JP7733796B2 - Molded coils and reactors - Google Patents

Description

The present invention relates to a molded coil formed by molding a coil with resin, and a reactor having this molded coil.

A reactor has a coil and a core. To electrically insulate the coil from the core, the core is usually covered with a resin material, and the wound coil is attached to the core from above the resin material. This reactor is a passive element that converts electrical energy into magnetic energy and stores and releases it.

Reactors are used in a wide variety of applications. Typical reactors include boost reactors incorporated into onboard boost circuits such as those used in the drive systems of hybrid and electric vehicles, series reactors connected in series to electric motor circuits to limit current during short circuits, parallel reactors that stabilize current sharing between parallel circuits, current-limiting reactors that limit current during short circuits to protect connected machinery, starting reactors connected in series to electric motor circuits to limit starting current, shunt reactors connected in parallel to transmission lines to compensate for leading reactive power and suppress abnormal voltages, neutral reactors connected between the neutral and ground to limit ground-fault current during ground faults in power systems, and arc-suppression reactors that automatically extinguish arcs that occur during single-phase ground faults in three-phase power systems.

Some reactors use molded coils, where the outer periphery of the coil is covered with resin. In this type of reactor, part of the coil surface is sometimes left exposed, rather than covered with molded resin, to ensure heat dissipation. To expose the coil surface, a proposal has been made to press a mold against the coil surface and fill the area around it with molded resin (see Patent Documents 1 to 3).

Patent No. 5869518 JP 2015-130410 A JP 2018-011019 A

The coil is made into a cylindrical shape by spirally winding conductive wire around a winding axis, with the winding position shifted for each turn, and has an outer shape consisting of four flat surfaces and four curved surfaces arranged alternately. Due to manufacturing precision reasons, the coil's surface is uneven and is not necessarily smooth. Therefore, even when attempting to fit the coil into a mold, a gap will form between the mold and the coil's surface. This can allow resin to seep in through this gap, potentially creating burrs on the exposed surface.

One way to prevent burrs from forming is to press the mold firmly against the surface of the coil. By pressing the mold firmly against the surface of the coil, it is possible to eliminate any gaps between the mold and the coil surface and to straighten any twists on the coil surface. However, pressing the mold firmly against the surface of the coil can cause damage to the coil or to the coating on the coil's conductive wire, resulting in a loss of insulation. Therefore, one option is to place a cover on the coil beforehand and press the coil with the mold through the cover to eliminate any unevenness or twists on the coil surface. When using a mold with upper and lower dies, a cover can be placed on the top surface of the coil facing the upper die, and another cover can be placed on the bottom surface of the coil facing the lower die.

When the underside of the coil is exposed, the cover placed on the underside of the coil is a rectangular frame. Here, the coil inside the mold is compressed by the resin injection pressure, shortening the length of the coil in the axial direction. To prevent gaps from forming between the edge of the coil's underside and the frame even when the coil is compressed, the frame placed on the underside of the coil must have thick frame sides and cover the edge area extending from the edge of the coil's underside toward the inside. The edge area is an area equivalent to the amount of compression of the coil plus a buffer.

By covering the edge area of the coil's underside with a frame, the end of the coil's underside remains overlapping with the frame edge, even when the coil is compressed. This prevents gaps from forming between the edge of the coil's underside and the frame, reducing the risk of resin leaking through the gap and burrs. However, because a buffer is required to cover the edge area with the frame edge of the frame body in advance, the overlap between the coil's underside and the frame body remains even after the resin is injected and molded. The underside of the coil cannot be exposed across the entire vertical width in the axial direction of the cylinder.

In reactors like this, where part of the coil surface is covered with molded resin and part of the surface is exposed from the molded resin, there is a need to prevent the coil from being damaged and to prevent the formation of burrs, but the above-mentioned conventional technology was unable to meet this need.

The present invention has been proposed to solve the problems of the prior art described above, and its object is to provide a molded coil that expands the exposed area of the coil while suppressing the formation of burrs in the molding resin, and a reactor equipped with this molded coil.

The molded coil of the present invention comprises a cylindrical coil whose outer shape is defined by a pair of coil end faces and side faces in which four flat surfaces and four curved surfaces are alternately arranged and perpendicular to the pair of coil end faces; a horizontal side wall and a U-shaped frame; a frame body defined by combining the horizontal side walls and the U-shaped frame into a rectangular shape, which is placed on the coil so that a first flat surface of the four flat surfaces is partially or completely contained within the frame; a molded resin that covers partially or completely the coil except for the interior of the frame body; a flat surface that covers one of the pair of coil end faces; and the horizontal side wall, which has a front surface that is not formed when the molded resin is absent. and an edge plate movable along the axial direction of the coil, wherein the U-shaped frame extends along the axial direction of the coil and has a pair of vertical side portions that are in close contact with the coil and a horizontal side portion that extends between the pair of vertical side portions, the horizontal side wall is in close contact with the coil end surface that is covered by the flat surface of the edge plate, and the horizontal side portion of the U-shaped frame is in close contact with the coil end surface opposite the edge plate, and the first flat surface of the coil is exposed from the molded resin over the entire vertical width range from one coil end surface that is in close contact with the horizontal side wall to the other coil end surface that is in close contact with the horizontal side portion.

The pair of vertical side portions may sandwich the first flat surface and be in close contact with the two curved surfaces adjacent to the first flat surface, and the coil may be configured such that at least the first flat surface is exposed from the molded resin across the entire width range from one of the curved surfaces to which the pair of vertical side portions are in close contact to the other curved surface.

The vertical side portion may have a contact surface that is in close contact with the coil, an end surface adjacent to the contact surface, extending along the cylindrical axis of the coil and expanding in a direction away from the contact surface, the end surface side being perpendicular to the first flat surface, and an outer surface adjacent to the end surface and forming the opposite side of the contact surface, wherein the angle formed between the contact surface and the end surface is approximately a right angle, and the angle formed between the end surface and the outer surface is also approximately a right angle.

The contact surface may be configured to contact not only the curved surface adjacent to the first plane, but also the flat surface perpendicular to the first plane.

The horizontal side walls may extend equal to the distance between the opposing surfaces of the pair of vertical side portions, and the frame body may be defined by the horizontal side walls fitting between the pair of vertical side portions.

