JP2002365258A - Gas sensor element, its manufacturing method and gas sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a gas sensor element having high mechanical/thermal strength and superior durability, a method for manufacturing the gas sensor element, and a gas sensor with the gas sensor element. SOLUTION: The gas sensor element 1 formed thick at one end side to the other end side has a shift part X which is formed to have the thickness gradually reduced from the one end side to the other end side. At least a surface layer of the shift part X is formed of a porous body 12. Moreover, the porous body is formed of a porous body not baked yet which includes an aggregate powder to be an aggregate when baked and a burned powder as a carbon powder with predetermined grain characteristics which forms voids when baked, whereby the gas sensor element is made particularly superior in the durability.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a sensor element, a method for manufacturing the same, and a gas sensor. More specifically, the present invention relates to a gas sensor element having high mechanical / thermal strength and excellent durability, a method for manufacturing such a gas sensor element, and a gas sensor including such a gas sensor element.

[0002]

2. Description of the Related Art As a gas sensor element for performing gas detection and concentration measurement, a gas sensor element having a detection portion on one surface of a flat substrate is known. In such a gas sensor element, it is often difficult to increase the thickness of the base on the side provided with the detecting portion to a certain degree or more. Further, in such a gas sensor element, the detecting portion is often covered with a porous material (protective layer) for protection purposes and the like. The thickness differs on the end side.

[0003]

In such a gas sensor element, when exposed to vibrations (mechanical shock), foreign matter collides with the corners near the edges of contact between the detecting portion and the protective layer and the substrate. In some cases, it may be the starting point of destruction (e.g., mechanical shock) or even when exposed to water during heating (thermal shock). Further, instead of the above-mentioned flat plate-like base having a substantially constant thickness, a base having only one end, which does not include the detecting portion, formed thick in a step-like shape can be used. The step-shaped substrate is usually obtained by firing an unfired body obtained by a method such as lamination of sheet materials or lamination of a thick film by printing. For this reason, since the end surface of the sheet-like material, the end surface of the thick film, and the like are formed substantially at right angles to the lamination surface, it is considered that the corner portion becomes a fracture starting point as described above.

The present invention has been made in view of the above-mentioned problems, and has a high mechanical / thermal strength and a high durability, a gas sensor element, a method of manufacturing such a gas sensor element, and such a gas sensor. It is an object to provide a gas sensor including an element.

[0005]

In the various gas sensor elements having different thicknesses at one end and the other end as described above, the mechanical and thermal strengths particularly at the portions where the thickness changes rapidly are different. It is expected that this will tend to be lower than the part. The present inventors have provided a transition portion in which the thickness changes more gradually in such a gas sensor element, and furthermore, the mechanical / thermal strength of the gas sensor element is reduced by forming at least the surface layer of the porous body. It has been found that the present invention can be improved, and the present invention has been completed.

A gas sensor element according to the present invention is a gas sensor element having a shape in which one end is thicker than the other end, and has a transition portion formed so that the thickness is gradually reduced from the one end to the other end. At least the surface layer of the transition portion is made of a porous material.

[0007] The "transition section" may be a part of the gas sensor element or may be the whole. It is particularly desirable that the gas sensor element of the present invention has the shape and configuration when the one end side is twice or more the thickness of the other end side.

[0008] The above "gradual decrease in thickness" means:
It indicates that the thickness is continuously reduced at the transition part, but even if the degree of the thickness reduction is always a constant rate,
The ratio may be irregular. In addition, it usually excludes that it is step-like. That is, the surface of the transition portion can be, for example, a curved surface, an inclined surface, or the like, and preferably has a shape that is smoother and has a continuously reduced thickness. In particular, in the case of a curved surface, the curved surface is preferably R0.2 or more.

The "porous body" is not particularly limited as long as it is porous. Since at least the surface layer of the transition portion is porous, it is possible to effectively suppress the occurrence of cracks due to thermal shock, in particular, while having sufficient mechanical impact resistance as compared with the case where the surface layer is dense. it can. The porosity of this porous body is 25 to 55% (particularly 30 to 50%)
It is preferable that If the porosity is less than 25%, the closed layer tends to have a large number of closed pores in the surface layer of the transition portion, making it difficult to sufficiently obtain the effect of being porous. This is because the number of parts tends to be small and the mechanical strength tends to be insufficient. Further, the average particle diameter of the particles constituting the transition portion is 10 μm.
Exceeding the range is not preferable because it is difficult to obtain a sufficient effect on thermal shock resistance due to coarsening of the lattice-like particle connecting portion.

