JP6517136B2 - Spark plug and method of manufacturing electrode - Google Patents

Description

  The present invention relates to a method of manufacturing a spark plug and an electrode.

  The spark plug realizes ignition of the mixture in the combustion chamber of the internal combustion engine by generating a spark discharge in the gap between the center electrode and the ground electrode. DESCRIPTION OF RELATED ART In order to improve the heat resistance of the electrode in a spark plug, the electrode which coat | covered the core part excellent in thermal conductivity by the coating | coated part is known as an electrode for spark plugs. Such an electrode is manufactured by extruding the composite material after producing a composite material in which the material forming the core portion and the material forming the covering portion are combined (Patent Documents 1 and 2) See).

JP-A-7-37678 JP, 2013-4326, A

  In the manufacturing method of patent document 1, since the front end side of the core part in an electrode tends to be tapered, there existed a possibility that heat conductivity of an electrode could not fully be ensured. In the manufacturing method of patent document 2, the subject that the dispersion | variation for every individual tends to generate | occur | produce in the shape at the front end side of the core part in an electrode occurred.

  The present invention has been made to solve the above-described problems, and can be realized as the following modes.

(1) An embodiment of the present invention manufactures an electrode for a spark plug having a core extending in the axial direction from the front end side to the rear end and a covering part covering the core from the front end to the side. , The manufacturing method of an electrode is provided. This manufacturing method has, as a raw material of the core, a small diameter portion forming a cylindrical shape, and a large cylindrical diameter portion connected to the rear end of the small diameter portion and having a diameter larger than the small diameter portion. Producing a core material; a bottomed material having an outer diameter larger than the small diameter portion of the core member and having a bottomed hole formed on the rear end side into which the small diameter portion can be inserted as a base material of the covering portion; Preparing a cylindrically-shaped coating material; inserting the small diameter portion of the core material into the bottomed hole of the coating material to form a combination of the core material and the coating material as the core material Producing a composite material having a gap between the large diameter portion and the rear end face of the coating material; and forming a large diameter hole portion having a larger hole diameter than the large diameter portion and coaxial with the large diameter hole portion A small diameter hole having a diameter smaller than that of the large diameter portion; That the mold is prepared; after the composite material into the large diameter hole portion of the die is inserted from the large diameter portion, characterized by extruding the composite material into the small-diameter hole portion. According to this aspect, since the gap is formed in advance between the large diameter portion of the core material and the rear end face of the coating material before the composite material is extruded, the core material becomes the coating material during the extrusion. When biting in, it is possible to suppress the difference in the amount of biting in between the inside and the outside on the tip side of the core material. Therefore, it can suppress stably that the front end side of the core part in an electrode becomes tapered.

(2) In the manufacturing method described above, the gap of the composite material may increase toward the radially outer side. According to this aspect, it is possible to further suppress the difference in the amount of biting between the inside and the outside on the tip side of the core material.

(3) In the manufacturing method described above, the gap of the composite material may be formed over the entire area between the large diameter portion and the rear end surface. According to this aspect, it is possible to further suppress the difference in the amount of biting between the inside and the outside on the tip side of the core material.

(4) In the manufacturing method described above, the large diameter portion and the rear end surface are in contact with each other in the radial direction, and the gap of the composite material is the radial outer side among the large diameter portion and the rear end surface. May be formed. According to this aspect, when producing the composite material, the small diameter portion of the core material can be easily inserted into the bottomed hole of the coating material with a constant insertion amount.

(5) In the manufacturing method described above, in the composite material, the size in the axial direction of the gap is formed between the tip of the small diameter portion of the core material and the bottom of the bottomed hole of the covering material. May be larger than the axial size of the other gaps. According to this form, it can prevent that a gap is formed between the tip side of a core part, and a covering part.

(6) In the manufacturing method described above, the maximum size in the axial direction of the gap of the composite material may be 1 μm or more and 50 μm or less. According to this aspect, it is possible to suppress the difference in the amount of biting in between the inside and the outside on the tip side of the core material.

(7) In the manufacturing method described above, the bottom surface of the bottomed hole of the covering material may form a convex curved surface toward the leading end side of the covering material. According to this aspect, it is possible to prevent a gap from being formed between the corner on the tip end side of the core and the cover.

(8) The electrode manufactured by the above-described manufacturing method may be used as at least one of the center electrode and the ground electrode of the spark plug. According to this aspect, the durability of the spark plug can be improved.

