JP3658560B2

JP3658560B2 - Inner yoke magnet type linear motor

Info

Publication number: JP3658560B2
Application number: JP2001393097A
Authority: JP
Inventors: 健一勝見; 毅森山; 哲村西; 修小久保; 助広赤間; 郁馬成吉
Original assignee: Toshiba Machine Co Ltd
Current assignee: Shibaura Machine Co Ltd
Priority date: 2001-12-26
Filing date: 2001-12-26
Publication date: 2005-06-08
Anticipated expiration: 2021-12-26
Also published as: JP2003199312A

Description

【０００１】
【発明の属する技術分野】
本発明は、光機器における自動焦点追随装置などに用いられる、内ヨーク磁石型リニアモータに関する。
【０００２】
【従来の技術】
内ヨーク磁石型リニアモータは、従来、次のような構成が採用されていた。
図７は、従来の内ヨーク磁石型リニアモータの構造図である。(ａ)は内ヨーク磁石型リニアモータの縦断面図であり、(ｂ)は、内ヨーク磁石型リニアモータの横断面図である。図より、従来の内ヨーク磁石型リニアモータは、外ヨーク101と、固定子コイル102-1、102-2と、内ヨーク103と、界磁磁石104-1、104-2と、絶縁筒105とを備える。
【０００３】
図(ｂ)に示すように外ヨーク101、固定子コイル102、内ヨーク103、界磁磁石104は、同軸的に配置される。界磁磁石104と内ヨーク103は一体に固定され移動方向106に移動する移動子を構成している。移動子は、界磁磁石104-1と界磁磁石104-2によって生成される界磁磁束と固定子コイル102-1、102-2に流れる電流との鎖交によってフレミング左手の法則に従った駆動力を得る。このときの界磁磁界の様子を電気的な等価回路で表すと次のようになる。
【０００４】
図８は、従来の内ヨーク磁石型リニアモータの等価回路図である。界磁磁束の通る磁気回路を電気的な等価回路で表した図である。図上Ｖ1、Ｖ2は、夫々界磁磁石104-1及び104-2の起磁力Ｕを電圧源に置き換えたものである。又ｉ1、ｉ2は、磁気回路を流れる磁束Φを電流で表したものである。同様に磁気回路中の磁気抵抗Ｑを電気抵抗Ｒで表したものである。ここでRoutは外ヨーク101の磁気抵抗、Rg1は界磁磁石104-1と外ヨーク101との間の空気及びコイルの磁気抵抗、Rg2は界磁磁石104-2と外ヨーク101との間の空気及びコイルの磁気抵抗、Rａは界磁磁石104-1と界磁磁石104-2との間の空気の磁気抵抗、Rinは内ヨーク103の磁気抵抗、ｒ1は界磁磁石104-1内の磁気抵抗、ｒ2は界磁磁石104-2内の磁気抵抗に夫々対応している。移動子が得る駆動力は、固定子コイル102-1、102-2を流れる電流が界磁磁石104-1、104-2の生成する界磁磁束を鎖交する鎖交磁束数に比例するが、この鎖交磁束数は等価回路上の電流ｉ1比例する。
【０００５】
【発明が解決しようとする課題】
ところで、上記のような従来の技術には、次のような解決すべき課題があった。
従来の内ヨーク磁石型リニアモータでは、固定子コイルを流れる電流と界磁磁石の生成する界磁磁束との鎖交磁束数を大きくすることが難しく、駆動力を大きく出来なかった。
【０００６】
【課題を解決するための手段】
本発明は以上の点を解決するため次の構成を採用する。
〈構成１〉
円筒状の外ヨークと、該外ヨークの内側に密着して、内ヨークの移動方向に並べられ、上記外ヨークと同軸的に配置された一対の環状の固定子コイルと、上記外ヨークの内側に同軸的に配置された棒状の内ヨークであって、内部に当該内ヨークとは別部材の磁性体が設けられていない内ヨークと、この内ヨークの外周に固着され、内ヨークの移動方向に空隙を空けて並べられ、当該内ヨークと同軸的に配置された一対の環状の界磁磁石と、上記一対の界磁磁石の間の上記空隙に挟みこまれるように配置された環状の補助磁石とを備え、上記一対の固定子コイルには、相互に反対極性の固定子磁界が励起され、上記一対の界磁磁石の磁化の方向は、いずれも、磁石の軸から外周面に向かう方向に平行であって、一方の界磁磁石の磁化の方向が、他方の界磁磁石の磁化の方向と反対方向になるようにされ、上記補助磁石の磁化の方向は、内ヨークの軸に平行な方向であって、補助磁石の磁極の極性は、補助磁石の磁極が接している上記界磁磁石の外周面の極性と一致していることを特徴とする、内ヨーク磁石型コアレスリニアモータ。
【０００７】
〈構成２〉
円筒状の外ヨークと、該外ヨークの内側に密着して内ヨークの移動方向に並べられ、上記外ヨークと同軸的に配置された３個以上の環状の固定子コイルと、上記外ヨークの内側に同軸的に配置された棒状の内ヨークであって、内部に当該内ヨークとは別部材の磁性体が設けられていない内ヨークと、この内ヨークの外周に固着され、内ヨークの移動方向に空隙を空けて並べられ、当該内ヨークと同軸的に配置された上記固定子コイルの個数以下の個数の環状の界磁磁石と、全ての界磁磁石の間の上記空隙に挟みこまれるように配置された環状の補助磁石とを備え、隣り合う上記固定子コイルには、相互に反対極性の固定子磁界が励起され、全ての界磁磁石の磁化の方向は、いずれも、磁石の軸から外周面に向かう方向に平行であって、隣り合う界磁磁石の磁化の方向は相互に反対方向になるようにされ、上記補助磁石の磁化の方向は、内ヨークの軸に平行な方向であって、補助磁石の磁化の方向は、補助磁石の磁極が接している上記界磁磁石の外周面の極性と一致していることを特徴とする、内ヨーク磁石型コアレスリニアモータ。
