JPH0648630B2 - Spark plug outer electrode and method of manufacturing the same - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an outer electrode of a spark plug arranged with a spark gap between it and a center electrode, and more particularly to a composite electrode of the outer electrode and a method for manufacturing the same. Regarding

[Prior Art] The outer electrode of the spark plug is generally rod-shaped and is joined to the end of the metal shell. Then, the outer electrode is arranged so that the end portion is opposed to the center electrode through the spark gap,
It has been bent.

Further, the outer electrode is generally made of Ni containing 95% or more of nickel with addition of silicon, chromium, aluminum, manganese, or the like.
It is made of alloy. This Ni alloy is excellent in corrosion resistance (especially spark consumption resistance) and heat resistance (high temperature strength), and also relatively excellent in heat conduction (heat conductivity).

However, in recent years, as the performance of engines has improved, there has been a demand for an outer electrode that is more excellent in heat dissipation than before.

Therefore, it has been proposed to arrange Cu, which is excellent in heat dissipation, in the core of the outer electrode.

[Problems to be Solved by the Invention] However, when actually manufacturing an outer electrode having a Cu core, the joint strength with the metal shell is weak, and after the outer electrode is bonded to the metal shell, the outer electrode is centered. When bent to face the electrode, a gap is created at the joint between the outer electrode and the metal shell, or when actually mounted on the engine, C
There was a problem that the heat-extracting effect of u was not sufficiently obtained.

The present invention has been made in view of the above circumstances, and an object thereof is to provide an outer electrode of a spark plug that has high joint strength with a metal shell and is excellent in heat dissipation.

[Means for Solving the Problems] In order to achieve the above object, the outer electrode of the spark plug of the present invention employs the following technical means.

A metal core excellent in heat dissipation, and a metal cover excellent in heat resistance and corrosion resistance that covers the tip and the periphery of the core are provided, and the core is exposed inside the cover. In the outer electrode, the rear end of which is joined to the metal shell of the spark plug by welding, the core portion is formed so that the end surface to be joined to the metal shell is exposed only inside the side to be joined to the metal shell. An outer electrode of a spark plug, which is provided with a joint reinforcement having high joint strength with the metal shell.

A method of manufacturing the outer electrode of the spark plug, comprising the following steps.

(a) A metal body with a brim at the end that is excellent in heat dissipation, and press-fitted into the recess at the center of the brim-side end, a metal body with high joint strength with the metal shell. A first step of forming a first joined body, and (b) a second step of forming the second joined body by inserting the first joined body into the recess of the metal forming the cup-shaped covering body. (C) A third step of pressing the second bonded body from the closed end side of the cup into a circular die having a circular die hole to form a thin cylindrical rod, (d) a flange portion at the end of the cylindrical rod. Step (e) the cylindrical rod is pressed into the rectangular die having a rectangular die hole from the closed end side of the cup to form a prismatic rod, (f) the joined body of the prismatic rods is A sixth step of cutting the exposed joint side.

[Operation and Effect of the Invention] In the present invention, the joint reinforcement provided inside the core portion is directly joined to the metal shell, so that the joint strength between the outer electrode and the metal shell is increased.

Further, since the joint reinforcement provided inside the core is provided only inside the side to be joined to the metal shell, the joint reinforcement does not significantly deteriorate the heat transfer of the core.

As a result, it is possible to obtain an outer electrode having a high bonding strength with the metal shell and excellent heat dissipation.

Further, the outer electrode of the present invention is manufactured by the above manufacturing method.

Example Next, the outer electrode of the spark plug of the present invention will be described based on an example shown in the drawings.

(Structure of Embodiment) FIG. 1 is a sectional view of a main part of an ignition plug arranged in a combustion chamber of an internal combustion engine, and FIG. 2 is a sectional area of an outer electrode.

The spark plug 1 is roughly composed of a center electrode 2, an insulator 3, and a metal shell 4.

The center electrode 2 is a metal body to which a high voltage is applied from an ignition device (not shown), and is a composite electrode in which a Cu core is enclosed in a Ni alloy. The insulator 3 is made of an insulating material such as alumina, and is a cylindrical body that covers the periphery of the center electrode 2 and insulates and holds the center electrode 2. The metal shell 4 is a tubular metal shell made of an iron-based material that is screwed into an internal combustion engine (not shown) while holding the insulator 3, and the outer electrode 5 is provided at the end of the metal shell 4.
It is joined by welding technology.

