ES2564759B1

ES2564759B1 - Gas sensor

Info

Publication number: ES2564759B1
Application number: ES201531137A
Authority: ES
Inventors: Francisco RAMOS PÉREZ; Jesús GARCÍA CANTÓN; Javier GARCÍA CAPDEVILA; Carlos LÓPEZ GÁNDARA
Original assignee: FRANCISCO ALBERO S A U; FRANCISCO ALBERO SAU
Current assignee: FRANCISCO ALBERO S A U; FRANCISCO ALBERO SAU
Priority date: 2015-07-30
Filing date: 2015-07-30
Publication date: 2017-01-25
Anticipated expiration: 2035-07-30
Also published as: ES2564759A1

Abstract

Sensor de gas que comprende al menos: una lámina de YSZ (4) de circonia establizada con itrio, dos electrodos (2, 3) situados a cada lado de la lámina de YSZ (4), unas pistas conductoras (21, 31) que contactan con cada electrodo (2, 3), un calefactor (7) compuesto por una sección de calentamiento (75) configurada por una pista con forma de meandros y por una sección de alimentación (74) configurada por dos pistas (71) que contactan con cada extremo de la sección de calentamiento (75), dos capas de alúmina (81, 82) que embeben el calefactor (7), pads de conexión (23, 33, 73) comunicados eléctricamente con las pistas (21, 31, 71); donde el material que forma la sección de calentamiento (75) es únicamente platino, mientras que la sección de alimentación (74) contiene paladio.Gas sensor comprising at least: a YSZ sheet (4) of zirconia stabilized with yttrium, two electrodes (2, 3) located on each side of the YSZ sheet (4), conductive tracks (21, 31) that contact with each electrode (2, 3), a heater (7) composed of a heating section (75) configured by a meander-shaped track and a power section (74) configured by two tracks (71) that contact with each end of the heating section (75), two layers of alumina (81, 82) that embed the heater (7), connection pads (23, 33, 73) electrically communicated with the tracks (21, 31, 71 ); where the material that forms the heating section (75) is only platinum, while the feeding section (74) contains palladium.

Description

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DESCRIPCIONDESCRIPTION

Sensor de gas.Gas sensor

Objeto de la invencionObject of the invention

El objeto de la invencion es un sensor de gas provisto de un calefactor y de elementos de conexionado configurados para mejorar la estabilidad y la precision en la medida, a la vez que reducen el coste de fabrication.The object of the invention is a gas sensor provided with a heater and connection elements configured to improve stability and precision in measurement, while reducing the manufacturing cost.

Campo de la invencionField of the Invention

Esta invencion es aplicable en la fabricacion de sensores de gas, existiendo un gran interes especialmente en el campo de los sensores de gas de escape de motores de combustion interna.This invention is applicable in the manufacture of gas sensors, there being a great interest especially in the field of internal combustion engine exhaust gas sensors.

Antecedentes de la invencionBackground of the invention

Una de las aplicaciones mas conocidas de los sensores de gas es la de determinar las concentraciones de los componentes del residuo gaseoso expulsado en una combustion. Sirven para influir en el ajuste de la mezcla de aire y combustible con la intention de reducir la cantidad de combustible empleado y la cantidad de gases contaminantes expulsados manteniendo la potencia requerida.One of the best known applications of gas sensors is to determine the concentrations of the components of the gaseous residue expelled in a combustion. They serve to influence the adjustment of the air and fuel mixture with the intention of reducing the amount of fuel used and the amount of pollutant gases expelled while maintaining the required power.

Un tipo muy comun de sensor de gas esta basado en laminas solidas de ceramica de circonia estabilizada con oxido de itrio (YSZ, del ingles “Yttria-Stabilized Zirconia”), las cuales actuan como material electrolltico conductor de iones de oxlgeno cuando se calientan por encima de los 400°C.A very common type of gas sensor is based on solid sheets of zirconia stabilized zirconia ceramic (YSZ), which act as electrolytic material conducting oxygen ions when heated by above 400 ° C.

