Coil device

Abstract

The invention provides a coil device capable of reducing thermal stress generated in a core. The coil device includes a core including a magnetic body, and a winding wire disposed in a coil shape around at least a portion of the core. The core includes a middle leg portion on which a winding portion of a winding wire is disposed, and a first base portion disposed at one end of the middle leg portion at a predetermined distance along a winding axis of the winding portion. 70% or more, preferably 80% or more, and further preferably 90% or more, or 95% or more of the volume of the midfoot section is located below the atmosphere-open surface of the heat-dissipating resin.

Description

Technical Field

[0001] The present invention is also applicable to a coil device such as a transformer. Background Art

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

[0003] Therefore, it is also considered to cover most of the core with heat dissipation resin, but in this configuration, the housing for storing the heat dissipation resin is too large, which goes against the requirement of miniaturization of the coil device. Therefore, sometimes the housing for storing the heat dissipation resin is reduced so that the winding part of the winding is immersed within the necessary minimum range. In this case, sometimes a part of the core, such as the core part located above along the winding axis of the winding, is exposed outside the heat dissipation resin.

[0004] In this case, there are parts in the core that are cooled by the heat dissipating resin and parts that are not cooled by the heat dissipating resin, and thermal stress is generated in the core, which may significantly reduce the durability of the core. In particular, with the increase in current of coil devices in recent years, reducing the thermal stress generated in the core has become a problem.

[0005] Even if part of the core is not exposed from the heat-dissipating resin, if the cooling temperature of the heat-dissipating resin varies greatly along the winding axis of the winding wire, excessive thermal stress may be generated in the core, and in this case, the durability of the core may be reduced.

[0006] Prior art literature

[0007] Patent Literature

[0008] Patent Document 1: Japanese Patent Application Publication No. 2014-36194 Summary of the invention

[0009] Problems to be solved by the invention

[0010] The present invention has been made in view of such actual circumstances, and an object of the present invention is to provide a coil device capable of reducing thermal stress generated in a core.

[0011] Technical solutions to solve problems

[0012] In order to achieve the above object, the present invention provides a coil device having:

[0013] a core comprising a magnetic body; and

[0014] a winding wire arranged in a coil shape around at least a portion of the core,

[0015] The core has:

[0016] a middle leg portion configured with a winding portion of the winding wire; and

[0017] a first base portion disposed at one end of the middle leg portion at a predetermined distance along the winding axis of the winding portion;

[0018] 70% or more, preferably 80% or more, more preferably 90% or more, or 95% or more of the volume of the middle leg portion is located below the atmosphere-opening surface of the heat-dissipating resin.

[0019] In this coil device, most of the volume of the middle leg is located below the open surface of the heat dissipating resin. Therefore, most of the volume of the middle leg and the winding part of the winding arranged around the middle leg is cooled by the heat dissipating resin, and the heat dissipation is improved. In addition, the first base part is arranged at one end of the middle leg part at a predetermined distance along the winding axis of the winding part. Therefore, even if a part of the first base part is exposed from the heat dissipating resin, the stress such as the thermal expansion force generated in the middle leg part will not be transmitted to the first base part. Therefore, it is possible to reduce the excessive thermal stress that may be generated in the first base part.

[0020] More than 30%, more than 50%, more than 80%, or more than 95% of the volume of the first base portion may also be exposed from the heat dissipating resin. By exposing most of the first base portion, the housing for accommodating the heat dissipating resin can be miniaturized, and the amount of the heat dissipating resin can also be reduced. Moreover, even in this case, since the first base portion is arranged at one end of the middle leg portion at a predetermined distance along the winding axis of the winding portion, stress such as thermal expansion force generated in the middle leg portion is not transmitted to the first base portion. Therefore, excessive thermal stress that may be generated in the first base portion can be reduced.

[0021] The core may further include a second base portion formed continuously with the other end of the middle leg portion along the winding axis. Alternatively, the core may further include a second base portion disposed at the other end of the middle leg portion at a predetermined distance apart along the winding axis.

[0022] The second base portion may also be close to a cooling wall surface of a housing filled with the heat dissipating resin. For example, when the cooling wall surface of the housing is the bottom surface of the housing, the core is accommodated inside the housing in a manner that the axis core of the winding portion of the winding 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 is accommodated inside the housing in a manner that the axis core of the winding portion of the winding is substantially parallel to the bottom surface of the housing.

[0023] It is preferred that an air layer of 1.9 mm or less exists between the first base portion and the one end of the middle leg portion. By the existence of the air layer between the first base portion and the one end of the middle leg portion, stress such as thermal expansion force generated in the middle leg portion is more reliably not transmitted to the first base portion. In addition, by setting the interval of the air layer to be less than a specified value, it is easy to form a magnetic circuit between the middle leg and the first base portion.

