JP2009287935A - Gas sensor and manufacturing method therefor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a gas sensor enhanced in corrosion resistance by eliminating the gap of the welded part of a main metal fitting and an outer cylinder. <P>SOLUTION: The gas sensor 1 is equipped with: a detection element 10, extending in an axial direction O and having a detection part 11 provided to its leading end; a main metal fitting 50 for holding the detection element in the state of being inserted through its inside so as to protrude the detection part, and an outer cylinder 65, connected to the main metal fitting so as to surround the outer periphery of the rear end part 57 of the main metal fitting and housing the rear-end side of the detection element therein. A caulking part 67 for caulking only the leading end part 65a of the outer cylinder from the outer peripheral side thereof is formed, and a welded part 99 liquid-tight over its whole periphery so as to straddle the leading end part of the outer cylinder and the main metal fitting is formed. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a gas sensor provided with a detection element for detecting the concentration of a gas to be detected and a method for manufacturing the same.

As a gas sensor for detecting the concentration of oxygen and NO _x in the exhaust gas of an automobile, having a detection device using a solid electrolyte are known.
In general, such a gas sensor is configured such that a metal shell that holds the vicinity of the center of a long detection element is attached to an exhaust pipe or the like, and the detection part at the tip of the detection element is exposed in the exhaust pipe so that gas can be detected. Yes. Further, a lead and a terminal for taking out an output signal from the detection unit are provided on the rear end side of the detection element, and the terminal is connected to an external circuit through a connector or the like. Therefore, in order to cover the rear end side of the detection element and hold the lead and the terminal, a cylindrical outer cylinder is joined to the rear end portion of the metal shell.
Usually, the joining of the metallic shell and the outer cylinder is performed by superposing the outer cylinder on the outer side of the rear end of the metallic shell, caulking appropriately, and then laser welding the entire circumference of the overlapping portion (Patent Document 1). 2)

JP 2004-354274 A JP 2001-147213 A

However, in the case of the techniques described in Patent Documents 1 and 2 described above, as shown in FIG. 5, the rear end side of the outer tube 650 is welded to form the welded portion 990, so that the tip 650 a of the outer tube 650 is formed. And a rear end portion 570 of the metal shell, there is a problem that when the gas sensor is submerged, water easily enters the gap due to capillary action. In particular, when the outer cylinder 650 is caulked to form the caulking portion 670, the tip 650a is turned up and the gap tends to increase. The welded part 990 is likely to be corroded, and there is a possibility that the welded part 990 is corroded in the vicinity of the welded part due to the fact that stainless steel used for the metal shell and the outer cylinder is vulnerable to crevice corrosion.
In FIG. 5, the metal shell 500 includes a flange portion 520 and a rear end portion 570 for engaging a hexagon wrench or the like, and the detection element 100 is inserted through the metal shell 500. An arrow indicates the tip side of the detection element 100.
Accordingly, an object of the present invention is to provide a gas sensor in which the gap between the welded portions of the metal shell and the outer cylinder is eliminated to improve the corrosion resistance.

In order to solve the above problems, the gas sensor of the present invention extends in the axial direction and has a detection element having a detection part on the tip side, and the detection element is inserted inside and held so that the detection part protrudes. In a gas sensor comprising: a metal shell, and a cylindrical outer cylinder that surrounds the outer periphery of the rear end portion of the metal shell and is connected to the metal shell and accommodates the rear end side of the detection element inside itself. A caulking portion is formed by caulking only the distal end portion of the outer cylinder, and a liquid-tight weld is formed over the entire circumference across the distal end portion of the outer cylinder and the metal shell.
With such a configuration, the tip of the outer cylinder is inserted into the metal shell and welded across the tip of the outer cylinder and the metal shell, so that there is no gap between the outer cylinder and the metal shell. Therefore, it is possible to easily obtain a welded portion and prevent water and the like from entering the welded portion.
Further, when the distal end portion of the outer cylinder is inserted into the metallic shell, only the distal end portion of the outer cylinder including the distal end of the outer cylinder is crimped, and the metallic shell is not crimped. Normally, the metal shell is made of thick metal and is hard, so there is a risk that the caulking tool will be worn if caulked together with the tip of the outer cylinder and the metal shell, or if the caulking force is too strong, the metal shell may be deformed. However, by caulking only the tip of the outer cylinder, it is possible to prevent tool wear and deformation of the metal shell and improve productivity and yield.

Furthermore, in the gas sensor of the present invention, the rear end portion of the metallic shell has a main body portion and a reduced diameter portion that reduces the diameter from the main body portion toward the rear end side, and the front end portion of the outer cylinder is The outer periphery of the reduced diameter portion may be surrounded and positioned on the rear end side from the main body portion, and the weld portion may be formed across the front end portion of the outer cylinder and the main body portion.
With such a configuration, by making the inner diameter of the distal end portion of the outer cylinder smaller than the outer diameter of the main body portion, when the distal end portion of the outer cylinder is inserted into the reduced diameter portion of the metal shell, the distal end portion of the outer cylinder becomes the main body. It is possible to easily position the insertion depth by contacting at the boundary between the portion and the reduced diameter portion.

Furthermore, in the gas sensor of the present invention, an inner diameter of a portion of the outer cylinder excluding the caulking portion is larger than an outer diameter of a portion surrounded by a front end portion of the outer cylinder in the rear end portion of the metal shell. Also good.
With such a configuration, even if a dimensional error occurs in the outer cylinder or metal shell in actual production, it can be tightened after loosely fitting them together, improving productivity without being affected by the dimensional error. Can be made.

  The gas sensor manufacturing method of the present invention includes a detection element that extends in the axial direction and has a detection portion on a distal end side, and a metal shell that is inserted and held inside the detection element so that the detection portion protrudes. A gas sensor manufacturing method comprising: a cylindrical outer cylinder that surrounds an outer periphery of a rear end portion of the metal shell and is connected to the metal shell and accommodates a rear end side of the detection element inside itself. An outer cylinder arranging step of arranging a front end portion of the outer cylinder so as to surround an outer periphery of a rear end portion of the metallic shell, a caulking step of caulking only the front end portion of the outer cylinder from the outer peripheral side, and the outer A welding step of forming a liquid-tight weld by performing laser welding over the entire circumference across the tip of the tube and the metal shell.

  By using such a manufacturing method, the manufactured gas sensor can easily obtain a liquid-tight welded part without any gap between the outer cylinder and the metal shell, and prevents water from entering the welded part. it can. In addition, by caulking only the tip of the outer cylinder, it is possible to prevent tool wear and deformation of the metal shell and improve productivity and yield.

Furthermore, in the gas sensor manufacturing method of the present invention, the rear end portion of the metal shell has a main body portion and a reduced diameter portion that reduces the diameter from the main body portion toward the rear end side, and the outer cylinder arranging step In the welding process, the front end portion of the outer cylinder surrounds the outer periphery of the reduced diameter portion and is arranged on the rear end side from the main body portion, and in the welding step, the straddle straddles the front end portion of the outer cylinder and the main body portion. Laser welding may be performed.
By making such a manufacturing method, the manufactured gas sensor has the inner cylinder tip inserted into the reduced diameter section of the metal shell by making the inner diameter of the outer cylinder tip smaller than the outer diameter of the main body. At this time, the distal end portion of the outer cylinder comes into contact with the boundary between the main body portion and the reduced diameter portion, and the insertion depth can be easily positioned.

  In the gas sensor manufacturing method of the present invention, an inner diameter of a portion of the outer cylinder excluding the caulking portion is larger than an outer diameter of a portion surrounded by a front end of the outer cylinder in a rear end portion of the metal shell, In the outer cylinder arranging step, the front end of the outer cylinder may be loosely fitted to the rear end of the metal shell.

  According to the present invention, it is possible to improve the corrosion resistance of the gas sensor by eliminating the gap between the welded portion of the metal shell and the outer cylinder, and to further improve the productivity and the yield.

Hereinafter, embodiments of the present invention will be described.
FIG. 1 shows a cross-sectional structure along the axial direction O of a gas sensor 1 according to an embodiment of the present invention. In this embodiment, the gas sensor 1 is inserted into the exhaust pipe of an automobile, the tip (arrow F side in FIG. 1) is exposed to the exhaust gas, and the entire region air-fuel ratio sensor detects the air-fuel ratio from the oxygen concentration in the exhaust gas. It has become. The detection element 10 is a known detection element that constitutes an oxygen concentration cell in which a pair of electrodes are stacked on an oxygen ion conductive solid electrolyte body and outputs a detection value corresponding to the amount of oxygen.
The lower side (arrow F side) in FIG. 1 is the front end side of the gas sensor 1, and the upper side in FIG. 1 is the rear end side of the gas sensor 1.

