JP6814079B2 - Manufacturing method of reactor and reactor - Google Patents

Description

The present invention relates to a reactor and a method for producing the reactor.

The reactor is used for the purpose of improving the power factor, suppressing the inrush current, smoothing the direct current, and the like by using the inductance of the coil. As a specific example, in a hybrid vehicle or an electric vehicle, a reactor is used as a component of a DC booster of a power supply system for driving a motor (see Japanese Patent Application Laid-Open No. 2016-25137).

It is necessary to increase the capacity of the reactor as the output of the motor of the hybrid vehicle and the electric vehicle increases, but on the other hand, the size of the reactor is required to be reduced. As a result of such an increase in capacity and miniaturization of the reactor, it has become important to improve the heat dissipation of the reactor.

The reactor described in the above publication has improved heat dissipation by mounting a coil formed by bending a rectangular wire on the outer circumference of a core having a rectangular cross section on a case via a heat dissipation member.

Further, the insulating layer of the insulated wire forming the coil of the reactor having a large output is required not to lose the insulating property by bending at the time of bending. On the other hand, paying attention to the excellent chemical resistance, heat resistance and electrical insulation of polyimide, a polyimide paint using an acid anhydride as a precursor as a paint for forming an insulating layer of an insulated wire for a coil. Has been proposed (see Japanese Patent Application Laid-Open No. 2016-183228). Further, a polyimide paint for forming an insulating layer using an acid anhydride component and a diamine component as precursors has been proposed (see JP-A-2016-151020), and by using the above-mentioned polyimide paint, mechanical properties and insulating properties It is said that an excellent insulating layer can be formed.

Japanese Unexamined Patent Publication No. 2016-25137 Japanese Unexamined Patent Publication No. 2016-183228 Japanese Unexamined Patent Publication No. 2016-151020

In the reactor disclosed in Japanese Patent Application Laid-Open No. 2016-25137, the heat radiating member comes into contact with a straight line portion (a portion arranged outside one side of the core having a rectangular cross section) facing the coil case, but the other coil The heat radiating member is not in contact with the straight portion or the bent portion. Therefore, it is desired to further improve the heat dissipation from the reactor coil.

The present invention has been made based on the above circumstances, and an object of the present invention is to provide a small reactor having excellent heat dissipation.

A reactor according to an aspect of the present invention made to solve the above problems has a core having a rectangular cross section, a conductor, and a flat-angle insulated wire having one or more insulating layers covering the conductor in an edgewise direction. A polyimide having a coil formed by bending and arranged on the outer periphery of the core, wherein the bending radius of the flat-angle insulated wire at the corner of the core is the average long side length in the cross section of the conductor. The insulating layer is 1/2 or less, and at least one of the insulating layers contains a polyimide derived from a polyimide precursor which is a reaction product of an aromatic tetracarboxylic acid dianhydride and an aromatic diamine as a main component, and the aromatic tetra The carboxylic acid dianhydride contains a biphenyltetracarboxylic acid dianhydride, and the proportion of the biphenyltetracarboxylic acid dianhydride in the aromatic tetracarboxylic acid dianhydride is 60 mol% or more and 75 mol% or less.

Further, a method for producing a reactor according to another aspect of the present invention, which has been made to solve the above problems, is a flat insulation having a core having a rectangular cross section, a conductor, and one or a plurality of insulating layers covering the conductor. A method for manufacturing a polyimide having a coil formed by bending an electric wire in an edgewise direction and arranged on the outer periphery of the core, wherein the bending radius of the flat-angle insulated electric wire is the average long side length in the cross section of the conductor. The flat-angle insulated wire forming step includes a step of bending the conductor so as to be halved or less, a step of applying a resin varnish on the outer peripheral side of the conductor, and a step of heating the coated resin varnish. The resin varnish contains a polyimide precursor which is a reaction product of an aromatic tetracarboxylic acid dianhydride and an aromatic diamine, and the aromatic tetracarboxylic acid dianhydride contains a biphenyltetracarboxylic acid dianhydride. The ratio of biphenyltetracarboxylic acid dianhydride to the aromatic tetracarboxylic acid dianhydride containing an anhydride is 60 mol% or more and 75 mol% or less.

The reactor according to one aspect of the present invention and the reactor produced by the method for producing a reactor according to another aspect of the present invention are small in size and excellent in heat dissipation.

FIG. 1 is a schematic plan view showing a reactor according to an embodiment of the present invention. FIG. 2 is a schematic cross-sectional view taken along the line AA in a state where the reactor of FIG. 1 is attached to the case. FIG. 3 is a schematic cross-sectional view of the flat-angle insulated wire forming the coil of the reactor of FIG.

[Explanation of Embodiments of the Present Invention]
The reactor according to one aspect of the present invention is formed by bending a core having a rectangular cross section, a conductor, and a flat-angle insulated wire having one or a plurality of insulating layers covering the conductor in an edgewise direction. A reactant comprising a coil arranged on the outer periphery of the conductor, wherein the bending radius of the flat-angle insulated wire at the corner of the core is 1/2 or less of the average long side length in the cross section of the conductor, and is at least 1. The insulating layer is mainly composed of a polyimide derived from a polyimide precursor which is a reaction product of an aromatic tetracarboxylic acid dianhydride and an aromatic diamine, and the aromatic tetracarboxylic acid dianhydride is a biphenyltetracarboxylic acid. It contains acid dianhydride, and the ratio of biphenyltetracarboxylic acid dianhydride in the aromatic tetracarboxylic acid dianhydride is 60 mol% or more and 75 mol% or less.

