Magnetic material, dust core and coil product, and method for manufacturing magnetic material

Abstract

The present invention provides a magnetic material that can achieve both high saturation magnetic flux density and low core loss at high frequencies of 100 kHz or more, a powder magnetic core and coil product that uses the magnetic material, and a method for manufacturing the magnetic material. The magnetic material comprises a magnetic powder and an insulating resin mixed with the magnetic powder, and has a saturation magnetic flux density of 0.6 T or more at room temperature. Furthermore, the core loss when the measurement frequency is 100 kHz and the applied magnetic flux density is 15 mT is 5 kW / m. 3 The powder magnetic core includes a magnetic material, and the coil product includes the powder magnetic core. The method for manufacturing the magnetic material includes a step of mixing a first resin containing a silicone resin as a main component with magnetic powder and coating the magnetic powder with the first resin, and a step of mixing the magnetic powder coated with the first resin with a second resin containing a phenol resin as a main component and bonding the first resins together via the second resin.

Description

[Technical Field]

[0001] The present invention relates to a magnetic material, a dust core, a coil product, and a method for manufacturing a magnetic material. [Background technology]

[0002] Conventional transformer cores for high frequencies above 100 kHz use Mn-Zn ferrite, which has low core loss even at frequencies above 100 kHz. However, Mn-Zn ferrite has a drawback: its low saturation magnetic flux density, which affects miniaturization. Specifically, the saturation magnetic flux density of Mn-Zn ferrite is 0.55 T or less. Therefore, in order to further miniaturize transformer cores, replacement with magnetic materials with high saturation magnetic flux density is being considered. However, high saturation magnetic flux density and low core loss at high frequencies above 100 kHz are in a trade-off relationship, making it difficult to achieve both.

[0003] Patent Document 1 discloses a composite material that has low iron loss, high saturation magnetization, and high strength. Specifically, Patent Document 1 discloses a composite material containing soft magnetic powder and a resin that encapsulates the soft magnetic powder in a dispersed state, wherein the soft magnetic powder includes a coarse-grained powder having an average particle size D1 of 50 μm or more and 500 μm or less and a fine-grained powder having an average particle size D2 of 0.1 μm or more and less than 30 μm, and the content of the soft magnetic powder relative to the entire composite material is 60% by volume or more and 80% by volume or less. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2017-224851 Summary of the Invention [Problem to be solved by the invention]

[0005] However, although the composite material of Patent Document 1 has a high saturation magnetic flux density of 1.22 to 1.26 T, the core loss (iron loss) at a measurement frequency of 20 kHz and an excitation magnetic flux density of 100 mT is 355 kW / m 3 Because of this large size, it was difficult to use it in transformer cores for high frequencies of 100 kHz or more.

[0006] The present invention has been made in view of the problems inherent in the prior art, and an object of the present invention is to provide a magnetic material that can achieve both high saturation magnetic flux density and low core loss at high frequencies of 100 kHz or higher, a powder magnetic core and coil product that use the magnetic material, and a method for manufacturing the magnetic material. [Means for solving the problem]

[0007] A magnetic material according to a first aspect of the present invention comprises a magnetic powder and an insulating resin mixed with the magnetic powder, and has a saturation magnetic flux density of 0.6 T or more at room temperature, and further has a core loss of 5 kW / m when the measurement frequency is 100 kHz and the applied magnetic flux density is 15 mT. 3 The following is the result.

[0008] A powder magnetic core according to a second aspect of the present invention includes the magnetic material.

[0009] A coil product according to a third aspect of the present invention includes the above-described powder magnetic core.

[0010] A manufacturing method for a magnetic material according to a fourth aspect of the present invention includes a step of mixing a first resin mainly composed of silicone resin with the magnetic powder and coating the magnetic powder with the first resin, and a step of mixing the magnetic powder coated with the first resin with a second resin mainly composed of phenolic resin and bonding the first resins together via the second resin. [Effects of the Invention]

[0011] According to the present invention, it is possible to provide a magnetic material that can achieve both high saturation magnetic flux density and low core loss at high frequencies of 100 kHz or more, a powder magnetic core and coil product that use the magnetic material, and a method for manufacturing the magnetic material. DETAILED DESCRIPTION OF THE INVENTION

[0012] The magnetic material, the powder magnetic core, the coil product, and the method for manufacturing the magnetic material according to the present embodiment will be described in detail below.

