WO2008080730A1 - Élément capteur avec fonction de diagnostic additionnelle - Google Patents

Élément capteur avec fonction de diagnostic additionnelle Download PDF

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Publication number
WO2008080730A1
WO2008080730A1 PCT/EP2007/063175 EP2007063175W WO2008080730A1 WO 2008080730 A1 WO2008080730 A1 WO 2008080730A1 EP 2007063175 W EP2007063175 W EP 2007063175W WO 2008080730 A1 WO2008080730 A1 WO 2008080730A1
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WIPO (PCT)
Prior art keywords
electrode
gas
gas space
resistance element
sensor element
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PCT/EP2007/063175
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German (de)
English (en)
Inventor
Detlef Heimann
Torsten Handler
Henrico Runge
Harald Guenschel
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Robert Bosch Gmbh
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Publication of WO2008080730A1 publication Critical patent/WO2008080730A1/fr

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    • 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
    • G01N27/4065—Circuit arrangements specially adapted therefor
    • 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
    • G01N27/4075—Composition or fabrication of the electrodes and coatings thereon, e.g. catalysts

Definitions

  • the invention is based on known sensor elements which are based on electrolytic properties of certain solids, ie the ability of these solids to conduct certain ions.
  • Such sensor elements are used in particular in motor vehicles to measure air-fuel-gas mixture compositions.
  • Such sensor elements are also known as "lambda probe" and play an essential role in the reduction of pollutants in exhaust gases, both in gasoline engines and in diesel technology.
  • Air ratio is measured by one or more sensor elements usually at one or more locations in the exhaust system of an internal combustion engine.
  • “rich” gas mixtures i.e., gas mixtures with a fuel surplus
  • “lean” gas mixtures i.e., gas mixtures with a fuel deficiency
  • Sensor elements in other areas of technology in particular combustion technology used, for example in aeronautical engineering or in the control of burners, z. B. in heating systems or power plants.
  • Such sensor elements are now known in numerous different embodiments.
  • One embodiment is the so-called "jump probe” whose measurement principle is based on the measurement of an electrochemical potential difference between a reference gas exposed reference electrode and a measuring gas exposed to the measured measuring electrode is based.
  • Reference electrode and measuring electrode are connected to one another via the solid electrolyte, wherein doped zirconium dioxide (eg yttrium-stabilized ZrO 2) or similar ceramics are generally used as the solid electrolyte due to its oxygen-ion-conducting properties.
  • Various exemplary embodiments of such jump probes which are also referred to as "Nernst cells” are described, for example, in DE 10 2004 035 826 A1, DE 199 38 416 A1 and DE 10 2005 027 225 A1.
  • pump cells are used in which an electrical “pump voltage” is applied to two electrodes connected via the solid electrolyte, the "pump current” being measured by the pump cell
  • both electrodes are connected to the gas mixture to be measured, whereby one of the two electrodes is exposed directly to the gas mixture to be measured (usually via a permeable protective layer) can not get directly to this electrode, but must first penetrate a so-called “diffusion barrier” to get into a cavity adjacent to this second electrode.
  • the diffusion barrier used is usually a porous ceramic structure with specifically adjustable pore radii.
  • the sensor elements are usually operated in the so-called limiting current operation, that is, in an operation in which the pumping voltage is selected such that the oxygen entering through the diffusion barrier is completely pumped to the counterelectrode.
  • the pumping current is approximately proportional to the partial pressure of the oxygen in the exhaust gas mixture, so that such sensor elements are often referred to as proportional sensors.
  • proportional sensors can be used as so-called broadband sensors over a comparatively wide range for the air ratio lambda.
  • the sensor principles described above are also combined, so that the sensor elements contain one or more sensors ("cells") operating according to the jump sensor principle and one or more proportional sensors by adding a snap cell (Nernst cell) to a "double cell.”
  • a snap cell Nest cell
  • a positive pumping current with a clear relationship to the oxygen content of the gas mixture is usually measured at a fixed pumping voltage in a lean gas mixture.
  • a positive pumping current is usually also measured, even if the applied pumping voltage (usually about 600-700 mV) is well below the decomposition voltage of water (about 1.23 V).
  • This positive pumping current is due essentially to the molecular hydrogen contained in the gas mixture, which influences the electrochemical potential of the anode, ie the first electrode, since water now forms on the first electrode from the oxygen ions leaving the solid electrolyte instead of molecular oxygen can be. Similar effects also play a role for other oxygen-supplying redox systems present in the gas mixture, for example CO 2 / CO.
  • the current is thus in the range of rich mixtures (fat pump current) by the hydrogen content in the region of the first electrode (eg anode) and the water vapor content (ie in particular the access of the water vapor by the above-described diffusion barrier) in the region of the second electrode (eg cathode).
  • a falsification of the pumping current by the hydrogen is also to be observed in the region of slightly lean non-equilibrium exhaust gases, which already exists in this area and provides a positive contribution to the pumping current.
  • a further problem of known broadband sensor elements in single cell arrangement is that the sensor elements should advantageously also be usable for diagnostic purposes for the monitoring of exhaust aftertreatment components.
  • OBD on-board diagnosis
  • Coated catalysts eg oxidation catalyst and NOx storage catalyst
  • the oxidation catalyst is responsible for the conversion of unburned hydrocarbons (HC) and CO. II Legislation that the oxidation catalyst be tested for catalytic coating effectiveness and recognized as defective if the emission exceeds 1.75 times the limit.
  • a method for measuring at least one gas component of a gas mixture in a gas space, which avoids the disadvantages described above. Furthermore, an electronic control device for carrying out the method and a system for carrying out the method are proposed.
  • the method uses at least one sensor element with at least one first electrode, at least one second electrode and at least one electrolyte connecting the at least one first electrode and the at least one second electrode.
  • One idea of the invention consists in achieving, on the one hand, a unique pumping current characteristic in that the at least one second electrode is shielded from the at least one gas chamber. In this way, fuel gas reactions are avoided at the at least one second electrode.
  • Another idea of the invention is to design the at least one first electrode as a fuel gas-sensitive electrode.
  • the at least one first electrode be designed in such a way that it comprises at least one mixed potential electrode which is sensitive to the gas composition, that is, in particular sensitive to hydrocarbons and carbon monoxide.
  • the proposed method comprises at least two operating states: at least one amperometric measuring state in which a pumping voltage is applied between the at least two electrodes and a pumping current is detected, wherein preferably at least one first gas component in the gas mixture is deduced from the at least one pumping current.
  • concentration is to be construed broadly and includes both a concentration in the classical sense as a particle number per unit volume, but also other variables that can be correlated with the concentration, such as, for example, partial pressure, mass percent or volume percent, molar fraction or the like or simply a Vohandensein or nonexistence For example, this may be an oxygen concentration.
  • At least one potentiometric measurement state is provided in the proposed method, in which at least one voltage between the at least one mixed potential electrode and the at least one second electrode is detected. From the at least one detected voltage is preferably closed to a concentration (which term is again interpreted broad, see above) at least one second gas component in the gas mixture, for example, as described above, to a fuel gas concentration, in particular hydrocarbons and / or carbon monoxide ,
  • the electrode function (electrode potential) of mixed potential electrodes is no longer thermodynamic, but kinetically determined.
  • the electrode potentials deviate from the Nernst equation and, depending on the gas mixture composition, mixing potentials are produced.
  • These mixed potentials lead to sensor signals which are in direct correlation with the non-equilibrium exhaust gases such as CO or HC.
  • the reference in potentiometric operation forms the shielded, at least one second electrode.
  • the at least one mixed potential electrode may comprise at least one electrode material which has a lower electrocatalytic activity than platinum.
  • a platinum electrode which has an admixture of a catalytically inactive or less catalytically active metal than platinum, in particular gold and / or silver and / or copper and / or lead.
  • metal mixtures have proven to be particularly suitable for reasons of compatibility with the production process (for example sintering conditions of the ceramic) and the operating conditions (temperature, atmosphere, etc.). For example, since gold accumulates predominantly on a platinum surface, even small amounts of gold (0.1 to 1%) massively influence the electrode activity and lead to a measurable fuel gas sensitivity of the electrode.
  • the gold concentration should be selected so that the fuel gas sensitivity is maintained over the lifetime of the sensor element. Accordingly, admixtures of gold, silver, copper or lead in the range between 0.05 wt .-% to 5 wt .-%, in particular between 0.1 wt .-% and 1.0 wt .-%, proposed.
  • an oxide electrode as the mixed potential electrode, in particular a metal oxide electrode, for example based on perovskite and / or chromite and / or gallate.
  • a metal oxide electrode for example based on perovskite and / or chromite and / or gallate.
  • ceramic-metal composites can be used, as well as mixtures of an oxide ceramic with gold, silver, copper and / or lead.
  • one of the described probes can be used upstream of the exhaust aftertreatment device and another downstream of the at least one exhaust aftertreatment device.
  • a sensor element after an exhaust gas turbocharger and a further sensor element after an oxidation catalyst and / or diesel particulate filter and / or storage catalyst can be placed.
  • the oxygen concentration or lambda is then measured and is available in the usual way to the corresponding software functions.
