JP2019144225A - Gas sensor element, gas sensor and method for manufacturing gas sensor element - Google Patents

Abstract

To provide a gas sensor element including an insulation protective layer having a porous part and capable of preventing damage from occurring even when used in a low temperature environment.SOLUTION: A gas sensor element for detecting a first component and a second component in a gas to be measured comprises an element body part, a first detector 101, second detectors 102 and 103 and an element protective part 124. When using the formation regions of the second detectors in a region in the axial direction as second detection regions and using the formation region of a porous part as a porous region, the element protective part is usually formed on a side surface 101C so as to cover at least the porous region and a region on the tip side from the porous region and is formed on a second detection side surface so as to cover at least a part of the regions on the tip side from the second detectors without covering the second detectors. Namely, the gas sensor element includes the element protective part formed so as to cover the porous part of the first detector without covering the second detectors.SELECTED DRAWING: Figure 5

Description

  The present disclosure relates to a gas sensor element, a gas sensor, and a method for manufacturing the gas sensor element.

A gas sensor including a gas sensor element that detects a specific gas contained in a measurement target gas is known.
For example, the gas sensor is provided in an exhaust pipe of an internal combustion engine such as an automobile and is used for detecting the concentration of a specific component (oxygen, NOx, etc.) in the exhaust gas of the internal combustion engine. Some gas sensor elements include a cell having a solid electrolyte body and an electrode, and an insulating protective layer laminated on the cell. Some insulating protective layers have a structure in which a porous portion for protecting a cell electrode is embedded in a part of the insulating protective layer.

  Such a gas sensor element is configured such that the porous portion covers the electrode of the cell. The porous portion protects the electrode by preventing foreign substances such as soot from coming into direct contact with the electrode while allowing gas to pass between the outside of the gas sensor element and the electrode.

Japanese Patent Laid-Open No. 2006-080684

  However, the gas sensor element described above causes the gas sensor element (particularly, the boundary between the insulating protective layer and the porous part) to be caused by a stress caused by a change in the volume of the water when the temperature falls below the freezing point in a state where the water is contained in the porous part. It may be damaged (such as cracks).

  That is, when the installation location of the gas sensor is an environment with a lot of moisture, moisture may be contained in the porous portion, and the volume of moisture may change due to a temperature drop, and the gas sensor element may be damaged. For example, an exhaust pipe of an internal combustion engine is likely to generate condensed water during a stop period of the internal combustion engine in a low temperature environment such as winter, and the condensed water reaches the gas sensor together with the exhaust gas when the internal combustion engine is started. Some parts may contain moisture.

  Accordingly, the present disclosure provides a gas sensor element including an insulating protective layer having a porous portion, which is not easily damaged even when used in a low temperature environment, and provides a gas sensor including such a gas sensor element. It is an object of the present invention to provide a method for manufacturing such a gas sensor element.

One aspect of the present disclosure is a gas sensor element that detects a first component and a second component in a gas to be measured, the element main body, a first detector, a second detector, an element protector, Is provided.
The element main body is formed in an elongated shape extending in the axial direction, and includes a front end surface formed at the front end in the axial direction, a rear end surface formed at the rear end in the axial direction, and a plurality extending from the front end surface to the rear end surface. And side surfaces. The first detection unit pumps or pumps the gas to be measured through the porous portion formed on at least one of the plurality of side surfaces, and detects the first component. A 2nd detection part is provided in the back end side rather than the front-end | tip of a porous part, and detects a 2nd component. The element protection part is configured to cover at least the porous part of the element body part.

The plurality of side surfaces include a second detection side surface on which the second detection unit is provided, and a normal side surface that is not the second detection side surface.
When the formation region of the second detection portion is the second detection region in the axial direction region and the formation region of the porous portion is the porous region, the element protection portion normally has the porous region and the porous region on the side surface. It is formed so as to cover at least the region on the tip side of the mass region, and on the second detection side, the second detection unit is not covered, and is formed so as to cover at least a part of the region on the tip side of the second detection unit. Has been.

  That is, this gas sensor element includes a porous portion and an element protection portion that covers the tip region more than the porous portion. Since the element protection part softens the thermal shock caused by the temperature drop and the temperature rise, the damage that occurs at the porous part or at the boundary of the porous part can be suppressed. The element protection part is formed so as to cover the porous part of the first detection part without covering the second detection part. As a result, the gas to be measured that tries to reach the second detection unit is not blocked by the element protection unit.

  Therefore, this gas sensor element can suppress the damage of the gas sensor element because the element protection part alleviates the thermal shock. Moreover, since the gas to be measured easily reaches the second detection unit, it is possible to suppress a decrease in detection accuracy in the second detection unit.

The porous portion is formed in the tip region of two regions obtained by equally dividing the element main body portion into two in the axial direction among a plurality of side surfaces.
Next, in the gas sensor element of the present disclosure, the element body may include a heater that heats the first detection unit and the second detection unit.

The heater includes a heat generating part. The heat generating part is disposed so as to overlap with at least one of the first detection part forming region and the second detection region in the axial direction.
The second detection unit includes a pair of detection electrodes. The pair of detection electrodes are arranged on the inner side of the arrangement area of the heat generating part in the width direction of the element main body part.

Compared with the case where the pair of detection electrodes configured in this manner is arranged in an area wider than the arrangement area of the heat generating part, the whole becomes easier to receive the heat of the heat generating part.
Therefore, this gas sensor element can suppress that the temperature distribution in a pair of electrodes arises, and can suppress that the detection accuracy of a 2nd detection part falls.

Next, in the gas sensor element of the present disclosure, the element protection part may include an inner protection part that contacts the element body part and an outer protection part that covers the inner protection part.
The inner protective part has a porous structure having a larger porosity than the outer protective part. The outer protective portion abuts on the element main body portion on the rear end side with respect to the inner protective portion.

  This gas sensor element has a structure in which the porosity of the inner protective layer is larger than the porosity of the outer protective portion, thereby suppressing the amount of gas movement between the porous portion and the inner protective layer from becoming too small. it can.

  Next, in the gas sensor element of the present disclosure, when a portion higher than the second detection unit in the height direction perpendicular to the second detection side surface is the specific protection unit, the second in the axial direction is used. The distance between the front end of the detection unit and the rear end of the specific protection unit may be 2.0 mm or more.

  In this way, by forming the element protection unit so that the tip of the second detection unit is separated from the rear end of the specific protection unit by a certain distance or more, the element protection unit in supplying the gas to be measured to the second detection unit is formed. The impact can be reduced. That is, this gas sensor element can suppress a reduction in the amount of gas to be measured supplied to the second detection unit as compared with the case where there is no element protection unit. Good gas detection.

  Next, in the gas sensor element of the present disclosure, a preliminary protection layer having a height lower than that of the second detection unit may be provided in a region between the second detection unit and the specific protection unit in the second detection side surface. Good. By providing such a preliminary protective layer, it is possible to suppress a reduction in the amount of gas to be measured supplied to the second detection unit while protecting the element body (second detection side surface).

  Note that the preliminary protective layer may be formed of the same material as that of the element protection portion, or may be formed of a material different from that of the element protection portion. Any material can be used for the preliminary protective layer as long as it can protect the element body from damage.

  Next, another aspect of the present disclosure is a gas sensor including a gas sensor element that detects a first component and a second component in a gas to be measured, and a housing that holds the gas sensor element. One of them is a gas sensor element.

Such a gas sensor, like the gas sensor element described above, makes it easier for the gas to be measured to reach the second detection unit, and therefore can suppress a decrease in detection accuracy at the second detection unit.
Next, another aspect of the present disclosure is a method of manufacturing a gas sensor element that detects a first component and a second component in a gas to be measured, and the gas sensor element includes an element main body portion, a first detection portion, At least a second detection unit and an element protection unit, and any one of the gas sensor elements described above, wherein the gas sensor element manufacturing method includes a first step, a second step, a third step, 4 steps.

  In the first step, a disappearing material that disappears by heating is applied so as to cover the second detection part in the element member including the element main body part, the first detection part, and the second detection part, or the element member is formed after firing. In the unfired element member, the disappearing material is applied so as to cover the pre-fired detection member that becomes the second detection portion after firing.

  In the second step, after the first step, the element protection unit and the element protection unit after firing so as to cover all of the second detection region and the region on the tip side of the second detection region among the element member or the unfired element member. Apply a protective material before firing. In the third step, the protective material before firing is fired to form the element protection portion, and the disappearing material is lost. In the fourth step, a region covering the second detection unit is removed from the element protection unit generated by baking the protective material before baking.

  In this manufacturing method, by having the first step, the third step, and the fourth step, in applying the protective material before firing in the second step, the second detection region and the region on the tip side of the second detection region A protective material before firing can be applied to cover all. That is, in manufacturing a gas sensor element including an element protection part that does not cover the second detection part, it is not necessary to take special measures such as avoiding the second detection part in the application work of the protective material before firing, and thus an increase in work load can be suppressed. .

  Further, the gas sensor element obtained by this manufacturing method can suppress the damage of the gas sensor element because the element protection part alleviates the thermal shock as in the case of the gas sensor element described above. Moreover, since the gas to be measured easily reaches the second detection unit, it is possible to suppress a decrease in detection accuracy in the second detection unit.

Next, another aspect of the present disclosure is a method for manufacturing a gas sensor element that detects a first component and a second component in a gas to be measured, and includes a protective part liquid adhesion step.
The gas sensor element includes at least an element main body, a first detection unit, a second detection unit, and an element protection unit, and is the gas sensor element according to any one of the above.

