JP6489267B2 - Ignition coil for internal combustion engine - Google Patents

Description

  The present invention relates to an ignition coil used in an internal combustion engine (engine), and more particularly to a heat dissipation technique for the ignition coil.

In recent years, for the purpose of improving the ignitability of an engine such as lean combustion for which fuel efficiency is reduced, various ignition devices that perform multiple ignition with an ignition plug, ignition devices that continue spark discharge, and the like have been developed. These techniques increase the load on the ignition coil, and as a result, the amount of heat generated by the ignition coil tends to increase in recent years.
When the amount of heat generated by the ignition coil increases, it is necessary to improve the heat dissipation of the ignition coil. Therefore, it is conceivable to provide a heat sink for heat dissipation in the ignition coil.

A technique disclosed in Patent Document 1 is known as a technique for providing a heat sink for heat dissipation in an ignition coil.
However, the heat sink disclosed in Patent Document 1 is for heat dissipation of an igniter (a circuit unit that switches between energization and deenergization of the primary coil) assembled in the ignition coil, and “the primary coil and the secondary coil are wound. Does not improve the heat dissipation of the coil winding body.

Therefore, unlike the technique of Patent Document 1, it is conceivable to provide a heat sink in the ignition coil for the purpose of improving the heat dissipation of the coil winding body.
However, when the outer core and the heat sink are thermally expanded and contracted with the heat generation of the ignition coil, there is a concern that thermal stress acts on the filling resin filled in the case of the ignition coil, and the filling resin cracks.
When a crack occurs in the filling resin, there is a concern that the crack reaches the coil winding body. When the crack reaches the coil winding body, the high voltage generated in the secondary coil leaks inside, and the high voltage cannot be supplied to the spark plug.

Japanese Patent Laid-Open No. 10-331753

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a highly reliable ignition coil for an internal combustion engine in which the heat dissipation of the ignition coil is improved and the filling resin does not crack.

  The ignition coil for an internal combustion engine of the present invention can increase the heat radiation amount from the surface of the case to the outside by providing a wide heat sink between the outer core and the case. Thereby, the heat dissipation of a coil winding body can be improved and it can respond even if it is a case where the load of an ignition coil increases.

Further, since the outer core and the heat sink are disposed outside the holder, even if the outer core and the heat sink are thermally expanded and contracted, the holder can prevent the influence of the thermal expansion and contraction force from reaching the filling resin. Thereby, even if the outer peripheral core and the heat sink are thermally expanded and contracted with the heat generation of the ignition coil, cracking of the filled resin can be prevented, and the reliability of the ignition coil can be improved. Furthermore, by configuring the outer core and the heat sink as separate bodies, the degree of freedom in the shape of the heat sink is increased, and the thermal conductivity can be set higher than that of the outer core, and a heat sink having an optimum heat radiation area is provided. be able to.
The holder is provided with an inner groove for assembling the outer peripheral core and an outer groove for assembling the heat sink.

(Example 1) which is principal part sectional drawing of the ignition coil for internal combustion engines. 1 is an exploded view of an ignition coil for an internal combustion engine (Example 1). FIG. (Example 2) which is principal part sectional drawing of the ignition coil for internal combustion engines. (Example 2) which is an exploded view of the ignition coil for internal combustion engines. (Example 3) which is principal part sectional drawing of the ignition coil for internal combustion engines. (Example 3) which is an exploded view of the ignition coil for internal combustion engines.

  Hereinafter, “DETAILED DESCRIPTION OF THE INVENTION” will be described in detail.

  A specific example (example) of the present invention will be described with reference to the drawings. The following “Example” discloses a specific example, and it goes without saying that the present invention is not limited to the “Example”.

[Example 1]
A first embodiment will be described with reference to FIGS.
The ignition coil in the first embodiment is used for an engine whose fuel consumption is reduced by lean combustion or the like. Specifically, (i) the ignition plug performs multiple ignition to “igniter that can improve ignitability”, or (ii) spark discharge generated by main ignition is continued for an arbitrary period. It is used for an “ignition device capable of improving ignitability” and the like, and has a large calorific value of the ignition coil.

  The ignition coil shown in the first embodiment is used in a DI (abbreviation of direct ignition) type corresponding to each ignition plug of each cylinder, and is mounted independently for each plug hole of the engine. .

