JP2008273800A - Glass flow path and method for manufacturing optical glass molded body using the flow path - Google Patents
Glass flow path and method for manufacturing optical glass molded body using the flow path Download PDFInfo
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Description
本発明は、所定量の光学ガラス塊を製造する技術に関する。 The present invention relates to a technique for producing a predetermined amount of optical glass block.
近年、デジタルカメラやプロジェクタなどの光学機器の分野においては、小型化、軽量化が要求され、それに伴い、使用レンズ枚数を減らすことができる非球面レンズの需要が増加している。 In recent years, in the field of optical devices such as digital cameras and projectors, there has been a demand for miniaturization and weight reduction, and accordingly, there is an increasing demand for aspheric lenses that can reduce the number of lenses used.
通常、光学系を構成するレンズには一般に球面レンズと非球面レンズがある。多くの球面レンズは、ガラス材料をリヒートプレス成形して得られたガラス成形品を研削研磨することによって製造される。一方、非球面レンズは、加熱軟化したプリフォームを、高精度な成形面をもつ金型でプレス成形し、金型の高精度な成形面の形状をプリフォーム材に転写して得る方法、すなわち、精密プレス成形によって製造されることが主流となっている。 In general, the lenses constituting the optical system generally include a spherical lens and an aspheric lens. Many spherical lenses are manufactured by grinding and polishing a glass molded product obtained by reheat press molding a glass material. On the other hand, an aspheric lens is a method in which a heat-softened preform is press-molded with a mold having a high-precision molding surface, and the shape of the high-precision molding surface of the mold is transferred to a preform material, that is, It is mainly produced by precision press molding.
精密プレス成形用プリフォームとしては、球形、楕円球又は扁平状ガラス成形体(ガラスゴブ)が使用されることが多いが、これらは、原料ガラスを坩堝等の溶融装置で溶融した後、溶融装置に連結されたノズル等から成形型上に流出させ、板状ガラスや棒状ガラス等に成形し、それらをさらに冷間加工することにより製造することができる。また、近年では、ノズル等の流路から流出する溶融ガラスを、シャーにより切断して、或いは表面張力を利用して分離し、例えばガスを噴出する多孔質型上に流下(滴下)させ、浮上成形させることにより、適当な大きさ及び形状のガラスゴブに調整する技術が用いられる。ただし前者ではシャーによる切断の痕跡がガラスゴブに残ることがあるため、近年ではもっぱら後者が用いられることが多い。 As a precision press-molding preform, a spherical, elliptical or flat glass molded body (glass gob) is often used. These materials are melted in a melting apparatus such as a crucible and then melted in a melting apparatus. It can be manufactured by allowing it to flow out from a connected nozzle or the like onto a mold, forming it into plate-like glass or rod-like glass, and further cold-working them. Further, in recent years, molten glass flowing out from a flow path such as a nozzle is cut by a shear or separated by using surface tension, and flows down (drops) onto, for example, a porous mold that ejects gas, and then floats. A technique for adjusting the glass gob to an appropriate size and shape by molding is used. However, in the former case, traces of cutting by the shear may remain on the glass gob, so in recent years the latter is often used.
上記のいずれの手段においても、流路からガラスを流出させる場合、そのガラス流の温度、流出量を制御するため、或いは成形の際に生じる脈理、失透等の不良発生を防ぐため、そのノズルについては様々な形状が考案されてきた。近年、光学ガラスの高屈折率化に伴う液相温度の高温化及び/又は粘性の低粘性化、あるいは低温軟化に伴う粘性の低粘性化に対応すべく様々な手法が考案されてきたが、十分には対応し切れていないのが現状である。 In any of the above means, when glass is caused to flow out of the flow path, in order to control the temperature and flow rate of the glass flow, or to prevent defects such as striae and devitrification occurring during molding, Various shapes have been devised for the nozzle. In recent years, various methods have been devised to cope with the increase in the liquid phase temperature and / or the decrease in the viscosity accompanying the increase in the refractive index of the optical glass, or the decrease in the viscosity associated with the softening at a low temperature. The current situation is not enough.
