Flat rectangular molded stranded wire and its manufacturing method

Abstract

To provide a rectangular shaped stranded wire having a high space factor of a conductor, and low loss due to an eddy current, and to provide a manufacturing method of the same.SOLUTION: A rectangular shaped stranded wire includes a plurality of first element wires twisted in a first direction, and a plurality of second element wires twisted in a second direction opposite to the first direction on the plurality of first element wires. The plurality of first element wires and the plurality of second element wires each include metal-containing conductors and insulation films for coating the conductors. The plurality of first element wires and the plurality of second element wires are fixed by fusion layers. An average value of cross-sectional areas of the conductors of the plurality of second element wires is equal to or more than an average value of cross-sectional areas of the conductors of the plurality of first element wires.SELECTED DRAWING: Figure 2A

Description

Technical Field

[0001] One embodiment of the present invention relates to a flat-angle formed twisted wire.

Background Art

[0002] The twisted wire used in an electromagnetic circuit, a motor, a reactor, etc. has a structure (referred to as a Litz wire) in which a plurality of enameled wires in which a conductor is coated with an insulating film (also called an insulating varnish) by applying and baking an insulating paint on the outer periphery of a linear conductor such as a copper wire are twisted. By using a twisted wire including a plurality of strands as compared with the case of using a single enameled wire having the same cross-sectional area as the total cross-sectional area of the conductor portions of the plurality of strands, it is possible to reduce the loss due to eddy current. In particular, a twisted wire formed into a flat cross-section is widely used because it has a high conductor occupancy ratio and is easy to wind in an aligned manner (see, for example, Patent Documents 1 to 3).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, in the conductors disclosed in Patent Documents 2 and 3, since the number of the plurality of divided strands is small, it is difficult to obtain a high conductor occupancy ratio of 80 to 90% or more. Further, in the flat-angle formed twisted wire disclosed in Patent Document 1, although the number of the plurality of divided strands is large, the outer diameter of the conductor used is 1.8 mm, and it is difficult to obtain a high conductor occupancy ratio when a thinner strand (conductor) diameter is required, such as when applied to a small motor.

[0005] One embodiment of the present invention aims to provide a flat rectangular molded stranded wire having a novel structure and a method for manufacturing the same. Alternatively, one embodiment of the present invention aims to provide a flat rectangular molded stranded wire with a high conductor space factor and low eddy current losses and a method for manufacturing the same. [Means for solving the problem]

[0006] One embodiment of the present invention is a rectangular molded stranded wire. The rectangular molded stranded wire includes a plurality of first strands twisted in a first direction, and a plurality of second strands twisted on the plurality of first strands in a second direction opposite to the first direction. Each of the plurality of first strands and the plurality of second strands has a conductor containing metal and an insulating coating covering the conductor. The plurality of first strands and the plurality of second strands are fixed together by a fusion layer. The average value of the cross-sectional area of ​​the conductors of the plurality of second strands is greater than or equal to the average value of the cross-sectional area of ​​the conductors of the plurality of first strands.

[0007] One embodiment of the present invention is a rectangular molded stranded wire. The rectangular molded stranded wire includes a plurality of first strands twisted in a first direction, a plurality of second strands twisted on the plurality of first strands in a second direction opposite to the first direction, and a plurality of third strands twisted on the plurality of second strands in the first direction. Each of the plurality of first strands, plurality of second strands, and plurality of third strands has a conductor containing metal and an insulating coating covering the conductor. The plurality of first strands, plurality of second strands, and plurality of third strands are fixed together by a fusion layer. The average value of the cross-sectional area of ​​the conductors of the plurality of second strands is greater than or equal to the average value of the cross-sectional area of ​​the conductors of the plurality of first strands, and less than or equal to the average value of the cross-sectional area of ​​the conductors of the plurality of third strands.

[0008] One embodiment of the present invention is a rectangular molded stranded wire. The rectangular molded stranded wire includes a plurality of first strands twisted in a first direction, a plurality of second strands twisted on the plurality of first strands in a second direction opposite to the first direction, a plurality of third strands twisted on the plurality of second strands in a first direction, and a plurality of fourth strands twisted on the plurality of third strands in a second direction. Each of the plurality of first strands, plurality of second strands, plurality of third strands, and plurality of fourth strands has a conductor containing metal and an insulating coating covering the conductor. The plurality of first strands, plurality of second strands, plurality of third strands, and plurality of fourth strands are fixed together by a fusion layer. The average value of the cross-sectional area of ​​the conductors of the plurality of second strands is greater than or equal to the average value of the cross-sectional area of ​​the conductors of the plurality of first strands. The average value of the cross-sectional area of ​​the conductors of the plurality of third strands is greater than or equal to the average value of the cross-sectional area of ​​the conductors of the plurality of second strands, and less than or equal to the average value of the cross-sectional area of ​​the conductors of the plurality of fourth strands.

[0009] One embodiment of the present invention is a method for manufacturing a rectangular stranded wire. The manufacturing method includes the steps of: twisting a plurality of first strands in a first direction to form a first winding; rolling the first winding; twisting a plurality of second strands on the rolled first winding in a second direction opposite to the first direction to form a second winding; rolling the second winding; annealing the rolled second winding; twisting a plurality of third strands on the annealed second winding in a first direction to form a third winding; and rolling the third winding. Each of the plurality of first strands, the plurality of second strands, and the plurality of third strands has a conductor containing metal and an insulating coating covering the conductor. In the third winding after rolling, the average value of the cross-sectional area of ​​the conductors of the plurality of second strands is greater than or equal to the average value of the cross-sectional area of ​​the conductors of the plurality of first strands, and less than or equal to the average value of the cross-sectional area of ​​the conductors of the plurality of third strands. [Brief explanation of the drawing]

[0010] [Figure 1] A schematic side view of a flat-angled twisted wire according to an embodiment of the present invention. [Figure 2A] A schematic end view of a flat-angled stranded wire according to an embodiment of the present invention. [Figure 2B] A schematic end view of a strand included in a flat rectangular molded stranded wire according to an embodiment of the present invention. [Figure 3] A flowchart illustrating a method for manufacturing flat rectangular stranded wire according to an embodiment of the present invention. [Figure 4] A schematic diagram showing a method for manufacturing flat rectangular stranded wire according to an embodiment of the present invention. [Figure 5] A schematic diagram showing a method for manufacturing flat rectangular stranded wire according to an embodiment of the present invention. [Figure 6A] A schematic end view of a strand used in a method for manufacturing flat rectangular stranded wire according to an embodiment of the present invention. [Figure 6B] A schematic end view illustrating a method for manufacturing a flat rectangular stranded wire according to an embodiment of the present invention. [Figure 6C] A schematic end view illustrating a method for manufacturing a flat rectangular stranded wire according to an embodiment of the present invention. [Figure 6D] A schematic end view illustrating a method for manufacturing a flat rectangular stranded wire according to an embodiment of the present invention. [Figure 7A] A schematic end view of a flat-angled stranded wire according to an embodiment of the present invention. [Figure 7B] A schematic end view of a flat-angled stranded wire according to an embodiment of the present invention. [Modes for carrying out the invention]

[0011] The embodiments of the present invention will be described below with reference to the drawings and other materials. However, the present invention can be implemented in various forms without departing from its spirit, and is not to be interpreted as being limited to the embodiments described below.

[0012] For the sake of clearer explanation, the drawings may schematically represent the width, thickness, shape, etc. of each part as compared to the actual embodiment, but this is merely an example and does not limit the interpretation of the present invention. In this specification and each figure, elements having the same functions as those described with respect to the previously presented figures may be denoted by the same reference numerals, and redundant explanations may be omitted. This reference numeral is used when collectively representing a plurality of identical or similar structures, and a hyphen and a natural number are added after the reference numeral when individually representing them. Further, when indicating a part of one structure, a lowercase alphabet may be appended after the reference numeral.

[0013] Hereinafter, a flat-angle formed twisted wire according to one embodiment of the present invention and a method for manufacturing the same will be described.

[0014] 1. Structure of the flat-angle formed twisted wire A flat rectangular molded stranded wire 100 according to one embodiment of the present invention is a winding that can be used in coils for electromagnetic circuits, various motors, reactors, etc. As shown in the schematic side view of the flat rectangular molded stranded wire 100 (Figure 1) and the schematic end face along the dashed line AA' in Figure 1 (Figure 2A), the flat rectangular molded stranded wire 100 includes a plurality of twisted strands 102 and a common insulating layer 108 covering the plurality of strands 102. As shown in Figure 6A, which will be described later, each individual strand 102 before twisting is a so-called enameled wire and includes a conductor 104 with a circular end face containing a metal with high electrical conductivity such as copper or aluminum, and an insulating coating 106 covering the conductor 104. In the embodiment shown in Figure 6A, a fusion layer 110 is further provided on the outer circumference of the insulating coating 106. The conductor 104 before twisting has an outer diameter of, for example, 0.2 mm or more and 1.1 mm or less. The insulating film 106 can be made of a polymer-containing material such as polyurethane, polyesterimide, polyamide, polyamideimide, or polyimide, and the insulating film 106 is formed by baking it onto the outer circumference of the conductor 104. Before twisting, the insulating film 106 has a thickness of, for example, 3 μm to 7 μm, and the insulating film 106 insulates the conductors 104 from each other. Therefore, the flat rectangular molded stranded wire 100 has a structure in which multiple strands 102 that are insulated from each other are twisted together, and for this reason, the flat rectangular molded stranded wire 100 is also called a flat rectangular litz wire, a rectangular split winding, a bundled stranded wire, a bundled conductor, or a bundled conductor. Compared to the case in which a winding composed of a single strand is used, eddy current loss is suppressed by constructing the flat rectangular molded stranded wire 100 with multiple strands, so that the use of the flat rectangular molded stranded wire 100 can provide highly efficient electromagnetic circuits and motors.

[0015] The fusion layer 110 contains a thermoplastic polymer having a melting point and a glass transition point lower than those of the insulating film 106. Examples of the flexible polymer include polyethersulfone, polyvinyl butyral, polyamide, polyester, and the like. As will be described later, the fusion layer 110 covering the insulating film 106 of each individual strand 102 before twisting melts in the annealing process described later and then solidifies again, so it functions as an adhesive for firmly fixing the plurality of strands 102. Therefore, in the flat-shaped formed stranded wire 100, adjacent strands 102 are fixed by the fusion layer 110 that functions as an adhesive.

[0016] The common insulating layer 108 contains a resin. Examples of the resin include polyolefin resins such as polyvinyl chloride and polyethylene, fluorine-containing resins such as perfluoroalkoxy alkane polymer (PFA) and polytetrafluoroethylene (PTFE), polyether ether ketone (PEEK) resin, polyimide, polyamide, polyester, and the like. The common insulating layer 108 has a thickness, for example, of 25 μm or more and 200 μm or less.

[0017] The flat-shaped formed stranded wire 100 has an overall flat-shaped end face that is square or nearly square due to the manufacturing method described later (Fig. 2A), and its aspect ratio (the ratio of the width W to the thickness T) is, for example, 1.0 or more and 2.0 or less. There are no restrictions on the thickness T and the width W, but for example, the thickness T can be appropriately selected from the range of 1.0 mm or more and 3.0 mm or less, and the width W can be appropriately selected from the range of 1.0 mm or more and 6.0 mm or less. Similarly, each individual strand 102 in the flat-shaped formed stranded wire 100 also has a square or nearly square end face shape (Fig. 2B). Its aspect ratio (the ratio of the width w to the thickness t) may also be 1.0 or more and 2.0 or less. However, the contour of the overall end face shape of the flat-shaped formed stranded wire 100 and the end face shape of each individual strand 102 may include only a plurality of curves or a combination of a plurality of curves and straight lines. Here, the width W is the maximum length of the end face in a direction perpendicular to the direction in which the flat-shaped formed stranded wire 100 extends, and the thickness T can be defined as the maximum length of the end face in a direction perpendicular to the width W. The same applies to the thickness t and the width w of the strand 102.

[0018] As can be seen from Figures 1 and 2A, the rectangular molded stranded wire 100 forms a three-layer structure, with each layer consisting of multiple strands 102. Specifically, the rectangular molded stranded wire 100 includes a plurality of (e.g., 2 to 10) first strands 102-1 located in its central portion, a plurality of (e.g., 6 to 24) second strands 102-2 arranged to surround the plurality of first strands 102-1, and a plurality of (e.g., 10 to 35) third strands 102-3 arranged to surround the plurality of second strands 102-2. The plurality of first strands 102-1, the plurality of second strands 102-2, and the plurality of third strands 102-3 constitute the first layer, the second layer, and the third layer, respectively. The third strand 102-3, which constitutes the third layer, is located on the outermost side within the common insulating layer 108 and is either in direct contact with the common insulating layer 108 or adjacent to the common insulating layer 108 via the fusion layer 110. The second strand 102-2, which constitutes the second layer, is located inside the third strand 102-3 and is adjacent to one or more of the third strands 102-3. The second strand 102-2 may be in direct contact with one or more of the third strands 102-3, or adjacent via the fusion layer 110. The second strand 102-2 is separated from the common insulating layer 108. The first strand 102-1, which constitutes the first layer, is located inside the second strand 102-2 and is adjacent to one or more of the second strands 102-2. The first strand 102-1 may be in direct contact with one or more of the second strands 102-2, or adjacent via the fusion layer 110. The first strand 102-1 is separated from the common insulating layer 108 and the third strand 102-3.

[0019] The number of second strands 102-2 constituting the second layer is greater than the number of first strands 102-1 constituting the first layer, and less than the number of third strands 102-3 constituting the third layer. The difference between the number of second strands 102-2 and the number of first strands 102-1 is preferably 5 or 6, and the difference between the number of second strands 102-2 and the number of third strands 102-3 is preferably 3 to 8. By setting the numbers of first strands 102-1, second strands 102-2, and third strands 102-3 as described above, the second strands 102-2 and third strands 102-3 can be arranged at high density around the first strands 102-1 and second strands 102-2, respectively, and as a result, a high conductor space factor of 80% or more (preferably 85% or more, more preferably 90% or more) can be achieved. Here, the conductor space factor is defined as follows. Conductor space ratio (%) = (Total cross-sectional area of ​​the conductor portion 104 of the strand 102) / (Cross-sectional area of ​​the flat rectangular molded stranded wire 100 - Cross-sectional area of ​​the thickness portion of the common insulating layer 108) × 100 In the embodiment shown in Figure 2A, a high conductor space factor of approximately 85% can be achieved. As the conductor space factor increases, the amount of current flowing through the flat rectangular molded stranded wire 100 can also be increased, thus contributing to the increased efficiency and miniaturization of electromagnetic circuits, motors, and reactors.

[0020] As shown in Figure 1, each strand 102 is twisted to form a helical structure. Specifically, multiple first strands 102-1 are twisted in a certain direction (for example, counterclockwise, or Z-twist) with a twist pitch (or average pitch; the same applies hereinafter) P1 of, for example, 15 mm to 20 mm, to form a first layer. Similarly, multiple second strands 102-2 are twisted on multiple first strands 102-1 with a twist pitch P3 that is larger than the twist pitch P1 of the first strands 102-1 (for example, 30 mm to 40 mm), in the opposite direction to the twist direction of the first strands 102-1 (for example, clockwise, or S-twist), to form a second layer. Furthermore, multiple third strands 102-3 are twisted around multiple second strands 102-2 with a twist pitch P3 greater than the twist pitch P2 of the second strands 102-2 (for example, 35 mm to 45 mm) in the opposite direction to the twist direction of the second strands 102-2 (i.e., in the same direction as the twist direction of the first strands 102-1, for example, Z-twist), forming a third layer. In each strand 102, the twist pitch is preferably 12 to 20 times the width. The first strand 102-1, the second strand 102-2, and the third strand 102-3 may be twisted in S-twist, Z-twist, and S-twist, respectively.

[0021] Furthermore, if the first strand 102-1 forming the first layer, the second strand 102-2 forming the second layer, and the third strand 102-3 forming the third layer were twisted in the same direction for each layer, the outer diameter of the strands before rolling would increase, making it difficult to form a flat rectangular twisted wire with a predetermined finished dimension. However, in this embodiment, the first strand 102-1 forming the first layer, the second strand 102-2 forming the second layer, and the third strand 102-3 forming the third layer are twisted in opposite directions for each layer (in the order of the first, second, and third layers, "Z twist, S twist, Z twist" or "S twist, Z twist, S twist"), the structure of the strands before forming into a rectangular shape and the finished outer diameter are stabilized, and the finished dimensions of the flat rectangular twisted wire can be stabilized.

[0022] Furthermore, the flat rectangular molded stranded wire 100 is constructed such that the area of ​​the end face of the conductor 104 of the strand 102 (hereinafter, the area of ​​the end face is referred to as the cross-sectional area) increases in the order of the first strand 102-1, the second strand 102-2, and the third strand 102-3. In other words, the average value of the cross-sectional areas of the conductors 104 of multiple second strands 102-2 is greater than or equal to the average value of the cross-sectional areas of the conductors 104 of multiple first strands 102-1, and less than or equal to the average value of the cross-sectional areas of the conductors 104 of multiple third strands 102-3. Alternatively, the average value of the cross-sectional areas of the conductors 104 of multiple second strands 102-2 may be greater than the average value of the cross-sectional areas of the conductors 104 of multiple first strands 102-1, and less than the average value of the cross-sectional areas of the conductors 104 of multiple third strands 102-3. The total cross-sectional area of ​​the strand 102 is, for example, 1.0 mm². 2 10.0 mm or more 2 The following is correct.

[0023] As can be seen from Figure 1, the strands 102 have increasing helical radii in the order of the first layer, second layer, and third layer, and the twist pitch of each strand 102 is as described above. 1st strand 102-1 < 2nd strand 102-2 < 3rd strand 102-3 As a result, the outer strands 102 become larger, so the length of each strand 102 per unit length of the flat rectangular twisted wire 100 is, First strand 102-1 > Second strand 102-2 > Third strand 102-3 Therefore, the resistance due to the length of each strand 102 is First strand 102-1 > Second strand 102-2 > Third strand 102-3 This is the result. Generally, due to work hardening, the conductors 104 of the strands 102 become harder after processing such as rolling, and the conductivity of the conductors 104 decreases. However, as will be described later, in the manufacturing process of the flat rectangular formed stranded wire 100, by performing an annealing process after the second rolling process of the second layer, the conductors 104 of the first strand 102-1 and the second strand 102-2, which have hardened due to rolling, become softer than before the annealing process, and the conductivity of each conductor 104 also increases. If an annealing process is not performed after the rolling process of the third layer, the conductivity of the conductor 104 of the third strand 102-3 will be lower than before the rolling process. Therefore, assuming that the cross-sectional area of ​​the strands 102 is the same or approximately the same regardless of the layer, the resistance of each strand 102 will be due to the twist pitch and work hardening. 1st strand 102-1 < 2nd strand 102-2 < 3rd strand 102-3 As a result, the resistance increases in the order of the first strand 102-1, the second strand 102-2, and the third strand 102-3, creating a large difference in resistance values ​​among these strands 102.

[0024] On the other hand, in the flat rectangular molded stranded wire 100, the cross-sectional area of ​​the conductor 104 of the strand 102 is, 1st strand 102-1 < 2nd strand 102-2 < 3rd strand 102-3 As a result, the resistance increases in the order of the first strand 102-1, the second strand 102-2, and the third strand 102-3. Therefore, there is no large resistance difference between the first strand 102-1, the second strand 102-2, and the third strand 102-3, and as a result, it becomes possible to pass a uniform current through all the strands 102, minimizing the overall resistance of the flat rectangular molded stranded wire 100. This contributes to reducing the characteristic variation of the flat rectangular molded stranded wire 100. For example, the cross-sectional area of ​​the conductor 104 of the strand 102 may be adjusted so that the average value of the resistance of the first strand 102-1 and the average value of the resistance of the third strand 102-3 are within ±5%, preferably within ±3%, and more preferably within ±1%, of the average value of the resistance of the second strand 102-2.

[0025] 2. Method for manufacturing flat rectangular stranded wire An example of a manufacturing method for the flat rectangular stranded wire 100 will be explained using the flowchart in Figure 3 and the schematic diagrams in Figures 4 to 6D. Note that in Figures 6B to 6D, the insulating coating 106 and the fusion layer 110 are omitted for clarity.

[0026] First, multiple first strands 102-1 are twisted together (Figure 3, first twisting step). Specifically, as shown in Figure 4, multiple bobbins 120, each wound with a first strand 102-1, are arranged. As described above, each strand 102 has a conductor 104 and an insulating film 106 covering the conductor 104, and further comprises a fusion layer 110 covering the insulating film 106 (Figure 6A). Multiple first strands 102-1 drawn from the bobbins 120 are joined together using a mandrel (not shown), and the multiple bobbins 120 are made to revolve (see dotted arrow in Figure 4). As a result, multiple first strands 102-1 are twisted in a certain direction (clockwise or counterclockwise), and a first winding 150 constituting the first layer is obtained.

[0027] Subsequently, the first winding 150 is rolled by a rolling mill 122 (first rolling process). In the first rolling process, tension is applied to the first winding 150 in the stretching direction by a take-up machine 124 (described later), and it is also compressed by the rolling mill 122. A known rolling mill can be used as the rolling mill 122; for example, the rolling mill 122 can be composed of a pair of rolling rolls 122-1 facing each other and a pair of rolling rolls 122-2 having a rotation axis perpendicular to the rotation axis of the pair of rolling rolls. By applying pressure from two directions perpendicular to the stretching direction of the first winding 150 and orthogonal to each other using the pair of rolling rolls 122-1 and the pair of rolling rolls 122-2, the first winding 150 is stretched and its nearly circular end face is formed into a square or nearly square rectangular shape (Figure 6B). Although not shown in the figures, the rolling mill 122 may be a mold equipped with a die hole having the end face shape required for the first winding 150, and the first rolling process may be performed by passing the first winding 150 through the die hole. Alternatively, a combination of a die hole and a rolling roll may be used as the rolling mill 122. The same applies to the rolling mills 128 and 136 described below.

[0028] The first winding 150 is then drawn out by the take-up machine 124 and used for the second twisting process. A known structure can be applied to the take-up machine 124, so a detailed explanation will be omitted, but for example, the take-up machine 124 can be made up of a pair of rollers, a pair of rotating belts, etc. The same applies to the take-up machines 130 and 138 described below.

[0029] Next, in the second twisting process, the second strands 102-2 are twisted onto the first winding 150 (i.e., the first strands 102-1 that have been twisted and then rolled). Specifically, bobbins 126 are arranged, each wound around more second strands 102-2 than the first strands 102-1. Similar to the first twisting process, multiple second strands 102-2 drawn from the bobbins 126 are brought together on the first winding 150, and the multiple bobbins 126 are made to revolve around the stretching direction of the first winding 150. The direction of revolving bobbins 126 at this time is opposite to that of the first twisting process (see the solid arrows in Figure 4). Through this process, multiple second strands 102-2 are twisted in a certain direction (opposite to the twisting direction of the first strands 102-1), and the second winding 152 is obtained.

[0030] Subsequently, similar to the first rolling process, the second winding 152 is rolled by the rolling mill 128 (second rolling process). In the second rolling process, tension is applied to the second winding 152 in the stretching direction, and pressure is applied to the second winding 152 by the rolling mill 128. The direction of the pressure applied in the second rolling process is the same as that in the first rolling process. As a result, the second winding 152 stretches and forms an end face having a square or nearly square rectangular shape around the first wire 102-1 (Figure 6C). The second layer is formed by the second wire 102-2. The second winding 152 is then drawn out by the taker 130 and subjected to the annealing process.

[0031] The annealing process involves melting and fluidizing the fusion layer 110 and allowing it to penetrate the gaps between the individual wires 102. The fluidized fusion layer 110 then cools and solidifies, functioning as an adhesive. As a result, the individual wires 102 contained in the first and second layers are firmly fixed, preventing problems such as delamination between them. In fact, the inventors have confirmed that without the annealing process, the adhesive force between the individual wires 102 is weak, which can cause the individual wires 102 to delaminate in the subsequent third twisting process, making it impossible to efficiently manufacture the flat rectangular twisted wire 100 and resulting in a low yield. Furthermore, the annealing process makes the conductors 104 of the first individual wire 102-1 and the second individual wire 102-2, which have hardened in the rolling process, softer than before the annealing process, and the conductivity of each conductor 104 becomes greater than that before the annealing process. The annealing process can be carried out, for example, by heat-treating the second winding 152 in a heating device 132. A known device can be used as the heating device 132, and for example, the heating device 132 can be composed of rollers or belts for conveying the second winding 152, a chamber that provides space for heating the second winding 152, and a heater for heating the chamber. The heating temperature in the annealing process should be above the melting point or glass transition temperature of the fused layer 110.

[0032] Next, a third twisting process is carried out. In this process, the third strand 102-3 is twisted onto the second winding 152 (i.e., the twisted and rolled first strand 102-1 and second strand 102-2). Specifically, as shown in Figure 5, multiple bobbins 134 are arranged, each wound with more third strands 102-3 than the second strand 102-2. Similar to the first twisting process, the multiple third strands 102-3 drawn from the bobbins 134 are brought together on the second winding 152, and the multiple bobbins 134 are made to revolve around the stretching direction of the second winding 152. The direction of revolving bobbins 134 at this time is the same as that of the first twisting process (see dotted arrow in Figure 5), and opposite to that of the second twisting process. In this process, multiple third strands 102-3 are twisted in a certain direction (the same direction as the twisting direction of the first strand 102-1) to obtain a third winding 154.

[0033] Subsequently, similar to the first rolling process, the third winding 154 is also rolled by the rolling mill 136 (third rolling process). In the third rolling process, tension is applied to the third winding 154 in the stretching direction, and pressure is applied to the third winding 154 by the rolling mill 136. The direction of the pressure applied in the third rolling process is the same as that in the first and second rolling processes. As a result, the third winding 154 stretches and forms an end face having a square or nearly square rectangular shape around the second wire 102-2 (Figure 6D). The third layer is formed by the third wire 102-3. Although not shown, an annealing process may also be performed on the rolled third winding 154. The third winding 154 is transported to the extruder 140 side by the taker 138 and then subjected to the coating process.

[0034] In the coating process, the surface of the third winding 154 is coated with a common insulating layer 108 using an extruder 140. A known extruder can be used as the extruder 140, so a detailed explanation is omitted, but the resin compressed by a screw (not shown) is heated and melted, and the molten resin is coated onto the surface of the third winding 154. The resin may then be cooled with a cooling device (not shown). The flat rectangular molded stranded wire 100 obtained through the coating process is wound onto a winding reel 142. Alternatively, the third winding 154 may be wound onto the winding reel 142 before forming the common insulating layer 108 on the third winding 154, and then the third winding 154 drawn from the winding reel 142 may be coated with the common insulating layer 108.

[0035] Here, the first strand 102-1, the second strand 102-2, and the third strand 102-3 before being subjected to the twisting process can be selected such that the diameter of the conductor 104 of the second strand 102-2 is less than or equal to the diameter of the conductor 104 of the first strand 102-1, and greater than or equal to the diameter of the conductor 104 of the third strand 102-3. Alternatively, the first strand 102-1, the second strand 102-2, and the third strand 102-3 before being subjected to the twisting process can be selected such that the diameter of the conductor 104 of the second strand 102-2 is smaller than the diameter of the conductor 104 of the first strand 102-1, and larger than the diameter of the conductor 104 of the third strand 102-3. For example, if the insulating coating 106 of the first strand 102-1, the second strand 102-2, and the third strand 102-3 before being subjected to the twisting process is set to a substantially constant thickness within the range of 3 μm to 7 μm, the diameter of the first strand 102-1 can be selected from the range of 0.28 mm to 0.95 mm, the diameter of the second strand 102-2 from the range of 0.25 mm to 0.85 mm, and the diameter of the third strand 102-3 from the range of 0.23 mm to 0.75 mm. Since the first strand 102-1, the second strand 102-2, and the third strand 102-3 are subjected to rolling processes three times, two times, and one time, respectively, they are stretched more and more in the order of the first strand 102-1, the second strand 102-2, and the third strand 102-3. Therefore, if strands 102 having conductors of the same diameter are used as the first strand 102-1, the second strand 102-2, and the third strand 102-3, the difference in diameter of each strand 102, i.e., the difference in diameter of each conductor 104, may become extremely large between the first strand 102-1, the second strand 102-2, and the third strand 102-3, depending on the tension and pressure applied in the rolling process and the twist pitch of the strands 102. However, by selecting each strand 102 such that the above relationship is satisfied, this problem can be resolved, and the cross-sectional area of ​​the conductor 104 of the strands 102 can be increased in the order of the first strand 102-1, the second strand 102-2, and the third strand 102-3. As a result, the flat rectangular molded stranded wire 100 can be constructed without creating a large resistance difference between the strands 102.

[0036] As described above, the flat rectangular molded stranded wire 100 according to one embodiment of the present invention includes first to third layers, each composed of a plurality of strands 102, and is configured such that the cross-sectional area of ​​the conductor 104 of the strands 102 increases in the order from the first to the third layer. Therefore, the resistance of the strands 102 is substantially the same among the first to the third layers, and a stranded wire with suppressed characteristic variations can be provided.

[0037] (Variation 1) As a variation, the flat rectangular molded stranded wire 200 shown in Figure 1 may have a structure without the third strand 102-3 (Figure 7A). The flat rectangular molded stranded wire 200 forms a two-layer structure, and each layer is composed of multiple strands 102. Specifically, the flat rectangular molded stranded wire 200 includes a plurality of (e.g., 2 to 10) first strands 102-1 arranged in its central part, and a plurality of (e.g., 6 to 24) second strands 102-2 arranged to surround the plurality of first strands 102-1. The plurality of first strands 102-1 and the plurality of second strands 102-2 constitute the first and second layers, respectively. The second strands 102-2 constituting the second layer are located on the outermost side within the common insulating layer 108 and are in direct contact with the common insulating layer 108 or adjacent to the common insulating layer 108 via the fusion layer 110. The first strand 102-1 constituting the first layer is located inward relative to the second strand 102-2 and is adjacent to one or more of the second strands 102-2. The first strand 102-1 may be in direct contact with one or more of the second strands 102-2, or it may be adjacent via the fusion layer 110. The first strand 102-1 is separated from the common insulating layer 108.

[0038] The number of second strands 102-2 constituting the second layer is greater than the number of first strands 102-1 constituting the first layer. The difference between the number of second strands 102-2 and the number of first strands 102-1 is preferably 5 or 6. By setting the number of first strands 102-1 and second strands 102-2 as described above, the second strands 102-2 can be arranged at high density around the first strands 102-1, and as a result, a high conductor space factor of 80% or more (approximately 85% in this embodiment) can be achieved. As the conductor space factor increases, the amount of current flowing through the flat rectangular molded stranded wire 200 can be increased, so the flat rectangular molded stranded wire 200 contributes to the increased efficiency and miniaturization of electromagnetic circuits, motors, and reactors.

[0039] Other structural features of the rectangular molded stranded wire 200 are the same as those of the first strand 102-1 and the second strand 102-2 in the rectangular molded stranded wire 100, so a detailed explanation is omitted.

[0040] The manufacturing method for the rectangular-shaped stranded wire 200 is the same as that for the rectangular-shaped stranded wire 100 up to the second rolling step shown in Figure 3, and after the second rolling step, a coating step of the common insulating layer 108 is performed.

[0041] (Modification 2) As another variation, a flat rectangular molded stranded wire 300 may be provided in which a fourth strand 102-4 is provided between the third strand 102-3 and the common insulating layer 108, as shown in Figure 1 (Figure 7B). The flat rectangular molded stranded wire 300 forms a four-layer structure, with each layer composed of multiple strands 102. Specifically, the flat rectangular molded stranded wire 300 further includes a plurality of (e.g., 11 to 56) fourth strands 102-4 provided so as to surround the plurality of third strands 102-3 in the flat rectangular molded stranded wire 100, thereby forming a fourth layer. The fourth strands 102-4 constituting the fourth layer are located on the outermost side within the common insulating layer 108 and are in direct contact with the common insulating layer 108 or adjacent to the common insulating layer 108 via the fusion layer 110. The average cross-sectional area of ​​the conductor 104 of the third strand 102-3 is less than or equal to the average cross-sectional area of ​​the conductor 104 of the fourth strand 102-4. The twist pitch P4 of the fourth strand 102-4 is greater than the twist pitch P3 of the third strand 102-3 (for example, 40 mm or more and 60 mm or less). Also, the fourth strand 102-4 is twisted in the opposite direction to the twist direction of the third strand 102-3. The difference between the number of third strands 102-3 and the number of fourth strands 102-4 is preferably 5 to 20.

[0042] By setting the number of the first strand 102-1, the second strand 102-2, the third strand 102-3, and the fourth strand 102-4 as described above, the conductors can be arranged at high density, resulting in a high conductor space factor of 80% or more (approximately 85% in this embodiment). As the conductor space factor increases, the amount of current flowing through the flat rectangular molded stranded wire 300 can also be increased, thus contributing to the increased efficiency and miniaturization of electromagnetic circuits, motors, and reactors.

[0043] If the insulating coating 106 of the first strand 102-1, second strand 102-2, third strand 102-3, and fourth strand 102-4 before being subjected to the twisting process is set to a substantially constant thickness within the range of 3 μm to 7 μm, the diameter of the fourth strand 102-4 can be selected from the range of 0.20 mm to 0.70 mm. In the flat rectangular molded stranded wire 300, the cross-sectional area of ​​the conductor 104 of the strand 102 can be increased in the order of the first strand 102-1, second strand 102-2, third strand 102-3, and fourth strand 102-4. As a result, similar to the flat rectangular molded stranded wire 100, the flat rectangular molded stranded wire 300 can be constructed in such a way that it does not create a large resistance difference between the strands 102.

[0044] Other structural features of the rectangular-shaped stranded wire 300 are the same as those of the first strand 102-1, second strand 102-2, and third strand 102-3 in the rectangular-shaped stranded wire 100, so a detailed explanation is omitted.

[0045] In the manufacturing method of the flat rectangular stranded wire 300, after the third rolling step shown in Figure 3, a fourth twisting step and a fourth rolling step are further included, followed by a coating step of the common insulating layer 108.

[0046] The embodiments described above as embodiments of the present invention can be combined and implemented as appropriate, insofar as they do not contradict each other. Furthermore, devices based on the display devices of each embodiment, in which a person skilled in the art has added, deleted, or modified components, or added, omitted, or modified processes, are also included within the scope of the present invention, as long as they retain the essence of the present invention.

[0047] Any effects or benefits other than those brought about by the embodiments described above, if they are clear from the description herein or easily predictable to a person skilled in the art, are naturally considered to be brought about by the present invention. [Explanation of Symbols]

[0048] 100: Flat rectangular stranded wire, 102: Strand, 102-1: First strand, 102-2: Second strand, 102-3: Third strand, 102-4: Fourth strand, 104: Conductor, 106: Insulating coating, 108: Common insulating layer, 110: Fusion layer, 120: Bobbin, 122: Rolling mill, 124: Taker, 126: Bobbin, 128: Rolling mill, 130: Taker, 132: Heating device, 134: Bobbin, 136: Rolling mill, 140: Extruder, 142: Winding reel, 150: First winding, 152: Second winding, 154: Third winding

Claims

1. A plurality of first strands twisted in a first direction, and The plurality of second strands are twisted on the plurality of first strands in a second direction opposite to the first direction, Each of the plurality of first strands and each of the plurality of second strands has a conductor containing metal and an insulating film covering the conductor. The plurality of first wires and the plurality of second wires are fixed by a fusion layer. The average value of the cross-sectional areas of the multiple second strands is greater than the average value of the cross-sectional areas of the multiple first strands. A flat rectangular molded stranded wire in which the twist pitch of the plurality of second strands is greater than the twist pitch of the plurality of first strands.

2. The number of the aforementioned plurality of first strands is 2 or more and 10 or less. The flat rectangular stranded wire according to claim 1, wherein the number of the plurality of second strands is 6 or more and 24 or less, and is greater than the number of the plurality of first strands.

3. Multiple first strands twisted in a first direction, A plurality of second strands twisted in a second direction opposite to the first direction on the plurality of first strands, and It includes a plurality of third strands twisted in the first direction on the plurality of second strands, Each of the plurality of first strands, the plurality of second strands, and the plurality of third strands has a conductor containing metal and an insulating coating covering the conductor. The plurality of first wires, the plurality of second wires, and the plurality of third wires are fixed by a fusion layer. The average value of the cross-sectional areas of the plurality of second strands is greater than the average value of the cross-sectional areas of the plurality of first strands, and less than the average value of the cross-sectional areas of the plurality of third strands. A flat rectangular stranded wire in which the twist pitch of the plurality of second strands is greater than the twist pitch of the plurality of first strands and smaller than the twist pitch of the third strand.

4. The number of the aforementioned plurality of first strands is 2 or more and 10 or less. The number of the plurality of second strands is 6 or more and 24 or less, and is greater than the number of the plurality of first strands. The flat rectangular stranded wire according to claim 3, wherein the number of the plurality of third strands is 10 or more and 35 or less, and is greater than the number of the plurality of second strands.

5. Multiple first strands twisted in a first direction, A plurality of second strands twisted on the plurality of first strands in a second direction opposite to the first direction, A plurality of third strands twisted in the first direction on the plurality of second strands, and It includes a plurality of fourth strands twisted in the second direction on the plurality of third strands, Each of the plurality of first strands, the plurality of second strands, the plurality of third strands, and the plurality of fourth strands has a conductor containing metal and an insulating coating covering the conductor. The plurality of first wires, the plurality of second wires, the plurality of third wires, and the plurality of fourth wires are fixed by a fusion layer. The average value of the cross-sectional areas of the plurality of second strands is greater than the average value of the cross-sectional areas of the plurality of first strands, the average value of the cross-sectional areas of the plurality of third strands is greater than the average value of the cross-sectional areas of the plurality of second strands, and smaller than the average value of the cross-sectional areas of the plurality of fourth strands. The twist pitch of the plurality of second strands is greater than the twist pitch of the plurality of first strands and smaller than the twist pitch of the third strand. A flat rectangular molded stranded wire in which the twist pitch of the fourth strand is greater than the twist pitch of the third strand.

6. The number of the aforementioned plurality of first strands is 2 or more and 10 or less. The number of the plurality of second strands is 6 or more and 24 or less, and is greater than the number of the plurality of first strands. The number of the plurality of third strands is 10 or more and 35 or less, and is greater than the number of the plurality of second strands. The flat rectangular stranded wire according to claim 5, wherein the number of the plurality of fourth strands is 11 or more and 56 or less, and is greater than the number of the plurality of third strands.

7. The flat rectangular molded stranded wire according to any one of claims 1 to 6, further comprising a common insulating layer covering the plurality of strands in the outermost layer.

8. The flat rectangular molded stranded wire according to claim 7, having a conductor space factor of 80% or more.

9. A process of twisting multiple first strands in a first direction to form a first winding, The process of rolling the first winding, A step of forming a second winding by twisting a plurality of second wires in a second direction opposite to the first direction on the rolled first winding, The process of rolling the second winding, A step of annealing the rolled second winding, A step of forming a third winding by twisting a plurality of third wires in the first direction on the annealed second winding, and The process includes rolling the third winding, Each of the plurality of first strands, the plurality of second strands, and the plurality of third strands has a conductor containing metal and an insulating coating covering the conductor. A method for manufacturing a flat rectangular stranded wire, wherein in the third winding after rolling, the average value of the cross-sectional areas of the conductors of the plurality of second strands is greater than the average value of the cross-sectional areas of the conductors of the plurality of first strands and less than the average value of the cross-sectional areas of the conductors of the plurality of third strands.

10. The method for manufacturing a flat rectangular stranded wire according to claim 9, wherein the average value of the cross-sectional areas of the conductors of the plurality of second strands before twisting is less than or equal to the average value of the cross-sectional areas of the conductors of the plurality of first strands before twisting, and is greater than or equal to the average value of the cross-sectional areas of the conductors of the plurality of third strands before twisting.

11. The number of the aforementioned plurality of first strands is 2 or more and 10 or less. The number of the plurality of second strands is 6 or more and 24 or less, and is greater than the number of the plurality of first strands. The method for manufacturing a flat rectangular stranded wire according to claim 9, wherein the number of the plurality of third strands is 10 or more and 35 or less, and is greater than the number of the plurality of second strands.

12. A step of twisting a plurality of fourth wires in the second direction on the third winding to form a fourth winding, and The process further includes rolling the fourth winding, The plurality of fourth strands each have a conductor containing metal and an insulating film covering the conductor. The method for manufacturing a flat rectangular stranded wire according to claim 9, wherein in the fourth winding after rolling, the average value of the cross-sectional areas of the plurality of third strands is smaller than the average value of the cross-sectional areas of the plurality of fourth strands.

13. The method for manufacturing a flat rectangular stranded wire according to claim 12, wherein the average value of the cross-sectional areas of the conductors of the plurality of third strands before twisting is equal to or greater than the average value of the cross-sectional areas of the conductors of the plurality of fourth strands before twisting.

14. The number of the aforementioned plurality of first strands is 2 or more and 10 or less. The number of the plurality of second strands is 6 or more and 24 or less, and is greater than the number of the plurality of first strands. The number of the plurality of third strands is 10 or more and 35 or less, and is greater than the number of the plurality of second strands. The method for manufacturing a flat rectangular stranded wire according to claim 12, wherein the number of the plurality of fourth strands is 11 or more and 56 or less, and is greater than the number of the plurality of third strands.

15. Each of the plurality of strands further has a fusion layer covering the insulating film, The method for manufacturing a rectangular stranded wire according to any one of claims 9 to 14, wherein the annealing is performed at a temperature above the melting point of the fused layer.

16. A method for manufacturing a rectangular molded stranded wire according to any one of claims 9 to 14, further comprising the step of forming a common insulating layer that covers the outermost winding of the rectangular molded stranded wire.

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