aluminiumoxid oder Cerdioxid. In einer alternativen Ausführungsform sind die keramischen Schichten aus einem sauerstoffionenleitenden Festelektrolytmaterial, wie beispielsweise mit Y2O3 stabilisiertem oder teilstabilisiertem ZrÜ2 ausgeführt, wobei in diesem Fall alle elektrisch leitfähigen Zuleitungen für Messelektroden oder ggf. Heizelement bzw. Temperaturfühler durch nicht dargestellte Isolierschichten aus einem elektrisch isolierenden keramischen Material gegenüber dem umgebenden Festelektrolytmaterial isoliert sind. Eine weitere Möglichkeit besteht in der Verwendung sogenannte Low Temperature Cofϊred Ceramics (LTCC) als Material der keramischen Schichten.FIG. 1 shows a basic structure of a first embodiment of the present invention. Denoted at 10 is a ceramic sensor element which serves to determine a particle concentration, such as the soot concentration, in a gas mixture surrounding the sensor element. The sensor element 10 comprises, for example, a plurality of ceramic layers 11a and 11b, which form a planar ceramic body. They are preferably made of an electrically insulating material such as alumina, barium-containing alumina or ceria. In an alternative embodiment, the ceramic layers of an oxygen-ion-conducting solid electrolyte material, such as with Y 2 O 3 stabilized or partially stabilized ZrÜ 2 executed, in which case all electrically conductive leads for measuring electrodes or optionally heating element or temperature sensor by insulating layers, not shown from a electrically insulating ceramic material relative to the surrounding solid electrolyte material are isolated. Another possibility is the use of so-called Low Temperature Cofϊred Ceramics (LTCC) as the material of the ceramic layers.
Die integrierte Form des planaren keramischen Körpers des Sensorelements 10 wird durch Zusammenlaminieren der mit Funktionsschichten bedruckten keramischen Folien und anschließendem Sintern der laminierten Struktur in an sich bekannter Weise hergestellt.The integrated shape of the planar ceramic body of the sensor element 10 is produced by laminating together the functional films printed with ceramic films and then sintering the laminated structure in a conventional manner.
Auf einer Großfläche des Sensorelementes sind beispielsweise zwei Messelektroden 15, 16 aufgebracht, die vorzugsweise als ineinander verzahnte Interdigitalelektroden ausgebildet sind. Die Verwendung von Interdigitalelektroden als Messelektroden 15, 16 ermöglicht eine besonders genaue Bestimmung des elektrischen Widerstandes bzw. der elektrischen Leitfähigkeit des sich zwischen den Messelektroden 15, 16 befindenden Oberflächenmaterials.On a large surface of the sensor element, for example, two measuring electrodes 15, 16 are applied, which are preferably formed as interdigitated interdigital electrodes. The use of interdigital electrodes as measuring electrodes 15, 16 enables a particularly accurate determination of the electrical resistance or the electrical conductivity of the surface material located between the measuring electrodes 15, 16.
Zur Kontaktierung der Messelektroden 15, 16 sind im Bereich eines dem Gasgemisch abgewandten Ende des Sensorelements Kontaktflächen 18, 20 vorgesehen, die durch Elektrodenzuleitungen 22, 24 mit den Messelektroden 15, 16 verbunden sind.For contacting the measuring electrodes 15, 16, contact surfaces 18, 20 are provided in the region of an end of the sensor element facing away from the gas mixture, which are connected to the measuring electrodes 15, 16 by electrode feed lines 22, 24.
