JP2014116527A - Method for manufacturing dust core - Google Patents
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本発明は、軟磁性材料粉を用いて構成された圧粉磁心の製造方法に関する。 The present invention relates to a method for manufacturing a dust core made of soft magnetic material powder.
家電機器の電源回路の初段部は、ＡＣ（交流）電圧からＤＣ（直流）電圧に変換するＡＣ／ＤＣコンバータ回路で構成されている。このコンバータ回路内での入力電流の波形と電圧波形との間で位相のずれが生じたり、電流波形自体が正弦波にならない現象が発生することが一般に知られている。このため、いわゆる力率が低下して無効電力が大きくなり、また高調波ノイズを発生させることになる。ＰＦＣ回路は、このようなＡＣ入力電流の波形を、ＡＣ入力電圧と同様な位相や波形に整形するように制御することで、無効電力及び高調波ノイズを低減するための回路である。近年、標準化団体であるＩＥＣ（Ｉｎｔｅｒｎａｔｉｏｎａｌ Ｅｌｅｃｔｒｏ−ｔｅｃｈｎｉｃａｌ Ｃｏｍｍｉｓｓｉｏｎ：国際電気標準会議）の主導で、各種機器はＰＦＣ制御の電源回路を搭載することが法令により必須となる状況になりつつある。前記回路で使用されるチョークを小型化・低背化等するために、それに用いられる磁心には、高飽和磁束密度、低コアロス、優れた直流重畳特性が要求されている。 The first stage part of the power supply circuit of the home appliance is composed of an AC / DC converter circuit that converts an AC (alternating current) voltage into a DC (direct current) voltage. It is generally known that a phase shift occurs between the waveform of the input current and the voltage waveform in the converter circuit, or that the current waveform itself does not become a sine wave. For this reason, the so-called power factor decreases, the reactive power increases, and harmonic noise is generated. The PFC circuit is a circuit for reducing reactive power and harmonic noise by controlling the waveform of such an AC input current so as to be shaped into the same phase and waveform as the AC input voltage. In recent years, under the leadership of the International Electro-technical Commission (IEC), which is a standardization organization, it is becoming necessary for various devices to be equipped with PFC-controlled power supply circuits by law. In order to reduce the size and height of a choke used in the circuit, a magnetic core used for the choke is required to have a high saturation magnetic flux density, a low core loss, and excellent direct current superposition characteristics.
また、近年、急速に普及しはじめたハイブリッド車や電気自動車等のモータ駆動の車両や太陽光発電装置などに搭載されている電源装置では、大電流に耐えるリアクトルが用いられている。かかるリアクトル用の磁心においても、同様に高飽和磁束密度、低損失が要求されている。 In recent years, a reactor that can withstand a large current is used in a power supply device mounted on a motor-driven vehicle such as a hybrid vehicle or an electric vehicle that has begun to spread rapidly, a solar power generation device, or the like. The reactor core is similarly required to have a high saturation magnetic flux density and a low loss.
上記要求に応えるものとして、高飽和磁束密度と低損失のバランスに優れる圧粉磁心が採用されている。圧粉磁心は、センダストやＦｅ−Ｓｉ系などの磁性粉末の表面を絶縁処理したのち成形して得られるもので、絶縁処理により電気抵抗が高められ、渦電流損失が抑制されている。特許文献１には、更なるコアロスＰｃｖの低減のために、第一の磁性体としてＦｅ基アモルファス合金薄帯の粉砕粉と、第二の磁性体としてＣｒを含むＦｅ基アモルファス合金アトマイズ粉とを主成分とする圧粉磁心が提案されている。 In order to meet the above requirements, a dust core excellent in the balance between high saturation magnetic flux density and low loss is employed. The dust core is obtained by forming a surface of a magnetic powder such as Sendust or Fe-Si after being subjected to insulation treatment. The insulation treatment increases the electrical resistance and suppresses eddy current loss. In Patent Document 1, in order to further reduce the core loss Pcv, an Fe-based amorphous alloy ribbon pulverized powder as a first magnetic body and an Fe-based amorphous alloy atomized powder containing Cr as a second magnetic body are disclosed. A dust core having a main component has been proposed.
特許文献１に記載の構成によれば、センダストやＦｅ−Ｓｉ系など、結晶質の軟磁性材料粉の圧粉磁心に比べて低いコアロスＰｃｖが得られている。しかしながら、アモルファス合金薄帯の粉砕粉は、厚さに対してそれに垂直な方向の寸法が大きい扁平粉であるため、高密度化が困難であった。高密度化のためには、加圧成形時の成形圧を上げることも一つの方法であるが、成形圧を上げること自体が困難である上に、成形圧が高くなると、それだけ磁性粉末に応力がかかり、コアロスが大きくなってしまう。そのため、磁性粉末の占積率の向上には限界があり、材料が有する高透磁率、高飽和磁束密度のポテンシャルを十分に活かすことができなかった。また、占積率のさらなる向上は、特許文献１に記載された合金薄帯の粉砕粉に限らず、他の軟磁性材料粉を用いた圧粉磁心にも要求されている課題であった。 According to the configuration described in Patent Document 1, a low core loss Pcv is obtained as compared with a powder magnetic core of crystalline soft magnetic material powder such as Sendust or Fe—Si. However, since the pulverized powder of the amorphous alloy ribbon is a flat powder having a dimension in a direction perpendicular to the thickness, it is difficult to increase the density. Increasing the molding pressure at the time of pressure molding is one method for increasing the density, but it is difficult to increase the molding pressure itself, and the higher the molding pressure, the more stress is applied to the magnetic powder. Will increase the core loss. For this reason, there is a limit to the improvement of the space factor of the magnetic powder, and the potential of the high magnetic permeability and high saturation magnetic flux density of the material cannot be fully utilized. Further improvement of the space factor is a problem required not only for the pulverized powder of the alloy ribbon described in Patent Document 1, but also for the dust core using other soft magnetic material powder.
そこで、上記問題点に鑑み、本発明は、軟磁性材料粉を用いて構成された圧粉磁心の提供に関して、コアロスの増加を抑えつつ占積率を向上するうえで好適な構成を提供することを目的とする。 Accordingly, in view of the above problems, the present invention provides a suitable configuration for improving the space factor while suppressing an increase in core loss, regarding the provision of a powder magnetic core composed of soft magnetic material powder. With the goal.
本発明の圧粉磁心の製造方法は、軟磁性材料粉を用いて構成された圧粉磁心の製造方法であって、前記軟磁性材料粉と、熱可塑性樹脂と、シリコーン樹脂とを混合する第１の工程と、前記第１の工程を経た混合物を加熱して、前記熱可塑性樹脂のガラス転移温度以上、かつ前記シリコーン樹脂のガラス転移温度以上の成形温度で加圧成形する第２の工程と、前記第２の工程を経た成形体を前記成形温度よりも高い温度で熱処理する第３の工程とを有することを特徴とする。 A method for producing a dust core according to the present invention is a method for producing a dust core made of soft magnetic material powder, wherein the soft magnetic material powder, a thermoplastic resin, and a silicone resin are mixed. And the second step of heating and pressing the mixture that has undergone the first step at a molding temperature that is equal to or higher than the glass transition temperature of the thermoplastic resin and equal to or higher than the glass transition temperature of the silicone resin. And a third step of heat-treating the molded body that has undergone the second step at a temperature higher than the molding temperature.
また、前記圧粉磁心の製造方法において、前記成形温度が前記シリコーン樹脂の融点以上であることが好ましい。 Moreover, in the manufacturing method of the said powder magnetic core, it is preferable that the said shaping | molding temperature is more than melting | fusing point of the said silicone resin.
さらに、前記圧粉磁心の製造方法において、前記熱可塑性樹脂のガラス転移温度と、前記シリコーン樹脂の融点との差が５０℃以内であることが好ましい。 Furthermore, in the manufacturing method of the said powder magnetic core, it is preferable that the difference of the glass transition temperature of the said thermoplastic resin and melting | fusing point of the said silicone resin is less than 50 degreeC.
さらに、前記圧粉磁心の製造方法において、前記成形温度が、前記熱可塑性樹脂のガラス転移温度と、前記シリコーン樹脂の融点のいずれか高い方の温度よりも、３０℃以上高いことが好ましい。 Furthermore, in the manufacturing method of the said powder magnetic core, it is preferable that the said shaping | molding temperature is 30 degreeC or more higher than the higher one of the glass transition temperature of the said thermoplastic resin, and the melting | fusing point of the said silicone resin.
さらに、前記圧粉磁心の製造方法において、前記シリコーン樹脂の添加量が前記軟磁性材料粉１００重量部に対して０.１〜１.０重量部であることが好ましい。 Furthermore, in the manufacturing method of the said powder magnetic core, it is preferable that the addition amount of the said silicone resin is 0.1-1.0 weight part with respect to 100 weight part of said soft-magnetic material powders.
さらに、前記圧粉磁心の製造方法において、前記第１の工程の前に、前記軟磁性材料粉の表面に湿式成膜方法によって非磁性の絶縁被膜を形成する工程を有することが好ましい。 Furthermore, it is preferable that the method for manufacturing a dust core includes a step of forming a nonmagnetic insulating film on the surface of the soft magnetic material powder by a wet film forming method before the first step.
本発明によれば、軟磁性合金薄帯の粉砕粉を用いて構成された圧粉磁心の製造方法において、コアロスの増加を抑えつつ占積率を向上するうえで好適な構成を提供することができる。 According to the present invention, in a method of manufacturing a powder magnetic core configured using a pulverized powder of soft magnetic alloy ribbon, it is possible to provide a preferable configuration for improving the space factor while suppressing an increase in core loss. it can.
以下、本発明に係る圧粉磁心の製造方法の実施形態を、具体的に説明するが、本発明はこれに限定されるものではない。
Hereinafter, although the embodiment of the manufacturing method of the dust core concerning the present invention is described concretely, the present invention is not limited to this.
図１は本発明に係る圧粉磁心の製造方法の実施形態を説明するための工程のフローである。図１に示す、軟磁性材料粉を用いて構成された圧粉磁心の製造方法は、軟磁性材料粉と、熱可塑性樹脂と、シリコーン樹脂とを混合する第１の工程と、第１の工程を経た混合物を加熱して、前記熱可塑性樹脂のガラス転移温度Ｔｇ１以上、かつ前記シリコーン樹脂のガラス転移温度Ｔｇ２以上の成形温度Ｔ１で加圧成形する第２の工程と、前記第２の工程を経た成形体を前記成形温度Ｔ１よりも高い温度Ｔ２で熱処理する第３の工程とを有する。 FIG. 1 is a process flow for explaining an embodiment of a method for producing a dust core according to the present invention. The manufacturing method of the powder magnetic core comprised using soft-magnetic material powder shown in FIG. 1 is the 1st process of mixing soft-magnetic material powder, thermoplastic resin, and silicone resin, and 1st process. The second step of heating and molding the mixture at a molding temperature T1 equal to or higher than the glass transition temperature Tg1 of the thermoplastic resin and equal to or higher than the glass transition temperature Tg2 of the silicone resin, and the second step. And a third step of heat-treating the passed molded body at a temperature T2 higher than the molding temperature T1.
