Insulating sheet and motor

Abstract

Provided is, inter alia, an insulating sheet comprising two outer layers disposed so as to face each other, and a base material layer disposed between the two outer layers, wherein at least one of the two outer layers contains at least one selected from the group consisting of mica, bentonite, and kaolinite.

Description

Insulation sheet and motor CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority from Japanese Patent Application No. 2024-042363, which is incorporated herein by reference.

[0002] The present invention relates to an insulating sheet that is a component of a motor, for example, and a motor that includes the insulating sheet.

[0003] BACKGROUND ART Conventionally, an insulating sheet has been known that includes at least two outer layers arranged to face each other and a base layer arranged between the two outer layers.

[0004] Known examples of this type of insulating sheet include motor insulating sheets. Specifically, motor insulating sheets are used as slot members disposed between the inner wall surfaces of slots in a stator core of a motor and the winding coils housed in the slots. For example, a motor insulating sheet of this type has a relative dielectric constant of 2.5 or less at 1 GHz and a three-layer laminate structure including surface layers constituting both surfaces and an intermediate layer disposed between the surface layers, the surface layers being made of wholly aromatic polyamide paper and the intermediate layer being made of a specific thermoplastic resin (see, for example, Patent Document 1).

[0005] In recent years, the drive voltage of motors for electric vehicles and other devices that require high output has been increasing. When a high-voltage AC electric field is applied to a motor, partial discharges are likely to occur, which can result in a deterioration of the motor's insulation performance. Therefore, there is a demand for an insulating sheet that can suppress the occurrence of partial discharges. The insulating sheet described in Patent Document 1 suppresses the occurrence of partial discharges to a certain extent.

[0006] Japanese Patent Application Publication No. 2015-109735

[0007] However, the insulating sheet described in Patent Document 1 may not be able to sufficiently suppress partial discharges in some cases. In particular, when the surface resistance of the insulating sheet is relatively high, partial discharges may occur more easily.

[0008] In view of the above problems, an object of the present invention is to provide an insulating sheet having a relatively low surface resistance and capable of sufficiently suppressing the occurrence of partial discharge, and to provide a motor including the insulating sheet.

[0009] In order to solve the above problems, the insulating sheet of the present invention comprises two outer layers arranged to face each other and a base material layer arranged between the two outer layers, and at least one of the two outer layers contains at least one material selected from the group consisting of mica, bentonite, and kaolinite.

[0010] A motor according to the present invention includes the insulating sheet described above.

[0011] Fig. 1 is a schematic cross-sectional view of an insulating sheet according to a first embodiment, cut in the thickness direction. Fig. 2 is a schematic cross-sectional view of an insulating sheet according to a second embodiment, cut in the thickness direction. Fig. 3 is a perspective view of a stator of a drive motor. Fig. 4 is a graph showing the measurement results of surface resistance. Fig. 5 is a graph showing the measurement results of partial discharge inception voltage.

[0012] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of an insulating sheet according to the present invention will be described with reference to the drawings. Specifically, a first embodiment and a second embodiment will be described.

[0013] The insulating sheet of the first embodiment has a five-layer structure as shown in Fig. 1. On the other hand, the insulating sheet of the second embodiment has a three-layer structure as shown in Fig. 2.

[0014] [First embodiment]

[0015] The insulating sheet 10 of the first embodiment includes two outer layers 13 arranged to face each other, two adhesive layers 12 arranged to face each other between the two outer layers 13, and a base material layer 11 arranged between the two adhesive layers 12. In other words, the insulating sheet 10 of the first embodiment includes one base material layer 11, two adhesive layers 12 arranged to sandwich the base material layer 11 in the thickness direction, and two outer layers 13 arranged to sandwich the two adhesive layers 12 in the thickness direction. In the insulating sheet 10 of the first embodiment, the base material layer 11 and one of the adhesive layers 12 are in direct contact, and the base material layer 11 and the other adhesive layer 12 are in direct contact. Furthermore, the adhesive layer 12 and the outer layer 13 are in direct contact on one side of the base material layer 11, and the adhesive layer 12 and the outer layer 13 are also in direct contact on the other side.

[0016] In the insulating sheet 10 of the first embodiment, at least one of the two outer layers contains at least one selected from the group consisting of mica, bentonite, and kaolinite. Preferably, both of the two outer layers contain at least one selected from the group consisting of mica, bentonite, and kaolinite. More preferably, both of the two outer layers contain mica. Note that each outer layer 13 may be the outermost layer of the insulating sheet 10.

[0017] The thickness of the insulating sheet 10 is, for example, 50 μm or more and 500 μm or less. The thickness of the insulating sheet 10 may be 100 μm or more, or 150 μm or more. The thickness of the insulating sheet 10 may be 450 μm or less, or 400 μm or less. The thickness of the insulating sheet 10 is preferably 150 μm or more, and more preferably 200 μm or more, in order to further improve the workability when inserting the insulating sheet 10 into the slots of a stator (described in detail later).

[0018] The thickness of the base layer 11 may be, for example, 25 μm or more and 200 μm or less, and is preferably 100 μm or less.

[0019] The thickness of the outer layer 13 (per layer) may be, for example, 10 μm or more and 200 μm or less. The thickness of the outer layer 13 is preferably 20 μm or more, more preferably 25 μm or more. The thickness of the outer layer 13 is preferably 125 μm or less, more preferably 100 μm or less. Of the two outer layers 13, it is preferable that the difference in thickness between one outer layer 13 and the other outer layer 13 is small. For example, the thickness of the other outer layer 13 may be 0.9 times or more and 1.1 times or less relative to the thickness of one outer layer 13.

[0020] The thickness of the adhesive layer 12 (per layer) may be, for example, 1 μm or more and 150 μm or less. The thickness of the adhesive layer 12 is preferably 5 μm or more and more preferably 20 μm or more. The thickness of the adhesive layer 12 is preferably 100 μm or less and more preferably 80 μm or less. Of the two adhesive layers 12, it is preferable that the difference in thickness between one adhesive layer 12 and the other adhesive layer 12 is small. For example, the thickness of one adhesive layer 12 may be 0.9 times or more and 1.1 times or less.

[0021] The thickness of each layer refers to the average thickness. The thickness of each layer is determined by averaging the thicknesses of at least five randomly selected locations. The thickness of each layer can be measured, for example, by observing the side surface of the insulating sheet 10 or a cross section of the insulating sheet 10 cut in the thickness direction with a digital microscope.

[0022] The ratio of the thickness of the base layer 11 to the total thickness of the insulating sheet 10 may be 0.10 or more, or 0.20 or more. This thickness ratio may be 0.50 or less, or 0.40 or less. A ratio of 0.20 or more has the advantage of further improving the electrical insulation of the insulating sheet 10.

[0023] The ratio of the total thickness of the outer layers 13 (the thickness of two layers) to the total thickness of the insulating sheet 10 is preferably 0.20 or more. However, this ratio may be 0.70 or less, or may be 0.65 or less. A ratio of 0.70 or less has the advantage of further improving the electrical insulation of the insulating sheet 10. The ratio of the thickness of each outer layer 13 (the thickness of one layer) to the total thickness of the insulating sheet 10 may be half the value of the ratio of the thickness of two layers.

[0024] The ratio of the total thickness of the adhesive layers 12 (the thickness of two layers) to the total thickness of the insulating sheet 10 may be 0.05 or more, or 0.10 or more. This ratio may also be 0.50 or less, or 0.40 or less. A ratio of 0.05 or more has the advantage of improving the adhesion between the outer layer 13 and the base layer 11 via the adhesive layer 12. The ratio of the thickness of each adhesive layer 12 (the thickness of one layer) to the total thickness of the insulating sheet 10 may be half the value of the ratio of the thickness of two layers.

