JP3272489B2 - Spark plug manufacturing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a spark discharge gap formed between an end of an outer spark durability improving material (made of a noble metal or a noble metal alloy) joined to an outer electrode and a side surface of a center electrode. And a method for manufacturing a spark plug.

[0002]

2. Description of the Related Art The following three techniques are known as methods for manufacturing a spark plug in which an outer electrode made of a noble metal or a noble metal alloy is joined to an outer electrode. (A) As shown in FIG. 12 and FIG.
Pt-Ir, by electric resistance welding, on the surface of the linear (before bending substantially L-shaped) outer electrode 120 joined to the outer electrode 120.
The outer spark durability improving material 130 such as a Pt-Ni alloy is joined, and then the spacer 150 is sandwiched between the end face of the center electrode 140 and the outer spark durability improving material 130 so as to form a spark discharge gap. The electrode 120 is bent into a substantially L-shape (first prior art). (B) As shown in FIG. 14, on the end face of the metal shell 110,
A short pedestal 160 extending in the cylinder direction is joined. Next, the outer electrode 120 having the outer spark durability improving material 130 formed in advance at the end is joined by electric resistance welding. During this joining, the side surface of the center electrode 140 and the outer spark durability improving material 13
The spacer 150 is sandwiched so that a spark discharge gap is formed between the spacer 150 and the first discharge gap (second prior art),
No. 04491). (C) As shown in FIG. 15, the linear outer electrode 120 joined to the metal shell 110 is joined, and then bent into a substantially L-shape. Next, the outer spark durability improving material 130 is joined to the distal end surface of the outer electrode 120 by electric resistance welding. At the time of this joining, the spacer 150 is sandwiched so that a spark discharge gap is formed between the end face of the center electrode 140 and the outer spark durability improving material 130 (third conventional technique),
No. 104491).

[0003]

The three techniques described above have the following disadvantages. (D) First, the manufacturing method shown in the first prior art (a) is as follows.
A spark discharge gap is formed between the end face of the center electrode 140 and the outer spark durability improving material 130. On the other hand, in the spark plug manufactured according to the present invention, a spark discharge gap is formed between the side surface of the center electrode 140 and the outer spark durability improving material 130. That is, the substantially L-shaped outer electrode 12
When 0 is adopted, the length of the outer electrode 120 of the present invention is:
It is shorter than before. For this reason, when the spark plug is manufactured using the first conventional technique (a), the outer spark durability improving material 130 joined to the outer electrode 120 is bent into a substantially L-shape by the center electrode obstructing insulation. After the body is assembled, it is impossible. (E) In the manufacturing method shown in the second prior art (b), when the outer electrode 120 is electric resistance welded to the pedestal 160, pressure is applied to the pedestal 160 by electric resistance welding, and the pedestal 160 is deformed. . When the base 160 is deformed, the performance of the spark plug is adversely affected. (F) In the manufacturing method shown in the third prior art (c), when the outer spark durability improving material 130 is electric resistance welded to the outer electrode 120, the curved portion of the outer electrode 120 is pressurized by electric resistance welding. Receiving welding electrode 170 is applied. However, it is difficult to stably obtain the contact between the welding electrode 170 and the curved portion of the outer electrode 120. If the stability between the welding electrode 170 and the outer electrode 120 is not obtained, welding between the outer electrode 120 and the outer spark durability improving material 130 cannot be stably performed.

[0004]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and has as its object the purpose of providing a structure between a side surface of a center electrode and an outer spark durability improving material using a noble metal bonded to an outer electrode. Another object of the present invention is to provide a manufacturing method capable of manufacturing a spark plug in which spark discharge is performed with high quality and high productivity.

[0005]

According to a first aspect of the present invention, there is provided a method for manufacturing a spark plug, comprising: a side surface of a central electrode extending in an axial shape; A spark plug manufacturing method for forming a spark discharge gap with an end of a spark durability improving material, comprising: (a) joining to an end surface of a cylindrical metal shell by electric resistance welding in which at least the end is directed inward; A first step of providing a shaped outer electrode. (B) After the first step, a rod-shaped outer spark durability improving material is applied to the outer electrode in a state where a part of the outer spark durability improving material projects inward from the inner end of the outer electrode. A second step of joining the metal shell to a surface of the metal shell facing one side in the cylindrical direction by electric resistance welding; (C) After the second step, it is manufactured by using each step of a third step of incorporating an insulator for insulating and holding the center electrode in the metal shell.