熱可塑性樹脂は、プレスで成形する際、粉体同士を結着させ、成形後のハンドリングに耐える強度を成形体に付与する。一方、シリコーン樹脂は第３の工程を経た圧粉磁心の強度を確保するために用いられる。ガラス転移温度は、温度上昇中に樹脂がガラス状態からゴム状態に転移する温度であり、該温度で急激に剛性、粘度が低下する。そのため、上記第２の工程において、熱可塑性樹脂およびシリコーン樹脂のガラス転移温度以上で加圧成形することで、圧粉磁心における占積率と強度を大幅に向上させることができる。従来のように室温で成形する場合には、占積率等の向上には大きな成形圧力が必要であるため、歪の影響でコアロスが増加してしまう。これに対して、上記第２の工程によれば、大きな圧力をかけなくても、占積率等の向上が可能であるため、コアロスの増加を抑えつつ占積率を向上させることができる。圧粉磁心における磁性粉の占積率が顕著に増加することで、透磁率や飽和磁束密度も大幅に増加する。さらに、上述のように、シリコーン樹脂は第３の工程を経た圧粉磁心の強度維持に寄与するが、その一方でコアロス増加の要因にもなる。第２の工程によればシリコーン樹脂量の増加以外の方法で強度の向上も実現できるため、コアロス増加を抑えつつ、圧粉磁心の強度も確保できる。 When the thermoplastic resin is molded by a press, the powders are bonded to each other to give the molded body a strength that can withstand handling after molding. On the other hand, the silicone resin is used to ensure the strength of the dust core that has undergone the third step. The glass transition temperature is a temperature at which the resin transitions from the glass state to the rubber state during the temperature rise, and the rigidity and the viscosity are rapidly decreased at the temperature. Therefore, in the second step, the space factor and the strength in the dust core can be greatly improved by performing pressure molding at the glass transition temperature or higher of the thermoplastic resin and the silicone resin. When molding at room temperature as in the prior art, a large molding pressure is required to improve the space factor and the like, and thus the core loss increases due to the influence of strain. On the other hand, according to the second step, since the space factor can be improved without applying a large pressure, the space factor can be improved while suppressing an increase in core loss. By significantly increasing the space factor of the magnetic powder in the dust core, the magnetic permeability and saturation magnetic flux density are also greatly increased. Furthermore, as described above, the silicone resin contributes to maintaining the strength of the dust core that has undergone the third step, but it also causes an increase in core loss. According to the second step, the strength can be improved by a method other than the increase in the amount of the silicone resin, so that the strength of the dust core can be secured while suppressing an increase in core loss.
熱可塑性樹脂やシリコーン樹脂のガラス転移温度が室温以下であると、第１の工程以降のハンドリングがしにくく、量産性に劣る。そのため、熱可塑性樹脂およびシリコーン樹脂は、ガラス転移温度が室温を超えるものを用い、室温を超える温度で成形を行う。なお、第１〜第３の各工程の間等に他の工程を追加することも可能である。以下、各工程ごとに詳細に説明する。 When the glass transition temperature of the thermoplastic resin or silicone resin is room temperature or lower, handling after the first step is difficult and the mass productivity is poor. Therefore, as the thermoplastic resin and the silicone resin, those having a glass transition temperature exceeding room temperature are used, and molding is performed at a temperature exceeding room temperature. In addition, it is also possible to add another process between 1st-3rd processes. Hereinafter, each step will be described in detail.
まず、第１の工程に供する軟磁性材料粉ついて説明する。軟磁性材料粉には、各種の金属系磁粉を用いることができる。例えば、Ｆｅ系、Ｆｅ−Ｓｉ系、Ｆｅ−Ｓｉ−Ａｌ系、Ｆｅ−Ｓｉ−Ｃｒ系等の磁性金属・磁性合金の他、Ｆｅ−Ｓｉ−Ｂ系等のＦｅ基やＣｏ基のアモルファス合金、Ｆｅ−Ｓｉ−Ｂ−Ｃｕ−Ｎｂ系、Ｆｅ−Ｃｕ−Ｂ系、Ｆｅ−Ｃｕ−Ｓｉ−Ｂ系、Ｆｅ−Ｎｉ−Ｃｕ−Ｓｉ−Ｂ系等のＦｅ基ナノ結晶合金を用いることができる。また、これらの元素の一部を置換した系および他の元素を添加した系を用いることもできる。軟磁性材料粉の形態もこれを特に限定するものではない。例えば、球状アトマイズ粉に代表される粒状粉を用いることもできるし、圧延、扁平化処理、粉砕等を経た薄片状粉（扁平粉）を用いることもできる。このうち、アモルファス合金やナノ結晶合金の合金薄帯等を粉砕して得られる薄片状の粉砕粉を用いる場合は、粒状粉を用いる場合に比べて圧粉磁心の高密度化がしにくい。そのため、圧粉磁心の高密度化に有利な本発明に係る構成は、かかる薄片状の粉砕粉を用いる圧粉磁心に適用することがより好ましい。そこで、以下は、軟磁性合金薄帯の粉砕粉を用いる場合を例に説明する。 First, the soft magnetic material powder used in the first step will be described. Various metallic magnetic powders can be used for the soft magnetic material powder. For example, Fe-based, Fe-Si-based, Fe-Si-Al-based, Fe-Si-Cr-based magnetic metals and magnetic alloys, Fe-Si-B-based Fe-based and Co-based amorphous alloys, Fe-based nanocrystalline alloys such as Fe-Si-B-Cu-Nb, Fe-Cu-B, Fe-Cu-Si-B, and Fe-Ni-Cu-Si-B can be used. A system in which a part of these elements is substituted and a system in which other elements are added can also be used. The form of the soft magnetic material powder is not particularly limited. For example, granular powder represented by spherical atomized powder can be used, and flaky powder (flat powder) that has undergone rolling, flattening treatment, pulverization, and the like can also be used. Among these, in the case of using a flaky pulverized powder obtained by pulverizing an alloy ribbon or the like of an amorphous alloy or a nanocrystalline alloy, it is difficult to increase the density of the powder magnetic core as compared with the case of using a granular powder. Therefore, it is more preferable to apply the configuration according to the present invention, which is advantageous for increasing the density of the dust core, to a dust core using such flaky pulverized powder. Therefore, the following description will be made taking as an example the case of using soft magnetic alloy ribbon pulverized powder.
軟磁性合金薄帯は、例えば、単ロール法のように合金溶湯を急冷することによって得られる。上述したアモルファス合金やナノ結晶合金の合金組成はこれを特に限定するものではなく、必要とされる特性に応じて選定することができる。例えば、アモルファス合金薄帯であれば、１.４Ｔ以上の高い飽和磁束密度Ｂｓを有するＦｅ基アモルファス合金薄帯を用いることができる。一方、ナノ結晶合金薄帯であれば、１.２Ｔ以上の高い飽和磁束密度Ｂｓを有するＦｅ基ナノ結晶合金薄帯を用いることができる。 The soft magnetic alloy ribbon is obtained, for example, by rapidly cooling the molten alloy as in the single roll method. The alloy composition of the amorphous alloy or nanocrystalline alloy described above is not particularly limited, and can be selected according to the required characteristics. For example, in the case of an amorphous alloy ribbon, an Fe-based amorphous alloy ribbon having a high saturation magnetic flux density Bs of 1.4 T or more can be used. On the other hand, if it is a nanocrystalline alloy ribbon, a Fe-based nanocrystalline alloy ribbon having a high saturation magnetic flux density Bs of 1.2 T or more can be used.
軟磁性合金薄帯の粉砕をするにあたって、あらかじめ脆化処理を行うことで粉砕性を高めることができる。例えば、Ｆｅ基アモルファス合金薄帯は３００℃以上の熱処理により脆化が起こり、粉砕しやすくなる性質を持っている。かかる熱処理の温度を上げると、より脆化し、粉砕しやすくなる。ただし、３８０℃を超えるとコアロスＰｃｖが増加する。好ましい脆化熱処理温度は、３２０℃以上３８０℃未満である。脆化処理は薄帯を巻回したスプールの状態で行うこともできるし、巻回されていない状態の薄帯を所定形状にプレスして得られた、整形された塊の状態で行うこともできる。但し、かかる脆化処理は必須ではない。例えば、ナノ結晶合金薄帯の場合は、脆化処理を省略してもよい。 When the soft magnetic alloy ribbon is pulverized, pulverization can be improved by carrying out embrittlement in advance. For example, an Fe-based amorphous alloy ribbon has the property of becoming brittle due to heat treatment at 300 ° C. or higher and easily pulverized. Increasing the temperature of such heat treatment makes it more brittle and easier to grind. However, if it exceeds 380 ° C., the core loss Pcv increases. A preferable embrittlement heat treatment temperature is 320 ° C. or higher and lower than 380 ° C. The embrittlement treatment can be performed in the state of a spool around which the ribbon is wound, or can be performed in the state of a shaped lump obtained by pressing the ribbon that has not been wound into a predetermined shape. it can. However, such embrittlement treatment is not essential. For example, in the case of a nanocrystalline alloy ribbon, the embrittlement treatment may be omitted.
一回の粉砕だけで粉砕粉を得ることも可能であるが、所望の粒径にするために、粉砕工程は、粗粉砕後、微粉砕のように、少なくとも２工程に分けて行い、段階的に粒径を落とすことが、粉砕能力及び粒径の均一性の点で好ましい。粗粉砕、中粉砕、微粉砕の３工程で行うことがより好ましい。 Although it is possible to obtain a pulverized powder by only one pulverization, the pulverization step is performed in steps of at least two steps, such as coarse pulverization and fine pulverization, in order to obtain a desired particle size. It is preferable to reduce the particle size from the viewpoint of grinding ability and particle size uniformity. More preferably, it is performed in three steps of coarse pulverization, medium pulverization, and fine pulverization.
最後の粉砕工程を経た粉砕粉は粒径をそろえるために分級することが好ましい。分級の方法はこれを特に限定するものではないが、篩による方法が簡便であり、好適である。かかる篩を用いた方法について説明する。目開きの異なる２種類の篩を用い、目開きの大きい篩を通過するとともに、目開きの小さい篩を通過しなかった粉砕粉を圧粉磁心用の原料粉末とする。この場合、分級後の粉砕粉の各粒子の最小径ｄは、目開きの大きい方の篩の目開き寸法に１．４を掛けた数値（目開きの対角寸法。以下上限値ともいう）以下となる。また、かかる最小径は、分級が精度よく行われたとすれば、目開きの小さい方の篩の目開き寸法に１．４を掛けた数値（目開きの対角寸法。以下下限値ともいう）よりも大きいものとみなせる。したがって、上記の分級を経た粉砕粉では、各粒子の最小径ｄは、篩の目開きから計算される上限値と下限値の範囲内の値を示す。分級を経た、加圧成形前の粉砕粉の粒径はこの最小径ｄの下限値と上限値で管理することができる。上述のように、粒径が小さい粒子は、それだけ粉砕によって導入された加工歪が大きいことを意味する。流動性等確保の観点から粗い粒子だけを除去して用いることも可能であるが、上述のように細かい粒子を除去することがより好ましい。低コアロスの観点からは、かかる最小径ｄの下限値を、軟磁性合金薄帯の厚さの２倍を超えるようにしておくことが好ましい。また、最小径ｄの上限値を軟磁性合金薄帯の厚さの６倍以下にしておくことで、加圧成形時の流動性を改善し、成形密度をより高めることができる。 The pulverized powder that has undergone the final pulverization step is preferably classified in order to make the particle sizes uniform. The classification method is not particularly limited, but a method using a sieve is simple and preferable. A method using such a sieve will be described. Two types of sieves with different openings are used, and the pulverized powder that passes through the sieve with a large opening and does not pass through the sieve with a small opening is used as a raw material powder for a dust core. In this case, the minimum diameter d of each particle of the pulverized powder after classification is a value obtained by multiplying the opening size of the sieve with the larger opening by 1.4 (diagonal size of the opening; hereinafter also referred to as the upper limit value). It becomes as follows. Further, the minimum diameter is a numerical value obtained by multiplying the opening size of the sieve with the smaller opening by 1.4 (the diagonal dimension of the opening; hereinafter also referred to as the lower limit value) if classification is performed with high accuracy. Can be considered larger. Therefore, in the pulverized powder that has been subjected to the above classification, the minimum diameter d of each particle indicates a value within the range between the upper limit value and the lower limit value calculated from the mesh opening of the sieve. The particle size of the pulverized powder before pressure molding after classification can be managed by the lower limit value and the upper limit value of the minimum diameter d. As described above, particles having a small particle size mean that the processing strain introduced by pulverization is large. Although it is possible to remove and use only coarse particles from the viewpoint of securing fluidity and the like, it is more preferable to remove fine particles as described above. From the viewpoint of low core loss, the lower limit value of the minimum diameter d is preferably set to exceed twice the thickness of the soft magnetic alloy ribbon. Further, by setting the upper limit of the minimum diameter d to 6 times or less of the thickness of the soft magnetic alloy ribbon, the fluidity during pressure molding can be improved and the molding density can be further increased.
