Gas sensor element, gas sensor, and method for manufacturing gas sensor element

Abstract

To provide a gas sensor element and the like in which occurrence of a crack causing erroneous detection of NOx concentration is suppressed.SOLUTION: A gas sensor element includes: a first cell 130 having a first insulating layer 131s, and a first electrode 132 and a second electrode 133 arranged on a first solid electrolyte body 131e; a second cell having a second solid electrolyte body including an opposed surface opposed to a surface of the first insulating layer 131s and an opposite surface on an opposite side of the opposed surface, a third electrode 123 arranged on the opposed surface, and a fourth electrode arranged on the opposite surface; and an insulating adhesive layer for bonding the first cell 130 and the second cell in a state where the first electrode 132 and the second electrode 133 are separated so as not to be electrically connected to the third electrode 123. The gas sensor element includes a buffer portion 200 on a surface of the third electrode 123 made of a ceramic made of a material having a shrinkage start temperature lower than that of a material for forming the adhesive layer so as to overlap a peripheral end portion 131e2 of the first solid electrolyte body 131e while overlapping a region R.SELECTED DRAWING: Figure 5

Description

Technical Field

[0001] The present invention relates to a gas sensor element, a gas sensor, and a method for manufacturing a gas sensor element.

Background Art

[0002] A gas sensor for measuring the concentration of a specific component (such as NO x etc.) in the exhaust gas of an internal combustion engine is known. This type of gas sensor includes a gas sensor element mainly composed of ceramic. The gas sensor element includes an Ip1 cell, a Vs cell, an Ip2 cell, a first measurement chamber, a reference oxygen chamber, a second measurement chamber, etc. (see, for example, Patent Document 1).

[0003] The Ip1 cell (first pump cell) pumps in or out (so-called pumping) oxygen in the exhaust gas between the first measurement chamber and the outside.

[0004] The Vs cell (detection cell) includes a solid electrolyte that separates the first measurement chamber and the reference oxygen chamber, a detection electrode (Vs-electrode) formed on one surface of the solid electrolyte and exposed to the atmosphere in the first measurement chamber, and a reference electrode (Vs+ electrode) formed on the other surface of the solid electrolyte and exposed to the atmosphere in the reference oxygen chamber. In the Vs cell, a certain minute current flows from the detection electrode (Vs-electrode) side toward the reference electrode (Vs+ electrode) side, so that a certain amount of oxygen is accumulated in the reference oxygen chamber. Note that oxygen that has accumulated too much in the reference oxygen chamber is released to the outside through the above-mentioned reference electrode (Vs+ electrode) and the lead wire connected thereto. The reference electrode (Vs+ electrode) and the lead wire are made of porous ceramic and have gas permeability.

[0005] The Ip2 cell (second pump cell) is for NO xIt is for detecting concentration, and includes a solid electrolyte body and a pair of electrodes (Ip2+ electrode, Ip2- electrode) formed on one surface of the solid electrolyte body. One electrode (Ip2+ electrode) of the Ip2 cell faces the reference electrode (Vs+ electrode) of the Vs cell with a reference oxygen chamber therebetween. The other electrode (Ip2- electrode) of the second pump cell is housed in the second measurement chamber. Such a pair of electrodes are arranged on the surface of the solid electrolyte body in a state of being separated from each other in a plan view.

[0006] Note that the surface of the solid electrolyte body in the Ip2 cell and the reference electrode (Vs+ electrode) of the Vs cell face each other with an insulating adhesive layer therebetween. In particular, the reference electrode (Vs+ electrode) has a portion (hereinafter referred to as the overlapping portion) extending from the tip side to the rear end side of the gas sensor element so as to overlap with the region (region where no electrode is formed) between the pair of electrodes (Ip2+ electrode, Ip2- electrode) of the Ip2 cell in a plan view and also overlap with the peripheral edge portion of the solid electrolyte of the second pump cell.

Prior Art Documents

Patent Documents

[0007]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0008] In such a gas sensor element, among the insulating adhesive layers interposed between the Vs cell and the Ip2 cell, cracks may occur along the thickness direction (lamination direction) in the portion sandwiched between the overlapping portion of the reference electrode (Vs+ electrode) of the Vs cell and the peripheral edge portion of the solid electrolyte body arranged between the pair of electrodes in the second pump cell.

[0009] When a crack occurs as described above, there is a risk that the reference oxygen chamber and the second measurement chamber will be spatially connected, and the oxygen stored in the reference oxygen chamber may flow into the second measurement chamber. When oxygen flows into the second measurement chamber, a pair of electrodes of the Ip2 cell will detect a larger current value than normal, and NO x false detection of the concentration will occur.

[0010] Such cracks are formed during the manufacture of the gas sensor element starting from the overlapping portion side of the Vs cell and growing toward the region side between the electrodes of the second pump cell. The causes of crack generation include that the thickness of the unfired reference electrode for forming the reference electrode (Vs+ electrode) of the Vs cell is large, so the shrinkage amount during its firing becomes large, and during firing, the unfired adhesive layer for forming the adhesive layer, which is in contact with the unfired reference electrode, shrinks faster than the unfired reference electrode, etc.

[0011] Also, among the surfaces of the Ip2 cell facing the Vs cell, the region between a pair of electrodes (the region where no electrodes are formed) and the vicinity of the peripheral end portion of the solid electrolyte body have more drastic undulations in the surface shape compared to other locations. When an adhesive layer is formed between the Vs cell and the Ip2 cell while following such a drastically undulating surface shape, the abundance of the adhesive layer in the portion corresponding to the surface shape tends to be relatively small. Since most of the adhesive layer is usually formed using an unfired green sheet or the like with a uniform thickness, the thickness (density) of the adhesive layer in the portion following the drastically undulating surface shape tends to be relatively small. Thus, the fact that the thickness (density) of the adhesive layer tends to be relatively small is also presumed to be one of the causes of the above-described crack generation.

[0012] An object of the present invention is to provide a gas sensor element or the like in which cracks that cause false detection of the NO x concentration are suppressed from occurring in the insulating adhesive layer interposed between the first cell (Ip2 cell) and the second cell (Vs cell).

