JP2008118160A - Method of manufacturing ignition coil for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of manufacturing an ignition coil for an internal combustion engine for suppressing the occurrence of insulation breakdown without increasing the size thereof , wherein the ignition coil is disposed in the mounting hole of an engine main body. <P>SOLUTION: This is a method for manufacturing the ignition coil 13 for the internal combustion engine. The internal combustion engine has a connection member 14 embedded with an igniter and an insertion member 15 disposed in a plug mounting hole. The insertion member 15 has an internal core 20, a primary coil 23, a secondary coil 28, an insulation layer 30, and an outer core 31. The insulation layer 30 comprising a single material is solely present between the secondary coil 28 and the external core 31. The method includes a step for disposing the internal core 20, the primary core 23, the secondary coil 28 and the igniter in the mold of a molding machine; a step for forming the connection member 14 and the insulation layer 30 through a machining process after an epoxy resin is filled in the mould and cured; a step of outwardly fitting an external core 31 to the circumference of the insulation layer 30. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a method for manufacturing an ignition coil for an internal combustion engine disposed in a plug mounting hole formed in an engine body.

  FIG. 3 is a schematic configuration diagram showing an ignition device provided in engine 100. As shown in the figure, spark plugs 103 are respectively provided in the plug mounting holes 101a formed in the cylinder head 101 of the engine 100 so as to correspond to the combustion chambers 102 of the respective cylinders. Each spark plug 103 is connected to a distributor 105 via a high voltage cord 104. The distributor 105 is connected to the ignition coil 106. The ignition coil 106 functions as a transformer for boosting the voltage of the battery 107 (usually 12V) to a high voltage of 30 kV or higher.

  In the ignition device as described above, the current flowing through the primary coil (not shown) of the ignition coil 106 is intermittently controlled by the igniter 109 based on the ignition signal generated by the electronic control device 108. The high voltage generated in the secondary coil (not shown) of the ignition coil 106 by this intermittent control is sequentially distributed to each spark plug 103 by the distributor 105.

  In the above ignition device, the high voltage generated in the ignition coil 106 is distributed to each ignition plug 103 by the distributor 105. However, in recent years, as shown in FIG. There has been proposed an ignition device that employs a so-called DLI ignition system (Distributor Less Ignition system) that does not require a distributor by providing each 106. In this apparatus, in addition to the distributor, a high voltage cord for supplying a high voltage from the distributor to the spark plug 103 is not necessary.

  Incidentally, in the ignition device shown in FIG. 4, the ignition coil 106 is attached to the cylinder head 101 of the engine 100, but such a configuration leads to an increase in the size of the engine 100.

  In order to avoid such an increase in the size of the engine 100, it is conceivable to employ a configuration in which the ignition coil 106 is disposed in the plug mounting hole 101a. [Patent Document 1] describes a rod-like ignition coil 106 applicable to such a configuration.

  As shown in FIG. 5, the ignition coil 106 includes a cylindrical case 200 made of a thermoplastic resin, a rod-shaped central iron core 201 provided in the case 200, and a bobbin 202 fitted on the central iron core. And an external iron core 203 fitted on the case 200. A primary winding 204 and a secondary winding 205 are wound around the bobbin 202. The bobbin 202 and the primary winding 204 constitute a primary coil 206, and the bobbin 202 and the secondary winding 205 constitute a secondary coil 207.

Inside the case 200, in order to fix the bobbin 202 and the like and to ensure insulation in the case 200, an insulating layer 208 is formed by filling and curing an epoxy resin which is a thermosetting resin.
JP-A-8-273949

  By the way, when dissimilar materials are brought into close contact like a thermoplastic resin and a thermosetting resin, the contact force becomes relatively weak. Therefore, in the ignition coil 106, when the epoxy resin (thermosetting resin) filled in the case (thermoplastic resin) 200 moves to the center side due to shrinkage during curing, it is insulated from the case 200. A minute gap may be formed between the layer 208. And since there is a low insulation resistance inside such a gap, there is a risk of discharge. When such a discharge occurs, the following problems occur.

