JP4426065B2 - Gas sensor element and gas sensor including the same - Google Patents

Description

【００３８】
表１において、「外周線の重なり具合」とは、参照電極部の外周線上の部分であって、検知電極部の外周線と平行な部分のうち、検知電極部の外周線との最短距離が、固体電解質体の厚さの所定値以下である部分の長さ／両電極部の外周線のうちの短いほうの外周線の長さを意味する。詳述すれば、参照電極部の外周線上の１点と検知電極部の外周線との最短距離として表される両電極部間の最短距離を、固体電解質体の厚さで除した値が所定値以下であるような点が連続的に形成されている参照電極部の外周線上の長さと、両電極部の外周線のうちの短いほうの長さと、の比を外周線の重なり具合を表すパラメータとするものである。尚、所定値は適宜設定することができるが、所定値が大きければ重なり具合にかかわりなく元々亀裂は発生し難いことを考えると、亀裂発生の有無を評価するうえでは所定値を３を越えて大きく設定することは好ましくない。
【００３９】
［２］で用意した素子を、少なくとも固体電解質体部分が完全に浸漬されるように水中に浸漬し、参照電極と水の間の抵抗値を測定して亀裂の有無を評価した。その結果、第１発明の素子（実験例１１及び１５）では亀裂がまったく発生しておらず、一方、第１発明に含まれない素子（例えば、実験例３及び７）では亀裂が発生した。また、固体電解質体の厚さが１２０μｍ以上（例えば、実験例２５及び２８）である場合は、亀裂の発生を十分に抑えることができる。更に、第１発明のように、固体電解質体に対して両電極部の厚さを相対的に薄くすれば（実験例２９〜３１と実験例３２〜３４との比較）、より効果的に亀裂の発生を抑えることができる。また、特に、第２発明のように、固体電解質体に基体の構成成分であるアルミナが１０〜８０質量％含有されている場合は、第１発明のように外周線の重なり具合を設定することにより、亀裂の発生を更に効果的に抑えることができる。
【００４０】
【発明の効果】
第１発明のような電極構成とすることにより、固体電解質体の亀裂の発生が抑制されるガスセンサ素子とすることができる。更に、第４発明によれば、このような素子を備えることにより、耐久性に優れたガスセンサとすることができる。
【図面の簡単な説明】
【図１】本発明のガスセンサ素子に用いられている参照電極と検知電極を模式的に表す平面図である。
【図２】ガスセンサ素子に用いられている従来の参照電極と検知電極を模式的に表す平面図である。
【図３】本発明のガスセンサ素子の製造工程を説明する解説図である。
【図４】本発明のガスセンサ素子の一例の横断面図である。
【図５】本発明のガスセンサの横断面図である。
【図６】中央部から素子形状を有する１０個の未焼成積層体を切り出すためのグリーンシートの平面図である。
【図７】図６に示すグリーンシートを４枚積層する様子を示す概略図である。
【符号の説明】
１；ガスセンサ素子、１１ａ；第１基体、１１ｂ；第２基体、１１１ａ；スルーホール、１２；発熱抵抗体、１２１；発熱部、１２２；ヒータリード部、１３；緩衝層、１４ａ；参照電極、１４１ａ；参照電極部、１４１１ａ；参照電極外周線、１４ｂ；検知電極、１４１ｂ；検知電極部、１４１１ｂ；検知電極外周線、１５ａ；第１固体電解質体、１５ｂ；第２固体電解質体、１５１；本体層、１５２；周辺層、１６ａ；第１絶縁層、１６ｂ；第２絶縁層、１６２；上部絶縁層、１７；多孔質層、１８ａ；第１保護層、１８ｂ第２保護層、２；ガスセンサ、２１：主体金具、２１１；主体金具ねじ部、３；グリーンシート、３１；貫通孔、３２；角孔。[0001]
BACKGROUND OF THE INVENTION
The present invention can detect oxygen gas, NOx gas, and the like contained in exhaust gas discharged from an internal combustion engine such as an automobile, and the outer periphery of each electrode portion of the reference electrode and the detection electrode is provided on the solid electrolyte body. The present invention relates to a gas sensor element that does not cause a crack as a starting point and a gas sensor including the gas sensor element.
