JP4722371B2

JP4722371B2 - Method and apparatus for producing tempered glass

Info

Publication number: JP4722371B2
Application number: JP2002170115A
Authority: JP
Inventors: 紘正富永; 和成依田
Original assignee: Asahi Glass Co Ltd
Current assignee: AGC Inc
Priority date: 2002-06-11
Filing date: 2002-06-11
Publication date: 2011-07-13
Anticipated expiration: 2022-06-11
Also published as: JP2004010462A

Description

【０００１】
【発明の属する技術分野】
本発明は、強化ガラスの製造方法および装置に関し、特に自動車窓用の強化ガラスの製造方法および装置に関する。
【０００２】
【従来の技術】
近年、環境問題への社会的関心が高まり、自動車業界においては、省燃費の自動車が強く求められている。そのため、車体を軽量化する必要があり、自動車部品の軽量化が今まで以上に求められ、自動車用窓ガラスに対してもその例外ではない。自動車用窓ガラスは、搭乗者の安全を確保するため、合わせガラスや強化ガラスが使用されている。一部の車種を除き、合わせガラスが使用されているフロントガラス以外の窓には強化ガラスが使用されているため、強化ガラスの軽量化を実現することが車体の軽量化を図るには重要である。自動車用強化ガラスの軽量化を図る場合、ガラス板の板厚を現在主流の約２．８〜５ｍｍより薄くする必要があるため、これからは軽量化のための薄板化がいっそう進行すると考えられるが、安全性の面から容易に実現できないのが実状である。
【０００３】
自動車用強化ガラスは、一般的に以下に説明するように風冷強化によって製造される。まず、ガラス板を加熱炉に搬入し、軟化点近くまで加熱する。ガラス板を成形後に炉外に取り出し、または炉外に取り出した後に成形し、直ちに冷媒である空気をガラス板の表面に吹き付けて冷却する。このとき、ガラス板の表面層の方が内部の層よりも温度降下が早いため、断面方向に温度差が発生し、それに起因した表面に引張、内部に圧縮の方向の熱応力が発生する。しかし、ガラス板が粘性流動を起こしているため、応力の緩和現象により熱応力は緩和消失し、ガラス板の断面方向に温度差は存在するがほとんど応力のない状態になる。
【０００４】
冷却が進み最終的にガラス板が室温状態になったとき、高温時に緩和した熱応力の分だけ力の方向が逆転して、ガラス板の表面に残留圧縮応力層が、内部に残留引張応力層が形成される。このように製造された強化ガラスの残留応力は冷却時に形成されるガラス板の断面方向の温度分布に依存する。そのため、ガラス板の板厚が薄いほど、ガラス板の表面とガラス板の内部の温度差を大きくする事が難しい。その結果として自動車用の強化ガラスとして定められた安全規格を満足するために必要となる残留応力を得られない場合が出てくる。
【０００５】
よって、薄板ガラスを強化するには、現在主流の板厚の強化ガラスを製造する時より冷却能を高めなければならない。ここでいう薄板ガラスとは、現在使用されている自動車用の強化ガラスの板厚よりも薄いガラス板のことである。
【０００６】
ここで従来の強化方法における冷却手段の冷却能の履歴を熱伝達係数で表わしたものを図９（ａ）に、冷却中の風冷強化装置の風圧の履歴を図９（ｂ）に、冷却中のガラス板とノズル先端の距離を図９（ｃ）に示す。従来のガラス板の強化方法は、図９（ｂ）、（ｃ）に示すように、風圧や、ガラス板とノズル先端との距離は冷却中ほぼ一定である。よって、図９（ａ）のように冷却開始時から冷却中の最大値に近い冷却能で冷却する。以下に、薄板ガラスを強化するために、単に冷却能を高めた従来の強化方法の問題点を説明する。
【０００７】
軟化点近くまで加熱されたガラス板を冷却すると、ガラス板の表面層と内部の層の温度差に起因してガラス板の表面に引張方向の熱応力が発生する。このとき、ガラス板は粘性流動を起こしているので、応力の緩和現象により、熱応力は緩和消失していく。しかしながら、従来の強化方法では、冷却開始直後に発生する熱応力が大きいため、緩和速度が熱応力の発生速度に追いつかず、ガラス板の表面に緩和しきれなかった熱応力が引張応力として生じている状態になる。それによりガラス板の表面に存在する微細な傷が発展し、ガラス板が破砕してしまう冷却割れと呼ばれる現象が発生することがある。そのため、ガラス板の薄板化に対応して冷却能を高めると、ガラス板の表面に発生する引張応力が増大し、より冷却割れが発生し易くなるという問題が発生する。
【０００８】
【発明が解決しようとする課題】
したがって従来の方法のように、冷却開始時から冷却中の最大値に近い冷却能で冷却すると冷却割れが発生し易く、さらに薄板ガラスを強化するには、冷却能を高くしなければならないため、薄板ガラスの製造時は冷却割れが多発するようになる。
【０００９】
一方、冷却開始時のガラス温度を高温化すると、応力緩和の速度が速くなり、ガラス板の表面に発生する引張応力を減少させることができるが、高温ガラスの搬送、成形に起因する光学品質の悪化という別の問題が発生するため、ガラス高温化による冷却割れ防止効果には限界がある。
【００１０】
そこで、本発明の目的は、物理強化法による強化ガラスの製造方法において、自動車用強化ガラスの薄板化に伴う高冷却能化に起因するガラス板の冷却割れを減少させることができる強化ガラスの製造方法を提供することにある。
【００１１】
【課題を解決するための手段】
前記課題を解決するために本発明は、ガラス板を軟化点近くまで加熱し、このガラス板の表面を冷却手段を使って冷却することにより、前記ガラス板の表面に残留圧縮応力層を形成しかつ前記ガラス板の内部に残留引張応力層を形成する物理強化による強化ガラスの製造方法において、冷却開始から１ｓｅｃ間は前記冷却手段の冷却能を増加傾向に制御し、１ｓｅｃ〜３ｓｅｃの間は前記冷却手段の冷却能を冷却中の最大の冷却能に達するように制御することを特徴とする強化ガラスの製造方法を提供する。
【００１２】
また、前記冷却手段の冷却能は、冷却開始から前記最大の冷却能に達するまでの期間の前半の増加量がこの期間の後半の増加量よりも大きいことが好ましい。また、前記冷却手段は、風冷、ミスト冷却、接触冷却のうちのいずれかが好ましい。
【００１３】
また、前記何れかの強化ガラスの製造方法において、前記最大の冷却能は、前記ガラス板と同形状かつ同板厚の強化ガラスが破砕したときに、前記強化ガラスの周縁から２０ｍｍの幅の領域と破砕開始点を中心とした半径７５ｍｍの円内とを除いた領域で５０ｍｍ×５０ｍｍの正方形の枠内に４０〜４５０個の破片を生じさせる残留引張応力層を形成させるのに必要となる冷却能であることが好ましい。
【００１４】
また、前記何れかの強化ガラスの製造方法において、前記冷却手段は、前記ガラス板に冷媒となる気体を吹き付けるノズル群が配設された風箱と、前記冷媒となる気体を前記風箱内に送風するダクトとを備えた風冷強化装置であることが好ましい。
【００１５】
また、前記風冷強化装置において、前記最大の冷却能は、前記ガラス板に冷媒として吹き付ける気体による対流熱伝達係数が５００Ｗ／ｍ^２Ｋ以上であることが好ましい。
【００１６】
また、前記ガラス板の板厚は、１．５〜５．０ｍｍであることが好ましい。
【００１７】
また、前記ガラス板は、自動車用強化ガラスであることが好ましい。
【００１８】
また、加熱されたガラス板に冷媒となる気体を吹き付けるノズル群が配設された風箱と、前記冷媒となる気体を前記風箱内に送風するダクトとこのダクトに接続された風圧可変装置とを備え、前記風圧可変装置は、冷却開始から１ｓｅｃ間における前記風箱内の静圧を増加傾向に制御し、１ｓｅｃ〜３ｓｅｃの間における前記風箱内の静圧を冷却中の最大の圧力に達するように制御することを特徴とする風冷強化装置を提供する。
【００１９】
また、加熱されたガラス板に冷媒となる気体を吹き付けるノズル群が配設された風箱と、前記冷媒となる気体を前記風箱内に送風するダクトと、前記風箱に前記ガラス板と前記ノズル群先端との距離を制御する駆動装置とを備え、前記駆動装置は、冷却開始から１ｓｅｃ間における前記風冷強化装置の冷却能を増加傾向に制御し、１ｓｅｃ〜３ｓｅｃの間における前記風冷強化装置の冷却能を冷却中の最大の冷却能に達するように前記ガラス板と前記ノズル先端との距離を制御する手段を備えたことを特徴とする風冷強化装置を提供する。
【００２０】
本発明は、従来の冷却開始時から冷却中の最大値に近い冷却能で冷却する場合に比べ、冷却開始直後にガラス板の表面に発生する引張応力を低減させることが出来、つまり急冷中に発生するガラスの冷却割れを減少させ、かつ所望の残留応力を形成させる効果を有する。
【００２１】
【発明の実施の形態】
次に、本発明の実施の形態について図を用いて説明する。実施の形態１は、本発明の製造方法の実施の形態であり、実施の形態２、３は、本発明の製造装置の実施の形態である。
【００２２】
（実施の形態１）
図１（ａ）は、ガラス板を軟化点近くまで加熱し、このガラス板の表面を冷却手段を使って冷却するときの、前記冷却手段の冷却能の履歴を熱伝達係数で表わしたグラフである。実線が本発明の実施の形態を示し、破線は冷却開始時から冷却中の最大値に近い冷却能で冷却する従来例を示したものである（以下同様）。
【００２３】
図１（ｂ）は、冷却手段がガラス板に冷媒となる気体を吹き付けるノズル群が配設された風箱と、冷媒となる気体を風箱内に送風するダクトとを備えた風冷強化装置の場合において、ガラス板とノズル先端の距離が一定の際に、図１（ａ）の冷却能の履歴となる風冷強化装置の風圧の履歴である。
【００２４】
図１（ｃ）は、冷却手段がガラス板に冷媒となる気体を吹き付けるノズル群が配設された風箱と、冷媒となる気体を風箱内に送風するダクトと、風箱にガラス板とノズル先端との距離を制御する駆動装置とを備えた風冷強化装置の場合において、その風圧が一定の際に、図１（ａ）の冷却能の履歴となるガラス板とノズル先端の距離の履歴である。
【００２５】
Ａは本実施の形態においての粘性流動が発生している期間、Ｂは従来例においての粘性流動が発生している期間である。Ｃの期間は、始点が冷却開始時であり、終点が１ｓｅｃ〜３ｓｅｃの間である。
【００２６】
図２（ｄ）は、本実施の形態と従来例におけるガラス板Ｇの表面層Ｐと中央層Ｒの冷却状態を示した温度履歴、図２（ｅ）は、ガラス板Ｇの表面層Ｐとその内側の層Ｑの冷却状態を示した温度履歴、図２（ｆ）は、ガラス板Ｇの表面層Ｐと中央層Ｒの温度差、図２（ｇ）は、ガラス板Ｇの表面層Ｐの応力発生状態を示したグラフである。ガラス板Ｇの表面層Ｐとは、図３に示すように、板厚がｔであるガラス板Ｇの断面図において、ガラス板Ｇの断面を表面から中心αまで分割した、最も表面側にあるＰ層のことであり、中央層とは最も中心線α側にあるＲ層のことで、表面層Ｐの内側の層とは、表面層Ｐの中心線α側に一つ隣の層であるＱ層のことである。
【００２７】
本実施の形態の冷却は、図１（ａ）に示すように、冷却開始時からＣの期間、冷却手段の冷却能は増加し、冷却中の最大の冷却能となるように制御することである。つまり、冷却開始後１ｓｅｃ間は冷却手段の冷却能を増加傾向に制御し、１ｓｅｃ〜３ｓｅｃの間は冷却手段の冷却能を冷却中の最大の冷却能に達するように制御することである。
【００２８】
Ｃの期間、本実施の形態の冷却能は、従来例の冷却能より小さいため、図２（ｅ）に示すように、本実施の形態は、従来例より表面層Ｐとその内側の層Ｑの温度差が最大となる時間がＤ遅くなる。そのため、冷却開始直後の熱応力の発生速度に緩和速度が追いつかずに表面層Ｐに大きな引張応力が発生するということがなくなる。さらに、その後、本実施の形態の冷却能は上昇していくが、徐々に温度差を発生させているため、表面層Ｐとその内側の層Ｑの温度差の最大値は従来例よりΔＴ_Ｘ小さくなり、熱応力が急激に発生することがなく、表面層の引張応力の発生の抑制に繋がる。つまり、本実施の形態では、従来例に比べ、ガラス板Ｇの断面方向に徐々に温度差を増加させているため、発生する熱応力の変化量が小さくなる。そのため、発生する熱応力に応力緩和が追いついて、緩和されずに蓄積されていく熱応力が小さくなる。よって、従来の冷却の冷却開始直後のような大きな引張応力は発生しなくなる。その結果、本実施の形態は、図２（ｇ）のように表面層に発生する引張応力の最大値が従来例よりΔσ低減され、表面層引張応力に起因した冷却割れが減少する。
【００２９】
一方、強化ガラスの残留応力は、熱応力の緩和量に依存している。本実施の形態の表面層Ｐと中央層Ｒの温度差は、図２（ｆ）に示すように、徐々に温度差が増加していき、従来の冷却より最大値となる時間が遅れ，わずかであるが温度差もΔＴ_Ｙ小さくなる。しかし、本実施の形態は、温度差ΔＴ_Ｙが小さく抑えられているため、従来の冷却とほぼ同等の大きさの表面層Ｐと中央層Ｒの温度差に起因した熱応力が生じている。また、本実施の形態は、温度降下が遅れるが、ガラス板が粘性流動を生じている時間が従来例よりＡ−Ｂの期間長くなるため、冷却時間全体では、熱応力の緩和量は従来例とほぼ同等となる。よって、緩和される熱応力に大きな減少がないため、室温時には所望の残留応力が得られる。
【００３０】
本実施の形態は、図１（ａ）に示すように、Ｃの期間、冷却能が増加傾向を辿るが、冷却能が一時的に減少したり、一定になったり、振動しても構わなく、増加傾向にあればよい。Ｃの期間の前半の冷却能の増加率がＣの期間の後半の増加率よりも大きくなることが、冷却能に対して効率的に残留応力を形成するために好ましい。本実施の形態における好ましい応力の発生状態は、冷却割れが発生しない程度にガラス板の表面層に引張応力が発生した後、発生する熱応力と応力緩和の速度を等しくすることである。また本実施の形態は、風冷、ミスト冷却、接触冷却など、冷却手段は問わない。
【００３１】
（実施の形態２）
図１（ｂ）のように、冷却中の風圧を変化させる強化ガラスの製造方法とその装置についての本発明の実施の形態を図を用いて以下に説明する。図４は、冷媒として気体を用いた風冷強化による強化ガラスの製造方法において、ガラス板３に吹き付ける気体の風圧を制御することにより対流熱伝達係数を変動させる本実施の形態の冷却手段である。図４に示すように、加熱されたガラス板３に冷媒となる気体を吹き付けるノズル群が配設された風箱４、５と、冷媒となる気体を風箱４、５内に送風するダクト６と、このダクト６に接続された風圧可変装置２、風圧可変装置２に接続された制御装置１を備えている。ガラス板３とノズル先端の距離ａは一定である。風圧は風箱４、５内の静圧のことを示し、ガラス板３に吹き付ける気体による対流熱伝達係数で冷却能を表現する。
【００３２】
従来例の強化ガラスの製造方法は、冷媒となる気体を送風するダクト６に配設されたダンパーの開閉により、冷却開始と同時に冷媒となる気体をガラス板に吹き付けるため、風圧を制御することはできなかった。本実施の形態では、図４の制御装置１に本実施の形態の図１（ａ）に基づく冷却能履歴、つまり対流熱伝達係数を入力しておく。加熱されたガラス板３が冷却リング７上に載置されて風箱４、５の間に移動してくると、制御装置１は現在の風圧と気体温度から図１（ａ）の冷却能履歴に基づいた最適な風圧の変動量を計算し、ダクト６に設置している風圧可変装置２に信号を送り、風圧可変装置２は風圧を増加させる、または減少させるように働き、冷却能を制御する。また、現在の風圧と気体の温度を計測する検出装置を風箱４、５に設置して制御装置１に情報を送り、冷却中は、常に最適な風圧となるように管理する。
