JP2008083060A - Manufacturing method for gas sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing method for a gas sensor and the gas sensor, which reduces the generation of a crack in a solid electrolyte caused by a dispersion in a thickness of an insulator, when burnt or aged, and a ratio of generating short circuiting between lead parts. <P>SOLUTION: Alumina is applied to bring an applied thickness of the alumina in the vicinity of the lead parts 24, 33 and the lead parts 34, 44 faced each other, into 1/6.5 (50 μm) of a thickness (325 μm) of each green sheet, when the green sheets 2, 3, 4 are layered (not shown in figure). The application of the alumina by this manner reduces the generation of cracks in the green sheets 2, 3, 4 caused by a dispersion in an applied thickness of the alumina, when burnt or aged, and the ratios of generating the short circuiting between the lead parts 24, 33, and between the lead parts 34, 44. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  In the present invention, a plurality of plate-like solid electrolytes having electrodes formed on at least one surface are laminated, a paste-like insulator is applied between the solid electrolytes, and the solid electrolyte and the insulator are integrated by firing. The present invention relates to a gas sensor manufacturing method and a gas sensor.

2. Description of the Related Art Conventionally, various types of gas sensors that are attached to an internal combustion engine such as an automobile and detect the concentration of a specific component contained in exhaust gas have been developed. As one of them, a plurality of long sheet members (hereinafter referred to as “green sheets”) made of a solid electrolyte such as zirconia are stacked to detect the concentration of nitrogen oxides in the exhaust gas. Nitrogen oxide sensors (hereinafter referred to as “NO _X sensors”) are known.

Generally, this order to manufacture the NO _X sensor, first, on both sides of the plurality of green sheets formed in an elongated shape, drying the paste of the alumina by screen printing. However, at this time, a portion where no alumina is printed is formed in a rectangular shape on one side or both sides at one end in the longitudinal direction of the green sheet.

  Then, a platinum paste that becomes a porous body when screened is screen-printed at a place where alumina is not printed, to form a rectangular electrode pattern (hereinafter referred to as an “electrode pattern”), and an oxygen pump cell or oxygen A concentration detection cell is configured. At this time, the platinum paste is also applied onto the dried alumina, and a long lead pattern (hereinafter referred to as “lead pattern”) from the electrode pattern toward one end on the opposite side of the electrode pattern. .).

  Next, the electrode pattern and the lead part pattern are insulated from the periphery around the electrode pattern and the upper part and the periphery of the lead part pattern, and paste-like alumina for bonding the green sheets together is screen-printed again. . In addition, the lead part pattern of each green sheet is formed so as to overlap with the lead part pattern of other green sheets facing each other through alumina, and a platinum wire for taking out an electric signal from each electrode. Are held between the leading ends of the lead pattern portions.

Then, after carbon printing for forming a gas chamber for introducing exhaust gas inside the NO _x sensor on the portion where the electrode pattern is formed, the respective green sheets are superimposed and pressure-bonded. It is exposed to an atmosphere of 1480 ° C. and baked to be integrated. Here, NO _X sensor integrated by firing, high temperature (e.g., 650 ° C.) in a state exposed to the atmosphere, a voltage is applied to the electrodes of the NO _X sensor (so-called aging process), the activation of the electrode Is done.

The NO _x sensor is manufactured by the above process.
By the way, the thermal expansion coefficient of zirconia which is a material of the green sheet is 9.3 × 10 ⁻⁶ / ° C. (20 to 700 ° C.), whereas the thermal expansion coefficient of alumina is 7.7 × 10 ⁻⁶ / ° C. (20 to 700 ° C.). For this reason, during firing and aging, the expansion and contraction of the green sheet are hindered by alumina, causing stress in the green sheet, and in some cases, cracks may occur in the green sheet. It has been experimentally confirmed that the occurrence of this crack is related to the thickness of the green sheet and the coating thickness of alumina.