[0002]
[Prior art]
Conventionally, a gas sensor element (hereinafter sometimes simply referred to as “element”) using a cylindrical solid electrolyte body or a plate-type solid electrolyte body is known. Among these, an element including a plate-type solid electrolyte body laminated in contact with an alumina substrate is disclosed in Japanese Patent Application Laid-Open No. 7-55758. In such a gas sensor element, a reference electrode that is not in direct contact with the gas to be detected and a detection electrode that is in contact with the gas to be detected are formed on the front and back surfaces of the solid electrolyte body, and a voltage generated between these electrodes is detected. By detecting the current flowing between these electrodes, the concentration of oxygen gas or the like contained in the gas to be detected can be detected.
[0003]
[Problems to be solved by the invention]
However, in such a gas sensor element, if the positions of the outer peripheral lines of the electrode portions of the reference electrode and the detection electrode formed on the front and back surfaces of the solid electrolyte body coincide with each other over a certain length, It has been found by the inventors' investigation that a crack is generated in the solid electrolyte body starting from the outer circumferential line. The cause of such cracks is that the solid electrolyte body in the vicinity of the outer peripheral line of the electrode portion is due to the difference in thermal shrinkage during firing between the electrode made of Pt or the like and the solid electrolyte body made of ceramics such as zirconia or alumina. It is presumed that this is because stress in the plane direction is applied to the surface. Therefore, cracks are more likely to occur when the solid electrolyte body is thin and when the electrode is relatively thick.
[0004]
In particular, when the solid electrolyte body is formed by printing, the thickness of the solid electrolyte body is generally 30 to 60 μm. To make the thickness 90 μm or more, the thickness is 3 times or more. There was a problem in cost, such as the need for a printing process. Furthermore, if the solid electrolyte body is made too thick, there is also a problem that cracks are likely to occur due to a difference in thermal expansion between the solid electrolyte body and the substrate. For this reason, it has been desirable to make the thickness thinner than 90 μm, particularly when a solid electrolyte body is formed by printing. However, for the reason described above, when such a thin solid electrolyte body is used, there is a problem that a crack is generated due to stress from the electrode.
[0005]
The present invention solves the above-described conventional problems, can suppress the occurrence of cracks in the solid electrolyte body in the vicinity of the outer peripheral line of the electrode part during production, and can also prevent the solid electrolyte body during use. An object of the present invention is to provide a gas sensor element excellent in durability, such as being able to suppress the occurrence of cracks, and a gas sensor including this element. In particular, it is an object of the present invention to provide a gas sensor element that suppresses the occurrence of cracks in a solid electrolyte body when the solid electrolyte body is formed thinner than 90 μm on an insulating substrate.
[0006]
[Means for Solving the Problems]
Means for solving the problem will be described below.
[0007]
A gas sensor element of a first invention is provided in contact with a solid electrolyte body, one surface of the solid electrolyte body, a reference electrode having a reference electrode portion and a reference electrode lead portion, and the other surface of the solid electrolyte body. disposed Te, the gas sensor element and a detection electrode having a detection electrode lead portion and the detection electrode, a portion of the peripheral line of the reference electrode section, parallel to the peripheral line of the detection electrode Among the portions, the length of the continuous portion in which the shortest distance from the outer circumference of the detection electrode portion is 3.0 times or less the thickness of the solid electrolyte body is equal to the outer circumference of the reference electrode portion and the detection. der 1/10 of the outer peripheral line shorter peripheral line of ones of the electrode portions is, the thickness of the reference electrode portion and the detection electrode is located at 1/3 or less of the thickness of the solid electrolyte body It is characterized by that.
[0008]
The “reference electrode part” and the “detection electrode part” are formed at opposite positions on the front and back surfaces of the solid electrolyte body, and the voltage accompanying oxygen ion movement generated between these electrode parts, or these electrodes The current flowing between the parts is detected and taken out as a signal. The shape, area, thickness, etc. of the reference electrode part and the detection electrode part are not particularly limited. However, the position of the “peripheral line” of each electrode part is opposed to the front and back surfaces of the solid electrolyte body and has a considerable length. When the reference electrode portion and the detection electrode portion are formed so that they coincide with each other (hereinafter, this state may be expressed as overlapping each other), these electrode portions Due to the difference in thermal expansion between the solid electrolyte body and the solid electrolyte body, a stress in the plane direction is applied to the solid electrolyte body, and cracks are generated in the solid electrolyte body starting from the outer peripheral line of each electrode portion.
