WO2014206662A1 - Capteur de détermination de la teneur d'un composant gazeux - Google Patents

Capteur de détermination de la teneur d'un composant gazeux Download PDF

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Publication number
WO2014206662A1
WO2014206662A1 PCT/EP2014/060760 EP2014060760W WO2014206662A1 WO 2014206662 A1 WO2014206662 A1 WO 2014206662A1 EP 2014060760 W EP2014060760 W EP 2014060760W WO 2014206662 A1 WO2014206662 A1 WO 2014206662A1
Authority
WO
WIPO (PCT)
Prior art keywords
sensor
gas
wall thickness
tube
inner tube
Prior art date
Application number
PCT/EP2014/060760
Other languages
German (de)
English (en)
Inventor
Marc Rosenland
Klaus-Peter Kugler
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 WO2014206662A1 publication Critical patent/WO2014206662A1/fr

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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
    • G01N27/4077—Means for protecting the electrolyte or the electrodes

Definitions

  • Devices are referred to as sensors, probes, probes, probes or similar term.
  • Gas mixture may be a concentration, a partial pressure, a volume or a further quantitative and / or qualitative variable that is suitable for this purpose.
  • gas is used in particular an exhaust gas of an internal combustion engine, preferably from the motor vehicle sector, wherein the gas flow moves in the exhaust line of an internal combustion engine.
  • a sensor comprises at least one sensor element, which with gas from the
  • Lambda probes are preferably in the exhaust system of
  • Lambda probes in particular universal lambda probes, balance two streams of material, preferably oxygen streams, between a cavity of the device and the gas stream.
  • One of the streams is here by concentration differences over a
  • the pumping current is preferably regulated in such a way that a constant, very low oxygen concentration is established in the cavity.
  • a concentration profile across the diffusion barrier is uniquely determined by a constant control point in the cavity, in particular by a constant setpoint voltage resulting in an oxygen concentration, and by an exhaust gas oxygen concentration.
  • An influx of oxygen molecules the gas flow to the cavity adjusts according to this unique concentration profile and corresponds to the regulated pumping current.
  • the pumping current serves as a measured value for the oxygen concentration in the gas stream, in particular for the exhaust gas applied oxygen concentration.
  • Lambda probes have, in particular at their exhaust-gas-side tip, so-called protective tubes, which project into the exhaust gas flow.
  • These protective tubes are usually configured substantially tubular and surround a housing in which the sensor element, preferably fixed by means of a sealing arrangement, is introduced.
  • Both the sensor element and the housing can have a great variety of shapes.
  • the housing may be constructed in one or more parts and, for example, have contours that allow positioning of the sensor element within a certain range in the housing.
  • the sensor element itself can also be designed in one or more parts.
  • the sensor is preferably positioned in the gas flow in such a way that it is arranged perpendicular to the gas flow in its longitudinal extent. Via inlet openings and outlet openings in the protective tubes, gas from the gas flow can flow around the sensor element.
  • the protective tube can be made in one piece, in two parts or in several parts.
  • DE 43 18 107 A1 describes a gas sensor which has a single-walled protective tube to protect the sensor element.
  • the protective tube has at least one opening for the entry of gas from the gas stream.
  • DE 199 24 319 A1 discloses a gas sensor which has a protective tube in two-part design with an inner tube and an outer tube surrounding the inner tube to protect a ceramic sensor element.
  • the inner tube has openings for the entry and exit of gas from the gas flow and is adapted to protect the ceramic sensor element from direct contact with the gas and / or possibly from forming exhaust gas condensate.
  • a lambda sensor only delivers from one
  • a reliable measurement signal while also referred to as the nominal temperature operating temperature of the lambda probe is typically in the range between 650 ° C and 850 ' ⁇ .
  • the sensor In order to achieve the nominal temperature as independent as possible from the ambient conditions in as short a time as possible, the sensor is electrically heated. To be as early as possible in this way To respond to the sensor and thus the earliest possible occurrence of usable measurement signals, a rapid heating of the sensor is required, in particular already in the warm-up phase of the internal combustion engine. During the warm-up phase, combustion in an internal combustion engine usually produces water vapor which condenses on the still cold surfaces of the exhaust gas line. Even in the case of a probe at operating temperature, this can be found in the
  • Exhaust gas condensate contained in the exhaust gas is a hazard. Meets a raised in the gas flow condensate drops on the hot ceramic sensor element, so local temperature differences occur, which can lead to high thermally induced voltages in the sensor, causing damage or destruction of the probe. This phenomenon is also called "thermal shock”.
  • a coating in particular of a woven or non-woven fabric, for thermal insulation and / or for the bonding of liquid to the at least to provide a protective tube. It is particularly advantageous in this case if the coating for thermal insulation of a ceramic, which preferably contains zirconium oxide is prepared.
  • dew-point temperature is understood to mean the temperature at which the so-called dew-point end is reached, ie. There is no liquid water in the exhaust line in the flow direction of the exhaust gas in front of the lambda probe. It is advantageous to take the time for reaching the condition of the dew point end as accurately as possible, so as to
  • Liquids is required, determined primarily by the thermally relevant size of all components in the exhaust system.
  • the disadvantage of the dew-point rating, however, is that within this time no regulation of the oxygen content in the
  • the object of the present invention is therefore to overcome the limitations and disadvantages of sensors known from the prior art for determining a proportion of a gas component in a gas mixture in a gas stream.
  • Gas component of a gas mixture in a gas stream in particular an exhaust gas of an internal combustion engine, proposed, which comprises at least one sensor element, which is acted upon with gas from the gas stream.
  • the sensor element may be a lambda probe having at least one cell, preferably one or two cells.
  • the sensor element is surrounded by a protective tube which projects into the gas flow.
  • the protective tube is in this case made in two parts and each has a separate inner tube and, surrounding the inner tube, separate outer tube.
  • the inner tube and the outer tube are arranged relative to each other and so separated from each other that they are preferably at least partially as a measuring gas space
  • At least one inlet opening for gas from the gas stream into the intermediate space and at least one outlet opening for gas from the intermediate space are provided.
