JP2007005521A - Ignition coil - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an ignition coil capable of suppressing dielectric breakdown in an insulator and also supporting downsizing. <P>SOLUTION: The ignition coil includes a rodlike center core, a primary coil and a secondary coil placed to concentrically wind the outer periphery of the center core, and the insulator made of an insulating material. The insulator is obtained by injecting the insulating material 50 into at least part of a case, and hardening it. The insulating material 50 contains epoxy resin 51, a hardening agent and a nano filler 52 with a thickness of 2 nm or less and an aspect ratio of 40 or less dispersed in the epoxy resin 51. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an ignition coil including a central core, a primary coil and a secondary coil, and an insulator in a case.

  An ignition coil used for generating a spark from a spark plug in an engine of a vehicle or the like includes a central core, and a primary coil and a secondary coil arranged on the outer periphery of the central core in a case. In the ignition coil, for example, an insulator made of an insulating material is used in order to ensure insulation between the primary coil and the secondary coil, or between the center coil and the primary coil or the secondary coil. Is provided. The insulator has been formed by injecting an insulating material into a desired part of the ignition coil and curing it.

  In recent years, there has been an increasing demand for miniaturization of automobile parts, and further miniaturization is demanded for the ignition coil. Therefore, as the insulating material, in order to cope with the thinning of the insulator, there has been a demand for a low-viscosity material that is further excellent in insulation and can be easily injected into a narrow gap.

  So far, as the insulating material, for example, an epoxy resin composition containing an epoxy resin and a silica filler has been developed (see Patent Document 1). In such an epoxy resin composition, since the viscosity before curing can be lowered, it can be easily injected into a desired portion of the ignition coil.

However, in an ignition coil in which an insulator made of the above-described conventional epoxy resin composition is disposed between coils, there is a risk that dielectric breakdown may occur in the insulator when a high voltage is applied to the ignition coil for a long time. It was. As a result, the insulator can no longer maintain its insulation, and the spark plug may not work.
On the other hand, in the said epoxy resin composition, generation | occurrence | production of a dielectric breakdown can be suppressed by increasing the quantity of a silica filler, and the insulation can be improved. However, on the other hand, increasing the amount of silica filler increases the viscosity of the epoxy resin composition. Therefore, it becomes difficult to inject into a desired portion of the ignition coil that is becoming smaller. As a result, it becomes difficult to reliably exhibit insulation at a desired site in the ignition coil.

JP 2000-169678 A

  The present invention has been made in view of such a conventional problem, and an object of the present invention is to provide an ignition coil that can suppress dielectric breakdown in an insulator and can cope with downsizing.

The present invention is an ignition coil comprising a rod-shaped center core, a primary coil and a secondary coil arranged so as to be wound concentrically around the outer periphery of the center core, and an insulator made of an insulating material in a case. There,
The insulator is formed by injecting the insulating material into at least a part of the case and curing the insulating material,
The insulating material includes an epoxy resin, a curing agent, and a nano filler having a thickness of 2 nm or less and an aspect ratio of 40 or less dispersed in the epoxy resin. ).

In the ignition coil of the present invention, the insulator is formed by curing the insulating material, and in the insulating material, the nano filler having a thickness of 2 nm or less and an aspect ratio of 40 or less is dispersed in the epoxy resin. Yes.
Therefore, in the insulator, even if the amount of the nano filler is small, the occurrence of dielectric breakdown can be suppressed, and the insulator can exhibit excellent insulating properties.

Hereinafter, the reason why the insulator can exhibit excellent insulation as described above will be discussed with reference to FIGS.
FIG. 5 shows a conventional insulating material 9 obtained by adding a filler 95 made of silica to an epoxy resin 90. As shown in the figure, the insulating material 9 is formed in a rectangular parallelepiped shape. A conductive paste is baked on one surface of the rectangular parallelepiped insulating material 9 to form a conductive surface 98, and the electrode needle 8 is inserted into the insulating material 9 from the surface facing the conductive surface 98. If a voltage over a certain level is continuously applied, dielectric breakdown occurs. FIG. 5 shows how the dielectric breakdown (indicated by a thick arrow in FIG. 5) progresses when dielectric breakdown occurs in the conventional insulating material 9.
As shown in FIG. 5, the dielectric breakdown of the insulating material 9 generally progresses while bypassing the filler 95 in the epoxy resin 90. Therefore, when the filler 95 is added, the progress distance (the length of the thick line arrow in FIG. 5) is increased by the detour amount, and dielectric breakdown is less likely to occur. As shown in the figure, since the conventional filler made of silica or the like has a large volume, it is difficult to increase the detour distance with a small amount of addition.

