Choke coil

Abstract

A choke coil 10 comprises a core, a coil member 30, and a case 40. The case 40 has a housing part 46 defined by an upper surface 42 and a lateral surface 44. The coil member 30 is constituted by a lead wire and has a coil main part 32, an extension part 34, and a terminal part 36. The coil main part 32 is wound around the core. The core and the coil main part 32 are housed in the housing part 46. The extension part 34 extends from the coil main part 32 and has a cross-sectional shape substantially the same as that of the coil main part 32. The extension part 34 has at least one bent part 341 and is at least partially drawn out to the outside of the housing part 46. The terminal part 36 extends from the extension part 34 and has a thickness smaller than the size of the diameter of the extension part 34. The terminal part 36 has an L-shaped form. A boundary 35 between the terminal part 36 and the extension part 34 is located on the lateral surface 44 of the case 40.

Description

choke coil

[0001] The present invention relates to a choke coil, and more particularly to a surface mount type choke coil.

[0002] Patent Document 1 discloses an example of a surface-mounted choke coil.

[0003] The choke coil of Patent Document 1 has a closed magnetic circuit core composed of a plate-shaped core and a concave core, and two concentrically wound coils. The coil is attached to the central magnetic leg of the concave core and housed within the closed magnetic circuit core. The lead end of the coil is formed into a plate shape by rolling. A claw portion is formed at the tip of the lead end. The lead end is drawn out of the closed magnetic circuit core and is arranged along a lead-out groove formed on the outer side surface of the concave core. The claw portion of the lead end is received in a recess formed on the outer bottom surface of the concave core.

[0004] Japanese Patent Application Laid-Open No. 2000-021655

[0005] In the choke coil of Patent Document 1, the lead ends (plate-shaped portions) extend from the inside of the closed magnetic core. In other words, the closed magnetic core partially accommodates the lead ends. Therefore, the closed magnetic core of the choke coil of Patent Document 1 has a size larger than the size required to accommodate the coil.

[0006] An object of the present invention is to provide a choke coil that can be made smaller.

[0007] One aspect of the present invention provides a first choke coil comprising a core, a coil member, and a case, wherein the case has a top surface and a side surface extending downward from the top surface, and has a housing portion defined by the top surface and the side surface, the coil member is made of a lead wire and has a coil main portion, an extension portion, and a terminal portion, the coil main portion is wound around the core, the core and the coil main portion are housed in the housing portion, the extension portion extends from the coil main portion and has substantially the same cross-sectional shape as the coil main portion, the extension portion has at least one bent portion and is at least partially drawn out to the outside of the housing portion, the terminal portion extends from the extension portion and has a thickness size smaller than the diameter size of the extension portion, the terminal portion has an L-shape, and the boundary between the terminal portion and the extension portion is located on the side surface of the case.

[0008] In a choke coil according to one aspect of the present invention, the coil member is made of a lead wire and has a coil main portion, an extension portion, and a terminal portion. The coil main portion is wound around a core and is housed together with the core in a housing portion of the case. The extension portion extends from the coil main portion and is at least partially drawn out to the outside of the housing portion. The terminal portion extends from the extension portion. The boundary between the terminal portion and the extension portion is located on a side surface of the case. Because the terminal portion is located outside the case, the choke coil according to one aspect of the present invention can be made smaller than conventional choke coils in which the terminal portion extends from inside the case to outside.

[0009] The objects of the present invention will be appreciated and its construction will be more completely understood by studying the following description of the best mode for carrying out the invention in conjunction with the accompanying drawings.

[0010] 1 is a bottom perspective view of a choke coil according to a first embodiment of the present invention. 2 is a top perspective view of the choke coil of FIG. 1. 3 is a bottom view of the choke coil of FIG. 1. 4 is a plan view of the choke coil of FIG. 1. 5 is a bottom perspective view of a core case that houses a core used in the choke coil of FIG. 1, and a lead wire partially wound around the core case. 6 is a bottom perspective view of an assembly in which the core case and lead wire of FIG. 5 are combined with a case. 7 is a plan view of the assembly of FIG. 8. 9 is a top perspective view of the assembly of FIG. 9. The lead wire is bent so as to follow the upper groove of the case. 10 is a top perspective view of the assembly of FIG. 10. The end of the lead wire is cut and pressed. 11 is a top perspective view of a choke coil according to a second embodiment of the present invention. 12 is a bottom perspective view of the choke coil of FIG. 11.

