JPH1064656A - Spark plug for internal combustion engine - Google Patents

Abstract

(57) [Problem] To specify the direction of an outer electrode 13 in a combustion chamber 2. SOLUTION: A metal shell 9 has a cylindrical portion 11 inserted into an insertion hole 5, and no screw is formed around the cylindrical portion. A recess 15 extending in the axial direction is provided around the metal shell 9, and the recess 15 is formed on the protrusion 6 of the cylinder head 3.
Engages. Thereby, the direction of the outer electrode 13 in the combustion chamber 2 is specified. As a means for fixing the metal shell 9 to the cylinder head 3, a fixing member 10 provided separately is used. The fixing member 10 is screwed into the mounting recess 4 of the cylinder head 3 and presses the metal shell 9 against the bottom of the mounting recess 4 to fix it. As described above, since the direction of the outer electrode 13 is specified and fixed, stable ignitability and heat resistance can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a spark plug which generates a spark discharge in a combustion chamber of an engine.

[0002]

2. Description of the Related Art A conventional spark plug is fixed to an engine by screwing a screw at a tip end provided on a metal shell into a cylinder head of the engine.

[0003]

The outer electrode provided at the tip of the spark plug is provided at the annular tip of the metallic shell. Since this metal shell is screwed into the cylinder head, there is a problem that the direction of the outer electrode cannot be specified in the combustion chamber. That is, for each cylinder,
The direction of the outer electrode is different from the direction of the mixture flow, and the ignitability and heat resistance of the spark plug are different from each other.

[0004]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a spark plug for an internal combustion engine capable of specifying the direction of an outer electrode in a combustion chamber.

[0005]

A spark plug for an internal combustion engine according to the present invention employs the following technical means. A spark plug for an internal combustion engine includes a center electrode to which a high voltage is applied, an insulator for insulating and holding the center electrode, and an outer electrode for generating a spark discharge between the center electrode and the center electrode. And a metal shell fixed to the engine while holding the insulator. The metal shell has a small-diameter cylindrical portion without a screw and a large-diameter trunk portion on the distal end side, holds the insulator in a bore, and prevents rotation of the engine. A rotation preventing means is provided on the cylindrical portion or the body, and is fixed to the engine by a fixing member provided separately from the metal shell.

According to a second aspect of the present invention, in the spark plug for an internal combustion engine according to the first aspect, the detent means is provided on an axially extending engaging portion provided on the cylindrical portion or the body portion of the metallic shell. And an engaged portion provided in the engine and extending in the axial direction to engage with the engaging portion.

According to a third aspect of the present invention, in the spark plug for an internal combustion engine according to the first aspect, the detent means connects the bottom of the body of the metallic shell with a seat surface of a mounting recess of the engine. It is characterized by being.

According to a fourth aspect of the present invention, in the spark plug for an internal combustion engine according to any one of the first to third aspects, the fixing member includes a screw screwed to the engine, and the screw is screwed to the engine. As a result, the metal shell is pressed against and fixed to the engine.

[0009]

In the spark plug for an internal combustion engine according to the present invention, the metal shell is prevented from rotating with respect to the engine by the detent means, and the metal shell is fixed to the engine by a separate fixing member. Have been. As described above, since the metal shell does not rotate with respect to the engine, the direction of the outer electrode can be directed to a direction designed in advance. For this reason, a spark plug is used for each cylinder.
Stable ignitability and heat resistance can be obtained.

[0010]

Next, an embodiment of the present invention will be described as a first embodiment.
The third embodiment will be described with reference to the drawings. FIGS. 1 and 2 are views for explaining the first embodiment. FIG. 1 is a sectional view showing a spark plug mounted on a cylinder head of an engine, and FIG. It is principal part sectional drawing which shows.

The spark plugs 1 are attached to the combustion chambers 2 of the respective cylinders of the engine, and discharge sparks to the respective combustion chambers 2. A mounting recess 4 for mounting the spark plug 1 to the cylinder head 3 is formed in the cylinder head 3 of the engine to which the spark plug 1 is assembled. A small diameter insertion hole 5 for guiding the end of the spark plug 1 into the combustion chamber 2 is formed at the bottom of the mounting recess 4. As shown in FIG. 2, a convex portion 6 for preventing rotation of the metal shell (corresponding to an engaged portion which engages with a concave portion described later) is provided on the upper side of the side wall of the mounting concave portion 4. Extend in the axial direction (the vertical direction in FIG. 1).

The spark plug 1 has a center electrode 7 receiving a high voltage, a substantially cylindrical insulator 8 for insulating and holding the center electrode 7, and is fixed to the cylinder head 3 while holding the insulator 8. By pressing the metal shell 9 and the metal shell 9 against the cylinder head 3, the spark plug 1 is formed.
And a cylindrical fixing member 10 for fixing the cylinder to the cylinder head 3 of the engine. The center electrode 7 and the insulator 8 shown in this embodiment are well-known.

The metal shell 9 is made of low-carbon steel and is a substantially cylindrical metal fitting for firmly holding the insulator 8 inside. The cylindrical metal part 11 is inserted into the insertion hole 5, and the cylindrical metal part 11 is
The body 12 has a larger diameter. The tubular portion 11 is a tubular body having no engine fastening screw formed around it, and an annular electrode 20 of the tubular portion 11 has an outer electrode made of a well-known nickel alloy opposed to the center electrode 7. 13 is fixed by welding or the like.

