JP2946277B2 - Plug cap for spark plug - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a spark plug plug cap for connecting a high voltage cable for supplying a high current to a spark plug of, for example, a gasoline engine for an automobile in a conductive state.

[0002]

2. Description of the Related Art Conventionally, for example, the periphery of a portion where a high-voltage cable for supplying a high-voltage current to a spark plug of a gasoline engine for an automobile is electrically connected to the spark plug is covered with a plug cap for the spark plug and the high-voltage current is ignited. Insulated to prevent leakage around the plug. By the way, in recent years, with the spread of a so-called twin cam engine, which has two camshafts on a cylinder head for opening and closing valves in order to cope with higher output and lower fuel consumption of the engine, a spark plug is attached to the cylinder head. It has come to be mounted deep inside the provided spark plug mounting hole. Therefore, a plug cap for an ignition plug improved so that a high-voltage cable can be easily connected to an ignition plug mounted deep in the ignition plug mounting hole is disclosed in Japanese Utility Model Laid-Open No. 49-114332 and the like. I have.

[0003] Such a plug cap 9 for an ignition plug.
3, a spark plug mounting hole 2 is formed in an engine head 1 of an automobile engine, and a spark plug mounting hole 2 is formed through the bottom 3 of the spark plug mounting hole 2. An ignition plug 7 is screwed into the through hole 4. The plug cap 90 for the ignition plug is provided with a connection fitting 23 attached to a terminal of the high-voltage cable 21 for supplying a high-voltage current to the ignition plug 7 by externally fitting to a terminal (not shown) of the ignition plug 7.
1 is connected to the ignition plug 7.

The insulating resin pipe 60 of the spark plug plug cap 90 is formed of a hard insulating resin material. The insulating resin pipe 60 covers the high-voltage cable 21 and the connection fitting 23 so that a high-voltage current supplied to the ignition plug 7 is supplied. It is insulated so as not to leak to the wall surface of the spark plug mounting hole 2. The end of the insulating resin pipe 60 on the side of the ignition plug 7 has an enlarged diameter, and is fitted with an annular insulating cap 30 having a substantially U-shaped cross section molded from soft insulating rubber. A waterproof cap 40, which is also made of soft insulating rubber, is fitted to the end of the insulating resin pipe 60 opposite to the spark plug 7. A flange portion 42 is integrally extended with the substantially cylindrical base portion 41 of the waterproof cap 40, and a tip portion of the base portion 41 is a fitting portion 43 which is fitted in the spark plug mounting hole 2. ing. Further, the base portion 41 is integrally provided with a contact portion 44 that is in close contact with the surface of the high-voltage cable 21.

When the insulating resin pipe 60 of the plug cap 90 for the ignition plug constructed as described above is inserted into the ignition plug mounting hole 2, the connection fitting 23 is fitted to a terminal (not shown) of the ignition plug 7. High voltage cable 21
Is connected to the spark plug 7 and the insulating cap 3
0 is fitted to the insulating portion 8 of the ignition plug 7 so as to be closely attached thereto, so that the opening of the insulating resin pipe 60 on the side of the ignition plug 7 is liquid-tightly sealed. At the same time, the waterproof cap 40
Of the waterproof cap fitting portion 5 of the spark plug mounting hole 2 and the tip of the flange 42 of the waterproof cap 40 abuts on the waterproof cap tight portion 6 of the spark plug mounting hole 2. The upper opening of the spark plug mounting hole 2 is hermetically sealed by a waterproof cap 40. Further, the base portion 41 of the waterproof cap 40 is externally fitted to the insulating resin pipe 60,
In addition, since the contact portion 44 is in close contact with the outer surface of the high-voltage cable 21, the opening of the insulating resin pipe 60 on the opposite side to the ignition plug 7 is liquid-tightly sealed by the waterproof cap 40.

[0006]

By the way, the waterproof cap 40 is provided with a communication hole 46 for communicating a space 70 formed between the ignition plug mounting hole 2 and the insulating resin pipe 60 with the outside air. When the air in the space 70 is expanded by being heated by the heat of the engine, the waterproof cap 4
0 is prevented from falling out of the spark plug mounting hole 2. Therefore, when the automobile travels in the rain or cleans the interior of the engine room using high-pressure steam, the small-diameter vent hole 4 provided at the upper end of the communication hole 46.
Water may enter into the space 70 through the space 5.

