JP6517686B2 - Gas sensor - Google Patents

Description

  The present invention relates to a gas sensor used to measure the gas concentration of a specific component contained in a measurement gas.

BACKGROUND ART In recent years, a urea SCR (selective catalytic reduction) system has attracted attention as a technology for purifying nitrogen oxides (NOx) contained in exhaust gas discharged from an internal combustion engine such as a diesel engine. The urea SCR system purifies nitrogen oxides contained in exhaust gas by chemically reacting ammonia (NH ₃ ) with nitrogen oxides (NOx) to reduce nitrogen oxides to nitrogen (N ₂ ). It is a system.

  In this urea SCR system, when the amount of ammonia supplied to the nitrogen oxides becomes excessive, there is a possibility that unreacted ammonia is released to the outside as it is contained in the exhaust gas. In order to suppress such emission of ammonia, a multi-gas sensor capable of measuring a plurality of types of gas concentrations including a sensor element for measuring the concentration of ammonia contained in exhaust gas is used in a urea SCR system (for example, Patent Document 1). In this urea SCR system, the amount of ammonia used for the reduction of nitrogen oxides is adjusted so that the concentration of ammonia measured by the multi-gas sensor, that is, the concentration of ammonia contained in the exhaust gas, falls within a predetermined range. .

JP, 2013-221931, A

Multi-gas sensor described in Patent Document 1 described above, as shown in FIG. 10, is provided with a NH ₃ detection cell 1200 to the surface of the NOx sensor 1100. The NH ₃ detection cell 1200 has a laminated structure in which a reference electrode 1220, a solid electrolyte body 1240 and a detection electrode 1260 are laminated in this order on the surface of the NOx sensor 1100, and an electromotive force between the reference electrode 1220 and the detection electrode 1260 Ammonia concentration in the gas to be measured is detected by the change.
Specifically, the gas to be measured reaches the three-phase interface between the gas-permeable electrode (reference electrode 1220 or detection electrode 1260) and the solid electrolyte body 1240 to cause an electrode reaction at the three-phase interface, and the electrode EMF changes. In this case, an exposed boundary portion S1 in which the interface between each of the electrodes 1220 and 1260 and the solid electrolyte body 1240 is exposed is formed over the entire circumference of the NH ₃ detection cell 1200. Arrive directly by the arrival paths 1220 Re and 1260 Re, respectively. Further, among the interfaces between the electrodes 1220 and 1260 of the NH ₃ detection cell 1200 and the solid electrolyte body 1240, an arrival path 1220 Ri passing through the electrodes 1220 and 1260 also to the (inside) internal boundary S2 not exposed to the outside. , And 1260 Ri reach the gas to be measured. Then, if the measurement gas atmosphere is constant, the measurement gas is appropriately supplied to the electrodes 1220 and 1260 via the arrival paths 1220 Re, 1260 Re, 1220 Ri, and 1260 Ri, and the ammonia concentration in the measurement gas is accurately determined. It can be detected well.

  By the way, normally, since the reference electrode 1220 and the detection electrode 1260 are formed by printing with paste etc. on the surface of the solid electrolyte body 1240, an allowance is provided inside the solid electrolyte body 1240 in consideration of printing deviation and each electrode Form. For this reason, as shown in FIG. 10, the exposed boundary portion S1 on the side of the reference electrode 1220 located on the lower layer side is covered with the solid electrolyte body 1240. Therefore, when the atmosphere of the gas to be measured changes rapidly, the gas substitution of the gas to be measured is not sufficiently performed in the lower layer side reference electrode 1220, and there is a problem that the responsiveness decreases. That is, as shown in FIG. 10, when the atmosphere of the gas to be measured changes rapidly, the supply of the gas to be measured to the inner boundary S2 of the electrodes 1220 and 1260 is not in time, and the exposed boundary exposed to the outside The section S1 is a site where the main electrode reaction is started. However, as described above, the exposed boundary portion S1 on the side of the reference electrode 1220 is covered with the solid electrolyte body 1240, so that the gas to be measured does not easily reach, and the responsiveness decreases.

  Here, if the end faces of the reference electrode 1220, the solid electrolyte body 1240, and the detection electrode 1260 can be flush with each other, the gas to be measured can easily reach the exposed boundary portion S1 on the reference electrode 1220 side, and the responsiveness decreases. Can be prevented. However, as described above, when the reference electrode 1220 and the detection electrode 1260 are formed, printing deviation occurs, so each electrode has to be formed with a margin inside the solid electrolyte body 1240 and each component of the cell 1200 It is practically difficult to make the end faces of the face flush.

  The present invention has been made to solve the above-mentioned problems, and provides a gas sensor having a cell of a laminated structure, in which the response when the atmosphere of the gas to be measured changes rapidly is improved. With the goal.

In order to solve the above problems, a gas sensor of the present invention has a base substrate, and a cell in which a reference electrode, a solid electrolyte body and a detection electrode are laminated in this order on the surface of the base substrate. The sensing electrode is a gas sensor exposed to the gas to be measured, and when viewed from the sensing electrode side along the stacking direction of the cells, the reference electrode is from at least a part of the edge of the solid electrolyte body The base substrate has a plate shape extending in the longitudinal direction, and a heater including a heat generating portion in a part of the base substrate. and, the protruding portion, said by the one edge and the other edge in the longitudinal direction of the detection electrode, Ru is arranged in the longitudinal direction, separated in a width direction perpendicular area.
According to this gas sensor, the reference electrode has a protrusion which protrudes from at least a part of the edge of the solid electrolyte body. Thus, an exposed boundary where the interface between the reference electrode and the solid electrolyte body is exposed to the outside can be formed at the edge of the solid electrolyte body without being covered by the solid electrolyte body. Here, when the atmosphere of the gas to be measured changes rapidly, this exposed boundary portion becomes a portion where the main electrode reaction starts.
Therefore, since the exposed boundary of the reference electrode is exposed directly to the outside and the measured gas easily reaches, even when the atmosphere of the measured gas changes rapidly, the exposed boundary of the reference electrode on the lower layer side is also obtained. The gas replacement of the measurement gas is sufficient, and the response can be improved.
Moreover, since the projection of the reference electrode protrudes from the solid electrolyte body, there is no need to make the end face of the solid electrolyte body and the end face of the reference electrode flush with each other, and printing deviation when forming the reference electrode by printing Can reduce the influence of
Further, according to this gas sensor, since the base substrate includes the heater including the heat generating portion in a part of the base substrate, the temperature gradient in the longitudinal direction due to the heat generation of the heater is generated in the base substrate. On the other hand, in the cell arranged on such a base substrate, by arranging the projecting part of the reference electrode in the above-mentioned area, the detection boundary of the detection electrode and the reference electrode is substantially the same in the longitudinal direction. It can be arranged, and the decrease in cell detection accuracy due to the temperature gradient can be suppressed.
The projecting portion of the reference electrode may be partially or entirely disposed in the region.

The projecting portion of the reference electrode may project radially from a part of the edge of the solid electrolyte body or may project radially from the entire edge of the solid electrolyte body .
Furthermore, the detection electrode may be formed only on the solid electrolyte body as long as the detection electrode is disposed so that the edge of the solid electrolyte body from which the projection of the reference electrode protrudes is not covered by the detection electrode. The projection of the reference electrode may be provided so as to project radially beyond the solid electrolyte body while avoiding the edge of the solid electrolyte body from which the projection protrudes.

