JP2006234790A - Gas sensor and method of manufacturing gas sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide of a gas sensor capable of securing necessary insulation performance even when the powder layer has absorbed with moisture in the wet environment. <P>SOLUTION: The gas sensor comprises: the detection electrode 31 provided on the tip of external surface of the element main body 20; the detection element 2 connected with the detection electrode 31 provided with the lead part 32 extending to the back ward end; the cylindrical main hardware 5 projecting from the tip of the tip part of the detecting element 2; the powder layer 10 filled in the gap between the detecting element 2 and the main hardware 5, and at least covering the lead part 32; and the insulation layer 40 which is provided between the powder layer 10 and the lead part 32. <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 during an internal combustion period, 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 an exhaust gas of an internal combustion engine, a bottomed cylindrical shape having a closed end and a ground detecting electrode on the inner and outer surfaces 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 gas housing provided with a metal housing (metal shell) so as to surround the gas detection element is known 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.

  The present invention has been made to solve the above problems. An object of this invention is to provide the gas sensor which can ensure required insulation, and the manufacturing method of a gas sensor, even when a powder layer absorbs moisture in a moisture environment.

(Claim 1)
The gas sensor of the present invention includes a gas sensor element including a detection electrode extending in the axial direction and provided on the outer surface on the front end side, and a lead portion connected to the detection electrode and extending toward the rear end side, and the gas sensor In a gas sensor comprising: a cylindrical metal shell that surrounds the element, and a tip end side of the gas sensor element protrudes from the tip; and a powder layer that fills a gap between the gas sensor element and the metal shell and covers at least the lead part. An insulating layer is provided between the powder layer and the lead portion.

  The gas sensor of the present invention has a structure in which the lead portion and the powder layer are not in direct contact by providing an insulating layer between the powder layer and the lead portion. Thereby, even when the powder layer absorbs moisture in an environment with moisture, necessary insulation can be ensured. Therefore, it is possible to prevent current from flowing between the metal shell and the lead portion, generating noise in the output, and hindering accurate gas concentration detection.

The lead portion may extend to the outer peripheral surface of the gas sensor element on the rear end side with respect to the powder layer. Further, the lead portion may be on the entire circumferential surface of the gas detection element, or may be formed to extend in a rod shape from the detection electrode toward the rear end side in a part of the circumferential direction of the gas sensor element. .

(Claim 2)
In the gas sensor of the present invention, the insulating layer preferably contains glass as a main component. By providing the insulating layer mainly composed of glass, heat resistance can be ensured while ensuring sufficient insulation.

(Claim 3)
In the gas sensor of the present invention, it is preferable that the insulating layer is composed of a plurality of layers. Thereby, the insulating layer mainly composed of glass can form an insulating layer without a hole, and can further prevent the insulating property from being lowered by the hole.

(Claim 4)
And the gas sensor of this invention WHEREIN: It is preferable that the 1st insulating layer adjacent to the said lead part is formed with crystallized glass among these layers. Since the first insulating layer adjacent to the lead portion is formed of crystallized glass, for example, when forming the second insulating layer adjacent to the first insulating layer, the first insulating layer is not easily softened, and the first The second insulating layer can be formed while maintaining the thickness of the insulating layer. Accordingly, a thick insulating layer can be provided, and further, a decrease in insulation can be prevented.

(Claim 5)
Usually, the gas sensor element is formed with a flange portion protruding radially outward, and this flange portion serves to fix the gas sensor element to the metal shell or the insulator with a packing interposed therebetween. A part of the powder layer may enter a gap between the gas sensor element and the metal shell or the insulator on the rear end side of the packing. Then, as described above, the powder layer absorbs moisture, so that the electrical resistance between the metal shell and the detection electrode or lead portion of the gas sensor element is lowered. For this reason, current flows between them, and noise is generated in the output, which may hinder accurate gas concentration detection.

  Therefore, in the gas sensor of the present invention, it is preferable that the insulating layer extends at least between the packing and the flange. The insulating layer extends at least between the packing and the flange, so that even if the powder layer that has entered the gap absorbs moisture, a short circuit between the metal shell and the detection electrode or lead is prevented. Can do.

  On the other hand, a gap is also formed between the gas sensor element and the metal shell on the tip side of the packing. When the gas sensor is attached to an exhaust pipe or the like, the gap between the gas sensor element and the metal shell is exposed to the gas to be measured, and carbon in the gas to be measured enters the gap to detect the gas. It will adhere to the surface of the element and the metal shell. As a result, a bonbon adheres to the detection electrodes and lead portions provided in the gas detection element. Then, the electrical resistance between the metal shell and the detection electrode and lead part of the gas sensor element decreases, current flows between them, and noise is generated in the output, which may hinder accurate gas concentration detection. There is sex.

(Claim 6)
Therefore, in the gas sensor of the present invention, it is preferable that the gas sensor element has a porous protective layer that covers at least a part of the detection electrode and overlaps at least the tip of the insulating layer. A protective layer is provided on the outer peripheral surface of the detection electrode of the gas sensor to suppress a decrease in detection accuracy of the gas sensor due to poisonous substances such as Pb in the measurement gas. Therefore, the protective layer and the tip side of the insulating layer are overlapped (that is, the tip side of the gas sensor element is covered with the protective layer and the insulating layer), so that the metal shell and the gas sensor element are located on the tip side of the packing. Even if carbon enters the gap between the main metal fitting and the gas sensor element, current flows between the main metal fitting and the detection electrode or lead by the protective layer or insulating layer, generating noise in the output. Thus, it is possible to effectively prevent troubles in accurate gas concentration detection.

(Claim 7)
Furthermore, in the gas sensor of the present invention, it is preferable that the protective layer covers the tip of the insulating layer. If the insulating layer covers the protective layer, the insulating layer may not enter well into the pores of the porous protective layer, and insulation may not be possible. On the other hand, insulation can be maintained because a protective layer covers the front-end | tip part of an insulating layer like this invention.

(Claim 8)
Furthermore, it is preferable that the insulating layer extends to the tip side from the tip of the metal shell. As a result, even if carbon or the like adheres to the metal shell or gas sensor element, current flows between the metal shell and the detection electrode or lead due to the insulating layer, generating noise in the output, which hinders accurate gas concentration detection. Can be effectively prevented.

(Claims 9 and 10)
The method of manufacturing a gas sensor according to the present invention is characterized in that the insulating layer is formed by an application step of applying a glass paste, a drying step of drying the glass paste, and a heat treatment step of heat-treating the glass paste. . 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 insulating layer in such a process, an insulating layer having a sufficient thickness and having insulating properties and heat resistance can be formed.

  ADVANTAGE OF THE INVENTION According to this invention, even when a powder layer absorbs moisture in an environment with moisture, the gas sensor which can ensure required insulation, and the manufacturing method of a gas sensor 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 a detection element 2 as a gas detection element, a heater 3, a metal shell 5, and the like. Among these, the heater 3 is a rod-shaped ceramic heater and is inserted into the detection element 2.

  The metal shell 5 has a threaded portion 51 for attaching the oxygen sensor 1 to an attachment portion such as an exhaust pipe on its outer peripheral surface, and a protruding portion 53 to which the attachment fitting is attached when the attachment is made to the attachment portion of the exhaust pipe. A gasket 7 is provided on the tip surface of the protruding portion 53.

  On the other hand, the metal shell 5 has a metal-side stepped portion 54 whose diameter decreases toward the tip side on the inner peripheral surface thereof. Furthermore, insulators 8 and 9 made of an insulating ceramic are provided between the metal shell 5 and the detection element 2, and the talc (talc) is compressed between the insulators 8 and 9. ) Etc. are disposed. The powder layer 10 seals between the detection element 2 and the metal shell 5 so as to ensure airtightness. Further, a packing 55 is provided between the front end of the insulator 9 and the metal side step 54, and an annular ring 57 is provided at the rear end of the insulator 8.

  A protector 11 that covers the detection unit 21 of the detection element 2 is attached to the distal end side of the metal shell 5. The protector 11 is provided with a plurality of gas permeation ports 12 for introducing a gas to be measured.

  An inner cylinder member 23 made of SUS304L is attached to the rear end side of the metal shell 5. The inner cylinder member 23 has a gas introduction hole 25 for taking the reference gas into the gas detection detection element.

  Further, an outer cylinder member 26 having a plurality of auxiliary gas introduction holes 27 provided at positions corresponding to the gas introduction holes 25 is provided outside the inner cylinder member 23. 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. On the other hand, 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 penetrate the rubber grommet 14 fixed to the rear end side of the outer cylinder member 26 and are connected to the outside.

