JP2004247409A - Magnetic core and inductance component using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a low cost magnetic core having excellent core loss characteristics and DC superimposition characteristics and to provide an inductance component using the same. <P>SOLUTION: The magnetic core includes at least one or more gaps of magnetic paths. A bonded magnet made of a rare earth element magnet powder having an intrinsic coercive force of 20×79 kAT/m (20 kOe) or more, a Curie temperature Tc of 300°C or higher and a powder mean particle size of 2.5 to 50 μm, is inserted into the gap of the magnetic core. The bonded magnet made of an SmCo magnet powder containing a composition of Sm(Fe<SB>0.15-0.25</SB>Cu<SB>0.06-0.08</SB>Zr<SB>0.02-0.03</SB>Co<SB>Bal</SB>)<SB>7.0-8.5</SB>and having a powder mean particle size of 2.5 to 50 μm and a resin is inserted into the gap. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

【００２３】
上記の条件で作製された試料の磁気特性の結果を表１に示す。
【００２４】
【表１】

【００２５】
表１より、ｙ＝０．０５以下では、保磁力が２０×７９ｋＡＴ／ｍ（２０ｋＯｅ）以下となり、ｙ＝０．０９では残留磁束密度が０．２８０Ｔ以下となり、磁気特性が劣化する。ｙ＝０．０６〜０．０８の範囲では、保磁力２０×７９ｋＡＴ／ｍ（２０ｋＯｅ）以上、Ｂｒが０．２８０Ｔ以上で、良好な特性を示すことがわかった。
【００２６】
これらのＳｍ−Ｃｏボンド磁石をＭｎ−Ｚｎ系フェライトコアの磁路の一部に挿入した場合の磁芯について、直流重畳特性を測定し、比較を行った例を示す。直流重畳特性は、各磁石を挿入したコアをＨｅｗｌｅｔｔ Ｐａｃｋａｒｄ製 ４２８４Ａ ＬＣＲメーターで交流磁場周波数１００ｋＨｚ、重畳磁場０〜１５．８ＡＴ／ｍ（２００Ｏｅ）の条件で、直流重畳特性を測定した。
【００２７】
実験に用いたフェライトコアは、Ｍｎ−Ｚｎ系フェライト材で作製された磁路長７．５ｃｍ、実効断面積０．７４ｃｍ^２のＥＥコアであり、その中芯に１．５ｍｍのギャップ加工をした。フェライトコアの中芯断面形状で、かつ高さ１．５ｍｍの形状に加工したボンド磁石をそのギャップ部に挿入した。また、この時の直流バイアス磁界の向きは、挿入時に着磁した磁石の磁化の向きとは逆になるように重畳電流を印加する。その測定結果を図１に示す。
【００２８】
図１より、ｙ＝０．０３のＳｍＣｏ磁石を挿入したコアについては、透磁率が高磁界側まで伸びず、磁石によるバイアス磁界の大きさが他のものに比べ非常に小さくなっていることが分かる。保磁力が７．１×７９ｋＡＴ／ｍ（７．１ｋＯｅ）と小さいため、大きく減磁し、重畳特性が他のものに比べ、非常に劣っていることが分かる。
【００２９】
ｙ＝０．０４〜０．０８ＳｍＣｏ磁石を挿入したコアについては、直流重畳特性は高磁界側まで伸び、良好な値を示した。また、ｙ＝０．０９のＳｍＣｏ磁石を挿入したコアについては、透磁率が高磁界側まで伸びず、他のものに比べ特性が劣っていることが分かる。これは残留磁化が小さいためバイアス量が減少したため、直流重畳特性が劣化したものと考えられる。
【００３０】
（実施例２）
実施例２による磁芯は、Ｓｍ（Ｆｅ_０．２Ｃｕ_{０．０６７}Ｚｒ_{０．０２８}Ｃｏ_Ｂａｌ）_γの遷移金属量を変化、即ちγを変化させた試料を作製し、それをＳｍ−Ｃｏボンド磁石の特性を測定し、比較を行った例を示す。
【００３１】
γの異なる試料（γ＝６．５〜９．０：計７個）を高周波溶解炉で作製し、その後、焼結を１２１５℃で３時間、溶体化を１１９５℃で１５時間、時効をそれぞれ８００℃で４０時間行って形成した。その後、金属棒で粉砕し２５０μｍ以下に分級を行った。これらのＳｍ−Ｃｏ磁石粉末に１０ｗｔ％に当たる量のバインダー（エポキシ樹脂）を混合した後、無磁場中で金型成形を行い、その後、１５０℃で３０分乾燥を行った。
【００３２】
作製条件