In the reactor, the bending radius of the flat-angle insulated wire at the corner of the core is equal to or less than the upper limit, so that the ratio of the straight portion to the total length of the flat-angle insulated wire is large, and the flat-angle insulated wire with respect to the member for heat dissipation. The contact area of the cable can be increased to improve heat dissipation. Further, the reactor contains a polyimide derived from a polyimide precursor in which at least one of the insulating layers is a reaction product of an aromatic tetracarboxylic dianhydride and an aromatic diamine as a main component, and the aromatic tetracarboxylic acid. The appearance is obtained by the fact that the dianhydride contains a biphenyltetracarboxylic dianhydride and the proportion of the biphenyltetracarboxylic dianhydride in the aromatic tetracarboxylic dianhydride is 60 mol% or more and 75 mol% or less. Excellent bending workability and moisture heat deterioration resistance. Therefore, in the reactor, the insulating layer is excellent in insulating property even though the bending radius of the flat-angle insulated wire is reduced as described above. The reason why the appearance, bending workability and moisture heat deterioration resistance are excellent by having the above structure is not clear, but it is presumed as follows. In the reactor, at least one of the one or more insulating layers of the flat-angle insulated wire contains a polyimide derived from a polyimide precursor containing biphenyltetracarboxylic dianhydride which is difficult to hydrolyze as a raw material. .. Since this polyimide contains a structure derived from biphenyltetracarboxylic dianhydride which is difficult to be hydrolyzed, it is difficult to be hydrolyzed even in a moist heat environment, and thus it is considered that the moisture resistance deterioration resistance of the insulating layer is improved.

The aromatic tetracarboxylic dianhydride further contains a pyromellitic dianhydride, and the proportion of the pyromellitic dianhydride in the aromatic tetracarboxylic dianhydride is 5 mol% or more and 40 mol% or less. Is preferable. As described above, when the aromatic tetracarboxylic dianhydride contains the pyromellitic dianhydride in the above ratio, a rigid structure can be introduced into the polyimide, so that the heat resistance of the insulating layer can be further improved.

The aromatic diamine may contain diaminodiphenyl ether. As described above, when the aromatic diamine contains diaminodiphenyl ether, the toughness of the insulating layer can be improved.

The average long side length of the conductor is preferably 1 mm or more and 15 mm or less. When the average long side length of the conductor is within the above range, the capacitance of the reactor can be increased more reliably.

It is preferable that the dielectric breakdown voltage of the insulating layer after the heating test held at 200 ° C. for 1000 hours is 50% or more of the dielectric breakdown voltage before the heating test. As described above, the heat resistance of the reactor is ensured because the dielectric breakdown voltage of the insulating layer does not decrease by the heating test.

A method for producing a reactor according to another aspect of the present invention is formed by bending a core having a rectangular cross section, a conductor, and a flat-angle insulated wire having one or a plurality of insulating layers covering the conductor in an edgewise direction. This is a method for manufacturing a polyimide including a coil arranged on the outer periphery of the core, in which the flat-angle insulated wire is bent so that the bending radius is 1/2 or less of the average long side length in the cross section of the conductor. The flat-angle insulated wire forming step includes a step of applying a resin varnish on the outer peripheral side of the conductor and a step of heating the coated resin varnish, and the resin varnish is aromatic. The aromatic tetracarboxylic acid dianhydride contains a polyimide precursor which is a reaction product of a group tetracarboxylic acid dianhydride and an aromatic diamine, and the aromatic tetracarboxylic acid dianhydride contains a biphenyltetracarboxylic acid dianhydride. The proportion of biphenyltetracarboxylic acid dianhydride in the dianhydride is 60 mol% or more and 75 mol% or less.

The method for manufacturing the reactor is compared by including a step of bending so that the bending radius of the flat-angle insulated wire at the corner of the core is 1/2 or less of the average long side length in the cross section of the conductor. It is possible to manufacture a reactor having a large target capacity and excellent heat dissipation. Further, the method for producing the reactor contains a polyimide precursor which is a reaction product of an aromatic tetracarboxylic dianhydride and an aromatic diamine, and the aromatic tetracarboxylic dianhydride is a biphenyltetracarboxylic dianhydride. Since a resin varnish containing a substance and having a ratio of biphenyltetracarboxylic dianhydride in the aromatic tetracarboxylic dianhydride of 60 mol% or more and 75 mol% or less is used, the flat-angle insulated wire is used in the bending process. Even if the bending radius is reduced, the insulating property of the insulating layer is not easily impaired.

The term "rectangular" means that the approximate shape is square, and the corners may be chamfered, or the outer edge may have small undulations. Further, the "main component" means a component having the highest mass content. The "dielectric breakdown voltage" of the insulating layer is a value measured in accordance with JIS-C2110-1 (2010) using a sample from which the insulating layer has been peeled off.

[Details of Embodiments of the present invention]
Hereinafter, embodiments of the reactor according to the present invention will be described in detail with reference to the drawings.

[Reactor]
The reactor according to the embodiment of the present invention shown in FIGS. 1 and 2 includes a core 1 having a rectangular cross section and a coil 2 arranged on the outer periphery of the core 1. Further, the reactor includes a heat radiating member 3 arranged so as to come into contact with the lower surface of the coil 2, and a holding body 4 for holding the core 1 and the coil 2.

As shown in FIG. 2, the reactor is attached so as to press-contact the heat radiating member 3 to, for example, the case 5 of a DC booster that uses the reactor. As a result, the heat of the coil 2 of the reactor is transferred to the case 5 via the heat radiating member 3 and dissipated from the case 5 into the atmosphere.

<Core>
The core 1 is formed in an annular shape in a plan view, and has a rectangular cross-sectional shape perpendicular to the magnetic path. The core 1 may be divided into a plurality of cores 1 in order to facilitate the formation of the coil 2. As a specific example, the core 1 is formed in a pair of U-shapes, and is arranged so as to form an annular shape in which the end faces are abutted against each other in the reactor.

The core 1 is formed of a soft magnetic material (a material having a large magnetic permeability and a small hysteresis). Specifically, the core 1 can be made by compression molding soft magnetic metal powder. Examples of the soft magnetic metal powder include iron, iron-silicon alloy, iron-nitrogen alloy, iron-nickel alloy, iron-carbon alloy, iron-boron alloy, iron-cobalt alloy, and iron-phosphorus alloy. Alloys, iron-nickel-cobalt alloys, iron-aluminum-silicon alloys and the like can be used.

