FR2954827A1 - Sensor element for seizing property of oxygen in measurement gas chamber to control exhaust fumes of automobile, has gas access path provided with gas passage opening that comprises two zones having different diameters - Google Patents

Abstract

The element (110) has an electrode (124) separated from a measurement gas chamber (114) by a layer of a laminated structure (112) and connected to the measurement gas chamber by a gas access path (128). The gas access path is provided with a gas passage opening (130) comprising two cylindrical or conical zones (148, 152) having different diameters. Maximum diameter of the gas passage opening is at a level of an upper surface (116) of the laminated structure. The electrode is placed in an electrode cavity (126). An independent claim is also included for a method for manufacturing a sensor element.

Description

FIELD OF THE INVENTION The present invention relates to a sensor element for capturing at least one property of a gas in a measurement gas chamber having a laminated structure with at least a first electrode, at least a second electrode and at least a second electrode. solid electrolytes connecting the first electrode and the second electrode. The invention also relates to a method for producing such a sensor element. STATE OF THE ART According to the state of the art, sensor elements are known for capturing a property of a gas in a measuring chamber (gas measurement chamber) based on the use of one or more solid electrolytes. Solid electrolytes are solid bodies, in particular ceramic solid bodies for conducting certain types of ions, for example oxygen ions. This property usually exists above a limit temperature or limit temperature range. Typical solid electrolytes are, for example, zirconium dioxide stabilized with yttrium or other type of metal oxide and typically doped oxide metals. Such sensor elements are used for example to capture a physical property and / or a chemical property of a gas in a measurement gas chamber. A typical example is the qualitative and / or quantitative detection of at least one component of a gas in the measuring chamber. It may be for such gas components, in particular oxygen. It is also possible in principle to detect other gas components. The content of the gas component can for example be entered as a percentage or also in the form of the partial pressure of the gas in the measuring gas chamber. Examples of such sensor elements are probes such as those described for example in the Robert Bosch GmbH document: Sensoren im Kraftfahrzeug, 2007 edition, pages 154/159. Such probes are used to detect oxygen and are installed, for example, in the exhaust pipe of a combustion engine or combustion engine.

The probes are for example known under the name of "jump probe" or "broadband probe". By way of example, from a Nernst voltage, it is possible to conclude directly or indirectly on the coefficient of air X. As a variant, from a pumping current in the solid electrolyte, it is also possible to determine the oxygen content. For many sensor elements according to the state of the art, at least one of the electrodes to which one can for example provide two or more electrodes, and inside a ceramic laminate structure, and it is thus covered. by at least one layer of this laminated structure. In many cases, these inner electrodes are in communication with the measurement gas chamber through a gas passage (also called GZL orifice) through at least partially the laminated structure.

The connection typically includes a diffusion barrier external to the gas passage and which limits the oxygen supply to the inner electrode. The gas passageway typically has a cylindrical shape of uniform diameter. Although such gas passage orifices having a characteristic and relatively simple construction and design, the gas orifices must meet many conditions relating to their characteristics and their manufacturing possibilities. In many cases, a gas orifice with a large diameter is required to regulate the access of the gas so that the gas passage orifice does not itself constitute a diffusion limiting element. For example, in the case of current broadband probes, with a thermal protection layer (TSP layer), gas through-holes with a diameter greater than 0.45 mm are required for the gas passage to remain open.

In addition, during the manufacture of the gas passage holes, the sensor element may be damaged. Thus, in conventional manufacturing processes, the gas passage orifices are drilled in the ceramic laminate structure before subjecting this laminated structure to the final sintering operation. But the drilling operation can cause mechanical damage or generate

3 dirt. For example, diffusion barriers within the laminate structure may be damaged. The protective layer against thermal shock TSP is generally applied at the end of the operation by atmospheric plasma spraying. Typically, this spraying is at an angle of 60 ° with respect to the upper surface of the sensor to effect the coating of the front surface of the sensor. But because of the spraying angle, the TSP layer may arrive in the gas orifice and contaminate the diffusion barrier, or even block it and significantly increase the resistance to diffusion. DISCLOSURE AND ADVANTAGES OF THE INVENTION To overcome these drawbacks, the invention relates to a sensor element characterized in that - the second electrode is separated from the measuring gas chamber by at least one layer of the laminated structure, - the second electrode is connected to the measurement gas chamber by at least one gas access path, - the gas access path includes at least one gas passage made in the laminated structure, and - the orifice gas passage comprises at least two zones having different diameters. The invention also proposes a method for manufacturing such a sensor element, characterized in that a laminated structure is produced with at least one first electrode, at least one second electrode and at least one solid electrolyte connecting the first electrode and the second electrode. second electrode, - separating the second electrode from the measuring chamber by at least one layer of the laminated structure, - connecting the second electrode to the measurement gas chamber by at least one gas path, - the gas access path has at least one gas passage opening in the laminated structure; the gas orifice is made so that it comprises at least two zones having different diameters.

Thus, a sensor element according to the invention and its manufacturing method make it possible to avoid to a very large extent the disadvantages of the sensor elements and their known manufacturing processes. The sensor element according to the invention can in particular be realized by a method according to the invention and conversely the method according to the invention makes it possible to produce a sensor element according to the invention. The sensor element according to the invention allows the capture of at least one property of a gas in a measurement gas chamber.

As indicated above, this property is in particular a physical and / or chemical property and in particular the content of the gaseous component in the gas, for example the oxygen content which can thus be determined qualitatively and / or quantitatively, for example in percentage or in the form of partial pressure. With regard to the possible embodiments of the sensor elements, reference will be made to the description given above. Other developments are in principle possible. The sensor element may be installed in particular in the exhaust pipe of a heat engine, for example in the exhaust gas line of a combustion engine (internal combustion engine) in the automotive field. Other fields of application are possible such as their use in combustion plants or for process control. The sensor element according to the invention has at least one laminated structure with at least one first electrode, at least one second electrode and at least one solid electrolyte connecting the first electrode to the second electrode. According to the invention, there is a laminated structure and generally an element composed of at least two superimposed layers and / or layer planes. The layers can be distinguished by the manufacture of the laminated structure and / or be made of different materials and / or from different raw materials. In particular, the laminated structure may be wholly or partially a layered ceramic material. The expression "solid electrolyte" according to the invention denotes, as indicated above, a solid body which at least from a predefined limit temperature has ion conduction characteristics, for certain ions such as oxygen ions. . In particular, the solid electrolyte comprises a metal oxide, in particular a doped metal oxide such as yttrium stabilized zirconium dioxide. Other solid electrolyte materials may be contemplated. In general, an electrode is an element for contacting the solid electrolyte to pass an electric current through the electrode and the solid electrolyte. The electrode comprises for this purpose an element integrating the ions in the solid electrolyte and / or for removing ions from the solid electrolyte. Typically, the electrodes comprise a noble metal electrode, for example a metal / ceramic electrode applied to the solid electrolyte or otherwise connected to the solid electrolyte. The characteristic materials of the electrodes are those of platinum-Cermet electrodes. Other noble metals such as for example gold and / or palladium are in principle usable and are known for this according to the state of the art. The laminated structure may be designed so that the first electrode and the second electrode are installed on the opposite sides of the solid electrolyte, for example on the opposite sides of a solid electrolyte layer such as for example an electrolyte film. solid or a solid electrolyte paste. Alternatively or additionally, at least the two electrodes may be located on the same side as the solid electrolyte. The electrodes and the solid electrolyte form in combination at least one cell. The sensor element may be a single-cell sensor element, with only one cell used for example as a Nernst cell or as a pump cell. Alternatively, the sensor element may also be embodied as a multi-cell sensor element, comprising a plurality of such cells performing different functions. For example, one can provide at least one pumping cell and in addition at least one Nernst cell as will be described next by way of example. At least one of the two electrodes which will hereinafter be referred to as the "electrode", (without giving any particular importance or classifying the electrodes) is thus installed according to the invention inside the laminated structure. In other words, the second electrode is

6 separated from the measurement gas chamber by at least one layer of the laminated structure. In particular, it may be a layer of at least one solid electrolyte. At least the second electrode is thus installed deeper in the plane of the layer of the laminated structure, that is to say in a plane of the layer, away from the upper surface of the solid electrolyte facing the chamber. measuring gas. At least one other electrode, that is to say according to the terminology used here, at least one first electrode can also be installed in a deeper layer plane, but also above, that is to say for example on the upper surface of the laminated structure facing the measuring gas chamber. The first electrode may also be an external electrode and be separated from the measurement gas chamber, for example only by a porous, gas-permeable protective layer and be otherwise, for example, directly in exchange for gas with the gas chamber measurement. Different achievements are possible. At least one second electrode is connected by at least one gas path to the measurement gas chamber. The term gas access path generally designates an element permitting the exchange of gas between the measurement gas chamber and the second electrode by performing either a total exchange of gases or only an exchange of certain components of the gas. . For example, the gas path may be one or more bores, channels, orifices, or the like. The gas access path may in particular be made to ensure the continuation of the arrival of the gas and / or a post-diffusion of the gas towards the second electrode from the measurement gas chamber or in the reverse direction, for example the continuation of the arrival and / or post-diffusion of oxygen. The gas path has at least one gas passage made in the laminate structure. The expression "gas passage orifice" designates an orifice passing through at least one plane of the layer of the laminated structure, in particular at least one layer separating at least one second electrode from the measurement gas chamber. The gas passage opening may in principle have any cross section, for example a round section or a polygonal section. The orifice of