The porosity is measured by the following method. That is, the apparent volume (including the pore volume) of only the porous body is V, and the mass of only the porous body in air is m.
In the case where the volume of water after the porous body alone is sufficiently hydrated in water by vacuum defoaming in water is m2, it is calculated by the following equation (1). {(M2-m1) / V} × 100 (%) (1)

Such a gas sensor element according to the present invention has a mechanical and thermal configuration in which the gas sensor element is provided with a base having one end side thicker than the other end side and a detection portion formed on the surface of the other end side of the base. It is effective for improving the target strength. That is, the shape in which one end of the gas sensor element is thicker than the other end is derived from the shape of the base constituting the gas sensor element, and furthermore, the detection portion is provided on the surface of the other end which is the thinner side of the base. It is a gas sensor element provided with.

The "detecting portion" formed on the surface of the "substrate" described later is a portion having a property capable of detecting gas or measuring the concentration, and its structure, material, size, etc. are limited. Not done. For example, in an oxygen gas sensor element (such as a λ sensor element) and a combustible gas sensor element (such as a hydrocarbon gas sensor element and a nitrogen oxide gas sensor element), at least one solid electrolyte body and the front surface (front and back surfaces) of the solid electrolyte body And at least two electrodes provided in the above.

The above-mentioned "base" supports the detecting portion, and can constitute a general shape of the gas sensor element of the present invention. The configuration, material, size and the like of the substrate are not particularly limited. Further, the base may be provided with a heating resistor inside to provide a purpose as a heater, or may have a lead portion or the like of an electrode constituting a detection unit. In general, the unfired substrate that constitutes the substrate in the gas sensor element of the present invention is integrally fired simultaneously with the other parts, and it is difficult to remove the substrate alone as a single component.

Examples of such a substrate include an alumina sintered body containing 95% by mass or more of alumina, a zirconia sintered body containing 95% by mass or more of zirconia, and a zirconia sintered body whose main part is a zirconia sintered body. Insulated zirconia sintered body in which necessary portions inside are covered with an insulating film containing alumina at 95% by mass or more, and alumina and zirconia as main components (95% by mass or more), and the total of alumina and zirconia is 100% by mass. 30% by mass of zirconia
An alumina / zirconia mixed sintered body contained below can be used. However, the entire substrate does not need to be made of the same material. For example, when laminating and molding, a plurality of types of unsintered alumina-zirconia mixed materials whose alumina content changes in a gradient manner are laminated and fired. A sintered body obtained can also be used.

[0015] Among such laminated substrates,
For the purpose of improving the mechanical strength and the thermal shock resistance, a step-like substrate reinforced by stacking another layer on a portion of the layer directly provided with the detecting portion except for the detecting portion can be used. That is, the fired laminate includes at least a first layer and a second layer laminated on one surface of the first layer, and has a corner formed by one surface of the first layer and an end surface of the second layer. Substrates can be used.

In this case, it is preferable that the gas sensor element of the present invention includes a porous body that fills corners while gradually reducing the thickness from the end face of the second layer to the one face of the first layer toward the other end. . That is, when the gas sensor element 1 of the present invention includes the base 11 having the corner A as shown in FIG.
Preferably, the transition portion X includes the porous body 12 so as to at least fill the corner portion A. However, in the cross-sectional view of FIG. 1, the entire corner A is filled with the porous body, but the entire corner A does not necessarily need to be filled.

Further, as a laminated base having no corners as described above, the end of the second layer laminated on the first layer is formed into a shape whose thickness gradually decreases toward one end. The substrate using the second layer may have a shape as shown in FIG. In this case, the first layer 11 is removed from the slope forming the end B of the second layer 112 whose thickness is gradually reduced.
It is preferable to provide the porous body 12 covering at least a part of one surface. However, in the cross-sectional view of FIG. 2, the upper end of the slope forming the end B is covered with the porous body, but the entire slope need not necessarily be covered with the porous body.

