Magnetic core and clamp core

Abstract

A magnetic core according to the present disclosure comprises a core body. The core body comprises: a laminate formed by laminating a plurality of belt-shaped layers made of a magnetic material in a thickness direction; and a covering body covering the laminate. The covering body includes an interposed portion interposed between two adjacent belt-shaped layers among the plurality of belt-shaped layers. When a thickness at a position of one end of the laminate in a width direction of the belt-shaped layers is defined as "t1", a thickness at a position of the other end of the laminate in the width direction of the belt-shaped layers is defined as "t2", and t1 ≤ t2, a relative difference Δt between t1 and t2 calculated by the formula is 10% or less.

Description

Magnetic Core and Clamping Core

[0001] The present disclosure relates to a magnetic core and a clamping core.

[0002] Conventionally, magnetic cores used as magnetic cores for noise filters, transformers, motors, etc. are known.

[0003] Patent Document 1 discloses an annular core as this type of magnetic core. The annular core described in Patent Document 1 includes a core case body, a roll body formed by winding a magnetic sheet impregnated with resin in the core case body, and a core case lid disposed at an opening of the core case body. Further, in the annular core described in Patent Document 1, a gap is formed in the roll body, and a spacer inserted into the gap is integrally formed with the core case lid. Patent Document 1 explains that the above configuration facilitates the operations of impregnating the roll body and inserting the spacer.

[0004] Patent Document 2 also discloses a laminated core as this type of magnetic core. The laminated core described in Patent Document 2 includes an annular body formed by laminating nanocrystalline alloy foils. In the laminated core described in Patent Document 2, a resin layer is disposed between layers formed of nanocrystalline alloy foils. The laminated core described in Patent Document 2 is divided into two or more parts in the circumferential direction. Patent Document 2 explains that by defining the thickness of the resin layer with respect to the thickness of the nanocrystalline alloy foil, the impedance is less likely to decrease even when the laminated core is divided.

[0005] Japanese Utility Model Publication No. 61-157312, Patent No. 7501890

[0006] In magnetic cores such as those described in Patent Documents 1 and 2, there is still room for improvement from the perspective of suppressing deterioration of magnetic characteristics.

[0007] An object of the present disclosure is to provide a magnetic core and a clamping core capable of suppressing deterioration of magnetic characteristics.

[0008] A magnetic core as a first aspect of the present disclosure is a magnetic core comprising: (1) a core body, the core body comprising: a laminate formed by stacking a plurality of strip-shaped layers made of a magnetic material in the thickness direction; and a covering body covering the laminate, the covering body including an intervening portion interposed between two adjacent strip-shaped layers among the plurality of strip-shaped layers, where "t1" is the thickness of the strip-shaped layer at one end of the laminate in the width direction, "t2" is the thickness of the strip-shaped layer at the other end of the laminate in the width direction, and when t1 ≤ t2, the relative difference Δt between t1 and t2 calculated by the following formula is 10% or less.

[0009] A magnetic core as one embodiment of the present disclosure is the magnetic core according to (1) above, comprising: (2) a housing that houses the core body, the housing comprising: an outer wall portion that covers an outer surface which is one side of the laminate in the thickness direction, an inner wall portion that covers an inner surface which is the other side of the laminate in the thickness direction, and a bottom wall portion that covers either one end face in the width direction of the laminate, and the covering body comprising a covering body portion interposed between the outer surface and the outer wall portion, between the inner surface and the inner wall portion, and between the end face and the bottom wall portion, or any of the above.

[0010] A magnetic core as one embodiment of the present disclosure is (3) the magnetic core described in (2) above, wherein the covering body portion of the covering is interposed between the bottom wall portion and the end face.

[0011] A magnetic core as one embodiment of the present disclosure is the magnetic core described in (2) or (3) above, wherein the laminate does not form a closed magnetic path on its own, but has a contact end face that is exposed to the outside and can form a closed magnetic path by contacting other magnetic materials.

[0012] A magnetic core as one embodiment of the present disclosure is the magnetic core described in (4) above, wherein the covering and the housing do not protrude outward beyond the contact end face.

[0013] A magnetic core as one embodiment of the present disclosure is (6) the magnetic core according to (5) above, wherein the covering body portion and the housing portion of the covering body have adjacent end faces adjacent to the periphery of the contact end face in a plan view taken from a direction perpendicular to the contact end face, and the adjacent end faces have inclined surface portions that are inclined to move away from the contact end face in a direction perpendicular to the contact end face as they move away from the contact end face in the plan view.

[0014] A magnetic core as one embodiment of the present disclosure is the magnetic core according to any one of (4) to (6) above, wherein the laminate has a longitudinal end face which is the end face in the longitudinal direction of the strip-shaped layer, and the bottom wall portion has a recess at the position of the longitudinal end face.

[0015] A clamp core as a second aspect of the present disclosure is a clamp core comprising: (8) a plurality of magnetic cores as described in any one of (4) to (7) above, wherein the plurality of magnetic cores can form a closed magnetic path by the contact end faces of the magnetic cores contacting each other, and a holding case capable of fixing the plurality of magnetic cores in the state in which the plurality of magnetic cores form a closed magnetic path.

[0016] A clamp core as one embodiment of the present disclosure is the clamp core according to (8) above, wherein the outer wall portion of the housing has an engaging portion, and the retaining case has an engaged portion that can engage with the engaging portion.

[0017] According to this disclosure, it is possible to provide a magnetic core and a clamp core that can suppress the deterioration of magnetic properties.

[0018] This is a plan view showing a clamp core as one embodiment of the present disclosure, which includes a magnetic core as one embodiment of the present disclosure. This is a diagram showing the clamp core when the two magnetic cores are changed to a closed state from the state shown in Figure 1. This is a perspective view of the magnetic core shown in Figure 1. This is a cross-sectional view along the line I-I in Figure 3. This is a plan view showing the housing unit shown in Figure 1 before the cutting process is performed. This is a cross-sectional view along the line II-II in Figure 5. This is a cross-sectional view along the line III-III in Figure 5. This is an enlarged view of section X in Figure 1. This is an enlarged view at the same position as Figure 8 showing a modified example of the magnetic core shown in Figure 1. This is a diagram showing a magnetic core as a second embodiment. This is a diagram showing a state in which two magnetic cores shown in Figure 10 are combined to form a closed magnetic circuit. This is a diagram showing a magnetic core as a third embodiment. This is a flowchart showing an example of a method for manufacturing the magnetic core shown in Figure 1.

[0019] Hereinafter, embodiments of the magnetic core and clamp core relating to this disclosure will be illustrated with reference to the drawings. In each figure, identical components are denoted by the same reference numerals.

[0020] The magnetic cores and clamp cores relating to this disclosure are used as noise filters, for example, attached to cables of electronic components, power generators, power supply units, communication equipment, and OA / FA equipment installed in automobiles, to suppress noise generated inside or outside these electronic components and electronic devices that propagate through the cables. However, the applications of the magnetic cores and clamp cores relating to this disclosure are not limited to noise filters. The magnetic cores and clamp cores relating to this disclosure can also be used, for example, as inductors, current transformers, etc., mounted on a substrate.

[0021] <First Embodiment> Figures 1 and 2 are plan views showing a clamp core 1 as one embodiment of a clamp core according to the present disclosure, which includes a magnetic core 2 as one embodiment of a magnetic core according to the present disclosure. As shown in Figures 1 and 2, the clamp core 1 includes a plurality of magnetic cores 2 and a holding case 5 that holds the plurality of magnetic cores 2. Specifically, the clamp core 1 of this embodiment includes two magnetic cores 2 and a holding case 5 that holds the two magnetic cores 2.

