JP3583262B2 - Electromagnetic sound transducer - Google Patents

Description

となる。
但し、ｋ_ｔ ＝ｋβｎ^２ Ａ_ｍ ^２／Ｚｃ^２
【００４８】
ここでＳ_１ は音声波形の時間変化信号に一定値をバイアスとして加えた形、すなわち
【００４９】
Ｓ_１ ＝α＋Ｖ（ｔ） ・・・（２）
【００５０】
なので
Ｆ＝ｋ_ｔ ・（α^２ ＋２αＶ（ｔ）＋Ｖ^２ ）（１／２）（１−ｃｏｓ４πｆ_ｓ ｔ）
となる。
【００５１】
ここでバイアスαを音声波形の大きさに比べて相当（１０倍以上）に大きくすれば、上式は次式（３）のように近似できる。
【００５２】

【００５３】
この式（３）で、第１項は直流反発力成分、第２項は音声波形ｖ（ｔ）による加振力成分、第３、第４項は周波数２ｆｓ［Ｈｚ］の振動加振力成分である。
次に振動板、弾性支持手段で形成される振動系において動く部分の質量をＭ、ばね定数をκ、機械抵抗をｒとすると機械インピーダンスＺ_ｍ は、角速度ω（＝２πｆ）として、Ｚ_ｍ ＝ｊωＭ＋Ｋ／ｊω＋Ｒである。ここで
【００５４】
ωＭ＝Ｋ／ω
となる共振周波数ｆ_０ を低音域の低い周波数例えば５０〜３００Ｈｚになるよう、振動板１０の質量及び弾性支持手段２０ａ、２０ｂのばね特性を選ぶ。
【００５５】
また前記の交番電圧の周波数ｆ_ｓ をｆ_０ に比して高く例えば５ｋ〜５０ｋＨｚに選ぶならば、式（５）の第３、第４項の振動加振力による振動は振動系の慣性抵抗によって−３０ｄＢ程度以下に小さく押さえられる。
【００５６】
このことの理解を深めるために図５を示す。この図は振動板１０の振動系機械インピーダンスＺｍの１事例について、振動周波数ｆを横軸にして描いたものである。図中に追記したｆ_０ が振動系の共振周波数、ｆ_ｓ が加振力の周波数の一例である交番電圧信号周波数、帯域Ａとあるのはこの発明のスピーカが再生する音声帯域である。
【００５７】
交番電圧信号ａ（ｔ）に基づく加振力に対するインピーダンス（Ｚ_２ｆｓ で図示）は音声再生帯域のインピーダンスＺ_ｓ に比べて非常に大きいことが分かる。従って振動板１０は音声信号ｖ（ｔ）にしたがった加振力を支配的な力として受けて振動し、音声再生音を放射することになる。
【００５８】
繰り返して説明するならば、この発明の基本的な特長は３つ有り、１つ目は、式（１）の示す電磁力の成分の中で非磁性、導電材の場合に支配的となる反発力を利用すること。２つ目は、式（３）に示されたように一定値αでバイアスされた音声信号ｖ（ｔ）を交番電圧信号ａ（ｔ）の変調信号とすること。３つ目は、振動板振動共振周波数に対して交番電圧信号ａ（ｔ）の周波数ｆ_ｓ を十分に大きくとって交番電磁力による振動放射音を極力抑制することである。
【００５９】
ここで、上記の電磁音響変換装置の構成要素の材質及びサイズ等を、図６を参照して具体的に説明する。但し、音声再生周波数帯域が１００〜７ｋＨｚであることを前提条件とする。
【００６０】
振動板１０にはアルミニウム金属円板を用いる。アルミニウムは導電率が高く、非磁性であるとともに、他の高導電金属に比較して比重が小さい。従って電磁反発力も得やすくかつ振動板１０の機械インピーダンスも小さいものが設計でき、スピーカとしての総合能率を高くすることができる。
【００６１】
また、振動板１０として必要な厚さは、スキンデプスの評価式（δ＝ＳＱＲＴ（２ρ／ωμ））から決定する。励磁周波数（交番電圧信号ａ（ｔ）の周波数）２０ｋＨｚのときのアルミニウムのスキンデプスδは約０．６ｍｍである。
従って、電話音声帯域を再生帯域とする場合は振動板の厚さは０．５〜２ｍｍとするのが望ましい。これより薄い板とすると、電磁力が減少する反面、ジュール発熱が増加する。なお、銅板の場合は、固有抵抗ρがアルミニウムより４０％ほど低いので、最適な板厚は０．４〜１．６ｍｍである。
【００６２】
弾性支持手段２０は、振動板１０の周縁部をリング状の数ｍｍ厚の高密度グラスウールで挟み込んだ構造とする。グラスウールは、ばね性と適度なダンピング特性を与え、耐熱性も有る。空隙Ｇは１〜２ｍｍ程度とする。空隙Ｇは狭いほど電磁力発生効率（単位アンペアターン当たりの電磁力）が良くなるが、振動板１０の振動ストロークが狭くなること及び、電磁力の空隙依存性が大きくなり、因って、再生音に非線型歪みが発生しやすくなる。前記した空隙長とするのは、最大ストローク長を１ｍｍ程度のスピーカとするためである。
【００６３】
次に、加振コイル３０は、励磁周波数に応じて、できるだけ細い（０．４ｍｍ程度以下）絶縁電線を撚り合わせたいわゆるリッツ線とするのが望ましい。これはコイルでの渦電流や、環流損失を抑制し、スピーカとしての総合能率を向上するためである。
【００６４】
磁極４０は、励磁電流が比較的高い（２０ｋＨｚ）ので、加振コイル３０と同じく渦電流の流れにくい材料、ここでは磁性粉体成形材料例えばフェライトで形成する。但し、磁極４０はこの発明のスピーカにおいて必ずしも必要なものではない。例えば、図６に示すように磁極４０は設けないで、基板５０ｃを高抵抗磁性材料としても良い。その代わり何らかのコイル支持手段を設ける。
【００６５】
枠体５０は、スチールやプラスティックなどの材料で、板金、成形などによって作る。枠体５０は弾性支持手段２０ａ、２０ｂ、および加振コイル３０を支持固定することにより、振動板１０と加振コイル３０の間の空隙を所定の長さに確保する役目を担う。また振動板１０、支持手段２０を合わせて、密閉に近い空間を確保し、振動板１０の背面からの放射音波を外部に出さないようにすることも枠体５０の役目である。但し、枠体５０に一部開放部を設け、バスレフ方式のスピーカとすることもできる。
【００６６】
交番電圧信号ａ（ｔ）の周波数の選択は、この発明のスピーカにとって最も重要な課題である。何故なら、電磁力の大きさ、それによって引き起こされる振動加振力の大きさ、電磁力発生効率、加振コイル３０の電気的インピーダンス、電子回路（特にパワートランジスタ）、放射周波数の聴感特性との係わりなどスピーカ性能に大きく係わるからでる。
【００６７】
２０ｋＨｚを交番電圧信号ａ（ｔ）の周波数に選ぶと、この信号ａ（ｔ）だけの場合は４０ｋＨｚの電磁加振力となる。この４０ｋＨｚは普通、人間の聞こえる限界周波数を大きく超える。また振動板１０の質量による慣性力により、高い周波数では、振動板１０は振動し難くなる。
【００６８】
周波数を高くし過ぎると、加振コイル３０や増幅回路のジュール損失が増えて、効率を悪くすることや、空中に不要輻射の電波を放出する割合が大きくなったりする。また、交番電圧発生手段７１は、オーディオ機器などで常用される、演算増幅用半導体集積回路、抵抗、コンデンサで構成されるＲＣ発振回路であって良い。加算手段７４、乗算手段７５も同様にて構成される。
【００６９】
電力増幅手段７３には、ターンオフ時間の短いパワートランジスタを用いる。但し、電力増幅手段７３の負荷である加振コイル３０はほとんどがリアクタンス成分であるところの高いインピーダンスを有する。従って、加振コイル３０に所定のアンペアターン：数１００ＡＴを供給するためには、高電圧の出力となることに留意が必要である。
【００７０】
上述のような材質及びサイズ等とすることにより、スピーカ本体６０の肉厚を５〜２０ｍｍ程度の薄型とすることができ、また１００℃を越える高温環境でも動作不能となることがない堅牢なスピーカとすることができる。
【００７１】
以上のように、この実施の形態１によれば、導電、非磁性の振動板１０、振動板１０と空隙Ｇを挟んで対向配置された加振コイル３０、振動板１０を支える弾性支持手段２０ａ、２０ｂ、弾性支持手段２０ａ、２０ｂと加振コイル３０を所定の配置で固定支持する枠体５０で構成されたスピーカ本体６０、一定の周波数の交番電圧信号ａ（ｔ）を発生する交番電圧発生手段７１、電気信号ｖ（ｔ）に予め変換された音声あるいは騒音信号に一定値のバイアス信号αを加えた信号ｓ_１ で、交番電圧信号ａ（ｔ）を変調し、この変調信号を出力する変調手段７２、変調手段７２の出力信号を電力増幅する電力増幅手段７３で構成される励磁装置７０から成り、励磁装置７０の出力電流をスピーカ本体６０の加振コイル３０に供給し、かかる加振コイル３０に流れる励磁電流と振動板１０に誘起される渦電流の間に働く電磁反発力によって変調信号ｅｓ（ｔ）に応じた振動加振力を得、かかる振動加振力によって音声あるいは騒音信号ｖ（ｔ）の再生音を放射するようにしたので、平板形状の振動板１０に直接振動力を生み出し、音声や、騒音信号を再生できる薄型の電磁音響変換装置とすることができ、また、剛性のある且つ温度などの使用環境適合性の高い材料で構成され、有機接着剤を使うことがないので、高温環境においても使用できる電磁音響変換装置とすることができる効果が得られる。
【００７２】
実施の形態２．
図７はこの発明の実施の形態２による電磁音響変換装置におけるスピーカ本体の構造断面図である。この図７において図２の各部に対応する部分には同一符号を付す。図７において、１５は振動板１０の一部分に磁極４０と対向する位置に固着された磁性材料による磁性板、３４は磁性板１５に対向する位置に加振コイル３０と並べて設けられた永久磁石手段である。
【００７３】
次に動作について説明する。
振動板１０には、式（３）の第１項に相当する直流的反発力が作用している。この力は、弾性支持手段２０に常時一定の応力をかけていることになるので、ばね効果の上下（図において）非対象性が現れやすくなり、よって放射音も歪んだものとなる可能性がある。
【００７４】
この実施の形態２は、その点を改良することを考えたものであり、磁性板１５と永久磁石手段３４との間に作用する磁気吸引力によって振動板１０に下向き（加振コイル３０向き）の力を加える。磁気吸引力は、磁性板１５と永久磁石手段３４の間にできる空隙長さや、磁性板１５の材料（比透磁率）を選択することにより調整でき、前記した直流的反発力と同程度の大きさとする。
【００７５】
このように調整することによって、スピーカとして動作中、振動板１０には、吸引力、反発力が拮抗して、直流的反発力がほとんどかからず、非線形振動による音質劣化が抑制される。
【００７６】
なお、加振コイル３０の発生する交番磁束が磁性板１５に鎖交するとその磁界による交番吸引力や渦電流による発熱が起こるので、できるだけ鎖交しないよう配置を工夫する必要がある。特に発熱は問題が大きい。但し、磁性板１５を磁性粉体成形やレジン含侵材料で作れば発熱は起こらない。
【００７７】
以上のように、この実施の形態２によれば、磁性板１５と永久磁石手段３４との間に作用する磁気吸引力によって振動板１０に加振コイル３０向きの力を加えるようにしたので、スピーカとして動作中、振動板１０に、吸引力、反発力が拮抗して、直流的反発力がほとんどかからず、非線形振動による音質劣化を抑制できる効果が得られる。
【００７８】
実施の形態３．
図８はこの発明の実施の形態３による電磁音響変換装置におけるスピーカ本体の構造断面図である。この図８において図７の各部に対応する部分には同一符号を付す。図８において、１２は振動板１０に埋め込まれるあるいは貼り合わされた実施の形態５〜８で詳細に説明する非磁性金属板、３５は図７に示した永久磁石手段３４に代えて設けられた加振コイル（第２加振コイル）、３６は永久磁石手段３４に代えて設けられ、加振コイル３５の横に配置された磁極、５０ａは枠体（第２枠体）、６０ａはスピーカ本体（第２スピーカ本体）である。
【００７９】
また、図９はこの発明の実施の形態３による電磁音響変換装置における励磁装置の回路構成図である。図９において、７０ａは励磁装置（第２励磁装置）、７２ａは変調手段（第２変調手段）、７９は音声信号ｖ（ｔ）の位相を１８０度反転する反転手段、８０は変調信号のバイアスとして用いるバイアス値αと反転された音声信号−ｖ（ｔ）を加算する加算手段、７７は加算手段８０の出力信号を既定値Ｃ倍する乗算手段、７８は乗算手段７７の出力信号で交番電圧信号ａ（ｔ）を変調する乗算手段、７３ａは乗算手段７８から出力される変調信号（第２変調信号）を電力増幅して加振コイル３５に励磁電流ｅ_ｒ （ｔ）を供給するための電力増幅手段（第２電力増幅手段）である。なお、加算手段７４、乗算手段７５、電力増幅手段７３、交番電圧発生手段７１は図３と同構成である。
【００８０】
次に動作について説明する。
上記実施の形態１及び２は、振動板１０の加振力に反発電磁力のみを利用したものであったが、この実施の形態３では、反発電磁力に加えて磁気吸引力（磁性体の表面に作用する磁気圧力）をも利用しようとするものである。このことにより振動板を加振する力は２倍にでき、放射音の音圧レベルを高めることができる。
【００８１】
音声信号ｖ（ｔ）を加算手段７４で一定値バイアスの後、乗算手段７５で交番電圧信号ａ（ｔ）を変調して加振コイル３０に励磁電流を流し、電磁反発力を得るための励磁系統にもう一つの励磁系統を加える。
【００８２】
すなわち、音声信号ｖ（ｔ）を反転手段７９で位相反転（デジタル数値の場合は符号反転）し、この反転音声信号−ｖ（ｔ）に加算手段８０でバイアス値αを加算し、更に乗算手段７７により既定値Ｃでスケーリングした後、交番電圧信号ａ（ｔ）を変調し、電力増幅７３ａで増幅した後、その出力ｅ_ｒ （ｔ）を、磁気吸引力を得るための加振コイル３５に供給する。
【００８３】
この追加された励磁系統は式（１）の電磁力表現式において、磁性体表面であること、従って透磁率μが大きいこと及び法線成分が多いことにより、第１項（Ｈ_ｓ ・ｎ）Ｈ_ｓ が第２項に比べて圧倒的に大きい。
【００８４】
従って、磁性板１５に働く電磁力は、∫Σμ_ｒ ・μ_０ （Ｈ_ｓ ・ｎ）Ｈ_ｓ として計算できる。Ｈ_ｓ は加振コイル３５に流れる励磁電流ｉ_ｒ と、加振コイルターン数ｎ_ｒ の積であるアンペアターンで作り出され、結局、吸引力は加振コイルアンペアターンの自乗に比例した形で表現できる。
【００８５】
そこで、加振コイル３５に供給する電流ｉ_ｒ は、加振コイル３５の電気的インピーダンスをＺ_ｒ とすると

但し、γは増幅手段の増幅率、Ｃは乗算手段７７の乗算係数、
ｓ_２ ＝−ｖ（ｔ）＋α
そこで吸引電磁力Ｆ_ｒ は、比例係数をｋ_ｒ とすると

ここでｓ_２ ＝α−Ｖ（ｔ）であるから、
【００８６】

となる。
【００８７】
この式（４）によっても、電磁力は、直流吸引力成分、音声波形による加振力成分、周波数ｆ_ｓ の２倍の振動加振力成分から成り立っていることが分かる。
【００８８】
ここで、式（３）のｋ_ｔ を参照して、ｋ_ｔｒ＝ｋｔとなるようγやＣを選ぶこととすると、振動板１０に加わる電磁力の合力は