[0025] In the insulating sheet 10, the ratio of the thickness of each adhesive layer 12 to the thickness of each outer layer 13 may be 0.10 or more, or 0.15 or more. Furthermore, this ratio may be 4.00 or less, 2.00 or less, 1.00 or less, or 0.80 or less. Having this ratio of 0.10 or more has the advantage of improving the adhesion between the outer layer 13 and the base layer 11 via the adhesive layer 12. Having this ratio of 1.00 or less has the advantage of allowing the total thickness of the insulating sheet 10 to be thinner.

[0026] It is preferable that the above-mentioned numerical ranges for the thicknesses of the outer layer 13 and the adhesive layer 12 are satisfied on at least one side or the other side of the base layer 11. It is more preferable that the ratio of the thickness of each adhesive layer 12 to the thickness of each outer layer 13 is within the above-mentioned numerical range on both sides of the base layer 11.

[0027] The base layer 11 is, for example, a resin film. Examples of the resin film include a heat-resistant resin film such as a polyimide resin film, a polyester resin film, etc. The resin film is preferably a polyester resin film.

[0028] Examples of the polyester resin film include films formed from a polymer of a dicarboxylic acid such as terephthalic acid or 2,6-naphthalenedicarboxylic acid and a diol such as ethylene glycol, 1,3-propanediol, 1,4-butanediol, or 1,4-cyclohexanedimethanol. Specific examples of the polyester resin film include polyethylene terephthalate resin (PET) film and polyethylene naphthalate resin (PEN) film.

[0029] The base layer 11 is more preferably a polyethylene naphthalate resin film.

[0030] The base material layer 11 may be a single layer as in this embodiment, or may be a laminate film in which a plurality of resin films are laminated.

[0031] As the base material layer 11, for example, a commercially available product such as the "Teonex" series (manufactured by Toyobo Co., Ltd.) can be used.

[0032] As described above, at least one of the two outer layers 13 constituting the insulating sheet 10 of the first embodiment contains at least one selected from the group consisting of mica, bentonite, and kaolinite. Only one outer layer 13 may contain mica, only the other outer layer 13 may contain mica, or both outer layers 13 may contain mica. The same applies to bentonite and kaolin. When at least one of the two outer layers 13 contains at least one selected from the group consisting of mica, bentonite, and kaolinite, the surface resistance of the insulating sheet 10 can be kept relatively low, and the insulating sheet 10 can more sufficiently suppress the occurrence of partial discharge. When both of the two outer layers 13 each contain at least one selected from the group consisting of mica, bentonite, and kaolinite, the surface resistance of the insulating sheet 10 can be kept lower, and the insulating sheet 10 can more sufficiently suppress the occurrence of partial discharge.

[0033] The mica is also called mica powder, and examples of mica include powders of white mica (muscovite), phlogopite, sericite, and synthetic mica.

[0034] The shape of each mica particle is, for example, a flat plate, and the longest diameter of each particle in the plane direction is, for example, 1 μm or more and 500 μm or less.

[0035] The above-mentioned bentonite is a clay mineral powder containing montmorillonite as a main component. Therefore, montmorillonite powder is included in the above-mentioned bentonite. Bentonite is distinguished, for example, by the cation species contained between the crystal layers of the main component montmorillonite. Examples of bentonite include sodium-type bentonite, calcium-type bentonite, and activated bentonite (sodium-exchanged bentonite).

[0036] The shape of each particle of the bentonite is, for example, flat, etc. The particle diameter of each particle of the bentonite is, for example, 1 μm or more and 500 μm or less.

[0037] The kaolinite is a powder of clay mineral with a specific composition among silicate minerals. It is also known as kaolin. The main components of kaolinite are Al, ４ Si ４ O １０ (OH) ８ is.