軟磁性合金薄帯は数十μｍ程度と薄いため、主面のアスペクト比が大きい粒子はアスペクト比が小さくなるように割れやすい。そのため、各粒子の主面（厚さ方向に垂直な一対の面）は異形ではあるものの、主面の面内方向の最小値ｄと最大値ｍとの差は小さくなり、棒状の粉砕粉は生じにくい。軟磁性合金薄帯の厚さｔは、１０μｍから５０μｍの範囲が好ましい。１０μｍ未満では、合金薄帯自体の機械的強度が低いため、安定に長尺の合金薄帯を鋳造することが困難である。また、５０μｍを超えると合金の一部が結晶化しやすくなり、その場合には特性が劣化する。かかる厚さは、より好ましくは１３〜３０μｍである。 Since the soft magnetic alloy ribbon is as thin as about several tens of μm, particles having a large aspect ratio on the main surface are easily cracked so that the aspect ratio becomes small. Therefore, although the main surface of each particle (a pair of surfaces perpendicular to the thickness direction) is irregular, the difference between the minimum value d and the maximum value m in the in-plane direction of the main surface is small, and the rod-shaped pulverized powder is Hard to occur. The thickness t of the soft magnetic alloy ribbon is preferably in the range of 10 μm to 50 μm. If the thickness is less than 10 μm, the mechanical strength of the alloy ribbon itself is low, and it is difficult to stably cast a long alloy ribbon. On the other hand, when the thickness exceeds 50 μm, a part of the alloy is easily crystallized, and in that case, the characteristics deteriorate. The thickness is more preferably 13 to 30 μm.
圧粉磁心においては、軟磁性合金薄帯の粉砕粉間の絶縁のための手段を講じることにより、渦電流損失を抑制し、低いコアロスを実現することができる。そのため、粉砕粉の表面に薄い絶縁被膜を設けることが好ましい。粉砕粉自体を酸化させて表面に酸化被膜を形成することも可能である。例えば、軟磁性合金薄帯の粉砕粉を湿潤雰囲気において１００℃以上で熱処理することにより、粉砕粉の表面のＦｅが酸化または水酸化され、酸化鉄または水酸化鉄の絶縁被膜が形成される。しかし、かかる方法で粉砕粉へのダメージを抑えながら、均一かつ信頼性の高い酸化被膜を形成することは必ずしも容易ではないため、粉砕粉の合金成分の酸化物とは別の酸化物被膜やリン酸塩被膜などの被膜を設けることが好ましい。すなわち、第１の工程の前に、予備工程として、軟磁性材料粉の表面に湿式成膜方法によって酸化物被膜等の非磁性の絶縁被膜を形成する工程を有することが好ましい。非磁性の酸化物被膜には、絶縁性に加えて、後述するように磁気ギャップとしての機能も持たせることができる。また、ゾルゲル法などの湿式成膜方法によれば、軟磁性材料粉の表面に均一な厚さの絶縁被膜を形成することができる。酸化物被膜の例としては、粉砕粉をＴＥＯＳ（テトラエトキシシラン）、エタノール、アンモニア水の混合溶液に含浸、撹拌後、乾燥することで、粉砕粉の表面に、シリコン酸化物（ＳｉＯ２）被膜を容易に形成することができる。該方法によれば、軟磁性合金薄帯の粉砕粉の表面自体の酸化等の化学反応を必要とせず、しかもシリコンと酸素が結合し、粉砕粉の表面に平面状かつネットワーク状にシリコン酸化物被膜が形成されるため、粉砕粉の表面に均一な厚さの絶縁被膜を形成できる。絶縁等を確実にするためには、シリコン酸化物被膜の厚さは５０ｎｍ以上が好ましい。一方、シリコン酸化物被膜が厚くなりすぎると圧粉磁心の占積率が低下し、軟磁性合金薄帯の粉砕粉間の距離が大きくなり、透磁率自体の低下が大きくなるため、かかる被膜は５００ｎｍ以下が好ましい。シリコン酸化物被膜の厚さは、走査電子顕微鏡（ＳＥＭ）による断面観察において、任意の５箇所で評価してその平均を用いればよい。 In the dust core, eddy current loss can be suppressed and low core loss can be realized by taking measures for insulation between the pulverized powders of the soft magnetic alloy ribbon. Therefore, it is preferable to provide a thin insulating film on the surface of the pulverized powder. It is also possible to oxidize the pulverized powder itself to form an oxide film on the surface. For example, when the pulverized powder of soft magnetic alloy ribbon is heat-treated at 100 ° C. or higher in a humid atmosphere, Fe on the surface of the pulverized powder is oxidized or hydroxylated to form an insulating film of iron oxide or iron hydroxide. However, it is not always easy to form a uniform and reliable oxide film while suppressing damage to the pulverized powder by such a method. Therefore, an oxide film or phosphor other than the oxide of the alloy component of the pulverized powder is not always easy. It is preferable to provide a film such as an acid salt film. That is, it is preferable to have a step of forming a nonmagnetic insulating film such as an oxide film on the surface of the soft magnetic material powder by a wet film forming method as a preliminary step before the first step. In addition to the insulating property, the nonmagnetic oxide film can also have a function as a magnetic gap as described later. In addition, according to a wet film forming method such as a sol-gel method, an insulating film having a uniform thickness can be formed on the surface of the soft magnetic material powder. As an example of the oxide film, the pulverized powder is impregnated with a mixed solution of TEOS (tetraethoxysilane), ethanol, and ammonia water, stirred, and then dried to form a silicon oxide (SiO 2 ) film on the surface of the pulverized powder. Can be easily formed. According to this method, there is no need for a chemical reaction such as oxidation of the surface of the soft magnetic alloy ribbon pulverized powder itself, and silicon and oxygen are bonded, and the surface of the pulverized powder is planar and network-like silicon oxide. Since the film is formed, an insulating film having a uniform thickness can be formed on the surface of the pulverized powder. In order to ensure insulation and the like, the thickness of the silicon oxide film is preferably 50 nm or more. On the other hand, if the silicon oxide film becomes too thick, the space factor of the powder magnetic core decreases, the distance between the pulverized powders of the soft magnetic alloy ribbon increases, and the permeability itself decreases greatly. 500 nm or less is preferable. The thickness of the silicon oxide film may be evaluated at an arbitrary five locations in the cross-sectional observation with a scanning electron microscope (SEM) and the average may be used.
上述のように、アモルファス合金等の合金薄帯を粉砕した薄片状の粉砕粉を用いる場合は、粒状粉を用いる場合に比べて圧粉磁心は高密度化しにくい。そのため、アモルファス合金アトマイズ粉などの粒状粉を混合して、高密度化を促進することもできる。ガスアトマイズや水アトマイズなどで作製されるアトマイズ粉は球状をなし、粉体の流動性向上に寄与する。また、球状粉は薄片状の粉砕粉間の空隙に入り込み、充填密度の向上にも寄与しうる。かかる観点からは、混合する粒状粉の粒径は薄片状の粉砕粉の厚さ未満が好ましく、より好ましくは該厚さの５０％以下である。粒状粉の組成は、合金薄帯の粉砕粉の組成と同じでもよいし、異なるものであってもよい。粒状粉は、軟磁性体に限らず、Ｃｕ等の非磁性体を用いることもできる。 As described above, in the case of using a flaky pulverized powder obtained by pulverizing an alloy ribbon such as an amorphous alloy, it is difficult to increase the density of the dust core compared to the case of using a granular powder. Therefore, it is possible to promote the densification by mixing granular powder such as amorphous alloy atomized powder. Atomized powder produced by gas atomization or water atomization has a spherical shape and contributes to improvement of the fluidity of the powder. Further, the spherical powder enters the gaps between the flaky pulverized powders, and can contribute to the improvement of the packing density. From this viewpoint, the particle size of the granular powder to be mixed is preferably less than the thickness of the flaky pulverized powder, and more preferably 50% or less of the thickness. The composition of the granular powder may be the same as or different from the composition of the pulverized powder of the alloy ribbon. The granular powder is not limited to a soft magnetic material, and a nonmagnetic material such as Cu can also be used.
次に、第１の工程において用いる熱可塑性樹脂およびシリコーン樹脂について説明する。熱可塑性樹脂は、プレスで成形する際、粉体同士を結着させるための有機バインダーである。熱可塑性樹脂の種類は、第２の工程の適用可能なものであれば、これを限定するものではないが、例えば、ポリエチレン、ポリビニルアルコール、アクリル樹脂等の各種熱可塑性樹脂を用いることができる。上述のように、第１の工程を経た混合物は第２の工程において加熱され、熱可塑性樹脂のガラス転移温度以上の成形温度で加圧成形されるため、該ガラス転移温度が高すぎると、それだけ加熱に係る設備が複雑になる。一方でガラス転移温度が室温よりもある程度高い方が、成形に供する混合物や成形体のハンドリングが容易である。そのため、熱可塑性樹脂のガラス転移温度は５０〜１５０℃の範囲であることが好ましい。 Next, the thermoplastic resin and silicone resin used in the first step will be described. The thermoplastic resin is an organic binder for binding powders when molded by a press. The type of the thermoplastic resin is not limited as long as it can be applied in the second step. For example, various thermoplastic resins such as polyethylene, polyvinyl alcohol, and acrylic resin can be used. As described above, the mixture that has undergone the first step is heated in the second step and is pressure-molded at a molding temperature that is equal to or higher than the glass transition temperature of the thermoplastic resin. Equipment for heating becomes complicated. On the other hand, when the glass transition temperature is somewhat higher than room temperature, it is easier to handle a mixture or a molded body used for molding. Therefore, the glass transition temperature of the thermoplastic resin is preferably in the range of 50 to 150 ° C.
一方、粉砕や成形の加工歪を除去するために、成形後に熱処理を行う。該熱処理により、有機バインダーである熱可塑性樹脂は熱分解によって概ね消失してしまう。したがって、熱可塑性樹脂のみの場合、熱処理後に粉末同士の結着力が失われ、成形体強度が維持困難になる。そこで、かかる熱処理後においても各粉末同士を結着させるために、高温用バインダーとしてシリコーン樹脂を用いる。シリコーン樹脂は、シロキサン結合による主骨格を持つ。代表的なシリコーン樹脂としては、例えばＳｉ上の官能基がメチル基やフェニル基であるメチルシリコーン樹脂やメチルフェニルシリコーン樹脂が挙げられる。シリコーン樹脂は、有機バインダーが熱分解して飛散してしまう温度領域で熱処理しても、粒子間にシリコン酸化物として固化、残存して粉末同士を結着する。かかる構成によって、熱処理後の成形体の機械的強度が高められるとともに、絶縁性向上にも寄与する。ここで、上述のように、第１の工程を経た混合物は第２の工程において加熱され、シリコーン樹脂のガラス転移温度以上、より好ましくは融点以上の成形温度で加圧成形されるため、該融点等が高すぎると、それだけ加熱に係る設備が複雑になる。一方で融点等が室温よりもある程度高い方が、成形に供する混合物や成形体のハンドリングが容易である。そのため、シリコーン樹脂のガラス転移温度または融点は５０〜１５０℃の範囲であることが好ましい。なお、ガラス転移温度や融点は、ＤＳＣやＴＭＡなどの熱分析で確認することができる。 On the other hand, heat treatment is performed after the molding in order to remove the processing distortion of the pulverization and molding. By the heat treatment, the thermoplastic resin as the organic binder is generally lost by thermal decomposition. Therefore, in the case of only the thermoplastic resin, the binding force between the powders is lost after the heat treatment, and it becomes difficult to maintain the compact strength. Therefore, in order to bind the powders even after the heat treatment, a silicone resin is used as a high temperature binder. Silicone resins have a main skeleton due to siloxane bonds. Typical silicone resins include, for example, methyl silicone resins and methyl phenyl silicone resins in which the functional group on Si is a methyl group or a phenyl group. Even if the silicone resin is heat-treated in a temperature range where the organic binder is thermally decomposed and scattered, it solidifies and remains as silicon oxide between the particles and binds the powders together. With such a configuration, the mechanical strength of the molded body after the heat treatment is increased and also contributes to an improvement in insulation. Here, as described above, the mixture that has undergone the first step is heated in the second step and is pressure-molded at a molding temperature equal to or higher than the glass transition temperature of the silicone resin, more preferably equal to or higher than the melting point. If it is too high, the equipment for heating becomes complicated accordingly. On the other hand, when the melting point or the like is somewhat higher than room temperature, it is easier to handle a mixture or a molded body used for molding. Therefore, it is preferable that the glass transition temperature or melting | fusing point of a silicone resin is the range of 50-150 degreeC. The glass transition temperature and melting point can be confirmed by thermal analysis such as DSC and TMA.
