EP0700518A1 - Procede et dispositif de detection de materiaux oxydables dans un espace - Google Patents

Procede et dispositif de detection de materiaux oxydables dans un espace

Info

Publication number
EP0700518A1
EP0700518A1 EP94916469A EP94916469A EP0700518A1 EP 0700518 A1 EP0700518 A1 EP 0700518A1 EP 94916469 A EP94916469 A EP 94916469A EP 94916469 A EP94916469 A EP 94916469A EP 0700518 A1 EP0700518 A1 EP 0700518A1
Authority
EP
European Patent Office
Prior art keywords
exhaust gas
sensor
gas outlet
voltage
sensors
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Withdrawn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
EP94916469A
Other languages
German (de)
English (en)
Inventor
Magnus Lindblad
Edward Jobson
Mikael Larsson
Sören ERIKSSON
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.)
Volvo AB
Original Assignee
Volvo AB
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 Volvo AB filed Critical Volvo AB
Publication of EP0700518A1 publication Critical patent/EP0700518A1/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Withdrawn legal-status Critical Current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
    • G01N27/02—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance
    • G01N27/04—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance by investigating resistance
    • G01N27/14—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance by investigating resistance of an electrically-heated body in dependence upon change of temperature
    • G01N27/16—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance by investigating resistance of an electrically-heated body in dependence upon change of temperature caused by burning or catalytic oxidation of surrounding material to be tested, e.g. of gas