The outer electrode 5 has a rod shape, and is bent in a substantially L shape so that the end thereof is arranged to face the center electrode 2 with a spark gap 1 therebetween.

The outer electrode 5 is a composite electrode including an inner core portion 6 and a cover 7 that covers the core portion 6.

The core portion 6 is made of Cu that excels in heat conduction. This core 6 is
A joining reinforcement body 8 is provided inside the joining side of the metal shell 4. The joint reinforcement 8 is directly joined to the metal shell 4. That is, in the single state of the outer electrode 5, the joining reinforcement 8 is provided so as to be exposed at the end surface joined to the metal shell 4. The joint reinforcement 8 is a metal having a high joint strength with the metal shell 4, and is, for example, pure Ni, a Ni alloy, or iron. The cross-sectional area of the joint reinforcement 8 is 60% or more of the cross-sectional area of the core 6.

Since the coating 7 is exposed to the combustion chamber and spark discharge is generated on the surface, it has excellent heat resistance (high temperature strength) and corrosion resistance (especially spark consumption resistance), such as pure Ni, Ni alloy, and Inconel. Further, it is made of metal having a high joint strength with the metal shell 4. The cover 7 covers the end (one end) on the side facing the center electrode 2 and the periphery of the core 6. Then, in the single state of the outer electrode 5, the end portion (the other end) on the side joined to the metal shell 4 exposes the core portion 6 inside,
It is directly joined to the metal shell 4. As shown in FIG. 2A, the area of Cu bonded to the metal shell 4 is set to 40% or less of the cross-sectional area of the outer electrode 5.

(Manufacturing Method) Next, an example of a manufacturing example of the outer electrode 5 will be described with reference to FIGS.
A brief description will be given with reference to the drawings.

As shown in FIG. 3, a metal body having a high joint strength with the metal shell 4 is provided in the central recessed portion 9b of the end portion of the cylindrical columnar body 9 made of Cu and having the flange portion 9a on the side of the flange portion 9a. Cylindrical piece made of pure Ni
10 is press-fitted and embedded by a press to form a first bonded body 11 in which the cylindrical body 9 and the cylindrical piece 10 are bonded (see FIG. 4).

The first bonded body 11 is inserted into the recess 12a of the Ni alloy cup 12 forming the cup-shaped cover 7 shown in FIG. 4 to bond the first bonded body 11 and the cup 12 together. The second bonded body 13 is formed (see FIG. 5).

From the closed end side of the Ni alloy cup,
The die hole is pressed into the circular die 14 to form a cylindrical rod 15 having a small diameter and a circular cross section (see FIG. 6).

The collar portion 16 formed on the Cu side end portion of the cylindrical rod 15 is cut (see FIG. 7).

The cylindrical rod 15 is pressed into a rectangular die 17 having a rectangular die hole from the closed end side of the Ni alloy cup to form a rectangular rod 18 having a rectangular cross section (see FIG. 8).

This prismatic rod 18 is cut to an appropriate length on the joining side where the joined body is exposed (see FIG. 9). At this time, the columnar body 18a of the prismatic rod 18 on the Cu joining side is cut. Then, the prismatic rod 18 is annealed.

As described above, the outer electrode 5 is formed.

After that, the cut portion of the cut outer electrode 5 is fixed to the end of the metal shell 4 by welding or the like.

Then, the end portion on the side of the center electrode 2 is bent into a substantially L shape so that the end portion on the side of the center electrode 2 faces the center electrode 2 via a predetermined spark gap l, and the metal shell 4 provided with the outer electrode 5 is formed.

(Experimental example) Next, the cross-sectional area of the core portion 6 and the length of the joint reinforcement body 8 were changed to perform an experiment of the joint strength between the metal shell 4 and the outer electrode 5 and the heat dissipation of the outer electrode 5. An experimental example is shown below.

In the first experiment, as shown in FIG. 10, the length a of the joint reinforcing member 8 was changed to examine the heat drawing effect. The experiment result is shown in the graph of FIG.

As can be seen from this graph, the shorter the joint reinforcing body 8, in other words, the smaller the proportion of the joint reinforcing body 8 in the core portion 6, the higher the heat transfer effect.

In the second experiment, the area of the core 6 was changed to examine the heat transfer effect, and the experimental results are shown in the graph of FIG.

