JP2008172162A - Soft magnetic material for ignition coil - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a soft magnetic material for ignition coil wherein an air gap of fixed size can be stably formed without variation for each product. <P>SOLUTION: The soft magnetic material 5 for ignition coil constitutes a part of a closed magnetic path of an ignition coil comprising a primary coil and a secondary coil. The soft magnetic material 5 are configured by interconnecting two pressed powder members 5A and 5B provided by compression-molding soft magnetic powder. The interconnecting part between the two pressed powder members 5A and 5B is provided with a gap-forming engaging part 50 which forms the air gap 501 of fixed size by engaging. One pressed powder member 5A of the two pressed powder members is configured by integral-molding a center core 51 arranged on an inner peripheral side of the primary coil and the secondary coil and a relay core arranged at another end part 512 in the axis direction of the center core 51. The other pressed powder member 5B is a relay core 52A arranged at one end part 511 in the axis direction of the center core 51. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a soft magnetic material constituting a part of a closed magnetic path of an ignition coil used for an internal combustion engine such as a vehicle engine.

  In an ignition coil used for an internal combustion engine such as a vehicle engine, a primary coil (primary coil) and a secondary coil (secondary coil) wound around an inner peripheral side and an outer peripheral side around the same axis line For example, a high voltage of 20 to 40 kV is generated in the secondary coil using the electromagnetic induction action. The high voltage generates a spark between a pair of electrodes in the spark plug connected to the secondary coil, and a combustion operation in the internal combustion engine is performed by the spark.

  A central core made of a soft magnetic material is arranged on the inner peripheral side of the primary coil and the secondary coil, and an outer core made of a soft magnetic material is arranged on the outer peripheral side of the primary coil and the secondary coil. Yes. A magnetic circuit is formed by passing the magnetic flux generated when the primary coil is energized through the central core and the outer core. In addition, the gap in the ignition coil is filled with an insulating resin such as an epoxy resin to fix each component such as the primary coil, secondary coil, and central core, and to ensure insulation between the components. is doing.

Also, for the reason that it is easy to ensure the required magnetic performance by forming into a desired shape, for example, as disclosed in the ignition coil of Patent Document 1, soft magnetic powder is compression-molded. A soft magnetic material made of a green compact has been produced.
Further, for example, in the ignition coil for an internal combustion engine disclosed in Patent Document 2, the second iron core is formed by forming the iron core material powder into a substantially hemispherical shape facing the stacking direction of the first iron core formed by laminating silicon steel plates. And the 3rd iron core is arranged and the closed magnetic circuit is formed between the 1st iron core, the 2nd iron core, and the 3rd iron core. Then, problems such as material saving and eddy current are solved, and an inexpensive and miniaturized ignition coil is formed.

By the way, when a magnetic circuit having a closed magnetic circuit is formed by using a center core and an outer core in the ignition coil and using a pair of relay cores that relay these at both ends in the axial direction, magnetic saturation is applied to the magnetic circuit. In order to suppress the occurrence of the air gap, an air gap (air gap) is formed at a predetermined position.
However, in the conventional ignition coil, the air gap is formed when the soft magnetic body of the central core, the outer peripheral core or the relay core is assembled with the components in the ignition coil. That is, the size of the air gap (the width of the air gap) is determined by the positional relationship between the soft magnetic material and other components. Therefore, it is not sufficient to stably form an air gap having a predetermined size.

JP 2004-186588 A JP 2005-142393 A

  The present invention has been made in view of such conventional problems, and an attempt is made to provide a soft magnetic body for an ignition coil that can stably form an air gap of a certain size without variation among products. To do.

The present invention is a soft magnetic material constituting a part of a closed magnetic circuit of an ignition coil having a primary coil and a secondary coil,
The soft magnetic body is formed by connecting two green compacts formed by compressing soft magnetic powder,
The connecting portion of the two green compacts is a soft magnetic body for an ignition coil that is provided with a gap forming engaging portion that engages with each other to form an air gap of a certain size ( Claim 1).

The soft magnetic body for an ignition coil according to the present invention is formed by connecting two green compacts, and is engaged with each other to form an air gap of a certain size (width) at a connecting portion of the two green compacts. A gap forming engagement portion is provided. Thereby, the soft magnetic body of this invention can always form the air gap of a fixed magnitude | size by connecting two green compacts. Therefore, it is possible to prevent variation in the size of the air gap for each ignition coil using a soft magnetic material.
Therefore, according to the soft magnetic body for an ignition coil of the present invention, an air gap having a certain size can be stably formed without variation among products.

