JPH09180856A - Spark plug for internal combustion engine, and plug cap of plug cord - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve durability and insulation resistance against high voltage to be applied to a spark plug. SOLUTION: In a spark plug, a corrugation part 7 of the insulation body upper part 21 is at three or less stages and a straight part 8 is 10mm or less or the straight part 8 is taper-shaped. A cap seal part in a plug cap of a plug cord is 7mm or more or the lower end edge of said cap seal part is 5mm or more away from an upper end edge 51 of a main bracket 5. Thereby, since the lower end edge is spaced from the main bracket 5 causing thermal deterioration of said cap seal part, thermal deterioration due to thermal conduction from the main bracket 5 is prevented, durability can be improved, and insulation resistance can be improved by expanding the covered range due to said cap seal part and prevention of said thermal deterioration.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an internal combustion engine, and more particularly to a spark plug attached to an internal combustion engine which burns a gaseous fuel such as natural gas, city gas, LPG gas, etc. and an internal combustion engine which burns a methanol mixed fuel. The present invention relates to the structure of a plug cap of a plug cord attached to a spark plug.

[0002]

2. Description of the Related Art Conventionally, a spark plug mounted on an internal combustion engine, particularly a gas fuel internal combustion engine and a methanol mixed fuel internal combustion engine, has a corrugation portion forming an upper portion of an insulator constituting the spark plug and an insulator together with the corrugation portion. The plug cap of the plug cord, which is placed above the straight portion that forms the upper part, and that electrically connects to the battery that is the supply source for the terminal electrode of this spark plug, has a rubber plug at its open end. It is applied to the spark plug by being equipped with a cap seal part formed by, for example, and by mounting the cap seal part so as to integrally cover the straight part formed with the corrugation part above the insulator. Those that insulate high voltage are common.

[0003]

However, in the case of the above-mentioned conventional one, in the case of the spark plug mounted on the internal combustion engine, particularly the gas fuel internal combustion engine and the methanol mixed fuel internal combustion engine, the gas fuel internal combustion engine to which the spark plug is mounted is mounted. Since the discharge voltage is generally high in the engine and the methanol-mixed fuel internal combustion engine, a high voltage is applied even to the plug cord for electrically connecting to the spark plug. If the dielectric strength of the plug cap in which the plug cord is connected to the terminal electrode held by the insulator is reduced, flashover, leak, etc. are likely to occur,
There is a problem that spark discharge cannot be effectively obtained in the combustion chambers of the gas fuel internal combustion engine and the methanol mixed fuel internal combustion engine having high discharge voltage.

Further, in the above gas fuel internal combustion engine and methanol mixed fuel internal combustion engine, the area around the plug in the cylinder head, especially around the metal shell forming the spark plug is narrow, and the temperature due to the heat conduction around the cylinder head. Is easily increased, the deterioration due to the heat is promoted in the plug cap of the plug cord integrally attached to the terminal electrode of the spark plug,
With the deterioration of the plug cap of the plug cord, the dielectric strength of the plug cap is reduced, and as a result, flashover, leakage, etc. are likely to occur, and as a result, the internal combustion engine of these gas fuel internal combustion engine and methanol mixed fuel internal combustion engine There is also a problem that spark discharge cannot be effectively obtained.

Therefore, the present invention solves the drawbacks of the above-mentioned conventional ones, and is mounted on a spark plug and this spark plug so as to sufficiently cope with deterioration due to application of high voltage or heat. The purpose is to improve the heat resistance and dielectric strength of the plug cap of the plug cord.

[0006]

To this end, a rubber of a plug cap which is integrally formed with a corrugation portion having an uneven upper portion of an insulator and a plug cord which is arranged continuously below the insulator and is fitted to a terminal electrode. It is formed from a straight portion that allows close contact with a cap seal portion such as a seal to form a seal, and the corrugation portion has 0 to 3 stages or less, and the corrugation portion is 5 to 10 from the upper end of the insulator.
Within 10 mm, and the straight part is 10 m
m or more, or the straight part that forms the upper part of the insulator together with the corrugation part has a taper shape that narrows the diameter upward, and the corrugation part that consists of the unevenness that forms the upper part of the insulator is integrated with the plug cord. The plug cap is disposed below the straight portion that enables close sealing with the cap seal portion of the plug cap.

