Choke coil

Abstract

To provide a choke coil which can be suitable for a high frequency circuit with a high space factor and a high producibility.SOLUTION: A choke coil 10 is a choke coil formed by arranging a pair of core pieces 20 and 20 so as to face an end surface of a division core, in which the pair of core pieces comprises: an arc-like division core 31 which becomes a toroidal shape by facing both end surface 32 and 32a; an insulation coated material 34 that performs an electric insulation coating of each division core, and has flanges 35 and 35 projected toward an outer direction from each end surface of each division core; a coated wire 40 wound to an outer periphery of the insulation coated material; and terminals 50 and 50 to which the coated wire is electrically connected and provided to the neighbor of each flange. A plurality of coated wires is wound in parallel without twisting at the outer periphery of the insulation coated material, and each coated wire is electrically connected with each terminal.SELECTED DRAWING: Figure 8

Description

[Technical Field]

[0001] The present invention relates to a choke coil used in high-frequency current suppression circuits, waveform shaping circuits, power factor correction circuits, and various switching power supply circuits in devices that handle alternating current, such as switching power supplies and inverter equipment. More specifically, the present invention relates to a choke coil that has a toroidal shape and is used in switching power supply circuits that are driven at a high frequency (frequency f) of approximately 10 kHz to 150 kHz, and that has a high space factor winding, but which is manufactured efficiently by making use of an automatic winding device using machinery, thereby achieving high quality and stable supply. [Background technology]

[0002] Choke coils used in the power supply circuits and high-frequency circuits of various AC devices are made by winding coated wire (magnet wire) multiple times around a toroidal core covered with an insulating coating material formed by a bobbin or surface treatment.

[0003] To wind a coated wire around a toroidal core, the coated wire must be passed through a central window and pulled out, a process that must be repeated for the required number of turns depending on the required characteristics. To miniaturize choke coils, the central window of the toroidal core must be designed to be as small as possible. This makes the winding difficult to mechanize and must be done manually. However, for relatively thin wire diameters, such as 0.8 mm or less, several hundred turns are required. For thicker wire diameters, such as 2.0 mm or more, the coated wire is hard, making it difficult to work with, even though the number of turns is small, resulting in a heavy burden on the worker, making continuous mass production difficult.

[0004] To solve the above-mentioned problems with windings, a choke coil has been proposed in which arc-shaped split cores are insulated, core pieces are wound with coated wire, and the core pieces are then reassembled to form a toroidal shape (see, for example, Patent Documents 1 and 2). The coated wire starts at one end edge of the split core, is wound around the body of the split core, and then is wound so as to terminate at the other end edge. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Microfilm of Utility Model Application No. 01-98725 (Utility Model Application No. 03-38603) [Patent Document 2] Japanese Patent Application Laid-Open No. 2001-52945 Summary of the Invention [Problem to be solved by the invention]

[0006] In recent years, the speed of power semiconductor elements used in switching power supplies and inverter equipment has increased dramatically, and there is a demand for the choke coils used in these power supply circuits to be smaller and have reduced high-frequency loss suitable for high-frequency circuits. Loss in a choke coil consists of iron loss and copper loss, and iron loss depends on the magnetic material used in the core.

[0007] On the other hand, one of the causes of copper loss is the DC resistance loss of the winding. To reduce the DC resistance loss of the winding, it is necessary to increase the ratio of the copper wire portion of the covered wire to the core, which is called the space factor. In the cases of Patent Documents 1 and 2, increasing the space factor and using a covered wire with a larger diameter while ensuring the number of turns around the divided core is effective for reducing the DC resistance loss. However, winding a covered wire with a larger diameter multiple times around an arc-shaped divided core is difficult, not only by machine but also by hand, and is not practical because it can cause the covered wire to shift position or become distorted when wound.