【０００８】
【発明の実施の形態】
以下、本発明の実施の形態を具体例を用いて説明する。
〈具体例１〉
具体例１の内ヨーク磁石型リニアモータでは、従来の内ヨーク磁石型リニアモータの２個の界磁磁石の間に挟みこまれるようにして補助磁石が配置される。この補助磁石の磁化方向は、移動子の移動方向に向けられる。極性は、この補助磁石が接している界磁磁石の外周面の極性と一致させてある。その結果、固定子コイルを流れる電流と界磁磁石の生成する界磁磁束との鎖交磁束数を大きくすることが可能になり、駆動力が大きくなる。以下に図を用いて詳細に説明する。
【０００９】
図１は、具体例１の内ヨーク磁石型リニアモータの構造図である。
(ａ)は内ヨーク磁石型リニアモータの縦断面図であり、(ｂ)は、内ヨーク磁石型リニアモータの横断面図である。図より、具体例１の内ヨーク磁石型リニアモータは、外ヨーク1と、固定子コイル2-1、2-2と、内ヨーク3と、界磁磁石4-1、4-2と、絶縁筒5と、補助磁石6とを備える。
【００１０】
外ヨーク1は、後に説明する界磁磁石4-1、4-2、補助磁石6及び内ヨーク3とから成る移動子の移動をガイドする部分であり、更に、後に説明する固定子コイル2-1、2-2を支持する部分でもある。円筒状の磁性材料によって構成される。その外径と長さは、当該モータの用途に合わせて設定される。例えば光機器における自動焦点追随装置などに用いられる場合には外径、長さとも数ｃｍ以下の小型の場合が多い。
【００１１】
固定子コイル2-1、2-2は、上記外ヨーク1の内側に密着して支持され、移動子の移動方向に並べて配置される２個一対の環状のコイルである。この２個の固定子コイル2-1、2-2には、相互に極性反対の固定子磁界が励起される。即ち、相互に正負反転した電圧が印加される。このとき流れる電流と、後に説明する界磁磁石4-1、4-2及び補助磁石6とによって生成される界磁磁束とが、鎖交する。この鎖交によってフレミング左手の法則に従った駆動力が発生される。このときの界磁磁束の通る磁気回路については、後に電気的等価回路を用いて詳細に説明する。
【００１２】
内ヨーク3は、上記外ヨーク1の中心線上に同軸的に配置される磁性体の棒(円柱)である。但し、図1に示すように円柱の中心を空洞にした筒状の棒であっても良い。上記のように後に説明する界磁磁石4-1、4-2、及び補助磁石6とから成る移動子を構成する部分である。この内ヨーク3を軸心にして後に説明する界磁磁石4-1、4-2及び補助磁石6が固着される。光機器における自動焦点追随装置などに用いられた場合には、この内ヨーク3の先端にレンズ支持機構が付着される。
【００１３】
界磁磁石4-1、4-2は、上記内ヨーク3に固着され移動子の移動方向に並べて上記固定子コイル2-1、2-2の内側に配置される環状の永久磁石である。一対の界磁磁石の磁化の方向は、いずれも、磁石の軸から外周面に向かう方向に平行であって、一方の界磁磁石の磁化の方向が、他方の界磁磁石の磁化の方向と反対方向になるようにされている。この詳細については、後に他の図を用いて詳細に説明する。
【００１４】
補助磁石6は、上記界磁磁石4-1及び4-2の２個の界磁磁石の間に挟みこまれるように配置されるリング状の永久磁石である。この磁化の方向は、上記内ヨーク3の軸に平行な方向であって、磁極の極性は、補助磁石が接している上記界磁磁石の外周面の極性と一致させてある。図中に点線が記載され補助磁石が、あたかも２個に分割されているように表してあるが、この理由は後に等価回路の説明で明らかにする。次に上記界磁磁石4-1、4-2及び補助磁石6の構成について他の図を用いて詳細に説明する。
【００１５】
図２は、界磁磁石及び補助磁石の説明図である。(ａ)は、界磁磁石を表す図であり、(ｂ)は、補助磁石を表す図である。環状の界磁磁石4-1及び4-2は(ａ)に示すような扇型に磁性材料を成型した後、磁石の軸から外周面に向かう方向に着磁処理を行なって製作される。ここでは、扇型の開いた角度を90度に表してあるが、本発明はこの例に限定されるものではない。即ち、複数個あわせて360度になるように分割して製作される。この理由は、磁石の軸から外周面に向かう方向への着磁処理を容易にするためである。又(ｂ)より、補助磁石は、磁性材料をリング状に成型したあと図に示すように内ヨークの方向に着磁処理して製作される。
【００１６】
再度図1に戻って、絶縁筒5は、固定子コイル2-1、2-2を保持するための筒である。上記の通り固定子コイル2-1、2-2は、外ヨーク1に密着して保持されるが、界磁磁石4-1、4-2との間に強い力が働くので、その保持を完全なものにするために用いられる。従って、ときには用いなくても良い場合もある。通常磁気回路への影響を考慮して非磁性体であって、かつ絶縁度の高い材料が用いられる。次に、本発明の内ヨーク磁石型リニアモータの磁気回路について説明する。
【００１７】
図３は、本発明の内ヨーク磁石型リニアモータの等価回路図である。(ａ)は、説明に必要な部分の拡大図であり(ｂ)は、その等価回路である。(ａ)に示すように補助磁石6は内ヨーク3の長さ方向の左側にＮ極、右側にＳ極が向くように配置されている。従って、補助磁石6の径方向外側のＮ極は、界磁磁石4-1のＮ極と接しており、補助磁石6の径方向外側のＳ極は、界磁磁石4-2のＳ極と接している。
【００１８】