熱可塑性樹脂の添加量は、軟磁性材料粉間に十分に行きわたり、十分な成形体強度を確保できる量にすればよい。一方、これが多すぎると密度や強度が低下するようになる。例えば、軟磁性材料粉１００重量部に対して、０.５〜３.０重量部にすることが好ましい。後述のように、第２の工程で所定の温間成形を行うことで、高占積率が実現される。そのため、通常の温度で成形する場合に比べて、少ない熱可塑性樹脂量で必要な機械的強度等を確保することができる。熱可塑性樹脂の添加量は、より好ましくは軟磁性材料粉１００重量部に対して０.５〜２.５重量部、さらに好ましくは０.５〜１.５重量部である。また、シリコーン樹脂の添加量も熱処理後の圧粉磁心に求められる機械的強度等に照らして決めることができる。機械的強度や絶縁性の観点からは、シリコーン樹脂が軟磁性材料粉間に十分に行きわたるような量を添加することが好ましい。例えば軟磁性材料粉１００重量部に対して、０.１〜１.５重量部にすればよい。一方、熱処理後も粉末間に残存するシリコーン樹脂の場合、その添加量が応力、ひいてはコアロスに影響する。その添加量を減らすことによって、コアロスの低減に寄与する。後述のように、第２の工程では所定の温間成形を行うため、高占積率が実現される。そのため、通常の温度で成形する場合に比べて、少ないシリコーン樹脂量で必要な機械的強度等を確保することができる。シリコーン樹脂の添加量は、より好ましくは軟磁性材料粉１００重量部に対して０.１〜１.０重量部である。シリコーン樹脂の添加量を熱可塑性樹脂の添加量の４０％以下にして、コアロスの低減を図ることができる。第２の工程の加圧成形をシリコーン樹脂のガラス転移温度以上の成形温度で行うことの効果については、さらに後述する。 The addition amount of the thermoplastic resin may be an amount that can be sufficiently distributed between the soft magnetic material powders or that can secure a sufficient molded body strength. On the other hand, if the amount is too large, the density and strength are lowered. For example, it is preferable to use 0.5 to 3.0 parts by weight with respect to 100 parts by weight of the soft magnetic material powder. As described later, a high space factor is realized by performing predetermined warm forming in the second step. Therefore, the required mechanical strength and the like can be ensured with a smaller amount of thermoplastic resin than in the case of molding at a normal temperature. The addition amount of the thermoplastic resin is more preferably 0.5 to 2.5 parts by weight, and still more preferably 0.5 to 1.5 parts by weight with respect to 100 parts by weight of the soft magnetic material powder. The amount of silicone resin added can also be determined in light of the mechanical strength required for the dust core after heat treatment. From the viewpoint of mechanical strength and insulation, it is preferable to add an amount that allows the silicone resin to be sufficiently distributed between the soft magnetic material powders. For example, it may be 0.1 to 1.5 parts by weight with respect to 100 parts by weight of the soft magnetic material powder. On the other hand, in the case of the silicone resin remaining between the powders even after the heat treatment, the addition amount affects the stress, and thus the core loss. By reducing the addition amount, it contributes to the reduction of core loss. As will be described later, since a predetermined warm forming is performed in the second step, a high space factor is realized. Therefore, the required mechanical strength and the like can be ensured with a small amount of silicone resin as compared with the case of molding at a normal temperature. The addition amount of the silicone resin is more preferably 0.1 to 1.0 part by weight with respect to 100 parts by weight of the soft magnetic material powder. It is possible to reduce the core loss by setting the addition amount of the silicone resin to 40% or less of the addition amount of the thermoplastic resin. The effect of performing the pressure molding in the second step at a molding temperature equal to or higher than the glass transition temperature of the silicone resin will be further described later.
前記軟磁性材料粉と、熱可塑性樹脂と、シリコーン樹脂との混合方法はこれを特に限定するものではない。従来から知られている混合方法、混合機を用いることができる。バインダーとして熱可塑性樹脂等が混合された状態では、その結着作用により、混合粉は広い粒度分布をもった凝集粉となっている。かかる混合粉を、例えば振動篩等を用いて篩に通すことによって、成形に適した所望の二次粒子径の造粒粉を得ることができる。また、加圧成形時の粉末と金型との摩擦を低減させるために、ステアリン酸、またはステアリン酸亜鉛等のステアリン酸塩の潤滑材を添加することが好ましい。また、潤滑材の添加は、後述する占積率向上に対しても有効である。潤滑材の添加量は、軟磁性材料粉合計１００重量部に対して０.５〜２.０重量部とすることが好ましい。一方、潤滑剤は、金型に塗布することも可能である。 The mixing method of the soft magnetic material powder, the thermoplastic resin, and the silicone resin is not particularly limited. Conventionally known mixing methods and mixers can be used. In a state where a thermoplastic resin or the like is mixed as a binder, the mixed powder is an agglomerated powder having a wide particle size distribution due to its binding action. By passing the mixed powder through a sieve using, for example, a vibration sieve or the like, a granulated powder having a desired secondary particle size suitable for molding can be obtained. Further, in order to reduce the friction between the powder and the mold during pressure molding, it is preferable to add a stearate or a stearate lubricant such as zinc stearate. The addition of the lubricant is also effective for improving the space factor described later. The addition amount of the lubricant is preferably 0.5 to 2.0 parts by weight with respect to 100 parts by weight of the total soft magnetic material powder. On the other hand, the lubricant can be applied to the mold.
次に、第１の工程を経た混合物を加熱して、熱可塑性樹脂のガラス転移温度Ｔｇ１以上、かつシリコーン樹脂のガラス転移温度Ｔｇ２以上の成形温度Ｔ１で加圧成形する第２の工程について説明する。かかる第２の工程に係る構成が、従来の圧粉磁心の製造方法と大きく異なり、また顕著な効果をもたらす大きな要因の一つである。第１の工程で得られた混合粉は、好適には上述のように造粒されて、第２の工程に供される。造粒された混合粉は、成形金型を用いて、トロイダル形状、直方体形状等の所定形状に加圧成形される。第２の工程における成形は、通常の室温での成形と異なり、混合物が加熱された状態で加圧成形される温間成形である。混合物は、成形金型に投入する前に予め加熱しておいてもよいし、成形金型内で加熱してもよい。その両方を採用することもできる。 Next, the second step of heating the mixture that has undergone the first step and performing pressure molding at a molding temperature T1 that is not lower than the glass transition temperature Tg1 of the thermoplastic resin and not lower than the glass transition temperature Tg2 of the silicone resin will be described. . The configuration according to the second step is greatly different from the conventional method of manufacturing a dust core and is one of the major factors that bring about a remarkable effect. The mixed powder obtained in the first step is preferably granulated as described above and provided for the second step. The granulated mixed powder is pressure-molded into a predetermined shape such as a toroidal shape or a rectangular parallelepiped shape using a molding die. Unlike the normal molding at room temperature, the molding in the second step is warm molding in which the mixture is pressure-molded in a heated state. The mixture may be preheated before being put into the molding die, or may be heated in the molding die. Both can be adopted.
成形温度は、上述のように、熱可塑性樹脂のガラス転移温度Ｔｇ１以上、かつシリコーン樹脂のガラス転移温度Ｔｇ２以上とする。すなわち、熱可塑性樹脂が軟化している状態、かつシリコーン樹脂が軟化している状態で加圧成形が行われる。熱可塑性樹脂は、そのガラス転移温度以上で軟化するため、成形温度を該ガラス転移温度以上にすることで、圧粉磁心における占積率を大幅に向上させることができる。さらに、シリコーン樹脂との関係においても、成形温度をガラス転移温度以上とする。すなわちシリコーン樹脂も成形時に軟化することで、圧粉磁心における占積率を向上させることができる。圧粉磁心における磁性粉の占積率が顕著に増加するため、透磁率や飽和磁束密度も大幅に増加する。すなわち、熱処理時に飛散する熱可塑性樹脂と、熱処理後の残存するシリコーン樹脂の両方を、成形時に軟化させることによって、飽和磁束密度の増加や上述したコアロスの低減など、磁気特性の向上が可能となるのである。シリコーン樹脂は、成形温度で軟化するものを用いてもよいし、溶融するものを用いることもできる。前者は、成形温度Ｔ１がシリコーン樹脂のガラス転移温度Ｔｇ２以上であることに相当し、後者は成形温度Ｔ１がシリコーン樹脂の融点Ｔｍ以上であることに相当する。ただし、成形温度をシリコーン樹脂の融点Ｔｍ以上にすると、すなわち、シリコーン樹脂が溶融して、液状化している状態で成形すると、占積率や強度の向上の効果が特に顕著になる。したがって、成形温度はシリコーン樹脂の融点Ｔｍ以上であることがより好ましい。 As described above, the molding temperature is set to a glass transition temperature Tg1 or higher of the thermoplastic resin and to a glass transition temperature Tg2 or higher of the silicone resin. That is, pressure molding is performed in a state where the thermoplastic resin is softened and in a state where the silicone resin is softened. Since the thermoplastic resin is softened above its glass transition temperature, the space factor in the dust core can be greatly improved by setting the molding temperature to be equal to or higher than the glass transition temperature. Furthermore, also in relation to the silicone resin, the molding temperature is set to the glass transition temperature or higher. That is, the space factor in the dust core can be improved by softening the silicone resin during molding. Since the space factor of the magnetic powder in the dust core increases significantly, the permeability and saturation magnetic flux density also increase significantly. That is, by softening both the thermoplastic resin scattered during the heat treatment and the remaining silicone resin after the heat treatment, it is possible to improve the magnetic properties such as increasing the saturation magnetic flux density and reducing the core loss described above. It is. As the silicone resin, one that softens at the molding temperature may be used, or one that melts may be used. The former corresponds to the molding temperature T1 being equal to or higher than the glass transition temperature Tg2 of the silicone resin, and the latter corresponds to the molding temperature T1 being equal to or higher than the melting point Tm of the silicone resin. However, when the molding temperature is higher than the melting point Tm of the silicone resin, that is, when molding is performed in a state where the silicone resin is melted and liquefied, the effect of improving the space factor and strength becomes particularly remarkable. Therefore, the molding temperature is more preferably not less than the melting point Tm of the silicone resin.
成形温度を上げることによって、熱可塑性樹脂等の流動性が高まり、占積率をより向上させることができる。かかる観点からは、成形温度Ｔ１は、熱可塑性樹脂のガラス転移温度と、シリコーン樹脂の融点のいずれか高い方の温度（以下Ｔｓともいう）よりも、３０℃以上高いことが好ましい。かかる構成によれば、例えば、アモルファス合金薄帯の粉砕粉を用いた場合、室温での成形比べて、占積率を１.０５倍以上に向上させることも可能である。一方、熱可塑性樹脂やシリコーン樹脂の溶融状態や軟化状態が維持される限りは、成形温度Ｔ１とＴｓとの温度差ΔＴの上限はこれを特に限定するものではない。但し、前記温度差ΔＴが大きくなりすぎると成形温度自体が高くなるため、実用的には、成形温度Ｔ１とＴｓとの温度差ΔＴの上限は１５０℃以下が好ましい。ここで、熱可塑性樹脂のガラス転移温度と、シリコーン樹脂の融点等との差が大きくなると、それだけ成形温度を上げる必要がある。一方、成形温度が高くなりすぎると、それだけ金型等加熱に係る設備が複雑になる。そのため、熱可塑性樹脂のガラス転移温度と、前記シリコーン樹脂の融点との差は５０℃以内にすることが好ましく、２０℃以内がより好ましい。加熱に係る設備の簡略化の観点からは、成形温度は７０〜２００℃が実用的な範囲である。 By raising the molding temperature, the fluidity of the thermoplastic resin and the like is increased, and the space factor can be further improved. From this viewpoint, the molding temperature T1 is preferably 30 ° C. or higher than the higher one of the glass transition temperature of the thermoplastic resin and the melting point of the silicone resin (hereinafter also referred to as Ts). According to such a configuration, for example, when the pulverized powder of an amorphous alloy ribbon is used, the space factor can be improved to 1.05 times or more as compared with molding at room temperature. On the other hand, as long as the molten state or softened state of the thermoplastic resin or silicone resin is maintained, the upper limit of the temperature difference ΔT between the molding temperatures T1 and Ts is not particularly limited. However, since the molding temperature itself increases when the temperature difference ΔT is too large, practically, the upper limit of the temperature difference ΔT between the molding temperatures T1 and Ts is preferably 150 ° C. or less. Here, as the difference between the glass transition temperature of the thermoplastic resin and the melting point of the silicone resin increases, it is necessary to raise the molding temperature accordingly. On the other hand, if the molding temperature becomes too high, the equipment for heating the mold and the like becomes complicated accordingly. Therefore, the difference between the glass transition temperature of the thermoplastic resin and the melting point of the silicone resin is preferably within 50 ° C, more preferably within 20 ° C. From the viewpoint of simplification of equipment related to heating, the molding temperature is in a practical range of 70 to 200 ° C.