As shown in FIG. 4, in a conventional plug cap 90 for an ignition plug, an insulating resin pipe 6 is provided.
0 is fitted to the high-voltage cable 21 with a gap of 1 mm or less. Therefore, when water enters the space 70, the insulating resin pipe 60 is grounded to the peripheral wall surface of the spark plug mounting hole 2, and the high-voltage current supplied to the high-voltage cable 21 is reduced. , The energy loss increases, and the ignition plug 7 easily misfires. Furthermore, since insulation breakdown of the insulating resin pipe 60 is likely to occur,
If the thickness is simply increased in order to increase the strength of the insulating resin pipe 60, not only the molding conditions of the insulating resin pipe 60 are deteriorated, but also molding defects such as generation of air bubbles in the molded product are generated, but also the insulating resin The weight and manufacturing cost of the pipe 60 will increase.

The insulating resin pipe 60 has a large diameter, and the insulating resin pipe 60 is connected to the high-voltage cable 21 and the connection fitting 24.
It is conceivable to fill an insulating material between the high-voltage cable 21 and the connection fitting 24 when filling the insulating material.
Is not easy to position at the center of the insulating resin pipe 60. Therefore, if an attempt is made to fill the inside of the insulating resin pipe 60 with an insulator, the molding process is complicated and the molding cost is greatly increased.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to solve the above-mentioned problems, and without increasing the weight and manufacturing cost of the spark plug plug cap, even if the inside of the spark plug mounting hole is flooded, the plug for the spark plug is used. An object of the present invention is to provide a good spark plug plug cap capable of reducing energy loss of the cap and preventing misfiring of the spark plug.

[0010]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a spark plug for connecting a high-voltage cable to a spark plug mounted at the bottom of a spark plug mounting hole formed in an engine. A plurality of cable support pieces projecting radially inward and extending substantially in the longitudinal direction along the central axis on the inner peripheral wall of the insulating resin pipe that covers the high-voltage cable; It is extended with an interval, an isolation space is formed between the outer surface of the high-voltage cable and the inner peripheral wall of the insulating resin pipe, and the high-voltage cable is held on the central axis of the insulating resin pipe. It can be achieved by a plug cap for an ignition plug characterized by the following.

Preferably, the diameter of the outer peripheral surface of the insulating resin pipe is increased so as to approach the peripheral wall surface of the ignition plug mounting hole. Preferably, a plurality of the cable support pieces are extended in parallel or spirally with respect to a center axis of the insulating resin pipe.

[0012]

According to the above construction, since the inner peripheral wall of the insulating resin pipe is separated from the outer surface of the high-voltage cable, an insulating layer made of air is formed therebetween. The high-voltage cable supported by the cable support piece is located at the center of the insulating resin pipe and does not contact the inner peripheral wall of the insulating resin pipe. Therefore, the high-voltage current supplied to the high-voltage cable does not easily leak outside through the insulating resin pipe, and the energy loss is reduced. In addition, by expanding the diameter of the insulating resin pipe so that the outer peripheral surface is close to the peripheral wall surface of the ignition plug mounting hole, the insulating layer made of air can be made thicker, and the outer peripheral surface of the insulating resin pipe can be made thicker. Water can be prevented from entering between the inner wall surface of the spark plug mounting hole and the inner wall surface.

[0013]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of a spark plug plug cap according to the present invention.
Here, FIG. 1 is an overall vertical sectional view of a plug cap for an ignition plug according to the present invention, and FIG. 2 is a sectional view taken along the line AA in FIG. As shown in FIG. 1, a spark plug 7 is screwed into a through hole 4 formed through a bottom 3 of a spark plug mounting hole 2 formed in an engine head 1 of an automobile engine. The spark plug plug cap 100 of the present embodiment is attached to the end of the high-voltage cable 21 that supplies a high-voltage current to the spark plug 7, in substantially the same manner as the conventional spark plug plug cap 90 shown in FIG. The high-voltage cable 21 is connected to the ignition plug 7 by externally fitting the connection fitting 23 to a terminal (not shown) of the ignition plug 7.

The insulating resin pipe 10 of the spark plug plug cap 100 is formed of a hard insulating resin material. The insulating resin pipe 10 covers the high-voltage cable 21 and the connection fitting 23 so that the high-voltage current supplied to the ignition plug 7 is reduced. It is insulated so as not to leak to the wall surface of the spark plug mounting hole 2. At the end of the insulating resin pipe 10 on the side of the ignition plug 7, an annular insulating cap 30 having a substantially U-shaped cross section molded from soft insulating rubber is fitted.

A waterproof cap 40, which is also made of soft insulating rubber, is fitted to the end of the insulating resin pipe 10 opposite to the spark plug 7.
Further, a substantially cylindrical base portion 41 of the waterproof cap 40 is provided.
A flange 42 is integrally extended with the base portion 41, and a distal end portion of the base portion 41 is a fitting portion 43 which is fitted in the spark plug mounting hole 2. Further, the base portion 41 is integrally provided with a contact portion 44 that is in close contact with the surface of the high-voltage cable 21.