Während des Betriebs des Sensorelementes 10 wird an die Messelektroden 15, 16 eine Spannung angelegt. Da die Messelektroden 15, 16 bspw. auf der Oberfläche der elektrisch isolierenden keramischen Schicht I Ia aufgebracht sind, kommt es zunächst im wesentlichen zu keinem Stromfluss zwischen den Messelektroden 15, 16. Enthält ein das Sensorelement 10 umströmendes Messgas elektrisch leitfähige Partikel, insbesondere Ruß, so lagern sich diese auf der Oberfläche der keramischen Schicht 1 Ia ab. Da Ruß eine bestimmte elektrische Leitfähigkeit aufweist, kommt es bei ausreichender Beladung der Oberfläche der keramischen Schicht 1 Ia mit Ruß zu einem ansteigenden Stromfluss zwischen den Messelektroden 15, 16, der mit dem Ausmaß der Beladung korreliert.During operation of the sensor element 10, a voltage is applied to the measuring electrodes 15, 16. Since the measuring electrodes 15, 16 are for example applied to the surface of the electrically insulating ceramic layer 11a, substantially no current flow initially occurs between the measuring electrodes 15, 16. If a measuring gas flowing around the sensor element 10 contains electrically conductive particles, in particular soot, so they are deposited on the surface of the ceramic layer 1 Ia. Since soot has a certain electrical conductivity, sufficient loading of the surface of the ceramic layer 11a with carbon black leads to an increasing current flow between the measuring electrodes 15, 16, which correlates with the extent of the loading.
Wird nun an die Messelektroden 15, 16 eine vorzugsweise konstante Gleich- oder Wechselspannung angelegt und der zwischen den Messelektroden 15, 16 auftretende Stromfluss ermittelt, so kann eine Impedanz- oder Kapazitätsänderung erfasst und die Beladung des Sensorelementes mit Ruß detektiert werden. Weiterhin kann aus dem Integral des Stromflusses über der Zeit auf die abgelagerte Partikelmasse bzw. auf den aktuellen Partikelmassenstrom, insbesondere Rußmassenstrom, und auf die Partikelkonzentration im Gasgemisch geschlossen werden. Mit dieser Messmethode wird die Konzentration all derjenigen Partikel in einem Gasgemisch erfasst, die die elektrische Leitfähigkeit des sich zwischen den Messelektroden 15, 16 befindenden keramischen Materials positiv oder negativ beeinflussen. Das Aufbringen der Elektrodenstrukturen der Messelektroden 15,16 auf die keramische Schicht I Ia kann direkt per Siebdruck in Cofiretechnik oder auch im Nachgang zur Herstellung des keramischen Grundträgers durch anschließendes Einbrennen der Struktur durch Postfiring erfolgen. Der Vorteil des Postfϊring liegt in der zusätzlichen Verwendbarkeit weiterer Materialien, die eine Sinterung im Rahmen des Cofiring bei ca. 1400 0C nicht überstehen würden. Zur Aufbringung der Messelektroden 15,16 mittels Postfiring bieten sich Beschichtungsprozesse an, die berührungslos arbeiten, wie z.B. Inkj et-Techniken.If now a preferably constant direct or alternating voltage is applied to the measuring electrodes 15, 16 and the current flow occurring between the measuring electrodes 15, 16 is determined, an impedance or capacitance change can be detected and the loading of the sensor element with soot can be detected. Furthermore, it can be concluded from the integral of the current flow over time on the deposited particle mass or on the current particle mass flow, in particular soot mass flow, and on the particle concentration in the gas mixture. With this measurement method, the concentration of all those particles in a gas mixture is detected, which influence the electrical conductivity of the located between the measuring electrodes 15, 16 ceramic material positive or negative. The application of the electrode structures of the measuring electrodes 15,16 on the ceramic layer I Ia can be done directly by screen printing in Cofiretechnik or in the wake of the production of the ceramic base support by subsequent baking of the structure by Postfiring. The advantage of Postfϊring lies in the additional usability of other materials that would not survive a sintering in the context of Cofiring at about 1400 0 C. For applying the measuring electrodes 15,16 by means of post fi ring coating processes offer that work without contact, such as Inkj et techniques.
Das Sensorelement 10 weist weiterhin vorzugsweise ein nicht dargestelltes keramisches Heizelement auf, das in Form einer elektrischen Widerstandsleiterbahn ausgeführt ist und der Aufheizung des Sensorelementes 10 insbesondere auf die Temperatur des zu bestimmenden Gasgemischs bzw. zum Abbrand der auf den Großflächen des Sensorelementes abgelagerten Rußpartikel dient. Die Widerstandsleiterbahn ist vorzugsweise in Form eines Mäanders ausgebildet. Durch Anlegen einer entsprechenden Heizspannung an die Widerstandsleiterbahn kann die Heizleistung des Heizelementes entsprechend reguliert werden.The sensor element 10 furthermore preferably has a ceramic heating element, not shown, which is designed in the form of an electrical resistance conductor and serves to heat the sensor element 10 in particular to the temperature of the gas mixture to be determined or to burn off the soot particles deposited on the large areas of the sensor element. The resistance conductor track is preferably designed in the form of a meander. By applying a corresponding heating voltage to the resistance track, the heating power of the heating element can be regulated accordingly.
