Tape-wrapped insulated wire and coil

Abstract

[Problem] To provide a tape-wrapped insulated wire and a coil that make it possible to achieve an equivalent or higher electrical breakdown voltage even when the thickness of an insulating coating is the same, or to achieve an equivalent or higher electrical breakdown voltage even when the thickness of an insulating coating is reduced and the diameter of an insulated wire is reduced. [Solution] The problem was solved by the following. An insulated wire 10 has a conductor 1 and an insulating coating 2 provided to the outer periphery of the conductor 1, the insulating coating 2 comprising a plurality of insulating layers (2a, 2b, 2c, 2d, 2e) formed respectively by winding in layers two to five pieces of insulating tape (11, 12, 13, 14, 15). The insulating coating 2 of this insulated wire 10 is configured so that: (1) if there are two or three insulating layers each formed by winding in layers the relevant insulating tape, then the sum of the number of winds of each of the insulating layers is no greater than a total number found by adding 1 to the sum of an integer component of the number of winds of each of the insulating layers; or (2) if there are four or five insulating layers each formed by winding in layers the relevant insulating tape, then the sum of the number of winds of each of the insulating layers is no greater than a total number found by adding 2 to the sum of an integer component of the number of winds of each of the insulating layers.

Description

Tape-wrapped insulated wire and coils

[0001] The present invention relates to a tape-wrapped insulated electric wire and coil used for coils of electronic components such as power transformers, and more specifically to a tape-wrapped insulated electric wire and a coil formed from the tape-wrapped insulated electric wire that can maintain the same or a higher breakdown voltage even when the thickness of the insulating coating is the same, or that can maintain the same or a higher breakdown voltage even when the thickness of the insulating coating is reduced to make the insulated electric wire thinner.

[0002] In electronic components such as transformers, inductors, and choke coils, triple-insulated wires that provide reinforced insulation in accordance with safety standards such as IEC are sometimes used to increase the space factor (see, for example, Patent Document 1).

[0003] Patent Document 1 discloses a multilayer insulated wire whose insulating layer is formed of three extruded coating layers, and whose solderability, heat resistance, delamination resistance, and electrical insulation meet IEC standards even when the insulating layer is thin. Because the first insulating layer of this multilayer insulated wire is formed from a polyamide resin with high mechanical strength and softening temperature, the collapse of the insulating layer caused by the winding tension during coil processing or the heat generated by the conductor during use of the coil does not extend to the conductor surface. Therefore, even when the total thickness of the three extruded coating layers is 100 μm or less, the space factor of the coil can be increased when used for coil winding.

[0004] Japanese Unexamined Patent Publication No. 6-139829

[0005] In recent years, there has been a demand for higher efficiency and smaller size through further improvements in the space factor of transformer coil windings. However, the conventional three-layer extruded coating described above has a limit of approximately 30 μm for each layer, making it difficult to further reduce the coating thickness and increase the space factor. While tape-wrapped insulation coatings, which use insulating tape as an alternative to extruded coatings, have been used, the tape thickness is limited to approximately 10 μm due to the coating strength and thickness of the tape material. However, thin tapes cannot provide sufficient insulation performance. With such conventional insulated wires for coil windings, it is difficult to reduce the thickness while maintaining a high withstand voltage, making it difficult to fully achieve a compact coil with an increased space factor.

[0006] The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide a tape-wrapped insulated electric wire and a coil formed from the tape-wrapped insulated electric wire that can maintain the same or a higher breakdown voltage even when the thickness of the insulating coating is the same, or that can maintain the same or a higher breakdown voltage even when the thickness of the insulating coating is reduced to make the insulated electric wire thinner.

[0007] (1) The tape-wrapped insulated wire according to the present invention is an insulated wire having a conductor and an insulating coating provided on the outer periphery of the conductor, wherein the insulating coating is composed of a plurality of insulating layers formed by overlappingly winding two to five insulating tapes, and wherein when the insulating coating has two or three insulating layers each overlappingly wound with the insulating tapes, the total number of turns of the individual insulating layers is equal to or less than the sum of the integer parts of the number of turns of the individual insulating layers plus one, or when the insulating coating has four or five insulating layers each overlappingly wound with the insulating tapes, the total number of turns of the individual insulating layers is equal to or less than the sum of the integer parts of the number of turns of the individual insulating layers plus two, and in any case where the individual insulating layers have two to five layers, the integer part of the number of turns is in the range of 1 to 4.

[0008] According to this invention, the conductor has an insulating coating composed of multiple insulating layers wound with two to five insulating tapes. When the number of individual insulating layers is two or three, the total number of turns of the individual insulating layers is equal to or less than the sum of the integer parts (in the range of 1 to 4) of the individual insulating layers plus one. When the number of individual insulating layers is four or five, the total number of turns is equal to or less than the sum of the integer parts (in the range of 1 to 4) of the individual insulating layers plus two. Therefore, the sum of the decimal parts, which are fractions of the integer parts of the overlapping turns of the individual insulating tapes, can be 1.0 or less or 2.0 or less. This allows the total thickness of the insulating coating to be reduced, thereby enabling the resulting insulated wire to have a smaller diameter. As a result, the space factor can be improved when the coil is manufactured.

[0009] Furthermore, by making the sum of the decimal parts 1.0 or less or 2.0 or less, the number of turns of the integer parts of the turns that overlap when the individual insulating tapes are lap-wound can be sufficiently ensured. As a result, compared to conventional insulated wires, the breakdown voltage can be equal to or higher even when the thickness of the insulating coating is the same, or the breakdown voltage can be equal to or higher even when the thickness of the insulating coating is reduced to reduce the diameter of the insulated wire. Furthermore, making the decimal part 1.0 or less or 2.0 or less is advantageous for reducing the diameter, but from the perspective of the actual number of turns (hereinafter referred to as the "minimum number of turns"), which is the sum of the integer parts, the minimum number of turns can be increased by one or two, thereby increasing the breakdown voltage. Note that since the breakdown voltage can be increased, if the breakdown voltage is sufficient at the same level, a thinner insulating coating can be used, contributing to a smaller diameter insulated wire and an improved coil space factor.

[0010] Such tape-wrapped insulated wires maintain or improve the breakdown voltage, are flexible and have excellent coil winding properties, and can increase the space factor and make the coils smaller. Furthermore, the insulation coating can be made thinner, which reduces the thermal resistance of the insulated wire and improves heat dissipation, thereby lowering the temperature of the insulated wire.

[0011] (2) In the tape-wrapped insulated wire according to the present invention described in (1) above, when the insulating coating is formed by overlapping the insulating tapes to form two or three insulating layers, and the number of turns of the first insulating tape is expressed as s.α turns, the number of turns of the second insulating tape is expressed as t.β turns, and the number of turns of the third insulating tape is expressed as u.γ turns, the sum of the integer parts is s+t if the insulating layer is two layers, and s+t+u if the insulating layer is three layers, and the sum of the decimal parts is α+β if the insulating layer is two layers, and α+β+γ if the insulating layer is three layers, and the sum of the decimal parts is 1.0 or less. In this case, when the insulating layer is two layers, the third insulating tape is not used.

[0012] (3) In the tape-wrapped insulated electric wire according to the present invention described in (2) above, when there are two insulating tapes, the sum of the integer parts is 2 to 8, the sum of the decimal parts is 1.0 or less, and the total number is 2.0 to 9.0; when there are three insulating tapes, the sum of the integer parts is 3 to 12, the sum of the decimal parts is 1.0 or less, and the total number is 3.0 to 13.0.

[0013] (4) In the tape-wrapped insulated electric wire according to the present invention described in (1) above, when the insulating coating is formed by overlapping the insulating tapes to form three individual insulating layers, the number of turns of the first insulating tape may be expressed as s.α turns, the number of turns of the second insulating tape as t.β turns, and the number of turns of the third insulating tape as u.γ turns, the sum of the integer parts is s+t+u and the sum of the decimal parts is α+β+γ, and the sum of the decimal parts may be 1.5 or less.

[0014] (5) In the tape-wrapped insulated electric wire according to the present invention described in (1) above, when the insulating coating is formed by overlapping the insulating tapes to form four or five insulating layers, and the number of turns of the first insulating tape is expressed as s.α turns, the number of turns of the second insulating tape is expressed as t.β turns, the number of turns of the third insulating tape is expressed as u.γ turns, the number of turns of the fourth insulating tape is expressed as v.δ turns, and the number of turns of the fifth insulating tape is expressed as w.ε turns, the sum of the integer parts is s+t+u+v if the insulating layer is four layers, and s+t+u+v+w if the insulating layer is five layers, and the sum of the decimal parts is α+β+γ+δ if the insulating layer is four layers, and α+β+γ+δ+ε if the insulating layer is five layers, and the sum of the decimal parts is 2.0 or less. In this case, if the individual insulating layers are four layers, the fifth insulating tape is not used.

[0015] (6) In the tape-wrapped insulated electric wire according to the present invention described in (5) above, the sum of the integer parts is 4 to 16, the sum of the decimal parts is 2.0 or less, and the total number is 4.0 to 18.0. When the number of insulating tapes is five, the sum of the integer parts is 5 to 20, the sum of the decimal parts is 2.0 or less, and the total number is 5.0 to 22.0.