  The gas sensor 1 is an assembly in which the detection element 10 is assembled in a predetermined housing. The gas sensor 1 includes a cylindrical metal shell 50 having a male thread 51 to be fixed to the exhaust pipe on the outer surface, an outer cylinder 65 connected to the rear end of the metal shell 50, and the metal shell 50. , A detection element 10 having a plate shape extending in the axial direction O, and a cylindrical flange portion 24 disposed in the metal shell 50 so as to surround the circumference of the detection element 10 in the radial direction. The sealing material 26 and the ceramic sleeve 27, the separator 60 surrounding the rear end of the detection element, the holding metal fitting 70 for holding the separator 60, and the connection terminal 61 electrically connected to the rear end of the detection element 10, And a grommet 75 that closes the rear end of the outer cylinder 65.

  The detection element 10 has a detection unit 11 (an electrode of the above-described oxygen concentration cell) at the tip, and a heater (not shown) is laminated. An electrode portion 12 provided with five electrode pads 16 (two shown in FIG. 1) for taking out a detection value output from the detection portion 11 and operating the heater is formed at the rear end of the detection element 10. Has been.

The metal shell 50 is formed in a substantially cylindrical shape, and in order from the front end side to the rear end side, the front end engaging portion 56, the male screw portion 51, the hexagon wrench, etc., are expanded in diameter, and the rear end portion. 57 and a caulking portion 53. In addition, a gasket 55 that prevents gas escape when attached to the exhaust pipe is fitted into a step portion between the front end surface of the flange portion 52 and the rear end of the male screw portion 51. The rear end portion 57 includes a main body portion 57a and a reduced diameter portion 57b that decreases in diameter from the main body portion toward the rear end side.
Further, the metal shell 50 has a through hole 58 that penetrates in the axial direction O, and the shelf 54 protrudes radially inward of the through hole 58, and the shelf 54 is inclined with respect to a plane perpendicular to the axial direction O. Is formed as an inwardly tapered surface.

Inside the through hole 58 of the metal shell 50, an annular ceramic ring 21, sealing materials 22 and 26 made of talc, and the above-mentioned ceramic sleeve 27 are arranged in this order in a state surrounding the circumference of the detection element 10 in the radial direction. It is laminated from the rear end side. A metal cup 20 is disposed between the ceramic ring 21 and the sealing material 22 and the metal shell 50, and the metal cup 20 is locked to the shelf 54. When the sealing material 22 is crushed, the ceramic ring 21, the sealing material 22, and the metal cup 20 become an integral flange portion 24 to hold the detection element 10 and maintain airtightness.
Accordingly, the detection element 10 is held by the metal shell 50 in a state where the front end side of the detection element 10 protrudes from the front end side of the through hole 58 and the electrode pad 16 protrudes from the rear end side of the through hole 58.
A caulking packing 29 is disposed along the shoulder 28 of the ceramic sleeve 27 between the ceramic sleeve 27 and the caulking portion 53 of the metal shell 50, and the caulking portion is interposed via the caulking packing 29. The ceramic sleeve 27 is pressed to the front end side by crimping 53 downward (front end side), and the sealing materials 22 and 26 are crushed.

  On the other hand, the outer periphery of the front end engaging portion 56 of the metal shell 50 covers the protruding portion of the detection element 10 and has a bottomed cylindrical shape having a plurality of holes 85 and 95 (for example, stainless steel) double. The outer protector 80 and the inner protector 90 are attached by welding or the like.

