JPS6362872B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for stably forming a noble metal chip on the discharge surface of an outer electrode opposite to the noble metal chip discharge surface on the end face of the center electrode of a spark plug.

Generally, in order to fully utilize the function of a spark plug, the opposing positional relationship between the noble metal chip on the outer electrode side and the noble metal chip on the center electrode side must be strictly controlled. For this purpose, the welding of the noble metal chip to the outer electrode is performed by first joining the center electrode 1 with the noble metal chip 2 welded to the tip surface to the insulator 3, as shown in the cross-sectional view of the completed state in Figure 1. Assemble to metal fitting 4. To form the outer electrode 5, one end of a Ni flat wire, that is, a wire with a rectangular cross section, is welded along the annular end surface 6 of the metal shell 4 so that the side surface including the long side of the rectangular cross section faces the center electrode 1. The rectangular wire material is cut into pieces 7 so that the dimension l to the other end is a predetermined dimension that forms a spark gap between the outer electrode 5 and the end face of the center electrode 1. During this cutting, as shown in FIG. 7, a sagging portion 8 is formed at the end, resulting in loss of flatness. Therefore, if a precious metal chip is welded to this tip, the precious metal chip 9 will be formed as shown in Figure 2.
A wedge-shaped gap 10 is formed between the tip of the noble metal chip 9 and the sagging portion 8 of the outer electrode 5, and the tip of the noble metal chip 9 becomes loose, preventing the welded structure of the discharge surface from becoming unstable. do not have. Therefore, the free portion of the precious metal chip 9 is exposed to the combustion gas from both sides and is damaged.

The present invention aims to eliminate the problems caused by the formation of the sagging portion and to provide a method for manufacturing an outer electrode having a noble metal chip that has excellent durability and stable discharge characteristics.

As shown in FIG. 7, the present invention involves welding one end of the rectangular wire 7 to the end surface 6 of the metal shell 4 and then cutting it to a predetermined length that forms a spark gap. Press 1 as shown in Figure 8
3, 13, etc., and the whole is formed into a flat surface on the same plane. Thereafter, by welding a noble metal chip 9 to the tip of this flat end face as shown in FIG. 9, a stable welded structure can be obtained without creating a gap between the fragment and the noble metal chip. That is, using the spark plug of the present invention shown in FIG. 9 and the conventional spark plug shown in FIG.
2000c.c. engine, idling for 1 minute
Figure 10 shows the results of a durability test in which 6000 cycles of 5000rpm, full-open heating and cooling tests were carried out for 1 minute.
The results are shown as the degree of chip separation (X _{1 +} It has significantly superior peeling resistance compared to other materials.

As described above, the present invention involves welding the rectangular wire serving as the outer electrode to the end face of the metal shell in advance to correct the sag during cutting, and then welding the noble metal tip to the flattened tip. It has a great effect.
That is, one end of a rectangular wire is welded to the end face of a conventional metal shell and cut to a length that takes into account the sagging part, and then a noble metal tip is welded to the flat tip, excluding the sagging part, and the sagging part is cut off. In this method, the material of the rectangular wire is wasted and the cost increases, whereas the method of the present invention does not waste the rectangular wire and can reduce the material cost. Figure 3 is also shown for comparison.
A rectangular wire as shown in FIG. 6 is cut in advance to a predetermined size including the necessary length to form a spark gap and the welding allowance to the metal shell, and the sag portion 12 of the piece 11 is clamped using presses 13, 13, etc. If a precious metal chip is welded to the tip of this flat end face by pressure straightening to make the whole flat end face, and this fragment 11 is welded to the end face 6 of the metal shell 4, there will be large variations due to the welding allowance on the end face of the metal shell, and the precious metal chip will be Since the position is uneven, there is a problem that abnormal wear such as deviation of the chip occurs during use of the engine, and the discharge pressure tends to increase. Since there is no variation, the mounting position of the chip is constant, so the above-mentioned abnormal consumption does not occur and the discharge voltage is low and stable, which has excellent effects.

[Brief explanation of drawings]

FIG. 1 is a front view of the main parts of a spark plug equipped with an outer electrode produced by the manufacturing method of the present invention, FIG. 2 is a cross-sectional view of the tip of the outer electrode produced by the conventional manufacturing method, and FIGS. This is shown for comparison, and shows an example of the process in which a rectangular wire fragment of the required dimensions is first formed and then attached to the end face of the metal shell. Figure 3 is a front view of the fragment, and Figure 4 is a state in which it is straightened by pressing. FIG. 5 is a front view of a precious metal chip welded to the flat end surface after straightening, FIG. 6 is a front view of the precious metal chip welded to the end surface of the metal shell, and FIG. This is a front view of a state in which the rectangular wire end of the material is welded to the end face of the main metal fitting as a fragment of the required dimension l, Fig. 8 is a front view of the state in which the sagging part is corrected, and Fig. 9 is a center view. FIG. 10 is a front view of an assembled insulator with electrodes attached thereto, and FIG. 10 is a graph showing peeling resistance. DESCRIPTION OF SYMBOLS 1... Center electrode, 2, 9... Precious metal chip, 3... Insulator, 4... Metal shell, 5... Outer electrode, 6... Annular end surface of metal shell, 7, 11... Fragment, 8, 12... Sagging portion, 10... gap.

Claims (1)

[Claims] 1. When forming a noble metal chip as the discharge surface of the outer electrode that is placed opposite to the end surface of the center electrode of the spark plug, one end of a rectangular wire made of a base metal material is welded to the annular end surface of the metal shell, and the length to the other end is The material is cut to a predetermined size to form a spark gap with the end face of the center electrode, and after correcting the sagging portion of the end caused by this cutting to form an overall flat surface, a precious metal chip is attached to the end. A method of manufacturing an outer electrode with a noble metal tip, characterized by welding.