The gas sensor of the present invention has a base substrate, and a cell in which a reference electrode, a solid electrolyte body and a detection electrode are laminated in this order on the surface of the base substrate, and the reference electrode and the detection electrode are respectively covered It is a gas sensor exposed to a measurement gas, and when viewed from the detection electrode side along the stacking direction of the cells, the reference electrode is from at least a part of the edge of the solid electrolyte body in the stacking direction The base substrate is in the form of a plate extending in the longitudinal direction, and the protrusion has a width direction perpendicular to the longitudinal direction in the solid electrolyte body. respectively protrude from both ends of.
According to this gas sensor, the reference electrode has a protrusion which protrudes from at least a part of the edge of the solid electrolyte body. Thus, an exposed boundary where the interface between the reference electrode and the solid electrolyte body is exposed to the outside can be formed at the edge of the solid electrolyte body without being covered by the solid electrolyte body. Here, when the atmosphere of the gas to be measured changes rapidly, this exposed boundary portion becomes a portion where the main electrode reaction starts.
Therefore, since the exposed boundary of the reference electrode is exposed directly to the outside and the measured gas easily reaches, even when the atmosphere of the measured gas changes rapidly, the exposed boundary of the reference electrode on the lower layer side is also obtained. The gas replacement of the measurement gas is sufficient, and the response can be improved.
Moreover, since the projection of the reference electrode protrudes from the solid electrolyte body, there is no need to make the end face of the solid electrolyte body and the end face of the reference electrode flush with each other, and printing deviation when forming the reference electrode by printing Can reduce the influence of
Furthermore, according to this gas sensor, the exposure boundary can be formed at at least two different positions, and a rapid change in the atmosphere of the gas to be measured can be obtained at the two or more exposure boundaries. The response can be further improved.

The gas sensor of the present invention has a base substrate, and a cell in which a reference electrode, a solid electrolyte body and a detection electrode are laminated in this order on the surface of the base substrate, and the reference electrode and the detection electrode are respectively covered It is a gas sensor exposed to a measurement gas, and when viewed from the detection electrode side along the stacking direction of the cells, the reference electrode is from at least a part of the edge of the solid electrolyte body in the stacking direction The base substrate is in the form of a plate extending in the longitudinal direction, and the two cells extend in the width direction perpendicular to the longitudinal direction on the base substrate. The protrusions of each of the two cells protrude at least from the inner end in the width direction of the solid electrolyte body .
According to this gas sensor, the reference electrode has a protrusion which protrudes from at least a part of the edge of the solid electrolyte body. Thus, an exposed boundary where the interface between the reference electrode and the solid electrolyte body is exposed to the outside can be formed at the edge of the solid electrolyte body without being covered by the solid electrolyte body. Here, when the atmosphere of the gas to be measured changes rapidly, this exposed boundary portion becomes a portion where the main electrode reaction starts.
Therefore, since the exposed boundary of the reference electrode is exposed directly to the outside and the measured gas easily reaches, even when the atmosphere of the measured gas changes rapidly, the exposed boundary of the reference electrode on the lower layer side is also obtained. The gas replacement of the measurement gas is sufficient, and the response can be improved.
Moreover, since the projection of the reference electrode protrudes from the solid electrolyte body, there is no need to make the end face of the solid electrolyte body and the end face of the reference electrode flush with each other, and printing deviation when forming the reference electrode by printing Can reduce the influence of
Furthermore, according to this gas sensor, in the base substrate extending in the longitudinal direction, the end in the width direction is likely to cause a temperature change due to the influence of the external atmosphere. Therefore, when two cells are arranged side by side in the width direction on the base substrate, the protrusions are arranged at the end of the base substrate when the protrusions are protruded from the outer end of the solid electrolyte body of the cell in the width direction. And is susceptible to temperature changes of the base substrate. Therefore, by causing the protrusion to protrude from the end on the inner side in the width direction of the solid electrolyte body of the cell, it becomes difficult to be affected by the temperature change of the base substrate, and it is possible to suppress the deterioration and variation of the detection accuracy of the two cells. .

In the gas sensor of the present invention, the detection electrode may be provided only on the solid electrolyte body.
According to this gas sensor, even in the detection electrode, the exposed boundary where the interface between the detection electrode and the solid electrolyte body is exposed can be formed over the entire circumference of the detection electrode, and the atmosphere of the gas to be measured changes rapidly Response can be further improved. Moreover, since the detection electrode can be disposed to avoid the edge of the solid electrolyte body from which the projection of the reference electrode protrudes, the projection of the reference electrode can be disposed at an appropriate position.
In the gas sensor of the present invention, the protrusions may protrude from both ends of the one end and the other end in the longitudinal direction of the solid electrolyte body.
According to this gas sensor, the exposed boundary where the interface between the reference electrode and the solid electrolyte body is exposed to the outside can be formed not only at both ends in the width direction of the edge of the solid electrolyte body but also at both ends in the longitudinal direction. . As a result, when the atmosphere of the gas to be measured changes rapidly, gas replacement of the gas to be measured becomes sufficient even at the exposed boundary portion of the reference electrode on the lower layer side, and the responsiveness can be further improved.
In the gas sensor of the present invention, the base substrate may be an NO _x sensor unit that detects the NO _x concentration in the gas to be measured, and the gas sensor may constitute a multi gas sensor.
According to this gas sensor, it is possible to realize a multi gas sensor capable of detecting the NO _x concentration as well as the specific component in the gas to be measured by the cell.

  According to the present invention, in the gas sensor having the cell of the laminated structure, it is possible to improve the responsiveness when the atmosphere of the gas to be measured changes rapidly.

It is a sectional view which meets an axial direction of a multi gas sensor concerning a 1st embodiment of the present invention. It is a block diagram which shows the structure of a multi gas sensor and a gas sensor control apparatus. It is sectional drawing which follows the width direction of a 1st ammonia sensor part and a 2nd ammonia sensor part. It is the top view seen along the lamination direction of the 1st ammonia sensor part and the 2nd ammonia sensor part. It is sectional drawing in alignment with the axial direction of the multi gas sensor which concerns on the 2nd Embodiment of this invention. It is sectional drawing in alignment with the width direction of the 1st ammonia sensor part concerning the 2nd embodiment, and the 2nd ammonia sensor part. It is the top view seen along the lamination direction of the 1st ammonia sensor part and the 2nd ammonia sensor part concerning a 2nd embodiment. It is the top view seen along the lamination direction of the 1st ammonia sensor part and the 2nd ammonia sensor part concerning a 3rd embodiment. It is a figure which shows the time change of the ammonia sensor output of an actual 1st ammonia sensor part and a 2nd ammonia sensor part. Is a schematic diagram showing the arrival path of the measuring gas to the 3-phase interface of the cell of the conventional gas sensor (NH ₃ detection cell).

Hereinafter, a multi gas sensor according to a first embodiment of the present invention will be described with reference to FIGS. 1 to 4. 1 is a cross-sectional view of the multigas sensor along the direction of the axis O (longitudinal direction), FIG. 2 is a block diagram for explaining the configuration of the multigas sensor device, and FIG. 3 is a configuration of the first ammonia sensor unit FIG. 4 is a top view seen along the stacking direction of the first ammonia sensor unit and the second ammonia sensor unit.
The multi gas sensor 200A corresponds to the "gas sensor" in the claims, and the first ammonia sensor unit 42x and the second ammonia sensor 42y correspond to the "cells" in the claims. Further, the NO _x sensor unit 30A described later corresponds to the “base substrate” in the claims.
The multi gas sensor device 400 of this embodiment is used in a urea SCR system that purifies nitrogen oxides (NOx) contained in exhaust gas (measured gas) discharged from a diesel engine. More specifically, the concentrations of nitrogen monoxide (NO), nitrogen dioxide (NO ₂ ) and ammonia contained in the exhaust gas after reaction of NOx contained in the exhaust gas with ammonia (urea) are measured. It is a thing.
The engine to which the multi-gas sensor device 400 of this embodiment is applied may be the above-described diesel engine or may be applied to a gasoline engine, and the type of engine is not particularly limited.

  As shown in FIG. 1, the multi gas sensor 200A is an assembly in which a multi gas sensor element unit 100A for detecting the ammonia concentration and the NOx concentration is assembled. The multi-gas sensor 200A includes a plate-shaped multi-gas sensor element portion 100A extending in the axial direction, a cylindrical metal shell 138 having an outer surface formed with a screw portion 139 for fixing to an exhaust pipe, and the multi-gas sensor element portion 100A. An inner wall surface of a cylindrical ceramic sleeve 106 disposed so as to surround the radial direction of and a contact insertion hole 168 penetrating in the axial direction is disposed so as to surround the rear end portion of the multi gas sensor element portion 100A. An insulating contact member 166 and a plurality of (only two shown in FIG. 1) connection terminals 110 disposed between the multi gas sensor element portion 100A and the insulating contact portion 166 are provided.

