Coated metal wire, stator, electric motor, and method for manufacturing stator

Abstract

To provide a covered metal wire, a stator, an electric motor, and a method for manufacturing a stator, which can improve the insulation between metal wires and eliminate the need of a step of inserting insulating paper when manufacturing the stator.SOLUTION: A coated metal wire 10 includes: a metal wire 11; and an insulating foamable adhesive sheet 20 wound around the metal wire 11.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present disclosure relates to a coated metal wire, a stator, an electric motor, and a method for manufacturing a stator. [Background technology]

[0002] Conventionally, copper wires used for coils are coated with enamel resin. Conventional electric motor stators may have insulating paper inserted along the inner walls of the slots. After that, a coil is inserted into the space formed by the insulating paper inserted into the slot, and varnish resin is then filled into the slot. This ensures insulation between the coil and the stator. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2022-149013 A Summary of the Invention [Problem to be solved by the invention]

[0004] In conventional stators, the insulation between the copper wires is ensured only by the enamel coating, which makes them unreliable. Also, if the insulating paper fails to be inserted during stator manufacturing, the manufacturing equipment must be stopped to remove the insulating paper.

[0005] The present disclosure provides a covered metal wire, a stator, an electric motor, and a method for manufacturing a stator, which can improve insulation between metal wires and eliminate the need for a process of inserting insulating paper when manufacturing a stator. [Means for solving the problem]

[0006] The embodiments of the present disclosure relate to the following [1] to [8].

[0007] [1] A coated metal wire comprising a metal wire and a foamable adhesive sheet wound around the metal wire.

[0008] [2] The coated metal wire according to [1], wherein the foamable adhesive sheet contains an epoxy resin, an acrylic resin compatible with the epoxy resin, a curing agent, and a foaming agent.

[0009] [3] The coated metal wire according to [1] or [2], wherein the side of the foamable adhesive sheet that is adhered to the metal wire has tackiness.

[0010] [4] The coated metal wire described in [3], wherein the tackiness of the foamable adhesive sheet on the side opposite to the side adhered to the metal wire is lower than the tackiness of the side adhered to the metal wire.

[0011] [5] A stator comprising: a stator core having a slot; a metal wire disposed in the slot; and a foamed resin portion disposed in the slot, the foamed resin portion existing around the entire circumference of the metal wire.

[0012] [6] An electric motor comprising a rotor and the stator described in [5] arranged around the rotor.

[0013] [7] A method for manufacturing a stator, comprising the steps of: preparing a coated metal wire as described in any one of [1] to [4]; placing the coated metal wire in a slot of a stator core; and foaming the foamable adhesive sheet of the coated metal wire in the slot to form a foamed resin portion around the metal wire.

[0014] [8] The method for manufacturing a stator described in [7], wherein the thickness of the foamable adhesive sheet before foaming is between 1 / 10 and 1 / 2 of the minimum distance between the metal wire and the inner wall surface of the stator core. Effect of the Invention

[0015] According to this embodiment, the insulation between the copper wires can be improved, and the step of inserting insulating paper during the manufacture of the stator can be eliminated. [Brief description of the drawings]

[0016] [Figure 1] FIG. 1 is a schematic perspective view showing a coated metal wire according to an embodiment. [Diagram 2] FIG. 2 is a cross-sectional view (cross-sectional view taken along line II-II in FIG. 1) showing the covered metal wire according to the embodiment. [Diagram 3] FIG. 3 is a cross-sectional view showing a foamable adhesive sheet for a covered metal wire according to one embodiment. [Figure 4] FIG. 4 is a schematic exploded perspective view showing the electric motor according to the embodiment. [Diagram 5] FIG. 5 is a cross-sectional view (cross-sectional view taken along line VV in FIG. 4) showing the stator according to the embodiment. [Figure 6] FIG. 6 is a partially enlarged cross-sectional view (enlarged view of part VI in FIG. 5) showing a slot of the stator according to the embodiment. [Figure 7] 7(a)-(e) are diagrams illustrating a method for manufacturing a coated metal wire according to one embodiment. [Figure 8] 8(a) and (b) are partially enlarged cross-sectional views showing a method for manufacturing the stator according to the embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017] The covered metal wire according to the present embodiment includes a metal wire and a foamable adhesive sheet wound around the metal wire. This makes it easier to obtain highly reliable insulation compared to a case where the metal wire is insulated only by an enamel resin coating. In addition, by foaming the foamable adhesive sheet during the manufacture of the stator, the voids in the slots of the stator can be filled with the foamable adhesive sheet. This makes it possible to more firmly fix the covered metal wire in the slot.

[0018] Hereinafter, one embodiment will be described in detail with reference to the drawings. Each of the figures shown below is a schematic illustration. Therefore, the size and shape of each part are appropriately exaggerated to facilitate understanding. In addition, it is possible to carry out appropriate modifications within the scope of the technical idea. In each of the figures shown below, the same parts are given the same reference numerals, and some detailed explanations may be omitted. In addition, the numerical values ​​such as dimensions of each member and the material names described in this specification are examples of embodiments, and are not limited thereto, and can be appropriately selected and used. In this specification, terms that specify shapes and geometric conditions, such as parallel, orthogonal, and vertical, are intended to include substantially the same state in addition to their strict meanings.

[0019] (Coated metal wire) As shown in FIGS. 1 and 2, a covered metal wire 10 according to the present embodiment includes a metal wire 11 and a foamable adhesive sheet 20 wound around the metal wire 11.

[0020] The metal wire 11 is located at the widthwise center of the coated metal wire 10. The metal wire 11 is made of a solid, elongated filament. The metal wire 11 is circular in cross section, but may be rectangular, square, or the like. The width W1 of the metal wire 11 may be 0.1 mm or more, or 0.5 mm or more. The width W1 of the metal wire 11 may be 10 mm or less, or 5 mm or less. In this specification, the width W1 of the metal wire 11 refers to the diameter of a circle inscribed in a cross section perpendicular to the longitudinal direction D1 of the metal wire 11. For example, when the metal wire 11 is circular in cross section, the width W1 of the metal wire 11 refers to the diameter of a circle constituting the cross section of the metal wire 11. When the metal wire 11 is square in cross section, the width W1 of the metal wire 11 refers to the length of one side of the square constituting the cross section of the metal wire 11.

[0021] The metal wire 11 may be made of a metal having good electrical conductivity. The material of the metal wire 11 may be, for example, a metal such as copper, gold, or aluminum, or an alloy thereof. The metal wire 11 may be a metal portion covered with a covering material. In this case, the metal portion may be made of a metal such as copper, gold, or aluminum, or an alloy thereof, and the covering material may be made of an insulator such as enamel resin.

[0022] The foamable adhesive sheet 20 is a sheet having foaming and adhesive properties. The foamable adhesive sheet 20 is repeatedly wrapped around the metal wire 11 along the circumferential direction D2. In this specification, the circumferential direction D2 of the metal wire 11 refers to a direction along the outer periphery of a cross section perpendicular to the longitudinal direction D1 of the metal wire 11. The foamable adhesive sheet 20 may be disposed such that its longitudinal direction D3 is parallel to the circumferential direction D2 of the metal wire 11, or may be disposed at an angle to the circumferential direction D2 of the metal wire 11.

[0023] The foamable adhesive sheet 20 may be wrapped around the metal wire 11 multiple times along the longitudinal direction D1. For example, one foamable adhesive sheet 20 having a predetermined length may be wrapped around one metal wire 11 multiple times to cover the metal wire 11. Alternatively, a plurality of foamable adhesive sheets 20 may be wrapped around one metal wire 11, respectively, to cover the metal wire 11. As a result, at least a portion of the metal wire 11 in the longitudinal direction D1 is covered with the insulating foamable adhesive sheet 20. Therefore, at least the region of the metal wire 11 covered with the foamable adhesive sheet 20 has high insulation properties.

[0024] The foamable adhesive sheet 20 has a side edge 20e at each end in the width direction. The side edges 20e of the foamable adhesive sheet 20 extend parallel to the longitudinal direction D3 of the foamable adhesive sheet 20. In a state where the foamable adhesive sheet 20 is wound around the metal wire 11 multiple times, the side edges 20e of the foamable adhesive sheet 20 may be in contact with the side edges 20e of the adjacent foamable adhesive sheets 20 without leaving any gaps. Alternatively, in order to further improve the insulation of the coated metal wire 10, the region near the side edge 20e of the foamable adhesive sheet 20 may overlap the region near the side edge 20e of the adjacent foamable adhesive sheet 20.

[0025] The width W2 of the foamable adhesive sheet 20 may be 2 mm or more, or may be 5 mm or more. The width W2 of the foamable adhesive sheet 20 may be 50 mm or less, or may be 30 mm or less. In this specification, the width W2 of the foamable adhesive sheet 20 refers to the length in the direction perpendicular to the longitudinal direction D3 of the foamable adhesive sheet 20.

