JP7574602B2 - Magnetic core unit and noise filter using same - Google Patents

Description

The present invention relates to a magnetic core unit having multiple annular magnetic cores covered with a resin case, and a noise filter such as a choke coil that uses the same.

Busbars (thick rod-shaped copper plates) are used in paths through which relatively large currents exceeding 100A flow, such as between the on-board charging circuit and external power source of hybrid or electric vehicles, or between AC motors and power supply circuits. Since the current flowing through the busbar can be a source of noise, a noise filter is constructed by placing a magnetic core in the current path and passing the busbar through it, taking into consideration its effect on surrounding electronic devices. In such noise filters, a magnetic core unit is used in which the magnetic core is covered with a resin material to insulate the busbar from the magnetic core or from other components.

There are various forms of magnetic core units, but Patent Document 1 discloses a noise filter with a core case structure in which circular magnetic cores are stacked coaxially. As shown in FIG. 17, it is composed of a resin case consisting of 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 storage section formed in the resin case. Slit grooves are provided on the inner circumference of the upper core case 510 and the lower core case 530, into which the connecting member 700 is fitted to connect them together with the intermediate core case 520, forming a core case structure in which the magnetic cores 610, 620 are housed in the annular storage section. The depth of the annular storage section corresponds to the thickness of the magnetic cores 610, 620, and the magnetic cores 610, 620 are sandwiched between the upper core case 510, the lower core case 530, and the intermediate core case 520 to fix the entire structure.

JP 2017-152549 A

In paths through which relatively large currents flow, metal-based 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 in which a ribbon of Fe-based amorphous alloys or Fe-based nanocrystalline alloys (hereinafter sometimes referred to as alloy ribbons) is wound into a ring shape tend to achieve high impedance over a wide frequency range from several kHz to several MHz, and are suitable for preventing malfunction of on-board electronic devices due to noise in automobiles that employ a vehicle control system that performs data communication between multiple electronic control devices via an on-board LAN (Local Area Network).

On the other hand, magnetic materials such as Fe-based amorphous alloys and Fe-based nanocrystalline alloys have characteristics such as large magnetostriction, sensitivity to shock and stress, and fragility of their ribbons. For this reason, when the magnetic core in the annular storage section is pressed and held by a core case, as in conventional noise filters, the magnetic properties can deteriorate, such as an increase in coercive force and a decrease in magnetic permeability. Furthermore, if the pressing force is insufficient, the magnetic core can move within the annular storage section, and there is a risk that the magnetic core itself will be damaged by a collision with the core case.

Therefore, the core case and the magnetic core are fixed with adhesive, with the annular storage section being made to be roughly the same thickness as the magnetic core or thicker. However, even when the magnetic core is fixed with adhesive, the magnetic core is subjected to stress due to shrinkage caused by hardening of the adhesive, and the problem of deterioration of the magnetic properties remains, although to varying degrees. Details will be described later, but this problem can be particularly noticeable in structures that use multiple magnetic cores, such as the conventional noise filter shown in Patent Document 1.

The present invention aims to provide a magnetic core unit that can secure the magnetic core inside the case with an adhesive while suppressing the deterioration of magnetic properties due to stress caused by shrinkage when the adhesive hardens, and a noise filter using the same.

The first invention is a magnetic core unit comprising a resin case formed by combining a plurality of case members and having a plurality of annular spaces arranged in the same axial direction, and annular magnetic cores housed in each of the annular spaces of the resin case, each of the case members having a plurality of protrusions protruding in the axial direction in the annular spaces, the annular magnetic cores being wound with an Fe-based amorphous alloy ribbon or an Fe-based nanocrystalline alloy ribbon and having end faces facing the inner and outer circumferences, the annular magnetic cores and the resin case being adhesively fixed so that the surface of the case member on which the protrusions are formed faces the end faces of the annular magnetic cores, and at least two of the annular magnetic cores being arranged side by side.

