EP1514099A1 - Procede permettant d'etalonner un element de detection con u pour une sonde de courant limite - Google Patents

Procede permettant d'etalonner un element de detection con u pour une sonde de courant limite

Info

Publication number
EP1514099A1
EP1514099A1 EP03735294A EP03735294A EP1514099A1 EP 1514099 A1 EP1514099 A1 EP 1514099A1 EP 03735294 A EP03735294 A EP 03735294A EP 03735294 A EP03735294 A EP 03735294A EP 1514099 A1 EP1514099 A1 EP 1514099A1
Authority
EP
European Patent Office
Prior art keywords
sensor element
diffusion
gas
pump
camera
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Withdrawn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
EP03735294A
Other languages
German (de)
English (en)
Inventor
Lothar Diehl
Karl-Heinz Friese
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 EP1514099A1 publication Critical patent/EP1514099A1/fr
Withdrawn legal-status Critical Current

Links

Classifications

    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
    • G01N27/26—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating electrochemical variables; by using electrolysis or electrophoresis
    • G01N27/416—Systems
    • G01N27/417—Systems using cells, i.e. more than one cell and probes with solid electrolytes
    • G01N27/4175—Calibrating or checking the analyser

Definitions

  • the invention is based on a method for calibrating a sensor element for a limit current probe, in particular for a planar broadband lambda probe, for determining the concentration of a gas component, in particular oxygen, in a gas mixture, in particular in the exhaust gas of internal combustion engines, according to the preamble of claim 1 ,
  • the diffusion barrier which separates the inner pump electrode of a pump cell from the exhaust gas together with a measuring or Nernst electrode of a Nernst cell, is produced using a screen printing process with a defined layer thickness, the layer thickness being checked in the manufacturing process.
  • the diffusion barrier is thus given a certain diffusion resistance, which is determined, for example, by the limit current in air with oxygen withdrawal from which the inner pump electrode and the Including measuring electrode can be determined by the Diffusio sbamere separated from the exhaust gas or measuring gas space. This diffusion resistance determines the sensitivity of the probe.
  • the layer thickness of the diffusion bamers is subject to production fluctuations, which are particularly amplified by the sintering process to which the sensor element is subjected at the end of its manufacture, so that the limit current supplied by the pump cell fluctuates not inconsiderably with different batches of the sensor elements.
  • the sintered sensor elements must therefore be subjected to calibration.
  • a gas access hole which is passed through oiesen essentially perpendicular to the surface of the solid electrolyte and which is enclosed in the end region by the diffusion camera, is specifically increased in diameter, as a result of which the diffusion resistance of the Diffusion camera is linearly adjustable.
  • a batch of identical, non-sintered sensor elements without a gas access hole is first produced, from which a sensor element is selected.
  • a gas access hole with a defined diameter is made in the selected sensor element and the sensor element is then sintered.
  • the limit current is measured at a preselected pump voltage and the target value of the measured limit current is compared by increasing the diameter of the gas access locomotive. With the optimized diameter of the gas access hole found in this way, the Gas access holes drilled in the remaining sensor elements of the batch and the sensor elements then sintered.
  • the method according to the invention for calibrating a sensor element for a limit current probe with the features of claim 1 has the advantage that the diffusion resistance of the diffusion barrier can be set with high precision while the limit current of the pump cell is being measured. At the same time, the material input achieves a homogenization effect with regard to the diffusion resistance within the diffusion barrier, since the sublimation of the precursor gas causes the material portions from the precursor gas to attach to the surfaces of the porous structure
  • Diffusion barrier comes and the larger pores in the structure are more strongly added than the smaller ones, so that the diffusion channels forming in the diffusion barrier over the layer thickness of the diffusion barrier have approximately the same diffusion resistance.
  • Another advantage of the method according to the invention is that it can also be used in sensor elements in which the diffusion barrier does not directly enclose the end region of the gas access hole to the inner pump electrode, but must be arranged withdrawn from the gas access hole for other reasons, so that the diffusion barrier enclosed annulus has a larger diameter than the bore diameter of the gas access hole in the solid electrolyte.
  • the known method described above with adjustment of the bore diameter of the gas access hole would not be applicable in this case.
  • Advantageous further developments and improvements of the method specified in claim 1 are possible through the measures listed in the further claims.
  • the sensor element is heated with a pump voltage applied to the pump cell to a temperature significantly above the later operating temperature and exposed to a highly concentrated precursor gas with a defined concentration of the gas component, preferably oxygen, until a limit current is passed through the pump cell for the set concentration of the gas component, preferably the oxygen, flows.
  • a limit current is passed through the pump cell for the set concentration of the gas component, preferably the oxygen, flows.
  • the pump voltage When the pump voltage is applied, a pump current flows in the pump cell that reaches saturation, the so-called limit current.
  • the process is terminated, with which the sensor element is calibrated, i.e. its diffusion barrier has the required diffusion resistance, and the probe thus has the required sensitivity to different concentrations of Sensing gas component, preferably oxygen, in the gas mixture with high precision.
  • the heating of the sensor element to the high temperature is achieved by applying an overvoltage above its operating voltage to an electrical resistance heater usually present in the sensor element. This allows the temperature required for the oxidation process to be obtained in a simple manner.