[0016] (7) In the tape-wrapped insulated electric wire according to the present invention described above in (1) to (6), any one or more of the two to five insulating tapes may be provided with an adhesive layer. In this case, the thickness of the insulating tape is preferably 0.002 to 0.1 mm.

[0017] (8) In the tape-wrapped insulated electric wire according to the present invention described above in (1) to (6), it is preferable that the insulating tape wound last among the plurality of insulating tapes has a bonding layer on its outward surface. In this case, it is preferable that the thickness of the insulating tape is 0.002 to 0.1 mm.

[0018] (9) A coil according to the present invention is characterized in that it is obtained by winding the tape-wrapped insulated electric wire according to the present invention described above in (1) to (6).

[0019] (10) A coil according to the present invention is characterized in that it is obtained by winding the tape-wrapped insulated electric wire according to the present invention described above in (7).

[0020] (11) A coil according to the present invention is characterized in that it is obtained by winding the tape-wrapped insulated electric wire according to the present invention described above in (8).

[0021] According to the tape-wrapped insulated wire of the present invention, the total thickness of the insulating coating can be reduced, allowing the diameter of the resulting insulated wire to be reduced. As a result, the space factor when a coil is manufactured can be improved. Furthermore, even if the thickness of the insulating coating is the same, the breakdown voltage can be maintained at the same level or higher. Alternatively, even if the thickness of the insulating coating is reduced and the diameter of the insulated wire is reduced, the breakdown voltage can be maintained at the same level or higher. As a result, the breakdown voltage can be maintained at the same level or higher, flexibility is excellent, coil winding properties are improved, and the space factor can be increased to enable a more compact coil. Furthermore, because the insulating coating can be made thinner, the thermal resistance of the insulated wire is reduced, heat dissipation is improved, and the temperature of the insulated wire can be lowered.

[0022] According to the coil of the present invention, since the coil is wound with the above-mentioned tape-wrapped insulated wire, it is possible to obtain a small coil with the same or improved breakdown voltage, high productivity, and a high space factor.

[0023] FIG. 1 is an external view of a tape-wrapped insulated electric wire according to the present invention. FIG. 2 is an example of a cross-sectional view of a tape-wrapped insulated electric wire according to the present invention, where (A) is an example of overlap winding with two insulating tapes and (B) is an example of overlap winding with three insulating tapes. FIG. 3 is another example of a cross-sectional view of a tape-wrapped insulated electric wire according to the present invention, where (A) is an example of overlap winding with four insulating tapes and (B) is an example of overlap winding with five insulating tapes. FIG. 3 is a cross-sectional view showing a form in which an adhesive layer is provided on an insulating tape, and (B) is a cross-sectional view showing a form in which a fusion layer is provided on an insulating tape. FIG. 4 is an explanatory diagram of a coil according to the present invention. FIG. 5 is a cross-sectional view of a tape-wrapped insulated electric wire of Example 1. FIG. 6 is a cross-sectional view of a tape-wrapped insulated electric wire of Comparative Example 1. FIG. 7 is a cross-sectional view of a tape-wrapped insulated electric wire of Example 2. FIG. 8 is a cross-sectional view of a tape-wrapped insulated electric wire of Comparative Example 2.

[0024] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A tape-wrapped insulated wire and a coil according to the present invention will be described below with reference to the drawings. However, the present invention is not limited to the illustrated embodiments.

[0025] [Tape-wrapped insulated wire] As shown in Figures 1 to 3 , a tape-wrapped insulated wire 10 (hereinafter, sometimes simply referred to as "insulated wire 10") according to the present invention is an insulated wire 10 having a conductor 1 and an insulating coating 2 provided on the outer periphery of the conductor 1, and the insulating coating 2 is composed of multiple insulating layers (2a, 2b, 2c, 2d, 2e) wound in layers with two to five insulating tapes (11, 12, 13, 14, 15). In this insulated wire 10, the insulating coating 2 is characterized in that (1) when the individual insulating layers wound with each insulating tape are two or three layers, the total number of turns of the individual insulating layers is equal to or less than the sum of the integer parts of the number of turns of the individual insulating layers plus one, or (2) when the individual insulating layers wound with each insulating tape are four or five layers, the total number of turns of the individual insulating layers is equal to or less than the sum of the integer parts of the number of turns of the individual insulating layers plus two, and the integer part of the number of turns is in the range of 1 to 4 in any of the cases where the individual insulating layers are two to five layers.

[0026] With this tape-wrapped insulated wire 10, the total thickness of the insulating coating 2 can be reduced, allowing the diameter of the resulting insulated wire 10 to be smaller. As a result, the space factor when producing a coil can be improved. Furthermore, even if the thickness of the insulating coating 2 is the same, the breakdown voltage can be maintained at the same level or higher. Alternatively, even if the thickness of the insulating coating 2 is reduced and the diameter of the insulated wire 10 is reduced, the breakdown voltage can be maintained at the same level or higher. As a result, the breakdown voltage can be maintained at the same level or higher, flexibility is excellent, coil winding properties are improved, and the space factor can be increased to enable a more compact coil. Furthermore, because the insulating coating 2 can be made thinner, the thermal resistance of the insulated wire is reduced, improving heat dissipation, and the temperature of the insulated wire 10 can be lowered.

[0027] Each component will be described below.

[0028] <Conductor> As shown in FIGS. 1 to 3 , the conductor 1 is not particularly limited as long as it is used as the central conductor of an insulated electric wire 10, particularly an insulated electric wire 10 for coils. Any type of conductor may be used, regardless of the material or twisting configuration. For example, the conductor may be composed of a single element wire extending in the longitudinal direction, a plurality of element wires twisted together, or a Litz wire. The element wire may be made of any conductive metal, but preferred examples include highly conductive metal conductors such as copper wire, copper alloy wire, aluminum wire, aluminum alloy wire, and copper-aluminum composite wire, as well as those with a plating layer applied to their surfaces. From the perspective of coil applications, copper wire and copper alloy wire are particularly preferred. Preferred plating layers include solder plating, tin plating, gold plating, silver plating, and nickel plating. Furthermore, the terms "conductor" and "element wire" as used herein also include those covered with an enamel layer for insulation, oxidation prevention, etc. The cross-sectional shape of the wire is not particularly limited, and may be a wire rod having a circular or nearly circular cross-sectional shape, or may be rectangular.

[0029] The cross-sectional shape of the conductor 1 is not particularly limited, but may be circular (including oval), rectangular, or the like. It is desirable for the cross-sectional size of the conductor 1 to be as large as possible so that the electrical resistance (AC resistance, conductor resistance) is small enough for favorable use in coils. For example, the outer diameter of a circular wire may be approximately 0.05 to 5 mm. Furthermore, in the case of a rectangular wire, the short side may be approximately 0.3 to 2 mm, and the long side may be approximately 0.5 to 5 mm. The cross-sectional size of the conductor 1 is appropriately selected depending on the application of the coil, but the smaller the cross-sectional size, the higher the adhesion and positioning accuracy of the insulating coating 2 (described below) must be.

[0030] <Insulating Coating> The insulating coating 2 is composed of two to five insulating layers (two to five insulating layers) wound around the conductor 1, each layer corresponding to one of the insulating tapes. Specifically, as shown in FIGS. 1 to 3 , the insulating coating 2 may be composed of two insulating layers (2a, 2b) wound around the conductor 1 using two insulating tapes (11, 12), three insulating layers (2a, 2b, 2c) wound around the conductor 1 using three insulating tapes (11, 12, 13), four insulating layers (2a, 2b, 2c, 2d) wound around the conductor 1 using four insulating tapes (11, 12, 13, 14), or five insulating layers (2a, 2b, 2c, 2d, 2e) wound around the conductor 1 using five insulating tapes (11, 12, 13, 14, 15). The insulating coating 2 must have a thickness sufficient to ensure a specified breakdown voltage, but it is preferable to make it as thin as possible if the specified breakdown voltage can be ensured. If the insulating coating 2 can be made thinner, the diameter of the insulated wire 10 can be made thinner and the space factor of the coil can be increased. The present invention has been completed with attention to these points.

[0031] (Number of layers of insulating coating) When the insulating coating 2 is formed by overlapping two or three insulating tapes, each of which has two or three insulating layers (for example, when two insulating tapes 11 and 12 are used, the insulating layers are the first insulating layer 2a and the second insulating layer 2b, and when three insulating tapes 11, 12, and 13 are used, the insulating layers are the first insulating layer 2a to the third insulating layer 2c), the total number of turns of the individual insulating layers is configured to be less than or equal to the total number obtained by adding 1 to the sum of the integer parts of the number of turns of the individual insulating layers.