<Coil>
The coil 2 is formed of a flat-angle insulated wire 6 having a rectangular cross-sectional shape. Specifically, the coil 2 is formed by bending a flat-angle insulated wire 6 on the outer periphery of the core 1 in an edgewise direction (direction in which the short side in the cross section is arranged on the inner peripheral side and the outer peripheral side).

As shown in FIG. 3, the flat-angle insulated wire 6 forming the coil 2 has a conductor 7 and one or a plurality of insulating layers 8 covering the conductor 7.

As the lower limit of the bending radius of the flat-angle insulated wire 6 at the corner of the core 1, 1/10 of the average long side length of the cross section of the conductor 7 is preferable, and 1/8 is more preferable. On the other hand, the upper limit of the bending radius of the flat-angle insulated wire 6 at the corner of the core 1 is 1/2 of the average long side length of the cross section of the conductor 7, preferably 9/20, and more preferably 2/5. If the bending radius of the flat-angle insulated wire 6 at the corner of the core 1 is less than the above lower limit, the flat-angle insulated wire 6 may not be easily bent, or the insulating layer 8 may be damaged by the bending. On the contrary, when the bending radius of the flat-angle insulated wire 6 at the corner of the core 1 exceeds the above upper limit, the straight portion of the flat-angle insulated wire 6 becomes shorter, so that the contact area of the coil 2 with the heat radiating member 3 becomes smaller. The heat dissipation of the reactor may be insufficient.

(conductor)
As the material of the conductor 7 of the flat-angle insulated wire 6, a metal having high conductivity and high mechanical strength is preferable. Examples of such metals include copper, copper alloys, aluminum, nickel, silver, soft iron, steel, stainless steel and the like. The conductor 7 of the flat-angle insulated wire 6 has a material in which these metals are linearly formed, or a multi-layer structure in which such a linear material is coated with another metal, for example, nickel-coated copper wire or silver-coated material. Copper wire, copper-coated aluminum wire, copper-coated steel wire and the like can be used.

The lower limit of the ratio of the average long side length (average flat surface width) to the average short side length (average edge surface width) in the cross section of the conductor 7 is 2, preferably 5. On the other hand, the upper limit of the ratio of the average long side length to the average short side length in the cross section of the conductor 7 is 15, preferably 10. If the ratio of the average long side length to the average short side length in the cross section of the conductor 7 forming the coil 2 is less than the above lower limit, the plane dimension of the coil 2 may become large. On the contrary, when the ratio of the average long side length to the average short side length in the cross section of the conductor 7 forming the coil 2 exceeds the above upper limit, the flat-angle insulated wire 6 may not be easily bent or due to bending. The insulating layer 8 may be damaged.

Further, as the lower limit of the average long side length of the cross section of the conductor 7 of the flat-angle insulated wire 6, 1 mm is preferable, and 5 mm is more preferable. On the other hand, the upper limit of the average long side length of the cross section of the conductor 7 is preferably 15 mm, more preferably 10 mm. If the average long side length of the cross section of the conductor 7 is less than the above lower limit, the capacitance of the reactor may not be increased, or the plane dimension of the reactor may be increased. On the contrary, when the average long side length of the cross section of the conductor 7 exceeds the above upper limit, the flat-angle insulated wire 6 may not be easily bent, or the insulating layer 8 may be damaged by the bending.

(Insulation layer)
The insulating layer 8 of the flat-angle insulated wire 6 is laminated on the outer peripheral side of the conductor 7. The average thickness of each insulating layer 8 can be, for example, 1 μm or more and 5 μm or less. When the flat-angle insulated wire 6 has a plurality of insulating layers 8, the average total thickness of the plurality of insulating layers 8 can be, for example, 10 μm or more and 200 μm or less. Further, the total number of layers of the plurality of insulating layers 8 can be, for example, two or more and 200 or less.

The lower limit of the ratio of the dielectric breakdown voltage after the heating test in which the insulating layer 8 is held at 200 ° C. for 1000 hours to the dielectric breakdown voltage before the heating test is preferably 50%, more preferably 80%. If the ratio of the dielectric breakdown voltage after the heating test of the insulating layer 8 to the dielectric breakdown voltage before the heating test is less than the above lower limit, a problem may occur due to dielectric breakdown when the reactor is used even in a high temperature environment. ..

At least one of the one or a plurality of insulating layers 8 contains a polyimide derived from a polyimide precursor which is a reaction product of an aromatic tetracarboxylic dianhydride and an aromatic diamine as a main component.

As the lower limit of the weight average molecular weight (polystyrene conversion value) of the polyimide precursor, 10,000 is preferable, and 15,000 is more preferable. On the other hand, as the upper limit of the weight average molecular weight, 180,000 is preferable, and 130,000 is more preferable. By setting the weight average molecular weight of the polyimide precursor to the above lower limit or more, it is possible to form a polyimide having excellent extensibility and easily maintaining a constant molecular weight even if hydrolysis occurs, and as a result, the insulating layer 8 can be formed. It is considered that the flexibility and the resistance to moisture and heat deterioration can be further improved. Further, by setting the weight average molecular weight of the polyimide precursor to the above upper limit or less, it is possible to suppress an extreme increase in viscosity of the resin varnish used for manufacturing the flat-angle insulated wire 6 and improve the coatability. Further, in the resin varnish, it becomes easy to improve the concentration of the polyimide precursor while maintaining excellent coatability. Here, the "weight average molecular weight" refers to a value measured by gel permeation chromatography (GPC) in accordance with JIS-K7252-1 (2008).

The molar ratio of the aromatic tetracarboxylic dianhydride used as the raw material of the polyimide precursor to the aromatic diamine (aromatic tetracarboxylic dianhydride / aromatic diamine) is from the viewpoint of easiness of synthesizing the polyimide precursor. Therefore, for example, it can be 95/105 or more and 105/95 or less.