  The metal shell 138 has a through hole 154 penetrating in the direction of the axis O, and is formed in a substantially cylindrical shape having a shelf 152 projecting inward in the radial direction of the through hole 154. Further, the metal shell 138 arranges the front end side of the multi gas sensor element portion 100A outside the front end side of the through hole 154, and arranges the electrode terminal portions 80A and 82A outside the rear end side of the through hole 154. The element portion 100A is held in the through hole 154. Furthermore, the shelf 152 is formed as an inward tapered surface having an inclination with respect to a plane perpendicular to the axial direction.

  In the through hole 154 of the metal shell 138, the ceramic holder 151 and powder filled layers 153 and 156 (hereinafter, also referred to as talc rings 153 and 156) in an annular shape surrounding the periphery of the multi gas sensor element 100A in the radial direction. And the above-mentioned ceramic sleeve 106 are laminated in this order from the front end side to the rear end side. Further, a caulking packing 157 is disposed between the ceramic sleeve 106 and the rear end portion 140 of the metal shell 138, and a talc ring 153 is provided between the ceramic holder 151 and the shelf portion 152 of the metal shell 138. And a metal holder 158 for holding the ceramic holder 151. The rear end portion 140 of the metal shell 138 is crimped so as to press the ceramic sleeve 106 to the tip side via the crimp packing 157.

  On the other hand, a metal (for example, stainless steel or the like) double external protector 142 having a plurality of holes while covering the protruding portion of the multi gas sensor element portion 100A on the tip outer side (lower side in FIG. 1) of the metal shell 138. And the inner protector 143 are attached by welding or the like.

  An outer cylinder 144 is fixed to the outer periphery of the metal shell 138 on the rear end side. Further, a plurality of lead wires 146 electrically connected to the electrode terminal portions 80A and 82A of the multi gas sensor element portion 100A are provided at the opening on the rear end side (upper side in FIG. 1) of the outer cylinder 144 (FIG. In this case, the grommet 150 in which the lead wire insertion holes 161 through which only three are inserted is formed is disposed. Although the electrode terminals on the front and back surfaces of the multigas sensor element unit 100A are represented by reference numerals 80A and 82A respectively in FIG. 1 for simplification, in actuality, the NOx sensor unit 30A to be described later, the first and the first Several electrode terminal parts are formed according to the number of electrodes etc. which the 2nd ammonia sensor parts 42x and 42y have.

  In addition, an insulating contact member 166 is disposed on the rear end side (upper side in FIG. 1) of the multi gas sensor element portion 100A which protrudes from the rear end portion 140 of the metal shell 138. The insulating contact member 166 is disposed around the electrode terminal portions 80A and 82A formed on the front and back surfaces of the rear end side of the multi gas sensor element portion 100A. The insulating contact member 166 is formed in a cylindrical shape having a contact insertion hole 168 penetrating in the axial direction, and is provided with a flange portion 167 projecting radially outward from the outer surface. The insulating contact member 166 is disposed inside the outer cylinder 144 by the flange portion 167 contacting the outer cylinder 144 via the holding member 169. The connection terminal 110 on the insulating contact member 166 side and the electrode terminal portions 80A and 82A of the multi gas sensor element portion 100A are electrically connected to each other and electrically conducted to the outside through the lead wire 146.

FIG. 2 is a block diagram showing the configuration of a multi gas sensor device 400 according to an embodiment of the present invention. In FIG. 2, for convenience of explanation, only a cross section along the direction of the axis O of the multi gas sensor element unit 100A housed in the multi gas sensor 200A is displayed.
The multi gas sensor device 400 includes a control device (controller) 300 and a multi gas sensor 200A (multi gas sensor element unit 100A) connected thereto. Control device 300 is mounted on a vehicle including an internal combustion engine (engine) (not shown), and control device 300 is electrically connected to ECU 220. The end of the lead wire 146 extending from the multi gas sensor 200A is connected to a connector, and this connector is electrically connected to the connector on the control device 300 side.

Next, the configuration of the multi gas sensor element unit 100A will be described. Multi-gas sensor element section 100A is provided with a NO _x sensor unit 30A having a structure similar to that of the known of the NO _x sensor, and two first ammonia sensor portion 42x ammonia sensor unit and the second ammonia sensor unit 42y, detail the first ammonia sensor portion 42x and the second ammonia sensor section 42y, as will be described later is formed on the outer surface of the NO _x sensor unit 30A.

First, the NO _x sensor unit 30A includes the insulating layer 23e, the first solid electrolyte body 2a, the insulating layer 23d, the third solid electrolyte body 6a, the insulating layer 23c, the second solid electrolyte body 4a, and the insulating layers 23b and 23a. It has a stacked structure in order. A first measurement chamber S1 is defined between the first solid electrolyte body 2a and the third solid electrolyte body 6a, and the first diffusion resistor 8a is disposed at the left end (inlet) of the first measurement chamber S1. Exhaust gas is introduced from the outside. A porous protective layer 9 is disposed on the outside of the first diffusion resistor 8a.
The second diffusion resistor 8b is disposed at the end of the first measurement chamber S1 opposite to the inlet, and communicates with the first measurement chamber S1 on the right side of the first measurement chamber S1 via the second diffusion resistor 8b. A second measurement chamber (corresponding to the "NO _x measurement chamber" of the present invention) S2 is defined. The second measurement chamber S2 penetrates the third solid electrolyte body 6a and is formed between the first solid electrolyte body 2a and the second solid electrolyte body 4a.

A long plate-like heating resistor 21 extending in the direction of the axis O of the multi gas sensor element unit 100A is embedded between the insulating layers 23b and 23a. The heat generating resistor 21 is provided with a heat generating portion on the tip end side in the direction of the axis O, and a pair of lead portions is provided from the heat generating portion toward the rear end side in the axial direction. The heat generating resistor 21 and the insulating layers 23 b and 23 a correspond to the “heater” in the claims. This heater is used to raise the temperature of the gas sensor to the activation temperature and to increase the oxygen ion conductivity of the solid electrolyte body to stabilize the operation.
The respective insulating layers 23a, 23b, 23c, 23d and 23e are mainly composed of alumina, and the first diffusion resistor 8a and the second diffusion resistor 8b are made of a porous material such as alumina. The heating resistor 21 is made of platinum or the like. Further, the heat generating portion of the heat generating resistor 21 is formed in, for example, a meander pattern, but is not limited thereto.

The first pumping cell 2 includes a first solid electrolyte body 2a mainly composed of zirconia having oxygen ion conductivity, an inner first pumping electrode 2b disposed to sandwich the first solid electrolyte body 2a, and an outer first pumping electrode serving as a counter electrode. 2c, and the inner first pumping electrode 2b faces the first measurement chamber S1. Each of the inner first pumping electrode 2 b and the outer first pumping electrode 2 c is mainly composed of platinum, and the surface of the inner first pumping electrode 2 b is covered with a protective layer 11 made of a porous material.
In addition, the insulating layer 23e corresponding to the upper surface of the outer first pumping electrode 2c is hollowed out and filled with the porous body 13, and the outer first pumping electrode 2c is communicated with the outside to allow gas (oxygen) to flow in and out. There is.

The oxygen concentration detection cell 6 includes a third solid electrolyte body 6a mainly composed of zirconia, and a detection electrode 6b and a reference electrode 6c arranged to sandwich the third solid electrolyte body 6a. The detection electrode 6b is an inner first pumping electrode 2b. It faces the first measurement chamber S1 further downstream. Each of the detection electrode 6b and the reference electrode 6c is mainly composed of platinum.
The insulating layer 23c is cut out so that the reference electrode 6c in contact with the third solid electrolyte body 6a is disposed inside, and the cut out portion is filled with a porous body to form the reference oxygen chamber 15 . Then, by supplying a weak constant current to the oxygen concentration detection cell 6 in advance using the Icp supply circuit 54, oxygen is sent from the first measurement chamber S1 into the reference oxygen chamber 15, which is used as the oxygen reference.