Darüber hinaus kann das Sensorelement 10 einen nicht dargestellten Temperaturmessfühler umfassen, der vorzugsweise in Form einer elektrischen Widerstandsleiterbahn ausgeführt ist oder alternativ als Thermoelement, NTC- bzw. PTC-Widerstand. Der Temperaturmessfühler dient der Messung der Temperatur des Gasgemischs und wird u.a. zur Korrektur des temperaturabhängigen gemessenen Widerstandes des sich zwischen den Messelektroden 15,16 befindenden keramischen Materials bzw. zur Korrektur der Diffusionsanlagerung verwendet.In addition, the sensor element 10 may include a temperature sensor, not shown, which is preferably designed in the form of an electrical resistance track or alternatively as a thermocouple, NTC or PTC resistor. The temperature sensor is used to measure the temperature of the gas mixture and is u.a. for correcting the temperature-dependent measured resistance of the ceramic material located between the measuring electrodes 15, 16 or for correcting the diffusion bonding.
Wird das Sensorelement in einem Sensor zur Bestimmung der Rußkonzentration in einem Abgassystem eingesetzt und existiert in diesem System ein separater Abgastemperatursensor oder alternativ ein Steuergerät mit einem als Kennfeld hinterlegten Temperaturmodell, so kann auf einen in das Sensorelement integrierten Temperaturmessfühler verzichtet werden.If the sensor element is used in a sensor for determining the soot concentration in an exhaust gas system and if a separate exhaust gas temperature sensor or alternatively a control device with a temperature model stored as a map exists, then a temperature measuring sensor integrated in the sensor element can be dispensed with.
Die Herstellung des Sensorelementes 10 erfolgt, indem zunächst mehrere keramische Sensorelemente auf einem gemeinsamen keramischen Substrat erzeugt und nachfolgend vereinzelt werden. Bedingt durch Fertigungstoleranzen bei der Herstellung der Sensorelemente, bspw. bei der Aufbringung der Messelektroden 15, 16 mittels Siebdruck, steht bei üblichen Sensorelementen nur ein begrenzter Bereich der Sensoroberfläche zur Verfügung, da bei Überschreitung dieses Bereichs die Gefahr besteht, dass die leitfähigen Pfade der Messelektroden bei der nachfolgenden Vereinzelung der Sensorelemente beschädigt werden und es zu einem Totalausfall des Sensorelementes kommt. Demgegenüber erfolgt die Anordnung der Messelektroden 15, 16 bzw. der Elektrodenzuleitungen 22 oder 24 bei einem Sensorelement gemäß der Erfindung in einer Weise, dass es bei Durchtrennung der leitfähigen Pfade einer der Messelektroden 15, 16 nicht zu einer Beeinträchtigung der Funktionalität der Messelektroden 15, 16 kommt. Die Messelektroden 15, 16 sind vorzugsweise als Interdigitalelektroden ausgeführt, wobei die Interdigitalelektroden eine Reihe ineinandergreifender Verzweigungen 15a, 16a aufweisen sowie jeweils einen Hauptstrang 15b, 16b, mit dem die Verzweigungen 15a, 16a elektrisch leitend verbunden sind, und wobei die Verzweigungen der Interdigitalelektroden 15a, 16a im wesentlichen parallel zu einer Längsachse des Sensorelementes 10 ausgerichtet sind. Dabei werden vorzugsweise die Hauptstränge 15b, 16b bis an die zu einer Längsachse des Sensorelementes 10 parallelen Außenkante der keramischen Schicht 1 Ia geführt und somit über die gesamte Breite des Sensorelementes 10 positioniert, sodass sie bei Vereinzelung des Sensorelementes 10 durchtrennt werden. Dabei kommt es jedoch nicht, wie bei üblichen Sensorelementen, zu einem Ausfall der entsprechenden Messelektrode, sondern es werden lediglich einzelne Verzweigungen 15a, 16a abgetrennt. Daraus ergeben sich minimale Unterschiede der Sensorelemente hinsichtlich ihrer Messelektroden 15, 16, die sich um maximal eine Verzweigung 15a, 16a unterscheiden, wodurch die Größe des sensitiven Bereichs um den Abstand zweier Verzweigungen 15a, 16a der ca. 40 bis 200 μm, insbesondere 60 bis 170 μm betragen kann, abweichen