[0032] When the insulating coating 2 is made up of four or five insulating tapes wound one over the other, each having four or five insulating layers (for example, when four insulating tapes 11, 12, 13, and 14 are used, the insulating layers are the first insulating layer 2a to the fourth insulating layer 2d, and when five insulating tapes 11, 12, 13, 14, and 15 are used, the insulating layers are the first insulating layer 2a to the fifth insulating layer 2e), the total number of turns of the individual insulating layers is configured to be less than or equal to the sum of the integer parts of the number of turns of the individual insulating layers plus two.

[0033] The reason for dividing the decimal portion into two or three layers and four or five layers is that dividing the decimal portion into two or three layers and four or five layers is practical and does not complicate manufacturing, from the viewpoint of reducing the total thickness of the insulating coating to reduce the diameter of the insulated wire and from the viewpoint of maintaining the same or higher breakdown voltage even when the insulating coating thickness is reduced or the same. Whether the individual insulating layers are two or three layers or four or five layers, the integer portion of the number of turns of each insulating layer is preferably in the range of 1 to 4. This integer portion may be in the range of 2 to 4, excluding 1, as in Examples 1 to 5, 7, 8, and 10 described below, or the integer portion of some layers may be 1 and the integer portion of the remaining layers may be 2 to 4, as in Examples 9 and 11 described below. The integer portion is set to 1 or greater because a minimum breakdown voltage cannot be ensured unless the minimum number of turns of each insulating layer is 1.0 or greater and the integer portion is 1 or greater. The integer portion is set to 4 or less because if the number of turns of each insulating layer exceeds 5.0, the number of turns becomes so large that it becomes difficult to count the integer and decimal portions, and the manufacturing process becomes more complicated.

[0034] In this tape-wrapped insulated electric wire 10, the sum of the decimal parts, which are fractions of the overlapping parts (integer parts) of the turns when the individual insulating tapes are lap-wrapped, is set to be equal to or greater than 0.0 and equal to or less than 1.0 or 2.0, so that the total thickness of the insulating coating 2 can be reduced, and the diameter of the obtained insulated electric wire 10 can be made smaller. As a result, the space factor can be improved when the coil is manufactured.

[0035] Furthermore, even if the thickness of the insulating coating 2 is the same as that of a conventional insulated wire, by making the sum of the decimal parts greater than or equal to 0.0 and less than or equal to 1.0 or less than or equal to 2.0, the integer overlapping parts of the turns when the individual insulating tapes are lap-wound can be sufficiently ensured. As a result, even if the thickness of the insulating coating 2 is the same as that of a conventional insulated wire, the breakdown voltage can be equal to or higher than that of a conventional insulated wire. Furthermore, by making the thickness of the insulating coating 2 thinner than that of a conventional insulated wire, even if the diameter of the insulated wire 10 is reduced, the integer overlapping parts of the turns when the individual insulating tapes are lap-wound can be sufficiently ensured. As a result, the breakdown voltage can be equal to or higher. Furthermore, while making the sum of the decimal parts greater than or equal to 0.0 and less than or equal to 1.0 or less than or equal to 2.0 is advantageous for reducing the diameter, from the perspective of the minimum number of turns, the minimum number of turns can be increased by one or two. As a result, the breakdown voltage can be increased. Note that since the breakdown voltage can be increased, if the breakdown voltage is sufficient at the same level, a thinner insulating coating 2 can contribute to reducing the diameter of the insulated wire 10 and improving the coil space factor.

[0036] (Conventional Lap Winding) Here, a description will be given of a conventional tape-wrapped insulated electric wire before the development of the tape-wrapped insulated electric wire 10 according to the present invention. Insulated electric wires, such as conventional tape-wrapped insulated electric wires, in which tape is wound around a round conductor, require a nearly circular shape and a smooth surface, so overlapping winding with a large amount of overlapping is typically used. To achieve a smooth surface, it is considered desirable to increase the tape overlap, for example, by winding the tape so that the overlap is 50% or more. Specifically, the tape is wound in 1.5 to 2.0 overlaps, 2.5 to 3.0 overlaps, or 3.5 to 4.0 overlaps, with a large decimal value to prevent steps at the tape end from being noticeable. Note that a "1.5 overlap" refers to a single overlap with an additional tape wound on top, resulting in a double-wrapped portion of 50%. A "double wrap" refers to a single overlap with an additional tape wound on top, resulting in a double-wrapped portion of 100%. Conventionally, such lap winding has formed multiple insulating layers (for example, first to third insulating layers or first to fourth insulating layers). On the other hand, conventionally, lap windings that slightly exceed an integral number of turns, such as 2.1 windings or 2.2 windings, tend to form a small triple-winding portion at the end of the tape, which is the fractional portion, and this tends to create a step between the tape and the other double-winding portions. If this step is narrow, the surface of the insulated wire becomes uneven, and therefore lap windings that slightly exceed an integral number of turns have not been preferred.

[0037] However, as explained in the above section on problems, in order to meet the demand for thinner insulated wires, the inventors thought that by reducing the number of turns of insulating tape wound around the conductor to 1.0 to 1.5 turns, 2.0 to 2.5 turns, 3.0 to 3.5 turns, or 4.0 to 4.5 turns, which narrow (small) the overlapping area, rather than 1.5 to 2.0 turns, 2.5 to 3.0 turns, or 3.5 to 4.0 turns, which widen (large) the overlapping area as in conventional insulating layers, it would be possible to reduce the total thickness of the insulating layer and thereby reduce the diameter of the insulated wire as well. Furthermore, because the insulating coating 2 is composed of multiple insulating layers, it was thought that the diameter could be reduced by taking into account the number of turns of the multiple layers.

[0038] (Aspects of overlap winding in the present invention) Taking the above-mentioned background into consideration, the aspect of overlap winding of the insulating tape of the present invention has been explained in the section above regarding (Number of layers of insulating coating). More specifically, the present invention is characterized in that the insulating coating 2 formed by overlap winding two to five insulating tapes is such that (1) when the individual insulating layers formed by overlap winding each insulating tape are two or three layers, the total number of turns of the individual insulating layers is equal to or less than the sum of the integer parts of the turns of the individual insulating layers plus one, or (2) when the individual insulating layers formed by overlap winding each insulating tape are four or five layers, the total number of turns of the individual insulating layers is equal to or less than the sum of the integer parts of the turns of the individual insulating layers plus two.

[0039] First, we will explain the case of (1) where the insulating layer is two or three layers. When the insulating coating 2 is formed by overlapping insulating tapes and each insulating layer is two or three layers, as described in the examples below, the number of turns of the first insulating layer 2a with the first insulating tape 11 is expressed as s.α turns, the number of turns of the second insulating layer 2b with the second insulating tape 12 is expressed as t.β turns, and the number of turns of the third insulating layer 2c with the third insulating tape 13 is expressed as u.γ turns. The sum of the integer parts s, t, and u is s + t in the two-layer case and s + t + u in the three-layer case. The sum of the decimal parts α, β, and γ is α + β in the two-layer case and α + β + γ in the three-layer case. The sum of the decimal parts is configured to be 1.0 or less. In this relationship, when the insulating layer is two or three layers, the sum of the decimal parts is 1.0 or less, and by reducing the sum of the decimal parts that do not contribute to the minimum number of turns (the actual number of turns consisting of the sum of the integer parts) to 1.0 or less, the diameter of the tape-wrapped insulated wire 10 can be reduced. Note that the minimum number of turns refers to the total number of turns of the integer parts on which the breakdown voltage of the tape-wrapped insulated wire depends. Note that the sum of the decimal parts "1.0 or less" also includes 0.0. Note that "dependence" means that the breakdown voltage is correlated with the integer part, and the breakdown voltage increases as the integer part increases.

[0040] In this case, when there are two insulating tapes, the integer parts of the number of turns of each insulating layer range from 1 to 4, so the sum of the integer parts is 2 to 8, and the sum of the decimal parts is 0.0 to 1.0, and the total of these is 2.0 to 9.0. When there are three insulating tapes, the integer parts of the number of turns of each insulating layer range from 1 to 4, so the sum of the integer parts is 3 to 12, and the sum of the decimal parts is 0.0 to 1.0, and the total of these is 3.0 to 13.0.

[0041] Next, the case of (2) having four or five insulating layers will be described. As will be described in the examples below, in this case as well, similarly to the two- or three-layer case described above, when the insulating coating 2 is formed by overlappingly winding insulating tapes to form four or five insulating layers, the number of turns of the first insulating layer 2a on the first insulating tape 11 is expressed as s.α turns, the number of turns of the second insulating layer 2b on the second insulating tape 12 is expressed as t.β turns, the number of turns of the third insulating layer 2c on the third insulating tape 13 is expressed as u.γ turns, the number of turns of the fourth insulating layer on the fourth insulating tape is expressed as v.δ turns, and the number of turns of the fifth insulating layer on the fifth insulating tape is expressed as w.ε turns. The sum of the integer parts s, t, u, v, and w is s+t+u+v in the case of four layers, and s+t+u+v+w in the case of five layers. The sum of the decimal parts α, β, γ, δ, and ε is α + β + γ + δ in the case of four layers, and α + β + γ + δ + ε in the case of five layers. The sum of these decimal parts is configured to be 2.0 or less. This relationship means that when the insulating layer has four or five layers, the sum of the decimal parts is 2.0 or less, so that the total number of decimal parts that do not contribute to the effective number of turns (the so-called minimum number of turns) is reduced to 2.0 or less, thereby enabling the diameter of the tape-wrapped insulated wire 10 to be reduced. Note that the "2.0 or less" sum of the decimal parts of the number of turns also includes 0.0.

