Coil device

Abstract

To provide a coil device capable of reducing thermal stress of a core, for example.SOLUTION: The core 2 is formed integrally with at least one end of a base part side 21a via a coupling part side 21c, and has an outer leg part side 21c projecting from the coupling part side 21b substantially in parallel with the axis of the winding part 40. The outer surface of the connecting portion side 21c is constituted by a chamfered outer surface side 21c1, and a first outer boundary 21a between the outer surface side 21a1 of the base portion side 21c1 and the chamfered outer surface side OB1 is located at a first predetermined distance relative to the inner surface side 21b of the outer leg portion 21b2 in a vertical distance. L1. The second outer boundary side 21b between the outer surface side 21b1 of the middle leg section side 21c1 and the chamfered outer surface side OB2 is positioned at a second prescribed vertical distance L2 from the inner surface side 21a of the base section side 21a2.SELECTED DRAWING: Figure 4A

Description

[Technical Field]

[0001] The present invention relates to a coil device that can be suitably used as a transformer, for example. [Background technology]

[0002] For example, as shown in Patent Document 1 below, E-shaped cores are commonly used in coil devices such as transformers. In conventional cores such as E-shaped cores, the outer corners between the outer legs and the base are generally sharp at approximately 90 degrees. Note that while right-angled corners may be chamfered, the curvature of the chamfered portion is usually 0.2 to 0.3 mm.

[0003] As the current flowing through the wires that make up the coil increases, core temperature rises become a problem. Higher core temperatures increase the thermal stress acting on the core, potentially resulting in damage to the core. In particular, when a portion of the core is cooled by a heat-dissipating resin, some parts are cooled by the resin and others are not, creating thermal stress in the core and potentially reducing the core's durability.

[0004] Even when air cooling is used without using a heat-dissipating resin, excessive thermal stress may occur in the core, which also reduces the durability of the core. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2014-36194 Summary of the Invention [Problem to be solved by the invention]

[0006] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a coil device that can reduce, for example, thermal stress in the core. [Means for solving the problem]

[0007] In order to achieve the above object, a coil device according to one aspect of the present invention comprises: a core including a magnetic material; a wire having a winding portion wound in a coil shape, The core is a middle leg portion around which the windings of the wire are disposed; and a base portion that is magnetically coupled to one end of the center leg portion in contact or non-contact state and extends in a direction substantially perpendicular to the axis of the winding portion; an outer leg portion that is integrally formed with at least one end of the base portion via a connecting portion and that protrudes from the connecting portion substantially parallel to the axis of the winding portion; The outer surface of the connecting portion is configured as a removable surface, a first outer boundary between the outer surface of the base portion and the removed surface is located at a first predetermined distance perpendicular to the inner surface of the outer leg portion; A second outer boundary between the outer surface of the middle leg portion and the removed surface is located at a second predetermined distance perpendicular to the inner surface of the base portion.

[0008] According to experiments conducted by the inventors, it was found that in conventional cores with right-angle corners, the heat generated by the magnetic flux concentrating at the inner corners between the base and outer legs is difficult to dissipate to the outside, and sufficient heat dissipation is not possible. In a coil device according to one aspect of the present invention, the outer surface of the connecting portion between the base and outer legs of the core is a chamfered surface rather than a corner that is close to a right angle.

[0009] As a result, the distance between the inner corner of the connecting part and the disconnected surface of the connecting part is shorter than before, and heat generated by the magnetic flux concentrating at the inner corner of the connecting part is more easily dissipated to the disconnected surface of the connecting part, improving heat dissipation. As a result, thermal stress in the core can also be reduced. In addition, the disconnected surface of the connecting part has the effect of suppressing stress concentration due to the shape of the connecting part. In addition, the flow of magnetic flux at the connecting part is smoother.

[0010] Preferably, the inner surface of the connecting portion is also configured as a chamfered inner surface. Preferably, a first inner boundary between the inner surface of the base portion and the chamfered inner surface is located at a third predetermined distance perpendicular to the inner surface of the outer leg portion. Also preferably, a second inner boundary between the inner surface of the center leg portion and the chamfered inner surface is located at a fourth predetermined distance perpendicular to the inner surface of the base portion. With this configuration, the inner surface of the connecting portion between the base portion and the outer leg portion of the core is chamfered rather than a nearly right-angled corner, which allows for smoother magnetic flux flow in that area. Furthermore, the distance between the chamfered inner surface and the removed surface is approximately constant along the magnetic flux flow, which allows for uniform heat dissipation from the chamfered inner surface to the removed surface, further improving heat dissipation.

[0011] The third predetermined distance is preferably substantially the same as the first predetermined distance, but may be different, and the fourth predetermined distance is preferably substantially the same as the second predetermined distance, but may be different. By making these substantially the same, it becomes easier to keep the distance between the chamfered inner surface and the removed surface substantially constant along the flow of magnetic flux, and heat dissipation from the chamfered inner surface to the removed surface becomes more uniform, further improving heat dissipation performance.

[0012] The first predetermined distance is preferably approximately the same as the second predetermined distance, but may be different from the second predetermined distance. Also, the first predetermined distance is defined as L1, the second predetermined distance is defined as L2, the thickness of the outer leg portion is defined as T1, and the thickness of the base portion is defined as T2. The direction of the first predetermined distance is defined as a positive direction from the inner surface of the outer leg portion toward the inside, and a negative direction from the inner surface of the outer leg portion toward the outside, When the direction of the second predetermined distance is defined as a positive direction from the inner surface of the base portion toward the inside and a negative direction from the inner surface of the base portion toward the outside, it is preferable that the following relationship holds.