On the other hand, it is preferable that the detecting section is covered with a porous body constituting the transition section. That is, the detection unit is usually covered with a porous material for the purpose of dust prevention, prevention of poisoning of the detection electrode provided in the detection unit, diffusion control of the gas to be measured, and the like. The mechanical strength of the gas sensor element can be further improved by using, as the porous material, a material having a composition and a raw material particle size that can be integrated with the porous body constituting the transition portion by firing. Further, it is preferable that the composition and the raw material particle size allow the porous body constituting the transition portion and the material constituting the surface of the base body in contact with the porous body to be integrated by firing. Thereby, the mechanical strength of the gas sensor element can be particularly improved.

In the case where a substrate having different thicknesses at one end and the other end as described above is not used, that is, when a plate-like substrate having a substantially uniform thickness is used, the detecting section is used. The detection unit is provided on one end side of the base, and the detection unit is usually covered with a porous material for the purpose of dust prevention or the like as described above. Therefore, FIG.
As shown in (1), the thickness of the gas sensor element differs between one end and the other end. In such a case, it is also possible to provide a transition portion provided with a porous body having a gradually reduced thickness so as not to cause a sudden change in thickness similarly to the gas sensor element including the base having the corners. preferable.

At this time, it is preferable that the porous body and the porous material covering the detection portion have a composition and a raw material particle size that can be integrated by firing, and further have the same composition and the same raw material particle size. Is preferred. In particular, by incorporating the same material as the material constituting the base, the porous body can be integrated at the boundary between the porous body and the base by firing to improve the strength of the entire gas sensor element. Is preferred.

The gas sensor element of the present invention includes an oxygen sensor element (such as a λ sensor element), a full area air-fuel ratio sensor element, a nitrogen oxide sensor element, a hydrocarbon gas sensor element,
Examples include a combustible gas sensor element and a humidity sensor element.

The method for manufacturing a gas sensor element according to the present invention is characterized in that it comprises an aggregate powder which is fired to become an aggregate of the porous body and a burnt-off powder which volatilizes by firing to form voids in the porous body. A step of applying the fired porous body to the substrate and / or the detection unit.

As the "aggregate powder", alumina powder, spinel powder, zirconia powder and the like can be used. Above all, it is preferable to use alumina powder because the mechanical strength and heat resistance of the porous body can be excellent, and further, 80 mass% of the whole aggregate powder is used.
The above is preferably alumina powder.

On the other hand, carbon powder, theobromine powder, starch powder and the like can be used as the above-mentioned "burned powder", and it is particularly preferable to use carbon powder. Further, among carbon powders, the maximum particle size is 15 μm.
It is preferable that the carbon powder is a true spherical carbon powder having a particle size of 10 μm or less and a cumulative volume from the smaller particle side of 50% in the volume-based particle size distribution.
However, when the average value of the diameters of five different points of one particle is defined as A, the maximum value of the diameters of the five points is L, and the minimum value is M, (A -L) / A and (AM) / A represent 0.07 or less.

By providing a porous body obtained by using the above-mentioned carbon powder and further a specific carbon powder,
The mechanical and thermal strength of the gas sensor element can be improved in a well-balanced manner. In particular, the thermal shock resistance can be greatly improved as compared with a gas sensor element having a dense transition portion. Similarly, it is preferable that the unfired porous body is also used as a porous layer covering the detection section. In this case, the detection electrode installed at the outermost part of the detection unit is Si,
Excellent protection from poisoning of Mn, P and Pb, etc., and the poisoning resistance can be greatly improved. Further, the above application step may be performed at any time before firing the gas sensor element.

A gas sensor according to the present invention includes the gas sensor element according to the present invention. As a result, high durability can be obtained even in a system that is exposed to a cold / hot cycle such as measurement of an exhaust gas component from an internal combustion engine.

[0027]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in more detail by way of examples. In the following manufacturing method, it is assumed that one element is manufactured for ease of unraveling. However, in the actual process, 10 unfired elements having a length of 42.85 mm and a width of 3.93 mm are cut. One for each unsintered sheet that can be put out
Zero printed patterns are formed, and the unsintered gas sensor elements are cut out after lamination. Further, in each unsintered sheet, a hole for alignment is formed in a peripheral portion, and each unsintered sheet is aligned by inserting a fixing pin into each of the holes (see FIG. 5).

The unsintered sheet is defined as the first layer lower part 111a, the unsintered first layer upper part 111b, the unsintered second layer
Each unsintered sheet to be the lower layer 112a and the unsintered second layer upper 112b. Further, the printing pattern includes a buffer layer 111c, an insulating layer lower part 113a, an insulating layer upper part 113b, a porous body 12, a reference electrode 131, a solid electrolyte body lower part 132a, a solid electrolyte body upper part 132b, a detection electrode 133, an electrode The terminals 133 bp and 131 bp are the heating resistor 14 and the heating resistor terminal 142 p (see FIG. 4).

