JP2005292119A - Gas sensor and method for manufacturing it - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for manufacturing a gas sensor which prevents welding defects such as a blowhole from occurring even in the case that a weld zone is formed after pressing/fixing a protector in a main fitting having oil solution attached to its surface. <P>SOLUTION: In the main fitting 121 being prepared, a large-diameter section 303 and a small diameter section 305 whose diameter is smaller than that of the large-diameter section 303 are formed on portions previously planned to make up overlapping sections 301 along with the protector 151. Then, the oil solution is attached to the surface of the main fitting 121, and the back edge 180 of the protector 151 (outside cover section 173) is engaged with the large-diameter section 303 of the main fitting 121. At this time, the engagement of the protector 151 is carried out until an annular space S is formed between the protector 151 and the small-diameter section 305 of the main fitting 121. Then, the weld zone W is made up so as to penetrate the annular space S from the external perimeter of the protector 151 existing on the outside in the radial direction of the small-diameter section 305. Therefore, degassing is carried out through the annular space S, and the weld zone W is made up stably. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a gas sensor, and more particularly to a gas sensor including a protector that covers a portion exposed to a gas to be measured among gas detection elements having a bottomed cylindrical shape or a plate shape.

  2. Description of the Related Art Conventionally, when performing air-fuel ratio control of an automobile, a gas sensor including a gas detection element whose electrical characteristics change according to the concentration of a specific gas component in exhaust gas has been used. As such a gas sensor, various sensors such as an oxygen sensor, a NOx sensor, and an HC sensor are known. By the way, such a gas sensor has a structure in which the gas detection element is held inside the metal shell so that the tip of the gas detection element protrudes. A specific gas component (for example, oxygen) in the measurement gas is detected by exposing to the measurement gas.

And in many gas sensors, in order to protect the front-end | tip part exposed to to-be-measured gas among gas detection elements from water etc., the metal protector which covers this front-end | tip part is attached to the metal shell. A plurality of gas flow holes are formed in the protector, and the gas to be measured is guided into the protector from the gas flow holes and comes into contact with the tip of the gas detection element. And in recent years, in order to improve the protection performance of the front-end | tip part of a gas detection element, what used the double structure which consists of two members, an inner cover part and an outer cover part, is often used for the protector. For example, Patent Documents 1 to 3 disclose gas sensors having such a protector.
JP-A-9-304332 JP 2000-28571 A JP 2001-99807 A

  By the way, fixing of the protector and the metal shell is performed by various methods, but in order to securely fix both, a cylindrical protector is fitted on the outer side in the radial direction of the tip of the metal shell, A method of forming a welded portion (for example, a laser welded portion) with respect to the fitting portion is often employed. As described above, when the protector is fitted outside the front end of the metal shell, the friction generated between the inner peripheral surface of the protector and the outer peripheral surface of the metal tip is reduced. In order to carry out smoothly, an oil agent is made to adhere to the surface of a metal shell, and a protector is fitted using the lubricating action of this oil agent. In addition, when forming an oil agent on the surface of the metal shell, it is usual to perform a process of attaching the oil agent to the entire surface of the metal shell in consideration of mass productivity. Further, when the protector is fitted to the distal end portion of the metal shell, it is usual to perform press-fitting to ensure the fixing.

  However, after attaching an oil agent to the surface of the metal shell and fitting the protector, if welding (lap welding) is performed on the fitting portion, there is no escape place for the gas of the oil component vaporized by welding heat input. In addition, welding defects such as blow holes may occur. Therefore, it is possible to selectively remove only the oil that has adhered to the surface of the part where the weld is to be formed after the oil has been attached to the surface of the metal shell. Has a problem that the manufacturing efficiency is lowered and the cost burden is increased because many process managements are required.

The present invention has been made in view of such problems, and even when a tubular protector is fitted to a metal shell with an oil agent attached to the surface and a welded portion is formed thereafter, a blowhole or the like can be used. It is an object of the present invention to provide a method for manufacturing a gas sensor that is free from welding defects and that does not require special processing such as selective removal of an oil agent and contributes to improvement in manufacturing efficiency.
It is another object of the present invention to provide a gas sensor having a high quality characteristic in which a stable weld is formed and the protector and the metal shell are firmly fixed.

And the solution means is a gas detection element that extends in the axial direction, the tip side is exposed to the gas to be measured,
In a state where the gas detection element protrudes from the front end side of the gas detection element, a cylindrical metal shell that surrounds the radially outer side of the gas detection element,
A cylindrical protector that is attached to the outer periphery of the distal end portion of the metal shell and covers the distal end side of the gas detection element;
A method of manufacturing a gas sensor comprising:
A metal fitting preparation step of preparing the metal shell with an oil agent attached to the outer periphery of the tip portion;
Moving at least one of the metal shell to which the oil agent is attached and the protector in a direction approaching each other, and a fitting portion for fitting the tip portion of the metal shell and the protector; An assembling step of assembling the metal shell and the protector such that a space forming portion where the tip portion and the protector overlap with each other via an annular space is generated along the axial direction;
A gas sensor manufacturing method comprising: a welding step of forming a weld through the annular space from an outer periphery of the protector, and welding the metal shell and the protector.

  In the gas sensor manufacturing method of the present invention, with the oil agent attached to the outer periphery of the front end portion of the metal shell, the protector is fitted to a specific part of the front end portion of the metal shell and assembled together, the metal shell and the protector The welding process of welding is performed in order.

  Here, in the assembling step in the gas sensor manufacturing method of the present invention, the fitting portion where the leading end portion of the metallic shell and the protector are fitted, and the space forming portion where the leading end portion of the metallic fitting and the protector overlap via the annular space Are generated along the axial direction. And in the welding process following an assembly process, the welding part which penetrates annular space is formed from the outer periphery of a protector.