  FIG. 6 shows an enlarged portion A of the ignition coil 106 shown in FIG. As shown in FIG. 5A, when a discharge occurs in the gap 210 formed between the case 200 and the insulating layer 208, the case 200 first burns out. This is because, in general, the thermoplastic resin that is the material of the case 200 has low durability against burning compared to the thermosetting resin that is the material of the insulating layer 208. As shown in FIG. 6B, the case 200 is burned to form a gap 210 from the insulating layer 208 to the outer core 203, while the insulating layer 208 is similarly burned out. Then, as shown in FIG. 6C, if a gap 210 is formed from the secondary coil 207 (secondary winding 205) to the outer core 203, dielectric breakdown occurs in the ignition coil 106, and the ignition coil There arises a problem that the durability of 106 is significantly lowered.

  Therefore, for example, by increasing the thickness of the case 200 and the thickness of the insulating layer 208 to increase the distance between the secondary coil 207 that generates a high voltage and the outer core 203 that is substantially at ground potential, It is conceivable to reduce the potential gradient at 210 to suppress the occurrence of discharge.

  However, such a configuration change inevitably increases the size of the ignition coil 106, and therefore it is not desirable to apply it to the ignition coil 106 disposed in the plug mounting hole 101a as described above. This is because the shape change allowed in the ignition coil 106 is limited by the size of the plug mounting hole 101a.

  The present invention has been made in view of such circumstances, and an object thereof is to suppress the occurrence of dielectric breakdown without causing an increase in size of an ignition coil disposed in a plug mounting hole of an engine body. An object of the present invention is to provide a method for manufacturing an ignition coil for an internal combustion engine.

In the following, means for achieving the above object and its effects are described.
(1) The invention according to claim 1 is arranged in the plug mounting hole so as to supply an ignition voltage to a spark plug mounted in the plug mounting hole of the engine body, A core, a coil provided on the outer periphery of the inner core, an insulating layer that covers the coil, and an outer core that is externally fitted to the insulating layer, and a single piece between the coil and the outer core. In the method of manufacturing an ignition coil for an internal combustion engine having only the insulating layer made of a material, the step A of arranging the inner core and the coil in a mold of a molding machine, and the single unit in the mold after the step A The present invention includes a step B in which the material is filled and cured to form the insulating layer, and a step C in which the outer core is fitted around the outer periphery of the insulating layer after the step B.

  According to the above invention, since the insulating layer is formed of a single material, there is no interface between different materials in which the air gap is likely to be formed in the insulating layer. Occurrence of the burning of the insulating layer due to this is suppressed. Therefore, it is possible to suppress the occurrence of dielectric breakdown without causing an increase in size of the ignition coil disposed in the plug mounting hole of the engine body.

  (2) The invention described in claim 2 is the method for manufacturing an ignition coil for an internal combustion engine according to claim 1, wherein in the step B, the single material is cured, and then the insulating layer is formed by machining. The gist is to form.

  (3) The invention described in claim 3 is the method for manufacturing an ignition coil for an internal combustion engine according to claim 1 or 2, wherein the ignition coil for the internal combustion engine includes a connection portion in which an igniter is incorporated, and the plug mounting hole. The insertion portion is constituted by the inner core, the coil, the insulating layer, and the outer core. In the step B, the single material is cured. The gist is to form an insulating layer for the connection portion and the insertion portion.

  (4) According to a fourth aspect of the present invention, in the method for manufacturing an internal combustion engine ignition coil according to the third aspect, in the step B, after the single material is cured, the connection portion and the ignition coil are machined. The gist is to form an insulating layer of the insertion portion.

  (5) The invention according to claim 5 is the method for producing an ignition coil for an internal combustion engine according to claim 3 or 4, wherein in the step A, the inner core and the coil are placed in the mold of the molding machine. The gist is to place an igniter.

  (6) The invention according to claim 6 is the method of manufacturing an ignition coil for an internal combustion engine according to any one of claims 3 to 5, wherein the insertion portion is a plug connection portion to which the ignition plug is attached. In the step B, the single material is cured to form the connection portion, the insulating layer of the insertion portion, and the plug connection portion of the insertion portion. Yes.

  (7) The invention according to claim 7 is arranged in the plug mounting hole so as to supply an ignition voltage to the spark plug mounted in the plug mounting hole of the engine body, A core, a coil provided on the outer periphery of the inner core, an insulating layer that covers the coil, and an outer core that is externally fitted to the insulating layer, and a single piece between the coil and the outer core. In the method of manufacturing an ignition coil for an internal combustion engine having only the insulating layer made of a material, the step A of disposing the inner core and the coil in a mold of a molding machine having a recess having the same shape as the outer shape of the insulating layer; After the step A, the mold is filled with the single material and cured to form the insulating layer, and after the step B, the outer core is fitted on the outer periphery of the insulating layer. Including the process C to be performed There.