7 gas passage may in particular be perpendicular to the plane of the layers of the laminated structure and have for example a cylindrical shape, for example a circular cylindrical shape. According to the invention, the gas passage orifice is made to have at least two zones with different diameters. The term "diameter" generally refers to the quantification of a lateral extension of the section of the gas passage. If the gas passage orifice has, for example, a circular section, the expression "diameter" is the effective diameter of this circle. But for another geometry or shape of the section, the expression diameter will designate a diameter equivalent, that is to say the diameter of a circle having the same area as that of the effective section. At least, the two zones may be adjacent directly or indirectly for example along the axis of the gas passage or they correspond to different segments on this axis. We can have two and more than two zones. The gas passage opening may open into the upper surface of the laminated structure, for example in the upper surface facing the measuring gas chamber. The gas passage orifice may in particular have its maximum diameter in this upper surface. Starting from this upper surface, the diameter of the gas passage opening can decrease by entering the laminated structure, for example continuously and / or in stages. For example, step reduction (or stepped reduction) may be provided starting from the upper surface with first a first zone having a first diameter continuing within the layered structure by at least a second zone, in direct or indirect connection, that is to say after a transient zone, and having a second diameter smaller than the first diameter. In this case, the gas passage orifice may for example have a stepped structure or bearing. At least the two zones can also be for example of conical, cylindrical or rounded shape or be made in another appropriate manner. At least the two zones may be concentric or coaxial, that is to say have for example the same axis of symmetry or the

8 same axis of drilling. But this is not necessarily the case. Thus, it is preferentially provided that at least the two zones are not concentric, that is to say that they are not coaxial with respect to each other. At least two zones may be offset, for example, from one another. An offset arrangement here means an assembly in which the central axis or axis of symmetry of one or more zones does not correspond to the central axis or axis of symmetry of one or more other zones of the gas orifice. . For example, this offset can be made in the direction perpendicular to the direction of extension of the gas passage. The sensor element may for example have a longitudinal extension axis parallel to its longitudinal extension and also parallel to the plane of the laminated structure. For example, the sensor element may protrude, in the direction of this longitudinal extension axis, encapsulated or unencapsulated in the measurement gas chamber. The end of the laminated structure farthest in the direction of the measuring gas chamber may for example be called the front face. This off-set arrangement may include locating the first zone having the largest diameter, closest to the upper surface in comparison with at least a second zone of reduced diameter, and which is offset from the front surface. In other words, by way of example, the central axis or axis of symmetry of the first zone may be further from the front face in the direction of longitudinal extension than the axis or axis of symmetry of the second area which lies deeper into the laminated structure of the sensor element. This staggered arrangement may favor, for example, an application which is at least one thermal shock-proofing layer, without the material of this thermal shock protection layer being able to arrive inside the passage opening of the device. gas. In particular, it is possible to use a spraying method for applying at least one thermal shock-protection layer, for example a plasma spraying method at an acute angle with respect to the plane of the layer, that is to say in a direction different from the normal direction to the laminated structure. By

For example, the sputtering method can be applied so that the thermal shock protection layer is applied to the end face. These staggered arrangements of at least two zones, among which for example the first zone is shifted more from the frontal side than the second lower zone having a smaller diameter, so as to effectively prevent the penetration of the material of the protective layer. against thermal shocks. The axis or axis of symmetry (for example the axis of the bore and / or the milling axis) of the first zone may be shifted from 50 to 700 microns relative to the axis or axis of symmetry of the second zone , for example the front face preferably of 80-500 microns and particularly preferably of 115 to 420 microns. The gas passage orifice may for example have a first diameter at the upper surface, in a first zone and at least a second zone with a second diameter, the second zone being located deeper in the laminate structure and the second diameter being smaller than the first. The first zone and / or the second zone and / or, where appropriate, other zones have a cylindrical or conical shape.