(1) Preparation of Unsintered Sheet Alumina powder (purity 99.99% or more, average particle size 0.3
μm) 100 parts by mass (hereinafter abbreviated as “parts”), 14 parts of butyral resin, and 7 parts of dibutyl phthalate were blended and mixed using a mixed solvent consisting of toluene and methyl ethyl ketone to form a slurry. 90mm long, 60mm wide by blade method and punching
Were produced. First layer lower part 111a
Each unsintered sheet to be the upper layer 112b and the second layer has a thickness of 0.55 mm, and each unsintered sheet to be the upper layer 111b and the lower layer 112a has a thickness of 0.40 mm.
mm.

(2) Formation of Heating Resistor Pattern Alumina powder (purity 99.99% or more, average particle size 0.3
μm) A paste containing 4 parts of platinum powder and 100 parts of platinum powder is printed and dried on one surface of the unsintered sheet serving as the lower part of the first layer, and a heating element pattern (after firing, heating element 141) and a heating element lead pattern are formed. Heating resistor pattern (after firing, heating resistor 14) composed of (heating portion leads 142)
Was formed. Next, a first layer through hole 111as for conducting the heating resistor is formed at one end of the unsintered sheet to be the lower part of the first layer, and the back of the unsintered sheet corresponding to the first layer through hole is fired on the back surface. A pad pattern to be the heating resistor terminal 142p for connecting the terminal was formed with the same paste as above. Thereafter, an unfired sheet to be the first upper portion 111b was laminated and pressed from above the heating resistor pattern.

(3) Formation of Buffer Layer Pattern On the unsintered sheet to be the first upper portion 111b laminated in (2), 80 parts of alumina and 20 parts of zirconia are blended to form a buffer layer 111c after firing. Paste 30 ±
It was printed at a thickness of 10 μm and dried to form a buffer layer pattern.

(4) Formation of reference electrode pattern On the buffer layer pattern formed in (3), zirconia powder (obtained by a coprecipitation method, containing 5.4 mol% of Y ₂ O _3, and having an average particle diameter of 0) The thickness which becomes the reference electrode 131 (composed of the reference electrode portion 131a and the reference electrode lead portion 131b) after firing using a paste in which 15 parts of Pt and 100 parts of platinum powder are blended. 20μm ± 1
A reference electrode pattern of 0 was formed.

(5) Formation of Lower Pattern of Solid Electrolyte Zirconia powder (purity 99.9% or more, average particle size 0.3
μm) 50 parts, alumina powder (purity 99.99% or more,
50 parts, average particle size 0.3 mm), butyl carbitol 3
3.3 parts, dibutyl phthalate 0.8 part, dispersant 0.5
Parts and 15 parts of binder, add the required amount of acetone,
After mixing for 4 hours, the acetone was evaporated to prepare a paste. This paste is applied 13 m in length from the other end of the unfired layer on the first layer so as to cover the reference electrode pattern.
m, printed and dried over a thickness of 25 ± 10 μm to form a solid electrolyte pattern that would become the solid electrolyte 132 after firing.

(6) Formation of lower pattern of insulating layer The slurry prepared in (1) was added to butyl carbitol 21
After adding 4 parts and the required amount of acetone and mixing for 4 hours,
The acetone was evaporated to prepare a paste. This paste is printed and dried at a thickness of 25 ± 10 μm on the buffer layer pattern and the reference electrode lead pattern excluding the portion where the solid electrolyte layer lower pattern is formed, and the insulating layer lower pattern that becomes the insulating layer lower 113a after firing. Was formed.

(7) Formation of Upper Pattern of Solid Electrolyte Body The paste prepared in (5) is made to have a length of 8 mm (shorter than the lower pattern of the solid electrolyte body) by aligning the other end position from the lower pattern of the solid electrolyte body. Is printed over 25 ± 10 μm, dried, and fired, and the solid electrolyte body upper part 132b is fired.
A solid electrolyte body upper pattern was formed.

