Coil component

Abstract

A coil component (1) includes: a coil (3); a magnetic core (2) accommodated inside the coil (3); and a fixing means (winding end (3b)) for fixing the magnetic core (2) to the coil (3) such that the magnetic core (2) is positioned inside the coil (3) in the axial direction. The coil (3) is constituted of a winding (3a) that extends in a spiral shape. The magnetic core (2) has high magnetic permeability and is accommodated inside a central core portion (3c), which is the inside of the coil (3).

Description

Coil parts

[0001] The present invention relates to a coil component including a magnetic core and a coil.

[0002] Coil components used in high-current circuits require improved superposition characteristics and reduced DC resistance, which necessitates larger coil components. In particular, magnetic materials used in large coil components are required to have high magnetic permeability. For example, some coil components are made by mixing metal powder with resin, then placing the mixture in a mold together with a coil and a magnetic core and compressing it to form a metal composite. As the size of coil components increases, molding machines for molding large coil components also need to increase the molding pressure, resulting in larger sizes and significant increases in costs.

[0003] To address the problems associated with the increased molding pressure, molding materials and molding methods that can be molded at low molding pressures are needed. Magnetic materials that can be molded at low pressures can be achieved by using relatively spherical metal magnetic powder, compounding a relatively large amount of thermosetting resin that melts at approximately 100°C or higher, and molding this at a temperature above the melting point of the resin. Such materials that can be thermoformed at low pressures have the disadvantage that they do not achieve high magnetic permeability because the metal powder is spherical and contains a large amount of non-magnetic resin components.

[0004] On the other hand, magnetic materials that can be thermoformed at low pressure do not have high magnetic permeability, which means they cannot meet the characteristics required for large coil components.

[0005] One solution to this problem is to place a pre-formed and sintered high-permeability magnetic core in part of the magnetic circuit of the coil component, and then embed this magnetic core and the coil in a single piece using the above-mentioned magnetic material that can be thermally molded at low pressure. From the perspective of stable characteristics, this method is best suited to placing a high-permeability magnetic core in the center of the core part of the coil.

[0006] The coil can be positioned within the mold by holding the ends of the flat wire of the coil using the flat wire in the mold. On the other hand, the high-permeability magnetic core must be enclosed in a material that can be thermoformed at low pressure and not exposed to the product surface to prevent rust and moisture absorption. Therefore, the high-permeability magnetic core cannot be positioned in contact with the inner surface of the mold. As a result, it has been difficult to position the high-permeability magnetic core placed in the center of the coil.

[0007] For example, in the coil component described in Patent Document 1, a molded body of a high-permeability magnetic material serving as a magnetic core has a flange portion, and the magnetic core and the coil are positioned by being mounted on the upper surface of the flange portion.

[0008] Japanese Patent Application Laid-Open No. 2020-167304

[0009] However, in the coil component of Patent Document 1, the flange of the magnetic core is formed larger than the center of the coil, so the high-permeability magnetic core including the flange cannot be enclosed by the coil. As a result, dimensional errors in each production run can cause changes in the flow of magnetic flux, resulting in unstable inductance.

[0010] Furthermore, when a magnetic core is embedded in a coil, the method described in Patent Document 1 cannot be used, and the magnetic core and the coil cannot be positioned properly. As a result, the magnetic core may transition from being housed in the coil to being protruding from the coil, which changes the flow of magnetic flux and makes the inductance unstable.

[0011] The present invention has been made in view of the above-mentioned problems, and provides a coil component in which the magnetic core and the coil can be positioned.

[0012] The coil component according to the present invention is characterized by having a coil, a magnetic core housed inside the coil, and a fixing means for fixing the magnetic core to the coil so that the magnetic core is positioned within the coil in the axial direction.

[0013] According to the present invention, the magnetic core can be fixed inside the coil, and the flow of magnetic flux is not changed, making it possible to stabilize the inductance.

[0014] FIG. 2 is a plan view of a coil component. FIG. 3 is a cross-sectional view of the coil component, showing the A-A cross section in FIG. 1. FIG. 4 is a plan view showing a coil. FIG. 5 is a plan view showing a state in which a magnetic core is inserted into the central core of the coil. FIG. 6 is a plan view showing a state after the winding end of the coil has been bent and deformed. FIG. 7 is a cross-sectional view of a coil component according to a first modified example, showing a cross section corresponding to the A-A cross section in FIG. 1. FIG. 8 is a cross-sectional view of a coil component according to a second modified example, showing a cross section corresponding to the A-A cross section in FIG. 1.

[0015] Hereinafter, embodiments of the present invention will be described with reference to the drawings. Note that the embodiments described below are merely examples for facilitating understanding of the present invention and are not intended to limit the present invention. In other words, the shapes, dimensions, arrangements, etc. of the components described below may be changed or improved without departing from the spirit of the present invention, and the present invention naturally includes equivalents thereof. Furthermore, the various components of the present invention do not necessarily have to exist independently. It is acceptable for multiple components to be configured as a single component, for one component to be divided into multiple components, for one component to be part of another component, or for part of one component to overlap with part of another component, etc.

[0016] In addition, in all drawings, like elements are denoted by like reference numerals, and redundant explanations are omitted where appropriate. Furthermore, although the present specification may refer to an up-down direction, this is set for the sake of convenience in explaining the relative relationships between elements, and does not limit the directions when manufacturing or using the product according to the present invention.

[0017] <Outline of Coil Component> First, an outline of the coil component 1 will be described mainly with reference to Fig. 1 and Fig. 2. Fig. 1 is a plan view of the coil component 1, and Fig. 2 is a cross-sectional view of the coil component 1 taken along the line A-A in Fig. 1.

[0018] The coil component 1 includes a coil 3, a magnetic core 2 housed inside the coil 3, and a fixing means (winding end 3b) for fixing the magnetic core 2 to the coil 3 so that the magnetic core 2 is positioned within the coil 3 in the axial direction.

[0019] The fixing means in this embodiment is a winding end 3b of the winding 3a that constitutes the coil 3 and intersects with at least a portion of the coil 3 in the axial direction. However, the above-mentioned "fixing means" is not limited to this configuration and may be an adhesive (not shown) or the like. In other words, the magnetic core 2 may be fixed to the coil 3 by the adhesive force of the adhesive.

[0020] According to the above configuration, the magnetic core 2 can be fixed within the coil 3 by the fixing means (winding end portion 3b), and the magnetic core 2 does not transition from a state where it is contained within the coil 3 to a state where it is protruded from the coil 3. This prevents a change in the flow of magnetic flux and stabilizes inductance. This makes it possible to obtain a large coil component 1 that has excellent inductance characteristics and is easy to mold.

[0021] <Configuration of Coil Component> Next, the configuration of each part of the coil component 1 will be described. The magnetic core 2 has a high magnetic permeability μ of 30 H / m or more and 100 H / m or less, and is formed by molding or sintering. The magnetic core 2 according to this embodiment is molded or sintered from an Fe-Si-Cr alloy (magnetic permeability μ = 60 H / m), and has an outer diameter of 15.6 mm and a height of 7.5 mm.

[0022] The coil 3 includes a winding 3a wound around the magnetic core 2. The axial dimension of the coil 3 is larger than the dimension of the magnetic core 2 in the winding axis direction. The coil 3 according to this embodiment is an edgewise coil made of an insulatingly coated rectangular wire, for example, with a width of 5.0 mm and a thickness of 1.0 mm. The inner diameter of the coil 3 is 16.0 mm, and the number of turns is 8.5.

[0023] 2, both axial ends (winding end portions 3b) of the coil 3 according to this embodiment are located axially outward of the magnetic core 2. The fixing means are the winding end portions 3b, which are the windings of the coil 3 at both ends, and the inner winding diameter of the coil 3 at (at least a part of) the winding end portions 3b is smaller than the outer diameters of the upper and lower surfaces of the magnetic core 2 that face the winding end portions 3b.

[0024] The "winding 3a" refers to a portion extending in a spiral shape, and the "inner winding diameter" refers to a length twice the radius of curvature of the winding 3a. The inner winding diameter of at least a portion of the end winding 3b is smaller than the outer diameter of the upper and lower surfaces of the magnetic core 2, so that the end winding 3b is positioned on an extension of the axial direction of the magnetic core 2. Furthermore, the height of the high-permeability magnetic core 2 disposed in the central portion 3c is lower than the distance between the two end windings 3b.

[0025] The inner diameter of at least a portion of the winding end portions 3b at both ends of the coil 3 is smaller than the outer diameter of the upper and lower surfaces of the magnetic core 2, so that the winding end portions 3b are positioned to overlap on an extension of the axial direction of the magnetic core 2. The total overlap width between the upper and lower winding end portions 3b and the magnetic core 2 is smaller than the wire width of the coil 3. The winding end portions 3b are formed so that the turns of the winding wire 3a adjacent to the winding end portions 3b on the top and bottom overlap with the winding end portions 3b. This configuration of the coil 3 makes it possible to prevent the magnetic powder 4 from getting between the windings 3a.

[0026] According to the above configuration, the inner diameter (at least a part of) of the winding end portions 3b at both ends of the coil 3 is smaller than the outer diameter of the upper and lower surfaces of the magnetic core 2, thereby restricting movement of the magnetic core 2 from both sides in the axial direction. In particular, because the magnetic core 2 can be positioned by the winding end portions 3b rather than by adhesive, cracks due to the application of heat, etc., do not occur, unlike in cases where an adhesive with a different thermal expansion coefficient from other materials is used.

[0027] Both ends (winding ends 3b) of the coil 3 may be in surface contact with the upper and lower surfaces of the magnetic core 2, respectively, and press against the upper and lower surfaces of the magnetic core 2 from both sides in the axial direction. In other words, the axial length of the coil 3 may be longer than the axial length of the winding ends 3b on both sides, and an elastic restoring force may be applied to the coil 3 inward in the axial direction relative to the magnetic core 2.

[0028] According to the above configuration, the magnetic core 2 and the coil 3 can be brought into close contact with each other, thereby suppressing relative movement (play) of the magnetic core 2 with respect to the coil 3. However, the present invention is not limited to this configuration, and gaps may be formed between the upper and lower winding ends 3b of the coil 3 and the magnetic core 2, as long as the magnetic core 2 can be accommodated within the central core 3c of the coil 3, thereby sufficiently stabilizing the inductance.

[0029] As shown in Figures 1 and 2, the coil component 1 further includes a coating (magnetic powder 4) having a lower magnetic permeability than the magnetic core 2, and the magnetic powder 4 encloses the coil 3 and the magnetic core 2.

[0030] Specifically, the magnetic powder 4 is a mixture of metal magnetic powder and thermosetting resin. More specifically, the magnetic powder 4 contains an alloy mainly composed of Fe—Si—Cr with an average particle size of approximately 10 μm, and a thermosetting epoxy resin, with the resin content being 3%.

[0031] The above phrase "the magnetic powder 4 encompasses the coil 3 and the magnetic core 2" specifically means that the magnetic powder 4 encompasses the coil 3 and the magnetic core 2, with the exception of the coil ends of the coil 3, without exposing them on the surface of the magnetic powder 4. According to the above configuration, the above effect can also be achieved in a coil component 1 that includes a coating. Conversely, the coil component 1 does not necessarily have to include the magnetic powder 4.

[0032] Additionally, a coreless coil component (not shown) was fabricated without inserting a high-permeability core as a central core, with the other steps being the same as those used in the manufacturing method of coil component 1, and the DC resistance was compared between the coreless coil component and coil component 1. Specifically, coil component 1 and the coreless coil component were designed to have the same product external dimensions of 30 mm length, 30 mm width, and 15 mm height, and the same inductance of 15.0 μH.

[0033] On the other hand, in order to make the product outer dimensions of the coreless coil component and coil component 1 equal, differences were made in the configuration of the coreless coil component and coil component 1. Specifically, the coreless coil component has an edgewise coil made of an insulatingly coated rectangular wire with a width of 5.0 mm and a thickness of 0.7 mm (thinner than coil component 1). The coil inner diameter of this component is 16.0 mm, and the number of turns is 11.5 (more than coil component 1). The coil was formed so that both ends, which serve as lead-out portions, extend parallel to each other.

[0034] The DC resistance of the coil component without a core was 4.2 mΩ, whereas the DC resistance of the coil component 1 according to this embodiment was 2.3 mΩ, and good DC superposition characteristics were obtained.

[0035] <Manufacturing Procedure of Coil Component> Next, the manufacturing procedure of the coil component 1 will be described with reference mainly to Fig. 3 to Fig. 5. Fig. 3 is a plan view showing the coil 3, Fig. 4 is a plan view showing the state in which the magnetic core 2 is inserted into the central core portion 3c of the coil 3, and Fig. 5 is a plan view showing the state after the winding end portion 3b of the coil 3 has been bent and deformed.

[0036] First, a rectangular wire is wound around a central core (not shown) which is a winding jig to form the winding 3a of the coil 3 shown in Fig. 3. At this time, each turn of the winding 3a is wound closely together to prevent the magnetic powder 4 from entering and causing a decrease in inductance characteristics. As shown in Fig. 3, before the magnetic core 2 is accommodated in the central core portion 3c of the coil 3, the ends of the coil 3 drawn out from the magnetic powder 4 are each formed to open outward (toward the side facing away) at an angle of approximately 10°.

[0037] In this embodiment, the winding jig is removed, and a magnetic core 2 with high magnetic permeability is inserted into the central core 3c of the coil 3 as shown in Figure 4. Then, as shown in Figure 5, the two winding end portions 3b at both ends of the coil 3 are wound tightly inside the inner diameter of the coil (the central core 3c, the outer periphery of the magnetic core 2).

[0038] Specifically, while the magnetic core 2 is temporarily fixed with a fixture (not shown), the winding ends 3b at both ends are bent inward (toward the axis) by crimping so that they extend parallel to each other as shown in Fig. 5. More specifically, when crimping the winding ends 3b at both ends, the winding ends 3b at both ends are deformed so that they approach each other so that they extend parallel to each other due to their elastic recovery. As shown in Figs. 2 and 5, the winding ends 3b at the upper and lower ends of the coil 3 are positioned closer to the center than the circumferential surface of the inserted high-permeability magnetic core 2, thereby fixing and positioning the magnetic core 2 to the winding ends 3b.

[0039] The method is not limited to the above-described method of simultaneously crimping the winding end portions 3b at both ends of the coil 3. It is also possible to crimp one winding end portion 3b, then insert the magnetic core 2 into the central core portion 3c so that it is positioned above the winding end portion 3b, and then crimp the other winding end portion 3b. Furthermore, as in a first modified example described below, only one side (lower side) of the winding 3a may be crimped so that the winding end portion 3b is positioned closer to the center than the circumferential surface of the magnetic core 2.

[0040] The coil 3 with the manufactured magnetic core 2 inserted therein is then set in a mold (not shown). The mold has inner dimensions of 30 mm in length and width. Granulated powder (magnetic powder 4) made by mixing metal magnetic powder and resin is then poured into the mold.

[0041] Then, a load is applied to the magnetic powder 4 in a mold (not shown) to perform compression molding. The molded body (not shown) is removed from the mold and subjected to a hardening heat treatment for 2 hours in a thermostatic chamber at 150°C. Thereafter, the coating is peeled off from the end of the coil 3 protruding from the molded body and the end is bent to form an external electrode.

[0042] Through the above steps, the coil component 1 shown in FIGS. 1 and 2 can be manufactured, having the high-permeability magnetic core 2 held in the central core portion 3c and having external dimensions of 30 mm length and width and 15 mm height.

[0043] <First Modification> In the above embodiment, both winding ends 3b at the upper and lower ends of the coil 3 are described as being crimped so as to be positioned closer to the center than the circumferential surface of the magnetic core 2. However, the present invention is not limited to this configuration. Next, a coil component 11 according to a first modification will be described with reference mainly to Fig. 6. Fig. 6 is a cross-sectional view of the coil component 11 according to the first modification, and is a view showing a cross section corresponding to the A-A cross section in Fig. 1.

[0044] In the coil component 11 according to this example, at least one (lower in this example) axial end (winding end 3b) of the coil 3 is located axially outward of the magnetic core 2. The fixing means for fixing the coil 3 is the winding end 3b, which is the winding 3a of the coil 3 at at least one (lower in this example) end. The inner diameter of the winding of the coil 3 at (at least a part of) the winding end 3b is smaller than the outer diameter of the upper or lower surface (lower in this example) of the magnetic core 2 that faces the winding end 3b. In addition, the overlap width between the winding end 3b and the magnetic core 2 is smaller than half the wire width of the coil 3. By configuring the coil 3 in this way, it is possible to prevent the magnetic powder 4 from getting between the windings 3a.

[0045] According to the above configuration, one of the winding end portions 3b of the coil 3, which has a smaller winding diameter, is positioned axially outward from the magnetic core 2, and the magnetic core 2 is inserted into the coil 3, thereby enabling the relative positioning of the magnetic core 2 and the coil 3.

[0046] With regard to the "upper or lower surface of the magnetic core 2 facing the winding end 3b," it is preferable that the winding end 3b, which has a small inner diameter, is located below the lower surface of the magnetic core 2. With this configuration, the magnetic core 2 and the winding end 3b come into contact with each other due to the weight of the magnetic core 2, making it easy to position the coil 3 and the magnetic core 2 relative to each other when molding the coating (magnetic powder 4).

[0047] <Second Modification> The coil 3 according to the above embodiment has been described as being a solenoid wound coil (single layer structure) made of rectangular wire, but the present invention is not limited to this structure, and may be made of round wire, or may be a multi-layer structure rather than a single layer structure.

[0048] Next, a coil component 21 according to a second modified example will be described with reference mainly to Fig. 7. Fig. 7 is a cross-sectional view of the coil component 21 according to the second modified example, which is a view showing a cross section corresponding to the A-A cross section in Fig. 1.

[0049] The coil component 21 includes a two-layer coil 23 having a round wire winding 23a. In the coil component 21 according to this example, at least one (lower in this example) axial end (winding end 23b) of the coil 23 is located axially outward of the magnetic core 2 housed in the central core 23c of the coil 23. The fixing means for fixing the coil 23 is at least one (lower in this example) end, the winding end 23b, which is provided on the inner layer of the winding 23a of the coil 23. The inner winding diameter of the coil 23 at (at least a part of) the winding end 23b is smaller than the outer diameter of the upper or lower surface (lower in this example) of the magnetic core 2 that faces the winding end 23b.

[0050] Furthermore, the combination of the winding end 23b provided on one axial end of the coil 23 (the lower end in this example) and the turn covering its outer periphery is formed to overlap the combination of the turn of the winding 3a adjacent above the winding end 23b and the turn covering the outer periphery of the winding 3a. Specifically, the turn covering the outer periphery of the winding end 23b is formed to overlap the turn of the winding 3a adjacent above the winding end 23b. This configuration of the coil 23 makes it possible to prevent the magnetic powder 4 from entering between the windings 23a.

[0051] As in this example, if the winding end 23b is formed only at the end where the winding starts of the coil 23, the coil 23 may have any number of layers (a configuration in which any number of layers are stacked in a direction perpendicular to the axial direction).

[0052] Furthermore, even in a coil with a multilayer structure (a structure in which layers are stacked in a direction perpendicular to the axial direction), winding ends may be provided at the top and bottom (winding start and winding end) ends. For example, such a structure can be realized as long as the coil has a multilayer structure but ends winding on the innermost layer (a coil in which the final turn of the winding is on the innermost layer).

[0053] The above embodiments and modifications encompass the following technical concepts: (1) A coil component comprising: a coil; a magnetic core housed inside the coil; and fixing means for fixing the magnetic core to the coil so that the magnetic core is positioned within the coil in the axial direction. (2) The coil component described in (1), wherein at least one end of the coil in the axial direction is located outside the magnetic core in the axial direction, the fixing means being a winding end portion of the coil at the at least one end, and the inner winding diameter of the coil at the winding end portion is smaller than the outer diameter of the top or bottom surface of the magnetic core facing the winding end portion. (3) The coil component described in (2), wherein both end portions of the coil in the axial direction are located outside the magnetic core in the axial direction, and the fixing means being a winding end portion of the coil at the both end portions, and the inner winding diameter of the coil at the winding end portion is smaller than the outer diameter of the top and bottom surfaces of the magnetic core facing the winding end portion. (4) The coil component according to (3), further comprising a coating having a magnetic permeability lower than that of the magnetic core, the coating enclosing the coil and the magnetic core, wherein the both ends of the coil are in surface contact with the upper surface and the lower surface of the magnetic core, respectively, and press the upper surface and the lower surface of the magnetic core from both sides in the axial direction. (5) The coil component according to any one of (1) to (4), further comprising a coating having a magnetic permeability lower than that of the magnetic core, the coating enclosing the coil and the magnetic core.

[0054] 1, 11, 21 Coil component 2 Magnetic core 3, 23 Coil 3a, 23a Winding 3b, 23b Winding end (fixing means) 3c, 23c Core 4 Magnetic powder (coating)

Claims

1. A coil and A magnetic core accommodated inside the coil; and a fixing means for fixing the magnetic core to the coil so that the magnetic core is positioned within the coil in the axial direction.

2. both ends of the coil in the axial direction are located outside the entirety of the magnetic core in the axial direction, and the magnetic core is contained within the coil in the axial direction, 2. The coil component according to claim 1, wherein the fixing means is a winding end portion which is a winding of the coil at both ends, and an inner winding diameter of the coil at the winding end portion is smaller than each of the outer diameters of the upper and lower surfaces of the magnetic core which face the winding end portion.

3. Both ends of the coil in the axial direction are located outside the magnetic core in the axial direction, the fixing means being winding ends of the coil at both ends, 2. The coil component according to claim 1, wherein the two ends of the coil are in surface contact with the upper and lower surfaces of the magnetic core that face the winding ends, respectively, and press the upper and lower surfaces of the magnetic core from both sides in the axial direction by the elastic restoring force of the coil.

4. The magnetic core further includes a coating having a lower magnetic permeability than the magnetic core. The coil component according to claim 1 , wherein the coating encloses the coil and the magnetic core.

5. At least one end of the coil in the axial direction is located outside the magnetic core in the axial direction, the fixing means being a winding end portion of the coil at the at least one end portion, The coil component according to claim 1 , wherein an overlapping width between the end portion and the magnetic core when viewed in the axial direction is smaller than half a line width of the coil.