  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 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 detection element 2. On the other hand, exhaust gas is introduced to the outside of the 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 detection element 2 in accordance with the difference in oxygen concentration 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.

Next, the detection element 2 will be described with reference to FIGS.
As shown in FIG. 2, the detection element 2 includes a bottomed cylindrical element body (base body) 20 made of an oxygen ion conductive solid electrolyte member mainly composed of zirconia or the like and having a closed tip. A flange 22 that protrudes radially outward is formed on the rear end side (upper side in the drawing) of the element body 20. As shown in FIG. 1, the flange portion 22 is fixed to the insulator 9 via a packing 58. In FIG. 2, in order to explain the laminated structure of the cross section of the detection element 2, the structure is schematically shown by changing the aspect ratio from that in FIG. 1.

  Further, inside the element main body 20, for example, an inner electrode 60 formed in a porous shape by Pt or a Pt alloy is provided. On the other hand, on the outside of the element body 20, for example, an outer electrode 30 is formed which is formed porous by Pt or a Pt alloy. A protective layer 50 made of a ceramic sprayed layer such as spinel is formed outside the detection electrode 31.

  As shown in FIG. 3, the outer electrode 30 is electrically connected to the detection electrode 31 formed so as to cover a substantially cross section of the detection unit 21, and the electrode is drawn out to the rear end side. The lead portion 32 and the ring portion 33 are configured. As shown in FIGS. 2 and 4, insulation is performed over the entire circumference so as to cover the outer side from the rear end side portion of the detection electrode 31 to the front side of the ring terminal portion 33 of the lead portion 32. A layer 40 is provided.

  Next, the insulating layer 40 which is a main part of the present invention will be described. The insulating layer 40 is provided between the powder layer 10 and the lead portion 32. Thus, the outer electrode 30 (mainly the lead portion 32) and the powder layer 10 are not in direct contact. As a result, even when the powder layer 10 absorbs moisture, the lead portion 32 in contact with the powder layer 10 is covered with the insulating layer 40, and the lead portion 32 and the powder layer 10 are not in direct contact with each other. Therefore, necessary insulation between the outer electrode 30 and the metal shell 5 can be ensured. Therefore, it is possible to prevent a short circuit between the metal shell and the lead portion, and to prevent noise from being generated in the output and hindering accurate gas concentration detection.

  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 having a smaller content of an alkali metal element that causes a decrease in insulation due to migration is preferable.

  Furthermore, as shown in FIG. 2, the insulating layer 40 is formed of a plurality of layers. Specifically, the first glass layer 411 and the second glass layer 412 are formed, and the first glass layer 411 and the second glass layer are the same component. In this way, by forming the insulating layer 40 with a plurality of layers of the first glass layer 411 and the second glass layer 412, the insulating layer 40 mainly composed of glass can be the insulating layer 40 without holes. It is possible to prevent the insulating properties from being lowered due to the holes. Moreover, since it crystallizes after formation and the softening temperature rises, when forming the 2nd glass layer 412, it becomes difficult to soften. For this reason, the 2nd glass layer 412 can be formed with the same material as the 1st glass layer 411, the insulating layer 40 with a thick film thickness can be provided, and also the fall of insulation can be prevented.

  Further, the insulating layer 40 extends between the packing 58 and the flange portion 22. Thereby, even if a part of the powder layer 10 enters the gap formed on the rear end side from the packing 58, it is possible to prevent a short circuit between the metal shell 5 and the ground detection electrode 31 or the lead portion 32 due to moisture absorption.

The insulating layer 40 extends to the tip side from the tip of the metal shell 5. When the gas sensor 1 is used by being attached to an exhaust pipe or the like, carbon or the like in the gas to be measured enters the gap between the detection element 2 and the metal shell 5 formed on the tip side of the packing 58. Even if it adheres to the surfaces of the gas detection element and the metal shell, the insulating layer 40 effectively prevents a short circuit between the metal shell 5 and the detection electrode 31 or the lead 32 due to the attached carbon.
Further, the insulating layer 40 is covered to the rear end of the detection electrode 31 as shown in FIG. As a result, a short circuit between the lead portions can be reliably prevented.

Furthermore, as shown in FIG. 2, the tip side of the insulating layer 40 is covered with a protective layer 50. As a result, the tip side of the gas sensor element 2 from the packing 58 is covered with either the protective layer 50 or the insulating layer 40. Therefore, even if carbon or the like enters the gap between the metal shell 5 and the gas sensor element 2 on the tip side of the packing 58 and the carbon or the like adheres to the metal shell 5 or the gas sensor element 2, the protective layer 50 or the insulating layer 40. As a result, it is possible to effectively prevent current from flowing between the metal shell 2 and the detection electrode 31 or the lead portion 32, generating noise in the output, and hindering accurate gas concentration detection.
In particular, since the protective layer 50 covers the tip of the insulating layer 40, the insulating properties can be ensured by the porous protective layer 50 and the insulating layer 40.

  Next, a method for manufacturing the 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. in an air atmosphere, for example.

  Next, the first glass paste is applied to the portion where the insulating layer 40 outside the substrate is to be formed (104). 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 is masked with a Teflon (registered trademark) tape 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 the rotating roller, rotate the element body in the opposite direction to the roller while abutting the roller to apply the glass paste, or attach the element body to the mask jig, A spraying method in which a glass paste is sprayed while rotating the main body can also be used.

  Next, after drying the glass paste using a heat gun or the like (105), the glass paste is crystallized by heat treatment using a muffle furnace or the like to form the first glass layer 411 (106). The heat treatment conditions are, for example, an air atmosphere at a temperature of 1170 ° C. and a time of 20 minutes.

  Next, a second glass paste application is performed on the glass layer as described above (107), and the glass paste is dried (108), followed by heat treatment (for example, in an air atmosphere at a temperature 1170 ° C.) to form the second glass layer 412 (109). Since the first glass layer 411 is crystallized, it is difficult to soften even if heat treatment is performed at 1170 ° C. Thus, by applying the glass paste twice to form the insulating layer 40, the insulating layer 40 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, the protective layer 50 is formed on the outside of the detection electrode 31 by plasma spraying or the like (110). This protective layer 50 consists of ceramic porous layers, such as a spinel, and thickness is about 100-180 micrometers.

  Next, a platinum electrode (inner electrode 60) is formed by electroless plating (111), and the platinum electrode is densified by heating (103). The conditions for the densification treatment are, for example, a temperature of 700 ° C. in a reducing atmosphere such as hydrogen.

  The detection element 2 on which the internal electrode 60 is formed is held by the metal shell 5 via the packing 58 and the 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. After that, the outer cylinder member 26, the filter 13, the grommet 14 and the like are mounted, and the oxygen sensor 1 is completed.

  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 where the outer electrode 30 and the insulating layer 40 are formed on the element body 20 is immersed in city water 70 as shown in FIG. Underwater insulation test was conducted. 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 insulation resistance of the insulating layer 40 formed by the above manufacturing process was about 5000 MΩ.

  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, as a first example, SiO ₂ is 45 mass%, Al ₂ O ₃ is 16 mass%, BaO is 15 mass%, ZnO is 10 mass%, CaO is 9 mass%, and Na ₂ O is 0.1 mass%. The oxygen sensor 1 in which the insulating layer 40 having a thickness of 70 μm was formed using crystallized glass containing 5% by mass was prepared. The oxygen sensor 1 was humidified for 60 hours in an environment of a temperature of 60 ° C. and a humidity of 95%, and then the insulation resistance was measured. As a result, an insulation resistance of about 100 MΩ or more could be obtained immediately after humidification. . On the other hand, as a comparative example, when the same measurement was performed with the oxygen sensor 1 not including the insulating layer 40, the insulation resistance was about 0.01 MΩ or less.

Similarly, as a second embodiment, 29 mass% of SiO ₂ , 54 mass% of BaO, 4 mass% of CaO, 3 mass% of B ₂ O ₃ and 0.5 mass% of Na ₂ O are included. The oxygen sensor 1 in which the insulating layer 40 having a thickness of 70 μm was formed using amorphous glass was produced. The oxygen sensor 1 was humidified for 60 hours in an environment of a temperature of 60 ° C. and a humidity of 95%, and then the insulation resistance was measured. As a result, an insulation resistance of about 200 MΩ or more could be obtained immediately after humidification. . On the other hand, as a comparative example, when the same measurement was performed with the oxygen sensor 1 not including the insulating layer 40, the insulation resistance was about 0.01 MΩ or less.

Similarly, as a third embodiment, SiO ₂ is 32 mass%, Al ₂ O ₃ is 16 mass%, CaO is 19 mass%, ZnO is 25 mass%, TiO ₂ is 10 mass%, Na ₂ O. The oxygen sensor 1 in which the insulating layer 40 having a thickness of 70 μm was formed from crystallized glass containing 0.1% by mass and 0.04% by mass of K ₂ O was prepared. The oxygen sensor 1 was humidified for 60 hours in an environment of a temperature of 60 ° C. and a humidity of 95%, and then the insulation resistance was measured. As a result, an insulation resistance of about 100 MΩ or more could be obtained even immediately after humidification. . On the other hand, as a comparative example, when the same measurement was performed with the oxygen sensor 1 that does not include the insulating layer 40, the insulation resistance was about 0.01 MΩ or less.

  As described above, in each of the above embodiments, even when the powder layer 10 absorbs moisture, it is possible to ensure an insulation resistance of 1000 times or more compared to the conventional oxygen sensor 1 and to suppress the generation of noise. It was possible to secure a good insulation.

  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 1 described above, and can be similarly applied to gas sensors that detect other types of gases.

  Moreover, as a formation method of the said 1st glass layer 411 and the 2nd glass layer 412, it is possible by changing the glass component of glass paste application | coating of the 1st time and glass paste application | coating of the 2nd time using the method of a present Example. It is. When the 1st glass layer is not crystallized, it is preferable to form a 2nd glass layer using the glass paste whose softening point is lower than the glass paste for 1st glass layers. Further, using a glass paste having a softening point higher than that of the glass paste for the first glass layer, the second heat treatment temperature is higher than the first heat treatment temperature within a range in which the film thickness of the first glass layer can be maintained. Thus, the second glass layer can be formed. In this case, the adhesion with the first glass layer and the second glass layer can be improved.

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 detection element of the oxygen sensor of FIG. The figure for demonstrating the structure of the detection element of the oxygen sensor of FIG. The figure for demonstrating the structure of the detection element of the oxygen sensor of FIG. The flowchart which shows the manufacturing process of a 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 ... 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 connection fitting, 19 ... Outer electrode connection fitting, 20 ... Element body, 21 ... Detection part, 22 ... Gutter part, 23 ... Inner cylinder member , 24 ... Step part, 25 ... Gas introduction hole, 26 ... Outer cylinder member, 27 ... Auxiliary gas introduction hole, 28 ... Heater connection terminal, 30 ... Outer electrode, 31 ... Detection electrode, 32 ... Lead part, 33 ... Ring , 40 ... Insulating layer, 50 ... Protective layer, 51 ... Threaded part, 52 ... Hex part, 53 ... Projection part, 54 ... Metal side step part, 55, 58 ... Packing, 56 ... Clamping part, 57 ... Ring , 60 ... inner electrode

Claims (10)

A gas sensor element that includes a detection electrode that extends in the axial direction and is provided on the outer surface on the front end side, and a lead portion that is connected to the detection electrode and extends toward the rear end side;
A cylindrical metal shell that surrounds the gas sensor element, and the tip side of the gas detection element protrudes from the tip,
In a gas sensor comprising a powder layer filled in a gap between the gas detection element and the metal shell and covering at least the lead portion,
A gas sensor, wherein an insulating layer is provided between the powder layer and the lead portion. The gas sensor according to claim 1, wherein
The gas sensor, wherein the insulating layer contains glass as a main component. The gas sensor according to claim 2, wherein
The gas sensor, wherein the insulating layer is composed of a plurality of layers. The gas sensor according to claim 3, wherein
Of the plurality of layers, the first insulating layer adjacent to the lead portion is formed of crystallized glass. The gas sensor according to any one of claims 1 to 4,
The gas sensor element protrudes radially outward, and has a flange portion that comes into contact with a packing provided on the tip side of the powder layer,
The gas sensor according to claim 1, wherein the insulating layer extends at least between the packing and the flange. The gas sensor according to any one of claims 1 to 5,
The gas sensor element has a porous protective layer that covers at least a part of the detection electrode and overlaps at least the tip of the insulating layer.
A gas sensor characterized by that. The gas sensor according to claim 6, wherein
The gas sensor according to claim 1, wherein the protective layer covers a rear end portion of the insulating layer. The gas sensor according to any one of claims 1 to 7,
The gas sensor according to claim 1, wherein the insulating layer extends to a tip side from a tip of the metal shell. A gas sensor manufacturing method for manufacturing the gas sensor according to claim 1,
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. In the manufacturing method of the gas sensor according to claim 9,
A method of manufacturing a gas sensor, 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.