[0008] The second cause of copper loss is the skin effect caused by high frequency current. As the frequency f increases, the internal resistance of the copper wire increases, causing the current to tend towards the surface. In the case of copper wire, the skin depth is 66.1 / f 1 / 2 It is expressed in mm, and it is known that a decrease in the effective cross-sectional area of ​​the copper wire increases losses and leads to heat generation, so the copper wire diameter in the choke coil must be selected to suit the frequency f, and the number of wires with a cross-sectional area according to the current capacity must be prepared.

[0009] One possible solution is to wind a litz wire (reference numeral 91 in FIGS. 13 to 15 ) around the split core 31. The wires 92 each have a cross-sectional area corresponding to the current capacity and are twisted together to prevent the wires from coming apart. However, as will be shown in the examples described below, the litz wire 91 has large gaps s between the copper wires 92, a bulky coating, and large gaps S between the thickly twisted wires, resulting in a poor space factor. As a result, the number of turns around the central window of the toroidal core is significantly reduced, resulting in an increased core size. Furthermore, the litz wire 91 tends to unwind during and after winding due to its residual stress (restoring force), resulting in a problem of bulging and increasing the size of the finished product. Furthermore, the litz wire must be specially designed and prepared for each frequency, with wire diameters and twist counts required, which inevitably requires time and money.

[0010] An object of the present invention is to provide a choke coil that has a high space factor and is suitable for high-frequency circuits with high manufacturing efficiency. [Means for solving the problem]

[0011] The choke coil according to the present invention comprises: an arc-shaped split core that forms a toroidal shape by arranging the end faces facing each other; an insulating coating material that electrically insulates the split core and has flanges that protrude outward from each end face of the split core; a coated wire wound around the outer periphery of the insulating coating material; terminals to which the coated wires are electrically connected and provided near the flanges; A pair of core pieces comprising: A choke coil in which the end faces of the split cores are arranged to face each other, A plurality of the coated wires are wound in parallel without being twisted around the outer periphery of the insulating coating material, and each coated wire is electrically connected to the terminal.

[0012] The coated wire is wound in layers around the circumferential surface of the insulating coating material, and the inner circumferential surface of the insulating coating material may be configured such that a first layer consisting of one coated wire is stacked on the side closer to the inner circumferential surface, and a second layer consisting of one coated wire is stacked around the first layer.

[0013] The coated wire can be folded back and wound around the terminal.

[0014] A plurality of coated wires can be wound around the insulating coating material without folding back.

[0015] It is desirable that the coated wire be wound so that the center bulges out on the inner peripheral surface of the insulating coating material.

[0016] The terminal can be electrically connected to the coated wire by resistance welding, a welding method, or soldering.

[0017] The choke coil product of the present invention is constructed by coating the outer periphery of the above-described choke coil with a resin. [Effects of the Invention]

[0018] According to the choke coil of the present invention, each core piece is wound with multiple covered wires in parallel, achieving a higher winding density than Litz wire and ensuring a higher space factor. This allows for a more compact and high-performance choke coil. Since the covered wire is wound around an insulating, arc-shaped divided core, it can be manufactured using an automated winding device, improving manufacturing efficiency. In particular, in a configuration in which multiple covered wires are wound in layers, a first layer consisting of one covered wire is stacked on the inner circumferential surface of the core piece, and a second layer consisting of one covered wire is stacked on the outer circumferential surface of the core piece, thereby providing the advantage of stable winding of the covered wire without misalignment, collapse, or unevenness of the covered wire.

[0019] Furthermore, a toroidal choke coil can be obtained by butting the end faces of a pair of core pieces together, which also improves the manufacturing efficiency of the choke coil as much as possible.

[0020] As mentioned above, the coated wire can be made by winding multiple single copper wires in parallel, eliminating the need for expensive Litz wires that require special designs. This means that costs can be reduced compared to Litz wires, and because it is not twisted, the space factor is high and the number of wires can be set as desired.