  In this way, even if oil is attached to the tip of the metal shell during the welding process by intentionally forming an annular space between the metal shell and the protector and forming a welded portion that penetrates the annular space. The gas of the vaporized oil component can be released to the outside from the rear end side or the front end side of the protector through this annular space. Thereby, according to the manufacturing method of the gas sensor of the present invention, even when the oil agent is attached to the entire surface of the metal shell, the oil agent at the site where the welded portion is expected to be formed is selectively removed. Without performing the processing, it is possible to obtain a favorable weld formation, and as a result, the manufacturing efficiency and the yield of the gas sensor can be improved. Further, according to the gas sensor manufacturing method of the present invention, when the protector and the metal shell are fixed, it is possible to stably achieve both positioning and welding by fitting and manufacture a gas sensor having high quality characteristics. can do.

  The metal fitting preparation step is to prepare a metal shell with an oil agent attached to at least the outer periphery of the tip, and a predetermined amount (target amount) of oil is applied to the surface of the metal shell formed in a predetermined shape. Any method can be used as long as it is attached, and the attaching method is not particularly limited. For example, a metal fitting for a gas sensor is formed into a predetermined shape through machining (plastic processing, cutting, grinding, etc.), but the oil used for lubrication and cooling during the processing (lubricating oil) Or cutting oil, grinding oil, etc.) may be adhered as residual oil. Therefore, the residual oil agent may be reduced or a new oil agent may be added so that a predetermined amount of oil agent is finally attached to the surface of the metal shell to which the residual oil agent has adhered. Alternatively, the metal shell to which the residual oil agent has adhered may be degreased and washed to remove all the residual oil agent, and then a predetermined amount of oil agent may be attached to the surface of the metal shell.

  The welded part in the above welding process is preferably formed by welding using a high-density energy beam such as laser welding, plasma welding, or electron beam welding, and among them, laser welding is used in consideration of manufacturing efficiency and manufacturing cost. If so, it is most preferable. Further, the welded portion may be an all-round welded portion formed continuously in the circumferential direction or a spot welded portion formed intermittently in the circumferential direction, but the protector In order to obtain a strong weld strength between the metal shells, it is preferable that the entire circumference welded portion.

  Furthermore, in the present invention, the protector attached to the metal shell so as to cover the distal end side of the gas detection element is not limited to a single structure, and has a plurality of structures formed using two or more cylindrical members. Also good. For example, the protector has a double structure consisting of an outer cover part and an inner cover part disposed on the inner side of the outer cover part. It is possible to adopt a configuration in which the front end side outer periphery of the metal shell is integrally welded to the front end of the metal shell and the cover. Alternatively, in the same manner as described above, the protector shall have a double structure of the outer cover portion and the inner cover portion, and either cover with the outer cover portion and the inner cover portion fixed in advance at any portion. Alternatively, a configuration may be adopted in which only the outer end of the metal shell is attached to the outer periphery of the metal shell, and the tip of the metal shell and any one of the covers are integrally welded.

  Further, in the gas sensor manufacturing method, an outer diameter of a portion of the metal shell that forms the space forming portion is A, and an inner diameter of a portion of the protector that forms the space forming portion is B. A gas sensor manufacturing method in which the size B-A of the annular space represented sometimes is 0.06 mm or more is preferable.

  Good gas venting effect by setting the size of the annular space formed between the metal shell constituting the space forming portion and the protector to 0.06 mm or more (the size represented by B-A). And a stable weld can be formed. If the size of the annular space is less than 0.06 mm, the gas venting effect may not be sufficiently obtained. In addition, the upper limit of the size of the annular space (the size represented by the above-mentioned B-A) is based on the metal material of the metal shell and the protector, the thickness of the protector, etc. What is necessary is just to set suitably to the magnitude | size which does not arise, for example, what is necessary is to set to 0.2 mm or less.

  Furthermore, in any of the above methods for manufacturing a gas sensor, the distal end portion of the metal shell includes a large diameter portion and a small diameter portion having an outer diameter smaller than the large diameter portion, and the fitting portion is The gas sensor manufacturing method is formed by fitting the large diameter portion and the protector, while the space forming portion is formed by overlapping the small diameter portion and the protector via the annular space. And good.

  In the present invention, a metal shell having a large-diameter portion and a small-diameter portion having an outer diameter smaller than the large-diameter portion is prepared in advance at the tip portion where the protector is scheduled to be mounted. In the assembling step, the fitting is performed by fitting the protector to the large-diameter portion of the metal shell so that an annular space is formed between the outer peripheral surface of the small-diameter portion of the metal shell and the inner peripheral surface of the protector. The joining portion and the space forming portion can be easily generated.

  Further, in the gas sensor manufacturing method according to any one of the above, the portion of the protector to be mounted on the outer periphery of the tip end portion of the metal shell has a small diameter portion and a large diameter having a larger inner diameter than the small diameter portion. The fitting portion is formed by fitting the small diameter portion and the tip end portion of the metal shell, while the space forming portion is formed by the large diameter portion and the metal shell. It is preferable that the gas sensor manufacturing method is formed by overlapping the tip with the annular space.

  In the present invention, a protector having a small-diameter portion and a large-diameter portion having an inner diameter larger than the small-diameter portion is prepared in advance at a site where the attachment of the metal shell to the tip portion is scheduled. Then, in the assembling process, the small diameter portion of the protector is fitted to the distal end portion of the metallic shell so that an annular space is formed between the inner circumferential surface of the large diameter portion of the protector and the outer circumferential surface of the distal end portion of the metallic shell. Thereby, the said fitting part and space formation part can be produced easily.

  Furthermore, the gas sensor manufacturing method according to any one of the above, wherein the fitting portion has an axial length of 0.8 mm or more.

  Positioning and fixing by fitting the protector to the tip of the metal shell in the assembly process by setting the axial length of the fitting portion where the protector and the metal shell tip are fitted to 0.8 mm or more Can be obtained satisfactorily, and the protector can be prevented from being displaced from the metal shell or falling off during conveyance to the welding process. The upper limit value of the length of the fitting portion in the axial direction is not particularly limited.

