JP3748130B2

JP3748130B2 - Optical element molding method

Info

Publication number: JP3748130B2
Application number: JP19725796A
Authority: JP
Inventors: 典弘山田; 征史五十川
Original assignee: Olympus Corp
Current assignee: Olympus Corp
Priority date: 1996-07-26
Filing date: 1996-07-26
Publication date: 2006-02-22
Anticipated expiration: 2016-07-26
Also published as: JPH1036131A

Description

【０００１】
【発明の属する技術分野】
本発明は、加熱炉によって加熱軟化した成形材料であるガラス素材を成形型によって押圧して所望の光学素子に成形する光学素子の成形方法に関する。
【０００２】
【従来の技術】
一般に、ガラス素材を成形可能な状態に加熱する際、加熱手段として電気炉等の加熱炉が用いられている。
このような加熱炉の例として、特開昭６２−１８２１２０号公報に記載されたものを図１及び図２に基づいて説明する。
【０００３】
図１は加熱炉の側断面図、図２は加熱炉の正面図であり、図１及び図２において、加熱炉１００は、円筒形状であるとともに発熱体であるヒーターとして抵抗線１０１を埋設した伝熱部材１０２と、伝熱部材１０２の内周面に設けられた石英ガラス１０３と、石英ガラス１０３の外側端面および伝熱部材１０２の外周を一体的に被覆する金属カバー１０４と、から構成されており、ボルト１０５によってベース１０６に固定された支持台１０７の上に、断熱材１０８を介して載せられている。
【０００４】
上記構成からなる加熱炉１００によると、抵抗線１０１に通電することで加熱を開始し、加熱炉１００内の温度が設定した温度で安定したら、図示省略した保持部材に図示省略したガラス素材を載置し、図示省略した搬送装置によって保持部材とともにガラス素材を加熱炉１００に搬送するとともに加熱炉１００内の一時待機位置（図１において、加熱炉１００内部のほぼ中央）にて所定時間停止し、ガラス素材を加熱軟化する。
【０００５】
加熱軟化されたガラス素材は、成形室（図示省略）に搬送され、所望の光学素子の形状を反転した成形面を有する一対の成形型（図示省略）によって押圧され、所望の光学素子の形状に成形される。
ここで、成形型による成形の際、ガラス素材を精度良く光学素子に成形するためには、ガラス素材が加熱炉１００による加熱軟化によって適切な粘度である最適粘度とになっている必要がある。
【０００６】
一般的には、加熱炉１００におけるガラス素材の粘度を直接測定して最適粘度であるか否かを判断しているのではなく、ガラス素材の粘度と温度には相関関係があるため、温度検出手段である熱電対（図示省略）を加熱炉１００内部におけるガラス素材の一時待機位置付近に備え、この熱電対（図示省略）を用いて測定した加熱炉１００の温度、正確には熱電対を接続している温度制御器（図示省略）の温度表示部（図示省略）に示された表示温度を基に、加熱軟化しているガラス素材が最適粘度となっているか否かを判断するとともに、表示温度が最適粘度に相当する温度となるよう、抵抗線の電流や電圧を調整している。
【０００７】
【発明が解決しようとする課題】
しかしながら、加熱炉１００を連続して長期間使用することで熱電対が劣化すると、加熱炉１００の設定温度が実際には変化していないにもかかわらず、加熱炉内１００の温度が変化していると誤動作する場合があり、誤った測定結果を基に加熱炉１００の温度を調整してしまい、ガラス素材の粘度を最適粘度に調整することが困難な場合があった。
【０００８】
また、加熱炉１００を連続して長期間使用することで加熱炉１００の抵抗線１０１が劣化すると、抵抗線１０１から発せられる伝導熱と輻射熱とのバランスが変化してガラス素材の昇温過程に変化を生じるため、加熱炉１００によってガラス素材の粘度を最適粘度に調整することが困難な場合があった。
また、光学素子の成形を連続して長期間行うことで、温度や湿度といった、加熱炉１００を含む成形装置周辺の雰囲気条件が変化してガラス素材の昇温過程に変化を生じるため、ガラス素材の粘度を最適粘度に調整することが困難な場合があった。
【０００９】
また、一定期間稼働して分解整備した加熱炉１００や、全て同一構成である他の加熱炉１００にて同一のガラス素材を加熱軟化する際、分解整備後の組み付け時や、加熱炉１００を製造する段階での抵抗線１０１の取り付け位置の僅かな差異により、ガラス素材と抵抗線１０１との距離及び抵抗線１０１と熱電対との距離が異なってしまうことがあり、このような場合、分解整備前後で、あるいは、加熱炉１００毎でガラス素材や熱電対に達する伝導熱と輻射熱とのバランスが異なるので、結果的に加熱されるガラス素材自体の昇温過程に差異を生じ、ガラスを最適粘度に加熱軟化することができない場合があった。
【００１０】
また、ガラス素材を保持する保持部材のガラス素材に近接する位置に設けた孔に熱電対の先端を挿入したり、ガラス素材自身に孔を設けてこの孔に熱電対の先端を挿入することで、測定された温度に応じて加熱炉１００内部の温度を調整する方法もあるが、保持部材やガラス素材に設けた上記各孔に対する熱電対の先端の密接面積が測定毎に異なり、常に同一の条件で正確に温度を測定するのが困難であるとともに、特に、ガラス素材自身に開けた孔に熱電対を挿入する場合、熱電対がガラスに密着して使用不能となることも考えられ、現実的でない。
【００１１】
請求項１乃至請求項３の発明は、熱電対の劣化による温度測定の不確実性、抵抗線の劣化、雰囲気条件の変化、加熱炉の分解整備後の組み付け及び加熱炉の固体差（加熱炉毎のバラツキ）に基づく昇温過程の変化や差異等、加熱炉の環境に影響されることなくガラス素材を最適粘度に加熱軟化し、高精度な光学素子を歩留まり良く安定して製造することのできる光学素子の成形方法を提供することを目的とする。
【００１２】
【課題を解決するための手段】
請求項１の発明は、加熱炉によりガラス素材を成形可能な状態に加熱軟化した後に成形型によってガラス素材を押圧成形して光学素子を得る光学素子の成形方法において、加熱炉によって加熱軟化した後に測定したガラス素材の変形量が、加熱軟化したガラス素材を成形型にて光学素子に成形する際に最適な粘度に相当する変形量となるよう、加熱炉の温度を調整することを特徴とする。
【００１３】
請求項２の発明は、加熱炉によりガラス素材を成形可能な状態に加熱軟化した後に成形型によってガラス素材を押圧成形して光学素子を得る光学素子の成形方法において、加熱炉によって加熱軟化した後に測定したガラス素材の変形量が、加熱軟化したガラス素材を成形型にて光学素子に成形する際に最適な粘度（最適粘度）に相当する変形量となるよう加熱炉の温度を調整する際に、加熱炉の温度の調整量である炉温変更量と、炉温変更量に基づいて温度を調整した加熱炉によって加熱軟化されたガラス素材の変形量との相関関係を示す表を基準に加熱炉の温度を調整することを特徴とする。
【００１４】
請求項３の発明は、加熱炉によりガラス素材を成形可能な状態に加熱軟化した後に成形型によってガラス素材を押圧成形して光学素子を得る光学素子の成形方法において、ガラス素材の粘度が、成形型による押圧成形によって光学素子を得るのに最適な粘度（最適粘度）となる加熱炉の温度を中心とし、中心とした温度から上下に一定の範囲内で、かつ、一定の温度差で複数個の温度条件を設定し、各温度条件について個々にガラス素材を加熱軟化してその変形量を測定し、上記中心とした温度から上記各温度条件の値を差し引いた値を炉温変更量とし、上記各温度条件に対応する各炉温変更量と加熱炉によって加熱軟化されるガラス素材の変形量との相関関係を示す表を作成し、加熱炉にて加熱軟化されたガラス素材の変形量が、上記最適粘度に相当する変形量に一致するよう、上記表を基準にして加熱炉の温度を調整すること、を特徴とする。
（作用）
請求項１の発明は、加熱炉によって加熱軟化されて自重変形したガラス素材の変形量を成形型による成形前に測定することで加熱軟化によるガラス素材の粘度を検査し、ガラス素材の粘度が成形型による押圧成形で所望の光学素子を得るのに最適な最適粘度となるよう加熱炉の温度を調整するので、加熱炉の環境に影響されなくなる。
【００１５】
請求項２及び請求項３の発明は、ガラス素材の粘度が、成形型による押圧成形で所望の光学素子を得るのに最適な粘度（最適粘度）となるよう加熱炉の温度を調整するための炉温変更量と、ガラス素材の粘度に対応するガラス素材の変形量との相関関係を示した表を予め作成し、加熱炉によってガラス素材を加熱軟化し、この加熱軟化によって自重変形したガラス素材の変形量を測定して上記表に照し合せ、変形量に応じた炉温変更量を選び、この炉温変更量の分だけ加熱炉の温度を調整するので、加熱炉の環境に影響されなくなる。
