DE102012208387A1 - Device for detecting part of e.g. exhaust gas in exhaust gas tract of motor car, has sensing element comprising electrodes, and contact surface staying in contact with electrolytes, where contact surface is smaller than electrode surface - Google Patents

Abstract

The device (110) has a sensing element (114) i.e. film structure (136), comprising passive measuring and/or small pumping electrodes (116) that are ion-conductively connected together by solid electrolytes (118). One of the electrodes is designed as a surface-reduced electrode (119) that comprises electrode surface (120) to be pointed away from the electrolytes. A contact surface (122) is in contact with the electrolytes and attached to the electrolytes and smaller than the electrode surface. The surface-reduced electrode is directly acted upon or over a gas-permeable element. The solid electrolytes are selected from zirconia -based solid electrolyte, ion-conducting solid electrolyte and oxygen ion conducting ceramic solid electrolyte.

Description

State of the art

Devices are known from the prior art for detecting at least a portion of at least one gas component of a gas, in particular an exhaust gas, in a measuring gas space, in particular in an exhaust gas tract. Usually, such devices comprise at least one sensor element. Such sensor elements are for example in Robert Bosch GmbH: Sensors in motor vehicles, first edition 2010, pages 160 to 165 , described. The proportion of the gas component of the gas can be detected, for example, in the form of a partial pressure and / or in the form of a percentage and / or in the form of a volume fraction. In particular, ceramic sensor elements are known from the prior art, which are based on the use of electrolytic properties of certain solids, ie ion-conducting properties of these solids. In particular, these solids can be ceramic solid electrolytes, such as, for example, zirconium dioxide, in particular yttrium-stabilized zirconium (YSZ) and / or scandium-doped zirconium dioxide (ScSZ).

The sensor element may be, for example, a lambda probe and / or a mixed potential sensor and / or a conventional NO _x limiting current meter; more preferably, the sensor element may be a ceramic integrative NO _x sensor. The integrative ceramic NO _x sensor can be regarded as an implementation of a measuring principle in which very small amounts of the gas, in particular of a gas to be detected, for example NO _x , occur in the integrative ceramic sensor in a reservoir separate from the exhaust gas equivalent amount of oxygen to be accumulated. In a method using the integrative ceramic NO _x sensor, it may be possible for a very small proportion of the gas component, especially at very low gas concentrations, for example below a resolution limit according to the prior art, for a defined time interval, an average concentration value of Proportion, in particular to detect the gas species, as well as to generate a continuous sensor signal, in particular for use as an OBD (On-Board Diagnostic) sensor for future exhaust gas legislations. For example, the ceramic integrative NO _x sensor may comprise a structure analogous to a combination of a conventional sensor and a substantially gas-tight closed accumulation chamber with one or two accumulation electrodes. For example, oxygen can be pumped into a closed chamber between a pumping electrode (NOE) and a first hollow-chamber electrode (HKE1). For example, at least one third electrode (LR), in particular an air reference electrode, can be located in a reference channel, which is in communication, for example, with an external air environment, in particular with approximately 21% O ₂ . Depending on the embodiment, a further electrode, in particular a second hollow-chamber electrode (HKE2), can be located in the closed chamber. Depending on the mode of operation, the further electrode can be combined with the HKE1 and / or the functionality of both electrodes (HKE1 and HKE2) can be replaced by a single hollow-chamber electrode, for example to minimize an electrode number. In order to achieve sufficient ion conductivity of the solid electrolyte comprising the sensor element, the sensor element can be set to a corresponding operating temperature by at least one heating element, in particular by an internal heater. At the NOE, for example a NO pump electrode, the gas species to be detected, for example NO and / or NO ₂ , can be replaced and / or an oxygen ion stream obtained from the decomposition can be conducted into the chamber. An integrating sensor with accumulation cell, in particular the ceramic integrative NO _x sensor, may further comprise at least one additional chamber, preferably two additional chambers, for example a first chamber and / or a second chamber. Furthermore, the integrative sensor may comprise at least one diffusion barrier, preferably a first diffusion barrier and / or a second diffusion barrier. Furthermore, the integrative NO _x sensor may comprise at least one outer O ₂ pumping electrode (APE) and / or at least one inner O ₂ pumping electrode (IPE).

Furthermore, a measuring method is known from the prior art, wherein in a separated from the exhaust gas chamber by a pumping process, for example, actively by a pumping voltage and / or passively by an autonomous pumping cell, a correlating for example with a NO _x concentration amount of oxygen are collected can. Usually, in the measuring process, this chamber is pumped empty before each new cycle. As soon as an accumulation process begins, usually correlated with the NO _x concentration, oxygen is transported into the chamber, preferably between the electrodes NOE and HKE 1, and accumulated in the closed chamber. In general, the measuring method, in particular a measuring principle, is divided into two phases. A first phase usually comprises an emptying of the accumulation chamber by a voltage or current-guided pumping process to a defined initial state via at least one hollow-chamber electrode, for example the HKE2, and for example the air reference electrode (LR). An associated one Measured variable, which can be detected for example, in particular a measured variable of a chamber state, is usually the Nernst voltage between the hollow chamber electrode and the air reference electrode U _{HKE2-LR, mess} . In a second phase, the oxygen obtained from the NO decomposition, which correlates in particular with the NO _x concentration, is usually pumped into the accumulation chamber by applying a pumping voltage between the NOE and the HKE 1. As a result, the O ₂ concentration in the accumulation chamber usually increases. The first phase may preferably comprise emptying and the second phase may preferably be an accumulation phase. In the case of the two-phase measuring principle, in particular an evaluation of the voltage _profile U _LR-HKE2 , in particular in the second phase, can take place.

An evaluation of the chamber state, in particular with respect to the oxygen content, for example, by a measurement of the Nernst voltage between the HKE2 and the LR, which usually correlates with the oxygen content in the accumulation chamber. A measured variable may be, for example, a time duration Δt, which is necessary until reaching a defined threshold value U _{LR-HKE2, trigger} , the Nernst voltage U _LR-HKE2 , wherein the Nernst voltage usually decreases with increasing oxygen concentration. Usually, as the NO concentration increases, the accumulation chamber is filled faster, resulting in a faster drop in the voltage between the hollow-chamber electrode and the air reference electrode U _LR-HKE2 .

