JPH0492383A - Manufacture of center electrode of spark plug - Google Patents

Abstract

PURPOSE:To prevent a long cylindrical plate from being cracked due to thermal expansion, and thereby enhance durability by forming a solder material layer high in shock absorbing effect against thermal expansion between the long cylindrical plate made of noble metal and a center electrode main body. CONSTITUTION:A round bar made of heat resistant and corrosion resistant base metal is cut off into a specified length, and the both end faces 11 and 12 of the bar are made parallel, so that a metallic body 1a is thereby formed. In the second place, a cup 1b made of metal is manufactured, and the leg section 61c of a copper rivet 6c is fitted in the cup 1b, so that an assembled body 8d is thereby formed. The assembled body 8d is extended to the direction of a cup 1e, the brim 64e of an extruded body 8e, which is projected out at the end of the copper rivet 6e, is cut off while, a body 8f with no brim is formed, and the tip end section of the body at the side of a cup 1f is then squeezed, so that a small diameter section 85 is thereby formed. A cap 87 made of noble metal is manufactured, the small diameter section 85 is fitted in the cup 87 while being soldered 88h, a rear end section 81i is formed with a brim projecting section 8i forming a brim section 82j, and the upper section of the brim section 82j is formed with a slit 84 in a cruci-form shape, so that the center electrode 9 of a spark plug to the tip end small diameter section 86j of which the cap 87 is surely soldered 88j, is thereby manufactured.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for manufacturing a center electrode of a spark plug whose tip portion is brazed with a noble metal.

[Prior art] In general, the thinner the center electrode of a spark plug is, the lower the discharge voltage and the less the electrode's flame-extinguishing effect, which can improve ignition performance. The effect also deteriorates, the electrode temperature rises, and when electrode materials such as ordinary nickel alloys are used, electrode wear increases.

Therefore, in order to achieve both ignitability and durability, corrosion resistance,
A noble metal material with excellent spark wear resistance is used for the discharge part of the center electrode. Furthermore, in order to achieve both ignitability, durability, and economic efficiency, it is desirable to limit the use of precious metal materials to the discharge portion (a portion requiring special characteristics) and to minimize the use of precious metal materials.

Spark plugs include multi-pole plugs with multiple outer electrodes around a center electrode, semi-creeping discharge plugs with outer electrodes around a center electrode, and full creeping discharge plugs that utilize the creeping discharge effect of an insulator. There is. In order to be compatible with these types of spark plugs and to achieve both ignitability, durability, and economic efficiency, we manufacture spark plug center electrodes by welding precious metals to the discharge part (the part that requires special characteristics) on the outer periphery of the center electrode tip. As a method, the special public
There is No. 191.

In the conventional spark plug center electrode manufacturing method described above, a hole is formed at the rear end of a cylindrical body made of a heat-resistant and corrosion-resistant metal mainly made of nickel by a predetermined press process to form a metal cup, and a metal cup is formed separately. A copper stud is manufactured that has a leg that fits into the hole and a head that is the same as the outside diameter of the cup, the leg of the copper stud is fitted into the cup, and the cup and copper stud are assembled by applying pressure. After pressurizing and fixing the cup, an annular groove for the coaxial center is formed on the tip surface of the cup, and a precious metal annular plate that fits into the annular groove is fitted and electrical resistance welded to form a precious metal attached assembly, and The noble metal combination was elongated by extrusion molding toward the cup side, the outer diameter of the combination was reduced, and the noble metal annular plate was formed in an elongated cylindrical shape on the side surface of the tip of the combination. .

[Problems to be Solved by the Invention] However, in the precious metal welded center electrode manufactured by this conventional spark plug center electrode manufacturing method, the long cylindrical plate made of precious metal may crack and break due to thermal expansion, and the durability is poor. There was a problem with sexuality.

Furthermore, since the annular plate is transformed into an elongated cylindrical plate using an extrusion molding process, the axial length of the noble metal elongated cylindrical plate cannot be increased, and the length cannot be formed with high precision.

An object of the present invention is to prevent the long cylindrical plate made of noble metal installed in the spark discharge part of the center electrode from cracking due to thermal expansion, to provide excellent durability, and to adjust the axial length with high precision. It is an object of the present invention to provide a method for manufacturing a center electrode of a spark plug, which can be formed into a central electrode of a spark plug and can therefore be applied to many types of spark plugs.