  The present invention can be realized in various forms different from the method for manufacturing an electrode for a spark plug, and for example, the method for manufacturing a spark plug, a manufacturing apparatus for manufacturing an electrode, and an electrode for spark plug It is feasible.

It is an explanatory view showing a partial cross section of a spark plug. It is explanatory drawing which shows the detailed structure of a center electrode. It is explanatory drawing which shows the cross section of a center electrode. It is explanatory drawing which shows the manufacturing method of a center electrode. It is explanatory drawing which shows core material. It is an explanatory view showing a covering material. It is an explanatory view showing a composite material. It is explanatory drawing which shows a metal mold | die. It is explanatory drawing which shows a mode that the composite material was inserted in the metal mold | die. It is explanatory drawing which shows a mode that extrusion molding of a composite material is carried out. It is an explanatory view showing a forming object. It is explanatory drawing which shows a mode that extrusion molding of a molded object is carried out. It is an explanatory view showing a forming object. It is explanatory drawing which shows the composite material in 2nd Embodiment. It is explanatory drawing which shows the composite material in 3rd Embodiment. It is an explanatory view showing a composite material in a 4th embodiment.

A. First Embodiment A-1. Configuration of Spark Plug FIG. 1 is an explanatory view showing a partial cross section of the spark plug 10. In FIG. 1, the external shape of the spark plug 10 is illustrated on the left side of the drawing with respect to the axial line CA with the axis CA as the axial center of the spark plug 10 as a boundary. The cross-sectional shape of the spark plug 10 is illustrated on the right of the drawing. ing. In the description of the present embodiment, the lower side of the spark plug 10 in FIG. 1 is referred to as the “front end side”, and the upper side of FIG. 1 is referred to as the “rear end side”.

  The spark plug 10 includes a center electrode 100, an insulator 200, a metal shell 300, and a ground electrode 400. In the present embodiment, the axis line CA of the spark plug 10 is also an axis of each member of the center electrode 100, the insulator 200 and the metal shell 300.

  Spark plug 10 has a gap SG formed between center electrode 100 and ground electrode 400 on the tip side. The gap SG of the spark plug 10 is also referred to as a spark gap. The spark plug 10 is configured to be attachable to the internal combustion engine 90 in a state in which the tip end side where the gap SG is formed protrudes from the inner wall 910 of the combustion chamber 920. When a high voltage (for example, 10,000 to 30,000 volts) is applied to the center electrode 100 with the spark plug 10 attached to the internal combustion engine 90, spark discharge occurs in the gap SG. The spark discharge generated in the gap SG realizes ignition of the air-fuel mixture in the combustion chamber 920.

  The insulator 200 of the spark plug 10 is a insulator having electrical insulation. The insulator 200 has a tubular shape extending about the axis CA. In the present embodiment, the insulator 200 is manufactured by firing an insulating ceramic material (for example, alumina). The insulator 200 has an axial hole 290 which is a through hole extending around the axis CA. The center electrode 100 is held on the axis CA in the axial hole 290 of the insulator 200 in a state where the center electrode 100 protrudes from the tip end side of the insulator 200.

  The metal shell 300 of the spark plug 10 is a conductive metal body. The metal shell 300 has a tubular shape extending around the axis line CA. In the present embodiment, the metal shell 300 is a member obtained by applying nickel plating to a low carbon steel formed into a cylindrical shape. In another embodiment, the metal shell 300 may be a galvanized member or a non-plated member (non-plated). The metal shell 300 is crimped to the outer surface of the insulator 200 in a state of being electrically insulated from the center electrode 100. An end surface 310 is formed on the front end side of the metal shell 300. From the center of the end face 310, the insulator 200 protrudes toward the tip side together with the center electrode 100. The ground electrode 400 is joined to the end face 310.

  The ground electrode 400 of the spark plug 10 is an electrode having conductivity. The ground electrode 400 extends from the end face 310 of the metal shell 300 toward the tip end and then bends toward the axis CA. The rear end side of the ground electrode 400 is joined to the metal shell 300. The ground electrode 400 forms a gap SG with the center electrode 100.