  • the operating mode of the lambda probe can be changed to potentiometric operation, so that, for example, hydrocarbon and carbon monoxide emissions before and after the catalysts can be measured. From this information, the conversion behavior of the catalysts can be determined qualitatively and / or quantitatively.
  • the monitoring may be carried out either passively, for example during a regeneration operation (for example of a diesel particulate filter and / or storage catalytic converter) or actively (for example by temperature regulation in the catalytic converter, for example by a corresponding post-injection).
  • the at least one first electrode can be connected to the at least one surrounding gas space via at least one flow resistance element, and the at least one second electrode can be connected by means of at least one diffusion resistance element. This can be at least -O-
  • a flow resistance element and the at least one diffusion resistance element be designed such that the limiting current of the at least one second electrode (usually the pump anode) is smaller than the limiting current of the at least one first electrode.
  • the limiting current of the at least one second electrode is 1 to 20 ⁇ A, more preferably 10 ⁇ A
  • the limiting current of the at least one first electrode is 500 ⁇ A to 6 mA, preferably 1.5 mA.
  • the limiting current of an electrode is defined as the saturation pumping current, d. H.
  • This limiting current can be defined, for example, for oxygen and oxygen ion transport through the solid electrolyte as the current which is achieved when all the oxygen molecules which reach the electrode operated as a cathode are completely transported through the solid electrolyte to the anode.
  • the sensor element is operated with this limiting current, i. H.
  • the pump current is approximately proportional to the gas molecule concentration, and the reverse current of the opposite electrode, which was previously operated as an anode, becomes experimentally polarized by reverse polarity determined, so that now the former anode is operated as a cathode.
  • the setting of the condition for the limiting current ratio can be fulfilled in particular in that the at least one diffusion resistance element has a greater diffusion resistance than the at least one flow resistance element.
  • the diffusion resistance is the resistance which an element opposes to a concentration difference between the two sides of the element and thus hinders diffusion.
  • the same diffusion medium for example, a porous material
  • the at least one diffusion resistance element and the at least one flow resistance element can be used, but in different layer thicknesses, so that, for example, before the at least one second electrode, a higher layer thickness is used than before the at least one first electrode.
  • an adjustment of the surface of the resistance elements can take place.
  • the limiting current increases at least approximately proportionally the available for the diffusion Queritesfiambae, and inversely proportional to the length or layer thickness of the resistive elements.
  • the at least one flow resistance element preferably has a greater flow resistance than the at least one diffusion resistance element.
  • the flow resistance is defined as that resistance which an element opposes to a pressure difference between both sides of the element and thus prevents a flow between both sides of the element.
  • the flow resistance can be adjusted, for example, by increasing or decreasing a pore size of a porous medium, and / or by varying a channel cross-section, a channel geometry or a channel length.
  • this shielding is effected by the at least one diffusion resistance element having a diffusion channel which connects the at least one first electrode to the at least one gas space and / or at least one reference space.
  • This diffusion channel should preferably have a large length, ie a length which is large in relation to the mean free path of the gas molecules at the corresponding operating temperature of the sensor element (for example 700 to 800 ° C.). In this way, the difference between gas phase diffusion and flow resistance can be maximally utilized in order to bring about a shielding of the at least one first electrode. If gas molecules in the diffusion channel (although of course also several diffusion channels can be used) have no collision partners other than the walls of the diffusion channel, transport would only occur via Knudent diffusion with the same behavior for flow and diffusion.
  • the at least one diffusion channel is provided with a height in the range between 2 L to 25 L and a width in the range of 2 L to 25 L and a length in the range between 0.5 mm and 20 mm.
  • L is the mean free path of the molecules of the gas mixture at an operating pressure of the sensor element, which is usually in the range of the normal pressure. This dimensioning of the at least one diffusion channel has proved to be particularly favorable to prevent the diffusion of grease gas to at least a first electrode.
  • the at least one second electrode can also be shielded in that it is completely separated from the gas space.
  • this at least one second electrode can be connected, for example, to a reference gas space, for example via an exhaust air duct.
  • This reference gas space is completely separated from the at least one gas space, which may be, for example, an engine room, which is separated from the exhaust line.
  • a porous element may then again be provided, for example once again an Al 2 O 3 ceramic.
  • the at least one first electrode may, for example, comprise a single electrode, wherein in each case switching should be made between amperometric and potentiometric measurement states.
  • a clocking occur, preferably not overlap amperometric and potentiometric clock cycles.
  • the clock cycles may, for example, be selected such that during the amperometric measurement state, a predetermined amount of the at least one first gas component to be detected is pumped from the at least one first electrode to the at least one second electrode to be there as reference during the subsequent potentiometric clock cycle to stand.
  • the at least one first electrode further comprises at least one pump electrode in addition to the at least one mixed potential electrode.
