Coil device

Abstract

Provided is a coil device capable of reducing thermal stress generated in a core. The coil device includes: a core including a magnetic body; and a conductive wire disposed helically around at least a portion of the core. 70% or more of the volume of the middle leg portion of the core is located below the atmosphere-open surface of the heat-dissipating resin. An outer dividing gap of the core is provided midway or at the end of the outer leg part, and the outer dividing gap is provided with a partial adhesive part in which an adhesive is sandwiched and an air layer in which no adhesive is sandwiched.

Description

Technical Field

[0001] The present invention relates to a coil device which can be suitably used as, for example, a transformer or the like. Background Art

[0002] In order to improve the heat resistance of the coil device, for example, a portion of the core is impregnated with a heat dissipating resin to improve the cooling effect in Patent Document 1. However, this technique has a technical problem that the portion covered with the heat dissipating resin is small, and a sufficient heat dissipating effect cannot be expected.

[0003] Therefore, it is also considered to cover most of the core with heat dissipation resin, but if it is configured in this way, the case for storing the heat dissipation resin becomes too large, which goes against the requirement of miniaturization of the coil device. Therefore, sometimes the heat dissipation resin is covered in a manner that the winding part of the conductor is impregnated within the necessary minimum range.

[0004] In the past, generally speaking, an outer leg of a core is arranged outside a middle leg of a core having a winding portion of a conducting wire, and the front end of the outer leg of the core is bonded to the front end of another outer leg by an adhesive over the entire surface. Since the temperature of the heat dissipating resin located inside the outer leg of the core is higher than the temperature of the heat dissipating resin located outside the outer leg, stress sometimes concentrates on the root portion between the outer leg and the base due to the thermal expansion of the heat dissipating resin located inside the outer leg. If the concentration of stress increases, cracks tend to be generated in the core. In particular, with the increase in the current of coil devices in recent years, the reduction of the thermal stress generated in the core has become a technical problem.

[0005] Prior art literature

[0006] Patent Literature

[0007] Patent Document 1: Japanese Patent Application Publication No. 2014-36194 Summary of the invention

[0008] 1. Technical issues to be resolved

[0009] The present invention has been made in view of the above-mentioned current situation, and an object of the present invention is to provide a coil device capable of reducing the thermal stress generated in the core.

[0010] (II) Technical solution

[0011] In order to achieve the above-mentioned object, a coil device according to a first aspect of the present invention comprises:

[0012] a core including a magnetic body; and

[0013] a wire disposed helically around at least a portion of the core,

[0014] The core has:

[0015] a middle leg portion, which is provided with a winding portion of the wire;

[0016] an outer leg portion disposed outside the winding portion of the wire; and

[0017] a base portion that magnetically connects the middle leg portion to the outer leg portion,

[0018] More than 70% of the volume of the middle leg portion is located below the surface of the heat dissipating resin open to the atmosphere.

[0019] An outer dividing gap is provided in the middle or at the end of the outer leg portion,

[0020] The outer dividing gap includes a partially bonded portion where an adhesive is interposed and an air layer where no adhesive is interposed.

[0021] The air layer is located below a surface of the heat-dissipating resin open to the atmosphere.

[0022] In this coil device, since most of the volume of the middle leg is located below the atmosphere-opening surface of the heat-dissipating resin, most of the volume of the winding portion of the conductor arranged around the middle leg is cooled by the heat-dissipating resin together with the middle leg, thereby improving the heat dissipation. In addition, since a partial bonding portion is provided in the middle or at the end of the outer leg, the assembly and handling of the split core to which the winding portion of the conductor is assembled are easy, and the manufacture of the coil device becomes easy.

[0023] In addition, since the outer dividing gap having an air layer is formed in the middle or at the end of the outer leg, the thermal expansion of the heat dissipating resin located inside the outer leg is easily absorbed by the middle or end portion of the outer leg having the dividing gap. That is, the air layer in the dividing gap can prevent the outer leg from being easily deformed and the thermal stress from being concentrated on a specific part of the core. As a result, the stress concentration that may be generated at the root portion between the outer leg and the base of the core can be reduced, and the generation of cracks can be suppressed.

[0024] In addition, since the outer leg has an adhesive portion, the connection portion of the split core (the connection between the outer legs or the connection between the outer leg and the base) is less likely to shift, and the increase in loss can also be prevented. In addition, since the outer leg has an adhesive portion, an inner split gap (gap) that does not require bonding can be formed in the middle leg, and the gap width can be freely adjusted. By adjusting the gap width, the leakage magnetic properties of the coil device can be adjusted. In addition, the adhesive portion can be provided in the middle leg, and a docking portion (a portion where only the split cores contact each other) without using an adhesive can also be provided.

[0025] The outer leg may include a first outer leg and a second outer leg, and the outer dividing gap may be provided between the front end of the first outer leg and the front end of the second outer leg. In addition, the outer dividing gap may be provided between one end of the outer leg and the inner surface of the base.

[0026] The area ratio of the partial bonding portion in the cross section of the outer segmentation gap is preferably 3% to 50%, 5% to 45%, 10% to 40%, or 15% to 35%. The larger the area ratio of the partial bonding portion, the more the bonding force between the outer legs or the bonding force between the outer legs and the base tends to be improved. In addition, the smaller the area ratio of the partial bonding portion, the larger the area ratio of the air layer is relatively, and the greater the tendency to relax the concentration of thermal stress.

[0027] A coil device according to a second aspect of the present invention includes:

[0028] a core including a magnetic body; and

[0029] a wire disposed helically around at least a portion of the core,

[0030] The core has:

[0031] a middle leg portion, which is provided with a winding portion of the wire;

[0032] an outer leg portion disposed outside the winding portion of the wire; and

[0033] a base portion that magnetically connects the middle leg portion to the outer leg portion,

[0034] More than 70% of the volume of the middle leg portion is located below the surface of the heat dissipating resin open to the atmosphere.