Means for Solving the Problem

[0013] Means for solving the above problems are as follows. That is, <1> A first cell having a first insulating layer, a first solid electrolyte body disposed on the surface side so that the peripheral end portion does not protrude from the surface of the first insulating layer in plan view, and a pair of first electrodes and a second electrode disposed on the surface of the first solid electrolyte body in a state of being separated from each other in plan view; a second solid electrolyte body including a facing surface facing the surface of the first insulating layer and an opposite surface on the opposite side of the facing surface; a third electrode disposed on the facing surface and disposed so as to overlap the peripheral end portion in plan view; and a fourth electrode disposed on the opposite surface; and an insulating adhesive layer interposed between the first cell and the second cell and bonding the first cell and the second cell in a state where the first electrode and the second electrode are separated so as not to conduct to the third electrode. A gas sensor element comprising a ceramic made of a material having a lower shrinkage start temperature than the material for forming the adhesive layer, and having a buffer portion formed on the surface of the third electrode so as to overlap a region between the first electrode and the second electrode and overlap the peripheral end portion of the first solid electrolyte body in plan view.

[0014] <2> The gas sensor element according to <1>, wherein the third electrode is made of a porous ceramic having gas permeability, and the buffer portion is made of a non-gas-permeable dense ceramic.

[0015] <3> The gas sensor element according to <1> or <2>, wherein the buffer portion is made of a ceramic containing zirconia as a main component.

[0016] <4> The gas sensor element according to any one of <1> to <3>, wherein the third electrode is made of a cermet containing platinum powder and ceramic powder.

[0017] <5> A gas sensor including the gas sensor element according to any one of <1> to <4>.

[0018] <6> A first insulating layer, a first solid electrolyte body disposed on the surface side so that the peripheral end does not protrude from the surface of the first insulating layer in plan view, and a pair of first electrodes and second electrodes disposed on the surface of the first solid electrolyte body in a state of being separated from each other in plan view. A first cell having the above, a second solid electrolyte body including a facing surface facing the surface of the first insulating layer and an opposite surface on the opposite side of the facing surface, and a third electrode disposed on the facing surface and overlapping the peripheral end portion in plan view. A second cell having a fourth electrode disposed on the opposite surface, and an insulating adhesive layer interposed between the first cell and the second cell and bonding the first cell and the second cell in a state where the first electrode and the second electrode are separated so as not to conduct to the third electrode. A method for manufacturing a sensor element, comprising: a first green sheet for forming the first insulating layer; and an unfired first solid electrolyte body for forming the first solid electrolyte body disposed on the surface side of the first green sheet. A first manufacturing step of producing an unfired first cell including a pair of unfired first electrodes and unfired second electrodes for forming the first electrode and the second electrode, which are disposed on the surface of the unfired first solid electrolyte in a state of being separated from each other in plan view.A second green sheet for forming the second solid electrolyte body including an unfired facing surface facing the surface of the first green sheet and an unfired opposite surface on the opposite side of the unfired facing surface; an unfired third electrode having a greater thickness than the unfired first electrode and the unfired second electrode and for forming the third electrode disposed on the unfired facing surface; and an unfired fourth electrode for forming the fourth electrode disposed on the unfired opposite surface. A second manufacturing step of manufacturing an unfired second cell having: an adhesion step of adhering the unfired first cell and the unfired second cell with an unfired adhesive sheet interposed therebetween so that the unfired first electrode and the unfired second electrode are separated from the unfired third electrode and the unfired third electrode overlaps with the unfired peripheral edge portion of the unfired first solid electrolyte body in a plan view; and a firing step of firing the laminate obtained after the adhesion step. In the second manufacturing step, an unfired buffer portion made of a material having a lower shrinkage start temperature than the material for forming the adhesion layer is formed on the surface of the unfired third electrode so as to overlap with the unfired peripheral edge portion while overlapping with the region between the unfired first electrode and the unfired second electrode in a plan view. A method for manufacturing a gas sensor element.

Effects of the Invention

[0019] According to the present invention, a gas sensor element or the like in which cracks that cause misdetection of NO concentration are suppressed from occurring in an insulating adhesive layer interposed between a first cell (Ip2 cell) and a second cell (Vs cell) can be provided. x Concentration can be provided.

Brief Description of the Drawings

[0020]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Figure 11

Mode for Carrying Out the Invention

[0021] <Embodiment 1> Hereinafter, Embodiment 1 of the present invention will be described with reference to FIGS. 1 to 10. FIG. 1 is a longitudinal sectional view of a gas sensor 1 according to Embodiment 1, FIG. 2 is a perspective view of a gas sensor element 10 according to Embodiment 1, FIG. 3 is a sectional view taken along line A-A of FIG. 2, and FIG. 4 is an exploded perspective view of the gas sensor element 10.

[0022] In FIG. 1, the axis AX of the gas sensor 1 is shown as a straight line (dashed-dotted line) along the vertical direction. In this specification, the direction along the axis AX direction of the gas sensor 1 may be referred to as the "longitudinal direction", and the direction perpendicular to the axis AX may be referred to as the "width direction". Further, in this specification, the lower side of the gas sensor 1 shown in FIG. 1 is referred to as the "tip side", and the opposite side (the upper side in FIG. 1) is referred to as the "rear end side". Also, for convenience of explanation, the upper side of FIGS. 2 to 4 is referred to as the "front side (surface side)" of the gas sensor element 10, and the lower side thereof is referred to as the "back side (back surface side)" of the gas sensor element 10.

[0023] The gas sensor 1 is NO in the exhaust gas which is the gas to be measured (detected gas) xIt is equipped with a gas sensor element 10 capable of detecting concentrations such as [etc.]. This gas sensor 1 is used by being attached to an exhaust pipe (not shown) of an internal combustion engine, and includes a cylindrical main fitting 20 having a screw portion 21 for fixing to the exhaust pipe formed at a predetermined position on the outer surface. The gas sensor element 10 generally has an elongated plate shape extending along the axis AX direction, and such a gas sensor element 10 is held inside the main fitting 20.

[0024] The gas sensor 1 includes a cylindrical holding member 60 having an insertion hole 62 into which the rear end portion 10k of the gas sensor element 10 is inserted, and six terminal members held inside this holding member 60. In FIG. 1, for convenience of explanation, only two of the six terminal members, terminal members 75 and 76, are shown.

[0025] As shown in FIG. 2, a total of six electrode terminal portions 13 to 18 having a rectangular shape in plan view are formed at the rear end portion 10k of the gas sensor element 10. In FIG. 1, only the electrode terminal portions 14 and 17 are shown. The aforementioned terminal members are elastically abutted and electrically connected to these electrode terminal portions 13 to 18 respectively. For example, the element abutting portion 75b of the terminal member 75 is elastically abutted and electrically connected to the electrode terminal portion 14, and the element abutting portion 76b of the terminal member 76 is elastically abutted and electrically connected to the electrode terminal portion 17.