(8) Formation of Upper Pattern of Insulating Layer The paste prepared in (6) is printed on the lower pattern of the insulating layer on which the upper pattern of the solid electrolyte layer is not formed, dried, and fired to form the upper layer of the insulating layer. An insulating layer upper pattern to be 113b was printed with a thickness of 25 ± 10 μm and dried.

(9) Formation of the sensing electrode pattern The paste prepared in (4) is printed on the solid electrolyte body upper pattern and the insulating layer upper pattern formed in (7) and (8), and dried. After firing, a detection electrode pattern having a thickness of 20 ± 10 μm to be the detection electrode 133 (consisting of the detection electrode portion 133a and the detection electrode lead portion 133b) was formed.

(10) Formation of a porous body pattern covering the sensing electrode The burned powder has a maximum particle size of about 17 μm, and the volume accumulated from the smaller particle size side in the particle size distribution based on the volume is 50%. A spherical carbon powder having a particle size of about 5.5 μm (data showing the particle size distribution of the carbon powder as the burnt-out powder is shown in FIG. 6) and an unsintered sheet of the same material as the aggregate powder Alumina was mixed so that the carbon powder was 45% by mass when the total of alumina and carbon powder was 100% by mass. After that, 10.0 parts by mass of butyral resin and 5 parts by mass of dibutyl phthalate were added in an external formulation in which the total of the alumina and the carbon powder was 100 parts by mass, and a slurry was formed using a solvent composed of toluene and methyl ethyl ketone. Using this slurry, the doctor blade method to 0.25-
A 0.30 mm sheet was formed. Place the obtained sheet on the solid electrolyte body upper pattern, 10 mm in length from the other end side.
Then, a porous body pattern to be a part of the porous layer 12 after firing was formed.

(11) Lamination of unfired sheets to be the lower and upper portions of the second layer The lower portion of the second layer 112a is fired so as to cover portions other than the porous material pattern formed in (10). The unsintered sheet and the unsintered sheet to be the upper second layer 112b after the sintering were laminated. In addition, through holes 112as and 112bs for conducting with each electrode are provided at one end side of each unsintered sheet.
Are formed, and after baking, the electrode terminals 131 bp and 133 bp for connecting the ends of the lead portions of the respective electrodes on the back surface corresponding to the through holes of the unfired sheet to be the upper part of the second layer.
Was formed.

(12) Formation of a porous body pattern constituting a transition portion A paste obtained by dissolving the sheet obtained in (10) using butyl carbitol is used to form a second paste laminated in (11). It was applied in a curved shape so as to fill a step between the unsintered sheet to be the lower layer and the unsintered sheet to be the upper layer and the porous material pattern formed in (10).

(13) Degreasing and firing The laminate obtained in (1) to (12) is heated from room temperature to 420 ° C. at a rate of 10 ° C./hour in an air atmosphere, and held for 2 hours. The organic binder was degreased. Thereafter, in the air atmosphere, the temperature is raised to 1100 ° C. at a rate of 100 ° C./hour, further raised to 1520 ° C. at a rate of 60 ° C./hour, and held at this temperature for 1 hour for firing. 300 gas sensor elements as shown in FIGS. 1 and 4 were obtained. In addition, the porosity of the obtained porous body of the gas sensor element 1 by the above method was 33% on average.

[2] Manufacture of gas sensor element in which the porosity of the porous body constituting the transition portion is different from each other The mass ratio of alumina to carbon powder is shown in Table 1 below.
A slurry for a porous body was prepared in the same manner as in (10) of [1] except that the slurry was mixed as a seed. (1) (1
The slurry obtained above is applied in a curved shape so as to fill the steps of the unfired gas sensor element obtained in the same manner as in 2), and then degreased and fired in the same manner as in [13] of [1]. Was performed to obtain ten types of gas sensor elements 1 having different porosity of the porous body.

[0043]

[Table 1]

[3] Manufacture of gas sensor element having no transition portion An unsintered gas sensor element was obtained in the same manner as in (1) to (1) to (11), and then (1) was performed without performing (12).
Degreasing and baking were performed in the same manner as in 3) to obtain a gas sensor element 1 '(Comparative Example 2) having no transition portion having a portion where the thickness rapidly changed stepwise.

[4] Manufacture of gas sensor element having dense transition portion An unsintered gas sensor element is obtained in the same manner as in (1) to (1) to (11), and thereafter, no carbon powder is contained in (12). The paste was applied in the same manner, followed by degreasing and firing in the same manner as in (13) to obtain a gas sensor element 1 "(Comparative Example 1) having a transition portion but a dense transition portion.