The second pumping cell 4 includes a second solid electrolyte body 4a mainly composed of zirconia, an inner second pumping electrode 4b disposed on the surface of the second solid electrolyte body 4a facing the second measurement chamber S2, and a counter electrode. And a second pumping counter electrode 4c. The inner second pumping electrode 4b and the second pumping counter electrode 4c are both mainly composed of platinum.
The second pumping counter electrode 4c is disposed in the cutout portion of the insulating layer 23c on the second solid electrolyte body 4a, and faces the reference oxygen chamber 15 so as to face the reference electrode 6c.
The inner first pumping electrode 2b, the sensing electrode 6b, and the inner second pumping electrode 4b are connected to reference potentials, respectively.

Next, the first ammonia sensor unit 42x and the second ammonia sensor unit 42y, which are two ammonia sensor units (cells), will be described.
As shown in FIG. 3, the multi gas sensor element unit 100A includes a first ammonia sensor unit 42x and a second ammonia sensor unit 42y which are separated in the width direction.

The first ammonia sensor portion 42x and the second ammonia sensor portion 42y are formed on the insulating layer 23a which is the outer surface (lower surface) of the NO _x sensor portion 30A. More specifically, in the first ammonia sensor portion 42x, the first reference electrode 42ax is formed on the insulating layer 23a, and the first solid electrolyte body 42dx is formed on the surface of the first reference electrode 42ax. Furthermore, a first detection electrode 42bx is formed on the surface of the first solid electrolyte body 42dx. The ammonia concentration in the gas to be measured is detected by the change in electromotive force between the first reference electrode 42 ax and the first detection electrode 42 b x.
Similarly, in the second ammonia sensor portion 42y, the second reference electrode 42ay is formed on the insulating layer 23a, and the second solid electrolyte body 42dy is formed on the surface of the second reference electrode 42ay. Furthermore, a second detection electrode 42by is formed on the surface of the second solid electrolyte body 42dy.
Here, the first reference electrode 42ax and the second reference electrode 42ay each correspond to a "reference electrode" in the claims. The first solid electrolyte body 42dx and the second solid electrolyte body 42dy respectively correspond to the "solid electrolyte body" in the claims. The first detection electrode 42bx and the second detection electrode 42by respectively correspond to the "detection electrode" in the claims.

The first detection electrode 42bx and the second detection electrode 42by can be formed of a material containing Au as a main component (for example, 70% by mass or more) and containing Pt or Pd. The first reference electrode 42 ax and the second reference electrode 42 ay can be formed of Pt alone or a material containing Pt as a main component (for example, 70% by mass or more). The first detection electrode 42bx and the second detection electrode 42by are electrodes which are difficult for ammonia gas to burn on the electrode surface. Ammonia reacts with oxygen ions (electrode reaction) at the three-phase interface described below to detect the concentration of ammonia.
The first solid electrolyte body 42dx and the second solid electrolyte body 42dy are made of, for example, partially stabilized zirconia (YSZ).

As shown in FIG. 4, the first reference electrode 42 ax and the second reference electrode 42 ay form a long rectangle in the width direction (direction perpendicular to the longitudinal direction (the direction of the axis O) of the multi gas sensor element unit 100 A). On the other hand, the first solid electrolyte body 42 dx and the second solid electrolyte body 42 dy each have a substantially square shape shorter in the width direction than the first reference electrode 42 ax and the second reference electrode 42 ay. Then, the first reference electrode 42 ax and the second reference electrode 42 ay respectively project (extrude) from both ends in the width direction of the first solid electrolyte body 42 dx and the second solid electrolyte body 42 dy, and form two protruding portions 42 ap 1 and 42 a p 2 respectively. doing. In the direction of the axis O, the first solid electrolyte body 42dx and the second solid electrolyte body 42dy respectively project (extrude) beyond the first reference electrode 42ax and the second reference electrode 42ay.
The “radial direction” perpendicular to the stacking direction may be all directions in the direction perpendicular to the stacking direction, but in the present embodiment, the “radial direction” corresponds to the width direction.

In addition, the first detection electrode 42bx and the second detection electrode 42by form a rectangle smaller than the first solid electrolyte body 42dx and the second solid electrolyte body 42dy, respectively, and the first solid electrolyte body 42dx and the second solid electrolyte respectively It is disposed inside the end edge of the body 42dy.
Then, reference electrode leads 42aL1 and 42aL2 extend on the insulating layer 23a from the protruding portions 42ap1 and 42ap2 of the first reference electrode 42ax and the second reference electrode 42ay on the outer side in the width direction toward the rear end side. Similarly, from the center in the width direction of the first detection electrode 42bx and the second detection electrode 42by to the rear end side, the detection electrode leads 42bL1 and 42bL2 are formed on the insulating layer 23a (a part of each is a first solid electrolyte body 42dx And the second solid electrolyte body 42dy).

  Thus, the first reference electrode 42ax (or the second reference electrode 42ay) and the first solid electrolyte can be obtained by providing the projection 42ap1 (or the projection 42ap2) on the first reference electrode 42ax (or the second reference electrode 42ay). The first solid electrolyte is not covered with the first solid electrolyte body 42dx (or the second solid electrolyte body 42dy) at the exposed boundary S10 where the interface with the body 42dx (or the second solid electrolyte body 42dy) is exposed to the outside. It can be formed at the edge of the body 42dx (or the second solid electrolyte body 42dy).

  Accordingly, since the exposed boundary portion S10 is directly exposed to the outside and the measured gas easily reaches, when the atmosphere of the measured gas changes rapidly, the lower first reference electrode 42ax (or the second reference side) Also in the electrode 42ay), the gas replacement of the measurement gas is sufficient, and the response can be improved.

  Furthermore, the first detection electrode 42bx (or the second detection electrode 42by) is located inside the edge of the first solid electrolyte body 42dx (or the second solid electrolyte body 42dy). That is, the first detection electrode 42bx (or the second detection electrode 42by) is provided only on the first solid electrolyte body 42dx (or the second solid electrolyte body 42dy). Therefore, also in the first detection electrode 42bx (or the second detection electrode 42by), the interface between the first detection electrode 42bx (or the second detection electrode 42by) and the first solid electrolyte body 42dx (or the second solid electrolyte body 42dy) An exposed boundary S1 exposed to the outside can be formed over the entire circumference of the first detection electrode 42bx (or the second detection electrode 42by).

Also in the reference electrode of a general cell, a lead which is drawn from the reference electrode and electrically connected to an external circuit protrudes from the solid electrolyte body. However, in the present invention, the purpose is to form a projection on the reference electrode itself in order to expose the solid electrolyte body on the solid electrolyte body to expose the three-phase interface (the above-mentioned exposed boundary S10) that causes the electrode reaction to occur positively. The above leads are not included.
For this reason, the first reference electrode 42ax or the second reference electrode 42ay (hereinafter referred to as “electrode” as appropriate) and the reference electrode lead 42aL1 or the reference electrode lead 42aL2 (hereinafter referred to as “lead”) Differentiate by sex. For example, a portion narrower than the narrowest portion of the width of the electrode overlapping the solid electrolyte body can be used as a lead. Also, by adding the material of the solid electrolyte body (composition) to the electrode material for the purpose of improving adhesion with the solid electrolyte body, etc., a portion where the electric resistance is increased is regarded as an electrode, and the electric resistance is lower than this. The site can be considered as a lead. In addition, it is possible to regard a portion with low density (high porosity) as an electrode for transmitting the gas to be measured and a portion with higher density than this as a lead. The “width” of the lead means the width in the direction perpendicular to the path of the current flowing through the lead.
For example, in the case of FIG. 4, the width of the narrowest portion of the first reference electrode 42ax (or the second reference electrode 42ay) in the portion overlapping the first solid electrolyte body 42dx (or the second solid electrolyte body 42dy) is W1 (axis O Since the width is the direction), a portion narrower than W1 (a portion whose width in the width direction is W2) is used as the reference electrode lead 42aL1 (or reference electrode lead 42aL2).

