Magnetic core unit and noise filter using it

Abstract

To provide a magnetic unit which can suppress reduction in magnetic characteristics due to a stress caused by shrinkage in curing of an adhesive used in fixation of a magnetic core while surely obtaining a fixation force of the magnetic core in a case, and a noise filter using the same.SOLUTION: A magnetic core unit has: a resin case that is formed by combining a plurality of case members 10 and 20 and has a plurality of annular space parts arranged in the same axial line direction; and annular magnetic cores 5 stored in each of the annular space parts of the resin case, in which each of the case members has a plurality of projections 71 projecting in the axial line direction in the annular space parts. The annular magnetic cores are wound bodies around which an Fe group amorphous alloy strip or an Fe group nanocrystal alloy strip is around, and that has an end face facing an inner periphery and an outer periphery, the annular magnetic cores and the resin case are bonded and fixed to each other so that a surface where the projections of the case member are formed and the end faces of the annular magnetic cores face each other, and a through hole is provided on the inner peripheral side of the annular magnetic cores.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a magnetic core unit including a plurality of annular magnetic cores covered with a resin case, and a noise filter such as a choke coil using the same.

Background Art

[0002] In a path where a relatively large current exceeding 100 A flows, such as between an in-vehicle charging circuit of a hybrid vehicle or an electric vehicle and an external power supply, or between an AC motor and a power supply circuit, a bus bar (a bar-shaped thick copper plate) is used. Since the current flowing through the bus bar becomes a noise source, in consideration of the influence on peripheral electronic devices, a magnetic core is arranged in the current path, and a noise filter is configured by passing the bus bar through it. In such a noise filter, a magnetic core unit in which the periphery of the magnetic core is covered with a resin member is used to insulate the bus bar from the magnetic core or other members.

[0003] Although the form of the magnetic core unit varies, Patent Document 1 discloses a noise filter having a core case structure in which annular magnetic cores are coaxially stacked. As shown in FIG. 17, it is composed of a resin case including an upper core case 510, a lower core case 530, an intermediate core case 520, and a connecting member 700, and a plurality of magnetic cores 610, 620 housed in an annular housing portion formed in the resin case. Slit grooves are provided on the inner peripheral sides of the upper core case 510 and the lower core case 530, and the connecting member 700 is fitted therein and connected together with the intermediate core case 520 to form a core case structure in which the magnetic cores 610, 620 are housed in the annular housing portion. The depth of the annular housing portion corresponds to the thickness of the magnetic cores 610, 620, and the magnetic cores 610, 620 are sandwiched by the upper core case 510, the lower core case 530, and the intermediate core case 520 and the whole is fixed.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

[0005] In paths where relatively large currents flow, metallic magnetic materials with a higher saturation magnetic flux density than ferrite are selected as the magnetic material for the magnetic core used in noise filters. For example, Fe-based amorphous alloys and Fe-based nanocrystalline alloys are often used. Noise filters using annular magnetic cores, which are made by winding thin strips of Fe-based amorphous alloy or Fe-based nanocrystalline alloy (hereinafter sometimes referred to as alloy strips) in a ring shape, can easily obtain high impedance over a wide frequency range of several kHz to several MHz, and are suitable for preventing malfunctions of in-vehicle electronic equipment due to noise in automobiles that employ vehicle control systems that perform data communication between multiple electronic control devices via an in-vehicle LAN (Local Area Network).

[0006] On the other hand, magnetic materials such as Fe-based amorphous alloys and Fe-based nanocrystalline alloys have characteristics such as high magnetostriction, sensitivity to shock and stress, and brittleness in their thin bands. Therefore, in conventional noise filters, the method of holding the magnetic core in the annular housing with a core case may result in deterioration of magnetic properties such as increased coercivity and decreased permeability. Furthermore, if the holding force is insufficient, the magnetic core may move within the annular housing, and there is a risk that the magnetic core itself may be damaged by collision with the core case.