[Means for Solving the Problems] In order to solve the above problems, the method for manufacturing a center electrode for a spark plug of the present invention includes the following steps: A hole is bored in one end surface of a cylindrical body made of heat-resistant and corrosion-resistant metal to have a bottomed hole. A cup is made, and a copper stud having a leg portion that fits into the bottomed hole of the cup and a head having the same diameter as the cup is separately manufactured, and the leg portion of the copper stud is fitted into the cup. ,
The combined body is pressed together and assembled, and the combined body is expanded by extrusion molding toward the cup side, the outer diameter of the combined body is reduced, and the tip of the combined body on the cup side is further squeezed to form a small diameter portion. A noble metal long cylindrical plate or a precious metal cup is separately manufactured to fit into the small diameter portion, and the noble metal long cylindrical plate or the precious metal cup is brazed to the small diameter portion. , a noble metal discharge part is formed on the side surface of the tip, and more specifically, the brazing is performed using a brazing material having a solidus temperature of 950° C. or higher, such as nickel brazing, palladium brazing, or gold brazing. It was adopted.

[Actions and Effects of the Invention] According to the method for manufacturing the center electrode of a spark plug of the present invention, the following features are achieved with respect to claim 1: The noble metal long cylindrical plate attached to the spark discharge part and the center electrode body are mainly made of nickel. A brazing material layer with a large buffering effect against thermal expansion is formed between the metal (made of heat-resistant and corrosion-resistant metal). Excellent in

(Function) Since the axial length of the precious metal long cylindrical plate or the precious metal cap can be set freely, (effect) the axial length of the precious metal long cylindrical plate or the precious metal cap can be increased, and the shaft of the The length in the direction can be formed with high precision, so it can be used with many types of spark plugs.

Regarding claim 2, (Effects) The brazing material layer exhibits sufficient heat resistance even if it is exposed to combustion gas in an engine for a long time.

[Example] Next, a method for manufacturing a center electrode of a spark plug according to the present invention will be described based on a first example shown in FIG.

(Step 1) A round bar made of base metal (Inconel 600: 8% Fe, 16% Cr, 2% CuO, remainder Ni) with excellent heat resistance and corrosion resistance is cut into a predetermined length of 4.7 m, and then both ends are pressed. 11.12 parallel metal body 1a
(Step 2) Next, the center of one end surface 11 is punched deeply to form a hole 34b to manufacture the metal cup 1b. (Step 3) ) Separately, a leg portion 61c that fits into the hole 34b of the cup 1b and a head portion 62 having an outer diameter equivalent to the outer diameter of the cup 1b.
In order to manufacture a copper stud 6C with good thermal conductivity, the copper stud 6C having the following characteristics (C) shown in the first figure is shown in FIG. The combined body 8d is press-fitted to form a combination body 8d (d in the first diagram). (Step 5) The combined body 8d that has been press-fitted is subjected to a diffusion treatment for 1 hour in an atmosphere of 930°C to reduce the outer diameter. The combination body 8d is extended by extrusion molding onto the side of the cup 1e (step 6), and then the extrusion body 8
A flange body 8f (f in the first diagram) performs flange removal to remove the bulge 64e protruding from the edge of the copper stud 6e of e, (Step 7) Squeeze the tip of the cup 1f of the flange body 8f to a diameter. Forming the small portion 85 (g in the first diagram) (Step 8) A cap 87 made of noble metal (platinum: Pt) that fits into the small diameter portion 85 is manufactured separately, and a cap made of noble metal is attached to the small diameter portion 85. Fit 87 and use palladium brazing filler metal to braze 88.
hL (h shown in the first drawing), (Step 9) Next, a flange 82i is formed on the rear end portion (upper end portion i shown in the first drawing) 811 of the flange body 8i (i shown in the first drawing), (Step 10) Next A center electrode 9 of a spark plug is manufactured which has a cap 87 made of noble metal (platinum), which has a cross-shaped slit 84j formed in the upper part of the flange 82j and is securely joined to the small diameter portion 86j by brazing 88j.
This is the one shown in Figure 1 j).