  On the other hand, as shown in FIG. 4, in the insulator 5 in the ignition coil of the present invention, the nano filler 52 having a very small thickness of 2 nm or less and an aspect ratio of 40 or less is dispersed in the epoxy resin 51. ing. Therefore, in the insulator 5, even if a relatively small amount is added, the progress distance of dielectric breakdown (the length of the thick arrow in FIG. 4) tends to be long. As a result, dielectric breakdown is unlikely to occur, and it is assumed that high insulation can be exhibited. FIG. 4 shows how the dielectric breakdown progresses when dielectric breakdown occurs when the electrode needle 8 is inserted into the rectangular parallelepiped-shaped insulator 5 on which the conductive surface 10 is formed and a voltage is applied to the insulator 5.

Furthermore, as described above, since the insulator can exhibit excellent insulating properties with a small amount of the nano filler, in the insulating material, the increase in the viscosity is suppressed by reducing the content of the nano filler as much as possible. can do. Therefore, even in a small ignition coil, it is possible to reliably inject the insulating material into a desired portion, and to reliably exhibit insulation. Further, as described above, since the insulator is excellent in insulation, sufficient insulation can be exhibited even if the insulator is thinned by downsizing the ignition coil. Therefore, the ignition coil can cope with downsizing.
Moreover, since the said insulator can exhibit the outstanding insulation with a small amount of said nano fillers, in the said insulator, it can maintain, without deteriorating the characteristics, such as heat resistance which the said epoxy resin originally has.

As described above, in the ignition coil of the present invention, the insulator is less susceptible to dielectric breakdown and can exhibit excellent insulating properties. In addition, since the viscosity of the insulating material before curing can be reduced, it can be easily injected into a desired portion of a small ignition coil, and the insulator can be formed.
Therefore, according to this invention, while being able to suppress the dielectric breakdown in an insulator, the ignition coil which can respond to size reduction can be provided.

Next, a preferred embodiment of the present invention will be described.
In the ignition coil of the present invention, the insulating material contains an epoxy resin, a curing agent, and a nanofiller having a thickness of 2 nm or less and an aspect ratio of 40 or less dispersed in the epoxy resin.
When the thickness of the nano filler exceeds 2 nm, or the aspect ratio exceeds 40, the specific surface area of the nano filler dispersed in the insulating material becomes small. Therefore, in this case, the progress distance of the dielectric breakdown in the insulating material tends to be short, and the insulating property of the insulating material may be lowered. On the other hand, when the aspect ratio exceeds 40, the excellent mechanical properties of the epoxy resin may be impaired.
The aspect ratio of the nanofiller can be represented by the ratio of the width (longest length) to the thickness (shortest length) of the nanofiller.
The thickness and width of the nanofiller in the insulating material can be obtained by measuring the cured insulating material by, for example, an X-ray diffraction method and a transmission electron microscope (TEM).

The insulating material comprises an organized clay formed by inserting a 2-4 quaternary organic ammonium ion formed by bonding 2-4 organic modifying groups to a nitrogen atom between layers of a layered clay mineral, and the epoxy resin. It is preferable to mix and disperse the layer constituting the organoclay in the epoxy resin as the nano filler (claim 2).
In this case, the insulating material in which the nano filler is dispersed in the epoxy resin can be easily manufactured.

The organoclay can be produced, for example, by immersing the lamellar clay mineral in a liquid such as an aqueous solution containing the organoammonium ions. Thereby, the said organic ammonium ion enters between the layers of the said layered clay mineral, and the layer space | interval can be expanded. And the said organized clay by which the organic ammonium ion was inserted between the layers of the said layered clay mineral, and the space | interval of a layer was expanded can be obtained.
Moreover, when the said organized clay and the said epoxy resin are mixed, the layer which comprises the said organized clay can be disperse | distributed in the said epoxy resin as the said nano filler.
That is, when the organized clay and the epoxy resin are mixed, the epoxy resin enters the interlayer of the organized clay, the bond between the layers is broken, and the layer constituting the organized clay is the epoxy resin as the nanosheet filler. Distributed in. As described above, in the organic clay, the organic ammonium ions are inserted between the layers, the distance between the layers is large, and the epoxy resin easily enters.

