JPH0722157A - Manufacture of spark plug - Google Patents

Abstract

PURPOSE:To manufacture spark plugs in high quality and with good mass- producibility, wherein the spark plug is to make spark discharging between the side face of a center electrode and an outside spark durability enhancing material using a noble metal joined with the outside electrode. CONSTITUTION:An L-form outside electrode 5 is formed at a cylindrical metal piece 2 as the body, and an outside spark durability enhancing material 6 is joined with the oversurface of the outside electrode 5 by means of the electric resistance welding before a center electrode 4 and an insulative material 3 are installed in the metal piece 2. The insulative material 3 is fixed in the metal piece 2 while the spark discharge gap G is maintained with an aligning ring, and gap adjustment takes place. Because the outside enhancing material 6 is joined with the bent outside electrode 5 by the electric resistance welding prior to the installation of the center electrode 4 and insulative material 3, the spark plug can be fabricated in high quality and with good producibility.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a spark discharge gap formed between an end portion 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. The present invention relates to a method for manufacturing a spark plug.

[0002]

2. Description of the Related Art The following three techniques are known as a method for manufacturing a spark plug in which an outer spark durability improving material made of a noble metal or a noble metal alloy is joined to an outer electrode. (A) As shown in FIGS. 12 and 13, the metal shell 11
On the surface of the linear outer electrode 120 (before bending into a substantially L shape) joined to 0, Pt-Ir,
The outer spark durability improving material 130 such as a Pt-Ni alloy is joined, and then the spacer 150 is sandwiched so that the end surface of the center electrode 140 and the outer spark durability improving material 130 form a spark discharge gap. The electrode 120 is bent into a substantially L shape (first conventional technique). (B) As shown in FIG. 14, on the end surface of the metallic 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 previously formed on the end portion is joined by electric resistance welding. At the time of this bonding, 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 spacers 150 and 0 (second prior art).
(See claim 7 of JP 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 tip end surface of the outer electrode 120 by electric resistance welding. At the time of this bonding, the spacer 150 is sandwiched so that a spark discharge gap is formed between the end surface of the center electrode 140 and the outer spark durability improving material 130 (third prior art),
(See claim 10 of Japanese Patent Laid-Open No. 104491).

[0003]

The three techniques described above have the following drawbacks, respectively. (D) First, the manufacturing method shown in the first related art (a) is
A spark discharge gap is formed between the end surface 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 will be shorter than before. Therefore, 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 insulated by bending the center electrode in a bending process into a substantially L shape. It is impossible after the body is assembled. (E) In the manufacturing method shown in the second related art (b), when the outer electrode 120 is electrically resistance-welded to the pedestal 160, a pressure is applied to the pedestal 160 to cause the pedestal 160 to deform. . When the pedestal 160 is deformed, the performance of the spark plug is adversely affected. (F) In the manufacturing method shown in the third related art (c), when the outer spark durability improving material 130 is resistance-welded to the outer electrode 120, pressure is applied to the curved portion of the outer electrode 120 by electric resistance welding. Welding electrode 170 is received. 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 of the welding electrode 170 and the outer electrode 120 is not obtained, there is a problem that the outer electrode 120 and the outer spark durability improving material 130 cannot be stably welded.

[0004]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and an object thereof is to provide a side surface of a center electrode and an outer spark durability improving material using a precious metal joined to the outer electrode. The present invention is to provide a manufacturing method capable of manufacturing a spark plug that causes a spark discharge with high quality and with high mass productivity.

[0005]

According to a first aspect of the present invention, there is provided an outer spark durability improving material using a side surface of an axially extending center electrode and a noble metal joined to the outer electrode and having excellent spark wear resistance. A spark plug that forms a spark discharge gap with the end is manufactured using the following steps. (A) A first step in which an outer electrode having at least an end portion directed inward is provided on an end of a tubular metal shell. (B) a rod-shaped outer spark durability improving material, with a part of the outer spark durability improving material protruding inward from an inner end portion of the outer electrode, in a cylindrical direction of the metal shell of the outer electrode. The second step of joining the one-sided surface by electric resistance welding. (C) A third step of incorporating an insulator for insulatingly holding the center electrode in the metal shell.

According to a second aspect of the present invention, in the spark plug manufacturing method according to the first aspect, in the first step, an outer electrode formed in a rectangular rod shape is joined to an end surface of the metal shell by welding. It is characterized by comprising a 1-1 step and a 1-2 step in which the outer electrode joined to the metal shell is bent into a substantially L-shape and the bent end portion is directed to the inside of the metal shell.

