JP3882767B2

JP3882767B2 - Manufacturing method of speaker diaphragm

Info

Publication number: JP3882767B2
Application number: JP2003046322A
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: 2003-02-24
Filing date: 2003-02-24
Publication date: 2007-02-21
Anticipated expiration: 2023-02-24
Also published as: JP2004260333A

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９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１０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９及び図１０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に厚さ０．１ｍｍ〜０．９ｍｍの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（ａ）と、第２に前記貼り合わせシート１５の中心部に小穴１２と該小穴１２を頂点とする略Ｖ字状の切り込み１１を設ける工程（ｂ）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（ｃ）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１１の縁部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（ｄ）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（ｅ）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（ｆ）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５０℃〜６０℃の乾燥温度で略１〜１０分間乾燥が行われて半乾燥する工程（ｇ）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１５を２次プレス加熱成形する工程（ｈ）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（ｉ）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（ｊ）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）上記（１）に記載のスピーカ用振動板３０の製造方法において、２次プレス加熱成形後の略ラッパ形状に成形された貼り合わせシート１５に離型剤４６を含ませて乾燥する工程（ｈ２）と、前記離型剤４６が含まされた貼り合わせシート１５を３次プレス加熱成形する工程（ｈ３）とを、貼り合わせシート１５に防湿剤１８を塗布する工程（ｉ）の前に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。
（３）上記（１）又は上記（２）に記載のスピーカ用振動板３０の製造方法において、熱硬化性樹脂１７が含まされた貼り合わせシート１５を半乾き状態になるまで半乾燥する工程（ｇ）の直後に、前記熱硬化性樹脂１７が半乾き状態の貼り合わせシート１５の重量測定を行い、規定値重量以下の貼り合わせシート１５を再度熱硬化性樹脂１７を含ませる工程（ｆ）に戻す重量適正化工程（ｇ１）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。
（４）上記（１）又は上記（２）に記載のスピーカ用振動板３０の製造方法において、２次プレス加熱成形する工程（ｈ）の直後に、２次プレス加熱成形後の貼り合わせシート１５の音波の伝搬速度測定を行い、規定値速度以下の貼り合わせシートを再度２次プレス加熱成形を行う工程（ｈ）に戻す伝搬速度適正化工程（ｈ１）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。
（５）上記（１）又は上記（２）又は上記（３）又は上記（４）に記載のスピーカ用振動板３０の製造方法において、少なくとも１次プレス加熱成形に使用されるプレス装置Ｐ１の下金型３２中心部に突起ピン３８を設けるとともに上金型３１中心部に前記突起ピン３８に嵌合する窪み３９を設け、プレス加熱成形時に貼り合わせシート１５の中心部に設けられた小穴１２を前記下金型３２中心部の突起ピン３８に挿入して位置決めした後にプレス加熱成形を行う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乃至第５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は本発明の第２及び第５の実施の形態の製造方法に係る付加された３次プレス加熱成形処理の工程を示す模式図である。図６は本発明の第４の実施の形態の製造方法に係る貼り合わせシートの音波の伝搬速度測定を行う計測装置を示す図である。図７は本発明の第５の実施の形態の製造方法に係る１次、２次プレスのためのプレス装置とプレス加熱成形工程を説明する図である。図８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。この略Ｖ字形状の切り込み１１の形状は完全なＶ字形状でなくともよく、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）になるような形状であればよい。
【００２６】
次に、幾つかのプレス成形工程等を経て最終的に図８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８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１１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１１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の第１の実施の形態の製造方法を図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１に係る第１の実施の形態のスピーカ用振動板３０の製造工程は、図１に示される破線で囲まれた工程を除くフローとなり、前述の予め素材準備段階で用意された木製シート１０を素材として（ａ）〜（ｊ）までの工程で構成され、（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、（ｄ）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】
上記各製造工程の詳細内容を以下順に説明する。
【００３４】
工程（ａ）・・・厚さ０．ｌｍｍ〜０．９ｍｍ（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。
【００３５】
工程（ｂ）・・・貼り合わせシート１５に対して、中心部に小穴１２とその小穴１２を頂点とする略Ｖ字状の切り込み１１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に設けられ、更には後述のプレス加熱成形時の位置合わせを簡単且つ正確に行うためのものであり、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。
【００３６】
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。
【００３７】
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。
【００３８】
工程（ｄ）・・・予め、セッティングの作業性の向上と成形性（しわや割れが少ない）を良好なものとするために貼り合わせシート１５の切り込み１１の両縁部１１ａ、１１ｂ同士を重ね合わせて図２の（ｄ）に示されるように略ラッパ形状になるように成形外領域（余白部分）をホッチキス（商標名）やクリップ等の掛止具２６で仮止め或いは前記成形外領域に互いに引っかける雄雌形状の掛止機構を設けることによって１次プレス加熱成形前に略ラッパ形状に掛止保持しておく。次に、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、下型３２に載置した前記潤滑剤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秒を好適とする。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。
【００３９】
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。
【００４０】
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。
【００４１】
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。
【００４２】
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秒を好適とする。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。
【００４３】
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、さらにシンナーを混合したものを用いる。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。
【００４４】
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。
【００４５】
上記完成した略ラッパ状のスピーカ用振動板３０は、製品検査を経て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。
【００４６】
上記第１の実施の形態のスピーカ用振動板３０の製造工程では、プレス加熱成形処理は１次、２次の２回であるが、より仕上がりの良い振動板として歩留まりの向上が図れる第２の実施の形態の製造方法として、上記２次プレス加熱成形工程（ｈ）における設定条件で、プレス時間のみを略２〜３０秒と短めの条件として、以下の工程（ｈ２）、（ｈ３）からなる３次プレス加熱成形処理を加えることも形状がより安定して仕上がりの良好な好ましい製造方法である。