[0038] The shape of each of the kaolinite particles is, for example, tabular. The longest diameter of each of the kaolinite particles in the plane direction is, for example, 0.1 μm or more and 3.0 μm or less.

[0039] Each outer layer 13 preferably contains at least one selected from the group consisting of mica, bentonite, and kaolinite in a total amount (total amount) of 5% by mass or more, and more preferably 15% by mass or more. Each outer layer 13 preferably contains at least one selected from the group consisting of mica, bentonite, and kaolinite in a total amount (total amount) of 60% by mass or less, and more preferably 50% by mass or less. This reduces the surface resistance of the insulating sheet 10 and enables the insulating sheet 10 to more effectively suppress the occurrence of partial discharge. Note that the above total amount refers to the mass% of the single type when each outer layer 13 contains only one of mica, bentonite, or kaolinite; it refers to the combined mass% of the two types when each outer layer 13 contains two of the above; and it refers to the combined mass% of the three types when each outer layer 13 contains all of the above.

[0040] At least one of the two outer layers 13 preferably contains aromatic polyamide paper and at least one selected from the group consisting of mica, bentonite, and kaolinite. More preferably, both of the two outer layers 13 contain aromatic polyamide paper and at least one selected from the group consisting of mica, bentonite, and kaolinite. By including aromatic polyamide paper in each outer layer 13, the insulating sheet 10 can have good heat resistance. Furthermore, after the insulating sheet 10 is placed in a slot of a motor stator, for example, good slip properties can be imparted when inserting a coil wire.

[0041] In the outer layer 13 containing aromatic polyamide paper and mica, the mica particles are disposed between the fibers inside the aromatic polyamide paper. In other words, the mica particles are dispersed between the fibers inside the aromatic polyamide paper. In the outer layer 13 containing aromatic polyamide paper and bentonite, similarly to the above, the bentonite particles are disposed between the fibers inside the aromatic polyamide paper. In the outer layer 13 containing aromatic polyamide paper and kaolinite, similarly to the above, the kaolinite particles are disposed between the fibers inside the aromatic polyamide paper.

[0042] The aromatic polyamide paper may be, for example, a wholly aromatic polyamide paper made from at least one of short fibers made of a wholly aromatic polyamide and synthetic pulp made of a wholly aromatic polyamide. When the aromatic polyamide paper is a wholly aromatic polyamide paper, the insulating sheet 10 can have better heat resistance. Examples of wholly aromatic polyamides that make up the short fibers or synthetic pulp include a condensation polymer of m-phenylenediamine and isophthalic acid, and a condensation polymer of p-phenylenediamine and terephthalic acid.

[0043] The outer layer 13 may be subjected to lamination, high-temperature and high-pressure calendaring, or surface treatment. The surface treatment may be performed using a coating agent containing a polyamide resin (e.g., a methoxymethylated polyamide resin in which the amide group is methoxymethylated). For example, a commercially available product (e.g., product name "Nomex" manufactured by DuPont) can be used as the outer layer 13.

[0044] The weight of each outer layer 13 is, for example, 20 g / m ２ 240g / m or more ２ It may be the following:

[0045] The two adhesive layers 12 in the first embodiment each contain, for example, a polymer component (adhesive component), a crosslinking agent, a tackifier, and the like.

[0046] The polymer component may be, for example, an acrylic polymer.

[0047] The acrylic polymer is preferably a polymer obtained by polymerizing at least a (meth)acrylic acid alkyl ester. The acrylic polymer may be, for example, a polymer of a (meth)acrylic acid alkyl ester, or a copolymer of a (meth)acrylic acid alkyl ester and another polymerizable monomer. In this specification, the term "(meth)acrylic" includes both "acrylic" and "methacrylic."

[0048] Examples of (meth)acrylic acid alkyl esters include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate [e.g., normal propyl (meth)acrylate, isopropyl (meth)acrylate, etc.], butyl (meth)acrylate [e.g., normal butyl (meth)acrylate, isobutyl (meth)acrylate, secondary butyl (meth)acrylate, tertiary butyl (meth)acrylate, etc.], 2-ethylhexyl (meth)acrylate, normal octyl (meth)acrylate, normal nonyl (meth)acrylate, and isononyl (meth)acrylate.

[0049] Examples of other polymerizable monomers include ethylene, styrene, vinyl chloride, acrylic acid, butadiene, and acrylonitrile.

[0050] Examples of the copolymer include an ethylene-(meth)acrylic acid alkyl ester copolymer, an ethylene-(meth)acrylic acid alkyl ester-acrylic acid copolymer, a styrene-(meth)acrylic acid alkyl ester-acrylic acid copolymer, a (meth)acrylic acid alkyl ester-vinyl chloride copolymer, a (meth)acrylic acid alkyl ester-acrylic acid copolymer, a (meth)acrylic acid alkyl ester-vinyl chloride copolymer, a styrene-(meth)acrylic acid alkyl ester-butadiene copolymer, and a (meth)acrylic acid alkyl ester-acrylonitrile copolymer.

[0051] The acrylic polymer is preferably polybutyl acrylate (PAB), which is a polymer of at least butyl (meth)acrylate. Such polybutyl acrylate (PAB) may have a carboxy group or a hydroxy group in the molecule.

[0052] The above acrylic polymers may be used alone or in combination of two or more.

[0053] Examples of the crosslinking agent include isocyanate compounds.

[0054] The isocyanate compound is preferably a polyfunctional isocyanate compound. Such a polyfunctional isocyanate compound is a compound having multiple isocyanate groups in the molecule. Examples of the polyfunctional isocyanate compound include diphenylmethane diisocyanate, tolylene diisocyanate, and hexamethylene diisocyanate. The polyfunctional isocyanate compound may be an adduct in which tolylene diisocyanate trimer is added to trimethylolpropane.

[0055] Examples of the tackifier include petroleum-based resins such as aliphatic copolymers, aromatic copolymers, aliphatic-aromatic copolymers, and alicyclic copolymers. Further examples include coumarone-indene resins, terpene resins, terpene phenol resins, rosin resins such as polymerized rosin, alkylphenol resins, xylene resins, and hydrogenated products thereof. One type of tackifier may be used alone, or two or more types may be used in combination.

[0056] The adhesive layer 12 preferably contains a polymeric compound that is a crosslinked reaction product of the polybutyl acrylate (PAB) as a polymer component and the isocyanate compound as a crosslinking agent. The adhesive layer 12 more preferably contains a crosslinked reaction product of the polybutyl acrylate (PAB) and the isocyanate compound, and an alkylphenol resin as a tackifier. This improves adhesion between the adhesive layer 12 and the outer layer 13 (especially aromatic polyamide paper). The amount of alkylphenol resin added is preferably 1 part by mass or more and 50 parts by mass or less, and more preferably 30 parts by mass or less, per 100 parts by mass of the polybutyl acrylate (PAB). The polybutyl acrylate (PAB) may have a carboxyl group in its molecule.

[0057] The adhesive layer 12 may be formed of, for example, a commercially available polymer. The adhesive layer 12 may be formed of, for example, a polymer composition in which a plurality of types of polymers are crosslinked.

[0058] The insulating sheet 10 of the first embodiment has good electrical insulation properties and a relatively high adhesive strength between the outer layer 13 and the adhesive layer 12. When the adhesive layer 12 contains the above-mentioned acrylic polymer, the adhesive strength can be further increased.

[0059] Next, an insulating sheet 10' according to a second embodiment will be described.