[0026] Also, different lead wires 71 are electrically connected to the six terminal members (such as terminal members 75 and 76) respectively. For example, as shown in FIG. 1, the core wire of the lead wire 71 is caulked and held by the lead wire gripping portion 77 of the terminal member 75. Also, the core wire of another lead wire 71 is caulked and held by the lead wire gripping portion 78 of the terminal member 76.

[0027] As shown in FIG. 2, of the two main surfaces 10a and 10b at the rear end portion 10k of the gas sensor element 10, an opening-shaped air inlet 10h is provided at a location on one (front side) main surface 10a that is on the tip side of the electrode terminal portions 13 to 15 and on the rear end side of a ceramic sleeve 45 (see FIG. 1) described later. The air inlet 10h is disposed within the insertion hole 62 of the holding member 60.

[0028] The main body fitting 20 is a cylindrical member having a through hole 23 that penetrates in the direction of the axis AX. This main body fitting 20 includes a shelf portion 25 that projects radially inward and forms a part of the through hole 23. The main body fitting 20 holds the gas sensor element 10 within the through hole 23 in a state where the tip portion 10s of the gas sensor element 10 projects to the outside of its tip side (below in FIG. 1) and the rear end portion 10k of the gas sensor element 10 projects to the outside of its rear end side (above in FIG. 1).

[0029] Also, within the through hole 23 of the main body fitting 20, an annular ceramic holder 42, two talc rings 43 and 44 formed by filling talc powder annularly, and a ceramic sleeve 45 are disposed. More specifically, the ceramic holder 42, the talc rings 43 and 44, and the ceramic sleeve 45 are stacked in this order from the tip side to the rear end side of the main body fitting 20 so as to surround the gas sensor element 10 extending in the direction of the axis AX.

[0030] A metal cup 41 is disposed between the ceramic holder 42 and the shelf portion 25 of the main body fitting 20. Also, a clamping ring 46 is disposed between the ceramic sleeve 45 and the clamping portion 22 of the main body fitting 20. Note that the clamping portion 22 of the main body fitting 20 is clamped so as to press the ceramic sleeve 45 toward the tip side via the clamping ring 46.

[0031] At the tip 20b of the main fitting 20, an external protector 31 and an internal protector 32 made of metal (e.g., stainless steel) having a plurality of holes are attached by welding so as to cover the tip 10s of the gas sensor element 10. Also, an outer cylinder 51 is attached to the rear end portion of the main fitting 20 by welding. The outer cylinder 51 is generally cylindrical and extends in the direction of the axis AX, surrounding the gas sensor element 10.

[0032] The holding member 60 is a cylindrical member made of an insulating material (e.g., alumina) and having an insertion hole 62 penetrating in the direction of the axis AX. In the insertion hole 62, the six terminal members (terminal members 75, 76, etc.) described above are arranged (see FIG. 1). At the rear end portion of the holding member 60, a flange portion 65 protruding radially outward is formed. The holding member 60 is held by the internal support member 53 in such a manner that the flange portion 65 abuts against the internal support member 53. Note that the internal support member 53 is held by a caulked portion 51g caulked inward in the radial direction of the outer cylinder 51.

[0033] An insulating member 90 is disposed on the rear end face 61 of the holding member 60. The insulating member 90 is made of an insulating material (e.g., alumina) and is generally annular. A total of six through holes 91 penetrating in the direction of the axis AX are formed in the insulating member 90. In the through holes 91, lead wire gripping portions 77, 78, etc. of the above-described terminal members are arranged.

[0034] Further, inside the outer cylinder 51, on the radially inner side of the rear end opening 51c disposed on the rear end side, an elastic seal member 73 made of fluororubber is arranged. A total of six cylindrical insertion holes 73c extending in the axial direction of the axis AX are formed in the elastic seal member 73. Each insertion hole 73c is constituted by the insertion hole surface 73b (cylindrical inner wall surface) of the elastic seal member 73. One lead wire 71 is inserted into each insertion hole 73c. Each lead wire 71 extends outside the gas sensor 1 through the insertion hole 73c of the elastic seal member 73. The elastic seal member 73 is elastically compressed and deformed in the radial direction by clamping the rear end opening 51c of the outer cylinder 51 inward in the radial direction, thereby bringing the insertion hole surface 73b into close contact with the outer peripheral surface 71b of the lead wire 71 and sealing the space between the insertion hole surface 73b and the outer peripheral surface 71b of the lead wire 71 in a watertight manner.

[0035] As shown in FIG. 3, the gas sensor element 10 includes plate-shaped insulating layers 111s, 121s, 131s, solid electrolyte bodies 111e, 121e, 131e, and insulators 140, 145. The insulators 140, 145 are each made of dense ceramic (for example, alumina). The insulator 140 is disposed between the insulating layer 111s and the insulating layer 121s, and the insulator 145 is disposed between the insulating layer 121s and the insulating layer 131s. Further, the gas sensor element 10 includes a heater 161 disposed on the back surface side of the solid electrolyte body 131e. The heater 161 includes two plate-shaped insulators 162, 163 mainly made of alumina, and a heater pattern 164 embedded therebetween. The heater pattern 164 is made of a film-shaped pattern mainly made of platinum (Pt).

[0036] Note that the solid electrolyte bodies 111e, 121e, and 131e are each substantially rectangular in plan view. The solid electrolyte body 111e is formed so as to overlap an opening 111a provided on the tip side (the left side in FIG. 4) of a plate-like insulating layer 111s extending in the axial direction of the axis AX. The solid electrolyte body 121e is formed so as to overlap an opening 121a provided on the tip side (the left side in FIG. 4) of a plate-like insulating layer 121s extending in the axial direction of the axis AX. The solid electrolyte body 131e is formed on the surface of a plate-like insulating layer 131s extending in the axial direction of the axis AX. The insulating layer 131s corresponds to the "first insulating layer" of the present invention. Note that each of the solid electrolyte bodies 111e and 121e may be formed so as to be respectively embedded in the corresponding openings 111a and 121a, or may be formed so as to transfer a separately prepared sheet-like member to a predetermined location.

[0037] The solid electrolyte bodies 111e, 121e, and 131e are made of zirconia, which is a solid electrolyte, and have oxygen ion conductivity. A porous Ip1+ electrode 112 is provided on the surface side of the solid electrolyte body 111e. Also, a porous Ip1- electrode 113 is provided on the back side of the solid electrolyte body 111e. Furthermore, the surface of the Ip1+ electrode 112 is covered with a porous layer 114. Note that an Ip1+ lead 116 is connected to the Ip1+ electrode 112. Also, an Ip1- lead 117 is connected to the Ip1- electrode 113.