【００４７】
工程（ｈ２）・・・工程（ｈ）の２次プレス加熱成形後の略ラッパ形状に成形された貼り合わせシート１５に離型剤４６を含ませて乾燥する。この離型剤４６には例えばシリコン（ケイ素）を用いる。
【００４８】
工程（ｈ３）・・・前記離型剤４６が含まされた貼り合わせシート１５をヒータ３３を備える上型３６と下型３７からなるプレス装置Ｐ３で３次プレス加熱成形する。ここで３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３６が略８０〜２００℃、下型３７が略１００〜２００℃、プレス時間が略２〜６０秒を好適とする。
【００４９】
次に、上記第１、第２の実施の形態のスピーカ用振動板３０の製造工程では貼り合わせシート１５に対する品質管理は製造工程中で特段明示されていないが、貼り合わせシート１５のひび・割れ等の外観不良物は当然に製造工程中に適宜振り落とされることを前提とする。この点、素材の木製シート１０が木材という自然物であることから貼り合わせシート１５には外観以外の個体差も不可避的に存在する。したがって、好ましくは製造工程中で貼り合わせシート１５に対するより細かな品質管理を行うことが一層望ましい製造方法と言える。また、完成後の製品検査段階で良品／不良品を選別するよりも製造工程中に品質検査して良品に至らない貼り合わせシートについては、可能であれば前の工程に戻って再処理する等して適正化を図って可及的に良品として救うことが歩留まりの向上にも資すると言える。そこで図１に示される製造工程フローにおいて、破線で囲まれた以下の工程を付加する製造方法が第３、第４の実施の形態として挙げられる。
【００５０】
本発明に係る第３の実施の形態のスピーカ用振動板３０の製造方法として、図１のスピーカ用振動板の製造工程フローにおいて、熱硬化性樹脂１７が含まされた貼り合わせシート１５を半乾き状態になるまで半乾燥する工程（ｇ）の直後に、前記熱硬化性樹脂１７が半乾き状態の貼り合わせシート１５の重量測定を行い、規定値重量以下の貼り合わせシートを再度熱硬化性樹脂１７を含ませる工程（ｆ）に戻してやり直す重量適正化工程（ｇ１）を設ける。
【００５１】
例えば、素材の木製シート１０の密度その他の特性によって熱硬化性樹脂１７の含浸の程度が適正な状態となっているか否かを重量評価で判定し、適正範囲であれば次の２次プレス加熱成形の工程（ｈ）へ進み、重すぎれば再生不可能としてこの時点で廃棄処分とし、軽すぎれば熱硬化性樹脂１７の含浸不足として上記工程（ｆ）へ戻るのである。
【００５２】
次に、本発明に係る第４の実施の形態のスピーカ用振動板３０の製造方法として、上記第１、第２の実施の形態の各製造方法において、２次プレス加熱成形する工程（ｈ）の直後に、２次プレス加熱成形後の貼り合わせシート１５の音波の伝搬速度測定を例えば、図６のようなＹＡＧレーザ（パルス駆動）４１により発生した超音波の挙動をプローブ４２及びプローブ４３を用いて計測し、変位計＆ＦＥＴ解析器４４よりそれらの時間遅れから伝搬速度を求める構成の伝搬速度計測装置４５によって行い、規定値速度以上のものは次の工程へ進み、規定値速度以下の貼り合わせシート１５は再度２次プレス加熱成形を行う工程（ｈ）に戻してやり直すという伝搬速度適正化工程（ｈ１）を設ける。
【００５３】
即ち、貼り合わせシート１５の個体差（密度等の違い）によって一律の２次プレス加熱成形による成形が不十分な場合も有り得るので、剛性に関係する音波の伝搬速度に多少のばらつきが生じ得る。そこで、伝搬速度評価をして規定値以下であれば、再度２次プレス加熱成形の工程（ｈ）を行うこととして伝搬速度の適正化を少なくとも１回は行うこととする。而してこの工程（ｈ１）の追加で品質（音響特性）の安定と歩留まりの向上が図れることとなるのである。
【００５４】
以上の貼り合わせシート１５の所定段階における重量適正化工程（ｇ１）或いは伝搬速度適正化工程（ｈ１）又はその双方を付加することで歩留まりの向上が達成され、木製のスピーカ用振動板３０の品質の安定も達成されることとなる。
【００５５】
次に、本発明に係る第５の実施の形態のスピーカ用振動板３０の製造方法として、前記各製造方法における１次〜３次のプレス加熱成形工程の内、図７に示されるように、少なくとも１次プレス加熱成形工程（ｄ）に使用されるプレス装置Ｐ１の下金型３２中心部に突起ピン３８を設けるとともに上金型３１中心部に前記突起ピン３８に嵌合する窪み３９を設け、プレス加熱成形時に貼り合わせシート１５の中心部に設けられた前記小穴１２を前記下金型３２中心部の突起ピン３８に挿入して位置決めした後にプレス加熱成形を行うようにする。而して当該プレス加熱成形の作業性、貼り合わせシート１５の成形の位置精度が高まることで量産効率と歩留まりの向上が図れることになる。勿論、１次プレス加熱成形工程（ｄ）のみならず２次プレス加熱成形工程（ｈ）のプレス装置Ｐ２や図５の（ｈ３）に示されるように３次プレス加熱成形工程のプレス装置Ｐ３にも同様の突起ピン３８と窪み３９を設けて位置合わせを正確且つ迅速に行うようにすることも好ましい。付言すれば、２次、３次プレス加熱成形工程の段階では、前の１次プレス加熱成形工程である程度形状が所定のラッパ形状に安定しているのでさほど問題ではないが、最初の１次プレス加熱成形工程（ｄ）では、貼り合わせシート１５の形状がプレス前で不安定なために上記小穴１２による位置合わせが特に有効となるのである。
【００５６】
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。
【００５７】
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。
【００５８】
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。
【００５９】
【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。
【００６０】
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。
【００６１】
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。
【００６２】
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。
【００６３】
プレス加熱成形工程において位置合わせが容易且つ正確にできるため、プレス機へのセッティングの作業性が向上し、仕上がりの良い振動板が実現できる。
【００６４】
重量適正化工程や伝搬速度適正化工程によって、歩留まりが向上するとともに安定した品質の木製振動板の安価供給が実現できる。
【００６５】
本スピーカ用振動板をダイナミック・スピーカ・ユニットに採用することで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得られる。
【００６６】
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乃至第５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】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】本発明の第２及び第５の実施の形態の製造方法に係る付加された３次プレス加熱成形処理の工程を示す模式図である。
【図６】本発明の第４の実施の形態の製造方法に係る貼り合わせシートの音波の伝搬速度測定を行う計測装置を示す図である。
【図７】本発明の第５の実施の形態の製造方法に係る１次、２次プレスのためのプレス装置とプレス加熱成形工程を説明する図である。
【図８】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９】従来の木製振動板の製造手順を示す図である。
【図１０】従来の木製振動板の製造手順を示す図である。
【図１１】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
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中心孔
２６掛止具
３０スピーカ用振動板
３１、３４、３６上型
３３ヒータ
３２、３５、３７下型
３８突起ピン
３９窪み
４１ＹＡＧレーザ（パルス駆動）
４２、４３プローブ
４４変位計＆ＦＥＴ解析器
４５伝搬速度計測装置
４６離型剤
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 method of manufacturing a wooden 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 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]
[Patent Document 2] includes (a) an arc-shaped cutout portion 1a in the center from one piece of wood thin plate 4 as in the manufacturing procedure shown in FIGS. 9 (a) and 9 (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]
Further, as in the manufacturing procedure shown in FIGS. 10A and 10B, a plurality of small pieces of wood 2a, 2b,..., 2L are bonded together with an adhesive to form a substantially trumpet shape as shown in FIG. 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 key point in the manufacture of wooden speaker diaphragms is how to cope with the property that wood is easily broken in molding and how to deal with secular change.
[0015]
In this respect, [Patent Document 1] is a flat plate diaphragm made of wood, and although the characteristics and advantages of being a wood are shown, the moldability when forming into a substantially trumpet shape (cone shape). Technical data on the problem is not provided because it is flat.