となり、直流反発力と吸引力が相殺して消滅し、音声信号成分の振動加振力と、音声波形で変調された交番電圧信号の２倍の周波数成分の交番電磁力のみとなる。
【００８９】
すでに説明しているように、後者の成分については、振動板１０の慣性質量の影響と、人間の聴覚限界から、再生音への影響は小さいので、式（５）は実質的には、音声信号による振動加振力だけと考える事ができる。
【００９０】
但し、加振コイル３０に流れる励磁電流と加振コイル３５に流れる励磁電流とは、一般的には位相が異なっており、従って電磁力のうち、交番電圧周波数の２倍の振動加振力も位相が異なっている。
【００９１】
このことを考慮すると、式（５）の第２項は補正されなければならないが、この発明の原理上では問題とならない。
【００９２】
更に、この実施の形態３によれば、Ｖ（ｔ）のレベルに対する制約条件は｜Ｖ（ｔ）｜≦αだけであり、極端には交番電圧信号ａ（ｔ）の振幅の半分まで取り得る。従って、加振力発生能率は実施の形態１の構成に比べ格段に向上する。
【００９３】
但し、この実施の形態３においては、反発力と吸引力の作用する場所が異なるため、振動板１０の剛性が小さい場合は、強制変形や変形振動を起こす欠点がある。これに対しては、図１０に示すように、振動板１０の両面あるいは片面において反発力と吸引力のそれぞれ力点を結びさらにその力点を延長した範囲に補強リブ１６を付けることで改善する。
【００９４】
また、図１１に示すように、従来コーン型スピーカで採用されているハネカム構造のハネカム振動板１０ａをアルミなどの導電性の高い金属で作り、そこに、アルミのドーナツリングと極薄の珪素鋼板で作成した磁性板１５を貼り合わせる構造としても良い。
【００９５】
以上のように、この実施の形態３によれば、電力増幅手段７３の出力電流を加振コイル３０に供給し、かかる加振コイル３０に流れる励磁電流と振動板１０に誘起される渦電流との間に働く電磁反発力によって変調信号に応じた振動加振力と直流的反発力を得、電力増幅手段７３ａの出力電流を加振コイル３５に供給し、かかる加振コイル３５と磁性板１５との間に働く磁気吸引力によって変調信号に応じた振動加振力と直流的吸引力を得、直流的反発力と直流的吸引力は互いに相殺し、振動加振力は合力として振動板１０に作用し、よって音声あるいは騒音信号の再生音を発生するようにしたので、弾性支持手段２０の静的な変位がなく、より非線形歪みの小さい、及び振動加振力が増大し、より再生音圧の高いスピーカとすることができる効果が得られる。
【００９６】
実施の形態４．
図１２はこの発明の実施の形態４による電磁音響変換装置におけるスピーカ本体の構造断面図である。この図１２において図６の各部に対応する部分には同一符号を付す。図１２（ａ）において、３０ａ，３０ｂは振動板１０を挟み同じ長さの空隙を有して対向配置された加振コイル（第３及び第４加振コイル）、４０ａ，４０ｂは加振コイル３０ａ，３０ｂを枠体（第３枠体）５０ｂに固定する支持体、６０ｂはスピーカ本体（第３スピーカ本体）である。但し、支持体４０ｂについては、図１２（ｂ）に外観を示すように、音の放射孔を確保できるような構造（例えば梁構造など）とすることが要件となる。
【００９７】
図１３はこの発明の実施の形態４による電磁音響変換装置における励磁装置の回路構成図である。図１３において、７０ｂは励磁装置（第３励磁装置）、７１は交番電圧信号発生手段、７２ｂは変調手段（第３変調手段）である。
【００９８】
次に動作について説明する。
この実施の形態４の特徴は変調手段７２ｂにある。この変調手段７２ｂは音声信号ｖ（ｔ）を２系統の回路に入力する。一方は一定値αを加算手段７４によって加算し、交番電圧信号ａ（ｔ）を乗算手段７５によって乗算（変調）し、この変調信号を電力増幅手段７３に出力する。
【００９９】
他方は、位相反転手段７９で位相を反転（デジタル数値信号の場合は符号反転）し、一定値αと加算手段８０で加算し、交番電圧信号ａ（ｔ）を乗算手段７８によって乗算（変調）し、この変調信号（第３変調信号）を電力増幅手段７３ａに出力する。
【０１００】
電力増幅手段７３，７３ａは、出力である励磁電流を、それぞれスピーカ本体６０ｂの加振コイル３０ａ，３０ｂにコネクタ６１ａ，６１ｂ、リード線３１ａ，３１ｂを経由して供給する。このようなスピーカ本体６０ｂの構成を、励磁方式としたことにより、振動板１０の受ける加振力は、以下のようになる。
【０１０１】
加振コイル３０ａによって発生する電磁反発力は、
Ｆ_ａ ＝ｋ_ｔ ・（α^２ ＋２αＶ（ｔ）＋Ｖ^２ ）（１／２）（１−ｃｏｓ４πｆ_ｓ ｔ）
一方、加振コイル３０ｂによって発生する電磁反発力は、力の方向が前者に対して逆であることを考慮して、
Ｆ_ｂ ＝−ｋ_ｔ ・（α^２ −２αＶ（ｔ）＋Ｖ^２ ）（１／２）（１−ｃｏｓ４πｆ_ｓ ｔ）
である。
【０１０２】
よって、振動板１０の受ける加振力は

【０１０３】
この式は前項の実施の形態における合成力を表す式（５）と同じ表現である。従って、直流電磁力は存在しない。また、この実施の形態４によれば、電磁力の空隙依存性が両側にある空隙が互いに非線形特性を補って、線形特性に近づけるので、放射音の非線形歪みは小さい。
【０１０４】
また、打ち消し合うように働く電磁反発力の振動板１０上の力点の位置は同一の個所（表裏は異なる）なので、直流反発力による振動板の変形は起こり難いし、交番電磁力による変形振動の発生も小さい。従って、振動板１０にことさら剛性をたかめるためのリブ補強は必要でない。
【０１０５】
更に、加振コイル３０ａ，３０ｂが音放射面側にも必要となる欠点があるが、振動板１０の設計尤度や励磁装置７０励磁回路の調整が容易であるなどの利点に加え、音質の良いスピーカが得られる利点がある。
【０１０６】
以上のように、この実施の形態４によれば、第１電力増幅手段７３の出力電流を第１加振コイル３０ａに供給し、この加振コイル３０ａに流れる励磁電流と振動板１０に誘起される渦電流の間に働く電磁反発力によって変調信号に応じた振動加振力と直流的反発力を得、第２電力増幅手段７３ａの出力電流を第２加振コイル３０ｂに供給し、この加振コイル３０ｂに流れる励磁電流と振動板に誘起される渦電流の間に働く電磁反発力によって変調信号に応じた振動加振力と直流的反発力を得、直流反発力は両者の作用方向が逆のために相殺し、一方、振動加振力は合力として振動板１０に作用することによって、音声あるいは騒音信号の再生音を発生するようにしたので、弾性支持手段２０の静的な変位及び振動板１０の静的な変形がなく、より非線形歪みが小さく、振動加振力が増大し、より再生音圧の高いスピーカとすることができる効果が得られる。
【０１０７】
実施の形態５．
図１４はこの発明の実施の形態５による電磁音響変換装置における振動板の構造断面図であり、この図において、１０ａは板１１と非磁性金属板１２とで構成された振動板、１１は振動板１０ａを構成する、木材、樹脂積層材、樹脂成形材などの有機材による板、１２は板１１に埋め込まれるか、貼り合わされた高導電、非磁性の金属による環状の非磁性金属板である。但し、振動板１０ａは、実施の形態１，２，４で説明したスピーカ本体６０，６０ａ，６０ｂのいずれかの振動板１０として適用可能である。
【０１０８】
次に動作について説明する。
非磁性金属板１２を流れる渦電流に相当する環電流によって電磁反発力が発生し、有機材の板１１の部分を一緒に振動させ音声波を放射する。非磁性金属板１２は円形の加振コイル３０に対向する位置に来るように、その内径ｒ１と外径ｒ２を選ぶ。このような振動板１０ａとすれば、振動加振力はほとんど減らないで、慣性質量が小さくなるので、スピーカとしての能率が向上する。
【０１０９】
以上のように、この実施の形態５によれば、振動板１０ａを木材、樹脂積層あるいは成形材の一部分に環状の高導電、非磁性金属板１２を埋め込むか、貼り合わせた構造としたことで、振動板１０ａの完成質量を小さくでき、よって、スピーカとしての再生能率を、より高くすることができる効果が得られる。
【０１１０】
実施の形態６．
図１５はこの発明の実施の形態６による電磁音響変換装置における振動板及び加振コイルの構造図である。また、図１５の（ａ）は分解図、（ｂ）は断面図である。図１５において、１０ｂは円形板１１ｂに非磁性金属板１２ｂを組み合わせた振動板、１１ｂは木材、樹脂の積層あるいは成形による円形板、１２ｂは導電、非磁性の金属による矩形状の非磁性金属板である。この場合、加振コイル３０は例えば矩形状に巻回した構造とする。但し、振動板１０ｂは、実施の形態１，２，４で説明したスピーカ本体６０，６０ａ，６０ｂのいずれかの振動板１０として適用可能である。
【０１１１】
次に動作について説明する。
金属板１０ｂと加振コイル３０を同じ矩形状とすることにより電磁反発力の発生効率（振動板単位面積当たりの力）が高くなる。この実施の形態６の要点は、振動板１０ｂが受ける振動加振力は矩形状の金属板１２ｂの周辺部に位置するのに対し、振動板１０ｂ全体の弾性振動モードの基本パターンは円形状（太鼓モード）であることから、弾性振動が起こりにくい点にある。従って、再生音質の劣化が抑制される。
【０１１２】
以上のように、この実施の形態６によれば、振動板１０ｂを木材、樹脂積層あるいは成形材の円形板１１ｂの中央部に、矩形状の導電及び非磁性金属板１２ｂを埋め込む構造としたことで、振動板１０ｂの剛性を高めることなく、弾性振動を抑制し、混変調歪みの、より小さい再生音とすることができる効果が得られる。
【０１１３】
実施の形態７．
図１６はこの発明の実施の形態７による電磁音響変換装置における振動板及び加振コイルの構造図である。また、図１６の（ａ）は分解図、（ｂ）は断面図である。図１６において、１０ｃは矩形板１１ｃに非磁性金属板１２ｃを組み合わせた振動板、１１ｃは木材、樹脂の積層あるいは成形による矩形板、１２ｃは導電、非磁性の金属による円形状の非磁性金属板である。この場合、加振コイル３０は例えば円形状に巻回した構造とする。但し、振動板１０ｃは、実施の形態１，２，４で説明したスピーカ本体６０，６０ａ，６０ｂのいずれかの振動板１０として適用可能である。
【０１１４】
次に動作について説明する。
非磁性金属板１２ｃと加振コイル３０を同じ円形状とすることにより電磁反発力の発生効率（振動板単位面積当たりの力）が高くなる。この実施の形態７の要点は、振動板１０ｃが受ける振動加振力は円形状の金属板１２ｃの周辺部に位置するのに対し、振動板１０ｃ全体の弾性振動モードの基本パターンは直線状（波板モード）であることから、弾性振動が起こりにくい点にある。従って、再生音質の劣化が抑制される。
【０１１５】
以上のように、この実施の形態７によれば、振動板１０ｃを木材、樹脂積層あるいは成形材の矩形状の非磁性金属板１１ｃの中央部に、円形状の導電、非磁性金属板１２ｃを埋め込む構造としたことで、振動板１０ｃの剛性を高めることなく、弾性振動を抑制し、混変調歪みの、より小さい再生音とすることができる効果が得られる。
【０１１６】
実施の形態８．
図８はこの発明の実施の形態８による電磁音響変換装置におけるスピーカ本体の断面構造図であり、この図において、１０は実施の形態５〜７で説明した振動板１０ａ，１０ｂ，１０ｃのいずれかを用いた振動板、１５は振動板１０に埋め込まれ、あるいは貼り合わされた実施の形態２，３で説明した高抵抗磁性板である。
【０１１７】
図１７はこの発明の実施の形態８による電磁音響変換装置における励磁装置の回路構成図であり、この図において、７０ｃは励磁装置、７２ｃは変調手段、７７はバイアス値αを既定値Ｃ倍する乗算手段、７３ａは乗算手段７７の出力を電力増幅する電力増幅手段である。
【０１１８】
次に動作について説明する。
励磁装置７０ｃは電力増幅手段７３が加振コイル３０に音声信号ｖ（ｔ）で変調された交番電圧信号ａ（ｔ）に対応した電流を供給すると同時に、電力増幅手段７３ａが加振コイル３５にバイアス値αに相当した電流を供給する。これによって、振動板１０に固着された磁性板１５が、加振コイル３５と磁極３６で形成される電磁石によって磁気吸引力を受ける。
【０１１９】
吸引力の大きさは、励磁電流によって決まり、すなわち変調信号のバイアス値αに相当したものとなっている。振動板１０に働く直流反発力はやはりαに相当したものであるから、乗算係数に当たる係数Ｃを適当な値に選べば、吸引力と直流反発力は振動板１０において相殺される。
【０１２０】
以上のように、この実施の形態８によれば、振動板１０を木材、樹脂積層あるいは成形材の円形状板の、中央部に磁性金属小円形板を、周縁部に導電、非磁性金属環を埋め込む構造としたので、振動板１０の慣性質量がより小さくなり、よってスピーカとしての再生能率を、より向上することができる効果が得られる。
【０１２１】
また、吸引力と直流反発力が振動板１０において相殺されるようにしたので、非線形歪みの小さい再生音が得られ、また吸引力の調整は電気的に行なえるので簡単且つ確実である効果が得られる。
【０１２２】
実施の形態９．
図１８はこの発明の実施の形態９による電磁音響変換装置における弾性支持手段の構造断面図である。但し、図１８の（ａ）はコイルばね、（ｂ）は板ばねの場合を示している。図１８において、２０ｃは枠体５０にボルトどめや溶接によって固定された金属製のコイルばね（金属製スプリング材）により形成された弾性支持手段、２０ｄは枠体５０にボルトどめや溶接によって固定された金属製の板ばね（金属製スプリング材）により形成された弾性支持手段、１０はアルミニウム等の金属板による振動板である。
【０１２３】
次に動作について説明する。
弾性支持手段２０ｃ，２０ｄ及び振動板１０が金属製なので、スピーカを極低温から３００度摂氏程度までの広範な温度環境、例えば自動車排気管で使用することができる。
【０１２４】
以上のように、この実施の形態９によれば、弾性支持手段２０ｃ、２０ｄを、振動板１０の端部の複数個所に溶着あるいはネジどめ固定した金属製スプリング材で構成したので、より厳しい環境で使用できるスピーカとすることができる効果が得られる。
【０１２５】
実施の形態１０．
図１９はこの発明の実施の形態１０による電磁音響変換装置における振動板の構造断面図であり、図において、１０は振動板、１４は振動板１０に接着、溶着、あるいはしぼり出し加工で設けたリブ（骨）材である。但し、振動板１０が円形状の場合は、リブ材１４は直線形状が望ましい。
【０１２６】
次に動作について説明する。
振動板１０にリブ材１４が固定されているので、軸対象状で加わった振動電磁力に対して、振動板は弾性振動を起こしにくくなり、歪み波成分の音放射を抑制することができる。なお、振動板にリブを設けるようなことは、従来のコーン型スピーカなどでは不可能か可能であっても得策ではなかった。平板の振動板１０を電磁反発力を利用して振動させる上記構成によって、特段に歪み波成分の音放射を抑制することができる。
【０１２７】
以上のように、この実施の形態１０によれば、振動板１０の外側あるいは内側面にリブ材１４を設け、弾性振動に対する剛性を高めたことで、弾性振動に対する剛性を高め、よって歪みの小さい再生音とすることができる効果が得られる。
【０１２８】
実施の形態１１．
図２０はこの発明の実施の形態１１による電磁音響変換装置における弾性支持手段の構造断面図であり、図において、２０ｃはコイルばね、２０ｅはグラスウール材、２０はグラスウール材２０ｅにコイルばね２０ｃを埋め込んで形成された弾性支持手段である。
【０１２９】
次に動作について説明する。
この弾性支持手段２０は、コイルばね２０ｃによる適度なばね性とグラスウール材２０ｅによる適度な機械抵抗を有する弾性支持手段２０を用いたので、音声の再生帯域を狭くすることで、再生音圧を大きくすることができる。
【０１３０】
以上のように、この実施の形態１３によれば、弾性支持手段２０を、グラスウール材２０ｅにコイルばね材２０ｃを埋め込んだ構造としたので、弾性支持手段２０が適度な機械抵抗を有するので音声の再生帯域が狭くなり、再生音圧を大きくすることができ、これによって設計裕度すなわち、より広い適用範囲のスピーカとすることができる効果が得られる。
【０１３１】
実施の形態１２．
図２１はこの発明の実施の形態１２による電磁音響変換装置における弾性支持手段の構造断面図である。この図２１（ａ）及び（ｂ）において、１０は円板状の振動板、２０ｅ，２０ｇは振動板１０の中心よりに配置されると共に加振コイル３０の上方に配置され、数本（図示では２本）の梁部５３，５４で支えられて固定された弾性支持手段であるグラスウール材、５３，５４はグラスウール材２０ｅ，２０ｇを支えて固定するための梁部である。
【０１３２】
次に動作について説明する。
この実施の形態１２の要件は、加振コイル３０が弾性支持手段２０ｅ，２０ｇの直下に配置されていることであり、このようにすることによって、電磁加振力が、振動板１０の弾性振動モードの節、すなわち支持されている５カ所に加わるのみであるから、強度変形が起こりにくく、変形振動を起こす危険性が小さくなる。
【０１３３】
以上のように、この実施の形態１２によれば、加振コイル３０と振動板１０との間にグラスウール材２０ｇを設けたので、強度変形が起こりにくく、変形振動を起こす危険性が小さくなり、このことによって振動板１０の強度変形による振動を抑制し、放射音特性を改善することができる効果が得られる。
【０１３４】
実施の形態１３．
図２２はこの発明の実施の形態１３による電磁音響変換装置における加振コイルの構造断面図であり、図において、３０ｃ，３０ｄは小型加振コイル、４０ａ，４０ｂは加振コイル３０ｃ，３０ｄを埋め込む磁極であり、加振コイル３０ｃ，３０ｄは電気的に直列接続される。
【０１３５】
次に動作について説明する。
上記実施の形態１〜１２においては、加振コイル３０は円形状、矩形状を問わず１個であった。図２３に示すように、振動板１０は剛性が小さい場合、電磁力の加わる加振コイル３０の近傍が変形しながら振動する、いわゆる変形振動が起こる。これは振動板１０が変形せずに前面一体となって振動する場合に比べ音波の放射能率を落とし、また指向特性にも影響を及ぼす可能性がある。実施の形態１３は、この問題を改善する。
【０１３６】
図２２に示すように、加振コイル３０ｃ，３０ｄを複数個用いると、これら加振コイル３０ｃ，３０ｄは電気的には直列に接続し、励磁装置６０から励磁電流の供給を受ける。このように加振コイル３０ｃ，３０ｄを複数個とすることにより、振動板１０への加振点が分散し、且つ均等な力での加振となるので変形振動を抑制することができる。なお、加振コイル３０ｃ，３０ｄを直列に接続するのは、各加振コイル３０ｃ，３０ｄに同じ電流が流れることによって、同じ電磁加振力が得られるからである。
【０１３７】
以上のように、この実施の形態１３によれば、加振コイル３０ｃ，３０ｄを複数個設けたので、振動板１０の強制変形や弾性振動を小さくし、非線形歪みの、より小さい再生音とすることができる効果が得られる。
【０１３８】
実施の形態１４．
図２４はこの発明の実施の形態１４による電磁音響変換装置における振動板の外形図であり、図において、１８は振動板１０に印刷あるいは彫刻された記号、文字、絵柄、または振動板１０に貼り付けられたシートに印刷された記号などの視覚的情報手段である。
【０１３９】
次に動作について説明する。
振動板１０に視覚的情報手段１８を付すことによって、音声波形の放射による聴覚的情報伝達と、同じ振動板１０により視覚的な情報伝達を同時に得ることができる。これは、コーン型スピーカなど従来のスピーカでは文字や図形の表示が不可能か、可能であっても視覚的情報については十分な情報伝達はできなかったが、この平板かつ樹脂積層板や、金属で形成する振動板１０であれば、視覚的情報手段１８を付すことが可能なので、視覚的情報伝達を行うことができる。
【０１４０】
以上のように、この実施の形態１４によれば、振動板１０の外面に視覚的情報手段１８を付したので、振動板１０を視覚的情報の伝達機能を兼ねるようにすることができ、スピーカと表示パネルの設置スペース効率を高め、よって携帯電子機器等にそのスピーカを用いれば機器の小型化が図れる効果が得られる。
【０１４１】
実施の形態１５．
図２５はこの発明の実施の形態１５による電磁音響変換装置のスピーカ本体の構造断面図であり、図において、２００は例えばＬＣＤパネル、ＥＬ（Ｅｌｅｃｔｒｏ Ｌｕｍｉｎｅｓｓｅｎｓｅ）、ＰＤ（Ｐｌａｓｍａ Ｄｉｓｐｌａｙ）、ＬＥＤ（Ｌｉｇｈｔ Ｅｍｉｔｔｅｄ Ｄｉｏｄｅ ）、ＶＦＤ（Ｖａｃｕｕｍ Ｆｌｕｐｈｏｒｅｓｓｅｎｓｅ Ｄｉｓｐｌａｙ ）などの電子的表示機能を有し、接着やねじ止めなどの方法で振動板１０に固定され、図では上側が表示面となる表示パネル、２０１は表示パネル２００に表示信号や、電気エネルギーを供給するための柔らかい可能性のあるケーブル、２０２はケーブル２０１と接続され、また図示せぬ外部の表示ドライバからのケーブルを接続し、枠体５０にねじ止めなどの方法で設けられたコネクタである。
【０１４２】
次に動作について説明する。
この実施の形態１５では振動加振力は振動板１０で発生し、振動板１０と一体となって振動する表示パネル２００が音声波形を外部に放射すると同時に表示パネル２００は電子的に制御された情報表示を行う。
【０１４３】
従って、表示パネル２００に表示された物語の文章文字を見ながら、その文章を朗読した音声を、あたかもその文字から出てくるがごとき印象で聞くことができ、歌っている歌手の姿や、顔を表示パネルで写すならば、あたかもその歌手（映像）の口から声が出てくるような印象を与えることができる。
【０１４４】
以上のように、この実施の形態１５によれば、振動板１０の外側に電子的表示機能を有する表示パネル２００、例えばＬＣＤパネルを固着し、表示パネル２００自体が振動板１０の一部を兼ねるようにしたので、スピーカと表示器の設置スペース効率を高めると共に、ＡＶソースの再生を、より臨場感のあるものとすることができる効果が得られる。
【０１４５】
実施の形態１６．
図２６はこの発明の実施の形態１６による電磁音響変換装置におけるスピーカ本体の構成を示す概念図であり、図において、６３は加振コイル３０のリード線３１とコネクタ６１の間に電気的に接続され、磁極４０と枠体５０で囲まれた位置に固定された進相用コンデンサ（静電容量素子）である。
【０１４６】
次に動作について説明する。
この発明のスピーカは加振力を得る原理から、加振コイル３０の電気的インピーダンスが極端にリアクティブであり、励磁電源の力率特性は非常に小さくならざるを得ない。従って、所定の電流を供給するためには励磁装置７０の電力増幅手段７３は高電圧の出力を必要とする。また励磁ケーブル６２にも耐電圧特性が要求されることになる。
【０１４７】
そこで、上記したように進相用コンデンサ６３を設ける。進相用コンデンサ６３の静電容量値は、加振コイル３０の時間平均的なリアクタンスをＬ、交番電圧信号の周波数ｆ_ｓ としたとき、Ｃ＝１／（２πｆ_ｓ ）^２ ・Ｌで求められる共振のための値の半分程度とする。
【０１４８】
これによりアンプ側から見たインピーダンスが半分程度に減少し、それに伴い、出力電圧も半分程度に下げることができる。また振動板１０の振動によるコイルのリアクタンス変動など、リアクタンスの変動による加振コイル電流への影響（惹いては再生音質への影響）も大きくはない。またケーブル６２の耐電圧も容易になる。
【０１４９】
以上のように、この実施の形態１６によれば、加振コイル３０のリード線３１と、枠体５０に設けたコネクタ６１との間に進相用コンデンサ６３を接続挿入したことにより、励磁装置７０の必要とする出力電圧を下げることができ、ケーブル６２も耐電圧特性も低いもので済むので、より安価なスピーカとすることができる効果が得られる。
【０１５０】
実施の形態１７．
図２７はこの発明の実施の形態１７による電磁音響変換装置の励磁装置の回路構成図であり、図において、７６は図３に示した励磁装置７０の加算手段７４と乗算手段７５との間に接続され、数値αでバイアスされた音声信号Ｓ１を補正した数値データＳ１ａを出力する数値変換テーブルによる数値変換手段である。また、この例では入力信号ｖ（ｔ）がデジタル化された信号であるものとし、この場合、増幅手段７３が、デジタル／アナログ変換手段を内蔵するものとする。
【０１５１】
次に動作について説明する。
電磁反発力は、図２８に示すように、振動板１０と加振コイル３０との間の空隙長に依存する。およそ指数関数の形で、空隙が大きくなるにつれて、反発力は小さくなる。振動板の振動ストロークが小さい場合は問題は小さいが、ストロークが大きくなると、再生音の波形歪みが無視できなくなる。
【０１５２】
そこで、実施の形態１７はその問題を解決する数値変換手段を提供するものである。数値変換手段７６は、数値αでバイアスされた音声信号Ｓ１を入力して補正を施した数値データＳ１ａを出力する。ここで、数値変換手段７６、即ち数値変換テーブルの中身は、空隙特性を補償する内容とし、全ての設計条件が定まった後で、具体的な変換数値を求めることになる。
【０１５３】
以上のように、この実施の形態１７によれば、励磁装置７０が、一定値でバイアスした音声信号波形瞬時値を変換する数値変換手段７６を擁し、電磁力の空隙依存性を補償するようにしたので、非線形歪みの、より小さい再生音を得ることが出来る効果が得られる。
【０１５４】
【発明の効果】
以上のように、請求項１記載の発明によれば、第１励磁装置の出力電流が供給された第１加振コイルに流れる励磁電流と振動板に誘起される渦電流との間に働く電磁反発力によって変調信号に応じた振動加振力を得、この振動加振力により音声あるいは騒音信号の再生音を発生するように構成したので、振動板に直接音声や、騒音信号の振動力を生み出す薄型のスピーカとすることができる効果がある。
【０１５５】
請求項２記載の発明によれば、振動板の一部分に電気的絶縁性磁性材による磁性板を設け、磁性板と対向する位置に永久磁石手段を設けて構成したので、永久磁石手段による振動板への吸引力により、加振コイルによる直流電磁反発力を減殺でき、よって弾性支持手段の偏移が抑制され、非線形歪みの、より小さい再生音を得ることができる効果がある。
【０１５６】
請求項３記載の発明によれば、直流的反発力と直流的吸引力が互いに相殺され、第１及び第２振動加振力が合力として振動板に作用することにより、音声あるいは騒音信号の再生音を発生するように構成したので、弾性支持手段の静的な変位がなく、より非線形歪みの小さい、及び振動加振力が増大し、より再生音圧の高いスピーカとすることができる効果がある。
【０１５７】
請求項４記載の発明によれば、双方の直流反発力が互いに作用方向が逆であることにより相殺され、双方の振動加振力が合力として振動板に作用することによって、音声あるいは騒音信号の再生音を発生するように構成したので、弾性支持手段の静的な変位及び振動板の静的な変形がなく、より非線形歪みの小さい、及び振動加振力が増大し、より再生音圧の高いスピーカとすることができる効果がある。
【０１５８】
請求項５記載の発明によれば、振動板を、単一有機材、複数種類の有機材の積層材、有機材の成形材のいずれかで形成された板と、この板に埋め込み或いは貼り合わせられた導電及び非磁性金属板とで構成したので、振動板の剛性を高めることなく、弾性振動を抑制し、混変調歪みの、より小さい再生音とすることができる効果がある。
【０１５９】
請求項６記載の発明によれば、振動板の板及び非磁性金属板を、複数種類の形状に成形して構成したので、振動板の剛性を高めることなく、弾性振動を抑制し、混変調歪みの、より小さい再生音とすることができる効果がある。
【０１６０】
請求項７記載の発明によれば、振動板を、０．４ｍｍ〜１．６ｍｍの銅板、あるいは０．５ｍｍ〜２．０ｍｍのアルミニウム板として構成したので、簡便で堅牢かつ安価なスピーカとすることができる効果がある。
【０１６１】
請求項８記載の発明によれば、弾性支持手段を、振動板の周辺部を挟み込む高密度グラスウール材あるいはゴム材により構成したので、ダンピング性能とスプリング性能を同一部材で得られ、より簡便安価なスピーカとすることができる効果がある。
【０１６２】
請求項９記載の発明によれば、弾性支持手段を、振動板の端部の複数箇所に溶接あるいはネジ止め固定した金属製スプリング材で構成したので、より厳しい環境で使用できるスピーカとすることができる効果がある。
【０１６３】
請求項１０記載の発明によれば、振動板の外面あるいは内面にリブ材を設けて構成したので、弾性振動に対する剛性を高め、よって歪みの小さい再生音とすることができる効果がある。
【０１６４】
請求項１１記載の発明によれば、弾性支持手段を、グラスウール材に金属製スプリング材を埋め込んで構成したので、弾性支持手段が適度な機械抵抗を有するので音声の再生帯域が狭くなり、再生音圧を大きくすることができ、これによって設計裕度すなわち、より広い適用範囲のスピーカとすることができる効果がある。
【０１６５】
請求項１２記載の発明によれば、弾性支持手段を、加振コイルと振動板との間に設けて構成したので、強度変形が起こりにくく、変形振動を起こす危険性が小さくなり、これによって振動板の強度変形による振動を抑制し、放射音特性を改善することができる効果がある。
【０１６６】
請求項１３記載の発明によれば、加振コイルを、電気的に直列接続して複数個設けて構成したので、振動板の強制変形や弾性振動を小さくし、非線形歪みの、より小さい再生音とすることができる効果がある。
【０１６７】
請求項１４記載の発明によれば、振動板の外面に、絵柄、文字、記号を書き込む或いは刷り込む、または絵柄、文字、記号を記したシートを張り合わせることによる視覚的情報手段を付して構成したので、スピーカと表示パネルの設置スペース効率を高め、よって携帯電子機器の小型化が計れる効果がある。
【０１６８】
請求項１５記載の発明によれば、振動板の外側に電子的表示機能を有する表示パネルを固着し、上記表示パネルが上記振動板の一部を兼ねるように構成したので、スピーカと表示器の設置スペース効率を高めると共に、ＡＶソースの再生を、より臨場感のあるものとすることができる効果がある。
【０１６９】
請求項１６記載の発明によれば、加振コイルのリード線と枠体に設けられたコネクタとの間に静電容量素子を接続して構成したので、励磁装置の必要とする出力電圧を下げることができ、ケーブルも耐電圧特性も低いもので済むので、より安価なスピーカとすることができる効果がある。
【０１７０】
請求項１７記載の発明によれば、励磁装置に、一定値でバイアスした音声信号の波形瞬時値を変換し、電磁力の空隙依存性を補償する数値変換手段を備えて構成したので、非線形歪みの、より小さい再生音を得ることが出来る効果がある。
【図面の簡単な説明】
【図１】この発明の実施の形態１による電磁音響変換装置の構成図である。
【図２】この発明の実施の形態１による電磁音響変換装置のスピーカ本体の構造断面図である。
【図３】この発明の実施の形態１による電磁音響変換装置の励磁装置の回路構成図である。
【図４】この発明の実施の形態１による電磁音響変換装置の励磁装置の動作を説明するための図である。
【図５】この発明の実施の形態１による電磁音響変換装置の動作を説明するための振動系機械インピーダンスの周波数依存性を示す図である。
【図６】この発明の実施の形態１による電磁音響変換装置の具体的な構成を説明するための断面図である。
【図７】この発明の実施の形態２による電磁音響変換装置のスピーカ本体の構造断面図である。
【図８】この発明の実施の形態３及び実施の形態８による電磁音響変換装置のスピーカ本体の構造断面図である。
【図９】この発明の実施の形態３による電磁音響変換装置の励磁装置の回路構成図である。
【図１０】図８に示すスピーカ本体の振動板の構造図である。
【図１１】図８に示すスピーカ本体の振動板の他の構造図である。
【図１２】この発明の実施の形態４による電磁音響変換装置のスピーカ本体の構造断面図である。
【図１３】この発明の実施の形態４による電磁音響変換装置の励磁装置の回路構成図である。
【図１４】この発明の実施の形態５による電磁音響変換装置の振動板の構造断面図である。
【図１５】この発明の実施の形態６による電磁音響変換装置の振動板と加振コイルの構造断面図である。
【図１６】この発明の実施の形態７による電磁音響変換装置の振動板と加振コイルの構造断面図である。
【図１７】この発明の実施の形態８による電磁音響変換装置の振動板と加振コイルの構造断面図である。
【図１８】この発明の実施の形態９による電磁音響変換装置の弾性支持手段の構造断面図である。
【図１９】この発明の実施の形態１０による電磁音響変換装置の振動板の外観図である。
【図２０】この発明の実施の形態１１による電磁音響変換装置における弾性支持手段の構造断面図である。
【図２１】この発明の実施の形態１２による電磁音響変換装置における弾性支持手段の構造断面図である。
【図２２】この発明の実施の形態１３による電磁音響変換装置の加振コイルの構造断面図である。
【図２３】この発明の実施の形態１３による電磁音響変換装置の振動板の静的力による変形の様子を示す図である。
【図２４】この発明の実施の形態１４による電磁音響変換装置の振動板の外観図である。
【図２５】この発明の実施の形態１５による電磁音響変換装置のスピーカ本体の構造断面図である。
【図２６】この発明の実施の形態１６による電磁音響変換装置のスピーカ本体の概念図である。
【図２７】この発明の実施の形態１７による電磁音響変換装置の励磁装置の回路構成図である。
【図２８】電磁音響変換装置の原理に関わる電磁力発生効率の空隙依存性を示す図である。
【図２９】従来の電磁音響変換装置の振動板の外観図である。
【図３０】従来の電磁音響変換装置の励磁装置の動作を説明するための電流波形図である。
【図３１】従来の電磁音響変換装置の励磁装置の動作を説明するための他の電流波形図である。
【符号の説明】
１０，１０ａ，１０ｂ，１０ｃ 振動板、１２，１２ｂ，１２ｃ 非磁性金属板、１４ リブ材、１５ 電気的絶縁性磁性板、１８ 視覚的情報手段、２０ 弾性支持手段、２０ｃ コイルばね（金属製スプリング材）、２０ｄ 板ばね（金属製スプリング材）、２０ｅ、２０ｇ グラスウール材、３０ 加振コイル（第１加振コイル）、３０ａ 加振コイル（第３加振コイル）、３０ｂ 加振コイル（第４加振コイル）、３０ｃ，３０ｄ 小型の加振コイル、３４ 永久磁石手段、３５ 加振コイル（第２加振コイル）、３６ 磁極、４０ 磁極）、５０ 枠体（第１枠体）、５０ａ 枠体（第２枠体）、５０ｂ 枠体（第３枠体）、６０ スピーカ本体（第１スピーカ本体）、６０ａ スピーカ本体（第２スピーカ本体）、６０ｂ スピーカ本体（第３スピーカ本体）、６１ コネクタ、６２ 励磁ケーブル、６３ 進相用コンデンサ（静電容量素子）、７０ 励磁装置（第１励磁装置）、７０ａ 励磁装置（第２励磁装置）、７０ｂ 励磁装置（第３励磁装置）、７１ 交番電圧発生手段、７２ 変調手段（第１変調手段）、７２ａ変調手段（第２変調手段）、７２ｂ 変調手段（第３変調手段）、７３ 電力増幅手段（第１電力増幅手段）、７３ａ 電力増幅手段（第２電力増幅手段）、７６ 数値変換手段、２００ 表示パネル。[0001]
TECHNICAL FIELD OF THE INVENTION
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electromagnetic acoustic conversion device which is a speaker for reproducing a sound or noise signal converted into an electric signal, and more particularly to an electromagnetic repulsion (Lorentz) generated between an eddy current induced on a conductive diaphragm and an exciting current. The present invention relates to an electromagnetic acoustic conversion device utilizing the principle that a diaphragm vibrates due to force.
[0002]
[Prior art]
FIG. 29 is a configuration diagram of a conventional electromagnetic acoustic conversion device which is a sounding body using an electromagnetic force disclosed in Japanese Patent Application Laid-Open No. 56-9797. 29, A is a speaker body, B is an exciting circuit device, 1 is a frame, 2 is a bottom plate, 3 is an exciting coil, 3a and 3b are lead wires, 4 is a magnetic pole, 5 is a magnetic substrate, and 6 is a permanent magnet. , 7 are diaphragms and 8, 9 are connectors.
[0003]
FIGS. 30 and 31 are diagrams showing waveform examples of the exciting current. In FIG. 30, a1 is a pulsed periodic current waveform having a period T0, a2 is an intermittent signal waveform having a period T1, a3 is a periodic current waveform interrupted at a period a2, and a4 is driven by an exciting current having a3. It is a vibration waveform of a diaphragm. In FIG. 31, b1 is a sinusoidal periodic current waveform of frequency f0, b2 is a modulation signal waveform of frequency f2, and b3 is a modulated periodic current waveform.
[0004]
Next, the operation will be described.
This electromagnetic acoustic conversion device is a speaker provided for sounding a signal such as an alarm clock. The excitation circuit device B supplies power to the excitation coil 3 after intermittently modulating the periodic current at a predetermined frequency as shown in FIG. 30 or modulating with a sine wave signal as shown in FIG.
[0005]
The exciting coil 3 forms an AC electromagnet together with the magnetic pole 4. The alternating magnetic field generated by the electromagnet applies an alternating electromagnetic force to the diaphragm 7 magnetically biased by the permanent magnet 6, and causes the diaphragm 7 to vibrate at a predetermined frequency. If the natural frequency of the diaphragm 7 and the period of the exciting current are matched, the diaphragm 7 vibrates violently. The frequency twice the excitation frequency is outside the audible limit, and the intermittent or modulation frequency is set to the frequency of the desired signal sound. , A signal-generated sound can be obtained efficiently.
[0006]
In this conventional technique, an electromagnetic force is directly generated and vibrated on a metal flat plate, so that the whole sounding body can be configured to be thin. Most of the components including the diaphragm 7 are made of metal or inorganic material, so that they can be applied to high temperature and low temperature environments.
[0007]
In addition to this example, a moving coil is attached to a cone-shaped diaphragm as an electromagnetic acoustic transducer that reproduces voice and noise signals, and the moving coil is placed in a magnetic field formed by permanent magnets. An electro-dynamic cone loudspeaker, which emits current by amplifying and generating an electric current and vibrating a diaphragm with an electromagnetic force (Faraday force) generated between a magnetic field line of a magnetic field and a coil current, is generally used. .
[0008]
[Problems to be solved by the invention]
Since the conventional electromagnetic acoustic transducer is configured as described above, a single signal sound is generated by utilizing the physical phenomenon of the natural vibration of the diaphragm 7 and the electromagnetic force (magnetic pressure) shown in FIG. Therefore, it cannot generate signal sounds composed of complex frequency components such as voice and noise signals, and even more, cannot reproduce voice and noise signals that have been recorded and converted to electrical signals. There were challenges.
[0009]
Further, in an electromagnetic acoustic transducer that is a cone-type speaker, a separate coil provided at the center of the cone-shaped diaphragm is necessary to obtain an exciting force, and therefore, the length occupying the entire speaker in the vibration direction is required. There was a problem that the size became large.
[0010]
Furthermore, in order to reduce the weight of the diaphragm, it is formed of fibrous material such as paper, or an organic adhesive is used, so that the temperature range that can be used is narrow. For this reason, the allowable range of the thickness is narrow like a portable device, and it is not suitable for a device used in various environments or a place where a thin and environment-resistant property is required such as for an automobile ANC (Active Noise Control). There were challenges.
[0011]
The present invention has been made to solve the above-described problems, and a function of reproducing voice and noise can be used in a thin structure and under severe environmental conditions such as high temperature, low temperature, high humidity, and high dust. An object is to obtain an electromagnetic acoustic transducer.
[0012]
[Means for Solving the Problems]
According to the first aspect of the present invention, there is provided an electroacoustic transducer that acts between an exciting current flowing through a first excitation coil supplied with an output current of a first exciting device and an eddy current induced in a diaphragm. A vibration exciting force corresponding to the modulation signal is obtained by the force, and a reproduced sound of a sound or a noise signal is generated by the vibration exciting force.
[0013]
According to a second aspect of the invention, there is provided an electromagnetic acoustic conversion device in which a magnetic plate made of an electrically insulating magnetic material is provided on a part of a diaphragm, and permanent magnet means is provided at a position facing the magnetic plate.
[0014]
According to a third aspect of the present invention, there is provided an electro-acoustic transducer, wherein an electromagnetic repulsion acts between an exciting current flowing through a first exciting coil to which an output current of a first exciting device is supplied and an eddy current induced in a diaphragm. The first vibration exciting force and the DC repulsion force corresponding to the first modulation signal are obtained by the force, and the magnetic attraction acts between the second exciting coil supplied with the output current of the second power amplifying means and the magnetic plate. A second vibration excitation force and a DC attraction force corresponding to the second modulation signal are obtained by the force, the DC repulsion force and the DC attraction force cancel each other, and the first and second vibration excitation forces vibrate as a combined force. By acting on the board, a reproduced sound of a voice or noise signal is generated.
[0015]
According to a fourth aspect of the present invention, there is provided an electro-acoustic transducer, wherein an electromagnetic current acting between an exciting current flowing through a third exciting coil supplied with an output current of the first power amplifying means and an eddy current induced on the diaphragm is provided. The repulsive force obtains a vibration exciting force and a DC repulsive force according to the first modulation signal, and the output current of the second power amplifying means is induced by the exciting current flowing through the supplied fourth exciting coil and the diaphragm. The vibration repulsion force and the DC repulsion force according to the third modulation signal are obtained by the electromagnetic repulsion force acting between the eddy current and the DC repulsion force. When the vibration excitation force acts on the diaphragm as a resultant force, a reproduced sound of a sound or a noise signal is generated.
[0016]
The electromagnetic acoustic transducer according to the invention according to claim 5, wherein the diaphragm is formed of one of a single organic material, a laminated material of a plurality of types of organic materials, and a molded material of an organic material. It is composed of a conductive and non-magnetic metal plate embedded or bonded.
[0017]
An electromagnetic acoustic transducer according to a sixth aspect of the present invention is obtained by forming a diaphragm plate and a non-magnetic metal plate into a plurality of types of shapes.
[0018]
In the electromagnetic acoustic transducer according to the seventh aspect of the present invention, the diaphragm is a copper plate of 0.4 mm to 1.6 mm or an aluminum plate of 0.5 mm to 2.0 mm.
[0019]
According to an eighth aspect of the present invention, in the electromagnetic acoustic transducer, the elastic supporting means is made of a high-density glass wool material or a rubber material which sandwiches a peripheral portion of the diaphragm.
[0020]
According to a ninth aspect of the present invention, in the electromagnetic acoustic transducer, the elastic supporting means is formed of a metal spring material which is welded or screwed and fixed to a plurality of positions at the end of the diaphragm.
[0021]
According to a tenth aspect of the invention, there is provided an electromagnetic acoustic conversion device in which a rib member is provided on an outer surface or an inner surface of the diaphragm.
[0022]
According to an eleventh aspect of the present invention, in the electromagnetic acoustic transducer, the elastic supporting means has a structure in which a metal spring material is embedded in a glass wool material.
[0023]
According to a twelfth aspect of the present invention, in the electromagnetic acoustic transducer, the elastic supporting means is provided between the excitation coil and the diaphragm.
[0024]
According to a thirteenth aspect of the present invention, there is provided the electromagnetic acoustic transducer, wherein a plurality of excitation coils are provided by being electrically connected in series.
[0025]
The electromagnetic acoustic transducer according to the invention according to claim 14 provides visual information means by writing or printing a pattern, character, or symbol on the outer surface of the diaphragm, or laminating a sheet on which the pattern, character, or symbol is written. It is attached.
[0026]
In the electromagnetic acoustic transducer according to a fifteenth aspect, a display panel having an electronic display function is fixed to the outside of the diaphragm, and the display panel also serves as a part of the diaphragm.
[0027]
An electromagnetic acoustic transducer according to a sixteenth aspect of the present invention is a device in which a capacitance element is connected between a lead wire of a vibrating coil and a connector provided on a frame.
[0028]
An electromagnetic acoustic transducer according to the invention according to claim 17 is provided with a numerical converter for converting the instantaneous value of the waveform of the audio signal biased at a constant value and compensating for the gap dependency of the electromagnetic force, in the exciting device. is there.
[0029]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, an embodiment of the present invention will be described.
Embodiment 1 FIG.
FIG. 1 is a configuration diagram of an electromagnetic acoustic conversion device according to Embodiment 1 of the present invention. However, the electromagnetic acoustic conversion device may be expressed as a speaker in the following description. In this figure, 60 is a speaker main body (first speaker main body), 70 is an exciting device (first exciting device), 62 is a connector connecting the exciting device 70 and the speaker main body 60 via a connector 61, An excitation cable for supplying a current to the main body 60, 100 is an audio output device such as an MD player that outputs a pre-recorded audio signal converted to an electric signal, and 101 transmits a signal from the audio output device 100 to the excitation device 70. Is a diaphragm made of a conductive and non-magnetic material, 20 is an elastic supporting means made of a flexible and elastic material, and 50 is a frame (first frame) forming a frame of the speaker body 60.
[0030]
As shown in FIG. 2 which is a cross-sectional view of the speaker main body 60, an exciting coil (first exciting coil) 30 is embedded in the diaphragm 10 so as to face the diaphragm 10 with a gap G interposed therebetween, and the magnetic pole 40 has a frame. It is installed on a substrate 50c which is a part of the body 50. The diaphragm 10 is supported by being sandwiched between elastic support means 20a and 20b, and the other surfaces of the elastic support means 20a and 20b are fixed to the frame 50. The excitation coil 30 is electrically connected to the excitation cable 62 through the connector 61 shown in FIG.
[0031]
As shown in FIG. 3, which is a circuit configuration diagram of the excitation device 70, the excitation device 70 includes an alternating voltage generation unit 71, a modulation unit (first modulation unit) 72, and a power amplification unit (first power amplification unit) 73. ing. The modulating means 72 comprises an adding means 74 for adding a fixed amount α to the audio signal v (t) as an input signal, and a multiplying means 75 for multiplying the output S1 of the adding means 74 by the alternating voltage signal a (t). I have.
[0032]
Next, the operation will be described.
The audio signal v (t) output from the audio output device 100 is supplied as a modulation signal to the modulation means 72 of the excitation device 70. The modulating means 72 modulates (ie, multiplies) the alternating voltage signal a (t) generated by the alternating voltage generating means 71 by the multiplying means 75 after biasing the audio signal v (t) by the constant value α by the adding means 74. ) And output. However, the frequency of the alternating voltage signal a (t) is set higher than the upper limit of the frequency band of the desired audio signal v (t).
[0033]
One example of each signal waveform in the modulating means 72 is shown in FIGS. (A) is a waveform of the audio signal v (t), (b) is a bias signal having a constant value α, (c) is a waveform of the alternating voltage signal a (t), and (d) is a modulated output waveform. In (a) to (d), the horizontal axis represents the time axis, and the vertical axis represents the amplitude.
[0034]
The power amplification unit 73 power-amplifies the modulated signal output from the modulation unit 72. The excitation device 70 supplies an excitation current to the speaker main body 60 via the excitation cable 62.
[0035]
The exciting current supplied to the speaker main body 60 flows through the exciting coil 30 via the lead wire 31 to excite the magnetic pole 40, thereby causing the diaphragm 10 to interlink alternating magnetic force lines modulated by an audio signal. At this time, the diaphragm 10 receives an electromagnetic repulsion acting between the eddy current induced therein and the exciting current flowing through the exciting coil 30.
[0036]
As will be described in detail later, the electromagnetic repulsion includes three components: a DC repulsion, a vibration excitation corresponding to the modulation signal, and a vibration excitation twice the frequency of the alternating voltage signal. The diaphragm 10 vibrates together with the elastic supporting means 20 by a vibration excitation force corresponding to the modulation signal therein, and emits sound.
[0037]
Here, the basic principle of the electromagnetic acoustic transducer (speaker) of the present invention will be described. Broadly, it is composed of a combination of three element principles.
[0038]
The first is the principle of acoustic emission that, when the diaphragm 10 is vibrated in accordance with the time-varying waveform of the audio signal, the sound reproduced from the sound is emitted into the atmosphere. The third is a modulation system in which an audio signal is applied as a modulating wave at a relatively high frequency (5 kHz to 20 kHz) as an exciting current, with the Lorentz force acting mainly between the vibrating plate 10 and the vibration plate 10. .
[0039]
The first principle is not different from the sound emission principle of the conventional cone speaker. Here, the gist of the present invention is the principle relating to the second means for generating an electromagnetic excitation force and the third means for modulating the audio signal.
[0040]
These principles will be described using mathematical expressions and graphs.
First, the notation is as follows.
v = v (t): voice or noise electric signal (time waveform signal).
a = A_m  sin2πf_s  t: Alternating voltage signal (basically a time-varying sine wave of frequency fs).
s₁  = V (t) + α: modulated signal (time-varying waveform), where α is a constant value.
e_s  = E_s  (T): Modulated alternating voltage signal after power amplification (time waveform) This power supply supplies an exciting current to the excitation coil 30.
i_c  ・ N = i_c  N (t): Product [AT] vector amount of the exciting coil current and the number of turns of the coil.
Hi = Hi (t): magnetic field intensity [AT / m] vector amount generated by the exciting current flowing through the exciting coil 30.
j = j (t): current density [A / m2] vector amount of the eddy current flowing through the diaphragm 10.
g: The length [m] of the gap existing between the diaphragm 10 and the excitation coil 30.
δ: skin depth (penetration depth of magnetic field lines: depth at which surface magnetic field attenuates to 1 / e) [m].
F = F (t): electromagnetic force [N].
f_s    : The frequency of the alternating voltage signal.
μ₀    : Permeability of air (4π × 10^-7).
[0041]
The output of the power amplifying means 73 is given by
e_s  = Β · s₁  ・ A_m  sin2πf_s  It is represented by t.
This output is supplied to the excitation coil 30, and the electrical impedance Z of the excitation coil 30_c  , The excitation coil current i_c  = E_s  / Z_c  Through the coil 30.
This coil current is expressed as i when the number of turns of the coil is n._c  Generates n magnetomotive forces. In an electromagnetic field having a magnetomotive force, various physical specifications are related and determined by the maxwell electromagnetic field equation. Here, the electromagnetic force acting on the surface of the diaphragm 10 is expressed by the following equation (1).
[0042]
F = ∫Σ ｛(H_s  ・ N) H_s  -(1/2) · H_s ²・ N｝ da ・ ・ ・ (1)
[0043]
Here, Σ indicates the entire area on the surface of the diaphragm 10, Hs indicates the magnetic field intensity on the surface of the diaphragm 10, n indicates the normal vector, and da indicates the area integral element. When the diaphragm 10 is non-magnetic, μ is μ0, which is the same as the magnetic permeability of air.
[0044]
The first term on the right side of the above equation (1) is a component of the suction force. The normal component of the magnetic field strength is small because it is weakened by the counter magnetic field due to the eddy current J. The second term is a component of the repulsive force. The second term is a dominant component because it is a normal component of the square of the magnetic field strength (vector product).
[0045]
Therefore, the total of the electromagnetic force is a repulsive electromagnetic force acting in a direction to move the diaphragm 10 away from the exciting coil 30. The repulsive electromagnetic force is efficiently generated when an electromagnetic field distribution having a large tangential component of the magnetic field strength on the surface of the diaphragm 10 and a small normal component is formed. Such a distribution is such that the smaller the specific electric resistance of the diaphragm 10, the larger the thickness and area of the diaphragm 10, the smaller the gap between the diaphragm 10, the exciting coil 30, and the magnetic pole, and the excitation frequency is somewhat higher. The higher, the larger.
[0046]
Expression (1) indicates that the magnitude of the electromagnetic force is proportional to the square of the magnitude of the magnetic field strength when the system (electromagnetic field distribution) is the same. Therefore, since the magnetic field strength is proportional to the magnetomotive force, the proportionality coefficient is represented by k.
[0047]

It becomes.
Where k_t  = Kβn²  A_m ²/ Zc²
[0048]
Where S₁  Is a form in which a constant value is added as a bias to the time-varying signal of the audio waveform,
[0049]
S₁  = Α + V (t) (2)
[0050]
So
F = k_t  ・ (Α²  + 2αV (t) + V²  ) (1/2) (1-cos4πf)_s  t)
It becomes.
[0051]
Here, if the bias α is made considerably larger (10 times or more) than the size of the audio waveform, the above equation can be approximated as the following equation (3).
[0052]

[0053]
In this equation (3), the first term is a DC repulsive force component, the second term is a vibrating force component based on the sound waveform v (t), and the third and fourth terms are vibrational vibrating force components at a frequency of 2 fs [Hz]. It is.
Next, assuming that the mass of the moving part in the vibration system formed by the diaphragm and the elastic support means is M, the spring constant is κ, and the mechanical resistance is r, the mechanical impedance Z_m  Is the angular velocity ω (= 2πf), Z_m  = JωM + K / jω + R. here
[0054]
ωM = K / ω
Resonance frequency f₀  The mass of the diaphragm 10 and the spring characteristics of the elastic support means 20a and 20b are selected so that the frequency of the low frequency range becomes low, for example, 50 to 300 Hz.
[0055]
The frequency f of the alternating voltage_s  To f₀  If the frequency is selected to be higher than, for example, 5 kHz to 50 kHz, the vibration due to the vibration excitation force in the third and fourth terms of the expression (5) is suppressed to about -30 dB or less due to the inertial resistance of the vibration system.
[0056]
FIG. 5 is shown for better understanding of this. In this figure, the vibration frequency f is plotted on the horizontal axis for one example of the vibration system mechanical impedance Zm of the diaphragm 10. F added in the figure₀  Is the resonance frequency of the vibration system, f_s  Is an alternating voltage signal frequency, which is an example of the frequency of the excitation force, and the band A is an audio band reproduced by the speaker of the present invention.
[0057]
The impedance (Z) with respect to the exciting force based on the alternating voltage signal a (t)_2fs  ) Is the impedance Z of the sound reproduction band._s  It can be seen that it is very large compared to. Therefore, the diaphragm 10 vibrates by receiving the exciting force according to the sound signal v (t) as a dominant force, and emits sound reproduced sound.
[0058]
To reiterate, there are three basic features of the present invention. The first is the repulsion that is dominant in the case of non-magnetic and conductive materials among the components of the electromagnetic force represented by the formula (1). Use the power. Second, the audio signal v (t) biased by the constant value α as shown in Expression (3) is used as a modulation signal of the alternating voltage signal a (t). The third is the frequency f of the alternating voltage signal a (t) with respect to the diaphragm vibration resonance frequency._s  Is sufficiently large to suppress the vibration radiation sound due to the alternating electromagnetic force as much as possible.
[0059]
Here, the materials, sizes, and the like of the components of the electromagnetic acoustic transducer will be specifically described with reference to FIG. However, it is assumed that the audio reproduction frequency band is 100 to 7 kHz.
[0060]
An aluminum metal disk is used for the diaphragm 10. Aluminum has high conductivity, is non-magnetic, and has a lower specific gravity than other highly conductive metals. Accordingly, it is possible to design an electromagnetic repulsion force which is easy to obtain and the mechanical impedance of the diaphragm 10 is small, so that the overall efficiency as a speaker can be increased.
[0061]
The thickness required for the diaphragm 10 is determined from the skin depth evaluation formula (δ = SQRT (2ρ / ωμ)). The skin depth δ of aluminum at an excitation frequency (frequency of the alternating voltage signal a (t)) of 20 kHz is about 0.6 mm.
Therefore, when the telephone voice band is used as the reproduction band, the thickness of the diaphragm is desirably 0.5 to 2 mm. If a thinner plate is used, the electromagnetic force decreases, but Joule heat increases. In the case of a copper plate, since the specific resistance ρ is about 40% lower than that of aluminum, the optimum plate thickness is 0.4 to 1.6 mm.
[0062]
The elastic supporting means 20 has a structure in which the periphery of the diaphragm 10 is sandwiched between ring-shaped high-density glass wools having a thickness of several mm. Glass wool provides springiness and moderate damping properties, and also has heat resistance. The gap G is about 1 to 2 mm. The smaller the gap G, the better the electromagnetic force generation efficiency (electromagnetic force per unit ampere turn), but the narrower the stroke of the vibration of the diaphragm 10 and the greater the gap dependency of the electromagnetic force. Non-linear distortion is likely to occur in sound. The above-mentioned gap length is used for a speaker having a maximum stroke length of about 1 mm.
[0063]
Next, the exciting coil 30 is preferably a so-called litz wire in which insulated wires as thin as possible (about 0.4 mm or less) are twisted according to the excitation frequency. This is for suppressing the eddy current and the circulation loss in the coil and improving the overall efficiency as a speaker.
[0064]
Since the magnetic pole 40 has a relatively high exciting current (20 kHz), the magnetic pole 40 is formed of a material in which an eddy current does not easily flow, like the excitation coil 30, here, a magnetic powder molding material, for example, ferrite. However, the magnetic pole 40 is not always necessary in the speaker of the present invention. For example, the substrate 50c may be made of a high-resistance magnetic material without providing the magnetic pole 40 as shown in FIG. Instead, some coil support means is provided.
[0065]
The frame 50 is made of a material such as steel or plastic by sheet metal, molding, or the like. The frame body 50 serves to secure a gap between the diaphragm 10 and the excitation coil 30 to a predetermined length by supporting and fixing the elastic support means 20a and 20b and the excitation coil 30. The role of the frame body 50 is to secure the space close to the seal by combining the vibration plate 10 and the support means 20 so as not to emit the sound wave radiated from the back surface of the vibration plate 10 to the outside. However, it is also possible to provide a part of the frame body 50 with an open portion to provide a bass reflex speaker.
[0066]
The selection of the frequency of the alternating voltage signal a (t) is the most important issue for the loudspeaker of the present invention. This is because the magnitude of the electromagnetic force, the magnitude of the vibration excitation force caused thereby, the electromagnetic force generation efficiency, the electrical impedance of the excitation coil 30, the electronic circuit (particularly, the power transistor), and the audible characteristics of the radiation frequency This is because it greatly affects the speaker performance.
[0067]
If 20 kHz is selected as the frequency of the alternating voltage signal a (t), only this signal a (t) results in an electromagnetic excitation force of 40 kHz. This 40 kHz is typically well above the threshold frequency at which humans can hear. In addition, due to the inertial force due to the mass of the diaphragm 10, the diaphragm 10 becomes difficult to vibrate at a high frequency.
[0068]
If the frequency is set too high, the Joule loss of the excitation coil 30 and the amplifier circuit increases, thereby lowering the efficiency and increasing the rate of emission of unnecessary radiation into the air. Further, the alternating voltage generating means 71 may be an RC oscillation circuit which is commonly used in audio equipment and the like, and is composed of a semiconductor integrated circuit for operational amplification, a resistor, and a capacitor. The adding means 74 and the multiplying means 75 are similarly configured.
[0069]
A power transistor having a short turn-off time is used as the power amplifying unit 73. However, the vibrating coil 30, which is a load of the power amplifying means 73, has a high impedance which is mostly a reactance component. Therefore, it is necessary to pay attention to a high voltage output in order to supply a predetermined ampere turn: several hundred AT to the excitation coil 30.
[0070]
By using the above-mentioned materials and sizes, the speaker body 60 can be reduced in thickness to about 5 to 20 mm, and can be operated in a high-temperature environment exceeding 100 ° C. It can be.
[0071]
As described above, according to the first embodiment, the conductive and non-magnetic vibrating plate 10, the vibrating coil 30 disposed to face the vibrating plate 10 with the gap G interposed therebetween, and the elastic supporting means 20 a supporting the vibrating plate 10 , 20b, a speaker body 60 composed of a frame 50 for fixedly supporting the elastic supporting means 20a, 20b and the vibrating coil 30 in a predetermined arrangement, generating an alternating voltage for generating an alternating voltage signal a (t) having a constant frequency. Means 71, a signal s obtained by adding a bias signal α of a fixed value to a voice or noise signal previously converted to an electric signal v (t)₁  , Modulates the alternating voltage signal a (t) and outputs the modulated signal. The exciter 70 includes a power amplifying device 73 that amplifies the output signal of the modulator 72 with power. Is supplied to the excitation coil 30 of the speaker body 60, and the modulation signal es (t) is generated by the electromagnetic repulsion acting between the excitation current flowing through the excitation coil 30 and the eddy current induced in the diaphragm 10. A vibration excitation force corresponding to the vibration excitation force is obtained, and the reproduced vibration sound or the noise signal v (t) is radiated by the vibration excitation force. It can be a thin electromagnetic acoustic transducer that can reproduce noise signals, and is made of a material that is rigid and highly compatible with the use environment such as temperature, and does not use an organic adhesive. You Effect may be an electromagnetic acoustic transducer which can be used is obtained.
[0072]
Embodiment 2 FIG.
FIG. 7 is a structural sectional view of a speaker main body in an electromagnetic acoustic conversion device according to Embodiment 2 of the present invention. In FIG. 7, portions corresponding to the respective portions in FIG. 2 are denoted by the same reference numerals. In FIG. 7, reference numeral 15 denotes a magnetic plate made of a magnetic material fixed to a portion of the vibration plate 10 at a position facing the magnetic pole 40, and reference numeral 34 denotes a permanent magnet means provided at a position facing the magnetic plate 15 in parallel with the vibrating coil 30. It is.
[0073]
Next, the operation will be described.
A DC repulsive force corresponding to the first term of the equation (3) acts on the diaphragm 10. Since this force applies a constant stress to the elastic support means 20 at all times, the asymmetry of the spring effect above and below (in the figure) is likely to appear, and the radiated sound may be distorted. is there.
[0074]
The second embodiment is intended to improve this point, and the magnetic plate 15 and the permanent magnet means 34 act on the diaphragm 10 downward (toward the vibrating coil 30) by magnetic attraction acting between the magnetic plate 15 and the permanent magnet means 34. Apply force. The magnetic attraction force can be adjusted by selecting the length of the gap formed between the magnetic plate 15 and the permanent magnet means 34 and the material (relative magnetic permeability) of the magnetic plate 15 and is as large as the DC repulsion described above. And
[0075]
By adjusting in this way, during operation as a speaker, the suction force and the repulsion force are opposed to the diaphragm 10 so that the DC repulsion force is hardly applied, and the sound quality deterioration due to the non-linear vibration is suppressed.
[0076]
When the alternating magnetic flux generated by the exciting coil 30 interlinks with the magnetic plate 15, the magnetic attraction causes an alternating attractive force or eddy current to generate heat. Therefore, it is necessary to devise an arrangement so as not to interlink as much as possible. Heat generation is particularly problematic. However, if the magnetic plate 15 is made of magnetic powder molding or a resin impregnated material, no heat is generated.
[0077]
As described above, according to the second embodiment, the force in the direction of the vibrating coil 30 is applied to the vibration plate 10 by the magnetic attraction force acting between the magnetic plate 15 and the permanent magnet means 34. During operation as a loudspeaker, an attractive force and a repulsive force are opposed to the diaphragm 10, and a DC repulsive force is hardly applied, so that an effect of suppressing sound quality deterioration due to non-linear vibration is obtained.
[0078]
Embodiment 3 FIG.
FIG. 8 is a structural sectional view of a speaker main body in an electromagnetic acoustic conversion device according to Embodiment 3 of the present invention. In FIG. 8, parts corresponding to the respective parts in FIG. 7 are denoted by the same reference numerals. In FIG. 8, reference numeral 12 denotes a non-magnetic metal plate embedded or bonded to the diaphragm 10 and described in detail in Embodiments 5 to 8, and reference numeral 35 denotes an additional member provided in place of the permanent magnet means 34 shown in FIG. The vibrating coil (second vibrating coil), 36 is provided in place of the permanent magnet means 34, magnetic poles arranged beside the vibrating coil 35, 50a is a frame (second frame), and 60a is a speaker body ( Second speaker body).
[0079]
FIG. 9 is a circuit configuration diagram of an excitation device in the electromagnetic acoustic conversion device according to Embodiment 3 of the present invention. In FIG. 9, 70a is an exciting device (second exciting device), 72a is a modulating device (second modulating device), 79 is an inverting device for inverting the phase of the audio signal v (t) by 180 degrees, and 80 is a bias of the modulated signal. Adding means for adding the bias value α used as the signal and the inverted audio signal -v (t); 77, a multiplying means for multiplying the output signal of the adding means 80 by a predetermined value C; 78, an output signal of the multiplying means 77; Multiplying means 73a which modulates the signal a (t), 73a power-amplifies the modulated signal (second modulated signal) output from the multiplying means 78, and supplies an exciting current e to the exciting coil 35._r  Power amplification means (second power amplification means) for supplying (t). The adding means 74, the multiplying means 75, the power amplifying means 73, and the alternating voltage generating means 71 have the same configuration as in FIG.
[0080]
Next, the operation will be described.
In the first and second embodiments, only the repulsive electromagnetic force is used as the excitation force of the diaphragm 10. However, in the third embodiment, in addition to the repulsive electromagnetic force, a magnetic attraction force (of a magnetic material) is used. (Magnetic pressure acting on the surface). As a result, the force for exciting the diaphragm can be doubled, and the sound pressure level of the radiated sound can be increased.
[0081]
After the audio signal v (t) is biased at a constant value by the adding means 74, the alternating voltage signal a (t) is modulated by the multiplying means 75 to supply an exciting current to the excitation coil 30 to obtain an electromagnetic repulsion force. Add another excitation system to the system.
[0082]
That is, the phase of the audio signal v (t) is inverted (the sign is inverted in the case of a digital value) by the inversion means 79, the bias value α is added to the inverted audio signal -v (t) by the addition means 80, and the multiplication means is further added. After scaling by the predetermined value C by 77, the alternating voltage signal a (t) is modulated, and after being amplified by the power amplifier 73a, its output e_r  (T) is supplied to a vibrating coil 35 for obtaining a magnetic attractive force.
[0083]
In the electromagnetic force expression of the equation (1), the added excitation system is a magnetic material surface, and therefore has a large magnetic permeability μ and a large number of normal components._s  ・ N) H_s  Is overwhelmingly larger than the second term.
[0084]
Therefore, the electromagnetic force acting on the magnetic plate 15 is ∫Σμ_r  ・ Μ₀  (H_s  ・ N) H_s  Can be calculated as H_s  Is the exciting current i flowing through the exciting coil 35_r  And the number n of excitation coil turns_r  The suction force can be expressed in a form proportional to the square of the exciting coil ampere-turn.
[0085]
Therefore, the current i supplied to the excitation coil 35_r  Represents the electric impedance of the exciting coil 35 as Z_r  Then

