JP2004363967A

JP2004363967A - Magnetostrictive speaker

Info

Publication number: JP2004363967A
Application number: JP2003160193A
Authority: JP
Inventors: Koji Maekawa; 孝治前川; Masatoshi Sato; 政敏佐藤; Nobuaki Takahashi; 宣章高橋
Original assignee: Tohoku Pioneer Corp; Pioneer Electronic Corp
Current assignee: Tohoku Pioneer Corp; Pioneer Corp
Priority date: 2003-06-05
Filing date: 2003-06-05
Publication date: 2004-12-24

Abstract

<P>PROBLEM TO BE SOLVED: To provide a magnetostrictive speaker capable of attaining reproduction over a broadband through the combination of a magnetostrictive element or an ultra-magnetostrictive element and a magnetic circuit. <P>SOLUTION: The magnetostrictive speaker is provided with: the magnetostrictive element; a magnetic field generating coil for generating a magnetic field in an extending / contracting direction of the magnetostrictive element; a support member for freely movably supporting both ends of the magnetostrictive element; the magnetic circuit for providing a DC magnetic field causing different polarities at both the ends of the magnetostrictive element; and a diaphragm fixed to one end of the magnetostrictive element. When a high frequency sound current (AC) flows through the magnetic field generating coil, the coil generates a magnetic field to extend / contract (vibrate) the magnetostrictive element in the direction of the magnetic field. The vibration of the magnetostrictive element is delivered to the diaphragm, which reproduces a high frequency sound. At the same time, when a low frequency sound current flows through the magnetic field generating coil, the polarities of the magnetostrictive element being a magnetic substance are changed. Since the magnetostrictive element is placed in the DC magnetic field formed by the magnetic circuit, the magnetostrictive element is vibrated in response to the polarities of the DC magnetic field by the magnetic circuit and the polarities of the magnetostrictive element, and the diaphragm reproduces a low frequency sound. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