同様に補助磁石6の径方向内側のＮ極は、界磁磁石4-1のＳ極と接しており、補助磁石6の径方向内側のＳ極は、界磁磁石4-1のＮ極と接している。そこで図(ａ)内に点線で示すように補助磁石6を径方向外側の磁石と径方向内側の磁石の２個に分割して表すこととする。
【００１９】
(ａ)図上Routは外ヨーク1の磁気抵抗に、Rg1は、界磁磁石4-1と外ヨーク1との間の空気及びコイルの磁気抵抗に、Rg2は、界磁磁石4-2と外ヨーク1との間の空気及びコイルの磁気抵抗に、Rg3は、界磁磁石4-1と界磁磁石4-2との間の空気の磁気抵抗に、Rinは内ヨーク3の磁気抵抗に、ｒ1は界磁磁石4-1内部の磁気抵抗に、ｒ2は界磁磁石4-2内部の磁気抵抗に、ｒ3は径方向内側の補助磁石6内部の磁気抵抗に、ｒ4は径方向外側の補助磁石6内部の磁気抵抗に夫々対応している。
【００２０】
(ｂ)図は、上記(ａ)図での定めに従って記述された電気的等価回路である。図上、V1は、界磁磁石4-1の起磁力を電圧源で表したものである。V2は、界磁磁石4-2の起磁力を電圧源で表したものである。V3は、径方向内側の補助磁石6の起磁力を電圧源で表したものである。V4は、径方向外側の補助磁石6の起磁力を電圧源で表したものである。以下に、この電気的等価回路上の電圧源V1、V2を有効として電圧源V3、V4を0と置いたときの各部の電流と、電圧源V3、V4を有効として電圧源V1、V2を0と置いたときの各部の電流とを求め、重畳の理を用いて解析する。
【００２１】
図４は、電圧源V1、V2を有効、電圧源V3、V4を0と置いた回路図である。(ａ)は、説明に必要な部分の拡大図であり(ｂ)は、その等価回路である。(ａ)に示すように界磁磁石4-1、4-2と補助磁石6との間に磁気抵抗R1、R2、R3、R4が発生している。この意味内容について説明する。
【００２２】
通常、界磁磁石4-1、4-2は異方性(ラジアル異方性)磁気材料を径方向に着磁して製作される。従って、磁石の軸から外周面に向かう方向への磁気抵抗(ここではr1に相当)は極めて小さい。一方、内ヨーク方向への磁気抵抗(ここではＲ１に相当)は極めて大きくなる。一方、補助磁石6は、異方性(アキシャル異方性)磁気材料を内ヨーク3の方向に着磁して製作される。従って、内ヨーク3の方向への磁気抵抗(ここではr3又はｒ4に相当)は極めて小さい。一方、磁石の軸から外周面に向かう方向への磁気抵抗(図示していない)は極めて大きくなる。
【００２３】
(ｂ)より、このときループV1、Rg1、Rout、Rg2、r2、V2、Rin、r1、V1を流れる電流(磁束)をｉ1、ループV1、Rg3、r2、V2、Rin、r1、V1を流れる電流(磁束)をｉ2と定める。尚、上記のように磁気抵抗R1、R2、R3、R4は、極めて大きいのでループV1、R1、r4、R3、r2、V2、R4、r3、R2、r1、V1を流れる電流(磁束)は、無視される。次に電圧源V3、V4を有効として電圧源V1、V2を0と置いたときの各部の電流とを求める。
【００２４】
図５は、電圧源V3、V4を有効、電圧源V1、V2を0と置いた回路図である。(ａ)は、説明に必要な部分の拡大図であり(ｂ)は、その等価回路である。(ａ)に示すように界磁磁石4-1、4-2と補助磁石6との間に磁気抵抗R1、R2、R3、R4が発生しているが、この位置が等価回路上で上記図5とは少し異なる。補助磁石6が発生する磁束は、界磁磁石4-1、4-2の内部へは侵入しにくく、外ヨーク1や内ヨーク3へ進むことを意味している。
【００２５】
(ｂ)より、V4、Rg1、Rout、Rg2、ｒ4、V4を流れる電流(磁束)をｉ3、ループV4、Rg3、ｒ4、V4を流れる電流(磁束)をｉ4、ループV3、Rin、r3、V3を流れる電流(磁束)をｉ5と定める。尚、上記のように磁気抵抗R1、R2、R3、R4は、極めて大きいのでループV4、R1、r1、R2、V3、r3、R4、r2、R3、r4、V4を流れる電流(磁束)は、無視される。
【００２６】
以上求めたｉ1、ｉ2、ｉ3、ｉ4、ｉ5を重畳することによって本発明による内ヨーク磁石型リニアモータの各部分を流れる磁束が求められる。固定子コイル2-1、2-2中を流れる電流と鎖交する磁束は、図4のｉ1と図5のｉ3とを加算した値に相当することが分る。ここで留意すべき点は以下の通りである。
【００２７】
ｉ1は既に説明した従来例の内ヨーク磁石型リニアモータにおいて求められたｉ1(図8)と同じ値である。従って、本発明による内ヨーク磁石型リニアモータでは、従来例の内ヨーク磁石型リニアモータに比較してｉ3に相当する磁束分鎖交磁束数が増加することになる。
【００２８】
また、本発明による内ヨーク磁石型リニアモータでは、内ヨーク3(図1)内を流れる磁束は、図4のｉ1とｉ2とを加算した値から図5のｉ5を減算した値に相当することが分る。従って、本発明による内ヨーク磁石型リニアモータでは、従来例の内ヨーク磁石型リニアモータに比較してｉ5に相当する分だけ内ヨーク3(図1)内を流れる磁束が、少なくなることが分る。このことは重要な意味を持っている。即ち、細い棒状の内ヨーク3中は、通常磁気飽和しやすいが、本発明によって磁束量を減少させることが出来るため、磁気飽和しにくくなる。
【００２９】
〈具体例1の効果〉
以上説明したように２個の界磁磁石の間に挟みこまれるように補助磁石が配置されることによって、大きさを変えることなく駆動力を増加することができる。また、細い棒状の内ヨーク3中での磁気飽和を防止することが出来るので精密な動作が可能になる。
【００３０】
〈具体例2〉
具体例2の内ヨーク磁石型リニアモータは、具体例1の内ヨーク磁石型リニアモータの拡張例であって、界磁磁石、補助磁石及び固定子コイルの個数を任意に増加させる構成をとる。その結果、駆動力が大きくなる。以下に図を用いて詳細に説明する。
