JPS6312699B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of manufacturing a head screw for a highly adhesive spark plug.

As shown in FIG. 1, the spark plug head screw 1 is made by applying heat-resistant cement C to the head screw hole 2a of the insulator 2 of the spark plug P, and then attaching the threaded portion 1a of the head screw 1 to the head screw hole 2a of the insulator 2 of the spark plug P. It is screwed into the screw hole 2a and adhered to the head of the insulator 2, and its upper end is connected to the power source, and its lower end is connected to the center electrode. (not shown).

Since heat and vibration are repeatedly applied to the spark plug over a long period of time, it is inevitable that the adhesiveness of the cement C at the adhesive part of the head screw 1 will deteriorate, and in the worst case, the head screw 1 may become loose. If the electrode comes off, there is a risk that sparks will not fly between the center electrode and the outer electrode. For this reason, the cement C of this head screw 1 is required to have high adhesive performance such as heat resistance and vibration resistance.

As a result of examining the thread shape of the threaded portion 1a of the head screw 1 while keeping the material of the cement C as it is, the present applicant found that a vertical groove 20b with a notched thread in the threaded portion 20a as shown in FIG. 3a. Head screw 20 with
It has been discovered that by employing this method, the adhesiveness of the head screw 20 can be greatly improved, and it can be put to practical use. This is because when the screw 20 is screwed into the threaded hole 2a of the spark plug and glued to the head of the insulator 2, the groove 20b and the spark plug threaded hole 2
cement C in the gap formed vertically between
This is because a vertical cement layer C' is formed.

By the way, the threaded portion 20a of the head screw 20 is
Although it is obtained by thread rolling the processed portion 11 of the thread material 10 shown in the figure, the groove 20b must be formed by turning with a milling machine or the like before thread rolling the threaded portion 20a. For this reason, the head screw 20
Compared to head screw 1, this requires one extra step and is expensive, so it could not be put to practical use.

The present invention aims to provide a highly adhesive head screw for a spark plug as shown in FIG. 2 at a low cost. 20b is left as a vertical groove, and this vertical groove is formed into a spiral shape, which is the easiest to design and manufacture for the rolling die.

FIG. 4 shows a head screw 30 manufactured according to the present invention.
, 30a is a threaded portion, and 30b is a spiral groove.Since the thread 30a is obtained by thread rolling the processed portion 11 of the thread material 10, the outer diameter of the processed portion 21 is equal to the effective diameter of the threaded portion 30a. Almost equal.

An embodiment of the invention will be described with reference to a head screw 30 in FIG.

FIG. 5 is an explanatory diagram of the die of a flat die type thread rolling machine for thread rolling the head screw 30 from the thread material 10. As shown in FIG.
and a moving die 42 that reciprocates back and forth parallel to this.
Consisting of

The fixed die 41 has a die surface ABCD and a top surface.
It is a rectangular parallelepiped consisting of ADHE, lower surface BCGF, side ABFE, and DCGH, and the moving die 42 is a die surface.
A′B′C′D′, top surface A′D′H′E′, bottom surface B′C′G′F′,
side
The die surface is a rectangular parallelepiped consisting of A′B′F′E′, D′C′GH′.
ABCD, A'B'C'D' have screw threads 41a, 42a and oblique grooves 41b, 42, respectively, as shown in FIG.
b is provided.

The dies 41, 42, as shown in FIG.
The respective die surfaces ABCD,
A′B′C′D′ are placed opposite each other. Then, on the die faces ABCD, A′B′C′D′, as shown in the same figure b,
When the lower surface BCGF of the fixed die 41 and the lower surface B'C'G'F' of the movable die 42 are brought together, the screw thread 41
Boundary line BC formed by the lower surfaces of b and 42b,
A plurality of diagonal grooves 41b, 42b are provided on the upper surface ADHE,
From A'D'H'E' to the lower surface BCGF, B'C'G'F', it intersects with the screw threads 41a, 42a, respectively, and then crosses the boundary lines BC, B'C' to form a straight line. To,
And the distance S between the diagonal grooves 41b and 42b is measured on the upper surface ADHE, A'D'H'E' of the die, and the thread material 1
One integer fraction of the outer circumference of the processed part 11 of 0 (however, ≦
1) The length is as follows. The depth of these diagonal grooves 41b, 42b is determined by the depth of the root of the threads 41a, 42a, as is clear from FIG.
It has reached almost 1c and 42c. Now, in Figure a, while moving the movable die 42 in the direction of the arrow, the machined part 11 of the thread material 10 is moved along the ridge line DC,
Dies 41, 42 from the entrance formed by D'C'
When the die is passed between die surfaces ABCD and A'B'C'D', the processed portion 11 is thread-rolled to form a threaded portion 30a. Then, the diagonal grooves 41b and 42b form the machining part 1.
1 is left as is, a spiral groove 30b is formed, and the head 30 is manufactured.