The frame may include a plate covering the flat surface located opposite the first flat surface, the plate having an eave portion extending beyond the position of the end surface covered by the edge plate, and the eave portion of the frame may be in contact with the side surface of the edge plate.

The pair of vertical side portions of the U-shaped frame and the horizontal side wall of the edge plate may have recesses and protrusions that restrict movement of the horizontal side wall toward the flat surface located opposite the first flat surface, and the recesses and protrusions may be fitted together.

The pair of vertical side portions may have recessed portions among the concave and convex portions and groove portions extending from the recessed portions along the cylindrical axis of the coil, and the horizontal side walls may have protruding portions among the concave and concave portions, which fit into the recessed portions and slide within the groove portions as the horizontal side walls move.

A reactor comprising this molded coil and a core containing a magnetic material to which the molded core is attached is also an aspect of the present invention.

According to the present invention, even if the exposed area of the coil is expanded, the occurrence of burrs is suppressed and heat dissipation is excellent.

FIG. 2 is a perspective view of the reactor, omitting members covering each portion. FIG. 10 is a bottom perspective view showing the coated coil. 1A is a perspective view showing each covering member of the coil, in which FIG. 1A shows an upper cover, FIG. 1B shows an edge plate, FIG. 1C shows a lower cover, and FIG. 1D shows a molded resin. FIG. 2 is a perspective view of the lower part of the coil and the upper cover. 1A and 1B are perspective views of a coil and an edge plate, where FIG. 1A is a perspective view of the front side as seen from below, and FIG. 1B is a perspective view of the rear side as seen from below. FIG. 2 is a perspective view of the lower part of the coil and the lower cover. FIG. 10 is an enlarged partial cross-sectional view of the coil and vertical side portion. FIG. 1 is a transition diagram illustrating the formation of a coil coating resin. FIG. 10 is a front view showing the coil in the mold as viewed from the edge plate side. FIG. 10 is an enlarged partial cross-sectional view showing the forces acting on the coil and the vertical side portion within the mold. FIG. 10 is a transition diagram showing compression of the coil within the mold. 10A and 10B are bottom views showing the compression of a coil within a mold, where (a) is before compression, (b) is after compression of the molded coil according to this embodiment, and (c) is after compression when the side wall and the U-shaped wall are connected.

The reactor according to an embodiment of the present invention will be described below with reference to the drawings. In each drawing, thickness, dimensions, positional relationships, ratios, shapes, etc. may be exaggerated for ease of understanding, but the present invention is not limited to such exaggeration.

Figure 1 is a perspective view showing the main components of the reactor of this embodiment; for ease of explanation, the materials covering each part have been omitted. The reactor 100 comprises two coils 5, 5 and one annular core 1. The two coils 5, 5 are attached to the core 1. When current is applied to the coils 5, 5, they generate magnetic flux according to the number of turns. The core 1 forms a closed magnetic circuit that passes the magnetic flux generated by the coils 5, 5 with a magnetic permeability higher than that of a vacuum. In other words, the reactor 100 is an electromagnetic component that converts electrical energy into magnetic energy and stores and releases it.

Core 1 contains a magnetic material such as a powder magnetic core, ferrite core, metal composite core, or laminated steel plate. A powder magnetic core is an annealed compact made by compressing magnetic powder. Magnetic powders are primarily iron-based, and examples include pure iron powder, iron-based permalloy (Fe-Ni alloy), Si-containing iron alloy (Fe-Si alloy), sendust alloy (Fe-Si-Al alloy), amorphous alloy, nanocrystalline alloy powder, or a mixture of two or more of these powders. A metal composite core is made by kneading and molding magnetic powder and resin.

The coil 5 is a cylindrically wound body of conductive wire 59, such as copper wire. The coil 5 is formed by winding the conductive wire 59 in a spiral shape along the winding axis, shifting the winding position for each turn. The conductive wire 59 extends from the beginning and end of each of the coils 5, 5. Each conductive wire 59 is electrically connected to the bus bar, so that the coils 5, 5 are electrically connected in parallel or in series.

This coil 5 is cylindrically defined by a first end face 55, a second end face 57, and side faces connecting the first end face 55 and the second end face 57. The first end face 55 and the second end face 57 are located at the start and end of the winding of the conductive wire 59 and are perpendicular to the cylindrical axis. The first end face 55 and the second end face 57 have an annular shape that matches the winding pattern of the conductive wire 59.

The side surface of the coil 5 is made up of four curved surfaces and four flat surfaces that are perpendicular to the first end surface 55 and second end surface 57 and parallel to the cylindrical axis, alternately connected together. That is, the coil 5 has a flat upper surface 51 that is parallel to the surface on which the annular shape of the core 1 appears, and a flat lower surface 52 on the opposite side of the upper surface 51. The coil 5 has two flat lateral surfaces 54 that are perpendicular to the upper surface 51 and the lower surface 52. The coil 5 has a lower curved surface 53 between the lower surface 52 and the lateral surface 54, and an upper curved surface 56 between the upper surface 51 and the lateral surface 54.

Note that the flat surface of the coil 5 refers to a surface that is flat relative to a curved surface, and includes a surface that forms a large arc with a gentle curvature due to the bulging of the conductive wire 59. The top and bottom refer to the upper and lower molds that house the coils 5, 5 when covering the coils 5, 5 by molding, and do not refer to the positional relationship or direction when the reactor 100 is installed in the actual device to be installed.

Hereinafter, the horizontal direction refers to the Y-axis direction, which is parallel to the bottom surface 52 of the coil 5 and perpendicular to the horizontal surface 54 of the coil 5. The direction from the cylindrical axis of the coil 5 to the horizontal surface 54 is referred to as the outer side in the horizontal direction of the coil. The opposite of the outer side in the horizontal direction of the coil is referred to as the inner side in the horizontal direction of the coil. The vertical direction refers to the X-axis direction, which is perpendicular to the horizontal direction, parallel to the bottom surface 52, along the cylindrical axis, and parallel to the horizontal surface 54. The direction from the center position equidistant between the first end surface 55 and the second end surface 57 to the first end surface 55 or the second end surface 57 is referred to as the outer side in the vertical direction of the coil. The opposite of the outer side in the vertical direction of the coil is referred to as the inner side in the vertical direction of the coil. The vertical direction refers to the Z-axis direction, which is perpendicular to the top surface 51 and the bottom surface 52. The direction from the bottom surface 52 toward the top surface 51 is referred to as the upper side, and the direction from the top surface 51 toward the bottom surface 52 is referred to as the lower side.

