JP3684104B2

JP3684104B2 - core

Info

Publication number: JP3684104B2
Application number: JP13062799A
Authority: JP
Inventors: 久典長瀬; 卓也石井
Original assignee: Panasonic Corp; Matsushita Electric Industrial Co Ltd
Current assignee: Panasonic Corp; Panasonic Holdings Corp
Priority date: 1999-05-11
Filing date: 1999-05-11
Publication date: 2005-08-17
Anticipated expiration: 2019-05-11
Also published as: JP2000323333A

Description

【０００１】
【産業上の利用分野】
本発明はスイッチング電源などにおけるスイッチングトランスやチョークコイルなどのインダクタンス部品に用いられる磁心に関するものである。
【０００２】
【従来の技術】
近年、電気機器に用いるスイッチング電源の小型化、薄型化、大出力化の要求が高まってきている。
スイッチング電源の小型化、薄型化、大出力化の要求を満たすためには、使用部品であるスイッチングトランスやチョークコイル等のインダクタンス部品の小型化と特性の向上が必要である。通常、インダクタンス部品は主にフェライト材から成る磁心に、導体を巻回した構造を有する。
【０００３】
以下、従来の磁心について図７、及び図８を参照して説明する。
図７の（ａ）は従来の磁心を用いたチョークコイルの正面図であり、同図（ｂ）は（ａ）のｂ−ｂ断面図である。
図７の（ａ）及び（ｂ）において、磁心半体９１は、高透磁率で低コア損失のフェライトなどの材料で形成された底板部９４、中足部９２、外足部９３から構成される。中足部９２は円柱形である。外足部９３は直方体である。底板部９４は、長方形である。巻き線９５は中足部９２の周りに巻き付けられる。
上記の磁心半体９１を用いてトランスやチョークコイルを形成するときには、図７の（ａ）に示すように２個の磁心半体９１をそれぞれの両外足部９３と中足部９２の端面が対向するように組み合わせる。
図８の（ａ）及び（ｂ）はそれぞれ実開平５−８７９１８号公報に記載された他の従来例の磁心半体を示す平面図及び正面図である。
図８の（ａ）及び（ｂ）において、磁心半体１００は、長円形の柱状の中足部１０１、長方形の外足部１０２、底板部１０３から構成される。底板部１０３は、中足部１０１の取り付け部１０３Ａの幅Ｌ３が、外足部１０２の取り付け部の幅Ｌ１より狭くなされている。中足部１０１の断面の長軸方向は外足部１０２の長手方向に向けられている。
【０００４】
【発明が解決しようとする課題】
上記図７に示す従来例では、磁心９１内部の磁束は最短の経路を通るので、中足部９２及び外足部９３と底板部９４との接続部の内側部の領域９２Ａ、９３Ａに磁束が集中することが知られている。巻線９５に高周波の交流電流が流れる場合、磁心材料に固有の磁気ヒステリシス特性によるヒステリシス損失が発生し、磁心９１自体が発熱する。図７の例では中足部９２の断面が円形であるため中足部９２の根本９２Ａでは外足部９３の根元９３Ａ付近よりもさらに磁束の集中度合いが大きくなる。ヒステリシス損失は一般には磁束密度の二乗又はそれ以上に比例して増大する。磁心の特定領域への磁束の集中があるとヒステリシス損失が増加し発熱量も増加することになる。
【０００５】
一方、図８に示す従来例の磁心では、中足部１０１の断面形状が長円形であり、その長軸方向が底板部１０３の幅方向であるので、中足部１０１と底板部１０３との接続部の内側根元部分の断面積が増加し、磁束集中が緩和される。しかしながら、このような中足部の単なる長円化は、磁心の損失低減にはなるものの、同じ断面積の円形の場合に比べて巻線の長さが長くなり、巻線抵抗が増加し、電流が流れることによる巻線の抵抗による損失の増加が問題であった。
【０００６】
本発明は上記問題点に鑑み、導体損失も考慮してインダクタンス部品として総合的に低損失で発熱の少ない磁心を提供することを目的とする。
【０００７】
【課題を解決するための手段】
この課題を解決するために本発明の磁心は、実質的に直方体の底板部と、前記底板部の一方の面の長辺側の両端部にそれぞれ前記底板部と一体に形成した一対の外足部と、前記底板部の実質的に中央部に、長軸方向が前記底板部の長辺の方向と一致して前記一対の外足部の間に配置され前記底板部と一体に形成した実質的に長方形の断面の柱である中足部を具備し、前記中足部の側面と前記外足部の内側面の対向する距離が一定であり、前記底板部の長辺の長さは前記底板部の短辺の長さの１．０倍以上１．５倍以下であり、前記中足部の長軸の長さの１．２倍以上２倍以下であることを特徴とする。
このように構成することにより磁心内部の磁束の分布がより均一になるので、ヒステリシス損失も減少するとともに巻線の導体損失も含めてインダクタンス部品として総合的に低損失で発熱の少ない磁心を提供することが可能となる。
【０００８】
別の観点による本発明の磁心は、実質的に楕円形の板状の底板部と、前記底板部の一方の面の短軸側の両端部にそれぞれ前記底板部と一体に形成した一対の外足部と、前記底板部の実質的に中央部に、長軸方向が前記底板部の長軸方向と一致して前記一対の外足部の間に配置され前記底板部と一体に形成した実質的に楕円形の断面の柱である中足部を具備し、前記中足部の側面と前記外足部の内側面の対向する距離が一定であり、前記底板部の長軸の長さは前記底板部の短軸の長さの１．０倍以上１．５倍以下であり、かつ前記中足部の長軸の１．２倍以上２倍以下であることを特徴とする。