[0009]
The generation of this crack will be described in detail with reference to FIGS.
FIG. 1 shows a planar shape of a reference electrode and a detection electrode in a gas sensor element in which a crack does not occur in a solid electrolyte body as in the first invention. On the other hand, FIG. 2 shows a planar shape of a reference electrode and a detection electrode in a conventional gas sensor element in which a crack may occur in the solid electrolyte body. 1 and 2, the reference electrode 14a includes a reference electrode portion 141a and a reference electrode lead portion 142a that extends to the reference electrode lead portion 142a and transmits a signal from the electrode portion to a signal extraction terminal. The detection electrode 14b includes a detection electrode portion 141b and a detection electrode lead portion 142b that extends to the detection electrode portion 141b and transmits a signal from the electrode portion to a signal extraction terminal. Each edge of the reference electrode lead portion and the detection electrode lead portion may be used as a signal extraction terminal as it is, or may be connected to a signal extraction terminal formed on the element surface by a through hole or the like.
[0010]
According to FIG. 1, the outer peripheral line 1411a of the reference electrode portion 141a and the outer peripheral line 1411b of the detection electrode portion 141b overlap at four points A, B, C, and D, but the lines do not overlap at all. Absent. This is a portion on the outer peripheral line of the reference electrode portion in the first invention, and of the portions parallel to the outer peripheral line of the detection electrode portion, the shortest distance from the outer peripheral line of the detection electrode portion is the thickness of the solid electrolyte body. This means that there is no continuous portion that is 3.0 times or less of the length, and if it is an element including a reference electrode and a detection electrode having such a shape, the solid electrolyte body starts from the outer periphery of the electrode portion. There will be no cracks.
[0011]
On the other hand, according to FIG. 2, the outer peripheral line 1411a of the reference electrode portion 141a and the outer peripheral line 1411b of the detection electrode portion 141b overlap with each other over a considerable length like the outer peripheral line L. This is a portion on the outer peripheral line of the reference electrode portion in the first invention, and of the portions parallel to the outer peripheral line of the detection electrode portion, the shortest distance from the outer peripheral line of the detection electrode portion is the thickness of the solid electrolyte body. 2 or less (in the outer circumferential line L in FIG. 2, the shortest distance of each outer circumferential line is the thickness of the solid electrolyte body itself, that is, one time the thickness of the solid electrolyte body). the length of the contiguous portion, reference shorter peripheral line of ones of the electrode portion peripheral line and the detection electrode portion of the peripheral line of (towards the peripheral line of the reference electrode portion in FIG. 2 is short.) 1/10 beyond the In the element including the reference electrode and the detection electrode having such a shape, a crack is generated in the solid electrolyte body starting from the outer peripheral line L.
[0012]
Further, even if there is a portion in which the outer peripheral line of the reference electrode and the outer peripheral line of the detection electrode are parallel over a length exceeding 1/10 of the shorter one of them, those outer peripheral lines Are separated, that is, when the shortest distance of each outer circumferential line is 2.0 times or more of the thickness of the solid electrolyte body, particularly 3.0 times or more, the occurrence of cracks in the solid electrolyte body is suppressed. be able to. Furthermore, even if the shortest distance of each outer peripheral line over a considerable length is not more than 3.0 times the thickness of the solid electrolyte body, the length of the outer peripheral line and the detection electrode part The solid electrolyte body will not crack if it is 1/10 or less, particularly 1/12 or less, of the shorter one of the outer circumferences.
[0013]
Furthermore, this crack is more easily generated when the portion where the outer peripheral lines overlap is linear, and the crack is more easily propagated than when it is curved. Therefore, in particular, it is more preferable that there are no portions where the outer peripheral lines overlap in a straight line. Therefore, it is preferable that each electrode part has a shape in which the outer peripheral line is formed by a curve, such as an ellipse rather than a rectangle. In this way, it is possible to obtain an element in which cracks are less likely to occur and even if cracks are generated.
[0014]
In addition, as the reference electrode portion and the detection electrode portion are relatively thick with respect to the solid electrolyte body, cracks are more likely to occur. In particular, when the solid electrolyte body is relatively thin, the influence of the thickness of each electrode portion. Becomes larger. Therefore, the thickness of each electrode portion is set to 1/3 or less of the thickness of the solid electrolyte body as in the first invention. Thus, cracking of the solid electrolyte body can be prevented more reliably by reducing the relative thickness of each electrode part.
