JP2010243422A - Gas sensor and method of manufacturing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a gas sensor that cannot be broken easily by force, such as an external shock, and that detects concentration of a specific gas constituent in gas to be measured, and to provide a method of manufacturing the gas sensor. <P>SOLUTION: The gas sensor 1 stores and fixes a nearly planar sensor element 10 extended in an axial direction to the inside of a nearly cylindrical insulating holding member 20 via sealing glass 30. In the gas sensor 1, a coating layer 31 that is made of an inorganic material and includes a porous structure is formed such that an outer periphery of the sensor element 10 is covered and not less than 80% of the surface of the sealing glass 30 is covered at a boundary between the sealing glass 30 and the sensor element 10. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a gas sensor for detecting the concentration of a specific gas component in a gas to be measured and a method for manufacturing the same.

Conventionally, as a gas sensor for detecting the concentration of a specific gas in a gas to be measured, a sensor element having a detection portion on the tip side, a substantially cylindrical insulator that holds the sensor element inserted therein, and the insulator There is known a housing constituted by a housing in which is inserted and disposed and a cover body which is disposed on the front end side of the housing and protects the sensor element.
As a sensor element used in such a gas sensor, it is formed using a solid electrolyte layer having specific ion conductivity such as zirconia, a pair of electrodes formed on the opposing surface, and an insulating material such as alumina. A laminated sensor element formed by laminating an element holding member, a heater layer incorporating a heating element, and the like and extending in the axial direction is widely used.
In Patent Document 1, a sealing glass in which a difference in thermal expansion coefficient between the insulator and the outer surface of the sensor element is within a specific range is filled between the inner surface side of the insulator and the outer surface of the sensor element, and is fixedly sealed. A gas sensor is disclosed.

  However, as described in Patent Document 1, even if the difference in thermal expansion coefficient between the sealing glass and the insulator is made small, it is difficult to make them completely coincident with each other, and residual stress is applied to the boundary portion between the sealing glass and the sensor element. There is a risk that the sensor element may be destroyed when a force such as a strong impact is applied from the outside during the assembly process of the gas sensor or the mounting to the gas flow path to be measured.

  Therefore, in view of such a situation, an object of the present invention is to provide a highly reliable gas sensor and a method for manufacturing the same, in which the sensor element is hardly damaged by a force such as an external impact in the gas sensor.

  In the first aspect of the invention, it is formed in a substantially plate shape extending in the axial direction, is exposed to the gas to be measured at least on the tip side, and detects the concentration of the specific gas component in the gas to be measured and the detection result on the base side. A sensor element having an output unit for extracting a corresponding output signal, a substantially cylindrical insulating holding member for holding the sensor element on the inside, and covering the detection unit of the sensor element while covering the insulating holding member. In a gas sensor comprising a housing that is held and fixed in a measurement gas, the sensor element and the insulating holding member are sealed and fixed via a sealing glass, and a boundary between the sensor element and the sealing glass In the part, a coating layer made of a heat-resistant inorganic material and having a multi-particle aggregate structure is formed so as to cover at least the periphery of the sensor element.

  In the second invention, the coating layer is formed so as to cover 80% or more of the surface of the sealing glass.

  In the third invention, the coating layer is formed to a thickness of 0.5 mm or more.

  In a fourth invention, the inorganic material contains at least one metal oxide of alumina, silica, zirconia, and titania as a main component, and generates colloidal particles made of the metal oxide or the metal oxide. An inorganic colloidal dispersion material in which colloidal particles composed of possible organometallic compounds are dispersed to form a paste is used as a precursor, and the metal and hydroxyl group compounds present on the surface of the colloidal particles are condensed at a heating temperature of 100 to 300 ° C. And an inorganic adhesive that cures while forming the metal oxide (claim 4).

