Gas sensor element and gas sensor

Abstract

Gas sensor element (10) comprising: - at least three ceramic layers (111, 121, 131) extending in the direction of an axial line (AX) and stacked one above the other, wherein the at least three ceramic layers (111, 121, 131) comprise a first ceramic layer (121), a second ceramic layer (131) and a third ceramic layer (111); - a first space (150) formed between the first ceramic layer (121) and the third ceramic layer (111) and into which a gas to be measured is introduced from the outside; - a second space (160) formed between the first ceramic layer (121) and the second ceramic layer (131) and at least partially overlapping the first space (150) when viewed in the stacking direction; - an introduction passage (125) forming a space passing through the first ceramic layer (121) in the stacking direction and allowing the gas to be measured introduced into the first space (150) to be introduced into the second space (160); - a first pumping cell (110) which pumps oxygen out of or into the first space (150) containing the gas to be measured, the first pumping cell (110) being formed from the third ceramic layer (111) adjacent to the first space (150), a first internal electrode (113) arranged on the third ceramic layer (111) and exposed to the first space (150), and a first counter electrode (112) paired with the first internal electrode (113); - an oxygen concentration detection cell (120) arranged downstream of the first pump cell (110) in an introduction direction (F) of the gas to be measured and measuring the oxygen concentration in the gas to be measured, wherein the oxygen concentration detection cell (120) is formed from the first ceramic layer (121) adjacent to the first space (150), a detection electrode (522) arranged on the first ceramic layer (121) and exposed to the first space (150), and a reference electrode (123) paired with the detection electrode (522); and - a second pumping cell (130) arranged downstream of the oxygen concentration detection cell (120) in the introduction direction (F) of the gas to be measured and through which an electric current corresponding to the concentration of a specific gas in the gas to be measured within the second space (160) flows, the second pumping cell (130) being formed from the second ceramic layer (131) adjacent to the second space (160), a second internal electrode (133) arranged on the second ceramic layer (131) and exposed to the second space (160), and a second counter electrode (132) paired with the second internal electrode (133), - wherein the first space (150) is partially delimited by first and second side walls (140s1, 140s2) extending in the direction of the axial line (AX), - wherein the detection electrode (522) extends continuously from a portion of a first virtual line (C1), which portion is arranged upstream of the introduction passage (125) in the introduction direction (F) of the gas to be measured, to a second virtual line (C2) through a region between the second side wall (140s2) and the introduction passage (125), wherein the first virtual line (C1) is parallel to the first side wall (140s1) and is in contact with an edge portion of the introduction passage (125), wherein the edge portion is arranged on a side of the first side wall (140s1), wherein the second virtual line (C2) is perpendicular to the second side wall (140s2) and is in contact with an edge portion of the introduction passage (125), which edge portion is arranged downstream in the introduction direction (F) of the gas to be measured, and - wherein the insertion passage (125) and the second inner electrode (133) overlap each other at least partially when viewed in the stacking direction.

Description

Technical area

[0001] The present invention relates to a gas sensor element suitably used to detect the concentration of a specific gas contained in a combustion gas or an exhaust gas of, for example, a burner or an internal combustion engine, and a gas sensor comprising the same. State of the art

[0002] Conventionally, a gas sensor (e.g., a NOx sensor) has been used to detect the concentration of a specific gas (e.g., the concentration of nitrogen oxides (NOx)) in the exhaust gas from an internal combustion engine (Patent Document 1). As described in Fig. As shown in Fig. 10, a general gas sensor (NOx sensor) includes a gas sensor element 1000 mainly comprising a first pumping cell 1100, an oxygen concentration detecting cell 1200, a second pumping cell 1300, a first space 1500, and a second space 1600.

[0003] The first pumping cell 1100 includes a solid electrolyte layer 1110 and a pair of electrodes 1120 and 1130 formed on opposite sides of the solid electrolyte layer 1110. The electrode 1130 is disposed to be exposed to the first space 1500 adjacent to the solid electrolyte layer 1110 in the stacking direction, and the electrode 1120 is disposed to be communicated with the outside through a porous layer 1900. The first pumping cell 1100 pumps oxygen from the first space 1500 containing the exhaust gas to the outside and pumps oxygen from the outside into the first space 1500. The oxygen concentration detection cell 1200 includes a solid electrolyte layer 1210 and a pair of electrodes 1220 and 1230 formed on opposite sides of the solid electrolyte layer 1210.The electrode 1220 is exposed to the first space 1500 adjacent to the solid electrolyte layer 1210 in the stacking direction, and the electrode 1230 is exposed to a reference chamber 1400 provided in the gas sensor element 1000. The oxygen concentration detection cell 1200 measures the oxygen concentration of the exhaust gas from which oxygen is pumped by the first pump cell 1100, and a current (Ip current) is supplied to the first pump cell 1100 so that an output voltage (electromotive force) corresponding to the oxygen concentration is constant.

[0004] The exhaust gas in the first space 1500, in which the oxygen concentration is controlled as described above, passes through a porous body 1520 serving as a diffusion control layer, and is then introduced into the second space 1600 through an introduction passage 1250 formed through a ceramic layer disposed between the first space 1500 and the second space 1600. The second pumping cell 1300 includes a solid electrolyte layer 1310 and a pair of electrodes 1320 and 1330 formed on the solid electrolyte layer 1310. The electrode 1330 is exposed to the second space 1600 adjacent to the solid electrolyte layer 1310 in the stacking direction, and the electrode 1320 is exposed to the reference chamber 1400 provided in the gas sensor element 1000. The second pumping cell 1300 is configured to detect the concentration of a specific gas (the concentration of NOx) in the exhaust gas introduced into the second space 1600.

[0005] Patent Document 2 discloses a sensor element having at least a first and a second cell each comprising two electrodes and a solid electrolyte, each embedded in a support member. State of the art documentPatent document Patent Document 1: Japanese Patent Application Laid-Open No. JP H11 - 72 478 A ( Fig. 1 and Fig. 9) Patent document 2: German laid-open patent application DE 10 2009 027 276 A1 Summary of the inventionProblems to be solved by the invention

[0006] The exhaust gas introduced into the gas sensor element 1000 flows from the first space 1500 to the second space 1600 along an introduction direction F. The concentration of oxygen in the exhaust gas flowing from the first space 1500 to the second space 1600 gradually decreases from the first space 1500 to the second space 1600, and therefore, a concentration gradient Gr exists.

[0007] Deterioration of the electrode 1130 of the first pumping cell 1100 or the temperature gradient of the gas sensor element 1000 itself caused by an increase in the flow velocity of the exhaust gas at the front end side of the gas sensor element 1000 may cause the concentration gradient to change from Gr to Gr1. In this case, the following problem occurs. The oxygen concentration on the detection electrode 1220 of the oxygen concentration detection cell 1200 in the case where the concentration gradient is Gr and that in the case where the concentration gradient is Gr1 are approximately the same. However, the oxygen concentration in the exhaust gas immediately before being introduced into the second space 1600 in the case where the concentration gradient is Gr is different from that in the case where the concentration gradient is Gr1, and this causes a decrease in the detection accuracy of the NOx concentration.

