JP4266115B2 - Mold press molding apparatus and glass optical element manufacturing method - Google Patents

Description

【００３９】
本実施態様のように、母型の発熱体に空隙からなる熱伝導調整部を設けると、成形型への熱伝導を調整できると同時に、発熱体の熱容量を小さくすることにより、消費電力を増加させずに、成形型の温度を高くすることができる。また、空隙からなる熱伝導調整部の位置、大きさ、数などを選択することによっても各成形型の温度を調整することができる。
【００４０】
［ガラス光学素子の製造方法］
以上のような構成のガラス光学素子製造装置を用いて、本発明に係るガラス光学素子を製造する方法の実施形態について説明する。
（ａ）加熱工程
前回の成形サイクルが終了した状態の上下成形型は、Ｔｇ付近の温度に冷却されているため、プレス成形に適した温度まで加熱する必要がある。すなわち、上母型と下母型の周囲を巻回する高周波誘導コイルに電流を流し、上下母型を発熱させ、この熱伝導によって上下の各成形型を所定温度まで加熱する。このとき、複数の成形型の温度のばらつきをできるだけ小さくすることが重要である。
上下成形型の温度設定値は、通常、上下とも同一とするが、成形されるレンズ形状や径などによっては、上下の成形型に温度差を設けてもよい。
なお、上下母型の熱容量が相違し、加熱効率に差のあることが多いため、この点も考慮して、高周波コイル巻き数、及び出力範囲を決定する。
【００４１】
（ｂ）ガラス素材供給工程
加熱された上下型間に、搬送されたガラス素材が供給され、下型上に配置される。ガラス素材の供給は、予め適切な重量の所定形状に予備成形されたガラス素材を用い、成形に適した粘度まで軟化したものを供給するか、あるいは、成形に適した温度よりも低温のガラス素材を上下型間に供給し、成形型においてさらに加熱してもよい。
予め、型の設定温度よりも高温に加熱し、軟化した状態のガラス素材を供給する場合には、特に、型温度の制御を精密に行う必要があるので、本発明を実施すると好適である。すなわち、上下母型における熱伝導調整部によって、複数の成形型に伝導される熱をそれぞれ調整し、各成形型のあいだの温度差が小さく（１０℃程度以内と）なるようにする。
このときのガラス素材の温度は、粘度で１０⁹ポアズ相当未満の温度とし、好ましくは１０^5.5〜１０^7.5ポアズ相当とする。
なお、軟化したガラス素材を搬送して下型上に配置するときには、ガラス素材が搬送部材に接触して、表面に欠陥が起きると、成形される光学素子の面形状に影響するため、軟化したガラス素材を気体により浮上させた状態で搬送し、下型上にガラス素材を落下させる治具を用いることが好ましい。
【００４２】
（ｃ）加圧工程
上下型とガラス素材がそれぞれ所定の温度範囲にあり、ガラス素材が加熱軟化した状態で、下母型を上昇させて加圧し、上下成形型の成形面を転写することによって、所定面形状をもったガラス光学素子を成形する。下型の上昇は、駆動手段(例えばサーボモータ)を作動させて行う。ガラス素材が加熱軟化した状態で供給される場合には、供給後直ちに加圧が行われる。
加圧のための下型の上昇ストロークは、予め、成形する光学素子の肉厚から設定された値であり、この後の冷却工程においてガラスが熱収縮する分を見込んで定めた量とする。加圧のスケジュールは、成形する光学素子の形状や大きさに応じて任意に設定することができ、初期加圧の後、荷重を開放したのち、二次加圧を行うなどの、複数回の加圧方法を採用することもできる。
【００４３】
（ｄ）冷却・離型工程
加圧を維持したまま、あるいは加圧を減じた状態で、成形されたガラス光学素子と成形型の密着を保ち、ガラスの粘度出１０¹²ポアズ相当の温度になるまで冷却したのち、離型する。離型温度は、１０^12.5〜１０^13.5ポアズ相当で行うことが好ましい。
【００４４】
（ｅ）取り出し工程
吸着部材を備えた取り出しアーム等により、成形されたガラス光学素子を自動的に取り出す。
【００４５】
次に、参考例と、本発明の成形装置と製造方法を用いてガラス光学素子の製造を行った実施例の結果を示す。
［参考例］
図１に示す、６個取りの成形装置によって、ガラス光学素子（Ｐ₂Ｏ₅：２４％、Ｂ₂Ｏ₃：４％、Ｌｉ₂Ｏ：２０％、Ｎａ₂Ｏ：１３％、Ｋ_２Ｏ：１％、 ＢａＯ : ４％、ＺｎＯ：２％、ＴｉＯ₂：５％、Ｎｂ₂Ｏ₅：２０％、ＷＯ₃：７％ （モル％表示）、Ｔｇ：４７８℃ Ｔｓ：５２７℃）を用いて、径１１ｍｍの凹メニスカスレンズを成形した。母型には、タングステン合金を用い、成形型にはＳｉＣを精密加工して成形面を形成し、成形面上に離型膜として炭素膜を設けたものを使用した。母型の形状は、図５（ａ）に示すもので、熱伝導調整部は設けていない。母型中心付近には、制御用温度センサ（図示せず）を設置した。