[0011] While the present invention may be embodied in various forms and variations, the following detailed description of specific embodiments thereof, as illustrated in the drawings, is by way of example only and is not intended to limit the invention to the specific forms disclosed herein, but to embrace all modifications, equivalents, and alternatives within the scope of the appended claims.

[0012] 1 to 4, a choke coil 10 according to a first embodiment of the present invention includes a core (not shown) housed in a core case 20, two coil members 30, and a case 40. In this embodiment, the choke coil 10 is a common mode choke coil. However, the present invention is not limited to this. The choke coil of the present invention may also be a normal mode choke coil including one coil member 30.

[0013] 3 and 5, the core (not shown) housed in the core case 20 is made of a ferromagnetic material and has a closed annular shape. In this embodiment, the core is a toroidal core having a circular annular shape. However, the present invention is not limited to this. The core may also have a racing track shape, an oval shape, or an elliptical shape. However, a toroidal core is preferred to obtain the desired magnetic characteristics. Furthermore, if the choke coil 10 is a normal mode choke coil, the core may have a gap.

[0014] As shown in FIGS. 3 and 5 , the core case 20 is made of insulating resin and includes an annular portion 22, a protrusion 24, and a frame portion 26. The annular portion 22 is hollow and accommodates a core (not shown). The protrusion 24 protrudes radially outward from the annular portion 22. The protrusion 24 restricts movement of the coil member 30 wound around the core case 20. The frame portion 26 surrounds the annular portion 22, dividing it into two. As can be seen from FIG. 3 , the frame portion 26 has an asymmetrical shape, and the case 40 has a recess corresponding to the shape of the frame portion 26. Therefore, the core case 20 cannot be inserted unless it is properly oriented relative to the case 40. In other words, the frame portion 26 functions as a guide when the core case 20 is inserted into the case 40. As a result, the lead wire 300 can be easily and correctly inserted into the hole 421 (see FIG. 4 ). In this way, the frame portion 26 facilitates the assembly of the choke coil 10 and prevents assembly errors. Furthermore, the frame portion 26 of the core case 20 and the recess in the case 40 restrict movement of the core case 20 relative to the case 40 after the core case 20 is housed in the case 40. Note that in order to prevent movement of the core case 20 relative to the case 40, the core case 20 may be fixed to the case 40 using an adhesive or the like.

[0015] As shown in FIGS. 1 to 4 , each of the coil members 30 has a coil main portion 32, two extension portions 34, and two terminal portions 36. In each of the coil members 30, the coil main portion 32 is located in the center of the coil member 30 (between the two extension portions 34) and is wound around a core (not shown) via the core case 20. The extension portions 34 extend from both ends of the coil main portion 32. The terminal portions 36 extend from the extension portions 34. The terminal portions 36 are located at both ends of the coil member 30. In the following description, unless otherwise specified, a description of one of the coil members 30 also applies to the other coil member 30. Furthermore, unless otherwise specified, a description of one of the extension portions 34 also applies to the other extension portion 34, and a description of one of the terminal portions 36 also applies to the other terminal portion 36.

[0016] As can be seen from FIGS. 1 and 2, the case 40 is a single component made of thermosetting resin. The case 40 has a top surface 42 and side surfaces 44. The side surfaces 44 extend downward from the top surface 42. In this embodiment, the side surfaces 44 are composed of four side surface portions 441, 443, 445, and 447. However, the present invention is not limited to this. The side surfaces 44 may have other shapes, such as a polygonal tube or a cylindrical shape. In this embodiment, the up-down direction is the Z direction. The +Z direction is upward, and the -Z direction is downward.

[0017] As can be seen from Figures 1 and 3, the top surface 42 and the side surface 44 define a housing portion 46. In other words, the case 40 has a housing portion 46 defined by the top surface 42 and the side surface 44. In this embodiment, the case 40 opens downward. In other words, in this embodiment, the case 40 does not have a bottom surface. However, the present invention is not limited to this. The case 40 may have a bottom surface. However, as long as insulation between the coil main portion 32 and the substrate when the choke coil 10 is mounted on the substrate, it is preferable that the case 40 does not have a bottom surface, as this can reduce manufacturing costs and simplify the manufacturing process.