特許文献1には、流路本体の径よりも流出口の径を大きくすることにより、例えば流路末端の溶融ガラス流出口をテーパー状に開くことにより、溶融ガラス流を流路流出口により長い時間滞留させ、ガラスの流下のタイミングを遅延制御することができるノズルが記載されている。 In Patent Document 1, the diameter of the outlet is made larger than the diameter of the channel main body, for example, the molten glass outlet at the end of the channel is opened in a tapered shape so that the molten glass flow is longer than the channel outlet. Nozzles are described that can be held for a period of time to delay the timing of glass flow.
特許文献2には、溶融ガラスが溶融装置から流れ始めて、パイプを通過し、流出口から流出する際に、内部に絞りを加えることにより流速分布を一様にさせ、成分が揮発した変質ガラスの滞留を抑え、脈理の発生を防ぐ方法が記載されている。また、絞りによる流量低下を防止するために、絞り部の温度を絞り部以外よりも高温に制御することが記載されている。 In Patent Document 2, when molten glass starts to flow from a melting apparatus, passes through a pipe, and flows out from an outlet, the flow velocity distribution is made uniform by adding a constriction inside, and the modified glass in which the components are volatilized is disclosed. A method is described that suppresses retention and prevents striae. In addition, it is described that the temperature of the throttle portion is controlled to be higher than that other than the throttle portion in order to prevent the flow rate from being reduced due to the throttle.
特許文献3には、流路の内部に抵抗部材を設けて流路断面の中央を流れるガラス流の流速を低減させ、取得できるガラスゴブの最大重量を増加させる方法が記載されている。 Patent Document 3 describes a method in which a resistance member is provided inside a flow path to reduce the flow velocity of the glass flow flowing through the center of the cross section of the flow path and increase the maximum weight of the glass gob that can be obtained.
しかし、上記従来の方法は以下のような問題点を有していた。 However, the above conventional methods have the following problems.
一般的には、溶融ガラスを、流路を介して溶融槽から流出させ、成形型にて成形する場合には、溶融槽から流出口まで低下させた温度制御を行い、成形に適した温度まで溶融ガラス温度を下げる必要がある。ここで、例えば流出後に、ガラス成分の揮発に由来する脈理が発生することがあるが、この場合には流路制御温度を下げることで対応しなければならない。しかしながら、溶融ガラス流は、すなわち高温側から低温側へ向かう高粘性流体の流れであり、ノズル内の温度は内壁面近傍が低く、断面重心付近が高くなる。また、流速分布は内壁面近傍では低く、断面重心付近では高い値を示す。 In general, when molten glass is flowed out of a melting tank through a flow path and molded with a molding die, temperature control is performed by reducing the temperature from the melting tank to the outlet to a temperature suitable for molding. It is necessary to lower the molten glass temperature. Here, for example, striae derived from the volatilization of the glass component may occur after the outflow, but in this case, it is necessary to cope with this by lowering the flow path control temperature. However, the molten glass flow is a flow of a highly viscous fluid that goes from the high temperature side to the low temperature side, and the temperature inside the nozzle is low near the inner wall surface and high near the center of gravity of the cross section. Further, the flow velocity distribution is low near the inner wall surface and is high near the center of gravity of the cross section.
ノズルの温度測定に基づく制御を行った場合、流路での測定温度は内壁面近傍のガラス温度をほぼ正確に表しているものの、ガラス流中心温度(すなわち流路内の流路断面重心付近を通過するガラス流の温度)とは乖離した低い温度を示す。そのため、液相温度が高いガラスでは、ガラス流中心が揮発を生じない温度に低下する以前に、流路温度(流路内壁近傍のガラス温度)は結晶を成長する温度、いわゆる失透温度まで低下してしまい、失透の発生を招くことがある。 When control based on nozzle temperature measurement is performed, the measured temperature in the flow path represents the glass temperature in the vicinity of the inner wall surface almost accurately. The temperature of the passing glass stream) is a low temperature. Therefore, in glass with a high liquidus temperature, the flow path temperature (the glass temperature near the inner wall of the flow path) drops to the temperature at which crystals grow, the so-called devitrification temperature, before the glass flow center drops to a temperature at which no volatilization occurs. This may cause devitrification.
特許文献1に記載される流路では、流出口がテーパー状に開き内径が大きくなっているため、内壁面とガラス流中心との温度差および流速差が増大し、上述の傾向がより顕著となる。 In the flow path described in Patent Document 1, since the outlet is tapered and the inner diameter is increased, the temperature difference and the flow velocity difference between the inner wall surface and the glass flow center are increased, and the above-described tendency is more prominent. Become.
