JP6631722B2 - Inductor - Google Patents

Description

  The present invention relates to inductors.

  2. Description of the Related Art Conventionally, inductors in which windings are sealed with a sealing material obtained by kneading a magnetic powder and a resin have been widely used. In the inductor disclosed in Japanese Patent Application Laid-Open No. 2006-119385, a coil is sandwiched between pressure-molded sealing members, and is molded by being further pressed.

  However, the above-described sealing material has a lower magnetic permeability than ferrite or a soft magnetic material, and in some cases, the number of turns of the coil must be increased in order to obtain a desired inductance. For this reason, there has been a problem that the DC resistance of the inductor tends to be high. In addition, when ferrite or a soft magnetic material is used instead of the sealing material, magnetic saturation is likely to occur, so that the current that can flow through the inductor tends to be small. Further, when driven at a high frequency, there is a problem that the loss due to the eddy current increases and the efficiency is reduced.

  In view of the above problems, an object of the present invention is to provide an inductor having a low DC resistance and a reduced eddy current value.

  The inductor of the present invention accommodates a core including a laminated portion in which soft magnetic layers and insulator layers are alternately laminated, a coil including a conductor wound around the core, and the core and the coil. The core is disposed so that a laminating direction of the laminating portion is orthogonal to a winding axis of the coil.

  Advantageous Effects of Invention According to the present invention, it is possible to provide an inductor having a low DC resistance and further suppressing the eddy current value.

FIG. 2 is a transparent perspective view of the inductor according to the first embodiment of the present invention. It is a perspective view of the coil used for the inductor of Example 1 of the present invention. FIG. 2 is a perspective view of a core used in the inductor according to the first embodiment of the present invention. FIG. 3 is an enlarged view of a top surface of a core used for the inductor according to the first embodiment of the present invention. FIG. 9 is an exploded perspective view of a core used for the inductor according to the second embodiment of the present invention. FIG. 9 is a perspective view of a core used for the inductor according to the second embodiment of the present invention. FIG. 6 is a transparent perspective view of an inductor according to a second embodiment of the present invention. FIG. 9 is a perspective view of a core used for an inductor according to a third embodiment of the present invention. FIG. 10 is a transparent perspective view of an inductor according to a third embodiment of the present invention. FIG. 4 is a transparent perspective view of the core, in which a magnetic flux passing through the core of the inductor is visualized. It is the transmission top view of the core which visualized the magnetic flux which passes through the core of an inductor. FIG. 4 is a transparent perspective view of the core, in which a magnetic flux passing through the core of the inductor is visualized. It is the transmission top view of the core which visualized the magnetic flux which passes through the core of an inductor.

  The inductor includes a core including a laminated portion in which soft magnetic layers and insulator layers are alternately laminated, a coil including a conductor wound around the core, and a body housing the core and the coil. The core is disposed such that the laminating direction of the laminating portion is orthogonal to the winding axis of the coil. Thereby, even if the desired inductance is achieved, the DC resistance is low, and the current value of the eddy current in the core is suppressed.

  The element body may be a pressure-formed body of a sealing material containing magnetic powder and resin, and may have a lower magnetic permeability than the core. Thereby, the DC resistance is lower, and the current value of the eddy current in the core is further suppressed.

  The core includes a plurality of laminated portions and a plate-shaped gap portion having a lower magnetic permeability than the soft magnetic material layer. The gap portion is sandwiched between two of the plurality of laminated portions, and an outer periphery of the laminated portion. It may be arranged to extend to the part. This effectively suppresses magnetic saturation. Further, there may be a plurality of gap portions, each of which may be interposed between the laminated portions. Thereby, magnetic saturation is suppressed more effectively. Further, the gap portion may be arranged so that the thickness direction of the gap portion and the stacking direction of the stacked portion are orthogonal to each other. Thereby, magnetic saturation is more effectively suppressed.

  The core may further include a ferrite portion disposed at each of both ends in the stacking direction of the stacked portion. Thereby, the current value of the eddy current can be further suppressed. The core has a gap portion having a lower magnetic permeability than the soft magnetic layer of the core in addition to the ferrite portion. The gap portion is sandwiched between the two laminated portions and extends to the outer peripheral portion of the laminated portion. May be arranged orthogonal to the lamination direction of the lamination part. Thereby, the current values of the magnetic saturation and the eddy current can be more effectively suppressed.