[0038] As shown in FIG. 4, plate-like dense layers 118B extending in the axial direction of the axis AX are laminated on the surfaces of the Ip1+ electrode 112 and the Ip1+ lead 116. The dense layer 118B is made of a gas-impermeable material such as alumina. An opening 118Ba having a rectangular shape in plan view is provided on the tip side of the dense layer 118B. Then, the above-described porous layer 114 is formed so as to fill the opening 118Ba.

[0039] As shown in FIG. 4, on the surface side of the dense layer 118B, a gas-impermeable dense layer 118 made of alumina or the like is disposed, including voids 10G. The voids 10G are formed inside a groove portion extending in the longitudinal direction (axis AX direction). A part of the porous layer 114 is exposed from the voids 10G. The voids 10G extend straight from the vicinity of the porous layer 114 to the portion communicating with the air inlet 10h in the plate-shaped dense layer 118 extending in the axis AX direction. And, in the plate-shaped dense layer 118 extending in the axis AX direction, through-holes for conducting with the electrode terminal portions 13, 14, and 15 are provided on the rear end side.

[0040] Also, a gas-impermeable dense layer 115 made of alumina or the like is laminated on the surface of the dense layer 118. By laminating the dense layer 115 in this way, the voids 10G are blocked by the dense layer 115.

[0041] An air inlet 10h is formed at a position overlapping the rear end of the voids 10G extending in the longitudinal direction (axis AX direction) in the dense layer 115. The air inlet 10h is an opening provided so as to penetrate the dense layer 115 in the thickness direction. Such an air inlet 10h is connected to the voids 10G. The air inlet 10h opens on the rear end side of the first porous body 151 described later, and air can be introduced instead of the exhaust gas. Thereby, the Ip1+ electrode 112 is exposed to the air introduced from the air inlet 10h through the porous layer 114.

[0042] The solid electrolyte body 111e, the Ip1+ electrode 112, and the Ip1− electrode 113 constitute the Ip1 cell (first pump cell) 110 (see FIG. 3). This Ip1 cell 110 performs oxygen pumping (so-called oxygen pumping), that is, pumping out and pumping in of oxygen, between the atmosphere in contact with the Ip1+ electrode 112 (the air in the voids 10G) and the atmosphere in contact with the Ip1− electrode 113 (the atmosphere in the first measurement chamber 150 described later. That is, the measurement target gas outside the gas sensor element 10) according to the pump current Ip1 (first pump current) flowing between the Ip1+ electrode 112 and the Ip1− electrode 113.

[0043] On the surface side of the solid electrolyte body 121e, a porous Vs - electrode 122 is provided. On the back side of the solid electrolyte body 121e, a porous Vs + electrode (reference electrode) 123 is provided. The Vs - electrode 122 corresponds to the "fourth electrode" of the present invention, and the Vs + electrode 123 corresponds to the "third electrode" of the present invention. Also, the solid electrolyte body 121e corresponds to the "second solid electrolyte body" of the present invention.

[0044] In the stacking direction, a first measurement chamber 150 is formed between the solid electrolyte body 111e and the solid electrolyte body 121e. This first measurement chamber 150 is an internal space where the measurement target gas (exhaust gas) flowing through the exhaust passage in the exhaust pipe is first introduced into the gas sensor element 10, and communicates with the outside of the gas sensor element 10 through a first porous body (diffusion resistance part) 151 (see FIGS. 2 and 4) having gas permeability and water permeability. The first porous body 151 is provided on the side of the first measurement chamber 150 as a partition from the outside of the gas sensor element 10. Such a first porous body 151 limits the flow rate (diffusion rate) of the exhaust gas per unit time into the first measurement chamber 150. The first porous body 151 is made of porous ceramic.

[0045] On the rear end side of the first measurement chamber 150 (the right side in FIG. 3), a second porous body 152 that limits the flow rate of the exhaust gas per unit time is provided as a partition between the first measurement chamber 150 and a second measurement chamber 160 described later.

[0046] The solid electrolyte body 121e, the Vs - electrode 122, and the Vs + electrode 123 constitute a Vs cell (detection cell) 120. This Vs cell 120 mainly generates an electromotive force according to the oxygen partial pressure difference between the atmospheres (the atmosphere in the first measurement chamber 150 in contact with the Vs - electrode 122 and the atmosphere in the reference oxygen chamber 170 in contact with the Vs + electrode 123) separated by the solid electrolyte body 121e. The Vs cell 120 corresponds to the "second cell" of the present invention.

[0047] On the surface side of the solid electrolyte body 131e, a porous Ip2+ electrode 132 and a porous Ip2- electrode 133 are provided. The Ip2+ electrode 132 corresponds to the "first electrode" of the present invention, and the Ip2- electrode 133 corresponds to the "second electrode" of the present invention. Further, the solid electrolyte body 131e corresponds to the "first solid electrolyte body" of the present invention.

[0048] A reference oxygen chamber 170 as an isolated small space is formed between the Ip2+ electrode 132 and the Vs+ electrode 123. This reference oxygen chamber 170 is constituted by an opening 145b formed in the insulator 145. Among the reference oxygen chamber 170, a porous body 171 made of ceramics is disposed on the side of the Ip2+ electrode 132 (see FIG. 3).

[0049] Also, in the stacking direction, a second measurement chamber 160 is formed at a position facing the Ip2- electrode 133. This second measurement chamber 160 is mainly constituted by an opening 145c that penetrates the insulator 145 in the stacking direction (thickness direction), an opening 125 that penetrates the insulating layer 121s in the stacking direction (thickness direction), and an opening 152a that penetrates the second porous body 152 in the stacking direction (thickness direction).

[0050] The first measurement chamber 150 and the second measurement chamber 160 communicate with each other through a second porous body 152 having gas permeability and water permeability. Therefore, the second measurement chamber 160 communicates with the outside of the gas sensor element 10 through the first porous body 151, the first measurement chamber 150, and the second porous body 152.

[0051] The solid electrolyte body 131e, the Ip2+ electrode 132, and the Ip2- electrode 133 constitute an Ip2 cell 130 (second pump cell) for detecting the NO x concentration. This Ip2 cell 130 moves oxygen (oxygen ions) derived from NO x decomposed in the second measurement chamber 160 to the reference oxygen chamber 170 through the solid electrolyte body 131e. At that time, between the Ip2+ electrode 132 and the Ip2- electrode 133, NO contained in the exhaust gas (measurement target gas) introduced into the second measurement chamber 160 xA current (second pump current) flows according to the concentration. Note that the Ip2 cell corresponds to the "first cell" of the present invention.