[0013] That is, it is preferable that L1 / T1 is in the range of -2 / 3 or more and 1 / 2 or less. It is also preferable that L2 / T2 is in the range of -2 / 3 or more and 1 / 2 or less. It is even more preferable that L1 / T1 is in the range of 0 or more and 1 / 2 or less, or 1 / 4 or more and 1 / 2 or less. It is also even more preferable that L2 / T2 is in the range of 0 or more and 1 / 2 or less, or 1 / 4 or more and 1 / 2 or less. When it is in such a range, heat dissipation performance is further improved and stress can be further reduced.

[0014] The third predetermined distance is preferably approximately the same as the fourth predetermined distance, but may be different from the fourth predetermined distance. Also, the third predetermined distance is defined as L3, the fourth predetermined distance is defined as L4, the thickness of the outer leg portion is defined as T1, and the thickness of the base portion is defined as T2. When the direction of the third predetermined distance is defined as positive in the direction from the inner surface of the outer leg toward the inside and negative in the direction from the inner surface of the outer leg toward the outside, and the direction of the fourth predetermined distance is defined as positive in the direction from the inner surface of the base portion toward the inside and negative in the direction from the inner surface of the base portion toward the outside, it is preferable that the following relationship holds.

[0015] That is, it is preferable that L3 / T1 is in the range of -2 / 3 or more and 1 / 2 or less. It is also preferable that L4 / T2 is in the range of -2 / 3 or more and 1 / 2 or less. It is even more preferable that L3 / T1 is in the range of 0 or more and 1 / 2 or less, or 1 / 4 or more and 1 / 2 or less. It is also even more preferable that L4 / T2 is in the range of 0 or more and 1 / 2 or less, or 1 / 4 or more and 1 / 2 or less. When it is in such a range, heat dissipation performance is further improved and stress can be further reduced.

[0016] At least a portion of the outer leg is preferably immersed in the heat-dissipating resin, and the second outer boundary is preferably located below the open-to-air surface of the heat-dissipating resin. In this case, at least a portion of the detachable surface of the connecting portion is directly immersed in the heat-dissipating resin, further improving heat dissipation.

[0017] The second outer boundary may be located between one end and the other end of the wire wound portion along the axis of the wire, which allows the coil device to have a low profile and improves heat dissipation.

[0018] The first outer boundary may be located between the outermost and innermost positions of the wound portion of the wire. In this case, it is possible to improve heat dissipation while reducing the width of the coil device.

[0019] The second inner boundary may be located between one end and the other end of the wire winding along the axis of the wire, which can reduce the height of the coil device and improve heat dissipation.

[0020] The first inner boundary may be located between the outermost and innermost positions of the wound portion of the wire. In this case, it is possible to improve heat dissipation while reducing the lateral size of the coil device.

[0021] The cut surface is preferably a curved surface, but may be a collection of one or more flat surfaces. This configuration further improves heat dissipation and reduces stress.

[0022] The chamfered inner surface is preferably a curved surface, but may be a collection of one or more flat surfaces. By configuring it in this way, heat dissipation can be further improved and stress can be further reduced.

[0023] Preferably, a heat sink is disposed on the outer side of the removed surface. This configuration further improves heat dissipation and reduces stress. The heat sink may cover the outer surface of the base, and a portion of the heat sink may be immersed in a heat-dissipating resin. [Brief explanation of the drawings]

[0024] [Figure 1] FIG. 1 is a schematic perspective view of a coil device according to one embodiment of the present invention. [Figure 2A] FIG. 2A is an exploded perspective view of the coil device shown in FIG. [Figure 2B] FIG. 2B is an exploded perspective view showing a modification of the coil device shown in FIG. 2A. [Figure 3] FIG. 3 is a schematic cross-sectional view of the coil device taken along line III-III shown in FIG. [Figure 4A] 4A is a partially enlarged schematic explanatory view showing details of the connecting portion of the core shown in FIG. [Figure 4B] 4B is a partially enlarged schematic explanatory view similar to FIG. 4A, illustrating the relationship between the heat sink and the connecting portion of the core shown in FIG. 2A. [Figure 5] FIG. 5 is a schematic perspective view of the bobbin shown in FIG. 2A, illustrating the relationship between the bobbin and the wire. DETAILED DESCRIPTION OF THE INVENTION

[0025] The following describes the embodiments.

[0026] A coil device 1 according to an embodiment of the present invention shown in Fig. 1 functions as, for example, a leakage transformer and is used in power supply circuits for in-vehicle chargers and various electrical devices. As shown in Fig. 2A, the coil device 1 has a core 2, a bobbin 3, and a case 8. In the drawing, the X-axis, Y-axis, and Z-axis are perpendicular to each other, and the Z-axis is parallel to the height direction of the coil device 1 (direction of the coil winding axis core). 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 is referred to as the inward direction, and the direction away from the center of the coil device 1 is referred to as the outward direction.

[0027] 3, a main bulkhead flange 31 for insulating the primary coil and secondary coil is provided at a midpoint along the Z axis of the cylindrical portion 30 of the bobbin 3 so as to protrude radially from the outer circumferential surface of the cylindrical portion 30. Above the main bulkhead flange 31 along the Z axis, a plurality of sub-bulhead flanges 32 are provided at predetermined intervals along the Z axis so as to protrude radially from the outer circumferential surface of the cylindrical portion 30. A first wire 4 is wound between the main bulkhead flange 31 and the sub-bulhead flanges 32 and between the sub-bulhead flanges 32 to form a first wire winding portion 40.

[0028] Similarly, below the main partition flange 31 along the Z axis, a plurality of sub-partition flanges 32 are provided at predetermined intervals along the Z axis so as to protrude radially from the outer circumferential surface of the tubular portion 30. A second wire 5 is wound in the partition gaps between the main partition flange 31 and the sub-partition flange 32 and in the partition gaps between the sub-partition flanges 32, forming second wire winding portions 50.

