JP4628920B2 - Gas sensor element - Google Patents

Description

  The present invention relates to a gas sensor element, and in particular, an improved multi-layer gas sensor element in which a plate-like body, at least one of which is a solid electrolyte body, is laminated and a plurality of electrodes are formed on the solid electrolyte body. Concerning structure.

Conventionally, there has been known a gas sensor element that measures the concentration (partial pressure) of a predetermined gas component in a gas atmosphere to be measured based on the principle of a concentration cell using the ionic conductivity of a solid electrolyte body. Yes. For example, a solid electrolyte body such as zirconia (ZrO ₂ ) having oxygen ion conductivity at a high temperature is used, and a plurality of electrodes are provided on the solid electrolyte body so as to be in contact therewith. As an electrode material provided to be in contact with a solid electrolyte body such as zirconia, or one that measures oxygen concentration (partial pressure) in combustion exhaust gas discharged from gas, industrial furnaces, boilers, etc. NOx (nitrogen oxide) NOx concentration (partial pressure) in exhaust gas and combustion exhaust gas can be measured by selecting and using noble metal materials such as Pt and Rh that have reducing or decomposing properties Etc. That is it. In addition, using a solid electrolyte body having various ion conductivity other than zirconia, each of hydrogen gas, carbon dioxide gas, hydrocarbon gas, SOx (sulfur oxide) gas, water vapor, etc. in the measurement gas atmosphere What measured a density | concentration (partial pressure) is also generally known.

  By the way, as a kind of gas sensor element using such a solid electrolyte body, a laminated body in which a plurality of plate-like bodies, at least one of which is a solid electrolyte body, and a solid electrolyte body in a portion on one end side of the laminated body are provided. A plurality of electrodes arranged in contact with the solid electrolyte body on the laminated surface with the other plate-like body, and at least one of the front surface and the back surface facing each other in the laminating direction at the other end side portion of the laminated body A plurality of terminal portions that are exposed to the outside on the surface, and a plurality of lead portions that are disposed so as to connect the plurality of electrodes and the plurality of terminal portions, respectively, to the laminate. There is a so-called laminated gas sensor that is integrated by bonding.

  Specifically, among the stacked gas sensor elements, for example, the NOx sensor element includes a plurality of plate-like bodies having a predetermined length including a plurality of solid electrolyte bodies such as zirconia, as shown in Patent Document 1 below. It has a device body (laminated body) that is laminated and integrated, with one end portion in the length direction serving as a detection portion and the other end portion serving as a connector portion. Then, a first gas chamber to be measured is introduced into the detection portion of the element body through the diffusion rate-limiting means, and an atmosphere in the first gas chamber to be measured is introduced through the diffusion-controlled passage. Pumping oxygen to the second measured gas chamber, the first atmospheric chamber communicated with the atmosphere, the second atmospheric chamber introducing the atmosphere as a reference gas, and the first measured gas chamber A pump cell, a monitor cell that monitors the oxygen concentration (partial pressure) of the atmosphere in the second measured gas chamber, and a sensor cell that detects the NOx concentration in the atmosphere of the second measured gas chamber are provided. .

  Of the three electrochemical cells provided in the detection unit, the pump cell includes an end portion of one solid electrolyte body located in the detection unit and another plate-like body of the solid electrolyte body. A pair of electrodes provided so as to be in contact with the solid electrolyte body in a state of being exposed to the first atmosphere chamber and the first measured gas chamber with respect to the laminated surface (both surfaces of the solid electrolyte body) And is composed of. The monitor cell has a second gas to be measured with respect to a laminated surface (both surfaces of the solid electrolyte body) of an end portion of another solid electrolyte body located in the detection unit and another plate-like body of the solid electrolyte body. It is comprised by a pair of electrode provided so that it might be exposed to the room | chamber interior and the 2nd air | atmosphere room | chamber respectively, and may be in contact with a solid electrolyte body. The sensor cell also has a second covered surface with respect to the laminated surface (both surfaces of the solid electrolyte body) of the end part on the detection unit side of the solid electrolyte body provided with the monitor cell and the other plate-like body of the solid electrolyte body. It is constituted by a pair of electrodes provided so as to be in contact with the solid electrolyte body in a state of being exposed to the measurement gas chamber and the second atmospheric chamber, respectively. Of the pair of electrodes constituting the sensor cell, the electrode exposed in the second gas chamber to be measured is configured to function as a NOx reduction or decomposition catalyst.

  On the other hand, the connector portion of the element body is formed with a plurality of terminal portions on both the front and back surfaces, and each terminal portion extends between the detection portion and the connector portion in the element body. The electrodes are electrically connected to the electrodes of the three electrochemical cells through a plurality of leads.

  Thus, in the laminated gas sensor element having such a structure, the oxygen concentration detected by the monitor cell is taken out through the terminal portion connected to the pair of electrodes in the monitor cell, and this oxygen concentration Based on the above, a predetermined voltage is applied to the pair of electrodes in the pump cell from the terminal portion connected thereto, so that the measured gas in the second measured gas chamber is generated by the pumping action of oxygen by the pump cell. The oxygen concentration in the atmosphere is controlled to a desired value. In such a state, NOx in the measured gas atmosphere in the second measured gas chamber is reduced, and oxygen generated at that time is pumped out to the second atmospheric chamber by the sensor cell. And at this time, the pump current value flowing between the pair of electrodes of the sensor cell is measured by an ammeter connected to the terminal portion connected to the pair of electrodes in the pump cell, based on the measured value, The concentration of NOx in the measured gas atmosphere is required.

  The laminated gas sensor element having such a structure is more complicated as described above than the conventional structure, that is, the structure using a bottomed cylindrical solid electrolyte. Since the ease of incorporation into a solid electrolyte body with a simple structure is sufficiently enhanced, the productivity can be improved, the cost can be reduced, and further downsizing can be advantageously achieved. is there.

  However, in such a conventional laminated gas sensor element, for example, as described in Patent Document 2 below, a plurality of terminal portions on the other end side of the laminated body, that is, a connector portion is a sensor of the sensor body. With respect to the inside of the element storage portion, it is inserted between a plurality of connection terminals electrically connected to an external power source, a predetermined measurement device, etc. while being pressed by a pressing spring or the like, As a result, the plurality of terminal portions and the plurality of connection terminals are brought into contact with each other, and electrical continuity between them is ensured and assembled to the sensor body. Therefore, when the gas sensor element is assembled to the sensor body, a part of the terminal portion exposed to the outside is scraped off by the connection terminal, etc. There is a concern that poor conduction occurs in the terminal portion.

  Further, in the conventional laminated gas sensor element, generally, a through-hole extending from the electrode forming surface of the solid electrolyte body toward the front surface or the back surface of the element body where the plurality of terminal portions are formed with respect to the connector portion, a so-called through-hole. A hole is formed, and the lead portion is extended from the electrode formation surface of the solid electrolyte body toward the front surface or the back surface of the element body through the through hole, and the electrode and the terminal portion pass through the lead portion. (For example, refer to Patent Document 1 below), when adopting such a connection structure between an electrode and a terminal part using a through hole, the number of electrodes and terminal parts is as follows. As the number increases, the number of through holes inevitably increases, thereby causing a problem that the strength of the entire gas sensor element is lowered.