The gas passage orifice may in particular be staggered or bearing with at least one stepped or shoulder-shaped transition or transition between the first and the second zone. The term staged transition or transition refers to the passage between a first diameter and a second diameter, with at least one planar surface extending substantially perpendicular to the axis of the gas passage. The expression "shoulder or bearing" designates the passage with a curved or planar surface and in the latter case, the surface is not necessarily perpendicular but may for example make an angle of between 80 ° and 10 ° with respect to the axis of the passage opening. Since at least a first zone or at least a second zone may also be offset, as indicated above, the shoulder may be asymmetrical. If there are for example two zones, for example at least two zones with a cylindrical and / or conical shape, and these two zones having at least a first diameter and at least a second diameter,

Then the first diameter may be at the largest coefficient k than the second diameter. The coefficient k will in particular be greater than 1.2 and preferably greater than 1.8 and, in a particularly preferred manner, it will be equal to at least 2.0. The coefficient k may especially be in a range between 1.2 and 5 and preferably in a range between 1.8 and 4.0 and particularly preferably in a range between 2.0 and 3, 0. In the case where there are at least two zones with at least 2 mm, ie at least one first diameter and at least one second diameter, the first diameter will be larger than the second diameter and the first diameter will be greater than for example in a range of between 0.15 mm and 1.0 mm and in particular in a range between 0.4 mm and 0.8 mm and particularly preferably in a range between 0.5 mm and 0.75 mm. The second diameter may especially be in a range between 0.1 mm and 0.5 mm and in particular in a range between 0.2 mm and 0.4 mm and particularly preferably, it will be equal to 0 , 25 mm. For example, the first diameter may be 0.6 mm or 0.8 mm or 1.0 mm. The second diameter will for example be equal to 0.25 mm. The first diameter can, according to one example, be equal to 0.8 mm and the second diameter equal to 0.25 mm. At least one second electrode will be installed in particular in an electrode cavity. This electrode cavity may be provided inside the laminated structure and have for example the shape of an open cavity. Alternatively, this electrode cavity may also be wholly or partially filled with a porous, gas-permeable material, for example with gas-permeable aluminum oxide. The electrode cavity may in particular be connected to the gas passage orifice by a diffusion barrier. In this case, the gas flow path comprises at least one second electrode, that is to say the gas diffusion passage orifice, the diffusion barrier or a channel in which the diffusion barrier is located, as well as the electrode cavity. The expression "diffusion barrier" generally designates an element which avoids or at least inhibits the direct supply of gas supply from the gas passage to

11 the electrode cavity. A diffusion barrier is thus an element that creates a strong resistance to flow (pressure drop) while the diffusion of the gas or a component of the gas is relatively easy through the diffusion barrier. The diffusion barrier comprises, for example, a porous ceramic element, in particular a fine porosity aluminum oxide. Such a diffusion barrier is provided and particularly preferably if it is set back relative to the gas passage orifice. The term "diffusion diffusion barrier" refers to a diffusion barrier that is not directly adjacent to the gas passage, but is recessed therefrom. For example, the diffusion barrier may be placed in a channel or other orifice forming part of the gas path; however, the diffusion barrier may not arrive directly at the transition between this channel or this opening and the gas orifice, but be removed from this passage. For example, the diffusion barrier may terminate at a distance of at least 0.05 mm and preferably at least 0.1 mm, or even at least 0.2 mm from this passage. This advantage of removing or shifting behind the diffusion barrier, as will be detailed later, that during the manufacture of the gas orifice, the barrier is not likely to be damaged because this operation can clear Dirt that could clog the diffusion barrier and generate irregularities in the establishment of the current limit defined by the width of the diffusion barrier. In addition, the embodiment described above improves the long-term stability of the operation, in particular with regard to fouling for example by ash particles (for example oil ash) and / or oxides. metal. According to another characteristic, the invention relates to a method of manufacturing a sensor element for capturing at least one property of a gas in a measurement gas chamber, in particular a sensor element according to one or more developments described hereinabove. above. The method provides a laminated structure with at least a first electrode, at least a second electrode and at least one solid electrolyte connecting the first electrode

