JP2004260328A

JP2004260328A - Manufacturing method of diaphragm for speaker

Info

Publication number: JP2004260328A
Application number: JP2003046264A
Authority: JP
Inventors: Satoshi Imamura; 智今村; Takeshi Hirano; 猛平野; Tomoaki Ogata; 知昭尾形; Toshikatsu Kuwahata; 敏勝桑波田
Original assignee: Victor Company of Japan Ltd
Current assignee: Victor Company of Japan Ltd
Priority date: 2003-02-24
Filing date: 2003-02-24
Publication date: 2004-09-16
Anticipated expiration: 2023-02-24
Also published as: JP3882766B2

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing method of a diaphragm for a wooden speaker excellent in mass-productivity. <P>SOLUTION: On one surface of a piece of wooden sheet 10, a nonwoven fabric or Japanese paper 13 is adhered to make an adhered sheet 15. An approximately V-shaped notch 11 is provided onto the adhered sheet 15, the adhered sheet 15 is wetted to be softened, and a lubricant 16 which acting like keeping water is impregnated thereinto. The edge portions 11a and 11b of the notch 11 of the adhered sheet 15 are overlapped with each other, and the area outside the molding portion is latched and kept with a latching tool 26 so that the adhered sheet 15 is made into an approximately horn shape by a first hot press molding. The adhered sheet 15 is then dried, impregnated with a thermosetting resin 17, and half-dried until the adhered sheet 15 is brought into a half-dried state. Further, the edge portions 11a and 11b of the notch 11 of the adhered sheet 15 are overlapped by an adhesive strength of the thermosetting resin 17 while a second hot press molding is applied to the adhered sheet 15 wherein the thermosetting resin 17 is in the half-dried state, a moisture-proof agent 18 is applied onto the adhered sheet 15, and a center hole 25 for a voice coil and periphery are removed to make a speaker diaphragm having a predetermined dimension and shape. <P>COPYRIGHT: (C)2004,JPO&NCIPI

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木製の振動板の製造方法に関する。
【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８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９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の製造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成形において如何に対処するか、また、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成形性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８及び図９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製造方法は、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するというスピーカ用振動板の製造方法は前記［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が認められるが、未だ量産に適う十分な成形処理の確立が達成されたとは言い難く、木製振動板の実用化に向けてより一層の成形性の歩留まりの向上、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、ダイナミック・スピーカの音響特性改善に有効で量産に適う木製のスピーカ用振動板の製造方法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枚の木製シートを素材として略ラッパ形状にプレス成形する工程を含むスピーカ用振動板の製造方法において、第１に１枚の木製シート１０の一面側に薄い不織布又は和紙１３を貼着して貼り合わせシート１５を作成する工程と、第２に前記貼り合わせシート１５の中心部に頂点が至る略Ｖ字状の切り込み１１を設ける工程と、第３に前記切り込み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中に水分を保持する作用を有する潤滑剤１６を含ませる工程と、第４に前記潤滑剤１６が含まされた貼り合わせシート１５を１次プレス加熱成形して前記切り込みの縁部１１ａ、１１ｂ同士が互いに重ねられた略ラッパ形状に仮成形する工程と、第５に仮成形された前記貼り合わせシート１５を乾燥する工程と、第６に乾燥後の前記貼り合わせシート１５に熱硬化性樹脂１７を含ませる工程と、第７に前記熱硬化性樹脂１７が含まされた前記貼り合わせシート１５を半乾き状態になるまで半乾燥する工程と、第８に前記熱硬化性樹脂１７が半乾き状態の貼り合わせシートを２次プレス加熱成形しつつ前記略Ｖ字状の切り込み１１の縁部１１ａ、１１ｂ同士を前記熱硬化性樹脂１７の接着力によって貼着する工程と、第９に前記２次プレス加熱成形後の貼り合わせシート１５に防湿剤１８を塗布する工程と、第１０に前記防湿剤１８が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する工程と、を設けたことを特徴とするスピーカ用振動板３０の製造方法を提供する。
（２）また、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する工程を含むスピーカ用振動板の製造方法において、第１に１枚の木製シート１０の一面側に薄い不織布又は和紙１３を貼着して貼り合わせシート１５を作成する工程と、第２に前記貼り合わせシート１５の中心部に頂点が至る略Ｖ字状の切り込み１１を設ける工程と、第３に前記切り込み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を含ませる工程と、第４に前記潤滑剤１６が含まされた貼り合わせシート１５の切り込み１１の縁部１１ａ、１１ｂ同士を互いに重ねて全体が略ラッパ形状に掛止保持されるように貼り合わせシート１５のプレス成形領域外の部分を掛止具２６で止める工程と、第５に前記掛止具２６で略ラッパ形状に保持され潤滑剤１６が含まされた貼り合わせシート１５を１次プレス加熱成形して略ラッパ形状に仮成形する工程と、第６に仮成形された前記貼り合わせシート１５を乾燥する工程と、第７に乾燥後の前記貼り合わせシート１５に熱硬化性樹脂１７を含ませる工程と、第８に前記熱硬化性樹脂１７が含まされた前記貼り合わせシート１５を半乾き状態になるまで半乾燥する工程と、第９に前記熱硬化性樹脂１７が半乾き状態の貼り合わせシートを２次プレス加熱成形しつつ前記略Ｖ字状の切り込みの縁部１１ａ、１１ｂ同士を前記熱硬化性樹脂１７の接着力によって貼着する工程と、第１０に前記２次プレス加熱成形後の貼り合わせシート１５に防湿剤１８を塗布する工程と、第１１に前記防湿剤１８が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する工程と、を設けたことを特徴とするスピーカ用振動板３０の製造方法を提供する。
【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のフロー図である。図２及び図３は前記製造工程の各加工状態の前半、後半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貼り合わせシートに設けた略Ｖ字状の切り込み及び掛止機構の例を示す図である。図６は本発明に係るスピーカ用振動板の貼り合わせシートを掛止具によって略ラッパ形状に掛止保持した状態を示す図である。図７は本発明に係る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の概略図である。
【００２４】
先ず、図４において、本発明のスピーカ用振動板３０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（ｂ）のように実際に振動板となる成形部分（破線の円形部分内）よりも大きめの適当な形状に切断されて大きな柾目の木製シート１０になる。例えば、口径８ｃｍ程度のダイナミック・コーン・スピーカの振動板では、一辺１２〜１４ｃｍ程度の正方形や矩形乃至直径１２ｃｍ程度の円形とする。
【００２５】
次に、製造段階に入って、前記木製シート１０は図２の（ａ）の不織布又は和紙１３の貼り合わせ工程を経て貼り合わせシート１５となり、これに対して図２の（ｂ）のように略Ｖ字形状の切り込み１１が設けられる。なお、上記略Ｖ字状の切り込み１１は単純なＶ字形状のみならず図５の（ａ）のような鋸歯状や図５の（ｂ）のような波状であってもよい。要は両縁を隙間なく重ね合わせると全体が略ラッパ状（コーン形状）になればよいのである。
【００２６】
次に、幾つかのプレス成形工程等を経て最終的に図７の概略図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３０となる（図３の（ｊ）の断面図も参照）。
【００２７】
図７に示される上記スピーカ用振動板３０の木目は、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生じないので、分割振動が抑えられるのである。
【００２８】
また、上記スピーカ用振動板３０は木製であることに基づく優れた音響特性と美しい木目の仕上がりを備えるとともに選択された潤滑剤や熱硬化性樹脂、防湿剤の含浸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ものとなっている。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。
【００２９】
ここで、本発明のスピーカ用振動板３０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。
【００３０】
【表１】

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。
【００３１】
次に、上記スピーカ用振動板３０の製造方法を図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。
【００３２】
先ず、請求項２に係る第１の実施の形態（Ｂ）のスピーカ用振動板３０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１１工程で構成され、（ａ）貼り合わせシート作成、（ｂ）Ｖ字状切り込みの形成、（ｃ）潤滑剤含浸、（ｄ１）略ラッパ形状に掛止、（ｄ２）仮成形の１次プレス、（ｅ）乾燥、（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）中心孔・外形抜きの順に行われてスピーカ用振動板の完成となる。
【００３３】
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厚の不織布又は和紙１３を貼り合わせ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を設ける。前記切り込み１１は、貼り合わせシート１５の木目方向（矢印ｆ）に概ね沿って設ける。なお、上記小穴１２は略ラッパ形状に成形する際の中心部の割れを防止するためのものであり、直径数ミリの円形、楕円形、六角形等であって形状に制限はない。
工程（ｃ）・・・Ｖ字切り込みした前記貼り合わせシート１５が軟化するように、貼り合わせシート１５の中に浸透して水分を与え且つ水分を保持する作用のある潤滑剤１６の液中に５〜６０分浸して十分に含浸させる。
【００３４】
これは後の１次プレス加熱成形を実施する時に割れを未然に防ぎ、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適する。
工程（ｄ１）・・・貼り合わせシート１５の切り込み１１の両縁部１１ａ、１１ｂ同士を重ね合わせて図６に示されるような略ラッパ形状になるように成形外領域（余白部分）を掛止具２６で掛止保持する。前記掛止具２６としてはホッチキス（商標名）やクリップ等の紙綴じ器が利用でき、前記両縁部１１ａ、１１ｂの延長上の余白部分を止めれば簡単に掛止保持することができ、１次プレス加熱成形の作業性、加工精度が良好となる。
工程（ｄ２）・・・ヒータ３３を各々備えた上型３１と下型３２の金型構成のプレス装置Ｐ１によって、前記潤滑剤１６を含浸させ掛止具２６で略ラッパ形状に保持させた貼り合わせシート１５を１次プレス加熱成形（仮成形）する。ここで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秒である。なお、上記噛み合わせ掛止機構１４によってプレス装置Ｐ１にセッティングする前から略ラッパ状に形状が保持されているため、セッティングの作業性が向上し、且つ１次プレス加熱成形（仮成形）の成形性の向上（しわや割れが少ない）が実現している。
工程（ｅ）・・・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を熱硬化性樹脂１７液中に略３０分〜１８０分浸し、十分に含浸させる。上記熱硬化性樹脂１７としてはフェノール樹脂が適する。
工程（ｇ）・・・熱硬化性樹脂１７の含浸直後、後工程の２次プレスを実施すると、金型に熱硬化性樹脂１７が貼り付いてしまい、プレス後に貼り合わせシート１５を剥がす時に割れや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、乾燥炉（５０℃〜６０℃）に略１〜１０分間入れて熱硬化性樹脂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、含浸させた熱硬化性樹脂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、この時点で重ね合わせて貼着された前記切り込み１１の縁部１１ａ、１１ｂ（斜線領域）同士はその段差が殆ど判別できない程度に密着しており、音響特性に与える影響は殆ど無いものとなっている。
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を塗布する。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。なお、塗布された上記防湿剤１８は自然乾燥又は乾燥炉で完全乾燥を行なう。
工程（ｊ）・・・防湿処理されたプレス加熱成形後の貼り合わせシート１５にボイスコイル用の中心孔２５と外形抜きが施されて所定の振動板形状に加工されてスピーカ用振動板３０が完成する。
【００３５】
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スピーカユニットに組み込まれる。
【００３６】
上記本発明に係る第１の実施の形態のスピーカ用振動板３０の製造工程（Ｂ）では、略ラッパ形状に掛止保持する工程（ｄ１）を含んでいたが、前記掛止具２６を用いずとも、図１に示される請求項１に係る第２の実施の形態の（Ａ）のフローの製造方法の工程（ｄ）の１次プレス加熱成形時の直前に貼り合わせシート１５における成形領域（破線の円形部分内）以外の外周の余白部分における両縁部１１ａ、１１ｂ近傍を作業者が手で摘まんで保持した状態で１次プレス加熱成形することも可能である。また、予め切り込み１１の両縁部１１ａ、１１ｂ同士を重ねて接着剤で固着させる方法もあるが、音響特性に影響を与える接着剤は可及的に控えることが望ましい。そこで、工程（ｂ）において図５の（ａ）、（ｂ）、（ｃ）、（ｄ）に示されるような貼り合わせシート１５の略Ｖ字状の切り込み１１の両縁部１１ａ、１１ｂの近傍の破線で囲んだ円形の成形領域外の余白部分に互いに引っかける雄雌形状の掛止機構１９（１９ａ、１９ｂ）を設けることによって１次プレス加熱成形前に掛止保持しておく方法が適用できる。なお、１次プレス加熱成形の後は両縁部１１ａ、１１ｂ同士は自然状態で離れない程度に貼着されており、略ラッパ形状が保持される。
【００３７】
以上の製造方法によって製造されたスピーカ用振動板３０は、本発明者の研究によれば、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て上記各実施の形態の製造方法にて製造された振動板が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ことが判った。
【００３８】
特に顕著に音響特性の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／秒の範囲で内部損失係数が０．０２〜０．０３の範囲の木材を選択して振動板に用いた場合であり、具体的にはカバ材（無垢）が最良であった。
【００３９】
勿論、本発明のスピーカ用振動板は、カバのみならず、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勿論である。
【００４０】
【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の製造方法は、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振動板を作ることができる。
【００４１】
従来の木製振動板のような柔軟化のためのボイル処理、物理的処理、化学的薬品を施さないので音質劣化の発生しない振動板を作ることができる。
【００４２】
プレス加熱成形時のしわや割れの発生が防止され、製造後の変形や割れといった経時変化が殆ど無い仕上がりの良い均一なプレス加熱成形品とすることができる。
【００４３】
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。
【００４４】
掛止具によってプレス加熱成形前から略ラッパ状に形状が保持されているため、プレス機へのセッティングの作業性が向上し、成形性の向上が実現して歩留まりが向上して、安価供給が実現できる。
【００４５】
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声音が経時変化なく出力される。
【００４６】
さらに、表面に自然の木目が表れているので、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成り立ちを説明するため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貼り合わせシートに設けた略Ｖ字状の切り込み及び掛止機構の例を示す図である。
【図６】本発明に係るスピーカ用振動板の貼り合わせシートを掛止具によって略ラッパ形状に掛止保持した状態を示す図である。
【図７】本発明に係る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の概略図である。
【図８】従来の木製振動板の製造手順を示す図である。
【図９】従来の木製振動板の製造手順を示す図である。
【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不織布又は和紙
１４噛み合わせ掛止機構
１４ａ凸部
１４ｂ切欠部
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
１９掛止機構
２５中心孔
２６掛止具
３０スピーカ用振動板
３１、３４上型
３３ヒータ
３２、３５下型
Ｐ１、Ｐ２プレス装置[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention belongs to the technical field of audio speakers, and more particularly to a method of manufacturing a wooden diaphragm used for a dynamic speaker.
[0002]
[Prior art]
Conventionally, the diaphragm of a dynamic speaker has been mostly 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 equal in all directions. Therefore, there is a problem that a standing wave is always generated and has a resonance point, the sound pressure frequency characteristic is deteriorated due to the divided vibration in a low frequency region, and the sense of reality is lost. Further, although the diaphragm made of paper pulp or plastic has a relatively large internal loss coefficient, it is inferior in rigidity (the magnitude of the Young's modulus), and the sound wave propagation speed is small, so the resolution of the reproduced sound is slightly dissatisfied. Will remain. On the other hand, although a diaphragm made of metal such as aluminum has a high sound wave propagation velocity, it has a small internal loss coefficient, and therefore has a disadvantage in that the attenuation of the amplitude is small and the division of the reproduced sound becomes unclear (so-called poor sound sharpness). .
[0003]
There is a demand for the realization of a wooden diaphragm as a speaker diaphragm capable of reproducing a more natural sound, instead of a diaphragm made of an existing material having advantages and disadvantages as described above.
[0004]
That is, although the sound wave propagation speed of wood differs depending on the type, it is generally higher than that of paper pulp, and further differs between the grain direction and the direction perpendicular to the grain direction. The propagation speed in the grain direction (vertical direction) is high, and is perpendicular to the grain direction. It has an anisotropic propagation property that the propagation speed in the direction (referred to as the lateral direction) is relatively slow. Wood generally has a suitable internal loss coefficient as a speaker diaphragm, and is lightweight and durable (high rigidity).
[0005]
Therefore, a wooden diaphragm made of wood itself hardly generates a standing wave and hardly has a resonance point, so that almost no split vibration occurs, and it is expected that sound pressure frequency characteristics in a low frequency region are improved. Compared with the diaphragm made of pulp and paper, the resolution of the reproduced sound can be improved and the crisp sound can be improved.
[0006]
Various proposals have already been made, for example, in the following known documents as a method for manufacturing the wooden diaphragm or a dynamic speaker using the wooden diaphragm or a wooden diaphragm.
[0007]
[Patent Document 1] described below discloses a flat thin plate made of WPC which is obtained by impregnating and hardening a plastic such as polyester into a flat thin plate made of a wooden material. The flat thin plate for a speaker has excellent characteristics such as dimensional stability, internal friction, and rigidity. A speaker used as a speaker has been proposed.
[0008]
In the following Patent Document 2, as shown in the manufacturing procedure shown in FIGS. 8A and 8B, (a) an arc-shaped notch 1a is formed at the center from a single thin wood plate 4. Then, a wood sheet 1 having a substantially trumpet-shaped expanded shape having a fan-shaped cutout portion 1b is cut out continuously, and (b) both edges b1 and b2 of the fan-shaped cutout portion 1b of the wood sheet 1 are glued. There has been proposed a cone diaphragm 5 formed by overlapping and pasting each other with an adhesive at a margin portion 1c, forming a trumpet shape, and then press forming.
[0009]
Also, as in the manufacturing procedure shown in FIGS. 9A and 9B, a plurality of pieces of wood pieces 2a, 2b,..., 2L are attached with an adhesive to form a substantially trumpet shape as shown in FIG. A cone diaphragm 2 formed and then pressed is proposed. Further, there has been proposed a cone diaphragm in which a physical moisture resistance treatment or a chemical moisture resistance treatment is applied to the

cone diaphragms

1 and 2.
[0010]
[Patent Document 3] described below discloses a softening treatment of a composite sheet composed of an ultrathin wood sheet sliced to 80 μm or less and a nonwoven fabric made of an adhesive resin adhered to the back surface thereof with a softener. There has been proposed an acoustic diaphragm which is formed by laminating a plurality of sheets and further heating and pressing to form a conical shape.
[0011]
[Patent Document 4] described below discloses that a flat thin wooden plate cut into a fan shape is boiled with high-temperature steam, hot water, or an alkaline solution having a pH of 10 or more in order to prevent cracking during molding, and then into a cone shape. A cone diaphragm formed by press molding has been proposed.
[0012]
In the following Patent Document 5, a laminated sheet in which a thin nonwoven fabric or Japanese paper is adhered to one surface side of one wooden sheet is prepared, and this is impregnated into a container containing a lubricant, and the impregnated laminated sheet is impregnated. Has been proposed in which a speaker diaphragm is formed into a substantially trumpet shape by press-heating.
[0013]
In the following Patent Document 6, in order to produce a wooden speaker diaphragm which does not generate wrinkles or cracks during press molding and has little change over time, a thin nonwoven fabric or Japanese paper or A speaker diaphragm has been proposed in which a laminated sheet having a carbon sheet attached thereto is formed, impregnated with a thermosetting resin, and then press-heat-molded to form a substantially trumpet shape.
[0014]
[Patent Document 1] JP-A-62-224196 [Patent Document 2] JP-A-1-288100 [Patent Document 3] JP-A-5-83792 [Patent Document 4] JP-A-6-178386 [ [Patent Document 5] Japanese Patent Application Laid-Open No. 10-304492 [Patent Document 6] Japanese Patent Application Laid-Open No. 2000-59883 [Problems to be Solved by the Invention]
A particular point in the manufacture of wooden speaker diaphragms is how to deal with the fragile nature of the wood material in molding and how to deal with aging.
[0015]
Regarding this point, [Patent Document 1] is directed to a wooden planar diaphragm, which has the characteristics and advantages of being made of wood, but the formability when forming into a substantially trumpet shape (cone shape). No technical data has been provided for this problem because it is flat.
[0016]
Further, in the manufacturing method as shown in FIGS. 8 and 9 of [Patent Document 2], since the wood sheet 1 or the small piece of wood sheets 2a, 2b,. In addition, there is a problem that cracks occur at the time of press molding or that the wood sheets are bonded to each other with an adhesive, so that the bonded portion becomes an obstacle and the desired acoustic characteristics cannot be obtained, and there is a problem that dimensional accuracy cannot be secured. .
[0017]
Also, the manufacturing method of [Patent Document 3] in which a plurality of ultra-thin wood sheets are laminated and press-molded has a drawback in processing accuracy, the number of adhesive layers increases, and the weight of the diaphragm itself increases due to the weight of the adhesive. As a result, the desired acoustic characteristics cannot be obtained, and a large amount of the adhesive adversely affects the sound pressure frequency characteristics.
[0018]
Further, 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 as in [Patent Document 4], a constituent material called lignin in wood is also removed, so that wood is removed. Cannot exhibit its original characteristics, which will adversely affect sound quality.
[0019]
Above all, the contents of [Patent Literature 2], [Patent Literature 3], and [Patent Literature 4] have many problems such as cracks, cracks, and wrinkles during manufacturing, and the yield in mass production is extremely high. It has become worse and commercialization has not been realized.
[0020]
Further, a thermosetting resin for preventing impregnation of a lubricant for extracting “tension” and “suppleness” in [Patent Document 5] and [Patent Document 6], preventing generation of wrinkles and cracks, and preventing a change with time is known. The method of manufacturing the speaker diaphragm by press-heating after impregnation has an advantage of the manufacturing process for mass production as compared with the above-mentioned [Patent Document 1] to [Patent Document 4], but it is still sufficient for mass production. It is hard to say that the establishment of the forming process has been achieved, and it is desired to further improve the yield of formability and 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 method of manufacturing a wooden speaker diaphragm that is effective for improving the acoustic characteristics of a dynamic speaker and is suitable for mass production.
[0022]
[Means for Solving the Problems]
The present invention, in order to solve the above problems,
(1) In a method of manufacturing a speaker diaphragm including a step of press-molding one wooden sheet as a raw material into a substantially trumpet shape, first, a thin nonwoven fabric or Japanese paper 13 is attached to one surface side of one wooden sheet 10. A second step of forming a bonded sheet 15 by attaching, a second step of providing a substantially V-shaped cut 11 having a vertex at the center of the bonded sheet 15, and a third step of forming a cut 11 provided with the cut 11. A step of adding a lubricant 16 having a function of retaining moisture to the laminated sheet 15 by imparting moisture to the laminated sheet 15 and fourthly, bonding the laminated sheet 15 containing the lubricant 16 to the primary A step of press-heating and temporarily forming a substantially trumpet shape in which the cut edges 11a and 11b are overlapped with each other; And a sixth step of including the thermosetting resin 17 in the dried bonded sheet 15 and a seventh step of bringing the bonded sheet 15 including the thermosetting resin 17 into a semi-dry state. Eighth, the step of semi-drying until the thermosetting resin 17 is subjected to secondary press heat molding of the laminated sheet in which the thermosetting resin 17 is semi-dried, and the

edges

11a and 11b of the substantially V-shaped cut 11 are joined together. A step of applying the adhesive by the adhesive force of the thermosetting resin 17, a ninth step of applying the desiccant 18 to the bonded sheet 15 after the secondary press heat molding, and a tenth step of applying the desiccant 18 Manufacturing a speaker diaphragm 30 characterized by providing a step of punching a center hole 25 for a voice coil and punching the outer shape of the bonded sheet 15 to form a predetermined dimension as a diaphragm. Method To provide.
(2) In a method for manufacturing a diaphragm for a speaker including a step of press-molding one wooden sheet 10 into a substantially trumpet shape using a single wooden sheet 10 as a raw material, first, one wooden sheet 10 has a thin nonwoven fabric or Japanese paper on one surface side. 13 to form a bonded sheet 15, a second step of providing a substantially V-shaped cut 11 having a vertex at the center of the bonded sheet 15, and a third step of forming the cut 11. A step of adding moisture to the provided laminated sheet 15 so as to soften the laminated sheet 15 and at the same time to include a lubricant 16 having the function of retaining moisture in the laminated sheet 15; and fourthly, a laminated sheet containing the lubricant 16 The

edges

11a and 11b of the cuts 15 are overlapped with each other, and the outside of the press forming area of the bonded sheet 15 is latched so that the whole is latched and held substantially in a trumpet shape. Fifth, a step of firstly press-molding the bonded sheet 15 held in the substantially trumpet shape by the latching tool 26 and containing the lubricant 16 and temporarily forming it into a substantially trumpet shape, Sixth, a step of drying the temporarily formed bonded sheet 15, seventh, a step of including a thermosetting resin 17 in the dried bonded sheet 15, and eighth, a step of drying the thermosetting resin 17. And a ninth step of semi-drying the bonded sheet 15 containing the resin to a semi-dried state, and a ninth step in which the thermosetting resin 17 is subjected to the second press heating and forming the bonded sheet in a semi-dried state. A step of attaching the

edges

11a and 11b of the letter-shaped cut to each other by the adhesive force of the thermosetting resin 17, and tenthly applying a moisture proofing agent 18 to the laminated sheet 15 after the secondary press heat molding. Process and A step of forming a center hole 25 for a voice coil and removing an outer shape from the bonded sheet 15 coated with the moisture-proof agent 18 to form a predetermined shape as a diaphragm. A method for manufacturing the speaker diaphragm 30 is provided.
[0023]
BEST MODE FOR CARRYING OUT THE INVENTION
An embodiment of a speaker diaphragm according to the present invention will be described with reference to the drawings. FIG. 1 is a flow chart of the manufacturing process of the speaker diaphragm of the first and second embodiments according to the present invention. 2 and 3 are schematic diagrams showing the first half and the second half of each processing state in the manufacturing process. FIG. 4 is a schematic diagram for explaining a processing stage of a shape of wood as a material of the speaker diaphragm according to the present invention. FIG. 5 is a view showing an example of a substantially V-shaped notch and latch mechanism provided on a bonded sheet of the speaker diaphragm according to the present invention. FIG. 6 is a view showing a state in which the bonded sheet of the speaker diaphragm according to the present invention is hooked and held in a substantially trumpet shape by a hook. FIG. 7 is a schematic diagram of a speaker diaphragm of a dynamic cone speaker having a substantially trumpet shape according to the present invention.
[0024]
First, in FIG. 4, wood used as a material of the speaker diaphragm 30 of the present invention is prepared as a preparation stage of manufacture, for example, as shown in FIG. As shown in (b), the sheet is cut into an appropriate shape that is larger than the molded part (inside of the dashed circle) that becomes the diaphragm as shown in FIG. For example, in the case of a diaphragm of a dynamic cone loudspeaker having a diameter of about 8 cm, a square having a side of about 12 to 14 cm or a rectangle or a circle having a diameter of about 12 cm is used.
[0025]
Next, in the manufacturing stage, the wooden sheet 10 becomes a bonded sheet 15 through a bonding process of the nonwoven fabric or the Japanese paper 13 shown in FIG. 2A, and as shown in FIG. A substantially V-shaped cut 11 is provided. Note that the above substantially V-shaped cut 11 may be not only a simple V-shape but also a saw-tooth shape as shown in FIG. 5A or a wavy shape as shown in FIG. 5B. The point is that if both edges are overlapped without any gap, the whole should be substantially trumpet-shaped (cone-shaped).
[0026]
Next, through several press molding steps and the like, finally a speaker diaphragm 30 of a dynamic cone speaker having a substantially trumpet shape as shown in the schematic diagram of FIG. 7 (cross-sectional view of FIG. 3 (j)) See also).
[0027]
When the grain of the speaker diaphragm 30 shown in FIG. 7 is viewed in the radial direction (for example, the da to dh direction) from the center hole 25 cut out for the voice coil, only the da direction is present along the grain direction. Instead, the other direction intersects the grain at an angle. Therefore, the same sound propagation velocity does not exist in almost all directions, and a standing wave is hardly generated, and a resonance point is hardly generated. Therefore, divided vibration is suppressed.
[0028]
In addition, the speaker diaphragm 30 has excellent acoustic characteristics based on being made of wood and has a beautiful grain finish, and is impregnated with a selected lubricant, thermosetting resin, or desiccant, and is formed by a series of press heat molding processes. Due to ingenuity and the like, there are no wrinkles or cracks, little change over time due to humidity, and a long life. It should be noted that the production process is simple but very high in yield, and the production cost is suppressed and excellent in mass productivity.
[0029]
Here, considering wood suitable for the material of the speaker diaphragm 30 of the present invention, the relationship between the internal loss coefficient and the sound propagation speed (vertical direction) of the various woods shown in FIG. As can be seen from the following table, which shows the density, Young's modulus, sound velocity, and internal loss coefficient (tan δ) of various types of wood, the plywood was roughly (G point, H point, I point, J point). It can be seen that the removed wood (solid wood) can be an excellent material having an appropriate internal loss coefficient and a high sound propagation speed. In particular, it is found that the birch (point A) and beech (point C) are optimal.
[0030]
[Table 1]

In addition, the point A in FIG. 10 is a hippopotamus (solid wood), and hereafter, the point B; china (solid wood), the point C: beech (solid wood), the point D: oak (solid wood), the point E: cherry (Solid wood), point F: spruce (solid wood), point G: plywood (concentric), point H: lauan plywood, point I: MFD, point J: particle board.
[0031]
Next, a method for manufacturing the speaker diaphragm 30 will be described with reference to the flowcharts of FIGS. 1A to 1J and the corresponding schematic diagrams of FIGS. .
[0032]
First, in the manufacturing process of the speaker diaphragm 30 of the first embodiment (B) according to the second aspect, as shown in FIG. (a) preparation of a laminated sheet, (b) formation of a V-shaped cut, (c) impregnation with a lubricant, (d1) hooking in a substantially trumpet shape, (a) to (j). d2) Primary press of temporary molding, (e) drying, (f) impregnation of thermosetting resin, (g) semi-dry, (h) secondary press, (i) application of moisture proofing agent, (j) center hole and outer shape It is performed in the order of removal, and the diaphragm for speaker is completed.
[0033]
The details of each of the above steps will be described below in order.
Step (a) ... 0. A nonwoven fabric or Japanese paper 13 having a thickness of about 0.02 to 0.30 mm is attached to one surface side of a wooden sheet 10 having a thickness of 1 mm to 0.9 mm (preferably about 0.3 mm) with an adhesive to form a bonded sheet 15. I do. The nonwoven fabric referred to here is a well-known material made of a carbon material or other synthetic resin, and one side of the bonded nonwoven fabric is the rear side of the completed diaphragm 30. The thickness of the wooden sheet 10 is appropriate for a speaker diaphragm in consideration of formability, 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 near the vertex are provided in the bonded sheet 15. The cut 11 is provided substantially along the grain direction (arrow f) of the bonded sheet 15. The small holes 12 are for preventing cracks at the center portion when forming into a substantially trumpet shape, and are not limited in shape, such as a circle having a diameter of several millimeters, an ellipse, and a hexagon.
Step (c): In a liquid of a lubricant 16 having a function of penetrating into the bonded sheet 15 to give moisture and to retain moisture so that the V-cut cut laminated sheet 15 is softened. Soak for 5-60 minutes to fully impregnate.
[0034]
This is because cracks are prevented beforehand when the primary press heat forming is performed later, and temporary forming is performed with good yield. According to the study of the present inventor, an aqueous solution in which a saccharide is dissolved is suitable as the lubricant 16 instead of a simple water or alkaline aqueous solution.
Step (d1): The outside edge (margin portion) of the cut sheet 11 is overlapped so that both

edges

11a and 11b of the cut 11 of the bonded sheet 15 are overlapped with each other to form a substantially trumpet shape as shown in FIG. It is hooked and held by the tool 26. A paper binding device such as a stapler (trade name) or a clip can be used as the hook 26, and the hook 26 can be easily hooked and held by stopping a margin on the extension of the both

edges

11a and 11b. Workability and processing accuracy of the next press heat forming are improved.
Step (d2): Pasting in which the lubricant 16 is impregnated by a press device P1 having a mold configuration of an upper mold 31 and a lower mold 32 each provided with a heater 33, and held in a substantially trumpet shape by a latch 26. The laminated sheet 15 is subjected to primary press heat forming (temporary forming). Here, the setting conditions of the primary press heat molding are as follows: the press pressure is about 1 to 10 kg, the mold temperature is about 80 to 150 ° C. for the upper mold 31, about 100 to 200 ° C. for the lower mold 32, and the press time is about 2 to 2. 60 seconds. In addition, since the shape is maintained substantially in a trumpet shape before the setting in the press device P1 by the engagement hooking mechanism 14, the workability of the setting is improved, and the forming of the primary press heat forming (temporary forming) is performed. Improved properties (less wrinkles and cracks) are realized.
Step (e): Complete drying is carried out by placing in a drying furnace (50-60 ° C.) for about 10-30 minutes.
Step (f): The dried bonded sheet 15 is immersed in the liquid 17 of the thermosetting resin for about 30 to 180 minutes to be sufficiently impregnated. A phenol resin is suitable as the thermosetting resin 17.
Step (g): Immediately after the impregnation of the thermosetting resin 17, if the secondary press in the subsequent step is performed, the thermosetting resin 17 is stuck to the mold, and is broken when the bonded sheet 15 is peeled off after the pressing. And tearing occurs and the yield is extremely reduced. Conversely, if it is completely dried, the moldability deteriorates and it becomes easy to break. In order to prevent this, the thermosetting resin 17 is placed in a drying oven (50 ° C. to 60 ° C.) for about 1 to 10 minutes to put the thermosetting resin 17 in a semi-dry state (a so-called “touch dry state” which does not stick when touched with a finger). ).
Step (h): The bonded sheet 15 in which the impregnated thermosetting resin 17 is in a semi-dry state is press-heat-formed again by the press device P2 having a known configuration similar to that of the step (d). Here, the setting conditions of the secondary press heat molding are as follows: the press pressure is about 20 to 40 kg, the mold temperature is about 80 to 200 ° C. for the upper mold 34, about 100 to 200 ° C. for the lower mold 35, and the press time is about 10 to 10. 100 seconds. After forming, the volatile components evaporate, and the bonded sheet 15 is stable in a substantially trumpet shape. At this time, the

edges

11a and 11b (hatched areas) of the cuts 11 which are superimposed and adhered are in close contact with each other to such an extent that the step can hardly be discriminated, and there is almost no influence on the acoustic characteristics. Has become.
Step (i): The moisture proofing agent 18 is applied to both the front and back surfaces of the bonded sheet 15 after the secondary pressing by applying with a brush or dipping in a jab. As the desiccant 18, for example, a mixture of a polyisocyanate and a polyester polyol is used. The applied moisture-proofing agent 18 is completely dried in a natural drying oven or a drying oven.
Step (j): A center hole 25 for a voice coil and an outer shape are formed on the bonded sheet 15 after the press heat molding subjected to the moisture proof treatment, and the sheet is processed into a predetermined diaphragm shape. Complete.
[0035]
The completed substantially trumpet-shaped speaker diaphragm 30 is assembled into a speaker unit in combination with a voice coil, a damper, an edge, a magnetic circuit, a frame, and the like, similarly to a conventional dynamic speaker.
[0036]
The manufacturing process (B) of the speaker diaphragm 30 according to the first embodiment of the present invention includes the process (d1) of hooking and holding in a substantially trumpet shape. At least, the forming area in the bonded sheet 15 immediately before the first press heat forming in the step (d) of the flow manufacturing method (A) of the second embodiment according to the first embodiment shown in FIG. It is also possible to perform primary press heat molding in a state where the operator picks up and holds the vicinity of both

edges

11a and 11b in the outer margin portion other than (in the broken circle portion) by hand. In addition, there is a method in which both

edges

11a and 11b of the cut 11 are overlapped with each other and fixed with an adhesive, but it is desirable to reduce an adhesive that affects acoustic characteristics as much as possible. Therefore, in step (b), both

edges

11a and 11b of the substantially V-shaped cut 11 of the bonded sheet 15 as shown in FIGS. 5 (a), (b), (c) and (d) are obtained. A method in which a male and female hooking mechanism 19 (19a, 19b) that hooks each other is provided in a margin portion outside a circular molding area surrounded by a broken line to hold and hold before the first press heat molding is applied. it can. After the primary press heat forming, the both