[0022] The two magnetic cores 2, by contacting each other, form an annular shape as a whole, creating a closed magnetic circuit. Conversely, each of the two magnetic cores 2 individually is non-annular and does not form a closed magnetic circuit. For the sake of explanation, in the following, the state in which the two magnetic cores 2 are in contact with each other and form a closed magnetic circuit will be described as the "closed state," and the state in which the two magnetic cores 2 do not form a closed magnetic circuit will be described as the "unclosed state." Figure 1 shows the clamp core 1 when the two magnetic cores 2 are in the unclosed state. Figure 2 shows the clamp core 1 when the state in which the two magnetic cores 2 are changed from the state shown in Figure 1 to the closed state.

[0023] As shown in Figure 2, the two magnetic cores 2, in a closed state, separate each other with a hollow section 3. When the clamp core 1 is used as a noise filter, a cable is inserted through this hollow section 3.

[0024] The retaining case 5 can fix the two magnetic cores 2 in a closed state. Specifically, the retaining case 5 comprises two case pieces 5a. Each of the two case pieces 5a holds each of the two magnetic cores 2. The two case pieces 5a are configured to be combinable with each other. The two magnetic cores 2 are in a closed state when the two case pieces 5a are combinable with each other. Conversely, the two magnetic cores 2 are in an uncombined state when the two case pieces 5a are disassembled. The two case pieces 5a are equipped with a locking mechanism 6. The two case pieces 5a are fixed in a combinable state with each other by the locking mechanism 6.

[0025] When attaching the clamp core 1 to a cable, first, the two case pieces 5a are separated. Next, the two case pieces 5a are combined while sandwiching the cable between them. This closes the two magnetic cores 2, and the cable is inserted into the hollow section 3 partitioned by the two magnetic cores 2. At this time, the two case pieces 5a are fixed by the locking mechanism 6. In this way, the clamp core 1 is attached to the cable.

[0026] Thus, the presence of the retaining case 5 makes it easy to switch the two magnetic cores 2 from an open state to a closed state, and also makes it easy to maintain the two magnetic cores 2 in a closed state. Furthermore, since the retaining case 5 is equipped with multiple (two in this embodiment) case pieces 5a that each hold one of the multiple (two in this embodiment) magnetic cores 2, it becomes easy to attach the clamp core 1 to the cable.

[0027] Examples of materials used to form the retaining case 5 include PBT (polybutylene terephthalate), PA (polyamide), PPS (polyphenylene sulfide), ABS (acrylonitrile butadiene styrene), ASA (acrylonitrile styrene acrylic rubber), silicone resins, and silicone elastomers.

[0028] The locking mechanism 6 of this embodiment includes a hook portion 6a provided on one of the two case pieces 5a, and a hook receiving portion 6b provided on the other case piece 5a. The hook portion 6a is configured to engage with the hook receiving portion 6b when the two case pieces 5a are combined with each other. However, the configuration of the locking mechanism 6 is not limited to the configuration of this embodiment and may be modified as appropriate.

[0029] The retaining case 5 may be provided with a biasing member that biases the two magnetic cores 2 so that they press against each other when closed. By pressing the two magnetic cores 2 together with the biasing member, the positions of the two magnetic cores 2 can be stabilized, making it easier to maintain the closed state of the two magnetic cores 2. The biasing member may be formed integrally with the retaining case 5, or it may be formed separately from the retaining case 5. If the biasing member is formed integrally with the retaining case 5, it may be a leaf spring formed inside each of the two case pieces 5a. If the biasing member is formed separately from the retaining case 5, it may be made of different forming materials than the retaining case 5 and the biasing member. In this case, the biasing member may be, for example, a metal leaf spring.

[0030] If the load exerted by the two magnetic cores 2 pressing against each other is too small, vibrations and shocks during use of the clamp core 1 may cause the two magnetic cores 2 to shift positions, making it impossible to maintain the closed state. As a result, the impedance and permeability may decrease. Conversely, if the load is too large, the magnetic cores 2 may deform, which may also decrease the impedance and permeability. Taking these factors into consideration, it is preferable that the biasing member be configured such that the load is between 5 and 100 times the mass of each magnetic core 2.

[0031] The clamp core 1 of this embodiment comprises two magnetic cores 2, but is not limited to this. The clamp core 1 may comprise three or more magnetic cores. Furthermore, the two magnetic cores 2 of this embodiment have a circular ring shape as a whole when closed, but are not limited to this. The multiple magnetic cores comprising the clamp core 1 may have external shapes such as an oval ring shape or a polygonal ring shape when closed. Moreover, each of the two magnetic cores 2 of this embodiment has a semicircular ring shape, but is not limited to this. The external shape of each of the multiple magnetic cores comprising the clamp core 1 may be appropriately set according to the overall external shape of the multiple magnetic cores when closed, and the number of magnetic cores comprising the clamp core 1. Specifically, the external shape of each of the multiple magnetic cores comprising the clamp core 1 may be arc-shaped, U-shaped, linear, etc. Furthermore, although the two magnetic cores 2 of this embodiment have the same external shape, the multiple magnetic cores comprising the clamp core 1 may have different external shapes.

[0032] The configuration of the retaining case 5 is not limited to that of this embodiment and may be modified as appropriate. For example, the retaining case 5 may include a string-like member. In such a case, the retaining case may be configured to fix the two magnetic cores 2 in a closed state by wrapping the string-like member around the two magnetic cores 2. Furthermore, the retaining case 5 may have a function not only to fix the two magnetic cores 2 but also to protect the two magnetic cores 2 from vibration, shock, water exposure, etc.

[0033] Next, we will explain the details of the magnetic core 2.

[0034] Figure 3 is a perspective view of the magnetic core 2 alone. Figure 4 is a cross-sectional view taken along the line I-I in Figure 3. As shown in Figure 3, the magnetic core 2 comprises a core body 10 and a housing 40 that houses the core body 10. The core body 10 comprises a laminate 20 and a coating 30.

[0035] The laminate 20 comprises a plurality of strip-shaped layers 20a made of magnetic material. For the sake of convenience of explanation, in the clamp core 1 and magnetic core 2, the thickness direction of the strip-shaped layer 20a will be simply referred to as "thickness direction A". Also, in the clamp core 1 and magnetic core 2, the width direction of the strip-shaped layer 20a will be simply referred to as "width direction B". Furthermore, in the clamp core 1 and magnetic core 2, the length direction of the strip-shaped layer 20a will be simply referred to as "length direction C".

[0036] The laminate 20 is formed by stacking a plurality of strip-shaped layers 20a in the thickness direction A. The laminate 20 is non-annular on its own and does not form a closed magnetic path. The laminate 20 is exposed to the outside of the magnetic core 2 and has contact end faces 25 that can form a closed magnetic path by contacting other magnetic materials, such as another laminate 20 of another magnetic core 2. Specifically, the contact end faces 25 in this embodiment are exposed to the outside of the cover 30 and the housing 40. For example, in the clamp core 1 described above, when the two magnetic cores 2 are in a closed state, the contact end faces 25 of the laminates 20 of the two magnetic cores 2 are in contact with each other. The laminate 20 has two contact end faces 25. The two contact end faces 25 are both end faces in the length direction C of the laminate 20. The contact end faces 25 are surfaces that are aligned with the thickness direction A and the width direction B. However, the contact end surface 25 may be a surface inclined with respect to at least one of the thickness direction A and the width direction B, or a surface that aligns with a direction perpendicular to the thickness direction A and the width direction B, as is the case with respect to the contact end surface 125 of the second embodiment shown in Figures 10 and 11, as long as it is possible to form a closed magnetic path by contacting another magnetic material.

