Wound iron core

Abstract

A wound core comprising a plurality of flat portions and a plurality of corner portions, the wound core being configured by laminating, in the thickness direction, a plurality of bent processed bodies obtained by molding a grain-oriented electromagnetic steel sheet, the wound core having a plurality of flat portions and a plurality of corner portions; the bent processed body has a plurality of flat regions and a plurality of bent regions adjacent to the flat regions; the radius of curvature of each of the curved regions is 5.0 mm or less; the bent body has one or more joining parts in which end surfaces in the longitudinal direction of the grain-oriented electrical steel sheet face each other; in the wound core, the average distance of the first group of joining parts and the average distance of the second group of joining parts, which are set under predetermined conditions, are 25 mm, whereby interference between plastic strain and elastic strain in a bending region and shear strain in the joining parts can be avoided, and iron loss can be suppressed.

Description

Technical Field

[0001] The present disclosure relates to wound cores.

[0002] This application claims priority based on Japanese Patent Application No. 2022-100292 filed on June 22, 2022, the contents of which are incorporated herein by reference. Background Art

[0003] Wound cores are widely used as magnetic cores for transformers, reactors, noise filters, etc. In the past, reducing the iron loss generated in the core has been one of the important issues from the viewpoint of improving efficiency, and research on reducing the iron loss has been conducted from various viewpoints.

[0004] For example, Patent Document 1 discloses a wound iron core in which a plurality of pieces of iron core material having a cut portion at at least one location in each roll are wound and a rectangular window portion is provided at the center, wherein the occupancy rate of the iron core material in the corners is lower than the occupancy rate of the iron core material in the sides other than the corners.

[0005] Prior art literature

[0006] Patent Literature

[0007] Patent Document 1: Japanese Patent Application Publication No. 2015-141930 Summary of the invention

[0008] Problems to be solved by the invention

[0009] However, a wound core having a suppressed iron loss as compared with the case of Patent Document 1 is required.

[0010] The present disclosure is an invention made in view of the above-mentioned problems, and provides a wound core with suppressed iron loss.

[0011] Means used to solve problems

[0012] In order to solve the above-mentioned problems, the present invention proposes the following technical solutions.

[0013] <1> The wound core according to claim 1 of the present invention is a wound core formed by laminating a plurality of bent bodies formed by forming a grain-oriented electromagnetic steel sheet in a sheet thickness direction.

[0014] The wound core has a plurality of flat portions and a plurality of corner portions.

[0015] The bending body has a plurality of flat regions and a plurality of curved regions adjacent to the flat regions.

[0016] The radius of curvature of each of the above-mentioned curved areas is less than 5.0 mm,

[0017] The bent body has one or more joints where the end faces in the longitudinal direction of the grain-oriented electromagnetic steel sheet face each other.

[0018] When the bending body disposed at the innermost side is set as the first bending body, and the flat region having the joint portion of the first bending body is set as the reference flat region, the joint portions of the plurality of bending bodies are located at the flat portion having the reference flat region.

[0019] In the side view of the wound core above,

[0020] When one of the curved regions adjacent to the reference flat region is defined as a first curved region,

[0021] The other curved region adjacent to the reference flat region is defined as a second curved region.

[0022] A virtual line passing through the end point of the first curved region on the reference flat region side and parallel to the plate thickness direction of the reference flat region is defined as a first virtual line.

[0023] A virtual line passing through the end point of the second curved region on the reference flat region side and parallel to the plate thickness direction of the reference flat region is defined as a second virtual line.

[0024] In each of the above-mentioned joints of the above-mentioned flat portion having the above-mentioned reference flat area, the above-mentioned joint located between the above-mentioned first imaginary line and the above-mentioned second imaginary line and having the shortest length of the above-mentioned end face of the above-mentioned joint from the above-mentioned first imaginary line to the above-mentioned first imaginary line side along the long side direction of the above-mentioned reference flat area is set as the first shortest joint,

[0025] In each of the above-mentioned joints of the above-mentioned bending work body located adjacent to the above-mentioned bending work body having the above-mentioned first shortest joint portion in the above-mentioned plate thickness direction, the above-mentioned joint portion located between the above-mentioned first imaginary line and the above-mentioned second imaginary line and having a shorter length from the above-mentioned first imaginary line to the above-mentioned end face of the above-mentioned joint portion on the above-mentioned first imaginary line side along the long side direction of the above-mentioned reference flat area is set as the first end joint portion,

[0026] In each of the above-mentioned joints of the above-mentioned flat portion having the above-mentioned reference flat area, the above-mentioned joint that is located between the above-mentioned first imaginary line and the above-mentioned second imaginary line and has the shortest length from the above-mentioned second imaginary line to the above-mentioned end face of the above-mentioned joint on the side of the above-mentioned second imaginary line along the long side direction of the above-mentioned reference flat area is set as the second shortest joint,

[0027] In each of the above-mentioned joints of the above-mentioned bending work body located adjacent to the above-mentioned bending work body having the above-mentioned second shortest joint portion in the above-mentioned plate thickness direction, the above-mentioned joint portion located between the above-mentioned first imaginary line and the above-mentioned second imaginary line and having a shorter length from the above-mentioned second imaginary line to the above-mentioned end face of the above-mentioned joint portion on the above-mentioned second imaginary line side along the long side direction of the above-mentioned reference flat area is set as the second end joint portion,

[0028] A virtual line A passes through the end surface on the first virtual line side of the first shortest joint and is parallel to the plate thickness direction of the reference flat region.

[0029] A virtual line passing through the end surface on the first virtual line side of the first end joint portion and parallel to the plate thickness direction of the reference flat region is defined as a virtual line B.

[0030] A virtual line passing through the end surface on the second virtual line side of the second shortest joint and parallel to the plate thickness direction of the reference flat region is defined as a virtual line C.

[0031] A virtual line passing through the end surface on the second virtual line side of the second end bonding portion and parallel to the plate thickness direction of the reference flat region is defined as a virtual line D.

[0032] Among the above-mentioned joints of the above-mentioned flat portion having the above-mentioned reference flat area, the above-mentioned joints located between the above-mentioned imaginary line A and the above-mentioned imaginary line B are set as the first group of joints,

[0033] Among the above-mentioned joints of the above-mentioned flat portion having the above-mentioned reference flat area, the above-mentioned joints located between the above-mentioned imaginary line C and the above-mentioned imaginary line D are set as the second group of joints,

[0034] The average value of the length from the first imaginary line to the end surface on the first imaginary line side of each of the first group of joints along the long side direction of the reference flat region is set to <L i >、

[0035] The average value of the length from the second imaginary line to the end surface on the second imaginary line side of each of the second group of joints along the long side direction of the reference flat region is set to <L O >When

[0036] Satisfy the following equation (1) and the following equation (2):

[0037] 25mm≤ <L i >…(1)

[0038] 25mm≤ <L o >…(2).

[0039] <2> Regarding the technical solution 2 of the present invention, it may also be that, in the wound core of the technical solution 1,

[0040] The number of the first group of joints is equal to the number of the second group of joints.

[0041] Among the quotient and remainder obtained by dividing the number of the above-mentioned joints in the above-mentioned flat portion located between the above-mentioned first imaginary line and the above-mentioned second imaginary line and having the above-mentioned reference flat area by the number of the above-mentioned first group of joints, the above-mentioned quotient, that is, k, satisfies the following formula (3):

[0042] 2≤k≤8…(3).

[0043] <3> Regarding the technical solution 3 of the present invention, it can also be that in the wound core of the technical solution 1 or 2,

[0044] The two opposing flat areas of each of the bent bodies have the above-mentioned joining portion.

[0045] The first bent body includes the reference flat region and a second reference flat region facing the reference flat region.

[0046] The joining portion of each of the plurality of bent bodies is located at the flat portion having the reference flat region and the flat portion having the second reference flat region.

[0047] In the side view of the wound core above,

[0048] When one of the curved regions adjacent to the second reference flat region is set as a third curved region,

[0049] The other curved region adjacent to the second reference flat region is defined as a fourth curved region.

[0050] A virtual line passing through the end point of the third curved region on the second reference flat region side and parallel to the plate thickness direction of the second reference flat region is defined as a third virtual line.

[0051] A virtual line passing through the end point of the fourth curved region on the second reference flat region side and parallel to the plate thickness direction of the second reference flat region is referred to as a fourth virtual line.

[0052] In each of the above-mentioned joining portions of the above-mentioned flat portion having the above-mentioned second reference flat area, the above-mentioned joining portion located between the above-mentioned third imaginary line and the above-mentioned fourth imaginary line and having the shortest length of the above-mentioned end face of the above-mentioned joining portion from the above-mentioned third imaginary line to the above-mentioned third imaginary line side along the long side direction of the above-mentioned second reference flat area is set as the third shortest joining portion,

[0053] In each of the above-mentioned joints of the above-mentioned bending work body located adjacent to the above-mentioned bending work body having the above-mentioned third shortest joint portion in the above-mentioned plate thickness direction, the above-mentioned joint portion located between the above-mentioned third imaginary line and the above-mentioned fourth imaginary line and having a shorter length from the above-mentioned third imaginary line to the above-mentioned end face of the above-mentioned joint portion on the above-mentioned third imaginary line side along the long side direction of the above-mentioned second reference flat area is set as the third end joint portion,

[0054] In each of the above-mentioned joints of the above-mentioned flat portion having the above-mentioned second reference flat area, the above-mentioned joint that is located between the above-mentioned third imaginary line and the above-mentioned fourth imaginary line and has the shortest length of the above-mentioned end face of the above-mentioned joint from the above-mentioned fourth imaginary line to the above-mentioned fourth imaginary line side along the long side direction of the above-mentioned second reference flat area is set as the fourth shortest joint,

[0055] In each of the above-mentioned joints of the above-mentioned bending work body located adjacent to the above-mentioned bending work body having the above-mentioned fourth shortest joint portion in the above-mentioned plate thickness direction, the above-mentioned joint portion located between the above-mentioned third imaginary line and the above-mentioned fourth imaginary line and having a shorter length from the above-mentioned fourth imaginary line to the above-mentioned end face of the above-mentioned joint portion on the above-mentioned fourth imaginary line side along the long side direction of the above-mentioned second reference flat area is set as the fourth end joint portion,

[0056] A virtual line passing through the end surface on the third virtual line side of the third shortest joint and parallel to the plate thickness direction of the second reference flat region is defined as a virtual line E.