[0016]
Further, in the manufacturing method as shown in FIGS. 9 and 10 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]
In addition, the manufacturing method in which a plurality of ultra-thin wood sheets of [Patent Document 3] are laminated and press-molded 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. Therefore, 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. Although the speaker diaphragm manufacturing method in which press-molding is performed after impregnation has superiority in the manufacturing process for mass production as compared with the above [Patent Document 1] to [Patent Document 4], it is still sufficient for mass production. It is difficult to say that the establishment of the molding process has been achieved, and it is desired to further improve the yield of moldability and to achieve a beautifully finished wooden diaphragm toward the practical use of the wooden diaphragm.
[0021]
The present invention has been made in view of the above circumstances, and provides a method for manufacturing a wooden speaker diaphragm that is effective in improving the acoustic characteristics of a dynamic speaker and is suitable for mass production.
[0022]
[Means for Solving the Problems]
In order to solve the above problems, the present invention
(1) In a method for manufacturing a speaker diaphragm including a step of press-molding a single wooden sheet into a substantially trumpet shape, first, a single wooden sheet 10 having a thickness of 0.1 mm to 0.9 mm A step (a) of creating a laminated sheet 15 by sticking a thin nonwoven fabric or Japanese paper 13 on one side, and secondly, a small hole 12 at the center of the laminated sheet 15 and an approximate V having the small hole 12 as a vertex. A step (b) of providing a character-shaped cut 11; and third, a lubricant 16 having an action of softening the bonded sheet 15 provided with the cut 11 by applying moisture to the bonded sheet 15 and retaining the moisture in the bonded sheet 15. And (4) the step of including the lubricant, and fourthly, the laminated sheet 15 containing the lubricant 16 is subjected to primary press thermoforming to form a substantially trumpet shape in which the edges of the cuts 11 are overlapped with each other. A step (d) of forming, a step (e) of drying the bonded sheet 15 that has been temporarily formed, and a step of including the thermosetting resin 17 in the bonded sheet 15 after being dried. (F) and seventhly, the laminated sheet 15 containing the thermosetting resin 17 is dried at a drying temperature of 50 ° C. to 60 ° C. for about 1 to 10 minutes until it is in a semi-dry state. A step (g) of drying, a step (h) of eighthly pressing the laminated sheet 15 in which the thermosetting resin 17 is in a semi-dried state, and a ninth step after the second press thermoforming of the secondary press. Step (i) of applying the moisture-proofing agent 18 to the bonded sheet 15, and tenth vibration of the laminated sheet 15 coated with the moisture-proofing agent 18 by removing the central hole 25 for the voice coil and removing the outer shape. Process of forming into a predetermined size and shape as a plate And j), to provide a method for manufacturing a speaker diaphragm 30, characterized in that a.
(2) In the method for manufacturing the speaker diaphragm 30 described in (1) above, the step of drying by including the release agent 46 in the bonding sheet 15 formed into a substantially trumpet shape after the secondary press thermoforming. (H2) and the step (h3) of press-molding the laminated sheet 15 containing the release agent 46 in the third press before the step (i) of applying the moisture-proofing agent 18 to the laminated sheet 15 A method for manufacturing the speaker diaphragm 30 is provided.
(3) In the method for manufacturing the speaker diaphragm 30 described in (1) or (2) above, the step of semi-drying the laminated sheet 15 containing the thermosetting resin 17 until it is in a semi-dry state ( Immediately after g), the weight of the laminated sheet 15 in which the thermosetting resin 17 is in a semi-dry state is measured, and the laminated sheet 15 having a weight equal to or less than the specified weight is included in the thermosetting resin 17 again (f). A method of manufacturing the speaker diaphragm 30 is provided, which is provided with a weight optimization step (g1) for returning to the above.