In the magnetic core unit of the present invention, it is preferable that the annular magnetic core has a through hole on the inner peripheral side thereof, and the through hole is partitioned in the axial direction by a partition portion formed by a plurality of case members.

In the magnetic core unit of the present invention, the resin case includes a first case member and a second case member, each of which has a groove-shaped opening in cross section cut in the axial direction, the first case member having one groove-shaped opening opening in the axial direction, and the second case member having two groove-shaped openings opening in the axial direction and opening in opposite directions, and it is preferable to combine two of the first case members with the second case member and combine the groove-shaped opening of the first case member with the groove-shaped opening of the second case member to form two annular storage sections.

In the magnetic core unit of the present invention, it is preferable that both ends of the resin case in the axial direction have a honeycomb structure.

The second invention is a noise filter composed of the magnetic core unit of the first invention and a plurality of bus bars, in which the bus bars are passed through the through holes of the magnetic core unit.

The present invention provides a magnetic core unit that uses an adhesive to secure the magnetic core inside the case while minimizing the degradation of magnetic properties due to stress caused by shrinkage when the adhesive hardens, and a noise filter using the same.

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

Below, an embodiment of the present invention will be described with reference to the drawings. However, the present invention is not limited to this. In this specification, the relative positional relationship in the description of the structure may be described with reference to the drawings, with one direction being the upper side and the opposite direction being the lower side, but this does not indicate a common positional relationship or direction between the drawings. In addition, in some or all of the figures, structural parts that are not necessary for the description are omitted, and some parts are illustrated enlarged to make the description easier. Unless otherwise specified, the shapes, etc. shown in the description are not limited to those descriptions, drawings, etc. Furthermore, in the description, the same names and symbols indicate the same or similar components, and detailed explanations may be omitted even if they are illustrated.

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 in the figure, the magnetic core unit 1 of this embodiment is an oval columnar shape with a flat surface facing the z-axis direction and a curved surface facing the x-axis direction on the side. By making it in this shape and arranging the flat surface of the magnetic core unit 1 so that it faces the xy plane, it is possible to make a noise filter with a low height 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 arranged between the first case members 10. Each of the first case member 10 and the second case member 20 is formed of a resin material by a known method such as injection molding. In the illustrated example, the first case members 10 located on both ends of the magnetic core unit 1 have the same structure, but may be different.

An annular magnetic core 5 is disposed on both sides of the second case member 20 in the y-axis direction. As will be described in detail later, the annular magnetic core 5 is housed in an annular space formed by combining the first case member 10 and the second case member 20, and is bonded and fixed to the first case member 10 and the second case member 20 by adhesive. The first case member 10 and the second case member 20 are structured to have protrusions that protrude inward in the annular space.

The wider the alloy ribbon that constitutes the annular magnetic core 5, the greater the waviness, and the more likely it is that the space factor of a magnetic core using such an alloy ribbon will decrease. It is known that a decrease in space factor affects the impedance characteristics of a noise filter. Therefore, in the magnetic core unit of this embodiment, multiple annular magnetic cores 5 are used that use alloy ribbons with small waviness obtained by cutting a wide alloy ribbon, thereby ensuring the cross-sectional area of the magnetic path and preventing a decrease in the space factor of the magnetic core, and preventing deterioration of noise filter characteristics such as an inability to obtain high impedance at a specified frequency.

In the magnetic core unit 1 constructed by combining the various components, the annular space is closed by the first case member 10 and the second case member 20, and the annular magnetic core 5 housed in the annular space is not visible from the outside. Both ends of the magnetic core unit 1 in the y-axis direction form a honeycomb structure 110 constructed as an assembly of a row of holes consisting of a plurality of bottomed holes 111, 112 formed in the first case member 10. Here, the hole shape in the honeycomb structure is not limited to a hexagonal shape. In addition, the magnetic core unit 1 has two through holes 131, 132 formed on the inner periphery of the annular magnetic core 5, through which a bus bar passes, separated by a partition portion 141.