【００３３】
上記の条件で作製された試料の磁気特性の結果を表２に示す。
【００３４】
【表２】

【００３５】
表２より、γ＝６．５以下では、保磁力が２０×７９ｋＡＴ／ｍ（２０ｋＯｅ）以下となり、γ＝０．９では残留磁束密度が２．８Ｔ以下となり、磁気特性が劣化する。γ＝７．０〜８．５の範囲では、保磁力２０×７９ｋＡＴ／ｍ（２０ｋＯｅ）以上、Ｂｒが２．８Ｔ以上で、良好な特性を示すことがわかった。
【００３６】
これらのＳｍ−Ｃｏボンド磁石をＭｎ−Ｚｎ系フェライトコアの磁路の一部に挿入した場合の直流重畳特性を測定し、比較を行った例を示す。直流重畳特性は、各磁石を挿入したコアをＨｅｗｌｅｔｔ Ｐａｃｋａｒｄ製４２８４Ａ ＬＣＲメーターで交流磁場周波数１００ｋＨｚ、重畳磁場０〜１５．８ＡＴ／ｍ（２００Ｏｅ）の条件で、直流重畳特性を測定した。
【００３７】
実験に用いたフェライトコアは、Ｍｎ−Ｚｎ系フェライト材で作製された磁路長７．５ｃｍ、実効断面積０．７４ｃｍ^２のＥＥコアであり、その中芯に１．５ｍｍのギャップ加工をした。フェライトコアの中芯断面形状で、かつ高さ１．５ｍｍの形状に加工したボンド磁石をそのギャップ部に挿入した。これらの形状を図３に示す。また、この時の直流バイアス磁界の向きは、挿入時に着磁した磁石の磁化の向きとは逆になるように重畳電流を印加する。その測定結果を図２に示す。
【００３８】
図２より、γ＝６．５のＳｍＣｏ磁石を挿入したコアについては透磁率が高磁界側まで伸びず、磁石によるバイアス磁界の大きさが他のものに比べ非常に小さくなっていることが分かる。γ＝７．０〜８．５のＳｍＣｏ磁石を挿入したコアについては、直流重畳特性は高磁界側まで伸び、良好な値を示した。また、γ＝９．０のＳｍＣｏ磁石を挿入したコアについては、透磁率が高磁界側まで伸びず、他のものに比べ特性が劣っていることが分かる。これは、残留磁化の大きさが小さいためバイアス量が減少し、直流重畳特性が劣化したものと考えられる。
【００３９】
（実施例３）
本発明の実施例３によるインダタンス部品について説明する。図３は、本発明の実施例３におけるインダクタンス部品の説明図である。図３にて、インダクタンス部品１０は、Ｅ型のフェライトコア１，２と、その中心部の空隙に挿入された磁石３と、巻線４とで構成されている。ここで、磁芯１１は、Ｅ型のフェライトコア１，２と磁石３との一体化して構成されたものである。このように構成することにより、直流重畳特性の良好なインダクタンス部品が提供できた。
【００４０】
【発明の効果】
以上、本発明によれば、優れたコアロス特性と直流重畳特性を有する、安価な磁芯およびそれを用いたインダクタンス部品を提供できる。
【図面の簡単な説明】
【図１】本発明の実施例１における磁芯の直流重畳特性を示す図。
【図２】本発明の実施例２における磁芯の直流重畳特性を示す図。
【図３】本発明の実施例３におけるインダクタンス部品の説明図。
【符号の説明】
１，２ フェライトコア
３ 磁石
４ 巻線
１０ インダクタンス部品
１１ 磁芯[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a magnetic core suitable for a choke coil and a transformer magnetic core used for a switching power supply and the like, and an inductance component using the same.
[0002]
[Prior art]
Good DC superposition characteristics are required for the choke coil and transformer cores, and ferrite and dust cores are used for the high-frequency cores. Ferrite cores have characteristics derived from material properties such as high initial permeability and low saturation magnetic flux density, and dust cores have low initial magnetic permeability and high saturation magnetic flux density. Therefore, the dust core is often used in a toroidal shape, and the ferrite is often used in the EE core, for example, by inserting a gap in the middle foot of the E-type core.
[0003]
However, due to the demand for miniaturization of electronic components accompanying the recent demand for miniaturization of electronic equipment, high permeability in a large superimposed magnetic field is strongly required for inductance components. Generally, in order to improve the DC bias characteristics, it is essential to select a magnetic core having a high saturation magnetization, that is, to select a magnetic core that does not cause magnetic saturation in a high magnetic field.
However, the saturation magnetization is inevitably determined by the composition of the material, and cannot be increased infinitely. For this reason, the conventional means for improving the DC superimposition characteristic requires a great deal of labor to slightly improve the saturation magnetization. there were.
[0004]
As a solution to this problem, insertion of a gap into one or more magnetic paths and insertion of a permanent magnet into the gap have been conventionally studied. This method is an excellent method for improving DC superimposition characteristics, but when using a sintered metal magnet, the core loss of the magnetic core increases significantly, and when using a ferrite magnet, the superposition characteristics are not stable. It was not practical. As means for solving these problems, for example, Patent Document 1 discloses that as a permanent magnet, a rare-earth magnet powder having a high coercive force and a binder are mixed and a compression-molded bond magnet is inserted. It has been shown that the temperature rise was improved.
[0005]
[Patent Document 1]
Japanese Patent Application Laid-Open No. 50-133453
[Problems to be solved by the invention]
However, in recent years, the demand for improving the power conversion efficiency of power supplies has become more and more severe, and it has become difficult to determine the superiority or inferiority of cores for choke coils and transformers by simply measuring the core temperature. I have. For this reason, it is indispensable to judge the measurement result by the core loss measuring device. In fact, as a result of the study by the present inventors, it is clear that the core loss characteristic is deteriorated with the low resistivity shown in Patent Document 1. Became.
[0007]
Therefore, we have to insert a permanent magnet having a specific coercive force of 10 × 79 kAT / m (10 kOe) or more, a Curie temperature Tc of 800 ° C. or more, and a specific resistance of 1.0 Ω · cm or more as a permanent magnet to be inserted into the gap. It has been found that good DC bias characteristics can be obtained without reducing core loss.
[0008]
However, there is a demand that exceeds these characteristic values, and in order to aim for further improvement in reliability, core loss characteristics, and superimposition characteristics, a high coercive force, a high residual magnetic flux density, and a high Curie temperature Tc of the permanent magnet inserted into the gap are required. It is necessary to develop magnets that can be combined.
[0009]
In view of the above problems, an object of the present invention is to provide an inexpensive magnetic core having excellent core loss characteristics and DC superimposition characteristics, and an inductance component using the same.
[0010]
[Means for Solving the Problems]
The present invention, as a result of examining a permanent magnet to be inserted to achieve the above-mentioned object, shows that when a permanent magnet having a specific resistance of 1.0 Ω · cm or more is used, an excellent DC superimposition characteristic is obtained, and the core loss characteristic is improved. It has been found that a magnetic core that does not deteriorate can be formed. It has been found that the magnet characteristics necessary for obtaining excellent DC superimposition characteristics are inherent coercive forces rather than energy products.
[0011]
A magnet having a high specific resistance and a high intrinsic coercive force is generally obtained by a rare earth bonded magnet formed by mixing a rare earth magnet powder with a binder. Rare earth magnet powders are classified into SmCo-based, NdFeB-based, and SmFeN-based, but in consideration of reflow conditions and oxidation resistance, the Curie temperature Tc is 800 ° C. or more, and the coercive force is 20 × 79 kAT / m (20 kOe) or more. Magnets are currently limited to Sm ₂ Co ₁₇ based magnets.
[0012]
Then, as a result of studying the Sm ₂ Co ₁₇ magnet, we found that Sm (Fe _{0.15 to 0.25} Cu _{0.06 to 0.08} Zr _{0.02 to 0.33} Co _{0.64 to 0 .77} ) _Among magnets having a composition of _{7.0 to 8.5} , a high-performance magnet having a Curie temperature Tc of 800 ° C. or more and a coercive force of 20 × 79 kAT / m (20 kOe) or more was found.
[0013]
BEST MODE FOR CARRYING OUT THE INVENTION
A magnetic core according to an embodiment of the present invention and an inductance component using the same will be described below.
[0014]