  Furthermore, in any of the above gas sensor manufacturing methods, the fitting portion may be a gas sensor manufacturing method formed by press-fitting the protector into the tip of the metal shell. By forming the fitting portion by press-fitting the front end portion of the metal shell and the protector, the fixing strength between the metal shell and the protector can be favorably obtained in the assembly process.

  Further, in the gas sensor manufacturing method described above, the surface of the large-diameter portion of the metal shell is a concave portion recessed radially inward, and is continuous from the leading edge to the trailing edge of the large-diameter portion. A gas sensor manufacturing method in which at least one recess is provided is preferable.

  By using a metal shell in which one or more of the above-mentioned recesses are formed in the large-diameter portion of the metal shell, when forming a weld that penetrates the annular space formed between the small-diameter portion of the metal shell and the protector, The vaporized oil component gas is allowed to escape to the outside through the annular space, and to the outside via the recess. Thereby, a more reliable degassing effect is brought about during the welding process, and the occurrence of welding defects such as blow holes can be more reliably suppressed. In addition, this recessed part may be provided at the time of metal shell shaping | molding, and may be provided by giving a knurling etc. to the metal shell after shaping | molding.

  The gas sensor of the present invention, which is another solution, includes a gas detection element that extends in the axial direction and whose tip side is exposed to the gas to be measured, and the gas detection element projects from the tip side of the gas detection element. A gas sensor comprising: a cylindrical metal shell that surrounds the periphery of a device; and a cylindrical protector that is attached to the outer periphery of the distal end portion of the metal shell and covers the front end side of the gas detection element. A fitting portion that fits the tip portion of the metal fitting with the protector; and a space forming portion where the tip portion of the metal shell and the protector overlap with each other via an annular space. The gas sensor is characterized in that it is welded to the metal shell by a welded portion formed so as to penetrate the space.

  The gas sensor according to the present invention has a fitting portion that fits when the tip portion of the metal shell and the cylindrical protector are viewed, and a space forming portion that overlaps through an annular space. It should be noted that the protector is welded to the metal shell by a welded portion formed so as to penetrate an annular space interposed between the front end of the metal shell. Thereby, the gas sensor of the present invention can be efficiently manufactured by, for example, the above-described excellent manufacturing method, a stable weld is formed, and high-quality characteristics in which the protector and the metal shell are firmly fixed are obtained. be able to. In addition, it is preferable that this welding part is formed over the circumferential direction from a viewpoint of ensuring the waterproofness between the front-end | tip part outer peripheral surface of a main metal fitting, and a protector inner peripheral surface.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
(First embodiment)
A sectional view of the gas sensor 101 according to the present embodiment is shown in FIG. 1, and a sectional view of the main part is shown in FIG. FIG. 3 is an explanatory diagram showing the internal structure of the protector 151. 1 to 3, the lower side is the front end side, and the upper side is the rear end side. The gas sensor 101 is an oxygen sensor that is attached to an exhaust gas pipe of an internal combustion engine and detects an oxygen concentration in exhaust gas that is a gas to be measured. As shown in FIGS. 1 and 2, the gas sensor 101 includes a gas detection element 103 extending in the direction of the axis C, a cylindrical metal shell 121 surrounding the gas detection element 103, and an exhaust gas among the gas detection elements 103. And a protector 151 that covers the front end portion 105 exposed to the gas.

  Among these, the gas detection element 103 has a bottomed cylindrical shape with a closed end 105S, and is mainly formed of partially stabilized zirconia in which yttria is dissolved as a stabilizer. An internal electrode layer 108 formed in a porous shape with Pt or a Pt alloy is formed on the inner peripheral surface of the gas detection element 103 so as to cover almost the entire surface, and a similar porous external layer is formed on the outer peripheral surface. An electrode layer 106 is provided. Further, an engagement flange portion 111 that protrudes radially outward is provided at a substantially intermediate position in the axial direction of the gas detection element 103. The engagement flange portion 111 is used to hold the gas detection element 103 on the metal shell 121 as will be described later. A ceramic heater 109 having a heating resistor is inserted inside the gas detection element 103 and is formed in a rod shape.

  The metal shell 121 has a cylindrical shape made of SUS430 and has a distal end portion 123 that is inserted into the protector 151. In addition, a shelf (support surface) 125 for holding the gas detection element 103 in the direction of the axis C is provided on the inner periphery of the metal shell 121 at a position on the rear end side from the front end portion 123. Further, a stepped portion 127 is also formed on the rear end side of the shelf 125. On the other hand, an attachment screw portion 129 for attaching the gas sensor 101 to the exhaust gas pipe is provided on the outer periphery of the metal shell 121 at a position on the rear end side of the front end portion 123. Further, a hexagonal flange portion 131 (tool engaging portion) used when the gas sensor 101 is attached to the exhaust gas pipe is provided on the rear end side of the attachment screw portion 129.

  The distal end portion 123 of the metal shell 121 is a portion to be inserted into the protector 151 as described above, and the distal end portion 123 overlaps with the protector 151 (in detail, an outer cover portion 173 described later). This corresponds to the part where the part 301 is generated. Here, the leading end portion 123 that generates the overlapping portion 301 between the metal shell 121 and the protector 151 (scheduled to generate the overlapping portion 301) has a large-diameter portion 303 (outer diameter 12.15 mm). A small-diameter portion 305 (outer diameter of 12.03 mm) smaller than the large-diameter portion 303 is provided at a position closer to the rear end side than the large-diameter portion 303 and further to the distal end side than the mounting screw portion 129. It has a structure.

  The metal shell 121 holds the gas detection element 103 coaxially in a state where the front end portion 105 of the gas detection element 103 protrudes from the front end surface of the metal shell 121. Specifically, as shown in FIG. 1, a first plate packing 133 is disposed on the shelf 125 of the metal shell 121. Furthermore, a cylindrical first fixing member 135 (made of alumina) having a stepped portion 136 on the inner periphery is disposed thereon. The gas detection element 103 is inserted into the first fixing member 135, and the engagement flange portion 111 of the gas detection element 103 is engaged with the stepped portion 136 of the first fixing member 135 via the second plate packing 137. doing. On the rear end side of the first fixing member 135, a filling sealing layer 139 in which talc is compressed and filled is disposed in a gap formed by the outer peripheral surface of the gas detection element 103 and the inner peripheral surface of the metal shell 121. Yes.