【００３３】
また本実施の形態は、図１（ａ）の冷却能履歴を実現するように図１（ｂ）に示す風圧履歴通りに風圧を変動させるよう制御装置１に風圧可変装置２の動きを入力しておけば、検出装置がなくとも図１（ａ）の冷却能履歴に従った強化ガラスの製造が実施できる。
【００３４】
（実施の形態３）
図１（ｃ）のように、冷却中のガラス板３とノズル先端との距離ａを変化させた強化ガラスの製造方法とその装置の本発明の実施の形態を図を用いて以下に説明する。図５は、冷媒として気体を用いた風冷強化による強化ガラスの製造方法において、ガラス板３とノズル先端の距離ａを制御することにより対流熱伝達係数を変動させる本実施の形態の冷却手段である。図５に示すように、加熱されたガラス板３に冷媒となる気体を吹き付けるノズル群が配設された風箱４、５と、冷媒となる気体を風箱４、５内に送風するダクトと、ガラス板３とノズル群先端の距離ａの変動用に風箱４、５に駆動装置９とを備えている。風圧は風箱４、５内の静圧のことを示し、ガラス板３に吹き付ける気体による対流熱伝達係数で冷却能を表現する。
【００３５】
従来例の強化ガラスの製造方法は、冷却中に風箱４、５がガラス板３に近づいたり、離れたりすることはなく、一定であった。本実施の形態では、図５の制御装置８に本実施の形態の図１（ａ）に基づく冷却能履歴、つまり熱伝達係数を入力しておく。加熱されたガラス板３が冷却リング７上に載置されて風箱４、５の間に移動してくると、制御装置８は現在の風圧と気体温度、風箱位置（ガラス板３とノズル先端の距離ａ）から図１（ａ）の冷却能履歴に基づいた最適なガラス板３とノズル先端の距離ａの変動量を計算し、風箱４、５に設置している駆動装置９に信号を送り、駆動装置９は、ガラス板３に接近する、または離れるように風箱４、５を動かし、冷却能を制御する。また、現在の風圧と気体温度、ガラス板３とノズル先端の距離ａを計測する検出装置を風箱４、５に設置して制御装置９に情報を送り、冷却中は、常に最適なガラス板３とノズル先端の距離ａとなるように管理する。
【００３６】
ここで、本実施の形態の風箱４、５の動き（ガラス板３とノズル先端の距離ａ）を図６に示す。図６（ａ）は、冷却開始時のガラス板３と風箱４、５の位置関係であり、本実施の形態のように、冷却が進むにつれて冷却能が増加する場合には、冷却が進むと図１（ｃ）のガラス板３とノズル先端の距離の履歴に従って、図６（ｂ）のように風箱４、５がガラス板３に接近していき、最終的には、図６（ｃ）のように図１（ａ）中の最大の冷却能になる位置まで接近する。
【００３７】
また本実施の形態は、図１（ａ）の冷却能履歴を実現するように、風圧が一定であり、図１（ｃ）に示すガラス板３とノズル先端の距離ａの履歴通りに風箱位置を変動させるよう制御装置８に駆動装置９の動きを入力しておけば、検出装置がなくとも図１（ａ）の冷却能履歴に従った強化ガラスの製造は可能である。風圧が一定でなくとも風圧履歴が既知であれば、ガラス板３とノズル先端の距離ａの履歴を予め求めておいて、制御装置８に駆動装置９の動きを入力しておけば、本実施の形態の強化ガラスの製造方法を実施することができる。
【００３８】
【実施例】
以下に本発明の実施例を図を用いて説明する。図７（ａ）は冷媒として空気を用いた物理強化による強化ガラスの製造方法において、加熱されたガラス板に冷媒となる空気を吹き付けるノズル群が配設された風箱と、前記冷媒となる空気を前記風箱内に送風するダクトを備えた風冷強化装置の冷却能の履歴を、ガラス板に吹き付ける気体による対流熱伝達係数で表現したものである。ここで、点線で示す実施例（１）は冷却中の最大の冷却能に達する時間が１ｓｅｃ、実線で示す実施例（２）は冷却中の最大の冷却能に達する時間が２ｓｅｃ、一点鎖線で示す実施例（３）は冷却中の最大の冷却能に達する時間が３ｓｅｃとなるものを表している。破線で示す比較例（１）は、冷却開始時から冷却中の最大値に近い冷却能で冷却する従来の冷却方法の冷却能の履歴を表したものである。実施例（１）〜（３）と比較例（１）の冷却能の最大値は、板厚が２．５ｍｍ以下のような薄板ガラスを物理強化するのに必要となる高い冷却能で７８１Ｗ／ｍ^２Ｋである。二点鎖線で示す比較例（２）は、冷却開始時から冷却中の最大値に近い冷却能で冷却する従来の冷却方法の冷却能の履歴を表したもので、冷却能の最大値が前述の従来例に比べて低く、６２０Ｗ／ｍ^２Ｋである。
【００３９】
図７（ａ）において、比較例（１）の対流熱伝達係数は、風箱の静圧が４０ｋＰａ、空気温度５０℃、ガラス板とノズル先端の距離３０ｍｍに相当し、比較例（２）は風箱の静圧２０ｋＰａ、空気温度５０℃、ガラス板とノズル先端の距離３０ｍｍに相当する。本実施例を冷媒となる空気の風圧を制御して実施した場合、実施例（１）は、空気温度５０℃、ガラス板とノズルの距離３０ｍｍで風箱の静圧を１ｓｅｃ後に４０ｋＰａになるよう時間に比例して上昇させた対流熱伝達係数の履歴に相当し、実施例（２）、実施例（３）も同様にそれぞれ２ｓｅｃ後、３ｓｅｃ後に風箱の静圧を４０ｋＰａまで上昇させた対流熱伝達係数の履歴に相当する。図７（ｂ）は、そのときの風圧履歴を示したグラフである。
【００４０】
また、ガラス板とノズル先端の距離を制御して図７（ａ）の冷却能履歴を実施した場合は、風箱静圧３０ｋＰａで一定、空気温度５０℃のときに、図７（ｃ）のガラス板とノズルの距離の履歴通りにノズル位置が移動したときの対流熱伝達係数の履歴に相当する。
【００４１】
図８（ｄ）は、板厚が２．５ｍｍのガラス板を６４０℃まで加熱し、図７（ａ）の実施例（１）〜（３）、比較例（１）、（２）の冷却能の履歴に従って急冷した場合に、ガラス板の表面層とその内側の層の温度差の履歴を示したものである。そのときの表面層と中央層の温度差の履歴が図８（ｅ）であり、表面層に発生する応力の履歴が図８（ｆ）である。ここでのガラス板の表面層とは、図３のように、２．５ｍｍのガラス板を断面方向に中心から表面まで１０分割したガラス板の表面側の層のことであり、その内側の層とは表面層から１つ中心側の層のことであり、中央層とは最も中心側の層のことである。
【００４２】
軟化点近くまで加熱されたガラス板を比較例（１）や比較例（２）のように冷却開始時から冷却中の最大値に近い冷却能で冷却した場合、図８（ｄ）に示すように冷却開始直後に表面層とその内側の層の温度差が最大となり、この温度差に応じた大きさの熱応力が冷却開始直後にガラス板の表面層に発生する。ガラス板が粘性流動を起こしていても、冷却開始直後に発生する熱応力はすべてが緩和されるわけではなく、ガラス板の表面層で緩和されなかった熱応力は図８（ｆ）のように引張応力として表れ、実施例（１）〜（３）に比べ、早い時期に最大となる。
【００４３】
実施例（１）〜（３）のように冷却能が最大となる時間を遅らせた冷却能履歴で冷却した場合、図８（ｄ）に示すように冷却開始直後の表面層とその内側の層の温度差は最大とはならず、実施例（１）、実施例（２）、実施例（３）のそれぞれは、冷却開始後１ｓｅｃ、１．６５ｓｅｃ、１．８５ｓｅｃで最大となる。よって、表面層とその内側の層に徐々に温度差を付けていくことになり、発生する熱応力の変動が小さくなる。そのため、応力緩和の遅れも小さくなり、比較例（１）に比べ、図８（ｆ）に示すようにガラス板の表面層に発生する引張応力を低減でき、冷却割れを減少させる効果を有する。
【００４４】
また、強化ガラスの残留応力値は急冷時にガラス板が粘性流動を起こしているときの熱応力の緩和量に依存している。そのため、ガラス板が粘性流動を起こしている間にガラス板の断面方向に大きな温度差を発生させることで、実施例（１）〜（３）のように冷却能が最大となる時間を遅らせた冷却能履歴で急冷した場合であっても、表面層と中央層の温度差を充分に付けることができ、所望の残留応力を形成できる。
【００４５】
図８（ｆ）に示す最大表面層引張応力と室温時の残留応力である中央残留引張応力を表１に示す。
【００４６】
【表１】