(4) In the method for manufacturing the speaker diaphragm 30 according to (1) or (2) above, the bonded sheet 15 after the secondary press thermoforming is performed immediately after the step (h) of secondary press thermoforming. For a speaker, characterized in that there is provided a propagation speed optimization step (h1) for measuring the propagation speed of the sound wave and returning the bonded sheet having a specified speed or less to the step (h) of performing secondary press thermoforming again. A method for manufacturing the diaphragm 30 is provided.
(5) In the method for manufacturing the speaker diaphragm 30 according to (1), (2), (3), or (4) above, at least under the press device P1 used for primary press thermoforming A protrusion pin 38 is provided at the center of the mold 32 and a recess 39 is provided at the center of the upper mold 31 to be fitted to the protrusion pin 38, and a small hole 12 provided at the center of the bonded sheet 15 is formed during press heat molding. A method of manufacturing the speaker diaphragm 30 is provided, which is press-molded after being inserted into the protruding pin 38 at the center of the lower mold 32 and positioned.
[0023]
DETAILED DESCRIPTION OF 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 flowchart of a manufacturing process of speaker diaphragms according to first to fifth embodiments of the present invention. 2 and 3 are schematic views showing the first half and the second half of each processing state of the manufacturing process. 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 showing the steps of the added third press thermoforming process according to the manufacturing methods of the second and fifth embodiments of the present invention. FIG. 6 is a view showing a measuring apparatus for measuring the propagation velocity of sound waves of a bonded sheet according to the manufacturing method of the fourth embodiment of the present invention. FIG. 7 is a view for explaining a press apparatus for primary and secondary presses and a press thermoforming process according to the manufacturing method of the fifth embodiment of the present invention. FIG. 8 is a schematic view of a speaker diaphragm of a substantially trumpet shaped dynamic cone speaker according to the present invention.
[0024]
First, in FIG. 4, the wood that is the material of the speaker diaphragm 30 of the present invention is cut out from a wood log 6 by a rotary method as shown in FIG. Then, it is peeled thinly from the circumferential direction and cut into a suitable shape larger than the molded part (inside the broken-line circular part) that actually becomes the diaphragm as shown in FIG. For example, a dynamic cone speaker diaphragm having a diameter of about 8 cm is a square having a side of about 12 to 14 cm or a rectangle or a circle having a diameter of about 12 cm.
[0025]
Next, entering the manufacturing stage, the wooden sheet 10 becomes a laminated sheet 15 through the bonding process of the nonwoven fabric or Japanese paper 13 of FIG. 2 (a), as shown in FIG. 2 (b). A substantially V-shaped cut 11 is provided. The shape of the substantially V-shaped notch 11 does not have to be a complete V-shape. In short, it may be any shape as long as the two edges are overlapped with no gap so that the whole becomes a substantially trumpet shape (cone shape).
[0026]
Next, after a number of press molding processes and the like, the speaker diaphragm 30 of the dynamic cone speaker having a substantially trumpet shape as shown in the schematic diagram of FIG. 8 is finally obtained (cross-sectional view of FIG. 3J). See also).
[0027]
The wood grain of the speaker diaphragm 30 shown in FIG. 8 is only in the da direction along the grain direction when viewed in the radial direction (for example, the da to dh directions) from the center hole 25 cut out for the voice coil. However, 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.
[0028]
In addition, the speaker diaphragm 30 has excellent acoustic characteristics based on being made of wood and a beautiful finish of the wood, and the selected lubricant, thermosetting resin, impregnation with a moisture-proofing agent, and a series of press heating molding processes. By contrivance and the like, there are no wrinkles or cracks, the change with time due to humidity is small, and the life is long. 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.
[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 (longitudinal direction) of various kinds of wood in FIG. As shown in [Table 1] below, which shows the density, Young's modulus, sound velocity, and internal loss factor (tan δ) of the various woods, the plywood is roughly (G point, H point, I point, J point). It can be seen that the wood (solid material) except it can be an excellent material having an appropriate internal loss factor and high sound propagation speed. In particular, it is found that hip (point A) and beech (point C) are optimal.
[0030]
[Table 1]