  In the fifth invention, in order to detect the concentration of a specific gas component in the gas to be measured, a substantially plate-like sensor element extending in the axial direction is housed and fixed in a substantially cylindrical insulating holding member via a sealing glass. In the method for manufacturing a gas sensor, at least, it has a substantially plate-like shape extending in the axial direction, has a detection unit on the distal end side, and has an output unit capable of taking out an output signal corresponding to the detection result of the detection unit on the proximal end side. A sensor element forming step for forming a sensor element, an insulating holding member forming step for forming a substantially cylindrical insulating holding member for storing and holding the sensor element, and the sensor element is inserted into the insulating holding member, Sealing glass is filled between the sensor element and the insulating holding member, and this is melted, cooled, solidified, or crystallized to hold the sensor element through the sealing glass layer. Keep airtight in the part A colloidal dispersion paste made of an inorganic material is applied to a boundary portion between the sealing glass layer forming step and the sealing glass layer and the sensor element so as to cover at least the outer periphery of the sensor element, and this is heated, dried and cured And a coating layer forming step of forming a coating layer.

According to the first invention, even if residual stress occurs at the boundary between the sensor element and the sealing glass due to a difference in thermal expansion coefficient between the sensor element and the sealing glass, the coating layer is multi-particulate. Because of the aggregate structure, the area of the contact portion between the particles is small, even if residual stress acts on the boundary between the coating layer and the sensor element and the boundary between the coating layer and the sealing glass, It is inferred that the residual tensile stress is reduced by the dimensional deformation at the contact portion between the particles and the periphery thereof.
Therefore, even if a residual stress is generated at the boundary between the sensor element and the sealing glass due to a difference in thermal expansion coefficient between the sensor element and the sealing glass, a layer having a very small residual stress is formed on the surface. Will be.
Further, when a bending moment is applied from the outside, the sensor element breaks when the sum of the bending moment and the residual tensile stress reaches the breaking stress of the sensor element.
In the case of a conventional gas sensor in which the coating layer is not formed, breakage occurs at a strength lower than the strength of the original sensor element by the residual tensile stress. According to the present invention, since the residual tensile stress on the surface of the coating layer is extremely small, a strength close to the original strength of the sensor element is exhibited at the boundary between the coating layer and the sensor element. Therefore, it is possible to realize a highly reliable gas sensor in which the sensor element is not easily damaged by the impact of the above.
In addition, since the coating layer has a multi-particle aggregate structure according to the inventors' intensive studies, when a bending moment is applied to the sensor element from the outside, the coating layer is formed at the boundary between the sensor element and the sealing glass. It has been found that the acting stress is dispersed and reduced by the coating layer, and the sensor element is hardly broken. The multi-particle aggregate structure refers to a structure in which the particles forming the coating layer are combined in a state having a minute space.

  As a result of diligent tests by the present inventors, it has been found that if the coating layer is formed within the scope of the second invention, a gas sensor in which the sensor element is hardly broken can be realized.

  As a result of diligent tests by the present inventors, it has been found that if the thickness of the coating layer is formed within the scope of the third invention, a gas sensor in which the sensor element is hardly broken can be realized.

  According to the fourth invention, the present inventors have conducted intensive tests, and the coating layer has a small difference in thermal expansion coefficient between the sensor element, the sealing glass, and the insulating holding member, and is 100 to 300. It has been found that when heated at a relatively low temperature of 0 ° C., a gas sensor can be realized in which a multi-particle aggregate structure has a high heat resistance and a high strength ceramic, and the sensor element is not easily broken.

  According to the fifth aspect of the present invention, the gas sensor according to the first and second aspects of the present invention can be realized very easily because the sensor element is unlikely to break.