[0029] The partition gaps along the Z axis between the main partition flange 31 and the sub-partition flange 32 and the partition gaps between the sub-partition flanges 32 are formed to be slightly larger than the outer diameter of the first wire 4 or the second wire 5, and each of these partition gaps is large enough to accommodate only one row of the wire 4 or 5 along the Z axis. This allows the wire 4 or 5 to be wound neatly around the outer peripheral surface of the tubular portion 30 of the bobbin 3.

[0030] 5, radial notches 31a, 32a are formed in at least one location (four locations in this embodiment) along the circumferential direction of the main bulkhead flange 31 and the sub-bulhead flanges 32 located on both sides of the main bulkhead flange 31 along the Z axis, and extend from the outer periphery of the flanges 31, 32 to the outer periphery of the tubular portion 30. At positions corresponding to these notches 31a, 32a, through holes 30a penetrating the inside and outside of the tubular portion 30 are formed in the tubular portion 30 of the bobbin 3. A heat dissipating resin 82, which will be described later, can easily spread from the inside to the outside of the tubular portion 30 through these through holes 30a.

[0031] 3 can move along the Z axis to the adjacent compartment gap through the notch 32a of the secondary partition flange 32, enabling continuous winding of the wire 4 or 5. The winding method of the wire 4 or 5 is not particularly limited, and examples thereof include normal winding and α winding.

[0032] In this embodiment, as shown in Fig. 3, the second wire winding portion 50 is arranged below the first wire winding portion 40 along the Z axis, but the opposite is also possible. In this embodiment, for example, the first wire winding portion 40 serves as the primary coil of a transformer, and the second wire winding portion 50 serves as the secondary coil of the transformer, but the opposite is also possible. The first wire winding portion 40 and the second wire winding portion 50 are separated in the Z axis direction by the main bulkhead flange 31, and the coupling coefficient and the like are adjusted.

[0033] In this embodiment, the first wire 4 and the second wire 5 are each made of a conductive wire, and may or may not be insulated, but are preferably insulated. The type of conductive wire is not particularly limited, and may be a conductive core wire such as a round wire, rectangular wire, twisted wire, Litz wire, or braided wire. The material of the adhesive layer or insulating layer covering the core wire is not particularly limited, but examples include polyurethane, polyamideimide, polyimide, and polyester.

[0034] In this embodiment, both the first wire 4 and the second wire 5 are made of self-bonding wire, but only one of them may be a self-bonding wire, or both may be made of other wires. At least one of the first wire winding portion 40 and the second wire winding portion 50 may be a flat coil. The wire diameters of the first wire 4 and the second wire 5 may be the same or different, and are not particularly limited, but are preferably within the range of 1.0 to 3.0 mm, for example.

[0035] 2A, lead portions 41a, 41b are formed at both ends of the first wire 4 that constitutes the first wire winding portion 40, and each of the lead portions 41a, 41b is drawn upward from the first winding portion 40 along the Z axis and connected to the terminals 6, 6, respectively, shown in Fig. 1. Also, lead portions 51a, 51b are formed at both ends of the second wire 5 that constitutes the second wire winding portion 50, and each of the lead portions 51a, 51b is drawn upward from the second winding portion 50 along the Z axis and connected to the terminals 6, 6, respectively.

[0036] 5, these multiple lead portions 41a, 41b, 51a, 51b are locked to lead locking portions 70 of the lead attachment portion 7 located on both sides along the X axis of the sub-partition flange 32 that is located at the topmost position along the Z axis of the bobbin 3. In this embodiment, each lead attachment portion 7 is molded integrally with the bobbin 3, but it may also be molded separately from the bobbin 3 and connected to the bobbin 3.

[0037] 5, in this embodiment, the lead portion 51a is locked by the guide protrusion 32b formed on the sub-partition flange 32 located below the main partition flange 31 along the Z axis, and then guided upward along the Z axis to be locked by the lead locking portion 70 of the lead attachment portion 7. The lead portion 51b is locked by the guide protrusion 32b formed on the main partition flange 31, and then guided upward along the Z axis to be locked by the lead locking portion 70 of the lead attachment portion 7.

[0038] 5, the lead portion 41a is locked by the guide protrusion 32b formed on the sub-partition flange 32 located above the main partition flange 31 along the Z axis, and then guided upward along the Z axis to be locked by the lead locking portion 70 of the lead attachment portion 7. The lead portion 41b is directly guided upward along the Z axis to be locked by the lead locking portion 70 of the lead attachment portion 7.

[0039] In this embodiment, as shown in Fig. 1, each terminal 6 has a wire connection portion 61 and an external connection portion 62. In this embodiment, the terminal 6 is separated from the lead attachment portion 7, but the terminal 6 may be attached to the lead attachment portion 7. The structure of each terminal 6 is not limited to the example shown in the figure, and may be a plug-in terminal or a terminal with another structure. The terminal 6 having the wire connection portion 61 and the external connection portion 62 is formed, for example, by pressing a single metal plate.

[0040] 2A, in this embodiment, the core 2 can be disassembled into a first core 21 disposed on the upper side along the Z axis, a second core 22 disposed on the lower side of the first core 21 along the Z axis, and a center leg portion 23 disposed between the first core 21 and the second core 22. The first core 21 is divided into two first divided cores 21α, 21α along the X axis, and similarly, the second core 22 is divided into two second divided cores 22α, 22α along the X axis.

[0041] Each first divided core 21α has a flat first base portion 21a and outer legs 21b, 21b that protrude downward along the Z axis from both sides of the first base portion 21a along the Y axis. Each second divided core 22α has a flat first base portion 22a and outer legs 22b, 22b that protrude upward along the Z axis from both sides of the first base portion 22a along the Y axis.