In addition, A point in FIG. 11 is a hippopotamus (solid wood), hereafter, 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.
[0031]
Next, the manufacturing method of the speaker diaphragm 30 according to the first embodiment will be described with reference to FIGS. 1 (a) to (j) and FIGS. 2 and 3 corresponding to (a) to (j). It demonstrates according to the schematic diagram until.
[0032]
First, the manufacturing process of the speaker diaphragm 30 according to the first embodiment of the present invention is a flow excluding the process surrounded by a broken line shown in FIG. 1 and prepared in advance in the material preparation stage described above. Constructed from the steps (a) to (j) using the wooden sheet 10 as a raw material, (a) creation of a laminated sheet, (b) formation of a V-shaped cut, (c) lubricant impregnation, (d) temporary molding (E) drying, (f) thermosetting resin impregnation, (g) semi-drying, (h) secondary pressing, (i) application of moisture-proofing agent, (j) center hole and outer shape removal. This completes the speaker diaphragm.
[0033]
The detailed contents of each manufacturing process will be described in the following order.
[0034]
Step (a): Thickness 0. A non-woven fabric or Japanese paper 13 having a thickness of about 0.02 to 0.30 mm is bonded to one surface side of a wooden sheet 10 of 1 mm to 0.9 mm (preferably about 0.3 mm) with an adhesive to create a bonded sheet 15. . 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.
[0035]
Step (b)... With respect to the bonded sheet 15, a small hole 12 and a substantially V-shaped cut 11 having the small hole 12 as a vertex are provided at the center. The cuts 11 are provided substantially along the grain direction (arrow f) of the bonded sheet 15. The small hole 12 is provided to prevent cracking of the center portion when being formed into a substantially trumpet shape, and is used for easy and accurate alignment during press heating forming described later, and has a diameter of There are no restrictions on the shape of a circle, ellipse, hexagon, etc. of several millimeters.
[0036]
Step (c): In the liquid of the lubricant 16 that has the function of permeating into the bonding sheet 15 to give moisture and holding moisture so that the V-cut laminated sheet 15 is softened. Soak for 5-60 minutes and fully impregnate.
[0037]
This is in order to prevent the cracking in the subsequent primary press heat forming and to perform temporary forming with a high yield. According to the study of the present inventors, the lubricant 16 is not simply water or an alkaline aqueous solution, but an aqueous solution in which saccharides are dissolved.
[0038]
Step (d): In order to improve the setting workability and formability (less wrinkles and cracks) in advance, the

edges

11a and 11b of the cut 11 of the laminated sheet 15 are overlapped with each other. At the same time, as shown in FIG. 2 (d), the molded outer region (margin) is temporarily fixed with a latch 26 such as a stapler (trademark) or a clip so as to have a substantially trumpet shape. By providing a male-female latching mechanism that hooks each other, it is latched and held in a substantially trumpet shape prior to primary press heat forming. Next, the lubricant 16 placed on the lower die 32 is impregnated and held in a substantially trumpet shape by the latching tool 26 by a press device P1 having a die configuration of an upper die 31 and a lower die 32 each having a heater 33. The bonded sheet 15 is subjected to primary press heat molding (temporary molding). 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 to 2. 60 seconds is preferred. In addition, after primary press thermoforming, both

edge parts

11a and 11b are stuck so that it may not leave | separate in a natural state, and a substantially trumpet shape is maintained.
[0039]
Step (e): Complete drying is carried out in a drying furnace (50-60 ° C.) for about 10-30 minutes.
[0040]
Step (f): The laminated sheet 15 after drying is immersed in the thermosetting resin 17 liquid for approximately 30 minutes to 180 minutes and sufficiently impregnated. As the thermosetting resin 17, a phenol resin is suitable.
[0041]
Step (g): Immediately after impregnation with the thermosetting resin 17, if the secondary press in the subsequent step is carried out, the thermosetting resin 17 is stuck to the mold, and cracks occur when the laminated sheet 15 is peeled off after pressing. As a result, tearing occurs and the yield decreases extremely. On the other hand, when it is completely dried, the moldability deteriorates and it becomes easy to crack. In order to prevent this, the thermosetting resin 17 is placed in a drying oven (50 ° C. to 60 ° C.) for approximately 1 to 10 minutes in a semi-dried state (so-called “finger-dried state” that is not sticky to the touch) ).
[0042]
Step (h): The laminated sheet 15 in which the impregnated thermosetting resin 17 is semi-dried is press-heated again by the 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. It should be noted that the