According to a second aspect of the present invention, in the method for manufacturing a spark plug according to the first aspect, the first step is to join an outer electrode formed in a square rod shape to an end face of the metal shell by electric resistance welding. 1-1 step to perform, and 1-1
After the step, the outer electrode joined to the metal shell is bent into a substantially L-shape, and a bent step is directed to an inner side of the metal shell.

According to a third aspect of the present invention, in the method for manufacturing a spark plug according to the second aspect, the first to second steps are:
After bending the outer electrode into a substantially L-shape, the inner end is cut to adjust the position of the inner end.

According to a fourth aspect of the present invention, in the method for manufacturing a spark plug according to the second or third aspect, when a plurality of the outer electrodes are provided, the plurality of the outer electrodes are simultaneously bent into a substantially L-shape. It is characterized by.

According to a fifth aspect of the present invention, in the method of manufacturing a spark plug according to any one of the first to fourth aspects, the outer spark durability improved in the second step is joined to the outer electrode. The inner end of the material protruding toward the center electrode is joined to a predetermined position assuming a spark discharge gap.

According to a sixth aspect of the present invention, there is provided a method of manufacturing a spark plug according to any one of the first to fifth aspects, wherein an end of the outer spark durability improving material and a side surface of the center electrode are provided. A fourth step of adjusting the spark discharge gap formed therebetween by attaching a centering ring having the same dimension as the spark discharge gap around the center electrode is provided.

[0011]

The operation of the first aspect will now be described. First,
In the process, an outer electrode is provided on the metal shell. The end of the outer electrode is directed toward the inside of the metal shell. In the next second step, the outer spark durability improving material is joined to the outer electrode by electric resistance welding. At the time of this joining, the outer spark durability improving material is joined to a surface of the outer electrode facing one side in the tube direction (for example, the upper or lower surface of the outer electrode when the tube direction goes upward or downward). Further, during this joining, a part of the outer spark durability improving material is joined to the outer electrode while projecting inward from the inner end of the outer electrode. In the next third step, an insulator holding the center electrode is incorporated in the metal shell.

[0012]

The invention of claim 1 has the following effects.
The outer spark durability improving material is joined to a surface of the outer electrode facing inward from the metal shell in one of the cylindrical directions. For this reason, since processing such as bending of the outer electrode is not performed thereafter, cracks do not enter the joint surface between the outer electrode and the outer spark durability improving material. Thereby, a high quality spark plug can be provided. Further, when performing the electric resistance welding between the outer electrode and the outer spark durability improving material, the outer electrode and the outer spark durability improving material are pressed in the cylinder direction of the metal shell by an electric resistance welding machine. The outer electrode portion joined to the outer spark durability improving material extends inside the metal shell. For this reason, the positional relationship between the outer electrode and the outer spark durability improving material is a relationship extending in the cylinder direction of the metal shell. Further, when performing the electric welding, since the center electrode and the insulator do not exist in the metal shell, the welding electrode for performing the electric welding can be easily arranged in the cylinder direction at the end of the outer electrode. For these reasons, the outer electrode and the outer spark durability improving material are stably pressed by the welding electrode that performs electric resistance welding. As a result, a spark plug of high quality can be provided using electric resistance welding excellent in productivity.

According to a second aspect of the present invention, the outer electrode has a substantially L-shape. That is, the present invention can be applied to a spark plug widely used.

According to a third aspect of the present invention, a long outer electrode is previously joined to a metal shell, and after joining, bent into a substantially L-shape.
This is a technique for cutting off unnecessary ends. According to this technique, since the longer outer electrode is bent into a substantially L-shape,
The outer electrode can be easily and stably bent into a substantially L-shape.

According to a fourth aspect of the present invention, when manufacturing a multi-pole opposed type spark plug having two or more outer poles, a plurality of outer electrodes are simultaneously bent into a substantially L-shape, thereby reducing the number of manufacturing steps.

