Coil device

Abstract

The invention provides a coil device capable of reducing thermal stress generated in a core. A coil device (1) includes a core (2) including a magnetic body, and a winding wire disposed in a coil shape around at least a portion of the core. 70% or more of the volume of the mid-leg section (23) of the core (2) is positioned below the atmosphere-open surface (82a) of the heat-dissipating resin (82), an air layer (37) is present between the first base section (21a) and one end of the mid-leg section (23), and a gap (37) of the air layer is positioned below the atmosphere-open surface (82a) of the heat-dissipating resin (82).

Description

Technical Field

[0001] The present invention relates to coil devices that can also be used as, for example, transformers. Background Technology

[0002] To improve the heat resistance of the coil device, for example, in Patent Document 1, a portion of the core is impregnated in a heat-dissipating resin to enhance the cooling effect. However, this technology suffers from the problem that the area covered by the heat-dissipating resin is small, and sufficient heat dissipation cannot be expected.

[0003] Therefore, it was also considered to cover most of the core with a heat-dissipating resin. However, this configuration would result in an excessively large housing for storing the heat-dissipating resin, which would violate the miniaturization requirements of the coil device. Therefore, sometimes a heat-dissipating resin covering is used to impregnate the winding portion of the coil within the necessary minimum area.

[0004] Typically, the middle leg of a core with a winding section is integrally connected to the base of the core. Heat generated at the middle leg is transferred to the base of the core and released to the cooling section of the housing that contacts the base. Therefore, a sharp temperature gradient is generated along the winding axis, particularly at the middle leg, creating thermal stress in the core and easily leading to deterioration of core losses. Especially with the increasing current in coil devices in recent years, reducing the thermal stress generated in the core has become a challenge.

[0005] Existing technical documents

[0006] Patent documents

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

[0008] The problem that the invention aims to solve

[0009] The present invention was made in view of this practical situation, and its object is to provide a coil device capable of reducing the thermal stress generated in the core.

[0010] Technical solutions for solving the problem

[0011] To achieve the above objectives, the present invention provides a coil device comprising:

[0012] The core, which contains a magnetic material; and

[0013] A winding, which is configured in a coil shape around at least a portion of the core.

[0014] The core has:

[0015] The middle foot portion, which is provided with the winding portion of the winding; and

[0016] The first base is disposed at one end of the middle foot portion along the winding axis of the winding portion.

[0017] More than 70%, preferably more than 80%, more preferably more than 90%, or more than 95% of the volume of the middle foot is located below the atmospheric open surface of the heat-dissipating resin.

[0018] An air layer exists between the first base and one end of the middle foot.

[0019] The air layer is located below the atmospheric open surface of the heat-dissipating resin.

[0020] In this coil assembly, because most of the volume of the middle leg is located below the atmospheric open surface of the heat-dissipating resin, most of the volume of the middle leg and the winding portion of the coil surrounding the middle leg is cooled by the heat-dissipating resin, thus improving heat dissipation. Furthermore, because an air layer exists between the first base and one end of the middle leg, heat from the middle leg is difficult to transfer to the first base, reducing the temperature distribution variation along the winding axis of the middle leg. The middle leg is uniformly cooled by the heat-dissipating resin. As a result, a sharp temperature gradient is less likely to occur in the middle leg along the winding axis of the coil, reducing thermal stress in the core and lowering core losses.

[0021] The first base and the middle foot may have minute protrusions or depressions on at least one surface that allow the first base and the middle foot to partially contact each other, and the air layer may be formed in the recesses of the minute protrusions or depressions.

[0022] That is, one end of the middle foot can also be abutted only with the surface of the first base. If a plurality of micro-protrusions are formed on at least one surface of the abutted first base and one end of the middle foot, an air layer with a gap corresponding to the surface roughness of the micro-protrusions is formed in the recess of the micro-protrusions.

[0023] In this case, the lower limit of the thickness of the air layer along the winding axis is determined by factors such as the surface roughness of minute irregularities, and is not particularly limited. For example, it is preferably 5 μm or more, or 8 μm or more, or 10 μm or more, or 12 μm or more. Furthermore, the upper limit of the thickness of the air layer along the winding axis is determined to be such that the heat-dissipating resin in a flowing state is difficult to penetrate between the first base and one end of the middle foot of the mating section. It is not particularly limited, and is preferably 50 μm or less, 40 μm or less, or 30 μm or less, or 20 μm or less, or 15 μm or less.

[0024] With a plurality of minute irregularities formed on at least one surface of the first base and one end of the middle leg, an air layer of this thickness can be easily formed by placing only one end of the middle leg on the surface of the first base. Furthermore, with an air layer of this thickness, it is difficult for the flowing heat-dissipating resin to enter the mating surface between the first base and one end of the middle leg, thus maintaining an air layer of the specified thickness. Additionally, the heat-dissipating resin can also slightly penetrate a portion of the air layer.

[0025] A sealing member may also be fitted to the outer periphery of one end of the middle foot. Additionally, by means of the sealing member alone, or by a combination of the sealing member and other members, an air layer with a predetermined interval may be formed between the first base and one end of the middle foot, thereby preventing the heat-dissipating resin from entering the air layer.

[0026] With this configuration, the heat-dissipating resin in a flowing state around the sealing member (or sealing member and other members) is effectively prevented from entering the air layer, thus maintaining an air layer of a specified thickness.

[0027] Alternatively, a cylindrical portion of the spool can be disposed between the middle leg portion and the winding portion of the coil. Alternatively, the other components may consist of an inner square protrusion formed at one end of the cylindrical portion of the spool, with the sealing member disposed between the inner square protrusion and the end of the middle leg portion.