[0026] (Foamable adhesive sheet) Next, the configuration of the foamable adhesive sheet 20 will be further described with reference to FIG.

[0027] FIG. 3 is a schematic cross-sectional view showing a foamable adhesive sheet 20 according to the present embodiment. As shown in FIG. 3, the foamable adhesive sheet 20 has a first adhesive layer 21 and a second adhesive layer 22 laminated on the first adhesive layer 21. The first adhesive layer 21 and the second adhesive layer 22 contain a curable adhesive. At least one of the first adhesive layer 21 and the second adhesive layer 22 further contains a foaming agent. The first adhesive layer 21 is located on the side opposite to the side bonded to the metal wire 11. The second adhesive layer 22 is located on the side bonded to the metal wire 11. The first adhesive layer 21 faces an inner wall surface 62a of a stator core 62 described later.

[0028] At least the side of the foamable adhesive sheet 20 that is adhered to the metal wire 11 has tackiness. That is, the second adhesive layer 22 has tackiness. The tackiness of the second adhesive layer 22 may be within a predetermined range. This can improve the adhesion between the foamable adhesive sheet 20 and the metal wire 11. In this case, peeling off or shifting of the foamable adhesive sheet 20 from the metal wire 11 can be suppressed.

[0029] The tackiness of the foamable adhesive sheet 20 on the side opposite to the side bonded to the metal wire 11 may be lower than that of the side bonded to the metal wire 11. That is, the tackiness of the first adhesive layer 21 may be lower than that of the second adhesive layer 22. The foamable adhesive sheet 20 on the side opposite to the side bonded to the metal wire 11 may be non-adhesive (tack-free). Since the tackiness of the first adhesive layer 21 is equal to or lower than a predetermined value, the first adhesive layer 21 is substantially non-adhesive (tack-free), and the first adhesive layer has good slipperiness. Therefore, when the coated metal wire 10 is arranged in the slot 63 of the stator 61 described later, the coated metal wire 10 can be smoothly arranged. This makes it possible to suppress the displacement of the coated metal wire 10 in the slot 63.

[0030] Here, "adhesion" is a concept that is included in "bonding." The two are sometimes distinguished in that "adhesion" is used to mean a temporary adhesive phenomenon, whereas "bonding" is used to mean a substantially permanent adhesive phenomenon (Iwanami Shoten Physics and Chemistry Dictionary, 5th Edition). "Adhesiveness" and "adhesive strength" refer to the property of adhesion through pressure and the adhesive strength at that time.

[0031] Each component of the foamable adhesive sheet 20 in this embodiment will be described below.

[0032] (1st adhesive layer) (1) Characteristics of the first adhesive layer The tack of the first adhesive layer 21 is 0 gf or more and less than 10 gf, and may be 5 gf or less, or may be 2 gf or less. When the tack of the first adhesive layer 21 is within the above range, the first adhesive layer 21 is made substantially non-sticky (tack-free), and the first adhesive layer 21 has good slip properties and blocking resistance.

[0033] Here, the tackiness of the first adhesive layer 21 is measured by a probe tack test in accordance with JIS Z3284-3: 2014. As a probe tack tester, a tack tester "TAC-II" manufactured by RHESCA is used.

[0034] In this embodiment, the tack of the first adhesive layer 21 is within a predetermined range, for example, by adjusting the composition of the first adhesive layer 21. Specifically, the adhesiveness of the first adhesive layer 21 may be reduced by using an epoxy resin that is solid at room temperature or a curing agent that is solid at room temperature in the first adhesive layer 21 containing an epoxy resin and a curing agent. Also, the adhesiveness of the first adhesive layer 21 may be reduced by including an epoxy resin with a high softening temperature or an epoxy resin with a large weight average molecular weight in the first adhesive layer 21 containing an epoxy resin and a curing agent. For example, the adhesiveness of the first adhesive layer 21 may be reduced by including multiple types of epoxy resins with different softening temperatures in the first adhesive layer 21. That is, the first adhesive layer 21 may include one epoxy resin and another epoxy resin whose softening temperature is 25° C. or higher and 10° C. or higher than the softening temperature of the one epoxy resin. Also, for example, the first adhesive layer 21 may contain a plurality of epoxy resins having different weight average molecular weights, thereby reducing the adhesiveness of the first adhesive layer 21. That is, the first adhesive layer 21 may contain one epoxy resin and another epoxy resin having a weight average molecular weight of 370 or more and 300 or more greater than the weight average molecular weight of the one epoxy resin. More specifically, the first adhesive layer 21 containing an epoxy resin and a hardener may contain a first epoxy resin having a low softening temperature and a low molecular weight, and a second epoxy resin having a high softening temperature and a high molecular weight, as the epoxy resin. This may reduce the adhesiveness of the first adhesive layer 21. Also, the first adhesive layer 21 containing an epoxy resin and a hardener may contain an acrylic resin compatible with the epoxy resin, thereby reducing the adhesiveness of the first adhesive layer 21.

[0035] (2) Material of the first adhesive layer The first adhesive layer 21 contains a curable adhesive.

[0036] (a) Hardening adhesive The curable adhesive contained in the first adhesive layer 21 may be a curable adhesive generally used in the adhesive layer of the foamable adhesive sheet 20. Examples of the curable adhesive include a heat-curable adhesive and a light-curable adhesive. Among them, a heat-curable adhesive is preferable.

[0037] Examples of the curable adhesive include epoxy resin adhesives, acrylic resin adhesives, phenol resin adhesives, unsaturated polyester resin adhesives, alkyd resin adhesives, urethane resin adhesives, and thermosetting polyimide resin adhesives.

[0038] Among them, the curable adhesive is preferably an epoxy resin adhesive. That is, the curable adhesive preferably contains an epoxy resin and a curing agent. In general, epoxy resin adhesives are excellent in mechanical strength, heat resistance, insulating properties, chemical resistance, etc., have small shrinkage upon curing, and can be used in a wide range of applications.

[0039] Hereinafter, an example will be described in which the curable adhesive is an epoxy resin adhesive.

[0040] (i) Epoxy resin Epoxy resins are compounds that have at least one epoxy or glycidyl group and are cured by a cross-linking polymerization reaction in combination with a curing agent. Epoxy resins also include monomers that have at least one epoxy or glycidyl group.

[0041] As the epoxy resin, an epoxy resin generally used in the adhesive layer of the foamable adhesive sheet 20 may be used. In particular, the curable adhesive preferably contains a first epoxy resin and a second epoxy resin as the epoxy resin. The first epoxy resin preferably has a softening temperature of 50° C. or higher and an epoxy equivalent of 5000 g / eq or lower. The second epoxy resin preferably has a softening temperature higher than that of the first epoxy resin and a weight average molecular weight of 20,000 or higher. By using the first epoxy resin and the second epoxy resin in combination, the adhesiveness (tackiness) of the first adhesive layer 21 can be reduced, and a foamable adhesive sheet 20 with good slip properties can be obtained. Furthermore, a first adhesive layer 21 with good blocking resistance and adhesiveness after foaming and curing can be obtained.

[0042] When the first epoxy resin has a relatively low softening temperature (relatively high crystallinity) and a low molecular weight (low epoxy equivalent), the first epoxy resin melts rapidly and changes to a low-viscosity liquid when the temperature reaches or exceeds the softening temperature. This makes it easier to improve the adhesiveness after foaming and hardening. On the other hand, the first epoxy resin has a relatively high crystallinity, so that it can suppress the occurrence of blocking compared to epoxy resins with relatively low crystallinity or epoxy resins without crystallinity. However, when only the first epoxy resin is used, there is a possibility that the effect of suppressing the occurrence of blocking is insufficient or that the adhesiveness (tackiness) of the first adhesive layer 21 becomes too high. For this reason, the effect of suppressing the occurrence of blocking is improved by further using a second epoxy resin with a relatively high softening temperature (relatively low crystallinity) and a high molecular weight. In addition, the adhesiveness (tackiness) of the first adhesive layer 21 can be suppressed low.

[0043] (i-1) First epoxy resin The first epoxy resin has a softening temperature of 50° C. or higher and an epoxy equivalent of 5000 g / eq or lower. The first epoxy resin has a relatively low softening temperature (relatively high crystallinity) compared to the second epoxy resin described below. The first epoxy resin has a relatively high crystallinity and a low molecular weight, which makes it easy to improve adhesion and blocking resistance after foaming and curing. In addition, since the first epoxy resin has a low molecular weight, the crosslinking density can be increased, and a first adhesive layer 21 having good mechanical strength, chemical resistance, and curing properties can be obtained. In addition, the first epoxy resin is preferably an epoxy resin that is solid at room temperature (23° C.).

[0044] The first epoxy resin may be a monofunctional epoxy resin, a difunctional epoxy resin, a trifunctional epoxy resin, or a tetrafunctional or higher functional epoxy resin.