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 bus bars 101 and 102. The bus bars 101 and 102 pass through through holes 131 and 132, which are partitioned by a partition 141 of the magnetic core unit 1, so that the plane direction is the same. The through holes 131 and 132 of the magnetic core unit 1 make it easy to position and arrange the bus bars 101 and 102. In addition, since the spatial distance between the bus bars 101 and 102 is determined by the partition 141, electrical insulation can be easily ensured. In addition, since the annular magnetic core 5 is arranged in an annular space closed by the first case member 10 and the second case member 20, electrical insulation between the bus bars 101 and 102 and the annular magnetic core 5 can also be easily ensured.

In the illustrated noise filter, both ends of the busbars 101, 102 are arranged at equal intervals and extend linearly. The shape of the busbars 101, 102 is not limited to this, and they can be modified into various shapes as long as they can pass through the through holes 131, 132 of the magnetic core unit 1. For example, the ends of the busbars 101, 102 may be bent, for example, formed into an L-shape, so that the spacing between the busbars 101, 102 is wider on at least one end side of the magnetic core unit 1.

The space in which a noise filter is placed is often limited, and there is always a demand for making the noise filter compact. When making a noise filter compact, the magnetic core unit 1 and the bus bars 101, 102 are naturally placed in close proximity to each other. When a large current flows through the bus bars 101, 102, the bus bars generate heat due to copper loss caused by resistance and reach a high temperature, and the magnetic core unit 1, which is in close proximity to the bus bars 101, 102, is also likely to reach a high temperature.
If the magnetic core unit 1 becomes extremely hot, the first case member 10 and the second case member 20 may be thermally damaged. In addition, there is a difference in the linear expansion coefficient between the case members 10 and 20, the annular magnetic core 5, and the adhesive that fixes them. The difference in linear expansion coefficients causes dimensional changes with temperature changes, which may change the stress applied to the annular magnetic core 5 and cause the magnetic properties to deteriorate. Furthermore, the adhesive fixation of the annular magnetic core 5 may be released, causing the annular magnetic core 5 to fall off within the annular space. To address such problems, the magnetic core unit 1 of this embodiment has a honeycomb structure at the end to increase the surface area and improve heat dissipation. This makes it possible to suppress temperature rise and prevent damage to the case members and deterioration of the magnetic properties.

As shown in Figures 1 and 2, the magnetic core unit of this embodiment is composed 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.

(Structure of first case member)
Figure 4 is a front view of the first case member, Figure 5 is a partial cross-sectional view taken along line bb' of the underside, Figure 6 is a rear view, Figure 7 is a partial cross-sectional view taken along line bb' of the right side, and Figure 8 is a partially enlarged view of a protrusion provided on the first case member.
Two through holes 55, 56 are formed side by side in the first case member 10 via a partition portion 51 provided in the center. The shape of through holes 55, 56 is not particularly limited as long as it does not impede the passage of the bus bars, but since the cross section of bus bars 101, 102 is rectangular, in the illustrated example, they have a half-arc ellipse with one arc portion cut off.

When the first case member 10 is viewed from the top side, the annular bottom plate portion 53 appears around the through holes 55, 56. As shown in Figs. 4 and 5, the inner edge and the outer edge have an inner cylindrical wall and an outer cylindrical wall that extend concentrically upward, and the upper end side is open. The inner cylindrical wall constitutes a part of the inner wall portion 81 of the first case member 10, and the outer cylindrical wall constitutes a 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 Figs. 5 and 7, the bottomed annular space 63 has a groove-shaped cross section that appears in a cross section cut in the penetrating direction of the through holes 55, 56. The depth is set according to the thickness (height) of the annular magnetic core 5, and can accommodate at least a part of the height direction of the annular magnetic core 5. 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.

The annular bottom plate portion 53 of the bottomed annular space 63 is provided with a plurality of protrusions 71 protruding toward the opening side. The protrusions 71 allow the end face 8 of the annular magnetic core housed in the bottomed annular space 63 to face one surface of the annular bottom plate portion 53 with a distance of at least the height of the protrusions 71 without directly contacting the surface. The shape of the protrusions 71 is not particularly limited, and may be circular, polygonal, or the like. In the examples shown in Figures 4 and 8, the protrusions 71 are disk-shaped with a flat upper end, but may be tapered into a hemispherical or truncated cone shape if the area in contact with the end face 8 of the annular magnetic core 5 is reduced. The shape seen from the top side may also be ring-shaped or divided into multiple parts. In the example shown, the protrusions 71 are provided axially symmetrically at four positions, but they may be formed at least in two or more positions at a predetermined interval where the annular magnetic core can be stably arranged.

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

(Structure of second case member)
Fig. 9 is a front view of the second case member, Fig. 10 is a partial cross-sectional view taken along line c-c' of the underside of the second case member, Fig. 11 is a partial cross-sectional view taken along line c-c' of the right side of the second case member, and Fig. 12 is a partially enlarged view of a protrusion provided on the second case member. The back of the second case member is omitted since it appears the same as in the front view.
The second case member 20 has two through holes 57, 58 arranged side by side via a partition portion 52 provided in the center thereof. The form of the through holes 57, 58 is similar to that of the through holes 55, 56 of the first case member 10, and there are no limitations on the shape, etc., as long as it does not impede the passage of the bus bars.

When the second case member 20 is viewed from above, the annular bottom plate portion 54 appears around the through holes 57 and 58. As shown in FIG. 10, the inner edge and the outer edge have an inner cylindrical wall and an outer cylindrical wall that extend concentrically upward, and the upper end side is open. The inner cylindrical wall constitutes a part of the inner wall portion 82 of the second case member 20, and the outer cylindrical wall constitutes a 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 FIG. 10 and FIG. 11, the bottomed annular space 64 has a groove-shaped cross section in the cross section of the through holes 57 and 58 in the penetrating direction. The depth is set according to the thickness (height) of the annular magnetic core 5, and can accommodate at least a part of the height direction of the annular magnetic core 5. In the illustrated example, the depth is approximately the same as the height of the annular magnetic core.

A step 32 is provided around the entire periphery 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 example shown, the upper end of the partition portion 52 is located 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. Note that the step may be located at a different position from the lower end of the step 32 to match the structure of the first case member 10.

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

Although not shown, the rear surface of the second case member 20 has an annular bottom plate portion 54 around the through holes 57 and 58, as seen from the front side. The structure seen from the rear side is the same as that seen from the front side, so a description is omitted. The second case member 20 has two groove-shaped bottomed annular spaces 64 that open in opposite directions in the penetration 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 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 becomes deeper, so that the outer shape of the second case member 20 tends to become larger. In the magnetic core unit of this embodiment, the bottomed annular spaces 64 of the second case member 20 are multiple, and each of them has a shallow depth. This reduces the effect of the draft on the external dimensions and increases the volume ratio available for housing the annular magnetic core 5 in the bottomed annular space 64.

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

(Annular core)
FIG. 13 is a perspective view showing the appearance of the annular magnetic core. The annular magnetic core 5 is a wound body having an inner peripheral surface 6 and an end surface 8 facing an outer peripheral surface 7, in which an Fe-based amorphous alloy ribbon or an Fe-based nanocrystalline alloy ribbon is wound, and the end surface 8 of the annular magnetic core 5 is a laminated surface where the ribbons are stacked. The Fe-based amorphous alloy ribbon preferably has a saturation magnetic flux density Bs of 1.4 T or more. For example, an Fe-based amorphous alloy ribbon such as an Fe-Si-B system represented by Metglas (registered trademark) 2605SA1 material can be used. Furthermore, compositions such as an Fe-Si-B-C system or an Fe-Si-B-C-Cr system containing other elements can also be adopted. A part of Fe may be replaced with Co, Ni, or the like. An example of the alloy composition of the Fe-based amorphous alloy ribbon used in the embodiment of the present invention is preferably represented by Fe _a Si _b B _c C _{d Me} (wherein M is at least one element selected from the group consisting of Cr, Mo, Mn, Zr and Hf, and the atomic percentages are 50≦a≦90, 2≦b≦15, 5≦c≦30, 0≦d≦3, 0≦e≦10, and a+b+c+d+e=100). The alloy composition is not particularly limited, and can be selected according to the required characteristics.