【００４７】
実施例（１）の場合は、比較例（１）の場合と比較して、中央残留引張応力の減少がほとんどなく、最大表面層引張応力を１１．２ＭＰａ減少させることができ、冷却割れを減少させる効果が得られる。また、比較例（２）の場合と比較しても、最大表面層引張応力はほぼ同等で、中央残留引張応力は５．６ＭＰａの増加という結果が得られる。よって、物理強化による強化ガラスの製造方法において、比較例（２）では所望の残留応力が得られず、比較例（１）のように冷却能を上げて残留応力を増加させようとしたが、冷却割れが発生するようになった場合に有効である。
【００４８】
実施例（２）の場合は、比較例（１）の場合と比較して、中央残留引張応力が４．５ＭＰａ減少してしまうが、最大表面層引張応力を２０．９ＭＰａと大幅に減少させることができ、冷却割れの減少に効果が得られる。また、比較例（２）の場合と比較しても、最大表面層引張応力を８．２ＭＰａ低く抑えることができ、中央残留引張応力は２．６ＭＰａ上回ることができ、冷却割れの減少、残留応力の両面で上回る効果が得られる。よって、実施例（１）で冷却割れが減少しない場合、比較例（２）で冷却割れが発生している場合、または残留応力値が小さい場合に有効である。
【００４９】
実施例（３）の場合は、比較例（２）の場合と比較して、最大表面層引張応力を１３．１ＭＰａ減少させることができ、冷却割れの減少に効果が得られ、中央残留引張応力もほぼ同等である。よって、比較例（２）で所望の残留応力が得られているが、冷却割れが発生している場合に有効である。
【００５０】
【発明の効果】
以上に説明したように本発明によれば、以下に記載する効果を奏する。物理強化による強化ガラスの製造方法において、ガラス板の急冷強化時に所望の残留応力が得られる範囲で冷却手段の冷却能が最大に達する時間を遅らせることにより、冷却時にガラス板の表面層に発生する引張応力を低減できるため、所望の残留応力を確保し、かつ冷却割れを減少させることができる。また、本発明を用いることにより、自動車用強化ガラスの薄板化を図る際に、所望の残留応力を得るために冷却能を増加させても、強化中の冷却割れを減少させることができるため、従来よりも効率的な生産ができる。
【図面の簡単な説明】
【図１】（ａ）本実施の形態と従来例の冷却能の履歴、（ｂ）図１（ａ）の冷却能の履歴を風圧制御で実施した場合の風圧の履歴、（ｃ）図１（ａ）の冷却能の履歴をガラス板とノズル先端の距離の制御で実施した場合のガラス板とノズル先端の距離の履歴を示したグラフである。
【図２】（ｄ）図１（ａ）の冷却能の履歴でガラス板を急冷強化したときのガラス板の表面層と中央層の温度の履歴、（ｅ）図１（ａ）の冷却能の履歴でガラス板を急冷強化したときのガラス板の表面層とその内側の層の温度差の履歴、（ｆ）図１（ａ）の冷却能の履歴でガラス板を急冷強化したときのガラス板の表面層と中央層の温度差の履歴、（ｇ）図１（ａ）の冷却能の履歴でガラス板を急冷強化したときのガラス板の表面層に発生する応力の履歴を示したグラフである。
【図３】ガラス板を層に分割した断面図である。
【図４】冷却能を風圧で制御するための装置構成を示すブロック図である。
【図５】冷却能をガラス板とノズル先端の距離で制御するための装置構成を示すブロック図である。
【図６】冷却能をガラス板とノズル先端の距離で制御したときの風箱位置を示す概略断面図である。
【図７】（ａ）本実施例と比較例の冷却能の履歴、（ｂ）図７（ａ）の冷却能の履歴を風圧制御で実施した場合の風箱静圧の履歴、（ｃ）図７（ａ）の冷却能の履歴をガラス板とノズル先端の距離の制御で実施した場合のガラス板とノズル先端の距離の履歴で示したグラフである。
【図８】（ｄ）図７（ａ）の冷却能の履歴でガラス板を急冷強化したときのガラス板の表面層とその内側の層の温度差の履歴、（ｅ）図７（ａ）の冷却能の履歴でガラス板を急冷強化した時のガラス板の表面層と中央層の温度差の履歴、（ｆ）図７（ａ）の冷却能の履歴でガラス板を急冷強化した時のガラス板の表面層に発生する応力の履歴である。
【図９】（ａ）従来例の冷却能の履歴、（ｂ）従来例の風圧の履歴、（ｃ）従来例のガラス板とノズル先端の距離の履歴を示したグラフである。
【符号の説明】
Ａ：本実施の形態での粘性流動発生期間
Ｂ：従来例での粘性流動発生期間
Ｃ：本実施の形態の冷却能が最大に達するまでの期間
Ｇ：ガラス板
Ｐ：表面層
Ｑ：内側の層
Ｒ：中央層
ｔ：板厚
α：中心線
ａ：ガラス板とノズル先端の距離
１：制御装置
２：風圧可変装置
３：ガラス板
４、５：風箱
６：冷媒となる気体の供給管
７：冷却リング
８：制御装置
９：駆動装置[0001]
BACKGROUND OF THE INVENTION
  The present invention relates to a method and apparatus for manufacturing tempered glass, and more particularly to a method and apparatus for manufacturing tempered glass for automobile windows.
[0002]
[Prior art]
  In recent years, social interest in environmental issues has increased, and in the automobile industry, fuel-saving automobiles are strongly demanded. Therefore, it is necessary to reduce the weight of the vehicle body, and it is required to reduce the weight of automobile parts more than ever, and this is no exception for automobile window glass. Laminated glass and tempered glass are used for automobile window glass in order to ensure the safety of passengers. Except for some models, tempered glass is used for windows other than windshields that use laminated glass, so reducing the weight of tempered glass is important for reducing vehicle weight. is there. In order to reduce the weight of tempered glass for automobiles, it is necessary to make the thickness of the glass plate thinner than the current mainstream of about 2.8 to 5 mm. Actually, it cannot be easily realized from the viewpoint of safety.
[0003]
  The tempered glass for automobiles is generally manufactured by air-cooling tempering as described below. First, a glass plate is carried into a heating furnace and heated to near the softening point. After the glass plate is formed, it is taken out of the furnace, or taken out of the furnace and then molded, and immediately, air as a coolant is blown onto the surface of the glass plate to cool it. At this time, since the temperature drop of the surface layer of the glass plate is faster than the inner layer, a temperature difference is generated in the cross-sectional direction, and a thermal stress in the direction of tension and compression in the surface is generated due to the temperature difference. However, since the glass plate is in a viscous flow, the thermal stress relaxes and disappears due to the stress relaxation phenomenon, and there is almost no stress although there is a temperature difference in the cross-sectional direction of the glass plate.
[0004]
  When cooling progresses and the glass plate finally reaches room temperature, the direction of force is reversed by the amount of thermal stress relaxed at high temperatures, and a residual compressive stress layer is formed on the surface of the glass plate and a residual tensile stress layer is formed on the inside. Is formed. The residual stress of the tempered glass manufactured in this way depends on the temperature distribution in the cross-sectional direction of the glass plate formed during cooling. Therefore, it is difficult to increase the temperature difference between the surface of the glass plate and the inside of the glass plate as the plate thickness of the glass plate is thinner. As a result, there may be a case where the residual stress necessary for satisfying the safety standard established for tempered glass for automobiles cannot be obtained.
[0005]
  Therefore, in order to strengthen the thin glass, it is necessary to increase the cooling ability compared with the case of manufacturing the currently mainstream tempered glass. The thin glass here is a glass plate thinner than the thickness of the tempered glass for automobiles currently used.
[0006]
  Here, FIG. 9 (a) shows the history of the cooling capacity of the cooling means in the conventional strengthening method as a heat transfer coefficient, and FIG. 9 (b) shows the history of the wind pressure of the air cooling strengthening apparatus during cooling. The distance between the inner glass plate and the nozzle tip is shown in FIG. In the conventional method for strengthening a glass plate, as shown in FIGS. 9B and 9C, the wind pressure and the distance between the glass plate and the nozzle tip are substantially constant during cooling. Therefore, as shown in FIG. 9A, cooling is performed with a cooling capacity close to the maximum value during cooling from the start of cooling. Below, the problem of the conventional tempering method which simply improved the cooling capability in order to strengthen the thin glass will be described.
[0007]
  When the glass plate heated to near the softening point is cooled, a thermal stress in the tensile direction is generated on the surface of the glass plate due to the temperature difference between the surface layer of the glass plate and the inner layer. At this time, since the glass plate is in a viscous flow, the thermal stress relaxes and disappears due to the stress relaxation phenomenon. However, in the conventional strengthening method, since the thermal stress generated immediately after the start of cooling is large, the relaxation rate cannot keep up with the generation rate of the thermal stress, and the thermal stress that could not be completely relaxed on the surface of the glass plate is generated as tensile stress. It will be in a state. As a result, fine flaws existing on the surface of the glass plate develop, and a phenomenon called cooling cracking in which the glass plate is crushed may occur. For this reason, when the cooling ability is increased in response to the thinning of the glass plate, the tensile stress generated on the surface of the glass plate increases, which causes a problem that cooling cracks are more likely to occur.
[0008]
[Problems to be solved by the invention]
  Therefore, as in the conventional method, cooling cracking is likely to occur when cooling with a cooling capacity close to the maximum value during cooling from the start of cooling, and to further strengthen the thin glass, the cooling capacity must be increased, Cooling cracks frequently occur during the production of thin glass.
[0009]
  On the other hand, when the glass temperature at the start of cooling is increased, the rate of stress relaxation increases, and the tensile stress generated on the surface of the glass plate can be reduced. Since another problem of deterioration occurs, there is a limit to the effect of preventing cooling cracking due to the high temperature of the glass.
[0010]
  Accordingly, an object of the present invention is to produce a tempered glass that can reduce cooling cracking of the glass plate due to the high cooling ability associated with the thinning of the tempered glass for automobiles in the method for producing tempered glass by a physical tempering method. It is to provide a method.
[0011]
[Means for Solving the Problems]
  In order to solve the above problems, the present invention forms a residual compressive stress layer on the surface of the glass plate by heating the glass plate to near the softening point and cooling the surface of the glass plate using a cooling means. And in the manufacturing method of tempered glass by physical strengthening which forms a residual tensile stress layer inside the glass plate, the cooling capacity of the cooling means tends to increase for 1 sec from the start of cooling.controlAnd the cooling capacity of the cooling means reaches the maximum cooling capacity during cooling for 1 to 3 seconds.controlA method for producing tempered glass is provided.
[0012]
  Moreover, it is preferable that the amount of increase in the first half of the period from the start of cooling until reaching the maximum cooling capacity is greater than the amount of increase in the second half of this period.Further, the cooling means is preferably any of air cooling, mist cooling, and contact cooling.
[0013]
  In any one of the methods for producing tempered glass, the maximum cooling capacity is a region having a width of 20 mm from the periphery of the tempered glass when the tempered glass having the same shape and thickness as the glass plate is crushed. Cooling required to form a residual tensile stress layer that generates 40 to 450 pieces in a square frame of 50 mm × 50 mm in a region excluding the inside of a circle having a radius of 75 mm centering on the crush start point Preferably.
[0014]
  In any one of the above-described methods for producing tempered glass, the cooling means includes a wind box in which a nozzle group that blows a gas that serves as a refrigerant is disposed on the glass plate, and a gas that serves as the refrigerant in the wind box. It is preferable that it is an air-cooling strengthening apparatus provided with the duct which ventilates.
