JPH0632258B2 - Method of joining precious metal chip electrode to spark plug electrode - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for joining a noble metal tip electrode to the tip of an electrode forming a spark discharge portion of an ignition plug.

(Prior Art) Generally, the thinner the spark plug electrode, the lower the discharge voltage,
In addition, the extinguishing (cooling) action of the electrode can be reduced and the ignitability can be improved, but when the electrode becomes thin, it is easy to be heated and the discharge action deteriorates, so the electrode temperature rises and the base metal electrode such as a normal nickel alloy electrode. For materials, electrode consumption is large. Therefore, a noble metal material excellent in corrosion resistance and spark consumption resistance is used by being made into a chip electrode and joined to the tip of the electrode.

Welding, forge welding, etc. are often used as this joining method. Among these welding methods, electric welding can be performed relatively easily, but melting points are significantly different, for example, both platinum and nickel alloys are welded together. Although it is difficult to do so and the above-mentioned difficulties of plasma arc welding, electron beam welding, laser welding and the like can be overcome, the apparatus becomes large and there is a problem in mass productivity and work safety. Further, the forged method has a drawback that the amount of expensive precious metal tip material used is large, the manufacturing process is complicated and the cost is high.

Therefore, the applicant of the present invention has disclosed in Japanese Patent Application Laid-Open No.
No. 7,154,780 proposes a joining method for brazing noble metal tip electrodes, which does not require an anti-oxidation flux as seen in the conventional brazing work and makes the brazing work simple and stable. It was found that the precious metal tip electrode can be brazed and joined under the conditions described above and has excellent mass productivity. However, in the above method, since the outer diameter of the noble metal tip and the outer diameter of the brazing material are the same, there is a drawback in that the joining strength of the tip is inferior because it does not cover the peripheral side of the noble metal tip when welded to the electrode body.

(Problems to be Solved by the Invention) The present invention is intended to solve the above problems, and an object thereof is to provide a joining method for brazing joining in which the joining strength of a noble metal tip electrode is enhanced.

(Means and Actions for Solving Problems) According to the present invention, after the precious metal thin plate and the heat-resistant brazing material are respectively molded into a predetermined shape, the both surfaces are preliminarily pressure-bonded or superposed at the same time to form the brazing material surface from a base metal. In the method of joining a noble metal tip electrode to an ignition plug electrode, in which the end face of the electrode body is butt-pressed and energized, and the brazing material is melted and joined by using electric Joule heat, the heat-resistant brazing material is After joining to the electrode body with an outer diameter larger than that of the noble metal thin plate, the joining portion made of the heat resistant brazing material is formed so as to cover at least the peripheral side of the noble metal thin plate. With this configuration, the peripheral side portion of the precious metal thin plate can be covered with the brazing material,
It is possible to increase the bonding strength with the electrode body.

The present invention will be described below based on embodiments shown in the drawings. 1 to 4, reference numeral 1 denotes a noble metal plate, and the noble metal material is made of Pt, Ru, Ir or an alloy thereof, for example, a noble metal alloy made of Pt-Ir, Pt-Ru, Ru-Ir or the like is rolled. It is a molded thin plate of about 0.1 to 0.5 mm. Reference numeral 2 is a heat-resistant brazing material for joining the precious metal to the electrode body described later, and here, the spark plug electrode has a temperature that is not abnormal even when exposed to combustion gas such as the maximum speed and high load of the internal combustion engine 950. A thin brazing sheet having a heat resistance of ℃ or more is used. As the brazing material, nickel brazing filler metal, palladium brazing filler metal, gold brazing filler metal, Pt—Ni or the like having a melting point (preferably solidus temperature) of 950 ° C. or higher is used. Particularly preferably, nickel brazing is Cr 0 to 20
%, B0 to 4.0%, Si3 to 10.5%, Fe0 to 5
%, C0-0.9% and the balance Ni alloy, Ni32% and Mn
68% alloy, Mn 68%, Ni 16% and Co 16% alloy, Ni 65%, Mn 23%, S 17% and Cu 5% alloy, Ni 71%, Cr 19% and Si 10% alloy, Ni 3
6%, Ir5% and Cu59% alloy, Ni39%, Cr3
3%, Pd 24% and Si 4% alloy, Palladium braze for Ag0-95%, Cu0-55%, Ni0-48% for Pd5-60% alloy, Gold braze for Au37-38% and balance Cu alloy, Au34.5- 35.5%, Ni2.5
~ 3.5%, balance Cu, and N as Pt-Ni alloy
i10 to 70% and the balance Pt are useful. The precious metal plate 1 and the heat-resistant brazing material are formed into disc-shaped stamping materials 3 and 4 as shown in FIGS. 3 and 4, and the outer diameters of both materials at this time are the brazing material. The material 4 is formed in a larger shape than the precious metal material 3, and both materials produce a rolled clad plate 5 as shown in FIG. Next, as shown in FIG. 6, an electrode body 6 made of, for example, a nickel alloy.
Is fixed by exposing the tip portion of the electrode body in the opening of the chuck electrode 7 of the electric welding machine.
Is arranged so that the brazing material surface 4 of the molding material 5 is in contact with
The pressing electrode 8 is lowered from above to apply pressure, and a large current is instantaneously supplied from a power supply 9 using a welding transformer between the chuck electrode 7 and the pressing electrode 8 via a power supply 10 to be a contact portion. Heat is generated between the material surface 4 and the tip surface of the electrode body 6 to soften and melt the brazing material to bond the noble metal plate 3. FIG. 7 shows the noble metal tip electrode 1 in which the brazing material 4 is bonded to the tip surface of the electrode body 6 formed through these steps so as to wrap at least the circumferential side 3a of the noble metal plate 3 in the axial direction.
1 is an electrode.

The electrode body for joining the tip electrodes is the center electrode and ground electrode of the spark plug, and it is needless to say that it can be applied to a form in which a heat conductive metal such as copper is sealed inside the center electrode. Needless to say, the materials of these noble metal tip electrodes and electrode bodies are not limited to those in the above-mentioned examples, and known noble metals and base metals can be applied.

As a joining method of another embodiment of the present invention, as shown in FIG. 8, the electrode body 6 is fixed to the chuck electrode 7 and the brazing filler metal formed in FIG. 4 is first formed on the tip surface 6a of the electrode body. The plate 4 is placed and the noble metal base plate 3 formed in FIG.
Are placed on top of each other, and pressure is applied by the pressing electrode 8 from above to energize,
The brazing material is softened and melted by heating to perform brazing and joining. Note that these blanks can also be formed by cutting a cylindrical rod. In addition, the joining method using these base plates reduces wasteful use of an expensive precious metal material and facilitates reprocessing. Particularly, in the simultaneous brazing joining method by electric heating, clad molding is not required, so that cost reduction is remarkable. Furthermore, the method of the present invention is disclosed in Japanese Patent Laid-Open No. 57-1.
Compared with the method of 54780, the joining strength of precious metal tip is 2
It can be increased by about 0%. Although not shown, a bottomed hole may be formed in the tip surface 6a of the electrode body 6, and a brazing material base plate and a noble metal base plate may be disposed in the bottomed hole and bonded in the same manner. In this case, the bonding strength can be further improved.

(Effects of the Invention) As described above, the method of joining the noble metal tip electrode to the electrode body of the present invention is relatively easy even if the noble metal tip electrode becomes a thin piece and can be joined easily and firmly without using an antioxidant. In particular, it can be effectively applied to the joining of dissimilar metal materials, which are difficult to be electrically welded because the melting points of both are greatly different.

[Brief description of drawings]

1 to 6 are joining process diagrams showing an embodiment of the present invention. FIG. 1 is a perspective view of a precious metal thin plate, FIG. 2 is a perspective view of a heat-resistant brazing material, and FIG. 3 is a perspective view of FIG. FIG. 4 is a perspective view of a base plate from which a thin noble metal plate has been punched out, FIG. 4 is a perspective view of a base plate from which the heat-resistant brazing material shown in FIG. 2 has been punched out, and FIG. 5 is a perspective view of a clad plate that combines the two. Is a partially cutaway sectional view showing a joined state of the chip electrode, FIG. 7 is a sectional view of an essential part of the electrode obtained by the present invention, and FIG. 8 is a joined state using the blank plates of FIGS. 3 and 4. It is a partially cutaway sectional view shown. 1 ... noble metal thin plate, 2 ... heat-resistant brazing material, 3 ... noble metal base plate, 4 ... brazing material base plate, 5 ... cladding plate, 6 ... electrode body, 6a ... tip surface

Claims (1)

[Claims] 1. A noble metal thin plate and a heat-resistant brazing material are respectively molded into a predetermined shape, and then both are pressure-bonded in advance, or they are superposed at the same time, and the brazing material surface is butted to the tip surface of an electrode body made of a base metal. In the method of joining the noble metal tip electrode to the spark plug electrode, in which the brazing material is melted and joined by using electric Joule heat, the heat-resistant brazing material has an outer diameter larger than that of the noble metal thin plate. A method for joining a noble metal tip electrode to an ignition plug electrode, characterized in that, after joining to the electrode body, the joining portion made of the heat-resistant brazing material is formed so as to cover at least the peripheral side of the noble metal thin plate.