El dispositivo mostrado en la patente EP1800117 es un ejemplo de este sensor para su uso en motores de combustion interna. Este tipo de sensor comprende una celda electroqulmica con electrodos de platino impresos en cada lado de la lamina de YSZ, la cual se situa en el interior del tubo de escape. Entre los dos electrodos se genera una fuerza electromotriz que, de acuerdo con la ecuacion de Nernst, depende de la diferencia de concentration de oxlgeno existente entre el lado del electrolito donde se encuentra el gas a medir y el lado donde se encuentra el gas de referencia utilizado.The device shown in EP1800117 is an example of this sensor for use in internal combustion engines. This type of sensor comprises an electrochemical cell with platinum electrodes printed on each side of the YSZ sheet, which is located inside the exhaust pipe. An electromotive force is generated between the two electrodes which, according to Nernst's equation, depends on the difference in oxygen concentration between the side of the electrolyte where the gas to be measured is located and the side where the reference gas is located used.

Debido a que este electrolito es aislante por debajo de los 400°C, se aprovecha la misma lamina de YSZ como soporte de las pistas conductoras que transmiten la senal hacia la zona de conexion del sensor, donde se encuentran las vlas metalicas. Estas son orificios rellenos de metal que atraviesan perpendicularmente las laminas de electrolito para contactar cada pista interna con un pad metalico situado en la superficie exterior del YSZ. Finalmente, estos pads contactan con cables electricos que envlan la senal a un dispositivo externo que se encarga de interpretar la medida y actuar en la gestion de la combustion.Because this electrolyte is insulating below 400 ° C, the same YSZ sheet is used to support the conductive tracks that transmit the signal to the sensor connection area, where the metal vlas are located. These are metal filled holes that perpendicularly pass through the electrolyte sheets to contact each inner race with a metal pad located on the outer surface of the YSZ. Finally, these pads contact electrical cables that send the signal to an external device that is responsible for interpreting the measure and acting in the management of combustion.

Para mantener constante la temperatura del electrolito a la que se consigue la conductividad ionica requerida, se suele integrar en el cuerpo de YSZ una resistencia electrica que actua como calefactor. Para aislarlo electricamente del electrolito, el calefactor se suele embeber en dos capas serigrafiadas de alumina. Este tipo de calefactor acostumbra a estar compuesto por una pista continua de platino serigrafiado, material cuyo punto de fusion es superior a la temperatura de sinterizado del YSZ y de la alumina. La pista presenta por un lado una section de calentamiento, situada en la zona de medicion y configurada en forma de meandros con el fin de aumentar la transferencia de calor en dicha zona. Por otro lado presenta la seccion de alimentation, configurada por dos pistas que van desde cada extremo de la seccion deTo keep the temperature of the electrolyte at which the required ionic conductivity is achieved constant, an electrical resistance that acts as a heater is usually integrated into the YSZ body. To electrically isolate it from the electrolyte, the heater is usually embedded in two screenprinted layers of alumina. This type of heater is usually composed of a continuous platinum-plated track, material whose melting point is higher than the sintering temperature of the YSZ and the alumina. The track has a heating section on the one hand, located in the measurement zone and configured in the form of meanders in order to increase the heat transfer in said zone. On the other hand it presents the section of feeding, configured by two tracks that go from each end of the section of

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calentamiento hasta sus vlas correspondientes, las cuales se encuentran situadas en la zona de conexion opuesta a la zona de medicion. Estas dos vlas contactan con sus respectivos pads en la superficie de la estructura. A traves de estos pads se le suministra la energla al calefactor aplicandoles una tension de alimentacion.heating up to their corresponding vlas, which are located in the connection zone opposite the measurement zone. These two vlas contact their respective pads on the surface of the structure. Through these pads the energy is supplied to the heater by applying a supply voltage.