According to a third aspect of the present invention, in the spark plug manufacturing method according to the second aspect, the first and 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 the 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 substantially L-shaped at the same time. It is characterized by bending to.

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

According to a sixth aspect of the present invention, in the method for manufacturing the spark plug according to any of the first to fifth aspects, between the end portion of the outer spark durability improving material and the side surface of the center electrode. It is characterized by comprising a fourth step of adjusting the spark discharge gap to be formed within a predetermined dimension.

[0011]

The operation of claim 1 will be described below. First of all
In the process, an outer electrode is provided on the metal shell. The end portion of the outer electrode faces 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 one surface of the outer electrode facing one side in the cylinder direction (for example, the upper surface or the lower surface of the outer electrode when the cylinder direction is upward or downward). Further, at the time of this joining, a part of the outer spark durability improving material is joined to the outer electrode in a state of protruding inward from the inner end portion of the outer electrode. In the next third step, the insulator holding the center electrode is incorporated into 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, the surface facing one side in the cylinder direction. For this reason, after that, since processing such as bending of the outer electrode is not performed, cracks do not occur in the joint surface between the outer electrode and the outer spark durability improving material. This can provide a high quality spark plug. When performing 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 by the electric resistance welding machine in the cylinder direction of the metal shell. The outer electrode portion joined to the outer spark durability improving material extends inside the metal shell. Therefore, the outer electrode and the outer spark durability improving material have a positional relationship in which the outer electrode extends in the cylinder direction of the metal shell. Furthermore, when performing this electric welding, since the center electrode and the insulator do not exist in the metal shell, the welding electrode for performing electric welding can be easily arranged in the cylinder direction at the end of the outer electrode. From these facts, 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 high-quality spark plug can be provided by using electric resistance welding with excellent productivity.

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

According to the third aspect of the invention, the longer outer electrode is joined to the metal shell in advance, and after joining, bent into a substantially L-shape, and thereafter.
This is a technique for cutting off unnecessary end portions. 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 the fourth aspect of the present invention, when manufacturing a spark plug having a plurality of poles facing each other and having two or more poles on the outer side, the plurality of outer electrodes are bent at the same time into a substantially L shape, so that the number of manufacturing steps is reduced.

According to a fifth aspect of the present invention, when the outer spark durability improving material is joined to the outer electrode, the position of the end face of the outer spark durability improving material is joined to the outer electrode assuming a spark discharge gap. is there. By using this technique, the spark discharge gap can be easily adjusted.

A sixth aspect of the present invention is a technique for adjusting the spark discharge gap between the outer spark endurance improving material and the center electrode after incorporating the insulator holding the center electrode in the metal shell. By using this technique, variations in the spark discharge gap can be suppressed.

[0018]

Next, a method of manufacturing a spark plug according to the present invention will be described based on an embodiment shown in the drawings. [Structure of First Embodiment] FIGS. 1 to 7 show an embodiment of the present invention. FIG. 1 is a sectional view of a spark plug manufactured by a manufacturing method of the present invention, and FIG. FIG. The spark plug 1 is roughly classified into a tubular metal shell 2 fixed to the engine, an insulator 3 held inside the metal shell 2, and a shaft extending insulatively held inside the insulator 3. The center 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 (the surface facing the one side of the metal shell 2 in the cylinder direction, as shown in FIGS. A rod-shaped outer spark durability improving material 6 is joined to the middle and upper surfaces).

The metal shell 2 is a tubular metal fitting made of a ferrous metal or a conductive metal such as low carbon steel that is screwed into the engine while holding the insulator 3 and is screwed into the engine. The screw portion 7 and the hexagonal bolt portion 8 that engages with a tool for fastening the screw portion 7 to the engine are provided. An annular collar-shaped portion 9 is formed between the screw portion 7 and the hexagonal bolt portion 8, that is, in the central portion of the metal shell. Further, the shaft hole 10 for inserting and holding the insulator 3 is provided inside the metal shell 2.
Are formed. In the shaft hole 10, a locking portion 11 that locks the insulator 3 is provided in an annular shape so as to project inward.

The insulator 3 is made of an insulating material having excellent heat resistance, such as a ceramic sintered body of alumina or the like.
By caulking the caulking part 12 at the end of the metal shell 2
It is held in the shaft hole 10 of.

The center electrode 4 is a conductor made of a rod-shaped nickel alloy or the like to which a high voltage is applied from an ignition device (not shown), and the tip of the center electrode 4 is the side surface of this tip and the outer spark durability improving material 6. In order to form a spark discharge gap G between them, the spark discharge gap G is held by the insulator 3 so as to project from the end of the insulator 3.