  • a sensor element produced by the method according to the invention is the subject of claim 10.
  • Advantageous embodiments of the sensor element according to the invention can be found in claims 11 to 13.
  • the drawing shows a schematic section of a longitudinal section of a sensor element exposed to a precursor gas for a broadband lambda probe.
  • the sensor element for a broadband lambda probe for measuring the oxygen concentration in the exhaust gas from internal combustion engines which is shown schematically in longitudinal section in the figure, is known per se and is described, for example, in DE 199 41 051 A1 in terms of structure and mode of operation. It has a plurality of oxygen ion conductive
  • Solid electrolyte layers 11 which are designed as ceramic films and laminated together. Two gas spaces are formed in the sensor element, namely a measuring gas space 12 and one Reference gas channel 13, which in the same
  • Solid electrolyte layer 11b arranged and separated from each other by a gas-tight partition 14.
  • a reference gas atmosphere e.g. Air
  • the measuring gas chamber 12 which has a circular shape, is connected to the exhaust gas via a gas access hole 16, which perpendicularly penetrates the solid electrolyte layer 11a.
  • an annular measuring electrode 17 is printed on the solid electrolyte layer 11c, which together with the reference electrode 15 forms a Nernst or concentration cell.
  • the measuring electrode 17 is arranged opposite an inner, also circular pump electrode 18 on the solid electrolyte layer 11a, which together with an outer, on the solid electrolyte layer 11a applied, circular, outer Pumpele trode 19 forms a pump cell.
  • the outer pump electrode 19 is covered by a porous protective layer 20.
  • a porous diffusion chamber 21 is arranged between the end region of the gas access hole 16 and the measurement gas space 12.
  • the porous diffusion camera 21 forms a diffusion resistance with respect to the exhaust gas diffusing into the measurement gas space 12 to the electrodes 17, 18.
  • the diffusion camera 21 consists, for example, of zirconium oxide (Zr0 2 ) or aluminum oxide (A1 2 0 3 ), which is applied, for example, to the solid electrolyte layer 11b using the screen printing method.
  • so-called pore formers for example thermal soot powder, which burns out during the sintering process, and / or evaporating components, such as, for example, theobromine or ammonium carbonate, are present in the Zr0 2 or A1 2 0 3 . and / or thermally decomposable components are added.
  • All electrodes 15, 17, 18, 19 consist of a catalytically active material, for example platinum, the electrode material being used as cermit in order to sinter with the ceramic films of the solid electrolyte layers 11.
  • All electrodes 15, 17, 18, 19 are contacted with a conductor track, of which only the conductor track 22 which is applied to the surface of the solid electrolyte layer 11a and leads to the outer pump electrode 19 can be seen. Between the solid electrolyte layers 11c and lld is one
  • Resistance heater 23 arranged, which is embedded in an electrical insulation 24, which consists for example of aluminum oxide (A1 2 0 3 ).
  • the sensor element is heated to the corresponding operating temperature of, for example, 750 ° C. by means of the resistance heater 23.
  • the layer thickness of the porous is used in the manufacture of the sensor element
  • Diffusion barrier 21 which is printed on the solid electrolyte layer 11c, dimensioned such that the diffusion barrier 21 has a diffusion resistance value that is smaller than a specified value, provided that all manufacturing tolerances are observed.
  • a material input is introduced into the diffusion barrier 21 on the finished, sintered sensor element by means of a precursor gas by sublimation, as a result of which the diffusion resistance of the diffusion barrier 21 increases.
  • the material input is dimensioned so that the diffusion resistance exactly reaches the specified value.
  • the sensor element is exposed in a closed chamber 25 to a precursor gas with a defined concentration.
  • a pump voltage is applied to the pump cell, that is to say between its pump electrodes 16, 19, and the one flowing across the pump cell
  • the sensor element is heated to a very high temperature of, for example, 1000-1200 ° C., which is significantly higher than the later operating temperature of the sensor element, which is, for example, 750 ° C.
  • This heating of the sensor element is brought about in that an overvoltage is applied to the resistance heater 23, which is substantially above the normal operating voltage of the resistance heater 23, for example 13 V.
  • Zirconium chloride (ZrCl 4 ), for example, is used as the precursor gas.
  • the precursor gas m penetrates the diffusion camera 21 (symbolized in the drawing by the arrows 26), the metal zirconium precipitating through the sublimation process reaching the hot structural surfaces inside the diffusion camera 21 and here oxidized.
  • the zirconium oxide (Zr0 2 ) that forms is deposited in layers on the structure, as a result of which the pores in the porous structure are increasingly reduced in size.
  • the limit current flowing in the pump cell is determined by pumping the oxygen out of the measuring gas chamber 12. The process must be carried out in a quasi-stationary manner, since the limit current decreases due to the oxygen requirement of the zirconium oxidation.
  • the calibration process is terminated by removing the sensor element from the chamber 25.
  • the sensor element thus calibrated is subjected to a post-sintering process at temperatures greater than 1200 ° C. in order to achieve the desired one Stabilize the crystal structure of the introduced Zr0 2 .
  • the sensor element thus calibrated has a diffusion resistance due to the material input introduced by sublimation of a precursor gas, which is within very narrow tolerance limits of, for example, ⁇ 2% around the default value, so that the broadband lambda probe has the required measuring accuracy.
  • the sensor element described is not based on a planar broadband lambda probe
  • Oxygen concentration in the exhaust gas from internal combustion engines limited. It can also be used with other gas probes with which the concentration of any gas component in a gas mixture is to be determined.