  In the laminated portion, the ratio of the thickness of the insulator layer to the thickness of the soft magnetic layer may be 0.2 or less. Thereby, the magnetic saturation characteristics are further improved. Further, the insulator layer may include at least one selected from the group consisting of an epoxy resin, a polyimide resin, and a polyimide amide resin. Thus, the insulator layer can be formed thin, so that the volume ratio of the soft magnetic layer to the whole core volume increases, and magnetic saturation can be suppressed more effectively. In addition, since the magnetic permeability of the core is also improved, the number of turns of the coil required for obtaining a predetermined inductance is reduced, and the DC resistance can be further reduced.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. However, the embodiments described below exemplify an inductor for embodying the technical idea of the present invention, and the present invention does not limit the inductor to the following. The members described in the claims are by no means limited to the members of the examples. In particular, the dimensions, materials, shapes, relative arrangements, and the like of the components described in the examples are not intended to limit the scope of the present invention thereto, unless otherwise specified, but are merely illustrative examples. It's just In addition, the size, positional relationship, and the like of the members illustrated in each drawing may be exaggerated for clarity of description. Further, in the following description, the same names and reference numerals denote the same or similar members, and a detailed description thereof will be omitted as appropriate. Further, each element constituting the present invention may be configured such that a plurality of elements are configured by the same member and one member also serves as the plurality of elements, or conversely, the function of one member may be performed by a plurality of members. It can also be realized by sharing. In addition, the contents described in some embodiments can be used in other embodiments.

First Embodiment An inductor according to a first embodiment will be described with reference to FIGS.
FIG. 1 is a transparent perspective view of the inductor according to the first embodiment of the present invention. FIG. 2 is a perspective view of a coil used for the inductor according to the first embodiment of the present invention. FIG. 3 is a perspective view of a core used in the inductor according to the first embodiment of the present invention. FIG. 4 is an enlarged view of the upper surface of the core used in the inductor according to the first embodiment of the present invention, that is, one of the surfaces parallel to the laminating direction that is not surrounded by the coil.

  As shown in FIG. 1, an inductor 10 according to a first embodiment includes a coil 11 formed by winding a conductor, a core 12 disposed inside the coil 11, and a body for sealing the core 12 and the coil 11. 13 is provided. The element body 13 is formed by applying pressure to a sealing material obtained by kneading a magnetic powder and a resin. Two ends of the coil 11 are drawn out and exposed on the side surface of the element body 13, that is, a surface parallel to the winding axis direction of the coil, and are electrically connected to an external terminal (not shown). Each end of the coil 11 may expose a cross section orthogonal to the length direction of the conductor, or may expose a side surface parallel to the length direction of the conductor.

  As shown in FIG. 2, the coil 11 is formed by winding a conductor having a rectangular cross section (hereinafter, referred to as a flat wire) coated with an insulating coating along a unidirectional winding axis. The outer shape of the coil 11 is elliptical, and the ends of the rectangular wire are drawn from the outermost periphery of the ellipse. The coil 11 has a space for accommodating the core 12.

  As shown in FIGS. 3 and 4, the core 12 is formed by alternately laminating a thin plate-shaped soft magnetic layer 12a and a flat plate-shaped insulator layer 12b thinner than the soft magnetic layer 12a. It is formed as a part. The widest surface of the soft magnetic layer 12a, that is, the surface of the outermost layer among the surfaces orthogonal to the laminating direction is referred to as a wide surface 12c. The magnetic permeability of the soft magnetic material layer 12 a forming the core 12 is higher than the magnetic permeability of the sealing material forming the element body 13. The magnetic permeability of the insulator layer 12b is lower than the magnetic permeability of the sealing material forming the element body 13.

  The core 12 is arranged inside the coil 11 so that the winding axis of the coil 11 and the wide surface 12c are parallel. That is, the core 12 is arranged so that the laminating direction of the laminating portion is orthogonal to the winding axis of the coil 11. Then, as shown in FIG. 4, the soft magnetic layers 12a and the insulator layers 12b are alternately arranged without gaps. The insulator layer 12b adheres the soft magnetic layers 12a and electrically insulates the soft magnetic layers 12a from each other.

