Gas sensor element and gas sensor

Abstract

Gas sensor element (100), comprising: a plate-shaped laminated structure (190) in which several ceramic layers (110, 120, 130) are laminated, wherein the several ceramic layers (110, 120, 130) have a solid electrolyte ceramic layer (110) with an electrode (212) formed on a surface (118) thereof, wherein the laminated structure (190) has a gap (180) formed between the solid electrolyte ceramic layer (110) and a second ceramic layer (120), which extends in a longitudinal direction (X) of the laminated structure (190), and to which the electrode (212) is exposed, wherein a cross-sectional shape of the gap (180) obtained by cutting the laminated structure (190) along a plane (YZ) orthogonal to the longitudinal direction (X), an endpoint A, which is one of the contact points with which the cross-sectional shape is in single-point contact with a virtual straight line (VLa) parallel to a lamination direction (Z) of the multiple ceramic layers (110, 120, 130), wherein one contact point is closest to a side surface (193) of the laminated structure (190) extending in the longitudinal direction (X) and in the lamination direction (Z), an endpoint B, which is one of the contact points closest to another side surface (194) of the laminated structure (190) opposite the one side surface (193), an endpoint C, which has the greatest distance from a straight line AB,which passes through endpoint A and endpoint B in the direction of the solid electrolyte ceramic layer (110), and has an endpoint D which is at the greatest distance from the straight line AB in the direction of the second ceramic layer (120); , a distance H1 between the straight line AB and the endpoint C and a distance H2 between the straight line AB and the endpoint D a relation 0.25 ≤ H1 / H2 < 1.00 or a relation 1.00 < H1 / H2 ≤ 4.00 must be satisfied; and a height H of the gap (180), which is the sum of the distance H1 and the distance H2, lies within a range of 10 µm to 100 µm, where the cross-sectional shape is convex in the direction towards endpoint C and is also convex in the direction towards endpoint D.

Description

Technical field

[0001] The present invention relates to a gas sensor element and a gas sensor. Background of the invention

[0002] A plate-shaped gas sensor element comprising several stacked ceramic layers is known as a gas sensor element used in gas sensors (see, for example, patents 1 to 3). Such a gas sensor element has a solid electrolyte ceramic layer as one of the ceramic layers. Electrodes for detecting a specific gas component contained in an object gas (the gas to be measured) are formed on the surfaces of the solid electrolyte ceramic layer. A gap for guiding a reference gas or the object gas to the corresponding electrode is provided in the gas sensor element. Generally, a gas sensor includes a heating element, and the electrical power required to heat the heating element can be reduced by reducing the size of the gas sensor.JP 2007-248 219 A discloses a ceramic laminate and its manufacturing process, which prevents the laminate from cracking or peeling. JP 4 272 962 B2 discloses a gas sensor element. patent specifications Patent specification 1: JP 2010 261727 A Patent specification 2: JP 2003 185622 A Patent specification 3: JP 2002 340845 A Summary of the invention

[0003] To meet the demand for reduced power consumption, the size of the gas sensor can be reduced by decreasing the height of the gap in the gas sensor element, thereby reducing its thickness. However, the gas sensor elements disclosed in patents 1 to 3 have a problem: when the gap height is reduced, the gas sensor element breaks during the manufacturing process and lacks sufficient strength. In particular, if a gas sensor element is used in an environment with relatively large temperature fluctuations (e.g., in the exhaust system of an internal combustion engine), it may break due to thermal shock caused by repeated rapid temperature rises and cooldowns, even if it does not break during the manufacturing process.Therefore, such a gas sensor element must have sufficient resistance to thermal shock (thermal shock resistance).

[0004] The present invention was developed to solve the problems described above and can be implemented in the following ways.

[0005] (1) According to one embodiment of the present invention, a gas sensor element is provided comprising a plate-shaped laminated structure in which several ceramic layers, comprising a solid electrolyte ceramic layer with an electrode formed on one surface thereof, are laminated, wherein the laminated structure has a gap formed between the solid electrolyte ceramic layer and a second ceramic layer, extending in a longitudinal direction of the laminated structure and to which the electrode is exposed. In the gas sensor element, a cross-sectional shape of the gap, which is obtained by cutting the laminated structure along a plane orthogonal to the longitudinal direction, has an endpoint A, which is one of contact points with which the cross-sectional shape is in single-point contact with a virtual straight line that is parallel to a lamination direction of the several ceramic layers.wherein one contact point is located closest to a side face of the laminated structure extending in the longitudinal direction and in the lamination direction, an endpoint B, which is one of the contact points located closest to another side face of the laminated structure opposite the first side face, an endpoint C, which is furthest from a straight line AB passing through endpoint A and endpoint B towards the solid electrolyte ceramic layer, and an endpoint D, which is furthest from the straight line AB towards the second ceramic layer. A distance H1 between the straight line AB and endpoint C and a distance H2 between the straight line AB and endpoint D satisfy a relation 0.25 ≤ H1 / H2 < 1.00 or a relation 1.00 < H1 / H2 ≤ 4.00, and a height H of the gap, which is the sum of the distance H1 and the distance H2.The gap height is in the range of 10 µm to 100 µm. It is noted that the cross-sectional shape of the gap is defined by the solid electrolyte ceramic layer and a second ceramic layer. This design makes it possible to suppress the formation of fractures in the gas sensor element during its manufacture. Therefore, it is possible to produce a sufficiently stable gas sensor element while reducing the gap height. As a result, the thickness of the gas sensor element can be reduced. Furthermore, the gap height H is in the range of 10 µm to 100 µm. This makes it possible to improve the thermal shock resistance of the gas sensor element while allowing a sufficient amount of air to pass through the gap. If the gap height H is less than 10 µm, the gap may not allow a sufficient amount of air to pass through.to pass through the gap. If the gap height H is greater than 100 µm, the thermal shock resistance of the gas sensor element deteriorates. Therefore, it is not preferred for the gap height H to be less than 10 µm or greater than 100 µm.