[0013] [Magnetic material] The magnetic material of this embodiment includes magnetic powder and an insulating resin in which the magnetic powder is dispersed. The magnetic material has a saturation magnetic flux density of 0.6 T or more at room temperature (25°C), and a core loss of 5 kW / m when the measurement frequency is 100 kHz and the applied magnetic flux density is 15 mT. 3 It is characterized by the following:

[0014] Core loss in a transformer core can be divided into hysteresis loss and eddy current loss, and the type of loss that has a greater impact varies depending on the switching frequency. At high frequencies of 100 kHz or higher, the impact of eddy current loss becomes greater, and to reduce this loss, it is necessary to increase the electrical resistivity of the magnetic material and reduce the particle size of the magnetic powder.

[0015] The magnetic material of this embodiment is a composite material containing magnetic powder and an insulating resin that encapsulates the magnetic powder in a dispersed state. This configuration allows a high-resistivity coating to be formed on the surface of the magnetic powder, thereby increasing the electrical resistivity of the magnetic material, reducing eddy current loss, and decreasing core loss.

[0016] In the magnetic material, the magnetic powder preferably includes a coarse-grained powder having an average particle size of 53 μm or less and a fine-grained powder having an average particle size smaller than that of the coarse-grained powder and an average particle size of 10 μm or less. Using a coarse-grained powder with such an average particle size as the magnetic powder can reduce eddy current loss and core loss. Furthermore, at high frequencies around 100 kHz, hysteresis loss, although smaller than eddy current loss, also affects core loss and must be reduced. Reducing the gaps between the magnetic powder particles is effective in reducing hysteresis loss. Therefore, by using a coarse-grained powder having an average particle size of 53 μm or less and a fine-grained powder having an average particle size of 10 μm or less, the fine-grained powder can penetrate into the gaps between adjacent coarse-grained powder particles, thereby reducing the gaps between the magnetic powder particles and reducing hysteresis loss.

[0017] The average particle size of the coarse-grained powder is preferably 30 μm or more and 53 μm or less, and more preferably 40 μm or more and 53 μm or less. The average particle size of the fine-grained powder is preferably 1 μm or more and 10 μm or less. In this specification, unless otherwise specified, the value of "average particle size" means the particle size at 50% of the cumulative value in the particle size distribution determined by the laser diffraction / scattering method.

[0018] In the magnetic powder, the mass ratio of the coarse powder to the fine powder is not particularly limited, but can be set to coarse powder:fine powder=60:40 to 90:10. By including the coarse powder and the fine powder in such a ratio, it is possible to reduce eddy current loss and hysteresis loss, thereby reducing core loss.

[0019] The magnetic powder is preferably a powder made of an Fe-Si-Al alloy or an Fe-based nanocrystalline alloy. That is, both the coarse-grained powder and the fine-grained powder may be powders made of an Fe-Si-Al alloy, or powders made of an Fe-based nanocrystalline alloy. Alternatively, one of the coarse-grained powder and the fine-grained powder may be powder made of an Fe-Si-Al alloy, and the other may be powder made of an Fe-based nanocrystalline alloy. As mentioned above, the core loss of a transformer core is affected by hysteresis loss and eddy current loss. Furthermore, the electrical resistivity of the magnetic powder itself is also important for reducing eddy current loss. In other words, eddy current loss can be reduced by reducing the electrical resistivity of the magnetic powder itself. Therefore, using an Fe-Si-Al alloy or an Fe-based nanocrystalline alloy, which has high saturation magnetic flux density and high electrical resistivity, as the magnetic powder can reduce eddy current loss and core loss.

[0020] The Fe-Si-Al alloy may contain 9-10% by mass of silicon, 5-6% by mass of aluminum, and the remainder being iron and unavoidable impurities. The Fe-based nanocrystalline alloy is an alloy in which nanometer-order microcrystals are precipitated in the amorphous phase by heat-treating an Fe-based amorphous alloy or an Fe-based alloy with a nanoheterostructure in which primary microcrystals exist in the amorphous phase. Examples of Fe-based nanocrystalline alloys include Fe-Nb-B, Fe-Co-Nb-B, Fe-Si-Nb-B-Cu, Fe-Co-Si-Nb-B-Cu, Fe-Si-PB-Cu, and Fe-Co-Si-PB.

[0021] In the magnetic material, the insulating resin preferably contains silicone resin and phenolic resin as its main components. As mentioned above, at high frequencies around 100 kHz, hysteresis loss, although smaller than eddy current loss, also affects core loss and therefore needs to be reduced. Reducing the gaps between the magnetic powder is effective in reducing hysteresis loss. Therefore, it is preferable to reduce the amount of resin added to the magnetic material as much as possible. On the other hand, if the amount of resin contained in the magnetic material is too small, it becomes difficult to mold it into a bulk body.

[0022] Therefore, in the magnetic material of this embodiment, a highly heat-resistant silicone resin is used to form a coating with high electrical resistance on the surface of the magnetic powder. Furthermore, by adding a phenolic resin (Bakelite) with low heat resistance, the amount of resin required for powder compaction can be secured, making it possible to mold it into a bulk body. Furthermore, as will be described later, the magnetic material of this embodiment can be heat-treated after powder compaction to thermally decompose part of the phenolic resin and reduce the amount of resin that ultimately remains. As a result, the amount of resin can be reduced while maintaining the compacted shape, making it possible to further reduce core loss.

[0023] The silicone resin in the insulating resin is not particularly limited as long as it has high heat resistance, but for example, a resin having at least one of a methyl group and a phenyl group on the side chain can be used.

[0024] In the magnetic material, the insulating resin preferably contains silicone resin and phenol resin as main components. Specifically, the insulating resin preferably contains silicone resin and phenol resin in a total amount of 50% by mass or more, preferably 70% by mass or more, and more preferably 90% by mass or more. The mass ratio of silicone resin to phenol resin in the insulating resin can be silicone resin:phenol resin = 50:50 to 80:20.

[0025] As mentioned above, reducing the gaps between magnetic powder particles is effective in reducing hysteresis loss in the core loss of a transformer core. To achieve this, it is preferable to reduce the amount of resin added to the magnetic material as much as possible. Therefore, it is preferable that the magnetic powder content be 96% by mass or more and the insulating resin content be 4% by mass or less relative to the entire magnetic material. This makes it possible to reduce hysteresis loss while ensuring the amount of resin required for powder compaction. It is more preferable that the insulating resin content be 1% by mass or more and 4% by mass or less relative to the entire magnetic material.

[0026] The magnetic material of this embodiment can be made into a bulk body by molding a mixture of magnetic powder and insulating resin. The molding method for the magnetic material is not particularly limited, and can be pressure molding or plastic molding. After molding the magnetic material, the molded body may be heat-treated. By heat-treating the molded body, a portion of the phenolic resin can be thermally decomposed, reducing the amount of resin that ultimately remains. As a result, the amount of resin can be reduced while maintaining the powder-molded shape, thereby reducing core loss.

[0027] As described above, the magnetic material of this embodiment includes a magnetic powder and an insulating resin mixed with the magnetic powder, and has a saturation magnetic flux density of 0.6 T or more at room temperature. Furthermore, when the measurement frequency is 100 kHz and the applied magnetic flux density is 15 mT, the core loss is 5 kW / m 3 The saturation magnetic flux density and core loss of the magnetic material of this embodiment are as follows. Since the saturation magnetic flux density and core loss are as described above, it is possible to achieve both high saturation magnetic flux density and low core loss at high frequencies of 100 kHz or higher. Therefore, the magnetic material of this embodiment can reduce the size of transformers compared to conventional Mn-Zn ferrite.