[0042] In this embodiment, the first divided core 21α and the second divided core 22α are each made of a U-shaped core that is approximately U-shaped in 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 core may be an I-shaped core.

[0043] The first base portions 21a of the pair of first split cores 21α are attached to the outer surface of a partition flange 32 provided at the upper end of the cylindrical portion 30 of the bobbin 3. The outer surface (upper surface 32c) of the partition flange 32 located at the upper end of the cylindrical portion 30 is provided with a positioning protrusion 33, which makes it possible to form a gap between the adjacent first base portions 21a, 21a. By forming such a gap, it is expected that heat dissipation will be improved.

[0044] The second base portions 22a of the pair of second split cores 22α are attached to the outer surface of a partition flange 32 provided at the lower end of the cylindrical portion 30 of the bobbin 3. The outer surface (lower surface 32d) of the partition flange 32 located at the lower end of the cylindrical portion 30 is provided with a positioning protrusion 33, which makes it possible to form a gap between adjacent second base portions 22a, 22a. By forming such a gap, it is expected that heat dissipation will be improved.

[0045] 2A, core guide walls 34 are provided on both sides along the X axis of partition flange 32 located at the upper end along the Z axis of tubular portion 30 of bobbin 3. Center leg portion 23 is inserted from above along the Z axis into a center leg attachment hole formed on the inner peripheral surface of tubular portion 30 of bobbin 3.

[0046] Thereafter, the base portions 21a of the pair of first split cores 21α are placed on the outer surface (upper surface 32c) of the partition flange portion 32 located between the pair of core guide walls 34. The outer leg portions 21b of the first core 21 cover the upper portion along the Z axis on both sides along the Y axis of the bobbin 3, respectively.

[0047] Additionally, core guide walls 35 are provided on both sides along the X-axis of the partition flange 32 located at the lower end along the Z-axis of the tubular portion 30 of the bobbin 3. Base portions 22a of a pair of second split cores 22α are installed on the outer surface (lower surface 32d) of the partition flange 32 located between the pair of core guide walls 35. The outer leg portions 22b of the second core 22 cover the lower portions along the Z-axis on both sides along the Y-axis of the bobbin 3. The tip ends 22b3 of the outer leg portions 22b are abutted against the tip ends 21b3 of the outer leg portions 21b of the first core 21 and are joined with an adhesive as necessary.

[0048] As shown in FIGS. 3 and 5 , the inner peripheral surface of the partition flange 32, located at the lower end of the tubular portion 30 of the bobbin 3 along the Z axis, is provided with multiple inward protrusions 36 that protrude inward from the inner peripheral surface of the tubular portion 30 at various locations along the circumferential direction. These inward protrusions 36 protrude from the inner peripheral surface of the tubular portion 30 to an extent that they do not block the lower end of the center leg attachment hole, which is formed on the inner peripheral surface of the tubular portion 30 along the Z axis. As shown in FIG. 3 , these inward protrusions 36 abut against the outer peripheral portion of the lower end of the center leg 23 along the Z axis. As a result, a gap 37 is formed between the lower end of the center leg 23 along the Z axis and the second base portion 22a of the second core 22. Heat-dissipating resin 82 is allowed to fill the gap 37. The size of the gap 37 can be adjusted by changing the design thickness of the inward protrusions 36 along the Z axis.

[0049] Furthermore, 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 tubular portion 30 along the Z-axis from the inward convex piece 33 to the upper surface 32c of the partition flange 32 located at the uppermost 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.

[0050] 3, this gap 38 is filled with heat-dissipating resin 82, but in another embodiment, the gap 38 may be configured so that at least a portion of the gap 38 is prevented from being filled with heat-dissipating resin 82 and yet still sufficiently cools the center leg 23. Specifically, the air-opening surface 82a of the heat-dissipating resin 82 filled inside the case 8 can be determined in relation to the volume of the center leg 23, etc.

[0051] For example, the air-opening surface 82 may be set so that 70% or more, preferably 80% or more, and more preferably 90% or more, or 95% or more of the volume of the center leg portion 23 is located below the air-opening surface 82a of the heat-dissipating resin 82, and furthermore, is located lower along the Z axis than the lower surface of the base portion 21a. By configuring it in this way, an air layer is formed in the gap 38, which the heat-dissipating resin 82 does not enter.

[0052] Furthermore, the air-opening surface 82a of the heat-dissipating resin 82 is determined so that the winding portion 50 of the second wire 5 is sufficiently immersed in the heat-dissipating resin 82, and so that preferably 80% or more, more preferably 95% or more, or substantially 100% or more of the winding portion 40 of the first wire 4 is immersed in the heat-dissipating resin 82. With this configuration, heat generated in the winding portion 40 or 50 of the wire 4 or 5 is also cooled by the heat-dissipating resin 82.

[0053] In this embodiment, heat transferred from the winding portion 40 or 50 of the wire 4 or 5 or the core 2 to the heat dissipating resin 82 is transferred through the case 8 to a cooling member (such as a cooling block with a cooling passage) installed on the underside of the bottom plate 80 of the case 8, and is dissipated. The air-opening surface 82a is the surface where the liquid surface formed by pouring the heat dissipating resin 82 in a fluid state into the case 8 has solidified.

[0054] In this embodiment, the cores 21, 22 and the center leg portion 23 are not particularly limited as long as they are cores having a magnetic material, and are made of, for example, ferrite, a metallic magnetic material, or a resin containing magnetic powder.

