JP7339220B2 - Spark plug and spark plug manufacturing method - Google Patents

Description

TECHNICAL FIELD The present invention relates to a spark plug used in an internal combustion engine and a manufacturing method thereof.

Spark plugs are used as ignition means for internal combustion engines such as automobile engines. A spark plug has a shaft-shaped center electrode, a cylindrical insulator that holds the center electrode inside, and a metal shell that holds the insulator inside. A substantially L-shaped ground electrode is attached to the front end of the metal shell by welding or the like so as to form a spark discharge gap with the center electrode (see, for example, Patent Document 1).

JP 2018-190673 A

The spark plug configured as described above is attached to an internal combustion engine by screwing a screw groove formed on the outer periphery of the metal shell into a screw hole of the internal combustion engine. When the spark plug is attached to the internal combustion engine, there is a problem that the arrangement position of the ground electrode located on the tip side of the metallic shell cannot be confirmed.

SUMMARY OF THE INVENTION An object of the present invention is to provide a spark plug in which the position of the ground electrode can be confirmed after being installed in an internal combustion engine.

A spark plug according to one aspect of the present invention includes an insulator and a metallic shell. In this spark plug, the metal shell includes a mounting portion that is mounted to the internal combustion engine, a ground electrode that is provided on the tip end side of the mounting portion, and a ground electrode that is positioned on the rear end side of the mounting portion and is positioned further than the mounting portion. and a large-diameter portion having a large diameter. A projecting portion projecting radially outward from a portion of the surface of the metal shell is formed on the rear end side of the large diameter portion including the large diameter portion.

According to the above configuration, since the overhanging portion is provided, the positional relationship between the overhanging portion and the ground electrode is grasped before the spark plug is attached to the internal combustion engine. After attachment, the position of the ground electrode can be easily identified from the position of the overhang. Therefore, a spark plug is obtained that allows the position of the ground electrode to be confirmed after installation in the internal combustion engine. The rear end side of the large-diameter portion including the large-diameter portion is a portion exposed to the outside when the spark plug is attached to the internal combustion engine.

In the spark plug according to one aspect of the present invention, a side surface of the large-diameter portion is provided with a mark and a protective layer provided so as to cover the mark, and the projecting portion includes the It may be formed as part of the protective layer.

According to the above configuration, the mark can be protected by providing the protective layer so as to cover the mark. Furthermore, since the projecting portion is formed as a part of the protective layer, the position of the ground electrode can be confirmed after installation in the internal combustion engine by using the protective layer of the mark attached to the spark plug. A spark plug is obtained.

In the spark plug according to one aspect of the present invention described above, a tip facing surface is provided on the tip end side of the large diameter portion, and the projecting portion is positioned on the rear end side of the tip facing surface. may

According to the above configuration, when the spark plug is attached to the internal combustion engine, it is possible to prevent the projecting portion from interfering with the internal combustion engine.

A method of manufacturing a spark plug according to another aspect of the present invention is a method of manufacturing the spark plug according to one aspect of the present invention. This manufacturing method includes a mark forming step of forming a mark on the side surface of the large-diameter portion, and a tip-facing surface positioned on the tip side of the large-diameter portion to prevent the coating material from scattering on the tip-facing surface. a plate member installing step of bringing into contact with a plate member protruding radially outward from the large-diameter portion, and after the plate member installing step, coating the mark on the mark while the plate member is in contact with the tip facing surface. and a protective layer forming step of applying a material to form a protective layer having the projecting portion.

According to the manufacturing method described above, when the coating material is applied, the plate member is arranged on the tip-facing surface of the large-diameter portion, so that the coating material can be prevented from scattering on the tip-facing surface. . Further, by applying the coating material while the plate member is installed on the tip-facing surface of the large-diameter portion, the projecting portion can be formed using the coating material that spreads over the surface of the plate member. By forming the protective layer having the protruding portion in this way, the spark plug can be easily checked for the position of the ground electrode after being installed in the internal combustion engine by using the mark attached to the spark plug. can be manufactured.

As described above, the spark plug according to one aspect of the present invention is provided with the protruding portion that protrudes radially outward from a portion of the surface of the metal shell on the rear end side of the large diameter portion. According to this configuration, by grasping the positional relationship between the overhanging portion and the ground electrode before the spark plug is attached to the internal combustion engine, the spark plug can be grounded from the position of the overhanging portion after the spark plug is attached to the internal combustion engine. The position of the electrodes can be easily identified. Therefore, according to the spark plug according to one aspect of the present invention, the position of the ground electrode can be confirmed after being attached to the internal combustion engine.

1 is a side view showing the appearance of a spark plug according to an embodiment of the present invention and an enlarged view of a mark attached to the spark plug; FIG. 4 is a flow chart showing part of the manufacturing process of the spark plug according to one embodiment of the present invention; FIG. 4 is a schematic diagram showing a state when forming a protective layer on the spark plug according to one embodiment of the present invention; 1 is a plan view showing an example of a plate member used when forming a protective layer on a spark plug according to one embodiment of the present invention; FIG. FIG. 4 is a plan view showing another example of a plate member used when forming a protective layer on the spark plug according to one embodiment of the present invention;

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following description, the same parts are given the same reference numerals. Their names and functions are also the same. Therefore, detailed description thereof will not be repeated.

In this embodiment, as an example of the spark plug of the present invention, a spark plug having a mark on the surface of the seat portion 34 of the metal shell 30 will be described. FIG. 1 shows the appearance of a spark plug 1 according to this embodiment. FIG. 1 also shows an enlarged view of a mark (specifically, a two-dimensional code 10) attached to the spark plug 1. As shown in FIG.

(Overall configuration of spark plug)
First, the overall structure of the spark plug 1 will be described with reference to FIG. The spark plug 1 has an insulator 50 and a metal shell 30 .

The insulator 50 is a substantially cylindrical member extending in the longitudinal direction of the spark plug 1 . The insulator 50 is made of a material with excellent insulation, heat resistance, and thermal conductivity. For example, the insulator 50 is made of alumina-based ceramic or the like. A center electrode 21 is provided at one end (tip) of the insulator 50 . A terminal fitting 52 is attached to the other end (rear end) of the insulator.

The center electrode 21 is held through a shaft hole of the insulator 50 with its tip protruding from the tip of the insulator 50 . The center electrode 21 is attached to the insulator 50 so that the tip thereof is positioned on the axis O of the substantially cylindrical insulator 50 . The center electrode 21 has a substantially cylindrical shape, and its tip portion is tapered to reduce its diameter.

The metal shell 30 is a substantially cylindrical member that is fixed to a screw hole of the internal combustion engine. The metal shell 30 is provided so as to partially cover the insulator 50 . The metal shell 30 is made of a conductive metal material. Examples of such metal materials include low-carbon steel, metal materials containing iron as a main component, and the like.

The metal shell 30 mainly includes a crimping portion 31, a tool engaging portion 32, a curved portion 33, a seat portion (large diameter portion) 34, a mounting portion 35, and the like.

The crimping portion 31 and the curved portion 33 are portions for attaching the metal shell 30 to the insulator 50 . The tool engaging portion 32 is a portion with which a tool such as a wrench is engaged when attaching the metal shell 30 to a screw hole of the internal combustion engine. The mounting portion 35 is located on the tip side of the insulator 50 . The attachment portion 35 is a portion that is press-fitted or screwed into a plug hole of the internal combustion engine when the spark plug 1 is attached to the internal combustion engine. When the spark plug 1 is attached to the internal combustion engine, for example, a screw groove formed on the outer periphery of the attachment portion 35 is screwed into a screw hole of the internal combustion engine.

The seat portion 34 is positioned on the rear end side of the mounting portion 35 (the side on which the terminal fitting 52 is arranged). In this embodiment, the seat portion 34 is positioned between the curved portion 33 and the mounting portion 35 . Since the seat portion 34 has a larger diameter than the mounting portion 35, it is also called a large diameter portion. In this embodiment, the diameter of the seat portion 34 is larger than the diameter of the mounting portion 35 and larger than the diameter of the curved portion 33 .

An annular gasket 42 is arranged on a front end surface 34 a of the seat portion 34 , which is an end face on the front end side of the seat portion 34 when the spark plug 1 is attached to the internal combustion engine. The tip facing surface 34a is also called a gasket mounting surface or a seating surface.

A ground electrode 41 is attached to the tip portion side of the metal shell 30 (the side where the attachment portion 35 is located). The ground electrode 41 is a rod-shaped body bent in a substantially L shape as a whole, and its base end side is joined and fixed to the front end surface of the metal shell 30 . The tip of the ground electrode 41 extends to a position through which an imaginary extension line of the axis O of the insulator 50 passes. A convex portion protruding toward the center electrode 21 side is formed in the vicinity of the tip portion of the ground electrode 41 .

The center electrode 21 and the ground electrode 41 are formed using, for example, a metal material such as a Ni-based alloy containing Ni (nickel) as a main component as a base material. Al (aluminum) etc. are mentioned as an alloying element added to a Ni-based alloy. The center electrode 21 and the ground electrode 41 may have inside thereof a core material made of a metal having excellent thermal conductivity, for example, a metal material such as Cu (copper) or a Cu alloy.

Also, the ground electrode 41 may contain, as a component other than Ni, at least one element selected from Mn (manganese), Cr (chromium), Al (aluminum), and Ti (titanium).

The distal end portion of the center electrode 21 can be composed of, for example, a cylindrical noble metal tip, which is joined to the distal end portion of the center electrode 21 by welding or the like.

A plated layer is formed on the surfaces of the metal shell 30 and the ground electrode 41 . By forming a plated layer on the surface, corrosion of the metal shell 30, the ground electrode 41, and the like can be suppressed. The plating layer contains, for example, Zn (zinc), Ni (nickel), Sn (tin), and Cr (chromium).

A plated layer similar to that described above is also formed on the surface of the terminal fitting 52 of the insulator 50 . Corrosion of the terminal fittings 52 can thereby be suppressed.

(Regarding the mark on the spark plug)
A two-dimensional code 10, which is an example of a mark, is attached to the spark plug 1. As shown in FIG. The two-dimensional code 10 is provided on the outer peripheral surface (side surface) of the seat portion 34 . The two-dimensional code 10 is, for example, a DataMatrix code, a QR code (registered trademark), or the like. The two-dimensional code 10 contains various kinds of information for identifying individual spark plugs, such as product information of the spark plug 1 and history information in the manufacturing process.

Note that the mark is not limited to the two-dimensional code in the present invention. Examples of marks other than two-dimensional codes include one-dimensional codes such as barcodes, characters, symbols, images, and the like. Also, the mark may be configured by combining some of one-dimensional codes, two-dimensional codes, characters, symbols, and images.

The two-dimensional code 10 has a first part 11 that is a set of rectangular cells and a second part 12 that is a set of rectangular cells having higher reflectance than the first part 11 . In this embodiment, the first section 11 is a dark module and the second section 12 is a bright module. A combination of the first part 11 and the second part 12 displays history information unique to products and parts. In this embodiment, as will be described later, the first portion 11 is formed of an oxide film, and the second portion 12 is formed of a base region. As for the more specific configuration of the two-dimensional code 10, the configuration of conventionally known marks (for example, the mark 40 disclosed in Patent Document 1, etc.) can be applied.

In the spark plug 1 according to this embodiment, the surface of the two-dimensional code 10 is covered with the protective layer 61 . As shown in FIG. 1, the protective layer 61 is formed in an area slightly wider than the area in which the two-dimensional code 10 is formed. That is, the region where the protective layer 61 is formed includes the region where the two-dimensional code 10 is formed.

The protective layer 61 has optical transparency. Here, that the protective layer 61 has optical transparency means that light such as visible light passes through the protective layer 61 and the lower surface of the protective layer 61 is visible. Since the protective layer 61 has optical transparency, the information of the two-dimensional code 10 formed under the protective layer 61 can be read. As will be described later, the protective layer 61 is formed by applying a coating material so as to cover the two-dimensional code 10 .

Since the surface of the two-dimensional code 10 is covered with the protective layer 61, it is possible to suppress the generation of rust from the two-dimensional code 10 and its surrounding area. In addition, since the protective layer 61 is provided, the two-dimensional code 10 can be prevented from being scratched or rubbed. Therefore, it is possible to prevent the two-dimensional code 10 attached to the spark plug 1 from being damaged and unreadable when a plurality of spark plugs 1 are packed together and transported.

The protective layer 61 also has an overhanging portion 62 projecting radially outward from the surface of the seat portion 34 . The projecting portion 62 is made of the same material as the coating material forming the protective layer 61 . In one example, as shown in FIG. 1, the protective layer 61 and the overhanging portion 62 have a substantially L-shape when viewed from the side.

The projecting portion 62 protrudes radially outward from a portion of the surface of the seat portion 34 . Such projecting portion 62 is used for checking the position of ground electrode 41 after the spark plug 1 is attached to the internal combustion engine.

When the spark plug 1 is attached to the internal combustion engine, the ground electrode 41 located on the tip side of the attachment portion 35 enters the plug hole of the internal combustion engine, so that the position of the ground electrode 41 cannot be grasped from the outside. In the spark plug 1 according to the present embodiment, the protective layer 61 has the projecting portion 62, so even when the mounting portion 35 of the metal shell 30 is mounted in the plug hole of the internal combustion engine, the diameter of the mounting portion 35 is larger than that of the mounting portion 35. The position of the projecting portion 62 projecting radially from the seat portion 34 having a large diameter can be easily confirmed.

Further, since the projecting portion 62 is a part of the protective layer 61 provided on the two-dimensional code 10, when the spark plug 1 is viewed from the rear end side in the axial direction, the position of the projecting portion 62 is It can be seen that the two-dimensional code 10 exists. Therefore, by forming the two-dimensional code 10 at a specific position on the side surface of the seat portion 34, the positional relationship between the two-dimensional code 10 and the ground electrode 41 can be specified.

For example, in the example shown in FIG. 1, the two-dimensional code 10 is positioned on the outer peripheral surface of the seat portion 34 at a position on the opposite side of the arrangement position of the ground electrode 41 (centered on the axis O with respect to the position of the ground electrode 41). ) is formed at a position where the angle of rotation between them is about 180°. Therefore, when the spark plug 1 is attached to the internal combustion engine and the spark plug 1 is viewed from the rear end side, it can be seen that the ground electrode 41 exists at a position on the opposite side of the projecting position of the projecting portion 62 . .

In the spark plug 1 according to the present embodiment, in order to confirm the position of the ground electrode 41 using a mark such as the two-dimensional code 10, the mark and the ground electrode 41 are arranged in advance so as to have a specific positional relationship. You may decide the formation position of a mark. In another example, the positional relationship between the ground electrode 41 and the mark may be confirmed before the spark plug 1 is attached to the internal combustion engine.

In the present embodiment, the projecting portion 62 is positioned on the distal end side of the seat portion 34 (that is, in the vicinity of the distal facing surface 34a) (see FIG. 1). Further, the projecting portion 62 is located on the rear end side of the front end facing surface 34 a of the seat portion 34 .

Here, when the projecting portion 62 is located on the rear end side of the distal end-facing surface 34a, the projecting portion 62 as a whole is located more than the imaginary extension plane X (indicated by the dashed line in FIG. 1) of the distal end-facing surface 34a. It means that it does not protrude to the tip side (mounting portion 35 side).

Since the projecting portion 62 is located on the rear end side of the tip facing surface 34a, it is possible to prevent the projecting portion 62 from interfering with the internal combustion engine when the spark plug 1 is attached to the internal combustion engine.

Further, in the present embodiment, the protruding portion 62 is formed along the edge of the protective layer 61 formed so as to cover the substantially rectangular two-dimensional code 10, which is closer to the tip-facing surface 34a. (See Figure 1). However, the arrangement position of the projecting portion 62 in the protective layer 61 is not limited to this. The arrangement position and shape of the overhanging portion 62 are not particularly limited as long as they are provided so as to protrude radially outward from a portion of the surface of the seat portion 34 .

For example, as shown in FIG. 1, in the protective layer 61 which is formed in a substantially square shape on the surface of the seat portion 34 in conformity with the shape of the two-dimensional code 10, at least one of its four edges A projecting portion 62 is preferably formed along the edge. As a result, the protruding portion 62 is positioned outside the area where the two-dimensional code 10 is formed, and it is possible to prevent the protruding portion 62 from interfering with the reading of the two-dimensional code 10 .

(Manufacturing method of spark plug)
Next, a method for manufacturing the spark plug 1 will be described. Here, among the manufacturing methods of the spark plug 1, the process of forming the marks of the two-dimensional code 10 and the protective layer 61 covering the marks will be mainly described. For the other manufacturing steps in the method for manufacturing the spark plug 1, the same manufacturing method as the conventional method for manufacturing a spark plug can be applied.

FIG. 2 shows steps related to forming the two-dimensional code 10 and the protective layer 61 in order. A case where the two-dimensional code 10 is formed on the finished spark plug 1 will be described below as an example. However, the two-dimensional code 10 may be formed on the components of the spark plug 1 in the process of being manufactured by a method similar to the method described below.

As shown in FIG. 2, the method for manufacturing the spark plug 1 includes a mark forming step (S11), a plate member installing step (S12), and a protective layer forming step (S13).

Before performing the mark forming step (S11), first, the spark plug 1 without the two-dimensional code 10 is prepared. In the mark forming step ( S<b>11 ), marks are formed on the mark forming surface of the spark plug 1 . Here, the mark forming surface is a region on the side surface of the seat portion 34 of the spark plug 1 where the mark is to be formed. In the example shown in FIG. 1, the mark forming surface is positioned on the outer peripheral surface of the seat portion 34 of the metallic shell 30 on the opposite side to the arrangement position of the ground electrode 41 (centering on the axis O with respect to the position of the ground electrode 41). ) is about 180°.

Laser processing, for example, is used to form the marks. When forming a mark using laser processing, first, a base region is formed on the mark forming surface. The background area is an area that serves as a background in the mark formation area. An oxide film is formed on the mark forming surface of the spark plug 1 by oxidizing the plating film. This oxide film may have unevenness in thickness and density.

Therefore, a base region is formed by irradiating the mark forming surface with a laser beam and removing the oxide film formed on the surface. As a result, it is possible to form a base region having a higher reflectance than the first portion 11 to be formed later. The background area constitutes the second part 12 when the mark is the two-dimensional code 10, for example.

Thereafter, the underlayer region is further irradiated with a laser beam to partially heat the underlayer region. This promotes the formation of an oxide film on the portion heated by irradiation with the laser beam. In this laser beam irradiation step, the laser beam is scanned using a scanning head to form an oxide film at a predetermined location within the underlying region. At this time, the laser output, scanning speed, focal diameter and focal depth of the laser beam are adjusted to irradiate the spark plug 1 with a laser beam having higher energy than that for forming the base region. This accelerates the oxidation of the portion irradiated with the laser beam, forming a blackened oxide film. This oxide film becomes the first part 11 of the two-dimensional code 10 .

The degree of oxidation of the oxide film forming the first portion 11 can be controlled by laser output. Therefore, the thickness and density of the oxide film forming the first portion 11 can be made substantially uniform.

As a more specific method for the mark forming step (S11), for example, a conventionally known mark forming method described in Patent Document 1 can be applied.

After the marks are formed on the spark plug 1 as described above, the steps for forming the protective layer 61 and the projecting portion 62 are performed. Specifically, a plate member installation step (S12) and a protective layer forming step (S13) are performed.

The plate member installation step (S12) is performed to prevent the coating material used in the protective layer forming step to be performed later from scattering on the front end facing surface 34a of the seat portion 34, which serves as the gasket mounting surface. In the plate member installation step (S12), the plate member 100 protruding outward from the seat portion 34 in the radial direction of the spark plug 1 (the direction orthogonal to the extending direction of the axis O) is brought into contact with the tip facing surface 34a of the seat portion 34. .

FIG. 3 shows a state where the plate member 100 is attached to the spark plug 1. As shown in FIG. In FIG. 3, for the sake of convenience, the two-dimensional code 10 provided on the side surface of the seat portion 34 is shown in an enlarged state.

The plate member 100 can be formed of, for example, a resin such as a plastic plate, or a metal such as an aluminum plate.

FIG. 4 shows an example of a plate member 100 attached to the spark plug 1. As shown in FIG. A plate member 100A shown in FIG. 4 is a substantially rectangular plate-like member. A substantially circular opening 101 is provided in the center of the plate member 100A. When the plate member 100A is attached to the spark plug 1, the spark plug 1 is inserted into the opening 101 from the tip end side (center electrode 21 side), and the plate member 100A is inserted into the tip facing surface 34a of the seat portion 34. the ends of the When forming the protective layer 61 using the plate member 100A, the plate member 100A is attached to the spark plug 1 before the gasket 42 is inserted into the spark plug 1. As shown in FIG.

FIG. 5 shows another example of the plate member 100 attached to the spark plug 1. As shown in FIG. A plate member 100B shown in FIG. 5 is a substantially rectangular plate-like member. The plate member 100B is provided with a notch portion 111 obtained by cutting out a portion of the plate from one end side toward the center portion. When attaching the plate member 100B to the spark plug 1, the plate member 100B is inserted from the side of the spark plug 1 on which the mark is formed. At this time, the periphery of the seat portion 34 of the spark plug 1 is made to enter the notch portion 111 of the plate member 100B. For example, in the example shown in FIG. 3, the spark plug 1 is inserted into the cutout portion 111 of the plate member 100B from the upper side in the figure. Then, the end portion of the notch portion 111 of the plate member 100B is brought into contact with the tip facing surface 34a of the seat portion 34. As shown in FIG.

After the plate member 100 is installed on the tip facing surface 34a of the spark plug 1 in the plate member installing step (S12), the protective layer forming step (S13) is performed. In the protective layer forming step (S13), as shown in FIG. 3, a coating material is applied onto the two-dimensional code 10 while the flat surface of the plate member 100 is in contact with the tip facing surface 34a of the seat portion 34 to protect it. A layer 61 is formed.

As a coating material used for forming the protective layer 61, for example, a resin material having properties such as rust resistance and water repellency is used. As the resin material, for example, a liquid material having a property of being cured by heating, light irradiation, or the like is preferably used. In this embodiment, a UV curable resin that is cured by irradiation with ultraviolet rays (UV) is used as the coating material.

Moreover, the coating material has optical transparency so that the reflected light of the light irradiated to the two-dimensional code 10 can be read by a reading device such as a code reader.

By applying such a coating material onto the two-dimensional code 10 , the coating material is cured and a colorless and transparent protective layer 61 is formed so as to cover the two-dimensional code 10 .

Further, when a liquid coating material having an appropriate viscosity is applied onto the two-dimensional cord 10 with the plate member 100 attached to the spark plug 1, part of the coating material reaches the surface of the plate member 100, It spreads over the surface of the plate member 100 . By curing the coating material in this state, the overhanging portion 62 is formed by the coating material spread over the surface of the plate member 100 .

Each of the steps described above may be performed before the gasket 42 is attached to the spark plug 1 or may be performed after the gasket 42 is attached to the spark plug 1 . When the above steps are performed after the gasket 42 is attached to the spark plug 1, for example, a plate member 100 having a notch 111 such as the plate member 100B is used. Further, when the plate member installation step (S12) is performed before attaching the gasket 42 to the spark plug 1, as shown in FIG. The plate member 100 is arranged so as to be sandwiched therebetween.

After the protective layer forming step (S13) is finished, the spark plug 1 is subjected to post-treatment such as cleaning, if necessary.

As described above, according to the method of manufacturing the spark plug 1 according to the present embodiment, a mark such as the two-dimensional code 10 can be attached to the surface of the seat portion 34 of the spark plug 1 . Further, according to the method of manufacturing the spark plug 1 according to the present embodiment, the protective layer 61 having the protruding portions 62 at predetermined positions can be formed.

(summary)
As described above, the spark plug 1 according to this embodiment includes the insulator 50 and the metallic shell 30 . The metal shell 30 includes an attachment portion 35 attached to the internal combustion engine, a ground electrode 41 provided on the front end side of the attachment portion 35, and a rear end side of the attachment portion 35 having a larger diameter than the attachment portion 35. and a seat portion (large diameter portion) 34 . A mark such as the two-dimensional code 10 and a protective layer 61 covering the mark are provided on the side surface of the seat portion 34 . The protective layer 61 has a projecting portion 62 projecting radially outward from a portion of the surface of the seat portion 34 .

According to the above configuration, the mark can be protected by providing the protective layer 61 so as to cover the mark. Therefore, deterioration of the marks such as rust and peeling can be suppressed during the distribution process of the spark plug 1 and the like.

Furthermore, since the protective layer 61 has the protruding portion 62, the positional relationship between the protruding portion 62 and the ground electrode 41 can be grasped before the spark plug 1 is attached to the internal combustion engine. After being attached, the position of the ground electrode 41 can be easily specified from the position of the projecting portion 62 . Therefore, according to the spark plug 1 of the present embodiment, the position of the ground electrode 41 can be easily confirmed after being attached to the internal combustion engine by using the mark attached to the spark plug.

The method for manufacturing the spark plug 1 according to this embodiment includes a mark forming process, a plate member installing process, and a protective layer forming process. In the plate member installation step, the plate member 100 protruding radially outward of the spark plug 1 from the seat portion 34 is brought into contact with the tip facing surface 34 a of the seat portion 34 . In the protective layer forming step, after the plate member installing step, a coating material is applied on the marks while the plate member 100 is in contact with the tip facing surface 34 a to form the protective layer 61 having the projecting portion 62 .

According to this manufacturing method, when the coating material is applied, the plate member 100 is arranged on the tip-facing surface 34a of the seat portion 34, so that the coating material scatters on the tip-facing surface 34a that serves as the gasket mounting surface. can be suppressed.

Further, by applying the coating material while the plate member 100 is placed on the tip facing surface 34 a of the seat portion 34 , the projecting portion 62 can be formed from the coating material spread on the surface of the plate member 100 . By forming the protective layer 61 having the protruding portion 62 in this way, the position of the ground electrode 41 can be easily confirmed by using the mark attached to the spark plug 1 after being attached to the internal combustion engine. It is possible to manufacture a spark plug 1 that can

In this embodiment, the overhanging portion is formed as a part of the protective layer for protecting the mark attached to the spark plug 1. As shown in FIG. However, the present invention is not limited to such a configuration. For example, part of the metal material used for the metal shell may be used to form the projecting portion.

It should be considered that the embodiments disclosed this time are illustrative in all respects and not restrictive. The scope of the present invention is indicated by the scope of the claims rather than the above description, and is intended to include all modifications within the scope and meaning of equivalents of the scope of the claims. Also, configurations obtained by combining configurations of different embodiments described herein are also included in the scope of the present invention.

1: Spark plug 10: Two-dimensional code (mark)
11: First part 12: Second part 30: Metal shell 34: Seat (large diameter part)
34a : Front facing surface 35 : Mounting portion 41 : Ground electrode 50 : Insulator 52 : Terminal fitting 61 : Protective layer 62 : Overhanging portion 100 : Plate member

Claims (3)

A spark plug comprising an insulator and a metal shell,
The metal shell is
a mounting portion attached to an internal combustion engine;
a ground electrode provided on the tip side of the mounting portion;
a large-diameter portion located on the rear end side of the mounting portion and having a larger diameter than the mounting portion;
On the side surface of the large diameter portion,
Mark and
a protective layer provided to cover the mark;
is provided,
A protruding portion projecting radially outward from a portion of the surface of the metal shell is formed on the rear end side of the large diameter portion including the large diameter portion ,
The spark plug , wherein the projecting portion is formed as part of the protective layer . A tip facing surface is provided on the tip side of the large diameter portion,
The protruding portion is located on the rear end side of the tip facing surface,
A spark plug according to claim 1. A method for manufacturing a spark plug according to claim 1 or 2,
a mark forming step of forming a mark on the side surface of the large diameter portion;
A plate member installation step of contacting a plate member that prevents the coating material from scattering on the tip-facing surface positioned on the tip side of the large-diameter portion and projects radially outward from the large-diameter portion. and,
a protective layer forming step of applying a coating material on the mark while the plate member is in contact with the tip facing surface to form a protective layer having the projecting portion after the plate member installing step;
A method of manufacturing a spark plug, comprising:

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