JP5129599B2 - Gas sensor and manufacturing method thereof - Google Patents

Description

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

  2. Description of the Related Art Conventionally, a gas sensor including a detection element having a detection unit for detecting the concentration of a gas to be detected in exhaust gas of an automobile or the like, for example, NOx (nitrogen oxide) or oxygen is known. Such a detection element is used by being held by a metal shell to be attached to an exhaust pipe of an automobile so that a detection portion provided on the front end side of the detection element is exposed in the exhaust pipe. In addition, an electrode for taking out an output signal from the detection unit is provided on the rear end side of the detection element, and the rear end side of the detection element including the electrode portion is exposed from the rear end side of the metal shell. . A lead wire for connecting to an external circuit is electrically connected to the electrode, and in order to protect the rear end portion of the detection element including this connection portion, a cylindrical outer part is provided on the rear end side of the metal shell. The cylinder is joined.

In the manufacturing process of such a gas sensor, the metal shell and the outer cylinder are usually joined by laser welding. Specifically, the front end of the outer cylinder is overlaid on the engagement portion formed on the rear end side of the metal shell, and after temporary fixing by caulking or in the state as it is, the laser is applied from the outer peripheral side of the outer cylinder to the entire circumference. Irradiation is performed to join the outer cylinder and the metal shell (for example, see Patent Document 1 and Patent Document 2).
JP 2004-354274 A JP 2001-147213 A

  However, in Patent Document 1 and Patent Document 2, the welded portion formed by laser bonding is located on the rear end side of the outer tube tip, and the portion from the outer tube tip to the welded portion is the outer tube. Although the inner peripheral surface of the metal plate and the outer peripheral surface of the metal shell are in close contact with each other, they are not joined, so there may be a slight gap. If the gas sensor is exposed to water during use, water droplets or the like may enter the gap due to capillarity, and the water droplets entering the gap are relatively difficult to volatilize. There is a risk of contact with water droplets. Especially in metal shells, the interface of the part once melted by laser welding is relatively susceptible to corrosion. Therefore, when the welded part is in contact with water droplets or the like for a long time, corrosion occurs at the interface between the welded part and the non-welded part. There was a fear.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a gas sensor that can prevent corrosion from occurring in a welded portion between a metal shell and an outer cylinder, and a method for manufacturing the same. To do.

In order to achieve the above object, a gas sensor according to a first aspect of the present invention includes a detection element that extends in the axial direction and has a detection unit for detecting a gas to be detected at the tip end of the gas sensor. A gas sensor having a metallic shell surrounding the radial periphery of the detection element, and a cylindrical outer cylinder fixed to the metallic shell and surrounding the radial circumference on the rear end side of the detection element The metal shell has a flange portion radially expanded in diameter and a rear end portion formed on the rear end side of the flange portion, and the front end of the outer cylinder is the rear end portion of the metal shell. Are arranged so as to surround at least a part of the circumference in the radial direction, and by melting a boundary portion between the tip of the outer tube and the rear end of the metal shell, the tip of the outer tube and the Formed across the rear end of the metal shell Contact portion is formed over the entire periphery, the thickness of the weld, and greater than the thickness of the outer cylinder.

  Further, in the gas sensor of the invention according to claim 2, in addition to the configuration of the invention of claim 1, the rear end portion of the metal shell is connected to a cylindrical portion and a rear end side of the cylindrical portion, A diameter-reducing portion that is smaller in diameter than the cylindrical portion, the distal end of the outer cylinder is disposed so as to surround a radial circumference of the reduced-diameter portion, and the welded portion is connected to the distal end of the outer cylinder. It is formed straddling between the cylindrical portions.

Further, in the gas sensor of the invention according to claim 3 , in addition to the configuration of the invention of claim 2 , the welded portion is formed such that its thickness in the radial direction is twice or more thicker than the thickness of the outer cylinder. It is characterized by.

Further, in the gas sensor of the invention according to claim 4 , in addition to the configuration of the invention according to any one of claims 1 to 3 , the distance between the front end of the welded portion and the rear end of the flange portion is 1 mm or more. It is characterized by.

In addition to the configuration of the invention according to any one of claims 2 to 4 , the gas sensor according to a fifth aspect of the invention extends over the tip of the outer cylinder and the cylindrical portion of the metal shell. And the crimping part which crimped both from the outer peripheral side is formed, It is characterized by the above-mentioned.

According to a sixth aspect of the present invention, in the gas sensor according to the sixth aspect , in addition to the configuration of the first aspect, the welded portion is formed between the tip of the outer cylinder and the flange of the metal shell. It is characterized by being.

Further, the gas sensor of the invention according to claim 7, in addition to the configuration of the invention according to claim 6, wherein the outer cylinder, the leading end of itself, has a enlarged diameter portion whose diameter increases radially outward, the The welded portion is formed between the enlarged diameter portion and the flange portion.

Further, the gas sensor of the invention according to claim 8, in addition to the configuration of the invention according to claim 6 or 7, wherein the weld toward the radially inner side, is formed to extend to the distal end side of the axial direction It is characterized by being.

According to a ninth aspect of the present invention, in addition to the configuration of the first aspect of the invention, the front end of the outer cylinder has a diameter of the rear end portion that is separated from the flange portion of the metal shell. It arrange | positions so that the surroundings of a direction may be surrounded, The said welding part is formed ranging over between the said front-end | tip of the said outer cylinder, and the said rear-end part of the said main metal fitting, It is characterized by the above-mentioned.

According to a tenth aspect of the present invention, in addition to the configuration of the ninth aspect of the invention, the welding portion is formed to extend toward the rear end side in the axial direction as it goes radially inward. It is characterized by that.

Further, the gas sensor of the invention according to claim 1 1, in addition to the configuration of the invention according to any one of claims 6 to 1 0, wherein the weld to be formed in a curved shape dented its outer surface Features.

A method of manufacturing a gas sensor of the invention according to claim 1 2, extends in the axial direction, a detecting element having a detecting part for detecting the detected gas to its distal end, the detector itself tip A gas sensor manufacturing method comprising: a metal shell that surrounds the periphery of the detection element in a radial direction while projecting from the tube; and a cylindrical outer cylinder that is fixed to the metal shell and surrounds the periphery of the detection element in the radial direction on the rear end side The metal shell is connected to the rear end side of the tubular portion formed on the rear end side of the flange portion, the tubular portion formed in the radial direction, the tubular portion, and more than the tubular portion. An outer cylinder arrangement having a reduced diameter portion that reduces the diameter, and that abuts the front end of the outer cylinder so as to surround the radial circumference of the reduced diameter portion, and abuts the surface facing the rear end of the cylindrical portion Near the boundary between the process and the tip of the outer cylinder and the cylindrical portion of the metal shell Laser welding is performed over the entire circumference, and a boundary portion between the tip of the outer cylinder and the cylinder portion of the metal shell is melted, whereby the tip of the outer cylinder and the cylinder portion of the metal shell are a welding step of forming a weld possess over between the thickness of the weld, and greater than the thickness of the outer cylinder.

A method of manufacturing a gas sensor of the invention according to claim 1 3, in addition to the configuration of the invention according to claim 1 2, in the welding process, than the thickness thickness of the outer cylinder in the radial direction of the weld Laser welding is performed over the entire circumference toward the vicinity of the boundary between the tip of the outer cylinder and the cylindrical portion of the metallic shell so as to be formed thick.

A method of manufacturing a gas sensor of the invention according to claims 1 to 4, in addition to the configuration of the invention according to claim 1 2 or 1 3, before the welding step after the outer cylinder arrangement step, the said outer cylinder It has a caulking process which forms a caulking part by caulking both from the outer peripheral side so as to straddle the tip and the cylindrical part of the metal shell.

The method for manufacturing a gas sensor of the invention according to claim 15 includes a detection element extending in the axial direction and having a detection unit for detecting a gas to be detected on its front end side, and the detection unit on its front end. A gas sensor manufacturing method comprising: a metal shell that surrounds the periphery of the detection element in a radial direction while projecting from the tube; and a cylindrical outer cylinder that is fixed to the metal shell and surrounds the periphery of the detection element in the radial direction on the rear end side The metal shell has a flange portion radially expanded in diameter and a rear end portion formed on the rear end side of the flange portion, and the front end of the outer cylinder is connected to the rear end portion. An outer cylinder arranging step for contacting the rear end facing surface of the flange while arranging so as to surround the circumference in the radial direction, and toward the vicinity of the boundary between the tip of the outer cylinder and the flange of the metal shell Laser welding is performed over the entire circumference, and the tip of the outer cylinder Said By melting the boundary portion between the flange portion of the metal shell, possess a welding step of forming a weld across between the flange portion of the tip and the metal shell of the outer cylinder, wherein The thickness of the welded portion is larger than the thickness of the outer cylinder .