【０００１】
【発明の属する技術分野】
本発明は、磁歪素子或いは超磁歪素子を使用したスピーカ装置に関する。
【０００２】
【従来の技術】
外部磁界に応じて素子寸法が変化する磁歪現象を示すものとして、磁歪素子が知られている。特に、ＴｂＦｅ_２系などのＲＦｅ_２ラーベス型金属間化合物は、磁歪量が極めて大きいため超磁歪素子と呼ばれている。磁歪素子にコイルを巻回し、このコイルに電流を流すと、電流の大きさとコイル巻数に比例した磁界が発生し、その磁界の大きさに応じて磁歪素子が伸縮する。磁歪素子のこのような性質を利用したスピーカが各種提案されている。
【０００３】
例えば、磁歪素子を用いてスピーカ振動板を駆動し、スピーカ全体を薄型の構成とした磁歪スピーカ（例えば、特許文献１を参照）が提案されている。また超磁歪ロッドの一端を円板状ヨークに固定するとともに、その他端を振動板に固定し、その超磁歪ロッドをハウジングなどに摺動させずに伸縮させるようにして、ノイズ等の防止を図るようにした超磁歪アクチュエータ及びこれを用いた超磁歪スピーカ（例えば、特許文献２を参照）が提案されている。
【０００４】
【特許文献１】
特開２０００−３４１７９１号公報
【特許文献２】
特開平１０−１４５８９２号公報
【０００５】
【発明が解決しようとする課題】
しかし、磁歪素子は高周波電流による磁界変化によっては振動速度が大きく、低周波電流による磁界変化によっては振動速度が小さいという性質を有するため、一般的に磁歪素子を利用したスピーカでは低域の再生が困難であった。
【０００６】
本発明が解決しようとする課題としては、上記のようなものが例として挙げられる。本発明は、低域から高域までの広帯域の再生が可能な磁歪形スピーカ装置を提供することを課題とする。
【０００７】
【課題を解決するための手段】
請求項１に記載の発明は、磁歪形スピーカ装置において、磁歪素子と、前記磁歪素子の伸縮方向に磁界を発生する磁界発生コイルと、前記磁歪素子の両端を移動自在に支持する支持部材と、前記磁歪素子の両端に異なる極性の直流磁界を付与する磁気回路と、前記磁歪素子の一端に固定された振動板と、を備えることを特徴とする。
【０００８】
請求項３に記載の発明は、磁歪形スピーカ装置において、磁歪素子と、前記磁歪素子の伸縮方向に磁界を発生する磁界発生コイルと、前記磁歪素子の一端を固定するとともに前記磁歪素子の他端側に空隙を有し、前記磁歪素子の両端に異なる極性の直流磁界を付与する磁気回路と、前記磁歪素子の他端を移動自在に支持する支持部材と、前記空隙内に配置されたコイルボビンと、前記コイルボビンに巻回された可動コイルと、前記コイルボビンに固定された低域用振動板と、前記磁歪素子の前記他端に固定された高域用振動板と、を備えることを特徴とする。
【０００９】
【発明の実施の形態】
本発明は、低域での振動速度が小さい磁歪素子（以下、「超磁歪素子」を含む）と、ヨーク及びバイアス磁界発生磁石などからなる磁気回路とを組み合わせて使用することで、低域から高域までの広帯域にわたって音の再生を可能とするスピーカ装置を提供する。
【００１０】
本発明の１つの観点では、磁歪形スピーカ装置は、磁歪素子と、前記磁歪素子の伸縮方向に磁界を発生する磁界発生コイルと、前記磁歪素子の両端を移動自在に支持する支持部材と、前記磁歪素子の両端に異なる極性の直流磁界を付与する磁気回路と、前記磁歪素子の一端に固定された振動板と、を備える。
【００１１】
上記の磁歪形スピーカ装置によれば、磁界発生コイルに高周波の音声電流（交流）が流れると磁界が発生し、磁歪素子はその磁界の方向に伸縮（振動）する。磁歪素子の振動は振動板へ伝達され、振動板から高域音声が再生される。一方、磁界発生コイルに低周波の音声電流が流れると、磁性体である磁歪素子の極性が変化する。磁歪素子は磁気回路が形成する直流磁界内に配置されているので、磁気回路による直流磁界の極性と磁歪素子の極性とに応じて、磁歪素子には反発／吸引力が作用する。この反発／吸引力により磁歪素子は振動し、その振動が振動板に伝えられて低域音声が再生される。こうして、磁歪素子を利用して、低域から高域までの音声再生が可能となる。
【００１２】
上記の磁歪形スピーカの一態様では、前記磁歪素子の前記両端に非磁性体を設け、前記磁歪素子を前記非磁性体を介して前記支持部材に支持し、一方の前記非磁性体に前記振動板を固定することができる。
【００１３】
本発明の他の観点では、磁歪形スピーカ装置は、磁歪素子と、前記磁歪素子の伸縮方向に磁界を発生する磁界発生コイルと、前記磁歪素子の一端を固定するとともに前記磁歪素子の他端側に空隙を有し、前記磁歪素子の両端に異なる極性の直流磁界を付与する磁気回路と、前記磁歪素子の他端を移動自在に支持する支持部材と、前記空隙内に配置されたコイルボビンと、前記コイルボビンに巻回された可動コイルと、前記コイルボビンに固定された低域用振動板と、前記磁歪素子の前記他端に固定された高域用振動板と、を備える。
【００１４】
上記の磁歪形スピーカ装置によれば、磁界発生コイルに高周波の音声電流（交流）が流れると磁界が発生し、磁歪素子はその磁界の方向に伸縮（振動）する。磁歪素子の振動は振動板へ伝達され、振動板から高域音声が再生される。一方、磁気回路の空隙内に配置された可動コイルに低周波の音声電流が流れると、可動コイルが巻回されたコイルボビンに電磁力が作用し、振動を生じる。この振動が振動板に伝えられて、低域音声が再生される。こうして、磁歪素子を利用して、低域から高域までの音声再生が可能となる。
【００１５】
上記の磁歪形スピーカの一態様では、前記磁界発生コイルと前記可動コイルを同一のコイルとすることができる。
【００１６】
上記の磁歪形スピーカの他の一態様では、前記磁界発生コイルと前記可動コイルとを並列接続してなる入力回路を備え、前記入力回路は、入力音声信号の高域成分を前記磁界発生コイルに供給する高域通過フィルタと、前記入力音声信号の低域成分を前記可動コイルに供給する低域通過フィルタと、を有する。この態様では、入力音声信号から、高域成分をフィルタリングして、高域成分を磁界発生コイルに供給し、低域成分を可動コイルに供給する。こうして、低域及び高域をそれぞれ再生することができる。
【００１７】
上記の磁歪形スピーカの他の一態様は、前記磁界発生コイルと前記可動コイルとを並列接続してなる入力回路を備え、前記入力音声信号は前記磁界発生コイルと前記可動コイルに並列に入力される。また、さらに他の一態様では、前記磁界発生コイルと前記可動コイルとを直列接続してなる入力回路を備え、前記入力音声信号は前記磁界発生コイルと前記可動コイルに直列に入力される。磁歪素子は基本的に高域信号に対してのみ大きな振動速度を生じる性質を有するので、入力音声信号を帯域制限せずに磁界発生コイルと可動コイルに供給してもかまわない。
【００１８】
上記の磁歪形スピーカ装置の他の一態様では、前記磁界発生コイルは、前記磁歪素子と非接触で前記磁気回路に固定される。この態様によれば、磁界発生コイルは磁歪素子と接触することなく、磁気回路、例えば円筒状をなすヨークの内壁に巻回するようにして固定される。よって、磁歪素子の伸縮（振動）が阻害されることなく、振動板に伝達される。
【００１９】
上記の磁歪形スピーカ装置の他の一態様では、前記磁歪素子には超磁歪素子が含まれる。これにより、スピーカ装置の特性に応じて磁歪変形量を大きくすることができる。
【００２０】
上記の磁歪形スピーカ装置の他の一態様では、前記支持部材は、前記磁歪素子を前記磁歪素子の伸縮方向に移動自在に支持する。これにより、磁歪素子による伸縮（振動）は支持部材によって阻害されることなく、忠実に振動板へと伝達される。
【００２１】
上記の磁歪形スピーカ装置の他の一態様では、前記磁気回路は、磁界発生手段と、前記磁界発生手段から生じる磁界に従って着磁したヨークと、を含む。この態様によれば、磁界発生手段により生じた磁気エネルギーは効率よくヨークに伝達され、その磁気エネルギーを空隙に与えることができる。
【００２２】
上記の磁歪形スピーカの他の一態様では、磁界発生手段は、磁石及び／又は導線が巻回されたコイルとすることができる。例えば永久磁石により、又は励磁コイルに巻回された導線に音声電流を流すことにより、前者又は後者に応じた大きさの磁界を発生することができる。また、スピーカ装置の特性などに応じて、その永久磁石及び励磁コイルの両方を採用することもできる。
【００２３】
【実施例】
以下、図面を参照して本発明の好適な実施例について説明する。
【００２４】
［第１実施例］
図１には、第１実施例に係るスピーカ装置１００の軸方向に沿った断面図が示される。
【００２５】
スピーカ装置１００は、主として、図１に示すように、棒状の磁歪素子１と、円板状のダンパー２ａ、２ｂと、非磁性体３ａ、３ｂと、円筒状のヨーク４と、バイアス磁界発生磁石５と、磁界発生コイル６と、円錐状のフレーム７と、円錐状の振動板８とを備える。磁歪素子１は、外部磁界からの大きさに応じて素子寸法が変位する（伸縮する）と共に、スピーカ装置１００の略中央に配置される。ダンパー２ａ、２ｂは、複数の同心円状に波型が形成されると共に、ヨーク４の開口部を閉塞する位置に設けられ、磁歪素子１を移動自在に支持する。非磁性体３ａ、３ｂは、磁歪素子１の端部１ａ、１ｂに夫々固定されると共に、ダンパー２ａ、２ｂの略中心部を貫通するようにして支持される。ヨーク４は、磁歪素子１及び非磁性体３ａ、３ｂを筒内に収容すると共に、ダンパー２ａ、２ｂの周縁部と夫々固定される。バイアス磁界発生磁石５はリング状であり、ヨーク４の略中央にヨーク４の外壁を覆うようにして設けられる。磁界発生コイル６は磁歪素子１とは接触させずにバイアス磁界発生磁石５の筒内内壁に沿って巻回してなり、円錐状のフレーム７はヨーク４の一端側の外壁を周方向に沿って覆うようにして固定される。振動板８は、一端を磁歪素子１と固定されていない非磁性体３ｂの一端に固定すると共に、エッジ部８ａ近傍の周縁部をフレーム７の周縁部に固定される。
【００２６】
かかる構成におけるスピーカ装置１００の低域又は高域における音の再生は、以下に示す方法により行われる。
【００２７】
先ず、低域音声信号の再生原理について述べる。低域では、可動鉄片形スピーカと類似した動作により音の再生が行われ、磁歪素子の磁歪現象は再生には寄与しない。具体的には、磁界発生コイル６に低周波の音声電流（交流電流）が流れると、その音声電流の極性（＋又は−）の変化に応じて磁歪素子１の極性がＮ極又はＳ極に変化する。一方、ヨーク４とバイアス磁界発生磁石５とにより構成される空隙９ａ、９ｂ内の極性はバイアス磁界発生磁石５により決まっている（本例では、空隙９ａがＳ極、空隙９ｂがＮ極）。よって、各空隙９ａ、９ｂの極性と磁歪素子１の極性との関係に応じて磁歪素子１には反発力又は吸引力が働き、磁歪素子１が図１における軸方向Ｘに変位する。この変位は、非磁性体３ｂを介して振動板８へと伝達され、振動板８から低域の音波が放射される。振動系の等価質量と、ダンパー２ａ、２ｂのコンプライアンスとによって発生する共振周波数を所定の値に選択することにより、所望の低域において磁歪素子１を振動させることができる。
【００２８】
次に、高域音声信号の再生原理について述べる。高域音声信号は磁歪素子の磁歪現象により再生が行われる。磁界発生コイル６に高周波の音声電流が流れると、磁歪素子１の軸方向Ｘに磁界の変化が生じる。そして、その磁界の変化に応じて磁歪素子１が軸方向Ｘに伸縮し、振動を発生させる。磁歪素子１によるこの振動は、非磁性体３ｂを介して振動板８に伝達され、振動板８から高域の音波が放射される。
【００２９】
このように第１実施例に係るスピーカ装置１００は、磁界発生コイル６及びヨーク４が形成する直流磁界と磁歪素子１の磁性との反発／吸引作用により低域信号を再生し、磁歪素子１の磁歪現象により高域信号を再生する。よって、低域から高域までの広帯域にわって音声信号を再生することができる。
【００３０】
第１実施例に係るスピーカ装置１００では、磁歪素子１の端部１ａをヨーク４に固定することなく、非磁性体３ａ、３ｂをダンパー２ａ、２ｂで支持することにより磁歪素子１を軸方向Ｘに変位可能としている。このため、磁歪素子１は、高域での振動が低減する一方、低域での振動が大きくなる。
【００３１】
この理由について、図１及び図２を参照しながら詳述する。図２には、図１に示すスピーカ装置１００の磁歪素子１の拡大図が示される。図２（ａ）は磁歪素子１の端部を固定しない場合を示し、図２（ｂ）は磁歪素子１の左側端部を固定した場合を示す。なお、図２（ａ）及び（ｂ）に示す磁歪素子１の長さは、共に同じ長さＬである。また、本例では、説明の便宜上、磁歪素子１が伸びるときの長さと、縮むときの長さは共に等しいものとする。また、図２（ａ）及び（ｂ）において、Ｌ２の長さはＬ１の長さの２倍である。
【００３２】
図２（ａ）に示すように、磁歪素子１は磁界発生コイル６に音声電流が流れると、各々の端部１ａ及び１ｂが長さＬ１だけ軸方向Ｘへ伸縮する。よって、図２（ａ）において磁歪素子１の右端部１ｂを非磁性体を介して振動板に固定すると、振動板が振動する振幅はＬ１となる。一方、図２（ｂ）のように磁歪素子１の左側端部を固定した状態で同じ音声電流を流すと、磁歪素子１の右側端部１ｂは長さＬ２（＝２×Ｌ１）だけ軸方向Ｘへ変位する。よって、左端部１ａを非磁性体を介して振動板に固定すると、振動板が振動する振幅はＬ２となり、磁歪素子１の端部を固定しない場合の２倍となる。
【００３３】
第１実施例では、磁歪素子１の端部を固定していないので、磁歪素子の振動量、即ち再生高域信号の振幅は磁歪素子を固定しない場合の１／２となる。しかし、磁歪素子は高域信号に対して振動速度が大きい性質がある。よって、本実施例では磁歪素子を固定しないこととして高域信号の振幅を抑制すると同時に、磁歪素子の伸縮によっては再生できない低域信号を上述の原理により増大することにより、再生帯域全体としては平坦な周波数特性を得ることが可能となる。
【００３４】
以上のように、第１実施例に係るスピーカ装置１００では、低域での振動速度が小さい磁歪素子１と、ヨーク４及びバイアス磁界磁石５などからなる磁気回路とを組み合わせて使用し、低域は可動鉄片形スピーカと類似した原理で、高域は磁歪素子１の振動原理で再生を行う。これにより、低域から高域までの広帯域の音声再生が可能となり、低域の延びたツィータを提供することが可能となる。
【００３５】
［第２実施例］
第２実施例では、磁歪素子１１からの振動により音波を放射する高域用の振動板に加えて、ヨーク１４などの動電形に類する磁気回路からの振動により音波を放射する低域用の振動板を設けることにより、低域から高域までの広帯域にわたって音の再生を可能とするスピーカ装置２００を提供する。
【００３６】
図３（ａ）には、スピーカ装置２００の軸方向に沿った断面図が示される。図３（ｂ）には、図３（ａ）に示されるスピーカ装置２００の磁気回路の部分の断面図が示される。また、図３（ｂ）に示される磁気回路では、符号ｓ３０に示される方向に沿って磁路が形成されている。尚、図３（ｂ）に示される磁気回路では、説明の便宜上、ヨーク１４、バイアス磁界発生磁石１５、及び磁歪素子１１以外の構成要素は省略している。
【００３７】
図３（ａ）に示すように、スピーカ装置２００は、主として、棒状の磁歪素子１１と、円板状のダンパー１２と、有底円筒状のヨーク１４と、リング状のバイアス磁界発生磁石１５と、磁界発生コイル１６と、円筒状のボイスコイルボビン２１と、可動コイル２０と、円錐状のフレーム１７と、低域再生用の振動板１８（ウーファ）と、高域再生用の振動板２２（ツィータ）と、を備える。
【００３８】
磁歪素子１１は、外部磁界からの大きさに応じて素子寸法が変位すると共に、スピーカ装置２００の略中央に配置される。ダンパー１２は、複数の同心円状に波型が形成されると共に、ヨーク１４の開口部を閉塞する位置に設けられ、磁歪素子１１を移動自在に支持する。ヨーク１４は、磁歪素子１１を筒内に収容すると共に、その磁歪素子１１の一端１１ａを固定する。バイアス磁界発生磁石１５は、ヨーク１４の略中央にヨーク１４の外壁を覆うようにして設けられる。第１の磁界発生コイル１６は、磁歪素子１１とは接触させずにヨーク１４の筒内内壁に沿って巻回してなる。ボイスコイルボビン２１は、磁歪素子１１の一端１１ｂとヨーク１４の開口部との間に介在させると共に、ダンパー１２の略中央を貫通する。可動コイル２０は、ヨーク１４の開口側の空隙１９内に配置されたボイスコイルボビン２１の外壁に巻回される。円錐状のフレーム１７は、ヨーク１４の一端側の外壁を周方向に沿って覆うようにして固定される。低域再生用の振動板１８は、ボイスコイルボビン２１の一端側の外壁を周方向に沿って覆うようにして固定されると共に、エッジ部１８ａ近傍の周縁部をフレーム１７の周縁部に固定される円錐状をなす。高域再生用の振動板２２は、磁歪素子１１の端部１１ｂに固定される円錐状をなす。
【００３９】
かかる構成における低域或いは高域における音の再生は、以下に示す方法により行われる。
【００４０】
先ず、低域の音を再生するための方法について述べる。図３（ａ）及び（ｂ）に示すように、可動コイル２０の位置にはヨーク１４による磁界が形成されており（図３（ｂ）に示される磁気回路中の符号ｓ３０を参照）、可動コイル２０に音声電流が流れると、ボイスコイルボビン２１に電磁力が働いて、紙面に向かって左右方向にボイスコイルボビン２１を振動させる。ボイスコイルボビン２１の振動は、低域再生用の振動板１８へと伝達され、その振動板１８から低域の音波が放射される。つまり、これは動電形スピーカと同様の音の再生方法である。
【００４１】
次に、高域の音を再生するための方法について述べるが、これは第１実施例で述べた方法と略同様である。即ち、磁界発生コイル１６に高周波の音声電流が流れると磁歪素子１１の軸方向に磁界の変化が生じて、磁歪素子１１がその軸方向Ｘに伸縮（振動）する。磁歪素子１１によるこの振動は、高域再生用の振動板２２へと伝達され、振動板２２から高域の音波が放射される。
【００４２】