  According to the above invention, since the insulating layer is formed of a single material, there is no interface between different materials in which the air gap is likely to be formed in the insulating layer. Occurrence of the burning of the insulating layer due to this is suppressed. Therefore, it is possible to suppress the occurrence of dielectric breakdown without causing an increase in size of the ignition coil disposed in the plug mounting hole of the engine body.

  (8) According to an eighth aspect of the present invention, in the method for manufacturing an internal combustion engine ignition coil according to the seventh aspect, the internal combustion engine ignition coil is disposed in a connection portion in which an igniter is incorporated and the plug mounting hole. And the insertion portion is constituted by the inner core, the coil, the insulating layer, and the outer core. In the step A, the insertion portion in a state in which the outer core is removed. In the molding machine having the concave portion having the same shape as the outer shape, the igniter is disposed in the mold together with the inner core and the coil, and in the step B, the single material is cured and the connection portion and the The gist is to integrally form the insulating layer of the insertion portion.

  (9) The invention according to claim 9 is arranged in the plug mounting hole so as to supply an ignition voltage to the spark plug mounted in the plug mounting hole of the engine body, A core, a coil provided on the outer periphery of the inner core, an insulating layer that covers the coil, and an outer core that is externally fitted to the insulating layer, and a single piece between the coil and the outer core. In the method of manufacturing an ignition coil for an internal combustion engine having only the insulating layer made of a material, a step A in which a cylindrical member that forms an outer peripheral portion of the insulating layer is formed of the single material, and the cylindrical member after the step A Step B in which each of the inner core and the coil is disposed inside the tube, and after the step B, the cylindrical member is filled with the single material and is cured so that the outer peripheral portion is formed from the cylindrical member. Forming the insulating layer It is summarized as to include a step C of.

  According to the above invention, since the insulating layer is formed of a single material, there is no interface between different materials in which the air gap is likely to be formed in the insulating layer. Occurrence of the burning of the insulating layer due to this is suppressed. Therefore, it is possible to suppress the occurrence of dielectric breakdown without causing an increase in size of the ignition coil disposed in the plug mounting hole of the engine body.

  (10) The invention according to claim 10 includes the step D of externally fitting the outer core on the outer periphery of the insulating layer after the step C in the method for manufacturing an ignition coil for an internal combustion engine according to claim 9. This is the gist.

  (11) The invention according to claim 11 is the method for manufacturing an ignition coil for an internal combustion engine according to claim 9 or 10, wherein the ignition coil for the internal combustion engine includes a connection portion in which an igniter is incorporated, and the plug mounting hole. The insertion portion is constituted by the inner core, the coil, the insulating layer, and the outer core, and in the step B, the connection made of the single material. The gist is to arrange each of the inner core and the coil inside the cylindrical member after joining the part and the cylindrical member.

1 and 2, an embodiment in which the present invention is applied to an ignition coil of a four-cylinder engine for a vehicle will be described.
As shown in FIG. 1, the cylinder head 11 of the engine 10 is formed with four plug mounting holes 12 that communicate with the combustion chamber (not shown) of each cylinder. A spark plug 33 (shown in FIG. 2) inserted into the plug mounting hole 12 is fixed to the cylinder head 11 such that a lower portion thereof protrudes into the combustion chamber.

  The ignition coil 13 includes a connection portion 14 located above the connection portion 14 and a columnar insertion portion 15 located below the connection portion 14. The ignition coil 13 is fixed in each plug attachment hole 12 by inserting the insertion portion 15 into each plug attachment hole 12 and fitting the lower portion of the insertion portion 15 into the upper portion of the ignition plug 33. . These ignition coils 13 are respectively connected to a control device 16 provided in the vehicle. In addition, an igniter (not shown) is built in the connection portion 14, and a socket 17 for connecting the ignition coil 13 and the control device 16 via a signal line is formed on the side portion thereof.

  FIG. 2 is a sectional view showing the ignition coil 13. The ignition coil 13 has an inner core 20 having a cylindrical shape at the center thereof. The inner core 20 is formed by laminating a plurality of silicon steel plates that are ferromagnetic materials.