Como se puede deducir, no es adecuado un aumento de temperatura por encima de los 400°C en la zona de conexion, ya que si el YSZ colindante aumenta su conductividad ionica, se generan corrientes parasitas entre las pistas y los pads de los electrodos, lo cual anade ruido a la medida. Usualmente se alslan las pistas de los electrodos respecto al sustrato de YSZ mediante una capa serigrafiada de alumina para evitar dichas corrientes parasitas. De todas formas, el aislamiento de las vlas es inviable a traves de las laminas de YSZ, por lo que se genera igualmente ruido en el caso de que aumente la temperatura en la zona de conexion. Desfavorablemente, el hecho de que el platino tenga un alto valor de Coeficiente de Temperatura en funcion de la Resistencia (RTC, por sus siglas en ingles “Resistance Temperature Coeficient”) hace que la seccion de alimentacion del calefactor aporte calor indebidamente a dicha zona. A la vez, el precio del platino es muy elevado, por lo que se han buscado alternativas de materiales para fabricar el calefactor.As can be deduced, a temperature rise above 400 ° C in the connection zone is not adequate, since if the adjacent YSZ increases its ionic conductivity, parasitic currents are generated between the tracks and the electrode pads, which adds custom noise. Usually the electrode tracks are smoothed with respect to the YSZ substrate by means of a screen-printed alumina layer to avoid such parasitic currents. In any case, the insulation of the vlas is unfeasible through the YSZ sheets, so that noise is also generated in the event that the temperature in the connection zone increases. Unfavorably, the fact that platinum has a high Resistance Temperature Coefficient (RTC) value causes the heater supply section to unduly heat this zone. At the same time, the price of platinum is very high, so we have sought alternatives of materials to manufacture the heater.

En el estado de la tecnica se pueden encontrar estructuras de calefactores disenadas tanto para concentrar la transferencia de calor exclusivamente en la zona de medicion como para reducir sus costes de fabricacion sin disminuir su durabilidad.In the state of the art, heater structures designed to concentrate heat transfer exclusively in the measurement zone and to reduce its manufacturing costs can be found without decreasing its durability.

Por ejemplo, en la patente US4952903 se describe un calefactor donde la seccion de calentamiento esta formada por un cermet que contiene ceramica y metal noble, y las pistas estan formadas por metal no noble con o sin ceramica. De esta forma se reduce la cantidad usada de metal noble a la vez que se aumenta la adhesion de las laminas de alumina que embeben el calefactor.For example, in US4952903 a heater is described where the heating section is formed by a cermet containing ceramic and noble metal, and the tracks are formed by non-noble metal with or without ceramic. In this way the amount of noble metal used is reduced while increasing the adhesion of the alumina sheets that embed the heater.

En la patente EP0963137 se define un ratio de resistencia entre la seccion calefactora y la seccion de las pistas para generar un gradiente de temperatura mas acusado en la zona de medicion. Este ratio esta determinado por la proporcion entre la alumina y los metales nobles usados en cada seccion.In EP0963137 a resistance ratio is defined between the heating section and the section of the tracks to generate a more pronounced temperature gradient in the measurement zone. This ratio is determined by the ratio between the alumina and the noble metals used in each section.

En la patente US5787866 se describe un calefactor que contiene platino y otro metal del grupo consistente en rodio, paladio o iridio, con la intencion de facilitar su fabrication y aumentar su durabilidad.Patent US5787866 describes a heater containing platinum and another metal of the group consisting of rhodium, palladium or iridium, with the intention of facilitating its fabrication and increasing its durability.

El problema que tienen las dos primeras estructuras es que al anadir alumina a la pista del calefactor se genera una distribution heterogenea de la densidad de corriente, lo que se traduce en un calentamiento irregular del YSZ que produce ruido en la medida. A la vez, esta heterogeneidad puede dar lugar a concentraciones de corriente que eleven excesivamente la temperatura en zonas puntuales, provocando as! una degradation de la estructura a mayor velocidad o incluso roturas ya en la fase de testeado. En la ultima estructura, al usar el mismo material tanto en la seccion de alimentacion como en la seccion de calentamiento, la distribucion de temperatura del sensor no se encuentra optimizada para mejorar la precision de la medida.The problem with the first two structures is that when adding alumina to the heater track, a heterogeneous distribution of the current density is generated, which results in an irregular heating of the YSZ that produces noise in the measurement. At the same time, this heterogeneity can lead to current concentrations that excessively raise the temperature in specific areas, thus causing! a degradation of the structure at higher speed or even breakage already in the testing phase. In the last structure, when using the same material both in the feeding section and in the heating section, the temperature distribution of the sensor is not optimized to improve the measurement accuracy.

Descripcion de la inventionDescription of the invention

El sensor de gas de la presente invencion comprende una zona de medicion y una zona de conexion. En la zona de medicion hay al menos una celda electroqulmica formada por electrodos de platino definidos a cada lado de al menos una lamina de YSZ (circonia estabilizada con itrio). En la zona de conexion hay unas pistas conductoras que dirigen la senal de los electrodos hacia el extremo opuesto del sensor, las cuales se encuentran serigrafiadasThe gas sensor of the present invention comprises a measurement zone and a connection zone. In the measurement zone there is at least one electrochemical cell formed by platinum electrodes defined on each side of at least one YSZ sheet (zirconia stabilized with yttrium). In the connection zone there are conductive tracks that direct the electrode signal to the opposite end of the sensor, which are screen printed

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en la misma lamina de YSZ. Al menos uno de los electrodos se expone al gas a medir. La pista que contacta con este electrodo se alsla de dicho gas con dos capas de alumina. El otro electrodo se expone a un gas de referencia con una concentration de oxlgeno constante. Este gas de referencia puede ser oxlgeno generado por el mismo electrodo o puede ser aire limpio que entra desde la zona de conexion del sensor a traves de un canal definido entre otras laminas de YSZ adheridas a la primera.in the same sheet of YSZ. At least one of the electrodes is exposed to the gas to be measured. The track that contacts this electrode is isolated from said gas with two layers of alumina. The other electrode is exposed to a reference gas with a constant oxygen concentration. This reference gas can be oxygen generated by the same electrode or it can be clean air that enters from the sensor connection zone through a defined channel between other YSZ sheets adhered to the first.

Unas vlas metalicas situadas en la zona de conexion atraviesan perpendicularmente las laminas de YSZ para contactar las pistas que se encuentren en el interior del cuerpo de YSZ con sus respectivos pads en la superficie externa del sensor.Metal vlas located in the connection zone cross perpendicularly the YSZ sheets to contact the tracks that are inside the YSZ body with their respective pads on the external surface of the sensor.

Adicionalmente, el sensor de gas contiene un calefactor embebido entre laminas serigrafiadas de alumina que lo alslan del YSZ. Este calefactor se basa en una pista resistiva electrica definida por serigrafla. La pista se divide por una parte en la section de calentamiento, la cual esta situada en la zona de medicion y configurada en forma de meandros, y por otra parte la seccion de alimentation, la cual esta configurada por dos pistas que contactan cada extremo de la seccion de calentamiento con sus respectivas vlas situadas en la zona de conexion, y estas con sus respectivos pads en la superficie del sensor.Additionally, the gas sensor contains a heater embedded between screenprinted sheets of alumina that alslan it from the YSZ. This heater is based on an electric resistive track defined by screen printing. The track is divided by one part in the heating section, which is located in the measurement zone and configured in the form of meanders, and on the other hand the feeding section, which is configured by two tracks that contact each end of the heating section with its respective vlas located in the connection zone, and these with their respective pads on the sensor surface.

