JP2000077164A - Spark plug for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a subject metal fitting of a spark plug for an internal combustion engine having excellent corrosion resistance, while maintaining easiness for processing when manufacturing it. SOLUTION: If low carbon steel, which is a material for a main metal fitting 5 to constitute a spark plug 1 for an internal combustion engine together with an insulating material 2, contains 14-26 wt.% of Cr, a passive coating is formed on its surface without substantially hardening the material. Therefore, it can be easily processed, in order to enhance productivity, and corrosion resistance can be sufficiently enhanced.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a spark plug used for an internal combustion engine, and more particularly to a metal shell constituting the spark plug.

[0002]

2. Description of the Related Art In general, a spark plug used in an internal combustion engine, particularly a metal shell constituting the spark plug, is made of carbon steel containing Fe as a main component and containing several% or less of carbon, for example, about 10C. In order to suppress the generation of rust, this metal shell has been subjected to a surface treatment such as zinc-plated colored chromate or nickel plating.

[0003]

However, with the recent diversification of leisure activities, personal watercrafts and boats equipped with an internal combustion engine as a power source have become remarkably widespread, and in this case, they are used for internal combustion engines. The spark plug will be exposed to a salt water atmosphere. At this time, the metal shell of the spark plug is made of low-carbon steel containing Fe as a main component and containing several percent or less of carbon similarly to the metal shell of a general spark plug. It is conceivable to perform surface treatment such as plating colored chromate or nickel plating. However, even with such a surface treatment, for example, the generation of white rust in zinc plating and the generation of red rust in nickel plating cannot be reliably suppressed. For this reason, the spark plug itself may be stuck to the plug hole of the internal combustion engine due to the generation of rust, and in the worst case, there may be a problem that the spark plug is forcibly removed and broken.

When used in an internal combustion engine using gas as a fuel, such as a cogeneration engine, highly acidic coagulated water generated by the combustion of the gas as a fuel adheres to the spark plug, and red rust is generated at an accelerated rate. Therefore, there is a disadvantage that the durability of the spark plug is significantly reduced. .

Accordingly, the present invention has been made to solve the above-mentioned conventional problems, and has an object to improve the corrosion resistance so as to prevent the generation of rust in a spark plug, and to improve the durability of the spark plug itself. .

[0006]

For this purpose, an insulator for holding the terminal electrode protruding from the rear end and the center electrode from the front end, and a center for holding the insulator so as to protrude from the front end of the insulator. In a spark plug for an internal combustion engine comprising a metal shell in which a ground electrode is integrally arranged at a position facing the tip of the electrode, the metal shell constituting the spark plug for an internal combustion engine together with an insulator is mainly composed of Fe. Contains at least 14 to 26 wt% of Cr.

Further, in the above-mentioned metal shell, at least from the metal hole to the middle of the metal hole and the screw portion are formed by plastic working, or the surface of the metal shell is plated with nickel.

In the above metal shell, Fe and C may be used.
0.15wt% of carbon contained together with r
In the following, the metal structure is ferrite or austenitic.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION In a metallic shell according to an embodiment of the present invention, at least 14 to
By setting the content to 26 wt%, a passivation film is formed on the surface of the metal shell while the processing into the metal shell is facilitated, so that generation of rust can be prevented, and the durability thereof can be improved. It will be. That is, when the content of Cr is less than 14% by weight, the low-carbon steel which is a main component of the metal shell does not harden remarkably, so that molding by plastic working becomes easy, but the passivation film on the surface of the metal shell is easily formed. The formation is incomplete and a sufficient rust resistance effect cannot be exhibited. On the other hand, when the Cr content is 26 wt% or more, the passivation film on the surface of the metal shell is sufficiently formed, but the low-carbon steel as the material of the metal shell is hardened remarkably.
Forming by plastic working becomes extremely difficult. For this reason, it is conceivable to attempt to form the metal shell by cutting, but the forming itself is possible by cutting,
The mass productivity is reduced and the production cost is significantly increased. It should be noted that if the metal shell does not significantly harden, at least from the metal hole to the middle of the metal hole and the screw part is formed by plastic working, processing becomes easy, and the increase in production cost is suppressed. Can be done.

Further, by subjecting the surface of the metallic shell to nickel plating, the corrosion resistance of the metallic shell surface is improved in combination with the passivation film formed on the metallic shell surface, and the failure due to rust can be more completely prevented. You can do it.

[0011] The metal shell for forming the spark plug for an internal combustion engine together with an insulator is made of Fe and C.
0.15wt% of carbon contained together with r
In the following, it is possible to improve the corrosion resistance of the metal shell itself by making the metal structure ferrite or austenitic.

[0012]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. (1) is a spark plug for an internal combustion engine according to an embodiment of the present invention. The spark plug for an internal combustion engine (1) projects a terminal electrode (3) from a rear end and a center electrode (4) from a front end. (2) and an insulator (2) that is fixedly held together, and a ground electrode is provided at a position facing the tip of a center electrode (4) that is held protruding from the tip of the insulator (2). It is composed of a metal shell (5) in which (6) is arranged integrally.

The metal shell (5) which constitutes the spark plug (1) for an internal combustion engine according to the embodiment of the present invention together with the insulator (2) contains at least 14 to 26 wt% of Cr with Fe as a main component. It is made.

Since the spark plug (1) for an internal combustion engine according to an embodiment of the present invention has the above-described structure, a low carbon material as a material of a metallic shell (5) constituting the spark plug (1) for an internal combustion engine is provided. When the steel contains Fe as a main component and at least 14 to 26 wt% of Cr, a passive film (10) is formed on the surface of the metal shell (5), so that generation of rust can be prevented, and internal combustion can be prevented. The durability of the engine spark plug (1) itself can be improved. At this time, in low-carbon steel which is a material of the metal shell (5) constituting the spark plug (1) for the internal combustion engine, Cr is used.
, Especially 16 to 20 wt% or 16 to 18 wt%
% Can prevent the generation of rust in a short time.
The metal shell (5) is formed at least from the metal hole (7) to the middle of the metal hole (8) and the screw (9) by plastic working, so that the metal shell (5) can be processed. It can be easier.

In addition, the surface of the metal shell (5) constituting the spark plug (1) for an internal combustion engine according to the embodiment of the present invention is plated with nickel so that the spark plug (1) for an internal combustion engine can be used. Corrosion resistance of the metal shell (5) can be further increased, and generation of rust can be more reliably prevented. The low-carbon steel, which is the material of the metal shell (5), was prepared by changing the content of carbon contained together with Fe and Cr to 0.15 wt.
% Or less, and the metal structure is ferrite or austenitic, the corrosion resistance of the metal shell (5) can be enhanced.

Therefore, in order to confirm the effect of the present invention, various tests were performed on the spark plug for an internal combustion engine according to the embodiment of the present invention. For example, the content of Cr is about 5 to 26 wt%, the content of C is about 0.8 wt%, and the content of Mn is about 0.8 wt% (Fe is a main component).
If the Cr content is 18 wt% or more, Ni is 9 wt%.
It is to be contained. A) a spark plug (1) for an internal combustion engine having a metal shell (5) made of a low-carbon steel of (c) was subjected to a neutral salt spray test, an acid resistance test and a cold workability test for the Cr content, The results were examined. As a result, the effect was remarkably confirmed in the embodiment of the present invention (see FIG. 3).

[0017]

As described above, the metal shell constituting the spark plug for the internal combustion engine is provided with a predetermined amount of C with respect to the low carbon steel.
By containing r, it is possible to easily process the material without causing significant hardening of the material, and it is possible to sufficiently reduce the production cost while improving the productivity.
Also, since a passive film is formed on the surface of the metal shell,
Corrosion resistance is remarkably improved, and when the surface of the metal shell is nickel-plated, the corrosion resistance is further improved.

[Brief description of the drawings]

FIG. 1 is a partial sectional view of a spark plug for an internal combustion engine according to an embodiment of the present invention.

FIG. 2 is an enlarged sectional view of a main part of a spark plug for an internal combustion engine according to an embodiment of the present invention.

FIG. 3 shows the results of a neutral salt spray test, an acid resistance test, and a cold workability test on a metal shell of a spark plug for an internal combustion engine according to an embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Spark plug for internal combustion engines 2 Insulator 3 Terminal electrode 4 Center electrode 5 Metal shell 6 Ground electrode 7 Large metal hole 8 Metal hole 9 Screw part 10 Passive film

Claims (4)

[Claims] An insulator for holding a terminal electrode protruding from a rear end thereof and a center electrode from a front end thereof, and a position opposed to a front end of the center electrode holding the insulator and protruding from the front end of the insulator. A spark plug for an internal combustion engine comprising a metal shell in which a ground electrode is integrally disposed, wherein the metal shell forming the spark plug for an internal combustion engine together with an insulator comprises Fe as a main component and at least 14 to 26 Cr.
A spark plug for an internal combustion engine containing wt%. 2. The spark for an internal combustion engine according to claim 1, wherein in the metal shell, the content of carbon contained together with Fe and Cr is 0.15 wt% or less, and the metal structure thereof is ferrite or austenitic. plug. 3. The spark plug for an internal combustion engine according to claim 1, wherein at least a portion of the metal fitting from the large hole to the middle of the middle hole and the screw portion are formed by plastic working. 4. The spark plug for an internal combustion engine according to claim 1, wherein a surface of said metal shell is plated with nickel.