JPH10112413A - Ignition coil - Google Patents

Abstract

PROBLEM TO BE SOLVED: To avoid leak/short of secondary coil's high voltage, by coating the surface of a primary coil with a silicon coating material. SOLUTION: An ignition coil comprises a center iron core 23 and a secondary coil 22 wound vertically against the center iron core 23's outside periphery, with a primary coil wound coaxially with the primary coil 22 on its outside periphery. The primary coil consists only of a primary winding copper wire 212 with no use of core, and the secondary coil 22 is constituted by winding a secondary winding copper wire 222 on the winding part of a secondary core 223. The primary winding copper wire 212 and an outside layer iron core 40 are integrated together, then its surface is coated with a silicon coating material 25. The silicon coating material 25 is covering the primary coil and the outside layer iron core 40 by application on surface and submerge-dip-coating, etc. Thus, the primary coil and a thermosetting resin 50 can be separated, not bonded, so even at thermal expansion/contraction, occurrence of crack with the thermosetting resin 50 is prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ignition coil used for an internal combustion engine for a vehicle.

[0002]

2. Description of the Related Art In an internal combustion engine, particularly for an automobile, an ignition coil is required to have a small size and high characteristics with the miniaturization of the internal combustion engine. Conventionally, in a double overhead cam type internal combustion engine, an ignition coil that does not require a distributor is arranged in a space created between cylinder heads, and various plug-in type ignition coils have been put to practical use in other types of internal combustion engines. ing. However, such an ignition coil is also required to have additional values such as improved output characteristics and the incorporation of an igniter, and it is actually difficult to reduce the size of the ignition coil body. It has become difficult to arrange the coils in the limited space of the internal combustion engine, especially the cylinder head.

Under the above circumstances, there have been proposed some types in which a part or all of an ignition coil is arranged in a space formed in a plug hole in which a spark plug is mounted. Generally, the outer diameter of a spark plug of a vehicle internal combustion engine is about 16 mm to 20 mm, and a plug hole into which the spark plug is inserted has an inner diameter of about 20 mm to 35 mm and a depth of about 100 mm.

The structure of the primary coil of an ignition coil including a conventional plug hole insertion type is generally a primary winding core (bobbin).
The primary coil is formed by winding a heat-fused copper wire without using a copper wire, or the primary coil is formed by winding a copper wire around a primary winding core In either case, the primary coil assembly is stored together with the secondary coil, the iron core, and other components in a case serving as a housing, and then thermoset in the case. The ignition coil is formed by filling and hardening the conductive resin.

[0005]

In the ignition coil having the above structure, the primary coil is bonded to the thermosetting resin enclosed in the entire case, and the thermosetting resin is connected to the primary copper wire and the primary coil.
It has been conventionally known that the adhesion to the next-wound copper wire, and all these adhesions, are extremely strong. However, if all of these parts are strongly adhered to each other, when a thermal shock corresponding to the use condition is repeatedly applied, a thermosetting resin having a relatively large thermal expansion coefficient and a conversely having a thermal expansion coefficient If a small primary winding copper wire pulls each other in a temperature change, a large distortion occurs in the thermosetting resin having a large thermal expansion coefficient, and when the yield stress exceeds the yield stress limit of the thermosetting resin. In addition, cracks occur in unspecified portions of the thermosetting resin, and a problem of frequent leak short-circuiting from the secondary coil to the primary coil via the crack has occurred.

The present invention has been made in consideration of the above problems, and has as its object to provide an ignition coil having a structure in which a high voltage of a secondary coil does not leak short.

[0007]

In order to solve the above problems, the present invention provides a secondary coil, a primary coil, a central iron core through which magnetic flux induced by the primary coil passes, a primary coil or a secondary coil. An ignition coil for an internal combustion engine having a central iron core at a central iron core insertion portion forming a secondary coil, wherein the surface of the primary coil is covered with a silicon coating material.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a side sectional view of an ignition coil according to an embodiment of the present invention, and FIG. 2 is a sectional view taken along the line AA of FIG.

