JP2018010767A - Method of manufacturing ignition plug - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of manufacturing ignition plug capable of making weld crack and lack of penetration difficult to occur.SOLUTION: Under a state where a jig was abutted against a tabular member and the tabular member was pressed against a main body metal fitting, the tabular member is laser welded to the main body metal fitting. Annular end face of the jig abuts on the tabular member around a through hole. Since welding is performed by abutting the end face of the jig against the tabular member and covering the through hole thereof, sputter can be prevented from entering the through hole. Since contact area of the tabular member and jig can be reduced by the end face, cooling rate of weld metal can be prevented from becoming excessive.SELECTED DRAWING: Figure 4

Description

  The present invention relates to a method for manufacturing a spark plug, and more particularly, to a method for manufacturing a spark plug that can hardly cause weld cracks or poor penetration.

  A spark plug is known in which a plate-like member having a through hole is disposed at one end of a cylindrical metal shell that holds an insulator having a shaft hole (for example, Patent Document 1). In the technique disclosed in Patent Document 1, a jig is fitted into a through-hole of a plate-like member, and the member is laser welded to the metal shell while the surface of the member is pressed with the jig.

JP 2009-238746 A

  However, in the conventional technique described above, the jig contacts the surface of the plate-like member and the inner surface of the through hole, so that the cooling rate of the weld metal becomes excessive due to the heat conduction of the jig, and welding cracks and poor penetration occur. May occur.

  The present invention has been made in order to solve the above-described problems, and an object of the present invention is to provide a method for manufacturing a spark plug that can hardly cause weld cracking or poor penetration.

Means for Solving the Problems and Effects of the Invention

  In order to achieve this object, according to the spark plug manufacturing method of the first aspect, an insulator having an axial hole extending in the axial direction, a cylindrical metal shell for holding the insulator inside, A spark plug is manufactured that includes a plate-like member that is disposed at one end portion and that has a through-hole formed in the center in the axial direction. The insulator is assembled inside the metallic shell by the assembling process, and the plate-like member is arranged at one end of the metallic shell to which the insulator is assembled by the arranging process. The plate-like member is laser-welded to the metal shell by a welding process in a state where the jig is brought into contact with the plate-like member and the plate-like member is pressed against the metal shell.

  As for a jig | tool, the cyclic | annular end surface contact | abuts to the plate-shaped member around a through-hole. In the welding process, since welding is performed in a state where the end face of the jig is in contact with the plate-like member and the through-hole of the plate-like member is covered, it is possible to prevent spatter from entering the through-hole. Further, the contact area between the plate-like member and the jig can be reduced by the amount that the jig does not contact the inner surface of the through hole. Since the cross-sectional area through which the amount of heat of the weld metal moves can be reduced, the cooling rate of the weld metal can be prevented from becoming excessive. As a result, there is an effect that it is difficult to cause weld cracks and poor penetration.

  According to the spark plug manufacturing method of the second aspect, the jig includes the protruding portion having a larger outer shape than the annular end surface at a position away from the end surface by a predetermined distance in the axial direction. In the welding process, since the overhanging portion faces the plate-like member with a predetermined interval, it is difficult to cause spatter to enter between the plate-like member and the overhanging portion. Therefore, in addition to the effect of the first aspect, there is an effect that it is difficult for the spatter to adhere to the plate-like member.

  According to the spark plug manufacturing method of the third aspect, the jig includes a cylindrical portion having an annular end surface and a base portion connected to the opposite side of the end surface of the cylindrical portion along the axis. Since the area of the end face is smaller than the area of the cross section perpendicular to the axis of the base portion, a difference is generated between the heat flux of the cylindrical portion and the heat flux of the base portion, and the cooling rate of the weld metal can be suppressed. As a result, in addition to the effect of Claim 1 or 2, there exists an effect which can make it hard to produce a weld crack and a penetration defect with a cylinder part and a base part.

It is sectional drawing of the ignition plug in one embodiment of this invention. It is sectional drawing to which the one end part of the ignition plug was expanded. (A) is a side view of a jig | tool, (b) is a bottom view of a jig | tool. (A) is a schematic diagram of an assembly | attachment process, (b) is a schematic diagram of an arrangement | positioning process, (c) is a schematic diagram of a welding process. (A) is a side view of the jig | tool in a modification, (b) is a bottom view of a jig | tool, (c) is sectional drawing of the jig | tool in the Vc-Vc line | wire of FIG.5 (b).

  Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings. FIG. 1 is a cross-sectional view of a spark plug 10 according to an embodiment of the present invention cut along a plane including an axis O. In FIG. 1, the lower side of the drawing is called the rear end side of the spark plug 10, and the upper side of the drawing is called the leading end side of the spark plug 10. As shown in FIG. 1, the spark plug 10 includes an insulator 20, a metal shell 30 that holds the insulator 20, and a ground electrode 40 (a plate-like member) disposed at the tip of the metal shell 30.

  The insulator 20 is a substantially cylindrical member formed of alumina or the like that is excellent in mechanical properties and insulation at high temperatures. The insulator 20 includes a shaft hole 21 penetrating in the direction of the axis O, and a flange 22 having the largest outer shape is formed at the center in the direction of the axis O. In the insulator 20, a rear body portion 23 is formed on the rear end side of the flange portion 22, and a front body portion 24 and a leg length portion 25 are formed on the front end side of the flange portion 22. The long leg portion 25 is a portion having an outer diameter smaller than the outer diameter of the front barrel portion 24, and a step portion 26 that is reduced in diameter toward the distal end side is formed between the front trunk portion 24 and the leg long portion 25. .

  The metal shell 30 is a substantially cylindrical member fixed to a screw hole (not shown) of the internal combustion engine, and is attached to the outer periphery of the insulator 20. The metal shell 30 is formed of a conductive metal material (for example, low carbon steel or the like), and includes a tool engaging portion 31 and a screw portion 34 formed on the tip side of the tool engaging portion 31. Yes. The threaded portion 34 is formed with an annular shelf 35 that projects inward in the radial direction at the center in the direction of the axis O. The shelf 35 is reduced in diameter toward the tip side. The tool engaging portion 31 is a portion that engages a tool such as a wrench when the spark plug 10 is attached to the internal combustion engine.

  The metal shell 30 is provided with a caulking portion 32 on the rear end side with respect to the tool engaging portion 31. Ring members 61 and 62 are interposed between the tool engaging portion 31 and the caulking portion 32 and the rear body portion 23, and a powder layer 63 filled with powder such as talc is formed between the ring members 61 and 62. The When the crimping portion 32 is crimped, the insulator 20 is pressed in the direction of the axis O through the ring members 61 and 62 and the powder layer 63. As a result, the packing 64 (see FIG. 2) disposed between the shelf portion 35 of the metal shell 30 and the step portion 26 of the insulator 20 is in close contact with the shelf portion 35 and the step portion 26.

  In the metal shell 30, a seat portion 33 is formed between the tool engaging portion 31 and the screw portion 34. An annular gasket 65 is fitted between the seat portion 33 and the screw portion 34. The gasket 65 is sandwiched between the seat portion 33 and the internal combustion engine and seals the gap between the metal shell 30 and the internal combustion engine when the screw portion 34 is fitted in the screw hole of the internal combustion engine (not shown).

  The metal shell 30 has a substantially circular ground electrode 40 (plate-like member) disposed in the opening 36 at the tip. In the insulator 20, the center electrode 50 is inserted at the front end side of the shaft hole 21, and the front end of the terminal fitting 60 is inserted at the rear end side of the shaft hole 21. The terminal fitting 60 is a rod-like member to which a high voltage cable (not shown) is connected, and is formed of a conductive metal material (for example, low carbon steel). The terminal fitting 60 is connected to the center electrode 50 by a conductive seal 66 having conductivity.

  FIG. 2 is an enlarged cross-sectional view of one end portion of the spark plug 10. As shown in FIG. 2, the ground electrode 40 is joined to the opening 36 at the tip of the metal shell 30, so that the ground electrode 40 is disposed on the tip side in the axis O direction with respect to the leg long portion 25 of the insulator 20. The ground electrode 40 includes an electrode base material 41 made of metal (for example, made of a nickel base alloy) whose outer periphery is joined to the metal shell 30, and a chip 42 joined to the electrode base material 41. The chip 42 is an annular member formed of a noble metal such as platinum, iridium, ruthenium, rhodium or an alloy containing these as a main component, and a through hole 43 penetrating in the direction of the axis O is formed at the center. The electrode base material 41 is an annular plate material in which the chip 42 is joined to the inner peripheral surface.