【００３１】
図６は、具体例２の内ヨーク磁石型リニアモータの構造図である。
(ａ)は内ヨーク磁石型リニアモータの縦断面図であり、(ｂ)は、内ヨーク磁石型リニアモータの横断面図である。図より、具体例2の内ヨーク磁石型リニアモータは、外ヨーク21と、固定子コイル2-1、2-2、2-3、2-4と、内ヨーク23と、界磁磁石4-1、4-2、4-3、4-4と、絶縁筒25と、補助磁石6-1、6-2、6-3とを備える。
【００３２】
ここでは、固定子コイル４個、界磁磁石４個、補助磁石３個が配置されているが、これは一例であって本発明は、この例に限定されるものではない。夫々の構成、機能は具体例1と全く同様なので説明を割愛する。
【００３３】
〈具体例2の効果〉
以上説明したように、固定子コイル等の個数を増加することによって具体例1の効果に加えて、モータの外形を大きくすることなく、駆動力を大きく、かつ、動作速度を早くすることが出来る。
【図面の簡単な説明】
【図１】具体例１の内ヨーク磁石型リニアモータの構造図である。(ａ)は、内ヨーク磁石型リニアモータの縦断面図であり、(ｂ)は、内ヨーク磁石型リニアモータの横断面図である。
【図２】界磁磁石及び補助磁石の説明図である。(ａ)は、界磁磁石を表す図であり、(ｂ)は、補助磁石を表す図である。
【図３】本発明の内ヨーク磁石型リニアモータの等価回路図である。(ａ)は、説明に必要な部分の拡大図であり、(ｂ)は、その等価回路である。
【図４】電圧源V1、V2を有効、電圧源V3、V4を0と置いた回路図である。(ａ)は、説明に必要な部分の拡大図であり、(ｂ)は、その等価回路である。
【図５】電圧源V3、V4を有効、電圧源V1、V2を0と置いた回路図である。(ａ)は、説明に必要な部分の拡大図であり、(ｂ)は、その等価回路である。
【図６】具体例２の内ヨーク磁石型リニアモータの構造図である。(ａ)は、内ヨーク磁石型リニアモータの縦断面図であり、(ｂ)は、内ヨーク磁石型リニアモータの横断面図である。
【図７】従来の内ヨーク磁石型リニアモータの構造図である。(ａ)は、内ヨーク磁石型リニアモータの縦断面図であり、(ｂ)は、内ヨーク磁石型リニアモータの横断面図である。
【図８】従来の内ヨーク磁石型リニアモータの等価回路図である。
【符号の説明】
1 外ヨーク
2-1 固定子コイル
2-2 固定子コイル
3 内ヨーク
4-1 界磁磁石
4-2 界磁磁石
5 絶縁筒
6 補助磁石[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an inner yoke magnet type linear motor used for an automatic focus tracking device in an optical device.
[0002]
[Prior art]
Conventionally, the following configuration has been adopted for the inner yoke magnet type linear motor.
FIG. 7 is a structural diagram of a conventional inner yoke magnet type linear motor. (a) is a longitudinal sectional view of the inner yoke magnet type linear motor, and (b) is a transverse sectional view of the inner yoke magnet type linear motor. From the figure, the conventional inner yoke magnet type linear motor includes an outer yoke 101, stator coils 102-1 and 102-2, an inner yoke 103, field magnets 104-1 and 104-2, and an insulating cylinder 105. With.
[0003]
As shown in FIG. 2B, the outer yoke 101, the stator coil 102, the inner yoke 103, and the field magnet 104 are arranged coaxially. The field magnet 104 and the inner yoke 103 constitute a moving element that is fixed integrally and moves in the moving direction 106. The mover obeyed Fleming's left-hand rule by the linkage between the field magnetic flux generated by the field magnet 104-1 and the field magnet 104-2 and the current flowing through the stator coils 102-1 and 102-2. Get driving force. The state of the field magnetic field at this time is represented by the following electrical equivalent circuit.