According to a fifth aspect of the present invention, when the outer spark durability improving material is joined to the outer electrode, the inner end portion of the outer spark durability improving material protruding toward the center electrode has a predetermined shape assuming a spark discharge cap. This is a technique of joining at a position. The use of this technique facilitates the adjustment of the spark discharge gap.

According to a sixth aspect of the present invention, after the insulator holding the center electrode is incorporated in the metal shell, a spark discharge gap between the outer spark durability improving material and the center electrode is formed around the center electrode. This technology adjusts the thickness by mounting a centering ring with the same size as the spark discharge gap. By using this technique, it is possible to suppress variations in the spark discharge gap.

[0018]

Next, a method of manufacturing a spark plug according to the present invention will be described with reference to an embodiment shown in the drawings. 1 to 7 show an embodiment of the present invention. FIG. 1 is a sectional view of a spark plug manufactured by the manufacturing method of the present invention, and FIG. It is a part perspective view. The spark plug 1 is roughly divided into a cylindrical metal shell 2 fixed to the engine, an insulator 3 held inside the metal shell 2, and a shaft extending insulated and held inside the insulator 3. A central electrode 4 and a substantially L-shaped outer electrode 5 joined to the end of the metal shell 2 are provided. The upper surface of the outer electrode 5 (a surface facing one side of the cylindrical direction of the metal shell 2, FIGS. 1 and 2) A rod-shaped outer spark durability improving material 6 is joined to the middle and upper surfaces).

The metallic shell 2 is a cylindrical metal fitting made of an iron-based metal or a conductive metal such as low carbon steel which is screwed to the engine while holding the insulator 3, and is screwed to the engine. A screw portion 7 is provided with a hexagon bolt portion 8 which engages with a tool for fastening the screw portion 7 to the engine. An annular flange 9 is formed between the screw 7 and the hexagonal bolt 8, that is, at the center of the metal shell. A shaft hole 10 for inserting and holding the insulator 3 is provided inside the metal shell 2.
Are formed. A locking portion 11 for locking the insulator 3 is provided in the shaft hole 10 in an annular shape so as to protrude inward.

The insulator 3 is made of an insulating material having excellent heat resistance, such as a sintered ceramic such as alumina.
The metal fitting 2 is formed by caulking the caulking portion 12 at the end of
Is held in the shaft hole 10.

The center electrode 4 is a rod-shaped conductor made of nickel alloy or the like to which a high voltage is applied from an igniter (not shown). The tip of the center electrode 4 has a side surface at the tip and an outer spark durability improving material 6. Are held by the insulator 3 so as to protrude from the end of the insulator 3 so as to form a spark discharge gap G therebetween.

The outer electrode 5 is a ground electrode which is grounded to the engine via the metal shell 2, and is a single metal material such as nickel alloy or inconel which is excellent in heat resistance and corrosion resistance.
Alternatively, the metal shell 2 is made of a composite electrode in which a material (eg, copper) excellent in heat removal is disposed, and the material excellent in heat removal is covered with a metal material excellent in heat resistance and corrosion resistance.
Is joined using welding technology. The outer electrode 5 extends upward (upward in FIGS. 1 and 2) from the end face of the metal shell 2 and has a substantially L-shape extending toward the side surface of the center electrode 4 after bending. The end face is provided facing the side face of the center electrode 4. The distance between the end surface of the outer electrode 5 and the side surface of the center electrode 4 is set slightly longer than the spark discharge gap G.

The outer spark durability improving material 6 has the shape of a rectangular pillar (having a cross-sectional area of 1 mm ² or less) made of a noble metal (for example, a platinum alloy) having excellent spark wear resistance. Are joined by electric resistance welding.
The outer spark durability improving material 6 is joined to the outer electrode 5 with one end protruding from the end surface of the outer electrode 5 on the side of the center electrode 4 toward the center electrode 4. A spark discharge gap G is formed between the end face of the outer spark durability improving material 6 (the end face protruding toward the center electrode 4) and the side face of the center electrode 4.