  Here, FIG. 8 is a graph showing the results when the crack generation rate is confirmed by changing the ratio of the thickness of the green sheet and the coating thickness of alumina. However, the ratio between the thickness of the green sheet and the coating thickness of alumina is set on the horizontal axis of the graph, and the occurrence rate of cracks is set on the vertical axis of the graph.

  From FIG. 8, if the alumina coating thickness is set so that the alumina coating thickness is 1 / 3.6 times (90 μm) the thickness of the green sheet (325 μm), no cracks will occur in the green sheet. I understand that.

  Based on such experimental results, the coating thickness of alumina between the green sheets was set according to the thickness of the green sheets. Specifically, in consideration of the coating thickness error in the gas sensor manufacturing apparatus, 1/41 (79 μm) of the thickness of the green sheet was set as the target coating thickness of alumina.

  By the way, at the boundary portion between the lead portion pattern and the periphery of the lead portion pattern (hereinafter referred to as “the vicinity of the lead portion”), the coating thickness of alumina is larger than the other portions by the thickness of the lead portion pattern. For this reason, even if alumina is applied so that the alumina coating thickness is 1 / 4.1 of the green sheet thickness, the alumina coating thickness is 1 / 3.6 of the green sheet thickness in the vicinity of the lead portion. In some cases, the green sheet cracked during firing or aging.

  On the other hand, if the coating thickness of alumina is set too thin in order to avoid the above problem, the lead portions that overlap each other via alumina are short-circuited at the site from the electrode to the platinum wire. In this case, the current from each electrode flowing in each lead part flows out to the other lead part on the way to the platinum wire, or the current in the other lead part flows in, so the voltage generated in each cell fluctuates. Therefore, there is a problem that the concentration of nitrogen oxides in the exhaust gas cannot be detected accurately.

  Therefore, in order to solve the above problems, the present invention reduces the rate of occurrence of cracks in the solid electrolyte during firing or aging due to variations in the thickness of the insulator or short-circuiting between the lead portions. An object of the present invention is to provide a method for manufacturing a gas sensor and a gas sensor.

  In order to achieve the above object, the invention according to claim 1 is characterized in that a plurality of plate-shaped solid electrolytes are stacked, an electrode is formed on at least one side of the solid electrolyte, and the surfaces of the solid electrolytes facing each other are formed. Lead portions extending along the surface of the solid electrolyte from the formed electrode are disposed so as to overlap each other, a paste-like insulator is applied between the solid electrolytes, and the solid electrolyte and the insulation are baked. A method of manufacturing a gas sensor integrated with a body, wherein a coating thickness of the insulator in the vicinity of the lead portion is 1 / 8.1 or more and 1 / 5.4 or less of a thickness of the solid electrolyte. The insulator is applied as described above.

  According to such a gas sensor manufacturing method, the insulating coating thickness does not become larger than 1 / 3.6 of the thickness of the solid electrolyte even in the vicinity of the lead portion where the insulating coating thickness is most likely to vary.

In addition, the ratio of the coating thickness of the insulating material between the lead portions that overlap each other is low enough to cause a short circuit between the lead portions.
That is, according to the present invention, it is possible to reduce the rate at which cracks occur in the solid electrolyte during firing and aging due to variations in the thickness of the insulator, and short circuits occur between the lead portions.

  Next, the invention described in claim 2 is formed by laminating a plurality of solid electrolytes each having a plate shape, and forming an electrode and a lead portion extending on the electrode on at least one surface of the solid electrolyte, A gas sensor manufacturing method in which a paste-like insulator is applied to a substrate and the solid electrolyte and the insulator are integrated by firing, each formed on the surface of the solid electrolyte facing each other across the insulator The lead portions are arranged at positions that do not overlap each other with the insulator interposed therebetween, and the coating thickness of the insulator in the vicinity of the lead portion is 1/32 or more of the thickness of the solid electrolyte, and 1/4. The insulator is applied so as to be 5 or less.