[0007] Therefore, the annular housing portion is made to be approximately the same thickness as, or thicker than, the magnetic core, and the core case and magnetic core are bonded and fixed together. However, even when the magnetic core is fixed by bonding, the problem of stress being applied to the magnetic core due to shrinkage caused by the hardening of the adhesive, resulting in deterioration of magnetic properties to varying degrees, still remains. As will be described in detail later, this problem was particularly pronounced in structures using multiple magnetic cores, such as the conventional noise filter shown in Patent Document 1.

[0008] Therefore, the present invention aims to provide a magnetic core unit that can obtain fixing force for the magnetic core within a case using an adhesive, while suppressing the deterioration of magnetic properties due to stress caused by shrinkage during adhesive curing, and a noise filter using the same. [Means for solving the problem]

[0009] The first invention is a core unit comprising a resin case having multiple annular spaces arranged in the same axial direction, and an annular magnetic core housed in each of the annular spaces of the resin case, wherein each of the case members is provided with multiple protrusions that extend in the axial direction in the annular space, the annular magnetic core is a wound body having an inner circumference and an outer circumference facing end faces, formed by winding a thin strip of Fe-based amorphous alloy or a thin strip of Fe-based nanocrystalline alloy, and the annular magnetic core and the resin case are bonded and fixed such that the surface of the case member on which the protrusions are formed faces the end face of the annular magnetic core, and at least two of the annular magnetic cores are arranged side by side.

[0010] In the magnetic core unit of the present invention, it is preferable that the annular magnetic core has a through hole on its inner circumference, and that the through hole is partitioned in the axial direction by a partition formed by a plurality of case members.

[0011] In the magnetic core unit of the present invention, the resin case includes a first case member and a second case member, and each of the first case member and the second case member has a groove-shaped opening in the cross-sectional shape when cut in the axial direction, the first case member has one groove-shaped opening that opens in the axial direction, and the second case member has two groove-shaped openings that open in the axial direction and in opposite directions to each other, and it is preferable to combine the second case member with two of the first case members and combine the groove-shaped openings of the first case member and the groove-shaped openings of the second case member to form two annular housing portions.

[0012] In the magnetic core unit of the present invention, it is preferable that both ends of the resin case in the axial direction be made into honeycomb structures.

[0013] The second invention is a noise filter composed of a plurality of busbars and a magnetic core unit of the first invention, wherein the busbar is passed through the through-hole of the magnetic core unit.

Advantages of the Invention

[0014] According to the present invention, it is possible to provide a magnetic core unit capable of suppressing a decrease in magnetic characteristics due to stress caused by shrinkage during curing of an adhesive while obtaining a fixing force of the magnetic core in a case by the adhesive, and a noise filter using the same.

Brief Description of the Drawings

[0015] [Figure 1] It is a perspective view of a magnetic core unit according to an embodiment of the present invention. [Figure 2] It is an exploded perspective view of the magnetic core unit shown in FIG. 1. [Figure 3] It is a perspective view of a noise filter using the magnetic core unit shown in FIG. 1. [Figure 4] It is a front view of a first case member used for a magnetic core unit according to an embodiment of the present invention. [Figure 5] It is a partial cross-sectional view taken along line b-b' of the lower surface of the first case member shown in FIG. 4. [Figure 6] It is a rear view of the first case member shown in FIG. 4. [Figure 7] It is a partial cross-sectional view taken along line b-b' of the right side surface of the first case member shown in FIG. 4. [Figure 8] It is an enlarged view of part A of the first case member shown in FIG. 7. [Figure 9] It is a front view of a second case member used for a magnetic core unit according to an embodiment of the present invention. [Figure 10] It is a partial cross-sectional view taken along line c-c' of the lower surface of the second case member shown in FIG. 9. [Figure 11] It is a partial cross-sectional view taken along line c-c' of the right side surface of the second case member shown in FIG. 9. [Figure 12]It is an enlarged view of part B of the second case member shown in FIG. 11. [Figure 13] It is a perspective view of an annular core used in a core unit according to an embodiment of the present invention. [Figure 14] It is a front view of a core unit according to an embodiment of the present invention. [Figure 15] It is a partial cross-sectional view taken along line a-a' of the lower surface of the core unit shown in FIG. 14. [Figure 16] It is a partial cross-sectional view taken along line a-a' of the right side surface of the core unit shown in FIG. 14. [Figure 17] It is an exploded perspective view of a conventional noise filter.