The body portion 12 is an annular body having a large diameter from the cylindrical portion 11 via a step 14.
As shown in the figure, a concave portion 15 for engaging with the convex portion 6 provided on the side wall of the mounting concave portion 4 and preventing rotation of the metal shell 9.
(Corresponding to an engagement portion) is formed to extend in the axial direction. The engagement between the concave portion 15 of the metal shell 9 and the convex portion 6 of the cylinder head 3 constitutes means A for preventing the metal shell 9 from rotating with respect to the engine.

Step 14 between cylindrical portion 11 and body 12
Is urged toward the bottom of the mounting recess 4 by the fixing member 10, and a gasket 16 for preventing the outflow of the combustion gas is interposed between the step 14 and the bottom of the mounting recess 4.

The fixing member 10 is a cylindrical metal member provided separately from the metal shell 9. Around the tip of the fixing member 10, a female screw 17 formed on the inner periphery of the mounting recess 4 is screwed. A matable male screw 18 is formed. In addition, the fixing member 10
A hexagonal portion 19 for fastening is formed around the upper side of the figure, and a male screw 18 is screwed into the female screw 17 by screwing the fixing member 10 with a fastening tool (not shown). Is pressed against the bottom of the mounting recess 4. Thereby, the spark plug 1 is fixed to the cylinder head 3 and the gasket 16
Is firmly sandwiched between the step 14 and the bottom of the mounting recess 4, and the combustion gas is kept airtight.

[Effect of the First Embodiment] In the spark plug 1 adopting the above configuration, the concave portion 15 of the metal shell 9 engages with the convex portion 6 of the cylinder head 3 so that the metal shell 9 is mounted on the cylinder head of the engine. 3, the metal shell 9 is fixed to the cylinder head 3 by a separate fixing member 10.

As described above, since the metal shell 9 does not rotate with respect to the cylinder head 3 of the engine, the direction of the outer electrode 13 can be directed in a previously designed direction in the combustion chamber. For this reason, the spark plug 1 can obtain stable ignitability and heat resistance for each cylinder.

[Second Embodiment] FIG.
FIG. 2 is a cross-sectional view showing the spark plug 1 attached to the cradle. In the first embodiment described above, the recess 15 is formed in the body 12 of the metal shell 9.
And the convex portion 6 is provided on the side wall of the mounting concave portion 4. In the second embodiment, the cylindrical portion 1 of the metallic shell 9 is provided.
1 is provided with a concave portion 15 and a convex portion 6 is provided on a side wall of the insertion hole 5.

[Third Embodiment] FIG. 4 shows a cylinder head 3
FIG. 2 is a cross-sectional view showing the spark plug 1 attached to the cradle. In the first and second embodiments, the recess 15 of the metal shell 9
Although the example in which the rotation preventing means A is provided by the convex portion 6 of the cylinder head 3 is shown, in the third embodiment, the metallic shell 9 and the cylinder head 3 are connected by the body 12 and the seating surface of the mounting concave portion 4. It is connected by knock pins 21 inserted into both sides, and prevents rotation of the metal shell 9 with respect to the cylinder head 3. That is, in this embodiment, the anti-rotation means A is constituted by the knock pin 21.

[Modification] In the first and second embodiments,
Although the example in which the concave portion 15 is provided in the metal shell 9 and the convex portion 6 is provided in the cylinder head 3 is shown, the convex portion 6 may be provided in the metal shell 9 and the concave portion 15 may be provided in the cylinder head 3.
The seating portion between the cylinder head 3 and the metal shell 9 (step 1
4), instead of the gasket 16, a tapered conical sheet surface may be provided to improve the airtightness and the heat drawing performance.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a spark plug mounted on a cylinder head of an engine (first embodiment).

FIG. 2 is a sectional view of a main part showing a rotation preventing means (first embodiment).

FIG. 3 is a sectional view showing a spark plug mounted on a cylinder head of an engine (second embodiment).

FIG. 4 is a sectional view showing a spark plug mounted on a cylinder head of an engine (third embodiment).

[Description of Signs] 1 Spark plug 3 Cylinder head (Component part of engine) 6 Convex part (engaged part) 7 Center electrode 8 Insulator 9 Metal shell 10 Fixing member 11 Cylindrical part 12 Body part 13 Outer electrode 15 Concave part (Engagement part) 18 male screw (screw of fixing member screwed to engine) A detent means

Claims (4)

[Claims] 1. A state in which a center electrode to which a high voltage is applied, an insulator for insulating and holding the center electrode, and an outer electrode for generating a spark discharge between the center electrode are provided. A spark plug for an internal combustion engine, comprising: a metal shell fixed to the engine at the end; wherein the metal shell includes a small-diameter cylindrical portion with no screw on the tip end side, and a large-diameter body portion, A detent means for holding the insulator and preventing rotation with respect to the engine is provided on the cylindrical portion or the body portion, and the engine is fixed by a fixing member provided separately from the metal shell. A spark plug for an internal combustion engine fixed to a spark plug. 2. The spark plug for an internal combustion engine according to claim 1, wherein said detent means includes an axially extending engaging portion provided on said cylindrical portion or said body portion of said metal shell, and said engine. A spark plug for an internal combustion engine, wherein the spark plug is an engaged portion that is provided and extends in the axial direction to engage with the engaging portion. 3. The spark plug for an internal combustion engine according to claim 1, wherein said detent means is a knock pin for connecting a bottom portion of said body portion of said metallic shell and a seat surface of a mounting recess of said engine. Spark plug for internal combustion engines. 4. The spark plug for an internal combustion engine according to claim 1, wherein the fixing member includes a screw screwed to the engine.
A spark plug for an internal combustion engine, wherein the screw is screwed into the engine to press and fix the metal shell against the engine.