Figure 2 is a bottom perspective view showing the coated coils 5, 5. As shown in Figure 2, each of the two coils 5, 5 is a molded coil 2. The molded coil 2 is formed by covering the coil 5 with coil coating resin 3. By being covered with the coil coating resin 3, the coils 5, 5 are electrically insulated from the core 1 and fitted into the core 1. Furthermore, by being covered with the coil coating resin 3, vibration of the coils 5, 5 is suppressed.

The coil coating resin 3 is preferably a resin with insulating and heat-resistant properties, such as PPS (Polyphenyl Sulfide), epoxy resin, unsaturated polyester resin, urethane resin, BMC (Bulk Molding Compound), PPS (Polyphenyl Sulfide), PBT (Polybutylene Terephthalate), or a composite of these. A thermally conductive filler may also be mixed into the material of the coil coating resin 3.

However, an opening 58 is formed in the coil coating resin 3 to improve the heat dissipation of the coil 5. The opening 58 exposes the entire lower surface 52 of the coil 5 in the coil horizontal direction and the lower edge region 53a of the lower curved surface 53 adjacent to the lower surface 52. Furthermore, the opening 58 exposes the entire lower surface 52 of the coil 5 in the coil vertical direction, from the boundary with the first end surface 55 to the boundary with the second end surface 57.

The opening 58 is defined by a frame 58a provided on the coil coating resin 3. The space within the frame 58a forms the opening 58. The frame 58a rises downward from the lower surface 52 along its entire periphery. The coil coating resin 3 is ultimately completed by resin injection molding, but the frame 58a prevents resin from flowing into the frame, forming the opening 58.

Figure 3 is a perspective view showing each component of the coil coating resin 3 equipped with this frame 58a. As shown in Figures 2 and 3(a) to 3(d), the coil coating resin 3 is composed of an upper cover 6 shown in Figures 2 and 3(a), an edge plate 8 shown in Figures 2 and 3(b), a lower cover 7 shown in Figures 2 and 3(c), and a molded resin 9 shown in Figures 2 and 3(d).

As shown in Figure 3(a), the upper cover 6 has an upper plate 61 and side curved plates 62. The upper plate 61 and side curved plates 62 are seamlessly connected as a single piece by, for example, integral molding. The upper plate 61 is a solid, flat plate extending parallel to the upper surface 51 of the coil 5, and covers the upper surface 51 of the coil 5. The side curved plates 62 extend from both outer edges of the upper plate 61 in the lateral direction of the coil, and cover the upper curved surface 56 and the upper edge region of the lateral surface 54 adjacent to the upper curved surface 56.

As shown in Figure 3(b), the edge plate 8 has a flat surface 83 that covers the conductive wires 59 that appear on the first end surface 55 of the coil 5. A horizontal side wall 81 that extends in the same plane as the flat surface 83 is formed at the lower end of the edge plate 8. The flat surface 83 and the horizontal side wall 81 are seamlessly connected together by integral molding or the like. The horizontal side wall 81 extends across the entire area of the lower surface 52 of the coil 5 in the coil horizontal direction and across both lower edge regions 53a of the lower curved surface 53 adjacent to the lower surface 52, and extends below the lower surface 52 in the vertical direction.

As shown in Figure 3(c), the lower cover 7 has a U-shaped frame 71 and an annular edge plate 74. The U-shaped frame 71 and the annular edge plate 74 are seamlessly connected together by integral molding or the like. The U-shaped frame 71 has a rectangular U-shaped frame shape with one side missing, and surrounds the entire lower surface 52 of the coil 5 and the lower edge region 53a of the lower curved surface 53 adjacent to the lower surface 52 on three sides. The U-shaped frame 71 extends downward below the lower surface 52.

On the other hand, in the upward direction, the U-shaped frame 71 extends to cover the lower curved surface 53 other than the lower edge region 53a, and the lower edge region 53a of the horizontal surface 54 adjacent to the lower curved surface 53. The edge annular plate 74 extends upward from the side of the U-shaped frame 71 extending in the coil horizontal direction, and extends upward perpendicular to the U-shaped frame 71, covering the second end face 57 of the coil 5.

The molded resin 9 is formed by placing the coil 5, on which the upper cover 6, lower cover 7, and edge plate 8 are installed, in a mold, and then injecting resin into the mold and allowing it to solidify. Within the mold, the upper cover 6 and lower cover 7 come into contact with the mold, except for the outer surface of the edge plate 8 facing outward in the longitudinal direction of the coil and the surface of the edge annular plate 74 of the lower cover 7 facing outward in the longitudinal direction of the coil.

As a result, as shown in Figure 3(d), this molded resin 9 covers the remaining portion of the lateral surface 54, which is the gap between the upper cover 6 and lower cover 7, the first end face 55, the second end face 57, and the inner peripheral surface of the coil 5. The molded resin 9 covers the first end face 55 from above the edge plate 8, and covers the second end face 57 from above the edge annular plate 74 of the lower cover 7.

The frame body 58a surrounding the opening 58 is defined by the U-shaped frame 71 of the lower cover 7 and the horizontal side walls 81 of the edge plate 8. The horizontal side walls 81 fit into the U-shaped frame 71, and the horizontal side walls 81 and the U-shaped frame 71 define the rectangular frame body 58a with sides on all four sides. The upper cover 6, edge plate 8, and lower cover 7 are described in further detail below.

Figure 4 is an enlarged perspective view of the coil 5 and upper cover 6. As shown in Figure 4, the upper cover 6 has an overhang portion 63. This overhang portion 63 protrudes outward from the coil 5 by extending the ends of the upper plate body 61 and the side curved plate 62 beyond the first end surface 55 of the coil 5 without changing the direction of extension. Before resin injection molding, the overhang portion 63 protrudes by a length equivalent to the thickness of the flat surface 83 of the edge plate 8. However, because the coil 5 is compressed during resin injection molding, after resin injection molding, the overhang portion 63 protrudes by a length equivalent to the amount of compression of the coil 5.