[0004]
FIG. 8 is an equivalent circuit diagram of a conventional inner yoke magnet type linear motor. It is the figure which represented the magnetic circuit through which a field magnetic flux passed with an electrical equivalent circuit. V1 and V2 in the figure are obtained by replacing the magnetomotive forces U of the field magnets 104-1 and 104-2 with voltage sources, respectively. I1 and i2 represent the magnetic flux Φ flowing in the magnetic circuit as a current. Similarly, the magnetic resistance Q in the magnetic circuit is represented by an electric resistance R. Here, Rout is the magnetic resistance of the outer yoke 101, Rg1 is the air and coil magnetic resistance between the field magnet 104-1 and the outer yoke 101, and Rg2 is the magnetic resistance between the field magnet 104-2 and the outer yoke 101. The magnetic resistance of air and coil, Ra is the magnetic resistance of air between the field magnet 104-1 and the field magnet 104-2, Rin is the magnetic resistance of the inner yoke 103, and r1 is in the field magnet 104-1. The magnetic resistance r2 corresponds to the magnetic resistance in the field magnet 104-2. The driving force obtained by the moving element is proportional to the number of interlinkage magnetic fluxes in which the current flowing through the stator coils 102-1 and 102-2 interlinks the field magnetic flux generated by the field magnets 104-1 and 104-2. The number of flux linkages is proportional to the current i1 on the equivalent circuit.
[0005]
[Problems to be solved by the invention]
By the way, the conventional techniques as described above have the following problems to be solved.
In the conventional inner yoke magnet type linear motor, it is difficult to increase the number of flux linkages between the current flowing through the stator coil and the field magnetic flux generated by the field magnet, and the driving force cannot be increased.
[0006]
[Means for Solving the Problems]
The present invention adopts the following configuration in order to solve the above points.
<Configuration 1>
A cylindrical outer yoke, a pair of annular stator coils that are in close contact with the inner side of the outer yoke and arranged in the moving direction of the inner yoke, and are arranged coaxially with the outer yoke, and the inner side of the outer yoke A rod-shaped inner yoke arranged coaxially with the inner yoke , in which a magnetic member different from the inner yoke is not provided , and fixed to the outer periphery of the inner yoke, and the moving direction of the inner yoke And a pair of annular field magnets arranged coaxially with the inner yoke, and an annular auxiliary member disposed so as to be sandwiched between the gaps between the pair of field magnets. The pair of stator coils are excited with a stator magnetic field having opposite polarities, and the magnetization directions of the pair of field magnets are all directed from the magnet axis toward the outer peripheral surface. The direction of magnetization of one field magnet is The direction of magnetization of the auxiliary magnet is a direction parallel to the axis of the inner yoke, and the polarity of the magnetic pole of the auxiliary magnet is the same as that of the auxiliary magnet. An inner yoke magnet type coreless linear motor characterized in that it matches the polarity of the outer peripheral surface of the field magnet in contact with the magnetic pole.
[0007]
<Configuration 2>
A cylindrical outer yoke, three or more annular stator coils arranged in close contact with the inner yoke in the moving direction of the inner yoke and arranged coaxially with the outer yoke, and the outer yoke A rod-shaped inner yoke that is coaxially disposed on the inner side, and has an inner yoke that is not provided with a magnetic member separate from the inner yoke, and is fixed to the outer periphery of the inner yoke, and the movement of the inner yoke Spaced in the direction and sandwiched in the space between all the field magnets and the number of annular field magnets equal to or less than the number of the stator coils arranged coaxially with the inner yoke The stator coils adjacent to each other are excited by opposite stator coils, and the magnetization directions of all the field magnets are the same as those of the magnets. Parallel to the direction from the shaft toward the outer peripheral surface, adjacent The magnetization directions of the field magnets are opposite to each other, the magnetization direction of the auxiliary magnet is parallel to the axis of the inner yoke, and the magnetization direction of the auxiliary magnet is the same as that of the auxiliary magnet. An inner yoke magnet type coreless linear motor characterized in that it matches the polarity of the outer peripheral surface of the field magnet in contact with the magnetic pole.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described using specific examples.
<Specific example 1>
In the inner yoke magnet type linear motor of Example 1, the auxiliary magnet is disposed so as to be sandwiched between two field magnets of the conventional inner yoke magnet type linear motor. The magnetization direction of the auxiliary magnet is directed to the moving direction of the mover. The polarity is matched with the polarity of the outer peripheral surface of the field magnet with which the auxiliary magnet is in contact. As a result, the number of flux linkages between the current flowing through the stator coil and the field magnetic flux generated by the field magnet can be increased, and the driving force is increased. This will be described in detail below with reference to the drawings.
[0009]
FIG. 1 is a structural diagram of the inner yoke magnet type linear motor of the first specific example.
(a) is a longitudinal sectional view of the inner yoke magnet type linear motor, and (b) is a transverse sectional view of the inner yoke magnet type linear motor. From the figure, the inner yoke magnet type linear motor of Example 1 is insulated from the outer yoke 1, the stator coils 2-1 and 2-2, the inner yoke 3, the field magnets 4-1 and 4-2. A cylinder 5 and an auxiliary magnet 6 are provided.
[0010]
The outer yoke 1 is a portion that guides the movement of a moving element composed of field magnets 4-1 and 4-2, an auxiliary magnet 6 and an inner yoke 3, which will be described later. Further, a stator coil 2- It is also the part that supports 1 and 2-2. It is composed of a cylindrical magnetic material. The outer diameter and length are set according to the application of the motor. For example, when used for an automatic focus tracking device in an optical device, the outer diameter and the length are often small and several centimeters or less.