[0037] The strip-shaped layer 20a is preferably made of a soft magnetic metal material with low coercivity and high permeability. As the soft magnetic metal material, for example, soft magnetic metals such as Fe-Ni alloys (permalloy) and Fe-Si alloys (silicon steel), amorphous alloys such as Co-based amorphous alloys and Fe-based amorphous alloys, and Fe-based nanocrystalline alloys can be used. When amorphous alloys or Fe-based nanocrystalline alloys are used as the soft magnetic metal material, for example, the general formula is: (Fe １－ａ M ａ )100-xy-z-b-c-dA ｘ M' ｙ M" ｚ X ｂ Si ｃ B ｄ (Atomic %) (wherein M is at least one element selected from Co and Ni, A is at least one element selected from Cu and Au, M' is at least one element selected from Ti, V, Zr, Nb, Mo, Hf, Ta and W, M'' is at least one element selected from Cr, Mn, Sn, Zn, Ag, In, platinum elements, Mg, N and S, X is at least one element selected from C, Ge, Ga, Al and P, and a, x, y, z, b, c and d are each 0 ≤ a ≤ An alloy with a composition expressed as (0.1, 0.1≦x≦3, 1≦y≦10, 0≦z≦10, 0≦b≦10, 11≦c≦17, 3≦d≦10, and 65≦100-x-y-z-b-c-d≦85) can be used. In this case, the component composition of the Fe-based nanocrystalline alloy is not particularly limited, but preferably, in atomic percent, Cu: 0.5-2.0%, Nb: 1.0-5.0%, Si: 11.0-15.0%, B: 5.0-10.0%, with the remainder being substantially Fe.

[0038] When an amorphous alloy or an Fe-based nanocrystalline alloy is used as the soft magnetic metal material for forming the strip layer 20a, if the thickness of the strip layer 20a is too large, the cooling rate of the strip layer 20a tends to be insufficient. Therefore, it becomes difficult to form the amorphous layer uniformly, and the magnetic permeability of the magnetic core 2 may decrease. Conversely, if the thickness of the strip layer 20a is too small, the strength of the strip layer 20a decreases, and defects such as pores and discontinuities are likely to occur on the surface of the strip layer 20a, and the strip layer 20a is likely to be distorted. If defects or distortions occur in the strip layer 20a, the magnetic permeability of the magnetic core 2 may decrease. Based on these considerations, the thickness of the strip layer 20a is preferably 10 μm or more and 30 μm or less, more preferably 12 μm or more and 25 μm or less, and still more preferably 14 μm or more and 20 μm or less.

[0039] The covering 30 covers the laminate 20. The covering 30 includes an intervening portion 31 interposed between two adjacent strip layers 20a among the plurality of strip layers 20a. When the strip layer 20a is formed of a soft magnetic metal material, it is difficult to commercialize the laminate 20 alone because its strength is insufficient. In contrast, the presence of the covering 30 including the intervening portion 31 can reinforce the laminate 20.

[0040] Here, in the laminate 20, let the thickness at the position of one end of the laminate 20 in the width direction B of the strip layer 20a be "t1", and the thickness at the position of the other end of the laminate 20 in the width direction B of the strip layer 20a be "t2" (see FIG. 4). At this time, it is assumed that t1 ≤ t2. That is, in the laminate 20, when the thicknesses at both ends of the laminate 20 in the width direction B are different, the smaller one of the thicknesses at the above two ends is "t1", and the larger one is "t2". Also, in the laminate 20, when the thicknesses at both ends of the laminate 20 in the width direction B are the same, either one of the thicknesses at the above two ends is "t1", and the other is "t2". In such a case, the relative difference Δt between t1 and t2 is calculated by the following formula.

[0041] [Equation 1]

[0042] The thickness in the laminate 20 means the length in the thickness direction A of the laminate 20. Also, t1 and t2 are values measured at the same position in the length direction C in the laminate 20. When the relative difference Δt varies depending on the position in the length direction C where t1 and t2 are measured, the maximum value of the relative difference Δt is used as a reference. t1 and t2 can be measured, for example, using a laser microscope or a three-dimensional shape measuring instrument.

[0043] The relative difference Δt is an index representing the degree of strain of the strip layer 20a of the laminate 20. Although it is difficult to measure the strain of the strip layer 20a in the state where the magnetic core 2 is formed, by calculating the relative difference Δt, the degree of strain of the strip layer 20a can be easily grasped, and the quality of the magnetic core 2 can be controlled. Specifically, the larger the relative difference Δt, the greater the tendency for the strain of the strip layer 20a of the laminate 20 to increase. When the strain of the strip layer 20a increases, there is a risk that the magnetic characteristics of the magnetic core 2 will deteriorate.

[0044] On the other hand, in the magnetic core 2 of the present embodiment, the relative difference Δt is 10% or less. Thereby, an increase in the strain of the strip layer 20a can be suppressed. As a result, a decrease in the magnetic characteristics of the magnetic core 2 can be suppressed.

[0045] The relative difference Δt is more preferably 5% or less, still more preferably 3% or less, and even more preferably 2% or less. This is because the smaller the relative difference Δt, the more the increase in the strain of the strip layer 20a can be suppressed.

[0046] The housing 40 comprises an outer wall portion 41 that covers the outer surface 21, which is one side of the laminate 20 in the thickness direction A; an inner wall portion 42 that covers the inner surface 22, which is the other side of the laminate 20 in the thickness direction A; and a bottom wall portion 43 that covers either end face of the laminate 20 in the width direction B. For the sake of explanation, the end face of the laminate 20 in the width direction B that is covered by the bottom wall portion 43 will be referred to as the "bottom surface 23," and the end face of the laminate 20 in the width direction B that is not covered by the bottom wall portion 43 will be referred to as the "top surface 24." The covering body 30 comprises a covering body portion 32 interposed between the outer surface 21 and the outer wall portion 41, between the inner surface 22 and the inner wall portion 42, and between the bottom surface 23 and the bottom wall portion 43, or any of these multiple locations. In this embodiment, the housing 40 and the laminate 20 are connected via the covering body 30 and formed as a single unit. By configuring the magnetic core 2 in this way, it is possible to suppress the increase in strain of the strip-shaped layer 20a that occurs during the manufacturing process of the magnetic core 2. The details of this will be explained below.

[0047] Figure 13 is a flowchart showing an example of a method for manufacturing the magnetic core 2 of this embodiment. The method for manufacturing the magnetic core 2 shown in Figure 13 includes a laminate formation step S1, a heat treatment step S2, a housing step S3, a coating formation step S4, a cutting step S5, and a polishing step S6.

[0048] In the laminate formation process S1, first, the metal foil is processed to a predetermined size and shape. Next, the processed metal foil is wound up to form a laminate 20 in which multiple strip-shaped layers 20a are laminated in the thickness direction A. The laminate 20 formed in the laminate formation process S1 has an annular shape, and becomes non-annular in the subsequent cutting process S5.

[0049] Next, a heat treatment step S2 is performed to remove the strain from the strip-shaped layer 20a of the laminate 20. In the heat treatment step S2, the laminate 20 is heated to a predetermined heat treatment temperature. At this time, if the metal foil constituting the strip-shaped layer 20a is made of an amorphous alloy, nanocrystals can be deposited inside the strip-shaped layer 20a by heat treatment. The heat treatment temperature may be, for example, 350°C or more and 700°C or less. The heat treatment of the laminate 20 may be performed, for example, in an atmosphere of an inert gas such as nitrogen or argon, or in a vacuum.

[0050] Next, a storage process S3 is performed in which the heat-treated laminate 20 is stored in the storage body 40. As described above, the storage body 40 includes an outer wall portion 41 that covers the outer surface 21 of the laminate 20, an inner wall portion 42 that covers the inner surface 22 of the laminate 20, and a bottom wall portion 43 that covers the bottom surface 23 of the laminate 20. In other words, the storage body 40 forms an annular storage recess 40a with the outer wall portion 41, the inner wall portion 42, and the bottom wall portion 43 (see Figure 5). In this embodiment, the laminate 20 is stored in the storage body 40 by being inserted into the storage recess 40a from the open end of the storage recess 40a at a position opposite the bottom wall portion 43.

[0051] Next, a coating formation step S4 is performed in which the coating 30 is formed with the laminate 20 housed in the container 40. Specifically, first, with the laminate 20 housed in the container 40, a liquid agent that will solidify to form the coating 30 is injected into the container 40. At this time, the temperature of the injected liquid agent is preferably 25°C to 60°C. Alternatively, the laminate 20 may be held under reduced pressure after the liquid agent is injected. The time for holding the laminate 20 under reduced pressure is preferably 10 minutes to 30 minutes. This immerses the laminate 20 in the liquid agent, allowing the liquid agent to penetrate between the laminate 20 and the container 40, and between the multiple strip-shaped layers 20a. After that, the coating 30 is formed as the liquid agent solidifies. Specifically, an intervening portion 31 is formed between two adjacent strip layers 20a of the multiple strip layers 20a, and a covering body portion 32 is formed between one or more of the following: the space between the outer surface 21 and the outer wall portion 41, the space between the inner surface 22 and the inner wall portion 42, and the space between the bottom surface 23 and the bottom wall portion 43. As a result, the laminate 20 is reinforced by the intervening portion 31 and the covering body portion 32, and the laminate 20 and the housing 40 are integrated by the covering body portion 32, forming an annular core.

[0052] Next, a cutting step S5 is performed to cut the annular core. Specifically, the annular core is cut along the thickness direction A and the width direction B. By cutting the annular core, magnetic cores 2 are formed as divided pieces of the annular core. The cutting step S5 may be performed with a wet outer peripheral slicer having a cutting wheel. The cutting wheel is preferably a GC grinding wheel using a resinoid binder. The degree of bonding of the cutting wheel is preferably in the range of K to P, the grit size of the cutting wheel is preferably 80 or more and 150 or less, and the thickness of the cutting wheel is preferably 0.5 mm or more and 1.5 mm or less.

[0053] Next, a polishing step S6 is performed to polish the contact end face 25 of the laminate 20 of the magnetic core 2. In this embodiment, the contact end face 25 is a cut surface (i.e., the end face in the length direction C) formed by cutting the annular core. If the contact end face 25 is too rough, a minute gap is likely to form between the contact end face 25 and other magnetic materials when the contact end face 25 is brought into contact with other magnetic materials. As a result, the flow of magnetic flux may be obstructed, and the permeability may decrease. With this in mind, the arithmetic mean roughness Ra of the contact end face 25 after polishing is preferably 0.7 μm or less, and more preferably 0.35 μm or less. The maximum height roughness Rz is preferably 10 μm or less, and more preferably 5 μm or less. The lower limits of the arithmetic mean roughness Ra and the maximum height roughness Rz are not particularly limited, but may be within the range possible in a mass production method. Furthermore, the flatness FL of the contact end face 25 after polishing is preferably 2.5 μm or less. If the flatness FL is greater than this, a gap is likely to form between the contact end faces 25, which can obstruct the flow of magnetic flux and potentially reduce the permeability. The lower limit of the flatness FL is not particularly limited, but it may be within the range possible in mass production methods.

[0054] Conventionally, the common method for forming a coating involved immersing the laminate in a liquid agent, then allowing the liquid agent to solidify while the laminate was exposed to the outside. However, this method had the problem that the liquid agent would move downward due to gravity during solidification, easily causing unevenness in the thickness of the coating. In particular, if the thickness of the intervening portion 31 of the coating 30 was uneven, the strip-shaped layer 20a would be prone to distortion. In contrast, in the magnetic core 2 of this embodiment, the laminate 20 is housed in the housing 40, and the laminate 20 is immersed in the liquid agent to form the coating 30. As a result, the movement of the liquid agent is restricted by the outer wall 41, inner wall 42, and bottom wall 43 of the housing 40, making it difficult for the liquid agent to move downward. Consequently, unevenness in the thickness of the coating 30 is less likely to occur, and unevenness in the thickness of the intervening portion 31 is also suppressed, thus suppressing an increase in the distortion of the strip-shaped layer 20a. In other words, the relative difference Δt can be made smaller.

[0055] Preferably, the outer wall portion 41 of the container 40 covers the entire outer surface 21 of the laminate 20, the inner wall portion 42 of the container 40 covers the entire inner surface 22 of the laminate 20, and the bottom wall portion 43 of the container 40 covers the entire bottom surface 23 of the laminate 20. This restricts the downward movement of the liquid due to gravity across the entire outer surface 21, inner surface 22, and bottom surface 23 of the laminate 20, further suppressing the increase in distortion of the strip-shaped layer 20a. Furthermore, it is preferable that the depth of the receiving recess 40a of the container 40 is greater than the length of the width B of the laminate 20. This allows the entire laminate 20 to be placed within the receiving recess 40a, making it easier to uniformly immerse the entire laminate 20 with the liquid. In addition, it is preferable that the container 40 is capable of holding the liquid injected inside without leaking it to the outside. This makes it difficult for liquid flow to occur inside the container 40, further suppressing the downward movement of the liquid due to gravity. As a result, the increase in strain in the strip-shaped layer 20a can be further suppressed.

[0056] For the sake of explanation, in the following, in the width direction B, the direction from the bottom surface 23 toward the top surface 24 may be referred to as "the upper side of width direction B" or simply "the upper side," and the opposite side may be referred to as "the lower side of width direction B" or simply "the lower side."

[0057] The container 40 does not cover the top surface 24 of the laminate 20. Therefore, with the laminate 20 housed in the container 40, the liquid can be injected from the upper side in the width direction B into the space between any two adjacent strip layers 20a (hereinafter sometimes simply referred to as "the interior of the laminate 20"), allowing the liquid to permeate. However, it is preferable to permeate the interior of the laminate 20 not only from the upper side in the width direction B but also from the lower side in the width direction B. In other words, by permeating the interior of the laminate 20 from both sides in the width direction B, the liquid can be uniformly permeated into the interior of the laminate 20. To permeate the laminate 20 from the lower side in the width direction B, for example, the liquid can be injected in advance at the position of the bottom wall portion 43 of the container 40 before housing the laminate 20 in the container 40, and the laminate 20 can be placed on top of the injected liquid. This allows the pre-injected liquid to permeate into the interior of the laminate 20 from the lower side in the width direction B. When the liquid is permeated into the interior of the laminate 20 from the lower side in the width direction B in this way, the covering body portion 32 of the covering body 30 is formed to be interposed at least between the bottom surface 23 of the laminate 20 and the bottom wall portion 43 of the containment body 40.

[0058] Figure 5 is a plan view showing the housing 40 alone before the cutting process S5 is performed. In Figure 5, the cutting position Y where the annular core is cut in the cutting process S5 described above is indicated by a dashed line. Figure 6 is a cross-sectional view taken along the line II-II in Figure 5. Figure 7 is a cross-sectional view taken along the line III-III in Figure 5. As shown in Figures 5 and 6, the bottom wall portion 43 of the housing 40 in this embodiment has a protrusion 45 that projects upward from the upper surface of the bottom wall portion 43. Therefore, when the laminate 20 is placed in the housing 40, the laminate 20 is supported by the protrusion 45, and a gap 80 is formed between the bottom surface 23 of the laminate 20 and the bottom wall portion 43. By filling this gap 80 with liquid, the liquid can be reliably penetrated into the interior of the laminate 20 from the lower side in the width direction B of the laminate 20. In Figure 6, the size of the protrusion 45 is exaggerated for the sake of explanation.

[0059] The height H of the gap 80 in the width direction B (hereinafter simply referred to as "height H of the gap 80") is equal to or approximately equal to the height of the protrusion 45 in the width direction B. The height H of the gap 80 may be adjusted as appropriate depending on the viscosity of the liquid, etc., but if the height H of the gap 80 is too small, it may not be possible to secure a sufficient amount of liquid to penetrate from the bottom of the laminate 20, and the liquid may not be able to penetrate uniformly into the interior of the laminate 20. Conversely, if the height H of the gap 80 is too large, the excess space will be large, and the overall volume of the magnetic core 2 will become excessive. Based on these considerations, the height of the protrusion 45 in the width direction B is preferably 0.01 mm or more, more preferably 0.1 mm or more, even more preferably 0.2 mm or more, and even more preferably 0.3 mm or more. Furthermore, the height of the protrusion 45 in the width direction B is preferably 1.0 mm or less, more preferably 0.8 mm or less, and even more preferably 0.7 mm or less.

[0060] As shown in Figure 5, the protrusions 45 have a rib-like outer shape that extends elongated along the thickness direction A. In addition, four protrusions 45 are formed on the bottom wall portion 43, spaced apart in the length direction C. However, the shape, number, and arrangement of the protrusions 45 are not limited to the configuration of this embodiment and may be changed as appropriate.

[0061] Instead of the protrusion 45, a recess that is recessed downwards may be formed on the upper surface of the bottom wall portion 43 to create a gap 80 between the bottom surface 23 of the laminate 20 and the bottom wall portion 43. In this case, the height of the gap 80 will be equal to or approximately equal to the depth of the recess in the width direction B.

[0062] As described above, the contact end face 25 of the magnetic core 2 in this embodiment is the end face in the longitudinal direction C of the laminate 20 (hereinafter simply referred to as the "longitudinal end face"). Also, as described above, the longitudinal end face (the contact end face 25 in this embodiment) is a cut surface formed by cutting the annular core. As shown in Figure 7, the bottom wall portion 43 of the housing 40 is provided with a recessed portion 46 that is recessed downwards at the cutting position Y where the annular core is cut, i.e., at the longitudinal end face (the contact end face 25 in this embodiment). Having such a recessed portion 46 allows for more liquid to be secured at the location of the recessed portion 46. This makes it possible to reliably reinforce the laminate 20 with the coating 30 at the location of the longitudinal end face (the contact end face 25 in this embodiment), which is exposed to the outside and susceptible to external forces. As shown in Figure 7, it is preferable that the bottom wall portion 43 of the housing 40 does not have a protrusion 45 (see Figure 6) at the cutting position Y where the annular core is cut, i.e., at the longitudinal end face of the magnetic core 2 (the contact end face 25 in this embodiment).

[0063] In the coating formation step S4, after immersing the laminate 20 in the liquid, heat treatment of the liquid may be performed as needed. Heat treatment makes it easier to solidify the liquid. The heat treatment temperature and heat treatment time may be adjusted as appropriate according to the liquid used, but for example, the heat treatment temperature may be 50°C or more and 500°C or less, and the heat treatment time may be 0.5 hours or more and 48 hours or less. The heat treatment of the liquid may be performed in stages, starting at a low temperature and divided into multiple steps.

[0064] Examples of materials used to form the containment 40 include resin materials such as PBT (polybutylene terephthalate), PA (polyamide), PPS (polyphenylene sulfide), ABS (acrylonitrile butadiene styrene), ASA (acrylonitrile styrene acrylic rubber), silicone resins, and silicone elastomers. When the material used to form the containment 40 is a resin material, the resin material may contain glass fibers, glass beads, carbon fibers, and other additives to adjust its strength, thermal expansion coefficient, and thermal conductivity. The material used to form the containment 40 is not limited to resin materials and may be metallic materials such as iron alloys, aluminum alloys, magnesium alloys, copper alloys, and zinc alloys, or ceramic materials such as alumina, boron nitride, and silicon carbide.

[0065] The liquid agent that constitutes the coating 30 when solidified is preferably one that easily penetrates between the laminate 20 and the containment 40, and between the multiple strip-shaped layers 20a. Specifically, examples of liquid agents that constitute the coating 30 when solidified include thermosetting resins as organic liquid agents such as acrylic resins, epoxy resins, polyimide resins, silicone resins, and silicone elastomers. If the liquid agent is a thermosetting resin, and the glass transition temperature of the thermosetting resin is low, then when the magnetic core 2 is used in a high-temperature environment, changes in the shape of the coating 30 and a decrease in adhesive strength due to aging will occur, making it difficult to maintain the shape of the laminate 20. As a result, distortion may occur in the strip-shaped layers 20a, and the magnetic permeability may decrease. For this reason, the glass transition temperature of the thermosetting resin is preferably 130°C or higher, and more preferably 150°C or higher. The liquid agent that serves as the raw material for the coating 30 may also be an inorganic liquid agent such as water glass, bentonite-based solvent, alumina-based solvent, or silica-based solvent. In this embodiment, the intervening portion 31 and the main body portion 32 of the covering 30 are formed from the same material.

[0066] The viscosity of the liquid may be, for example, 2000 mPa·s or less. If the viscosity of the liquid is too high, the viscosity of the liquid can be adjusted by controlling the temperature or adding a diluent such as an organic solvent, or by aspirating the liquid, so that the liquid can penetrate evenly between the laminate 20 and the containment 40, and between the multiple strip-shaped layers 20a. It is also effective to vibrate the laminate 20 when the liquid is being permeated into the laminate 20.

[0067] The proportion of the strip-shaped layer 20a that occupies the laminate 20 can be adjusted by changing the tension when winding the metal foil in the laminate formation process S1. If the proportion of the strip-shaped layer 20a decreases, the permeability of the magnetic core 2 also decreases. Therefore, if the proportion of the strip-shaped layer 20a is too small, it becomes difficult to ensure the performance of the magnetic core 2. Conversely, if the proportion of the strip-shaped layer 20a increases, the interlayer distance between two adjacent strip-shaped layers 20a becomes smaller. Therefore, if the proportion of the strip-shaped layer 20a is too large, it becomes difficult for the liquid to penetrate deep into the interior of the laminate 20. Taking these factors into consideration, it is preferable that the proportion of the strip-shaped layer 20a be, for example, 65 vol% or more and 85 vol% or less.

[0068] Furthermore, if the proportion of the intervening portion 31 occupying the internal voids of the laminate 20 is too small, the strip-shaped layers 20a may not be sufficiently reinforced, and the strain of the strip-shaped layers 20a may increase. For this reason, the proportion of the intervening portion 31 is preferably 90% or more, more preferably 95% or more, and even more preferably 98% or more. The internal voids of the laminate 20 refer to the sum of the voids between two adjacent strip-shaped layers 20a among the multiple strip-shaped layers 20a in the laminate 20. In other words, it is not necessary for the intervening portion 31 to be located in all of the internal voids of the laminate 20. That is, the intervening portion 31 of the coating 30 does not have to be located between all the layers formed by the multiple strip-shaped layers 20a of the laminate 20, and may be located between only some of the layers, for example. However, as mentioned above, a high proportion of the intervening portion 31 is preferable from the viewpoint of suppressing the increase in strain of the strip-shaped layers 20a. Therefore, it is preferable that the intervening portion 31 of the coating 30 is located between all the layers formed by the multiple strip-shaped layers 20a of the laminate 20. The proportion of the internal voids of the laminate 20 occupied by the intervening portion 31 can be calculated by scanning the magnetic core 2 with X-rays or ultrasound and measuring the volume of the internal voids of the laminate 20 and the intervening portion 31.

[0069] The covering body portion 32 of the covering body 30 is preferably interposed in multiple places, such as between the outer surface 21 and the outer wall portion 41, between the inner surface 22 and the inner wall portion 42, and between the bottom surface 23 (which serves as an end surface) and the bottom wall portion 43. It is more preferable that it is interposed in all of the places between the outer surface 21 and the outer wall portion 41, between the inner surface 22 and the inner wall portion 42, and between the end surface and the bottom wall portion 43. By doing so, the integrity between the laminated body 20 and the housing body 40 can be increased.

[0070] Figure 8 is an enlarged view of section X in Figure 1. As shown in Figure 8, it is preferable that the coating 30 and the housing 40 do not protrude outward from the contact end surface 25. Specifically, the coating body 32 of the coating 30 and the housing 40 of this embodiment have adjacent end surfaces 50 that are adjacent to the periphery of the contact end surface 25 in a plan view taken from a direction perpendicular to the contact end surface 25. The adjacent end surfaces 50 are not located outside the contact end surface 25 in the direction perpendicular to the contact end surface 25 (in this embodiment, the longitudinal direction C). "Outside the contact end surface 25 in the direction perpendicular to the contact end surface 25" means the direction away from the laminate 20 in the direction perpendicular to the contact end surface 25, and in Figure 8, this is below the contact end surface 25. This makes it easier for the contact end surface 25 to come into contact with other magnetic materials. As a result, the flow of magnetic flux is improved and the permeability can be increased. Conversely, if the coating 30 and housing 40 protrude outward from the contact end surface 25 in a direction perpendicular to the contact end surface 25, the coating 30 and housing 40 are more likely to come into contact with other magnetic materials before the contact end surface 25, creating a gap between the contact end surface 25 and other magnetic materials, which may reduce the magnetic permeability. If the coating 30 and housing 40 are made of resin material, the hardness of the laminate 20 is higher than the hardness of the coating 30 and housing 40, so when the contact end surface 25 is polished in the polishing process S6, it is easy to process it so that the contact end surface 25 is located outside the coating 30 and housing 40. However, if the distance Z (see Figure 8) between the contact end surface 25 and the adjacent end surface 50 is too large, the proportion of the laminate 20 that is exposed to the outside increases, which may make the laminate 20 more susceptible to damage. Based on this, the distance Z (see Figure 8) between the contact end face 25 and the adjacent end face 50 is preferably 1 μm or more and 100 μm or less, more preferably 5 μm or more and 50 μm or less, and even more preferably 10 μm or more and 30 μm or less.

[0071] Figure 9 is an enlarged view of a modified example of the magnetic core 2 at the same position as in Figure 8. As shown in Figure 9, it is preferable that the adjacent end face 50 has an inclined surface portion 51 which is inclined so as it moves away from the contact end face 25 in a plan view from a direction perpendicular to the contact end face 25 (outward in the left-right direction in Figure 9), it moves away from the contact end face 25 in a direction perpendicular to the contact end face 25. This prevents the adjacent end face 50 from contacting another magnetic material before the contact end face 25 when the contact end face 25 contacts another magnetic material, making it easier for the contact end face 25 to contact the other magnetic material. In addition, the distance Z between the contact end face 25 and the adjacent end face 50 (see Figure 8) can be made smaller or eliminated. The angle at which the inclined surface portion 51 is inclined with respect to the direction perpendicular to the contact end face 25 may be, for example, 30 degrees or more and 60 degrees or less. The inclined surface portion 51 can be formed, for example, by chamfering the covering body portion 32 and the housing 40.

[0072] As shown in Figures 1 to 3, the outer wall portion 41 of the housing 40 is provided with an engaging portion 60. Also, as shown in Figures 1 and 2, the holding case 5 is provided with an engaged portion 70 that can engage with the engaging portion 60. The presence of such an engaging portion 60 and an engaged portion 70 allows the magnetic core 2 to be positioned relative to the holding case 5 and prevents the magnetic core 2 from falling out of the holding case 5.

[0073] Specifically, the engaging portion 60 in this embodiment is a convex portion that protrudes outward from the housing 40. The engaged portion 70 is a recess formed on the inside of the case piece 5a of the holding case 5 that can be fitted into the convex portion of the engaging portion 60. However, the configuration of the engaging portion 60 and the engaged portion 70 is not limited to this. For example, the engaging portion 60 may be a recess that is recessed inward from the housing 40, and the engaged portion 70 may be a convex portion that can be fitted into the recess of the engaging portion 60. The inside of the housing 40 means the side of the housing 40 where the core body 10 is located, and the outside of the housing 40 means the side of the housing 40 opposite to the inside.

[0074] Furthermore, as shown in Figures 1 to 3, the outer wall portion 41 of the housing 40 is provided with a positioning portion 65. When polishing the contact end surface 25 in the polishing process S6, the magnetic core 2 may be placed on a flat surface. In this case, the positioning portion 65 allows the magnetic core 2 to be placed on the flat surface in a positioned state. Conversely, if the positioning portion 65 is not present, the magnetic core 2 will roll around when placed on a flat surface, and its position will not be stable. Specifically, the positioning portion 65 in this embodiment is two protrusions that protrude outward from the housing 40. When placing the magnetic core 2 on a flat surface, the position of the magnetic core 2 can be stabilized by placing the magnetic core 2 on the flat surface so that the two protrusions acting as the positioning portion 65 contact the surface. However, the configuration of the positioning portion 65 is not limited to this. The positioning portion 65 may be, for example, a flat surface of the outer wall portion 41 formed by cutting off a part of the outer wall portion 41.

[0075] The polishing of the contact end face 25 may be performed without using the positioning part 65, for example, by fixing the magnetic core 2 to a fixing jig using the engaging part 60.

[0076] As shown in Figure 1, in the plan view shown in Figure 1 (i.e., a plan view of the magnetic core 2 viewed from above in the width direction B), it is preferable that the engaging portion 60 has a parallel surface 61 that is parallel or substantially parallel to the contact end surface 25. Having such a parallel surface 61 makes it easier to position the magnetic core 2 in the desired position using the parallel surface 61 of the engaging portion 60 as a reference when the magnetic core 2 is fixed to a fixing jig using the engaging portion 60 and the contact end surface 25 is polished. This improves the machining accuracy of the contact end surface 25. It is preferable that the parallelism between the contact end surface 25 and the parallel surface 61 be 0.2 mm or less.

