JP3337698B2 - Spark plug for internal combustion engine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a spark plug for an internal combustion engine having a composite outer electrode.

[0002]

2. Description of the Related Art Conventionally, for example, Japanese Patent Application Laid-Open No. 58-1409
In Patent Publication No. 85, as shown in FIG. 5, the nickel alloy 101 having excellent corrosion resistance (particularly, spark wear resistance) and heat resistance (high-temperature strength) has excellent heat drawing (thermal conductivity) inside. An ignition plug 100 for an internal combustion engine with a composite outer electrode 103 in which copper 102 is embedded is described.

[0003]

However, when the ignition plug 100 is manufactured using the composite outer electrode 103 and used in an internal combustion engine, that is, the ignition plug 100 is disposed in a combustion chamber of the internal combustion engine and is exposed to a high temperature state. And nickel alloy 101 and copper 1
There is a possibility that a thermal stress is generated in the composite outer electrode 103 due to a difference in thermal expansion coefficient between the composite outer electrode 103 and the composite outer electrode 103. That is, as shown by the dashed line in FIG. 5, the composite outer electrode 103 is separated from the tip of the center electrode 104 by, for example, about 0.1 mm, and the spark discharge gap 1 between the composite outer electrode 103 and the center electrode 104 under use conditions.
There was a problem that it was difficult to keep 05 at an appropriate value.

An object of the present invention is to provide an ignition plug for an internal combustion engine having a composite outer electrode for an ignition plug capable of maintaining a spark discharge gap between the composite outer electrode and the center electrode at an appropriate value even under use conditions.

[0005]

A spark plug for an internal combustion engine according to the present invention has a rear end joined to a metal shell and a front end opposed to a center electrode via a spark discharge gap. An ignition plug for an internal combustion engine provided with a composite outer electrode bent as described above, wherein the composite outer electrode is fitted to a core material formed of a second metal disposed at the center and an outer periphery of the core material. Technical means such as comprising a fitting body formed of a third metal and a covering body formed of a first metal that covers the periphery of the fitting body and the core material.

As the first metal forming the cover, a nickel alloy containing nickel as a main component, which is excellent in heat resistance and corrosion resistance, can be considered. As the second metal forming the core, the thermal expansion coefficient is almost the same as the first metal, and the thermal conductivity is excellent.
That pure nickel is conceivable nickel alloy mainly containing pure iron or nickel. As the third metal forming the fitted body, copper or a copper alloy containing copper as a main component, which has better thermal conductivity than the first metal and the second metal, can be considered.

[0007]

The composite outer electrode provided in the ignition plug for an internal combustion engine according to the present invention comprises a first metal made of a nickel alloy containing nickel as a main component and pure nickel, pure iron, or pure iron having a thermal expansion coefficient substantially equal to that of the first metal. The first metal and the second metal are interposed between a second metal composed of a nickel alloy containing nickel as a main component.
A third metal made of copper or a copper alloy containing copper as a main component, which is superior in heat conductivity to metal, is sandwiched. Therefore, even if the temperature changes, the thermal stress caused by the difference in the thermal expansion coefficient is reduced, and the change in the shape of the composite outer electrode is suppressed. That is, even when the composite outer electrode is disposed in the combustion chamber of the internal combustion engine and is exposed to a high temperature state, the change in shape is suppressed, and the spark discharge gap formed opposite to the center electrode is appropriately formed. Value can be kept.

Further, in the use state, the heat of the composite outer electrode is transmitted to the third metal, and is guided to the ignition plug component adjacent to the composite outer electrode. For this reason, the spark discharge gap between the composite outer electrode and the center electrode is maintained at an appropriate value under use conditions.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A method for manufacturing a composite outer electrode for a spark plug according to the present invention will be described with reference to one embodiment shown in FIGS. FIG.
2 is a process diagram showing an example of manufacturing a composite outer electrode, and FIGS. 2 and 3 are diagrams showing an ignition plug for an internal combustion engine. Spark plug 1
Includes a composite center electrode 2 in which a copper core is sealed in a nickel alloy, an insulator 3 fitted on the outer periphery of the composite center electrode 2, and a metal shell 4 fitted on the outer periphery of the insulator 3. A composite outer electrode 5 is joined to the tip of the metal shell 4 by welding.

The composite outer electrode 5 has a rectangular rod shape, and is bent into a substantially L-shape so that the distal end thereof is opposed to the distal end surface of the composite center electrode 2 with a spark discharge gap 6 therebetween. ing. The composite outer electrode 5 includes a core member 7 arranged at the center, a fitting body 8 fitted on the outer periphery of the core material 7, and a covering body 9 covering the periphery of the fitting body 8.

The core 7 is made of a second metal having substantially the same thermal expansion coefficient as the covering 9 and relatively excellent thermal conductivity, and is made of, for example, pure nickel (Ni) or pure iron (Fe). Pure nickel has a coefficient of thermal expansion of 1.3 (10 ⁻⁵ / deg.).
), And the thermal conductivity is 68 (kcal / m · h · deg). Pure iron has a coefficient of thermal expansion of 1.2 (10 ⁻⁵ / deg.).
), And the thermal conductivity is 68 (kcal / m · h · deg). One end of the core material 7 is sealed in the cover 9 together with the fitting body 8, and the other end is joined to the distal end of the metal shell 4 together with the fitting body 8 and the cover 9.

The fitting 8 is made of a third metal having excellent thermal conductivity, and is made of, for example, copper (Cu). Copper has a thermal expansion coefficient of 1.7 (10 ⁻⁵ / deg) and a thermal conductivity of 340.
(Kcal / m · h · deg). The cross-sectional area of the fitting body 8 is, for example, 20% to 50% of the cross-sectional area of the composite outer electrode 5.
Is provided in the range of.

The coating 9 is exposed to the combustion chamber of the internal combustion engine and generates a spark discharge on the surface. The coating 9 is made of a Ni—Mn—Si alloy, Ni—Mn—Si—C
It is made of a first metal such as r alloy, nickel alloy such as Ni-Mn-Si-Cr-Al alloy, Inconel 600, etc., which has excellent heat resistance and corrosion resistance and has high bonding strength with the metal shell 4.

Next, an example of a method of manufacturing the composite outer electrode 5 will be briefly described with reference to FIG. First, a first metal such as a nickel alloy or Inconel 600 is extruded backward to form a cylindrical side wall 91 and a circular closed end at one end of the cylindrical side wall 91 as shown in FIG. Part 9
2, and a cup-shaped cover 9 having a circular open end 93 at the other end of the cylindrical side wall is formed.

Further, as shown in FIG. 1 (A), a cylindrical fitting body made of a first metal such as copper is mounted on the outer periphery of a round bar-shaped core material 7 made of a second metal such as pure nickel or pure iron. The long shaft body (not shown) fitted with 8 is cut at a predetermined axial dimension to form a round bar-shaped clad material 10. The axial dimension of the clad material 10 is the same as that of the cylindrical side wall 9 of the cover 9.
It is cut so as to be shorter than one axial dimension.

Next, as shown in FIG. 1B, the clad material 10 is sealed in the cylindrical side wall 91 of the cover 9 and the clad material 10 is coated by pressing with a press (not shown) or the like. The body 9 and the clad material 10 are integrated, and the cover 9 and the clad material 10 are tightly fitted. At this time, the clad material 10 is held by the cover 9 such that one end surface is in contact with the inner wall of the closed end portion 92 and the other end surface is located in the middle of the cylindrical side wall 91 of the cover 9.

The covering 9 and the clad material 10
As shown in FIG. 1 (C), the open end 93 of the cover 9 is
Is inserted by a punch 12 into a die 11 having a circular die hole. Therefore, the open end portion 93 is closed by the closed portion 94 of the cylindrical side wall 91, and the composite body 13 in which the entire circumference of the clad material 10 is surrounded by the covering body 9 is formed.

Next, as shown in FIG. 1 (D), the composite 13 is placed with the closed portion 94 of the covering 9 at the top.
A die hole is inserted into a die 14 having a rectangular shape by a punch 15, and a rectangular prism portion 21 having a rectangular cross section and an outer diameter of the rectangular prism portion 21 and a flange portion 2 having a circular cross section are formed.
2 is formed.