[0008] To reduce the influence of the change in the concentration gradient Gr, it is preferable that the oxygen concentration detection cell 1200 (the detection electrode 1220) be arranged at a position as close as possible to the second space 1600. If the porous body 1520 is arranged between the first space 1500 and the second space 1600, the concentration gradient Gr in the porous body 1520 may become more complex, and the oxygen concentration may fluctuate greatly. For example, Fig. 9 in Patent Document 1 proposes a structure in which a detection electrode is disposed in a diffusion control layer (porous body), but this is not preferable in terms of the accuracy of detecting NOx concentration. It has been found that the detection electrode 1220 must be disposed at a location other than the porous body 1520.

[0009] As in Fig. 11, it is therefore considered that the porous body 1520 is omitted and the detection electrode 1220 is brought close to the insertion passage 1250 adjacent to the second space 1600, that is, the detection electrode 1220 is disposed within the first space 1500 so as to surround the insertion passage 1250.

[0010] In order to reduce the influence of the change in the concentration gradient Gr, it is preferable to reduce the dimensions of the first space 1500 and the second space 1600, that is, to reduce the size of the gas sensor element. However, in this case, as shown by dashed lines in Fig. As shown in FIG. 11, the width of a solid electrolyte layer 1210x decreases, and the distance D between the insertion passage 1250 and a wall surface of the first space 1500 also decreases. Considering the printing misalignment when the detection electrode 1220 is formed by printing, the smaller the distance D, the more difficult it is to form the detection electrode 1220 between the insertion passage 1250 and the wall surface of the first space 1500. Therefore, it is difficult to reduce the influence of the change in the concentration gradient Gr.

[0011] Accordingly, it is an object of the present invention to provide a gas sensor element which is reduced in size and in which the influence of a change in the gradient of the oxygen concentration introduced into the gas sensor element is reduced to enable high accuracy in detecting the concentration of a specific gas. Means to solve the problems

[0012] A gas sensor element of a first aspect of the present invention that solves the above-described problem comprises: at least three ceramic layers extending in an axial line direction and stacked one on top of the other, the at least three ceramic layers including a first ceramic layer, a second ceramic layer, and a third ceramic layer; a first space formed between the first ceramic layer and the third ceramic layer, into which a gas to be measured is introduced from the outside; a second space formed between the first ceramic layer and the second ceramic layer and at least partially overlapping the first space when viewed in the stacking direction; an introduction passage forming a space passing through the first ceramic layer in the stacking direction and allowing the gas to be measured introduced into the first space to be introduced into the second space;a first pumping cell that pumps oxygen out of or into the first space containing the gas to be measured, the first pumping cell being formed of the third ceramic layer adjacent to the first space, a first internal electrode disposed on the third ceramic layer and exposed to the first space, and a first counter electrode paired with the first internal electrode; an oxygen concentration detection cell disposed downstream of the first pumping cell in an introduction direction of the gas to be measured and measuring the concentration of oxygen in the gas to be measured, the oxygen concentration detection cell being formed of the first ceramic layer adjacent to the first space, a detection electrode disposed on the first ceramic layer and exposed to the first space, and a reference electrode paired with the detection electrode;and a second pumping cell disposed downstream of the oxygen concentration detection cell in the introduction direction of the gas to be measured, through which an electric current corresponding to the concentration of a specific gas in the gas to be measured within the second space flows. The second pumping cell is formed of the second ceramic layer adjacent to the second space, a second internal electrode disposed on the second ceramic layer and exposed to the second space, and a second counter electrode paired with the second internal electrode. In the gas sensor element of the first embodiment, the first space is partially defined by first and second side walls extending in the axial line direction;the detection electrode extends continuously from a portion of a first virtual line, the portion being located upstream of the introduction passage in the introduction direction of the gas to be measured, to a second virtual line through a region between the second side wall and the introduction passage, the first virtual line being parallel to the first side wall and in contact with an edge portion of the introduction passage, the edge portion being located on a side toward the first side wall, the second virtual line being perpendicular to the second side wall and in contact with an edge portion of the introduction passage, the edge portion being downstream in the introduction direction of the gas to be measured; and the introduction passage and the second internal electrode at least partially overlap each other as viewed in the stacking direction.

[0013] In this gas sensor element, it is only necessary that the detection electrode be arranged so that it extends from the first virtual line parallel to the first side wall through the wide area between the second side wall and the insertion passage. Therefore, even if the gas sensor element is reduced in size, the detection electrode can be reliably formed near the insertion passage, even considering printing misalignment when the detection electrode is formed by printing and other manufacturing errors.

[0014] The detection electrode partially surrounds the insertion passage from the upstream side in the insertion direction. Therefore, the gas to be measured flowing on the upstream side of the first space always flows into the insertion passage on the downstream side through the detection electrode, preventing a decrease in measurement accuracy. This makes it possible to reduce the influence of changes in the concentration gradient of oxygen in the gas to be measured within the gas sensor element, allowing the specific gas concentration to be detected with high accuracy.

[0015] If the detection electrode is not located in the first space, the influence of the concentration gradient change can be reduced. However, in this case, the distance between the first pump cell (the first internal electrode) and the detection electrode is too large, and the detection response of the oxygen concentration of the gas to be measured decreases. By arranging the detection electrode in the first space, the accuracy of the oxygen concentration detection and the response can be achieved simultaneously.

[0016] The detection electrode is exposed to the first space. Specifically, the main surface (end face) of the detection electrode is positioned in the first space so that it can be visually observed and is not located within a diffusion control layer (porous body). Since the oxygen concentration is not detected in the diffusion control layer (porous body), where the oxygen concentration gradient is complex and the oxygen concentration fluctuates greatly, the specific gas concentration can be detected with higher accuracy.

[0017] Since the second internal electrode and the insertion passage overlap each other at least partially in the stacking direction, the second internal electrode is located close to the insertion passage. This allows the detection electrode to detect the oxygen concentration near the insertion passage close to the second internal electrode. Therefore, the influence of the change in the concentration gradient of oxygen flowing from the first space to the second space within the gas sensor element can be further reduced, and the specific gas concentration can be detected with high accuracy.

[0018] A gas sensor element of a second aspect of the present invention that solves the above-described problem comprises: at least three ceramic layers extending in an axial direction and stacked one on top of the other, the at least three ceramic layers including a first ceramic layer, a second ceramic layer, and a third ceramic layer, the second ceramic layer being disposed within the first ceramic layer, the first ceramic layer and the second ceramic layer constituting a composite layer; a first space formed between the third ceramic layer and the composite layer, into which a gas to be measured is introduced from the outside;a first pumping cell that pumps oxygen from or into the first space containing the gas to be measured, the first pumping cell being formed from the third ceramic layer adjacent to the first space, a first internal electrode disposed on the third ceramic layer and exposed to the first space, and a first counter electrode paired with the first internal electrode; an oxygen concentration detection cell disposed downstream of the first pumping cell in an introduction direction of the gas to be measured and measuring the oxygen concentration in the gas to be measured, the oxygen concentration detection cell being formed from the first ceramic layer adjacent to the first space, a detection electrode disposed on the first ceramic layer and exposed to the first space, and a reference electrode paired with the detection electrode;and a second pumping cell disposed downstream of the oxygen concentration detection cell in the introduction direction of the gas to be measured, through which an electric current corresponding to the concentration of a specific gas in the gas to be measured within the first space flows. The second pumping cell is composed of the second ceramic layer adjacent to the first space, a second internal electrode disposed on the second ceramic layer and exposed to the first space, and a second counter electrode paired with the second internal electrode. In the gas sensor element of the second aspect, the first space is partially defined by first and second side walls extending in the axial direction;the detection electrode extends continuously from a portion of a third virtual line, the portion being located upstream of the second internal electrode in the introduction direction of the gas to be measured, to a fourth virtual line through a region between the second side wall and the second internal electrode, the third virtual line being parallel to the first side wall and in contact with an edge portion of the second internal electrode, the edge portion being on a side toward the first side wall, the fourth virtual line being perpendicular to the second side wall and in contact with an edge portion of the second internal electrode, the edge portion being located downstream in the introduction direction of the gas to be measured;