WO 2010/003826 describes a sensor element and a method for the determination of gas components in gas mixtures. For this purpose, one of the gas component to be determined equivalent amount of oxygen is accumulated in a gas-tightly sealed inner space of the sensor element. Subsequently, a removal of the accumulated oxygen by applying a pumping voltage to an electrochemical pumping cell of the sensor element, wherein the oxygen is removed from the gas-tight sealed inner space of the sensor element.

DE 10 2009 047 359 A1 describes a method which has the following phases: an initialization phase, wherein in the initialization phase establishing or restoring a defined initial state in a gas-tight chamber by pumping and an accumulation phase, wherein in the accumulation phase accumulation of an amount of oxygen in the gas-tight chamber by pumping via a pumping cell, wherein the amount of oxygen is a measure of a part of the gas species in the measuring gas.

WO 2011/069733 A1 describes a solid electrolyte sensor with two pump cells for measuring nitrogen oxides and a method for detecting a proportion of at least one gas species in a sample gas space. The method has an initialization phase, wherein in the initialization phase, a manufacturing or restoring a defined Ausganszustandes in a gas-tight chamber by pumping, and an accumulation phase, wherein in the accumulation phase, an accumulation of an amount of oxygen in the gas-tight chamber by pumping via a pumping cell wherein the amount of oxygen is a measure of a proportion of the gas species in the measurement gas. From a potential curve of the potential of a measuring electrode is closed to the proportion of gas species.

WO 2010/003820 A1 describes a method for measuring a low concentration gas species characterized by the steps of: accumulating an amount of oxygen equivalent to the concentration of the gas species to be measured by pumping into a gas tight chamber, detecting a characteristic concentration threshold of the accumulated gas by measuring voltage, determining the time interval Δt to reach the Characteristic concentration threshold of the accumulated gas and a restoration of a defined initial state in the gastight chamber by pumping.

As electrode material, in particular the electrodes of the devices and sensor elements, as are known from the prior art and described above, for example, so-called cermet electrodes, comprising a ceramic oxygen ion-conducting scaffold and electrically conductive precious metal components, usually platinum, are used as standard. The cermet electrodes usually include an open-porous system, which achieves the highest possible pumpability for oxygen due to its large surface area and / or three-phase boundary. Associated with a large two-phase boundary and / or a large three-phase boundary is usually simultaneously a high double-layer capacitance of the electrodes. The cermet electrodes may, especially in a standard electrode configuration, comprise a plurality of grains, for example Pt grains and / or YSZ grains. These grains may for example be arranged on at least one YSZ film and / or on at least one YSZ layer. For example, an electrode known from the prior art can be applied in a planar manner to an ion-conducting solid electrolyte layer. The solid electrolyte layer may be both a film and a printed layer. In this case, it is usually essential that the entire electrode paste is applied flatly to the film, in particular during manufacture, and thus throughout the entire range the film is in communication. For example, the standard electrode assembly may further include a lead and a lead insulation.

The known devices of the prior art have some disadvantages. For example, in the prior art, the same electrode structures are used as standard for all pumping electrodes and measuring electrodes, only with NO _x sensors, if necessary, are additional Au or Rh components added, in particular to the electrode structures. As a result, there is usually the disadvantage that the electrodes are not optimized to the actual, sometimes very different, electrode functions. Usually, the electrodes are trimmed to a high pumpability and used both for high power pumping cells and for low pumping cells as well as for pure measuring cells. However, this generally has the disadvantage that at the same time a high electrode capacity is connected, which usually leads to poorer dynamic properties of the electrodes, for example to long recharging times of the electrodes, and consequently to poorer dynamic properties of the sensor signal. For example, highly porous and thus highly pumpable electrodes with a high two-phase limit and / or three-phase limit are also used in the prior art for low-pumping and passive-measuring electrodes and / or cells. Associated with this, usually due to an associated high electrode capacitance, essentially determined by the electrochemical double layer between a Pt electrode system and the YSZ film, slow reloading processes occur, which, for example, impair the dynamic properties and / or the signal quality. It would therefore be desirable to increase the signal quality and / or the signal dynamics of ceramic exhaust gas sensors, for example of integrative ceramic NO _x sensors and / or lambda probes.

Disclosure of the invention

Accordingly, a device is proposed for detecting at least a portion of at least one gas component of a gas in a measuring gas space, which at least largely avoids the disadvantages of known devices. The proportion of the gas component may be, for example, a partial pressure and / or a percentage and / or a volume fraction of at least one gas component. The gas component may in principle be any gas. Preferably, the gas component may be one or more of the following gas components: O ₂ , NO _x , NO, NO ₂ , CO, HC (or generally hydrocarbons), and NH ₃ . In principle, other types of gas components and / or combinations of gas components can also be detected. In principle, the measurement gas space can be any space which is exposed to the gas and / or can be acted upon. Particularly preferably, the measuring gas space may be an exhaust gas tract, in particular an exhaust gas tract of a combustion power plant, for example an exhaust gas tract of a motor vehicle.

The device comprises at least one sensor element. In principle, the sensor element can be any device for detecting at least one of the gas components. The sensor element may in particular be a sensor element for detecting oxygen and / or nitrogen oxides in an exhaust gas of an internal combustion engine. The sensor element may preferably be an electrochemical sensor element. The detection may in principle be a qualitative detection, particularly preferably a quantitative detection. The gas may in principle be any gas. Particularly preferably, the gas may be an exhaust gas, for example an internal combustion engine, particularly preferably in a motor vehicle and / or in a heating system. The sensor element may be, for example, a lambda probe, in particular a lambda jump probe, and / or a broadband lambda probe and / or a mixed potential sensor and / or a conventional NO _x sensor and / or a ceramic integrated NO _x sensor.