[5] Evaluation (1) Flexural Strength Test (Evaluation of Mechanical Strength) Each gas sensor element 1 (10) obtained in [1] to [4]
Seed), gas sensor element 1 ′ (one kind) and gas sensor element 1 ″ (one kind), each of which is fixed with a vise as shown in FIG. 7, and a load of 1 mm from the tip of the gas sensor element is applied as shown in FIG. As a point, the load is 1 per minute
Loading was performed at a speed of 0 mm. And the bending strength at the time of breaking at the transition part was measured. Similarly, the average value of the transverse rupture strengths of the 30 specimens was calculated, and the results are shown in Table 2 and shown as a graph in FIG.

[0047]

[Table 2]

(2) Water Wet Test (Evaluation of Thermal Shock Strength) Each gas sensor element 1 (10) obtained in [1] to [4]
Species), 10 gas sensor elements 1 ′ (1 type) and 10 gas sensor elements 1 ″ (1 type), respectively. The following tests were performed. That is, a gas sensor element heated and maintained at 150 ° C. (constant power control) was tested. After dripping 3 μl of water with a micro syringe into the porous material constituting the transition part, the output of the oxygen partial pressure obtained between the reference electrode and the detection electrode is measured, and the presence or absence of abnormality in the measured value is observed. The presence or absence of cracks was examined, and the red water-soluble ink was applied, and the presence or absence of cracks was examined. The same test was repeated up to 450 ° C. while increasing the heating / holding temperature by 25 ° C. The results are also shown in Table 2 and shown as a graph in FIG.

From Table 2 and FIG. 8, it can be seen that the higher the porosity, the lower the bending strength. However, it can be seen that when the porosity exceeds 57%, the transverse rupture strength sharply decreases as the porosity increases. In the wet test, the higher the porosity,
It can be seen that the temperature at which cracks occur increases. In particular, it can be seen that when the porosity is 23% or more, the thermal shock characteristics start to be stabilized. Therefore, it is understood that the porosity is particularly preferably in the range of 25 to 55% in order to exhibit particularly high mechanical and thermal strength.

[5] Manufacture of gas sensor The gas sensor element 1 obtained in [1] is fitted into an adapter 211 made of alumina, and the adhesive uncured material (the adhesive 212 after curing) is inserted into the gap between the adapter and the gas sensor element. Was charged. Thereafter, the assembly was heated to cure the uncured adhesive. Next, the assembly obtained above was inserted into a holder 21 made of alumina and having an inner diameter reduced so that the adapter could be locked at one end and the adapter at one end, and held coaxially.

Thereafter, a mixed powder of talc and glass, which becomes the buffer material 213 after heating and solidification, was filled between the holder and the gas sensor element. Next, glass powder to be a sealing material 214 was further filled. During these fillings, vibration was applied from below to achieve high filling. Next, the powder and the glass component of the sealing material were melted in a heating furnace, and then allowed to cool and solidify.

Thereafter, the holder enclosing the gas sensor element is inserted into the metal shell 22 to which the protectors 221 and 222 are welded, and a talc 223 is inserted into a gap between the holder and the metal shell.
After filling, the stopper 224 was fitted. Then
One end of the inner cylinder 225 was fitted between the metal shell and the stopper, and the inner cylinder was fixed by caulking the end of the metal shell. Thereafter, a lead wire side assembly 23 in which a lead wire or the like for conducting the lead wire led out from the gas sensor element to the connector is attached by fitting an outer cylinder 231 from above the inner cylinder to the inner cylinder. The oxygen sensor 2 was obtained by caulking the fitting portion between the and the outer cylinder.

[0053]

According to the gas sensor element of the present invention, it has high mechanical and thermal strength, especially high thermal shock resistance,
Excellent durability. Further, according to the manufacturing method of the present invention, such an excellent gas sensor element can be stably and reliably obtained. Furthermore, the gas sensor of the present invention has excellent durability because it has the above-mentioned gas sensor element.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view of an example of a gas sensor element of the present invention.

FIG. 2 is a schematic sectional view of another example of the gas sensor element of the present invention.

FIG. 3 is a schematic sectional view of still another example of the gas sensor element of the present invention.

FIG. 4 is a schematic exploded perspective view of an example of the gas sensor element of the present invention.