La principal novedad de la presente invencion reside en que la seccion de calentamiento del calefactor esta hecha solo de platino y, en cambio, las pistas, las vlas y los pads de todo el sensor de gas contienen paladio. Esto se justifica porque el platino tiene un valor de RTC mayor que el paladio, por lo que a temperaturas mayores a 400°C el platino ofrece mayor resistencia electrica y emite mas calor. En consecuencia, que la seccion de calentamiento solo tenga platino permite que la transferencia de calor en dicha zona sea mayor que conteniendo paladio y mas homogenea que conteniendo alumina. Por otro lado, el hecho de que la seccion de alimentacion del calefactor este formada con menos platino hace que la transferencia de calor en la zona de conexion sea menor que si estuviera formada solo por platino. Todo ello se traduce en una reduction de ruido en la medida y un consumo energetico optimizado.The main novelty of the present invention is that the heating section of the heater is made only of platinum and, instead, the tracks, vlas and pads of the entire gas sensor contain palladium. This is justified because platinum has an RTC value greater than palladium, so at temperatures above 400 ° C the platinum offers greater electrical resistance and emits more heat. Consequently, that the heating section only has platinum allows the heat transfer in said area to be greater than containing palladium and more homogeneous than containing alumina. On the other hand, the fact that the heater supply section is formed with less platinum makes the heat transfer in the connection area smaller than if it was formed only by platinum. All this translates into a reduction of noise in the measure and an optimized energy consumption.

A la vez, la sustitucion de al menos una parte del platino por paladio, tanto en las pistas de conexion de los electrodos como en las vlas y los pads, permite reducir el coste del sensor. Es por ello que dichos componentes estan hechos al menos de paladio en una quinta parte, proportion a partir de la cual los costes de production de la mezcla empiezan a ser menores que el ahorro en materia prima durante la fabrication en masa del sensor de gas. En la situation mas rentable economicamente, dichos componentes estan hechos unicamente de paladio. En este caso la ceramica utilizada tiene una temperatura de sinterizado menor a la ceramica convencional utilizada en los sensores de gas, ya que la temperatura de fusion del paladio es muy cercana a la temperatura convencional de coccion y habrla riesgo de degradation de los componentes durante este proceso.At the same time, the replacement of at least a part of the platinum with palladium, both in the electrode connection tracks and in the rods and pads, allows to reduce the cost of the sensor. That is why these components are made of at least one fifth palladium, a proportion from which the production costs of the mixture begin to be lower than the savings in raw material during mass production of the gas sensor. In the most economically profitable situation, these components are made only of palladium. In this case the ceramic used has a sintering temperature lower than the conventional ceramic used in the gas sensors, since the melting temperature of the palladium is very close to the conventional cooking temperature and there will be a risk of degradation of the components during this process.

Otra novedad anadida a la anterior invention es que el espesor de las capas serigrafiadas de alumina que embeben el calefactor es como maximo el doble del espesor del calefactor. Esto se justifica porque el calefactor no contiene alumina y este pierde adherencia con las capas que lo embeben. Ya que la expansion termica del platino y del paladio es diferente a la de la alumina, es adecuado que los espesores de las serigraflas de todos estos materiales sean parecidos para evitar la aparicion de grietas o de delaminacion entre capas. Finalmente, se anade otra capa de YSZ que embebe el conjunto de calefactor y alumina en el cuerpo de YSZ, reforzando as! la adhesion entre los componentes.Another novelty added to the previous invention is that the thickness of the screenprinted layers of alumina that embed the heater is at most twice the thickness of the heater. This is justified because the heater does not contain alumina and it loses adhesion with the layers that embed it. Since the thermal expansion of platinum and palladium is different from that of the alumina, it is appropriate that the thicknesses of the silkscreens of all these materials are similar to avoid the appearance of cracks or delamination between layers. Finally, another layer of YSZ is added that embeds the heater and alumina assembly in the body of YSZ, thus reinforcing! the adhesion between the components.

Description de las figurasDescription of the figures

La figura 1 es una vista en perspectiva isometrica de una realization preferente del sensor de gas de la presente invencion.Figure 1 is an isometric perspective view of a preferred embodiment of the gas sensor of the present invention.

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La figura 2 es una vista explosionada de la realization del sensor de gas mostrado en la figura 1.Figure 2 is an exploded view of the realization of the gas sensor shown in Figure 1.