但し、第２実施例に係るスピーカ装置２００は、第１実施例に示すスピーカ装置１００とは異なり、磁歪素子１１の一端１１ａがヨーク１４に固定されている、よって、第１実施例に係るスピーカ装置１００と比べ、磁歪素子１１の振動の振幅の大きさは概ね２倍となる。よって、第２実施例に係るスピーカ装置２００は、より高域の音の再生が可能である。
【００４３】
以上のように、第２実施例に係るスピーカ装置２００は、高域再生に適した磁歪素子を利用したスピーカ装置に対して、動電形スピーカの原理を適用して低域の再生を可能としているので、低域から高域までの広帯域にわたって音声信号の再生が可能となる。よって、低域の延びたツィータを提供することが可能となる。
【００４４】
次に、第２実施例に係るスピーカ装置２００に適用可能な電子回路の各種例を図４（ａ）〜図４（ｃ）に示す。
【００４５】
先ず、図４（ａ）には、高域再生用の振動板２２（ツィータ）を駆動する閉回路Ｃ２と、低域再生用の振動板１８（ウーファ）を駆動する閉回路Ｃ３とを並列接続した電子回路Ｃ１００が示される。
【００４６】
図４（ａ）に示す閉回路Ｃ２では、高域再生用の振動板２２を駆動する磁界発生コイル１６と、ハイパスフィルタＨｆとを直列接続することにより閉回路を構成している。このため、入力端子Ｓ１に音声電流が印加されると、閉回路Ｃ２ではハイパスフィルタＨｆが低周波成分の音声電流をカットして、一定の高周波成分の音声電流を磁界発生コイル１６側へ供給する。そして、磁界発生コイル１６に一定の高周波の音声電流が流れると、磁歪素子１１がスピーカ装置２００の軸方向に伸縮（振動）し、高域再生用の振動板２２を振動させる。よって、閉回路Ｃ２により、高域再生用の振動板２２を通じて高域の音声が再生される。
【００４７】
一方、図４（ａ）に示す閉回路Ｃ３では、低域再生用の振動板１８を駆動する可動コイル２０と、ローパスフィルタＬｆとを直列接続することにより閉回路を構成している。このため、入力端子Ｓ１に音声電流が印加されると、閉回路Ｃ３ではローパスフィルタＬｆが高周波成分の音声電流をカットして、一定の低周波成分の音声電流を可動コイル２０へ供給する。そして、可動コイル２０に一定の低周波の音声電流が流れると、ボイスコイルボビン２１が変位し、低域再生用の振動板１８を振動させる。よって、閉回路Ｃ３により、低域再生用の振動板１８を通じて低域の音声が再生される。
【００４８】
このように、図４（ａ）に示す電子回路Ｃ１００をスピーカ装置２００に適用することにより、低域から高域までの広帯域の音声再生が可能となる。
【００４９】
次に、図４（ｂ）には、高域再生用の振動板２２を駆動する閉回路Ｃ５と、低域再生用の振動板１８を駆動する閉回路Ｃ６とを並列接続した電子回路Ｃ２００が示される。
【００５０】
図４（ｂ）に示す閉回路Ｃ５では、上述した図４（ａ）に示す閉回路Ｃ２と異なり、ハイパスフィルタＨｆを設けていない。したがって、閉回路Ｃ５では、入力端子Ｓ１に低周波成分及び高周波成分を含む音声電流が印加されると、その音声電流が磁界発生コイル１６に流れる。しかし、磁歪素子１１は、低周波成分の音声電流に対応する磁界の変化によっては振動速度が小さい性質があるため、高周波成分の音声電流に対応する磁界の変化のみによって大きな振動速度で振動することになる。よって、閉回路Ｃ５により、高域再生用の振動板２２を通じて高域の音声信号のみが再生される。
【００５１】
また、図４（ｂ）に示す閉回路Ｃ６では、上述した図４（ａ）に示す閉回路Ｃ３と異なり、ローパスフィルタＬｆを設けていない。しかし、閉回路Ｃ６において、入力端子Ｓ１に低周波成分の音声電流を印加することにより、その音声電流が可動コイル２０に流れ、ボイスコイルボビン２１をスピーカ装置２００の軸方向に振動させる。これにより、低域再生用の振動板１８を振動させる。よって、閉回路Ｃ６により、低域再生用の振動板１８を通じて低域の音声信号が再生される。
【００５２】
このように、図４（ｂ）に示す電子回路Ｃ２００をスピーカ装置２００に適用した場合には、ハイパスフィルタＨｆやローパスフィルタＬｆを設けることなく、低域から高域までの広帯域にわたって音声信号の再生が行われる。
【００５３】
図４（ｃ）には、高域再生用の振動板２２を駆動する磁界発生コイル１６と、低域再生用の振動板１８を駆動する可動コイル２０とを直列接続した電子回路Ｃ３００が示される。
【００５４】
図４（ｃ）に示す電子回路Ｃ３００では、入力端子Ｓ１に低周波成分及び高周波成分を含む音声電流が印加されると、その音声電流が磁界発生コイル１６及び可動コイル２０へと流れる。これにより、磁歪素子１１は高周波成分の音声電流に対応する磁界の変化のみによって大きな振動速度で振動し、高域再生用の振動板２２を通じて高域の音声を再生する。一方、可動コイル２０に低周波成分の音声電流が流れると、ボイスコイルボビン２１をスピーカ装置２００の軸方向に振動させる。これにより、低域再生用の振動板１８を通じて低域の音声を再生する。
【００５５】
よって、図４（ｃ）に示す電子回路Ｃ３００をスピーカ装置２００に適用した場合には、図４（ｂ）に示す電子回路Ｃ２００と同様にハイパスフィルタＨｆやローパスフィルタＬｆを設けることなく、低域から高域までの広帯域にわたって音の再生をすることができる。
【００５６】
［第３実施例］
第３実施例に係るスピーカ装置３００は、上述した第２実施例に係るスピーカ装置２００における磁界発生コイル１６と可動コイル２０を１つのコイルにより構成したものである。
【００５７】
図５にスピーカ装置３００の軸方向に沿った断面図が示される。スピーカ装置３００の構成は、上述した第２実施例に係るスピーカ装置２００の構成と殆ど同様である。このため、第２実施例に係るスピーカ装置２００と異なる構成の部分についてのみ説明する。なお、図示のスピーカ装置３００では、第２実施例に係るスピーカ装置２００と同様の構成部分については同様の符号を付している。
【００５８】
本実施例のスピーカ装置３００は、図５に示すように、ダンパー１２近傍から磁歪素子１１の一端１１ａ近傍に至る長いボイスコイルボビン１２１を使用し、コイル１２０をボイスコイルボビン１２１の外壁に巻回している。このコイル１２０は、第２実施例における磁界発生コイル１６及び可動コイル２０の両方の機能を備える。
【００５９】
かかる構成のスピーカ装置３００では、コイル１２０に低周波成分の音声電流が流れると、電磁作用の原理により、ボイスコイルボビン１２１がスピーカ装置３００の軸方向Ｘに振動する。そして、この振動が低域再生用の振動板１８へと伝達され、その振動板１８から低域の音波が放射される。尚、このとき、磁歪素子１１内にも磁界の変化が生じるが、磁歪素子１１は低周波成分の音声電流に対応する磁界の変化によっては振動速度が小さい。一方、磁界発生コイル１２０に高周波成分の音声電流が流れると、磁歪素子１１の軸方向Ｘに磁界の変化が生じ、磁歪素子１１を軸方向Ｘに伸縮（振動）させる。そして、磁歪素子１１による振動が高域再生用の振動板２２へと伝達され、その振動板２２から高域の音波が放射される。
【００６０】
このように、第３実施例に係るスピーカ装置３００は、１つのコイルを利用して、低域から高域までの広帯域にわたって音声再生が可能となる。
【００６１】
［変形例］
第１乃至第３実施例においては、スピーカ装置１００、２００、３００に磁界を発生させるためバイアス磁界発生磁石５、１５を設けたが、これに代えて或いはこれに加えて、導線を巻回したコイルを設けて、その導線に電流を流すことにより、磁界を発生させるように構成してもよい。さらに、このコイルに前記電流に音声電流を重畳するようにしてもよい。
【図面の簡単な説明】
【図１】本発明の第１実施例に係るスピーカ装置の軸方向に沿った断面図を示す。
【図２】磁歪素子の一端を固定した場合と両端を固定しない場合の各磁歪素子の変位状態を示す。
【図３】本発明の第２実施例に係るスピーカ装置の軸方向に沿った断面図及び磁気回路部分の断面図を示す。
【図４】本発明の第２実施例に係るスピーカ装置に適用可能な電子回路の各種例を示す。
【図５】本発明の第３実施例に係るスピーカ装置の軸方向に沿った断面図を示す。
【符号の説明】
１、１１磁歪素子
４、１４ヨーク
５、１５バイアス磁界発生磁石
６、１６磁界発生コイル
７、１７フレーム
８、１８、２２振動板
９、１９空隙
２０可動コイル
２１、１２１ボイスコイルボビン
１００、２００、３００スピーカ装置[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a speaker device using a magnetostrictive element or a giant magnetostrictive element.
[0002]
[Prior art]
2. Description of the Related Art A magnetostrictive element has been known as a magnetostrictive phenomenon in which the element size changes according to an external magnetic field. In particular, TbFe ₂ RFe of system ₂ The Laves-type intermetallic compound has an extremely large magnetostriction and is called a giant magnetostrictive element. When a coil is wound around the magnetostrictive element and a current flows through the coil, a magnetic field is generated in proportion to the magnitude of the current and the number of turns of the coil, and the magnetostrictive element expands and contracts according to the magnitude of the magnetic field. Various speakers utilizing such a property of the magnetostrictive element have been proposed.
[0003]
For example, there has been proposed a magnetostrictive speaker in which a speaker diaphragm is driven by using a magnetostrictive element and the whole speaker is configured to be thin (for example, see Patent Document 1). In addition, one end of the giant magnetostrictive rod is fixed to the disk-shaped yoke, and the other end is fixed to the diaphragm, so that the giant magnetostrictive rod is expanded and contracted without sliding on the housing or the like, thereby preventing noise and the like. A giant magnetostrictive actuator configured as described above and a giant magnetostrictive speaker using the same (for example, see Patent Document 2) have been proposed.
[0004]
[Patent Document 1]
JP-A-2000-341791
[Patent Document 2]
JP-A-10-145892
[0005]
[Problems to be solved by the invention]
However, the magnetostrictive element has a property that the vibration speed is large depending on the magnetic field change due to the high-frequency current, and the vibration speed is small depending on the magnetic field change due to the low-frequency current. It was difficult.
[0006]
The problems to be solved by the present invention include the above-mentioned ones as examples. An object of the present invention is to provide a magnetostrictive speaker device capable of reproducing a wide band from a low band to a high band.
[0007]
[Means for Solving the Problems]
The invention according to claim 1 is the magnetostrictive speaker device, wherein the magnetostrictive element, a magnetic field generating coil that generates a magnetic field in the direction of expansion and contraction of the magnetostrictive element, and a support member that movably supports both ends of the magnetostrictive element; A magnetic circuit for applying DC magnetic fields of different polarities to both ends of the magnetostrictive element, and a diaphragm fixed to one end of the magnetostrictive element are provided.
[0008]
The invention according to claim 3 is the magnetostrictive speaker device, wherein the magnetostrictive element, a magnetic field generating coil that generates a magnetic field in the direction of expansion and contraction of the magnetostrictive element, and one end of the magnetostrictive element are fixed and the other end of the magnetostrictive element is fixed. A magnetic circuit that applies a DC magnetic field of a different polarity to both ends of the magnetostrictive element, a support member that movably supports the other end of the magnetostrictive element, and a coil bobbin disposed in the air gap. A movable coil wound around the coil bobbin, a low-frequency diaphragm fixed to the coil bobbin, and a high-frequency diaphragm fixed to the other end of the magnetostrictive element. .
[0009]
BEST MODE FOR CARRYING OUT THE INVENTION
The present invention uses a magnetostrictive element having a low vibration speed in a low frequency range (hereinafter, referred to as a “super magnetostrictive element”) in combination with a magnetic circuit including a yoke and a bias magnetic field generating magnet to reduce the low frequency range. A speaker device capable of reproducing sound over a wide band up to a high frequency is provided.
[0010]
