JP2019191148A - Gas sensor element, heater, and gas sensor - Google Patents

Abstract

To provide a gas sensor element for suppressing disconnection.SOLUTION: An ammonia electrode lead 21d (lead) is electrically connected to an ammonia electrode 21c (electrode), without direct contact, via a joint portion 70. The joint portion 70 (component region) contains Au at the percentage of a magnitude between the content percentage of Au (first metal) in the ammonia electrode 21c and the content percentage of Au in the ammonia electrode lead 21d.SELECTED DRAWING: Figure 4

Description

  The present invention relates to a gas sensor element, a heater, and a gas sensor.

In recent years, various gas sensors have been developed. For example, a gas sensor including a sensor element that measures the concentration of ammonia contained in exhaust gas discharged from an internal combustion engine such as a diesel engine is known (see, for example, Patent Document 1).
The sensor element used for this gas sensor has a structure in which electrodes and leads are connected. When the sensor element is manufactured, the connection portion between the two is formed by baking the paste for forming the electrode and the paste for forming the lead in an overlapping state.

JP 2013-221931 A

However, the metal element of the electrode moves to the lead, and there is a possibility that the electrode is partially hollowed and disconnected.
Further, depending on the type of sensor element, a heat generating part is provided, and the heat generating part and the lead are connected. In this sensor element, when the sensor element is manufactured, the paste for forming the heat generating portion and the paste for forming the lead are baked in an overlapped state, thereby forming a connection portion therebetween. In this sensor element as well, as described above, after firing, the metal element in the heat generating part may move to the lead and break at the connection part.
The present invention has been made in view of the above circumstances, and an object thereof is to suppress disconnection. The present invention can be realized as the following forms.

(1) an electrode mainly composed of a first metal;
A lead connected to the electrode and comprising a second metal as a main component,
The electrode and the lead are gas sensor elements connected directly or indirectly through a joint portion,
In the case where the electrode and the lead are directly connected, the bonding portion between the electrode and the lead is the bonding of the metal having a smaller specific gravity of the first metal and the second metal. There is a component region that is a content ratio between the content ratio in the electrode excluding the part and the content ratio in the lead excluding the joint,
In the case where the electrode and the lead are indirectly connected through the joint portion, the electrode has the smaller specific gravity of the first metal and the second metal in the joint portion. A gas sensor element characterized in that a component region having a content ratio between the content ratio in the lead and the content ratio in the lead exists.

When heat treatment is performed with the paste that forms the electrode and the paste that forms the lead in direct contact with each other, liquid locally differs in density difference, reducing the metal concentration (density) difference. Thus, the metal element is moved, and the metal element having a low specific gravity tends to flow to the metal element side having a high specific gravity. Therefore, in the configuration in which the electrode mainly composed of the first metal and the lead mainly composed of the second metal are in direct contact with each other, a cavity caused by a rapid concentration gradient of the metal element is generated at the junction of the different metal. It becomes easy to break.
In this configuration, when the electrode and the lead are directly connected, the junction between the electrode and the lead is excluded from the metal having the smaller specific gravity of the first metal and the second metal. In addition, there is a component region having a size content ratio between the content ratio in the electrode and the content ratio in the lead excluding the joint. In addition, when the electrode and the lead are indirectly connected via the joint portion, the joint portion has a smaller proportion of the first metal and the second metal, the content ratio in the electrode, There is a component region having a content ratio between the content ratio in the lead and the content ratio. Therefore, the concentration gradient of the metal having the smaller specific gravity of the first metal and the second metal becomes gentle between the electrode and the lead, and a cavity due to abrupt movement of the metal element hardly occurs and disconnection is suppressed. .

(2) The electrode and the lead are indirectly connected via the joint portion,
The component region is a content ratio of a size between a content ratio in the electrode and a content ratio in the lead with respect to a metal having a larger specific gravity of the first metal and the second metal. The gas sensor element according to (1), which is characterized.

  Since a joint portion having an intermediate concentration between the electrode and the lead is provided, the concentration gradient becomes gradual, a cavity due to abrupt movement of the metal element hardly occurs, and disconnection is suppressed.

(3) a second electrode different from the electrode;
A solid electrolyte body disposed between the electrode and the second electrode,
The gas sensor element according to (2), wherein the second electrode is composed of the second metal as a main component and is a mixed potential type.

A mixed potential type gas sensor element is known in which the metal species as a main component is different between the electrode and the second electrode, and the reactivity to the gas to be measured is different. In this case, at least one of the electrodes must be formed of a metal different from the lead. For this reason, a junction of dissimilar metals is formed, and cavities are generated due to a rapid concentration gradient of the metal element, which easily breaks.
In this gas sensor element, by applying the present invention assuming that the electrode is formed of a metal different from the lead, the effect of suppressing disconnection is effectively exhibited.

(4) The gas sensor element according to (2) or (3), wherein the metal element in the joint portion is substantially composed of the first metal and the second metal.

  Even if the joint portion contains a metal element other than the first metal and the second metal, the other metal element does not contribute to the relaxation of the concentration gradient of the metal. According to this configuration, since the metal element in the joint portion is substantially only the metal element that relieves the metal concentration gradient, the concentration gradient relieving effect is high.

(5) The concentration of the first metal in the joint part is 30 to 70% by mass when the total amount of the first metal and the second metal in the joint part is 100% by mass,
The concentration of the second metal in the joint is 30 to 70% by mass when the total amount of the first metal and the second metal in the joint is 100% by mass (2 The gas sensor element according to any one of (4) to (4).

  In the gas sensor element having this configuration, by using a joint portion having a specific metal concentration, a steep concentration gradient of the metal element can be relaxed and the movement of the metal element can be effectively suppressed.

(6) The electrode and the lead are directly connected by covering the electrode with the lead, and the electrode and the lead are not directly overlapped with each other, and the electrode and the lead. An overlapping connecting portion, and a lead single portion where the electrode and the lead do not overlap,
The thickness of the connection part is thicker than the thickness of the electrode single part and the lead single part plus the thickness,
When observing the cross section of the connecting portion,
Exclude the surface side of the connection part by the thickness of the lead single part, and
(2) The gas sensor element according to (1), wherein the back surface side of the connection portion is excluded by the thickness of the electrode single portion, and the remaining portion is the joint portion.

In the gas sensor element of this embodiment, the thickness of the connection portion is thicker than the thickness obtained by adding the thickness of the electrode single portion and the lead single portion. Then, when observing the cross section of the connection portion, the surface side of the connection portion is excluded by the thickness of the single lead portion, and the back surface side of the connection portion is excluded by the thickness of the single electrode portion, and the remaining portion (" The “remaining portion” is also a joint portion.
Conventionally, since there is no remaining portion, the first metal moves to a lead from a portion functioning as an electrode in the connection portion, and there is a fear of disconnection.
In the connection part of this embodiment, the remaining part is arranged between the part functioning as an electrode (the thickness of the single electrode part) and the part functioning as the lead (the thickness of the single lead part) to move the first metal. Therefore, the outflow of the first metal from the portion functioning as an electrode can be suppressed. As a result, disconnection at the connecting portion is suppressed.

(7) The electrode and the lead are directly connected by covering the electrode on the lead,
An electrode single part where the electrode and the lead do not overlap, a connection part where the electrode and the lead overlap, and a lead single part where the electrode and the lead do not overlap,
The thickness of the connection part is thicker than the thickness of the electrode single part and the lead single part plus the thickness,
When observing the cross section of the connecting portion,
Exclude the surface side of the connection part by the thickness of the electrode single part, and exclude the back side of the connection part by the thickness of the lead single part, and the remaining part is the joint part The gas sensor element according to (1), which is characterized.

In the gas sensor element of this embodiment, the thickness of the connection portion is thicker than the thickness obtained by adding the thickness of the electrode single portion and the lead single portion. Then, when observing the cross section of the connection portion, the surface side of the connection portion is excluded by the thickness of the single electrode portion, and the back surface side of the connection portion is excluded by the thickness of the single lead portion. The “remaining portion” is also a joint portion.
Conventionally, since there is no remaining portion, the first metal moves to a lead from a portion functioning as an electrode in the connection portion, and there is a fear of disconnection.
In the connection part of this embodiment, the remaining part is arranged between the part functioning as an electrode (the thickness of the single electrode part) and the part functioning as the lead (the thickness of the single lead part) to move the first metal. Therefore, the movement of the first metal from the portion functioning as an electrode to the lead can be suppressed. As a result, disconnection at the connecting portion is suppressed.

(8) The gas sensor element according to any one of (1) to (7), wherein the specific gravity of the first metal is lower than the specific gravity of the second metal.

  When the specific gravity of the first metal is lower than the specific gravity of the second metal, movement of the first metal due to firing can be suppressed, and disconnection between the electrode and the lead is suppressed.

(9) The gas sensor element according to any one of (1) to (8), wherein the first metal is gold and the second metal is platinum.

  In the case where the first metal is gold and the second metal is platinum, the metal element is likely to move by firing. In this case, the presence of the component region makes a remarkable effect of suppressing disconnection.

(10) The gas sensor element according to any one of (1) to (9), wherein the concentration of ammonia contained in the gas to be measured is measured.

  In the case of a gas sensor element that measures the concentration of ammonia as a specific gas, the presence of the component region relaxes the concentration gradient, suppresses the movement of metal elements during heat treatment, and causes a cavity that causes disconnection. It becomes difficult to generate.

(11) a heat generating part mainly composed of a first metal;
A heater lead connected to the heat generating part and mainly composed of a second metal;
The heater and the heater lead are connected directly or indirectly through a heater joint,
When the heat generating portion and the heater lead are directly connected, the heater junction between the heat generating portion and the heater lead is a metal having a smaller specific gravity of the first metal and the second metal. In addition, there is a component region that is a content ratio between the content ratio in the heat generating portion excluding the heater joint portion and the content ratio in the heater lead excluding the heater joint portion,
When the heat generating portion and the heater lead are indirectly connected via the heater joint portion, the heater joint portion has a metal having a smaller specific gravity of the first metal and the second metal. In the heater, there is a component region having a content ratio between the content ratio in the heat generating portion and the content ratio in the heater lead.