Definitions

  • the present invention relates to a method for detection of oxidizable materials in accordance with the subsequent claim 1.
  • the present invention also relates to a device for detec ⁇ tion of oxidizable materials in accordance with the subsequent claim 5.
  • pellistors It is known from GB-A-2 185 579 to detect combustible gaseous hydrocarbons by means of a measuring bridge which comprises pellistors.
  • a pellistor is a resistor with a temperature-dependent resistance of a special kind, which is described below in greater detail.
  • the design of pellistors is described in greater detail in GB 2 044 937, for example.
  • pellistors have in common that they have been utilized within areas where there is a desire to detect the presence of certain harmful substances, due to the risk for explosions, such as hydrocarbons in mines, ships etc., without striving for any indication of a directly readable measured value, such as the percentage or ppm rate of a certain substance.
  • the object of the present invention is to achieve a method and a device which may be applied within new fields of application.
  • Fig. 1 schematically shows an example of an exhaust gas sensor in the form of a pellistor
  • Fig. 2 shows schematically an example of a detection device according to the invention
  • FIG. 3 shows schematically a system for diagnosis of a catalytic converter
  • Fig. 4 shows an exhaust gas sensor according to an alter ⁇ native embodiment
  • Fig. 5 is a side view of the exhaust gas sensor according to Figure 4.
  • the name pellistor is derived from "a pellet- shaped resistor".
  • the pellistor is an element of electrical resistance in the shape of a platinum wire 2 of small dimensions, for example with a diameter of 50 ⁇ , which is dipped in aluminium oxide and inserted in a sleeve 3 in the form of a catalyst, which for example is based on palladium, platinum, nickel or rhodium.
  • the ends 4, 5 of the platinum wire protrude from the sleeve and form the pellistor's two connections to other components in the measuring device.
  • a maximum ratio between the area and the volume has been sought.
  • this has been achieved by forming the sleeve 3 from a thin film, wherein resistance wires with a surrounding sleeve are formed as a cylinder, which is straight or, for example, bent like a U. With a U- shaped sleeve, one of the sides may be exposed to air and the other side to the gas to be measured.
  • the pellistor is a kind of resistor with a temperature- dependent resistance which also develops heat with a relatively high temperature, for example 500-600°C, when a voltage is applied across the pellistor.
  • the detection device is designed as a measuring bridge which, in the shown example, is a Wheatstone bridge with a first branch in which a first exhaust gas sensor in the form of the pellistor described above is connected. In the follo ⁇ wing, this is referred to as the active pellistor D.
  • a second exhaust gas sensor in the form of a second pellistor R is connected, which lacks the above described catalytic sleeve and thus forms a non-active reference pellistor which is intended to compensate for certain environmental factors such as temperature, pressu ⁇ re, flow, humidity etc.
  • the resistance elements of the exhaust gas sensors R, D do not necessarily have to be pellet-shaped, but other geometric shapes are also possible.
  • a voltage measuring device 16 which, for example, comprises a signal amplifier for amplification of the voltage signal from the Wheatstone bridge by, for example, a magnitude of 10.
  • the detection device and in particular the two pellistors, are placed in a space with oxidizable materials at the same time as the voltage source 11 is connected so that the temperature in the sleeve 3 of the sensor pellis ⁇ tor rises to a value which causes oxidazable materials to burn on the surface, the resistance of the sensor pellistor will increase. This will result in a non-balance in the measuring bridge so that a voltage arises between the point 14 and 15, which may be read directly from the voltage measuring device 16 in the form of a measured value, or may after signal treatment indicate the presence and also the content of oxidizable materials.
  • the detection device is especially intended for measuring the operating conditions of combustion engines.
  • One example of such a detection is the detection of the combustion of the fuel, which can be utilized for laboratory tests as well as for a continous supervision of the operation.
  • the detection device may be comprised in an automatic control ⁇ ling system for adjustment of parameters which influence the combustion conditions so that an optimal combustion may be obtained, for example controlling the fuel injection or the timing of the ignition.
  • the detection device is arranged with at least one pair of pellistors, i.e. both the active pellistor and the reference pellistor, in the outlet of the combustion chambers, immediately after these or further away in the exhaust system.
  • the detection device may also detect the function of a catalytic converter in the exhaust outlet of a combustion engine.
  • the detection device may be placed after the catalytic converter in order to analyze the exhaust gases and more precisely the presence or the content of non-burnt oxidizable materials, or for determi ⁇ ning the conversion ratio of the catalytic converter, i.e. the coefficient of efficiency of the catalytic converter.
  • a twin system with two pairs of pellistors is used, one pair being arranged before the catalytic converter and one after the catalytic converter.
  • double measuring bridges double output signals are obtained, which are compared and signal-treated in a signal treatment system.
  • FIG 3 there is schematically shown a system for diagnosis of a catalytic converter 17, which comprises an exhaust gas sensor 18 which comprises a first, active pellistor D and a second pellistor R (see also Figure 2) .
  • the exhaust gas sensor 18, which is arranged upstream in relation to the catalytic converter 17, is part of a measuring bridge in accordance with the above-mentioned.
  • the measuring bridge comprises a voltage measuring device 16 which is connected to a computer-based control unit 19, which is adapted to register the values of the voltage in the measuring bridge being measured by the voltage easu- ring device 16.
  • an additio ⁇ nal exhaust gas sensor 20 in the form of a second pair of pellistors (which comprises two pellistors, analogous to what has been mentioned above) arranged downstream of the catalytic converter 17.
  • the second exhaust gas sensor 20 is connected to the control unit 19 via a second voltage measuring device 21.
  • the values being measured in the voltage measuring devices 16 and 21 of the voltage non-balance in the two respective measuring bridges in which the exhaust gas sensors 18, 20 are a part are delivered to the control unit 19. There ⁇ after, in the control unit 19 a conversion of the measured voltage values to measures of the concentration of CO and HC compounds in the exhaust gases occurs. This conversion takes place through the fact that CO and HC compounds react with oxygen on the catalytic surfaces of the exhaust gas sensors 18, 20. These reactions generate heat which increases the temperature of said catalytic surfaces. The higher the concentration of combustible material, the greater the heat generation will take place, provided that there is a sufficient amount of oxygen. The increase of temperature provides an increased resistance in the measuring device, which results in a voltage difference being measured in the voltage measuring devices 16, 21, respectively.