Descripcion de una realizacion preferenteDescription of a preferred embodiment

El sensor de gas que se describe a continuation es una posible ejecucion de la presente invention. Concretamente se detalla un sensor de gas con una unica celda electroqulmica, pero la invencion puede extrapolarse a otras configuraciones de sensores de gas con material electrolltico basado en YSZ. Dado que su estructura y funcionamiento han sido ampliamente reportados en la literatura, la siguiente descripcion hara mention principalmente a los componentes que ayuden a interpretar la invencion propuesta.The gas sensor described below is a possible embodiment of the present invention. Specifically, a gas sensor with a single electrochemical cell is detailed, but the invention can be extrapolated to other gas sensor configurations with YSZ-based electrolytic material. Since its structure and operation have been widely reported in the literature, the following description will mention mainly the components that help interpret the proposed invention.

A la vista de las mencionadas figuras, se puede observar en ellas el ejemplo de realizacion preferente de la invencion que se describe a continuacion.In view of the aforementioned figures, the example of preferred embodiment of the invention described below can be observed in them.

La figura 1 muestra una perspectiva isometrica del sensor de gas (1), donde se puede ver una zona de conexion (11) y una zona de medicion (12).Figure 1 shows an isometric perspective of the gas sensor (1), where a connection zone (11) and a measurement zone (12) can be seen.

En la figura 2 se puede ver una vista explosionada del sensor de gas (1). Dos electrodos (2, 3) de platino definidos por serigrafla se situan a cada lado de una lamina de YSZ (4), formando una celda electroqulmica hallada en la zona de medicion (12).An exploded view of the gas sensor (1) can be seen in Figure 2. Two platinum electrodes (2, 3) defined by screen printing are placed on each side of a YSZ sheet (4), forming an electrochemical cell found in the measurement zone (12).

Contactadas a los electrodos (2, 3) se encuentran unas pistas conductoras (21, 31) serigrafiadas en la misma lamina de YSZ (4) que dirigen la senal de los electrodos (2, 3) hacia la zona de conexion (11). En la superficie externa (41) de la lamina de YSZ (4) se encuentran serigrafiados dos pads (23, 33) de conexion. Uno de los pads (23) contacta con la pista externa (21) y el otro pad (33) contacta con la pista interna (31) a traves de una via metalica (32) que atraviesa la lamina de YSZ (4).Connected to the electrodes (2, 3) are conductive tracks (21, 31) screen printed on the same YSZ sheet (4) that direct the electrode signal (2, 3) towards the connection area (11). On the outer surface (41) of the YSZ sheet (4) two connection pads (23, 33) are screen printed. One of the pads (23) contacts the outer track (21) and the other pad (33) contacts the inner track (31) through a metal track (32) that crosses the YSZ sheet (4).

La pista conductora (21) externa se alsla tanto del gas a medir como de la lamina de YSZ (4) mediante dos capas serigrafiadas de alumina (5). El electrodo (3) interno y la pista conductora (31) interna estan situados en un canal de referencia (6) formado por dos capas de YSZ (61, 62), la primera de ellas (61) con un canal (6) troquelado y la segunda (62) cubriendo dicho canal. A traves de este canal (6) entra aire limpio, el cual sirve como gas de referencia con proportion de oxlgeno constante.The external conductive track (21) is isolated from both the gas to be measured and the YSZ sheet (4) by means of two screenprinted layers of alumina (5). The internal electrode (3) and the internal conductive track (31) are located in a reference channel (6) formed by two layers of YSZ (61, 62), the first one (61) with a die-cut channel (6) and the second (62) covering said channel. Clean air enters this channel (6), which serves as a reference gas with a constant oxygen ratio.