[0011]
The stator coils 2-1 and 2-2 are two pairs of annular coils that are supported in close contact with the inner side of the outer yoke 1 and arranged side by side in the moving direction of the mover. The two stator coils 2-1 and 2-2 are excited by stator magnetic fields having opposite polarities. In other words, voltages that are opposite to each other are applied. The current flowing at this time and the field magnetic flux generated by the field magnets 4-1 and 4-2 and the auxiliary magnet 6 described later are linked. This linkage generates a driving force according to Fleming's left-hand rule. The magnetic circuit through which the field magnetic flux passes will be described in detail later using an electrical equivalent circuit.
[0012]
The inner yoke 3 is a magnetic rod (column) arranged coaxially on the center line of the outer yoke 1. However, as shown in FIG. 1, it may be a cylindrical rod having a hollow cylinder. As described above, this is a part that constitutes a mover composed of field magnets 4-1, 4-2, and auxiliary magnet 6, which will be described later. The field magnets 4-1 and 4-2 and the auxiliary magnet 6, which will be described later, are fixed to the inner yoke 3 as an axis. When used in an automatic focus tracking device or the like in an optical device, a lens support mechanism is attached to the tip of the inner yoke 3.
[0013]
The field magnets 4-1 and 4-2 are annular permanent magnets fixed to the inner yoke 3 and arranged in the stator coils 2-1 and 2-2 in the moving direction of the moving element. The magnetization directions of the pair of field magnets are both parallel to the direction from the magnet axis toward the outer peripheral surface, and the magnetization direction of one field magnet is the same as the magnetization direction of the other field magnet. It is supposed to be in the opposite direction. Details of this will be described later in detail with reference to other drawings.
[0014]
The auxiliary magnet 6 is a ring-shaped permanent magnet disposed so as to be sandwiched between the two field magnets 4-1 and 4-2. The direction of this magnetization is parallel to the axis of the inner yoke 3, and the polarity of the magnetic pole is matched with the polarity of the outer peripheral surface of the field magnet in contact with the auxiliary magnet. The dotted line is shown in the figure, and the auxiliary magnet is represented as if it was divided into two. The reason for this will be clarified later in the explanation of the equivalent circuit. Next, the configuration of the field magnets 4-1, 4-2 and the auxiliary magnet 6 will be described in detail with reference to other drawings.
[0015]
FIG. 2 is an explanatory diagram of a field magnet and an auxiliary magnet. (a) is a figure showing a field magnet, (b) is a figure showing an auxiliary magnet. The annular field magnets 4-1 and 4-2 are manufactured by forming a magnetic material in a fan shape as shown in (a) and performing a magnetizing process in a direction from the magnet axis toward the outer peripheral surface. Here, the fan-shaped open angle is represented as 90 degrees, but the present invention is not limited to this example. That is, it is manufactured by dividing a plurality of pieces to 360 degrees. The reason for this is to facilitate the magnetization process in the direction from the magnet axis toward the outer peripheral surface. Also, from (b), the auxiliary magnet is manufactured by molding a magnetic material into a ring shape and then magnetizing it in the direction of the inner yoke as shown in the figure.
[0016]
Returning to FIG. 1 again, the insulating cylinder 5 is a cylinder for holding the stator coils 2-1 and 2-2. As described above, the stator coils 2-1 and 2-2 are held in close contact with the outer yoke 1, but a strong force acts between the field magnets 4-1 and 4-2. Used for completeness. Therefore, sometimes it may not be used. Usually, a nonmagnetic material and a high insulation material are used in consideration of the influence on the magnetic circuit. Next, the magnetic circuit of the inner yoke magnet type linear motor of the present invention will be described.
[0017]
FIG. 3 is an equivalent circuit diagram of the inner yoke magnet type linear motor of the present invention. (a) is an enlarged view of a part necessary for the explanation, and (b) is an equivalent circuit thereof. As shown in (a), the auxiliary magnet 6 is arranged so that the N pole is directed to the left side of the inner yoke 3 in the length direction and the S pole is directed to the right side. Accordingly, the N pole on the radially outer side of the auxiliary magnet 6 is in contact with the N pole of the field magnet 4-1 and the S pole on the radially outer side of the auxiliary magnet 6 is in contact with the S pole of the field magnet 4-2. Touching.
[0018]
Similarly, the N pole on the radially inner side of the auxiliary magnet 6 is in contact with the S pole of the field magnet 4-1, and the S pole on the radially inner side of the auxiliary magnet 6 is in contact with the N pole of the field magnet 4-1. Touching. Therefore, the auxiliary magnet 6 is divided into two parts, a radially outer magnet and a radially inner magnet, as indicated by a dotted line in FIG.
[0019]
(a) In the figure, Rout is the magnetic resistance of the outer yoke 1, Rg1 is the magnetic resistance of the air and coil between the field magnet 4-1 and the outer yoke 1, and Rg2 is the field magnet 4-2. Rg3 is the magnetic resistance of the air between the outer yoke 1, Rg3 is the magnetic resistance of the air between the field magnet 4-1 and the field magnet 4-2, and Rin is the magnetic resistance of the inner yoke 3. , R1 is the magnetic resistance inside the field magnet 4-1; r2 is the magnetic resistance inside the field magnet 4-2; r3 is the magnetic resistance inside the auxiliary magnet 6 inside in the radial direction; and r4 is outside the radial direction. Each corresponds to the magnetic resistance in the auxiliary magnet 6.