The method for manufacturing a gas sensor of the invention according to claim 16 extends in the axial direction and has a detection element having a detection unit for detecting the inside of the gas to be detected at the tip side of the gas sensor, Production of a gas sensor having a metallic shell surrounding the radial periphery of the detection element while protruding from the tip, and a cylindrical outer cylinder fixed to the metallic shell and surrounding the radial circumference on the rear end side of the detection element In the method, the metal shell has a flange portion radially expanded in diameter and a rear end portion formed on the rear end side of the flange portion, and the tip of the outer cylinder is connected to the metal shell. An outer cylinder arrangement step of arranging the outer cylinder so as to surround the radial periphery of the rear end while being separated from the flange, and toward the vicinity of the boundary between the tip of the outer cylinder and the rear end of the metal shell Laser welding is performed over the entire circumference, and the tip of the outer cylinder A welding step of forming a welded portion straddling between the front end of the outer cylinder and the rear end portion of the metallic shell by melting a boundary portion between the end and the rear end portion of the metallic shell. Yes, and the thickness of the weld, and greater than the thickness of the outer cylinder.

A method of manufacturing a gas sensor of the invention according to claim 1 7, in addition to the configuration of the invention according to claim 1 5 or 1 6, in the welding process, forming a curved shape recessed outer surface of the weld It is characterized by being.

  In the gas sensor according to the first aspect of the present invention, the distal end of the outer cylinder is disposed so as to surround at least a part of the rear end portion of the metallic shell in the radial direction, and the welded portion straddles the distal end of the outer cylinder and the metallic shell. The outer cylinder and the metal shell are joined together, and the welded portion is formed over the entire circumference, so that the outer peripheral surface of the rear end portion of the metal shell and the inner peripheral surface of the front end of the outer cylinder It is possible to seal in a state in which the gap is blocked from the outside. Then, even if the gas sensor is flooded during use, the welded portion blocks the space between the front end of the outer cylinder that can be an entrance to the gap and the rear end of the metal shell. And the like can be prevented from entering. Therefore, a state in which water droplets or the like that have entered the gap does not come into contact with the welded portion exposed in the gap for a long period of time, and as a result, waterdrops or the like that have been in contact with the welded portion for a long time occurs. It is possible to prevent the occurrence of corrosion.

  Thus, in forming the welded portion straddling between the rear end portion of the metal shell and the front end of the outer cylinder, the rear end portion of the metal shell is stepped like the invention according to claim 2. If it is formed and has a cylindrical portion and a reduced diameter portion, the tip of the outer cylinder can be brought into contact with the cylindrical portion while being engaged with the reduced diameter portion, and when the outer cylinder and the metal shell are joined. It is easy to position and temporarily fix both. When joining the outer cylinder and the metal shell, for example, using laser welding, the tip of the outer cylinder is brought into contact with the cylinder portion of the metal shell as described above, and the abutting position (the boundary between the outer cylinder and the metal shell) If the laser is irradiated from the direction orthogonal to the axial direction of the gas sensor, the melting state of the metal shell and the melting state of the outer cylinder can be brought closer to a uniform state, and the gap due to the formation of the welded portion can be brought closer. Sealing can be performed more reliably. However, even if the laser irradiation position is biased to the metal shell side or the outer cylinder side with respect to the abutting position, the welded portion formed by melting by the laser straddles the outer cylinder and the metal shell. If formed, the gap can be sufficiently sealed.

Then, it is desirable that the thickness in the radial direction of the welded portion to form a weld to be thicker than the thickness of the outer cylinder, more specifically, in the invention according to claim 3, the diameter of the weld It is preferable to form the weld by adjusting the laser output so that the thickness in the direction is twice or more thicker than the thickness of the outer cylinder. In this way, the outer cylinder and the metal shell can be reliably melted and mixed with each other in the formation of the welded portion, the joint strength between them can be increased, the outer peripheral surface of the rear end of the metal shell and the outer cylinder The gap between the tip and the inner peripheral surface can be reliably sealed.

Further, as in the invention according to claim 4 , it is preferable that the tip of the formed welded part is separated from the rear end of the collar part of the metal shell, more specifically, the tip of the welded part and the collar in the axial direction. It is desirable that the distance from the rear end of the part is 1 mm or more. When joining the outer cylinder and the metal shell using, for example, laser welding, the laser is irradiated aiming at the abutment position (boundary between the outer cylinder and the metal shell) between the tip of the outer cylinder and the cylindrical portion of the metal shell. It will be. At this time, if the laser irradiation position and the collar part of the metal shell are separated from each other, the operation can be easily performed, and the distance is such that the tip of the formed welded part is A distance of 1 mm or more from the rear end is sufficient. On the other hand, when the distance between the front end of the formed weld and the rear end of the collar is less than 1 mm, the laser irradiation position is close to the collar, so that the laser does not hit the collar and the butting position It may be difficult to irradiate the laser from the direction perpendicular to the axial direction of the gas sensor. If the laser is applied to the buttocks, it is difficult to achieve a uniform state of melting of the main metal shell and of the outer cylinder, and there is a risk that the aesthetic appearance of the finish may be impaired. It may be necessary to change the angle or increase the irradiation accuracy.

Further, as in the invention according to claim 5 , the outer cylinder can be temporarily fixed to the metal shell by caulking both from the outer peripheral side so as to straddle the tip of the outer cylinder and the cylinder portion of the metal shell. It is possible to prevent occurrence of displacement between the metal shell and the outer cylinder in the process of forming the welded portion, and to ensure that the welded portion connecting the two is formed across the two.

By the way, a welding part may be formed so that it may straddle both, making the front-end | tip of an outer cylinder associate with the collar part of a metal shell like the invention which concerns on Claim 6 . In this way, if the portion that can be the entrance portion to the gap between the inner peripheral surface at the front end of the outer cylinder and the outer peripheral surface of the rear end portion of the metal shell can be filled with the welded portion, the sealing of the gap is ensured. Can be done.

Furthermore, like the invention which concerns on Claim 7, it has a diameter-expanding part which expands to a radial direction outer side in the front-end | tip of an outer cylinder, and a welding part may be formed ranging over the diameter-expanding part and a collar part. . More specifically, the enlarged-diameter portion is a portion in a form in which the front end of the outer cylinder is folded back radially outward, and the distal end in the axial direction of the enlarged-diameter portion is brought into contact with the rear end of the flange portion of the metal shell, thereby expanding the diameter. A weld that straddles the enlarged diameter portion and the flange portion is formed at a step formed between the radial tip of the diameter portion and the rear end of the flange portion. Even if it has an enlarged diameter portion at the tip of the outer cylinder, if a welded portion is formed between the tip of the outer cylinder and the flange of the metal shell, the inner peripheral surface of the tip of the outer cylinder Since the portion that can be an entrance portion to the gap between the metal shell and the outer peripheral surface of the rear end portion of the metal shell is filled with the welded portion, the gap can be reliably sealed.

By the way, when the welded portion that straddles the front end of the outer cylinder and the collar portion of the metal shell is formed by using, for example, laser welding, as in the invention according to claim 8 , the front end side in the axial direction is increased toward the inner side in the radial direction. If the welded portion is formed by irradiating the laser so as to extend, the welded portion can be formed up to the inside of the metal shell, and the joint strength between the outer cylinder and the metal shell can be further increased. In addition, what is necessary is just to irradiate a laser in said direction so that the butting | matching position of the front-end | tip of an outer cylinder and the collar part of a metal shell may be included.

Further, as in the invention according to claim 9 , a welded portion is formed straddling between the front end of the outer cylinder and the rear end portion of the metal shell in a state where the front end of the outer cylinder is separated from the flange portion of the metal shell. May be. In this way, if the portion that can be the entrance portion to the gap between the inner peripheral surface at the front end of the outer cylinder and the outer peripheral surface of the rear end portion of the metal shell can be filled with the welded portion, the sealing of the gap is ensured. Can be done.

Then, a weld across a rear end portion of the distal end of the outer tube and the metal shell, for example, in the case of forming by using a laser welding, as in the invention according to claim 1 0, axial post as the directed radially inward If the welded portion is formed by irradiating the laser so as to extend to the end side, the welded portion can be formed up to the inside of the metal shell, and the bonding strength between the outer cylinder and the metal shell can be further increased. In addition, what is necessary is just to irradiate a laser in said direction so that the butting | matching position of the front-end | tip of an outer cylinder and the rear-end part of a metal shell may be included.

The formation of the welded portion of such forms, since the desire butt position of the outer tube and the metal shell, the form of joining the two surfaces bent inwardly at its butt position, the invention according to claim 1 1 If the outer surface of the formed welded part is formed in a curved shape that is recessed, the inlet part to the gap between the tip of the outer cylinder and the metal shell has a thickness for sealing with the welded part. Thus, the gap can be more reliably sealed.

In the manufacturing method of the gas sensor of the invention according to claim 1 2, the outer tube arrangement step, since the contact with the rear end side of the cylindrical portion while engaging the distal end of the outer tube to the reduced diameter portion of the metal shell, It is easy to position and temporarily fix the outer cylinder and metal shell. In this state, laser welding is performed over the entire circumference toward the vicinity of the boundary between the outer cylinder and the metallic shell in the welding process. Can be formed. If the laser irradiation at this time is performed from the direction orthogonal to the axial direction, the melting state of the main metal shell and the melting state of the outer cylinder can be brought closer to a uniform state, and the gap is sealed by forming the welded portion. Can be performed more reliably. The laser irradiation is preferably performed toward the boundary where the tip of the outer cylinder and the cylindrical portion of the metal shell are in contact with each other. Even if it is biased, the gap can be sufficiently sealed if the welded portion formed by being melted by the laser is formed across the outer cylinder and the metal shell. Therefore, laser welding is preferably performed near the boundary between the tip of the outer cylinder and the cylindrical portion of the metal shell.

  In this way, the gap between the outer peripheral surface of the rear end portion of the metal shell and the inner peripheral surface of the front end of the outer tube is formed between the front end of the outer tube and the cylindrical portion of the metal shell. Can be sealed in a state of being blocked from the outside. Then, even if the gas sensor is flooded during use, the welded portion blocks the space between the front end of the outer cylinder that can be an entrance to the gap and the rear end of the metal shell. And the like can be prevented from entering. Therefore, a state in which water droplets or the like that have entered the gap does not come into contact with the welded portion exposed in the gap for a long period of time, and as a result, waterdrops or the like that have been in contact with the welded portion for a long time occurs. It is possible to prevent the occurrence of corrosion.

Further, in the invention according to the claims 1 to 3, by forming the welded portion to a thickness thicker than the thickness of the outer cylinder in the radial direction of the welded portion, the welded portion, and the outer tube distal end diameter Since it is formed between the metal shell in each of the inner side in the direction, the gap can be sealed more reliably by forming the welded portion.

Further, in the invention according to the claims 1 to 4, subjected to crimping process before the welding process after the outer tube arrangement step, both to span the a cylindrical portion of the tip and the metal shell of the outer tube from the outer circumferential side pressure If tightened, the outer cylinder can be temporarily fixed to the metal shell. If it does in this way, it can prevent that position shift with an outer cylinder arises in a welding process, and can form a welding part over both.

Further, as in the invention according to claim 15 , a welded portion straddling both ends of the outer cylinder while abutting the front end of the outer shell while engaging the rear end of the outer wall of the metallic shell A portion that can be an entrance portion to the gap between the inner peripheral surface of the outer cylinder tip and the outer peripheral surface of the rear end of the metal shell, that is, the contact between the tip of the outer cylinder and the flange of the metal shell The portion can be filled with the welded portion, and the gap can be reliably sealed.

Similarly, as in the invention according to claim 16 , with the rear end of the metal shell engaged with the front end of the outer cylinder, the both ends are spaced apart from the flange of the metal shell. Even when the welded portion is formed, a portion that can be an entrance portion to the gap between the inner peripheral surface of the outer cylinder at the front end and the outer peripheral surface of the rear end of the main metal shell, that is, the front end of the outer cylinder and the rear end of the main metal shell The boundary portion with the portion can be filled with the welded portion, and the gap can be reliably sealed.

In addition, since formation of the weld part of such a form becomes a form which joins the two surfaces bent inward at the bending position, the outer surface of the formed weld part as in the invention according to claim 17 Can be formed to have a thickness that seals the entrance portion to the gap between the front end of the outer cylinder and the rear end portion of the metal shell with a welded portion. This can be done more reliably.

  Hereinafter, an embodiment of a gas sensor and a manufacturing method thereof embodying the present invention will be described with reference to the drawings. First, as a first embodiment of a gas sensor according to the present invention, the structure of a gas sensor 1 will be described as an example with reference to FIGS. FIG. 1 is a longitudinal sectional view of the gas sensor 1. FIG. 2 is a cross-sectional view of the gas sensor 1 in which the portion of the circle A in FIG. 1 is enlarged. The gas sensor 1 is used by being attached to an exhaust pipe (not shown) of an automobile. At this time, the side exposed in the exhaust pipe (the lower side in FIG. 1) is the tip side in the direction of the axis O, and the opposite side. Assume that (the upper side in FIG. 1) is the rear end side.

  A gas sensor 1 shown in FIG. 1 is attached to an exhaust pipe (not shown) of an automobile, and a detection unit 11 provided on the front end side of a detection element 10 held inside is exposed to exhaust gas flowing in the exhaust pipe. The so-called full-range air-fuel ratio sensor detects the air-fuel ratio of the exhaust gas from the oxygen concentration in the exhaust gas. When the air-fuel ratio of the exhaust gas is lean, a detection value (current value) corresponding to the amount of oxygen surplus with respect to the theoretical air-fuel ratio is obtained from the detection element 10, and when it is rich, unburned gas A detection value (current value) corresponding to the amount of oxygen necessary to completely burn the gas is obtained. Based on these detection values, the air-fuel ratio of the exhaust gas is obtained by a sensor control circuit (not shown) and output to an ECU (electronic control unit) for use in air-fuel ratio feedback control and the like.

  First, the detection element 10 will be described. The detection element 10 is a narrow and plate-like element extending in the direction of the axis O as is well known, and includes a gas detection body that detects the oxygen concentration, and a heater that heats the gas detection body for early activation. The body is integrated as a laminated body bonded in the thickness direction (in FIG. 1, the left-right direction on the paper surface is shown as the thickness direction (plate thickness direction), and the front-back direction on the paper surface is shown as the width direction). The gas detector is composed of a solid electrolyte body mainly composed of zirconia and a detection electrode mainly composed of platinum (both not shown), and the detection electrode is disposed in the detection section 11 on the distal end side of the detection element 10. ing. And in order to protect a detection electrode from poisoning by exhaust gas, the protective layer 15 is formed in the detection part 11 of the detection element 10 so that the outer peripheral surface may be wrapped. Further, the electrode portion 12 provided on the rear end side of the detection element 10 has five electrode pads 16 (two electrode pads 16 are shown in FIG. 1) for taking out the electrodes from the gas detection body and the heater body. Is formed). In the first embodiment, the detection element 10 is described as a “detection element” in the present invention. However, strictly speaking, a heater body is not necessarily required as the configuration of the detection element 10, and the gas detection body is not a main element. It may correspond to the “detection element” of the invention.

  Next, the flange portion 24 will be described. A metal cup 20 made of metal having a bottomed cylindrical shape with the detection element 10 inserted therein is disposed slightly on the front end side of the central portion 13 of the detection element 10. The metal cup 20 is a holding member for holding the detection element 10 in the metal shell 50, and the detection portion 11 of the detection element 10 protrudes from the opening 25 at the bottom of the cylinder. Moreover, the front-end | tip peripheral part 23 of the edge part of a cylinder bottom is formed in the taper shape over the outer peripheral surface. A ceramic ring 21 made of alumina and a sealing material 22 made of talc powder are accommodated in the metal cup 20 with the detection element 10 inserted therethrough. The sealing material 22 is crushed in the metal cup 20 to be filled in detail, whereby the metal cup 20, the ceramic ring 21, and the sealing material 22 are integrated and serve as the flange portion 24 in the radial direction of the detection element 10. The detection element 10 is integrally assembled so as to surround the periphery.

  Next, the metal shell 50 will be described. The metal shell 50 is for attaching and fixing the gas sensor 1 to an exhaust pipe (not shown) of the automobile, and has a cylindrical shape in which a through hole 58 is formed. The center portion 13 of the detection element 10 is held in the through hole 58 of the metal shell 50 together with the flange portion 24. The metal shell 50 is made of, for example, low carbon steel such as SUS430, and has a male screw portion 51 in which a thread for attachment to the exhaust pipe is formed on the outer peripheral tip side. A distal end engaging portion 56 to which a protector 8 described later is engaged is formed on the distal end side of the male screw portion 51. Further, a tool engaging portion 52 with which a tool for attachment is engaged is formed at the center of the outer periphery of the metal shell 50. And between the front end surface of the tool engaging part 52 and the rear end of the external thread part 51, the gasket 55 for preventing the gas escape at the time of attaching to an exhaust pipe is inserted. Note that the tool engaging portion 52 corresponds to a “hook portion” in the present invention.