  • an inner tube which has a first average wall thickness
  • an outer tube which has a second average wall thickness, wherein the first average wall thickness of the inner tube is less than the second average wall thickness of the inner tube.
  • Wall thickness of the inner tube has a value which is in a range of at least 0.5 times, preferably at least 0.7 times, more preferably at least 0.75 times, and at most 0.95 times, preferably at most 0.9 times, more preferably at most 0.85 times, in particular 0.8 times, the second average wall thickness of the outer tube corresponds, wherein the first middle
  • Wall thickness of the inner tube is always less than the second average wall thickness of the Au .rohrs.
  • From the wall thickness of a pipe can be at a known radius and known length of the pipe to determine the associated volume of the tube. Since the material from which the tube is formed is also known, its specific gravity is also known, from which the mass of the tube can be determined from the known volume of the tube and the known specific density. Since the specific heat capacity of the material used is known, the heat capacity of the pipe in question can be determined in this way.
  • the heat capacity of a body which is also referred to as thermal mass, includes that thermal energy, which the body with respect to a
  • Temperature change is able to absorb.
  • the higher the heat capacity of the body the more thermal energy is required to heat the body to a certain predetermined temperature. Therefore, in order to heat a body by means of the lowest possible thermal energy, it is necessary to equip it with the lowest possible heat capacity, the heat capacity of the body is given by the product of the mass of the body with its specific heat capacity. This requirement is met according to the invention by a reduction in the mass or volume of the body, since the mass of the body is related to its volume via the specific gravity of the body.
  • a material is therefore selected for the inner tube and the outer tube, which has the same specific heat capacity, in particular the same material.
  • the heat capacity of the inner tube assumes a lower value as the heat capacity of the outer tube.
  • the inner tube and the outer tube at least in each case on their surfaces a high temperature resistant alloy, in particular the same high temperature resistant alloy, wherein both the inner tube and the outer tube preferably each completely from the
  • the inner tube is arranged around the sensor element in such a way that it is completely enclosed by the outer tube is. This arrangement causes the inner tube itself does not protrude directly into the gas stream, but only on the acted upon with gas from the gas stream
  • the Au trohr is designed such that it is closed at the side facing the gas flow.
  • the outer tube in particular on the gas flow side facing a cover, in particular in the form of a cap, which projects into the gas flow.
  • the sensor element preferably at a side facing the gas flow within the inner tube, wherein the closed configuration of the Au zrohrs here in particular the protection of the sensor element from the heat from the gas stream is used. In this way, the life of the sensor element and thus the entire probe is extended.
  • the sensor element has at least one pump cell with an outer electrode, with an inner electrode and with a solid electrolyte connecting the outer electrode and the inner electrode.
  • the outer electrode with gas from the
  • Electrode cavity is arranged, which is acted upon via a diffusion barrier with gas from the intermediate space.
  • a fixed voltage is applied between the outer electrode and the inner electrode.
  • Oxygen concentration in the electrode cavity is close to zero, a potential, in particular a Nernst potential, increases sharply and partially compensates for the applied voltage. As a result, in this lambda probe with a cell with good accuracy, a constant oxygen concentration in the electrode cavity can be adjusted.
  • the sensor element further comprises at least one Nernst cell.
  • the Nernst cell comprises at least one Nernst electrode located in the electrode cavity, at least one reference electrode located in a reference gas space, and at least one solid electrolyte connecting the two electrodes, which may be at least partially the same solid electrolyte as in the pump cell.
  • the control takes place in such a way that the oxygen concentration in the cavity does not change significantly.
  • the advantage of the sensor according to the invention which has a protective tube in a two-part design with an inner tube and an outer tube, wherein the inner tube has a lower average wall thickness compared to the outer tube, is that the inner protective tube heat up faster compared to externa ßeren protective tube leaves. In this way, the nominal temperature of the lambda probe is reached earlier than in the prior art.
  • Figure 1 an embodiment of a sensor according to the invention in the form of a
  • FIG. 1 shows an exemplary embodiment of a sensor 10 according to the invention
  • the sensor 1 10 comprises a sensor element 1 14, which is surrounded by a protective tube which projects into the gas flow.
  • the protective tube has an inner tube 1 16 and an outer tube 1 18, wherein the inner tube 1 16 and the Au DTrohr 1 18 are arranged such that they form a loadable with the gas mixture 1 12 120 space.
  • the inner tube 1 16 is in this case arranged such that it is completely from the outer tube 1 18th
  • the outer tube 1 18 is designed to be closed at the side facing the gas flow 1 12 side 122 and has a cap 124, which projects into the gas stream 1 12.
  • the sensor element 1 14 is disposed on a side facing the gas flow 1 12 side 122 within the inner tube 1 16 and the closed design of the
  • Outer tube serves in particular to protect the sensor element 1 14 from the heat from the gas stream 1 12. Furthermore, inlet openings 126 are provided for gas from the gas stream 1 12 in the intermediate space 120 and outlet openings 128 for gas from the intermediate space 120.
  • the protective tube is connected to a housing 130, which serves to further protect the probe 1 10.
  • the inner tube 1 16 has a wall thickness of 0.4 mm, while the Au DTrohr 1 18 has a wall thickness of 0.5 mm.
  • the quotient of the wall thickness of the inner tube 1 16 divided by the wall thickness of the Au nchrohrs 1 18 assumes a value of 0.8. It has
  • the life of the sensor is particularly long.
  • the material for both the inner tube and the outer tube was Cr-Ni steel 1 .4845 or nickel-based alloy 2.4851.
  • the sensor 1 10 comprises a sensor element (not shown), which is surrounded by a protective tube in two-part design.
  • the protective tube protrudes into the gas flow 1 12 and has an outer tube 1 18 which completely encloses an inner tube (not shown).
  • the inner tube is separated from the outer tube by a gap (not shown).
  • the Au .rohr 1 18 is closed at the gas stream 1 12 facing side 122 designed and has at the, the Gas flow 1 12 side 122 facing a cap 124, which projects into the gas stream 1 12.
  • inlet openings 1 18 for gas from the gas stream 1 12 in the space (not shown) are provided.
  • the protective tube is also connected to a housing 130 here.