[0018] As shown in Figures 1 and 3, the core case 20 that houses the core (not shown) and the coil main portion 32 are housed in the housing portion 46 of the case 40. As shown in Figures 1, 2, and 4, each of the extension portions 34 is at least partially drawn out to the outside of the housing portion 46. The extension portions 34 have at least one bent portion 341 and extend along the top surface 42 and the side surface 44 of the case 40. In this embodiment, each of the extension portions 34 has two or three bent portions 341. The terminal portion 36 extends from the side surface 44 of the case 40 to the underside of the case 40.

[0019] 4 and 7, at least two holes 421 are provided in the top surface 42 of the case 40. In this embodiment, four holes 421 are provided in the top surface 42 of the case 40. The holes 421 are divided into two sets. These sets of holes 421 correspond to the coil members 30, respectively. The holes 421 in each set correspond to the extension portions 34 of the corresponding coil members 30. The extension portions 34 of the coil members 30 are drawn out from the accommodation portions 46 of the case 40 onto the top surface 42 of the case 40 through the corresponding holes 421.

[0020] As shown in FIGS. 4 and 7 , at least two upper grooves (groove portions) 423 are further formed in the top surface 42 of the case 40. In this embodiment, four upper grooves 423 are formed in the top surface 42 of the case 40. In this embodiment, the upper grooves 423 are grooves that partially do not have bottoms. The upper grooves 423 correspond to the holes 421, respectively. The upper grooves 423 also correspond to the extensions 34, respectively. The upper grooves 423 extend from the corresponding holes 421 to the side surface 44 of the case 40 and have end portions 425 at positions away from the holes 421. In this embodiment, each extension 34 is at least partially received in the corresponding upper groove 423 and extends along the upper groove 423.

[0021] As can be seen from Figures 1, 2, and 3, the side surface portions 441, 443, 445, and 447 that make up the side surface 44 face in different directions. The side surface portions 441 and 443 face forward and backward, respectively, in the front-to-rear direction, which is perpendicular to the up-down direction. The side surface portions 445 and 447 face outward in the lateral direction, which is perpendicular to both the up-down direction and the front-to-rear direction. In this embodiment, the front-to-rear direction is the X direction. The -X direction is the front, and the +X direction is the rear. The lateral direction is the Y direction.

[0022] 1 to 4 and 6, side grooves 451 are formed in the side surfaces 44 of the case 40, each of which is continuous with the upper groove (groove portion) 423. In the present embodiment, two side grooves 451 are formed in each of the side surface portions 441 and 443. The side grooves 451 extend in the vertical direction from the end portion 425 of the upper groove 423 to the lower end of the case 40. The extension portions 34 of the coil member 30 are partially received in the corresponding side grooves 451 and extend along the side grooves 451.

[0023] As shown in FIG. 1 , each of the terminal portions 36 is bent and L-shaped. In other words, the terminal portion 36 has a first portion 361 extending from the extension portion 34 and a second portion 363 extending from the first portion 361. The first portion 361 extends vertically and is received in the side groove 451. The second portion 363 is located below the case 40 and extends longitudinally. The second portion 363 also protrudes downward from the bottom end of the case 40. Because the terminal portion 36 protrudes downward from the bottom end of the case 40, when the choke coil 10 is mounted on a substrate (not shown), only the terminal portion 36 contacts the substrate. The case 40, the core case 20, and the coil main portion 32 do not contact the substrate. In other words, the choke coil 10 is supported only by the terminal portion 36. As described above, in this embodiment, the choke coil 10 is supported only by the terminal portion 36, but the mounting strength is not reduced, and the terminal portion 36 can be reliably connected to the board. However, the present invention is not limited to this. The lower end of the case 40 may be in contact with the board. However, a configuration in which only the terminal portion 36 is in contact with the board is preferable, because this more reliably ensures insulation between the coil main portion 32 and the board, even if the case 40 does not have a bottom surface.

