JPH0227682A - Spark plug for internal combustion engine - Google Patents

Abstract

PURPOSE:To improve airtightness and durability by constituting an insulator with a long leg section made of heat conducting ceramic and the other portion made of alumina or the like and locating its connection section between the dia-section of a main body metal and the packing contact face. CONSTITUTION:A long leg section 7 constituting an insulator 2 is made of A.N and the other portion of the insulator 2 is made of alumina or the like, the long leg section 7 and the other portion are connected by a connecting material 8 made of glass such as high-melting point glass or ceramic with high insulation and the softening point of 600 deg.C or above. Or at the connection section 9 between the long leg section 7 and the other portion, the long leg section 7 is used as an inner cylinder 14, the other portion is used as an outer cylinder 15 made of a material with the linear expansion coefficient larger than that of the inner cylinder 14, they are coupled and connected. The position of the connection section g between the long leg section 7 and the other portion is located between the dia-section 4 of a main body metal 3 and the packing contact face. The connection portion 9 is more firmly connected and can sufficiently cope with the stress from the lateral direction.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a spark plug used in an internal combustion engine.

(Prior Art) Conventionally, the insulator of spark plugs used in internal combustion engines is generally made of alumina, etc., which is sintered and molded in one piece, but since alumina has extremely low thermal conductivity,
AI can easily promote the occurrence of pre-ignition.
Although efforts are being made to introduce ceramics with good thermal conductivity such as N, the cost of the ceramics themselves with good thermal conductivity is extremely high, so AIN is applied only to the long legs of the insulator, where pre-ignition is likely to occur. The conventional method described above, however, uses a ceramic with good thermal conductivity, and alumina is used for the other parts, and these are bonded together to form an insulator (problem to be solved by the invention). A ceramic with good thermal conductivity such as AIN is used only for the long legs of the insulator,
If the other parts are made of alumina and are bonded together to form an insulator, the long leg part made of a ceramic with good thermal conductivity such as AIN and the other parts made of alumina are bonded. Since the position of the joint part was not specified, if the position of the joint part was set below the gasket, the joint part between the long leg part and other parts using alumina would be exposed inside the combustion chamber, and the joint part would be held. The joint material that is connected to the engine is eroded by the high-temperature combustion gas, and the long legs fall into the combustion chamber, resulting in damage to the internal combustion engine itself. With this setting, if stress is applied from the side when installing the spark plug, the long leg remains firmly attached to the internal combustion engine, and only the upper insulator tends to come off. Furthermore, the bonding material that holds the bonded portion is difficult to sufficiently hold even when a ceramic adhesive is used, making it difficult to maintain airtightness within the center electrode and causing breakage. Therefore, the present invention aims to improve the drawbacks of the above-mentioned conventional spark plugs, and provides a spark plug that has excellent insulation resistance and airtightness resistance, and has a wider range.

(Means for solving the problem) For this purpose, AIN is used for the long legs that constitute the insulator,
In addition to using alumina etc. as an insulator for other parts, the long leg part and other parts are made of a bonding material made of glass or ceramic, such as high melting point glass, which has a softening point of 600°C or more and has high insulation properties. At the joint between the long leg part and other parts, the long leg part is made into an inner cylinder, and the other parts are made into an outer cylinder made of a material with a larger coefficient of linear expansion than the inner cylinder, and by fitting them together. The joint between the long leg portion and the other portion is located between the diamond portion of the metal shell and the packing contact surface.

(Function) With the above configuration, even when the joint is heated by high-temperature combustion gas, the joining material that holds the joint is made of glass or ceramic material such as high-melting point glass that has high insulation properties. Therefore, it is possible to prevent falling off while maintaining airtightness, and by making the long leg part the inner cylinder and the other parts the outer cylinder made of a material with a higher coefficient of linear expansion than the inner cylinder, it can withstand high temperatures. Even if it is, compressive stress is generated from the outer cylinder side toward the inner cylinder, making the joint more firmly connected, and by positioning the joint between the diamond part of the metal shell and the packing contact surface. , it can sufficiently cope with stress from the lateral direction.

