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

Abstract

To suppress occurrence of cracks around space that becomes a measurement chamber.SOLUTION: A gas sensor element 100 includes: a second ceramic layer including a pump cell 110 in which a first electrode 112 and a second electrode 113 are provided on a surface of a first solid electrolyte body 111; a first ceramic layer that the first electrode 112 faces and that includes a measurement chamber into which a measurement object gas flows; a porous body covering the second electrode 113; and a dense layer that has a void and prevents permeation of a measurement object gas. The second electrode 113 and the void communicate via the porous body. A reinforcing layer which is porous and contains, as a main component, a component having a lower firing start temperature than a main component of the porous body is interposed between the second electrode 113 and the porous body at a position overlapping the void in a thickness direction of the porous body.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The technology disclosed by this specification relates to a gas sensor element, a gas sensor, and a method for manufacturing a gas sensor element.

Background Art

[0002] As a gas sensor for measuring the concentration of a specific component in the exhaust gas of an internal combustion engine, for example, a gas sensor described in Japanese Patent Application Laid-Open No. 2021-51058 (hereinafter referred to as Patent Document 1) is known. This gas sensor includes a sensor element mainly composed of ceramic. Inside the sensor element, there are a first measurement chamber used as a measurement chamber, a void for introducing the atmosphere serving as a reference gas therein, and an Ip1 cell disposed between the first measurement chamber and the void and including a solid electrolyte body and a pair of electrodes. A porous layer that allows the passage of the atmosphere is disposed on the surface of the electrodes. Such a sensor element is formed by laminating a plurality of ceramic green sheets and then firing them.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] ]> In the sensor element having the above configuration, during firing, the solid electrolyte body may warp convexly toward the first measurement chamber side and cracks may occur, and improvement has been demanded.

Means for Solving the Problems

[0005] A gas sensor element disclosed herein comprises a second ceramic layer including a pump cell on which a first electrode and a second electrode are provided on the surface of a solid electrolyte; a first ceramic layer including a measurement chamber facing the first electrode and into which a gas to be measured flows; a porous body covering the second electrode; and a dense layer having voids and not permeable to the gas to be measured, wherein the second electrode and the voids are in communication via the porous body, and a porous reinforcing layer is interposed between the second electrode and the porous body at a position overlapping the voids in the thickness direction of the porous body, the main component of which is a component with a lower sintering start temperature than the main component of the porous body.

[0006] Furthermore, the gas sensor disclosed in this embodiment includes the above-mentioned gas sensor element.

[0007] Furthermore, the method for manufacturing a gas sensor element disclosed herein comprises a second ceramic layer including a pump cell on which a first electrode and a second electrode are provided on the surface of a solid electrolyte; a first ceramic layer including a measurement chamber facing the first electrode and into which a gas to be measured flows; a porous body covering the second electrode; and a dense layer having voids and not permeable to the gas to be measured, wherein the second electrode and the voids are in communication via the porous body, and the method for manufacturing a gas sensor element comprises a lamination step of forming an unfired laminate which is the gas sensor element before firing, and the The process includes a firing step, which involves firing the unfired laminate after the lamination step to produce the gas sensor element, wherein the gas sensor element has a porous reinforcing layer interposed between the second electrode and the porous body at a position overlapping the void in the thickness direction of the porous body, the reinforcing layer being mainly composed of a component with a lower sintering start temperature than the main component of the porous body, and the lamination step includes filling the region of the unfired dense layer that becomes the void after firing with a disappearable material that disappears by firing, and forming an unfired reinforcing layer between the unfired second electrode and the unfired porous body. [Effects of the Invention]

[0008] According to the gas sensor element, gas sensor, and method for manufacturing the gas sensor element disclosed herein, it is possible to suppress the occurrence of cracks around the space that serves as the measurement chamber. [Brief explanation of the drawing]

[0009] [Figure 1] Figure 1 is a cross-sectional view of the gas sensor according to the embodiment. [Figure 2] Figure 2 is a side view of the gas sensor element of the embodiment, viewed from a direction perpendicular to the first insulating layer. [Figure 3] Figure 3 is a cross-sectional view of AA in Figure 2. [Figure 4] Figure 4 is an exploded perspective view of the gas sensor element of the embodiment. [Figure 5] Figure 5 is a cross-sectional view showing the gas sensor element of the embodiment in the process of being manufactured. [Modes for carrying out the invention]

[0010] [Summary of the Embodiment] (1) A gas sensor element disclosed herein comprises a second ceramic layer including a pump cell on which a first electrode and a second electrode are provided on the surface of a solid electrolyte; a first ceramic layer including a measurement chamber facing the first electrode and into which a gas to be measured flows; a porous body covering the second electrode; and a dense layer having voids and not permeable to the gas to be measured, wherein the second electrode and the voids are in communication via the porous body, and a porous reinforcing layer is interposed between the second electrode and the porous body at a position overlapping with the voids in the thickness direction of the porous body, the main component of which is a component with a lower sintering start temperature than the main component of the porous body.