[0015]
Note that the reference electrode and the detection electrode can be formed of a noble metal element having a catalytic action such as platinum, ruthenium, osmium, iridium, rhodium, palladium, or a conductive material containing these noble metal elements as a main component. These electrodes are formed as a thin film on the front and back surfaces of the solid electrolyte body by an ordinary method such as a printing method, a plating method, or a sputtering method.
[0016]
The “solid electrolyte body” only needs to have oxygen ion conductivity. For example, a zirconia-based sintered body or LaGaO ₃ -based sintered body having oxygen ion conductivity can be used.
[0017]
It is preferable to provide a protective layer on the solid electrolyte body. With this protective layer, a part of the solid electrolyte body is covered to prevent the occurrence of cracks and the like, and at the same time, the detection electrode can be covered and protected from the environment such as outside air. This protective layer preferably has an insulation property of 100 times or more as compared with the solid electrolyte body at a temperature of 900 ° C. Furthermore, it is preferable to provide airtightness of a degree having a relative density of 94% or more. The method for producing this protective layer is not particularly limited. For example, the protective layer can be produced by printing an insulating paste and drying it, and then integrally firing together with other members. However, the solid electrolyte body needs to be strong enough to suppress the force to be peeled off from the substrate, and is preferably manufactured by laminating an unfired ceramic sheet on another member and then firing it integrally.
[0018]
In general, the element of this element is preferably provided with a plate-like substrate, and the solid electrolyte is preferably formed in a layered manner in contact with at least a part of one surface of the substrate. The element of the present invention can be produced using, for example, a technique for forming a laminate disclosed in JP-A-7-55758. Further, in the formation of the solid electrolyte body, a laminate of unfired sheets may be used, but it is preferably formed by printing a paste. In this case, it is preferable that the substrate on which these layers are laminated has an integral plate shape. Thereby, handling at the time of manufacture becomes especially easy.
[0019]
As in the second invention, the solid electrolyte body preferably contains 10 to 80% by mass, particularly 40 to 60% by mass, of the constituent components of the substrate. Thereby, the thermal shock resistance of the solid electrolyte body can be improved to further improve the occurrence of cracks and the like. When the content of the component constituting the substrate exceeds 80% by mass, it is difficult to obtain sufficient characteristics as a solid electrolyte body, which is not preferable. On the other hand, if it is less than 10% by mass, the thermal shock resistance is not sufficiently improved. Further, as in the third invention, it is preferable that the solid electrolyte body is mainly composed of zirconia and alumina, and the substrate is mainly composed of alumina. Thus, the gas sensor element including the solid electrolyte body containing a large amount of alumina is preferable because it is inexpensive and has high durability.
[0020]
A gas sensor according to a fourth aspect of the invention includes the gas sensor element according to the first to third aspects of the invention.
This gas sensor is inexpensive and has high durability. The form of the gas sensor 2 is not particularly limited. For example, the outer surface of the metal shell 21 is provided so that the element 1 is disposed in the metal shell 21 and the detection unit disposed on the front side protrudes into the exhaust pipe or the like. Can be used by being exposed to a gas to be measured (exhaust gas). According to this gas sensor, the gas to be detected can be detected stably for a long period of time.
[0021]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described in more detail with reference to examples.
[1] Method for Manufacturing Element Provided with Peripheral Part and Upper Insulating Layer on Peripheral Part The element manufacturing method will be described with reference to FIGS. 3, 6, and 7.
In the following manufacturing method, for ease of understanding, each pattern is printed on a sheet with a size of one element using FIG. 3 and described as if it were laminated, but in the actual process, After printing and stacking a required number of green sheets having a size capable of manufacturing a plurality of elements, an element-shaped green laminate was cut out.
[0022]
More specifically, circular through holes 31 for alignment are formed as shown in FIG. 6 in the vicinity of the short side of each green sheet 3 produced in the following (1). A pin fixed to a printing machine or a laminating machine was inserted into the through-hole and aligned. The size of the element is 42.85 mm in length and 3.93 mm in width at the time of printing. After printing the print patterns for 10 elements in parallel at the center of each of the first to fourth green sheets, As shown in FIG. Next, the laminated body laminated integrally was cut along the broken line in FIG. 6 or FIG. 7 to obtain 10 unfired laminated bodies having an element shape, which were degreased and fired to produce an element.