成形は、例えば１.０ＧＰａ以上、かつ３.０ＧＰａ以下の圧力で、数秒程度の保持時間で行えばよい。占積率を高めるために成形圧を高く設定すると、成形機の大型化、金型のかじり、摩耗などの問題が顕在化するおそれがある。これに対して、上述のように熱可塑性樹脂等が軟化等する温度に加熱された状態で成形することによって、より低圧で占積率を高めることができる。２.０ＧＰａ以下の圧力で成形し、成形の負荷を低減することもできる。圧粉磁心は、強度・特性の観点から、実用的には７５.０％以上の占積率になるように圧密化しておくことが好ましい。より好ましい占積率は８０.０％超である。また、実用上の観点から、トロイダル形状の圧粉磁心の場合、その圧環強度は１０.０ＭＰａ以上が好ましく、１２.０ＭＰａ以上であることがより好ましい。 The molding may be performed, for example, at a pressure of 1.0 GPa or more and 3.0 GPa or less and a holding time of about several seconds. If the molding pressure is set high in order to increase the space factor, problems such as an increase in the size of the molding machine, galling of the mold, and wear may become apparent. On the other hand, the space factor can be increased at a lower pressure by molding in a state heated to a temperature at which the thermoplastic resin or the like is softened as described above. Molding can be performed at a pressure of 2.0 GPa or less to reduce the molding load. From the viewpoint of strength and characteristics, the powder magnetic core is preferably compacted so as to practically have a space factor of 75.0% or more. A more preferable space factor is more than 80.0%. Further, from a practical point of view, in the case of a toroidal powder magnetic core, the crushing strength is preferably 10.0 MPa or more, and more preferably 12.0 MPa or more.
次に、第２の工程を経た成形体を成形温度Ｔ１よりも高い温度Ｔ２で熱処理する第３の工程について説明する。第２の工程を経た成形体は、成形後、室温のような熱可塑性樹脂等のガラス転移温度等未満の温度まで冷却してから、第３の工程に供してもよいし、冷却せずにそのまま第３の工程に供してもよい。成形等で導入された応力歪を緩和して良好な磁気特性を得るために、第２の工程を経た成形体は、成形温度Ｔ１よりも高い温度Ｔ２で熱処理される。また、かかる熱処理温度で、成形体中の熱可塑性樹脂も飛散する。例えば、Ｆｅ基アモルファス合金薄帯の粉砕粉の場合であれば、応力緩和の効果を十分に発揮させるためには３５０℃以上で熱処理することが好ましい。一方、粉砕粉の一部に粗大な結晶粒が析出することを防ぎ、低いコアロスＰｃｖを得る観点からは、４２０℃以下の温度で熱処理することが好ましい。更に、安定して低いコアロスＰｃｖを得るためには３８０℃以上、かつ４１０℃以下がより好ましい。一方、ナノ結晶合金薄帯の粉砕粉を用いる場合、工程のいずれかの段階で結晶化処理が行われる。粉砕前に結晶化処理してもよいし、粉砕後に結晶化処理してもよい。結晶化処理は加圧成形後の歪緩和の熱処理を兼ねてもよいし、歪緩和の熱処理とは別工程として行うこともできる。ただし、製造工程の簡略化の観点からは、結晶化処理が加圧成形後の歪緩和の熱処理を兼ねることが好ましい。例えば、Ｆｅ基ナノ結晶合金薄帯の場合であれば、結晶化処理を兼ねた、加圧成形後の熱処理は、３９０℃〜４８０℃の範囲で行えばよい。一方、結晶質の軟磁性材料粉を用いる場合には、結晶化等の問題の制約がないため、より高温で熱処理することもできる。例えば７００〜９００℃（の範囲で熱処理することができる。保持時間は、圧粉磁心の大きさ、処理量、特性ばらつきの許容範囲などによって適宜設定されるものであるが、０.５〜３時間が好ましい。 Next, the 3rd process of heat-processing the molded object which passed through the 2nd process at temperature T2 higher than molding temperature T1 is explained. The molded body that has undergone the second step may be subjected to the third step after being cooled to a temperature lower than the glass transition temperature such as a thermoplastic resin such as room temperature after molding, or without cooling. You may use for a 3rd process as it is. In order to relieve stress strain introduced by molding or the like and obtain good magnetic properties, the molded body that has undergone the second step is heat-treated at a temperature T2 that is higher than the molding temperature T1. Further, the thermoplastic resin in the molded body is also scattered at the heat treatment temperature. For example, in the case of a pulverized powder of an Fe-based amorphous alloy ribbon, it is preferable to perform heat treatment at 350 ° C. or higher in order to sufficiently exert the stress relaxation effect. On the other hand, it is preferable to perform heat treatment at a temperature of 420 ° C. or lower from the viewpoint of preventing coarse crystal grains from being deposited on a part of the pulverized powder and obtaining a low core loss Pcv. Furthermore, in order to obtain a stable and low core loss Pcv, 380 ° C. or higher and 410 ° C. or lower is more preferable. On the other hand, when the pulverized powder of the nanocrystalline alloy ribbon is used, crystallization treatment is performed at any stage of the process. Crystallization may be performed before pulverization, or crystallization may be performed after pulverization. The crystallization treatment may serve as a heat treatment for strain relaxation after pressure molding, or may be performed as a separate process from the heat treatment for strain relaxation. However, from the viewpoint of simplifying the manufacturing process, it is preferable that the crystallization treatment also serves as a heat treatment for strain relaxation after pressure molding. For example, in the case of a Fe-based nanocrystalline alloy ribbon, the heat treatment after pressure forming, which also serves as a crystallization treatment, may be performed in the range of 390 ° C to 480 ° C. On the other hand, when a crystalline soft magnetic material powder is used, heat treatment can be performed at a higher temperature because there is no restriction of problems such as crystallization. For example, the heat treatment can be performed in the range of 700 to 900 ° C. (The holding time is appropriately set according to the size of the dust core, the processing amount, the allowable range of characteristic variation, etc., but is 0.5 to 3). Time is preferred.
上記のようにして得られる圧粉磁心は、圧粉磁心自体優れた効果を発揮する。例えば、軟磁性材料粉として軟磁性合金薄帯の粉砕粉を用いて構成された圧粉磁心であって、占積率が８０.０％を超える圧粉磁心は、強度、透磁率に優れる。より好ましくは占積率が８１.０％以上、さらに好ましくは占積率が８３.０％以上である。さらに、軟磁性合金薄帯の粉砕粉の表面が、厚さ２００ｎｍ以上の、シリコン酸化物被膜等の非磁性酸化物被膜で覆われるとともに、占積率が８１.０％以上である圧粉磁心は、上記特徴に加えて特に、直流重畳特性に優れる。シリコン酸化物被膜を厚くすることで、増分透磁率μΔに代表される直流重畳特性が向上する。 The dust core obtained as described above exhibits an excellent effect of the dust core itself. For example, a dust core made of pulverized powder of soft magnetic alloy as a soft magnetic material powder and having a space factor exceeding 80.0% is excellent in strength and magnetic permeability. More preferably, the space factor is 81.0% or higher, and still more preferably the space factor is 83.0% or higher. Further, the surface of the pulverized powder of the soft magnetic alloy ribbon is covered with a non-magnetic oxide film such as a silicon oxide film having a thickness of 200 nm or more, and the space factor is 81.0% or more. In addition to the above features, the direct current superposition characteristics are particularly excellent. By thickening the silicon oxide film, thereby improving the DC superposition characteristics typified by the incremental permeability mu delta.
シリコン酸化物被膜のような非磁性酸化物被膜は、磁性体としての粉砕粉間の磁気ギャップとして機能する。上述のようなＴＥＯＳ等を用いたゾルゲル法によれば、粉砕粉表面を非磁性酸化物で均一に覆うことができる。軟磁性合金薄帯の粉砕粉の表面が、シリコン酸化物被膜等の非磁性酸化物被膜で覆われた構成は、粉砕粉間に均一かつ確実な磁気ギャップを形成し、直流重畳特性の向上に寄与する。かかる構成は、圧粉磁心の占積率を高めたときに特に有効となる。例えば、成形圧を上げて占積率を上げると、それだけ粉砕粉の接触機会が増えるが、粉砕粉側に非磁性酸化物被膜を形成しておくことで、確実に磁気ギャップを形成することができるからである。軟磁性合金薄帯の粉砕粉は２００℃程度まで加熱しても塑性変形しないため、占積率を上げていくと、隣り合う板状粒子の主面（板面）同士が略平行に対向している割合が大きくなる。したがって、粉砕粉の表面に非磁性酸化物被膜を形成しておくことで、粉砕粉間の磁気ギャップを確保しつつ、そのバラツキを低減することができる。板状の主面同士を略平行にして隣り合う粉砕粉粒子間の磁気ギャップは４００ｎｍ以上を確保することが好ましい。 A nonmagnetic oxide film such as a silicon oxide film functions as a magnetic gap between pulverized powders as a magnetic material. According to the sol-gel method using TEOS or the like as described above, the pulverized powder surface can be uniformly covered with a nonmagnetic oxide. The structure where the surface of the pulverized powder of the soft magnetic alloy ribbon is covered with a non-magnetic oxide film such as a silicon oxide film forms a uniform and reliable magnetic gap between the pulverized powder and improves the DC superposition characteristics. Contribute. Such a configuration is particularly effective when the space factor of the powder magnetic core is increased. For example, increasing the molding pressure to increase the space factor increases the contact opportunity of the pulverized powder, but by forming a nonmagnetic oxide film on the pulverized powder side, a magnetic gap can be reliably formed. Because it can. Since the pulverized powder of soft magnetic alloy ribbon does not plastically deform even when heated to about 200 ° C., as the space factor increases, the main surfaces (plate surfaces) of adjacent plate-like particles face each other substantially in parallel. The ratio that is increased. Therefore, by forming a non-magnetic oxide film on the surface of the pulverized powder, the variation can be reduced while ensuring a magnetic gap between the pulverized powder. It is preferable to secure a magnetic gap of 400 nm or more between the pulverized powder particles adjacent to each other with the plate-like main surfaces substantially parallel to each other.
軟磁性合金薄帯粉の表面を均一に覆い、かつ非磁性のものであれば、非磁性酸化物被膜の種類は特に限定されるものではないが、シリコン酸化物被膜が絶縁性、耐熱性等にも優れるので好ましい。 The type of non-magnetic oxide film is not particularly limited as long as the surface of the soft magnetic alloy powder is uniformly covered and non-magnetic, but the silicon oxide film is insulating, heat resistant, etc. Is also preferable.
