JPS6258114B2 - - Google Patents

Description

[Detailed Description of the Invention] (Field of Industrial Application) This invention saves energy and extends the life of an ignition plug for internal combustion engines by equipping the tip surfaces of the center electrode and ground electrode, which form the spark gap, with precious metal chips. This invention relates to a method for joining precious metal chips in spark plugs.

(Prior art) Conventionally, this type of spark plug uses a platinum alloy with excellent heat resistance and wear resistance, such as Pt-Ir, Pt-Rh, Pt-, for the spark discharge part of the center electrode and ground electrode.
It is known, including U.S. Patent No. 2,296,033, that thin plates made of precious metals such as Ni and Pt--Pd are joined by electric welding or the like to extend the life of the plug.

(Problem to be Solved by the Invention) However, in the above conventional spark plug, the total volume of the center electrode and the ground electrode that form the spark gap is large, so that the thermal energy of the flame generated in the spark gap is transferred to both electrodes containing precious metals. It had the disadvantage that it was easily absorbed by water and had poor ignitability. In addition, recent ignition system circuits are lighter,
In order to reduce costs, the voltage applied to the spark plug, which was previously limited to negative polarity, is now being replaced by an ignition power source that uses bipolar polarity, and conventional spark plugs discharge depending on the polarity of the applied voltage. It had drawbacks that affected its performance.

Therefore, in order to reduce the flame-extinguishing effect of the electrode, if the tip of the noble metal is thinned, for example, if a wire with a diameter of 1.0 mmφ or less is electrically welded to the tip surface of the electrode base material, the welding area between the electrode base material and the precious metal is small. The joint strength of noble metals could not be obtained, and combined with the difference in thermal expansion coefficients between the two materials, there was a risk that they would easily fall off when used in actual equipment. In order to improve this problem, a large-diameter flange is provided on the noble metal chip and welded to the electrode base material, or the chip is placed in a recess in the electrode base material, and the tip of the recess is crimped inward at the same time. Welding is known from Japanese Patent Publication No. 56-45264, etc., but in both cases, a significantly large amount of precious metal is used, and in addition, the flange is formed in advance, and the flange can reach the melting temperature at the time of welding. This has the disadvantage that heating is uneven, making it difficult to weld with stable bonding strength to the electrode base material and excellent peeling resistance.

(Means and effects for solving the problem) The present invention has been made to improve the problem, and when forming a noble metal chip at the tip of the center electrode and ground electrode of a spark plug, After fixing the head and coaxially disposing the required amount of wire or square precious metal chips to the head, holding the side surface of the upper half of the precious metal chip and applying electricity while pressing it in the axial direction, the upper half of the chip A spark plug characterized by suppressing undesirable deformation in which the part bulges in the horizontal direction, softening the lower half of the noble metal chip to form an enlarged flange, and joining the head with the welded surface of the flange. Due to the noble metal chip bonding method of the electrode,
The use of precious metal chips in spark plug electrodes increases the welding surface with the chip electrode base material and easily and uniformly raises the temperature of the flange to a high temperature, increasing bonding strength and superior durability, and reducing the amount of chips used. The present invention aims to provide a joining method.

(Example) Hereinafter, the present invention will be explained in detail by referring to an example shown in the drawings.

FIG. 1 is a half-sectional view showing an embodiment of a spark plug in which a precious metal chip can be seen by the joining method of the present invention.
Reference numeral 2 denotes an insulator made of high alumina or the like, and is fixed in the inner cavity of the metal shell 1 through a packing 3 by a known method such as caulking. 4 is a nickel alloy, such as a Ni-Si-Cr-Al alloy, a Ni-Cr alloy,
The center electrode is a Ni-Cr-Fe alloy or a copper core encapsulated inside the alloy, and this center electrode is connected to the insulator 2.
The resistor 5 is inserted into the shaft hole 2a of the shaft hole 2a and is disposed to protrude from the tip end surface, and a resistor 5 is integrally heat-sealed within the shaft hole with a conductive glass seal 6 interposed therebetween and a terminal electrode 7 interposed therebetween. Reference numeral 8 denotes a ground electrode made of a nickel alloy material and protruding from the annular end surface 1a of the metal shell 1.

In the present invention, a thin wire (cylindrical) noble metal chip 9 is welded to the tip end surface 4a of the center electrode 4 to form a flange 9a enlarged at the welding surface. Further, a noble metal chip 10 made of a thin wire or square material is similarly welded to the tip end surface 8a of the ground electrode 8 with a flange 10a. These precious metal chips 9 and 10 have a cross-sectional area of 0.8 mm ² or less, and the chip 1
0 is 1.3mm ² or less Pt―Ir, Pt―Rh, Pt―Ni, Pt―
A platinum alloy such as Pd is used, and the lower limit cross-sectional area is 0.2
Approximately 0.5 mmφ of mm ² is practical.