The sensor element comprises at least two electrodes. An electrode may, for example, be an electrical conductor which, in particular in interaction with another electrical conductor, in particular a counterelectrode, interacts with a medium located between the electrode and the counterelectrode. The electrode can be acted upon, for example, by at least one feed line, in particular an electrode feed line, with an electrical voltage and / or with an electrical current. For example, the electrode may participate in at least one chemical reaction, in particular at least one electrochemical reaction.

An electrode may in particular be an electron-conducting element, at which a conversion of an electron current into an ion current and / or an ion current into an electron current can take place, in particular at a two-phase boundary and / or a three-phase boundary of the electrode. The electrode may, for example, be a porous electrode, wherein the porous electrode is at least partially metallic and / or ceramic components Preferably, the porous electrode may be composed of metallic and ceramic components. For example, the electrode may have at least one surface or at least one layer, which is made at least partially from at least one metallic material. In particular, this may be at least one metallic surface and / or at least one metallic layer. Alternatively or additionally, the electrode may also have at least one surface and / or at least one layer of a composite material comprising at least one metallic material. For example, the electrode may have at least one surface and / or at least one layer with at least one metal-ceramic composite material (CERMET). The electrode should in particular be in contact with the solid electrolyte, ie have at least one interface with the solid electrolyte, so that an electric current can be converted into an ion current through the solid electrolyte at the electrode or vice versa. Alternatively or additionally, an oxidation and / or reduction of gas molecules take place at the electrode and / or a conversion of gas molecules into ions or vice versa. For example, an incorporation of ions into the solid electrolyte can take place at the electrode, for example a conversion of molecular oxygen into oxygen ions and incorporation of the oxygen ions in the solid electrolyte. Alternatively, for example, an expansion of ions from the solid electrolyte can take place at the electrode, for example an expansion of oxygen ions, and a generation of corresponding gas molecules, for example molecular oxygen. The electrode may in particular be connected via the solid electrolyte to at least one counterelectrode, so that a voltage can be measured between the electrode and the counterelectrode, in particular a Nernst voltage, and / or that a current can flow between the electrode and the counterelectrode, for example a pumping current.

The electrode may in particular be a platinum electrode and / or an electrode which comprises platinum. Particularly preferably, the electrode can be constructed at least partially from at least one metallic material. By way of example, the electrode may be a cermet electrode comprising, for example, a ceramic oxygen ion-conducting scaffold and / or electrically conductive precious metal moieties, for example platinum moieties. The electrode may comprise, for example, an open-porous system. An electrode may in particular be an electrical conductor which is not completely enclosed and / or covered by an electrically insulating material, in particular an insulator.

The electrodes are connected in an ion-conducting manner via at least one solid electrolyte. The solid electrolyte may in particular be a ceramic solid electrolyte, preferably an oxygen ion-conducting ceramic solid electrolyte, for example a zirconia-based solid electrolyte. For example, the solid electrolyte may be a solid electrolyte as described above. By the term "ionically conductive" it can be understood, in particular, that an ionic current can flow through the solid electrolyte between the two electrodes. For example, at least one mechanical and / or electrical contact between the solid electrolyte and the electrodes may be present. The solid electrolyte may be, for example, a YSZ film. At least one of the electrodes is configured as a surface-reduced electrode. In principle, the sensor element can also comprise two area-reduced electrodes. For example, all the electrodes of the sensor element can be surface-reduced electrodes. The area-reduced electrode has at least one electrode surface facing away from the solid electrolyte and at least one contact surface facing the solid electrolyte in contact with the solid electrolyte. The electrode surface may, for example, be a surface of the electrode which is exposed to the gas from the measurement gas space directly and / or via at least one gas-permeable element and / or which of an atmosphere in a space formed separately from the measurement gas space, for example a reference gas space. is exposed directly and / or via a gas-permeable element. In particular, the electrode surface may be an area between the electrode and the gas. The contact surface may in particular be a surface of the electrode which is in direct contact with the solid electrolyte, for example at least one solid electrolyte film. The contact surface may have, for example, at least one two-phase boundary and / or at least one three-phase boundary, in particular between the solid electrolyte and / or the gas and / or the electrode. Particularly preferably, the three-phase boundary may be an area within the electrode, in particular a porous electrode, and the gas and / or the measurement gas and / or the oxygen and / or the proportion of the gas and / or the exhaust gas. The contact surface and / or the electrode surface may each comprise separate partial surfaces. By way of example, the contact surface and / or the electrode surface can each be designed to be continuous and / or separate.

The contact area is smaller than the electrode surface. For example, the extent of the contact surface may be smaller than the extent the electrode surface. In particular, an interface between the electrode and the solid electrolyte may be smaller than an interface between the electrode and the gas. The interface may preferably be a two-phase boundary and / or a three-phase boundary.

The area-reduced electrode can be acted upon directly or via at least one gas-permeable element with gas from the sample gas space. The gas-permeable element may be, for example, at least one diffusion barrier. For example, the diffusion barrier can be understood as meaning a layer of a material which suppresses a flow of the gas and / or a fluid, during which the layer promotes diffusion of the gas and / or the fluid and / or ions. The gas-permeable element may in particular be a porous element, for example a porous layer, for example a protective layer. For example, the area-reduced electrode can be acted upon directly or via at least one gas-permeable element with a reference gas, for example from a reference gas space and / or from the ambient air. The area-reduced electrode can be connected, for example, to at least one cavity and / or at least one reference gas space and / or at least one reference gas channel and / or at least one sample gas space, for example a reference air channel. The cavity can be, for example, at least one hollow chamber and / or at least one accumulation chamber. The cavity may be understood to mean a space within the sensor element which, although structurally separated from the measurement gas space, can nevertheless be exposed to the gas from the measurement gas space, for example via at least one gas access path and / or via the diffusion barrier, and / or at which an exchange, in particular at least a portion of the gas and / or a portion of the gas, by at least one pumping process, such as oxygen ions, can be carried into the cavity, for example in the accumulation chamber and / or in the hollow chamber, in particular in an accumulation chamber of the integrative NO _x sensor, since in this case there is usually no direct gas inlet, in particular no gas access path. For example, the cavity may be a partially or completely closed chamber, wherein access to the gas, in particular to the exhaust gas, may be possible by at least one pumping process and / or at least one pumping process. The cavity may be, for example, a chamber. The cavity and / or the reference gas space and / or the reference gas channel may be wholly or partially open, but may also be wholly or partially filled with at least one gas-permeable medium, for example a porous medium, for example porous alumina. The cavity and / or the reference gas space may in particular be designed to store a supply of a gas component, for example of oxygen and / or air, for example, before this supply can possibly be delivered to another room. The term "acted upon" may in particular be understood to mean that the area-reduced electrode, in particular the electrode surface, makes contact with the gas from the sample gas space and / or the reference gas and / or is surrounded by it and / or is overflowed by it.