  • the pumping voltage is then applied between the pumping electrode and the at least one second electrode and the pumping current is measured between these electrodes.
  • the potentiometric measurement state on the other hand, the voltage between the at least one mixed potential electrode and the at least one second electrode is measured. In this way, the potentiometric measurements, for example, at least temporarily make the same time for amperometric measurement.
  • FIG. 1 shows a first exemplary embodiment of a sensor element which can be used according to the invention with two possibilities of shielding the pump anode;
  • FIG. 2 shows a pumping current characteristic in the case of a shielded anode
  • FIG. 3 shows a second exemplary embodiment of an inventively usable sensor element with internal pump anode
  • FIG. 4 shows a further exemplary embodiment of a sensor element with external electrodes
  • Figure 5 shows another exemplary embodiment of a sensor element with internal
  • FIG. 6 shows an exemplary embodiment of a sensor element with an outer cathode, an inner anode and an exhaust air duct;
  • FIG. 7 shows an exemplary embodiment of a sensor element in which the mixed potential electrode and the pump cathode are separated
  • FIG. 8A shows a first exemplary embodiment of a system for measuring a gas component
  • FIG. 8B shows a second exemplary embodiment of a system for measuring a gas component.
  • 1 shows a first embodiment of a sensor element 110 is shown, which is used for the erf ⁇ ndungswashe method.
  • This is a sensor element 110, which can be used, for example, in a lambda probe or as a lambda probe in order to determine the gas composition (air ratio) in a gas space 112.
  • the sensor element 110 is designed as a radial design (whereby linear designs are also possible) with a solid electrolyte 114, on which on opposite sides an inner pumping cathode 116 is arranged as the first electrode and an outer side, on the side facing the gas chamber 112 Pump anode 118 are arranged as a second electrode.
  • the pump cathode 116 is in this case designed as a fuel gas-sensitive electrode and has, for example, a platinum electrode with a gold admixture. Other configurations than mixed potential electrode according to the above description are possible.
  • a cathode cavity 120 in the form of a rectangular cavity is formed.
  • gas mixture from the gas space 122 enters the sensor element 110 and can pass from there into the cathode cavity 120.
  • a flow resistance element 124 in the form of a porous, dense material is arranged, which limits the limiting current of the pump cathode 116 and thus substantially determines the slope of the pump current characteristic.
  • two different possibilities are illustrated for suppressing gaseous gas reactions at the pump anode 118 and thus achieving a unique pumping current characteristic.
  • the pump anode 118 While the pump anode 118 is shielded from the gas space 112 by a diffusion resistance element in the form of a porous protective layer 126 in the right-hand part of the diagram (FIG. 1), the pump anode 118 in the left part of this schematic illustration (in FIG denotes) a geometrically configured diffusion resistance element 128.
  • the pump anode 118 is surrounded by a gas-impermeable cover layer 130, in which, above the pump anode 118, a rectangular cavity 132 is formed. This cavity 132 is connected to the gas inlet hole 122 via a long diffusion channel 134, which opens into the gas inlet hole 122.
  • a long diffusion channel 134 For the advantageous dimensions of the diffusion channel 134 reference is made to the above description.
  • a widening 136 is provided to prevent the diffusion channel 134 is added by entering from the gas space 112 dirt.
  • oxygen which forms at the pump anode 118
  • combustion chamber gases are made difficult to penetrate into the cavity 132 above the pump anode 118 by the long diffusion path.
  • the cavity 132 additionally causes a spatial possibility for the reaction of penetrating fuel gases, such as hydrogen, before they reach the pump anode 118 and there can trigger unwanted anode reactions.
  • the sensor element 110 according to the exemplary embodiment in FIG. 1 can be modified in many ways. Thus, unlike the radial design shown here, a linear design can also be selected. The two options A and B shown can be implemented individually or in combination. Furthermore, it can be seen in FIG. 1 that below the pump anode 118, pump cathode 116 and solid electrolyte 114, which together form a pump cell 138, a heating element 140 is provided, which is composed of insulator layers 142 and heating resistors 144 arranged between them.
  • this heating element 140 which acts as a tempering element 146 can be, for example, an operating temperature of the sensor element 110 to typically 700-800 0 C set, the temperature is adjusted, for example, to optimize the electrolytic properties of the solid electrolyte 114.
  • FIG. 2 schematically shows the effect of the measures described above on the characteristic curve (pumping current I p as a function of the air ratio ⁇ ) of the sensor element 110 shown in FIG.
  • the pumping current I p is plotted against the air ratio ⁇ .
  • the pumping current I p in the rich region 210 should be at zero, ie on the ⁇ axis.