[0028] In the magnetic material of this embodiment, the magnetic powder may include a coarse-grained powder having an average particle size of 53 μm or less, and a fine-grained powder having an average particle size smaller than that of the coarse-grained powder and an average particle size of 10 μm or less. The coarse-grained powder and the fine-grained powder may be an Fe-Si-Al alloy or an Fe-based nanocrystalline alloy. The insulating resin may contain a silicone resin and a phenolic resin as main components. Furthermore, the content of the magnetic powder may be 96 mass% or more and the content of the insulating resin may be 4 mass% or less relative to the entire magnetic material. With this configuration, the saturation magnetic flux density is 0.6 T or more, and further, the core loss when the measurement frequency is 100 kHz and the applied magnetic flux density is 15 mT is 5 kW / m 3 Therefore, it is possible to achieve both a high saturation magnetic flux density and low core loss at high frequencies of 100 kHz or more.

[0029] [Method of manufacturing magnetic materials] Next, a method for manufacturing the magnetic material of this embodiment will be described.

[0030] In the manufacturing method of this embodiment, first, a first resin containing a silicone resin as a main component and magnetic powder are prepared. The first resin may contain the above-mentioned silicone resin as a main component. However, the first resin preferably contains 50% by mass or more of silicone resin, preferably 70% by mass or more, and more preferably 90% by mass or more. In addition, to improve the dispersibility of the first resin, the first resin may be dissolved in an organic solvent. As the organic solvent, one that can dissolve the first resin can be used. As the magnetic powder, a mixture of the above-mentioned coarse powder and fine powder can be used.

[0031] Next, the first resin and the magnetic powder are mixed to obtain a mixture. If the first resin is dissolved in an organic solvent, the mixture may be heat-treated to remove the organic solvent. The heat treatment can be carried out in air by heating at a temperature at which the organic solvent can be removed.

[0032] Next, a second resin is mixed with the mixture of the first resin and magnetic powder to obtain a composite material. The second resin may contain the above-mentioned phenolic resin as a main component. However, the second resin preferably contains 50% by mass or more of the phenolic resin, more preferably 70% by mass or more, and even more preferably 90% by mass or more. In addition, to improve the dispersibility of the second resin, the second resin may be dissolved in an organic solvent. The organic solvent that can dissolve the second resin can be used.

[0033] In the case of a composite material of a first resin, a second resin, and magnetic powder, in which the second resin is dissolved in an organic solvent, the composite material may be subjected to a heat treatment in order to remove the organic solvent. The heat treatment can be carried out in air by heating at a temperature at which the organic solvent can be removed.

[0034] Then, a composite material of the first resin, the second resin, and the magnetic powder is molded. The method for molding the composite material is not particularly limited, but can be carried out by pressure molding or plastic molding.

[0035] After molding the composite material, the molded body may be heat-treated as needed. By heat-treating the molded body, a portion of the phenolic resin can be thermally decomposed, thereby reducing the amount of resin that ultimately remains. As a result, the amount of resin can be reduced while maintaining the powder-molded shape, thereby reducing core loss. The heat treatment temperature for the composite material can be, for example, 400 to 600°C.

[0036] The method for producing the magnetic material of this embodiment includes the steps of mixing a first resin, primarily composed of silicone resin, with magnetic powder and coating the magnetic powder with the first resin, and mixing the magnetic powder coated with the first resin with a second resin, primarily composed of phenolic resin, and bonding the first resins together via the second resin. This method allows for the production of a magnetic material that combines high saturation magnetic flux density with low core loss at high frequencies of 100 kHz or higher.

[0037] [Powder cores and coil products] The powder magnetic core of this embodiment includes the above-mentioned magnetic material. The magnetic material of this embodiment has a saturation magnetic flux density of 0.6 T or more at room temperature, and further has a core loss of 5 kW / m when the measurement frequency is 100 kHz and the applied magnetic flux density is 15 mT. 3 Since the core loss is less than 100 kHz, it achieves both high saturation magnetic flux density and low core loss at high frequencies of 100 kHz or more. Therefore, by using such a powder magnetic core, it is possible to miniaturize transformers.