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 capteur (110) servant à déterminer la teneur d'un composant d'un mélange de gaz dans un flux de gaz (112). Le capteur comprend au moins un élément détecteur (114) auquel le gaz provenant du flux de gaz (112) est appliqué. L'élément détecteur (114) est entouré d'un tube protecteur qui plonge dans le flux de gaz (112). Le tube protecteur comporte un tube intérieur (116) et un tube extérieur (118), le tube intérieur (116) et le tube extérieur (118) étant disposés de manière à former un espace intermédiaire (120) dans lequel le mélange de gaz peut circuler. Selon l'invention, le tube intérieur (116) et le tube extérieur (118) sont configurés de telle façon que le tube intérieur (116) possède une première épaisseur de paroi moyenne et le tube extérieur (118) une deuxième épaisseur de paroi moyenne, la première épaisseur de paroi moyenne étant inférieure à la deuxième épaisseur de paroi moyenne. L'avantage du capteur (110) selon l'invention est qu'il permet de réduite la durée nécessaire avant que le retraitement catalytique des gaz d'échappement soit prêt à fonctionner. Une sonde lambda peut fonctionner plus tôt, ce qui permet notamment de réduire la proportion de gaz d'échappement nocifs, formés principalement lors du démarrage à froid des moteurs à combustion interne. En outre, le tube intérieur (116) est exposé à une contrainte thermique considérablement moindre, ce qui se traduit en particulier par une plus grande durée de vie du tube intérieur (116) et donc de l'ensemble du capteur (110).
PCT/EP2014/060760 2013-06-27 2014-05-26 Capteur de détermination de la teneur d'un composant gazeux WO2014206662A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
DE201310212362 DE102013212362A1 (de) 2013-06-27 2013-06-27 Sensor zur Bestimmung eines Anteils einer Gaskomponente
DE102013212362.0 2013-06-27