[0011] Furthermore, the gas sensor disclosed in this embodiment includes the above-mentioned gas sensor element.

[0012] Furthermore, the method for manufacturing a gas sensor element disclosed herein comprises a second ceramic layer including a pump cell on which a first electrode and a second electrode are provided on the surface of a solid electrolyte; a first ceramic layer including a measurement chamber facing the first electrode and into which a gas to be measured flows; a porous body covering the second electrode; and a dense layer having voids and not permeable to the gas to be measured, wherein the second electrode and the voids are in communication via the porous body, and the method for manufacturing a gas sensor element comprises a lamination step of forming an unfired laminate which is the gas sensor element before firing, and the The process includes a firing step, which involves firing the unfired laminate after the lamination step to produce the gas sensor element, wherein the gas sensor element has a porous reinforcing layer interposed between the second electrode and the porous body at a position overlapping the void in the thickness direction of the porous body, the reinforcing layer being mainly composed of a component with a lower sintering start temperature than the main component of the porous body, and the lamination step includes filling the region of the unfired dense layer that becomes the void after firing with a disappearable material that disappears by firing, and forming an unfired reinforcing layer between the unfired second electrode and the unfired porous body. Here, the unfired dense layer is the dense layer before firing, the unfired porous body is the porous body before firing, and the unfired reinforcing layer is the reinforcing layer before firing.

[0013] The cracks around the measurement chamber are thought to be caused by the second ceramic layer warping during firing, causing it to protrude towards the measurement chamber. By interposing a reinforcing layer with a lower sintering start temperature than the porous body between the second electrode and the porous body, and having this reinforcing layer begin sintering before the second ceramic layer during firing, the warping of the second ceramic layer can be mitigated and crack formation can be suppressed.

[0014] (2) In the gas sensor element or gas sensor described in (1) above, the reinforcing layer may be mainly composed of zirconia.

[0015] (3) In the gas sensor element or gas sensor of (1) or (2) above, the reinforcing layer may be arranged so as to overlap with the measurement chamber arrangement region in which the measurement chamber is located, when viewed from the thickness direction of the first ceramic layer.

[0016] In the second ceramic layer, warping is likely to occur in a portion overlapping with the measurement chamber arrangement region. By arranging a reinforcing layer at a position overlapping with the measurement chamber arrangement region, generation of cracks can be more effectively suppressed.

[0017] (4) In any of the gas sensor elements or gas sensors according to (1) to (3) above, the reinforcing layer has an outer shape larger than the measurement chamber arrangement region, and may overlap with the entire measurement chamber arrangement region.

[0018] According to such a configuration, even if there is some displacement in the reinforcing layer during the manufacture of the gas sensor element, generation of cracks can be suppressed.

[0019] [Details of Embodiment] Specific examples of the technology disclosed by this specification will be described below with reference to FIGS. 1 to 5. Note that the present invention is not limited to these examples, and is intended to be shown by the claims and to include all modifications within the meaning and scope equivalent to the claims.

[0020] [Overall Configuration of Gas Sensor 1] The gas sensor 1 of the present embodiment is installed in a flow path of exhaust gas discharged from an engine (internal combustion engine) in a vehicle, and is a NOx sensor used for measuring the concentration of nitrogen oxides contained in the exhaust gas.

[0021] As shown in FIG. 1, the gas sensor 1 includes a gas sensor element 100, a main body fitting 11, an external protector 12, an internal protector 13, an outer cylinder 14, a holding member 18, an insulating member 19, and a plurality (six in the present embodiment) of terminal members 20. The gas sensor element 100 has an elongated plate shape extending in the axial direction AX (the vertical direction in FIG. 1) and is held inside the main body fitting 11. In the following description, the lower side in FIG. 1 is taken as the tip side, and the upper side in FIG. 1 is taken as the rear end side.

[0022] The main fitting 11 is a cylindrical member having a through hole 11A that penetrates in the direction of the axis AX. The main fitting 11 holds the gas sensor element 100 within the through hole 11A with the tip of the gas sensor element 100 protruding outwards from its tip side and the rear end of the gas sensor element 100 protruding outwards from its rear end side.