[0055] 3, case 8 has a substantially rectangular bottom plate 80 and side plates 81 that extend upward along the Z axis from the four sides of bottom plate 80 to form a bottomed storage space inside, with an upper opening formed at the top along the Z axis. Case 8 is preferably made of a metal such as aluminum that has excellent thermal conductivity, but may also be made of resin.

[0056] Heat dissipating resin 82 is also called potting resin, and is made of silicone resin, urethane resin, epoxy resin, or the like that remains soft even after injection, and the potting resin preferably has a longitudinal elastic modulus of 0.1 to 100 MPa. In this embodiment, for example, heat generated in first winding portion 40, second winding portion 50, and core 2 can be efficiently dissipated from the bottom of case 8 to the outside via heat dissipating resin 82 and case 8, thereby improving the cooling efficiency of coil device 1.

[0057] The heat dissipating resin 82 may be filled in advance inside the case 8, and then the bobbin (with wire wound around it) 3 with the core 2 attached as shown in FIG. 2A may be housed inside the case 8, or the heat dissipating resin 82 may be poured into the case 8 after the bobbin (with wire wound around it) 3 with the core 2 attached is housed inside the case 8.

[0058] 3, core 2 has center leg 23 around which windings 40, 50 of wires 4, 5 are disposed, and bases 21a, 22a that are magnetically coupled in contact or non-contact with one end of center leg 23 along the Z axis and extend in a direction (e.g., the Y axis direction) substantially perpendicular to the axial center (Z axis) of windings 40, 50. Core 2 also has outer legs 21b, 22b that are integrally formed with at least one end of bases 21a, 22a via connecting portions 21c, 22c and protrude from connecting portions 21c, 22c substantially parallel to the Z axis.

[0059] In this embodiment, as shown in Fig. 4A, the connecting portion 21c1 of the first core 21 is defined as a portion that integrally connects the base portion 21a and the outer leg portion 21b, and the outer surface of the connecting portion 21c is configured as a chamfered surface 21c1, which is an arc-shaped outer surface with a curvature radius R. Note that in this embodiment, the chamfered surface 21c1 is configured as a curved surface, but it may not be limited to a curved surface and may be a single flat surface or a collection of multiple flat surfaces. The same applies to the chamfered inner surface 21c2 described later.

[0060] Furthermore, outer surface 21a1 and inner surface 21a2 of base portion 21a are preferably flat surfaces parallel to the plane containing the X-axis and Y-axis, but may have some irregularities or may be partially curved. Furthermore, outer surface 21b1 and inner surface 21b2 of outer leg portion 21b are preferably flat surfaces parallel to the plane containing the X-axis and Z-axis, but may have some irregularities or may be partially curved.

[0061] In this embodiment, a first outer boundary OB1 between the outer surface 21a1 of the base portion 21a and the removed surface 21c1 is located at a first predetermined distance L1 perpendicular to the inner surface 21b2 of the outer leg portion 21b. A second outer boundary OB2 between the outer surface 21b1 of the middle leg portion 21b and the removed surface 21c1 is located at a second predetermined distance L2 perpendicular to the inner surface 21a2 of the base portion 21a.

[0062] 2A, the second core 22 also has a configuration similar to that of the first core 21, and the connecting portion 22c1 of the second core 22 is similar to the connecting portion 21c1 of the first core 21. That is, as shown in FIG. 4A, the connecting portion 22c1 is defined as a portion that integrally connects the base portion 22a and the outer leg portion 22b, and the outer surface of the connecting portion 22c is configured as a removed surface 22c1, which is an arc-shaped outer surface with a curvature radius R. Note that, although the removed surface 22c1 is configured as a curved surface in this embodiment, it may be a single flat surface or a collection of multiple flat surfaces instead of a curved surface.

[0063] Furthermore, outer surface 22a1 and inner surface 22a2 of base portion 22a are preferably flat surfaces parallel to the plane including the X-axis and Y-axis, but may have some irregularities or may be partially curved. Furthermore, outer surface 22b1 and inner surface 22b2 of outer leg portion 22b are preferably flat surfaces parallel to the plane including the X-axis and Z-axis, but may have some irregularities or may be partially curved.

[0064] In this embodiment, a first outer boundary OB1 between the outer surface 22a1 of the base portion 22a and the removed surface 22c1 is located at a first predetermined distance L1 perpendicular to the inner surface 22b2 of the outer leg portion 22b. A second outer boundary OB2 between the outer surface 22b1 of the middle leg portion 22b and the removed surface 22c1 is located at a second predetermined distance L2 perpendicular to the inner surface 22a2 of the base portion 22a.

[0065] Experiments conducted by the inventors have revealed that in conventional cores having right-angled corners (including chamfered portions with a radius of less than 0.5 mm), heat generated by magnetic flux concentrating at the inner corners is difficult to dissipate to the outside, resulting in insufficient heat dissipation. In the coil device 1 according to this embodiment, the outer surface 21c1 (22c1) of the connecting portion 21c (22c) between the base portion 21a (22a) and the outer leg portion 21b (22b) of the core 2 is not a nearly right-angled corner (including chamfered portions with a radius of 0.5 mm or less), but is a chamfered surface 21c1 (22c1) with a radius of preferably 1 mm or more, and more preferably 2 mm or more.

[0066] Therefore, the distance from the chamfered inner surface 21c2 (22c2) of the connecting portion 21c1 (22c1) to the unfaced surface 21c1 (22c1) is shorter than in the past, and heat generated by magnetic flux concentrating at the corners is more easily dissipated to the unfaced surface 21c1 (22c1) of the connecting portion 21c (22c), improving heat dissipation. As a result, thermal stress in the two cores can be reduced. Furthermore, the unfaced surface 21c1 (22c1) of the connecting portion 21c1 (22c1) also has the effect of suppressing stress concentration due to the shape of the connecting portion 21c1 (22c1). Furthermore, the flow of magnetic flux in the connecting portion 21c1 (22c1) is smoother.