  Further, on the rear end side of the filling sealing layer 139, a cylindrical second fixing member 141 (made of alumina) through which the gas detection element 103 passes is disposed. A caulking ring 145 is disposed on the rear end side of the second fixing member 141, and the rear end portion 132 of the metal shell 121 is caulked inward in the radial direction, so that the gas detection element 103 is hermetically sealed in the metal shell 121. Held in a state.

  The protector 151 is a double body having a cylindrical inner cover portion 153 that covers the distal end portion 105 of the gas detection element 103 with a gap, and a cylindrical outer cover portion 173 disposed on the outer periphery of the inner cover portion 153. Make a structure.

  Of these, the outer cover portion 173 is made of SUS310S having a wall thickness of 0.5 mm, and includes an outer cylindrical portion 175 having an outer diameter of 13.15 mm and an outer bottom portion 177 positioned on the tip side. The outer cylindrical portion 175 is provided with six outer gas circulation holes 176 through which exhaust gas can be introduced into the outer cover portion 175 from the outside. The outer gas circulation holes 176 each have an oval shape, and each outer gas circulation hole 176 is formed at equal intervals in the circumferential direction at a position closer to the tip than the center when viewed in the axis C direction. In addition, the outer bottom portion 177 is provided with a circular outer tip circulation hole 179 connected to the outside in the tip direction from the protector 151 at the center thereof.

  The inner cover portion 153 is made of SUS310S having a wall thickness of 0.3 mm, and includes an inner cylindrical portion 155 having an outer diameter of 8.50 mm and an inner bottom portion 175 located on the tip side. Unlike the outer cylindrical portion 175, the inner cylindrical portion 155 does not have a gas flow hole. On the other hand, the inner bottom portion 157 is provided with a circular inner tip circulation hole 159 connected to the outside in the tip direction than the protector 151 at the center thereof.

  Further, as shown in FIGS. 2 and 3, the protector 151 is provided on the outer side of the inter-cover portion space 171 between the inner cylindrical portion 155 of the inner cover portion 153 and the outer cylindrical portion 175 of the outer cover portion 173. On the rear end side of the gas flow hole 176, there is a blocking portion 181 that intermittently blocks the inter-cover space 171 in the circumferential direction. The blocking portion 181 of the present embodiment is composed of a flange portion 183 that protrudes radially outward at six locations from the rear end of the inner cylindrical portion 155. The area of the shielding part 181 (the flange part 183) with respect to the opening area of the outer gas circulation hole 176 (projected area when the shielding part 181 is projected in the axial direction) is about 30%. The flange portion 183 is provided with six leg portions 185 that protrude from the radially outer end toward the rear end side in the axis C direction.

  The inner cover portion 153 and the outer cover portion 173 are partially spot-welded at four locations, the inner bottom portion 157 and the outer bottom portion 177 at the peripheral portion 157W of the inner tip vent hole 159 and the peripheral portion 177W of the outer tip circulation hole 179. Thus, they are fixed to each other through a gap of about 0.1 mm. As a result, the inner tip circulation hole 159 and the outer tip circulation hole 179 communicate with each other.

  In such a protector 151, as shown in FIG. 2, the rear end portion 180 (the rear end portion of the outer cylindrical portion 175) of the outer cover portion 173 is press-fitted into the large diameter portion 303 of the front end portion 123 of the metal shell 121. In addition to being fixed, laser welding is performed with the annular gap S interposed in the small diameter portion 305 of the tip end portion 123.

Since the fixing structure of the protector 151 and the metal shell 121 corresponds to the main part of the present invention, it will be described in more detail.
Of the metal shell 121, the front end portion 123 that generates the overlapping portion 301 with the rear end portion 180 of the outer cover portion 173 of the protector 151 has the large diameter portion 303 and the small diameter portion 305 described above. The cover part 173 is fitted into the large-diameter part 303 (in this embodiment, press-fitted). The outer cover portion 173 has an annular space S formed between the inner peripheral surface of the outer cover portion 173 and the outer peripheral surface of the small-diameter portion 303, and a welded portion formed by laser welding so as to penetrate the annular space S. W is formed over the circumferential direction of the outer cover portion 173. That is, the protector 151 (outer cover part 173) and the metal shell 121 are fixed by press-fitting and laser welding. Further, the leg portion 185 connected to the shielding portion 181 is in contact with the distal end surface 123S of the distal end portion 123 of the metal shell 121. In the gas sensor 101 of the present embodiment, a portion where the large diameter portion 303 and the outer cover portion 173 are fitted forms a fitting portion 501, and the small diameter portion 303 and the outer cover portion 173 form the annular space S. The part which overlaps via has comprised the space formation part 503. FIG.

  In the gas sensor 101 of the present embodiment, the outer diameter (maximum outer diameter) of the small-diameter portion 305 of the metal shell 121 is A, and the inner diameter (minimum) of the protector 151 (outer cover portion 173) located on the radially outer side of the small-diameter portion 305. The size B-A of the annular space S expressed when the inner diameter is B is 0.12 mm (= 12.15-12.03 mm). Further, the length of the fitting portion 501 in the direction of the axis C, that is, the large diameter portion 303 is set so that positioning by fitting (press fitting) between the outer cover portion 173 and the large diameter portion 303 of the metal shell 121 is performed satisfactorily. A length D (see FIG. 4) in the direction of the axis C from the leading edge to the trailing edge is 1 mm.