An example of the gas sensor element used for the gas sensor in the 1st Embodiment of this invention is shown, (a) is a perspective view, (b) is sectional drawing in A plane. Sectional drawing which shows the state which formed the coating layer which is the principal part of this invention in the sensor element inserted and fixed through the sealing glass in the insulator used for the gas sensor in the 1st Embodiment of this invention. The longitudinal cross-sectional view which shows the outline | summary of the gas sensor in the 1st Embodiment of this invention. The other embodiment of this invention and a comparative example are shown, this figure (a1) is principal part sectional drawing of Example 2, (a2) is the top view, This figure (b), (c) is respectively The principal part sectional drawing of Example 3, 4 and this figure (d), (e) are principal part sectional drawings of the comparative examples 1 and 2, respectively. (A) is sectional drawing which shows the test method for confirming the effect of this invention, (b) is sectional drawing which shows the measuring method of breakage length. The test result for confirming the effect of this invention is shown, (a) is principal part sectional drawing which shows the state broken at the coating layer end surface, (b) is principal part cross section which shows the state broken at the sealing glass end surface Figure. The characteristic view which shows the effect of this invention with a comparative example. The schematic diagram for demonstrating the effect of this invention. Sectional drawing which shows the outline | summary of the gas sensor in other embodiment of this invention. Sectional drawing which shows the outline | summary of the gas sensor in other embodiment of this invention.

The gas sensor of the present invention is a gas sensor provided in a combustion exhaust passage of a combustion engine for measuring the concentration of a specific gas component in a gas to be measured. The gas sensor is formed in a substantially flat plate shape extending in the axial direction as a sensor element, and is detected on the tip side. This is suitable for a gas sensor using a so-called laminated gas sensor element in which an output portion for providing an output signal corresponding to a detection result is provided on the base end side. The gas sensor of the present invention is not limited to the type of specific gas component to be detected by the sensor element used, and can be applied to various gas sensors such as NH ₃ sensor, NOx sensor, O ₂ sensor, PM sensor, and the like. It is a thing.

  Hereinafter, with respect to the gas sensor 1 according to the first embodiment of the present invention, an example of an oxygen sensor that detects a concentration of oxygen components in a measurement gas using a combustion exhaust flow discharged from an internal combustion engine such as an automobile engine as a measurement gas will be described. A description will be given with reference to FIGS. In the following description, the upper side of the figure is referred to as the base end side, and the lower side is referred to as the front end side.

As shown in FIG. 1A, the gas sensor element 10 is formed in a substantially flat plate shape extending in the axial direction, a detection unit 11 is provided on the distal end side, and an output unit 12 is provided on the proximal end side. Further, as shown in FIG. 4B, a reference electrode layer 110 is formed on the surface of the oxygen ion conductive solid electrolyte body 100 that is exposed to the atmosphere introduced as a reference gas, and is used as a gas to be measured. A measurement electrode 120 is formed on the exposed surface. Furthermore, a reference gas chamber forming layer 151 that is laminated on the reference electrode layer 110 side and partitions the reference gas chamber 130, a heating element 140 for heat-activating the solid electrolyte layer 100, and an insulating layer that insulates and seals the heating element 140 150 is formed.
A diffusion resistance layer 160 that is laminated on the measurement electrode layer 120 side and imparts a predetermined diffusion resistance is formed.
Further, a porous protective layer 161 is formed so as to cover the outer periphery of the detection unit 11 so as to suppress cracking of the sensor element 10 due to adhesion of water droplets from the outside.
The reference electrode layer 110 and the measurement electrode layer 120 are respectively connected to a reference electrode terminal 112 and a measurement electrode terminal 122 formed on the proximal end surface of the sensor element 10 via a reference electrode lead 111 and a measurement electrode lead 121 (not shown), respectively. It is connected.
The heating element 140 is connected to a pair of energization terminals 142a and 142b formed on the base end side surface via a pair of lead portions 141a and 141b.