[0019] Also, in this gas sensor element, like the gas sensor element of the first aspect, even when the gas sensor element is downsized, the detection electrode can be reliably formed even near the insertion passage, even considering printing misalignment when the detection electrode is formed by printing and other manufacturing errors. The gas to be measured always flows into the insertion passage on the downstream side through the detection electrode, and a reduction in measurement accuracy can be prevented. This makes it possible to reduce the influence of the change in the concentration gradient of oxygen in the gas to be measured within the gas sensor element, so that the specific gas concentration can be detected with high accuracy.

[0020] Since the detection electrode is arranged in the first space as in the gas sensor element according to the first aspect, the accuracy of detecting the oxygen concentration and the response can be achieved at the same time.

[0021] Since the oxygen concentration is not detected in the diffusion control layer (porous body) in which the oxygen concentration gradient is complicated and the oxygen concentration fluctuates greatly, the specific gas concentration can be detected more accurately than in the gas sensor element according to the first aspect.

[0022] Since no insertion passage is provided and the second internal electrode is arranged directly in a position where an insertion passage is usually provided, the detection electrode is located closer to the second internal electrode. This further reduces the influence of the change in the concentration gradient and allows the specific gas concentration to be detected with high accuracy.

[0023] In the gas sensor element of the first or second aspect of the present invention, the detection electrode may be in contact with the first side wall.

[0024] When the detection electrode is in contact with the first side wall, the detection electrode is also present in a region between the first side wall and the first or third virtual line. Therefore, the gas to be measured flowing through the upstream side of the first space into the introduction passage on the downstream side always flows through the detection electrode, and a reduction in measurement accuracy can be further prevented. This makes it possible to reduce the influence of the change in the concentration gradient of oxygen in the gas to be measured within the gas sensor element, so that the specific gas concentration can be detected with high accuracy.

[0025] The gas sensor element of the first or second aspect of the present invention may be configured such that the first ceramic layer is formed of an insulating material, a solid electrolyte body is disposed in the first ceramic layer such that the solid electrolyte body and the first ceramic layer form a single layer, and the detection electrode is in contact with an entire surface of one side of the solid electrolyte body such that an outer peripheral edge of the detection electrode surrounds an outer peripheral edge of the solid electrolyte body.

[0026] When the first ceramic layer is electrically insulating and the solid electrolyte body, which is smaller than the first ceramic layer, is arranged in the first ceramic layer, the size of the solid electrolyte body used can be reduced, and a reduction in cost can be achieved.

[0027] The outer peripheral edge of the detection electrode may be located at least 0.15 mm outside the outer peripheral edge of the solid electrolyte body.

[0028] In this case, even if misalignment occurs during the formation of the detection electrode due to printing or other manufacturing defects, the detection electrode can be reliably formed on the front side of the solid electrolyte body, and the solid electrolyte body can be prevented from being partially exposed.

[0029] A gas sensor of the present invention comprises a gas sensor element for detecting a specific gas in a gas to be measured; and a metallic shell holding the gas sensor element, wherein the gas sensor element is the gas sensor element of the first or second aspect of the present invention. Effects of the invention

[0030] According to the present invention, the gas sensor element can be reduced in size and the influence of the change in the concentration gradient of the oxygen introduced into the gas sensor element can be reduced, so that the specific gas concentration can be detected with high accuracy. Short description of the drawings Fig. 1 shows a cross-sectional view of a gas sensor (NOx sensor) according to an embodiment of the first aspect of the present invention, the cross-sectional view being shown along an axial line. Fig. 2 shows a cross-sectional view of a gas sensor element according to the embodiment of the first aspect, the cross-sectional view being shown along an axial line. Fig. 3 shows an exploded view of the gas sensor element according to the embodiment of the first aspect. Fig. Fig. 4 shows a plan view around a Vs electrode in the embodiment of the first aspect. Fig. 5 shows a top view corresponding Fig. 4 and shows a Vs electrode in an example not included in the invention, in which a slit is formed in the Vs electrode. Fig. 6 shows a top view corresponding Fig. 4 and shows a Vs electrode in an example not included in the invention, in which the V electrode extends only to a position upstream of an edge portion of an insertion passage. Fig. 7 shows a top view corresponding Fig. 4 and shows a Vs electrode in an example included in the invention, although the Vs electrode is not in contact with a first side wall. Fig. 8 shows a cross-sectional view of a gas sensor element according to an embodiment of the second aspect of the present invention, the cross-sectional view being shown along an axial line. Fig. Fig. 9 shows a plan view around a Vs electrode in the embodiment of the second aspect. Fig. 10 shows a cross-sectional view of a gas sensor element of a conventional NOx sensor, the cross-sectional view being shown along an axial line. Fig. 11 shows an illustration of a virtual sensing electrode 1220 arranged in a first space to surround the insertion passage. Embodiments of the invention

[0031] Embodiments of the present invention are described below. Embodiment of the first aspect of the invention

[0032] Fig. 1 is a longitudinal cross-sectional view of a gas sensor (NOx sensor) 1 according to an embodiment of the first aspect of the present invention (a cross-sectional view taken along an axial line AX), and Fig. 2 is a cross-sectional view of a gas sensor element 10 according to the embodiment of the first aspect, the cross-sectional view being taken along the axial line AX. Fig. 3 is an exploded perspective view of the gas sensor element 10 and Fig. 4 is a plan view around a Vs electrode 522.

[0033] The gas sensor 1 is a NOx sensor including the gas sensor element 10 capable of detecting the concentration of a specific gas (NOx) in the exhaust gas, which is a gas to be measured (a gas to be measured). In use, the gas sensor 1 is attached to an exhaust pipe (not shown) of an internal combustion engine. The gas sensor 1 includes a tubular metallic shell 20 having a threaded portion 21 formed at a prescribed position on the outer surface of the gas sensor 1 and used to fix the gas sensor 1 to the exhaust pipe. The gas sensor element 10 is in the form of an elongated plate extending in the direction of the axial line AX and held within the metallic shell 20.

[0034] More specifically, the gas sensor 1 comprises a holding member 60 having an insertion hole 62 into which a rear end portion 10k (an upper end portion in Fig. 1) of the gas sensor element 10; and six connection elements held in the holding element 60. In Fig. 1, only two connection elements (in particular connection elements 75 and 76) out of the six connection elements are shown.