[0021] The choke coil of the present invention is suitable for use in high-frequency current suppression circuits, waveform shaping circuits, power factor correction circuits, and various switching power supply circuits in devices that handle AC, such as switching power supplies and inverter equipment. Furthermore, because the coated wire can be wound stably without misalignment, collapse, or variation, variations in the frequency characteristics and inductance characteristics of high-frequency choke coils due to these factors can be reduced. In particular, the choke coil can be used in switching power supply circuits driven at high frequencies (frequency f) of approximately 10 kHz to 150 kHz. While the choke coil has a toroidal shape, which is an efficient ideal magnetic circuit, it also has a high space factor. By utilizing an automated winding machine, high manufacturing efficiency, high quality, and stable supply can be achieved. [Brief explanation of the drawings]

[0022] [Figure 1] FIG. 1 is a perspective view of a choke coil according to the present invention. [Figure 2] FIG. 2 is a perspective view of a split core whose surfaces except for the end surfaces are coated with resin. [Figure 3] FIG. 3 is a perspective view of a core piece around which a covered wire is wound (before a terminal is attached). [Figure 4] FIG. 4 is a plan view of FIG. [Figure 5] FIG. 5 is a cross-sectional view of the core piece, showing steps (a) to (c) of winding the covered wire in layers. [Figure 6]FIG. 6 shows (a) a cross-sectional view of a core piece around which a covered wire (only the central window side is shown) is wound, and (b) an enlarged view of the enclosed portion A. [Figure 7] FIG. 10 is a cross-sectional view showing a state in which the coated wire is wound until the central window on the inner periphery side of the core piece is almost closed. [Figure 8] FIG. 8 is a perspective view of a pair of core pieces before terminals are attached, arranged so that their end faces face each other. [Figure 9] FIG. 9 is a perspective view of a pair of core pieces with terminals attached, arranged so that their end faces face each other. [Figure 10] FIG. 10 is a set of explanatory diagrams (a) to (c) showing the process of clamping and fusing a covered wire into a terminal. [Figure 11] FIG. 11 is a perspective view showing the process of attaching the core piece to the casing. [Figure 12] FIG. 12 is a perspective view of a choke coil product in which the choke coil of the present invention is housed in a casing by being covered with resin. [Figure 13] FIG. 13 shows (a) a cross-sectional view of a core piece wound with a litz wire for comparison, and (b) a cross-sectional view of a core piece wound with a litz wire until the central window is almost completely closed. [Figure 14] FIG. 14 is an enlarged view of the boxed area B in FIG. [Figure 15] FIG. 15 is an explanatory diagram comparing the space factor of (a) the core piece of the present invention and (b) a core piece wound with a Litz wire. DETAILED DESCRIPTION OF THE INVENTION

[0023] A choke coil 10 according to one embodiment of the present invention will be described below with reference to the drawings.

[0024] 1 is a perspective view of the appearance of a choke coil 10 according to one embodiment of the present invention. As will be described in detail below with reference to the manufacturing process, the choke coil 10 is configured by placing arc-shaped core pieces 20, 20, around which a coated wire 40 is wound, on a resin base 60. End edges 40a, 40a of the coated wire 40 are electrically connected to terminals 50, respectively. Three terminals 50 are shown in the figure.

[0025] The choke coil 10 having the above configuration can be fabricated in the following manner.

[0026] The core piece 20 is constructed by winding a covered wire 40 around the outer periphery of the trunk portion of a covered core 30 shown in FIG. 2 as shown in FIGS. 3 and 4, and by attaching a terminal 50 as shown in FIG.

[0027] As shown in Fig. 2, the coated core 30 is configured by covering the outer periphery of an arc-shaped split core 31 (the cross-sectional shape of the split core 31 is shown in Fig. 5) made of a magnetic material with a bobbin 34 made of an electrically insulating coating material. More specifically, the split core 31 is covered with the bobbin 34 except for the end faces 32, 32a. Note that instead of the bobbin 34, an insulating coating material formed by surface treatment can also be used.