The ignition coil of this embodiment is
(A) a coil winding body 3 disposed in a state where the primary coil 1 and the secondary coil 2 are wound around the central core;
(B) a holder 4 disposed around the coil winding body 3;
(C) a laminated outer peripheral core 5 disposed on the outer surface of the holder 4;
(D) a heat sink 6 for heat dissipation disposed on the outer surface of the outer peripheral core 5 and wider than the thickness dimension of the outer peripheral core 5 in the stacking direction;
(E) a case 7 for accommodating a coil accommodation including a coil winding body 3, a holder 4, an outer peripheral core 5, and a heat sink 6;
(F) a filling resin 8 filling the internal space α of the case 7 in which the coil housing is assembled;
It is configured with.
In the following description, for convenience of explanation, “up and down direction in FIG. 1” is described as “height direction” or “up and down direction” (of course, there is no limitation).

The primary coil 1 is obtained by winding a primary electric wire around a central core. Alternatively, a primary electric wire is wound around a resin primary spool mounted on the outer periphery of the central core.
The secondary coil 2 is obtained by winding a secondary electric wire around a resin-made secondary spool 2a attached to the outer periphery of the primary coil 1. The primary wire and the secondary wire are magnet wires with insulation coating on the surface, the secondary wire is thinner than the primary wire, and the number of turns of the secondary coil 2 is larger than the number of turns of the primary coil 1. It is.

  The central core is an iron core having, for example, a quadrangular prism shape disposed at the center of the primary coil 1 and the secondary coil 2, and is formed by laminating a number of electromagnetic steel plates.

The holder 4 is a frame disposed around the coil winding body 3 and is provided by a resin material (for example, thermoplastic resin: PP, PBT, etc.).
Here, as shown in FIG. 2, the ignition coil of this embodiment is provided with a connector 9 for external connection on the side surface of the case 7. For this reason, the holder 4 is provided in a U shape so as to surround the coil winding body 3 except for the surface on which the connector 9 is provided.
More specifically, the coil winding body 3 has a substantially rectangular shape when viewed from the height direction. Of the four surfaces around the coil winding body 3 viewed from the height direction, the connector is a connector. The holder 4 is provided in a U shape so as to surround three surfaces excluding the surface on which 9 is provided.

On the outer peripheral surface of the holder 4, an inner groove 4 a for assembling the outer core 5 and an outer groove 4 b for assembling the heat sink 6 are provided. The inner groove 4a is formed on the bottom surface of the outer groove 4b.
The depth dimension of the inner groove 4 a is provided so as to substantially coincide with the thickness dimension of the outer peripheral core 5. Further, the height dimension of the inner groove 4 a is provided so as to substantially coincide with the height dimension (plate width dimension) of the outer core 5.
The depth dimension of the outer groove 4 b is provided to substantially coincide with the thickness dimension of the heat sink 6. The height dimension of the outer groove 4b is provided so as to be substantially the same as the height dimension (plate width dimension) of the heat sink 6.
For this reason, in a state where the outer peripheral core 5 and the heat sink 6 are assembled to the holder 4, the holder 4 and the outer peripheral core 5 are substantially in close contact, and the outer peripheral core 5 and the heat sink 6 are substantially in close contact. Thereby, the heat inside the holder 4 is easily transmitted in the order of the holder 4 → the outer peripheral core 5 → the heat sink 6.

  Here, the thickness of the bottom surface of the inner groove 4 a and the inner surface of the holder 4 (thickness of the bottom portion of the inner groove 4 a) is provided thin as long as the strength of the holder 4 is maintained. That is, the heat of the coil winding body 3 (that is, the heat of the primary coil 1 and the secondary coil 2) is provided to be easily transmitted to the heat sink 6 through the outer core 5.

The outer peripheral core 5 is a substantially B-shaped iron core that is assembled around the coil winding body 3 in a state where it is assembled to the holder 4, and is formed by laminating a large number of electromagnetic steel sheets in the same manner as the central core.
As a specific example, the outer peripheral core 5 of this embodiment is divided into two in an L shape, and the outer periphery core 5 divided into two in an L shape is assembled to the outer surface (inner groove 4a) of the holder 4 so that coil winding is performed. It is provided in a square shape surrounding the wire body 3.

The heat sink 6 is provided separately from the outer peripheral core 5.
The heat sink 6 is assembled to the holder 4 in the same manner as the outer core 5, and is assembled in the case 7 in a state assembled to the holder 4.
The heat sink 6 is provided by a metal material excellent in heat conduction. In this embodiment, the heat sink 6 is provided by soft iron which is a ferromagnetic material.
The heat sink 6 is provided wider than the heat sink 6 for the purpose of improving heat dissipation, and the height dimension (band width dimension) of the heat sink 6 is set to the height dimension (band width dimension: stacking direction) of the outer core 5. Dimension).
The thickness of the heat sink 6 is set to such a thickness that heat can be easily transferred and a magnetic flux can be easily formed.
The heat sink 6 is provided in a shape that surrounds the periphery of the outer core 5. Specifically, the heat sink 6 has a U shape like the holder 4, and is formed in a U shape by, for example, pressing.

The case 7 is an ignition coil housing having a bottomed cup shape having an internal space α having a substantially rectangular parallelepiped shape, and is provided with a resin material (for example, thermoplastic resin: PP, PBT, etc.).
Above the case 7 is an opening of the internal space α, and coil accommodation (coil winding body 3, holder 4, outer core 5, heat sink 6 and the like) is incorporated into the internal space α from this opening.

  Here, the thickness of the case 7 at least in a portion facing the outer surface of the heat sink 6 is thin as long as the strength required for the case 7 is maintained. That is, the heat of the heat sink 6 is provided to be easily transmitted to the space around the case 7.

A cylindrical portion 7a extending downward is provided at the bottom of the case 7, and the cylindrical portion 7a is inserted into the plug hole with an insulating rubber (not shown) attached to the outer periphery. An output terminal that is electrically connected to one end of the secondary coil 2 is provided inside the cylindrical portion 7a, and this output terminal is electrically connected to a terminal fitting of the spark plug.
Further, a bolt insertion hole 7b extending in the vertical direction is formed on the outer surface of the case 7, and by fastening screws (bolts or the like) inserted into the bolt insertion hole 7b to the engine head cover, The connected ignition coil is fixed to the engine.

The filling resin 8 is a potting agent that fills the internal space α of the case 7 after incorporating the coil accommodation (the coil winding body 3, the holder 4, the outer core 5, the heat sink 6 and the like) into the internal space α of the case 7. In this embodiment, a thermosetting epoxy resin is used.
As described above, the coil winding body 3 accommodated in the case 7 can be insulated and sealed by filling the internal space α with the filling resin 8 after incorporating the coil accommodation in the internal space α of the case 7. .

  This embodiment includes a capacitor 10, a diode 11, and an igniter 12 in the coil housing. After being incorporated into the space α, the case 7 is sealed with the filling resin 8.

(Effect 1 of Example 1)
When the coil winding body 3 (the primary coil 1 and the secondary coil 2) generates heat by the operation of the ignition device, the heat of the coil winding body 3 is transmitted to the wide heat sink 6 via the central core and the outer peripheral core 5, and the case Heat is radiated from the surface of 7 to the space around the ignition coil.
As shown in FIG. 1, the heat sink 6 is provided wider than the outer core 5 (that is, the height is larger than the outer core 5), so that the heat radiation from the surface of the case 7 to the outside is increased. The heat dissipation of the primary coil 1 and the secondary coil 2 can be improved. For this reason, even if the load of the ignition coil increases and the amount of heat generated by the ignition coil increases as compared with the prior art, it is possible to cope with the increase in the amount of heat generated by using the ignition coil of this embodiment.

(Effect 2 of Example 1)
In the ignition coil of the first embodiment, the outer core 5 and the heat sink 6 are arranged on the outer periphery of the holder 4. Thereby, even if the outer peripheral core 5 and the heat sink 6 are thermally expanded and contracted as the ignition coil generates heat, the holder 4 can prevent the influence of the thermal expansion and contraction force from reaching the filling resin 8. Further, since the volume of the holder 4 and the heat sink 6 and the amount of the filling resin 8 can be reduced, the resin stress generated by the filling resin 8 can be reduced. For this reason, the malfunction that the filling resin 8 produces a crack can be avoided, and the reliability of an ignition coil can be improved.

(Effect 3 of Example 1)
In the ignition coil according to the first embodiment, the heat sink 6 surrounding the periphery of the outer core 5 is provided by a magnetic material (such as an electromagnetic steel plate or pure iron). Thereby, the heat sink 6 can be utilized as a part of the outer periphery core 5, the magnetic flux amount of an ignition coil can be increased, and the performance of an ignition coil can be improved.

(Effect 4 of Example 1)
The ignition coil of the first embodiment is provided in a U shape similar to that of the holder 4. Thereby, the heat sink 6 can be easily assembled to the holder 4, and the manufacturing cost of the ignition coil can be reduced by increasing the efficiency of manufacturing the ignition coil.

(Effect 5 of Example 1)
The ignition coil according to the first embodiment employs a structure in which the heat sink 6 is accommodated in the case 7 and the heat sink 6 does not directly contact air. For this reason, the malfunction that the heat sink 6 rusts can be avoided.
Further, even when the heat sink 6 is rusted due to some unexpected factor in the case 7, it is possible to avoid the problem that the case 7 and the holder 4 cause cracks in the filling resin 8 due to the rust of the heat sink 6.

(Effect 6 of Example 1)
Since the heat sink 6 is provided separately from the outer peripheral core 5, the degree of freedom of the shape and material of the heat sink 6 can be increased. This makes it possible to provide the heat sink 6 in an optimal shape in order to increase the thermal conductivity of the heat sink 6 or to improve the heat dissipation.