[0006] (2) In the gas sensor element described above, the distance H1 and the distance H2 can satisfy a ratio of 0.25 ≤ H1 / H2 ≤ 0.67 or a ratio of 1.50 ≤ H1 / H2 ≤ 4.00. The strength of the gas sensor element can be further increased in this way.

[0007] (3) In the gas sensor element described above, the cross-sectional shape can be convex towards endpoint C and also convex towards endpoint D. In this way, stress generated near the gap can be distributed. As a result, the strength of the gas sensor element can be increased.

[0008] (4) In the gas sensor element described above, the gap can be an air inlet opening for directing air to the electrode. In this way, it is possible to manufacture the gas sensor element with sufficient stability while reducing the height of the air inlet opening.

[0009] (5) In the gas sensor element described above, the height H can be in a range of 10 µm to 40 µm. Therefore, it is possible to further improve the thermal shock resistance of the gas sensor element while allowing a sufficient amount of air to pass through the gap.

[0010] The present invention can be implemented in various forms other than the gas sensor element. For example, the present invention can be implemented in the form of a gas sensor comprising the gas sensor element described above or a manufacturing process for producing the gas sensor element described above. Brief description of the drawings Fig. Figure 1 is a cross-sectional view of a gas sensor. Fig. Figure 2 is an external perspective view of a gas sensor element. Fig. Figure 3 is a stretched perspective view of the gas sensor element. Fig. Figure 4 is a cross-sectional view of the gas sensor element along the line F4 - F4 of the Fig. 2. Fig. Figure 5 is a cross-sectional view of the gas sensor element along the line F5 - F5 of the Fig. 2. Fig.Figure 6 is an explanatory view that schematically shows the cross-sectional shape of a gap. Fig. Figure 7 is a table showing the results of an evaluation test that was carried out for different values ​​of the distances H1 and H2. Fig. Figure 8 is a cross-sectional view of a laminated structure of sample 1. Fig. Figure 9 is a cross-sectional view of a laminated structure of sample 6. Fig. Figure 10 is a cross-sectional view of a laminated structure of sample 5. Fig. Figure 11 is a cross-sectional view of a laminated structure of sample 7. Fig. Figure 12 is a flowchart showing a process for manufacturing a gas sensor element. Fig. Figure 13 is a flowchart showing a method for manufacturing a gas sensor element according to another embodiment. Detailed Description A. Design A-1. Structure of the Gas Sensor

[0011] Fig. Figure 1 is a cross-sectional view of a gas sensor 10. The cross-section of the Fig. Figure 1 is a cross-section obtained by cutting the gas sensor 10 along a plane passing through an axial line AX, which is the central axis of the gas sensor 10. In the description of the present embodiment, one side of the gas sensor 10, which is located at the bottom of the sheet of Fig. 1 is arranged, referred to as a "front side", and a side of the gas sensor 10, which is located on top of the sheet of the Fig. A side arranged in 1 is referred to as a "rear end".

[0012] The gas sensor 10 is an oxygen sensor which is mounted in the exhaust system of an internal combustion engine and is designed to detect oxygen (O2) contained in the exhaust gas. The gas sensor 10 comprises a gas sensor element 100, a protective device 300, a metallic casing or housing 400, an element holding section 500, an outer tube 600, an insulator 700 and a cable 800.

[0013] The gas sensor element 100 of the gas sensor 10 is a plate-shaped laminated ceramic device in which several ceramic layers are laminated. The gas sensor element 100 forms an oxygen concentration cell which, as a sensor output, provides an electromotive force corresponding to the partial pressure of oxygen. The details of the gas sensor element 100 are described later.

[0014] The gas sensor element 100 is electrically connected via cable 800 to a processing circuit (not shown) for processing the sensor output from the gas sensor element 100. In the present embodiment, the cable 800 comprises four connecting wires 810a, 810b, 810c, and 810d and connecting terminals 820a, 820b, 820c, and 820d, which are electrically connected to the gas sensor element 100 and are crimped onto the corresponding connecting wires. The connecting terminals 820a, 820b, 820c, and 820d are mechanically and electrically connected to electrode contact surfaces (which will be described later) of the gas sensor element 100 while being pressed against the electrode contact surfaces.

[0015] The protective device 300 of the gas sensor 10 is a metallic element in the form of a cylindrical tube with a base. The protective device 300 is attached to the front end of the metallic casing 400 and covers the gas sensor element 100, which protrudes from the front end of the metallic casing 400. Consequently, the protective device 300 protects a front-end section of the gas sensor element 100. The protective device 300 has through openings for introducing an object gas towards the gas sensor element 100.

[0016] The metallic casing 400 of the gas sensor 10 is a metallic element in the shape of a cylindrical tube. The gas sensor element 100 is held securely within the metallic casing 400 by the element holding section 500.

[0017] The element holding section 500 of the gas sensor 10 is a section for holding the gas sensor element 100 within the metallic casing 400. The gas sensor element 100 extends through the center of the element holding section 500. In the present embodiment, the element holding section 500 has a ceramic holder 510, a talc ring 520, a talc ring 530, and a ceramic sleeve 540, which are arranged in this order from the front.

[0018] The ceramic holder 510 of the element holding section 500, which is a tubular ceramic element, is inserted into the metallic casing 400 and positions the sensor element 100 within the metallic casing 400. The talc ring 520 and the talc ring 530 of the element holding section 500 are formed beforehand by compressing talc powder into a solid. The talc ring 520 and the talc ring 530 are arranged between the ceramic holder 510 and the ceramic sleeve 540 in a state in which they are pushed forward by the ceramic sleeve 540. The ceramic sleeve 540 of the element holding section 500 is a tubular ceramic element. The ceramic sleeve 540 is attached to the rear end of the metallic casing 400 by means of compression in a state in which the ceramic sleeve 540 is pushed forward in order to position the gas sensor element 100 inside the metallic casing 400.