[0023]
In addition, the opening part (square hole 32) is formed in the first to third green sheets from the top of FIG. 7 when each green sheet is laminated and then cut into elements. This is because, as shown in FIG. 1, sheets having different lengths are aligned to form a stacked shape. Referring to FIG. 1, the first green sheet from the top in FIG. 7 is 18b in FIG. 1, the second green sheet from the top is 18a, the third green sheet from the top is 11b, and the green at the bottom. Each sheet corresponds to 11a. Although the lengths of 11b and 11a are the same, a square hole is opened in the third green sheet from the top in FIG. 7 because this square hole is for alignment of the lamination. The end face of this square hole does not coincide with the end face on the front end side of 11b.
[0024]
(1) Preparation of unsintered alumina sheet 100 parts by mass (hereinafter abbreviated as “part”) of alumina powder (purity 99.99% or more, average particle size 0.3 μm), 14 parts of butyral resin, and dibutyl phthalate 7 After mixing with a mixed solvent consisting of toluene and methyl ethyl ketone to form a slurry, four green sheets for printing having a length of 90 mm and a width of 60 mm were prepared by a doctor blade method. The first and fourth green sheets were 0.4 mm thick, and the second and third green sheets were 0.25 mm thick.
[0025]
(2) Heater pattern formation After firing a conductive layer paste containing 4 parts of alumina powder (purity 99.99% or more, average particle size 0.3 μm) and 100 parts of platinum powder, the lower half of the substrate ( 11a; printed on one surface of the first green sheet to be a first substrate) and dried to form a heating part pattern and a heater lead pattern, and after firing, the heating resistor 12 (the heating part 121 and the heater lead part) 122.), a heater pattern is formed. Next, a through hole 111a for conducting the heating resistor is formed near the base end of the first green sheet, and an electrode pad 19a for connecting a terminal after firing at a position corresponding to the through hole 111a on the back surface. After the heater pad pattern to be formed was formed, a second green sheet serving as the upper half (11b; second substrate) of the substrate was laminated from the top of the heater pattern and bonded by pressure bonding.
[0026]
(3) Formation of buffer layer pattern On the second green sheet of the ceramic laminate produced in (2), a buffer layer paste containing 80 parts of alumina and 20 parts of zirconia is printed, dried, and fired. Then, a buffer layer pattern having a thickness of 30 ± 10 μm to be the buffer layer 13 was formed.
[0027]
(4) Formation of Reference Electrode Pattern On the buffer layer pattern formed in (3), the conductive layer paste used in (2) is printed, dried and baked, and then the reference electrode 14a (reference electrode portion 141a and A reference electrode pattern having a thickness of 20 μm ± 10 was formed. The planar shape of the reference electrode pattern was such that the reference electrode 14a of FIG. 1 was formed.
[0028]
(5) Formation of first solid electrolyte pattern 50 parts of zirconia powder (purity 99.9% or more, average particle size 0.3 μm), alumina powder (purity 99.99% or more, average particle size 0.3 mm) In addition, 33.3 parts of butyl carbitol, 0.8 part of dibutyl phthalate, 0.5 part of a dispersant and 15 parts of a binder were added with a required amount of acetone, mixed for 4 hours, and then evaporated to obtain a solid electrolyte. A paste was prepared. This solid electrolyte paste is printed with a length of 13 mm in the length direction of the first green sheet (and the second green sheet) to a thickness of 25 ± 10 μm so as to cover the electrode part pattern portion of the reference electrode pattern. Then, after drying and firing, a first solid electrolyte pattern was formed to be the first solid electrolyte body 15a constituting a part of the main body portion and the peripheral portion of the solid electrolyte body.
[0029]
(6) Formation of first insulating layer pattern To the slurry prepared in (1), 21 parts of butyl carbitol and a required amount of acetone are added and mixed for 4 hours, and then acetone is evaporated to form an insulating layer paste. Was formulated. The insulating layer paste is printed on a portion of the buffer layer pattern where the first solid electrolyte layer pattern is not printed, dried, baked, and then the first insulating layer 16a that is a part of the insulating layer; A first insulating layer pattern having a thickness of 25 ± 10 μm was formed.