As can be seen from this graph, as shown in (b) of FIG. 2, it is sufficient to set the cross-sectional area of the core portion 6 not including the joint reinforcement 8 to 20% or more of the cross-sectional area of the outer electrode 5. It was possible to obtain a heat-conducting effect. In the third experiment, a joint reinforcement 8 having a constant size was used, the cross-sectional area of the core 6 was changed, and the joint strength when the outer electrode 5 was electrically welded to the metal shell 4 was examined. The experimental results are shown in the graph of FIG.

As can be seen from this graph, by setting the area of Cu bonded to the metal shell 4 to 40% or less of the cross-sectional area of the outer electrode 5, sufficient bonding strength could be obtained.

(Effect of Example) As shown in the above three experimental results, since the joining reinforcing body 8 is provided only inside the core portion 6 on the side to be joined to the metal shell 4, the inside of the core portion 6 is provided. Even if the joint reinforcing member 8 is provided, a large heat conducting effect can be obtained.

The cover 7 is firmly joined to the metal shell 4 by welding on the outside of Cu, and the joint reinforcement 8 is also firmly joined to the metal shell 4 by welding on the inside of Cu. Therefore, the outer electrode 5 is bonded to the metal shell 4 with high bonding strength.

Further, since the outer electrode 5 can be manufactured by partially diverting the manufacturing method of the center electrode, the composite outer electrode 5 can be manufactured at low cost.

(Modification) The present invention includes the following embodiments in addition to the above embodiments.

In this embodiment, the spark plug 1 provided with one outer electrode 5 is illustrated, but a plurality of outer electrodes may be used.

The present invention is applied to the outer electrode 5 bent into a substantially L shape,
It may be applied to the outer electrode 5 having another shape such as a C-shape, or may be applied to the oblique outer linear electrode facing the tip peripheral edge of the center electrode.

[Brief description of drawings]

FIG. 1 is a sectional view of a main part of an ignition plug, FIGS. 2 (a) and 2 (b) are sectional views of an outer electrode, and FIGS. 3 to 9 are process diagrams showing an example of manufacturing the outer electrode. FIG. 10 is a sectional view of the outer electrode for explaining the experimental sample of the first experiment, and FIGS. 11 to 13 are graphs showing the experimental results. In the figure, 1 ... Spark plug, 4 ... Metal shell, 5 ... Outer electrode, 6 ... Core, 7 ... Cover, 8 ... Joint reinforcement, 9 ... Cylindrical, 9a ... Collar, 9b. Recessed part, 10 …… Cylinder piece 11 …… First joined body, 12 …… Cup 12a …… Recessed part, 13 …… Second joined body 14 …… Circular die, 15 …… Cylinder rod 16 …… Flange part, 17… … Short die 18 …… Square bar, 18a …… Cylinder

Claims (2)

[Claims] 1. A core part made of a metal that excels in heat dissipation, and a metal cover body that covers the tip and the periphery of the core part and that is excellent in heat resistance and corrosion resistance are provided inside the cover body. In the outer electrode, the rear end of which the core is exposed is welded to the metal shell of the spark plug by welding, the core has an end surface bonded to the metal shell only inside the side bonded to the metal shell. An outer electrode of a spark plug, wherein a joint reinforcement having high joint strength with the metal shell is provided so as to be exposed. 2. A core part made of a metal that excels in heat dissipation, and a metal cover that covers the tip and the periphery of the core part and that has excellent heat and corrosion resistance, and the core is inside the cover. In the outer electrode, the rear end of which the exposed portion is joined to the metal shell of the spark plug by welding, (a) of the metal columnar body having a flange at the end and excellent in heat conduction, the end on the flange side A first step of forming a first joined body by press-fitting a metal body having a high joint strength with the metal shell into the recess provided in the center, (b) a metal recessed portion forming a cup-shaped covering body A second step of inserting the first bonded body into the second bonded body to form a second bonded body, and (c) pushing the second bonded body into a circular die having a circular die hole from the closed end side of the cup to form a small diameter. The third step of forming the cylindrical rod of (d), the fourth step of cutting the flange portion at the end of the cylindrical rod, (e) the closed end of the cup of the cylindrical rod. Manufacturing the outer electrode of the spark plug, which comprises a fifth step of pressing the die into a rectangular die having a rectangular shape to form a prismatic rod, and (f) a sixth step of cutting the joint side where the joined body of the prismatic rod is exposed. Method.