[0057] A virtual line passing through the end surface on the third virtual line side of the third end joint portion and parallel to the plate thickness direction of the second reference flat region is defined as a virtual line F.

[0058] A virtual line passing through the end surface on the fourth virtual line side of the fourth shortest joint and parallel to the plate thickness direction of the second reference flat region is defined as a virtual line G.

[0059] A virtual line passing through the end surface on the fourth virtual line side of the fourth end joint portion and parallel to the plate thickness direction of the second reference flat region is defined as a virtual line H.

[0060] Among the above-mentioned joints of the above-mentioned flat portion having the above-mentioned second reference flat area, the above-mentioned joints located between the above-mentioned imaginary line E and the above-mentioned imaginary line F are set as the third group of joints,

[0061] Among the above-mentioned joints of the above-mentioned flat portion having the above-mentioned second reference flat area, the above-mentioned joints located between the above-mentioned imaginary line G and the above-mentioned imaginary line H are set as the fourth group of joints,

[0062] The average value of the length from the third imaginary line to the end surface on the third imaginary line side of each of the third group of joints along the long side direction of the second reference flat region is set to <L 2i >、

[0063] The average value of the length from the fourth imaginary line to the end surface on the fourth imaginary line side of each of the fourth group of joints along the long side direction of the second reference flat region is set to <L 2O >When

[0064] Satisfies the following equation (4) and the following equation (5):

[0065] 25mm≤ <L 2i >…(4)

[0066] 25mm≤ <L 2o >…(5).

[0067] <4> Regarding the technical solution 4 of the present invention, it may also be that, in the wound core of the technical solution 3,

[0068] The number of the third group of joints is equal to the number of the fourth group of joints.

[0069] In the second quotient and the second remainder obtained by dividing the number of the above-mentioned joints in the above-mentioned flat portion located between the above-mentioned third imaginary line and the above-mentioned fourth imaginary line and having the above-mentioned second reference flat area by the number of the above-mentioned third group of joints, the above-mentioned second quotient, i.e., k2, satisfies the following formula (6):

[0070] 2≤k2≤8…(6).

[0071] <5> Regarding a fifth aspect of the present invention, in the wound core of any one of the first to fourth aspects,

[0072] The bending angle of the above-mentioned bending area is 30° to 60°.

[0073] Effects of the Invention

[0074] According to the above-described aspects of the present disclosure, it is possible to provide a wound core with suppressed iron loss. BRIEF DESCRIPTION OF THE DRAWINGS

[0075] Figure 1 It is a perspective view showing a wound core according to the first technical solution.

[0076] Figure 2 yes Figure 1 Side view of the wound core.

[0077] Figure 3 It is a side view showing a wound core according to the second technical solution.

[0078] Figure 4 It is a side view showing a wound core related to the third technical solution.

[0079] Figure 5 It is a side view showing a wound core related to the fourth technical solution.

[0080] Figure 6 Yes Figure 1 An enlarged side view of the wound core near the corner.

[0081] Figure 7 This is an enlarged side view of an example of a curved region.

[0082] Figure 8 yes Figure 1 A side view of a bent body of a wound core.

[0083] Fig. 9 It is a side view showing the wound core of the fifth technical solution.

[0084] Fig.10 It is a side view of the wound core of the sixth technical solution.

[0085] Fig.11 It is a side view of the wound core of the seventh technical solution.

[0086] Fig.12 It is an explanatory diagram showing a first example of a wound iron core manufacturing apparatus used in a wound iron core manufacturing method.

[0087] Fig.13 It is a schematic diagram showing the dimensions of the wound core produced at the time of characteristic evaluation. DETAILED DESCRIPTION

[0088] (Wound Core)

[0089] The wound core of the present disclosure is described below. In addition, in the numerical ranges described below, the lower limit and the upper limit are included in the range. The values ​​expressed as "exceeding" or "less than" are not included in the numerical range. In addition, unless otherwise specified, "%" with respect to the chemical composition means "mass %".

[0090] In addition, the terms such as "parallel", "perpendicular", "same", "right angle", etc., used in this specification to determine the shape, geometric conditions and their degree, length, angle values, etc., are not limited to the strict meaning, but are interpreted within the range of the degree that the same function can be expected. In addition, in this disclosure, approximately 90° means that an error of ±3° is allowed, which means a range of 87° to 93°.

[0091] The wound core disclosed in the present invention is a wound core formed by stacking a plurality of bent bodies formed from a directional electromagnetic steel sheet in the plate thickness direction. The directional electromagnetic steel sheet used for the wound core is preferably a coated directional electromagnetic steel sheet having a coating formed on at least one side of the directional electromagnetic steel sheet. In addition, in the case of a coated directional electromagnetic steel sheet, the wound core disclosed in the present invention is preferably a wound core formed by stacking a plurality of bent bodies formed from a directional electromagnetic steel sheet with the coating of the directional electromagnetic steel sheet on the outside in the plate thickness direction.

[0092] The bent body of the wound core disclosed in the present invention has a flat region and a bent region adjacent to the flat region. Furthermore, the bent body of the wound core disclosed in the present invention has one or more joints facing the end faces of the directional electromagnetic steel sheet in the long side direction. In the following description, the case where the directional electromagnetic steel sheet is a directional electromagnetic steel sheet with a coating is described, but the present invention is not limited to the following structure. The following describes the various structures of the wound core disclosed in the present invention in detail.

[0093] "Direct-oriented electrical steel sheet with coating"

[0094] The grain-oriented electrical steel sheet with coating in the present disclosure includes at least a grain-oriented electrical steel sheet (sometimes referred to as “base steel sheet” in the present disclosure) and a coating formed on at least one surface of the base steel sheet.

[0095] The grain-oriented electrical steel sheet with coating has at least a primary coating as the coating, and may further have other layers as necessary. Examples of other layers include a secondary coating provided on the primary coating.

[0096] Hereinafter, the structure of the grain-oriented electrical steel sheet with a coating will be described.

[0097] <Oriented Magnetic Steel Sheet>

[0098] In the grain-oriented electromagnetic steel sheet with coating constituting the wound core 10 according to the present disclosure, the base steel sheet has a grain orientation highly concentrated in {110} <001> The base steel plate has excellent magnetic properties in the rolling direction.

[0099] The base steel plate used in the wound core disclosed in the present invention is not particularly limited. Among the base steel plates, known directional electromagnetic steel plates can be used selectively as appropriate. As a directional electromagnetic steel plate, for example, a directional electromagnetic steel strip described in JISC 2553:2019 can be used. An example of a base steel plate is described below, but the base steel plate is not limited to the following example.

[0100] The chemical composition of the base steel plate is not particularly limited, and for example, it preferably contains, by mass%, Si: 0.8% to 7%, C: higher than 0% and less than 0.085%, acid-soluble Al: 0% to 0.065%, N: 0% to 0.012%, Mn: 0% to 1%, Cr: 0% to 0.3%, Cu: 0% to 0.4%, P: 0% to 0.5%, Sn: 0% to 0.3%, Sb: 0% to 0.3%, Ni: 0% to 1%, S: 0% to 0.015%, Se: 0% to 0.015%, and the remainder is composed of Fe and impurity elements.

[0101] The chemical composition of the base steel plate is controlled so that the crystal orientation is concentrated on {110} <001> The chemical composition is optimized due to the orientation of the Goss group structure.

[0102] Among the elements in the base steel plate, Si and C are basic elements (essential elements) except Fe. When the Si content of the base steel plate is 2.0% or more by mass%, the eddy current loss of the wound core is suppressed, which is preferred. The Si content of the base steel plate is more preferably 3.0% or more. In addition, when the Si content of the base steel plate is 5.0% or less by mass%, it is preferred because the steel plate is less likely to break during the hot rolling process and cold rolling. The Si content of the base steel plate is more preferably 4.5% or less.

[0103] As arbitrary elements, the base steel plate may contain acid-soluble Al, N, Mn, Cr, Cu, P, Sn, Sb, Ni, S and Se. These arbitrary elements may be contained according to their purpose, so the lower limit is 0%. In addition, even if these arbitrary elements are contained as impurity elements, the effects of the present disclosure are not impaired.

[0104] Grain-oriented electrical steel sheets generally undergo purification annealing during secondary recrystallization. During purification annealing, inhibitor forming elements are discharged out of the system. In particular, the concentrations of N and S decrease significantly, becoming less than 50 ppm. Under normal purification annealing conditions, as long as purification annealing is performed sufficiently at less than 9 ppm, and further less than 6 ppm, it reaches a level that cannot be detected by general analysis (less than 1 ppm).

[0105] In the base steel plate, the remainder of the basic elements and the optional elements is composed of Fe and impurity elements. Here, "impurity elements" refer to elements that are unintentionally mixed from raw material ores, scrap steel, or the manufacturing environment when the base steel plate is manufactured industrially.

[0106] The chemical composition of the base steel plate can be measured by a general analysis method for steel. For example, the chemical composition of the base steel plate can be measured using ICP-AES (Inductively Coupled Plasma-Atomic Emission Spectrometry). Specifically, for example, a 35 mm square test piece can be obtained from the center position in the width direction of the base steel plate after the coating is removed, and the chemical composition can be determined by measuring with ICPS-8100 (measuring device) manufactured by Shimadzu Corporation under conditions based on a pre-made calibration line (calibration line). In addition, C and S can be measured using the combustion-infrared absorption method, and N can be measured using the inert gas melting-thermal conductivity method.