  • the voltage may be measured for known gas mixtures, after which a relationship between this increase of the temperature and the concentration of CO of HC compounds is calculated. This relationship, which has proven to be substantially linear over a very large temperature range, may then be employed when determining the concentration of CO and HC compounds in a certain exhaust gas mixture.
  • the value of the coefficient of efficiency 77 is then used for indicating whether the catalytic converter is not operating or has a reduced capacity for purifying the exhaust gases. On the other hand, it is also important to be able to determine that the catalytic converter 17 is not defective if the vehicle for some other reason has too high emissions.
  • only one exhaust gas sensor 20 (in the form of just one pair of pellistors) may be utilized, arranged downstream of the catalytic con ⁇ verter 17.
  • the emissions and thus also the coefficient of efficiency of the catalyst may be determined for every given condition of operation (i.e. the relationship between load and engine speed) by comparing a measured value and a stored value corresponding to the emissions from a normal engine.
  • the values of the CO and HC compounds which have been calculated according to that mentioned above, may be utilized in a feedback loop in order to minimize the emissions after the catalytic converter.
  • the measured values which are delivered from the exhaust gas sensor may, for example, be used to increase or decrease the amount of injected fuel, adjust the ignition point or change the amount of EGR (Exhaust gas recir- culation) .
  • the values which have been measured by the voltage measu ⁇ ring devices 16, 21 may also be used in order to determine a value of the temperature of the exhaust gases.
  • a value of the exhaust gas temperature is derived from the resistance of one of the resistor elements of the exhaust gas sensor.
  • the value of the exhaust gas temperature is utilized for protecting the exhaust system (in particular the catalytic converter) from being overheated.
  • the delivery of fuel and the ignition may be controlled so that one gets closer to the limit of the allowable temperature but without risking that the tempera ⁇ ture becomes too high. This will lead to a decreased fuel comsumption (for certain driving conditions) .
  • the exhaust gas temperature may be used for an auxiliary control of the efficiency of the catalytic converter.
  • the exhaust gas temperature may be used for determining the light-off temperature of a specific catalytic converter.
  • the signal from the exhaust gas sensor may be analyzed during a starting procedure for detecting at what point of time the catalytic converter will ignite (the so called "light-off time”) .
  • the detection device may also be used for detecting and analyzing the vapour pressure of the fuel directly in the fuel tank, in which a pair of pellistors detects the quantity of hydro- carbons above the liquid surface of a liquid fuel in the tank. Due to the fact that the fuel in the gaseous phase in the tank has an excess of combustible materials at "normal" temperatures, the amount of oxygen in the tank is in reality detected.
  • the vapour pressure may then be cal ⁇ culated from this.
  • the measurement takes place immediately before a cold start, possibly with a warm start when stability has commenced, i.e. a stability in the tank due to a communication with the atmosphere. With stable conditions, the outside temperature is also measured in order to create a reference and a correction factor.
  • the device When arranging the pellistor pair of the detection device in the exhaust gas outlet of a combustion engine, the device may be used for detecting incorrect ignition by analyzing the combustion heat. Furthermore, transient emissions may be characterized by examining the output signal of the detection device. In this regard, the amount of non-burnt materials in the emissions may be analyzed at varying engine speeds, particularly during acceleration and retardation.
  • the exhaust gas flow does not have too rich a mixture, which is a result of too rich a fuel/air mixture.
  • the pellistors may be arranged in a by-pass flow where there is added air in order to make the mixture leaner.
  • a voltage may be applied over a ceramic carrier (ion pump) which on one of its sides has access to the atmosphere and on its other side has access to the gas environment being analyzed.
  • FIG 4 there is shown an embodiment of an exhaust gas sensor 22 which delivers oxygen to the exhaust gases.
  • the exhaust gas sensor 22 comprises an essentially box-shaped sensor body 23 which is formed by an ion-conducting ceramic substance, preferably Zr0 2 .
  • a first active electrode 25 which is preferably formed by a platinum conductor pattern.
  • the sensor 22 also comprises a reference electrode 26, which likewise comprises a conducting platinum pattern.
  • the electrodes 25 and 26, respectively, correspond to the pellistor pair D and R, respectively, which have been described above with reference to Figure 2.
  • the sensor 22 also comprises a third electrode 27 which is arranged on the underside of the cover 24 and which is composed of a metal which allows dissociation of oxygen, e.g. nickel or platinum.
  • the third electrode 27 is arranged so that it is in contact with the surrounding air.
  • a current is directed from the first, active electrode 25 on the exhaust gas side to the third electrode 27.
  • the oxygen will react with excess hydrocar ⁇ bons and carbon monoxide.
  • a proper measu ⁇ ring signal is also obtained from the exhaust gas sensor also "rich" exhaust gases, i.e. exhaust gases having an oxygen deficit.
  • the reading of the exhaust gas sensor 22 thus becomes independent of the oxygen content of the exhaust gases.
  • the exhaust gas sensor 22 does not have to be arranged in a by-pass flow, but may also be arranged in connection with the exhaust gas outlet itself.
  • excess of oxygen may be provided by adding oxygen only, or alternatively some oxygen-containing gas such as for example air.
  • Non-burned remains in the exhaust system of a combustion engine may be formed by a plurality of substances.
  • materials with different ignition temperature may be selected by giving the sensor pellistor different operating voltages, and thereby different temperatures created by the resistance. This may be solved either by providing twin detection devices with different operating voltages, or by operating one single detection device in different modes or intervals with separate voltage levels for the different time intervals, with an analysis which in a corresponding way is time-divided in connection with the signal treat ⁇ ment.
  • the measuring bridge may be designed with another circuit solution.
  • the fixed resistor 8 as well as the potentiometer 12, for example, may be omitted.