[0045] Examples of the first epoxy resin include aromatic epoxy resins, aliphatic epoxy resins, alicyclic epoxy resins, and heterocyclic epoxy resins. Specific examples of the first epoxy resin include bisphenol-type epoxy resins such as bisphenol A-type epoxy resins and bisphenol F-type epoxy resins, novolac-type epoxy resins such as bisphenol A novolac-type epoxy resins and cresol novolac-type epoxy resins, and modified epoxy resins such as urethane-modified epoxy resins and rubber-modified epoxy resins. Other specific examples include biphenyl-type epoxy resins, stilbene-type epoxy resins, triphenolmethane-type epoxy resins, alkyl-modified triphenolmethane-type epoxy resins, triazine-nucleus-containing epoxy resins, dicyclopentadiene-modified phenol-type epoxy resins, naphthalene-type epoxy resins, glycol-type epoxy resins, and pentaerythritol-type epoxy resins. The first epoxy resin may be one type or two or more types.

[0046] Bisphenol A type epoxy resins can exist in a liquid state or a solid state at room temperature depending on the number of repeating units of the bisphenol skeleton. Bisphenol A type epoxy resins having, for example, 2 to 10 bisphenol skeletons in the main chain are solid at room temperature. In particular, bisphenol A type epoxy resins are preferred in that they can improve heat resistance.

[0047] In particular, the first epoxy resin is preferably a bisphenol A novolac type epoxy resin represented by the following general formula (1).

[0048] [ka]

[0049] In the general formula (1), R 1 is C m H 2m (m is 1 or more and 3 or less), 2 and R 3 are each independently p H 2p+1 (p is 1 or more and 3 or less), and n is 0 or more and 10 or less.

[0050] In the general formula (1), R 1 m in is 1, that is, R 1 is preferably -CH2-. Similarly, R 2 and R 3 p in is 1, that is, R2 and R 3 is preferably -CH3. Furthermore, the hydrogen bonded to the benzene ring in general formula (1) may be substituted with other elements or other groups.

[0051] The content of the first epoxy resin may be, for example, 1 part by mass or more, 3 parts by mass or more, 5 parts by mass or more, 10 parts by mass or more, 15 parts by mass or more, or 25 parts by mass or more, when the resin component contained in the first adhesive layer 21 is taken as 100 parts by mass. If the content of the first epoxy resin is too small, the adhesiveness and blocking resistance after foaming and curing may be reduced. On the other hand, the content of the first epoxy resin may be, for example, 90 parts by mass or less, 80 parts by mass or less, 70 parts by mass or less, 60 parts by mass or less, 50 parts by mass or less, or 40 parts by mass or less, when the resin component contained in the first adhesive layer 21 is taken as 100 parts by mass. If the content of the first epoxy resin is too high, the content of the second epoxy resin and the acrylic resin will be relatively low. In this case, it may not be possible to balance the non-stickiness, blocking resistance, adhesion to the substrate after foaming and curing, cracking resistance after foaming and curing, and adhesiveness after foaming and curing.

[0052] (i-2) Second epoxy resin The second epoxy resin has a higher softening temperature than the first epoxy resin and a weight average molecular weight of 20,000 or more. The second epoxy resin has a relatively high softening temperature (relatively low crystallinity) compared to the above-mentioned first epoxy resin. The second epoxy resin has relatively low crystallinity and high molecular weight, which makes it easy to improve blocking resistance. Furthermore, the second epoxy resin has relatively low crystallinity and high molecular weight, which can suppress an increase in adhesion (tackiness) caused by the first epoxy resin. In addition, the second epoxy resin is preferably an epoxy resin that is solid at room temperature (23°C).

[0053] The second epoxy resin may be a monofunctional epoxy resin, a difunctional epoxy resin, a trifunctional epoxy resin, or a tetrafunctional or higher functional epoxy resin.

[0054] The softening temperature of the second epoxy resin is usually higher than that of the first epoxy resin. The difference between the two is, for example, 10°C or more, and may be 20°C or more, or may be 30°C or more. The softening temperature of the second epoxy resin is, for example, 80°C or more, and may be 90°C or more. On the other hand, the softening temperature of the second epoxy resin is, for example, 180°C or less.

[0055] The configuration of the second epoxy resin is similar to that of the first epoxy resin described above, and therefore will not be described here.

[0056] The content of the second epoxy resin may be, for example, 10 parts by mass or more, 15 parts by mass or more, 20 parts by mass or more, 25 parts by mass or more, 30 parts by mass or more, 35 parts by mass or more, 40 parts by mass or more, or 45 parts by mass or more, when the resin component contained in the first adhesive layer 21 is taken as 100 parts by mass. If the content of the second epoxy resin is too small, the adhesion may be high and the blocking resistance may be reduced. On the other hand, the content of the second epoxy resin may be, for example, 90 parts by mass or less, 85 parts by mass or less, 80 parts by mass or less, or 75 parts by mass or less, when the resin component contained in the first adhesive layer 21 is taken as 100 parts by mass. If the content of the second epoxy resin is too high, the content of the first epoxy resin and the acrylic resin will be relatively low. In this case, it may not be possible to balance the non-adhesiveness, blocking resistance, adhesion to the substrate after foaming and curing, cracking resistance after foaming and curing, and adhesion after foaming and curing.

[0057] The ratio of the first epoxy resin to the total of the first epoxy resin and the second epoxy resin is, for example, 5 mass% or more, or may be 10 mass% or more, 15 mass% or more, or may be 20 mass% or more, while the ratio of the first epoxy resin is, for example, 80 mass% or less, or may be 75 mass% or less, or may be 60 mass% or less.

[0058] Furthermore, the total proportion of the first epoxy resin and the second epoxy resin to all epoxy resins contained in the first adhesive layer 21 is, for example, 50 mass% or more, may be 70 mass% or more, may be 90 mass% or more, or may be 100 mass%.

[0059] (ii) Acrylic resin When the curable adhesive is an epoxy resin adhesive, the first adhesive layer 21 may further contain an acrylic resin compatible with the epoxy resin. The acrylic resin is a resin compatible with the epoxy resin. Since the acrylic resin is compatible with the epoxy resin, it is easy to improve the toughness of the first adhesive layer 21. As a result, the adhesiveness after foaming and curing can be improved. Furthermore, the acrylic resin acts as a compatibilizer for the foaming agent (for example, a foaming agent whose shell part is an acrylonitrile copolymer resin), and is uniformly dispersed and foamed, which is considered to improve the adhesiveness after foaming and curing. In addition, the flexibility of the acrylic resin is exerted, and it is possible to improve the adhesion to the substrate after foaming and curing and the crack resistance after foaming and curing. In addition, the compatibility of the acrylic resin with the epoxy resin allows the hardness of the surface of the first adhesive layer 21 to be kept high. On the other hand, if the acrylic resin is incompatible with the epoxy resin, a soft portion is formed on the surface of the first adhesive layer 21, which may make the interface with the adherend less slippery and reduce workability.

[0060] The acrylic resin in the present embodiment is compatible with the epoxy resin. Here, the compatibility of the acrylic resin with the epoxy resin can be confirmed, for example, by observing the cross section of the first adhesive layer 21 of the foamable adhesive sheet 20 with a scanning electron microscope (SEM) or a transmission electron microscope (TEM) and finding that no micron-sized islands are generated. More specifically, the average particle size of the islands is preferably 1 μm or less. In particular, the average particle size of the islands may be 0.5 μm or less, or may be 0.3 μm or less. It is preferable that the number of samples is large, for example, 100 or more. The area to be observed is in the range of 100 μm×100 μm, or in the case where the average thickness of the first adhesive layer 21 is 100 μm or less, in the range of the average thickness×100 μm.

[0061] The acrylic resin may have a polar group, such as an epoxy group, a hydroxyl group, a carboxyl group, a nitrile group, or an amide group.

[0062] The acrylic resin may be a homopolymer of an acrylic acid ester monomer, a mixed component containing two or more of the above homopolymers, or a copolymer of two or more of the acrylic acid ester monomers, a component containing one or more copolymers. The acrylic resin may also be a mixed component of the above homopolymer and the above copolymer. The "acrylic acid" of the acrylic acid ester monomer also includes the concept of methacrylic acid. Specifically, the acrylic resin may be a mixture of a methacrylate polymer and an acrylate polymer, or an acrylic acid ester polymer such as acrylate-acrylate, methacrylate-methacrylate, or methacrylate-acrylate. Among them, the acrylic resin preferably contains a copolymer of two or more of the acrylic acid ester monomers ((meth)acrylic acid ester copolymer).

[0063] Examples of the monomer components constituting the (meth)acrylic acid ester copolymer include the monomer components described in JP 2014-065889 A. The monomer components may have the above-mentioned polar group. Examples of the (meth)acrylic acid ester copolymer include ethyl acrylate-butyl acrylate-acrylonitrile copolymer, ethyl acrylate-acrylonitrile copolymer, and butyl acrylate-acrylonitrile copolymer. Note that "acrylic acid" such as methyl acrylate and ethyl acrylate also includes "methacrylic acid" such as methyl methacrylate and ethyl methacrylate.