特許文献2のような絞りを有する流路を使用した場合、ガラス流の流出速度分布の一様化の効果はあるが、流路断面重心付近の高温のガラス流を取り出すことになるため、流出時に揮発由来の脈理を防止することは困難である。揮発を抑えようと制御温度を下げると、直ちに失透発生・成長を生じやすく、これにより絞り部の流路を塞いでしまい、流出そのものが停止しやすい。実施例では、絞りによる流量低下を抑制するために、絞り部の温度を絞り部以外よりも高温に設定しており、近年の高屈折率ガラスの製造に適した方法ではないことが明らかである。 When a flow path having a restriction as in Patent Document 2 is used, there is an effect of uniforming the flow velocity distribution of the glass flow, but a high temperature glass flow near the center of gravity of the cross section of the flow channel is taken out. Sometimes it is difficult to prevent striae from volatilization. If the control temperature is lowered to suppress volatilization, devitrification is likely to occur and grow immediately, thereby blocking the flow path of the throttle portion, and the outflow itself is likely to stop. In the example, in order to suppress the flow rate drop due to the restriction, the temperature of the restriction part is set to a temperature higher than that other than the restriction part, and it is clear that this is not a method suitable for the production of high refractive index glass in recent years. .
特許文献3に記載される流路は、内部の中央に設けた抵抗部材によって中央部の溶融ガラスの流下速度を遅延させており、流出速度の速度分布の一様化は成されるものの、熱容量の小さい貴金属を主成分とする小さな抵抗部材では、直ちに高温のガラス流中心温度になってしまう。そのため、ガラス流中心温度を下げる効果は得られず、揮発由来の脈理の抑制効果はない。また、特許文献3中の図3のように支持部材を用いて抵抗部材を固定する必要があり、白金等の貴金属を主成分とするガラス流出用流路として加工するのは極めて困難である。 The flow path described in Patent Document 3 delays the flow rate of the molten glass at the center by a resistance member provided at the center of the inside, and the velocity distribution of the outflow rate is made uniform, but the heat capacity In a small resistance member mainly composed of a small noble metal, the glass flow center temperature immediately becomes high. Therefore, the effect of lowering the glass flow center temperature cannot be obtained, and there is no effect of suppressing striae derived from volatilization. Further, as shown in FIG. 3 in Patent Document 3, it is necessary to fix the resistance member using a support member, and it is extremely difficult to process the glass outlet channel mainly containing a noble metal such as platinum.
また、特許文献3の請求項4にはルツボ底部に複数の流路が設けられ、当該複数の流路の各々の先端部は、互いに連結されることにより一つの流路口を構成していることを特徴としているが、複数流路の各々の中心で高温のガラス流が発生し、流下するガラス流中心温度を低下させる効果は得られない。これらのような複雑な構造を適用すると、ガラスの温度、粘度、濡れ、密度及び液圧に適応するための構造の変更が極めて困難なため、流速や温度分布も複雑化するため、その点においても、より単純な構造が求められていた。 Further, in claim 4 of Patent Document 3, a plurality of channels are provided at the bottom of the crucible, and tip portions of the plurality of channels are connected to each other to form one channel port. However, the high temperature glass flow is generated at the center of each of the plurality of flow paths, and the effect of lowering the glass flow center temperature flowing down cannot be obtained. Applying such a complicated structure makes it very difficult to change the structure to adapt to the temperature, viscosity, wetting, density, and fluid pressure of the glass, which also complicates the flow rate and temperature distribution. However, a simpler structure was sought.
本発明では、通常、中央付近の流速が大きくなる傾向があるガラス流路において、その流速を平均化することにより、脈理や失透の発生を低減させる。そして、その結果として、成形条件の選定が非常に難しい近年の高屈折ガラスあるいは低温軟化ガラスのガラス塊を、簡単かつ高品質に得るための流路を提供するものである。さらに、従来のガラスにおいても、簡単かつ短距離での制御を可能とし、装置の小型化が可能な流路を提供することを目的とする。 In the present invention, the occurrence of striae and devitrification is usually reduced by averaging the flow velocity in the glass flow path where the flow velocity near the center tends to increase. As a result, the present invention provides a flow path for obtaining a glass lump of recent high refractive glass or low temperature softened glass which is very difficult to select molding conditions easily and with high quality. It is another object of the present invention to provide a flow path that enables simple and short-distance control even in conventional glass, and that can reduce the size of the apparatus.