[0024] The one end of the middle leg portion may be located below the atmosphere-exposure surface of the heat-dissipating resin. With this configuration, the heat dissipation of the middle leg portion and the winding portion of the winding disposed around the middle leg portion is improved.

[0025] The one end of the middle leg portion may be located above the atmosphere-opening surface of the heat-dissipating resin. With this configuration, an air layer of 1.9 mm or less is easily formed between the first base portion and the one end of the middle leg portion.

[0026] The atmosphere-exposure surface of the heat-dissipating resin is preferably located at a position where the heat-dissipating resin covers the winding portion of the winding wire disposed around the middle leg portion. With this configuration, heat dissipation is improved.

[0027] An adhesive or the heat-dissipating resin may be interposed at least partially between the other end of the middle leg and the surface of the second base. In addition, the other end of the middle leg and the second base may be formed integrally.

[0028] A bobbin tube may be disposed between the middle leg and the winding portion of the winding wire. Alternatively, a winding portion of the winding wire (eg, an air-core coil) may be disposed around the middle leg without disposing a bobbin.

[0029] The coil device may further include a terminal block for holding a lead portion of the winding wire. The terminal block may be mounted on a bobbin, a case for accommodating the heat-dissipating resin, or the first base portion. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 It is a schematic perspective view of a coil device according to one embodiment of the present invention.

[0031] Figure 2 yes Figure 1 A schematic exploded perspective view of the coil device shown.

[0032] Figure 3 It is along Figure 1 In the schematic cross-sectional view taken along line III-III shown, illustration of the terminals is omitted.

[0033] Figure 4A It is along Figure 3 A schematic cross-sectional view of the core taken along line IV-IV is shown.

[0034] Figure 4B yes Figure 4A A schematic cross-sectional view of a modified example of the core shown.

[0035] Figure 4C yes Figure 4A A schematic cross-sectional view of another modified example of the core shown.

[0036] Figure 4D yes Figure 4A A schematic cross-sectional view of yet another modified example of the core shown.

[0037] Figure 4E yes Figure 4A A schematic cross-sectional view of yet another modified example of the core shown.

[0038] Figure 5 yes Figure 3 A cross-sectional perspective view of the main parts of the spool is shown.

[0039] Figure 6 Yes means Figure 5 A cross-sectional perspective view of the main parts of a modified example of the bobbin shown.

[0040] Figure 7 is from Figure 2 The spool shown is a partially exploded perspective view of the spool with a portion of the core removed and the spool and the core viewed from different angles. DETAILED DESCRIPTION

[0041] Hereinafter, the embodiments of the present invention will be described with reference to the accompanying drawings. In addition, the contents of the drawings are merely for the purpose of illustrating and exemplifying the present invention, and the appearance and dimensional ratios may be different from the actual objects. In addition, the present invention is not limited to the following embodiments.

[0042] (First Embodiment)

[0043] Figure 1 The coil device 1 according to the embodiment of the present invention shown in FIG. 1 functions as, for example, a leakage transformer, and is used in a vehicle charger, a power supply circuit of various electronic devices, and the like. Figure 2 As shown, the coil device 1 has a core 2, a bobbin 3, a terminal block 7 combined with a wiring lower cover 70, and a housing 8. 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 (winding axis direction of the coil) of the coil device 1. In the following description, with respect to 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.

[0044] like Figure 3As shown, a main partition wall flange 31 for insulating the primary side coil and the secondary side coil is provided at a midway position along the Z axis of the barrel portion 30 of the bobbin 3, and the main partition wall flange 31 is configured to protrude in the radial direction from the outer peripheral surface of the barrel portion 30. A plurality of sub-partition wall flanges 32 are provided at a predetermined interval along the Z axis at an upper position of the main partition wall flange 31, and the plurality of sub-partition wall flanges 32 are configured to protrude in the radial direction from the outer peripheral surface of the barrel portion 30. The first winding 4 is wound between the main partition wall flange 31 and the sub-partition wall flange 32, and between the sub-partition wall flanges 32, to form a first winding winding portion 40.

[0045] In addition, similarly, a plurality of secondary partition wall flanges 32 are provided at predetermined intervals along the Z axis at a lower position along the Z axis of the main partition wall flange 31, and the plurality of secondary partition wall flanges 32 are configured to protrude in the radial direction from the outer peripheral surface of the cylinder portion 30. The second winding 5 is wound around the partition gap between the main partition wall flange 31 and the secondary partition wall flange 32 and the partition gap between the secondary partition wall flanges 32, thereby forming a second winding winding portion 50.