このように構成することにより磁心内部の磁束の分布がより均一になるのでヒステリシス損失も減少するとともに巻線の導体損失も含めたインダクタンス部品として総合的に低損失で発熱の少ない磁心を提供することが可能となる。
【０００９】
別の観点による本発明の磁心は、前記底板部の長軸方向の両端部を短軸と平行であり、かつ前記外足部の端面に一致する直線状に形成したことを特徴とする。このように構成することにより磁心内部の磁束の分布がより均一になるのでヒステリシス損失も減少するとともに巻線の導体損失も含めたインダクタンス部品として総合的に低損失で発熱の少ない磁心を提供することが可能となる。
【００１０】
【発明の実施の形態】
以下、本発明の磁心を示す好適な実施例を添付の図面を参照しつつ説明する。
【００１１】
《実施例１》
図１の（ａ）及び（ｂ）はそれぞれ本発明の実施例１における磁心の構成を示す平面図及び正面図である。
図１の（ａ）及び（ｂ）において、磁心半体１は、高磁化率で低コア損失のフェライトなどの材料で形成された中足部１１、外足部１２、底板部１３から構成されている。底板部１３は短辺の長さＷ１、長辺の長さＬ１の長方形を上面及び底面とする直方体である。中足部１１は、長円形であり、その長軸の長さをＬ２とする。中足部１１はその長軸方向が前記底板部１３の長辺方向と一致するように底板部１３と一体に形成した長円形の断面の柱の構造を有している。外足部１２は底板部１３の一方の面の長辺側の両端部にそれぞれ底板部１３と一体に形成されている。また外足部１２の内側面１２Ａは、中足部１１の側面との距離Ｗ３が一定であるように形成されている。
【００１２】
上記の磁心半体１を用いてチョークコイルやトランスを構成する場合、同形状の２個の磁心半体１をそれぞれの中足部１１と両外足部１２の端面が対向するように組み合わせ、中足部１１に電線を巻き付けてコイル１０（図２）を形成する。２つの磁心半体１を組み合わせたときに正面及び背面に開口部ができるので、ここから中足部１１に巻き付けたコイル１０の端末を外部へ引き出す。このような構造にする利点について以下に説明する。
図２、図３を用いて本実施例の磁心を用いたトランスまたはチョークコイルの磁束の分布について説明する。
図２は、本実施例の磁心半体１を２個組み合わせた磁心の磁束の分布を示す垂直断面図であり、図３は、磁心半体１の磁束の分布を示した水平断面図である。
図３において、コイル１０は図示を省略している。
【００１３】
中足部１１の付け根部分は、水平断面形状が長円形である。このため中足部１１の付け根部分の面積が増大し、中足部１１の付け根部分への磁束の集中が緩和され同領域でのヒステリシス損失が低減する。
図２に示すように、巻き線１０に流れる電流によって磁心半体１の中心部および外足部１２の内側付け根近くに磁束が集中している。さらに図３に示すように、磁束は中足部１１においては、紙面に垂直に手前から奥へ向かっており、矢印付点線で示すように底板部１３を経て外足部１２に向かって通り、外足部１２で手前に向かっている。これらの磁力線は磁心１の中で最短距離を通る。
【００１４】
図７、８の従来例の磁心と、本実施例の磁心において、磁束の経路上の任意の場所での磁心の断面積が、少なくとも中足部１１の断面積と同等以上であるとき、中足部１１の断面積、高さ、距離Ｗ３、ギャップ距離ｇ、巻き線の巻き数及び電流の大きさを同一とした場合、磁心内の総磁束は従来例のものも本実施例のものとほぼ同じになる。
しかしながら本実施例の磁心１における中足部１１および外足部１２の周長の方が長いため、中足部１１、外足部１２の付け根で磁束がより分散される。
【００１５】
図１の（ａ）に示すように、中足部１１の外側面と外足部１２の内側面の距離Ｗ３が実質上一定になるように形成することで、中足部１１から底板部１３を通り外足部１２に至る磁力線の最短経路上での磁気抵抗がほぼ一定となる。このため特定の経路に磁束が集中することを防ぐことができる。したがって中足部１１から底板部１３を通り外足部１２に至る磁束の分布がより均一になり底板部１３でのヒステリシス損失が低減される。
【００１６】
外足部１２において、中足部１１の長軸の長さＬ２よりも底板部１３の長辺の長さＬ１が長く、特に長さＬ１がＬ２の１．２倍以上２倍以下であれば、磁束は底板部１３と外足部１２では中足部１１の付け根部分よりもさらに分散される。そのため外足部１２内部の磁束の分布がより均一になり、外足部１２でのヒステリシス損失が低減される。なお、長さＬ１がＬ２の２倍以上になると外足部のうち中足部から離れすぎる部分が増えてくるので、この部分には磁力線が通らずヒステリシス損失低減には寄与しなくなる。
一般に、底板部１３の長辺の長さが短辺の長さの１．０倍または中足部の長辺の１．２倍よりも小さい場合、巻線の導体損失の減少よりも磁心のヒステリシス損失の増加が上回ってインダクタンス部品全体としての損失が増加してしまう。一方、底板部１３の長辺の長さが短辺の長さの２．０倍または中足部の長軸の２．０倍よりも大きい場合、磁心のヒステリシス損失の減少よりも巻線の導体損失の増加が上回ってインダクタンス部品全体としての損失が増加してしまう。
図４（ａ）、図４（ｂ）はそれぞれ磁心半体１の寸法比Ｌ１／Ｗ１、Ｌ１／Ｌ２と、磁心半体１を用いたトランスの各種損失（磁心のヒステリシス損失、巻線の導通損失及びそれらの和となる全損失）の関係を表すグラフを示す。それぞれ、寸法比Ｌ１／Ｌ２およびＬ１／Ｗ１を１．５倍に固定している。図４（ａ）、図４（ｂ）から明らかなとおりＬ１がＷ１の１倍以上１．５倍以下、Ｌ１がＬ２の１．２倍以上２倍以下ならば、トランスの全損失が低減される。
【００１７】