[0060] 2 , an insulating sheet 10′ according to a second embodiment includes two outer layers 13 arranged to face each other and a base material layer 11 arranged between the two outer layers 13. In other words, an insulating sheet 10′ according to the second embodiment includes, for example, one base material layer 11 and two outer layers 13 arranged to sandwich the base material layer 11 in the thickness direction. In the insulating sheet 10 according to the second embodiment, the base material layer 11 and one of the outer layers 13 are in direct contact with each other, and the base material layer 11 and the other outer layer 13 are in direct contact with each other.

[0061] The substrate layer 11 includes, for example, a specific thermoplastic resin. Examples of the specific thermoplastic resin include a cyclic polyolefin resin such as a norbornene resin or an ethylene-norbornene copolymer resin, a syndiotactic polystyrene resin, a poly(4-methyl-1-pentene) resin, or an ethylene-tetrafluoroethylene copolymer resin. These specific resins are commercially available in the form of a resin film.

[0062] The insulating sheet 10 of each of the above-described embodiments has a size of, for example, 1×10 １３ The insulating sheet 10 has a volume resistivity of 1×10 Ω·cm or more. １４ It is preferably Ω·cm or more.

[0063] Next, a method for manufacturing the insulating sheet 10 of the above embodiment will be described.

[0064] In the method for producing the insulating sheet 10 of the first embodiment, for example, a mixture containing the components that will constitute the adhesive layer 12 and an organic solvent (if necessary) is prepared, and the mixture is applied to both sides of the base layer 11, and the organic solvent contained in the applied mixture is volatilized (if necessary) to produce two adhesive layers 12. The insulating sheet 10 can then be produced by bonding the outer layer 13 to each adhesive layer 12. Note that a roll coater, for example, can be used as the coating device.

[0065] As the organic solvent, for example, ethyl acetate, methyl ethyl ketone (MEK), or toluene can be used.

[0066] A common coating method such as die coating or reverse coating can be used when applying the mixture containing an organic solvent to the outer layer 13. The temperature during application is, for example, room temperature (15 to 25° C.).

[0067] On the other hand, in the manufacturing method of the insulating sheet 10 of the second embodiment, for example, the insulating sheet 10 can be continuously manufactured by extruding a molten resin that will form the base layer 11 in a strip shape from a T-die or the like, and then bonding strip-shaped outer layers to both sides of the extruded molten material.

[0068] The insulating sheet 10 manufactured as described above is used, for example, as a component of a motor. The insulating sheet 10 may be used, for example, as an insulating sheet for a drive motor of an automobile. Specifically, it can be used as slot insulating paper for a motor stator. The insulating sheet 10 can be used, for example, in a heated state.

[0069] For example, when insulating sheet 10 having two outer layers, one of which contains mica, is used as an insulating sheet for a motor, the one outer layer containing mica may be disposed so as to face the inner wall surface of the slot of the stator core of the motor, or the other outer layer containing mica may be disposed so as to face the winding coil housed in the slot of the stator core.

[0070] Examples of the automobile include a hybrid electric vehicle (HEV) and an electric vehicle (EV). Examples of the drive motor include an HV motor, a motor generator, an alternator, a 4WD motor, an oil pump motor, an EPS motor, a compressor motor, and an in-wheel motor.

[0071] Next, an embodiment of a motor according to the present invention will be described with reference to the drawings.

[0072] The motor of this embodiment includes the above-described insulating sheet 10. The insulating sheet 10 is, for example, an insulating sheet for a motor.

[0073] For example, the motor is a drive motor mounted on a hybrid vehicle or an electric vehicle.

[0074] The drive motor of an automobile includes a rotor equipped with a permanent magnet and a stator 20 that generates a force to rotate the rotor. As shown in Fig. 3, the stator 20 has a coil 21 and a stator core 22. The stator 20 is configured to rotate the rotor by generating a magnetic field in the coil 21.