When heat treatment is performed in a state where the paste that forms the heat generating portion and the paste that forms the heater lead are in direct contact with each other, liquid locally differs in density difference, resulting in a difference in metal concentration (density). The metal element is moved so as to relax, and the metal element having a low specific gravity tends to flow on the metal element side having a high specific gravity. Therefore, in the configuration in which the heat generating portion mainly composed of the first metal and the heater lead mainly composed of the second metal are in direct contact, a cavity caused by a rapid concentration gradient of the metal element is formed at the joint portion of the different metal. It occurs and it becomes easy to break.
In this configuration, when the heat generating part and the heater lead are directly connected, the heater joining part between the heat generating part and the heater lead is made of a heater having a smaller specific gravity of the first metal and the second metal. There is a component region having a size content ratio between the content ratio in the heat generating portion excluding the joint portion and the content ratio in the heater lead excluding the heater joint portion. Further, when the heat generating portion and the heater lead are indirectly connected via the heater joint portion, the heater joint portion includes a heat generating portion for a metal having a smaller specific gravity of the first metal and the second metal. There is a component region having a content ratio between the content ratio in and the content ratio in the heater lead. For this reason, the concentration gradient of the metal having the smaller specific gravity of the first metal and the second metal becomes gentle between the heat generating portion and the heater lead, so that a cavity due to a sudden movement of the metal element hardly occurs and disconnection is suppressed. Is done.

(12) A gas sensor comprising the gas sensor element according to any one of (1) to (10) or the heater according to (11).

  In the gas sensor of this configuration, the steep concentration gradient of the metal element is relaxed between the electrode and the lead or between the heat generating part and the heater lead, and the movement of the metal element during the heat treatment is suppressed, causing the disconnection. It becomes difficult to generate a cavity.

It is sectional drawing which follows the longitudinal direction explaining the structure of the multi gas sensor which concerns on 1st Embodiment. It is a block diagram explaining the structure of the multi-gas sensor apparatus which concerns on 1st Embodiment. It is an expanded view explaining the structure of an ammonia sensor part. It is sectional drawing explaining the structure of an ammonia electrode. It is sectional drawing which follows the longitudinal direction explaining the structure of the gas sensor which concerns on 2nd Embodiment. It is a perspective view explaining the structure of a ceramic heater. It is a disassembled perspective view explaining the internal structure of a ceramic heater. It is sectional drawing explaining the structure of a heating resistor. It is an expanded view explaining the structure of the ammonia sensor part which concerns on 3rd Embodiment. It is sectional drawing explaining the connection structure of the ammonia electrode and ammonia electrode lead in 3rd Embodiment. It is sectional drawing explaining the connection structure of the ammonia electrode and ammonia electrode lead in 4th Embodiment.

<First Embodiment>
A multi-gas sensor device 1 including a gas sensor element (ammonia sensor unit 21) according to a first embodiment of the present invention will be described with reference to FIGS. The multi-gas sensor device 1 of this embodiment is used for a urea SCR system that purifies nitrogen oxides (NOx) contained in exhaust gas (gas to be measured) discharged from a diesel engine. More specifically, the concentration of nitrogen monoxide (NO), nitrogen dioxide (NO ₂ ), and ammonia contained in the exhaust gas after reacting NOx contained in the exhaust gas with ammonia (urea) is measured. Is.

  Note that the engine to which the multi-gas sensor device 1 of the present embodiment is applied may be the above-described diesel engine or can be applied to a gasoline engine, and the type of the engine is not particularly limited.

As shown in FIG. 1 and FIG. 2, the multi-gas sensor device 1 controls the multi-gas sensor 2 (corresponding to the gas sensor of the present invention) which is a sensor main body and the multi-gas sensor 2 and calculates the sensor output. A control unit 3 for calculating concentrations of NO, NO ₂ and ammonia is mainly provided.

  As shown in FIG. 1, the multi-gas sensor 2 is mainly provided with a sensor element unit 10, a metal shell 110, a separator 134, and a connection terminal 138. In the following description, the side (lower side in FIG. 1) where the sensor element unit 10 of the multi-gas sensor 2 is arranged is the front end side, and the side where the connection terminal 138 is arranged (upper side in FIG. 1) is the rear end. Indicated as side.

  The sensor element unit 10 has a plate shape extending in the axis O direction. Electrode terminal portions 10 </ b> A and 10 </ b> B are disposed at the rear end of the sensor element portion 10. In FIG. 1, for ease of illustration, the electrode terminal portions formed on the sensor element portion 10 are only the electrode terminal portion 10A and the electrode terminal portion 10B. A plurality of electrode terminal portions are formed according to the number of electrodes and the like that the ammonia sensor portion 21 has. A more detailed description of the sensor element unit 10 will be described later.

  The metal shell 110 is a cylindrical member in which a screw portion 111 that fixes the multi-gas sensor 2 to an exhaust pipe of a diesel engine is formed on the outer surface. The metal shell 110 is mainly provided with a through hole 112 penetrating in the axial direction and a shelf 113 projecting radially inward of the through hole 112. The shelf 113 is formed as an inwardly tapered surface having an inclination that approaches the front end side from the radially outer side of the through hole 112 toward the center.

  The metal shell 110 holds the sensor element unit 10 in a state where the front end side of the sensor element unit 10 protrudes from the through hole 112 to the front end side and the rear end side of the sensor element unit 10 protrudes to the rear end side of the through hole 112. Is.

  Inside the through-hole 112 of the metal shell 110, in order from the front end side to the rear end side, a ceramic holder 114 that is a cylindrical member surrounding the radial periphery of the sensor element unit 10, and a talc ring that is a powder-filled layer 115 and 116 and a ceramic sleeve 117 are laminated.

  A caulking packing 118 is disposed between the ceramic sleeve 117 and the end portion on the rear end side of the metal shell 110. A metal holder 119 is disposed between the ceramic holder 114 and the shelf 113 of the metal shell 110. The metal holder 119 holds the talc ring 115 and the ceramic holder 114. The end portion on the rear end side of the metal shell 110 is a portion that is crimped so as to press the ceramic sleeve 117 toward the distal end side via the crimping packing 118.

  An external protector 121 and an internal protector 122 are provided at the end of the metal shell 110 on the front end side. The external protector 121 and the internal protector 122 are cylindrical members formed of a metal material such as stainless steel whose end on the distal end side is closed. The internal protector 122 is welded to the metal shell 110 in a state where the end of the sensor element unit 10 on the front end side is covered, and the external protector 121 is welded to the metal shell 110 in a state where the internal protector 122 is covered.

  At the end on the rear end side of the metal shell 110, the end portion on the front end side of the outer cylinder 131 formed in a cylindrical shape is fixed. Furthermore, a grommet 132 that closes the opening is disposed in an opening that is an end portion on the rear end side of the outer cylinder 131.

  The grommet 132 is formed with a lead wire insertion hole 133 through which the lead wire 141 is inserted. The lead wire 141 is electrically connected to the electrode terminal portion 10A of the sensor element portion 10 and the electrode terminal portion 10B.

  The separator 134 is a cylindrical member disposed on the rear end side of the sensor element unit 10. A space formed inside the separator 134 is an insertion hole 135 penetrating in the axial direction. On the outer surface of the separator 134, a flange 136 that protrudes radially outward is formed.

  The rear end portion of the sensor element portion 10 is inserted into the insertion hole 135 of the separator 134, and the electrode terminal portions 10 </ b> A and 10 </ b> B are disposed inside the separator 134.

  Between the separator 134 and the outer cylinder 131, a holding member 137 formed in a cylindrical shape is disposed. The holding member 137 contacts the flange 136 of the separator 134 and also contacts the inner surface of the outer cylinder 131, thereby fixing and holding the separator 134 with respect to the outer cylinder 131.

  The connection terminal 138 is a member disposed in the insertion hole 135 of the separator 134, and electrically connects the electrode terminal portion 10A and the electrode terminal portion 10B of the sensor element portion 10 and the lead wire 141 independently of each other. It is a conductive member. In FIG. 1, only two connection terminals 138 are shown for ease of illustration.

As shown in FIG. 2, the control unit 3 of the multigas sensor device 1 is electrically connected to an ECU 200 that is a vehicle-side control device of a vehicle on which the multigas sensor device 1 is mounted. The ECU 200 receives data indicating the NO concentration, NO ₂ concentration, and ammonia concentration in the exhaust gas calculated by the control unit 3, and executes control processing of the operation state of the diesel engine based on the received data, or the catalyst The accumulated NOx purification process is executed.

  Here, the detail of a structure of the sensor element part 10 is demonstrated, referring FIG. For convenience of explanation, FIG. 2 shows only a cross-sectional view along the longitudinal direction of the sensor element unit 10.

  The sensor element unit 10 is mainly provided with a NOx sensor unit (NOx detection element) 11 and an ammonia sensor unit (corresponding to the gas sensor element of the present invention) 21. The NOx sensor unit 11 in the present embodiment has the same configuration as a known NOx sensor.

  The NOx sensor unit 11 mainly includes an insulating layer 10e, a first solid electrolyte body 12a, an insulating layer 10d, a third solid electrolyte body 16a, an insulating layer 10c, a second solid electrolyte body 18a, and insulating layers 10b and 10a. The structure is laminated in this order. Each of the insulating layers 10a, 10b, 10c, 10d, and 10e described above is formed mainly of alumina.

  Further, in the NOx sensor unit 11, the first measurement chamber S1 is provided between the first solid electrolyte body 12a and the third solid electrolyte body 16a, and the second measurement chamber S2 corresponding to the NOx measurement chamber is provided in the first solid state. A third solid electrolyte body 16a is provided between the electrolyte body 12a and the second solid electrolyte body 18a.