  The center electrode 100 of the spark plug 10 is an electrode having conductivity. The center electrode 100 is in the shape of a rod extending around the axis CA. The outer surface of the center electrode 100 is electrically isolated from the outside by an insulator 200. The tip side of the center electrode 100 protrudes from the tip side of the insulator 200. The rear end side of the center electrode 100 is electrically connected to the rear end side of the insulator 200. In the present embodiment, the rear end side of the center electrode 100 is electrically connected to the rear end side of the insulator 200 through the terminal fitting 190.

  FIG. 2 is an explanatory view showing a detailed configuration of the center electrode 100. As shown in FIG. In FIG. 2, the external shape of the center electrode 100 is illustrated on the left side of the drawing with respect to the axis CA, and the cross-sectional shape of the center electrode 100 is illustrated on the right of the drawing. FIG. 3 is an explanatory view showing a cross section of the center electrode 100. As shown in FIG. The cross-sectional shape of the center electrode 100 cut | disconnected by arrow F3-F3 of FIG. 2 is shown in figure by FIG. The center electrode 100 has a core 110 and a cover 120.

  The core portion 110 of the center electrode 100 has a shape extending from the front end side to the rear end side. In the present embodiment, the cross-sectional shape of the core portion 110 is circular. The material of the core portion 110 has higher thermal conductivity than the covering portion 120. In the present embodiment, the material of the core portion 110 is a nickel alloy containing nickel (Ni) as a main component.

  The covering portion 120 of the center electrode 100 is shaped to cover the core portion 110 from the tip to the side. In the present embodiment, the cross-sectional shape of the covering portion 120 is circular. In the present embodiment, the material of the covering portion 120 is an alloy containing copper as a main component.

  In the present embodiment, on the rear end side of the center electrode 100, a protruding portion 108 that protrudes outward in the radial direction is formed. The protrusion 108 of the center electrode 100 fits inside the metal shell 300. Thus, the center electrode 100 is positioned on the metal shell 300.

  FIG. 4 is an explanatory view showing a method of manufacturing the center electrode 100. As shown in FIG. The manufacturer of the center electrode 100 produces a core material 110p as a material of the core portion 110 (process P110).

  FIG. 5 is an explanatory view showing the core material 110p. The axis CA of FIG. 5 corresponds to the axis CA of the spark plug 10, the tip end side of FIG. 5 corresponds to the tip end side of the spark plug 10, and the rear end side of FIG. It corresponds. The same applies to the axis CA in the other drawings described in the method of manufacturing the center electrode 100. The core material 110p has a small diameter portion 112p and a large diameter portion 114p. The small diameter portion 112p of the core material 110p has a cylindrical shape. The large diameter portion 114p of the core material 110p is connected to the rear end of the small diameter portion 112p and has a diameter larger than that of the small diameter portion 112p. In the core material 110p, the small diameter portion 112p is located on the front end side, and the large diameter portion 114p is located on the rear end side. In the axial direction along the axis CA, the length L1 of the small diameter portion 112p is longer than the large diameter portion 114p.

  After producing the core material 110p (process P110), the manufacturer produces the coating material 120p as a raw material of the coating portion 120 (process P120). In another embodiment, the manufacturer may make coating material 120p prior to making core material 110p.

  FIG. 6 is an explanatory view showing the coating material 120p. The covering material 120p has a main body 122p and a tip 128p. The main portion 122p of the covering material 120p has an outer diameter larger than the small diameter portion 112p of the core material 110p. The front end portion 128p of the covering material 120p is a portion obtained by chamfering the front end side of the main body portion 122p. At the rear end side of the main body portion 122p, a rear end face 121p facing the rear end side is formed. The bottom end hole 123p which can insert the small diameter part 112p is formed in the rear end surface 121p. The bottomed hole 123p has a bottom surface 124p and a side surface 125p. In the axial direction along the axis CA, the length L2 of the bottomed hole 123p is shorter than the length L1 of the small diameter portion 112p in the core material 110p.

  After producing the coating material 120p (process P120), the manufacturer inserts the small diameter portion 112p of the core material 110p into the bottomed holes 123p of the coating material 120p to combine the core material 110p and the coating material 120p. The composite material 100p is produced as (step P130).