このときの条件は図４（ａ）、図４（ｂ）ではＷ１＝２４mm、Ｌ２＝１８mmで固定し、磁心材料を日立金属（株）製ＭＬ−２４Ｄ材を用い、１次巻線を厚さ０．５mmの打ち抜き銅板の２ターン、２次巻線を厚さ０．５mmの打ち抜き銅板の１ターンとした。また１次巻線の自己インダクタンスを１７μＨ（中足部にギャップを入れて調整）、印加電流として１次巻線が２３Ａp-o、２次巻線が−４０Ａp-o（１次巻線とは逆相）の１３０ｋＨｚ正弦波交流とした。
【００１８】
なお、以上の説明では中足部１１の水平断面形状を長円形としたが、長方形や長方形の四隅を適当な半径で丸めた扁平形状であればよく、その長軸方向が底板部長辺方向と一致していれば同様の効果が得られる。
また、上記の構成であれば、例えば底板部の四隅及びそれに付随する外足部の丸め加工などの変形があっても同等の効果が得られる。
【００１９】
《実施例２》
図５の（ａ）及び（ｂ）はそれぞれ本発明の実施例２における磁心の構成を示す平面図及び正面図である。
図５において、磁心半体２０は高磁化率で低コア損失のフェライトなどの材料で形成された中足部２１、外足部２２，底板部２３からなる。底板部２３は短軸の長さＷ１０、長軸の長さＬ１０の楕円の板状体である。
中足部２１は、底板部２３の中央部に設けられた、長軸方向が底板部２３の長軸方向と一致する楕円形の断面の柱である。中足部２３は、水平断面の長軸長さがＬ２０、短軸長さがＷ２０とする。外足部２２は底板部２３の上面の短軸側の両端部にそれぞれ底板部２３と一体に形成されている。外足部２２は、その内側面２２Ａと中足部２１の外側面２１Ａとの距離Ｗ３が一定であるように設けられている。
上記磁心半体２０を用いてチョークコイルやトランスを構成する場合、２個の磁心半体２０をそれぞれの中足部２１及び両外足部２２の端面が対向するように組み合わせ中足部２１に電線を巻き付ける。
【００２０】
こうした構造にすることにより以下の効果を生じる。
中足部２１の水平断面形状を楕円形にして、中足部２１の水平断面面積に対しての付け根部分の領域を増大させることにより中足部２１の付け根部分への磁束の集中が緩和される。
また距離Ｗ３を一定にすることにより特定の経路への磁束の集中が防止される。
さらに中足部２１の長軸方向の長さＬ２０よりも底板部２３の長辺方向の長さＬ１０が長く、特に長さＬ１０がＬ２０の１．２倍以上２倍以下および長さＬ１０をＷ１０の１．０倍〜１．５倍とすることにより、磁束の分布が均一化され、磁心のヒステリシス損失と巻線の導通損失の和が最少となる。
【００２１】
さらに、外足部２２の厚さが実施例１よりもより均一になっているので、外足部２２を通る磁束が外足部全体により均一に分布するようになる。これにより磁心形成に要する磁心材料が削減される。また磁心の他の部分に余剰材料を振り向けることで、磁心全体で見た磁束の集中が防止でき、磁心の損失低減が可能となる。
また磁心半体２０の形状を楕円形にすることで、同一仕様の実施例１のものに比べて磁心の設置面積の低減が可能となる。さらに底板部２３の外足部２２のない両端部分が張り出した格好となっているため、中足部２１に巻かれた巻線及びその引き出し部分からの漏れ磁束の放射を抑制する効果をも有する。
【００２２】
《実施例３》
図６はそれぞれ本発明の実施例３における磁心の構成を示す（ａ）平面図及び（ｂ）正面図である。
図６において、磁心半体３０は、高磁化率で低コア損失のフェライトなどの材料で形成された中足部３１、外足部３２、底板部３３からなる。中足部３１は水平断面の長軸長さがＬ２５短軸長さがＷ２５の楕円形とする。底板３３は底板部の長軸方向の両端部を短軸と平行であり、かつ外足部３２の端面に一致する直線状に形成している。つまり底板部３３は、楕円の板状体の長軸方向の両端部を短軸に平行にかつ外足部の端面に一致する直線状に形成した構造である。
外足部３２は底板部３３上面の短軸側の両端部にそれぞれ底板部と一体に形成され、外足部３２の内側面と、中足部３１の外側面との距離Ｗ３が一定となるようになされている。
上記のこの構造を除いたその他の構成は実施例２と同様である。
このような形状にすることにより、以下の効果を生じる。
中足部３１の水平断面形状を楕円形とし、中足部３１の水平断面積に対しての付け根部分の領域を増大させることにより、中足部３１の付け根部分への磁束の集中が緩和される。
距離Ｗ３を一定にすることにより特定経路への磁束の集中が防止される。
中足部３１の長軸方向の長さＬ２５よりも底板部３３の長辺方向の長さＬ１が長く、特に長さＬ１をＬ２５の１．２倍以上２倍以下および長さＬ１をＷ１の１．０倍〜１．５倍にすることにより磁束の分布が均一化するとともに損失が最少になる。本実施例では、実施例２に比較して磁心材料が節約できる効果を持つだけでなく、実施例２よりも磁心の設置面積の削減が可能となる。
【００２３】
【発明の効果】
以上のように本発明によれば、磁心の中足部の水平断面形状の扁平化、中足部側面とそれに対面する外足部側面との間の距離の一定化、外足部を中足部よりも長くすること、底板部底面形状での縦横比の制限、等を行うことにより、磁心のヒステリシス損失及び巻線の導通損失を総合的に低減し、発熱が少なくなるという効果が得られる。
【図面の簡単な説明】
【図１】本発明の実施例１による磁心を示す（ａ）は平面図及び（ｂ）は正面図
【図２】本発明の実施例１による磁心の磁束分布を示すコアの断面図
【図３】図２のIII−III断面図
【図４】（ａ）及び（ｂ）は本発明の実施例１に係る磁心によるＬ１／Ｗ１およびＬ１／Ｌ２と損失との関係を示すグラフ
【図５】本発明の実施例２による磁心を示す（ａ）は平面図及び（ｂ）は正面図
【図６】本発明の実施例３による磁心を示す（ａ）は平面図及び（ｂ）は正面図