Next, as shown in FIG. 1 (E), the extruded product 20 is inserted into the die 18 and placed thereon, and the punch 19 is pressed to remove the flange 22 by trimming. Thereafter, the extruded body 20 is cut into a predetermined size, welded to the tip of the metal shell 4, and bent so as to be substantially L-shaped so as to face the composite center electrode 2. As described above, the composite outer electrode 5 is manufactured.

The composite outer electrode 5 manufactured according to this embodiment
Has a copper fitting body 8 sandwiched between a core body 7 and a covering body 9 having substantially the same thermal expansion coefficient and excellent heat and corrosion resistance. For this reason, even if the composite outer electrode 5 is arranged in the combustion chamber of the internal combustion engine and exposed to a high temperature, the thermal stress caused by the difference in the coefficient of thermal expansion is reduced, and the change in the shape of the composite outer electrode 5 is suppressed. Further, in the use state, the heat of the composite outer electrode 5 is transmitted through the fitting body 8 and guided to the metal shell 4, so that the composite outer electrode 5 having high heat conduction efficiency, that is, excellent in heat drawing can be obtained. . Therefore, even when the composite outer electrode 5 is disposed in the combustion chamber of the internal combustion engine and is exposed to a high temperature, the spark discharge gap 6 between the composite outer electrode 5 and the composite center electrode 2 can be maintained at an appropriate value.

(Modification) In this embodiment, as shown in FIG. 1D, the composite 13 is inserted into a die 14 by a punch 15 to form an extruded body 20, but as shown in FIG. Then, an extruded body 30 is formed in the die 16, and then the extruded body 30 containing the extruded body 30 is punched by the punch 17.
The composite 13 may be inserted into 6 and then extruded to form an extruded body 40.

[0022]

According to the present invention, the shape change of the composite outer electrode can be suppressed even under the conditions of use, that is, even when the composite outer electrode is disposed in the combustion chamber of the internal combustion engine and exposed to a high temperature. Can be maintained at an appropriate value. Further, since the composite outer electrode has a good heat pull due to its core material and lowers the temperature, electrode consumption is reduced and preignition by the outer electrode can be suppressed.

[Brief description of the drawings]

FIG. 1 is a process chart showing an example of manufacturing a composite outer electrode.

FIG. 2 is a sectional view showing a spark discharge portion of the ignition plug.

FIG. 3 is a sectional view taken along line AA of FIG. 2;

FIG. 4 is a process diagram showing a modified example of the production example of the composite outer electrode.

FIG. 5 is a sectional view showing a spark discharge section of a conventional ignition plug.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Spark plug 5 Composite outer electrode 6 Spark discharge gap 7 Core material 8 Fitting body 9 Coating body 10 Clad material 20 Extruded body 91 Cylindrical side wall 92 Closed end 93 Open end

Continuation of front page (56) References JP-A-2-295085 (JP, A) JP-A-51-55832 (JP, A) JP-A-55-163786 (JP, A) JP-A-61-143974 (JP) JP-A-4-43585 (JP, A) JP-A-3-15184 (JP, A) JP-A-4-118881 (JP, A) JP-A-4-118882 (JP, A) 4-294085 (JP, A) JP-A-2-121290 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01T 13/00-21/06

Claims (1)

(57) [Claims] 1. An internal combustion engine having a composite outer electrode having a rear end joined to a metal shell and a front end bent so as to be opposed to a center electrode via a spark discharge gap. An ignition plug, wherein the composite outer electrode is disposed at the center, and formed of a core material made of pure nickel, pure iron, or a second metal made of a nickel alloy containing nickel as a main component, and an outer periphery of the core material. A fitting body formed of the fitted third metal, and a covering body that covers the fitting body and the core material and is formed of a first metal made of a nickel alloy containing nickel as a main component, The second metal has better thermal conductivity than the first metal.
And an ignition plug for an internal combustion engine , wherein the third metal is made of copper or a copper alloy containing copper as a main component, which has higher thermal conductivity than the first metal and the second metal.