  In order for the core 12 to have a high saturation magnetic flux density, the ratio of the thickness b of the insulator layer 12b to the thickness a of the soft magnetic layer 12a (b / a, hereinafter also referred to as “thickness ratio”) is 0.2 or less. It is preferable that the thickness is preferably 0.1 or less and the thickness b of the insulator layer 12b is several μm. The insulator layer 12b is formed of, for example, a material containing at least one selected from the group consisting of an epoxy resin, a polyimide resin, and a polyimide amide resin.

  Here, an example of a method for obtaining the thickness ratio (b / a) will be described. The thickness ratio (b / a) is obtained by dividing the average value of the thickness a of the insulating layer 12b by the average value of the thickness a of the soft magnetic layer 12a constituting the laminated portion. The average value of the thickness a is obtained as an average value of the measured maximum thicknesses of ten soft magnetic material layers 12a arbitrarily selected in the cross-sectional observation image of the core. The average value of the thickness b is obtained by measuring the minimum thickness of each of the ten insulating layers 12b arbitrarily selected in the cross-sectional observation image of the core, and obtaining the average value of the measured values.

  In FIG. 1, the core is formed such that the wide surface of the core 12 and the longitudinal direction of the elliptical coil 11 are parallel to each other. The core may be formed so as to be parallel, and the wide surface of the core 12 and the longitudinal direction of the elliptical coil 11 may intersect at an arbitrary angle.

  1 and 2, the coil 11 is formed in a so-called α-winding shape (for example, see Japanese Patent Application Laid-Open No. 2009-239076), but may be formed by an edgewise winding, a plated conductor pattern, or the like. Good.

The inductor having such a structure has the following advantages.
A first advantage is that the DC resistance of the inductor is low. Since the core is constituted by a laminated portion including a soft magnetic layer having high magnetic permeability, the number of turns of the coil for obtaining a predetermined inductance is small, and the DC resistance can be reduced.

  The second advantage is that the loss of the inductor due to the eddy current is small. Generally, in an inductor using a core in which conductor plates are laminated, eddy current loss Pe caused by eddy current is proportional to the square of the thickness of the conductor plate. The thickness of the conductor plate in the inductor of the first embodiment, that is, the thickness of the soft magnetic layer is sufficiently small. Therefore, the eddy current loss Pe generated by the magnetic flux of the coil can be reduced.

  A third advantage is that magnetic saturation is unlikely. For the soft magnetic layer 12a, a material having a high saturation magnetic flux density Bs is used. By increasing the ratio of the soft magnetic layer 12a to the thickness of the soft magnetic layer 12a and the insulator layer 12b, a core having high magnetic saturation characteristics can be obtained. For example, if the thickness a of the soft magnetic layer 12a is 19 and the thickness b of the insulator layer 12b is 1, the magnetic saturation characteristic of 95% of the saturation magnetic flux density Bs of the material forming the soft magnetic layer is assumed. Core.

  Such an inductor has a magnetic circuit in which a soft magnetic layer 12a having a high magnetic permeability and a body 13 having a low magnetic permeability and a high magnetic resistance are connected in series, and the magnetic flux is suppressed by the high magnetic resistance characteristics of the body 13. As a result, the structure is less likely to be magnetically saturated. As described above, by increasing the ratio of the soft magnetic layer to the insulator layer and increasing the saturation magnetic flux density Bs of the core 12 itself, the inductor becomes less likely to be magnetically saturated.

Second Embodiment An inductor according to a second embodiment will be described with reference to FIGS.
FIG. 5 is an exploded perspective view of a core used in the inductor according to the second embodiment of the present invention. FIG. 6 is a perspective view of a core used in the inductor according to the second embodiment of the present invention. FIG. 7 is a transparent perspective view of the inductor according to the second embodiment of the present invention. In the inductor according to the second embodiment, the core is divided by a plate-shaped gap having low magnetic permeability.