A preferred embodiment of the present invention described above will be described.
In the present invention, the soft magnetic powder constituting the soft magnetic material can be composed, for example, of iron-based powder having an insulating coating as a main component. As the iron-based powder, for example, a Fe-Si-based alloy powder or the like having a surface formed with an insulating resin film can be used. The soft magnetic material can be compression-molded by binding a number of iron-based powders with a binder.

  The soft magnetic body includes a central core disposed on the inner peripheral side of the primary coil and the secondary coil, and an outer peripheral core in which an axial end portion of the central core is disposed on the outer peripheral side of the primary coil and the secondary coil. One of the two green compacts is the central core, and the other is the relay core disposed at one axial end of the central core. (Claim 2). In this case, when the center core and the relay core are engaged with each other, an air gap having a certain size can be stably formed between them.

  The soft magnetic body includes a central core disposed on the inner peripheral side of the primary coil and the secondary coil, and an outer peripheral core in which an axial end portion of the central core is disposed on the outer peripheral side of the primary coil and the secondary coil. One of the two green compacts is formed by integrally molding the central core and the relay core disposed at the other axial end of the central core. The other may be the relay core disposed at one end of the central core in the axial direction (Claim 3). Also in this case, when the central core and the relay core are engaged with each other, an air gap having a certain size can be stably formed between them.

  In addition, the gap forming engagement portion may be configured such that a plurality of protrusions protruding from an inner peripheral surface of the relay core are brought into contact with an outer peripheral surface of one axial end portion of the central core. 4). In this case, an air gap of a certain size can be stably formed between the central core and the relay core by the outer peripheral surface of the central core and the plurality of protrusions in the relay core.

  In addition, the gap forming engagement portion may be configured such that a plurality of protrusions that protrude from the outer peripheral surface of one axial end portion of the central core abut on the inner peripheral surface of the relay core. 5). In this case, an air gap having a certain size can be stably formed between the central core and the relay core by the plurality of protrusions in the central core and the inner peripheral surface of the relay core.

  In addition, the gap forming engagement portion abuts a plurality of protrusions protruding from the outer peripheral surface of one axial end portion of the central core to the inner peripheral surface of the relay core and one axial end of the central core. A plurality of protrusions protruding from the inner peripheral surface of the relay core may be brought into contact with the outer peripheral surface of the part (claim 6). In this case, a plurality of protrusions in the central core and a plurality of protrusions in the relay core can be used together to stably form an air gap of a certain size between the central core and the relay core. .

  A locking recess for locking the protrusion is formed on the outer peripheral surface of the central core facing the at least one of the plurality of protrusions or the inner peripheral surface of the relay core. It is preferable to prevent rotation of the two green compacts in the circumferential direction by the recess. In this case, it is possible to prevent the center core and the relay core from being displaced in the circumferential direction.

  The soft magnetic body includes a central core disposed on the inner peripheral side of the primary coil and the secondary coil, and an outer peripheral core in which an axial end portion of the central core is disposed on the outer peripheral side of the primary coil and the secondary coil. And one of the two green compacts is formed by integrally forming a part of the central core and the relay core disposed at one end of the central core in the axial direction. On the other hand, the other part may be formed by integrally molding the remaining part of the central core and the relay core disposed at the other axial end of the central core. In this case, when a part of the central core and the remaining part of the central core are engaged with each other, an air gap having a certain size can be stably formed between them.

  Further, the gap forming engagement portion includes an axial projection formed on an axial center side end surface of a part of the central core, and an axial concave portion formed on an axial center side end surface of the remaining portion of the central core. By engaging, the air gap can be formed between the center side end faces (claim 9). In this case, an air gap having a certain size can be stably formed between a part of the central core and the remaining part of the central core by the engagement between the axial protrusion and the axial recess.

Hereinafter, embodiments of a soft magnetic body for an ignition coil according to the present invention will be described with reference to the drawings.
(Example 1)
As shown in FIG. 3, the soft magnetic body 5 for the ignition coil in this example constitutes a part of the closed magnetic circuit of the ignition coil 1 including the primary coil 21 and the secondary coil 22. As shown in FIGS. 1 and 2, the soft magnetic body 5 is formed by connecting two green compacts 5A and B formed by compression-molding soft magnetic powder. A gap forming engagement portion 50 that engages with each other to form an air gap (gap) 501 having a certain size (width) is provided at a connecting portion of the two green compacts 5A and 5B.