[0035] A total of six electrode connection sections 13 to 18 with a rectangular shape in plan view (see Fig. 3, only electrode connection sections 14 and 17 are in Fig. 1) is formed at the rear end portion 10k of the gas sensor element 10. The above-described terminal members elastically abut against the electrode terminal portions 13 to 18 to establish electrical connection therebetween. For example, an element abutment portion 75b of the terminal member 75 elastically abuts against the electrode terminal portion 14 to establish electrical connection therebetween. For example, an element abutment portion 75b of the terminal member 75 elastically abuts against the electrode terminal portion 14 to establish electrical connection therebetween. An element abutment portion 76b of the terminal member 76 elastically abuts against the electrode terminal portion 17 to establish electrical connection therebetween.

[0036] Six different lead wires 71 are electrically connected to the respective six terminal elements (such as terminal elements 75 and 76). For example, as shown in Fig. 1, a lead wire holding portion 77 of the terminal member 75 is crimped so that the core of one lead wire 71 is held by the wire holding portion 77. A lead wire holding portion 78 of the terminal member 76 is crimped so that the core of another lead wire 71 is held by the lead wire holding portion 78.

[0037] The metallic shell 20 is a tubular member having a through-hole 23 extending in the direction of the axial line AX. The metallic shell 20 has an inwardly projecting ridge 25 forming a part of the through-hole 23. The metallic shell 20 holds the gas sensor element 10 within the through-hole 23 with a front end portion 10s of the gas sensor element 10 projecting outward from the front end of the metallic shell 20 (downward in Fig. 1) and the rear end portion 10k of the gas sensor element 10 projecting outwardly from the rear end of the metallic shell 20 (upward in Fig. 1) protrudes.

[0038] An annular ceramic holder 42, two talc rings 43 and 44 formed by compacting talc powder into an annular shape, and a ceramic sleeve 45 are arranged within the through-hole 23 of the metallic shell 20. Specifically, the ceramic holder 42, the talc rings 43 and 44, and the ceramic sleeve 45 are formed in this order from the front axial end side of the metallic shell 20 (the lower side in Fig. 1) towards the rear axial end side (the upper side in Fig. 1) stacked to surround the radial circumference of the gas sensor element 10.

[0039] A metal cup 41 is disposed between the ceramic holder 42 and the ledge 25 of the metallic shell 20. A crimping ring 46 is disposed between the ceramic sleeve 45 and a crimping portion 22 of the metallic shell 20. The crimping portion 22 of the metallic shell 20 is crimped to press the ceramic sleeve 45 toward the front end side by the crimping ring 46.

[0040] An outer protector 31 and an inner protector 32 made of a metal (particularly stainless steel) and having a plurality of holes are welded to a front end portion 20b of the metallic shell 20 to cover the front end portion 10s of the gas sensor element 10. An outer tube 51 is welded to a rear end portion of the metallic shell 20. The outer tube 51 has a tubular shape extending in the direction of the axial line AX and surrounding the gas sensor element 10.

[0041] The holding member 60 is a tubular member formed of an insulating material (particularly aluminum oxide) and has the insertion hole 62 extending through the holding member 60 in the direction of the axial line AX. The above-described six terminal members (such as the terminal members 75 and 76) are disposed within the insertion hole 62 (see Fig. 1). A radially outwardly projecting flange portion 65 is formed at the rear end of the holding member 60. The holding member 60 is held by an inner support member 53, with the flange portion 65 abutting against the inner support member 53. The inner support member 53 is held by the outer tube 51 by a crimping portion 51g of the outer tube 51, which is crimped radially inward.

[0042] An insulating member 90 is disposed on a rear end surface 61 of the holding member 60. The insulating member 90 is formed of an electrically insulating material (particularly, alumina) and has a cylindrical shape. The insulating member 90 has a total of six through-holes 91 penetrating in the direction of the axial line AX. The lead wire holding portions (such as the lead wire holding portions 77 and 78) of the above-described terminal members are disposed in the respective through-holes 91.

[0043] An elastic sealing member 73 formed of fluorocarbon rubber is provided on the radially inner side of a rear end portion 51c of the outer tube 51 located at the rear end (an upper end in Fig. 1) of the outer tube 51 in the axial direction. The portion 51c of the 51 is located at the rear end of the outer tube 51 in the axial direction. A total of six cylindrical insertion holes 73c are formed in the elastic sealing member 73, extending in the direction of the axial line AX. The insertion holes 73c of the elastic sealing member 73 are defined by insertion hole surfaces 73b (cylindrical inner wall surfaces).

[0044] The lead wires 71 are inserted into their respective insertion holes 73c. The lead wires 71 extend through the insertion holes 73c of the elastic sealing member 73 to the outside of the gas sensor 1. When the rear opening portion 51c of the outer tube 51 is crimped radially inward, the elastic sealing member 73 is elastically compressed and radially deformed. The insertion hole surfaces 73b come into intimate contact with the outer peripheral surfaces 71b of the lead wires 71, and the gaps between the insertion hole surfaces 73b and the outer peripheral surfaces 71b of the lead wires 71 are hermetically sealed.

[0045] As in Fig. As shown in Figure 2, the gas sensor element 10 includes three plate-shaped solid electrolyte bodies 111, 121, and 131 extending in the direction of the axial line AX, and insulators 140 and 145 disposed between the solid electrolyte bodies 111, 121, and 131, having a structure in which these elements are stacked in their stacking direction. The gas sensor element 10 further includes a heater 161 stacked on the back of the solid electrolyte body 131. Fig. 2, the side where an insulating layer 115 is arranged in the stacking direction is referred to as the "front side," and the side where the heater 161 is arranged in the stacking direction is referred to as the "rear side." The side where an Ip1 cell 110 is arranged in the axial line AX direction is referred to as the "front end side," and the side where an Ip2 cell 130 is arranged in the axial line AX direction is referred to as the "rear end side."

[0046] The upstream and downstream sides in an insertion direction F are simply referred to as the “upstream and downstream sides”, omitting the term “in the insertion direction F”.

[0047] The heater 161 includes plate-shaped insulators 162 and 163 formed mainly of alumina and a heating conductor 164 (mainly formed of Pt) embedded between the insulators 162 and 163.

[0048] The solid electrolyte bodies 111, 121, and 131 are formed of zirconium oxide, which is a solid electrolyte with oxygen ion conductivity. The solid electrolyte bodies 111, 121, and 131 are stacked in this order, and the insulator 140 is arranged between the solid electrolyte bodies 111 and 121. A through-hole 140h is formed in the insulator 140 (see Fig. 3). The through-hole 140h serves as a first space 150 formed between the two solid electrolyte bodies 111 and 121.

[0049] The insulator 145 is arranged between the solid electrolyte bodies 121 and 131. A through hole 145c is formed in the insulator 145 (see Fig. 3). The through-hole 145c serves as a second space 160 formed between the two solid electrolyte bodies 121 and 131.

[0050] The solid electrolyte bodies 111, 121 and 131 correspond to the “ceramic layers” in the claims.

[0051] A cylindrical introduction passage 125 extends in the stacking direction through the solid electrolyte body 121, which is located between the first space 150 and the second space 160, and the first space 150 and the second space 160 communicate with each other through the introduction passage 125. The gas to be measured introduced into the first space 150 flows in the direction of the axial line AX, then flows in the stacking direction through the introduction passage 125 and is introduced into the second space 160. The introduction direction (flow direction) of the gas to be measured is denoted by symbol F.