  The protection part liquid adhering step is a process of immersing the element body in a protection part liquid that becomes an element protection part by firing and attaching the protection part liquid to the element body. In the protection part liquid adhesion step, the porous part of the first detection part is on the lower side, the second detection part is on the upper side, and the element body part is inclined with respect to the liquid surface of the protection part liquid. The protection part liquid is attached to the element body part by lowering the element body part to a position where the mass part is immersed in the protection part liquid and the second detection part is not immersed in the protection part liquid.

  Thereby, without performing the process of providing carbon (sublimation material) so that a 2nd detection part may be covered, and the process of removing an element protection part, element protection which does not cover a 2nd detection part while covering a porous region The part can be formed. Therefore, according to this method for manufacturing a gas sensor element, the process can be simplified, and the complexity of manufacturing the gas sensor element can be reduced.

  Next, in the manufacturing method of the gas sensor element of this indication, when a gas sensor element is provided with a preliminary protection layer, you may have a preliminary paste formation process. The preliminary protection layer is a protection layer provided in a region between the second detection unit and the specific protection unit in the second detection side surface, and is a protection layer having a height lower than that of the second detection unit. The preliminary paste forming step is a step that is executed before the protective part liquid adhering step, and is a step of forming a preliminary paste that becomes a preliminary protective layer on the element body by firing.

  Thereby, in addition to an element protection part, a preliminary | backup protection layer can be provided and it can suppress that a damage arises in the element main-body part in the area | region between a 2nd detection part and a specific protection part among 2nd detection side surfaces. That is, the amount of the gas to be measured supplied to the second detection unit while protecting the element main body (second detection side surface) by performing the preliminary paste formation step first and then the protection unit liquid adhesion step. Can be produced.

It is sectional drawing which shows the internal structure of a multi gas sensor. 1 is a diagram illustrating a schematic configuration of a multi-gas detection device 1. FIG. It is sectional drawing which shows the structure of a 1st ammonia detection part and a 2nd ammonia detection part. It is a perspective view showing the appearance of a sensor element part. It is the perspective view which expanded the part with which the 1st ammonia detection part and the 2nd ammonia detection part are provided among the front-end | tip parts of a sensor element part. It is a schematic diagram for demonstrating the relative position of the heat-emitting part of a heater, and a pair of electrode in an ammonia detection part. It is explanatory drawing which showed from (A) 1st step to (D) 4th step in the formation method of an element protection part in steps. It is explanatory drawing which shows the structure of the front-end | tip part of the 2nd sensor element part of 2nd Embodiment. It is explanatory drawing which shows the formation position of the preliminary | backup protective layer and protective layer (a 1st ammonia detection part, a 2nd ammonia detection part) in a 2nd sensor element part. In a protection part liquid adhesion process, it is explanatory drawing showing the state which immerses the 2nd sensor element part of the previous stage in which a 2nd element protection part is formed in the protection part liquid stored in the container. It is the analysis result which carried out the simulation analysis of the change state of the gas flow rate with respect to the space | interval dimension D1. It is the measurement result which compared the gas detection precision of the sensor element part of 1st Embodiment, and the 2nd sensor element part of 2nd Embodiment.

Embodiments to which the present invention is applied will be described below with reference to the drawings.
In addition, this invention is not limited to the following embodiment at all, and it cannot be overemphasized that various forms may be taken as long as it belongs to the technical scope of this invention.

[1. First Embodiment]
[1-1. overall structure]
As a first embodiment, a multi-gas sensor 2 provided in an internal combustion engine such as an automobile will be described.

The multi-gas sensor 2 is configured as shown in FIG. 1 and is configured to detect an oxygen concentration, a NOx concentration, and an ammonia concentration (NH ₃ concentration). The multi gas sensor 2 constitutes a part of the multi gas detection device 1.

The multi-gas detection device 1 is mounted on a vehicle and used for a urea SCR system that purifies nitrogen oxides contained in exhaust gas discharged from a diesel engine. More specifically, the multi-gas detection device 1 detects the concentrations of ammonia, nitrogen dioxide, and nitrogen oxides contained in the exhaust gas. Hereinafter, a vehicle equipped with the multi-gas detection device 1 is referred to as a host vehicle. Nitrogen dioxide and nitrogen oxides are also referred to as NO ₂ and NOx, respectively. SCR is an abbreviation for Selective Catalytic Reduction.

The multi-gas detection device 1 includes a multi-gas sensor 2 and a control unit 3 shown in FIG.
The control unit 3 is electrically connected to an electronic control device 200 (also referred to as an ECU 200) mounted on the host vehicle. The electronic control unit 200 receives data indicating the NO ₂ concentration, NOx concentration and ammonia concentration (NH ₃ concentration) in the exhaust gas calculated by the control unit 3, and controls the operation state of the diesel engine based on the received data. A process is executed, or a purification process of NOx accumulated in the catalyst is executed.

[1-2. Multi gas sensor]
As shown in FIG. 1, the multigas sensor 2 includes a sensor element unit 5, a metal shell 10, a separator 34, and a connection terminal 38. In the following description, the side where the sensor element unit 5 of the multi-gas sensor 2 is arranged (that is, the lower side in FIG. 1) is the tip side, and the side where the connection terminal 38 is arranged (ie, the upper side in FIG. 1). ) Is called the rear end side.

  The sensor element unit 5 has a plate shape extending in the axis O direction. Electrode terminal portions 5A and 5B are arranged at the rear end of the sensor element portion 5. In FIG. 1, for ease of illustration, the electrode terminal portions formed in the sensor element portion 5 are only the electrode terminal portion 5A and the electrode terminal portion 5B. A plurality of electrode terminal portions are formed according to the number of electrodes and the like included in the first ammonia detection unit 102 and the second ammonia detection unit 103.

  The metal shell 10 is a cylindrical member in which a screw portion 11 for fixing the multigas sensor 2 to an exhaust pipe of a diesel engine is formed on the outer surface. The metal shell 10 includes a through hole 12 that penetrates in the direction of the axis O, and a shelf 13 that protrudes radially inward of the through hole 12. The shelf portion 13 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 12 toward the center.

The metal shell 10 holds the sensor element portion 5 in a state where the front end side of the sensor element portion 5 protrudes from the through hole 12 toward the front end side and the rear end side of the sensor element portion 5 protrudes toward the rear end side of the through hole 12.
Inside the through hole 12 of the metal shell 10, a ceramic holder 14 that is a cylindrical member that surrounds the periphery of the sensor element portion 5 in the radial direction in order from the front end side to the rear end side, and a talc that is a powder-filled layer Rings 15 and 16 and ceramic sleeve 17 are laminated.

  A caulking packing 18 is disposed between the ceramic sleeve 17 and the end portion on the rear end side of the metal shell 10. A metal holder 19 is disposed between the ceramic holder 14 and the shelf 13 of the metal shell 10. The metal holder 19 accommodates the talc ring 15 and the ceramic holder 14 therein, and the talc ring 15 is compressed and filled so that the metal holder 19 and the talc ring 15 are integrated in an airtight manner. The end portion on the rear end side of the metal shell 10 is a portion that is caulked so as to press the ceramic sleeve 17 toward the front end side via the caulking packing 18. Further, the talc ring 16 is compressed and filled inside the metal shell 10, so that airtightness between the inner peripheral surface of the metal shell 10 and the outer peripheral surface of the sensor element portion 5 is ensured.

  An external protector 21 with a gas flow hole and an internal protector 22 with a gas flow hole are provided at the end of the metal shell 10 on the front end side. The external protector 21 and the internal protector 22 are cylindrical members formed of a metal material such as stainless steel whose end on the distal end side is closed. The internal protector 22 is welded to the metal shell 10 while covering the end of the sensor element portion 5 on the front end side, and the external protector 21 is welded to the metal shell 10 while covering the internal protector 22.

  On the outer periphery of the end portion on the rear end side of the metal shell 10, an end portion on the front end side of the outer cylinder 31 formed in a cylindrical shape is fixed by welding. Further, a grommet 32 that closes the opening is disposed in an opening that is an end portion on the rear end side of the outer cylinder 31.

  The grommet 32 is formed with a lead wire insertion hole 33 into which the lead wire 41 is inserted. The lead wire 41 is electrically connected to the electrode terminal portion 5A and the electrode terminal portion 5B of the sensor element portion 5.

  The separator 34 is a cylindrical member disposed on the rear end side of the sensor element unit 5. A space formed inside the separator 34 is an insertion hole 35 penetrating in the direction of the axis O. On the outer surface of the separator 34, a flange portion 36 that protrudes radially outward is formed.

The rear end portion of the sensor element portion 5 is inserted into the insertion hole 35 of the separator 34, and the electrode terminal portions 5 </ b> A and 5 </ b> B are disposed inside the separator 34.
Between the separator 34 and the outer cylinder 31, a metal holding member 37 formed in a cylindrical shape is disposed. The holding member 37 holds the separator 34 in a fixed state with respect to the outer cylinder 31 by contacting the flange 36 of the separator 34 and the inner surface of the outer cylinder 31.

  The connection terminal 38 is a member that is disposed in the insertion hole 35 of the separator 34, and is a conductive member that electrically connects the electrode terminal portion 5 </ b> A and the electrode terminal portion 5 </ b> B of the sensor element portion 5 and the lead wire 41 independently. It is a member. In FIG. 1, only two connection terminals 38 are shown for ease of illustration.