[0064] The (meth)acrylic acid ester copolymer is preferably a block copolymer, and more preferably an acrylic block copolymer such as a methacrylate-acrylate copolymer. Examples of (meth)acrylates constituting the acrylic block copolymer include methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, lauryl acrylate, 2-ethylhexyl acrylate, cyclohexyl acrylate, and benzidyl acrylate. These "acrylic acids" also include "methacrylic acid."

[0065] Specific examples of methacrylate-acrylate copolymers include acrylic copolymers such as methyl methacrylate-butyl acrylate-methyl methacrylate (MMA-BA-MMA) copolymers. MMA-BA-MMA copolymers also include block copolymers of polymethyl methacrylate-polybutyl acrylate-polymethyl methacrylate (PMMA-PBA-PMMA).

[0066] The acrylic copolymer may not have a polar group, or may be a modified product having the above-mentioned polar group partially introduced therein. The modified product is easily compatible with the epoxy resin, and therefore the adhesiveness is further improved.

[0067] Among them, the acrylic resin is preferably a (meth)acrylic acid ester copolymer having a first polymer portion having a glass transition temperature (Tg) of 10° C. or lower and a second polymer portion having a glass transition temperature (Tg) of 20° C. or higher. Such a (meth)acrylic acid ester copolymer has the first polymer portion that becomes a soft segment and the second polymer portion that becomes a hard segment.

[0068] The manifestation of the above-mentioned effect can be presumed as follows. By using an acrylic resin having both a soft segment and a hard segment, such as the above-mentioned (meth)acrylic acid ester copolymer, the hard segment contributes to heat resistance, and the soft segment contributes to toughness and flexibility. Therefore, the first adhesive layer 21 has good heat resistance, toughness, and flexibility.

[0069] At least one of the first polymer portion and the second polymer portion contained in the (meth)acrylic acid ester copolymer has compatibility with epoxy resins. When the first polymer portion has compatibility with epoxy resins, flexibility can be increased. Furthermore, when the second polymer portion has compatibility with epoxy resins, cohesion and toughness can be increased.

[0070] The Tg of the second polymer portion contained in the above (meth)acrylic acid ester copolymer is 20°C or higher, and can be within the range of 20°C or higher and 150°C or lower, particularly within the range of 30°C or higher and 150°C or lower, and particularly within the range of 40°C or higher and 150°C or lower.

[0071] The second polymer portion contained in the (meth)acrylic acid ester copolymer may be a homopolymer or a copolymer, but is preferably a homopolymer. The monomer component constituting the second polymer portion may be any monomer component capable of obtaining a second polymer portion having a Tg in a predetermined range, and examples thereof include acrylic acid ester monomers such as methyl methacrylate, other monomers such as acrylamide, styrene, vinyl chloride, amide, acrylonitrile, cellulose acetate, phenol, urethane, vinylidene chloride, methylene chloride, and methacrylonitrile, and polar group-containing monomers containing the above-mentioned polar groups.

[0072] A specific example of the (meth)acrylic acid ester copolymer having the above-mentioned first polymer portion and second polymer portion is the above-mentioned MMA-BA-MMA copolymer.

[0073] The content of the acrylic resin is, for example, 1 part by mass or more, 3 parts by mass or more, 5 parts by mass or more, 7 parts by mass or more, or 10 parts by mass or more, when the resin component contained in the first adhesive layer 21 is taken as 100 parts by mass. If the content of the acrylic resin is too small, the adhesion to the substrate after foaming and curing, the crack resistance after foaming and curing, and the adhesiveness after foaming and curing may decrease. On the other hand, the content of the acrylic resin is, for example, 60 parts by mass or less, 50 parts by mass or less, 40 parts by mass or less, 35 parts by mass or less, or 30 parts by mass or less, when the resin component contained in the first adhesive layer 21 is taken as 100 parts by mass. If the content of the acrylic resin is too high, the contents of the first epoxy resin and the second epoxy resin become relatively low. In this case, it may not be possible to balance the non-stickiness, blocking resistance, adhesion to the substrate after foaming and curing, the crack resistance after foaming and curing, and the adhesiveness after foaming and curing. In addition, if the content of the acrylic resin is too high, the film strength may decrease.

[0074] (iii) Hardener As the curing agent in this embodiment, a curing agent generally used in an epoxy resin adhesive can be used. The curing agent is preferably solid at room temperature (23° C.). A curing agent that is solid at room temperature can have a longer storage stability (pot life) than a curing agent that is liquid at room temperature. The curing agent may be a latent curing agent. The curing agent may be a curing agent that undergoes a curing reaction by heat, or may be a curing agent that undergoes a curing reaction by light. In this embodiment, the curing agent may be used alone or in combination of two or more kinds.

[0075] Specific examples of the curing agent include imidazole-based curing agents, phenol-based curing agents, amine-based curing agents, acid anhydride-based curing agents, isocyanate-based curing agents, and thiol-based curing agents.

[0076] Examples of imidazole-based curing agents include imidazole, 2-phenyl-4,5-dihydroxymethylimidazole, 2-phenyl-4-methyl-5-hydroxymethylimidazole, 2-methylimidazole, 2-ethylimidazole, 2-ethyl-4-methylimidazole, 2-isopropylimidazole, 2-phenylimidazole, carboxylates of imidazole compounds, and adducts with epoxy compounds. It is also preferable that the imidazole-based curing agent has a hydroxyl group. Since crystallization occurs due to hydrogen bonds between hydroxyl groups, the reaction initiation temperature tends to be high.

[0077] Examples of the phenol-based curing agent include phenol resins. Examples of the phenol resin include resol-type phenol resins and novolac-type phenol resins. From the viewpoint of adhesion to the substrate after foaming and curing and crack resistance after foaming and curing, phenol-type novolac resins having a Tg of 110° C. or less are particularly preferred. Also, a phenol-based curing agent and an imidazole-based curing agent may be used in combination. In this case, it is preferable to use an imidazole-based curing agent as a curing catalyst.

[0078] Examples of the amine-based curing agent include aliphatic amines such as diethylenetriamine (DETA), triethylenetetramine (TETA), and metaxylylenediamine (MXDA); aromatic amines such as diaminodiphenylmethane (DDM), m-phenylenediamine (MPDA), and diaminodiphenylsulfone (DDS); alicyclic amines; and polyamidoamines. In addition, examples of the amine-based curing agent that can be used include dicyandiamide-based curing agents such as dicyandiamide (DICY), organic acid dihydrazide-based curing agents, amine adduct-based curing agents, and ketimine-based curing agents.

[0079] Examples of acid anhydride curing agents include alicyclic acid anhydrides (liquid acid anhydrides) such as hexahydrophthalic anhydride (HHPA) and methyltetrahydrophthalic anhydride (MTHPA); and aromatic acid anhydrides such as trimellitic anhydride (TMA), pyromellitic anhydride (PMDA), and benzophenonetetracarboxylic acid (BTDA).

[0080] The isocyanate-based curing agent may, for example, be a blocked isocyanate.

[0081] Examples of the thiol-based curing agent include ester-bonded thiol compounds, aliphatic ether-bonded thiol compounds, and aromatic ether-bonded thiol compounds.

[0082] The content of the curing agent is, for example, 1 part by mass or more and 40 parts by mass or less, when the resin component contained in the first adhesive layer 21 is taken as 100 parts by mass. For example, when an imidazole-based curing agent is used as the main component as the curing agent, the content of the curing agent is preferably, for example, 1 part by mass or more and 15 parts by mass or less, when the resin component contained in the first adhesive layer 21 is taken as 100 parts by mass. On the other hand, when a phenol-based curing agent is used as the main component as the curing agent, the content of the curing agent is preferably, for example, 5 parts by mass or more and 40 parts by mass or less, when the resin component contained in the first adhesive layer 21 is taken as 100 parts by mass. Note that using an imidazole-based curing agent or a phenol-based curing agent as the main component as the curing agent means that the mass ratio of the imidazole-based curing agent or the phenol-based curing agent is the highest in the curing agent.

[0083] (b) Foaming agent The first adhesive layer 21 in this embodiment may or may not contain a foaming agent, but it is preferable that the first adhesive layer 21 contains a foaming agent. By containing a foaming agent, the surface roughness is increased, the friction coefficient is decreased, and the slipperiness is further improved. For this reason, it is preferable that the first adhesive layer 21, which has low tackiness, of the first adhesive layer 21 and the second adhesive layer 22 contains a foaming agent.

[0084] The foaming agent may be any foaming agent that is generally used in the adhesive layer of the foamable adhesive sheet 20. The foaming agent may be one that undergoes a foaming reaction due to heat, or one that undergoes a foaming reaction due to light.

[0085] The foaming agent may be, for example, a microcapsule type foaming agent, which preferably has a thermal expansion agent such as a hydrocarbon as a core and a resin such as an acrylonitrile copolymer as a shell.