[0028] The inside of the coated core 30 may have an arc-shaped configuration with a semicircular recess that will form the central window 21 of the toroidal core. The pair of coated cores 30, 30 are arranged with their end faces 32, 32a facing each other to form a ring-shaped body in a planar view. The coated cores 30, 30 (split cores 31, 31) may be combined to form an elliptical, track-shaped, rectangular, or other shape in a planar view. The cross-sectional shape of the split core 31 is not limited, but is shown as a substantially rectangular shape in the figure. Examples of the split core 31 include dust cores and ferrite cores formed by compacting and sintering magnetic powder. The arc-shaped split cores 31 can be cut from a toroidal shape or pre-formed into an arc shape. However, because dust cores are affected by high molding pressure, it is preferable to cut the toroidal shape rather than pre-form it into an arc shape. Furthermore, when the ferrite core is fired into an arc shape, the shape of the end faces 32, 32a that become the abutment surfaces is affected by firing deformation, so it is desirable to cut the toroidal shape. In either case, the cut split core has better magnetic properties, so it is desirable to create the split cores by cutting the toroidal shape.

[0029] The bobbin 34 can be produced by forming an insulating resin on the outer periphery of the split core 31 by insert molding or the like, and can have flanges 35, 35 protruding from the end faces 32, 32a of the split core 31.

[0030] The coated core 30 can be produced, for example, by insert-molding a toroidal core to coat the bobbin 34, and then cutting along the flange 35. Cutting can be performed using a water-cooled grindstone rotary cutting, a wire saw, fiber laser cutting using a laser, water laser cutting, or the like.

[0031] A coated wire 40 is wound around the coated core 30 from one end face 32 to the other end face 32a to form the core piece 20 as shown in Figures 3 and 4. The coated wire 40 may be a solid wire, and may be an insulating coated copper wire such as a magnet wire, or a fusion wire with an additional fusion function on the surface of the insulating coating.

[0032] Specifically, as shown in the figures, the covered wire 40 is formed by winding multiple single-wire covered wires 40 in parallel around the covered core 30. For example, as shown in Fig. 5(a), first, the first covered wire 41 is wound around the covered core 30. The first covered wire 41 is wound along the inner circumferential surface of the covered core 30 (on the side of the central window 21) until it almost completely fills the inner circumferential surface, thereby forming a first layer 41b of the covered wire 40. It is desirable that the end edge of the covered wire 41 protrude outside the flange 35, as shown by reference numeral 40a in Figs. 3 and 4 and reference numeral 41a in Fig. 5(a).

[0033] Next, as shown in FIG. 5(b), the second covered wire 42 is wound. The second covered wire 42 is wound so that it overlaps the first layer 41b on the side of the central window 21 to form a second layer 42b (see FIG. 6(b), where only the covered wire on the side of the central window 21 is shown). The second covered wire 42 is preferably wound so that it fits into the valleys formed between the first covered wires 41 that are in close contact with each other in the first layer 41b, forming a stacked state similar to that of a rice bag. This reduces the gap s between the covered wires 41, 42, thereby improving the space factor. The second covered wire 42 is wound so that it fits into the gaps between the first covered wires 41 that are adjacent to each other on the outer periphery of the covered core 30. The end edge of the second covered wire 42, like the first covered wire, is protruded outside the flange portion 35 as shown by reference numeral 40a in FIGS. 3 and 4 and reference numeral 42b in FIG. 5(b).

[0034] Furthermore, as shown in FIG. 5(c), a third covered wire 43 is wound. The third covered wire 43 is wound on the central window 21 side so as to fit into the valley portion formed between the second adjacent covered wires 42, similar to the second layer 42b (see FIG. 6(b)). The third covered wire 43 is wound on the outer periphery of the covered core 30 so as to fit between the first and second covered wires 41, 42 if there is a gap between them, or so as to fit into the valley portion between these covered wires 41, 42 if there is no gap. The edge of the third covered wire 43 also extends outside the flange 35, as shown by reference numeral 40a in FIGS. 3 and 4 and reference numeral 43b in FIG. 5(c).

