Method for manufacturing a powder magnetic core and powder magnetic core

Abstract

A powder magnetic core is produced by pressing a magnetic powder in a mold while heating it at a prescribed temperature. At least a part of the magnetic powder is covered with a covering agent. The mold is composed of a die, an upper plunger, and a lower plunger. The upper plunger is positioned above the lower plunger in the vertical direction. The mold is provided with a low-temperature portion and a high-temperature portion. The temperature of the low-temperature portion is lower than the temperature of the high-temperature portion by 10°C or more.

Description

Technical Field

[0001] This invention relates to a method for manufacturing pressed powder magnetic cores and to pressed powder magnetic cores. Background Technology

[0002] As a method for manufacturing pressed powder magnetic cores, there exists, for example, the method disclosed in Patent Document 1. In the method for manufacturing pressed powder magnetic cores in Patent Document 1, magnetic powder with its surface covered by an insulating agent is heated and pressed in a mold to form a pressed powder magnetic core. According to this manufacturing method, the magnetic powder and the binder used to bind the magnetic powder are softened by heat. Therefore, according to this manufacturing method, compared with the method of pressing and molding magnetic powder at room temperature, a high filling rate of magnetic powder can be achieved.

[0003] Existing technical documents

[0004] Patent documents

[0005] Patent Document 1: Japanese Patent No. 6651082. Summary of the Invention

[0006] The problem the invention aims to solve

[0007] However, the manufacturing method in Patent Document 1 has the following problems: the manufactured powder core is prone to breakage and bulging; the manufactured powder core cannot obtain the desired electromagnetic characteristics.

[0008] Therefore, the object of the present invention is to provide a method for manufacturing a pressed powder magnetic core, which does not produce breakage or bulging and achieves the desired electromagnetic characteristics. Furthermore, the object of the present invention is to provide a pressed powder magnetic core manufactured by this method.

[0009] Solution for solving the problem

[0010] The applicant has conducted an in-depth study on the causes of the above-mentioned problems, focusing on the following aspects: In a typical hot press, magnetic powder is pressurized in a mold located in a heating chamber; thereby, the mold as a whole forms a uniform temperature.

[0011] Specifically, the applicant has discovered the following phenomenon: when the binder is a thermosetting resin, the temperature distribution of the mold is uniform, therefore, overall curing begins from the outer part of the pressed powder core in contact with the mold. Based on this phenomenon, the applicant has discovered the following: due to the cured resin on the outer part of the pressed powder core, the release of air remaining between the magnetic powder particles to the outside of the pressed powder core is hindered; due to the cured resin on the outer part of the pressed powder core, the release of gas generated by the binder, etc., to the outside of the pressed powder core is hindered; therefore, the pressed powder core may crack or bulge.

[0012] Furthermore, the applicant has also discovered the following phenomenon: when the magnetic powder crystallizes through heat treatment, the temperature distribution of the mold is uniform throughout, thus the overall solidification begins from the outer portion of the pressed powder core in contact with the mold. Based on this phenomenon, the applicant has discovered the following: the heat generated by the crystallization of the outer portion of the pressed powder core is transmitted inside the pressed powder core, causing overheating in the center of the pressed powder core; due to the aforementioned heat, Fe-B compound phases that degrade the soft magnetic properties precipitate in the center of the pressed powder core; therefore, the electromagnetic properties of the pressed powder core deteriorate.

[0013] In other words, the applicant discovered that the aforementioned problem was caused by the uniform temperature distribution throughout the mold. Based on this, the applicant proposed a solution to make the temperature of the mold partially non-uniform, and thus completed this invention.

[0014] The first aspect of the present invention provides a method for manufacturing a pressed powder magnetic core, wherein the method for manufacturing the first pressed powder magnetic core is as follows:

[0015] Powder-pressed magnetic cores are manufactured by heating magnetic powder at a specified temperature and applying pressure within a mold.

[0016] At least a portion of the magnetic powder is covered by a covering agent.

[0017] The mold consists of a pressure mold, an upper pressure head, and a lower pressure head.

[0018] The upper pressure head is positioned above the lower pressure head in the vertical direction.

[0019] The mold is provided with a low-temperature section and a high-temperature section, wherein the temperature of the low-temperature section is more than 10°C lower than the temperature of the high-temperature section.

[0020] A second aspect of the present invention provides a pressed powder magnetic core, as a first pressed powder magnetic core.

[0021] It contains at least a portion of magnetic powder that is covered by a coating agent.

[0022] The magnet powder contains nanocrystals.

[0023] The pressed powder magnetic core has a first surface, a second surface, and a peripheral surface.

[0024] The first surface faces the first position in the specified direction.

[0025] The second face faces a second direction opposite to the first direction.

[0026] The circumferential surface intersects with an orthogonal direction, and the orthogonal direction is orthogonal to the specified direction.

[0027] When the crystallinity of the first surface is C1, the crystallinity of the second surface is C2, and the crystallinity of the peripheral surface is C, the following condition is met: .

[0028] A third aspect of the present invention provides a pressed powder magnetic core, as a second pressed powder magnetic core.

[0029] It contains at least a portion of magnetic powder that is covered by a coating agent.

[0030] The magnet powder is a metallic glass with a glass transition point.

[0031] The pressed powder magnetic core has a first surface, a second surface, and a peripheral surface.

[0032] The first surface faces the first position in the specified direction.

[0033] The second face faces a second direction opposite to the first direction.

[0034] The circumferential surface intersects with an orthogonal direction, and the orthogonal direction is orthogonal to the specified direction.

[0035] When the surface resistance of the first surface is R1, the surface resistance of the second surface is R2, and the surface resistance of the circumferential surface is R, the following conditions are met: .

[0036] Invention Effects

[0037] The method for manufacturing the pressed powder magnetic core of the present invention is configured such that a mold is provided with a low-temperature section and a high-temperature section; the temperature of the low-temperature section is at least 10°C lower than the temperature of the high-temperature section. Therefore, in the method for manufacturing the pressed powder magnetic core of the present invention, the outer surface of the pressed powder magnetic core includes a first portion in contact with the low-temperature section of the mold and a second portion in contact with the high-temperature section of the mold, and the curing of the binder in the first portion is delayed compared to the curing of the binder in the second portion. Therefore, since air remaining between the magnetic powder particles and gases generated by the binder are released from the first portion, the pressed powder magnetic core will not crack or bulge. Furthermore, according to the method for manufacturing the pressed powder magnetic core of the present invention, since the heat generated during the crystallization of the magnetic powder is dissipated to the outside of the pressed powder magnetic core via the low-temperature section of the mold, the center of the pressed powder magnetic core will not overheat even in the final stage of the crystallization reaction. Therefore, according to the method for manufacturing the pressed powder magnetic core of the present invention, Fe-B compound phases that degrade the soft magnetic properties of the pressed powder magnetic core will not precipitate in the pressed powder magnetic core. That is, in the manufacturing method of the pressed powder magnetic core of the present invention, a pressed powder magnetic core that does not break or bulge and has the desired electromagnetic properties can be obtained.

[0038] Furthermore, the pressed powder magnetic core of the present invention is configured such that the magnetic powder contains nanocrystals; when the crystallinity of the first surface is C1, the crystallinity of the second surface is C2, and the crystallinity of the peripheral surface is C, the following conditions are met: Therefore, the pressed powder magnetic core of the present invention will not break or bulge, and has the desired electromagnetic properties.