[0086] As the foaming agent, for example, organic foaming agents or inorganic foaming agents may be used. Examples of organic foaming agents include azo foaming agents such as azodicarbonamide (ADCA), azobisformamide, and azobisisobutyronitrile, fluorinated alkane foaming agents such as trichloromonofluoromethane, hydrazine foaming agents such as paratoluenesulfonylhydrazide, semicarbazide foaming agents such as p-toluenesulfonylsemicarbazide, triazole foaming agents such as 5-morpholyl-1,2,3,4-thiatriazole, and N-nitroso foaming agents such as N,N-dinitrosoterephthalamide. On the other hand, examples of inorganic foaming agents include ammonium carbonate, ammonium hydrogen carbonate, ammonium nitrite, ammonium borohydride, and azides.

[0087] The content of the foaming agent is, for example, 0.5 parts by mass or more, 2 parts by mass or more, 3 parts by mass or more, 4 parts by mass or more, or 5 parts by mass or more, based on 100 parts by mass of the resin component contained in the first adhesive layer 21. On the other hand, the content of the foaming agent is, for example, 25 parts by mass or less, 20 parts by mass or less, or 15 parts by mass or less, based on 100 parts by mass of the resin component contained in the first adhesive layer 21. If the content of the foaming agent is too small, the static friction coefficient of the surface of the first adhesive layer 21 may be large. Also, if the content of the foaming agent is too large, the content of the curable adhesive is relatively small, so that the adhesiveness after foaming and curing may be reduced.

[0088] (c) Other ingredients In the present embodiment, when the curable adhesive is an epoxy resin adhesive, the first adhesive layer 21 may contain only epoxy resin and acrylic resin as the resin component, or may further contain other resins such as urethane resin.

[0089] The total ratio of the first epoxy resin, the second epoxy resin and the acrylic resin to the resin components contained in the first adhesive layer 21 is, for example, 70 mass% or more, may be 80 mass% or more, may be 90 mass% or more, or may be 100 mass%.

[0090] The content of the resin component in the first adhesive layer 21 is, for example, 60% by mass or more, optionally 70% by mass or more, optionally 80% by mass or more, or optionally 90% by mass or more.

[0091] The first adhesive layer 21 may contain additives such as a silane coupling agent, a filler, an antioxidant, a light stabilizer, an ultraviolet absorber, a lubricant, a plasticizer, an antistatic agent, a crosslinking agent, and a colorant, as necessary. Examples of the silane coupling agent include an epoxy-based silane coupling agent. Examples of the filler include inorganic fillers such as calcium carbonate, aluminum hydroxide, magnesium hydroxide, antimony trioxide, zinc borate, a molybdenum compound, and titanium dioxide. Examples of the antioxidant include a phenol-based antioxidant and a sulfur-based antioxidant.

[0092] (3) Configuration of the first adhesive layer When the first adhesive layer 21 further contains a foaming agent, the first adhesive layer 21 can be foamed at an expansion ratio of, for example, 4 times or more and 15 times or less. For example, when only the first adhesive layer 21 of the first adhesive layer 21 and the second adhesive layer 22 contains a foaming agent, the expansion ratio may be, for example, 5 times or more, 7 times or more, or 9 times or more. In the above case, the expansion ratio may be, for example, 14 times or less, 13 times or less, or 12 times or less. On the other hand, when both the first adhesive layer 21 and the second adhesive layer 22 of the first adhesive layer 21 and the second adhesive layer 22 contain a foaming agent, the expansion ratio may be, for example, 5 times or more, 6 times or more, or 7 times or more. In the above case, the expansion ratio may be, for example, 14 times or less, 12 times or less, or 10 times or less. If the expansion ratio is too small or too large, the adhesiveness after foaming and curing may decrease.

[0093] Here, the expansion ratio can be calculated by the following formula. Expansion ratio (times)=thickness of first adhesive layer 21 after foaming and hardening / thickness of first adhesive layer 21 before foaming and hardening

[0094] The average thickness of the first adhesive layer 21 is not particularly limited, but when the first adhesive layer 21 contains a foaming agent, it is preferably equal to or greater than the average particle size of the foaming agent, for example, 10 μm or more, may be 15 μm or more, or may be 20 μm or more. If the first adhesive layer 21 is too thin, there is a possibility that the adhesion to the substrate and the adhesiveness after foaming and curing cannot be sufficiently obtained. On the other hand, the average thickness of the first adhesive layer 21 is, for example, 200 μm or less, may be 150 μm or less, or may be 100 μm or less. If the first adhesive layer 21 is too thick, there is a possibility that the surface quality will deteriorate.

[0095] The average thickness of the first adhesive layer 21 is a value measured from a cross section in the thickness direction of the foamable adhesive sheet 20 observed with a transmission electron microscope (TEM), a scanning electron microscope (SEM), or a scanning transmission electron microscope (STEM), and is the average value of thicknesses at 10 randomly selected points. The same method for measuring the average thickness of other layers of the foamable adhesive sheet 20 is also applied.

[0096] The first adhesive layer 21 can be formed, for example, by applying an adhesive composition containing the above-mentioned curable adhesive and a foaming agent, etc., and then removing the solvent. Examples of the application method include roll coating, reverse roll coating, transfer roll coating, gravure coating, gravure reverse coating, comma coating, rod coating, blade coating, bar coating, wire bar coating, die coating, lip coating, dip coating, etc.

[0097] The adhesive composition may or may not contain a solvent. In this specification, the solvent is used in a broad sense including not only a strict solvent (a solvent that dissolves a solute) but also a dispersion medium. The solvent contained in the adhesive composition is volatilized and removed when the adhesive composition is applied and dried to form an adhesive layer.

[0098] The adhesive composition can be obtained by mixing the above-mentioned components and kneading and dispersing them as necessary.As a mixing and dispersing method, a general kneading and dispersing machine, for example, a two-roll mill, a three-roll mill, a pebble mill, a tron ​​mill, a Szegvari attritor, a high-speed impeller dispersing machine, a high-speed stone mill, a high-speed impact mill, a disperser, a high-speed mixer, a ribbon blender, a co-kneader, an intensive mixer, a tumbler, a blender, a disperser, a homogenizer, or an ultrasonic dispersing machine can be used.

[0099] (Second adhesive layer) (1) Characteristics of the second adhesive layer In this embodiment, the tack of the second adhesive layer 22 is 10 gf or more, may be 30 gf or more, or may be 50 gf or more. If the tack of the second adhesive layer 22 is too low, the adhesion between the second adhesive layer 22 and the metal wire 11 may decrease when the second adhesive layer 22 is bonded to the metal wire 11. In addition, when the metal wire 11 is disposed in the slot 63 of the stator core 62, the adhesion of the foamed resin part 20A after foaming and hardening may decrease or the adhesive strength may vary due to poor adhesion between the second adhesive layer 22 and the metal wire 11. In addition, the tack of the second adhesive layer 22 is 400 gf or less, may be 300 gf or less, or may be 200 gf or less. If the tack of the second adhesive layer 22 is too high, the reworkability may decrease, and it may be difficult to correct the positional deviation of the foamable adhesive sheet 20 when the second adhesive layer 22 is bonded to the metal wire 11.

[0100] Here, the method for measuring the tackiness of the second adhesive layer 22 is the same as the method for measuring the tackiness of the first adhesive layer 21 described above.

[0101] In this embodiment, the tackiness of the second adhesive layer 22 can be controlled, for example, by adjusting the composition of the second adhesive layer 22. Specifically, when an epoxy resin that is liquid at room temperature or a curing agent that is liquid at room temperature is used in the second adhesive layer 22 containing an epoxy resin and a curing agent, the adhesiveness of the second adhesive layer 22 tends to increase. In addition, when an epoxy resin with a low softening temperature or an epoxy resin with a small weight average molecular weight is contained in the second adhesive layer 22 containing an epoxy resin and a curing agent, the adhesiveness of the second adhesive layer 22 tends to increase. In addition, the adhesiveness of the second adhesive layer 22 tends to increase by adding a tackifier resin to the second adhesive layer 22. Note that, when a curing agent that is liquid at room temperature is used, the adhesiveness tends to increase, but the storage stability may decrease. For this reason, it is preferable to adjust the tackiness of the second adhesive layer 22 by adjusting the properties and type of components other than the curing agent, such as the epoxy resin.

[0102] (2) Material for the second adhesive layer The second adhesive layer 22 in the present embodiment contains a curable adhesive.

[0103] (a) Hardening adhesive The curable adhesive contained in the second adhesive layer 22 in the present embodiment may be the same as the curable adhesive used in the first adhesive layer 21. In particular, the curable adhesive is preferably an epoxy resin adhesive.

[0104] Hereinafter, an example will be described in which the curable adhesive is an epoxy resin adhesive.

[0105] (i) Epoxy resin The epoxy resin in this embodiment may be the same as the epoxy resin used in the first adhesive layer 21 described above.

[0106] As the epoxy resin, an epoxy resin generally used for the adhesive layer of the foamable adhesive sheet 20 can be used.