[0015]
  In the wind-cooling strengthening apparatus, the maximum cooling capacity is such that a convective heat transfer coefficient by a gas blown as a refrigerant on the glass plate is 500 W / m.²It is preferable that it is K or more.
[0016]
  Moreover, it is preferable that the plate | board thickness of the said glass plate is 1.5-5.0 mm.
[0017]
  Moreover, it is preferable that the said glass plate is tempered glass for motor vehicles.
[0018]
  A wind box provided with a nozzle group for blowing a gas serving as a refrigerant to a heated glass plate; a duct for blowing the refrigerant gas into the wind box; and a wind pressure variable device connected to the duct. The wind pressure variable device tends to increase the static pressure in the wind box during 1 sec from the start of cooling.controlAnd the static pressure in the wind box between 1 sec and 3 sec reaches the maximum pressure during cooling.controlAn air cooling strengthening device is provided.
[0019]
  Further, a wind box provided with a nozzle group for blowing a gas serving as a refrigerant to the heated glass plate, a duct for blowing the gas serving as the refrigerant into the wind box, the glass plate and the wind box The distance from the nozzle group tipcontrolThe drive device tends to increase the cooling capacity of the air-cooling strengthening device in 1 second from the start of cooling.controlAnd a means for controlling the distance between the glass plate and the nozzle tip so that the cooling capacity of the air-cooling strengthening device between 1 sec and 3 sec reaches the maximum cooling capacity during cooling. An air cooling strengthening device is provided.
[0020]
  The present invention can reduce the tensile stress generated on the surface of the glass plate immediately after the start of cooling, compared to the case of cooling with a cooling capacity close to the maximum value during cooling from the start of conventional cooling, that is, during rapid cooling. It has the effect of reducing the generated cooling cracks of the glass and forming a desired residual stress.
[0021]
DETAILED DESCRIPTION OF THE INVENTION
  Next, embodiments of the present invention will be described with reference to the drawings. Embodiment 1 is an embodiment of a manufacturing method of the present invention, and Embodiments 2 and 3 are embodiments of a manufacturing apparatus of the present invention.
[0022]
  (Embodiment 1)
  FIG. 1 (a) is a graph showing the history of cooling ability of the cooling means as a heat transfer coefficient when the glass plate is heated to near the softening point and the surface of the glass plate is cooled using a cooling means. is there. A solid line indicates an embodiment of the present invention, and a broken line indicates a conventional example in which cooling is performed with a cooling capacity close to the maximum value during cooling from the start of cooling (the same applies hereinafter).
[0023]
  FIG. 1B shows a wind-cooling strengthening apparatus including a wind box in which a nozzle group for blowing a gas serving as a refrigerant on a glass plate is provided by a cooling unit and a duct for blowing the gas serving as a refrigerant into the wind box. In this case, when the distance between the glass plate and the nozzle tip is constant, the air pressure history of the air cooling strengthening device becomes the history of the cooling performance of FIG.
[0024]
  FIG. 1 (c) shows a wind box in which a nozzle group for blowing a gas serving as a refrigerant on a glass plate is provided by a cooling means, a duct for blowing a gas serving as a refrigerant into the wind box, and a glass plate on the wind box. The distance from the nozzle tipcontrolWhen the wind pressure is constant in the case of a wind-cooling strengthening device provided with a driving device that performs the above, the history of the distance between the glass plate and the tip of the nozzle, which is the history of the cooling performance of FIG.
[0025]
  A is a period during which viscous flow is occurring in the present embodiment, and B is a period during which viscous flow is occurring in the conventional example. In the period of C, the start point is when cooling starts and the end point is between 1 sec and 3 sec.
[0026]
  FIG. 2D shows a temperature history showing the cooling state of the surface layer P and the central layer R of the glass plate G in the present embodiment and the conventional example, and FIG. 2E shows the surface layer P of the glass plate G. 2 (f) shows the temperature difference between the surface layer P and the central layer R of the glass plate G, and FIG. 2 (g) shows the surface layer P of the glass plate G. It is the graph which showed the stress generation | occurrence | production state of. As shown in FIG. 3, the surface layer P of the glass plate G is on the most surface side in which the cross section of the glass plate G is divided from the surface to the center α in the cross-sectional view of the glass plate G whose thickness is t. The P layer is the R layer that is closest to the center line α side, and the inner layer of the surface layer P is the layer next to the center line α side of the surface layer P. Q layer.
[0027]
  In the cooling of the present embodiment, as shown in FIG. 1A, the cooling capacity of the cooling means increases during the period C from the start of cooling so that the maximum cooling capacity during cooling is obtained.controlIt is to be. In other words, the cooling capacity of the cooling means tends to increase for 1 second after the start of cooling.controlAnd between 1 sec and 3 sec, the cooling capacity of the cooling means reaches the maximum cooling capacity during cooling.controlIt is to be.
[0028]
  Since the cooling capacity of the present embodiment is smaller than the cooling capacity of the conventional example during the period C, as shown in FIG. 2 (e), the present embodiment has a surface layer P and a layer Q inside thereof as compared with the conventional example. The time during which the temperature difference becomes maximum D is delayed. As a result, the relaxation rate does not catch up with the generation rate of the thermal stress immediately after the start of cooling, and a large tensile stress is not generated in the surface layer P. Further, after that, the cooling capacity of the present embodiment increases, but since the temperature difference is gradually generated, the maximum value of the temperature difference between the surface layer P and the inner layer Q is ΔT from the conventional example._XIt becomes small, thermal stress does not generate | occur | produce rapidly, and it leads to suppression of generation | occurrence | production of the tensile stress of a surface layer. That is, in this embodiment, since the temperature difference is gradually increased in the cross-sectional direction of the glass plate G, the amount of change in the generated thermal stress is smaller than in the conventional example. Therefore, the stress relaxation catches up with the generated thermal stress, and the thermal stress accumulated without being relaxed becomes small. Therefore, a large tensile stress that occurs immediately after the start of cooling in the conventional cooling is not generated. As a result, in the present embodiment, as shown in FIG. 2G, the maximum value of the tensile stress generated in the surface layer is reduced by Δσ from the conventional example, and cooling cracks due to the surface layer tensile stress are reduced.
[0029]
  On the other hand, the residual stress of tempered glass depends on the relaxation amount of thermal stress. As shown in FIG. 2 (f), the temperature difference between the surface layer P and the center layer R of the present embodiment gradually increases, and the time when the maximum value is reached is delayed slightly compared to the conventional cooling. However, the temperature difference is also ΔT_YGet smaller. However, in this embodiment, the temperature difference ΔT_YTherefore, the thermal stress due to the temperature difference between the surface layer P and the central layer R, which is approximately the same size as that of the conventional cooling, is generated. In addition, in this embodiment, the temperature drop is delayed, but the time during which the glass plate is in a viscous flow is longer than the conventional example by the period AB, so that the amount of thermal stress relaxation is the conventional example over the entire cooling time. Is almost the same. Therefore, since there is no significant decrease in the thermal stress to be relaxed, a desired residual stress can be obtained at room temperature.
[0030]
  In the present embodiment, as shown in FIG. 1A, the cooling capacity continues to increase during the period C. However, the cooling capacity may be temporarily reduced, become constant, or oscillate. If it is in an increasing trend. It is preferable that the increase rate of the cooling capacity in the first half of the period C is larger than the increase rate in the second half of the period C in order to efficiently form the residual stress with respect to the cooling capacity. A preferred stress generation state in the present embodiment is to make the generated thermal stress equal to the rate of stress relaxation after tensile stress is generated in the surface layer of the glass plate to such an extent that cooling cracks do not occur. In the present embodiment, any cooling means such as air cooling, mist cooling, contact cooling, etc. may be used.
[0031]
  (Embodiment 2)
  As shown in FIG. 1B, an embodiment of the present invention for a method and apparatus for producing tempered glass that changes the wind pressure during cooling will be described below with reference to the drawings. FIG. 4 shows the cooling means of the present embodiment in which the convective heat transfer coefficient is varied by controlling the wind pressure of the gas blown onto the glass plate 3 in the method for producing tempered glass by wind cooling strengthening using gas as the refrigerant. . As shown in FIG. 4, a