[0052] As in Fig. 3, first porous bodies 151 having gas permeability and water permeability are arranged on opposite side portions of the first space 150. The first space 150 communicates with the outside of the gas sensor element 10 via the first porous bodies 151, and this allows the gas to be measured to be introduced into the first space 150. The first porous bodies 151 serve as partition walls between the gas sensor element 10 and the outside and limit the amount of exhaust gas flowing into the first space 150 per unit time.

[0053] In the present embodiment, the diameter of the insertion passage 125 is smaller than the dimensions of the first space 150 and the second space 160 as viewed in the stacking direction, and the insertion passage 125 is narrower than the first space 150 and the second space 160. The insertion passage 125 is arranged in a position offset toward the center of the drawing sheet from the center in the width direction (a direction orthogonal to the direction of the axial line AX) (see the Fig. 3 and Fig. 4).

[0054] A porous Ip1+ electrode 112 is arranged on the front side of the solid electrolyte body 111. A porous Ip1- electrode 113 is arranged on the back side of the solid electrolyte body 111. An Ip1+ line 112r (see Fig. 3) is connected to the Ip1+ electrode 112. An Ip1- line 113r (see Fig. 3) is connected to the Ip1 electrode 113. The solid electrolyte body 111, the Ip1+ electrode 112, and the Ip1- electrode 113 form the Ip1 cell 110.

[0055] The Ip1+ electrode 112, the Ip1- electrode 113 and the Ip1 cell 110 correspond to the “first counter electrode”, the “first internal electrode” and the “first pump cell” in the claims, respectively.

[0056] The insulating layer 115 made of alumina is stacked on the front surface of the Ip1+ electrode 112 and the Ip1+ line 112r. A substantially rectangular through-hole surrounding the Ip1+ electrode 112 is formed in a front end portion of the insulating layer 115, and a porous layer 190 is embedded in the through-hole. Gas can flow between the Ip1+ electrode 112 and the outside through the porous layer 190.

[0057] The Ip1 cell 110 pumps oxygen between the atmosphere in contact with the Ip1+ electrode 112 (the atmosphere outside the gas sensor element 10) and the atmosphere in contact with the Ip1- electrode 113 (the atmosphere in the first space 150) (i.e., performs so-called oxygen pumping) according to a pumping current Ip1 applied between the Ip1+ electrode 112 and the Ip1- electrode 113.

[0058] The solid electrolyte body 121 is arranged to face the solid electrolyte body 111 in the stacking direction with the insulator 140 interposed therebetween. A porous Vs electrode 522 is arranged on the front side of the solid electrolyte body 121. More specifically, the Vs electrode 522 is arranged within the first space 150 to be downstream (rearward) of the Ip1 electrode 113 in the insertion direction F of the gas to be measured (see the Fig. 3 and Fig. 4) to be arranged.

[0059] A porous Vs+ electrode 123 is arranged on the back of the solid electrolyte body 121. A Vs- line 552r (see Fig. 3) is connected to the Vs- electrode 522, and a Vs+ line 123r (see Fig. 3) is connected to the Vs+ electrode 123.

[0060] The solid electrolyte body 121, the Vs- electrode 522, and the Vs+ electrode 123 constitute a Vs cell 120. The Vs cell 120 generates an electromotive force mainly according to the difference in oxygen partial pressure between the atmospheres separated by the solid electrolyte body 121 (the atmosphere in the first space 150 in contact with the Vs- electrode 522 and the atmosphere in a later-described reference oxygen chamber 170 in contact with the Vs+ electrode 123).

[0061] The Vs- electrode 522, the Vs+ electrode 123 and the Vs-cell 120 correspond to the “detection electrode”, the “reference electrode” and the “oxygen concentration detection cell” in the claims.

[0062] The solid electrolyte body 131 is arranged to face the solid electrolyte body 121 in the stacking direction with the insulator 145 interposed therebetween.

[0063] A porous Ip2+ electrode 132 and a porous Ip2-electrode 133 are arranged on the front side of the solid electrolyte body 131. An Ip2+ line 132r (see Fig. 3) is connected to the Ip2+ electrode 132 and an Ip2- line 133r (see Fig. 3) is connected to the Ip2 electrode 133.

[0064] The reference oxygen chamber 170, which is a small insulated space, is formed between the Ip2+ electrode 132 and the Vs+ electrode 123. The reference oxygen chamber 170 is formed as an opening 145b formed in the insulator 145. A ceramic-made porous body is disposed in the reference oxygen chamber 170.

[0065] The Ip2 electrode 133 is arranged in the second space 160.

[0066] The solid electrolyte body 131, the Ip2+ electrode 132, and the Ip2- electrode 133 constitute the Ip2 cell 130 for detecting the concentration of nitrogen oxides (NOx). In the Ip2 cell 130, oxygen (oxygen ions) originating from the NOx decomposed in the second space 160 moves through the solid electrolyte body 131 to the reference oxygen chamber 170. At this time, a current corresponding to the concentration of nitrogen oxide contained in the exhaust gas (gas to be measured) introduced into the second space 160 flows between the Ip2+ electrode 132 and the Ip2- electrode 133.

[0067] The Ip2+ electrode 132, the Ip2- electrode 133 and the Ip2 cell 130 correspond to the “second counter electrode”, the “second internal electrode” and the “second pumping cell” in the claims, respectively.

[0068] The detection of the NOx concentration by the gas sensor 1 of the present embodiment will be briefly described.

[0069] As the temperature of the heating conductor 164 increases, the solid electrolyte bodies 111, 121, and 131 of the gas sensor element 10 are heated and activated. This enables the Ip1 cell 110, the Vs cell 120, and the Ip2 cell 130 to operate.

[0070] The exhaust gas (the gas to be measured) flowing through an exhaust port (not shown) is introduced into the first space 150, while the flow rate of the exhaust gas is restricted by the first porous bodies 151. At this time, a weak current Icp is applied to the Vs cell 120 to flow from the Vs+ electrode 123 to the Vs- electrode 522. Therefore, oxygen in the exhaust gas can receive electrons from the Vs- electrode 522, which serves as a negative electrode within the first space 150, and become oxygen ions. The oxygen ions flow through the solid electrolyte body 121 and move into the reference oxygen chamber 170. Specifically, the flow of the current Icp between the Vs- electrode 522 and the Vs+ electrode 123 causes oxygen in the first space 150 to be introduced into the reference oxygen chamber 170.

[0071] When the oxygen concentration in the exhaust gas introduced into the first space 150 is lower than a prescribed value, the pumping current Ip1 is applied to the Ip1 cell 110, so that the Ip1+ electrode 112 serves as a negative electrode, thereby pumping oxygen from the outside of the gas sensor element 10 into the first space 150. When the oxygen concentration in the exhaust gas introduced into the first space 150 is higher than the prescribed value, the pumping current Ip1 is applied to the Ip1 cell 110, so that the Ip1 electrode 113 serves as a negative electrode, thereby pumping oxygen from the first space 150 to the outside of the gas sensor element 10.