[0107] Examples of the epoxy resin include aromatic epoxy resin, aliphatic epoxy resin, alicyclic epoxy resin, and heterocyclic epoxy resin. Specific examples of the epoxy resin may be the same as the specific examples of the first epoxy resin used in the first adhesive layer 21.

[0108] The epoxy resin may be a monofunctional epoxy resin, a difunctional epoxy resin, a trifunctional epoxy resin, or a tetrafunctional or higher functional epoxy resin.

[0109] Among them, it is preferable to use, as the epoxy resin, an epoxy resin that is liquid at room temperature, such as a bisphenol A type epoxy resin or a bisphenol F type epoxy resin, and an epoxy resin with a low softening point, because by using these epoxy resins, the tackiness of the second adhesive layer 22 can be easily adjusted to within a predetermined range.

[0110] (ii) Acrylic resin When the curable adhesive is an epoxy resin adhesive, the second adhesive layer 22 may further contain an acrylic resin that is compatible with the epoxy resin, which can improve film-forming properties.

[0111] The acrylic resin may be the same as the acrylic resin used for the first adhesive layer 21.

[0112] (iii) Hardener The curing agent in this embodiment may be the same as the curing agent used in the above-mentioned first adhesive layer 21. In addition, as the curing agent, a curing agent that is solid at room temperature or a curing agent that is liquid at room temperature may be used, but from the viewpoint of storage stability, it is preferable to use a curing agent that is solid at room temperature.

[0113] (b) Foaming agent The second adhesive layer 22 in the present embodiment may or may not contain a foaming agent, but preferably contains a foaming agent. By containing a foaming agent in both the first adhesive layer 21 and the second adhesive layer 22, the adhesion of the first adhesive layer 21 and the second adhesive layer 22 after foaming and curing can be improved.

[0114] The foaming agent may be the same as that used in the first adhesive layer 21.

[0115] (c) Other ingredients In the present embodiment, when the curable adhesive is an epoxy resin adhesive, the second adhesive layer 22 may contain only epoxy resin and acrylic resin as the resin component, or may further contain other resins such as urethane resin.

[0116] The total proportion of epoxy resin and acrylic resin to the resin components contained in the second adhesive layer 22 is, for example, 70 mass% or more, may be 80 mass% or more, may be 90 mass% or more, or may be 100 mass%.

[0117] The content of the resin component in the second adhesive layer 22 is, for example, 60% by mass or more, optionally 70% by mass or more, optionally 80% by mass or more, or optionally 90% by mass or more.

[0118] The second adhesive layer 22 may contain an additive as necessary. The additive may be the same as the additive used in the first adhesive layer 21.

[0119] (3) Configuration of the second adhesive layer When the second adhesive layer 22 further contains a foaming agent, the second adhesive layer 22 can be foamed at an expansion ratio of, for example, 1.5 times or more and 12 times or less. For example, when both the first adhesive layer 21 and the second adhesive layer 22 contain a foaming agent, the expansion ratio may be, for example, 2 times or more, 3 times or more, or 4 times or more. In the above case, the expansion ratio may be, for example, 10 times or less, 9 times or less, or 8 times or less. If the expansion ratio is too small or too large, the adhesiveness after foaming and curing may decrease.

[0120] The average thickness of the second adhesive layer 22 may be the same as the average thickness of the first adhesive layer 21 described above.

[0121] The method for forming the second adhesive layer 22 may be the same as the method for forming the first adhesive layer 21 described above.

[0122] (Other configurations) The foamable adhesive sheet 20 in this embodiment may have a substrate between the first adhesive layer 21 and the second adhesive layer 22. When a substrate is disposed between the first adhesive layer 21 and the second adhesive layer 22, the foamable adhesive sheet 20 is easy to handle and easy to work with. On the other hand, when no substrate is disposed between the first adhesive layer 21 and the second adhesive layer 22, the overall thickness of the foamable adhesive sheet 20 can be made thin, and the foamable adhesive sheet 20 can be inserted into a narrow gap.

[0123] The substrate is preferably insulating. The substrate is preferably in the form of a sheet. The substrate may have a single layer structure or a multi-layer structure. The substrate may or may not have a porous structure inside.

[0124] Examples of the substrate include a resin substrate and a nonwoven fabric.

[0125] Examples of the resin contained in the resin substrate include polyester resins such as polyethylene terephthalate (PET), polybutylene terephthalate, polyethylene naphthalate (PEN), and aromatic polyester; polycarbonate; polyarylate; polyurethane; polyamide resins such as polyamide and polyetheramide; polyimide resins such as polyimide, polyetherimide, and polyamideimide; polysulfone resins such as polysulfone and polyethersulfone; polyetherketone resins such as polyetheretherketone and polyetheretherketone; polyphenylene sulfide (PPS); and modified polyphenylene oxide. The glass transition temperature of the resin is, for example, 80° C. or higher, may be 140° C. or higher, or may be 200° C. or higher. In addition, a liquid crystal polymer (LCP) may be used as the resin.

[0126] Examples of the nonwoven fabric include nonwoven fabrics containing fibers such as cellulose fibers, polyester fibers, nylon fibers, aramid fibers, polyphenylene sulfide fibers, liquid crystal polymer fibers, glass fibers, metal fibers, and carbon fibers.

[0127] 5. Foam adhesive sheet The average thickness of the foamable adhesive sheet 20 is, for example, 10 μm or more, and may be 20 μm or more. The average thickness of the foamable adhesive sheet 20 is, for example, 1000 μm or less, and may be 200 μm or less.

[0128] The foamable adhesive sheet 20 preferably has high adhesiveness after foaming and curing. The shear strength (adhesive strength) based on JIS 6850 corresponding to ISO 4587 may be, for example, 1.50 MPa or more, 1.80 MPa or more, or 2.10 MPa or more at 23°C. The shear strength (adhesive strength) may be, for example, 0.50 MPa or more, 0.75 MPa or more, or 1.00 MPa or more at 130°C. For example, in a high-strength acrylic foam adhesive tape that does not require heating, the shear strength (adhesive strength) is about 1 MPa or more and 2 MPa or less at room temperature, and it does not have heat resistance at 200°C. Therefore, if the shear strength (adhesive strength) is within the above range at 23°C, it has an advantage in terms of strength. If the shear strength (adhesive strength) is within the above range at 130°C, it can be applied to applications that require heat resistance around an automobile engine or similar.

[0129] The foamable adhesive sheet 20 preferably has high electrical insulation after foaming and curing. The dielectric breakdown voltage based on JIS C2107 corresponding to IEC 60454-2 is preferably, for example, 3 kV or more, more preferably 5 kV or more. When the dielectric breakdown voltage is within the above range, it becomes possible to apply the sheet to rust prevention and around copper wires. In addition, the adhesive sheet after foaming and curing preferably has a thermal conductivity of, for example, 0.1 W / mK or more, more preferably 0.15 W / mK or more. When the thermal conductivity is within the above range, it is possible to miniaturize the parts and promote the curing reaction during heating.

[0130] (Stator and motor) Next, the configurations of a stator and an electric motor produced using the coated metal wire 10 according to this embodiment will be described.

[0131] Fig. 4 is a schematic exploded perspective view showing electric motor 50 according to the present embodiment. Fig. 5 is a cross-sectional view showing stator 61 of electric motor 50 according to the present embodiment. Fig. 6 is an enlarged cross-sectional view showing the periphery of one slot 63 of stator 61.

[0132] 4 and 5, electric motor 50 according to this embodiment includes a rotating shaft 51, rotor 52, stator 61, and bracket 71. Rotor 52 is attached to rotating shaft 51. Stator 61 is disposed around rotor 52 and electrically connected to an inverter (not shown). Bracket 71 houses rotor 52 and stator 61, and attaches rotor 52 and stator 61 to a case (not shown).

[0133] The rotor 52 is attached to the rotating shaft 51 by shrink fitting, spline fitting, or the like. The rotor 52 has a rotor core 53 and permanent magnets 54. The rotor core 53 may be formed by stacking a plurality of rotor members. A plurality of permanent magnets 54 (eight in this case) are provided. The permanent magnets 54 are each inserted into a through hole 53a of the rotor core 53. The through hole 53a of the rotor core 53 passes through the rotor core 53 in the axial direction near the outer circumferential surface. The permanent magnets 54 are arranged such that the magnetic lines of force are oriented in the radial direction. The plurality of permanent magnets 54 may be arranged such that the magnetic poles of every other magnet are reversed.

[0134] As shown in FIG. 5, the stator 61 includes a stator core 62, a coil 11A, and a foamed resin portion 20A. The stator core 62 is formed into a cylindrical shape as a whole. The stator core 62 has a yoke portion 64 and teeth portions 65. The yoke portion 64 is located on the outer periphery of the stator core 62 and has a cylindrical shape. The teeth portions 65 protrude from the yoke portion 64 to the inner periphery side. A plurality of (16 in this case) slots 63 are formed on the inner surface of the stator core 62 along the circumferential direction. The slots 63 are located between a pair of adjacent teeth portions 65.