[0019] The outer tube 600 of the gas sensor 10 is a metallic element in the shape of a cylindrical tube. The outer tube 600 is welded to the rear end of the metallic casing 400 and covers the gas sensor element 100, which protrudes from the rear end of the metallic casing 400. Consequently, the outer tube 600 protects a rear end section of the gas sensor element 100. The cable 800 is held at the rear end of the outer tube 600.

[0020] The insulator 700 of the gas sensor 10 is a tubular element made of electrically insulating ceramic. The insulator 700 is fixedly arranged inside the outer tube 600 and holds the connection terminals 820a, 820b, 820c and 820d. A-2. Structure of the gas sensor element

[0021] Fig. Figure 2 is an external perspective view of the gas sensor element 100. Fig.Figure 3 is a stretched perspective view of the gas sensor element 100. Fig. Figure 4 is a cross-sectional view of the gas sensor element 100 along the line F4 - F4 of the Fig. 2. Fig. 5 a cross-sectional view of the gas sensor element 100 along the line F5 - F5 of the Fig. 2. X, Y, and Z axes that intersect each other perpendicularly are in Fig. 2 shown. The X, Y, and Z axes of the Fig. 2 correspond to the X, Y and Z axes in other drawings.

[0022] From the X, Y, and Z axes of the Fig.2. The X-axis is an axis along the longitudinal direction of the gas sensor element 100. In a state where the gas sensor element 100 is inserted into the gas sensor 10, the X-axis of the gas sensor element 100 extends along the axial line AX. Of the X-axis directions along the X-axis, a +X-axis direction corresponds to an axial direction from the front towards the rear end (along the axial line AX), and a -X-axis direction is a direction opposite to the +X-axis direction.

[0023] From the X, Y and Z axes of the Fig. 2. The Y-axis is an axis along the lateral direction of the gas sensor element 100. Of the Y-axis directions along the Y-axis, a +Y-axis direction is a direction from the top of the leaf. Fig. 2 in the direction towards its rear end, and a -Y-axis direction is a direction which is opposite to the +Y-axis direction.

[0024] From the X, Y and Z axes of the Fig. 2. The Z-axis is an axis along the thickness direction of the gas sensor element 100. Of the Z-axis directions along the Z-axis, a +Z-axis direction is a direction from the underside of the sheet of the Fig. 2 in the direction towards its top side, and a -Z-axis direction is a direction which is opposite to the +Z-axis direction.

[0025] The gas sensor element 100 has a plate-shaped laminated structure 190 in which several ceramic layers are laminated together. The laminated structure 190 is a rectangular or right-angled parallelepiped with outer surfaces 191, 192, 193, 194, 195 and 196.

[0026] The outer surface 191 of the laminated structure 190 is a surface that points in the +Z-axis direction, and the outer surface 192 of the laminated structure 190 is a surface that points in the -Z-axis direction. The outer surface 193 of the laminated structure 190 is a surface that points in the -Y-axis direction, and the outer surface 194 of the laminated structure 190 is a surface that points in the +Y-axis direction. The outer surface 195 of the laminated structure 190 is a surface that points in the +X-axis direction, and the outer surface 196 of the laminated structure 190 is a surface that points in the -X-axis direction.

[0027] The gas sensor element 100 comprises a sensor section 102 for detecting a specific gas component (O2) contained in an object gas (exhaust gas), and a heating section 104 for heating the sensor section 102. In the present embodiment, the heating section 104 is integrally formed with the sensor section 102 as part of the laminated structure 190. In other embodiments, the heating section 104 can be formed separately from the sensor section 102.

[0028] The gas sensor element 100 comprises, as the sensor section 102, a solid electrolyte ceramic layer 110, a ceramic layer 120, a ceramic layer 130, a porous section 140, a conductor layer 210, a conductor layer 220, an electrode contact surface 290a, and an electrode contact surface 290b.

[0029] A gap 180, extending longitudinally along the X-axis of the laminated structure 190, is formed between the solid electrolyte ceramic layer 110 and the ceramic layer 120. In the present embodiment, one end of the gap 180 is open on the +X-axis side towards the outside of the outer surface 195. Another end of the gap 180, on the -X-axis side, is closed at a position located on the inside of the outer surface 194. In the present embodiment, the gap 180 serves as an air inlet opening for introducing air (reference gas) to the conductor layer 210, which forms an electrode.

[0030] The solid electrolyte ceramic layer 110 of the gas sensor element 100 is a rectangular, plate-shaped ceramic layer. In the present embodiment, the material of the solid electrolyte ceramic layer 110 is yttrium oxide, which is partially stabilized by zirconia formed by adding yttrium oxide (Y₂O₃) to zirconia (zirconium dioxide (ZrO₂)). In other embodiments, the material of the solid electrolyte ceramic layer 110 can be partially stabilized zirconia formed by adding one or more oxides of at least one of calcium oxide (CaO), scandium oxide (Sc₂O₃), ytterbium oxide (Yb₂O₃), gadolinium oxide (Gd₂O₃), neodymium oxide (Nd₂O₃), and terbium oxide (Tb₂O₃) to zirconia.

[0031] The conductor layer 210 is formed on the surface of the solid electrolyte ceramic layer 110, which is arranged on the side of the -Z axis. The conductor layer 220 is formed on the surface of the solid electrolyte ceramic layer 110, which is arranged on the side of the +Z axis. A through opening 281a, which is provided for a conductor for electrically connecting the conductor layer 210 and the electrode contact surface 290a, is formed in the solid electrolyte ceramic layer 110. In the present embodiment, the material of the conductor in the through opening 281a is platinum (Pt).