  A core used in the inductor according to the second embodiment will be described. As shown in FIG. 5, the core 22 is divided into two laminated portions 22a in which soft magnetic layers and insulating layers are alternately laminated, and the core is divided into two portions sandwiched between the two laminated portions 22a. It is composed of a plate-shaped gap portion 22b. Then, as shown in FIG. 6, the outer peripheral portion of the gap portion 22b is exposed to the outside of the core on the side surface of the core. That is, the gap portion 22b extends to the outer peripheral portion of the stacked portion 22a. The gap portion 22b is arranged in contact with the laminated portion 22a such that its thickness direction is orthogonal to each of the two laminated portions 22a in the laminating direction.

  The laminated portion 22a is formed by alternately laminating soft magnetic layers 12a and insulator layers 12b, similarly to the core 12 of the first embodiment. The gap portion 22b is made of a substance that bonds the stacked portions 22a to each other. The magnetic permeability of the gap portion 22b is smaller than the magnetic permeability of the soft magnetic layer of the laminated portion 22a. The magnetic permeability of the gap portion 22b may be higher, lower, or the same as the magnetic permeability of the insulator layer forming the stacked portion 22a.

  In FIG. 6, the two stacked portions 22a sandwich the gap portion 22b so that their respective stacking directions are parallel, but the respective stacking directions of the two stacked portions 22a intersect at right angles or at any angle, The gap portion 22b may be sandwiched so as to be orthogonal to the thickness direction of the gap portion 22b.

  As shown in FIG. 7, the inductor 20 includes a core 22, a coil 11 having the core 22 in an internal space, and a body 13 that seals the coil 11 and the core 22. The core 22 is arranged in the space inside the coil 11 so that the winding axis of the coil 11 and the wide surface 12c are parallel. The magnetic permeability of the sealing material forming the element body 13 is higher than the magnetic permeability of the gap portion and lower than the magnetic permeability of the soft magnetic layer forming the core.

  In FIG. 7, the core 22 is formed such that the wide surface of the core 22 and the longitudinal direction of the elliptical coil 11 are parallel to each other. May be formed parallel to each other, and the wide surface of the core 22 and the longitudinal direction of the elliptical coil 11 may intersect at an arbitrary angle. In addition, the wide surface of one laminated portion 22a constituting the core 22 and the longitudinal direction of the elliptical coil 11 are parallel, and the wide surface of the other laminated portion 22a and the short direction of the elliptical coil 11 are parallel. They may be parallel.

  Further, in FIG. 7, the coil 11 is formed in a so-called α-winding shape, but may be formed by an edgewise winding, a plated conductor pattern, or the like.

  The inductor 20 has the following characteristics. As compared with the core 12 of the first embodiment, the core 22 has a smaller shape magnetic anisotropy in the winding axis direction of the coil 11 and has a magnetic gap of a low magnetic permeability material or a non-magnetic material inside the core. , The magnetic resistance in the winding axis direction also increases. Therefore, the magnetic flux density inside the laminated portion 22a constituting the core 22 is smaller than that of the inductor of the first embodiment. As a result, the core 22 is less likely to be magnetically saturated and the loss due to the eddy current is reduced.

  As an inductor, the advantage described in the first embodiment is that magnetic saturation is less likely to occur while maintaining a low DC resistance to some extent, or a decrease in the L value due to superposition of DC current is reduced, and AC loss is reduced. As a result, the Q value increases.

Third Embodiment An inductor according to a third embodiment will be described with reference to FIGS.
FIG. 8 is a perspective view of a core used in the inductor according to the third embodiment of the present invention. FIG. 9 is a transparent perspective view of the inductor according to the third embodiment of the present invention. FIG. 10 is a transmission diagram of the core visualizing the magnetic flux passing through the core of the inductor. In the inductor according to the third embodiment, the core includes the ferrite portions on the wide surfaces that are both ends in the stacking direction of the stacked portion.

  As shown in FIG. 8, similarly to the core 12 of the first embodiment, the core 32 is disposed at a laminated portion 32a in which the soft magnetic layer 12a and the insulating layer 12b are laminated, and at both ends in the laminating direction of the laminated portion 32a. And a thin flat ferrite portion 32b. The ferrite portion 32b is attached so as to cover the wide surface 12c which is the lamination surface at both ends of the core 32 in the lamination direction. The magnetic permeability of the ferrite portion 32b is lower than the magnetic permeability of the soft magnetic layer 12a and higher than the magnetic permeability of the element body 13.