  The sensor element unit 5 includes a NOx detection unit 101, a first ammonia detection unit 102, a second ammonia detection unit 103, and an element protection unit 124. The second ammonia detector 103 is not shown in FIG. 2 but shown in FIG. The first ammonia detection unit 102 and the second ammonia detection unit 103 are arranged in the width direction of the NOx detection unit 101 (that is, at substantially the same position as the reference electrode 143 in the longitudinal direction of the NOx detection unit 101 (that is, the horizontal direction in FIG. 2). 2 are arranged in parallel so that their positions in the depth direction in FIG. 2 are different from each other. For this reason, FIG. 2 shows only the first ammonia detection unit 102 out of the first ammonia detection unit 102 and the second ammonia detection unit 103.

  The NOx detection unit 101 is configured by sequentially laminating an insulating layer 113, a ceramic layer 114, an insulating layer 115, a ceramic layer 116, an insulating layer 117, a ceramic layer 118, an insulating layer 119, and an insulating layer 120. The insulating layers 113, 115, 117, 119, 120 and the ceramic layers 114, 116, 118 are mainly formed of alumina.

  The NOx detection unit 101 includes a first measurement chamber 121 formed between the ceramic layer 114 and the ceramic layer 116. The NOx detection unit 101 exhausts from the outside to the inside of the first measurement chamber 121 via a diffusion resistor 122 disposed between the ceramic layer 114 and the ceramic layer 116 so as to be adjacent to the first measurement chamber 121. Introduce gas. The diffusion resistor 122 is made of a porous material such as alumina.

The NOx detection unit 101 includes a first pumping cell 130. The first pumping cell 130 includes a solid electrolyte layer 131 and pumping electrodes 132 and 133.
The solid electrolyte layer 131 is formed mainly of zirconia having oxygen ion conductivity. A portion of the ceramic layer 114 in the region in contact with the first measurement chamber 121 is removed, and the solid electrolyte layer 131 is filled (embedded).

  The pumping electrodes 132 and 133 are formed mainly of platinum. The pumping electrode 132 is disposed on the surface that contacts the first measurement chamber 121 in the solid electrolyte layer 131. The pumping electrode 133 is disposed on the surface of the solid electrolyte layer 131 on the side opposite to the pumping electrode 132 with the solid electrolyte layer 131 interposed therebetween. The insulating layer 113 in the region where the pumping electrode 133 is disposed and the surrounding region is removed, and the porous body 134 is filled. The porous body 134 allows gas (for example, oxygen) to enter and exit between the pumping electrode 133 and the outside.

The NOx detection unit 101 includes an oxygen concentration detection cell 140. The oxygen concentration detection cell 140 includes a solid electrolyte layer 141, a detection electrode 142, and a reference electrode 143.
The solid electrolyte layer 141 is formed mainly of zirconia having oxygen ion conductivity. A portion of the ceramic layer 116 in the region on the rear end side (that is, the right side in FIG. 2) from the solid electrolyte layer 131 is removed, and the solid electrolyte layer 141 is filled (embedded).

  The detection electrode 142 and the reference electrode 143 are formed mainly of platinum. The detection electrode 142 is disposed on the surface in contact with the first measurement chamber 121 in the solid electrolyte layer 141. The reference electrode 143 is disposed on the surface of the solid electrolyte layer 141 on the side opposite to the detection electrode 142 with the solid electrolyte layer 141 interposed therebetween.

  The NOx detection unit 101 includes a reference oxygen chamber 146. The reference oxygen chamber 146 is a through hole formed by removing the insulating layer 117 in the region where the reference electrode 143 is disposed and the surrounding region.

  The NOx detection unit 101 includes a second measurement chamber 148 on the downstream side of the first measurement chamber 121. The second measurement chamber 148 is formed through the solid electrolyte layer 141 and the insulating layer 117 on the rear end side of the detection electrode 142 and the reference electrode 143. The NOx detector 101 introduces exhaust gas discharged from the first measurement chamber 121 into the second measurement chamber 148.

The NOx detection unit 101 includes a second pumping cell 150. The second pumping cell 150 includes a solid electrolyte layer 151 and pumping electrodes 152 and 153.
The solid electrolyte layer 151 is formed mainly of zirconia having oxygen ion conductivity. The ceramic layer 118 in the region in contact with the reference oxygen chamber 146 and the second measurement chamber 148 and the surrounding region is removed, and a solid electrolyte layer 151 is filled (embedded) instead of the ceramic layer 118.

  The pumping electrodes 152 and 153 are formed mainly of platinum. The pumping electrode 152 is disposed on the surface in contact with the second measurement chamber 148 in the solid electrolyte layer 151. The pumping electrode 153 is disposed on the surface of the solid electrolyte layer 151 on the side opposite to the reference electrode 143 across the reference oxygen chamber 146. A porous body 147 is disposed inside the reference oxygen chamber 146 so as to cover the pumping electrode 153.

  The NOx detection unit 101 includes a heater 160. The heater 160 is a heating resistor that is formed mainly of platinum and generates heat when energized. The heater 160 is disposed between the insulating layer 119 and the insulating layer 120.

  The first ammonia detector 102 is formed on the outer surface of the NOx detector 101, more specifically, on the insulating layer 120. The first ammonia detection unit 102 is disposed at the same position in the axis O direction (that is, the left-right direction in FIG. 2) with the reference electrode 143 in the NOx detection unit 101.

  The first ammonia detector 102 includes a first reference electrode 211 formed on the insulating layer 120, a first solid electrolyte body 212 that covers the surface and side surfaces of the first reference electrode 211, and the first solid electrolyte body 212. And a first detection electrode 213 formed on the surface. Similarly, as shown in FIG. 3, the second ammonia detection unit 103 includes a second reference electrode 221 formed on the insulating layer 120 and a second solid electrolyte body that covers the surface and side surfaces of the second reference electrode 221. 222 and a second detection electrode 223 formed on the surface of the second solid electrolyte body 222.

The first reference electrode 211 and the second reference electrode 221 are mainly composed of platinum as an electrode material, and specifically, are composed of a material containing Pt and zirconium oxide. The first solid electrolyte body 212 and the second solid electrolyte body 222 are made of an oxygen ion conductive material such as yttria-stabilized zirconia. The first detection electrode 213 and the second detection electrode 223 are mainly composed of gold as an electrode material, and specifically, are composed of a material containing Au and zirconium oxide. The electrode materials of the first detection electrode 213 and the second detection electrode 223 are selected so that the ratio between the sensitivity to ammonia and the sensitivity to NO ₂ is different in the first ammonia detection unit 102 and the second ammonia detection unit 103. ing.

  The first ammonia detector 102 and the second ammonia detector 103 are integrally covered with a protective layer 230 using a porous material. The protective layer 230 prevents the poisonous substances from adhering to the first detection electrode 213 and the second detection electrode 223, and diffuses the ammonia flowing into the first ammonia detection unit 102 and the second ammonia detection unit 103 from the outside. Is to adjust. Thus, the first ammonia detection unit 102 and the second ammonia detection unit 103 function as a mixed potential type sensing unit.

[1-3. Element protection part]
As shown in FIGS. 2 and 4, the sensor element unit 5 includes an element protection unit 124 that covers the tip side region of the NOx detection unit 101.

The element protection part 124 has a porous structure and is configured to allow gas to pass therethrough.
The element protection part 124 is formed so as to cover at least the porous body 134 in the NOx detection part 101. The element protection unit 124 also covers the diffusion resistor 122 in the NOx detection unit 101.

  The NOx detection unit 101 includes a front end surface 101a, a rear end surface 101b, three normal side surfaces 101c, and one ammonia detection side surface 101d as its outer surface. The three normal side surfaces 101c are the normal side surface 101c from which the porous body 134 is exposed, and the two normal side surfaces 101c connected to both sides thereof. On the ammonia detection side surface 101d, a first ammonia detection unit 102 and a second ammonia detection unit 103 are formed.

  Of the region in the axial direction of the NOx detector 101, the region where the first ammonia detector 102 (second ammonia detector 103) (specifically, the protective layer 230) is formed is defined as the second detection region RE2, and the second A region on the front end side from the detection region RE2 is defined as a first detection region RE1, and a region on the rear end side from the second detection region RE2 is defined as a third detection region RE3. Further, the formation region of the porous body 134 is defined as the fourth detection region RE4, the region on the front end side with respect to the fourth detection region RE4 is defined as the fifth detection region, and the rear end side with respect to the fourth detection region RE4 is defined. The region is defined as a sixth detection region RE6. Here, in the axial direction, the front end of the second detection region RE2 is located on the front end side with respect to the rear end of the fourth detection region RE4, and a part of the second detection region RE2 and one of the fourth detection regions RE4. The part overlaps.

  The porous body 134 is formed in the tip region of two regions (the three normal side surfaces 101c and the one ammonia detection side surface 101d) obtained by dividing the NOx detection unit 101 into two equal parts in the axial direction. Yes. The first detection region RE1 is the entire tip surface 101a and a part of the side surface (a part of the three normal side surfaces 101c and a part of the one ammonia detection side surface 101d) of the NOx detection unit 101.

  The element protection unit 124 is formed so as to cover at least the fourth detection region RE4 and the fifth detection region RE5 on the three normal side surfaces 101c. Furthermore, the element protection unit 124 is configured to cover a part of the sixth detection region RE6 on the three normal side surfaces 101c. Specifically, the element protection part 124 is formed so as to cover at least the formation region of the second pumping cell 150. Here, the element protection part 124 covers at least a part of the fourth detection region RE4 and the sixth detection area RE6, so that the boundary between the porous body 134 and the insulating layer 113 is also covered by the element protection part 124.

  As shown in FIGS. 2 and 5, the element protection unit 124 does not cover the first ammonia detection unit 102 (second ammonia detection unit 103) (specifically, the protective layer 230) on the ammonia detection side surface 101d. It is formed so as to cover at least a part of the first detection region RE1. In addition, the element protection unit 124 includes a communication unit 124 c formed on the outer side in the width direction of the first ammonia detection unit 102 and the second ammonia detection unit 103. The communication portion 124c is a portion formed on the ammonia detection side surface 101d of the element protection portion 124, and is in a region of the ammonia detection side surface 101d excluding the first ammonia detection portion 102 and the second ammonia detection portion 103. It is formed. The communication portion 124c is provided in a form communicating with a portion of the element protection portion 124 that is normally formed on the side surface 101c. The element protection part 124 can reduce the peeling from the normal side surface 101c and the ammonia detection side surface 101d by having the communication part 124c.

  That is, the sensor element unit 5 is an element protection unit formed so as to cover the porous body 134 (the porous part of the NOx detection unit 101) without covering the first ammonia detection unit 102 and the second ammonia detection unit 103. 124 is provided. As a result, the exhaust gas (measured gas) that attempts to reach the first ammonia detection unit 102 and the second ammonia detection unit 103 is not blocked by the element protection unit 124.

As shown in FIG. 2, the element protection part 124 includes an inner protection part 124a that contacts the NOx detection part 101, and an outer protection part 124b that covers the inner protection part 124a.
The inner protective part 124a is made of alumina and has a porous structure with a porosity of 70%. The outer protection part 124b is made of alumina and has a porous structure with a porosity of 46%. That is, the inner protective part 124a has a porous structure having a larger porosity than the outer protective part 124b.

The outer protection part 124b contacts the NOx detection part 101 at the rear end side of the three normal side faces 101c with respect to the inner protection part 124a.
[1-4. Ammonia detector and heater]
The NOx detecting unit 101 includes the heater 160 as described above.

The heater 160 heats the first pumping cell 130, the oxygen concentration detection cell 140, the second pumping cell 150, the first ammonia detection unit 102, and the second ammonia detection unit 103.
As shown in FIG. 6, the heater 160 includes a heat generating portion 160a and a pair of heater lead portions 160b. The heat generating portion 160a is configured by using a heat generating resistor that generates heat when current is passed through the heater lead portion 160b.

  In the axial direction, the heat generating part 160a is “the formation area of the first pumping cell 130, the oxygen concentration detection cell 140, the second pumping cell 150” and “the formation area of the first ammonia detection part 102, the second ammonia detection part 103”. Are arranged so as to overlap at least one of them.

  In the width direction of the NOx detection unit 101, the heat generation unit 160a is arranged inside the arrangement region that expands by the heater width dimension L1 in the width direction (vertical direction in FIG. 6) with the central axis C1 of the NOx detection unit 101 as the center. .

  The first ammonia detection unit 102 includes a pair of detection electrodes (a first reference electrode 211 and a first detection electrode 213). The second ammonia detection unit 103 includes a pair of detection electrodes (second reference electrode 221 and second detection electrode 223).

  A pair of electrodes (first reference electrode 211 and first detection electrode 213) in the first ammonia detection unit 102, and a pair of electrodes (second reference electrode 221 and second detection electrode 223) in the second ammonia detection unit 103. Are arranged in the width direction of the NOx detection unit 101 inside the arrangement region that extends in the width direction (vertical direction in FIG. 6) by the detection width dimension L2 with the central axis C1 of the NOx detection unit 101 as the center.

  The detection width dimension L2 is smaller than the heater width dimension L1. That is, the pair of electrodes in the first ammonia detection unit 102 and the second ammonia detection unit 103 are arranged inside the arrangement region of the heat generating unit 160 a in the width direction of the NOx detection unit 101.

  The pair of electrodes in the first ammonia detection unit 102 and the second ammonia detection unit 103 configured in this manner are entirely the heat generation unit as compared with the case where the electrodes are disposed in a region wider than the region in which the heat generation unit 160a is disposed. It becomes easier to receive the heat of 160a.

[1-5. Manufacturing method of sensor element section]
A method for manufacturing the sensor element unit 5 will be described.
First, a method for manufacturing the NOx detection unit 101, the first ammonia detection unit 102, and the second ammonia detection unit 103, which are the base of the sensor element unit 5, will be described.

  First, unsintered to become a solid electrolyte layer and a solid electrolyte body using a green base material containing 20 mass% of alumina powder in a zirconia powder in which a yttria stabilizer is dissolved and kneaded with a binder (polyvinyl butyral). A solid electrolyte sheet is prepared. In addition, this unbaked solid electrolyte sheet is a magnitude | size which can cut out a some solid electrolyte layer and a solid electrolyte body.

  In addition, an unfired alumina sheet that becomes an insulating layer or a ceramic layer after firing is produced using a raw material obtained by kneading alumina powder together with a binder (polyvinyl butyral). In the unfired alumina sheet that becomes an insulating layer or ceramic layer having a through hole (not shown) after firing, a through hole that becomes a through hole is formed.

  In an unfired alumina sheet that becomes a ceramic layer after firing, an opening for placing a solid electrolyte layer or the like is formed. After embedding the unfired solid electrolyte sheet in the opening of the unfired alumina sheet (or filling the raw material), a conductive paste mainly composed of platinum is printed in a predetermined pattern on a predetermined area on the sheet. And drying to form electrodes (pumping electrodes 132, 133, etc.) and conductor patterns to be lead portions. In an unfired alumina sheet having a through hole serving as a through hole, a conductive paste is applied to the inner wall surface of the through hole. Thereby, the unbaked alumina sheet used as a ceramic layer after baking is obtained.

  In addition, in the unfired alumina sheet on which the heater 160 is formed, a conductive pattern similar to the above is printed and dried in a predetermined pattern shape in a predetermined region to form a conductive pattern that becomes the heat generating portion 160a and the heater lead portion 160b. In addition, the conductor paste is filled into the inner wall surface of the through hole that becomes the through hole. An unfired sheet for heaters can be obtained by laminating another unfired alumina sheet on the surface on which the conductive pattern of the unfired alumina sheet is printed and press-bonding under reduced pressure.

  Then, an unfired alumina sheet that becomes an insulating layer after firing, an unfired alumina sheet that becomes a ceramic layer after firing, an unfired sheet for heaters, and the like are laminated in a predetermined order, and are pressed under reduced pressure to obtain an assembly.

  At this time, the slurry in which the alumina powder, the carbon powder as the pore-forming agent, the binder made of polyvinyl butyral, and the dispersant are mixed is filled in the portion where the porous body 134, the diffusion resistor 122, and the like are formed. In addition, a slurry in which carbon powder as a pore forming agent is mixed is filled in a site where the first measurement chamber 121 and the second measurement chamber 148 are formed.

  And this assembly is cut | disconnected by a well-known method, and several (for example, 10 pieces) unbaking laminated bodies are cut out. And after degreasing | defatting this unbaking laminated body in air | atmosphere and carrying out a binder removal process, the NOx detection part 101 is obtained by baking at 1500 degreeC for 1 hour.

  Thereafter, the first ammonia detection unit 102 and the second ammonia detection unit 103 are formed at predetermined positions of the NOx detection unit 101. After forming the first ammonia detector 102 and the second ammonia detector 103, a protective layer 230 is formed so as to cover the first ammonia detector 102 and the second ammonia detector 103.

In addition, since the manufacturing method of the 1st ammonia detection part 102, the 2nd ammonia detection part 103, and the protective layer 230 can employ | adopt a well-known manufacturing method, detailed description is abbreviate | omitted here.
In this way, the sensor element unit 5 at the stage before the element protection unit 124 is formed (in other words, an element including the NOx detection unit 101, the first ammonia detection unit 102, the second ammonia detection unit 103, and the protection layer 230). Member) is obtained.

Next, a method for forming the element protection part 124 will be described.
First, in the first step, as shown in FIG. 7A, the sensor element unit 5 (the NOx detection unit 101, the first ammonia detection unit 102, and the second ammonia detection unit before the element protection unit 124 is formed). 103, an element member provided with the protective layer 230), the vanishing material 171 is applied so as to cover the protective layer 230 (the first ammonia detector 102 and the second ammonia detector 103). The vanishing material 171 is a slurry mainly composed of carbon powder.

  In the next second step, as shown in FIG. 7B, after the first step, all of the second detection region RE2 and the first detection region RE1 are covered after the first step, and the third detection region RE3 is covered. A pre-firing protective material 124p is applied so as to cover a part of the film. The pre-firing protection material 124p is a material that becomes the element protection portion 124 after firing, and is a slurry liquid.

  This slurry liquid is composed of alumina powder (average particle size <1 μm), alumina fiber (average fiber length 50 μm), carbon powder (average particle size 20 μm), alumina sol (external blend), organic solvent (for example, ethanol, propylene glycol, Butyl carbitol) was added, stirred and adjusted to an appropriate viscosity. The content of each component of the slurry liquid is, for example, 60 to 80% by volume of the total amount of alumina powder (average particle size <1 μm) and alumina fibers (average fiber length 50 μm), carbon powder (average particle size 20 μm). 20 to 40% by volume and 10% by weight of alumina sol (outside formulation).

  In addition, the average particle diameter of the powder constituting the slurry liquid can be obtained by a laser diffraction scattering method, and the ceramic fiber length can be obtained by averaging the lengths of the ceramic fibers before mixing with the slurry liquid.