[0039] Furthermore, the pressed powder magnetic core of the present invention is configured as follows: the magnetic powder is a metallic glass having a glass transition point; when the surface resistance of the first surface is R1, the surface resistance of the second surface is R2, and the surface resistance of the peripheral surface is R, the following conditions are met: Therefore, the pressed powder magnetic core of the present invention will not break or bulge, and has the desired electromagnetic properties.

[0040] By referring to the accompanying drawings and discussing the following description of the best embodiments, the object of the present invention can be accurately understood and its structure can be more fully understood. Attached Figure Description

[0041] Figure 1 This is a top view showing the pressed powder magnetic core according to the first embodiment of the present invention.

[0042] Figure 2 To indicate Figure 1 A bottom view of the pressed powder magnetic core.

[0043] Figure 3 For illustrative purposes Figure 1 A flowchart of the manufacturing method of pressed powder magnetic core.

[0044] Figure 4 For illustrative purposes Figure 1 A diagram illustrating the manufacturing method of pressed powder magnetic cores. In the diagram, the upper and lower pressure heads of the mold are in their initial state.

[0045] Figure 5 For illustrative purposes Figure 1 Another diagram shows the manufacturing method of the pressed powder magnetic core. In the diagram, the upper and lower pressure heads are in the process of pressurizing the magnetic powder.

[0046] Figure 6 For illustrative purposes Figure 1 Another diagram illustrating the manufacturing method of the pressed powder magnetic core. In the diagram, the upper and lower pressure heads are in a state where the magnetic powder has been pressurized.

[0047] Figure 7 This is a top view showing the pressed powder magnetic core according to the second embodiment of the present invention.

[0048] Figure 8 To indicate Figure 7 A bottom view of the pressed powder magnetic core.

[0049] Figure 9 For illustrative purposes Figure 7 A diagram illustrating the manufacturing method of pressed powder magnetic cores. In the diagram, the upper and lower pressure heads of the mold are in their initial state.

[0050] Figure 10 For illustrative purposes Figure 1 and Figure 7 A diagram illustrating a variation of the manufacturing method for pressed powder magnetic cores. In the diagram, the upper and lower pressure heads of the mold are in their initial state. Detailed Implementation

[0051] This invention can be implemented in various modifications and methods. As an example, the specific embodiments shown in the accompanying drawings are described in detail below. The drawings and embodiments do not limit the invention to the specific methods disclosed. All modifications, equivalents, and alternatives within the scope of the appended claims are included in the scope of this invention.

[0052] (First Implementation)

[0053] like Figure 1 As shown, the pressed powder magnetic core 600 of this embodiment contains magnetic powder 100 covered by the covering agent 110. However, the present invention is not limited to this; the pressed powder magnetic core 600 may contain at least a portion of the magnetic powder 100 covered by the covering agent 110. That is, a portion of the magnetic powder 100 may not be covered by the covering agent 110.

[0054] (Magnetic powder)

[0055] The magnetic powder 100 of this embodiment contains nanocrystals in an amorphous phase. That is, the magnetic powder 100 precipitates nanocrystals in an amorphous state through heat treatment. Specifically, the magnetic powder 100 is of the Fe-B-Si-PC-Cu system, Fe-B-Si-Nb-Cu system, Fe-(Nb,Zr)-B system, etc. The magnetic powder 100 has a crystallization temperature Tc.

[0056] (cover)

[0057] The purpose of the covering agent 110 in this embodiment is to improve the insulation and mechanical strength of the magnetic powder 100. The covering agent 110 is composed of organic materials such as resins and inorganic materials such as metal oxides. Examples of resins constituting the covering agent 110 include thermosetting resins such as silicone resins, epoxy resins, phenolic resins, polyamide resins, and polyimide resins, as well as thermoplastic resins such as PPS resins and PEEK resins. Examples of inorganic materials constituting the covering agent 110 include metal oxides such as alumina, silica, and magnesium oxide, low-melting-point glasses such as phosphate-based, borate-based, and silicate-based materials, and inorganic polymers such as polysilanes and polysilazanes. Alternatively, the covering agent 110 may be composed solely of organic materials. The covering agent 110 may also be composed solely of inorganic materials. The covering agent 110 may also be composed of a composite material of organic and inorganic materials. More specifically, the covering agent 110 can be configured as follows: the covering agent 110 consists of a two-layer structure, an inner layer and an outer layer; the inner layer is in contact with the surface of the magnetic powder 100; the inner layer is formed of an inorganic material; the outer layer is located outside the inner layer; the outer layer is formed of an organic material. Furthermore, the covering agent 110 can be made from a variety of materials. The covering agent 110 can be formed from two or more layers of different materials to create a multi-layer structure.

[0058] like Figure 1 and Figure 2 As shown, the pressed powder magnetic core 600 of this embodiment has a first surface 620, a second surface 640, and a peripheral surface 660.

[0059] like Figure 1 As shown, in this embodiment, the first surface 620 faces a first position within a predetermined direction. The first surface 620 is a plane orthogonal to the predetermined direction. Figure 2 As shown, in this embodiment, the second surface 640 faces a second direction opposite to the first direction. The second surface 640 is a plane orthogonal to a predetermined direction. Here, in this embodiment, the predetermined direction is the Z direction. Furthermore, the predetermined direction is also the up-down direction. Here, up is the +Z direction, and down is the -Z direction. In addition, the first direction is the +Z direction, and the second direction is the -Z direction. That is, the first direction is up, and the second direction is down.

[0060] like Figure 1 As shown, in this embodiment, the peripheral surface 660 intersects with an orthogonal direction, which is orthogonal to a predetermined direction. When the pressed powder core 600 is viewed from the predetermined direction, the peripheral surface 660 has an outer edge shaped like an athletic track.

[0061] In the pressed powder magnetic core 600 of this embodiment, when the crystallinity of the first surface 620 is C1, the crystallinity of the second surface 640 is C2, and the crystallinity of the peripheral surface 660 is C, the following conditions are met: That is, in the pressed powder magnetic core 600 of this embodiment, when the maximum value among the crystallinity C1 of the first surface 620, the crystallinity C2 of the second surface 640, and the crystallinity C of the peripheral surface 660 is Cmax, and the minimum value among the crystallinity C1 of the first surface 620, the crystallinity C2 of the second surface 640, and the crystallinity C of the peripheral surface 660 is Cmin, the following condition is met: Therefore, the pressed powder magnetic core 600 of the present invention will not break or bulge, and has the desired electromagnetic properties. Specifically, in this embodiment, among the crystallinity C1 of the first surface 620, the crystallinity C2 of the second surface 640, and the crystallinity C of the peripheral surface 660, the crystallinity C of the peripheral surface 660 is the maximum. That is, in this embodiment, Here, the crystallinity C1, C2, and C of the first surface 620, the second surface 640, and the peripheral surface 660 are calculated by analyzing the measurement results obtained from X-ray diffraction using the WPPD method (Whole-powder-pattern decomposition method).

[0062] (Manufacturing method of pressed powder magnetic core)

[0063] Reference Figures 1 to 6 The pressed powder magnetic core 600 of this embodiment is manufactured as follows.

[0064] Figure 3 This is a flowchart illustrating the manufacturing method of the pressed powder magnetic core 600 according to this embodiment. Specifically, the pressed powder magnetic core 600 is manufactured by sequentially performing a covering process, a preforming process, a filling process, and a pressurizing and heating process. The details of each process will be described below.