wind box

4, 5 provided with a nozzle group for blowing a gas serving as a refrigerant to the heated glass plate 3, and a duct 6 for blowing the gas serving as a refrigerant into the

wind box

4, 5. And a wind pressure variable device 2 connected to the duct 6 and a control device 1 connected to the wind pressure variable device 2. The distance a between the glass plate 3 and the nozzle tip is constant. The wind pressure indicates the static pressure in the

wind boxes

4 and 5, and the cooling ability is expressed by a convective heat transfer coefficient by the gas blown to the glass plate 3.
[0032]
In the conventional method for producing tempered glass, the air pressure is controlled by opening and closing the damper disposed in the duct 6 for blowing the refrigerant gas, so that the refrigerant gas is blown onto the glass plate simultaneously with the start of cooling. could not. In the present embodiment, the cooling capacity history based on FIG. 1A of the present embodiment, that is, the convective heat transfer coefficient is input to the control device 1 of FIG. When the heated glass plate 3 is placed on the cooling ring 7 and moves between the

wind boxes

4 and 5, the control device 1 determines the cooling capacity history of FIG. 1A from the current wind pressure and gas temperature. The optimal amount of fluctuation in wind pressure is calculated based on the above, and a signal is sent to the wind pressure variable device 2 installed in the duct 6, and the wind pressure variable device 2 works to increase or decrease the wind pressure and control the cooling capacity. To do. Further, a detection device for measuring the current wind pressure and gas temperature is installed in the

wind boxes

4 and 5 to send information to the control device 1 and managed so as to always have an optimum wind pressure during cooling.
[0033]
  Further, in the present embodiment, the movement of the wind pressure variable device 2 is input to the control device 1 so as to vary the wind pressure according to the wind pressure history shown in FIG. 1B so as to realize the cooling performance history of FIG. In this case, the tempered glass can be manufactured according to the cooling capacity history of FIG.
[0034]
  (Embodiment 3)
  As shown in FIG. 1 (c), an embodiment of the present invention of a tempered glass manufacturing method and its apparatus in which the distance a between the glass plate 3 being cooled and the nozzle tip is changed will be described below with reference to the drawings. . FIG. 5 shows the cooling means of the present embodiment in which the convective heat transfer coefficient is varied by controlling the distance a between the glass plate 3 and the nozzle tip in a method for producing tempered glass by air cooling strengthening using gas as a refrigerant. is there. As shown in FIG. 5,

wind boxes

4 and 5 in which nozzle groups for blowing a gas that serves as a refrigerant to the heated glass plate 3 are disposed, and a duct that blows the gas that serves as a refrigerant into the

wind boxes

4 and 5. The

windboxes

4 and 5 are provided with driving devices 9 for changing the distance a between the glass plate 3 and the nozzle group tip. The wind pressure indicates the static pressure in the

wind boxes

4 and 5, and the cooling ability is expressed by a convective heat transfer coefficient by the gas blown to the glass plate 3.
[0035]
The manufacturing method of the tempered glass of a prior art example was constant, without the

windboxes

4 and 5 approaching or leaving the glass plate 3 during cooling. In the present embodiment, the cooling capacity history based on FIG. 1A of the present embodiment, that is, the heat transfer coefficient, is input to the control device 8 of FIG. When the heated glass plate 3 is placed on the cooling ring 7 and moves between the

wind boxes

4 and 5, the control device 8 determines the current wind pressure and gas temperature, the wind box position (the glass plate 3 and the nozzle). From the tip distance a), the amount of variation in the distance between the optimum glass plate 3 and nozzle tip a based on the cooling performance history of FIG. A signal is sent, and the drive device 9 moves the