【図７】従来例の磁心を示す（ａ）は平面図及び（ｂ）は正面図
【図８】従来例の磁心を示す（ａ）は平面図及び（ｂ）は正面図
【符号の説明】
１、２０、３０、９１、１００磁心半体
１０コイル
１１、２１、３１中足部
１２、２２、３２外足部
１３、２３、３３底板部[0001]
[Industrial application fields]
The present invention relates to a magnetic core used for an inductance component such as a switching transformer or a choke coil in a switching power supply.
[0002]
[Prior art]
In recent years, there has been an increasing demand for smaller, thinner, and higher output switching power supplies used in electrical equipment.
In order to satisfy the demands for switching power supplies that are smaller, thinner, and larger in output, it is necessary to reduce the size of inductance components such as switching transformers and choke coils that are used and to improve their characteristics. Usually, the inductance component has a structure in which a conductor is wound around a magnetic core mainly made of a ferrite material.
[0003]
Hereinafter, a conventional magnetic core will be described with reference to FIGS.
FIG. 7A is a front view of a conventional choke coil using a magnetic core, and FIG. 7B is a cross-sectional view taken along line bb in FIG.
7A and 7B, the magnetic core half 91 is composed of a bottom plate portion 94, a middle foot portion 92, and an outer foot portion 93 formed of a material such as ferrite having a high magnetic permeability and a low core loss. The The middle foot portion 92 has a cylindrical shape. The outer leg part 93 is a rectangular parallelepiped. The bottom plate portion 94 is rectangular. The winding wire 95 is wound around the middle foot portion 92.
When a transformer or choke coil is formed using the magnetic core half 91, the two magnetic core halves 91 are connected to the end surfaces of the outer legs 93 and the middle legs 92 as shown in FIG. Combine to face each other.
FIGS. 8A and 8B are a plan view and a front view showing a magnetic core half of another conventional example described in Japanese Utility Model Laid-Open No. 5-87918, respectively.
8A and 8B, the magnetic core half body 100 is composed of an oval columnar middle foot portion 101, a rectangular outer foot portion 102, and a bottom plate portion 103. In the bottom plate portion 103, the width L3 of the attachment portion 103A of the middle foot portion 101 is narrower than the width L1 of the attachment portion of the outer foot portion 102. The major axis direction of the cross section of the middle foot portion 101 is directed to the longitudinal direction of the outer foot portion 102.