  At this time, the layer which comprises the said organized clay may be disperse | distributed by the single layer in an epoxy resin, but may be disperse | distributed in the state which laminated | stacked two or more layers. Preferably, it is dispersed in a single layer. In this case, the thickness of the nano filler can be reduced to, for example, about 1 nm. In this case, the addition of a small amount (by weight) of the organoclay can increase the total surface area of the nanofiller in the insulating material, thereby further reducing the dielectric breakdown of the insulator. Can be suppressed.

  Further, the thickness and width of the nano filler dispersed in the epoxy resin can be changed by appropriately selecting the layered clay mineral. Accordingly, when the type of the layered clay mineral is selected, the approximate thickness and width of the nanofiller can be determined.

In addition, when a primary organic ammonium ion in which one organic modifying group is bonded to a nitrogen atom is used as the organic ammonium ion, when the insulating material is cured by heating to form the insulator, the primary organic ammonium ion is used. Ammonium may adversely affect the curing reaction of the epoxy resin, and the insulating property of the insulator may be reduced.
The structures of secondary to quaternary organic ammonium ions are shown in the following formulas (1) to (3), respectively. In the formulas (1) to (3), R _{1 to} R ₃ represent organic modifying groups.

As shown in the above formulas (1) to (3), in the organic ammonium ion, the N atom to which the organic modifying group is bonded has a positive charge. Therefore, when the organic ammonium ion and the layered clay mineral are brought into contact with each other, the organic ammonium ion enters the layer of the layered clay mineral by, for example, the positive charge of the N atom, and is bonded to the surface of the layer. The interlayer distance of minerals can be increased (organic treatment, see FIG. 3).
The layered clay mineral into which the organic ammonium ions are inserted, that is, the organic clay, has a large interlayer distance. Therefore, the epoxy resin can easily enter between the layers of the organized clay by mixing and dispersing the organized clay and the epoxy resin. As a result, the layer spacing of the organized clay is further expanded, the bonds between the organized clay layers are broken, and the layer constituting the organized clay can be dispersed in the epoxy resin as the nanofiller.

In the organic ammonium ion, examples of the organic modifying group include an alkyl group,
There are hydrocarbon groups such as a cycloalkyl group and an alkenyl group. In addition, these organic modification groups may contain functional groups having relatively high polarity and high reactivity, such as hydroxyl groups and carboxyl groups.
Preferably, the organic modifying group of the organic ammonium ion has 30 or less carbon atoms (Claim 3).
When the number of carbon atoms exceeds 30, the organic ammonium ions may not easily enter the clay mineral layer. For this reason, it is difficult to sufficiently increase the interlayer distance of the organic clay, and it may be difficult to sufficiently disperse the nano filler in the epoxy resin.

Moreover, it is preferable that at least one of the organic modification groups of the organic ammonium ion has 2 or more carbon atoms.
If any of the organic modifying groups in the organic ammonium ion has less than 2 carbon atoms, the interlayer distance of the organoclay cannot be sufficiently increased. It may be difficult to sufficiently disperse the resin. More preferably, at least one of the organic modifying groups of the organic ammonium ion has 10 or more carbon atoms, more preferably 15 or more carbon atoms.

One of the organic modification groups of the organic ammonium ion preferably has 2 or more carbon atoms, and the other has 30 or less carbon atoms.
In this case, the organic ammonium ion can easily enter between the layers of the clay mineral and can sufficiently increase the interlayer distance of the clay mineral.

The insulating material contains a curing agent.
As the curing agent, for example, an acid anhydride or an amine compound can be used.
Examples of the acid anhydride include hexahydro acid anhydride, phthalic anhydride, maleic anhydride, methyl CD acid anhydride, CD acid anhydride, methyl hymic acid, hymic acid, succinic anhydride, tetrahydro acid anhydride, Ricacid HL, Chlorendic anhydride, methyltetrahydrophthalic anhydride, trialkyltetrahydrophthalic anhydride, 3 methylhexahydrophthalic anhydride, 4 methylhexahydrophthalic anhydride, trialkyltetrahydrophthalic anhydride maleic acid adduct, methylhexahydrophthalic anhydride Acid, benzophenone tetracarboxylic acid, dodecenyl succinic anhydride, trimellitic anhydride, pyromellitic anhydride, and methyl nadic acid.
Moreover, it is preferable that content of the said hardening | curing agent is 30 weight part-170 weight part with respect to 100 weight part of said epoxy resins.
In this case, it can be cured without impairing the original properties of the epoxy resin.

  As the layered clay mineral, one or more selected from montmorillonite, fluorinated mica, saponite, beidellite, nontronite, hectorite, and stevensite can be used (Claim 6).

Moreover, it is preferable that the said insulating material contains 1-35 weight part of said nano fillers with respect to 100 weight part of said epoxy resins.
When the blending ratio of the nano filler is within the above range, the effect of the present invention can be more remarkably exhibited that excellent insulation can be exhibited with a small amount of nano filler. More preferably, the content of the nano filler in the insulating material is 1 to 20 parts by weight, and more preferably 1 to 10 parts by weight.

  Examples of the epoxy resin include bisphenol A type epoxy resin, bisphenol F type epoxy resin, bisphenol S type epoxy resin, hexahydrobisphenol A type epoxy resin, tetramethylbisphenol A type epoxy resin, pyrocatechol type epoxy resin, and resorcinol. 1 selected from type epoxy resin, cresol novolac type epoxy resin, tetrabromobisphenol A type epoxy resin, trihydroxybiphenyl type epoxy resin, bisresorcinol type epoxy resin, tetramethylbisphenol F type epoxy resin, xylenol type epoxy resin, etc. More than seeds can be used.

  The insulating material can be formed by filling the insulating material into a desired portion in the case of the ignition coil and curing it by heating, for example. As described above, the insulating material contains the epoxy resin and the nanofiller dispersed in the epoxy resin. Therefore, in the insulator, the nano filler is dispersed in the cured epoxy resin.

In addition, one of the primary coil and the secondary coil is disposed so as to be concentrically wound around the other outer periphery, and the insulator includes the primary coil and the secondary coil. It is preferable to arrange | position between (claim 8).
In this case, the insulation between the primary coil and the secondary coil can be reliably maintained by utilizing the excellent insulating property of the insulator. In this case, the heat resistance of the insulator can be used to prevent the insulator from being cracked due to thermal stress. That is, generally, since a high voltage is applied to the primary coil and the secondary coil, the ambient temperature tends to rise. On the other hand, in the insulator, since the high insulating property can be exhibited with a small amount of the nano filler as described above, the epoxy resin having excellent heat resistance can be maintained as it is. Therefore, by disposing the insulator between the primary coil and the secondary coil as described above, the insulator exhibits not only insulating properties but also heat resistance, and cracks can be prevented.

Example 1
Next, an embodiment of the present invention will be described with reference to FIGS.
As shown in FIG. 1, the ignition coil 1 of this example includes a rod-shaped center core 3, a primary coil 21 and a secondary coil 22 arranged so as to be wound concentrically on the outer periphery thereof, and an insulating material made of an insulating material. The body 5 is provided in the case 20. The insulator 5 is formed by injecting an insulating material into at least a part of the case 20 and curing it by, for example, heating.
As shown in FIG. 2, the insulating material 50 includes an epoxy resin 51, a nanofiller 52 having a thickness of 2 nm or less and an aspect ratio of 40 or less dispersed in the epoxy resin 51, and a curing agent (not shown). To do.
This will be described in detail below.

As shown in FIG. 1, the ignition coil 1 of this example is of a stick type that is used by inserting the cylindrical portion 2 into a plug hole of an engine.
The cylindrical portion 2 is formed by inserting a peripheral spool 24, a primary coil 21, a secondary coil 22, and a central core 3 into a case 20. The primary coil 21 is formed by winding an insulation-coated wire around the outer peripheral surface of a cylindrical primary spool 211, and the secondary coil 22 is formed on the outer peripheral surface of the cylindrical secondary spool 221 more than the primary coil 21. It is made by winding a wire coated with insulation with a large number of turns. The secondary coil 22 is inserted on the inner peripheral side of the primary coil 21, and a rod-shaped metal central core 3 is disposed on the inner peripheral side of the secondary coil 22.
The central core 3 is formed by laminating a plurality of steel plates in the radial direction in order to suppress the generation of eddy currents due to the formation of magnetic flux generated by passing a current through the primary coil 21. Further, in this example, an insulating sheet 4 made of polyethylene terephthalate (PET) is wound around the outer peripheral surface of the central core 3. The insulating sheet 4 is formed in close contact with the outer peripheral surface of the central core 3 with an adhesive layer (not shown) made of an acrylic adhesive.

  The magnetic flux generated by passing a current through the primary coil 21 can be increased by passing the central core 3. In addition, permanent magnets 321 are disposed at both end portions 32 of the central core 3 in the axial direction. The permanent magnet 321 is disposed so as to have a polarity opposite to the excitation pole of the central core 3, and can further increase the magnetic flux generated by passing a current through the primary coil 21. It should be noted that an elastic member can be provided at both ends 32 of the central core 3 instead of the permanent magnet.

  In this example, the primary coil 21 is formed by winding a wire coated with insulation around the outer peripheral surface of the cylindrical primary spool 211 as described above, but the wire coated with insulation is cylindrical. It is also possible to use a wire that has been wound into a cylindrical shape by bonding the wound wires together with a fusing agent or the like.

Further, in the case 20 of the ignition coil 1 of the present example, the primary coil 21 is between the primary coil 21 and the secondary coil 22 (more precisely, between the primary spool 211 and the secondary coil 22). An insulator 5 is formed in each gap 29 such as between the outer peripheral spool 24 and the outer periphery spool 24. As shown in FIG. 2, the insulator 5 is formed by filling the gap 29 with an insulating material 50 in which nanofillers 52 are dispersed in an epoxy resin 51 and curing the insulating material 50. Therefore, in the insulator 5, the nano filler is dispersed in the cured epoxy resin.
In this example, the insulating sheet 4 is wound around the outer peripheral surface of the central core 3 as described above to ensure the insulation between the secondary coil 22 and the central core. The insulator 5 can also be formed between the core and the secondary coil 22 (more precisely, between the central core and the secondary spool 221).

Moreover, the cylindrical part 2 has the plug attachment port 26 for attaching a spark plug to the axial direction front-end | tip part 201 inserted and arrange | positioned in the plug hole of an engine. A high voltage terminal 27 that is electrically connected to one end (high voltage side end) of the secondary coil 22 and a coil spring 28 that contacts the high voltage terminal 27 are disposed in the plug attachment port 26.
Further, the cylindrical portion 2 is formed with an igniter arrangement concave portion 25 for arranging an igniter 251 for supplying power to the primary coil 21 at the axial base end portion 202 opposite to the axial tip portion 201. Yes. The igniter arrangement recess 25 is filled with the insulator 5 made of the same insulating material as the insulator 5 filled in the gaps 29 with the igniter 251 disposed. The igniter 251 includes a power control circuit that uses a switching element or the like that operates in response to a signal from an ECU (electronic control unit).

  When a spark generation signal is transmitted from the ECU to the igniter 251, a switching element or the like in the igniter 251 operates to cause a current to flow through the primary coil 21, and accordingly, an induced electromotive force due to electromagnetic induction in the secondary coil 22. (Back electromotive force) is generated, and a spark can be generated from the spark plug.

Next, the insulator 5 in the ignition coil 1 of this example will be described in more detail.
As described above, the insulator 5 is obtained by heat-curing the insulating material 50, and the insulating material 50 contains the epoxy resin 51 and the nano filler 52 dispersed therein (see FIGS. 1 and 2). ).
In this example, as the insulating material 50, the organized clay 7 is configured by mixing the organized clay 7 in which the organic ammonium ions 59 are inserted between the layers 61 of the layered clay mineral 6 and the epoxy resin 51. A layer obtained by dispersing the layer 61 in the epoxy resin 51 as the nanofiller 52 was used (see FIGS. 3A and 3B and FIG. 2).
Specifically, the insulating material was produced as follows.
First, as layered clay mineral 6, montmorillonite (Na-montmorillonite) having a layered structure in which a plurality of layers 61 are laminated was prepared (see FIG. 3A). This layered clay mineral was dispersed in water.
Next, trimethylstearyl ammonium chloride which is an organic ammonium salt was prepared, and this organic ammonium salt was dissolved in water to prepare an organic ammonium aqueous solution. In this organic ammonium aqueous solution, there is an organic ammonium ion (trimethylstearyl ammonium ion) represented by the following formula (4).