  As a result, the leading end 123 of the metal shell 121, the outer cylindrical portion 175, and the inner cylindrical portion 155 pass the gas to be measured (exhaust gas) introduced from the outer gas flow hole 176 to the inner cover portion 153. An inner gas introduction path 191 that leads to a gap between the front end portion 105 of the gas detection element 103 is configured. More specifically, the inner gas introduction path 191 passes the gas to be measured introduced from the outer gas circulation hole 176 between the outer cylindrical portion 175 and the inner cylindrical portion 155 and guides it to the rear end side. . Thereafter, when the exhaust gas is viewed in the direction of the axis C from the inner peripheral surface side edge 123ST of the connecting surface (front end surface) connecting the inner peripheral surface and the outer peripheral surface of the front end portion 123 of the metal shell 121, the front end is seen. On the side, the rear end of the inner tubular portion 155 is made to pass. Then, the gas to be measured is guided to the gap between the inner cover portion 153 and the distal end portion 105 of the gas detection element 103, and discharged to the outside of the protector 151 through the inner distal end circulation hole 159 and the outer distal end circulation hole 179.

  Next, returning to FIG. 1, the tip end portion 201 </ b> S of the cylindrical metal outer tube 201 is fixed from the outside by full-circle laser welding on the rear end side of the hexagonal flange portion 131 of the metal shell 121. Further, a grommet 203 made of fluoro rubber is inserted into the rear end side opening 201K of the metal outer cylinder 201, and the metal outer cylinder 201 is caulked toward the inner side in the radial direction. It is fixed in an airtight state. A through hole is provided in the central portion of the grommet 203, and a filter member 205 that prevents air from entering while the atmosphere is introduced inside the metal outer tube 201 is disposed in the through hole. Further, a separator 207 made of insulating alumina is disposed on the front end side of the grommet 203. The sensor output lead wires 211 and 212 and the heater lead wires 213 and 214 are disposed through the grommet 203 and the separator 207. In the separator 207, the connector portions 215B and 216B of the first and second sensor terminal fittings 215 and 216 and the heater terminal fittings 217 and 218 are disposed while being insulated from each other, and the rear end side of the ceramic heater 109 is accommodated. Has been.

  The first sensor terminal fitting 215 has a connector portion 215B that grips and electrically connects the sensor output lead wire 211 by caulking, and an insertion portion 215C is inserted into the bottomed hole of the gas detection element 103. The internal electrode layer 108 is electrically connected. The second sensor terminal fitting 216 has a connector portion 216B that grips and electrically connects the sensor output lead wire 121 by caulking, and the grip portion 216C has an outer periphery near the rear end of the gas detection element 103. And is electrically connected to the external electrode layer 106. In addition, the two heater terminal fittings 217 are electrically connected to the heater lead wire 213 (note that one heater lead wire is omitted because FIG. 1 is a cross-sectional view), and ceramic Each of the heater pads 109 is electrically connected to the pair of electrode pad portions 109B by bonding.

  The separator 207 is formed with a flange portion 207C protruding outward in the radial direction, while the metal outer cylinder 201 is formed with four inner convex portions 201C at equal intervals along the circumferential direction. ing. Then, in a state where the rear end surface of the flange portion 207C is brought into contact with the inner convex portion 201C, the separator 207 is energized rearward by using the biasing member 219, whereby the separator 207 is disposed inside the metal outer cylinder 201. Is held in. The urging member 219 has a cylindrical shape and is held by the separator 207 by its own elastic force, and is deformed by crimping the metal outer cylinder 201 positioned on the radially outer side thereof to the radially inner side. It is comprised so that the collar part 207C of 207 may be urged | biased to the back side.

The gas sensor 101 is manufactured as follows.
First, plastic working and cutting are performed on the steel material of SUS430 to form a cylindrical metal shell 121 having a hexagonal flange portion 131, a mounting screw portion 129, a shelf portion 133, a tip portion 123, and the like. At this time, a large-diameter portion 303 and a large-diameter portion 303 are located on the rear end side of the large-diameter portion 303 at the leading end portion 123 where the overlapping portion 301 is expected to be generated between the protector 151 (outer cover portion 173). The metal shell 121 is formed so that a small diameter portion 305 having an outer diameter smaller than the diameter portion 303 is formed.

  Next, a predetermined amount of oil is adhered to the surface of the metallic shell 121. Below, the oil agent adhesion method in this embodiment is demonstrated. At the time of molding (plastic processing, cutting) of the metal shell 121 described above, an oil agent is used for lubrication and cooling, and a residual oil agent adheres to the surface of the metal shell 121 after molding. Therefore, first, the metal shell 121 to which the residual oil agent is adhered is immersed in a degreasing liquid, and is removed from the degreasing liquid and washed with water, so that all of the residual oil agent adhered to the metal shell 121 is removed. Then, the washed metal shell 121 is immersed in an oil solution (for example, an approximately 30% aqueous solution of alkylamine oxide) in which water-soluble oil is dissolved in water, taken out from the oil solution, dried, and newly applied to its surface. The metal shell 121 to which the oil agent is attached is obtained. It should be noted that a predetermined amount of oil agent can be adhered to the surface of the metal shell 121 by appropriately adjusting the concentration of the oil agent liquid. In this way, the metallic shell 121 having a predetermined shape and having the oil agent attached to the surface including the tip portion 123 is prepared.

  On the other hand, an outer cover portion 173 and an inner cover portion 153 having a bottomed cylindrical shape made of SUS310S that are preliminarily molded to a predetermined size are prepared. Then, spot welding is performed at four locations in the peripheral portion 157W of the inner tip circulation hole 159 and the peripheral portion 177W of the outer tip circulation hole 179, thereby fixing the inner cover portion 153 and the outer cover portion 173 coaxially, The protector 151 is obtained.

