JP2006226889A - Gas sensor, and manufacturing method for the gas sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a gas sensor and a manufacturing method for the gas sensor capable of securing the required insulating properties, even when a powder layer absorbs moisture in an environment containing moisture, and that will not incur productivity and durability from deteriorating. <P>SOLUTION: This gas sensor is constituted to form an outer electrode 30, comprising a detecting part electrode 31 for covering the substantially whole face of a detecting part 21 in a tip part, a vertical lead part electrode 32 for extracting the electrode on the rear end side, and a ring lead part electrode 33, at the outside of an element body 20. An insulating layer 40 is provided to cover the outside of an area ranging over from the rear-end side portion of the detecting part electrode 31 up to this side of the ring lead part electrode 33 in the vertical lead part electrode 32, and an intermediate layer 41 comprising a ceramic, is provided in the under layer of the insulating layer 40. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a gas sensor for detecting a gas such as oxygen in a gas to be measured, such as an exhaust gas of an internal combustion engine, and a method for manufacturing the gas sensor.

  Conventionally, as a gas sensor for detecting a specific gas in a gas to be measured, for example, a gas sensor for detecting oxygen or the like in exhaust gas of an internal combustion engine, an electrode layer is formed on the inner and outer surfaces with a bottomed cylindrical shape with a closed end portion. A device having a gas detection element having the following is known. In such a gas sensor, for example, the atmosphere is introduced as the reference gas inside the gas detection element, the gas to be measured is brought into contact with the outside, and the electromotive force generated according to the gas concentration difference between the inside and outside of the detection element is measured. Detect concentration.

In addition, in the gas sensor described above, a metal housing (metal shell) is known so as to surround the rear end side of the gas detection element in order to support the gas detection element at a predetermined position. And what hold | maintained the powder layer between these in order to maintain the airtightness between a gas detection element and metal housings is also known (for example, refer patent document 1).
JP 2001-281209 A

  However, it has been found that the conventional gas sensor described above has the following problems. That is, when exposed to moisture (high humidity), the powder layer absorbs moisture, thereby reducing the electrical resistance between the metal housing and the outer electrode of the gas sensor element. For this reason, current flows between them, and noise is generated in the output, which may hinder accurate gas concentration detection. In addition, in order to prevent the generation of such current, if the outer electrode is covered with glass, the adhesion between the electrode made of metal and the glass becomes insufficient, the glass is easily peeled off, the productivity is lowered and the durability is decreased. There is also a problem of incurring a decline in sex.

  The present invention has been made to solve the above problems. The present invention provides a gas sensor and a method for manufacturing the gas sensor that can ensure necessary insulation even when the powder layer absorbs moisture in an environment with moisture, and that does not cause a decrease in productivity or a decrease in durability. The purpose is to provide.

(Claim 1)
The gas sensor of the present invention has a gas sensor element that extends in the axial direction and whose detection part is exposed to the gas to be measured, and a cylinder that surrounds the radially outer side of the gas sensor element and projects the detection part of the gas detection element from its tip. In the gas sensor comprising: a metal shell, and a powder layer that fills a gap between the gas detection element and the metal shell and seals between them, the gas detection element is at least from the detector An electrode extending to the outer peripheral surface of the gas detection element corresponding to the powder layer, and glass is provided between the powder layer and the electrode formed on the outer peripheral surface of the gas detection element corresponding to the powder layer. An insulating layer as a main component is provided, and an intermediate layer made of ceramic is provided between the insulating layer and the electrode.

  The gas sensor of the present invention has a structure in which the electrode and the powder layer are not in direct contact by providing an insulating layer between the powder layer and the electrode. Thereby, even when the powder layer absorbs moisture in an environment with moisture, necessary insulation can be ensured. In particular, since the insulating layer is mainly composed of glass, heat resistance can be ensured while ensuring sufficient insulation. An intermediate layer made of ceramic is provided between the insulating layer mainly composed of glass and the electrode. Since such a ceramic intermediate layer has irregularities formed on the surface, the insulating layer mainly composed of glass enters the recesses on the surface of the intermediate layer, the insulating layer and the intermediate layer are in close contact, and the insulating layer is not peeled off. It can be prevented from occurring.

  In addition, when a powder layer is located in the approximate center of a gas detection element, an electrode may extend to the rear end side on the opposite side to a detection part over the outer peripheral surface of the gas detection element corresponding to a powder layer. The electrode may be on the entire surface of the gas detection element, or may be formed to extend from the detection portion to the gas detection element corresponding to the powder layer on the outer peripheral surface at a part in the circumferential direction of the gas detection element. Also good.