The area-reduced electrode may be arranged completely or partially in at least one gas space formed separately from the measurement gas space. The gas space may be, for example, the cavity and / or the reference gas channel and / or the reference gas space and / or the chamber. In principle, the gas space may be a space which is at least partially separated from the measurement gas, for example a space that is completely, in particular completely, separated from the measurement gas. The gas space may be, for example, a cavity in a broadband lambda probe or in the case of a NO _x sensor. For example, the gas space may also be an air duct and / or an exhaust duct and / or the reference gas duct, for example in the case of a broadband lambda probe or a jumping probe.

The contact surface may have a size less than 90%, in particular less than 80% and particularly preferably less than 60% of the size of the electrode surface. For example, a difference in size, in particular with regard to a surface, between the contact surface and the electrode surface may be functionally adapted, in particular for the respective sensor function of the electrode, in particular the area-reduced electrode. The sensor element may comprise electrodes, in particular at least one area-reduced electrode, with different size differences. A high, in particular clear, difference in size between the contact surface and the electrode surface can be used in particular for low-pumping cells, in particular for electrodes of low-pumping cells, and / or passive-measuring cells, in particular for electrodes of passive-measuring cells, in particular passively measuring electrodes, be desirable.

The size, in particular the area, of the contact surface can be reduced by at least one insulating layer in comparison to the size, in particular the surface, of the electrode surface. The insulation layer can at least be partially disposed between the area-reduced electrode and the solid electrolyte. In principle, the insulating layer can be at least one layer of an insulating, in particular electrically and / or ionically insulating, material. The insulation layer may comprise, for example, at least one insulating ceramic material and / or at least one non-metallic material. For example, the insulating layer may be wholly or partly made of a non-conductive metal oxide, for example an alumina, for example Al ₂ O ₃ and / or for example wholly or partly of a non-ionic conductive and / or electrically conductive or low ionic conductive and / or low electrical conductive Zirconia and / or a suitable yttrium-doped zirconia. In particular, the insulating layer can partially insulate, in particular electrically isolate and / or ionically isolate the areal reduced electrode from the solid electrolyte. In particular, the insulation layer may be designed to at least partially prevent and / or suppress a compound, in particular at least one ionically conductive compound and / or at least one electrical connection, between the area-reduced electrode and the solid electrolyte.

The insulation layer may in particular have at least one opening, in particular at least one window, wherein the opening is preferably completely enclosed by the insulation layer. Through the opening of the insulating layer, the area-reduced electrode can be in contact with the solid electrolyte. In this way, the opening can limit the contact surface of the surface-reduced electrode facing the solid electrolyte, in particular laterally, ie in a layer plane parallel to the surface-reduced electrode. In particular, the contact surface of the area-reduced electrode facing the solid electrolyte can be completely surrounded by the at least one insulation layer.

The area-reduced electrode and the insulation layer can at least partially intermesh with one another in at least one layer plane of a layer structure of the device. In principle, a layer structure can be a construction of several, in particular planar, layers. For example, several layers can be arranged one on top of another in a layer structure. The expression "intermeshing" may in particular mean that at least one layer of the layer structure is at least partially made up of the insulation layer and an electrode layer, in particular comprising the electrode. For example, a layer of the layer structure may comprise at least a part of the insulation layer and at least a part of the electrode layer, wherein the electrode layer may at least partially form the electrode and / or the area-reduced electrode. For example, the insulating layer can be at least partially embedded in the area-reduced electrode and / or used and / or melted down. By way of example, the insulation layer may comprise at least one partial layer of the electrode, in particular of the electrode layer.

The insulating layer may be at least partially configured in a manner selected from a round configuration, a rectangular configuration, a frame-shaped configuration, a strip-like configuration, a comb-like configuration, an interdigitated structure, and an island-like configuration. In the island-like embodiment, the insulation layer may comprise at least one, preferably a plurality, islands of insulating material, in particular insulation portions. The insulating layer is preferably at least partially attached between the electrode and the solid electrolyte, but for example, the electrode may also be at least partially part of the electrode. For example, the insulating layer can also be configured by a mixture of the aforementioned modes. By way of example, a layer comprising an insulation layer and an electrode, in particular an electrode layer, can be designed like an inlay. In particular, the electrode layer and the insulating layer may be arranged in one another and / or one another such that they comprise at least one planar surface and / or form together, in particular an electrode surface with insulating inclusions. In principle, the insulation layer can be configured in any desired shape and / or manner.

The sensor element can be configured at least partially as a layer structure. The layer structure may in particular comprise a plurality of layers, for example at least one insulation layer and / or at least one electrode layer and / or at least one solid electrolyte layer. The layer structure may comprise at least one film. The layer structure can be produced, for example, by a printing technique, in particular a printing. By way of example, the layer structure may comprise at least one solid electrolyte layer, for example the YSZ foil, and / or at least one layer of the first electrode and / or at least one layer of the second electrode and / or at least one insulation layer. The layers may in particular be planar layers.