The spiral groove 30b has an outer diameter equal to the outer diameter of the processed portion 11, that is, the effective diameter of the threaded portion 30a of the head screw 30, and has a spiral shape because the oblique grooves 41b and 42b are straight. Moreover, the number of spiral grooves 30b is
For example, if the length of S is 1/2 of the outer circumference of the processed part, two
1/3 means 3 pieces, and 1 means 1 piece. Furthermore, the third
In order to form a straight vertical groove 20b as shown in FIG. Furthermore, since the outer diameter of the diagonal groove 30b is equal to the effective diameter of the threaded portion 30a, the inner diameter of the head screw hole 2a of the insulator 2 of the ignition plug P is made large so that the head screw 30 can be screwed in without any problem. There is a need.

The above explanation has been made using a flat die type screw rolling machine, but as shown in Figure 6a, a fixed die 4
The head screw 3 is similarly used in a planetarium type system in which a segment die 51 is used instead of the head screw 1, and a rotating rotary die 52 is used instead of the movable die 42.
0 is obtained.

FIG. 6 is an explanatory diagram of a die of a planetarium type thread rolling machine for thread rolling the head screw 30 from the thread material 10. The segment die 51 has an arcuate die surface EFGH, an upper surface 51c, and a lower surface 51.
d, an arcuate block shape consisting of side surfaces 51e and 51f, and the rotary die 52 has an upper surface 52c,
It has a disk shape formed by a lower surface 52d and an outer circumferential side surface, and the outer circumferential side surface is a die surface.

The dice 51 and 52 are arranged with their respective dice faces facing each other with a certain interval as shown in FIG. As shown in FIG.
When 1d and 52d are brought together, the threads 51a,
52a is the thread 41a of the dies 41, 42,
42a, and the diagonal grooves 51b and 52b are also similar to the diagonal grooves 41b and 42b of the dies 41 and 42, respectively. Then, in the same figure a, while rotating the rotary die 52, the screw material 10 is
When passing between the die faces of the dies 51 and 52 through the entrance formed by the outer periphery of the die 52, the head screw 3
0 is produced.

As described above, the present invention has high practical value because it allows the production of a head screw for a spark plug that exhibits high adhesion performance extremely simply by using a pair of rolling dies provided with a simple diagonal groove.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of the head of a general spark plug, and FIG. 2 is an external view of the head screw material. FIG. 3a is an external view of an example of a highly adhesive head screw, and FIG. 3b is a sectional view showing a state in which this head screw is adhered to the head of a spark plug. Fourth
The figure is an external view of a highly adhesive head screw manufactured according to the present invention. FIGS. 5a, b, c, and d are explanatory diagrams of dies of the flat die type thread rolling machine for manufacturing the head screw of FIG. 4. 6a and 6b are explanatory diagrams of dies of a planetarium type thread rolling machine for manufacturing the head screw of FIG. 4; FIG. 1...Head screw, 10...Screw material, 30...
Head screw, 30b... spiral groove, 41, 42, 5
1,52...Dice, 41b, 42b, 51b,
52b...Diagonal groove.

Claims (1)

[Claims] 1. In a manufacturing method in which a highly adhesive head screw for a spark plug is manufactured from a screw material using a thread rolling machine, a rectangular fixed die is rotated with a rectangular parallelepiped movable die that reciprocates back and forth, or a circular arc block-shaped segment die. When the lower surfaces of the disc-shaped rotary dies are brought together, threads are provided on each die surface so that the threads are in a straight line beyond the boundary line formed by the lower surfaces, and multiple diagonal threads are provided on each die surface. The groove intersects the thread diagonally from the top surface to the bottom surface, and then crosses the boundary line to form a straight line, and the spacing between each diagonal groove is measured on the top surface of the die to determine the outer circumference of the machined part of the thread material. A method for manufacturing a head screw for a highly adhesive spark plug, characterized in that a diagonal groove is provided so that the length is a fraction of an integer (but ≦1).