[0024] As shown in FIGS. 1 and 2 , the boundary 35 between the extension 34 and the terminal 36 is located on the side surface 44 of the case 40 or within the side groove 451. Near the boundary 35, the extension 34 and the terminal 36 extend in the same direction (up and down). In other words, the coil member 30 is not bent at the boundary 35. The cross-sectional shapes of the extension 34 and the terminal 36 are different from each other. If the coil member 30 is bent at the boundary 35 where the cross-sectional shapes differ, a decrease in strength is likely to occur in that portion. In this embodiment, the coil member 30 extends straight near the boundary 35, so such a decrease in strength does not occur. Furthermore, because the entire terminal 36 or the boundary 35 is located outside the case 40, a smaller size can be achieved compared to conventional choke coils in which the terminal extends from the inside to the outside of the case.

[0025] As can be seen from Fig. 5, each of the coil members 30 is made up of a lead wire 300. In other words, the lead wire 300 is used to manufacture the choke coil 10. In this embodiment, the lead wire 300 is an integrated member made up of a solid conductor (not shown) and an insulating coating (not shown) surrounding the conductor.

[0026] 5, during manufacturing, a portion of the lead wire 300 is wound around the core case 20. The portion of the lead wire 300 wound around the core case 20 becomes the main coil portion 32. The extension portion 34 is a portion extending from the main coil portion 32. The terminal portion 36 is formed later by pressing and bending a portion of the lead wire 300.

[0027] As can be seen from Figure 5, there is no clear boundary between the coil main portion 32 and the portion that becomes the extension portion 34. Therefore, the extension portion 34 has substantially the same cross-sectional shape as the coil main portion 32. Here, "the extension portion 34 and the coil main portion 32 have substantially the same cross-sectional shape" means that their cross-sectional shapes are the same except for the portion that has been deformed by bending. In this embodiment, the cross-sectional shape is circular.

[0028] 6 and 7, during the manufacture of the choke coil 10, the core case 20 around which the lead wire 300 is wound is inserted into the housing portion 46 from below the case 40. As a result, the core case 20 that houses the core (not shown) and the coil main portion 32 are housed in the housing portion 46. At this time, both ends of the lead wire 300 are pulled out of the case 40 through the corresponding holes 421.

[0029] The diameter of the conductor (not shown) of the lead wire 300 used in the coil member 30 may be determined depending on the application of the choke coil 10. In this embodiment, the diameter of the conductor is 0.8 mm or more to accommodate a relatively large predetermined current. Also, in this embodiment, the diameter of the conductor is 1.8 mm or less in consideration of ease of processing.

[0030] Furthermore, the inner diameter of the hole 421 in the case 40 is slightly larger than the outer diameter of the coil member 30. A smaller inner diameter of the hole 421 is preferable. This is to prevent a decrease in the strength of the case 40 and to prevent heat from entering the case 40 during the reflow process in which the choke coil 10 is mounted on a substrate (not shown).

[0031] As shown in FIG. 8 , the lead wire 300 is bent to fit into the corresponding upper groove (groove portion) 423 and is partially received in the upper groove 423. The end of the lead wire 300 is then cut to an appropriate length. If necessary, solder (not shown) is formed on the surface of the end of the cut lead wire 300. When solder is formed, the insulating coating is removed from the portion of the lead wire 300 that will become the terminal portion 36 (see FIG. 9 ). If solder is not formed, it is necessary to remove the insulating coating from the portion of the lead wire 300 that will become the terminal portion 36.

[0032] As shown in Figure 9, the end of the lead wire 300 (see Figure 8) is pressed to form a plate-like portion 38 that will become the terminal portion 36. At this time, a boundary 35 is formed between the extension portion 34 of the coil member 30 and the terminal portion 36. Since only a limited range of the lead wire 300, i.e., the portion that will become the terminal portion 36, is pressed, a small press can be used. Furthermore, the ends of multiple lead wires 300 can be pressed simultaneously.