[0032] A surface 118, which is convex in the direction of the +Z axis, is formed on the -Z axis side of the solid electrolyte ceramic layer 110. The surface 118 defines the +Z axis side of the gap 180.

[0033] The ceramic layer 120 of the gas sensor element 100 is a rectangular, plate-shaped ceramic layer of the same size as the solid electrolyte ceramic layer 110 and is laminated to the side of the solid electrolyte ceramic layer 110 along the -Z-axis direction. The ceramic layer 120 is made of an electrically insulating ceramic. In the present embodiment, the material of the ceramic layer 120 is alumina (aluminum oxide (Al₂O₃)).

[0034] A surface 128, which is convex in the direction of the -Z-axis, is formed on the +Z-axis side of the ceramic layer 120. The surface 128 defines the -Z-axis side of the gap 180.

[0035] The ceramic layer 130 of the gas sensor element 100 is a rectangular, plate-shaped ceramic layer of the same size as the solid electrolyte ceramic layer 110 and is laminated to the +Z-axis side of the solid electrolyte ceramic layer 110. The ceramic layer 130 is made of an electrically insulating ceramic. In the present embodiment, the material of the ceramic layer 130 is alumina.

[0036] Electrode contact surfaces 290a and 290b are formed on the surface of the ceramic layer 130, which is located on the side of the +Z axis. Through openings 282a and 282b are formed in the ceramic layer 130. Through opening 282a is for a conductor that electrically connects the conductor layer 210 and the electrode contact surface 290a, and through opening 282b is for a conductor that electrically connects the conductor layer 220 and the electrode contact surface 290b. In the present embodiment, conductive paste is filled into the through openings 282a and 282b to form the respective conductors, and its material is platinum (Pt).

[0037] The porous section 140 of the gas sensor element 100 is a porous body with continuous pores through which the object gas diffuses. The porous section 140 is formed in the ceramic layer 130 at a position near its end, which is arranged on the -X-axis side such that the porous section 140 extends from the +Z-axis side of the ceramic layer 130 to its -Z-axis side. The porous section 140 is made of an electrically insulating ceramic. In the present embodiment, the material of the porous section 140 is alumina.

[0038] The conductor layer 210 of the gas sensor element 100 is a conductor pattern formed on the side of the -Z-axis direction of the solid electrolyte ceramic layer 110. In the present embodiment, the material of the conductor layer 210 is platinum (Pt). The conductor layer 210 has an electrode section 212, a conductor section 214, and a terminal section 216.

[0039] The electrode section 212 of the conductor layer 210 is a rectangular electrode extending over a region of the surface 118 of the solid electrolyte ceramic layer 110, where the porous section 140 is present on the side of the +Z-axis direction. The electrode section 212 is exposed to the interior of the gap 180. As in Fig.As shown in Figure 4, in the present embodiment the surface of the electrode section 212 protrudes from the surface 118 of the solid electrolyte ceramic layer 110 on the side of the -Z-axis direction. In other embodiments, the electrode section 212 can cover the entire area of ​​the surface 118, or it can be flush with the surface 118.

[0040] The conductor section 214 of the conductor layer 210 is straight and connects the electrode section 212 and the terminal section 216. The terminal section 216 of the conductor layer 210 is wider than the conductor section 214 and is located adjacent to the through opening 281a of the solid electrolyte ceramic layer 110.

[0041] The conductor layer 220 of the gas sensor element 100 is a conductor pattern formed on the side of the +Z-axis direction of the solid electrolyte ceramic layer 110. In the present embodiment, the material of the conductor layer 220 is platinum (Pt). The conductor layer 220 has an electrode section 222, a conductor section 224, and a terminal section 226.

[0042] The electrode section 222 of the conductor layer 220 is a rectangular electrode extending over a region of the +Z-axis-side interface of the solid electrolyte ceramic layer 110, where the porous section 140 is present on the +Z-axis side. The electrode section 222 is located adjacent to the porous section 140. The conductor section 224 of the conductor layer 220 is straight and connects the electrode section 222 and the terminal section 226. The terminal section 226 of the conductor layer 220 is wider than the conductor section 224 and is located adjacent to the through opening 282b of the ceramic layer 130.

[0043] The electrode contact surface 290a of the gas sensor element 100 is a conductor pattern formed on the surface of the ceramic layer 130 on the side of the +Z-axis direction and arranged adjacent to the through opening 282a. In the present embodiment, the material of the electrode contact surface 290a is platinum (Pt). When the gas sensor element 100 is inserted into the gas sensor 10, the electrode contact surface 290a is mechanically and electrically connected to the terminal 820a.

[0044] The electrode contact surface 290b of the gas sensor element 100 is a conductor pattern formed on the surface of the ceramic layer 130 on the side of the +Z-axis direction and arranged adjacent to the through opening 282b. In the present embodiment, the material of the electrode contact surface 290b is platinum (Pt). When the gas sensor element 100 is inserted into the gas sensor 10, the electrode contact surface 290b is mechanically and electrically connected to the terminal 820b.

[0045] In the present embodiment, air (reference gas) is supplied to electrode section 212 of the conductor layer 210 through the gap 180, and exhaust gas (object gas) is supplied to electrode section 222 of the conductor layer 220 through the porous section 140. The solid electrolyte ceramic layer 110, electrode section 212, and electrode section 222 form an oxygen concentration cell. An electromotive force, corresponding to the difference in oxygen partial pressure between the air and the exhaust gas, is generated between electrode section 212 and electrode section 222. This electromotive force is output to an external circuit or the like via electrode contact surfaces 290a and 290b as a result of the detection of oxygen contained in the exhaust gas.

