JPH06283250A - Converged shock wave induction spark plug - Google Patents

Abstract

PURPOSE:To increase the intensity of a long distance discharge spark plug and at the same time to make the shock waves generated by discharge to be reflected, converged and made to interfere with an ignition flame as intense shock waves soas to strengthen the ignition function. CONSTITUTION:A hollow part with almost elliptically cylindrical or cylindrical shape and surrounded by an insulator 2 is formed around a center electrode 1. The outside of the insulator is wrapped with an earth side metal 3, and in this case, only one part 3' is projected to get closer to the center electrode 1 and the thickness of the insulator 2' of the part is made especially thin. An earth electrode 5 is so set as to slightly come out of the upper end of the insulator 2'.

Description

Detailed Description of the Invention

[0001]

INDUSTRIAL APPLICABILITY According to the present invention, a spark plug having a very high ignition ability for a combustible mixture can be manufactured. In a spark ignition engine, it is possible to operate with a lean air-fuel mixture and with a large amount of exhaust gas recirculation, and while suppressing the emission of harmful substances such as CO, CH, and NO _x , high thermal efficiency and low fuel consumption rate are achieved. Can produce an internal combustion engine.

[0002]

2. Description of the Related Art As a spark plug having a high ignition ability, there is already a long-distance discharge spark plug. This is a shape in which a long center electrode is wrapped with a thin insulator, because a discharge spark is formed in a long distance between its tip and the ground electrode of its foot, and it heats a large amount of air-fuel mixture. , The ignition ability becomes high.

[0003]

[Problems to be Solved by the Invention]

A conventional long-distance spark igniter is composed of a long center electrode and a very thin-walled cylindrical insulator surrounding the center electrode. Since the center electrode projects into the combustion chamber, overheating,
It is easily damaged, the ignitability is lowered due to the disturbance of the surrounding air-fuel mixture, the insulator is also easily broken, and the life is short. In the present invention, the strength of the insulator on the electrode side surface is increased, the center electrode is shortened to prevent overheating, and the ignition region is made hollow to avoid the influence of turbulence of the air-fuel mixture, and further, shock waves are utilized. The purpose is to improve the ignition ability.

[0005]

In order to achieve the above object, the spark plug of the present invention has an appropriate width and depth around the discharge part at one end of the center electrode surrounded by the insulator except both ends. It has a structure in which the cavity is surrounded by a metal that is in contact with the earth electrode, and its surface is covered with an insulator such as an insulator.

One portion of the earth side metal forming the cavity is projected within a width of 5 mm so that the distance from the center electrode edge is about 0.5 to 2.0 mm, and the thickness of the insulator on the surface is particularly large. The thickness is reduced to about 0.2 to 1.0 mm, and the earth electrode is attached to the insulator so as to protrude from the insulator by about 0.5 to 2.0 mm at the upper end of the cavity separated from the center electrode.

The discharge spark is formed between the center electrode end at the bottom of the cavity and the ground electrode end at the top of the cavity in a space slightly separated from the surface of the insulator.

The shape of the cavity is an elliptic cylinder having the discharge position as the first focal point, a cylinder having the center electrode as the center, or a shape close thereto.

[0009]

The function of the spark plug having the above-described structure is as follows.
There, shock waves are generated and propagate radially. When the cavity is an elliptical cylinder, the shock wave collides with the inner wall of the cavity, is reflected, and propagates while converging toward the second focus of the ellipse. On the other hand, the spark ignites and the flame propagates in the air-fuel mixture while spreading almost radially. When this reaches the vicinity of the second focus of the ellipse, it converges and becomes stronger and collides with the shock wave with increased temperature and pressure, and it receives interference and increases the reaction rate, becomes a powerful flame nucleus, and becomes easier to ignite and burn. .

If the cavity is a cylinder or a shape close to it,
After being reflected by the inner wall of the cavity, the shock wave from the discharge spark also converges to some extent, becomes a strong shock wave, interferes with the flame, forms a powerful flame nucleus, and accelerates ignition.