Next, an aqueous organic ammonium solution was added to the dispersion of the layered clay mineral 6 prepared above. As a result, as shown in FIG. 3B, the positive charge of, for example, N atoms in the organic ammonium ion 59 attracts the negative charge of the layer 61 constituting the layered clay mineral 6, and the layered clay mineral (montmorillonite) 6 Organic ammonium ions 59 enter between the layers 61, and the organized clay 7 is produced.
Next, the precipitate of organic clay 7 was collected by filtration, washed three times with water, and freeze-dried to obtain organic clay (organic montmorillonite) 7.

Next, 100 parts by weight of a bisphenol A type epoxy resin as an epoxy resin, 7 parts by weight of an organized clay prepared as described above, and 85 parts by weight of hexahydroacid anhydride as a curing agent at a temperature of 60 ° C. The mixture was stirred and mixed for about 60 minutes while vacuum degassing (3 to 5 torr). Thereby, an epoxy resin enters between the layers of the organized clay, and the layers of the organized clay fall apart. As a result, each layer of the organized clay was dispersed in the epoxy resin 51 as the nanofiller 52 to obtain the insulating material 50 (see FIG. 1).
Next, the insulating material 50 was cured by heating, and the thickness and width of the nanofiller 52 contained in the cured insulating material 50 were measured by an X-ray diffraction method and a transmission electron microscope (TEM). The layers constituting the layered clay mineral were separated into almost a single layer, and a plate-like nanofiller 52 having a thickness of about 1 nm and a width of 100 nm × 100 nm was dispersed in the epoxy resin 51. Moreover, the content rate of the nano filler in the insulating material 50 was the same as that of the organic clay, and was 7 parts by weight with respect to 100 parts by weight of the epoxy resin.

  In this example, the insulating material 50 produced as described above is used to arrange the gap 29 or the igniter arrangement in the case 20 of the ignition coil 1 in which the central core 3, the primary coil 21, the secondary coil 22, and the like are arranged. The recess 25 was filled and the insulating material 50 was cured by heating to form the insulator 5 (see FIG. 1).

In the ignition coil 1 of this example, the insulator 5 is formed by curing the insulating material 50, and in the insulating material 50, a small nanofiller 52 having a thickness of 2 nm or less and an aspect ratio of 40 or less is contained in the epoxy resin 51. Are distributed.
Therefore, in the insulator 5, the progress distance of the dielectric breakdown can be increased even with a relatively small addition amount. Therefore, in the insulator 5, even with a small amount of nanofiller of 7 parts by weight with respect to 100 parts by weight of the epoxy resin, the occurrence of dielectric breakdown can be sufficiently suppressed, and the insulator 5 is excellent. Insulation can be exhibited.

Furthermore, since the insulator 5 can exhibit excellent insulating properties with such a small amount of nanofiller 52 added, the insulating material 50 can be easily reduced in viscosity. Therefore, even when the ignition coil 1 is downsized, the insulating material 50 can be reliably injected into a desired portion in the ignition coil 1. Further, as described above, since the insulator 5 is excellent in insulation, sufficient insulation can be exhibited even if the insulator 5 is thinned by downsizing. Therefore, the ignition coil 1 of this example can cope with downsizing.
In addition, since the insulator 5 can exhibit excellent insulating properties with a small amount of the nanofiller 52 as described above, the heat resistance and other characteristics inherent to the epoxy resin 51 can be maintained.
As described above, the ignition coil 1 of the present example can suppress dielectric breakdown in the insulator 5 and can cope with downsizing.

(Example 2)
In the present example, an insulating material that is a material for the insulator of the ignition coil is considered. That is, in this example, five types of insulating materials (sample E1 to sample E3, sample C1, and sample C2) are produced by changing the kind and amount of the additive dispersed in the epoxy resin, and the characteristics are compared and evaluated. .

Specifically, first, an insulating material similar to the insulating material used for the ignition coil of Example 1 was prepared. This is designated as Sample E1.
That is, the sample E1 was prepared in the same manner as in Example 1 except that 100 parts by weight of a bisphenol A type epoxy resin and 7 parts by weight of an organized clay in which trimethylstearylammonium ions, which are quaternary organic ammonium ions, were inserted between montmorillonite layers. And 85 parts by weight of hexahydroacid anhydride as a curing agent.

Sample E2 is a mixture of 100 parts by weight of a bisphenol A type epoxy resin, 7 parts by weight of an organized clay in which trimethylstearyl ammonium ions are inserted between hectorite layers, and 85 parts by weight of hexahydro acid anhydride as a curing agent. It was produced. That is, sample E2 was produced in the same manner as the insulating material of Example 1 (sample E1 above) except that hectorite was used as the layered clay mineral. Also in the sample E2, like the insulating material of the first embodiment (the sample E1), the layered structure constituting the hectorite is separated into almost a single layer, and is a plate having a thickness of about 1 μm and a width of about 100 nm × about 100 nm. The nanofiller was dispersed in the epoxy resin.
Sample E3 consists of 100 parts by weight of bisphenol A type epoxy resin, 7 parts by weight of organic clay in which trimethylstearylammonium ions are inserted between the layers of fluorinated mica, 85 parts by weight of hexahydroacid anhydride as a curing agent, It was produced by mixing. That is, sample E3 was produced in the same manner as the insulating material of Example 1 (sample E1 above) except that fluorinated mica was used as the layered clay mineral. Also in the sample E3, the layered structure constituting the fluorinated mica is separated into almost a single layer as in the insulating material of the first embodiment (the sample E1), and has a thickness of about 1 μm and a width of about 100 nm × about 100 nm. A plate-like nanofiller was dispersed in the epoxy resin.

Moreover, in this example, the insulating material (sample C1 and sample C2) was produced using the filler which consists of silica instead of a nano filler for the comparison of the sample E1-sample E3.
Specifically, first, a silica filler was prepared. This silica filler is made of silica particles having a particle size of 1 to 100 μm.
Next, 50 parts by weight of this silica filler, 100 parts by weight of a bisphenol A type epoxy resin as an epoxy resin, and 85 parts by weight of hexahydroacid anhydride as a curing agent were added at a temperature of 60 ° C. as in Example 1. The mixture was stirred and mixed for about 60 to 180 minutes while vacuum degassing (500 Pa) to produce an insulating material. This is designated as Sample C1. In sample C1, a silica filler having a particle size of 1 to 100 μm was dispersed as it was in the epoxy resin.

Sample C2 contains 70 parts by weight of a silica filler, 100 parts by weight of a bisphenol A type epoxy resin as an epoxy resin, and 85 parts by weight of hexahydroacid anhydride as a curing agent. That is, the sample C2 was produced in the same manner as the sample C1 except that the content of the silica filler of the sample C1 was changed.
Table 1 shows the compositions of the insulating materials of Sample E1 to Sample E3, Sample C1, and Sample C2.

Next, the viscosity, glass transition temperature (Tg), and withstand voltage of the five types of insulating materials (Sample E1 to Sample E3, Sample C1, and Sample C2) produced as described above were measured. The results are shown in Table 2.
The viscosity was measured by weighing about 80 ml of each sample in a sample bottle (35φ, 110 ml) and immersing it in a silicone oil bath adjusted to 60 ° C. using a B-type rotational viscometer (manufactured by Tokyo Keiki Co., Ltd.). Tg is measured by TMA (Thermomechanical Analysys) method after heating each sample for 17 hours at 90 ° C. and then for 15 hours at 170 ° C. It measured by making it heat up with the temperature increase rate of 2.0 degree-C / min using (vacuum Riko Co., Ltd. product).

The withstand voltage was measured using a dielectric breakdown tester (manufactured by Yamayo Tester Co., Ltd.).
Specifically, as shown in FIG. 6, first, the insulating material of each sample cured by heating as described above was formed into a cubic test piece 5. Next, the conductive paste was baked on one surface of the cube-shaped test piece 5 to form the electrode surface 10. Next, the needle electrode 8 (φ30 μm) is inserted into the test piece 5 from the surface facing the electrode surface 10, a voltage is applied between the needle electrode 8 and the electrode surface, and the time until breakdown (breakdown time) occurs. It was measured. The distance d between the needle electrode 8 and the electrode surface 10 was 2 mm.
Next, a voltage (withstand voltage) at which the destruction time was 1000 hours was calculated from the relationship between the destruction time and the applied voltage.