  The center electrode 50 is a rod-like electrode in which a core material 51 that is more excellent in thermal conductivity than an electrode base material is embedded in an electrode base material formed in a bottomed cylindrical shape. The core material 51 is made of copper or an alloy containing copper as a main component. The center electrode 50 includes a shaft portion 52 that extends in the shaft hole 21 toward the front end side along the axis O, and a head portion 53 provided on the rear end side of the shaft portion 52. The head 53 is locked to a receiving portion 27 formed in the shaft hole 21 of the insulator 20 (front barrel portion 24).

  The tip of the shaft portion 52 is disposed in the shaft hole 21 and the tip 54 is joined to the tip. The chip 54 is a columnar member formed of a noble metal such as platinum, iridium, ruthenium, rhodium, or an alloy containing these as a main component. The center electrode 50 has a tip (tip 54) disposed in the shaft hole 21 of the insulator 20 at a distance from the tip 42 of the ground electrode 40. As a result, a cavity 37 communicating with the through hole 43 of the ground electrode 40 is formed between the ground electrode 40 and the center electrode 50.

  Next, a method for manufacturing the spark plug 10 will be described with reference to FIGS. FIG. 3A is a side view of the jig 70 used in the welding process, and FIG. 3B is a bottom view of the jig 70. 4A is a schematic diagram of the assembly process, FIG. 4B is a schematic diagram of the arrangement process, and FIG. 4C is a schematic diagram of the welding process. The arrow in FIG. 4C indicates laser light. 4A to 4C, for the sake of simplicity, the illustration of the screw of the metal shell 30, the illustration of the tip 42 of the ground electrode 40, the illustration of the core 51 and the tip 54 of the center electrode 50 are omitted. Has been.

  As shown in FIG. 4A, the insulator 20 with the center electrode 50 assembled in advance is prepared, and the insulator 20 is assembled inside the metal shell 30 by the assembly process. Next, the ground electrode 40 is disposed on one end of the metal shell 30 by an arranging step (see FIG. 4B). Next, as shown in FIG. 4C, the jig 70 is brought into contact with the ground electrode 40 in the welding process.

  Returning to FIG. 3, the jig 70 will be described. The jig 70 includes a grip portion 71 that is gripped by a chuck (not shown) such as a work hand that moves the jig 70 up and down, a conical base portion 72 that is connected in the direction of the axis O of the grip portion 71, and the base portion 72. A columnar protruding portion 73 connected in the axis O direction and a cylindrical portion 74 connected to the end surface of the protruding portion 73 in the axis O direction are provided. The jig 70 is made of metal, synthetic resin, or the like.

  The cylindrical portion 74 is formed with an annular end surface 75 that contacts the ground electrode 40 around the through hole 43. The end face 75 is formed with an inner diameter larger than the inner diameter of the through hole 43. This is because when the welding is performed, the end surface 75 of the jig 70 is brought into contact with the ground electrode 40 to press the ground electrode 40 against the metal shell 30 to cover the through hole 43.

  The overhang portion 73 is a portion provided at a position away from the end surface 75 in the axis O direction by a predetermined distance, and has an outer shape larger than that of the end surface 75. In the present embodiment, the overhanging portion 73 has an outer shape set to the same size as or larger than the outer shape of the metal shell 30.

  The cylindrical portion 74 having the annular end surface 75 has a length in the axis O direction (distance from the protruding portion 73 to the end surface 75) set to about 0.1 mm to 0.9 mm. The end surface 75 has a length in the radial direction orthogonal to the axis O set to about 0.1 mm to 0.5 mm. The jig 70 has a grip 71, a base 72, and an overhang 73 formed in a solid shape. Therefore, the area of the cross section orthogonal to the axis O of the cylindrical portion 74 (the area of the end surface 75) is smaller than the area of the cross section orthogonal to the axis O of the base 72 and the overhang 73.