Embodiments for Carrying Out the Invention

[0016] Hereinafter, embodiments of the present invention will be described with reference to the drawings. However, the present invention is not limited thereto. In this specification, in the description of the structure, as a relative positional relationship, in some cases, one direction will be described as the upper side and the opposite direction as the lower side with reference to the drawings, but this does not indicate a common positional relationship or direction among the drawings. Also, in part or all of the figures, structural parts that are unnecessary for the description are omitted, and there are parts that are enlarged or otherwise illustrated to facilitate the description. The shapes and the like shown in the description are not limited only to those descriptions and drawings unless otherwise specified. Furthermore, in the description, the same names and reference numerals indicate the same or similar members, and detailed descriptions may be omitted even if they are illustrated.

[0017] Figure 1 is a perspective view showing one embodiment of the magnetic core unit, and Figure 2 is an exploded perspective view thereof. As shown, the magnetic core unit 1 of this embodiment has an oval prism shape with a plane facing the z-axis direction and a curved surface facing the x-axis direction on its side. By arranging the plane of the magnetic core unit 1 to face the xy plane, it is possible to create a low-profile noise filter in the z-axis direction. Two first case members 10 are arranged in the y-axis direction of the magnetic core unit 1, and a second case member 20 is positioned between the first case members 10. Each of the first case member 10 and the second case member 20 is formed from a resin material by a known method such as injection molding. In the illustrated example, the first case members 10 located at both ends of the magnetic core unit 1 have the same structure, but they may be different.

[0018] Annular magnetic cores 5 are positioned on both sides of the second case member 20 in the y-axis direction. As will be described in detail later, the annular magnetic cores 5 are housed in an annular space formed by combining the first case member 10 and the second case member 20, and are bonded and fixed to the first case member 10 and the second case member 20, respectively, by adhesive. The first case member 10 and the second case member 20 have a structure in which they are provided with protrusions that extend inward in the annular space.

[0019] The alloy strips that make up the annular magnetic core 5 tend to have greater waviness the wider they are made, and the packing factor of a magnetic core using such alloy strips tends to decrease. It is known that a decrease in packing factor affects the impedance characteristics of the noise filter. Therefore, in the magnetic core unit of this embodiment, by using multiple annular magnetic cores 5 made of alloy strips with small waviness obtained by cutting wide alloy strips, the magnetic path cross-sectional area is secured and the decrease in the packing factor of the magnetic core is prevented, thereby preventing deterioration of the characteristics of the noise filter, such as the inability to obtain high impedance at a predetermined frequency.

[0020] In the magnetic core unit 1, which is constructed by combining the various components, the annular space is closed by the first case member 10 and the second case member 20, so that the annular magnetic core 5 housed in the annular space is not visible on the surface. Both ends of the magnetic core unit 1 in the y-axis direction are honeycomb structure parts 110, which are constructed as a collection of rows of holes formed by multiple bottomed holes 111 and 112 in the first case member 10. Here, the shape of the holes in the honeycomb structure is not limited to a hexagonal shape. In addition, the magnetic core unit 1 has two through holes 131 and 132 formed on the inner circumference side of the annular magnetic core 5, through which a busbar separated by a partition part 141 passes.

[0021] Figure 3 is an external perspective view of a noise filter according to one embodiment of the present invention. The noise filter includes a magnetic core unit 1 and busbars 101 and 102. Busbars 101 and 102 are passed through through holes 131 and 132, respectively, which are separated by a partition portion 141 of the magnetic core unit 1, with their planes facing the same direction. The through holes 131 and 132 of the magnetic core unit 1 allow for easy positioning and placement of the busbars 101 and 102. Furthermore, since the spatial distance between busbars 101 and 102 is determined by the partition portion 141, electrical insulation can be easily ensured. In addition, since the annular magnetic core 5 is placed in an annular space closed by the first case member 10 and the second case member 20, it is also easy to ensure electrical insulation between the busbars 101 and 102 and the annular magnetic core 5.

[0022] In the illustrated noise filter, the ends of the busbars 101 and 102 are aligned at equal intervals and extend in a straight line. The shape of the busbars 101 and 102 is not limited to this, and they can be transformed into various shapes as long as they can pass through the through holes 131 and 132 of the magnetic core unit 1. For example, the ends of the busbars 101 and 102 may be bent, for example, and they may be formed in an L-shape so that the spacing between the busbars 101 and 102 widens at at least one end of the magnetic core unit 1.

[0023] The space in which noise filters are placed is often limited, and there is always a requirement to make noise filters small. When trying to make a noise filter small, the magnetic core unit 1 and the busbars 101 and 102 are naturally placed in close proximity. When power is supplied to the busbars 101 and 102 and a large current flows through them, the busbars generate heat due to copper losses due to resistance and become hot, so the magnetic core unit 1, which is in close proximity to the busbars 101 and 102, is also prone to becoming hot. If the magnetic core unit 1 becomes excessively hot, the first case member 10 and the second case member 20 may suffer thermal damage. Furthermore, there are differences in the coefficient of linear expansion between each case member 10, 20, the annular magnetic core 5, and the adhesive used to fix them. As temperature changes, dimensional changes due to the difference in the coefficient of linear expansion can alter the stress applied to the annular magnetic core 5, potentially degrading its magnetic properties. In addition, the adhesive fixing of the annular magnetic core 5 may come undone, causing the annular magnetic core 5 to fall out within the annular space. To address these problems, the magnetic core unit 1 of this embodiment has a honeycomb structure at its ends to increase its surface area and improve heat dissipation. This suppresses temperature rise and prevents damage to the case members and degradation of magnetic properties.

[0024] As shown in Figures 1 and 2, the magnetic core unit of this embodiment consists of two types of case members, a first case member and a second case member, and an annular magnetic core. The structure and materials of each will be described in detail.

[0025] (Structure of the first case component) Figure 4 is a front view of the first case member, Figure 5 is a partial cross-sectional view of its lower surface along line b-b', Figure 6 is a rear view thereof, Figure 7 is a partial cross-sectional view of its right side along line b-b', and Figure 8 is a partially enlarged view of a projection provided on the first case member. The first case member 10 has two through holes 55 and 56 arranged side by side via a partition 51 located in its center. The shape of the through holes 55 and 56 is not particularly limited as long as it does not obstruct the passage of the busbars, but since the cross-sections of the busbars 101 and 102 are rectangular, in the illustrated example they are oval-shaped with one of the circular arcs cut off.

[0026] When the first case member 10 is viewed from the top, an annular bottom plate portion 53 appears around the through holes 55 and 56. As shown in Figures 4 and 5, its inner and outer edges have an inner cylindrical wall and an outer cylindrical wall that extend concentrically upward, with the upper end being open. The inner cylindrical wall constitutes part of the inner wall portion 81 of the first case member 10, and the outer cylindrical wall constitutes part of the outer wall portion 91. The inner wall portion 81 (inner cylindrical wall), the outer wall portion 91 (outer cylindrical wall), and the annular bottom plate portion 53 form a bottomed annular space 63 (opening). As shown in Figures 5 and 7, the bottomed annular space 63 has a groove-shaped cross-section when cut in the direction of the through holes 55 and 56. Its depth is set according to the thickness (height) of the annular magnetic core 5, and it is capable of accommodating at least a portion of the annular magnetic core 5 in the height direction. In the illustrated example, the upper end of the partition 51 is formed flat and at the same height as the inner wall 81 and the outer wall 91, but it may be at a different height.

[0027] Furthermore, the annular base plate portion 53 of the closed annular space 63 is provided with a plurality of projections 71 that protrude toward the opening side. The projections 71 allow the end face 8 of the annular magnetic core housed in the closed annular space 63 to face one surface of the annular base plate portion 53 without directly contacting it, with a gap of at least the height of the projections 71 between them. The shape of the projections 71 is not particularly limited, and can be circular, polygonal, etc. In the examples shown in Figures 4 and 8, the projections 71 are disc-shaped with a flat upper end, but they may be formed in a hemispherical or truncated conical shape to taper towards the end face 8 of the annular magnetic core 5 if the area in contact with it is reduced. The shape visible from the top side may also be ring-shaped or divided into multiple parts. In the illustrated examples, projections 71 are provided at four axially symmetrical positions, but at least two or more projections should be formed at predetermined intervals in positions where the annular magnetic core can be stably positioned.

[0028] A honeycomb structure 110 is formed on the lower surface of the first case member 10. The honeycomb structure 110 is located below the bottomed annular space 63 and includes a plurality of bottomed holes 111 and 112 arranged in multiple layers around the through holes 55 and 56. The shape of the bottomed holes 111 and 112 is not particularly limited. The bottomed holes 111 adjacent to the through holes 55 and 56, and the bottomed holes 112 surrounding them, are partitioned by radial walls connected to the inner wall 81 and the outer wall 91, as well as walls provided between the bottomed holes 111 and 112, thereby increasing the surface area and ensuring strength.

[0029] (Structure of the second case component) Figure 9 is a front view of the second case member, Figure 10 is a partial cross-sectional view of its lower surface along line c-c', Figure 11 is a partial cross-sectional view of its right side along line c-c', and Figure 12 is a partially enlarged view of a projection provided on the second case member. The back of the second case member appears the same as in the front view, so it is omitted. The second case member 20 has two through holes 57 and 58 arranged side by side, separated by a partition 52 located in its center. The shape of the through holes 57 and 58 is the same as that of the through holes 55 and 56 of the first case member 10, and there are no limitations on their shape as long as they do not obstruct the passage of the busbar.

[0030] When the second case member 20 is viewed from the top, an annular bottom plate portion 54 appears around the through holes 57 and 58. As shown in Figure 10, its inner and outer edges have an inner cylindrical wall and an outer cylindrical wall that extend concentrically upward, with the upper end being open. The inner cylindrical wall constitutes part of the inner wall portion 82 of the second case member 20, and the outer cylindrical wall constitutes part of the outer wall portion 92. The inner wall portion 82 (inner cylindrical wall), the outer wall portion 92 (outer cylindrical wall), and the annular bottom plate portion 53 form a bottomed annular space 64 (opening). As shown in Figures 10 and 11, the bottomed annular space 64 has a groove-shaped cross-section in the direction of penetration of the through holes 57 and 58. Its depth is set according to the thickness (height) of the annular magnetic core 5, and it is possible to accommodate at least a part of the annular magnetic core 5 in the height direction. In the illustrated example, the depth is approximately the same as the height of the annular magnetic core.

[0031] A step 32 is provided around the entire circumference of the upper ends of the inner wall portion 82 and the outer wall portion 92, and is shaped to receive the upper ends of the inner wall portion 82 and the outer wall portion 92 of the first case member 10. In the illustrated example, the upper end of the partition portion 52 is lower than the inner wall portion 82 and the outer wall portion 92, is formed flat, and is at the same height as the lower end of the step 32. However, depending on the structure of the first case member 10, it may be at a different position from the lower end of the step 32.

[0032] As shown in Figures 11 and 12, the annular bottom plate portion 54 of the closed annular space 64 is provided with a plurality of projections 72 that protrude toward the opening side. The projections 72 allow the end face 8 of the annular magnetic core housed in the closed annular space 64 to face the annular bottom plate portion 54 without directly contacting it, with a gap of at least the height of the projections 72. The shape of the projections 72 is the same as that of the projections 71 of the first case member 10. The number, position, dimensions, etc., may be the same as or different from those of the projections 71.

[0033] Although not shown in the diagram, the back surface of the second case member 20, as viewed from the front, has an annular bottom plate portion 54 around the through holes 57 and 58. The structure viewed from the back is the same as that viewed from the front, so no explanation is given. The second case member 20 has two groove-shaped bottomed annular spaces 64 that open in opposite directions in the through-direction of the through holes 57 and 58, and the bottomed annular spaces 64 are formed in parallel in the same direction via a partition wall 59. In the second case member 20 formed by injection molding, a draft angle of about 0.5 to 2° is provided on the inner wall on the bottomed annular space 64 side. As a result, the bottomed annular space 64 is wider on the opening side and narrower on the annular bottom plate portion 54 side, and the difference becomes larger as the depth increases, making it easy for the outer shape of the second case member 20 to become larger. In the magnetic core unit of this embodiment, the bottomed annular spaces 64 of the second case member 20 are made into multiple spaces, and the depth of each is made shallow. This reduces the influence of the draft angle on the external dimensions and increases the effective volume ratio for accommodating the annular magnetic core 5 in the bottomed annular space 64.

[0034] The first case member 10 and the second case member 20 are preferably formed from a resin having excellent insulating properties, heat resistance, and moldability. Specifically, polyphenylene sulfide, liquid crystal polymer, polyethylene terephthalate, polybutylene terephthalate, nylon 66, etc., are preferred.

[0035] (Tonal magnetic core) Figure 13 is a perspective view showing the appearance of an annular magnetic core. It is a wound body having an inner circumferential surface 6, an outer circumferential surface 7, and an end face 8 facing the annular magnetic core 5, formed by winding an Fe-based amorphous alloy strip or an Fe-based nanocrystalline alloy strip. The end face 8 of the annular magnetic core 5 is a laminated surface that appears as a stack of strips. The Fe-based amorphous alloy strip preferably has a saturation magnetic flux density Bs of 1.4 T or higher. For example, Fe-based amorphous alloy strips such as the Fe-Si-B system represented by Metglas® 2605SA1 material can be used. Furthermore, compositions such as Fe-Si-BC system and Fe-Si-BC-Cr system containing other elements can also be adopted. A portion of Fe may be substituted with Co, Ni, etc. An example of the alloy composition of the Fe-based amorphous alloy strip used in the embodiments of the present invention is Fe a Si b B c C d M e (However, M is preferably at least one element selected from the group consisting of Cr, Mo, Mn, Zr, and Hf, and expressed in atomic percent as follows: 50≦a≦90, 2≦b≦15, 5≦c≦30, 0≦d≦3, 0≦e≦10, a+b+c+d+e=100). The alloy composition is not particularly limited and can be selected according to the required properties.

[0036] Fe-based nanocrystalline alloy thin strips are preferably those having a saturation magnetic flux density Bs of 1.2T or higher. Specifically, for example, amorphous alloy thin strips for Fe-based nanocrystalline alloys such as Fe-Si-B-Cu-Nb, Fe-Cu-Si-B, Fe-Cu-B, and Fe-Ni-Cu-Si-B systems can be used. Alloys in which some of these elements are substituted, and alloys with other elements added may also be used. An example of an alloy composition used in the embodiments of the present invention is Fe 100-x-y Ax X y (However, A is Cu and / or Au, and X is at least one element selected from the group consisting of B, Si, S, C, P, Al, Ge, B, Sn, Nb, Mo, and Cr), preferably represented by atomic percentages of 0 < x ≦ 5 and 10 ≦ y ≦ 24. A part of Fe may be replaced with Ni or Co, and the replacement amount is preferably 5 or less in atomic percentage. Note that a nanocrystal is a fine crystal structure with a particle size of 100 nm or less.

[0037] (Core unit) FIG. 14 is a front view showing a state in which the first case member and the second case member are combined, FIG. 15 is a partial cross-sectional view taken along the line a-a' of its lower surface, and FIG. 16 is a partial cross-sectional view taken along the line a-a' of its right side surface. The configuration shown in FIG. 14 is the same as the back surface of the first case member 10 shown in FIG. 6, so the description is omitted. Also, the annular core is omitted from each figure, and the positional relationship of each member, etc., will be described while referring to FIGS. 1, FIG. 2, etc.

[0038] As shown in FIG. 15, the second case member 20 is centered, and the first case member 10 is combined so as to be positioned above and below it. The inner cylindrical wall and the outer cylindrical wall of the first case member 10 are fitted into the step 32 of the second case member 20, so that the inner circumference 151 and the outer circumference 152 of the core unit 1 can be formed substantially without a step.

[0039] When the first case member 10 and the second case member 20 are combined, the through holes 55, 57 and the through holes 56, 58 communicate with each other to form the through holes 131, 132 of the core unit 1. Also, the partition portion 51 of the first case member 10 and the partition portion 52 of the second case member 20 are connected to form the partition portion 141 of the core unit 1. Further, a plurality of annular space portions 161 arranged in the same axial direction are formed by the bottomed annular spaces 63 and 64 of each case member, and an annular core 5 is arranged in each of them as shown in FIG. 2.

[0040] Protrusions 71 and 72 project from the annular space 161 so as to face the end 8 of the annular core 5. In the state where the first case member 10 and the second case member 20 are combined, the interval w determined by the upper ends of the protrusions 71 and 72 is wider than the height h of the annular core 5 (w>h), so as not to press the annular core 5. Also, during assembly, the protrusions 71 and 72 restrict the movement of the annular core 5 within the annular space 161. If the interval w between the protrusions 71 and 72 has an upper limit of +0.5 mm with respect to the height h of the annular core 5 (0<w - h≦0.5), it is preferable because the movement amount of the annular core 5 can be further restricted.

[0041] (Method for manufacturing a core unit) Next, an example of a method for manufacturing the core unit 1 will be described. First, the second case member 20 is placed vertically so that its bottomed annular space 64 appears vertically. Next, after applying a predetermined amount of adhesive on the surface of the annular bottom plate portion 54, the annular core 5 is housed in the bottomed annular space 64. Further, the first case member 10 with a predetermined amount of adhesive applied to the annular bottom plate portion 53 is combined so as to cover the annular core 5 from above (the first step). Subsequently, the core unit being assembled is turned upside down, a predetermined amount of adhesive is applied to the other annular bottom plate portion 54 of the second case member 20, and then another annular core 5 is housed in the bottomed annular space 64. Then, another first case member 10 with a predetermined amount of adhesive applied to the annular bottom plate portion 53 is combined so as to cover the annular core 5 from above (the second step). Next, the adhesive is cured to adhesively fix each case member 10, 20 and the annular core 5 (the third step), and the core unit 1 is completed. The adhesive is not particularly limited as long as it can adhere each member, but a thermosetting adhesive can be used, and among them, a silicone adhesive or an epoxy adhesive having a viscosity that is difficult to sag even on a vertical surface is preferable.

[0042] During the assembly process, the adhesive is not yet cured, so the annular magnetic core 5 can move easily, and in the vertical position, it sinks into the annular space 161 due to its own weight. For example, after the second step is completed, the annular magnetic core 5 in the upper annular space 161 may be shifted towards the annular bottom plate portion 54 of the second case member 20, and the annular magnetic core 5 in the lower annular space 161 may be shifted towards the annular bottom plate portion 53 of the first case member 10. If projections 71 and 72 protruding from the annular space 161 are not provided, one end face 8 of the annular magnetic core 5 will come into contact with one surface of the annular bottom plate portion 53 or annular bottom plate portion 54, and the interposed adhesive is likely to spread thinly over the end face 8 of the annular magnetic core 5. On the other end face 8 side, the gap with the annular bottom plate portion 53 or annular bottom plate portion 54 widens, and the bonding area is likely to be insufficient. In this condition, after the adhesive has hardened, the annular magnetic core 5 is susceptible to stress caused by shrinkage during the hardening of the adhesive, which may lead to deterioration of its magnetic properties or insufficient adhesion, resulting in an inability to reliably obtain a fixing force.