Hereinafter, the soft magnetic body 5 for the ignition coil of this example will be described in detail with reference to FIGS.
As shown in FIGS. 1 to 3, in the ignition coil 1 of this example, a soft core disposed on the outer peripheral side of the central core 51 and the relay core 52, and the primary coil 21 and the secondary coil 22, which are configured by the soft magnetic body 5. A magnetic circuit having a closed magnetic circuit is constituted by the outer core 23 made of a magnetic material. Then, an air gap 501 in the closed magnetic path is formed by the gap forming engagement portion 50. In addition, the outer peripheral surface of each relay core 52 is connected to the inner peripheral surface at both axial ends of the outer core 23.

  As shown in FIG. 1, the soft magnetic body 5 of this example includes a central core 51 disposed on the inner peripheral side of the primary coil 21 and the secondary coil 22, and axially opposite ends 511 and 512 of the central core 51. And a relay core 52 for relaying to each other. One of the two green compacts 5A is formed by integrally forming the central core 51 and the relay core 52B disposed at the other axial end 512 of the central core 51, and the other 5B is the axis of the central core 51. This is a relay core 52 </ b> A arranged at one end 511 in the direction. The soft magnetic body 5 (the green compacts 5A and 5B) of this example is formed by compression-molding a number of iron-based powders (Fe-Si alloy powders or the like) having a coating made of an insulating resin in a state where they are bound by a binder. Become.

As shown in the figure, the center core 51 has a cylindrical shape, and the relay core 52B integrally formed with the center core 51 has a disk shape. The relay core 52 </ b> A formed separately from the center core 51 has an annular shape with an insertion hole 520 for inserting the center core 51.
The gap forming engagement portion 50 of this example is formed by the outer peripheral surface 510 of the axial end portion 511 of the central core 51 and a plurality of protrusions 53 that protrude from the inner peripheral surface 521 of the insertion hole 520 of the relay core 52A. It is. The air gap 501 of this example is formed between the plurality of protrusions 53 when the plurality of protrusions 53 in the relay core 52A are brought into contact with the outer peripheral surface 510 of the axial one end 511 of the center core 51. Void. The protrusions 53 of this example are formed at three locations on the inner peripheral surface 521 of the insertion hole 520 of the relay core 52 in order to stabilize the engagement between the two green compacts 5A and 5B. In addition, this protrusion 53 can also be formed, for example in four places.

In addition to the above, the gap forming engagement portion 50 using the two green compacts 5A and 5B can have various configurations.
Specifically, as shown in FIGS. 4 and 5, the gap forming engagement portion 50 includes a plurality of protrusions 53 that protrude from the outer peripheral surface 510 of the axial one end 511 of the central core 51 and are inserted into the relay core 52A. It can also be set as the structure contact | abutted to the internal peripheral surface 521 in the hole 520. FIG.

  In addition, as shown in FIGS. 6 and 7, the gap forming engagement portion 50 includes a plurality of protrusions 53 that protrude from the outer peripheral surface 510 of the axial one end 511 of the central core 51 in the insertion hole 520 of the relay core 52A. A structure in which a plurality of protrusions 53 protruding from the inner peripheral surface 521 of the insertion hole 520 of the relay core 52A are brought into contact with the outer peripheral surface 510 of the axial one end 511 of the central core 51 while being in contact with the inner peripheral surface 521. It can also be. Then, the protrusions 53 are formed at two opposite positions on the outer peripheral surface 510 of the central core 51, and the inner peripheral surface 521 of the relay core 52 is opposed to each other with a 90 ° phase shift from the protrusion 53 of the central core 51. The protrusions 53 can be formed at two locations.

  As shown in FIG. 8, when the plurality of protrusions 53 are formed on the relay core 52 </ b> A, the first protrusion 53 </ b> A that is one of the plurality of protrusions 53 in the relay core 52 </ b> A is the remaining protrusion 53. A locking recess 54 that locks the first protrusion 53A can be formed at a position opposite to the outer peripheral surface 510 of the central core 51 that has a protruding height larger than the two protrusions 53B and faces the first protrusion 53A. . Then, by locking the first protrusion 53A in the locking recess 54, it is possible to prevent rotation in the circumferential direction between the two green compacts 5A and B. Thereby, it can prevent that the center core 51 and the relay core 52 perform position shift in the circumferential direction.