  Here, if the length of the cylindrical portion 74 in the direction of the axis O is shorter than 0.1 mm, the heat transfer from the ground electrode 40 to the overhang portion 73 cannot be ignored, and the cooling rate of the weld metal cannot be suppressed. There is a fear. On the other hand, when the length in the direction of the axis O is longer than 0.9 mm, there is a possibility that spatter easily enters the gap between the ground electrode 40 and the overhang portion 73.

  If the length of the end surface 75 in the radial direction is shorter than 0.1 mm, the strength may decrease and the end surface 75 may be easily damaged. On the other hand, if the length in the radial direction is longer than 0.5 mm, the area of the end face 75 becomes large, so that the cooling rate of the weld metal may not be suppressed.

  Returning to FIG. 4C, the welding process will be described. As shown in FIG. 4C, in the welding process, the end surface 75 of the jig 70 is brought into contact with the ground electrode 40 around the through-hole 43, and the ground electrode 40 is pressed against the metal shell 30 by the jig 70. The entire circumference of the ground electrode 40 is laser welded to the metal shell 30. Laser light is emitted from the outer periphery of the metal shell 30 toward the ground electrode 40 (in the direction of the arrow in FIG. 4C).

  At the time of welding, the ground electrode 40 is pressed against the metal shell 30 by the jig 70, so that the ground electrode 40 can be prevented from floating from the metal shell 30 due to the impact or thermal effect of welding. Therefore, it is possible to prevent the ground electrode 40 from being welded to the metal shell 30 in a state where the ground electrode 40 is lifted.

  Since welding is performed with the end face 75 of the jig 70 in contact with the ground electrode 40 and covering the through hole 43, it is possible to prevent spatter from entering the through hole 43 and the cavity 37. Therefore, it is possible to prevent a short circuit between the center electrode 50 and the ground electrode 40 due to sputtering, a decrease in withstand voltage, and the like.

  Note that the jig 70 covers the through-hole 43 because the jig 70 is not open at both ends in the direction of the axis O, but one side of the jig 70 in the direction of the axis O (opposite of the end face 75). Indicates that is closed. Since one end of the jig 70 in the direction of the axis O is closed, the through hole 43 can be covered with the jig 70 when the end face 75 of the jig 70 is pressed against the ground electrode 40.

  Since the ground electrode 40 is only in contact with the end face 75 of the jig 70, the contact area between the ground electrode 40 and the jig 70 can be reduced. Since the cross-sectional area in which the amount of heat of the weld metal moves by the end face 75 can be reduced, the cooling rate of the weld metal can be prevented from becoming excessive. As a result, it is possible to make it difficult for weld cracks and penetration defects to occur.

  Since the jig 70 has an area of a cross section perpendicular to the axis O of the cylindrical portion 74 (area of the end surface 75) smaller than that of a cross section orthogonal to the axis O of the base 72, the heat flux of the cylindrical portion 74 and the base A difference can be made to the 72 heat flux. As a result, it is possible to prevent the cooling rate from becoming excessive while ensuring the heat transfer of the weld metal, so that it is difficult for weld cracks and penetration defects to occur due to differences in the cross-sectional areas of the cylindrical portion 74 and the base portion 72.

  In the welding process, since the overhanging portion 73 faces the ground electrode 40 with a small gap, it is difficult for the spatter to enter the gap between the ground electrode 40 and the overhanging portion 73. Therefore, it is possible to make it difficult for spatter to adhere to the ground electrode 40.

  The present invention has been described above based on the embodiments. However, the present invention is not limited to the above embodiments, and various improvements and modifications can be made without departing from the spirit of the present invention. It can be easily guessed. For example, the shapes and dimensions of the insulator 20, the metal shell 30, and the ground electrode 110 are examples and can be appropriately set.

  In the above-described embodiment, the spark plug 10 in which discharge is generated between the ground electrode 40 (plate-like member) welded to the tip of the metal shell 30 and the center electrode 50 has been described, but the present invention is not necessarily limited thereto. Absent. Apart from a plate-like member welded to the tip of the metal shell 30 (corresponding to the ground electrode 40 in the above embodiment), a ground electrode is arranged on the inner periphery of the metal shell 30, and the ground electrode and the center electrode 50 are arranged. It is naturally possible to apply this embodiment to a spark plug that generates a discharge between the two.