As shown in FIG. 2, the sensor element 10 is inserted into an insulating holding member (hereinafter referred to as an insulator) 20 formed in a substantially cylindrical shape made of high-purity alumina or the like, and is sealed in the insulator 20 by a sealing glass 30. It is fixed to.
Further, at the boundary between the sealing glass 30 and the sensor element 10, at least 80% or more of the surface of the sealing glass 30 while the coating layer 31 using the inorganic material, which is the main part of the present invention, covers the outer periphery of the sensor element 10. Covering. In the present embodiment, the coating layer 31 covers the entire surface of the sealing glass 30 (100%), and the thickness t is 0.5 mm or more.
In the present embodiment, the insulator 20 has an element insertion hole 210 into which the sensor element 10 is inserted at the center, and a sealing glass filling portion 211 for filling the sealing glass 30 on the base end side.
As the sealing glass 30, it is desirable that the difference in thermal expansion coefficient between the sensor element 10 and the insulator 20 is as small as possible. However, even if a known material widely used as the sealing glass is used, the effect of the present invention is achieved. Is demonstrated.
Specifically, a crystallized glass such as B ₂ O ₃ —ZnO—SiO ₂ —Al ₂ O ₃ —BaO—MgO as described in Patent Document 1 is preferably used.
The sealing glass 30 is formed in a substantially cylindrical shape for easy assembly of the powdery sealing glass raw material, and is inserted into the sealing glass filling portion 211 of the insulator 20.
When the sensor element 10, the insulator 20, and the sealing glass 30 are temporarily assembled and heated to about 900 ° C. to crystallize the sealing glass 30, the sensor element 10 is placed inside the insulator 20 through the sealing glass 30. The airtight state is maintained.

As a material used for the coating layer 31, when using a commercial item, it turned out that the material shown in Table 1 is suitable by the present inventors' earnest test.
For example, inorganic adhesives such as Asahi Chemical Industry Co., Ltd., Sumiceram S-208D, S-30B-21, S-18C, S-301, Toa Gosei Co., Ltd., Aron Ceramic C, D, E, etc. can be used. is there.
These materials are generally used as heat-resistant inorganic adhesives capable of bonding ceramics, glass, metals and the like used in a high temperature environment, and are cured at a relatively low temperature of about 100 to 300 ° C.
After curing, it becomes a ceramic with excellent heat conductivity and high hardness, and becomes a porous film that can withstand high temperatures of 1000 to 2000 ° C., and the coating layer 31 of the multi-particle aggregate structure of the present invention can be easily formed.
In addition, it is desirable to select suitably the heat resistant inorganic material contained in the inorganic adhesive to be used according to the thermal expansion coefficient of the sensor element 10, the insulator 20, and the sealing glass 30.
Further, the present invention is not limited to these commercially available products, and the metal oxide or organometallic compound that becomes an aggregate of one or more metal oxide particles of alumina, silica, and zirconia after curing is in a colloidal state. Silanol polymer (—O—Si—O—), aluminol heavy by dehydration / condensation of silanol groups (Si—OH) and aluminol groups (Al—OH) present on the surface of colloidal particles that are dispersed by heating It is presumed that any metal oxide polymer such as a coalescence (—O—Al—O—) can be used as long as it is formed and cured.

  As shown in FIG. 3, the gas sensor 1 according to the first embodiment of the present invention includes a sensor element 10 inserted and fixed in the insulator 20 through the sealing glass 30, and the sensor element 10 and the sealing glass 30. The coating layer 31 formed at the boundary and the insulator 20 are held, the housing 40 on which the measuring unit 11 of the sensor element 10 is placed inside the gas flow path 80 to be measured, and the tip side of the housing 40 are provided. Cover bodies 70 and 71 for protecting the measurement unit 11 of the element 10 and a pair of signal lines provided on the proximal end side of the housing 40 and connected to the output unit 12 of the sensor element 10 to extract an output signal corresponding to the detection result 114 and 124 and a casing 50 that protects the pair of energized wires 144a and 144b that energize the heating element 140 that heats and activates the sensor element 10. It is.

The housing 40 is made of a metal such as stainless steel and is formed in a substantially cylindrical shape. A casing 50 is fitted to the boss portion 42 on the proximal end side, and double cylindrical cover bodies 70 and 71 are attached to the distal end portion 44. Is fixed.
A screw part 43 is formed in the middle outer peripheral part of the housing 40 and is screwed to a combustion exhaust passage 80 of an internal combustion engine (not shown) via a gasket, so that the measurement part 11 of the sensor element 10 can measure the gas flow to be measured. It is disposed inside the path 80 and is fixed in a state covered with the cover bodies 70 and 71. A hexagonal portion 45 for tightening the screw portion 43 is formed on the outer periphery of the housing 40.