[0042] In this case, when there are four insulating tapes, the sum of the integer parts is 4 to 16, the sum of the decimal parts is 0.0 or more and 2.0 or less, and the total number of these sums is 4.0 to 18.0. When there are five insulating tapes, the sum of the integer parts is 5 to 20, the sum of the decimal parts is 0.0 or more and 2.0 or less, and the total number of these sums is 5.0 to 22.0.

[0043] The tape-wrapped insulated wire 10 having such an insulating coating 2 has the same or improved breakdown voltage, is flexible and has excellent coil winding properties, and can increase the space factor and reduce the coil size. Furthermore, since the insulating coating 2 can be made thinner, the thermal resistance of the insulated wire decreases, improving heat dissipation, and lowering the temperature of the insulated wire 10.

[0044] The decimal parts will now be explained in detail. In the present invention, the cases where the insulating tape is wound in an overlapping manner are divided into two or three individual insulating layers and four or five individual insulating layers, and the sum of the decimal parts is set to 0.0 to 1.0 and 0.0 to 2.0, respectively. (1) When the insulating tape has two individual insulating layers, the sum of the decimal parts is 0.0 to 1.0, so that the sum of the decimal parts is 1.0 or less, the number of turns of the decimal part of each insulating layer can be set to 0.0 to 0.5 or less. (2) When the insulating tape has three individual insulating layers, the sum of the decimal parts is 0.0 to 1.0, so that the sum of the decimal parts is 1.0 or less, the number of turns of the decimal part of each insulating layer can be set to 0.0 to 0.333 or less. (3) When the individual insulating layers are four, the sum of the decimal points is between 0.0 and 2.0, inclusive. Therefore, in order to keep the sum of the decimal points at 2.0 or less, the number of turns of the decimal points of each insulating layer should be between 0.0 and 0.5, inclusive. (4) When the individual insulating layers are five, the sum of the decimal points is between 0.0 and 2.0, inclusive. Therefore, in order to keep the sum of the decimal points at 2.0 or less, the number of turns of the decimal points of each insulating layer should be between 0.0 and 0.4, inclusive.

[0045] Considering these aspects (1) to (4), in the case of (2) where each insulating layer is three, the number of turns of the decimal portion of each insulating layer must be 0.333 or less in order for the sum of the decimal portions to be 1.0 or less, which results in a smaller tolerance for the decimal portions from a manufacturing standpoint compared to other cases. In light of this, in the present invention, it is preferable to change the sum of the decimal portions when each insulating layer is three layers from the initial range of 0.0 to 1.0 to 0.0 to 1.5. This allows the number of turns of the decimal portion of each insulating layer when each insulating layer is three layers to be 0.0 to 0.5, making it comparable to the other cases (1), (3), and (4). In addition, even if the sum of the decimal parts when the individual insulating layers is three is between 0.0 and 1.5, the same effects as when the sum is between 0.0 and 1.0 (the total thickness of the insulating layers can be reduced, the diameter of the insulated wire can be made smaller, the breakdown voltage is the same or improved, flexibility is excellent and coil winding ease is achieved, and the space factor is increased to make the coil more compact) can be maintained. That is, in the case of an insulated wire 10 having a conductor 1 and an insulating coating 2 provided on the outer periphery of the conductor 1, in which the insulating coating 2 is configured of three insulating layers (2a, 2b, 2c) wound in laps with three insulating tapes (11, 12, 13), the insulating coating 2 has three insulating layers wound in laps with the insulating tapes, and the total number of turns of the individual insulating layers is equal to or less than the sum of the integer parts of the turns of the individual insulating layers plus 1.5, and the integer part of the number of turns may be in the range of 1 to 4.

[0046] (Insulating Tape) Multiple insulating tapes are wound around the outer periphery of the conductor 1 in overlapping fashion. In the present invention, "multiple" refers to two to five tapes. The reason for limiting the number of insulating tapes to two to five is that using at least two insulating tapes makes it easier to ensure the required breakdown voltage. The reason for limiting the number of insulating tapes to five is that using six or more tapes increases the complexity of the manufacturing process, which increases manufacturing costs and makes it difficult to achieve further improvements in effectiveness. For this reason, the present invention is described as an embodiment in which two to five insulating tapes are wound in overlapping fashion.

[0047] The material of the insulating tape is not particularly limited, but preferable examples include insulating resin materials such as polyethylene resin, polyester resin (PET, PEN, etc.), polyimide resin, polyamide resin, polyamideimide resin, polyphenylene sulfide resin, PEEK (polyether ether ketone), etc. Among these resin materials, low-dielectric-constant fluorine-based resins such as PFA, ETFE, and FEP, which are used as dielectric materials, and resins such as polyphenylene ether resin, polyolefin resin such as polypropylene, and polyester resin may also be used.

[0048] The thickness of the insulating tape is not particularly limited, as long as it is thick enough to ensure the necessary dielectric strength of the insulating coating 2 after overlap-wrapping of multiple (2 to 5) insulating tapes. The thickness of each insulating tape can be, for example, approximately 0.002 to 0.1 mm. The thickness is preferably selected based on the number of insulating tapes used and the number of overlap windings, taking into account the final thickness of the insulating coating 2 obtained by overlap-wrapping the insulating tapes used. If the insulating tape is provided with an adhesive layer 5 or a fusion layer 6 (described below), the thickness of the insulating tape includes the thickness of the adhesive layer 5 or the fusion layer 6. The width of the insulating tape is also not particularly limited, but may be any width that allows overlap winding around the outer periphery of the conductor 1 or on an already wrapped insulating tape. For example, a width of 2 to 12 times the diameter of the conductor 1 is preferred. The width of the insulating tape is typically preferably in the range of 0.4 to 50 mm. The two to five insulating tapes used may have the same thickness and width, or may have different thicknesses and widths. The winding pitch during overlap winding is set to a winding pitch that allows the overlap winding pattern described below to be realized. The winding direction of each insulating tape is not particularly limited, but it is preferable that the insulating tape be wound in the opposite direction to the adjacent insulating tape.

[0049] 4A, the adhesive layer 5 may be provided on one or more of the first to fifth insulating tapes as needed. The term "as needed" means that the adhesive layer 5 may or may not be provided, and is optional.

[0050] As the insulating tape provided with the adhesive layer 5, a resin tape 4 with an adhesive layer 5 is preferably used, which is made of a material described in the description of the insulating tape material above and has the adhesive layer 5 provided thereon. The thickness of the adhesive layer 5 is not particularly limited, but if it is too thick, the overall thickness will be too large, so it is preferably 5 μm or less. The lower limit of the thickness of the adhesive layer is also not particularly limited, but it can be, for example, 0.5 μm.

[0051] The adhesive layer 5 may be provided on one or both sides of the insulating tape, and is not particularly limited, but is preferably provided on one side. The insulating tape may be wound with the adhesive layer 5 on one side facing inward (the conductor side) or outward. The first insulating tape 11, which is wound first among the multiple insulating tapes, is advantageously wound with the adhesive layer 5 on one side facing inward (the conductor side), which allows the insulating coating 2 to be tightly attached to the conductor 1. On the other hand, the first insulating tape 11, which is wound first, can also be wound with the adhesive layer 5 on one side facing outward (the opposite side to the conductor), which has the advantage of making it easier to peel off the insulating coating 2.

[0052] Alternatively, to make it easier to peel off the insulating coating 2, the first insulating tape 11 may be wound without an adhesive layer on the inside. In this case, the adhesive layer 5 may be present on the outside of the first insulating tape 11 and on the inside of the second insulating tape 12, or the adhesive layer 5 may be present on either the outside of the first insulating tape 11 or the inside of the second insulating tape 12. The third insulating tape 13, which has an adhesive layer 5 on one side, is wound on the second insulating layer 2b with the adhesive layer 5 facing inward. The fourth insulating tape 14 and the fifth insulating tape 15, which have an adhesive layer 5 on one side, are also wound with the adhesive layer 5 facing inward.

[0053] To reduce the outer diameter of the insulated wire 10, any one of the two to five insulating tapes, except for the fifth insulating tape, can be an insulating tape without an adhesive layer. For example, if the first insulating tape 11 does not have an adhesive layer 5, the second to fifth insulating tapes are wound with their adhesive layers facing inward. If the second insulating tape 12 does not have an adhesive layer 5, the first insulating tape 11 is wound with its adhesive layer 5 facing outward, and the third to fifth insulating tapes are wound with their adhesive layers 5 facing inward. Similarly, if the third insulating tape 13 or the fourth insulating tape 14 does not have an adhesive layer 5, the insulating tape inside the insulating layer without the adhesive layer 5 is wound with its adhesive layer 5 facing outward, and the insulating tape outside the insulating layer without the adhesive layer 5 is wound with its adhesive layer 5 facing inward. In this way, a strong insulating coating 2 can be formed.