  In FIG. 8, the ferrite portions 32b are arranged only at both ends in the stacking direction of the stacked portion 32a, but the ferrite portions 32b may be further arranged on other surfaces of the stacked portion 32a. For example, the ferrite portion 32b may be arranged on a side surface including both ends of the laminated portion 32a.

  Generally, when the inductor of the first embodiment is driven at a high frequency, the magnetic flux generated from the coil passes through the core. At this time, when the current amount of the coil is small, the magnetic flux passing through the core is concentrated on both ends of the core in the stacking direction. An eddy current is generated in a portion where the magnetic flux is concentrated, and an eddy current loss Pe increases. In order to reduce the eddy current loss Pe, the inductor 30 according to the third embodiment has a structure described below.

  As shown in FIG. 9, the inductor 30 includes a core 32, a coil 11 having the core 32 in an internal space, and a body 13 that seals the coil 11 and the core 32. The core 32 is arranged in the space inside the coil such that the winding axis of the coil 11 and the wide surface 12c are parallel to each other. By arranging the ferrite portions 32b made of a ferrite plate having a lower magnetic permeability than the soft magnetic layer 12a at both ends in the stacking direction of the core 32, the magnetic flux density concentrated at both ends of the core 32 can be reduced. . Further, since the ferrite portion 32b has a higher electrical resistivity than the soft magnetic layer 12a, an eddy current hardly occurs. For the above reasons, the eddy current loss Pe of the inductor 30 can be suppressed, and the Q value can be improved.

  Simulations have been performed on the magnetic flux density of the core, and will be described with reference to FIGS. FIGS. 10A to 10D are transmission diagrams of the core in which the magnetic flux density obtained by the harmonic magnetic field analysis at a frequency of 1 MHz using the finite element method analysis software Femtet (Murata Software Inc.) is shown. FIG. 10A is a transparent perspective view of a core without a ferrite portion, and FIG. 10B is a transparent plan view of the core without a ferrite portion as viewed from above. FIG. 10C is a transparent perspective view of a core having ferrite portions disposed at both ends of the core, and FIG. 10D is a transparent plan view of a core having ferrite portions disposed at both ends of the core as viewed from above. The magnetic permeability of the soft magnetic layer constituting the core is higher than the magnetic permeability of the ferrite portion, and the magnetic permeability of the ferrite portion is higher than that of the sealing material forming the element body.

  As shown in FIGS. 10A and 10B, the magnetic flux passing through the core without the ferrite portion is concentrated at both ends in the stacking direction of the core, and the magnetic flux density at both ends is as large as about 10 mT to 32 mT, and about 12 mT There are many parts indicating the above. As shown in FIGS. 10C and 10D, the magnetic flux passing through both ends of the core in which the ferrite portions are arranged in the stacking direction is concentrated at both ends of the core in the stacking direction, but is smaller than in FIGS. 10A and 10B. The magnetic flux density is about 12 mT or less at both ends. As described above, by arranging the ferrite portions at both ends of the core in the stacking direction, the amount of magnetic flux concentrated at both ends of the core in the stacking direction can be suppressed. As a result, the eddy current loss Pe of the inductor is suppressed, and the Q value can be improved.

  In FIG. 9, the core is formed so that the wide surface of the core 32, that is, the wide surface of the ferrite portion 32b and the longitudinal direction of the elliptical coil 11 are parallel to each other. The core may be formed so that the short direction of the coil 11 is parallel. Further, the wide surface of the core 32 and the longitudinal direction of the elliptical coil 11 may intersect at an arbitrary angle.

  Further, in FIG. 9, the coil 11 is formed in a so-called α winding shape, but may be formed in an edgewise winding, a plated conductor pattern, or the like.

The embodiments have been described above, but the present invention is not limited to the embodiments.
The core shape does not have to be a shape in which the inside of the coil is entirely buried. It may have a prismatic shape, a cylindrical shape, or any shape as long as it is arranged inside the coil. Further, the height dimension of the core may not be the same as the height of the coil. Depending on the characteristics desired for the inductor, the height of the core may be larger or smaller than the height of the coil. Further, the laminating direction of the laminated portion forming the core may be not only perpendicular to the longitudinal direction of the elliptical coil as shown in FIG. 1 but may be parallel to the longitudinal direction of the coil. Can be set arbitrarily in the longitudinal direction. It is only necessary that the wide surface of the soft magnetic layer is parallel to the winding axis of the coil. That is, the lamination direction of the lamination portion and the winding axis of the coil need only be orthogonal.

  Furthermore, the laminated portions of the core divided into two in the second embodiment need not have the same laminating direction. Further, the number of the laminated portions is not limited to two, and may be three or more, and the laminating directions of the respective laminated portions may not be the same. The number of gap portions is not limited to one, and may be two or more. When the core is composed of a plurality of laminated portions having different laminating directions, it is preferable to provide the gap portion since the eddy current loss can be further reduced due to the presence of the gap.

  The soft magnetic layer constituting the core is made of, for example, iron, silicon steel, permalloy, sendust, permendur, soft ferrite, amorphous magnetic alloy, nanocrystal magnetic alloy, or an alloy thereof. In addition, other materials may be used as long as they have a high magnetic permeability, without being limited to the soft magnetic material.

  The shape of the insulator layer forming the core is not limited to a flat plate shape, and may be any shape as long as insulation between the soft magnetic layers can be obtained.

  The conductor constituting the coil is not limited to a rectangular wire, but may be a round wire having a circular cross section, or may have another shape. The shape of the coil is not limited to an elliptical shape, but may be a substantially circular shape or the like.

  The material constituting the body was a sealing material obtained by kneading a magnetic powder and a resin, but the magnetic powder may be a metal magnetic powder or a ferrite-based magnetic powder. The element body is not limited to a sealing material obtained by kneading a magnetic powder and a resin. The element body may be made of another material such as ferrite.

  The inductor is not limited to the embodiment. For example, an inductor using a core including both a gap portion and a ferrite portion by combining the second and third embodiments may be used.

  The disclosure of Japanese Patent Application No. 2006-213578 (filing date: October 31, 2016) is incorporated herein by reference in its entirety. All documents, patent applications, and technical standards described herein are to the same extent as if each individual document, patent application, and technical standard were specifically and individually stated to be incorporated by reference. Incorporated herein by reference.

Claims (4)

A flat soft magnetic layer and a flat insulating layer, which is thinner than the soft magnetic layer and contains at least one selected from the group consisting of an epoxy resin, a polyimide resin, and a polyimide amide resin , are alternately formed. A core including a laminated portion,
A coil including a conductor wound around the core;
A pressure-molded body of a sealing material containing the core and the coil and including a magnetic powder and a resin, and a body having a lower magnetic permeability than the core ;
With
The coil is formed by winding a conducting wire having a rectangular cross section in an elliptical shape as viewed from the upper surface of the element body in two steps so that both ends are located on the outer periphery, with the wide surface being parallel to the winding axis. Formed
The core is arranged such that the lamination direction of the lamination portion is orthogonal to the winding axis of the coil, and has a length in a direction perpendicular to the lamination direction of the soft magnetic material layer and the insulator layer and the winding axis direction of the coil. Is closer to the center of the core in the stacking direction, and is longer. The stacked portion is disposed between the upper and lower ends of the coil in the winding axis direction of the coil. And a gap portion having a magnetic permeability lower than that of the soft magnetic material layer and extending to an outer peripheral portion of the stacked portion, between the two divided stacked portions, wherein the gap portion includes: An inductor in which the thickness direction and the lamination direction of the lamination portion are arranged orthogonally . The core is disposed at each of both ends in the stacking direction of the stacked unit, and further includes a ferrite portion having a magnetic permeability higher than the magnetic permeability of the element body and lower than the magnetic permeability of the soft magnetic material layer. An inductor according to claim 1 . The inductor according to claim 2, wherein the ferrite portion is vertically divided into two portions between upper and lower ends of the coil, and the gap portion is provided between the two divided ferrite portions . The laminate portion, the ratio of the thickness of the insulator layer to the thickness of the soft magnetic layer is 0.2 or less, inductor according to any one of claims 1 to 3.

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