[0030]
(7) Formation of second solid electrolyte body pattern The same solid electrolyte paste as in (5) is printed on the first solid electrolyte body pattern with the tip position aligned to a length of 8 mm and a thickness of 25 ± 10 μm. After drying and firing, a second solid electrolyte pattern was formed to be the second solid electrolyte body 15b constituting a part of the solid electrolyte body. Thus, the solid electrolyte pattern includes a portion having a thickness of 50 μm that becomes a main body portion after firing and a portion having a thickness of 25 μm that becomes a peripheral portion after firing.
[0031]
(8) Formation of the second insulating layer pattern The same insulating layer paste as in (6) is printed on the first insulating layer pattern on which the second solid electrolyte layer pattern is not formed, dried, and fired. The second insulating layer 16b constituting a part of the insulating layer, in particular, the upper part of the first solid electrolyte pattern, becomes an upper insulating layer 162 (which is a part of the second insulating layer 16b) after firing, 25 ± 10 μm. A second insulating layer pattern having a thickness of 5 mm was formed. In the vicinity of the base ends of the first and second insulating layer patterns, through holes 161a and 161b were formed for electrical connection with the respective electrodes.
[0032]
(9) Formation of sensing electrode pattern On the second solid electrolyte pattern and the second insulating layer pattern formed in (7) and (8), the conductive layer paste prepared in (2) is printed and dried. After firing, a detection electrode pattern having a thickness of 20 μm ± 10 to be the detection electrode 14b (configured by the detection electrode portion 141b and the detection electrode lead portion 142b) was formed. The planar shape of the detection electrode pattern was such that the detection electrode 14b of FIG. 1 was formed.
[0033]
(10) Formation of porous layer pattern In the same insulating layer paste as in (6), carbon powder having an average particle size of 5 μm is mixed at a volume ratio of 45% by volume with alumina to prepare a porous layer paste. Printed on the 2 solid electrolyte pattern, dried, and after firing, a porous layer pattern having a length of 10 mm and a thickness of 50 μm or more to be the porous layer 17 was formed.
[0034]
(11) The third green sheet to be the first protective layer 18a after firing and the second green after firing so as to cover the portion excluding the porous layer pattern formed by the lamination (10) of the third and fourth green sheets. The 4th green sheet used as the protective layer 18b was laminated | stacked. In the vicinity of the base ends of the third and fourth green sheets, through holes 181a and 181b are formed for electrical connection with the respective electrodes, and at positions corresponding to the through holes on the back surface of the fourth green sheet, After firing, a heater pad pattern to be an electrode pad 19b for connecting terminals was formed.
[0035]
(12) Degreasing and firing The laminate obtained in (1) to (11) is heated from room temperature to 420 ° C. at a temperature rising rate of 10 ° C./hour in an air atmosphere and held for 2 hours. Degreasing treatment was performed. Thereafter, the temperature is increased to 1100 ° C. at a temperature increase rate of 100 ° C./hour, and further increased to 1520 ° C. at a temperature increase rate of 60 ° C./hour, and kept at this temperature for 1 hour for firing. As shown in FIG. 4, 300 gas sensor elements were obtained in which the solid electrolyte body had a main body portion and a peripheral portion, and the solid electrolyte body and the detection electrode lead portion were separated by the upper insulating layer.
[0036]
[2] In the same process as the element [1] in which the shape of the detection electrode is changed, the shape of the reference electrode is fixed, and the shape of the detection electrode, the positional relationship with respect to the reference electrode, and the thickness of the solid electrolyte body are changed in various ways. In addition, 300 elements were prepared in which the distance between the outer peripheral line of the reference electrode and the outer peripheral line of the detection electrode and the degree of overlap were changed as shown in Table 1.
[0037]
[Table 1]

[0038]
In Table 1, “peripheral line overlap” is a part on the outer peripheral line of the reference electrode part, and the shortest distance from the outer peripheral line of the detection electrode part is a part parallel to the outer peripheral line of the detection electrode part. means the length of the shorter peripheral line of ones of the outer peripheral line of length / the electrodes of the predetermined value or less part of the thickness of the solid electrolyte body. More specifically, a value obtained by dividing the shortest distance between the two electrode parts represented by the shortest distance between one point on the outer peripheral line of the reference electrode part and the outer peripheral line of the detection electrode part by the thickness of the solid electrolyte body is predetermined. The ratio of the length on the outer circumference of the reference electrode portion where the points that are less than or equal to the value are continuously formed and the shorter length of the outer circumference of both electrode portions represents the degree of overlap of the outer circumference It is a parameter. Although the predetermined value can be set as appropriate, considering that it is difficult to generate a crack originally regardless of the degree of overlap if the predetermined value is large, the predetermined value exceeds 3 when evaluating the presence or absence of cracks. Setting a large value is not preferable.
[0039]
The element prepared in [2] was immersed in water so that at least the solid electrolyte part was completely immersed, and the resistance value between the reference electrode and water was measured to evaluate the presence or absence of cracks. As a result, no cracks occurred in the elements of the first invention (Experimental Examples 11 and 15), while cracks occurred in elements not included in the first invention (for example, Experimental Examples 3 and 7). In addition, when the thickness of the solid electrolyte body is 120 μm or more (for example, Experimental Examples 25 and 28), the occurrence of cracks can be sufficiently suppressed. Further, as in the first aspect of the invention, if the thickness of both electrode portions is made relatively thin with respect to the solid electrolyte body (comparison between Experimental Examples 29-31 and Experimental Examples 32-34), the cracks are more effectively caused. Can be suppressed. In particular, as in the second invention, when the solid electrolyte body contains 10 to 80% by mass of alumina which is a constituent component of the substrate, the degree of overlap of the outer peripheral lines should be set as in the first invention. Thus, the generation of cracks can be more effectively suppressed.
[0040]
【The invention's effect】
By setting it as an electrode structure like 1st invention, it can be set as the gas sensor element by which generation | occurrence | production of the crack of a solid electrolyte body is suppressed. Furthermore, according to the fourth aspect of the present invention, by including such an element, a gas sensor having excellent durability can be obtained.
[Brief description of the drawings]
FIG. 1 is a plan view schematically showing a reference electrode and a detection electrode used in a gas sensor element of the present invention.
FIG. 2 is a plan view schematically showing a conventional reference electrode and detection electrode used in a gas sensor element.
FIG. 3 is an explanatory diagram for explaining a manufacturing process of the gas sensor element of the present invention.
FIG. 4 is a cross-sectional view of an example of a gas sensor element of the present invention.
FIG. 5 is a cross-sectional view of the gas sensor of the present invention.
FIG. 6 is a plan view of a green sheet for cutting out 10 unfired laminated bodies having an element shape from a central portion.
7 is a schematic diagram showing a state in which four green sheets shown in FIG. 6 are stacked. FIG.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1; Gas sensor element 11a; 1st base | substrate, 11b; 2nd base | substrate, 111a; Through hole, 12; Heat generating resistor, 121; Heat generating part, 122: Heater lead part, 13: Buffer layer, 14a; Reference electrode, 141a Reference electrode part, 1411a; Reference electrode outer periphery line, 14b; Detection electrode, 141b; Detection electrode part, 1411b; Detection electrode outer periphery line, 15a; First solid electrolyte body, 15b; Second solid electrolyte body, 151; 152; peripheral layer, 16a; first insulating layer, 16b; second insulating layer, 162; upper insulating layer, 17; porous layer, 18a; first protective layer, 18b second protective layer, 2; : Metal shell, 211; metal shell screw part, 3; green sheet, 31; through hole, 32; square hole.

Claims (4)

A solid electrolyte body, a reference electrode disposed in contact with one surface of the solid electrolyte body, and having a reference electrode portion and a reference electrode lead portion; and a detection electrode portion disposed in contact with the other surface of the solid electrolyte body And a sensing electrode having a sensing electrode lead portion, wherein the sensing electrode portion is a portion of the reference electrode portion on the outer circumferential line and parallel to the outer circumferential line of the sensing electrode portion. The length of the continuous portion where the shortest distance to the outer peripheral line is 3.0 times or less the thickness of the solid electrolyte body is short of the outer peripheral line of the reference electrode portion and the outer peripheral line of the detection electrode portion 1/10 or less of the outer perimeter line,
The gas sensor element characterized in that the thickness of the reference electrode part and the detection electrode part is 1/3 or less of the thickness of the solid electrolyte body.   2. The gas sensor element according to claim 1, wherein the solid electrolyte body is disposed on a surface of an insulating substrate, and the solid electrolyte body contains 10 to 80 mass% of a component of the substrate.   The gas sensor element according to claim 1, wherein the solid electrolyte body includes zirconia and alumina as main components, and the base includes alumina as a main component.   A gas sensor comprising the gas sensor element according to any one of claims 1 to 3.

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