[0065] (Covering process)

[0066] In the coating process, magnetic powder 100 with a coating agent 110 coated on its surface is prepared as the raw material for the pressed powder core 600. However, the present invention is not limited thereto. As the raw material for the pressed powder core 600, a mixture of magnetic powder 100 coated with the coating agent 110 and magnetic powder 100 not coated with the coating agent 110 may also be prepared.

[0067] The method of coating the magnet powder 100 can be selected from various methods such as powder mixing, impregnation, spraying, flow layer, sol-gel, CVD, or PVD, depending on the type of coating material and economic considerations.

[0068] (Preforming process)

[0069] After the covering process, the magnet powder 100 is pre-formed.

[0070] (Filling process)

[0071] Reference Figure 4 After the preforming process, the preformed body is housed in a predetermined mold 300. The mold 300 used in the manufacture of the powder core 600 in this embodiment will be described in detail below.

[0072] Figure 4 As shown, the mold 300 used in the manufacture of the pressed powder magnetic core 600 in this embodiment is composed of a pressing mold 310, an upper pressing head 350, and a lower pressing head 330.

[0073] Reference Figure 4 In an orthogonal plane orthogonal to the vertical direction, the die 310 of this embodiment surrounds the upper pressure head 350. In the same orthogonal plane, the die 310 surrounds the lower pressure head 330. The die 310 has a first opening 316, a second opening 318, an inner wall 312, and a receiving portion 314. The first opening 316 is located at the upper end of the die 310 in the vertical direction. The second opening 318 is located at the lower end of the die 310 in the vertical direction. In a direction orthogonal to the vertical direction, the first opening 316 has a larger outer perimeter than the second opening 318. The inner wall 312 tapers downwards in the vertical direction. That is, the die 310 has an inner wall 312 that tapers downwards in the vertical direction. The receiving portion 314 has a hole that penetrates the die 310 in the vertical direction. The receiving portion 314 connects the first opening 316 and the second opening 318.

[0074] like Figure 4 As shown, in this embodiment, the upper pressure head 350 is partially housed in the receiving portion 314 of the mold 310. The upper pressure head 350 is located above the lower pressure head 330 in the vertical direction.

[0075] like Figure 4 As shown, in this embodiment, the lower pressure head 330 is partially housed in the receiving portion 314 of the mold 310. The lower pressure head 330 is located below the upper pressure head 350 in the vertical direction.

[0076] Reference Figure 4 The preformed body is received into the mold 300, that is, the magnetic powder 100 is filled into the mold 300 as follows: with the lower pressure head 330 inserted into the receiving portion 314 from the lower side of the second opening 318 of the mold 300, the magnetic powder 100 is fed into the receiving portion 314 of the mold 300 from the first opening 316; after the magnetic powder 100 is fed in, the upper pressure head 350 is partially inserted into the receiving portion 314 from the first opening 316.

[0077] (Pressure and heating process)

[0078] Reference Figures 4 to 6After the filling process, the magnetic powder 100 is pressed and heated within the mold 300 to obtain the pressed powder magnetic core 600 as a molded body. That is, the pressed powder magnetic core 600 of this embodiment is manufactured by pressing and heating the magnetic powder 100 covered by the covering agent 110 within the mold 300 at a predetermined temperature T. However, the present invention is not limited to this. The pressed powder magnetic core 600 can also be manufactured by pressing and heating at a predetermined temperature T within the mold 300 with at least a portion of the magnetic powder 100 covered by the covering agent 110. In other words, the pressed powder magnetic core 600 can also be manufactured by pressing and heating both the magnetic powder 100 covered by the covering agent 110 and the magnetic powder 100 not covered by the covering agent 110 within the mold 300 at a predetermined temperature T. Furthermore, the predetermined temperature T is higher than the crystallization temperature Tc of the magnetic powder 100.

[0079] Specifically, the magnetic powder 100 filled into the mold 300 is heated while being subjected to molding pressure. At this time, the higher the molding pressure, the greater the high-density effect. However, excessively increasing the molding pressure will saturate the high-density effect, increasing the risk of mold 300 breakage. Therefore, the molding pressure is set in the range of 100 to 2000 MPa. Furthermore, the filled magnetic powder 100 is heated by setting the temperature in a manner that produces the temperature distribution described later in the mold 300.

[0080] like Figure 4 As shown, the mold 300 of this embodiment is provided with a low-temperature section 400 and a high-temperature section 500. The temperature Tl of the low-temperature section 400 is at least 10°C lower than the temperature Th of the high-temperature section 500. More specifically, the high-temperature section 500 is a pressing mold 310, and the low-temperature section 400 is an upper pressing head 350. However, the present invention is not limited to this, and the low-temperature section 400 may also be a lower pressing head 330. In addition, the crystallization temperature Tc of the magnetic powder 100 is lower than the temperature Th of the high-temperature section 500. The temperature difference between the temperature Tl of the low-temperature section 400 and the temperature Th of the high-temperature section 500 is preferably 650°C or less. More preferably, the temperature difference between the temperature Tl of the low-temperature section 400 and the temperature Th of the high-temperature section 500 is 420°C or less.

[0081] like Figure 4 As shown, the mold 300 of this embodiment is further provided with an additional high-temperature section 520. The temperature Tm of the additional high-temperature section 520 is between the temperature Tl of the low-temperature section 400 and the temperature Th of the high-temperature section 500. It should be noted that the temperature Tm of the additional high-temperature section 520 is preferably 10°C or more higher than the temperature Tl of the low-temperature section 400. In this embodiment, the additional high-temperature section 520 is the lower pressure head 330. In addition, when the lower pressure head 330 is the low-temperature section 400, the upper pressure head 350 is the additional high-temperature section 520.

[0082] Reference Figures 4 to 6The magnetic powder 100 is subjected to molding pressure and heating in the following manner.

[0083] First, a compressive force is applied to the upper pressure head 350 and the lower pressure head 330 to compress the magnetic powder 100 filled into the mold 300. Next, the low-temperature section 400, the high-temperature section 500, and the additional high-temperature section 520 of the mold 300 are heated using a heater, high-frequency induction heating, or a burner, with the temperature Th of the high-temperature section 500 being at least 10°C higher than the temperature Tl of the low-temperature section 400, and the temperature Tm of the additional high-temperature section 520 being between the temperatures Tl of the low-temperature section 400 and Th of the high-temperature section 500. Afterward, the mold 300 is cooled, and the resulting pressed powder magnetic core 600 is removed from the mold 300, thus obtaining the pressed powder magnetic core 600 as a molded body. Furthermore, by performing this pressurization and heating process, nanocrystals precipitate in the amorphous phase of the pressed powder magnetic core 600 in this embodiment.

[0084] pass Figure 1 , Figure 2 as well as Figure 4 It is understandable that the first surface 620 of the manufactured pressed powder magnetic core 600 is the portion that contacts the upper pressure head 350 of the mold 300 when the magnetic powder 100 is pressed and formed in the mold 300. That is, the first surface 620 is the portion that contacts the low-temperature section 400 of the mold 300 when the magnetic powder 100 is pressed and formed in the mold 300. Furthermore, the second surface 640 of the manufactured pressed powder magnetic core 600 is the portion that contacts the lower pressure head 330 of the mold 300 when the magnetic powder 100 is pressed and formed in the mold 300. That is, the second surface 640 is the portion that contacts the additional high-temperature section 520 of the mold 300 when the magnetic powder 100 is pressed and formed in the mold 300. Additionally, the peripheral surface 660 of the manufactured pressed powder magnetic core 600 is the portion that contacts the inner wall 312 of the mold 310 when the magnetic powder 100 is pressed and formed in the mold 300. That is, the peripheral surface 660 is the part that comes into contact with the high-temperature part 500 of the mold 300 when the magnetic powder 100 is pressed and formed in the mold 300.

[0085] As described above, the first surface 620, the second surface 640, and the peripheral surface 660 of the pressed powder magnetic core 600 are the parts that contact the upper pressure head 350, the lower pressure head 330, and the pressing mold 310 of the mold 300 used in manufacturing, respectively. Therefore, the physical properties of the first surface 620, the second surface 640, and the peripheral surface 660 reflect the temperature setting of the parts that contact the mold 300.

[0086] The above-described method for manufacturing the pressed powder magnetic core 600 includes a covering process, a preforming process, a filling process, and a pressurizing and heating process, but the present invention is not limited thereto. The method for manufacturing the pressed powder magnetic core 600 may also be modified to manufacture the pressed powder magnetic core 600 without performing the preforming process. That is, the pressed powder magnetic core 600 can be manufactured by sequentially performing the covering process, the filling process, and the pressurizing and heating process. Furthermore, the method for manufacturing the pressed powder magnetic core 600 may be modified to further perform heat treatment on the pressed powder magnetic core 600 manufactured through the pressurizing and heating process.

[0087] (Second Implementation)

[0088] like Figure 7 and Figure 8 As shown, the pressed powder magnetic core 600A of this embodiment contains magnetic powder 100A covered by a covering agent 110A. However, the present invention is not limited to this; the pressed powder magnetic core 600A may contain at least a portion of the magnetic powder 100A covered by the covering agent 110A. That is, a portion of the magnetic powder 100A may not be covered by the covering agent 110A.

[0089] (Magnetic powder)

[0090] The magnet powder 100A in this embodiment is a metallic glass with a glass transition point. Specifically, the magnet powder 100A is of the FePCBSiGa system, FeSiBM (M is a transition metal) system, or FePBM (M is a transition metal) system. The magnet powder 100A has a glass transition temperature Tg.

[0091] (cover)

[0092] The purpose of the covering agent 110A in this embodiment is to improve the insulation and mechanical strength of the magnet powder 100A. The covering agent 110A is composed of organic substances such as resin and inorganic substances such as metal oxides. Here, the same resin as the covering agent 110 in the first embodiment can be used as the resin constituting the covering agent 110A.

[0093] like Figure 7 and Figure 8 As shown, the pressed powder magnetic core 600A of this embodiment has a first surface 620A, a second surface 640A, and a peripheral surface 660A.

[0094] like Figure 7 As shown, in this embodiment, the first surface 620A faces a first position within a predetermined direction. The first surface 620A is a plane orthogonal to the predetermined direction. Figure 8As shown, in this embodiment, the second surface 640A faces a second direction opposite to the first direction. The second surface 640A is a plane orthogonal to a predetermined direction. In this embodiment, the peripheral surface 660A intersects with an orthogonal direction, which is orthogonal to the predetermined direction. When the pressed powder core 600A is viewed from the predetermined direction, the peripheral surface 660A has an outer edge in the shape of an athletic track.

[0095] In the pressed powder magnetic core 600A of this embodiment, when the surface resistance of the first surface 620A is set to R1, the surface resistance of the second surface 640A is set to R2, and the surface resistance of the peripheral surface 660A is set to R, the following conditions are met: That is, in the pressed powder magnetic core 600A of this embodiment, when the maximum value among the surface resistance values ​​R1 of the first surface 620A, R2 of the second surface 640A, and R of the peripheral surface 660A is Rmax, and the minimum value among the surface resistance values ​​R1, R2, and R of the first surface 620A, R40A, and R660A is Rmin, Rmin / Rmax ≤ 0.95 is satisfied. Therefore, the pressed powder magnetic core 600A of the present invention will not break or bulge, and has the desired electromagnetic characteristics. Here, the probes of the tester are brought into contact with the surfaces of the first surface 620A, the second surface 640A, and the peripheral surface 660A with a probe-to-probe distance of 10.5 mm, and the surface resistance values ​​R1, R2, and R of the first surface 620A, the second surface 640A, and the peripheral surface 660A are measured.

[0096] (Manufacturing method of pressed powder magnetic core)

[0097] Reference Figures 3 to 9 The pressed powder magnetic core 600A of this embodiment is manufactured as follows.

[0098] The pressed powder magnetic core 600A of this embodiment is manufactured in the same manner as the pressed powder magnetic core 600 of the first embodiment, by sequentially performing a covering process, a preforming process, a filling process, and a pressurizing and heating process. Here, the covering process and the preforming process are the same as in the first embodiment, and detailed descriptions are omitted.

[0099] (Filling process)

[0100] Reference Figure 9 After the preforming process, magnetic powder 100A is filled into a predetermined mold 300. The mold 300 of this embodiment has the same structure as the mold 300 of the first embodiment described above, therefore a detailed description is omitted.

[0101] Reference Figure 9The filling of the magnetic powder 100A into the mold 300 is carried out as follows: with the lower pressure head 330 inserted into the receiving part 314 from the lower side of the second opening 318 of the mold 300, the magnetic powder 100A is injected into the receiving part 314 of the mold 300 through the first opening 316. After the injection of the magnetic powder 100A is completed, the upper pressure head 350 is partially inserted into the receiving part 314 from the first opening 316.

[0102] (Pressure and heating process)

[0103] Reference Figure 9 and Figures 4 to 6 After the filling process, the magnetic powder 100A is pressed and heated in the mold 300 to obtain the pressed powder magnetic core 600A as a molded body. That is, the pressed powder magnetic core 600A of this embodiment is manufactured by pressing the magnetic powder 100A covered with the covering agent 110A in the mold 300 while heating it at a predetermined temperature TA. However, the present invention is not limited to this. The pressed powder magnetic core 600A may also be manufactured by pressing at a predetermined temperature TA in the mold 300 with at least a portion of the magnetic powder 100A covered with the covering agent 110A. In other words, the pressed powder magnetic core 600A may also be manufactured by pressing both the magnetic powder 100A covered with the covering agent 110A and the magnetic powder 100A not covered with the covering agent 110A in the mold 300 while heating it at a predetermined temperature TA.

[0104] Specifically, the magnetic powder 100A filled into the mold 300 is heated while being subjected to molding pressure. At this time, the higher the molding pressure, the better the high-density effect. However, excessively increasing the molding pressure will saturate the high-density effect, increasing the risk of mold 300 breakage. Therefore, the molding pressure is preferably in the range of 100 to 2000 MPa. Furthermore, the temperature is set to produce a temperature distribution in the mold 300 as described later, and the filled magnetic powder 100A is heated accordingly.

[0105] like Figure 9 As shown, the mold 300 of this embodiment is provided with a low-temperature section 400 and a high-temperature section 500. The temperature Tl of the low-temperature section 400 is at least 10°C lower than the temperature Th of the high-temperature section 500. More specifically, the high-temperature section 500 is a pressure mold 310, and the low-temperature section 400 is an upper pressure head 350. However, the present invention is not limited to this, and the low-temperature section 400 may also be a lower pressure head 330. The temperature difference between the temperature Tl of the low-temperature section 400 and the temperature Th of the high-temperature section 500 is preferably 650°C or less. More preferably, the temperature difference between the temperature Tl of the low-temperature section 400 and the temperature Th of the high-temperature section 500 is 420°C or less.