12 to the second electrode. This laminated structure can be achieved by using the film technique and / or the thick film technique and / or other ceramic layer techniques. The second electrode is separated from the measurement gas chamber by at least one layer of the laminated structure, in particular by at least one solid electrolyte layer. The second electrode is connected by at least one gas access path to the gas measuring chamber; the gas path has at least one gas passage in the laminate structure. The gas passage orifice is made according to the invention so as to have at least two zones having a different diameter. For the other developments of this orifice, reference will be made to the explanations already given above. The realization of the gas passage orifice can be done in different ways. In a particularly preferred manner, the gas passage orifice is made by a mechanical drilling method and / or at least by a mechanical milling method. As already indicated above, at least two zones have been provided so that a method of drilling with a stepped drill bit will be used in particular. The term "stepped drill" refers to a drill having at least two drill segments axially offset with different diameters. Between these drill segments, there may be transient zones, for example shoulders. However, a drilling method with a stepped drill bit can generally be applied only to the realization of coaxially or concentrically aligned zones.

In the case of offset zones with respect to one another, for example, several holes will be made such that at least a first hole to make the first zone and at least a second hole to make the second zone, by shifting the axes of the holes. Alternatively or in addition to the mechanical drilling method, a mechanical milling method can also be applied. Such a mechanical milling method can also be used to manufacture offset zones relative to each other using a single milling step or several milling steps, for example, separate milling steps for at least the first zone. and for at least the second zone.

However, it is possible to use at least one other method, for example a laser drilling method or another type of drilling and / or drawing process giving different shapes.

At least one piercing method may be used especially at the time of manufacture, when the laminated structure is not yet hardened or will not be completely hardened. The piercing method can be applied at the moment when the laminated structure is not yet fired and / or is still in the blank state, that is to say that it is not completely cured; the hardening itself will be done by a subsequent heat treatment step that is to say by a sintering step. The sensor element as proposed, as well as its method of manufacture, has many advantages with respect to known sensor elements and known manufacturing processes: the gas orifice with zones of different diameters, for example a stepped gas passage, in particular a staggered passage orifice, in principle improves the manufacturing possibilities and the functionality of the sensor element. This is particularly noticeable advantageously in the case of wide-band sensor elements. In particular, it will be possible to make large diameter gas passage orifices, for example with a diameter greater than 0.45 mm. This allows open gas access. Without a stepped gas passage orifice or without the implementation of the design according to the invention of the gas orifice, there would be the risk that the diffusion barrier would be damaged during the production of the orifice. gas passage, for example, may be initiated by drilling. This can result in additional dispersion of the limiting current. In addition, according to the usual method, a recessed diffusion barrier, which is not directly adjacent to the gas orifice can not be completely realized. Such diffusion barriers directly adjacent to the gas passage orifice nevertheless have the additional risk, in operation of the sensor element, that the diffusion barrier is fouled by dirt from the gas measuring chamber. that is to say,

14 stuffed with this filth. This can result in a significant change in the current limit thus influenced by the diffusion barrier because the current limit depends significantly on the properties of the diffusion barrier. However, the invention makes it possible to produce the gas passage orifice so that, in particular at the level of the diffusion barrier, it has a smaller diameter, which always makes it possible to have a recessed diffusion barrier. This avoids both the risk of damaging the diffusion barrier and that of fouling of the diffusion barrier.

The sensor element may carry at least one thermal shock protection layer (TSP layer), and this thermal shock protection layer may be provided on the upper surface of the laminate structure facing the measurement gas chamber. and / or on a front surface of the laminate structure. Such layers of protection against thermal shock are known in themselves. The thermal shock protection layers typically consist of at least two or more layers, but improving the resistance of the laminated structure to thermal shocks, for example by avoiding the formation of cracks in the body. ceramic material or at least reducing the risk of crack formation. Thanks to the realization of the gas orifice with different diameters, for example a stepped embodiment of the gas passage orifice, in particular a stepped and staggered embodiment, it is possible for the material of the protective layer to be protected against the thermal shocks do not arrive inside the stratified structure, in particular towards the diffusion barrier. As explained above, the thermal shock protection layer can be applied for example after the sintering operation of the laminated structure. As a coating method, for example, an optional spraying method or in combination with other coating methods can be envisaged. The stepped realization of the gas passage orifice in particular with offset zones makes it possible to avoid dirtying the lower layer planes which could further lower or disperse the limiting current. In particular, it can be avoided

