JPH0613156A - Spark plug - Google Patents

Abstract

PURPOSE:To make a spark plug compact by setting the diagonal line R of a hexagon to be 12.5-16.0mm, the outer diameter D of the head part of an insulator to be 8.0-11.0mm, and the length L from the seal face to the center axis rear end to be 29-35mm. CONSTITUTION:A center axis 3 consists of a center electrode 5 in the tip side and a terminal rod 6 in the rear end side which are fixed by a conductive adhesive. The electrode 5 has a tip part with a small diameter which is projected out of the tip end of an insulator 2 and works as a sparking part 51, and the terminal rod 6 has a rear end part with a large diameter which is projected out of the rear end of the insulator 2 and is a fitting part 61 with a terminal of a plug cap. The hexagonal diagonal line R of a hexagon part is set to be 12.5<=R<=16.0mm. the length L from the seal face 13 to the rear end of the center axis 3 is set to be 20<=L<=35mm, the outer diameter D of the head part 25 of the insulator 2 is set to be 8.0<=11.0mm. Consequently, the necessary functions such as engine output, high voltage resistance, vibration resistance, etc., are prevented from degrading and spark plugs are made compact as much as possible without deteriorating the durability.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a spark plug having a reduced size.

[0002]

2. Description of the Related Art In a small general-purpose gasoline engine, when the size of the spark plug is reduced, the area of the intake port and the exhaust port increases,
Combustion efficiency can be improved by reducing the weight, and the plug cover part of the engine can be downsized, resulting in overall compactness.

[0003]

However, miniaturization of the spark plug generally leads to deterioration of necessary performance such as withstand voltage and vibration resistance, and is accompanied by a drawback that durability is impaired. An object of the present invention is to make the spark plug as compact as possible without impairing durability, and to contribute to improvement of combustion efficiency and compactness of a small gasoline engine.

[0004]

[Means for Solving the Problem] Hexagonal opposite side dimension R of hexagonal portion
12.5 to 16.0 mm, the outer diameter D of the long head of the insulator
Was set to have a diameter of 8.0 to 11.0 mm, and a length L (upper seat dimension) from the sealing surface to the rear end of the center shaft was set to 20 to 35 mm.

[0005]

According to the present invention, the hexagonal side length R of the hexagonal portion, the head outer diameter D of the insulator, and the seat top dimension L are used.
Is set to the optimum value, the physique of the spark plug can be minimized.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows a spark plug according to the present invention. An insulator 2 with a shaft hole 20 is provided in a substantially cylindrical (hollow) metal shell 1 having an L-shaped outer electrode 10 welded to the tip surface. Has been fitted. Both ends 3A, 3 of the shaft hole 20
The center shaft 3 is fitted so that B is projected.

The metal shell 1 has a large-diameter middle portion having a tip screw portion 11 having a screw for mounting on an engine formed on the outer periphery thereof, a hexagonal portion 12 on the rear end side, and a sealing surface 13 with a gasket on the tip end side. It has a body portion 14. A thin portion 15 is provided at the rear end of the hexagonal portion 12, and the stepped seat 1 is provided on the inner circumference corresponding to the body portion 14.
7 are formed. The gasket 4 is externally fitted between the screw portion 11 and the body portion 14.

The insulator 2 includes a small-diameter tip leg portion 21, a medium-diameter waist portion 22 connected to the leg portion 21, and a large-diameter intermediate collar portion 2.
3, and corrugation 24 consisting of double grooves on the outer circumference
Is formed of a slightly large diameter rear end head long portion 25. In this insulator 2, a part of the leg portion 21, the waist portion 22, the collar portion 23, and the head portion 25 is inserted into the metal shell 1,
The front end side surface of the waist portion 22 is locked to the step seat 17 of the metal shell 1 through the packing 18, and the hexagonal portion 12 of the metal shell 1
It is fixed to the metal shell 1 by crimping the thin portion 15 of.

The center electrode 5 on the front end side and the terminal rod 6 on the rear end side of the center shaft 3 are fixed by a conductive adhesive material 31.
The center electrode 5 has a small-diameter tip portion protruding from the tip end of the insulator 2 to form an ignition portion 51, and the terminal rod 6 has a large-diameter rear end portion protruding from the rear end of the insulator 2 to form a plug cap. Is a fitting portion 61 with the terminal.

This spark plug, as shown in FIG.
The hexagonal part 12 of the metal shell has a hexagonal side width R of 14 m.
m, the dimension L from the sealing surface 13 to the rear end of the center shaft is 26 m
m, and the outer diameter D of the long head portion 25 of the insulator 2 is set to 10.5 mm. Further, the fitting portion 61 of the terminal rod 6 has a cylindrical shape with a bulging portion having a diameter of 6 mm and a length of 3 mm. The outer diameter of the body 14 is 16.7 mm, and the leg 11 is JI
12 mm screw of S standard is cut. The cylinder head mounting screw diameter is applied to 10 to 14 mm screws, and is particularly useful for screw diameters of 12 and 10 mm type.

The hexagonal opposite side dimension R of the hexagonal part 12 is 12.
5 mm ≤ R ≤ 16.0 mm, the distance L from the sealing surface 13 to the rear end of the center shaft 3 is set to 20 mm ≤ L ≤ 35 mm, and the outer diameter D of the long head portion 25 of the insulator 2 is set to 8 mm ≤ D ≤ 11.0 mm. By doing so, required performances such as engine output, withstand voltage, and vibration resistance can be prevented from deteriorating, and the spark plug can be made as compact as possible without impairing durability.

[Brief description of drawings]

FIG. 1 is a sectional view of a spark plug according to the present invention.

FIG. 2 is a dimensional diagram of the spark plug of FIG.

[Explanation of symbols]

 1 Metal shell 2 Insulator 3 Middle shaft 4 Gasket 5 Center electrode 6 Terminal rod 12 Hexagonal part 13 Sealing surface 25 Head long part

Claims (1)

[Claims] 1. A hollow structure comprising a tip screw portion having an engine mounting screw formed on its outer periphery, a rear hexagonal portion, and a large-diameter intermediate barrel portion on the tip side which is a sealing surface with a gasket. The metal shell has a shaft hole in which both ends of the center shaft project and are fitted, and a rod-shaped insulator made up of a long tip leg portion, a large diameter intermediate brim portion, and a long head portion is fitted and fixed. In the spark plug, the hexagonal side width R of the hexagonal part is 12.5 to 16.0 m.
m, the outer diameter D of the long head portion of the insulator is 8.0-1
A spark plug having 1.0 mm and a length L from the sealing surface to the rear end of the center shaft set to 20 to 35 mm.