As shown in FIG. 9, when the plurality of protrusions 53 are formed on the central core 51, the first protrusion 53 </ b> A that is one of the plurality of protrusions 53 in the central core 51 is the remaining protrusion 53. The protrusion height can be made larger than that of the two protrusions 53B, and a locking recess 54 for locking the first protrusion 53A can be formed at an opposing portion of the outer peripheral surface 510 of the relay core 52A that faces the first protrusion 53A. . Further, when the protrusions 53 are formed on the center core 51 and the relay core 52A, the first protrusions 53A and the locking recesses 54 can be formed in the same manner.
Although illustration is omitted, the central core 51 and the relay core 52B disposed at the other axial end 512 of the central core 51 can be connected after molding without being integrally molded. Also in this case, one of the two green compacts 5A can be used as the central core 51, and the other 5B can be used as the relay core 52A arranged at one end 511 in the axial direction of the central core 51.

As shown in FIG. 3, the ignition coil 1 of this example is of a stick type in which a coil portion 2 including a primary coil 21 and a secondary coil 22 is disposed and used in a plug hole of an engine (cylinder head cover). .
The primary coil 21 is wound around the outer periphery of a primary spool 211 made of a thermoplastic resin having an annular cross section. The secondary coil 22 uses an electric wire having a diameter smaller than that of the primary coil 21, and is wound around the outer periphery of the secondary spool 221 made of a thermoplastic resin having an annular cross section with a number of turns greater than the number of turns of the primary coil 21. Turn. The primary coil 21, the secondary coil 22, the center core 51, and the outer core 23 are accommodated in a coil case 31 made of a thermoplastic resin.

  As shown in the figure, the high voltage side end of the coil case 31 is made of a thermoplastic resin having an annular cross section, and a high voltage terminal 42 connected to the high voltage side end 225 of the secondary coil 22 is provided. A high voltage tower 33 accommodated therein is connected. The high voltage tower 33 is made of an insulating rubber having an annular cross section, and is attached with a plug mounting member 34 for mounting a spark plug. On the inner peripheral side of the high voltage tower 33, a spring 43 that contacts the terminal portion at the tip of the insulator portion of the spark plug mounted on the inner peripheral side of the plug mounting member 34 is disposed in a state of being in conduction with the high voltage terminal 42. It is.

As shown in FIG. 3, a connector case portion 32 for attaching a connector connection portion 321 for electrically connecting the ignition coil 1 to an ECU (electronic control unit) of the engine is formed at the low voltage side end portion of the coil case 31. It is. An igniter 41 having a power control circuit is disposed in the connector case portion 32 of this example.
Further, the gap in the ignition coil 1, that is, the gap in the space surrounded by the connector case portion 32, the coil case 31 and the high voltage tower 33 is filled with the filler 11 made of thermosetting resin.

In addition, since the central core 51 of this example is configured by the soft magnetic body 5, irregularities such as edges are not formed on the outer peripheral surface 510 of the central core 51. Therefore, in order to prevent the filler 11 from cracking, a resin or rubber tape or tube disposed on the outer periphery of the central core 51 can be eliminated.
Moreover, the axial direction one end part 511 side of the center core 51 of this example was arrange | positioned at the spark plug side. On the other hand, the axial direction other end part 512 side of the center core 51 can also be arrange | positioned at the spark plug side.

In addition to the above, the ignition coil 1 to which the central core 51 and the relay core 52 configured from the soft magnetic body 5 are applied can have various configurations.
For example, the ignition coil 1 can have a shape in which the coil portion 2 is disposed outside the plug hole as shown in FIG.

  Further, as shown in FIG. 11, the ignition coil 1 is a rectangular type in which the primary coil 21 and the secondary coil 22 are arranged outside the plug hole of the engine (cylinder head cover) (perpendicular to the axial direction of the plug hole). It can also be. In this case, as shown in FIG. 12, the relay cores 52 </ b> A and 52 </ b> B do not need to have an annular shape or a disk shape protruding toward the entire circumference of the central core 51, but from a part in the circumferential direction of the central core 51. It can be formed in a shape protruding outward. Moreover, the outer periphery core 23 can be formed in the cross-section circular arc shape along the circular arc part in the outer peripheral surface of relay core 52A, B. As shown in FIG.