[0135] The coil 11A is composed of a metal wire 11 as a winding wound around the stator core 62. The metal wire 11 is disposed in the slot 63. The metal wire 11 corresponds to the metal wire 11 of the coated metal wire 10 described above. The foamed resin portion 20A is formed in the slot 63 by foaming the foamable adhesive sheet 20 of the coated metal wire 10 described above between the inner wall surface 62a of the stator core 62 and the metal wire 11. For convenience, FIG. 5 shows one of the 16 slots 63 without the metal wire 11 and the foamed resin portion 20A.

[0136] As shown in FIG. 6, inside the slot 63, a part of the metal wire 11 extends parallel to the axial direction of the rotating shaft 51 (see FIG. 4). Furthermore, in the cross section of the slot 63, a plurality of (four in this case) parts of the metal wire 11 are arranged at intervals from each other. Specifically, in the cross section of the slot 63, the parts of the metal wire 11 are arranged at intervals from each other in the radial direction of the stator 61. Note that the metal wire 11 located inside each stator 61 is actually formed by winding one metal wire multiple times. In this case, a plurality of parts of the metal wire 11 are arranged in the cross section of the slot 63.

[0137] The foamed resin portion 20A is present in the slot 63 and around the metal wire 11. As described above, the foamed resin portion 20A is formed by foaming the foamable adhesive sheet 20 of the coated metal wire 10. Therefore, the foamed resin portion 20A spreads more around the metal wire 11 than the foamable adhesive sheet 20, filling the slot 63. The foamed resin portion 20A is present all around the metal wire 11.

[0138] In FIG. 6, the region corresponding to the foamable adhesive sheet 20 before foaming is indicated by a virtual line. The thickness T1 of the foamable adhesive sheet 20 before foaming may be 1 / 10 or more, or 1 / 5 or more, of the minimum distance P1 between the metal wire 11 and the inner wall surface 62a of the stator core 62. The thickness T1 of the foamable adhesive sheet 20 before foaming may be 1 / 2 or less, or 1 / 3 or less, of the minimum distance P1 between the metal wire 11 and the inner wall surface 62a of the stator core 62. By making the thickness T1 1 / 10 or more of the minimum distance P1, the foamed resin portion 20A can be sufficiently spread in the slot 63, and the metal wire 11 can be firmly fixed to the stator core 62. By making the thickness T1 1 / 2 or less of the minimum distance P1, it is possible to suppress a decrease in the adhesiveness between the metal wire 11 and the stator core 62 due to the foamed resin portion 20A.

[0139] The foamed resin portion 20A is filled between the metal wire 11 and the inner wall surface 62a of the stator core 62. The foamed resin portion 20A is also present between parts of the metal wire 11 within the slot 63. The foamed resin portion 20A may be present only in a part of the slot 63 excluding the metal wire 11, but it is preferable that the foamed resin portion 20A is present in the entire area of ​​the slot 63 excluding the metal wire 11.

[0140] In this embodiment, the foamed resin portion 20A is formed by foaming the foamable adhesive sheet 20 in the slot 63. Therefore, it is not necessary to arrange, for example, insulating paper or a foamed sheet along the inner wall surface 62a of the stator core 62 in the slot 63. That is, the foamed resin portion 20A can ensure insulation between the metal wire 11 and the stator core 62 and insulation between parts of the metal wire 11 without providing insulating paper or a foamed sheet. In addition, the coated metal wire 10 provided with the foamable adhesive sheet 20 is used as the coil 11A of the stator 61. Therefore, by foaming the foamable adhesive sheet 20, it is possible to make the slot 63 substantially free of voids, and the metal wire 11 can be strongly fixed in the slot 63.

[0141] (Method of manufacturing coated metal wire) Next, a method for manufacturing the coated metal wire 10 according to the present embodiment will be described with reference to Figures 7(a) to 7(e). Figures 7(a) to 7(e) are diagrams illustrating the method for manufacturing the coated metal wire 10 according to the present embodiment.

[0142] First, as shown in FIG. 7( a ), an adhesive composition for forming the first adhesive layer 21 is applied onto the first separator 26 and dried to form the first adhesive layer 21 .

[0143] 7(b), an adhesive composition for forming the second adhesive layer 22 is applied onto the second separator 27 and dried to form the second adhesive layer 22. As shown in FIG.

[0144] 7(c), the laminate of the first separator 26 and the first adhesive layer 21 and the laminate of the second separator 27 and the second adhesive layer 22 are laminated together. This results in a foamable adhesive sheet 20. Since the first adhesive layer 21 is substantially non-adhesive (tack-free), the first separator 26 may be peeled off after lamination to provide the foamable adhesive sheet 20.

[0145] The first separator 26 and the second separator 27 are not particularly limited as long as they can be peeled off from the first adhesive layer 21 and the second adhesive layer 22, respectively. The first separator 26 and the second separator 27 have a strength sufficient to protect the first adhesive layer 21 and the second adhesive layer 22, respectively. Examples of such first separator 26 and second separator 27 include a release film and a release paper. Furthermore, the first separator 26 and the second separator 27 may have a single-layer structure or a multi-layer structure.

[0146] 7(d), a metal wire 11 is prepared. The metal wire 11 may be, for example, a metal wire such as a copper wire, a gold wire, an aluminum wire, or a metal wire containing an alloy thereof. The metal wire 11 may be coated with a coating material such as enamel resin.

[0147] 7(e), the foamable adhesive sheet 20 is wound around the metal wire 11. During this process, the first separator 26 and the second separator 27 are first peeled off and removed from the foamable adhesive sheet 20. Next, the foamable adhesive sheet 20 is wound around the metal wire 11 multiple times so that the second adhesive layer 22 of the foamable adhesive sheet 20 adheres to the metal wire 11. It is preferable that the metal wire 11 is covered with the foamable adhesive sheet 20 without any gaps, at least in an area excluding both longitudinal ends.

[0148] In this manner, the coated metal wire 10 shown in FIGS. 1 and 2 is obtained.

[0149] (Method of manufacturing the stator) Next, a method for manufacturing a stator 61 using the coated metal wire 10 according to the present embodiment will be described with reference to Figures 8(a) and (b). Figures 8(a) and (b) are diagrams for explaining the method for manufacturing a stator 61 according to the present embodiment, and are diagrams showing the periphery of one slot 63 of the stator 61.

[0150] First, prepare the coated metal wire 10. The coated metal wire 10 may be manufactured by, for example, the method shown in Fig. 7(a)-(e).

[0151] 8(a), the coated metal wire 10 is wound around the stator core 62. At this time, the coated metal wire 10 is placed in the slots 63 of the stator core 62. The coated metal wire 10 may be formed, for example, by distributed winding, so that the portions attached to the slots 63 of the stator core 62 are aligned in a row in the radial direction of the stator core 62. In this case, parts of the coated metal wire 10 may be in contact with each other in the radial direction of the stator core 62 within the slot 63. It is not necessary to place, for example, insulating paper or a foam sheet along the inner wall surface 62a of the stator core 62 within the slot 63.

[0152] As described above, the side of the foamable adhesive sheet 20 opposite to the side to be adhered to the metal wire 11 may be non-adhesive (tack-free). In this case, the outer surface of the coated metal wire 10 has good slipperiness. Therefore, when the coated metal wire 10 is arranged in the slot 63 of the stator 61, the coated metal wire 10 can be smoothly arranged. This makes it possible to suppress displacement of the coated metal wire 10 in the slot 63.

[0153] 8(b), the foamable adhesive sheet 20 of the covered metal wire 10 is foamed and cured in the slot 63. This causes the foamable adhesive sheet 20 to foam and cure, forming a foamed resin portion 20A. The foamable adhesive sheet 20 changes into the foamed resin portion 20A, thereby fixing the metal wire 11 in the slot 63. Specifically, the foamed resin portion 20A bonds the metal wire 11 to the inner wall surface 62a of the stator core 62. Furthermore, the foamed resin portion 20A bonds parts of the metal wire 11 to each other.

[0154] Examples of methods for foaming and curing the foamable adhesive sheet 20 include heating and light irradiation. Among these, it is preferable to foam and cure the foamable adhesive sheet 20 by heating. The heating method is also applicable to cases where the foamable adhesive sheet 20 is present in a non-transparent member such as the stator core 62. The heating conditions are appropriately set according to the types of curable adhesive and foaming agent contained in the foamable adhesive sheet 20, the type of base material, and the like. The heating temperature can be, for example, 130° C. or higher and 200° C. or lower. The heating time can be, for example, 3 minutes or higher and 3 hours or lower.

[0155] In this manner, the foamable adhesive sheet 20 of the coated metal wire 10 is foamed and cured in all of the slots 63, thereby obtaining the stator 61 shown in FIGS.