  Then, as shown in FIG. 4A, the protector 151 is moved from the front end side of the metal shell 123, and the protector 151 is moved until the rear end of the outer cover portion 173 contacts the front end surface of the mounting screw portion 129. Thus, the rear end portion 180 of the outer cover portion 173 is attached to the outside of the front end portion 123 of the metal shell 121. At this time, the outer cover portion 173 is fitted (press-fitted in this embodiment) to the large-diameter portion 303 of the distal end portion 123 of the metal shell 121, but the oil agent adheres to the surface of the metal shell 121. Therefore, it is possible to smoothly press-fit. Further, since the protector 151 is moved (press-fitted) until the rear end of the outer cover portion 173 comes into contact with the front end surface of the mounting screw portion 129, an annular shape is formed between the small diameter portion 305 and the outer cover portion 173 of the front end portion 123. A space S is formed. In the present embodiment, the outer diameter of the small-diameter portion 305 of the metal shell 121 is adjusted at the time of molding so that the size B-A of the annular space S is 0.12 mm. Thereby, a fitting portion 501 in which the large diameter portion 303 and the outer cover portion 173 are fitted, and a space forming portion 503 in which the small diameter portion 305 and the outer cover portion 173 overlap with each other via the annular space S are formed.

  Next, as shown in FIG. 4B, laser light is irradiated from the outer peripheral surface of the outer cover portion 173 located on the radially outer side of the small-diameter portion 305 of the metal shell 121 so as to penetrate through the annular space S. The part W is formed over the entire circumference, and the protector 151 and the metal shell 121 are laser-welded. Thereby, the protector 151 and the metal shell 121 are firmly fixed by press-fitting and laser welding.

  Here, at the time of this welding process, since the oil agent adheres to the surface of the small diameter portion 305 of the metal shell 121, the oil agent component is vaporized by heat input by laser welding. However, in the present embodiment, since the laser welding is performed with the annular space S interposed, the gas in which the oil component is vaporized escapes from the rear end side of the outer cover portion 173 to the outside. Therefore, in the welded portion W, the occurrence of welding defects such as blow holes due to this gas generation is suppressed, and stable welded portion W formation is brought about. In the present embodiment, the rear end of the outer cover portion 173 is brought into contact with the front end surface of the mounting screw portion 129 of the metal shell 121. 0.03 mm), it is possible to vent the gas from the rear end side of the outer cover portion 173.

  In the metal shell 121 to which the protector 151 is fixed, the first plate packing 133, the first fixing member 135, the second plate packing 137, the gas detection element 103, the talc ring that serves as the filling sealing layer 139, the second The fixing member 141 and the caulking ring 145 are sequentially inserted. Thereafter, the rear end portion 132 of the metal shell 121 is caulked inward in the radial direction, and the talc ring is compressed and filled to form the filling sealing layer 139, while the gas detecting element 103 is held in the metal shell 121 and the lower portion An assembly 401 (see FIG. 5) is produced.

  Next, the sensor output lead wires 211 and 212 and the heater lead wire 213 are connected to the first and second sensor terminal fittings 215 and 216 and the two heater terminal fittings 217, respectively, and the ceramic heater 109 is connected to the first sensor terminal fitting 215. The lead wires 211, 212, and 213 (the remaining one is not shown) are inserted into the separator 207 while being positioned inside. An urging member 219 is attached in advance around the front end side of the flange 207C of the separator 207. Thus, the separator 207 having the lead wires 211, 212, and 213 inserted therein is inserted into the metal outer tube 201. Next, the lead wires 211, 212, and 213 are inserted into lead wire insertion holes formed in the grommet 203, and the grommet 203 is fitted into the rear end side opening 201 </ b> K of the metal outer cylinder 201. Thereby, the upper assembly 402 (see FIG. 5) is manufactured.

  Then, as shown in FIG. 5, the upper assembly 402 is moved toward the lower assembly 401, and the upper assembly 402 is moved until the tip 201 </ b> S of the metal outer cylinder 201 contacts the hexagonal flange 131 of the metal shell 121. Move. At this time, the heater 15 is inserted into the gas detection element 103. Thereafter, the distal end portion 201S of the metal outer cylinder 201 and the metal shell 121 located inside the metal outer cylinder 201 are temporarily connected by crimping with a caulking jig while pressing the metal outer cylinder 201 toward the distal end side.

  Next, in the metal outer cylinder 201, a portion located on the radially outer side of the biasing member 219 is crimped toward the radially inner side to deform the biasing member 219, and the biasing member 219 and the inner convex portion. The flange portion 207C of the separator 207 is sandwiched between 201C. As a result, the separator 207 is held in the metal outer cylinder 201. Thereafter, a portion of the metal outer cylinder 201 that is located on the radially outer side of the grommet 203 is crimped toward the radially inner side to fix the grommet 203 to the metal outer cylinder 201 in an airtight state. And the gas sensor 101 is completed by carrying out the laser welding of the front-end | tip part 201S and the metal shell 121 of the metal outer cylinder 201 already temporarily connected.

(Second Embodiment)
A gas sensor 601 according to a second embodiment of the present invention will be described. A cross-sectional view of the main part of the gas sensor 601 is shown in FIG. The gas sensor 601 is an oxygen sensor that detects the oxygen concentration in the exhaust gas, similar to the gas sensor 101 of the first embodiment, but the front end portion 123 of the metal shell 121 and the protector 151 (specifically, the outer cover portion). 173) and the structure of the mounting part are different. Therefore, below, it demonstrates centering on a different part from the gas sensor 101 of 1st Embodiment, attaches | subjects the same symbol and number about the same part, and abbreviate | omits or simplifies description.

  In the gas sensor 601 of the present embodiment, in the outer cover portion 173 of the protector 151, the rear end portion 180 that generates the overlapping portion 301 with the front end portion 123 of the metal shell is the protector side small diameter portion 611 and the protector side small diameter. A protector-side large-diameter portion 613 having an inner diameter larger than that of the portion 611 is provided. Moreover, the front-end | tip part 123 of the metal shell 121 does not have the large diameter part 303 and the small diameter part 305 like the said 1st Embodiment, and the outer diameter is formed substantially the same.