The aromatic tetracarboxylic dianhydride contains biphenyltetracarboxylic dianhydride (BPDA). Examples of the biphenyltetracarboxylic dianhydride include 3,3', 4,4'-biphenyltetracarboxylic dianhydride (3,3', 4,4'-BPDA), 2,3,3', 4 '-Biphenyltetracarboxylic dianhydride (2,3,3', 4'-BPDA), 2,2', 3,3'-biphenyltetracarboxylic dianhydride (2,2', 3,3' -BPDA) and the like, and among these, 3,3', 4,4'-biphenyltetracarboxylic dianhydride is preferable.

The lower limit of the ratio of the biphenyltetracarboxylic dianhydride in the aromatic tetracarboxylic dianhydride is 60 mol%, preferably 63 mol%, and more preferably 65 mol%. On the other hand, the upper limit of the ratio of the biphenyltetracarboxylic dianhydride in the aromatic tetracarboxylic dianhydride is 75 mol%, preferably 72 mol%, and more preferably 70 mol%. If the proportion of biphenyltetracarboxylic dianhydride is less than the above lower limit, the insulating property of the insulating layer 8 may easily deteriorate in a moist heat environment. On the contrary, when the ratio of biphenyltetracarboxylic dianhydride exceeds the above upper limit, the molecular regularity and molecular rigidity of the polyimide increase, and as a result, the insulating layer 8 becomes cloudy or the environment changes due to the accumulation of internal stress. For example, when exposed to a moist heat environment, cracks may easily occur.

Among the aromatic tetracarboxylic dianhydrides used as the raw material of the polyimide precursor, the aromatic tetracarboxylic dianhydrides other than the biphenyltetracarboxylic dianhydride include, for example, pyromellitic dianhydride (PMDA). 3,3', 4,4'-benzophenonetetracarboxylic dianhydride (BTDA), 4,4'-oxydiphthalic acid dianhydride, 2,2', 3,3'-benzophenonetetracarboxylic dianhydride, 2,2-bis (3,4-dicarboxyphenyl) propane dianhydride, 2,2-bis (2,3-dicarboxyphenyl) propane dianhydride, 1,1-bis (3,4-dicarboxyphenyl) Phenyl) ethane dianhydride, 1,1-bis (2,3-dicarboxyphenyl) ethane dianhydride, bis (3,4-dicarboxyphenyl) methane dianhydride, bis (2,3-dicarboxyphenyl) ) Methane dianhydride, bis (3,4-dicarboxyphenyl) sulfonate dianhydride, bis (3,4-dicarboxyphenyl) ether dianhydride, 1,2,5,6-naphthalenetetracarboxylic dianhydride Examples thereof include 2,3,6,7-naphthalenetetracarboxylic dianhydride and the like. The above-mentioned other aromatic tetracarboxylic dianhydride may be used alone or in combination of two or more.

The aromatic tetracarboxylic dianhydride used as a raw material for the polyimide precursor further contains pyromellitic dianhydride, 3,3', 4,4'-benzophenonetetracarboxylic dianhydride, or a combination thereof. Is preferable. In particular, by using pyromellitic dianhydride having a rigid structure as a raw material for the polyimide precursor, a rigid structure can be introduced into the imidized polyimide, so that the heat resistance of the insulating layer 8 can be improved.

The lower limit of the proportion of pyromellitic dianhydride in the aromatic tetracarboxylic dianhydride used as the raw material of the polyimide precursor is preferably 5 mol%, more preferably 8 mol%. On the other hand, the upper limit of the proportion of pyromellitic dianhydride is preferably 40 mol%. If the proportion of pyromellitic dianhydride is less than the above lower limit, the heat resistance of the insulating layer 8 may be insufficient. On the contrary, when the ratio of the pyromellitic dianhydride exceeds the above upper limit, the structure derived from the biphenyltetracarboxylic dianhydride cannot be sufficiently introduced into the polyimide which is the main component of the insulating layer 8. As a result, the insulating layer 8 may easily deteriorate in a moist heat environment.

The ratio of 3,3', 4,4'-benzophenonetetracarboxylic dianhydride in the aromatic tetracarboxylic dianhydride used as the raw material of the polyimide precursor is not particularly limited, but is, for example, 0 mol% or more. It can be 20 mol% or less.

Examples of the aromatic diamine used as the raw material of the polyimide precursor include 4,4'-diaminodiphenyl ether (4,4'-ODA), 3,4'-diaminodiphenyl ether (3,4'-ODA), 3,3. Diaminodiphenyl ethers (ODA) such as'-diaminodiphenyl ether (3,3'-ODA), 2,4'-diaminodiphenyl ether (2,4'-ODA), 2,2'-diaminodiphenyl ether (2,2'-ODA) ), 2,2-Bis [4- (4-aminophenoxy) phenyl] propane (BAPP), 4,4'-bis (4-aminophenoxy) biphenyl (BABP), 4,4'-diaminodiphenylmethane, 3, 4'-diaminodiphenylmethane, 3,3'-diaminodiphenylmethane, 2,4'-diaminodiphenylmethane, 2,2'-diaminodiphenylmethane, 4,4'-diaminodiphenylsulfone, 3,4'-diaminodiphenylsulfone, 3, 3'-diaminodiphenylsulfone, 2,4′-diaminodiphenylsulfone, 2,2′-diaminodiphenylsulfone, 4,4′-diaminodiphenylsulfide, 3,4′-diaminodiphenylsulfide, 3,3′-diaminodiphenyl Sulphide, 2,4'-diaminodiphenyl sulfide, 2,2'-diaminodiphenyl sulfide, paraphenylenediamine (PPD), metaphenylenediamine, p-xylylene diamine, m-xylylene diamine, 2,2'-dimethyl- 4,4'-Diaminobiphenyl, 1,5-diaminonaphthalene, 4,4'-benzophenonediamine, 3,3'-dimethyl-4,4'-diaminodiphenylmethane, 3,3', 5,5'-tetramethyl -4,4'-diaminodiphenylmethane and the like can be mentioned. These aromatic diamines may be used alone or in combination of two or more, but preferably contain diaminodiphenyl ether that can improve the toughness of the insulating layer 8.