[0156] As described above, according to this embodiment, the foamable adhesive sheet 20 is wound around the metal wire 11. The foamable adhesive sheet 20 foams and hardens in the slot 63 of the stator 61 to become the foamed resin portion 20A. This improves the insulation between the metal wire 11 and the slot 63. It also improves the insulation between the parts of the metal wire 11 in the slot 63. Furthermore, by foaming the foamable adhesive sheet 20, the slot 63 is substantially free of voids, so that the metal wire 11 can be firmly fixed to the stator 61.

[0157] As described above, by foaming the foamable adhesive sheet 20, the slot 63 is substantially free of voids. In this case, unlike the case where insulating paper is inserted into the slot of the stator and then the slot is filled with mold resin or varnish to fix the metal wire, no voids remain in the slot 63. This makes it possible to suppress the position of the metal wire 11 from being displaced due to vibrations or the like that occur during use of the electric motor 50. Furthermore, unlike the case where mold resin or varnish is filled, the mold resin or varnish does not adhere to unintended parts during the manufacture of the electric motor 50. Therefore, the operation of removing the mold resin or varnish is not required, and the productivity of the electric motor 50 is suppressed from decreasing.

[0158] In the present embodiment, the foamable adhesive sheet 20 may contain an epoxy resin, an acrylic resin compatible with the epoxy resin, a hardener, and a foaming agent, thereby improving the adhesiveness of the foamed resin portion 20A after foaming and hardening.

[0159] In the present embodiment, the side of the foamable adhesive sheet 20 that is adhered to the metal wire 11 may have tackiness. This allows the foamable adhesive sheet 20 to be firmly adhered to the metal wire 11 when the foamable adhesive sheet 20 is wound around the metal wire 11.

[0160] In this embodiment, the tackiness of the side of the foamable adhesive sheet 20 opposite to the side adhered to the metal wire 11 may be lower than the tackiness of the side adhered to the metal wire 11. This allows the coated metal wire 10 to be smoothly arranged in the slot 63 of the stator 61. As a result, displacement of the coated metal wire 10 within the slot 63 can be suppressed.

[0161] [Example] Next, a specific example of this embodiment will be described.

[0162] First, the adhesive composition constituting the first adhesive layer and the adhesive composition constituting the second adhesive layer were mixed in the following materials and ratios to prepare the layers. A release film (PET separator, manufactured by Nippa, PET50x1-J2, thickness 50 μm) was used as the substrate. The above adhesive composition was applied to the release-treated surface of the release film using an applicator so that the thickness after application was 45 μm. After that, the layers were dried in an oven at 100°C for 3 minutes to prepare a laminate of the substrate and the first adhesive layer and a laminate of the substrate and the second adhesive layer.

[0163] <Materials / Composition> <First adhesive layer> Epoxy resin 1: Bisphenol A novolac type, solid at room temperature, softening temperature: 70°C, epoxy equivalent: 210g / eq, Mw: 1300, melt viscosity at 150°C: 0.5 Pa·s, mass parts of solid content: 32.7 Epoxy resin 2: BPA phenoxy type, solid at room temperature, softening temperature: 110°C, epoxy equivalent: 8000g / eq, Mw: 50,000, mass part of solid content: 34.3 Acrylic resin: PMMA-PBuA-PMMA (partially acrylamide groups), Tg: -20°C, 120°C, Mw: 150,000, solid content: 10.6 Hardener 1: α-(hydroxy(or dihydroxy)phenylmethyl)-ω-hydropoly[biphenyl-4,4'-diylmethylene(hydroxy(or dihydroxy)phenylene methylene)], solid content 4.9 parts by mass Hardener 2: 2-phenyl-4,5-dihydroxymethylimidazole, average particle size: 3 μm, melting point: 230°C, reaction start temperature: 145°C to 155°C, active region: 155°C to 173°C, solid mass part: 6.5 Foaming agent: Thermally expandable microcapsules, average particle size 13μm, expansion start temperature 123℃~133℃, maximum expansion temperature 168℃~178℃, core: hydrocarbon, shell: thermoplastic polymer, solid content 11.0 Solvent: Methyl ethyl ketone

[0164] <Second adhesive layer> Epoxy resin 3: Bisphenol A novolac type, solid at room temperature, softening temperature: 70°C, epoxy equivalent: 210g / eq, Mw: 1300, melt viscosity at 150°C: 0.5 Pa·s, mass parts of solid content: 5.5 Epoxy resin 4: Bisphenol A type, liquid at room temperature, epoxy equivalent: 184g / eq to 194g / eq, mass part of solid content: 11.0 Epoxy resin 5: Diaminodiphenylmethane type, high viscosity liquid, epoxy equivalent: 110g / eq~130g / eq, solid content mass part 28.6 Epoxy resin 6: Silicone modified, epoxy equivalent: 1200g / mol Hardener 3: α-(hydroxy(or dihydroxy)phenylmethyl)-ω-hydropoly[biphenyl-4,4'-diylmethylene(hydroxy(or dihydroxy)phenylenemethylene)], solid content 8.8 parts by mass Silane coupling agent: 3-glycidoxypropyltrimethoxysilane, 0.9 parts by weight of solid content Acrylic resin: PMMA-PBuA-PMMA (partially acrylamide groups), Tg: -20°C, 120°C, Mw: 150,000, solid content: 17.6 Hardener 3: α-(hydroxy(or dihydroxy)phenylmethyl)-ω-hydropoly[biphenyl-4,4'-diylmethylene(hydroxy(or dihydroxy)phenylenemethylene)], solid content 5.5 parts by mass Hardener 4: Dicyandiamide, particle size: 10 μm or less, melting point: 209 ° C (manufactured by Evonik Degussa, DYHARD100SH), solid content: 6.2 Hardener 5: Epoxy resin amine adduct (AmiCure MY-H, manufactured by Ajinomoto Fine-Techno Co., Ltd.), solid content by mass 4.0 Foaming agent: Thermally expandable microcapsules, average particle size 13μm, expansion start temperature 123℃~133℃, maximum expansion temperature 168℃~178℃, core: hydrocarbon, shell: thermoplastic polymer, solid content 11.9 parts by mass Solvent: Methyl ethyl ketone

[0165] Next, the surface of the second adhesive layer of the laminate having the substrate and the second adhesive layer was laminated onto the surface of the first adhesive layer of the laminate having the substrate and the first adhesive layer, thereby obtaining a foamable adhesive sheet in which the substrate, the first adhesive layer, the second adhesive layer, and the substrate were arranged in this order.

[0166] Next, the foamable adhesive sheet was wrapped around a copper wire (diameter 1 mm) while both substrates of the foamable adhesive sheet were peeled off. Specifically, the foamable adhesive sheet was wrapped around a copper wire so that the second adhesive layer and the copper wire were in contact with each other, to obtain a covered metal wire.

[0167] Next, this coated metal wire was wound around the slot of the stator core. The foamable adhesive sheet was then heated at 180°C for 30 minutes to foam and harden the foamable adhesive sheet, thereby obtaining a foamed resin part. In the stator thus obtained, even though there was no process of inserting insulating paper into the slot, the foamed resin part was densely filled between the copper wire and the inner wall surface of the stator core, ensuring insulation between the copper wire and the stator core. In addition, the copper wire was firmly fixed in the slot without using adhesive varnish or molded resin.

[0168] It is also possible to combine the multiple components disclosed in the above embodiment and modified examples as necessary. Alternatively, some components may be deleted from all the components shown in the above embodiment and modified examples. [Explanation of symbols]

[0169] 10 Covered metal wire 11 Metal Wire 20. Foam adhesive sheet 20A Foam resin part 50 Electric motor 51 Rotation axis 52 Rotor 53 Rotor core 61 Stator 62 Stator core 63 Slots 71 Bracket

Claims

1. A coated metal wire, A metal wire; and a foamable adhesive sheet wound around the metal wire.

2. 2. The coated metal wire according to claim 1, wherein the foamable adhesive sheet contains an epoxy resin, an acrylic resin compatible with the epoxy resin, a curing agent, and a foaming agent.

3. 2. The coated metal wire according to claim 1, wherein the foamable adhesive sheet has a side that is bonded to the metal wire and has tackiness.

4. 4. The coated metal wire according to claim 3, wherein the foamable adhesive sheet has a lower tackiness on a side opposite to the side to be adhered to the metal wire than on the side to be adhered to the metal wire.

5. a stator core having slots; a metal wire disposed within the slot; a foam portion disposed within the slot; A stator, wherein the foamed resin portion exists around the entire circumference of the metal wire.

6. A rotor; An electric motor comprising: a stator according to claim 5 disposed around the rotor.

7. A step of preparing a coated metal wire according to any one of claims 1 to 4; placing the coated metal wire within a slot of a stator core; and foaming the foamable adhesive sheet on the coated metal wire within the slot to form a foamed resin portion around the metal wire.

8. The method for manufacturing a stator according to claim 7 , wherein a thickness of the foamable adhesive sheet before foaming is between 1 / 10 and 1 / 2 of a minimum distance between the metal wire and the inner wall surface of the stator core.

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