A cylindrical outer cylinder 65 is fixed around the outer periphery of the rear end portion 57 of the metal shell 50, and the outer cylinder 65 accommodates the rear end side of the detection element 10. A separator 60 surrounding the electrode portion 12 of the detection element 10 is disposed inside the outer cylinder 65. The separator 60 has a cylindrical shape having a contact insertion hole 60a penetrating in the axial direction, and the connection terminals 61 provided on the inner surface of the contact insertion hole 60a are electrically connected to the electrode pads 16 of the detection element 10, respectively. It has become. Then, five lead wires 64 (only three in FIG. 1) connected to the connection terminal 61 are drawn out to the rear end side of the outer cylinder 65 through the contact insertion holes 60a.
A cylindrical metal holding metal fitting 70 is disposed between the separator 60 and the outer cylinder 65, and the rear end of the holding metal fitting 70 is bent inward to form the support portion 71. Then, the enlarged diameter flange portion 62 provided on the rear end side of the separator 60 is locked to the support portion 71, and the separator 60 is held by the holding metal fitting 70. The holding metal fitting 70 is swaged inward together with the outer cylinder 65 and fixed to a predetermined position of the outer cylinder 65.
Further, the grommet 75 closes the rear end opening of the outer cylinder 65, and each lead wire 64 is inserted airtight through a lead wire insertion hole 76 that penetrates the grommet 75 in the axial direction, and is drawn out. The grommet 75 is crimped inward together with the outer cylinder 65 to be fixed to the rear end of the outer cylinder 65, and further presses the rear surface of the separator 60 toward the front end side.

Next, referring to FIG. 2 which is a partially enlarged view of FIG. 1, a welded portion between the metal shell and the outer cylinder, which is a characteristic part of the present invention, will be described. 2 is an enlarged view of a portion indicated by a circle A in FIG.
In FIG. 2, the rear end portion 57 of the metal shell before welding has a main body portion 57a and a reduced diameter portion 57b connected in a stepped manner (broken line indicated by an arrow B), and the inner diameter of the outer cylinder 65 is It is larger than the outer diameter of the reduced diameter portion 57b and smaller than the outer diameter of the main body portion 57a. Therefore, as will be described in detail later, when the distal end portion 65a of the outer cylinder is inserted into the reduced diameter portion 57b, a gap P is generated between them, and the distal end portion 65a of the outer cylinder abuts on the stepped portion, and the distal end portion 65a and main body 57a are abutted. At this time, an overlapping portion is formed between the metal shell (the reduced diameter portion 57b) and the outer cylinder 65 through the gap P.
In this state, only the distal end portion 65a of the outer cylinder is crimped from the outer peripheral side so as to include the distal end of the outer cylinder, and comes into contact with the inner surface of the reduced diameter portion 57b, thereby forming the crimped portion 67. Furthermore, since the thickness of the step in the radial direction is substantially the same as the thickness D of the outer cylinder 65, the outer surfaces of the outer cylinder 65 and the main body 57a after crimping are substantially flush with each other.

The caulking portion 67 is thus formed, and the joint (groove) B between the outer cylinder 65 and the main body portion 57a is welded over the entire circumference (for example, laser welding), whereby the distal end portion 65a of the outer cylinder and the metal shell A liquid-tight welded portion 99 is formed over the entire periphery of the main body 57a.
In the present invention, the “tip portion 65 a of the outer cylinder 65” refers to a region having a predetermined spread in the axial direction O including the tip of the outer cylinder 65. Further, the tip of the outer cylinder 65 is clearly present before welding, but since it melts by welding, the tip of the outer cylinder 65 cannot be defined as a clear one point. However, since welding is usually performed near the middle of the abutting portion between the outer cylinder and the metal shell, when viewed from the axial direction O, the center of the melted portion (point B in FIG. 1) is the tip of the outer cylinder 65. It is considered as the position.
In the present invention, the distal end portion 65a of the outer cylinder 65 is inserted into the metal shell 50 and the distal end portion 65a of the outer cylinder 65 is welded. The weld 99 can be easily obtained, and water or the like can be prevented from entering the weld 99 of the gas sensor 1 obtained.
In the present invention, when the tip 65a of the outer cylinder 65 is inserted into the metal shell 50, only the tip 65a of the outer cylinder 65 is crimped, and the metal shell 50 is not crimped. Usually, the metal shell 50 is made of a thick metal and is hard. Therefore, if the caulking tool is worn together with the distal end portion 65a of the outer cylinder 65 and the metal shell 50, the caulking tool is worn or if the caulking force is too strong. May be deformed. Therefore, by caulking only the distal end portion 65a of the outer cylinder 65, tool wear and deformation of the metal shell 50 can be prevented, and productivity and yield can be improved.