[0035] In the above manner, the coated wire 40 can be wound in layers according to the required performance. FIG. 6 shows a core piece 20 in which the coated wire 40 (41-47) is wound around the coated core 30 in seven layers (41b-47b) (only the coated wire is shown on the side facing the center window 21), and an enlarged view of the enclosed area A. In enlarged view 6(b), the coated wire 40 is wound in seven overlapping layers, as indicated by the reference numerals 1-7, on the side facing the center window 21 of the coated core 30. If each of the coated wire layers has 35 turns, then the seven-layer parallel winding results in 7 x 35 = 245 turns, forming a coil suitable for high frequencies.

[0036] 7 shows the state in which the coated wire 40 has been wound until the central window 21 of the coated core 30 is almost completely filled. In the illustrated example, the coated wire 40 is wound in 10 overlapping layers, so that the central window 21 side is slightly bulging toward the center of the arc, that is, the winding is performed so that it is in contact with the line connecting the end faces 32, 32a. As a result, if the number of windings of one coated wire 40 is 35 turns, as in the above, a total of 10 layers of parallel winding (10 x 35 = 350 turns) can be applied. This allows for the formation of a coil that is even more suitable for high frequencies.

[0037] The covered wire 40 can be wound in the same direction from one end face 32 to the other end face 32a of the covered core 30, i.e., without turning back. Alternatively, the covered wire 40 may be wound from one end face 32 to the other end face 32a (forward winding) and then turned back from the end face 32a to the end face 32 (return winding). In this case, the covered wire 40 is turned back 180 degrees from the forward winding and wound in the opposite direction on the return winding, i.e., the covered wire 40 is wound around the covered core 30 in the same winding direction as seen from the one end face 32. Either method can be used to automatically wind the covered wire 40 using an automatic winding device with a nozzle, such as a flyer-type winding machine. This allows for precise winding of the covered wire 40 and accurate control of the number of turns. Furthermore, the use of an automatic winding device enables high manufacturing efficiency, high quality, and stable supply.

[0038] While winding the covered wire 40, it is desirable to clamp the end edges 41a, etc. of the already wound covered wire 40 with a jig in order. This prevents the end edges 41a, etc. from varying or unwinding. Note that instead of using a jig, the end edges may be clamped in order at the bent portion 51 of the terminal 50 (see FIG. 9).

[0039] Then, as shown in FIG. 9, a terminal 50 is attached to the covered wire 40 wound around the core piece 20, and the end edge 40a (41a to 47a) of the covered wire 40 is electrically connected to the terminal 50. For example, the terminal 50 may have an external contact portion 52 formed on the lower side and a bent portion 51 formed on the upper side that sandwiches the covered wire 40, as shown in FIG. 10(a). In this case, first, as shown in FIG. 10(a), the end edge 40a (41a to 47a) of the covered wire 40 (41 to 47) is sandwiched between the bent portion 51, and as shown in FIG. 10(b), the bent portion 51 is bent with electrode terminals 80, 81 for fusing, which is thermal crimp welding using electrical resistance, and a fusing process is performed. This removes the insulating coating from the end edge 40a (41a to 47a) of the covered wire 40 (41 to 47), and the end edge 40a and the terminal 50 can be electrically and structurally connected as shown in FIG. 10(c). The insulated wire 40 and the terminal 50 may be joined by various welding methods such as resistance welding, TIG welding, and plasma welding, or by soldering after mechanical stripping or stripping the coating using chemicals such as strong acids or strong alkalis. Either method can be used to remove the insulating coating from the insulated wire 40 and electrically connect it to the terminal 50.