[Manufacturing method] Next, the spark plug 1
FIGS. 3 to 7 show a method of manufacturing (a main part according to the present invention).
This will be described with reference to FIG. (1-1 step in the first step) First, as shown in FIG. 3, an outer electrode 5 formed in a rod shape having a rectangular cross section is attached to an end face of a metal shell 2 formed in a cylindrical shape by a welding technique (for example, (Electric resistance welding). In addition, the length of the rod-shaped outer electrode 5 to be joined is set to be slightly longer than necessary in order to easily and surely bend when bending into a substantially L-shape in the next step. .

(Step 1-2 in the first step)
As shown in FIG. 4, the rod-shaped outer electrode 5 joined to the metal shell 2 is bent into a substantially L-shape so that the bending direction is directed toward the inside of the metal shell 2. Due to this bending, the end is directed in a direction perpendicular to the cylinder direction (axial direction) of the metal shell 2. The forming machine that performs this bending process includes a bending inner mold 2 having a forming surface 21 having a shape corresponding to a predetermined bending shape of the outer electrode 5.
2 and the metal shell 2 are moved in the cylindrical direction (from the upper side to the lower side in the figure) to bend the outer electrode 5 into the molding surface 2 of the inner mold 22.
1 is provided with a bending punch 23 which is pressed against and plastically deforms. Note that, when the outer electrode 5 is bent in the 1-2 step, the concentration of stress occurs in a part of the outer electrode 5 because the length of the outer electrode 5 is longer than a required length in advance. It is possible to easily and surely bend it into a predetermined shape without any problem.

Next, as shown in FIG. 5, an unnecessary portion of the end of the outer electrode 5 is cut, and the position of the inner end of the outer electrode 5 is adjusted. The cutting machine for performing the cutting includes a cutting holder 24 fitted into the shaft hole 10 of the metal shell 2, a cutting punch 25 that moves downward from above in the figure to cut unnecessary portions of the outer electrode 5, and the like. ing. At the time of this cutting, a groove for fitting the outer spark durability improving material 6 may be formed on the upper surface of the end of the outer electrode 5.

(Second Step) Next, as shown in FIG. 6, the upper surface of the end of the outer electrode 5 in the drawing (this surface is
The rod-shaped outer spark durability improving material 6 is joined by electric resistance welding. By this joining, a part of the outer spark durability improving material 6 protrudes inward from the end of the outer electrode 5, and the position of the inner end is joined to a position where a spark discharge gap G is assumed in advance. . The welding machine for performing the electric resistance welding includes a welding ground electrode 2 fitted in a shaft hole 10 of the metal shell 2.
6 and a welding mother electrode 27 which moves downward from above in the figure to press the outer spark durability improving material 6 against the outer electrode 5 to apply a high voltage. The outer diameter φ of the welding ground electrode 26 is provided to have the same size as the inner diameter of the locking portion 11 of the metal shell 2, and the positioning step 28 for adjusting the position of the end of the outer spark durability improving material 6. Is provided so as not to always change with respect to the metal shell 2. Thereby, the position of the end of the outer spark durability improving material 6 is
Since the distance falls within the predetermined position range, the gap adjustment performed in a later step can be easily performed. In addition, an insulating layer 29 is provided on the positioning step 28 of the welding earth electrode 26, and the welding earth electrode 2 is
6 is prevented from flowing electricity directly.

(Third Step) Next, after subjecting the metal shell 2 to a surface treatment (plating), as shown in FIG. 7, an insulating material holding the center electrode 4 in a shaft hole 10 of the metal shell 2 is formed. Incorporate body 3.

(Fourth Step) Next, as shown in FIG. 7, a centering ring 30 having the same size as the spark discharge gap G is mounted around the center electrode 4 so that the center electrode 4 and the outer spark endurance are fixed. The spark discharge gap G with the property improving material 6 is set to be in a predetermined dimension. Then, while maintaining this state,
The caulking portion 12 at the end of the metal shell 2 is swaged, and the metal shell 2
The insulator 3 is firmly fixed inside. As a result, the spark discharge gap G between the center electrode 4 and the outer spark durability improving material 6 is adjusted to a predetermined size. Through the above steps,
The spark plug 1 is formed. The fourth step is not essential, and in the second step, the assumed position of the spark discharge gap G between the end of the outer spark durability improving material 6 and the insulating layer 29 is accurately and accurately determined. When the dimensional accuracy of the metal fitting 2 such as the axial hole size, the center electrode diameter, and the insulator outer diameter is improved, a predetermined spark discharge gap G can be formed by assembling in the third step, and the fourth step is omitted. be able to.

[Effects of the First Embodiment] According to the method of manufacturing the spark plug 1 of the present embodiment, the outer spark durability improving material 6 is used.
Is joined to the upper surface of the outer electrode 5 after being bent into a substantially L-shape. Therefore, after joining the outer spark durability improving material 6,
No force such as plastic deformation is applied to the outer electrode 5. As a result,
There is no crack at the joint surface between the outer electrode 5 and the outer spark durability improving material 6. Thereby, a high quality spark plug 1 can be provided. When the outer electrode 5 and the outer spark durability improving material 6 are joined by electric resistance welding,
The outer electrode 5 and the outer spark durability improving material 6 are pressed by the welding machine in the cylinder direction (vertical direction) of the metal shell 2. The portion of the outer electrode 5 to which the outer spark durability improving material 6 is joined extends perpendicularly to the cylinder direction of the metal shell 2. Therefore, the outer electrode 5 and the outer spark durability improving material 6 are stably pressurized between the welding earth electrode 26 and the welding mother electrode 27 for performing electric resistance welding. As a result, the outer electrode 5 and the outer spark durability improving material 6 can be reliably welded by electric resistance welding excellent in mass productivity, and a high quality spark plug 1 can be provided with good mass productivity.

Further, when the outer electrode 5 and the outer spark durability improving material 6 are subjected to electric resistance welding, the center electrode 4 and the insulator 3 do not exist in the shaft hole 10 of the metal shell 2.
Therefore, at the time of electric resistance welding, the welding ground electrode 26 for performing electric resistance welding could be arranged in the shaft hole 10 of the metal shell 2. As a result, the outer electrode 5 and the outer spark durability improving material 6 can be joined with good productivity, and the position of the end of the outer spark durability improving material 6 can be accurately determined for securing the spark discharge gap G. Location.

[Second Embodiment] FIGS. 8 to 10 are explanatory views of a main part of a spark plug manufacturing method according to a second embodiment of the present invention. This embodiment shows a technique for manufacturing an outer two-pole facing type spark plug 1 using two substantially L-shaped outer electrodes 5. First, the outer electrodes 5 are respectively joined to the upper surface of the metal shell 2 by a welding technique (Step 1-1). In addition, the length of the two outer electrodes 5 used in the present embodiment is slightly longer than necessary in order to make the bending easy and reliable when being bent into a substantially L-shape in the next step. Is provided.

Next, as shown in FIG. 8, the two outer electrodes 5 joined to the metal shell 2 are bent into a substantially L-shape so that their ends are directed toward the inside of the metal shell 2 (first). -2
Process). By this bending, the end of the outer electrode 5 is directed in a direction perpendicular to the cylinder direction of the metal shell 2. The forming machine for performing the bending process includes the bending inner mold 31 fitted into the shaft hole 10 of the metal shell 2 and the end of the two outer electrodes 5 moving downward from the upper side in the figure to the bending inner mold 31. Bending punch 3 that simultaneously presses against the surface of the steel and plastically deforms into an approximately L-shape
2 and so on. The bending punch 32 has a forming surface 33 having a shape corresponding to a predetermined bending shape of the outer electrode 5.

Next, unnecessary portions of the ends of the two outer electrodes 5 are simultaneously cut to adjust the positions of the inner ends of the outer electrodes 5.

