KR20090057577A - Spark plug with variable spark gap - Google Patents

Abstract

The present invention relates to a spark gap variable spark plug, it is possible to improve the ignition stability by making the spark gap naturally smaller or larger according to the change in the combustion chamber temperature, increase in durability by improving the cooling performance to meet the trend of miniaturization of the spark plug The inside of the ground electrode is made of copper or a copper alloy, which has a high thermal conductivity and a high coefficient of thermal expansion, and the outside of the ground electrode is made of nickel or a nickel alloy, which has a low thermal expansion coefficient but excellent high temperature durability.

Description

Spark plug with variable spark gap

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a spark plug, and more particularly, to a spark gap variable spark plug such that a spark gap is changed according to a temperature change in a combustion chamber because the inside and the outside of the ground electrode are made of materials having different thermal expansion coefficients.

Conventional spark plugs are mounted on the cylinder head of an internal combustion engine, and interrupt the primary coil connected to the battery to induce high voltage current generated in the secondary coil to the center electrode of the spark plug, causing sparks between the ground electrodes fitted to the cylinder. Mainly functions to ignite fuel.

As shown in FIG. 1, the conventional spark plug includes an electrode consisting of a center electrode 1 and a ground electrode 2, an insulator 3 surrounding the center electrode 1, and protecting the insulator. The cell 4 which consists of a part, a mounting screw part, and the flat part for clamping a wrench is provided.

In addition, a spark gap a of a predetermined size is formed between the center electrode 1 and the ground electrode 2.

In addition, the spark plug receives the high voltage generated by the ignition coil, generates sparks in the fuel in the cylinder, and directly causes an explosion to operate the engine, so that the spark plug operates under severe conditions, and thus, heat resistance, corrosion resistance, heat dissipation, It should have the characteristics that the spark discharge performance and the electrode consumption which require thermal conductivity, electrical insulation etc. are low.

In recent years, since the spark plug has been miniaturized, such a miniaturization trend enables the engine combustion chamber to be compactly designed, and the cooling water passage of the cylinder head can be easily secured, thereby increasing the output of the engine.

However, when the spark plug is downsized, it is difficult to quickly release the high temperature of the combustion chamber to the outside through the ground electrode. In addition, due to the miniaturization of the spark plug, the temperature of the electrode is increased to about 60 degrees, which not only promotes consumption of the electrode but also causes damage to the electrode in severe cases. In order to alleviate this temperature rise, precious metals are attached to the center electrode and the ground electrode to reduce wear of the electrode, thereby improving durability, and a material having high thermal conductivity as shown in FIG. 2 inside the base material of the ground electrode. Although the method of reducing the temperature of the electrode by inserting and increasing the heat transfer effect has been used, this method has a problem of increasing the manufacturing cost of the spark plug.

In addition, the conventional spark plug is always kept constant irrespective of the temperature inside the combustion chamber of the spark gap a, and thus has a disadvantage of poor ignition stability.

Accordingly, the present invention has been made in view of the above-described circumstances, and the spark gap is naturally reduced or enlarged according to the change in the combustion chamber temperature to improve the ignition stability, and the durability is improved by improving the cooling performance corresponding to the miniaturization trend of the spark plug. It is an object of the present invention to provide a spark gap variable spark plug that can be increased.

The present invention for achieving the above object, the inside of the ground electrode is made of copper or copper alloy, a material having a high thermal conductivity and a large coefficient of thermal expansion, the outside of the ground electrode is a material having a low thermal expansion coefficient but excellent high temperature durability Or nickel alloys.

According to the spark gap variable spark plug according to the present invention, the inner side of the ground electrode is made of a material having a high thermal conductivity and a large coefficient of thermal expansion, while the outer side of the ground electrode is made of a material having a small coefficient of thermal expansion and excellent high temperature durability, the conventional cooling performance Compared with spark plugs made of copper or the like, the durability can be improved by the same or higher cooling effect, and the spark gap becomes smaller when the temperature inside the combustion chamber is low, whereas the spark gap becomes larger when the temperature inside the combustion chamber is lower, thereby improving the ignition stability. There is an effect such as.

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

3 shows a partially cut spark gap variable spark plug according to the present invention when the combustion chamber temperature is relatively low, that is, an electrode consisting of a center electrode 11 and a ground electrode 12, and the center electrode ( 11) is the same as the conventional configuration in that it includes a cell formed of an insulator surrounding the insulator, a part for protecting the insulator, a mounting screw part and a flat part for fitting the wrench.

However, the present invention is characterized in that the ground electrode 12 is made of different materials.

That is, the inside of the ground electrode 12 is made of a material 12a having a high thermal conductivity and a large coefficient of thermal expansion, for example, copper or a copper alloy, and the outside of the ground electrode has a relatively small thermal expansion coefficient but a high temperature durability 12b. For example nickel or nickel alloys.

As a result, compared to the spark plug when a material such as copper having excellent thermal conductivity is inserted into the base material of the ground electrode to improve the conventional cooling performance, it is possible to improve the cooling effect by heat transfer equal or higher.

And when the engine is under a low load operating condition, that is, the combustion chamber temperature is relatively low, the spark gap (b) is relatively small to improve the ignition stability.

However, as shown in FIG. 4, when the engine has a high load operating condition, that is, the combustion chamber temperature is relatively high, the spark gap c has a relatively large gap compared with the low temperature of FIG. 3 due to thermal expansion of the ground electrode. Ignition stability will also be improved.

Therefore, while maintaining a large spark gap in the high load operating conditions of the engine, while maintaining a small gap in the low load operating conditions it is possible to simultaneously improve the ignition stability and durability.

1 is a detailed view of a spark plug according to the prior art,

2 is a detailed view of the main portion of the spark plug according to another conventional embodiment,

3 is an explanatory diagram of a spark gap in an engine low load operating region of a spark plug according to the present invention;

4 is an explanatory diagram of a spark gap in the engine high load operating region of the spark plug according to the present invention.

<Description of Symbols for Main Parts of Drawings>

1-center electrode 2-ground electrode

3-insulator 4-cell

11-center electrode 12-ground electrode

Claims (3)

A spark gap variable spark plug having an inner side of the ground electrode 12 made of a material 12a having a high thermal conductivity and a large coefficient of thermal expansion, and an outer side of the ground electrode made of a material 12b having a small thermal expansion coefficient but excellent high temperature durability. The spark gap variable spark plug of claim 1, wherein an inner side of the ground electrode is made of copper or a copper alloy. The spark gap variable spark plug of claim 1, wherein an outer side of the ground electrode is made of nickel or a nickel alloy.

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