  A first diffusion resistor 14 is disposed at the inlet end (left end in FIG. 2) of the first measurement chamber S1 into which the gas to be measured is introduced. A second diffusion resistor 15 that partitions the first measurement chamber S1 and the second measurement chamber S2 is disposed at the end opposite to the inlet end in the first measurement chamber S1 (the right end in FIG. 2). . The first diffusion resistor 14 and the second diffusion resistor 15 described above are made of a porous material such as alumina, and have permeability to the gas to be measured.

  The NOx sensor unit 11 is further provided with a heater 19 that raises the temperature of the NOx sensor unit 11 and the ammonia sensor unit 21 to the activation temperature and increases the conductivity of oxygen ions in the solid electrolyte body constituting each sensor. ing. The heater 19 is formed of platinum or an alloy containing platinum in the shape of a long plate extending along the longitudinal direction of the sensor element unit 10, and is embedded between the insulating layer 10b and the insulating layer 10a. .

  In addition, the NOx sensor unit 11 is provided with a first pumping cell 12, an oxygen concentration detection cell 16, and a second pumping cell 18.

  The first pumping cell 12 is mainly composed of a first solid electrolyte body 12a mainly composed of zirconia having oxygen ion conductivity, and an inner first pumping electrode 12b and outer first pumping electrode 12c mainly composed of platinum. Has been.

  The inner first pumping electrode 12b is provided on the surface of the first solid electrolyte body 12a exposed to the first measurement chamber S1. Further, the inner first pumping electrode 12b has a surface on the first measurement chamber S1 side covered with a protective layer 12d made of a porous body.

  The outer first pumping electrode 12c is an electrode serving as a counter electrode for the inner first pumping electrode 12b, and is disposed with the first solid electrolyte body 12a sandwiched between the inner first pumping electrode 12b. A portion corresponding to a region where the outer first pumping electrode 12c is disposed in the insulating layer 10e is hollowed out and filled with the porous body 12e. The porous body 12e allows gas (oxygen) to enter and exit between the outer first pumping electrode 12c and the outside.

  The oxygen concentration detection cell 16 is mainly composed of a third solid electrolyte body 16a mainly composed of zirconia, and a detection electrode 16b and a reference electrode 16c mainly composed of platinum and arranged with the third solid electrolyte body 16a interposed therebetween. It is configured.

  The detection electrode 16b is a surface exposed to the first measurement chamber S1 of the third solid electrolyte body 16a, and is provided downstream of the inner first pumping electrode 12b, in other words, in a region on the second diffusion resistor 15 side. It has been.

  A reference electrode 16c, which is a counter electrode of the detection electrode 16b, is disposed inside a reference oxygen chamber 17 formed by cutting out the insulating layer 10c. The reference oxygen chamber 17 is filled with a porous body. In the reference oxygen chamber 17, there is oxygen sent from the first measurement chamber S1, and oxygen in the reference oxygen chamber 17 is used as an oxygen reference.

  The second pumping cell 18 mainly includes a second solid electrolyte body 18a mainly composed of zirconia, an inner second pumping electrode (electrode) 18b mainly composed of platinum, and a second pumping counter electrode (electrode) 18c. Has been.

  The inner second pumping electrode 18b is provided in a region exposed to the second measurement chamber S2 in the second solid electrolyte body 18a. The second pumping counter electrode 18c is a region exposed to the reference oxygen chamber 17 in the second solid electrolyte body 18a, and is provided in a portion facing the reference electrode 16c.

  Further, the inner first pumping electrode 12b, the detection electrode 16b, and the inner second pumping electrode 18b are each connected to a reference potential.

  On the other hand, the ammonia sensor unit 21 is formed on the outer surface of the NOx sensor unit 11, more specifically, on the insulating layer 10e. The ammonia sensor unit 21 is disposed at substantially the same position (for example, the upper side in FIG. 2) in the direction of the axis O with the reference electrode 16c in the NOx sensor unit 11.

  In the present embodiment, when the control temperature of the second solid electrolyte body 18a of the NOx sensor unit 11 is 600 ° C., the ammonia sensor unit 21 is disposed at a position where the temperature of the outer surface of the NOx sensor unit 11 is 650 ° C. Has been.

  As shown in FIGS. 2 and 3, the ammonia sensor unit 21 includes a reference electrode 21a mainly composed of platinum (corresponding to the second electrode of the present invention) and an ammonia solid electrolyte body 23 mainly composed of zirconia (the present invention). ), An intermediate layer (electrode) 21b mainly composed of cobalt oxide and zirconia, and an ammonia electrode (corresponding to the electrode of the present invention) 21c mainly composed of gold. . Furthermore, the ammonia sensor unit 21 is integrally covered with a porous protective layer 24.

  The reference electrode 21a is an electrode in which a combustible gas burns on the electrode surface, and is made of, for example, Pt alone or a material containing Pt as a main component. Furthermore, the reference electrode 21a is a rectangular electrode disposed on the outer surface (the upper surface in FIG. 3) of the insulating layer 10e, and platinum that extends in the longitudinal direction (the left-right direction in FIG. 3) of the insulating layer 10e. A main reference electrode lead 25 is provided. The end portion on the rear end side (right side in FIG. 3) of the reference electrode lead 25 forms an electrode terminal portion.

  The ammonia solid electrolyte body 23 is made of an oxygen ion conductive material such as yttria-stabilized zirconia (YSZ), and is disposed with the reference electrode 21a sandwiched between the insulating layer 10e.

The intermediate layer 21b is an outer surface of the ammonia solid electrolyte body 23 and is disposed at a position facing the reference electrode 21a.
In the present embodiment, the intermediate layer 21b is mainly composed of cobalt oxide and zirconia. However, the intermediate layer 21b contains 50 mass% or more of an oxygen ion conductive solid electrolyte component (that is, zirconia), and Mn, Cu, Ni And a layer containing a first metal oxide which is an oxide of one or more metals selected from the group consisting of Ce and Ce. Further, for example, when the first metal oxide is cobalt oxide (Co ₃ O ₄ ), the fluctuation of the sensitivity of the ammonia concentration in the ammonia sensor unit 21 is suppressed by H ₂ O contained in the gas to be detected. Is done. The first metal oxide described above takes the form of a metal oxide or a composite oxide. The solid electrolyte component contained in the intermediate layer 21b may have the same composition as the solid electrolyte body constituting the gas sensor of the present invention, or may be a different component.

  The ratio of the first metal oxide contained in the intermediate layer 21b is preferably 1% by mass to 50% by mass. When the content ratio of the first metal oxide is less than 1% by mass, there is a possibility that the selectivity of the intermediate layer 21b with respect to the ammonia gas cannot be ensured sufficiently. Moreover, when the content rate of a 1st metal oxide exceeds 50 mass%, there exists a possibility that the ratio of the solid electrolyte component of the intermediate | middle layer 21b may decrease, and the oxygen ion conductivity of the intermediate | middle layer 21b may fall.

  Furthermore, the intermediate layer 21b is preferably porous. By forming the intermediate layer 21b from a porous body, the selectivity of the intermediate layer 21b with respect to ammonia gas is improved, and the ammonia gas detection sensitivity in the ammonia sensor unit 21 is improved.

  Whether or not the first metal oxide is contained in the intermediate layer 21b can be confirmed by analyzing the cross section of the ammonia sensor unit 21 with an EPMA (electron beam microanalyzer). In general, three portions of the cut surface are analyzed by EPMA, and the average value of the analysis results can be confirmed.

  The ammonia electrode 21c is disposed on the outer surface of the intermediate layer 21b. In other words, the ammonia electrode 21c is disposed with the solid electrolyte for ammonia 23 and the intermediate layer 21b sandwiched between the reference electrode 21a.

  An ammonia electrode lead (corresponding to a lead of the present invention) 21d is formed on the ammonia electrode 21c so as to extend from the ammonia electrode 21c toward the rear end side. Specifically, as shown in FIG. 4, an ammonia electrode lead 21d is electrically connected to the ammonia electrode 21c via a joint portion (corresponding to a component region of the present invention) 70. Details of the joint portion 70 will be described later. The ammonia electrode lead 21d is formed of a material whose main component is platinum. That is, the ammonia electrode lead 21d contains 50% by mass or more of platinum. Platinum corresponds to the second metal of the present invention. Further, the end portion on the rear end side of the ammonia electrode lead 21d forms an electrode terminal portion.

  The ammonia electrode 21c is mainly composed of Au (gold). That is, the ammonia electrode 21c is an electrode formed from a material containing 70% by mass or more of Au and serves as a detection electrode. Gold corresponds to the first metal of the present invention. The ammonia electrode 21c may or may not contain the first metal oxide described above, but if it is not included, combustion of ammonia gas at the ammonia electrode 21c is suppressed. Thus, the ammonia gas that reaches the interface between the ammonia electrode 21c and the intermediate layer 21b is unlikely to decrease. In other words, the detection accuracy of the ammonia sensor unit 21 is improved, and in particular, low concentration ammonia near 10 ppm can be detected with high accuracy.

  Moreover, the capability as a collector in the ammonia electrode 21c is ensured by forming the ammonia electrode 21c from a material containing 70% by mass or more of Au. Note that when the ammonia electrode 21c is formed using a material having an Au content of less than 70% by mass, it is difficult to secure the capability of the ammonia electrode 21c as a current collector. That is, it becomes difficult to detect ammonia gas by the ammonia sensor unit 21.

  The ammonia electrode 21c is a porous electrode including a second metal oxide that is an oxide of one or more metals selected from the group consisting of Zr (zirconium), Y (yttrium), Al (aluminum), and Si (silicon). As a result, gas permeability can be imparted to the ammonia electrode 21c. Therefore, ammonia gas can permeate the ammonia electrode 21c and can easily reach the interface between the ammonia electrode 21c and the intermediate layer 21b. In addition, it is preferable that the ammonia electrode 21c contains the 2nd metal oxide in the ratio from 5 mass% to 30 mass%.