Next, as shown in FIG. 9, rod-shaped outer spark durability improving members 6 are joined to the upper surfaces of the ends of the two outer electrodes 5 by electric resistance welding (second).
Process). By this joining, a part of each outer spark durability improving material 6 protrudes inward from the end of the outer electrode 5, and the position of this inner end is joined to a position assuming the spark discharge gap G in advance. Is done. The welding machine that performs this electric resistance welding presses the welding earth electrode 26 fitted into the shaft hole 10 of the metal shell 2 and the outer spark durability improving material 6 by moving downward from above in the figure to the outer electrode 5. It is composed of a welding mother electrode 27 to which a high voltage is applied. On the upper surface of the welding ground electrode 26, there is provided a positioning step 28 for aligning the ends of the two outer spark durability improving members 6. As a result, the position of the end of the outer spark durability improving material 6 falls within the predetermined position range, so that the gap adjustment performed in a later step can be easily performed. Note that an insulating layer is provided on the surface of the step portion 28 to prevent a current from flowing directly from the outer spark durability improving material 6 to the welding ground electrode 26.

Next, as shown in FIG. 10, the insulator 3 holding the center electrode 4 is incorporated into the shaft hole 10 of the metal shell 2 (third step).

Next, as shown in FIG. 10, a centering ring 30 having the same thickness as the spark discharge gap G is mounted around the center electrode 4, and the center electrode 4 and two outer spark durability improving materials are attached. 6 is set to a state in which the spark discharge gap G is within a predetermined dimension. Next, while maintaining this state, the caulking portion 12 at the end of the metal shell 2 is swaged, and the insulator 3 is firmly fixed in the metal shell 2 (fourth step). Thereby, the spark discharge gap G between the center electrode 4 and the two outer spark durability improving materials 6 is adjusted to be within a predetermined dimension. Through the above steps, the spark plug 1 is formed.

Third Embodiment FIG. 11 is an explanatory view of a main part of a spark plug manufacturing method according to a third embodiment. The present embodiment is a technique of a second step of joining the outer spark durability improving material 6 to the lower surface of the outer electrode 5 (the surface facing the other side in the cylindrical direction of the metal shell 2) by electric resistance welding. The welding machine used in the second step includes a welding earth electrode 26 fitted in the shaft hole 10 of the metal shell 2 and an outer spark durability improving material 6 which moves downward from above in the figure to the outer electrode 5. It is composed of a welding mother electrode 27 for applying a high pressing voltage. An alignment step 28 is formed on the upper surface of the welding ground electrode 26, and the position of the end of the outer spark durability improving material 6 is set within a predetermined position range. Thereby, the gap adjustment performed in the next step can be easily performed.

[Modification] In the above-described embodiment, an example is shown in which the shape of the outer spark durability improving material is a square pole.
For example, any shape, such as a cylinder, a triangular prism, or a polygonal prism having five or more pentagonal pillars, may be used as long as it is joined to the upper or lower surface of the outer electrode and projects toward the center electrode 4. The material of each component used in the above embodiment is used to facilitate understanding of the embodiment, and the present invention is not limited to the material of the embodiment. To give a specific example,
Although an example using platinum as an example of a noble metal material used for the outer spark durability improving material was shown, such as iridium, palladium, rhodium, gold or an alloy mainly containing these,
Other noble metal materials may be used. A noble metal having excellent spark wear resistance may be used on the side surface of the center electrode facing the outer spark durability improving material. The number of outer electrodes is one and two
Although an example using one is shown, three or more may be used. Although the example in which the outer electrode is formed in a substantially L-shape is shown, a linear electrode extending from the inner peripheral surface at the end of the metal shell toward the center electrode may be used. Further, the outer electrode is provided in a ring shape integral with the metal shell (provided like an air-discharge or semi-surface discharge type outer electrode), and one or more rod-shaped outer spark durability improving materials are joined on the upper surface thereof. You may.

In the case where the outer electrode is formed in a substantially L-shape, an example in which the longer outer electrode is joined to the metal shell in advance, and the unnecessary portion is cut after bending is shown. May be joined to the metal shell and bent. As an example of adjusting the spark discharge gap, an example in which the insulator is adjusted when the insulator is fixed in the metal shell has been described.After fixing the insulator in the metal shell, the outer spark durability improving material or the center electrode is polished. If the outer electrode can be plastically deformed in the direction perpendicular to the cylindrical direction of the metal shell, the gap can be adjusted by other means, such as by adjusting the gap by cutting, or by slightly bending the outer electrode. May be adjusted. Each direction of the metal shell in each process, in order to help understand the example,
Although the example in which the outer electrode is located above has been described, the present invention is not limited to the embodiment, and the direction of the metal shell is in any direction such as a top-to-bottom direction, a horizontal direction, and an oblique direction. Is also good.