(Claim 2)
One aspect of the gas sensor of the present invention is characterized in that the intermediate layer is a porous layer. In this way, by making the intermediate layer a porous layer, it is possible to infiltrate the material mainly composed of the glass of the insulating layer up to the void portion of the intermediate layer, and to firmly bond the insulating layer and the intermediate layer. It is possible to reliably prevent the insulating layer from peeling off.

(Claim 3)
One aspect of the gas sensor of the present invention is characterized in that the intermediate layer is a ceramic sprayed layer obtained by spraying ceramic. When the intermediate layer is formed of the ceramic sprayed layer in this way, the formed intermediate layer (sprayed layer) can be sufficiently bonded to the gas detection element, and an intermediate layer that is difficult to peel off from the gas detection element is easily formed. be able to.

(Claim 4)
One aspect of the gas sensor of the present invention is characterized in that the gas sensor element has a protective layer covering at least the detection portion, and the protective layer and the intermediate layer are integrally formed. The outer peripheral surface of the detection part of the gas sensor is provided with a protective layer that suppresses a decrease in detection accuracy of the gas sensor due to poisonous substances such as Pb in the measurement gas. By forming the protective layer and the intermediate layer integrally, the intermediate layer can be formed without increasing the number of steps. In addition, with this structure, the electrode formed on the tip side in the axial direction from the powder layer is covered with an intermediate layer (protective layer), and carbon or the like that enters the gap between the metal shell and the gas detection element adheres. It is possible to prevent a decrease in insulation due to the operation. The protective layer can also be formed by ceramic spraying, and by forming the protective layer and the intermediate layer integrally by spraying, any of the formed layers can be sufficiently bonded to the gas detection element. , A protective layer and an intermediate layer which are difficult to peel off.

(Claims 5 and 6)
The method of manufacturing a gas sensor according to the present invention includes forming the intermediate layer by a thermal spraying process of spraying ceramic, then applying a glass paste, drying a glass paste, and heat-treating the glass paste. The insulating layer is formed by a heat treatment step. Moreover, one aspect of the method for producing a gas sensor of the present invention is characterized in that the insulating layer is formed by repeating a series of steps including the coating step, the drying step, and the heat treatment step at least twice. To do. By forming the intermediate layer and the insulating layer in such a process, it is possible to form an intermediate layer and an insulating layer that have sufficient insulation and heat resistance and are difficult to peel off. In addition, although the insulation of an insulating layer improves, so that there are many repetitions, when considering the cost etc., 4 times or less are preferable.

  ADVANTAGE OF THE INVENTION According to this invention, even when a powder layer absorbs moisture in an environment with moisture, the necessary insulation can be ensured, and the production of a gas sensor and a gas sensor that does not cause a decrease in productivity and a decrease in durability A method can be provided.

  Hereinafter, an embodiment in which a gas sensor of the present invention is applied to an oxygen sensor will be described with reference to the drawings. FIG. 1 shows a schematic configuration of an oxygen sensor according to an embodiment of the gas sensor of the present invention.

  As shown in the figure, the oxygen sensor 1 includes an oxygen detection element 2 as a gas detection element and a heater 3. The oxygen detection element 2 is formed in a bottomed cylindrical shape with a closed tip. The heater 3 is a rod-shaped ceramic heater or the like, and is inserted into the oxygen detection element 2.

  As shown in FIG. 2, the oxygen detection element 2 includes an element body (base body) 20 made of an oxygen ion conductive solid electrolyte member mainly composed of zirconia or the like. And the front-end | tip part (lower side in a figure) is made into the detection part 21, and the collar part 22 which protrudes to a radial direction outer side is formed in the rear end side (upper side in the figure) of the detection part 21. FIG. In FIG. 2, in order to describe the laminated structure of the cross section of the oxygen detection element 2, the structure is schematically shown by changing the aspect ratio from that in FIG. 1.

  In addition, an outer electrode 30 made of, for example, Pt or a Pt alloy is formed outside the element body 20. As shown in FIG. 3, the outer electrode 30 includes a detection unit electrode 31 formed so as to cover substantially the entire surface of the detection unit 21, and is electrically connected to the detection unit electrode 31. It is composed of a vertical lead part electrode 32 for drawing out and a ring lead part electrode 33.