The area-reduced electrode may preferably be a passive-measuring and / or low-pumping electrode. The passive-measuring electrode may be in particular act to an electrode, which forms in combination with another electrode, a passive-measuring cell, such as a Nernst cell. The passive-measuring electrode can be, in particular, an electrode on which only little oxidation and / or reductions take place. A passive-measuring electrode may in particular be an electrode, through which no currents flow and / or no currents, for example at least one pump current, are driven. A low-pumping electrode may in particular be an electrode which, in combination with another electrode, forms a cell through which only a small electrical current and / or a low ion current flows and / or is driven.

The sensor element can be, for example, an integrative NO _x sensor. The integrative NO _x sensor may be, for example, at least partially an integrative NO _x sensor as known from the prior art, wherein, in contrast to the prior art, this sensor element has at least one area-reduced electrode. At least one of the electrodes can be configured as a hollow-chamber electrode. The hollow-chamber electrode may, for example, be a surface-reduced electrode. For example, the hollow-chamber electrode can also be an electrode, as known from the prior art, for example with the same size electrode surface and contact surface. The hollow-chamber electrodes may preferably have a low double-layer capacitance, for example as a surface-reduced electrode. The hollow-chamber electrode may, for example, be an electrode which is arranged in a closed chamber. The closed chamber can be, for example, a cavity, in particular as described above, wherein the closed chamber can be acted upon exclusively by at least one solid electrolyte with gas. Particularly preferably, the hollow-chamber electrodes, in particular as area-reduced electrodes, can have a lower double-layer capacitance.

For example, the sensor element may be a lambda probe. The lambda probe may, in particular, be a sensor element which is set up to determine a proportion of oxygen in the gas. In particular, the sensor element may be a lambda-jump probe. A lambda probe and / or a jump probe may in particular be set up to determine a lambda value, wherein lambda = 1 usually characterizes a stoichiometric ratio of fuel and oxygen. The lambda jump probe may in particular be a lambda probe with a cell, in particular with a Nernst cell. In principle, the lambda probe can also be a broadband lambda probe, in particular with two cells, preferably with at least one pump cell and at least one Nernst cell. The at least two electrodes may have at least one outer electrode exposed to the gas in the measurement gas space and at least one reference electrode arranged in a reference gas space, in particular in the lambda jump probe and / or in the broadband lambda probe. In the case of the lambda-jump probe, for example, the reference electrode arranged in the reference gas space and / or the outer electrode exposed to the measuring gas space can be configured as a surface-reduced electrode.

The sensor element may have at least one reduced two-phase limit and / or at least one reduced three-phase limit, in particular reduced by at least one insulation layer in each case. For example, the area-reduced electrode may have at least one reduced two-phase limit and / or three-phase limit. Particularly preferably, the contact surface may have at least one reduced two-phase limit and / or at least one reduced three-phase limit. By reducing the two-phase limit and / or the three-phase limit, in particular a chamber capacity and / or an electrode capacity can be reduced. In particular, the two-phase boundary may be a boundary between a solid electrolyte and an electrode. The two-phase boundary may be, for example, the contact area. The two-phase boundary and / or the three-phase boundary and / or the contact surface may, for example, comprise at least one charge zone, for example analogously to a capacitor. A reduction and / or reduction of the charge zone and / or the contact surface and / or the two-phase boundary and / or an increase in a distance between charge carriers can, for example analogously to a capacitor, lead to a smaller capacity, in particular to a smaller chamber capacity and / or electrode capacity, to lead. The two-phase boundary may, for example, be a contact surface of a Pt grain of an electrode, for example the area-reduced electrode, with a YSZ grain of an electrolyte layer, for example a YSZ foil, in particular of the solid electrolyte. For example, the three-phase boundary may be a contact surface of a Pt grain with a YSZ grain and the gas, particularly in an open-porous system.

The device according to the present invention may have a number of advantages over known devices. Through the use of the device according to the invention, in particular the invention Electrode structures, for example the area-reduced electrodes, with a high electrode surface area, in particular with a high gas-side electrode area and at the same time reduced contact area with the YSZ foil, can be achieved by the reduced capacities, in particular by the reduced overall capacities, an accelerated transhipment of the electrodes. When using the device according to the invention, in particular when using the device according to the invention, for example in the case of the integrative ceramic NO _x sensor, this can enable a significant increase in a signal swing and thus a signal quality. Furthermore, by reducing the total chamber capacity, in particular the capacity, a shortening of an accumulation time without disadvantages in the signal quality can be made possible.

The use of electrodes having a reduced two-phase limit, in particular for low-pumping and / or passive-measuring electrodes and / or cells, can for example enable both a previous measuring function and low pumping functions as well as the substantial advantage of accelerated reloading processes, the accelerated reloading processes significantly improving dynamic properties, such as For example, a response time and / or a cooldown and / or signal quality. Furthermore, a signal level can be significantly increased by the device according to the invention, in particular by use of the modified electrodes, in particular the area-reduced electrode, in particular by a significantly lower double-layer capacitance.

Brief description of the drawings

Embodiments of the invention are illustrated in the figures and are explained in more detail in the following description.

Show it:

1A a reduced area electrode of a first embodiment of a device according to the invention in a sectional view;

1B the area-reduced electrode of the first embodiment of the device according to the invention in plan view;

2A a reduced area electrode of a second embodiment of a device according to the invention in a sectional view;

2 B the area-reduced electrode of the second embodiment of the device according to the invention in plan view;

3A a reduced area electrode of a third embodiment of a device according to the invention in a sectional view;

3B the area-reduced electrode of the third embodiment of the device according to the invention in plan view;

4 a reduced area electrode of a fourth embodiment of a device according to the invention in a sectional view;

5 A fifth embodiment of an inventive device as an integrative NO _x sensor; and

6 A sixth embodiment of a device according to the invention 110 for detecting at least a portion of a gas in a sample gas space 112 shown.