【００１６】
【発明の実施の形態】
以下、本発明の実施の形態について図３乃至図７を用いて説明する。
図３及び図４は成形装置の断面図であるとともにガラス素材を加熱軟化して変形量を測定する工程を説明するための図、図５は成形装置の断面図であるとともに加熱軟化されたガラス素材を成形型によって成形する工程を説明するための図、図６は加熱炉にて加熱軟化されたガラス素材の状態を示すとともに加熱軟化後の変形量を測定する部位を示した図、図７は炉温調整作業の手順を示すフローチャートである。
【００１７】
図３に示す通り、成形装置１は、成形材料であるガラス素材２を加熱軟化するための加熱炉３と、加熱炉３で加熱軟化されたガラス素材２を成形するための成形室４とから構成される。
成形室４は、所望の光学素子であるレンズの形状が高精度に転写された成形面５ａ，６ａをそれぞれ有するとともに、成形面５ａ，６ａが同軸に対向配置された一対の成形型である上型５および下型６と、上型５の基端を保持する上型保持具７と、下型６の基端を保持するとともに図示省略したエアシリンダによって上型５の軸心方向に進退自在である下型保持具８と、上型保持具７および下型保持具８内に埋設されるとともに、上型５および下型６の基端の外周を囲むように埋設された発熱体である上型ヒーター９および下型ヒーター１０と、上型５および下型６の周囲を囲むとともにガラス素材搬入搬出口１１ａを有するハウジング１１と、より構成されている。
【００１８】
上記ハウジング１１に隣接する加熱炉３は、内径側が上記ハウジング１１のガラス素材搬入搬出口１１ａと連通した円筒形状であるとともに発熱体であるヒーターとして抵抗線１２を埋設した伝熱部材１３と、伝熱部材１３の内径面に備えられた円筒状の石英ガラス１４と、石英ガラス１４の長手方向の外側端面及び伝熱部材１３の長手方向の外側端面及び伝熱部材１３の外周を一体的に被覆する金属カバー１５と、石英ガラス１４の内壁の上側であるとともに、加熱炉３内に搬送されて加熱軟化されるガラス素材２の一時待機位置（図３において、加熱炉３内部のほぼ中央）付近に備えられた熱電対１６と、から構成されている。
【００１９】
熱電対１６と上記抵抗線１２とは加熱炉の温度制御器１９に接続されており、抵抗線１２によって加熱される加熱炉３内のガラス素材２の一時待機位置付近の温度は、熱電対１６によって測定されるとともに温度制御器１９の温度表示部（図示省略）により作業者が目視で確認できるよう表示される。
また、上記加熱炉３の上記成形室１とは反対側には、図示省略した駆動源によって加熱炉３の外から加熱炉３および成形室４内にかけて進退する板状の搬送装置１７が備えられており、搬送装置１７の先端には、ガラス素材２を載置して保持する保持部材１８を載置できるよう、保持部材１８の下側の外径よりも若干大径である円形の貫通孔である載置孔１７ａが設けられている。
【００２０】
載置孔１７ａに載せられる保持部材１８は、その上側端部に載置孔１７ａよりも大きなフランジ部１８ａを有することで載置孔１７ａからの落下が規制されているとともに、保持部材１８の内径側には、上記下型６の成形面６ａ付近の外径よりも若干大径である段部１８ｂが形成され、この段部１８ｂにはガラス素材２が係止されて保持される。
【００２１】
ガラス素材２には、外径が８ｍｍ、厚さが１ｍｍの円盤状で、ガラス転移温度が５０５℃、軟化温度が６３５℃である重フリント系ガラスを用いている。
次に、上記成形装置１によって所望形状のレンズを得るのに最適な成形条件を探り出すための条件出し成形を行う。
条件出し成形によって決定する主要なの成形条件は、上型５および下型６による押圧成形によって所望形状のレンズを得るのに最適な粘度となるようガラス素材２を加熱するための加熱炉３の温度、加熱炉３によるガラス素材２の加熱時間、上型５及び下型６の加熱温度、上型５及び下型６によってガラス素材を押圧成形する際の圧力の程度、である。
【００２２】
まず、図３に示す加熱炉３内の温度がガラス素材２の軟化温度よりも高くなるよう抵抗線１２に通電して伝熱部材１３と石英ガラス１４とを加熱するとともに、上型５および下型６の温度がガラス素材２の転移温度以上かつ軟化温度以下となるよう上型ヒーター９及び下型ヒーター１０に通電し、同時に成形室４内を非酸化性雰囲気である窒素雰囲気（Ｎ₂雰囲気）とする。
【００２３】
加熱炉３内の温度および上型５、下型６の温度が安定したら、図示省略の駆動源により搬送装置１７を左方向へ後退した状態、即ち、搬送装置１７の先端の載置孔１７ａを加熱炉３の外へ出した状態で、段部１８ｂにガラス素材２を載置した保持部材１８を搬送装置１７の載置孔１７ａに載せ、上記駆動源によって搬送装置１７を右方向に駆動して保持部材１８及びガラス素材２を加熱炉３内に搬送するとともに保持部材１８及びガラス素材２を一時待機位置にて停止し、保持部材１８上のガラス素材２を加熱軟化させるとともにガラス素材２の熱膨脹によりガラス素材２と保持部材１８とを熱嵌合し、ガラス素材２の粘度が成形可能となる程度に自重変形するまで加熱軟化する。
【００２４】
次に、搬送装置１７によってガラス素材２を加熱炉３から成形室４内の上型５と下型６との間に搬送して上型５及び下型６の軸心とガラス素材２の中心とを一致させて搬送を停止した後、図示省略のエアシリンダを作動して下型保持具８及び下型６を上型５の軸心方向に上昇して載置孔１７ａから保持部材１８とともにガラス素材２を突き上げ、図５に示す通り、上型５と下型６とによってガラス素材２を押圧するとともに一定時間保持して冷却し、ガラス素材２が自重で変形できない温度以下まで冷却されてレンズ１９となったら、下型保持具８とともに下型６を下降してレンズ１９とともに保持部材１８を載置孔１７ａに戻し、搬送装置１７を左方向へ後退することで成形室４からガラス素材搬入搬出口１１ａ及び加熱炉３を通過して加熱炉３の外にレンズ１９を排出する。
【００２５】
成形したレンズ１９が十分に冷却されると、レンズ１９が収縮して保持部材１８との嵌合が解かれるので、保持部材１８からレンズ１９を取り出し、このレンズ１９が所望の形状に成形されているか否か検査する。
検査の結果、成形したレンズ１９が所望の形状となっていなければ、所望の形状が得られるまで、上記各種の成形条件の適宜変更、レンズ１９の成形、成形したレンズ１９の形状の検査といった一連の工程を繰り返し、レンズ１９が所望の形状となる成形条件を得られたら、上記と同様の加熱軟化からレンズ１９の形状の検査に至る工程を１２０回連続して繰り返し、歩留まりを求める。
【００２６】
歩留まりは高い程不良の発生が少ないことを示すものであり、本実施の形態では歩留まりを９０％以上と決め、求めた歩留まりが９０％以下であれば、上記各種の成形条件を適宜変更し、加熱軟化からレンズ１９の形状の検査に至る工程を繰り返し、歩留まりが９０％以上となる成形条件を探り出す。
本実施の形態によると、歩留まりが９０％以上となる成形条件は、加熱炉３の温度を温度制御器１９の温度表示部による表示温度で８２５℃（以下、最適温度と称する）、加熱炉３によるガラス素材２の加熱時間を９０秒、上型５及び下型６の温度を５３５℃、上型５及び下型６によってガラス素材２を押圧する圧力を６．０ＭＰａ、上型５及び下型６によってガラス素材２を押圧後に保持して冷却する時間を２４秒、成形室１内の雰囲気を非酸化性雰囲気であるＮ₂雰囲気、と決定した。
【００２７】
次に、図３に示す通り、抵抗線１２に通電して加熱炉３内の温度を表示温度で最適温度の８２５℃に保ち、ガラス素材２を載置した保持部材１８を搬送装置１７の載置孔１７ａに載置し、搬送装置１７を図示省略した駆動源によって右方向に前進して保持部材１８及びガラス素材２を加熱炉３に搬送するとともに保持部材１８及びガラス素材２を一時待機位置にて停止し、ガラス素材２を加熱軟化して自重変形させるとともにガラス素材２の熱膨脹によりガラス素材２と保持部材１８とを熱嵌合させ、ガラス素材２を本成形と同様の９０秒間加熱軟化した後、図４に示す通り搬送装置１７を左方向に後退して保持部材１８及びガラス素材２を加熱炉の外に排出する。
【００２８】
ガラス素材２が十分に冷却されて保持部材１８との熱嵌合が解かれたら保持部材１８からガラス素材２を取り出して変形量を測定する。
測定する箇所は、図６に示す通り、ガラス素材２の中心部の厚さＡ、及び、ガラス素材２の外周側上端面からガラス素材２の中心部の最下端までの厚さＢであり、これらをマイクロメーター等の測定器具により測定し、平均をとるため、この作業を１２０個分繰り返して平均化し、最適温度８２５℃での加熱軟化に対するガラス素材２の変形量の分布を求めた。
【００２９】
