JPS6117111B2 - - Google Patents

Description

[Detailed description of the invention] (1) Industrial application field The present invention is applicable to internal combustion engines with mounting screw diameters of 10, 12, and 14 mm.
This relates to a long reach spark plug with a length of the cylinder head embedded part of 19 mm or more, and a flat sheet type spark plug that is screwed onto the cylinder head via a gasket.

(2) Prior Art As shown in Fig. 1, a conventional spark plug for an internal combustion engine has a porcelain insulator 3 that holds a center electrode 2 sealed in a metal shell 21, and is connected to a cylinder head 26 by screws. When the mounting screw diameter of the main metal fitting 21 to be attached is 14 mm or 12 mm, the length (reach) L of the cylinder head implantation part is 12.7 mm or 19 mm, and when the screw diameter is 10 mm, 12.7 mm is mainly used. . Furthermore, the reach portion is almost completely threaded and is fastened to the cylinder head via the gasket 5.

(3) Problems to be solved by the invention By the way, the above-mentioned spark plugs with a long reach of 19 mm and a spark plug with a thread diameter of 10 mm and a reach of 19 mm and a full thread also have a main metal whose strength is reduced by the thickness of the root diameter. It becomes thin and deteriorates, deforms due to strain during fastening, and the airtightness between it and the insulator is likely to be incomplete, and in severe cases, there is a risk of breakage. Furthermore, extending the insulator in the axial direction within a limited range in the radial direction tends to cause distortion during firing, which reduces productivity. Furthermore, the long threaded portion naturally makes it extremely troublesome to attach and detach the plug. In particular, these trends become more significant as the screw diameter becomes smaller;
For 10mm long reach products, it is difficult to satisfy performance when using conventional full threads.

(4) Means for Solving the Problems The present invention has been made to solve such problems, and is a half-thread type spark plug in which a threaded portion is provided only on the tip side of the main metal fitting of the spark plug, and The object of the present invention is to provide a long reach flat sheet type spark plug that has a gasket drop-off effect that prevents the gasket from falling off as a result of this.

(5) Examples The present invention will be explained below with reference to embodiments shown in the drawings.

FIG. 2 is a longitudinal sectional view of one and a half of the main parts of a spark plug according to an embodiment of the present invention, showing the state in which it is attached to a cylinder head. Components common to those of the conventional spark plug are designated by the same reference numerals. Reference numeral 1 denotes a metal shell, in which a main body 7 and a body 8 equipped with mounting screws for the cylinder head 6 are connected via a stepped flat sheet 9, and a center electrode is provided in the inner cavity of the metal shell 1 according to known specifications. A porcelain insulator 3 holding 2 is sealed and fixed. 4 is the main metal fitting 1
A ground electrode 5 is welded to the end face of the cylinder head 6, and a gasket 5 is interposed between the upper face of the cylinder head 6 and the flat sheet 9, and is made of a generally used plate material. In the present invention, the body portion 8 of the metal shell 1
The male screw 1b for attachment is screwed into the tip portion near the combustion chamber 12, and this portion extends approximately 1/2 of the reach L of the entire length of the body. The mounting screw diameter A is available in various sizes such as 10, 12, and 14 mm, and the reach L is 19 mm.
That's about it. The remaining body of this threaded portion 1a is a non-threaded portion 1d, which is slightly smaller than the thread diameter A.
It is formed into a columnar shape with a diameter B larger than the valley diameter, and R
It is connected to the flat sheet 9 through the section 1e. A convex portion 1f is formed on the upper side surface of this non-threaded portion 1d, and a concave portion 1c is provided between it and the flat sheet 9, and the gasket 5 is supported in this concave portion 1c between it and the flat sheet 9 to prevent it from falling off. The outer diameter of the convex portion 1f is equal to or slightly larger than the inner diameter C of the gasket 5, and is formed to protrude by approximately 0.1 to 0.4 mm. It is desirable that the convex portion 1f has a tapered portion 1g on the side of the threaded portion 1a to facilitate insertion of the gasket 5 from the tip of the body. It is not necessarily necessary to form the convex portions 1f over the entire circumference of the body, and it is sufficient that the convex portions 1f be formed at at least three points so that the gasket 5 does not fall off. Formed by molding method.