Embodiments of the invention

The device 110 includes at least one sensor element 114 , The sensor element 114 includes at least two electrodes 116 , The electrodes 116 are about at least one solid electrolyte 118 ionically connected. At least one of these electrodes 116 is as a reduced-area electrode 119 designed. The area-reduced electrode 119 has at least one of the solid electrolyte 118 away-facing electrode surface and at least one of the solid electrolyte 118 assigning contact surface 122 in contact with the solid electrolyte 118 on. The contact surface 122 is smaller than the electrode surface 120 , The area-reduced electrode 119 For example, lambda jump probes 164 and / or lambda broadband probes and / or mixed potential sensors and / or conventional NO _x sensors, in particular for passive-measuring electrodes, be used. In the device 110 For example, it may be a lambda jump probe 164 and / or a lambda broadband probe and / or a mixed potential sensor and / or a conventional NO _x sensor, preferably comprising at least one area-reduced electrode 119 for passive-measuring electrodes, and / or a ceramic integrated NO _x sensor 142 act.

The area-reduced electrode 119 can be direct or via at least one gas permeable element 124 with gas from the sample gas chamber 112 be acted upon. For example, the area-reduced electrode 119 at least partially, for example completely, in particular completely, be separated from the measuring gas space, for example in a hollow-chamber electrode 144 of the integrative ceramic NO _x sensor 142 , In the gas-permeable element 124 For example, it can be at least one diffusion barrier, for example around a first diffusion barrier 126 and / or a second diffusion barrier 128 , act. For example, it may be in the gas-permeable element 124 a protective layer 130 act. The area-reduced electrode 119 may be wholly or partly in at least one of the sample gas space 112 be arranged separately formed gas space. The contact surface 122 For example, a size less than 90%, in particular less than 80% and particularly preferably less than 60% of the size of the electrode surface 120 exhibit. The size of the contact surface 122 can through at least one insulation layer 132 compared to the size of the electrode surface 120 be reduced. The insulation layer 132 can at least partially between the area-reduced electrode 119 and the solid electrolyte 118 be arranged. The area-reduced electrode 119 and the insulation layer 132 can in at least one layer level 134 a layer structure 136 the device 110 at least partially interlock.

The insulation layer 132 may be at least partially configured in a manner selected from a round configuration, a rectangular configuration 138 , a frame-shaped configuration, a strip-like configuration, a comb-like configuration, an interdigital structure-forming configuration, and an island-like configuration 140 , The island-like configuration may in particular be an arrangement of individual islands of insulating material, such as in 4 shown. The device according to the invention 110 may in particular have at least one comb structure and / or at least one interdigital structure, in particular in the layer structure 136 , In principle, the area-reduced electrode can be used 119 Implemented in many ways in other embodiments, in particular, the insulating layer 132 be configured in many ways.

The sensor element 114 can at least partially as a layer structure 136 be designed. For example, the area-reduced electrode 119 be a passive-measuring and / or a low-pumping electrode. In the device according to the invention 110 can, in particular in contrast to the prior art, each functionally adapted electrodes 116 , For example, a reduced-area electrode 119 or an electrode according to the prior art, be used for a respective sensor function.

The sensor element 114 For example, an integrative NO _x sensor 142 be like in 5 shown. At least one of the electrodes 116 can as a hollow chamber electrode 144 be designed. The integrative NO _x sensor 142 can be operated, for example, with potentiometric and / or amperometric methods for evaluating the chamber state, such as in WO 2010/003820 A1 . WO 2011/069733 A1 . DE 10 2009 047 359 A1 and WO 2010/003826 A1 described.

In principle, the device according to the invention 110 in various fields of application, in particular as a sensor with the area-reduced electrode 119 , in particular as an electrode system according to the invention, used and / or used and / or used. In 5 is in particular an embodiment of a device according to the invention 110 as an integrative NO _x sensor 142 shown. Analogously, it may be in the device 110 also be an at least partially conventional NO _x sensor, wherein, for example, an NO electrode (NOE) and / or an air reference electrode (LR) 162 as area-reduced electrodes 119 can be configured. 5 shows in particular an integrative ceramic NO _x sensor 142 without a galvanic isolation. In principle, the device according to the invention 110 , designed in particular as a NO _x sensor, comprise a galvanic isolation. For example, it may be in the hollow chamber electrodes 144 around modified hollow chamber electrodes 144 act, for example, area-reduced electrodes 119 as in the embodiments according to the 1A . 1B . 2A . 2 B . 3A . 3B and 4 shown. In general, for the electrodes 116 of the integrative NO _x sensor 142 does not require high pumpability, especially since only very low oxygen ion currents occur, usually in an nA range, with NO _x concentrations usually occurring in a cat OBD. The galvanic isolation can be, for example, electrically isolated functional layers. In the modified hollow chamber electrodes 144 it may be in particular hollow chamber electrodes 144 with lower double-layer capacity, in particular as area-reduced electrode 119 designed, acted. The device according to the invention 110 , such as in 5 represented and as an integrative NO _x sensor 142 configured, for example, at least one gas access 146 and / or at least one heating element 148 , in particular designed as a heater, and / or at least one outer pumping electrode (APE) 150 and / or at least a first inner pumping electrode (IPE1) 152 and / or at least one second inner pumping electrode (IPE2) 154 and / or at least one pump electrode (NOE) 156 and / or at least one first hollow-chamber electrode (HKE1) 158 and / or at least one second hollow-chamber electrode (HKE2) 160 , in particular at least one hollow-chamber electrode 144 and / or at least one first hollow-chamber electrode 158 and / or at least one second hollow-chamber electrode 160 with low double-layer capacity, especially as area-reduced electrodes 119 , and / or at least one air reference electrode (LR) 162 include. In 5 is in particular an integrative ceramic NO _x sensor 142 with galvanically connected functional layers and modified hollow-chamber electrodes 144 , in particular as area-reduced electrodes 119 designed, shown with low double-layer capacity.

In particular, at low NO _x concentrations, as may occur, for example, in the cat-OBD, usually a gain by an accumulation chamber is given by a total chamber capacity, in particular with respect to a physical accumulation and / or an electrochemical amplification by a steep curve. The greater the chamber capacity, in particular the total chamber capacity, the smaller is the gain usually. Here, usually the essential part of the capacity is on the double layer of the electrodes 116 due. In particular, a signal level can accordingly by use of the device according to the invention 110 , In particular, the modified electrodes, in particular by a significantly lower double-layer capacitance, are significantly increased, in particular both when evaluating a time difference .DELTA.t (.DELTA.c (NO)) and when evaluating a voltage difference at a defined time .DELTA.U (.DELTA.c (NO)). Alternatively or additionally, the HKE1 and / or the HKE2 and / or the IPE2 and / or the NOE and / or the RE and / or the NORE, in particular as an NO reference electrode, as area-reduced electrode 119 , in particular as an electrode structure according to the invention, be used, in particular in a NO _x sensor. The time difference .DELTA.t (.DELTA.c (NO)) may in particular be a time difference until reaching a voltage trigger, in particular a threshold value and / or a limit value, in particular during an accumulation phase.

The sensor element 114 For example, a lambda jump probe 164 be. The at least two electrodes 116 At least one of the gases in the sample gas space 112 exposed outer electrode 166 and at least one reference electrode arranged in a reference gas space 168 exhibit. In particular in 6 is an embodiment of a device according to the invention 110 as lambda jump probe 164 shown, wherein the device 110 can also be designed as a mixed potential sensor for various gas species analog. The device according to the invention 110 as lambda jump probe 164 in particular, at least one area-reduced electrode can be configured 119 , in particular a modified electrode, preferably as outer electrode (AE) 166 , and / or at least one area-reduced electrode 119 as reference electrode (RE) 168 exhibit. Especially there with this sensor type, in particular with lambda jump probes 164 , usually no high pumpability is necessary, can by the area-reduced electrodes 119 , in particular by the modified electrodes, a faster transhipment and thus an improved dynamic property, for example a better starting time and / or a better decay time and / or a better alternating frequency, can be achieved. This in 6 illustrated embodiment of the device according to the invention 110 includes at least one air reference 170 and / or at least one heating element 148 , designed for example as a heater.

Alternatively or additionally, the device according to the invention 110 be designed as a broadband lambda probe and / or as a lambda probe, wherein the area-reduced electrode 119 for example, a Nernst electrode and / or a reference electrode 168 can be. The device according to the invention 110 , as in 6 represented, in particular as lambda jump probe 164 configured, may in particular have a lower double-layer capacitance than lambda jump probes, which are known from the prior art. In the device 110 , such as in 6 shown, it may be in the area-reduced electrodes 119 in particular to be modified electrodes with lower double-layer capacity.

The device according to the invention 110 , in particular the sensor element 114 , in particular, can have a reduced two-phase limit 172 and / or at least one reduced three-phase limit 174 in particular by in each case at least one insulating layer 132 reduced. The device according to the invention 110 , in particular the area-reduced electrode 119 , may in particular be designed such that the contact surface 122 , in particular a direct contact surface 122 between the sensor electrode and the YSZ foil 178 , is reduced, especially since this with its high proportion of two-phase boundary 172 usually significantly increases the electrode capacity. The reduction of the contact area can be limited 122 , Particularly in a design of an embodiment of a device according to the invention 110 , by a maximum pumping current of the contact area. The maximum pumping current of the contact region is, however, usually designed to be significantly lower in passive and / or low-pumping electrode systems, in particular in the nA to μA range, in particular in NO measurements with an integrative and / or conventional NO _x sensor than, for example, for a pump cell of O ₂ removal, in particular in a mA range. Preferred is in the device according to the invention 110 also, in particular for emptying an accumulation chamber, for example in the case of integrative NO _x sensor 142 , a large electrode surface 120 , in particular a large gas-side surface, available, preferably to remove oxygen as quickly and / or homogeneously from the accumulation chamber.

The device according to the invention 110 can in particular at least one control 176 exhibit. The control 176 may be arranged to provide a method for detecting at least a portion of at least one gas component of the gas in the sample gas space 112 perform. The control 176 For example, with the sensor element 114 connected and / or connectable. Under the control 176 may be understood a device which is adapted to at least one function of the device 110 , in particular of the sensor element 114 to support and / or control. By "connectable", for example, a property can be understood in which an electrical connection can be made or already exists. The control 176 can be completely or partially separated from the sensor element 114 be configured, but can also be wholly or partly in the sensor element 114 be integrated, for example, in at least one plug of the sensor element 114 and / or the device 110 , The control 176 may comprise at least one voltage measuring device and / or at least one current measuring device for detecting at least one pumping current and / or at least one pumping voltage and / or for regulating the pumping voltage and / or for regulating the pumping current. Alternatively or additionally, the control 176 and / or the sensor element 114 and / or the device 110 have at least one loading device. The application device may in particular comprise at least one voltage source and / or at least one current source. For example, the application device can be set up to the sensor element 114 to apply the pumping current and / or the pumping voltage. The control 176 may further comprise at least one data processing device.

In the 1A . 1B . 2A . 2 B . 3A . 3B and 4 are in particular parts of embodiments of the device according to the invention 110 , in particular area-reduced electrodes 119 represented. In particular, embodiments of the device according to the invention are 110 , in particular of electrode structures, in which case a reduction of the two-phase limit is preferred 172 and / or the three-phase boundary 174 can be achieved.

1A shows a sectional view of a first embodiment of a reduced-area electrode according to the invention 119 and 1B shows an associated plan view. In the 1A and 1B In particular, an outlined inventive electrode structure, in particular a first embodiment shown.

In the 1A . 2A . 3A and 4 These are in particular side views, at least of parts of embodiments of the device according to the invention 110 , In the 1B . 2 B and 3B in particular, these can in each case be associated top views, in particular plan views.