[0054] In order to further reduce the outer diameter of the insulated wire 10 while maintaining the shape of the insulating layer, an insulating tape having an adhesive layer 5 provided inside the outermost insulating tape can be used. This eliminates the adhesive layers of the insulating tape for the other insulating layers (layers other than the outermost layer, for example, in the case of a five-layer winding, this means that an adhesive layer is provided on the fifth layer and no adhesive layers are provided on the first to fourth layers), thereby forming a flexible insulating coating.

[0055] Preferred materials for the adhesive layer 5 include thermoplastic resins such as acrylic, polyester, urethane, polyimide, PVC, and EVA, and thermosetting resins such as epoxy and bismalimide. The adhesive layer 5 can be formed by dissolving such a resin in an organic solvent and applying an adhesive coating to a predetermined thickness using a coating device such as a gravure printer. The adhesive layer 5 can be formed by heating or the like when or after wrapping the insulating tape around the conductor 1.

[0056] (Fusing Layer) As shown in FIG. 4(B), the fusing layer 6 can be provided on one or more of the two to five insulating tapes as needed. The fusing layer 6 may be provided instead of the adhesive layer 5 described above. Typically, a resin tape 4 with a fusing layer 6 can be used, in which the resin tape 4 is made of the material described in the section describing the insulating tape material and the fusing layer 6 is provided on the resin tape 4. The fusing layer 6 is preferably provided facing outward on the insulating tape that is wound last among the multiple insulating tapes. By doing so, when a coil is produced using the resulting tape-wrapped insulated electric wire 10, the fusing layer 6 can be melted to fix the insulated electric wires together.

[0057] The material of the fusion layer 6 is preferably a thermoplastic resin composition or a resin composition mainly composed of a thermoplastic resin, and preferably has the property of being able to maintain its thermoplasticity at a certain temperature, for example, 80 to 130°C, thereby temporarily bonding the insulating tapes together, and of undergoing a crosslinking reaction at a specific temperature or higher, for example, 160 to 200°C, thereby self-fusing and bonding the insulated wires 10 together. The fusion layer 6 having such properties allows the insulating tapes to be temporarily bonded together and maintain their shape as a self-fusing tape-wrapped insulated wire, and by heating to a specific temperature or higher after coil winding during coil manufacturing, a crosslinking reaction occurs, allowing the self-fusing insulated wires to be bonded together, and the coil shape after winding can be maintained.

[0058] Examples of materials for the fusion layer 6 include thermosetting resins such as polyurethane resin, polyamide resin, polyester resin, and polyesterimide resin. Of these, polyurethane resin and polyester resin are preferred. The resin composition for forming the fusion layer 6 contains a crosslinking agent and a solvent. Various additives may also be included as needed. The crosslinking agents, solvents, and additives are not particularly limited, and various crosslinking agents, solvents, and additives are used as needed depending on the type of polyurethane resin, polyester resin, polyesterimide resin, etc., and the required characteristics (properties described above). The thickness of the fusion layer 6 is not particularly limited, but since a too large thickness increases the outer diameter of the insulated wire 10, it is preferable that the thickness be within the range of 1 to 15 μm, for example.

[0059] [Coil] As shown in FIG. 5 , the coil 20 according to the present invention is a transformer coil using the insulated wire 10 according to the present invention, and can be obtained by winding the insulated wire 10 around a transformer bobbin 21. The coil 20 thus obtained is wound with the tape-wrapped insulated wire 10, and therefore has the same or improved breakdown voltage, is highly productive, and can be a small coil with a high space factor. Furthermore, a high-voltage transformer that meets the IEC 62368 standard can be manufactured without wrapping an interlayer paper between the primary and secondary windings, as in the conventional method. As a result, the coil can be suitably used as a transformer coil with high insulation, a wound component such as a high-frequency coil, a circuit board equipped with a wound component such as a high-frequency coil, etc.

[0060] The present invention will be explained in more detail with reference to examples and comparative examples. The present invention is not limited to the following examples, and those skilled in the art may make various changes, modifications, and alterations within the scope of the present invention. In Figs. 6 to 9, which explain the embodiments and comparative examples, coordinates are indicated vertically and horizontally to make it easier to understand where the ends of the insulating tape are located. The coordinates are expressed as (x, y), where "x" is the value on the abscissa and "y" is the value on the ordinate.

[0061] Example 1 A tape-wrapped insulated wire 10 of Example 1 will be described with reference to Figure 6. A copper conductor with a diameter of 1.00 mm was used as the conductor 1, and an insulating coating 2 was provided around the conductor. The insulating coating 2 was composed of three insulating layers (2a, 2b, 2c) formed by overlapping and winding first to third insulating tapes (11, 12, 13). The first insulating layer 2a, closest to the conductor 1, was formed by overlapping and winding the first insulating tape 11, the outer second insulating layer 2b was formed by overlapping and winding the second insulating tape 12, and the outer third insulating layer 2c was formed by overlapping and winding the third insulating tape 13.

[0062] A first insulating layer 2a was formed by wrapping a first insulating tape 11 made of polyimide resin with a thickness of 7.5 μm (total thickness 9.5 μm), a tape width of 7.0 mm, and a 2 μm thick adhesive layer on the conductor 1 2.3 times, with the adhesive layer facing outward to prevent adhesion to the conductor 1. From the coordinates in Figure 6, the coordinates of the ends of the first insulating tape 11 that form the first insulating layer 2a are (10, 3) and (32, 1), and when wound half a turn, the coordinates of the ends of the first insulating tape 11 are (15, -3) and (37, -1), and when wound another half turn, the coordinates of the ends of the first insulating tape 11 are (20, 3) and (42, 1). The first insulating layer 2a is a layer wound two or three times, so that on the upper side of the conductor 1 shown in Figure 6, it is wound three times at x-coordinates 1 to 2, 10 to 12, 20 to 22, 30 to 32, and 40 to 42, and is wound double everywhere else. On the lower side of the conductor 1, it is wound three times at x-coordinates 5 to 7, 15 to 17, 25 to 27, 35 to 37, and 45 to 46, and is wound double everywhere else.

[0063] Next, a second insulating tape 12 made of polyimide resin with a thickness of 7.5 μm (total thickness: 9.5 μm) and a tape width of 7.0 mm and a 2 μm adhesive layer was placed on the inside so that its adhesive layer was attached to the first insulating layer 2a. The second insulating tape 12 was wound 2.2 times over the first insulating layer 2a, with the winding direction reversed from that of the first insulating tape 11, to form the second insulating layer 2b. Figure 6 shows that the second insulating tape 12 is aligned with the edge of the first insulating layer 2a. The coordinates of the ends of the second insulating tape 12 that form the second insulating layer 2b are (8, 5) and (29, 3). The coordinates of the ends of the second insulating tape 12 after a half-wrap are (13, -5) and (34, -3). The coordinates of the ends of the second insulating tape 12 after another half-wrap are (18, 5) and (39, 3). Since the second insulating layer 2b is a 2.2-fold wound layer, on the upper side of the conductor 1 shown in Figure 6, the x-coordinates of 8 to 9, 18 to 19, 28 to 29, and 38 to 39 are triple wound, and the other areas are double wound. On the lower side of the conductor 1, the x-coordinates of 3 to 4, 13 to 14, 23 to 24, 33 to 34, and 43 to 44 are triple wound, and the other areas are double wound.

[0064] Next, a third insulating tape 13 made of polyimide resin with a thickness of 7.5 μm (total thickness: 9.5 μm) and a tape width of 7.5 mm and provided with a 2 μm thick adhesive layer was placed on the inside so that its adhesive layer was attached to the second insulating layer 2b, and the wrapping direction was reversed from that of the second insulating tape 12. The third insulating tape 13 was wrapped 2 or 3 times over the second insulating layer 2b to form a third insulating layer 2c. Figure 6 shows that the third insulating tape 13 is aligned along the edge of the second insulating layer 2b. The coordinates of the ends of the third insulating tape 13 forming the third insulating layer 2c are (5, 7) and (27, 5). The coordinates of the ends of the third insulating tape 13 when wound halfway are (10, -7) and (32, -5). The coordinates of the ends of the third insulating tape 13 after another halfway winding are (15, 7) and (37, 5). Therefore, the third insulating layer 2c is wound 2 or 3 times. Therefore, on the upper side of the conductor 1 shown in FIG. 6, the x-coordinates of 5 to 7, 15 to 17, 25 to 27, 35 to 37, and 45 to 46 are triple-wound, while the remaining areas are double-wound. On the lower side of the conductor 1, the x-coordinates of 1 to 2, 10 to 12, 20 to 22, 30 to 32, and 40 to 42 are triple-wound, while the remaining areas are double-wound. In this way, the tape-wrapped insulated electric wire of Example 1 was obtained.