On the other hand, in the plug cap of the plug cord integrally mounted to achieve electrical conduction with the terminal electrode projectingly held on the upper portion of the insulator, the upper portion of the insulator of the spark plug for an internal combustion engine is formed together with the corrugation portion. The seal length L of the sealing portion of the cap sealing portion that closely adheres to the straight portion is set to 7 mm or more, or the lower end edge of the cap sealing portion such as rubber of the plug cap constitutes a spark plug together with an insulator. It is located above the metal shell at a distance of 5 mm or more.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In practicing the present invention,
The upper part of the insulator is closely adhered to the corrugation part made of the unevenness and the cap seal part such as rubber of the plug cap which is arranged continuously below and is integrated with the plug cord fitted to the terminal electrode. It should be formed from a straight portion that enables sealing, the corrugation portion should be 0 to 3 steps or less, the corrugation portion should be arranged within 5 to 10 mm from the upper end of the insulator, and the straight portion should be 10 mm or more. Or, or by making the straight portion that forms the upper part of the insulator together with the corrugation portion into a taper shape that is reduced in diameter upward,
Since the range covered by the cap seal portion of the plug cap can be expanded, the dielectric strength against the high voltage applied to the spark plug via the plug cord can be improved, and the upper part of the insulator can be improved. By arranging the corrugation portion formed by the unevenness to be placed below the straight portion that enables sealing by closely contacting with the cap seal portion of the plug cap that is integral with the plug cord, the straight portion is formed. Is separated from the metal shell that composes the spark plug, that is, the cap seal made of rubber or the like of the plug cap is separated from the metal shell that becomes hot, so the plug cap itself is less susceptible to heat, and It is possible to prevent deterioration, that is, deterioration of durability and dielectric strength.

On the other hand, in the plug cap of the plug cord, the sealing length L of the sealing portion of the cap sealing portion, which seals the upper portion of the insulator of the spark plug for an internal combustion engine in close contact with the straight portion formed with the corrugation portion, is 7 mm. As a result of the above, the range covered by the cap seal part is expanded, so that the dielectric strength against high voltage applied to the spark plug is improved, or the lower end edge of the cap seal part such as rubber of the plug cap is joined with the insulator. 5 from the upper edge of the metal shell that constitutes the spark plug
By locating the upper part at a distance of more than mm, the cap seal part of the plug cap is separated from the metal shell that is heated to a high temperature by receiving combustion heat, and deterioration due to heat can be prevented and heat resistance can be improved. It also improves the dielectric strength against voltage.

[0010]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. (1) is a spark plug for an internal combustion engine which is an embodiment of the present invention. The spark plug (1) for an internal combustion engine has a center electrode (3) at its tip and a terminal electrode (4) at its rear end. ) Is protruded and held, and an insulator (2),
This insulator (2) is held inside and the insulator (2)
It comprises a metal shell (5) having a ground electrode (6) arranged at a position facing the center electrode (3) which is projected and held by.

The insulator upper part (21) is integrally formed with the corrugation part (7) formed of unevenness and the plug cord (9) which is arranged continuously below the corrugation part (7) and is fitted to the terminal electrode (4). The plug corrugated portion (7) is formed from a straight portion (8) which is in close contact with the cap sealing portion (15) made of rubber or the like of the plug cap (13) and enables sealing. The corrugation part (7) is made the following, and the insulator upper end (22)
5 to 10 mm, the straight part (8) is made 10 mm or more (see FIG. 1), and the straight part (8) forming the insulator upper part (21) together with the corrugation part (7) is located above. Taper shape (see Fig. 2) that decreases in diameter toward
Corrugation part (7) consisting of irregularities forming 1)
Is disposed below the straight portion (8) that enables tight sealing by closely contacting with the cap seal portion (15) of the plug cap (13) that is integrated with the plug cord (9). (See Figure 3).