  Therefore, in recent years, a connection side portion with the terminal portion in the lead portion is provided so as to be exposed to the outside with respect to the side surface of the connector portion in the element body, and this is used as the side surface conduction portion. In contrast, the electrode and the terminal part are connected to each other via the lead part having the side conduction part by connecting the connection side part of the lead part provided on the electrode forming surface of the solid electrolyte body. The structure made to do is considered (for example, refer the following patent document 3). According to such a connection structure between the electrode and the terminal portion, the number of through holes can be reduced to zero or advantageously reduced, and as a result, a reduction in strength of the gas sensor element due to formation of the through holes is advantageously prevented. It becomes possible to do.

  However, in the gas sensor element adopting the connection structure between the electrode and the terminal portion by the lead portion having such a side surface conductive portion, the side surface conductive portion is provided to be exposed to the outside like the terminal portion. Therefore, when inserting the connector portion into the sensor element storage portion, not only the terminal portion, but also part of the side surface conductive portion is scraped off by the connection terminal, etc., and peeled off from the connector portion, As a result, in addition to the terminal portion, there is a possibility that poor conduction occurs in the lead portion.

JP 2004-93199 A Japanese Utility Model Publication No. 6-37326 Japanese Patent Laid-Open No. 7-190863

  Here, the present invention has been made in the background of the circumstances as described above, and the problem to be solved is a terminal portion and a side surface that are exposed to the outside in a laminated gas sensor element. A novel structure in which the peeling strength of the conductive part can be advantageously increased and the occurrence of poor conduction due to peeling of the terminal part and side conductive part during assembly to the gas sensor body can be advantageously prevented. It is to provide.

  In order to solve this problem, the present inventors paid attention to the composition of the conductive material formed by the terminal portion and the side surface conductive portion in the course of various studies. In the conventional gas sensor element, the terminal portion and the side surface conductive portion are generally configured by a cermet formed using a conductive material made of a mixture of a noble metal powder such as Pt, Pd, Rh, and zirconia powder. . Therefore, the present inventors mixed a ceramic powder other than zirconia powder with a noble metal powder as a ceramic component of such a cermet to obtain a conductive material, which is fired to obtain a cermet. The idea was to improve the adhesion of the solid electrolyte body of the part and side conduction part.

As a result of further earnest research based on this concept, the cermet is composed of a conductive material made of a mixture of noble metal powder and alumina (Al ₂ O ₃ ) powder, so that the terminal portion and the side surface conduction It has been found that the adhesion strength with the solid electrolyte body of the portion can be dramatically increased. The improvement in adhesion strength is due to the fact that the conductive material made of a mixture of noble metal powder and alumina powder exhibits superior sinterability than the conductive material made of a mixture of noble metal powder and zirconia powder. it is conceivable that.

That is, the present invention has been completed based on such knowledge, and the gist of the present invention is that a laminate in which a plurality of plate-like bodies, at least one of which is a solid electrolyte body, is laminated, and the laminate A plurality of electrodes arranged in contact with the solid electrolyte body on the surface of the solid electrolyte body and the other plate-like body at the one end portion side of the body; a plurality of terminals disposed exposed Oite outside on at least one side of the front and back facing position in the stacking direction, relative to the laminate, the plurality of electrodes and the plurality of terminals and a plurality of lead portions which are arranged to connect each part is made are integrated I by the sintering, the connection side with the terminal portion of and those of at least one lead portion of the plurality of The part is exposed to the outside on the side surface of the laminate. If the position is allowed to extend in the stacking direction of the laminate, the gas sensor element which is a side conductive portion which is brought into connection to the terminal portion, and the said side conductive portions of the lead portions and the front Symbol pin portion, respectively using a conductive material obtained by mixing a noble metal powder and the alumina powder, in a gas sensor element, characterized by being made form.

  In the gas sensor element according to the present invention, each of the plurality of terminal portions exposed to the outside is formed using a conductive material made of a mixture of noble metal powder and alumina powder. The adhesion strength of the portion with the solid electrolyte body can be sufficiently increased, and thereby the peel strength of each terminal portion with respect to the solid electrolyte body can be effectively improved.

  Therefore, in the gas sensor element according to the present invention as described above, peeling of the terminal portion at the time of assembly to the gas sensor main body can be prevented in advance, and occurrence of poor conduction due to peeling of the terminal portion is advantageous. Can be prevented. As a result, in a state configured as a gas sensor, electrical continuity in the connector portion provided with a plurality of terminal portions can be secured extremely stably, and thus a predetermined gas concentration in the measured gas atmosphere The measurement accuracy can be effectively stabilized, and the reliability of the measurement accuracy can be dramatically improved.

Aspects of the Invention

  By the way, the present invention can be suitably implemented at least in various aspects as listed below.

(1) On a laminated surface of a laminate obtained by laminating a plurality of plate-like bodies, at least one of which is a solid electrolyte body, and another plate-like body of the solid electrolyte body at a portion on one end side of the laminate, A plurality of electrodes arranged in contact with the solid electrolyte body, and exposed to the outside on at least one of the front surface and the back surface facing each other in the laminating direction at the other end portion side of the laminated body A plurality of terminal portions, and a plurality of lead portions arranged so as to connect the plurality of electrodes and the plurality of terminal portions to the laminate, respectively, are integrated by sintering. The gas sensor element, wherein the plurality of terminal portions are each formed using a conductive material obtained by mixing a noble metal powder and an alumina powder.

(2) In the aspect (1) described above, the terminal portion is formed of a thin film having a thickness in the range of 2 to 40 μm.

  According to this aspect, the terminal portion is formed as a thin film having an appropriate thickness, and the resistance value in the terminal portion can be advantageously stabilized. For example, the terminal portion is assembled into the gas sensor main body by insertion into the sensor element housing portion. When attached, sliding resistance generated between the terminal portion and the gas sensor main body can be effectively suppressed, and peeling of the terminal portion can be advantageously prevented. Therefore, the occurrence of poor conduction at the terminal portion can be prevented more reliably, and therefore a gas sensor that can measure the predetermined gas concentration in the measured gas atmosphere more accurately and stably can be obtained with certainty. It becomes.

(3) On the laminated surface of a laminate obtained by laminating a plurality of plate-like bodies, at least one of which is a solid electrolyte body, and the other plate-like body of the solid electrolyte body at a portion on one end side of the laminate, A plurality of electrodes arranged in contact with the solid electrolyte body, and arranged to be exposed to the outside on at least one of the front surface and the back surface opposed to each other in the stacking direction at the other end portion side of the stacked body. A plurality of terminal portions and a plurality of lead portions arranged so as to connect the plurality of electrodes and the plurality of terminal portions to the laminate, respectively, are integrated by sintering, In the gas sensor element in which at least one of the plurality of lead portions is connected to the terminal portion on a side-side conductive portion exposed to the outside on the side surface of the multilayer body. And the plurality of terminals Gas sensor element at least one of said side conductive portions of de unit, characterized in that it is formed respectively by using a conductive material obtained by mixing a noble metal powder and the alumina powder.

  In this embodiment, the plurality of terminal portions and the plurality of side surface conductive portions exposed to the outside are formed using a conductive material made of a mixture of noble metal powder and alumina powder. The adhesion strength with the electrolyte body and the adhesion strength with the solid electrolyte body of each side conduction part can be increased sufficiently, whereby the peel strength of each terminal part with respect to the solid electrolyte body and the solid electrolyte body of each side conduction part The peel strength against can be effectively improved.

  Therefore, according to this aspect, the separation of the terminal portion and the side surface conduction portion during assembly to the gas sensor main body can be effectively prevented, and the conduction failure caused by the separation of the terminal portion and the side surface conduction portion can be prevented. Occurrence can be advantageously prevented. As a result, under the state of being configured as a gas sensor, the electrical continuity in the connector portion provided with the terminal portion and the side surface conductive portion can be extremely effectively stabilized, so that a predetermined amount in the measured gas atmosphere The measurement accuracy of the gas concentration can be stabilized effectively, and the reliability in the measurement accuracy can be dramatically improved.

(4) In the mode (3) described above, each of the terminal portion and the side surface conductive portion is constituted by a thin film having a thickness in the range of 2 to 40 μm.

  According to this aspect, both the terminal portion and the side surface conductive portion have an appropriate thickness, which can advantageously stabilize the resistance value in the terminal portion and the side surface conductive portion. The sliding resistance generated between the terminal part and the gas sensor body or between the side surface conduction part and the gas sensor body during assembly to the gas sensor body by insertion into the gas sensor body can be effectively suppressed. Can be advantageously prevented. Therefore, the occurrence of conduction failure in the terminal portion and the side surface conduction portion can be prevented more reliably, so that a gas sensor that can measure the predetermined gas concentration in the measured gas atmosphere more accurately and stably is ensured. Will be obtained.

(5) In any one of the above-described embodiments (1) to (4), the conductive material has a composition of noble metal powder / alumina powder = 95/5 to 40/60 by volume ratio. Doing things. According to this aspect, alumina powder is contained in an appropriate amount in the conductive material, thereby ensuring sufficient conductivity in the terminal portion and the side surface conductive portion, while the terminal portion and the side surface conductive portion. The adhesion strength to the solid electrolyte body can be effectively increased.

(6) In any one of the above-described embodiments (1) to (5), the alumina powder contained in the conductive material has a BET specific surface area in the range of 10 to 80 m ² / g. Doing things. According to this aspect, the conductive material can be configured in a state where the alumina powder and the noble metal material are more uniformly mixed, and the sinterability of the conductive material is advantageously enhanced. Thus, the adhesion strength to the solid electrolyte body of the terminal portion and the side surface conductive portion made of such a conductive material, and further the peel strength can be effectively increased.

  (7) In any one of the modes (1) to (6) described above, in the surface on which the plurality of terminal portions are formed, of the surface and the back surface of the laminate, the surface and the plurality An insulating layer made of alumina powder is further laminated between the terminal portion and the insulating layer, and the insulating layer is integrated with the laminated body, the electrode, the terminal portion, and the lead portion by sintering. It must be a precise structure. In this embodiment, not only short-circuiting between a plurality of terminal portions can be advantageously prevented, but also the adhesion strength of each terminal portion to the solid electrolyte body and further the peel strength can be effectively improved. .

(8) In the aspect (7) described above, the alumina powder forming the insulating layer has a BET specific surface area within a range of 10 to 80 m ² / g. According to this aspect, the sinterability of the insulating layer is advantageously enhanced, and the insulating layer can be further densified more effectively. As a result, the adhesion strength of the terminal portion to the solid electrolyte body and further the peel strength can be effectively increased.

  Hereinafter, in order to clarify the present invention more specifically, embodiments of the present invention will be described in detail with reference to the drawings.

  First, FIGS. 1 and 2 schematically show a NOx (nitrogen oxide) sensor element according to an embodiment of a gas sensor element according to the present invention in a vertical cross-sectional form and an exploded perspective form, respectively. . In these drawings, reference numeral 1 denotes a sensor element having an elongated plate-like body shape, and the sensor element 1 includes a plurality of solid electrolyte bodies made of dense air-tight oxygen ion conductive plates. 4a, 4b, 4c, 4d, and 4e, and has a laminated structure including a laminated body 5 in which those plate-like bodies are laminated in the vertical direction. Further, in the sensor element 1, the tip side portion at one end in the length direction is the detection unit 2 that detects the concentration (partial pressure) of the NOx component in the measured gas atmosphere. The opposite base portion is a connector portion 3 attached to a sensor body of a NOx sensor (not shown). Each of the solid electrolyte bodies 4a to 4e is formed using a known oxygen ion conductive solid electrolyte material such as zirconia porcelain.

  And in the detection part 2 of this sensor element 1, the 1st internal space 6 and the 2nd internal space 8 which each exhibit a rectangular planar form are located in the front end side of the sensor element 1. The reference air introduction passage 10 is arranged in the longitudinal direction of the sensor element 1 in a form that is arranged separately and in a state of being squeezed and is independent of the first and second internal cavities 6 and 8. It is provided to extend. The reference air introduction passage 10 is opened at the end of the sensor element 1 on the connector portion 3 side, and communicates with the atmosphere. Here, in the first and second internal cavities 6 and 8 and the reference air introduction passage 10, the corresponding vacant spaces formed in the solid electrolyte body 4b are covered with the upper and lower solid electrolyte bodies 4a and 4c. By this, it is formed in a state that is located on substantially the same plane.

  In addition, the solid electrolyte body 4a that covers the first internal space 6 from above is provided with a through-hole penetrating in the thickness direction. A first diffusion-controlling passage 12 is formed to allow the station 6 to communicate with the external space. As a result, an external atmosphere is guided into the first internal space 6 under a predetermined diffusion resistance through the first diffusion-controlling passage 12. Furthermore, the second diffusion rate-determining passage 14 for allowing the two internal cavities 6 and 8 to communicate with the solid electrolyte body 4b portion located between the first internal vacancy 6 and the second internal vacancy 8 is provided. And the atmosphere in the first internal space 6 is introduced into the second internal space 8 under a predetermined diffusion resistance through the second diffusion-controlling passage 14. It has become.

  Further, on the layered surface (lower surface) of the solid electrolyte body 4a with the solid electrolyte body 4b, a portion exposed in the first internal space 6 is provided with a thin film-like inner electrode 16 in contact therewith. . Further, a thin film-like outer electrode 18 is provided at a portion corresponding to the inner electrode 16 on the outer surface (upper surface) opposite to the laminated surface of the solid electrolyte body 4a so as to be in contact therewith. The inner and outer electrodes 16 and 18 and the solid electrolyte body 4a constitute a first electrochemical pump cell (pump cell). Note that the inner electrode 16 and the outer electrode 18 are porous cermet electrodes made of Pt and zirconia, for example, which have weakened or reduced / decomposable ability for NOx components in the gas to be measured. It is configured.

  Further, on the surface (upper surface) of the solid electrolyte body 4c and the solid electrolyte body 4b, a portion exposed in the first internal space 6 is provided with a thin film-like measurement electrode 20 in contact therewith. . Further, a thin film-like reference electrode 22 is provided in contact with a portion exposed in the reference air introduction passage 10 on the laminated surface of the solid electrolyte body 4c. The measurement electrode 20, the reference electrode 22, and the solid electrolyte body 4c constitute an electrochemical sensor cell (monitor cell). In addition, the measurement electrode 20 and the reference electrode 22 are also reduced in the reduction / decomposition ability with respect to the NOx component in the gas to be measured, as in the case of the inner electrode 16 and the outer electrode 18, or have no reduction / decomposition ability. It is composed of a porous cermet electrode made of Pt and zirconia.

  Furthermore, a thin film-like internal pump electrode 24 is provided in contact with the portion exposed in the second internal space 8 on the surface where the solid electrolyte body 4c is laminated with the solid electrolyte body 4b. The internal pump electrode 24 is composed of, for example, a porous cermet made of Rh, which is a noble metal capable of reducing / decomposing NOx, and zirconia as a ceramic, whereby the atmosphere in the second internal space 8 is obtained. It can function as a NOx reduction catalyst capable of reducing / decomposing NOx present therein. The internal pump electrode 24, the reference electrode 22, and the solid electrolyte body 4c constitute a second electrochemical pump cell (sensor cell).