The material of the thermal shock protection layer does not reach the diffusion barrier. A stepped drill bit and / or a milling cutter makes it possible, in particular, to produce a gas passage orifice whose diameter is, for example, equal to 0.25 mm, which corresponds to the diameter of the usual passage openings for gas. In the upper zone, that is to say at the level of the upper surface, there can be a second zone having a larger diameter, for example a diameter of 0.6 mm, 0.8 mm or 1.0 mm. This ensures open access to the gas at the top surface, for example after applying a coating with the thermal shock protection layer. Due to the design of the gas orifice, it is avoided that the material of the thermal shock protection layer arrives in the lower gas passage, preferably in the narrow portion of the this orifice, during the application of the coating and / or during the production of the protective layer against thermal shock, which may result for example after drilling the access port. In summary, the proposed design of the gas passage, including the stepped design, the boundary current dispersion, increases the resistance to fouling of the diffusion barrier and thus its long-term stability. Drawings: The present invention will be described in more detail below with the aid of exemplary embodiments shown in the accompanying drawings in which: FIG. 1 shows a first embodiment of a sensor element according to FIG. The invention and its manufacturing method according to the invention, - Figures 2-4 show different views of a second embodiment of a sensor element according to the invention with a stepped and staggered gas orifice . DESCRIPTION OF THE EMBODIMENTS OF THE INVENTION FIG. 1 shows a first exemplary embodiment of a sensor element 110 according to the invention. This representation will also make it possible to describe an exemplary embodiment of a method

The sensor element 110 has a laminated structure 112 made by a ceramic film and / or thick ceramic film process. The laminated structure 112 has an upper surface 116 facing a measurement gas chamber 114 with a first electrode 118. In the embodiment shown in FIG. 1, the first electrode 118 has for example an annular shape because the element The sensor 110 of FIG. 1 is largely symmetrical in rotation. Other achievements, however, are possible. The first electrode 118 is separated from the measuring gas chamber 114, for example by a protective layer 120 which is permeable to gases. The laminated structure 112 of the exemplary embodiment shown comprises one or more solid electrolytes 122. The solid electrolytes 122 can be manufactured for example in the form of electrolyte films and / or in the thick film technique. The solid electrolyte 122 may comprise, for example, zirconium dioxide stabilized with yttrium (YSZ). The laminated structure 112 of the embodiment of FIG. 1 comprises on one side of the solid electrolyte 122 opposite to the first electrode 118, at least one second electrode 124. This second electrode 124 can be, for example, also installed with rotational symmetry and in the embodiment shown, it is formed of several parts. The second electrode 124 is installed in an electrode cavity 126. The electrode cavity 126 is part of a gas path 128 connected to the measurement gas chamber 114 by the second electrode 124. The path the gas 128 comprises as another component, a gas passage opening 130 extending perpendicularly to the plane of the layers of the laminated structure 112, from the upper surface 116 down into the laminate structure 112. The cavity For example, the electrode 126 may surround the gas passage opening 130 in an annular shape. Other achievements are also possible. Between the gas passage port 130 and the electrode cavity 126 there is a channel 132 but is also part of the gas path 128. This channel 132 houses a diffusion barrier 134 which reduces or avoids

The gas supply inlet of the measurement gas chamber 114 into the electrode cavity 126 and allows only diffusion. The diffusion barrier 134 makes it possible to regulate the limit current of a pumping cell 136 comprising a first electrode 118, a second electrode 124 and solid electrolyte 122. The sensor element 110 of the embodiment shown has a air reference channel 138 connected for example to the environment whose oxygen content is known. This air reference channel 138 comprises, for example, a reference electrode 140. This reference electrode 140 and the second electrode 124 or another measuring electrode installed in the electrode cavity 126 make it possible, for example, to adjust the pumping current in the pumping cell 136, to have the condition = 1 or another known composition in the electrode cavity 126. The sensor element 110 also has at least one heating element 142 which makes it possible to adjust the solid electrolyte temperature 122 and or the whole of the laminated structure 112 or parts thereof at an operating temperature. The heating element 142 may also include one or more insulating layers 144.

The sensor element 110 of the exemplary embodiment of FIG. 1 is a two-cell sensor element; in addition to the pump cell 136, it comprises a measuring cell 146 with a reference electrode 140, the solid electrolyte 122 and the second electrode 124 and / or another measuring electrode installed in the electrode cavity 126. For example, the sensor element 110 is designed as a wideband sensor and can correspond as far as is known to commercially available sensor elements 110, for example sensor elements of the LSU4.9 type. The upper surface 116 may comprise a thermal shock protection layer (TSP layer) to avoid damaging the laminated structure 112 by stresses generated by thermal shock. FIG. 1 further shows that the gas passage opening 130 according to the invention comprises several zones. In the embodiment thus presented, starting from the upper surface 116, there is firstly a first zone 148 having a first

18 di diameter continuing after a transitional zone-shaped shoulder 150 by a second zone 152 having a diameter d2. The first zone 148 and the second zone 152 of the embodiment shown are examples of cylindrical zones. Other developments may also be foreseen. The transient zone 150 may for example be of conical shape. The second zone 152 may for example join its end on a conical shape or have a tip. In a variant, it is also possible to have a flat end for this second zone 152. In another variant, it is possible to have additional zones as an option. The first diameter di is larger than the second diameter d2. For example, the diameter di may be 0.55 mm, 0.65 mm or 0.75 mm. The second zone 152 may for example have a diameter d2 of 0.25 mm or 0.3 mm or 0.35 mm. As further shown in FIG. 1, the diffusion barrier 132 is set back with respect to the gas passage orifice 130, that is to say placed behind without joining directly into the channel 132, the orifice In practice, this prevents the fouling of the diffusion barrier. By the choice of the smaller diameter of the two for the second zone 152 of the gas passage opening 130, it is avoided for example that during the manufacture of the gas passage opening 130, the diffusion barrier 134 does not risk of being initiated by drilling. The diffusion barrier 134, set back, thus remains protected and intact. It avoids damaging the diffusion barrier 134, which would result in a dispersion of the limit current. In addition, the transient zone 150 also constitutes a receiving plate which prevents the entry of the material of the thermal shock protection layer to the diffusion barrier 134. This also has a positive influence avoiding the dispersion of the currents. limits. To achieve the gas passage hole 130, it is possible to use for example a stepped drill 154. The stepped drill bit 154 will for example have a first drill segment 156 of diameter di and a second drill segment 158 of diameter d2 and a zone corresponding transient 160 which corresponds to the transient zone 150. This avoids starting by piercing the insulation layer 144 of the heating device.

Figures 2 to 4 show a second embodiment of a sensor element 110 according to the invention. Figure 2 is a view similar to that of Figure 1 while Figure 3 is a detail view of the gas passage hole 130 and Figure 4 a microscopic sectional view of the detail shown in Figure 3. L Sensor element 110 corresponds essentially to the embodiment of FIG. 1, so reference is made to the description of the structure and operation of the various elements given in the description of FIG. In the embodiment of Figure 1, the gas passage opening 130 of the example shown in Figures 2 to 4 is staggered and shifted. The gas passage opening 130 of the example embodiment thus represented also comprises two zones 148, 152; the first zone 148 has a first diameter 01 and the second zone 152 a second diameter 02. For example, the first diameter may range from 600 to 1000 microns. The second diameter may range, for example, from 150 to 300 microns. The edges of the zones 148, 152 closest to the front face 166 of the sensor element 110 may be offset relative to each other by a value of 8 which represents, for example, more than 5 microns and less than 70 microns. The thickness d of the solid electrolyte layer 122 is, for example, a film thickness; it is preferably at least 320 microns. The two zones 148,152 each have a first axis 162 and a second axis 164, for example a drilling axis and a milling axis. The axes 162, 164 are, for example, offset from the offset A which may be for example equal to (115 microns - 420 microns). This offset A makes, for example, that the axis 162 of the zone 148 is distant from the distance A of the front phase 166 with respect to the second axis 164. The zones 148 and 152 can be produced in different ways. For example, it is possible to make separate holes with offset drilling axes. Alternatively or additionally, zones 148 and 152 may also be made by other manufacturing methods, for example by single milling or multiple milling. The sensor element 110 may be coated with a thermal shock protection layer 168 not shown in FIGS. 1 to 3, this layer being applied, for example, after

The sintering operation. For this purpose, a projection method is used, for example a plasma projection method. This projection is made with reference not perpendicular to the surface 116. In FIG. 3, the projection direction has been schematically indicated and the reference 170 has been placed. This projection direction 170 can be chosen for example so that the front face 166 is at least partially coated with the thermal shock protection layer 168. FIG. 4 shows a sectional view of the detail of FIG. 3 of the sensor element 110. The dimensions are given by way of example. FIG. 4 shows that for the projection direction 170 of FIG. 3, no material of the thermal shock protection layer 168 or only extremely small quantities of this material arrive in the second zone 152 and in particular in the opening to the diffusion barrier 134.15 NOMENCLATURE 110 sensor element 112 laminated structure 114 measuring gas chamber 116 upper surface 118 first electrode 120 gas-permeable protective layer 122 solid electrolyte 124 second electrode 128 gas access path 130 flow port gas 132 channel 134 diffusion barrier 138 reference channel 140 reference electrode 142 heating element 144 insulation layer 148 first zone 150 transient zone 152 second zone 154 stepped drill 156 first drill segment 158 second drill segment 160 transient zone 162 first axis 164 second axis 166 front surface 168 protective layer against shocks 170 direction of spray