[0065] In the obtained tape-wrapped insulated wire, the insulating coating 2, including the first insulating layer 2a, the second insulating layer 2b, and the third insulating layer 2c, had an average thickness of 64 μm at each portion in the longitudinal direction T. The sum (minimum number of turns) of the integer portions of the first insulating layer 2a, the second insulating layer 2b, and the third insulating layer 2c was 2 + 2 + 2 = 6, with the decimal portions all being 0.5 or less, and the sum of the decimal portions being 0.8 or less, which is 1.0 or less. The total number of turns obtained by adding these was 6.8, which was 7 or less, calculated by adding 1 to the sum of the integer portions. The number of turns of each insulating layer can be seen from Figure 2(B). Reference numeral 1 denotes a conductor, around which a first insulating tape 11 is wound clockwise 2.3 times. A second insulating tape 12 is wound counterclockwise 2.2 times around the conductor, and a third insulating tape 13 is wound clockwise 2.3 times around the conductor.

[0066] Comparative Example 1 A tape-wrapped insulated wire 10 of Comparative Example 1 will be described with reference to Figure 7. A copper wire with a diameter of 1.00 mm was used as the conductor 1, and the insulating coating 2 provided around the conductor was composed of three insulating layers (2a, 2b, 2c) formed by overlapping and winding three insulating tapes (11, 12, 13) on the outer periphery of the conductor. A first insulating tape 11 made of polyimide resin with a thickness of 7.5 µm (total thickness 9.5 µm) and a tape width of 8.5 mm and provided with a 2 µm thick adhesive layer was wound 2.8 times around the conductor 1 with the adhesive layer facing outward to prevent adhesion to the conductor 1, forming a first insulating layer 2a. Next, a second insulating tape 12 made of polyimide resin, 7.5 μm thick (total thickness: 9.5 μm), and 7.5 mm wide, with a 2 μm thick adhesive layer was wound on the inside so that the adhesive bonded to the first insulating layer 2a, in the opposite winding direction from the first insulating tape 11, and wrapped 2.3 times around the first insulating layer 2a to form the second insulating layer 2b. Next, a third insulating tape 13 made of polyimide resin, 7.5 μm thick (total thickness: 9.5 μm), and 6.0 mm wide, with a 2 μm thick adhesive layer was wound on the inside so that the adhesive bonded to the second insulating layer 2b, in the opposite winding direction from the second insulating tape 12, and wrapped 1.8 times around the second insulating layer 2b to form the third insulating layer 2c. This tape-wrapped insulated wire of Comparative Example 1 was thus obtained.

[0067] In the obtained tape-wrapped insulated wire, the insulating coating 2 having the first insulating layer 2a, the second insulating layer 2b, and the third insulating layer 2c had an average thickness of 64 μm at each portion in the longitudinal direction T. The sum of the integer turns of the first insulating layer 2a, the second insulating layer 2b, and the third insulating layer 2c (the minimum number of turns) was 2 + 2 + 1 = 5, and the sum of the decimal turns was 1.9, exceeding 1.0. The total number of turns obtained by adding these integer turns to the sum of the integer turns was 6.9, exceeding the total of 6 obtained by adding 1 to the sum of the integer turns.

[0068] Example 2 A tape-wrapped insulated wire 10 of Example 2 will be described with reference to Figure 8. A copper conductor with a diameter of 0.55 mm was used as the conductor 1, and the insulating coating 2 provided around the conductor was composed of two insulating layers (2a, 2b) formed by overlapping a first insulating tape 11 and a second insulating tape 12. The first insulating tape 11, which was made of polyimide resin and had a thickness of 7.5 µm (total thickness 9.5 µm) and a tape width of 5.5 mm and was provided with a 2 µm-thick adhesive layer, was wound 3.2 times around the conductor 1 with the adhesive layer facing outward to prevent adhesion to the conductor 1, forming the first insulating layer 2a. Next, a second insulating tape 12 made of polyimide resin with a thickness of 7.5 μm (total thickness: 9.5 μm), a tape width of 4.0 mm, and a 2 μm thick adhesive layer was wound on the first insulating layer 2a in the opposite direction to the first insulating tape 11, forming a second insulating layer 2b. A third insulating layer was not formed. In this manner, the tape-wrapped insulated wire of Example 2 was obtained.

[0069] In the obtained tape-wrapped insulated wire, the insulating coating 2 having the first insulating layer 2a and the second insulating layer 2b had an average thickness of 48 μm at each portion in the longitudinal direction T. The sum of the integer turns of the first insulating layer 2a and the second insulating layer 2b (minimum number of turns) was 3 + 2 = 5, and the decimal turns were both 0.5 or less, with the sum of the decimal turns being 0.3 or less, which was 1.0 or less. The total number of turns obtained by adding these integer turns to 5.3 was 6 or less, which was the sum of the integer turns plus 1.

[0070] Comparative Example 2 A tape-wrapped insulated wire 10 of Comparative Example 2 will be described with reference to Figure 9. A copper wire with a diameter of 0.55 mm was used as the conductor 1, and the insulating coating 2 provided around the conductor was composed of three insulating layers (2a, 2b, 2c) formed by overlapping three insulating tapes (11, 12, 13). A first insulating tape 11 made of polyimide resin with a thickness of 7.5 µm (total thickness 9.5 µm) and a tape width of 3.0 mm and provided with a 2 µm thick adhesive layer was wound 1.9 times around the conductor 1 with the adhesive layer facing outward to prevent adhesion to the conductor 1, forming a first insulating layer 2a. Next, a second insulating tape 12 made of polyimide resin, 7.5 μm thick (total thickness: 9.5 μm), and 5.0 mm wide, with a 2 μm thick adhesive layer was wound on the inside so that the adhesive bonded to the first insulating layer 2a, in the opposite winding direction from the first insulating tape 11, and wrapped 2.7 times around the first insulating layer 2a to form the second insulating layer 2b. Next, a third insulating tape 13 made of polyimide resin, 7.5 μm thick (total thickness: 9.5 μm), and 3.5 mm wide, with a 2 μm thick adhesive layer was wound on the inside so that the adhesive bonded to the second insulating layer 2b, in the opposite winding direction from the second insulating tape 12, and wrapped 1.8 times around the second insulating layer 2b to form the third insulating layer 2c. This resulted in the tape-wrapped insulated wire of Comparative Example 2.

[0071] In the obtained tape-wrapped insulated wire, the insulating coating 2 having the first insulating layer 2a, the second insulating layer 2b, and the third insulating layer 2c had an average thickness of 57 μm at each portion in the longitudinal direction T. The sum of the integer turns of the first insulating layer 2a, the second insulating layer 2b, and the third insulating layer 2c (minimum number of turns) was 1 + 2 + 1 = 4, and the decimal turns all exceeded 0.5, resulting in a total of 2.4, exceeding 1.0. The total number of turns obtained by adding these integer turns to the sum of the integer turns was 6.4, exceeding the total of 5 obtained by adding 1 to the sum of the integer turns.

[0072] [Example 3] The conductor 1 was a Litz wire made of 33 twisted copper wires with a diameter of 0.1 mm. The insulating coating 2 around the conductor 1 was composed of two insulating layers (2a, 2b) formed by overlapping a first insulating tape 11 and a second insulating tape 12. The first insulating tape 11, made of polyimide resin and having a thickness of 7.5 μm (total thickness 9.5 μm), a tape width of 6.5 mm, and a 2 μm adhesive layer, was wound 3.2 times around the conductor 1, with the adhesive layer facing outward to prevent adhesion to the conductor 1, to form the first insulating layer 2a. Next, the second insulating tape 12, made of polyimide resin and having a thickness of 7.5 μm (total thickness 9.5 μm), a tape width of 7.0 mm, and a 2 μm adhesive layer, was wound 3.1 times around the first insulating layer 2a, with the adhesive facing inward to adhere to the first insulating layer 2a, in the opposite winding direction to the first insulating tape 11, to form the second insulating layer 2b. The third insulating layer was not provided. In this manner, the tape-wrapped insulated wire of Example 3 was obtained.

[0073] In the obtained tape-wrapped insulated wire, the insulating coating 2 having the first insulating layer 2a and the second insulating layer 2b had an average thickness of 63 μm at each portion in the longitudinal direction T. The sum of the integer turns of the first insulating layer 2a and the second insulating layer 2b (minimum number of turns) was 3 + 3 = 6, and the decimal turns were both 0.5 or less, resulting in a total of 0.3, which was 1.0 or less. The total number of turns obtained by adding these integer turns to 6.3 was 7 or less, calculated by adding 1 to the sum of the integer turns.

[0074] Example 4: A conductor 1 was a copper wire with a diameter of 0.45 mm, and the insulating coating 2 around the conductor 1 was composed of two insulating layers (2a, 2b) formed by overlapping a first insulating tape 11 and a second insulating tape 12. The first insulating tape 11, which was made of polyimide resin and had a thickness of 5.0 μm (total thickness 7.5 μm), a tape width of 4.8 mm, and a 2.5 μm adhesive layer, was wound 3.4 times around the conductor 1, with the adhesive layer facing outward to prevent adhesion to the conductor 1, to form a first insulating layer 2a. Next, a second insulating tape 12, which was made of polyimide resin and had a thickness of 5.0 μm (total thickness 7.5 μm), a tape width of 4.8 mm, and a 2.5 μm adhesive layer, was wound 3.1 times around the first insulating layer 2a, with the adhesive facing inward to adhere to the first insulating layer 2a, in the opposite winding direction to the first insulating tape 11, to form a second insulating layer 2b. The third insulating layer was not provided. In this manner, the tape-wrapped insulated wire of Example 4 was obtained.