(Example) This invention will be further explained with reference to an example shown in the drawings. (1) is a spark plug for an internal combustion engine which is an example of the invention. This spark plug for an internal combustion engine (1) has a terminal electrode ( 10), a main body having an insulator (2) for sealing a resistor (11) and a center electrode (12) in a shaft hole (13) via a conductive glass sealing material (18), and a fastening portion (4); It consists of a metal fitting (3), a threaded part (5), and an outer electrode (6), and the insulator (2) is connected to the long leg part (7), diamond part (19), and head part (20) exposed to the combustion chamber. Nari, long leg part (7)
In addition to using a ceramic with good thermal conductivity such as AIN, and using alumina etc. in other parts, the long leg part (7)
and other parts are bonded together using a bonding material (8) made of glass or ceramic, such as high-melting point glass, which has a softening point of 600°C or higher and has high insulation properties. ) is heated by high-temperature combustion gas, the joint (9) does not fall off and can maintain airtightness. Note that the wall thickness at the joint (9) and the joint length l (Fig. 3) are 0.2≦t≦ considering the uniformity of glass sintering or pressability of the glass.
Q, 8 mm, 1≧3.0 mm is appropriate. In addition, the insulator (2) is connected to the joint (9), and the long leg portion (7) is connected to the inner cylinder (
14) Furthermore, the other portion may be made of an outer cylinder (15) made of a material with a larger coefficient of linear expansion than the inner cylinder, and may be joined by fitting together. At this time, the inner cylinder (14
) has a linear expansion coefficient of 3.4 (xl
O/"C), and the linear expansion coefficient of alumina constituting the outer cylinder (15 mm) is 8.0 (XIO"/'C), so
The gap between the inner cylinder (14) and the outer cylinder (15), that is, the joint (9)
After inserting a cylindrical glass powder press product or a glass vibrator formed by a mold press with a wall thickness of 0.2 to 0.8 mm into ), the above joint part (9) is melted,
By cooling, the outer cylinder (15) made of a material with a large coefficient of linear expansion applies compressive stress to the inner cylinder (14), and is firmly joined to the inner cylinder (14). And the long leg part <7
) and other parts (9) is located at the insulator (2).
) by being located between the diamond part (19) and the seal contact surface 17), the joint part (9) is connected to the joint material (8).
In addition to the chemical bonding force, the mechanical bonding force due to caulking of the metal shell (3) is added, so a stronger bonding force is obtained and the joint part (9) does not come into direct contact with the combustion gas. This prevents the joints caused by high-temperature combustion gas (9
) can reduce the impact on Therefore, in order to confirm the improvement in the strength of the joint (9), the long leg part (
The joining position of 7) and other parts is the diamond part (19)
, above the diamond part (1), and the integrated insulator was checked using a Charpy tester to confirm the angle and location of the damage. The part (19) is located at the joint part (19).
It was confirmed that the same strength as that of an integrated insulator without 9) can be obtained (effects of the invention). Consists of other parts,
By locating the joint between the diamond part of the metal shell and the seal contact surface, it is possible to design a spark plug for internal combustion engines that has a wide range of heat dissipation, and also This has the excellent effect of improving the required airtightness and durability.

[Brief explanation of the drawing]

FIG. 1 is a partial sectional view of a spark plug for an internal combustion engine having a first embodiment of the present invention, and FIG.
FIG. 3 is a schematic front view of the manufacturing process of the spark plug for an internal combustion engine according to the embodiment, and FIG. 3 is an enlarged sectional view of the main part showing changes in the firing process. 1...Spark plug for internal combustion engine 2...Insulator 3
...Main metal fitting 4...Diamond part 5...Threaded part
6...Outer electrode 7...Long leg portion 8...Jointing material 9...Joint portion 13...Shaft hole 14...Inner cylinder
15...Outer cylinder 16...Glass powder pressed product Figure 1 Patent applicant Agent Patent attorney Miyuki Fujiki Figure 2 Figure 3

Claims (3)

[Claims] (1) AIN is used for the long legs that make up the insulator, and alumina or the like is used for the other parts of the insulator, and the long legs and other parts have a softening point of 600°C or higher and have high insulation properties. A spark plug for an internal combustion engine, which is bonded with a bonding material made of glass or ceramic, such as high melting point glass. (2) At the joint between the long leg part and other parts, the long leg part is made into an inner cylinder, and the other parts are made into an outer cylinder made of a material with a larger coefficient of linear expansion than the inner cylinder, and the parts are joined by fitting together. A spark plug for an internal combustion engine according to claim (1). (3) The spark plug for an internal combustion engine according to claim 1 or 2, wherein the joint between the long leg portion and the other portion is located between the diamond portion of the metal shell and the packing contact surface.