JP5212329B2 - Ignition coil manufacturing method - Google Patents

Description

The present invention relates to a method for manufacturing an ignition coil used for generating a spark in a combustion chamber in an internal combustion engine such as an engine.

An ignition coil used for an internal combustion engine has a primary core arranged on the inner and outer circumferences and a soft magnetic central core on the inner circumference side of the secondary coil, and the central core when the energization to the primary coil is cut off. Due to the change of the passing magnetic flux, a high voltage is generated in the secondary coil, and a spark is generated from the spark plug. The central core may be formed by laminating electromagnetic steel sheets, or may be formed by compression molding a powder material.
For example, in the ignition coil of Patent Document 1, electromagnetic steel plates are stacked to form a central core. Then, a centering recess is provided in the center core so that the cap covering the end of the center core and the spool wound with the coil do not come into contact with each other. Are disclosed.

JP 2004-128191 A

  However, in patent document 1, the alignment recessed part is only provided for the purpose of the alignment of the center core formed by laminating electromagnetic steel sheets. Therefore, when forming a central core by compression molding a dust material, further improvements are required to improve the magnetic performance of the central core and increase the energy generated in the secondary coil of the ignition coil. Is done.

The present invention has been made in view of such conventional problems, and in the case of forming a central core by compression molding a dust material, the magnetic performance of the central core is improved and the secondary coil of the ignition coil is improved. An object of the present invention is to provide a method for manufacturing an ignition coil capable of increasing the energy to be generated.

In the present invention, a primary coil and a secondary coil arranged on the inner and outer circumferences, and a soft magnetic central core arranged on the inner circumference side of the primary coil and the secondary coil are arranged in the case. In the method of manufacturing an ignition coil, the gap is filled with an insulating fixing resin, the primary coil is arranged on the inner peripheral side of the secondary coil, and the primary coil is directly wound around the central core .
When the dust core material is disposed between a pair of compression molds having convex portions, the pair of compression molds are relatively moved to compress the powder dust material, and the central core is formed.
The distance between the end faces of the compression-type convex portions is shorter than the distance between the peripheral end surfaces where the convex portions are not formed,
The length before compression of the dust material at the central portion corresponding to the convex portion of the compression mold is A1, the length after compression of the dust material at the central portion is A2, and the end surface around the convex portion of the compression mold The compression ratio of the central part (A1-A2) where B1 is the length before compression of the dust material in the remaining part corresponding to 1 and B2 is the length after compression of the dust material in the remaining part / A1 is larger than the compression ratio (B1-B2) / B1 of the remaining part,
Due to the compression type convex portion, in the axial direction of the central core through which the magnetic flux from the primary coil passes, the high voltage side end face located on the high voltage side of the secondary coil and the low voltage side of the secondary coil Forming a recess for increasing the molding density near the center in the axial direction of the central core at the axial center position of the low-voltage side end face located ;
In the method of manufacturing an ignition coil, the concave portion in the high voltage side end face is formed at an inner peripheral side position of a portion where the primary coil is not wound at the high voltage side end portion of the central core. (Claim 1).

The ignition coil of the present invention is configured using a central core (hereinafter, referred to as a “powder center core”) formed by compression molding a dust material.
The dust core core of the present invention is formed by forming a recess at the axial center position in at least one of the high voltage side end face and the low voltage side end face in the axial direction. Thereby, the dust core core of the present invention can increase the molding density in the vicinity of the middle in the axial direction as compared with a conventional dust core core that does not have a recess, and the entire dust core core is molded. The density can also be increased.

By the way, in the conventional dust core core, when the dust material is compression-molded from both sides in the axial direction using a pair of compression molds, the molding density near the center in the axial direction is the molding density near the remaining end. It is considered to be lower than
On the other hand, the dust core core of the present invention, in particular, compresses the dust material using the compression mold provided with the convex portions, thereby increasing the amount of the dust material in the axial direction by the convex portions of the compression mold. It can be collected near the middle. And a recessed part is formed in the end surface of a compacting center core by the convex part of a compression type, and the fall of the molding density near the center of the axial direction in a compacting center core can be suppressed. Therefore, the molding density of the whole dust core can be increased, and the magnetic performance of the dust core can be improved by increasing the molding density of the dust center core.