The outer electrode 5 is a ground electrode that is grounded to the engine through the metal shell 2, and is a simple metallic material such as nickel alloy or Inconel having excellent heat resistance and corrosion resistance.
Alternatively, a composite electrode in which a material excellent in heat dissipation (for example, copper) is disposed inside and a material excellent in heat dissipation is covered with a metal material excellent in heat resistance and corrosion resistance is used.
It is joined to the end face of the using welding technology. The outer electrode 5 has a substantially L-shape that extends upward (upper side in FIGS. 1 and 2) from the end surface of the metal shell 2 and extends toward the side surface of the center electrode 4 after bending. The end surface is provided so as to face the side surface 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 to be slightly longer than the spark discharge gap G.

The outer spark durability improving material 6 is in the form of a square pole (having a cross-sectional area of 1 mm ² or less) made of a noble metal (for example, platinum alloy) excellent in spark wear resistance, and has an upper surface of the outer electrode 5. Are joined by electric resistance welding.
The outer spark durability improving material 6 is joined to the outer electrode 5 in a state where one end thereof partially projects from the end surface of the outer electrode 5 on the center electrode 4 side toward the center electrode 4 side. A spark discharge gap G is formed between the end surface of the outer spark durability improving material 6 (the end surface on the side protruding toward the center electrode 4) and the side surface of the center electrode 4.

[Manufacturing Method] Next, the above spark plug 1
The manufacturing method (main part of the present invention) of FIG.
Will be explained. (Step 1-1 in Step 1) First, as shown in FIG. 3, an outer electrode 5 formed in a rod shape having a rectangular cross section is welded to an end surface of a metal shell 2 formed in a tubular shape by a welding technique (for example, Join by electric resistance welding). The length of the rod-shaped outer electrode 5 to be joined is set to be a little longer than the required length in order to easily and surely bend when the rod-shaped outer electrode 5 is bent into a substantially L shape in the next step. .

(Step 1-2 of Step 1) Next,
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 to the inside of the metal shell 2. By this bending process, the end portion is oriented in the direction perpendicular to the tubular direction (axial direction) of the metal shell 2. The molding machine that performs this bending process includes a bending inner mold 2 having a molding surface 21 having a shape corresponding to a predetermined bending shape of the outer electrode 5.
2, and the metal shell 2 is moved in the cylinder direction (moved from the upper side to the lower side in the drawing) to bend the outer electrode 5 into the molding surface 2 of the inner mold 22.
A bending punch 23 that is pressed against 1 to be plastically deformed is provided. When the outer electrode 5 is bent in the 1-2 step, since the length of the outer electrode 5 is set longer than a required length in advance, stress is concentrated on a part of the outer electrode 5. Without this, it can be bent easily and surely into a predetermined shape.

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

(Second Step) Next, as shown in FIG. 6, a surface above the end of the outer electrode 5 in the figure (this surface is the metal shell 2).
Of the rod-shaped outer spark endurance improving material 6 by electric resistance welding. By this joining, a part of the outer spark durability improving material 6 projects inward from the end of the outer electrode 5, and the position of this inner end is joined in advance to a position where the spark discharge gap G is assumed. . The welding machine that performs this electric resistance welding is equipped with a welding ground electrode 2 fitted in the shaft hole 10 of the metal shell 2.
6, and a welding mother electrode 27 that moves downward from above in the drawing 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 earth electrode 26 is provided in the same size as the inner diameter of the locking portion 11 of the metal shell 2, and the alignment step portion 28 for aligning the position of the end portion of the outer spark durability improving material 6 is provided. Is provided so that it does not always change with respect to the metal shell 2. As a result, the position of the end portion of the outer spark durability improving material 6 becomes
Since it is within the predetermined position range, it is possible to easily perform the gap adjustment performed in the subsequent process. An insulating layer 29 is provided on the positioning step portion 28 of the welding earth electrode 26 so that the welding spark electrode 2 is welded from the outer spark durability improving material 6.
The electricity is prevented from flowing directly to 6.

(Third Step) Next, after subjecting the metal shell 2 to a surface treatment (plating), as shown in FIG. 7, an insulating material in which the center electrode 4 is held in the 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 thickness as the spark discharge gap G is attached around the center electrode 4 to endure the center electrode 4 and the outer spark. The spark discharge gap G with the property improving material 6 is set within a predetermined dimension. Then, while maintaining this state,
Caulking the caulking portion 12 at the end of 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 within a predetermined dimension. By the above process,
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 portion of the outer spark durability improving material 6 and the insulating layer 29 is accurately and When the dimensional accuracy of the shaft hole dimension, the center electrode diameter, the insulator outer diameter, etc. of the metal fitting 2 is improved, the predetermined spark discharge gap G can be formed by the assembly in the third step, and the fourth step is omitted. be able to.