[0033] As can be seen from FIG. 9 , FIG. 1 , and FIG. 2 , the plate-shaped portion 38 is then bent to form the terminal portion 36. In this manner, the terminal portion 36 is formed by pressing the conductor of the lead wire 300 (see FIG. 8 ) and then bending it. In other words, the terminal portion 36 is not a separate component connected to the lead wire 300 by welding or the like. In this embodiment, the terminal portion 36 is at least partially covered with solder. Note that the solder may be formed after the formation of the terminal portion 36. However, if solder is formed after pressing, problems such as uneven soldering are likely to occur, so it is preferable to form the solder before pressing, as described above.

[0034] As can be seen from FIG. 9 , the thickness of the plate-shaped portion 38 that becomes the terminal portion 36 is smaller than the diameter of the extension portion 34. Specifically, the thickness of the plate-shaped portion 38 is between ¼ and ¾ of the diameter of the extension portion 34. The thickness of the plate-shaped portion 38 may be, for example, between 0.2 mm and 0.6 mm. If the thickness of the plate-shaped portion 38 is too small, cracks are likely to occur in the solder during bending. If the thickness of the plate-shaped portion 38 is too large, bending becomes difficult. In this embodiment, the thickness of the terminal portion 36 is equal to the thickness of the plate-shaped portion 38. That is, in this embodiment, the size of the terminal portion 36 is between ¼ and ¾ of the diameter of the extension portion 34. In this embodiment, the thickness of the terminal portion 36 may be between 0.2 mm and 0.6 mm.

[0035] 9 and 2, the extensions 34 are further bent to fit along the corresponding side grooves 451. As a result, the first portions 361 of the terminals 36 are received in the side grooves 451. As a result, the distance between the two terminals 36 of each of the coil members 30 is determined. The distance between the terminals 36 depends on the size of the case 40, and therefore there is little variation between products. As such, according to this embodiment, the distance (pitch) between the terminals 36 of each of the coil members 30 can be accurately determined by the simple process of bending the extensions 34.

[0036] As can be seen from FIG. 7 , the distance D1 between the ends 425 of the two upper grooves 423 extending from the two holes 421 in each set is longer than the distance D2 between the two holes 421 in each set. Because the side grooves 451 extend in the up-down direction, the distance between the side grooves 451 in the front-to-rear direction depends on the distance D1 between the ends 425 of the upper grooves 423. As a result, as can be seen from FIGS. 3 and 4 , the distance between the terminal portions 36 of the coil member 30 in the front-to-rear direction depends on the distance D1 between the ends 425 of the upper grooves 423 and is longer than the distance D2 between the holes 421. As such, according to this embodiment, the distance between the terminal portions 36 can be made longer than the distance between the positions (holes 421) where the extension portions 34 are drawn to the outside of the case 40. This is advantageous for ensuring insulation between the pads to which the terminal portions 36 are connected when the choke coil 10 is mounted on a substrate. Moreover, because the distance between the terminal portions 36 depends on the distance D1 between the ends 425, variation is less likely to occur. Therefore, this configuration is advantageous for reducing the size of the choke coil 10.

[0037] As can be seen from Figure 2, in this embodiment, the extension 34 is routed from the top surface 42 to the side surface 44 of the case 40. In other words, in this embodiment, the coil member 30 is positioned so that the portion of the coil member 30 exposed to the outside of the case 40 is long. As a result, heat generated in the coil member 30 is efficiently dissipated to the outside of the case 40. Therefore, the configuration of the choke coil 10 of this embodiment has excellent heat dissipation efficiency and is suitable for large current applications.

[0038] (Second embodiment) Referring to Figures 10 and 11, a choke coil 10A according to a second embodiment of the present invention differs from the choke coil 10 according to the first embodiment in that it has a case 40A instead of the case 40.

[0039] 10 and 11 , the case 40A has a main body 400 and an upper lid 410. The main body 400 has a bottom surface 402 and a side surface 404 extending upward from the bottom surface 402. The main body 400 is open upward and has an upper opening (not shown). The upper lid 410 is combined with the main body 400 to close the upper opening of the main body 400. The upper lid 410 and the side surface 404 of the main body 400 define a core case (not shown) that houses a core (not shown) and an accommodation portion (not shown) that houses a main coil portion (not shown) of the coil member 30.