[0040] Two core pieces 20, each electrically connecting the terminal 50 and the coated wire 40, are then paired together, and the end faces 32, 32a of one split core 31 are butted against the end faces 32, 32a of the other split core 31, and the flanges 35, 35 of the other split core 31 are also butted against each other. Then, as shown in Fig. 11, the split cores are placed on a base 60, thereby obtaining the choke coil 10 shown in Fig. 1. To obtain the desired DC superposition characteristics (inductance vs. current), the end faces of the split cores 31, 31 may be butted against each other in close contact, or an electrically insulating spacer may be inserted to form a gap.

[0041] The resulting choke coil 10 allows the covered wire 40 to be densely wound around each core piece 20, increasing the space factor of the covered wire 40 to 60% to 70% or more, as shown in FIG. 15 (described later). Improving the space factor of the choke coil 10 increases inductance and also allows the choke coil 10 itself to be made smaller, lighter, more efficient, and have lower DC resistance. In particular, the covered wire 40 can be made of a general-purpose solid wire of various diameters, such as a magnet wire, eliminating the need for a specially designed, expensive, and time-consuming litz wire. This reduces costs and shortens manufacturing lead times compared to litz wire. Furthermore, because the wire is not twisted, the space factor is high and the number of wires can be freely selected.

[0042] Furthermore, since the core pieces 20 are formed with flanges 35, 35, electrical insulation is achieved between the covered wires 40, 40 of the core pieces 20, 20, preventing electrical contact or short circuit between them. It is desirable to achieve electrical insulation between the covered wires 40, 40 by inserting an electrically insulating resin plate or the like on the central window 21 side of the core pieces 20, 20.

[0043] The choke coil 10 is simply constructed by placing core pieces 20, 20 on a base 60. Because the core pieces 20, 20 are not fixed to each other, gaps may form where the pieces meet, causing them to open up. While adhesive is typically used to secure the core pieces 20, as shown in FIG. 12, the choke coil 10 can be resin-coated using insert molding or resin casting (potting) and then housed in a casing 70 to produce a choke coil product 11. Enclosing the choke coil 10 in the casing 70 improves heat dissipation characteristics and promotes uniform heat distribution. The casing 70 can be made of a highly thermally conductive resin or have a heat sink. Furthermore, as shown in FIG. 12, heat dissipation can be further improved by flattening the top surface of the casing 70 and increasing the contact area with a heat sink or chassis to facilitate heat dissipation. The casing 70 has a flat top surface, and the insulating and heat dissipating functions of the casing 70 enable improved heat dissipation, including set mounting, without the need for an insulating silicone sheet with high thermal conductivity.

[0044] The choke coil product 11 having the above configuration can be mounted on a substrate or the like and used as a choke coil in noise prevention circuits, waveform shaping circuits, resonant circuits, various switching circuits, and the like in AC devices such as power supply circuits and inverters. The choke coil product 11 of the present invention can be suitably used as a choke coil to counter high-frequency distortion currents in circuits equipped with power factor correction circuits in switching power supplies and the like used as choke coil products for high frequencies above 10 kHz, and can also be used as an impedance matching or high-frequency smoothing choke coil. However, even for high-frequency applications, it is not suitable for filter applications that obtain attenuation at high frequencies, such as common mode choke coils or normal mode choke coils.

[0045] The above description is for the purpose of explaining the present invention, and should not be construed as limiting the invention described in the claims or narrowing its scope. Furthermore, the configuration of each part of the present invention is not limited to the above embodiment, and various modifications are possible within the technical scope described in the claims. [Example]

[0046] We created a core piece 20 consisting of a parallel-wound coated wire 40 of the present invention and a core piece 90 wound with a litz wire 91, and compared their space factors. The inventive example had 245 turns, with 7 layers of 35 turns each, as shown in Figure 6. The comparative example had 7 strands of litz wire 91 wound around the outer periphery of the coated core, as shown in Figure 13(a), and then wound 35 turns, as shown in Figure 13(b), for a total of 245 turns. A cross-sectional view of the winding portion of the coated wire 40 of the inventive example is shown in Figure 6(b), and a cross-section of the enclosed area B in Figure 13(b) for the core piece 90 of the comparative example is shown in Figure 14. Furthermore, the clearance areas that do not contribute to the space factor are shown in black in Figures 6(b) and 14(b) in Figures 15(a) and (b), respectively.