[0107] The chemical composition of the base steel sheet is obtained by analyzing the components of a base steel sheet obtained by removing a glass film and a film containing phosphorus described later from a grain-oriented electrical steel sheet by a method described later.

[0108] <One-time lamination>

[0109] The primary coating is a coating formed directly on the surface of the grain-oriented electromagnetic steel sheet as the base steel sheet without any other layer or film. As the primary coating, for example, a glass coating can be cited. As the glass coating, for example, a coating having a crystalline structure composed of forsterite (Mg2SiO4), spinel (MgAl2O4) and cordierite (Mg2Al4Si5O 16 ) In addition, for example, instead of forming a glass coating on the surface of the grain-oriented electrical steel sheet, a coating containing phosphorus described later may be formed as a primary coating.

[0110] When the primary coating is a glass coating, the method for forming the glass coating is not particularly limited and can be appropriately selected from known methods. For example, the following method can be cited: a method in which a cold-rolled steel sheet is coated with an annealing separator and then subjected to finishing annealing, wherein the annealing separator contains one or more selected from magnesium oxide (MgO) and aluminum oxide (Al2O3).

[0111] Annealing separators also have the effect of inhibiting the sticking of steel sheets during finishing annealing. For example, when finishing annealing is performed after applying an annealing separator containing magnesium oxide, silicon dioxide contained in the base steel sheet reacts with the annealing separator to form a glass film containing forsterite (Mg2SiO4) on the surface of the base steel sheet.

[0112] The thickness of the primary coating is not particularly limited, but is preferably, for example, 0.5 μm or more and 3 μm or less from the viewpoint of being formed on the entire surface of the base steel plate and suppressing separation.

[0113] <Other coatings>

[0114] The directional electromagnetic steel sheet with coating may also have a coating other than the primary coating. For example, as another film (secondary coating) on ​​the primary coating, it is preferred to have a coating containing phosphorus. By having a coating containing phosphorus, the insulation can be improved. The coating containing phosphorus is a coating formed on the outermost surface of the directional electromagnetic steel sheet. In the case where the directional electromagnetic steel sheet has a glass coating or an oxide coating as a primary coating, it is formed on the primary coating. By forming a coating containing phosphorus on the glass coating formed on the surface of the base steel sheet as a primary coating, a higher adhesion can be ensured.

[0115] The phosphorus-containing coating can be appropriately selected from conventionally known coatings. As the phosphorus-containing coating, a phosphate coating is preferred, and in particular, a coating containing one or more of aluminum phosphate and magnesium phosphate as a main component and one or more of chromium and silicon oxide as a secondary component is preferred. The phosphate coating ensures the insulation of the steel sheet, applies tension to the steel sheet, and is excellent in reducing iron loss.

[0116] When the other film is a coating film containing phosphorus, the thickness of the coating film containing phosphorus is not particularly limited, but is preferably 0.5 μm or more and 3 μm or less in order to ensure insulation properties.

[0117] <Plate thickness>

[0118] The thickness of the coated grain-oriented electrical steel sheet is not particularly limited and may be appropriately selected depending on the intended use, but is generally within a range of 0.10 mm to 0.50 mm, preferably 0.13 mm to 0.35 mm, and more preferably 0.15 mm to 0.30 mm.

[0119] (Structure of wound core)

[0120] by Figure 1 , Figure 2 The structure of the wound core disclosed in the present invention is described by taking the wound core 10 as an example. Figure 1 is a three-dimensional diagram of the wound core 10, Figure 2 yes Figure 1 10 is a side view of the wound core 10.

[0121] In the present disclosure, the side view refers to the width direction ( Figure 1 Observe in the Y-axis direction).

[0122] A side view is a view showing the shape visually observed from the side ( Figure 1The plate thickness direction is the plate thickness direction of the oriented electromagnetic steel sheet. In the wound core 10 of the present disclosure, when the wound core is formed into a rectangular shape, the plate thickness direction is perpendicular to the peripheral surface of the wound core.

[0123] The direction perpendicular to the peripheral surface is the direction perpendicular to the peripheral surface when the peripheral surface is viewed from the side. When the peripheral surface is curved in the side view, the direction perpendicular to the peripheral surface (plate thickness direction) is the direction perpendicular to the tangent of the curve formed by the peripheral surface.

[0124] The wound core 10 is formed by stacking a plurality of bent bodies 1 in the plate thickness direction. Figure 1 , Figure 2 As shown, the wound core 10 has a roughly rectangular stacked structure formed by a plurality of bent bodies 1. The wound core 10 has a stacked body 2 formed by stacking a plurality of bent bodies 1. The wound core 10 can also be used directly as a wound core. The wound core 10 can also be fixed using a fastening tool such as a known binding tape as needed. In addition, the bent body 1 is formed of a directional electromagnetic steel sheet as a base steel sheet. The number of bent bodies 1 (the number of stacked sheets) is not particularly limited, for example, the number of bent bodies 1 is preferably 200 or more.

[0125] like Figure 1 and Figure 2 As shown, the wound core 10 is preferably formed into a rectangular shape by alternating four flat portions 4 and four corner portions 3 along the circumferential direction. The wound core 10 has a plurality of flat portions 4 and a plurality of corner portions 3. The angle formed by two flat portions 4 adjacent to each corner portion 3 is preferably approximately 90°. Here, the circumferential direction refers to the direction of the winding core 10 around the axis.

[0126] In the corner portion 3 of the wound core 10, the bent body 1 has two bending regions 5 ( Figure 2 ). The bending region 5 is a region having a curved shape in the side view of the bending workpiece 1. A detailed description of the bending region will be described later. For the two bending regions 5, the total bending angle in the side view of the bending workpiece 1 is preferably approximately 90°.

[0127] In each corner 3 of the wound core 10, the bent body 1 may have one or more bent regions 5 as long as the directional electromagnetic steel sheet is bent at approximately 90 degrees. As in the wound core 10A according to the second technical solution of the present disclosure, in each corner 3 of the wound core 10, the bent body 1 may have three bent regions 5 ( Figure 3). In addition, the corners 3 of the wound core 10 may be respectively as in the wound core 10B of the third technical solution, in which the bent body 1 has a bending area 5 ( Figure 4 ). In addition, the corners 3 of the wound core 10 may be respectively as in the wound core 10G of the fourth technical solution, in which the bent body 1 has a bending area 5 ( Figure 5 ) In addition, like the wound core 10G, the lengths of the opposing flat portions 4 may be different.

[0128] (Flat area)

[0129] like Figure 2 As shown, the bent body 1 has a flat region 8 adjacent to the bent region 5. As the flat region 8 adjacent to the bent region 5, there are two flat regions 8 shown in the following (1A) and (1B).

[0130] (1A) In one corner portion 3 , a flat region 8 (a flat region at the corner) located between the curved regions 5 (between two curved regions 5 adjacent to each other in the circumferential direction) and adjacent to each curved region 5 .

[0131] (1B) The flat regions 8 adjacent to the curved regions 5 are the flat portions 4 .

[0132] (corner)

[0133] Figure 6 Yes Figure 1 FIG. 1 is an enlarged side view of the vicinity of the corner 3 of the wound core 10 .

[0134] like Figure 6 As shown, in a corner portion 3, when the bending processing body 1a has two bending areas, namely the bending area 5a and the bending area 5b, the bending area 5a (curved portion) is continuous from the flat area 8a of the flat portion 4 which is a flat area belonging to the bending processing body 1a, and further, at its front end, the flat area 7a (straight portion), the bending area 5b (curved portion) and the flat area 8b (straight portion) belonging to the flat portion 4b are continuous.

[0135] In the wound core 10, Figure 6The area from line segment A-A' to line segment B-B' in is the corner 3. Point A is the end point on the side of the flat area 8a in the bending area 5a of the innermost bending workpiece (first bending workpiece) 1a arranged on the wound core 10. Point A' is the intersection of a straight line in the vertical direction (plate thickness direction) passing through point A and perpendicular to the plate surface of the bending workpiece 1a and the outermost surface of the wound core 10 (the outer peripheral surface of the outermost bending workpiece 1 arranged on the wound core 10). Similarly, point B is the end point on the side of the flat area 8b in the bending area 5b of the innermost bending workpiece 1a arranged on the wound core 10. Point B' is the intersection of a straight line in the vertical direction (plate thickness direction) passing through point B and perpendicular to the plate surface of the bending workpiece 1a and the outermost surface of the wound core 10. In Figure 6 In the example, the angle formed by the two adjacent flat portions 4a and 4b across the corner portion 3 (the angle formed by the intersection of the extended lines of the flat portions 4a and 4b) is θ. Figure 6 In the example of FIG. 5 , the angle of the bending area 5a and the bending area 5b will be described later, but Figure 6 , the total value of the bending angles φ1+φ2 of the bending areas 5a and 5b is approximately 90°. The bending angle φ1 of the bending area 5a is, for example, 30° to 60°. Similarly, the bending angle φ2 of the bending area 5b is, for example, 30° to 60°. Since the bending angles φ1 and φ2 of the bending areas 5a and 5b are less deformed than 90°, the elastic stress caused by the bending, i.e., the bending recovery, becomes smaller, and the angle variation becomes smaller, so the bending angles φ1 and φ2 of the bending areas 5a and 5b are particularly preferably 30° to 60°.

[0136] (Bending area)

[0137] Reference Figure 7 The bending region 5 will be described in detail. Figure 7 : is an enlarged side view of an example of the bending region 5 of the bending workpiece 1. The bending angle φ of the bending region 5 refers to the angle difference generated between the flat region on the rear side of the bending direction and the flat region on the front side of the bending direction in the bending region 5 of the bending workpiece 1. Specifically, the bending angle φ of the bending region 5 is expressed as the angle φ of the supplementary angle of the angle formed by two imaginary lines Lb extension line 1 (Lb-elongation1) and Lb extension line 2 (Lb-elongation2) obtained by extending the straight line portions adjacent to each point from the points (points F and G) on both sides of the curved portion included in the line Lb representing the outer surface of the bending workpiece 1 in the bending region 5.