  The pre-firing protection material 124p includes a pre-firing inner material 124ap that becomes the inner protective portion 124a after firing, and a pre-firing outer material 124bp that becomes the outer protective portion 124b after firing. In addition, the porosity of each of the inner protective part 124a and the outer protective part 124b after firing can be controlled to different values by adjusting the content of each component in each of the inner material 124ap before firing and the outer material 124bp before firing. For example, by adjusting the content of the carbon powder as the pore forming material, the porosity of the inner protective portion 124a can be controlled to be larger than the porosity of the outer protective portion 124b.

  In the second step, first, the tip of the element member (the sensor element part 5 at the previous stage where the element protection part 124 is formed) is immersed in the slurry liquid of the pre-firing inner material 124ap, and is predetermined around the tip of the element member. An inner coating layer having a thickness (for example, 100 μm) is formed. Thereafter, in order to eliminate excess organic solvent in the inner coating layer, the element member provided with the inner coating layer is placed in a dryer set at 20 to 200 ° C. and dried for several hours.

  Next, the tip of the element member on which the dried inner coating layer is formed is immersed in a slurry solution of the outer material 124 bp before firing to form an outer coating layer having a predetermined thickness (for example, 400 μm) around the tip of the element member. To do. The thickness dimension can be controlled, for example, by adjusting the number of times of immersion in the slurry liquid, the viscosity of the slurry liquid, and the like. Thereafter, in order to eliminate excess organic solvent in the outer coating layer, the element member provided with the outer coating layer is placed in a dryer set at 20 to 200 ° C. and dried for several hours.

  In the next third step, as shown in FIG. 7C, the element member having the inner coating layer and the outer coating layer is baked in the atmosphere at 900 to 1100 ° C. for 3 hours to thereby form the inner protective portion 124a. And the element protection part 124 which has the outer side protection part 124b is obtained. During the firing, the disappearing material 171 disappears due to the high temperature, so that a space is provided between the protective layer 230 (the first ammonia detecting unit 102 and the second ammonia detecting unit 103) and the inner surface of the element protecting unit 124.

  In the next fourth step, as shown in FIG. 7D, the element protection part 124 (inner protection part 124a) generated by firing the pre-fired protective material 124p (the pre-fired inner material 124ap, the pre-fired outer material 124bp). , The portion that covers the protective layer 230 (the first ammonia detection unit 102 and the second ammonia detection unit 103) is removed from the outer protection unit 124b). A part of the element protection unit 124 can be removed using, for example, a laser processing machine or an ultrasonic cutter.

As a result, the protective layer 230 (the first ammonia detection unit 102 and the second ammonia detection unit 103) is exposed, and the sensor element unit 5 in which the element protection unit 124 is formed is obtained.
Note that although the inner coating layer and the outer coating layer are simultaneously fired here, the outer coating layer may be fired after the inner coating layer is fired.

  The multi-gas sensor 2 can be manufactured by assembling the sensor element unit 5 manufactured by the above-described method to a housing (the metal shell 10, the outer cylinder 31, etc.) according to a predetermined method.

[1-6. Control unit]
As shown in FIG. 2, the control unit 3 includes a control circuit 180 and a microcomputer 190 (hereinafter, microcomputer 190).

  The control circuit 180 is an analog circuit arranged on the circuit board. The control circuit 180 includes an Ip1 drive circuit 181, a Vs detection circuit 182, a reference voltage comparison circuit 183, an Icp supply circuit 184, a Vp2 application circuit 185, an Ip2 detection circuit 186, a heater drive circuit 187, and an electromotive force detection circuit 188.

  The pumping electrode 132, the detection electrode 142, and the pumping electrode 152 are connected to a reference potential. The pumping electrode 133 is connected to the Ip1 drive circuit 181. The reference electrode 143 is connected to the Vs detection circuit 182 and the Icp supply circuit 184. The pumping electrode 153 is connected to the Vp2 application circuit 185 and the Ip2 detection circuit 186. The heater 160 is connected to the heater drive circuit 187.

  The Ip1 drive circuit 181 supplies the first pumping current Ip1 by applying the voltage Vp1 between the pumping electrode 132 and the pumping electrode 133, and detects the supplied first pumping current Ip1.

The Vs detection circuit 182 detects the voltage Vs between the detection electrode 142 and the reference electrode 143, and outputs the detected result to the reference voltage comparison circuit 183.
The reference voltage comparison circuit 183 compares the reference voltage (for example, 425 mV) with the output of the Vs detection circuit 182 (that is, the voltage Vs), and outputs the comparison result to the Ip1 drive circuit 181. The Ip1 drive circuit 181 controls the flow direction of the first pumping current Ip1 and the magnitude of the first pumping current Ip1 so that the voltage Vs becomes equal to the reference voltage, and also controls the oxygen concentration in the first measurement chamber 121. , And adjust to a predetermined value that does not decompose NOx.

  The Icp supply circuit 184 flows a weak current Icp between the detection electrode 142 and the reference electrode 143. As a result, oxygen is sent from the first measurement chamber 121 to the reference oxygen chamber 146 via the solid electrolyte layer 141, so that the reference oxygen chamber 146 is set to a predetermined oxygen concentration as a reference.

  The Vp2 application circuit 185 applies a constant voltage Vp2 (for example, 450 mV) between the pumping electrode 152 and the pumping electrode 153. Thereby, in the second measurement chamber 148, NOx is dissociated by the catalytic action of the pumping electrodes 152 and 153 constituting the second pumping cell 150. Oxygen ions obtained by this dissociation move through the solid electrolyte layer 151 between the pumping electrode 152 and the pumping electrode 153, whereby a second pumping current Ip2 flows. The Ip2 detection circuit 186 detects the second pumping current Ip2.

  The heater driving circuit 187 drives the heater 160 by applying a positive voltage for energizing the heater to one end of the heater 160 that is a heating resistor and applying a negative voltage for energizing the heater to the other end of the heater 160. .

  The electromotive force detection circuit 188 includes an electromotive force between the first reference electrode 211 and the first detection electrode 213 (hereinafter referred to as a first ammonia electromotive force) and a second reference electrode 221 and the second detection electrode 223. An electromotive force (hereinafter, second ammonia electromotive force) is detected, and a signal indicating the detection result is output to the microcomputer 190.

The microcomputer 190 includes a CPU 191, a ROM 192, a RAM 193, and a signal input / output unit 194.
The CPU 191 executes a process for controlling the sensor element unit 5 based on a program stored in the ROM 192. The signal input / output unit 194 is connected to the Ip1 drive circuit 181, the Vs detection circuit 182, the Ip2 detection circuit 186, the heater drive circuit 187, and the electromotive force detection circuit 188. The signal input / output unit 194 converts the voltage value of the analog signal from the Ip1 drive circuit 181, Vs detection circuit 182, Ip2 detection circuit 186 and electromotive force detection circuit 188 into digital data and outputs the digital data to the CPU 191.

  In addition, the CPU 191 outputs a drive signal to the heater drive circuit 187 via the signal input / output unit 194, thereby energizing the power supplied to the heater 160 by pulse width modulation so that the heater 160 reaches a target temperature. I have to. In addition, the energization control of the heater 160 is a known method of detecting the impedance of a cell (for example, the oxygen concentration detection cell 140) constituting the NOx detection unit 101 and controlling the amount of power supplied so that the detected impedance becomes a target value. It can be realized by a technique.

  Further, the CPU 191 reads various data from the ROM 192 and performs various arithmetic processes from the value of the first pumping current Ip1, the value of the second pumping current Ip2, the value of the first ammonia electromotive force, and the value of the second ammonia electromotive force.

The arithmetic processing executed by the CPU 191 can use a known method, and a detailed description thereof is omitted here. Note that the CPU 191 first, for example, based on the first pumping current Ip1, the second pumping current Ip2, the first ammonia electromotive force, and the second ammonia electromotive force, the oxygen concentration, the NOx concentration output, the first ammonia concentration output, and the first 2. Calculation processing for obtaining the ammonia concentration output. Then, the CPU 191 uses the oxygen concentration, NOx concentration output, first ammonia concentration output, and second ammonia concentration output to perform a calculation using a predetermined correction formula, so that the ammonia concentration and NO ₂ concentration in the exhaust gas are obtained. And determine the NOx concentration.

  Various functions of the microcomputer 190 are realized by the CPU executing a program stored in a non-transitional tangible recording medium. In this example, the ROM corresponds to a non-transitional tangible recording medium that stores a program. Further, by executing this program, a method corresponding to the program is executed. The number of microcomputers constituting the control unit 3 may be one or more. Further, some or all of the functions executed by the microcomputer may be configured in hardware by one or a plurality of ICs.

The multi-gas detection device 1 including the control unit 3 configured as described above includes the exhaust gas using the multi-gas sensor 2 including the NOx detection unit 101, the first ammonia detection unit 102, and the second ammonia detection unit 103. The concentration of ammonia, NO ₂ and NOx is calculated.

[1-7. effect]
As described above, the multi-gas sensor 2 of the present embodiment includes the sensor element unit 5 having the element protection unit 124.

  The sensor element unit 5 includes an element protection unit 124 formed so as to cover the porous body 134 (the porous part of the NOx detection unit 101) without covering the first ammonia detection unit 102 and the second ammonia detection unit 103. Prepare. Thereby, a thermal shock is relieve | moderated and damage to the sensor element part 5 can be suppressed. In addition, the exhaust gas (measured gas) that attempts to reach the first ammonia detection unit 102 and the second ammonia detection unit 103 is not blocked by the element protection unit 124.