  Therefore, according to the ignition coil of the present invention, when the dust core material is compression molded to form the central core, the magnetic performance of the central core is improved and the energy generated in the secondary coil of the ignition coil is increased. Can be made.

Cross-sectional explanatory drawing which shows the ignition coil in an Example. Cross-sectional explanatory drawing which shows the center core which wound the primary coil in the Example directly. Cross-sectional explanatory drawing which shows the state which attached the ignition coil to the engine in an Example. The graph which shows the relationship of both taking the length of the compact center core on the horizontal axis and taking the forming density on the vertical axis in the examples. In the Example, the horizontal axis represents the molding density and the vertical axis represents the secondary energy, showing the relationship between the two. Cross-sectional explanatory drawing which shows the state which compression-molds a center core with a pair of compression type | mold in an Example.

A preferred embodiment of the present invention described above will be described.
In the present invention, the axial center position means a central position in a cross section perpendicular to the axial direction of the central core. In particular, when the central core has a circular cross section, the axial center position means the circular center position.
The said powder compact material can be comprised from iron-type powder provided with insulating coatings, such as resin, and can use Fe-Si type alloy powder etc. as iron-type powder, for example. Moreover, the powdered material can contain a binder with respect to the iron-based powder.

In the cross section perpendicular to the axial direction, the ratio X / S × 100 (%) of the cross-sectional area X of the recess to the cross-sectional area S of the general part of the central core is preferably 2 to 10%. (Claim 2).
When the ratio X / S × 100 (%) of the cross-sectional area is less than 2%, there is a possibility that the molding density in the vicinity of the center in the axial direction of the central core cannot be improved due to the formation of the concave portion. When the cross-sectional area ratio X / S × 100 (%) is more than 10%, the cross-sectional area in the cross-section of the central core decreases due to the formation of the recess, and the area through which the magnetic flux passes decreases. Conversely, the magnetic performance of the central core may be reduced.

The ratio D / L × 100 (%) of the axial depth D of the recess to the axial length L of the central core is preferably 3 to 15%.
When the ratio D / L × 100 (%) of the axial depth is less than 3%, there is a possibility that the molding density in the vicinity of the center in the axial direction of the central core cannot be improved due to the formation of the concave portion. Moreover, when the ratio D / L × 100 (%) of the axial depth is more than 15%, there is a possibility that the hollow portion in the central core increases, and conversely the magnetic performance of the central core decreases. is there.

Moreover, the said recessed part is formed in both the said high voltage side end surface and the said low voltage side end surface .
Thereby , the center core alignment (center positioning) at the time of assembling the ignition coil can be performed using the recesses on both axial sides.

The primary coil is directly wound around the central core, and the recess formed in the high-voltage side end face is a portion of the central core where the primary coil is not wound at the high-voltage side end. It is formed at the inner peripheral side position .
Thereby , a recessed part will be formed in the site | part of the central core in which the primary coil is not wound, and it can prevent that the magnetic performance of a central core falls by formation of a recessed part.

Embodiments of the ignition coil according to the present invention will be described below with reference to the drawings.
As shown in FIG. 1, the ignition coil 1 of this example includes a primary coil 21 and a secondary coil 22 that are arranged on the inner and outer circumferences, and a soft magnetic center that is arranged on the inner circumference side of the primary coil 21 and the secondary coil 22. The core 4 is disposed in the case 3, and a gap in the case 3 is filled with an insulating fixing resin 15.
As shown in FIG. 2, the central core 4 is formed by compressing the dust material 40 and is located on the high voltage side of the secondary coil 22 in the axial direction C in which the magnetic flux from the primary coil 21 passes. Concave portions 43 </ b> A and 43 </ b> B are formed at axial center positions of the side end surface 41 and the low voltage side end surface 42 located on the low voltage side of the secondary coil 22.