[0138] Preferably, the bending angle of each bent region 5 is approximately 90° or less, and the total value of the bending angles of all the bent regions 5 of the bent body 1 present at one corner 3 of the wound core 10 is approximately 90°.

[0139] In the side view of the bending workpiece 1, when points D and E on the line La representing the inner surface of the bending workpiece 1, and points F and G on the line Lb representing the outer surface of the bending workpiece 1 are defined as follows, the bending area 5 represents the area surrounded by (2A) a line divided by points D and E on the line La representing the inner surface of the bending workpiece 1, (2B) a line divided by points F and G on the line Lb representing the outer surface of the bending workpiece 1, (2C) a straight line connecting the above-mentioned point D and the above-mentioned point G, and (2D) a straight line connecting the above-mentioned point E and the above-mentioned point F.

[0140] Here, point D, point E, point F, and point G are defined as follows.

[0141] In the side view, the point where the straight line AB obtained by connecting the center point A and the intersection point B of the above-mentioned two imaginary lines Lb extension line 1 (Lb-elongation1) and Lb extension line 2 (Lb-elongation2) and the line La representing the inner surface of the bending processing body 1 intersect is set as the origin C, the above-mentioned center point A is the center point of the curvature radius in the curved portion contained in the line La representing the inner surface of the bending processing body 1, and the intersection point B of the above-mentioned two imaginary lines Lb extension line 1 (Lb-elongation1) and Lb extension line 2 (Lb-elongation2) is the intersection point obtained by extending the straight line portions adjacent to both sides of the curved portion contained in the line Lb representing the outer surface of the bending processing body 1.

[0142] A point D is a point that is separated from the origin C in one direction by a distance m represented by, for example, the following formula (A) along a line La indicating the inner surface of the bent body 1 .

[0143] A point E is defined as a point that is separated from the origin C by the distance m in another direction along a line La indicating the inner surface of the bent body.

[0144] The intersection point G is the straight line portion of the straight line portion opposite to the point D included in the line Lb representing the outer surface of the bent body and an imaginary line drawn perpendicularly to the straight line portion opposite to the point D and passing through the point D.

[0145] The intersection of the straight line portion opposed to the point E among the straight line portions included in the line Lb representing the outer surface of the bent body and the imaginary line drawn perpendicularly to the straight line portion opposed to the point E and passing through the point E is defined as point F. In addition, the intersection point A is the intersection point obtained by extending the line segment EF and the line segment DG inwardly on the opposite side to the point B.

[0146] m=r×(π×φ / 180)…(A)

[0147] In formula (A), m represents the distance from the origin C, and r represents the distance from the center point A to the origin C (curvature radius). In addition, the curvature radius r of the bending processing body 1 arranged on the inner surface side of the wound core 10 is preferably, for example, not less than 1 mm and not more than 5 mm. Here, the curvature radius of the bending processing body 1 is the curvature radius of the bending area 5. The curvature radius of the bending processing body 1 is not more than 5.0 mm. By making the curvature radius of the bending processing body 1 not more than 5.0 mm, the iron loss is improved. The curvature radius of the bending processing body 1 is preferably not less than 0.1 mm. The curvature radius of the bending processing body 1 is more preferably not less than 0.3 mm. The particularly preferred curvature radius of the bending processing body is not less than 1.0 mm. The more preferred curvature radius of the bending processing body 1 is not more than 2.9 mm.

[0148] Figure 8 yes Figure 1 A side view of the bent body 1 of the wound core 10. Figure 8 As shown, the bending body 1 is formed by bending a grain-oriented electromagnetic steel sheet, and has a flat region 8 and a curved region 5 adjacent to the flat region 8. The bending body 1 has a plurality of flat regions 8 and a plurality of curved regions 5. In addition, the bending body 1 has four bending body corners 30 and four bending body flat portions 40, whereby one sheet of grain-oriented electromagnetic steel sheet forms a substantially rectangular ring in a side view. More specifically, a gap (joint portion) 6 obtained by facing both end faces in the long side direction of the grain-oriented electromagnetic steel sheet is provided in one bending body flat portion 40, and the other three bending body flat portions 40 do not include the gap 6. In the joint portion 6 of the bending body 1 constructed as described above, there are one or more joint portions obtained by facing the end faces 13 and 14 in the long side direction of the bending body 1. The size of the gap in the joint portion 6 is, for example, 0.1 mm to 5.0 mm, preferably 1.0 mm to 2.0 mm.

[0149] The wound core 10 preferably has a stacked structure that is substantially rectangular in side view as a whole. The wound core 10 may also have a structure in which two bent flat portions 40 include gaps (joint portions) 6, and the other two bent flat portions 4 do not include gaps 6. In this case, the bent body is formed of two directional electromagnetic steel sheets.

[0150] It is desirable that no gap is generated between two adjacent layers in the plate thickness direction during the manufacture of the wound core. Therefore, in the two adjacent layers of the bent bodies, the length of the steel plate and the position of the bending area are adjusted so that the outer circumference of the bent body flat portion 40 of the bent body arranged on the inner side is equal to the inner circumference of the bent body flat portion 40 of the bent body arranged on the outer side.

[0151] (Joint configuration)

[0152] like Figure 2 As shown, when the bending body arranged at the innermost side is the first bending body 1a and the flat area having the joint portion 6 of the first bending body 1a is the reference flat area 11, the joint portions 6 of each of the plurality of bending bodies 1 are located in the flat portion 4 having the reference flat area 11. By forming such a structure, the winding can be easily assembled.

[0153] (Distance between the first group of joints and the second group of joints)

[0154] The wound core 10 is wound so that the average distance between the first group of joints described later and the first group of joints present in the vicinity of the corner 3 is <L i >Average distance from the second group of joints described later <L O >The joint 6 is arranged so as to satisfy the following formula (1) and the following formula (2).

[0155] Plastic strain and elastic strain are introduced into the bending region 5, and strain due to shearing is introduced into the end of the joint portion 6. Due to the interference of these strains, the iron loss is further deteriorated.

[0156] In the wound core 10 of the present disclosure, the average distance between the first group of joints is <L i > and average length <L O >Satisfying the following equations (1) and (2) can avoid interference between the plastic strain and elastic strain of the bending region 5 and the shear strain of the joint 6, thereby suppressing iron loss.

[0157] 25mm≤ <L i >…(1)

[0158] 25mm≤ <lo>…(2)

[0159] (First group of joints V i )

[0160] Next, a plurality of first group joint portions V are provided. i The first group of joints V is described by taking the case of a plurality of second group joints as an example. i and the second group of joints V O . Fig. 9 A plurality of first group joints V i and a plurality of second group joint portions V O A side view of a wound core 10D according to the fifth technical solution. Fig. 9 The portion "..." between the bent bodies 1 and the bent bodies 1 of the wound core 10D also has a plurality of bent bodies 1 stacked. The wound core 10D is a wound core formed by stacking bent bodies 1 having one joint 6. Fig. 9 In the winding core 10D, the bent body disposed on the innermost side is the first bent body 1a, and the flat region having the joint 6 of the first bent body 1a is the reference flat region 11. In the winding core 10D, each joint 6 is provided in the flat portion 4 having the reference flat region 11. Fig. 9 In FIG. 1 , the flat portion 4 having the bonding portion 6 is a flat portion parallel to the X direction.

[0161] In addition, one of the bending regions adjacent to the reference flat region 11 is defined as the first bending region 12a, and the other bending region adjacent to the reference flat region 11 is defined as the second bending region 12b. An imaginary line passing through the end point of the first bending region 12a on the reference flat region 11 side and parallel to the plate thickness direction of the reference flat region 11 is defined as the first imaginary line H1, and an imaginary line passing through the end point of the second bending region 12b on the reference flat region 11 side and parallel to the plate thickness direction of the reference flat region 11 is defined as the second imaginary line H2.

[0162] In each of the joints 6 of the flat portion 4 having the reference flat region 11, the joint 6 whose length from the first imaginary line H1 to the end surface 13 of the joint 6 on the first imaginary line H1 side along the long side direction of the reference flat region 11 is the shortest is set as the first shortest joint 6a. In each of the joints 6 of the bent work bodies 1c and 1d adjacent in the plate thickness direction to the bent work body 1b having the first shortest joint 6a, the joint 6 whose length from the first imaginary line H1 to the end surface 13 of the joint 6 on the first imaginary line H1 side along the long side direction of the reference flat region 11 is the shortest is set as the first end joint 6b.

[0163] An imaginary line passing through the end surface 13a on the first imaginary line H1 side of the first shortest joint 6a and parallel to the plate thickness direction of the reference flat region 11 is defined as an imaginary line A. An imaginary line passing through the end surface 13b on the first imaginary line H1 side of the first end joint 6b and parallel to the plate thickness direction of the reference flat region 11 is defined as an imaginary line B. Of the joints 6 of the flat portion 4 having the reference flat region 11, the joints 6 between the imaginary line A and the imaginary line B are defined as a first group of joints V. i Here, the first group of joints V i Yes V i1 ~V in , totaling n (n is a natural number).

[0164] (Average distance of joints in group 1 <L i >)

[0165] Suppose that along the long side direction of the reference flat region 11, from the first imaginary line H1 to each first group of joint portions V i The average length of the end surface on the first imaginary line H1 side is the first group of joints V i The average distance <L i >. The first group of joints V i The average distance <L i >The following method can be used to measure. Use an optical microscope or the like to obtain an observation image of the side surface of the wound core. In the obtained observation image, the first group of joints is determined based on the above definition. Next, image processing software is used to measure the distance from the first imaginary line H1 to each first group of joints V along the long side direction of the reference flat area 11. i The length Li of the end face on the first imaginary line H1 side is obtained. The average value of each Li obtained is calculated and the average value is taken as the average distance of the first group of joints. <L i >.