[0052] In the present embodiment, an alumina insulating layer 119 is formed at a portion of the back surface of the insulating layer 111s excluding the Ip1 - electrode 113 and the like. The Ip1 - electrode 113 contacts the solid electrolyte body 111e through a through - hole 119b (see FIG. 4) penetrating the alumina insulating layer 119 in the stacking direction.

[0053] Also, an alumina insulating layer 128 (see FIG. 3) is formed at a portion of the surface of the insulating layer 121s excluding the Vs - electrode 122 and the like. In FIG. 4, for convenience of explanation, the alumina insulating layer 128 is omitted. The Vs - electrode 122 contacts the solid electrolyte body 121e through a through - hole (not shown) penetrating the alumina insulating layer 128 in the stacking direction.

[0054] Also, an alumina insulating layer 129 (see FIG. 3) is formed at a portion of the back surface of the insulating layer 121s excluding the Vs + electrode 123 and the like. In FIG. 4, for convenience of explanation, the alumina insulating layer 129 is omitted. The Vs + electrode 123 contacts the solid electrolyte body 121e through a through - hole (not shown) penetrating the alumina insulating layer 129 in the stacking direction.

[0055] Here, with reference to FIGS. 5 to 8 and the like, the positional relationship and the like between the Ip2 + electrode 132 and the Ip2 - electrode 133 included in the Ip2 cell 130 and the Vs + electrode 123 included in the Vs cell 120 will be described. FIG. 5 is an explanatory diagram showing the positional relationship of the Ip2 + electrode 132, the Ip2 - electrode 133, and the Vs + electrode 123 in a plan view, FIG. 6 is an explanatory diagram showing the Ip2 cell 130 in a plan view, FIG. 7 is a cross - sectional view of a laminate L including the Ip2 cell 130 and the Vs cell 120 cut along the axial direction, and FIG. 8 is a cross - sectional view of a laminate L including the Ip2 cell 130 and the Vs cell 120 cut along the width direction.

[0056] The laminate L forms part of the gas sensor element 10 and includes at least the Ip2 cell 130, the Vs cell 120, and the insulator 145. The insulator 145 corresponds to the "adhesive layer" of the present invention. Note that the cutting direction of the cross-sectional view shown in FIG. 7 corresponds to the direction of line B-B in FIG. 5, and the cutting direction of the cut surface shown in FIG. 8 corresponds to the direction of line C-C in FIG. 5.

[0057] The Ip2 cell (first cell) 130 has an insulating layer (first insulating layer) 131s, a solid electrolyte body (first solid electrolyte body) 131e disposed on the surface 131s1 side such that the peripheral end portion 131e2 does not protrude from the surface 131s1 of the insulating layer 131s in plan view, and a pair of Ip2+ electrodes (first electrodes) 132 and Ip2- electrodes (second electrodes) 133 each disposed on the surface 131e1 of the solid electrolyte body 131e in a state of being separated from each other in plan view. In FIGS. 5 and 6, the longitudinal lead wire 132b (see FIG. 4) connected to the Ip2+ electrode 132 and the longitudinal lead wire 133b (see FIG. 4) connected to the Ip2- electrode 133 are omitted. The solid electrolyte body 131e is formed on the surface 131s1 of the insulating layer 131s. That is, the solid electrolyte body 131e is disposed on the surface side of the insulating layer 131s.

[0058] As shown in FIG. 6, when the Ip2 cell (first cell) 130 is viewed in plan from the front side, there is a region R where no electrode is formed between the Ip2+ electrode 132 and the Ip2- electrode 133. Note that finally, a part of the insulator 145 is filled in the region R between the Ip2+ electrode 132 and the Ip2- electrode 133.

[0059] The Vs cell (second cell) 120 has a solid electrolyte body (second solid electrolyte body) 121e including a facing surface 121e1 facing the surface 131s1 of the insulating layer (first insulating layer) 131s and an opposite surface 121e2 on the opposite side of the facing surface 121e1, a Vs+ electrode (third electrode) 123 disposed on the facing surface 121e1 and arranged to overlap the peripheral end portion 131e2 in plan view, and a Vs- electrode (fourth electrode) 122 (see FIGS. 3 and 4) disposed on the opposite surface 121e2. In FIGS. 5, 7, and 8, the Vs- electrode (fourth electrode) 122 is omitted.

[0060] As shown in FIG. 3, the solid electrolyte body (second solid electrolyte body) 121e separates the first measurement chamber 150 and the reference oxygen chamber 170 within the gas sensor element 10. The Vs+ electrode (third electrode) 123 is exposed to the atmosphere within the reference oxygen chamber 170, and the Vs− electrode (fourth electrode) 122 is exposed to the atmosphere within the first measurement chamber 150. The Vs+ electrode (third electrode) 123 is made of a porous ceramic having gas permeability. The Vs+ electrode (third electrode) 123 is made of, for example, a cermet containing platinum powder and ceramic powder. Further, the Vs− electrode (fourth electrode) 122 is also made of a porous ceramic having gas permeability. The Vs− electrode (fourth electrode) 122 is made of, for example, a cermet containing platinum powder and ceramic powder.

[0061] As shown in FIG. 5, the Vs+ electrode (third electrode) 123 of the Vs cell 120 faces the solid electrolyte body 131e in the Ip2 cell 130 in the stacking direction. In particular, the Vs+ electrode 123 overlaps with the region R (region where no electrode is formed) between the Ip2+ electrode 132 and the Ip2− electrode 133 on the solid electrolyte body 131e in plan view, and overlaps with the peripheral end portion 131e2 of the solid electrolyte body 131e of the Ip2 cell 130, and includes a portion (overlapping portion) 123a extending from the front end side to the rear end side of the gas sensor element 10.

[0062] In the Vs cell (second cell) 120, a certain minute current flows from the Vs− electrode 122 side toward the Vs+ electrode 123 side, whereby a certain amount of oxygen is accumulated in the reference oxygen chamber 170. The oxygen that has accumulated too much in the reference oxygen chamber 170 enters the inside of the Vs+ electrode 123 and moves to the rear end side of the gas sensor element 10 through the inside of the longitudinal lead wire 123b connected to the Vs+ electrode 123. Then, the oxygen is released to the outside from the rear end 123b1 of the lead wire 123b (see FIG. 4). The Vs+ electrode 123 and the lead wire 123b are made of a porous ceramic having gas permeability.

[0063] The insulator (adhesive layer) 145 is made of a dense ceramic (e.g., alumina) as described above and has insulating properties. Such an insulator (adhesive layer) 145 is interposed between the Ip2 cell (first cell) 130 and the Vs cell (second cell) 120, and adheres the Ip2 cell (first cell) 130 and the Vs cell (second cell) 120 in a state where the Ip2+ electrode (first electrode) 132 and the Ip2− electrode (second electrode) 133 are separated so as not to be electrically connected to the Vs+ electrode (third electrode) 123.

[0064] As shown in FIG. 5, the gas sensor element 10 of the present embodiment includes a buffer portion 200 formed on the surface of the Vs+ electrode 123 so as to overlap a region R between the Ip2+ electrode 132 and the Ip2− electrode 133 and overlap a peripheral end portion 131e2 of the solid electrolyte body 131e in a plan view. The buffer portion 200 is formed so as to cover at least the overlapping portion 123a of the Vs+ electrode 123 described above. The buffer portion 200 of the present embodiment is formed in a strip shape along the Vs+ electrode 123 extending generally in the front-rear direction. The width of the buffer portion 200 (the length in the left-right direction in FIG. 5) is larger than the width of the Vs+ electrode 123 (the length in the left-right direction in FIG. 5), and in the width direction, the buffer portion 200 is provided so that the Vs+ electrode 123 does not protrude outward. Note that the buffer portion 200 may be formed so as to cover at least the overlapping portion 123a of the Vs+ electrode 123 as described above. In other embodiments, for example, it may be formed in a strip shape along the edge portion closer to the Ip2− electrode 133 in the Vs+ electrode 123 extending generally in the front-rear direction in a plan view (in this case, in the width direction, the edge portion of the Vs+ electrode 123 farther from the Ip2− electrode 133 may protrude outside the buffer portion 200). The buffer portion 200 is made of a ceramic made of a material having a lower shrinkage start temperature than the material for forming the insulator (adhesive layer) 145.

[0065] In addition, in this specification, the "shrinkage start temperature" means the temperature at which the green sheet having the same composition as each ceramic layer (for example, the buffer portion 200 and the insulator 145) is prepared, heated in an air atmosphere, and fired to progress, and the multiplication factor becomes 1.05 when each ceramic layer is formed. The multiplication factor is also referred to as the firing shrinkage rate, and is calculated by the vertical or horizontal dimension of the green sheet before firing when the vertical or horizontal dimension of the ceramic layer after firing is set to 1. That is, the multiplication factor = (the vertical or horizontal dimension of the green sheet before firing) / (the same-direction dimension of the ceramic layer after firing).

[0066] The buffer portion 200 is formed by printing as described later. The gas sensor element 10 of the present embodiment includes such a buffer portion 200, so that cracks are suppressed from occurring in the insulating adhesive layer (insulator) 145 interposed between the Ip2 cell (first cell) 130 and the Vs cell (second cell) 120 during the manufacture of the gas sensor element 10.

[0067] The buffer portion 200 is made of a non-gas-permeable dense ceramic. Therefore, even when it is in contact with the Vs+ electrode 123 made of porous ceramic, the entry of oxygen passing through the inside of the Vs+ electrode 123 into the buffer portion 200 is suppressed. That is, it is suppressed that the flow rate per unit time when oxygen moves inside the Vs+ electrode 123 and the lead wire 123b is affected by the buffer portion 200 and decreases.

[0068] The material for forming the buffer portion 200 is made of a ceramic containing zirconia as a main component. In this specification, the "main component" is a component having a content (content ratio) of 50% by mass or more in each composition. That is, in the present embodiment, the buffer portion 200 contains 50% by mass or more of zirconia.

[0069] Next, NO by the gas sensor 1 of the present embodiment xA method for detecting concentration will be briefly described. The solid electrolytes 111e, 121e, and 131e of the gas sensor element 10 are heated and activated as the heater pattern 164 is heated up. As a result, the Ip1 cell 110, the Vs cell 120, and the Ip2 cell 130 operate respectively.

[0070] Exhaust gas flowing through an exhaust passage (not shown) in the exhaust pipe is introduced into the first measurement chamber 150 while being restricted in flow rate by the first porous body 151. At this time, a weak current (minute current) Icp flows from the Vs+ electrode 123 side to the Vs- electrode 122 side in the Vs cell 120. Therefore, oxygen in the exhaust gas can receive electrons from the Vs- electrode 122 in the first measurement chamber 150 on the negative electrode side, become oxygen ions, flow through the solid electrolyte 121e, and move into the reference oxygen chamber 170. That is, by flowing the current Icp between the Vs- electrode 122 and the Vs+ electrode 123, oxygen in the first measurement chamber 150 is sent into the reference oxygen chamber 170.

[0071] When the oxygen concentration of the exhaust gas introduced into the first measurement chamber 150 is lower than a predetermined value, a current Ip1 is passed through the Ip1 cell 110 so that the Ip1+ electrode 112 side becomes the negative electrode, and oxygen is drawn into the first measurement chamber 150 from the outside of the gas sensor element 10.

[0072] On the contrary, when the oxygen concentration of the exhaust gas introduced into the first measurement chamber 150 is higher than the predetermined value, a current Ip1 is passed through the Ip1 cell 110 so that the Ip1- electrode 113 side becomes the negative electrode, and oxygen is pumped out from the first measurement chamber 150 to the outside of the gas sensor element 10.

[0073] In this way, the exhaust gas whose oxygen concentration has been adjusted in the first measurement chamber 150 is introduced into the second measurement chamber 160 through the second porous body 152. NO in the exhaust gas that has come into contact with the Ip2- electrode 133 in the second measurement chamber 160 xWhen a voltage Vp2 is applied between the Ip2+ electrode 132 and the Ip2- electrode 133, on the Ip2- electrode 133, it is decomposed (reduced) into nitrogen and oxygen, and the decomposed oxygen becomes oxygen ions and flows through the solid electrolyte body 131e and moves into the reference oxygen chamber 170. At this time, the residual oxygen left in the first measurement chamber 150 is also moved into the reference oxygen chamber 170 by the Ip2 cell 130. As a result, a current derived from NO x and a current derived from the residual oxygen flow through the Ip2 cell 130. The oxygen that has moved into the reference oxygen chamber 170 is released to the outside (atmosphere) through the Vs+ electrode 123 in contact with the reference oxygen chamber 170 and the Vs+ lead (lead wire 123b). For this reason, the Vs+ lead is porous.