予め熱間で、扁平球形状に予備成形したガラスプリフォームを、加熱室２０で５９０℃（１０^７ポアズ相当）に予熱し、アーム２５に取り付けられた浮上治具上で浮上状態のまま搬送し、これを下母型上に直線配置された各下型成形面上に同時落下させて供給した。このとき、上下成形型の波形は、母型中心において５３０℃となるよう、温度センサを用い、加熱時間を調整しておいた。
ただちに、アームを退避させ、下母型を上昇させることによって、上下成形面を接近させ、１００Kgf/ｃｍ²でプレス成形した。成形面を成形された素子に密着させたまま、Ｔｇ温度まで冷却し、離型して素子を取出した。プレス成形のときの、各型の温度は、母型に埋めこんだ熱電対（図示せず）により測定した。
その結果、測定温度と、成形された６個の光学素子（ガラスレンズ）は以下のようになった。
【００４６】
【表２】

【００４７】
［実施例１］
タングステン合金からなる上下の母型に、図５（ｂ）と同一形状の空隙からなる熱伝導調整部を形成した。この熱伝導調整部の空隙には雰囲気ガスが充満した状態であった。母型に、６個のＳｉＣ製成形型（参考例１と同じもの）を配置し、参考例と同様の手順で、ガラスレンズを成形した。その結果を表３に示す。
【００４８】
【表３】

【００４９】
［実施例２］
次に、実施例１で用いた上下母型の空隙の、図５（ｃ）に示すように、空隙の一端側の隣接した位置に銅を埋め込んで熱伝導調整部を形成した。この母型を用いて、参考例と同様のプレス成形を行なった。その結果を表４に示す。
【００５０】
【表４】

【００５１】
上記の結果から、母型に熱伝導調整部を形成すると、複数の成形型のあいだにおける温度差が小さくなって、製造されるガラス光学素子の光学性能が均一化することが判明した。
【００５２】
【発明の効果】
以上のように、本発明によれば、母型に支持された成形型の均熱化を図ることができ、特に複数の成形型による複数取りにおいて、均一性能の光学素子が生産性よく製造できる。
本発明は、母型中で発生する熱伝導が、非点対称であるような、非円形の母型において、特に顕著な効果が得られる。すなわち、長尺状の母型上に、ほぼ直線状に配置された成形型を、本発明のように構成して加熱すると、コイルと発熱体表皮部（最も発熱する部分）及び成形型の位置を近接させることができ、加熱効率を上げるとともに、均熱化を行うこともできる。
【図面の簡単な説明】
【図１】図１は、本発明を適用するモールドプレス成形装置の一実施形態を示す概略平面図である。
【図２】図２は、本発明を適用する成形装置の第一実施形態を示す側断面図である。
【図３】図３は、本発明を適用した成形装置の１／４概略断面斜視面である。
【図４】図４は、熱伝導調整部を形成しない成形装置の１／４概略平面図である。
【図５】図５（ａ）は熱伝導調整部を形成しない成形装置の熱分布状態を示す１／４概略平面図であり、（ｂ）は空隙からなる熱伝導調整部を形成した成形装置の熱分布状態を示す１／４概略平面図であり、（ｃ）は空隙の一部に銅を埋め込んでなる熱伝導調整部を形成した成形装置の熱分布状態を示す１／４概略平面図である。
【符号の説明】
１０ 光学ガラス製造装置
２０ 加熱室
４０ 成形室
４１ プレス装置
４１０ａ，４１０ｂ 高周波誘導コイル
４１１ａ，４１１ｂ 母型
４１３ａ，４１３ｂ 成形型[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a mold press that heat-softens a plurality of preformed glass materials (preforms) in a manufacturing process of an optical lens or the like and press-molds them with a plurality of molds to simultaneously mold a plurality of glass optical elements. The present invention relates to a molding apparatus and a method for manufacturing a glass optical element.
[0002]
[Prior art]
In precision presses for glass optical elements, it is known to use high-frequency induction heating that provides a rapid and sufficient heating capacity as means for heating the mold.
In this case, if the mold is made of a material that easily generates heat by high-frequency induction, the thermal efficiency is most likely to be improved and heat deviation is unlikely to occur. However, the mold can be processed with high surface accuracy and shape accuracy. Since a material that can withstand the high heat and load of press molding is required, it has been difficult to select an optimal material as a molding die. Therefore, the mold is heated by heat conduction from a heating element that generates heat by induction heating. However, it is not easy to uniformly heat the mold.
[0003]
For this reason, various improvements and improvements have been made in press forming apparatuses (methods) using high frequency induction heating.
For example, when the glass lens to be molded has a large diameter or a plurality of cavities are provided, a heat insulating ring body and a heating backup body are provided on the back surface of the die plate in order to avoid heating from concentrating only on the portion near the heating coil. A press forming apparatus that compensates for the temperature difference in the radial direction of the die plate has been proposed (see Patent Document 1).
However, in the press molding apparatus described in Patent Document 1, the apparatus configuration becomes large, and the heat capacity of the entire apparatus is increased for soaking, so the thermal efficiency is extremely low. Further, since the cooling efficiency is low and the molding cycle time becomes long, there is a problem that it is necessary to use a cooling means for supplying an inert gas to the molding space.
[0004]
As another example, at least one of the upper mold, the lower mold, the body mold, the release member, etc. is formed of a cemented carbide or ceramic, and the other is molded of a cemented carbide or ceramic having different heat capacity and thermal conductivity. An apparatus has been proposed (see Patent Document 2).
In the apparatus described in Patent Document 2, the temperature distribution inside the lens to be molded is intentionally non-uniform so as to suppress sink marks and sagging, but the soaking of the molding surface or a plurality of molding dies No consideration has been given to improving the molding accuracy by each soaking.
[0005]
On the other hand, it is known that it is effective to form a mother die for supporting the mold with a heating element by induction heating and to heat the molding mold by heat conduction from the heating element. However, in induction heating, most of the induced current is concentrated on the skin portion of the heating element (the portion within several millimeters from the surface).
This is because the eddy current generated by induction heating is larger as it is closer to the surface of the heating element and decreases exponentially as it is located inside. Therefore, the mold placed on the mother die is heated by the heat conduction in the heating element from the skin portion of the heating element to the inside of the mother die on which the molding die is arranged. The heat conduction behavior of the material greatly affects the heating efficiency and temperature distribution of the mold.
[0006]
From the viewpoint of heating efficiency, the smaller the distance from the coil, the larger the magnetic flux density generated, and the larger the eddy current generated in the skin of the heating element, so the closer the coil and the heating element are preferable. Further, it is preferable that the distance between the skin portion of the heating element and the mold is short because the mold is heated quickly. From these points, it is very advantageous to make the heating element of the mother die non-circular, preferably elongated, and to arrange a plurality of molding dies in a substantially linear shape.
In this way, the distance between the skin portion of the heating element and the molding die can be reduced, and a compact design with high heating efficiency can be achieved. Because you can't do much.
As a mold supported by a long mother mold, for example, a plurality of molds are arranged in a row on a long mother mold, and the periphery of the mother mold, which is a heating element, is wound with an induction heating coil. There is a press molding apparatus (see Patent Document 3).
[0007]
In addition, as shown in Patent Document 1, in the case where the molds are arranged symmetrically on the circular mother mold, the difference in the distance from the skin of the heating element becomes large depending on the part of the mold, so that the temperature is not uniform. Is likely to occur. Moreover, the surface area of the heating element is increased and the loss is large.
[0008]
[Patent Document 1]
JP-A 64-45735
[Patent Document 2]
JP-A-2-275722
[Patent Document 3]
JP-A-11-29333
[0009]
[Problems to be solved by the invention]
According to the press molding apparatus shown in Patent Document 3, in which a plurality of molding dies are arranged in a row on a long mother die, and the periphery of the mother die that is a heating element is wound with an induction heating coil, Since a plurality of molds that are compact and arranged are at a short distance from the coil (that is, at a short distance from the skin portion of the heating element), a press molding apparatus with high heating efficiency can be obtained.
By the way, soaking is a problem when the heating element is made non-circular. The thermal conditions are likely to be different between both ends and the center of the placed mold, and the surface accuracy and thickness of the molded lens are likely to be uneven.
[0010]
The present invention suppresses temperature unevenness of the mold and molds a glass optical element with high surface accuracy and thickness accuracy even in a compact molding apparatus in which a plurality of molds are arranged on a non-circular matrix. An object of the present invention is to provide a mold press molding apparatus and a glass optical element manufacturing method that can be used.
[0011]
[Means for Solving the Problems]
In order to achieve the above object, a mold press molding apparatus of the present invention comprises a pair of upper and lower sides having molding surfaces processed into a predetermined shape. plural A mold, a pair of upper and lower mother molds that respectively support the upper and lower molds, and a high-frequency induction heating coil wound around the mother mold, and the upper and lower mother molds generate heat by high-frequency induction. A body, and at least one of the upper and lower matrixes Heating element Is Consists of a gap formed in the heating element outside the mold supported by the mother mold. The heat conduction adjusting portion is formed.
[0012]
According to the present invention having such a configuration, a heat conduction adjusting portion having a different heat conductivity is provided in the heat conduction path from the mother die to the mold, and here, the heat conductivity transmitted to each mold is adjusted. Therefore, it is possible to equalize each mold on the mother mold.
[0013]
In this case, you may form by filling atmospheric gas in the said space | gap of the said heat conduction adjustment part.
[0014]
In this case, the atmospheric gas usually has a lower thermal conductivity than the heating element, so that it acts as a heat insulating material and reliably reduces the thermal conductivity.
[0015]
The mold press molding apparatus of the present invention is Elongate It is suitable for use in a molding apparatus in which a plurality of molding dies are arranged on a substantially straight line on the mother die.
[0016]
Elongate In a molding device of a type in which a plurality of molds are arranged almost linearly on the master mold, the temperature in each mold tends to be non-uniform, so the thermal conductivity adjustment part adjusts the thermal conductivity to each mold. By doing so, it is possible to equalize each mold.
[0017]
In addition, the method for producing a glass optical element of the present invention includes a pair of upper and lower parts heated and softened to a predetermined temperature having a molding surface processed into a predetermined shape from a heat-softened glass material. plural In the method of manufacturing a glass optical element by press molding with a molding die, a mother die supporting the molding die is formed with a heating element, In the matrix, Mother mold A gap formed in the heating element on the outside of the mold supported by A heat conduction adjusting portion is formed, and the heat conduction adjusting portion is used to heat the forming die while adjusting heat conduction from a heating element that generates heat by high frequency induction to the forming die.
[0018]
According to such a method, soaking can be achieved in each mold,
The optical performance of the plurality of optical elements to be molded can be kept constant.
[0019]
Further, in the method for producing a glass optical element of the present invention, during the press molding, the heat distribution is performed so that the difference in temperature distribution between the molding surfaces of the plurality of molding dies arranged on the mother die is within 10 ° C. Of the conduction adjustment section Location and size Is preferably set.