[0004]
[Problems to be solved by the invention]
In the conventional example shown in FIG. 7, since the magnetic flux inside the magnetic core 91 passes through the shortest path, the magnetic flux is generated in the regions 92A and 93A inside the connecting portion between the middle foot portion 92 and the outer foot portion 93 and the bottom plate portion 94. It is known to concentrate. When a high-frequency alternating current flows through the winding 95, hysteresis loss due to magnetic hysteresis characteristics inherent in the magnetic core material occurs, and the magnetic core 91 itself generates heat. In the example of FIG. 7, since the cross section of the middle foot portion 92 is circular, the concentration of magnetic flux is greater at the root 92 </ b> A of the middle foot portion 92 than near the root 93 </ b> A of the outer foot portion 93. The hysteresis loss generally increases in proportion to the square of the magnetic flux density or higher. If the magnetic flux concentrates in a specific area of the magnetic core, hysteresis loss increases and the amount of heat generation also increases.
[0005]
On the other hand, in the conventional magnetic core shown in FIG. 8, the cross-sectional shape of the middle foot portion 101 is oval and the major axis direction is the width direction of the bottom plate portion 103. The cross-sectional area of the inner base portion of the connection portion increases, and the magnetic flux concentration is alleviated. However, such an oval mere lengthening of the middle foot portion reduces the loss of the magnetic core, but the length of the winding becomes longer compared to a circular shape with the same cross-sectional area, and the winding resistance increases. The increase in loss due to the resistance of the winding due to the flow of current was a problem.
[0006]
In view of the above problems, an object of the present invention is to provide a magnetic core with a low overall loss and less heat generation as an inductance component in consideration of conductor loss.
[0007]
[Means for Solving the Problems]
In order to solve this problem, the magnetic core of the present invention has a substantially rectangular parallelepiped bottom plate portion and a pair of outer legs formed integrally with the bottom plate portion at both ends on the long side of one surface of the bottom plate portion. And a substantially central portion of the bottom plate portion, the major axis direction is aligned with the direction of the long side of the bottom plate portion, and is disposed between the pair of outer legs and formed integrally with the bottom plate portion. A middle leg portion having a rectangular cross section, the distance between the side surface of the middle foot portion and the inner side surface of the outer foot portion is constant, and the length of the long side of the bottom plate portion is It is 1.0 to 1.5 times the length of the short side of the bottom plate part, and is 1.2 to 2 times the length of the long axis of the midfoot part.
With this configuration, the distribution of magnetic flux inside the magnetic core becomes more uniform, thereby reducing hysteresis loss and providing a magnetic core with low loss and low heat generation as an inductance component including conductor loss of the winding. It becomes possible.
[0008]
The magnetic core according to another aspect of the present invention includes a pair of outer plates formed integrally with the bottom plate portion at both ends of the substantially elliptical plate-like bottom plate portion and the short axis side of one surface of the bottom plate portion. Substantially formed in the foot plate and the substantially central portion of the bottom plate portion so that the long axis direction coincides with the long axis direction of the bottom plate portion and is disposed between the pair of outer foot portions and integrally with the bottom plate portion. A middle foot part that is a column having an elliptical cross section, the distance between the side surface of the middle foot part and the inner side surface of the outer foot part is constant, and the length of the major axis of the bottom plate part is It is 1.0 times or more and 1.5 times or less of the length of the short axis of the bottom plate part, and 1.2 times or more and 2 times or less of the long axis of the midfoot part.
With this configuration, the distribution of magnetic flux inside the magnetic core becomes more uniform, so hysteresis loss is reduced and a magnetic core with low loss and low heat generation is provided as an inductance component including the conductor loss of the winding. Is possible.
[0009]
The magnetic core of the present invention according to another aspect is characterized in that both end portions in the major axis direction of the bottom plate portion are formed in a straight line that is parallel to the minor axis and coincides with the end surface of the outer foot portion. With this configuration, the distribution of magnetic flux inside the magnetic core becomes more uniform, so hysteresis loss is reduced and a magnetic core with low loss and low heat generation is provided as an inductance component including the conductor loss of the winding. Is possible.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, preferred embodiments showing a magnetic core of the invention will be described with reference to the accompanying drawings.
[0011]
Example 1
FIGS. 1A and 1B are a plan view and a front view, respectively, showing the configuration of the magnetic core in the first embodiment of the present invention.
1A and 1B, the magnetic core half 1 is composed of a middle foot portion 11, an outer foot portion 12, and a bottom plate portion 13 formed of a material such as ferrite having a high magnetic susceptibility and a low core loss. ing. The bottom plate portion 13 is a rectangular parallelepiped having a rectangle with a short side length W1 and a long side length L1 as an upper surface and a bottom surface. The middle foot portion 11 has an oval shape, and the length of the long axis is L2. The middle foot portion 11 has an oval cross-section column structure formed integrally with the bottom plate portion 13 so that the major axis direction thereof coincides with the long side direction of the bottom plate portion 13. The outer legs 12 are integrally formed with the bottom plate 13 at both ends on the long side of one surface of the bottom plate 13. Further, the inner side surface 12A of the outer foot portion 12 is formed such that the distance W3 with the side surface of the middle foot portion 11 is constant.