[0075] In the obtained tape-wrapped insulated wire, the insulating coating 2 having the first insulating layer 2a and the second insulating layer 2b had an average thickness of 51 μm at each portion in the longitudinal direction T. The sum of the integer turns of the first insulating layer 2a and the second insulating layer 2b (minimum number of turns) was 3 + 3 = 6, and the decimal turns of each were both 0.5 or less, resulting in a total of 0.5 or less, which was 1.0 or less. The total number of turns obtained by adding these integer turns to 6.5 was 7 or less, calculated by adding 1 to the sum of the integer turns.

[0076] [Line-to-Line Voltage Withstand Test] For Examples 1 to 4 and Comparative Examples 1 and 2, samples were prepared by twisting two tape-wrapped insulated wires. After applying 8 kV for 1 minute as specified in the reinforced insulation test, a test voltage was applied between the conductors at a voltage increase rate of 500 V / s to measure the breakdown voltage. Measurements were performed using a voltage withstand tester (manufactured by Tokyo Seiden Co., Ltd.) in accordance with JIS C 3216 (winding test method). The results are shown in Table 1. In Table 1, "Tape Thickness" refers to the thickness of the insulating tape excluding the thickness of the adhesive layer, "Total Tape Thickness" refers to the total thickness of the insulating tape including the thickness of the adhesive layer, "Integer" refers to the sum of the integer parts of each insulating layer (minimum number of turns), "Decimal" refers to the sum of the decimal parts of each insulating layer, "Total" refers to the sum of the "Integer" and "Decimal", and "Coating Thickness" refers to the thickness of the entire insulating coating, including the first through third layers.

[0077]

[0078] The breakdown voltage of Example 1 was 16.95 kV, which was 1.38 kV higher than the 15.57 kV of Comparative Example 1. In both cases, the insulating coating 2 was composed of the same first to third insulating layers (2a, 2b, 2c), the thickness of the insulating coating 2 was also the same, and the total number (the sum of the integer and decimal parts) was also the same. However, in Example 1, the decimal part was 0.8, which is 1.0 or less, while in Comparative Example 1, the decimal part was 1.9, which is greater than 1.0. Therefore, the total integer part (minimum number of turns) on which the breakdown voltage depends is larger in Example 1, and therefore it can be said that Example 1 has a higher breakdown voltage than Comparative Example 1. The results of Example 2 and Comparative Example 2 show that even if the coating thickness and total number (the sum of the integer and decimal parts) are the same, a higher breakdown voltage can be obtained by keeping the sum of the decimal parts to 1.0 or less and increasing the sum of the integer parts.

[0079] The breakdown voltage was 21.30 kV in Example 2, which was 4.99 kV higher than the 16.31 kV in Comparative Example 2. The thickness of the insulating coating 2 was 48 μm in Example 2 and 57 μm in Comparative Example 2. Although Example 2 was 9 μm thinner than Comparative Example 2, the breakdown voltage was 4.99 kV higher. This can be attributed to the fact that the sum of the integer parts (minimum number of turns) on which the breakdown voltage depends was 5 in Example 2, which was larger than the 4 in Comparative Example 2. The results of Example 2 and Comparative Example 2 show that a sufficient breakdown voltage can be obtained even with a thin coating thickness by making the sum of the integer parts 1.0 or less and increasing the sum of the decimal parts.

[0080] The breakdown voltage was 21.5 kV in Example 3 and 22.86 kV in Example 4. In both cases, the sum of the decimal parts was 1.0 or less and the sum of the integer parts was large, and it can be seen that a sufficient breakdown voltage can be obtained. Furthermore, in Example 4, the thickness of the insulating tape was reduced to reduce the total thickness of the insulating coating 2. However, even in this case, it can be seen that a sufficient breakdown voltage can be obtained by making the sum of the decimal parts 1.0 or less and the sum of the integer parts large.

[0081] [Examples 5 to 11] Two to five insulating tapes identical to the first insulating tape 11 of Example 1 were used at random, and the number of turns of each insulating layer in the overlapping winding of each insulating tape was varied. Otherwise, insulated wires 10 of Examples 5 to 11 having the configuration shown in Figures 2 and 3 were produced in the same manner as Example 1. Table 2 shows the number of turns of each insulating layer. In Table 2, the "integer portion" is the sum of the integer portions for each insulating layer, the "decimal portion" is the sum of the decimal portions for each insulating layer, and the "total number" is the sum of the sum of the integer portions and the decimal portions.

[0082] The insulated wire 10 of Example 5 was formed by winding the first insulating tape 11 4.3 times to form the first insulating layer 2a, and then winding the second insulating tape 12 4.2 times on top of that to form the second insulating layer 2b. The sum of the integer parts was 8, the sum of the decimal parts was 0.5, and the total number, which was the sum of these, was 8.5.

[0083] The insulated wire 10 of Example 6 was formed by winding the first insulating tape 11 1.5 times to form the first insulating layer 2a, and then winding the second insulating tape 12 1.4 times on top of that to form the second insulating layer 2b. The sum of the integer parts was 2, the sum of the decimal parts was 0.9, and the total number obtained by adding these together was 2.9.

[0084] The insulated wire 10 of Example 7 was formed by winding the first insulating tape 11 3.3 times to form the first insulating layer 2a, winding the second insulating tape 12 3.2 times on top of that to form the second insulating layer 2b, and winding the third insulating tape 13 3.3 times on top of that to form the third insulating layer 2c, and the sum of the integer parts was 9, the sum of the decimal parts was 0.8, and the total number, which was the sum of these, was 9.8.

[0085] The insulated wire 10 of Example 8 was formed by winding the first insulating tape 11 4.2 times to form the first insulating layer 2a, winding the second insulating tape 12 4.4 times on top of that to form the second insulating layer 2b, winding the third insulating tape 13 3.3 times on top of that to form the third insulating layer 2c, and winding the fourth insulating tape 14 3.4 times on top of that to form the fourth insulating layer 2d, and the sum of the integer parts was 14, the sum of the decimal parts was 1.3, and the total number, which was the sum of these, was 15.3.

[0086] The insulated wire 10 of Example 9 was formed by winding the first insulating tape 11 2.3 times to form the first insulating layer 2a, winding the second insulating tape 12 2.4 times on top of that to form the second insulating layer 2b, winding the third insulating tape 13 1.3 times on top of that to form the third insulating layer 2c, and winding the fourth insulating tape 14 1.4 times on top of that to form the fourth insulating layer 2d, and the sum of the integer parts was 6, the sum of the decimal parts was 1.4, and the total number, which was the sum of these, was 7.4.

[0087] In the insulated wire 10 of Example 10, the first insulating tape 11 was wound 2.3 times to form the first insulating layer 2a, the second insulating tape 12 was wound 2.2 times on top of that to form the second insulating layer 2b, the third insulating tape 13 was wound 2.3 times on top of that to form the third insulating layer 2c, the fourth insulating tape 14 was wound 2.4 times on top of that to form the fourth insulating layer 2d, and the fifth insulating tape 15 was wound 2.2 times on top of that to form the fifth insulating layer 2e, and the sum of the integer parts was 10, the sum of the decimal parts was 1.4, and the total number, which was the sum of these, was 11.4.

[0088] In the insulated wire 10 of Example 11, the first insulating tape 11 was wound 2.3 times to form the first insulating layer 2a, the second insulating tape 12 was wound 1.3 times on top of that to form the second insulating layer 2b, the third insulating tape 13 was wound 1.3 times on top of that to form the third insulating layer 2c, the fourth insulating tape 14 was wound 1.4 times on top of that to form the fourth insulating layer 2d, and the fifth insulating tape 15 was wound 2.3 times on top of that to form the fifth insulating layer 2e, and the sum of the integer parts was 7, the sum of the decimal parts was 1.7, and the total number, which was the sum of these, was 8.7.

[0089]

[0090] From the results in Table 2, it is possible to arbitrarily use two to five insulating tapes and arbitrarily design the number of overlapping turns of each insulating tape to constitute the insulating tape of the present invention. In this way, the effects of the present invention described above can be realized with a high degree of design freedom.

[0091] Example 12 The same insulating tapes as those used in Example 1 were used as the first insulating tape 11 and the second insulating tape 12, but the number of turns of each insulating tape in the overlapping first to third layers was changed as shown in Table 2. Otherwise, an insulated wire of Example 12 was produced in the same manner as in Example 1. In this insulated wire, the integer parts of the first to third layers are the same, and the decimal parts are successively smaller from the first to the third layers, thereby eliminating steps and further improving flatness. The sum of the integer parts is 6, the sum of the decimal parts is 0.6, and the total number obtained by adding them is 6.6.