  An insulating tape 21 is wound around the outer periphery of the inner core 20, and a primary coil 22 is formed by laminating and winding a primary winding 22 on the insulating tape 21. Thus, the primary coil 23 in this embodiment has a bobbin-less structure.

  A secondary bobbin 25 having a substantially cylindrical shape is externally fitted to the primary coil 23. The secondary bobbin 25 is made of modified polyphenylene ether (PPE) having excellent heat resistance and insulation resistance. A plurality of flanges 26 are formed on the outer periphery of the secondary bobbin 25, and secondary windings 27 are laminated and wound between the flanges 26. The secondary bobbin 25 and the secondary winding 27 constitute a secondary coil 28.

  The outer periphery of the secondary coil 28 is covered with an insulating layer 30 over the entire periphery. The insulating layer 30 is formed of an epoxy resin that is a thermosetting resin material. Similarly, the connecting portion 14 is formed of an epoxy resin. A cylindrical outer core 31 is fitted on the outer periphery of the insulating layer 30. The outer core 31 is formed of a silicon steel plate, like the inner core 20.

  A mounting hole (not shown) extending in the axial direction is formed inside the lower portion of the insertion portion 15, and an output terminal (not shown) electrically connected to the secondary coil 28 is provided. The upper terminal of the spark plug 33 is fitted in the mounting hole and is electrically connected in contact with the output terminal.

  When the ignition coil 13 is manufactured, the internal core 20, the coils 23 and 28, the igniter and the like are arranged in a mold of a molding machine, filled with epoxy resin in the mold and cured. Further, this is machined into the shape shown in FIG. Thereafter, the outer core 31 is fitted on the outer periphery of the insulating layer 30. The molding method may be either injection molding or vacuum molding, but it is desirable to employ vacuum molding in order to prevent the generation of voids between the strands of the secondary winding 27. In addition to a metal mold, a resin mold can be used. When a resin mold is adopted, it is desirable to coat the inner peripheral surface of the mold with a fluororesin in order to improve the releasability.

Or the following manufacturing methods are also employable.
For example, the connecting portion 14 containing the igniter or the like is formed in advance by machining or the like, and the connecting portion 14 has the same shape as the outer shape of the insertion portion 15 (excluding the outer core 31) together with the inner core 20, the coils 23 and 28, etc. It arrange | positions in the type | mold which has a recessed part. The ignition coil 13 may be manufactured by filling the mold with an epoxy resin and curing it so that the insertion portion 15 is formed integrally with the connection portion 14.

  Alternatively, a cylindrical material corresponding to the outer peripheral portion of the insulating layer 30 is formed by extruding an epoxy resin. Then, the cylindrical material is joined to the connecting portion 14 incorporating an igniter or the like, and components such as the inner core 20 are arranged inside the cylindrical material. Then, you may make it manufacture the ignition coil 13 by filling the inside of the cylindrical material with an epoxy resin and hardening it. If this manufacturing method is adopted, a mold for forming the insulating layer 30 becomes unnecessary.

  In the ignition coil 13 manufactured as described above, the current flowing through the primary coil 23 is intermittently controlled by the igniter based on the ignition signal from the control device 16, whereby the secondary coil 28 has the battery 50. Is increased to the ignition voltage (35 kV). When this ignition voltage is supplied to the ignition plug 33, a spark is generated between electrodes (not shown) of the ignition plug 33, and the air-fuel mixture in the combustion chamber is ignited.

  As described above, when an ignition voltage is generated in the secondary coil 28, an extremely large potential gradient is generated between the secondary coil 28 and the external core 31 held at a substantially ground potential. For this reason, if there is a gap in the insulating layer 30 between the secondary coil 28 and the outer core 31, there is a possibility that the insulating layer 30 will burn out due to the occurrence of discharge in the gap. Further, when this burning progresses, a gap that communicates the secondary winding 27 and the outer core 31 is formed in the insulating layer 30, and there is a possibility that the dielectric breakdown of the ignition coil 13 occurs in the gap.

  For example, when a case made of a thermoplastic resin is filled with a thermosetting resin and cured, the adhesion between the inner peripheral surface of the case and the thermosetting resin is poor, so the resin is cured. When shrinking, the above gaps are likely to be formed between the two. Further, as described above, in the configuration in which the thickness of the case and the thermosetting resin is increased to reduce the potential gradient between the secondary winding 27 and the outer core 31, the discharge as described above is performed. Although generation | occurrence | production of is suppressed, the enlargement of the ignition coil 13 will be caused.

  In this regard, according to the present embodiment, since the insulating layer 30 is formed only by an epoxy resin that is a single material, in the insulating layer 30, between the secondary winding 27 and the outer core 31. There is no interface between dissimilar materials in which voids are likely to be formed. For this reason, the space | gap in the insulating layer 30 reduces, and the burning of the insulating layer 30 resulting from the discharge in the space | gap is suppressed. As a result, according to the present embodiment, it is possible to prevent dielectric breakdown of the ignition coil 13 and improve its durability. Further, the ignition coil 13 according to the present embodiment is suitable for the ignition coil 13 disposed in the plug mounting hole 12 because it can prevent dielectric breakdown without causing an increase in size.

  Furthermore, in this embodiment, an epoxy resin that is a thermosetting resin is adopted as a material for forming the insulating layer 30. Therefore, thermal deformation and melting of the insulating layer 30 are suppressed. For example, when the insulating layer 30 is made of a thermoplastic resin, the insulating layer 30 is thermally deformed or melted by the heat of the cylinder head 11, the primary coil 23, or the secondary coil 28 in the plug mounting hole 12. In this case, the maintainability of the engine 10 is significantly reduced. According to the present embodiment, since the insulating layer 30 is not thermally deformed or melted, it is possible to avoid the above-described deterioration in maintainability.

  In general, a thermothermosetting resin such as an epoxy resin has a higher insulation resistance than, for example, a thermoplastic resin. For this reason, according to this embodiment, the dielectric breakdown in the insulating layer 30 is further suppressed, and the durability of the ignition coil 13 can be further improved.

(Other embodiments)
The said embodiment can also be implemented by changing a structure as follows. Even if the configuration is changed in this way, it is possible to achieve substantially the same effect as the above-described embodiment.

  In the above embodiment, the primary winding 22 is wound around the outer periphery of the inner core 20 via the insulating tape 21, and the secondary bobbin 25 in which the secondary winding 27 is wound around the outer periphery of the primary winding 22 is removed. I try to fit it. On the other hand, a bobbin may be fitted on the inner core 20 and a primary coil and a secondary coil may be configured by winding a primary winding and a secondary winding on the same bobbin. Further, the secondary coil 28 can be disposed on the inner side of the primary coil 23.

In the above embodiment, the igniter is built in the connection portion 14 of the ignition coil 13, but this igniter may be provided outside the ignition coil 13.
-You may make it add reinforcing materials, such as glass fiber, in the epoxy resin which forms the said insulating layer 30. FIG. Thus, the addition of a reinforcing material in the epoxy resin is effective in increasing the rigidity of the ignition coil 13 in which the thickness of the insulating layer 30 is limited because it is disposed in the plug mounting hole 12. .

  In the above embodiment, the insulating layer 30 is formed of an epoxy resin that is a thermosetting resin. However, the insulating layer 30 may be formed of a thermoplastic resin, for example.

The schematic block diagram which shows the engine provided with the ignition coil. Sectional drawing which shows the ignition coil. The schematic block diagram which shows the structural example of an ignition device. The schematic block diagram which shows the structural example of an ignition device. Sectional drawing which shows the conventional ignition coil. Sectional drawing which expands and shows the A section of FIG.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Engine, 11 ... Cylinder head, 12 ... Plug attachment hole, 13 ... Ignition coil, 14 ... Connection part, 15 ... Insertion part, 16 ... Control apparatus, 17 ... Socket, 20 ... Inner core, 21 ... Insulation tape, 22 ... primary winding, 23 ... primary coil, 25 ... secondary bobbin, 26 ... flange, 27 ... secondary winding, 28 ... secondary coil, 30 ... insulating layer, 31 ... outer core, 33 ... spark plug, 50 ... Battery.

