JP3773493B2 - Ignition coil for internal combustion engine - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an ignition coil for an internal combustion engine, for example, an internal combustion engine, which is attached to an engine of an automobile and supplies a high voltage for generating a spark discharge to a spark plug provided at the bottom of a plug hole of the engine.
[0002]
[Prior art]
Conventionally, a secondary coil, a primary coil fitted to the inner periphery of an insulating case having an open upper surface and a primary terminal protruding outward, and an outer ring surrounding the secondary coil Containing at least a coil-core assembly comprising a closed magnetic circuit core having a straight core portion penetrating to the inner periphery of the core portion and the primary coil and having both end portions connected to the inner periphery of the outer ring core portion; An ignition coil for an internal combustion engine in which a coil-iron core assembly is buried and fixed inside an insulating case by a solidified layer of an insulating resin cast inside the insulating case is well known (for example, Patent Document 1 of the present applicant). reference).
[0003]
[Patent Document 1]
JP 2000-294434 A (paragraphs [0009] to [0022], FIGS. 1, 2, and 3)
[0004]
[Problems to be solved by the invention]
In order to use the ignition coil for the internal combustion engine of the above-mentioned Patent Document 1 and spark discharge to the spark plug, when a high voltage is generated in the ignition coil and spark discharge starts, a steep surge voltage is generated and a high voltage current flows. High-frequency radio waves are generated from the ignition coil main body and the wiring portion between the ignition coil and the ignition plug. Experimentally, frequency components of several hundred kHz to several GHz are included, and the magnitude of this electromagnetic wave has an adverse effect on car-mounted radios and electronic components or car peripherals. It becomes difficult to hear, and if an abnormal operation is given to an electronic product, particularly a computer, it becomes impossible to control, and in the worst case, the car becomes inoperable.
[0005]
For this reason, in the method of distributing high voltage using a high-tension cord using a conventional distributor, the high-tension cord has a resistance of up to several kΩ to reduce the magnitude of the noise. Further, in a recent method directly connected to a spark plug and not using a distributor, a resistance of several kΩ is mounted between the ignition coil and the spark plug to similarly reduce the magnitude of noise. However, the impedance value of a resistor of several tens of MHz or more has a large capacitance component, so that the noise reduction effect is small and it is difficult to further reduce it.
[0006]
[Means for Solving the Problems]
The present invention has been developed in order to reduce the electromagnetic wave to further reduce the noise, the upper surface is opened, the inside of the insulating case having a first terminal protruding to the outside, and the secondary coil, the A primary coil that is concentrically fitted to the inner periphery, an outer ring core that surrounds the secondary coil, and the inner periphery of the primary coil pass through both ends at the inner periphery of the outer ring core. A coil-iron core assembly comprising at least a closed magnetic circuit core having a connected straight core portion is accommodated, and the coil-core core assembly is provided inside the insulating case by a solidified layer of insulating resin cast inside the insulating case. In the ignition coil for an internal combustion engine in which is embedded and fixed, a conductive layer is provided on the inner surface of the insulating case, a metal plate is mounted on the open upper surface of the insulating case, and the metal plate and the conductive layer on the inner surface of the insulating case are electrically connected. characterized in that the connecting Moreover, it is preferable to electrically connect the conductive layer provided on the inner surface of the insulating case and the ground terminal of the primary terminal.
[0007]
DETAILED DESCRIPTION OF THE INVENTION
In the embodiment shown in FIGS. 1 and 2, as is well known, 11 is a cylindrical primary coil, and 12 is a secondary coil fitted concentrically outside the primary coil. Reference numerals 13 and 14 denote an endless outer ring core for forming a closed magnetic circuit, and a straight core that traverses the interior surrounded by the outer ring core. The straight core 14 is a bobbin of the primary coil 11. The coils 11 and 12 that are concentrically fitted through the inner periphery are supported, whereby the iron core portions 13 and 14 and the coils 11 and 12 constitute a coil-iron assembly 15 having a closed magnetic circuit. The
[0008]
Reference numeral 17 denotes an insulating case formed of a synthetic resin for horizontally supporting the iron core portions 13 and 14 on the inwardly stepped portion 17 'on the inner periphery and fixing the coil-iron core assembly. Since this insulating case 17 accommodates the lower part 12 'of the secondary coil 12 protruding from the lower surfaces of the iron core parts 13, 14, it follows the lower part of the secondary coil below the inwardly stepped part 17', and the bottom. A high-pressure cylinder 22 holding a high-voltage terminal 21 is integrally provided on the inward-facing step portion 17 ′, and surrounds the outer ring core portion 13. A primary socket 23 of a primary terminal is integrally provided with a cylindrical upper portion 20 protruding outward from a side surface.
[0009]
In order to configure the ignition coil, as is well known, the outer ring core portion 13 is placed on the inner peripheral inward stepped portion 17 ', and the coil-core assembly 15 is accommodated inside the insulating case. The end of the winding is connected to the high voltage terminal 21, and the primary coil is connected to the primary terminal of the primary socket 23, and an insulating resin such as a thermosetting epoxy resin is cast and filled in the insulating case 17. Thus, the coil-iron core assembly 15 is fixed in the insulating case, and the high voltage terminal 21 is fixed in the high voltage cylinder 22.