  The ammonia gas that reaches the interface between the ammonia electrode 21c and the intermediate layer 21b reacts with oxygen ions (electrode reaction) at the interface. Therefore, the ammonia electrode 21c and the intermediate layer 21b can function as an ammonia gas detector. Here, the presence of the first metal oxide at the interface between the ammonia electrode 21c and the intermediate layer 21b reduces the sensitivity of the ammonia electrode 21c and the intermediate layer 21b to gases other than ammonia gas such as HC gas. The selectivity of ammonia gas can be improved.

The reason why the selectivity of ammonia gas is improved is not clear, but it is considered that the first metal oxide interposed in the above-described interface modifies the electrode reaction field. Furthermore, since the first metal oxide has an acidic property, it is considered that the first metal oxide interacts strongly with NH ₃ that is a basic molecule, and the electrode reaction with respect to NH ₃ proceeds more favorably than other gases. From these facts, it is considered that the selectivity of ammonia gas in the ammonia electrode 21c and the intermediate layer 21b is improved.

  In the present embodiment, the ammonia electrode 21c and the intermediate layer 21b are provided separately. However, the intermediate layer 21b may be omitted by making the ammonia electrode 21c contain cobalt oxide contained in the intermediate layer 21b. .

The protective layer 24 adjusts the diffusion rate of the gas to be measured flowing from the outside into the ammonia sensor unit 21 while preventing the poisonous substance from adhering to the ammonia electrode 21c. Examples of the material for forming the protective layer 24 include at least one material selected from the group consisting of alumina (aluminum oxide), spinel (MgAl ₂ O ₄ ), silica alumina, and mullite. The diffusion rate of the gas to be measured by the protective layer 24 is adjusted by adjusting the thickness, particle size, particle size distribution, porosity, blending ratio, etc. of the protective layer 24.

  The protective layer 24 may be provided as in the above-described embodiment, or the ammonia electrode 21c and the like may be exposed without providing the protective layer 24, and is not particularly limited.

  As shown in FIG. 2, the control unit 3 includes a control circuit 50 that is an analog circuit disposed on a circuit board, and a microcomputer 60.

  The microcomputer 60 controls the entire control unit 3. The microcomputer 60 mainly includes a CPU 61 as a central processing unit, a RAM 62 and a ROM 63 as storage means, a signal input / output unit 64, an A / D converter 65, and a clock (not shown). Is provided. The microcomputer 60 performs various processes when the CPU 61 executes a program stored in advance in the ROM 63 or the like.

  The control circuit 50 includes a reference voltage comparison circuit 51, an Ip1 drive circuit 52, a Vs detection circuit 53, an Icp supply circuit 54, an Ip2 detection circuit 55, a Vp2 application circuit 56, a heater drive circuit 57, and an electromotive force. The detection circuit 58 is mainly configured.

  The Ip1 drive circuit 52 is electrically connected to the first outer pumping electrode 12c of the NOx sensor unit 11, and the Vs detection circuit 53 and the Icp supply circuit 54 are electrically connected in parallel to the reference electrode 16c. The Ip2 detection circuit 55 and the Vp2 application circuit 56 are electrically connected in parallel to the second pumping counter electrode 18 c, and the heater drive circuit 57 is electrically connected to the heater 19.

  The electromotive force detection circuit 58 is electrically connected to the reference electrode 21a and the ammonia electrode 21c in the ammonia sensor unit 21. Further, the electromotive force detection circuit 58 detects an ammonia electromotive force EMF, which is an electromotive force between the reference electrode 21a and the ammonia electrode 21c, and outputs it to the microcomputer 60.

  The Ip1 drive circuit 52 supplies the first pumping current Ip1 between the inner first pumping electrode 12b and the outer first pumping electrode 12c, and detects the supplied first pumping current Ip1.

  The Vs detection circuit 53 detects the voltage Vs between the detection electrode 16b and the reference electrode 16c, and outputs the detected result to the reference voltage comparison circuit 51. The reference voltage comparison circuit 51 compares the reference voltage (for example, 425 mV) with the output (voltage Vs) of the Vs detection circuit 53, and outputs the comparison result to the Ip1 drive circuit 52.

  The Ip1 drive circuit 52 controls the flow direction and magnitude of the Ip1 current so that the voltage Vs becomes equal to the above-described reference voltage, and has a predetermined value that does not decompose the oxygen concentration in the first measurement chamber S1. To adjust.

  The Icp supply circuit 54 allows a weak current Icp to flow between the detection electrode 16b and the reference electrode 16c. By supplying the current Icp, oxygen is sent into the reference oxygen chamber 17 from the first measurement chamber S1. The reference electrode 16c is exposed to a predetermined oxygen concentration as a reference.

The Vp2 application circuit 56 applies a constant voltage Vp2 (for example, 450 mV) between the inner second pumping electrode 18b and the second pumping counter electrode 18c, and decomposes NOx into nitrogen and oxygen. The constant voltage Vp2 is such a voltage that the NOx gas in the gas to be measured is decomposed into oxygen and N ₂ gas.

  The Ip2 detection circuit 55 detects the second pumping current Ip2 flowing through the second pumping cell 18. The second pumping current Ip2 is a current that flows when oxygen generated by the decomposition of NOx is pumped from the second measurement chamber S2 to the second pumping counter electrode 18c side through the second solid electrolyte body 18a.

  The Ip1 drive circuit 52 outputs the detected value of the first pumping current Ip1 to the A / D converter 65, and the Ip2 detection circuit 55 supplies the detected value of the second pumping current Ip2 to the A / D converter 65. Output. The A / D converter 65 digitally converts the values of the first pumping current Ip1 and the second pumping current Ip2 and outputs them to the CPU 61 via the signal input / output unit 64.

  Next, a manufacturing method of the sensor element unit 10 in which the NOx sensor unit 11 and the ammonia sensor unit 21 are formed will be described. Here, a manufacturing method of the ammonia sensor unit 21 will be described. In addition, since the manufacturing method of the NOx sensor part 11 is a well-known manufacturing method, the detailed description is abbreviate | omitted in this embodiment.

A method for manufacturing the ammonia sensor unit 21 will be described below with reference to FIGS.
First, an electrode paste (hereinafter referred to as “Pt-based paste”) containing Pt, alumina (an inorganic oxide used as a common substrate), a binder and an organic solvent for forming the reference electrode 21a on the insulating layer 10e. It arrange | positions by screen printing and bakes at predetermined temperature (about 1400 degreeC or more).

  On the baked reference electrode 21a, a paste containing oxide powder, binder, and organic solvent, which are components of the solid electrolyte body forming the solid electrolyte body 23 for ammonia, is disposed by screen printing, and a predetermined temperature (for example, 1500). ℃). Thus, the reference electrode 21a and the ammonia solid electrolyte body 23 are formed.

  Next, a paste containing the first metal oxide forming the intermediate layer 21b and the solid electrolyte component is disposed on the solid electrolyte body 23 for ammonia by screen printing and fired at a predetermined temperature (for example, 1000 ° C.). Thereby, the intermediate layer 21b is formed.

  Further, a Pt-based paste for forming the ammonia electrode lead 21d is disposed on the intermediate layer 21b by screen printing. And the paste which forms the joint part 70 is arrange | positioned by screen printing so that it may overlap with the edge part of this Pt-type paste. Next, an Au-based paste for forming the ammonia electrode 21c is arranged by screen printing so as to overlap the paste for forming the joint portion 70, and is baked at a predetermined temperature (for example, 1000 ° C.), whereby the ammonia electrode 21c. Is formed. Finally, a paste containing alumina or the like is disposed by screen printing so as to cover the reference electrode 21a, the solid electrolyte for ammonia 23, the intermediate layer 21b, and the ammonia electrode 21c, and fired at a predetermined temperature (for example, 1000 ° C.). Thus, the protective layer 24 is formed. Thus, the ammonia sensor unit 21 is formed.

Next, the joint portion 70 between the ammonia electrode 21c and the ammonia electrode lead 21d, which is a feature of this embodiment, will be described.
The joint portion 70 contains a total of 50 mass% or more of Au (first metal) and Pt (second metal). The joint portion 70 has an Au content ratio that is between the Au content ratio in the ammonia electrode 21c and the Au content ratio in the ammonia electrode lead 21d. That is, the concentration of Au in the joint portion 70 is lower than that of the ammonia electrode 21c and higher than that of the ammonia electrode lead 21d. Further, the Pt content in the joint portion 70 is a size between the Pt content in the ammonia electrode 21c and the Pt content in the ammonia electrode lead 21d. That is, the Pt concentration in the joint portion 70 is lower than the ammonia electrode lead 21d and higher than the ammonia electrode 21c. That is, regarding the Au concentration, the joint portion 70 has a concentration between the ammonia electrode 21c and the ammonia electrode lead 21d. Further, regarding the Pt concentration, the joint portion 70 has a concentration between the ammonia electrode 21c and the ammonia electrode lead 21d.
The concentration of Au in the joint part 70 is preferably 30 to 70% by mass, more preferably 40 to 60% by mass, when the total amount of Au and Pt in the joint part 70 is 100% by mass. More preferably, it is 45-55 mass%.
The Pt concentration in the joint part 70 is preferably 30 to 70% by mass, more preferably 40 to 60% by mass, when the total amount of Au and Pt in the joint part 70 is 100% by mass. More preferably, it is 45-55 mass%.
The metal component in the joint portion 70 is preferably substantially made of Au and Pt. Here, “substantially consists of Au and Pt” means that the metal components other than Au and Pt are substantially 0% (specifically, less than 5.0% by mass). To do.