Since the spark plug (1) for an internal combustion engine, which is one of the embodiments of the present invention, has the above structure,
And, as shown in FIG. 2, the insulator upper part (21) constituting the spark plug (1) is formed by the corrugation part (7) consisting of uneven steps, and the insulator (2) is arranged continuously below the corrugation part (7). ) A cap seal part (15) made of rubber or the like in a plug cap (13) which is integrated with a plug cord (9) fitted to apply a high voltage to a terminal electrode (4) projectingly held at the tip of It is assumed that the corrugation portion (7) is formed from a straight portion (8) which can be tightly adhered between the corrugated portion (7) and the corrugation portion (7) for the purpose of preventing leaks, dust and water, and can be sealed. Connect the corrugation part (7) from the insulator upper end (22) to 5
By arranging within 10 mm and setting the straight portion (8) to 10 mm or more (see FIG. 1),
Further, the straight portion (8) forming the insulator upper portion (21) together with the corrugation portion (7) is formed into a taper shape in which the diameter is reduced upward (see FIG. 2).
Since the coverage of the plug seal (15) of the plug cap (13) of the plug cord (9) for leak prevention, dustproofing, and waterproofing can be expanded, the spark plug (9) can be connected via the spark plug (9). It is possible to improve the dielectric strength of the cap seal portion (15) of the plug cap (13) of the plug cord (9) to the high voltage applied to 1).

Further, the corrugation portion (7) having an uneven shape forming the insulator upper portion (21) of the insulator (2) constituting the spark plug (1) is formed on the plug cap (13) which is integrated with the plug cord. Cap seal part (1
By arranging the plug cap (13) of the plug cord (9) at a lower position with respect to the straight part (8) which is in close contact with and is capable of sealing, a high voltage can be achieved. To prevent leaks and dust,
The straight portion (8) sealed for waterproofing is separated from the metal shell (5) constituting the spark plug (1), that is, the cap sealing portion (15) made of rubber or the like of the plug cap (13) is the internal combustion engine. As a result of being separated from the metal shell (5) which becomes high temperature due to the conduction of combustion heat generated by the combustion of the air-fuel mixture in the combustion chamber of
The plug cap (13), particularly the cap seal portion (15) formed of rubber or the like for sealing between the plug upper portion (21) and the straight portion (8) forming the upper portion (21) of the insulator together with the corrugation portion (7) is a metal shell ( Since it is less likely to be affected by heat conducted from 5), deterioration due to heat can be prevented, and deterioration of durability and dielectric strength of the plug cap 13 can be prevented.

On the other hand, (9) is a plug cord which is one of the embodiments of the present invention. This plug cord (9)
Is a plug cord body (10) made of a cable with winding resistance, and in the plug cord body (10),
The terminal (12) connected to the electromagnetic coil is provided at one end, and the coil cap (11) covering the terminal (12) is provided, and the other end is provided with the spark plug (1). The terminal (14) is inserted into the terminal electrode (4) which is projected and held at the rear end of the body (2).
The plug cord body (10) is held by the synthetic resin cap body (17), and the cap body (17)
While sealing the fitting portion side of the terminal (14) and the terminal electrode (4) with the cap seal portion (15) integrally formed of rubber or the like, the insulator (2) is corrugated (7). It is composed of a plug cap (13) for the purpose of closely adhering to and covering the straight portion (8) formed together with it.

Then, a plug cord mounted integrally with the terminal electrode (4) projectingly held in the insulator upper portion (21) of the insulator (2) constituting the spark plug (1) so as to establish electrical continuity. (9) Plug cap (1
In 3), for the purpose of preventing leakage, dust-proofing, and waterproofing by applying a rear voltage to the straight portion (8) that forms the insulator upper portion (21) of the internal combustion engine spark plug (1) together with the corrugation portion (7). The seal length (L) of the seal portion (16) of the cap seal portion (15) for closely contacting and sealing is set to 7 mm or more (see FIG. 4), or the cap seal portion (1) made of rubber or the like for the plug cap (13) is used.
The lower edge (17) of 5) is located above the upper edge (51) of the metal shell (5) that constitutes the spark plug (1) together with the insulator (2) by 5 mm or more. (See Figure 5).

Since the plug cap (13) of the plug cord (9) which is one of the embodiments of the present invention has the above-mentioned structure, the insulation of the insulator (2) which constitutes the spark plug (1) for an internal combustion engine is insulated. The seal length L in the seal portion (16) of the cap seal portion (15) for tightly sealing the upper part (21) of the corrugation portion (7) with the straight portion (8) is 7 mm or more. Then, the plug cap (1) for the straight portion (8) forming the insulator upper portion (21) of the insulator (2) constituting the spark plug (1) together with the corrugation portion (7)
Since the coverage of the cap seal portion (15) in 3) is expanded, the plug cap (13) of the plug cord (9) against the high voltage applied to the spark plug (1) according to the embodiment of the present invention. The dielectric strength of can be improved.