[0067] In this embodiment, the inner surface of the connecting portion 21c1 (22c1) is also configured with a chamfered inner surface 21c2 (22c2). Preferably, a first inner boundary IB1 between the inner surface 21a2 (22a2) of the base portion 21a1 (22a1) and the chamfered inner surface 21c2 (22c2) is located at a third predetermined distance L3 perpendicular to the inner surface 21b2 (22b2) of the outer leg portion 21b (22b). Preferably, a second inner boundary IB2 between the inner surface 21b2 (22b2) of the center leg portion 21b (22b) and the chamfered inner surface 21c2 (22c2) is located at a fourth predetermined distance L4 perpendicular to the inner surface 21a2 (22a2) of the base portion 21a (22a).

[0068] With this configuration, the inner surface of the connecting portion (21c (22c)) between the base portion 21a (22a) and the outer leg portion (21b (22b)) of the core 2 is not a nearly right-angled corner but a chamfered inner surface 21c2 (22c2), which allows for a smoother flow of magnetic flux in that portion. In addition, the distance between the chamfered inner surface 21c2 (22c2) and the unfaced surface 21c1 (22c1) is approximately constant along the flow of magnetic flux, which allows for uniform heat dissipation from the chamfered inner surface 21c2 (22c2) to the unfaced surface 21c1 (22c1), further improving heat dissipation.

[0069] The third predetermined distance L3 is preferably approximately the same as the first predetermined distance L1, but may be different, and the fourth predetermined distance L4 is preferably approximately the same as the second predetermined distance L2, but may be different. Making these approximately the same makes it easier to keep the distance between the chamfered inner surface 21c2 (22c2) and the removed surface 21c1 (22c1) approximately constant along the flow of magnetic flux, and heat dissipation from the chamfered inner surface 21c2 (22c2) to the removed surface 21c1 (22c1) becomes more uniform, further improving heat dissipation.

[0070] The first predetermined distance L1 is preferably approximately the same as the second predetermined distance L2, but may be different. Furthermore, assuming that the first predetermined distance L1 is L1, the second predetermined distance L2, the thickness of the outer leg 21b (22b), and the thickness of the base 21a (22a), the direction of the first predetermined distance L1 is defined as a positive direction from the inner surface 21b2 (22b2) of the outer leg 21b (22b) toward the inside and a negative direction from the inner surface 21b2 (22b2) of the outer leg 21b (22b), and the direction of the second predetermined distance L2 is defined as a positive direction from the inner surface 21a2 (22a2) of the base 21a (22a) toward the inside and a negative direction from the inner surface 21a2 (22a2) of the base 21a (22a), the following relationship is preferably satisfied:

[0071] That is, it is preferable that L1 / T1 is in the range of -2 / 3 or more and 1 / 2 or less. It is also preferable that L2 / T2 is in the range of -2 / 3 or more and 1 / 2 or less. It is even more preferable that L1 / T1 is in the range of 0 or more and 1 / 2 or less, or 1 / 4 or more and 1 / 2 or less. It is also even more preferable that L2 / T2 is in the range of 0 or more and 1 / 2 or less, or 1 / 4 or more and 1 / 2 or less. When L1 / T1 or L2 / T2 is in such a range, heat dissipation can be further improved and stress can be further reduced. Note that if L1 / T1 or L2 / T2 is too large, the size of the coil device 1 tends to increase or the space for the wire winding portion 40 (50) arranged inside the base portion 21a (22a) and the outer leg portion 21b (22b) tends to be narrow.

[0072] The third predetermined distance L3 is preferably approximately the same as the fourth predetermined distance L4, but may be different. Furthermore, assuming that the third predetermined distance L3 is L3, the fourth predetermined distance L4, the thickness of the outer leg 21b (22b) is T1, and the thickness of the base 21a (22a), the direction of the third predetermined distance L3 is defined as a positive direction from the inner surface 21b2 (22b2) of the outer leg 21b (22b) toward the inside and a negative direction from the inner surface 21b2 (22b2) of the outer leg 21b (22b), and the direction of the fourth predetermined distance L is defined as a positive direction from the inner surface 21a2 (22a2) of the base 21a (22a) toward the inside and a negative direction from the inner surface 21a2 (22a2) of the base 21a (22a), respectively, the following relationship is preferably satisfied:

[0073] That is, it is preferable that L3 / T1 is in the range of -2 / 3 or more and 1 / 2 or less. It is also preferable that L4 / T2 is in the range of -2 / 3 or more and 1 / 2 or less. It is even more preferable that L3 / T1 is in the range of 0 or more and 1 / 2 or less, or 1 / 4 or more and 1 / 2 or less. It is even more preferable that L4 / T2 is in the range of 0 or more and 1 / 2 or less, or 1 / 4 or more and 1 / 2 or less. When L3 / T1 or L4 / T2 is in such a range, heat dissipation can be further improved and stress can be further reduced. Note that if L3 / T1 or L4 / T2 is too large, the size of the coil device 1 tends to increase or the space for the wire winding portion 40 (50) arranged inside the base portion 21a (22a) and the outer leg portion 21b (22b) tends to be narrow.

[0074] In this embodiment, boundaries OB1, OB2, IB1, and IB2 can be defined as boundaries that transition from the curved surface (which may be a single plane or a collection of planes) of connecting portion 21c (22c) to a plane including the X-axis and Y-axis, or a plane including the X-axis and Z-axis, that constitutes at least a part of the outer or inner surface of the base portion or outer leg portion.