In the gas sensor element (ammonia sensor portion 21) of the present embodiment, due to the presence of the joint portion 70, the abrupt concentration gradient of the metal element becomes gentle, and Au of the ammonia electrode 21c to the ammonia electrode lead 21d even during firing (during heat treatment). Difficult to move. Therefore, cavities due to the movement of Au hardly occur, and disconnection is suppressed.
When the first metal is Au and the second metal is Pt, the metal element is likely to move during firing, but the metal element movement can be effectively suppressed by interposing the joint portion 70. .

Second Embodiment
A gas sensor 310 according to a second embodiment of the present invention will be described with reference to FIGS.
FIG. 5 is an explanatory diagram showing the configuration of the gas sensor 310. The gas sensor 310 includes an oxygen detection element 320 (corresponding to the gas sensor element of the present invention), a metal shell 311, an inner terminal member 330, an outer terminal member 340, and a ceramic heater 300 (corresponding to the heater of the present invention). Prepare.

  The oxygen detection element 320 has a front end 320s (lower side in FIG. 5) closed, a rear end 320k (upper side in FIG. 5) opened, and a substantially U-shaped cross section extending in the axial direction (vertical direction in FIG. 5) along the axis AX. It has a bottomed cylindrical shape. The oxygen detection element 320 includes a solid electrolyte body 321 having oxygen ion conductivity, an outer electrode layer (not shown) formed by plating or the like on a part of the outer circumferential surface of the solid electrolyte body 321, and an inner circumference of the solid electrolyte body 321. An inner electrode layer (not shown) formed by plating or the like is provided on a part of the surface. In addition, on the outer peripheral surface of the oxygen detection element 320, an engagement flange portion 320f protruding outward in the radial direction is provided at an intermediate portion in the axis AX direction, and is engaged with a metal shell 311 described later.

  The metal shell 311 is formed in a cylindrical shape surrounding a part of the outer periphery of the oxygen detection element 320, and is engaged with metal packings 381, 382, 383, insulators 313, 313b, and ceramic powder 314 interposed therebetween. The oxygen detecting element 320 is held by engaging with the flange portion 320f. Thereby, the oxygen detection element 320 is kept airtight inside the metal shell 311. A protector 315 is attached to the metallic shell 311 so as to cover the distal end portion of the oxygen detecting element 320 protruding from the opening on the distal end side of the metallic shell 311. The protector 315 has a double structure of an outer protector 315a and an inner protector 315b, and the outer protector 315a and the inner protector 315b are formed with a plurality of gas permeation ports through which exhaust gas permeates. An outer electrode layer (not shown) of the oxygen detection element 320 can come into contact with the exhaust gas through the gas permeation port of the protector 315.

  The metal shell 311 includes a connecting portion 311d on the rear end side of the hexagonal portion 311c formed on the outer peripheral surface. In the connection portion 311d, the distal end side of the cylindrical metal outer cylinder 316 is fixed from the outside by full-circle laser welding. The rear end side opening of the metal outer cylinder 316 is caulked and sealed by inserting a grommet 317 made of fluoro rubber. A separator 318 made of an insulating alumina ceramic is disposed on the tip side of the grommet 317. Sensor output lead wires 319 and 319b and heater lead wires 312b and 312c are disposed through the grommet 317 and the separator 318. A through-hole is formed in the center of the grommet 317 along the axis AX, and a metal pipe 386 in a state where a sheet-like filter 385 having both water repellency and air permeability is covered is fitted into the through-hole. Yes. As a result, the atmosphere outside the gas sensor 310 is introduced into the metal outer cylinder 316 via the filter 385 and then into the internal space G of the oxygen detection element 320.

  The outer terminal member 340 is made of a stainless steel plate, and an outer fitting part 341 having a substantially C-shaped cross section in the direction perpendicular to the axis AX, and a separator insertion part 342 extending from the vicinity of the center of the rear end side of the outer fitting part 341 to the rear end side. Further, a connector portion 343 is provided which is located on the rear end side, grips the core wire of the sensor output lead wire 319b by caulking, and electrically connects the outer terminal member 340 and the sensor output lead wire 319b. The separator insertion portion 342 is inserted into the separator 318, and the separator contact portion 342d that branches and protrudes from the separator insertion portion 342 elastically contacts the holding hole 318d, so that the outer terminal member 340 itself is attached. It is held in the separator 318. Further, the outer fitting portion 341 is formed such that the diameter of the inscribed circle in the radial cross section is smaller than the diameter of the outer peripheral surface on the rear end side of the oxygen detection element 320. Therefore, in a state where the outer terminal member 340 is assembled to the oxygen detection element 320, the outer fitting portion 341 causes a pressing force to be applied to the outer electrode layer formed on the outer peripheral surface of the oxygen detection element 320 by its own elastic force. In order to make contact, electrical conduction with the outer electrode layer is maintained. Therefore, the electromotive force generated in the outer electrode layer is extracted to the outside through the outer fitting portion 341 and the sensor output lead wire 319b.

  The inner terminal member 330 is made of a stainless steel plate and has an insertion portion 333 whose cross section in the direction perpendicular to the axis AX is a horseshoe shape, a separator insertion portion 332 extending from the vicinity of the center of the rear end side of the insertion portion 333 to the rear end side, and The connector part 331 is located on the end side, grips the core wire of the sensor output lead wire 319 by caulking, and electrically connects the inner terminal member 330 and the sensor output lead wire 319. The separator insertion portion 332 is inserted into the separator 318, and a separator contact portion 332d that branches off and protrudes from the separator insertion portion 332 elastically contacts the holding hole 318d, and the inner terminal member 330 itself is It is held in the separator 318. The insertion portion 333 includes a heater pressing portion 336 that protrudes toward the distal end side. When viewed from the direction of the axis AX, the heater pressing portion 336 is formed in a substantially arc shape, and when the insertion portion 333 is assembled in the oxygen detection element 320, the side surface of the ceramic heater 300 is the oxygen detection element. The ceramic heater 300 is pressed so as to contact the inner peripheral surface of 320.

  The insertion portion 333 is formed such that the diameter of the circumscribed circle in the radial cross section is larger than the diameter of the inner peripheral surface on the rear end side of the oxygen detection element 320. Therefore, in a state where the inner terminal member 330 is assembled to the oxygen detection element 320, the insertion portion 333 causes a pressing force to be applied to the inner electrode layer formed on the inner peripheral surface of the oxygen detection element 320 by its own elastic force. Because of the contact, electrical continuity with the inner electrode layer is maintained. Therefore, the electromotive force generated in the inner electrode layer is extracted to the outside through the insertion portion 333 and the sensor output lead wire 319.

  The ceramic heater 300 is disposed in the internal space G and is maintained by the inner terminal member 330 to maintain the posture. In the ceramic heater 300, a terminal member 430 described later is connected to the heater lead wires 312b and 312c, and the inner peripheral surface of the solid electrolyte body 321 is heated by the supply of electric power from the heater lead wires 312b and 312c. The configuration of the ceramic heater 300 will be described in detail later.

  FIG. 6 is an explanatory view showing the configuration of the ceramic heater. FIG. 7 is an exploded perspective view showing the internal structure of the ceramic heater. As shown in FIG. 6, the ceramic heater 300 is formed in a round bar shape (substantially cylindrical shape). Then, as shown in FIG. 5, the oxygen detection element 320 is heated by being inserted into the oxygen detection element 320. Of the both ends of the ceramic heater 300 in the longitudinal direction, the side (left side in FIG. 6) provided with the heat generating portion will be referred to as “front end side”, and the opposite end will be described as “rear end side”.

  The ceramic heater 300 includes a ceramic base body 402, an electrode pad 421, and a terminal member 430. As shown in FIG. 7, the ceramic base 402 is manufactured by winding green sheets 440 and 446 made of alumina ceramic having high insulating properties around the outer periphery of a round bar-shaped alumina ceramic tube 401 and firing them. .

  On the green sheet 440, a heating resistor 441 mainly composed of a Pt-based material as a heater pattern is formed. The heat generating resistor 441 further includes a heat generating portion 442 and a pair of lead portions 443 (in the present invention) connected to both ends of the heat generating portion 442 through joint portions (corresponding to the heater joint portion and the component region of the present invention) 450, respectively. Equivalent to a heater lead). The rear end side of the green sheet 440 is electrically connected to an electrode pad 421 formed on the outer surface of the ceramic heater 300 through two through holes 444.

On the green sheet 440, a Pd-based paste for forming the lead portion 443 is disposed by screen printing. And the paste which forms the joint part 450 is arrange | positioned by screen printing so that it may overlap with the edge part of this Pt-type paste. Next, a Pt-based paste for forming the heat generating portion 442 is arranged by screen printing so as to overlap the paste for forming the joint portion 450.
The green sheet 446 is pressure-bonded to the surface of the green sheet 440 where the heating resistor 441 is formed. Alumina paste is applied to the surface of the green sheet 446 opposite to the pressure-bonding surface, and the green sheets 440 and 446 are wound around the tub tube 401 and pressed inward from the outer periphery with the coating surface facing inward. Thus, a ceramic heater molded body is formed. Thereafter, the ceramic base body 402 is formed by firing the ceramic heater molded body.

Next, the joint portion 450 between the heat generating portion 442 and the lead portion 443, which is a feature of the present embodiment, will be described.
The joint portion 450 contains 50 mass% or more in total of Pt (first metal) and Pd (second metal). The joint portion 450 has a Pt content ratio that is between the Pt content ratio in the heat generating portion 442 and the Pt content ratio in the lead portion 443. That is, the Pt concentration in the joint portion 450 is lower than that of the heat generating portion 442 and higher than that of the lead portion 443. Further, the Pd content in the joint portion 450 is a size between the Pd content in the heat generating portion 442 and the Pd content in the lead portion 443. That is, the Pd concentration in the joint portion 450 is lower than that of the lead portion 443 and higher than that of the heat generating portion 442. That is, regarding the Pt concentration, the joint portion 450 has a concentration between the heat generating portion 442 and the lead portion 443. Further, regarding the Pd concentration, the joint portion 450 has a concentration between the heat generating portion 442 and the lead portion 443.
The Pt concentration in the joint portion 450 is preferably 30 to 70 mass%, more preferably 40 to 60 mass%, when the total amount of Pt and Pd in the joint portion 450 is 100 mass%. More preferably, it is 45-55 mass%.
The concentration of Pd in the joint portion 450 is preferably 30 to 70 mass%, more preferably 40 to 60 mass%, when the total amount of Pt and Pd in the joint portion 450 is 100 mass%. More preferably, it is 45-55 mass%.
The metal component in the joint portion 450 is preferably substantially composed of Pt and Pd. Here, “substantially consists of Pt and Pd” means that the other metal components other than Pt and Pd are substantially 0% (specifically, less than 5.0% by mass). To do.

In the present embodiment, due to the presence of the joint portion 450, the steep concentration gradient of the metal element becomes gentle, and Pd of the lead portion 443 hardly moves to the heat generating portion 442 even during firing (during heat treatment). Therefore, a cavity due to the movement of Pd hardly occurs, and disconnection is suppressed.
When the first metal is Pt and the second metal is Pd, the metal element is likely to move after firing, but the metal element movement can be effectively suppressed by interposing the joint portion 450. .

<Third Embodiment>
A multi-gas sensor device (corresponding to a gas sensor of the present invention) 1 including a gas sensor element (ammonia sensor unit 21) according to a third embodiment will be described with reference to FIGS. Note that the multi-gas sensor device 1 of the third embodiment has the same configuration as the multi-gas sensor device 1 of the first embodiment except for a part thereof, and will be described with reference to FIGS. Moreover, in the following description, about the structure similar to the multi-gas sensor apparatus 1 of 1st Embodiment, the detailed description is abbreviate | omitted using the code | symbol similar to 1st Embodiment.

The multi-gas sensor device 1 of the third embodiment is mainly provided with a multi-gas sensor 2 and a control unit 3 as in the multi-gas sensor device 1 (see FIGS. 1 and 2) of the first embodiment. Since the control part 3 is the structure similar to the control part 3 of the multi-gas sensor apparatus 1 of 1st Embodiment, description is abbreviate | omitted. As shown in FIG. 1, the multigas sensor 2 is mainly provided with a sensor element unit 10, a metal shell 110, a separator 134, and a connection terminal 138. The sensor element section 10 is mainly provided with a NO _x sensor section (NO _x detection element) 11 and an ammonia sensor section (corresponding to the gas sensor element of the present invention) 21. The NO _x sensor unit (NO _x detection element) 11 has the same configuration as the NO _x sensor unit (NO _x detection element) 11 of the first embodiment, and a description thereof will be omitted.

  As shown in FIGS. 2 and 9, the ammonia sensor unit 21 includes a reference electrode 21a mainly composed of platinum, a solid electrolyte body 23 for ammonia mainly composed of zirconia, and an intermediate layer (electrodes composed mainly of cobalt oxide and zirconia). ) 21b and an ammonia electrode mainly composed of gold (corresponding to the electrode of the present invention) 21c. Furthermore, the ammonia sensor unit 21 is integrally covered with a porous protective layer 24. An ammonia electrode lead (corresponding to a lead of the present invention) 21d is formed on the ammonia electrode 21c so as to extend from the ammonia electrode 21c toward the rear end side. The ammonia electrode 21c and the ammonia electrode lead 21d are directly connected. The connection structure between the ammonia electrode 21c and the ammonia electrode lead 21d will be described in detail later.

Next, a manufacturing method of the sensor element unit 10 in which the NO _x sensor unit 11 and the ammonia sensor unit 21 are formed will be described. Here, a manufacturing method of the ammonia sensor unit 21 will be described. Since the production method of the NO _x sensor 11 is a known manufacturing method, a detailed description thereof will be omitted in this embodiment.

A method for manufacturing the ammonia sensor unit 21 will be described below with reference to FIGS.
First, an electrode paste (hereinafter referred to as “Pt-based paste”) containing Pt, an alumina (inorganic oxide used as a common substrate) binder, and an organic solvent for forming the reference electrode 21a on the insulating layer 10e is screened. It arrange | positions by printing and it bakes at predetermined temperature (about 1400 degreeC or more).

  On the baked reference electrode 21a, a paste containing oxide powder, binder, and organic solvent, which are components of the solid electrolyte body forming the solid electrolyte body 23 for ammonia, is disposed by screen printing, and a predetermined temperature (for example, 1500). ℃). Thus, the reference electrode 21a and the ammonia solid electrolyte body 23 are formed.

  Next, a paste containing the first metal oxide forming the intermediate layer 21b and the solid electrolyte component is disposed on the solid electrolyte body 23 for ammonia by screen printing and fired at a predetermined temperature (for example, 1000 ° C.). Thereby, the intermediate layer 21b is formed.

Further, an Au-based paste for forming the ammonia electrode 21c is disposed on the intermediate layer 21b by screen printing. Then, a Pt paste for forming the ammonia electrode lead 21d is placed by screen printing so as to overlap the end of the Au paste, and the ammonia electrode 21c is fired at a predetermined temperature (for example, 1000 ° C.). It is formed.
Finally, a paste containing alumina or the like is disposed by screen printing so as to cover the reference electrode 21a, the solid electrolyte for ammonia 23, the intermediate layer 21b, and the ammonia electrode 21c, and fired at a predetermined temperature (for example, 1000 ° C.). Thus, the protective layer 24 is formed. Thus, the ammonia sensor unit 21 is formed.

Here, a detailed connection structure between the ammonia electrode 21c and the ammonia electrode lead 21d will be described.
As shown in FIG. 10, in this connection structure, the ammonia electrode 21c and the ammonia electrode lead 21d do not overlap with each other, the electrode single portion 73, the ammonia electrode 21c and the ammonia electrode lead 21d overlap, and the ammonia electrode 21c. There is a single lead portion 75 that does not overlap with the ammonia electrode lead 21d. The connecting portion 71 is a region where the ammonia electrode 21c and the ammonia electrode lead 21d overlap in the thickness direction.
The connecting portion 71 is formed on the ammonia electrode 21c so as to cover the ammonia electrode lead 21d.

The specific gravity of the first metal that is the main metal component (noble metal component) of the electrode single portion 73 is set lower than the specific gravity of the second metal that is the main metal component (noble metal component) of the lead single portion 75. In the present embodiment, the first metal is Au, and the second metal is Pt.
As shown in FIG. 10, the thickness (T3) of the connecting portion 71 is thicker than the thickness (T1 + T2) obtained by adding the thickness (T1) of the electrode single portion 73 and the thickness (T2) of the lead single portion 75. Has been.
Further, as shown in FIG. 10, when the cross section of the connecting portion 71 is observed, the surface side of the connecting portion 71 is excluded by the thickness (T2) of the lead single portion 75, and the back surface side of the connecting portion 71 is the electrode alone. Excluding the thickness (T1) of the portion 73, there is a remaining portion 77 (corresponding to the joint portion and component region of the present invention, which is a cross-hatched portion in FIG. 10).
The Au content ratio in the remaining portion 77 is between the Au content ratio in the electrode single portion 73 and the Au content ratio in the lead single portion 75. That is, the content ratio of Au with respect to the metal component (noble metal component) contained in the remaining portion 77 is lower than the content ratio of Au with respect to the metal component (noble metal component) in the electrode single portion 73, and the metal component ( The composition is higher than the content ratio of Au with respect to the noble metal component).
“When the cross section of the connecting portion 71 is observed” is synonymous with “when the ammonia sensor portion 21 is cut along the axial direction with the ammonia electrode 21c and observed from the thickness direction”.

Although the thickness (T1) of the electrode single part 73 is not specifically limited, From a viewpoint of ensuring the detection precision of ammonia gas, 5 micrometers-40 micrometers are preferable, 10 micrometers-30 micrometers are more preferable, and 15 micrometers-25 micrometers are still more preferable.
The thickness (T2) of the lead single part 75 is not particularly limited, but is preferably 5 μm to 40 μm, more preferably 10 μm to 30 μm, from the viewpoint of ensuring high conductivity and the amount of expensive noble metal used. 15 micrometers-25 micrometers are still more preferable.
The thickness of the remaining portion 77 is not particularly limited, but is preferably 1 μm to 40 μm, more preferably 5 μm to 30 μm, and more preferably 10 μm to 20 μm from the viewpoint of effectively suppressing disconnection and the amount of expensive noble metal used. Is more preferable.
As shown in FIG. 10, the thickness (T2) of the lead single portion 75 is a thickness excluding a portion (the left end portion of the lead single portion 75 in FIG. 10) that is partially thick in the vicinity of the connection portion 71. Moreover, each thickness is taken as the average value of three places each, when a cross section near a connection part is observed by SEM at 300 times, for example.

  A method for forming this connection structure will be described. When the Au-based paste for forming the ammonia electrode 21c is arranged by screen printing, the Au-based paste is applied thicker at the portion to be the connection portion 71 than the portion to be the electrode-only portion 73. The Au-based paste applied thickly forms the remaining portion 77 described above. However, the remaining portion 77 has a smaller Au content ratio than the electrode single portion 73. This is because, during firing, Au moves from the Au paste forming the remaining portion 77 to the Pt paste forming the ammonia electrode lead 21d.

  The content ratio of Au with respect to the metal component (noble metal component) in the electrode single part 73, the lead single part 75, and the remaining part 77 is measured by elemental analysis using an electron beam microanalyzer (EPMA). As the content ratio of Au in each part, an average value of measured values obtained by measuring a plurality of parts in each part cross section is adopted.