When the insulating resin pipe 10 of the plug cap 100 for an ignition plug configured as described above is inserted into the ignition plug mounting hole 2, the connection fitting 23 is fitted to a terminal (not shown) of the ignition plug 7. High voltage cable 2
1 is connected to the spark plug 7, and at the same time, the insulating cap 30 is fitted to the insulating portion 8 of the spark plug 7 so as to be in close contact therewith. You. At the same time, the fitting portion 43 of the waterproof cap 40 comes into close contact with the inner wall surface of the waterproof cap fitting portion 5 of the ignition plug mounting hole 2 and the waterproof cap 40
The tip of the flange 42 abuts on the waterproof cap contacting portion 6 of the spark plug mounting hole 2, and the upper opening of the spark plug mounting hole 2 is liquid-tightly sealed by the waterproof cap 40. Furthermore, since the base portion 41 of the waterproof cap 40 is externally fitted to the insulating resin pipe 10 and the contact portion 44 is in close contact with the outer surface of the high-voltage cable 21, the ignition plug 7 of the insulating resin pipe 10
The opening on the opposite side is sealed by a waterproof cap 40 in a liquid-tight manner.

At this time, the outer peripheral surface 13 of the insulating resin pipe 10 is set so that the insulating resin pipe 10 can be inserted into the ignition plug mounting hole 2 within a range where the ignition plug mounting hole 2 can be inserted.
The diameter is enlarged so as to be sufficiently close to the peripheral wall surface. Therefore, the space 51 formed between the outer peripheral surface 13 of the insulating resin pipe 10 and the peripheral wall surface of the spark plug mounting hole 2 is formed between the outer peripheral surface 62 of the conventional insulating resin pipe 60 shown in FIG. The capacity is greatly reduced as compared with the space 70 formed between the inner wall surface of the first and second inner walls. Therefore,
In the spark plug plug cap 100 of the present embodiment, it is difficult for water to enter the space 51 formed between the outer peripheral surface 13 of the insulating resin pipe 10 and the inner wall surface of the ignition plug mounting hole 2. The amount will be small.

Further, the inner peripheral wall 1 of the insulating resin pipe 10
4, four cable support pieces 12 projecting inward in the radial direction and extending in the longitudinal direction along the central axis are extended in parallel at substantially equal intervals in the circumferential direction.
The outer surface of the high-voltage cable 21 and the insulating resin pipe 1
The high-voltage cable 21 is held on the central axis of the insulating resin pipe 10 while an isolation space 52 is formed between the insulating resin pipe 10 and the inner peripheral wall 14. The lower ends of the cable support pieces 12 are cut out so as not to interfere with the ignition plug 7.

As a result, the high-voltage cable 21 and the connection fitting 23 are separated from each other by two pairs of the cable support pieces 1 facing each other.
2, it is positioned so as to be located on the central axis of the insulating resin pipe 10 and is held so as not to contact the inner peripheral wall 14 of the insulating resin pipe 10.
2, a good insulating layer made of air is formed. That is,
The insulating layer made of air is lighter than resin material,
An ideal insulator whose insulating property is restored again after dielectric breakdown can be obtained. Therefore, according to the insulating resin pipe 10, the high-voltage current supplied to the high-voltage cable 21 does not easily leak outside through the insulating resin pipe 10, and energy loss is reduced.

In particular, the space 5 formed between the outer peripheral surface 13 of the insulating resin pipe 10 and the inner wall surface of the spark plug mounting hole 2
Even if the water enters into the inside 1 and the insulating resin pipe 10 is grounded to the inner wall surface of the ignition plug mounting hole 2, since the high voltage cable 21 is insulated by the air layer in the isolation space 52, The high-voltage current supplied to the cable 21 does not easily leak to the insulating resin pipe 10, so that the energy loss is reduced and the ignition plug 7 does not easily misfire.

Therefore, the insulating resin pipe 10 of the spark plug plug cap 100 is unlikely to cause a decrease in strength due to dielectric breakdown, and does not need to be unnecessarily thickened. Also, it is possible to prevent the manufacturing cost from increasing. In order to assemble the plug cap 100 for the ignition plug, when the connection fitting 23 attached to the end of the high-voltage cable 21 is inserted into the insulating resin pipe 10, the friction caused by the tip of the cable support piece 12. Since only resistance works,
Easy insertion and good assembly workability.