Hereinafter, the ignition coil 1 of this example will be described in detail with reference to FIGS.
As shown in FIG. 3, the ignition coil 1 of this example is used for an engine as an internal combustion engine, and is placed in a lateral state (the plug hole 83 of the plug hole 83) outside the plug hole 83 of the engine (cylinder head 81 and cylinder head cover 82). The primary coil 21 and the secondary coil 22 are arranged and used in a state in which the axial directions of the primary coil 21 and the secondary coil 22 are orthogonal to the axial direction. The ignition coil 1 of this example is attached to the spark plug 7 disposed in the plug hole 83 of the engine, and the coil main body 11 in which the primary coil 21, the secondary coil 22, the central core 4 and the like are disposed is connected to the plug hole 83. It is used by placing it outside in a horizontal state.

As shown in FIG. 1, on the outer side of the central core 4, the primary coil 21 and the secondary coil 22, there are inner surfaces on the end surfaces (the high voltage side end surface 41 and the low voltage side end surface 42) on both sides in the axial direction C of the central core 4. The soft magnetic outer core 45 having a frame shape is disposed in a state where the two are opposed to each other. The outer peripheral core 45 is disposed in the case 3 so that the openings are positioned up and down. A permanent magnet 47 for improving the characteristics of the magnetic circuit formed by the center core 4 and the outer core 45, and a core gap are provided between the low-voltage side end face 42 of the center core 4 and the inner surface of the outer core 45. (Gap) 48 is provided.
The ignition coil 1 includes an igniter 12 formed by molding an electronic component with a resin. The igniter 12 includes a switching control circuit for energizing the primary coil 21 and interrupting the energization.

  The ignition coil 1 has a primary coil 21, a secondary coil 22, a central core 4, an outer core 45 and an igniter 12 disposed in a case 3 made of a thermoplastic resin, and an insulation fixing made of a thermosetting resin in the case 3. The resin 15 is filled and each component is fixed in an insulated state. When the ignition coil 1 is assembled, the recesses 43A and 43B are formed on the high-voltage side end surface 41 and the low-voltage side end surface 42 of the central core 4, and thus the pair of recesses 43A and 43B are used for ignition. The center core 4 can be aligned (centered) when the coil 1 is assembled.

As shown in FIG. 1 and FIG. 3, the case 3 includes a tower portion 31 for arranging a high voltage terminal 23 conducted to a high voltage side winding end portion of the secondary coil 22, and a conductive terminal in the igniter 12. A connector portion 32 for connecting to an external device such as an ECU (electronic control unit) and an attachment portion 33 for attaching the ignition coil 1 to the engine are formed to project.
A rubber plug cap 61 is attached to the tower portion 31, and an insulator portion 71 of the spark plug 7 is attached to the plug cap 61. On the inner peripheral side of the plug cap 61, the terminal portion 72 of the spark plug 7 is connected to the high voltage terminal 23 via the coil spring 62.

  As shown in FIG. 2, the primary coil 21 of this example is formed by winding a magnet wire having an insulating coating directly around the outer periphery of the central core 4. Further, the secondary coil 22 is wound around the resin spool 221 on the outer peripheral side of the primary coil 21 with a magnet wire thinner than the magnet wire forming the primary coil 21 with a greater number of turns than the primary coil 21. Formed.

  The concave portion 43 </ b> A formed in the high voltage side end face 41 is formed at the inner peripheral side position of the non-winding portion 44 around which the primary coil 21 is not wound at the high voltage side end portion of the central core 4. The high-voltage side end face 41 in the non-winding portion 44 protrudes from the axial end face 211 of the primary coil 21 by a predetermined length. And the axial direction depth D1 of the recessed part 43A formed in the high voltage side end surface 41 is shallower (shorter) than the predetermined length L1 from which the non-winding part 44 protrudes. As a result, the recess 43A is formed in the non-winding portion 44 of the central core 4 around which the primary coil 21 is not wound, and the magnetic performance of the central core 4 is reduced due to the formation of the recess 43A. Can be prevented.

In addition, a flange 420 that secures an area where the permanent magnets 47 are arranged to face each other is formed at the low voltage side end of the central core 4. The low voltage side end face 42 of this example is formed as an end face of the flange 420.
The recess 43B formed in the low voltage side end face 42 is formed up to the inner peripheral side position of the portion where the primary coil 21 is wound at the low voltage side end of the central core 4. However, since the core gap (gap) 48 exists adjacent to the low voltage side end face 42, the magnetic permeability in the vicinity of the low voltage side end face 42 is originally small, and the magnetic performance is large even if the recess 43 B exists. There is no effect.