Next, a modified example of the shape of the noble metal forming the discharge portion of the center electrode will be described with reference to FIG. 2, and a modified example of the shape of the tip of the center electrode to which the noble metal is connected will be described with reference to FIG.

The shape of the noble metal that forms the discharge part is that of the noble metal cap 8.
In addition to type 7 (FIG. 2a), a noble metal perforated cap type 87B (FIG. 2b) or a precious metal elongated cylindrical plate 87C type (FIG. 2C) may be used.

In the above embodiment, the outer circumferential side surface of the center electrode body and the outer circumferential side surface of the noble metal cap are formed in a 10-mm shape, and if they are made flush, the tip shape will be a perforated cap shape (FIG. 3a).
The temporary shape is a long cylindrical shape (Fig. 3b), but the diameter of the outer circumferential side of the noble metal discharge part may be made smaller. In that case, a cap type (Fig. 3c) - a hole-shaped cap type (Fig. 3d) is formed. Alternatively, it becomes an elongated cylindrical temporary mold (Fig. 3e).

FIG. 4.5 is a sectional view of a plug incorporating the center electrode 9 manufactured by the method for manufacturing a center electrode of a spark plug according to the present invention, and an enlarged view of the side of the tip.

The plug 91 includes a multipolar outer electrode 93 at a tip 92a,
Hollow metal shell 92 with mounting screws 92b provided on the outer periphery
, a cylindrical insulator 94 fitted into the metal shell 92, a rod-shaped center electrode 9 inserted into the hole of the cylindrical insulator 94 with its tip 86 protruding, and a rear end at the rear end of the hole. It consists of a terminal electrode 95 inserted with a protruding portion. A noble metal cap 87 is connected to the protruding small-diameter tip portion 86j of the center electrode 9 by brazing 88j and is attached to the multipolar outer electrode 93.
A spark discharge gap is formed between the two.

(Effects) 1. A brazing material layer is formed between the noble metal long cylindrical plate attached to the spark discharge part and the center electrode body (made of heat-resistant and corrosion-resistant metal mainly composed of nickel), which has a large buffering effect against thermal expansion. Therefore, the cylindrical noble metal can be prevented from cracking due to thermal expansion, and therefore has excellent durability.

2. Since the axial length of the precious metal long cylindrical plate or the precious metal cap can be freely set, it can be used with many types of spark plugs.

3. Since the precious metal is formed thinly in the spark discharge part, the use of the precious metal material can be limited to areas that require characteristics, and the amount of precious metal material used can be reduced, making it possible to manufacture the device at low cost.

The present invention includes the following modifications.

(2) As the brazing material, in addition to the palladium soldering material described above, a brazing material having a solidus temperature of 950° C. or higher, such as nickel soldering or gold soldering, may be used.

[Brief explanation of drawings]

FIG. 1 is a process diagram showing a first embodiment of the method for manufacturing a center electrode of a spark plug according to the present invention, FIG.
The figure is a sectional view showing a modified example of the shape of the center electrode tip connected to a noble metal, FIG. 4 is a sectional view of a spark plug incorporating the center electrode manufactured according to the present invention, and FIG. 5 is an enlarged view of the tip. It is a diagram.

Claims (1)

[Claims] 1) A cup having a bottomed hole is made by drilling a hole in one end surface of a cylindrical body made of a heat-resistant and corrosion-resistant metal, and separately, a leg portion that fits into the bottomed hole of the cup and the cup are provided. manufacturing a copper stud having a head equivalent to the outer diameter of the copper stud, fitting the legs of the copper stud into the cup, integrating them under pressure, and elongating the assembled body by extrusion molding toward the cup side; The outer diameter of the combination body is made smaller, the tip of the cup side of the combination body is further reduced to form a small diameter part, and a precious metal orthosis cylindrical plate or a noble metal device is separately fitted to the small diameter part. Manufacturing a center electrode of a spark plug, comprising: manufacturing a cup, and brazing the long cylindrical plate made of noble metal or the cup made of noble metal to the small diameter portion to form a discharge portion made of noble metal on the side surface of the tip. Method. 2) The method for manufacturing a center electrode of a spark plug according to claim 1, wherein the brazing process uses a brazing material having a solidus temperature of 950° C. or higher, such as nickel brazing, palladium brazing, or gold brazing.