In the present embodiment, the NO _x sensor portion 30A constituting the base substrate has a plate shape extending in the longitudinal direction (the direction of the axis O) and also has a heater. Then, the heater for (heat-generating resistor 21 specifically) is having a heat generating portion in a part of the axis O direction, the temperature gradient (distribution) NO _x sensor in the longitudinal direction (direction of the axis O) by heat generation of the heater It occurs in the part 30A.
Therefore, the projection 42ap1 (or the projection 42ap2) is disposed in the region R divided in the width direction by the front end 42bf and the rear end 42be of the first detection electrode 42bx (or the second detection electrode 42by). As a result, the first detection electrode 42bx (or the second detection electrode 42by) and the first reference electrode 42ax (or the second reference electrode 42ay) can be placed at substantially the same position in the longitudinal direction (axis O direction). It is possible to suppress a decrease in detection accuracy of the first ammonia sensor unit 42x and the second ammonia sensor unit 42y due to the temperature gradient of the _x sensor unit 30A.

  Further, in the present embodiment, the protrusions 42ap1 (or the protrusions 42ap2) protrude from both ends in the width direction of the first solid electrolyte body 42dx (or the second solid electrolyte body 42dy). Therefore, the exposure boundary S10 can be formed at at least two different positions, and a rapid change in the atmosphere of the gas to be measured can be obtained at the two or more exposure boundaries S10. It can be further improved.

Furthermore, the first ammonia sensor portion 42x and the second ammonia sensor portion 42y are integrally covered by a porous protective layer 23g.
The protective layer 23g prevents adhesion of the poisoning substance to the first detection electrode 42bx and the second detection electrode 42by, and at the same time, the gas to be measured flows from the outside into the first ammonia sensor portion 42x and the second ammonia sensor portion 42y. It adjusts the diffusion rate. As a material for forming the protective layer 23g, alumina (aluminum oxide), spinel (MgAl ₂ O _4), silica-alumina, and can be exemplified by at least one material selected from the group consisting of mullite. The diffusion rate of the gas to be measured by the protective layer 23g is adjusted by adjusting the thickness, particle size, particle size distribution, porosity, compounding ratio, and the like of the protective layer 23g.
The protective layer 23g may be provided as in the above-described embodiment, or the first ammonia sensor portion 42x and the second ammonia sensor portion 42y may be exposed without providing the protective layer 23g, which is particularly limited. It is not a thing. Moreover, when adjusting the sensitivity ratio of the 1st ammonia sensor part 42x and the 2nd ammonia sensor part 42y by 23 g of protective layers, you may provide a protective layer not with the above-mentioned embodiment, respectively.

Next, referring back to FIG. 2, an example of the configuration of the control device 300 will be described. The controller 300 includes an (analog) control circuit 59 and a microcomputer (microcomputer) 60 on a circuit board. The microcomputer 60 controls the entire control device 300, and includes a CPU (central processing unit) 61, a RAM 62, a ROM 63, a signal input / output unit 64, an A / D converter 65, and a clock (not shown). The program is executed by the CPU.
The control circuit 59 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 a first ammonia sensor. A first electromotive force detection circuit 58a and a second electromotive force detection circuit 58b that detect electromotive forces of the unit 42x and the second ammonia sensor unit 42y are provided.
The control circuit 59 controls the NO _x sensor unit 30A, NO _x sensor unit first pumping current flowing through 30A Ip1, and outputs to the microcomputer 60 detects the second pumping current Ip2.
The first electromotive force detection circuit 58 a and the second electromotive force detection circuit 58 b detect the ammonia concentration output (electromotive force) between the electrodes of the first ammonia sensor unit 42 x and the second ammonia sensor unit 42 y, and Output.

Specifically, the outer first pumping electrode 2c of the NO _x sensor unit 30A is connected to the Ip1 drive circuit 52, and the reference electrode 6c is connected in parallel to the Vs detection circuit 53 and the Icp supply circuit 54. The second pumping counter electrode 4c is connected in parallel to the Ip2 detection circuit 55 and the Vp2 application circuit 56. The heater circuit 57 is connected to a heater (specifically, the heating resistor 21).
The pair of electrodes 42ax and 42bx of the first ammonia sensor portion 42x are connected to the first electromotive force detection circuit 58a. Similarly, the pair of electrodes 42ay and 42by of the second ammonia sensor unit 42y are connected to the second electromotive force detection circuit 58b, respectively.

Each of the circuits 51 to 57 has the following function.
The Ip1 drive circuit 52 supplies a first pumping current Ip1 between the inner first pumping electrode 2b and the outer first pumping electrode 2c, and detects the first pumping current Ip1 at that time.
The Vs detection circuit 53 detects the voltage Vs between the detection electrode 6 b and the reference electrode 6 c and outputs the detection result to the reference voltage comparison circuit 51.
The reference voltage comparison circuit 51 compares a 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. Then, Ip1 drive circuit 52 controls the direction and magnitude of flow voltage Vs of equal manner Ip1 current to the reference voltage, the predetermined value of the degree to which the oxygen concentration in the first measurement chamber S1 is NO _x does not decompose Adjust to
The Icp supply circuit 54 supplies a weak current Icp between the detection electrode 6b and the reference electrode 6c to supply oxygen from the first measurement chamber S1 into the reference oxygen chamber 15, and a predetermined oxygen concentration based on the reference electrode 6c. Exposed to
The Vp2 application circuit 56 has a constant voltage Vp2 (for example, 450 mV) between the inner second pumping electrode 4b and the second pumping counter electrode 4c such that the NO _x gas in the gas to be measured is decomposed into oxygen and N ₂ gas. Is applied to decompose NO _x into nitrogen and oxygen.
Ip2 detection circuit 55, when the oxygen generated by the decomposition of the NO _x is pumped into the second pumping counter electrode 4c side from the second measurement chamber S2 through the second solid electrolyte body 4a, the second pumping cell 4 A flowing second pumping current Ip2 is detected.

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

Next, an example of control using the control circuit 59 will be described. First, when the engine is started and power is supplied from the external power supply, the heater operates through the heater circuit 57 to bring the first pumping cell 2, the oxygen concentration detection cell 6 and the second pumping cell 4 up to the activation temperature. Heat up. Further, the Icp supply circuit 54 supplies a weak current Icp between the detection electrode 6b and the reference electrode 6c to supply oxygen from the first measurement chamber S1 into the reference oxygen chamber 15, which is used as an oxygen reference.
Further, when the NO _x sensor section 30A is heated to a suitable temperature by a heater, NO _x first ammonia sensor unit on the sensor unit 30A 42x and the second ammonia sensor unit 42y is also heated to the desired temperature accordingly.

Then, when each cell is heated to the activation temperature, the first pumping cell 2 pumps oxygen in the measurement gas (exhaust gas) flowing into the first measurement chamber S1 from the inner first pumping electrode 2b to the outer first pumping Pump toward the electrode 2c.
At this time, the oxygen concentration in the first measurement chamber S1 corresponds to the inter-electrode voltage (inter-terminal voltage) Vs of the oxygen concentration detection cell 6, so that the inter-electrode voltage Vs becomes the reference voltage. controls the first pumping current Ip1 to Ip1 drive circuit 52 flows through the first pumping cell 2, the oxygen concentration in the first measurement chamber S1 is nO _x adjusted so as not to decompose.

The measurement gas whose oxygen concentration has been adjusted further flows toward the second measurement chamber S2. Then, the Vp2 application circuit 56 sets a constant voltage Vp2 (oxygen concentration detection) to the extent that the NO _x gas in the gas to be measured is decomposed into oxygen and N ₂ gas as the inter-electrode voltage (inter-terminal voltage) of the second pumping cell 4 A voltage higher than the value of the control voltage of the cell 6, for example 450 mV, is applied to decompose the NO _x into nitrogen and oxygen. Then, as the oxygen generated by the decomposition of the NO _x is pumped out from the second measurement chamber S2, the second pumping current Ip2 flows into the second pumping cell 4. At this time, since there is a linear relationship between the second pumping current Ip2 and the NO _x concentration, the Ip 2 detection circuit 55 detects the second pumping current Ip 2 to detect the NO _x concentration in the gas to be measured. Can.