  Then, as shown in FIGS. 2 and 4, the entire circumference is covered so as to cover the outer side from the rear end side portion of the detection unit electrode 31 to the region before the ring lead unit electrode 33 of the vertical lead unit electrode 32. An insulating layer 40 is provided over the area. The insulating layer 40 is provided on the outer portion of the oxygen detection element 2 that comes into contact with the powder layer 10 to be described later, and has a structure in which the outer electrode 30 (mainly the longitudinal lead electrode 32) and the powder layer 10 are not in direct contact. Has been. Thereby, even when the powder layer 10 absorbs moisture, necessary insulation between the outer electrode 30 and the metal shell 5 can be ensured.

  The insulating layer 40 needs to have sufficient insulation and heat resistance. For this reason, the material of the insulating layer 40 is preferably composed mainly of glass. As this glass, a glass containing silica as a main component and having a lower content of an alkali metal element that causes a decrease in insulation due to migration is preferable.

  Further, as shown in FIG. 2, a protective layer 50 made of ceramic is formed on the outside of the detection unit electrode 31. An intermediate layer 41 made of ceramic is formed integrally with the protective layer 50 so as to extend to the flange portion 22 and the rear end side and to be positioned on the lower layer side of the insulating layer 40. The intermediate layer 41 is interposed between the insulating layer 40 and the outer electrode 30 (mainly the vertical lead portion electrode 32). Since the intermediate layer 41 has irregularities on the surface, the insulating layer 40 mainly composed of glass enters the concave portion on the surface of the intermediate layer 41 and the insulating layer 40 and the intermediate layer 41 are in close contact with each other. Therefore, it plays a role of preventing the insulation layer 40 from peeling off when the insulation layer 40 is directly formed on the outer electrode 30 made of a metal such as Pt or a Pt alloy.

  The intermediate layer 41 is a porous layer. By using the porous layer in this way, the material mainly composed of glass of the insulating layer 40 can be permeated into the pores of the intermediate layer 41, and the insulating layer 40 and the intermediate layer 41 are firmly bonded. It is possible to reliably prevent the insulating layer 40 from peeling off.

  The protective layer 50 and the intermediate layer 41 can be formed at the same time in the manufacturing process, and are formed of, for example, a ceramic sprayed layer such as spinel. If the intermediate layer 41 is formed by using ceramic spray in this way, the formed intermediate layer 41 can be sufficiently bonded to the oxygen detection element 2, and the intermediate layer 41 that is difficult to peel off from the oxygen detection element 2 can be easily formed. Can be formed.

  Further, an inner electrode 60 formed porous by, for example, Pt or a Pt alloy is provided inside the element body 20.

  As shown in FIG. 1, a metal shell 5 made of SUS430 is provided to surround the vicinity of the flange portion 22 of the oxygen detection element 2. The metal shell 5 includes a screw portion 51 for attaching the oxygen sensor 1 to an attachment portion such as an exhaust pipe, and a hexagonal portion 52 to which the attachment fitting is attached when the exhaust pipe is attached to the attachment portion. A gasket 7 is provided on the tip surface of the hexagonal portion 52. A metal side stepped portion 54 that decreases in diameter toward the tip end portion is provided on the inner peripheral surface of the metal shell 5, and an insulator 9 described later is supported on the metal side stepped portion 54 via a packing 55. ing.

  Insulators 8 and 9 made of an insulating ceramic are provided between the metal shell 5 and the oxygen detection element 2, and talc is compressed between these insulators 8 and 9. A powder layer 10 such as is arranged. The powder layer 10 seals between the oxygen detection element 2 and the metal shell 5 so as to ensure airtightness. An annular ring 57 is provided on the rear end side of the insulator 8.

  A protector 11 is attached to the front end side of the metal shell 5 so as to cover the front end side (the detection unit 21) of the oxygen detection element 2. The protector 11 is provided with a plurality of gas permeation ports 12 for introducing the gas to be measured and bringing it into contact with the distal end side (detection unit 21) of the oxygen detection element 2.

  An inner cylinder member 23 made of SUS304L is attached to the rear end side of the metal shell 5 and fixed by a caulking portion 56 provided at the rear end of the metal shell 5. The inner cylinder member 23 has a step portion 24 whose diameter decreases toward the rear end side at a substantially intermediate position, and a gas introduction hole 25 for taking the reference gas into the gas detection element is provided on the rear end side of the step portion 24. A plurality are provided at predetermined intervals along the circumferential direction. Further, the outer cylinder member 26 made of SUS304L is caulked and fixed at the front end side of the step portion 24 of the inner cylinder member 23. The outer cylinder member 26 is also provided with a plurality of auxiliary gas introduction holes 27 at positions corresponding to the gas introduction holes 25. A filter 13 that covers the gas introduction hole 25 is formed between the gas introduction hole 25 and the auxiliary gas introduction hole 27. The filter 13 is fixed by caulking the front end side and the rear end side of the auxiliary gas introduction hole 27 of the outer cylinder member 26.