[0074] Since the concentration of the residual oxygen left in the first measurement chamber 150 is adjusted to a predetermined value as described above, the current derived from the residual oxygen can be regarded as substantially constant. That is, the current derived from the residual oxygen has little influence on the variation of the current derived from NO x and the current (second pump current) flowing through the Ip2 cell 130 is proportional to the NO x concentration. Therefore, the current Ip2 (second pump current) flowing through the Ip2 cell 130 is measured, and based on the current value, the NO x concentration in the exhaust gas is detected.

[0075] Subsequently, with reference to FIGS. 9 to 11 and the like, the manufacturing method of the gas sensor element 10 described above will be described. FIG. 9 is a flowchart showing each step in the manufacturing method of the gas sensor element 10. As shown in FIG. 9, the manufacturing method of the gas sensor element 10 of the present embodiment includes at least a first manufacturing step S11, a second manufacturing step S12, an adhesion step S13, and a firing step S14. In addition, the manufacturing method of the gas sensor element 10 includes known steps such as a step of manufacturing the Ip1 cell 110 in addition to these steps. In this specification, the description of known steps is omitted. FIG. 10 is an explanatory diagram schematically showing the content of the manufacturing method of the gas sensor element 10.

[0076] The first manufacturing step S11 is a step of manufacturing an unfired first cell 130U including a first green sheet 131sU for forming an insulating layer (first insulating layer) 131s, an unfired first solid electrolyte body 131eU for forming a solid electrolyte body (first solid electrolyte body) 131e disposed on the surface side of the first green sheet 131sU, and a pair of unfired first electrodes 132U and unfired second electrodes 133U for forming a first electrode 132 and a second electrode 133, each of which is disposed on the surface of the unfired first solid electrolyte body 131eU in a state of being separated from each other in plan view.

[0077] The unfired first solid electrolyte body 131eU is previously formed on a separately prepared sheet-like member, and is disposed on the surface 131sU1 side of the first green sheet 131sU in a form of transferring the unfired first solid electrolyte body 131eU on the member.

[0078] Note that a protective layer 210U mainly composed of alumina is formed on the surface of the unfired first cell 130U so as to cover the unfired first electrode 132U, the unfired first solid electrolyte body 131eU, etc. On the surface of the unfired first cell 130U, the unfired second electrode 133U is not covered by the protective layer 210U and is exposed from the opening 210Ua of the protective layer 210U. The protective layer 210U is provided in a form following the surface shape (such as unevenness) of the unfired first cell 130U. When the protective layer 210U is fired, it finally becomes a part of the insulator 145.

[0079] The second manufacturing step S12 is a step of manufacturing an unfired second cell 120U having a second green sheet (unfired second solid electrolyte body) 121eU for forming a solid electrolyte body (second solid electrolyte body) 121e including an unfired opposed surface 121eU1 facing the surface of the first green sheet 131sU and an unfired opposite surface 121eU2 on the opposite side of the unfired opposed surface 121eU1, an unfired third electrode 123U for forming a Vs+ electrode 123 disposed on the unfired opposed surface 121eU1, and an unfired fourth electrode 122U for forming a Vs- electrode 122 disposed on the unfired opposite surface.

[0080] In such a second manufacturing process S12, in a plan view, an unfired buffer portion 200U for forming a buffer portion 200 is formed on the surface of the unfired third electrode 123U so as to overlap with a region RU between the unfired first electrode 132U and the unfired second electrode 133U and also overlap with the unfired peripheral end portion 131eU2. The unfired buffer portion 200U is made of a material having a lower shrinkage start temperature than the material for forming the insulator (adhesive layer) 145. Such an unfired buffer portion 200U is formed on the surface of the unfired third electrode 123U with a predetermined thickness by printing.

[0081] The second green sheet (unfired second solid electrolyte body) 121eU is provided in an opening 121aU of a green sheet 121sU for forming an insulating layer 121s. The second green sheet 121eU has an opening 121eUa in a portion overlapping with the fired second electrode 133U in a plan view. On the surface of the unfired facing surface 121eU1 side of the unfired second cell 120U, a protective layer 220U mainly composed of alumina is formed so as to cover the unfired third electrode 123U, the unfired buffer portion 200U, the green sheet 121sU, etc. The protective layer 220U is provided in a shape following the surface shape of the unfired second cell 120U. The protective layer 220U has an opening 220Ua in a portion overlapping with the unfired second electrode 133U in a plan view. When the protective layer 220U is fired, it finally becomes a part of the insulator 145.

[0082] The bonding process S13 is a process of bonding the unfired first cell 132U and the unfired second cell 133U with an unfired bonding sheet 145U for forming an insulator (adhesive layer) 145 interposed therebetween between the unfired first cell 130U and the unfired second cell 120U in a state where the unfired first electrode 132U and the unfired second electrode 133U are separated from the unfired third electrode 123U and the unfired third electrode 123U overlaps with the unfired peripheral end portion 131eU2 of the unfired first solid electrolyte body 131eU in a plan view. The unfired bonding sheet 145U has an opening 145Ua in a portion overlapping with the unfired second electrode 133U in a plan view.

[0083] The firing step S14 is a step of firing the laminate obtained after the bonding step S13. In the firing step S14, the laminate is fired under predetermined temperature conditions to obtain the gas sensor element 10.

[0084] As described above, the unfired buffer portion 200U is made of a material having a lower shrinkage start temperature than the material for forming the insulator (adhesive layer) 145. Therefore, in the firing step S14, the unfired buffer portion 200U starts to shrink earlier than the unfired adhesive sheet 145U independently of the unfired adhesive sheet 145U. Moreover, it can be said that the unfired buffer portion 200U is considerably smaller in size and has a smaller shrinkage amount than the unfired adhesive sheet 145U. Therefore, even when such an unfired buffer portion 200U is in contact with the unfired third electrode 123U, cracks are suppressed from occurring in the unfired third electrode 123U during the shrinkage of the unfired buffer portion 200U in the firing step S14. Also, when the unfired adhesive sheet 145U and the unfired third electrode 123U shrink respectively, the presence of the unfired buffer portion 200U suppresses the occurrence of cracks in the fired third electrode 123U.

[0085] Therefore, in the gas sensor element 10 obtained by the method for manufacturing a gas sensor element according to the present embodiment, cracks that cause misdetection of the NO x concentration are suppressed from occurring in the insulating adhesive layer (insulator) 145 interposed between the first cell (Ip2 cell) 130 and the second cell (Vs cell) 120.