edges

11a and 11b (shaded areas) of the cuts 11 that are overlapped and stuck at this point are in close contact with each other so that the level difference is hardly discernable, and there is almost no influence on the acoustic characteristics. It has become.
[0043]
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 jab immersion. As the moisture-proof agent 18, for example, a mixture of polyisocyanate and polyester polyol and further thinner is used. The applied moisture-proofing agent 18 is naturally dried or completely dried in a drying furnace.
[0044]
Step (j)... The voice coil center hole 25 and the outer shape of the laminated sheet 15 after press thermoforming that has been subjected to moisture-proofing are cut out into a predetermined diaphragm shape, and the speaker diaphragm 30 is formed. Complete.
[0045]
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 after a product inspection in the same manner as a conventional dynamic speaker.
[0046]
In the manufacturing process of the speaker diaphragm 30 according to the first embodiment, the press thermoforming process is performed twice for the primary and secondary times. However, the second process can improve the yield as a diaphragm having a better finish. The manufacturing method of the embodiment includes the following steps (h2) and (h3) under the setting conditions in the secondary press thermoforming step (h), with only the press time being as short as about 2 to 30 seconds. Adding a third press thermoforming treatment is also a preferable production method with a more stable shape and good finish.
[0047]
Step (h2)... A release agent 46 is included in the bonded sheet 15 formed into a substantially trumpet shape after the secondary press heat forming in the step (h) and dried. For example, silicon is used for the release agent 46.
[0048]
Step (h3): The laminated sheet 15 containing the release agent 46 is subjected to tertiary press thermoforming with a press device P3 including an upper die 36 and a lower die 37 provided with a heater 33. Here, the setting conditions of the third press thermoforming are as follows: the press pressure is about 20 to 40 kg, the mold temperature is about 80 to 200 ° C. for the upper die 36, the lower die 37 is about 100 to 200 ° C., and the press time is about 2 to 2. 60 seconds is preferred.
[0049]
Next, in the manufacturing process of the speaker diaphragm 30 according to the first and second embodiments, quality control for the bonded sheet 15 is not clearly specified in the manufacturing process, but the bonded sheet 15 is cracked or cracked. It is assumed that a defective appearance such as the above is naturally shaken off during the manufacturing process. In this respect, the laminated sheet 15 inevitably has individual differences other than the appearance because the material wooden sheet 10 is a natural object called wood. Therefore, it can be said that it is a more desirable manufacturing method to perform finer quality control on the laminated sheet 15 preferably during the manufacturing process. Rather than selecting good / defective products at the product inspection stage after completion, for bonded sheets that do not result in quality inspection during the manufacturing process, return to the previous process and reprocess if possible. Therefore, it can be said that the optimization and the saving as good as possible contributes to the improvement of the yield. Therefore, in the manufacturing process flow shown in FIG. 1, a manufacturing method for adding the following processes surrounded by a broken line is given as the third and fourth embodiments.
[0050]
As a method of manufacturing the speaker diaphragm 30 according to the third embodiment of the present invention, the laminated sheet 15 including the thermosetting resin 17 is semi-dried in the manufacturing process flow of the speaker diaphragm of FIG. Immediately after the step (g) of semi-drying until it reaches a state, the thermosetting resin 17 measures the weight of the laminated sheet 15 in a semi-dried state, and the laminated sheet having a weight equal to or less than a specified value is again measured. A weight optimizing step (g1) is provided by returning to step (f) including 17 and starting over.
[0051]
For example, it is determined by weight evaluation whether or not the degree of impregnation of the thermosetting resin 17 is in an appropriate state according to the density and other characteristics of the wooden sheet 10 of the raw material. The process proceeds to the molding step (h), and if it is too heavy, it cannot be regenerated and discarded at this point. If it is too light, the impregnation with the thermosetting resin 17 is insufficient and the process returns to the above step (f).
[0052]
Next, as a method of manufacturing the speaker diaphragm 30 according to the fourth embodiment of the present invention, in the manufacturing methods of the first and second embodiments described above, the step (h) of secondary press thermoforming Immediately after, the propagation speed measurement of the sound wave of the laminated sheet 15 after the secondary press thermoforming is carried out, for example, the behavior of the ultrasonic wave generated by the YAG laser (pulse drive) 41 as shown in FIG. The measurement is performed by the propagation velocity measuring device 45 configured to obtain the propagation velocity from the time delay from the displacement meter & FET analyzer 44. If the velocity exceeds the specified value velocity, the process proceeds to the next step, and the velocity below the specified value velocity is pasted. The laminated sheet 15 is provided with a propagation speed optimizing step (h1) in which it is returned to the step (h) in which the secondary press thermoforming is performed again.
[0053]
That is, there may be cases where the uniform secondary press thermoforming is insufficient due to individual differences (differences in density or the like) of the laminated sheet 15, and thus there may be some variation in the propagation speed of sound waves related to rigidity. Therefore, if the propagation velocity is evaluated and the value is not more than the specified value, the propagation velocity is optimized at least once by performing the secondary press thermoforming step (h) again. Thus, by adding this step (h1), the quality (acoustic characteristics) can be stabilized and the yield can be improved.
[0054]
The yield improvement is achieved by adding the weight optimizing step (g1) and / or the propagation speed optimizing step (h1) at the predetermined stage of the bonded sheet 15, and the quality of the wooden speaker diaphragm 30 is improved. This also achieves stability.
[0055]
Next, as a manufacturing method of the speaker diaphragm 30 according to the fifth embodiment of the present invention, as shown in FIG. 7 among the primary to tertiary press thermoforming steps in each manufacturing method, A projection pin 38 is provided at the center of the lower mold 32 of the press device P1 used in at least the primary press thermoforming step (d), and a recess 39 is provided at the center of the upper mold 31 to fit the projection pin 38. The press hole forming is performed after the small hole 12 provided in the center portion of the laminated sheet 15 is inserted into the projecting pin 38 in the center portion of the lower mold 32 and positioned at the time of press heat forming. Thus, the workability of the press heat forming and the positional accuracy of forming the bonded sheet 15 are improved, so that the mass production efficiency and the yield can be improved. Of course, not only in the primary press thermoforming step (d) but also in the press device P2 in the secondary press thermoforming step (h) or in the press device P3 in the tertiary press thermoforming step as shown in (h3) of FIG. It is also preferable to provide the same projection pin 38 and recess 39 so that the alignment can be performed accurately and quickly. In addition, at the stage of the secondary and tertiary press thermoforming process, the shape is stable to some extent in the previous primary press thermoforming process, so there is no problem, but the first primary press In the thermoforming step (d), the alignment by the small holes 12 is particularly effective because the shape of the bonded sheet 15 is unstable before pressing.
[0056]
According to the present inventors' research, the speaker diaphragm 30 manufactured by the above manufacturing method has a longitudinal propagation velocity of 4.5 to 6.0 km / second and a lateral propagation velocity of 2.0 to 4. The vibration plate manufactured by the manufacturing method according to each of the above embodiments by selecting wood in the range of 5 km / second clearly has a resolution of reproduced sound as compared with a conventional paper pulp diaphragm or aluminum diaphragm. It has been found that improvement and improvement in crisp sound can be obtained.
[0057]
The remarkable improvement in acoustic characteristics is particularly noticeable when the longitudinal propagation velocity is 4.5 to 6.0 km / sec and the lateral propagation velocity is 2.0 to 2.5 km / sec. This is the case where wood in the range of 0.02 to 0.03 is selected and used for the diaphragm, and specifically, the cover material (solid) is the best.
[0058]
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.
[0059]
【The invention's effect】
As described above, the speaker diaphragm manufacturing method according to the present invention uses a single piece of wood as a raw material, and digests with chemicals or beats wood fibers that exist in the process of manufacturing a conventional paper pulp diaphragm. Since no processing is applied, it is possible to make a diaphragm that does not cause deterioration in sound quality.
[0060]
Since a boil treatment, a physical treatment, and a chemical agent are not applied for softening like a conventional wooden diaphragm, a diaphragm that does not cause deterioration in sound quality can be produced.
[0061]
Occurrence of wrinkles and cracks during press thermoforming is prevented, and a uniform press thermoformed product having a good finish with little change over time such as deformation and cracking after production can be obtained.
[0062]
Light and durable cone diaphragms can be manufactured, and diaphragms can be manufactured for all bands from woofers to full-range speakers.
[0063]
Since positioning can be performed easily and accurately in the press thermoforming process, the workability of setting in the press machine is improved, and a diaphragm with good finish can be realized.
[0064]
Through the weight optimization process and the propagation speed optimization process, the yield can be improved and the cheap supply of a stable quality wooden diaphragm can be realized.
[0065]
By adopting this diaphragm for a speaker in a dynamic speaker unit, a re-voiced sound approaching the raw sound due to natural vibration because it is made of wood can be obtained.
[0066]
Furthermore, the natural wood grain appears on the surface, so it has a high-quality appearance.
[Brief description of the drawings]
FIG. 1 is a flowchart of manufacturing steps of speaker diaphragms according to first to fifth 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 showing the steps of an added third press thermoforming process according to the manufacturing methods of the second and fifth embodiments of the present invention.
FIG. 6 is a view showing a measuring apparatus for measuring the propagation velocity of sound waves of a bonded sheet according to the manufacturing method of the fourth embodiment of the present invention.
FIGS. 7A and 7B are diagrams illustrating a press device for primary and secondary presses and a press thermoforming process according to the manufacturing method of the fifth embodiment of the present invention. FIGS.
FIG. 8 is a schematic view of a speaker diaphragm of a substantially trumpet-shaped dynamic cone speaker according to the present invention.
FIG. 9 is a diagram showing a manufacturing procedure of a conventional wooden diaphragm.
FIG. 10 is a diagram showing a manufacturing procedure of a conventional wooden diaphragm.
FIG. 11 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 as conventional materials.
[Explanation of symbols]
6 Log 7 Cutting blade 10 Wooden sheet 11 V-shaped