[0077] Similarly, as shown in Figure 1, in the plan view shown in Figure 1, it is preferable that the virtual straight line L passing through the tips of the two protrusions that serve as the positioning portion 65 is parallel or substantially parallel to the contact end surface 25. By configuring the two protrusions that serve as the positioning portion 65 in this way, when polishing the magnetic core 2, the magnetic core 2 can be positioned in the desired orientation using the two protrusions that serve as the positioning portion 65 as a reference. As a result, the machining accuracy of the contact end surface 25 can be improved. It is preferable that the parallelism between the contact end surface 25 and the virtual straight line L is 0.2 mm or less.

[0078] The laminate 20 of this embodiment has a semi-annular outer shape. Therefore, both of the two contact end faces 25 of the laminate 20 are parallel or substantially parallel to the parallel surface 61. Similarly, both of the two contact end faces 25 of the laminate 20 are parallel or substantially parallel to the imaginary straight line L.

[0079] <Second Embodiment> Figure 10 shows a magnetic core 102 as a second embodiment. The magnetic core 102 of this embodiment differs from the magnetic core 2 of the first embodiment (see Figure 1, etc.) in shape and the position of the contact end face, but other components are the same. Here, we will mainly explain the differences mentioned above, and will omit the explanation of components that are common with the magnetic core 2 of the first embodiment.

[0080] As shown in Figure 10, the magnetic core 102 of this embodiment comprises a core body 110 and a housing 140 that houses the core body 110. The core body 110 comprises a laminate 120 and a covering 30. As shown in Figure 10, the laminate 120 of the magnetic core 102 of this embodiment is non-annular on its own and does not form a closed magnetic path. The laminate 120 is exposed to the outside of the magnetic core 102 and has a contact end face 125 that can form a closed magnetic path by contacting other magnetic materials. Specifically, the contact end face 125 of this embodiment is exposed to the outside of the covering 30 and the housing 140. Here, the contact end face 25 of the first embodiment was the end face in the length direction C of the laminate 20, but the contact end face 125 of this embodiment is the end face in the width direction B of the laminate 120. Specifically, in the magnetic core 102 of this embodiment, one of the two end faces of the laminate 120 in the width direction B is covered by the housing 140. The other end face of the laminate 120 in the width direction B is not covered by the covering 30 and the housing 140, and constitutes the contact end face 125.

[0081] Figure 11 shows a state in which two magnetic cores 102 are combined to form a closed magnetic circuit. In Figure 11, the two magnetic cores 102 are schematically depicted for ease of explanation. As shown in Figure 11, the magnetic cores 102 of this embodiment are configured to form a closed magnetic circuit when combined with the same magnetic core 102. Specifically, in Figure 11, the two magnetic cores 102 are stacked in the width direction B such that their contact end faces 125 are in contact with each other. At this time, the discontinuous portions 150 of the stacked bodies 120 of the two magnetic cores 102 are arranged so that they do not overlap when viewed from the width direction B in a plan view. In this state, the two magnetic cores 102 form a closed magnetic circuit.

[0082] When the magnetic core 102 is used as a noise filter, a cable is inserted through the hollow portion 160 partitioned by each of the two magnetic cores 102, as shown in Figure 11.

[0083] The contact end surface 125 in this embodiment is a surface that aligns with directions perpendicular to the thickness direction A and the width direction B. In other words, the contact end surface 125 in this embodiment is a surface that aligns with the length direction C. However, the contact end surface 125 may be a surface inclined with respect to the length direction C, or a surface that aligns with the thickness direction A and the width direction B, as is the case with the contact end surface 25 of the first embodiment (see Figure 3, etc.), as long as it is possible to form a closed magnetic path by contacting another magnetic material. Furthermore, the magnetic core 102 in this embodiment has a C-shaped curved outer shape, but is not limited to this. The outer shape of the magnetic core 102 may be, for example, U-shaped. The magnetic core 102 in this embodiment can be manufactured in the same process as the magnetic core 2 of the first embodiment described above.

[0084] <Third Embodiment> Figure 12 shows a magnetic core 202 as a third embodiment. The magnetic core 202 of this embodiment differs from the magnetic core 2 of the first embodiment (see Figure 1, etc.) in that it forms a closed magnetic circuit on its own, but other configurations are the same. Here, we will mainly explain the differences mentioned above, and will omit the explanation of configurations common to the magnetic core 2 of the first embodiment.

[0085] As shown in Figure 12, the magnetic core 202 of this embodiment comprises a core body 210 and a housing 240 that houses the core body 210. The core body 210 comprises a laminate 220 and a coating 30.

[0086] As shown in Figure 12, the laminated body 220 of the magnetic core 202 in this embodiment forms an annular shape on its own, forming a closed magnetic circuit. When the magnetic core 202 of this embodiment is used as a noise filter, a cable is inserted through the through-hole 260 partitioned by the magnetic core 202.

[0087] The magnetic core 202 of this embodiment has a circular ring shape, but is not limited thereto. The magnetic core 202 may have an outer shape such as an oval ring shape or a polygonal ring shape.

[0088] The magnetic core 202 of this embodiment can be manufactured using the same process as the magnetic core 2 of the first embodiment described above. However, when manufacturing the magnetic core 202 of this embodiment, the cutting process S5 and the polishing process S6 (see Figure 13) described above are not required.

[0089] The magnetic core and clamp core relating to this disclosure are not limited to the specific configurations shown in the embodiments and modifications described above, and various modifications, changes, and combinations are possible without departing from the scope of the claims.

[0090] For example, in the above-described embodiment, it was explained that by keeping the relative difference Δt calculated by the above-described [Equation 1] to 10% or less, the increase in strain of the strip layer can be suppressed, and the decrease in magnetic properties can be suppressed. Furthermore, in the above-described embodiment, it was also explained that by configuring the magnetic core to include a housing, the increase in strain of the strip layer can be suppressed. However, the magnetic core may suppress the increase in strain of the strip layer without including a housing. As an example, there is a method in which the laminate is immersed in a liquid without being housed in a housing, and then the liquid is solidified while the laminate is rotated in a predetermined direction to form a coating. This prevents the liquid from concentrating in one direction of the laminate due to gravity. As a result, unevenness in the thickness of the coating is less likely to occur, and the increase in strain of the strip layer can be suppressed. Another example is a method in which the laminate is housed in a silicone mold or a metal split mold, and then immersed in a liquid, and the silicone mold or metal split mold is removed from the laminate after the coating is formed. In this method, the use of a silicone mold or a metal split mold prevents the liquid from concentrating in one direction of the laminate due to gravity. As a result, unevenness in the thickness of the coating is less likely to occur, and the increase in distortion of the strip layer can be suppressed. Another example is to make the length of the magnetic core in the width direction smaller than usual. This makes it less likely for the liquid to be unevenly distributed in the width direction due to gravity. As a result, unevenness in the thickness of the coating in the width direction is less likely to occur, and the increase in distortion of the strip layer can be suppressed. For example, by making the length of the magnetic core in the width direction 5 mm or less, the increase in distortion of the strip layer can be suppressed.

[0091] Next, an embodiment of the magnetic core according to the present invention will be described.