  According to such a gas sensor manufacturing method, not only the same effect as the invention of claim 1 can be obtained, but also the vicinity of the lead portion where the coating thickness of the insulator is the largest does not overlap each other. The range in which the coating thickness varies is narrowed. In addition, since the lead portions are arranged as described above, no short circuit occurs between the lead portions even if the coating thickness of the insulator is set thin.

  That is, according to the present invention, it is possible to reliably reduce the rate of occurrence of cracks in the solid electrolyte during firing or aging due to variations in the thickness of the insulator or short-circuiting between the lead portions.

  In addition, since the range in which the coating thickness of the insulator varies varies, it is possible to provide a gas sensor having a more uniform quality than conventional ones. Here, the phrase “arranging the lead portions at positions that do not overlap each other with the insulator interposed therebetween” may mean that the entire lead portions may be disposed at positions that do not overlap each other, or from the electrode to the opposite electrode. At least some sections up to the vicinity of the tip of the lead portion positioned on the side may be arranged at positions where they do not overlap each other.

In addition, as described in claim 3, the main component of the solid electrolyte may be made of zirconia, and the main component of the insulator may be made of alumina.
According to a fourth aspect of the present invention, there is provided a gas sensor in which a plurality of plate-shaped solid electrolytes each having an electrode and a lead portion extending from the electrode are laminated on at least one side, the gas sensors facing each other. The lead portions respectively formed on the surfaces are arranged so as not to overlap each other.

  In the gas sensor configured as described above, the lead portions are not short-circuited at the time of manufacture or use, and therefore fluctuations in the electrical signal of the electrode due to the short-circuit between the lead portions can be prevented. And since there is no possibility of a short circuit, the application | coating thickness of an insulator can be suppressed to required minimum, and a gas sensor can be comprised thinner. As in the second aspect, “disposing the lead portions at positions where they do not overlap each other” means that the entire lead portions may be disposed at positions where they do not overlap each other, or from the electrode to the opposite side of the electrodes. You may arrange | position at the position where at least one partial area to the tip part vicinity of the located lead part does not mutually overlap.

Here, as in claim 5, it is preferable that all the solid electrolytes have the same thickness.
Such a gas sensor can be easily mass-produced because it is not necessary to manufacture a plurality of types of solid electrolytes having different thicknesses.

Embodiments of the present invention will be described below with reference to the drawings.
[First Embodiment]
First, FIG. 1 is a perspective view showing the external shape of a NO _x sensor manufactured by the manufacturing method according to the present invention.

As shown in FIG. 1, the NO _X sensor 1 is formed by sequentially laminating three long green sheets 2, 3 and 4 having a length of 50 mm, a width of 4.5 mm, and a thickness of 325 μm mainly composed of zirconia. In addition, between the green sheets 2 and 3 and between the green sheets 3 and 4, platinum wires 5, 6, 7 and 8 having a length of 10 mm and a diameter of 200 μm are arranged in the longitudinal direction of the NO _x sensor 1. It is clamped so as to protrude from one end. On the outer surface of the green sheet 2, a porous electrode 21 that pumps oxygen from the outside into the NO _X sensor 1 and pumps oxygen from the NO _X sensor 1 to the outside is provided with a platinum wire protruding end. Is provided in the vicinity of one end on the opposite side (hereinafter referred to as “electrode forming end”).

Here, FIG. 2 is an AA cross-sectional view in FIG.
As shown in FIG. 2, the NO _X sensor 1 includes a first oxygen pump cell (hereinafter referred to as “first pump cell”) 20 in which porous electrodes 21 and 22 are formed on both surfaces of a green sheet 2, and green. an oxygen concentration detection cell obtained by forming an electrode 31 and 32 of porous on both sides of the sheet 3 (hereinafter referred to as "detection cell".) 30, the electrode 41 on the surface of the NO _X sensor 1 internal side of the green sheet 4, 42 and a second oxygen pump cell (hereinafter referred to as “second pump cell”) 40, and insulating layers 50 and 60 mainly composed of alumina are interposed between the cells. .