[0040] 10 and 11 , in this embodiment, the extensions 34 of the coil member 30 are each pulled out from inside the case 40A at the upper end of the side surface 404 of the case 40A and extend downward. As such, in the present invention, the extensions 34 may be pulled out from the side surface 404 of the case 40A to the outside of the case 40A and extend along the side surface 404 of the case 40A. However, pulling the coil member 30 out from the top surface 42 of the case 40, as in the choke coil 10 according to the first embodiment, results in a longer portion exposed outside the case 40 and provides superior heat dissipation.

[0041] 10 and 11, in this embodiment as well, the boundary 35 between the extension 34 and the terminal 36 is on the side surface 404 of the case 40A. Furthermore, near the boundary 35, the extension 34 and the terminal 36 extend in the same direction. In other words, the lead wire is not bent at the boundary 35 between the crushed and uncrushed portions of the lead wire. Therefore, a predetermined strength is maintained at the boundary 35 of the coil member 30. Furthermore, because the entire terminal 36 or the boundary 35 is outside the case 40A, the coil can be made smaller than conventional choke coils in which the terminal extends from the inside to the outside of the case.

[0042] The present invention has been described above using several embodiments, but the present invention is not limited to the above-described embodiments, and various modifications and changes are possible within the scope of the gist of the present invention.

[0043] For example, in the above embodiment, the coil member 30 (lead wire 300) is wound around the core case 20 that houses the core (not shown), but the coil member 30 (lead wire 300) may also be wound around a core (painted core) whose surface is painted with insulating paint.

[0044] Furthermore, in the above embodiment, the case 40 is made of a thermosetting resin, but the case 40 may be made of other insulating materials such as ceramic.

[0045] The present invention is based on Japanese Patent Application No. 2023-171545 filed with the Japan Patent Office on October 2, 2023, the contents of which are incorporated herein by reference.

[0046] Although the best mode for carrying out the present invention has been described, it will be apparent to those skilled in the art that modifications can be made to the present invention without departing from the spirit of the present invention, and such modifications are within the scope of the present invention.

[0047] REFERENCE SIGNS LIST 10 choke coil 20 core case 22 annular portion 24 protrusion 26 frame portion 30 coil member 300 lead wire 32 coil main portion 34 extension portion 341 bent portion 35 boundary 36 terminal portion 361 first portion 363 second portion 38 plate-shaped portion 40, 40A case 400 main body 402 bottom surface 404 side surface 410 upper cover 42 upper surface 421 hole 423 upper groove (groove portion) 425 end portion 44 side surface 441, 443, 445, 447 side surface portion 451 side groove 46 accommodation portion

Claims

1. A choke coil comprising a core, a coil member, and a case, wherein the case has a top surface and a side surface extending downward from the top surface, and has a housing portion defined by the top surface and the side surface, the coil member is made of a lead wire and has a coil main portion, an extension portion, and a terminal portion, the coil main portion is wound around the core, the core and the coil main portion are housed in the housing portion, the extension portion extends from the coil main portion and has substantially the same cross-sectional shape as the coil main portion, the extension portion has at least one bent portion and is at least partially drawn out to the outside of the housing portion, the terminal portion extends from the extension portion and has a thickness size smaller than a diameter size of the extension portion, the terminal portion is L-shaped, and the boundary between the terminal portion and the extension portion is located on the side surface of the case.

2. A choke coil according to claim 1, wherein the core has a closed annular shape.

3. A choke coil as claimed in claim 1 or 2, wherein the terminal portion is at least partially covered with solder, and the thickness of the terminal portion is between 1 / 4 and 3 / 4 of the diameter of the extension portion.

4. A choke coil according to claim 3, wherein the thickness of the terminal portion is 0.2 mm or more and 0.6 mm or less.

5. A choke coil as claimed in any one of claims 1 to 4, wherein at least two holes are provided on the top surface of the case, and the extension is led out onto the top surface of the case through the holes.

6. A choke coil as claimed in claim 5, wherein at least two grooves each continuing with one of said holes are further formed on said top surface of said case, each of said grooves having an end portion remote from said hole, and the distance between said ends being longer than the distance between said holes.

7. A choke coil as claimed in any one of claims 1 to 6, wherein the case is made of a single component, and the terminal portion protrudes downward from the lower end of the case.

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