上記のようにして得られた圧粉磁心と、前記圧粉磁心の周囲に巻装されたコイルとを用いてコイル部品が提供される。コイルは導線を圧粉磁心に巻回して構成してもよいし、ボビンに巻回して構成してもよい。前記圧粉磁心と前記コイルとを有するコイル部品は、例えばチョーク、インダクタ、リアクトル、トランス等として用いられる。例えば、該コイル部品は、テレビやエアコンなど家電機器で採用されているＰＦＣ回路や、太陽光発電やハイブリッド車・電気自動車などの電源回路等に使用され、これらの機器、装置における小型化、低損失化に寄与する。 A coil component is provided using the powder magnetic core obtained as described above and a coil wound around the powder magnetic core. The coil may be configured by winding a conductive wire around a powder magnetic core, or may be configured by winding it around a bobbin. A coil component having the dust core and the coil is used as, for example, a choke, an inductor, a reactor, a transformer, or the like. For example, the coil parts are used in PFC circuits used in household appliances such as televisions and air conditioners, and power supply circuits for solar power generation, hybrid vehicles, and electric vehicles. Contributes to loss.
（軟磁性材料粉末の作製）
軟磁性材料粉末として、平均厚さ１８μｍのＦｅ−Ｎｉ−Ｃｕ−Ｓｉ−Ｂ系Ｆｅ基ナノ結晶合金薄帯材料を用いた。具体的な組成は、Ｆｅｂａｌ．Ｎｉ１Ｓｉ４Ｂ１４Ｃｕ１．４（原子％）である。かかる組成の急冷薄帯に対して、粗粉砕、中粉砕、微粉砕を異なる粉砕機により順次行った。合金薄帯粉砕粉を目開き１０６μｍ（対角１５０μｍ）の篩に通した。更に、目開き３５μｍ（対角４９μｍ）の篩により通過する合金薄帯粉砕粉を除去した。粉砕粉をＳＥＭで観察した。金属薄帯の二主面には粉砕加工された形態がほとんど認められず、二主面の端部のエッジが明瞭に確認できた。
(Production of soft magnetic material powder)
As the soft magnetic material powder, an Fe—Ni—Cu—Si—B-based Fe-based nanocrystalline alloy ribbon material having an average thickness of 18 μm was used. The specific composition is Fe bal. Ni 1 Si 4 B 14 Cu 1.4 (atomic%). Rough pulverization, medium pulverization, and fine pulverization were sequentially performed with different pulverizers on the quenched ribbon having such a composition. The alloy ribbon pulverized powder was passed through a sieve having an aperture of 106 μm (diagonal 150 μm). Further, the alloy strip pulverized powder passing through a sieve having an opening of 35 μm (diagonal 49 μm) was removed. The ground powder was observed with SEM. Almost no pulverized form was observed on the two main surfaces of the metal ribbon, and the edges of the ends of the two main surfaces were clearly confirmed.
（軟磁性材料粉末表面へのシリコン酸化物被膜形成）
前記合金薄帯粉砕粉と、ＴＥＯＳ（テトラエトキシシラン、Ｓｉ（ＯＣ２Ｈ５）４）との質量比を２５：１とし、それらをアンモニア水溶液と、エタノールとともに混合し、３時間撹拌した。次に、ろ過することで、合金薄帯粉砕粉を分離し、１００℃のオーブンで乾燥した。乾燥後、合金薄帯の粉砕粉の断面をＳＥＭで観察したところ、粉砕粉の表面にはシリコン酸化物被膜が形成され、その厚さは１２５ｎｍであった。
(Silicon oxide film formation on soft magnetic material powder surface)
The mass ratio of the alloy strip pulverized powder and TEOS (tetraethoxysilane, Si (OC 2 H 5 ) 4 ) was 25: 1, and these were mixed with an aqueous ammonia solution and ethanol and stirred for 3 hours. Next, the alloy ribbon pulverized powder was separated by filtration and dried in an oven at 100 ° C. When the cross section of the pulverized powder of the alloy ribbon was observed with SEM after drying, a silicon oxide film was formed on the surface of the pulverized powder, and the thickness thereof was 125 nm.
（第１の工程（混合工程））
前記粉砕粉８０重量部に対して、平均粒径５μｍのＦｅ基アモルファス合金アトマイズ球状粉（組成：Ｆｅｂａｌ．Ｂ１１Ｓｉ１１Ｃ２Ｃｒ２（原子％））（エプソンアトミックス株式会社製）を２０重量部（２０質量％添加）加えた合計１００重量部に対して、シリコーン樹脂として粉末状のメチルフェニルシリコーン樹脂：旭化成ワッカーシリコーン株式会社製ＳＩＬＲＥＳ Ｈ４４）を１.０重量部、熱可塑性樹脂としてエマルジョンのアクリル樹脂系のバインダー（昭和高分子株式会社製ポリゾールＡＰ−６０４）を１.０重量部、それぞれ計りとって、株式会社ダルトン製の万能混合撹拌機で混合した。混合粉は、１２０℃で１０時間乾燥した。なお、熱可塑性樹脂とシリコーン樹脂に対する熱分析（ＴＧ−ＤＴＡ）等の結果から、使用した熱可塑性樹脂のガラス転移温度は７５℃、シリコーン樹脂のガラス転移温度は５４℃、融点は７３℃と評価された。すなわち、熱可塑性樹脂のガラス転移温度と、シリコーン樹脂の融点との差は２℃であった。なお、潤滑剤として使用した後述のステアリン酸亜鉛の融点は１２０℃と評価された。
(First step (mixing step))
Fe-based amorphous alloy atomized spherical powder (composition: Fe bal. B 11 Si 11 C 2 Cr 2 (atomic%)) (manufactured by Epson Atmix Co., Ltd.) with an average particle size of 5 μm with respect to 80 parts by weight of the pulverized powder 20 parts by weight (added by 20% by mass) 1.0 parts by weight of a powdered methylphenyl silicone resin: SILRES H44 manufactured by Asahi Kasei Wacker Silicone Co., Ltd. 1.0 part by weight of an acrylic resin binder (Polysol AP-604 manufactured by Showa Polymer Co., Ltd.) was measured and mixed with a universal mixing stirrer manufactured by Dalton Co., Ltd. The mixed powder was dried at 120 ° C. for 10 hours. From the results of thermal analysis (TG-DTA) for thermoplastic resin and silicone resin, the glass transition temperature of the used thermoplastic resin is 75 ° C., the glass transition temperature of the silicone resin is 54 ° C., and the melting point is 73 ° C. It was done. That is, the difference between the glass transition temperature of the thermoplastic resin and the melting point of the silicone resin was 2 ° C. In addition, the melting point of zinc stearate described later used as a lubricant was evaluated as 120 ° C.
（第２の工程（成形工程））
乾燥後の混合粉を目開き４２５μｍの篩を通して造粒粉を得た。目開き４２５μｍの篩を通すことで、約６００μｍ以下の粒径の造粒粉が得られる。この造粒粉に、粉砕粉およびアトマイズ球状粉の合計１００重量部に対して０.４重量部の割合で、ステアリン酸亜鉛を添加、混合して成形用の混合物を得た。得られた混合粉は、金型を加熱する機能を備えたプレス機を使用して、表１に示す温度で加圧成形した。成形圧は２ＧＰａ、保持時間は２秒とした。得られた外径１４ｍｍ、内径８ｍｍ、高さ６ｍｍのトロイダル形状の成形体に、歪取と結晶化を兼ねて、オーブンにて、昇温速度を１０℃／ｍｉｎとし、大気中、４２０℃、０.５時間の熱処理を施し、圧粉磁心を得た。
(Second process (molding process))
The mixed powder after drying was passed through a sieve having an opening of 425 μm to obtain granulated powder. By passing through a sieve having an opening of 425 μm, a granulated powder having a particle size of about 600 μm or less is obtained. To this granulated powder, zinc stearate was added and mixed at a ratio of 0.4 parts by weight with respect to 100 parts by weight of the pulverized powder and atomized spherical powder in total to obtain a mixture for molding. The obtained mixed powder was pressure-molded at a temperature shown in Table 1 using a press machine having a function of heating a mold. The molding pressure was 2 GPa and the holding time was 2 seconds. The obtained toroidal shaped molded body having an outer diameter of 14 mm, an inner diameter of 8 mm, and a height of 6 mm is combined with strain relief and crystallization, and is heated in an oven at a heating rate of 10 ° C./min. A heat treatment for 0.5 hour was performed to obtain a dust core.
（磁気特性の測定）
以上の工程により作製した圧粉磁心の密度をその寸法および質量から算出した。また、占積率を圧粉磁心の密度を軟磁性材料粉の密度で除して算出した。ここで軟磁性材料粉の密度は、Ｆｅ基ナノ結晶合金薄帯の密度７.４０×１０３ｋｇ／ｍ３、およびＦｅ基アモルファス合金アトマイズ球状粉の密度７.２０×１０３ｋｇ／ｍ３、から、と、それらの混合比から平均密度として算出したもの（７.３６×１０３ｋｇ／ｍ３）を用いた。また、トロイダル形状の圧粉磁心の径方向に荷重をかけ、コア破壊時の最大加重Ｐ（Ｎ）を測定し、次式から圧環強度σｒ（ＭＰａ）を求めた。
σｒ＝Ｐ（Ｄ−ｄ）／Ｉｄ２
（ここで、Ｄ：コアの外径（ｍｍ）、ｄ：コアの肉厚（ｍｍ）、Ｉ：コアの高さ（ｍｍ）である。）
さらに、一次側と二次側それぞれ２９ターンの巻線を施した。岩通計測株式会社製Ｂ−ＨアナライザーＳＹ−８２３２により、最大磁束密度１５０ｍＴ、周波数２０ｋＨｚの条件でコアロスＰｃｖを測定した。また、初透磁率μｉは、前記トロイダル形状の圧粉磁心に直径０.５ｍｍの絶縁被覆導線を３０回巻回し、ヒューレット・パッカード社製４２８４Ａにより、周波数１００ｋＨｚで測定した。結果を表１に示す。
(Measurement of magnetic properties)
The density of the dust core produced by the above steps was calculated from its dimensions and mass. The space factor was calculated by dividing the density of the dust core by the density of the soft magnetic material powder. Here, the density of the soft magnetic material powder is such that the density of the Fe-based nanocrystalline alloy ribbon is 7.40 × 10 3 kg / m 3 and the density of the Fe-based amorphous alloy atomized spherical powder is 7.20 × 10 3 kg / m 3. , And the average density (7.36 × 10 3 kg / m 3 ) calculated from their mixing ratio was used. In addition, a load was applied in the radial direction of the toroidal dust core, the maximum load P (N) at the time of core breakage was measured, and the crushing strength σr (MPa) was obtained from the following equation.
σr = P (D−d) / Id 2
(Here, D: outer diameter of the core (mm), d: thickness of the core (mm), I: height of the core (mm))
Further, 29 turns of winding were applied to the primary side and the secondary side, respectively. The core loss Pcv was measured with a BH analyzer SY-8232 manufactured by Iwatsu Measurement Co., Ltd. under the conditions of a maximum magnetic flux density of 150 mT and a frequency of 20 kHz. Further, the initial permeability μi was measured at a frequency of 100 kHz using a 4284A manufactured by Hewlett-Packard Co., Ltd., by winding an insulating coated conductor wire having a diameter of 0.5 mm around the toroidal powder magnetic core 30 times. The results are shown in Table 1.