[0075] In the above-described drive motor, the coil 21 is composed of, for example, a plurality of segment conductors connected to each other. In the above-described drive motor, a core such as a stator core 22 or a rotor core has a plurality of slots, and each of the plurality of slots accommodates a coil 21. In addition, in the above-described drive motor, a motor insulating sheet is used to ensure insulation between the coil 21 and the inner wall surfaces of the slots. The motor insulating sheet and the coil 21 are accommodated in each slot. More specifically, the motor insulating sheet is accommodated in the slot while being wrapped around the coil 21. The coil 21 wrapped around the motor insulating sheet is then fixed in the slot via an insulating resin (e.g., epoxy varnish) impregnated into the slot.

[0076] The insulating sheet and motor of this embodiment are as exemplified above, but the present invention is not limited to the insulating sheet or motor exemplified above. In other words, various forms used in general insulating sheets or motors can be adopted as long as they do not impair the effects of the present invention.

[0077] In the above embodiment, at least one of the two outer layers contains at least one selected from the group consisting of mica, bentonite, and kaolinite, but the present invention is not limited to this. For example, at least one of the two outer layers may contain a powder of a silicate mineral such as talc or smectite instead of or in addition to mica, bentonite, or kaolinite.

[0078] The present specification discloses the following: (1) An insulating sheet comprising two outer layers arranged to face each other and a substrate layer arranged between the two outer layers, wherein at least one of the two outer layers contains at least one material selected from the group consisting of mica, bentonite, and kaolinite. An insulating sheet having such a configuration has a relatively low surface resistance and can sufficiently suppress the occurrence of partial discharge. (2) The insulating sheet according to (1) above, wherein at least one of the two outer layers contains at least one material selected from the group consisting of mica, bentonite, and kaolinite in a total amount of 5% by mass to 60% by mass. (3) The insulating sheet according to (1) or (2) above, wherein at least one of the two outer layers contains aromatic polyamide paper and the mica. (4) The insulating sheet according to any one of (1) to (3) above, wherein both of the two outer layers contain at least one material selected from the group consisting of mica, bentonite, and kaolinite. (5) The insulating sheet according to any one of (1) to (4) above, further comprising two adhesive layers disposed between the two outer layers so as to face each other and sandwich the base material layer. (6) A motor comprising the insulating sheet according to any one of (1) to (5) above.

[0079] The present invention will now be described in more detail with reference to experimental examples, but the present invention is not limited to these examples.

[0080] The materials or raw materials for the outer layer, adhesive layer, and base layer used to manufacture the insulating sheet are shown below.

[0081] <Outer layer materials> - Mica-containing: outer layer containing wholly aromatic polyamide paper (PA paper) and mica Contains 47% by mass of mica based on the total weight of the outer layer Product name: "Nomex 818" series (manufactured by DuPont) Thickness: 80 μm per layer - Mica-free: wholly aromatic polyamide paper (PA paper) Product name: "Nomex" series (manufactured by DuPont) <Ingredients of adhesive layer> [Polymer component] Polybutyl acrylate (PAB) (commercially available product): 100 parts by mass Contains carboxyl group in the molecule [Crosslinking agent] Isocyanate compound (commercially available product): 5 parts by mass [Tackifier] Alkylphenol resin (commercially available product): 20 parts by mass

[0082] <Material of base layer> Polyethylene naphthalate resin film (PEN) Product name "Teonex Q51" (manufactured by Toyobo Co., Ltd.) Thickness: 75 μm

[0083] (Examples 1 to 4, Comparative Examples 1 and 2) The configurations (thickness and material of each layer, etc.) of the insulating sheets of each example and comparative example are shown in Table 1. Note that each of the insulating sheets of the examples and comparative examples has a five-layer laminate structure as shown in FIG.