  FIG. 7 is an explanatory view showing the composite material 100p. The composite material 100p has a structure in which the small diameter portion 112p of the core material 110p is inserted into the bottomed hole 123p of the covering material 120p. Since the length L1 of the small diameter portion 112p is longer than L2 of the bottomed hole 123p, the composite material 100p has a gap GP1 between the large diameter portion 114p of the core material 110p and the rear end surface 121p of the covering material 120p. In the present embodiment, the gap GP1 is formed over the entire area between the large diameter portion 114p and the rear end surface 121p. From the viewpoint of suppressing the tapering of the core portion 110 in the center electrode 100, the maximum value of the gap GP1 in the axial direction along the axis line CA is preferably 1 μm to 50 μm.

  In the composite material 100p, the size in the axial direction of the gap GP1 is the axial direction of another gap GPt formed between the tip of the small diameter portion 112p of the core material 110p and the bottom surface 124p of the bottomed hole 123p of the covering material 120p. Larger than in size. In the present embodiment, in the composite material 100p, the small diameter portion 112p of the core material 110p contacts at least a part of the bottom surface 124p of the bottomed hole 123p in the coating material 120p. Therefore, in the present embodiment, there is no other gap GPt in the composite material 100p. In another embodiment, in the composite material 100p, the small diameter portion 112p of the core material 110p may not be in contact with the bottom surface 124p of the bottomed hole 123p in the covering material 120p.

  After producing the composite material 100p (process P130), the manufacturer prepares a mold 810 for processing the composite material 100p (process P140).

  FIG. 8 is an explanatory view showing a mold 810. As shown in FIG. The mold 810 includes a large diameter hole portion 812 and a small diameter hole portion 814. The large diameter hole portion 812 of the mold 810 has a larger hole diameter than the large diameter portion 114p of the core material 110p. The small diameter hole 814 of the mold 810 is formed coaxially with the large diameter hole 812 and has a smaller diameter than the large diameter hole 812.

  After preparing the mold 810 (process P140), the manufacturer inserts the composite material 100p into the large diameter hole portion 812 of the mold 810 from the large diameter portion 114p side (process P150).

  FIG. 9 is an explanatory view showing the composite material 100 p inserted into the mold 810. In the mold 810, the rear end side of the composite material 100p faces the small diameter hole 814.

  After inserting the composite material 100p into the mold 810 (process P160), the manufacturer extrudes the composite material 100p into the small diameter holes 814 (process P160).

  FIG. 10 is an explanatory view showing how the composite material 100p is extruded. The manufacturer pushes the core material 110 p into the small diameter hole 814 by inserting the push rod 820 into the large diameter hole 812. Thereby, the composite material 100p is processed into a molded body 100q having a more elongated shape than the composite material 100p.

  FIG. 11 is an explanatory view showing a molded body 100 q. The molded body 100 q includes a core portion 110 q, a large diameter portion 114 q, and a covering portion 120 q. The core portion 110 q of the molded body 100 q is derived from the small diameter portion 112 p of the core material 110 p, and has a more elongated shape than the small diameter portion 112 p. The large diameter portion 114 q of the core portion 110 q is derived from the large diameter portion 114 p of the core material 110 p, and has a shape elongated from the large diameter portion 114 p. The covering portion 120 q of the molded body 100 q is derived from the covering material 120 p and has a more elongated shape than the covering material 120 p. Molded body 100 q has a gap GP2 between large diameter portion 114 q and covering portion 120 q. The gap GP2 of the molded body 100q is derived from the gap GP1 of the composite material 100p and is larger than the gap GP1.

  In the present embodiment, after producing the molded body 100q from the composite material 100p (process P160), the manufacturer cuts the molded body 100q along the cutting line CL1 to form the rear end from the covering portion 120q in the molded body 100q. Cut out the side. Thereafter, the manufacturer extrudes the molded body 100 q to produce a molded body 100 r having a more elongated shape than the molded body 100 q.

  FIG. 12 is an explanatory view showing the extrusion molding of the molded body 100 q. The manufacturer uses the mold 830 and the push rod 840 thinner than the mold 810 and the push rod 820 to extrude the molded body 100 q in the same manner as the extrusion of the composite material 100 p. As a result, the molded body 100 q is processed into a molded body 100 r which has a more elongated shape than the molded body 100 q.

  FIG. 13 is an explanatory view showing a molded body 100r. The molded body 100 r includes a core portion 110 r and a covering portion 120 r. The core portion 110r of the molded body 100r is derived from the small diameter portion 112q of the core portion 110q, and has a more elongated shape than the small diameter portion 112q. The covering portion 120r of the molded body 100r is derived from the covering portion 120q, and has a more elongated shape than the covering portion 120q.