[0035] An inner dividing gap is provided in the middle or at the end of the middle leg portion,

[0036] The inner dividing gap is provided with an adhesive portion at least partially filled with an adhesive,

[0037] An outer dividing gap is provided in the middle or at the end of the outer leg portion,

[0038] An air layer is provided in the outer dividing gap,

[0039] The adhesive portion and the air layer are located below a surface of the heat-dissipating resin open to the atmosphere.

[0040] In this coil device, since most of the volume of the middle leg portion is located below the atmosphere-opening surface of the heat-dissipating resin, the winding portion of the conductor arranged around the middle leg portion is cooled by the heat-dissipating resin together with the middle leg portion, thereby improving the heat dissipation. In addition, since the bonding portion is provided in the middle or at the end of the middle leg portion, the assembly and handling of the split cores to which the winding portion of the conductor is assembled are easy, and the manufacture of the coil device becomes easy.

[0041] In addition, since the outer dividing gap having an air layer is formed in the middle or at the end of the outer leg, the thermal expansion of the heat dissipating resin located inside the outer leg is easily absorbed by the middle or end portion of the outer leg having the dividing gap. That is, the air layer in the dividing gap can prevent the outer leg from being easily deformed and the thermal stress from being concentrated on a specific part of the core. As a result, the stress concentration that may be generated at the root portion between the outer leg and the base of the core can be reduced, and the generation of cracks can be suppressed.

[0042] In addition, since the middle leg portion has an adhesive portion, it is no longer necessary to provide an adhesive portion on the outer leg portion, and it is easy to form an outer dividing gap having an air layer in the middle or at the end of the outer leg portion. The area ratio of the air layer in the cross section of the outer dividing gap is preferably 50% or more, 60% or more, 70% or more, 80% or more, 90% or more, 95% or more, or 98% or more. The larger the area ratio of the air layer, the greater the tendency to alleviate the concentration of thermal stress. In the outer dividing gap where the air layer is not formed, an adhesive portion may be formed, a heat dissipating resin may be allowed to enter, and a butt joint portion (a portion where only the divided cores are in contact with each other) where no adhesive or resin is sandwiched may exist.

[0043] The middle leg portion may also include a first middle leg portion and a second middle leg portion, and the inner dividing gap may also be provided between the front end of the first middle leg portion and the front end of the second middle leg portion. In addition, the inner dividing gap may also be provided between one end of the middle leg portion and the inner surface of the base portion.

[0044] Preferably, the gap width of the outer dividing gap is a thickness to which the heat dissipating resin existing around the outer dividing gap does not enter. The upper limit of the gap width is preferably 50 μm or less, 40 μm or less, 30 μm or less, or 20 μm or less. In addition, the lower limit of the gap width is preferably 5 μm or more, 8 μm or more, or 10 μm or more. The larger the gap width, the greater the stress relaxation effect tends to be, and the smaller the gap width, the easier it tends to form an air layer.

[0045] The base may also be close to the cooling wall surface of the housing filled with the heat-dissipating resin. When the cooling wall surface of the housing is the bottom surface of the housing, the core is preferably housed inside the housing in a manner that the axial core of the winding portion of the wire is substantially perpendicular to the bottom surface of the housing. In addition, when the cooling wall surface of the housing is the side surface of the housing, the core may also be housed inside the housing in a manner that the axial core of the winding portion of the wire is substantially parallel to the bottom surface of the housing. With such a configuration, the heat dissipation of the middle leg portion and the winding portion of the wire arranged around it is improved.

[0046] Preferably, the heat dissipating resin is arranged at a position covering the winding portion of the conductive wire, and the winding portion of the conductive wire is arranged around the middle leg portion. With this configuration, heat dissipation is improved.

[0047] The coil device may further include a terminal block for holding the lead portion of the conductive wire. The terminal block may be mounted on the bobbin or on a housing that accommodates the heat dissipating resin. Alternatively, the terminal block may be mounted on the core. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] Figure 1 It is a schematic perspective view of a coil device according to one embodiment of the present invention.

[0049] Figure 2 yes Figure 1 A schematic exploded perspective view of the coil device shown.

[0050] Figure 3A It is along Figure 1 A schematic cross-sectional perspective view of IIIA-IIIA.

[0051] Figure 3B It is along Figure 3A A schematic cross-sectional view of the core of IIIB-IIIB.

[0052] Fig.4A1 It is only a rough representation Figure 3A A cross-sectional view of the core, housing, and heat-dissipating resin is shown.

[0053] Figure 4A2 is an exaggeration Fig.4A1 A schematic cross-sectional view showing thermal deformation of a core when a temperature difference occurs in the heat-dissipating resin around the core.

[0054] Figure 4B1 It is a rough representation Fig.4A1 A cross-sectional view of a modified example of the core shown.

[0055] Figure 4B2 is an exaggeration Figure 4B1 A schematic cross-sectional view showing thermal deformation of a core when a temperature difference occurs in the heat-dissipating resin around the core.

[0056] Figure 4C yes Fig.4A1 A schematic cross-sectional view of another modified example of the core shown.

[0057] Figure 4D yes Fig.4A1 A schematic cross-sectional view of yet another modified example of the core shown.

[0058] Figure 4E yes Fig.4A1 A schematic cross-sectional view of yet another modified example of the core shown.

[0059] Figure 4F yes Fig.4A1 A schematic cross-sectional view of another modified example of the core shown.

[0060] Figure 4G yes Fig.4A1 A schematic cross-sectional view of yet another modified example of the core shown.

[0061] Figure 4H yes Figure 4B1 A schematic cross-sectional view of yet another modified example of the core shown.

[0062] Description of reference numerals:

[0063] 1, 1B: coil device; 2, 2B~2H: core; 21: first core; 21a: first base; 21a1: inner surface; 21b: outer leg; 21b1: front end; 21c: middle leg; 21c1: front end; 22: second core; 22a: second base; 22a1: inner surface; 22b: outer leg; 22b1: front end; 22c: middle leg; 22c1: front end; 23: middle leg; 23a: lower end; 23b: upper end; 24: step shaped protrusion; 25: outer leg portion; 26, 26a, 26b: outer dividing gap; 27, 27a, 27b: inner dividing gap; 4: first wire; 40: first wire winding portion; 41a, 41b: lead portion; 5: second wire; 50: second wire winding portion; 51a, 51b: lead portion; 8: shell; 80: bottom plate; 81: side plate; 82: heat dissipating resin; 82a: atmosphere open surface; 9: partial bonding portion; 9a: bonding portion; 10: air layer. DETAILED DESCRIPTION

[0064] Hereinafter, the embodiments of the present invention will be described with reference to the accompanying drawings. In addition, the contents of the drawings are only schematically and exemplarily shown for the purpose of understanding the present invention, and the appearance, dimensional ratio, etc. may be different from the actual object. In addition, the present invention is not limited to the following embodiments.

[0065] (First embodiment)

[0066] Figure 1 The coil device 1 according to the embodiment of the present invention shown in the figure functions as, for example, a leakage transformer, and is used in a vehicle charger, a power supply circuit of various electrical equipment, and the like. Figure 2 As shown, the coil device 1 includes a core 2 , a winding portion 40 of a conductor 4 , a winding portion 50 of a conductor 5 , and a housing 8 .

[0067] In addition, in the drawings, the X-axis, the Y-axis, and the Z-axis are perpendicular to each other, and the Z-axis is parallel to the height direction of the coil device 1. In the following description, for each of the X-axis, the Y-axis, and the Z-axis, the direction toward the center of the coil device 1 is referred to as the inner side, and the direction away from the center of the coil device 1 is referred to as the outer side.

[0068] like Figure 2 As shown, in this embodiment, the core 2 is composed of a combination of multiple split cores, including: a first core 21 arranged on the lower side along the Z axis, a second core 22 arranged on the upper side of the first core 21 along the Z axis, and a middle leg portion 23 arranged between the first core 21 and the second core 22, which are separated and formed.

[0069] The first core 21 has: a flat plate-shaped first base 21a; outer leg portions 21b, 21b protruding upward along the Z axis from both sides of the first base 21a along the Y axis; and a middle leg portion 21c protruding upward along the Z axis from the approximate center of the first base 21a along the Y axis. In addition, the second core 22 has: a flat plate-shaped second base 22a; outer leg portions 22b, 22b protruding downward along the Z axis from both sides of the second base 22a along the Y axis; and a middle leg portion 22c protruding downward along the Z axis from the approximate center of the second base 22a along the Y axis.

[0070] In the present embodiment, the first core 21 and the second core 22 are respectively formed of an E-shaped core having a substantially E-shaped cross section parallel to a plane including the Z axis and the Y axis, and the first core 21 and the second core 22 have the same shape as each other, but may also be different from each other. For example, one core may be an E-shaped core and the other core may be a U-shaped core. The cores 21 and 22 are not particularly limited as long as they are cores having a magnetic body, and may be formed of, for example, ferrite, a metal magnetic body, or a resin containing magnetic powder.

[0071] In this embodiment, if Figure 3AAs shown, a first wire winding portion 40 wound with a first wire 4 is arranged around the middle leg portion 21c of the first core 21, and a second wire winding portion 50 wound with a second wire 5 is arranged around the middle leg portion 22c of the second core. In addition, in the present embodiment, the second wire winding portion 50 is arranged on the upper side of the first wire winding portion 40 along the Z axis, but the reverse may be true. In addition, for example, the first wire winding portion 40 is a primary side coil of a transformer, and the second wire winding portion 50 is a secondary side coil of a transformer, but the reverse may be true.

[0072] The first conductor 4 and the second conductor 5 can be directly wound around the middle legs 21c and 22c to form the first conductor winding portion 40 and the second conductor winding portion 50, respectively. However, the first conductor winding portion 40 and the second conductor winding portion 50 can also be prepared as air-core coils that are wound in advance and then arranged around the middle legs 21c and 22c. The outer legs 21b and 22b are arranged outside the winding portions 40 and 50 arranged around the middle legs 21c and 22c, respectively. The winding method of the conductor 4 or 5 is not particularly limited, and examples thereof include normal winding and α winding.

[0073] In the present embodiment, the first conductive wire 4 and the second conductive wire 5 are respectively formed of conductive wires, which may not be covered with insulation, but are preferably covered with insulation. The type of conductive wire is not particularly limited, and it can be a conductive core wire such as a round wire, a flat wire, a stranded wire, a Litz wire, or a braided wire. The material of the welding layer or the insulating layer covering the core wire is not particularly limited, and examples thereof include polyurethane, polyamide-imide, polyimide, polyester, and the like.

[0074] In addition, in the present embodiment, the first conductive wire 4 and the second conductive wire 5 are both composed of self-fusing conductive wires, but only one of them may be a self-fusing conductive wire, or both of them may be composed of other conductive wires. In addition, at least one of the first conductive wire winding portion 40 and the second conductive wire winding portion 50 may be a flat coil. The wire diameters of the first conductive wire 4 and the second conductive wire 5 may be the same or different, and both are not particularly limited, but are preferably within the range of 1.0 to 3.0 mm, for example.

[0075] like Figure 2 As shown, lead portions 41a and 41b are formed at both ends of the first wire 4 constituting the first wire winding portion 40, and each lead portion 41a and 41b is led out from the first winding portion 40 along the Z-axis upward side and is connected to a terminal or the like which is not shown. In addition, lead portions 51a and 51b are formed at both ends of the second wire 5 constituting the second wire winding portion 50, and each lead portion 51a and 51b is led out from the second winding portion 50 along the Z-axis upward side and is connected to a terminal or the like.

[0076] The terminals to which the lead portions 41a, 41b, 51a, and 51b are respectively connected may be mounted on, for example, a terminal block not shown in the figure. The terminal block may be mounted on the upper surface of the second core 22 of the core 2, or on the housing 8, or on a bobbin not shown in the figure.

[0077] like Figure 3A As shown, the first core 21 with the first winding portion 40 installed and the second core 22 with the second winding portion 50 installed are assembled in a manner such that the front ends 21c1, 22c1 of the middle legs 21c, 22c face each other and the front ends 21b1, 22b1 of the outer legs 21b, 22b face each other.

[0078] If Figure 3A The winding portions 40 and 50 are omitted in the illustration. Fig.4A1 As shown, in this embodiment, the front end portions 21b1, 22b1 of the outer leg portions 21b, 22b are aligned with each other along the Z axis ( Figure 3A The winding axes of the winding parts 40 and 50 shown in the figure are opposite to each other at a predetermined interval (gap width) t1, and there is an outer dividing gap 26 of the core 2 between them. In addition, in the present embodiment, the front end portions 21c1, 22c1 of the middle leg portions 21c, 22c are mutually connected along the Z axis ( Figure 3A The winding axes of the winding parts 40 and 50 shown in the figure are opposite to each other at a predetermined interval (gap width) t2, and there is an inner dividing gap 27 of the core 2 between them. The dividing gaps 26 and 27 refer to the gaps at the butt joints (combined parts or joints) of the divided first core 21 and the second core 22 constituting the core 2.

[0079] In the present embodiment, the inner divided gap 27 of the predetermined interval t2 constitutes a gap in the core 2, and the heat dissipating resin 82 preferably enters the gap 27, but the gap may be a gap to the extent that the heat dissipating resin 82 does not necessarily enter. Alternatively, the front end portions 21c1, 22c1 of the middle leg portions 21c, 22c may contact each other so that the predetermined interval t2 is 0.

[0080] In addition, in this embodiment, if Figure 3B As shown, in the outer divided gap 26 of the predetermined interval t1, a partial bonding portion 9 is provided at a substantially central position along the X axis. Fig.4A1 The space between the front end portions 21 b 1 , 22 b 1 of the outer leg portions 21 b , 22 b shown in the figure is partially filled with adhesive, and these front end portions 21 b 1 , 22 b 1 are partially joined.

[0081] like Figure 3B As shown in FIG. 1 , each partially bonded portion 9 has an air layer 10 on both sides along the X axis where no adhesive is present. The air layer 10 is defined as a layer formed between Fig.4A1The front ends 21b1 and 22b1 of the outer legs 21b and 22b shown in the figure have a gap of a predetermined interval t1 between them. No adhesive is interposed in the gap (air layer 10) of the predetermined interval t1, and the predetermined interval t1 is adjusted so that the heat dissipating resin 82 does not enter.

[0082] The upper limit of the predetermined interval (gap width) t1 is preferably 50 μm or less, 40 μm or less, 30 μm or less, or 20 μm or less. In addition, the lower limit of the predetermined interval t1 is preferably 5 μm or more, 8 μm or more, or 10 μm or more. The larger the predetermined interval t1, the greater the stress relaxation effect tends to be, and the smaller the gap width, the easier it tends to form an air layer.

[0083] like Figure 3B As shown, the area ratio of the partial bonding portion 9 in the cross section of the outer divided gap 26 of the core is preferably 3% to 50%, 5% to 45%, 10% to 40%, or 15% to 35% relative to the entire cross section of the outer divided gap 26. The larger the area ratio of the partial bonding portion, the more the bonding force between the outer legs or the bonding force between the outer legs and the base tends to be improved. In addition, the smaller the area ratio of the partial bonding portion, the larger the area ratio of the air layer is relatively, and the greater the tendency to alleviate the concentration of thermal stress. In addition, the entire cross section of the outer divided gap 26 is also the entire area of ​​the front end portions 21b1, 22b1 of the outer legs 21b, 22b.

[0084] In addition, in the present embodiment, partial adhesive portions 9 are provided at approximately the center of the outer divided gap 26 along the X-axis, and preferably, air layers 10 are provided on both sides of the partial adhesive portions 9 along the X-axis, but the present invention is not limited thereto. For example, partial adhesive portions 9 may be provided at a plurality of locations along the X-axis of the outer divided gap 26, and air layers 10 may be disposed between them. In addition, in the present embodiment, partial adhesive portions 9 are provided at the front end portions 21b1, 22b1 of the outer leg portions 21b, 22b in a continuous manner along the Y-axis, but may be provided intermittently. In addition, air layers 10 may be provided on one or both sides of the partial adhesive portion 9 along the Y-axis.

[0085] In the coil device 1, as Fig.4A1 As shown, most of the volume of the middle leg portions 21c and 22c is located below (on the side of the heat dissipating resin 82) the atmosphere open surface 82a of the heat dissipating resin 82. That is, the atmosphere open surface 82a is set so that 70% or more, preferably 80% or more, more preferably 90% or more, or 95% or more of the volume of the middle leg portions 21c and 22c is located below the atmosphere open surface 82a of the heat dissipating resin 82.

[0086] In addition, if Figure 3A As shown, the open-air surface 82a of the heat-dissipating resin 82 is determined such that the winding portion 50 of the second wire 5 is sufficiently impregnated with the heat-dissipating resin 82, and preferably 80% or more, more preferably 95% or more, or substantially 100% or more of the winding portion 40 of the first wire 4 is impregnated with the heat-dissipating resin 82. By configuring in this way, the heat generated in the winding portions 40 or 50 of the wires 4 or 5 is also cooled by the heat-dissipating resin 82.

[0087] In addition, in the present embodiment, the heat transferred from the winding portions 40 or 50 of the wires 4 or 5 or the core 2 to the heat-dissipating resin 82 is transferred through the housing 8 to a cooling member (such as a cooling block with a cooling passage) provided on the lower surface of the bottom plate 80 of the housing 8 for heat dissipation. In addition, the open-air surface 82a refers to the surface formed by solidifying the liquid surface formed by flowing the heat-dissipating resin 82 in a flowing state into the housing 8.

[0088] As Figure 1 shown, the housing 8 has a substantially rectangular bottom plate 80 and side plates 81. The side plates 81 stand up upward along the Z-axis from the four-side positions of the bottom plate 80, and a bottomed accommodation space is formed inside, and an upper opening is formed in the upper part along the Z-axis. The housing 8 is preferably made of a metal such as aluminum with excellent heat conductivity, but it can also be made of resin.

[0089] The heat-dissipating resin 82 is also called a potting resin and is composed of a silicone resin (Japanese: シリコーン樹脂), a urethane resin (Japanese: ウレタン樹脂), an epoxy resin, etc. that are also soft after injection. The longitudinal elastic modulus of the potting resin is preferably 0.1 to 100 MPa. In the present embodiment, for example, through the heat-dissipating resin 82 and the housing 8, the heat generated in the first winding portion 40, the second winding portion 50, and the core 2 can be efficiently dissipated from the bottom of the housing 8 to the outside, improving the cooling efficiency of the coil device 1.

[0090] In addition, after the heat-dissipating resin 82 is pre-filled into the housing 8, the core 2 accommodating and mounting the Figure 2 shown winding portions 40 and 50 of the wires can be installed, or after the core 2 accommodating and mounting the winding portions 40 and 50 of the wires is installed inside the housing 8, the heat-dissipating resin 82 can be made to flow into the housing 8.

[0091] In the coil device 1 of the present embodiment, as Figure 3A and Fig.4A1As shown in FIG. 1 , since most of the volume of the middle legs 21c and 22c of the core 2 is located below the atmosphere exposed surface 82a of the heat dissipation resin 82, the winding portions 40 and 50 of the conductors 4 and 5 arranged around the middle legs 21c and 22c are cooled by the heat dissipation resin 82 together with the middle legs 21c and 22c, and the heat dissipation is improved. That is, the atmosphere exposed surface 82a of the heat dissipation resin 82 is located at a position where the heat dissipation resin 82 covers the winding portions 40 and 50 of the conductors 4 and 5 arranged around the middle legs 23, and thus the heat dissipation of the winding portions 40 and 50 is improved.

[0092] Furthermore, in the present embodiment, in the middle of the outer leg portions 21b, 22b, that is, between the front end portions 21b1, 22b1 of the outer leg portions 21b, 22b, an air layer 10 is provided as well as a partial bonding portion 9. Therefore, the assembly and handling of the divided first core 21 and the second core 22 in which the winding portions 40, 50 in which the conductors 4, 5 are respectively assembled are easy, and the manufacture of the coil device 1 becomes easy.

[0093] In addition, the outer dividing gap 26 having the air layer 10 is formed in the middle of the outer leg portions 21b and 22b. Therefore, the thermal expansion of the heat dissipating resin 82 located inside the outer leg portions 21b and 22b is easily absorbed by the middle portion of the outer leg portions 21b and 22b where the dividing gap 26 is formed. That is, the air layer 10 of the dividing gap 26 is formed. Figure 4A2 As shown, it is possible to suppress the outer leg portions 21b and 22b from being easily deformed outward and the thermal stress from being concentrated on a specific portion of the core 2. As a result, it is possible to reduce the stress concentration that may occur at the root portion between the outer leg portion 22b and the base portion 22a of the core 2, especially on the inner side of the connection portion between the outer leg portion 22b and the second base portion 22a, and to suppress the occurrence of cracks and the like.

[0094] In addition, since the partial bonding portion 9 is provided in the middle (between) of the outer legs 21b and 22b, the connection portion of the split core (the connection between the outer legs 21b and 22b) is less likely to shift, and the increase in loss can be prevented. In addition, in the coil device 1 of the present embodiment, in the absence of the partial bonding portion 9, the connection portion of the split core (the connection between the outer legs 21b and 22b) is likely to shift, and the loss tends to increase.

[0095] Furthermore, in this embodiment, if Fig.4A1 As shown, since there is a partial bonding portion 9 between the outer legs 21b and 22b, an inner dividing gap (gap) 27 of a predetermined interval t2 that does not require bonding can be formed between the front end portions 21c1 and 22c1 of the middle legs 21c and 22c, and the predetermined interval (gap width) t2 can be freely adjusted. By adjusting the gap width t2, the leakage magnetic characteristics of the coil device 1 can be adjusted.

[0096] In addition, in the present embodiment, the lower limit of the prescribed interval t2 may be 0, and the front end portions 21c1 and 22c1 of the middle leg portions 21c and 22c may be butted with the prescribed interval t2 being 0. Alternatively, the prescribed interval t2 may be, for example, 10 μm or more, 30 μm or more, 50 μm or more, or 60 μm or more. When the prescribed interval t2 is less than 50 μm, it is difficult for the heat dissipating resin 82 to enter the dividing gap 27, and an air layer is easily formed in the gap 27. When the prescribed interval t2 is 50 μm or more, the heat dissipating resin 82 tends to easily enter the gap 27. In addition, a bonding portion similar to the partial bonding portion 9 may be formed in at least a portion of the gap 27, other resins or spacers may be interposed, and an air layer may be formed in at least a portion.

[0097] In addition, in the present embodiment, the first base portion 21a is close to the bottom plate 80, which is a cooling wall surface of the housing 8 filled with the heat dissipating resin 82. When the cooling wall surface of the housing 8 is the bottom surface of the housing 8, the core 2 is preferably accommodated inside the housing 8 in a manner such that the axial cores of the winding portions 40 and 50 of the conductors 4 and 5 are substantially perpendicular to the bottom surface of the housing 8.

[0098] In addition, in another embodiment, when the cooling wall surface of the shell 8 is the side surface of the shell 8 (side plate 81), the core 2 can also be accommodated inside the shell 8 in a manner such that the axial core of the winding portion 40, 50 of the conductor 4, 5 is approximately parallel to the bottom surface of the shell 8.

[0099] (Second embodiment)

[0100] like Figure 4B1 as well as Figure 4B2 As shown, the coil device 1B of this embodiment is the same as the coil device 1 of the above-mentioned embodiment except for the following, and has the same function and effect. That is, in the core 2B of the coil device 1B of this embodiment, the inner dividing gap 27 of the core is provided in the middle of the middle legs 21c, 22c, that is, between the front ends 21c1, 22c1 of the middle legs 21c, 22c. The inner dividing gap 27 is provided with an adhesive portion 9a at least partially filled with an adhesive. In addition, the outer dividing gap 26 of the core is provided in the middle of the outer legs 21b, 22b, that is, between the front ends 21b1, 22b1 of the outer legs 21b, 22b. The outer dividing gap 26 is provided with an air layer 10, and the adhesive portion 9a and the air layer 10 are located below the atmosphere open surface 82a of the heat dissipating resin 82.

[0101] In the coil device 1B, most of the volume of the middle legs 21c and 22c is also located below the atmosphere open surface 82a of the heat dissipation resin 82, so that most of the volume of the winding parts 40 and 50 of the conductor is also cooled by the heat dissipation resin together with the middle legs 21c and 22c, and the heat dissipation is improved. In addition, the bonding part 9a is provided in the middle of the middle legs 21c and 22c, so the assembly and handling of the split cores to which the winding parts 40 and 50 of the conductor are assembled are easy, and the manufacture of the coil device 1B becomes easy.

[0102] In addition, an outer dividing gap 26 having an air layer 10 is formed in the middle of the outer leg portions 21b and 22b, so that the thermal expansion of the heat dissipating resin 82 located inside the outer leg portions 21b and 22b is easily absorbed by the middle portion of the outer leg portions 21b and 22b where the dividing gap 26 is formed. Figure 4B2 As shown, the outer legs 21b and 22b can be prevented from being easily deformed and the thermal stress can be prevented from being concentrated on a specific part of the core by the air layer 10 that divides the gap 26. As a result, the stress concentration that may be generated at the root part between the outer legs 22b and the base 22a of the core can be reduced, and the generation of cracks can be prevented.

[0103] In addition, since the middle leg portions 21c and 22c have the adhesive portion 9a, it is no longer necessary to provide the adhesive portion in the outer leg portions 21b and 22b, and it is easy to form the outer divided gap 26 having the air layer 10 in the middle of the outer leg portions 21b and 22b. The area ratio of the air layer 10 in the cross section of the outer divided gap 26 is preferably 50% or more, 60% or more, 70% or more, 80% or more, 90% or more, 95% or more, or 98% or more. The larger the area ratio of the air layer 10, the greater the tendency to alleviate the concentration of thermal stress. In the outer divided gap 26 where the air layer 10 is not formed, an adhesive portion may be formed, the heat dissipating resin 82 may be inserted, or there may be a butt joint (a portion where only the divided cores are in contact with each other) where no adhesive or resin is sandwiched.

[0104] In the present embodiment, the gap width t1a of the outer dividing gap 26 is preferably a thickness such that the heat dissipating resin 82 existing around the outer dividing gap 26 does not enter. The upper limit of the gap width t1a is preferably 50 μm or less, 40 μm or less, 30 μm or less, or 20 μm or less. In addition, the lower limit of the gap width t1a is preferably 5 μm or more, 8 μm or more, or 10 μm or more. The larger the gap width t1a, the greater the stress relaxation effect tends to be, and the smaller the gap width t1a, the easier it tends to form an air layer.

[0105] In addition, the specified interval t2a of the inner dividing gap 27 having the adhesive portion 9a can be a gap of a degree that allows the front end portion 21c1 of the middle leg portion 21c to be joined to the front end portion 22c1 of the middle leg portion 22c by an adhesive, for example, it can be greater than 10μm, greater than 30μm, greater than 50μm or greater than 60μm.

[0106] (Third Embodiment)

[0107] like Figure 4C As shown, the coil device of this embodiment is the same as the coil device 1 of the first embodiment described above except for the following, and has the same effect. That is, the coil device of this embodiment has the same structure and has the same effect except for having a core 2C different from the core 2 of the previous embodiment.

[0108] In the core 2C of the present embodiment, unlike the core 2 of the aforementioned embodiment, one end (lower end) 23a of the single middle leg portion 23 is magnetically connected to the inner surface 21a1 of the base 21a of the first core 21 via a first inner dividing gap 27a of a predetermined interval t3. In addition, the other end (upper end) 23b of the middle leg portion 23 is magnetically connected to the inner surface 22a1 of the base 22a of the second core 22 via a second inner dividing gap 27a of a predetermined interval t4. The predetermined intervals t3 and t4 are not particularly limited, and for example, the sum of the predetermined intervals t3 and t4 determines the leakage magnetic characteristics of the coil device, and therefore, is determined to be equal to Fig.4A1 The prescribed intervals t2 shown are equal.

[0109] The core 2C of this embodiment is similar to the first embodiment in that the outer divided gap 26 having the partial bonding portion 9 is provided in the middle of the outer leg portions 21 b and 22 b , and the same operation and effect are achieved.

[0110] In the present embodiment, the atmosphere open surface 82a is set so that 70% or more, preferably 80% or more, more preferably 90% or more or 95% or more of the volume of the middle leg portion 23 is located below the atmosphere open surface 82a of the heat dissipating resin 82 and below the inner surface 22a1 of the base portion 22a along the Z axis. With such a configuration, an air layer into which the heat dissipating resin 82 does not enter is formed in the gap 27b. The heat dissipating resin may or may not enter the gap 27a. For example, by setting the predetermined interval t3 to be less than 50 μm, the heat dissipating resin is difficult to enter, and an air layer is easily formed.

[0111] In this embodiment, when an air layer consisting of the gap 27a is formed between the first base 21a and one end (lower end 23a) of the middle leg 23, the heat of the middle leg 23 is difficult to be transferred to the first base 21a, and the change in the temperature distribution along the winding axis of the middle leg 23 is reduced. The middle leg 23 is uniformly cooled by the heat dissipating resin. As a result, in the middle leg 23, it is difficult to generate a sharp temperature gradient along the winding axis (parallel to the Z axis) of the conductor 4 or 5, and the thermal stress generated in the core 2 (especially the middle leg 23) is reduced, thereby reducing the core loss.

[0112] In this embodiment, a gap 27b consisting of an air layer may be formed between the inner surface 22a1 of the second base 22a and the upper end 23b of the middle leg 23. The air layer is preferably 3 mm or less, more preferably 2 mm or less, and even more preferably 1.9 mm or less. The presence of an air layer between the second base 22a and the upper end 23b of the middle leg 23 makes it difficult for stress such as thermal expansion tension generated in the middle leg 23 to be transmitted to the second base 22a, thereby reducing the thermal stress that may be generated in the second base 22a. As a result, the possibility of the occurrence of defects such as rupture and defect of the core can be further reduced.

[0113] In addition, in the present embodiment, 30% or more, 50% or more, 80% or more, or 95% or more, preferably 100% or more of the volume of the second base portion 22a is exposed from the heat dissipating resin 82. By exposing most of the second base portion 22a, it is possible to achieve miniaturization of the housing 8 that accommodates the heat dissipating resin 82, and also to reduce the amount of the heat dissipating resin 82. Moreover, even in this case, since the second base portion 22a is separated from the upper end of the middle leg portion 23 along the Z axis by the gap 27b of a predetermined interval, stress such as thermal expansion tension generated in the middle leg portion 23 where heat is easily accumulated is not transmitted to the second base portion 22a.

[0114] In the present embodiment, the upper end 23b of the middle leg portion 23 may be located below the atmosphere open surface 82a of the heat dissipating resin 82. With such a configuration, the heat dissipation of the middle leg portion 23 and the winding portions 40, 50 of the conductors 4, 5 disposed therearound is improved. Even in this case, the atmosphere open surface 82a may be located in the middle of the gap 27b so that an air layer is formed in the gap 27b. In addition, the upper end 23b of the middle leg portion 23 may be located above the atmosphere open surface 82a of the heat dissipating resin 82.

[0115] (Fourth Embodiment)

[0116] like Figure 4DAs shown, the coil device of this embodiment is the same as the coil device of the third embodiment described above except for the following, and has the same effect. That is, the coil device of this embodiment has the same structure and has the same effect except for having a core 2D different from the core 2C of the previous embodiment.

[0117] The core 2D of this embodiment is different from the core 2C of the aforementioned embodiment in that a stepped protrusion 24 is formed on the inner surface of the base 21a opposite to the upper end or lower end of the middle leg portion 23 along the Z axis. The protruding height (along the Z axis) of the stepped protrusion 24 is not particularly limited as long as a gap 27b or 27a is formed between the front end of the stepped protrusion 24 along the Z axis and the upper end or lower end of the middle leg portion 23.

[0118] However, it is desirable that the protruding height of the stepped protrusion 24 facing the upper end of the middle leg portion 23 is as small as possible. The other structures and effects are the same as those of the above-mentioned embodiment, and the description of the overlapping parts is omitted.

[0119] (Fifth Embodiment)

[0120] like Figure 4E The coil device of this embodiment is similar to the coil device of the third embodiment described above (see Figure 4C That is, the coil device of this embodiment has the same structure and has the same effect, except that it has a core 2E different from the core 2C of the above-mentioned embodiment.

[0121] In the core 2E of the present embodiment, the second core 22 is a core having a U-shaped cross section, and the inner surface 22a1 of the second core 22 at the substantially central portion along the Y axis is opposite to the front end portion 21c1 of the middle leg portion 21c with a predetermined interval of the inner gap 27b, wherein the middle leg portion 21c is integrally formed with the base 21a of the first core 21. In the present embodiment, the interval of the inner gap 27b along the Z axis is approximately Figure 4C The gap shown is the sum of the prescribed intervals t3 and t4.

[0122] (Sixth Embodiment)

[0123] like Figure 4F The coil device of this embodiment is similar to the coil device of the third embodiment described above (see Figure 4C That is, the coil device of this embodiment has the same structure and has the same effect, except that it has a core 2F different from the core 2C of the above-mentioned embodiment.

[0124] The core 2F of this embodiment is different from the core 2C of the aforementioned embodiment. The first core 21 has a first base 21a independent of the outer leg 25, and the second core 22 has a second base 22a independent of the outer leg 25. The outer leg 25 has the following structure: the outer leg 21b and the outer leg 22b opposite to each other along the Z-axis direction of the aforementioned embodiment are integrated and separated and independent of their respective bases 21a and 22a. In this embodiment, a first outer dividing gap 26a is provided at one end (lower end) of the outer leg 25. The first outer dividing gap 26a has a partial bonding portion 9 and an air layer 10 (see Figure 3B ), and at the other end (upper end) of the outer leg portion 25, there is a second outer dividing gap 26b, which has a partial bonding portion 9 and an air layer 10 (refer to Figure 3B ). Other structures and effects are the same as those in the above-mentioned embodiment, and the description of the repeated parts is omitted.

[0125] (Seventh Embodiment)

[0126] like Figure 4G The coil device of this embodiment is similar to the coil device of the sixth embodiment ( Figure 4F That is, the coil device of this embodiment has the same structure and has the same effect, except that it has a core 2G which is different from the core 2F of the above-mentioned embodiment.

[0127] The core 2G of this embodiment is different from the core 2F of the aforementioned embodiment, in that the upper end of the middle leg portion 22c is formed integrally with the second base portion 22a of the second core 22. That is, the first core 21 is a core having a U-shaped cross section, and the inner surface 21a1 of the substantially central portion along the Y axis of the first core 21 is opposite to the front end portion 22c1 of the middle leg portion 22c with an inner gap 27a at a predetermined interval, wherein the middle leg portion 22c is formed integrally with the base portion 22a of the second core 22. In this embodiment, the interval of the inner gap 27a along the Z axis is approximately Figure 4C The gap is the sum of the predetermined intervals t3 and t4 shown. The other structures and effects are the same as those in the above-mentioned embodiment, and the description of the overlapping parts is omitted.

[0128] (Eighth Implementation Method)

[0129] like Figure 4H As shown, the coil device of this embodiment is the same as the coil device 1B of the second embodiment described above except for the following, and has the same effects. That is, the coil device of this embodiment has the same structure and has the same effects except for having a core 2H different from the core 2B of the embodiment described above.

[0130] The core 2H of this embodiment is different from the aforementioned Figure 4B1 The core 2B of the embodiment shown is different, and the front end portion 22c1 of the middle leg portion 22c integrally formed in the second base portion 22a is opposite to the inner surface 21a1 of the first base portion 21a of the first core 21 with a predetermined interval of the inner side dividing gap 27a. In addition, an adhesive portion 9a is formed in the gap 27a to join the front end portion 22c1 of the middle leg portion 22c to the inner surface 21a1 of the first base portion 21a of the first core 21. Other structures and effects are the same as those of the above-mentioned embodiment, and the description of the repeated parts is omitted.

[0131] In addition, the present invention is not limited to the above-mentioned embodiment, and various changes can be made within the scope of the present invention.

[0132] For example, in the above-described embodiment, the core 2 is composed of a combination of two to four divided cores, but the number of divisions is not limited to this, and for example, the core 2 may be composed of a combination of five or more divided cores.

[0133] In addition, in the present embodiment, the Z axis is substantially parallel to the winding axis of the wire winding portion 40 or 50, but the winding axis of the wire winding portion 40 or 50 may be accommodated in the housing 8 in a manner substantially parallel to the X axis or the Y axis. Even in this case, it is preferred that the gaps 26, 26a having the partial bonding portion 9 or the gaps 27, 27a having the bonding portion 9a are located below the atmosphere open surface 82a.

[0134] Moreover, in the above-mentioned embodiment, the coil device without a bobbin barrel between the middle leg portions 21c, 22c, 23 and the winding portions 40, 50 of the conductors 4, 5 is described, but the coil device of this embodiment can also be a coil device with a bobbin barrel arranged therebetween.

Claims

1. A coil device, comprising: a core including a magnetic body; and a wire disposed helically around at least a portion of the core, The core has: a middle leg portion, which is provided with a winding portion of the wire; an outer leg portion disposed outside the winding portion of the wire; and a base portion that magnetically connects the middle leg portion to the outer leg portion, More than 70% of the volume of the middle leg portion is located below the surface of the heat dissipating resin open to the atmosphere. An outer dividing gap is provided in the middle or at the end of the outer leg portion, The outer dividing gap includes a partially bonded portion where an adhesive is interposed and an air layer where no adhesive is interposed. The air layer is located below a surface of the heat-dissipating resin open to the atmosphere.

2. The coil device according to claim 1, characterized in that The outer leg has a first outer leg and a second outer leg, The outer dividing gap is provided between the front end of the first outer leg portion and the front end of the second outer leg portion.

3. The coil device according to claim 1, characterized in that The outer dividing gap is provided between one end of the outer leg portion and the inner surface of the base portion.

4. The coil device according to any one of claims 1 to 3, characterized in that: An area ratio of the partial bonding portion in a cross section of the outer divided gap is greater than or equal to 3% and less than or equal to 50%.

5. A coil device, comprising: a core including a magnetic body; and a wire disposed helically around at least a portion of the core, The core has: a middle leg portion, which is provided with a winding portion of the wire; an outer leg portion disposed outside the winding portion of the wire; and a base portion that magnetically connects the middle leg portion to the outer leg portion, More than 70% of the volume of the middle leg portion is located below the surface of the heat dissipating resin open to the atmosphere. An inner dividing gap is provided in the middle or at the end of the middle leg portion, The inner dividing gap is provided with an adhesive portion at least partially filled with an adhesive, An outer dividing gap is provided in the middle or at the end of the outer leg portion, An air layer is provided in the outer dividing gap, The adhesive portion and the air layer are located below a surface of the heat-dissipating resin open to the atmosphere.

6. The coil device according to claim 5, characterized in that The middle leg portion has a first middle leg portion and a second middle leg portion, The inner dividing gap is provided between the front end of the first middle leg portion and the front end of the second middle leg portion.

7. The coil device according to claim 5, characterized in that The inner dividing gap is provided between one end of the middle leg portion and the inner surface of the base portion.

8. The coil device according to claim 1 or 5, characterized in that: The gap width of the outer dividing gap is a thickness to such an extent that the heat-dissipating resin existing around the outer dividing gap does not enter.

9. The coil device according to claim 8, characterized in that The gap width is 50 μm or less.

10. The coil device according to claim 1 or 5, characterized in that: The base portion is close to a cooling wall surface of a housing filled with the heat-dissipating resin.

11. The coil device according to claim 1 or 5, characterized in that: The heat dissipating resin is arranged at a position covering the winding portion of the conductive wire, and the winding portion of the conductive wire is arranged around the middle leg portion.

12. The coil device according to claim 1 or 5, characterized in that: A terminal block is also provided for holding the lead portion of the wire.

13. The coil device according to claim 12, characterized in that The terminal block is mounted on a bobbin, a housing accommodating the heat-dissipating resin, or the core.

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