[0020]
FIG. 4B is an electrical equivalent circuit described in accordance with the definition in FIG. In the figure, V1 represents the magnetomotive force of the field magnet 4-1 as a voltage source. V2 represents the magnetomotive force of the field magnet 4-2 as a voltage source. V3 represents the magnetomotive force of the auxiliary magnet 6 on the radially inner side as a voltage source. V4 represents the magnetomotive force of the auxiliary magnet 6 on the radially outer side as a voltage source. Below, the voltage sources V1 and V2 on this electrical equivalent circuit are enabled and the voltage sources V3 and V4 are set to 0, the currents of each part, and the voltage sources V3 and V4 are enabled and the voltage sources V1 and V2 are set to 0. The current of each part is determined and analyzed using the superposition theory.
[0021]
FIG. 4 is a circuit diagram in which the voltage sources V1 and V2 are set valid and the voltage sources V3 and V4 are set to 0. (a) is an enlarged view of a part necessary for the explanation, and (b) is an equivalent circuit thereof. As shown in (a), magnetic resistances R1, R2, R3, and R4 are generated between the field magnets 4-1 and 4-2 and the auxiliary magnet 6. This semantic content will be described.
[0022]
Usually, the field magnets 4-1 and 4-2 are manufactured by magnetizing an anisotropic (radial anisotropic) magnetic material in the radial direction. Accordingly, the magnetic resistance (corresponding to r1 here) in the direction from the magnet axis toward the outer peripheral surface is extremely small. On the other hand, the magnetic resistance in the direction of the inner yoke (corresponding to R1 here) becomes extremely large. On the other hand, the auxiliary magnet 6 is manufactured by magnetizing an anisotropic (axial anisotropic) magnetic material in the direction of the inner yoke 3. Therefore, the magnetic resistance in the direction of the inner yoke 3 (here, corresponding to r3 or r4) is extremely small. On the other hand, the magnetic resistance (not shown) in the direction from the magnet axis toward the outer peripheral surface becomes extremely large.
[0023]
From (b), the current (magnetic flux) flowing through the loops V1, Rg1, Rout, Rg2, r2, V2, Rin, r1, and V1 at this time is i1, and the current flows through the loops V1, Rg3, r2, V2, Rin, r1, and V1. The current (magnetic flux) is defined as i2. As described above, since the magnetic resistances R1, R2, R3, R4 are extremely large, the current (magnetic flux) flowing through the loops V1, R1, r4, R3, r2, V2, R4, r3, R2, r1, V1, It will be ignored. Next, the current of each part when the voltage sources V3 and V4 are enabled and the voltage sources V1 and V2 are set to 0 is obtained.
[0024]
FIG. 5 is a circuit diagram in which the voltage sources V3 and V4 are set valid and the voltage sources V1 and V2 are set to 0. (a) is an enlarged view of a part necessary for the explanation, and (b) is an equivalent circuit thereof. As shown in (a), magnetic resistances R1, R2, R3, and R4 are generated between the field magnets 4-1 and 4-2 and the auxiliary magnet 6; A little different from 5. The magnetic flux generated by the auxiliary magnet 6 does not easily enter the field magnets 4-1 and 4-2, and proceeds to the outer yoke 1 and the inner yoke 3.
[0025]
From (b), the current (magnetic flux) flowing through V4, Rg1, Rout, Rg2, r4, V4 is i3, and the current (magnetic flux) flowing through the loop V4, Rg3, r4, V4 is i4, loop V3, Rin, r3, V3. Is defined as i5. As described above, since the magnetic resistances R1, R2, R3, R4 are extremely large, the current (magnetic flux) flowing through the loops V4, R1, r1, R2, V3, r3, R4, r2, R3, r4, V4 is It will be ignored.
[0026]
By superimposing i 1, i 2, i 3, i 4, i 5 obtained as described above, the magnetic flux flowing through each part of the inner yoke magnet type linear motor according to the present invention is obtained. It can be seen that the magnetic flux interlinking with the current flowing in the stator coils 2-1 and 2-2 corresponds to a value obtained by adding i1 in FIG. 4 and i3 in FIG. The points to be noted here are as follows.
[0027]
i1 is the same value as i1 (FIG. 8) obtained in the previously described inner yoke magnet type linear motor. Therefore, in the inner yoke magnet type linear motor according to the present invention, the number of magnetic flux separation fluxes corresponding to i3 is increased as compared with the conventional inner yoke magnet type linear motor.
[0028]
In the inner yoke magnet type linear motor according to the present invention, the magnetic flux flowing in the inner yoke 3 (FIG. 1) corresponds to a value obtained by subtracting i5 in FIG. 5 from a value obtained by adding i1 and i2 in FIG. I understand. Therefore, in the inner yoke magnet type linear motor according to the present invention, the magnetic flux flowing in the inner yoke 3 (FIG. 1) is reduced by an amount corresponding to i5 as compared with the conventional inner yoke magnet type linear motor. The This has important implications. That is, in the thin rod-shaped inner yoke 3, normally, magnetic saturation is likely to occur, but since the amount of magnetic flux can be reduced according to the present invention, magnetic saturation is difficult to occur.
[0029]
<Effect of specific example 1>
As described above, by arranging the auxiliary magnet so as to be sandwiched between the two field magnets, the driving force can be increased without changing the size. Further, since magnetic saturation in the thin rod-shaped inner yoke 3 can be prevented, precise operation becomes possible.