  Further, as shown in FIG. 2, a rear end engaging portion 57 is formed on the rear end side of the tool engaging portion 52 to be engaged with a front end 66 of an outer cylinder 65 described later. In the first embodiment, the rear end engaging portion 57 includes a cylindrical portion 571 on the tool engaging portion 52 side, and a reduced diameter portion that is smaller in diameter than the cylindrical portion 571 on the rear end side from the cylindrical portion 571. 572. The size in the radial direction of the surface 574 (hereinafter referred to as “rear end facing surface” 574. In FIG. 2, the position of the rear end facing surface 574 before welding is indicated by a dotted line) consisting of both stepped portions is as follows. The thickness of the outer cylinder 65 described later is substantially the same. A caulking portion 53 for caulking and holding the detection element 10 in the metal shell 50 is formed further on the rear end side than the rear end engaging portion 57. The rear end engaging portion 57 corresponds to the “rear end portion” in the present invention.

  Further, as shown in FIG. 1, a stepped portion 54 having a step shape is formed in the vicinity of the male screw portion 51 on the inner periphery of the through hole 58 of the metal shell 50. The step 54 is engaged with the peripheral edge 23 of the metal cup 20 that forms the flange 24 integrated with the detection element 10. Further, a sealing material 26 made of talc powder is loaded on the inner periphery of the metal shell 50 from the rear end side of the flange portion 24 in a state where the detection element 10 is inserted through the metal shell 50 itself. A cylindrical sleeve 27 is fitted into the metal shell 50 so as to hold the sealing material 26 from the rear end side. A shoulder portion 28 having a step shape is formed on the outer periphery of the rear end side of the sleeve 27, and an annular caulking packing 29 is disposed on the shoulder portion 28. In this state, the crimping portion 53 of the metal shell 50 is crimped so as to press the shoulder portion 28 of the sleeve 27 toward the distal end side via the crimping packing 29. The sealing material 26 is crushed in the metal shell 50 and filled in details, and the flange portion 24 and the detection element 10 are mainly composed of the sealing material 26 and the sealing material 22 loaded in advance in the metal cup 20. It is positioned and held in the metal fitting 50. The airtightness in the metal shell 50 is maintained by the caulking packing 29 interposed between the caulking portion 53 and the shoulder portion 28 of the sleeve 27, and the outflow of combustion gas is prevented.

  Next, the structure of the rear end side of the metal shell 50 of the gas sensor 1 will be described. From the rear end (caulking portion 53) of the metal shell 50, a portion on the rear end side including the electrode portion 12 of the detection element 10 held inside protrudes. The electrode portion 12 is covered with a cylindrical separator 60 made of insulating ceramics. The separator 60 includes five connection terminals 61 (in FIG. 1, two connection terminals 61 are shown) that are brought into contact (electrically connected) with each of the plurality of electrode pads 16 formed on the electrode portion 12 of the detection element 10. Is held inside. Further, each connection terminal 61, five lead wires 64 connected to each connection terminal 61 and drawn out of the gas sensor 1 (three lead wires 64 are shown in FIG. 1) and each. The connecting portion is also accommodated in the separator 60 and protected.

  The above-described outer cylinder 65 is made of stainless steel (for example, SUS304) and has a cylindrical shape. The outer cylinder 65 is attached to the rear end side of the metal shell 50 and is exposed from the rear end of the metal shell 50 and includes the electrode portion 12 of the detection element 10 and the separator 60. It covers and protects the surroundings. As shown in FIG. 2, the outer cylinder 65 is configured so that the inner peripheral surface 68 of its own tip 66 is opposed to the outer peripheral surface 573 of the reduced diameter portion 572 of the rear end engaging portion 57 of the metal shell 50. The end engaging portion 57 is engaged. In this state, the vicinity of the abutting position between the front end surface 69 of the outer cylinder 65 (the position of the front end surface 69 before welding is indicated by a dotted line in FIG. 2) and the rear end facing surface 574 of the rear end engaging portion 57. A range from the tip 66 to the cylindrical portion 571 is crimped in a ring shape from the outer peripheral side to the circumferential direction so as to straddle (near the boundary between both indicated by the arrow B), and is formed as a crimped portion 67. . Furthermore, in this caulking portion 67, by aiming near the portion indicated by the arrow B described above and irradiating, for example, a known YAG laser in the circumferential direction of the outer cylinder 65, the cylindrical portion 571 and the outer cylinder of the metal shell 50 are irradiated. Laser welding for joining the tip 66 of 65 is performed. The range from the tip 66 to the tube portion 571 is melted in the direction of the axis O by the laser irradiation, and a welded portion 99 is formed across the two, whereby the tube portion 571 and the tip 66 are joined. The welded portion 99 is a laser so that the thickness of the gas sensor 1 in the radial direction (the size indicated by the arrow C in FIG. 2) is at least larger than the thickness of the outer cylinder 65 (the size indicated by the arrow D in FIG. 2). The output at the time of welding is adjusted and formed. More specifically, the laser output is adjusted so that the thickness of the formed welded portion 99 is at least twice the thickness of the outer cylinder 65 in the radial direction of the gas sensor 1. By forming the weld 99 having such a thickness (depth), the outer cylinder 65 and the metal shell 50 can be reliably melted and the components of each other can be mixed, and the joint strength between them can be increased.

  The weld 99 has a distance of 3 mm between the position of its tip and the position of the rear end of the tool engaging portion 52 of the metal shell 50 in the axis O direction (the size indicated by the arrow E in FIG. 2). And is formed at a position of 1 mm or more.

  In addition, as shown in FIG. 1, a metal-made cylindrical holding metal fitting 70 is disposed in the gap between the outer cylinder 65 and the separator 60. The holding metal fitting 70 has a support portion 71 formed by bending its rear end inward, and supports a large-diameter portion 62 provided in a bowl shape on the outer periphery of the rear end side of the separator 60 inserted into itself. The separator 60 is supported by being engaged with 71. In this state, the outer peripheral surface of the outer cylinder 65 where the holding metal fitting 70 is disposed is crimped, and the holding metal fitting 70 that supports the separator 60 is fixed in the outer cylinder 65.

  A fluorine rubber grommet 75 is fitted into the opening on the rear end side of the outer cylinder 65. The grommet 75 has a plurality of insertion holes 76, and a plurality of lead wires 64 drawn from the separator 60 are inserted into the insertion holes 76 in an airtight manner. In this state, the grommet 75 is crimped from the outer periphery of the outer cylinder 65 while pressing the separator 60 toward the front end side, and is fixed to the rear end of the outer cylinder 65.

  Next, the structure of the front end side of the metal shell 50 of the gas sensor 1 will be described. The detection portion 11 of the detection element 10 held inside protrudes from the tip (tip engagement portion 56) of the metal shell 50. The tip engaging portion 56 protects the detecting portion 11 of the detecting element 10 from contamination caused by deposits (toxic substances such as fuel ash and oil components) in exhaust gas, breakage due to water, and the like. A protector 8 is fitted and fixed by spot welding or laser welding. The protector 8 is a double structure constituted by a bottomed cylindrical inner protector 90 and a cylindrical outer protector 80 that surrounds the periphery in the radial direction with a gap between the outer peripheral surface of the inner protector 90. Have

  The inner protector 90 includes a plurality of inner introduction holes 95 on the rear end side of the peripheral wall 92, a plurality of drain holes 96 on the front end side of the peripheral wall 92, and a discharge port 97 on the bottom wall 93 (wall portion on the front end side). Is open. The base end portion 91 on the opening end side (rear end side) is engaged with the outer periphery of the distal end engaging portion 56 of the metal shell 50, and in this state, laser welding is performed around the outer periphery. Is fixed to the metal shell 50.

  Further, the outer protector 80 has a plurality of outer introduction holes 85 opened on the distal end side of the peripheral wall 82. Then, the base end portion 81 on the opening end side is engaged with the outer periphery of the base end portion 91 of the inner protector 90, and spot welding is performed on the outer periphery in this state, and the outer protector 80 is also connected via the inner protector 90. It is fixed to the metal shell 50. Furthermore, the tip 83 of the outer protector 80 is bent inward toward the peripheral wall 92 of the inner protector 90 so as to close the gap between the outer protector 80 and the inner protector 90.