[0084] <Production of insulating sheet> A mixture containing the above components that would form the adhesive layer and an organic solvent (methyl ethyl ketone (MEK)) was prepared. Each of these mixtures was applied to one side of a substrate layer using a bar coater so that the adhesive layer would have a predetermined thickness after drying. The organic solvent contained in the applied mixture was evaporated (dried) by a drying process at 105°C for 3 minutes, creating an adhesive layer on one side of the substrate layer. An outer layer was then attached to the adhesive layer at 90°C to create a three-layer laminate sheet. Subsequently, an adhesive layer and an outer layer were created on the other side of the substrate layer in the same manner as above. In this manner, each of the five-layer insulating sheets was produced.

[0085]

[0086] The insulating sheets produced in the examples and comparative examples were evaluated for their surface resistance suppressing performance as follows.

[0087] <Measurement of Surface Resistivity> Measurement was performed in accordance with JIS C2139-3-2:2018, "Dielectric and Resistivity Properties of Solid Electrical Insulating Materials - Part 3-2: Measurement of Resistivity Properties by Applying DC Voltage." Specifically, a three-terminal measurement circuit was employed using the concentric ring electrodes described in 5.3.6, and the surface resistivity was determined by reading the resistance value after 1 minute at 500 V. When only one of the two outer layers contained mica, the outer layer containing mica was placed on the concentric ring electrode side, and measurement was performed. A graph showing the measured surface resistance values ​​for each example and comparative example is shown in Figure 4.

[0088] Furthermore, the insulating sheets manufactured in each of the examples and comparative examples were evaluated for their ability to suppress the occurrence of partial discharge as follows.

[0089] As can be seen from FIG. 4, the insulating sheets of the examples had a lower surface resistance than the insulating sheets of the comparative examples.

[0090] <Measurement of Partial Discharge Inception Voltage> A square test piece with a side of 50 mm was cut out from the manufactured insulating sheet, and the partial discharge inception voltage of the test piece was measured. A partial discharge measuring instrument (model number "DAC-PD-3") manufactured by Soken Denki Co., Ltd. was used as the measuring instrument. During measurement, the test piece was sandwiched between a stainless steel plate and a brass electrode, and an AC voltage was applied to the stainless steel plate and the brass electrode at a voltage increase rate of 50 Vrms / second. The voltage value was determined when the discharge charge measured by the partial discharge measuring instrument reached 100 pC. Note that when only one of the two outer layers contained mica, the outer layer containing mica was placed on the brass electrode side and the measurement was carried out. Figure 5 is a graph showing the increase in discharge charge with the application of AC voltage for Example 1, Example 2, and Comparative Example 1.

[0091] As can be seen from FIG. 5, the insulating sheets of the examples suppressed the occurrence of partial discharge compared to the insulating sheets of the comparative examples.

[0092] In the above examples and comparative examples, an outer layer containing mica was used, but it is fully expected that similar results would be obtained even if an outer layer containing bentonite (e.g., montmorillonite) or kaolinite was used.

[0093] The insulating sheet of the present invention is preferably used, for example, as a component of a motor, for example, as a slot material provided in a motor.

[0094] 11: Base material layer, 12: Adhesive layer, 13: Outer layer, 10: Insulating sheet.

Claims

1. An insulating sheet comprising two outer layers arranged to face each other and a substrate layer arranged between the two outer layers, wherein at least one of the two outer layers contains at least one material selected from the group consisting of mica, bentonite, and kaolinite.

2. The insulating sheet according to claim 1, wherein at least one of the two outer layers contains at least one selected from the group consisting of mica, bentonite, and kaolinite in a total amount of 5% by mass or more and 60% by mass or less.

3. The insulating sheet according to claim 1 or 2, wherein at least one of the two outer layers comprises aromatic polyamide paper and the mica.

4. The insulating sheet according to claim 1 or 2, wherein both of the two outer layers contain at least one material selected from the group consisting of mica, bentonite, and kaolinite.

5. The insulating sheet according to claim 1 or 2, further comprising two adhesive layers disposed between the two outer layers so as to face each other and sandwich the base material layer.

6. A motor comprising the insulating sheet according to claim 1 or 2.

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