[0030]
<Specific example 2>
The inner yoke magnet type linear motor of Example 2 is an extended example of the inner yoke magnet type linear motor of Example 1, and has a configuration in which the number of field magnets, auxiliary magnets, and stator coils is arbitrarily increased. As a result, the driving force increases. This will be described in detail below with reference to the drawings.
[0031]
FIG. 6 is a structural diagram of the inner yoke magnet type linear motor of the second specific example.
(a) is a longitudinal sectional view of the inner yoke magnet type linear motor, and (b) is a transverse sectional view of the inner yoke magnet type linear motor. From the figure, the inner yoke magnet type linear motor of Example 2 is composed of an outer yoke 21, stator coils 2-1, 2-2, 2-3, 2-4, an inner yoke 23, and a field magnet 4- 1, 4-2, 4-3, 4-4, an insulating cylinder 25, and auxiliary magnets 6-1, 6-2, 6-3.
[0032]
Here, four stator coils, four field magnets, and three auxiliary magnets are arranged, but this is an example, and the present invention is not limited to this example. Since the configuration and function of each are the same as those in Example 1, description thereof will be omitted.
[0033]
<Effect of specific example 2>
As described above, by increasing the number of stator coils and the like, in addition to the effect of Example 1, the driving force can be increased and the operating speed can be increased without increasing the outer shape of the motor. .
[Brief description of the drawings]
FIG. 1 is a structural diagram of an inner yoke magnet type linear motor of Example 1. FIG. (a) is a longitudinal sectional view of the inner yoke magnet type linear motor, and (b) is a transverse sectional view of the inner yoke magnet type linear motor.
FIG. 2 is an explanatory diagram of a field magnet and an auxiliary magnet. (a) is a figure showing a field magnet, (b) is a figure showing an auxiliary magnet.
FIG. 3 is an equivalent circuit diagram of the inner yoke magnet type linear motor of the present invention. (a) is an enlarged view of a part necessary for the explanation, and (b) is an equivalent circuit thereof.
FIG. 4 is a circuit diagram in which voltage sources V1 and V2 are valid and voltage sources V3 and V4 are set to 0. (a) is an enlarged view of a part necessary for the explanation, and (b) is an equivalent circuit thereof.
FIG. 5 is a circuit diagram in which voltage sources V3 and V4 are set to be effective and voltage sources V1 and V2 are set to 0; (a) is an enlarged view of a part necessary for the explanation, and (b) is an equivalent circuit thereof.
6 is a structural diagram of an inner yoke magnet type linear motor of Example 2. FIG. (a) is a longitudinal sectional view of the inner yoke magnet type linear motor, and (b) is a transverse sectional view of the inner yoke magnet type linear motor.
FIG. 7 is a structural diagram of a conventional inner yoke magnet type linear motor. (a) is a longitudinal sectional view of the inner yoke magnet type linear motor, and (b) is a transverse sectional view of the inner yoke magnet type linear motor.
FIG. 8 is an equivalent circuit diagram of a conventional inner yoke magnet type linear motor.
[Explanation of symbols]
1 Outer yoke
2-1 Stator coil
2-2 Stator coil
3 Inner yoke
4-1 Field magnet
4-2 Field magnet
5 Insulating cylinder
6 Auxiliary magnet

Claims

A cylindrical outer yoke;
A pair of annular stator coils that are in close contact with the inner side of the outer yoke and are arranged in the direction of movement of the inner yoke and arranged coaxially with the outer yoke;
A rod-shaped inner yoke arranged coaxially inside the outer yoke, and an inner yoke in which a magnetic body separate from the inner yoke is not provided ;
A pair of field magnets fixed to the outer periphery of the inner yoke, arranged with a gap in the moving direction of the inner yoke, and arranged coaxially with the inner yoke;
An annular auxiliary magnet disposed so as to be sandwiched in the gap between the pair of field magnets,
The pair of stator coils is excited with a stator magnetic field having opposite polarities,
The direction of magnetization of the pair of field magnets is parallel to the direction from the magnet axis toward the outer peripheral surface, and the direction of magnetization of one field magnet is the direction of magnetization of the other field magnet. To be in the opposite direction,
The direction of magnetization of the auxiliary magnet is parallel to the axis of the inner yoke, and the polarity of the magnetic pole of the auxiliary magnet matches the polarity of the outer peripheral surface of the field magnet that is in contact with the magnetic pole of the auxiliary magnet. An inner yoke magnet type coreless linear motor.

A cylindrical outer yoke;
Three or more annular stator coils that are closely attached to the inner side of the outer yoke and arranged in the moving direction of the inner yoke, and are arranged coaxially with the outer yoke;
A rod-shaped inner yoke arranged coaxially inside the outer yoke, and an inner yoke in which a magnetic body separate from the inner yoke is not provided ;
An annular field magnet having a number equal to or less than the number of the stator coils, which is fixed to the outer periphery of the inner yoke, arranged with a gap in the moving direction of the inner yoke, and arranged coaxially with the inner yoke,
An annular auxiliary magnet arranged so as to be sandwiched in the gap between all the field magnets,
The adjacent stator coils are excited with stator magnetic fields having opposite polarities, and the magnetization directions of all field magnets are all parallel to the direction from the magnet axis toward the outer circumferential surface. The directions of magnetization of adjacent field magnets are made to be opposite to each other,
The direction of magnetization of the auxiliary magnet is parallel to the axis of the inner yoke, and the direction of magnetization of the auxiliary magnet coincides with the polarity of the outer peripheral surface of the field magnet in contact with the magnetic pole of the auxiliary magnet. An inner yoke magnet type coreless linear motor.