The Fe-based nanocrystalline alloy ribbon preferably has a saturation magnetic flux density Bs of 1.2 T or more. Specifically, for example, amorphous alloy ribbons 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 can be used. Alloys in which some of these elements are replaced and alloys to which other elements are added may also be used. An example of an alloy composition used in an embodiment of the present invention is preferably represented by Fe _100-x-y A _x X _y (wherein 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), and is preferably represented by 0<x≦5, 10≦y≦24 in atomic %. A part of Fe may be replaced by Ni or Co, and the amount of replacement is preferably 5 atomic % or less. Note that nanocrystals are microcrystalline structures with grain sizes of 100 nm or less.

(Magnetic core unit)
Fig. 14 is a front view showing the state in which the first case member and the second case member are assembled, Fig. 15 is a partial cross-sectional view taken along line a-a' of the lower surface, and Fig. 16 is a partial cross-sectional view taken along line a-a' of the right side surface. Note that the configuration shown in Fig. 14 is similar to the rear surface of the first case member 10 shown in Fig. 6, so a description thereof will be omitted. The annular magnetic core is also omitted from each figure, and the positional relationship of each member will be described with reference to Figs. 1 and 2.

As shown in FIG. 15, the second case member 20 is placed in the center, and the first case member 10 is placed above and below it. The inner and outer cylindrical walls 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 magnetic core unit 1 can be formed with virtually no steps.

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 magnetic core unit 1. 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 magnetic core unit 1. The bottomed annular spaces 63 and 64 of each case member form a plurality of annular space portions 161 aligned in the same axial direction, and annular magnetic cores 5 are disposed in each of them as shown in FIG. 2.

Protrusions 71, 72 protrude into the annular space 161 so as to face the end 8 of the annular magnetic core 5. When the first case member 10 and the second case member 20 are combined, the distance w determined by the upper ends of the protrusions 71, 72 is wider than the height h of the annular magnetic core 5 (w>h) so as not to press down on the annular magnetic core 5. During assembly, the protrusions 71, 72 limit the movement of the annular magnetic core 5 within the annular space 161, and it is preferable to set the upper limit of the distance w between the protrusions 71, 72 to +0.5 mm (0<w-h≦0.5) relative to the height h of the annular magnetic core 5, thereby further limiting the amount of movement of the annular magnetic core 5.

(Method of manufacturing the magnetic core unit)
Next, an example of a method for manufacturing the magnetic core unit 1 will be described. First, the second case member 20 is placed vertically so that its bottomed annular space 64 appears at the top and bottom. Next, a predetermined amount of adhesive is applied to the surface of the annular bottom plate portion 54, and then the annular magnetic core 5 is stored in the bottomed annular space 64. Furthermore, the first case member 10, which has a predetermined amount of adhesive applied to its annular bottom plate portion 53, is assembled so as to cover the annular magnetic core 5 from above (first process). Next, the magnetic core unit in the middle of assembly 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 magnetic core 5 is stored in the bottomed annular space 64. Then, another first case member 10, which has a predetermined amount of adhesive applied to its annular bottom plate portion 53, is assembled so as to cover the annular magnetic core 5 from above (second process). Next, the adhesive is hardened to bond and fix each case member 10, 20 to the annular magnetic core 5 (third process), and the magnetic core unit 1 is completed. There are no particular limitations on the adhesive as long as it can bond the various components together, but a thermosetting adhesive can be used, and among these, a silicone adhesive or an epoxy adhesive that has a viscosity that does not easily cause bending on vertical surfaces is preferred.