The ends of this eaves portion 63 are folded in so that they are perpendicular to the cylindrical axis of the coil 5, and overlap with part of the edge of the first end face 55 in the longitudinal direction of the coil. Furthermore, the upper plate 61 has cutouts 64 formed on both sides of the first end face 55 and the second end face 57, cutting out the central edge of the upper plate 61, and the eaves portion 63 is divided by the cutouts 64 in the transverse direction of the coil.

Figure 5 is an enlarged perspective view of the coil 5 and edge plate 8, with (a) being a perspective view from below the front and (b) being a perspective view from the back side. The flat surface 83 of the edge plate 8 has a ring shape that mimics the winding pattern of the conductive wire 59 of the coil 5, and the cylindrical axis region is open. The horizontal side wall 81 extends without changing direction, extending the flat surface 83, and extends downward beyond the lower surface 52 of the coil 5. In other words, the horizontal side wall 81 extends from the upper limit of one of the lower edge regions 53a that fits into the opening 58, or above this upper limit, to below the lower surface 52 that fits into the opening 58.

The length of the horizontal side wall 81 along the coil horizontal direction extends from the outer edge of one lower edge region 53a that fits into the opening 58 to the outer edge of the other lower edge region 53a. The lowermost edge of the horizontal side wall 81 extends linearly in the coil horizontal direction at a constant height. This horizontal side wall 81 has protrusions 82 formed on both sides in the coil horizontal direction. The protrusions 82 protrude from the horizontal side wall 81 in the coil horizontal direction.

Figure 6 is an enlarged perspective view of the coil 5 and lower cover 7. As shown in Figure 6, the U-shaped frame 71 of the lower cover 7 has a U-shape with a pair of vertical sides 72 and one horizontal side 73. The pair of vertical sides 72 are aligned parallel to one another, and the one horizontal side 73 connects the aligned ends of the pair of vertical sides 72.

The vertical side portion 72 has a vertical portion 722. This vertical portion 722 is part of the wall of the frame body 58a that rises around the opening 58. In the up-down direction, the vertical portion 722 begins in close contact with the upper limit position of the lower edge region 53a exposed from the opening 58, rises perpendicular to the plane on which the lower surface 52 of the coil 5 extends, and extends below the lower surface 52. In other words, the vertical portions 722 of the pair of vertical side portions 72 are separated by a distance equal to the total width of the lower surface 52 of the coil 5 plus the lower edge regions 53a of the lower curved surfaces 53 exposed from the opening 58.

The vertical portion 722 extends in the longitudinal direction of the coil, in other words, along the axial direction of the coil 5, and the lowest edge of the vertical portion 722 extends linearly at a constant height in the longitudinal direction of the coil. The end of the vertical portion 722 on the first end surface 55 side protrudes by the same amount as or more than the thickness of the horizontal wall 81 of the edge plate 8 beyond the coil 5 before it is compressed by the injection pressure of the molded resin 9.

The horizontal side portion 73 extends perpendicular to the coil horizontal direction, in other words, the cylindrical axis direction of the coil 5, and parallel to the lower surface 52 of the coil 5, extending along the second end surface 57 of the coil 5, completely across the second end surface 57. The length of the horizontal side portion 73 along the coil horizontal direction extends from the outer end of one lower edge region 53a that fits within the opening 58 to the outer end of the other lower edge region 53a. The horizontal side portion 73 also extends downward below the lower surface 52 so that the lower surface 52 can fit within the opening 58. The lowest edge of the horizontal side portion 73 extends linearly at the same height as the vertical portion 722.

In this U-shaped frame 71, the horizontal side wall 81 of the edge plate 8 fits between the vertical portions 722 of the vertical side portions 72, and the horizontal side wall 81 and horizontal side portion 73 of the edge plate 8 form opposing sides, resulting in a rectangular frame body 58a being formed by the vertical portions 722 of the vertical side portions 72, the horizontal side wall 81, and the horizontal side portion 73.

Figure 7 is an enlarged partial cross-sectional view of the coil 5 and the vertical side portion 72. As shown in Figures 6 and 7, the vertical side portion 72 has a contact portion 721 in addition to the vertical portion 722. The contact portion 721 extends seamlessly from the upper end of the vertical portion 722, and the vertical side portion 72 is in contact with the lower curved surface 53 at this contact portion 721. Except for the connection area with the vertical portion 722 and the connection area with the horizontal side portion 73, the contact portion 721 is defined by a contact surface 721a, an upper end surface 721b, and an outer surface 721c. Going around the vertical side portion 72, there is the contact surface 721a, the contact surface 721a followed by the upper end surface 721b, the upper end surface 721b followed by the outer surface 721c, the outer surface 721c followed by the vertical portion 722, and the vertical portion 722 followed by the contact surface 721a.

The contact surface 721a is the inner peripheral surface of the contact portion 721. The contact surface 721a is curved to coincide with the arc range from the upper limit of the lower edge region 53a of the coil 5 to the upper limit of the lower curved surface 53, and further extends linearly along the lateral surface 54 of the coil 5. This contact surface 721a is in close contact with the upper side of the upper limit of the lower edge region 53a of the lower curved surface 53 and the lower region of the lateral surface 54.

The upper end surface 721b is the upper end surface adjacent to the contact surface 721a. The upper end surface 721b is adjacent to the contact surface 721a and extends in a direction away from the lateral surface 54. The upper end surface 721b extends in a direction that is approximately perpendicular to the contact surface 721a and the lateral surface 54. The outer surface 721c is adjacent to the upper end surface 721b and forms the outer peripheral surface of the contact portion 721. The outer surface 721c is the surface opposite the contact surface 721a. The outer surface 721c extends so that the angle it forms with the upper end surface 721b is approximately perpendicular, and is parallel to the lateral surface 54 and the contact surface 721a.

These approximately right angles are angles at which external forces acting on the boundary between the upper end surface 721b and the outer surface 721c are efficiently transmitted to the boundary between the contact surface 721a and the upper end surface 721b. In other words, an approximately right angle refers to a specified angle range including 90 degrees, so long as the lower curved surface 53 of the coil 5 is corrected and the upper end of the vertical side portion 72 does not bend outward in the horizontal direction of the coil due to the injection pressure of the molded resin 9.