熱可塑性樹脂のガラス転移温度以上かつ、シリコーン樹脂の融点以上の温度で成形したＮｏ２〜５の圧粉磁心は、室温で成形したものに比べて、密度が大幅に上昇し、いずれも６.０×１０３ｋｇ／ｍ３以上の高い値を示した。それに伴い占積率も大幅に向上し、８０.０％を超える占積率が得られた。圧環強度も１２.０ＭＰａ未満のＮｏ１の圧粉磁心に比べて、Ｎｏ２〜５の圧粉磁心は劇的に向上し、２０.０ＭＰａ以上の圧環強度が得られた。さらに、表１から成形温度とＴｓとの温度差ΔＴが大きくなるに伴い占積率も向上することがわかる。ΔＴが３０℃以上のＮｏ３〜５の圧粉磁心では、２５℃（室温）で成形したＮｏ１のものに比べて占積率が１.０５倍以上に上昇し、８３.０％以上になった。さらにΔＴが大きいＮｏ４および５の圧粉磁心では、室温で成形したＮｏ１のものに比べて占積率が１.０６倍以上に上昇した。さらに、初透磁率も成形温度の上昇とともに増加し、７０以上の水準が得られた。その一方で、コアロスは室温で成形した場合に比べて大きな変化はなく、１６０ｋＷ／ｍ３以下の低い水準を維持できることもわかる。 The No. 2-5 powder magnetic cores molded at a temperature above the glass transition temperature of the thermoplastic resin and above the melting point of the silicone resin have a significantly increased density compared to those molded at room temperature, both of which are 6.0. A high value of × 10 3 kg / m 3 or more was exhibited. As a result, the occupancy rate improved significantly, and an occupancy rate exceeding 80.0% was obtained. Compared with the No. 1 dust core having a crushing strength of less than 12.0 MPa, the No. 2-5 dust core was dramatically improved, and a crushing strength of 20.0 MPa or more was obtained. Furthermore, it can be seen from Table 1 that the space factor increases as the temperature difference ΔT between the molding temperature and Ts increases. In the powder cores of Nos. 3 to 5 with ΔT of 30 ° C. or higher, the space factor increased 1.05 times or more to 83.0% or more compared to No. 1 molded at 25 ° C. (room temperature). . Further, in the No. 4 and No. 5 dust cores having a large ΔT, the space factor increased by 1.06 times or more as compared with No. 1 molded at room temperature. Furthermore, the initial magnetic permeability increased with an increase in molding temperature, and a level of 70 or more was obtained. On the other hand, it can be seen that the core loss does not change much compared to the case of molding at room temperature, and can maintain a low level of 160 kW / m 3 or less.
次に、上述の実施例で作製した混合物を用い、加熱しないで２５℃（室温）で成形した場合と、１３０℃に加熱して成形した場合とで、成形圧を変えて圧粉磁心を作製した。その評価結果を表２に示す。 Next, using the mixture prepared in the above-mentioned Examples, a powder magnetic core is prepared by changing the molding pressure between the case where it is molded at 25 ° C. (room temperature) without heating and the case where it is molded by heating at 130 ° C. did. The evaluation results are shown in Table 2.
表２に示すように、室温での成形では、成形圧を１.１ＧＰａから２.０ＧＰａへと上げても、占積率は８０.０％未満であった。一方、１３０℃で温間成形したＮｏ１０〜１３の圧粉磁心では、いずれも占積率は８０.０％を超えていた。すなわち、上記温間成形によって軟磁性合金薄帯の粉砕粉を用いる場合でも、２ＧＰａ以下の圧力による成形で、８０.０％を超える占積率を実現することが可能であることがわかる。同時に、１ＧＰａ以上の成形圧があれば１５.０ＭＰａ以上の圧環強度が得られることもわかる。また、成形圧を上げることによって占積率および圧環強度は上昇し、８２.０％以上の占積率および２０ＭＰａ以上の圧環強度、さらには８３.０％以上の占積率および２５ＭＰａ以上の圧環強度も実現可能であることがわかる。さらに、初透磁率も成形圧の上昇とともに増加した。一方、室温での成形では２.０ＧＰａの成形圧でも占積率、圧環強度は、それぞれ８０.０％未満、１２.０ＭＰａ未満であった。そのコアロスは成形圧の増加とともに増加しており、さらに成形圧を上げて占積率等を高めるためには、コアロスの大幅な増加が避けられないこともわかる。、また、室温成形において温間成形なみの圧環強度を得るためには、さらに大幅に成形圧を上げる必要があり、室温成形において温間成形なみの圧環強度を得ることが非常に困難であることもわかる。一方、１３０℃で温間成形したＮｏ１０〜１３の圧粉磁心では、１６０ｋＷ／ｍ３以下の低水準のコアロスが維持されており、上記温間成形がコアロスの増加を抑えつつ占積率を向上するうえで好適であることがわかる。 As shown in Table 2, in the molding at room temperature, the space factor was less than 80.0% even when the molding pressure was increased from 1.1 GPa to 2.0 GPa. On the other hand, in No. 10-13 powder magnetic cores warm-formed at 130 ° C., the space factor exceeded 80.0%. That is, it can be seen that even when soft magnetic alloy ribbon pulverized powder is used in the warm forming, a space factor exceeding 80.0% can be realized by forming with a pressure of 2 GPa or less. At the same time, it can be seen that if there is a molding pressure of 1 GPa or more, a crushing strength of 15.0 MPa or more can be obtained. Further, by increasing the molding pressure, the space factor and the crushing strength are increased, and the space factor of 82.0% or more and the crushing strength of 20 MPa or more, and further the space factor of 83.0% or more and the crushing force of 25 MPa or more. It can be seen that strength is also feasible. Furthermore, the initial permeability increased with increasing molding pressure. On the other hand, in molding at room temperature, the space factor and the crushing strength were less than 80.0% and less than 12.0 MPa even at a molding pressure of 2.0 GPa. The core loss increases as the molding pressure increases, and it can be seen that a significant increase in core loss is unavoidable in order to increase the molding pressure and increase the space factor. Also, in order to obtain a crushing strength similar to warm forming in room temperature molding, it is necessary to further increase the molding pressure, and it is extremely difficult to obtain a crushing strength similar to warm forming in room temperature molding. I understand. On the other hand, in the No. 10-13 powder magnetic core warm-formed at 130 ° C., a low level core loss of 160 kW / m 3 or less is maintained, and the warm forming improves the space factor while suppressing the increase in core loss. It turns out that it is suitable for doing.
次に、添加物の組み合わせを変えた混合物を用い、加熱しないで２５℃（室温）で成形したものと、１３０℃に加熱して成形したものとで比較評価を行った。添加物の組み合わせは、熱可塑性樹脂のみ、熱可塑性樹脂およびシリコーン樹脂、並びに熱可塑性樹脂、シリコーン樹脂および潤滑材の三通りである。添加物の構成や成形温度以外は上述の実施例と同様とした。評価結果を表３に示す。 Next, using a mixture in which the combination of additives was changed, a comparative evaluation was performed between one formed at 25 ° C. (room temperature) without heating and one formed by heating at 130 ° C. There are three combinations of additives: thermoplastic resin only, thermoplastic resin and silicone resin, and thermoplastic resin, silicone resin and lubricant. Except for the composition of the additive and the molding temperature, it was the same as the above-described example. The evaluation results are shown in Table 3.
熱可塑性樹脂は熱処理で飛散してしまうため、熱処理後の圧粉磁心の強度を維持するためにシリコーン樹脂を添加する。しかしながら、表３のＮｏ１４とＮｏ１６の評価結果から、通常の室温成形では、シリコーン樹脂を添加すると占積率は低下してしまうことがわかる。これに対して、熱可塑性樹脂のガラス転移温度以上かつ、シリコーン樹脂の融点以上の温度で成形することにより、占積率は大きく上昇した（Ｎｏ１７）。ここで、Ｎｏ１５の圧粉磁心のように熱可塑性樹脂だけを添加した場合でも、上述の温間成形によって占積率は向上する。しかしながら、Ｎｏ１７の圧粉磁心の占積率はＮｏ１５の圧粉磁心よりもさらに高く、上述の温間成形の場合には、シリコーン樹脂添加によって占積率がさらに向上することがわかる。すなわち、室温成形の場合と比べてシリコーン樹脂添加による影響が逆転していることが明らかとなった。また、熱可塑性樹脂およびシリコーン樹脂に加えてさらに潤滑材としてステアリン酸亜鉛を添加したＮｏ１９の圧粉磁心は、それを添加していないＮｏ１７の圧粉磁心に比べて、さらに占積率が向上しており、潤滑剤の添加も占積率向上に効果があることが確認された。 Since the thermoplastic resin is scattered by the heat treatment, a silicone resin is added to maintain the strength of the dust core after the heat treatment. However, from the evaluation results of No. 14 and No. 16 in Table 3, it can be seen that in normal room temperature molding, when a silicone resin is added, the space factor decreases. On the other hand, the space factor greatly increased by molding at a temperature higher than the glass transition temperature of the thermoplastic resin and higher than the melting point of the silicone resin (No17). Here, even when only a thermoplastic resin is added like the powder magnetic core of No15, a space factor improves by the above-mentioned warm forming. However, the space factor of the No. 17 dust core is higher than that of the No. 15 dust core, and in the case of the above-described warm molding, it can be seen that the space factor is further improved by the addition of the silicone resin. That is, it became clear that the influence of silicone resin addition was reversed compared with the case of room temperature molding. In addition to the thermoplastic resin and silicone resin, the No. 19 dust core added with zinc stearate as a lubricant further improved the space factor compared to the No. 17 dust core not added with it. It was confirmed that the addition of a lubricant was effective in improving the space factor.
次に、ナノ結晶合金薄帯の代わりに、Ｆｅ基アモルファス合金薄帯である、平均厚さ２５μｍの日立金属株式会社製Ｍｅｔｇｌａｓ（登録商標）２６０５ＳＡ１材を用いて圧粉磁心を作製した。該２６０５ＳＡ１材は、Ｆｅ−Ｓｉ−Ｂ系材料である。Ｆｅ基アモルファス合金薄帯を、乾燥した大気雰囲気のオーブンで３６０℃、２時間加熱し、脆化させた。ナノ結晶合金薄帯を用いた場合と同様にして、粉砕、分級、シリコン酸化物被膜形成を行った。なお、シリコン酸化物被覆は２００ｎｍの厚さに形成した。前記粉砕粉８０重量部に対して、平均粒径５μｍのＦｅ基アモルファス合金アトマイズ球状粉（組成：Ｆｅ７４Ｂ１１Ｓｉ１１Ｃ２Ｃｒ２）（エプソンアトミックス株式会社製）を２０重量部（２０質量％添加）加えた合計１００重量部の混合粉を用いて、上記ナノ結晶合金薄帯を用いた場合と同様にして成形用の造粒粉を作製した。なお、メチルフェニルシリコーン樹脂：旭化成ワッカーシリコーン株式会社製ＳＩＬＲＥＳ Ｈ４４）の添加量は０.６重量部、熱可塑性樹脂であるアクリル樹脂系のバインダー（昭和高分子株式会社製ポリゾールＡＰ−６０４）の添加量は１.５重量部、ステアリン酸亜鉛の添加量は０.４重量部とした。成形温度を２０℃（室温）および１３０℃とした以外は、上記ナノ結晶合金薄帯を用いた場合と同様にして成形体を行った。成形後の成形体は、オーブンにて、大気雰囲気中、４００℃、１時間の熱処理を施した。得られた圧粉磁心の評価結果を表４に示す。 Next, instead of the nanocrystalline alloy ribbon, a powder magnetic core was prepared using a Metglas (registered trademark) 2605SA1 material manufactured by Hitachi Metals Co., Ltd., which is an Fe-based amorphous alloy ribbon and having an average thickness of 25 μm. The 2605SA1 material is an Fe—Si—B-based material. The Fe-based amorphous alloy ribbon was embrittled by heating at 360 ° C. for 2 hours in a dry atmospheric oven. In the same manner as in the case of using the nanocrystalline alloy ribbon, pulverization, classification, and silicon oxide film formation were performed. The silicon oxide coating was formed to a thickness of 200 nm. 20 parts by weight of 20 parts by weight of Fe-based amorphous alloy atomized spherical powder (composition: Fe 74 B 11 Si 11 C 2 Cr 2 ) (manufactured by Epson Atmix Co., Ltd.) with respect to 80 parts by weight of the pulverized powder (Mass% addition) Using the total 100 parts by weight of the mixed powder, a granulated powder for molding was produced in the same manner as in the case of using the nanocrystalline alloy ribbon. The addition amount of methylphenyl silicone resin: SILRES H44 manufactured by Asahi Kasei Wacker Silicone Co., Ltd. is 0.6 parts by weight, and the addition of an acrylic resin-based binder (Polysol AP-604 manufactured by Showa Polymer Co., Ltd.) which is a thermoplastic resin. The amount was 1.5 parts by weight, and the amount of zinc stearate added was 0.4 parts by weight. Except that the molding temperature was 20 ° C. (room temperature) and 130 ° C., a molded body was produced in the same manner as in the case of using the nanocrystalline alloy ribbon. The molded body after molding was subjected to heat treatment in an oven at 400 ° C. for 1 hour in an air atmosphere. Table 4 shows the evaluation results of the obtained powder magnetic core.