[0010]
In accordance with the present invention, a conductive layer 30 is provided in advance on the inner surface of the insulating case 17.
[0011]
In the illustrated embodiment, the conductive layer 30 is formed on the inward stepped portion 17 ', on the inner periphery of the cylindrical upper portion 20 and on the inner periphery of the funnel-shaped bottom portion 19 as shown in FIGS. 1 (a) and 1 (b). It is provided integrally.
[0012]
Then, a part of the partition wall 24 that separates the cylindrical upper part 20 and the primary socket 23 is cut out, and the base part of the ground terminal 25 among the primary terminals in the primary socket 23 is inserted into the cutout, and the conductive layer 30 is electrically connected to the conductive layer 30. In contact. The primary terminal is one in which the insulating case 17 is integrally formed with the primary socket 23 and is fixed in the primary socket with an insert mold.
[0013]
The conductive layer 30 may be a conductive paint layer coated with a conductive paint, a vacuum deposited layer of a conductive material, or an electroplated layer.
[0014]
Further, as shown in FIGS. 3A and 3B, a molded body 31 along the inner surface of the insulating case is formed with a metal foil having a thickness of 0.1 mm such as aluminum or copper. It may be inserted from above, and if necessary, fixed to the inner surface of the insulating case with an adhesive or the like.
[0015]
4 is formed with a metal plate such as a brass plate or an aluminum plate, and a thermosetting insulating resin is cast and filled in the insulating case 17, and the insulating case is filled. When fixing the coil-iron assembly 15 accommodated in the cover, if the cover 32 is put on the upper surface of the insulating case before the insulating resin is hardened, the downward claw pieces 33 provided on the cover 32 will become the inner surface of the insulating case. When the insulating resin is solidified by being in electrical contact with the conductive layer 30, the coil-iron core assembly housed in the insulating case and the high voltage terminal are fixed, and at the same time, the lid 32 is also fixed to the upper surface of the insulating case. (See Figure 2c).
[0016]
【The invention's effect】
In the ignition coil of the present invention, even if a high-frequency current sparked by the electrode of the spark plug flows and is radiated as an electromagnetic wave in the space, most of it reaches the conductive layer on the inner surface of the insulating case, where the high-frequency electromagnetic wave The induced voltage is radiated to the space outside the insulating case of the ignition coil by the conductive layer, and becomes an attenuated electromagnetic wave. Therefore, the influence on the vehicle-mounted radio and electronic parts becomes very small. Therefore, the reliability of the automobile using this ignition coil is enhanced. Further, since the lid for closing the upper surface of the insulation case is electrically connected to the conductive layer of the inner surface of the insulating case by the claw piece, by the induced voltage is capped with a high-frequency electromagnetic wave by the spark discharge of the spark plug, the insulation Radiated as an attenuated electromagnetic wave from the upper surface of the case, further enhancing the above-described effects. In a further, since the conductive layer of the inner surface of the insulating case are electrically connected to the ground terminal of the primary terminal, the induced high frequency current is grounded along the ground terminal of the primary terminals, outside of the insulating case The electromagnetic wave radiated to is further attenuated.
[Brief description of the drawings]
FIG. 1A is a plan view of an embodiment of an ignition coil insulating case according to the present invention, and FIG. 1B is a longitudinal side view of the same.
2 (a) is a longitudinal side view of an embodiment of an ignition coil insulation case according to the present invention, FIG. 2 (b) is a plan view before casting the insulating resin, and FIG. 2 (c) is a view of (b). Sectional drawing in the cc line.
3A is a plan view of a conductive layer formed of a metal foil, and FIG. 3B is a cross-sectional view taken along line bb of FIG. 3A.
4A is a plan view of a lid that closes the top surface of the insulating case, FIG. 4B is a side view of the lid, and FIG. 4C is a front view of the same.
[Explanation of symbols]
11 Primary coil 12 Secondary coil 15 Coil-iron assembly 17 Insulating case 18 Solidified layer 21 of thermosetting insulating resin 21 High voltage terminal 23 Primary socket 25 Primary terminal ground terminal 30 Conductive layer 31 Conductive layer of metal foil Molded body 32 Lid (made of metal plate)
33 Down nails on the lid

Claims (2)

A secondary coil, a primary coil fitted concentrically to the inner periphery of the secondary coil, and an outer ring surrounding the outside of the secondary coil inside an insulating case having an open upper surface and a primary terminal protruding outward Containing at least a coil-core assembly comprising a closed magnetic circuit core having a straight core portion penetrating the inner periphery of the core portion and the primary coil and having both end portions connected to the inner periphery of the outer ring core portion; In the ignition coil for an internal combustion engine in which the coil-iron core assembly is buried and fixed inside the insulating case by the solidified layer of insulating resin cast inside the insulating case,
A conductive layer is provided on the inner surface of the insulating case ,
A metal plate is mounted on the open upper surface of the insulating case, and the conductive layer on the inner surface of the metal plate and the insulating case is electrically connected .
An ignition coil for an internal combustion engine. The ignition coil for an internal combustion engine according to claim 1 ,
The electrically conductive layer provided on the inner surface of the insulating case was electrically connected to the ground terminal of the primary terminal.
An ignition coil for an internal combustion engine.

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