[0038] The coil product of this embodiment includes the above-described powder magnetic core. The powder magnetic core of this embodiment uses a magnetic material that combines high saturation magnetic flux density and low core loss at high frequencies, allowing the powder magnetic core to be miniaturized, and therefore the coil product to be miniaturized as well. Examples of coil products that include the above-described powder magnetic core include fixed coils and variable coils. [Example]

[0039] Hereinafter, the present embodiment will be described in more detail with reference to examples and comparative examples, but the present embodiment is not limited to these examples.

[0040] [Example 1] <Preparation of magnetic powder for testing> As the coarse-grained powder, an alloy powder made of an Fe-Si-Al alloy with an average particle size D1 of 50 μm was prepared, and as the fine-grained powder, an alloy powder made of an Fe-Si-Al alloy with an average particle size D2 of 10 μm was prepared. The average particle sizes and manufacturers of the coarse-grained powder and fine-grained powder are summarized in Table 1.

[0041] Next, the coarse powder and the fine powder were weighed out so that they were 75% by mass and 25% by mass, respectively, and then mixed together to obtain a magnetic powder.

[0042] Next, a silicone resin was prepared as the first resin. The silicone resin used was a high-hardness methyl / phenyl silicone resin KR-300 manufactured by Shin-Etsu Chemical Co., Ltd. The first resin was diluted with xylene as a solvent, and then added to and mixed with the magnetic powder to obtain a mixture. The mixture was then heat-treated in air at 150°C for 0.5 hours, dried, and then crushed.

[0043] Next, bakelite was prepared as the second resin. The bakelite used was phenolic resin PC-1 (non-volatile content 60%, solvent: methanol / acetone) manufactured by Sumitomo Bakelite Co., Ltd. The second resin was diluted with ethanol, which was the solvent, and then added to the crushed magnetic powder and mixed to obtain a mixture. The mixture was then heat-treated in air at 150°C for 0.5 hours and dried.

[0044] After drying, the composite magnetic powder was placed on a sieve with an opening of 850 μm (20 mesh) and sieved, and then further classified with a sieve with an opening of 300 μm (48 mesh) to be used as the magnetic powder for testing. In this magnetic powder for testing, the resin amounts of the silicone resin and Bakelite were both 2% by mass, and the insulating resin amount was 4% by mass in total.

[0045] <Creating test specimens> First, a powder compaction die of a predetermined shape was prepared. Next, the test magnetic powder was filled into the powder compaction die and pressed at 1200 MPa using a hand press to perform powder compaction. The compact obtained by powder compaction was pre-sintered by heating in air at 150°C for 0.5 hours, and then heat-treated in a nitrogen atmosphere at 500°C for 2 hours to obtain a test piece for measuring magnetic properties. The test piece for measuring magnetic properties was toroidal, with an outer diameter of 13 mm, an inner diameter of 8 mm, and a thickness of 3 mm.

[0046] [Table 1]

[0047] [Examples 2 to 4 and Comparative Examples 1 to 8] The magnetic powders, coarse and fine, and the first and second resins shown in Tables 2 and 3 were used, with the silicone resin and Bakelite resin amounts being equal, and the total amount of insulating resin was adjusted as shown in Tables 2 and 3. Except for these, the test magnetic powders for each example were prepared in the same manner as in Example 1.

[0048] The magnetic powder for testing of each example was then subjected to powder compaction in the same manner as in Example 1 to obtain a test piece for measuring magnetic properties of each example.

[0049] [Comparative Examples 9 to 12] The magnetic powders, which are coarse-grained powder and fine-grained powder, and the first resin shown in Tables 2 and 3 were used, and the total amount of insulating resin was adjusted as shown in Tables 2 and 3. Except for these, the test magnetic powders for each example were prepared in the same manner as in Example 1.

[0050] The magnetic powder for testing of each example was then subjected to powder compaction in the same manner as in Example 1 to obtain a test piece for measuring magnetic properties of each example.