[0106] like Figure 9As shown, the mold 300 of this embodiment is further provided with an additional high-temperature section 520. The temperature Tm of the additional high-temperature section 520 is between the temperature Tl of the low-temperature section 400 and the temperature Th of the high-temperature section 500. It should be noted that the temperature Tm of the additional high-temperature section 520 is preferably 10°C or more higher than the temperature of the low-temperature section 400. In this embodiment, the additional high-temperature section 520 is the lower pressure head 330. It should be noted that when the lower pressure head 330 is the low-temperature section 400, the upper pressure head 350 is the additional high-temperature section 520.

[0107] Reference Figure 9 and Figures 4 to 6 Molding pressure and heating are applied to the magnet powder 100A in the following manner.

[0108] First, a clamping force is applied to the upper pressure head 350 and the lower pressure head 330 to compress the magnetic powder 100A filled into the mold 300. Next, the low-temperature section 400, the high-temperature section 500, and the additional high-temperature section 520 of the mold 300 are heated using a heater, high-frequency induction heating, or a burner, such that the temperature Th of the high-temperature section 500 is at least 10°C higher than the temperature Tl of the low-temperature section 400, and the temperature Tm of the additional high-temperature section 520 is between the temperature Tl of the low-temperature section 400 and the temperature Th of the high-temperature section 500. Then, the mold 300 is cooled, and the resulting pressed powder magnetic core 600A is removed from the mold 300, thus obtaining the pressed powder magnetic core 600A as a molded body.

[0109] pass Figures 7 to 9 It is understandable that the first surface 620A of the manufactured pressed powder magnetic core 600A is the portion that contacts the upper pressure head 350 of the mold 300 when the magnetic powder 100A is pressed and formed in the mold 300. That is, the first surface 620A is the portion that contacts the low-temperature section 400 of the mold 300 when the magnetic powder 100A is pressed and formed in the mold 300. Furthermore, the second surface 640A of the manufactured pressed powder magnetic core 600A is the portion that contacts the lower pressure head 330 of the mold 300 when the magnetic powder 100A is pressed and formed in the mold 300. That is, the second surface 640A is the portion that contacts the additional high-temperature section 520 of the mold 300 when the magnetic powder 100A is pressed and formed in the mold 300. Additionally, the peripheral surface 660A of the manufactured pressed powder magnetic core 600A is the portion that contacts the inner wall 312 of the mold 310 when the magnetic powder 100A is pressed and formed in the mold 300. That is, the peripheral surface 660A is the part that comes into contact with the high-temperature part 500 of the mold 300 when the magnetic powder 100A is pressed and formed in the mold 300.

[0110] As described above, the first surface 620A, the second surface 640A, and the peripheral surface 660A of the pressed powder magnetic core 600A are the portions that contact the upper pressure head 350, the lower pressure head 330, and the die 310 of the mold 300 used for manufacturing, respectively. Therefore, the physical properties of the first surface 620A, the second surface 640A, and the peripheral surface 660A reflect the temperature setting of the portions that contact the mold 300.

[0111] The above-described method for manufacturing the pressed powder magnetic core 600A includes a covering process, a preforming process, a filling process, and a pressurizing and heating process, but the present invention is not limited thereto. The method for manufacturing the pressed powder magnetic core 600A can also be modified to manufacture the pressed powder magnetic core 600A without performing the preforming process. That is, the pressed powder magnetic core 600A can be manufactured by sequentially performing the covering process, the filling process, and the pressurizing and heating process.

[0112] The mold 300 used in the manufacturing method of the pressed powder magnetic core 600, 600A in the above embodiments can be deformed in the following manner.

[0113] like Figure 10 As shown, the mold 300B in this modified example is composed of a pressure mold 310, an upper pressure head 350B, and a lower pressure head 330. Here, the pressure mold 310 and the lower pressure head 330 are the same as those of the mold 300 in the above embodiment, and detailed descriptions are omitted.

[0114] like Figure 10 As shown, in this modified example, the upper pressure head 350B is located above the lower pressure head 330 in the vertical direction. The upper pressure head 350B is constructed by combining multiple components. The multiple components constituting the upper pressure head 350B include a low-temperature component 352B and a high-temperature component 356B.

[0115] like Figure 10As shown, the mold 300B of this modified example is provided with a low-temperature section 400B, a high-temperature section 500, an additional high-temperature section 520, and an auxiliary high-temperature section 540. The temperature Tl of the low-temperature section 400B is at least 10°C lower than the temperature Th of the high-temperature section 500. The temperature Tm of the additional high-temperature section 520 is between the temperature Tl of the low-temperature section 400B and the temperature Th of the high-temperature section 500. The temperature Td of the auxiliary high-temperature section 540 is between the temperature Tl of the low-temperature section 400B and the temperature Th of the high-temperature section 500. Furthermore, the temperature difference between the temperature Tl of the low-temperature section 400B and the temperature Th of the high-temperature section 500 is preferably 650°C or less. The temperature difference between the temperature Tl of the low-temperature section 400B and the temperature Th of the high-temperature section 500 is more preferably 420°C or less. Additionally, the temperature Tm of the additional high-temperature section 520 is preferably at least 10°C higher than the temperature Tl of the low-temperature section 400B, and the temperature Td of the auxiliary high-temperature section 540 is preferably at least 10°C higher than the temperature Tl of the low-temperature section 400B. Furthermore, the temperature Td of the auxiliary high-temperature section 540 can be the same as the temperature Th of the high-temperature section 500. In this modified example, the low-temperature section 400B is a low-temperature component 352B, the high-temperature section 500 is a mold 310, the additional high-temperature section 520 is a lower pressure head 330, and the auxiliary high-temperature section 540 is a high-temperature component 356B. Figure 10 As shown, the low-temperature section 400B is configured to be sandwiched between two auxiliary high-temperature sections 540 in the Y direction, but the present invention is not limited thereto. That is, the configuration of the low-temperature section 400B and the auxiliary high-temperature section 540 can be reversed. That is, the auxiliary high-temperature section 540 can also be configured to be sandwiched between two low-temperature sections 400B in the Y direction. Furthermore, the pressing head 330 can also be composed of multiple components including the low-temperature component 352B and the high-temperature component 356B.

[0116] (Compression molding)

[0117] Reference Figure 10 The magnetic powders 100 and 100A are filled and pressurized into the mold 300B in the same manner as in the above-described embodiments.

[0118] (Powder-pressed magnetic core)

[0119] In a modified example, as described above, the magnetic powder 100 and 100A covered by the covering agent 110 and 110A can be pressurized and heated under specified conditions to obtain the pressed magnetic core 600 and 600A containing the magnetic powder 100 and 100A covered by the covering agent 110 and 110A.

[0120] The embodiments of the present invention will be described in further detail below with reference to the examples.

[0121] (Examples 1-26, A1-A15 and Comparative Examples 1-9, A1-A6)

[0122] As the magnet powder 100, Fe was used 80.9 Si3B6P 8.5 Cr1Cu 0.6 (at%). A P2O5-ZnO-R2O-based insulating covering agent 110 was mixed into the magnetic powder 100 at a weight ratio of 1.0 wt% relative to the mixture, and the magnetic powder 100 was covered with the insulating covering agent 110. The magnetic powder 100 covered with the insulating covering agent 110 and phenolic resin as a binder were mixed at a weight ratio of 0.4 wt% relative to the mixture to prepare a mixture. This mixture (weight: 37 g) was filled into a mold 300 and molded at a pressure of 8 t / cm. 2 The mixture was heated and pressed under the temperature conditions shown in Table 1 below to produce a pressed powder magnetic core with a length of 55.69 mm, a width of 23 mm, and a thickness of 4.5 mm. Additionally, Fe... 80.9 Si3B6P 8.5 Cr1Cu 0.6 The precipitation temperature (crystallization temperature Tc) of α-Fe is 400℃. 80.9 Si3B6P 8.5 Cr1Cu 0.6 The precipitation temperature of the Fe-B compound is 499℃. The evaluation results of the fabricated powder core are shown in Table 1.