wind boxes

4 and 5 so as to approach or leave the glass plate 3 to control the cooling capacity. In addition, a detection device for measuring the current wind pressure and gas temperature and the distance a between the glass plate 3 and the nozzle tip is installed in the

wind boxes

4 and 5 to send information to the control device 9, and during cooling, the optimum glass plate is always used. 3 and the distance a between the nozzle tip is managed.
[0036]
Here, the movement (distance a between the glass plate 3 and the nozzle tip a) of the

wind boxes

4 and 5 of the present embodiment is shown in FIG. FIG. 6A shows the positional relationship between the glass plate 3 and the

wind boxes

4 and 5 at the start of cooling. When the cooling capacity increases as the cooling proceeds as in the present embodiment, the cooling proceeds. In accordance with the history of the distance between the glass plate 3 and the nozzle tip in FIG. 1 (c), the

wind boxes

4 and 5 approach the glass plate 3 as shown in FIG. 6 (b). As shown in c), the position approaches the position where the maximum cooling capacity in FIG.
[0037]
  Further, in the present embodiment, the wind pressure is constant so as to realize the cooling performance history of FIG. 1A, and the wind box follows the history of the distance a between the glass plate 3 and the nozzle tip shown in FIG. If the movement of the driving device 9 is input to the control device 8 so as to change the position, the tempered glass can be manufactured according to the cooling performance history of FIG. If the wind pressure history is known even if the wind pressure is not constant, the history of the distance a between the glass plate 3 and the nozzle tip is obtained in advance, and if the movement of the drive device 9 is input to the control device 8, this implementation is performed. The manufacturing method of the tempered glass of the form can be implemented.
[0038]
【Example】
  Embodiments of the present invention will be described below with reference to the drawings. FIG. 7 (a) shows a method for producing tempered glass by physical strengthening using air as a refrigerant, a wind box provided with a nozzle group for blowing air as refrigerant on a heated glass plate, and air as the refrigerant. The history of the cooling ability of the air-cooling strengthening device provided with the duct for blowing the air into the wind box is expressed by the convective heat transfer coefficient by the gas blown to the glass plate. Here, in Example (1) indicated by the dotted line, the time to reach the maximum cooling capacity during cooling is 1 sec, and in Example (2) indicated by the solid line, the time to reach the maximum cooling capacity during cooling is 2 sec. The example (3) shown represents that the time to reach the maximum cooling capacity during cooling is 3 seconds. The comparative example (1) indicated by a broken line represents a history of cooling ability of a conventional cooling method in which cooling is performed with a cooling ability close to the maximum value during cooling from the start of cooling. The maximum value of the cooling capacity of Examples (1) to (3) and Comparative Example (1) is 781 W / in, which is a high cooling capacity required for physically strengthening a thin glass having a thickness of 2.5 mm or less. m²K. The comparative example (2) indicated by the two-dot chain line represents the history of the cooling capacity of the conventional cooling method in which cooling is performed with the cooling capacity close to the maximum value during cooling from the start of cooling. 620W / m²K.
[0039]
  In FIG. 7A, the convective heat transfer coefficient of Comparative Example (1) corresponds to a static pressure of the wind box of 40 kPa, an air temperature of 50 ° C., and a distance between the glass plate and the nozzle tip of 30 mm, and Comparative Example (2) is This corresponds to an air box static pressure of 20 kPa, an air temperature of 50 ° C., and a distance of 30 mm between the glass plate and the nozzle tip. When this embodiment is carried out by controlling the wind pressure of the air serving as the refrigerant, the embodiment (1) is such that the static pressure of the wind box becomes 40 kPa after 1 sec at an air temperature of 50 ° C. and a distance between the glass plate and the nozzle of 30 mm. This corresponds to the history of the convection heat transfer coefficient increased in proportion to the time, and the convection in which the static pressure of the wind box was increased to 40 kPa after 2 sec and 3 sec, respectively, in the examples (2) and (3). Corresponds to the history of heat transfer coefficient. FIG. 7B is a graph showing the wind pressure history at that time.
[0040]
  Further, when the cooling capacity history of FIG. 7 (a) is performed by controlling the distance between the glass plate and the nozzle tip, when the wind box static pressure is constant at 30kPa and the air temperature is 50 ° C., FIG. 7 (c). This corresponds to the history of the convective heat transfer coefficient when the nozzle position moves according to the history of the distance between the glass plate and the nozzle.
[0041]
  FIG.8 (d) heats the glass plate whose plate | board thickness is 2.5 mm to 640 degreeC, and cools Example (1)-(3) of FIG. 7 (a), Comparative example (1), (2). The graph shows the history of the temperature difference between the surface layer of the glass plate and the inner layer when quenched according to the performance history. FIG. 8E shows the history of the temperature difference between the surface layer and the central layer at that time, and FIG. 8F shows the history of the stress generated in the surface layer. The surface layer of the glass plate here is a layer on the surface side of the glass plate obtained by dividing a 2.5 mm glass plate from the center to the surface in the cross-sectional direction as shown in FIG. The term “layer” refers to a layer on the center side from the surface layer, and the center layer refers to a layer on the most central side.
[0042]
  When the glass plate heated to near the softening point is cooled with the cooling ability close to the maximum value during cooling from the start of cooling as in Comparative Example (1) and Comparative Example (2), as shown in FIG. In addition, immediately after the start of cooling, the temperature difference between the surface layer and the inner layer becomes maximum, and thermal stress having a magnitude corresponding to this temperature difference is generated in the surface layer of the glass plate immediately after the start of cooling. Even if the glass plate is in a viscous flow, the thermal stress generated immediately after the start of cooling is not all relieved, and the thermal stress that has not been relieved by the surface layer of the glass plate is as shown in FIG. Appears as a tensile stress, and becomes maximum at an earlier time than Examples (1) to (3).
[0043]
  When cooling is performed with a cooling capacity history in which the time for which the cooling capacity is maximized is delayed as in Examples (1) to (3), the surface layer immediately after the start of cooling and the inner layer thereof as shown in FIG. The temperature difference of (1), (2), and (3) is maximum at 1 sec, 1.65 sec, and 1.85 sec after the start of cooling. Therefore, a temperature difference is gradually made between the surface layer and the inner layer, and the fluctuation of the generated thermal stress is reduced. Therefore, the delay of stress relaxation is reduced, and the tensile stress generated in the surface layer of the glass plate can be reduced as shown in FIG.
[0044]
  Further, the residual stress value of the tempered glass depends on the amount of relaxation of thermal stress when the glass plate is causing viscous flow during rapid cooling. Therefore, by generating a large temperature difference in the cross-sectional direction of the glass plate while the glass plate is undergoing viscous flow, the time when the cooling capacity is maximized is delayed as in Examples (1) to (3). Even in the case of rapid cooling due to the cooling capacity history, a sufficient temperature difference between the surface layer and the central layer can be provided, and a desired residual stress can be formed.
[0045]
  Table 1 shows the maximum surface layer tensile stress shown in FIG. 8 (f) and the central residual tensile stress which is the residual stress at room temperature.
[0046]
[Table 1]