[0075] 4A, it is preferable that at least a portion of the outer leg portion 21b (22b) is immersed in the heat dissipating resin 82, and it is preferable that the second outer boundary OB2 is located below the atmospheric opening surface 82a of the heat dissipating resin 82. In this case, at least a portion of the surface removal surface 21c1 (22c1) of the connecting portion 21c (22c) is directly immersed in the heat dissipating resin 82, further improving heat dissipation.

[0076] In the example shown in Figure 4A, the atmospheric open surface 82a is located above the inner surface 21a2 of the base portion 21a of the core 21, and the winding portion 40 (50) and the core 2 located below the lower part of the base portion 21a are covered with heat-dissipating resin 82, but this embodiment is not limited to this.

[0077] For example, the air-opening surface 82a may be substantially flush with the inner surface 21a2 of the base portion 21a or may be located lower along the Z-axis than the inner surface 21a. Preferably, the air-opening surface 82a is located above the upper end of the winding portion 40 (50) along the Z-axis, but it may also be flush with or lower than the upper end. The position of the air-opening surface 82a may be determined in relation to the position of the upper end of the center leg portion 23 shown in FIG. 2A. For example, the upper end of the center leg portion 23 may be located above the air-opening surface 82a of the heat-dissipating resin 82. In this case, an air layer may be formed in the gap between the center leg portion 23 and the base portion 21a. The upper end of the center leg portion 23 may be flush with the air-opening surface 82a of the heat-dissipating resin 82 or may be located lower than the air-opening surface 82a.

[0078] In this embodiment, the second outer boundary OB2 is preferably located between one end and the other end of the winding portion 40 (50) of the wire 4 (5) along the axis (substantially parallel to the Z-axis) of the wire 4 (5). In this case, the coil device 1 can be made low-profile and have improved heat dissipation.

[0079] In this embodiment, the first outer boundary OB1 is preferably located between the outermost and innermost positions of the winding portion 40 (50) of the wire 4 (5). In this case, the width of the coil device 1 along the Y axis can be reduced while improving heat dissipation.

[0080] The second inner boundary IB2 is preferably located between one end and the other end along the Z axis of the winding portion 40 (50) of the wire 4 (5). In this case, the height of the coil device 1 can be reduced and heat dissipation can be improved.

[0081] The first inner boundary IB1 is preferably located between the outermost and innermost positions of the winding portion 40 (50) of the wire 4 (5). In this case, the width size of the coil device 1 along the Y axis can be reduced while improving heat dissipation.

[0082] As shown in FIG. 2A, the connecting portion 92 of the heat sink 9 is preferably disposed on the outside of the removed surface 21c1 of the core 21, which is disposed on the upper side along the Z axis. As shown in FIG. 2A, the heat sink 9 is composed of a pair of divided heat sinks 9a that match the divided core 21α of the core 21, but it may also be a single heat sink. Each divided heat sink 9a has a top plate portion 90, a side plate portion 91, and a connecting portion 82. The heat sink 9 can be formed by bending a plate material such as a metal with excellent thermal conductivity.

[0083] 4A, the top plate 90 is in close contact with the outer surface 21a1 of the base portion 21a of the core 21 to absorb heat, the connecting portion 92 is arranged in contact with or without contact with the outer surface 21c1 of the connecting portion 21c of the core 21, the side plate 91 is arranged in contact with or without contact with the outer surface 21b1 of the outer leg portion 21b, and at least the lower end of the side plate 91 along the Z axis is immersed in the heat dissipation resin 82, thereby dissipating heat from the core 21 to the heat dissipation resin 82. With this configuration, the heat dissipation performance of the coil device 1 is further improved and stress can be further reduced.

[0084] 4B, to ensure that the connecting portion 92 of the heat sink 9 is in contact with the outer surface 21c1 of the connecting portion 21c of the core 21 and that the side plate portion 91 is in contact with the outer surface 21b1 of the outer leg 21b, for example, each divided heat sink 9a may be divided into two along the Y axis to form a pair of sub-divided heat sinks 9a1, as shown in FIG. 2B. Each of the sub-divided heat sinks 9a1 has a single connecting portion 92 and a single side plate portion 91, which makes it easier to ensure that the connecting portion 92 of the heat sink 9 is in contact with the outer surface 21c1 of the connecting portion 21c of the core 21 and that the side plate portion 91 is in contact with the outer surface 21b1 of the outer leg 21b.

[0085] The present invention is not limited to the above-described embodiment, and various modifications can be made within the scope of the present invention.

[0086] For example, in the above-described embodiment, the tubular portion 30 of the bobbin 3 is arranged between the center leg portion 23 and the winding portions 40, 50 of the wires 4, 5, but the winding portions (e.g., air-core coils) 40, 50 of the wires 4, 5 may be arranged around the center leg portion 23 without placing the bobbin 3.

[0087] In the above-described embodiment, the coil device 1 has the lead attachment portion 7 that holds the lead portions 41a, 41b, 51a, and 51b of the wires 4 and 5 formed integrally with the bobbin 3, but these may be separate members. In the above-described embodiment, the terminals 6 are not attached to the lead attachment portion 7, but they may be attached to a terminal block, and the terminal block may be attached to the lead attachment portion 7. In that case, the terminal block may also serve as the lead attachment portion 7.