  • the pump current I p should then increase approximately linearly with the air ratio ⁇ , which is shown in dashed lines in FIG. 2 by the theoretical characteristic curve 214.
  • the characteristic curve 220 shows the pump anode 118 shown in B in FIG. 1, in which the diffusion resistance element 128 is realized. It can clearly be seen that this characteristic curve 220 closely approximates the theoretical course 214. Thus, a measurement down to small ⁇ values, ie ⁇ -numbers just above 1, is possible.
  • FIG. 3 shows a further exemplary embodiment of a sensor element 110, which in turn has a pump cell 138 with a pump cathode 116 and a pump anode 118 and a solid electrolyte 114 located therebetween.
  • the pump cathode 116 is in turn, as described above, wholly or partially made of the combustible gas-sensitive material.
  • the pump cathode 116 is arranged on top of the solid electrolyte 114, and the pump anode 118 is located on the inside.
  • a gas-impermeable cover layer 130 is arranged above the pump cathode 116 for shielding from the gas space 112, so that an approximately rectangular cathode cavity 120 again forms above the pump cathode 116.
  • This cathode cavity 120 is shielded from the gas space 112 by the flow resistance element 124, which is designed, for example, as in the exemplary embodiment according to FIG.
  • a gas inlet hole 122 is provided, which in this case, however, does not serve the purpose of gas supply to the pump anode 118 (as in the exemplary embodiment according to FIG. 1 for gas supply to the pump cathode 116), but rather an escape of oxygen from a cavity 132 in the interior of the sensor element 110, FIG.
  • the gas inlet hole 122 which in this case is no longer an "access hole" may be configured, for example, with a smaller cross-section than the gas inlet hole 122 in the embodiment of FIGURE 1.
  • the diffusion resistance is further increased 3 shows a part of a diffusion resistance element 128, which prevents or reduces a diffusion of fuel gases from the gas space 112 into the cavity 132 above the pump anode 118 and at the same time allows an outflow of oxygen from the cavity 132.
  • a porous element 310 which is advantageously a coarse-pored, porous element.
  • FIG. 4 shows a third exemplary embodiment of a sensor element 110 which realizes a layer structure with pump cathode 116 and pump anode 118 arranged on the same side of the solid electrolyte 114.
  • pump anode 118, pump cathode 116 and solid electrolyte 114 form a pumping cell 138, but now the pumping current flows in a substantially horizontal direction, parallel to the layer planes, between the electrodes 116, 118.
  • a cathode cavity 120 is formed, which is shielded from the gas space 122 by a gas-tight cover layer 130.
  • the cathode cavity 120 is separated with the gas space 122 via a flow resistance element 124 in the form of a dense, small-pored ceramic layer, analogous to the preceding embodiments.
  • a cavity 132 is formed, which is likewise separated off from the gas space 122 by the gas-tight cover layer 130.
  • the hollow space 132 is separated from the gas space 122 by the one diffusion channel 134, wherein a porous element 310, analogous to the exemplary embodiment in FIG. 3, is introduced into the diffusion channel 134. Diffusion channel 134 and porous element 310 act together as a diffusion - -
  • a heating element 140 is again provided in the exemplary embodiment according to FIG.
  • an asymmetric heating is realized in the example according to FIG. 4, in which pump anode 118 and diffusion resistance element 128 are heated in the spatial average at a temperature which is approximately 20% below the average temperature of pumping cathode 116 and flow resistance element 124 is located.
  • the heating element 140 is arranged such that laterally the pump anode 118 and the diffusion resistance element 128 are not completely covered since the heating element 140 does not extend to the same extent to the right edge of the sensor element 110 as to the left edge.
  • a gas inlet which is indicated symbolically in FIG. 4 by 410, from the gas space 122 into the cathode cavity 120 through the porous flow resistance element 124 (diffusion process) is favored.
  • an outflow of oxygen gas outflow 412 from the cavity 132 into the gas space 122 is allowed, but diffusion of fuel gases from the gas space 122 into the cavity 132 through the diffusion channel 134 and the porous element 310 are suppressed due to the lower temperature.
  • FIG. 5 shows an exemplary embodiment of a sensor element 110 which can also be used according to the invention, in which the pump anode 118 is completely separated from the gas space 112 and instead is connected via an exhaust air duct 510 to a reference gas space 512, for example an engine compartment of a motor vehicle.
  • the sensor element 110 has on the side facing the gas space 112 a first solid electrolyte 114, for example, again an yttrium-stabilized zirconium dioxide Electrolytes, on.
  • a second solid electrolyte 514 arranged inside the sensor element 110 is provided.
  • the solid electrolytes 114, 514 are contacted by a pump cathode 116 and a pump anode 118, which are each formed in two parts, with an upper, the upper solid electrolyte 114 contacting partial cathode 516, a lower part cathode 518, which contacts the lower solid electrolyte 514 a upper part anode 520, which contacts the upper solid electrolyte 114 and a lower partial anode 522, which in turn contacts the lower solid electrolyte 514.
  • the two partial cathodes 516 and 518 and the two partial anodes 520, 522 are each connected to one another and thus together form the pumping cathode 116 and the pumping anode 118.
  • the splitting into a plurality of partial electrodes causes an enlarged electrode surface and thus a reduced internal resistance of the sensor element 110.
  • a cathode cavity 120 is provided between the partial cathodes 516, 518, and an anode cavity 132 is provided between the two partial anodes 520, 522.
  • the cathode cavity 120 communicates with the gas space 120 via a gas inlet hole and a flow resistance element 124.
  • the pump cathode 116 is in turn, as described above, made of fuel gas-sensitive material.
  • the pumping cathode 218 is electrically contacted by a cathode lead 524 disposed on the lower solid electrolyte 514.
  • the pumping cathode 116 can be connected to a corresponding electronic control device (compare FIGS. 8A and 8B below) and, for example, supplied with a voltage.
  • the anode cavity 132 is connected to the reference gas space 512 via the exhaust air duct 510.
  • Anodenhohlraum 132 and exhaust duct 510 are either unfilled or filled with an oxygen-permeable porous filling element 530 on Al 2 ⁇ 3 basis.
  • the exhaust air channel 510 serves to discharge oxygen with comparatively low flow resistance to the reference gas chamber 512, so that no or only a small amount in the anode cavity 132 Overpressure is created.
  • the potentiometric measuring state on the other hand, here as well as in the previous - o ⁇
  • the anode cavity 132 and the exhaust air duct 510 in each case with the porous filling element 530, as an air reference for the potentiometric determination of the potential difference between the electrodes 116, 118.
  • the pump anode 118 is electrically contacted via an anode feed line 532 and connected via a further electrical feedthrough 534 in the solid electrolyte 114 to an anode connection 536 arranged on the upper side of the solid electrolyte 114. Via this anode connection 536, the pump anode 118 can also be connected, for example, to the electronic control device (see FIGS. 8A and 8B below) so that, for example (in the amperometric measurement state), a voltage (for example a constant voltage) is applied between pump anode 118 and pump cathode 116 can be and / or a pumping current can be measured.
  • Anode supply line 532 and cathode supply line 524 are arranged side by side lying in the embodiment of Figure 5 and separated by the exhaust duct 510 against each other. Alternatively, a superimposed arrangement of the supply line 524, 532 can be realized.
  • a heating element 140 is arranged, in which a heating resistor 144 between two insulator layers 142 is embedded.
  • the heating resistor 144 can be electrically contacted via through-holes 538 in a carrier substrate 540 and heating contacts 542 and acted upon by a heating current.
  • this heating current can be regulated with a regulation which, for example, sets a constant internal resistance of the sensor element 110.
  • the unique characteristic 220 shown in FIG. 2 can be realized.
  • a pumping current corresponding to the oxygen partial pressure is measured in the lean region 212, but no current in the rich region 210, since there is no free oxygen and since the selected pumping voltage is advantageously below the decomposition voltage of the water.
  • fuel gas oxidation may occur at the inner, shielded, fuel gas-blind pump anode 118.
  • This can be a cost-effective, built as a single cell Realize sensor element 210, which is suitable for example for use in diesel vehicles.
  • FIG. 6 shows a further exemplary embodiment of a sensor element 110 which can be used according to the invention.
  • This sensor element 110 combines essential features of the exemplary embodiments according to FIGS. 3 and 5.
  • the sensor element 110 in turn has a solid electrolyte 114, wherein, analogously to the exemplary embodiment in FIG. 3, a pump cathode 116 is arranged on the side of the solid electrolyte 114 facing the gas space 112. and on the gas chamber 112 facing away from the inner side of the solid electrolyte 114 a pump anode 118.
  • the pump cathode 116 is again formed as a mixed potential electrode, in this embodiment, a cermet electrode 610 and a contact frame 612.
  • Analogous to the embodiment in Figure 3 is the Cathode shielded by a gas-impermeable cover layer 130 relative to the gas space 112, wherein in turn a flow resistance element 124 is provided which allows penetration of gas mixture from the gas space 112 into the cathode cavity 120.
  • the pump cathode 116 is in turn electrically contacted by a cathode feed line 524, which is arranged on the upper side of the solid electrolyte 114, and a cathode connection 526.
  • the inner pump anode 118 does not communicate with the gas space 112 via a gas inlet hole 122, but is completely separated from the gas space 112, analogously to the exemplary embodiment in FIG. 5, and is located via an exhaust air duct 510 with a reference gas space 512 in connection.
  • an anode cavity 132 is again provided below the pump cathode 118.
  • Anode cavity 132 and exhaust duct 510 are in turn filled with a porous filling element 530.
  • the exhaust air duct 510 or the anode cavity 132 serves to remove oxygen from the anode region or as a reference gas chamber for a potentiometric measurement.
  • the pump anode 118 is in turn electrically contacted via an anode feed line 532, an electrical through-connection 534 and an anode connection 536 on the surface of the solid electrolyte 114.
  • the anode lead 532 and the exhaust duct 510 partially formed overlapping.
  • the construction of the sensor element 110 according to the exemplary embodiment in FIG. 6 offers substantially the same advantages as the structure according to FIG. 5, but one of the technically complicated plated-through holes in the upper solid electrolyte 114 can be dispensed with.
  • the exemplary embodiments of the sensor element 110 according to FIGS. 1, 3, 4, 5 and 6 have as the first electrode only the pump cathode 116.
  • This pumping cathode 116 is thus used both in the amperometric measuring state (in this case only being a true "pumping electrode") and in the potentiometric measuring state Since amperometric measurement and potentiometric measurement are difficult to carry out simultaneously, the used above described clocked or cyclic operation in which is switched between the measurement states.
  • FIG. 7 shows an exemplary embodiment in which pump cathode 116 and mixed potential electrode 710 are formed as separate electrodes.
  • the structure of the sensor element 110 essentially corresponds to the structure of the sensor element 110 according to FIG. 5, so that with respect to the individual elements and the construction, reference can be made largely to the above description of this figure.
  • two-piece, juxtaposed, internal pumping electrodes 116, 118 are provided, wherein the pumping cathode 116 can be acted upon via a gas inlet hole 122 and a flow resistance element 124 with gas mixture from the gas space.
  • the pump cathode 116 is preferably of a conventional, i. H.
  • the pump cathode 118 is completely shielded from the gas space 112 and connected to the reference gas space 512 via an exhaust air duct 510.
  • the sensor element 110 has the described mixed potential electrode 710 on the upper side of the upper solid electrolyte 114 facing the gas space 112, which is arranged such that it overlaps in its perpendicular projection at least partially with the pump anode.
  • the mixed potential electrode 710 has one of the fuel gas-sensitive electrode materials described above.
  • the mixed potential electrode 710 is connected via a mixed potential electrode lead 712, which is also arranged on the surface of the solid electrolyte 114, connected to a potential contact 714, so that the sensor element 110 now has 3 electrode contacts 526, 536 and 714 on its surface.
  • the pump cell and the potential cell each component-identical composed of the electrodes 116, 118 and the solid electrolyte 114, 514, pump cell and potential cell are now separated. While the pump cell is still formed from the electrodes 116, 118 and the solid electrolytes 114, 514, the mixed potential electrode 710, the upper solid electrolyte 114 and the pump anode 118 now additionally form the potential cell.
  • FIGS. 8A and 8B show two exemplary embodiments of systems 810 by means of which at least one gas component of a gas mixture in the gas space 112 can be measured with the aid of the sensor elements 110 described above.
  • the system 810 in each case has at least one sensor element 110, for example one of the sensor elements described above.
  • a plurality of sensor elements 110 are used, for example, sensor elements in the exhaust system before and after corresponding exhaust aftertreatment devices. For simplicity, however, only one sensor element 110 is shown here.
  • the exemplary embodiment according to FIG. 8A shows an example in which a sensor element 110 is used, in which the at least one first electrode 116 is formed in one piece.
  • the first electrode is formed in two pieces, with a mixed potential electrode 710 which is arranged separately from the pump cathode 116, analogously to the exemplary embodiment according to FIG.
  • the erfmdungs contemporary system 810 includes, in addition to the at least one sensor element 110, an electronic control device 812, which is shown only schematically and symbolically in these figures.
  • the electronic control device 812 can be designed, for example, as an integral part of the sensor element 110, as a separate component, or it can be decentralized and partially integrated into the sensor element 110.
  • the electronic control device comprises an amperometric measuring device 814 and a potentiometric measuring device 816.
  • the amperometric measuring device has a voltage source 818, for example a controllable voltage source, by means of which the pumping electrodes 116, 118 can be subjected to a pumping voltage in the at least one amperometric measuring state.
  • a current measuring device 820 is provided, by means of which the pumping current I p can be measured in the at least one amperometric measuring state.
  • Pump voltage source 818 and current measuring device 820 are driven or read by a central control unit 822, which may contain, for example, electronic components and / or a microcomputer.