[0023] Inside the through-hole 11A of the main fitting 11 are an annular ceramic holder 15, two talc rings 16A and 16B filled with talc powder in an annular shape, and a ceramic sleeve 17. In detail, the ceramic holder 15, talc rings 16A and 16B, and ceramic sleeve 17 are arranged in this order, overlapping from the front end to the rear end of the main fitting 11, surrounding the gas sensor element 100.

[0024] An external metal protector 12 and an internal metal protector 13 are attached to the tip of the main fitting 11 by welding. The internal metal protector 13 is cylindrical in shape and extends in the axial direction AX, surrounding the tip of the gas sensor element 100. The external metal protector 12 is cylindrical in shape and extends in the axial direction AX, surrounding the internal metal protector 13. The external metal protector 12 and the internal metal protector 13 have multiple holes. An outer cylinder 14 is attached to the rear end of the main fitting 11 by welding. The outer cylinder 14 is cylindrical in shape and extends in the axial direction AX, surrounding the rear end of the gas sensor element 100.

[0025] Inside the outer cylinder 14, a retaining member 18 and an insulating member 19 are arranged in that order from the tip side. The retaining member 18 is made of an insulating material (specifically alumina) and is a cylindrical member having an insertion hole 18A that penetrates in the direction of the axis AX. The rear end of the gas sensor element 100 is placed inside the insertion hole 18A. The insulating member 19 is made of an insulating material (specifically alumina) and has a plurality of through holes 19A that penetrate in the direction of the axis AX.

[0026] Each terminal member 20 is made of a conductive material such as metal and includes an element contact portion 20A and a lead connection portion 20B connected to the element contact portion 20A. The element contact portion 20A is located inside the insertion hole 18A and is in contact with the gas sensor element 100. The lead connection portions 20B are located inside each of the multiple through holes 19A and are connected to the terminal ends of the lead wires 21. Note that Figure 1 shows two of the six terminal members 20 as examples.

[0027] An elastic sealing member 22 made of fluororubber is positioned at the rear end opening of the outer cylinder 14. Multiple lead wires 21 connected to multiple terminal members 20 are led out to the outside by passing through the elastic sealing member 22.

[0028] [Configuration of gas sensor element 100] As shown in Figure 3, the gas sensor element 100 includes a pump cell 110, a Vs cell 120, a detection cell 130, a first measurement chamber R1, a second measurement chamber R2, a reference oxygen chamber R3, and a heater 170.

[0029] As shown in Figures 3 and 4, the gas sensor element 100 has a structure in which the third dense layer 146C, the second dense layer 146B, the first dense layer 146A, the second insulating layer 142, the first insulating layer 141, the third insulating layer 143, the fourth insulating layer 144, the fifth insulating layer 145, the sixth insulating layer 171, and the seventh insulating layer 172 are stacked in this order. The first solid electrolyte 111 is formed on the second insulating layer 142. The second solid electrolyte 121 is formed on the third insulating layer 143. The third solid electrolyte 131 is formed on the fifth insulating layer 145.

[0030] The first measurement chamber R1 is a small space located between a layer composed of a second insulating layer 142 and a first solid electrolyte 111, and a layer composed of a third insulating layer 143 and a second solid electrolyte 121, and penetrates the first insulating layer 141. The first measurement chamber R1 is separated from the external space by a first diffusion resistor 151 through which gas can pass. The first diffusion resistor 151 limits the amount of exhaust gas flowing from the outside into the first measurement chamber R1 per unit time.

[0031] The second measurement chamber R2 is a small space provided between the layer composed of the second insulating layer 142 and the first solid electrolyte 111 and the layer composed of the fifth insulating layer 145 and the third solid electrolyte 131, and penetrates the first insulating layer 141, the third insulating layer 143, and the fourth insulating layer 144. The first measurement chamber R1 and the second measurement chamber R2 are separated by a second diffusion resistor 152 through which gas can pass. The second diffusion resistor 152 limits the amount of exhaust gas flowing from the first measurement chamber R1 to the second measurement chamber R2 per unit time.

[0032] The reference oxygen chamber R3 is a small space provided between the layer composed of the third insulating layer 143 and the second solid electrolyte 121 and the layer composed of the fifth insulating layer 145 and the third solid electrolyte 131, and penetrates the fourth insulating layer 144. Inside the reference oxygen chamber R3, a first porous body 161 that allows gas to pass through is arranged.

[0033] The second dense layer 146B has an air intake space 100G. The air intake space 100G is a small space provided between the first dense layer 146A and the third dense layer 146C, and penetrates the second dense layer 146B. The third dense layer 146C has an air inlet 100H that connects the air intake space 100G with the space outside the gas sensor element 100. Air, which will be a reference gas, is introduced into the air intake space 100G through the air inlet 100H. The first dense layer 146A has a porous second porous body 162 formed therein that allows air to pass through.

[0034] The insulating layers 141, 142, 143, 144, 145, 146A, 146B, 146C, 171, and 172 are dense layers mainly composed of alumina. The porous bodies 161, 162, and the diffusion resistors 151, 152 are porous bodies mainly composed of alumina. The solid electrolytes 111, 121, and 131 are mainly composed of zirconia having oxygen ion conductivity. In this embodiment, "main component" means a content of 50% by mass or more.

[0035] A first reinforcing layer 191 is interposed between the first dense layer 146A and the second insulating layer 142. The entire first reinforcing layer 191 is embedded inside the gas sensor element 100. The first reinforcing layer 191 is a porous material that allows air to pass through, and one surface (the top surface in Figure 3) is in contact with the second porous material 162. The first reinforcing layer 191 is mainly composed of a component (zirconia in this embodiment) that has a lower shrinkage initiation temperature than the main component (alumina in this embodiment) of the second porous material 162. The first reinforcing layer 191 is porous.

[0036] The first reinforcing layer 191 has a larger outer shape than the measurement chamber arrangement region Ar where the measurement chambers R1 and R2 are located, when viewed from a direction perpendicular to the first insulating layer 141 (the thickness direction of the first insulating layer 141 in Figure 3), and is arranged to overlap with the entire measurement chamber arrangement region Ar (see Figure 2). In this embodiment, when the gas sensor element 100 has multiple measurement chambers R1 and R2, the measurement chamber arrangement region Ar is an area that covers all of the multiple measurement chambers R1 and R2 when viewed from a direction perpendicular to the first insulating layer 141.

[0037] The pump cell 110 comprises a first solid electrolyte 111, a first electrode 112 positioned on the surface of the first solid electrolyte 111 (the lower surface in Figure 3), and a second electrode 113 positioned on another surface of the first solid electrolyte 111 (the upper surface in Figure 3) and paired with the first electrode 112. The first electrode 112 is positioned facing the first measurement chamber R1. The second electrode 113 is positioned outside the first measurement chamber R1 and is in contact with the surface of the first reinforcing layer 191 opposite to the surface in contact with the second porous body 162 (the lower surface in Figure 3). That is, the first reinforcing layer 191 is interposed between the second electrode 113 and the second porous body 162.

[0038] The Vs cell 120 comprises a second solid electrolyte 121, a third electrode 122 positioned on the surface of the second solid electrolyte 121 (upper surface in Figure 3), and a fourth electrode 123 positioned on the other surface of the second solid electrolyte 121 (lower surface in Figure 3) and paired with the third electrode 122. The third electrode 122 is positioned facing the first measurement chamber R1. The fourth electrode 123 is positioned facing the reference oxygen chamber R3.

[0039] The detection cell 130 comprises a third solid electrolyte 131, a fifth electrode 132 positioned on the surface of the third solid electrolyte 131 (the upper surface in Figure 3), and a sixth electrode 133 positioned on the surface of the third solid electrolyte 131 (the upper surface in Figure 3) and paired with the fifth electrode 132. The fifth electrode 132 is positioned facing the second measurement chamber R2. The sixth electrode 133 is positioned facing the reference oxygen chamber R3 and opposite the fourth electrode 123.

[0040] The first electrode 112, the third electrode 122, and the fifth electrode 132 are each connected to a reference potential.

[0041] Between the first insulating layer 141 and the second insulating layer 142, an alumina insulating layer 181 is positioned except for the first electrode 112. Between the first insulating layer 141 and the third insulating layer 143, between the third insulating layer 143 and the fourth insulating layer 144, and between the fourth insulating layer 144 and the fifth insulating layer 145, alumina insulating layers 182, 183, and 184 are interposed, respectively, except for electrodes 122, 123, 132, 133 and the second measurement chamber R2. For the sake of clarity in the drawing, the alumina insulating layers 182, 183, and 184 are omitted in Figure 4.

[0042] Second reinforcing layers 192A and 192B are positioned between the alumina insulating layer 181 and the first insulating layer 141, and between the first insulating layer 141 and the third insulating layer 143, along the opening edge of the first measurement chamber R1. A third reinforcing layer (not shown) is positioned between the third dense layer 146C and the second dense layer 146B, and between the second dense layer 146B and the first dense layer 146A, along the opening edge of the air intake space 100G. The second reinforcing layers 192A, 192B, and the third reinforcing layer are mainly composed of zirconia, similar to the first reinforcing layer 191. Note that, for the sake of readability, the second reinforcing layers 192A, 192B, and the third reinforcing layer are omitted in Figure 3. Furthermore, although not shown in detail, a reinforcing layer mainly composed of zirconia is also provided at the edge of the surface of the third insulating layer 143 that faces the fourth insulating layer 144 (the lower surface in Figure 3).

[0043] The heater 170 comprises a sixth insulating layer 171, a seventh insulating layer 172, and a resistance heating element 173 embedded between the sixth insulating layer 171 and the seventh insulating layer 172, which generates heat when an electric current is passed through it. The heater 170 is used to heat the solid electrolytes 111, 121, and 131 to a temperature at which they are activated, thereby increasing the conductivity of oxygen ions in the solid electrolytes 111, 121, and 131 and stabilizing their operation.

[0044] The electrodes 112, 113, 122, 123, 132, 133 and the resistance heating element 173 are mainly composed of platinum.

[0045] The surface of the gas sensor element 100 is arranged with six electrodes 112, 113, 122, 123, 132, and 133, each of which is electrically connected to six electrode terminal portions Ts via leads and through holes. The element contact portions 20A of the six terminal members 20 are elastically in contact with the six electrode terminal portions Ts, respectively.

[0046] [Operating mode of gas sensor 1] The process of measuring nitrogen oxides in the vehicle's exhaust gas using the gas sensor 1 described above will be briefly explained.

[0047] When the vehicle engine is started and a drive current flows through the resistive heating element 173, the resistive heating element 173 heats up, and the solid electrolytes 111, 121, and 131 are heated and activated. This causes the pump cell 110, Vs cell 120, and sensing cell 130 to operate.

[0048] The exhaust gas enters the first measurement chamber R1, its flow rate restricted by the first diffusion resistor 151. At this time, a weak current Ip1 flows through the Vs cell 120 from the fourth electrode 123 to the third electrode 122. As a result, the oxygen in the exhaust gas in the first measurement chamber R1 can receive electrons from the third electrode 122, which acts as the negative electrode, and become oxygen ions. These ions then flow through the second solid electrolyte 121 and move into the reference oxygen chamber R3. In other words, the oxygen in the first measurement chamber R1 is sent into the reference oxygen chamber R3.

[0049] If the oxygen concentration of the exhaust gas in the first measurement chamber R1 is lower than a predetermined value, a current Ip1 is passed through the pump cell 110 so that the second electrode 113 becomes the negative electrode, and oxygen is drawn into the first measurement chamber R1 from the outside. On the other hand, if the oxygen concentration of the exhaust gas introduced into the first measurement chamber R1 is higher than a predetermined value, a current Ip1 is passed through the pump cell 110 so that the first electrode 112 becomes the negative electrode, and oxygen is drawn out from the first measurement chamber R1 to the outside.

[0050] In the first measurement chamber R1, the exhaust gas, whose oxygen concentration has been adjusted, enters the second measurement chamber R2 while its flow rate is restricted by the second diffusion resistor 152. In the second measurement chamber R2, nitrogen oxides in the exhaust gas that come into contact with the fifth electrode 132 are decomposed into nitrogen and oxygen on the fifth electrode 132 when a voltage Vp2 is applied between the fifth electrode 132 and the sixth electrode 133. The oxygen generated by the decomposition becomes oxygen ions and flows through the third solid electrolyte 131, moving into the reference oxygen chamber R3. At this time, the current Ip2 flowing through the detection cell 130 shows a value corresponding to the nitrogen oxide concentration, so the nitrogen oxide concentration in the exhaust gas can be determined based on this current value.

[0051] [Manufacturing method for gas sensor element 100] Next, an example of a method for manufacturing the gas sensor element 100 with the above configuration will be explained with reference to Figure 5.

[0052] First, an unfired laminate L, which is the gas sensor element 100 before firing, is manufactured (lamination process). The unfired laminate L is a laminate that includes, from bottom to top, an unfired fifth ceramic layer 145U which will become the fifth insulating layer 145 after firing, an unfired fourth ceramic layer 144U which will become the fourth insulating layer 144 after firing, an unfired third ceramic layer 143U which will become the third insulating layer 143 after firing, an unfired first ceramic layer 141U which will become the first insulating layer 141 after firing, an unfired second ceramic layer 142U which will become the second insulating layer 142 after firing, an unfired dense layer 146AU which will become the first dense layer 146A after firing, and an unfired dense layer 146BU which will become the second dense layer 146B after firing. An unfired third solid electrolyte 131U, which will become the third solid electrolyte 131 after firing, is formed on the unfired fifth ceramic layer 145U. An unfired fifth electrode 132U, which will become the fifth electrode 132 after firing, and an unfired sixth electrode 133U, which will become the sixth electrode 133, are formed on the surface of the unfired third solid electrolyte 131U. An unfired fourth ceramic layer 144U and an unfired third ceramic layer 143U are sequentially formed on this unfired fifth ceramic layer 145U, with unfired insulating layers 183U and 184U, which will become the alumina insulating layers 183 and 184 after firing, sandwiched in between. An unfired first porous body 161U, which will become the first porous body 161 after firing, is formed on the unfired fourth ceramic layer 144U at the position that will become the reference oxygen chamber R3. An unfired third ceramic layer 143U has an unfired second solid electrolyte 121U formed on it, which will become the second solid electrolyte 121 after firing. An unfired third electrode 122U and an unfired fourth electrode 123U are formed on the surface of the unfired second solid electrolyte 121U, which will become the third electrode 122 and the fourth electrode 123 after firing.

[0053] Next, an unfired first ceramic layer 141U is formed on the unfired third ceramic layer 143U, with an unfired insulating layer 182U, which will become an alumina insulating layer 182 after firing, sandwiched in between. A first through-hole H1 is formed through the unfired first ceramic layer ceramic green sheet 141U in the thickness direction, and an unfired first diffusion resistor 151U, which will become a first diffusion resistor 151 after firing, is formed inside this first through-hole H1.

[0054] Furthermore, a second through-hole H2 is formed through the unfired second ceramic layer 142U, and an unfired first solid electrolyte 111U, which will become the first solid electrolyte 111 after firing, is formed inside this second through-hole H2. Then, an unfired first electrode 112U, which will become the first electrode 112 after firing, is formed on one surface of the unfired first solid electrolyte 111U, and an unfired second electrode 113U, which will become the second electrode 113 after firing, is formed on the other surface.

[0055] Furthermore, a third through-hole H3 is formed through the unfired dense layer 146AU, and an unfired second porous body 162U, which will become the second porous body 162 after firing, is embedded inside this third through-hole H3. The unfired second porous body 162U is a sheet containing, for example, a first ceramic material made of ceramics and a disappearing material that disappears upon firing. The first ceramic material is, for example, alumina powder, and the disappearing material is, for example, carbon powder.

[0056] Furthermore, a fourth through-hole H4, which serves as an air intake space 100G, is formed through the unfired dense layer 146BU, and this fourth through-hole H4 is filled with a disappearing paste Pd containing a disappearing material that disappears during firing. The disappearing material is, for example, carbon powder.

[0057] An unfired reinforcing layer 191U is formed on the surface of the unfired second ceramic layer 142U, containing a ceramic material and a disappearing material that burns away during firing, and having a lower shrinkage start temperature than the unfired second porous body 162U, so as to cover the unfired second electrode 113U.

[0058] Furthermore, other unfired dense layers and unfired ceramic layers are formed to become the third dense layer 146C, the sixth insulating layer 171, and the seventh insulating layer 172. The resistive heating element 173 and the air inlet 100H are formed in these unfired dense layers and unfired ceramic layers. Note that in Figure 5, these unfired dense layers and unfired ceramic layers are omitted for clarity. The unfired laminate L is formed in the manner described above.

[0059] After the lamination process, the unfired laminate L is fired to produce the gas sensor element 100 (firing process).

[0060] The resulting gas sensor element 100 may have cracks around the space that forms the first measurement chamber R1. Observation of the gas sensor element 100 reveals that the second insulating layer 142 is warped so as to be convex toward the first measurement chamber R1, indicating that the crack originates on the first measurement chamber R1 side. From this, it is inferred that tensile stress is generated at the interface of the second insulating layer 142 toward the first measurement chamber R1. In this embodiment, an unfired reinforcing layer 191U, which has a lower shrinkage start temperature than the unfired second porous body 162U, is interposed between the unfired second electrode 113U, which forms the second electrode 113, and the unfired second porous body 162U, which forms the second porous body 162. During firing, the unfired reinforcing layer 191U shrinks before the unfired second porous body 162U, thereby mitigating the tensile stress generated at the interface of the second insulating layer 142 toward the first measurement chamber R1. This reduces warping of the second insulating layer 142 and suppresses the occurrence of cracks.

[0061] [Effects and Effects] As described above, according to this embodiment, the gas sensor element 100 includes a second insulating layer 142 which includes a pump cell 110 on the surface of a first solid electrolyte 111 with a first electrode 112 and a second electrode 113 provided thereon; a first insulating layer 141 which includes a first measurement chamber R1 into which the first electrode 112 faces and into which the gas to be measured flows; a second porous body 162 which covers the second electrode 113; and a dense layer 146 which has an atmospheric introduction space 100G and does not allow the gas to be measured to pass through. A, 146B, 146C are provided, and the second electrode 113 and the atmospheric introduction space 100G are in communication via the second porous body 162, wherein a first reinforcing layer 191 is interposed between the second electrode 113 and the second porous body 162 at a position overlapping with the atmospheric introduction space 100G in the thickness direction of the second porous body 162, the first reinforcing layer 191 being porous and mainly composed of a component with a lower sintering start temperature than the main component of the second porous body 162.

[0062] Furthermore, the manufacturing method for the gas sensor element 100 of this embodiment comprises a second insulating layer 142 including a pump cell 110 on the surface of a first solid electrolyte 111 with a first electrode 112 and a second electrode 113 provided thereon, a first insulating layer 141 including a first measurement chamber R1 facing the first electrode 112 and through which the gas to be measured flows, a second porous body 162 covering the second electrode 113, and a first dense layer 146A, a second dense layer 146B, and a third dense layer 146C having an atmospheric introduction space 100G and not permeating the gas to be measured, wherein the second electrode 113 and the atmospheric introduction space 100G are in communication via the second porous body 162, and the manufacturing method for the gas sensor element 100 comprises a lamination step of forming an unfired laminate L which is the gas sensor element 100 before firing, A method for manufacturing a gas sensor element 100, comprising: a firing step after a lamination step, in which an unfired laminate L is fired to produce a gas sensor element 100, wherein the gas sensor element 100 has a porous first reinforcing layer 191 interposed between a second electrode 113 and a second porous body 162 at a position in the thickness direction of the second porous body 162 that overlaps with the air introduction space 100G, the first reinforcing layer 191 having a component whose sintering start temperature is lower than that of the main component of the second porous body 162, and the lamination step includes filling the region of the unfired dense layers 146AU, 146BU that will become the air introduction space 100G after firing with a disappearable paste Pd that will disappear by firing, and forming an unfired reinforcing layer 191U between the unfired second electrode 113U and the unfired second porous body 162U.

[0063] The cracks around the first measurement chamber R1 are thought to be caused by the second insulating layer 142 warping during firing, becoming convex towards the first measurement chamber R1. By interposing a first reinforcing layer 191, mainly composed of zirconia and having a lower shrinkage start temperature than the second porous body 162, between the second electrode 113 and the second porous body 162, and causing this first reinforcing layer 191 to shrink before the second porous body 162 during firing, the warping of the second insulating layer 142 can be mitigated and the occurrence of cracks can be suppressed.

[0064] Furthermore, the first reinforcing layer 191 is positioned so as to overlap with the measurement chamber arrangement region Ar, where the measurement chambers R1 and R2 are located, when viewed from the thickness direction of the first insulating layer 141.

[0065] In the second insulating layer 142, warping is likely to occur in the area that overlaps with the measurement chamber arrangement area Ar. By placing the first reinforcing layer 191 in the area that overlaps with the measurement chamber arrangement area Ar, the occurrence of cracks caused by warping of the second insulating layer 142 can be suppressed more effectively.

[0066] Furthermore, the first reinforcing layer 191 has a larger outer shape than the measurement chamber placement area Ar and overlaps with the entire measurement chamber placement area Ar. With this configuration, even if there is some misalignment of the first reinforcing layer 191 during the manufacturing of the gas sensor element 100, the first reinforcing layer 191 can be reliably positioned in a location that overlaps with the measurement chamber placement area Ar, thereby suppressing the occurrence of cracks.

[0067] <Other Embodiments> (1) In the above embodiment, the gas sensor was a NOx sensor that measures nitrogen oxides in exhaust gas, but the type of gas sensor is not limited to the above embodiment, and for example, it may be an oxygen sensor that measures the oxygen concentration in the gas to be measured. Also, the gas to be measured is not limited to exhaust gas, and various gases can be measured. (2) In the above embodiment, the gas sensor element 100 had a first measurement chamber R1 and a second measurement chamber R2, but the number of measurement chambers provided in the gas sensor element is arbitrary, and for example, the gas sensor element may have only one measurement chamber. [Explanation of symbols]

[0068] 1: Gas sensor 20: Terminal member 20A: Element contact portion 100: Gas sensor element 100G: Air intake space (gap) 100H: Air intake port 110: Pump Cell 111: First solid electrolyte (solid electrolyte) 111U: Unfired first solid electrolyte (unfired solid electrolyte) 112: First electrode 112U: Unfired first electrode 113: Second electrode 113U: Unfired second electrode 121: Second solid electrolyte 121U: Uncalcined second solid electrolyte 122: Third electrode 122U: Unfired third electrode 123: Fourth electrode 123U: Unfired fourth electrode 131: Third solid electrolyte 131U: Uncalcined third solid electrolyte 132: Fifth electrode 132U: Unfired fifth electrode 133: 6th electrode 133U: Unfired 6th electrode 141: First insulating layer (first ceramic layer) 141U: Unfired first ceramic layer 142: Second insulating layer (second ceramic layer) 142U: Unfired second ceramic layer 143: Third insulating layer 143U: Unfired third ceramic layer 144: Fourth insulating layer 144U: Unfired fourth ceramic layer 145: Fifth insulating layer 145U: Unfired fifth ceramic layer 146A: First dense layer (dense layer) 146AU: Unfired dense layer 146B: Second dense layer (dense layer) 146BU: Unfired dense layer 146C: 3rd layer compacta (layer compacta) 151: First diffusion resistor 151U: Unfired first diffusion resistor 152: Second diffusion resistor 152U: Unfired second diffusion resistor 161: First porous material 161U: Unfired first porous material 162: Second porous material (porous material) 162U: Unfired second porous material (unfired porous material) 171: Sixth insulating layer 172: Seventh insulating layer 173: Resistive heating element 181: Alumina insulating layer 182: Alumina insulating layer 182U: Unfired insulating layer 183: Alumina insulating layer 183U: Unfired insulating layer 184: Alumina insulating layer 184U: Unfired insulating layer 191: First reinforcement layer (reinforcement layer) 191U: Unfired reinforcement layer Ar: Measurement chamber placement area H1: First through hole; H2: Second through hole; H3: Third through hole; H4: Fourth through hole (space). L: Unfired laminate Pd: disappearing material (disappearing material) R1: First testing chamber (testing chamber) R2: Second testing chamber (testing chamber) R3: Standard oxygen chamber Ts: Electrode terminal section

Claims

1. A second ceramic layer includes a pump cell on which a first electrode and a second electrode are provided on the surface of a solid electrolyte, A first ceramic layer, which includes a measurement chamber into which the first electrode faces and into which the gas to be measured flows, A porous body covering the second electrode, It comprises a dense layer having voids and not permeable to the gas to be measured, The second electrode and the void are in communication via the porous body, forming a gas sensor element. A gas sensor element comprising a porous reinforcing layer interposed between the second electrode and the porous body at a position overlapping with the void in the thickness direction of the porous body, the reinforcing layer having a main component with a lower sintering start temperature than the main component of the porous body.

2. The gas sensor element according to claim 1, wherein the reinforcing layer is mainly composed of zirconia.

3. The gas sensor element according to claim 1, wherein the reinforcing layer is arranged to overlap with the measurement chamber arrangement region where the measurement chamber is located, when viewed from the thickness direction of the first ceramic layer.

4. The gas sensor element according to claim 3, wherein the reinforcing layer has an outer shape larger than the measurement chamber arrangement area and overlaps with the entire measurement chamber arrangement area.

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

6. A second ceramic layer includes a pump cell on which a first electrode and a second electrode are provided on the surface of a solid electrolyte, A first ceramic layer, which includes a measurement chamber into which the first electrode faces and into which the gas to be measured flows, A porous body covering the second electrode, It comprises a dense layer having voids and not permeable to the gas to be measured, A method for manufacturing a gas sensor element, wherein the second electrode and the void are in communication via the porous body, A lamination process for forming an unfired laminate which is the gas sensor element before firing, The process includes, after the lamination process, a firing process in which the unfired laminate is fired to produce the gas sensor element, The gas sensor element has a reinforcing layer interposed between the second electrode and the porous body at a position overlapping with the void in the thickness direction of the porous body, the reinforcing layer being porous and having a main component that has a lower sintering start temperature than the main component of the porous body. The aforementioned lamination process is In the unfired dense layer, the regions that become voids after firing are filled with a disappearing material that vanishes during firing. Forming an unfired reinforcing layer between the unfired second electrode and the unfired porous body, A method for manufacturing a gas sensor element, including

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