[0012]
When a choke coil or a transformer is configured using the magnetic core half 1, the two magnetic core halves 1 having the same shape are combined so that the end surfaces of the middle leg portion 11 and the outer leg portions 12 face each other, An electric wire is wound around the middle foot 11 to form the coil 10 (FIG. 2). When the two magnetic core halves 1 are combined, an opening is formed in the front and back, and the terminal of the coil 10 wound around the middle foot 11 is pulled out from here. Advantages of such a structure will be described below.
The distribution of the magnetic flux of the transformer or choke coil using the magnetic core of this embodiment will be described with reference to FIGS.
FIG. 2 is a vertical cross-sectional view showing the magnetic flux distribution of a magnetic core obtained by combining two magnetic core halves 1 of this embodiment, and FIG. 3 is a horizontal cross-sectional view showing the magnetic flux distribution of the magnetic core half 1. .
In FIG. 3, the coil 10 is not shown.
[0013]
The base portion of the middle foot 11 has an oval horizontal cross-sectional shape. For this reason, the area of the base part of the middle foot part 11 increases, the concentration of the magnetic flux on the base part of the middle foot part 11 is relaxed, and the hysteresis loss in the same region is reduced.
As shown in FIG. 2, the magnetic flux is concentrated near the center of the magnetic core half 1 and the inner root of the outer foot 12 by the current flowing through the winding 10. Further, as shown in FIG. 3, in the middle foot portion 11, the magnetic flux is directed from the front to the back perpendicularly to the paper surface, and passes through the bottom plate portion 13 toward the outer foot portion 12 as indicated by the dotted line with an arrow. The outer leg 12 is facing forward. These magnetic field lines pass through the shortest distance in the magnetic core 1.
[0014]
7 and 8 and the magnetic core of the present embodiment, when the cross-sectional area of the magnetic core at an arbitrary place on the path of the magnetic flux is at least equal to or larger than the cross-sectional area of the middle foot 11, When the cross-sectional area, height, distance W3, gap distance g, number of turns of the windings, and current magnitude are the same, the total magnetic flux in the magnetic core is the same as that of the conventional example and that of the present embodiment. It will be almost the same.
However, since the circumferences of the middle foot portion 11 and the outer foot portion 12 in the magnetic core 1 of the present embodiment are longer, the magnetic flux is more dispersed at the roots of the middle foot portion 11 and the outer foot portion 12.
[0015]
As shown in FIG. 1A, by forming the distance W3 between the outer side surface of the middle foot part 11 and the inner side surface of the outer foot part 12 to be substantially constant, the middle foot part 11 and the bottom plate part 13 are formed. The magnetic resistance on the shortest path of the magnetic field lines that pass through and reach the outer foot 12 becomes substantially constant. For this reason, it can prevent that magnetic flux concentrates on a specific path | route. Therefore, the distribution of magnetic flux from the middle foot portion 11 through the bottom plate portion 13 to the outer foot portion 12 becomes more uniform, and hysteresis loss in the bottom plate portion 13 is reduced.
[0016]
In the outer foot portion 12, the length L1 of the long side of the bottom plate portion 13 is longer than the length L2 of the long axis of the middle foot portion 11, and particularly when the length L1 is 1.2 times or more and 2 times or less of L2. The magnetic flux is further dispersed in the bottom plate portion 13 and the outer foot portion 12 than in the base portion of the middle foot portion 11. Therefore, the distribution of the magnetic flux inside the outer foot 12 becomes more uniform, and the hysteresis loss at the outer foot 12 is reduced. Note that when the length L1 is twice or more of L2, the portion of the outer foot portion that is too far from the middle foot portion increases, so that the magnetic field lines do not pass through this portion and do not contribute to the reduction of hysteresis loss.
In general, when the length of the long side of the bottom plate portion 13 is smaller than 1.0 times the length of the short side or 1.2 times the long side of the midfoot portion, the magnetic core is less than the decrease in the conductor loss of the winding. The increase in hysteresis loss exceeds the loss as a whole of the inductance component. On the other hand, when the length of the long side of the bottom plate portion 13 is greater than 2.0 times the length of the short side or 2.0 times the long axis of the midfoot, the winding of the winding is less than the decrease in the hysteresis loss of the magnetic core. The increase in the conductor loss exceeds the loss of the entire inductance component.
4 (a) and 4 (b) show the dimension ratios L1 / W1 and L1 / L2 of the magnetic core half 1, and various losses of the transformer using the magnetic core half (magnetic core hysteresis loss, winding conduction). The graph showing the relationship of a loss and the total loss which becomes those sums is shown. The dimensional ratios L1 / L2 and L1 / W1 are fixed to 1.5 times, respectively. As is clear from FIGS. 4A and 4B, if L1 is 1 to 1.5 times W1 and L1 is 1.2 to 2 times L2, the total loss of the transformer is reduced. The
[0017]
The conditions at this time are fixed at W1 = 24 mm and L2 = 18 mm in FIGS. 4A and 4B, and the magnetic core material is ML-24D made by Hitachi Metals, and the primary winding is thick. Two turns of a punched copper plate having a thickness of 0.5 mm and the secondary winding were made one turn of a punched copper plate having a thickness of 0.5 mm. Also, the self-inductance of the primary winding is 17μH (adjusted with a gap in the middle leg), and the applied current is 23 Ap-o for the primary winding and -40 Ap-o for the secondary winding (what is the primary winding? A reverse phase (130 kHz sine wave alternating current) was used.