[0123] [Table 1]

[0124]

[0125] The pressed powder magnetic cores 600 of Examples 1-4, 6-9, 11-18, 20-26, A5, and A10 in Table 1 were manufactured using a mold 300 whose temperature Tl of the upper pressure head 350 (serving as the low-temperature section 400) is at least 10°C lower than the temperature Th of the pressing mold 310 (serving as the high-temperature section 500). Table 1 shows the following: The pressed powder magnetic cores 600 of Examples 1-4, 6-9, 11-18, 20-26, A5, and A10 have good appearance; the pressed powder magnetic cores 600 of Examples 1-4, 6-9, 11-18, 20-26, A5, and A10 do not precipitate compound phases, and therefore have good electromagnetic properties. The pressed powder magnetic cores 600 of Examples 5, 10, 19, A1, A5, A6, A10, and A15 in Table 1 were manufactured using a mold 300 whose temperature Tl of the lower pressure head 330 (serving as the low-temperature section 400) was at least 10°C lower than the temperature Th of the mold 310 (serving as the high-temperature section 500). Table 1 shows the following: the pressed powder magnetic cores 600 of Examples 5, 10, 19, A1, A5, A6, A10, and A15 have good appearance; the pressed powder magnetic cores 600 of Examples 5, 10, 19, A1, A5, A6, A10, and A15 did not precipitate compound phases, and therefore have good electromagnetic properties. On the other hand, the pressed powder magnetic cores of Comparative Examples 1 to 8 and A1 to A6 in Table 1 were manufactured under conditions where the temperature difference between the mold 310 and the upper pressure head 350 and the lower pressure head 330 was less than 10°C. Table 1 shows the following: the powder cores of Comparative Examples 1-8 and A1-A6 exhibited cracks in appearance; the powder cores of Comparative Examples 1-8 and A1-A6 precipitated compound phases, resulting in poor electromagnetic properties. Furthermore, the powder core of Comparative Example 9 in Table 1 was manufactured under conditions where the temperature difference between the die 310 and the upper and lower pressure heads 350 was less than 10°C. Table 1 shows that in the powder core of Comparative Example 9, since heating was performed at a temperature below the crystallization temperature Tc, crystallization was not promoted, resulting in poor electromagnetic properties.

[0126] The pressed powder magnetic cores 600 of Examples A2, A3, A7, A8, A11, A12, and A14 in Table 1 were manufactured using a mold 300 whose temperature Th (of the low-temperature section 400) is at least 10°C lower than the temperature Tl (of the upper pressure head 350, which is the high-temperature section 500). Table 1 shows the following: The pressed powder magnetic cores 600 of Examples A2, A3, A7, A8, A11, A12, and A14 have good appearance; the pressed powder magnetic cores 600 of Examples A2, A3, A7, A8, A11, A12, and A14 do not precipitate compound phases, and therefore have good electromagnetic properties. The pressed powder magnetic cores 600 of Examples A2, A4, A7, A9, A11, A13, and A14 in Table 1 were manufactured using a mold 300 whose temperature Th (of the low-temperature section 400) is at least 10°C lower than the temperature Tl (of the lower pressure head 330, which is the high-temperature section 500). Table 1 shows the following: The powder cores 600 of Examples A2, A4, A7, A9, A11, A13, and A14 have good appearance; The powder cores 600 of Examples A2, A4, A7, A9, A11, A13, and A14 do not precipitate compound phases, and therefore have good electromagnetic properties.

[0127] The crystallinity C1 of the first surface 620, the crystallinity C2 of the second surface 640, and the crystallinity C of the peripheral surface 660 of the powder cores 600 of Examples 1-26 and A1-A15 were measured. Similarly, the crystallinity of the first surface, the crystallinity of the second surface, and the crystallinity of the peripheral surface of the powder cores of Comparative Examples 1-9 and A1-A6 were also measured. The measurement results are shown in Tables 2 and 3.

[0128] [Table 2]

[0129]

[0130] [Table 3]

[0131]

[0132] Tables 1, 2, and 3 show the tendency for the crystallinity C1 of the first surface 620, the crystallinity C2 of the second surface 640, and the crystallinity C of the peripheral surface 660 to increase with increasing heating temperature. Furthermore, Tables 1, 2, and 3 show that the greater the difference between the heating temperature of the peripheral surface 660 and the heating temperature of the first surface 620, the greater the difference in crystallinity C between the peripheral surface 660 and the first surface 620. Similarly, Tables 1, 2, and 3 show that the greater the difference between the heating temperature of the peripheral surface 660 and the heating temperature of the second surface 640, the greater the difference in crystallinity C between the peripheral surface 660 and the second surface 640. In Example 1, where the difference between the heating temperature of the peripheral surface 660 (520°C) and the heating temperature of the first surface 620 (510°C) is 10°C, the difference between the crystallinity C (51%) of the peripheral surface 660 and the crystallinity C1 (50%) of the first surface 620 is 1%. Furthermore, in Example 10, where the difference between the heating temperature of the peripheral surface 660 (500°C) and the heating temperature of the second surface 640 (490°C) is 10°C, the difference between the crystallinity C (50%) of the peripheral surface 660 and the crystallinity C2 (49%) of the second surface 640 is 1%. In Examples A1 and A5, where the difference between the heating temperature of the peripheral surface 660 (520°C) and the heating temperature of the second surface 640 (510°C) is 10°C, the difference between the crystallinity C (51%) of the peripheral surface 660 and the crystallinity C2 (50%) of the second surface 640 is 1%. In Examples A2 and A3, where the difference between the heating temperature of the peripheral surface 660 (510°C) and the heating temperature of the first surface 620 (520°C) is 10°C, the difference between the crystallinity C (50%) of the peripheral surface 660 and the crystallinity C1 (51%) of the first surface 620 is 1%. In Example A4, where the difference between the heating temperature of the peripheral surface 660 (510°C) and the heating temperature of the second surface 640 (520°C) is 10°C, the difference between the crystallinity C (50%) of the peripheral surface 660 and the crystallinity C2 (51%) of the second surface 640 is 1%. In Example A11, where the difference between the heating temperature of the peripheral surface 660 (490°C) and the heating temperature of the first surface 620 (500°C) is 10°C, the difference between the crystallinity C (49%) of the peripheral surface 660 and the crystallinity C1 (50%) of the first surface 620 is 1%. These results indicate that, according to the manufacturing method of this embodiment, it is possible to manufacture a powder core 600 in which the maximum value of the crystallinity C1 of the first surface 620, the crystallinity C2 of the second surface 640, and the crystallinity C of the peripheral surface 660, i.e., max(C1, C2, C), is greater than or equal to the minimum value of the crystallinity C1 of the first surface 620, the crystallinity C2 of the second surface 640, and the crystallinity C of the peripheral surface 660, i.e., min(C1, C2, C).Furthermore, these results indicate that in a powder core with an unknown manufacturing method, if the difference between the maximum value (max(C1, C2, C)) of the crystallinity C1 of the first surface 620, the crystallinity C2 of the second surface 640, and the crystallinity C of the peripheral surface 660, and the minimum value (min(C1, C2, C)) of the crystallinity C1 of the first surface 620, the crystallinity C2 of the second surface 640, and the crystallinity C of the peripheral surface 660, is 1% or more, then it can be presumed that it is a powder core 600 manufactured by the manufacturing method of the present invention. Additionally, for Examples 1 to 26, the maximum value (max(C1, C2, C)) of the crystallinity C1 of the first surface 620, the crystallinity C2 of the second surface 640, and the crystallinity C of the peripheral surface 660 is the crystallinity C of the peripheral surface 660. That is, for Examples 1 to 26, max(C1, C2, C) = C.