次に、最適温度８２５℃を衝（中心）とし、最適温度８２５℃に対して、温度制御器１９の温度表示部による表示温度で５℃毎に±１５℃の範囲で温度条件を設定し、各温度条件毎にガラス素材２の加熱軟化およびガラス素材２の変形量の測定を行い、各温度条件についてガラス素材２の変形量を１２０個分繰り返して平均化するとともに各温度条件におけるガラス素材２の変形量の分布を求め、最適温度８２５℃から上述のように設定した温度条件の値を差し引いた値を加熱炉の温度の調整量である炉温変更量とするとともに最適温度８２５℃のときの炉温変更量を０℃とし、これら炉温変更量とガラス素材２の変形量との相関関係を示す表を表１のように作成する。
【００３０】
【表１】

【００３１】
表の作成が終了したら、成形条件を上述した最適なものに戻し、多数個を製造するための本成形に入る。
まず、図３に示した抵抗線１２に通電して伝熱部材１３と石英ガラス１４とを加熱し、加熱炉３内の温度を熱電対１６にて測定しつつ加熱炉３内の温度を温度制御器１９の温度表示部での表示温度で最適温度の８２５℃に保つとともに、上型ヒーター９及び下型ヒーター１０に通電して上型５及び下型６を５３５℃に加熱し、成形室４内にＮ₂を供給する。
【００３２】
加熱炉３と上型５及び下型６の温度が安定したら、図示省略の駆動源により搬送装置１７を左方向へ後退し、搬送装置１７の先端、即ち、載置孔１７ａを加熱炉３の外へ出した状態で、ガラス素材２を載置した保持部材１８を載置孔１７ａに載置し、搬送装置１７を上記駆動源によって右方向に前進して保持部材１８及びガラス素材２を加熱炉３内に搬送するとともに保持部材１８及びガラス素材２を一時待機位置にて停止し、ガラス素材２を加熱軟化して自重変形させるとともにガラス素材２の熱膨脹によりガラス素材２と保持部材１８とを熱嵌合させ、ガラス素材２を９０秒間加熱軟化した後、保持部材１８及びガラス素材２を搬送装置１７によって加熱炉３から成形室４内の上型５と下型６との間に搬送し、上型５及び下型６の軸心とガラス素材２の中心とが一致した位置で搬送を停止する。
【００３３】
そして、図示省略のエアシリンダを作動して下型保持具８とともに下型６を上昇し、搬送装置１７の載置孔１７ａから保持部材１８に熱嵌合したガラス素材２を突き上げ、図５に示す通り、上型５及び下型６の成形面５ａ，６ａによってガラス素材２を６．０ＭＰａの圧力で押圧して成形面５ａ，６ａの形状をガラス素材２に転写するとともに２４秒間保持して冷却し、ガラス素材２が自重で変形できない温度以下となってレンズ１９となったらエアシリンダを作動して下型保持具８とともに下型６を下降することでレンズ１９とともに保持部材１８を搬送装置１７の載置孔１７ａに戻し、搬送装置１７を左方向へ後退することで成形室４からガラス素材搬入搬出口１１ａ及び加熱炉３を通過してレンズ１９および保持部材１８を成形装置１の外に排出する。
【００３４】
排出されたレンズ１９が十分に冷却され、レンズ１９が収縮して保持部材１８との嵌合が解かれたら、保持部材１８からレンズ１９を取り出す。
以後、上記のような成形を繰り返すことで、多数個のレンズ１９を製造するのであるが、適宜（例えば、５００個成形毎に、あるいは１時間経過毎に、等）、加熱炉３で加熱軟化されるガラス素材２の変形量を測定し、ガラス素材２が最適粘度となるように加熱軟化されているか否かをチェックし、最適粘度に加熱軟化されてない場合は、加熱炉３に対して炉温調整作業を行う。
【００３５】
以下、この炉温調整作業について、図３、図４及び図７のフローチャートを基に説明する。
まず、図３に示す通り、抵抗線１２に通電して加熱炉３内の温度を最適温度の８２５℃に保ったまま（図７（ａ）参照）、ガラス素材２を載置した保持部材１８を搬送装置１７の載置孔１７ａに載置し、搬送装置１７を図示省略した駆動源によって右方向に前進して保持部材１８及びガラス素材２を加熱炉３に搬送するとともに保持部材１８及びガラス素材２を一時待機位置にて停止し、ガラス素材２を加熱軟化する（図７（ｂ）参照）とともにガラス素材２の熱膨脹によりガラス素材２と保持部材１８とを熱嵌合させ、ガラス素材２を本成形と同様の９０秒間加熱軟化して自重変形させた後、図４に示す通り、搬送装置１７を左方向に後退して保持部材１８及びガラス素材２を加熱炉３の外に排出する。
【００３６】
ガラス素材２が十分に冷却されて保持部材１８との熱嵌合が解かれたら保持部材１８からガラス素材２を取り出してマイクロメータ等の測定器具により変形量Ａ，Ｂを測定し（図７（ｃ）参照）、変形量Ａ及びＢが所定の量、即ち、炉温変更量が０℃である場合の変形量、具体的には、表１に示される通り、変形量Ａが１．０４ｍｍ以上１．０５ｍｍ未満、変形量Ｂが１．３０ｍｍ以上１．４０ｍｍ未満であるか否かを判断する（図７の（ｄ）参照）。
【００３７】
ガラス素材２の変形量が所定の変形量であればガラス素材２の粘度が成形に適すると判断し（図７の（ｅ）参照）、特に炉温調整作業を行わずに、本成形に戻る。
しかしながら、上述したような加熱炉２の環境の変化（熱電対１６の劣化による温度測定の不確実性、抵抗線１２の劣化、雰囲気条件の変化、加熱炉３の分解整備後の組み付け及び加熱炉３の固体差に基づく昇温過程の変化や差異等）により、温度制御器１９の温度表示部による表示温度が最適温度８２５℃であるにも関わらず、加熱軟化されたガラス素材２の変形量が所定の変形量でなければガラス素材２の粘度が成形に適しないと判断して温度制御器１９の温度表示部の表示温度を８２５℃＋α℃（α：表１に基く炉温変更量）に変更する（図７（ｆ）参照）。
【００３８】
具体的には、例えば、測定した変形量Ａが１．０３ｍｍ、変形量Ｂが１．２５ｍｍの場合、表１に照し合わせると、炉温変更量は＋５℃であるため、加熱炉３の温度を温度制御器１９の温度表示部の表示温度で８２５℃＋５℃である８３０℃に変更し、加熱炉３の温度が安定したら、加熱炉３によってガラス素材２を再び加熱し（図７（ｂ）参照）、上記と同じ方法で上記ガラス素材２の変形量を測定し（図７（ｃ）参照）、所定の変形量、すなわち、炉温変更量が０℃のときに相当する変形量であるか否かを判断する（図７（ｄ）参照）。
【００３９】
そして、測定した変形量Ａ，Ｂが、表１に示される炉温変更量０℃のときの変形量の範囲内となるまで上記加熱炉３の炉温の調整作業を繰り返し、加熱軟化されるガラス素材２の変形量が、表１に示される炉温変更量０℃のときの変形量の範囲となったら、多数個成形向けの本成形を再開する（図７（ｅ）参照）。
尚、上記炉温調整作業の中で、図７の（ｄ）において、加熱軟化後のガラス素材２の変形量Ａ及びＢがそれぞれ１．０２ｍｍ未満、１．１５ｍｍ未満の場合、表１の範囲外（＋１５℃を越える）であるため、一旦加熱炉３の温度を温度制御器１９の温度表示部上で１５℃上昇させ、加熱炉３の温度が安定した後、ガラス素材２の変形量を測定し、再び表１を基準にして上記と同様の手順で炉温の調整作業を行う。
【００４０】
また、これとは逆に、炉温調整作業の中で、図７の（ｄ）において、加熱軟化後のガラス素材２の変形量Ａ及びＢがそれぞれ１．０７ｍｍ以上、１．６５ｍｍ以上の場含は、一旦加熱炉３の温度を温度制御器１９の温度表示部上で１５℃下げ、加熱炉３の温度が安定した後、ガラス素材２の変形量を測定し、表ｌを基準にして上記と同様の手順で、炉温の調整を行う。
【００４１】
さらに、上記変形量Ａ及びＢのそれぞれに対応する炉温変更量がそれぞれ異なる場合、例えば、変形量Ａが１．０２ｍｍで変形量Ｂが１．２６ｍｍの場合には、変形量Ｂに対応する炉温変更量＋５℃を採用する。
ここで、上記のような炉温調整作業を行わずに加熱炉３の表示温度を８２５℃のまま変更しない場合と、上記の様にガラス素材２の変形量測定を行い、表１を基準にしての炉温調整作業を行って、加熱炉３の表示温度を８２５℃から８３０℃に変更した場合とで、各々１２０個の連続成形を行って歩留まりを比較したところ、前者は２５％で後者は９９％であった。
【００４２】
尚、上記炉温調整作業は、温度制御器１９の温度表示部の表示温度に基づいて作業者が温度制御器１９を手動操作で行っても良いし、表１に示したような炉温変更量とガラス素材２の変形量との相関関係を温度制御器１９に予めプログラムし、温度制御器に１９による自動操作で行っても良い。
（効果）
本実施の形態によると、加熱炉で加熱軟化した後のガラス素材の変形量を測定し、この変形量と炉温変更量との相関関係を示す表を基準に加熱炉の温度を調整することでガラス素材を成形に最適な粘度に加熱軟化しているため、熱電対の劣化による温度測定の不確実性、抵抗線の劣化、雰囲気条件の変化、加熱炉の分解整備後の組み付け及び加熱炉の固体差に基づく昇温過程の変化や差異等、加熱炉の環境に影響されることなくガラス素材を最適粘度に加熱軟化することができる。
【００４３】
従って、高精度な光学素子を歩留まり良く安定して製造することができる。
尚、本実施の形態では、ある特定のレンズを成形するに際し、条件出し成形を行い、最適な成形条件を求めた後に多数個の製造向けの本成形を行い、本成形の途中でガラス素材２が加熱炉３によって最適粘度に加熱軟化されているか否かを判断し、必要な時に炉温度調整作業を行っているが、特に、初めから最適な成形条件が分かっていて、その上で加熱炉３の炉温の調整が必要であると思われる様な場合、例えば、加熱炉３の分解整備後や同一構成で他の加熱炉３に交換した時、といった様な場合には、条件出し成形を行わずに、本成形を行う直前に上記の様な炉温調整作業を行うことにより、短時間で加熱炉３の炉温の調整を終了することができる。
【００４４】
尚、上述した発明の実施の形態には、以下に記載する構成（１）乃至構成（４）を有する発明が含まれており、これら各構成に対応する作用及び効果は次の通りである。
（１）ガラス素材を成形可能状態に加熱軟化処理するための光学素子成形装置の加熱炉におけるガラス素材の粘度調節方法において、
加熱炉でガラス素材を任意時間加熱軟化した後、ガラス素材の変形量を測定し、該変形量を基に前記加熱炉のガラス素材の位置する部分の温度を所定の温度に設定することにより、加熱炉内部でのガラス素材の粘度を調節することを特徴とする光学素子成形装置の加熱炉におけるガラス素材の粘度調節方法。
（２）変形量を基に加熱炉のガラス素材の位置する部分の温度を所定の温度に設定することが、ガラス素材が加熱されたときの変形量を測定した後、前記加熱炉のガラス素材が位置する部分の温度を示す表示値を上記測定された変形量に応じた値を加えた表示値に変更し、また、該測定された変形量に応じた値が予め設定されていることを特徴とする構成（１）の光学素子成形装置の加熱炉におけるガラス素材の粘度調節方法。
【００４５】
上記構成（１）及び（２）の作用は、成形装置の加熱炉でガラス素材を加熱軟化した後任意時間後にガラス素材を加熱炉から引き出し、ガラス素材の変形量を測定し、変形量と加熱炉内部でのガラス素材の粘度とを対応させることにより該粘度を調節することである。
また、上記構成（１）及び（２）の効果は、ガラス素材を加熱炉で加熱軟化した後、該ガラス素材の変形量を測定し、該変形量を基に前記加熱炉のガラス素材の位置する部分の温度を所定の温度に設定することが出来るので、前記加熱炉内部でのガラス素材の粘度を光学素子の成形に適した粘度に、熱電対の劣化の進行、抵抗線の配置の僅かな差異による昇温過程の違いに左右されることなく、正確に調節可能となることである。
（３）ガラス素材を予め加熱炉で加熱軟化し、対向配置する一対の型で押圧成形する光学素子の成形方法において、
前記加熱炉でガラス素材を任意時間加熱軟化した後、ガラス素材の変形量を測定し、該変形量を基に前記加熱炉のガラス素材の位置する部分の温度を所定の温度に設定することにより、前記加熱炉内部での加熱軟化時の粘度を調節することを特徴とする光学素子の成形方法。
（４）変形量を基に加熱炉のガラス素材の位置する部分の温度を所定の温度に設定することが、ガラス素材が加熱されたときの変形量を測定した後、前記加熱炉のガラス素材が位置する部分の温度を示す表示値を上記測定された変形量に応じた値を加えた表示値に変更し、また、該測定された変形量に応じた値が予め設定されていることを特徴とする構成（３）の光学素子の成形方法。
【００４６】
上記構成（３）及び（４）の作用は、ガラス素材を押圧成形するに先立ち加熱炉内部でのガラス素材の粘度を構成（１）又は（２）の作用により調節することにより、成形工程にて所望の光学素子を安定して得ることである。
上記構成（３）及び（４）の効果は、ガラス素材を加熱炉で加熱軟化した後、該ガラス素材の変形量を測定し、該変形量を基に前記加熱炉のガラス素材の位置する部分の温度を所定の温度に設定することにより、前記加熱炉内部でのガラス素材の粘度を光学素子の成形に適した粘度に調節できるので、熱電対の劣化の進行、抵抗線の配置の僅かな差異による昇温過程の違いに左右されることなく、非常によい歩留まりで光学素子の成形が安定して出来ることである。
【００４７】
【発明の効果】
請求項１乃至請求項３の発明によると、熱電対の劣化、雰囲気条件の変化、加熱炉の分解整備や加熱炉の固体差に基づく昇温過程の変化および差異等、加熱炉の環境に影響されることなくガラス素材を最適粘度に加熱軟化し、高精度な光学素子を歩留まり良く安定して製造することができる。
【図面の簡単な説明】
【図１】従来の加熱炉の側断面図である。
【図２】従来の加熱炉の正面図である。
【図３】発明の実施の形態における成形装置の側断面図であるとともにガラス素材を加熱軟化して変形量を測定する工程を説明するための図である。
【図４】発明の実施の形態における成形装置の断面図であるとともにガラス素材を加熱軟化する工程を説明するための図である。
【図５】発明の実施の形態における成形装置の側断面図であるとともに加熱軟化されたガラス素材を成形する工程を説明するための図である。
【図６】発明の実施の形態における加熱炉にて加熱軟化されたガラス素材の状態を示すとともに変形量を測定する部位を示した図である。
【図７】発明の実施の形態における炉温調整作業の手順を示すフローチャートである。
【符号の説明】
２ガラス素材
３加熱炉
５上型
６下型
１２抵抗線
１６熱電対
１９温度制御器[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for molding an optical element in which a glass material, which is a molding material heated and softened by a heating furnace, is pressed by a molding die into a desired optical element.
[0002]
[Prior art]
Generally, when a glass material is heated to a formable state, a heating furnace such as an electric furnace is used as a heating means.
As an example of such a heating furnace, one described in Japanese Patent Laid-Open No. 62-182120 will be described with reference to FIGS.
[0003]
1 is a side sectional view of the heating furnace, and FIG. 2 is a front view of the heating furnace. In FIGS. 1 and 2, the heating furnace 100 has a cylindrical shape and a resistance wire 101 embedded as a heater that is a heating element. The heat transfer member 102, the quartz glass 103 provided on the inner peripheral surface of the heat transfer member 102, and the metal cover 104 that integrally covers the outer end surface of the quartz glass 103 and the outer periphery of the heat transfer member 102. It is placed on a support base 107 fixed to the base 106 with bolts 105 via a heat insulating material 108.
[0004]
According to the heating furnace 100 having the above configuration, heating is started by energizing the resistance wire 101, and when the temperature in the heating furnace 100 is stabilized at the set temperature, the glass material not shown is placed on the holding member not shown. The glass material is transferred to the heating furnace 100 together with the holding member by a transfer device (not shown) and stopped at a temporary standby position in the heating furnace 100 (in the middle of the heating furnace 100 in FIG. 1) for a predetermined time, Softens glass material by heating.
[0005]
The heat-softened glass material is transported to a molding chamber (not shown) and pressed by a pair of molding dies (not shown) having a molding surface that is the reverse of the shape of the desired optical element, so that the desired optical element shape is obtained. Molded.
Here, in order to form a glass material into an optical element with high accuracy during molding using a molding die, the glass material needs to have an optimum viscosity that is an appropriate viscosity by heat softening by the heating furnace 100.
[0006]
In general, the viscosity of the glass material in the heating furnace 100 is not directly measured to determine whether or not it is the optimum viscosity. A thermocouple (not shown) as a means is provided in the vicinity of the temporary standby position of the glass material inside the heating furnace 100, and the temperature of the heating furnace 100 measured using this thermocouple (not shown), more precisely, the thermocouple is connected. Based on the display temperature shown in the temperature display (not shown) of the temperature controller (not shown), it is judged whether or not the glass material being heat-softened has the optimum viscosity and displayed. The resistance wire current and voltage are adjusted so that the temperature corresponds to the optimum viscosity.
[0007]
[Problems to be solved by the invention]
However, when the thermocouple deteriorates due to continuous use of the heating furnace 100 for a long time, the temperature in the heating furnace 100 changes even though the set temperature of the heating furnace 100 does not actually change. If it is, the temperature of the heating furnace 100 may be adjusted based on an erroneous measurement result, and it may be difficult to adjust the viscosity of the glass material to the optimum viscosity.
[0008]
In addition, when the resistance wire 101 of the heating furnace 100 deteriorates due to continuous use of the heating furnace 100 for a long time, the balance between conduction heat and radiant heat generated from the resistance wire 101 changes, and the temperature rise process of the glass material is performed. Due to the change, it may be difficult to adjust the viscosity of the glass material to the optimum viscosity by the heating furnace 100.
Further, since the molding of the optical element is continuously performed for a long time, the atmospheric conditions around the molding apparatus including the heating furnace 100 such as the temperature and the humidity are changed to cause a change in the temperature raising process of the glass material. In some cases, it was difficult to adjust the viscosity to an optimum viscosity.
[0009]
In addition, when the same glass material is heated and softened in the heating furnace 100 that has been operated for a certain period of time and decomposed or in another heating furnace 100 that has the same structure, the heating furnace 100 is manufactured at the time of assembly after decomposition and maintenance. The distance between the glass material and the resistance wire 101 and the distance between the resistance wire 101 and the thermocouple may be different due to a slight difference in the attachment position of the resistance wire 101 at the stage of repairing. Since the balance between conduction heat and radiant heat reaching the glass material or thermocouple differs before and after or for each heating furnace 100, the resulting temperature rise process of the heated glass material itself results in an optimum viscosity of the glass. In some cases, it could not be softened by heating.
[0010]
In addition, by inserting the tip of the thermocouple into the hole provided in the position close to the glass material of the holding member that holds the glass material, or by providing the hole in the glass material itself and inserting the tip of the thermocouple into this hole There is also a method of adjusting the temperature inside the heating furnace 100 according to the measured temperature, but the close area of the tip of the thermocouple with respect to each hole provided in the holding member or the glass material differs for each measurement, and is always the same. It is difficult to measure the temperature accurately under certain conditions.In particular, when a thermocouple is inserted into a hole in the glass material itself, the thermocouple may be in close contact with the glass and become unusable. Not right.
[0011]
The inventions of claims 1 to 3 include uncertainty of temperature measurement due to deterioration of thermocouple, deterioration of resistance wire, change of atmospheric conditions, assembly after disassembling the heating furnace, and solid difference of the heating furnace (heating furnace The glass material is heated and softened to the optimum viscosity without being affected by the environment of the heating furnace, such as changes and differences in the heating process based on the variation of each), and high-precision optical elements can be manufactured stably with high yield. An object of the present invention is to provide a method for molding an optical element.
[0012]
[Means for Solving the Problems]
The invention of claim 1 is an optical element molding method for obtaining an optical element by press-molding a glass material with a molding die after heat-softening the glass material into a moldable state with a heating furnace, and after heating and softening with a heating furnace. The temperature of the heating furnace is adjusted so that the measured amount of deformation of the glass material becomes the amount of deformation corresponding to the optimum viscosity when the heat-softened glass material is molded into an optical element with a mold. .
[0013]
The invention of claim 2 is an optical element molding method for obtaining an optical element by press-molding a glass material with a molding die after heat-softening the glass material into a moldable state with a heating furnace, and after heating and softening with a heating furnace. When adjusting the temperature of the heating furnace so that the measured amount of deformation of the glass material becomes the amount of deformation equivalent to the optimum viscosity (optimum viscosity) when the heat-softened glass material is molded into an optical element with a mold. Heating based on a table showing the correlation between the furnace temperature change amount, which is the temperature adjustment amount of the heating furnace, and the deformation amount of the glass material heat-softened by the heating furnace whose temperature is adjusted based on the furnace temperature change amount It is characterized by adjusting the temperature of the furnace.
[0014]
The invention of claim 3 is an optical element molding method in which an optical element is obtained by press-molding a glass material with a molding die after heat-softening the glass material into a moldable state in a heating furnace. Centering on the temperature of the heating furnace, which is the optimum viscosity (optimum viscosity) for obtaining optical elements by press molding with a mold, multiple pieces within a certain range above and below the center temperature and with a certain temperature difference Set the temperature condition of each, for each temperature condition to heat soften the glass material individually and measure the amount of deformation, the value obtained by subtracting the value of each temperature condition from the center temperature, the furnace temperature change amount, A table showing the correlation between each furnace temperature change amount corresponding to each of the above temperature conditions and the deformation amount of the glass material heated and softened by the heating furnace is created, and the deformation amount of the glass material heated and softened in the heating furnace is , Above optimal To match the deformation amount corresponding to time, adjusting the temperature of the heating furnace based on the above table, characterized by.
(Function)
According to the first aspect of the present invention, the viscosity of the glass material by heat softening is inspected by measuring the amount of deformation of the glass material that has been softened and deformed by heating in a heating furnace before forming by the mold, and the viscosity of the glass material is molded. Since the temperature of the heating furnace is adjusted so as to obtain an optimum viscosity that is optimal for obtaining a desired optical element by press molding with a mold, it is not affected by the environment of the heating furnace.
[0015]
The invention of claim 2 and claim 3 is for adjusting the temperature of the heating furnace so that the viscosity of the glass material becomes an optimum viscosity (optimum viscosity) for obtaining a desired optical element by press molding with a mold. A table showing the correlation between the furnace temperature change amount and the deformation amount of the glass material corresponding to the viscosity of the glass material is created in advance, the glass material is heated and softened by the heating furnace, and the glass material is deformed by its own weight The amount of deformation is measured and compared with the above table, the furnace temperature change amount corresponding to the deformation amount is selected, and the temperature of the heating furnace is adjusted by the amount of the furnace temperature change amount. Disappear.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to FIGS.
3 and 4 are cross-sectional views of the forming apparatus and a view for explaining a process of measuring the amount of deformation by heating and softening the glass material, and FIG. 5 is a cross-sectional view of the forming apparatus and heat-softened glass. FIG. 6 is a diagram for explaining a process of forming a material with a mold, FIG. 6 is a diagram showing a state of a glass material heat-softened in a heating furnace, and a portion for measuring a deformation amount after heat-softening, FIG. These are flowcharts which show the procedure of a furnace temperature adjustment operation.
[0017]
As shown in FIG. 3, the molding apparatus 1 includes a heating furnace 3 for heating and softening a glass material 2 as a molding material, and a molding chamber 4 for molding the glass material 2 heated and softened in the heating furnace 3. Composed.
The molding chamber 4 is a pair of molding dies each having molding surfaces 5a and 6a onto which the shape of a lens, which is a desired optical element, is transferred with high accuracy, and the molding surfaces 5a and 6a are coaxially opposed to each other. The mold 5 and the lower mold 6, the upper mold holder 7 that holds the base end of the upper mold 5, and the air cylinder that holds the base end of the lower mold 6 and can be moved forward and backward in the axial direction of the upper mold 5 by an unillustrated air cylinder. And a heating element embedded in the upper mold 5 and the lower mold 6 so as to surround the outer periphery of the base end of the upper mold 5 and the lower mold 6. The upper die heater 9 and the lower die heater 10, and the housing 11 surrounding the upper die 5 and the lower die 6 and having a glass material loading / unloading port 11 a are configured.
[0018]
The heating furnace 3 adjacent to the housing 11 has a cylindrical shape in which the inner diameter side communicates with the glass material loading / unloading port 11a of the housing 11 and a heat transfer member 13 in which a resistance wire 12 is embedded as a heater as a heating element. The cylindrical quartz glass 14 provided on the inner diameter surface of the heat member 13, the outer end surface in the longitudinal direction of the quartz glass 14, the outer end surface in the longitudinal direction of the heat transfer member 13, and the outer periphery of the heat transfer member 13 are integrally covered. Near the temporary standby position of the glass material 2 to be heated and softened by being transported into the heating furnace 3 (almost the center in the heating furnace 3 in FIG. 3), which is above the inner wall of the metal cover 15 and the quartz glass 14 And a thermocouple 16 provided in the above.
[0019]
The thermocouple 16 and the resistance wire 12 are connected to a temperature controller 19 of the heating furnace, and the temperature near the temporary standby position of the glass material 2 in the heating furnace 3 heated by the resistance wire 12 is the thermocouple 16. And a temperature display unit (not shown) of the temperature controller 19 is displayed so that the operator can confirm it visually.
Further, on the side opposite to the molding chamber 1 of the heating furnace 3, a plate-like transport device 17 is provided that advances and retreats from the outside of the heating furnace 3 to the inside of the heating furnace 3 and the molding chamber 4 by a driving source (not shown). And a circular through-hole having a slightly larger diameter than the outer diameter of the lower side of the holding member 18 so that the holding member 18 for placing and holding the glass material 2 can be placed at the tip of the transport device 17. A mounting hole 17a is provided.
[0020]
The holding member 18 mounted on the mounting hole 17a has a flange portion 18a larger than the mounting hole 17a at the upper end thereof, so that dropping from the mounting hole 17a is restricted, and the inner diameter of the holding member 18 On the side, a step portion 18b having a slightly larger diameter than the outer diameter in the vicinity of the molding surface 6a of the lower mold 6 is formed, and the glass material 2 is locked and held on the step portion 18b.
[0021]
As the glass material 2, heavy flint glass having a disk shape with an outer diameter of 8 mm and a thickness of 1 mm, a glass transition temperature of 505 ° C., and a softening temperature of 635 ° C. is used.
Next, the above-described molding apparatus 1 performs conditional molding for finding the optimal molding conditions for obtaining a lens having a desired shape.
The main molding conditions determined by the conditional molding are the temperature of the heating furnace 3 for heating the glass material 2 so as to obtain an optimum viscosity for obtaining a lens having a desired shape by press molding with the upper mold 5 and the lower mold 6. The heating time of the glass material 2 in the heating furnace 3, the heating temperature of the upper mold 5 and the lower mold 6, and the degree of pressure when the glass material is pressed by the upper mold 5 and the lower mold 6.
[0022]
First, the resistance wire 12 is energized to heat the heat transfer member 13 and the quartz glass 14 so that the temperature in the heating furnace 3 shown in FIG. 3 is higher than the softening temperature of the glass material 2. The upper heater 9 and the lower heater 10 are energized so that the temperature of the mold 6 is not lower than the transition temperature of the glass material 2 and not higher than the softening temperature, and at the same time, the inside of the molding chamber 4 is a nitrogen atmosphere (N ₂ Atmosphere).
[0023]
When the temperature in the heating furnace 3 and the temperature of the upper mold 5 and the lower mold 6 are stabilized, the conveying device 17 is retracted to the left by a driving source (not shown), that is, the mounting hole 17a at the tip of the conveying device 17 is moved. The holding member 18 on which the glass material 2 is placed on the step portion 18b is placed on the placement hole 17a of the conveying device 17 while being moved out of the heating furnace 3, and the conveying device 17 is driven rightward by the driving source. The holding member 18 and the glass material 2 are conveyed into the heating furnace 3 and the holding member 18 and the glass material 2 are stopped at the temporary standby position to heat and soften the glass material 2 on the holding member 18 and The glass material 2 and the holding member 18 are thermally fitted by thermal expansion, and are softened by heating until the glass material 2 is deformed by its own weight so that the viscosity of the glass material 2 can be molded.
[0024]
Next, the glass material 2 is conveyed from the heating furnace 3 between the upper mold 5 and the lower mold 6 in the molding chamber 4 by the conveying device 17, and the axes of the upper mold 5 and the lower mold 6 and the center of the glass material 2 are used. , The air cylinder (not shown) is actuated to raise the lower mold holder 8 and the lower mold 6 in the axial direction of the upper mold 5, together with the holding member 18 from the mounting hole 17 a. The glass material 2 is pushed up, and as shown in FIG. 5, the glass material 2 is pressed by the upper mold 5 and the lower mold 6 and held and cooled for a certain period of time. When the lens 19 is obtained, the lower mold 6 is lowered together with the lower mold holder 8, the holding member 18 is returned to the mounting hole 17 a together with the lens 19, and the conveying device 17 is moved backward in the left direction to thereby move the glass material from the molding chamber 4. Pass through the loading / unloading port 11a and the heating furnace 3 The lens 19 is discharged out of the furnace 3.
[0025]
When the molded lens 19 is sufficiently cooled, the lens 19 contracts and the fitting with the holding member 18 is released. Therefore, the lens 19 is taken out from the holding member 18, and the lens 19 is molded into a desired shape. Check whether there is any.
If the molded lens 19 does not have a desired shape as a result of the inspection, a series of appropriate changes in the various molding conditions, molding of the lens 19, and inspection of the shape of the molded lens 19 are performed until the desired shape is obtained. When the molding conditions for obtaining the desired shape of the lens 19 are obtained, the process from heat softening to inspection of the shape of the lens 19 is repeated 120 times in succession to obtain the yield.
[0026]
The higher the yield, the less the occurrence of defects.In this embodiment, the yield is determined to be 90% or more, and if the obtained yield is 90% or less, the above various molding conditions are changed as appropriate, The process from the heat softening to the inspection of the shape of the lens 19 is repeated to find out the molding conditions with a yield of 90% or more.
According to the present embodiment, the molding condition that yields 90% or more is that the temperature of the heating furnace 3 is 825 ° C. (hereinafter referred to as the optimum temperature) as indicated by the temperature display part of the temperature controller 19, and the heating furnace 3 The heating time of the glass material 2 is 90 seconds, the temperature of the upper mold 5 and the lower mold 6 is 535 ° C., the pressure of pressing the glass material 2 by the upper mold 5 and the lower mold 6 is 6.0 MPa, the upper mold 5 and the lower mold 6 for holding the glass material 2 after being pressed and cooling it for 24 seconds, and the atmosphere in the molding chamber 1 is a non-oxidizing atmosphere. ₂ The atmosphere was determined.
[0027]
Next, as shown in FIG. 3, the resistance wire 12 is energized to keep the temperature in the heating furnace 3 at the optimum temperature of 825 ° C. at the display temperature, and the holding member 18 on which the glass material 2 is placed is placed on the transfer device 17. Placed in the mounting hole 17a, the conveying device 17 is advanced to the right by a drive source (not shown) to convey the holding member 18 and the glass material 2 to the heating furnace 3, and the holding member 18 and the glass material 2 are temporarily held at the standby position. The glass material 2 is softened by heating and softening, and the glass material 2 and the holding member 18 are thermally fitted by thermal expansion of the glass material 2, and the glass material 2 is softened by heating for 90 seconds as in the main molding. After that, as shown in FIG. 4, the conveying device 17 is moved backward to discharge the holding member 18 and the glass material 2 out of the heating furnace.
[0028]
When the glass material 2 is sufficiently cooled and the thermal fitting with the holding member 18 is released, the glass material 2 is taken out from the holding member 18 and the amount of deformation is measured.
As shown in FIG. 6, the location to be measured is the thickness A of the center portion of the glass material 2 and the thickness B from the outer peripheral side upper end surface of the glass material 2 to the lowest end of the center portion of the glass material 2, These were measured with a measuring instrument such as a micrometer, and in order to take an average, this operation was repeated 120 times and averaged, and the distribution of the deformation amount of the glass material 2 with respect to heat softening at an optimum temperature of 825 ° C. was obtained.
[0029]
Next, the optimum temperature 825 ° C. is set as the center, and the temperature condition is set in the range of ± 15 ° C. every 5 ° C. at the display temperature by the temperature display unit of the temperature controller 19 with respect to the optimum temperature 825 ° C. The glass material 2 is heated and softened for each temperature condition and the deformation amount of the glass material 2 is measured, and the deformation amount of the glass material 2 is averaged by repeating 120 times for each temperature condition, and the glass material 2 at each temperature condition is averaged. When the optimum temperature is 825 ° C., the value obtained by subtracting the value of the temperature condition set as described above from the optimum temperature 825 ° C. is used as the furnace temperature change amount that is the adjustment amount of the heating furnace temperature. Table 1 shows the correlation between the furnace temperature change amount and the deformation amount of the glass material 2 as shown in Table 1.
[0030]
[Table 1]

[0031]
When the preparation of the table is completed, the molding conditions are returned to the optimum ones described above, and the main molding for manufacturing a large number of pieces is started.
First, the resistance wire 12 shown in FIG. 3 is energized to heat the heat transfer member 13 and the quartz glass 14, and the temperature inside the heating furnace 3 is measured while the temperature inside the heating furnace 3 is measured by the thermocouple 16. The temperature displayed on the temperature display section of the controller 19 is maintained at the optimum temperature of 825 ° C., and the upper mold heater 9 and the lower mold heater 10 are energized to heat the upper mold 5 and the lower mold 6 to 535 ° C. N in 4 ₂ Supply.
[0032]
When the temperatures of the heating furnace 3 and the upper mold 5 and the lower mold 6 are stabilized, the conveying device 17 is moved backward by a driving source (not shown), and the tip of the conveying device 17, that is, the mounting hole 17 a is moved to the heating furnace 3. The holding member 18 on which the glass material 2 is placed is placed in the placement hole 17a in the state where it is exposed outside, and the holding device 18 and the glass material 2 are heated by moving the transport device 17 rightward by the driving source. While being transported into the furnace 3, the holding member 18 and the glass material 2 are stopped at the temporary standby position, the glass material 2 is softened by heating and deformed by its own weight, and the glass material 2 and the holding member 18 are thermally expanded by thermal expansion of the glass material 2. After the heat fitting and the glass material 2 is heated and softened for 90 seconds, the holding member 18 and the glass material 2 are conveyed between the upper mold 5 and the lower mold 6 in the molding chamber 4 from the heating furnace 3 by the conveying device 17. , The axis of the upper mold 5 and the lower mold 6 The center of Las material 2 stops conveyance at position match.
[0033]
Then, the air cylinder (not shown) is actuated to raise the lower die 6 together with the lower die holder 8, and the glass material 2 thermally fitted to the holding member 18 is pushed up from the mounting hole 17a of the conveying device 17, and FIG. As shown, the glass material 2 is pressed with a pressure of 6.0 MPa by the molding surfaces 5a and 6a of the upper mold 5 and the lower mold 6 to transfer the shape of the molding surfaces 5a and 6a to the glass material 2 and held for 24 seconds. When the glass material 2 is cooled to a temperature below the temperature at which it cannot be deformed by its own weight and becomes the lens 19, the air cylinder is actuated to lower the lower mold 6 together with the lower mold holder 8 to move the holding member 18 together with the lens 19. 17 is returned to the mounting hole 17a, and the conveying device 17 is moved backward to the left to pass the glass material loading / unloading port 11a and the heating furnace 3 from the molding chamber 4 to move the lens 19 and the holding member 18 to the molding device 1. It is discharged to the outside.
[0034]
When the discharged lens 19 is sufficiently cooled and the lens 19 contracts and the fitting with the holding member 18 is released, the lens 19 is taken out from the holding member 18.
Thereafter, a large number of lenses 19 are manufactured by repeating the molding as described above, but heat softening is performed in the heating furnace 3 as appropriate (for example, every 500 moldings or every hour). The amount of deformation of the glass material 2 to be measured is measured, it is checked whether or not the glass material 2 is heated and softened so as to have an optimum viscosity. Perform furnace temperature adjustment.
[0035]
Hereinafter, this furnace temperature adjustment operation will be described based on the flowcharts of FIGS. 3, 4, and 7.
First, as shown in FIG. 3, the resistance member 12 is energized and the temperature in the heating furnace 3 is kept at the optimum temperature of 825 ° C. (see FIG. 7A), and the holding member 18 on which the glass material 2 is placed. Is placed in the mounting hole 17a of the conveying device 17, and the conveying device 17 is advanced to the right by a driving source (not shown) to convey the holding member 18 and the glass material 2 to the heating furnace 3, and the holding member 18 and the glass. The material 2 is stopped at the temporary standby position, the glass material 2 is heated and softened (see FIG. 7B), and the glass material 2 and the holding member 18 are heat-fitted by the thermal expansion of the glass material 2, so that the glass material 2 After being softened by heating and softening for 90 seconds in the same manner as in the main molding, the conveying device 17 is moved backward to the left as shown in FIG. 4 and the holding member 18 and the glass material 2 are discharged out of the heating furnace 3. .
[0036]
When the glass material 2 is sufficiently cooled and the thermal fitting with the holding member 18 is released, the glass material 2 is taken out from the holding member 18 and the deformation amounts A and B are measured with a measuring instrument such as a micrometer (FIG. 7 ( c)), the deformation amounts A and B are predetermined amounts, that is, the deformation amount when the furnace temperature change amount is 0 ° C., specifically, as shown in Table 1, the deformation amount A is 1.04 mm. It is judged whether or not it is less than 1.05 mm and the deformation amount B is 1.30 mm or more and less than 1.40 mm (see (d) of FIG. 7).
[0037]
If the deformation amount of the glass material 2 is a predetermined deformation amount, it is determined that the viscosity of the glass material 2 is suitable for molding (see (e) of FIG. 7), and the process returns to the main molding without particularly performing the furnace temperature adjustment work. .
However, changes in the environment of the heating furnace 2 as described above (temperature measurement uncertainty due to deterioration of the thermocouple 16, deterioration of the resistance wire 12, changes in atmospheric conditions, assembly of the heating furnace 3 after disassembly and maintenance, and the heating furnace 3), the amount of deformation of the heat-softened glass material 2 even though the temperature indicated by the temperature display unit of the temperature controller 19 is the optimum temperature 825 ° C. If the temperature is not a predetermined deformation amount, it is determined that the viscosity of the glass material 2 is not suitable for molding, and the display temperature of the temperature display portion of the temperature controller 19 is 825 ° C. + α ° C. (α: furnace temperature change amount based on Table 1) (Refer to FIG. 7F).
[0038]
Specifically, for example, when the measured deformation amount A is 1.03 mm and deformation amount B is 1.25 mm, the amount of change in the furnace temperature is + 5 ° C. in comparison with Table 1, When the temperature is changed to 830 ° C. which is 825 ° C. + 5 ° C. at the temperature display section of the temperature controller 19 and the temperature of the heating furnace 3 is stabilized, the glass material 2 is again heated by the heating furnace 3 (FIG. 7 ( b)), the amount of deformation of the glass material 2 is measured by the same method as described above (see FIG. 7C), and the predetermined amount of deformation, that is, the amount of deformation corresponding to when the furnace temperature change amount is 0 ° C. Is determined (see FIG. 7D).
[0039]
Then, the furnace temperature adjustment operation of the heating furnace 3 is repeated until the measured deformation amounts A and B are within the deformation amount range when the furnace temperature change amount is 0 ° C. shown in Table 1, and heat softening is performed. When the deformation amount of the glass material 2 falls within the deformation amount range when the furnace temperature change amount is 0 ° C. shown in Table 1, the main forming for forming a large number of pieces is resumed (see FIG. 7E).
In addition, in the furnace temperature adjustment work in FIG. 7D, when the deformation amounts A and B of the glass material 2 after heat softening are less than 1.02 mm and less than 1.15 mm, respectively, the ranges shown in Table 1 Since the temperature of the heating furnace 3 is once increased by 15 ° C. on the temperature display portion of the temperature controller 19 and the temperature of the heating furnace 3 is stabilized, the deformation amount of the glass material 2 is reduced. Then, the furnace temperature is adjusted again in the same procedure as described above with reference to Table 1 again.
[0040]
On the contrary, in the furnace temperature adjustment work, in FIG. 7D, when the deformation amounts A and B of the glass material 2 after heat softening are 1.07 mm or more and 1.65 mm or more, respectively. Including, once the temperature of the heating furnace 3 is lowered by 15 ° C. on the temperature display portion of the temperature controller 19 and the temperature of the heating furnace 3 is stabilized, the deformation amount of the glass material 2 is measured, and Table 1 is used as a reference. The furnace temperature is adjusted in the same procedure as above.
[0041]
Furthermore, when the furnace temperature change amounts corresponding to the deformation amounts A and B are different, for example, when the deformation amount A is 1.02 mm and the deformation amount B is 1.26 mm, the deformation amount B corresponds. Adopt furnace temperature change + 5 ° C.
Here, when the display temperature of the heating furnace 3 remains unchanged at 825 ° C. without performing the furnace temperature adjustment work as described above, the deformation amount of the glass material 2 is measured as described above, and Table 1 is used as a reference. When the furnace temperature adjustment operation was performed and the display temperature of the heating furnace 3 was changed from 825 ° C. to 830 ° C., 120 pieces were continuously formed and the yield was compared. The former was 25% and the latter Was 99%.
[0042]
The furnace temperature adjustment operation may be performed manually by the operator based on the temperature displayed on the temperature display section of the temperature controller 19 or by changing the furnace temperature as shown in Table 1. The correlation between the amount and the deformation amount of the glass material 2 may be programmed in the temperature controller 19 in advance, and the temperature controller may be automatically operated by 19.
(effect)
According to the present embodiment, the amount of deformation of the glass material after heating and softening in the heating furnace is measured, and the temperature of the heating furnace is adjusted based on a table showing the correlation between the amount of deformation and the amount of change in furnace temperature. Because the glass material is heated and softened to the optimal viscosity for molding, temperature measurement uncertainty due to thermocouple deterioration, resistance wire deterioration, changes in atmospheric conditions, assembly after heating furnace decomposition and heating furnace The glass material can be heated and softened to an optimum viscosity without being affected by the environment of the heating furnace, such as a change or difference in the temperature rising process based on the solid difference.
[0043]
Therefore, a highly accurate optical element can be stably manufactured with a high yield.
In the present embodiment, when molding a specific lens, conditional molding is performed, and after obtaining optimum molding conditions, the main molding for a large number of manufacturing is performed. It is determined whether or not is heated and softened to the optimum viscosity by the heating furnace 3, and the furnace temperature adjustment work is performed when necessary. In particular, the optimum molding conditions are known from the beginning, and then the heating furnace If it seems that the adjustment of the furnace temperature of 3 is necessary, for example, when the heating furnace 3 is disassembled and replaced or replaced with another heating furnace 3 with the same configuration, the condition-controlled molding is performed. By performing the furnace temperature adjustment operation as described above immediately before performing the main molding without performing the above, the adjustment of the furnace temperature of the heating furnace 3 can be completed in a short time.
[0044]
The above-described embodiments of the invention include inventions having configurations (1) to (4) described below, and the operations and effects corresponding to these configurations are as follows.
(1) In the method for adjusting the viscosity of a glass material in a heating furnace of an optical element molding apparatus for heat-softening the glass material into a moldable state,
After heating and softening the glass material for an arbitrary time in the heating furnace, measuring the deformation amount of the glass material, by setting the temperature of the portion where the glass material of the heating furnace is located to a predetermined temperature based on the deformation amount, A method for adjusting the viscosity of a glass material in a heating furnace of an optical element molding apparatus, wherein the viscosity of the glass material inside the heating furnace is adjusted.
(2) After setting the temperature of the portion where the glass material of the heating furnace is located to a predetermined temperature based on the deformation amount, after measuring the deformation amount when the glass material is heated, the glass material of the heating furnace The display value indicating the temperature of the portion where the is located is changed to a display value obtained by adding a value corresponding to the measured deformation amount, and the value corresponding to the measured deformation amount is set in advance. A method for adjusting the viscosity of a glass material in a heating furnace of an optical element molding apparatus having the feature (1).
[0045]
The operation of the above configurations (1) and (2) is that after the glass material is heated and softened in the heating furnace of the molding apparatus, the glass material is pulled out from the heating furnace after an arbitrary time, and the amount of deformation of the glass material is measured. This is to adjust the viscosity by making it correspond to the viscosity of the glass material inside the furnace.
Further, the effects of the above configurations (1) and (2) are obtained by measuring the amount of deformation of the glass material after the glass material is heated and softened in a heating furnace, and based on the amount of deformation, the position of the glass material of the heating furnace. Since the temperature of the portion to be heated can be set to a predetermined temperature, the viscosity of the glass material inside the heating furnace is set to a viscosity suitable for molding of the optical element, the progress of deterioration of the thermocouple, and the arrangement of the resistance wire is slightly It is possible to adjust accurately without being influenced by the difference in the temperature rising process due to the difference.
(3) In a method for molding an optical element in which a glass material is heated and softened in a heating furnace in advance and press-molded with a pair of opposed molds,
After heating and softening the glass material in the heating furnace for an arbitrary time, measuring the deformation amount of the glass material, and setting the temperature of the portion where the glass material of the heating furnace is located to a predetermined temperature based on the deformation amount A method for molding an optical element, comprising adjusting a viscosity at the time of heat softening in the heating furnace.
(4) After setting the temperature of the portion where the glass material of the heating furnace is located to a predetermined temperature based on the deformation amount, after measuring the deformation amount when the glass material is heated, the glass material of the heating furnace The display value indicating the temperature of the portion where the is located is changed to a display value obtained by adding a value corresponding to the measured deformation amount, and the value corresponding to the measured deformation amount is set in advance. A method for forming an optical element having the feature (3).
[0046]
The operations of the above configurations (3) and (4) can be applied to the molding process by adjusting the viscosity of the glass material inside the heating furnace by the operation of the configuration (1) or (2) before pressing the glass material. Thus, a desired optical element can be stably obtained.
The effects of the above configurations (3) and (4) are that the glass material is heated and softened in a heating furnace, the deformation amount of the glass material is measured, and the portion of the heating furnace where the glass material is located based on the deformation amount Is set to a predetermined temperature, the viscosity of the glass material inside the heating furnace can be adjusted to a viscosity suitable for molding of the optical element. The optical element can be stably molded with a very good yield without being influenced by the difference in the temperature raising process due to the difference.
[0047]
【The invention's effect】
According to the inventions of claims 1 to 3, there is an influence on the environment of the heating furnace, such as deterioration of the thermocouple, change of atmospheric conditions, decomposition and maintenance of the heating furnace, and changes and differences in the temperature rising process based on the differences in the heating furnace. Accordingly, the glass material can be heated and softened to an optimum viscosity, and a high-precision optical element can be stably manufactured with a high yield.
[Brief description of the drawings]
FIG. 1 is a side sectional view of a conventional heating furnace.
FIG. 2 is a front view of a conventional heating furnace.
FIG. 3 is a side sectional view of a molding apparatus in an embodiment of the invention and is a view for explaining a process of measuring the amount of deformation by heating and softening a glass material.
FIG. 4 is a cross-sectional view of a molding apparatus according to an embodiment of the present invention and a view for explaining a step of heating and softening a glass material.
FIG. 5 is a side sectional view of the molding apparatus according to the embodiment of the present invention and is a view for explaining a process of molding the heat-softened glass material.
FIG. 6 is a view showing a state of a glass material heated and softened in a heating furnace according to an embodiment of the invention and a portion for measuring a deformation amount.
FIG. 7 is a flowchart showing a procedure of furnace temperature adjustment work in the embodiment of the invention.
[Explanation of symbols]
2 Glass material
3 Heating furnace
5 Upper mold
6 Lower mold
12 Resistance wire
16 Thermocouple
19 Temperature controller

Claims

In the method of molding an optical element to obtain an optical element by press-molding the glass material with a molding die after heating and softening the glass material into a moldable state by a heating furnace,
The amount of deformation of the glass material measured after being heated and softened by a heating furnace is the amount of deformation corresponding to the optimum viscosity when the heat-softened glass material is molded into an optical element with a mold.
A method for molding an optical element, comprising adjusting a temperature of a heating furnace.

In the method of molding an optical element to obtain an optical element by press-molding the glass material with a molding die after heating and softening the glass material into a moldable state by a heating furnace,
Heating furnace so that the amount of deformation of the glass material measured after heating and softening with a heating furnace is equivalent to the optimal viscosity (optimum viscosity) when the heat-softened glass material is molded into an optical element with a mold. When adjusting the temperature of
Heating furnace based on a table showing the correlation between the furnace temperature change amount, which is the temperature adjustment amount of the heating furnace, and the deformation amount of the glass material heat-softened by the heating furnace whose temperature is adjusted based on the furnace temperature change amount A method for molding an optical element, wherein the temperature of the optical element is adjusted.

In the method of molding an optical element to obtain an optical element by press-molding the glass material with a molding die after heating and softening the glass material into a moldable state by a heating furnace,
The viscosity of the glass material is centered on the temperature of the heating furnace at which the optimum viscosity (optimum viscosity) for obtaining an optical element by press molding with a molding die is centered, within a certain range up and down from the center temperature, and Set multiple temperature conditions with a certain temperature difference,
For each temperature condition, heat and soften the glass material individually to measure the deformation,
A value obtained by subtracting the value of each temperature condition from the temperature at the center is defined as a furnace temperature change amount, and each furnace temperature change amount corresponding to each temperature condition and a deformation amount of the glass material to be heated and softened by the heating furnace. Create a table showing the correlation,
Adjusting the temperature of the heating furnace based on the above table so that the deformation amount of the glass material heat-softened in the heating furnace matches the deformation amount corresponding to the optimum viscosity,
The method for molding an optical element according to claim 2.