[0028] With this configuration, the sealing member and the inner square protrusion effectively prevent the heat-dissipating resin in a flowing state around the inner square protrusion of the sealing member and the spool from entering the air layer, thereby maintaining an air layer of a specified thickness.

[0029] The sealing member may also be composed of an O-ring. Alternatively, the other members may be composed of an annular spacer that is in close contact with the surface of the base, on which the O-ring is disposed and held at the outer periphery of one end of the middle foot.

[0030] With this configuration, even without a spool, the sealing member and spacer effectively prevent the heat-dissipating resin in its flow state around the spacer and sealing member from entering the air layer, thus maintaining an air layer of a specified thickness.

[0031] Furthermore, when using a sealing component, the heat-dissipating resin can also slightly penetrate a portion of the air layer. Additionally, besides the air layer, another resin layer can be formed in the gap between the first base and one end of the middle foot.

[0032] When using a sealing member, the upper limit of the thickness of the air layer along the winding axis is not particularly limited, but is determined based on factors such as leakage flux characteristics required for the coil device. It is not particularly limited, but preferably 3 mm or less, more preferably 2 mm or less, and even more preferably 1 mm or less. Furthermore, the lower limit of the thickness of the air layer along the winding axis is determined such that the heat transfer from one end of the middle foot to the surface of the first base is less than in the case without an air layer; for example, preferably 5 μm or more, or 8 μm or more, or 10 μm or more, or 12 μm or more.

[0033] The core may also have a second base continuously formed along the winding axis and at the other end of the middle leg. Alternatively, the core may also have a second base disposed at the other end of the middle leg at a predetermined distance along the winding axis.

[0034] An air layer, preferably less than 2 mm and more preferably less than 1.9 mm, may also exist between the second base and the other end of the middle foot. By having an air layer between the second base and the other end of the middle foot, stresses such as thermal expansion forces generated in the middle foot are less likely to be transmitted to the second base, thereby reducing the thermal stress that may be generated at the second base.

[0035] The first base may also be close to the cooling wall of the shell filled with the heat-dissipating resin. In this case, the first base is particularly prone to temperature difference due to cooling, but because an air layer is formed between one end of the middle foot and the first base, the unevenness of temperature distribution along the winding axis of the middle foot can be improved.

[0036] Furthermore, when the cooling wall surface of the housing is the bottom surface of the housing, the core is housed inside the housing with the shaft of the winding portion of the coil approximately perpendicular to the bottom surface of the housing. Conversely, when the cooling wall surface of the housing is the side surface of the housing, the core is housed inside the housing with the shaft of the winding portion of the coil approximately parallel to the bottom surface of the housing. This configuration improves the heat dissipation of the central foot and the winding portion of the coil arranged around it.

[0037] The other end of the middle foot can also be located lower than the atmospheric open surface of the heat-dissipating resin. With this configuration, the heat dissipation of the middle foot and the winding portion of the coil disposed around it is improved.

[0038] The other end of the middle foot can also be located higher than the atmospheric open surface of the heat-dissipating resin. With this configuration, it is easy to form an air layer between the second base and the other end of the middle foot.

[0039] Preferably, the atmospheric open surface of the heat-dissipating resin is located at the position where the heat-dissipating resin covers the wound portion of the winding disposed around the middle foot. This configuration improves heat dissipation.

[0040] The coil assembly may also have a terminal block that holds the lead portion of the winding. The terminal block may be mounted on a spool or on a housing containing the heat-dissipating resin. Alternatively, the terminal block may be mounted on a second base disposed along the winding axis at the other end of the middle leg. Attached Figure Description

[0041] Figure 1A This is a schematic perspective view of a coil device according to an embodiment of the present invention.

[0042] Figure 1B This is a schematic perspective view of a coil device according to another embodiment of the present invention.

[0043] Figure 2A yes Figure 1A A schematic exploded perspective view of the coil device shown.

[0044] Figure 2B yes Figure 1B A schematic exploded perspective view of the coil device shown.

[0045] Figure 3A1 It is along Figure 1A A schematic three-dimensional cross-section of IIIA-IIIA.

[0046] Figure 3A2 It is along Figure 1A A schematic cross-sectional view of IIIA-IIIA.

[0047] Figure 3B1 It is along Figure 1B A schematic three-dimensional cross-section of IIIB-IIIB.

[0048] Figure 3B2 It is along Figure 1B A schematic cross-sectional view of IIIB-IIIB.

[0049] Figure 4A It is only a general representation Figure 3A2 The cross-sectional view of the core is shown.

[0050] Figure 4B yes Figure 4A A schematic cross-sectional view of a modified example of the core shown.

[0051] Figure 4C yes Figure 4A A schematic cross-sectional view of another modified example of the core shown.

[0052] Figure 4D yes Figure 4A A schematic cross-sectional view of another modified example of the core shown.

[0053] Figure 4E yes Figure 4A A schematic cross-sectional view of another modified example of the core shown. Detailed Implementation

[0054] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. Furthermore, the illustrations are merely schematic and exemplary depictions for the purpose of understanding the present invention, and their appearance and size ratios may differ from the actual product. Additionally, the present invention is not limited to the following embodiments.

[0055] (First Implementation)

[0056] Figure 1A The coil device 1 shown in the embodiment of the present invention functions as, for example, a leakage transformer, in the power circuit of a vehicle charger and various electronic devices. Figure 2A As shown, the coil device 1 has a core 2, a winding portion 40 of a winding 4, a winding portion 50 of a winding 5, and a housing 8.

[0057] Furthermore, in the accompanying drawings, the X-axis, Y-axis, and Z-axis are perpendicular to each other, with the Z-axis parallel to the height direction of the coil device 1. In the following description, for each of the X-axis, Y-axis, and Z-axis, the direction toward the center of the coil device 1 will be referred to as the inner side, and the direction away from the center of the coil device 1 will be referred to as the outer side.

[0058] like Figure 2A As shown, in this embodiment, the core 2 has a first core 21 disposed on the lower side along the Z-axis, a second core 22 disposed on the upper side along the Z-axis of the first core 21, and a middle leg portion 23 disposed between the first core 21 and the second core 22, which are separately formed.

[0059] The first core 21 has a flat first base 21a and side feet 21b, 21b that protrude upward from both sides along the Z-axis along the Y-axis of the first base 21a. The second core 22 has a flat second base 22a and side feet 22b, 22b that protrude downward from both sides along the Z-axis along the Y-axis of the second base 22a.

[0060] In this embodiment, the first core 21 and the second core 22 are each composed of a U-shaped core having a generally U-shaped form on a cross section parallel to the plane containing the Z-axis and the Y-axis. They have the same shape as each other, but they can also be different. For example, one core can be a U-shaped core and the other core can be an I-shaped core.

[0061] The cores 21, 22 and the middle foot 23 are not particularly limited as long as they are cores with magnetic materials, and can be made of, for example, ferrite, metallic magnetic materials, or resin containing magnetic powder.

[0062] In this embodiment, a first winding portion 40 with a first winding 4 and a second winding portion 50 with a second winding 5 are arranged around the middle foot portion 23. In this embodiment, the second winding portion 50 is arranged above the first winding portion 40 along the Z-axis, but the opposite is also possible. For example, the first winding portion 40 may be the primary winding of the transformer, and the second winding portion 50 may be the secondary winding of the transformer, but the opposite is also possible.

[0063] like Figure 3A1 and Figure 3A2 As shown, the first winding 4 and the second winding 5 can also be directly wound around the middle leg 23 to form the first winding portion 40 and the second winding portion 50. However, the first winding portion 40 and the second winding portion 50 can also be prepared as pre-wound air core coils and then arranged around the middle leg 23. The winding method of winding 4 or 5 is not particularly limited, and examples include ordinary winding or α winding.

[0064] In this embodiment, the first winding 4 and the second winding 5 are each composed of conductive windings, and may not be insulated, but are preferably insulated. The type of winding is not particularly limited, and can be a round wire, flat wire, stranded wire, braided wire, or other conductive core wire. The material used as the welding layer or insulation layer covering the core wire is not particularly limited, and examples include polyurethane, polyamide-imide, polyimide, and polyester.

[0065] Furthermore, in this embodiment, both the first winding 4 and the second winding 5 are composed of self-fusion type windings, but only one of them may be a self-fusion type winding, or both may be composed of other types of windings. Additionally, at least one of the first winding portion 40 and the second winding portion 50 may be a flat coil. The wire diameters of the first winding 4 and the second winding 5 may be the same or different, and there is no particular limitation on either; for example, it is preferably in the range of 1.0 to 3.0 mm.

[0066] like Figure 2A As shown, lead portions 41a and 41b are formed at both ends of the first winding 4 constituting the first winding section 40. Each lead portion 41a and 41b extends upward along the Z-axis from the first winding section 40 and is connected to terminals (not shown in the figure). Similarly, lead portions 51a and 51b are formed at both ends of the second winding 5 constituting the second winding section 50. Each lead portion 51a and 51b extends upward along the Z-axis from the second winding section 50 and is connected to terminals (not shown in the figure).

[0067] The terminals that connect to these multiple lead portions 41a, 41b, 51a, 51b can also be mounted on, for example, a terminal block (not shown in the diagram). The terminal block can be mounted on the upper surface of the second core 22 of core 2, or it can be mounted on the housing 8, or it can be mounted on... Figure 2B The spool 3 is shown.

[0068] like Figure 3A1 and Figure 3A2 As shown, in this embodiment, an O-ring 6, serving as a sealing member, is fitted tightly against the outer periphery of the lower end 23a along the Z-axis of the middle foot 23. Preferably, the lower end of the O-ring 6 along the Z-axis is approximately flush with the lower end 23a or slightly protrudes downward, but it may also be located above the lower end 23a to form the gap 37 described later.

[0069] In addition, in this embodiment, a spacer 7, which also functions as part of the sealing member, is disposed below the O-ring 6. The rectangular spacer 7 is in close contact with the inner surface 21a1 of the first base 21a, and the O-ring 6 is in close contact with the outer periphery of the lower end 23a of the middle leg 23 and the upper surface of the spacer 7. With this configuration, a predetermined interval t1 (see reference) is formed between the lower surface of the lower end 23a of the middle leg 23 and the inner surface 21a1 of the first base 21a. Figure 4A The gap 37 is sealed from its surroundings by the spacer 7 and the O-ring 6, preventing the heat-dissipating resin 82 from entering the gap 37 and forming an air layer.

[0070] The material of the O-ring 6 is not particularly limited as long as it can seal the gap between the spacer 7 and the outer periphery of the lower end 23a of the middle leg 23. It is preferably made of an insulating elastic member such as synthetic resin or rubber. Similarly, the spacer 7 is not particularly limited as long as it is made of a material that can fit tightly against the inner surface 21a1 of the first base 21a and also against the O-ring 6. It is preferably made of an insulating elastic member such as synthetic resin or rubber. Furthermore, in this embodiment, the spacer 7 may not necessarily be installed. For example, the O-ring 6 alone can be used to form a spacer t1 (see reference t1) between the middle leg 23 and the first base 21a. Figure 4A The air layer formed by the gap 37.

[0071] In this embodiment, the length of the middle foot 23 along the Z-axis is determined relative to the combined length of the side feet 21b and 22b, such that a predetermined interval t2 is formed between the upper end 23b of the middle foot 23 and the inner surface 22a1 of the second base 22a (refer to...). Figure 4A The gap is 38. (e.g.) Figure 4AAs shown, the front end 21b1 of the side foot 21b and the front end 22b1 of the side foot 22b are joined together and bonded with adhesive as needed.

[0072] like Figure 3A2 As shown, the position of the atmospheric opening surface 82a of the heat-dissipating resin 82 is determined by its relationship with the position of the upper end 23b of the middle foot 23, such that an air layer is preferably formed in the gap 38 between the upper end 23b of the middle foot 23 and the inner surface 22a1 of the second base 22a. For example, the atmospheric opening surface 82a of the heat-dissipating resin 82 filled into the interior of the housing 8 is determined by its relationship with the volume of the middle foot 23, such that at least a portion of the heat-dissipating resin 82 does not enter the gap 38, and the middle foot 23 is sufficiently cooled.

[0073] That is, the atmospheric open surface 82a is set such that 70% or more, preferably 80% or more, more preferably 90% or more, or 95% or more of the volume of the middle foot 23 is located below the atmospheric open surface 82a of the heat-dissipating resin 82, and is located below the inner surface 22a1 of the base 22a along the Z-axis. With this configuration, an air layer is formed in the gap 38 in which the heat-dissipating resin 82 does not enter.

[0074] Furthermore, the atmospheric open surface 82a of the heat-dissipating resin 82 is defined such that the winding portion 50 of the second winding 5 is sufficiently impregnated with the heat-dissipating resin 82, and preferably 80% or more, more preferably 95% or more, or practically 100% or more of the winding portion 40 of the first winding 4 is impregnated with the heat-dissipating resin 82. With this configuration, the heat generated in the winding portion 40 or 50 of the winding 4 or 5 is also cooled by the heat-dissipating resin 82.

[0075] Furthermore, in this embodiment, the heat transferred from the winding portion 40 or 50 of the winding 4 or 5, or the core 2 to the heat-dissipating resin 82 is dissipated by the housing 8 through a cooling member (e.g., a cooling block with cooling passages) provided on the lower surface of the base plate 80 of the housing 8. Additionally, the atmospheric open surface 82a is a surface where the liquid surface formed by the flowing heat-dissipating resin 82 into the housing 8 solidifies.

[0076] like Figure 1A As shown, the housing 8 has a generally rectangular base plate 80 and side plates 81 that rise upwards along the Z-axis from the four sides of the base plate 80 and form receiving spaces with bottoms inside. An upper opening is formed at the upper part along the Z-axis. The housing 8 is preferably made of a metal such as aluminum with excellent thermal conductivity, but it can also be made of resin.

[0077] The heat-dissipating resin 82, also known as potting resin, is composed of silicone resin, polyurethane resin, epoxy resin, etc., which remain soft after injection. The longitudinal elastic modulus of the potting resin is preferably 0.1 to 100 MPa. In this embodiment, for example, the heat generated by 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 via the heat-dissipating resin 82 and the housing 8, thereby improving the cooling efficiency of the coil device 1.

[0078] In addition, the heat-dissipating resin 82 can also be pre-filled into the interior of the housing 8 to accommodate the installation of... Figure 2A The spool (with winding) 3 of the core 2 shown can also be housed inside the housing 8, after which the heat-dissipating resin 82 flows into the interior of the housing 8.

[0079] In the coil device 1 of this embodiment, as Figure 3A1 and Figure 3A2 As shown, most of the volume of the middle leg portion 23 of the core 2 is located below the atmospheric open surface 82a of the heat dissipation resin 82. Therefore, most of the volume of the winding portions 40 and 50 of the windings 4 and 5 arranged together with the middle leg portion 23 around the middle leg portion 23 is also cooled by the heat dissipation resin 82, thus improving heat dissipation.

[0080] Furthermore, an air layer consisting of a gap 37 exists between the first base 21a and one end (lower end 23a) of the middle foot 23. Therefore, heat from the middle foot 23 is not easily transferred to the first base 21a, and the temperature distribution along the winding axis of the middle foot 23 is less varied. The middle foot 23 is uniformly cooled by the heat-dissipating resin. As a result, a sharp temperature gradient is less likely to occur along the winding axis (parallel to the Z-axis) of the winding 4 or 5 in the middle foot 23, reducing the thermal stress generated in the core 2 (especially in the middle foot 23) and reducing core loss.

[0081] Furthermore, an O-ring 6, serving as a sealing member, is fitted around the lower end 23a of the middle leg 23. An air layer (gap 37) with a predetermined interval is formed between the first base 21a and the lower end 23a of the middle leg 23, either alone or in combination with the spacer 7. This configuration effectively prevents the heat-dissipating resin 82, which is in a flowing state around the O-ring 6 (or the O-ring 6 and the spacer 7), from entering the gap 37 of the air layer, maintaining an air layer of a predetermined thickness.

[0082] Furthermore, when using sealing components such as O-rings 6 and spacers 7, some heat-dissipating resin can easily enter a portion of the gap 37. Additionally, a resin layer other than an air layer may be formed in the gap between the first base 21a and the lower end 23a of the middle leg 23. However, the area of ​​the air layer formed by the gap 37 (the area perpendicular to the winding axis) is preferably 50% or more of the area of ​​the lower end 23a of the middle leg 23, and more preferably 60% or more, 70% or more, 80% or more, 90% or more, 98% or more, 99% or more, or 100% or more.

[0083] When using sealing components such as O-rings 6 and spacers 7, the thickness t1 of the air layer formed in the gap 37 along the winding axis (parallel to the Z-axis) (refer to...) Figure 4A The upper limit of the thickness t1 of the air layer is not particularly limited, and is determined according to the leakage magnetic characteristics required as a coil device, etc., and is not particularly limited, but is preferably 3 mm or less, more preferably 2 mm or less, and more preferably 1 mm or less. In addition, the lower limit of the thickness t1 of the air layer along the winding axis is determined to be such that the heat transfer from the lower end of the middle foot 23 to the surface of the first base 21a is less than that without the air layer, for example, preferably 5 μm or more, or 8 μm or more, or 10 μm or more, or 12 μm or more.

[0084] In this embodiment, the core 2 may also have a second base 22a continuously formed along the winding axis and the other end (upper end 23b) of the middle leg 23. However, in this embodiment, the core 2 also has a second base 22a disposed at the other end (upper end 23b) of the middle leg 23 at a predetermined distance t2 along the winding axis.

[0085] In this embodiment, a gap 38, preferably less than 3 mm, more preferably less than 2 mm, and more preferably less than 1.9 mm, exists between the inner surface 22a1 of the second base 22a and the upper end 23b of the middle foot 23. Because of this air layer, stresses such as thermal expansion forces generated in the middle foot 23 are less likely to be transmitted to the second base 22a, thus reducing the thermal stress that may be generated in the second base 22a. As a result, the possibility of defects such as core breakage and damage is reduced.

[0086] Furthermore, in this embodiment, at least 30%, 50%, 80%, or 95%, preferably 100%, of the volume of the second base 22a is exposed from the heat-dissipating resin 82. By exposing most of the second base 22a, the housing 8 containing the heat-dissipating resin 82 can be miniaturized, and the amount of heat-dissipating resin 82 can also be reduced. Moreover, even in this case, because the second base 22a is disposed at the upper end of the middle foot 23 with a predetermined gap 38 along the Z-axis, the stress such as thermal expansion force generated in the middle foot 23, where heat easily accumulates, is not transmitted to the second base 22a. Therefore, excessive thermal stress that may be generated in the second base 22a can be reduced.

[0087] In addition, in this embodiment, the first base 21a is close to the cooling wall surface, i.e., the bottom plate 80, of the housing 8 filled with heat-dissipating resin 82. When the cooling wall surface of the housing 8 is the bottom surface of the housing 8, it is preferable to house the core 2 inside the housing 8 so that the shaft cores of the winding portions 40 and 50 of the windings 4 and 5 are substantially perpendicular to the bottom surface of the housing 8.

[0088] Furthermore, in another embodiment, where the cooling wall surface of the housing 8 is the side surface (side plate 81) of the housing 8, the core 2 can be housed inside the housing 8 so that the core of the winding portions 40 and 50 of the windings 4 and 5 is approximately parallel to the bottom surface of the housing 8. Even in any case, especially when the first base 21a is cooled, a temperature difference is easily generated. However, because a gap 37 consisting of an air layer is formed between one end (lower end 23a) of the middle foot 23 and the first base 21a, the unevenness of the temperature distribution along the winding axis of the middle foot 23 can be improved.

[0089] In this embodiment, the upper end 23b of the middle foot 23 can also be located lower than the atmospheric open surface 82a of the heat-dissipating resin 82. With this configuration, the heat dissipation of the middle foot 23 and the winding portions 40, 50 of the windings 4, 5 disposed around the middle foot 23 is improved. In this case, it is also preferable that the atmospheric open surface 82a is located in the middle of the gap 38, so that an air layer is formed in the gap 38. Alternatively, the upper end 23b of the middle foot 23 can also be located higher than the atmospheric open surface 82a of the heat-dissipating resin 82. With this configuration, it is easy to form a gap 38 consisting of an air layer between the second base 22a and the upper end 23b of the middle foot 23.

[0090] The atmospheric open surface 82a of the heat-dissipating resin 82 is located at the position where the heat-dissipating resin 82 covers the winding portions 40 and 50 of the windings 4 and 5 arranged around the middle foot portion 23. With this configuration, the heat dissipation of the winding portions 40 and 50 is improved.

[0091] (Second Implementation)

[0092] like Figure 1B , Figure 2B , Figure 3B1 and Figure 3B2 As shown, the coil device 1A of this embodiment is the same as the coil device 1 of the above-described embodiment, except as shown below, and achieves the same functional effects. That is, in this embodiment, especially as shown below... Figure 3B2 As shown, a bobbin 30 is disposed between the middle foot 23 and the winding portions 40 and 50 of the windings 4 and 5.

[0093] Along the Z-axis of the cylindrical portion 30 of the spool 3, at a midpoint, there is a main partition wall flange 31 for insulating the primary and secondary coils. This main partition wall flange 31 is configured to protrude radially from the outer peripheral surface of the cylindrical portion 30. Below the Z-axis of the main partition wall flange 31, at predetermined intervals along the Z-axis, the multiple secondary partition wall flanges 32 are configured to protrude radially from the outer peripheral surface of the cylindrical portion 30. A first winding 4 is wound between the main partition wall flange 31 and the secondary partition wall flanges 32, and between the secondary partition wall flanges 32, forming a first winding portion 40.

[0094] Similarly, along the Z-axis of the main partition wall flange 31, at a predetermined interval, a plurality of secondary partition wall flanges 32 are provided at an upper position along the Z-axis. The plurality of secondary partition wall flanges 32 are configured to protrude radially from the outer peripheral surface of the cylindrical portion 30. A second winding 5 is wound around the dividing gap between the main partition wall flange 31 and the secondary partition wall flanges 32, and the dividing gap between the secondary partition wall flanges 32, to form a second winding portion 50.

[0095] Furthermore, the dividing gaps along the Z-axis between the main dividing wall flange 31 and the secondary dividing wall flange 32, and the dividing gaps between the secondary dividing wall flanges 32, are formed to be slightly larger than the outer diameter of the first winding 4 or the second winding 5. These dividing gaps allow only one row of windings 4 or 5 to enter along the Z-axis. Therefore, the windings 4 or 5 can be neatly wound around the outer circumferential surface of the bobbin 3's cylindrical portion 30.

[0096] At least one location along the circumference of each sub-partition flange 32 has a radial cut extending from the outer periphery of the flange 32 to the outer periphery of the cylinder 30. Through this cut, the winding wire 4 or 5 can move along the adjacent dividing gap along the Z-axis, enabling continuous winding operations of the winding wire 4 or 5. Furthermore, the winding method of the winding wire 4 or 5 is not particularly limited; examples include, for instance, ordinary winding or α-winding.

[0097] The second winding portion 50 is positioned above the first winding portion 40 along the Z-axis, but the opposite is also possible. In this embodiment, for example, the first winding portion 40 becomes the primary winding of the transformer, and the second winding portion 50 becomes the secondary winding of the transformer, but the opposite is also possible. The first winding portion 40 and the second winding portion 50 are separated by the main partition flange 31 in the Z-axis direction to adjust the coupling coefficient, etc.

[0098] like Figure 3B2 As shown, on the inner circumferential surface of the sub-partition flange 32 at the lower end of the cylindrical portion 30 along the Z-axis of the spool 3, an inner square protrusion 36 protruding inward from the inner circumferential surface of the cylindrical portion 30 is continuously formed along the circumferential direction. The inner square protrusion 36 protrudes from the lower end of the cylindrical portion 30 along the Z-axis to the extent that it does not block the through hole formed on the inner circumferential surface of the cylindrical portion 30, and fits tightly against and abuts against the O-ring 6 fitted to the outer circumferential portion of the lower end 23a of the middle foot portion 23 along the Z-axis. As a result, a gap 37 is formed between the lower end 23a of the middle foot portion 23 along the Z-axis and the inner surface 21a1 of the first base 21a.

[0099] The lower surface of the annular inner square protrusion 36 is in close contact with the inner surface 21a1 of the first base 21a, and the O-ring 6 seals the gap between the lower end 23a of the middle foot 23 and the inner square protrusion 36, so that the heat-dissipating resin 82 does not enter the gap 37. An air layer of a predetermined thickness is formed in the gap 37 to prevent the heat-dissipating resin 82 from entering. Furthermore, the spacing of the gap 37 can be adjusted by changing the designed thickness of the inner square protrusion 36 along the Z-axis.

[0100] like Figure 2B As shown, core guide walls 34 are provided on both sides of the partition wall flange 32 located at the upper end of the cylindrical portion 30 of the spool 3 along the Z-axis, along the X-axis. Core guide walls 35 are provided on both sides of the partition wall flange 32 located at the lower end of the cylindrical portion 30 of the spool 3 along the Z-axis, along the X-axis. The base 21a of the first core 21 is provided on the outer surface (lower surface 32b) of the partition wall flange portion 32 located between the pair of core guide walls 35. The side feet 21b of the first core 21 cover the lower part along the Y-axis of the spool 3 and along the Z-axis on both sides.

[0101] The O-ring 6, serving as a sealing component, is fitted onto the lower outer circumference of the center leg 23 and inserted from above the Z-axis into a through hole formed on the inner circumferential surface of the cylindrical portion 30 of the spool 3. For example... Figure 3B2 As shown, the O-ring 6 abuts against the inner square protrusion 36 formed on the inner circumferential surface of the lower end of the cylindrical portion 30 of the spool 3, and holds the lower end 23a of the middle foot portion 23 with a predetermined gap 37.

[0102] Then, core 2 is assembled onto spool 3 such that the base 22a of the second core 22 is located between core guide walls 34, 34. As a result, the base 22a of the second core 22 is provided on the outer surface (upper surface 32a) of the partition flange 32 located between the pair of core guide walls 34. The side legs 22b of the second core 22 cover the upper part along the Y-axis and along the Z-axis on both sides of the spool 3, respectively. The front end 22b1 of each side leg 22b abuts against the front end 21b1 of the side leg 21b of the first core 21, and is joined using adhesive as needed.

[0103] In the coil device 1A of this embodiment, as in Figure 4A As shown, similar to the first embodiment, a gap 37 consisting of air layers with a predetermined interval t1 is formed, and a gap 38 with a predetermined interval t2 can be formed as needed. In this embodiment, the gap 37 is as follows: Figure 3B2 As shown, the combination of the inner square protrusion 36 formed at the lower end of the cylindrical portion 30 of the spool 3 and the O-ring 6 effectively prevents the flowing heat-dissipating resin 82 from entering the gap 37 formed by the air layer, thus maintaining an air layer of a specified thickness. Other structural and functional effects of this embodiment are the same as those of the first embodiment described above.

[0104] (Third Implementation)

[0105] like Figure 4B As shown, the coil device of this embodiment is the same as the coil device 1 or 1A of the first or second embodiment described above, except as shown below, and achieves the same functional effect. That is, the coil device of this embodiment has the same structure and achieves the same functional effect, except that it has a core 2A that is different from the core 2 of the above-described embodiments.

[0106] The core 2A in this embodiment differs from the core 2 in the embodiment described above. A stepped protrusion 24 is formed on the inner surface of the base 21a, which faces the upper or lower end of the middle foot 23 along the Z-axis. The protrusion height of the stepped protrusion 24 (along the Z-axis) is not particularly limited, as long as a gap 38 or 37 is formed between the front end of the stepped protrusion 24 along the Z-axis and the upper or lower end of the middle foot 23.

[0107] However, it is desirable that the protrusion height of the stepped protrusion 24, which faces the upper end of the middle foot 23, be as small as possible. Especially when the protrusion height of the stepped protrusion 24 formed on the first base 21a is high, since the stepped protrusion 24 functions as the middle foot 23, it is preferable that the protrusion height of the stepped protrusion 24 is at least less than half the height of the side foot 21b along the Z-axis. Other structural and functional effects are the same as in the embodiment described above, and repeated descriptions are omitted.

[0108] (Fourth Implementation)

[0109] like Figure 4C As shown, the coil device of this embodiment is the same as the coil device 1 of the first to third embodiments described above, except as shown below, and achieves the same functional effect. That is, the coil device of this embodiment has the same structure and achieves the same functional effect, except that it has a core 2B that is different from the core 2 or 2A of the embodiments described above.

[0110] Compared to the core 2 of the above-described embodiment, the core 2B of this embodiment has the following differences: the first core 21 has a first base 21a independent of the side foot 25, and the second core 22 has a second base 22a independent of the side foot 25. The side foot 25 has a structure that integrates the side feet 21b and 22b facing each other along the Z-axis direction of the above-described embodiment and separates them from their respective bases 21a and 22a. Other structures and effects are the same as in the above-described embodiment, and repeated descriptions are omitted.

[0111] (Fifth Implementation)

[0112] like Figure 4D As shown, the coil device of this embodiment is the same as the coil device 1 of the first to fourth embodiments described above, except as shown below, and achieves the same functional effect. That is, the coil device of this embodiment has the same structure and achieves the same functional effect, except that it has a core 2C that is different from the cores 2, 2A, or 2B of the embodiments described above.

[0113] The core 2C in this embodiment differs from the core 2 in the embodiment described above. The upper end of the middle leg 23C is integrally formed with the second base 22a of the second core 22. Other structures and effects are the same as in the embodiment described above, and repeated descriptions are omitted.

[0114] (Sixth Implementation Method)

[0115] like Figure 4E As shown, the coil device of this embodiment is the same as the coil device 1 of the first to fifth embodiments described above, except as shown below, and achieves the same functional effect. That is, the coil device of this embodiment has the same structure and achieves the same functional effect, except that it has a core 2D that is different from the cores 2, 2A, 2B or 2C of the above embodiments.

[0116] The chip 2D in this embodiment is the same as described above. Figure 4C The core 2B in the illustrated embodiment differs in that the upper end of the middle leg 23C is integrally formed with the second base 22a of the second core 22. Other structures and effects are the same as in the embodiments described above, and repeated descriptions are omitted.

[0117] (Seventh Implementation)

[0118] Although the illustrations are omitted, the coil device in this embodiment, for example, does not use... Figure 3A2 The O-ring 6 and / or spacer 7 shown make the lower end 23a of the middle leg contact the inner surface 21a1 of the base 21a of the first core 21. The surface of the lower end 23a of the middle leg, or the surface of the inner surface 21a1 of the first base 21a (at least the surface corresponding to the lower end 23a), is pre-roughened to form minute irregularities. The surface roughening process is not particularly limited and can include mechanical surface roughening, physical surface roughening, electrochemical surface roughening, chemical surface roughening, etc. Specifically, examples include shot peening, grinding, plasma processing, laser processing, etching, etc.

[0119] When the surface of the lower end 23a of the middle foot and the surface of the inner surface 21a1 of the first base 21a are joined without the use of adhesives or the like, the heat-dissipating resin 82 will not enter the joining surface, and the gap of the recess corresponding to the slight surface roughness becomes an air layer. In addition, the depth of the recess is equivalent to the thickness of the air layer (the thickness of the winding portion in the direction parallel to the winding axis).

[0120] In this case, the lower limit of the thickness of the air layer along the winding axis (the depth of the recess) depends on the surface roughness of the minute irregularities and is not particularly limited, but is preferably 5 μm or more, or 8 μm or more, or 10 μm or more, or 12 μm or more. Furthermore, the upper limit of the thickness of the air layer along the winding axis is determined such that the heat-dissipating resin in a flowing state does not easily enter between the first base 21a and the lower end 23a of the middle foot 23, and is not particularly limited, but is preferably 50 μm or less, 40 μm or less, or 30 μm or less, or 20 μm or less, or 15 μm or less.

[0121] The width of the tiny unevenness forming the air layer is not particularly limited, but is preferably 1 / 4 to 4 times the depth of the unevenness. When the area of ​​the mating portion between the lower end 23a of the middle foot and the inner surface 21a1 of the first base 21a (which is also the area of ​​the lower end 23a) is set to 100%, the area of ​​the unevenness (the area of ​​the air layer) is not particularly limited, but is preferably 20% to 90%, more preferably 30% to 80%. The unevenness can be continuous, but it can also be formed intermittently.

[0122] With a plurality of minute irregularities formed on at least one surface of the first base 21a and the lower end 23a of the middle leg 23, an air layer of this thickness can be easily formed by placing only the lower end 23a of the middle leg 23 on the inner surface 21a1 of the first base 21a. Furthermore, with an air layer of this thickness, the heat-dissipating resin in a flowing state does not easily enter the mating surface between the first base 21a and the lower end 23a of the middle leg 23, and the air layer of the specified thickness is maintained. Additionally, some heat-dissipating resin 82 can also enter a portion of the air layer.

[0123] Furthermore, the present invention is not limited to the embodiments described above, and various modifications can be made within the scope of the present invention.

[0124] For example, in the above embodiments, core 2 is composed of cores with three or four divisions, but is not limited to these number of divisions. For example, it can also be composed of cores with two, five or more divisions.

[0125] In this embodiment, the Z-axis is substantially parallel to the winding axis of the winding portion 40 or 50, but the winding axis of the winding portion 40 or 50 may also be accommodated inside the housing 8 in a manner substantially parallel to the X-axis or Y-axis. Even in this case, it is preferable that the gap 37 forming the air layer is located along the Z-axis below the atmospheric open surface 82a of the heat-dissipating resin 82.

[0126] Explanation of reference numerals in the attached figures

[0127] 1. 1A...coil device

[0128] 2. 2A~2D……core

[0129] 21...First Chip

[0130] 21a……First base

[0131] 21a1……Inner surface

[0132] 21b……Side foot

[0133] 21b1...Frontend

[0134] 22……Second Core

[0135] 22a……Second base

[0136] 22a1……Inner surface

[0137] 22b……Side foot

[0138] 22b1...Frontend

[0139] 23, 23C... Midfoot

[0140] 23a……lower end

[0141] 23b……Top

[0142] 24……Step-shaped protrusion

[0143] 25……Side foot

[0144] 3... spools

[0145] 30……Cylinder section

[0146] 31……Main partition wall flange

[0147] 32……Secondary partition wall flange

[0148] 32a……Upper surface

[0149] 32b...lower surface

[0150] 34, 35... Core guide wall

[0151] 36…inner convex part

[0152] 37, 38... gaps (air layers)

[0153] 4……First winding

[0154] 40……First winding section

[0155] 41a, 41b...lead section

[0156] 5……Second winding

[0157] 50……Second winding section

[0158] 51a, 51b...lead section

[0159] 6...O-rings (sealing components)

[0160] 7……spacer

[0161] 8……shell

[0162] 80... base plate

[0163] 81……Side panel

[0164] 82……Heat-dissipating resin

[0165] 82a……Atmospheric Open Surface

Claims

1. A coil device, wherein: have: a core comprising a magnetic body; and a winding wire arranged in a coil shape around at least a portion of the core, The core has: a middle leg portion configured with a winding portion of the winding wire; and A first base portion is disposed at one end of the middle leg portion along the winding axis of the winding portion, At least 70% of the volume of the middle leg portion is located below the surface of the heat dissipating resin open to the atmosphere. There is an air layer between the first base portion and the one end of the midfoot portion, 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, wherein: At least one surface of the first base portion and the one end of the middle leg portion has a plurality of minute projections and depressions that partially contact the first base portion and the one end of the middle leg portion, and the air layer is formed in the concave portions of the minute projections and depressions.

3. The coil device according to claim 2, wherein: The thickness of the air layer along the winding axis is 5 μm or more and 50 μm or less.

4. The coil device according to claim 1, wherein: A sealing member is mounted on the outer periphery of the one end of the middle leg portion, The sealing member alone or in combination with other members forms an air layer with a predetermined distance between the first base portion and the one end of the middle leg portion, thereby preventing the heat-dissipating resin from entering the air layer.

5. The coil device according to claim 4, wherein: A bobbin tube is disposed between the middle leg portion and the winding portion of the winding wire. The other member is composed of an inner convex portion formed at one end of the barrel of the bobbin. The sealing member is arranged between the inner convex portion and the one end of the middle leg portion.

6. The coil device according to claim 4, wherein: The sealing member is composed of an O-ring, The other member is composed of an annular spacer in close contact with the surface of the base. The O-ring held on the outer periphery of the one end of the middle leg portion is arranged on the spacer.

7. The coil device according to claim 1, wherein: The thickness of the air layer along the winding axis is 5 μm or more and 3 mm or less.

8. The coil device according to claim 1, wherein: The core further has a second base portion formed continuously with the other end of the middle leg portion along the winding axis.

9. The coil device according to claim 1, wherein: The core further includes a second base portion that is disposed at the other end of the middle leg portion at a predetermined distance along the winding axis.

10. The coil device according to claim 1, wherein: The first 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 8 or 9, wherein: The other end of the middle leg portion is located below the atmosphere-opening surface of the heat-dissipating resin.

12. The coil device according to claim 8 or 9, wherein: The other end of the middle leg portion is located above the atmosphere-opening surface of the heat-dissipating resin.

13. The coil device according to claim 1, wherein: The heat dissipating resin is arranged at a position covering the winding portion of the winding wire arranged around the middle leg portion.

14. The coil device according to claim 1, wherein: The invention further comprises a terminal block which holds the lead wire portion of the winding wire.

15. The coil device according to claim 14, wherein: The terminal block is mounted on a bobbin, a housing accommodating the heat-dissipating resin, or a second base portion disposed at the other end of the middle leg portion along the winding axis.

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