As is known from Table 2, the insulating material (sample E1 to sample E3) containing the nano-filler having a thickness of 2 nm or less and an aspect ratio of 40 or less in the epoxy resin is 7 wt. A high withstand voltage of 150 kV / mm was exhibited with a small amount of the filler. Therefore, in the samples E1 to E3, dielectric breakdown hardly occurs and excellent insulating properties can be exhibited.
On the other hand, the insulating material (sample C1) containing a filler made of silica having a particle diameter of 1 to 100 μm in the epoxy resin has a withstand voltage despite containing a large amount of filler of 50 parts by weight. There was only 80 kV / mm and insulation was low.
Moreover, it can be seen that the withstand voltage can be improved by increasing the amount of the filler made of silica as in the sample C2. However, as shown in Table 2, in this case, since the viscosity is high, it may be difficult to sufficiently fill the insulating material into a narrow gap in the ignition coil.

  Samples E1 to E3 can exhibit a glass transition point Tg as high as that of conventional insulating materials (samples C1 and C3) containing a filler made of silica. Therefore, the samples E1 to E3 can be used even in a high temperature region, and are suitable as an insulating material for an ignition coil whose temperature environment tends to be high.

As described above, it can be seen that the insulating materials of Sample E1 to Sample E3 in which the nano filler is dispersed in the epoxy resin have excellent insulating properties and can cope with downsizing of the ignition coil.
In this example, as described above, an insulating material was prepared using an organized clay prepared using a quaternary organic ammonium ion (trimethylstearyl ammonium ion) as the organic ammonium ion. Although not clearly shown in this example, for example, a secondary organic ammonium ion (N-methyl n octadecyl ammonium ion) represented by the following formula (5) and a tertiary organic ammonium ion (N) represented by the formula (6) , N-dimethyl-n-octadecylammonium ion), in the same manner as in the above samples E1 to E3, an insulating material having excellent insulating properties containing a nanofiller having a thickness of 2 nm or less and an aspect ratio of 40 or less can be obtained. I have confirmed that.

Explanatory drawing which shows the cross section of the ignition coil concerning an Example. FIG. 3 is an explanatory diagram illustrating a configuration of an insulating material according to the first embodiment. Explanatory drawing (a) which shows the layered structure of the layered clay mineral concerning Example 1, (b) which shows the structure of the organized clay in which the organic ammonium ion was inserted between the layers of the layered clay mineral. Explanatory drawing which shows the mode of the dielectric breakdown which progresses in the insulating material of this invention. Explanatory drawing which shows the mode of the dielectric breakdown which progresses in the conventional insulating material. Explanatory drawing which shows the measuring method of withstand voltage concerning Example 1. FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Ignition coil 2 Cylindrical part 20 Case 21 Primary coil 211 Primary spool 22 Secondary coil 221 Secondary spool 3 Central core 5 Insulator 50 Insulating material 51 Epoxy resin 52 Nano filler

Claims (8)

An ignition coil comprising a rod-shaped center core, a primary coil and a secondary coil arranged so as to be wound concentrically around the outer periphery of the center core, and an insulator made of an insulating material in a case,
The insulator is formed by injecting the insulating material into at least a part of the case and curing the insulating material,
The said insulating material contains an epoxy resin, a hardening | curing agent, and a nano filler with a thickness of 2 nm or less and an aspect ratio of 40 or less dispersed in the epoxy resin.   In Claim 1, the said insulating material is an organized clay formed by inserting a 2-4 quaternary organic ammonium ion formed by bonding 2-4 organic modifying groups to a nitrogen atom between layers of a layered clay mineral; An ignition coil, wherein the epoxy resin is mixed and a layer constituting the organic clay is dispersed in the epoxy resin as the nanofiller.   3. The ignition coil according to claim 2, wherein the organic modifying group of the organic ammonium ion has 30 or less carbon atoms.   4. The ignition coil according to claim 2, wherein at least one of the organic modification groups of the organic ammonium ion has 2 or more carbon atoms.   The ignition coil according to any one of claims 2 to 4, wherein one of the organic modification groups of the organic ammonium ion has 2 or more carbon atoms, and the other has 30 or less carbon atoms. .   The layered clay mineral according to any one of claims 2 to 5, wherein the layered clay mineral is at least one selected from montmorillonite, fluorinated mica, saponite, beidellite, nontronite, hectorite, and stevensite. Ignition coil.   The ignition coil according to any one of claims 1 to 6, wherein the insulating material contains 1 to 35 parts by weight of the nano filler with respect to 100 parts by weight of the epoxy resin.   In any one of Claims 1-7, one side is arrange | positioned so that the outer periphery of the other of the said primary coil and the said secondary coil may be wound concentrically, The said insulator is the said An ignition coil, which is disposed between a primary coil and the secondary coil.

Images