Returning to Figure 6, the vertical side portion 72 has a recess 75 at the end of the vertical portion 722 on the first end surface 55 side. The recess 75 is formed on the side of the vertical side portion 722 on the inner side in the coil horizontal direction, i.e., the side facing the inside of the U-shaped frame 71, and is deep in the outer side in the coil horizontal direction. The recess 75 has walls at the top, bottom, and outer side in the coil horizontal direction. The recess 75 and the protrusion 82 formed on the horizontal side wall 81 of the edge plate 8 are identical in shape. Furthermore, a groove 76 is formed in the vertical side portion 72. The groove 76 continues from the recess 75 and extends along the coil vertical direction on the inner side in the coil horizontal direction of the vertical portion 722. The cross section of each position of the groove 76 coincides with the recess 75.

As a result, the recess 75 and the protrusion 82 can fit together. Furthermore, the protrusion 82 fitted into the recess 75 restricts the vertical position of the coil 5 because the recess 75 is deep in the coil horizontal direction, has walls at the top and bottom, and the protrusion 82 protrudes in the coil horizontal direction. On the other hand, the protrusion 82 fitted into the recess 75 can slide within the groove 76 along the coil vertical direction.

The method for forming the coil coating resin 3 using the upper cover 6, lower cover 7, edge plate 8, and molded resin 9 is as follows. Figure 8 is a transition diagram showing the formation of the coil coating resin 3. As shown in Figure 8(a), with the lower cover 7 placed in the lower mold, the coil 5 is placed inside the lower mold and the coil 5 is placed on the lower cover 7. The coil 5 is placed so that it is sandwiched between the contact portions 721 of the lower cover 7, with the lateral surface 54 and lower curved surface 53 of the coil 5 aligned with the contact surface 721a of the contact portion 721. In addition, the second end surface 57 of the coil 5 is aligned with the edge annular plate 74 of the lower cover 7.

The lower cover 7 rests on the lower die at the vertical portion 722. When the coil 5 is placed on the lower cover 7, which has a vertical portion 722 that extends below the lower surface 52, the lower surface 52 is floating above the lower die. Furthermore, the U-shaped frame 71 contains the entire lower surface 52 and the lower edge region 53a of the lower curved surface 53 in the coil horizontal direction.

As shown in Figure 8 (b), after placing the coil 5 on the lower cover 7, the edge plate 8 is installed so that the flat surface 83 contacts the first end surface 55. At this time, the convex portions 82 protruding outward on both sides of the horizontal side wall 81 in the coil horizontal direction are fitted into the concave portions 75 formed on the vertical side portions 72 of the lower cover 7, which become deeper toward both sides of the coil horizontal direction. The horizontal side walls 81 are fitted inside the U-shaped frame 71 so that the end faces on both sides of the horizontal side wall 81 in the coil horizontal direction contact the side faces on both sides of the vertical side portions 72 in the coil horizontal direction.

As a result, the horizontal side wall 81 is positioned on the opposite side of the horizontal side portion 73 of the U-shaped frame 71, and the horizontal side wall 81 and the U-shaped frame 71 define a rectangular frame body 58a. This frame body 58a contains the entire lower surface 52 and the lower edge region 53a of the lower curved surface 53 in the coil horizontal direction. Furthermore, because the horizontal side wall 81 contacts the first end surface 55 and the horizontal side portion 73 contacts the second end surface 57, the frame body 58a contains the entire lower surface 52 from the boundary with the first end surface 55 to the boundary with the second end surface 57 in the coil vertical direction. Furthermore, the downward extension amount is set so that the horizontal side wall 81 and the lowest end of the U-shaped frame 71 are at the same height, so the frame body 58a sits tightly against the lower mold around its entire circumference.

As shown in Figure 8 (c), after the edge plate 8 is placed along the first end surface 55 of the coil 5, the upper cover 6 is placed on the coil 5. The upper plate 61 of the upper cover 6 is aligned with the top surface 51 of the coil 5, and the side curved plate 62 is aligned with the upper curved surface 56 of the coil 5. At this time, the eaves portion 63 covers the upper surface 83a of the edge plate 8. Because the upper surface 83a of the edge plate 8 and the inner surface of the eaves portion 63 each have a position and shape that matches the outer shape of the first end surface 55, the eaves portion 63 comes into contact with the upper surface 83a of the edge plate 8.

However, the procedure for placing the coil 5, upper cover 6, lower cover 7, and edge plate 8 into the lower mold is not limited to this. For example, the coil 5 with the lower cover 7, edge plate 8, and upper cover 6 attached may be placed into the lower mold. The attachment procedure may also be in the order of lower cover 7, edge plate 8, and upper cover 6, or a different attachment procedure may be used. If the coil coating resin 3 excluding the molding resin 9 is attached to the coil 5 before placing it in the lower mold, the coil 5 is protected by the coil coating resin 3 excluding the molding resin 9, and the coil 5 can be prevented from accidentally colliding with the mold when being placed into the mold.

When the coil 5 is protected by the coil coating resin 3 (excluding the molding resin 9) and then attached to the mold, the eaves portion 63 of the upper cover 6 covers the edge plate 8 and the annular edge plate 74, preventing the lower cover 7 and edge plate 8 from falling off and improving the transportability of the coil 5 into the mold.

After placing the coil 5, upper cover 6, lower cover 7, and edge plate 8 in the lower mold, the upper mold is placed over the upper cover 6, and molding resin 9 is injected into the mold. Figure 9 is a front view of the coil inside the mold, viewed from the edge plate side. As shown in Figure 9, inside the mold, the upper mold presses the upper plate 61 of the upper cover 6, and a downward force P1 acts on the upper cover 6. The coil 5, which is covered by the upper cover 6, is also pressed downward via the upper cover 6.

This coil 5 is placed on the lower cover 7 inside the mold. As a result, a force P2 acts on the lower cover 7 in the direction of the lower mold via the coil 5, causing the U-shaped frame 71 of the lower cover 7 to adhere closely to the lower mold. Therefore, inside the mold, resin from the mold resin 9 is prevented from entering the frame body 58a between the U-shaped frame 71 and the lower mold.

The lower cover 7 and edge plate 8 are fitted together by fitting the recess 75 on the lower cover 7 with the protrusion 82 on the edge plate 8. A downward force P3 is transmitted from the lower cover 7 to the edge plate 8 via the recess 75 and protrusion 82, and a force P4 is generated on the side wall 81 of the edge plate 8, pressing it against the lower mold. This force P4 causes the side wall 81 of the edge plate 8 to adhere closely to the lower mold. As a result, although the side wall 81 is separated from the U-shaped frame 71, the side wall 81 is pressed against the lower mold by the force P4 generated by the fitting of the recess 75 and protrusion 82. This prevents the resin of the molded resin 9 from entering the frame body 58a between the side wall 81 and the lower mold.