  The first electromotive force detection circuit 58a detects the ammonia concentration output (electromotive force) between the pair of electrodes 42ax and 42bx, and the second electromotive force detection circuit 58b outputs the ammonia concentration between the pair of electrodes 42ay and 42by ( By detecting the electric power), it is possible to detect the ammonia concentration in the measurement gas as described later.

Next, a process of calculating various gas concentrations by the microcomputer 60 of the control device 300 will be described.
First, the reason for providing two ammonia sensor parts, the first ammonia sensor part 42x and the second ammonia sensor part 42y, is as follows. That is, since the ammonia sensor unit detects not only ammonia but also NO ₂ , if the gas to be detected contains NO ₂ gas other than ammonia, the detection accuracy of ammonia is lowered. Therefore, if two ammonia sensor units with different ratios of sensitivity to ammonia and sensitivity to NOx are provided, values from different sensitivities from two ammonia sensor units are calculated for two unknown concentrations of ammonia gas and NO ₂ gas. Since the detection is performed, the concentrations of ammonia gas and NO ₂ can be calculated. Here, the ratio of the sensitivity of the ammonia sensor to ammonia and the sensitivity to NOx refers to the ratio of the detection sensitivity of ammonia to the total sensitivity (ammonia and NO _x ) detected by the ammonia sensor. In the present embodiment, the ammonia sensor does not detect NO gas, so "ratio of sensitivity of ammonia sensor to ammonia to sensitivity of NOx" = "ratio of sensitivity of ammonia sensor to ammonia to sensitivity to NO ₂ It is judged as ". When the ammonia sensor does not detect NO ₂ gas, it is determined as the ratio of the sensitivity of the ammonia sensor to ammonia to the sensitivity of NOx = the ratio of the sensitivity of the ammonia sensor to ammonia to the sensitivity of NO. It is also good.
That is, the sensor output of the ammonia sensor unit is represented by F (x, y, D) with respect to x: ammonia concentration, y: NO ₂ gas concentration, D: O ₂ concentration, but the sensitivity ratio is different 2 If one NO ₂ sensor unit is used, two expressions of F ₁ (mx, ny, D) and F ₂ (sx, ty, D) (m, n, s, t are coefficients) are obtained. Since F ₁ , F ₂ and D are obtained from the sensor output, it is sufficient to solve two unknowns (x, y) from two equations. Specifically, it can be calculated by removing y from the above two equations and obtaining an equation of x as in the following equations (1) to (3).

Next, details of detection of NO ₂ and ammonia by the first ammonia sensor unit 42 x and the second ammonia sensor unit 42 y and calculation of the concentrations of NO ₂ and ammonia will be described.
An electromotive force is generated between the first reference electrode 42 ax of the first ammonia sensor unit 42 x and the first detection electrode 42 b x according to the concentration of ammonia contained in the measurement gas. The first electromotive force detection circuit 58a detects an electromotive force between the first reference electrode 42ax and the first detection electrode 42bx as a first ammonia electromotive force. Similarly, an electromotive force is generated between the second reference electrode 42ay of the second ammonia sensor unit 42y and the second detection electrode 42by according to the ammonia concentration. The second electromotive force detection circuit 58b detects an electromotive force between the second reference electrode 42ay and the second detection electrode 42by as a second ammonia electromotive force.

Here, the ROM 63 of the microcomputer 60 stores various data (relational expressions) described below. The CPU 61 reads the various data from the ROM 63 and performs various arithmetic processing from the value of the first pumping current Ip1, the value of the second pumping current Ip2, the first ammonia electromotive force and the second ammonia electromotive force.
Here, the ROM 63, "the first ammonia electromotive force - first ammonia concentration output relationship", "second ammonia electromotive force - the second ammonia concentration output relationship", "first pumping current Ip1-O ₂ concentration output Relational Expressions, "Second Pumping Current Ip2-NOx Concentration Output Relational Expression", "First Ammonia Concentration Output & Second Ammonia Concentration Output & O ₂ Concentration Output-Corrected Ammonia Concentration Output Relational Expression" (correction expression (1): see), "first ammonia concentration output and the second ammonia concentration output and O ₂ concentration output - correction NO ₂ concentration output relationship" (correction equation (2)), "NOx concentration output and correcting the ammonia concentration output and correction NO ₂ concentration An output-correction NOx concentration output relational expression (correction expression (3)) is stored.
The various data may be set as a predetermined relational expression as described above, or may be set as a table, for example, as long as it calculates various gas concentrations from the output of the sensor. In addition, it may be a value (a relational expression, a table, etc.) obtained in advance using a gas model whose gas concentration is known.

The “first ammonia electromotive force-first ammonia concentration output relational expression” and the “second ammonia electromotive force-second ammonia concentration output relational expression” are output from the first ammonia sensor unit 42 x and the second ammonia sensor unit 42 y It is a formula showing the relation between ammonia electromotive force and ammonia concentration output concerning ammonia concentration of to-be-measured gas.
The “first pumping current Ip1-O ₂ concentration output relational expression” is an expression representing the relationship between the first pumping current Ip 1 and the O ₂ concentration of the gas to be measured.
The "second pumping current Ip2-NOx concentration output relational expression" is an expression representing the relationship between the second pumping current Ip2 and the NOx concentration of the measured gas.
"The first ammonia concentration output and the second ammonia concentration output and O ₂ concentration output - correction ammonia concentration output relationship" is an oxygen concentration and NO ₂ concentration affected ammonia concentration output of the (first, second), oxygen It is a formula showing the relation of the correction ammonia concentration output which removed the influence of concentration and NO ₂ concentration.
"The first ammonia concentration output and the second ammonia concentration output and O ₂ concentration output - correction NO ₂ concentration output relationship" is a NO ₂ concentration output affected by the oxygen concentration and the ammonia concentration, the influence of the oxygen concentration and the ammonia concentration Is an expression representing the relationship between the corrected NO ₂ concentration output from which the
"NOx concentration output and correction ammonia concentration output and correction NO ₂ concentration output - correction NOx concentration output relationship" is, and the NOx concentration output affected by the ammonia concentration and NO ₂ concentration, the effect of the ammonia concentration and NO ₂ concentration It is an expression representing the relationship between the corrected and corrected NOx concentration output that has been removed and corrected.

Next, about the arithmetic processing which is executed in the CPU 61 of the microcomputer 60 to obtain the NOx concentration and the ammonia concentration from the first pumping current Ip1, the second pumping current Ip2, the first ammonia electromotive force EMF and the second ammonia electromotive force EMF explain.
CPU61, the first pumping current Ip1, the second pumping current Ip2, when the first ammonia electromotive force and the second ammonia electromotive force is inputted, O ₂ concentration output, NOx concentration output, first ammonia concentration output and a second ammonia An arithmetic process is performed to obtain a density output. Specifically, from the ROM 63, "first ammonia electromotive force-first ammonia concentration output relational expression", "second ammonia electromotive force-second ammonia concentration output relational expression", "first pumping current Ip1-O ₂ concentration output The relational expression and the "second pumping current Ip2-NOx concentration output relational expression" are called, and processing of calculating each concentration output is performed using the relational expression.
The "first ammonia electromotive force-first ammonia concentration output relational expression" and "second ammonia electromotive force-second ammonia concentration output relational expression" are used by the first ammonia sensor unit 42x and the second ammonia sensor unit 42y. In the entire range of EMF that can be output in the environment, the equation is set such that the ammonia concentration in the gas to be measured and the ammonia concentration converted output of the sensor have a substantially linear relationship. Converting with such a conversion formula enables calculation using changes in inclination and offset in a later correction formula.
When the O ₂ concentration output, the NOx concentration output, the first ammonia concentration output, and the second ammonia concentration output are obtained, the CPU performs the calculation using the correction formula described below to obtain the ammonia concentration of the gas to be measured and Determine the NOx concentration.