  In the above-described embodiment, the case where the ground electrode 40 and the center electrode 50 each include the chips 42 and 54 has been described. However, the present invention is not necessarily limited thereto. Of course, it is possible to omit the chips 42 and 54.

  In the above embodiment, the case where the jig 70 includes the overhanging portion 73 has been described, but the present invention is not necessarily limited thereto. In the ground electrode 40 described in the embodiment, since the holes other than the through hole 43 are not formed, the overhanging portion 73 can be omitted. A jig 80 in a modification in which the overhanging portion 73 is omitted will be described with reference to FIG. 5A is a side view of the jig 80 in the modification, FIG. 5B is a bottom view of the jig 80, and FIG. 5C is a view taken along the line Vc-Vc in FIG. 5B. 3 is a cross-sectional view of a jig 80. FIG.

  The jig 80 includes a grip part 81 that is gripped by a chuck (not shown), a columnar base part 82 that is connected in the direction of the axis O of the grip part 81, and a cylinder that is connected to the end face of the base part 82 in the direction of the axis O. Part 83. The cylindrical portion 83 is formed with an annular end surface 84 that contacts the ground electrode 40 around the through hole 43 (see FIG. 2). The end face 84 is formed with an inner diameter larger than the inner diameter of the through hole 43.

  Since welding is performed with the end face 84 of the jig 80 contacting the ground electrode 40 (see FIG. 2) and covering the through hole 43, it is possible to prevent spatter from entering the through hole 43 and the cavity 37. In addition, the jig 80 has a smaller cross-sectional area (area of the end face 84) perpendicular to the axis O of the cylinder portion 83 than the cross-sectional area perpendicular to the axis O of the base 82. Because the difference in cross-sectional area can cause a difference in the heat flux of the cylinder portion 83 and the heat flux of the base portion 82, the cooling rate of the weld metal can be suppressed, and weld cracks and poor penetration can hardly occur.

  In the above embodiment, the plate-like member (including the ground electrode 40) has been described with respect to the case where the through hole 43 is formed on the axis O (the center of the plate-like member), but is not necessarily limited thereto. Absent. Even if the through hole 43 is not on the axis O, its position can be appropriately set as long as it is formed at the center of the plate-like member.

  In the above embodiment, the case where one through hole 43 is formed in a plate-like member (including the ground electrode 40) has been described. However, the present invention is not necessarily limited to this, and the through-hole 43 is formed in the plate-like member. Of course, it is possible to form a plurality of layers.

DESCRIPTION OF SYMBOLS 10 Spark plug 20 Insulator 21 Shaft hole 30 Metal shell 40 Ground electrode (plate-shaped member)
43 Through hole 70, 80 Jig 72, 82 Base 73 Overhang 74, 83 Tube 75, 84 End face O Axis

Claims (3)

An insulator having an axial hole extending in the axial direction, a cylindrical metal shell that holds the insulator inside, and a through hole that is disposed at one end of the metal shell and penetrates in the axial direction are formed in the center A spark plug comprising a plate-shaped member,
An assembly step of assembling the insulator inside the metal shell;
An arrangement step of arranging the plate-like member at one end of the metal shell assembled with the insulator;
A welding step of laser welding the plate-like member to the metal shell in a state where a jig is brought into contact with the plate-like member and the plate-like member is pressed against the metal shell,
The jig includes an annular end surface that comes into contact with the plate-shaped member around the through-hole,
The method of manufacturing an ignition plug, wherein the welding step includes performing welding in a state where the end face of the jig is in contact with the plate-like member and covers the through-hole of the plate-like member. The jig includes a projecting portion having a larger outer shape than the annular end surface at a position away from the end surface by a predetermined distance in the axial direction.
2. The spark plug manufacturing method according to claim 1, wherein, in the welding step, the overhanging portion faces the plate-like member with a predetermined interval. The jig includes a cylindrical portion provided with the annular end surface, and a base portion connected to the opposite side of the cylindrical portion along the axis.
The spark plug manufacturing method according to claim 1, wherein an area of the end face is smaller than an area of a cross section perpendicular to the axis of the base.

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