JPS60100388A - Ignition plug - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] The present invention relates to improvements in spark plugs for internal combustion engines.

A conventional spark plug will be explained based on FIG. 2, and its problems will be described. A spark plug 1 is screwed into a cylinder head 2 of an internal combustion engine with its lower end facing a combustion chamber 3. Reference numeral 4 has a threaded portion that is screwed into a threaded hole 2a formed in the cylinder head 2. A center electrode 5 and an outer electrode 6 are arranged below the threaded portion 4, and a spark gap 7 is formed by the center electrode 5 and outer electrode 6. is formed.

On the other hand, at the upper end of the spark plug 1 is a terminal 8 which is a power receiving terminal.
This terminal 8 is electrically connected to the center electrode 5 at the lower end via the center shaft, and constitutes a center electrode portion. An insulator 9 is provided on the lower side of the terminal 8 so as to surround the center electrode part, and has a hexagonal part 10 at the upper part and a metal housing having a threaded part 4 with the outer electrode (6) at the lower part. 11, and a metal fitting part 12 with a larger diameter is formed between the hexagonal part 10 and the threaded part 40.

The spark plug 1 as described above is connected to the cylinder head 2 of an internal combustion engine.
When inserting several screws JL2a, the metal part 12 and the screw hole 2
A washer 13 is interposed between a and the upper opening periphery.

A plug cap 14 is attached to the spark plug 1 described above. The plug cap 14 is a cylindrical body bent in a 5-shape, and has a cord locking portion 14a into which the power supply cord 15 is inserted and locked.
and a plug cap boot 14 attached to the spark plug 1.
It consists of b.

The insulating part 16 is formed inside the corner of the plug cap 140, and this I [-! Inside the edge 16, the Yuden ir inside the cord 15
'j! 15a and the terminal 8 of the spark plug 1 are provided.

In the above, a high voltage is applied between the center electrode 5 and the outer electrode 6 in order to prevent sparks from flying into the spark gap 7, but in order to effectively generate sparks, it is necessary to apply a high voltage to the center electrode part (especially the power receiving terminal). and insulation of the outer electrode section must be ensured. In order to ensure such insulation, the creepage distance of the insulator 9 can be increased, and for this purpose, there are methods such as increasing the length of the spark plug in the axial direction or forming corrugations on the surface of the insulator. In this way, the electric field strength is reduced, the flashover voltage (the voltage at which the electrodes are shorted due to discharge) can be increased, and high insulation can be ensured without causing discharge.

However, in recent years, as the output of internal combustion engines has increased, the compression ratio has increased, and the applied voltage for ignition has tended to increase in order to widen the spark gap of the ignition plug in order to improve combustion. Furthermore, the demand for smaller and lighter spark plugs to improve fuel efficiency extends to J.1 spark plugs, and as a result, the electric field strength tends to increase. Therefore, the insulating performance of the spark plug deteriorates, which is undesirable, and in order to improve the insulating performance of the conventional spark plug, K needs to be increased in size, which goes against the purpose of development.

An object of the present invention is to provide a spark plug that can maintain high insulation performance between a center electrode portion and an outer electrode portion even when the size of the spark plug is reduced.

A feature of the present invention is that a spark plug has a center electrode portion and an outer electrode portion, and an insulator is interposed between both electrode portions.
An insulating layer is applied to the second-class portion of the outer electrode portion connected to the insulator, thereby substantially increasing the distance in the /1'i plane of the insulating portion.

An embodiment of the present invention will be described in detail below based on the accompanying drawings.

FIG. 1 shows a longitudinal sectional view of a spark plug according to the present invention, and the same elements as explained in FIG. 2 are given the same reference numerals.

In FIG. 1, reference numeral 18 indicates the upper and lower parts, and the upper end of the center electrode part 18 is the terminal 8, and the lower end is the center electrode 7, which are exposed to the outside. Most of the insulator 9 is inserted into the central axis portion of the insulator 9.The insulator 9 forms a corrugation 9a from the second part to the approximately central part, thereby increasing the creepage distance. ing.

An outer electrode portion 19 is attached to the outer periphery of the insulator 9 from the center to the bottom. The outer electrode part 19 has a hexagonal part 10 formed at the negative part, a metal fitting part 12 at the medium heat part, and a threaded part 4 equipped with the outer electrode 6 at the lower part, and the whole is integrally formed of conductive metal. be done. Such a shape is the same as that previously described as the shape of a conventional spark plug.

The outer electrode portion 19 is fixed to the insulator by caulking its two wires into a recess formed in the center of the insulator 9 with a ring 20 interposed therebetween. In such a state where the outer electrode part 19 is connected to the insulator 9, the center electrode 5
A spark gap 7 is formed between the outer electrode 6 and the outer electrode 6 .

In the drawing, 14 is a plug gap, and the plug cap 14 has a cord locking part 14a into which the power supply cord 15 is inserted and locked, and a plug gap boot 14b which is attached to the spark plug 1. Connection 17 provided
The conductive wire 15a and the terminal 8 are connected through the terminal 8.

In the spark plug 1 as described above, according to the present invention, an insulating layer 21 is formed on the upper surface of the hexagonal part 10 of the outer electrode part 19. The insulating layer 21 is formed by coating with a highly insulating material such as enamel or heat-resistant resin.

The creepage distance between the lower edge of the terminal 8 and the upper edge of the hexagonal part 10 of the outer electrode part 19 is preferably long in order to reduce the electric field strength therebetween. Therefore, as described above, the corrugation 9a is formed on the surface of the insulator 90 to increase the creepage distance, and the insulating layer 21
The creepage distance is substantially increased by forming a . A feature of the present invention is that by forming the insulating layer 21, the creepage distance can be substantially increased without increasing the dimensions.

In addition, the insulator 90 of the boot 14b of the plug cap 14
It is also possible to form an underrib 14b-2 that expands outward below the lip portion 14b-1 that contacts the surface, and to bring this underrip 14b-2 into contact with the insulating layer 21, thereby maintaining high insulation performance. can.

Note that the thickness of the insulating layer 21 needs to be extremely small compared to the creeping distance formed by the insulating layer 21.

As is clear from the above description, according to the present invention, the creepage distance between the center electrode portion (terminal serving as a power receiving terminal) and the outer electrode portion is substantially increased while the spark plug is dimensionally reduced. This reduces flashover voltage and improves insulation performance.
It is possible to achieve miniaturization of the spark plug.

[Brief explanation of drawings]

FIG. 1 is a vertical cross-sectional view of a spark plug and a plug cap according to the present invention, and FIG. 2 is a partial vertical cross-sectional view of a conventional spark plug device. In the drawing, 1 is a spark plug, 9 is an insulator, 14 is a plug cap, 15 is a power supply cord, 18 is a center electrode portion, 19 is an outer electrode portion, and 21 is an insulating layer. Patent applicant: Honda Motor Co., Ltd., Japan Spark Plug Co., Ltd., agent, patent attorney, Roko Shimo, patent attorney, Department of Technology Department, patent attorney, Kuni Ohashi, patent attorney, Yu Koyama

Claims (1)

[Claims] In a spark plug having a center electrode part and an outer electrode part and with an insulator interposed between both electrode parts, an insulating layer is formed in a "second class part of the outer electrode part that is connected to the insulator". A spark plug characterized by: