Inductor

Abstract

This inductor comprises: a magnetic core formed by mixing and pressure forming a magnetic material in powder form and a binding agent; and a coil element buried in the magnetic core. The coil element is wound so as to have a toroidal coil shape.

Description

[Technical Field]

[0001] The present disclosure relates to inductors used in various electronic devices. [Background Art]

[0002] In recent years, along with the performance improvement of electronic devices, demands for inductors have also diversified to include high inductance, support for large current, superimposition characteristics and the like. For this reason, a toroidal coil obtained by winding a conductive wire around a ferrite toroidal core has been proposed (for example, Patent Document 1). Further, a dust-core type inductor has been proposed in which a magnetic core is formed by embedding a coil element in a mixed powder of metal magnetic powder and a binder made of thermosetting resin and performing pressure molding (for example, Patent Document 2). [Prior Art Literature] [Patent Literature]

[0003] [Patent Document 1] Japanese Unexamined Patent Application Publication No. 2012-124396 [Patent Document 2] Japanese Unexamined Patent Application Publication No. 2010-87240 [Summary of the Invention]

[0004] The inductor includes a magnetic core obtained by mixing powdered magnetic material and a binder and performing pressure molding, and a coil element embedded in the magnetic core. The coil element is wound to have a toroidal coil shape.

[0005] This inductor increases the initial inductance value, and can suppress a decrease in inductance value even when a large current flows therethrough. [Brief Description of the Drawings]

[0006] [Figure 1] FIG. 1 is a perspective perspective view of an inductor according to an embodiment of the present disclosure. [Figure 2] FIG. 2 is a cross-sectional view of the inductor in FIG. 1 taken along line II-II. [Figure 3A] Figure 3A illustrates a method for manufacturing an inductor in one embodiment. [Figure 3B] Figure 3B illustrates a method for manufacturing an inductor in one embodiment. [Figure 3C] Figure 3C illustrates a method for manufacturing an inductor in one embodiment. [Figure 3D] Figure 3D illustrates a method for manufacturing an inductor in one embodiment. [Modes for carrying out the invention]

[0007] Figure 1 is a perspective view of inductor 501 in one embodiment of the present disclosure. Figure 2 is a cross-sectional view of inductor 501 shown in Figure 1 along line II-II.

[0008] The inductor 501 comprises a magnetic core 11 and a coil element 12 embedded in the magnetic core 11.

[0009] The magnetic core 11 is formed by pressure molding a composite magnetic material obtained by mixing a powdered metallic magnetic material made of an Fe-Si-Cr alloy with a binder. A coil element 12 is embedded inside the magnetic core 11, and the end of the coil element 12 protrudes from the end face of the magnetic core 11, and is electrically and mechanically connected to an external electrode 13 provided on the end face of the magnetic core 11. The external shape of the magnetic core 11 is a rectangular parallelepiped with a square area of ​​approximately 7 mm and a height of approximately 4 mm.

[0010] Embed inside the magnetic core 11 is a coil element 12 made of a copper wire with a diameter of approximately 0.3 mm, which is insulated and wound around the core. The wire of the coil element 12 is wound helically around the core portion 12a, which is a virtual region having a toroidal shape extending in the circumferential direction D12 surrounding the central axis 12p, thus forming a toroidal coil shape. The inner diameter of the core portion 12a of the coil element 12 is approximately 2 mm. A ferrite material 14 is placed on the core portion 12a of the coil element 12, which is wound in a toroidal coil shape. The ferrite material 14 is made by sintering ferrite powder and has a C-shape with a part of the donut shape cut out.

[0011] The shape of the ferrite material 14 is preferably C-shaped or U-shaped when viewed in the direction in which the central axis 12p extends. Helically winding the wire around a ring-shaped ferrite material is difficult to automate. If the shape of the ferrite material 14 is C-shaped or U-shaped, the ferrite material 14 can be inserted into a coil made of pre-wound wire, making assembly easier.

[0012] As described above, the coil element 12 wound in a toroidal coil shape enhances magnetic efficiency, the ferrite material 14 with high initial permeability increases the initial inductance value at low currents, and the metallic magnetic material of the magnetic core 11, which is less prone to magnetic saturation even at high currents, reduces the decrease in inductance value. In addition, in a toroidal coil using a C-shaped ferrite material 14, a magnetic gap occurs in the unconnected parts of the ferrite material 14, causing the inductance value to decrease. However, in the embodiment of this disclosure, the unconnected parts of the ferrite material 14 are filled with the metallic magnetic material that is the material of the magnetic core 11, thus suppressing the decrease in inductance value.

[0013] Toroidal coils have minimal magnetic flux leakage and readily achieve high inductance, but when large currents flow, the ferrite toroidal core undergoes magnetic saturation, leading to a degradation in inductance and a problem with superposition characteristics. Furthermore, the process of winding wires around the toroidal coil is difficult to automate, resulting in high costs. On the other hand, powder-type inductors offer better superposition characteristics than toroidal coils, but are still not entirely satisfactory, and achieving high inductance values ​​remains challenging.

[0014] In the inductor 501 of this embodiment, as described above, the decrease in the inductance value can be suppressed.

[0015] It is desirable that the volume of the ferrite material 14 be 90% or less of the volume of the core portion 12a of the coil element 12 wound in a toroidal coil shape. If the volume of the ferrite material 14 is greater than 90% of the volume of the core portion 12a, the proportion of metallic magnetic material decreases, and the inductance value tends to deteriorate at high currents.

[0016] Furthermore, it is desirable to place the ferrite material 14 on the outer side of the toroidal shape, as shown in Figure 2. Because the spacing between the wires of the coil element 12 is narrower on the inner side than on the outer side of the toroidal shape, magnetic saturation is more likely to occur on the inner side of the toroidal shape of the winding core portion 12a compared to the outer side. Therefore, by placing a larger proportion of the metallic magnetic material on the inner side of the toroidal shape than on the outer side to reduce magnetic saturation, and by placing a larger proportion of the ferrite material 14 on the outer side of the toroidal shape, it becomes easier to obtain a high inductance value.

[0017] When a coil element wound in a generally toroidal shape is placed in a mold and subjected to compacting, the coil element is easily deformed under pressure. When the coil element is deformed, variations occur in the inductance value. In contrast, in one embodiment, compacting is performed in a state where a ferrite material (14) is disposed on the core portion (12a) of the coil element (12) wound into a toroidal shape, whereby the ferrite material (14) serves as a support, deformation of the coil element (12) can be suppressed, and the inductance value of the inductor (501) can be stabilized.

[0018] In the above embodiment, the ferrite material 14 is obtained by sintering ferrite powder, but it may also be obtained by mixing ferrite powder with a resin and curing the mixture. The same effect can be obtained as long as the material cured with resin can withstand the pressure of compacting.

[0019] Further, instead of the ferrite material, a material formed by mixing metallic magnetic powder with resin, compression-curing the mixture into a C-shape or U-shape may also be used. By this arrangement, the inductor 501 having more excellent superimposition characteristics can be obtained.

[0020] Next, a method for manufacturing an inductor according to an embodiment of the present invention will be described. FIGS. 3A to 3D are diagrams illustrating the method for manufacturing the inductor 501.

[0021] First, a copper wire provided with an insulating coating is wound around a core, and then removed from the core to form the coil element 12 as shown in FIG. 3A. On the other hand, ferrite powder is mixed with a binder, molded, and sintered to produce the C-shaped ferrite material 14 as shown in FIG. 3B. Note that the ferrite material 14 may also be obtained by mixing ferrite powder with resin and curing the mixture. The same effect can be obtained as long as the material cured with resin can withstand the pressure of compacting.

[0022] Next, the ferrite material 14 is inserted into the core portion 12a of the coil element 12. Since the ferrite material 14 is C-shaped, it can be inserted into the core portion 12a of the coil element 12 from the open part of the annular shape. By inserting the C-shaped ferrite material 14 into the core portion 12a of the coil element 12, the coil element 12 is wound into a toroidal coil shape. The use of the above construction method facilitates automation of the winding process of the coil element 12, and simplifies the assembly process.

[0023] Next, the coil element 12 with the ferrite material 14 inserted therein and a composite magnetic material obtained by mixing powdered metallic magnetic material made of Fe-Si-Cr alloy and a binder are placed in a mold and press-molded to form the magnetic core 11, and a molded body as shown in Fig. 3C is obtained. At this time, the magnetic core 11 is molded such that both end portions of the coil element 12 are exposed at the end surface of the magnetic core 11. After heat-curing the magnetic core 11, external electrodes 13 are formed on the end surface of the magnetic core 11 where both end portions of the coil element 12 are exposed, whereby an inductor 501 as shown in Fig. 3D can be obtained. [Industrial Applicability]

[0024] The inductor according to the present disclosure is industrially useful because it is excellent in superimposition characteristics and can easily provide an inductor with a high inductance value. [Description of Reference Signs]

[0025] 11 Magnetic core 12 Coil element 12a Core portion 13 External electrode 14 Ferrite material

Claims

1. A magnetic core formed by mixing powdered magnetic material and a binder and then press-molding it, A coil element embedded in the magnetic core and having an end exposed from the end face of the magnetic core, An external electrode electrically and mechanically connected to the end of the coil element, An inductor equipped with, The coil element is wound to have a toroidal coil shape, Furthermore, the coil element is helically wound around a toroidal core portion that extends circumferentially around the central axis. The inductor further comprises a ferrite material arranged in the winding portion of the magnetic core. Inductor.

2. A magnetic core formed by mixing powdered magnetic material and a binder and then press-molding it, A coil element embedded in the magnetic core and having an end exposed from the end face of the magnetic core, An external electrode electrically and mechanically connected to the end of the coil element, An inductor equipped with, The coil element is wound to have a toroidal coil shape, Furthermore, the coil element is helically wound around a toroidal core portion that extends circumferentially around the central axis. The inductor further comprises a ferrite material arranged in the winding portion of the magnetic core, The ferrite material has a C-shape or a U-shape when viewed in the direction in which the central axis extends. Inductor.

3. A magnetic core formed by mixing powdered magnetic material and a binder and then press-molding it, A coil element embedded in the magnetic core and having an end exposed from the end face of the magnetic core, An external electrode electrically and mechanically connected to the end of the coil element, An inductor equipped with, The coil element is wound to have a toroidal coil shape, Furthermore, the coil element is helically wound around a toroidal core portion that extends circumferentially around the central axis. The inductor further comprises a ferrite material arranged in the winding portion of the magnetic core, The volume of the ferrite material is 90% or less of the volume of the core portion. Inductor.

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