  In the ignition coil 1 of this example, when a current is passed through the primary coil 21 by a pulsed spark generation signal from the ECU, a magnetic field that passes through the central core 51, the relay cores 52A and 52B, and the outer peripheral core 23 is formed. . Next, when the current flowing through the primary coil 21 is interrupted, a voltage is generated in the primary coil 21 by the self-induction action, and a high-voltage induced electromotive force is generated in the secondary coil 22 by the mutual induction action. A spark can be generated between a pair of electrodes in the attached spark plug. In addition, since the air gap 501 is formed between the axial one end 511 of the central core 51 and the relay core 52A, the magnetic flux is closed in the closed magnetic circuit formed by the central core 51, the relay cores 52A and 52B, and the outer peripheral core 23. A decrease in magnetic energy due to saturation can be suppressed.

The soft magnetic body 5 for the ignition coil in this example is formed by connecting the two green compacts 5A and B as described above, and is engaged with each other at a connecting portion of the two green compacts 5A and 5B. A gap forming engagement portion 50 for forming an air gap 501 having a size is provided. Thereby, the soft magnetic body 5 of this example can always form the air gap 501 of a fixed size by connecting the two green compacts 5A and 5B.
The air gap 501 can be formed stably before the soft magnetic body 5 is assembled to the ignition coil 1. Therefore, it is possible to prevent variation in the size of the air gap 501 for each ignition coil 1 using the soft magnetic body 5.
Therefore, according to the soft magnetic body 5 for the ignition coil of this example, it is possible to stably form the air gap 501 having a certain size without variation for each product.

(Example 2)
In this example, the gap forming engagement portion 50 is formed at an intermediate portion in the axial direction of the central core 51.
As shown in FIGS. 13 and 14, one of the two green compacts 5A of this example is formed by integrally molding a part of the central core 51 and a relay core 52A disposed at one end 511 in the axial direction of the central core 51. The other 5B is formed by integrally molding the remaining portion of the central core 51 and the relay core 52B disposed at the other axial end portion 512 of the central core 51. The gap forming engagement portion 50 of this example is formed on the axial projection 55 formed on the axial center side end surface 513 in a part of the central core 51 and the axial center side end surface 513 in the remaining portion of the central core 51. By engaging the formed axial recess 56, the air gap 501 can be formed between the center side end faces 513.

As shown in FIGS. 13 and 14, the axial protrusion 55 of this example is formed at the center in the cross-sectional direction of the center side end surface 513 in a part of the central core 51, and the axial recess 56 is formed on the central core 51. The remaining portion is formed at the center of the center side end surface 513. Further, the axial protrusion 55 and the axial recess 56 can be formed in various shapes. For example, as shown in FIGS. 15 and 16, the axial protrusion 55 protrudes in a flat plate shape, and the axial recess is formed. 56 can be formed in a groove shape to engage with the flat plate-like axial protrusion 55.
Also in this example, other configurations are the same as those of the first embodiment, and the same effects as those of the first embodiment can be obtained.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective explanatory view showing two green compacts constituting a soft magnetic body for an ignition coil in Example 1. Sectional explanatory drawing which shows the state which connected the two compacts in Example 1, and formed the air gap. Sectional explanatory drawing which shows the ignition coil in Example 1. FIG. The perspective explanatory drawing which shows the other two green compacts which comprise the soft-magnetic body for ignition coils in Example 1. FIG. Sectional explanatory drawing which shows the state which connected the other two green compacts in Example 1, and formed the air gap. The perspective explanatory drawing which shows the other two green compacts which comprise the soft-magnetic body for ignition coils in Example 1. FIG. Sectional explanatory drawing which shows the state which connected the other two green compacts in Example 1, and formed the air gap. Cross-sectional explanatory drawing which shows the state which connected the other two green compacts in Example 1, and formed the air gap, and stopped these circumference directions. Cross-sectional explanatory drawing which shows the state which connected the other two green compacts in Example 1, and formed the air gap, and stopped these circumference directions. Sectional explanatory drawing which shows the other ignition coil in Example 1. FIG. Sectional explanatory drawing which shows the other ignition coil in Example 1. FIG. FIG. 3 is a perspective explanatory view showing two green compacts constituting a soft magnetic body for another ignition coil in the first embodiment. The perspective explanatory view which shows the two compacts which comprise the soft-magnetic body for ignition coils in Example 2. FIG. Side surface explanatory drawing which shows the state which connected the two compacts in Example 2, and formed the air gap. The perspective explanatory drawing which shows the other two green compacts which comprise the soft-magnetic body for ignition coils in Example 2. FIG. Side surface explanatory drawing which shows the state which connected the other two green compacts in Example 2, and formed the air gap.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Ignition coil 2 Coil part 21 Primary coil 22 Secondary coil 23 Outer core 31 Coil case 5 Soft magnetic body 5A, B Compact 50 Gap formation engaging part 501 Air gap 51 Central core 510 Outer peripheral surface 511 One axial end part 512 Axial other end 52A, B Relay core 521 Inner peripheral surface 53 Protrusion 53A First protrusion 53B Second protrusion 54 Locking recess 55 Axial protrusion 56 Axial recess