[0072] The gas to be measured, whose oxygen concentration in the first space 150 has been adjusted as described above, is introduced into the second space 160 through the introduction passage 125. A specific gas component (NOx component) in the gas in contact with the Ip2- electrode 133 in the second space 160 is decomposed (i.e., reduced) into nitrogen and oxygen on the Ip2- electrode 133 at the voltage Vp2 when a voltage Vp2 is applied between the Ip2- electrode 133 and the Ip2+ electrode 132. The oxygen generated by the decomposition becomes oxygen ions, and the oxygen ions flow through the solid electrolyte body 131 and move into the reference oxygen chamber 170. Then, a current Ip2 flowing through the Ip2 cell 130 is detected, and the concentration of NOx in the gas to be measured can be recognized based on the current value.

[0073] With reference to Fig. 4, the Vs electrode 522 is described. Let a first virtual line C1 be a straight line parallel to a first side wall 140s1 partially defining the first space 150 and extending in the direction of the axial line AX, and in contact with an edge portion of the introduction passage 125, which edge portion is on the first side wall 140s1 side. Let a second virtual line C2 be a straight line perpendicular to a second side wall 140s2 and in contact with an edge portion 125e of the introduction passage 125, which edge portion 125e is on the downstream side in the introduction direction F of the gas to be measured.

[0074] The Vs electrode 522 extends from a portion of the first side wall 140s1 located upstream of the insertion passage 125, crossing the first virtual line C1, through a region between the second side wall 140s2 and the insertion passage 125 (a region on the distance D2 side), and reaches the second virtual line C2 in contact with the edge portion 125e of the insertion passage 125, which is on the downstream side. Specifically, the Vs electrode 522 extends continuously to form an approximately quadrant arc and partially surround the insertion passage 125 from the upstream side. In this case, the Vs electrode 522 is in contact with the first side wall 140s1. On the side of the edge portion 125e of the insertion passage 125, the Vs electrode 522 is electrically connected to the Vs line 522r. The Vs electrode 522 may extend downstream beyond the edge portion 125e of the insertion passage 125.

[0075] As in Fig. 2, the Ip2 electrode 133 and the insertion passage 125 overlap in the stacking direction.

[0076] As described above, the Vs electrode 522 is arranged to extend from the first side wall 140s1 and pass through the region between the second side wall 140s2 and the insertion passage 125. In this case, the Vs electrode 522 may be arranged not in a region with a small distance D1, but in the region with a large distance D2. Therefore, even if the dimensions of the first space 150 and the insertion passage 125 are reduced, that is, the gas sensor element 10 is reduced in size, the Vs electrode 522 can be reliably formed near the insertion passage 125, even considering the printing misalignment when the Vs electrode 522 is formed by printing and other manufacturing errors.

[0077] The Vs electrode 522 partially surrounds the introduction passage 125 in a region located upstream of the edge portion 125e of the introduction passage 125 in the insertion direction F. Therefore, the gas to be measured flowing through the upstream side of the first space 150 into the introduction passage 125 on the downstream side always flows through the Vs electrode 522. Since the gas to be measured flows through the Vs electrode 522, a reduction in the accuracy of measuring the specific gas concentration (NOx concentration) can be prevented.

[0078] Since the Ip2 electrode 133 and the introduction passage 125 overlap in the stacking direction, the Ip2 electrode 133 for detecting the specific gas concentration (NOx concentration) is located near the introduction passage 125. This allows the Vs electrode 522 to detect the oxygen concentration near the introduction passage 125, which is close to the Ip2 electrode 133. Therefore, the influence of the change in the concentration gradient of oxygen flowing from the first space 150 to the second space 160 in the gas sensor element 10 can be reduced, and the specific gas concentration (NOx concentration) can be detected with high accuracy.

[0079] The Vs electrode 522 is exposed to the first space 150. Specifically, the Vs electrode 522 is arranged in the first space 150 so that it can be visually observed and is not located within a diffusion control layer (porous body). Since the oxygen concentration is not detected in the diffusion control layer (porous body), where the oxygen concentration gradient Gr is complex and the oxygen concentration fluctuates greatly, the specific gas concentration (NOx concentration) can be detected with higher accuracy.

[0080] If the Vs electrode 522 is not disposed in the first space 150 (for example, the Vs electrode 522 is formed on a wall surface of the introduction passage 125), the influence of the change in the concentration gradient can be reduced. However, since the distance between the Ip1 electrode 113 and the Vs electrode 522 is too large, the response of detecting the oxygen concentration of the gas to be measured decreases. If the Vs electrode 522 is provided at least on the first space 150 side, the accuracy of detecting the oxygen concentration can be improved.

[0081] In the embodiment of the first aspect (and a second aspect to be described later), it is preferable that the Vs electrode 522 is formed to extend continuously from the first side wall 140s1 through the area between the second side wall 140s2 and the introduction passage 125 so that the introduction passage 125 is partially surrounded from the upstream side in a reliable manner.

[0082] However, as in Fig. 7, which will be described later, it is only necessary that the Vs electrode 522 extends continuously from the first virtual line C1 to the second virtual line C2. Specifically, the Vs electrode 522 may not be in contact with the first sidewall 140s1, and the Vs electrode 522 may be absent in a gap G3 between the first sidewall 140s1 and the first virtual line C1.

[0083] Fig. 5 shows a Vs electrode 522 that is not continuously formed in a region upstream of the edge portion 125e of the insertion passage 125 (i.e., a Vs electrode 522 with a slit 522c). This Vs electrode 522 is unsuitable because the gas to be measured flows into the insertion passage 125 through the slit 522c without passing through the Vs electrode 522, so that a sufficient amount of the gas to be measured does not flow through the Vs electrode 522, and the measurement accuracy decreases.

[0084] Fig. 6 shows a Vs electrode 522 that is not completely formed in a region upstream of the edge portion 125e of the insertion passage 125; that is, it terminates at a position located upstream of the edge portion 125e. This Vs electrode 522 is not suitable because, in a region downstream of one end 522e of the Vs electrode 522 and upstream of the edge portion 125e of the insertion passage 125, the gas to be measured flows into the insertion passage 125 without passing through the Vs electrode 522, whereby a sufficient amount of the gas to be measured does not flow through the Vs electrode 522, and the measurement accuracy is reduced. The Vs line 522r is electrically connected to the downstream end 522e and the gas to be measured comes into contact with the Vs line 522r.However, since the Vs line 522r does not have a sufficient detection function, the gas to be measured that comes into contact with the Vs line 522r is not considered to have passed through the Vs electrode 522, and the measurement accuracy decreases.

[0085] Fig. 7 shows a Vs electrode 522 that is not in contact with the first side wall 140s1 but is in contact with the first virtual line C1. In this case, the introduction passage 125 does not protrude in the direction of the axial line AX from the Vs electrode 522. Although a small amount of the gas to be measured may flow into the introduction passage 125 through a gap between the Vs electrode 522 and the first side wall 140s1 without passing through the Vs electrode 522, the reduction in measurement accuracy is very small, and this Vs electrode 522 is included in the first aspect of the present invention.