Claims (1)

CLAIMS1 °) Sensor element (110) for capturing at least one property of a gas in a measurement gas chamber (114) having a laminated structure (112) with at least a first electrode (118), at least one second electrode (124) and at least solid electrolytes (122) connecting the first electrode (118) and the second electrode (124), a sensor element characterized in that - the second electrode (124) is separated from the gas chamber of measuring (114) by at least one layer of the laminated structure (112), - the second electrode (124) is connected to the measurement gas chamber (114) by at least one gas access path (128), the gas path (128) has at least one gas passage (130) formed in the laminate structure (112) and the gas passage (130) has at least two zones (148). 152) having different diameters. 2) sensor element (110) according to claim 1, characterized in that the gas passage (130) opens into the upper surface (116) of the laminate structure (112). Sensor element (110) according to claim 1, characterized in that the gas passage (130) has a maximum diameter at the upper surface (116). 4 °) sensor element (110) according to one of claims 2 and 3, characterized in that the gas passage (130) has a first diameter at the upper surface (116), and the gas passage port (130) has at least a first zone (148) having the first diameter and at least a second zone (152) having a second diameter, the second zone (152) is located further in the structure laminate (112) as the first zone (148), and the second diameter is smaller than the first diameter. 5 °) sensor element (110) according to claim 1, characterized in that the first zone (148) and / or the second zone (152) are cylindrical or conical. 6 °) sensor element (110) according to one of claims 4 and 5, characterized in that the gas passage (130) is stepped with in particular a transition (150) shaped step or shoulder between the first zone (148) and the second zone (152). Sensor element (110) according to one of Claims 4, 5, 6, characterized in that the first zone (148) and / or the second zone (152) are offset relative to one another. 'other. Sensor element (110) according to claim 1, characterized in that the gas access port (130) has at least a first zone (148) with a first diameter and at least a second zone ( 152) with at least a second diameter, - the first diameter being greater than a coefficient (k) at the second diameter, - the coefficient (k) being greater than 1.2 and preferably greater than 1.8 and particularly less than 2.0. 9 °) sensor element (110) according to claim 8, characterized in that the coefficient (k) is in a range between 1.2 and 5 and in particular in a range between 1.8 and 4.0 and particularly preferably in a range of 2.0 to 3.0. Sensor element (110) according to claim 1, characterized in that the gas passage (130) has at least a first zone (148) with at least a first diameter and at least a second zone. (152) with at least a second diameter, - the first diameter being greater than the second diameter, - the first diameter being in a range of between 0.15 mm and 1.0 mm, especially in a range between 0.4 mm and 0.8 mm and especially in a range between 0.55 mm and 0.75 mm and the second diameter is in a range of between 0.1 mm and 0.5 mm and in particular in a range between between 0.2 mm and 0.4 mm and preferably it is equal to 0.25 mm. Sensor element (110) according to claim 1, characterized in that the second electrode (124) is in an electrode cavity (126), the electrode cavity (126) being connected to the orifice passing gas (130) through at least one diffusion barrier (134); - the diffusion barrier (134) is recessed with respect to the gas passage (130). 12 °) A method of manufacturing a sensor element (110) for capturing at least one property of a gas in a measurement gas chamber (114), in particular a sensor element (110) according to one of the claims 1 to 11, characterized in that - a laminated structure (112) is made with at least one first electrode (118), at least one second electrode (124) and at least one solid electrolyte (122) connecting the first electrode (118) and the second electrode (124) - the second electrode (124) is separated from the measurement chamber (114) by at least one layer of the laminated structure (112) - the second electrode (124) is connected to the measuring gas chamber (114) by at least one gas path (128), the gas path (128) has at least one gas passage (130) in the laminated structure (112), - the gas passage (130) is formed so that it comprises at least two zones (148, 152) having di different ameters. 13) A method of manufacturing a sensor element (110) according to claim 12, characterized in that for producing the gas passage (130), at least one piercing method and / or less a milling process.