Here, γ is the amplification factor of the amplification means, C is the multiplication coefficient of the multiplication means 77,
s₂  = −v (t) + α
Then the attractive electromagnetic force F_r  Is proportional to k_r  Then

Where s₂  = Α-V (t),
[0086]

It becomes.
[0087]
Also according to this equation (4), the electromagnetic force is a DC attraction force component, an exciting force component based on a voice waveform,_s  It can be seen that the vibration excitation force component is twice as large.
[0088]
Here, k in equation (3)_t  With reference to k_tr= Kt, the resultant of the electromagnetic force applied to the diaphragm 10 is

Then, the DC repulsive force and the attraction force cancel each other and disappear, and only the vibration excitation force of the audio signal component and the alternating electromagnetic force of the frequency component twice as high as the alternating voltage signal modulated by the audio waveform are obtained.
[0089]
As already described, the influence of the inertial mass of the diaphragm 10 and the limit of human hearing limit on the reproduced sound is small for the latter component. It can be considered only the vibration excitation force by the signal.
[0090]
However, the exciting current flowing through the exciting coil 30 and the exciting current flowing through the exciting coil 35 generally have different phases, and therefore, of the electromagnetic force, the vibration exciting force that is twice the alternating voltage frequency also has a phase. Are different.
[0091]
In consideration of this, the second term of the equation (5) must be corrected, but this is not a problem on the principle of the present invention.
[0092]
Further, according to the third embodiment, the constraint on the level of V (t) is only | V (t) | ≦ α, and can be extremely up to half the amplitude of alternating voltage signal a (t). . Therefore, the exciting force generation efficiency is significantly improved as compared with the configuration of the first embodiment.
[0093]
However, in the third embodiment, since the locations where the repulsive force and the suction force act are different, if the rigidity of the diaphragm 10 is small, there is a drawback that forced deformation or deformation vibration occurs. In order to solve this problem, as shown in FIG. 10, the improvement can be achieved by connecting the respective points of repulsion and suction on both sides or one side of the diaphragm 10 and attaching the reinforcing ribs 16 in a range where the points of force are extended.
[0094]
As shown in FIG. 11, a honeycomb diaphragm 10a having a honeycomb structure, which is conventionally used in a cone type speaker, is made of a highly conductive metal such as aluminum, in which an aluminum donut ring and an ultra-thin silicon steel plate are provided. The magnetic plate 15 prepared in the above may be bonded.
[0095]
As described above, according to the third embodiment, the output current of the power amplifying means 73 is supplied to the excitation coil 30, and the excitation current flowing through the excitation coil 30 and the eddy current induced in the diaphragm 10 are reduced. A vibration exciting force and a DC repulsive force corresponding to the modulation signal are obtained by the electromagnetic repulsive force acting between them, and the output current of the power amplifying means 73a is supplied to the exciting coil 35, and the exciting coil 35 and the magnetic plate 15 A vibration excitation force and a DC attraction force corresponding to the modulation signal are obtained by a magnetic attraction force acting between the vibration plate 10 and the DC repulsion force and the DC attraction force cancel each other, and the vibration excitation force is a combined force as the vibration plate 10. Therefore, since the reproduced sound of the voice or noise signal is generated, there is no static displacement of the elastic support means 20, the nonlinear distortion is smaller, the vibration excitation force is increased, and the reproduced sound is more increased. High pressure speaker Effect can be obtained.
[0096]
Embodiment 4 FIG.
FIG. 12 is a structural sectional view of a speaker main body in an electromagnetic acoustic conversion device according to Embodiment 4 of the present invention. In FIG. 12, portions corresponding to the respective portions in FIG. 6 are denoted by the same reference numerals. In FIG. 12A, reference numerals 30a and 30b denote excitation coils (third and fourth excitation coils) opposed to each other with a gap of the same length with respect to the diaphragm 10, and reference numerals 40a and 40b denote excitation coils. A support for fixing the frames 30a and 30b to the frame (third frame) 50b, and 60b is a speaker body (third speaker body). However, as shown in FIG. 12B, the support 40b needs to have a structure (for example, a beam structure or the like) that can secure a sound emission hole.
[0097]
FIG. 13 is a circuit configuration diagram of an excitation device in an electromagnetic acoustic conversion device according to Embodiment 4 of the present invention. In FIG. 13, 70b is an exciting device (third exciting device), 71 is an alternating voltage signal generating means, and 72b is a modulating means (third modulating means).
[0098]
Next, the operation will be described.
The feature of the fourth embodiment resides in a modulating means 72b. The modulating means 72b inputs the audio signal v (t) to two circuits. On the other hand, the constant value α is added by the adding means 74, the alternating voltage signal a (t) is multiplied (modulated) by the multiplying means 75, and this modulated signal is output to the power amplifying means 73.
[0099]
On the other hand, the phase is inverted by a phase inversion means 79 (the sign is inverted in the case of a digital numerical signal), added to a constant value α by an addition means 80, and multiplied by an alternating voltage signal a (t) by a multiplication means 78 (modulation). Then, this modulated signal (third modulated signal) is output to the power amplifying means 73a.
[0100]
The power amplifying means 73 and 73a supply an exciting current as an output to the vibrating coils 30a and 30b of the speaker body 60b via the connectors 61a and 61b and the lead wires 31a and 31b, respectively. When the configuration of the speaker main body 60b is the excitation type, the excitation force received by the diaphragm 10 is as follows.
[0101]
The electromagnetic repulsion generated by the excitation coil 30a is
F_a  = K_t  ・ (Α²  + 2αV (t) + V²  ) (1/2) (1-cos4πf)_s  t)
On the other hand, the electromagnetic repulsive force generated by the exciting coil 30b takes into account that the direction of the force is opposite to the
F_b  = -K_t  ・ (Α²  -2αV (t) + V²  ) (1/2) (1-cos4πf)_s  t)
It is.
[0102]
Therefore, the excitation force received by diaphragm 10 is