Any material having soft magnetic properties is effective for the core for the choke coil and the transformer, but generally, MnZn-based or Ni-Zn-based ferrite, dust core, silicon steel sheet, amorphous, etc. Is used. The shape of the magnetic core is not particularly limited, and the present invention can be applied to magnetic cores of any shape such as a toroidal core, an EE core, and an EI core. A gap is provided in at least one portion of the magnetic path of these cores, and a permanent magnet is inserted into the gap. There is no particular limitation on the gap length, but if the gap length is too narrow, the DC superposition characteristics deteriorate, and if the gap length is too wide, the magnetic permeability is too low, so the gap length to be inserted naturally is determined.
[0015]
Next, the required characteristics of the permanent magnet inserted into the gap are as follows: the specific coercive force requires a coercive force of 20 × 79 kAT / m (20 kOe) or more in order to secure reliability and suppress hysteresis loss. The larger the value, the better, but if it is 1.0 Ω · cm or more, it will not be a major factor in eddy current loss deterioration. When the average maximum particle diameter of the powder is 50 μm or more, the core loss characteristics deteriorate. Therefore, it is desirable that the maximum particle diameter of the powder be 50 μm or less, and when the minimum particle diameter is 25 μm or less, magnetization by powder oxidation during heat treatment and reflow of the powder. In order to make the reduction of remarkable, a particle size of 2.5 μm or more is required.
[0016]
A magnetic core according to an embodiment of the present invention is a magnetic core having a gap at at least one location in a magnetic path, wherein the gap has a specific coercive force of 20 × 79 kAT / m (20 kOe) or more and a Curie temperature of 300 ° C. This is a configuration in which a bonded magnet made of a resin and a rare earth magnet powder having a powder average particle diameter of 2.5 to 50 μm is inserted. Powder having a composition of Sm (Fe _{0.15 to 0.25} Cu _{0.06 to 0.08} Zr _{0.02 to 0.03} Co _{0.64 to 0.77} ) _{7.0 to 8.5 in} the gap. A bonded magnet made of SmCo magnet powder having an average particle size of 2.5 to 50 μm and a resin is inserted, and the bonded magnet has a resin content of 20% or more by volume and a specific resistance of 1 Ωcm or more.
[0017]
An inductance component according to an embodiment of the present invention is an inductance component including the magnetic core and at least one or more turns of the magnetic core.
[0018]
【Example】
Embodiments of the magnetic core of the present invention and an inductance component using the same will be described below.
[0019]
(Example 1)
The magnetic core according to Example 1 was prepared as follows. A sample was prepared by changing a Cu content: y of Sm (Fe _0.2 Cu _y Zr _0.028 Co _Bal ) _8.3 , and the sample was used as an Sm-Co bonded magnet. The following shows an example in which the characteristics were measured and compared.
[0020]
Samples with different amounts of Cu: y (y = 0.03 to 0.09: 7 in total) were prepared in a high-frequency melting furnace, followed by sintering at 1215 ° C. for 3 hours, and solution heat treatment at 1195 ° C. for 15 hours. Aging was performed at 800 ° C. for 40 hours each. Then, it was pulverized with a metal rod and classified to 250 μm or less.
[0021]
After mixing the binder (epoxy resin) in an amount corresponding to 10 wt% to these Sm-Co magnet powders, they were molded in a magnetic field-free condition, and then dried at 150 ° C. for 30 minutes to form the magnet powder.
[0022]
Manufacturing conditions

[0023]
Table 1 shows the results of the magnetic properties of the samples manufactured under the above conditions.
[0024]
[Table 1]

[0025]
According to Table 1, when y = 0.05 or less, the coercive force becomes 20 × 79 kAT / m (20 kOe) or less, and when y = 0.09, the residual magnetic flux density becomes 0.280 T or less, deteriorating the magnetic characteristics. It was found that in the range of y = 0.06 to 0.08, good characteristics were exhibited when the coercive force was 20 × 79 kAT / m (20 kOe) or more and Br was 0.280 T or more.
[0026]
An example in which the DC superposition characteristics of the magnetic core when these Sm-Co bonded magnets are inserted into a part of the magnetic path of the Mn-Zn-based ferrite core is measured and compared is shown. The DC superposition characteristics were measured by using a 4284A LCR meter manufactured by Hewlett Packard for the core into which each magnet was inserted, under the conditions of an AC magnetic field frequency of 100 kHz and a superposition magnetic field of 0 to 15.8 AT / m (200 Oe).
[0027]
The ferrite core used in the experiment was an EE core having a magnetic path length of 7.5 cm and an effective area of 0.74 cm ² made of a Mn—Zn-based ferrite material, and a 1.5 mm gap was formed on the center of the core. . A bonded magnet processed into a ferrite core having a core cross-sectional shape and a height of 1.5 mm was inserted into the gap. The superimposed current is applied such that the direction of the DC bias magnetic field at this time is opposite to the direction of magnetization of the magnet magnetized at the time of insertion. FIG. 1 shows the measurement results.
[0028]
From FIG. 1, it can be seen that, for the core in which the SmCo magnet with y = 0.03 is inserted, the magnetic permeability does not extend to the high magnetic field side, and the magnitude of the bias magnetic field by the magnet is much smaller than the others. I understand. It can be seen that the coercive force is as small as 7.1 × 79 kAT / m (7.1 kOe), so that it is greatly demagnetized and the superimposition characteristics are very inferior to those of the others.
[0029]
As for the core in which y = 0.04 to 0.08 SmCo magnet was inserted, the DC superimposition characteristics extended to the high magnetic field side, and showed good values. Further, it can be seen that the magnetic permeability of the core in which the SmCo magnet with y = 0.09 is inserted does not extend to the high magnetic field side, and is inferior in characteristics to other cores. This is presumably because the amount of bias was reduced due to the small residual magnetization, and the DC bias characteristics were degraded.
[0030]
(Example 2)
The magnetic core according to Example 2 was prepared by changing a transition metal amount of Sm (Fe _0.2 Cu _0.067 Zr _0.028 Co _Bal ) _γ , that is, preparing a sample in which γ was changed, and then bonding it to an Sm-Co bond. An example in which characteristics of magnets are measured and compared is shown.
[0031]
Samples with different γ (γ = 6.5-9.0: 7 in total) were prepared in a high frequency melting furnace, and then sintering was performed at 1215 ° C. for 3 hours, solution heat treatment was performed at 1195 ° C. for 15 hours, and aging was performed. The film was formed at 800 ° C. for 40 hours. Then, it was pulverized with a metal rod and classified to 250 μm or less. After mixing the binder (epoxy resin) in an amount corresponding to 10 wt% to these Sm-Co magnet powders, a mold was formed in the absence of a magnetic field, and then dried at 150 ° C. for 30 minutes.
[0032]
Manufacturing conditions

[0033]
Table 2 shows the results of the magnetic properties of the samples manufactured under the above conditions.
[0034]
[Table 2]

