JPS62298662A - Spark plug for internal combustion engine - Google Patents

Abstract

PURPOSE:To make fixation of a tip by simple and uncostly method, by furnishing a hole at a spark discharge part of at least one of the electrodes, and fixing the tip in this hole in mechanically contacting state through pressurization and hot deformation. CONSTITUTION:Metal tips 3a, 3b with higher resistance against wear because of sparks than the mother metal are fixed to the spark discharge opposing parts of a center electrode 1 and a grounding electrode 2. Here the grounding electrode 2 is provided with a through hole 4, wherein the two surfaces 4a, 4b are greater and which consists of a three-step construction with smaller central part 4c. The tip 3b to be inserted in said through hole 4 is formed convex and located by major dia. part 4a by inserting from the spark part side. Thereafter current is supplied to the tips 3bb in pressurized condition, and the tip 3b is hot deformed into a specified configuration to be fixed to the grounding electrode 2. Accordingly the tip 3b and grounding electrode 2 are in mechanical contact simply, which should prevent generation of thermal stress at the interface between the two.

Description

Detailed Description of the Invention 3. Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a parking plug for an internal combustion engine, and relates to a fixing structure for fixing a metal tip to a spark discharge part.

[Conventional technology]

Improving the wear resistance of spark plugs is strongly demanded by society as part of the trend of expanding the maintenance of automobile parts. In order to meet this demand, various inventions have been made for joining and fixing chips made of materials with excellent wear resistance, mainly noble metals. This invention is divided into two types: one is the drawing process as in Japanese Patent Publication No. 56-45265; A mechanical fixing method involves plastically deforming the opening after inserting the tip and fixing it by caulking.Another method is to join the noble metal tip and the base material of the electrode using resistance welding or laser. This is the way to do it.

[Problem that the invention seeks to solve]

Each of the above methods has problems. That is, the drawing process is limited to materials whose chips are highly ductile and malleable. When fixing by caulking, the hardness of the plastically deformed part of the base metal decreases due to high temperature combustion gas, and the caulking force decreases.

In addition, stress remains in plastically deformed parts, particularly in places where the deformation is large, and therefore corrosion tends to occur intensively due to combustion gas. Furthermore, considering the spring back of the plastically deformed portion, this fixing method has poor reliability and durability.

On the other hand, in the method of joining and fixing by welding, thermal stress is generated on the joint surface because the linear expansion coefficients of the chip and the base metal are different. Thermal stress follows the operating conditions of the internal combustion engine and occurs repeatedly, resulting in cracks occurring at the joint surface between the chip and the base material, leading to the chips falling off. Therefore, JP-A-59-47436, JP-A-59-
As in 94391, it is necessary to alleviate thermal stress, and therefore it is difficult to say that it is economical in terms of costs such as man-hours and material costs.

[Failure to solve the problem]

The present invention aims to solve the above problem, and includes a hole in the spark discharge part of at least one of the two electrodes, and a material that is more resistant to spark wear than the base metal of the one electrode. and is fixed to the above Omukai by its own deformation,
The device has a metal chip arranged therein, and the chip and the base metal are in mechanical contact with each other.

〔Example〕 The present invention will be explained in detail below using specific examples.

In FIGS. 1 and 2, FIG. 1 is an enlarged view of the firing part of the plug, and 1 is a center electrode and 2 is a ground electrode.

Metal chips 3a, 3b having superior spark abrasion resistance compared to their base metals are provided on the spark discharge opposing portions of each electrode 1.2.
is fixed. The configuration will be explained using processing and assembly methods. On the ground electrode side, there is a through hole 4 in three stages as shown in Figure 2 fa).
will be established.

The through hole 4 is large on the surface sides 4a and 4b of the ground electrode 2, and small on the central portion 4C. The chip 3b having spark wear resistance inserted here has a convex shape, and is inserted from the ignition part side as shown in FIG. 2 (C1) and positioned at the large diameter part 4a of the through hole. Figure 2 (d+
As shown in FIG.
The chip 3b is fixed to the ground electrode 2 by heating and deforming it into the shape shown in FIG. 2(e). According to this method,
Since the chip 3b and the ground electrode 2 are not welded and are only in mechanical contact, no thermal stress is generated at the interface between the chip 3b and the ground electrode 2 due to the difference in linear expansion coefficient. do not. Therefore, restrictions on joining and drawing different materials can be avoided, and concerns due to a decrease in caulking force that can be seen in caulking fixation are eliminated, and durability can be ensured. Note that the deformation of the chip 3b can be performed by applying a large amount of power under pressure, applying pressure in a heated state, or applying pressure at room temperature. Examples of the center electrode 1 are shown in FIGS. 3(a) to 3(h). Figure 3 fan, (b)
is a diagram in which a groove for holding a chip is provided, and the groove 5 has a concave cross section. Figure 3 (cl, (d), (e) is
This shows the state when the chip 3a is inserted. The shape of the tube 3d is shown in FIG. 4 (al to fd). Thereafter, as in the case of the ground electrode, high power is applied under pressure to heat and deform the chip 3a as shown in FIGS. Therefore, the fixed portion can obtain the same effect as the above-mentioned ground electrode.

The chips 3a and 3b are preferably made of platinum group elements, alloys thereof, or base metals that have good resistance to spark abrasion. Note that ceramic powder may be added to these to form a cermet.

5 and 6(a) to 6(C) show other embodiments of the present invention, these embodiments include chips 3a and 3b.
The cross section is approximately triangular.

Further, in the present invention, the present invention may be applied to one electrode instead of both the center electrode and the ground electrode as in the above embodiment.

〔Effect of the invention〕

As described above, according to the present invention, various conventional problems can be solved at once.

[Brief explanation of drawings]

, FIG. 1 is a sectional view showing the main parts of an embodiment of the present invention, and FIG.
Figures (at, (bl, (cl, (di, and (e
l is a cross-sectional view showing the process of joining the metal chip to the ground electrode in Fig. 1, Fig. 3 (at, (b), (c), (
di, (e), (fl, (gl, (h) is the first
A diagram showing the process of joining the metal tip to the center electrode in the figure.
Figure 4 (al, (b), (C), and (di) indicate the metal chip in Figure 3, Figure 4 + a) is a left side view, Figure 4 (b) is a plan view, and Figure 4 (b) is a plan view. 4(C) is a right side view, FIG. 4(d) is a front view, FIG. 5 is a sectional view showing another embodiment of the present invention, and FIGS. 6(a), (bl, and ()).
C) shows still another embodiment of the present invention, which is shown in FIG.
al is a plan view, FIG. 6 (bl is a partial cross-sectional front view, and FIG. 6 (C) is a partial side view. 1... Center electrode, 2... Ground electrode, 3a, 3b・・・
・Metal tip, 4, 5...hole.

Claims (1)

[Claims] A spark plug for an internal combustion engine in which a spark discharge gap is formed between two electrodes, wherein at least one of the two electrodes has a hole in the spark discharge part, and the material is more resistant to spark wear than the base metal of the one electrode. A spark for an internal combustion engine, characterized in that it has a metal tip fixed and arranged in the hole by deformation of itself, and the tip and the base metal are in mechanical contact with each other. plug.