Publications (1)

Publication Number Publication Date
WO2014206662A1 true WO2014206662A1 (fr) 2014-12-31

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PCT/EP2014/060760 WO2014206662A1 (fr) 2013-06-27 2014-05-26 Capteur de détermination de la teneur d'un composant gazeux

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WO (1) WO2014206662A1 (fr)

Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE4318107A1 (de) 1993-06-01 1994-12-08 Bosch Gmbh Robert Meßfühleranordnung in einer Gasleitung
DE19924319A1 (de) 1999-05-27 2000-12-21 Bosch Gmbh Robert Gasmeßfühler
EP1471346A1 (fr) * 2003-03-31 2004-10-27 Ngk Insulators, Ltd. Capteur de gaz
DE102007030795A1 (de) 2006-07-19 2008-01-24 Robert Bosch Gmbh Gassensor
EP2388577A2 (fr) * 2010-05-18 2011-11-23 NGK Insulators, Ltd. Chapeau de protection d'un capteur de gaz
US20130126352A1 (en) * 2011-11-18 2013-05-23 Ngk Insulators, Ltd. Gas sensor

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE4318107A1 (de) 1993-06-01 1994-12-08 Bosch Gmbh Robert Meßfühleranordnung in einer Gasleitung
DE19924319A1 (de) 1999-05-27 2000-12-21 Bosch Gmbh Robert Gasmeßfühler
EP1471346A1 (fr) * 2003-03-31 2004-10-27 Ngk Insulators, Ltd. Capteur de gaz
DE102007030795A1 (de) 2006-07-19 2008-01-24 Robert Bosch Gmbh Gassensor
EP2388577A2 (fr) * 2010-05-18 2011-11-23 NGK Insulators, Ltd. Chapeau de protection d'un capteur de gaz
US20130126352A1 (en) * 2011-11-18 2013-05-23 Ngk Insulators, Ltd. Gas sensor

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
"Sensoren im Kraftfahrzeug", 2012, SPRINGER VIEWEG, pages: 160 - 165

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