本発明者は、複数の穴を有する仕切板を用いて流路を仕切り、場合によってはその穴の面積を、流速との関係で所定の値に制限することにより、温度・流速分布を平均化させることに加え、所望の温度・流速分布が得られ、結果として脈理等の不利益を抑えることができることを見出し、上記課題を解決するに至った。 The present inventors partition the flow path using a partition plate having a plurality of holes, and in some cases limit the area of the holes to a predetermined value in relation to the flow velocity, thereby averaging the temperature / flow velocity distribution. In addition to the above, the inventors have found that a desired temperature / flow velocity distribution can be obtained, and as a result, disadvantages such as striae can be suppressed, and the above problems have been solved.
本発明の第1の構成は、溶融ガラス槽に接続され、溶融ガラスを流出させる流路であり、溶融ガラスの流出方向に略垂直に設置された1以上の仕切板により複数の部分に仕切られ、当該仕切板にはガラス流を通過させるための穴が複数個設けられていることを特徴とする前記流路である。 A first configuration of the present invention is a flow path that is connected to a molten glass tank and allows molten glass to flow out, and is partitioned into a plurality of parts by one or more partition plates that are installed substantially perpendicular to the flowing direction of the molten glass. The partition plate is provided with a plurality of holes for allowing glass flow to pass therethrough.
本発明の第2の構成は、前記仕切板に設けられた複数個の穴は、流路断面の重心からの距離が大きいほど、その面積が小さいことを特徴とする前記構成1の流路である。 According to a second configuration of the present invention, the plurality of holes provided in the partition plate have a smaller area as the distance from the center of gravity of the channel cross section is larger. is there.
本発明の第3の構成は、前記仕切板設置位置において、仕切板がない場合の流路断面中心での流速をa、流路断面重心から半径方向にrだけ離れた位置の流速をbとし、設置される仕切板の中心の穴の断面積をc、仕切板の中心から半径方向にrだけ離れた位置の穴の断面積をdとした場合に、b×c=a×dの関係が成立するように、ガラス流を通過させる穴が設けられている前記構成2の流路である。 In the third configuration of the present invention, at the partition plate installation position, a flow velocity at the center of the channel cross section when there is no partition plate is a, and b is a flow velocity at a position r away from the center of gravity of the channel cross section in the radial direction. B × c = a × d, where c is the cross-sectional area of the center hole of the partition plate to be installed, and d is the cross-sectional area of the hole located at a distance r from the center of the partition plate in the radial direction. The flow path of the configuration 2 is provided with a hole through which the glass flow passes so that the above is established.
本発明の第4の構成は、ガラス原料を溶融槽にて溶融し、溶融槽に接続されたノズルを介して溶融ガラス流を成形型へ流出させガラス成形体を成形することを含むガラス成形体の製造方法であって、溶融ガラスを、前記構成1〜3の流路を通過させることにより流路内の温度分布を平均化させる工程を含む前記製造方法である。 According to a fourth aspect of the present invention, there is provided a glass molded body comprising melting a glass raw material in a melting tank and flowing a molten glass flow into a molding die through a nozzle connected to the melting tank. It is a manufacturing method of this, Comprising: It is the said manufacturing method including the process of averaging the temperature distribution in a flow path by allowing molten glass to pass through the flow path of the said structures 1-3.
以下、本発明の流路について詳細に説明するが、本発明は、以下の実施形態に何ら限定されるものではなく、本発明の目的の範囲内において、適宜変更を加えて実施することができる。 Hereinafter, the flow path of the present invention will be described in detail. However, the present invention is not limited to the following embodiments, and can be implemented with appropriate modifications within the scope of the object of the present invention. .