cuts

11a and 11b Both edges 12 Small holes 13 Non-woven fabric or Japanese paper 15 Laminate sheet 16 Lubricant 17 which acts to give moisture and retain moisture 17 Thermosetting Resin 18 Moisture-proofing agent 25 Center hole 26 Stopper 30

Speaker diaphragm

31, 34, 36 Upper mold 33

Heater

32, 35, 37 Lower mold 38 Projection pin 39 Recess 41 YAG laser (pulse drive)
42, 43 Probe 44 Displacement meter & FET analyzer 45 Propagation velocity measuring device 46 Release agent P1, P2 Press device

Claims

In the manufacturing method of the speaker diaphragm including the step of press-molding a single wooden sheet into a substantially trumpet shape,
First, a process of creating a laminated sheet by attaching a thin non-woven fabric or Japanese paper to one side of a single wooden sheet having a thickness of 0.1 mm to 0.9 mm; and second, a center part of the laminated sheet A step of providing a small hole and a substantially V-shaped cut having the small hole as a vertex, and a third function of imparting moisture to the laminated sheet provided with the cut and softening and retaining moisture in the laminated sheet A step of including the lubricant having, and a step of temporarily forming the laminated sheet including the lubricant into a substantially trumpet shape in which the edges of the cuts are overlapped with each other by first press-molding. Fifth, the step of drying the bonded sheet that has been temporarily formed, sixth the step of including a thermosetting resin in the bonded sheet after drying, and seventh, the thermosetting resin is included. The pasting A step of semi-drying is carried out dry approximately 1 to 10 minutes at a drying temperature of 50 ° C. to 60 ° C. until a sheet in a semi-dry state was, the thermosetting resin in the eighth bonding sheet semidry state A second press thermoforming step, a ninth step of applying a moisture-proof agent to the bonded sheet after the second press-heat forming step, and a tenth step with respect to the bonded sheet coated with the dehumidifying agent. A method of manufacturing a speaker diaphragm, comprising: a step of punching a center hole for a coil and a step of forming an outer shape to form a predetermined size shape as a diaphragm.

The method for manufacturing a speaker diaphragm according to claim 1, wherein a step of including a release agent in a bonding sheet formed into a substantially trumpet shape after secondary press thermoforming and drying, and the release agent A method for manufacturing a speaker diaphragm, comprising: a step of subjecting an included laminated sheet to a third press thermoforming, and a step of applying a moisture-proofing agent to the laminated sheet.

The method for manufacturing a speaker diaphragm according to claim 1 or 2, wherein the thermosetting resin is immediately after the step of semi-drying the laminated sheet containing the thermosetting resin until it is in a semi-dry state. The speaker diaphragm is characterized in that a weight optimizing step is provided for measuring the weight of the laminated sheet in a semi-dry state and returning the laminated sheet having a weight equal to or less than the specified weight to the step of including the thermosetting resin again. Manufacturing method.

3. The method for manufacturing a speaker diaphragm according to claim 1 or 2, wherein immediately after the step of secondary press thermoforming, the propagation velocity of the sound wave of the bonded sheet after the secondary press thermoforming is measured and specified. A method for manufacturing a speaker diaphragm, comprising a step of optimizing a propagation speed for returning a bonded sheet having a value speed or less to a step of performing secondary press thermoforming again.

5. The method for manufacturing a speaker diaphragm according to claim 1, or claim 2, or claim 3 or claim 4, wherein a protruding pin is provided at the center of a lower die of a press device used for at least primary press thermoforming. And a recess that fits into the projection pin at the center of the upper mold, and after positioning by inserting a small hole provided in the center of the laminated sheet into the projection pin at the center of the lower mold during press thermoforming A method for manufacturing a speaker diaphragm, comprising performing press thermoforming.