kann.The production of the sensor element 10 takes place by first producing a plurality of ceramic sensor elements on a common ceramic substrate and subsequently separating them. Due to manufacturing tolerances in the production of the sensor elements, for example. In the application of the measuring electrodes 15, 16 by screen printing, is in conventional sensor elements, only a limited range of the sensor surface available because exceeding this range there is a risk that the conductive paths of the measuring electrodes be damaged in the subsequent separation of the sensor elements and there is a total failure of the sensor element. In contrast, the arrangement of the measuring electrodes 15, 16 or the electrode leads 22 or 24 in a sensor element according to the invention in such a way that it does not affect the functionality of the measuring electrodes 15, 16 when the conductive paths of one of the measuring electrodes 15, 16 comes. The measuring electrodes 15, 16 are preferably designed as interdigital electrodes, the interdigital electrodes having a series of intermeshing branches 15a, 16a, and a main strand 15b, 16b, respectively, to which the branches 15a, 16a are electrically connected, and the branches of the interdigital electrodes 15a, 16a are aligned substantially parallel to a longitudinal axis of the sensor element 10. In this case, the main strands 15b, 16b are preferably guided up to the outer edge of the ceramic layer 11a parallel to a longitudinal axis of the sensor element 10 and thus positioned over the entire width of the sensor element 10, so that they are severed when the sensor element 10 is singulated. However, as with conventional sensor elements, this does not lead to a failure of the corresponding measuring electrode, but only individual branches 15a, 16a are cut off. This results in minimal differences of the sensor elements with respect to their measuring electrodes 15, 16, which differ by a maximum of a branch 15a, 16a, whereby the size of the sensitive area by the distance between two branches 15a, 16a of about 40 to 200 .mu.m, in particular 60 to 170 microns may vary.
Der besondere Vorteil dieser Elektrodenanordnung besteht darin, dass der sensitive Bereich des Sensorelementes 10 gebildet durch die ineinander greifenden Messelektroden 15, 16 maximiert wird und dass der sensitive Bereich insbesondere auch in den Bereich der Außenkanten der keramischen Schicht I Ia erweitert wird, der für die Sensitivität des Sensorelementes 10 von hoher Bedeutung ist.The particular advantage of this electrode arrangement is that the sensitive area of the sensor element 10 formed by the interdigitated measuring electrodes 15, 16 is maximized and that the sensitive area is extended, in particular, into the area of the outer edges of the ceramic layer 11a, which is responsible for the sensitivity of the sensor element 10 is of great importance.
Um diese Elektrodenanordnung zu realisieren, wird vorzugsweise mindestens eine der Elektrodenzuleitungen 22, 24 in einer anderen Schichtebene des Sensorelementes 10 geführt, beispielsweise in der Schichtebene der keramischen Schicht I Ib. Die Kontaktierung der in einer anderen Schichtebene des keramischen Sensorelementes 10 geführten Elektrodenzuleitung 22 erfolgt mittels Durchkontaktierungen, um die elektrische Verbindung der Elektrodenzuleitung 22 mit der Kontaktstelle 20 bzw. der Messelektrode 15 zu gewährleisten.In order to realize this electrode arrangement, preferably at least one of the electrode leads 22, 24 is guided in another layer plane of the sensor element 10, for example in the layer plane of the ceramic layer 11b. The contacting of the electrode feed line 22 guided in another layer plane of the ceramic sensor element 10 takes place by means of plated-through holes in order to ensure the electrical connection of the electrode feed line 22 to the contact point 20 or the measuring electrode 15.
