JP2004071911A - Ignition coil for internal combustion engine - Google Patents

Abstract

Provided is a long-life ignition coil that prevents an epoxy resin from flowing into a buffer material and prevents cracks from being generated in the epoxy resin.
A secondary coil (3) and a primary coil (5) are concentrically arranged outside a center iron core (1), and each gap between them is filled with epoxy resin. The center iron core 1 is formed in a rod shape having a substantially octagonal cross section, and a buffer tape 13 is wound around the outer peripheral surface thereof, leaving both longitudinal end portions 1c. At both ends in the longitudinal direction of the central iron core 1, cap-shaped cushioning materials 14 are attached. The inner diameter of the opening of the cushioning material 14 is formed smaller than the outer diameter of the center iron core 1 on which the buffer tape 13 is wound, and the cushioning material 14 is forcibly fitted to the end of the center iron core 1 and mounted. Is done.
[Selection diagram] Fig. 4

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an ignition coil for an internal combustion engine which is attached to a plug hole of an engine of an automobile or the like and is used by attaching a spark plug to a tip portion.
[0002]
[Prior art]
As an ignition coil for an internal combustion engine, a secondary coil wound around a secondary bobbin is arranged outside a rod-shaped central iron core, and further outside, a primary coil wound around a primary bobbin is arranged. What is housed in a coil case having an igniter at the top is known.
[0003]
In such an ignition coil, it is necessary to make the gap between the members uniform so as to prevent dielectric breakdown between the members. For that purpose, the center iron core must be correctly positioned at the center of the secondary bobbin, and the secondary bobbin must be correctly positioned at the center of the primary bobbin. Then, in order to eliminate the gap and ensure such an insulating state, the space between the center iron core and the secondary bobbin and between the secondary bobbin and the primary bobbin are filled with epoxy resin as an insulator. You.
[0004]
Incidentally, such an ignition coil is heated to a high temperature during operation of the engine, and is cooled to a normal temperature when the engine is stopped. However, since the respective members are adhered to each other by the hard epoxy resin, the respective members having different thermal expansion coefficients expand and contract with a change in temperature, so that the respective members receive strong stress from each other. In addition, where there is a difference in the amount of epoxy resin, a difference occurs in the gelling temperature during thermal curing of the epoxy resin, the heating time of the epoxy resin itself during the gelation time or during curing, and the physical properties, strength, A boundary was generated due to a change in the amount of shrinkage, and cracks were easily generated in the epoxy resin. In particular, the upper portion of the ignition coil had a large amount of epoxy resin per unit volume, but the vicinity of the primary coil and the secondary coil had a small amount of epoxy resin, so that boundaries were formed and cracks were easily generated.
[0005]
Therefore, conventionally, as described in Japanese Patent Application Laid-Open No. 2000-91144, a molded body (cushion material) molded into a cap shape is fitted and provided at the end of the center iron core, and then the center iron core is attached to the secondary core. It is known to arrange in a coil and fill a gap between both members with epoxy resin.
[0006]
[Problems to be solved by the invention]
However, in the above-described conventional method, when the epoxy resin is filled, the epoxy resin flows into the cap-shaped buffer material, and there is a possibility that cracks may occur in the epoxy resin around the buffer material due to aging thermal stress. In particular, this is likely to occur in the case of a central iron core formed by laminating steel plates having different width dimensions and forming a substantially octagonal cross section.
[0007]
That is, the eight corners in the cross section of the center iron core and the corners of each steel plate constituting the center iron core act as edges and act on the epoxy resin, causing a crack to occur. Also, even if caps are attached to both ends of the center iron core, the inner diameter of the cap and the maximum diameter of the center iron core are set to be the same, and the center iron core has a substantially octagonal cross section as described above. The epoxy resin may enter the cap from the gap between each end face and the cap, causing cracks in the epoxy resin, and the cracks may spread out of the cap.
[0008]
When a crack occurs in this way and the crack expands, a short circuit occurs between the central iron core and the secondary coil due to electric discharge, and a voltage exceeding the withstand voltage design value is applied, and the ignition coil is damaged. Alternatively, there is a possibility that the output may be reduced.
[0009]
The present invention has been made in view of the above circumstances, and a main object of the present invention is to prevent the epoxy resin from flowing into the cap-shaped cushioning material and prevent cracks from being generated in the epoxy resin, thereby achieving a long service life. To provide an ignition coil.
[0010]
[Means for Solving the Problems]
In order to achieve the above object, the ignition coil for an internal combustion engine of the present invention has a center iron core, a primary coil wound on a primary bobbin, and a secondary coil wound on a secondary bobbin, which are arranged concentrically, In an ignition coil for an internal combustion engine in which an insulating resin is filled between the respective members, a substantially cylindrical cap-shaped cushioning material opened only at one end surface is attached to at least one end of the central iron core. The inner diameter is smaller than the maximum diameter of the central iron core.
[0011]
Further, in the ignition coil for an internal combustion engine of the present invention, a secondary coil wound around a secondary bobbin is concentrically arranged outside the central iron core, and a primary coil wound around a primary bobbin is arranged outside the secondary coil. The coils are arranged concentrically, and an insulating resin is filled between the center iron core and the secondary coil and between the secondary coil and the primary coil. The central iron core is formed in a rod shape having a substantially octagonal cross section, and a resin buffer tape is wound around its outer peripheral surface, leaving both ends in the longitudinal direction. At both ends in the longitudinal direction of the central iron core, a substantially cylindrical cap-shaped cushioning material opened only at one end surface is mounted, and the opening of the cushioning material is located at the center on the back side where the cushioning tape is not wound. A small-diameter hole in which the iron core is disposed is formed, and a large-diameter hole in which the portion around which the buffer tape is wound is disposed on the front side. The inner diameter of the large-diameter hole on the opening side is formed to be smaller than the outer diameter of the center iron core on which the buffer tape is wound, and the cushioning material is forcibly fitted and attached to the end of the center iron core. It is characterized by the following.
[0012]
Further, in the ignition coil for an internal combustion engine of the present invention, in addition to any one of the above configurations, the opening of the cushioning material is formed as a tapered hole whose diameter decreases toward the opening.
[0013]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, the ignition coil for an internal combustion engine of the present invention will be described in more detail.
FIG. 1 is a schematic longitudinal sectional view showing one embodiment of the ignition coil of the present invention. The ignition coil is attached to a plug hole of the engine, and has a spark plug attached to a tip portion thereof, thereby directly supplying a high voltage to the spark plug.
[0014]
As shown in this figure, the ignition coil of the present embodiment has a secondary coil 3 in which a secondary winding is wound around a central iron core 1, a secondary bobbin 2, and a primary winding around a primary bobbin 4, in order from the center. Are wound concentrically, and they are housed in a substantially cylindrical case 6. Further, on the outer peripheral surface of the primary coil 3, an exterior iron core 7 made of a steel plate bent in a substantially cylindrical shape with a cutout in a part in the circumferential direction is mounted. Note that magnets that generate a magnetic flux in the opposite direction to the magnetic flux generated by the primary coil 5 may be attached to both ends in the longitudinal direction of the central iron core 1 in order to suppress saturation of the magnetic flux of the iron core.
[0015]
The case 6 is filled with a thermosetting epoxy resin. This resin penetrates between the central iron core 1 and the secondary coil 3, between the secondary coil 3 and the primary coil 5, and between the primary coil 5 and the case 6, respectively, and maintains insulation between them. A large-diameter portion 6a for accommodating an igniter 8 described later is formed in the upper portion of the case 6, and the epoxy resin is also filled in the large-diameter portion 6a. The epoxy resin is injected and filled from the upper opening of the case 6, and is cured by being held in a furnace maintained at a uniform curing atmosphere temperature for a certain period of time.
[0016]
An igniter 8 as an ignition drive circuit for turning on and off the primary current is provided at an upper portion of the case 6, and a primary current input connector terminal 9 for supplying a primary current to the igniter 8 is provided. The igniter 8 is provided with a heat sink.
[0017]
A spring 11 is provided at a lower portion of the case 6 via a secondary high-voltage terminal 10 electrically connected to the secondary coil 3. An ignition plug is connected to the lower part of the case 6 via the spring 11. The connection portion is built in a protector 12 provided at a lower portion of the case 6 so that a high voltage does not leak to a metal portion such as a plug hole.
[0018]
FIG. 2 is a schematic perspective view showing the upper portion of the center iron core 1 in an enlarged manner. As shown in this figure, the central iron core 1 is formed by laminating a large number of plate members 1a, 1a,... Made of a magnetic material such as a silicon steel plate into a rod shape having a substantially octagonal cross section. In that case, the width dimension of the silicon steel plate is made smaller as it is superimposed on the outside, and the cross section is formed in a substantially octagonal shape as a whole. In the present embodiment, the steel plates are caulked and fixed at several locations 1b in the longitudinal direction. Alternatively, or alternatively, the steel plates may be bonded.
[0019]
A buffer tape 13 is wound around the outer peripheral surface of the central iron core 1. The buffer tape 13 of this embodiment is a thin polyester film, and a rectangular film having an adhesive applied to the inner surface is wound on the outer peripheral surface of the central iron core. Note that the buffer tape 13 is formed to be slightly shorter in the axial direction than the stop iron core 1, and is wound around the center iron core 1 with both upper and lower ends 1 c, 1 c being slightly left. As a result, the upper and lower ends 1c, 1c of the central iron core 1 are exposed to the outside.
[0020]
As shown in FIG. 3, cap-shaped cushioning members 14 are attached to both ends 1c, 1c of the central iron core 1. The cushioning member 14 is formed of silicon, has a substantially cylindrical shape opened at one end surface in the axial direction, and the end of the central iron core 1 is fitted into the circular hole (14a, 14b). The circular hole of the cushioning member 14 is a stepped hole having a slightly reduced diameter on the back side from the axial center of the cushioning member 14. As shown in FIG. 4, the exposed portion 1c of the central iron core 1 on which the buffer tape 13 is not wound is disposed in the small diameter portion 14a on the back side, and the buffer tape 13 is disposed in the large diameter portion 14b on the opening side. The end of the wound center iron core 1 is fitted. In the present embodiment, the axial depth of the small diameter portion 14a is approximately 1.4 mm, and the axial depth of the large diameter portion 14b is approximately 1.9 mm.
[0021]
In the present embodiment, the large-diameter portion 14b of the circular hole of the buffer member 14 is formed on an inclined surface slightly inclined inward toward the opening side. That is, the diameter is slightly reduced toward the opening. For example, it is inclined inward at an angle of α = about 2 ° in FIG. 3 with respect to the axial direction. The inner diameter of the opening is formed slightly smaller than the outer diameter of the central iron core 1. For example, when the outer diameter of the central iron core 1 is about 9.1 to 9.5 mm (the theoretical value on the drawing is 9.1 mm due to the above-described method of manufacturing the central iron core, but as a product, The maximum diameter can be about 9.5 mm), and the inside diameter of the opening of the cushioning material 14 is set to about 8.9 mm.
[0022]
As described above, in the present embodiment, the inner diameter of the cushioning member 14 is made smaller than the maximum diameter of the central iron core 1 by a predetermined amount, so that the epoxy resin can be prevented from flowing into the cushioning member 14, Since the crack of the resin can be prevented, the life of the ignition coil can be extended. In addition, since the inner diameter of the cushioning material 14 is smaller than the outer diameter of the central iron core 1, the tightening of the cushioning material 14 is strengthened, and further, the tapered portion having a larger diameter toward the inner side at the inside of the opening end of the cushioning material 14. The provision of 14b makes it possible to completely prevent the cushioning material 14 from falling off.
[0023]
In this embodiment, as described above, the outer peripheral surface of the central iron core 1 is wound with the buffer tape 13, and the upper and lower ends of the center iron core 1 are forcibly covered with the cap-shaped buffer members 14, 14 so that the epoxy resin does not enter. It is fitted. Therefore, even if the center iron core 1 having a substantially octagonal cross section is used, it is possible to reliably prevent the occurrence of cracks in the epoxy resin.
[0024]
【The invention's effect】
As described above in detail, according to the ignition coil for an internal combustion engine of the present invention, the epoxy resin is prevented from flowing into the cap-shaped cushioning material. Therefore, the generation of cracks in the epoxy resin can be prevented, and the life of the ignition coil can be further extended.
[Brief description of the drawings]
FIG. 1 is a schematic longitudinal sectional view showing one embodiment of an ignition coil of the present invention.
FIG. 2 is a schematic perspective view showing, on an enlarged scale, an upper portion of a central iron core of the ignition coil of FIG. 1;
FIG. 3 is a schematic longitudinal sectional view showing a cushioning material of the ignition coil of FIG. 1;
FIG. 4 is a schematic longitudinal sectional view showing a state in which the cushioning material of FIG. 3 is mounted on the upper part of the center iron core.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Center iron core 2 Secondary bobbin 3 Secondary coil 4 Primary bobbin 5 Primary coil 6 Case 7 Exterior iron core 8 Igniter 9 Connector terminal (primary current input part)
Reference Signs List 10 Secondary high voltage terminal 11 Spring 12 Protector 13 Buffer tape 14 Buffer material

Claims (3)

A central iron core, a primary coil wound on a primary bobbin, and a secondary coil wound on a secondary bobbin are arranged concentrically, and an ignition coil for an internal combustion engine in which an insulating resin is filled between these members. ,
At least one end of the central iron core is fitted with a substantially cylindrical cap-shaped cushioning material opened only at one end surface,
The ignition coil for an internal combustion engine, wherein the inner diameter of the cushioning material is smaller than the maximum diameter of the central iron core. A secondary coil wound around a secondary bobbin is arranged concentrically outside the center iron core, and a primary coil wound around a primary bobbin is arranged concentrically outside the secondary coil. In an ignition coil for an internal combustion engine in which an insulating resin is filled between a secondary coil and between a secondary coil and a primary coil,
The central iron core is formed in a rod shape having a substantially octagonal cross section, and a resin buffer tape is wound around its outer peripheral surface, leaving both ends in the longitudinal direction.
At both ends in the longitudinal direction of the central iron core, a substantially cylindrical cap-shaped cushioning material opened only at one end face is attached,
The opening of this cushioning material is a small-diameter hole in which the center iron core on which the buffer tape is not wound is disposed on the back side, and a large-diameter hole in which the portion on which the buffer tape is wound is disposed on the front side. And
The inner diameter of the opening side of the large diameter hole is formed smaller than the outer diameter of the central iron core around which the buffer tape is wound,
An ignition coil for an internal combustion engine, wherein the cushioning material is forcibly fitted and attached to an end of the center iron core. The ignition coil for an internal combustion engine according to claim 1 or 2, wherein the opening of the cushioning material is formed in a tapered hole whose diameter decreases toward an opening side.

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