[0166] (Second group of joints V O )

[0167] Next, the second group of joints V will be described. O In each of the joints 6 of the flat portion 4 having the reference flat region 11, the joint portion in which the length of the end face 14 of the joint portion 6 from the second imaginary line H2 to the second imaginary line H2 side along the long side direction of the reference flat region 11 is the shortest is set as the second shortest joint portion 6c. In each of the joints 6 of the bending work body 1f, 1g adjacent in the plate thickness direction to the bending work body 1e having the second shortest joint portion 6c, the joint portion 6 in which the length of the end face 14 of the joint portion 6 from the second imaginary line H2 to the second imaginary line H2 side along the long side direction of the reference flat region 11 is short is set as the second end joint portion 6d.

[0168] An imaginary line passing through the end surface 14a on the second imaginary line H2 side of the second shortest joint 6c and parallel to the plate thickness direction of the reference flat region 11 is defined as an imaginary line C. An imaginary line passing through the end surface 14b on the second imaginary line H2 side of the second end joint 6d and parallel to the plate thickness direction of the reference flat region 11 is defined as an imaginary line D. Of the joints 6 of the flat portion 4 having the reference flat region 11, the joints 6 between the imaginary lines C and C are defined as the second group of joints V. O Here, the second group of joints V O Yes V O1 ~V Om , a total of m (m is a natural number).

[0169] (Average distance of joints in group 2 <L O >)

[0170] Suppose that along the long side direction of the reference flat region 11, from the second imaginary line H2 to each second group of joint portions V O The average length of the end surface on the second imaginary line H2 side is the second group of joints V O The average distance <L O >. Second group of joints V O The average distance <L O >It can be measured by the following method. Using an optical microscope or the like, obtain an observation image of the side surface of the wound core. In the obtained observation image, the second group of joints V is determined based on the above definition. O Next, using image processing software, the distance from the second imaginary line H2 to each second group of joints V along the long side direction of the reference flat region 11 is measured. O The length L of the end surface on the second imaginary line H2 side O . Find the L obtained O The average value is taken as the average distance of the second group of joints. <L O >.

[0171] In the wound core 10D, the joints 6 are preferably arranged so as to be offset from each other in a step-like manner in the circumferential direction. In the wound core 10D, the circumferential direction is the same as the long side direction of the reference flat area 11. The circumferential position of the joint 6 in the bending workpiece 1 gradually shifts from the circumferential first imaginary line H1 side (the first group of joints Vi side) to the second imaginary line H2 side (the second group of joints Vo side) as it moves from the bending workpiece 1 located on the inner side in the radial direction toward the bending workpiece 1 located on the outer side in the radial direction. The radial direction refers to the direction orthogonal to the axis of the wound core 10D. Hereinafter, the pattern of the arrangement of such joints 6 is referred to as a step-like pattern. In the present embodiment, the joints 6 are arranged in a pattern of multiple repeated steps in the radial direction. In the first embodiment, among the joints 6 arranged in a step-like pattern, the joints 6 of the bent body 1 located most radially inward are included in the first group of joints Vi, and the joints 6 of the bent body 1 located most radially outward are included in the second group of joints Vo. By staggering the joints 6 in sequence along the circumferential direction, it is possible to suppress obstruction of the flow of magnetic flux in the wound core 10D.

[0172] In the wound core 10D, the first group of joint portions V i The number is preferably the same as the second group of joints V O In addition, in the wound core 10D, if the number of the joints 6 in the flat portion 4 having the reference flat region 11 between the first imaginary line H1 and the second imaginary line H2 is divided by the number of the first group of joints V i The quotient and remainder obtained by the number of is defined as k, then k satisfies the following formula (3). Fig. 9 In the case of V, the quantity k is equal to the value of V along the thickness direction of the plate. i1 ~V o1 The number of junctions between the first group of junctions V and between the first imaginary line H1 and the second imaginary line H2. i To the distance from the first group of joints V i The nearest second group of joints V O The number of the joints 6 arranged in a staggered manner in a step-like manner. The number k is the number of joints included in one stair-like pattern. By arranging the joints 6 in this way, the iron loss can be further suppressed.

[0173] 2≤k≤8…(3)

[0174] exist Fig. 9 In the embodiment, the flat portion 4 having the joint portion 6 is a flat portion parallel to the X direction, but the position of the joint portion is not limited to Fig. 9 For example, you can also Fig.10 In the wound core 10E according to the sixth aspect of the present invention, the flat portion 4 having the joint portion 6 is a flat portion parallel to the Z direction.

[0175] In the wound core 10E, the first group of joint portions V i The average distance <L i > and the second group of joints V O The average distance <L O >Satisfy the above equations (1) and (2). By making the average distance of the first group of joints <L i > and average length <L O >Satisfying the above-mentioned equations (1) and (2) can avoid interference between the plastic strain and elastic strain of the bending region 5 and the shear strain of the joint 6, thereby suppressing iron loss.

[0176] In the wound core 10E, the joints 6 are preferably arranged so as to be shifted from each other in a step-like manner in the circumferential direction. By sequentially shifting the joints 6 in the circumferential direction, it is possible to suppress obstruction of the flow of magnetic flux in the wound core 10E.

[0177] In the wound core 10E, similarly to the wound core 10D, the first group of joint portions V i The number is preferably the same as the second group of joints V O In addition, in the wound core 10E, the number of the joints 6 in the flat portion 4 having the reference flat region 11 between the first imaginary line H1 and the second imaginary line H2 is divided by the number of the first group of joints V i The number k obtained by the number of satisfies the above formula (3). It is preferable that the iron loss can be further suppressed by configuring the joint 6 in this way.

[0178] exist Fig. 9 and Fig.10 In the embodiment of the invention, an example of a bending body 1 having one joint 6 is described. However, in the present invention, the number of joints is not limited to one. Fig.11 As in the wound core 10F of the seventh technical solution, each of the two flat areas 8 facing each other in each bent body 1 has a joint 6. When each bent body 1 has two joints 6, the first bent body 1a of the wound core 10F has a reference flat area 11 and a second reference flat area 11b facing the reference flat area 11.

[0179] (Distance between the third group of joints and the fourth group of joints)

[0180] The wound core 10F preferably has an average distance of a third group of joints to be described later that exists near the corner 3. <L 2i >Average distance from the fourth group of joints described later <L 2O >The joint 6 is arranged so as to satisfy the following formula (4) and the following formula (5).

[0181] Plastic strain and elastic strain are introduced into the bending region 5, and strain due to shearing is introduced into the end of the joint portion 6. Due to the interference of these strains, the iron loss is further deteriorated.

[0182] In the wound core 10F of the present disclosure, the average distance of the first group of joints is <L i > and average length <L O >Satisfies the following formula (1) and formula (2), and further satisfies the following formula (4) and formula (5), thereby further suppressing iron loss. In addition, when the bent body 1 constituting the wound core has two joints 6, when the plurality of joints 6 of only one of the two flat portions 4 having the joints 6 satisfies the above formula (1) and formula (2), the flat portion 4 having the plurality of joints 6 satisfying the above formula (1) and formula (2) is set as the flat portion 4c having the reference flat region 11.

[0183] 25mm≤ <L 2i >…(4)

[0184] 25mm≤ <l2o>…(5)

[0185] (Third group of joints V 2i )

[0186] Next, Fig.11 The third group of joints V is described as an example of the wound core 10F. 2i and the fourth group of joints V 2o In addition, regarding the plurality of first group joint portions V i and a plurality of second group joint portions V O Description omitted. Fig.11 A plurality of third group joints V 2i and a plurality of fourth group joints V 2O The wound core 10F is a side view of a wound core 10F. The wound core 10F is a wound core obtained by stacking bent bodies 1 having one joint portion 6. Fig.11 In the embodiment, the bending body arranged at the innermost side is the first bending body 1a. The first bending body 1a has a reference flat region 11 and a second reference flat region 11b. The second reference flat region 11b is a flat region opposite to the reference flat region 11 and has a joint 6. The joints 6 of the plurality of bending bodies 1 are located between the flat portion 4c having the reference flat region 11 and the flat portion 4d having the second reference flat region 11b. Fig.11 In FIG. 1 , the flat portions 4 c and 4 d having the joint portion 6 are flat portions parallel to the X direction.

[0187] One of the bending regions adjacent to the second reference flat region 11b is defined as the third bending region 12c, and the other bending region adjacent to the second reference flat region 11b is defined as the fourth bending region 12d. An imaginary line passing through the end point of the third bending region 12c on the second reference flat region 11b side and parallel to the plate thickness direction of the second reference flat region 11b is defined as the third imaginary line H1a, and an imaginary line passing through the end point of the fourth bending region 12d on the second reference flat region 11b side and parallel to the plate thickness direction of the second reference flat region 11b is defined as the fourth imaginary line H2a.

[0188] In each of the joints 6 of the flat portion 4d having the second reference flat region 11b, the joint 6 whose length from the third imaginary line H1a to the end face 13 of the joint 6 on the third imaginary line H1a side along the long side direction of the second reference flat region 11b is the shortest is set as the third shortest joint 6e. In each of the joints 6 of the bent work bodies 1i and 1j adjacent in the plate thickness direction to the bent work body 1h having the third shortest joint 6e, the joint 6 whose length from the third imaginary line H1a to the end face 13 of the joint 6 on the third imaginary line H1a side along the long side direction of the second reference flat region 11b is short is set as the third end joint 6f.

[0189] An imaginary line passing through the end surface 13c on the third imaginary line H1a side of the third shortest joint 6e and parallel to the plate thickness direction of the second reference flat region 11b is defined as an imaginary line E. An imaginary line passing through the end surface 13d on the third imaginary line H1a side of the third end joint 6f and parallel to the plate thickness direction of the second reference flat region 11b is defined as an imaginary line F. Of the joints 6 having the flat portion 4d of the second reference flat region 11b, the joints 6 between the imaginary line E and the imaginary line F are defined as a third group of joints V. 2i Here, the third group of joints V 2i The number is V 2i1 ~V 2in , totaling n (n is a natural number).