Claims (9)

A soft magnetic material constituting a part of a closed magnetic circuit of an ignition coil including a primary coil and a secondary coil,
The soft magnetic body is formed by connecting two green compacts formed by compressing soft magnetic powder,
A soft magnetic body for an ignition coil, characterized in that a gap forming engagement portion that engages with each other to form an air gap of a certain size is provided at a connecting portion of the two green compacts. 2. The soft magnetic body according to claim 1, wherein the soft magnetic body is disposed on the inner peripheral side of the primary coil and the secondary coil, and the axial end of the central core is disposed on the outer peripheral side of the primary coil and the secondary coil. And a relay core for relaying to the outer peripheral core
One of the two green compacts is the central core, and the other is the relay core disposed at one axial end of the central core. 2. The soft magnetic body according to claim 1, wherein the soft magnetic body is disposed on the inner peripheral side of the primary coil and the secondary coil, and the axial end of the central core is disposed on the outer peripheral side of the primary coil and the secondary coil. And a relay core for relaying to the outer peripheral core
One of the two green compacts is formed by integrally molding the central core and the relay core disposed at the other axial end of the central core, and the other is formed at one axial end of the central core. A soft magnetic body for an ignition coil which is the relay core to be disposed.   4. The gap forming engagement portion according to claim 2, wherein the gap forming engagement portion is configured to abut a plurality of protrusions that protrude from an inner peripheral surface of the relay core on an outer peripheral surface of one axial end portion of the central core. A soft magnetic material for an ignition coil characterized by   4. The gap forming engagement portion according to claim 2, wherein the gap forming engagement portion is configured to abut a plurality of protrusions formed to protrude from an outer peripheral surface of one axial end portion of the central core to an inner peripheral surface of the relay core. A soft magnetic material for an ignition coil characterized by   4. The gap forming engagement portion according to claim 2, wherein the gap forming engagement portion has a plurality of protrusions formed to protrude from an outer peripheral surface of one axial end portion of the central core in contact with an inner peripheral surface of the relay core, and the center. A soft magnetic body for an ignition coil, wherein a plurality of protrusions that protrude from an inner peripheral surface of the relay core are brought into contact with an outer peripheral surface of one end portion in the axial direction of the core.   The latch which latches the said protrusion in the opposing part of the outer peripheral surface of the said center core or the inner peripheral surface of the said relay core which opposes at least 1 of these protrusions in any one of Claims 2-6 A soft magnetic body for an ignition coil, wherein a recess is formed, and the locking recess is used to prevent rotation of the two green compacts in the circumferential direction. 2. The soft magnetic body according to claim 1, wherein the soft magnetic body is disposed on the inner peripheral side of the primary coil and the secondary coil, and the axial end of the central core is disposed on the outer peripheral side of the primary coil and the secondary coil. An outer peripheral core and a relay core for relaying,
One of the two green compacts is formed by integrally molding a part of the central core and the relay core disposed at one axial end of the central core, and the other is the remaining part of the central core and the remaining part of the central core. A soft magnetic body for an ignition coil, which is integrally formed with the relay core disposed at the other axial end of the central core.   9. The gap forming engagement portion according to claim 8, wherein the gap forming engagement portion includes an axial protrusion formed on an axially central end surface of a part of the central core, and an axially formed axial end surface of the remaining part of the central core. A soft magnetic body for an ignition coil, wherein the air gap is formed between the center side end faces by engaging a directional recess.

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