[0086] <Conventional Example> Next, while referring to FIG. 11, the configuration of the conventional gas sensor element 10P will be briefly described. FIG. 11 is a cross-sectional view of a part of the conventional gas sensor element 10P cut along the axial direction. FIG. 11 shows a laminate LP including an Ip2 cell 130 and a Vs cell 120 as a part of the conventional gas sensor element 10P. Different from the gas sensor element 10 of Embodiment 1, the conventional gas sensor element 10P does not include a buffer portion 200. That is, in the conventional gas sensor element 10P, an insulator (adhesive layer) 145P is in direct contact with the Vs+ electrode 123P. Note that the conventional gas sensor element 10P has the same configuration as the gas sensor element 10 of Embodiment 1 except for not including the buffer portion 200.

[0087] The Ip2 cell 130P has an insulating layer 131sP, a solid electrolyte body 131eP disposed on the surface 131sP1 side so that the peripheral end portion 131eP2 does not protrude from the surface 131sP1 of the insulating layer 131sP in plan view, and a pair of Ip2+ electrodes 132P and an Ip2− electrode (not shown) each disposed on the surface 131eP1 of the solid electrolyte body 131eP in a state of being separated from each other in plan view. When the Ip2 cell 130 is viewed in plan from the front side, there is a region RP where no electrode is formed between the Ip2+ electrode 132 and the Ip2− electrode (not shown), similar to Embodiment 1.

[0088] The Vs cell 120P has a facing surface 121eP1 facing the surface 131sP1 of the insulating layer 131sP, a solid electrolyte body 121eP including an opposite surface 121eP2 on the opposite side of the facing surface 121eP1, a Vs+ electrode 123P having a thickness larger than that of the Ip2+ electrode 132P and the Ip2− electrode (not shown), disposed on the facing surface 121eP1 and arranged to overlap the peripheral end portion 131Pe in plan view, and a Vs− electrode (not shown) disposed on the opposite surface 121eP2. A longitudinal lead wire 123bP is connected to the Vs+ electrode 123P.

[0089] In such a conventional gas sensor element 10P, as shown in FIG. 11, among the insulating adhesive layer (insulator) 145P interposed between the Vs cell 120P and the Ip2 cell 130P, the Vs+ electrode 123P of the Vs cell 120P and the peripheral end portion 131e2 of the solid electrolyte body 131eP arranged in the vicinity of the region RP between the Ip2+ electrode 132P and the Ip2− electrode (not shown) in the Ip2 cell 130P, there was a case where a crack X occurred along the thickness direction (lamination direction) in the sandwiched portion.

Explanation of reference numerals

[0090] 1… Gas sensor, 10… Gas sensor element, 120… Second cell, 121e… Second solid electrolyte body, 121e1… Opposite surface, 121e2… Opposite surface, 123… Third electrode, 124… Fourth electrode, 130… First cell, 131s… First insulating layer, 131e… First solid electrolyte body, 131e2… Peripheral end portion, 132… First electrode, 133… Second electrode, 145… Adhesive layer, 200… Buffer portion

Claims

1. A first cell having a first insulating layer, a first solid electrolyte body disposed on the surface side such that the peripheral end portion does not protrude from the surface of the first insulating layer in plan view, and a pair of first and second electrodes disposed on the surface of the first solid electrolyte body in a state of being separated from each other in plan view; A second cell having a second solid electrolyte body including a facing surface facing the surface of the first insulating layer and an opposite surface on the opposite side of the facing surface, a third electrode disposed on the facing surface and disposed so as to overlap the peripheral end portion in plan view, and a fourth electrode disposed on the opposite surface; An insulating adhesive layer interposed between the first cell and the second cell and bonding the first cell and the second cell in a state where the first electrode and the second electrode are separated so as not to conduct to the third electrode, wherein the sensor element is: A gas sensor element comprising a ceramic made of a material having a lower shrinkage start temperature than the material for forming the adhesive layer, and having a buffer portion formed on the surface of the third electrode so as to overlap a region between the first electrode and the second electrode and overlap the peripheral end portion of the first solid electrolyte body in plan view.

2. The third electrode is made of a porous ceramic having gas permeability. The gas sensor element according to claim 1, wherein the buffer portion is made of a non-gas-permeable dense ceramic.

3. The gas sensor element according to claim 1 or 2, wherein the buffer portion is made of a ceramic containing zirconia as a main component.

4. The gas sensor element according to any one of claims 1 to 3, wherein the third electrode is made of a cermet containing platinum powder and ceramic powder.

5. A gas sensor comprising the gas sensor element according to any one of claims 1 to 4.

6. A first insulating layer, a first solid electrolyte body disposed on the surface side so that the peripheral end portion does not protrude from the surface of the first insulating layer in plan view, and a pair of first electrodes and second electrodes each disposed on the surface of the first solid electrolyte body in a state of being separated from each other in plan view. A first cell having a second solid electrolyte body including an opposing surface facing the surface of the first insulating layer and an opposing surface on the opposite side of the opposing surface, a third electrode disposed on the opposing surface and disposed so as to overlap the peripheral end portion in plan view, and a fourth electrode disposed on the opposing surface. A second cell having a second cell, and an insulating adhesive layer interposed between the first cell and the second cell and bonding the first cell and the second cell in a state where the first electrode and the second electrode are separated so as not to conduct to the third electrode. A method for manufacturing a sensor element, A first manufacturing step of producing an unfired first cell including a first green sheet for forming the first insulating layer, an unfired first solid electrolyte body for forming the first solid electrolyte body disposed on the surface side of the first green sheet, and a pair of unfired first electrodes and unfired second electrodes for forming the first electrode and the second electrode each disposed on the surface of the unfired first solid electrolyte body in a state of being separated from each other in plan view. A second manufacturing step of producing an unfired second cell including a second green sheet for forming the second solid electrolyte body including an unfired opposing surface facing the surface of the first green sheet and an unfired opposing surface on the opposite side of the unfired opposing surface, an unfired third electrode for forming the third electrode disposed on the unfired opposing surface, and an unfired fourth electrode for forming the fourth electrode disposed on the unfired opposing surface. An adhesion step of adhering the unfired first cell and the unfired second cell with an unfired adhesive sheet for forming the adhesive layer interposed between the unfired first cell and the unfired second cell in a state where the unfired first electrode and the unfired second electrode are separated from the unfired third electrode and the unfired third electrode overlaps the unfired peripheral end portion of the unfired first solid electrolyte body in plan view. A firing step of firing the laminate obtained after the adhesion step. In the second manufacturing step, on the surface of the unfired third electrode, an unfired buffer portion for forming a buffer portion made of a material having a lower shrinkage start temperature than the material for forming the adhesive layer is formed so as to overlap the unfired peripheral portion while overlapping the region between the unfired first electrode and the unfired second electrode in the plan view. A method for manufacturing a gas sensor element.

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