[0018]
In the above description, the horizontal cross-sectional shape of the middle foot portion 11 is an oval shape, but it may be a rectangular shape or a flat shape obtained by rounding the four corners of the rectangle with an appropriate radius, and the long axis direction is the long side direction of the bottom plate portion. If they match, the same effect can be obtained.
Moreover, if it is said structure, even if there exists deformation | transformation, such as rounding of the four corners of a baseplate part and the outer leg part accompanying it, an equivalent effect will be acquired.
[0019]
Example 2
FIGS. 5A and 5B are a plan view and a front view, respectively, showing the configuration of the magnetic core in the second embodiment of the present invention.
In FIG. 5, the magnetic core half 20 includes a middle foot portion 21, an outer foot portion 22, and a bottom plate portion 23 formed of a material such as ferrite having a high magnetic susceptibility and a low core loss. The bottom plate portion 23 is an elliptical plate-like body having a short axis length W10 and a long axis length L10.
The middle foot portion 21 is a column having an elliptical cross section provided in the central portion of the bottom plate portion 23 and having a major axis direction coinciding with a major axis direction of the bottom plate portion 23. The middle foot portion 23 has a major axis length L20 and a minor axis length W20 of the horizontal section. The outer legs 22 are integrally formed with the bottom plate 23 at both ends on the short axis side of the upper surface of the bottom plate 23. The outer leg portion 22 is provided such that the distance W3 between the inner side surface 22A and the outer side surface 21A of the middle foot portion 21 is constant.
When a choke coil or a transformer is configured using the magnetic core half body 20, the two magnetic core half bodies 20 are combined with the middle leg portion 21 so that the end surfaces of the middle leg portion 21 and the outer leg portions 22 face each other. Wrap the wire.
[0020]
Such a structure produces the following effects.
By making the horizontal cross-sectional shape of the midfoot 21 elliptical and increasing the area of the base portion with respect to the horizontal cross-sectional area of the midfoot 21, the concentration of magnetic flux on the base portion of the midfoot 21 is alleviated. The
Further, by making the distance W3 constant, the concentration of magnetic flux on a specific path is prevented.
Furthermore, the length L10 of the long side direction of the bottom plate portion 23 is longer than the length L20 of the middle foot portion 21 in the long axis direction, and particularly the length L10 is 1.2 times to 2 times L20 and the length L10 is set to W10. 1.0 to 1.5 times the magnetic flux, the magnetic flux distribution is made uniform, and the sum of the magnetic core hysteresis loss and the winding conduction loss is minimized.
[0021]
Furthermore, since the thickness of the outer foot portion 22 is more uniform than that of the first embodiment, the magnetic flux passing through the outer foot portion 22 is more uniformly distributed throughout the outer foot portion. Thereby, the magnetic core material required for magnetic core formation is reduced. Further, by diverting the surplus material to the other part of the magnetic core, it is possible to prevent the concentration of magnetic flux as seen in the entire magnetic core and to reduce the loss of the magnetic core.
Further, by making the shape of the magnetic core half 20 into an ellipse, it is possible to reduce the installation area of the magnetic core as compared with that of the first embodiment of the same specification. Further, since both end portions of the bottom plate portion 23 without the outer foot portion 22 are projected, there is also an effect of suppressing radiation of leakage magnetic flux from the winding wound around the middle foot portion 21 and the lead-out portion. .
[0022]
Example 3
6A is a plan view and FIG. 6B is a front view showing the configuration of the magnetic core in the third embodiment of the present invention.
In FIG. 6, the magnetic core half 30 includes a middle foot portion 31, an outer foot portion 32, and a bottom plate portion 33 formed of a material such as ferrite having a high magnetic susceptibility and a low core loss. The middle foot portion 31 has an elliptical shape with a major axis length L25 of the horizontal section and a minor axis length W25. The bottom plate 33 is formed so that both ends of the bottom plate portion in the long axis direction are parallel to the short axis and coincide with the end surface of the outer foot portion 32. That is, the bottom plate portion 33 has a structure in which both ends in the major axis direction of the elliptical plate-like body are formed in a straight line parallel to the minor axis and coincident with the end surface of the outer leg portion.
The outer legs 32 are integrally formed with the bottom plate at both ends on the short axis side of the upper surface of the bottom plate 33, and the distance W3 between the inner surface of the outer legs 32 and the outer surface of the middle foot 31 is constant. It is made like that.
The rest of the configuration excluding this structure is the same as that of the second embodiment.
By adopting such a shape, the following effects are produced.
By making the horizontal cross-sectional shape of the midfoot part 31 elliptical and increasing the area of the base part with respect to the horizontal cross-sectional area of the midfoot part 31, the concentration of magnetic flux on the base part of the midfoot part 31 is alleviated. The
By making the distance W3 constant, the concentration of the magnetic flux on the specific path is prevented.