[Example 2]
The second embodiment will be described with reference to FIGS. 3 and 4, but portions that overlap with the first embodiment are omitted.
In the second embodiment, both end members of the outer core 5 are bent in the stacking direction to form a heat sink 6 for heat dissipation that is wider than the stack thickness of the outer core 5, and the outer core 5 and the heat sink are formed outside the holder 4. 6 is arranged and incorporated in the internal space α of the case 7, and then sealed in the case 7 by the filling resin 8.

(Effect of Example 2)
Since the outer peripheral core 5 and the heat sink 6 are integrally formed, the assembly of the heat sink 6 can be improved and the heat dissipation of the coil portion can be improved. Can be prevented by the holder 4 from reaching the filling resin 8.

[Example 3]
The third embodiment will be described with reference to FIGS. 5 and 6, but portions that overlap with the first embodiment are omitted.
In the third embodiment, a bent portion 5a is formed by bending both end materials of the outer peripheral core 5 in the stacking direction, and is provided separately on the outer surface of the outer core 5 so that the heat dissipation is wider than the stacked thickness of the outer core 5. The heat sink 6 is provided in a shape that surrounds the periphery of the outer core 5. Specifically, the heat sink 6 has a U shape like the holder 4, and is formed in a U shape by, for example, pressing. In addition, the outer peripheral core 5 and the heat sink 6 are disposed outside the holder 4, and after being incorporated into the internal space α of the case 7, it is sealed in the case 7 by the filling resin 8.

(Effect of Example 3)
The bent portion 5a of the outer core 5 can enlarge the heat conduction area from the outer core 5 to the heat sink 6, and the heat sink 6 is provided separately from the outer core 5. Therefore, the degree of freedom with respect to shape and material is increased and heat is increased. The conductivity can also be increased, and an optimum shape can be obtained by improving the heat dissipation of the coil. Further, even when the outer core 5 and the heat sink 6 are thermally expanded and contracted, the holder 7 can prevent the influence of the thermal expansion and contraction force from reaching the filling resin 8.

  In addition, although Examples 1-3 mentioned above are comprised by the laminated | stacked outer periphery core 5, you may use the outer periphery core 5 made from a compact formed by compressing magnetic material powders, such as a pure iron.

  In the above embodiment, an example in which the heat sink 6 is provided with iron for the purpose of combining the heat dissipation performance and the magnetic property improvement effect has been shown. Any material that is excellent, such as aluminum or copper, may be used.

  In the above-described embodiment, an example in which the heat sink 6 is provided in a U-shape has been shown, but the shape of the heat sink 6 is not limited. In the above embodiment, the heat sink 6 is provided as one component. However, the heat sink 6 may be provided as a plurality of components.

  A fin having an uneven shape may be provided on the surface of the heat sink 6 for the purpose of improving heat dissipation.

  In the embodiment described above, an example in which the holder 4 is provided in a U-shape has been shown, but the shape of the holder 4 is not limited. Further, in the above-described embodiment, an example in which the holder 4 is provided by one component has been described.

  In the above embodiment, an example in which the present invention is applied to an ignition coil of an “ignition device capable of improving ignitability” has been described. However, an “ignition device having a relatively small load (multi-point The present invention may be applied to an ignition coil of an ignition device that does not continue fire or spark discharge).

DESCRIPTION OF SYMBOLS 1 Primary coil 2 Secondary coil 3 Coil winding body 4 Holder 4a Inner groove 4b Outer groove 5 Outer core 6 Heat sink 7 Case 8 Filling resin alpha Internal space

Claims (3)

A coil winding body (3) around which a primary coil (1) and a secondary coil (2) are wound;
A resin holder (4) disposed around the coil winding body (3);
An outer peripheral core (5) made of a magnetic material disposed on the outer surface of the holder (4);
A heat sink (6) for heat dissipation disposed on the outer surface of the outer peripheral core (5) and provided wider than the thickness of the outer peripheral core (5);
A resin case (7) for accommodating a coil accommodation including the coil winding body (3), the holder (4), the outer core (5), and the heat sink (6);
A filling resin (8) filling the internal space (α) of the case (7) in which the coil accommodation is assembled;
With
The holder (4) is provided with an inner groove (4a) for assembling the outer peripheral core (5) and an outer groove (4b) for assembling the heat sink (6). coil. The ignition coil for an internal combustion engine according to claim 1,
The internal combustion engine ignition coil, wherein the heat sink (6) is made of a material having higher thermal conductivity than the outer core (5). The ignition coil for an internal combustion engine according to claim 1,
The internal combustion engine ignition coil, wherein the heat sink (6) is made of a magnetic material.

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