[0046] Fig.Figure 6 is an explanatory view that schematically shows the cross-sectional shape of the gap 180. The cross-sectional shape of the gap 180 in Fig. 6 is a cross-sectional shape obtained by cutting the laminated structure 190 along the YZ plane orthogonal to the longitudinal direction (the X-axis direction) and has endpoints A, B, C, and D. In the present embodiment, the cross-sectional shape of the gap 180 is defined by the solid electrolyte ceramic layer 110 and the ceramic layer 120.

[0047] The endpoint A in the cross-sectional shape of the gap 180 is one of the contact points where the cross-sectional shape of the gap 180 is in single-point contact with a virtual straight line VLa, which is parallel to the lamination direction (the Z-axis direction) of the several ceramic layers in the laminated structure 190, with one contact point being closest to the outer surface 193 of the laminated structure 190. The outer surface 193 of the laminated structure 190 is one of the side surfaces of the laminated structure 190, which extends in the longitudinal direction (the X-axis direction) and in the lamination direction (the Z-axis direction).

[0048] Endpoint B in the cross-sectional shape of the gap 180 is one of the contact points where the cross-sectional shape of the gap 180 is in single-point contact with a virtual straight line VLb, which is parallel to the lamination direction (the Z-axis direction) of the several ceramic layers in the laminated structure 190, with one contact point being closest to the outer surface 194 of the laminated structure 190. The outer surface 194 of the laminated structure 190 is the other of the side surfaces of the laminated structure 190, which extends in the longitudinal direction (the X-axis direction) and in the lamination direction (the Z-axis direction).

[0049] The endpoint C in the cross-sectional shape of the gap 180 is furthest from a straight line AB, which passes through endpoint A and endpoint B in the direction of the solid electrolyte ceramic layer 110. On the side of the straight line AB in the direction of the +Z axis, the cross-sectional shape of the gap 180 is convex in the direction of endpoint C.

[0050] The endpoint D in the cross-sectional shape of the gap 180 is furthest from the straight line AB, which passes through endpoint A and endpoint B towards the ceramic layer 120 (another ceramic layer). On the side of the straight line AB in the direction of the -Z-axis, the cross-sectional shape of the gap 180 is convex towards endpoint D.

[0051] Preferably, a distance H1 between the straight line AB and the endpoint C and a distance H2 between the straight line AB and the endpoint D satisfy a relationship 0.25 ≤ H1 / H2 < 1.00 or a relationship 1.00 < H1 / H2 ≤ 4.00. Particularly preferably, the distance H1 and the distance H2 satisfy a relationship 0.25 ≤ H1 / H2 ≤ 0.67 or a relationship 1.50 ≤ H1 / H2 ≤ 4.00. Preferably, the cross-sectional shape of the gap 180 satisfies the relationship between the distance H1 and the distance H2 described above, at least in a region where the electrode section 212 and the electrode section 222 are present. The cross-sectional shape of the gap 180 preferably fulfills the relationship described above over the entire area of ​​the gap 180. The height H of the gap 180, which is the sum of the distance H1 and the distance H2, preferably lies within a range of 10 µm (micrometers) to 100 µm and is particularly preferably within a range of 10 µm to 40 µm.An evaluation of the relationship between distance H1 and distance H2 is described later.

[0052] In the present embodiment, the distance H1 and the distance H2 satisfy the relation 1.00 < H1 / H2 ≤ 4.00 in the area where the electrode section 212 and the electrode section 222 are present, as shown in Fig. 4 shown. In the present embodiment, the distance H1 and the distance H2 satisfy the relation 1.00 < H1 / H2 ≤ 4.00 even in a region where the electrode section 212 and the electrode section 222 are not present, as shown in Fig.Figure 5 shows. In particular, in the present embodiment, over the entire area of ​​the gap 180, the average of the radii of curvature of the cross-sectional shape of the gap 180 on the side of the +Z-axis direction of the straight line AB is smaller than the average of the radii of curvature of the cross-sectional shape of the gap 180 on the side of the -Z-axis direction of the straight line AB.

[0053] The gas sensor element 100 comprises the heating section 104, a ceramic layer 160, a ceramic layer 170, a conductor layer 260, an electrode contact surface 290c and an electrode contact surface 290d.

[0054] The ceramic layer 160 of the gas sensor element 100 is a rectangular, plate-shaped ceramic layer of the same size as the solid electrolyte ceramic layer 110 and is laminated to the side of the -Z-axis direction of the ceramic layer 170. The ceramic layer 160 is made of an electrically insulating ceramic. In the present embodiment, the material of the ceramic layer 160 is alumina.

[0055] The conductive layer 260 is formed on the surface of the ceramic layer 160, which is oriented on the side of the +Z axis. The electrode contact surfaces 290c and 290d are formed on the surface of the ceramic layer 160, which is oriented on the side of the -Z axis. Through openings 286c and 286d are formed in the ceramic layer 160. The through opening 286c is for a conductor that electrically connects the conductive layer 260 and the electrode contact surface 290c, and the through opening 286d is for a conductor that electrically connects the conductive layer 260 and the electrode contact surface 290d. In the present embodiment, conductive paste is filled into the through openings 286c and 286d to form the respective conductors, and its material is platinum (Pt).

[0056] The ceramic layer 170 of the gas sensor element 100 is a rectangular, plate-shaped ceramic layer of the same size as the solid electrolyte ceramic layer 110 and is laminated to the side of the -Z-axis direction of the ceramic layer 120. The ceramic layer 170 is made of an electrically insulating ceramic. In the present embodiment, the material of the ceramic layer 170 is alumina.

[0057] The conductor layer 260 of the gas sensor element 100 is a conductor pattern formed on the side of the +Z-axis direction of the ceramic layer 160. In the present embodiment, the material of the conductor layer 260 is platinum (Pt). The conductor layer 260 has a heat generation section 262, a conduction section 264, a conduction section 265, a connection section 266, and a connection section 267.

[0058] The heat-generating section 262 of the conductor layer 260, which generates Joule heating, is formed in a region of the surface of the ceramic layer 160 that is located on the side of the +Z axis direction, with the electrode section 212 and the electrode section 222 being located on the side of the +Z axis direction. The conduction section 264 of the conductor layer 260 is a straight section that connects the electrode section 262 and the terminal section 266. The conduction section 265 of the conductor layer 260 is a straight section that connects the electrode section 262 and the terminal section 267. The terminal section 266 of the conductor layer 260 is wider than the conduction section 264 and is located adjacent to the through opening 286d of the ceramic layer 160. The connection section 267 of the conductor layer 260 is wider than the conductor section 265 and is located adjacent to the through opening 286c of the ceramic layer 160.

[0059] The electrode contact surface 290c of the gas sensor element 100 is a conductor pattern formed on the surface of the ceramic layer 160 on the side of the -Z-axis direction and connected to the conductor in the through opening 286c. In the present embodiment, the material of the electrode contact surface 290c is platinum (Pt). When the gas sensor element 100 is inserted into the gas sensor 10, the electrode contact surface 290c is mechanically and electrically connected to the terminal 820c.

[0060] The electrode contact surface 290d of the gas sensor element 100 is a conductor pattern formed on the surface of the ceramic layer 160 on the side of the -Z-axis direction and connected to the conductor in the through opening 286d. In the present embodiment, the material of the electrode contact surface 290d is platinum (Pt). In a state in which the gas sensor element 100 is included in the gas sensor 10, the electrode contact surface 290d is mechanically and electrically connected to the terminal 820d. A-3. Assessment test

[0061] Fig. Table 7 shows the results of an evaluation test performed for different values ​​of the distances H1 and H2. The results of the evaluation test are presented in Fig.As shown in Figure 7, several gas sensor elements (samples) were produced in which the ratio between the distance H1 and the distance H2 differed, and the initial fracture conditions and thermal shock strengths of these samples were evaluated. The evaluation test, the results of which are presented in Figure 7, shows that the gas sensor elements were produced in the following ways: Fig. As shown in Figure 7, several samples were produced for each of the different ratios between distance H1 and distance H2, with different distances H1 and H2. The ratio between distance H1 and distance H2, the distance H1 and distance H2 of each sample are shown in Figure 7. Fig. 7 shown.

[0062] The initial breakage ratio is the ratio of the number of manufactured unused samples (gas sensor elements) with breakages. Thermal shock resistance is the resistance of each gas sensor element to a thermal shock caused by a heat cycle, which will be described later.

[0063] In a test to evaluate the initial fracture ratio, ten samples, which were not used after their manufacture, were prepared for each of the different ratios between the distance H1 and the distance H2, and a cross-sectional area of ​​each sample was observed using a scanning electron microscope (SEM). The criteria for evaluating the initial fracture ratio are as follows. A (excellent): The initial fraction ratio is 0%. B (moderate): The initial fraction ratio is greater than 0% but not greater than 10%. x (not acceptable): The initial fraction ratio is greater than 10%.

[0064] A thermal shock test was performed on each sample rated "A (excellent)" or "B (fair)" in the initial fracture ratio evaluation test described above. In the thermal shock evaluation test, a voltage (21 V), 1.5 times the maximum voltage under normal use, was applied to the heating section of each sample for 10 seconds to heat the sample to approximately 1000 °C. The heated sample was then forced cooled using air for 30 seconds. One cycle (thermal cycle), consisting of heating and cooling, was repeated 1000 times for each sample, and then each sample was tested to determine whether it functioned normally as a gas sensor element.The thermal cycle, consisting of heating and cooling, was repeated 9000 times for each sample that functioned normally as a gas sensor element. Each sample was then tested to determine its continued functionality. The criteria for evaluating thermal shock resistance are as follows. A (excellent): The failure rate after 1000 cycles is 0%, and the failure rate after 10000 cycles is 0%. B (moderate): The failure rate after 1000 cycles is greater than 0% but not greater than 10%. x (not acceptable): The failure rate after 1000 cycles is greater than 10%.

[0065] The in Fig.The results of the evaluation test shown in Figure 7 demonstrate that, from the perspective of the initial fracture ratio, the distance H1 and the distance H2 preferably satisfy the relationship 0.25 ≤ H1 / H2 < 1.00 or 1.00 < H1 / H2 ≤ 4.00, and particularly preferably satisfy the relationship 0.25 ≤ H1 / H2 ≤ 0.67 or 1.50 ≤ H1 / H2 ≤ 4.00. The results also show that, from the perspective of thermal shock resistance, the gap height H, which is the sum of the distance H1 and the distance H2, preferably lies within the range of 10 µm to 100 µm, and particularly preferably within the range of 10 µm to 40 µm.

[0066] Fig.Figure 8 is a cross-sectional view of the laminated structure 190A of sample 11-1. In sample 11-1, H1 = 0, and stress around the gap 180A is concentrated at endpoint A and endpoint B. Therefore, fractures CkA are likely to propagate from endpoint A and endpoint B towards the porous section 140. When the fractures CkA propagating from endpoint A and endpoint B reach the porous section 140, sample 11-1 will be unable to function normally as a gas sensor element.

[0067] Unlike sample 11-1, where H1 = 0, in sample 1-1 H2 = 0, and the stress is concentrated at endpoint A and endpoint B of the gap in the laminated structure. Therefore, fractures CkA likely propagate from endpoint A and endpoint B towards heating section 104. When the fractures CkA propagating from endpoint A and endpoint B reach heating section 104, sample 1-1 will be unable to function normally as a gas sensor element.

[0068] Fig.Figure 9 is a cross-sectional view of the laminated structure 190B of sample 6-1. In sample 6-1, H1 = H2, and the stress around the gap 180B is distributed to surface 118 and surface 128. However, fractures CkB likely propagate from endpoint A and endpoint B towards the exterior of the laminated structure 190B (outer surfaces 193 and 194) along the junction between the solid electrolyte ceramic layer 110 and the ceramic layer 120. The strength of the laminated structure 190B is relatively low at the junction between the solid electrolyte ceramic layer 110 and the ceramic layer 120. If the fractures CkB propagating from endpoint A and endpoint B reach the exterior of the laminated structure 190B, the sample 6-1 will be unable to function normally as a gas sensor element.

[0069] Fig.Figure 10 is a cross-sectional view of the laminated structure 190C of sample 7-1. In sample 7-1, H1 < H2, and the stress around the gap 180C is distributed across surface 118 and surface 128. Fractures CkC likely grow from endpoint A and endpoint B towards the exterior of the laminated structure 190C (outer surface 193 and outer surface 194) along directions inclined to the +Z-axis direction with respect to the junction between the solid electrolyte ceramic layer 110 and the ceramic layer 120. The distances over which the fractures CkC grow from endpoint A and endpoint B to the exterior of the laminated structure 190C in sample 7-1 are greater than the distances over which the fractures CkB grow from endpoint A and endpoint B to the exterior of the laminated structure 190B in sample 6-1.Therefore, sample 7-1 is considered superior to sample 6-1 in terms of initial fracture ratio and thermal shock resistance.

[0070] In specimens 8-1 and 9-1, fracture generation is presumably suppressed because stress is distributed to a greater extent on surfaces 118 and 128 compared to specimen 7-1. Therefore, specimens 8-1 and 9-1 are considered superior to specimen 7-1 with respect to the initial fracture ratio and thermal shock resistance.

[0071] Fig.Figure 11 is a cross-sectional view of the laminated structure 190D of sample 5-1. In sample 5-1, H1 > H2, and the stress around the gap 180D is distributed across surface 118 and surface 128. Fractures CkD likely grow from endpoint A and endpoint B towards the exterior of the laminated structure 190D (outer surface 193 and outer surface 194) along directions inclined to the side of the -Z-axis direction with respect to the junction between the solid electrolyte ceramic layer 110 and the ceramic layer 120. The distances over which the fractures CkD grow from endpoint A and endpoint B to the exterior of the laminated structure 190D in sample 5-1 are greater than the distances over which the fractures CkB grow from endpoint A and endpoint B to the exterior of the laminated structure 190B in sample 6-1.Therefore, sample 5-1 is considered superior to sample 6-1 in terms of initial fracture ratio and thermal shock resistance.

[0072] In specimens 3-1 and 4-1, fracture generation is presumably suppressed because stress is distributed to a greater extent on surfaces 118 and 128 compared to specimen 5-1. Therefore, specimens 3-1 and 4-1 are considered superior to specimen 5-1 with respect to the initial fracture ratio and thermal shock resistance. A-4. Manufacturing process for the gas sensor element

[0073] Fig.Figure 12 is a flowchart illustrating a method for manufacturing the gas sensor element 100. In the manufacturing process, the conductive layer 210 and the conductive layer 220 are first formed on a green layer 110p, which will become the solid electrolyte ceramic layer 110 (step P110). In the present embodiment, the conductive layer 210 and the conductive layer 220 are formed by printing conductive paste onto the green layer 110p.

[0074] After forming the conductor layer 210 and the conductor layer 220 on the green layer 110p (step P110), carbon paste 180p is applied by printing to a section of the green layer 110p in which the gap 180 is to be formed (step P120).

[0075] After applying the paste 180p to the green layer 110p by printing (step P120), the green layer 110p is subjected to a stamping pressure, whereby the carbon paste 180p is pressed into the green layer 110p (step P130). In the present embodiment, the stamping pressure is carried out by pressing the green layer 110p through plate-shaped hollow forms 912 and 914, which hold the green layer 110p between them.

[0076] After the die-cutting process (step P130), other green layers are laminated onto the green layer 110p, forming a laminated structure 190p (step P140). In the present embodiment, green layers 120p, 130p, 160p and 170p, which become the ceramic layers 120, 130, 160 and 170, are laminated onto the green layer 110p.

[0077] After the laminated structure 190p is formed (step P140), it is fired (step P150). The carbon paste 180p burns and disappears as a result of the firing, and the gap 180 is formed at the location where the carbon paste 180p was previously present. These steps complete the gas sensor element 100.

[0078] Fig. Figure 13 is a flowchart showing an alternative method for manufacturing the gas sensor element 100. When manufacturing the gas sensor element 100, the conductor layer 210 and the conductor layer 220 are first formed on a green layer 110p, which will become the solid electrolyte ceramic layer 110 (step P210).

[0079] After forming the conductor layer 210 and the conductor layer 220 on the green layer 110p (step P210), carbon paste 180p is applied by printing onto a section of the green layer 110p in which the gap 180 is to be formed (step P220).

[0080] After applying the 180p paste to the 110p green layer by printing (step P220), other green layers are laminated onto the 110p green layer, forming a laminated structure 190p (step P230). Subsequently, the laminated structure 190p is subjected to a die-cutting process, which presses the 180p carbon paste into the 110p green layer (step P240).