  The gap between the outer protector 80 and the inner protector 90 causes the exhaust gas introduced from the outside through the outer introduction hole 85 to generate a swirling flow in a state of surrounding the outer periphery of the peripheral wall 92 of the inner protector 90, and thereby the gas component It is provided to separate water and moisture. The gas component is introduced into the inner protector 90 from the inner introduction hole 95, contacts the detection element 10, and is discharged to the outside from the discharge port 97, while moisture enters the inner protector 90 from the drain hole 96. , And is configured to be discharged from the discharge port 97 to the outside. With this configuration, the detection unit 11 of the detection element 10 is protected from contamination due to deposits in the exhaust gas, breakage due to thermal shock caused by moisture, and the like.

  Incidentally, as described above, in the gas sensor 1 of the first embodiment, the metal shell 50 and the outer cylinder 65 are joined by laser welding over one circumference in the circumferential direction of the outer cylinder 65. The welded portion 99 formed by the laser welding is formed so as to straddle the two by melting between the cylindrical portion 571 and the tip 66, and joins them together. A manufacturing method capable of realizing such a configuration of the gas sensor 1 will be described with reference to FIGS. FIG. 3 is a diagram illustrating a manufacturing process of the gas sensor 1. In the following, the process of joining the metal shell 50 and the outer cylinder 65 constituting the gas sensor 1 will be mainly described, and the manufacturing process of other parts of the gas sensor 1 is well-known, so that the description is omitted or simplified. It shall be.

[Metal forming process]
In the manufacturing process of the gas sensor 1, the metal shell 50 is manufactured as follows. First, a pipe-shaped steel material made of a low carbon steel material such as SUS430 is set in a cold forging machine (not shown) and subjected to forging such as extrusion. Then, a cutting machine (not shown) is used to cut the outer peripheral surface and the inside of the cylindrical hole serving as the through hole 58. Then, using a rolling die (not shown), a thread is rolled on the male screw portion 51 to complete the metal shell 50.

[Each part assembly process]
On the other hand, the detection element 10 shown in FIG. 1 is a state in which an unfired gas detection body formed by laminating a solid electrolyte body, an electrode, an insulator, and the like and an unfired heater body are laminated in the thickness direction (plate thickness direction). And a protective layer 15 is formed on the detection part 11 of the fired body, thereby producing an elongated plate-like element. A metal cup 20 containing a ceramic ring 21 and a sealing material 22 is attached to the detection element 10 so as to be fitted from the electrode part 12 side of the detection element 10, and is arranged slightly on the front end side of the central part 13. In this state, the sealing material 22 is pressed toward the ceramic ring 21 side and is crushed to fill a gap in the metal cup 20, so that the detection element 10 and the flange portion 24 are integrated.

  As shown in FIG. 3, the detection element 10 integrated with the flange portion 24 is disposed in the through hole 58 of the metal shell 50 in which the protector 8 manufactured in a separate process is joined to the tip engagement portion 56. The Further, a sealing material 26, a sleeve 27, and a packing 29 (see FIG. 1) are inserted into the detection element 10 from the electrode portion 12 side. When the crimping portion 53 of the metal shell 50 is crimped, the squeezed seal material 26 fills the gap between the metal shell 50 and the detection element 10, and the detection element 10 is held in the metal shell 50. In another process, the outer cylinder 65 is formed in a cylindrical shape from stainless steel such as SUS304. In the outer cylinder 65, a separator 60 that accommodates a connection terminal 61 to which a lead wire 64 is connected in advance, a holding metal fitting 70 that holds the separator 60, and a grommet 75 are disposed (see FIG. 1). The outer peripheral surface of the cylinder 65 is fixed in the outer cylinder 65 by caulking.

[Outer cylinder placement process]
As shown in FIG. 3, the outer cylinder 65 is covered from the rear end side of the metal shell 50 so as to accommodate the rear end side portion including the electrode portion 12 of the detection element 10 therein. At this time, the front end surface 69 of the outer cylinder 65 is brought into contact with the rear end facing surface 574 between the cylindrical portion 571 and the reduced diameter portion 572 of the rear end engaging portion 57 of the metal shell 50, as shown in FIG. As described above, the inner peripheral surface 68 of the tip 66 and the outer peripheral surface 573 of the reduced diameter portion 572 are arranged to face each other.

[Casting process]
Next, as shown in FIG. 3, the rear end portion of the metal shell 50 is straddled so as to straddle the vicinity of the abutting position between the front end surface 69 and the rear end facing surface 574 (near the boundary between both indicated by arrow B in FIG. 2). A range from the cylindrical portion 571 of the joint portion 57 to the distal end 66 of the outer tube 65 is caulked in a ring shape over the entire circumference as shown by an arrow M, and is formed as a caulking portion 67. By this caulking, the outer cylinder 65 is temporarily fixed to the metal shell 50.

[Welding process]
Further, in this caulking portion 67, laser welding is performed over the entire circumference of the outer cylinder 65 as indicated by an arrow L, aiming near the tip surface 69 of the outer cylinder 65 (in the vicinity of the portion indicated by the arrow B in FIG. 2). Is done. At this time, the laser is irradiated from a direction orthogonal to the direction of the axis O in order to make the melting condition of the outer cylinder 65 and the melting condition of the metal shell 50 substantially equal. Here, as described above, the distance between the position of the tip of the welded portion 99 in the direction of the axis O and the position of the rear end of the tool engaging portion 52 of the metal shell 50 (the size indicated by the arrow E in FIG. 2). The abutting position between the front end surface 69 and the rear end facing surface 574 of the outer cylinder 65 is positioned so that the weld 99 is formed at a position where the distance is 1 mm or more. That is, the laser irradiation position and the tool engaging portion 52 are separated from each other, and the operation can be easily performed when the laser is irradiated from the direction orthogonal to the axis O direction. By this laser welding, a portion from the tube portion 571 to the tip 66 is melted in the direction of the axis O, and a welded portion 99 straddling the tube portion 571 and the tip 66 is formed, and both are joined, and the gas sensor 1 is completed.

  In the gas sensor 1 according to the first embodiment manufactured as described above, as shown in FIG. 2, the weld metal 99 is formed between the tip 66 and the cylindrical portion 571, thereby forming the metal shell 50. The gap between the outer peripheral surface 573 of the cylindrical portion 571 and the inner peripheral surface 68 of the tip 66 of the outer cylinder 65 is sealed in a state where it is blocked from the outside. Therefore, even when the gas sensor 1 is flooded when the gas sensor 1 is used, the weld 99 may cause water droplets or the like to enter the gap between the outer peripheral surface 573 of the cylindrical portion 571 and the inner peripheral surface 68 of the tip 66. Absent. That is, between the front end surface 69 of the outer cylinder 65 and the rear end facing surface 574 of the rear end engaging portion 57 which can be an entrance portion into the gap between the inner peripheral surface 68 of the front end 66 and the outer peripheral surface 573 of the cylindrical portion 571. The gap is sealed when the weld 99 is formed. For this reason, generation | occurrence | production of the corrosion which is easy to occur when a water drop etc. contact the interface of the welding part 99 and the metal shell 50 for a long period of time can be prevented. In addition, the interface with the welded portion 99 is exposed on the outer peripheral surface of the cylindrical portion 571, and water droplets or the like may adhere to the portion, but unlike the case where it enters the gap, it contacts the outside air with a wide area. Since it is in a state, water droplets and the like are easily volatilized, and the above-described corrosion hardly occurs.

  Further, when forming the welded portion 99 straddling between the rear end engaging portion 57 of the metal shell 50 and the front end 66 of the outer cylinder 65, the rear end engaging portion 57 of the metal shell 50 is contracted with the cylinder portion 571. If it is formed in a step shape having the diameter portion 572, the tip 66 of the outer cylinder 65 can be brought into contact with the cylinder portion 571 while being engaged with the reduced diameter portion 572. It is easy to perform positioning and temporary fixing of both at the time of joining. When joining the outer cylinder 65 and the metal shell 50 using, for example, laser welding, the tip 66 of the outer cylinder 65 is brought into contact with the cylinder portion 571 of the metal shell 50 as described above, and the abutting position (outer cylinder) If the laser is irradiated from the direction orthogonal to the axis O aiming at the boundary between the metal shell 50 and the metal shell 50, the melting state of the metal shell 50 and the melting state of the outer cylinder 65 can be brought closer to a more uniform state, The gap can be more reliably sealed by forming the weld 99. However, even if the laser irradiation position is biased toward the metal shell 50 side or the outer cylinder 65 side relative to the butting position, the welded portion 99 formed by being melted by the laser is formed with the outer cylinder 65 and the main body. If the gap is formed across the metal fitting 50, the gap can be sufficiently sealed.

  And if the welding part 99 is formed so that the thickness in the radial direction of the welding part 99 may become thicker than the thickness of the outer cylinder 65, the welding part 99 will be in each of the front end side and radial direction inner side of the outer cylinder 65. Since it is formed between the metal shell 50, the gap can be more reliably sealed by forming the welded portion 99.

  Further, the outer cylinder 65 can be temporarily fixed to the metal shell 50 by crimping both ends from the outer peripheral side so as to straddle the tip 66 of the outer cylinder 65 and the cylinder portion 571 of the metal shell 50, and the welded portion. In the process of forming 99, occurrence of misalignment between the metallic shell 50 and the outer cylinder 65 can be prevented, and the welded portion 99 straddling both can be reliably formed.

  Next, a second embodiment of the gas sensor and the manufacturing method thereof according to the present invention will be described with reference to FIGS. FIG. 4 is an enlarged partial cross-sectional view showing a state in which the metal shell 150 and the outer cylinder 165 are joined in the gas sensor 101 of the second embodiment, corresponding to the circle A in FIG. FIG. 5 is a diagram illustrating a manufacturing process of the gas sensor 101 according to the second embodiment.

  The gas sensor 101 according to the second embodiment is obtained by joining the metal shell 50 and the outer cylinder 65 of the gas sensor 1 of the first embodiment in different forms. Therefore, here, the joining structure between the metal shell 150 of the gas sensor 101 and the outer cylinder 165 and the joining method in the manufacturing process of the gas sensor 101 will be described, and the configuration and manufacturing method of other parts will be described in the first embodiment. Since it is the same as the above, it will be omitted or simplified.

  As shown in FIG. 4, the metal shell 150 of the gas sensor 101 of the second embodiment is different from the metal shell 50 of the first embodiment in that the rear end engaging portion 157 is not formed in a step shape. . Further, the outer cylinder 165 is formed to have an inner diameter that allows the inner peripheral surface 168 of the front end 166 to be engaged with the outer peripheral surface 158 of the rear end engaging portion 157, and the front end surface 169 of the outer cylinder 165 is formed of the metal shell 150. The tool engaging portion 152 has a length that can be abutted against the rear end surface 159.

  As shown in FIG. 5, in the manufacturing process of the gas sensor 101, as in the first embodiment, the front end side of the gas sensor 101 in which the protector 8, the detection element 10, and the like (see FIG. 1) are assembled to the metal shell 150. The part and the part on the rear end side of the gas sensor 101 in which the separator 60, the grommet 75, etc. (see FIG. 1) are assembled to the outer cylinder 165 are assembled. In the outer cylinder arranging step, the outer cylinder 165 is covered from the rear end side of the metal shell 150 so as to accommodate the rear end side portion including the electrode portion 12 of the detection element 10 therein. At this time, as shown in FIG. 4, in the second embodiment, the inner peripheral surface 168 of the front end 166 and the outer peripheral surface 158 of the rear end engaging portion 157 are arranged to face each other, and The front end surface 169 (in FIG. 4, the position of the front end surface 169 before welding is indicated by a dotted line) is abutted against the rear end surface 159 of the tool engaging portion 152 of the metal shell 150.

  Next, in the welding process, as shown in FIG. 5, the abutting position (near the boundary) between the front end surface 169 of the outer tube 165 and the rear end surface 159 of the tool engaging portion 152 is aimed, and the outer tube is Laser welding is performed over the circumference of 165 in the circumferential direction. At this time, in order to make the melting condition of the outer cylinder 165 and the melting condition of the metal shell 150 substantially equal, the laser is irradiated from the rear end side rather than the direction orthogonal to the axis O direction. Thereby, the front end 166 including the front end surface 169 of the outer cylinder 165 and the tool engaging portion 152 of the metal shell 150 are melted and integrated. This laser irradiation is performed over the entire circumference in the radial direction, and a welded portion 199 is formed across the tool engaging portion 152 of the metal shell 150 and the tip 166 of the outer cylinder 165, and the gas sensor 101 is completed. In accordance with the laser irradiation direction, the formed welded portion 199 has a shape extending toward the tip end side in the axis O direction as it goes radially inward in the circumferential cross section.

  As shown in FIG. 4, the outer surface of the welded portion 199 is preferably formed in a curved shape that is recessed in a meniscus shape, and in this way, the tip 166 of the outer tube 165, the metal shell 150, It is possible to have a thickness that seals the entrance portion to the gap between the welded portions 199, so that the gap can be more reliably sealed. Further, the output is adjusted during laser welding, and the thickness (the size indicated by the arrow C in FIG. 4) in the radial direction (left and right direction in the drawing) of the welded portion 199 after formation is at least the thickness of the outer cylinder 165 (FIG. 4). In the same manner as in the first embodiment, it is desirable to increase the bonding strength between the metal shell 150 and the outer cylinder 165 if the size is larger than the size indicated by the arrow D in FIG.

  Also in the gas sensor 101 according to the second embodiment manufactured in this way, a welded portion 199 is formed across a portion from the tip 166 of the outer cylinder 165 to the tool engaging portion 152 of the metal shell 150. The gap between the outer peripheral surface 158 of the rear end engaging portion 157 of the metal shell 150 and the inner peripheral surface 168 of the front end 166 of the outer cylinder 165 is sealed in a state where it is blocked from outside air. Therefore, when the gas sensor 101 is used, even if the gas sensor 101 is flooded, the welded portion 199 causes water droplets or the like in the gap between the outer peripheral surface 158 of the rear end engaging portion 157 and the inner peripheral surface 168 of the front end 166. There is no infiltration. That is, the front end surface 169 of the outer cylinder 165 and the rear end surface 159 of the tool engaging portion 152 that can be an entrance portion into the gap between the inner peripheral surface 168 of the front end 166 and the outer peripheral surface 158 of the rear end engaging portion 157. Since the gap between them is sealed by the formation of the welded portion 199, it is possible to prevent the occurrence of corrosion that tends to occur when water droplets or the like contact the interface between the welded portion 199 and the metal shell 150 for a long period of time. Note that the interface between the welded portion 199 and the tool engaging portion 152 exposed on the rear end surface 159 of the tool engaging portion 152 is a case where water droplets or the like enter a narrow gap as in the first embodiment. Unlike water, it is in a state of being in contact with the outside air with a large area, so that water droplets and the like are easily volatilized, and the above-described corrosion hardly occurs.

  Next, a third embodiment of the gas sensor and the manufacturing method thereof according to the present invention will be described with reference to FIGS. FIG. 6 is a partial cross-sectional enlarged view showing a state in which the metal shell 150 and the outer cylinder 265 are joined in the gas sensor 201 of the third embodiment, corresponding to the circle A in FIG. FIG. 7 is a diagram illustrating a manufacturing process of the gas sensor 201 according to the third embodiment.

  The gas sensor 201 according to the third embodiment joins the outer cylinder 265 to the metal shell 150 used in the second embodiment, and the joining form is the first and second embodiments. This was done in a different form. Therefore, here, a structure for joining the outer cylinder 265 of the gas sensor 201 to the metal shell 150 and a joining method of both in the manufacturing process of the gas sensor 201 will be described. Since this embodiment is the same as the second embodiment, it will be omitted or simplified.

  As shown in FIG. 6, the outer cylinder 265 of the gas sensor 201 of the third embodiment is formed to be short in the direction of the axis O while having an inner diameter substantially equal to that of the outer cylinder 165 of the second embodiment. Yes. For this reason, in the gas sensor 201, the outer cylinder 265 and the metal shell 150 are joined with the tip 266 of the outer cylinder 265 being separated from the tool engaging portion 152 of the metal shell 150.

  As shown in FIG. 7, in the manufacturing process of the gas sensor 201, as in the second embodiment, the front end side of the gas sensor 201 in which the protector 8, the detection element 10, and the like (see FIG. 1) are assembled to the metal shell 150. The part and the part on the rear end side of the gas sensor 201 in which the separator 60, the grommet 75, etc. (see FIG. 1) are assembled to the outer cylinder 265 are assembled. Then, in the outer cylinder placement step, the outer cylinder 265 is covered from the rear end side of the metal shell 150 so as to accommodate the rear end side portion including the electrode portion 12 of the detection element 10 therein. At this time, as shown in FIG. 6, in the third embodiment, the inner peripheral surface 268 of the front end 266 and the outer peripheral surface 158 of the rear end engaging portion 157 are arranged to face each other, and The front end surface 269 (in FIG. 6, the position of the front end surface 269 before welding is indicated by a dotted line) is arranged in a state of being separated from the rear end surface 159 of the tool engaging portion 152 of the metal shell 150.