[0046] In addition, the partition gap along the Z axis between the main partition wall flange 31 and the auxiliary partition wall flange 32, and the partition gaps between the auxiliary partition wall flanges 32 are formed to be slightly larger than the outer diameter of the first winding 4 or the second winding 5, and these partition gaps become gaps for only one row of windings 4 or 5 to enter along the Z axis. Therefore, the windings 4 or 5 can be neatly wound on the outer peripheral surface of the barrel portion 30 of the bobbin 3.

[0047] A radial cutout is formed at least at one location along the circumference of each secondary partition wall flange 32, extending from the outer circumference of the flange 32 to the outer circumference of the barrel 30. Through the cutout, the winding 4 or 5 can move along the Z-axis toward the adjacent divided gap, and a continuous winding operation of the winding 4 or 5 can be performed. The winding method of the winding 4 or 5 is not particularly limited, and examples thereof include normal winding and α winding.

[0048] In addition, in the present embodiment, the second winding portion 50 is arranged on the lower side along the Z axis of the first winding portion 40, but the reverse may be used. In the present embodiment, for example, the first winding portion 40 becomes the primary coil of the transformer and the second winding portion 50 becomes the secondary coil of the transformer, but the reverse may be used. The first winding portion 40 and the second winding portion 50 are separated by the main partition wall flange 31 in the Z axis direction to adjust the coupling coefficient, etc.

[0049] In the present embodiment, the first winding 4 and the second winding 5 are respectively composed of conductive windings, which may not be covered with insulation, but are preferably covered with insulation. The type of the conductive winding is not particularly limited, and it can be a conductive core wire such as round wire, flat wire, stranded wire, twisted wire, braided wire, etc. 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, etc.

[0050] In addition, in the present embodiment, the first winding 4 and the second winding 5 are both composed of self-welding type windings, but only one of them may be a self-welding type winding, or both may be composed of other windings. In addition, at least one of the first winding winding portion 40 and the second winding 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 both are not particularly limited, and are preferably within the range of 1.0 to 3.0 mm, for example.

[0051] Lead portions 41a and 41b are formed at both ends of the first winding 4 constituting the first winding winding portion 40. The lead portions 41a and 41b are led out from the first winding portion 40 upward along the Z axis and are connected to the first winding portion 40. Figure 1 Connect the terminals 6 and 6 as shown. Figure 3 The two ends of the second winding 5 constituting the second winding winding portion 50 are respectively formed with Figure 2 The lead portions 51 a and 51 b shown are led out from the second winding portion 50 in the upper direction along the Z axis and are connected to the terminals 6 and 6 respectively.

[0052] The plurality of terminals 6 connected to the plurality of lead parts 41a, 41b, 51a, 51b are mounted on a pair of terminal blocks 7. A wiring lower cover 70 is mounted on each terminal block 7. By combining the wiring lower cover 70 with the terminal block 7, the pair of terminals 6 are fixed to the terminal block 7 at a predetermined interval along the Y axis. The terminal block 7 and the wiring lower cover 70 are preferably made of an insulating member such as a synthetic resin, and may be made of the same insulating material, or may be made of different insulating materials.

[0053] In this embodiment, if Figure 1 As shown, the terminal block 7 is mounted on the upper end of the side plate 81 of the housing 8 together with the wiring lower cover 70. For example, the wiring lower cover 70 includes a bottom plate piece 71 that covers the wiring portion 61 of the terminal 6 embedded in the terminal block 7 from below along the Z axis, and a side plate piece 72 that is integrally formed substantially perpendicularly to the bottom plate 71, and the side plate piece 72 is provided with a mounting groove 73.

[0054] The assembly groove 73 of the side plate piece 72 is consistent with the shape of the upper end of the side plate 81, so that the upper end 81a of the side plate 81 located on both sides along the X-axis of the housing 8 enters the assembly groove 73 of the side plate piece 72. By the upper end of the side plate 81 located on both sides along the X-axis of the housing 8 entering the assembly groove 73 of each wiring lower cover 70, each wiring lower cover 70 is assembled to the housing 8.

[0055] It is preferred that the terminal block 7 and the lower wiring cover are separate bodies, and when each of the lead parts 41a, 41b, 51a, 51b is connected to the wiring part 61 of the terminal 6, it is easy to operate by separating the lower wiring cover from the terminal block. Any of the lead parts 41a, 41b, 51a, 51b is connected to the wiring part 61 by riveting, thermal compression, laser welding, welding, etc. It is preferred that after any of the lead parts 41a, 41b, 51a, 51b is connected to the wiring part 61 of each terminal 6, the terminal block 7 and the lower wiring cover 70 are combined and installed on the housing 8 and / or the bobbin 3.