The aromatic diamine used as a raw material for the polyimide precursor preferably contains diaminodiphenyl ether (ODA), 2,2-bis [4- (4-aminophenoxy) phenyl] propane, or a combination thereof. In particular, by using diaminodiphenyl ether as a raw material for the polyimide precursor, the toughness of the insulating layer 8 can be improved. As the diaminodiphenyl ether, 4,4'-diaminodiphenyl ether is preferable.

The lower limit of the ratio of diaminodiphenyl ether in the aromatic diamine is preferably 50 mol%, more preferably 90 mol%, still more preferably 99 mol%. By setting the ratio of the diaminodiphenyl ether to the above lower limit or more in this way, the toughness of the insulating layer 8 can be further improved. The proportion of the diaminodiphenyl ether is particularly preferably 100 mol%. The ratio of diaminodiphenyl ether and 2,2-bis [4- (4-aminophenoxy) phenyl] propane in the aromatic diamine can be, for example, 0 mol% or more and 50 mol% or less.

The polyimide precursor may be a reaction product obtained by polymerizing an aromatic tetracarboxylic dianhydride or an aromatic diamine with another raw material. Examples of the other raw materials include aliphatic tetracarboxylic dianhydrides such as 1,2,4,5-cyclohexanetetracarboxylic dianhydride, and aliphatic diamines such as hexamethylenediamine.

It is preferable that the polyimide precursor is a reaction product obtained by substantially using only biphenyltetracarboxylic dianhydride, pyromellitic dianhydride and diaminodiphenyl ether as raw materials. That is, it is preferable that the polyimide, which is the main component of the insulating layer 8 of the flat-angle insulated wire 6, is substantially formed only by a structure derived from biphenyltetracarboxylic dianhydride, pyromellitic dianhydride, and diaminodiphenyl ether. .. Specifically, the lower limit of the total ratio of biphenyltetracarboxylic dianhydride, pyromellitic dianhydride and diaminodiphenyl ether in all the raw materials of the polyimide precursor is preferably 95 mol%, more preferably 99 mol%. .. The total ratio is most preferably 100 mol%.

In the plurality of insulating layers 8, it is preferable that all the insulating layers 8 contain the above-mentioned polyimide as a main component, but the main components of some of the insulating layers 8 are polyimides other than the above-mentioned polyimide or other synthetic resins. It may be. As the other synthetic resin, for example, polyamide-imide, polyesterimide, polyurethane, polyetherimide and the like can be used.

The flat-angle insulated wire 6 may have another layer laminated on the outer peripheral side of one or a plurality of insulating layers 8. Examples of the other layer include a surface lubrication layer and the like.

<Heat dissipation member>
The heat radiating member 3 is formed of a material that has at least thermal conductivity in the thickness direction and preferably has insulating properties. Further, the heat radiating member 3 preferably has elasticity so that the contact with the coil 2 can be made more reliable and the contact area can be increased.

Examples of the material for forming the heat radiating member 3 include a resin composition containing a resin such as silicone as a main component.

Further, the resin composition forming the heat radiating member 3 may contain a filler (fine particles) having thermal conductivity. The material of the filler having thermal conductivity, for example, such as aluminum nitride (AlN), silicon nitride _{(Si 3 N} 4), alumina _{(Al 2 O} 3), boron nitride (BN), like can be mentioned beryllium oxide (BeO) Be done.

<Holder>
The holding body 4 integrally holds the core 1 that can be formed by being divided into a plurality of pieces, and holds the coil 2 at a predetermined position of the core 1. The holding body 4 shown in the drawing has a pair of wall portions that sandwich the coil 2 from both sides in the axial direction, and exposes the side portions and the upper portion of the coil 2.

The holding body 4 is formed of an insulating resin composition or the like. Further, the material forming the holding body 4 preferably has thermal conductivity, and may contain the same thermal conductive filler as the heat radiating member 3.

<Advantage>
As described above, the reactor can have a larger capacity than its volume by bending the flat-angle insulated wire 6 in the edgewise direction to form the coil 2. Further, in the reactor, since the bending radius of the flat-angle insulated wire 6 at the corner of the core 1 is relatively small, the ratio of the straight portion to the total length of the flat-angle insulated wire 6 is large, and the flat-angle insulated wire 6 with respect to the heat radiating member 3 It has a large contact area and excellent heat dissipation. Further, since the reactor is mainly composed of polyimide derived from a precursor having the above-mentioned composition in the insulating layer 8 of the flat-angle insulated wire 6, it is excellent in appearance, bending workability and moisture heat deterioration resistance. Therefore, in the reactor, the insulating layer 8 is excellent in insulating property even though the bending radius of the flat-angle insulated wire 6 is reduced as described above.

[Reactor manufacturing method]
The reactor of FIG. 1 can be produced by the method for producing a reactor according to another embodiment of the present invention. The reactor manufacturing method includes a step of forming the flat-angle insulated wire 6 <flat-angle insulated wire forming step> and a step of bending the flat-angle insulated wire 6 on the outer periphery of the core 1 to form a coil 2 <bending-processing step. > And. Further, the method for manufacturing the reactor includes a step of further holding the core 1 and the coil 2 by the holding body 4 <holding step> and a step of arranging the heat radiating member 3 so as to be in close contact with the coil 2 <dissipating member arranging step>. It is preferable to provide with.

<Flat angle insulated wire forming process>
In the flat-angle insulated wire forming step, the flat-angle insulated wire 6 is formed so that the ratio of the average long side length to the average short side length in the cross section is within the above range. Specifically, the flat-angle insulated wire forming step includes a step of applying a resin varnish to the outer peripheral side of the conductor 7 in which the ratio of the average long side length to the average short side length in the cross section is within the above range. It has a step of heating the machined resin varnish.

(Coating process)
In the coating step, the conductor 7 is coated with the resin varnish containing the above-mentioned polyimide precursor. The method for coating the resin varnish is not particularly limited, and examples thereof include a method using a coating device including a resin varnish tank for storing the resin varnish and a coating die. According to this coating device, the resin varnish adheres to the outer peripheral surface of the conductor 7 by passing through the resin varnish tank, and then the resin varnish adheres to the outer peripheral surface of the conductor 7 by passing through the coating die. It is left with a uniform thickness. In this step, the resin varnish may be directly applied to the outer peripheral surface of the conductor 7, and an intermediate layer such as an adhesion improving layer is provided in advance on the outer peripheral surface of the conductor 7, and the resin is provided on the outer peripheral side of the intermediate layer. Varnish may be applied.

As the resin varnish used in this coating step, it is preferable to use a resin varnish that further contains an organic solvent in addition to the polyimide precursor.

The polyimide precursor can be obtained by a polymerization reaction of the above-mentioned aromatic tetracarboxylic dianhydride and an aromatic diamine. The method of the polymerization reaction can be the same as that of the conventional synthesis of the polyimide precursor. Specific methods of the above-mentioned polymerization reaction include, for example, a method of mixing an aromatic tetracarboxylic dianhydride and an aromatic diamine in an organic solvent and heating the mixed solution. By this method, the aromatic tetracarboxylic dianhydride and the aromatic diamine are polymerized, and a solution in which the polyimide precursor is dissolved in an organic solvent can be obtained.

The reaction conditions for the above polymerization may be appropriately set depending on the raw materials used and the like. For example, the reaction temperature can be 10 ° C. or higher and 100 ° C. or lower, and the reaction time can be 0.5 hours or longer and 24 hours or lower.

The molar ratio of aromatic tetracarboxylic dianhydride to aromatic diamine (aromatic tetracarboxylic dianhydride / aromatic diamine) used in the above polymerization is 100/100 from the viewpoint of efficiently advancing the polymerization reaction. The closer it is, the more preferable. The molar ratio can be, for example, 95/105 or more and 105/95 or less.

Examples of the organic solvent used for the above-mentioned polymerization include aprotic polar organic solvents such as N-methyl-2-pyrrolidone (NMP), N, N-dimethylformamide, N, N-dimethylacetamide, dimethyl sulfoxide, and γ-butyrolactone. Can be used. These organic solvents may be used alone or in combination of two or more. Here, the "aprotic polar organic solvent" refers to a polar organic solvent having no group that releases a proton.

The amount of the organic solvent used is not particularly limited as long as the amount of the aromatic tetracarboxylic dianhydride and the aromatic diamine can be uniformly dispersed. The amount of the organic solvent used may be, for example, 100 parts by mass or more and 1000 parts by mass or less with respect to 100 parts by mass in total of the aromatic tetracarboxylic dianhydride and the aromatic diamine.

As the resin varnish used in the coating step, a solution in which the polyimide precursor is dissolved in an organic solvent in the above-mentioned method for synthesizing the polyimide precursor can be used as it is. Further, the resin varnish is prepared by purifying the polyimide precursor from a solution in which the polyimide precursor is dissolved in an organic solvent, and then mixing the obtained purified polyimide precursor with other components such as an organic solvent. You may use it.

The organic solvent contained in the resin varnish improves the coatability of the resin varnish. Further, when the resin varnish containing the organic solvent is formed by repeating the coating step and the heating step on the peripheral surface side of the conductor 7 to form a plurality of insulating layers 8, the resin varnish is contained in the resin varnish in the second and subsequent coating steps. Since the organic solvent of the above slightly dissolves the polyimide of the base layer (the insulating layer 8 formed in the previous coating step and the heating step), the adhesion between each layer of the plurality of insulating layers 8 formed can be improved. it can.

As the organic solvent, an aprotic polar organic solvent is preferable. Since the polyimide precursor has high solubility in an aprotic polar organic solvent, the polyimide is used even when the concentration of the polyimide precursor in the resin varnish is increased by using the aprotic polar organic solvent as the organic solvent. The precursor can be reliably dissolved. Further, by using an aprotic polar organic solvent as the organic solvent, the organic solvent in the resin varnish easily dissolves the polyimide of the base layer in the second and subsequent coating steps described above, so that a plurality of the organic solvents are formed. The adhesion between the layers of the insulating layer 8 can be further improved.

Examples of the aprotic polar organic solvent include N-methyl-2-pyrrolidone (NMP), N, N-dimethylformamide, from the viewpoint of improving the solubility of the polyimide precursor and improving the adhesion between the plurality of insulating layers 8. N, N-dimethylacetamide, dimethyl sulfoxide, γ-butyrolactone and combinations thereof are preferable, and NMP is more preferable.

As the organic solvent, as described above, the organic solvent used for the polymerization reaction of the polyimide precursor may be used as it is, or may be added separately after obtaining the polyimide precursor, but from the viewpoint of workability. , It is preferable to use the organic solvent used for the polymerization reaction of the polyimide precursor as it is. The content of the organic solvent in the resin varnish can be, for example, in the range of 100 parts by mass or more and 1,000 parts by mass or less with respect to 100 parts by mass of the polyimide precursor.

In addition to the above-mentioned components, the resin varnish may contain various additives such as pigments, dyes, inorganic or organic fillers, lubricants, adhesion improvers, and reactive low molecules. Further, the resin varnish may contain other resins as long as the gist of the present invention is not impaired. When the resin varnish contains the above-mentioned components, the content of the above-mentioned components in the resin varnish can be, for example, 0.5 parts by mass or more and 30 parts by mass or less with respect to 100 parts by mass of the polyimide precursor. ..