[0047] 6(a) and 13(b), even with the same number of turns, the inventive example can be wound thinner without bulging toward the center window 21 compared to the comparative example. This is evident from comparing FIG. 6(b) with FIG. 14, in the inventive example, the coated wires 40 are tightly packed together and wound in layers without any clearance, whereas in the comparative example, gaps exist between the litz wires 91 and even between the copper wires 92 that make up the litz wire 91. More specifically, as shown by the black dots in FIG. 15(a) and FIG. 15(b), the inventive example has relatively small gaps s between the coated wires 40 (40-47), while the comparative example is wound with gaps S between the litz wires 91 in addition to the gaps s between the copper wires 92. As a result, the space factor of the inventive example was approximately 65%, while that of the comparative example was approximately 45%, a space factor that was approximately 20% lower. By improving the space factor by 20% with the same core size, the inductance value can be increased by 1.2 squared (1.44). In other words, to achieve the same performance, the core size of the example can be reduced by approximately 20% compared to the comparative example.

[0048] In the example of the invention, since a single coated wire 40 can be used, there is a greater degree of freedom in the wire diameter and material compared to the Litz wire 91. In the example of the invention, simply increasing the wire space factor by 10% (for example, increasing the wire diameter from 0.5 mm to 0.55 mm) can reduce copper loss (DC resistance) and heat generation by approximately 17%. [Explanation of symbols]

[0049] 10 Choke coil 11 Choke coil products 20 Core Pieces 21 Central window 30 coated core 31 Split Core 32 End face 32a End face 34 Bobbin 35 Tsuba 40(41~47) coated wire 40a(41a~47a) Edge 50 terminals

Claims

1. an arc-shaped split core having end faces facing each other to form a toroidal shape; an insulating covering material that electrically insulates the split core and has flanges that protrude outward from each end face of the split core; A coated wire wound around the outer periphery of the insulating coating material; terminals to which the coated wires are electrically connected and provided near the flanges; A pair of core pieces comprising: A choke coil in which the end faces of the split cores are arranged to face each other, The coated wires are wound in layers around the outer periphery of the insulating coating material in parallel without being twisted, and on the inner periphery side of the insulating coating material, a first layer consisting of one coated wire is stacked on the side close to the inner periphery, and a second layer consisting of one coated wire is stacked on the outer periphery of the first layer, and each coated wire is electrically connected to the terminal. Choke coil.

2. The coated wire is folded back and wound around the terminal. The choke coil according to claim 1 .

3. an arc-shaped split core having end faces facing each other to form a toroidal shape; an insulating covering material that electrically insulates the split core and has flanges that protrude outward from each end face of the split core; A coated wire wound around the outer periphery of the insulating coating material; terminals to which the coated wires are electrically connected and provided near the flanges; A pair of core pieces comprising: A choke coil in which the end faces of the split cores are arranged to face each other, The coated wire is wound in parallel around the outer periphery of the insulating coating material without being twisted, Each coated wire is folded back and wound around the terminal and is electrically connected to the terminal. Choke coil.

4. A plurality of coated wires are wound around the insulating coating material without being folded back. The choke coil according to claim 1 .

5. The coated wire is wound so that the center bulges on the inner peripheral surface side of the insulating coating material.

5. The choke coil according to claim 1.

6. The terminal electrically connects the coated wire by resistance welding, a welding method, or soldering.

6. The choke coil according to claim 1.

7. The choke coil according to any one of claims 1 to 6, wherein the outer periphery of the choke coil is coated with a resin. Choke coil products.

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