In the above configuration, in order to support the gasket in the concave portion 1c, the gasket 5 is inserted from the tip of the threaded portion 1a of the metal shell 1, and if the gasket diameter is slightly smaller than the diameter of the convex portion 1f, the gasket 5 is inserted beyond the convex portion 1f. The gasket 5 is inserted by being elastically expanded and forcibly pushed in, and the gasket 5 is fixed in the recess 1c between the flat sheet 9 and the projection 1f. In addition, if the outer diameter of the protrusion 1f is equal to the inner diameter of the gasket 5, it is necessary to take measures to prevent the gasket from falling off after it is fitted into the gasket recess 1c. This is possible by forming a known protrusion or the like and locally forming the inner diameter of the gasket to be smaller than the outer diameter of the convex portion 1f.

This spark plug is screwed onto the cylinder head 6, which has a fitting hole 6b with a gap of approximately 0.2 to 1.2 mm between the internal thread 6a of the cylinder head 6 and the non-threaded portion 1d of the metal shell 1.
FIG. 3 shows another embodiment of the spark plug of the present invention, and is a vertical cross-sectional view of one and a half of the main parts. There is a non-threaded part 1 with a diameter B' larger than the thread diameter A on the main body side.
1d, and the upper end thereof has the above-mentioned diameter.
A convex portion 11f is formed which is larger than B' and has the same diameter as the inner diameter C' of the gasket 5 or is 0.1 to 0.4 mm larger in diameter, and a recessed portion 11c is provided. The metal shell 11 of the spark plug, which is fixed in the recess 11c by inserting the gasket 5 through the threaded end thereof, is screwed onto the cylinder head 16 via the gasket 5. Since the diameter of the body of this spark plug is set larger than the outer diameter of the threaded part, the strength of the main metal fitting can be further improved, and it is possible to manufacture a porcelain insulator with uniform quality, as well as withstand voltage strength. can be increased.

As mentioned above, the long reach flat sheet type spark plug of the present invention has a screw diameter of 10 mm that is screwed into the cylinder head on the tip side of the metal shell.
A threaded part of one type of 12 mm, 14 mm, etc. is carved, and an unthreaded body part on the base side following this threaded part is provided, and the body part is loosely fitted between the cylinder head and the gasket is fitted into the body part. A convex portion equal to or slightly larger than the inner diameter of the gasket is formed at the upper end, and a concave portion is provided between the gasket and the flat seat, and the gasket is inserted through the convex portion and fixed in the concave portion, thereby making it easier to install the spark plug when installing the spark plug. This increases the strength of the metal shell to prevent gas leakage between it and the porcelain insulator, and facilitates the production of the porcelain insulator. In addition, the half-thread type not only makes it easier to attach and detach the plug, but also has the effect of preventing the gasket from falling off, so even if the plug is attached and detached several times, the gasket will not fall off and maintain airtightness. I can do it. Furthermore, it is possible to advantageously develop spark plugs with a small thread diameter of 10 mm and a long reach of 19 mm without impairing performance.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a main part showing how the cylinder head of a conventional spark plug is installed, and FIGS. 2 and 3 are sectional views of one-half of the main part showing how the cylinder head of the spark plug of the present invention is installed. . 1, 11... Metal shell, 1a, 11a... Threaded portion, 1b, 11b... Male thread, 1c, 11c...
Recessed portion, 1d, 11d...Threadless portion, 1f, 11
f... Convex portion, 5... Gasket, 6, 16... Cylinder head, 7... Main body, 8... Body, 9...
...Flat seat, 12...Combustion chamber.

Claims (1)

[Claims] 1. The body 8 equipped with a mounting screw screwed into the cylinder head is connected to the large-diameter main body 7 via a stepped flat sheet 9, and a gasket is placed between the flat sheet 9 and the cylinder head to ensure airtightness. In a spark plug having a metal shell holding a main body, the tip of the body is formed as a threaded part 1a for attaching to the cylinder head, and the remaining body 8 is formed as a non-threaded part 1b that loosely fits into the cylinder head 6,
A long reach flat sheet in which the head of the non-threaded portion is formed as a convex portion 1f having a diameter at least larger than the inner diameter of the gasket, and a concave portion 1c for supporting the gasket is formed between the convex portion 1f and the flat sheet 9. type spark plug.