[0086] Embodiment of the second aspect of the invention With reference to the Fig. 8 and Fig. 9, an embodiment of the second aspect of the present invention will be described. A gas sensor element of the embodiment of the second aspect is the same as the gas sensor element 10 according to the embodiment of the first aspect shown in Fig. 2, except that the insertion passage 125 is omitted, a solid electrolyte body 131F is embedded in a solid electrolyte body 121F through an insulator 147F to thereby form a single composite layer 201F, and the Ip2- electrode 133 and the Ip2+ electrode 132 are formed on the front and back surfaces of the solid electrolyte body 131F, respectively, so as to oppose each other. The same components are denoted by the same reference numerals, and their descriptions are omitted.

[0087] Fig. 8 is a cross-sectional view of a gas sensor element 10F according to the embodiment of the second aspect, the cross-sectional view being taken along the axial line AX. Fig. 9 is a plan view around the Vs electrode 522. Let a third virtual line C3 be a straight line parallel to the first side wall 140s1 partially defining the first space 150 and extending in the direction of the axial line AX, and in contact with an edge portion of the Ip2 electrode 133, which edge portion is on the first side wall 140s1 side. Let a fourth virtual line C4 be a straight line perpendicular to the second side wall 140s2 and in contact with an edge portion of the Ip2 electrode 133, which edge portion is located below the downstream side in the introduction direction F of the gas to be measured.

[0088] The gas sensor element 10F in Fig. 8 is the same as the gas sensor element 10 according to the embodiment of the first aspect shown in Fig. 2, except that the solid electrolyte body 131F is embedded in the solid electrolyte body 121F through the insulator 147F to thereby form the single composite layer 201F in which the solid electrolyte body 131F is flush with the insulator 147F, and the Ip2 electrode 133 and the Ip2+ electrode 132 are formed on the front and back surfaces of the solid electrolyte body 131F so as to oppose each other.

[0089] More precisely, as in Fig. As shown in FIG. 9, a prescribed rectangular portion is cut away from the solid electrolyte body 121F, and the rectangular solid electrolyte body 131F is embedded in the hollow portion through the frame-shaped insulator 147F. A reference oxygen chamber 170E serving as a small insulated space is formed by cutting off a part of the insulator 145 facing the back surface of the Vs+ electrode 123 and the Ip2+ electrode 132 formed on the back surface of the solid electrolyte body 131F (see FIG. Fig. 8). A ceramic-like porous body is arranged in the reference oxygen chamber 170E.

[0090] As in Fig. 8, in the present embodiment, the solid electrolyte body 121F is not flush with the solid electrolyte body 131F, and the front and back surfaces of the solid electrolyte body 131F are recessed from the solid electrolyte body 121F in the stacking direction. Even if the solid electrolyte body 121F is not flush with the solid electrolyte body 131F, the solid electrolyte body 131F and the solid electrolyte body 121F are regarded as "a single layer."

[0091] A Vs cell including the Vs electrode 522 and the solid electrolyte body 121F is designated by reference numeral 120F. An Ip2 cell including the solid electrolyte body 131F is designated by reference numeral 130F.

[0092] The solid electrolyte bodies 121F and 131F correspond to the "first ceramic layer" and the "second ceramic layer" in the claims, respectively. The solid electrolyte body 111 corresponds to the "third ceramic layer" in the claims.

[0093] As in Fig. 9, the Vs electrode 522 is arranged in the same area as in the embodiment of the first aspect according to Fig. 4. The rectangular Ip2 electrode 133 is in substantially the same position as that of the insertion passage 125 in Fig. 4. The Vs electrode 522 extends from a portion of the first sidewall 140s1 located upstream of the Ip2 electrode 133, crosses the third virtual line C3, passes through a region between the second sidewall 140s2 and the Ip2 electrode 133 (a region on the distance D2 side), and reaches the fourth virtual line C4 in contact with an edge portion 133e of the Ip2 electrode 133 on the downstream side. Specifically, the Vs electrode 522 extends continuously to form an approximately quadrant arc and partially surround the Ip2 electrode 133 from the upstream side.

[0094] On the downstream side of the first space 150, a rectangular portion near the first side wall 140s1 is cut away from the solid electrolyte body 121F. The rectangular insulator 147F is inserted into the hollow portion, and the rectangular solid electrolyte body 131F is embedded within the insulator 147F. In the single composite layer 201F, the solid electrolyte bodies 121F and 131F are insulated from each other by the insulator 147F.

[0095] In the embodiment of the second aspect, the Vs electrode 522 needs to extend at least to the edge portion 133e of the Ip2 electrode 133 on the downstream side (ie, the fourth virtual line C4).

[0096] In the gas sensor element 10F, as in the gas sensor element 10, the influence of the change in the concentration gradient of oxygen flowing in the gas sensor element 10F from the first space 150 to the second space 160 is reduced, and the concentration of the specific gas (NOx concentration) can be detected with high accuracy.

[0097] Specifically, in the gas sensor element 10F, the insertion passage 125 is omitted, and the Ip2 electrode 133 is disposed directly in the position of the insertion passage 125. Therefore, the Vs electrode 522 is closer to the Ip2 electrode 133, and the influence of the change in the concentration gradient can be further reduced.

[0098] It should be understood that the present invention is not limited to the embodiments described above and includes various modifications and equivalents within the spirit and scope of the present invention.

[0099] For example, in the above embodiments, a diffusion control layer (porous body) that restricts the flow rate of the gas to be measured per unit time and serves as a partition between the first space 150 and the second space 160 is not provided, but the diffusion control layer may be provided. However, as described above, the oxygen concentration fluctuates greatly in the diffusion control layer, and this causes the accuracy of detecting oxygen to decrease. Therefore, it is necessary to dispose the diffusion control layer in a portion other than the Vs electrode 522. Specifically, for example, the diffusion control layer may be disposed between the Ip1 electrode 113 and the Vs electrode 522, or between the Vs electrode 522 and the Ip2 electrode 133 along the introduction direction F of the gas to be measured.

[0100] The number of ceramic layers stacked in the gas sensor element is not limited to three as long as the gas sensor element has at least three ceramic layers stacked one on top of the other.

[0101] There is no limitation on the shapes of the insertion passage and the electrodes, and a circular shape, a rectangular shape and irregular shapes can be used.

[0102] In the above embodiments, the entire first ceramic layer is formed from the solid electrolyte body, but this is not a limitation. The first ceramic layer may be formed from an insulator such as alumina. In this case, a portion of the first ceramic layer is cut away, and the solid electrolyte body is embedded in the cavity. In this embodiment, the first ceramic layer is made of, for example, alumina, which is less expensive than zirconia, and thus the manufacturing cost can be further reduced.