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  • Chemical & Material Sciences (AREA)
  • General Health & Medical Sciences (AREA)
  • General Physics & Mathematics (AREA)
  • Physics & Mathematics (AREA)
  • Health & Medical Sciences (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Analytical Chemistry (AREA)
  • Electrochemistry (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Biochemistry (AREA)
  • Immunology (AREA)
  • Pathology (AREA)
  • Combined Controls Of Internal Combustion Engines (AREA)
  • Investigating Or Analyzing Materials By The Use Of Electric Means (AREA)
  • Investigating Or Analyzing Materials Using Thermal Means (AREA)
  • Exhaust Gas After Treatment (AREA)

Abstract

Procédé et dispositif de détection de matériaux oxydables dans l'orifice de sortie des gaz d'échappement d'un moteur à combustion, à l'aide d'un dispositif de mesure comprenant au moins un pont de mesure pourvu d'au moins deux capteurs (D, R) qui sont placés dans ledit orifice de sortie, le pont de mesure étant exposé à une tension électrique de fonctionnement. On transforme un des capteurs en capteur actif (D) en brûlant lesdits matériaux oxydables sur sa surface chauffée par la résistance, ce qui augmente sa résistance dépendant de la température, alors qu'on utilise l'autre capteur (R) comme référence en modifiant la résistance de manière analogue au capteur actif en fonction de paramètres environnants analogues sans en augmenter la température par la présence de matières combustibles. On détecte les matériaux oxydables en mesurant des variations de tension dans le pont de mesure. Selon l'invention, un flux d'air peut être amené à l'orifice des gaz d'échappement en amont de la position du capteur actif (D).
EP94916469A 1993-05-19 1994-05-19 Procede et dispositif de detection de materiaux oxydables dans un espace Withdrawn EP0700518A1 (fr)

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
SE9301715 1993-05-19
SE9301715A SE510091C2 (sv) 1993-05-19 1993-05-19 Förfarande och anordning för detektering av oxiderbara ämnen i ett avgasutlopp
PCT/SE1994/000468 WO1994027139A1 (fr) 1993-05-19 1994-05-19 Procede et dispositif de detection de materiaux oxydables dans un espace

Publications (1)

Publication Number Publication Date
EP0700518A1 true EP0700518A1 (fr) 1996-03-13

Family

ID=20389989

Family Applications (1)

Application Number Title Priority Date Filing Date
EP94916469A Withdrawn EP0700518A1 (fr) 1993-05-19 1994-05-19 Procede et dispositif de detection de materiaux oxydables dans un espace

Country Status (4)

Country Link
EP (1) EP0700518A1 (fr)
JP (1) JPH09500959A (fr)
SE (1) SE510091C2 (fr)
WO (1) WO1994027139A1 (fr)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP2641837A1 (fr) 2012-03-20 2013-09-25 Sociedad Anónima Minera Catalano-Aragonesa Récipient multicouche opaque

Families Citing this family (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
SE503265C2 (sv) * 1994-09-23 1996-04-29 Forskarpatent Ab Förfarande och anordning för gasdetektion
SE515412C2 (sv) * 1995-10-25 2001-07-30 Appliedsensor Sweden Ab Sensor med katalytisk yta för detektering av oförbrända kolväten
DE19610912A1 (de) * 1996-03-20 1997-09-25 Dittrich Elektronik J Pellistor
FR2757213B1 (fr) * 1996-12-13 1999-02-12 Renault Procede et dispositif permettant de determiner la richesse du melange carbure d'un moteur
DE102005022471B4 (de) * 2005-05-14 2007-06-28 Dräger Safety AG & Co. KGaA Schaltungsanordnung mit mindestens einem als Pellistor ausgebildeten katalytischen Messelement
DE102006033110A1 (de) * 2006-07-18 2008-01-24 Volkswagen Ag Sensor und Verfahren zur Messung eines Gehaltes von Kohlenwasserstoffen in einer Gasatmosphäre

Family Cites Families (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
AT266496B (de) * 1963-09-12 1968-11-25 Bosch Gmbh Robert Meßkopf für elektrische Meßgeräte zur Abgasprüfung an Brennkraftmaschinen
GB2091882B (en) * 1981-01-26 1985-05-01 Nat Res Dev Electrical catalytic gas detection systems
DK172281A (da) * 1981-04-15 1982-10-16 O Johannsen Apparat til analyse af forbraendingsgas
DE69208401T2 (de) * 1991-06-28 1996-07-04 Ford Werke Ag Verfahren und Vorrichtung zum Feststellen von Katalysator-Funktionsstörungen
WO1993007477A1 (fr) * 1991-09-30 1993-04-15 Siemens Aktiengesellschaft Detecteur de gaz d'echappement en technologie planaire pour le reglage de moteurs de vehicules automobiles

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
See references of WO9427139A1 *

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP2641837A1 (fr) 2012-03-20 2013-09-25 Sociedad Anónima Minera Catalano-Aragonesa Récipient multicouche opaque

Also Published As

Publication number Publication date
WO1994027139A1 (fr) 1994-11-24
JPH09500959A (ja) 1997-01-28
SE9301715L (sv) 1994-11-20
SE510091C2 (sv) 1999-04-19
SE9301715D0 (sv) 1993-05-19

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