  Therefore, since the sensor element unit 5 easily reaches the first ammonia detection unit 102 and the second ammonia detection unit 103, the detection accuracy of the first ammonia detection unit 102 and the second ammonia detection unit 103 is reduced. Can be suppressed.

  Next, in the sensor element part 5, the porosity of the inner side protection part 124a is larger than the porosity of the outer side protection part 124b. For this reason, the sensor element part 5 can suppress that the moving amount | distance of the gas between the porous body 134 (porous part of the NOx detection part 101) and the inner side protection part 124a becomes too small.

  Next, a pair of electrodes (first reference electrode 211 and first detection electrode 213; second reference electrode 221 and second detection electrode 223) in each of the first ammonia detection unit 102 and the second ammonia detection unit 103 are as follows. In the width direction of the NOx detection unit 101, the NOx detection unit 101 is disposed inside the arrangement region of the heat generating unit 160a.

  The pair of electrodes in the first ammonia detection unit 102 and the second ammonia detection unit 103 configured in this manner are entirely the heat generation unit as compared with the case where the electrodes are disposed in a region wider than the region in which the heat generation unit 160a is disposed. It becomes easier to receive the heat of 160a.

  Therefore, the sensor element unit 5 can suppress the occurrence of bias in the temperature distribution of each pair of electrodes in the first ammonia detection unit 102 and the second ammonia detection unit 103, and the first ammonia detection unit 102 and the second ammonia detection It can suppress that the detection accuracy of the part 103 falls.

  Further, the multi-gas sensor 2 including the sensor element unit 5 can suppress a decrease in detection accuracy in the first ammonia detection unit 102 and the second ammonia detection unit 103, similarly to the sensor element unit 5.

  Next, in the manufacturing method of the sensor element unit 5, the first step, the third step, and the fourth step have the first step, the third step, and the fourth step. In the second step, the protective material 124p before firing (the inner material 124ap before firing, the outer material 124bp before firing). In the application, the pre-firing protection material 124p can be applied so as to cover all of the second detection region RE2 and the first detection region RE1. That is, in manufacturing the sensor element unit 5 including the element protection unit 124 that does not cover the first ammonia detection unit 102 and the second ammonia detection unit 103, the first ammonia detection unit 102 and the second ammonia detection unit 124p are applied in the pre-firing protection material 124p application operation. Special measures such as avoiding the ammonia detector 103 are not required. For this reason, as a method for applying the pre-firing protective material 124p, a method (dip method) in which the element member is immersed in the slurry liquid can be employed. Since this method is a simple method in which the element member is immersed in the slurry liquid as it is, it is possible to suppress an increase in work load in the application work of the pre-firing protective material 124p.

[1-8. Correspondence of wording]
Here, the correspondence between words will be described.
The sensor element unit 5 corresponds to a gas sensor element, and the NOx detection unit 101 corresponds to an element main body unit and a first detection unit. The front end surface 101a corresponds to the front end surface, the rear end surface 101b corresponds to the rear end surface, the three normal side surfaces 101c and one ammonia detection side surface 101d correspond to a plurality of side surfaces, and the ammonia detection side surface 101d serves as the second detection side surface. The normal side surface 101c corresponds to the normal side surface, and the porous body 134 corresponds to the porous portion.

  The first ammonia detection unit 102 and the second ammonia detection unit 103 correspond to an example of a second detection unit, the element protection unit 124 corresponds to an example of an element protection unit, and the inner protection unit 124a corresponds to an example of an inner protection unit. The outer protection portion 124b corresponds to an example of the outer protection portion. The vanishing material 171 corresponds to an example of the vanishing material, and the protective material 124p before firing, the inner material 124ap before firing, and the outer material 124bp before firing correspond to an example of the protective material before firing.

  The second detection region RE2 corresponds to the second detection region, the first detection region RE1 corresponds to the tip side region relative to the second detection region, the heater 160 corresponds to the heater, and the heat generating portion 160a corresponds to the heat generating portion. The first reference electrode 211 and the first detection electrode 213 correspond to a pair of detection electrodes, and the second reference electrode 221 and the second detection electrode 223 correspond to a pair of detection electrodes. The fourth detection region RE4 corresponds to a porous region.

The multi gas sensor 2 corresponds to an example of a gas sensor, and the metal shell 10 corresponds to an example of a housing.
[2. Second Embodiment]
[2-1. Second sensor element section]
As the second embodiment, the second sensor element unit 105 will be described. Since the second sensor element unit 105 is different from the sensor element unit 5 of the first embodiment in the form of the element protection unit, the description will focus on the different parts.

In the following description, the same reference numerals are given to the same components in the second sensor element unit 105 as those in the first embodiment, and detailed descriptions thereof are omitted.
As shown in FIG. 8, the second sensor element unit 105 includes a NOx detection unit 101, a first ammonia detection unit 102, a second ammonia detection unit 103, a second element protection unit 224, and a spare protection layer 232. .

  In addition, in FIG. 8, the front-end | tip part is illustrated in the 2nd sensor element part 105, and illustration of the rear-end part is abbreviate | omitted. In FIG. 8, the second element protection unit 224 is represented by a dotted line, and a portion of the second sensor element unit 105 covered with the second element protection unit 224 (a part of the NOx detection unit 101, one part of the spare protection layer 232). Are represented by solid lines.

  The second element protection unit 224 is made of the same material as the element protection unit 124 of the first embodiment. The second element protection unit 224 has a rear end portion that covers the normal side surface 101c on which the porous body 134 is formed, rather than a rear end portion that covers the ammonia detection side surface 101d (hereinafter also referred to as a first rear end portion 224a). The end portion (hereinafter also referred to as the second rear end portion 224b) is formed so as to be positioned on the rear end side of the NOx detecting portion 101. Further, the second element protection part 224 is formed such that the first rear end part 224a is located on the front end side of the protective layer 230 and the second rear end part 224b is located on the rear end side of the protective layer 230. ing.

  Here, in the second element protection unit 224, the protective layer 230 (the first ammonia detection unit 102, the second ammonia detection unit) in a direction (height direction; vertical direction in FIG. 8) perpendicular to the ammonia detection side surface 101d. 103) is defined as a specific protection unit 224c (region shown by hatching in FIG. 8). In the axial direction of the second sensor element unit 105 (left and right direction in FIG. 8), the distance between the front end of the protective layer 230 (the first ammonia detection unit 102 and the second ammonia detection unit 103) and the rear end of the specific protection unit 224c. D1 is 2.5 mm. That is, the 2nd sensor element part 105 is comprised so that the space | interval dimension D1 may be 2.0 mm or more.

  The preliminary protection layer 232 is made of the same material as the second element protection unit 224. As shown in FIG. 8, the preliminary protective layer 232 is configured to be lower than the protective layer 230. The height dimension H2 of the preliminary protective layer 232 is 0.10 mm, and the height dimension H1 of the protective layer 230 is 0.15 mm. As shown in FIG. 9, the preliminary protective layer 232 is on the front end side in the axial direction from the protective layer 230 (the first ammonia detecting unit 102 and the second ammonia detecting unit 103) in the ammonia detecting side surface 101 d of the NOx detecting unit 101. Is arranged. Further, the preliminary protection layer 232 is covered with the second element protection part 224 at the tip side region.

  That is, as shown in FIG. 8, the preliminary protection layer 232 is provided in a region between the first ammonia detection unit 102 (second ammonia detection unit 103) and the specific protection unit 224c in the ammonia detection side surface 101d. .

Next, a method for manufacturing the second sensor element unit 105 will be described.
First, the manufacturing method of the NOx detection unit 101, the first ammonia detection unit 102, the second ammonia detection unit 103, and the protective layer 230, which is the base of the second sensor element unit 105, is the same as the sensor element unit 5 of the first embodiment. The description is omitted because it is similar.

  The second sensor element unit 105 (in other words, the NOx detection unit 101, the first ammonia detection unit 102, the second ammonia detection unit 103, the protective layer) at the stage before the second element protection unit 224 and the preliminary protection layer 232 are formed. After obtaining the element member having 230, a preliminary paste forming step and a protective part liquid adhering step are performed.

  The preliminary paste forming step is a step executed before the protective part liquid attaching step. The preliminary paste forming step is a step of applying the preliminary paste 232a to a predetermined region (see FIG. 9) of the ammonia detection side surface 101d of the NOx detection unit 101.

  The preliminary paste 232a is a paste that becomes the preliminary protective layer 232 by firing. This preliminary paste 232a is composed of alumina powder (average particle size <1 μm), alumina fiber (average fiber length 50 μm), carbon powder (average particle size 20 μm), alumina sol (external blend), and an organic solvent (eg, ethanol, propylene glycol). , Butyl carbitol) was added, stirred and adjusted to an appropriate viscosity. The content of each component of the preliminary paste 232a is, for example, 60 to 80% by volume of the total amount of alumina powder (average particle size <1 μm) and alumina fibers (average fiber length 50 μm), carbon powder (average particle size 20 μm). ) 20 to 40% by volume, and alumina sol (outside formulation) is 10% by weight.

  Thereafter, in order to eliminate excess organic solvent in the preliminary paste 232a, an element member to which the preliminary paste 232a is applied (the second sensor element unit 105 at the stage before the second element protection unit 224 is formed) is replaced with 20 Place in a dryer set at ~ 200 ° C and allow to dry for several hours.