Weiterhin werden die Elektrodenzuleitungen 22, 24 vorzugsweise mit einem Sicherheitsabstand zu den Außenkanten des Sensorelementes 10 auf der keramischen Schicht I Ia, I Ib aufgebracht, da bei einer Durchtrennung derselben die zugehörige Messelektrode 15,16 funktionsuntüchtig würde. Auf diese Weise weisen die Verzweigungen 15a, 16a zumindest bereichsweise einen größeren Abstand zu einer Längssymmetrieachse des Sensorelementes 10 auf als die Elektrodenzuleitungen 22, 24. Eine weitere Ausführungsform der vorliegenden Erfindung ist Figur 2 dargestellt. Dabei ist vorzugsweise eine der beiden Messelektroden 15, 16 in Form von zwei Teilelektroden 151, 1511 ausgeführt. Beide Teilelektroden 151, 1511 weisen eine gemeinsame Elektrodenzuleitung 22 auf, die sich beispielsweise im Bereich der Messelektrode 15 verzweigt, wobei jede Teilelektroden 151, 1511 durch eine Verzweigung kontaktiert wird. Die beiden Teilelektroden 151, 1511 sind dabei derart auf der Oberfläche der keramischen Schicht I Ia positioniert, dass insbesondere mittig zwischen den beiden Teilelektroden 151, 1511 die Elektrodenzuleitung 24 der zweiten Messelektrode 16 geführt werden kann, ohne dass es zu einem elektrischen Kontakt mit einer der beiden Teilelektroden 151, 1511 kommt. Da sich jedoch die Elektrodenzuleitungen 22, 24 bei dieser Anordnung der Messelektroden 15,16 kreuzen, sind beide Elektrodenzuleitungen 22, 24 zumindest in dem Bereich, indem sie sich kreuzen in verschiedenen Schichtebenen des Sensorelementes 10 geführt oder zumindest durch eine isolierende keramischen Schicht voneinander getrennt aufgebracht. Eine alternative Lösungen sieht vor, dass jede der Teilelektroden 151, 1511 eine separate Elektrodenzuleitung aufweist und somit drei Kontaktstellen zur Kontaktierung der Messelektroden 151, 1511, 16 vorgesehen sind.Furthermore, the electrode leads 22, 24 are preferably applied with a safety margin to the outer edges of the sensor element 10 on the ceramic layer I Ia, I Ib, as in a separation of the same, the associated measuring electrode 15,16 would be inoperative. In this way, the branches 15 a, 16 a at least in regions a greater distance from a longitudinal axis of symmetry of the sensor element 10 than the electrode leads 22, 24th Another embodiment of the present invention is shown in FIG. In this case, one of the two measuring electrodes 15, 16 is preferably designed in the form of two partial electrodes 151, 1511. Both sub-electrodes 151, 1511 have a common electrode lead 22, which branches, for example, in the region of the measuring electrode 15, wherein each sub-electrode 151, 1511 is contacted by a branch. The two sub-electrodes 151, 1511 are positioned on the surface of the ceramic layer 11a in such a way that the electrode lead 24 of the second measuring electrode 16 can be guided centrally between the two sub-electrodes 151, 1511 in particular without causing electrical contact with one of the electrodes two partial electrodes 151, 1511 comes. However, since the electrode feed lines 22, 24 intersect in this arrangement of the measuring electrodes 15, 16, both electrode feed lines 22, 24 are guided in different layer planes of the sensor element 10 at least in the region by being intersected or at least separated from one another by an insulating ceramic layer , An alternative solution provides that each of the sub-electrodes 151, 1511 has a separate electrode lead and thus three contact points for contacting the measuring electrodes 151, 1511, 16 are provided.
Das Sensorelement gemäß vorliegender Erfindung eignet sich insbesondere zur Bestimmung der Rußkonzentration in Abgasen von Verbrennungsmotoren oder stationären Verbrennungseinrichtungen wie Heizanlagen, Turbinen oder Kraftwerken. Es eignet sich jedoch auch zur Bestimmung der Partikelkonzentration in Fluiden, wie sie beispielsweise in der chemischen Industrie zum Einsatz kommen. The sensor element according to the present invention is particularly suitable for determining the soot concentration in exhaust gases of internal combustion engines or stationary combustion devices such as heating systems, turbines or power plants. However, it is also suitable for determining the particle concentration in fluids, as used for example in the chemical industry.