  And the protector side small diameter part 611 of the outer side cover part 173 is fitted by the front-end | tip part of the metal shell 121 (it press-fits in this embodiment), and the inner peripheral surface of the protector side large diameter part 613 of the outer side cover part 173 and An annular space S is formed between the outer surface of the front end portion 123 of the metal shell 121, and a welded portion W formed by laser welding so as to penetrate the annular space S extends in the circumferential direction of the outer cover portion 173. Is formed. That is, in the gas sensor 601 of the present embodiment, the portion where the protector side small diameter portion 611 and the tip end portion 123 of the metal shell 121 are fitted forms the fitting portion 651, and the protector side large diameter portion 613 and the metal shell are connected. A portion where the front end portion 123 of 121 overlaps with the annular space S forms a space forming portion 653.

  In the gas sensor 601 of the present embodiment, the inner diameter (minimum inner diameter) of the protector-side large-diameter portion 613 of the outer cover portion 173 is B, and the distal end of the metal shell 121 located on the radially inner side of the protector-side large-diameter portion 613. The size B-A of the annular space S expressed when the outer diameter of the portion 123 is A is 0.10 mm (= 12.25 mm-12.15 mm). In addition, the length of the fitting portion 651 in the axis C direction, that is, the positioning by the fitting (press-fit) of the front end portion 123 of the metal shell 121 and the protector side small diameter portion 611 of the outer cover portion 173, that is, The length in the axis C direction from the front end edge to the rear end edge of the protector side small diameter portion 611 is 0.8 mm.

The gas sensor 601 is manufactured as follows.
First, similarly to the first embodiment, plastic working and cutting are performed on the steel material of SUS430 to form the cylindrical metal shell 121. Next, a predetermined amount of oil is adhered to the surface of the metallic shell 121. The method of attaching the oil agent to the metal shell 121 is the same as in the first embodiment.

  On the other hand, an outer cover portion 173 and an inner cover portion 153 having a bottomed cylindrical shape made of SUS310S that are preliminarily molded to a predetermined size are prepared. At this time, the protector side small-diameter part 611 and the protector-side small diameter part 611 are positioned on the rear end side at the rear end part 180 where the overlapping part 301 is expected to occur between the front end part 123 of the metal shell 121. The outer cover portion 173 is formed such that the protector-side large-diameter portion 613 having an inner diameter larger than the protector-side small-diameter portion 611 is formed. And the inner side cover part 153 and the outer side cover part 173 are adhere | attached coaxially, and the protector 151 is obtained.

  Then, the protector 151 is moved from the front end side of the metal shell 123, and the protector 151 is moved until the rear end of the outer cover portion 173 contacts the front end surface of the mounting screw portion 129, whereby the rear end of the outer cover portion 173 is reached. The portion 180 is attached to the outside of the distal end portion 123 of the metal shell 121. At this time, the protector-side small-diameter portion 611 of the outer cover portion 173 is press-fitted into the distal end portion 123 of the metal shell 121, but since the oil agent is attached to the surface of the metal shell 121, the smoothness is smoothly achieved. Press fitting can be performed. In addition, since the protector 151 is moved until it comes into contact with the distal end surface of the mounting screw portion 129, an annular gap S is formed between the distal end portion 123 and the protector-side large-diameter portion 613 of the outer cover portion 173. Become.

  Next, laser light is irradiated from the outer peripheral surface of the protector-side large-diameter portion 613 of the outer cover portion 173 to form the welded portion W over the entire circumference so as to penetrate the annular gap S, and the protector 151 and the metal shell 121 are formed. Laser welding. In this welding process, since the oil agent is attached to the surface of the front end portion 123 of the metal shell 121, the oil agent component is vaporized by heat input by laser welding. However, in the present embodiment, since the laser welding is performed with the annular space S interposed, the gas in which the oil component is vaporized escapes from the rear end side of the outer cover portion 173 to the outside. And after attaching the protector 151 to the front-end | tip part 123 of the metal shell 121, the gas sensor 601 is completed by passing through the process similar to the said 1st Embodiment.

In the above, the present invention has been described with reference to the embodiments. However, the present invention is not limited to the above embodiments, and it is needless to say that the present invention can be appropriately modified and applied without departing from the gist thereof.
For example, in the above embodiment, an element having a shape in which the tip 105S is closed is used as the gas detection element 103. However, the shape may be appropriately changed according to a detection target or the like, and a plate-shaped gas detection element may be used. it can.

  Further, in the above embodiment, during laser welding of the outer cover portion 173 and the small diameter portion 305 of the metal shell 121, the oil component gas is allowed to escape from the annular space S to the outside from the rear end of the protector 151 (outer cover portion 173). However, it may be escaped from the front end side of the metal shell 121. Specifically, after the metal shell 121 having the predetermined shape is formed through plastic processing and cutting, the surface of the large diameter portion 303 of the distal end portion 123 is subjected to grooving or knurling, and the distal end of the large diameter portion 303 is formed. A plurality of recesses formed continuously from the edge to the base end edge are formed.

  And after making an oil agent adhere to the surface of the main metal fitting 121 which formed the several recessed part in the surface of the large diameter part 303, the protector 151 is press-fit in the procedure mentioned above, and the small diameter part 305 and the protector 151 (outer cover part 173). ) To penetrate through the annular space S, the weld W is formed by laser welding. Thereby, even if the oil agent adheres to the surface of the small-diameter portion 305 of the metal shell 121, the vaporized oil component gas can be released from the rear end of the protector 151 (outer cover portion 173) to the outside through the annular space S. In addition, it is possible to escape from the front end side of the metallic shell 121 to the outside through the spaces in the plurality of recesses. Thereby, at the time of the welding process of the small diameter part 305 and the outer side cover part 173 of the metal shell 121, the degassing effect is more reliably brought about and the more stable welded part W can be formed.

  Further, in the above embodiment, the large diameter portion 303 is formed at the distal end portion 123 of the metal shell 121 and the small diameter portion 305 is formed on the rear end side of the large diameter portion 303. The small diameter portion 305 may be formed. In this case, by fitting the outer cover portion 173 to the large diameter portion 303, an annular space S is formed between the small diameter portion 305 and the outer cover portion 173, and the welded portion W that penetrates the annular space S is formed. The oil component gas generated at the time of formation escapes from the front end side of the protector 151 to the outside through the annular space S.