[0088] The pair of terminal blocks may be located on opposite sides of each other along the X-axis of the coil device 1, or one of the pair of terminal blocks may be located on one side of the X-axis of the coil device 1 and the other terminal block may be located on one side of the Y-axis of the coil device 1. The terminal block may be formed integrally with the bobbin 3, or may be a separate member, or may be attached to the bobbin or the case 8. [Explanation of symbols]

[0089] 1...Coil device 2...Core 21...1st core 21α…First divided core 21a...First base section 21a1…External surface 21a2...Inner 21b...Outer leg 21b1…External surface 21b2…Inner self 21b3...tip 21c...Connection part 21c1...Removed surface 21c2... Chamfered inner surface 22...Second core 22α…Second divided core 22a...Second base part 22a1…External surface 22a2…Inner surface 22b...Outer leg 22b1…External surface 22b2…Inner self 22b3...tip 22c...Connection part 22c1...Removed surface 22c2...chamfered inner surface 23...middle leg 23a…lower end 23b…Top end 24...Step-shaped convex part 25...Outer leg 3...Bobbin 30...Cylinder part 31...Main bulkhead flange 31a...notch 31b...Guide protrusion 32...Sub-bulkhead flange 32a...notch 32b...Guide protrusion 32c…Top surface 32d…bottom surface 34, 35...Core guide wall 36...Inward convex piece 37,38...Gap 4...First wire 40...First wire winding portion 41a, 41b...Lead section 5...Second wire 50...Second wire winding portion 51a, 51b...Lead section 6...Terminal 61...Connection section 62...External connection part 7...Lead attachment part 70...Lead retaining part 8…Case 80...Bottom plate 81...Side panel 82…Heat dissipating resin 82a...Open to the atmosphere 9…Heat sink 9a…Divided heat sink 9a1…Sub-divided heat sink 90...Top plate 91...Side plate part 92…Connecting Section

Claims

1. a core including a magnetic material; a wire having a winding portion wound in a coil shape, The core is a middle leg portion around which the windings of the wire are disposed; and a base portion that is magnetically coupled to one end of the center leg portion in contact or non-contact state and extends in a direction substantially perpendicular to the axis of the winding portion; an outer leg portion that is integrally formed with at least one end of the base portion via a connecting portion and that protrudes from the connecting portion substantially parallel to the axis of the winding portion; The outer surface of the connecting portion is configured as a removable surface, a first outer boundary between the outer surface of the base portion and the removed surface is located at a first predetermined distance perpendicular to the inner surface of the outer leg portion; A coil device in which a second outer boundary between the outer surface of the middle leg portion and the removed surface is positioned at a second predetermined distance perpendicular to the inner surface of the base portion.

2. The inner surface of the connecting portion is configured as a chamfered inner surface, a first inner boundary between the inner surface of the base portion and the chamfered inner surface is located at a third predetermined distance perpendicular to the inner surface of the outer leg portion; The coil device according to claim 1 , wherein a second inner boundary between the inner surface of the middle leg portion and the chamfered inner surface is located at a fourth predetermined distance perpendicular to the inner surface of the base portion.

3. The coil device according to claim 2 , wherein the third predetermined distance is substantially the same as or different from the first predetermined distance, and the fourth predetermined distance is substantially the same as or different from the second predetermined distance.

4. the first predetermined distance is substantially the same as or different from the second predetermined distance; The first predetermined distance is L1, the second predetermined distance is L2, the thickness of the outer leg portion is T1, and the thickness of the base portion is T2, The direction of the first predetermined distance is defined as a positive direction from the inner surface of the outer leg portion toward the inside, and a negative direction from the inner surface of the outer leg portion toward the outside, When the direction of the second predetermined distance is defined as a positive direction from the inner surface of the base portion toward the inside and a negative direction from the inner surface of the base portion toward the outside, L1 / T1 is in the range of -2 / 3 or more and 1 / 2 or less, 4. The coil device according to claim 1, wherein L2 / T2 is in the range of -2 / 3 to 1 / 2.

5. L1 / T1 is in the range of 0 to 1 / 2, 5. The coil device according to claim 4, wherein L2 / T2 is in the range of 0 to 1 / 2.

6. the third predetermined distance is substantially the same as or different from the fourth predetermined distance; The third predetermined distance is L3, the fourth predetermined distance is L4, the thickness of the outer leg portion is T1, and the thickness of the base portion is T2, The direction of the third predetermined distance is defined as a positive direction from the inner surface of the outer leg portion toward the inside, and a negative direction from the inner surface of the outer leg portion toward the outside, When the direction of the fourth predetermined distance is defined as a positive direction from the inner surface of the base portion toward the inside and a negative direction from the inner surface of the base portion toward the outside, L3 / T1 is in the range of -2 / 3 or more and 1 / 2 or less, 4. The coil device according to claim 2, wherein L4 / T2 is in the range of -2 / 3 to 1 / 2.

7. L3 / T1 is in the range of 0 to 1 / 2, 7. The coil device according to claim 6, wherein L4 / T2 is in the range of 0 to 1 / 2.

8. At least a portion of the outer leg is immersed in a heat-dissipating resin, 4. The coil device according to claim 1, wherein the second outer boundary is located below a surface of the heat dissipating resin that is open to the atmosphere.

9. 4. The coil device according to claim 1, wherein the second outer boundary is located between one end and the other end of the wound portion of the wire along the axis of the wound portion.

10. 4. The coil device according to claim 1, wherein the first outer boundary is located between the outermost and innermost positions of the wound portion of the wire.

11. The coil device according to claim 2 or 3, wherein the second inner boundary is located between one end and the other end of the wire winding along the axis of the wire winding.

12. The coil device according to claim 2 or 3, wherein the first inner boundary is located between an outermost position and an innermost position of the winding portion of the wire.

13. The coil device according to any one of claims 1 to 3, wherein the surface to be removed is a curved surface or a set of one or more flat surfaces.

14. The coil device according to claim 2 or 3, wherein the chamfered inner surface is a curved surface or a set of one or more flat surfaces.

15. 4. The coil device according to claim 1, wherein a heat sink is disposed on the outside of the removed surface.

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