FIG. 5 is an explanatory view schematically illustrating a part of the manufacturing process of the gas sensor element of the present invention.

FIG. 6 is an explanatory diagram of a particle size analysis result of burnt powder used in the examples, where a represents a measured particle size distribution and b represents a in a graph.

FIG. 7 is an explanatory diagram for explaining a bending strength test performed in an example.

FIG. 8 is a graph showing the correlation between the porosity, bending strength, and porosity obtained in the examples and the crack generation temperature in the wet test.

FIG. 9 is a schematic sectional view of the gas sensor of the present invention.

[Explanation of symbols]

1: gas sensor element, 111; first layer, 111a; first
Lower layer, 111b; First layer upper, 111as; First layer through hole, 111c; Buffer layer, 112; Second layer, 11
2a; lower part of second layer, 112b; upper part of second layer, 112b
s; second layer through hole, 113a; lower part of insulating layer, 11
3b; insulating layer upper portion, 113as; insulating layer lower through hole, 113bs; insulating layer upper through hole, 12; porous body, 131; reference electrode, 131a; reference electrode portion, 13
1b; reference electrode lead portion, 132a; lower portion of solid electrolyte body, 132b; upper portion of solid electrolyte, 133; detection electrode, 1
33a; detection electrode section, 133b; detection electrode lead section, 1
33 bp, 131 bp; electrode terminal, 14; heating resistor,
141; heat generating portion, 142; heat generating resistor lead portion, 142
p; terminal for heating resistor, 2; oxygen sensor, 21; holder, 211; adapter, 212; adhesive, 213; cushioning material, 214; sealing material, 22;
2; protector, 223; talc, 224;
25; inner cylinder; 23; lead wire side assembly; 231: outer cylinder;
3: Vice.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Shinya Awano 14-18 Takatsuji-cho, Mizuho-ku, Nagoya-shi, Aichi Prefecture Inside Nihon Tokuhoku Tougyo Co., Ltd. No. 18 F-term in Japan Special Ceramics Co., Ltd. (reference) 2G004 BB04 BC02 BD04 BE04 BE10 BE13 BF04 BF05 BF09 BF18 BF27 BH09 BJ03 BM04 BM07 BM10

Claims (10)

[Claims] 1. A gas sensor element having one end side thicker than the other end side, the gas sensor element having a transition portion formed so as to gradually reduce the thickness from the one end side to the other end side, and at least one of the transition portions. A gas sensor element wherein the surface layer is made of a porous material. 2. The gas sensor element according to claim 1, further comprising: a base body having one end side thicker than the other end side; and a detection unit formed on a surface of the base body on the other end side. 3. The substrate according to claim 1, wherein the substrate comprises at least a first layer,
A fired laminate comprising a second layer laminated on one surface of the layer, having a corner formed by the one surface and an end surface of the second layer, and from the end surface to the one surface on the other end side. The gas sensor element according to claim 2, further comprising the porous body filling the corner with a shape whose thickness gradually decreases. 4. The substrate according to claim 1, wherein the base comprises at least a first layer,
And a second layer having an end portion whose thickness is gradually reduced toward the other end side, which is stacked on one surface of the layer, from a slope constituting the end portion to at least a part of the one surface. The gas sensor element according to claim 2, further comprising the porous body that covers the gas sensor. 5. The gas sensor element according to claim 2, wherein the porous body extends to cover the detection unit. 6. A flat substrate and a detector formed on one end surface of the substrate, wherein the detector is covered with the porous body, and the porous body is provided on the other end side. 2. The method according to claim 1, wherein the substrate is covered up to the surface of the substrate so as to gradually reduce its thickness.
The gas sensor element according to any one of the preceding claims. 7. The gas sensor element according to claim 1, wherein the porous body has a porosity of 25% to 55%. 8. An unfired porous body containing an aggregate powder that is fired to become an aggregate of the porous body and a burnt powder that volatilizes by firing to form voids in the porous body, The method according to any one of claims 1 to 7, further comprising a step of applying the gas sensor element to the detection unit. 9. The burnt powder has a true spherical shape having a maximum particle size of 15 μm or less, and a particle size of 10 μm or less at which the cumulative volume from the small particle side in the volume-based particle size distribution becomes 50%. 9. The method according to claim 8, wherein the gas sensor element is carbon powder. 10. A gas sensor comprising the gas sensor element according to claim 1. Description: