JP3882762B2

JP3882762B2 - Speaker diaphragm

Info

Publication number: JP3882762B2
Application number: JP2003041356A
Authority: JP
Inventors: 智今村; 猛平野; 知昭尾形; 敏勝桑波田
Original assignee: Victor Company of Japan Ltd
Current assignee: Victor Company of Japan Ltd
Priority date: 2003-02-19
Filing date: 2003-02-19
Publication date: 2007-02-21
Anticipated expiration: 2023-02-19
Also published as: JP2004254013A

Description

【０００１】
【発明の属する技術分野】
本発明は、オーディオ用スピーカの技術分野に属し、特にダイナミック・スピーカに用いられるスピーカ用振動板に関する。
【０００２】
【従来の技術】
従来、ダイナミック・スピーカの振動板としては、紙パルプ製、プラスチック製又はアルミ等の金属製のものが殆どであった。これら従来の振動板は均一材料をプレス成形して成るので中心から半径方向の音の伝搬速度があらゆる方向で等しくなっている。したがって、必ず定在波が発生して共振ポイントを持ち、低周波領域での分割振動による音圧周波数特性の悪化を招き、しかも臨場感が欠落するという難点がある。また、紙パルプ製やプラスチック製の振動板は比較的大きな内部損失係数を有するものの、逆に剛性（ヤング率の大小）の点では劣り、音波伝搬速度は小さいので再生音の解像度にやや不満が残る。一方、アルミ等の金属製振動板は音波伝搬速度が高いものの内部損失係数が小さいので振幅の減衰が小さく再生音の区切りが不明瞭となる（所謂、音のメリハリが悪い。）という難点がある。
【０００３】
上記のような一長一短のある既存素材の振動板に代わって、より自然に近い音を再現できるスピーカ用振動板として木製振動板の実現が望まれている。
【０００４】
即ち、木材の音波伝搬速度はその種類によって異なるが、一般に紙パルプよりも高く、さらに木目の方向とその直角方向とで異なり、木目方向（縦方向という。）の伝搬速度は速く、木目と直角方向（横方向という。）の伝搬速度は比較的遅いという異方性の伝搬性質を有している。また、木材は一般にスピーカ用振動板として適当な内部損失係数を有しており、且つ軽量で丈夫（高剛性）である。
【０００５】
したがって、木材そのものを素材とする木製振動板は定在波が発生しにくく共振ポイントが殆ど現れないので分割振動が殆ど発生せず、低周波領域の音圧周波数特性の改善が期待され、既存の紙パルプ製の振動板に比べて再生音の解像度向上や歯切れ良い音の向上が図れるのである。
【０００６】
上記木製振動板若しくは木製振動板を用いたダイナミック・スピーカや木製振動板の製造方法として、例えば以下に挙げる公知文献に種々の提案が既に為されている。
【０００７】
下記［特許文献１］には、木質材の平板状薄板にポリエステル等のプラスチックを含浸硬化したＷＰＣ化処理木材の平面薄板を寸法安定性、内部摩擦、剛性などの特性において優れるスピーカ用平面振動板として用いたスピーカが提案されている。
【０００８】
下記［特許文献２］には、図７の（ａ）、（ｂ）に示す製造手順のように、（ａ）一枚の木材薄板４から中心部に円弧状の切り欠き部１ａを有し、それに連続して扇形の切り欠き部１ｂを有する略ラッパ形状の展開形状である木材シート１を切り出し、（ｂ）木材シート１の扇形状の切り欠き部１ｂの両縁部ｂ１、ｂ２を糊代部分１ｃで互いに接着剤で重ね貼り合わせてラッパ状に形成し、その後にプレス成形してなるコーン振動板５が提案されている。
【０００９】
また、図８の（ａ）、（ｂ）に示す製造手順のように、複数の木材小片シート２ａ、２ｂ・・・、２Ｌを接着剤で貼り合わせて（ｂ）のように略ラッパ状に形成し、その後にプレス成形してなるコーン振動板２が提案されている。また、上記コーン振動板１、２に物理的耐湿処理或いは化学的耐湿処理を加えたコーン振動板が提案されている。
【００１０】
下記［特許文献３］には、８０μｍ以下にスライスされた極薄木材シートと、その裏面に貼付された接着性の樹脂からなる不織布と、から構成される複合シートを、柔軟剤で柔軟化処理して複数枚積層し、さらに加熱及び加圧して円錐形状に成形した音響用振動板が提案されている。
【００１１】
下記［特許文献４］には、扇形形状に切断した平板状の木材薄板を成形時に割れ発生を防止するために高温度の蒸気、熱湯、又はｐＨ１０以上のアルカリ溶液でボイルした後、円錐状にプレス成形してなるコーン振動板が提案されている。
【００１２】
下記［特許文献５］には、１枚の木製シートの一面側に薄い不織布又は和紙を貼着した貼り合わせシートを作成し、これを潤滑剤入りの容器に含浸し、含浸された貼り合わせシートをプレス加熱成形して略ラッパ状に成形したスピーカ用振動板が提案されている。
【００１３】
下記［特許文献６］には、プレス成形時にしわや割れの生じない、かつ、経時変化の少ない木製のスピーカ用振動板を作るために、１枚の木製シートの一面側に薄い不織布又は和紙又はカーボンシートを貼着した貼り合わせシートを作成し、これを熱硬化性樹脂に含浸させた後、プレス加熱成形して略ラッパ状に成形してなるスピーカ用振動板が提案されている。
【００１４】
【特許文献１】
特開昭６２−２２４１９６号公報
【特許文献２】
特開平１−２８８１００号公報
【特許文献３】
特開平５−８３７９２号公報
【特許文献４】
特開平６−１７８３８６号公報
【特許文献５】
特開平１０−３０４４９２号公報
【特許文献６】
特開２０００−５９８８３号公報
【発明が解決しようとする課題】
木製のスピーカ用振動板において特にポイントとなるのは、木材という素材の割れ易いという性質に如何に対処するか、また、成形性の悪さ、経年変化に如何に対処するかである。
【００１５】
この点、［特許文献１］は対象が木製の平面振動板であって、木製であることの特質・利点は示されているものの、略ラッパ状（コーン状）に成形加工する際の問題点に関する技術的資料は平面であるが故に何ら提供されていない。
【００１６】
また、［特許文献２］の図７及び図８のような製造方法では、木材シート１若しくは木材小片シート２ａ、２ｂ・・が木の素材のみの状態で成形されているために、取り扱いの際やプレス成形時に割れが生じてしまったり、木材シートを互いに接着剤で貼り合わせるため、貼着部が障害となって所望の音響特性が得られないという問題や寸法精度が確保できないという問題がある。
【００１７】
また、［特許文献３］の極薄木材シートを複数枚積層してプレス成形する方法は、加工精度に難点があり、接着層が増えて接着剤の重量により振動板自体の重量が増加して所望の音響特性が得られず、多量の接着剤が音圧周波数特性にも悪影響を与えるので好ましくない。
【００１８】
また、［特許文献４］のようにプレス成形前に高温水蒸気やＰＨ１０以上のアルカリ溶液でのボイル処理が含まれる製造工程による場合は、木材の中のリグニンという構成物質をも取り去ってしまうので木材の本来の特徴を発揮できず、音質に悪影響を与えることになる。
【００１９】
そして何よりも上記［特許文献２］、［特許文献３］、［特許文献４］の内容は製造中での割れ、ひび、しわの発生といった不具合が多く発生し、量産面での歩留まりが非常に悪くなって製品化が実現していないのである。
【００２０】
また、［特許文献５］や［特許文献６］における“張り”や“しなやかさ”を引き出すための潤滑剤の含浸及びしわや割れの発生防止、経時変化を防止するための熱硬化性樹脂の含浸後にプレス加熱成形してなるスピーカ用振動板は前記［特許文献１］〜［特許文献４］に比べて量産に向けた製造工程の優位性は認められるが、未だ十分な成形性、成形処理の確立が達成されたとは言えず、木製振動板の実用化に向けてより一層の成形性の向上、延いては美しい仕上がりの木製振動板の実現が望まれる。
【００２１】
本発明は、上記事情に鑑みてなされたものであり、オーディオ用スピーカの音響特性改善に有効で量産性に優れる木製のスピーカ用振動板を提供するものである。
【００２２】
【課題を解決するための手段】
本発明は上記課題を解決するために、
（１）１枚の木製シート１０を素材として略ラッパ形状にプレス成形してなるスピーカ用振動板において、１枚の木製シート１０に対して、中心部に頂点が至る略Ｖ字状の切り込み１１を設け、前記切り込みを設けた木製シート１０に水分を与えて軟化させるとともに木製シート１０中に水分を保持する作用を有する潤滑剤１６を含ませ、前記潤滑剤１６が含まされた木製シート１０は１次プレス加熱成形によって前記略Ｖ字状の切り込み１１の縁部１１ａ、１１ｂ同士が重ね合わされて略ラッパ状に仮成形され、仮成形の後に乾燥され、乾燥後に熱硬化性樹脂１７が含まされ、前記熱硬化性樹脂１７が半乾き状態になるまで５０℃〜６０℃の乾燥温度で略１〜１０分間乾燥が行われて半乾燥され、前記熱硬化性樹脂１７の半乾き状態で２次プレス加熱成形され、前記２次プレス加熱成形の後に防湿剤１８が塗布され、前記防湿剤１８の塗布された木製シート１０に対してボイスコイル用の中心孔２５抜きと外形抜きを行って振動板としての所定寸法形状に成形してなることを特徴とするスピーカ用振動板２０を提供する。
（２）１枚の木製シート１０を素材として略ラッパ形状にプレス成形してなるスピーカ用振動板において、１枚の木製シート１０の一面側に薄い不織布又は和紙１３を貼着してなる貼り合わせシート１５に対して、中心部に頂点が至る略Ｖ字状の切り込み１１を設け、前記切り込み１１を設けた貼り合わせシート１５に水分を与えて軟化させるとともに貼り合わせシート１５中に水分を保持する作用を有する潤滑剤１６を含ませ、前記潤滑剤１６が含まされた貼り合わせシート１５は１次プレス加熱成形によって前記略Ｖ字状の切り込み１１の縁部１１ａ、１１ｂ同士が重ね合わされて略ラッパ状に仮成形され、仮成形の後に乾燥され、乾燥後に熱硬化性樹脂１７が含まされ、前記熱硬化性樹脂１７が半乾き状態になるまで５０℃〜６０℃の乾燥温度で略１〜１０分間乾燥が行われて半乾燥され、前記熱硬化性樹脂１７の半乾き状態で２次プレス加熱成形され、前記２次プレス加熱成形の後に防湿剤１８が塗布され、前記防湿剤１８の塗布された貼り合わせシート１５に対してボイスコイル用の中心孔２５抜きと外形抜きを行って振動板としての所定寸法形状に成形してなることを特徴とするスピーカ用振動板３０を提供する。
（３）１枚の木製シート１０を素材として略ラッパ形状にプレス成形してなるスピーカ用振動板において、１枚の木製シート１０の一面側の略全面と反対面側の中心部分に薄い不織布又は和紙１３、１３′を貼着してなる貼り合わせシート１５′に対して、中心部に頂点が至る略Ｖ字状の切り込み１１を設け、前記切り込み１１を設けた貼り合わせシート１５′に水分を与えて軟化させるとともに貼り合わせシート１５′中に水分を保持する作用を有する潤滑剤１６を含ませ、前記潤滑剤１６が含まされた貼り合わせシート１５′は１次プレス加熱成形によって前記略Ｖ字状の切り込み１１の縁部１１ａ、１１ｂ同士が重ね合わされて略ラッパ状に仮成形され、仮成形の後に乾燥され、乾燥後に熱硬化性樹脂１７が含まされ、前記熱硬化性樹脂１７が半乾き状態になるまで半乾燥され、前記熱硬化性樹脂１７の半乾き状態で２次プレス加熱成形され、前記２次プレス加熱成形の後に防湿剤１８が塗布され、前記防湿剤１８の塗布された貼り合わせシート１５′に対してボイスコイル用の中心孔２５抜きと外形抜きを行って振動板としての所定寸法形状に成形してなることを特徴とするスピーカ用振動板４０を提供する。
（４）上記（１）又は（２）又は（３）に記載のスピーカ用振動板２０、３０、４０において、素材とする木製シート１０は、木目に沿った縦方向の音波伝搬速度が４．５〜６．０ｋｍ／秒の範囲内であり、且つ内部損失係数が０．０２〜０．０３の範囲にある無垢材から切り出されたものであることを特徴とするスピーカ用振動板を提供する。
（５）上記（１）又は（２）又は（３）に記載のスピーカ用振動板２０、３０、４０において、振動板上に複数のコニカルドーム３７が２次プレス加熱成形によって形成されていることを特徴とするスピーカ用振動板５０を提供する。
【００２３】
【発明の実施の形態】
本発明に係るスピーカ用振動板の実施の形態数例について図面に基づいて説明する。図１は本発明に係る第１及び第２の実施の形態のスピーカ用振動板の製造工程フロー図である。図２及び図３は前記製造工程フローの各加工状態を示す模式図である。図４は本発明に係るスピーカ用振動板の素材である木材の形状の加工段階を説明する模式図である。図５は本発明に係るスピーカ用振動板の第３の実施の形態の特徴を説明する模式図である。図６は本発明に係るスピーカ用振動板の第４の実施の形態の特徴を説明する模式図である。
【００２４】
先ず、図４において、本発明のスピーカ用振動板の素材となる木材は、製造の準備段階として、例えば（ａ）に示されるように、木材の丸太６からロータリー方式により削り出し用刃７で円周方向から薄く剥がされて実際に振動板となる成形部分よりも大きめの適当な形状に切断されて（ｂ）のような大きな柾目の木製シート１０になる。次に製造段階に入って、前記木製シート１０の中心部に頂点が至る略Ｖ字状の切り込み１１が設けられる。そして幾つかのプレス成形工程等を経て最終的に（ｃ）のような略ラッパ形状のダイナミック・コーン・スピーカのスピーカ用振動板となる（図３の（ｋ）の縦断面のスピーカ用振動板２０、３０も参照）。
【００２５】
上記スピーカ用振動板の木目は概ね図４の（ｃ）の概略図のようになり、ボイスコイル用に切り抜かれた中心孔２５から半径方向（例えば、ｄａ〜ｄｈ方向）をみると、木目方向に沿うのはｄａ方向しか存在しなく、他方向は木目とある角度をもって交差している。したがって、殆どの方向において同一の音伝搬速度は存在しないことになり、定在波が発生しにくく共振ポイントが殆ど発生しないので、分割振動が抑えられるのである。
【００２６】
また、上記スピーカ用振動板は木製であることに基づく優れた音響特性を備えるとともに特殊な潤滑剤や熱硬化性樹脂の含浸、防湿剤の塗布及び一連のプレス加熱成形工程の工夫等により、しわや割れが無く、湿度による経時変化が小さく寿命の長い木目の美しい仕上がりとなっている。そして特筆すべきは、その製造工程は簡単でありながら非常に歩留まり良く、製造コストを抑えた量産性に優れたものとなっている。
【００２７】
ここで、本発明のスピーカ用振動板の素材に適する木材について考察すると、図１０の各種木材の有する内部損失係数と音波伝搬速度（縦方向）についての関係を従来の材料であるアルミと紙と共に表したグラフ及び各種木材の密度、ヤング率、音速、内部損失係数（ｔａｎδ）を表した下記［表１］から判るように、概ね合板を（Ｇ点、Ｈ点、Ｉ点、Ｊ点）除く木材（無垢材）が適度な内部損失係数と高い音波伝搬速度を有する優れた素材となり得ることが判る。特に、カバ（Ａ点）やブナ（Ｃ点）が最適であることが判る。
【００２８】
【表１】

【００２９】
なお、図１０中のＡ点はカバ（無垢材）であり、以下、Ｂ点；シナ（無垢材）、Ｃ点；ブナ（無垢材）、Ｄ点；オーク（無垢材）、Ｅ点；チェリー（無垢材）、Ｆ点；スプルース（無垢材）、Ｇ点；シナ合板（共芯）、Ｈ点；ラワン合板、Ｉ点；ＭＦＤ、Ｊ点；パーティクルボードである。
【００３０】
次に、本発明の請求項２に係るスピーカ用振動板の製造手順を図１の（ａ）から（ｊ）までのフロー図及び図２、図３の対応する（ａ）から（ｊ）までの模式図に従って説明する。
【００３１】
請求項２に係るスピーカ用振動板３０の第１の実施の形態（Ａ）の製造工程は、図１に示されるように予め素材準備段階で（ｐ）木製シートの作成の後の（ａ）〜（ｊ）までの１０工程で構成され、（ａ）貼り合わせ、（ｂ）Ｖ字状切り込み、（ｃ）潤滑剤含浸、（ｄ）１次プレス、（ｅ）乾燥１、（ｆ）熱硬化性樹脂含浸、（ｇ）半乾燥、（ｈ）２次プレス、（ｉ）防湿剤塗布、（ｊ）中心・外形抜きの順に行われてスピーカ用振動板３０の完成となる。
【００３２】
上記各工程の詳細内容を以下順に説明する。
工程（ａ）・・・０．ｌｍｍ〜０．９ｍｍ厚（好ましくは０．３ｍｍ程度）の木製シート１０の一面側に、接着剤により略０．０２〜０．３０ｍｍ厚の薄い不織布又は和紙１３を接着剤で貼着して貼り合わせシート１５を作成する。ここにいう不織布はカーボン材その他の合成樹脂からなる周知材料であり、貼り合わせた一面側が完成した振動板３０の背面側となる。上記木製シート１０の厚さは成形性と音響特性及びダイナミック・スピーカの口径を考慮した上でのスピーカ用振動板として適正な厚さである。
工程（ｂ）・・・貼り合わせシート１５に対して、中心部に頂点が至る略Ｖ字状の切り込み１１とその頂点近傍に小穴１２とを設ける。前記小穴１２は切り込み１１の前に設けることで切り込み１１加工時に頂点付近で割れが発生するのを防止する作用を有する。なお、前記切り込み１１はその中心線ｍが貼り合わせシート１５の木目方向（矢印ｆ）に概ね沿うように設ける。
工程（ｃ）・・・Ｖ字切り込みした前記貼り合わせシート１５に水分を与えて軟化させるとともに貼り合わせシート１５中に水分を保持する作用を有する潤滑剤１６を含ませる。例えば、容器中に溜めた潤滑剤１６の液中に貼り合わせシート１５を５〜６０分浸して十分に含浸させる。
【００３３】
これは後の１次プレス加熱成形を実施する際のシートの割れを未然に防ぎ、歩留まり良く仮成形するためである。本発明者の研究によれば、前記潤滑剤１６としては単なる水若しくはアルカリ水溶液ではなく、糖類を溶解させた水溶液が成形性向上に有効であることが判った。
工程（ｄ）・・・ヒータ３３を各々備えた上型３１と下型３２からなる金型構成のプレス装置Ｐ１によって、前記潤滑剤１６が含まされた貼り合わせシート１５は１次プレス加熱成形によって前記略Ｖ字状の切り込み１１の縁部１１ａ、１１ｂ同士が重ね合わされて略ラッパ状に仮成形される。ここで上記１次プレス加熱成形の設定条件は、プレス圧力が略１〜１０Ｋｇ、金型温度は上型３１が略８０〜１５０℃、下型３２が略１００〜２００℃、プレス時間が略２〜６０秒が好適である。
工程（ｅ）・・・上記仮成形された貼り合わせシート１５は乾燥炉（５０〜６０℃）に略１０〜３０分間入れて完全乾燥を行なう。
工程（ｆ）・・・乾燥後の貼り合わせシート１５に熱硬化性樹脂１７が含まされる。例えば、容器に溜めた熱硬化性樹脂１７液中に略３０分〜１８０分浸し、十分に含浸させる。この熱硬化性樹脂１７としてはフェノール樹脂が良好である。工程（ｇ）・・・前記熱硬化性樹脂１７の含浸直後に後工程の２次プレス加熱成形を実施すると、金型に熱硬化性樹脂１７が張り付いてしまい、プレス後に貼り合わせシート１５を剥がす時に割れ、引きちぎれが発生して歩留まりが極度に低下する。逆に完全に乾燥させると成形性が悪くなって割れやすくなる。これを防止するために、本発明では乾燥炉（５０℃〜６０℃）に略１〜１０分間入れて貼り合わせシート１５に含まされた熱硬化性樹脂１７を半乾燥状態（指で触ってもべたつかない程度の所謂“指触乾燥状態”である。）にする。
工程（ｈ）・・・前記工程（ｄ）と同様の周知の構成のプレス装置Ｐ２によって、前記熱硬化性樹脂１７が半乾燥状態の貼り合わせシート１５を再度プレス加熱成形する。ここで２次プレス加熱成形の設定条件は、プレス圧力が略２０〜４０Ｋｇ、金型温度は上型３４が略８０〜２００℃、下型３５が略１００〜２００℃、プレス時間が略１０〜１００秒が好適である。成形後は揮発成分が蒸散して成形形状が略ラッパ状に安定した貼り合わせシート１５となる。なお、貼り合わせシート１５の略Ｖ字状の切り込み１１の縁部１１ａ、１１ｂ同士の重ね合わせ部分は前記熱硬化性樹脂１７の硬化によって接着され且つプレス成形で殆ど段差が見分け付かない程度に成形される。
工程（ｉ）・・・２次プレス後の貼り合わせシート１５の表裏両面に筆による塗布若しくはジャブ漬けにより防湿剤１８を塗布して自然乾燥又は乾燥炉で完全乾燥させる。この防湿剤１８としては例えば、ポリイソシアネートとポリエステルポリオールを混合したものを用いる。この防湿剤１８によってスピーカ用振動板として湿度による経年変化が小さい耐久性に優れたものとなる。
工程（ｊ）・・・前記防湿剤１８の塗布された貼り合わせシート１５に対してボイスコイル用の中心孔２５抜きと外形抜きを行って振動板としての所定寸法形状に成形されてスピーカ用振動板３０が完成する。
【００３４】
上記完成した略ラッパ状のスピーカ用振動板３０は、従来のダイナミック・スピーカと同様にボイスコイル、ダンパー、エッジ、磁気回路、フレーム等と組み合わされてダイナミック・スピーカのユニットに組み込まれる。
【００３５】
上記本発明に係る第１の実施の形態（Ａ）では、不織布又は和紙１３を貼り合わせる工程（ａ）を含んでいたが、前記不織布や和紙１３を木製シート１０の一面側に貼り合わせなくても、図１に示される本発明の請求項１に係る第２の実施の形態（Ｂ）のフローの製造工程を経てなるスピーカ用振動板２０も実現可能である。即ち、工程（ａ）が無い木製シート１０のみでも工程（ｂ）のＶ字状切り込み工程以降の工程を同じくすればスピーカ用木製振動板２０が製造できる。その製造方法は、前述の工程（ｂ）以下の説明における「貼り合わせシート１５」を「木製シート１０」と置き換えることで説明される。
【００３６】
尤も、厚さが０．１〜０．９ｍｍ程度の木製シート１０は取り扱い上非常に割れ易いので、予め工程（ａ）を施して不織布又は和紙１３で補強することが望ましいといえる。
【００３７】
次に、本発明の請求項３に係る第３の実施の形態につき前述の第１の実施の形態（Ａ）との相違点に絞って図５を用いて説明する。
【００３８】
この第３の実施の形態の特徴は、プレス加熱成形時のひび割れを一層防止するためと、振動板のボイスコイル用の中心孔２５の周囲のネック部の強度を向上させるために、木製シート１０の一面側のみならずその反対面の中心部分にも不織布又は和紙１３′を貼り合わせている点にある。
【００３９】
即ち、図１の工程（ａ）の木製シート１０への不織布又は和紙の貼り合わせ工程時に、図５の（ａ）のように木製シート１０の一面（裏面）全体に不織布又は和紙１３を貼り合わせるとともに、その反対面（表面）の中心部分にダストキャップ３６の口径サイズ以下で中心孔２５よりも大きい円形の不織布又は和紙１３′を接着剤で貼り合わせる。次に表面側を表す図５の（ｂ）のようにＶ字状の切り込み１１を設ける。以下、図１の第１の実施の形態（Ａ）の工程（ｃ）から工程（ｋ）までを実施する。最終的に図５の（ｃ）の振動板４０ように表面側の最も振幅の大きいボイスコイル用の中心孔２５の周囲のネック部が不織布又は和紙１３′で補強されたものとなる。且つ図５の（ｄ）のスピーカユニットの断面模式図から判るように前記表面側の不織布又は和紙１３′はダストキャップ３６で覆い隠されて外観を損なわないものとなる。
【００４０】
次に、本発明に係る第４の実施の形態について図６、図９を用いて説明する。
【００４１】
先ず、公知技術として図９は従来のコニカルドーム付紙パルプ製振動板６０の模式断面図である。これは振動板６２に発生する分割振動を抑えるために、通常の略ラッパ状の振動板６２の表面に別部材のドーム形状した紙製のコニカルドーム６１を複数個接着固定したものである。
【００４２】
本発明の木製のスピーカ用振動板２０、３０、４０では、素材が異方性の木材であるために前述のように分割振動は殆ど発生しないが、完璧な分割振動の発生を抑えるべく、図６の（ａ）に示されるように本発明のスピーカ用振動板の製造工程におけるプレス装置Ｐ２による２次プレス加熱成形時に、予め金型の上型３４、下型３５にそれぞれコニカルドーム３７の凹形状３８と凸形状３９を特に作っておき、貼り合わせシート１５又は木製シート１０の成形加工と同時に一体プレス成形でコニカルドーム３７を形成している。これにより、従来必要としていた別部材のコニカルドームの接着工程が不要になり、安価に図６の（ｂ）のようなスピーカ用振動板５０と一体のコニカルドーム３７が形成されることになる。
【００４３】
本発明者の研究によれば、上記各実施の形態において、明確に従来の紙パルプ製の振動板やアルミ製の振動板に比べて再生音の解像度向上や歯切れ良い音の向上が得られるのは、縦方向伝搬速度が４．５〜６．０ｋｍ／秒、横方向伝搬速度が２．０〜４．５ｋｍ／秒の範囲の木材を選定した場合であった。
【００４４】
特に顕著に音質向上が実感されるのは、縦方向伝搬速度が４．５〜６．０ｋｍ／秒、横方向伝搬速度が２．０〜２．５ｋｍ／秒、内部損失係数が０．０２〜０．０３の範囲内の木材を選定した場合であり、具体的にはカバ材（無垢）が好適であった。
【００４５】
勿論、本発明のスピーカ用振動板は、カバ材のみならず、ブナ、オーク、チェリー、シナ等の他の材木を適用することもできることは言うまでもない。
【００４６】
【発明の効果】
上記のように本発明に係るスピーカ用振動板は薄い１枚の木材を素材とし、従来の紙パルプ製振動板の製造過程に存在するような化学薬品での蒸解や木材繊維の叩解処理が加えられていないので音質劣化が発生しない。
【００４７】
さらに、柔軟化のためのボイル処理、物理的処理、化学的薬品が施されていないので音質劣化が発生しない。
【００４８】
プレス加熱成形時のしわや割れの発生が防止されて、仕上がりの良い均一なプレス加熱成形品となっており、変形や割れといった経時変化が少ない。
【００４９】
しかも軽くて丈夫なコーン振動板が製造可能になり、ウーハーからフルレンジスピーカまで全ての帯域に対応した振動板が製造できる。
【００５０】
また、既存の製造工程が利用でき、歩留まりが良好で量産性に優れていて、安価供給が実現できる。
【００５１】
本スピーカ用振動板がスピーカユニットに採用された際には、木製であるが故の自然な振動による生音に迫る再生音が経時変化なく出力される。
【００５２】
さらに、表面に自然の木目が出ているので、高級感のある外観体裁となる。
【図面の簡単な説明】
【図１】本発明に係る第１及び第２の実施の形態のスピーカ用振動板の製造工程フロー図である。
【図２】前記製造工程フロー図の各加工状態（前半）を示す模式図である。
【図３】前記製造工程フロー図の各加工状態（後半）を示す模式図である。
【図４】本発明に係るスピーカ用振動板の素材である木材の形状の加工段階を説明する模式図である。
【図５】本発明に係るスピーカ用振動板の第３の実施の形態の特徴を説明する模式図である。
【図６】本発明に係るスピーカ用振動板の第４の実施の形態の特徴を説明する模式図である。
【図７】従来の木製振動板の製造手順を示す図である。
【図８】従来の木製振動板の製造手順を示す図である。
【図９】従来のコニカルドーム付紙パルプ製振動板の模式断面図である。
【図１０】各種木材の有する内部損失係数と音伝搬速度（縦方向）についての関係を従来の材料であるアルミと紙と共に表したグラフである。
【符号の説明】
６丸太
７削り出し用刃
１０木製シート
１１略Ｖ字状の切り込み
１１ａ、１１ｂ両縁部
１２小穴
１３、１３′ 不織布又は和紙
１５貼り合わせシート
１６水分を与え且つ水分を保持する作用のある潤滑剤
１７熱硬化性樹脂
１８防湿剤
２５中心穴
２０、３０、４０、５０スピーカ用振動板
３１、３４上型
３３ヒータ
３２、３５下型
３６ダストキャップ
３７コニカルドーム
３８上型の凹形状
３９下型の凸形状
６０コニカルドーム付紙パルプ製振動板
６１コニカルドーム
６２振動板
Ｐ１、Ｐ２プレス装置[0001]
BACKGROUND OF THE INVENTION
The present invention belongs to the technical field of audio speakers, and particularly relates to a speaker diaphragm used for dynamic speakers.
[0002]
[Prior art]
Conventionally, most diaphragms of dynamic speakers are made of paper pulp, plastic, or metal such as aluminum. Since these conventional diaphragms are formed by pressing a uniform material, the sound propagation speed in the radial direction from the center is the same in all directions. Therefore, a standing wave always occurs and has a resonance point. This causes a problem that sound pressure frequency characteristics are deteriorated due to divided vibrations in a low frequency region, and a sense of reality is lost. Paper pulp and plastic diaphragms have a relatively large internal loss factor, but on the contrary, they are inferior in terms of rigidity (Young's modulus), and the sound propagation speed is low, so the resolution of the reproduced sound is somewhat unsatisfactory. Remain. On the other hand, although a metal diaphragm such as aluminum has a high sound wave propagation speed, the internal loss coefficient is small, so that the attenuation of amplitude is small and the division of reproduced sound is unclear (so-called sound sharpness is poor). .
[0003]
Instead of the existing diaphragms having the advantages and disadvantages as described above, it is desired to realize a wooden diaphragm as a diaphragm for a speaker that can reproduce a more natural sound.
[0004]
That is, the sound wave propagation speed of wood varies depending on the type, but is generally higher than that of paper pulp. Further, the propagation speed differs in the direction of the wood grain and the direction perpendicular thereto, and the propagation speed in the wood grain direction (referred to as the vertical direction) is fast and perpendicular to the wood grain. The propagation velocity in the direction (referred to as the transverse direction) has an anisotropic propagation property that it is relatively slow. In addition, wood generally has an appropriate internal loss factor as a speaker diaphragm, and is light and strong (high rigidity).
[0005]
Therefore, a wooden diaphragm made of wood itself is unlikely to generate a standing wave and hardly has a resonance point. Therefore, divided vibration hardly occurs, and improvement of sound pressure frequency characteristics in a low frequency region is expected. Compared with a paper pulp diaphragm, the resolution of the reproduced sound can be improved and the sound can be improved crisply.
[0006]
Various proposals have already been made, for example, in the following publicly known literatures as methods for manufacturing the wooden diaphragm or the dynamic speaker using the wooden diaphragm or the wooden diaphragm.
[0007]
In the following [Patent Document 1], a flat plate made of WPC made by impregnating and hardening a plastic material such as polyester on a flat plate made of wood material is a flat plate diaphragm for a speaker excellent in characteristics such as dimensional stability, internal friction, and rigidity. The speaker used as is proposed.
[0008]
The following [Patent Document 2] has (a) an arc-shaped cutout portion 1a at the center from one piece of wood sheet 4 as in the manufacturing procedure shown in FIGS. 7 (a) and 7 (b). Then, the wood sheet 1 which is a substantially trumpet-shaped developed shape having a fan-shaped cutout portion 1b is cut out, and (b) both edges b1 and b2 of the fan-shaped cutout portion 1b of the wood sheet 1 are glued. A cone diaphragm 5 has been proposed which is formed in a trumpet shape by being overlapped and bonded to each other at an allowance portion 1c and then press-molded.
[0009]
Moreover, like the manufacturing procedure shown to (a) of FIG. 8, (b), several wood piece sheet | seats 2a, 2b ..., 2L are bonded together with an adhesive agent, and it becomes a substantially trumpet shape like (b). A cone diaphragm 2 formed and then press-molded has been proposed. Further, there has been proposed a cone diaphragm obtained by adding physical moisture resistance treatment or chemical moisture resistance treatment to the

cone diaphragms

1 and 2.
[0010]
In the following [Patent Document 3], a composite sheet composed of an ultrathin wood sheet sliced to 80 μm or less and a non-woven fabric made of an adhesive resin attached to the back surface thereof is softened with a softening agent. Thus, there has been proposed an acoustic diaphragm in which a plurality of sheets are stacked and further heated and pressed to form a conical shape.
[0011]
In the following [Patent Document 4], a flat timber sheet cut into a fan shape is boiled with high-temperature steam, hot water, or an alkaline solution having a pH of 10 or more to prevent cracking during molding, and then conical. A cone diaphragm formed by press molding has been proposed.
[0012]
In the following [Patent Document 5], a laminated sheet in which a thin non-woven fabric or Japanese paper is pasted on one side of one wooden sheet is prepared, and this is impregnated into a container containing a lubricant, and the impregnated laminated sheet There has been proposed a loudspeaker diaphragm that is press-heated and formed into a substantially trumpet shape.
[0013]
The following [Patent Document 6] describes a thin non-woven fabric or Japanese paper on one side of one wooden sheet in order to produce a wooden speaker diaphragm that does not cause wrinkles or cracks during press molding and has little change over time. There has been proposed a speaker diaphragm in which a bonded sheet with a carbon sheet attached is prepared, impregnated with a thermosetting resin, and then press-heat molded to form a substantially trumpet shape.
[0014]
[Patent Document 1]
JP-A-62-2224196
[Patent Document 2]
JP-A-1-288100
[Patent Document 3]
JP-A-5-83792
[Patent Document 4]
JP-A-6-178386
[Patent Document 5]
JP-A-10-304492
[Patent Document 6]
JP 2000-59883 A
[Problems to be solved by the invention]
The point of particular importance for wooden speaker diaphragms is how to deal with the fragile nature of the material wood, how to deal with poor formability and aging.
[0015]
In this respect, [Patent Document 1] is a wooden flat diaphragm, and although the characteristics and advantages of being a wooden are shown, there are problems in forming into a substantially trumpet shape (cone shape). No technical data is provided because it is flat.
[0016]
Further, in the manufacturing method as shown in FIGS. 7 and 8 of [Patent Document 2], the wood sheet 1 or the small piece pieces 2a, 2b,. Or cracking during press molding, or because the wood sheets are bonded to each other with an adhesive, there is a problem that the adhesive part becomes an obstacle and desired acoustic characteristics cannot be obtained, and dimensional accuracy cannot be secured. .
[0017]
Further, the method of laminating a plurality of ultra-thin wood sheets of [Patent Document 3] has a difficulty in processing accuracy, and the adhesive layer increases and the weight of the diaphragm itself increases due to the weight of the adhesive. The desired acoustic characteristics cannot be obtained, and a large amount of adhesive adversely affects the sound pressure frequency characteristics, which is not preferable.
[0018]
In addition, as in [Patent Document 4], in the case of a manufacturing process including boil treatment with high-temperature steam or an alkaline solution having a pH of 10 or more before press molding, a constituent material called lignin in the wood is also removed. The original characteristics of the sound cannot be exhibited, and the sound quality will be adversely affected.
[0019]
Above all, the contents of the above [Patent Document 2], [Patent Document 3], and [Patent Document 4] have many defects such as cracks, cracks and wrinkles during production, and the yield in mass production is very high. It is getting worse and not commercialized.
[0020]
In addition, in [Patent Document 5] and [Patent Document 6], a thermosetting resin is used to impregnate a lubricant for extracting “tension” and “flexibility”, prevent wrinkles and cracks from occurring, and prevent change over time. The speaker diaphragm formed by press heat molding after impregnation has superior manufacturing process for mass production compared with the above [Patent Document 1] to [Patent Document 4], but still has sufficient moldability and molding processing. Therefore, it is desired to further improve the moldability and to realize a beautifully finished wooden diaphragm for practical use of the wooden diaphragm.
[0021]
The present invention has been made in view of the above circumstances, and provides a wooden speaker diaphragm that is effective in improving the acoustic characteristics of an audio speaker and is excellent in mass productivity.
[0022]
[Means for Solving the Problems]
In order to solve the above problems, the present invention
(1) In a speaker diaphragm formed by pressing one wooden sheet 10 into a substantially trumpet shape, a substantially V-shaped cut 11 having a vertex at the center of one wooden sheet 10. The wooden sheet 10 provided with the lubricant 16 is provided with a lubricant 16 having an action of imparting moisture to the wooden sheet 10 provided with the cut and softening and retaining the moisture in the wooden sheet 10. The edges 11a and 11b of the substantially V-shaped cut 11 are overlapped with each other by primary press thermoforming to be temporarily formed into a substantially trumpet shape, dried after temporary forming, and include a thermosetting resin 17 after drying. Until the thermosetting resin 17 is in a semi-dry state Drying is performed at a drying temperature of 50 ° C. to 60 ° C. for about 1 to 10 minutes. Semi-dried and secondarily press-molded with the thermosetting resin 17 in a semi-dried state, and after the second press-heated molding, a moisture-proofing agent 18 is applied to the wooden sheet 10 to which the moisture-proofing agent 18 is applied. Thus, a speaker diaphragm 20 is provided, which is formed by removing a central hole 25 and an outer shape for a voice coil and forming the diaphragm into a predetermined size shape as a diaphragm.
(2) In a speaker diaphragm formed by pressing a single wooden sheet 10 into a substantially trumpet shape, bonding is performed by attaching a thin non-woven fabric or Japanese paper 13 to one side of one wooden sheet 10. A substantially V-shaped cut 11 having a vertex at the center is provided to the sheet 15, moisture is applied to the laminated sheet 15 provided with the cut 11 to be softened, and moisture is retained in the laminated sheet 15. The bonded sheet 15 containing the lubricant 16 including the lubricant 16 is overlapped with the edges 11a and 11b of the substantially V-shaped cut 11 by primary press thermoforming. Until the thermosetting resin 17 is in a semi-dried state. Drying is performed at a drying temperature of 50 ° C. to 60 ° C. for about 1 to 10 minutes. Semi-dried and secondarily press-molded in the semi-dried state of the thermosetting resin 17. After the second press-heated molding, a moistureproof agent 18 is applied to the laminated sheet 15 to which the moistureproof agent 18 is applied. On the other hand, a speaker diaphragm 30 is provided, which is formed by removing a central hole 25 and an outer shape for a voice coil and molding the voice coil into a predetermined shape.
(3) In a speaker diaphragm formed by pressing a single wooden sheet 10 into a substantially trumpet shape, a thin non-woven fabric is formed in a central portion on the opposite side to the substantially entire surface of one wooden sheet 10. A substantially V-shaped cut 11 having a vertex at the center is provided to a bonded sheet 15 ′ formed by sticking

Japanese paper

13, 13 ′, and moisture is applied to the bonded sheet 15 ′ provided with the cut 11. A lubricant 16 having an action of holding and softening the laminated sheet 15 'is contained in the laminated sheet 15', and the laminated sheet 15 'containing the lubricant 16 is substantially V-shaped by primary press thermoforming. The edges 11a and 11b of the cut-out notch 11 are overlapped and temporarily formed into a substantially trumpet shape, dried after the temporary forming, and after drying, the thermosetting resin 17 is included, and the thermosetting resin 17 is semi-dried until it is in a semi-dry state, and is subjected to secondary press heat molding in the semi-dry state of the thermosetting resin 17. After the secondary press heat molding, a moisture-proof agent 18 is applied, and the moisture-proof agent 18 A speaker diaphragm 40 is provided, which is formed by removing a voice coil center hole 25 and an outer shape from the applied laminated sheet 15 'to form a diaphragm having a predetermined size and shape. .
(4) In the

speaker diaphragms

20, 30, and 40 described in (1), (2), or (3) above, the wooden sheet 10 used as a material has a longitudinal acoustic wave propagation velocity of 4. Provided is a loudspeaker diaphragm characterized by being cut from a solid material having a range of 5 to 6.0 km / sec and an internal loss factor of 0.02 to 0.03. .
(5) In the

speaker diaphragms

20, 30, and 40 described in (1), (2), or (3) above, a plurality of conical domes 37 are formed on the diaphragm by secondary press thermoforming. A speaker diaphragm 50 is provided.
[0023]
DETAILED DESCRIPTION OF THE INVENTION
Several embodiments of the speaker diaphragm according to the present invention will be described with reference to the drawings. FIG. 1 is a manufacturing process flow chart of speaker diaphragms according to the first and second embodiments of the present invention. 2 and 3 are schematic views showing each processing state of the manufacturing process flow. FIG. 4 is a schematic diagram for explaining the processing stage of the shape of the wood that is the material of the speaker diaphragm according to the present invention. FIG. 5 is a schematic diagram for explaining the characteristics of the third embodiment of the speaker diaphragm according to the present invention. FIG. 6 is a schematic diagram for explaining the features of the fourth embodiment of the speaker diaphragm according to the present invention.
[0024]
First, in FIG. 4, the wood used as the material for the speaker diaphragm of the present invention is prepared by a rotary cutting method 7 from a wood log 6 as shown in FIG. It is peeled thinly from the circumferential direction, and cut into a suitable shape larger than the molded part that actually becomes the diaphragm, to obtain a large square wooden sheet 10 as shown in FIG. Next, at the manufacturing stage, a substantially V-shaped cut 11 having a vertex at the center of the wooden sheet 10 is provided. After a number of press molding processes, etc., the speaker diaphragm of the dynamic cone speaker having a substantially trumpet shape as shown in FIG. 3C is obtained (the speaker diaphragm having a longitudinal section in FIG. 3 (k)). See also 20, 30).
[0025]
The grain of the speaker diaphragm is substantially as shown in the schematic diagram of FIG. 4C. Looking at the radial direction (for example, da to dh direction) from the center hole 25 cut out for the voice coil, the grain direction Only the da direction exists along the other direction, and the other direction intersects with the grain at a certain angle. Therefore, the same sound propagation speed does not exist in most directions, and standing waves are hardly generated and resonance points are hardly generated, so that divided vibration is suppressed.
[0026]
The speaker diaphragm has excellent acoustic characteristics based on being made of wood and is wrinkled by impregnation with a special lubricant or thermosetting resin, application of a moisture-proofing agent, and a series of press heat forming processes. There are no cracks, the change with time due to humidity is small, and the wood grain has a beautiful finish with a long life. It should be noted that the manufacturing process is simple but has a very good yield and is excellent in mass productivity with reduced manufacturing costs.
[0027]
Here, when considering wood suitable for the material of the speaker diaphragm of the present invention, the relationship between the internal loss coefficient and the sound wave propagation speed (longitudinal direction) of the various types of wood in FIG. As shown in [Table 1] below, which shows the graph and the density, Young's modulus, sound velocity, and internal loss coefficient (tan δ) of various types of wood, the plywood is largely excluded (G point, H point, I point, J point) It can be seen that wood (solid wood) can be an excellent material with a reasonable internal loss factor and high sound propagation velocity. In particular, it is found that hip (point A) and beech (point C) are optimal.
[0028]
[Table 1]

[0029]
In addition, A point in FIG. 10 is a hip (solid wood), and below, B point; China (solid wood), C point; Beech (solid wood), D point; Oak (solid wood), E point; Cherry (Solid wood), F point; spruce (solid wood), G point; China plywood (core), H point; Lauan plywood, I point; MFD, J point; particle board.
[0030]
Next, the manufacturing procedure of the speaker diaphragm according to claim 2 of the present invention will be described with reference to the flow chart from (a) to (j) of FIG. 1 and the corresponding (a) to (j) of FIGS. It demonstrates according to the schematic diagram.
[0031]
The manufacturing process of the first embodiment (A) of the loudspeaker diaphragm 30 according to claim 2 is (a) after the preparation of the wooden sheet in the material preparation stage in advance as shown in FIG. ~ (J) is composed of 10 steps, (a) bonding, (b) V-shaped cut, (c) lubricant impregnation, (d) primary press, (e) drying 1, (f) heat The speaker diaphragm 30 is completed in the order of curable resin impregnation, (g) semi-drying, (h) secondary press, (i) application of a moisture-proofing agent, and (j) center and outer shape removal.
[0032]
The detailed contents of the above steps will be described in the following order.
Step (a) ... 0. A thin non-woven fabric or Japanese paper 13 having a thickness of approximately 0.02 to 0.30 mm is attached to one side of a wooden sheet 10 having a thickness of 1 mm to 0.9 mm (preferably about 0.3 mm) with an adhesive. A matching sheet 15 is created. The non-woven fabric here is a well-known material made of a carbon material or other synthetic resin, and the bonded one surface side is the back surface side of the completed diaphragm 30. The thickness of the wooden sheet 10 is an appropriate thickness for a speaker diaphragm in consideration of moldability, acoustic characteristics, and the diameter of a dynamic speaker.
Step (b): A substantially V-shaped cut 11 having a vertex at the center and a small hole 12 in the vicinity of the vertex are provided on the laminated sheet 15. By providing the small hole 12 in front of the notch 11, the small hole 12 has an action of preventing cracks from occurring near the apex when the notch 11 is processed. The notch 11 is provided so that the center line m is substantially along the grain direction (arrow f) of the laminated sheet 15.
Step (c): A lubricant 16 having an action of retaining moisture in the bonded sheet 15 while containing moisture in the bonded sheet 15 cut into a V shape is included. For example, the laminated sheet 15 is immersed in the liquid of the lubricant 16 stored in the container for 5 to 60 minutes and sufficiently impregnated.
[0033]
This is to prevent the sheet from cracking when the subsequent primary press heat forming is performed, and to perform temporary forming with a high yield. According to the inventor's research, it has been found that the lubricant 16 is not simply water or an alkaline aqueous solution, but an aqueous solution in which saccharides are dissolved is effective in improving moldability.
Step (d)... The bonded sheet 15 containing the lubricant 16 is subjected to primary press thermoforming by a press device P1 having a mold configuration including an upper die 31 and a lower die 32 each provided with a heater 33. The edges 11a and 11b of the substantially V-shaped cut 11 are overlapped and temporarily formed into a substantially trumpet shape. Here, the setting conditions of the primary press thermoforming are as follows: the press pressure is approximately 1 to 10 kg, the mold temperature is approximately 80 to 150 ° C. for the upper die 31, approximately 100 to 200 ° C. for the lower die 32, and the press time is approximately 2 ~ 60 seconds is preferred.
Step (e): The temporarily formed bonded sheet 15 is completely dried in a drying furnace (50 to 60 ° C.) for about 10 to 30 minutes.
Step (f)... The thermosetting resin 17 is included in the bonded sheet 15 after drying. For example, it is immersed in the thermosetting resin 17 liquid stored in the container for about 30 to 180 minutes and sufficiently impregnated. As the thermosetting resin 17, a phenol resin is preferable. Step (g): When the secondary press thermoforming in the subsequent step is performed immediately after impregnation with the thermosetting resin 17, the thermosetting resin 17 is stuck to the mold, and the laminated sheet 15 is attached after pressing. When peeled off, cracks and tearing occur and the yield is extremely reduced. On the other hand, when it is completely dried, the moldability deteriorates and it becomes easy to crack. In order to prevent this, in the present invention, the thermosetting resin 17 contained in the laminated sheet 15 is placed in a drying furnace (50 ° C. to 60 ° C.) for approximately 1 to 10 minutes, and the semi-dried state (even if touched with a finger). It is a so-called “touch dry state” that is not sticky.)
Step (h): The laminated sheet 15 in which the thermosetting resin 17 is in a semi-dried state is press-heated again by a press device P2 having a known configuration similar to the step (d). Here, the setting conditions of the secondary press thermoforming are as follows: the press pressure is approximately 20 to 40 kg, the mold temperature is approximately 80 to 200 ° C. for the upper die 34, approximately 100 to 200 ° C. for the lower die 35, and the press time is approximately 10 to 10 ° C. 100 seconds is preferred. After molding, the volatile component is evaporated, and the bonded sheet 15 is formed in a stable shape in a substantially trumpet shape. Note that the overlapping portions of the edges 11a and 11b of the substantially V-shaped cut 11 of the bonded sheet 15 are bonded to each other by the curing of the thermosetting resin 17 and are formed to such an extent that a step is hardly recognized by press molding. Is done.
Step (i)... The moisture-proof agent 18 is applied to both the front and back surfaces of the bonded sheet 15 after the secondary press by brush application or jabbing and dried naturally or in a drying oven. As this moisture-proof agent 18, what mixed polyisocyanate and polyester polyol is used, for example. This moisture-proofing agent 18 makes the speaker diaphragm excellent in durability with little secular change due to humidity.
Step (j): A voice coil central hole 25 is removed from the laminated sheet 15 to which the moisture-proofing agent 18 is applied, and an outer shape is removed to form a vibration plate for a speaker. The board 30 is completed.
[0034]
The completed substantially trumpet-shaped speaker diaphragm 30 is combined with a voice coil, a damper, an edge, a magnetic circuit, a frame, and the like in the same manner as a conventional dynamic speaker, and is incorporated into a dynamic speaker unit.
[0035]
In 1st Embodiment (A) which concerns on the said invention, although the process (a) which bonds a nonwoven fabric or Japanese paper 13 was included, the said nonwoven fabric and Japanese paper 13 were not bonded on the one surface side of the wooden sheet 10. FIG. However, the speaker diaphragm 20 obtained through the flow manufacturing process of the second embodiment (B) according to claim 1 of the present invention shown in FIG. 1 can also be realized. That is, the wooden diaphragm 20 for a speaker can be manufactured even if only the wooden sheet 10 without the step (a) is the same as the step after the V-shaped cutting step of the step (b). The manufacturing method will be described by substituting “wood sheet 10” for “bonded sheet 15” in the following description of step (b).
[0036]
However, since the wooden sheet 10 having a thickness of about 0.1 to 0.9 mm is very easy to handle, it can be said that it is desirable to perform the step (a) in advance and reinforce it with a nonwoven fabric or Japanese paper 13.
[0037]
Next, a third embodiment according to claim 3 of the present invention will be described with reference to FIG. 5 while focusing on differences from the first embodiment (A).
[0038]
The feature of the third embodiment is that the wooden sheet 10 is used to further prevent cracking during press heat forming and to improve the strength of the neck portion around the central hole 25 for the voice coil of the diaphragm. The non-woven fabric or Japanese paper 13 'is bonded to the central portion of the opposite surface as well as the one surface side.
[0039]
That is, in the step of bonding the non-woven fabric or Japanese paper to the wooden sheet 10 in the step (a) of FIG. 1, the non-woven fabric or Japanese paper 13 is bonded to the entire surface (back surface) of the wooden sheet 10 as shown in FIG. At the same time, a circular non-woven fabric or Japanese paper 13 'which is smaller than the diameter of the dust cap 36 and larger than the center hole 25 is bonded to the center of the opposite surface (surface) with an adhesive. Next, a V-shaped cut 11 is provided as shown in FIG. Hereinafter, steps (c) to (k) of the first embodiment (A) of FIG. 1 are performed. Finally, like the diaphragm 40 in FIG. 5C, the neck portion around the central hole 25 for the voice coil having the largest amplitude on the surface side is reinforced with a nonwoven fabric or Japanese paper 13 '. Further, as can be seen from the schematic cross-sectional view of the speaker unit in FIG. 5D, the surface-side nonwoven fabric or Japanese paper 13 'is covered with a dust cap 36 and does not impair the appearance.
[0040]
Next, a fourth embodiment according to the present invention will be described with reference to FIGS.
[0041]
First, as a known technique, FIG. 9 is a schematic sectional view of a conventional paper pulp diaphragm 60 with a conical dome. In order to suppress the divided vibration generated in the diaphragm 62, a plurality of paper conical domes 61, each of which is a dome-shaped member, are bonded and fixed to the surface of a normal substantially trumpet-shaped diaphragm 62.
[0042]
In the

wooden speaker diaphragms

20, 30, 40 of the present invention, since the material is anisotropic wood, split vibration hardly occurs as described above. However, in order to suppress perfect split vibration, FIG. 6 (a), when the secondary press heat molding is performed by the press device P2 in the manufacturing process of the speaker diaphragm of the present invention, the concave portions of the conical dome 37 are previously formed in the upper die 34 and the lower die 35 of the mold, respectively. The shape 38 and the convex shape 39 are made in particular, and the conical dome 37 is formed by integral press molding simultaneously with the forming process of the bonded sheet 15 or the wooden sheet 10. As a result, the step of bonding the conical dome, which has been conventionally required, becomes unnecessary, and the conical dome 37 integrated with the speaker diaphragm 50 as shown in FIG. 6B is formed at a low cost.
[0043]
According to the inventor's research, in each of the above-described embodiments, it is possible to clearly improve the resolution of reproduced sound and improve sharp sound compared to conventional paper pulp diaphragms and aluminum diaphragms. Was the case of selecting wood having a vertical propagation speed of 4.5 to 6.0 km / second and a horizontal propagation speed of 2.0 to 4.5 km / second.
[0044]
It is particularly noticeable that the sound quality is improved in that the vertical propagation velocity is 4.5 to 6.0 km / second, the lateral propagation velocity is 2.0 to 2.5 km / second, and the internal loss factor is 0.02 to 0.02. This is the case where wood in the range of 0.03 is selected, and specifically, birch (solid) is suitable.
[0045]
Of course, it goes without saying that the speaker diaphragm of the present invention can be applied not only to birch but also other timbers such as beech, oak, cherry, and china.
[0046]
【The invention's effect】
As described above, the loudspeaker diaphragm according to the present invention is made of a thin piece of wood, and is subjected to digestion with chemicals and beating of wood fibers that exist in the manufacturing process of conventional paper pulp diaphragms. No sound quality degradation occurs because it is not done.
[0047]
Further, since no boil treatment, physical treatment, or chemical chemicals are applied for softening, the sound quality does not deteriorate.
[0048]
Occurrence of wrinkles and cracks during press thermoforming is prevented, resulting in a uniform press thermoformed product with good finish, and there is little change over time such as deformation and cracking.
[0049]
Moreover, a light and durable cone diaphragm can be manufactured, and a diaphragm corresponding to all bands from a woofer to a full range speaker can be manufactured.
[0050]
In addition, existing manufacturing processes can be used, yield is good, mass productivity is excellent, and inexpensive supply can be realized.
[0051]
When this speaker diaphragm is employed in a speaker unit, a reproduced sound approaching the raw sound due to natural vibration because it is made of wood is output without change over time.
[0052]
In addition, the natural wood grain appears on the surface, giving it a high-quality appearance.
[Brief description of the drawings]
FIG. 1 is a manufacturing process flowchart of speaker diaphragms according to first and second embodiments of the present invention.
FIG. 2 is a schematic diagram showing each processing state (first half) of the manufacturing process flow chart.
FIG. 3 is a schematic diagram showing each processing state (second half) of the manufacturing process flow chart.
FIG. 4 is a schematic diagram for explaining a processing stage of a shape of wood that is a material of a speaker diaphragm according to the present invention.
FIG. 5 is a schematic diagram for explaining the characteristics of a third embodiment of a speaker diaphragm according to the present invention;
FIG. 6 is a schematic diagram for explaining the characteristics of a fourth embodiment of a speaker diaphragm according to the present invention.
FIG. 7 is a diagram showing a manufacturing procedure of a conventional wooden diaphragm.
FIG. 8 is a diagram showing a manufacturing procedure of a conventional wooden diaphragm.
FIG. 9 is a schematic cross-sectional view of a conventional paper pulp diaphragm with a conical dome.
FIG. 10 is a graph showing the relationship between the internal loss coefficient and sound propagation speed (longitudinal direction) of various kinds of wood together with aluminum and paper, which are conventional materials.
[Explanation of symbols]
6 logs
7 Cutting blade
10 Wooden sheet
11 V-shaped notch
11a, 11b both edges
12 Small hole
13, 13 'Nonwoven fabric or Japanese paper
15 Bonding sheet
16 Lubricant that provides moisture and retains moisture
17 Thermosetting resin
18 Moisturizer
25 Center hole
20, 30, 40, 50 Diaphragm for speaker
31, 34 Upper mold
33 Heater
32, 35 Lower mold
36 dust cap
37 Conical Dome
38 Concave shape of upper mold
39 Convex shape of lower mold
60 Paper pulp diaphragm with conical dome
61 Conical Dome
62 Diaphragm
P1, P2 press machine

Claims

In a speaker diaphragm formed by pressing a single wooden sheet into a substantially trumpet shape,
A substantially V-shaped cut having a vertex at the center is provided for one wooden sheet, and the wooden sheet provided with the cut has moisture and is softened and has a function of retaining moisture in the wooden sheet. Lubricant is included, and the wood sheet containing the lubricant is temporarily formed into a substantially trumpet shape by overlapping the edges of the substantially V-shaped cuts by primary press thermoforming, and is dried after the temporary forming. A thermosetting resin is contained after drying, and drying is performed at a drying temperature of 50 ° C. to 60 ° C. for approximately 1 to 10 minutes until the thermosetting resin is in a semi-dried state, and the thermosetting resin is semi-dried. A secondary press heat molding is performed in a semi-dry state of the water-soluble resin, a moisture-proofing agent is applied after the secondary press-heating molding, and a central hole punching for a voice coil and an outer shape are removed from the wooden sheet coated with the moistureproofing agent. Make vibration Speaker diaphragm, characterized in that formed by molding into a predetermined size and shape as.

In a speaker diaphragm formed by pressing a single wooden sheet into a substantially trumpet shape,
For a laminated sheet formed by sticking a thin non-woven fabric or Japanese paper on one side of a single wooden sheet, a substantially V-shaped cut having a vertex at the center is provided, and the laminated sheet provided with the cut A lubricant having a function of softening by adding moisture and holding moisture in the bonded sheet is included, and the bonded sheet containing the lubricant is subjected to primary press thermoforming to form the substantially V-shaped cut. The edges are overlapped and temporarily formed into a substantially trumpet shape, dried after the temporary forming, and after drying, a thermosetting resin is included, and the thermosetting resin is in a semi-dried state at 50 ° C. to 60 ° C. Drying is carried out at a drying temperature for approximately 1 to 10 minutes and semi-dried, followed by secondary press heat molding in a semi-dry state of the thermosetting resin, and a moisture-proofing agent is applied after the secondary press heat molding, Medicinal Speaker diaphragm, characterized in that formed by molding into a predetermined size and shape as the vibrating plate by performing a center punching and outer vent for a voice coil relative to the fabric has been bonded sheet.

In a speaker diaphragm formed by pressing a single wooden sheet into a substantially trumpet shape,
A substantially V-shaped notch is provided in the center of the laminated sheet that is formed by sticking a thin non-woven fabric or Japanese paper to the central part on the opposite side of the entire surface of one wooden sheet. The laminated sheet provided with the notches is softened by adding moisture to the laminated sheet, and the laminated sheet contains a lubricant having an action of retaining moisture, and the laminated sheet containing the lubricant is subjected to primary press heating. The edges of the substantially V-shaped cuts are overlapped with each other by molding, are temporarily molded into a substantially trumpet shape, dried after the temporary molding, contain a thermosetting resin after drying, and the thermosetting resin is semi-dried A laminated sheet that is semi-dried until it reaches a state, is heat-molded in a secondary press in a semi-dry state of the thermosetting resin, is coated with a moisture-proofing agent after the secondary-press heat-molding, and is coated with the moisture-proofing agent Speaker diaphragm, characterized in that formed by molding into a predetermined size and shape as the vibrating plate by performing a center punching and outer vent for the voice coil against.

4. The loudspeaker diaphragm according to claim 1, wherein the wooden sheet used as a material has a longitudinal sound wave propagation velocity along a grain of 4.5 to 6.0 km / sec. The speaker diaphragm is cut out from a solid material having an internal loss coefficient in the range of 0.02 to 0.03.

4. The speaker diaphragm according to claim 1, wherein a plurality of conical domes are formed on the diaphragm by secondary press thermoforming.