In one aspect of the present invention, a magnetostrictive speaker device includes a magnetostrictive element, a magnetic field generating coil that generates a magnetic field in a direction in which the magnetostrictive element expands and contracts, a support member that movably supports both ends of the magnetostrictive element, The magnetostrictive element includes a magnetic circuit for applying DC magnetic fields having different polarities to both ends of the magnetostrictive element, and a diaphragm fixed to one end of the magnetostrictive element.
[0011]
According to the magnetostrictive speaker device described above, when a high-frequency audio current (AC) flows through the magnetic field generating coil, a magnetic field is generated, and the magnetostrictive element expands and contracts (vibrates) in the direction of the magnetic field. The vibration of the magnetostrictive element is transmitted to the diaphragm, and a high-frequency sound is reproduced from the diaphragm. On the other hand, when a low-frequency audio current flows through the magnetic field generating coil, the polarity of the magnetostrictive element, which is a magnetic material, changes. Since the magnetostrictive element is arranged in a DC magnetic field formed by the magnetic circuit, a repulsion / attraction force acts on the magnetostrictive element according to the polarity of the DC magnetic field generated by the magnetic circuit and the polarity of the magnetostrictive element. The repulsion / attraction force causes the magnetostrictive element to vibrate, and the vibration is transmitted to the diaphragm to reproduce low-frequency sound. In this way, it is possible to reproduce sound from a low frequency to a high frequency using the magnetostrictive element.
[0012]
In one aspect of the above-described magnetostrictive speaker, a nonmagnetic material is provided at the both ends of the magnetostrictive element, the magnetostrictive element is supported by the support member via the nonmagnetic material, and the vibration is applied to one of the nonmagnetic materials. The board can be fixed.
[0013]
According to another aspect of the present invention, a magnetostrictive speaker device includes a magnetostrictive element, a magnetic field generating coil that generates a magnetic field in a direction in which the magnetostrictive element expands and contracts, and fixes one end of the magnetostrictive element and the other end of the magnetostrictive element. A magnetic circuit that provides a DC magnetic field having different polarities to both ends of the magnetostrictive element, a support member that movably supports the other end of the magnetostrictive element, and a coil bobbin disposed in the air gap, A movable coil wound around the coil bobbin; a low-frequency diaphragm fixed to the coil bobbin; and a high-frequency diaphragm fixed to the other end of the magnetostrictive element.
[0014]
According to the magnetostrictive speaker device described above, when a high-frequency audio current (AC) flows through the magnetic field generating coil, a magnetic field is generated, and the magnetostrictive element expands and contracts (vibrates) in the direction of the magnetic field. The vibration of the magnetostrictive element is transmitted to the diaphragm, and a high-frequency sound is reproduced from the diaphragm. On the other hand, when a low-frequency audio current flows through the movable coil disposed in the gap of the magnetic circuit, an electromagnetic force acts on the coil bobbin around which the movable coil is wound, causing vibration. This vibration is transmitted to the diaphragm, and low-frequency sound is reproduced. In this way, it is possible to reproduce sound from a low frequency to a high frequency using the magnetostrictive element.
[0015]
In one aspect of the magnetostrictive speaker, the magnetic field generating coil and the movable coil may be the same coil.
[0016]
In another aspect of the above-described magnetostrictive speaker, the input device includes an input circuit in which the magnetic field generating coil and the movable coil are connected in parallel, and the input circuit transmits a high-frequency component of an input audio signal to the magnetic field generating coil. A high-pass filter that supplies a low-frequency component of the input audio signal to the movable coil. In this embodiment, the high frequency component is filtered from the input audio signal, the high frequency component is supplied to the magnetic field generating coil, and the low frequency component is supplied to the movable coil. In this way, the low and high frequencies can be reproduced respectively.
[0017]
Another aspect of the above magnetostrictive speaker includes an input circuit formed by connecting the magnetic field generating coil and the movable coil in parallel, and the input audio signal is input to the magnetic field generating coil and the movable coil in parallel. You. In still another aspect, the apparatus further comprises an input circuit formed by connecting the magnetic field generating coil and the movable coil in series, and the input audio signal is input to the magnetic field generating coil and the movable coil in series. Since the magnetostrictive element basically has a property of generating a large vibration velocity only for a high-frequency signal, the input audio signal may be supplied to the magnetic field generating coil and the movable coil without band limitation.
[0018]
In another aspect of the magnetostrictive speaker device, the magnetic field generating coil is fixed to the magnetic circuit without contacting the magnetostrictive element. According to this aspect, the magnetic field generating coil is fixed so as to be wound around a magnetic circuit, for example, an inner wall of a cylindrical yoke without contacting the magnetostrictive element. Therefore, the transmission is performed to the diaphragm without obstructing expansion and contraction (vibration) of the magnetostrictive element.
[0019]
In another aspect of the magnetostrictive speaker device, the magnetostrictive element includes a giant magnetostrictive element. Thereby, the amount of magnetostriction deformation can be increased according to the characteristics of the speaker device.
[0020]
In another aspect of the above-described magnetostrictive speaker device, the support member supports the magnetostrictive element movably in a direction in which the magnetostrictive element expands and contracts. Thus, expansion and contraction (vibration) by the magnetostrictive element is faithfully transmitted to the diaphragm without being hindered by the support member.
[0021]
In another aspect of the magnetostrictive speaker device, the magnetic circuit includes a magnetic field generating unit and a yoke magnetized according to a magnetic field generated from the magnetic field generating unit. According to this aspect, the magnetic energy generated by the magnetic field generating means is efficiently transmitted to the yoke, and the magnetic energy can be given to the air gap.
[0022]
In another aspect of the magnetostrictive speaker, the magnetic field generating means may be a coil around which a magnet and / or a conductive wire is wound. For example, a magnetic field having a magnitude corresponding to the former or the latter can be generated by flowing an audio current through a permanent magnet or a conducting wire wound around an exciting coil. Further, both the permanent magnet and the exciting coil can be adopted according to the characteristics of the speaker device.
[0023]
【Example】
Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings.
[0024]
[First embodiment]
FIG. 1 shows a cross-sectional view along the axial direction of a speaker device 100 according to the first embodiment.
[0025]
As shown in FIG. 1, the speaker device 100 mainly includes a rod-shaped magnetostrictive element 1, disk-shaped dampers 2a and 2b, non-magnetic members 3a and 3b, a cylindrical yoke 4, and a bias magnetic field generating magnet. 5, a magnetic field generating coil 6, a conical frame 7, and a conical diaphragm 8. The magnetostrictive element 1 is displaced (expands and contracts) in accordance with the magnitude of the external magnetic field, and is disposed substantially at the center of the speaker device 100. The dampers 2a and 2b have a plurality of concentric corrugations and are provided at positions where the openings of the yoke 4 are closed, and movably support the magnetostrictive element 1. The non-magnetic members 3a and 3b are fixed to the ends 1a and 1b of the magnetostrictive element 1, respectively, and are supported so as to penetrate substantially the center of the dampers 2a and 2b. The yoke 4 accommodates the magnetostrictive element 1 and the non-magnetic members 3a and 3b in a cylinder, and is fixed to the periphery of the dampers 2a and 2b, respectively. The bias magnetic field generating magnet 5 has a ring shape and is provided substantially at the center of the yoke 4 so as to cover the outer wall of the yoke 4. The magnetic field generating coil 6 is wound along the inner wall of the cylinder of the bias magnetic field generating magnet 5 without contacting the magnetostrictive element 1, and the conical frame 7 extends along the outer wall on one end side of the yoke 4 along the circumferential direction. It is fixed so as to cover. The diaphragm 8 has one end fixed to one end of the non-magnetic body 3 b not fixed to the magnetostrictive element 1, and a peripheral edge near the edge 8 a fixed to the peripheral edge of the frame 7.
[0026]
The sound reproduction in the low or high frequency range of the speaker device 100 having such a configuration is performed by the following method.
[0027]
First, the principle of reproducing a low-frequency audio signal will be described. In the low frequency range, sound is reproduced by an operation similar to that of the movable iron loudspeaker, and the magnetostrictive phenomenon of the magnetostrictive element does not contribute to reproduction. Specifically, when a low-frequency audio current (alternating current) flows through the magnetic field generating coil 6, the polarity of the magnetostrictive element 1 changes to the N-pole or the S-pole in accordance with a change in the polarity (+ or-) of the audio current. Change. On the other hand, the polarities in the air gaps 9a and 9b formed by the yoke 4 and the bias magnetic field generating magnet 5 are determined by the bias magnetic field generating magnet 5 (in this example, the air gap 9a is an S pole and the air gap 9b is an N pole). Therefore, a repulsive force or an attractive force acts on the magnetostrictive element 1 according to the relationship between the polarities of the gaps 9a and 9b and the polarity of the magnetostrictive element 1, and the magnetostrictive element 1 is displaced in the axial direction X in FIG. This displacement is transmitted to the diaphragm 8 via the non-magnetic body 3b, and a low-frequency sound wave is emitted from the diaphragm 8. By selecting the resonance frequency generated by the equivalent mass of the vibration system and the compliance of the dampers 2a and 2b to a predetermined value, the magnetostrictive element 1 can be vibrated in a desired low band.
[0028]
Next, the principle of reproducing a high-frequency audio signal will be described. The high-frequency audio signal is reproduced by the magnetostrictive phenomenon of the magnetostrictive element. When a high-frequency audio current flows through the magnetic field generating coil 6, a change in the magnetic field occurs in the axial direction X of the magnetostrictive element 1. Then, the magnetostrictive element 1 expands and contracts in the axial direction X according to the change in the magnetic field, and generates vibration. This vibration by the magnetostrictive element 1 is transmitted to the diaphragm 8 via the non-magnetic body 3b, and a high-frequency sound wave is emitted from the diaphragm 8.
[0029]
As described above, the speaker device 100 according to the first embodiment reproduces the low-frequency signal by the repulsion / attraction effect of the DC magnetic field formed by the magnetic field generating coil 6 and the yoke 4 and the magnetism of the magnetostrictive element 1, The high frequency signal is reproduced by the magnetostriction phenomenon. Therefore, an audio signal can be reproduced over a wide band from a low band to a high band.
[0030]
In the speaker device 100 according to the first embodiment, the non-magnetic members 3a, 3b are supported by the dampers 2a, 2b without fixing the end 1a of the magnetostrictive element 1 to the yoke 4, so that the magnetostrictive element 1 can be moved in the axial direction X. To be displaceable. Therefore, in the magnetostrictive element 1, the vibration in the high frequency range is reduced, while the vibration in the low frequency range is large.
[0031]
The reason for this will be described in detail with reference to FIGS. FIG. 2 is an enlarged view of the magnetostrictive element 1 of the speaker device 100 shown in FIG. FIG. 2A shows a case where the end of the magnetostrictive element 1 is not fixed, and FIG. 2B shows a case where the left end of the magnetostrictive element 1 is fixed. The length of the magnetostrictive element 1 shown in FIGS. 2A and 2B is the same length L. Further, in this example, for convenience of explanation, it is assumed that the length when the magnetostrictive element 1 expands and the length when it contracts are both equal. In FIGS. 2A and 2B, the length of L2 is twice as long as L1.
[0032]
As shown in FIG. 2A, when an audio current flows through the magnetic field generating coil 6 of the magnetostrictive element 1, each end 1a and 1b expands and contracts in the axial direction X by the length L1. Therefore, when the right end 1b of the magnetostrictive element 1 is fixed to the diaphragm via the non-magnetic material in FIG. 2A, the vibration amplitude of the diaphragm becomes L1. On the other hand, when the same audio current is applied while the left end of the magnetostrictive element 1 is fixed as shown in FIG. 2B, the right end 1b of the magnetostrictive element 1 is moved in the axial direction by a length L2 (= 2 × L1). Displace to X. Therefore, when the left end 1a is fixed to the diaphragm via the non-magnetic material, the vibration amplitude of the diaphragm becomes L2, which is twice as large as when the end of the magnetostrictive element 1 is not fixed.
[0033]
In the first embodiment, since the end of the magnetostrictive element 1 is not fixed, the amount of vibration of the magnetostrictive element, that is, the amplitude of the reproduced high-frequency signal is １／ of the case where the magnetostrictive element is not fixed. However, the magnetostrictive element has a property that the vibration speed is high with respect to a high-frequency signal. Therefore, in this embodiment, the amplitude of the high-frequency signal is suppressed by not fixing the magnetostrictive element, and at the same time, the low-frequency signal that cannot be reproduced by expansion and contraction of the magnetostrictive element is increased by the above-described principle, so that the entire reproduction band is flat. Frequency characteristics can be obtained.
[0034]
As described above, in the speaker device 100 according to the first embodiment, the magnetostrictive element 1 having a low vibration speed in the low frequency band and the magnetic circuit including the yoke 4 and the bias magnetic field magnet 5 are used in combination. Is based on a principle similar to that of a movable iron loudspeaker, and reproduction is performed in the high frequency range based on the vibration principle of the magnetostrictive element 1. As a result, sound reproduction in a wide band from a low band to a high band becomes possible, and it is possible to provide a tweeter whose low band is extended.
[0035]
[Second embodiment]
In the second embodiment, in addition to a high-frequency diaphragm that emits a sound wave by vibration from the magnetostrictive element 11, a low-frequency diaphragm that emits a sound wave by vibration from a magnetic circuit similar to an electrokinetic type such as the yoke 14 is provided. Provided is a speaker device 200 that can reproduce sound over a wide band from a low band to a high band by providing a diaphragm.
[0036]
FIG. 3A is a cross-sectional view of the speaker device 200 along the axial direction. FIG. 3B is a sectional view of a magnetic circuit portion of the speaker device 200 shown in FIG. In the magnetic circuit shown in FIG. 3B, a magnetic path is formed along the direction indicated by reference numeral s30. In the magnetic circuit shown in FIG. 3B, components other than the yoke 14, the bias magnetic field generating magnet 15, and the magnetostrictive element 11 are omitted for convenience of explanation.
[0037]
As shown in FIG. 3A, the speaker device 200 mainly includes a rod-shaped magnetostrictive element 11, a disk-shaped damper 12, a bottomed cylindrical yoke 14, and a ring-shaped bias magnetic field generating magnet 15. , A magnetic field generating coil 16, a cylindrical voice coil bobbin 21, a movable coil 20, a conical frame 17, a low-frequency reproduction diaphragm 18 (woofer), and a high-frequency reproduction diaphragm 22 (tweeter) ).
[0038]
The size of the magnetostrictive element 11 is displaced in accordance with the magnitude of an external magnetic field, and the magnetostrictive element 11 is disposed substantially at the center of the speaker device 200. The damper 12 has a plurality of concentric corrugations and is provided at a position where the opening of the yoke 14 is closed, and supports the magnetostrictive element 11 movably. The yoke 14 accommodates the magnetostrictive element 11 in a cylinder and fixes one end 11 a of the magnetostrictive element 11. The bias magnetic field generating magnet 15 is provided substantially at the center of the yoke 14 so as to cover the outer wall of the yoke 14. The first magnetic field generating coil 16 is wound along the inner wall of the yoke 14 without contacting the magnetostrictive element 11. The voice coil bobbin 21 is interposed between one end 11 b of the magnetostrictive element 11 and the opening of the yoke 14 and penetrates substantially the center of the damper 12. The movable coil 20 is wound around the outer wall of the voice coil bobbin 21 disposed in the gap 19 on the opening side of the yoke 14. The conical frame 17 is fixed so as to cover the outer wall on one end side of the yoke 14 along the circumferential direction. The diaphragm 18 for low-frequency reproduction is fixed so as to cover the outer wall on one end side of the voice coil bobbin 21 along the circumferential direction, and the peripheral part near the edge part 18 a is fixed to the peripheral part of the frame 17. Form a cone. The diaphragm 22 for high-frequency reproduction has a conical shape fixed to the end 11 b of the magnetostrictive element 11.
[0039]
Reproduction of sound in the low or high range in such a configuration is performed by the following method.
[0040]
First, a method for reproducing low-frequency sound will be described. As shown in FIGS. 3A and 3B, a magnetic field is formed by the yoke 14 at the position of the movable coil 20 (see reference numeral s30 in the magnetic circuit shown in FIG. 3B). When a voice current flows through the coil 20, an electromagnetic force acts on the voice coil bobbin 21 to vibrate the voice coil bobbin 21 in the left-right direction toward the paper surface. The vibration of the voice coil bobbin 21 is transmitted to the diaphragm 18 for low-frequency reproduction, and a low-frequency sound wave is emitted from the diaphragm 18. That is, this is a sound reproduction method similar to that of the electrodynamic speaker.
[0041]
Next, a method for reproducing high-frequency sounds will be described, which is substantially the same as the method described in the first embodiment. That is, when a high-frequency audio current flows through the magnetic field generating coil 16, a change in the magnetic field occurs in the axial direction of the magnetostrictive element 11, and the magnetostrictive element 11 expands and contracts (vibrates) in the axial direction X. This vibration by the magnetostrictive element 11 is transmitted to the diaphragm 22 for high-frequency reproduction, and a high-frequency sound wave is emitted from the diaphragm 22.
[0042]
However, the speaker device 200 according to the second embodiment differs from the speaker device 100 according to the first embodiment in that one end 11a of the magnetostrictive element 11 is fixed to the yoke 14, and therefore, the speaker according to the first embodiment is different. Compared with the device 100, the amplitude of the vibration of the magnetostrictive element 11 is approximately doubled. Therefore, the speaker device 200 according to the second embodiment can reproduce higher frequency sounds.
[0043]
As described above, the speaker device 200 according to the second embodiment enables the low-frequency reproduction by applying the principle of the electrodynamic loudspeaker to the speaker device using the magnetostrictive element suitable for high-frequency reproduction. Therefore, it is possible to reproduce the audio signal over a wide band from a low band to a high band. Therefore, it is possible to provide an extended tweeter in a low frequency range.
[0044]
Next, various examples of electronic circuits that can be applied to the speaker device 200 according to the second embodiment are shown in FIGS.
[0045]
First, in FIG. 4A, a closed circuit C2 for driving the diaphragm 22 (tweeter) for high-frequency reproduction and a closed circuit C3 for driving the diaphragm 18 (woofer) for low-frequency reproduction are connected in parallel. The illustrated electronic circuit C100 is shown.
[0046]
In the closed circuit C2 shown in FIG. 4A, a closed circuit is configured by connecting the magnetic field generating coil 16 for driving the diaphragm 22 for high-frequency reproduction and the high-pass filter Hf in series. Therefore, when a voice current is applied to the input terminal S1, the high-pass filter Hf cuts the low-frequency component voice current in the closed circuit C2 and supplies a constant high-frequency component voice current to the magnetic field generating coil 16 side. . When a constant high-frequency audio current flows through the magnetic field generating coil 16, the magnetostrictive element 11 expands and contracts (vibrates) in the axial direction of the speaker device 200, and vibrates the diaphragm 22 for high-frequency reproduction. Therefore, the high-frequency sound is reproduced through the high-frequency reproduction diaphragm 22 by the closed circuit C2.
[0047]
On the other hand, in a closed circuit C3 shown in FIG. 4A, a closed circuit is configured by connecting a movable coil 20 for driving the diaphragm 18 for low-frequency reproduction and a low-pass filter Lf in series. For this reason, when a voice current is applied to the input terminal S1, the low-pass filter Lf cuts the high-frequency component voice current in the closed circuit C3 and supplies a constant low-frequency component voice current to the movable coil 20. When a constant low-frequency audio current flows through the movable coil 20, the voice coil bobbin 21 is displaced, and the diaphragm 18 for low-frequency reproduction vibrates. Therefore, the low-frequency sound is reproduced through the low-frequency reproduction diaphragm 18 by the closed circuit C3.
