JP2023060489A - Spark plug and method for manufacturing spark plug - Google Patents

Abstract

To provide a spark plug capable of suppressing peeling of a mark made on the surface thereof, and a method for manufacturing the same.SOLUTION: In a spark plug, an identification unit is formed on the outer surface of a metal shell or an insulator, the identification unit includes a first layer formed on the outer surface, and a second layer formed on a part of the surface of the first layer and distinguishable from the first layer, and the thickness of the part of the first layer on which the second layer is formed is thicker than the thickness of the exposed part of the first layer.SELECTED DRAWING: Figure 2

Description

The present invention relates to a spark plug and a method for manufacturing a spark plug.

Spark plugs are used as ignition means for internal combustion engines such as automobile engines. A spark plug has, for example, a shaft-shaped center electrode, a substantially cylindrical insulator that holds the center electrode inside, and a metal shell that holds the insulator inside.

In general, spark plugs are marked with characters, symbols, images, and the like, such as manufacturer names, logos, and product numbers. For example, Patent Document 1 discloses a spark plug in which a marking layer representing characters, symbols, images, etc. is formed on the surface of the spark plug.

JP-A-2004-22227

The inventors of the present invention considered that there is room for improvement in the accuracy of reading marks on the surface of spark plugs.

SUMMARY OF THE INVENTION An object of the present invention is to provide a spark plug whose surface marks can be read with high accuracy.

A spark plug according to one aspect of the present invention includes a tubular metal shell, and an insulator held inside the metal shell and protruding from the rear end side of the metal shell in an axial direction. Alternatively, in a spark plug in which an identification portion is formed on the outer surface of the insulator, the identification portion is formed on the outer surface and includes a first layer and a part of the surface of the first layer. and a second layer formed and distinguishable from the first layer, wherein the thickness of the portion of the first layer on which the second layer is formed is the thickness of the first layer It is thicker than the thickness of the exposed part.

According to the above configuration, the identification section is composed of the first layer and the second layer formed on a part of the surface of the first layer and distinguishable from the first layer, so that the identification section is a single layer. It is possible to suppress the deterioration of the reading accuracy due to scratches and stains on the outer surface as in the case of the case consisting of. In addition, the identification portion may rub against each other during shipping of the spark plug and may be partially peeled off, but compared to the case where the second layer is peeled off from the first layer in the region where the identification portion is formed, If the first layer is peeled off from the outer surface, the reading accuracy will be significantly reduced. Here, according to the above configuration, the thickness of the portion of the first layer on which the second layer is formed is thicker than the exposed portion of the first layer. It is possible to suppress the peeling of the exposed portion, which is particularly easy to peel off during shipping, and to prevent the deterioration of the reading accuracy.

In the spark plug according to one aspect of the present invention, the insulator is mainly composed of alumina, the identifier is formed on the insulator, and the first layer has a brightness of 7 or more. and the second layer may have a brightness of 5 or less.

According to the above configuration, the insulator containing alumina as the main component and the first layer having a brightness of 7 or more have the same color, so even if a part of the first layer is peeled off, the reading accuracy is remarkable. You can suppress the decline. In addition, since there is a difference in brightness between the first layer and the second layer, a contrast is generated between the first layer and the second layer, making it easier to read the identification portion.

In the spark plug according to one aspect of the present invention, the surface roughness Ra of the second layer may be larger than the surface roughness Ra of the first layer.

According to the above configuration, the reflectance of the irradiation light for reading on the surface can be suppressed in the second layer, which is positioned further outside than the first layer, so that the readability of the identification portion is prevented from deteriorating. can be suppressed.

In a spark plug according to one aspect of the present invention, the first layer may be opaque.

According to the above configuration, it is possible to suppress deterioration in reading accuracy of the identification section due to the state of the outer surface.

A method for manufacturing a spark plug according to another aspect of the present invention is a method for manufacturing a spark plug having an identification portion formed on its outer surface, wherein the identification portion is visible on the outer surface. a first step of forming a first layer, and a second step of forming a second layer that is distinguishable from the first layer and visible on a part of the first layer after the first step and

According to the above configuration, the identification section is composed of the first layer and the second layer formed on a part of the surface of the first layer and distinguishable from the first layer, so that the identification section is a single layer. It is possible to suppress the deterioration of the reading accuracy due to scratches and stains on the outer surface as in the case of the case consisting of.

In the spark plug manufacturing method according to another aspect of the present invention, in the second step, the second layer is formed by removing part of the layer laminated on the first layer. may be formed.

According to the above configuration, it is possible to form an identification portion with a higher shape accuracy.

In the spark plug manufacturing method according to another aspect of the present invention, further, in the second step, when removing a part of the layer laminated on the first layer, the outer surface is not exposed. may be removed.

According to the above configuration, it is possible to prevent the outer surface from being damaged when removing a part of the layer laminated on the first layer.

1 is an external view of a spark plug according to a first embodiment; FIG. FIG. 2 is a schematic diagram showing a cross-sectional configuration of an identification portion forming region in the spark plug shown in FIG. 1; 2A to 2C are schematic diagrams showing a process of forming an identification portion in the spark plug shown in FIG. 1 in order of steps;

First embodiment:
FIG. 1 is an external view of the spark plug according to the first embodiment. 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 mainly of alumina. A center electrode 21 is provided at one end (tip 51 ) of the insulator 50 . A terminal fitting 52 is attached to the other end (rear end) of the insulator 50 . A glaze layer may be provided on the surface of the insulator 50. In that case, the insulator 50 is defined as an "insulator" including the glaze layer.

The center electrode 21 is held through a shaft hole of the insulator 50 with its tip portion projecting from the tip portion 51 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. Note that the tip of the center electrode 21 may be composed of, for example, a noble metal tip shaped like a cylinder.

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, and examples of such a metal material include low-carbon steel and iron-based metal materials. Note that the metal shell may be provided with a plated layer, in which case the metal shell including the plated layer is defined as the "metal shell" according to the present invention.

The metal shell 30 mainly includes a crimping portion 31, a tool engaging portion 32, a curved portion 33, a seat portion 34, a body 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 seat portion 34 is positioned between the tool engaging portion 32 and the body portion 35 . An annular gasket is arranged on the seat portion 34 when the spark plug 1 is attached to the internal combustion engine. The trunk portion 35 is positioned on the tip portion 51 side of the insulator 50 . When the spark plug 1 is attached to the internal combustion engine, the thread groove formed on the outer periphery of the body portion 35 is screwed into the threaded hole of the internal combustion engine.

A ground electrode 41 is attached to the front end side of the metallic shell 30 (the side on which the trunk portion 35 is located). The ground electrode 41 is a plate-like body bent in an L shape as a whole, and the base end side thereof 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. Although not shown, a convex portion may be formed in the vicinity of the tip portion of the ground electrode 41 so as to protrude toward the center electrode 21 side.

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) or the like can be mentioned as an alloying element added to the Ni-based alloy. The center electrode 21 and the ground electrode 41 may have inside thereof a core material made of a metal material having excellent thermal conductivity, such as Cu (copper) or a Cu alloy.

(Regarding the identification part of the spark plug)
A two-dimensional code 10, which is an example of an identification portion, is attached to the spark plug 1. As shown in FIG. 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.

In addition, in the present invention, the identification part is not limited to the two-dimensional code. Identification units other than two-dimensional codes include, for example, one-dimensional codes such as barcodes, characters, symbols, images, and the like. Also, the identification section may be configured by combining some of one-dimensional codes, two-dimensional codes, characters, symbols, and images.

In one embodiment, as shown in FIG. 1, the two-dimensional code 10 is attached to an arbitrary position on the outer peripheral surface of the insulator 50 . A region where the two-dimensional code 10 is formed on the outer surface of the insulator 50 is called an identification portion forming region 10a.

FIG. 2 shows a cross-sectional structure of the identification portion forming region 10a of the spark plug 1. As shown in FIG. Two-dimensional code 10 formed on insulator 50 has first layer 11 formed on insulator 50 and second layer 12 formed on part of first layer 11 . Note that the first layer 11 and the second layer 12 are in a distinguishable state. Also, the thickness A of the portion of the first layer 11 on which the second layer 12 is formed is thicker than the thickness B of the portion on which the second layer 12 is not formed. As a result, since the portion of the first layer 11 on which the second layer 12 is not formed on the surface is deep from the surface of the identification part, it is possible to suppress peeling off due to external force during shipping.

In the present embodiment, materials for the first layer 11 and the second layer 12 are not particularly limited, but the first layer 11 is made of, for example, white ink with a brightness of 7 or more, and the second layer 12 is made of, for example, a white ink with a brightness of 5. It consists of ink of a color different from that of the first layer 11 described below. When the first layer 11 has a lightness of 7 or more, even if the first layer 11 is peeled off, the two-dimensional code 10 can be read because the insulator 50 mainly composed of alumina and the first layer 11 have the same color. It is possible to suppress a significant decrease in the reading accuracy of In addition, since the second layer 12 has a brightness of 5 or less, contrast occurs between the first layer 11 and the second layer 12 due to the difference in brightness from the first layer 11 having a brightness of 7 or more, and the reading of the identification part becomes easier.

Furthermore, it is preferable that the surface roughness of the second layer 12 is greater than the surface roughness of the first layer 11 . In addition, the "surface roughness" according to the present invention indicates average arithmetic surface roughness. As a result, in the second layer 12 positioned further outside than the first layer 11, the reflectance of the irradiation light for reading on the surface can be suppressed, so that the readability of the two-dimensional code 10 is lowered. can be suppressed.

Also, the first layer 11 is preferably opaque. As a result, even if the portion of the insulator 50 where the first layer 11 is formed is scratched or dirty, the first layer 11 covers the scratch or dirt, thereby improving the reading accuracy of the two-dimensional code 10 . You can suppress the decline.
(Manufacturing method of spark plug)

Next, a method for manufacturing the spark plug 1 will be described. Here, among the methods of manufacturing the spark plug 1, the process of forming marks such as the two-dimensional code 10 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.

FIGS. 3(a) to 3(c) show the formation process of the two-dimensional code 10 included in the manufacturing method 1 of the spark plug in order of steps. 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.

First, a spark plug without the two-dimensional code 10 is prepared. Then, the first layer 11 is formed on the surface of the insulator 50 (see FIG. 3A). The first layer 11 can be formed, for example, by printing white ink as described above on the surface of the insulator 50 .

Subsequently, a layer that will later become the second layer 12 (hereinafter referred to as an intermediate formation layer 13) is formed on the formed first layer 11 (see FIG. 3B). The intermediate formation layer 13 can be formed, for example, by printing an ink different in color from that of the first layer 11 as described above on the surface of the first layer 11 of the first layer 11 .

After the intermediate formation layer 13 is formed on the first layer 11, a predetermined region of the intermediate formation layer 13 is irradiated with a laser L, and the intermediate formation layer 13 is partially shaved so that the first layer is exposed. A second layer 12 is formed (see FIGS. 3B and 3C). Also, at this time, the first layer 11 is not scraped until the surface of the metal shell 30 is exposed in the laser-irradiated region. The type of laser L is not particularly limited. For example, YAG laser or fiber laser can be used for pulse irradiation or continuous irradiation.

Although the embodiments of the present invention have been described above, the present invention is not limited to the embodiments, and can be implemented in various forms without departing from the gist of the present invention.

Although the two-dimensional cord 10 is formed on the surface of the insulator 50 in the above embodiment, it is of course possible to form it on the metallic shell 30 .

Reference Signs List 1: spark plug 10: two-dimensional cord 11: first layer 12: second layer 13: intermediate forming layer 21: center electrode 30: metal shell 41: ground electrode 50: insulator

Claims (7)

a tubular metal shell, and an insulator held inside the metal shell and protruding from the rear end side of the metal shell in the axial direction,
A spark plug in which an identification portion is formed on the outer surface of the metal shell or the insulator,
The identification part is formed on the outer surface and consists of a first layer and a second layer that is formed on a part of the surface of the first layer and can be distinguished from the first layer,
A spark plug in which a portion of the first layer on which the second layer is formed is thicker than an exposed portion of the first layer. The insulator is formed mainly of alumina,
The identification unit is formed on the insulator,
3. The spark plug according to claim 1, wherein the first layer has a brightness of 7 or more and the second layer has a brightness of 5 or less. 4. The spark plug according to any one of claims 1 to 3, wherein the surface roughness Ra of the second layer is greater than the surface roughness Ra of the first layer. 4. The spark plug of any preceding claim, wherein said first layer is opaque. A method for manufacturing a spark plug having an identification portion formed on its outer surface,
The identification unit
a first step of forming a visible first layer on the outer surface;
a second step of forming a second layer that is identifiable from the first layer and visible on a portion of the first layer after the first step;
A method for manufacturing a spark plug formed by 6. The method of manufacturing a spark plug according to claim 5, wherein in the second step, the second layer is formed by removing part of a layer laminated on the first layer. 7. The method of manufacturing a spark plug according to claim 6, wherein in said second step, when removing a portion of the layer laminated on said first layer, said outer surface is removed so as not to be exposed.

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