[0035]
According to Table 2, when γ = 6.5 or less, the coercive force becomes 20 × 79 kAT / m (20 kOe) or less, and when γ = 0.9, the residual magnetic flux density becomes 2.8T or less, deteriorating the magnetic characteristics. In the range of γ = 7.0 to 8.5, it was found that good characteristics were exhibited when the coercive force was 20 × 79 kAT / m (20 kOe) or more and Br was 2.8 T or more.
[0036]
An example in which DC superimposition characteristics when these Sm-Co bonded magnets are inserted into a part of a magnetic path of a Mn-Zn ferrite core is measured and compared is shown. The DC superposition characteristics were measured by using a 4284A LCR meter manufactured by Hewlett Packard for the core into which each magnet was inserted, under the conditions of an AC magnetic field frequency of 100 kHz and a superposition magnetic field of 0 to 15.8 AT / m (200 Oe).
[0037]
The ferrite core used in the experiment was an EE core having a magnetic path length of 7.5 cm and an effective area of 0.74 cm ² made of a Mn—Zn-based ferrite material, and a 1.5 mm gap was formed on the center of the core. . A bonded magnet processed into a ferrite core having a core cross-sectional shape and a height of 1.5 mm was inserted into the gap. These shapes are shown in FIG. The superimposed current is applied such that the direction of the DC bias magnetic field at this time is opposite to the direction of magnetization of the magnet magnetized at the time of insertion. FIG. 2 shows the measurement results.
[0038]
From FIG. 2, it can be seen that the magnetic permeability of the core in which the SmCo magnet with γ = 6.5 is inserted does not extend to the high magnetic field side, and the magnitude of the bias magnetic field by the magnet is much smaller than those of other cores. . With respect to the core in which the SmCo magnet with γ = 7.0 to 8.5 was inserted, the DC superimposition characteristics extended to the high magnetic field side, and showed good values. Further, it can be seen that the magnetic permeability of the core in which the SmCo magnet with γ = 9.0 is inserted does not extend to the high magnetic field side, and is inferior in characteristics to other cores. This is considered to be because the amount of bias was reduced because the magnitude of the residual magnetization was small, and the DC bias characteristics were deteriorated.
[0039]
(Example 3)
Third Embodiment An inductance component according to a third embodiment of the present invention will be described. FIG. 3 is an explanatory diagram of an inductance component according to a third embodiment of the present invention. In FIG. 3, the inductance component 10 includes E-type ferrite cores 1 and 2, a magnet 3 inserted in a gap at the center thereof, and a winding 4. Here, the magnetic core 11 is formed by integrating the E-type ferrite cores 1 and 2 and the magnet 3. With such a configuration, an inductance component having good direct-current superposition characteristics can be provided.
[0040]
【The invention's effect】
As described above, according to the present invention, an inexpensive magnetic core having excellent core loss characteristics and DC superimposition characteristics and an inductance component using the same can be provided.
[Brief description of the drawings]
FIG. 1 is a diagram showing a DC superimposition characteristic of a magnetic core according to a first embodiment of the present invention.
FIG. 2 is a diagram illustrating a DC superposition characteristic of a magnetic core according to a second embodiment of the present invention.
FIG. 3 is an explanatory diagram of an inductance component according to a third embodiment of the present invention.
[Explanation of symbols]
1, 2 Ferrite core 3 Magnet 4 Winding 10 Inductance component 11 Magnetic core

Claims (4)

A magnetic core having a gap in at least one position of a magnetic path, wherein the gap has a specific coercive force of 20 × 79 kAT / m (20 kOe) or more and a Curie temperature of 800 ° C. or more, and has an average powder particle size of 2.5 to 2.5 ° C. A magnetic core in which a bonded magnet made of a 50 μm rare earth magnet powder and a resin is inserted. The rare earth magnet powder, the composition formula is a _{Sm (Fe x Cu y Zr z} Co 1-x-y-z) γ, 0.15 ≦ x ≦ 0.25,0.06 ≦ y ≦ 0.08 , 0.02 ≦ z ≦ 0.03, 7.0 ≦ γ ≦ 8.5. The magnetic core according to claim 1, wherein the bonded magnet has a resin amount of 20% or more in volume ratio and a specific resistance of 1 Ωcm or more. 4. An inductance component, comprising: the magnetic core according to any one of claims 1 to 3; and a winding having at least one turn wound around the magnetic core.

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