During the assembly process, the adhesive is not yet hardened, so the annular magnetic core 5 can easily move, and when placed vertically, it sinks in the annular space 161 due to its own weight. For example, when the second process is completed, the annular magnetic core 5 in the upper annular space 161 may be biased toward the annular bottom plate 54 of the second case member 20, and the annular magnetic core 5 in the lower annular space 161 may be biased toward the annular bottom plate 53 of the first case member 10. If the protrusions 71 and 72 protruding into the annular space 161 are not provided, one of the end faces 8 of the annular magnetic core 5 will come into contact with one surface of the annular bottom plate 53 or the annular bottom plate 54, and the adhesive present therein will tend to spread thinly over the end face 8 of the annular magnetic core 5. On the other end face 8 side, the gap between the annular bottom plate 53 or the annular bottom plate 54 will widen, and the adhesive surface area will tend to be insufficient. In this state, after the adhesive hardens, the annular magnetic core 5 is susceptible to stress caused by shrinkage as the adhesive hardens, which can lead to deterioration of the magnetic properties or insufficient adhesion that results in insufficient fixing force.

On the other hand, by providing the protrusions 71 and 72 protruding into the annular space 161, even if the annular magnetic core 5 is offset in 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 53 or the annular bottom plate 54, and the end face 8 of the annular magnetic core 5 does not come into contact with the annular bottom plate 53 or the annular bottom plate 54. Since the applied adhesive accumulates in the space, even if the annular magnetic core 5 moves between the protrusions 71 and 72, it is possible to prevent the adhesive from spreading unnecessarily over the end face 8 of the annular magnetic core 5. In addition, by limiting the amount of movement of the annular magnetic core 5 between the protrusions 71 and 72, it is possible to prevent the adhesive area of the end face 8 of the annular magnetic core 5 from becoming insufficient. As a result, it is possible to reliably obtain the 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 when the adhesive hardens.

In addition, by limiting the amount of movement of the annular magnetic core 5 and reducing the movement energy imparted 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 portion 161 and being damaged.

1 Magnetic core unit 5 Annular magnetic core 10 First case member 20 Second case member 71, 72 Protrusion 161 Annular space 101, 102 Bus bar

Claims (4)

The magnetic core includes a resin case formed by combining a plurality of case members and having a plurality of annular spaces arranged in the same axial direction, and annular magnetic cores accommodated in the respective annular spaces of the resin case,
Each of the case members is provided with a plurality of protrusions protruding in the axial direction in the annular space portion,
the annular magnetic core is a wound body formed by winding an Fe-based amorphous alloy ribbon or an Fe-based nanocrystalline alloy ribbon, and has an inner circumference and an end face facing the outer circumference,
the annular magnetic core and the resin case are adhesively fixed together such that a surface of the case member on which the protrusion is formed faces an end face of the annular magnetic core;
At least two of the toroidal cores are arranged side by side ,
The magnetic core unit has honeycomb structure portions on both ends of the resin case in the axial direction . The magnetic core unit according to claim 1,
A through hole is provided on the inner peripheral side of the annular magnetic core,
The through hole is partitioned in the axial direction by a partition portion formed by a plurality of case members. The magnetic core unit according to claim 1 or 2,
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 an opening having a groove-shaped cross section cut in the axial direction,
The first case member has a groove-shaped opening portion 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 to each other,
A magnetic core unit in which two of the first case members are combined with the second case member, and a groove-shaped opening of the first case member is combined with a groove-shaped opening of the second case member to form two annular housing portions. A noise filter comprising the core unit according to any one of claims 1 to 3 and a plurality of bus bars.

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