  A ceramic separator 15 is formed inside the inner cylinder member 23. The ceramic separator 15 includes lead wires 16 and 17 corresponding to an outer electrode connecting bracket 19 connected to the outer electrode 30, an inner electrode connecting bracket 18 connected to the inner electrode 60, and a heater connecting terminal 28 connected to the heater 3, respectively. , 29 so as to be connected. The lead wires 16, 17, and 29 are connected to the outside through the rubber grommet 14 fixed to the rear end side of the outer cylinder member 26.

  The oxygen sensor 1 is used in a state where the front end side (lower side in FIG. 1) of the screw portion 51 is located in the exhaust pipe and the rear end side (upper side in FIG. 1) is located in the outside atmosphere. The The oxygen detection element 2 is heated and activated by a heater 3 disposed inside thereof. The atmosphere as the reference gas passes through the auxiliary gas introduction hole 27, the filter 13, and the gas introduction hole 25 in this order, and is introduced into the oxygen detection element 2. On the other hand, exhaust gas is introduced to the outside of the oxygen detection element 2 through the gas permeation port 12 of the protector 11.

  As a result, an oxygen concentration cell electromotive force is generated in the oxygen detection element 2 in accordance with the oxygen concentration difference between the inner and outer surfaces. Then, the oxygen concentration cell electromotive force is used as a detection signal of the oxygen concentration in the exhaust gas, and the inner electrode 60, the inner electrode connection fitting 18, the lead wire 17, and the outer electrode 30, the outer electrode connection fitting 19, and the lead wire 16 are sent. The oxygen concentration in the exhaust gas is detected.

  When the oxygen sensor 1 detects the oxygen concentration in the exhaust gas as described above, the oxygen sensor 1 may be exposed to an environment containing moisture, and the powder layer 10 may absorb moisture. Even when the powder layer 10 absorbs moisture as described above, according to the present embodiment, the outer portion of the oxygen detecting element 2 in contact with the powder layer 10 is covered with the insulating layer 40 and the outer electrode 30 (mainly the vertical lead). Since the partial electrode 32) and the powder layer 10 are not in direct contact with each other, necessary insulation between the outer electrode 30 and the metal shell 5 can be ensured.

  In this way, the insulating layer 40 is for ensuring insulation between the outer electrode 30 and the metal shell 5. Therefore, it is only necessary to be provided at least at a portion where the outer electrode 30 and the powder layer 10 may be in contact with each other, and it is not always necessary to provide the entire circumference of the oxygen detection element 2 as shown in FIG. There is no. For example, the outer electrode 30 may be provided so as to cover the outer side along the vertical lead electrode 32. In this case, the intermediate layer 41 may also be provided only in the lower part of the insulating layer 40.

  Further, in the example shown in FIG. 4, the insulating layer 40 is provided over a region from the flange portion 22 to the rear end portion of the detection portion 21. That is, the insulating layer 40 is provided even in a portion where the powder layer 10 is not likely to contact. This is to prevent the carbon contained in the exhaust gas from adhering to the gap 65 (see FIG. 1) between the metal shell 5 and the oxygen detection element 2 and causing insulation failure.

  Next, a method for manufacturing the oxygen detection element 2 will be described with reference to FIG. As shown in the figure, first, a substrate (element body 20) made of an oxygen ion conductive solid electrolyte member mainly composed of zirconia or the like is fired (101).

  Next, a platinum electrode (outer electrode 30) is formed on the outer portion of the substrate by electroless plating (102), and the platinum electrode is densified by heating (103). The heating is performed at a temperature of 1230 ° C., for example, in an air atmosphere.

  Next, the protective layer 50 is formed outside the detection unit 21 by plasma spraying or the like, and the intermediate layer 41 is formed on the rear end side of the protective layer 50 continuously with the protective layer 50 (104). The protective layer 50 and the intermediate layer 41 are preferably formed of ceramics such as spinel, alumina, zirconia, and the like, and are preferably porous layers. In addition, various treatments for roughening the surface of the intermediate layer 41 may be performed in order to improve the adhesion of the insulating layer 40. The thickness is, for example, about 100 to 180 μm.