  On the other hand, the connector part 3 of the sensor element 1 is provided with a plurality of terminal parts 26 to 38 exposed to the outside. That is, among the plurality of solid electrolyte bodies 4a to 4e stacked on each other, on the outer surface (upper surface) opposite to the laminated surface with the solid electrolyte body 4b in the base portion side portion of the solid electrolyte body 4a located at the uppermost position, A plurality of (four in this case) terminal portions 26, 28, 30, 32 in the form of a thin film are provided, and the solid electrolyte body 4e positioned at the lowest of them is provided. A plurality of I-shaped or L-shaped (three in this case) terminal portions 34, 36 in the form of a thin film are also formed on the outer surface (lower surface) on the side opposite to the surface on which the solid electrolyte body 4 d is laminated. , 38 are provided.

  Here, one thin insulating layer 40, 42 is directly provided on each outer surface of the solid electrolyte bodies 4a, 4e provided with a plurality of terminal portions 26-38, respectively. . As a result, the respective electric insulating layers 40 and 42 are interposed between the respective solid electrolyte bodies 4a and 4e and the respective terminal portions 26 to 38, and the four terminal portions 26 to 32 through the solid electrolyte body 4a. Short circuit between each other and short circuit between the three terminal portions 34 to 38 through the solid electrolyte body 4e are prevented.

  And among the said 5 electrodes 16-24 provided in the detection part 2 of the sensor element 1, the outer side electrode 18 is continuously extended in the length direction on the outer surface of the solid electrolyte body 4a. The inner electrode is connected to one terminal portion 26 among the four terminal portions 26 to 32 provided on the outer surface of the solid electrolyte body 4a via the formed thin-film lead portion 44. 16, the measurement electrode 20, and the reference electrode 22, on the stacked surface of the solid electrolyte bodies 4 a and 4 c with the solid electrolyte body 4 b with respect to each of the remaining three terminal portions 28 to 32, The thin film-like lead portions 46, 48, and 50 formed so as to extend continuously in the vertical direction are connected to each other. Further, the internal pump electrode 24 is connected to the solid electrolyte body via a thin film-like lead portion 52 formed so as to continuously extend in the length direction on the laminated surface of the solid electrolyte body 4c with the solid electrolyte body 4b. It is connected to one terminal portion 34 among the three terminal portions 34 to 38 provided on the outer surface of the body 4e.

  Here, in particular, the four lead portions 46 to 52 connecting the four electrodes 16, 20 to 24 except the outer electrode 18 and the terminal portions 28 to 36 are respectively connected to the solid electrolyte bodies 4 a and 4 c. Of the solid electrolyte body 4a or the outer surface side of the solid electrolyte body 4e, that is, the sensor element, is bent and extended in the width direction at the base side portion of the solid electrolyte body. Side surface conducting portions 54, 56, 58, and 60 that extend toward the upper surface and the lower surface of 1 are provided. Then, as shown in FIG. 3 and FIG. 4, each of the side surface conductive portions 54 to 60 is exposed and positioned outside on the side surface of the connector portion 3 of the sensor element 1 (laminated body 5). It is connected to each terminal part 28-34 in the front-end | tip.

  Further, as shown in FIGS. 1 and 2, in the sensor element 1, two insulating ceramic layers 62a and 62b made of porous alumina are sandwiched between and applied to the solid electrolyte bodies 4c and 4e. The solid electrolyte bodies 4c and 4e and the solid electrolyte body 4d are integrally laminated in a form surrounded on three sides. A heater element 64 is sandwiched and positioned between the two insulating ceramic layers 62a and 62b. Therefore, the heater element 64 is embedded in the sensor element 1. It is structured.

  The heater element 64 has a heat generating portion 66 and two lead portions 68a and 68b. The heat generating portion 66 is positioned corresponding to the formation site of the second internal space 8 in the detection portion 2 of the sensor element 1, while the two lead portions 68 a and 68 b are connectors of the sensor element 1. It is extended to the portion 3 side and connected to the two terminal portions 36 and 38 of the three terminal portions 34 to 38 provided on the outer surface of the solid electrolyte body 4e. .

  Further, the two lead portions 68a and 68b of the heater element 64 also include four lead portions 46 to 52 for connecting the four electrodes 16, 20 to 24 and the four terminal portions 28 to 34, respectively. Similarly, side conduction portions 70a and 70b extending toward the lower surface of the sensor element 1 are respectively provided at the distal ends of the connector portion 3 of the sensor element 1 that are bent in the width direction. And as FIG. 4 shows, each of these side surface conduction | electrical_connection part 70a, 70b is exposed and located outside in the side surface of the connector part 3 of the sensor element 1 (laminated body 5), and in each front-end | tip, It is connected to each terminal part 36,38.

  In the sensor element 1 having such a laminated structure, the electrodes 16 to 24 and the terminal portions 26 to 38 are formed on the unfired solid electrolyte bodies 4a, 4b, 4c, and 4e, for example, as in the prior art. The lead portions 44 to 52, the side surface conductive portions 54 to 60, 71a and 70b, the electric insulating layers 40 and 42, the insulating ceramic layers 62a and 62b, and the heater element 64 are printed by a screen printing method or the like. Then, the unfired solid electrolyte bodies 4a, 4b, 4c, 4e and the unfired solid electrolyte body 4d are respectively laminated, and then the laminate is fired (sintered), thereby all of them. It can be easily obtained by integrating them.

  Thus, in the sensor element 1 as described above, as in the conventional case, for example, it is inserted into the connector part 3 and assembled to the sensor element storage part (not shown) in the sensor body of the NOx sensor. Then, the plurality of terminal portions 26 to 38 are respectively connected to predetermined circuits, and are arranged in the measured gas existence space in the detection unit 2 under the assembled state to the sensor body. A gas to be measured is introduced into the first internal space 6 through the first diffusion-controlling passage 12 and under a predetermined diffusion resistance.

  Then, a desired voltage is applied by the external variable power source 72 between the inner electrode 16 and the outer electrode 18 of the first electrochemical pump cell through the terminal portions 26 and 28, and in a predetermined direction. By flowing an electric current, oxygen in the atmosphere in the first internal space 6 is pumped out to the external measurement gas existence space, or conversely, oxygen is extracted from the external measurement gas existence space. It can be pumped into the first internal space 6.

  Further, based on the oxygen concentration (partial pressure) difference between the atmosphere in the first internal space 6 and the reference air in the reference air introduction passage 10, the measurement electrode 20 and the reference electrode 22 of the electrochemical sensor cell. Is taken out from the terminal portions 30 and 32 and measured by the potentiometer 74, whereby the oxygen concentration (partial pressure) in the atmosphere in the first internal space 6 is measured. Is to be detected. Based on the value of the oxygen concentration in the atmosphere in the first internal space 6 detected by the potentiometer 74, the voltage of the variable power source 72 is controlled. The oxygen concentration in the atmosphere can be maintained at a constant value.

  Further, a constant voltage is applied between the internal pump electrode 24 and the reference electrode 22 of the second electrochemical pump cell by the constant voltage power source 76 through the terminal portions 34 and 32, so that The oxygen in the atmosphere in the station 8 is pumped into the reference air introduction passage 10. Further, NOx existing in the atmosphere in the second internal space 8 is reduced by the internal pump electrode 24 that functions as a NOx reduction catalyst. The constant voltage power supply 76 is of a magnitude that gives a limiting current to the pumping of oxygen generated during NOx decomposition by the second electrochemical pump cell under the limited NOx inflow by the second diffusion rate limiting passage 14. A voltage can be applied.

