JPS6131945B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION FIELD OF INDUSTRIAL APPLICATION This invention relates to a method for bonding a noble metal tip electrode to the tip of an electrode forming the spark discharge portion of a spark plug.

Problems to be Solved by the Prior Art and the Invention In general, the thinner the spark plug electrode is, the lower the discharge voltage and the less the extinguishing (cooling) effect of the electrode, which can improve ignition performance. The thinner the electrode, the easier it is to heat up and the discharge effect to deteriorate, resulting in a higher electrode temperature, and with ordinary base metal electrode materials such as nickel alloy, electrode wear is large. Therefore, a noble metal material with excellent corrosion resistance and spark abrasion resistance is used in the form of a chip electrode and bonded to the tip of the electrode.

Welding, forge welding, etc. are often used for this joining method. Among these weldings, electric welding in particular can join relatively easily, but it is also used to weld platinum and nickel alloys, which have significantly different melting points, such as platinum and nickel alloys. Although it is possible to overcome the above-mentioned difficulties of plasma arc welding, electron beam welding, laser welding, etc., the equipment becomes large and there are problems with mass production and work stability. Furthermore, the forge welding method has the drawback of using a large amount of expensive precious metal chips, making the manufacturing process complicated and increasing costs.

Purpose of the Invention In order to solve these problems, the present invention proposes a joining method for joining noble metal chip electrodes by brazing, and in particular, does not require oxidation-preventing flux as seen in conventional brazing work. The object of the present invention is to provide a method for brazing noble metal chip electrodes, which allows the brazing operation to be carried out easily and under stable conditions, and which is excellent in mass production.

Means for Solving the Problems The present invention is characterized by cladding a thin noble metal plate with a heat-resistant brazing filler metal, forming it into a predetermined shape, and abutting the filler metal surface of this molded material against the tip surface of an electrode body made of a base metal to conduct an electrical connection. A method of joining using Joule heat,
Alternatively, after forming a noble metal thin plate and a heat-resistant brazing material into a predetermined shape, the two may be pressure-welded in advance, or they may be overlapped at the same time, and the surface of the brazing material may be butted against the tip surface of an electrode body made of a base metal to generate electric shock. This is a method of joining using

Embodiments The present invention will be described below based on embodiments shown in the drawings. In Figures 1 to 5, 1 is a precious metal plate;
This precious metal material includes Pt, Pt-Ir, Pt-
It is a thin plate of 0.1 to 0.5 mm formed by rolling W, Au-Pd, Au-Pd-Cr, Au-Pd-Ag, etc.
2 is a heat-resistant brazing material for joining the noble metal to the electrode body described later, and here the temperature is 950°C, which is a temperature that does not cause abnormality even when the spark plug electrode is exposed to combustion gas at the maximum speed of an internal combustion engine, high load, etc. A thin brazing plate having heat resistance of ℃ or higher is used. As this brazing material, nickel solder, palladium solder, gold solder, etc., having a melting point (preferably solidus temperature) of 950° C. or higher, is used. Particularly preferably nickel wax is Cr0~20%, B0~4.0%, Si3~10.5%, Fe0~
5%, C0~0.9% and balance Ni alloy, Ni32% and Mn68%
Alloy, Mn68%, Ni16% and Co16% alloy, Ni65%,
Mn23%, Si7% and Cu5% alloy, Ni71%, Cr19%
Si10% alloy, Ni36%, Ir5% and Cu59% alloy, Ni39
%, Cr33%, Pd24% and Si4% alloy, palladium solder with Ag0~95%, Cu0~55%, Ni0~48%
Pd5~60% alloy, Au37~38% and balance as gold filler
Cu alloy, Au34.5~35.5%, Ni2.5~3.5% and balance
Cu etc. are useful. 3 is a clad plate in which the noble metal thin plate 1 and the heat-resistant brazing filler metal are pressed together, as shown in FIG. In FIG. 4, a molded material 4 is produced by punching out the clad plate 3 into a cylindrical shape matching the shape of the electrode joint. Next, as shown in FIG. 5, an electrode body 5 made of, for example, a nickel alloy is fixed in an opening hole of a chuck electrode 6 of an electric welding machine with the tip of the electrode body exposed. 5a so that the brazing material surface 2 of the molding material 4 is in contact with the molding material 4,
Pressure is applied by lowering the pressure electrode 7 from above, and a large current is instantaneously supplied between the chuck electrode 6 and the pressure electrode 7 via an electric wire 9 from a power source 8 using a welding transformer. Heat is generated on the material surface 2 and the tip end surface of the electrode body 5 to soften and melt the brazing material, thereby joining the noble metal 1. FIG. 6 shows an electrode having a noble metal chip electrode 1 on the tip end surface of an electrode body 5 formed through these steps.

The electrode body to which the chip electrode is connected is the center electrode and ground electrode of the spark plug, and it goes without saying that it can also be applied to forms in which a thermally conductive metal such as copper is sealed inside the center electrode. It goes without saying that the materials of these noble metal chip electrodes and electrode bodies are not limited to those of the above embodiments, and that known noble metals and base metals can be used.

As a joining method of another embodiment of the present invention, the first
The noble metal thin plate 1 and brazing material 2 shown in FIGS. 7 and 2 are punched out into predetermined shapes as shown in FIGS. 7 and 8 to form a cylindrical noble metal blank 11 and a brazing filler metal blank 12, respectively. . These two blank plates are stacked and pressed against each other to form a molded material 14, which is then joined by brazing in the same manner as shown in FIG. Alternatively, as shown in FIG. 10, the electrode body 5 is fixed to the chuck electrode 6, and the brazing material blank 12 formed in FIG.
The noble metal blanks 11 formed as shown in the figure are placed one on top of the other, and a pressure is applied from above using a pressing electrode 7, and electricity is applied to generate heat to soften and melt the brazing material, thereby joining the brazing material. Note that these blank plates can also be formed by cutting a cylindrical bar. Furthermore, the joining method using these blank plates reduces wasteful use of expensive precious metal materials and facilitates reprocessing.

Functions and Effects As described above, the method of brazing a noble metal chip electrode to an electrode body of the present invention allows the noble metal chip electrode to be joined relatively easily and without using an antioxidant, even if the noble metal chip electrode becomes a thin piece. In particular, it can be effectively applied to the compatibility of dissimilar metal materials whose melting points differ widely and are difficult to electrically weld. Furthermore, in the case of the second joining method of the present invention in which a noble metal blank and a brazing metal blank are overlapped and bonded to an electrode body, in addition to the above-mentioned effects of the present invention, cladding of the noble metal and the brazing metal is difficult. It is useful for materials, and since no cladding is required, reprocessing of precious metals is easy, and material costs are significantly reduced accordingly.

[Brief explanation of the drawing]

Figures 1 to 5 are joining process diagrams showing examples of the present invention. Figure 1 is a perspective view of a precious metal thin plate, Figure 2 is a perspective view of a heat-resistant brazing material, and Figure 3 is a composite of both. FIG. 4 is a perspective view of the plate, FIG. 5 is a partially cutaway sectional view showing the bonded state of the chip electrode, and FIG. 6 is the electrode obtained by the present invention. , FIG. 7 is a perspective view of a blank plate punched out of the precious metal thin plate shown in FIG. 1, FIG. 8 is a perspective view of a blank plate punched out of the heat-resistant brazing material shown in FIG. FIG. 10 is a partially cutaway sectional view showing a joined state using the blank plates shown in FIGS. 7 and 8. FIG. 1...Precious metal thin plate, 2...Heat-resistant brazing material, 3...
Cladding plate, 4, 14...molding material, 5...electrode body, 5a...tip surface.

Claims (1)

[Scope of Claims] 1. A thin noble metal plate is clad with a heat-resistant brazing material, then formed into a predetermined shape, and the surface of the formed material is brought into contact with the tip surface of an electrode body made of a base metal, pressurized, and energized to generate electricity. 1. A method for joining a noble metal chip electrode to a spark plug electrode, characterized in that the soldering material is melted and joined using target resin heat. 2. After forming a noble metal thin plate and a heat-resistant brazing material into a predetermined shape, they are either pre-press-molded or simultaneously stacked and the surface of the brazing material is butted against the tip surface of an electrode body made of a base metal, and pressurized and energized. . A method of joining a noble metal chip electrode to a spark plug electrode, characterized in that the brazing material is melted and joined using electric shock.