[0051] [Table 2]

[0052] [Table 3]

[0053] [evaluation] <Core loss measurement> Core loss measurements were carried out on test pieces for measuring magnetic properties in accordance with the provisions of the Japanese Industrial Standard JIS C2560-2:2006 (Ferrite magnetic cores - Part 2: Test methods). Specifically, a toroidal test piece with an outer diameter of 13 mm, an inner diameter of 8 mm, and a thickness of 3 mm was wound with five turns on the primary side and five turns on the secondary side. Then, using a BH analyzer, the core loss (kW / m) was measured at room temperature, a frequency of 100 kHz, and an applied magnetic flux density of 15 mT. 3 The core loss of each test piece was measured. 3 The following cases are evaluated as "○" and 5kW / m 3 When the value exceeded this, the evaluation was made as "×." The evaluation results of the test pieces of each example are summarized in Tables 2 and 3.

[0054] <Measurement of saturation magnetic flux density> First, a cube with a side length of 2 mm was cut out from each test piece for measuring magnetic properties. The cut test piece was subjected to VSM (vibrating sample magnetic measurement) to measure the saturation magnetic flux density. A vibrating sample magnetometer was used for the measurement, and the saturation magnetic flux density was measured at room temperature, an applied magnetic field of 5000 Oe (398 kA / m), and a sweep speed of 5 min / loop (initial magnetization curve: 1 min). When the saturation magnetic flux density of each test piece was 0.6 T or more, it was evaluated as "○", and when it was less than 0.6 T, it was evaluated as "×". The evaluation results of the test pieces of each example are summarized in Tables 4 and 5.

[0055] [Table 4]

[0056] [Table 5]

[0057] As shown in Tables 2 to 4, the magnetic materials of Examples 1 to 4 have a saturation magnetic flux density of 0.6 T or more at room temperature, a measurement frequency of 100 kHz, and a core loss of 5 kW / m when the applied magnetic flux density is 15 mT. 3 Therefore, it has both a high saturation magnetic flux density and low core loss at high frequencies of 100 kHz or more, and can be suitably used as a powder magnetic core for a transformer.

[0058] In contrast, the magnetic materials of Comparative Examples 1 and 2 had an average particle size D1 of the coarse powder exceeding 53 μm, and the magnetic materials of Comparative Examples 3 and 4 had an average particle size D2 of the fine powder exceeding 10 μm. The magnetic materials of Comparative Examples 5 and 6 had a total of more than 4 mass% of silicone resin and bakelite. Comparative Examples 7 and 8 used Fe powder or Fe-Ni alloy powder as the magnetic powder. Comparative Examples 9 to 12 used only either silicone resin or bakelite as the insulating resin. Therefore, Comparative Examples 1 to 12 were inferior in at least one of saturation magnetic flux density and core loss.

[0059] Although the present embodiment has been described above, the present embodiment is not limited to this, and various modifications are possible within the scope of the gist of the present embodiment.

Claims

1. Magnetic powder, an insulating resin mixed with the magnetic powder; Equipped with At room temperature, the saturation magnetic flux density is 0.6 T or more, and further, the core loss is 5 kW / m when the measurement frequency is 100 kHz and the applied magnetic flux density is 15 mT. ３ The magnetic material is as follows:

2. The magnetic powder includes a coarse-grained powder having an average particle size of 53 μm or less, and a fine-grained powder having an average particle size smaller than that of the coarse-grained powder and having an average particle size of 10 μm or less, the coarse-grained powder and the fine-grained powder are Fe—Si—Al alloys or Fe-based nanocrystalline alloys; the insulating resin contains a silicone resin and a phenolic resin as main components; 2. The magnetic material according to claim 1, wherein the content of the magnetic powder is 96% by mass or more and the content of the insulating resin is 4% by mass or less relative to the entire magnetic material.

3. A powder magnetic core comprising the magnetic material according to claim 1 or 2.

4. A coil product comprising the powder magnetic core according to claim 3.

5. 3. A method for producing a magnetic material according to claim 2, comprising: a step of mixing a first resin containing a silicone resin as a main component with the magnetic substance powder and coating the magnetic substance powder with the first resin; a step of mixing the magnetic powder coated with the first resin with a second resin containing a phenolic resin as a main component, and bonding the first resins together via the second resin; A method for producing a magnetic material comprising the steps of:

Images