[Brief description of the drawings]

FIG. 1 is a sectional view of a spark plug (first embodiment).

FIG. 2 is a perspective view of a main part of the spark plug (first embodiment).

FIG. 3 is an explanatory view showing a 1-1 step (first embodiment).

FIG. 4 is an explanatory view showing a 1-2 step (first embodiment).

FIG. 5 is an explanatory diagram showing cutting of an unnecessary portion of an outer electrode in a 1-2 step (first embodiment).

FIG. 6 is an explanatory view showing a second step (first embodiment).

FIG. 7 is an explanatory view showing a third step and a fourth step (first embodiment).

FIG. 8 is an explanatory view showing a 1-2 step (second embodiment).

FIG. 9 is an explanatory view showing a second step (second embodiment).

FIG. 10 is an explanatory view showing a third step and a fourth step (second embodiment).

FIG. 11 is an explanatory view showing a second step (third embodiment).

FIG. 12 is an explanatory view showing a step of joining an outer spark durability improving material to an outer electrode (first conventional technique).

FIG. 13 is an explanatory view showing a step of bending an outer electrode into a substantially L shape (first conventional technique).

FIG. 14 is an explanatory view showing a step of joining an outer electrode to which an outer spark durability improving material has been joined to a pedestal (second conventional technique).

FIG. 15 is an explanatory view showing a step of joining an outer spark durability improving material to an outer electrode bent in a substantially L shape (third conventional technique).

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Spark plug 2 Metal shell 3 Insulator 4 Center electrode 5 Outer electrode 6 Outer spark durability improving material G Spark discharge gap

Claims (6)

(57) [Claims] 1. A spark discharge gap is formed between a side surface of a central electrode extending axially and an end of an outer spark durability improving material made of a noble metal having excellent spark erosion resistance and joined to the outer electrode. In the method for manufacturing a spark plug to be formed , (a) a first step of providing an outer electrode joined to an end face of a cylindrical metal shell by electric resistance welding in which at least the end faces inward. (B) After the first step, a rod-shaped outer spark durability improving material is applied to the outer electrode in a state where a part of the outer spark durability improving material projects inward from the inner end of the outer electrode. A second step of joining the metal shell to a surface of the metal shell facing one side in the cylindrical direction by electric resistance welding; (C) A third step of incorporating an insulator for insulating and holding the center electrode in the metal shell after the second step. Characterized by being manufactured using each of the steps of
Rug manufacturing method . 2. The method of manufacturing a spark plug according to claim 1, wherein in the first step, an outer electrode formed in a square rod shape is joined to an end face of the metal shell by electric resistance welding.
One step and a 1-2 step in which the outer electrode joined to the metal shell is bent into a substantially L-shape after the 1-1 step, and the bent end faces toward the inside of the metal shell. Spark plug manufacturing method. 3. The method for manufacturing a spark plug according to claim 2, wherein in the 1-2 step, after bending the outer electrode into a substantially L-shape, the inner electrode is cut to form an inner electrode. A method for manufacturing a spark plug, comprising adjusting a position. 4. The spark plug manufacturing method according to claim 2, wherein, when a plurality of said outer electrodes are provided, a plurality of said outer electrodes are simultaneously bent into a substantially L-shape. Plug manufacturing method. 5. The method of manufacturing a spark plug according to any one of claims 1 to 4, the center electrode side of the outer spark durability improvement material to be joined to the outer electrode in the second step inner end of the protruding side is the,
A method for manufacturing a spark plug, wherein the spark plug is joined at a predetermined position assuming a spark discharge gap. 6. The method for manufacturing a spark plug according to any one of claims 1 to 5, is formed between the side surface of the end portion and the center electrode of the outer spark durability material a spark discharge gap, the center electrode
Around the center of the spark discharge gap.
A method for manufacturing a spark plug, comprising a fourth step of mounting and adjusting a spark plug.