JPS58216378A - Spark 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 a spark plug that can prevent spark discharge defects due to carbon deposition on the surface of an insulator.

FIG. 1 is a configuration diagram of a conventional spark plug. (2) - is a terminal, 2 is a spark plug body made of a conductive material, 3 is a hexagonal part of the spark plug body 2, 4 is an insulator, and 5 is a gasket.

The tip 6 of the insulator 4 protrudes a little from the tip 13 of the spark plug body 2 in the axial direction, and there is a gap between the cylindrical side-shaped inner circumference of the spark plug body 2 and the conical side-shaped outer circumference of the insulator 4. An annular gap 7 is formed.The rod-shaped center electrode 10 extends through the center of the insulator 4, reaches the tip 11, and is exposed from the tip 6 of the insulator 4 by a predetermined length. The ground electrode 12 is connected to the tip 13 of the spark plug body 2 and extends at right angles.The tip 11 of the center electrode 10 and the ground electrode 12
A spark gap 14 of six predetermined dimensions is formed between the two.

If such a spark plug is used for a long time under low temperature and rich mixture conditions such as when the choke is operating,
Combustion products such as carbon generated due to incomplete combustion accumulate on the surface of the insulator 4, making it difficult to ignite the air-fuel mixture due to leakage discharge due to poor insulation on the surface of the insulator 4. A situation arises.

SUMMARY OF THE INVENTION An object of the present invention is to provide a spark plug that can avoid ignition failure due to the accumulation of carbon and carbon on the surface of the insulator and element.

- In order to achieve this object, according to the spark plug of the present invention, a recess is provided in the tip end face of the insulator, and the center electrode extends through the recess in the axial direction.

Further, according to the spark plug of the present invention, a angular projection surrounding the center electrode and extending in an annular shape is provided on the surface of the tip of the insulator.

The present invention will be described in detail with reference to FIG.

The difference from the spark plug shown in FIG. A recess I8 is provided with a radial distance a.
= 4-5 birds, b = 1-2? There is IImte. Note that the spark gap 14 is 0.8 to 1.1. ,,is. Therefore, the center electrode 1o is exposed to the air from the bottom of the recess 18, and passes through the recess 18 in the axial direction. An angular protrusion 19 is formed on the opening edge of the concave FI 718 and extends in an annular manner surrounding the center "center pole 10" and protrudes in the direction of the @ line. Angular protrusions 20 are provided in two rows in the axial direction, extending annularly surrounding the center and projecting outward in the radial direction. In the embodiment, the height of the protrusions 19 is 0.5 to 2. .0 dishes.

Since fuel droplets floating in the combustion chamber are significantly less likely to enter the recess 18 than the air gap 7, carbon deposition on the inner circumferential surface of the recess 18 is suppressed even under conditions of low temperature and rich mixture. Ru. Since the insulation distance is increased by the recess 18, the time required for carbon to accumulate on the surface of the insulator 40 can be lengthened, so that leakage discharge is suppressed and good sparks are generated in the spark gap 14. Furthermore, since the voltage generated by the leak discharge becomes high, the carbon deposited in the recess 18 is burned off by the sparks generated during the leak discharge and is removed from the inner surface of the recess 18.

In addition, the angular protrusions 19 and 20 on the end face and outer peripheral surface of the tip 6 increase the insulation distance, and the fuel droplets at the tips of the angular protrusions 19 and 20 are easily cut, and the blast wave during the explosion stroke causes the angular protrusions 19 and 20 to be cut off easily. , 20 is blown away, and carbon is difficult to accumulate at the tips of the angular protrusions 19, 20, so that leakage discharge is significantly suppressed.

According to the present invention, a recess is provided in the end face of the insulator from which the center electrode protrudes, or a angular protrusion that surrounds the center electrode and extends in an annular shape is provided in the tip of the insulator. This increases the insulation distance on the insulator and suppresses the accumulation of combustion products such as carbon on the insulator surface, thereby preventing spark plug spurt and obtaining good ignition at low engine temperatures. I can do it.

[Brief explanation of the drawing]

Fig. 1 is a block diagram of a well-known spark plug shown as a prior art, and Fig. 2 is a block diagram of main parts of an embodiment of the present invention.・・・
recess, 19, 20 - angular process;

Claims (1)

[Scope of Claims] 1. A spark plug characterized in that a recess is provided in the tip end face of an insulator, and a center electrode extends through the recess in the axial direction. 2. A horn-like projection extending in an annular shape surrounding the center electrode is provided on the surface of the tip of the insulator,
``Nee J-; -word, -≠ spark plug.