[0190] (Average distance of joints in group 3 <L 2i >)

[0191] Suppose that along the long side direction of the second reference flat region 11b, from the third imaginary line H1a to each third group of joint portions V 2i The average length of the end surface 13 on the third imaginary line H1a side is the third group of joints V 2i The average distance <L 2i >. The third group of joints V 2i The average distance <L 2i >The following method can be used for measurement. Using an optical microscope or the like, obtain an observation image of the side surface of the wound core. In the obtained observation image, the third group of joints is determined based on the above definition. Next, image processing software is used to measure the distance from the third imaginary line H1a to each third group of joints V along the long side direction of the second reference flat area 11b (the flat area opposite to the first reference flat area). 2i The length L of the end surface 13 on the third imaginary line H1a side 2i . Find the L obtained 2i The average value is taken as the average distance of the third group of joints. <L 2i >.

[0192] (4th group joint V2o)

[0193] Next, the fourth group of joints V2o will be described. Among the joints 6 of the flat portion 4d having the second reference flat region 11b, the joint 6 whose end surface 14 length from the fourth imaginary line H2a to the fourth imaginary line H2a side is the shortest, located between the third imaginary line H1a and the fourth imaginary line H2a and along the long side direction of the second reference flat region 11b, is set as the fourth shortest joint 6g. Among the joints 6 of the bending bodies 11 and 1m adjacent in the plate thickness direction to the bending body 1k having the fourth shortest joint 6g, the joint 6 whose end surface 14 length from the fourth imaginary line H2a to the fourth imaginary line H2a side is short, located between the third imaginary line H1a and the fourth imaginary line H2a and along the long side direction of the second reference flat region 11b, is set as the fourth end joint 6h.

[0194] An imaginary line passing through the end surface 14c on the fourth imaginary line H2a side of the fourth shortest joint 6g and parallel to the plate thickness direction of the second reference flat region 11b is defined as an imaginary line G. An imaginary line passing through the end surface 14d on the fourth imaginary line H2a side of the fourth end joint 6h and parallel to the plate thickness direction of the second reference flat region 11b is defined as an imaginary line H. Of the joints 6 having the flat portion 4d of the second reference flat region 11b, the joint 6 between the imaginary line G and the imaginary line H is defined as a fourth group of joints V. 2O Here, the fourth group of joints V 2O Yes V 2O1 ~V 2Om , totaling m (m is a natural number).

[0195] (Average distance of joints in group 4 <L 2O >)

[0196] Suppose that along the long side direction of the second reference flat region 11b, from the fourth imaginary line H2a to each fourth group of joint portions V 2O The average length of the end surface 14 on the fourth virtual line H2a side is the fourth group of joints V 2o The average distance <L 2O >. 4th group joint V 2o The average distance <L O >It can be measured by the following method. Using an optical microscope or the like, obtain an observation image of the side surface of the wound core. In the obtained observation image, the fourth group of joints V is determined based on the above definition. 2o Next, image processing software is used to measure the distance from the fourth imaginary line H2a to each fourth group of joint portions V along the long side direction of the second reference flat region 11b. 2O The length L of the end surface on the fourth imaginary line H2a side 2O . Find the L obtained 2O The average value is taken as the average distance of the fourth group of joints. <L 2O >.

[0197] In the wound core 10F, the joints 6 are preferably arranged so that each joint 6 is offset from each other in a step-like manner in the circumferential direction. The circumferential position of the joint 6 in the bending body 1 gradually shifts from the circumferential third imaginary line H1a side (the first group of joints Vi side) to the 4th imaginary line H2a side (the second group of joints Vo side) as it moves from the bending body 1 located on the inner side in the radial direction toward the bending body 1 located on the outer side in the radial direction. In the flat portion 4d, the joints 6 are arranged in a pattern of multiple steps repeated in the radial direction. In the wound core 10F, among the joints 6 arranged in a step-like pattern, the joint 6 of the bending body 1 located closest to the inner side in the radial direction is included in the third group of joints V0. 2i The joint portion 6 of the bent body 1 located most radially outward is included in the fourth group of joint portions V. 2o By sequentially shifting the joint portions 6 in the circumferential direction in this manner, it is possible to suppress the flow of magnetic flux in the wound core 10F from being hindered.

[0198] In the wound core 10F, the third group of joints V 2i The number of the joints 6 in the flat portion 4d having the second reference flat region 11b between the third imaginary line H1a and the fourth imaginary line H2a is preferably equal to the number of the fourth group of joints V2o. In the wound core 10F, if the number of the joints 6 in the flat portion 4d having the second reference flat region 11b between the third imaginary line H1a and the fourth imaginary line H2a is divided by the number of the joints 6 in the third group of joints V 2i The second quotient and the second remainder obtained by dividing the number by 2 are defined as k2, and k2 satisfies the following formula (6). Fig.11 In the case of V, the number k2 is equal to the value of V along the thickness direction of the plate. 2i1 ~V 2o1 That is, the number of junctions V determined from the third group of junctions V 2i To the 3rd group joint V 2i The nearest 4th group joint V 2o The number of the joints 6 arranged in a staggered manner in a step-like manner. The number k2 is the number of the joints included in one stair-like pattern. By arranging the joints 6 in this way, the iron loss can be further suppressed.

[0199] 2≤k2≤8…(6)

[0200] <Method for manufacturing wound core>

[0201] Next, the manufacturing method of the wound core disclosed in the present invention is described. The method for manufacturing the directional electromagnetic steel sheet constituting the bent processed body 1 is not particularly limited, and a manufacturing method of the directional electromagnetic steel sheet known in the past can be appropriately selected. As a preferred specific example of the manufacturing method, for example, after a processed steel sheet (slab) having the chemical composition of the above-mentioned directional electromagnetic steel sheet is heated to above 1000°C and hot-rolled, the hot-rolled sheet is annealed as needed, and then a cold-rolled steel sheet is obtained by cold rolling once or by cold rolling twice or more with intermediate annealing. The following method can be cited: the cold-rolled steel sheet is heated to 700 to 900°C in a wet hydrogen-inert gas environment, for example, and decarburization annealing is performed, and nitriding annealing is further performed as needed, and after applying an annealing separator, finishing annealing is performed at about 1000°C, and an insulating coating is formed at about 900°C. Furthermore, coating for adjusting the dynamic friction coefficient can also be implemented afterwards.

[0202] In the method for manufacturing a wound core disclosed in the present invention, for a wound core 10 formed of a grain-oriented electromagnetic steel sheet having the above-described form, when the bent body 1 has one joint 6, the grain-oriented electromagnetic steel sheet is bent so that the first group of joints V is i The average distance <L i >Satisfying the above formula (1), the second group of joints V O The average distance <L O > In a manner satisfying the above formula (2), the directional electromagnetic steel sheet is sheared, bent, and stacked in the thickness direction. In addition, when the bent body 1 has two joints 6, it is preferred that the first group of joints V i The average distance <L i >Satisfying the above formula (1), the second group of joints V O The average distance <L O >Satisfying the above formula (2), the third group of joints V 2i The average distance <L 2i > and satisfying the above formula (4), the fourth group of joints V 2o The average distance <L 2O > In a manner that satisfies the above formula (5), the directional electromagnetic steel sheets are sheared, bent, and stacked in the thickness direction. The directional electromagnetic steel sheets are assembled in a manner that the end faces of each roll are opposed to each other with at least one joint 6 between them. The manufacturing method disclosed in the present invention manufactures a wound core in a manner that satisfies the above conditions by adjusting the feed amount of the directional electromagnetic steel sheets, the timing of bending, and the timing of shearing the directional electromagnetic steel sheets.

[0203] (Wound core manufacturing device)

[0204] Next, a manufacturing device for the wound core of the present disclosure will be described. The following manufacturing device is an example of a manufacturing device for manufacturing the wound core 10 of the present disclosure. Fig.12 As shown, the wound core manufacturing device 40 is a wound core manufacturing device 40 that bends and stacks steel plates (directional electromagnetic steel plates) 21. It is provided with a bending device 20 that bends the directional electromagnetic steel plates 21, and a feed roller 60 that feeds the directional electromagnetic steel plates 21 to the bending device 20. The wound core manufacturing device 40 disclosed in the present invention may also include a decoiler 50 and a cutting device 70.

[0205] "Unwinding Machine"

[0206] The uncoiler 50 unwinds the grain-oriented electromagnetic steel sheet 21 from the coil 27 of the grain-oriented electromagnetic steel sheet 21. The grain-oriented electromagnetic steel sheet 21 unwinded from the uncoiler 50 is conveyed toward the feed roller 60.

[0207] "Feed Roller"

[0208] The feed roller 60 feeds the grain-oriented electromagnetic steel sheet 21 to the bending device 20. The feed roller 60 adjusts the feeding direction 25 of the grain-oriented electromagnetic steel sheet 21 before being fed into the bending device 20. The feed roller 60 feeds the grain-oriented electromagnetic steel sheet 21 to the bending device 20 after adjusting the feeding direction 25 of the grain-oriented electromagnetic steel sheet 21 to the horizontal direction.

[0209] The cutting device 70 is provided between the feed roller 60 and the bending device 20. The grain-oriented electromagnetic steel sheet 21 is bent after being cut by the cutting device 70. The cutting method is not particularly limited. The cutting method is, for example, shearing.

[0210] "Bending device"

[0211] The bending device 20 bends the directional electromagnetic steel sheet 21 fed from the feed roller 30. The bending body 1 has a bent region after the bending process and a flat region adjacent to the bent region. In the bending body 1, the bending body flat portion and the bending body corner portion are alternately continuous. At each corner portion, the angle formed by two adjacent flat portions is preferably approximately 90°.