Landscapes

  • 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)
  • Pathology (AREA)
  • Measuring Oxygen Concentration In Cells (AREA)

Abstract

L'invention concerne un procédé permettant d'étalonner un élément de détection conçu pour une sonde de courant limite, en particulier pour une sonde lambda plane à large bande, qui est pourvue d'une cellule de pompage comportant deux électrodes de pompage (18, 19), une électrode de pompage interne (18) étant protégée au moyen d'une barrière de diffusion poreuse (21). Pour ajuster la résistance de diffusion de cette barrière de diffusion (21) avec un degré de précision élevé, de façon qu'elle atteigne une valeur prédéfinie, l'épaisseur de la barrière de diffusion (21) est dimensionnée lors de la production de l'élément de détection, de sorte que cette barrière de diffusion (21) présente une valeur de résistance de diffusion inférieure à la valeur prédéfinie et que les tolérances de production soient respectées. Un matériau destiné à accroître la résistance de diffusion pour qu'elle atteigne la valeur prédéfinie est intégré, par sublimation au moyen d'un gaz précurseur, dans la barrière de diffusion (21) de l'élément de détection produit.
EP03735294A 2002-05-31 2003-05-12 Procede permettant d'etalonner un element de detection con u pour une sonde de courant limite Withdrawn EP1514099A1 (fr)

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
DE2002124055 DE10224055B4 (de) 2002-05-31 2002-05-31 Verfahren zum Kalibrieren eines Sensorelements für eine Grenzstromsonde
DE10224055 2002-05-31
PCT/DE2003/001519 WO2003102570A1 (fr) 2002-05-31 2003-05-12 Procede permettant d'etalonner un element de detection conçu pour une sonde de courant limite

Publications (1)

Publication Number Publication Date
EP1514099A1 true EP1514099A1 (fr) 2005-03-16

Family

ID=29557406

Family Applications (1)

Application Number Title Priority Date Filing Date
EP03735294A Withdrawn EP1514099A1 (fr) 2002-05-31 2003-05-12 Procede permettant d'etalonner un element de detection con u pour une sonde de courant limite

Country Status (4)

Country Link
EP (1) EP1514099A1 (fr)
JP (1) JP2005528608A (fr)
DE (1) DE10224055B4 (fr)
WO (1) WO2003102570A1 (fr)

Families Citing this family (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE102004029375A1 (de) * 2004-06-17 2006-01-05 Robert Bosch Gmbh Verfahren zum Kalibrieren eines Sensorelements für eine Grenzstromsonde
DE102009055421A1 (de) * 2009-12-30 2011-07-07 Robert Bosch GmbH, 70469 Sensorelement mit verbessertem Gaszutritt
CN113155899A (zh) * 2021-02-22 2021-07-23 厦门海赛米克新材料科技有限公司 一种保护性强的家电用空燃比传感器及其制备方法

Family Cites Families (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE3841611A1 (de) * 1988-12-10 1990-06-13 Bosch Gmbh Robert Sensorelement fuer grenzstromsensoren zur bestimmung des (lambda)-wertes von gasgemischen
DE19817012A1 (de) * 1997-05-28 1998-12-03 Bosch Gmbh Robert Sensorelement für Grenzstromsonden zur Bestimmung des Lambda-Wertes von Gasgemischen und Verfahren zu dessen Kalibrierung
DE19836127A1 (de) * 1998-08-10 2000-02-24 Siemens Ag Verfahren und Vorrichtung zum Kalibrieren eines Sondensystems, bestehend aus einer Abgassonde und einer Regelschaltung für ein Kraftfahrzeug

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
See references of WO03102570A1 *

Also Published As

Publication number Publication date
DE10224055B4 (de) 2007-12-27
DE10224055A1 (de) 2003-12-18
JP2005528608A (ja) 2005-09-22
WO2003102570A1 (fr) 2003-12-11

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