[Effect of First Embodiment] According to the method for manufacturing the spark plug 1 of the present embodiment, the outer spark durability improving material 6
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,
No cracks occur at the joint surface between the outer electrode 5 and the outer spark durability improving material 6. As a result, 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 tubular direction of the metal shell 2. Therefore, the outer electrode 5 and the outer spark durability improving material 6 are stably pressed between the welding earth electrode 26 and the welding mother electrode 27 that perform 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 having excellent mass productivity, and the spark plug 1 of high quality can be provided with good mass productivity.

Further, when the electric resistance welding of the outer electrode 5 and the outer spark durability improving material 6 is performed, 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 earth electrode 26 for performing electric resistance welding can 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 bonded with good productivity, and the position of the end portion of the outer spark durability improving material 6 can be accurately adjusted to secure the spark discharge gap G. Can be position.

[Second Embodiment] FIGS. 8 to 10 are explanatory views of a main part of a method for manufacturing a spark plug according to a second embodiment of the present invention. This embodiment shows a technique for manufacturing an outer two-pole opposed type spark plug 1 using two substantially L-shaped outer electrodes 5. First, the outer electrodes 5 are 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 the necessary length in order to easily and surely bend the outer electrodes 5 when they are bent into a substantially L shape in the next step. It 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 the ends of the two outer electrodes 5 face the inside of the metal shell 2 (first). -2
Process). By this bending process, the end portion of the outer electrode 5 is directed in the direction perpendicular to the tubular direction of the metal shell 2. The molding machine for performing this bending process includes a bending inner mold 31 fitted in the shaft hole 10 of the metal shell 2 and an end portion of the two outer electrodes 5 that move downward from above in the drawing to bend the bending inner mold 31. Bending punch 3 that presses simultaneously on the surface of the plate and plastically deforms it into a substantially L shape
It is composed of 2 etc. The bending punch 32 has a molding surface 33 having a shape corresponding to the predetermined bending shape of the outer electrode 5.

Next, unnecessary portions of the ends of the two outer electrodes 5 are cut at the same time to adjust the position of the inner ends of the outer electrodes 5.

Next, as shown in FIG. 9, rod-shaped outer spark endurance improvers 6 are joined to the upper surfaces of the ends of the two outer electrodes 5 in the figure by electric resistance welding (second).
Process). By this joining, a part of each outer spark durability improving material 6 projects inward from the end of the outer electrode 5, and the position of this inner end is joined to a position where the spark discharge gap G is assumed in advance. To be done. The welding machine that performs this electric resistance welding is equipped with a welding earth electrode 26 fitted in the shaft hole 10 of the metal shell 2, and moves downward from above in the drawing to push the outer spark durability improving material 6 against the outer electrode 5. It is composed of a welding mother electrode 27 and the like for applying a high voltage. On the upper surface portion of the welding earth electrode 26, there is provided an alignment step 28 for aligning the positions of the ends of the two outer spark durability improving materials 6. As a result, the position of the end portion of the outer spark durability improving material 6 falls within the predetermined position range, so that the gap adjustment performed in the subsequent process can be easily performed. An insulating layer is provided on the surface of the step portion 28 to prevent a current from directly flowing from the outer spark durability improving material 6 to the welding earth 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 the two outer spark durability improving materials are attached. The spark discharge gap G between the first and second electrodes 6 is within a predetermined size. Next, while maintaining this state, the caulking portion 12 at the end of the metal shell 2 is caulked to firmly fix the insulator 3 in the metal shell 2 (fourth step). As a result, the spark discharge gap G between the center electrode 4 and the two outer spark durability improving materials 6 is adjusted 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 method for manufacturing a spark plug according to a third embodiment. The present embodiment is a technique of the 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 of the metal shell 2 in the cylinder direction) by electric resistance welding. The welding machine used in the second step includes the welding earth electrode 26 fitted in the shaft hole 10 of the metal shell 2 and the outer spark durability improving material 6 on the outer electrode 5 by moving downward from the upper side in the drawing. It is composed of a welding mother electrode 27 for applying a high voltage by pressing. A positioning step 28 is formed on the upper surface of the welding earth electrode 26 so that the position of the end of the outer spark durability improving material 6 is within a predetermined position range. This makes it possible to easily perform the gap adjustment that will be performed in the next step.

[Modification] In the above-mentioned embodiment, the outer spark durability improving material is in the shape of a square rod, but
For example, any shape such as a cylinder, a triangular prism, or a polygonal prism having five or more prisms may be used as long as the shape is joined to the upper surface or the lower surface of the outer electrode and protrudes toward the center electrode 4. The material of each component used in the above-mentioned embodiment is used to help 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 was shown as an example of the precious metal material used for the outer spark durability improving material, iridium, palladium, rhodium, gold or an alloy mainly composed of these,
Other precious metal materials may be used. A noble metal excellent in 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 1, and 2
Although an example in which three are used 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 straight electrode extending from the inner peripheral surface of the end of the metal shell toward the center electrode may be used. Furthermore, the outer electrode is provided in a ring shape integrated with the metal shell (provided like an air discharge or semi-creeping discharge type outer electrode), and one or more rod-shaped outer spark durability improving materials are joined to the upper surface thereof. You may.

In the case where the outer electrode is formed in a substantially L-shape, an example is shown in which the longer outer electrode is joined to the metal shell in advance, the unnecessary portion is cut after bending, but the outer electrode having a length that does not generate the unnecessary portion is shown. It may be bent by joining to the metal shell. As an example of adjusting the spark discharge gap, an example was shown when adjusting the insulator in the metal shell.After fixing the insulator in the metal shell, the outer spark durability improving material or the center electrode was polished. , Adjust the gap by cutting, or if the outer electrode is plastically deformable in the direction perpendicular to the cylinder direction of the metal shell, adjust the gap by a slight bending of the outer electrode to adjust the gap. You may adjust. Each direction of the metal shell in each process is to help understanding of the embodiment,
Although the example in which the outer electrode is located above is shown, the present invention is not limited to the embodiment, and the direction of the metal shell may be any direction such as the vertical direction, the horizontal direction, and the oblique direction. Is also good.

[Brief description of 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 diagram showing a first-first step (first example).

FIG. 4 is an explanatory diagram showing a first-second process (first embodiment).

FIG. 5 is an explanatory view showing cutting of an unnecessary portion of the outer electrode in the first-second process (first embodiment).

FIG. 6 is an explanatory diagram showing a second step (first example).

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

FIG. 8 is an explanatory diagram showing a first-second process (second embodiment).

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

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

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

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

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

FIG. 14 is an explanatory view showing a step of joining the outer electrode to which the outer spark durability improving material is joined to the 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]

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

Claims (6)

[Claims] 1. A spark discharge gap is formed between a side surface of an axially extending center electrode and an end portion of an outer spark durability improving material that is joined to the outer electrode and uses a precious metal having excellent spark wear resistance. A method for manufacturing a spark plug, characterized in that the spark plug to be formed is manufactured using the following steps. (A) A first step in which an outer electrode having at least an end portion directed inward is provided on an end of a tubular metal shell. (B) a rod-shaped outer spark durability improving material, with a part of the outer spark durability improving material protruding inward from an inner end portion of the outer electrode, in a cylindrical direction of the metal shell of the outer electrode. The second step of joining the one-sided surface by electric resistance welding. (C) A third step of incorporating an insulator for insulatingly holding the center electrode in the metal shell. 2. The method of manufacturing a spark plug according to claim 1, wherein the first step includes a first-first step in which an outer electrode formed in a rectangular rod shape is joined to an end surface of the metal shell by welding. The first electrode in which the outer electrode joined to the metal shell is bent into a substantially L shape, and the bent end portion is directed to the inside of the metal shell.
A method for manufacturing a spark plug comprising two steps. 3. The method for manufacturing a spark plug according to claim 2, wherein, in the step 1-2, after bending the outer electrode into a substantially L shape, the inner end is cut to remove the inner end. A method for manufacturing a spark plug, comprising adjusting a position. 4. The method of manufacturing a spark plug according to claim 2, wherein when a plurality of outer electrodes are provided, the plurality of outer electrodes are bent at the same time into a substantially L shape. And a method for manufacturing a spark plug. 5. The spark plug manufacturing method according to claim 1, wherein a position of an inner end portion of the outer spark durability improving member joined to the outer electrode in the second step. The method for manufacturing a spark plug, wherein the spark plug is joined to the outer electrode in consideration of a spark discharge gap. 6. The spark plug manufacturing method according to claim 1, wherein a spark discharge is formed between an end portion of the outer spark durability improving material and a side surface of the center electrode. A method for manufacturing a spark plug, comprising a fourth step of adjusting a gap within a predetermined dimension.