Furthermore, the edge plate 8 is covered by the eaves portion 63 of the upper cover 6, and a force P5 is generated in which the eaves portion 63 presses downward on the upper surface 83a of the edge plate 8. This force P5 is added to the force P4 that presses the side wall 81 against the lower mold, allowing the side wall 81 to be pressed more reliably against the lower mold.

Figure 10 is an enlarged partial cross-sectional view showing the forces acting on the coil 5 and vertical side portion 72 within the mold. Inside the mold, the outer surface 721c of the vertical side portion 72 of the lower cover 7 abuts against the lower mold. When the upper mold presses the upper cover 6, a force P6 is generated on the lower curved surface 53 of the coil 5, pressing it against the contact surface 721a of the vertical side portion 72. This vertical side portion 72 is supported by the lower mold at its outer surface 721c. As a result, the lower curved surface 53 of the coil 5 is crushed between the coil 5 and the contact portion 721 of the vertical side portion 72.

Due to manufacturing precision reasons, the surface of the coil 5 has twists and irregularities, and is not necessarily smooth. In particular, the lower curved surface 53 of the coil 5 must maintain a constant curvature throughout each turn, and the same curvature must be maintained for all turns. This makes twists and irregularities prone to occur, and the irregularities can easily become large. However, the lower curved surface 53 of the coil 5 is pressed against the contact portion 721, correcting any twists or irregularities, and closely contacting the vertical side portion 72 with no gaps. This prevents the resin of the molded resin 9 from seeping into the frame 58a between the vertical side portion 72 and the coil 5.

The angle between the contact surface 721a and the upper end surface 721b and the angle between the upper end surface 721b and the outer surface 721c are both right angles. Therefore, the force of the lower mold supporting the outer surface 721c efficiently generates a force P7 that brings the horizontal surface 54 and the vertical side portion 72 into close contact on the upper end surface 721b side. This force P7 firmly blocks the upper boundary between the vertical side portion 72 and the coil 5, which could be an entrance for the resin of the molded resin 9 to enter the frame body 58a. It is desirable for the angle between the contact surface 721a and the upper end surface 721b and the angle between the upper end surface 721b and the outer surface 721c to be right angles, as this achieves the most balance. However, they may be angled toward obtuse or acute angles rather than strictly right angles, depending on the injection pressure of the molded resin 9.

Furthermore, the vertical side portion 72 extends until the upper end surface 721b rests on the horizontal surface 54. Here, when force P1 pressing against the upper cover 6 is transmitted and the force of the coil 5 pressing against the lower cover 7 is transmitted from the lower curved surface 53 to the vertical side portion 72, a component of force is generated that moves outward in the horizontal direction of the coil. However, the horizontal surface 54 is perpendicular to the direction of force P1 pressing against the upper cover 6. Therefore, no force acts from the horizontal surface 54 to the vertical side portion 72 in the horizontal direction of the coil. Therefore, the force with which the lower mold supports the outer surface 721c near the upper end surface 721b is not offset by the force component that moves outward in the horizontal direction of the coil, and is transformed into force P7, which more efficiently brings the horizontal surface 54 and the vertical side portion 72 into tight contact with each other.

Figure 11 is a transition diagram showing the compression of the coil within the mold. When the coil 5 is placed within the mold and the upper cover 6 is pressed by the upper die, the molding resin 9 is injected into the mold. The resin injection port for the molding resin 9 is provided at least in a position opposite the first end face 55 of the coil 5, and the molding resin 9 is injected toward the first end face 55 of the coil 5 along the axial direction of the coil 5. In other words, an injection pressure P8 is applied to the coil 5 in a direction toward the inside of the coil's longitudinal direction.

The injection pressure P8 acting inward in the longitudinal direction of the coil compresses the coil 5 by a length D1, reducing the longitudinal length of the coil 5 from length L1 before compression to length L2 after compression. Here, the edge plate 8 covers the first end surface 55 of the coil 5, and the injection pressure P8 is applied to the flat surface 83 of the edge plate 8, so the coil 5 receives the injection pressure P8 via the edge plate 8.

The edge plate 8 is an independent member separate from the upper cover 6 and lower cover 7, and is movable in the coil's longitudinal direction. That is, the engagement between the convex portion 82 and the concave portion 75 restricts the edge plate 8's movement in the vertical direction, but does not restrict the edge plate 8's movement in the coil's longitudinal direction. Therefore, when the coil 5 receives injection pressure P8 through the edge plate 8 and this injection pressure P8 compresses the coil 5 by a length D1, the edge plate 8 also moves inward in the coil's longitudinal direction by the length D1 and remains in close contact with the first end surface 55 of the coil 5.

At this time, the protrusion 82 extending from the horizontal side wall 81 slides in the groove 76 continuing from the recess 75. As a result, the horizontal side wall 81 of the edge plate 8 continues to be restricted in the vertical direction even while moving in the vertical direction of the coil due to injection pressure P8, and maintains close contact with the lower mold. Therefore, the resin of the molded resin 9 is prevented from entering the frame body 58a between the horizontal side wall 81 and the lower mold, even while the horizontal side wall 81 is moving in the vertical direction of the coil due to injection pressure P8.

Figure 12 is a bottom view showing the compression of the coil 5 within the mold, where (a) shows the state before compression, (b) shows the state after compression of the molded coil according to this embodiment, and (c) shows the state after compression when the side wall and the U-shaped wall are connected.

As shown in Figures 12(a) and (b), the horizontal side wall 81 is separated from the U-shaped frame 71 and can move independently, so the length of the frame body 58a in the coil's vertical direction changes to match the length of the coil 5 after compression, and the coil 5 and frame body 58a remain in close contact all around. Therefore, even if the vertical length of the coil 5 changes, it is possible to prevent the mold resin 9 from entering the opening 58 and causing burrs.

That is, as shown in Figures 12(a) and (c), let's assume that the horizontal side wall 81 and the U-shaped frame 71 are integral and the position of the horizontal side wall 81 is immovable. In this case, even if the length of the coil 5 after compression changes, the length of the frame body 58a in the coil's vertical direction remains unchanged. This would result in a gap 58b being created between the first end surface 55 of the coil 5 and the horizontal side wall 81, preventing the coil 5 and frame body 58a from maintaining close contact around the entire circumference.

To prevent this gap 58b from occurring, if the position of the horizontal side wall 81 is fixed, the lower part of the horizontal side wall 81 must be folded back along the underside 52 of the coil 5 by a length equal to or greater than the gap 58b. Even if a gap 58b occurs, the horizontal side wall 81 must cover and conceal the gap 58b. However, because the length of the gap 58b varies from coil to coil, a buffer is required for the fold back along the underside 52 of the horizontal side wall 81. As a result, even after the coil 5 is compressed, this fold will hang over the underside 52 of the coil 5. Therefore, the entire underside 52 of the coil 5 cannot be exposed to the opening 58 in the coil's vertical direction.

On the other hand, if the horizontal side wall 81 is separated from the U-shaped frame 71 and is able to move independently, no gap 58b is created, and therefore there is no need to fold the lower part of the horizontal side wall 81 back along the lower surface 52, leaving the entire lower surface 52 of the coil 5 exposed to the opening 58 in the lower coil longitudinal direction. As a result, in this molded coil 2, the coil coating resin 3 consisting of the molded resin 9, upper cover 6, lower cover 7, and edge plate 8 exposes the entire lower surface 52 in the coil longitudinal direction, and the entire lower surface 52 and both lower edge regions 53a of both lower curved surfaces 53 in the coil horizontal direction, while suppressing the occurrence of burrs.

As described above, this molded coil 2 and reactor 100 include a frame 58a placed on the coil 5, and molded resin 9 that covers the coil 5 except for the frame of this frame 58a. The frame 58a has a horizontal side wall 81 and a U-shaped frame 71, and is defined by combining the horizontal side wall 81 and the U-shaped frame 71 into a rectangular shape, with the lower surface 52, for example, being contained within the frame as the first flat surface of the four flat surfaces.

The horizontal side wall 81 is attached to the edge plate 8, which has a flat surface 83 that covers the first end surface 55 and is movable along the axial direction of the coil 5 when the molded resin 9 is not present. Meanwhile, the U-shaped frame 71 extends along the axial direction of the coil 5 and has a pair of vertical side portions 72 that are in close contact with the coil 5, and a horizontal side portion 73 that extends between the pair of vertical side portions 72.

The horizontal side wall 81 is in close contact with the first end surface 55 covered by the flat surface 83 of the edge plate 8, and the horizontal side portion 73 of the U-shaped frame 71 is in close contact with the second end surface 57 opposite the edge plate 8. The coil 5 has a first flat surface, such as the underside 52, exposed from the molded resin 9 across the entire vertical width range from the first end surface 55 with which the horizontal side wall 81 is in close contact to the second end surface 57 with which the horizontal side portion 73 is in close contact.

As a result, even when the coil 5 is compressed in the coil longitudinal direction by the injection pressure P8, the horizontal side wall 81 follows and continues to adhere to the first end surface 55, so no burrs are generated and the entire first flat surface, such as the lower surface 52, can be contained within the opening 58 in the coil longitudinal direction, thereby improving the heat dissipation effect of the molded coil 2 and reactor 100.

The pair of vertical side portions 72 sandwich a first flat surface, such as the lower surface 52, and are in close contact with two curved surfaces, such as the lower curved surface 53, adjacent to the first flat surface. At least the first flat surface of the coil 5 is exposed from the molded resin 9 across the entire width from one curved surface where the pair of vertical side portions 72 are in close contact to the other curved surface. This corrects any twists or irregularities that may occur in the coil 5, and allows the coil 5 and the vertical side portions 72 to be in close contact with each other. Therefore, a wider exposed area can be formed on the coil 5 without generating burrs, further improving the heat dissipation effect.

Furthermore, in the vertical side portion 72, the angle formed between the contact surface 721a and the upper end surface 721b is approximately a right angle, and the angle formed between the upper end surface 721b and the outer surface 721c is also approximately a right angle. The contact surface 721a is in close contact with the curved surface adjacent to the first flat surface. The upper end surface 721b is adjacent to the contact surface 721a, extends along the cylindrical axis of the coil 5, expands in a direction away from the contact surface 721a, and is perpendicular to the first flat surface. The outer surface 721c is adjacent to the upper end surface 721b and is the opposite surface to the contact surface 721a. This allows the contact surface 721a to be pressed firmly against the coil 5, more accurately correcting twists and unevenness in the coil 5 and further adhering the coil 5 to the vertical side portion 72. This further reduces the occurrence of burrs.

Furthermore, the contact surface 721a is designed to contact flat surfaces, such as the horizontal surface 54, which is perpendicular to a first flat surface, such as the lower surface 52. This allows the force with which the lower mold supports the vertical side portion 72 to efficiently press the contact surface 721a against the coil 5, more efficiently bringing the coil 5 and the vertical side portion 72 into close contact. In other words, this force is not offset by the force component in the horizontal direction of the coil that is generated from the lower curved surface 53 of the coil 5 to the vertical side portion 72. Furthermore, the entrance to the gap between the coil 5 and the vertical side portion 72 can be sealed.

A plate covering the flat surface opposite the first flat surface, for example, an upper plate 61 covering the top surface 51, is provided, and this plate has an eave portion 63 extending beyond the position of the first end surface 55 covered by the edge plate 8. As a result, the eave portion 63 contacts the upper surface 83a of the edge plate 8, and when the upper cover 6 is pressed by the upper mold, it presses the edge plate 8 having the horizontal side wall 81 via the upper surface 83a of the edge plate 8. Therefore, the horizontal side wall 81 remains in close contact with the lower mold even when separated from the U-shaped frame 71, preventing resin from leaking into the frame body 58a from between the horizontal side wall 81 and the lower mold.

The pair of vertical side portions 72 of the U-shaped frame 71 and the horizontal side wall 81 of the edge plate 8 have recesses 75 and protrusions 82 that restrict movement of the horizontal side wall 81 toward the flat surface opposite the first flat surface, and the recesses 75 and protrusions 82 fit together. This allows the recesses 75 and protrusions 82 to hold the horizontal side wall 81 downward even if it attempts to move up or down. Therefore, the horizontal side wall 81 remains in close contact with the lower mold even when separated from the U-shaped frame 71, preventing the resin of the molded resin 9 from leaking into the frame body 58a between the horizontal side wall 81 and the lower mold.

Continuing from this recess 75 is a groove 76 that extends along the cylindrical axis of the coil 5, and the horizontal side wall 81 is designed to slide within the groove 76 at the protrusion 82. This allows the horizontal side wall 81 to continue to adhere to the lower mold while moving in response to the compression of the coil 5, preventing the resin of the molded resin 9 from leaking into the frame of the frame body 58a from between the horizontal side wall 81 and the lower mold.

The above-described embodiments of the present invention are presented as examples and are not limited to the above-described embodiments. The above-described embodiments can be implemented in a variety of other forms, and various omissions, substitutions, and modifications can be made without departing from the scope of the invention. The embodiments and their modifications are included within the scope of the present invention.

First, the coil 5 may be covered by the coil coating resin 3 excluding the upper cover 6. That is, the upper cover 6 may be eliminated. In this case, the upper mold may be pressed directly against the edge plate 8 and the upper surface 51 of the coil 5. For example, the lower surface 52 of the coil 5 is in contact with a metal cooling plate or the like via a heat dissipation sheet, so scratches on the lower surface of the coil 5 may cause insulation problems. However, no metal parts or the like are located near the upper surface 51 of the coil 5, and scratch prevention measures for the upper surface 51 of the coil 5 do not need to be taken as for the lower surface 52. In such cases, the upper cover 6 is not required.

Also, the convex portion 82 of the edge plate 8 and the concave portion 75 and groove portion 76 of the vertical side portion 72 of the lower cover 7 may be eliminated. If the pressing force P1 from the upper mold can be transmitted directly or indirectly to the edge plate 8, the horizontal side wall 81 can be tightly attached to the lower mold. The engagement of the convex portion 82, concave portion 75, and groove portion 76 allows the horizontal side wall 81 to be more securely attached to the lower mold and to be more securely held downward even when moving due to injection pressure. On the other hand, if the convex portion 82, concave portion 75, and groove portion 76 are not present, the horizontal side wall 81 will be more likely to move in accordance with the coil 5.

100 Reactor 1 Core 2 Molded coil 3 Coil coating resin 5 Coil 51 Upper surface 52 Lower surface 53 Lower curved surface 53a Lower edge region 54 Horizontal surface 55 First end surface 56 Upper curved surface 57 Second end surface 58 Opening 58a Frame body 58b Gap 59 Conductive wire 6 Upper cover 61 Upper plate body 62 Side curved plate 63 Eaves portion 64 Notch 7 Lower cover 71 U-shaped frame 72 Vertical side portion 721 Contact portion 721a Contact surface 721b Upper end surface 721c Outer surface 722 Vertical portion 73 Horizontal side portion 74 Edge annular plate 75 Recess 76 Groove portion 8 Edge plate 81 Horizontal side wall 82 Convex portion 83 Flat surface 83a Upper surface 9 Molded resin

Claims (7)

a cylindrical coil whose outer shape is defined by a pair of coil end surfaces and side surfaces in which four flat surfaces and four curved surfaces are alternately arranged and which are orthogonal to the pair of coil end surfaces;
A frame body having a horizontal side wall and a U-shaped frame, which is defined by combining the horizontal side wall and the U-shaped frame in a rectangular shape, and which is placed on the coil so that a part or all of a first flat surface of the four flat surfaces is contained within the frame;
a molding resin that covers a part or all of the coil except for the inside of the frame of the frame body;
an edge plate having a flat surface covering one of the pair of coil end surfaces and the horizontal side wall, the edge plate being movable along the axial direction of the coil when the molding resin is absent;
Equipped with
The U-shaped frame is
a pair of vertical side portions extending along the cylindrical axis of the coil and in close contact with the coil;
a horizontal side portion extending between the pair of vertical side portions;
and
the horizontal side wall is in close contact with the coil end surface covered by the flat surface of the edge plate,
The horizontal side of the U-shaped frame is in close contact with the coil end surface opposite to the edge plate,
The pair of vertical side portions of the U-shaped frame and the horizontal side wall of the edge plate have irregularities that restrict movement of the horizontal side wall toward the flat surface located opposite the first flat surface, and the irregularities engage with each other,
the first flat surface of the coil is exposed from the molding resin over the entire vertical width range from one coil end surface with which the horizontal side wall is in close contact to the other coil end surface with which the horizontal side portion is in close contact;
A molded coil characterized by: the pair of vertical side portions sandwich the first flat surface and are in close contact with the two curved surfaces adjacent to the first flat surface,
the coil has at least the first flat surface exposed from the molding resin over the entire width range from one of the curved surfaces where the pair of vertical side portions are in close contact to the other of the curved surfaces;
2. The molded coil according to claim 1, wherein: The vertical side portion is
a contact surface that is adjacent to the first flat surface and that is in close contact with the curved surface;
an end surface on the flat surface side that is adjacent to the contact surface, extends along the cylindrical axis of the coil, and expands in a direction away from the contact surface and is perpendicular to the first flat surface;
an outer surface adjacent to the end surface and opposite the contact surface;
and
the angle formed between the contact surface and the end surface is approximately a right angle,
the angle formed between the end surface and the outer surface is approximately a right angle;
3. The molded coil according to claim 2, wherein: the contact surface contacts not only the curved surface adjacent to the first flat surface but also the flat surface perpendicular to the first flat surface;
4. The molded coil according to claim 3, wherein: The horizontal side walls extend equal to the distance between the opposing surfaces of the pair of vertical side portions,
the frame body is defined by the horizontal side wall being fitted between the pair of vertical side portions;
5. The molded coil according to claim 1, wherein: The pair of vertical side portions have a recessed portion among the concave and convex portions, and a groove portion continuing from the recessed portion and extending along the cylindrical axis of the coil,
The horizontal side wall has a convex portion among the concave and convex portions,
the protrusion is fitted into the recess and slides within the groove in accordance with the movement of the horizontal side wall;
2. The molded coil according to claim 1, wherein: A molded coil according to any one of claims 1 to 6;
a core including a magnetic body to which the molded coil is attached;
A reactor comprising: