JP2004071917A - Ignition coil for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an ignition coil having a long lifetime by relaxing the effect of a central core on epoxy resin, thereby preventing the epoxy resin from cracking. <P>SOLUTION: The ignition coil for an internal combustion engine comprises a central core 1, a primary coil 5 wound around a primary bobbin 4, and a coaxial secondary coil 3 wound around a secondary bobbin 2, wherein the gaps between respective members are filled with insulating resin. The central core 1 formed to have an octagonal cross-section by laminating steel plates 1a, 1a, ... having different widthwise dimensions has eight rounded corners 1x, 1x, .... Each steel plate 1a having an angle 1y, constituting the central core 1 also has rounded corners. <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 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. Note that, as a central iron core, a structure in which rectangular silicon steel plates having different widths are laminated as described in JP-A-9-7860 is conventionally 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]
[Problems to be solved by the invention]
However, when the center iron core is formed by simply stacking silicon steel sheets having different width dimensions as in the above-described conventional method, each corner of each silicon steel sheet group constituting the iron core is formed on the outer periphery of the iron core. By acting as an edge, there is a possibility that the resin located on the outer peripheral side of the central iron core may crack. In addition, when a silicon steel sheet is laminated to form a central iron core, cracks may occur in the epoxy resin around the central iron core due to differences in the thermal expansion coefficients in the laminating direction of the steel sheet and the direction perpendicular thereto. It was also a cause.
[0005]
In addition, 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.
[0006]
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.
[0007]
The present invention has been made in view of the above circumstances, and a main object of the present invention is to ensure that even when a silicon steel plate is laminated to form a central iron core, cracks occur in the epoxy resin around the central iron core. To provide a long life ignition coil.
[0008]
[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 around a primary bobbin, and a secondary coil wound around 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 members, a central iron core formed by laminating steel plates having different width dimensions and having a substantially octagonal cross section is rounded at each of the eight corners. It is characterized by having.
[0009]
In the ignition coil for an internal combustion engine of the present invention, 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 insulation is provided between these members. In an ignition coil for an internal combustion engine filled with a conductive resin, a central iron core formed by laminating steel plates having different width dimensions and having a substantially octagonal cross section is formed by rounding each corner of each steel plate arranged on the outer peripheral side. It is characterized by having been done.
[0010]
In addition, in addition to any of the above configurations, the center iron core is provided with the rounding only at both ends in the longitudinal direction, and the outer peripheral surface of the center iron core is made of a resin buffer except for both ends in the longitudinal direction. A tape is wound, and 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 in a state where the cushioning tape is partially overlapped with the cushioning tape. An ignition coil for an internal combustion engine, characterized in that:
[0011]
In the ignition coil for an internal combustion engine of the present invention, 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 insulation is provided between these members. In the ignition coil for an internal combustion engine filled with a conductive resin, the central iron core is formed by laminating steel plates having different width dimensions to have a substantially octagonal cross section, and the coefficient of thermal expansion in the laminating direction of the steel plate group and the steel plate group The thermal expansion coefficient in the direction orthogonal to the laminating direction is balanced.
[0012]
And preferably, in addition to the above configuration, the steel sheet group is welded so as to balance the coefficient of thermal expansion in the stacking direction of the group of steel sheets forming the central iron core with the coefficient of thermal expansion in a direction perpendicular to the stacking direction of the group of steel sheets. An ignition coil for an internal combustion engine.
[0013]
More specifically, in addition to the above configuration, the welding is performed on both end surfaces in the longitudinal direction of the central iron core, and at a central portion in a direction orthogonal to the laminating direction, the welding length in the laminating direction is changed. Wherein the coefficients of thermal expansion are balanced.
[0014]
In the ignition coil for an internal combustion engine of the present invention, 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 insulation is provided between these members. In the ignition coil for an internal combustion engine filled with a conductive resin, both ends in the longitudinal direction of the central iron core are formed in a tapered surface tapering toward the end.
[0015]
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.
[0016]
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.
[0017]
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.
[0018]
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.
[0019]
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.
[0020]
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.
[0021]
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 around the outer peripheral surface of the central iron core. Note that the buffer tape 13 is wound around the central iron core 1 while leaving a small amount of the upper and lower ends 1c, 1c. As a result, the upper and lower ends 1c, 1c of the central iron core 1 are exposed to the outside.
[0022]
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.
[0023]
The ignition coil of the present invention basically has the above-described structure, and is characterized by the structure of the central iron core 1 among them. Hereinafter, this point will be described in detail.
[0024]
FIG. 5 is a cross-sectional view showing a first embodiment of the center iron core 1 of the ignition coil. As described above, the central iron core 1 is formed by laminating steel plates 1a, 1a,... In the present embodiment, the eight corners 1x, 1x,... Of the central iron core 1 are rounded and rounded. Thereby, the space between the center iron core 1 and the secondary bobbin 2 is secured, and the epoxy resin thickness outside each corner 1x can be secured. Moreover, the effect of the rounding itself on each corner 1x is also superimposed, the durability against the thermal stress from the central iron core 1 is improved, and the occurrence of cracks in the epoxy resin is prevented.
[0025]
FIG. 6 is a plan view showing a second embodiment of the center iron core 1 of the ignition coil. In this embodiment, the edges of the steel plates 1a constituting the central iron core 1 are rounded. That is, each corner (each corner protruding without being overlapped with an adjacent steel plate) 1y of each steel plate 1a arranged on the outer peripheral side of the center iron core 1 is rounded. Thereby, thermal stress from the center iron core 1 to the epoxy resin can be reduced, and generation of cracks in the epoxy resin can be prevented.
[0026]
In this embodiment, welding is performed on both end surfaces in the longitudinal direction of the central iron core 1 so that the steel sheet groups 1a, 1a,. In the illustrated example, welding is applied to a portion 1z indicated by oblique lines in the center of the center iron core 1. That is, welding is performed in the laminating direction (vertical direction in FIG. 6) at the center of the direction perpendicular to the laminating direction of the steel plate 1a (left-right direction in FIG. 6). By changing the welding length, the coefficient of thermal expansion in the stacking direction of the group of steel sheets is balanced with the coefficient of thermal expansion in the direction orthogonal to the direction of stacking of the group of steel sheets. For example, welding is performed for a length of about half (in the range of 1/3 to 2/3) of the diameter of the center iron core 1 in the laminating direction. In FIG. 6, when the entire area in the vertical direction is welded, the edges of the upper and lower thin plate portions cause stress concentration, while when no welding is performed, stress concentrates on the left and right edges at the center of the laminated portion.
[0027]
By balancing the coefficient of thermal expansion in the laminating direction of the steel sheets and the direction perpendicular to the lamination direction, cracks in the epoxy resin due to warpage of each steel sheet due to the difference in the coefficient of thermal expansion are prevented. That is, since the stress on the epoxy resin due to the thermal expansion of the center iron core 1 can be averaged, the stress concentration site on the epoxy resin can be eliminated, and the occurrence of cracks on the epoxy resin can be prevented. .
[0028]
FIG. 7 is a side view showing a third embodiment of the center iron core 1 of the ignition coil, and shows an upper part of the center iron core 1. The center iron core 1 of this embodiment is formed such that both ends in the longitudinal direction are tapered surfaces tapering toward the end. As a result, the thickness of the epoxy resin at the portion where the thermal stress from the central iron core 1 to the epoxy resin concentrates can be increased, the durability of the thermal stress from the central iron core can be improved, and cracks on the epoxy resin can be prevented. Occurrence can be prevented.
[0029]
It should be noted that the ignition coil of the present invention is not limited to the configuration of the above embodiment, but can be appropriately changed. For example, the processing performed on the center iron core 1 can be combined with those of the above embodiments. That is, for example, by combining the first embodiment and the second embodiment, not only are rounded corners 1y, 1y... Of each steel plate group, but also eight corners 1x, 1 of a substantially octagonal shape formed of the steel plate group. 1x ... can also be attached. Further, by applying the third embodiment, the upper and lower ends of such a central iron core 1 may be tapered. Further, the welding to both end surfaces of the center iron core can be applied not only to the second embodiment but also to the center iron core 1 of the first embodiment and the like.
[0030]
Further, the rounding of the first embodiment and the second embodiment may be performed on the entire area of the central iron core 1 in the longitudinal direction, or may be performed only on both ends in the longitudinal direction. The upper end of the central iron core 1 is liable to cause cracks in the epoxy resin and has a large effect when it occurs. Therefore, it is effective to take measures against only that portion.
[0031]
【The invention's effect】
As described above in detail, according to the ignition coil for an internal combustion engine of the present invention, the stress from the central iron core to the surrounding epoxy resin can be reduced, and the occurrence of cracks in the epoxy resin can be prevented. Therefore, the life of the ignition coil can be 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.
FIG. 5 is a cross-sectional view showing a first embodiment of a center iron core of the ignition coil of FIG. 1;
FIG. 6 is a plan view showing a second embodiment of the center iron core of the ignition coil of FIG. 1;
FIG. 7 is a side view showing a third embodiment of the center iron core of the ignition coil of FIG. 1, showing only 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 (7)

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. ,
An ignition coil for an internal combustion engine, characterized in that a central iron core formed by laminating steel plates having different width dimensions and having a substantially octagonal cross-section has rounded eight corners. 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. ,
An ignition coil for an internal combustion engine, wherein a central iron core formed by laminating steel plates having different width dimensions and having a substantially octagonal cross section is formed by rounding each corner of each steel plate arranged on the outer peripheral side. The center iron core, the radius is applied only to both ends in the longitudinal direction,
A resin buffer tape is wound around the outer peripheral surface of the center iron core, leaving both ends in the longitudinal direction.
A substantially cylindrical cap-shaped cushioning material having an opening only at one end surface is attached to both ends in the longitudinal direction of the central iron core in a state where the cushioning tape is partially overlapped with the cushioning tape. Or an ignition coil for an internal combustion engine according to claim 2. 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. ,
The central iron core is formed by laminating steel sheets having different width dimensions to form a substantially octagonal cross section, and balances the thermal expansion coefficient of the steel sheet group in the laminating direction and the thermal expansion coefficient of the steel sheet group in a direction orthogonal to the laminating direction. An ignition coil for an internal combustion engine, which is combined. The steel sheet group is welded to balance the thermal expansion coefficient of the steel sheet group constituting the central iron core in the stacking direction with the thermal expansion coefficient of the steel sheet group in a direction perpendicular to the stacking direction. An ignition coil for an internal combustion engine according to the above. The welding is performed on both longitudinal end surfaces of the central iron core,
6. The ignition coil for an internal combustion engine according to claim 5, wherein the thermal expansion coefficient is balanced by changing a welding length in the laminating direction at a central portion in a direction orthogonal to the laminating direction. 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. ,
An ignition coil for an internal combustion engine, wherein both ends in the longitudinal direction of the center iron core are formed in a tapered surface tapering toward an end.

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