[0043] On the other hand, by providing projections 71 and 72 that protrude into the annular space 161, even if the annular magnetic core 5 shifts to one side within the annular space 161 during assembly, a space is secured between the end face 8 of the annular magnetic core 5 and the annular bottom plate portion 53 or annular bottom plate portion 54, preventing the end face 8 of the annular magnetic core 5 from coming into contact with the annular bottom plate portion 53 or annular bottom plate portion 54. Since the applied adhesive accumulates in the space, even if the annular magnetic core 5 moves between the projections 71 and 72, it is possible to prevent the adhesive from unnecessarily wetting and spreading across the end face 8 of the annular magnetic core 5. Furthermore, by limiting the amount of movement of the annular magnetic core 5 between the projections 71 and 72, it is possible to prevent insufficient bonding area on the end face 8 of the annular magnetic core 5. This ensures a secure fixing force between the annular magnetic core 5 and each case member 10, 20 while suppressing the deterioration of magnetic properties due to stress caused by shrinkage during adhesive curing.

[0044] Furthermore, by limiting the amount of movement of the annular magnetic core 5 and reducing the amount of kinetic energy supplied to the annular magnetic core 5 even if the annular magnetic core 5 becomes loose after bonding, it is possible to prevent the annular magnetic core 5 from colliding with the inner wall of the case in the annular space 161 and being damaged. [Explanation of symbols]

[0045] 1. Magnetic core unit 5. Annular magnetic core 10. First case component 20. Second case component 71, 72 Protrusion 161 Circular space 101, 102 Bus Bar

Claims

1. It comprises a resin case composed of multiple case members and having multiple annular spaces arranged in the same axial direction, and an annular magnetic core housed in each of the multiple annular spaces of the resin case, Each of the aforementioned case members is provided with a plurality of protrusions that extend in the axial direction in each of the aforementioned annular spaces, The aforementioned annular magnetic core is a wound body having an inner circumference and an outer circumference with opposing end faces, formed by winding a thin strip of Fe-based amorphous alloy or a thin strip of Fe-based nanocrystalline alloy. The annular magnetic core and the resin case are bonded and fixed together such that the surface on which the plurality of protrusions are formed in each of the plurality of case members faces the end face of the annular magnetic core. At least two of the aforementioned annular magnetic cores are arranged side by side, A magnetic core unit in which the end face of the annular magnetic core is not in direct contact with the surface.

2. A magnetic core unit according to Claim 1, A magnetic core unit in which the end face and the surface of the annular magnetic core face each other with a distance equal to the height of each of the plurality of protrusions.

3. A magnetic core unit according to Claim 1, A magnetic core unit in which each of the inner walls of the aforementioned multiple annular spaces is provided with a draft angle of 0.5° to 2°.

4. A magnetic core unit according to Claim 1, The aforementioned plurality of case members include a first case member and a second case member. The first case member has a first surface on which a first projection is formed, The second case member has a second surface on which a second projection is formed, In the state in which the first case member and the second case member are combined, Let w be the distance between the upper end of the first projection and the upper end of the second projection. When the height of the annular magnetic core in the direction of the aforementioned interval is h, A magnetic core unit where w > h holds true.

5. A magnetic core unit according to claim 1, The annular magnetic core has a through hole on its inner circumference side, A magnetic core unit in which the through hole is partitioned in the axial direction by a partition formed by a plurality of case members.

6. A magnetic core unit according to claim 1, The resin case includes a first case member and a second case member. Each of the first case member and the second case member has a groove-shaped opening in the cross-sectional shape when cut in the axial direction. The first case member has a groove-shaped opening that opens in the axial direction, The second case member has two groove-shaped openings that open in the axial direction and in opposite directions from each other. A magnetic core unit comprising two first case members combined with the second case member, and two annular housing sections formed by combining the groove-shaped opening of the first case member with the groove-shaped opening of the second case member.

7. A noise filter comprising a magnetic core unit according to any one of claims 1 to 6 and a plurality of busbars.

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