[0047]
  In the case of Example (1), compared with the case of Comparative Example (1), there is almost no decrease in the central residual tensile stress, the maximum surface layer tensile stress can be reduced by 11.2 MPa, and cooling cracks are reduced. Effect is obtained. Further, even when compared with the case of Comparative Example (2), the maximum surface layer tensile stress is almost the same and the central residual tensile stress is increased by 5.6 MPa. Therefore, in the method for producing tempered glass by physical strengthening, the desired residual stress was not obtained in Comparative Example (2), and the residual stress was increased by increasing the cooling capacity as in Comparative Example (1). This is effective when cooling cracks are generated.
[0048]
  In the case of Example (2), the central residual tensile stress is reduced by 4.5 MPa as compared with the case of Comparative Example (1), but the maximum surface layer tensile stress is greatly reduced to 20.9 MPa. This is effective in reducing cooling cracks. Also, compared with the case of Comparative Example (2), the maximum surface layer tensile stress can be suppressed by 8.2 MPa, the central residual tensile stress can exceed 2.6 MPa, the cooling crack can be reduced, the residual stress The effect which exceeds in both sides is acquired. Therefore, it is effective when cooling cracks are not reduced in Example (1), when cooling cracks are generated in Comparative Example (2), or when the residual stress value is small.
[0049]
  In the case of Example (3), the maximum surface layer tensile stress can be reduced by 13.1 MPa as compared with the case of Comparative Example (2), and an effect is obtained in reducing the cooling cracks, and the central residual tensile stress. Is almost equivalent. Therefore, although the desired residual stress is obtained in the comparative example (2), it is effective when a cooling crack is generated.
[0050]
【The invention's effect】
  As described above, according to the present invention, the following effects can be obtained. In the manufacturing method of tempered glass by physical strengthening, it is generated in the surface layer of the glass plate at the time of cooling by delaying the time when the cooling ability of the cooling means reaches the maximum within the range where the desired residual stress can be obtained at the time of rapid strengthening of the glass plate. Since the tensile stress can be reduced, a desired residual stress can be ensured and cooling cracks can be reduced. In addition, by using the present invention, when thinning the tempered glass for automobiles, even if the cooling capacity is increased to obtain a desired residual stress, cooling cracks during strengthening can be reduced. More efficient production than before.
[Brief description of the drawings]
1A is a history of cooling performance of the present embodiment and the conventional example, FIG. 1B is a history of cooling pressure when the history of cooling performance of FIG. 1A is implemented by wind pressure control, and FIG. It is the graph which showed the log | history of the distance of the glass plate and the nozzle tip at the time of implementing the log | history of the cooling capacity of (a) by control of the distance of a glass plate and a nozzle tip.
2D is a history of the temperature of the surface layer and the center layer of the glass plate when the glass plate is quenched and strengthened with the history of the cooling capability shown in FIG. 1A, and FIG. 2E is the cooling capability shown in FIG. The history of the temperature difference between the surface layer of the glass plate and the inner layer when the glass plate is quenched and tempered with the history of (f), the glass when the glass plate is quenched and strengthened with the history of the cooling capacity of FIG. History of temperature difference between surface layer and center layer of plate, (g) Graph showing history of stress generated in surface layer of glass plate when quenching and strengthening glass plate with history of cooling ability in FIG. It is.
FIG. 3 is a sectional view in which a glass plate is divided into layers.
FIG. 4 is a block diagram showing an apparatus configuration for controlling the cooling capacity by wind pressure.
FIG. 5 is a block diagram showing an apparatus configuration for controlling the cooling capacity by the distance between the glass plate and the nozzle tip.
FIG. 6 is a schematic cross-sectional view showing the wind box position when the cooling capacity is controlled by the distance between the glass plate and the nozzle tip.
7A is a history of cooling capacity of the present embodiment and the comparative example, FIG. 7B is a history of cooling capacity of the wind box when the history of cooling capacity of FIG. It is the graph which showed the log | history of the distance of the glass plate and nozzle tip at the time of implementing the log | history of the cooling capability of Fig.7 (a) by control of the distance of a glass plate and a nozzle tip.
8D is a history of the temperature difference between the surface layer of the glass plate and the inner layer when the glass plate is quenched and strengthened with the history of cooling ability in FIG. 7A; FIG. The history of the temperature difference between the surface layer and the central layer of the glass plate when the glass plate is quenched and strengthened with the history of cooling ability of (f) When the glass plate is quenched and strengthened with the history of cooling ability of FIG. It is the history of the stress which generate | occur | produces in the surface layer of a glass plate.
FIGS. 9A and 9B are graphs showing a history of cooling performance in a conventional example, a history of wind pressure in a conventional example, a history of distance between a glass plate and a nozzle tip in a conventional example, and FIG.
[Explanation of symbols]
A: Viscous flow generation period in this embodiment
B: Viscous flow generation period in the conventional example
C: Period until the cooling capacity of the present embodiment reaches the maximum
G: Glass plate
P: Surface layer
Q: inner layer
R: Central layer
t: thickness
α: Center line
a: Distance between glass plate and nozzle tip
1: Control device
2: Wind pressure variable device
3: Glass plate
4, 5: Wind box
6: Gas supply pipe as refrigerant
7: Cooling ring
8: Control device
9: Drive device

Claims

By heating the glass plate to near the softening point and cooling the surface of the glass plate using a cooling means, a residual compressive stress layer is formed on the surface of the glass plate and a residual tensile stress layer is formed inside the glass plate. In the manufacturing method of tempered glass by physical strengthening to form the cooling capacity, the cooling capacity of the cooling means is controlled to increase for 1 sec from the start of cooling, and the cooling capacity of the cooling means is the maximum during cooling for 1 sec to 3 sec. The manufacturing method of the tempered glass characterized by controlling so that cooling ability may be reached.

2. The tempered glass according to claim 1, wherein the cooling capacity of the cooling means is controlled such that an increase in the first half of the period from the start of cooling to the maximum cooling capacity is greater than an increase in the second half of this period. Manufacturing method.

Said cooling means Gami strike cooling method for tempered glass according to claim 1 or 2 is whether contact cooling Neu deviation.

The cooling means is air-cooled, and the maximum cooling capacity is that when a tempered glass having the same shape and thickness as the glass plate is crushed, an area having a width of 20 mm from the periphery of the tempered glass and crushing start. This is the cooling ability required to form a residual tensile stress layer that generates 40 to 450 pieces in a 50 mm × 50 mm square frame in a region excluding a circle with a radius of 75 mm centered on a point. method for producing a tempered glass according to claim 1 or 2.

The cooling means includes a wind box provided with a nozzle group that blows a gas that serves as a refrigerant on the glass plate, a duct that blows the gas that serves as the refrigerant into the wind box, and the wind cooling strengthening device includes a wind pressure variable device . Ri air cooling tempering apparatus der with the wind pressure variable unit, the static pressure in the air box is controlled to increase between 1sec start of cooling, the static pressure in the air box between 1sec~3sec largest manufacturing method of strengthening glass according to claim 1, 2 or any one of 4 you and controls so as to reach the pressure during cooling.

The cooling means includes a wind box in which a nozzle group that blows a gas that serves as a refrigerant on the glass plate, a duct that blows the gas that serves as a refrigerant into the wind box, the glass plate, and a tip of the nozzle group. And a driving device for controlling the distance of the air cooling strengthening device, wherein the driving device controls the cooling capacity of the air cooling strengthening device in an increasing tendency for 1 sec from the start of cooling, and for 1 sec to 3 sec. The means of controlling the distance of the said glass plate and the said nozzle front-end | tip so that the cooling capacity of the said wind-cooling strengthening apparatus may reach the maximum cooling capacity during cooling is provided. The manufacturing method of the tempered glass as described in any one.

The maximum cooling capacity, method of manufacturing a glass reinforced according to claim 5 or 6 convective heat transfer coefficient due to the gas is 500 W / m 2 ^K or more blowing as a refrigerant to said glass plate.

The thickness of the glass plate, at 1.5 to 5.0 mm, the manufacturing method of the tempered glass according to any one of claims 1 to 7 that is used as a window glass of an automobile.

A wind box provided with a nozzle group for blowing a gas serving as a refrigerant onto a heated glass plate, a duct for blowing the gas serving as a refrigerant into the wind box, and a wind pressure variable device connected to the duct. ,
The wind pressure variable device controls the static pressure in the wind box in an increasing tendency for 1 sec from the start of cooling so that the static pressure in the wind box reaches the maximum pressure during cooling for 1 sec to 3 sec. An air cooling strengthening device characterized by controlling.

A wind box provided with a nozzle group for blowing a gas to be a refrigerant on a heated glass plate, a duct for blowing the gas to be a refrigerant into the wind box, the glass plate and the nozzle group in the wind box A drive device for controlling the distance from the tip,
The drive device controls the cooling capacity of the wind-cooling strengthening apparatus in an increasing tendency for 1 sec from the start of cooling, and reaches the maximum cooling capacity during cooling of the cooling capacity of the wind-cooling strengthening apparatus between 1 sec and 3 sec. As described above, an air cooling strengthening device comprising means for controlling the distance between the glass plate and the tip of the nozzle.