  In the protection part liquid attaching step, the second sensor element part 105 at the stage before the second element protection part 224 is formed is immersed in the protection part liquid 225, and the protection part liquid 225 is attached to a predetermined region of the NOx detection part 101. It is a process.

  The protection part liquid 225 is a slurry liquid that becomes the second element protection part 224 by firing. This slurry liquid is composed of alumina powder (average particle size <1 μm), alumina fiber (average fiber length 50 μm), carbon powder (average particle size 20 μm), alumina sol (external blend), organic solvent (for example, ethanol, propylene glycol, Butyl carbitol) was added, stirred and adjusted to an appropriate viscosity. The content of each component of the slurry liquid is, for example, 60 to 80% by volume of the total amount of alumina powder (average particle size <1 μm) and alumina fibers (average fiber length 50 μm), carbon powder (average particle size 20 μm). 20 to 40% by volume and 10% by weight of alumina sol (outside formulation).

  In the protective part liquid attaching step, as shown in FIG. 10, the element member (the second sensor element part 105 at the stage before the second element protective part 224 is formed) is applied to the protective part liquid 225 stored in the container 226. Soak). At this time, with respect to the element member, the porous body 134 of the NOx detection unit 101 is on the lower side, the first ammonia detection unit 102 (second ammonia detection unit 103) is on the upper side, and the liquid surface of the protection unit liquid 225 Then, the element member is immersed in the protective part liquid 225 after the NOx detecting part 101 is in an inclined state. At this time, the element member is lowered to a position where the porous body 134 is immersed in the protective part liquid 225 and the first ammonia detector 102 (second ammonia detector 103) is not immersed in the protective part liquid 225. In this way, the protection part liquid 225 can be attached to the element member (the second sensor element part 105 at the stage before the second element protection part 224 is formed).

Then, in order to make the excess organic solvent in the protection part liquid 225 disappear, the element member provided with the protection part liquid 225 is placed in a dryer set to 20 to 200 ° C. and dried for several hours.
Next, the second sensor in which the preliminary protective layer 232 and the second element protective portion 224 are formed by firing the element member including the preliminary paste and the protective portion liquid 225 in the atmosphere at 900 to 1100 ° C. for 3 hours. The element part 105 is obtained.

  Then, the multi-gas sensor 2 can be manufactured by assembling the second sensor element unit 105 manufactured in this way to a housing (the metal shell 10, the outer cylinder 31, etc.) according to a predetermined method.

[2-2. Simulation analysis results and measurement results]
Here, when supplying the gas to be measured to the second sensor element unit 105, the first ammonia detection unit 102 and the second ammonia detection unit 103 are reached when the interval dimension D1 of the second sensor element unit 105 is changed. An analysis result obtained by performing a simulation analysis on the change state of the flow velocity of the gas to be measured will be described.

The interval dimension D1 is a distance in the axial direction between the front end of the protective layer 230 (the first ammonia detection unit 102 and the second ammonia detection unit 103) and the rear end of the specific protection unit 224c.
The simulation analysis of the change state of the flow rate is based on the measurement target that reaches the first ammonia detection unit 102 and the second ammonia detection unit 103 when the measurement gas is supplied to the sensor element unit that does not include the second element protection unit 224. The simulation analysis was performed with the gas flow rate as the reference value (100%). In the simulation analysis, a plurality of second sensor element portions 105 having different interval dimensions D1 are used. For the flow velocity analyzed in each of the second sensor element portions 105, a relative ratio with respect to a reference value is calculated, and the calculation result is expressed as gas. The flow rate was assumed.

  According to the simulation analysis result shown in FIG. 11, when the gap dimension D1 is 1.5 mm or more, the gas flow rate is 90% or more, and the target to be supplied to the first ammonia detection unit 102 and the second ammonia detection unit 103 is obtained. It can be seen that the amount of measurement gas can be significantly reduced, and a decrease in gas detection accuracy can be suppressed. Furthermore, if the distance dimension D1 is 2.0 mm or more, the gas flow rate is almost 100%, and the gas to be measured can be sufficiently supplied to the first ammonia detection unit 102 and the second ammonia detection unit 103. It can be seen that the accuracy is good.

  According to the simulation analysis result, the second element protection unit 224 is formed such that the front end of the first ammonia detection unit 102 (second ammonia detection unit 103) is separated from the rear end of the specific protection unit 224c by a certain distance or more. Thus, the influence of the second element protection unit 224 on the supply of the gas to be measured to the first ammonia detection unit 102 (second ammonia detection unit 103) can be reduced. In other words, the second sensor element unit 105 having the distance dimension D1 of 2.0 mm or more is a gas to be measured supplied to the first ammonia detection unit 102 (second ammonia detection unit 103) as compared with the case where there is no element protection unit. Can be suppressed, and the gas detection by the first ammonia detection unit 102 (second ammonia detection unit 103) is improved while the second element protection unit 224 is provided.

  Next, measurement results comparing the gas detection accuracy of the sensor element unit 5 of the first embodiment and the second sensor element unit 105 of the second embodiment will be described. In this measurement, the detection signals of the first ammonia detection unit 102 and the second ammonia detection unit 103 when the same gas to be measured was supplied were measured for the sensor element unit 5 and the second sensor element unit 105, respectively. Then, based on the recording result, it was evaluated how the detection accuracy (the magnitude of the detection signal) varies depending on the shape of the element protection part.

  Regarding the difference in the shape of the element protection part, the element protection part 124 of the sensor element part 5 is a communication part 124c formed on the outer side in the width direction of the first ammonia detection part 102 and the second ammonia detection part 103 (see FIG. 5). It has. On the other hand, the second element protection unit 224 of the second sensor element unit 105 does not include a portion formed on the outer side in the width direction of the first ammonia detection unit 102 and the second ammonia detection unit 103 (see FIG. 8). ).

  In this measurement, the first ammonia detection unit 102 and the second ammonia detection in the case of using a sensor element unit (noted as “no element protection unit” in FIG. 12) that does not include an element protection unit as a comparison reference. The detection signal of each unit 103 was used as a reference value (100%). The measurement result was calculated as a relative value (output change rate) with respect to the reference value.

  As shown in FIG. 12, both the second sensor element unit 105 and the sensor element unit 5 have an output change rate exceeding about 80%, and the gas detection accuracy is larger than that in the case where there is no element protection unit. It turns out that it can suppress that it falls. In FIG. 12, the output change rate of the sensor element unit that does not include the element protection unit is expressed as “no element protection unit”.

  In particular, in the second sensor element unit 105, the output change rate of each of the first ammonia detection unit 102 and the second ammonia detection unit 103 is larger than that of the sensor element unit 5. For this reason, compared with the structure provided with the communication part 124c like the element protection part 124 of the sensor element part 5, like the 2nd element protection part 224 of the 2nd sensor element part 105, the 1st ammonia detection part 102 and the 1st 2 It can be seen that the configuration that does not have a portion formed on the outer side in the width direction of the ammonia detection unit 103 is excellent in detection accuracy of ammonia contained in the gas to be measured.

[2-3. effect]
As described above, the second sensor element unit 105 of the second embodiment includes the second element protection unit 224. As for the 2nd sensor element part 105, the space | interval dimension D1 of the front-end | tip of the 1st ammonia detection part 102 (2nd ammonia detection part 103) and the specific protection part 224c in an axial direction is 2.0 mm or more.

  As shown in the simulation analysis result (FIG. 11) described above, the second element protection is performed such that the front end of the first ammonia detection unit 102 (second ammonia detection unit 103) is separated from the rear end of the specific protection unit 224c by a certain distance or more. By forming the part 224, the influence of the second element protection part 224 on the supply of the measurement gas to the first ammonia detection part 102 (second ammonia detection part 103) can be reduced. That is, the second sensor element unit 105 can suppress a reduction in the amount of gas to be measured supplied to the first ammonia detection unit 102 (second ammonia detection unit 103), compared to the case where there is no element protection unit. In addition, the gas detection by the first ammonia detection unit 102 (second ammonia detection unit 103) is improved while the second element protection unit 224 is provided.

  Next, the second sensor element unit 105 includes a preliminary protective layer 232 between the protective layer 230 (the first ammonia detecting unit 102 and the second ammonia detecting unit 103) and the specific protective unit 224c in the ammonia detection side surface 101d. It has. By providing such a preliminary protection layer 232, the NOx detection unit 101 (ammonia detection side surface 101d) is protected and the measurement target supplied to the protection layer 230 (first ammonia detection unit 102, second ammonia detection unit 103) is provided. It can suppress that the quantity of gas reduces.

  Next, in the method for manufacturing the second sensor element unit 105, a protection unit liquid adhesion step is performed. Accordingly, the porous body 134 can be formed without performing the step of providing carbon (sublimation material) so as to cover the first ammonia detection unit 102 (second ammonia detection unit 103) and the step of removing the element protection unit. A second element protection unit 224 that covers the first ammonia detection unit 102 (second ammonia detection unit 103) but does not cover it can be formed.

  Therefore, according to the manufacturing method of the 2nd sensor element part 105, compared with the manufacturing method of the sensor element part 5 of 1st Embodiment, a process can be simplified and the complexity of manufacture of a gas sensor element can be reduced. .

  Next, in the manufacturing method of the second sensor element unit 105, a preliminary paste forming step is executed. As a result, a preliminary protective layer 232 can be provided in addition to the second element protection unit 224, and the protective layer 230 (the first ammonia detection unit 102, the second ammonia detection unit, among the ammonia detection side surfaces 101d of the NOx detection unit 101). 103) and the specific protection unit 224c can be prevented from being damaged in the NOx detection unit 101.