[0092] Example 13 The first insulating tape 11 was made of polyimide resin and had a thickness of 7.5 μm (total thickness of 9.5 μm), a tape width of 10.5 mm, and a 2 μm adhesive layer. The second insulating tape 12 was made of polyimide resin and had a thickness of 7.5 μm (total thickness of 9.5 μm), a tape width of 10.5 mm, and a 2 μm adhesive layer. The third insulating tape 13 was made of polyimide resin and had a thickness of 7.5 μm (total thickness of 9.5 μm), a tape width of 10.5 mm, and a 2 μm adhesive layer. The number of turns of each insulating tape in the first to third layers of overlapping winding was changed as shown in Table 2. The insulated wire of Example 13 was otherwise fabricated in the same manner as Example 1. This insulated wire has the same integer part for each of the first to third layers to make it easier to manufacture, and then the decimal parts are successively smaller from the first to the third layer to eliminate steps and further improve flatness. The sum of the integer parts is 9, the sum of the decimal parts is 0.9, and the total number is 9.9.

[0093] Example 14: The first insulating tape 11 was made of polyimide resin and had a thickness of 7.5 μm (total thickness: 9.5 μm), a width of 6.0 mm, and a 2 μm adhesive layer. The second insulating tape 12 was made of polyimide resin and had a thickness of 7.5 μm (total thickness: 9.5 μm), a width of 6.5 mm, and a 2 μm adhesive layer. The third insulating tape 13 was made of polyimide resin and had a thickness of 7.5 μm (total thickness: 9.5 μm), a width of 6.5 mm, and a 2 μm adhesive layer. A copper conductor with a diameter of 0.80 mm was used as the conductor 1, and the number of turns of the first to third layers of insulating tape around the conductor was as shown in Table 2. The insulated wire of Example 14 was fabricated in the same manner as Example 1, except for the above. In this insulated wire, the integer parts of the first to third layers are all the same to facilitate manufacturing, and the decimal parts of the first to third layers are each 0.5 or less, with the sum of the decimal parts being 1.3 or less, which is 1.5. The sum of the integer parts is 6, the sum of the decimal parts is 1.3, and the sum of these is 7.3. Although the insulated wire of Example 13 has a sum of the decimal parts of 1.3, it can maintain the same effects as when the sum is 1.0 or less (the total thickness of the insulating layers can be made thinner, the insulated wire can be made smaller in diameter, the breakdown voltage is the same or improved, flexibility is excellent and coil winding is easy, and a space factor is increased to make the coil more compact).

[0094] Example 15: The first insulating tape 11 was made of polyimide resin and had a thickness of 7.5 μm (total thickness: 9.5 μm), a tape width of 4.5 mm, and a 2 μm adhesive layer. The second insulating tape 12 was made of polyimide resin and had a thickness of 7.5 μm (total thickness: 9.5 μm), a tape width of 3.0 mm, and a 2 μm adhesive layer. The third insulating tape 13 was made of polyimide resin and had a thickness of 7.5 μm (total thickness: 9.5 μm), a tape width of 5.0 mm, and a 2 μm adhesive layer. A copper conductor with a diameter of 0.60 mm was used as the conductor 1, and the number of turns of each insulating tape around the conductor in the first to third layers was as shown in Table 2. The insulated wire of Example 15 was fabricated in the same manner as Example 1, except for the above. In this insulated wire, the decimal parts of the first to third layers are each 0.5 or less, and the sum of the decimal parts is 1.3, which is 1.5 or less. The sum of the integer parts is 5, the sum of the decimal parts is 1.3, and the total number obtained by adding them together is 6.3. Although the insulated wire of Example 15 also has a sum of decimal parts of 1.3, it can maintain the same effects as when the sum is 1.0 or less (the total thickness of the insulating layers can be made thinner, the insulated wire can also be made thinner, the dielectric breakdown voltage is the same or improved, flexibility is excellent and coil winding ease is achieved, and a space factor is increased to enable a more compact coil).

[0095] As shown in Examples 1 to 15 above, two to five insulating tapes can be used arbitrarily, and the number of overlapping turns of each insulating tape can be arbitrarily designed to constitute the insulating tape of the present invention. This allows for a high degree of design freedom to achieve the effects of the present invention described above. Regarding the results in Tables 1 and 2, whether the individual insulating layers are two or three layers or four or five layers, the integer portion of the number of turns of each insulating layer may be in the range of 2 to 4, excluding 1, as in Examples 1 to 5, 7, 8, and 10, or the integer portion of some layers may be 1 and the integer portion of the remaining layers may be 2 to 4, as in Examples 9 and 11.

[0096] REFERENCE SIGNS LIST 1 conductor 2 insulating coating 2a first insulating layer 2b second insulating layer 2c third insulating layer 2d fourth insulating layer 2e fifth insulating layer 4 resin tape 5 adhesive layer 6 fusion layer 10 tape-wrapped insulated wire 11 first insulating tape 12 second insulating tape 13 third insulating tape 14 fourth insulating tape 15 fifth insulating tape 20 coil 21 transformer bobbin T longitudinal direction

Claims

1. An insulated electric wire having a conductor and an insulating coating provided around the conductor, the insulating coating being composed of a plurality of insulating layers formed by overlapping and winding two to five insulating tapes, wherein when the insulating coating has two or three insulating layers each formed by overlapping and winding the insulating tapes, the total number of turns of the individual insulating layers is equal to or less than the sum of the integer parts of the number of turns of the individual insulating layers plus one, or when the insulating coating has four or five insulating layers each formed by overlapping and winding the insulating tapes, the total number of turns of the individual insulating layers is equal to or less than the sum of the integer parts of the number of turns of the individual insulating layers plus two, and in any case where the individual insulating layers have two to five layers, the integer part of the number of turns is in the range of 1 to 4.

2. The tape-wrapped insulated electric wire according to claim 1, wherein, in the case where the insulating coating is formed by wrapping the insulating tapes in layers, each of the insulating layers is two or three layers, the number of turns of the first insulating tape is expressed as s.α turns, the number of turns of the second insulating tape is expressed as t.β turns, and the number of turns of the third insulating tape is expressed as u.γ turns, the sum of the integer parts is s+t when the insulating layer is two layers, and s+t+u when the insulating layer is three layers, the sum of the decimal parts is α+β when the insulating layer is two layers, and α+β+γ when the insulating layer is three layers, and the sum of the decimal parts is 1.0 or less.

3. The tape-wrapped insulated electric wire according to claim 2, wherein, when there are two insulating tapes, the sum of the integer parts is 2 to 8, the sum of the decimal parts is 1.0 or less, and the total number is 2.0 to 9.0, and when there are three insulating tapes, the sum of the integer parts is 3 to 12, the sum of the decimal parts is 1.0 or less, and the total number is 3.0 to 13.

0.

4. The tape-wrapped insulated electric wire according to claim 1, wherein, in the case where the insulating coating is formed by wrapping the insulating tapes in layers, and the number of turns of the first insulating tape is expressed as s.α turns, the number of turns of the second insulating tape is expressed as t.β turns, and the number of turns of the third insulating tape is expressed as u.γ turns, the sum of the integer parts is s+t+u, the sum of the decimal parts is α+β+γ, and the sum of the decimal parts is 1.5 or less.

5. The tape-wrapped insulated electric wire according to claim 1, wherein, in the case where the insulating coating is formed by wrapping the insulating tapes in layers, each of the insulating layers is four or five layers, the number of turns of the first insulating tape is expressed as s.α turns, the number of turns of the second insulating tape is expressed as t.β turns, the number of turns of the third insulating tape is expressed as u.γ turns, the number of turns of the fourth insulating tape is expressed as v.δ turns, and the number of turns of the fifth insulating tape is expressed as w.ε turns, the sum of the integer parts is s+t+u+v when the insulating layer is four layers, and s+t+u+v+w when the insulating layer is five layers, the sum of the decimal parts is α+β+γ+δ when the insulating layer is four layers, and α+β+γ+δ+ε when the insulating layer is five layers, and the sum of the decimal parts is 2.0 or less.

6. The tape-wrapped insulated electric wire according to claim 5, wherein, when the number of the insulating tapes is four, the sum of the integer parts is 4 to 16, the sum of the decimal parts is 2.0 or less, and the total number is 4.0 to 18.0, and when the number of the insulating tapes is five, the sum of the integer parts is 5 to 20, the sum of the decimal parts is 2.0 or less, and the total number is 5.0 to 22.

0.

7. The tape-wrapped insulated electric wire according to any one of claims 1 to 6, wherein one or more of the two to five insulating tapes have an adhesive layer provided on one side.

8. A tape-wrapped insulated electric wire according to any one of claims 1 to 6, wherein the last of the plurality of insulating tapes to be wound has a fusion layer provided on its outward surface.

9. A coil obtained by winding the tape-wrapped insulated electric wire according to any one of claims 1 to 6.

10. A coil obtained by winding the tape-wrapped insulated electric wire according to claim 7.

11. A coil obtained by winding the tape-wrapped insulated electric wire according to claim 8.

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