Between the first oxygen pump cell 20 and the detection cell 30 at the electrode forming end of the NO _X sensor 1, a first diffusion resistor 25 made of a porous material, through the first diffusion resistor 25 A first chamber 26 for introducing a gas to be measured from the outside is formed. A hollow second diffusion resistor 35 made of a porous material is formed in the inner part of the first chamber 26.

  The detection cell 30 has a plane shape congruent with the hollow portion of the second diffusion resistor 2, and takes in the gas to be measured introduced into the first chamber 26 via the second diffusion resistor 35. 36 is formed.

  The insulating layer 60 is formed with a second chamber 61 for introducing the gas to be measured taken into the diffusion hole 36 so that the electrode 41 of the second pump cell 40 is exposed to the second chamber 61. Yes.

In the NO _x sensor 1 having such a structure, a long heater (not shown) is laminated on the surface of the green sheet 2 on which the electrode 21 is formed, and an activation temperature (for example, 750 ° C.) is formed by this heater. The concentration of NO _{x in} the gas to be measured is detected while being heated up to Details of the detection method are described in, for example, Japanese Patent Application Laid-Open No. 10-212298, and are not related to the gist of the present invention.

Hereinafter, a manufacturing method of the NO _X sensor 1 will be described with reference to exploded perspective view of the NO _X sensor 1 shown in FIG.
First, a through hole 27 penetrating through the green sheet 2 in the thickness direction of the green sheet 2 is formed at a position (the front right end in the drawing of the green sheet 2) on the lower surface of the green sheet 2 in the figure. Then, a platinum paste is applied to the inner wall surface of the through hole 27 so that both ends of the through hole 27 have electrical continuity.

  Next, paste-like alumina (not shown) is screen-printed with a coating thickness of 10 μm on both sides of the green sheet 2 and dried. However, the portions where the alumina is not printed are formed in a rectangular shape on both surfaces of the electrode forming end of the green sheet 2. Further, alumina is not printed on the portions where the through holes 27 are formed on both surfaces of the green sheet 2.

  Then, a paste made of platinum having a catalytic function (hereinafter referred to as “electrode paste”) is screen-printed on a rectangular portion where alumina is not printed, and the pattern of the rectangular electrodes 21 and 22 is printed. Form. At this time, an electrode paste is applied on the dried alumina from the pattern of the electrodes 21 and 22 toward the protruding end of the platinum wire, so that the long lead portion narrower than the electrodes 21 and 22 is formed. Patterns 23 and 24 are formed. However, the pattern of the lead portion 23 is formed so as to be positioned at the center portion in the short direction of the green sheet 2 in the section from the electrode 21 to the vicinity of the protruding end of the platinum wire. At the protruding end of the platinum wire, the pattern of the lead portion 23 is located on the front side of the green sheet 2 in the drawing, and the tip portion thereof is formed so as to cover the through hole 27. Moreover, the pattern of the lead part 24 is formed so as to be located on the back side in the drawing of the green sheet 2 from the electrode 22 to the protruding end of the platinum wire.

  After forming the electrode pattern and the lead portion pattern on the green sheet 2 in this way, a platinum paste (hereinafter referred to as “platinum wire paste” for integrating the platinum wires 5, 6, 7 and 8 into the lead portion pattern. 70) is applied in a thickness of 10 to 30 μm to the tip of the pattern of the lead portion 24 on the lower surface of the green sheet 2 and the portion where the through hole 27 is formed and the platinum wire 5 is sandwiched.

  When the application of the platinum wire paste 70 is finished, paste-like alumina is applied to a portion of the upper surface of the green sheet 2 excluding the pattern of the electrode 21 in a thickness of 10 to 30 μm (not shown), and the lead portion 23. Insulate the pattern from the outside.