  Next, in the welding process, as shown in FIG. 7, aiming at the abutting position (near the boundary) between the front end surface 269 of the outer cylinder 265 and the outer peripheral surface 158 of the rear end engaging portion 157 of the metal shell 150, As shown, laser welding is performed over the entire circumference of the outer cylinder 265. At this time, in order to make the melting condition of the outer cylinder 265 and the melting condition of the metal shell 150 substantially equal, the laser is irradiated from the tip side rather than the direction orthogonal to the axis O direction. Thereby, the front end 266 including the front end surface 269 of the outer cylinder 265 and the rear end engaging portion 157 of the metal shell 150 are melted and integrated. This laser irradiation is performed over the entire circumference in the radial direction, and a welded part 299 is formed between the rear end engaging part 157 of the metal shell 150 and the front end 266 of the outer cylinder 265 to complete the gas sensor 201. . According to the laser irradiation direction, the formed welded portion 299 has a shape extending toward the rear end side in the axis O direction as it goes radially inward in the circumferential cross section.

  As shown in FIG. 6, it is desirable that the outer surface of the welded portion 299 be formed in a curved shape that is recessed in a meniscus shape. In this way, the tip 266 of the outer cylinder 265, the metal shell 150, It is possible to have a thickness that seals the entrance portion to the gap between the welded portions 299, so that the gap can be more reliably sealed. Further, the output is adjusted at the time of laser welding, and the thickness (the size indicated by the arrow C in FIG. 6) in the radial direction (left and right direction in the drawing) of the welded portion 299 after formation is at least the thickness of the outer cylinder 265 (see FIG. As in the first and second embodiments, it is desirable to increase the bonding strength between the metal shell 150 and the outer cylinder 265 if it is larger than the size indicated by the arrow D in FIG.

  Also in the gas sensor 201 of the third embodiment manufactured in this way, the welded portion 299 is formed across the both ends at the portion from the front end 266 of the outer cylinder 265 to the rear end engaging portion 157 of the metal shell 150. As a result, the gap formed by the outer peripheral surface 158 of the rear end engaging portion 157 of the metal shell 150 and the inner peripheral surface 268 of the front end 266 of the outer cylinder 265 is sealed in a state of being blocked from the outside air. Therefore, when the gas sensor 201 is used, even if the gas sensor 201 is submerged, the welded portion 299 causes water droplets or the like in the gap between the outer peripheral surface 158 of the rear end engaging portion 157 and the inner peripheral surface 268 of the front end 266. There is no infiltration. That is, in the state before joining, the front end surface 269 of the outer cylinder 265 and the tool engaging portion 152 that can be an entrance portion to the gap between the inner peripheral surface 268 of the front end 266 and the outer peripheral surface 158 of the rear end engaging portion 157. Since the gap between the rear end engaging portion 157 and the outer peripheral surface 158 is sealed by the formation of the welded portion 299, when a water droplet or the like is in contact with the interface between the welded portion 299 and the metal shell 150 for a long period of time. It is possible to prevent the occurrence of corrosion that tends to occur. Note that the interface between the welded portion 299 exposed outwardly on the outer peripheral surface 158 of the rear end engaging portion 157 and the rear end engaging portion 157 is narrow, as in the first and second embodiments. Unlike the case where water droplets or the like enter the gap, the water contact with the outside air has a wide area, so that the water droplets or the like are easily volatilized, and the above-described corrosion hardly occurs.

  The present invention is not limited to the above-described embodiments, and various modifications can be made. For example, in the first embodiment, the rear end engaging portion 57 and the tool engaging portion 52 of the metal shell 50 do not have to be continuous, for example, deformed when the caulking portion 53 is caulked, In order to disperse the repulsive force applied to the caulking portion 53 so as to maintain the crimped state, a portion that is deformed at the time of caulking may be provided. The same applies to the second and third embodiments.

  In the first embodiment, the front end surface 69 of the outer cylinder 65 is in contact with the rear end facing surface 574 of the cylindrical portion 571 and the reduced diameter portion 572 of the rear end engaging portion 57 of the metal shell 50. At this time, the front end surface 69 and the cylindrical portion 571 and the rear end facing surface 574 may be in contact with each other, or there may be a gap between them. It may be in a state having As for the laser irradiation position, the abutting position between the front end surface 69 of the outer cylinder 65 and the rear end facing surface 574 of the cylindrical portion 571 and the reduced diameter portion 572 of the rear end engaging portion 57 of the metal shell 50 (that is, It is preferable to aim at the vicinity of the boundary between the metal shell 50 and the outer cylinder 65. However, the outer cylinder 65 may be biased to irradiate the laser, and the outer cylinder 65 and the metallic shell 50 may be connected by the melted portion (welded portion 99), or the metallic shell 50 may be biased to irradiate the laser. Alternatively, both may be joined via a weld 99 formed by the melted portion. That is, by laser welding, the weld 99 is formed across the tip 66 of the outer tube 65 and the tube 571 of the metal shell 50 in the direction of the axis O, and joins them together. It suffices if the gap between the inner peripheral surface 68 and the outer peripheral surface 573 of the reduced diameter portion 572 of the metal shell 50 is sealed by the welded portion 99.

  Also in the second and third embodiments, the tips 166 and 266 of the outer cylinders 165 and 265 may be crimped to the metal shell 150 as in the first embodiment. Alternatively, in the first embodiment, the metal shell 50 and the outer cylinder 65 are not swaged so that the front end 66 of the outer cylinder 65 is not easily detached when engaged with the rear end engaging portion 57. The diameter difference between the inner diameter of the outer cylinder 65 and the outer diameter of the reduced diameter portion 572 of the rear end engaging portion 57 may be made uniform.

  In the second embodiment, for example, a gas sensor 301 shown in FIG. 8 may have a diameter increasing portion 330 that expands radially outward at the tip 366 of the outer cylinder 365. In this case, the inner peripheral surface 368 of the front end 366 of the outer cylinder 365 is formed so that the inner diameter thereof can be engaged with the outer peripheral surface 158 of the rear end engaging portion 157 as in the second embodiment. The enlarged diameter portion 330 abuts the axial front end surface 331, which is the surface facing the front end in the direction of the axis O (the vertical direction in the drawing), with the rear end surface 159 of the tool engaging portion 152 of the metal shell 150, and the radial direction (see FIG. The position of the radial front end surface 369 that is the surface facing the front end in the left-right direction of the middle paper surface is arranged on the rear end surface 159 of the tool engaging portion 152. Then, the radial front end surface 369 of the diameter-enlarged portion 330 and the rear end surface 159 of the tool engaging portion 152 are arranged so as to expand toward the rear end side in the axial direction as they go radially outward with respect to the abutting position (near the boundary). . By irradiating the laser toward the abutting position, the welded portion 399 can be formed so as to straddle the outer cylinder 365 and the metal shell 150 more evenly, and the distal end 366 of the outer cylinder 365 having the abutting position as an entrance. The gap between the inner peripheral surface 368 and the outer peripheral surface 158 of the rear end engaging portion 157 of the metal shell 150 can be reliably sealed. Further, the axial front end surface 331 of the enlarged diameter portion 330 and the rear end surface 159 of the tool engaging portion 152 may be joined by resistance welding before the formation of the welded portion 399 by laser welding. In this way, the gap between the axial front end surface 331 of the enlarged diameter portion 330 and the rear end surface 159 of the tool engaging portion 152 can be reliably sealed, and the inner peripheral surface 368 of the front end 366 and the rear end engagement can be reliably sealed. Intrusion of water droplets or the like into the gap between the outer peripheral surface 158 of the portion 157 can be completely prevented. Moreover, since the radial front end surface 369 of the enlarged diameter portion 330 can be positioned and fixed with respect to the rear end surface 159 of the tool engaging portion 152 during laser welding, laser welding can be easily performed. In laser welding, if the abutting position between the radial front end surface 369 of the enlarged diameter portion 330 and the rear end surface 159 of the tool engaging portion 152 is reliably melted, the laser is irradiated along the axis O direction. Then, the welded portion 399 may be formed.