The spark plug plug cap of the present invention is not limited to the above-described embodiment, and the number of the cable support pieces may be changed or the intervals between the cable support pieces in the circumferential direction may be changed based on the gist of the present invention. It goes without saying that various changes such as changing as appropriate are possible. For example, in the above-described embodiment, the four cable support pieces 12 extend in parallel with the inner peripheral wall of the insulating resin pipe 10 at substantially equal intervals in the circumferential direction. 23 is an insulating resin pipe 10
May be located on the central axis of

Further, the cable supporting piece according to the present invention protruding from the inner peripheral wall of the insulating resin pipe may be extended spirally with respect to the center axis of the insulating resin pipe. With the support pieces, the high-voltage cable 21 and the connection fitting 23 can be positioned on the central axis of the insulating resin pipe 10.

[0024]

According to the plug cap for an ignition plug of the present invention, since the inner peripheral wall of the insulating resin pipe is separated from the outer surface of the high voltage cable, an insulating layer made of air is formed therebetween. The high-voltage cable supported by the cable support piece is located at the center of the insulating resin pipe and does not contact the inner peripheral wall of the insulating resin pipe. Therefore, the high-voltage current supplied to the high-voltage cable does not easily leak outside through the insulating resin pipe, and the energy loss is reduced.

Further, by expanding the diameter of the insulating resin pipe so that the outer peripheral surface is close to the peripheral wall surface of the ignition plug mounting hole, the insulating layer made of air can be made thicker and the insulating resin pipe can be made thicker. Water can be prevented from easily entering between the outer peripheral surface and the inner wall surface of the spark plug mounting hole. Further, even if water enters into the space formed between the outer peripheral surface of the insulating resin pipe and the inner wall surface of the ignition plug mounting hole, and the insulating resin pipe is grounded to the inner wall surface of the ignition plug mounting hole. Since the high-voltage cable is insulated by an insulating layer made of air, the high-voltage current supplied to the high-voltage cable does not easily leak to the insulating resin pipe, the energy loss is reduced, and the ignition plug is easily misfired. There is nothing.

Therefore, the insulating resin pipe hardly suffers from a decrease in strength due to dielectric breakdown, and does not need to be unnecessarily thickened. Therefore, the manufacturing cost increases due to an increase in weight and deterioration of molding conditions. Can also be prevented. Also, in order to assemble the plug cap for the ignition plug, when inserting the connection fitting attached to the end of the high-voltage cable into the insulating resin pipe, only the frictional resistance due to the tip of the cable support piece acts, Easy insertion and good assembly workability. Therefore, even if the inside of the spark plug mounting hole is flooded, energy loss of the spark plug plug cap can be reduced, and misfire of the spark plug can be prevented without increasing the weight and manufacturing cost of the spark plug plug cap. A good spark plug plug cap can be provided.

[Brief description of the drawings]

FIG. 1 is an overall vertical sectional view of a plug cap for an ignition plug according to an embodiment of the present invention.

FIG. 2 is a diagram showing a spark plug plug cap A shown in FIG. 1;
FIG.

FIG. 3 is an overall vertical sectional view of a conventional spark plug plug cap.

4 is a cross-sectional view of the conventional spark plug plug cap shown in FIG.

DESCRIPTION OF SYMBOLS 1 Engine head 2 Ignition plug mounting hole 7 Ignition plug 10 Insulating resin pipe 12 Cable support piece 21 High voltage cable 30 Insulation cap 40 Waterproof cap 51 Space 52 Isolation space 100 Plug plug for ignition plug

Continuation of the front page (58) Field surveyed (Int. Cl. ⁶ , DB name) F02P 13/00 303 F02P 15/00 303

Claims (4)

(57) [Claims] An ignition plug plug cap for connecting a high-voltage cable to a spark plug mounted on a bottom portion of a spark-plug mounting hole formed in an engine in a conductive state, the insulation covering the high-voltage cable. On the inner peripheral wall of the resin pipe,
A plurality of cable support pieces protruding inward in the radial direction and extending substantially in the longitudinal direction along the central axis are extended at substantially equal intervals in the circumferential direction, and the outer surface of the high-voltage cable and the insulating resin pipe are provided. A plug cap for an ignition plug, characterized in that an isolation space is formed between the inner peripheral wall and the high-pressure cable and the high-voltage cable is held on the central axis of the insulating resin pipe. 2. The plug cap for an ignition plug according to claim 1, wherein an outer peripheral surface of the insulating resin pipe is enlarged so as to be close to a peripheral wall surface of the ignition plug mounting hole. 3. The spark plug plug cap according to claim 1, wherein the plurality of cable support pieces extend in parallel with a central axis of the insulating resin pipe. . 4. The spark plug according to claim 1, wherein the plurality of cable support pieces are spirally extended with respect to a center axis of the insulating resin pipe. cap.