edges

11a and 11b are stuck together so that they do not separate from each other in a natural state, and a substantially trumpet shape is maintained.
[0037]
According to the study of the present inventors, the speaker diaphragm 30 manufactured by the above manufacturing method has a vertical propagation velocity of 4.5 to 6.0 km / sec and a horizontal propagation velocity of 2.0 to 4.0 km / sec. A diaphragm manufactured by the manufacturing method of each of the above-described embodiments by selecting wood in a range of 5 km / sec clearly has a higher resolution of reproduced sound than a conventional diaphragm made of paper pulp or an aluminum diaphragm. It has been found that improvement and crisp sound improvement can be obtained.
[0038]
Particularly remarkable improvement in acoustic characteristics is realized when the internal loss coefficient is in the range of 4.5 to 6.0 km / sec in the vertical propagation velocity and 2.0 to 2.5 km / sec in the horizontal propagation velocity. This is a case where wood in the range of 0.02 to 0.03 was selected and used for the diaphragm. Specifically, birch wood (pure) was the best.
[0039]
Needless to say, the speaker diaphragm of the present invention can be applied not only to the hippopotamus but also to other lumber such as beech, oak, cherry, china, and the like.
[0040]
【The invention's effect】
As described above, the method for manufacturing a speaker diaphragm according to the present invention uses a single piece of wood as a raw material, and digests or beats wood fibers with a chemical as is present in the process of manufacturing a conventional paper pulp diaphragm. Since no processing is performed, it is possible to produce a diaphragm in which sound quality does not deteriorate.
[0041]
Since a boil process for softening, a physical process, and a chemical agent are not applied to the conventional diaphragm, it is possible to produce a diaphragm that does not deteriorate in sound quality.
[0042]
The generation of wrinkles and cracks at the time of press heat molding is prevented, and it is possible to obtain a uniform press heat molded article having a good finish and substantially no change with time such as deformation and cracks after production.
[0043]
Light and durable cone diaphragms can be manufactured, and diaphragms for all bands from woofers to full-range speakers can be manufactured.
[0044]
Since the shape of the trumpet is held by the hooks in the shape of a trumpet before press heat forming, the workability of setting to the press machine is improved, the formability is improved, the yield is improved, and low-cost supply is achieved. realizable.
[0045]
When this speaker diaphragm is used in a speaker unit, a re-voiced sound approaching a raw sound due to natural vibration due to being made of wood is output without change over time.
[0046]
Further, since natural wood grain appears on the surface, the appearance is luxurious.
[Brief description of the drawings]
FIG. 1 is a manufacturing process flow chart for explaining the formation of speaker diaphragms according to first and second embodiments according to the present invention.
FIG. 2 is a schematic view 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 illustrating a processing stage of a shape of wood as a raw material of the speaker diaphragm according to the present invention.
FIG. 5 is a view showing an example of a substantially V-shaped notch and latch mechanism provided on a bonded sheet of a speaker diaphragm according to the present invention.
FIG. 6 is a view showing a state in which a bonded sheet of the speaker diaphragm according to the present invention is hooked and held in a substantially trumpet shape by a hook.
FIG. 7 is a schematic diagram of a speaker diaphragm of a substantially cone-shaped dynamic cone speaker according to the present invention.
FIG. 8 is a diagram showing a procedure for manufacturing a conventional wooden diaphragm.
FIG. 9 is a view showing a procedure for manufacturing a conventional wooden diaphragm.
FIG. 10 is a graph showing the relationship between the internal loss coefficient of various types of wood and the sound propagation speed (vertical direction) together with aluminum and paper, which are conventional materials.
[Explanation of symbols]
Reference Signs List 6 Log 7 Cutting blade 10 Wooden sheet 11 Substantially V-shaped

cuts

11a, 11b Both edges 12 Small hole 13 Nonwoven fabric or Japanese paper 14 Mesh locking mechanism 14a Convex portion 14b Cutout 15 Bonded sheet 16 Lubricating agent 17 that retains moisture 17 Thermosetting resin 18 Moistureproofing agent 19 Hook mechanism 25 Center hole 26 Hook 30 Speaker diaphragm 31, 34 Upper die 33

Heater

32, 35 Lower die P1, P2 Press device

Claims

In a method for manufacturing a speaker diaphragm, the method includes a step of press-molding a single wooden sheet as a material into a substantially trumpet shape.
First, a step of attaching a thin nonwoven fabric or Japanese paper to one surface side of one wooden sheet to form a bonded sheet, and second, a substantially V-shaped notch having a vertex at the center of the bonded sheet. A third step of providing a lubricant having an action of giving moisture to the bonded sheet provided with the cuts to soften the laminated sheet and retaining the moisture in the laminated sheet; and a fourth step of providing the lubricant And a step of temporarily forming the bonded sheet containing the slabs by primary press heating and forming into a substantially trumpet shape in which the edges of the cuts are overlapped with each other, and drying the temporarily formed bonded sheet in a fifth step And a sixth step of including a thermosetting resin in the dried bonded sheet; and a seventh step of semi-drying the bonded sheet containing the thermosetting resin until it becomes a semi-dry state. Eighth, the substantially V-shaped cut edges are adhered to each other by the adhesive force of the thermosetting resin while the thermosetting resin is semi-dried in a semi-dry state while being subjected to secondary press heat molding. Ninth, a step of applying a desiccant to the bonded sheet after the secondary press heat molding, and tenthly, punching a center hole for a voice coil in the bonded sheet coated with the desiccant. And forming a shape of a predetermined size as a diaphragm by removing the outer shape.

In a method for manufacturing a speaker diaphragm, the method includes a step of press-molding a single wooden sheet as a material into a substantially trumpet shape.
First, a step of attaching a thin nonwoven fabric or Japanese paper to one surface side of one wooden sheet to form a bonded sheet, and second, a substantially V-shaped notch having a vertex at the center of the bonded sheet. A third step of providing a lubricant having an action of giving moisture to the bonded sheet provided with the cuts to soften the laminated sheet and retaining the moisture in the laminated sheet; and a fourth step of providing the lubricant The step of stopping the part outside the press forming area of the bonded sheet with a latch so that the edges of the cuts of the bonded sheet are overlapped with each other and the whole is latched and held substantially in a trumpet shape, 5: a step of primary press-heating and forming a bonded sheet containing a lubricant held in a substantially trumpet shape by the latching tool and temporarily forming the bonded sheet to a substantially trumpet shape; C Drying, a seventh step of including a thermosetting resin in the laminated sheet after drying, and an eighth step until the laminated sheet containing the thermosetting resin becomes a semi-dry state. And a ninth step of performing a semi-drying process, and performing a second press heat molding on the bonded sheet in which the thermosetting resin is in a semi-dry state, and bonding the edges of the substantially V-shaped cuts to each other with an adhesive force of the thermosetting resin. And a tenth step of applying a desiccant to the laminated sheet after the secondary press heat molding, and an eleventh step for applying a voice coil to the laminated sheet coated with the desiccant. A method of forming a center hole and an outer shape to form a shape having a predetermined size as a diaphragm.