The length L1 of the long side direction of the bottom plate portion 33 is longer than the length L25 of the middle foot portion 31 in the long axis direction, and in particular, the length L1 is 1.2 times to 2 times L25 and the length L1 is W1. By making it 1.0 to 1.5 times, the distribution of magnetic flux becomes uniform and the loss is minimized. In this embodiment, not only can the magnetic core material be saved compared to the second embodiment, but also the installation area of the magnetic core can be reduced as compared with the second embodiment.
[0023]
【The invention's effect】
As described above, according to the present invention, the horizontal cross-sectional shape of the midfoot portion of the magnetic core is flattened, the distance between the side surface of the midfoot portion and the side surface of the outer foot portion facing it is constant, By making the length longer than the portion, limiting the aspect ratio in the bottom plate bottom shape, etc., it is possible to comprehensively reduce the hysteresis loss of the magnetic core and the conduction loss of the winding, and the effect that heat generation is reduced is obtained. .
[Brief description of the drawings]
1A is a plan view of a magnetic core according to a first embodiment of the present invention, and FIG. 2B is a front view thereof. FIG. 2 is a cross-sectional view of a core showing magnetic flux distribution of the magnetic core according to the first embodiment of the present invention. 3 is a cross-sectional view taken along the line III-III in FIG. 2. FIGS. 4A and 4B are graphs showing the relationship between L1 / W1 and L1 / L2 and loss due to the magnetic core according to Example 1 of the present invention. FIG. 6A is a plan view showing a magnetic core according to a second embodiment of the present invention, and FIG. 6B is a front view thereof. FIG. 6A is a plan view showing a magnetic core according to a third embodiment of the present invention, and FIG. 7A is a plan view and FIG. 8B is a front view showing the magnetic core of the conventional example. FIG. 8A is a plan view showing the magnetic core of the conventional example, and FIG. Description】
1, 20, 30, 91, 100 Magnetic core half body 10 Coils 11, 21, 31 Middle foot parts 12, 22, 32 Outer foot parts 13, 23, 33 Bottom plate part

Claims

実質的に直方体の底板部と、前記底板部の一方の面の長辺側の両端縁部にそれぞれ前記底板部と一体に形成した一対の外足部と、前記底板部の実質的に中央部に、長軸方向が前記底板部の長辺の方向と実質的に一致して前記一対の外足部の間に配置され前記底板部と一体に形成した実質的に長方形の断面の柱である中足部を具備し、前記中足部の各側面と前記外足部の内側面の対向する距離が実質的に一定であり、前記底板部の長辺の長さは前記底板部の短辺の長さの１．０倍以上１．５倍以下であり、前記中足部の長軸の長さの１．２倍以上２倍以下であることを特徴とする磁心。A substantially rectangular parallelepiped bottom plate portion, a pair of outer legs integrally formed with the bottom plate portion at both end edges on the long side of one surface of the bottom plate portion, and a substantially central portion of the bottom plate portion In addition, the column having a substantially rectangular cross section formed between the pair of outer legs and the long axis direction substantially coincides with the direction of the long side of the bottom plate portion and formed integrally with the bottom plate portion. A length of the long side of the bottom plate portion is the short side of the bottom plate portion, and the distance between the side surfaces of the middle foot portion and the inner side surface of the outer foot portion is substantially constant. 1.0 to 1.5 times the length of the core, and 1.2 to 2 times the length of the long axis of the midfoot part.

実質的に楕円形の板状の底板部と、前記底板部の一方の面の短軸側の両端部にそれぞれ前記底板部と一体に形成した一対の外足部と、前記底板部の実質的に中央部に、長軸方向が前記底板部の長軸方向と実質的に一致して前記一対の外足部の間に配置され前記底板部と一体に形成した実質的に楕円形の断面の柱である中足部を具備し、前記中足部の側面と前記外足部の内側面の対向する距離が実質的に一定であり、前記底板部の長軸の長さは前記底板部の短軸の長さの１．０倍以上１．５倍以下であり、かつ前記中足部の長軸の１．２倍以上２倍以下であることを特徴とする磁心。A substantially oval plate-like bottom plate portion, a pair of outer legs formed integrally with the bottom plate portion at both ends on the short axis side of one surface of the bottom plate portion, and a substantial portion of the bottom plate portion; A substantially elliptical cross-section formed in one piece with the bottom plate portion disposed between the pair of outer legs so that the long axis direction substantially coincides with the long axis direction of the bottom plate portion. A middle foot portion that is a pillar, a distance between a side surface of the middle foot portion and an inner surface of the outer foot portion is substantially constant, and a length of a long axis of the bottom plate portion is equal to that of the bottom plate portion. A magnetic core characterized by being 1.0 to 1.5 times the length of the short axis and 1.2 to 2 times the long axis of the midfoot.

前記底板部の長軸方向の両端部を短軸と平行であり、かつ前記外足部の端面に一致する直線状に形成したことを特徴とする請求項２に記載の磁心。3. The magnetic core according to claim 2, wherein both end portions in the major axis direction of the bottom plate portion are formed in a straight line that is parallel to the minor axis and coincides with an end surface of the outer foot portion.