The first pump cell 20 is manufactured as described above.
Next, a hole penetrating the green sheet 3 in the thickness direction of the green sheet 3 is formed in the vicinity of the center of the green sheet 3 in the longitudinal direction to form a diffusion hole 36. Further, a through hole 37 that penetrates the green sheet 3 is formed in a portion facing the lead portion 24 of the green sheet 2 in the vicinity of the protruding end of the platinum wire of the green sheet 3, and both ends of the through hole 37 are electrically connected. A platinum paste is applied to the inner wall surface of the through-hole 37 so as to have it.

  Then, paste-like alumina (not shown), which becomes the insulating layers 50 and 60 when fired, is screen-printed with a coating thickness of 10 μm on both sides of the green sheet 3 and dried. However, the portions where the alumina is not printed are formed in a rectangular shape near the electrode formation end rather than the diffusion holes 36 on both surfaces of the green sheet 3. Also, alumina is not printed on the portions where the diffusion holes 36 and the through holes 37 are formed on both surfaces of the green sheet 3.

  When the alumina has been dried, electrode paste is screen-printed on the areas where the alumina is not printed, thereby forming rectangular patterns 31 and 32. At this time, an electrode paste is applied from the pattern of the electrodes 31 and 32 toward the protruding end of the platinum wire on the dried alumina, and a long lead portion narrower than the electrodes 31 and 32 is formed. 33 and 34 patterns are formed. However, the pattern of the lead portion 33 is formed so as to face the lead portion 24 of the green sheet 2 and cover the through hole 37. The pattern of the lead portion 34 is formed so as to be positioned on the front side in the drawing of the green sheet 3 in the section from the electrode 32 to the vicinity of the platinum wire protruding end. The sheet 3 is formed so as to be located on the back side in the drawing.

The detection cell 30 is produced as described above.
Subsequently, paste-like alumina (not shown), which becomes the insulating layer 60 when fired, is screen-printed on the upper surface of the green sheet 4 with a coating thickness of 10 μm and dried. However, in the vicinity of the center of the green sheet 4 in the longitudinal direction, two places where the alumina is not printed are formed in a rectangular shape so as to be adjacent to each other.

  Then, an electrode paste is screen-printed on a rectangular portion where alumina is not printed to form a pattern of rectangular electrodes 41 and 42. At this time, an electrode paste is applied on the dried alumina from the pattern of the electrodes 41 and 42 toward the protruding end of the platinum wire, so that the long lead portion narrower than the electrodes 41 and 42 is formed. Patterns 43 and 44 are formed. However, the electrode 41 is formed closer to the center in the longitudinal direction of the green sheet 4 than the electrode 42. And the pattern of the lead part 43 is formed so that it may be located in the back | inner side in the figure of the green sheet 4 from the electrode 41 to the platinum wire protrusion end. The pattern of the lead part 43 is set shorter than the lead part 44 and is formed from a part where the pattern of the electrode 41 in the green sheet 4 is formed to a part facing the through hole 37 of the green sheet 3. Further, the pattern of the lead portion 44 is formed so as to be positioned on the front side in the drawing of the green sheet 4 from the electrode 42 to the protruding end of the platinum wire.

  When the formation of the electrode pattern and the lead part pattern is finished, the platinum wire paste is applied to the tip part of the lead part 44 sandwiching the platinum wire 7 and the part located on the extension line of the lead part 43 in the vicinity of the platinum wire protruding end. 70 is applied in a thickness of 10 to 30 μm.

Further, alumina for reinforcing the green sheet 4 is applied to the entire lower surface of the green sheet 4 in the drawing with a thickness of 10 to 26 μm (not shown).
The second pump cell 40 is produced as described above.