When a plurality of insulating layers 8 are formed by the method for manufacturing a flat-angle insulated wire 6, that is, when this coating step and the heating step described later are repeated, in some of the plurality of coating steps, the above A resin varnish other than the resin varnish may be used.

(Heating process)
In the heating step, the resin varnish coated on the conductor 7 is heated by, for example, a method of running the conductor 7 coated with the resin varnish in a heating furnace. By this heating step, the polyimide precursor contained in the resin varnish is imidized, volatile components such as an organic solvent are removed, and an insulating layer 8 which is a baking layer is formed on the outer peripheral side of the conductor 7. The heating method is not particularly limited, and can be performed by a conventionally known method such as hot air heating, infrared heating, or high frequency heating. The heating temperature can be, for example, 350 ° C. or higher and 500 ° C. or lower. The heating time can be, for example, 5 seconds or more and 100 seconds or less. When the conductor 7 coated with the resin varnish is heated by running in the heating furnace, the set temperature in the heating furnace is regarded as the heating temperature, and the distance from the inlet to the outlet of the heating furnace is the distance of the conductor 7. The value divided by the linear velocity shall be regarded as the above heating time.

When the coating step and the heating step are repeated in the flat-angle insulated wire forming step, the number of times the coating step and the heating step are repeated can be, for example, 2 times or more and 200 times or less.

<Bending process>
In the bending process, the coil 2 is formed by bending the flat-angle insulated wire 6 on the outer circumference of the core 1 in the edgewise direction. At this time, by setting the bending radius of the flat-angle insulated wire 6 at the corner of the core 1 to be within the above range, the contact area with the heat radiating member 3 can be increased to improve the heat radiating property of the reactor. it can.

<Holding process>
In the holding step, the holding body 4 integrally holds the core 1 which is divided into a plurality of pieces, and holds the coil 2 at a predetermined position of the core 1. The core 1 and the coil 2 are held by the holding body 4. The holding body 4 can be formed by insert molding in which the core 1 and the coil 2 are arranged in a mold and the resin composition is injected.

<Heat dissipation member placement process>
In the heat radiating member disposing step, the heat radiating member 3 is brought into close contact with the coil 2. This heat radiating member disposing step may be performed before the accommodating step. For example, when the holding body 4 is formed by insert molding, the heat radiating member 3 may be arranged together with the core 1 and the coil 2 in the mold.

<Advantage>
In the method for producing the reactor, since the insulating layer 8 of the flat-angle insulated wire 6 is formed by using a resin varnish containing a precursor having the above-mentioned composition, the bending radius of the flat-angle insulated wire 6 is reduced as described above. It is possible to manufacture a reactor having excellent insulating properties of the insulating layer 8 while improving heat dissipation.

[Other Embodiments]
The disclosed embodiments should be considered in all respects as exemplary and not restrictive. The scope of the present invention is not limited to the configuration of the above embodiment, but is indicated by the scope of claims, and is intended to include all modifications within the meaning and scope equivalent to the scope of claims. To.

In the reactor, the heat dissipation member and the holder are not essential. Similarly, in the method for manufacturing the reactor, the accommodating step and the heat radiating member arrangement step are not essential.

Hereinafter, the present invention will be described in detail based on Examples, but the present invention is not limitedly interpreted based on the description of this Example.

As described below, an insulated wire No. 1 in which a plurality of resin varnishes having different components are prepared and an insulating layer is formed on the outer peripheral surface of the conductor using the resin varnishes. Trials 1 to 12 were made, and their appearance, bending workability, extensibility, moisture and heat deterioration resistance, and heat resistance were confirmed.

[Insulated wire No. 1-11]
First, 4,4'-ODA was dissolved in N-methyl-2-pyrrolidone, PMDA and 3,3', 4,4'-BPDA were added to the obtained solution, and the mixture was stirred under a nitrogen atmosphere. .. Then, the mixture was reacted at 80 ° C. for 3 hours with stirring and then cooled to room temperature to prepare a resin varnish for an insulated wire in which the polyimide precursor was dissolved in N-methyl-2-pyrrolidone as an organic solvent. .. The concentration of the polyimide precursor in this resin varnish is 30% by mass. The ratio (mol%) of 3,3', 4,4'-BPDA in the acid dianhydride of the polyimide precursor in each resin varnish for insulated wires is shown in Table 1 below.

Subsequently, a step of preparing a flat wire containing copper as a main component, having a cross-sectional width of 1 mm and a cross-sectional length of 6 mm as a conductor, and applying the above resin varnish to the outer peripheral surface of the conductor, and a conductor coated with the resin varnish. By repeating the process of heating in a heating furnace under the conditions of a heating temperature of 400 ° C. and a heating time of 30 seconds 10 times each, the conductor and an insulating layer having an average thickness of 35 μm laminated on the outer peripheral surface of the conductor are formed. Insulated wire No. 1 to 11 were obtained.

[Insulated wire No. 12]
A resin varnish containing polyamide-imide (PAI) as a main component, which is generally used for forming an insulating layer of an insulated wire, is prepared, and the insulated wire No. Insulated wire No. 1 provided with an insulating layer having an average thickness of 35 μm by repeating the same coating process and heating process as in 1 to 11. I got twelve.

[appearance]
As for the appearance of the insulating layer, the appearance of the insulating layer of the insulated wire was visually observed to confirm whether white turbidity, color unevenness, etc. occurred.

[Bending workability]
The bending workability of the insulating layer is such that the insulated wire is bent at a bending radius of 2.5 mm (0.41 times the cross-sectional length) in the edgewise direction at 90 ° and held in that state for 10 seconds or longer, and then the insulation of the bent portion is obtained. The presence or absence of cracks in the layer was visually confirmed, and the dielectric breakdown voltage (BDV) was measured.

[Extension]
The insulated wire was extended by 10% in the longitudinal direction, and the presence or absence of cracks in the insulating layer was visually confirmed and the dielectric breakdown voltage was measured.

