JP2004169619A - Ignition coil for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an ignition coil for an internal combustion engine capable of preventing a crack due to thermal stress by flaking a boundary between an iron core with a small coefficient of thermal expansion and insulating resin filled thereat. <P>SOLUTION: The ignition coil for an internal combustion engine is equipped with a cylindrical primary coil bobbin and secondary coil bobbin around which a primary coil and a secondary coil are respectively wound and which are concentrically arranged, an iron core constituting a magnetic circuit by passing through a cylindrical inner periphery of the primary coil bobbin and an outer periphery of the secondary coil bobbin, and an insulation case for accommodating the bobbins and the iron core. The iron core, coil and the like are fixed by the insulating resin filled in the insulation case. An exfoliating material is applied between the insulating resin and the iron core to flake the insulating resin and the iron core. By so doing, the ignition coil can prevent the occurrence of the inside stress generated between the iron core with a small coefficient of thermal expansion and the filled insulating resin with a large coefficient of thermal expansion. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an ignition coil for an internal combustion engine for supplying a high voltage to an ignition plug of an internal combustion engine such as an automobile and performing spark discharge.
[0002]
[Prior art]
In general, an ignition coil for an internal combustion engine is formed by punching a silicon steel sheet into a predetermined shape, laminating and forming an iron core to form a closed magnetic circuit, and secondary current is generated by a change in magnetic flux generated in the iron core by a current flowing through the primary coil. A high-voltage current is generated in the coil. FIG. 6 is a longitudinal sectional view showing an example of a conventional ignition coil for an internal combustion engine. It has an E-shaped iron core 2 housed inside an insulating case 1 and an I-shaped iron core 3 connected to the E-shaped iron core 2 to form a closed magnetic circuit. The E-shaped iron core 2 and the I-shaped iron core 3 are formed by laminating a plurality of silicon steel plates, and constitute a magnetic circuit forming a closed magnetic circuit as a whole. The winding ratio between the primary coil 6 and the secondary coil 7 for generating a high-voltage current is set to, for example, about 1:80 to 120.
[0003]
Also, in order to increase the change in magnetic flux, in a magnetic circuit forming a closed magnetic circuit type, an air gap 4 (generally about 0.5 to 1.5 mm) is provided or permanent in order to eliminate magnetic flux saturation of the iron core. A high voltage current is generated in the secondary coil by mounting the magnet 5 so that a magnetic flux flows in a direction opposite to the use state and increasing a change in the magnetic flux.
[0004]
The magnetic resistance of the air gap 4 is proportional to the gap length / cross-sectional area. If the resistance value of the air gap portion is the same, the larger the cross-sectional area, the larger the gap length, and the manufacturing variation of the gap length. And the like, the allowable range becomes larger. In addition, when the permanent magnet 5 is mounted, it is possible to increase the change in the magnetic flux by flowing the magnetic flux in the opposite direction to the magnetic saturation point of the iron core used.
Further, the E-shaped iron core 2, the I-shaped iron core 3, and the primary and secondary coils 6 and 7 housed in the insulating case 1 are fixed by filling the insulating resin 8.
[0005]
[Problems to be solved by the invention]
However, in the conventional ignition coil for an internal combustion engine configured as described above, the insulating resin part having a large thermal expansion coefficient and the iron core part having a small thermal expansion coefficient are sealed in an insulating case in a tight contact state. When the internal temperature rises, internal stress is generated between the insulating resin portion and the iron core portion, which also causes cracks in the insulating resin portion.
[0006]
The present invention has been proposed in view of the above-mentioned circumstances, and provides an ignition coil for an internal combustion engine that can separate an insulating resin portion and an iron core portion and prevent a crack from being generated in the insulating resin portion. The purpose is to:
[0007]
[Means for Solving the Problems]
In order to achieve the above object, an invention according to claim 1 includes a cylindrical primary coil bobbin and a secondary coil bobbin wound around a primary coil and a secondary coil, and disposed concentrically, and a cylinder of the primary coil bobbin. An internal combustion engine including an iron core part forming a magnetic path passing through the inner circumference and the outer circumference of the secondary coil bobbin, and an insulating case for housing the core part, and fixing the iron core part, the coil, and the like with an insulating resin filled in the insulating case. An ignition coil for a vehicle, wherein a separating material is applied between the insulating resin and the iron core to separate the insulating resin and the iron core.
[0008]
According to a second aspect of the present invention, in addition to the first aspect, the release material is applied to the entire outer periphery of the iron core.
[0009]
According to a third aspect of the present invention, in addition to the first aspect, the release material is a silicon-based resin.
[0010]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, the present invention will be described in detail with reference to the drawings showing one embodiment. FIG. 1 is a longitudinal sectional view showing an example of an ignition coil for an internal combustion engine according to the present invention, and FIG. 2 is a plan view of the ignition coil for an internal combustion engine of the present invention. Here, the ignition coil 10 for an internal combustion engine winds a primary coil 11 and a secondary coil 12, respectively, and concentrically arranges a cylindrical primary coil bobbin 11a and a secondary coil bobbin 12a, and a cylindrical inner periphery of the primary coil bobbin. An iron core 13 forming a magnetic path through the outer periphery of the secondary coil bobbin, and an insulating case 14 for accommodating them. At the same time, a release material 16 is interposed between the insulating resin 15 and the iron core 13.