[0056] In the present embodiment, each terminal 6 is preferably insert-molded in a manner that the wiring portion 61 and the external connection portion 62 are exposed relative to the terminal block 7. Each terminal 6 is fixed to the terminal block 7 so that the wiring portion 61 protrudes outward along the X-axis relative to the terminal block 7, and the external connection portion 62 protrudes upward along the Z-axis relative to the terminal block 7. The external connection portion 62 is a portion connected to an external connection terminal not shown or a terminal connection recess of a circuit substrate. The terminal 6 having the wiring portion 61 and the external connection portion 62 is formed, for example, by stamping a metal plate.

[0057] like Figure 2 As shown, in this embodiment, the core 2 can be decomposed into a first core 21 arranged on the upper side along the Z axis, a second core 22 arranged on the lower side along the Z axis of the first core 21, and a middle leg portion 23 arranged between the first core 21 and the second core 22. In addition, the first core 21 is divided into two first split cores 21α along the X axis, and similarly, the second core 22 is also divided into two second split cores 22α along the X axis.

[0058] Each first split core 21α has a flat first base portion 21a and side legs 21b and 21b protruding downward along the Z axis from both sides along the Y axis of the first base portion 21a. In addition, each second split core 22α has a flat second base portion 22a and side legs 22b and 22b protruding upward along the Z axis from both sides along the Y axis of the second base portion 22a.

[0059] In the present embodiment, the first split core 21α and the second split core 22α are respectively composed of U-shaped cores having a substantially U-shaped cross section parallel to a plane including the Z axis and the Y axis, and have the same shape, but may be different from each other. For example, one core may be a U-shaped core and the other may be an I-shaped core.

[0060] Before the pressing core member 92 is mounted on the bobbin 3, the first base portions 21a of the pair of first split cores 21α are mounted on the outer surface of the partition wall flange 32 provided at the upper end of the barrel 30 of the bobbin 3. In addition, the outer surface (upper surface 32a) of the partition wall flange 32 located at the upper end of the barrel 30 is provided with a positioning protrusion 33, and a gap can be formed between the adjacent first base portions 21a, 21a. By forming such a gap, it can be expected that heat dissipation can be improved.

[0061] The second base portions 22a of the pair of second split cores 22α are attached to the outer surface of the partition wall flange 32 provided at the lower end of the barrel portion 30 of the bobbin 3. In addition, a positioning protrusion 33 is provided on the outer surface (lower surface 32b) of the partition wall flange 32 located at the lower end of the barrel portion 30, so that a gap can be formed between the adjacent second base portions 22a, 22a. By forming such a gap, it is expected that heat dissipation can be improved.

[0062] like Figure 2 As shown, a core guide wall 34 is provided on both sides along the X axis of a partition wall flange 32 located at the upper end along the Z axis of the barrel portion 30 of the bobbin 3. A core pressing piece 92 is arranged inside the core guide wall 34. Before each core pressing piece 92 is arranged inside the core guide wall 34, first, the middle leg portion 23 is inserted into a through hole formed on the inner peripheral surface of the barrel portion 30 of the bobbin 3 from above the Z axis.

[0063] Then, the base portion 21a of the first core 21 composed of a pair of first split cores 21α is set on the outer surface (upper surface) of the partition wall flange portion 32 located between the pair of core guide walls 34. The side leg portions 21b of the first core 21 cover the upper portion along the Y axis of the bobbin 3 and along the Z axis on both sides. Then, on the inner side of the core guide wall 34, the core pressing member 92 is inserted into the gap between the core guide wall 34 and the core 21.

[0064] like Figure 7As shown, core guide walls 35 are provided on both sides along the X-axis of the partition wall flange 32 located at the lower end of the barrel portion 30 of the bobbin 3 along the Z-axis. The base portion 22a of the second core 22 composed of a pair of second split cores 22α is provided on the outer surface (lower surface) of the partition wall flange portion 32 located between the pair of core guide walls 35. The side leg portions 22b of the second core 22 cover the lower portion along the Y-axis of the bobbin 3 and along the Z-axis on both sides. The front end portion 22b1 of each side leg portion 22b is butted against the front end portion 21b1 of the side leg portion 21b of the first core 21, and is bonded by an adhesive as needed.

[0065] On the inner circumferential surface of the partition wall flange 32 located at the lower end along the Z axis of the barrel 30 of the bobbin 3, inner convex pieces 36 protruding inward from the inner circumferential surface of the barrel 30 are formed at multiple locations along the circumferential direction. These inner convex pieces 36 protrude from the inner circumferential surface of the barrel 30 to such an extent that the lower end along the Z axis of the through hole formed on the inner circumferential surface of the barrel 30 is not blocked. Figure 3 As shown, the inner convex piece 36 abuts against the outer peripheral portion of the lower end of the middle leg portion 23 along the Z axis. As a result, a gap 37 can be formed between the lower end of the middle leg portion 23 along the Z axis and the second base portion 22a of the second core 22. The heat dissipating resin 82 enters the gap 37. In addition, the interval of the gap 37 can be adjusted by changing the design thickness of the inner convex piece 36 along the Z axis.

[0066] In addition, by adjusting the length of the middle leg portion 23 along the Z axis to be shorter by a predetermined length relative to the height of the cylinder portion 30 along the Z axis from the inner protrusion 36 to the upper surface 32a of the partition wall flange 32 located at the upper end, a gap 38 can be formed between the upper end of the middle leg portion 23 along the Z axis and the first base portion 21a of the first core 21.

[0067] In the present embodiment, the open-to-air surface 82a of the heat-dissipating resin 82 filled in the housing 8 is determined based on the relationship with the volume of the middle leg 23, etc., so that at least a part of the heat-dissipating resin 82 does not enter the gap 38 and the middle leg 23 is sufficiently cooled. That is, the open-to-air 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 23 is located below the open-to-air surface 82a of the heat-dissipating resin 82 and is located below the lower surface of the base portion 21a along the Z axis. With this configuration, an air layer into which the heat-dissipating resin 82 does not enter is formed in the gap 38.

[0068] In addition, the open-to-the-air surface 82a of the heat-dissipating resin 82 is determined so that the winding portion 50 of the second winding 5 is fully impregnated with the heat-dissipating resin 82, and preferably more than 80%, more preferably more than 95%, or substantially more than 100% of the winding portion 40 of the first winding 4 is impregnated with the heat-dissipating resin 82. With such a 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. In addition, in the present 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 transferred to the cooling member (for example, a cooling block with a cooling passage, etc.) provided on the lower surface of the bottom plate 80 of the housing 8 through the housing 8 and is dissipated. In addition, the open-to-the-air surface 82a is a surface where the liquid surface formed by the heat-dissipating resin 82 in a flowing state flowing into the housing 8 is solidified.

[0069] In the present embodiment, the cores 21 and 22 and the middle leg portion 23 are not particularly limited as long as they are cores having a magnetic body, and are made of, for example, ferrite, a metal magnetic body, or a resin containing magnetic powder.

[0070] like Figure 1 As shown, the housing 8 has a substantially rectangular bottom plate 80, and side plates 81 that rise upward along the Z axis from the four sides of the bottom plate 80 and form a bottomed storage space inside, and an upper opening is formed at the upper portion along the Z axis. The housing 8 is preferably made of metal such as aluminum with excellent thermal conductivity, but may also be made of resin.

[0071] The heat dissipation resin 82 is also called a potting resin, and is composed of a silicone resin, a polyurethane resin, an epoxy resin, etc. that is soft even after injection, and 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 dissipation resin 82 and the housing 8, thereby improving the cooling efficiency of the coil device 1.

[0072] Alternatively, the heat dissipating resin 82 may be pre-filled into the housing 8 and then mounted thereon. Figure 2 The bobbin (wound with the winding wire) 3 of the core 2 shown may be installed in the housing 8 and then the heat dissipating resin 82 may be poured into the housing 8 .

[0073] In the coil device 1 of this embodiment, as Figure 3As shown, most of the volume of the middle leg portion 23 of the core 2 is located below the atmosphere open surface 82a of the heat dissipation resin 82. Therefore, in the winding portions 40 and 50 of the windings 4 and 5 arranged around the middle leg portion 23 together with the middle leg portion 23, most of their volumes are also cooled by the heat dissipation resin 82, and the heat dissipation is improved. In addition, the first base portion 21a is arranged at one end (upper end) of the middle leg portion 23 separated by a gap 38 of a predetermined distance along the Z axis. Therefore, even if a part of the first base portion 21a is exposed from the heat dissipation resin 82, the stress such as the thermal expansion force generated in the middle leg portion 23 is not transmitted to the first base portion 21a. Therefore, it is possible to reduce the excessive thermal stress that may be generated in the first base portion 21a.

[0074] Furthermore, in the prior art, the core 2 housed inside the shell 8 is usually an integrated core of a base 21a located on the upper side along the Z axis and a middle leg 23. Therefore, the temperature difference between the base 21a and the middle leg 23 becomes larger, thereby causing stress to be concentrated on the base in particular, which may cause adverse conditions such as rupture and defect of the core.

[0075] In this embodiment, even if the temperature difference between the base 21a and the middle leg 23 increases, there is a gap with an air layer between the base 21a and the middle leg 23, so stress is difficult to concentrate on the base, and the possibility of causing defects such as cracks and defects in the core can be reduced. According to the experiment of the inventors, it can be confirmed that the maximum back stress generated at the base of the core in this embodiment is reduced by about 25% or more compared with the maximum back stress of the base generated in the conventional core.

[0076] 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 first base portion 21a is exposed from the heat dissipating resin 82. By exposing most of the first base portion 21a, the housing 8 that accommodates the heat dissipating resin 82 can be miniaturized, and the amount of the heat dissipating resin 82 can also be reduced. Moreover, even in this case, the first base portion 21a is arranged at the upper end of the middle leg portion 23 separated by a gap 38 of a predetermined distance along the Z axis, so that stress such as thermal expansion force generated in the middle leg portion 23 where heat is easily accumulated is not transmitted to the first base portion 21a. Therefore, excessive thermal stress that may be generated in the first base portion 21a can be reduced.

[0077] The core 2 may also have a second base portion 22a formed continuously with the other end (lower end) of the middle leg portion 23 along the Z axis, but in the present embodiment, the core 2 also has a second base portion 22a separated from the lower end of the middle leg portion 23 by a gap 37 of a prescribed distance along the Z axis.

[0078] The second base portion 22a is close to the cooling wall surface of the housing 8 filled with the heat dissipating resin 82, that is, the bottom plate 80. In the present embodiment, since the cooling wall surface of the housing 8 is the bottom surface of the housing 8, the core 2 is accommodated inside the housing 8 in a manner that the axial cores of the winding portions 40, 50 of the windings 4, 5 are substantially perpendicular to the bottom surface of the housing 8. In addition, in another embodiment, when the cooling wall surface of the housing 8 is the side surface of the housing 8 (side plate 81), the core 2 may be accommodated inside the housing 8 in a manner that the axial cores of the winding portions 40, 50 of the windings 4, 5 are substantially parallel to the bottom surface of the housing 8.

[0079] In this embodiment, there is an air layer of 1.9 mm or less in the gap 38 between the first base portion 21a and the upper end of the middle leg portion 23. Since there is an air layer in the gap 38 where the heat dissipating resin 82 does not enter, stress such as thermal expansion force generated in the middle leg portion 23 is more reliably not transmitted to the first base portion 21a. In addition, by setting the spacing of the air layer in the gap 38 to be less than a specified value, it is easy to form a magnetic circuit between the middle leg portion 23 and the base portion 21a. Figure 4A As shown, the interval t1 of the gap 38 along the Z axis and the interval t2 of the gap 37 along the Z axis may be the same or different, but are preferably both less than 3 mm, less than 2 mm, or less than 1.9 mm.

[0080] In this embodiment, the upper end of the middle leg portion 23 may be located below the atmosphere open surface 82a of the heat dissipating resin 82 along the Z axis. With this configuration, the heat dissipation of the middle leg portion and the winding portion of the winding arranged around it is improved. Even in this case, it is preferable that the atmosphere open surface 82a is located in the middle of the gap 38 so that an air layer is formed in the gap 38.

[0081] Alternatively, the upper end of the middle leg portion 23 may be located above the atmosphere open surface 82a of the heat dissipating resin 82. With such a configuration, it is easy to form an air layer of 1.9 mm or less in the gap 38.

[0082] In the present embodiment, the atmosphere open surface 82a of the heat dissipating resin 82 is located at a position where the winding portions 40 and 50 of the windings 4 and 5 arranged around the middle leg portion 23 are covered with the heat dissipating resin 82. With this configuration, the heat dissipation is further improved.

[0083] In this embodiment, an adhesive or heat-dissipating resin 82 may be interposed at least partially between the lower end of the middle leg portion 23 along the Z axis and the surface of the second base portion 22a. The lower end of the middle leg portion 23 and the second base portion 22a may be formed integrally.

[0084] Furthermore, in this embodiment, the barrel portion 30 of the bobbin 3 is arranged between the middle leg portion 23 and the winding portions 40, 50 of the windings 4, 5, but the winding portions (for example, air-core coils) 40, 50 of the windings 4, 5 may be arranged around the middle leg portion 23 without arranging the bobbin 3.

[0085] In addition, in this embodiment, the coil device 1 also has a terminal block 7 for holding the lead portions 41a, 41b, 51a, 51b of the windings 4 and 5. The terminal block 7 is held by the bobbin 3 or the housing 8, but can also be directly fixed or assembled to the first base portion 21a of the core 2.

[0086] (Second Embodiment)

[0087] like Figure 6 As shown, the coil device of this embodiment is the same as the coil device 1 of the above-mentioned embodiment except for the following, and achieves the same effect. That is, in this embodiment, a convex frame 39 is formed along the periphery of the through hole in a manner that protrudes from the surface of the partition wall flange 32 located at the top along the Z axis of the bobbin 3 and is continuous from the inner circumferential surface of the barrel 30. The top surface of the convex frame 39 is, for example, Figure 3 The inner surface of the base portion 21 a shown is protruding. Therefore, the protruding height of the protruding frame 39 also becomes a factor in adjusting the spacing of the gap 38 along the Z axis.

[0088] Due to the presence of the convex frame 39, even if the atmosphere open surface 82a of the heat dissipating resin 82 is higher than the upper surface 32a of the partition wall flange 32, the heat dissipating resin 82 is difficult to enter the gap 38 from the periphery of the convex frame 39, and an air layer is easily formed in the gap. The other structures and effects are the same as those in the above-mentioned embodiment, and the repeated description is omitted.

[0089] (Third Embodiment)

[0090] like Figure 4B As shown, the coil device of this embodiment is the same as the coil device 1 of the first embodiment or the second embodiment described above, except for the following, and achieves the same effect. That is, the coil device of this embodiment has the same structure and achieves the same effect except that it has a core 2A different from the core 2 of the above-mentioned embodiment.

[0091] The core 2A of this embodiment is different from the core 2 of the above-mentioned embodiment in that a stepped protrusion 24 is formed on the inner surface of the base 21a, 22a facing the upper end or lower end of the middle leg 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 38 or 37 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 23.

[0092] However, the protruding height of the step-shaped convex portion 24 facing the upper end of the middle leg portion 23 is preferably as small as possible. In order to form an air layer in the gap 38, it is preferred that the atmosphere-opening surface 82a of the heat dissipating resin is located within the range of the height position along the Z axis of the gap 38, but it is preferred to adjust the protruding height of the step-shaped convex portion 24 so that the atmosphere-opening surface 82a is not low. The other structures and effects are the same as those in the above-mentioned embodiment, and the repeated description is omitted.

[0093] (Fourth Embodiment)

[0094] 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 for the following, and achieves the same effects. That is, the coil device of this embodiment has the same structure and achieves the same effects except for having a core 2B different from the core 2 or 2A of the above-mentioned embodiment.

[0095] The core 2B of this embodiment is different from the core 2 of the above-mentioned embodiment. The first core 21 has a first base 21a independent from the side foot 25, and the second core 22 has a second base 22a independent from the side foot 25. The side foot 25 has a structure that integrates the side foot 21b and the side foot 22b facing each other along the Z-axis direction of the above-mentioned embodiment and separates and independently from each base 21a, 22a. The other structures and effects are the same as those of the above-mentioned embodiment, and the description of the repeated parts is omitted.

[0096] (Fifth Embodiment)

[0097] 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 for the following, and achieves the same effect. That is, the coil device of this embodiment has the same structure and achieves the same effect except for having a core 2C different from the core 2, 2A or 2B of the above-mentioned embodiment.

[0098] The core 2C of this embodiment is different from the core 2 of the above embodiment in that the lower end of the middle leg portion 23C is integrally formed with the second base portion 22a of the second core 22. The other structures and effects are the same as those of the above embodiment, and the repeated description is omitted.

[0099] (Sixth Embodiment)

[0100] like Figure 4EAs shown, the coil device of this embodiment is the same as the coil device 1 of the first to fifth embodiments described above except for the following, and achieves the same effects. That is, the coil device of this embodiment has the same structure and achieves the same effects except for having a core 2D different from the core 2, 2A, 2B or 2C of the above-mentioned embodiments.

[0101] The core 2D of this embodiment is different from the above-mentioned Figure 4C Unlike the core 2B of the illustrated embodiment, the lower end of the middle leg portion 23C is formed integrally with the second base portion 22a of the second core 22. The other structures and effects are the same as those of the above-described embodiment, and the description of the overlapping parts is omitted.

[0102] 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.

[0103] For example, in the above-mentioned embodiment, the core 2 is composed of a combination of five-part cores and seven-part cores, but the number of divisions is not limited to these, and for example, it can also be composed of a combination of two-part, three-part, four-part, or other number of divisions.

[0104] Furthermore, as described above, the bobbin 3 may not be provided, and the air-core coil composed of the first winding portion 40 and the second winding portion 50 may be arranged around the middle leg portion 23 without the bobbin 3 being interposed.

[0105] In the case where the winding portion 40 or 50 of the winding wire is directly arranged around the middle leg portion 23 of the core 2 without the barrel portion 30 of the bobbin 3, the first winding wire 4 and the second winding wire 5 are preferably composed of self-welding type conducting wires having a welding layer and an insulating layer. In addition, it is preferred that the first winding portion 40 wound with the first winding wire 4 and the second winding portion 50 wound with the second winding wire 5 are respectively pre-formed into a coil shape, for example, preferably provided in the form of an air-core coil.

[0106] In addition, the terminal block 7 having the wiring lower cover 70 can also be mounted on the housing 8, but can also be directly mounted on the base 21a of the core 2 located on the upper side along the Z axis. In addition, as a method for directly fixing the terminal block 7 to the core 2, there is no particular limitation, and examples thereof include bonding, welding, fixing with tape, and the like, including all fixing methods except fixing with a bobbin.

[0107] In addition, in the above-mentioned embodiment, for example Figure 2 As shown, the heat sink divided bodies 9a, 9a of the heat sink 9 are arranged to cover the base parts 21a, 21a and the side legs 21b, 22b of the core 2, but the structure of the heat sink 9 is not limited to the example shown in the figure. Figure 2The heat sink 9 shown has the top plate 90 and the side plate 91, respectively. However, the pair of heat sinks 9a may be continuous. Alternatively, the heat sink 9 may not be provided.

[0108] Description of Reference Numerals

[0109] 1...Coil device

[0110] 2. 2A~2D……Core

[0111] 21...First Core

[0112] 21α……First split core

[0113] 21a……First base

[0114] 21b... Lateral foot

[0115] 21b1...Front End

[0116] 22... Second Core

[0117] 22α……The second split core

[0118] 22a……Second base

[0119] 22b... Lateral foot

[0120] 22b1...Front End

[0121] 23, 23C… mid-foot

[0122] 24... Step-shaped convex part

[0123] 25...lateral foot

[0124] 3. Spool

[0125] 30……Cylinder

[0126] 31... Main dividing wall flange

[0127] 32...Secondary partition wall flange

[0128] 32a...upper surface

[0129] 32b...lower surface

[0130] 33……Locating the convex part

[0131] 34, 35... Core guide wall

[0132] 36...Inner square convex piece

[0133] 37, 38... Gap

[0134] 39...convex frame

[0135] 4...First winding

[0136] 40: First winding section

[0137] 41a, 41b...lead portion

[0138] 5... Second winding

[0139] 50... Second winding section

[0140] 51a, 51b...lead portion

[0141] 6...Terminal

[0142] 61……Connection section

[0143] 62……External connection

[0144] 7...Terminal block

[0145] 70... Wiring under cover

[0146] 71... Bottom plate

[0147] 72...Side panels

[0148] 73...Mounting slot

[0149] 8……Housing

[0150] 80...base plate

[0151] 81...Side panels

[0152] 81a……top

[0153] 82...Heat dissipation resin

[0154] 82a……Atmospheric open surface

[0155] 9. Heat sink

[0156] 9a...Radiator plate splitter

[0157] 90……Top plate

[0158] 91……Side panel

[0159] 92……Pressure core

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 disposed at one end of the middle leg portion at a predetermined distance along the winding axis of the winding portion; 70% or more of the volume of the middle leg portion is located below the atmosphere-opening surface of the heat-dissipating resin.

2. The coil device according to claim 1, wherein: 30% or more of the volume of the first base portion is exposed from the heat-dissipating resin.

3. 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.

4. 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.

5. The coil device according to claim 3 or 4, wherein: The second base portion is close to a cooling wall surface of a housing filled with the heat-dissipating resin.

6. The coil device according to claim 1, wherein: An air layer of 1.9 mm or less exists between the first base portion and the one end of the mid-leg portion.

7. The coil device according to claim 6, wherein: The one end of the middle leg portion is located below the atmosphere-opening surface of the heat-dissipating resin.

8. The coil device according to claim 6, wherein: The one end of the middle leg portion is located above the atmosphere-opening surface of the heat-dissipating resin.

9. The coil device according to claim 7 or 8, wherein: The atmosphere-opening surface of the heat-dissipating resin is located at a position where the heat-dissipating resin covers the winding portion of the winding wire disposed around the middle leg portion.

10. The coil device according to claim 4, wherein: An adhesive or the heat-dissipating resin is interposed at least partially between the other end of the middle leg portion and the surface of the second base portion.

11. The coil device according to claim 1, wherein: A cylindrical portion of the bobbin is disposed between the middle leg portion and the winding portion of the winding wire.

12. 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.

13. The coil device according to claim 12, wherein: The terminal block is mounted on a bobbin, a case accommodating the heat-dissipating resin, or the first base portion.

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