Here, if the inner diameter of the outer cylinder 65 is substantially the same as the outer diameter of the rear end portion of the metal shell 50 (in this embodiment, the reduced diameter portion 57b), both can be tightly fitted and temporarily fixed. . However, this method is not preferable because a dimensional error occurs in actual production. Therefore, if the inner diameter of the outer cylinder 65 is configured to be larger than the outer diameter of the rear end portion (in this embodiment, the reduced diameter portion 57a) of the metal shell 50, the two can be loosely fitted and then crimped, resulting in a dimensional error. Productivity can be improved without being affected by the above.
Further, as described above, the rear end portion 57 of the metal shell is formed so that the main body portion 57a and the reduced diameter portion 57b are stepped, and the inner diameter of the outer cylinder 65 is larger than the outer diameter of the reduced diameter portion 57b. If the outer diameter of the portion 57a is made smaller, when the outer tube 65 is inserted into the metal shell 50, the distal end portion 65a of the outer tube 65 contacts the stepped portion, so that the insertion depth can be easily positioned and produced. The property can be further improved. Furthermore, since the front-end | tip part 65a and the main-body part 57a are faced | matched in the up-and-down position of a step part, the liquid-tight welded part 99 is easily obtained by aiming at a butted part and welding.
As described above, when the thickness of the step in the radial direction is substantially the same as the thickness of the outer cylinder 65, the outer surfaces of the outer cylinder 65 and the main body 57a after crimping are flush with each other, and the material thickness is also equal. As a result, the degree of fusion between the two becomes uniform, and the liquid-tight weld 99 can be easily obtained.

  In FIG. 2, it is preferable to adjust the welding conditions so that the welding depth (penetration depth) C of the welded portion 99 is twice or more the thickness D of the outer cylinder 65 because the welding strength is improved. When viewed from the axial direction O, the distance E between the front end of the welded portion 99 and the rear end of the flange 52 of the metal shell is preferably 1 mm or more, and more preferably 3 mm or more. This is because, when the interval E is less than 1 mm, the melted portion 99 by welding spreads to the flange portion 52, and the strength of the flange portion 52 may be reduced or the appearance may be deteriorated.

Next, a method for manufacturing the gas sensor 1 according to the embodiment of the present invention will be described with reference to FIGS. FIG. 3 shows the outline of the whole manufacturing process of the gas sensor 1, and FIG. 4 shows the details of the outer cylinder arranging process and the caulking process.
In FIG. 3, the detection element 10 is held by the metal shell 50 as described in FIG. 1, and the protector 8 is joined to the tip of the metal shell 50. Then, the outer cylinder 65 is put on the assembly from above (the rear end side 12 of the detection element 10) (each part assembly step).
And the front-end | tip part 65a of the outer cylinder 65 is arrange | positioned so that the outer periphery of the rear-end part 57 (this embodiment diameter reduction part 57b) of the metal shell 50 may be enclosed (outer cylinder arrangement | positioning process). Here, as described above, the rear end portion 57 of the metal shell 50 is formed so that the main body portion 57a and the reduced diameter portion 57b form a step, and the front end portion 65a of the outer cylinder 65 is brought into contact with the rear surface 57x of the step. The outer cylinder 65 is arranged in a contact state, and a boundary (butting portion after caulking) B is formed between the outer cylinder 65 and the reduced diameter portion 57b. Further, the rear end portion 57 (the reduced diameter portion 57b in this embodiment) and the outer cylinder 65 form an overlapping portion while loosely fitting.

Further, only the distal end portion 65b of the outer cylinder 65 included in the overlapping portion is caulked from the outer peripheral side over the entire circumference (reference numeral M) to form a caulking portion 67 (caulking step). Thereby, the outer cylinder 65 is temporarily fixed to the metal shell 50.
Next, aiming near the butt portion B, laser welding is performed across the distal end portion 65a and the main body portion 57a of the metal shell from the outer peripheral side to the entire periphery, thereby forming a liquid-tight weld 99 (welding process). At this time, by irradiating the laser from the direction orthogonal to the axial direction O, the melting state of the outer cylinder 65 and the metal shell 50 becomes substantially equal. However, as long as the welded portion 99 can be formed so as to straddle the outer cylinder 65 and the metal shell 50, the laser irradiation position may be offset from the butted portion B in the axial direction O.