  After each cell is manufactured in this way, the portion where the electrode 22 and the platinum wire paste 70 are applied on the lower surface of the green sheet 2 and the center of the green sheet 2 in the short direction on the lower surface of the electrode forming end of the green sheet 2. The paste-like alumina (not shown) which becomes the insulating layer 50 when fired again is applied by screen printing to the places other than. Similarly, a paste-like material that forms insulating layers 50 and 60 when fired at locations on both sides of the green sheet 3 and on the upper surface of the green sheet 4 except for the portions where the electrodes and the platinum wire paste 70 are applied. Alumina (not shown) is again applied by screen printing.

  However, when alumina is applied again to each green sheet, the thickness of the alumina applied to the lower surface of the green sheet 2, both surfaces of the green sheet 3, and the upper surface of the green sheet 4 in the above process is measured with a surface roughness meter. Here, when the alumina coating thickness deviates significantly from the target coating thickness (10 μm), the printing speed, printing pressure, and printing of the manufacturing apparatus are reduced so that the error between the alumina coating thickness and the target coating thickness is reduced. Adjust gaps. Further, when the green sheets 2, 3, 4 are laminated, the alumina coating thickness in the vicinity of the portion sandwiched between the lead portions facing each other includes the alumina coating thickness applied in the above process. Alumina is screen-printed so that it becomes 1 / 8.1 or more and 1 / 5.4 or less (here, 50 μm) of the thickness of 3 or 4. When screen printing is performed, the target coating thickness of alumina is not applied at once, but the coating thickness is measured several times (for example, four times) while measuring the coating thickness with a surface roughness meter. And good.

Then, a porous body (not shown) for forming the first diffusion resistor 25 and the second diffusion resistor 35 on the green sheet 3 and a carbon material (not shown) for forming the first chamber 26 and the second chamber 61. ) And the like, and then, all the green sheets are laminated while sandwiching the platinum wires 5, 6, 7, and 8, and are pressed at a predetermined pressure (4.9 × 10 ⁵ Pa).

Here, the green sheets 2, 3, and 4 that have been pressure-bonded are exposed to an atmosphere of 1480 ° C. for 1 hour and fired. The NO _x sensor 1 is obtained by subjecting 21 and 22 to aging treatment.

In the NO _x sensor 1 manufactured as described above, alumina is 1 / 8.1 or more of the thickness of the green sheet in the vicinity of the lead portion where the coating thickness of the alumina constituting the insulating layers 50 and 60 is the largest. Therefore, the coating thickness of alumina in the vicinity of the lead portion may be larger than 1 / 3.6 (90 μm) of the thickness of the green sheets 2, 3, 4. Absent. In addition, the ratio of the coating thickness of alumina between the lead portions 24 and 33 that overlap each other to such a thickness that causes a short circuit between the lead portions 24 and 33 is low.

That is, according to the manufacturing method of the present embodiment, it is possible to reduce the rate at which cracks occur in the solid electrolyte during firing or aging due to variations in the thickness of the insulator, or short circuits occur between the lead portions.
[Second Embodiment]
Next, a second embodiment will be described.

Incidentally, NO _X sensor of the present embodiment, the NO _X sensor 1 of the first embodiment is different only arrangement of the pattern of the lead portion of the upper surface of the detection cell (pasty constituting the insulating layer 50 and 60 The target coating thickness of alumina is the same as in the first embodiment.) Accordingly, the same parts as those in the first embodiment are denoted by the same reference numerals and the description thereof is omitted, and only different parts are described in detail.

Here, FIG. 4 is an exploded perspective view of the NO _X sensor 10 of the present embodiment.
As shown in FIG. 4, in the detection cell 90 of the NO _X sensor 10, the pattern of the long lead portion 93 extending from the rectangular electrode 91 formed on the upper surface of the green sheet 9 is from the electrode 91. In the section reaching the vicinity of the protruding end of the platinum wire, the green sheet 9 is formed so as to be positioned on the near side in the drawing. In the vicinity of the protruding end of the platinum wire, the pattern of the lead portion 93 covers the through hole 37 and faces the pattern of the lead portion 24 on the lower surface of the green sheet 2 on the back side in the drawing of the green sheet 9. It is formed to be located.