Next, talking about the method of joining precious metal chips, Figures 2 to 4 show the joining state.
A central electrode base material 4-1 made of a nickel alloy with a copper core enclosed therein is made by known plastic working.The tip of the electrode base material 4-1 has a tapered trapezoidal tip surface 4-1a. form. This tip surface can be easily processed during the production of the electrode base material or by cutting. This electrode base material 4-1 is inserted into the lower chuck 12 of an electric resistance welding machine and fixed with the tip portion exposed by the dimension (1) as shown in FIG. On the other hand, a wire noble metal chip 9-1 is inserted into the upper chuck 13, the upper side surface is fixed, and the tip is exposed by the dimension (2) and similarly fixed, and the chuck is inserted into the inner cavity of the chuck 13. 1
A shaft 14 is provided that presses the rear end surface of the tip 9-1 so as to move downward in conjunction with the tip 9-1. The chuck 13 is lowered and the tip of the tip 9-1 is pressed so as to come into contact with the tip surface 4-1a of the electrode base material 4-1, and in this state, a current is applied to make it red hot, and the upper half of the tip is heated in the lateral direction. As shown in FIG. 3, a large-diameter flange 9-1a is formed on the chip 9-1 and welded to the electrode base material 4-1 (A) to suppress the expansion of the center electrode shown in FIG. 4 is produced. The large-diameter flange portion 9-1a is set by adjusting the above-mentioned exposed dimensions ₁ and ₂ and welding conditions such as voltage, current, time, and pressing force.

Now, using Inconel 600, the center electrode base material 4-1 with a diameter of 2.6 mmφ has a trapezoidal tip surface (1.5 mmφ).
When a chip 9-1 made of Pt-Ir with a diameter of 0.8 mmφ and a length of 1.4 mm is welded to this, the diameter is approximately 1.4 mm.
A collar portion 9-1a having a diameter of mmφ is formed and joined. This center electrode is assembled to the insulator and the metal shell. On the other hand, the tip surface 8a of the ground electrode 8 is made of Inconel 600 with a width of 2.7 mm and a thickness of 1.3 mm for the metal shell.
A spark plug was prepared in which a chip 10 with a width of 1.0 mm and a thickness of 1.0 mm was welded with similar dimensions to form a spark gap between the chip 9 and the end face of the chip 9. As a result of a 100-hour durability test, it was confirmed that the precious metal chips had no abnormalities and had good bonding. In the past, it was necessary to perform diffusion treatment to form an alloy layer after welding the noble metal chip 9-1 to the electrode base material 4-1, but in the case of the present invention, the lower half of the chip can be selectively deformed. This has the advantage that a sufficient welding area can be obtained by welding the flange, so that such processing can be omitted.

Further, as shown in FIG.
A recess 11 is provided in the axis of each of a and 8-1a, and precious metal chips 9 and 10 are placed in this recess and welded in the same manner, so that a part or all of the flanges 9a and 10a are buried. It's okay. In this case, welding burrs can be prevented from protruding, and a stable flange shape can be obtained. Furthermore, it is desirable that the protruding dimension of the chip from the tip surface of the electrode base material is in the range of 0.4 to 1.5 mm.

(Effects of the Invention) As described above, the method of joining a noble metal chip to a spark plug electrode of the present invention suppresses the deformation of the upper halves of the noble metal chips at the tips of the center electrode and the ground electrode, and at the same time only the lower halves. The cross-sectional area of the precious metal chip is 0.8 mm ² or less on the center electrode side and 1.3 mm ² or less on the ground electrode side by deforming and welding it so that the welding surface with the electrode base material has an enlarged flange. It maintains good bonding strength with the electrode base material even in the state of thin wires, has the excellent durability of precious metal chips, and is effective in providing spark plugs with improved discharge characteristics and ignitability. be.

[Brief explanation of the drawing]

FIG. 1 is a half-sectional view showing an embodiment of a spark plug equipped with a noble metal chip by the joining method of the present invention;
2 to 4 are state diagrams showing the bonding of the electrode base material and the noble metal chip, and FIG. 5 is a state diagram showing another bonding of the electrode base material and the noble metal chip. 4... Center electrode, 4-1... Center electrode base material, 4-1
a... Tip surface, 8... Ground electrode, 8-1... Ground electrode base material, 8-1a... Tip surface, 9, 10... Precious metal chip, 9a, 10a... Flange portion, 12... Recessed portion.

Claims (1)

[Scope of Claims] 1. When forming precious metal chips at the tips of the center electrode and ground electrode of a spark plug, the head of the electrode base material is fixed, and the required amount of wire or square precious metal chips is attached to the head. After coaxially arranging the noble metal chips, the side surfaces of the upper half of the chips are held and energized while being pressed in the axial direction, causing the lower half of the precious metal chips to soften and change to form an enlarged flange, and the welded surface of the chips is A method for joining a noble metal chip of a spark plug electrode, which is characterized in that the spark plug electrode is joined to the head thereof. 2 A recess is provided in the axis of the tip surface of the electrode base material,
2. The method of joining a noble metal chip of a spark plug electrode according to claim 1, wherein at least a portion of the collar of the noble metal chip is buried in the recess.