[Moisture and heat deterioration resistance]
To check the moisture resistance and heat deterioration of the insulating layer, the stretched insulating wire was placed in an autoclave airtight container containing water and held in a constant temperature bath at 120 ° C. for 500 hours, and then the insulating layer cracked. The presence or absence was visually confirmed and the dielectric breakdown voltage was measured.

[Heat-resistant]
After holding the insulated wire that had not been pre-stretched in a constant temperature bath at 200 ° C. for 1000 hours, it was confirmed whether or not a decrease in dielectric breakdown voltage (10% or more) had occurred.

The composition of the resin varnish and the evaluation results of the insulated wire are summarized in Table 1 below.

As shown by this result, the insulating electric wire No. in which the insulating layer was formed by using the resin varnish in which the ratio of the biphenyltetracarboxylic dianhydride in the aromatic tetracarboxylic dianhydride was 60 mol% or more and 75 mol% or less. .. It was confirmed that 5 to 8 had excellent bending workability and did not deteriorate even in a moist heat environment and a high temperature environment. Therefore, these insulated wires No. The reactor formed by bending 5 to 8 with a small bending radius in the edgewise direction to form a coil is small, but the contact area with the heat radiating member is relatively large, so that the reactor has excellent heat radiating properties. it can.

The reactor according to one embodiment of the present invention and the reactor obtained by the method for producing a reactor according to another embodiment of the present invention shall be particularly preferably used for a DC booster for a hybrid vehicle, an electric vehicle, or a fuel cell vehicle. Can be done.

1 Core 2 Coil 3 Heat dissipation member 4 Holder 5 Case 6 Flat-angle insulated wire 7 Conductor 8 Insulated layer

Claims (3)

Comprising cross and a rectangular core, a rectangular insulated wire having a conductor and multiple insulating layers you covering the conductor is formed by bending edgewise direction, and a coil disposed on the outer periphery of the core It ’s a reactor,
The bending radius of the flat-angle insulated wire at the corner of the core is ½ or less of the average long side length in the cross section of the conductor.
At least one of the above insulating layers contains a polyimide derived from a polyimide precursor which is a reaction product of an aromatic tetracarboxylic dianhydride and an aromatic diamine as a main component.
The aromatic tetracarboxylic dianhydride contains biphenyltetracarboxylic dianhydride.
The ratio of biphenyltetracarboxylic dianhydride in the aromatic tetracarboxylic dianhydride is 60 mol% or more and 75 mol% or less.
The aromatic tetracarboxylic dianhydride further comprises pyromellitic dianhydride.
The ratio of pyromellitic dianhydride in the aromatic tetracarboxylic dianhydride is 5 mol% or more and 40 mol% or less.
The aromatic diamine contains diaminodiphenyl ether and contains
The ratio of the average long side length to the average short side length in the cross section of the conductor is 5 or more and 10 or less.
The average long side length of the cross section of the conductor is 5 mm or more and 10 mm or less.
There are a plurality of the insulating layers, the average thickness of each insulating layer is 1 μm or more and 5 μm or less, and the average total thickness of the plurality of insulating layers is 10 μm or more and 200 μm or less.
The weight average molecular weight of the polyimide precursor is 10,000 or more and 180,000 or less.
The molar ratio of the aromatic tetracarboxylic dianhydride used as the raw material of the polyimide precursor to the aromatic diamine is 95/105 or more and 105/95 or less.
A reactor in which the total ratio of biphenyltetracarboxylic dianhydride, pyromellitic dianhydride and diaminodiphenyl ether in all the raw materials of the polyimide precursor is 95 mol% or more. The reactor according to claim 1, wherein the dielectric breakdown voltage of the insulating layer after a heating test held at 200 ° C. for 1000 hours is 50% or more of the dielectric breakdown voltage before the heating test. The core includes a core having a rectangular cross section, and a coil formed by bending a conductor and a flat-angle insulated wire having one or a plurality of insulating layers covering the conductor in an edgewise direction and arranged on the outer periphery of the core. It is a manufacturing method of the reactor.
The process of forming the above flat-angle insulated wire and
It is provided with a step of bending the flat-angle insulated wire so that the bending radius is 1/2 or less of the average long side length in the cross section of the conductor.
The flat-angle insulated wire forming process
The process of applying resin varnish to the outer peripheral side of the conductor and
It has a process of heating the above-coated resin varnish,
The resin varnish contains a polyimide precursor which is a reaction product of an aromatic tetracarboxylic dianhydride and an aromatic diamine.
The aromatic tetracarboxylic dianhydride contains biphenyltetracarboxylic dianhydride.
The ratio of biphenyltetracarboxylic dianhydride in the aromatic tetracarboxylic dianhydride is 60 mol% or more and 75 mol% or less.
The aromatic tetracarboxylic dianhydride further comprises pyromellitic dianhydride.
The ratio of pyromellitic dianhydride in the aromatic tetracarboxylic dianhydride is 5 mol% or more and 40 mol% or less.
The aromatic diamine contains diaminodiphenyl ether and contains
The ratio of the average long side length to the average short side length in the cross section of the conductor is 5 or more and 10 or less.
The average long side length of the cross section of the conductor is 5 mm or more and 10 mm or less.
There are a plurality of the insulating layers, the average thickness of each insulating layer is 1 μm or more and 5 μm or less, and the average total thickness of the plurality of insulating layers is 10 μm or more and 200 μm or less.
The weight average molecular weight of the polyimide precursor is 10,000 or more and 180,000 or less.
The molar ratio of the aromatic tetracarboxylic dianhydride used as the raw material of the polyimide precursor to the aromatic diamine is 95/105 or more and 105/95 or less.
A method for producing a reactor in which the total ratio of biphenyltetracarboxylic dianhydride, pyromellitic dianhydride and diaminodiphenyl ether in all the raw materials of the polyimide precursor is 95 mol% or more.

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