As shown in FIG. 4, in the outer cylinder arranging step, the rear end portion 57 of the metallic shell is formed so that the main body portion 57a and the reduced diameter portion 57b are stepped, and the inner diameter of the outer cylinder 65 is the reduced diameter portion 57b. If it is larger than the outer diameter and smaller than the outer diameter of the main body portion 57a, when the outer cylinder is inserted into the metal shell, the front end portion 65a of the outer cylinder abuts on the rear surface 57x of the stepped portion and positioning is performed.
And in the caulking step, by caulking the overlapping portion (the portion corresponding to the length in the axial direction O of the reduced diameter portion 57b) of the distal end portion 65a of the outer cylinder 65 and the reduced diameter portion 57b, A caulking portion 67 is formed.
In the welding process, laser welding is performed aiming at the vicinity of the butt portion B, so that the melted portion spreads from the butt portion B toward the front end and the rear end and in the axial direction, and a welded portion 99 is formed.

  It goes without saying that the present invention is not limited to the above-described embodiment, but extends to various modifications and equivalents included in the spirit and scope of the present invention.

It is a sectional structure figure which meets an axial direction of a gas sensor concerning an embodiment of the present invention. It is the elements on larger scale of FIG. It is process drawing which shows the manufacturing method of the gas sensor which concerns on embodiment of this invention. FIG. 4 is a detailed view of FIG. 3. It is a partial expanded sectional view of the welding part vicinity of the conventional gas sensor.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Gas sensor 10 Detection element 11 Detection part 50 Main metal fitting 57 Rear end part 57a Main body part 57b Diameter reduction part 65 Outer cylinder 65a End part of outer cylinder 67 Clamping part 99 Welding part O Axial direction F End direction

Claims (6)

A detection element extending in the axial direction and having a detection part on the tip side;
A metal shell that holds the detection element inserted inside thereof so that the detection unit protrudes,
In the gas sensor comprising a cylindrical outer cylinder that surrounds the outer periphery of the rear end portion of the metal shell and is connected to the metal shell and accommodates the rear end side of the detection element inside thereof.
A gas sensor in which a crimped portion in which only the distal end portion of the outer cylinder is crimped is formed, and a liquid-tight welded portion is formed over the entire circumference across the distal end portion of the outer cylinder and the metal shell.   The rear end portion of the metal shell has a main body portion and a reduced diameter portion that decreases in diameter from the main body portion toward the rear end side, and the front end portion of the outer cylinder surrounds the outer periphery of the reduced diameter portion. The gas sensor according to claim 1, wherein the gas sensor is located on a rear end side from the main body portion, and the welding portion is formed to straddle a front end portion of the outer cylinder and the main body portion.   3. The gas sensor according to claim 1, wherein an inner diameter of a portion excluding the caulking portion of the outer cylinder is larger than an outer diameter of a portion surrounded by a front end portion of the outer cylinder in a rear end portion of the metal shell. . A detection element extending in the axial direction and having a detection part on the tip side;
A metal shell that holds the detection element inserted inside thereof so that the detection unit protrudes,
A gas sensor manufacturing method comprising a cylindrical outer cylinder that surrounds the outer periphery of the rear end portion of the metal shell and is connected to the metal shell and accommodates the rear end side of the detection element inside itself.
An outer cylinder arranging step of arranging the tip of the outer cylinder so as to surround the outer periphery of the rear end of the metal shell;
A caulking step of caulking only the tip of the outer cylinder from the outer peripheral side;
A gas sensor manufacturing method comprising: a welding step of forming a liquid-tight weld by performing laser welding over the entire circumference across the tip of the outer cylinder and the metal shell. The rear end portion of the metal shell has a main body portion, and a reduced diameter portion that decreases in diameter from the main body portion toward the rear end side,
In the outer cylinder arranging step, the front end of the outer cylinder is arranged on the rear end side from the main body while surrounding the outer periphery of the reduced diameter part,
The method for manufacturing a gas sensor according to claim 4, wherein in the welding step, the laser welding is performed across the distal end portion of the outer cylinder and the main body portion. Of the outer cylinder, the inner diameter of the portion excluding the caulking portion is larger than the outer diameter of the portion surrounded by the front end of the outer cylinder in the rear end portion of the metal shell,
The method of manufacturing a gas sensor according to claim 4 or 5, wherein, in the outer cylinder arranging step, a distal end portion of the outer cylinder is arranged in a loosely fitted state on a rear end portion of the metal shell.

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