表４に示したように、アモルファス合金薄帯を用いた場合でも、熱可塑性樹脂のガラス転移温度以上かつ、シリコーン樹脂の融点以上の温度で成形することによって、占積率は大幅に向上し、８０.０％を超える水準の占積率が得られた。また、圧環強度や初透磁率も劇的に向上し、それぞれ１２.０ＭＰａ以上、６０以上の水準が得られた。一方、かかる占積率、圧環強度、初透磁率の大幅な向上が実現される場合でも、コアロスの低下は見られず、むしろ室温成形の場合に比べてコアロスは若干減少した。 As shown in Table 4, even when an amorphous alloy ribbon is used, the space factor is greatly improved by molding at a temperature above the glass transition temperature of the thermoplastic resin and above the melting point of the silicone resin. A space factor exceeding 80.0% was obtained. Moreover, the crushing strength and the initial permeability were dramatically improved, and levels of 12.0 MPa or more and 60 or more were obtained, respectively. On the other hand, even when such a significant increase in the space factor, the crushing strength, and the initial permeability was realized, the core loss was not reduced, but rather the core loss was slightly reduced as compared with the case of room temperature molding.
次に、表４に示す圧粉磁心と同じ軟磁性材料粉を用い、シリコーン樹脂であるメチルフェニルシリコーン樹脂の添加量を変えた圧粉磁心を作製し、占積率およびコアロスを評価した。熱可塑性樹脂であるアクリル樹脂系のバインダー（昭和高分子株式会社製ポリゾールＡＰ−６０４）の添加量は２.５重量部とした点、成形温度を１３０℃とした以外は、上記表４に示した評価を行った圧粉磁心の同様の条件で圧粉磁心を作製した。占積率、圧環強度、コアロス、初透磁率の評価結果を表５に示す。 Next, using the same soft magnetic material powder as the powder magnetic core shown in Table 4, powder magnetic cores with different amounts of addition of methylphenyl silicone resin, which is a silicone resin, were produced, and the space factor and core loss were evaluated. The amount of addition of acrylic resin binder (Polysol AP-604 manufactured by Showa Polymer Co., Ltd.) which is a thermoplastic resin is 2.5 parts by weight, except that the molding temperature is 130 ° C. A dust core was produced under the same conditions as the evaluated dust core. Table 5 shows the evaluation results of the space factor, the crushing strength, the core loss, and the initial permeability.
表５に示すように圧環強度はシリコーン樹脂の添加量が増えるにしたがって増加した。一方、シリコーン樹脂の添加量が増えるにしたがい、初透磁率は減少し、コアロスも増加した。特に、その添加量が１.０重量部（熱可塑性樹脂の２／３）を超えるとコアロスが大きくなっていた。表３に示すコアロスはいずれも実用上は問題のないレベルであるが、シリコーン添加量を１.０重量部（熱可塑性樹脂の４０％）以下にすることでより低いコアロスが維持できることがわかる。 As shown in Table 5, the crushing strength increased as the amount of silicone resin added increased. On the other hand, the initial permeability decreased and the core loss increased as the amount of silicone resin added increased. In particular, when the addition amount exceeds 1.0 parts by weight (2/3 of the thermoplastic resin), the core loss is increased. The core loss shown in Table 3 is a level that causes no problem in practical use, but it can be seen that a lower core loss can be maintained by setting the amount of silicone added to 1.0 part by weight (40% of the thermoplastic resin) or less.
次に上記Ｎｏ２０、２１の圧粉磁心と同じ合金薄帯粉砕粉を用い、ＴＥＯＳの量とアンモニア水の濃度を調整して、シリコン酸化物被膜の厚さが異なる粉砕粉を作製した。かかる粉砕粉を用い、Ｎｏ２０、２１の圧粉磁心と同様にして成形用の混合物を得た。得られた混合粉は、成形温度１３０℃、成形圧２.０ＧＰａの条件で成形を行い、それ以外はＮｏ２０、２１の圧粉磁心と同様にして圧粉磁心を得た（Ｎｏ１７〜２２）。また、比較のためシリコン酸化物（ＳｉＯ２）被膜の厚さが２００ｎｍの粉砕粉を用い、成形温度２０℃（室温）、成形圧２.０ＧＰａまたは１.６ＧＰａの条件で成形し、比較用の圧粉磁心（Ｎｏ３１、３２）を作製した。占積率等の評価結果を表６に示す。μΔは１０ｋＡ／ｍの直流バイアス磁界が印加された状態で測定した増分透磁率である。なお、コアロスＰｃｖは最大磁束密度１５０ｍＴ、周波数２０ｋＨｚの条件で測定した。 Next, using the same alloy ribbon pulverized powder as the No. 20 and No. 21 powder magnetic cores, the amount of TEOS and the concentration of ammonia water were adjusted to prepare pulverized powders having different silicon oxide coating thicknesses. Using this pulverized powder, a molding mixture was obtained in the same manner as the No. 20 and 21 dust cores. The obtained mixed powder was molded under the conditions of a molding temperature of 130 ° C. and a molding pressure of 2.0 GPa. Otherwise, dust cores were obtained in the same manner as the powder cores of Nos. 20 and 21 (Nos. 17 to 22). For comparison, a pulverized powder having a silicon oxide (SiO 2 ) film thickness of 200 nm was molded under the conditions of a molding temperature of 20 ° C. (room temperature) and a molding pressure of 2.0 GPa or 1.6 GPa. A dust core (No. 31, 32) was produced. Table 6 shows the evaluation results such as the space factor. μ Δ is an incremental magnetic permeability measured with a 10 kA / m DC bias magnetic field applied. The core loss Pcv was measured under the conditions of a maximum magnetic flux density of 150 mT and a frequency of 20 kHz.
表６に示すように、シリコン酸化物被膜を厚くすることで、コアロスＰｃｖが減少するのみならず、増分透磁率μΔが増加した。増分透磁率が高くなるということは、直流重畳特性が向上していることを意味する。上述のようにＴＥＯＳによって形成したシリコン酸化物被膜は粉砕粉表面を均一に覆うため、磁性体間に均一かつ確実な磁気ギャップを形成する効果がある。一方、表６の結果から明らかなようにシリコン酸化物被膜を厚くすることは、強磁性部の占積率の低下を招く。しかしながら、温間成形を用いた場合は占積率を格段に高くできるため、８１％以上の占積率を確保しながら、シリコン酸化物被膜を厚くして増分透磁率μΔの改善を図ることができる。しかも、占積率が高められた圧粉磁心ほど、平板状の粉砕粉の板面が揃うため、シリコン酸化物被膜が形成する磁気ギャップが、均一な磁気ギャップとしてより有効に機能するようになる。図２に、温間成形によるＮｏ２８の圧粉磁心の断面ＳＥＭ写真（図２（ａ））を、室温成形による圧粉磁心の断面ＳＥＭ写真（図２（ｂ））とともに示す。室温成形による圧粉磁心は平板状の粉砕粉の板面が不規則な方向に向きやすく、均一な磁気ギャップを形成することが困難であるのに対して、温間成形による圧粉磁心では、隣接する粉砕粉の板面が平行に維持された状態で、その間隔が小さくなっており、シリコン酸化物被膜を介した均一な磁気ギャップが形成できることがわかる。例えば図２（ａ）では、隣接する五つ以上の粉砕粉が、シリコン酸化物被膜による磁気ギャップを介して平行に配置されている。表６に示すように、シリコン酸化物被膜が２００ｎｍ以上であるＮｏ２８〜３０の圧粉磁心では、３４.９以上の優れた増分透磁率μΔが得られた。また、シリコン酸化物被膜が２００ｎｍ以上で増分透磁率μΔの増加が飽和傾向になっており、安定性の観点からは、２００ｎｍを超えるようにシリコン酸化物被膜の厚さを設定することがより好ましいこともわかる。 As shown in Table 6, by increasing the thickness of the silicon oxide film, not only the core loss Pcv decreased but also the incremental permeability μΔ increased. An increase in the incremental permeability means that the direct current superimposition characteristics are improved. Since the silicon oxide film formed by TEOS as described above uniformly covers the pulverized powder surface, it has the effect of forming a uniform and reliable magnetic gap between the magnetic bodies. On the other hand, as is apparent from the results in Table 6, increasing the thickness of the silicon oxide film causes a decrease in the space factor of the ferromagnetic portion. However, in the case of using the warm molding because it significantly increases the space factor, while ensuring the space factor of more than 81%, to improve the incremental permeability mu delta and thick silicon oxide film Can do. In addition, as the powder magnetic core has an increased space factor, the plate surfaces of the flat pulverized powder are aligned, so that the magnetic gap formed by the silicon oxide film functions more effectively as a uniform magnetic gap. . FIG. 2 shows a cross-sectional SEM photograph (FIG. 2 (a)) of a No. 28 dust core by warm forming together with a cross-sectional SEM photograph (FIG. 2 (b)) of the dust core by room temperature forming. The powder magnetic core formed by room temperature molding tends to face the irregular direction of the plate-like pulverized powder, and it is difficult to form a uniform magnetic gap. It can be seen that the distance between the adjacent pulverized powder plates kept in parallel is small, and a uniform magnetic gap can be formed through the silicon oxide film. For example, in FIG. 2A, five or more adjacent pulverized powders are arranged in parallel via a magnetic gap formed by a silicon oxide film. As shown in Table 6, in the dust core of the silicon oxide film is 200nm or more No28～30, 34.9 or more excellent incremental permeability mu delta was obtained. In addition, when the silicon oxide film is 200 nm or more, the increase in the incremental permeability μ Δ tends to be saturated. From the viewpoint of stability, it is more preferable to set the thickness of the silicon oxide film to exceed 200 nm. It can also be seen that it is preferable.
これに対して、２０℃で成形して得られたＮｏ３１の圧粉磁心は、占積率も低く、同じシリコン酸化物被膜のＮｏ２８の圧粉磁心に比べて増分透磁率μΔは大幅に低いものとなった。また、占積率を低下させることは、磁性体（粉砕粉）間の磁気ギャップが増えることを意味するが、表６の結果からは、Ｎｏ３２のように成形圧を下げることで占積率を低下させると、増分透磁率μΔはいっそう低下することがわかる。すなわち、増分透磁率μΔを改善するためには、シリコン酸化物被膜を厚く形成した粉砕粉を用いて構成され、占積率を高めた圧粉磁心が、有効であることが明らかとなった。 On the other hand, the powder magnetic core of No. 31 obtained by molding at 20 ° C. has a low space factor, and the incremental permeability μ Δ is significantly lower than the powder magnetic core of No. 28 of the same silicon oxide film. It became a thing. Moreover, decreasing the space factor means increasing the magnetic gap between the magnetic bodies (pulverized powder). From the results in Table 6, the space factor can be reduced by lowering the molding pressure as in No. 32. It can be seen that the incremental permeability μ Δ is further reduced when the value is lowered. That is, in order to improve the incremental permeability mu delta is constructed with a pulverized powder that formed thick silicon oxide film, dust core having an increased space factor, it was revealed that an effective .
１：粉砕粉 1: ground powder
Claims (6)
前記軟磁性材料粉と、熱可塑性樹脂と、シリコーン樹脂とを混合する第１の工程と、
前記第１の工程を経た混合物を加熱して、前記熱可塑性樹脂のガラス転移温度以上、かつ前記シリコーン樹脂のガラス転移温度以上の成形温度で加圧成形する第２の工程と、
前記第２の工程を経た成形体を前記成形温度よりも高い温度で熱処理する第３の工程とを有することを特徴とする圧粉磁心の製造方法。 A method of manufacturing a powder magnetic core composed of soft magnetic material powder,
A first step of mixing the soft magnetic material powder, a thermoplastic resin, and a silicone resin;
A second step of heating the mixture having undergone the first step and press-molding at a molding temperature equal to or higher than the glass transition temperature of the thermoplastic resin and equal to or higher than the glass transition temperature of the silicone resin;
And a third step of heat-treating the molded body that has undergone the second step at a temperature higher than the molding temperature.
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