Correction formula (1): x = F (A, B, D)
= (eA-c) * (jB-h-fA + d) / (eA-c-iB + g) + fA-d
Correction formula (2): y = F '(A, B, D)
= (jB-h-fA + d) / (eA-c-iB + g)
Correction equation (3): z = C-ax + by
Here, x is the ammonia concentration, y is the NO ₂ concentration, and z is the NOx concentration. A is a first ammonia concentration output, B is a second ammonia concentration output, C is a NOx concentration output, and D is an O 2 concentration output. And F and F 'of Formula (1), (2) represent that x is a function of (A, B, D). Further, a, b are correction coefficients, c, d, e, f, g, h, i, j are coefficients calculated using the O ₂ density output D (coefficient determined by D).
Substitute the first ammonia concentration output (A), the second ammonia concentration output (B), the NOx concentration output (C) and the O ₂ concentration output (D) into the above-mentioned correction equations (1) to (3). The ammonia concentration and the NOx concentration of the gas to be measured are determined by computing.
The correction equations (1) and (2) are equations determined based on the characteristics of the first ammonia sensor unit 42x and the second ammonia sensor unit 42y, and the correction equation (3) is determined based on the characteristics of the NOx sensor unit It is a formula. The equations (1) to (3) are merely examples of correction equations, and other correction equations or coefficients may be appropriately changed according to the gas detection characteristics.

  As described above, by using the multi-gas sensor 200A according to the embodiment of the present invention, ammonia and NOx can be separated and accurately detected even in an environment where ammonia and NOx coexist and oxygen concentration changes. .

Next, a multi gas sensor (gas sensor) according to a second embodiment of the present invention will be described with reference to FIGS. The multi-gas sensor according to the second embodiment is the first except that the configuration and the arrangement position of the first ammonia sensor unit 42x1 and the second ammonia sensor unit 42y1 which are two ammonia sensor units (cells) are different. This embodiment is the same as the embodiment of the present invention, so the description of the configuration of the same part is omitted.
As shown in FIG. 5, the ammonia sensor portions 42x1 and 42y1 are provided on the surface of the insulating layer 23e which forms the outer surface (upper surface) of the NO _x sensor portion 30A.

More specifically, as shown in FIG. 6, in the first ammonia sensor portion 42x1, the first reference electrode 42ax1 is formed on the insulating layer 23e, and the first solid electrolyte body 42dx1 is formed on the surface of the first reference electrode 42ax1. ing. Furthermore, the first detection electrode 42bx1 is formed on the surface of the first solid electrolyte body 42dx1. The ammonia concentration in the gas to be measured is detected by the change in electromotive force between the first reference electrode 42ax1 and the first detection electrode 42bx1.
Similarly, in the second ammonia sensor portion 42y1, a second reference electrode 42ay1 is formed on the insulating layer 23e, and a second solid electrolyte body 42dy1 is formed on the surface of the second reference electrode 42ay1. Furthermore, a second detection electrode 42by1 is formed on the surface of the second solid electrolyte body 42dy1.

  As shown in FIG. 7, the first reference electrode 42 ax 1 and the second reference electrode 42 a y 1 form a substantially square. On the other hand, the first solid electrolyte body 42dx1 and the second solid electrolyte body 42dy1 are substantially in the form of a square smaller than the first reference electrode 42ax1 and the second reference electrode 42ay1, respectively. It is arranged inside 42ay1. For this reason, the first reference electrode 42ax1 and the second reference electrode 42ay1 respectively project (extrude) from the entire edge of the first solid electrolyte body 42dx1 and the second solid electrolyte body 42dy1, and the first solid electrolyte body 42dx1 and the second solid electrode 42ay1 respectively The protrusions 42ap5 and 42ap6 are formed to surround substantially the entire circumference of the two solid electrolyte body 42dy1. However, in the portions overlapping with the detection electrode leads 42bL3 and 42bL4, which will be described later, of the projecting portions 42ap5 and 42ap6, notches 42ar are formed to prevent short circuits, and the projecting portions 42ap5 and 42ap6 are on the rear end side The opening is formed in a substantially U-shape.

In addition, the first detection electrode 42bx1 and the second detection electrode 42by1 form a rectangle smaller than the first solid electrolyte body 42dx1 and the second solid electrolyte body 42dy1, respectively, and the first solid electrolyte body 42dx1 and the second solid electrolyte respectively It is disposed inside the end edge of the body 42 dy 1.
Then, after extending further outward in the width direction from the protrusion portions 42ap5 and 42ap6 of the width direction outer sides of the first reference electrode 42ax1 and the second reference electrode 42ay1, respectively, the reference electrode lead 42aL3, 42aL3 extend on the insulating layer 23e. Similarly, from the widthwise center of the first detection electrode 42bx1 and the second detection electrode 42by1 toward the rear end side on the insulating layer 23e (a part of the first solid electrolyte body 42dx1 and the second solid electrolyte body 42dy1 respectively) Up) sense electrode leads 42bL3, 42bL4 extend.

Thus, the first reference electrode 42ax1 (or the second reference electrode 42ay) is provided with the projection 42ap5 (or the projection 42ap6), whereby the first reference electrode 42ax1 (or the second reference electrode 42ay1) and the first solid electrolyte can be obtained. The first solid electrolyte is not covered with the first solid electrolyte body 42dx1 (or the second solid electrolyte body 42dy1) at the exposed boundary S10 where the interface with the body 42dx1 (or the second solid electrolyte body 42dy1) is exposed to the outside It can be formed at the edge of the body 42dx1 (or the second solid electrolyte body 42d1) (in FIG. 7, only one of the four exposure boundaries S10 is described).
On the other hand, the exposure boundary portion S1 is exposed at the edge of the first detection electrode 42bx1 (or the second detection electrode 42by1).

  Therefore, as in the first embodiment, the first reference electrode 42ax1 (or the second reference electrode 42ay1) is exposed directly to the outside to form an exposed boundary portion S10 to which the gas to be measured easily reaches, so Even if the atmosphere of the gas changes rapidly, the gas replacement of the measurement gas is sufficient and the response can be improved.

  In the case of FIG. 7, the width of the narrowest portion of the first reference electrode 42ax1 (or the second reference electrode 42ay1) in the portion overlapping with the first solid electrolyte body 42dx1 (or the second solid electrolyte body 42dy1) is W1 (axis O The width (direction width) and the width narrower than W1 (the width is W2 and W3) is used as a reference electrode lead 42aL3 (or reference electrode lead 42aL4). That is, the reference electrode lead 42aL3 (or the reference electrode lead 42aL4) is wider in the width direction than the outer edge in the width direction of the protrusion 42ap5 (42ap6) of the first reference electrode 42ax1 (or the second reference electrode 42ay1). A portion of width W3 which further extends, and a portion of width W2 which extends from this portion toward the rear end side and extends.

  Further, in the present embodiment, the protrusions 42ap5 (or the protrusions 42ap6) also protrude to both ends in the longitudinal direction (the direction of the axis O) of the first solid electrolyte body 42dx1 (or the second solid electrolyte body 42dy1). Therefore, the exposed boundary S10 can be formed not only at both ends in the width direction of the first solid electrolyte body 42dx1 (or the second solid electrolyte body 42dy1) but also at both ends in the longitudinal direction, and the atmosphere of the gas to be measured is rapid. In the case of the above-described exposed boundary portion of the reference electrode on the lower layer side, the gas replacement of the measurement gas is sufficient, and the response can be further improved.

  Next, a multi-gas sensor (gas sensor) according to a third embodiment of the present invention will be described with reference to FIG. The multigas sensor according to the third embodiment is the same as the first embodiment except that the configurations of the first ammonia sensor unit 42x2 and the second ammonia sensor unit 42y2 which are two ammonia sensor units (cells) are different. Since they are the same, the description of the configuration of the same part is omitted.

  More specifically, as shown in FIG. 8, in the first ammonia sensor portion 42x2, the first reference electrode 42ax2 is formed on the insulating layer 23a, and the first solid electrolyte body 42dx2 is formed on the surface of the first reference electrode 42ax2. ing. Furthermore, the first detection electrode 42bx2 is formed on the surface of the first solid electrolyte body 42dx2. The ammonia concentration in the gas to be measured is detected by the change in electromotive force between the first reference electrode 42ax2 and the first detection electrode 42bx2.

Similarly, in the second ammonia sensor portion 42y2, a second reference electrode 42ay2 is formed on the insulating layer 23a, and a second solid electrolyte body 42dy2 is formed on the surface of the second reference electrode 42ay2. Furthermore, a second detection electrode 42by2 is formed on the surface of the second solid electrolyte body 42dy2.
Furthermore, as shown in FIG. 8, the first reference electrode 42 ax 2 and the second reference electrode 42 a y 2 form a rectangle that is long in the width direction. On the other hand, the first solid electrolyte body 42dx2 and the second solid electrolyte body 42dy2 form a substantially square shorter in the width direction than the first reference electrode 42ax2 and the second reference electrode 42ay2, respectively. Then, the first reference electrode 42ax2 and the second reference electrode 42ay2 respectively project (extrude) from the end in the width direction of the first solid electrolyte body 42dx2 and the second solid electrolyte body 42dy2, and the two projecting portions 42ap7 and 42ap8 are respectively formed. It is formed. In the direction of the axis O, the first solid electrolyte body 42dx2 and the second solid electrolyte body 42dy2 respectively project (project) beyond the first reference electrode 42ax2 and the second reference electrode 42ay2.

In addition, the first detection electrode 42bx2 and the second detection electrode 42by2 form a rectangle smaller than the first solid electrolyte body 42dx2 and the second solid electrolyte body 42dy2, respectively, and the first solid electrolyte body 42dx2 and the second solid electrolyte respectively It is disposed inside the end edge of the body 42dy2.
Then, reference electrode leads 42aL5 and 42aL6 extend on the insulating layer 23a from the first reference electrode 42ax2 and the second reference electrode 42ay2 toward the rear end side, respectively. Similarly, detection electrode leads 42bL5 and 42bL6 extend on the insulating layer 23a from the center in the width direction of the first detection electrode 42bx2 and the second detection electrode 42by2 toward the rear end side. The reference electrode leads 42aL5 and 42aL6 and the detection electrode leads 42bL5 and 42bL6 extend in parallel.

  Thus, in the base substrate 30A extending in the longitudinal direction, the end portion in the width direction is likely to cause temperature change due to the influence of the external atmosphere. Therefore, when the first ammonia sensor portion 42x2 and the second ammonia sensor portion 42y2 are arranged side by side in the width direction on the insulating layer 23a, the projecting portion is the first ammonia sensor portion 42x2 (or the second ammonia sensor portion 42y2) When the first solid electrolyte body 42dx2 (or the second solid electrolyte body 42dy2) protrudes from the outer end in the width direction of the first solid electrolyte body 42dx2, the protrusion is disposed at the end of the base substrate 30A, and the influence of the temperature change of the base substrate It is easy to receive. Therefore, like the protruding portions 42ap7 and 42ap8, the protruding portion is located inside in the width direction of the first solid electrolyte body 42dx2 (or second solid electrolyte body 42dy2) of the first ammonia sensor portion 42x2 (or the second ammonia sensor portion 42y2). By projecting from the end toward the inside in the width direction, it becomes difficult to be affected by the temperature change of the base substrate 30A, and it is possible to suppress the decrease and the variation in the detection accuracy of the two cells.

It is needless to say that the present invention is not limited to the above embodiments, but extends to various modifications and equivalents included in the spirit and scope of the present invention.
For example, the shapes of the reference electrode, the protrusion, the detection electrode, and the solid electrolyte body are not limited to the above embodiment.
Moreover, in the said embodiment, although the protrusion part was formed in two or more places with respect to each reference electrode, one protrusion may be formed with respect to one reference electrode. Moreover, although two ammonia sensor parts (cells) were provided in the said embodiment, one ammonia sensor part (cell) may be sufficient.
Furthermore, in the above embodiment, although the multi-gas sensor in which the ammonia sensor portion is disposed on the NOx sensor portion is not limited to the NOx sensor portion, it is a gas sensor in which the ammonia sensor portion is disposed on the base substrate Also good.

Next, with reference to FIG. 9, the time change of the ammonia sensor output of the 1st ammonia sensor part and the 2nd ammonia sensor part by having provided the projection part in the standard electrode is explained.
As an example, a multi gas sensor 200A according to the first embodiment of the present invention shown in FIGS. 1 to 4 was prepared. As a comparative example, as shown in FIG. 10 in which the cross-sectional structures of the first ammonia sensor unit and the second ammonia sensor unit are shown (without providing a protrusion), the multi gas sensor 200A according to the first embodiment is used. A multi gas sensor of the same structure was prepared.
Then, each multi gas sensor is placed in the model gas flow, and the atmosphere of the model gas is changed rapidly at point P in FIG. 9 (ammonia is added rapidly at point P and oxygen concentration is decreased at point P) The time change of the ammonia sensor output of the 1st ammonia sensor part of each multi gas sensor and the 2nd ammonia sensor part was measured.

As a result, as shown in FIG. 9, in the case of the embodiment, the time from the point P until the ammonia sensor output reaches the steady value (100%) is short, and the response when the measurement gas atmosphere changes is excellent. I found that.
On the other hand, in the case of the comparative example, the time from the point P until the ammonia sensor output reaches the steady value is longer than in the example, and the response is inferior.

21, 23b, 23a Heater 30A Base substrate (NOx sensor section)
42ax, 42ay, 42ax1, 42ay1, 42ax2, 42ay2 Reference electrode 42bx, 42by, 42bx1, 42by1, 42bx2, 42by2 detection electrode 42dx, 42dy, 42dx1, 42dy1, 42dx2, 42dy2 solid electrolyte body 42x, 42y, 42x1, 42y1, 42x1 42y2 cell 42ap1 to 42ap8 protrusion 200A gas sensor (multi gas sensor)
O axis R area

Claims (6)

A base substrate,
A gas sensor comprising: a cell in which a reference electrode, a solid electrolyte body, and a detection electrode are laminated in this order on the surface of the base substrate, wherein the reference electrode and the detection electrode are exposed to a gas to be measured,
When viewed from the detection electrode side along the stacking direction of the cells, the reference electrode protrudes from at least a part of the edge of the solid electrolyte body in the radial direction perpendicular to the stacking direction Have a department ,
The base substrate has a plate shape extending in the longitudinal direction, and has a heater provided with a heat generating portion on a part of the base substrate.
Said projection, said by the one edge and the other edge in the longitudinal direction of the detection electrode, the longitudinal direction the width direction perpendicular to the delimited arranged Ru gas sensor in the region. A base substrate,
A gas sensor comprising: a cell in which a reference electrode, a solid electrolyte body, and a detection electrode are laminated in this order on the surface of the base substrate, wherein the reference electrode and the detection electrode are exposed to a gas to be measured,
When viewed from the detection electrode side along the stacking direction of the cells, the reference electrode protrudes from at least a part of the edge of the solid electrolyte body in the radial direction perpendicular to the stacking direction Have a department,
The base substrate is in the form of a longitudinally extending plate,
The said protrusion part is a gas sensor which each protrudes from the both ends of the width direction perpendicular | vertical to the said longitudinal direction among the said solid electrolyte bodies . A base substrate,
A gas sensor comprising: a cell in which a reference electrode, a solid electrolyte body, and a detection electrode are laminated in this order on the surface of the base substrate, wherein the reference electrode and the detection electrode are exposed to a gas to be measured,
When viewed from the detection electrode side along the stacking direction of the cells, the reference electrode protrudes from at least a part of the edge of the solid electrolyte body in the radial direction perpendicular to the stacking direction Have a department,
The base substrate is in the form of a plate extending in the longitudinal direction, and the two cells are arranged side by side in a width direction perpendicular to the longitudinal direction on the base substrate,
The gas sensor , wherein the projection of each of the two cells protrudes at least from the end in the width direction of the solid electrolyte body . The gas sensor according to any one of claims 1 to 3, wherein the detection electrode is provided only on the solid electrolyte body . 3. The gas sensor according to claim 2, wherein the protrusion protrudes from both ends of the one end edge and the other end edge in the longitudinal direction of the solid electrolyte body. The base substrate is NO _x sensor unit for detecting the concentration of NO _x in the measurement gas, the gas sensor according to any one of claims 1 to 5, wherein the gas sensor constitutes a multi-gas sensor.

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