Claims

Ansprüche claims
1. Sensorelement zur Bestimmung einer Gaskomponente oder von Partikeln in einem Messgas, mit einer ersten und einer zweiten Messelektrode (15, 16), dadurch gekennzeichnet, dass die Messelektroden (15, 16) als Interdigitalelektroden ausgeführt sind, wobei die Interdigitalelektroden eine Reihe ineinandergreifender Verzweigungen (15a, 16a) aufweisen sowie jeweils einen Hauptstrang (15b, 16b), mit dem die Verzweigungen (15a, 15b) elektrisch leitend verbunden sind, und wobei die Verzweigungen (15a, 16a) der Interdigitalelektroden im wesentlichen parallel zu einer Längsachse des Sensorelementes (10) ausgerichtet sind.A sensor element for determining a gas component or particles in a sample gas, comprising a first and a second measuring electrode (15, 16), characterized in that the measuring electrodes (15, 16) are designed as interdigital electrodes, the interdigital electrodes being a series of intermeshing branches (15a, 16a) and each having a main strand (15b, 16b) to which the branches (15a, 15b) are electrically connected, and wherein the branches (15a, 16a) of the interdigital electrodes substantially parallel to a longitudinal axis of the sensor element ( 10) are aligned.
2. Sensorelement zur Bestimmung einer Gaskomponente oder von Partikeln in einem Messgas, mit einer ersten und einer zweiten Messelektrode (15, 16), dadurch gekennzeichnet, dass die Messelektroden (15, 16) als Interdigitalelektroden ausgeführt sind, wobei die Interdigitalelektroden (15, 16) eine Reihe ineinandergreifender Verzweigungen (15a, 16a) aufweisen sowie jeweils einen Hauptstrang (15b, 16b), mit dem die Verzweigungen (15a, 16a) elektrisch leitend verbunden sind, und wobei die Verzweigungen (15a, 16a) zumindest einer Interdigitalelektrode zumindest bereichsweise mit einem größeren Abstand zu einer Längssymmetrieachse des Sensorelementes (10) positioniert sind als die Elektrodenzuleitung (22, 24) der Interdigitalelektroden.2. Sensor element for determining a gas component or of particles in a measuring gas, with a first and a second measuring electrode (15, 16), characterized in that the measuring electrodes (15, 16) are designed as interdigital electrodes, wherein the interdigital electrodes (15, 16 ) Have a number of interlocking branches (15a, 16a) and each have a main strand (15b, 16b) to which the branches (15a, 16a) are electrically connected, and wherein the branches (15a, 16a) at least one interdigital electrode at least partially with a greater distance to a longitudinal axis of symmetry of the sensor element (10) are positioned as the electrode lead (22, 24) of the interdigital electrodes.
3. Sensorelement zur Bestimmung einer Gaskomponente oder von Partikeln in einem Messgas, mit einem aus mindestens zwei keramischen Schichten (I Ia, 1 Ib) aufgebauten Sensorkörper und mit einer ersten und einer zweiten Messelektrode (15, 16), wobei die erste und die zweite Messelektrode (15, 16) jeweils eine Elektrodenzuleitung (22, 24) aufweist, dadurch gekennzeichnet, dass die Elektrodenzuleitung (22) der ersten Messelektrode (15) zumindest bereichsweise in einer anderen keramischen Schichtebene (1 Ib) geführt ist als die Elektrodenzuleitung (24) der zweiten Messelektrode (16).3. Sensor element for determining a gas component or of particles in a measurement gas, comprising a sensor body constructed from at least two ceramic layers (I Ia, Ib) and having a first and a second measuring electrode (15, 16), wherein the first and the second Measuring electrode (15, 16) each having an electrode lead (22, 24), characterized in that the electrode lead (22) of the first measuring electrode (15) at least partially in another ceramic layer plane (1 Ib) is guided as the electrode lead (24) the second measuring electrode (16).