It is a whole sectional view of a gas sensor concerning an embodiment. It is sectional drawing which shows the fixing structure of the protector and metal shell which are the principal part of the gas sensor concerning embodiment. It is explanatory drawing which shows the protector which makes | forms a double structure among the gas sensors concerning embodiment. (A) It is explanatory drawing which shows a mode that a protector is mounted | worn outward from the front-end | tip part of a metal shell, (b) It is explanatory drawing which shows a mode that a small diameter part of a metal shell and the outer side cover part of a protector are laser-welded. It is explanatory drawing which shows a mode that an upper assembly is assembled | attached with respect to the lower assembly of the state which hold | maintained the gas detection element in the metal shell. It is sectional drawing which shows the fixing structure of the protector and metal shell which are the principal part of the gas sensor concerning 2nd Embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 101, 601 ... Gas sensor, 103 ... Gas detection element, 106 ... External electrode layer, 108 ... Internal electrode layer, 109 ... Ceramic heater, 121 ... Metal fitting, 123 ... Tip portion (of metal shell), 129... Mounting screw portion, 151... Protector, 153... Inner cover portion, 173 .. outer cover portion, 201. Overlapping part, 303 ... large diameter part, 305 ... small diameter part, 501, 651 ... fitting part, 503, 653 ... space forming part, 611 ... protector side small diameter part, 613.・ Protector side large diameter part, S ・ ・ ・ annular space, W ・ ・ ・ welded part

Claims (12)

A gas detection element extending in the axial direction and having the tip side exposed to the gas to be measured;
In a state where the gas detection element protrudes from the front end side of the gas detection element, a cylindrical metal shell that surrounds the radially outer side of the gas detection element,
A cylindrical protector that is attached to the outer periphery of the distal end portion of the metal shell and covers the distal end side of the gas detection element;
A method of manufacturing a gas sensor comprising:
A metal fitting preparation step of preparing the metal shell with an oil agent attached to the outer periphery of the tip portion;
Moving at least one of the metal shell to which the oil agent is attached and the protector in a direction approaching each other, and a fitting portion for fitting the tip portion of the metal shell and the protector; An assembling step of assembling the metal shell and the protector such that a space forming portion where the tip portion and the protector overlap with each other via an annular space is generated along the axial direction;
A gas sensor manufacturing method comprising: a welding step of forming a welded portion penetrating the annular space from an outer periphery of the protector, and welding the metal shell and the protector. It is a manufacturing method of the gas sensor according to claim 1,
The size of the annular space represented when the outer diameter of the portion of the metal shell forming the space forming portion is A and the inner diameter of the portion of the protector forming the space forming portion is B. A method for manufacturing a gas sensor, wherein B-A is 0.06 mm or more. It is a manufacturing method of the gas sensor according to claim 1 or 2,
The tip of the metal shell includes a large diameter part and a small diameter part having an outer diameter smaller than the large diameter part,
The fitting portion is formed by fitting the large diameter portion and the protector, while the space forming portion is formed by overlapping the small diameter portion and the protector via the annular space. A method for manufacturing a gas sensor. It is a manufacturing method of the gas sensor according to claim 1 or 2,
Of the protector, the portion to be mounted on the outer periphery of the tip of the metal shell includes a small diameter portion and a large diameter portion having an inner diameter larger than the small diameter portion,
The fitting portion is formed by fitting the small-diameter portion and the tip portion of the metal shell, while the space forming portion is formed by the large-diameter portion and the tip portion of the metal shell. A manufacturing method of a gas sensor formed by overlapping through an annular space. It is a manufacturing method of the gas sensor according to any one of claims 1 to 4,
A method for manufacturing a gas sensor, wherein the fitting portion has an axial length of 0.8 mm or more. It is a manufacturing method of the gas sensor according to any one of claims 1 to 5,
The fitting part is a method for manufacturing a gas sensor, which is formed by press-fitting the protector into the tip part of the metal shell. It is a manufacturing method of the gas sensor given in any 1 paragraph of Claims 1-6,
The said welding part is a manufacturing method of the gas sensor formed by laser welding. It is a manufacturing method of the gas sensor according to claim 3,
A gas sensor is provided on the surface of the large-diameter portion of the metal shell. The gas sensor has at least one concave portion that is recessed radially inward and continuous from the leading edge to the trailing edge of the large-diameter portion. Manufacturing method. A gas detection element extending in the axial direction and having the tip side exposed to the gas to be measured;
In a state where the gas detection element protrudes from the front end side of the gas detection element, a cylindrical metal shell surrounding the periphery of the gas detection element;
A cylindrical protector that is attached to the outer periphery of the distal end portion of the metal shell and covers the distal end side of the gas detection element;
A gas sensor comprising:
A fitting portion in which the tip portion of the metal shell and the protector are fitted, and a space forming portion in which the tip portion of the metal shell and the protector overlap via an annular space;
The gas sensor according to claim 1, wherein the protector is welded to the metal shell by a weld formed so as to penetrate the annular space. The gas sensor according to claim 6,
The protector and the metal shell are gas sensors welded by the welded portion formed in the circumferential direction. The gas sensor according to claim 9 or 10, wherein
The distal end portion of the metal shell includes a large diameter portion and a small diameter portion having an outer diameter smaller than the large diameter portion,
The gas sensor in which the large diameter portion and the protector are fitted to form the fitting portion, and the small diameter portion and the protector overlap with each other via the annular space to form the space forming portion. The gas sensor according to claim 9 or 10, wherein
Of the protector, the portion to be mounted on the outer periphery of the tip of the metal shell includes a small-diameter portion and a large-diameter portion having an inner diameter larger than the small-diameter portion,
The small diameter portion and the tip end portion of the metal shell are fitted to form the fitting portion, and the large diameter portion and the tip portion of the metal shell overlap with each other via the annular space. A gas sensor.