[0212] The bending device 20 includes, for example, a die 22 and a punch 24 for stamping. Furthermore, the bending device includes a guide 23 for fixing the directional electromagnetic steel sheet 21 and a cover (not shown). The cover covers the die 22, the punch 24, and the guide 23. The directional electromagnetic steel sheet 21 may be cut by the cutting device 70 after the bending device 20 has bent the directional electromagnetic steel sheet 21. The bending device 20 may also perform the bending after the cutting device 70 has cut the directional electromagnetic steel sheet 21.

[0213] The grain-oriented electromagnetic steel sheet 21 is conveyed in the conveying direction 25 and fixed at a predetermined position. Then, the punch 24 is pressed at a predetermined force at a predetermined position in the pressing direction 26 to obtain a bent body 1 having a bending region with a desired bending angle φ.

[0214] (Layered)

[0215] The bending device 20 stacks the plurality of bending bodies 1 in the plate thickness direction. The bending bodies 1 are stacked by aligning the corners 3 of the bending bodies 1 with each other and overlapping in the plate thickness direction, for example, to form a stacked body 2 that is substantially rectangular in side view. Thus, a low iron loss wound core according to the present disclosure can be obtained. When the bending body 1 has only one joint 6, the bending device 20 makes the first group of joints V i The average distance <L i >Satisfying the above formula (1), the second group of joints V O The average distance <L O > In a manner that satisfies the above formula (2), the bent bodies 1 are stacked in the plate thickness direction. When the bent body 1 has two joints 6, it is preferred that the first group of joints V i The average distance <L i >Satisfying the above formula (1), the second group of joints V O The average distance <L O >Satisfying the above formula (2), the third group of joints V 2i The average distance <L 2i >Satisfying the above formula (4), the fourth group of joints V 2o The average distance <L 2O > In a manner satisfying the above-mentioned formula (5), the bent bodies 1 are stacked in the plate thickness direction. The obtained wound core may be further fixed using a known binding tape or a fastening tool as required.

[0216] The present disclosure is not limited to the above-mentioned embodiments. The above-mentioned embodiments are illustrative, and any embodiment having substantially the same structure and having the same effect as the technical idea described in the claims of the present disclosure is included in the technical scope of the present disclosure. The method for manufacturing a wound core of the present disclosure uses the above-mentioned winding core manufacturing device to manufacture a wound core.

[0217] Example

[0218] The following describes embodiments (experimental examples), but the wound core of the present disclosure is not limited to the following embodiments. The wound core of the present disclosure can adopt various conditions as long as it does not deviate from the main purpose of the present disclosure and achieves the purpose of the present disclosure. In addition, the conditions in the embodiments shown below are condition examples adopted to confirm the feasibility and effect.

[0219] <Experimental Example 1>

[0220] [Manufacturing of wound core]

[0221] The directional electromagnetic steel sheets (sheet width 152.4 mm, sheet thickness: 0.23 mm or 0.18 mm, Si content 3.45 mass %) having the sheet thicknesses shown in Tables 1A to 1K were sheared and bent to produce the bent bodies to form the first group of joints V shown in Tables 2A to 2K. i The average distance <L i >, the second group of joints V O The average distance <L O >, the third group of joints V 2i The average distance <L 2i >, 4th group joint V 2o The average distance <L 2O >, the values ​​of the number k and the number k2 are obtained by stacking the bent body in the plate thickness direction. Fig.13 The winding core has the dimensions indicated in . The bending angle φ of the winding core is assumed to be 45°. In addition, L1 is the length of the flat portion parallel to the X-axis direction. L2 is the length of the flat portion parallel to the Z-axis direction. L3 is the winding thickness of the winding core (thickness in the stacking direction). L4 is the length in the 23 circumferential direction of the innermost flat area in the corner of the winding core. In each embodiment, L1: 344mm, L2: 122mm, L3: 94.1mm, L4: 4mm. In addition, the radius of curvature in each bending area is assumed to be 1.5mm. Fig.13 Although the joints are omitted, the joints of each embodiment are formed in the above-mentioned stepped pattern. Let the wound core having one joint be core A, and the wound core having two joints be core B. The two joints of each bent body of core B are located in two opposing flat areas. The column of joint 1 in Tables 2A to 2K refers to the joint of the flat portion having a reference flat area, and joint 2 refers to the joint of the flat portion having a second reference flat area. In addition, in the case where two flat portions each have a joint, when the multiple joints of only one of the flat portions satisfy the conditions of the average distance of the above-mentioned formulas (1) and (2), the joint of the flat portion that satisfies the conditions of the average distance of the above-mentioned formulas (1) and (2) is set as joint 1.

[0222] [Evaluation of Iron Loss]

[0223] In the measurement of iron loss, the wound cores of Experiments No. 1 to No. 276 in Tables 1A to 2K were measured using the exciting current method described in JIS C 2550-1 under the conditions of a frequency of 50 Hz and a magnetic flux density of 1.7 T, and the iron loss value (core iron loss) WA of the wound core was measured. In addition, a sample of 100 mm in width × 500 mm in length was taken from a hoop (sheet width 152.4 mm) of a grain-oriented electromagnetic steel sheet used in the core, and the sample was measured by the electromagnetic steel sheet single plate magnetic property test based on the H-coil method described in JIS C 2556 under the conditions of a frequency of 50 Hz and a magnetic flux density of 1.7 T, and the iron loss value (blank iron loss) WB of the billet steel sheet single plate was measured. Next, the iron loss value WA was divided by the iron loss value WB to obtain the core iron loss / blank iron loss (WA / WB). The case where the core iron loss / the billet iron loss was 1.05 or less was considered acceptable.

[0224] Table 1A

[0225]

[0226] Table 1B

[0227]

[0228] Table 1C

[0229] Table 1D

[0230] Table 1E

[0231] Table 1F

[0232] Table 1G

[0233]

[0234] Table 1H

[0235] Table II

[0236] Table 1J

[0237]

[0238] Table 1K

[0239]

[0240] Table 2A

[0241]

[0242] Table 2B

[0243]

[0244] Table 2C

[0245] Table 2D

[0246]

[0247] Table 2E

[0248] Table 2F

[0249]

[0250] Table 2G

[0251]

[0252] Table 2H

[0253]

[0254] Table 2I

[0255]

[0256] Table 2J

[0257]

[0258] Table 2K

[0259]

[0260] As shown in Tables 2A to 2K, when the joint portion is one core A, and <lo> When the diameter is 25 mm or more, the iron loss is improved.< / lo> and <lo>When the thickness is 25 mm or more and the number k is 2 to 8, the iron loss is further improved.

[0261] In addition, as shown in Tables 2A to 2K, when there are two joints,< / lo> 、 <lo>is 25mm or more, and <L 2i > and <L 2O >25mm or more, the iron loss is improved.< / lo> 、 <lo>, <L 2i > and <L 2O > is 25 mm or more, and when the numbers k and k2 are 2 to 8, the iron loss is further improved.

[0262] <Experimental Example 2>

[0263] [Manufacturing of wound core]

[0264] The directional electromagnetic steel sheets having the sheet thickness shown in Table 3 (sheet width 152.4 mm, sheet thickness: 0.23 mm or 0.18 mm, Si content: 3.45 mass%) were sheared and bent to produce the bent bodies so as to form the first group of joints V shown in Table 4. i The average distance <L i >, the second group of joints V O The average distance <L O >, the third group of joints V 2i The average distance <L 2i >, 4th group joint V 2o The average distance <L 2O >, the values ​​of number k and number k2, the bent body is stacked in the plate thickness direction, thereby obtaining Fig.13 The winding core. The bending angle of the bending area, the curvature radius of the bending area, and each dimension of each experimental example are set as shown in Table 3. In Experiments No. 1A, 3A, 5A to 10A, the number of joints is set to one, and in Experiments No. 2A and 4A, the number of joints is set to two. The two joints of each bent body of Experiments No. 2A and 4A are in two opposing flat areas. The column of Joint 1 in Table 4 refers to a joint having a flat portion of a reference flat area, and Joint 2 refers to a joint having a flat portion of a second reference flat area.

[0265] [Evaluation of Iron Loss]

[0266] In the measurement of iron loss, the wound cores of Experiments No. 1A to No. 10A in Table 4 were measured using the exciting current method described in JIS C 2550-1 under the conditions of a frequency of 50 Hz and a magnetic flux density of 1.7 T, and the iron loss value (core iron loss) WA of the wound core was measured. In addition, a sample with a width of 100 mm and a length of 500 mm was taken from a hoop (sheet width of 152.4 mm) of a grain-oriented electromagnetic steel sheet used in the core, and the sample was measured by the electromagnetic steel sheet single plate magnetic property test based on the H-coil method described in JIS C 2556 under the conditions of a frequency of 50 Hz and a magnetic flux density of 1.7 T, and the iron loss value (blank iron loss) WB of the billet steel sheet single plate was measured. Next, the iron loss value WA was divided by the iron loss value WB to obtain the core iron loss / blank iron loss (WA / WB). The case where the core iron loss / the billet iron loss was 1.05 or less was considered acceptable.

[0267] As shown in Table 4, in the case of an iron core having one joint, by using< / lo> and <lo> When the diameter is 25 mm or more, the iron loss is improved.< / lo> and <lo>When the thickness is 25 mm or more and the number k is 2 to 8, the iron loss is further improved.

[0268] Furthermore, as shown in Table 4, the iron loss is improved by setting the curvature radius to 5.0 mm or less. The iron loss of Test No. 7A using the iron core e having a curvature radius exceeding 5.0 mm is poor.

[0269] Table 3

[0270]

[0271] Table 4

[0272]

[0273] Industrial Applicability

[0274] According to the present disclosure, the iron loss of the wound core can be suppressed, and thus the industrial applicability is high.

[0275] Description of symbols

[0276] 1 bending body; 2 laminated body; 3 corner portion; 4, 4a, 4b flat portion; 5, 5a, 5b bending region; 6 joining portion; 8 flat region; 10 winding core; 20 bending device; 40 manufacturing device; 21 oriented electromagnetic steel sheet; 22 die; 23 guide portion; 24 punch; 25 conveying direction; 26 pressing direction.< / lo> < / lo>

Claims

1. A wound core, comprising: laminating a plurality of bent bodies formed by forming a directional electromagnetic steel sheet in a sheet thickness direction; The wound core has a plurality of flat portions and a plurality of corner portions. The bending body has a plurality of flat regions and a plurality of curved regions adjacent to the flat regions. The radius of curvature of each of the above-mentioned curved areas is less than 5.0 mm, The bent body has one or more joints where the end faces in the longitudinal direction of the grain-oriented electromagnetic steel sheet face each other. When the bending body disposed at the innermost side is set as the first bending body, and the flat region having the joint portion of the first bending body is set as the reference flat region, the joint portions of the plurality of bending bodies are located at the flat portion having the reference flat region. In the side view of the wound core above, When one of the curved regions adjacent to the reference flat region is defined as a first curved region, The other curved region adjacent to the reference flat region is defined as a second curved region. A virtual line passing through the end point of the first curved region on the reference flat region side and parallel to the plate thickness direction of the reference flat region is defined as a first virtual line. A virtual line passing through the end point of the second curved region on the reference flat region side and parallel to the plate thickness direction of the reference flat region is defined as a second virtual line. In each of the above-mentioned joints of the above-mentioned flat portion having the above-mentioned reference flat area, the above-mentioned joint located between the above-mentioned first imaginary line and the above-mentioned second imaginary line and having the shortest length of the above-mentioned end face of the above-mentioned joint from the above-mentioned first imaginary line to the above-mentioned first imaginary line side along the long side direction of the above-mentioned reference flat area is set as the first shortest joint, In each of the above-mentioned joints of the above-mentioned bending work body located adjacent to the above-mentioned bending work body having the above-mentioned first shortest joint portion in the above-mentioned plate thickness direction, the above-mentioned joint portion located between the above-mentioned first imaginary line and the above-mentioned second imaginary line and having a shorter length from the above-mentioned first imaginary line to the above-mentioned end face of the above-mentioned joint portion on the above-mentioned first imaginary line side along the long side direction of the above-mentioned reference flat area is set as the first end joint portion, In each of the above-mentioned joints of the above-mentioned flat portion having the above-mentioned reference flat area, the above-mentioned joint that is located between the above-mentioned first imaginary line and the above-mentioned second imaginary line and has the shortest length from the above-mentioned second imaginary line to the above-mentioned end face of the above-mentioned joint on the side of the above-mentioned second imaginary line along the long side direction of the above-mentioned reference flat area is set as the second shortest joint, In each of the above-mentioned joints of the above-mentioned bending work body located adjacent to the above-mentioned bending work body having the above-mentioned second shortest joint portion in the above-mentioned plate thickness direction, the above-mentioned joint portion located between the above-mentioned first imaginary line and the above-mentioned second imaginary line and having a shorter length from the above-mentioned second imaginary line to the above-mentioned end face of the above-mentioned joint portion on the above-mentioned second imaginary line side along the long side direction of the above-mentioned reference flat area is set as the second end joint portion, A virtual line A passes through the end surface on the first virtual line side of the first shortest joint and is parallel to the plate thickness direction of the reference flat region. A virtual line passing through the end surface on the first virtual line side of the first end joint portion and parallel to the plate thickness direction of the reference flat region is defined as a virtual line B. A virtual line passing through the end surface on the second virtual line side of the second shortest joint and parallel to the plate thickness direction of the reference flat region is defined as a virtual line C. A virtual line passing through the end surface on the second virtual line side of the second end bonding portion and parallel to the plate thickness direction of the reference flat region is defined as a virtual line D. Among the above-mentioned joints of the above-mentioned flat portion having the above-mentioned reference flat area, the above-mentioned joints located between the above-mentioned imaginary line A and the above-mentioned imaginary line B are set as the first group of joints, Among the above-mentioned joints of the above-mentioned flat portion having the above-mentioned reference flat area, the above-mentioned joints located between the above-mentioned imaginary line C and the above-mentioned imaginary line D are set as the second group of joints, The average value of the length from the first imaginary line to the end surface on the first imaginary line side of each of the first group of joints along the long side direction of the reference flat region is set to <L i >、 The average value of the length from the second imaginary line to the end surface on the second imaginary line side of each of the second group of joints along the long side direction of the reference flat region is set to <L O >When Satisfy the following equation (1) and the following equation (2): 25mm≤<L i >…(1) 25mm≤<L o >…(2)。 2. The wound core according to claim 1, The number of the first group of joints is equal to the number of the second group of joints. Among the quotient and remainder obtained by dividing the number of the above-mentioned joints in the above-mentioned flat portion located between the above-mentioned first imaginary line and the above-mentioned second imaginary line and having the above-mentioned reference flat area by the number of the above-mentioned first group of joints, the above-mentioned quotient, that is, k, satisfies the following formula (3): 2≤k≤8…(3)。 3. The wound core according to claim 1 or 2, The two opposing flat areas of each of the bent bodies have the above-mentioned joining portion. The first bent body includes the reference flat region and a second reference flat region facing the reference flat region. The joining portion of each of the plurality of bent bodies is located at the flat portion having the reference flat region and the flat portion having the second reference flat region. In the side view of the wound core above, When one of the curved regions adjacent to the second reference flat region is set as a third curved region, The other curved region adjacent to the second reference flat region is defined as a fourth curved region. A virtual line passing through the end point of the third curved region on the second reference flat region side and parallel to the plate thickness direction of the second reference flat region is defined as a third virtual line. A virtual line passing through the end point of the fourth curved region on the second reference flat region side and parallel to the plate thickness direction of the second reference flat region is referred to as a fourth virtual line. In each of the above-mentioned joining portions of the above-mentioned flat portion having the above-mentioned second reference flat area, the above-mentioned joining portion located between the above-mentioned third imaginary line and the above-mentioned fourth imaginary line and having the shortest length of the above-mentioned end face of the above-mentioned joining portion from the above-mentioned third imaginary line to the above-mentioned third imaginary line side along the long side direction of the above-mentioned second reference flat area is set as the third shortest joining portion, In each of the above-mentioned joints of the above-mentioned bending work body located adjacent to the above-mentioned bending work body having the above-mentioned third shortest joint portion in the above-mentioned plate thickness direction, the above-mentioned joint portion located between the above-mentioned third imaginary line and the above-mentioned fourth imaginary line and having a shorter length from the above-mentioned third imaginary line to the above-mentioned end face of the above-mentioned joint portion on the above-mentioned third imaginary line side along the long side direction of the above-mentioned second reference flat area is set as the third end joint portion, In each of the above-mentioned joints of the above-mentioned flat portion having the above-mentioned second reference flat area, the above-mentioned joint that is located between the above-mentioned third imaginary line and the above-mentioned fourth imaginary line and has the shortest length of the above-mentioned end face of the above-mentioned joint from the above-mentioned fourth imaginary line to the above-mentioned fourth imaginary line side along the long side direction of the above-mentioned second reference flat area is set as the fourth shortest joint, In each of the above-mentioned joints of the above-mentioned bending work body located adjacent to the above-mentioned bending work body having the above-mentioned fourth shortest joint portion in the above-mentioned plate thickness direction, the above-mentioned joint portion located between the above-mentioned third imaginary line and the above-mentioned fourth imaginary line and having a shorter length from the above-mentioned fourth imaginary line to the above-mentioned end face of the above-mentioned joint portion on the above-mentioned fourth imaginary line side along the long side direction of the above-mentioned second reference flat area is set as the fourth end joint portion, A virtual line passing through the end surface on the third virtual line side of the third shortest joint and parallel to the plate thickness direction of the second reference flat region is defined as a virtual line E. A virtual line passing through the end surface on the third virtual line side of the third end joint portion and parallel to the plate thickness direction of the second reference flat region is defined as a virtual line F. A virtual line passing through the end surface on the fourth virtual line side of the fourth shortest joint and parallel to the plate thickness direction of the second reference flat region is defined as a virtual line G. A virtual line passing through the end surface on the fourth virtual line side of the fourth end joint portion and parallel to the plate thickness direction of the second reference flat region is defined as a virtual line H. Among the above-mentioned joints of the above-mentioned flat portion having the above-mentioned second reference flat area, the above-mentioned joints located between the above-mentioned imaginary line E and the above-mentioned imaginary line F are set as the third group of joints, among the above-mentioned joints of the above-mentioned flat portion having the above-mentioned second reference flat area, the above-mentioned joints located between the above-mentioned imaginary line G and the above-mentioned imaginary line H are set as the fourth group of joints, and the average value of the lengths from the above-mentioned third imaginary line to the above-mentioned end surface on the side of the above-mentioned third imaginary line of each of the above-mentioned third group of joints along the long side direction of the above-mentioned second reference flat area is set as <L 2i >, set the average value of the length from the fourth imaginary line to the end surface on the fourth imaginary line side of each of the fourth group of joints along the long side direction of the second reference flat region to be <L 2O >When Satisfies the following equation (4) and the following equation (5): 25mm≤<L 2i >…(4) 25mm≤<L 2o >…(5)。 4. The wound core according to claim 3, The number of the third group of joints is equal to the number of the fourth group of joints. In the second quotient and the second remainder obtained by dividing the number of the above-mentioned joints in the above-mentioned flat portion located between the above-mentioned third imaginary line and the above-mentioned fourth imaginary line and having the above-mentioned second reference flat area by the number of the above-mentioned third group of joints, the above-mentioned second quotient, i.e., k2, satisfies the following formula (6): 2≤k2≤8…(6)。 5. The wound core according to claim 1 or 2, The bending angle of the above-mentioned bending area is 30° to 60°.

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