Further, as shown in FIG. 2, in the cross section orthogonal to the axial direction C, the ratio X1 / S × 100 (%) of the cross-sectional area X1 of the recess 43A in the high-voltage side end face 41 with respect to the cross-sectional area S of the general part of the central core 4 ) Is 2 to 10%, and the ratio X2 / S × 100 (%) of the cross-sectional area X2 of the recess 43B in the low-voltage side end face 42 with respect to the cross-sectional area S of the general part of the central core 4 is also 2 to 10%. %It has become. The ratio D1 / L × 100 (%) of the axial depth D1 of the recess 43A in the high-voltage side end face 41 with respect to the axial length L of the central core 4 is 3 to 15%. The ratio D2 / L × 100 (%) of the axial depth D2 of the recess 43B on the low voltage side end face 42 with respect to the axial length L is also 3 to 15%.
When the above X1, X2, D1, and D2 satisfy each condition, the molding density near the center in the axial direction C of the central core 4 can be increased, and the overall molding density of the central core 4 can also be increased. .

  In the ignition coil 1 of this example, when the primary coil 21 is energized by the operation of the switching control circuit of the igniter 12 according to a command from the ECU, a magnetic field passing through the central core 4 and the outer core 45 is formed. Next, when the energization of the primary coil 21 is cut off, a high voltage induced electromotive force is generated in the secondary coil 22 due to the mutual induction action, and a spark is generated between the pair of electrodes 73 in the spark plug 7 attached to the ignition coil 1. Can be generated.

The ignition coil 1 of this example is configured by using a central core 4 (hereinafter referred to as a “powder center core 4”) formed by compression molding a dust material 40. In FIG. 4, the horizontal axis represents the length (mm) of the green compact core, and the vertical axis represents the molding density (g / cm ³ ).
As shown in the figure, in the conventional dust core core, when the dust material 40 is compression molded from both sides in the axial direction using a pair of compression molds, the molding density in the vicinity of the middle in the axial direction C remains. It turned out that it becomes low compared with the molding density near the end. In the figure, the forming density of the conventional powder compact core is shown by a solid line.
On the other hand, the dust core core 4 of this example is formed with recesses 43A and 43B at axial center positions on the high-voltage side end face 41 and the low-voltage side end face 42 in the axial direction C, respectively. Thereby, the green compact core 4 of this example can make the molding density near the center in the axial direction C higher than the conventional green powder core that does not form the recesses 43A and 43B. The overall molding density of the central core 4 can also be increased. In the figure, the molding density of the green compact core 4 of this example is indicated by a broken line.

As can be seen from the figure, in the conventional green compact core, the molding density in the vicinity of the center E of about 50% in the axial direction C with respect to the total length L is lower than in other parts. On the other hand, in the green compact core 4 of the present example, the molding density in the vicinity of the middle E can be brought close to the molding density of other parts.
In the present example, the center vicinity E of the central core 4 refers to a portion excluding a range of about 15% from both ends in the axial direction C.

FIG. 5 shows the relationship between the horizontal axis with the molding density (g / cm ³ ) and the vertical axis with the secondary energy (energy generated in the secondary coil 22) (mJ). As shown in the figure, the green compact core b of the present example in which the concave portions 43A and 43B are formed is increased with respect to the conventional green compact core a in which the concave portions 43A and 43B are not formed. Secondary energy can also be increased.

In addition, the pair of recesses 43 </ b> A and 43 </ b> B in the dust core core 4 of this example is formed when the dust material 40 is compression-molded using the compression mold 5 having the protrusions 51.
As shown in FIG. 6, when compressing the dust core core 4, the dust material 40 is disposed between the pair of compression dies 5 having the convex portions 51, and the pair of compression dies 5 are moved relative to each other. Compression molding. At this time, the distance between the front end surfaces 511 of the convex portions 51 in the compression mold 5 is shorter than the distance between the peripheral end surfaces 512 where the convex portions 51 are not formed. The dust material 40 located in the corresponding central part 401 is in a state where it is more easily compressed than the remaining part 402.

That is, the length before compression of the dust material 40 at the central portion 401 corresponding to the convex portion 51 of the compression mold 5 is A1, and after the compression of the dust material 40 at the central portion 401 corresponding to the convex portion 51 of the compression die 5 A2 is the length A2, the length before compression of the dust material 40 in the remaining portion 402 corresponding to the peripheral end surface 512 of the convex portion 51 of the compression mold 5 is B1, and the peripheral end surface of the convex portion 51 of the compression mold 5 When the length after compression of the dust material 40 in the remaining part 402 corresponding to 512 is B2, the compression ratio (A1-A2) / A1 of the central part 401 is set to the compression ratio (B1- B2) / B1 can be made larger.
Thereby, when the compacting material 40 is compression-molded by using the compression mold 5 provided with the convex portions 51, the convex portions 51 can collect more dust material 40 near the middle in the axial direction C. And the recessed part 43A, 43B is formed in the end surface of the compacting center core 4 by the convex part 51 of the compression mold | type 5, and the fall of the molding density near the center of the axial direction C in the compacting center core 4 can be suppressed. Therefore, the molding density of the whole dust core core 4 can be increased, and the magnetic performance of the dust core core 4 can be improved due to the high molding density of the dust core core 4.

Moreover, in the dust core core 4 of this example, the usage-amount (material cost) of the dust material 40 of the volume corresponding to the convex part 51 of the compression type | mold 5 can be reduced. Moreover, by forming the concave portions 43A and 43B by compression molding the compacted material 40, the concave portions 43A and 43B can be easily formed as compared with a laminated core in which electromagnetic steel sheets are laminated.
Therefore, according to the ignition coil 1 of this example, when the dust material 40 is compression-molded to form the dust core core 4, the magnetic performance of the dust core core 4 is improved. The energy generated in the secondary coil 22 can be increased.

DESCRIPTION OF SYMBOLS 1 Ignition coil 15 Insulation fixing resin 21 Primary coil 22 Secondary coil 3 Case 4 Center core 41 High voltage side end surface 42 Low voltage side end surface 43A, 43B Concave part 5 Compression type 51 Convex part C Axial direction

Claims (3)

A primary coil and a secondary coil arranged on the inner and outer circumferences, and a soft magnetic central core arranged on the inner circumference side of the primary coil and the secondary coil are arranged in the case, and are insulated and fixed in a gap in the case. In the method of manufacturing an ignition coil, in which the primary coil is disposed on the inner peripheral side of the secondary coil, and the primary coil is directly wound around the central core .
When the dust core material is disposed between a pair of compression molds having convex portions, the pair of compression molds are relatively moved to compress the powder dust material, and the central core is formed.
The distance between the end faces of the compression-type convex portions is shorter than the distance between the peripheral end surfaces where the convex portions are not formed,
The length before compression of the dust material at the central portion corresponding to the convex portion of the compression mold is A1, the length after compression of the dust material at the central portion is A2, and the end surface around the convex portion of the compression mold The compression ratio of the central part (A1-A2) where B1 is the length before compression of the dust material in the remaining part corresponding to 1 and B2 is the length after compression of the dust material in the remaining part / A1 is larger than the compression ratio (B1-B2) / B1 of the remaining part,
Due to the compression type convex portion, in the axial direction of the central core through which the magnetic flux from the primary coil passes, the high voltage side end face located on the high voltage side of the secondary coil and the low voltage side of the secondary coil Forming a recess for increasing the molding density near the center in the axial direction of the central core at the axial center position of the low-voltage side end face located ;
The method of manufacturing an ignition coil according to claim 1, wherein the concave portion in the high voltage side end face is formed at an inner peripheral side position of a portion where the primary coil is not wound at the high voltage side end portion of the central core .   2. The method of manufacturing an ignition coil according to claim 1, wherein a ratio X / S × 100 (%) of a cross-sectional area X of the concave portion with respect to a cross-sectional area S of the general portion of the central core in a cross section orthogonal to the axial direction. Is set to 2 to 10%, the manufacturing method of the ignition coil characterized by the above-mentioned.   3. The method of manufacturing an ignition coil according to claim 1, wherein a ratio D / L × 100 (%) of the axial depth D of the recess to the axial length L of the central core is 3 to 15%. A method for manufacturing an ignition coil.

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