[0048]
As described above, by applying the electronic circuit C100 shown in FIG. 4A to the speaker device 200, it is possible to reproduce sound in a wide band from a low band to a high band.
[0049]
Next, FIG. 4B shows an electronic circuit C200 in which a closed circuit C5 for driving the diaphragm 22 for high-frequency reproduction and a closed circuit C6 for driving the diaphragm 18 for low-frequency reproduction are connected in parallel. Is shown.
[0050]
Unlike the closed circuit C2 shown in FIG. 4A, the closed circuit C5 shown in FIG. 4B does not include the high-pass filter Hf. Therefore, in the closed circuit C5, when a sound current including a low-frequency component and a high-frequency component is applied to the input terminal S1, the sound current flows through the magnetic field generating coil 16. However, since the magnetostrictive element 11 has a property that the oscillation speed is small depending on the change in the magnetic field corresponding to the audio current of the low frequency component, the magnetostrictive element 11 oscillates at a large oscillation speed only by the change of the magnetic field corresponding to the audio current of the high frequency component. become. Therefore, only the high-frequency audio signal is reproduced through the high-frequency reproduction diaphragm 22 by the closed circuit C5.
[0051]
Further, unlike the closed circuit C3 shown in FIG. 4A, the closed circuit C6 shown in FIG. 4B does not include the low-pass filter Lf. However, in the closed circuit C6, when the audio current of the low frequency component is applied to the input terminal S1, the audio current flows through the movable coil 20, and the voice coil bobbin 21 vibrates in the axial direction of the speaker device 200. Thereby, the diaphragm 18 for low-frequency reproduction is vibrated. Therefore, the low-frequency audio signal is reproduced through the low-frequency reproduction diaphragm 18 by the closed circuit C6.
[0052]
As described above, when the electronic circuit C200 shown in FIG. 4B is applied to the speaker device 200, the reproduction of the audio signal over a wide band from the low band to the high band without providing the high-pass filter Hf or the low-pass filter Lf. Is performed.
[0053]
FIG. 4C shows an electronic circuit C300 in which the magnetic field generating coil 16 for driving the diaphragm 22 for high-frequency reproduction and the movable coil 20 for driving the diaphragm 18 for low-frequency reproduction are connected in series. .
[0054]
In the electronic circuit C300 shown in FIG. 4C, when a sound current including a low frequency component and a high frequency component is applied to the input terminal S1, the sound current flows to the magnetic field generating coil 16 and the movable coil 20. As a result, the magnetostrictive element 11 vibrates at a large vibration speed only by a change in the magnetic field corresponding to the audio current of the high frequency component, and reproduces high-frequency sound through the high-frequency reproduction diaphragm 22. On the other hand, when a voice current of a low-frequency component flows through the movable coil 20, the voice coil bobbin 21 vibrates in the axial direction of the speaker device 200. Thus, low-frequency sound is reproduced through the low-frequency reproduction diaphragm 18.
[0055]
Therefore, when the electronic circuit C300 shown in FIG. 4C is applied to the speaker device 200, the low-pass filter Hf and the low-pass filter Lf are not provided similarly to the electronic circuit C200 shown in FIG. The sound can be reproduced over a wide band from to high frequencies.
[0056]
[Third embodiment]
The speaker device 300 according to the third embodiment is configured such that the magnetic field generating coil 16 and the movable coil 20 in the speaker device 200 according to the second embodiment described above are configured by one coil.
[0057]
FIG. 5 shows a cross-sectional view of the speaker device 300 along the axial direction. The configuration of the speaker device 300 is almost the same as the configuration of the speaker device 200 according to the second embodiment described above. For this reason, only the configuration different from that of the speaker device 200 according to the second embodiment will be described. In the illustrated speaker device 300, the same components as those of the speaker device 200 according to the second embodiment are denoted by the same reference numerals.
[0058]
As shown in FIG. 5, the speaker device 300 of this embodiment uses a long voice coil bobbin 121 extending from the vicinity of the damper 12 to the vicinity of one end 11a of the magnetostrictive element 11, and the coil 120 is wound around the outer wall of the voice coil bobbin 121. . This coil 120 has both functions of the magnetic field generating coil 16 and the movable coil 20 in the second embodiment.
[0059]
In the speaker device 300 having such a configuration, when an audio current of a low-frequency component flows through the coil 120, the voice coil bobbin 121 vibrates in the axial direction X of the speaker device 300 due to the principle of electromagnetic action. Then, this vibration is transmitted to the diaphragm 18 for low-frequency reproduction, and a low-frequency sound wave is emitted from the diaphragm 18. At this time, a change in the magnetic field also occurs in the magnetostrictive element 11, but the vibration speed of the magnetostrictive element 11 is small depending on the change in the magnetic field corresponding to the audio current of the low frequency component. On the other hand, when an audio current of a high-frequency component flows through the magnetic field generating coil 120, a change in the magnetic field occurs in the axial direction X of the magnetostrictive element 11, causing the magnetostrictive element 11 to expand and contract (vibrate) in the axial direction X. Then, the vibration by the magnetostrictive element 11 is transmitted to the diaphragm 22 for high-frequency reproduction, and high-frequency sound waves are emitted from the diaphragm 22.
[0060]
As described above, the speaker device 300 according to the third embodiment can reproduce sound over a wide band from a low band to a high band using one coil.
[0061]
[Modification]
In the first to third embodiments, the bias magnetic field generating magnets 5 and 15 are provided to generate a magnetic field in the speaker devices 100, 200 and 300. However, instead of or in addition to this, a conductive wire is wound. A coil may be provided and a magnetic field may be generated by passing a current through the conductor. Further, an audio current may be superimposed on the current on the coil.
[Brief description of the drawings]
FIG. 1 is a sectional view taken along an axial direction of a speaker device according to a first embodiment of the present invention.
FIG. 2 shows a displacement state of each magnetostrictive element when one end of the magnetostrictive element is fixed and when both ends are not fixed.
FIG. 3 shows a sectional view of a speaker device according to a second embodiment of the present invention along an axial direction and a sectional view of a magnetic circuit portion.
FIG. 4 shows various examples of an electronic circuit applicable to the speaker device according to the second embodiment of the present invention.
FIG. 5 is a sectional view taken along an axial direction of a speaker device according to a third embodiment of the present invention.
[Explanation of symbols]
1,11 magnetostrictive element
4, 14 York
5, 15 Bias magnetic field generating magnet
6, 16 magnetic field generating coil
7, 17 frames
8, 18, 22 diaphragm
9, 19 void
20 Moving coil
21, 121 Voice coil bobbin
100, 200, 300 speaker device

Claims

A magnetostrictive element,
A magnetic field generating coil for generating a magnetic field in the direction of expansion and contraction of the magnetostrictive element,
A support member for movably supporting both ends of the magnetostrictive element,
A magnetic circuit for applying DC magnetic fields of different polarities to both ends of the magnetostrictive element,
A diaphragm fixed to one end of the magnetostrictive element.

A non-magnetic material is provided at the both ends of the magnetostrictive element,
The magnetostrictive speaker device according to claim 1, wherein the magnetostrictive element is supported by the support member via the nonmagnetic material, and the diaphragm is fixed to one of the nonmagnetic materials. .

A magnetostrictive element,
A magnetic field generating coil for generating a magnetic field in the direction of expansion and contraction of the magnetostrictive element,
A magnetic circuit that fixes one end of the magnetostrictive element and has a gap on the other end side of the magnetostrictive element, and applies a DC magnetic field of a different polarity to both ends of the magnetostrictive element,
A support member for movably supporting the other end of the magnetostrictive element,
A coil bobbin arranged in the gap,
A movable coil wound around the coil bobbin;
A low-frequency diaphragm fixed to the coil bobbin,
A high-frequency diaphragm fixed to the other end of the magnetostrictive element.

The magnetostrictive speaker device according to claim 3, wherein the magnetic field generating coil and the movable coil are the same coil.

An input circuit formed by connecting the magnetic field generating coil and the movable coil in parallel, the input circuit comprising: a high-pass filter that supplies a high-frequency component of an input audio signal to the magnetic field generating coil; The magnetostrictive speaker device according to claim 3, further comprising: a low-pass filter that supplies the low-frequency component to the movable coil.

4. The input circuit according to claim 3, further comprising an input circuit formed by connecting the magnetic field generating coil and the movable coil in parallel, wherein the input audio signal is input to the magnetic field generating coil and the movable coil in parallel. Magnetostrictive speaker device.

4. The input circuit according to claim 3, further comprising an input circuit formed by connecting the magnetic field generating coil and the movable coil in series, wherein the input audio signal is input to the magnetic field generating coil and the movable coil in series. Magnetostrictive speaker device.

The magnetostrictive speaker device according to any one of claims 1 to 6, wherein the magnetic field generating coil is fixed to the magnetic circuit without contacting the magnetostrictive element.

The magnetostrictive speaker device according to any one of claims 1 to 7, wherein the magnetostrictive element includes a giant magnetostrictive element.

9. The magnetostrictive speaker device according to claim 1, wherein the support member supports the magnetostrictive element movably in a direction in which the magnetostrictive element expands and contracts. 10.

The magnetostrictive speaker device according to any one of claims 1 to 9, wherein the magnetic circuit includes a magnetic field generating means and a yoke magnetized according to a magnetic field generated by the magnetic field generating means.

The magnetostrictive speaker device according to claim 10, wherein the magnetic field generating means is a coil around which a magnet and / or a conductive wire is wound.