  Next, the first glass paste is applied to the portion where the insulating layer 40 outside the substrate is to be formed (105). For the glass paste application, for example, a dipping method in which the part other than the glass paste application part of the element body 20 is masked with a Teflon (registered trademark) tape or the like and immersed in the glass paste can be used. In this case, for example, the glass paste has a ratio of 10 to 15 g of powdered glass, 10 ml of pure water, and 0.1 to 1.0 g of binder. Also, while pouring the glass paste onto a rotating roller, the element body 20 is rotated in the opposite direction to the roller while contacting the roller to apply the glass paste, or the element body 20 is attached to a mask jig. Also, a spraying method in which a glass paste is sprayed while rotating the element body can be used.

  Next, after drying the glass paste using a heat gun or the like (106), heat treatment is performed using a muffle furnace or the like (107). The heat treatment conditions are, for example, a temperature of 1170 ° C. and a time of 20 minutes in an air atmosphere.

  Next, on the above glass layer, the second glass paste is applied in the same manner as the first time (108), and after drying the glass paste (109), heat treatment (for example, in the atmosphere in the atmosphere, Temperature 1170 ° C.) (110). Thus, by applying the glass paste twice to form the insulating layer 40, a glass layer without holes can be formed, and the insulation resistance can be prevented from being lowered by the holes. The glass layer formed by such a process has a thickness of about 40 to 300 μm. When the thickness is less than 40 μm, there is a high possibility that sufficient insulation cannot be obtained when the sensor is used.

  Next, a platinum electrode (inner electrode 60) is formed by electroless plating (111), and the platinum electrode is densified by heating (112). The conditions for the densification treatment are, for example, a temperature of 700 ° C. in a reducing atmosphere such as hydrogen.

  The oxygen detection element 2 having the internal electrode 60 formed thereon is held by the metal shell 5 through a packing 55 and an insulator 9 by a known method, and is internally provided in the order of the powder layer 10, the insulator 8, and the annular ring 57, and the inner cylinder. The caulking portion 56 is formed while the front end portion of the member 23 is mounted on the rear end portion of the metal shell 5. Thereafter, the outer cylinder member 26, the filter 13, the grommet 14 and the like are mounted, and the oxygen sensor 1 is completed.

Actually, as an example, the intermediate layer 41 is formed of a spinel sprayed film having a thickness of approximately 120 μm, and on top of that, 45% by mass of SiO ₂ , 16% by mass of Al ₂ O ₃ , 15% by mass of BaO, Ten oxygen sensor elements 2 in which an insulating layer 40 having a thickness of 40 μm was formed by using crystallized glass containing 10% by mass of ZnO, 9% by mass of CaO and 0.5% by mass of Na ₂ O were produced. As a result of observing the appearance of this example, all the ten insulating layers 40 were not peeled off, and the oxygen sensor element 2 in a good state could be obtained.

  On the other hand, as a comparative example, only the point that the intermediate layer 41 is not provided is different, and the other 10 oxygen sensor elements 2 were formed under the same conditions as in the above example. When the appearance of this comparative example was observed, peeling of the insulating layer 40 occurred in three of the ten pieces.

  From the above results, it has been found that by providing the intermediate layer 41 and forming the insulating layer 40 thereon, it is possible to reliably prevent the insulating layer 40 from being peeled off.

  Next, the underwater insulation test was done about the insulating layer 40 formed by said manufacturing process. That is, the element body 20 in a state in which the outer electrode 30, the protective layer 50, the intermediate layer 41, and the insulating layer 40 are formed on the element body 20 is immersed in city water 70 as shown in FIG. The insulation resistance was measured at 71 to perform an underwater insulation test. Note that a portion without the insulating layer 40 on the rear end side (lower side in the figure) of the element body 20 was insulated by winding a silicon insulating tape 72. The underwater insulation test was performed by applying DC 500V and measuring the insulation resistance after charging for 10 seconds. As a result, the insulating layer 40 formed by the above manufacturing process had an insulation resistance of about 5000 MΩ.

  On the other hand, when the insulating layer 40 is formed by applying a glass paste once, there is a high possibility that a hole is formed in the glass layer, and if this hole is formed on the outer electrode layer 30, sufficient Insulation resistance could not be obtained.