  That is, the preliminary paste forming step is performed first, and then the protective portion liquid adhering step is performed, thereby protecting the NOx detection portion 101 (ammonia detection side surface 101d) while protecting the protective layer 230 (first ammonia detection portion 102, first step). 2) A gas sensor element capable of suppressing a reduction in the amount of gas to be measured supplied to the ammonia detector 103) can be manufactured.

[2-4. Correspondence of wording]
Here, the correspondence between words will be described.
The second sensor element unit 105 corresponds to an example of a gas sensor element, the second element protection unit 224 corresponds to an example of an element protection unit, the specific protection unit 224c corresponds to an example of a specific protection unit, and the spare protection layer 232 includes The protective part liquid 225 corresponds to an example of the preliminary protective layer, and the protective part liquid 225 corresponds to an example of the protective part liquid.

[3. Other Embodiments]
As mentioned above, although embodiment of this invention was described, this invention is not limited to the said embodiment, In the range which does not deviate from the summary of this invention, it is possible to implement in various aspects.

  For example, in the above embodiment, the pre-firing protective material 124p is applied to the element member after firing (element member including the NOx detection unit 101, the first ammonia detection unit 102, the second ammonia detection unit 103, and the protective layer 230). Although the manufacturing method of applying and baking the protective material 124p before baking to form the element protection portion 124 has been described, the manufacturing method is not limited to this. Specifically, the pre-fired protective material 124p may be applied to the element member before firing, and the unfired element member and the pre-fired protective material 124p may be fired simultaneously.

  Moreover, in the said embodiment, the sensor by which the 2nd detection part (the 1st ammonia detection part 102 and the 2nd ammonia detection part 103) was formed in the side surface near the heater 160 among the side surfaces of the NOx detection part 101 as a sensor element part. Although the element part 5 was demonstrated, it is not restricted to such a form. Specifically, the second detection unit may be provided on any one of the three normal side surfaces 101 c of the NOx detection unit 101.

  Furthermore, in the sensor element unit 5 of the first embodiment, the dimension (interval dimension) of the gap portion between the protective layer 230 (the first ammonia detection unit 102 and the second ammonia detection unit 103) and the element protection unit 124 in the axial direction. ) May be 2.0 mm or more.

  Further, in the sensor element unit 5 of the first embodiment, of the ammonia detection side surface 101d of the NOx detection unit 101, the protective layer 230 (the first ammonia detection unit 102 and the second ammonia detection unit 103) and the element protection unit 124 are included. A preliminary protective layer may be provided in a region between the two.

  The preliminary protective layer 232 is not limited to the same material as that of the second element protection part 224, and may be formed of a material different from that of the second element protection part 224. As the preliminary protective layer 232, any material can be used as long as it can protect the NOx detector 101 (element body) from damage.

  Further, the above-mentioned various numerical values (particle size, content, volume%, thickness dimension, etc.) are not limited to the above numerical values, and may take arbitrary values within the technical scope described in the claims. it can.

  Next, the function of one component in each of the above embodiments may be shared by a plurality of components, or the function of a plurality of components may be exhibited by one component. Moreover, you may abbreviate | omit a part of structure of each said embodiment. In addition, at least a part of the configuration of each of the above embodiments may be added to or replaced with the configuration of the other above embodiments. In addition, all the aspects included in the technical idea specified from the wording described in the claims are embodiments of the present disclosure.

  In addition to the above-described microcomputer 190, a system including the microcomputer 190 as a constituent element, a program for causing the computer to function as the microcomputer 190, a non-transition actual recording medium such as a semiconductor memory storing the program, a concentration calculation method, and the like The present disclosure can be realized in various forms.

DESCRIPTION OF SYMBOLS 1 ... Multi gas detection apparatus, 2 ... Multi gas sensor, 5 ... Sensor element part, 10 ... Main metal fitting, 101 ... NOx detection part, 101a ... Front end surface, 101b ... Rear end surface, 101c ... Normal side surface, 101d ... Ammonia detection side surface, DESCRIPTION OF SYMBOLS 102 ... 1st ammonia detection part, 103 ... 2nd ammonia detection part, 105 ... 2nd sensor element part, 122 ... Diffusion resistor, 124 ... Element protection part, 124a ... Inner protection part, 124ap ... Inner material before baking, 124b ... outer protective part, 124 bp ... outer material before firing, 124p ... protective material before firing, 130 ... first pumping cell, 134 ... porous body, 140 ... oxygen concentration detection cell, 150 ... second pumping cell, 160 ... heater, 160a ... heat generating part, 171 ... disappearing material, 211 ... first reference electrode, 212 ... first solid electrolyte body, 213 ... first detection electrode, 221 Second reference electrode, 222 ... second solid electrolyte body, 223 ... second detection electrode, 224 ... second element protection section, 224c ... specific protection section, 225 ... protection section liquid, 230 ... protection layer, 232 ... preliminary protection layer , L1 ... heater width dimension, L2 ... detection width dimension, RE1 ... first detection area, RE2 ... second detection area.

Claims (9)

A gas sensor element for detecting a first component and a second component in a gas to be measured,
A longitudinal surface formed in an elongated shape extending in the axial direction, a distal end surface formed at the distal end in the axial direction, a rear end surface formed at the rear end in the axial direction, and a plurality of portions extending from the distal end surface to the rear end surface An element body having a side surface;
A first detector that pumps or pumps the gas under measurement through a porous portion formed on at least one of the plurality of side surfaces, and detects the first component;
A second detection unit that is provided on the rear end side of the front end of the porous portion and detects the second component;
An element protection part covering at least the porous part of the element body part;
With
The plurality of side surfaces include a second detection side surface on which the second detection unit is provided on its own surface, and a normal side surface that is not the second detection side surface,
When the formation region of the second detection portion is a second detection region in the axial direction region, and the formation region of the porous portion is a porous region,
The element protection unit is formed so as to cover at least the porous region and a region on the tip side of the porous region on the normal side surface, and the second detection unit is covered on the second detection side surface. First, formed so as to cover at least a part of the tip side region from the second detection unit,
Gas sensor element. The element body includes a heater for heating the first detection unit and the second detection unit,
The heater includes a heat generating portion arranged so as to overlap with at least one of the first detection portion formation region and the second detection region in the axial direction,
The second detection unit includes a pair of detection electrodes,
The pair of detection electrodes are arranged inside the arrangement region of the heat generating part in the width direction of the element main body part,
The gas sensor element according to claim 1. The element protection part includes an inner protection part that contacts the element body part, and an outer protection part that covers the inner protection part,
The inner protective part is a porous structure having a larger porosity than the outer protective part,
The outer protective portion is in contact with the element main body on the rear end side of the inner protective portion,
The gas sensor element according to claim 1 or 2. In the height direction perpendicular to the second detection side surface, when a part higher than the second detection unit of the element protection unit is a specific protection unit,
The distance between the front end of the second detection unit and the rear end of the specific protection unit in the axial direction is 2.0 mm or more.
The gas sensor element according to any one of claims 1 to 3. Of the second detection side surface, in a region between the second detection unit and the specific protection unit, a preliminary protection layer having a height lower than that of the second detection unit is provided.
The gas sensor element according to claim 4. A gas sensor element for detecting a first component and a second component in the gas to be measured;
A housing for holding the gas sensor element;
A gas sensor comprising:
The gas sensor element is the gas sensor element according to any one of claims 1 to 5.
Gas sensor. A method for producing a gas sensor element for detecting a first component and a second component in a gas to be measured,
6. The gas sensor element according to claim 1, wherein the gas sensor element includes at least an element body, a first detection unit, a second detection unit, and an element protection unit. And
Applying a disappearing material that disappears by heating so as to cover the second detection part in the element member provided with the element main body part, the first detection part, and the second detection part, or not to become the element member after firing In the firing element member, a first step of applying the disappearing material so as to cover the pre-firing detection member that becomes the second detection unit after firing,
After the first step, the element protection unit after firing so as to cover all of the element member or the unfired element member so as to cover the second detection region and the region on the tip side of the second detection region. A second step of applying a pre-firing protective material comprising:
A third step of firing the protective material before firing to form the element protection portion and causing the disappearance material to disappear,
A fourth step of removing a portion covering the second detection unit from the element protection unit generated by firing the protective material before firing;
The manufacturing method of the gas sensor element which has this. A method for producing a gas sensor element for detecting a first component and a second component in a gas to be measured,
6. The gas sensor element according to claim 1, wherein the gas sensor element includes at least an element body, a first detection unit, a second detection unit, and an element protection unit. And
The manufacturing method of the gas sensor element includes a protection part liquid adhesion step in which the element body part is immersed in a protection part liquid that becomes the element protection part by firing, and the protection part liquid is attached to the element body part. And
In the protection part liquid adhesion step, the porous part of the first detection part is on the lower side, the second detection part is on the upper side, and the element main body part is oblique with respect to the liquid surface of the protection part liquid In such a state, the element body part is lowered to a position where the porous part is immersed in the protection part liquid and the second detection part is not immersed in the protection part liquid. Attaching the protective part liquid;
A method for manufacturing a gas sensor element. It is a manufacturing method of the gas sensor element according to claim 8,
The gas sensor element includes a preliminary protective layer having a height lower than that of the second detection unit in a region between the second detection unit and the specific protection unit.
As a step to be executed before the protective part liquid adhesion step, it has a preliminary paste forming step of forming a preliminary paste to be the preliminary protective layer by firing on the element main body.
A method for manufacturing a gas sensor element.