In the 2A and 2 B are in particular representations of a sketched inventive electrode structure of a second embodiment of the device according to the invention 110 shown. In the 3A and 3B is a third embodiment of a device according to the invention 110 , in particular as a sketched inventive electrode structure shown. 4 shows at least a part of a fourth embodiment of a device according to the invention 110 , In particular a sketched electrode structure according to the invention. In the 1A . 1B . 2A . 2 B . 3A . 3B and 4 In particular, each is a YSZ film 178 as a solid electrolyte 118 and one electrode area each in contact with the YSZ foil 178 , in particular as a contact surface 122 represented. Furthermore, the first embodiment and the second embodiment and the third embodiment include a lead 180 and a lead insulation 182 , In the first embodiment, as in the 1A and 1B shown, is the contact surface 122 with direct contact to the supply line 180 with a rectangular configuration 138 designed. The insulation layer 132 is in the first embodiment, in particular at least partially designed frame-shaped. In the second embodiment, as in the 2A and 2 B shown, is the contact surface 122 rectangular shaped and substantially centered on the electrode 116 arranged. The insulation layer 132 of the second embodiment, as in the 2A and 2 B shown, may be configured in particular frame-shaped. In the 3A and 3B is in particular a third embodiment of a device according to the invention 110 , In particular, a sketched inventive electrode structure shown. The insulation layer 132 of the third embodiment, as in the 3A and 3B is shown, in particular designed rectangular. The contact surface 122 is in the third embodiment, as in the 3A and 3B represented, in particular designed frame-shaped. 4 shows a fourth embodiment of a device according to the invention 110 , in particular a sketched electrode structure according to the invention. The insulation layer 132 and / or the contact area 122 of the fourth embodiment, as in 4 shown is designed in particular island-like. The island-like design 140 In particular, an arrangement of several, for example, at least partially separated from each other, preferably not directly or indirectly interconnected, insulating layers 132 and / or islands of insulating material.

In principle, the features of the embodiments described and illustrated in the figures of the device according to the invention 110 can be combined arbitrarily.

The device according to the invention 110 can in particular with the electrode structures according to the invention and / or as inventively modified device 110 , in dependence of a sensor variant, in particular a type of the sensor element 114 , distinguishable for example by a structure and / or an electrode material, and / or depending on the measurement principle and / or in dependence on the temperature for a quantitative determination of various gas components, for example O ₂ and / or NO _x and / or NO and / or NO ₂ and / or CO and / or HC and / or NH ₃ , for example as NO _x sensor, in particular integratively and / or with conventional limiting current, and / or as lambda jump probe 164 and / or lambda broadband probe and / or mixed potential sensor for various species. The electrode 116 , in particular the area-reduced electrode 119 , In the embodiments of the device according to the invention 110 preferably in contact with the gas.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• WO 2010/003826 [0005]
• DE 102009047359 A1 [0006, 0047]
• WO 2011/069733 A1 [0007, 0047]
• WO 2010/003820 A1 [0008, 0047]
• WO 2010/003826 A1 [0047]

Cited non-patent literature

• Robert Bosch GmbH: Sensors in motor vehicles, first edition 2010, pages 160 to 165 [0001]

Claims (12)

Contraption ( 110 ) for detecting at least a portion of a gas in a measuring gas space ( 112 ) comprising at least one sensor element ( 114 ), wherein the sensor element ( 114 ) at least two electrodes ( 116 ), wherein the electrodes ( 116 ) via at least one solid electrolyte ( 118 ) are connected in an ion-conducting manner, wherein at least one of the electrodes ( 116 ) as area-reduced electrode ( 119 ), wherein the area-reduced electrode ( 119 ) at least one of the solid electrolyte ( 118 ) away electrode surface ( 120 ) and at least one of the solid electrolyte ( 118 ) assigning contact surface ( 122 ) in contact with the solid electrolyte ( 118 ), wherein the contact surface ( 122 ) is smaller than the electrode surface ( 120 ). Contraption ( 110 ) according to the preceding claim, wherein the area-reduced electrode ( 119 ) directly or via at least one gas-permeable element ( 124 ) with gas from the sample gas space ( 112 ) can be acted upon. Contraption ( 110 ) according to one of the preceding claims, wherein the area-reduced electrode ( 119 ) wholly or partly in at least one of the sample gas space ( 112 ) is arranged separately formed gas space. Contraption ( 110 ) according to one of the preceding claims, wherein the contact surface ( 122 ) has a size smaller than 90%, in particular smaller than 80% and particularly preferably smaller than 60% of the size of the electrode surface ( 120 ) having. Contraption ( 110 ) according to one of the preceding claims, wherein the size of the contact surface ( 122 ) by at least one insulating layer ( 132 ) compared to the size of the electrode surface ( 120 ), the insulation layer ( 132 ) at least partially between the area-reduced electrode ( 119 ) and the solid electrolyte ( 118 ) is arranged. Contraption ( 110 ) according to the preceding claim, wherein the area-reduced electrode ( 119 ) and the insulation layer ( 132 ) in at least one layer plane ( 134 ) of a layer structure ( 136 ) of the device ( 110 ) at least partially intermesh. Contraption ( 110 ) according to one of the two preceding claims, wherein the insulating layer ( 132 ) is at least partially configured in a manner selected from a round configuration, a rectangular configuration ( 138 ), a frame-shaped configuration, a strip-like configuration, a comb-like configuration, an interdigital structure-forming embodiment and an island-like configuration ( 140 ). Contraption ( 110 ) according to one of the preceding claims, wherein the sensor element ( 114 ) at least partially as a layer structure ( 136 ) is configured. Contraption ( 110 ) according to one of the preceding claims, wherein the area-reduced electrode ( 119 ) a passively measuring and / or low-pumping electrode ( 116 ). Contraption ( 110 ) according to one of the preceding claims, wherein the sensor element ( 114 ) an integrative NO _x sensor ( 142 ), wherein at least one of the electrodes ( 116 ) as a hollow chamber electrode ( 144 ) is configured. Contraption ( 110 ) according to one of the preceding claims, wherein the sensor element ( 114 ) a lambda jump probe ( 164 ), wherein the at least two electrodes ( 116 ) at least one gas in the sample gas space ( 112 ) exposed external electrode ( 166 ) and at least one reference electrode arranged in a reference gas space ( 168 ) exhibit. Contraption ( 110 ) according to one of the preceding claims, wherein the sensor element ( 114 ) at least one reduced two-phase limit ( 172 ) and / or three-phase boundary ( 174 ), in particular by at least one insulating layer ( 132 ) decreased.

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