  In actual use, the insulation resistance of the insulating layer 40 is sufficient if it is about 15 MΩ, and if it is about 5 MΩ at least, the flowing current can be suppressed to 1 μA or less, so that the generation of noise can be suppressed. Therefore, the insulation resistance of the insulating layer 40 formed by the above measuring method is preferably 5 MΩ or more, and more preferably 15 MΩ or more.

  Actually, the oxygen sensor of the above-described embodiment was humidified for 60 hours in an environment of a temperature of 60 ° C. and a humidity of 95%, and after that, when the insulation resistance was measured, an insulation resistance of about 100 MΩ or more was obtained even immediately after humidification. I was able to get it. On the other hand, as a comparative example, when the same measurement was performed using an oxygen sensor not including the insulating layer 40, the insulation resistance was 0.01 MΩ or less.

  As described above, in the above embodiment, even when the powder layer absorbs moisture, it is possible to ensure an insulation resistance of 1000 times or more compared to the conventional oxygen sensor, and insulation sufficient to suppress the generation of noise. Was able to secure.

  The insulating layer 40 is not limited to the above-described material, and may be formed of any material as long as the insulation resistance is preferably 5 MΩ or more, more preferably 15 MΩ or more. good. Further, the present invention is not limited to the oxygen sensor described above, and can be similarly applied to gas sensors that detect other types of gases.

The figure which shows the structure of the oxygen sensor which concerns on embodiment of this invention. The figure which shows the cross-sectional structure of the oxygen detection element of the oxygen sensor of FIG. The figure for demonstrating the structure of the oxygen detection element of the oxygen sensor of FIG. The figure for demonstrating the structure of the oxygen detection element of the oxygen sensor of FIG. The flowchart which shows the manufacturing process of an oxygen detection element. The figure for demonstrating the implementation method of the underwater insulation test of an insulating layer.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Oxygen sensor, 2 ... Oxygen detection element, 3 ... Heater, 5 ... Metal fitting, 7 ... Gasket, 8, 9 ... Insulator, 10 ... Powder layer, 11 ... Protector, 12 ... Gas permeation port, 13 ... Filter, 14 ... Grommet, 15 ... Ceramic separator, 16, 17, 29 ... Lead wire, 18 ... Inner electrode connecting bracket, 19 ... Outer electrode connecting bracket, 20 ... Element body, 21 ... Detector, 22 ... Hut, 23 ... Inner cylinder 24, stepped portion, 25 ... gas introduction hole, 26 ... outer cylinder member, 27 ... auxiliary gas introduction hole, 28 ... heater connection terminal, 30 ... outer electrode, 31 ... detection portion electrode, 32 ... vertical lead portion electrode, 33 ... Ring lead electrode, 40 ... Insulating layer, 41 ... Intermediate layer, 50 ... Protective layer, 51 ... Threaded part, 52 ... Hexagonal part, 54 ... Hardware side step part, 55 ... Packing, 56 ... Clamping part, 57 ... annular ring, 60 ... inside The pole.

Claims (6)

A gas sensor element extending in the axial direction and having the detection unit exposed to the gas to be measured;
A cylindrical metal shell that surrounds the radially outer side of the gas sensor element and projects the detection part of the gas detection element from its tip,
In a gas sensor comprising a powder layer that is filled in a gap between the gas detection element and the metal shell and seals between them,
The gas detection element has an electrode extending from the detection portion to the outer peripheral surface of the gas detection element corresponding to the powder layer at least.
An insulating layer mainly composed of glass is provided between the powder layer and the electrode formed on the outer peripheral surface of the gas detection element corresponding to the powder layer,
A gas sensor, wherein an intermediate layer made of ceramic is provided between the insulating layer and the electrode.   The gas sensor according to claim 1, wherein the intermediate layer is a porous layer.   3. The gas sensor according to claim 1, wherein the intermediate layer is a ceramic sprayed layer obtained by spraying ceramic. The gas sensor element has a protective layer covering at least the detection unit,
The gas sensor according to any one of claims 1 to 3, wherein the protective layer and the intermediate layer are integrally formed. A gas sensor manufacturing method for manufacturing the gas sensor according to claim 1,
The intermediate layer is formed by a thermal spraying process of spraying ceramic, and then
An application process of applying a glass paste;
A drying step of drying the glass paste;
A heat treatment step of heat treating the glass paste;
The insulating layer is formed by the method of manufacturing a gas sensor.   6. The method of manufacturing a gas sensor according to claim 5, wherein the insulating layer is formed by repeating a series of steps including the coating step, the drying step, and the heat treatment step at least twice.

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