Claims (11)

An internal core and a coil provided on the outer periphery of the internal core are arranged in the plug mounting hole to supply an ignition voltage to a spark plug mounted in the plug mounting hole of the engine body. And an insulating layer that covers the coil, and an external core that is externally fitted to the insulating layer, the internal combustion engine having only the insulating layer made of a single material between the coil and the external core. In the method of manufacturing an ignition coil,
Arranging the inner core and the coil in a mold of a molding machine; and
Step B after the step A is filled with the single material in the mold and cured to form the insulating layer;
A method of manufacturing an ignition coil for an internal combustion engine, comprising: a step C of fitting the outer core around the outer periphery of the insulating layer after the step B. In the manufacturing method of the ignition coil for internal-combustion engines according to claim 1,
In the step B, the insulating layer is formed through machining after the single material is cured. A method for manufacturing an ignition coil for an internal combustion engine. In the manufacturing method of the ignition coil for internal-combustion engines according to claim 1 or 2,
The ignition coil for an internal combustion engine includes a connection portion that houses an igniter and an insertion portion that is disposed in the plug mounting hole, and the insertion portion is constituted by the inner core, the coil, the insulating layer, and the outer core. Is,
In the step B, the single material is cured to form an insulating layer of the connection portion and the insertion portion. A method of manufacturing an ignition coil for an internal combustion engine, comprising: In the manufacturing method of the ignition coil for internal-combustion engines according to claim 3,
In the step B, the insulating material of the connection portion and the insertion portion is formed through machining after the single material is cured. A method of manufacturing an ignition coil for an internal combustion engine, comprising: In the manufacturing method of the ignition coil for internal-combustion engines according to claim 3 or 4,
In the step A, the igniter is disposed together with the inner core and the coil in a mold of the molding machine. In the manufacturing method of the ignition coil for internal-combustion engines according to any one of claims 3 to 5,
The insertion portion is configured to include a plug connection portion to which the spark plug is attached,
In the step B, the single material is cured to form the connection portion, the insulating layer of the insertion portion, and the plug connection portion of the insertion portion. An internal core and a coil provided on the outer periphery of the internal core are arranged in the plug mounting hole to supply an ignition voltage to a spark plug mounted in the plug mounting hole of the engine body. And an insulating layer that covers the coil, and an external core that is externally fitted to the insulating layer, the internal combustion engine having only the insulating layer made of a single material between the coil and the external core. In the method of manufacturing an ignition coil,
Arranging the inner core and the coil in a mold of a molding machine having a recess having the same shape as the outer shape of the insulating layer; and
Step B after the step A is filled with the single material in the mold and cured to form the insulating layer;
A method of manufacturing an ignition coil for an internal combustion engine, comprising: a step C of fitting the outer core around the outer periphery of the insulating layer after the step B. In the manufacturing method of the ignition coil for internal-combustion engines according to claim 7,
The ignition coil for an internal combustion engine includes a connection portion that houses an igniter and an insertion portion that is disposed in the plug mounting hole, and the insertion portion is constituted by the inner core, the coil, the insulating layer, and the outer core. Is,
In the step A, for the molding machine having a recess having the same shape as the outer shape of the insertion part excluding the outer core, the igniter is disposed in the mold together with the inner core and the coil,
In the step B, the single material is cured to integrally form the connection portion and the insulating layer of the insertion portion. A method for manufacturing an ignition coil for an internal combustion engine, comprising: An internal core and a coil provided on the outer periphery of the internal core are arranged in the plug mounting hole to supply an ignition voltage to a spark plug mounted in the plug mounting hole of the engine body. And an insulating layer that covers the coil, and an external core that is externally fitted to the insulating layer, the internal combustion engine having only the insulating layer made of a single material between the coil and the external core. In the method of manufacturing an ignition coil,
Forming a cylindrical member forming the outer peripheral portion of the insulating layer from the single material; and
Step B for disposing each of the inner core and the coil inside the cylindrical member after Step A;
And after the step B, the cylinder member is filled with the single material and cured to form the insulating layer whose outer peripheral portion is formed of the cylinder member. A method of manufacturing an ignition coil for an engine. In the manufacturing method of the ignition coil for internal-combustion engines according to claim 9,
A method of manufacturing an ignition coil for an internal combustion engine, comprising the step D of fitting the outer core around the outer periphery of the insulating layer after the step C. In the manufacturing method of the ignition coil for internal-combustion engines according to claim 9 or 10,
The ignition coil for an internal combustion engine includes a connection portion that houses an igniter and an insertion portion that is disposed in the plug mounting hole, and the insertion portion is constituted by the inner core, the coil, the insulating layer, and the outer core. Is,
In the step B, the internal core and the coil are arranged inside the cylindrical member after joining the connecting portion made of the single material and the cylindrical member, respectively. Coil manufacturing method.

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