Further, the lower end edge (17) of the cap seal portion (15) such as rubber of the plug cap (13) constitutes the spark plug (1) according to the embodiment of the present invention together with the insulator (2). By placing the metal fitting (5) at an upper portion 5 mm or more away from the upper edge (51) of the metal fitting (5), the heat of combustion generated by the combustion of the air-fuel mixture in the combustion chamber of the internal combustion engine is transferred to a high temperature. ), The cap seal portion (15) of the plug cap (13) is separated, so that the heat conducted from the metal shell (5) deteriorates the cap seal portion (15) such as rubber in the plug cap (13). Prevent and plug cap (1
The heat resistance of the plug cord (9) itself can be improved together with (3), and the cap seal part (1) of the plug cap (13), especially the plug cap (13) can be improved.
By preventing the thermal deterioration in 5), the dielectric strength against a high voltage applied in the spark plug (1) for an internal combustion engine according to the embodiment of the present invention mounted on the gas fuel internal combustion engine and the methanol mixed fuel internal combustion engine is also improved. It can be made.

[0018]

As described above, by improving the heat resistance and dielectric strength of the spark plug and the plug cap of the plug cord, the internal combustion engine equipped with the spark plug and the plug cord, particularly the gas fuel internal combustion engine and the methanol mixture. Since the high voltage applied in the fuel internal combustion engine enables effective spark discharge in the combustion chamber, fuel saving and reliable output can be achieved, and thermal deterioration in the plug cap, especially in the cap seal portion is prevented. Since the durability is improved by preventing it,
It has an excellent effect that the maintenance interval becomes long and the maintenance cost including the spark plug can be sufficiently reduced.

[Brief description of the drawings]

FIG. 1 is a front view of a spark plug for an internal combustion engine that is an embodiment of the present invention.

FIG. 2 is an enlarged front view of a main part of a spark plug for an internal combustion engine according to another embodiment of the present invention.

FIG. 3 is an enlarged front view of a main part of a spark plug for an internal combustion engine according to another embodiment of the present invention.

FIG. 4 is a front view of the plug cord according to the embodiment of the present invention.

FIG. 5 is an enlarged sectional view of a main part of a plug cord fitted to a spark plug which is another embodiment of the present invention.

[Explanation of reference numerals] 1 spark plug for internal combustion engine 2 insulator 21 insulator upper portion 22 insulator upper end 3 center electrode 4 terminal electrode 5 metal shell 51 (upper edge of metal shell) 6 ground electrode 7 corrugation portion 8 straight portion 9 plug Cord 10 Plug cord main body 11 Coil cap 12 Terminal 13 Plug cap 14 Terminal 15 Cap seal part 16 Seal part 17 (Lower edge of cap seal part)

Claims (5)

[Claims] 1. A corrugation portion having an uneven upper surface of an insulator, and a cap seal portion made of rubber or the like of a plug cap which is arranged continuously downward from the corrugation portion and is integrated with a plug cord fitted to a terminal electrode. It is formed from a straight portion that closely adheres to each other to enable sealing, and the corrugation portion is set to 0 to 3 steps or less, and the corrugation portion is arranged within 5 to 10 mm from the upper end of the insulator.
A spark plug for an internal combustion engine having a straight portion of 10 mm or more. 2. The spark plug for an internal combustion engine according to claim 1, wherein the straight portion formed together with the corrugation portion on the upper portion of the insulator has a taper shape in which the diameter is reduced upward. 3. An internal combustion engine in which a corrugation portion on an upper portion of an insulator is arranged below a straight portion which enables tight sealing by closely contacting with a cap seal portion of a plug cap integrated with a plug cord. Spark plug for. 4. A spark plug for an internal combustion engine according to any one of claims 1 to 3, wherein a plug cap of a plug cord is integrally mounted to electrically connect with a terminal electrode projectingly held on an upper portion of the insulator. A plug cap of a plug cord having a seal length L of 7 mm or more in the seal portion of the cap seal portion that seals the upper portion of the insulator with the straight portion formed together with the corrugation portion by sealing. 5. A lower end edge of a cap seal portion such as rubber of a plug cap that closely adheres to and seals a straight portion forming an upper portion of an insulator of a spark plug for an internal combustion engine together with a corrugation portion together with the insulator. The plug cap of the plug cord according to claim 4, which is located at an upper portion 5 mm or more away from the upper edge of the metal shell forming the spark plug according to any one of items 1 to 3.