本発明において「流路」とは、溶融ガラスを溶融及び/又は保持する溶融槽に接続され、溶融ガラスを型(例えば成形型)に流出させる際の、ガラス流が通過する流路全体及び流出口を含む概念である。つまり、いわゆるパイプ、オリフィス、ノズルを包括する概念である。また「流路断面重心」とは、たとえば流路の流出方向に垂直な断面が円や楕円の場合はその中心を意味し、仕切板設置位置における流路断面重心は、当該位置に仕切り板がなかった場合の流路の断面重心を意味する。 In the present invention, the “flow path” is connected to a melting tank for melting and / or holding molten glass, and the entire flow path and flow path through which the glass flow passes when the molten glass flows out into a mold (for example, a mold). It is a concept that includes an exit. That is, it is a concept that encompasses so-called pipes, orifices, and nozzles. The “flow path cross-sectional center of gravity” means, for example, the center when the cross section perpendicular to the outflow direction of the flow path is a circle or an ellipse, and the flow path cross-sectional center of gravity at the partition plate installation position is the partition plate at that position. This means the center of gravity of the cross section of the flow channel when there is no channel.
通常、流路の温度制御は流路も種々の方法により加熱されるが、流路を流れる溶融ガラスの温度分布は、流路内の流速が大きく影響しており、流速の最も速い流路断面重心(流路断面が略円形の場合は、断面方向中心)付近が最も高く、また、流速の最も遅い内壁面近傍が最も低い。前述のように、本発明では流路内に仕切板を設置してガラス流を一旦塞き止め、或いは流速を遅くすることにより、かかる温度分布及び流速の位置によるギャップを緩和しようとするものである。 Normally, the temperature control of the flow path is also heated by various methods, but the temperature distribution of the molten glass flowing through the flow path is greatly influenced by the flow velocity in the flow path, and the cross-section of the flow path with the fastest flow velocity The vicinity near the center of gravity (the center in the cross-section direction when the channel cross section is substantially circular) is the highest, and the vicinity near the inner wall surface with the slowest flow velocity is the lowest. As described above, in the present invention, a partition plate is installed in the flow path to temporarily block the glass flow, or to slow down the flow velocity, thereby reducing the gap due to the temperature distribution and the position of the flow velocity. is there.
図1は本発明の流路を表す一例である。図1に示すように、仕切板1は流路2の内壁に接していることが好ましい。しかし、その設置法は特に限定されるものではなく、溶接により設置しても良いし、例えば流路内壁に溝を設ける等の加工を施すことにより、はめ込み式にすることもできる。はめ込み式であれば溶融されるガラスの種類により、適宜仕切板を変更することが可能となる。なお、仕切板は略垂直に設置されていることが好ましい。 FIG. 1 is an example showing the flow path of the present invention. As shown in FIG. 1, the partition plate 1 is preferably in contact with the inner wall of the flow path 2. However, the installation method is not particularly limited, and it may be installed by welding, or it may be a fitting type by performing a process such as providing a groove on the inner wall of the flow path. If it is a built-in type, the partition plate can be appropriately changed depending on the type of glass to be melted. In addition, it is preferable that the partition plate is installed substantially vertically.
仕切板1の材質は特に限定されるものではないが、溶融ガラス流の熱的負荷及び圧力負荷に耐えうるだけの耐熱性と強度を併せ持つことが必要である。従って、公知の白金合金、強化材を分散させた強化白金合金、又は濡れ性を向上させた金含有強化白金合金を使用することが好ましい。 The material of the partition plate 1 is not particularly limited, but it is necessary to have both heat resistance and strength sufficient to withstand the thermal load and pressure load of the molten glass flow. Therefore, it is preferable to use a known platinum alloy, a reinforced platinum alloy in which a reinforcing material is dispersed, or a gold-containing reinforced platinum alloy with improved wettability.
なお仕切板周囲全体が、流路内壁と接していることが好ましい。仕切板周囲と流路内壁との間に隙間があると、仕切板を保持する効果が減じられ、変形しやすくなるからである。また後述の仕切板に設けられた穴と流速との綿密な調整がしにくくなるからである。 The entire periphery of the partition plate is preferably in contact with the inner wall of the flow path. This is because if there is a gap between the periphery of the partition plate and the inner wall of the flow path, the effect of holding the partition plate is reduced and deformation is likely to occur. In addition, it is difficult to make precise adjustments between the holes provided in the partition plate described later and the flow velocity.