The content ratio of Au to the metal component (noble metal component) in the electrode single part 73 is preferably 80% by weight or more, more preferably 80% by weight or more, and still more preferably 86% by weight or more. The upper limit of the content ratio of Au with respect to the metal component (noble metal component) in the electrode single part 73 may be 100% by weight.
Thus, the electrode single part 73 uses Au as the main metal component (noble metal component). Therefore, the capability as a collector in the electrode single part 73 is ensured.
Note that the electrode single part 73 may or may not contain the first metal oxide described above, but if it is not included, the combustion of ammonia gas in the electrode single part 73 Is suppressed, and the ammonia gas reaching the interface between the electrode single part 73 and the intermediate layer 21b is difficult to decrease. In other words, the detection accuracy of the ammonia sensor unit 21 is improved, and in particular, low concentration ammonia near 10 ppm can be detected with high accuracy.
The electrode single part 73 includes a second metal oxide that is an oxide of one or more metals selected from the group consisting of Zr (zirconium), Y (yttrium), Al (aluminum), and Si (silicon). By forming it as an electrode, gas permeability can be imparted to the electrode single part 73. Therefore, ammonia gas can permeate the electrode single part 73 and can easily reach the interface between the electrode single part 73 and the intermediate layer 21b. In addition, it is preferable that the electrode single part 73 contains the 2nd metal oxide in the ratio from 5 weight% to 30 weight%, when the electrode single part 73 whole is 100 weight%.

  The content ratio of Au with respect to the metal component (noble metal component) in the lead single part 75 is lower than the content ratio of Au in the electrode single part 73. The content ratio of Pt with respect to the metal component (noble metal component) in the lead single part 75 is preferably 50% by weight or more, more preferably 70% by weight or more, and still more preferably 90% by weight or more.

Further, the content ratio of Au to the metal component (noble metal component) in the remaining portion 77 is larger than the content ratio of Au to the metal component (noble metal component) in the lead single portion 75.
As described above, the content ratio of Au with respect to the metal component (noble metal component) in the remaining portion 77 is usually lower than the content ratio of Au in the electrode single portion 73.

Next, the effect of this embodiment is demonstrated.
In the ammonia sensor portion 21 of the present embodiment, the connection portion 71 remains between a portion functioning as an electrode (a thickness of the electrode single portion 73) and a portion functioning as a lead (a thickness of the lead single portion 75). A portion 77 is provided. Therefore, since the site where Au moves can be retained at the remaining portion 77, the outflow of Au from the portion functioning as an electrode can be suppressed. As a result, disconnection at the connecting portion 71 is suppressed.

<Fourth embodiment>
The fourth embodiment differs from the third embodiment in the connection structure between the ammonia electrode 21c and the ammonia electrode lead 21d. This point will be described with reference to FIG. Since other configurations are the same as those of the third embodiment, description thereof is omitted.
As shown in FIG. 11, in this connection structure, the electrode electrode part 83 where the ammonia electrode 21c and the ammonia electrode lead 21d do not overlap, the connection part 81 where the ammonia electrode 21c and the ammonia electrode lead 21d overlap, and the ammonia electrode 21c There is a single lead portion 85 that does not overlap the ammonia electrode lead 21d. The ammonia electrode 21c and the ammonia electrode lead 21d are directly connected.
The connecting portion 81 is formed on the ammonia electrode lead 21d so as to cover the ammonia electrode 21c.

The specific gravity of the first metal which is the main metal component (noble metal component) of the electrode single part 83 is set lower than the specific gravity of the second metal which is the main metal component (noble metal component) of the lead single part 85. In the present embodiment, the first metal is Au, and the second metal is Pt.
As shown in FIG. 11, the thickness (T6) of the connecting portion 81 is thicker than the thickness (T4 + T5) obtained by adding the thickness (T4) of the electrode single portion 83 and the thickness (T5) of the lead single portion 85. Has been.
In addition, as shown in FIG. 11, when the cross section of the connection portion 81 is observed, the surface side of the connection portion 81 is excluded by the thickness (T4) of the electrode single portion 83, and the back surface side of the connection portion 81 is the lead alone. Excluding only the thickness (T5) of the portion 85, there is a remaining portion 87 (corresponding to the joint portion and component region of the present invention, which is a cross-hatched portion in FIG. 11).
The Au content ratio relative to the metal component (noble metal component) contained in the remaining portion 87 is larger than the Au content ratio relative to the metal component (noble metal component) in the lead single portion 85.
“When the cross section of the connecting portion 81 is observed” is synonymous with “when the ammonia sensor portion 21 is cut along the axial direction with the ammonia electrode 21c and observed from the thickness direction”.

Although the thickness (T4) of the electrode single part 83 is not specifically limited, From a viewpoint of ensuring the detection precision of ammonia gas, 5 micrometers-40 micrometers are preferable, 10 micrometers-30 micrometers are more preferable, and 15 micrometers-25 micrometers are still more preferable.
The thickness (T5) of the lead single part 85 is not particularly limited, but is preferably 5 μm to 40 μm, more preferably 10 μm to 30 μm, from the viewpoint of ensuring high conductivity and the amount of expensive noble metal used. 15 micrometers-25 micrometers are still more preferable.
The thickness of the remaining portion 87 is not particularly limited, but is preferably 1 μm to 40 μm, more preferably 5 μm to 30 μm, and more preferably 10 μm to 20 μm from the viewpoint of effectively suppressing disconnection and the amount of expensive noble metal used. Is more preferable.

  A method for forming this connection structure will be described. When the Au-based paste for forming the ammonia electrode 21c is arranged by screen printing, the Au-based paste is applied thicker at the site to be the connection part 81 than at the site to be the electrode-only part 83. The Au-based paste applied thickly forms the remaining portion 87 described above. However, the remaining portion 87 has a smaller Au content ratio than the electrode single portion 83. This is because, during firing, Au moves from the Au-based paste that forms the remaining portion 87 to the Pt-based paste that forms the ammonia electrode lead 21d.

  The content ratio of Au with respect to the metal component (noble metal component) in the electrode single part 83, the lead single part 85, and the remaining part 87 is measured by elemental analysis using an electron beam microanalyzer (EPMA). As the content ratio of Au in each part, an average value of measured values obtained by measuring a plurality of parts in each part cross section is adopted.

The content ratio of Au to the metal component (noble metal component) in the electrode single part 83 is preferably 70% by weight or more, more preferably 80% by weight or more, and still more preferably 90% by weight or more. The upper limit of the content ratio of Au with respect to the metal component (noble metal component) in the electrode single part 83 may be 100% by weight.
Thus, the electrode single part 83 uses Au as the main metal component (noble metal component). Therefore, the capability as a current collector in the electrode single part 83 is ensured.
The electrode single part 83 may or may not contain the first metal oxide described above, but if it is not included, the combustion of ammonia gas in the electrode single part 83 Is suppressed, and the ammonia gas reaching the interface between the electrode single part 83 and the intermediate layer 21b is difficult to decrease. In other words, the detection accuracy of the ammonia sensor unit 21 is improved, and in particular, low concentration ammonia near 10 ppm can be detected with high accuracy.
The electrode single part 83 includes a porous material including a second metal oxide that is an oxide of one or more metals selected from the group consisting of Zr (zirconium), Y (yttrium), Al (aluminum), and Si (silicon). By forming it as an electrode, gas permeability can be imparted to the electrode single part 83. Therefore, ammonia gas can permeate through the electrode single part 83 and can easily reach the interface between the electrode single part 83 and the intermediate layer 21b. In addition, it is preferable that the electrode single part 83 contains the 2nd metal oxide in the ratio from 5 weight% to 30 weight%, when the electrode single part 83 whole is 100 weight%.

  The content ratio of Au to the metal component (noble metal component) in the lead single part 85 is lower than the content ratio of Au in the electrode single part 83. The content ratio of Pt with respect to the metal component (noble metal component) in the lead single part 85 is preferably 50% by weight or more, more preferably 70% by weight or more, and still more preferably 90% by weight or more.

Further, the content ratio of Au to the metal component (noble metal component) in the remaining portion 87 is larger than the content ratio of Au to the metal component (noble metal component) in the lead single portion 85.
As described above, the content ratio of Au with respect to the metal component (noble metal component) in the remaining portion 87 is lower than the content ratio of Au in the electrode single portion 83.

Next, the effect of this embodiment is demonstrated.
In the ammonia sensor portion 21 of the present embodiment, the connection portion 81 remains between a portion functioning as an electrode (for the thickness of the single electrode portion 83) and a portion functioning as a lead (for the thickness of the single lead portion 85). A portion 87 is provided. Therefore, since the site where Au moves can be retained in the remaining portion 87, the outflow of Au from the portion functioning as an electrode can be suppressed. As a result, disconnection at the connecting portion 81 is suppressed.

The present invention will be described more specifically with reference to examples.
1. Preparation of Sample An electrode having the same configuration as that shown in FIG. 4 of the first embodiment was prepared.
The paste for the Pt-based electrode contains Pt, Au, ethyl cellulose, butyl carbitol, and zirconia. The composition of the paste for the Pt-based electrode was prepared so that the Pt / Au ratio was the following value after firing.
Pt / Au ratio = 14/86 (mass%)
The paste for Pd-based electrodes contains Pd, Au, ethyl cellulose, butyl carbitol, and zirconia. The composition of the paste for the Pd-based electrode was prepared so that the Pd / Au ratio would be the following value after firing.
Pd / Au ratio = 7/93 (mass%)
The lead paste contains Pt, ethyl cellulose, butyl carbitol, and zirconia. The composition of the lead paste was prepared so that Pt had the following value after firing.
Lead: Pt100 mass%

The paste for the joint portion contains Pt, Au, ethyl cellulose, butyl carbitol, and zirconia. The paste for the joint portion was prepared so that the Pt / Au ratio was the following value after firing.
(1) Pt / Au ratio = 70/30 (mass%)
(2) Pt / Au ratio = 43/57 (mass%)
(3) Pt / Au ratio = 30/70 (mass%)

A lead paste was placed on the alumina substrate by screen printing. Then, the paste for the joint portion was disposed by screen printing so as to overlap the end portion of the lead paste. Next, the electrode paste was placed by screen printing so as to overlap the joint paste, and fired at a predetermined temperature (1100 ° C.).
In this way, a total of six types of samples including two types of electrodes and three types of joints were prepared as examples.
For comparison, a sample in which the electrode and the lead were in direct contact without using a joint portion was prepared as a comparative example. In the comparative example, an electrode was formed using the above-described Pt-based electrode paste, and a lead was formed using the above-described lead paste. A lead paste was placed on the alumina substrate by screen printing. Then, the Pt-based electrode paste was placed by screen printing so as to overlap the end portion of the lead paste, and fired at a predetermined temperature (1100 ° C.).

2. Evaluation In the comparative example, the color of the portion of the electrode where the lead was in direct contact was observed. This color was used as a reference color. In the comparative example, since Au of the electrode moved to the lead, the zirconia white color was conspicuous in the portion of the electrode where the lead was in direct contact, and the reference color was a white color.
In the example, the color of the portion of the electrode where the joint portion is in contact was observed. This color was compared with the reference color. In the example, if the movement of the electrode to the Au lead is less than that of the comparative example, the white color of zirconia becomes inconspicuous and a darker color than the reference color is observed. Therefore, the case where a darker color than the reference color was observed was judged as good (◯). On the other hand, in the example, when the movement of the electrode to the Au lead is equal to or more than that of the comparative example, the white color of zirconia becomes more conspicuous, and the color that is equal to or brighter than the reference color is obtained. Observed. Therefore, a case where a color equivalent to the reference color or brighter than the reference color is observed is defined as defective (x).
<Evaluation>
○: Darker than the reference color.
X: A color equivalent to or brighter than the reference color.

3. Results The results are shown in Table 1.
In each of the examples using the joint portion, the presence of the joint portion makes the steep concentration gradient of the metal element gentle, and the Au of the electrode is suppressed from flowing into the lead. Therefore, the zirconia of the electrode is conspicuous. It was difficult. Therefore, a darker color than the reference color was observed.

<Other Embodiment (Modification)>
In addition, this invention is not restricted to said Example and embodiment, In the range which does not deviate from the summary, it is possible to implement in various aspects.

(1) In the above embodiment, the case where the specific gas is ammonia has been described as an example, but the specific gas is not limited to ammonia.
(2) In the above embodiment, when the first metal is Au and the second metal is Pt, the case where the first metal is Pt and the second metal is Pd has been described as an example. However, the first metal and the second metal are described. Any combination having different specific gravities may be used, and the present invention is not limited to the above embodiments.
Examples of the metal species adopted for the electrode, the heat generating portion, and the lead include Au, Pt, etc. for the electrode, Pt, Pd, W, etc. for the heat generating portion, and Pd, Pt, etc. for the lead. Used. In this case, a combination in which the first metal is Au and the second metal is Pd, and a combination in which the first metal is Rh and the second metal is Pt are preferably exemplified.
(3) In the above embodiment, the ceramic heater that heats the bottomed cylindrical oxygen detection element as illustrated in FIG. 5 has been described as an example of the heater, but the form of the heater is not limited to this, for example, The present invention can also be applied to the heater 19 disclosed in the first embodiment.
(4) In the second embodiment, the configuration in which the heat generating portion 442 and the lead portion 443 are indirectly connected via the joint portion 450 is exemplified. However, the ammonia electrode 21c and the ammonia electrode lead in the fourth embodiment are exemplified. The structure may be such that the heat generating portion 442 and the lead portion 443 are directly connected as in the connection structure with 21d (see FIG. 11). Specifically, a configuration in which the heat generating portion 442 covers the lead portion 443 may be employed. In this connection structure, the heat generating unit alone part (not shown) where the heat generating part 442 and the lead part 443 do not overlap, the connection part (not shown) where the heat generating part 442 and the lead part 443 overlap, the heat generating part 442 and the lead part. There is a single lead portion (not shown) that does not overlap with 443. The connection portion is a region where the heat generating portion 442 and the lead portion 443 overlap in the thickness direction. When observing the cross section of the connection part, the surface side of the connection part is excluded by the thickness of the heating part single part, and the back side of the connection part is excluded by the thickness of the lead single part, which is the remaining part Part (corresponding to the heater joint of the present invention, the component region) exists.
The Au content ratio in the remaining portion is between the Au content ratio in the single heat generating portion and the Au content ratio in the single lead portion. That is, the content ratio of Au with respect to the metal component (noble metal component) contained in the remaining part is lower than the content ratio of Au with respect to the metal component (noble metal component) in the heating part single part, and the metal component (noble metal component) in the lead single part ) With respect to the Au content.
Moreover, the structure which the lead | read | reed part 443 covers on the heat generating part 442 may be sufficient like the connection structure (refer FIG. 10) of the ammonia electrode 21c and the ammonia electrode lead 21d of 3rd Embodiment. Even in this connection structure, the surface portion of the connection portion is excluded by the thickness of the lead single portion, and the back surface side of the connection portion is excluded by the thickness of the heat generation portion single portion. Corresponding to the heater joint and component region).

1 ... Multi gas sensor device 2 ... Multi gas sensor (gas sensor)
21 ... Ammonia sensor (gas sensor element)
21a: reference electrode (second electrode)
21c Ammonia electrode (electrode)
21d: Ammonia electrode lead (lead)
23 ... Solid electrolyte body for ammonia (solid electrolyte body)
70 ... Joint part (component region)
71 ... Connection part 73 ... Electrode single part 75 ... Lead single part 77 ... Remaining part (remaining part, joint part, component region)
81 ... Connection part 83 ... Electrode single part 85 ... Lead single part 87 ... Remaining part (remaining part, joint part, component region)
300 ... Ceramic heater (heater)
402 ... Ceramic substrate 442 ... Heat generating part 443 ... Lead part (heater lead)
450 ... Heater joint (component region)

Claims (12)

An electrode mainly composed of a first metal;
A lead connected to the electrode and comprising a second metal as a main component,
The electrode and the lead are gas sensor elements connected directly or indirectly through a joint portion,
In the case where the electrode and the lead are directly connected, the bonding portion between the electrode and the lead is the bonding of the metal having a smaller specific gravity of the first metal and the second metal. There is a component region that is a content ratio between the content ratio in the electrode excluding the part and the content ratio in the lead excluding the joint,
In the case where the electrode and the lead are indirectly connected through the joint portion, the electrode has the smaller specific gravity of the first metal and the second metal in the joint portion. A gas sensor element characterized in that a component region having a content ratio between the content ratio in the lead and the content ratio in the lead exists. The electrode and the lead are indirectly connected via the joint portion;
The component region is a content ratio of a size between a content ratio in the electrode and a content ratio in the lead with respect to a metal having a larger specific gravity of the first metal and the second metal. The gas sensor element according to claim 1. A second electrode different from the electrode;
A solid electrolyte body disposed between the electrode and the second electrode,
3. The gas sensor element according to claim 2, wherein the second electrode is composed of the second metal as a main component and is of a mixed potential type.   The gas sensor element according to claim 2 or 3, wherein the metal element in the joint portion is substantially composed of the first metal and the second metal. The concentration of the first metal in the joint part is 30 to 70% by mass when the total amount of the first metal and the second metal in the joint part is 100% by mass,
The concentration of the second metal in the joint part is 30 to 70% by mass when the total amount of the first metal and the second metal in the joint part is 100% by mass. The gas sensor element of any one of 2-4. By covering the lead on the electrode, the electrode and the lead are directly connected,
An electrode single part where the electrode and the lead do not overlap, a connection part where the electrode and the lead overlap, and a lead single part where the electrode and the lead do not overlap,
The thickness of the connection part is thicker than the thickness of the electrode single part and the lead single part plus the thickness,
When observing the cross section of the connecting portion,
Exclude the surface side of the connection part by the thickness of the lead single part, and
2. The gas sensor element according to claim 1, wherein the back surface side of the connection portion is excluded by the thickness of the electrode single portion, and the remaining portion is the joint portion. The electrode is covered on the lead so that the electrode and the lead are directly connected to each other, and the electrode alone portion where the electrode and the lead do not overlap, and the connection portion where the electrode and the lead overlap And a lead single part where the electrode and the lead do not overlap,
The thickness of the connection part is thicker than the thickness of the electrode single part and the lead single part plus the thickness,
When observing the cross section of the connecting portion,
Exclude the surface side of the connection part by the thickness of the electrode single part, and exclude the back side of the connection part by the thickness of the lead single part, and the remaining part is the joint part The gas sensor element according to claim 1.   The gas sensor element according to claim 1, wherein a specific gravity of the first metal is lower than a specific gravity of the second metal.   The gas sensor element according to any one of claims 1 to 8, wherein the first metal is gold and the second metal is platinum.   The gas sensor element according to any one of claims 1 to 9, wherein the concentration of ammonia contained in the gas to be measured is measured. A heat generating part mainly composed of a first metal;
A heater lead connected to the heat generating part and mainly composed of a second metal;
The heater and the heater lead are connected directly or indirectly through a heater joint,
When the heat generating portion and the heater lead are directly connected, the heater junction between the heat generating portion and the heater lead is a metal having a smaller specific gravity of the first metal and the second metal. In addition, there is a component region that is a content ratio between the content ratio in the heat generating portion excluding the heater joint portion and the content ratio in the heater lead excluding the heater joint portion,
When the heat generating portion and the heater lead are indirectly connected via the heater joint portion, the heater joint portion has a metal having a smaller specific gravity of the first metal and the second metal. In the heater, there is a component region having a content ratio between the content ratio in the heat generating portion and the content ratio in the heater lead.   A gas sensor comprising the gas sensor element according to claim 1 or the heater according to claim 11.

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