Therefore, in the sensor element 1, the oxygen partial pressure (oxygen concentration) in the atmosphere of the gas to be measured introduced into the first internal space 6 through the first diffusion rate controlling passage 12 is electrochemical. By the cooperative action of the sensor cell and the first electrochemical pump cell, NOx is not reduced, for example, it is controlled to a low value of about 1.01 Pa (10 ⁻⁶ atm). Then, the atmosphere in the first internal space 6 in which the oxygen partial pressure is controlled is guided into the second internal space 8 through the second diffusion-controlling passage 14, and NOx in the atmosphere is changed. Then, oxygen that is reduced by the internal pump electrode 24 and pumped at that time is pumped from the second internal space 8 into the reference air introduction passage 10 by the pumping action of the second electrochemical cell. At this time, since the oxygen partial pressure in the atmosphere in the second internal space 8 is controlled to be constant, the internal pump electrode 24 and the reference electrode 22 of the second electrochemical cell are interposed between them. The pump current is proportional to the NOx concentration.

  Thus, the pump current flowing between the internal pump electrode 24 and the reference electrode 22 is taken from the terminals 34 and 32 and measured by an ammeter 78, and based on this measurement value, The concentration of NOx in the measured gas atmosphere is required.

  By the way, in the sensor element 1 of this embodiment having such a structure, when the sensor element is inserted into the sensor element storage portion in the sensor body of the NOx sensor and assembled to the sensor body, the sensor element is stored. Connected to all the terminal portions 26 to 38 that are exposed to the outside on the upper surface, the lower surface, or the side surface of the connector portion 3 that contacts the inner surface of the portion, and the four electrodes 16 and 20 to 24 except the outer electrode 18 The side conduction parts 54 to 60 in the lead parts 46 to 52 and the side conduction parts 70 a and 70 b in the lead parts 68 a and 68 b of the heater element 64 are formed from the materials for forming the electrodes 16 to 24 provided in the detection part 2. It is formed using a conductive material obtained by mixing noble metal powder and alumina powder, which is different from the above. And the electroconductive material obtained by mixing this noble metal powder and alumina powder is the electroconductivity obtained by mixing the noble metal powder and zirconia powder which are the forming materials of each electrode 16-24 provided in the detection part 2. Excellent sinterability compared to the material.

  Therefore, in each of the terminal portions 26 to 38 and the side surface conductive portions 54 to 60, 68a, and 68b formed by firing integrally with the solid electrolyte bodies 4a to 4e using such a conductive material, The adhesion strength with respect to the solid electrolyte bodies 4a, 4b, 4c, 4e can be sufficiently increased, and thus the peel strength with respect to the solid electrolyte bodies 4a, 4b, 4c, 4e can be effectively improved. It becomes. Here, portions of the lead portions 46 to 52 excluding the side surface conducting portions 54 to 60, 68a, and 68b and the entire lead portion 44 connected to the outer electrode 18 form the respective electrodes 16 to 24. It is formed using a conductive material similar to the material.

  Here, the noble metal powder contained in the conductive material forming the terminal portions 26 to 38 and the side surface conductive portions 54 to 60, 68a, and 68b is included in the forming material of the electrodes 16 to 24. Noble metal powders similar to those used are used. That is, for example, a single noble metal such as Pt, Rh, Pd, Au, or Hg or a plurality of types of alloys selected from such noble metals is used.

Moreover, what has a BET specific surface area in the range of 10-80 m < ² > / g is preferably used for the alumina powder contained in this electroconductive material. This is because when alumina powder having a BET specific surface area exceeding 80 m ² / g is used, since the alumina powder is too small, uniform mixing with noble metal powder is difficult, and mixing of these alumina powder and noble metal powder is uneven. It is easy to become. And when it becomes so, in each terminal part 26-38 and each side surface conduction part 54-60, 68a, 68b by which such a conductive material is baked, the adhesion strength with respect to the solid electrolyte bodies 4a, 4c, 4e varies. This is because there is a greater risk that the peel strength with respect to the solid electrolyte bodies 4a, 4c, 4e will be reduced. In addition, when a large alumina powder having a BET specific surface area of less than 10 m ² / g is used, the sinterability of the conductive material obtained by mixing with the noble metal powder is lowered, so that the conductive material is In each of the terminal portions 26 to 38 and the side surface conductive portions 54 to 60, 68a, and 68b that are baked, the adhesion strength to the solid electrolyte bodies 4a, 4b, 4c, and 4e, and the peel strength are sufficiently high. This is because there is a concern that it is difficult to ensure.

  Further, the conductive material forming each of the terminal portions 26 to 38 and the side surface conductive portions 54 to 60, 68a, and 68b has a composition in which the composition of the noble metal powder and the alumina powder is noble metal powder / alumina powder. It is desirable that the ratio is 95/5 to 40/60. In the case where the conductive material contains alumina powder in an amount exceeding 60% by volume and noble metal powder is contained in an amount of less than 40%, such conductive material is fired. There is a possibility that the resistance value of each of the obtained terminal portions 26 to 38 and the side surface conductive portions 54 to 60, 68a, and 68b increases, and the conductivity is lowered. On the other hand, when the conductive material contains the alumina powder in an amount of less than 5% by volume and the precious metal powder is contained in an amount exceeding 95%, the effect of adding the alumina powder becomes small. Therefore, the adhesion of the terminal portions 26 to 38 and the side surface conductive portions 54 to 60, 68a, and 68b obtained by firing such a conductive material to the solid electrolyte bodies 4a, 4b, 4c, and 4e, and further peeling. There is a concern that the strength will be lowered.

  Therefore, in the conductive material forming the terminal portions 26 to 38 and the side surface conductive portions 54 to 60, 68a and 68b, stable conductivity and sufficient for the solid electrolyte bodies 4a, 4b, 4c and 4e. In order to ensure a good balance between high adhesion and high peel strength, it is preferable that the volume ratio has a composition of noble metal powder / alumina powder = 95/5 to 40/60.

  Moreover, each terminal part 26-38 and each side surface conduction | electrical_connection part 54-60, 68a, 68b which consist of an electroconductive material which mixed such a noble metal powder and alumina powder, as mentioned above, for example by a screen printing technique, The solid electrolyte bodies 4a, 4b, 4c and 4e are formed in a thin film form, and the thickness thereof is preferably set to a value in the range of 2 to 40 μm.

  This is because when the thicknesses of the terminal portions 26 to 38 and the side surface conductive portions 54 to 60, 68a, and 68b are less than 2 μm, the terminal portions 26 to 38 and the side surfaces are too thin. This is because the resistance values in the conductive portions 54 to 60, 68a, 68b become unstable, and it may be difficult to ensure stable conductivity, and the thickness may exceed 40 μm. Then, since it is too thick this time, when the connector part 3 is inserted into the sensor element storage part of the sensor body, the terminal parts 26 to 38 and the side surface conduction parts 54 to 60, 68a and 68b and the sensor element storage part Excessive sliding resistance is generated between the inner surface and the terminal portions 26 to 38 and the side surface conductive portions 54 to 60, 68a, and 68b are likely to be separated from the upper and lower surfaces and side surfaces of the connector portion 3. Because The

  Further, as described above, the connector portion 3 in the sensor element 1 of the present embodiment includes the solid electrolyte body 4a between the upper surface of the solid electrolyte body 4a and the four terminal portions 26 to 32 provided therein, and the solid electrolyte body. Thin-film electrical insulating layers 40 and 42 are respectively provided between the lower surface of 4e and the three terminal portions 34 to 38 provided there. Here, these electrical insulating layers 40 are provided. , 42 are each composed of a ceramic layer having a dense structure as a thin film layer made of alumina powder is integrally fired with the solid electrolyte bodies 4a, 4e.

  Thereby, in the sensor element 1, when the terminal portions 26 to 38 made of a conductive material obtained by mixing noble metal powder and alumina powder, the solid electrolyte bodies 4 a and 4 e, and the electrical insulating layers 40 and 42 are integrally fired, The terminal portions 26 to 38 and the electrical insulating layers 40 and 42 are more firmly bonded to each other between the alumina powders, so that the terminal portions 26 to 38 are connected to the solid electrolyte bodies 4a and 4e. Further, it is possible to make the contact more firmly through the electric insulating layers 40 and 42.

Further, as the alumina powder for forming such electrical insulating layers 40 and 42, those having a BET specific surface area in the range of 10 to 80 m ² / g are preferably used. This is because an alumina powder having a BET specific surface area within such a range is superior in sinterability as compared with an alumina powder having a BET specific surface area outside such a range. , 42 can be made more precise, and the adhesion strength of each terminal portion 26 to 38 to the solid electrolyte bodies 4a, 4e, as well as the peel strength, can be increased more effectively. It is.

  Although the thickness of the electrical insulating layers 40 and 42 is not particularly limited, sufficient insulation is ensured, and when the connector part 3 is inserted into the sensor element storage part of the sensor body, In order to prevent an excessive sliding resistance from occurring between the terminal portions 26 to 38 and the side surface conductive portions 54 to 60, 68a and 68b and the inner surface of the sensor element storage portion, the range is about 5 to 40 μm. It is desirable that the value of

  Thus, in the sensor element 1 of the present embodiment, the terminal portions 26 to 38 and the side surface conductive portions 54 to 60, 68a, and 68b exposed to the outside on the upper surface, the lower surface, and the side surface of the connector portion 3 are precious metal powder. Are formed by using a conductive material formed by mixing alumina powder and alumina powder, so that the solid electrolyte bodies 4a, 4b, 4a, 4b of the terminal portions 26 to 38 and the side surface conductive portions 54 to 60, 68a and 68b are formed. When the adhesion strength to 4c and 4e and further the peel strength are effectively increased, for example, when the connector portion 3 is inserted into the sensor element storage portion of the sensor body and assembled to the sensor body. The terminal portions 26 to 38 and the side surface conductive portions 54 to 60, 68a, and 68b can be prevented from peeling off, and the occurrence of poor conduction due to the peeling can be advantageously prevented.

  Therefore, in the sensor element 1 according to the present embodiment as described above, the terminal portions 26 to 38 and the side surface conductive portions 54 to 60, The electrical continuity in the connector part 3 provided with 68a, 68b can be ensured extremely stably. As a result, the measurement accuracy of the predetermined gas concentration in the gas atmosphere to be measured can be effectively stabilized, and the reliability of the measurement accuracy can be greatly improved.

  Further, in the sensor element 1, the composition of the noble metal powder and the alumina powder in the conductive material forming the terminal portions 26 to 38 and the side surface conductive portions 54 to 60, 68a and 68b, and the terminal portions 26 to 38 and each of the side surface conductive portions 54 to 60, 68a, 68b have values within a specific range, and the alumina powder contained in the conductive material has a BET specific surface area within a predetermined range. Is used, the adhesion strength and peel strength of the terminal portions 26 to 38 and the side surface conductive portions 54 to 60, 68a, and 68b with respect to the solid electrolyte bodies 4a, 4b, 4c, and 4e are further improved. It can be increased more effectively.

  In addition to this, the terminal portions 26 to 38 are provided on the outer surfaces of the solid electrolyte bodies 4a and 4e in the connector portion 3 via the electrically insulating layers 40 and 42 having a dense structure made of alumina powder. As a result, the adhesion strength and peel strength of the terminal portions 26 to 38 to the solid electrolyte bodies 4a and 4e can be further effectively increased.

  Accordingly, in the present embodiment, the terminal portions 26 to 38 and the side surface conductive portions 54 to 60, 68a, and 68b thus obtained are improved in adhesion strength and peel strength to the solid electrolyte bodies 4a, 4b, 4c, and 4e. However, the stabilization of the electrical continuity in the connector part 3 can be ensured more advantageously, and the measurement accuracy of the predetermined gas concentration in the measurement gas atmosphere and the improvement of the reliability can be further effectively achieved. It can be done.

  By the way, in this embodiment, the specific example of what was assembled | attached to the NOx sensor used in order to measure the density | concentration of NOx in to-be-measured gas, and was applied to the NOx sensor element used is shown. However, the present invention is assembled in a gas sensor used for measuring the concentration of a gas other than NOx in the gas to be measured, for example, hydrogen gas, carbon dioxide gas, hydrocarbon gas, SOx gas, water vapor, etc. It goes without saying that the present invention can be advantageously applied to the gas sensor element used.

  Further, even when applied to a NOx sensor element, the shape and number of solid electrolyte bodies or the shape and number of electrodes and lead portions provided on the solid electrolyte body are particularly limited to those illustrated. It is not something.

  Furthermore, in the said embodiment, all the terminal parts 26-38 and all the side surface conduction | electrical_connection parts 54-60, 68a, 68b are formed using the electroconductive material formed by mixing a noble metal powder and an alumina powder. However, if at least one of the side surface conduction part and the terminal part of the lead part connected to one electrode is formed using a conductive material obtained by mixing noble metal powder and alumina powder. good. As a result, peeling from the solid electrolyte due to a decrease in adhesion strength and peeling strength of the side surface conductive portion and terminal portion to the solid electrolyte, and further occurrence of poor conduction can be advantageously prevented.

  Furthermore, even if a part or all of the lead part connecting the electrode and the terminal part is formed with a known through-hole structure, there is no problem.

  The specific configuration of the present invention has been described in detail above. However, this is merely an example, and the present invention can be implemented in various forms. Accordingly, various embodiments relating to various changes, modifications, and improvements of the present invention adopted based on the knowledge of those skilled in the art are all within the scope of the present invention without departing from the spirit of the present invention. It should be understood that it belongs.

  In the following, typical examples of the present invention will be shown to further clarify the features of the present invention, but the present invention is not limited by the description of such examples. It goes without saying.

<Example 1>
First, as a gas sensor element for a test, it has a structure as shown in FIG. 1 to FIG. 4, and all terminal portions and side surface conductive portions in all lead portions are made of Pt powder and a BET specific surface area of 10 m ² / The NOx sensor element formed using the electroconductive material obtained by mixing alumina powder which is g so that it may become a composition of Pt powder / alumina powder = 90/10 by volume ratio was prepared. This was designated as Sample 1.

  In the NOx sensor element of the sample 1, the internal pump electrode is composed of a porous cermet made of Pt and zirconia that functions as a NOx reduction / decomposition catalyst, while the inner electrode and the outer electrode are measured. The electrode, the reference electrode, and the portion other than the side surface conductive portion in the lead portion were composed of a porous cermet made of Pt and zirconia with reduced reduction / decomposition capability for NOx or no reduction / decomposition capability. And the thickness of all the electrodes, the lead portions, the terminal portions, and the side surface conductive portions was set to 10 to 30 μm.

  Moreover, as a gas sensor element for a test different from the test sample 1, all terminal portions and side surface conductive portions have a volume ratio of Pt powder / alumina powder, Pt powder / alumina powder = 85/15. A NOx sensor element having the same structure and configuration as that of the test sample 1 is prepared except that the conductive material obtained by mixing so as to have the composition is prepared. 2.

  Furthermore, as a gas sensor element for test, which is further different from those of the test sample 1 and the test sample 2, all terminal portions and side surface conductive portions are composed of Pt powder and alumina powder in a volume ratio of Pt powder / A NOx sensor element having the same structure and configuration as those of the specimen 1 and the specimen 2 except that the conductive powder obtained by mixing the alumina powder = 60/40 is used. This NOx sensor element was prepared and used as a specimen 3.

  For comparison, all terminal portions and side surface conductive portions are obtained by mixing Pt powder and zirconia powder in a volume ratio such that Pt powder / zirconia powder = 60/40. A NOx sensor element having the same structure and configuration as those of the test sample 1, the test sample 2, and the test sample 3 is prepared except that the NOx sensor element is formed using a conductive material. It was.

  And in order to investigate the peeling strength of the side surface conduction | electrical_connection part in each of four NOx sensor elements of the test samples 1-3 prepared in this way, and the comparative product 1, it shows below with respect to each of these NOx sensor elements. Such a peel test was performed according to the following procedures.

  That is, first, as shown in FIG. 5, a guide rail 100 extending in the horizontal direction is provided with a base 102 provided on the upper surface, and the guide rail 100 is positioned over the guide rail 100 on the base 102. 100, while being slidable in the horizontal direction while being guided by 100, the position is fixed on the base 102 with the sample fixing jig 104 configured to be able to clamp the NOx sensor element on one end surface in the moving direction. Although the vertical movement of the support member 106 and the support member 106 at a position spaced apart from the base 102 by a predetermined distance is permitted, the horizontal movement is prevented. And a load-loading mechanism 110 provided on the support member 106 with a structure capable of applying an arbitrary load to the carbide blade 108. Were prepared testing device which is configured to include.

  Next, the NOx sensor element 1 of the sample 1 is placed in a horizontal direction so that the side surface on which the side surface conductive portion is formed is positioned up and down, and at the end on the detection unit 2 side, the sample of the measuring device is sampled. The fixing jig 104 was fixed by being clamped so as to be movable together.

  Thereafter, the tip of the carbide blade 108 is brought into contact with the side surface of the NOx sensor element 1 of the sample 1 where the side surface conductive portion is formed, and a load set in advance by the load load mechanism 110 is applied. Was loaded. As a result, the tip of the carbide blade 108 was brought into pressure contact with the side surface where the side surface conductive portion of the NOx sensor element 1 of the sample 1 was formed with a pressing force based on a preset load. At this time, the tip of the cemented carbide blade 108 was brought into contact with a portion located on the extension line of the side surface conduction portion in the intermediate portion between the connector portion 3 and the detection portion 2 of the NOx sensor element 1.

  Thereafter, from this state, the sample fixing jig 104 together with the NOx sensor element 1 of the sample 1 along the guide rail 100 along the guide rail 100 is a direction opposite to the fixed side of the NOx sensor element 1. The slide was slowly moved in the direction indicated by the arrow in FIG. As a result, the side surface conductive portion was scratched while being pressed with a predetermined pressing force at the tip of the carbide blade 108.

  Then, the sample fixing jig 104 slides and moves to a position (a position indicated by a two-dot chain line in FIG. 5) where the contact state of the tip of the cemented carbide blade 108 with the side surface of the NOx sensor element 1 of the sample 1 is eliminated. When it was swallowed, the slide movement of the sample fixing jig 104 was stopped at that time. Thereafter, it is visually confirmed whether or not the side surface conductive portion provided on the side surface of the NOx sensor element 1 of the sample 1 has been peeled off from the side surface by scratching with the carbide blade 108, and peeling is confirmed. When it was done, the presence or absence of the increase in the electrical resistance value between a side surface conduction | electrical_connection part and a terminal part was investigated.

  In this way, the sample fixing jig 104 and the NOx sensor element 1 of the sample 1 are both slid together while being pressed and contacted with a pressing force based on a load value applied to the carbide blade 108. Then, after scratching the side surface conductive portion with the tip of the carbide blade 108, a series of operations for examining whether the side surface conductive portion is peeled off and whether there is an increase in electric resistance value are performed by the load mechanism 106. The test was repeated while gradually increasing the load value applied to 108. Then, the load value applied to the cemented carbide blade 108, in other words, the pressing force applied from the cemented carbide blade 108 to the side conduction part, and the side conduction conducted by the scratching by the cemented carbide blade 108. The relationship between the probability of an increase in electrical resistance between the terminal portion and the terminal portion was investigated. The results are shown in FIG. Note that the “load value” on the horizontal axis in the graph of FIG. 6 indicates the load value applied to the carbide blade 108, and the “exfoliation occurrence rate” on the vertical axis is due to scratching by the carbide blade 108. The probability (percentage) of occurrence of an increase in the electrical resistance value between the side conduction part to be peeled off and the terminal part is shown.

  Next, in the same manner as the peel test for the NOx sensor element of the specimen 1 as described above, the peel test for each NOx sensor element of the specimen 2 and the specimen 3 and the NOx sensor element of the comparative specimen 1 is performed. , Respectively. The results are also shown in FIG.

  As is clear from FIG. 6, when the load values are the same, the peeling occurrence rate in each of the NOx sensor elements of the test sample 1 to the test sample 3 is the load value of the NOx sensor element of the comparative product 1. It is recognized that the value is clearly smaller than that of. For example, when the peel rate in each NOx sensor element when the load value is 80 g is compared, in the NOx sensor of the comparative product 1, it is about 12%, whereas the NOx sensor element of the test sample 1 Is about 0.45%, about 0.27% for the NOx sensor element of the specimen 2, and about 0.1% for the NOx sensor element of the specimen 3.

  This is because, in the NOx sensor element, the terminal portion and the side surface conductive portion in the lead portion are formed using a conductive material obtained by mixing Pt powder and alumina powder, and the Pt powder of such conductive material is used. It clearly shows that the peeling strength between the terminal portion and the side surface conductive portion can be effectively increased by making the composition of the alumina powder within the range defined in the present invention.

<Example 2>
First, as the test gas sensor elements, four NOx sensor elements of the test samples 1 to 3 and the comparative product 1 prepared in Example 1 were prepared. In addition, apart from them, all the terminal parts and the side surface conduction parts are formed using a conductive material made of only Pt powder, and the same structure and configuration as those of the specimens 1 to 3 and the comparative product 1 A NOx sensor element having NO was prepared, and this NOx sensor element was designated as Comparative Product 2.

  Next, in order to examine the adhesion strength of the side conductive portion to the solid electrolyte body in each of the five NOx sensor elements of the specimens 1 to 3 and the comparative articles 1 and 2 thus prepared, the adhesion to each of these NOx sensor elements. The strength measurement test was carried out according to the following procedure according to the well-known Sebastian method (see “Thin Film Handbook” edited by the Japan Society for the Promotion of Science / Thin Film Committee No. 131 [Ohm Corp.]).

  That is, first, the NOx sensor element of the test sample 1 is cut to a predetermined size to produce a test piece having a side conduction part provided on the side surface, and then the side conduction part of the test piece is made of copper. A stud pin having a diameter of 1.3 mm was bonded with an epoxy adhesive. Thereafter, using an autograph, the test piece and the stud pin were peeled off, and the strength when the side surface conductive portion was peeled was measured.

  Next, in the same manner as the adhesion strength test for the NOx sensor element of the test sample 1 as described above, each NOx sensor element of the test sample 2 and the test sample 3 and each NOx sensor of the comparative product 1 and the comparative product 2 An adhesion strength test with respect to the device was performed.

  And based on the result of the adhesion strength test with respect to each NOx sensor element of the specimens 1 to 3 and the result of the adhesion strength test with respect to the NOx sensor element with the comparison ratio 2, the terminal portion and the side surface conduction portion are made of Pt powder. The relationship between the amount of Pt in the conductive material (composition of Pt powder and alumina powder) in the NOx sensor element formed by using a conductive material obtained by mixing alumina powder and the adhesion strength of the side surface conductive portion was investigated. It was. The results are shown in FIG.

  On the other hand, based on the result of the adhesion strength test with respect to the NOx sensor element of the comparative product 1 and the result of the adhesion strength test with respect to the NOx sensor element with the comparison ratio 2, the terminal portion and the side surface conduction portion are made of Pt powder. The relationship between the amount of Pt in the conductive material (composition of Pt powder and zirconia powder) in the NOx sensor element formed by using a conductive material obtained by mixing zirconia powder and the adhesion strength of the side conduction part was investigated. It was. The results are also shown in FIG. Note that F (t) in FIG. 7 indicates the cumulative failure probability.

  As apparent from FIG. 7, in the NOx sensor element A in which the terminal portion and the side surface conductive portion in the lead portion are formed using a conductive material obtained by mixing Pt powder and zirconia powder, such a conductive property is obtained. With the decrease in the content of Pt powder in the conductive material, that is, the increase in the content of zirconia powder, the adhesion strength with respect to the solid electrolyte body of the side conduction part is from the value when the conductive material is composed only of Pt powder. It is observed that it gradually decreases. On the other hand, in the NOx sensor element B in which the terminal portion and the side surface conductive portion in the lead portion are formed using a conductive material obtained by mixing Pt powder and alumina powder, such a conductive material is used. Despite a decrease in the content of Pt powder in the inside, that is, an increase in the content of alumina powder, the adhesion strength of the side surface conductive portion to the solid electrolyte body is substantially the same value as when the conductive material is composed only of Pt powder. Is allowed to be maintained.

  As a result, the NOx sensor element A in which the terminal portion and the side surface conductive portion in the lead portion are formed using the conductive material obtained by mixing the Pt powder and the alumina powder, the Pt powder and the alumina of the conductive material are formed. Regardless of the composition of the powder, a conductive material obtained by mixing the Pt powder and the zirconia powder in the terminal part and the side conductive part in the lead part in the adhesion strength of the terminal part and the side conductive part to the solid electrolyte body is used. It can be clearly recognized that this is sufficiently superior to the NOx sensor element B formed in this way.

<Example 3>
First, with respect to the Pt powder, the alumina powder having the BET specific surface area shown in the following Table 1 is represented by the volume ratio in the composition shown in the following Table 1 (only the amount of the alumina powder is shown in the following Table 1). 11 having the same structure and configuration as the specimen 1 prepared in Example 1 except that the terminal portion and the side surface conductive portion are formed using the conductive material obtained by mixing as described above. Each NOx sensor element was prepared as a test gas sensor element. And these 11 NOx sensor elements were made into specimens 4-14, respectively, as shown in Table 1 below. For comparison, the NOx sensor element of Comparative Product 1 prepared in Example 1 was prepared.

  Next, twelve NOx sensor elements of the prepared specimens 4 to 14 and the comparative article 1 were used, and a peel test was performed in the same manner as in Example 1. And from each result of the peeling test for each of these NOx sensor elements, the value of the load value when the peeling occurrence rate was 0.1% was examined for each NOx sensor element. The results are shown in Table 2 below.

  As is apparent from the results in Table 2, the terminal portion and the side surface conductive portion in the lead portion are obtained by mixing Pt powder and alumina powder having a BET specific surface area within the range defined in the present invention. When the conductive material is formed and the composition of the Pt powder and the alumina powder of the conductive material is within the range defined in the present invention, the peel strength between the terminal portion and the side surface conductive portion is The peel strength of the terminal portion and the side surface conductive portion formed using a conductive material made of Pt powder and zirconia powder can be effectively increased.

It is a cross-sectional enlarged explanatory drawing which shows the principal part of one Embodiment of the gas sensor element according to this invention. FIG. 2 is an exploded perspective view of the gas sensor element shown in FIG. 1. FIG. 2 is a partially enlarged explanatory view showing a right side surface of a connector portion in the gas sensor element shown in FIG. 1. FIG. 2 is a partially enlarged explanatory view showing a left side surface of a connector part in the gas sensor element shown in FIG. 1. It is front explanatory drawing which shows the test apparatus used for the peeling test implemented with respect to the test sample and the comparative product in the Example. It is a graph which shows the relationship between the load value calculated | required by the peeling test implemented with respect to the test sample and the comparative product in the Example, and peeling incidence. It is a graph which shows the relationship between Pt amount calculated | required by the adhesive strength test implemented with respect to the test sample and the comparative product in the Example, and adhesive strength.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Sensor element 2 Detection part 3 Connector part 4 Solid electrolyte body 16 Inner electrode 18 Outer electrode 20 Measuring electrode 22 Reference electrode 24 Internal pump electrode 26, 28, 30, 32, 34, 36, 38 Terminal part 40, 42 Electrical insulation layer 44, 46, 48, 50, 52, 68 Lead part 54, 56, 58, 60, 70 Side conduction part

Claims (7)

The solid electrolyte body is provided on a laminate surface of a laminate in which a plurality of plate bodies, at least one of which is a solid electrolyte body, and another plate-like body of the solid electrolyte body at a portion on one end side of the laminate body. A plurality of electrodes arranged in contact with each other, and a plurality of electrodes arranged to be exposed to the outside on at least one of a front surface and a back surface facing each other in the stacking direction at a portion on the other end side of the stacked body A terminal part and a plurality of lead parts arranged so as to connect the plurality of electrodes and the plurality of terminal parts to the laminate, respectively, are integrated by sintering, and the plurality A portion of at least one of the lead portions connected to the terminal portion is exposed to the outside on the side surface of the laminate and is positioned so as to extend in the stacking direction of the laminate , a side conductive portion that is allowed to connect to In a gas sensor element,
Gas sensor element and the side conductive portion of said lead portion and said terminal portion, respectively, using a conductive material obtained by mixing a noble metal powder and the alumina powder, characterized in that it is made form. 2. The gas sensor element according to claim 1 , wherein each of the terminal portion and the side surface conductive portion is configured by a thin film having a thickness in a range of 2 to 40 μm. Wherein the conductive material is, by volume, gas sensor element according to claim 1 or claim 2 has a composition of the noble metal powder / alumina powder = 95 / 5-40 / 60. The gas sensor element according to claim 1, wherein the conductive material has a composition of noble metal powder / alumina powder = 90/10 to 40/60 by volume ratio. The gas sensor element according to any one of claims 1 to 4 , wherein the alumina powder contained in the conductive material has a BET specific surface area within a range of 10 to 80 m ² / g. Of the front and back surfaces of the laminate, an insulating layer made of alumina powder is further formed between the surface and the plurality of terminal portions on the surface where the plurality of terminal portions are formed. The layer according to any one of claims 1 to 5 , wherein the layer is integrated by sintering together with the laminate, the electrode, the terminal portion, and the lead portion. The gas sensor element described. The gas sensor element according to claim 6 , wherein the alumina powder forming the insulating layer has a BET specific surface area within a range of 10 to 80 m ² / g.

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