JP3099240B2 - Terminal electrode for spark plug - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a terminal electrode of a spark plug used in an internal combustion engine.

[Prior art]

Conventionally, the terminal electrodes that are heated and sealed by a glass seal together with the center electrode in the shaft hole of the insulator that constitutes the spark plug used in the internal combustion engine are equivalent to S10C in consideration of the workability during cold operation. Generally, a steel material is used.

[Problems to be solved by the invention]

However, in the above-mentioned conventional one, with the center electrode in the shaft hole of the insulator, the one that uses a steel material of S10C equivalent material for the terminal electrode heated and sealed by the glass seal, it is made of steel material of S10C equivalent material When the terminal electrode is heated and sealed in a shaft hole of the insulator by a glass seal, the terminal electrode is likely to be softened. When a plug cap that secures electrical conductivity is fitted to the terminal electrode that constitutes the softened spark plug through the base, it is particularly suitable for driving internal combustion engines with large vibrations and high rotation. In the internal combustion engine, abrasion due to the vibration generated by the internal combustion engine occurs between the base portion of the plug cap fitted to the terminal electrode in order to secure the electrical conductivity, and the terminal electrode and the base of the plug cap are formed. Abrasion powder generated by abrasion of the portion stays between the plug cap and the corrugation disposed on the outer periphery of the insulator, and as a result, insulation resistance is reduced, which may cause flashover. Therefore, in order to prevent the terminal electrode from softening at the time of sealing and heating by the glass seal, to SCM435 stipulated in JIS G4025, a material is used that has been added with Cr to improve the hardenability. However, in the case of the Cr-added material, the terminal electrode of the Cr-added material has a nickel plating layer provided on the surface during the glass sealing process during cooling in the glass sealing process in which the maximum temperature is 930 to 950 ° C. When the layer is formed, it is peeled off due to low adhesion to the Cr-added material which is a material to be plated, and there is a problem that oxidation and red rust cannot be prevented when used as a product. In addition, during the nickel plating operation, the addition of Cr deteriorates the plating solution quickly due to the incorporation of Cr ions into the plating layer, resulting in poor workability. In view of the above, the present invention has been made to solve the above-mentioned conventional problems, and has an object to prevent softening of a terminal electrode during glass sealing without impairing oxidation resistance of the surface.

[Means for Solving the Problems]

Therefore, together with the center electrode in the insulator shaft hole, a spark plug having a terminal electrode that is heated and sealed by a glass seal, and a steel material that constitutes the terminal electrode includes:
0.25 to 0.40% by weight, Si: 0.2% by weight, and Mn: 0.9 to 1.50% by weight.

[Action]

With the above structure, by adding Mn instead of adding Cr, the adhesion of the nickel plating layer is improved, and even during rapid cooling in the glass sealing step, the terminal electrode is formed, containing C. In the steel material, the softening of the steel material constituting the terminal electrode can be prevented by mantellite transformation or bainite transformation that produces needle-like crystals, and the steel material is generated between the plug cap and the base of the plug cap by the vibration generated by the internal combustion engine. Wear can be suppressed.

【Example】

The present invention will be further described with reference to an embodiment shown in the drawings. (1) is a spark plug for an internal combustion engine according to an embodiment of the present invention.
Holds the center electrode (3) at the tip inside the shaft hole (6), and the terminal electrode (4) at the rear end inside the shaft hole (6) with the resistor (5) and the conductive glass seal (7). The insulator (2), which is heated and sealed by the glass seal (11) via the intermediary, faces the tip of the center electrode (3) held at the tip inside the shaft hole (6) of the insulator (2). An outer electrode (9) is provided at a position, and a metal shell (10) screwed and fixed to a side periphery of the outer electrode (9) when screwing and fixing the internal combustion engine spark plug (1) to the internal combustion engine (1). 8). The terminal electrode (4), which is heated and sealed by the glass seal (11) together with the center electrode (3) and the resistor (5) in the shaft hole (6) of the insulator (2), has a C: 0.25 ~ 0.40
%, Si: 0.2% by weight, and Mn: 0.9 to 1.50% by weight. Since the terminal electrode (4) of the spark plug (1) for an internal combustion engine according to the embodiment of the present invention has the above-described configuration, the terminal electrode (4) is used in the cooling step of the glass seal for rapidly cooling from a high temperature. In (4), softening can be prevented by the generation of needle-like crystals due to the mantelsite transformation or bainite transformation. Therefore, the terminal electrode (4) and the cap portion of the plug cap caused by the vibration generated by the internal combustion engine can be prevented. The addition of Mn improves the adhesion to the nickel plating layer provided on the surface of the terminal electrode (4) for preventing oxidation, and the quenching of the nickel plating layer during the glass sealing process. Since peeling can be prevented, oxidation resistance when used as a product can be improved. Therefore, S10C and SCM435 (Cr added) equivalent materials conventionally used for the terminal electrode (4), and steel materials in which the addition amounts of the addition elements C, Mn, and Si and the balance Fe in each of the examples were changed, When the Vickers hardness (Hv) after cooling in the glass sealing step was compared, it was confirmed that a terminal electrode (4) having sufficiently high hardness could be manufactured (Table). It is to be noted that a composition ratio other than that described in the claims is not preferable because the mold life during header processing is shortened.

【The invention's effect】

As described above, by adding Mn or the like instead of Cr to the steel material used for the terminal electrode, the strength of the nickel plating layer is improved, the Vickers hardness of the terminal electrode is improved, and the base portion of the plug cap and Has an excellent effect of preventing the occurrence of flashover in corrugation of the insulator by preventing wear of the insulator. Also, because Cr is not added, the adhesion of nickel plating is good, and the plating solution is less deteriorated.
Workability can be improved.

[Brief description of the drawings]

FIG. 1 is an enlarged sectional view of a spark plug for an internal combustion engine according to an embodiment of the present invention. 1 ... spark plug for internal combustion engine, 2 ... insulator, 3 ...
... Center electrode, 4 ... Terminal electrode 5 ... Resistor, 6 ... Shaft hole, 7 ... Conductive glass seal, 8 ... Metal shell 9 ... Outer electrode, 10 ... Screw, 11 ... Glass sticker

Continuation of front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H01T 13/00-21/06

Claims (1)

(57) [Claims] 1. A spark plug comprising a terminal electrode which is heated and sealed by a glass seal together with a center electrode in an insulator shaft hole, wherein a steel material constituting said terminal electrode has C: 0.
A spark plug obtained by adding 25 to 0.40% by weight, Si: 0.2% by weight, and Mn: 0.9 to 1.50% by weight.