  By forming the pattern of the lead portion 93 in this way, when the green sheets 2 and 9 are laminated in the portion from the electrode 91 to the vicinity of the protruding end of the platinum wire, the lead portion 24 and the lead portion 93 are Since they do not overlap, the range in which the coating thickness of alumina varies varies. In addition, even if the coating thickness of alumina is set to be thin, no short circuit occurs between the lead portion 24 and the lead portion 93 in the region from the electrode 91 to the vicinity of the protruding end of the platinum wire. Even if the lead portion 24 and the lead portion 93 are short-circuited in the vicinity of the protruding end of the platinum wire where the lead portion 24 and the lead portion 93 overlap each other, the section leading to the platinum wire 6 is short, so that a large voltage drop occurs. Will not occur.

That is, according to the manufacturing method of the present embodiment, the rate of occurrence of cracks in the solid electrolyte during firing or aging due to variations in the thickness of the insulator or short-circuit between the lead portions is reliably reduced. be able to. In addition, since the variation range of the coating thickness of alumina is narrow, it is possible to provide a NO _x sensor having a more uniform quality than conventional ones.

Further, in the NO _x sensor 10 in which the pattern of the lead portion 93 is arranged as described above, the lead portion 24 and the lead portion 93 are not short-circuited during manufacturing or use. It is possible to prevent fluctuations in the electrical signals of the electrodes 22 and 91 due to the short circuit. Moreover, since the coating thickness of alumina can be minimized between the first pump cell 20 and the detection cell 90, the NO _x sensor 10 can be made thinner.

Tables 1 and 2 show the results of verification experiments conducted by the inventors to verify the above effects.
In this demonstration experiment, the NO _X sensor 1 manufactured by the manufacturing method of the first embodiment is used in Example 1, the NO _X sensor 10 manufactured by the manufacturing method of the second embodiment is used in Example 2, and the conventional manufacturing is performed. A NO _x sensor manufactured by the method (the target coating thickness of alumina constituting the insulating layer is set to 79 μm) is used as a comparative example.

Then, in the demonstration experiment, Examples 1 and 2 and Comparative Example 10 were manufactured, the cross section of each manufactured NO _X sensor was examined, and the alumina coating thickness in the vicinity of the lead portion between the first pump cell and the detection cell. The coating thicknesses t4 and t5 of alumina between t1 to t3 and the lead portions of the first pump cell and the detection cell facing each other are measured (see FIGS. 5 to 7).

Here, Table 1 shows the measurement results of the lead portion coating thickness of the alumina in the vicinity of t1~t3 between the first pump cell and a detection cell in the NO _X sensor. Table 2 shows measurement results of the alumina coating thicknesses t4 and t5 between the lead portion of the first pump cell and the lead portion of the detection cell facing each other.

  As shown in Table 1, in the comparative example, the coating thickness t3 of alumina sometimes became larger than 1 / 3.6 of the thickness of the green sheet (325 μm) at a rate of 30%, whereas in Example 1, In No. 2, the coating thicknesses t1 and t2 of alumina did not become larger than 1 / 3.6 of the thickness of the green sheet. In Example 2, the standard deviation between the alumina coating thickness and the target coating thickness was smaller than that in Example 1, and the variation in the alumina coating thickness was small.

As shown in Table 2, Example 1 ensured a sufficient coating thickness of alumina to prevent a short circuit between the lead portions facing each other, as in the comparative example.
As a result of this demonstration experiment, by using the manufacturing method according to the present invention, cracks occur in the solid electrolyte during firing or aging due to variations in the thickness of the insulator, or short circuits occur between the lead portions. It has been demonstrated that the rate is reduced.

  In the second embodiment, the target coating thickness of alumina is set to 50 μm. However, from the above experimental results, in the manufacturing method of the second embodiment, the target coating thickness of alumina is 72.2 μm (the thickness of the green sheet). 1 / 4.5), it was found that the alumina coating thickness in the vicinity of the lead portion does not exceed 90 μm.

  Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and it goes without saying that various forms can be taken as long as they belong to the technical scope of the present invention. .

For example, in the above embodiment, the present invention is used for manufacturing a NO _x sensor. However, the present invention may be applied to manufacturing another gas sensor in which a plurality of plate-shaped solid electrolytes are stacked.
In the above embodiment, the green sheet is made of zirconia. May be.

  Further, in the second embodiment, the electrode 91 to the vicinity of the tip of the lead part 93 located on the opposite side of the electrode 91 are arranged so as not to overlap with the lead part 24 in the green sheet 2. The entire portion 93 may be disposed so as not to overlap the lead portion 24. In this case, one platinum wire to be connected to the lead portion 93 may be added.

1 is a perspective view of a NO _X sensor 1 according to a first embodiment. FIG. 2 is a cross-sectional view of the NO _X sensor 1 taken along the line AA in FIG. 1 is an exploded perspective view of a NO _X sensor 1. FIG. It is an exploded perspective view of the NO _X sensor 10 of the second embodiment. 1 is a cross-sectional view of a NO _X sensor of Example 1. FIG. 3 is a cross-sectional view of a NO _X sensor of Example 2. FIG. It is a cross-sectional view of the NO _X sensor of the comparative example. It is a graph which shows the result at the time of confirming the crack generation rate by changing the ratio of the thickness of a green sheet and the coating thickness of alumina.

Explanation of symbols

1, 10 ... NO _X sensor, 2,3,4,9 ... green sheets 5, 6, 7, 8 ... platinum wire, 20 ... first pump cell, 21,22,31,32,41,42,91 ... Electrode, 23, 24, 33, 34, 43, 44, 93 ... Lead portion, 25 ... First diffusion resistor, 26 ... First chamber, 27, 37 ... Through hole, 30, 90 ... Detection cell, 35 ... First 2 diffusion resistors, 36: diffusion holes, 40: second pump cell, 50, 60: insulating layer, 61: second chamber, 70: platinum wire paste.

Claims (5)

A plurality of plate-shaped solid electrolytes are stacked, and an electrode is formed on at least one surface of the solid electrolyte, and extends along the surface of the solid electrolyte from the electrodes formed on the surfaces of the solid electrolyte facing each other. A lead sensor is disposed so as to overlap each other, a paste-like insulator is applied between the solid electrolytes, and the solid electrolyte and the insulator are integrated by firing, and the gas sensor manufacturing method comprises:
A gas sensor characterized in that the insulator is applied so that a coating thickness of the insulator in the vicinity of the lead portion is 1 / 8.1 or more and 1 / 5.4 or less of a thickness of the solid electrolyte. Production method. A plurality of plate-shaped solid electrolytes are stacked, and an electrode and a lead portion extending to the electrode are formed on at least one surface of the solid electrolyte, and a paste-like insulator is applied between the solid electrolytes, followed by firing. A method of manufacturing a gas sensor by integrating the solid electrolyte and the insulator,
The lead portions respectively formed on the surfaces of the solid electrolytes facing each other with the insulator interposed therebetween are arranged at positions that do not overlap each other with the insulator interposed therebetween, and the coating thickness of the insulator in the vicinity of the lead portion is A method for producing a gas sensor, comprising applying the insulator so that the thickness of the solid electrolyte is 1/32 or more and 1 / 4.5 or less. 3. The method of manufacturing a gas sensor according to claim 1, wherein the main component of the solid electrolyte is made of zirconia, and the main component of the insulator is made of alumina. A gas sensor formed by laminating a plurality of plate-shaped solid electrolytes on which electrodes and lead portions extending from the electrodes are formed on at least one surface,
A gas sensor, wherein the lead portions respectively formed on the surfaces of the solid electrolytes facing each other are arranged so as not to overlap each other. The gas sensor according to claim 4, wherein all the solid electrolytes are set to have the same thickness.

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