[0092] <Examples 1-10 and Comparative Examples 1-5> Laminates were fabricated by stacking thin metal strips (strip-shaped layers). First, a molten alloy consisting of Cu: 1%, Nb: 3%, Si: 13.5%, B: 9% atomically, with the remainder being substantially Fe, was rapidly cooled by the single-roll method to obtain a 10 mm wide strip-shaped Fe-based amorphous alloy. The thickness of the thin metal strips (strip-shaped layers) in each example and comparative example is shown in Table 1. The Fe-based amorphous alloy was wound to form a cylindrical shape with an outer diameter of 28.5 mm, an inner diameter of 18.0 mm, and a width (height) of 10 mm. The cylindrical Fe-based amorphous alloy was inserted into a heat treatment furnace maintained at 600°C under an argon atmosphere and heat-treated for 30 minutes. A laminate made of Fe-based nanocrystalline alloy was then fabricated.

[0093] Next, in Examples 1 to 10, the obtained laminates were placed in a container. In this state, a liquid agent kept warm at 50°C was injected into the laminate. When the laminate was to be held under reduced pressure, after injecting the liquid agent, the laminate was held for 20 minutes under the reduced pressure conditions shown in Table 1. On the other hand, in Comparative Examples 1 to 5, the laminate was not placed in a container, but the laminate was impregnated with the liquid agent by immersing it in a liquid agent kept warm at 50°C for 20 minutes under the reduced pressure conditions shown in Table 1. When "0.0" is written in the "reduced pressure" column of Table 1, it means under atmospheric pressure. The liquid agents used in Examples 1 to 10 and Comparative Examples 1 to 5 are liquid agents obtained by mixing the main component of epoxy resin and the curing agent in a fixed specified ratio.

[0094] Next, the laminate was left for 2 hours under the curing temperature conditions shown in Table 1 to cure the liquid agent. This yielded the magnetic cores of Examples 1 to 10 and Comparative Examples 1 to 5.

[0095] The magnetic properties of the magnetic cores of Examples 1 to 10 and Comparative Examples 1 to 5, completed in the process described above, were measured. Specifically, the impedance relative permeability and impedance Z of the magnetic cores of Examples 1 to 10 and Comparative Examples 1 to 5 were measured. A Keysight 4294A impedance analyzer was used to measure the impedance relative permeability. In addition, using a lead wire measurement fixture (16047E), the impedance Z at 100 kHz was measured in a single-turn state by passing a Tanaka Electric Wire H-PCV, Φ0.5 mm single-wire lead wire through the laminated core. The impedance Z was measured using a magnetic core that was not cut, i.e., in a state where it formed a closed magnetic circuit on its own.

[0096] Furthermore, the Δt of the magnetic cores of Examples 1 to 10 and Comparative Examples 1 to 5, completed in the process described above, was calculated. Specifically, each magnetic core was cut along the thickness and width directions, and the t1 and t2 of the laminate at the cut surface were measured with a laser microscope. As a result, a tendency for Δt to increase with higher curing temperatures was observed. This is thought to be because, at higher curing temperatures, the viscosity of the liquid decreases, making it easier for the liquid to concentrate in one direction due to gravity between the multiple strip-shaped layers. In addition, a tendency for Δt to increase was observed when the laminate was vacuumed (reduced pressure was applied). This is thought to be because the strip-shaped layers become more easily distorted when vacuumed (reduced pressure is applied).

[0097] As shown in Table 1, the Δt of the magnetic cores in Examples 1 to 10 was all within 10%. Furthermore, the impedance Z of the magnetic cores in Examples 1 to 10 was 10Ω or higher. On the other hand, the Δt of the magnetic cores in Comparative Examples 1 to 5 was greater than 10%. Furthermore, the impedance Z of the magnetic cores in Comparative Examples 1 to 5 was less than 10Ω. These results confirm that the impedance Z of the magnetic core can be maintained at a high level by keeping Δt within 10%. In other words, it was confirmed that the deterioration of the magnetic properties of the magnetic core can be suppressed by keeping Δt within 10%.

[0098] Furthermore, as mentioned above, the Δt of the magnetic cores in Examples 1 to 10 was all within 10%, but the Δt of the magnetic cores in Comparative Examples 1 to 5 was all greater than 10%. These results confirm that the presence of a housing makes it easier to reduce Δt.

[0099]

[0100] This disclosure relates to magnetic cores and clamp cores.

[0101] 1: Clamp core 2, 102, 202: Magnetic core 3, 160: Hollow section 5: Holding case 5a: Case piece 6: Locking mechanism 6a: Hook section 6b: Hook receiving section 10, 110, 210: Core body 20, 120, 220: Laminate 20a: Strip-shaped layer 21: Outer surface 22: Inner surface 23: Bottom surface 24: Top surface 25, 125: Contact end surface 30: Covering body 31: Intervening section 32: Covering body section 40, 140, 240: Housing section 40a: Housing recess 41: Outer wall section 42: Inner wall section 43: Bottom wall section 45: Convex section 46: Recessed section 50: Adjacent end surface 51: Inclined surface section 60: Engaging section 61: Parallel surface 65: Positioning section 70: Engaged section 80: Gap 150: Discretion 160: Hollow 260: Through hole A: Thickness direction B: Width direction C: Length direction H: Gap height L: Imaginary straight line Y: Cutting position

Claims

1. A magnetic core comprising a core body, the core body comprising a laminate formed by stacking a plurality of strip-shaped layers made of a magnetic material in the thickness direction, and a covering body covering the laminate, the covering body including an intervening portion interposed between two adjacent strip-shaped layers among the plurality of strip-shaped layers, where "t1" is the thickness of the strip-shaped layer at one end of the laminate in the width direction, and "t2" is the thickness of the strip-shaped layer at the other end of the laminate in the width direction, and when t1 ≤ t2, the relative difference Δt between t1 and t2 calculated by the following formula is 10% or less.

2. The magnetic core according to claim 1, comprising a housing that houses the core body, the housing comprising an outer wall portion that covers an outer surface which is one side of the laminate in the thickness direction, an inner wall portion that covers an inner surface which is the other side of the laminate in the thickness direction, and a bottom wall portion that covers either one end face in the width direction of the laminate, and the covering body comprising a covering body portion interposed between the outer surface and the outer wall portion, between the inner surface and the inner wall portion, and between the end face and the bottom wall portion, or any one of these.

3. The magnetic core according to claim 2, wherein the covering body portion of the covering is interposed between the bottom wall portion and the end face.

4. The magnetic core according to claim 2 or 3, wherein the laminate does not form a closed magnetic path on its own, but has a contact end face that is exposed to the outside and can form a closed magnetic path when it comes into contact with another magnetic material.

5. The magnetic core according to claim 4, wherein the covering and the housing do not protrude outward beyond the contact end face.

6. The magnetic core according to claim 5, wherein the covering body and the housing of the covering body have adjacent end faces adjacent to the contact end face in a plan view taken from a direction perpendicular to the contact end face, and the adjacent end faces have inclined surfaces that are inclined to move away from the contact end face in a direction perpendicular to the contact end face as they move away from the contact end face in the plan view.

7. The magnetic core according to claim 4, wherein the laminate has a longitudinal end face which is the end face in the longitudinal direction of the strip-shaped layer, and the bottom wall portion has a recess at the position of the longitudinal end face.

8. A clamp core comprising a plurality of magnetic cores as described in claim 4, wherein the plurality of magnetic cores can form a closed magnetic path by contacting each other's contact end faces, and a holding case capable of fixing the plurality of magnetic cores in the state in which the plurality of magnetic cores form a closed magnetic path.

9. The clamp core according to claim 8, wherein the outer wall portion of the housing is provided with an engaging portion, and the holding case is provided with an engaged portion that can engage with the engaging portion.

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