[0081] After the die-cutting process (step P240), the laminated structure 190p is fired (step P250). The carbon paste 180p burns away and disappears as a result of the firing, and the gap 180 is formed at the location where the carbon paste 180p was present. These steps complete the gas sensor element 100. A-5. Effects

[0082] According to the embodiment described above, the relationship 0.25 ≤ H1 / H2 < 1.00 or the relationship 1.00 < H1 / H2 ≤ 4.00 is satisfied. Therefore, it is possible to suppress the formation of fractures in the gas sensor element 100 during its manufacture. Accordingly, it is possible to manufacture the gas sensor element 100 with sufficient stability while reducing the height of the gap 180 in the laminated structure 190. As a result, the thickness of the gas sensor element 100 can be reduced. If, furthermore, the relationship 0.25 ≤ H1 / H2 ≤ 0.67 or the relationship 1.50 ≤ H1 / H2 ≤ 4.00 is satisfied, the gas sensor element 100 can exhibit higher strength. Since the cross-sectional shape of the gap 180 is convex towards endpoint C and also convex towards endpoint D, a stress generated near the gap 180 can be distributed. As a result, the strength of the gas sensor element 100 can be increased.

[0083] If the height H of the gap 180 lies within the range of 10 µm to 100 µm, it is also possible to improve the thermal shock resistance of the gas sensor element 100 while allowing a sufficient amount of air to pass through the gap 180. In particular, the thermal shock resistance of the gas sensor element 100 can be further improved if the height H of the gap 180 lies within the range of 10 µm to 40 µm. Therefore, a height H of the gap 180 within such a range is preferred for the gas sensor 10, which is used for the exhaust system of an internal combustion engine, an environment in which a relatively large temperature change occurs. B. Other embodiments

[0084] The present invention is not limited to the embodiments, examples, and modifications described above and can be implemented in various configurations without departing from the scope of protection of the invention. For example, the technical features in the embodiments, examples, and modifications, which correspond to the technical features of the types described in the abstract, can be freely combined or replaced by other features in order to partially or completely solve the problems described above or to partially or completely achieve the effects described above. A technical feature (or features) can also be omitted at will, unless the technical feature(s) is / are described as an essential feature (or features) in the existing description.

[0085] The configuration of gap 180 in the embodiment described above can be applied not only to an oxygen sensor, but also to a NOx sensor that detects nitrogen oxide (NOx). The configuration of gap 180 in the embodiment described above can be applied not only to a gap for introducing a reference gas, but also to a gap for introducing an object gas. Description of reference symbols 10 Gas sensor 100 gas sensor elements 102 Sensor section 104 Heating section 110 Solid electrolyte ceramic layer 110p, 120p, 130p, 160p, 170p Green layer 118, 128 surface 120, 130, 160, 170 ceramic layer 140 porous section 180, 180A, 18013, 180C, 180D gap 180p carbon paste 190, 190A, 19013, 190C, 190D, 190p laminated structure 191, 192, 193, 194, 195, 196 Exterior area 120, 210, 220, 260 conductor layer 212, 222 Electrode section 214, 224, 264, 265 Line section 216, 226, 266, 267 Connection section 262 Heat generation section 281a, 282a, 282b, 286c, 286d continuous opening 290a, 290b, 290c, 290d Electrode contact area 300 protective device 400 metallic sheathing 500 element holding section 510 ceramic holders 520, 530 Talk-Ring 540 ceramic sleeve 600 outer pipe 700 insulator 800 cables 810a, 810b, 810c, 810d Conductor wire 820a, 820b, 820c, 820d terminal block 912 Hollow form 914 Hollow form

Claims

[1] Gas sensor element (100), comprising: a plate-shaped laminated structure (190) in which several ceramic layers (110, 120, 130) are laminated, wherein the several ceramic layers (110, 120, 130) have a solid electrolyte ceramic layer (110) with an electrode (212) formed on a surface (118) thereof, wherein the laminated structure (190) has a gap (180) formed between the solid electrolyte ceramic layer (110) and a second ceramic layer (120), which extends in a longitudinal direction (X) of the laminated structure (190), and to which the electrode (212) is exposed, wherein a cross-sectional shape of the gap (180) obtained by cutting the laminated structure (190) along a plane (YZ) orthogonal to the longitudinal direction (X), an endpoint A, which is one of the contact points with which the cross-sectional shape is in single-point contact with a virtual straight line (VLa) parallel to a lamination direction (Z) of the multiple ceramic layers (110, 120, 130), wherein one contact point is closest to a side surface (193) of the laminated structure (190) extending in the longitudinal direction (X) and in the lamination direction (Z), an endpoint B, which is one of the contact points closest to another side surface (194) of the laminated structure (190) opposite the one side surface (193), an endpoint C, which has the greatest distance from a straight line AB,which passes through endpoint A and endpoint B in the direction of the solid electrolyte ceramic layer (110), and has an endpoint D which is at the greatest distance from the straight line AB in the direction of the second ceramic layer (120); , a distance H1 between the straight line AB and the endpoint C and a distance H2 between the straight line AB and the endpoint D a relation 0.25 ≤ H1 / H2 < 1.00 or a relation 1.00 < H1 / H2 ≤ 4.00 must be satisfied; and a height H of the gap (180), which is the sum of the distance H1 and the distance H2, lies within a range of 10 µm to 100 µm, where the cross-sectional shape is convex in the direction towards endpoint C and is also convex in the direction towards endpoint D. [2] Gas sensor element (100) according to claim 1, wherein the distance H1 and the distance H2 satisfy a relation 0.25 ≤ H1 / H2 ≤ 0.67 or a relation 1.50 ≤ H1 / H2 ≤ 4.

00. [3] Gas sensor element (100) according to one of claims 1 or 2, wherein the gap (180) is an air inlet opening for directing air to the electrode. [4] Gas sensor element (100) according to one of claims 1 to 3, wherein the height H is within a range of 10 µm to 40 µm. [5] Gas sensor comprising a gas sensor element (100) according to any one of claims 1 to 4.

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