A continuacion de la anterior capa de YSZ (62) se encuentra emplazado un conjunto formado por un calefactor (7) aislado por dos capas serigrafiadas de alumina (81, 82). Este calefactor (7) esta configurado por un pista que se divide por una parte en una section de calentamiento (75), la cual esta configurada en forma de meandros y situada en la zona de medicion (12), y por otra parte una seccion de alimentation (74), la cual esta configurada por dos pistas (71) que contactan cada extremo de la seccion de calentamiento (75) con sus respectivas vlas (72) situadas en la zona de conexion (11). Una ultima capa de YSZ (9) refuerza la sujecion del conjunto (7, 8) a la anterior capa de YSZ (62). La capa mas externa de alumina (82) esta disenada para que no tape las vlas (72), por lo que estas solamente atraviesan la ultima capa de YSZ (9) hasta contactar con los respectivos pads (73).Next to the previous YSZ layer (62), an assembly formed by a heater (7) is insulated by two screen-printed layers of alumina (81, 82). This heater (7) is configured by a track that is divided by a part in a heating section (75), which is configured in the form of meanders and located in the measurement zone (12), and on the other hand a section supply (74), which is configured by two tracks (71) that contact each end of the heating section (75) with their respective rods (72) located in the connection area (11). A last layer of YSZ (9) reinforces the fastening of the assembly (7, 8) to the previous layer of YSZ (62). The outermost layer of alumina (82) is designed so that it does not cover the vlas (72), so they only pass through the last layer of YSZ (9) until contacting the respective pads (73).

El material que forma la seccion de calentamiento (75) es unicamente platino, mientras que en este ejemplo concreto las pistas conductoras (21, 31, 71), las vlas (32, 72) y los pads (23, 33, 73) de todo el sensor de gas (1) estan hechos unicamente de paladio.The material that forms the heating section (75) is only platinum, while in this specific example the conductive tracks (21, 31, 71), the vlas (32, 72) and the pads (23, 33, 73) of The entire gas sensor (1) is made only of palladium.

El grosor de las dos capas de alumina (81, 82) que embeben al calefactor (7) es 1,5 veces el grosor de este, lo que evita grietas y delaminacion entre las dos capas de alumina (81, 82).The thickness of the two layers of alumina (81, 82) that embed the heater (7) is 1.5 times the thickness of this, which prevents cracks and delamination between the two layers of alumina (81, 82).

Claims

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ES 2 564 759 A1

1. Gas sensor (1) comprising at least one YSZ sheet (stabilized zirconia

with yttrium), at least two electrodes (2, 3) located on each side of the YSZ sheet (4), about

conductive tracks (21, 31) that contact each electrode (2, 3), a heater (7)

composed of a heating section (75) configured by a meander-shaped track and a power section (74) configured by two conductive tracks (71) that contact each end of the heating section (75), two layers of alumina

(81, 82) embedding the heater (7), connecting pads (23, 33, 73) communicated

electrically with the conductive tracks (21, 31, 71) by direct contact or through metal rods (32, 72), characterized in that the material that forms the heating section (75) is only platinum, while the power section ( 74) contains palladium.

2. Gas sensor according to claim 1, characterized in that the tracks (21, 31) that contact the electrodes (2, 3) contain palladium.

3. Gas sensor according to any of the preceding claims, characterized in that the pads (23, 33, 73) contain palladium.

4. Gas sensor according to any of the preceding claims, characterized in that the vlas (32, 72) contain palladium.

5. Gas sensor according to any of the preceding claims, characterized in that the supply section (74) of the heater (7) is made of at least one fifth of palladium.

6. Gas sensor according to any of the preceding claims, characterized in that the tracks (21, 31) are made of at least one fifth of palladium.

7. Gas sensor according to any of the preceding claims, characterized in that the pads (23, 33, 73) are made of at least one fifth of palladium.

8. Gas sensor according to any of the preceding claims, characterized in that the vlas (32, 72) are made of at least one fifth of palladium.

9. Gas sensor according to any of the preceding claims, characterized in that the power section (74) of the heater (7) is palladium.

10. Gas sensor according to any of the preceding claims, characterized in that the tracks (21, 31) are made of palladium.

11. Gas sensor according to any of the preceding claims, characterized in that the pads (23, 33, 73) are palladium.

12. Gas sensor according to any of the preceding claims, characterized in that the vlas (32, 72) are made of palladium.

13. Gas sensor according to any one of the preceding claims, characterized in that the thickness of the two layers of alumina (81, 82) that embed the heater (7) is at most twice the thickness of the heater (7).