4. Sensorelement zur Bestimmung einer Gaskomponente oder von Partikeln in einem Messgas, mit einer ersten und einer zweiten Messelektrode (15, 16), wobei die erste und die zweite Messelektrode jeweils eine Elektrodenzuleitung (22, 24) aufweist, dadurch gekennzeichnet, dass eine der Messelektroden (15) aus zwei Halbelektroden (151, 1511) ausgeführt ist, die lediglich über eine Elektrodenzuleitung (22) elektrisch leitend miteinander verbunden sind.4. Sensor element for determining a gas component or of particles in a measuring gas, with a first and a second measuring electrode (15, 16), wherein the first and the second measuring electrode each having an electrode lead (22, 24), characterized in that one of Measuring electrodes (15) of two half electrodes (151, 1511) is executed, the only electrically conductive via an electrode lead (22) connected to each other.
5. Sensorelement nach einem der Ansprüche 3 und 4, dadurch gekennzeichnet, dass die Messelektroden (15, 16) als Interdigitalelektroden ausgeführt sind.5. Sensor element according to one of claims 3 and 4, characterized in that the measuring electrodes (15, 16) are designed as interdigital electrodes.
6. Sensorelement nach einem der vorhergehenden Ansprüche, dadurch gekennzeichnet, dass mindestens eine der Messelektroden (15, 16) zumindest bereichsweise an einer Außenkante des Sensorelementes (10) positioniert ist.6. Sensor element according to one of the preceding claims, characterized in that at least one of the measuring electrodes (15, 16) is at least partially positioned on an outer edge of the sensor element (10).
7. Sensorelement nach einem der Ansprüche 1, 2 und 5, dadurch gekennzeichnet, dass der Abstand zweier benachbarter Verzweigungen (15a, 16a) derselben Messelektrode zwischen 40 und 200 μm beträgt.7. Sensor element according to one of claims 1, 2 and 5, characterized in that the distance between two adjacent branches (15a, 16a) of the same measuring electrode is between 40 and 200 microns.
8. Sensorelement nach einem der vorhergehenden Ansprüche, dadurch gekennzeichnet, dass ein Heizelement oder ein Temperaturmessfühler vorgesehen ist.8. Sensor element according to one of the preceding claims, characterized in that a heating element or a temperature sensor is provided.
9. Verfahren zur Herstellung eines Sensorelementes zur Bestimmung einer Gaskomponente oder von Partikeln in einem Messgas, insbesondere eines Sensorelementes nach einem der vorhergehenden Ansprüche, bei dem mindestens zwei Sensorelemente auf einem gemeinsamen Substrat erzeugt werden und nachfolgend vereinzelt werden, dadurch gekennzeichnet, dass bei der Vereinzelung mindestens eine Elektrode (15, 16) des Sensorelementes durchtrennt wird.9. A method for producing a sensor element for determining a gas component or of particles in a measuring gas, in particular a sensor element according to one of the preceding claims, wherein at least two sensor elements are produced on a common substrate and subsequently separated, characterized in that during singulation at least one electrode (15, 16) of the sensor element is severed.
10. Verfahren nach Anspruch 9, dadurch gekennzeichnet, dass die mindestens eine Elektrode (15, 16) als Interdigitalelektrode mit einer Reihe ineinandergreifender Verzweigungen (15a, 16a) und einem Hauptstrang (15b, 16b), der mit den Verzweigungen (15a, 16a) elektrisch leitend verbunden ist, ausgeführt wird, und dass bei der Vereinzelung mindestens einer der Hauptstränge (15b, 16b) durchtrennt wird.10. The method according to claim 9, characterized in that the at least one electrode (15, 16) as an interdigital electrode with a series of interlocking branches (15a, 16a) and a main strand (15b, 16b) with the branches (15a, 16a) is electrically conductively connected, is executed, and that at the separation of at least one of the main strands (15b, 16b) is severed.
11. Verwendung eines Sensorelementes nach einem der Ansprüche 1 bis 8 zur Bestimmung von Ruß in Abgasen von Verbrennungsmotoren oder von stationären Verbrennungsanlagen. 11. Use of a sensor element according to one of claims 1 to 8 for the determination of soot in exhaust gases of internal combustion engines or stationary incinerators.
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