In FIGS. 1 and 2, an ignition plug 30 is disposed at the bottom of the plug hole 10, and an ignition coil 20 as described below is provided immediately above the ignition plug 30. The ignition coil 20 is wound around a center iron core 23 disposed on the cylinder axis of the plug hole 10, an outer periphery of the center iron core 23, and a direction perpendicular to the longitudinal direction of the center iron core 23. 2
A secondary coil 22; a primary coil 21 wound around the outer periphery of the secondary coil 22 coaxially; an outer core 40 between the coils and the case 27; A high voltage output section 29 for outputting an output to a spark plug 30 is embedded in the plug hole 10, and a switching control element 25 of a coil such as a power transistor is provided outside the plug hole 10.
A primary connector 26 for inputting the next voltage is provided, and the components forming the above-mentioned ignition coil 20 are embedded in a case 27, and are integrated by filling and curing a thermosetting resin 50.

In the above embodiment, the primary coil 21 does not use a winding core and is composed of only the primary winding copper wire 212, and the secondary coil 22 is connected to the winding portion of the secondary winding core 223 by two windings. Next winding copper wire 222
Is wound.

The surface of the primary wound copper wire 212 and the outer iron core 40 are covered with a silicon coating material 25 after they are integrated. This silicon coating material 25 is applied to the surface, or dipped by dip coating.
The secondary coil 21 and the outer iron core 40 are covered.

Although the present embodiment describes an ignition coil in which each coil and the central iron core 23 are mounted in the plug hole 10, the ignition coil of the present invention is not limited to such an ignition coil. Needless to say, the same effect can be obtained with other types of ignition coils or ignition coils using a core as the primary coil 21. Further, in the above embodiment, the primary wound copper wire 212 and the outer core 40 are integrated and then coated with the silicon coating material 25. However, if at least the primary wound copper wire 212 is coated, a certain degree of stress relaxation can be achieved. It can be secured.

In the above-described embodiment, the secondary coil 22 is provided on the outer periphery of the center iron core 23 and the primary coil 21 is provided on the outer periphery. The coil 22 may be used.

[0014]

As is well known, silicone rubber (silicone coating material 25) does not adhere to thermosetting resin composed of, for example, epoxy resin at all. As described above, in the conventional ignition coil, the primary and secondary coils and the respective iron cores are inserted into the case 27, and then the thermosetting resin is filled, heated and cured, and the primary and secondary thermosetting resins are combined with the thermosetting resin. Although each component having a different coefficient of thermal expansion, such as a coil, is securely bonded in all directions, in the ignition coil of the present invention, between the primary coil 21 and the thermosetting resin 50, this resin is not bonded. Since the silicon coating material 25 is interposed, the primary coil 21 and the thermosetting resin 50 can be separated without bonding, so that the block formed by the primary coil 21 and the secondary coil 22 and the thermosetting resin can be separated. 50, and the block formed by the central iron core 23 can be divided into two, and even when the ignition coil is thermally expanded and contracted, no crack is generated in the entire thermosetting resin 50. Therefore, insulation failure and leak short which have occurred through cracks are improved, and a stable and high quality ignition coil can be provided.

[Brief description of the drawings]

FIG. 1 is a side sectional view showing a state where an ignition coil according to an embodiment of the present invention is mounted on an internal combustion engine.

FIG. 2 shows a view of the ignition coil of FIG.

[Explanation of symbols]

 In the drawings, the same reference numerals indicate the same or corresponding parts. Reference Signs List 20 ignition coil 21 primary coil 212 primary wound copper wire 22 secondary coil 222 secondary wound copper wire 223 secondary winding core 23 center iron core 25 silicon coating material 40 outer layer iron core 50 thermosetting resin 70 electric insulating sheet

Claims (1)

[Claims] 1. A secondary coil, a primary coil, a central iron core through which magnetic flux induced by the primary coil passes, and a central iron core inserted into a central iron core insertion portion forming the primary coil or the secondary coil. The ignition coil for an internal combustion engine provided, wherein the surface of the primary coil is covered with a silicon coating material.