JPS59953B2 - Spark plug housing caulking method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION In the spark plug manufacturing process of the present invention, a housing that has been surface-treated with plating or (and) colored chromate is pressed and caulked using a press die, and the housing is fitted into the housing and insulated. This invention relates to a housing caulking method for fixing a body.

As shown in Figure 1, a spark plug is made by fitting an insulator (■) into which a center electrode (■) is inserted into a housing (■) that has been surface-treated, such as colored chromate treatment, and then injecting ceramic powder (■) into the gap between the housing (■) and the insulator (■). After that, the upper end of the housing is caulked inward using a press (after caulking, the tip of the housing (■) deforms as shown in 0), and the insulator (2) is fixed inside the housing (2).

However, during this caulking work, a large surface pressure is applied to the contact area (2) between the press die (2) and the housing (2), and the coating formed by the surface treatment of the housing (2) is likely to be damaged due to peeling or the like.

Such damage to the coating reduces the anti-corrosion ability of the product and also worsens its appearance.

Conventionally, in order to prevent damage to the coating due to surface treatment during caulking work, there has been a method of plating the contact area ■ of the press die ■, or a method of applying oil to the contact area ■ between the mold ■ and the housing ■. Although attempts have been made, the former has short plating life and is not suitable for mass production, while the latter has drawbacks such as oil contaminating the product and press machine, and the uneven thickness of the oil film making precision machining difficult. there were.

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for caulking a spark plug housing, which eliminates these drawbacks, reliably prevents damage to the coating, and allows precise machining without contaminating the product or press machine.

In the present invention, a water-soluble acrylic resin is added to hot water, which is the final step of surface treatment of the spark plug housing, so that the resin concentration is 0.2 to 40% by weight, and basic water such as ammonia, caustic soda, etc. The pH of the substance in hot water is 7 to PH.
9, and the housing is washed with hot water and dried to form a solid acrylic resin film on the housing surface.Then, an insulator is fitted into the housing, and the housing is pressed and caulked to form an insulator. The main point of this invention is to fix the inside of the housing, and the present invention will now be described in detail.

The spark plug housing metal fittings are galvanized to prevent rust, and the housing is further chromate-treated to protect the zinc layer. More preferably, an aqueous solution of a water-soluble acrylic resin rust preventive agent such as Dipsol Fu 443 or Bian 444, manufactured by Dipsol Co., Ltd., with a weight ratio of 5 to 6, has a pH of 7 to 9, preferably a pH of 7.5 to
It is immersed in hot water to which a basic substance such as ammonia or caustic soda is added so that the pH is in the range of 8.5.

Next, the housing is taken out of the hot water and dried at a temperature of around 40° C., and the sol-like liquid film of the acrylic resin becomes a gel-like solid film.

In the above, the lower limit of the concentration of the water-soluble acrylic resin aqueous solution was set at 0.2% by weight because if a more dilute aqueous solution is used, the film will become too thin, break during caulking, and damage the film due to surface treatment. The reason why the upper limit was set at 40% by weight was because if the aqueous solution became thicker than this, the viscosity of the aqueous solution would become too high and the film would become too thick, which would impede the caulking action. It is.

Further, the hydrogen ion concentration of the aqueous solution is set to be between PH7 and PH9, because at a pH of 7 or less, the water-soluble acrylic resin gels and becomes unusable, and at a pH of 9 or higher, the antirust effect on the plated surface decreases.

As shown in Figure 2, when the insulator ■ is lowered into the housing ■ on which the solid film ■ has been formed by the above method and is tightened by pressing, the film ■ has a lubricating effect between the press die ■ and the housing ■. As a result, the surface pressure at the contact portion (3) is reduced, and the coating formed by galvanizing and colored chromate treatment is prevented from being damaged.

Note that the surface treatment film of the housing is not limited to zinc plating or colored chromate treatment, but damage can be similarly prevented by coating only by zinc plating or by plating with other metals.

Example I Dipsol A44, a water-soluble acrylic resin rust preventive agent
Aqueous ammonia was added to the 5-weight polyhydric solution of 2 to make the pH 7.
After immersing the housing, in which the housing metal fittings were galvanized and colored chromate-treated, in hot water prepared as No. 5 for 1 minute, the housing was removed from the hot water and dried in the atmosphere at a temperature of 40°C to form a solid acrylic resin film. An insulator was fitted inside the housing and pressed as shown in FIG. 2 to fix the insulator inside the housing.

As a result, it was confirmed that the coating of the 1,000 test housings, which had been subjected to galvanizing and colored chromate treatment, was not damaged at all, and the products and the press machine were not contaminated.

Example 2 Dipsol A44, a water-soluble acrylic resin rust preventive agent
Add ammonia water to the 10 weight aqueous solution of 4 to adjust the pH to 8.
A solid acrylic resin film was formed on the housing using diluted hot water in the same manner as in Example I, and an insulator was fitted and pressed to obtain the same results as in Example 1.

Note that water-soluble acrylic resin does not necessarily have to be a rust preventive agent, but when a water-soluble acrylic resin-based rust preventive agent is used, the solid resin coating has the effect of rust-preventing the housing, so it has a rust-preventing effect. can be further improved.

As described above, in the spark plug housing caulking method of the present invention, since the housing is caulked after forming a solid acrylic resin coating, damage to the coating due to the surface treatment applied to the housing can be prevented, and the product and press Precise caulking is possible without contaminating the machine.

[Brief explanation of the drawing]

FIG. 1 shows a conventional spark plug housing caulking method, and FIG. 2 shows a spark plug housing caulking method according to the present invention. In the figure, ■・・・Housing, ■・・・Insulator, ■・・・Coating.

Claims (1)

[Claims] 1. In crimping the housing, which is done to fix the insulator after fitting it into the surface-treated spark plug housing, the surface-treated housing is coated with a water-soluble acrylic resin. The housing is immersed in hot water with a pH of 7 to 9 by adding a basic substance to an aqueous solution with a weight ratio of 2 to 40%, and then dried to form a solid resin film on the housing surface.The housing is then fitted with an insulator that forms a solid resin film on the housing surface. A spark plug housing caulking method characterized by caulking. 2. The spark plug housing caulking method according to claim 1, wherein the surface treatment is zinc plating and colored chromate treatment. 3. The spark plug housing caulking method according to claim 1 or 2, wherein the water-soluble acrylic resin is a water-soluble acrylic resin rust preventive agent.