  In the present embodiment, after the molded body 100r is produced from the molded body 100q, the manufacturer cuts the molded body 100r along the cutting line CL2 to be left as a processing allowance in the covering portion 120r of the molded body 100r. Remove the distal end side. Thereafter, the manufacturer further produces the center electrode 100 from the molded body 100r by extruding the molded body 100r. After these steps, the center electrode 100 is completed.

  According to the first embodiment described above, before extruding the composite material 100p (process P130), the gap GP1 is formed in advance between the large diameter portion 114p of the core material 110p and the rear end face 121p of the covering material 120p. Since the core material 110p bites into the coating material 120p during extrusion molding (process P150), it is possible to suppress the difference in the amount of biting that occurs between the inside and the outside on the tip side of the core material 110p. Therefore, the tip end side of the core portion 110 in the center electrode 100 can be stably suppressed from being tapered.

  Further, the gap GP1 of the composite material 100p is formed over the entire area between the large diameter portion 114p and the rear end surface 121p. By this, it is possible to further suppress the difference in the amount of biting between the inner side and the outer side on the tip side of the core material 110p.

  In the composite material 100p, the size of the gap GP1 in the axial direction is the size of another gap GPt formed between the tip of the small diameter portion 112p of the core material 110p and the bottom surface 124p of the bottomed hole 123p of the covering material 120p. Larger than the size in the axial direction. This can prevent a gap from being formed between the distal end side of the core portion 110 and the covering portion 120.

  In addition, the maximum size of the gap GP1 of the composite material 100p in the axial direction is 1 μm to 50 μm. Thereby, it is possible to suppress the difference in the amount of biting in between the inside and the outside on the tip side of the core material 110p.

B. Second Embodiment FIG. 14 is an explanatory view showing a composite material 102p in a second embodiment. The configuration of the spark plug 10 in the second embodiment is similar to that of the first embodiment. The method of manufacturing the spark plug 10 according to the second embodiment is the same as that of the first embodiment except that the composite material 102p is used instead of the composite material 100p.

  The composite material 102p of the second embodiment is the same as the first embodiment except that the gap GP1 increases in the radial outward direction. In the present embodiment, the outer diameter of the large diameter portion 114p decreases toward the small diameter portion 112p at the connection portion with the small diameter portion 112p. Thus, the gap GP1 increases toward the radially outer side.

  According to the second embodiment described above, it is possible to further suppress the difference in the amount of biting in between the inside and the outside on the tip side of the core material 110p. Therefore, the tip end side of the core portion 110 in the center electrode 100 can be further stably suppressed from being tapered.

C. Third Embodiment FIG. 15 is an explanatory view showing a composite material 103p according to a third embodiment. The configuration of the spark plug 10 in the third embodiment is similar to that of the first embodiment. The method of manufacturing the spark plug 10 according to the third embodiment is the same as that of the first embodiment except that the composite material 103p is used instead of the composite material 100p.

  In the composite material 103p of the third embodiment, the large diameter portion 114p and the rear end surface 121p are in contact with each other on the inner side in the radial direction, and the gap GP1 is on the radial outer side among the large diameter portion 114p and the rear end surface 121p. The second embodiment is the same as the first embodiment except that it is formed. In the present embodiment, the outer diameter of the large diameter portion 114p decreases stepwise toward the small diameter portion 112p.

  According to the third embodiment described above, as in the first embodiment, the leading end side of the core portion 110 in the center electrode 100 can be stably suppressed from being tapered. Further, when producing the composite material 103p, the small diameter portion 112p of the core material 110p can be easily inserted into the bottomed hole 123p of the covering material 120p with a fixed insertion amount.

D. Fourth Embodiment FIG. 16 is an explanatory view showing a composite material 104p in a fourth embodiment. The configuration of the spark plug 10 in the fourth embodiment is the same as that of the first embodiment. The manufacturing method of the spark plug 10 in the fourth embodiment is the same as that of the first embodiment except that the composite material 104p is used instead of the composite material 100p.

  The composite material 104p of the fourth embodiment is the same as the first embodiment except that the bottom surface 124p of the bottomed hole 123p of the covering material 120p forms a convex curved surface toward the tip side. In the present embodiment, the small diameter portion 112p of the core material 110p does not contact the bottom surface 124p of the bottomed hole 123p in the covering material 120p. The size of the gap GP1 is larger than the gap GPt formed between the small diameter portion 112p and the bottom surface 124p.