  Moreover, you may join a metal shell and a protector using the joining method of the metal shell and an outer cylinder which concern on this invention. However, the protector that is attached to the front end side of the male thread of the metal shell is the part that is exposed inside the exhaust pipe when the gas sensor is attached to the exhaust pipe of an automobile, and is different from the outer cylinder that is exposed outside the exhaust pipe. Exposure to high temperature exhaust gas (eg 800 ° C.). For this reason, even if water droplets or the like enter the gap between the protector and the metal shell, it is relatively easy to volatilize. Therefore, applying the present invention to the joining between the metal shell and the outer cylinder prevents corrosion of the joint portion. It has a higher effect.

  The present invention can be applied to gas sensors such as oxygen sensors, NOx sensors, HC sensors, and manufacturing methods thereof.

1 is a longitudinal sectional view of a gas sensor 1. FIG. It is sectional drawing of the gas sensor 1 which expanded the part of the circle | round | yen A of FIG. FIG. 3 is a diagram showing a manufacturing process of the gas sensor 1 In the gas sensor 101 of 2nd Embodiment, it is corresponded to the part of the circle | round | yen A of FIG. 1, and it is a fragmentary sectional enlarged view which shows the state which joined the metal shell 150 and the outer cylinder 165. FIG. It is a figure which shows the manufacture process of the gas sensor 101 of 2nd Embodiment. In the gas sensor 201 of 3rd Embodiment, it is equivalent to the part of the circle | round | yen A of FIG. 1, and it is a fragmentary sectional enlarged view which shows the state which joined the metal shell 150 and the outer cylinder 265. FIG. It is a figure which shows the manufacture process of the gas sensor 201 of 3rd Embodiment. In the gas sensor 301 as a modified example, it corresponds to the portion of the circle A in FIG. 1, and is a partial cross-sectional enlarged view showing a state in which the metal shell 150 and the outer cylinder 365 are joined.

DESCRIPTION OF SYMBOLS 1 Gas sensor 10 Detection element 11 Front-end | tip part 50 Metal fitting 52 Tool engaging part 57 Rear-end engaging part 65 Outer cylinder 66 Front end 67 Clamping part 99 Welding part 571 Cylindrical part 572 Reduced diameter part

Claims (17)

A detection element that extends in the axial direction and has a detection unit for detecting a gas to be detected on its tip side;
A metal shell that surrounds the periphery of the detection element in the radial direction while causing the detection unit to protrude from its tip,
A gas sensor having a cylindrical outer cylinder fixed to the metal shell and surrounding a radial periphery on the rear end side of the detection element,
The metal shell has a flange portion radially expanded in diameter, and a rear end portion formed on the rear end side of the flange portion,
A boundary portion between the front end of the outer cylinder and the rear end portion of the metal shell is disposed so that the front end of the outer cylinder surrounds at least a portion of the rear end portion of the metal shell in the radial direction. By welding, a welded portion formed across the front end of the outer cylinder and the rear end portion of the metal shell is formed over the entire circumference, and the thickness of the welded part is greater than the thickness of the outer cylinder. A gas sensor characterized by being large . The rear end portion of the metal shell has a cylindrical portion and a reduced diameter portion that is connected to the rear end side of the cylindrical portion and has a diameter smaller than that of the cylindrical portion,
The distal end of the outer cylinder is disposed so as to surround the circumference of the reduced diameter portion in the radial direction,
The gas sensor according to claim 1, wherein the welded portion is formed between the tip of the outer cylinder and the cylinder portion. 3. The gas sensor according to claim 2 , wherein the welded portion is formed such that a thickness of the welded portion in the radial direction is twice or more thicker than a thickness of the outer cylinder. The gas sensor according to any one of claims 1 to 3 , wherein a distance between a front end of the welded portion and a rear end of the flange portion is 1 mm or more. So as to straddle said cylindrical portion of the metal shell and the tip of the outer cylinder, one of the claims 2 to 4, characterized in that caulking portions tightening both from the outer circumferential side pressure is formed The gas sensor according to Crab.   The gas sensor according to claim 1, wherein the welded portion is formed between the tip of the outer cylinder and the flange portion of the metal shell. The outer cylinder has a diameter-expanding portion that expands radially outward at the tip thereof.
The gas sensor according to claim 6 , wherein the welded portion is formed between the enlarged diameter portion and the flange portion. The weld toward the radially inner side, the gas sensor according to claim 6 or 7, characterized in that it is formed to extend on the distal end side of the axial direction. The front end of the outer cylinder is disposed so as to surround the radial periphery of the rear end portion while being separated from the flange portion of the metal shell,
2. The gas sensor according to claim 1, wherein the welded portion is formed between the front end of the outer cylinder and the rear end portion of the metal shell. The gas sensor according to claim 9 , wherein the welded portion is formed to extend toward the rear end side in the axial direction as it goes radially inward. The gas sensor according to any one of claims 6 to 10 , wherein the welded portion is formed in a curved shape having a concave outer surface. A detection element that extends in the axial direction and has a detection unit for detecting a gas to be detected on its tip side;
A metal shell that surrounds the periphery of the detection element in the radial direction while causing the detection unit to protrude from its tip,
A gas sensor manufacturing method comprising: a cylindrical outer cylinder fixed to the metal shell and surrounding a radial direction of the rear end side of the detection element;
The metallic shell is connected to the rear end side of the tubular portion formed on the rear end side of the collar portion, the tubular portion formed on the rear end side of the collar portion, and has a diameter smaller than that of the cylindrical portion. Having a reduced diameter portion,
An outer cylinder placement step of bringing the tip of the outer cylinder into contact with the rear end-facing surface of the cylinder part while arranging the circumference of the reduced diameter part to surround the radial direction;
Laser welding is performed over the entire circumference toward the vicinity of the boundary between the tip of the outer cylinder and the cylinder portion of the metal shell, and the boundary portion between the tip of the outer cylinder and the cylinder portion of the metal shell is melted. it is, possess a welding step of forming a weld across between the cylindrical portion of the tip and the metal shell of the outer cylinder, the thickness of the welded portion is greater than the thickness of the outer cylinder A method for producing a gas sensor. In the welding step, the entire thickness of the welded portion is increased toward the boundary between the tip of the outer tube and the cylindrical portion of the metal shell so that the thickness in the radial direction of the welded portion is greater than the thickness of the outer tube. The method of manufacturing a gas sensor according to claim 12 , wherein laser welding is performed over a circumference. After the outer cylinder placement step and before the welding step, a caulking portion is formed by caulking both from the outer peripheral side so as to straddle the tip of the outer cylinder and the cylinder portion of the metal shell. method for producing a gas sensor according to claim 12 or 13, characterized in that it has a clamping step. A detection element that extends in the axial direction and has a detection unit for detecting a gas to be detected on its tip side;
A metal shell that surrounds the periphery of the detection element in the radial direction while causing the detection unit to protrude from its tip,
A gas sensor manufacturing method comprising: a cylindrical outer cylinder fixed to the metal shell and surrounding a radial direction of the rear end side of the detection element;
The metal shell has a flange portion radially expanded in diameter, and a rear end portion formed on the rear end side of the flange portion,
An outer cylinder placement step of bringing the tip of the outer cylinder into contact with the rear-end-facing surface of the flange while placing the tip of the outer cylinder so as to surround the periphery of the rear end in the radial direction;
Laser welding is performed over the entire circumference toward the vicinity of the boundary between the tip of the outer cylinder and the flange of the metal shell, and the boundary between the tip of the outer cylinder and the flange of the metal shell is melted. it is, possess a welding step of forming a weld across between the flange portion of the tip and the metal shell of the outer cylinder, the thickness of the welded portion is greater than the thickness of the outer cylinder A method for producing a gas sensor. A detection element that extends in the axial direction and has a detection unit for detecting a gas to be detected on its tip side;
A metal shell that surrounds the periphery of the detection element in the radial direction while causing the detection unit to protrude from its tip,
A gas sensor manufacturing method comprising: a cylindrical outer cylinder fixed to the metal shell and surrounding a radial direction of the rear end side of the detection element;
The metal shell has a flange portion radially expanded in diameter, and a rear end portion formed on the rear end side of the flange portion,
An outer cylinder arranging step of arranging the front end of the outer cylinder so as to surround the rear end portion in the radial direction while being separated from the flange portion of the metal shell,
Laser welding is performed over the entire circumference toward the vicinity of the boundary between the tip of the outer cylinder and the rear end of the metal shell, and the boundary portion between the tip of the outer cylinder and the rear edge of the metal shell is by melting, possess a welding step of forming a weld across between the rear end portion of the tip and the metal shell of the outer cylinder, the thickness of the welded portion, the thickness of the outer cylinder method of manufacturing a gas sensor and greater than. The method for manufacturing a gas sensor according to claim 15 or 16 , wherein, in the welding step, the outer surface of the welded portion is formed in a curved shape.

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