[0011]

Embodiments will be described with reference to the drawings.
In FIG. 1, a cavity C surrounded by an insulator 2 is formed on the tip of the center electrode 1, and the outside thereof is surrounded by a ground side metal 3. One point 3'of the earth side metal is projected, the distance g from the center electrode edge is set to about 0.5-2.0 mm, and the thickness t of the insulator 2'on the surface is set to about 0.2-1.0 mm. To do. 0.5-2.0m from the insulator 2'on the 3 '
Weld the ground electrode 5 so that it protrudes by about m. Cavity depth d
Is 1.5 mm or more. A discharge spark is formed between the center electrode and the ground electrode 5 as indicated by s.

When the hollow shape is an elliptic cylinder, as shown in FIG. 2, when discharging into a combustible air-fuel mixture at the elliptic first focal point F ₁ , a Joule heat of the discharge generates a shock wave, and an arrow in the figure As shown by, spreads radially and propagates. It strikes the wall surface of the elliptical tubular insulator, reflects and converges toward the second focal point F ₂ of the ellipse. By converging, the shock wave becomes stronger and the temperature and pressure rise. It is ignited at the first focal point F ₁ by the same discharge spark, and collides with the flame propagating radially behind the shock wave in the vicinity of the second focal point, and interferes and interferes with the reaction to accelerate the powerful flame kernel. Make and spread the combustion wave in the main combustion chamber.

When the hollow shape is a cylinder or a shape close to it, it is not the same as in the case of an elliptic cylinder, but as shown in the lower part of FIG.
_The shock wave generated by the discharge at ₁ collides with the inner wall of the cavity, is reflected and converges to some extent to form a strong shock wave. It collides with the flame and interferes with it to form a powerful flame kernel and enhance the ignition ability.

[0014]

Since the present invention has the structure described above, if it is used in a combustible mixture such as in the combustion chamber of a spark ignition engine, the following effects are obtained.

By providing an elliptic cylinder, a cylinder or a cavity having a shape close to that in the central electrode discharge area, a powerful flame nucleus is created by colliding and interfering with a strong shock wave that has just been ignited. Increase the ignition ability.

Although the discharge is performed according to the long-distance discharge spark plug theory, since the thin portion of the insulator is limited to a part of a narrow range, the strength of the insulator becomes large and the life of the spark plug becomes long.

Since the center electrode becomes shorter, it is less likely to overheat and less likely to be damaged.

[Brief description of drawings]

FIG. 1 is a plan view and a vertical sectional view in the vicinity of a spark plug head discharge region.

FIG. 2 is an explanatory diagram of a propagation state of a shock wave generated by electric discharge, where the upper case is an elliptic cylindrical cavity and the lower case is a cylindrical cavity.

[Explanation of symbols]

 1 center electrode 2 insulator 2'discharge surface insulator 3 earth side metal body 3'earth side protrusion 4 screw part 5 earth electrode C cavity d distance between center electrode and earth electrode g distance between discharge surface insulator and center electrode t Discharge surface insulator thickness s Discharge spark

Claims (4)

[Claims] 1. A metal surface contacting a ground electrode is formed around a center electrode, which is cylindrically wrapped in an insulator except for both ends, and has a proper width and depth. A spark discharge spark plug covered with an insulator. 2. A portion of the metal in contact with the ground electrode, having a width of 5
Within 0.5 mm, the distance from the center electrode is 0.5 to 2.0 m
The protrusion is formed so as to have a length of about m, and the insulator on the surface is made particularly thin to have a thickness of about 0.2 to 0.0 mm. The earth electrode is attached to the upper end of the insulator so as to protrude from the insulator to the center electrode by 0.5 to 2.0 mm, and the discharge spark flies between the center electrode and the earth electrode end, slightly away from the insulator surface. 3. The shape of the cavity is an elliptic cylinder whose discharge position is the first focal point, and shock waves generated by a discharge fire and propagating in a radial direction collide with the wall surface of the elliptic cylinder and are reflected to converge on the second focal point. Structure. 4. A structure in which a shock wave from a discharge spark is reflected by an inner wall of a cavity and converges to a certain extent in a cylindrical shape or a shape close thereto.