The insulator 20 is fixed in a housing 40 by crimping a crimping portion 41 via a powder seal member 60, an insulating packing member 61, an insulating holding member 62, a metal sealing member 63, and the like.
The sensor element 10 is inserted into the insulator 20, and the sensor element 10 is fixed by the sealing glass 30. A heat-resistant inorganic material that is a main part of the present invention is provided at the boundary between the sensor element 10 and the sealing glass 30. The coating layer 31 having a multi-particle assembly structure is formed.

The cover bodies 70 and 71 are made of a heat-resistant metal such as stainless steel and have a double cylinder structure including a substantially bottomed cylindrical outer cover 70 and an inner cover 71.
The outer cover 70 and the inner cover 71 are formed with openings 701, 702, 711, and 712 for introducing water to be measured into the sensor element 10 and preventing the sensor element 10 from being wet, and the base end side is formed at the distal end portion 44 of the housing 40. It is fixed.

  The pair of signal lines 114 and 124 and the pair of energization lines 144a and 144b are held at the base end portion of the casing 50 by a sealing material 64 made of an elastic member such as heat resistant rubber, and the connection fittings 113, 123, 143a, The sensor electrode 10 is connected to the measurement electrode terminal 112, the reference electrode terminal 122, and the heating element energization terminals 142a and 142b via the 143b, and is covered with a protective member 170 to ensure their conduction.

  The sealing material 64 is provided with a reference gas inlet 51, and the atmosphere introduced from the reference gas inlet 51 through the water repellent filter 52 is introduced into the reference gas chamber 130 of the gas sensor element 10. .

  When the heating element 140 is energized by an energization control device (not shown) and the solid electrolyte layer 100 is activated by the heating element 140, the oxygen concentration in the measurement gas in contact with the measurement electrode layer 120 through the diffusion resistance layer 160 is increased. And the difference in oxygen concentration in the atmosphere introduced into the reference gas chamber 130 in contact with the reference electrode layer 110 causes a potential difference between the two electrodes. By measuring this difference, the oxygen concentration in the gas to be measured is measured. The concentration of a specific gas component in the measurement gas can be detected.

With reference to FIGS. 1 to 3, an outline of a manufacturing method of the gas sensor 1 according to the first embodiment of the present invention will be briefly described.
In the sensor element forming step, a substantially plate-like shape extending in the axial direction into the insulator 23 as a substantially cylindrical insulating holding member through the sealing glass 30 in order to detect the concentration of the specific gas component in the gas to be measured. In the manufacturing method of the gas sensor 1 in which the sensor element 10 is housed and fixed, a solid electrolyte material 100 such as zirconia is formed from a solid electrolyte material 100 by a known manufacturing method such as a doctor blade method, and a reference electrode layer 110, a measurement electrode The layer 120, the reference gas chamber 130, the heater 140, the insulating layers 150 and 151, the diffusion resistance layer 160, the protective layer 161, and the like are formed by a known method and formed in a substantially plate shape extending in the axial direction as shown in FIG. A sensor element 10 having a detection unit 11 on the distal end side and an output unit 12 capable of extracting an output signal corresponding to the detection result of the detection unit 11 on the proximal end side is formed.
In the insulating holding member forming step, as a substantially cylindrical insulating holding member for storing and holding the sensor element 10, using a heat-resistant insulating material such as alumina or titania, a known manufacturing method such as CIP, FIG. A substantially cylindrical insulator 20 as shown in FIG. 3 is formed.
In the sealing glass layer forming step, the sensor element 10 is inserted into the insulator 20, and the sealing glass material described above is filled between the sensor element 10 and the insulator 20, and this is melted, cooled and solidified, or crystal precipitation treatment. Then, the sensor element 10 is airtightly held in the upper insulator 20 through the sealing glass layer 30.
In the coating layer forming step, which is the main part of the present invention, any of alumina, silica, zirconia, and titania as a main component so as to cover at least the outer periphery of the sensor element 10 at the boundary between the sealing glass layer 30 and the sensor element 10. An inorganic colloidal dispersion material in which a colloidal particle comprising one or more metal oxides and comprising a metal oxide or a colloidal particle comprising an organometallic compound capable of forming the metal oxide is dispersed to form a paste Table 1 shows an inorganic adhesive that cures while forming a metal oxide by condensing a compound of a metal and a hydroxyl group present on the surface of the colloidal particles at a heating temperature of 100 to 300 ° C. by using a precursor. An inorganic adhesive is applied, and this is heated, dried and cured to form a coating layer 31 having a multi-particle aggregate structure.
Through the above steps, the sensor element 10 is sealed and fixed to the insulator 20 through the sealing glass 30, and the coating layer 31 which is a main part of the present invention is formed so as to cover the periphery of the sensor element 10. This is assembled to the housing 40 formed in a substantially cylindrical shape by a known method, held and fixed by a known method, and the cover body 70, the pair of signal wires 114, 124, the pair of energization wires 144a, 144b, By assembling the casing 50 and the like, the gas sensor 1 for detecting the concentration of the specific gas component in the gas to be measured as shown in FIG. 3 is completed.

The effects of the present invention will be described below with reference to FIGS.
An example in which the sensor element 10 in the first embodiment of the present invention shown in FIG. 2 is fixed in the insulator 20 via the sealing glass 30 and the coating layer 31 is formed is taken as Example 1.
As shown in FIG. 4, the formation range and thickness of the coating layer 31 are changed to provide other examples 2, 3, and 4 of the present invention, and the comparison examples 1 and 2 in which the coating layer 31 is not formed are used. A test was conducted to confirm the effect of the invention.
In Example 2, as shown in the drawings (a ₁ ) and (a ₂ ), the coating layer 31 a covers the surface of the sealing glass 30 with a thickness ta (0.5 to 0.8 mm) by 80% or more. It is formed in such a range.
In Example 3, the coating layer 31b has a thickness tb (1.8 to 2.2 mm) and is formed so as to cover the entire surface of the sealing glass 30, as shown in FIG.
In Example 4, the coating layer 31c has a thickness tc (2.8 to 3.2 mm) and covers the entire surface of the sealing glass 30 as shown in FIG. It is formed so as to fill the gap.
In Comparative Example 1, the coating layer 31 is not formed as shown in FIG.
In Comparative Example 2, as shown in FIG. 4E, the upper surface of the sealing glass 30 is further filled with the sealing glass 30y with a thickness ty (2.8 to 3.2 mm) instead of the coating layer 31. It is formed so as to fill the gap in the sealing glass filling part 211.

FIG. 5 shows a test method for investigating the effect of the present invention.
As shown to this figure (a), the insulator 20 is fixed with the fixing jig 90, and about Example 1, 2, 3, 4, from the upper end surface of the coating layers 31, 31a, 31b, 31c, it is a comparative example 1. For No. 2, the pressing load was increased in the thickness direction at a predetermined distance A (fixed to 5 mm) from the upper end surfaces of the sealing glasses 30 and 30y, and the breakage load P (kgf) was measured. Since the actual breakage position varies, the bending moment M (= P × B) at breakage is calculated from the breakage load P and the actual breakage length B after breakage, as shown in this figure (b). This was used as an evaluation standard.
A sensor element 10 having a plate thickness of 1.4 mm and an element width of 3.5 mm is fixed in an insulator 20 having an inner diameter of 6.5 mm via a sealing glass 30, and the measurement is performed 8 by 8 for the conditions of each example. The average value was measured. Table 2 and FIGS. 6 and 7 show the results of this test.

As shown in FIG. 6 (a), the sensor element was broken at the end face of the coating layer, and the sensor element was broken at the end face of the sealing glass as shown in FIG. 6 (b).
As shown in Table 2, in Example 1 and Example 2, what was broken at the end face of the sealing glass 30 was found, but in Example 3 and Example 4, all were broken at the end face of the coating layer 31. In Comparative Example 1, all were broken at the end surface of the sealing glass 30, and in Comparative Example 2, all were broken at the end surface of the sealing glass 30y formed on the upper surface of the sealing glass 30.

Further, as shown in Table 2 and FIG. 7, in Examples 1, 3, and 4 in which the coating layer 31 was formed so as to cover the entire surface of the sealing glass 30, the bending moment M at the time of breakage was the thickness t of the coating layer, Regardless of tb and tc, the average was 51 kgf · mm (47 to 55 kgf · mm).
In Example 2, the bending moment M at the time of breakage was an average of 39 kgf · mm (35 to 41 kgf · mm).
In Comparative Example 1, the bending moment M at breakage was an average of 29 kgf · mm (24 to 33 kgf · mm).
In Comparative Example 2, the bending moment M at breakage was an average of 29 kgf · mm (25 to 32 kgf · mm).

From the above, by forming the coating layer 31 so as to cover the outer periphery of the sensor element 10 at the boundary between the sealing glass 30 and the sensor element 10, the bending strength of the sensor element is improved and the impact from the outside is reduced. On the other hand, it has been found that a gas sensor that is not easily broken can be realized.
Further, the coating layer 31 is effective if it is formed so as to cover at least 80% or more of the surface of the sealing glass 30, and it is desirable to form the coating layer 31 so as to cover the entire surface. It was found that the effect of the present invention can be obtained if the thickness is desirably 0.8 mm or more.

Subsequently, the coating layer was formed on the same conditions as Example 1 by changing the inorganic adhesive used about the effect by the difference in the kind of inorganic adhesive shown in Table 1, and the bending moment at the time of breakage was measured. The results are shown in Table 3.
Due to the difference in the main component, there is a difference in the coefficient of thermal expansion from the sensor element 10, so that a slight difference occurs in the effect. However, by forming a coating layer, any of Examples 1, 5, 6, 7, and 8 Also, the bending moment at the time of breakage is higher than those of Comparative Examples 1 and 2.

For the force acting on the boundary between the sensor element 10 and the sealing glass 30, the coating layer 31 is composed of a multi-particle aggregate in which the inorganic material particles 310 are aggregated. As shown in a model diagram of an aggregate of spherical particles in FIG. 8, a load P is applied to the sensor element 10 and a tensile force due to a bending moment acts on the surface of the coating layer 31 (in this figure, the center of the tensile force). (This figure shows only a part as an example, but the figure shows only a part.) It is presumed that the force acting on the boundary between the sensor element 10 and the sealing glass 30 is reduced and the sensor element 10 is less likely to break.
When a tensile force due to a bending moment acts on the boundary between the sensor element 10 and the coating layer 31, as described above, the residual tensile stress is reduced by the dimensional deformation at the contact portion between the particles and the periphery thereof. It is assumed that the element 10 is less likely to break.
As shown in FIG. 8, the coating layer 31 is a combination of a large number of inorganic material particles 310, and a multi-particle aggregate structure in a state where the inorganic material particles 310 are combined with a minute space. It is what makes.

9 and 10 show gas sensors 1a and 1b according to another embodiment of the present invention. The same components as those in the above embodiment are denoted by the same reference numerals, and the description thereof will be omitted. Only differences will be briefly described.
In the gas sensor 1a shown in FIG. 9, the connection fittings 113a, 123a, 143a, 143b are elastically deformable springs so that they are elastically abutted against the output unit 12, and are connected to the sensor element 10 from the outside. It has a structure that can absorb the impact. By forming the coating layer 31 of the present invention on the gas sensor 1a having such a structure, a gas sensor that is more resistant to impact can be realized.
In the gas sensor 1b shown in FIG. 10, in addition to making the connection fittings 113a, 123a, 143a, and 143b into a spring shape that can be elastically deformed, an insulator 170b that insulates and holds them is provided by a holder 171 having a spring portion. The structure is elastically held in the casing 50b, so that an external impact on the sensor element 10 is absorbed, and the element is not easily broken.
By forming the coating layer 31 of the present invention on the gas sensor 1b having such a structure, a gas sensor that is more resistant to impact can be realized.

DESCRIPTION OF SYMBOLS 1 Gas sensor 10 Sensor element 11 Detection part 12 Output part 100 Solid electrolyte layer 110 Reference electrode layer 120 Measurement electrode layer 130 Reference gas chamber 140 Heat generating body 150, 151 Insulating layer 160 Diffusion resistance layer 161 Protection layer 112, 122 Output terminals 142a, 142b Current-carrying terminals 113, 123, 143a, 143b Connection fittings 114, 124 Signal lines 144a, 144b Current-carrying wires 170 Terminal joining member 20 Insulating holding member (insulator)
21 Insulator base end portion 210 Element insertion hole 211 Sealing glass filling portion 22 Insulator locking portion 23 Insulator leading end portion 30 Sealing glass 31 Inorganic material coating layer 40 Housing 50 Casing 51 Air introduction holes 60, 61, 62, 63, 64 Sealing member 70, 71 Cover body 701, 702, 711, 712 Measurement gas introduction hole 80 Measurement gas flow path 90 Fixing jig for test

JP 2003-4694 A

Claims (5)

Formed in a substantially plate shape extending in the axial direction, at least the tip side is exposed to the gas to be measured and detects the concentration of the specific gas component in the gas to be measured, and the output signal corresponding to the detection result is taken out from the base side A sensor element having an output part; a substantially cylindrical insulating holding member that holds the sensor element inside; and the detection part of the sensor element is held in the gas to be measured while covering the insulating holding member. In a gas sensor comprising a housing to be fixed,
While sealing and fixing the sensor element and the insulating holding member through a sealing glass,
A gas sensor comprising a coating layer made of a heat-resistant inorganic material and having a multi-particle aggregate structure so as to cover at least the periphery of the sensor element at the boundary between the sensor element and the sealing glass.   The gas sensor according to claim 1, wherein the coating layer is formed to cover 80% or more of the surface of the sealing glass.   The gas sensor according to claim 1, wherein the coating layer is formed to a thickness of 0.5 mm or more.   The inorganic material includes, as a main component, one or more metal oxides of alumina, silica, zirconia, and titania, and colloidal particles made of the metal oxide, or an organometallic compound capable of generating the metal oxide. The metal oxide is formed by condensing a compound of a metal and a hydroxyl group present on the surface of the colloidal particles at a heating temperature of 100 to 300 ° C. using an inorganic colloidal dispersion material in which the colloidal particles are dispersed to form a paste. The gas sensor according to any one of claims 1 to 3, wherein the gas sensor is an inorganic adhesive that forms and cures. In a gas sensor manufacturing method in which a substantially plate-like sensor element extending in the axial direction is housed and fixed in a substantially cylindrical insulating holding member through a sealing glass so as to detect the concentration of a specific gas component in a gas to be measured. ,
At least a sensor element that is formed in a substantially plate shape extending in the axial direction, has a detection part on the distal end side, and has an output part on the base end side that can take out an output signal according to the detection result of the detection part. Forming process;
An insulating holding member forming step of forming a substantially cylindrical insulating holding member for storing and holding the sensor element;
The sensor element is inserted into the insulating holding member, and a sealing glass is filled between the sensor element and the insulating holding member, and this is melted, cooled, solidified, or crystallized, and sealed. A sealing glass layer forming step of hermetically holding the sensor element in the insulating holding member via a glass layer;
A coating in which a colloidal dispersion paste made of an inorganic material is applied to the boundary between the sealing glass layer and the sensor element so as to cover at least the outer periphery of the sensor element, and this is heated, dried and cured to form a coating layer A gas sensor manufacturing method comprising: a layer forming step.

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