[0103]
This expression is the same expression as Expression (5) representing the combined power in the embodiment of the preceding paragraph. Therefore, there is no DC electromagnetic force. Further, according to the fourth embodiment, the gaps on both sides of which the gap dependency of the electromagnetic force complements the non-linear characteristics and approximates the linear characteristics, so that the nonlinear distortion of the radiated sound is small.
[0104]
In addition, since the positions of the force points on the diaphragm 10 of the electromagnetic repulsive force acting so as to cancel each other are the same point (the front and back are different), the deformation of the diaphragm due to the DC repulsive force is unlikely to occur, and the deformation vibration due to the alternating electromagnetic force is not generated. Occurrence is small. Therefore, rib reinforcement for increasing the rigidity of the diaphragm 10 is not necessary.
[0105]
Further, there is a disadvantage that the excitation coils 30a and 30b are also required on the sound radiation surface side. However, in addition to the advantages such as the design likelihood of the diaphragm 10 and the easy adjustment of the excitation circuit of the excitation device 70, the sound quality is improved. There is an advantage that a good speaker can be obtained.
[0106]
As described above, according to the fourth embodiment, the output current of the first power amplifying means 73 is supplied to the first exciting coil 30a, and the exciting current flowing through the exciting coil 30a and the induced current in the diaphragm 10 are generated. A vibration excitation force and a DC repulsion force corresponding to the modulation signal are obtained by an electromagnetic repulsion force acting between the eddy currents, and an output current of the second power amplifying means 73a is supplied to the second excitation coil 30b. The electromagnetic repulsive force acting between the exciting current flowing through the vibration coil 30b and the eddy current induced in the diaphragm obtains a vibration exciting force and a DC repulsive force according to the modulation signal. On the other hand, the vibration excitation force acts on the vibration plate 10 as a resultant force to generate a sound or a reproduced sound of a noise signal. There is no static deformation of the diaphragm 10, Ri nonlinear distortion is small, the vibration exciting force is increased, the effect is obtained that can have high more reproduction sound pressure speaker.
[0107]
Embodiment 5 FIG.
FIG. 14 is a structural sectional view of a diaphragm in an electromagnetic acoustic transducer according to Embodiment 5 of the present invention. In this figure, 10a is a diaphragm composed of a plate 11 and a non-magnetic metal plate 12, and 11 is a vibration plate. The plate 10a is a plate made of an organic material such as wood, a resin laminate, a resin molding material, and the like, and 12 is an annular non-magnetic metal plate made of a highly conductive, non-magnetic metal embedded or bonded to the plate 11. . However, diaphragm 10a is applicable as diaphragm 10 of any of speaker bodies 60, 60a, and 60b described in the first, second, and fourth embodiments.
[0108]
Next, the operation will be described.
A ring current corresponding to the eddy current flowing through the non-magnetic metal plate 12 generates an electromagnetic repulsive force, and vibrates the organic material plate 11 together to emit a sound wave. The inner diameter r1 and the outer diameter r2 of the non-magnetic metal plate 12 are selected so that the non-magnetic metal plate 12 comes to a position facing the circular excitation coil 30. With such a diaphragm 10a, the vibration excitation force is hardly reduced, and the inertial mass is reduced, so that the efficiency as a speaker is improved.
[0109]
As described above, according to the fifth embodiment, the diaphragm 10a has a structure in which the annular high-conductivity, non-magnetic metal plate 12 is embedded or bonded to a part of wood, a resin laminate, or a molded material. Thus, the effect is obtained that the completed mass of the diaphragm 10a can be reduced, and the reproduction efficiency as a speaker can be further increased.
[0110]
Embodiment 6 FIG.
FIG. 15 is a structural diagram of a diaphragm and a vibrating coil in an electromagnetic acoustic transducer according to Embodiment 6 of the present invention. 15A is an exploded view, and FIG. 15B is a cross-sectional view. In FIG. 15, 10b is a diaphragm in which a non-magnetic metal plate 12b is combined with a circular plate 11b, 11b is a circular plate formed by laminating or molding wood or resin, and 12b is a rectangular non-magnetic metal plate made of a conductive and non-magnetic metal. It is. In this case, the excitation coil 30 has a structure wound, for example, in a rectangular shape. However, diaphragm 10b can be applied as diaphragm 10 of any of speaker bodies 60, 60a, and 60b described in the first, second, and fourth embodiments.
[0111]
Next, the operation will be described.
By making the metal plate 10b and the exciting coil 30 have the same rectangular shape, the efficiency of generating the electromagnetic repulsive force (force per unit area of the diaphragm) is increased. The essential point of the sixth embodiment is that the vibration excitation force received by the diaphragm 10b is located at the periphery of the rectangular metal plate 12b, while the basic pattern of the elastic vibration mode of the entire diaphragm 10b is circular ( (Drum mode), it is difficult for elastic vibration to occur. Therefore, deterioration of the reproduction sound quality is suppressed.
[0112]
As described above, according to the sixth embodiment, the diaphragm 10b has a structure in which the rectangular conductive and non-magnetic metal plate 12b is embedded in the center of the circular plate 11b made of wood, resin laminated or molded material. Thus, the effect of suppressing the elastic vibration without increasing the rigidity of the diaphragm 10b and obtaining a reproduced sound with less intermodulation distortion can be obtained.
[0113]
Embodiment 7 FIG.
FIG. 16 is a structural diagram of the diaphragm and the exciting coil in the electromagnetic acoustic transducer according to Embodiment 7 of the present invention. 16A is an exploded view, and FIG. 16B is a sectional view. In FIG. 16, reference numeral 10c denotes a diaphragm obtained by combining a non-magnetic metal plate 12c with a rectangular plate 11c, 11c denotes a rectangular plate formed by laminating or molding wood or resin, and 12c denotes a circular non-magnetic metal plate made of a conductive and non-magnetic metal. It is. In this case, the excitation coil 30 has a structure wound, for example, in a circular shape. However, diaphragm 10c is applicable as diaphragm 10 of any of speaker bodies 60, 60a, and 60b described in the first, second, and fourth embodiments.
[0114]
Next, the operation will be described.
By making the nonmagnetic metal plate 12c and the vibrating coil 30 have the same circular shape, the efficiency of generating electromagnetic repulsion (force per unit area of the diaphragm) is increased. The point of the seventh embodiment is that the vibration excitation force received by the diaphragm 10c is located at the periphery of the circular metal plate 12c, whereas the basic pattern of the elastic vibration mode of the entire diaphragm 10c is linear ( (Corrugated plate mode), so that elastic vibration hardly occurs. Therefore, deterioration of the reproduction sound quality is suppressed.
[0115]
As described above, according to the seventh embodiment, the diaphragm 10c is provided at the center of the rectangular non-magnetic metal plate 11c made of wood, resin laminated or molded material, and the circular conductive and non-magnetic metal plate 12c is provided at the center. With the embedded structure, the elastic vibration can be suppressed without increasing the rigidity of the diaphragm 10c, and an effect that a reproduced sound with less intermodulation distortion can be obtained can be obtained.
[0116]
Embodiment 8 FIG.
FIG. 8 is a sectional view of a speaker main body in an electromagnetic acoustic transducer according to an eighth embodiment of the present invention. In this figure, reference numeral 10 denotes one of diaphragms 10a, 10b, and 10c described in the fifth to seventh embodiments. Is a high-resistance magnetic plate described in Embodiments 2 and 3 embedded in or adhered to the diaphragm 10.
[0117]
FIG. 17 is a circuit configuration diagram of an exciting device in an electromagnetic acoustic transducer according to Embodiment 8 of the present invention. In this figure, 70c is an exciting device, 72c is a modulating means, and 77 is a bias value α multiplied by a predetermined value C. The multiplying means 73a is a power amplifying means for amplifying the power of the output of the multiplying means 77.
[0118]
Next, the operation will be described.
In the excitation device 70c, the power amplifying unit 73a supplies a current corresponding to the alternating voltage signal a (t) modulated by the audio signal v (t) to the exciting coil 30 while the power amplifying unit 73a supplies the exciting coil 35 to the exciting coil 35. A current corresponding to the bias value α is supplied. Thus, the magnetic plate 15 fixed to the vibration plate 10 receives a magnetic attraction force by the electromagnet formed by the excitation coil 35 and the magnetic pole 36.
[0119]
The magnitude of the attraction force is determined by the exciting current, that is, it corresponds to the bias value α of the modulation signal. Since the DC repulsive force acting on the diaphragm 10 is also equivalent to α, if the coefficient C corresponding to the multiplication coefficient is selected to an appropriate value, the attractive force and the DC repulsive force are canceled by the diaphragm 10.
[0120]
As described above, according to the eighth embodiment, the diaphragm 10 is made of a circular plate made of wood, resin laminated or molded material, the magnetic metal small circular plate at the center, and the conductive and non-magnetic metal ring at the periphery. Embedded in the diaphragm 10, the inertial mass of the diaphragm 10 becomes smaller, and the effect that the reproduction efficiency as a speaker can be further improved can be obtained.
[0121]
Further, since the suction force and the DC repulsion force are offset in the diaphragm 10, a reproduced sound with a small nonlinear distortion can be obtained, and the adjustment of the suction force can be performed electrically, so that an effect that is simple and reliable can be obtained. can get.
[0122]
Embodiment 9 FIG.
FIG. 18 is a structural sectional view of the elastic support means in the electromagnetic acoustic transducer according to Embodiment 9 of the present invention. 18A shows a case of a coil spring, and FIG. 18B shows a case of a leaf spring. In FIG. 18, reference numeral 20c denotes elastic supporting means formed by a metal coil spring (metal spring material) fixed to the frame body 50 by bolting or welding, and reference numeral 20d denotes bolting or welding to the frame body 50 by bolting or welding. The elastic support means 10 formed by a fixed metal leaf spring (metal spring material) is a diaphragm made of a metal plate such as aluminum.
[0123]
Next, the operation will be described.
Since the elastic supporting means 20c and 20d and the diaphragm 10 are made of metal, the speaker can be used in a wide temperature environment from a very low temperature to about 300 degrees Celsius, for example, an automobile exhaust pipe.
[0124]
As described above, according to the ninth embodiment, the elastic support means 20c and 20d are formed of the metal spring material which is welded or screwed and fixed at a plurality of positions at the end of the diaphragm 10, so that the rigidity is more severe. An effect that a speaker that can be used in an environment can be obtained.
[0125]
Embodiment 10 FIG.
FIG. 19 is a structural sectional view of a diaphragm in an electromagnetic acoustic conversion device according to Embodiment 10 of the present invention. In the figure, reference numeral 10 denotes a diaphragm, and 14 denotes a diaphragm provided by bonding, welding, or squeezing. It is a rib (bone) material. However, when the diaphragm 10 has a circular shape, it is desirable that the rib member 14 has a linear shape.
[0126]
Next, the operation will be described.
Since the rib member 14 is fixed to the diaphragm 10, the diaphragm is less likely to generate elastic vibration with respect to a vibrating electromagnetic force applied in an axially symmetrical manner, and it is possible to suppress sound radiation of a distorted wave component. It is not advisable to provide a rib on the diaphragm even if it is impossible or possible with a conventional cone-type speaker or the like. With the above configuration in which the flat diaphragm 10 is vibrated by using the electromagnetic repulsion, it is possible to particularly suppress the sound radiation of the distorted wave component.
[0127]
As described above, according to the tenth embodiment, the rib members 14 are provided on the outer or inner side surfaces of the diaphragm 10 to increase the rigidity against elastic vibrations, thereby increasing the rigidity against elastic vibrations, and thereby reducing distortion. An effect that can be reproduced sound is obtained.
[0128]
Embodiment 11 FIG.
FIG. 20 is a structural sectional view of the elastic support means in the electromagnetic acoustic transducer according to Embodiment 11 of the present invention. In the figure, reference numeral 20c denotes a coil spring, 20e denotes a glass wool material, and 20 denotes a glass wool material 20e in which the coil spring 20c is embedded. This is an elastic supporting means formed by:
[0129]
Next, the operation will be described.
Since the elastic supporting means 20 uses the elastic supporting means 20 having an appropriate spring property by the coil spring 20c and an appropriate mechanical resistance by the glass wool material 20e, the reproducing sound pressure is increased by narrowing the sound reproducing band. can do.
[0130]
As described above, according to the thirteenth embodiment, the elastic support means 20 has a structure in which the coil spring material 20c is embedded in the glass wool material 20e. The reproduction band is narrowed, and the reproduction sound pressure can be increased. As a result, there is obtained an effect that the speaker can be designed to have a wider design range, that is, a wider application range.
[0131]
Embodiment 12 FIG.
FIG. 21 is a structural sectional view of the elastic support means in the electromagnetic acoustic transducer according to Embodiment 12 of the present invention. In FIGS. 21 (a) and (b), reference numeral 10 denotes a disk-shaped diaphragm, 20e and 20g are disposed above the center of the diaphragm 10 and above the excitation coil 30, and several (as shown) The glass wool material is elastic support means supported and fixed by two beam portions 53 and 54, and 53 and 54 are beam portions for supporting and fixing the glass wool materials 20e and 20g.
[0132]
Next, the operation will be described.
The requirement of the twelfth embodiment is that the excitation coil 30 is disposed immediately below the elastic supporting means 20e and 20g, whereby the electromagnetic excitation force causes the elastic vibration of the diaphragm 10 to be reduced. Since it only joins the nodes of the mode, that is, the five supported positions, strength deformation is unlikely to occur, and the risk of deformation vibration is reduced.
[0133]
As described above, according to the twelfth embodiment, since the glass wool material 20g is provided between the excitation coil 30 and the diaphragm 10, strength deformation is less likely to occur, and the risk of causing deformation vibration is reduced. As a result, the effect of suppressing vibration due to the strength deformation of the diaphragm 10 and improving the radiation sound characteristics can be obtained.
[0134]
Embodiment 13 FIG.
FIG. 22 is a structural sectional view of a vibrating coil in an electromagnetic acoustic transducer according to Embodiment 13 of the present invention. In the figure, 30c and 30d are small vibrating coils, and 40a and 40b are vibrating coils 30c and 30d. It is a magnetic pole, and the excitation coils 30c and 30d are electrically connected in series.
[0135]
Next, the operation will be described.
In the first to twelfth embodiments, the number of the vibrating coil 30 is one irrespective of a circular shape or a rectangular shape. As shown in FIG. 23, when the diaphragm 10 has low rigidity, so-called deformed vibration occurs in which the vibrating plate 30 vibrates while being deformed in the vicinity of the exciting coil 30 to which the electromagnetic force is applied. This lowers the radioactivity of the sound wave as compared with the case where the diaphragm 10 vibrates integrally with the front surface without being deformed, and may affect the directivity. The thirteenth embodiment improves this problem.
[0136]
As shown in FIG. 22, when a plurality of excitation coils 30 c and 30 d are used, these excitation coils 30 c and 30 d are electrically connected in series and receive an excitation current supplied from the excitation device 60. By providing a plurality of the vibrating coils 30c and 30d in this way, the vibrating points on the diaphragm 10 are dispersed and the vibrating is performed with a uniform force, so that the deformation vibration can be suppressed. The reason why the exciting coils 30c and 30d are connected in series is that the same electromagnetic exciting force can be obtained when the same current flows through each of the exciting coils 30c and 30d.
[0137]
As described above, according to the thirteenth embodiment, since a plurality of excitation coils 30c and 30d are provided, forced deformation and elastic vibration of diaphragm 10 are reduced, and reproduced sound with less nonlinear distortion is obtained. The effect that can be obtained is obtained.
[0138]
Embodiment 14 FIG.
FIG. 24 is an external view of a diaphragm in an electromagnetic acoustic transducer according to Embodiment 14 of the present invention. In the drawing, reference numeral 18 denotes a symbol, a character, a pattern printed or engraved on the diaphragm 10, or affixed to the diaphragm 10. It is a visual information means such as a symbol printed on the attached sheet.
[0139]
Next, the operation will be described.
By attaching the visual information means 18 to the diaphragm 10, audible information transmission by radiating an audio waveform and visual information transmission by the same diaphragm 10 can be simultaneously obtained. This is because conventional speakers such as cone-type speakers cannot display characters or figures, or even if they can, they cannot transmit enough visual information. The visual information means 18 can be attached to the diaphragm 10 formed by the above, so that visual information can be transmitted.
[0140]
As described above, according to the fourteenth embodiment, the visual information means 18 is provided on the outer surface of the diaphragm 10, so that the diaphragm 10 can also have a function of transmitting visual information. Thus, the installation space efficiency of the display panel is enhanced, and thus, if the speaker is used in a portable electronic device or the like, the effect of reducing the size of the device can be obtained.
[0141]
Embodiment 15 FIG.
FIG. 25 is a structural sectional view of a speaker main body of an electromagnetic acoustic transducer according to Embodiment 15 of the present invention. In the figure, reference numeral 200 denotes, for example, an LCD panel, an EL (Electro Luminescence), a PD (Plasma Display), and an LED (Light Emitted). A display panel having an electronic display function such as a diode (V. Diode) or a VFD (Vacuum Fluosense Sense Display) is fixed to the diaphragm 10 by a method such as bonding or screwing. A cable 202 having a possibility of being soft for supplying a display signal and electric energy to the frame 202 is connected to the cable 201, and a cable from an external display driver (not shown) is connected to the frame 50. Provided by the way Connector.
[0142]
Next, the operation will be described.
In the fifteenth embodiment, the vibration exciting force is generated by the diaphragm 10, and the display panel 200, which vibrates integrally with the diaphragm 10, emits a sound waveform to the outside, and the display panel 200 is controlled electronically. Display information.
[0143]
Therefore, while watching the sentence characters of the story displayed on the display panel 200, the user can hear the voice reading the sentence as if it were coming out of the characters, and can hear the singing singer's face and face. Is displayed on the display panel, it is possible to give the impression that the voice comes out of the mouth of the singer (video).
[0144]
As described above, according to the fifteenth embodiment, the display panel 200 having an electronic display function, for example, an LCD panel is fixed to the outside of the diaphragm 10, and the display panel 200 itself also serves as a part of the diaphragm 10. As a result, the effect of increasing the installation space efficiency of the speaker and the display device and making the reproduction of the AV source more realistic can be obtained.
[0145]
Embodiment 16 FIG.
FIG. 26 is a conceptual diagram showing a configuration of a speaker body in an electromagnetic acoustic conversion device according to Embodiment 16 of the present invention. In the drawing, reference numeral 63 denotes an electrical connection between the lead wire 31 of the excitation coil 30 and the connector 61. A phase-advancing capacitor (capacitance element) fixed at a position surrounded by the magnetic pole 40 and the frame 50.
[0146]
Next, the operation will be described.
In the loudspeaker of the present invention, the electrical impedance of the exciting coil 30 is extremely reactive due to the principle of obtaining the exciting force, and the power factor characteristic of the exciting power supply must be very small. Therefore, in order to supply a predetermined current, the power amplifying means 73 of the excitation device 70 needs to output a high voltage. Also, the excitation cable 62 is required to have a withstand voltage characteristic.
[0147]
Therefore, the phase advance capacitor 63 is provided as described above. The capacitance value of the phase-advancing capacitor 63 is represented by L, the time-average reactance of the exciting coil 30, and the frequency f of the alternating voltage signal._s  Where C = 1 / (2πf_s  )²  ・ Approximately half the value for resonance determined by L.
[0148]
As a result, the impedance as viewed from the amplifier side is reduced to about half, and accordingly, the output voltage can be reduced to about half. In addition, the influence on the exciting coil current (and the effect on the reproduced sound quality) due to the change in the reactance such as the change in the reactance of the coil due to the vibration of the diaphragm 10 is not large. In addition, the withstand voltage of the cable 62 becomes easy.
[0149]
As described above, according to the sixteenth embodiment, the phase-advancing capacitor 63 is connected and inserted between the lead wire 31 of the excitation coil 30 and the connector 61 provided on the frame body 50. Since the required output voltage of the speaker 70 can be reduced and the cable 62 has a low withstand voltage characteristic, an effect that a more inexpensive speaker can be obtained is obtained.
[0150]
Embodiment 17 FIG.
FIG. 27 is a circuit diagram of an exciting device of an electromagnetic acoustic transducer according to Embodiment 17 of the present invention. In the drawing, reference numeral 76 denotes a circuit between the adding means 74 and the multiplying means 75 of the exciting device 70 shown in FIG. It is a numerical conversion means by a numerical conversion table which is connected and outputs numerical data S1a obtained by correcting the audio signal S1 biased by the numerical value α. In this example, it is assumed that the input signal v (t) is a digitized signal, and in this case, the amplifying unit 73 has a built-in digital / analog converting unit.
[0151]
Next, the operation will be described.
The electromagnetic repulsion depends on the gap length between the diaphragm 10 and the excitation coil 30, as shown in FIG. The repulsion decreases with increasing air gap, approximately in the form of an exponential function. The problem is small when the vibration stroke of the diaphragm is small, but when the stroke is large, the waveform distortion of the reproduced sound cannot be ignored.
[0152]
Therefore, the seventeenth embodiment provides a numerical value conversion means for solving the problem. The numerical value conversion means 76 receives the audio signal S1 biased by the numerical value α, and outputs corrected numerical data S1a. Here, the numerical value conversion means 76, that is, the contents of the numerical value conversion table have contents for compensating for the air gap characteristics, and after all the design conditions are determined, a specific converted value is obtained.
[0153]
As described above, according to the seventeenth embodiment, the excitation device 70 has the numerical value conversion means 76 that converts the instantaneous value of the audio signal waveform biased at a constant value, and compensates for the gap dependency of the electromagnetic force. As a result, an effect of obtaining a reproduced sound with less nonlinear distortion can be obtained.
[0154]
【The invention's effect】
As described above, according to the first aspect of the present invention, the electromagnetic force acting between the exciting current flowing through the first exciting coil supplied with the output current of the first exciting device and the eddy current induced on the diaphragm. Vibration exciting force according to the modulation signal is obtained by the repulsive force, and a sound or noise signal reproduction sound is generated by this vibration exciting force. There is an effect that a thin speaker can be produced.
[0155]
According to the second aspect of the present invention, a magnetic plate made of an electrically insulating magnetic material is provided on a part of the diaphragm and a permanent magnet means is provided at a position facing the magnetic plate. Due to the attraction force, the DC electromagnetic repulsive force generated by the excitation coil can be reduced, so that the displacement of the elastic support means is suppressed, and a reproduced sound with less nonlinear distortion can be obtained.
[0156]
According to the third aspect of the present invention, the direct current repulsive force and the direct current attractive force cancel each other, and the first and second vibration exciting forces act on the diaphragm as a resultant force, thereby reproducing a sound or noise signal. Since it is configured to generate sound, there is no static displacement of the elastic support means, less non-linear distortion, and vibration excitation force is increased, so that a speaker having a higher reproduction sound pressure can be obtained. is there.
[0157]
According to the fourth aspect of the present invention, the two DC repulsive forces are offset by the opposite directions of action, and the two vibration exciting forces act on the diaphragm as a resultant force, thereby producing a sound or noise signal. Since it is configured to generate the reproduced sound, there is no static displacement of the elastic support means and no static deformation of the diaphragm, and the nonlinear distortion is small, and the vibration exciting force is increased, and the reproduced sound pressure is reduced. There is an effect that a high speaker can be obtained.
[0158]
According to the invention as set forth in claim 5, the diaphragm is embedded or bonded to a plate formed of any one of a single organic material, a laminated material of a plurality of types of organic materials, and a molded material of an organic material. Since it is composed of the conductive and non-magnetic metal plates provided, the elastic vibration is suppressed without increasing the rigidity of the diaphragm, and there is an effect that a reproduced sound with less intermodulation distortion can be obtained.
[0159]
According to the invention of claim 6, since the plate of the diaphragm and the non-magnetic metal plate are formed into a plurality of shapes, the elastic vibration is suppressed without increasing the rigidity of the diaphragm, and the intermodulation is suppressed. There is an effect that a reproduced sound with less distortion can be obtained.
[0160]
According to the seventh aspect of the present invention, since the diaphragm is formed of a copper plate of 0.4 mm to 1.6 mm or an aluminum plate of 0.5 mm to 2.0 mm, a simple, robust and inexpensive speaker can be provided. There is an effect that can be.
[0161]
According to the eighth aspect of the present invention, since the elastic supporting means is made of a high-density glass wool material or a rubber material which sandwiches the peripheral portion of the diaphragm, the damping performance and the spring performance can be obtained by the same member, which makes it easier and less expensive. There is an effect that the speaker can be used.
[0162]
According to the ninth aspect of the present invention, since the elastic supporting means is formed of a metal spring material welded or screwed and fixed to a plurality of positions at the end of the diaphragm, a speaker which can be used in a more severe environment can be provided. There is an effect that can be done.
[0163]
According to the tenth aspect of the present invention, since the rib is provided on the outer surface or the inner surface of the diaphragm, there is an effect that the rigidity with respect to the elastic vibration can be increased, and the reproduced sound can be reduced in distortion.
[0164]
According to the eleventh aspect of the present invention, since the elastic support means is configured by embedding a metal spring material in glass wool material, the elastic support means has an appropriate mechanical resistance, so that the sound reproduction band is narrowed, The pressure can be increased, which has the effect of allowing a design margin, that is, a speaker having a wider application range.
[0165]
According to the twelfth aspect of the present invention, since the elastic supporting means is provided between the excitation coil and the diaphragm, strength deformation is less likely to occur, and the risk of causing deformation vibration is reduced. Vibration due to strength deformation of the plate is suppressed, and the radiation sound characteristics can be improved.
[0166]
According to the thirteenth aspect of the present invention, since a plurality of excitation coils are electrically connected in series and provided, the forced deformation and elastic vibration of the diaphragm are reduced, and the reproduced sound having less nonlinear distortion is obtained. There is an effect that can be.
[0167]
According to the fourteenth aspect of the present invention, a visual information means by writing or printing a pattern, character, or symbol on the outer surface of the diaphragm or laminating a sheet on which the pattern, character, or symbol is written is attached. Therefore, the installation space efficiency of the speaker and the display panel can be increased, and the size of the portable electronic device can be reduced.
[0168]
According to the invention of claim 15, a display panel having an electronic display function is fixed to the outside of the diaphragm, and the display panel is configured to also serve as a part of the diaphragm. There is an effect that the installation space efficiency can be improved and the reproduction of the AV source can be made more realistic.
[0169]
According to the sixteenth aspect of the present invention, since the capacitance element is connected between the lead wire of the excitation coil and the connector provided on the frame, the output voltage required by the excitation device is reduced. Since the cable and the withstand voltage characteristics are low, there is an effect that a cheaper speaker can be obtained.
[0170]
According to the seventeenth aspect of the present invention, since the exciting device is provided with numerical value conversion means for converting the instantaneous value of the waveform of the audio signal biased at a constant value and compensating for the gap dependency of the electromagnetic force, the nonlinear distortion Therefore, there is an effect that a smaller reproduced sound can be obtained.
[Brief description of the drawings]
FIG. 1 is a configuration diagram of an electromagnetic acoustic conversion device according to a first embodiment of the present invention.
FIG. 2 is a structural sectional view of a speaker body of the electromagnetic acoustic conversion device according to Embodiment 1 of the present invention;
FIG. 3 is a circuit configuration diagram of an excitation device of the electromagnetic acoustic conversion device according to the first embodiment of the present invention;
FIG. 4 is a diagram for explaining an operation of the excitation device of the electromagnetic acoustic conversion device according to the first embodiment of the present invention.
FIG. 5 is a diagram illustrating the frequency dependence of the vibration system mechanical impedance for describing the operation of the electromagnetic acoustic transducer according to the first embodiment of the present invention.
FIG. 6 is a cross-sectional view for explaining a specific configuration of the electromagnetic acoustic conversion device according to the first embodiment of the present invention.
FIG. 7 is a structural sectional view of a speaker main body of the electromagnetic acoustic conversion device according to Embodiment 2 of the present invention.
FIG. 8 is a structural sectional view of a speaker body of an electromagnetic acoustic transducer according to Embodiments 3 and 8 of the present invention.
FIG. 9 is a circuit configuration diagram of an excitation device of the electromagnetic acoustic transducer according to Embodiment 3 of the present invention.
FIG. 10 is a structural view of a diaphragm of the speaker body shown in FIG.
11 is another structural view of the diaphragm of the speaker main body shown in FIG. 8;
FIG. 12 is a structural sectional view of a speaker main body of an electromagnetic acoustic conversion device according to Embodiment 4 of the present invention.
FIG. 13 is a circuit configuration diagram of an excitation device of an electromagnetic acoustic conversion device according to Embodiment 4 of the present invention.
FIG. 14 is a structural sectional view of a diaphragm of an electromagnetic acoustic transducer according to Embodiment 5 of the present invention.
FIG. 15 is a structural sectional view of a diaphragm and a vibrating coil of an electromagnetic acoustic transducer according to Embodiment 6 of the present invention.
FIG. 16 is a structural sectional view of a diaphragm and an exciting coil of an electromagnetic acoustic transducer according to Embodiment 7 of the present invention.
FIG. 17 is a structural sectional view of a diaphragm and a vibrating coil of an electromagnetic acoustic transducer according to an eighth embodiment of the present invention.
FIG. 18 is a structural sectional view of an elastic supporting means of the electromagnetic acoustic transducer according to Embodiment 9 of the present invention.
FIG. 19 is an external view of a diaphragm of an electromagnetic acoustic conversion device according to Embodiment 10 of the present invention.
FIG. 20 is a structural sectional view of an elastic supporting means in an electromagnetic acoustic transducer according to Embodiment 11 of the present invention;
FIG. 21 is a structural sectional view of an elastic supporting means in an electromagnetic acoustic transducer according to Embodiment 12 of the present invention;
FIG. 22 is a structural sectional view of a vibrating coil of an electromagnetic acoustic transducer according to Embodiment 13 of the present invention;
FIG. 23 is a diagram showing a state of deformation of a diaphragm of an electromagnetic acoustic conversion device according to Embodiment 13 of the present invention due to static force.
FIG. 24 is an external view of a diaphragm of an electromagnetic acoustic transducer according to Embodiment 14 of the present invention.
FIG. 25 is a structural sectional view of a speaker main body of the electromagnetic acoustic transducer according to Embodiment 15 of the present invention.
FIG. 26 is a conceptual diagram of a speaker main body of an electromagnetic acoustic conversion device according to Embodiment 16 of the present invention.
FIG. 27 is a circuit configuration diagram of an excitation device of an electromagnetic acoustic transducer according to Embodiment 17 of the present invention;
FIG. 28 is a diagram showing the gap dependence of the electromagnetic force generation efficiency related to the principle of the electromagnetic acoustic transducer.
FIG. 29 is an external view of a diaphragm of a conventional electromagnetic acoustic transducer.
FIG. 30 is a current waveform diagram for explaining the operation of the excitation device of the conventional electromagnetic acoustic conversion device.
FIG. 31 is another current waveform diagram for explaining the operation of the exciting device of the conventional electromagnetic acoustic transducer.
[Explanation of symbols]
10, 10a, 10b, 10c diaphragm, 12, 12b, 12c non-magnetic metal plate, 14 rib material, 15 electrically insulating magnetic plate, 18 visual information means, 20 elastic support means, 20c coil spring (metal spring) Material), 20d leaf spring (metal spring material), 20e, 20g glass wool material, 30 excitation coil (first excitation coil), 30a excitation coil (third excitation coil), 30b excitation coil (fourth excitation coil) Excitation coil), 30c, 30d small excitation coil, 34 permanent magnet means, 35 excitation coil (second excitation coil), 36 magnetic poles, 40 magnetic poles, 50 frame (first frame), 50a frame Body (second frame), 50b frame (third frame), 60 speaker body (first speaker body), 60a speaker body (second speaker body), 60b speaker body (third frame) Speaker body, 61 connector, 62 excitation cable, 63 phase-advancing capacitor (capacitance element), 70 excitation device (first excitation device), 70a excitation device (second excitation device), 70b excitation device (third excitation device) Device), 71 alternating voltage generating means, 72 modulating means (first modulating means), 72a modulating means (second modulating means), 72b modulating means (third modulating means), 73 power amplifying means (first power amplifying means) 73a, power amplifying means (second power amplifying means), 76 numerical value converting means, 200 display panel.

Claims (17)

An alternating voltage generating means for generating an alternating voltage signal having a constant frequency; and a signal obtained by adding a constant bias signal to a voice or noise signal previously converted into an electric signal, and modulating the alternating voltage signal. A first excitation device having first modulation means for outputting one modulation signal; first power amplification means for power-amplifying the modulation signal; and a first excitation coil to which an output current of the first excitation device is supplied A conductive member which is disposed opposite to the first exciting coil with an air gap therebetween and receives an electromagnetic repulsive force acting between the eddy current induced by the exciting current flowing through the first exciting coil and the exciting current A first speaker main body including a non-magnetic diaphragm, elastic supporting means for supporting the diaphragm, and a first frame for fixedly supporting the elastic supporting means and the first excitation coil in a predetermined arrangement; Electromagnetic acoustic transducer with Apparatus. 2. The electromagnetic acoustic transducer according to claim 1, wherein a magnetic plate made of an electrically insulating magnetic material is provided on a part of the diaphragm, and permanent magnet means is provided at a position facing the magnetic plate. An alternating voltage generating means for generating an alternating voltage signal having a constant frequency; and a first modulating signal output by modulating the alternating voltage signal with a signal obtained by adding a constant bias signal to a voice or noise signal previously converted into an electric signal. At the same time, a signal obtained by inverting the phase or sign of the voice or noise signal and the bias signal are added, and the alternating voltage signal is modulated with a signal obtained by multiplying the added signal by a predetermined value to output a second modulated signal. A second excitation device including a second modulation unit, a first power amplification unit for power-amplifying the first modulation signal, and a second power amplification unit for power-amplifying the second modulation signal; and the first excitation device. A first exciting coil to which the output current is supplied, and an eddy current which is disposed opposite to the first exciting coil with an air gap therebetween, and which is induced according to an exciting current flowing through the first exciting coil. excitation A conductive and non-magnetic diaphragm receiving an electromagnetic repulsive force acting between the current flow, a second vibrating coil to which an output current of the second power amplifying means is supplied, and a part provided on the diaphragm; A magnetic plate made of an electrically insulating magnetic material that is disposed at a position facing the second excitation coil and in which a magnetic attraction force acts between the second excitation coil and elastic support means for supporting the vibration plate; An electromagnetic acoustic conversion device comprising: a second speaker main body having the elastic support means and a second frame body fixedly supporting the first and second excitation coils at predetermined positions. An alternating voltage generating means for generating an alternating voltage having a constant frequency, and a first modulated signal output by modulating the alternating voltage signal with a signal obtained by adding a bias signal having a fixed value to an audio or noise signal previously converted into an electric signal. A third modulating means for modulating an alternating voltage signal with a signal obtained by adding the bias signal to a signal obtained by inverting or reversing the phase of the voice or noise signal and outputting a third modulation signal; Power amplification means for amplifying the power of the third modulation signal, a third excitation device having a second power amplification means for amplifying the power of the third modulation signal, and the third excitation to which the output current of the first power amplification means is supplied A coil, the fourth excitation coil to which the output current of the second power amplifying means is supplied, and the third and fourth excitation coils are symmetrically arranged from both surfaces with an air gap therebetween, and Exciting carp Receiving an electromagnetic repulsive force acting between the eddy current induced by the exciting current flowing through the fourth exciting coil and the exciting current, and the eddy current induced by the exciting current flowing through the fourth exciting coil and the exciting current A conductive and non-magnetic vibrating plate receiving an electromagnetic repulsive force acting between the vibrating plate, elastic supporting means for supporting the vibrating plate, and fixedly supporting the elastic supporting means and the third and fourth vibrating coils in a predetermined arrangement. An electromagnetic acoustic conversion device, comprising: a third speaker main body having a third frame body. The diaphragm is made up of a plate formed of one of a single organic material, a laminated material of a plurality of types of organic materials, and a molded material of an organic material, and a conductive and non-magnetic metal plate embedded or bonded in the plate. The electromagnetic acoustic transducer according to any one of claims 1 to 4, wherein the electromagnetic acoustic transducer is configured. The electromagnetic acoustic conversion device according to claim 5, wherein the diaphragm plate and the non-magnetic metal plate are formed into a plurality of shapes. The diaphragm according to any one of claims 1 to 4, wherein the diaphragm has a structure including a copper plate of 0.4 mm to 1.6 mm or an aluminum plate of 0.5 mm to 2.0 mm. Electromagnetic acoustic transducer. The electromagnetic acoustic conversion device according to any one of claims 1 to 7, wherein the elastic support means is made of a high-density glass wool material or a rubber material sandwiching a peripheral portion of the diaphragm. The electromagnetic acoustic device according to any one of claims 1 to 7, wherein the elastic supporting means is formed of a metal spring material welded or screwed to a plurality of locations at the end of the diaphragm. Conversion device. The electromagnetic acoustic transducer according to any one of claims 1 to 9, wherein a rib material is provided on an outer surface or an inner surface of the diaphragm. The electromagnetic acoustic transducer according to any one of claims 1 to 7, wherein the elastic support means has a structure in which a metal spring material is embedded in a glass wool material. The electromagnetic acoustic transducer according to any one of claims 1 to 7, wherein the elastic support means is provided between the excitation coil and the diaphragm. 13. The electromagnetic acoustic conversion device according to claim 1, wherein a plurality of excitation coils are provided. 14. The visual information means by writing or printing a pattern, character, or symbol on the outer surface of the diaphragm, or attaching a sheet on which the pattern, character, or symbol is written is attached. The electromagnetic acoustic conversion device according to any one of the above. 14. The display panel according to claim 1, wherein a display panel having an electronic display function is fixed outside the diaphragm, and the display panel also serves as a part of the diaphragm. Item 7. The electromagnetic acoustic conversion device according to Item 1. The electromagnetic acoustic transducer according to any one of claims 1 to 15, wherein a capacitance element is connected between a lead wire of the excitation coil and a connector provided on the frame. . 17. The exciting device according to claim 1, further comprising: a numerical converter for converting a waveform instantaneous value of the audio signal biased at a constant value to compensate for a gap dependency of an electromagnetic force. 2. The electromagnetic acoustic conversion device according to claim 1.

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