[0133] (Examples 27-40, A16-A23 and Comparative Examples 10-15, A7-A14)

[0134] As the magnet powder 100A, Fe was used 77.1 B1 4.4 P 5.5 Cr1Nb2 (at%) metallic glass powder. A P2O5-ZnO-R2O insulating covering agent 110A was mixed into magnetic powder 100A at a weight ratio of 1.0 wt% relative to the mixture, thus covering the magnetic powder 100A with the insulating covering agent 110A. A mixture was prepared by mixing the magnetic powder 100A covered with the insulating covering agent 110A and phenolic resin as a binder at a weight ratio of 0.4 wt% relative to the mixture. This mixture (weight: 37 g) was filled into mold 300 and molded at a pressure of 8 t / cm. 2 The mixture was heated and pressed under the temperature conditions shown in Table 4 below to produce a pressed powder magnetic core with a length of 55.69 mm, a width of 23 mm, and a thickness of 4.5 mm. Additionally, Fe, as a metallic glass powder... 77.1 B1 4.4 P 5.5 The glass transition temperature (Tg) of Cr1Nb2 is 484℃. Fe, as a metallic glass powder... 77.1 B1 4.4 P 5.5 The crystallization temperature of Cr1Nb2 is 511℃. The evaluation results of the fabricated powder cores are shown in Table 4.

[0135] [Table 4]

[0136]

[0137] The pressed powder magnetic cores 600A of Examples 27-29, 33-35, 39, 40, A19, and A23 in Table 4 were manufactured using a mold 300 whose temperature Tl of the upper pressure head 350 (serving as the low-temperature section 400) is at least 10°C lower than the temperature Th of the mold 310 (serving as the high-temperature section 500). Table 4 shows the following: The pressed powder magnetic cores 600A of Examples 27-29, 33-35, 39, 40, A19, and A23 have good appearance; the pressed powder magnetic cores 600A of Examples 27-29, 33-35, 39, 40, A19, and A23 do not precipitate compound phases, and therefore have good electromagnetic properties. The pressed powder cores 600A of Examples 30-32, 36-38, A19, and A23 in Table 4 were manufactured using a mold 300 whose temperature Tl of the lower pressure head 330 (serving as the low-temperature section 400) was at least 10°C lower than the temperature Th of the mold 310 (serving as the high-temperature section 500). Table 4 shows the following: the pressed powder cores 600A of Examples 30-32, 36-38, A19, and A23 have good appearance; the pressed powder cores 600A of Examples 30-32, 36-38, A19, and A23 did not precipitate compound phases, and therefore have good electromagnetic properties. On the other hand, the pressed powder cores of Comparative Examples 10-15 and A7-A14 in Table 4 were manufactured under conditions where the temperature difference between the mold 310 and the upper pressure head 350 and the lower pressure head 330 was less than 10°C. Table 4 shows that in the pressed powder cores of Comparative Examples 10-15 and A7-A14, cracks appeared in their appearance.

[0138] The pressed powder magnetic cores 600A of Examples A16, A17, A20, and A21 in Table 4 were manufactured using a mold 300 whose temperature Th (of the low-temperature section 400) was at least 10°C lower than the temperature Tl (of the upper pressure head 350, which is the high-temperature section 500). Table 4 shows the following: The pressed powder magnetic cores 600A of Examples A16, A17, A20, and A21 have good appearance; the pressed powder magnetic cores 600A of Examples A16, A17, A20, and A21 do not precipitate compound phases, and therefore have good electromagnetic properties. The pressed powder magnetic cores 600A of Examples A16, A18, A20, and A22 in Table 4 were manufactured using a mold 300 whose temperature Th (of the low-temperature section 400) was at least 10°C lower than the temperature Tl (of the lower pressure head 330, which is the high-temperature section 500). Table 4 shows the following: The powder core 600A of Examples A16, A18, A20, and A22 has a good appearance; The powder core 600A of Examples A16, A18, A20, and A22 does not precipitate compound phases, and therefore has good electromagnetic properties.

[0139] In addition, the surface resistance values ​​R1 of the first surface 620A, R2 of the second surface 640A, and R of the peripheral surface 660A in the powder cores 600A of Examples 27-40 and A16-A23 were measured. Similarly, the surface resistance values ​​of the first surface, the second surface, and the peripheral surface in the powder cores of Comparative Examples 10-15 and A7-A14 were also measured. The measurement results are shown in Tables 5 and 6.

[0140] [Table 5]

[0141]

[0142] [Table 6]

[0143]

[0144] Tables 4, 5, and 6 show the tendency for the surface resistivity values ​​R1 of the first surface 620A, R2 of the second surface 640A, and R of the peripheral surface 660A to increase with increasing heating temperature. Furthermore, Tables 4, 5, and 6 show that the greater the difference between the heating temperature of the peripheral surface 660A and the heating temperature of the first surface 620A, the smaller the ratio of the surface resistivity R1 of the first surface 620A to the surface resistivity R of the peripheral surface 660A. Similarly, Tables 4, 5, and 6 show that the greater the difference between the heating temperature of the peripheral surface 660A and the heating temperature of the second surface 640A, the smaller the ratio of the surface resistivity R2 of the second surface 640A to the surface resistivity R of the peripheral surface 660A. In Example 27, where the difference between the heating temperature of the peripheral surface 660A (500°C) and the heating temperature of the first surface 620A (490°C) is 10°C, the surface resistivity R1 of the first surface 620A is 9.5 * 10⁻⁶. 5 Ω) relative to the surface resistance value R (1.0*10) of 660A on the circumference. 6 The ratio of Ω) is 0.95. Furthermore, in Example 30, where the difference between the heating temperature of the peripheral surface 660A (500°C) and the heating temperature of the second surface 640A (490°C) is 10°C, the surface resistivity R2 of the second surface 640A is 9.5*10 5 Ω) relative to the surface resistance value R (1.0*10) of 660A on the circumference. 6 The ratio of Ω) is 0.95. In embodiment A17, where the difference between the heating temperature of the peripheral surface 660A (490°C) and the heating temperature of the first surface 620A (500°C) is 10°C, the surface resistivity R of the peripheral surface 660A is 9.5*10 5 Ω) relative to the surface resistance value R1 (1.0*10) of the first surface 620A. 6The ratio of Ω) is 0.95. In Example A18, where the difference between the heating temperature of the peripheral surface 660A (490°C) and the heating temperature of the second surface 640A (500°C) is 10°C, the surface resistivity R of the peripheral surface 660A is 9.3*10 5 Ω) relative to the surface resistance value R2 (1.0*10) of the second surface 640A. 6 The ratio of Ω) is 0.93. In embodiment A21, where the difference between the heating temperature of the peripheral surface 660A (420°C) and the heating temperature of the first surface 620A (430°C) is 10°C, the surface resistivity R of the peripheral surface 660A is 3.1*10 5 Ω) relative to the surface resistance value R1 (3.8*10) of the first surface 620A. 5 The ratio of Ω) is 0.82. In Example A22, where the difference between the heating temperature of the peripheral surface 660A (420°C) and the heating temperature of the second surface 640A (430°C) is 10°C, the surface resistivity R of the peripheral surface 660A is 3.1*10 5 Ω) relative to the surface resistance value R2 (3.7*10) of the second surface 640A. 5 The ratio of the surface resistivity R1 of the first surface 620A, the surface resistivity R2 of the second surface 640A, and the surface resistivity R of the peripheral surface 660A is 0.84. These results indicate that, according to the manufacturing method of this embodiment, it is possible to manufacture a powder core 600A with a ratio of the minimum value of the surface resistivity R1 of the first surface 620A, the surface resistivity R2 of the second surface 640A, and the maximum value of the surface resistivity R of the peripheral surface 660A, i.e., max(R1, R2, R), to the maximum value of the surface resistivity R1 of the first surface 620A, the surface resistivity R2 of the second surface 640A, and the surface resistivity R of the peripheral surface 660A, i.e., max(R1, R2, R), to the maximum value of the surface resistivity R1 of the first surface 620A, the surface resistivity R2 of the second surface 640A, and the surface resistivity R of the peripheral surface 660A, i.e., max(R1, R2, R), to the maximum value of the surface resistivity R1 of the first surface 620A, the surface resistivity R2 of the second surface 640A, and the surface resistivity R of the peripheral surface 660A, i.e., max(R1, R2, R), to the maximum value of the surface resistivity R of the first surface 620A, the surface resistivity R2 of the second surface 640A, and the maximum value of ...). Furthermore, these results indicate that, in a powder-pressed magnetic core with an unknown manufacturing method, if the ratio of the minimum (min(R1, R2, R)) of the surface resistance values ​​R1 of the first surface 620A, R2 of the second surface 640A, and R of the peripheral surface 660A to the maximum (max(R1, R2, R)) of the surface resistance values ​​R1 of the first surface 620A, R2 of the second surface 640A, and R of the peripheral surface 660A is 0.95 or less, then it can be presumed that it is a powder-pressed magnetic core 600A manufactured by the manufacturing method of the present invention. Additionally, in Examples 27, 29-34, and 36-40, the maximum (max(R1, R2, R)) of the surface resistance values ​​R1 of the first surface 620A, R2 of the second surface 640A, and R of the peripheral surface 660A is the surface resistance value R of the peripheral surface 660A. That is, for Examples 27, 29-34, and 36-40, max(R1, R2, R) = R.