[0103] In this case, the outer peripheral edge of the sensing electrode can be positioned at least 0.15 mm outside the outer peripheral edge of the embedded solid electrolyte body. In this configuration, even if the edge of the sensing electrode is blurred during the formation of the sensing electrode by printing, the solid electrolyte body around the sensing electrode is prevented from being exposed. Description of reference symbols 1 gas sensor 10, 10F gas sensor element 110 first pump cell 111, 121, 131 Solid electrolyte body (ceramic layer) 121, 121F solid electrolyte body (first ceramic layer) 131, 131F solid electrolyte body (second ceramic layer) 111 Solid electrolyte body (third ceramic layer) 112 first counter electrode (Ip1+ electrode) 113 first inner electrode (Ip1 electrode) 120, 120F oxygen concentration detection cell 522 Detection electrode (Vs electrode) 123 Reference electrode (Vs+ electrode) 125 insertion passage 125e Edge portion of the introduction passage on the downstream side in the direction of introduction of the gas to be measured 130, 130F second pump cell 132 second counter electrode (Ip2+ electrode) 133 second inner electrode (Ip2 electrode) 140s1 first side wall that borders the first room 140s2 second side wall that borders the first room C1 first virtual line C2 second virtual line C3 third virtual line C4 fourth virtual line 147F Insulator 150 first room 160 second room 201F composite layer F Direction of introduction of the gas to be measured AX axial direction T Width direction

Claims

[1] Gas sensor element (10) comprising: - at least three ceramic layers (111, 121, 131) extending in the direction of an axial line (AX) and stacked one above the other, wherein the at least three ceramic layers (111, 121, 131) comprise a first ceramic layer (121), a second ceramic layer (131) and a third ceramic layer (111); - a first space (150) formed between the first ceramic layer (121) and the third ceramic layer (111) and into which a gas to be measured is introduced from the outside; - a second space (160) formed between the first ceramic layer (121) and the second ceramic layer (131) and at least partially overlapping the first space (150) when viewed in the stacking direction; - an introduction passage (125) forming a space passing through the first ceramic layer (121) in the stacking direction and allowing the gas to be measured introduced into the first space (150) to be introduced into the second space (160); - a first pumping cell (110) which pumps oxygen out of or into the first space (150) containing the gas to be measured, the first pumping cell (110) being formed from the third ceramic layer (111) adjacent to the first space (150), a first internal electrode (113) arranged on the third ceramic layer (111) and exposed to the first space (150), and a first counter electrode (112) paired with the first internal electrode (113); - an oxygen concentration detection cell (120) arranged downstream of the first pump cell (110) in an introduction direction (F) of the gas to be measured and measuring the oxygen concentration in the gas to be measured, wherein the oxygen concentration detection cell (120) is formed from the first ceramic layer (121) adjacent to the first space (150), a detection electrode (522) arranged on the first ceramic layer (121) and exposed to the first space (150), and a reference electrode (123) paired with the detection electrode (522); and - a second pumping cell (130) arranged downstream of the oxygen concentration detection cell (120) in the introduction direction (F) of the gas to be measured and through which an electric current corresponding to the concentration of a specific gas in the gas to be measured within the second space (160) flows, the second pumping cell (130) being formed from the second ceramic layer (131) adjacent to the second space (160), a second internal electrode (133) arranged on the second ceramic layer (131) and exposed to the second space (160), and a second counter electrode (132) paired with the second internal electrode (133), - wherein the first space (150) is partially delimited by first and second side walls (140s1, 140s2) extending in the direction of the axial line (AX), - wherein the detection electrode (522) extends continuously from a portion of a first virtual line (C1), which portion is arranged upstream of the introduction passage (125) in the introduction direction (F) of the gas to be measured, to a second virtual line (C2) through a region between the second side wall (140s2) and the introduction passage (125), wherein the first virtual line (C1) is parallel to the first side wall (140s1) and is in contact with an edge portion of the introduction passage (125), wherein the edge portion is arranged on a side of the first side wall (140s1), wherein the second virtual line (C2) is perpendicular to the second side wall (140s2) and is in contact with an edge portion of the introduction passage (125), which edge portion is arranged downstream in the introduction direction (F) of the gas to be measured, and - wherein the insertion passage (125) and the second inner electrode (133) overlap each other at least partially when viewed in the stacking direction. [2] Gas sensor element (10F) comprising: - at least three ceramic layers (111, 121F, 131F) extending in the direction of an axial line (AX), wherein the at least three ceramic layers (111, 121F, 131F) comprise a first ceramic layer (121F), a second ceramic layer (131F) and a third ceramic layer (111), wherein the second ceramic layer (131F) is arranged in the first ceramic layer (121F), wherein the first ceramic layer (121F) and the second ceramic layer (131F) form a composite layer (201F) and the composite layer (201F) and the third ceramic layer (111) are stacked one on top of the other; - a first space (150) formed between the third ceramic layer (111) and the composite layer (201F) and into which a gas to be measured is introduced from the outside; - a first pumping cell (110) which pumps oxygen out of and into the first space (150) containing the gas to be measured, the first pumping cell (110) consisting of the third ceramic layer (111) adjacent to the first space (150), a first internal electrode (113) arranged on the third ceramic layer (111) and exposed to the first space (150), and a first counter electrode (112) paired with the first internal electrode (113); - an oxygen concentration detection cell (120F) arranged downstream of the first pump cell (110) in an introduction direction (F) of the gas to be measured and measuring the oxygen concentration in the gas to be measured, wherein the oxygen concentration detection cell (120F) consists of the first ceramic layer (121F) adjacent to the first space (150), a detection electrode (522) arranged on the first ceramic layer (121F) and exposed to the first space (150), and a reference electrode (123) paired with the detection electrode (522); and - a second pumping cell (130F) arranged downstream of the oxygen concentration detection cell (120F) in the introduction direction (F) of the gas to be measured and through which an electric current flows which corresponds to the concentration of a specific gas in the gas to be measured within the first space (150), the second pumping cell (130F) consisting of the second ceramic layer (131F) adjacent to the first space (150), a second internal electrode (133) arranged on the second ceramic layer (131F) and exposed to the first space (150), and a second counter electrode (132) paired with the second internal electrode (133), - wherein the first space (150) is partially delimited by first and second side walls (140s1, 140s2) extending in the direction of the axial line (AX), - wherein the detection electrode (522) extends continuously from a portion of a third virtual line (C3), which portion is arranged upstream of the second internal electrode (133) in the introduction direction (F) of the gas to be measured, to a fourth virtual line (C4) through a region between the second side wall (140s2) and the second internal electrode (133), wherein the third virtual line (C3) is parallel to the first side wall (140s1) and is in contact with an edge portion of the second internal electrode (133), wherein the edge portion is arranged on a side of the first side wall (140s1), wherein the fourth virtual line (C4) is perpendicular to the second side wall (140s2) and is in contact with an edge portion of the second internal electrode (133), wherein the edge portion is downstream in the introduction direction (F) of the gas to be measured. [3] The gas sensor element (10, 10F) according to claim 1 or 2, wherein the detection electrode (522) is in contact with the first side wall (140s1). [4] The gas sensor element (10, 10F) according to any one of claims 1 to 3, wherein the first ceramic layer (121, 121F) is formed of an insulating material, and wherein a solid electrolyte body is disposed in the first ceramic layer (121, 121F) such that the solid electrolyte body and the first ceramic layer (121, 121F) form a single layer, and wherein the detection electrode (522) is in contact with an entire surface of one side of the solid electrolyte body such that an outer peripheral edge of the detection electrode (522) surrounds an outer peripheral edge of the solid electrolyte body. [5] The gas sensor element (10, 10F) according to claim 4, wherein the outer peripheral edge of the detection electrode (522) is located at least 0.15 mm outside the outer peripheral edge of the solid electrolyte body. [6] A gas sensor (1) comprising: a gas sensor element (10, 10F) for detecting a specific gas in a gas to be measured; and a metallic shell holding the gas sensor element (10, 10F), wherein the gas sensor element (10, 10F) is the gas sensor element (10, 10F) according to any one of claims 1 to 5.

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