  • the potentiometric measuring device has a voltage measuring device 824. While in the exemplary embodiment according to FIG. 8A the voltage measuring device 824 measures the voltage between the two pumping electrodes 116, 118, in the exemplary embodiment according to FIG. 8B a measurement takes place between the mixed potential electrode 710 and the pump anode 118, the latter in this case not acting as a pumping electrode but as a potential electrode.
  • the potentiometric measuring device 816 is also actuated and read out via the central control unit 822.
  • the central control unit 822 is connected to other components via an interface 826, so that, for example, control signals for controlling an internal combustion engine and / or exhaust aftertreatment devices can be issued by the electronic control device 812, or the electronic control device 812 can be correspondingly activated from the outside
  • control signals for controlling an internal combustion engine and / or exhaust aftertreatment devices can be issued by the electronic control device 812, or the electronic control device 812 can be correspondingly activated from the outside
  • the electronic control device 812 may also contain a device for clocking the measurement states, for example to set a regular change between an amperometric and a potentiometric measurement state.
  • the information obtained by the electronic control device 812 can be used, for example, in the context of an on-board diagnosis (OBD), be used by a central engine control for controlling the internal combustion engine and / or transmitted via an on-board computer to a driver.
  • OBD on-board diagnosis
  • a malfunction of a catalyst ie exceeding a predetermined Limit values with respect to, for example, a fuel gas emission, immediately detected and issued a warning.

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Abstract

La présente invention concerne un procédé pour la mesure d'au moins un composant gazeux dans un espace gazeux (112) au moyen d'un élément capteur (110). Le ou les éléments capteur (110) comportent au moins une première électrode (116), au moins une deuxième électrode (118) et au moins un électrolyte solide (114, 514) reliant les deux électrodes ou plus (116, 118). La ou les premières électrodes (116) comportent au moins une électrode à potentiel mixte (116; 710). La ou les deuxièmes électrodes sont protégées par rapport à l'espace gazeux (112). Le procédé comprend au moins deux états de fonctionnement : au moins un état de fonctionnement ampérométrique dans lequel une tension est appliquée entre les deux électrodes (116, 118) et un courant de pompage est mesuré, et au moins un état de mesure potentiométrique, dans lequel une tension est détectée entre la ou les électrodes à potentiel mixte (116; 710) et la ou les deuxièmes électrodes (118).
PCT/EP2007/063175 2006-12-29 2007-12-03 Élément capteur avec fonction de diagnostic additionnelle WO2008080730A1 (fr)

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DE200610062051 DE102006062051A1 (de) 2006-12-29 2006-12-29 Sensorelement mit zusätzlicher Diagnosefunktion
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DE102009055336B4 (de) * 2009-12-28 2015-03-19 Enotec Gmbh, Prozess- Und Umweltmesstechnik Gassensor
DE102012217832A1 (de) 2012-09-28 2014-04-03 Robert Bosch Gmbh Verfahren zur Überwachung einer Schadstoff-Konvertierungsfähigkeit einer Abgasnachbehandlungskomponente
DE102012221551A1 (de) 2012-11-26 2014-05-28 Robert Bosch Gmbh Verfahren und Vorrichtung zum Betreiben einer Abgasanlage für eine Brennkraftmaschine
DE102012221901A1 (de) 2012-11-29 2014-06-05 Robert Bosch Gmbh Verfahren und Vorrichtung zum Betreiben einer Abgasanlage für eine Brennkraftmaschine
DE102014222748A1 (de) * 2014-11-07 2016-05-12 Continental Automotive Gmbh Verfahren, Vorrichtung, System, Computerprogramm und Computerprogrammprodukt zum Betreibeneines Sensorelements zum Erfassen einer Gaskonzentration
DE102016003452B4 (de) * 2016-03-23 2023-05-11 Dräger Safety AG & Co. KGaA Elektrochemischer Gassensor

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GB2288874A (en) * 1994-04-28 1995-11-01 Univ Middlesex Serv Ltd Reducing gas analysis apparatus
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DE4408504A1 (de) * 1994-03-14 1995-09-21 Bosch Gmbh Robert Sensor zur Bestimmung der Konzentration von Gaskomponenten in Gasgemischen
GB2288874A (en) * 1994-04-28 1995-11-01 Univ Middlesex Serv Ltd Reducing gas analysis apparatus
DE19932048A1 (de) * 1999-07-09 2001-01-11 Bosch Gmbh Robert Meßfühler zur Bestimmung einer Konzentration von Gaskomponenten in Gasgemischen
DE19947240A1 (de) * 1999-09-30 2001-05-10 Bosch Gmbh Robert Verfahren zum Betrieb einer Mischpotential-Abgassonde und Schaltungsanordnungen zur Durchführung der Verfahren

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