[0145] The present invention has been specifically described above by giving examples of embodiments, but the present invention is not limited thereto and can be modified and altered in various ways.

[0146] This invention is based on Japanese Patent Application No. 2020-164976, filed with the Japan Patent Office on September 30, 2020, the contents of which are incorporated herein by reference.

[0147] Although the preferred embodiments of the invention have been described, it will be apparent to those skilled in the art that modifications can be made to the embodiments without departing from the spirit of the invention, and such modifications are within the scope of the invention.

[0148] Explanation of reference numerals in the attached figures

[0149] 100, 100A: Magnet powder

[0150] 110, 110A: Covering agent

[0151] 300, 300B: Mold

[0152] 310: Compression molding

[0153] 312: Inner wall

[0154] 314: Containment Department

[0155] 316: First Opening

[0156] 318: Second opening

[0157] 330: Downward pressure head

[0158] 350, 350B: Upper pressure head

[0159] 352B: Low-temperature components

[0160] 356B: High-temperature components

[0161] 400, 400B: Cryogenic section

[0162] 500: High temperature department

[0163] 520: Additional High-Temperature Section

[0164] 540: Auxiliary High Temperature Section

[0165] 600, 600A: Powder-pressed magnetic core

[0166] 620, 620A: First page

[0167] 640, 640A: Second page

[0168] 660, 660A: Peripheral

Claims

1. A pressed powder magnetic core, comprising at least a portion of magnetic powder covered by a covering agent, The magnet powder contains nanocrystals. The pressed powder magnetic core has a first surface, a second surface, and a peripheral surface. The first surface faces the first position in the specified direction. The second face faces a second direction opposite to the first direction. The circumferential surface intersects with an orthogonal direction, and the orthogonal direction is orthogonal to the specified direction. When the crystallinity of the first surface is C1, the crystallinity of the second surface is C2, and the crystallinity of the peripheral surface is C, the following condition is met: ， The first surface of the manufactured pressed powder magnetic core is the part that contacts the upper pressure head of the mold when the magnetic powder is pressed and formed in the mold. The second surface of the manufactured pressed powder magnetic core is the part that contacts the lower pressure head of the mold when the magnetic powder is pressed and formed in the mold.

2. The pressed powder magnetic core according to claim 1, wherein, 。 3. A pressed powder magnetic core, comprising at least a portion of magnetic powder covered by a covering agent, The magnet powder is a metallic glass with a glass transition point. The pressed powder magnetic core has a first surface, a second surface, and a peripheral surface. The first surface faces the first position in the specified direction. The second face faces a second direction opposite to the first direction. The circumferential surface intersects with an orthogonal direction, and the orthogonal direction is orthogonal to the specified direction. When the surface resistance of the first surface is R1, the surface resistance of the second surface is R2, and the surface resistance of the circumferential surface is R, the following conditions are met: ， The first surface of the manufactured pressed powder magnetic core is the part that contacts the upper pressure head of the mold when the magnetic powder is pressed and formed in the mold. The second surface of the manufactured pressed powder magnetic core is the part that contacts the lower pressure head of the mold when the magnetic powder is pressed and formed in the mold.

4. The pressed powder magnetic core according to claim 3, wherein, 。 5. A method for manufacturing a pressed powder magnetic core, wherein the pressed powder magnetic core is the pressed powder magnetic core according to any one of claims 1 to 4. The pressed powder magnetic core is manufactured by heating and pressurizing the magnetic powder inside the mold. The mold consists of a pressure mold, an upper pressure head, and a lower pressure head. The upper pressure head is positioned above the lower pressure head in the vertical direction. The mold is provided with a low-temperature section and a high-temperature section. The temperature of the low-temperature section is more than 10°C lower than the temperature of the high-temperature section. The high-temperature part is the pressure mold.

6. The method for manufacturing a pressed powder magnetic core according to claim 5, wherein, The mold is also equipped with an additional high-temperature section. The additional high-temperature section is the downward pressure head. The temperature of the additional high-temperature section is more than 10°C higher than the temperature of the low-temperature section.

7. The method for manufacturing a pressed powder magnetic core according to claim 5, wherein, The die has an inner wall that tapers downwards in the vertical direction. The low-temperature section is the upper pressure head.

8. The method for manufacturing a pressed powder magnetic core according to claim 5, wherein, The upper pressure head is composed of multiple components. The plurality of components includes components for cryogenic use and components for high-temperature use. The mold is also equipped with an auxiliary high-temperature section. The low-temperature section is the low-temperature component. The auxiliary high-temperature section is the high-temperature component. The temperature of the auxiliary high-temperature section is more than 10°C higher than the temperature of the low-temperature section.

9. The method for manufacturing a pressed powder magnetic core according to claim 5, wherein, When the pressed powder magnetic core is the pressed powder magnetic core according to claim 1 or 2 During the pressurization of the pressed powder magnetic core, nanocrystals precipitate in the amorphous phase of the pressed powder magnetic core.

10. The method for manufacturing a pressed powder magnetic core according to claim 5, wherein, A portion of the magnet powder was not covered by the covering agent.

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