  According to the fourth embodiment described above, as in the first embodiment, the distal end side of the core portion 110 in the center electrode 100 can be stably suppressed from being tapered. Moreover, it can prevent that a space | interval is formed between the corner by the side of the tip of core part 110, and a covering part.

E. Other Embodiments The present invention is not limited to the above-described embodiment, examples, and modifications, and can be implemented with various configurations without departing from the scope of the invention. For example, among the technical features in the embodiments, examples, and modifications, those corresponding to the technical features in the respective forms described in the section of the summary of the invention are for solving some or all of the problems described above. Alternatively, replacements and combinations can be made as appropriate to achieve some or all of the above-described effects. In addition, technical features that are not described as essential in the present specification can be deleted as appropriate.

  In order to improve the durability of the center electrode 100, a noble metal tip may be provided on the tip side of the center electrode 100. In order to improve the durability of the ground electrode 400, a noble metal tip may be provided on the tip side of the ground electrode 400. Similarly to the center electrode 100, an electrode having a core and a covering may be applied to the ground electrode 400.

DESCRIPTION OF SYMBOLS 10 spark plug 90 internal-combustion engine 100 center electrode 100p composite material 100q molded body 100r molded body 102p, 103p, 104p composite material 108 projecting portion 110 core portion 110p core material 110q core portion 110r Core portion 112p: Small diameter portion 112q: Small diameter portion 114p: Large diameter portion 120: Coating portion 120p: Coating material 120q: Coating portion 120r: Coating portion 121p: Rear end face 122p: Body portion 123p: Bottomed hole 124p ... Bottom surface 125 p ... Side surface 128 p ... Tip 190 ... Terminal fitting 200 ... Insulator 290 ... Shaft hole 300 ... Main metal fitting 310 ... End face 400 ... Ground electrode 810 ... Die 812 ... Large diameter hole 814 ... Small diameter hole 820 ... Push rod 830 ... mold 840 ... push rod 910 ... inner wall 920 ... combustion chamber

Claims (8)

A manufacturing method of an electrode for manufacturing an electrode for a spark plug, comprising: a core portion axially extending from a front end side to a rear end side; and a covering portion covering the core portion from the front end to the side.
Producing a core material having, as a raw material of the core, a small diameter portion forming a cylindrical shape, and a columnar large diameter portion connected to the rear end of the small diameter portion and having a diameter larger than the small diameter portion ,
A coating material having a cylindrical shape with a bottom, which has an outer diameter larger than that of the small diameter portion of the core material and has a bottomed hole into which the small diameter portion can be inserted. To make
By inserting the small diameter portion of the core material into the bottomed hole of the coating material, the large diameter portion of the core material and the coating material are used as a material in which the core material and the coating material are combined. Make a composite material with a gap between it and the end face,
Preparing a mold comprising: a large diameter hole having a diameter larger than the large diameter; and a small diameter hole coaxially formed with the large diameter hole and having a diameter smaller than the large diameter;
A method of manufacturing an electrode, comprising inserting the composite material into the large diameter hole of the mold from the large diameter side, and thereafter extruding the composite material into the small diameter hole.   The method according to claim 1, wherein the gap of the composite material is increased radially outward.   The method according to claim 1, wherein the gap of the composite material is formed over the entire area between the large diameter portion and the rear end surface.   The large diameter portion and the rear end surface are in contact with each other in the radial direction, and the gap of the composite material is formed on the radially outer side between the large diameter portion and the rear end surface. The manufacturing method of the electrode of Claim 2.   In the composite material, the size in the axial direction of the gap is the size in the axial direction of another gap formed between the tip of the small diameter portion of the core material and the bottom of the bottomed hole of the covering material. The manufacturing method of the electrode as described in any one of Claim 1- Claim 4 larger than.   The manufacturing method of the electrode as described in any one of Claim 1- Claim 5 whose largest magnitude | size in the axial direction of the said clearance gap of the said composite material is one to 50 micrometer.   The method for manufacturing an electrode according to any one of claims 1 to 6, wherein a bottom surface of the bottomed hole of the coating material forms a convex curved surface toward the tip side of the coating material. A method for producing a spark plug, using an electrode produced by the method for producing an electrode according to any one of claims 1 to 7 as at least one of a center electrode and a ground electrode of a spark plug.

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