仕切板には、溶融ガラス流を通過するための穴が複数設けられていることが好ましい。これは溶融ガラス流通過用の穴として、広い穴が1つだけ設けられている場合には、その穴を通過する一連のガラス流に新たな変則的な温度分布が生じ、新たな流速の偏りを生じやすくなるからである。他方、狭い穴が1つだけ設けられている場合には、ガラス流の塞き止め効果は過剰となり、温度分布の平均化は促進できるが、ガラス流の流れが悪くなるため、却って失透を生じる恐れが生じる。また流出速度も著しく減じられるため、生産性の観点からも現実的ではない。従ってこれらの理由から、仕切板に設けられている穴の断面積は、流路断面積の好ましくは10%以上、より好ましくは20%以上、最も好ましくは30%以上であり、好ましくは90%以下、より好ましくは85%以下、最も好ましくは80%以下である。 The partition plate is preferably provided with a plurality of holes for passing the molten glass flow. This is because when only one wide hole is provided as a hole for passing the molten glass flow, a new irregular temperature distribution is generated in a series of glass flows passing through the hole, and a new flow velocity bias is generated. It is because it becomes easy to produce. On the other hand, if only one narrow hole is provided, the blocking effect of the glass flow becomes excessive and the averaging of the temperature distribution can be promoted, but the flow of the glass flow deteriorates, so that devitrification is avoided. There is a fear that it will occur. Moreover, since the outflow rate is significantly reduced, it is not realistic from the viewpoint of productivity. Therefore, for these reasons, the cross-sectional area of the hole provided in the partition plate is preferably 10% or more, more preferably 20% or more, most preferably 30% or more, preferably 90% of the flow-path cross-sectional area. Hereinafter, it is more preferably 85% or less, and most preferably 80% or less.
仕切板に設けられた複数個の穴は、流路断面の重心からの距離が大きいほど、その面積が小さいことが好ましい。すなわち、流路断面が略円形である場合には、円の中心付近の穴が大きく、中心から離れるに従い小さい穴となる。 The plurality of holes provided in the partition plate preferably have a smaller area as the distance from the center of gravity of the cross section of the flow path increases. That is, when the cross section of the flow path is substantially circular, the hole near the center of the circle is large and becomes smaller as the distance from the center increases.
前述のように流路を流れるガラス流の流速は、その流路断面重心付近が最も早く流路内壁に近づくほど小さくなる。一方、円管内を流れる流体の平均流速は、流路の断面積にも依存し、流路の断面積が小さくなるほどガラス流の平均流速は大きくなる。本発明においては、流路全体における流速を平均化することが所望であるため、流路中心付近に比べ、内壁近傍の流速を相対的に上げればよい。 As described above, the flow velocity of the glass flow flowing through the flow path becomes smaller as the vicinity of the flow path cross-sectional center of gravity becomes the earliest and approaches the flow path inner wall. On the other hand, the average flow velocity of the fluid flowing in the circular pipe also depends on the cross-sectional area of the flow channel, and the average flow velocity of the glass flow increases as the cross-sectional area of the flow channel decreases. In the present invention, since it is desired to average the flow velocity in the entire flow path, the flow velocity in the vicinity of the inner wall may be relatively increased as compared with the vicinity of the flow path center.
本発明の仕切板には複数の穴が設けられているため、それぞれの穴を小さな流路と仮定すれば、ガラス流を大きい穴を通過させる場合よりも小さい穴を通過させる場合のほうが、流速を大きく保つ効果が大きい。従って、流速の大きい流路中央付近のガラス流を比較的大きな穴に通し、流速の小さい内壁近傍のガラス流を小さい穴に通すことにより、もともと存在した流路内の流速のギャップを緩和し、より均一に近い流速分布を実現することが可能となる。 Since the partition plate of the present invention is provided with a plurality of holes, assuming that each hole is a small flow path, the flow rate is smaller when the glass flow is made to pass through the smaller holes than when the larger holes are passed. The effect of keeping large is great. Therefore, by passing the glass flow near the center of the flow path with a large flow velocity through a relatively large hole and passing the glass flow near the inner wall with a small flow velocity through the small hole, the gap in the flow velocity in the flow path that originally existed is relaxed, It becomes possible to realize a more uniform flow velocity distribution.
具体的に仕切板の穴の大きさを決定する場合には、次のように決定することが好ましい。仕切板を設置しようとする流路位置において、仕切板がない場合の流路断面重心での流速がa、流路断面重心から半径方向にrだけ離れた位置の流速がbであるとき、前記仕切板の中心の穴の断面積をc、仕切板の中心から半径方向にrだけ離れた位置の穴の断面積をdとしたときの関係がb×c=a×dとなるように、穴を設けることが好ましい。かかる関係を具備する仕切板を設けることにより、流路内の流速分布を平均化することができ、脈理や失透などの不利益が生じにくくなる。 Specifically, when determining the size of the hole of the partition plate, it is preferable to determine as follows. When the flow rate at the flow path position where the partition plate is to be installed has a flow velocity at the flow path cross-section center of gravity when there is no partition plate, and the flow speed at a position r away from the flow path cross-section center of gravity in the radial direction is b, The relationship when the cross-sectional area of the hole at the center of the partition plate is c and the cross-sectional area of the hole at a position r away from the center of the partition plate in the radial direction is d is b × c = a × d. It is preferable to provide a hole. By providing the partition plate having such a relationship, the flow velocity distribution in the flow channel can be averaged, and disadvantages such as striae and devitrification are less likely to occur.
本発明の仕切板は1つの流路内に複数設置されても良い。特に、仕切板を通過したガラス流も流路を進むに従い、次第に新たな流速分布を生じさせる傾向があるため、複数箇所に仕切板を設けることにより、流速分布の平均化をいっそう促進することができる。 A plurality of the partition plates of the present invention may be installed in one flow path. In particular, since the glass flow that has passed through the partition plate also tends to generate a new flow velocity distribution as it passes through the flow path, it is possible to further promote the averaging of the flow velocity distribution by providing partition plates at a plurality of locations. it can.
仕切板の設置位置は特に限定するものではないが、各位置は、ガラスの熱伝導率、熱容量、流路径、流量、所望の温度/温度分布等を勘案しながら決定される。流路の全長にも当然に依存するが、あまり上流過ぎると流速分布を一旦平均化させても、新たな流速分布を生じやすくなり、本発明において期待される効果が得にくくなる。したがって、好ましくは流路全体の下流側50%、より好ましくは下流側45%、最も好ましくは下流側40%までの範囲に、前記仕切板を1以上有する。また、場合によっては流路の最下端(すなわち、流路出口)に設けられていてもよい。 The installation position of the partition plate is not particularly limited, but each position is determined in consideration of the thermal conductivity, heat capacity, flow path diameter, flow rate, desired temperature / temperature distribution, and the like of the glass. Although it naturally depends on the total length of the flow path, if it is too upstream, a new flow velocity distribution is likely to be generated even if the flow velocity distribution is once averaged, and it is difficult to obtain the effect expected in the present invention. Therefore, it is preferable to have one or more of the partition plates in a range of 50% downstream of the entire flow path, more preferably 45% downstream, and most preferably 40% downstream. Moreover, depending on the case, you may provide in the lowest end (namely, flow-path exit) of a flow path.
本発明の流路は、流路自体及び/又は外部からの付加手段による加熱及び/又は冷却を妨げるものではない。流路自体の加熱としては、流路に直接通電させることによる公知の加熱方法が使用できるし、外部からの付加手段としてはガスバーナー、電熱式ヒーター、赤外線放射、高周波加熱などの公知の手法を適宜使用してよい。さらに、ガラス流出口付近をリングバーナー等で覆い、保温することにより、失透、脈理等の不良をいっそう抑えることができる。 The flow path of the present invention does not hinder heating and / or cooling by the flow path itself and / or external addition means. As the heating of the channel itself, a known heating method by directly energizing the channel can be used, and as an external addition means, a known method such as a gas burner, an electric heater, infrared radiation, high frequency heating or the like can be used. You may use suitably. Further, by covering the vicinity of the glass outlet with a ring burner or the like and keeping it warm, defects such as devitrification and striae can be further suppressed.
本発明の流路を使用したガラスの成形手段は特に制限されるものではない。光学ガラスの成形としては、成形型にガラス流として連続的に流出させ、板状或いは棒状ガラス等に連続成形してもよいし、シャー又は表面張力によりガラスゴブを分離し、多孔質型上にて浮上成形させることによりガラスゴブを成形するものでもよい。 The glass forming means using the flow path of the present invention is not particularly limited. As optical glass molding, it may be continuously flown out as a glass flow into a mold, and may be continuously molded into a plate-like or rod-like glass, etc., or the glass gob is separated by shear or surface tension, and on a porous mold. A glass gob may be formed by floating molding.
本発明の流路の材質は、通常、ガラスの溶融工程に使用される材質を使用することができ、例えば白金、強化白金、金、強化金、ロジウム、その他貴金属及びそれらの合金、或いは石英が使用できる。また、公知の手法によりメッキされた材質、例えば内面を金メッキ、あるいはSiCなどのセラミックを成膜した白金を使用しても良い。 As the material of the flow path of the present invention, materials usually used in the glass melting process can be used, for example, platinum, reinforced platinum, gold, reinforced gold, rhodium, other noble metals and their alloys, or quartz. Can be used. Further, a material plated by a known method, for example, platinum having a gold-plated inner surface or a ceramic film such as SiC may be used.
本発明は、流路の内部構造を規定するものであるから、流路流出口付近の雰囲気を適宜変更しても良い。例えば窒素雰囲気、アルゴン等の不活性ガス雰囲気にしてもよい。また場合によっては、加熱雰囲気にて流路流出口を覆ってもよい。 Since the present invention defines the internal structure of the flow path, the atmosphere in the vicinity of the flow path outlet may be appropriately changed. For example, a nitrogen atmosphere or an inert gas atmosphere such as argon may be used. In some cases, the channel outlet may be covered with a heated atmosphere.
以下、本発明の具体的な実施例を示す Specific examples of the present invention are shown below.
(実施例1)
本実施例においては、光学ガラスを白金坩堝にて溶融させ、坩堝に接続された流路を介して溶融ガラスをその末端の流出口から流出させ、ガスを噴出するタングステンカーバイド製多孔質成形型上にて浮上成形させ、精密プレス成形用プリフォームとして使用するためのガラスゴブを取得した。
Example 1
In this example, the optical glass is melted in a platinum crucible, and the molten glass is discharged from the outlet at the end of the molten glass through a flow path connected to the crucible. The glass gob for use as a precision press-molding preform was obtained.
流路としては前述の図3と同じ形状の強化白金流路を使用した。ここで、流路内径は3mm(断面積7.07mm2)で、流出口は6mmまで拡開している。流路全長、すなわち坩堝の出口から流路末端の流出口までの長さは2mであった。 As the flow path, a reinforced platinum flow path having the same shape as that shown in FIG. 3 was used. Here, the inner diameter of the flow path is 3 mm (cross-sectional area 7.07 mm 2 ), and the outlet is expanded to 6 mm. The total length of the channel, that is, the length from the outlet of the crucible to the outlet at the end of the channel was 2 m.
流路内の仕切板は、流出口から50mmの地点に取り付けられ、厚さは1mmであった。仕切板を取り付けた部分のガラス流路の面積は3.23mm2であった。すなわち当該仕切板が設置された場所の流路断面積は、そうでない場所の約46%であった。 The partition plate in the flow path was attached to a point 50 mm from the outlet and the thickness was 1 mm. The area of the glass flow path at the part where the partition plate was attached was 3.23 mm 2 . That is, the flow path cross-sectional area where the partition plate was installed was about 46% of the place where the partition plate was not installed.
受け型は、多孔質ステンレスで作られ、その受面から空気を噴出している状態で、溶融ガラスを受けることにより、受け型から浮上した状態で溶融ガラスを受け、ガラスゴブを得た。 The receiving mold was made of porous stainless steel, and received molten glass in a state where air was blown from the receiving surface thereof. Thus, the molten glass floated from the receiving mold to receive glass gob.
使用したガラスは、酸化ホウ素及び酸化ランタンを主成分とする光学ガラスを溶融した。坩堝は約1200℃に保たれ、流出パイプは通電加熱により約1100℃に保たれた。流出口からは、溶融ガラスを液滴状に分離している状態にした。この時の溶融ガラスの流出量は毎分80gであった。 The glass used was melted optical glass mainly composed of boron oxide and lanthanum oxide. The crucible was kept at about 1200 ° C., and the outflow pipe was kept at about 1100 ° C. by electric heating. From the outlet, the molten glass was separated into droplets. The amount of molten glass flowing out at this time was 80 g per minute.
このガラスゴブには、失透及び脈理などの光学欠陥を目視で観察したところ、そのような不良は発見できず、光学素子成形用プリフォームとして使用できる高品質のガラスゴブであった。 When this glass gob was visually observed for optical defects such as devitrification and striae, such a defect could not be found, and it was a high-quality glass gob that could be used as a preform for molding an optical element.
1 仕切板
2 流路
3 仕切板に設けられた穴
1 partition plate 2 flow path 3 hole provided in the partition plate
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