[0011]
In the present embodiment, as shown in FIGS. 2 and 3, the iron core portion 13 is configured by combining an E-type iron core 13a and an I-type iron core 13b.
[0012]
As the release material 16, a synthetic resin having appropriate elasticity and insulating properties can be used. For example, a silicon-based resin can be used. As shown in FIGS. 3 to 5, a release material 16 is applied to the outer periphery of the iron core 13 to a predetermined thickness. Then, it is housed in the insulating case 14 together with the primary coil 11 and the secondary coil 12, and is filled with the insulating resin 15. At this time, since the insulating resin 15 and the release material 16 do not adhere to each other, for example, a silicon-based resin, the core 13 and the insulating resin 15 do not separate and adhere to each other.
[0013]
In the internal combustion engine ignition coil configured as described above, when the internal temperature increases, both the iron core 13 and the insulating resin 15 expand. However, the iron core 13 and the insulating resin 15 are disposed via the release material 16 and do not directly adhere to each other. Therefore, the insulating resin 15 having a large thermal expansion coefficient can freely expand. Even if the thermal expansion coefficients of the core 13 and the insulating resin 15 are different, no thermal stress is generated because they are not in close contact. The maximum temperature of the insulating resin 15 at the time of curing is 140 ° C., and at this time, the state becomes a stress-free state. Unless this maximum temperature is exceeded, the stress between the iron core 13 and the insulating resin 15 due to thermal expansion is reduced. There is no occurrence.
[0014]
When the internal temperature decreases, both the iron core 13 and the insulating resin 15 shrink. At this time, since the core portion 13 and the insulating resin 15 are not in close contact with each other, they can contract independently, and no tensile stress is generated at the boundary surface. Therefore, even if the expansion and contraction are repeated, no thermal stress is generated between the iron core 13 and the insulating resin 15, and there is no possibility that the insulating resin 15 is cracked.
[0015]
In the above embodiment, an example in which a silicon-based resin is used as the release material 16 has been described. However, similar effects can be obtained with another synthetic resin.
[0016]
【The invention's effect】
Since the present invention has the above-described configuration, the following effects can be obtained.
[0017]
According to the first aspect of the present invention, the primary coil and the secondary coil are respectively wound, and the cylindrical primary coil bobbin and the secondary coil bobbin arranged concentrically, and the inner circumference of the primary coil bobbin and the outer circumference of the secondary coil bobbin An ignition core for an internal combustion engine, comprising: Since a release material was applied between the insulating resin and the iron core portion, and the insulating resin and the iron core portion were peeled off, between the iron core having a small coefficient of thermal expansion and the insulating resin having a large coefficient of thermal expansion filled around. The generation of the generated internal stress can be prevented beforehand.
[0018]
According to the second aspect of the present invention, in addition to the configuration of the first aspect of the present invention, since the release material is applied to the entire outer periphery of the iron core, the iron core in all directions is provided. It is possible to absorb the elongation due to the difference in the thermal expansion coefficient between the insulating resin 13 and the insulating resin 15 and prevent the occurrence of cracks due to internal stress.
[0019]
Further, in the invention according to claim 3, in addition to the configuration of the invention described in claim 1, since the release material is a silicon-based resin, the core portion and the insulating resin are reliably separated from each other, and The stress can be released. Therefore, generation of cracks due to internal stress can be prevented.
[Brief description of the drawings]
FIG. 1 is a longitudinal sectional view showing an example of an ignition coil for an internal combustion engine according to the present invention.
FIG. 2 is a plan view of the ignition coil for the internal combustion engine.
FIG. 3 is a plan view showing an assembled state of an iron core used for the ignition coil for the internal combustion engine.
FIG. 4 is a side view of the iron core.
FIG. 5 is a front view of the iron core.
FIG. 6 is a longitudinal sectional view showing an example of a conventional ignition coil for an internal combustion engine.
[Explanation of symbols]
Reference Signs List 10 ignition coil for internal combustion engine 11 primary coil 11a primary coil bobbin 12 secondary coil 12a secondary coil bobbin 13 iron core part 14 insulating case 15 insulating resin 16 release material

Claims (3)

A cylindrical primary coil bobbin and a secondary coil bobbin wound around a primary coil and a secondary coil, respectively, and arranged concentrically, and an iron core portion forming a magnetic path through the inner circumference of the cylinder of the primary coil bobbin and the outer circumference of the secondary coil bobbin. An ignition coil for an internal combustion engine, comprising: an insulating case for accommodating these, and fixing an iron core portion and a coil by an insulating resin filled in the insulating case,
An ignition coil for an internal combustion engine, wherein a release material is applied between the insulating resin and the iron core to separate the insulating resin and the iron core. The ignition coil for an internal combustion engine according to claim 1, wherein the release material is applied to the entire outer periphery of the iron core portion. The ignition coil according to claim 1, wherein the release material is a silicon-based resin.

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