If the difference in temperature distribution between the molding surfaces of the molding dies is within 10 ° C., there will be no difference in optical performance between the optical elements molded by the molding dies.
[0020]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
In the following, the present invention will be described in accordance with an embodiment in which the present invention is applied to a glass optical element manufacturing apparatus. However, the mold press molding apparatus of the present invention is not limited to this embodiment, and is a resin optical element. The present invention can also be applied to manufacturing or parts manufacturing other than glass and resin optical elements.
[0021]
[Glass optical element manufacturing equipment]
FIG. 1 is a schematic cross-sectional view when the mold press molding apparatus according to the present invention is applied to a glass optical element manufacturing apparatus.
The manufacturing apparatus shown in FIG. 1 presses a spherical glass preform to manufacture a small collimator lens. In general, a plurality of (six in the illustrated example) spherical glass preforms are simultaneously supplied into the manufacturing apparatus casing, softened by heating, pressed by a mold, cooled, and carried out of the casing. Is done. By repeating this, a large number of collimator lenses are continuously manufactured.
[0022]
As shown in FIG. 1, the glass optical element manufacturing apparatus 10 includes a heating chamber 20 and a molding chamber 40. The heating chamber 20 and the molding chamber 40 are communicated with each other through a passage 60 provided with an opening / closing valve 61, and the heating chamber 20, the molding chamber 40 and the passage 60 form a single sealed space that is blocked from the outside. ing. The outer wall of the sealed space is formed of stainless steel or other members, and the hermeticity is maintained by a sealing material. The sealed space formed by the heating chamber 20, the molding chamber 40, and the passage 60 is set to an inert gas atmosphere when the glass optical element is molded. That is, the air in the space is exhausted by a gas exchange device (not shown) and filled with an inert gas instead. As an inert gas, nitrogen gas (for example, N ₂ + 0.02vol% H ₂ ) Is preferably used.
[0023]
The heating chamber 20 is an area for preheating prior to pressing the glass preform to be supplied. In this area, a preform supply device 22, a preform transport device 23, and a preform heating device 24 are installed. The In addition, a supply preparation chamber 21 for supplying the glass preform from the outside into the heating chamber 20 is installed. Six supply trays (not shown) are arranged in the supply preparation chamber 21, and six glass preforms are placed thereon using a robot arm (not shown). The glass preform on the tray is adsorbed by the suction pad of the preform supply device 22 installed in the supply preparation chamber 21 and is carried into the heating chamber 20. In order to prohibit the inflow of air into the heating chamber 20, the supply preparatory chamber 21 is sealed and replaced with an inert gas atmosphere after the glass preform is placed on the receiving tray.
[0024]
The preform conveying device 23 receives the glass preform carried in from the supply preparation chamber 21, conveys the glass preform to a heating region by the preform heating device 24, and further conveys the heat-softened glass preform to the molding chamber 40. The preform conveying device 23 includes six plates 26 at the tip of the arm 25, and holds the glass preform thereon.
In the embodiment, the arm 25 including the dish 26 is horizontally supported by the drive unit 23a fixed in the heating chamber 20, and the arm 25 is rotated in the horizontal direction with a rotation angle of approximately 90 degrees. In addition, the arm 25 is configured to be capable of withdrawing and retracting in the radial direction with the drive unit 23 a as the center, and thereby, the held glass preform is conveyed to the molding chamber 40.
[0025]
The preform transport device 23 includes an arm opening / closing mechanism (not shown) in the drive unit 23a, thereby opening the tip of the arm 25 and dropping the glass preform on the tray 26 onto the mold.
[0026]
The preform heating device 24 is for heating the supplied glass preform to a temperature corresponding to a predetermined viscosity. In order to stably raise the temperature of the glass preform to a certain temperature, it is preferable to use a heating device (for example, an Fe—Cr heater) by resistance heating using a resistance element. The preform heating device 24 has a substantially U-shape when viewed from the side, and includes heater members on the upper and lower surfaces thereof. As shown in FIG. 1, the preform heating device 24 is installed on the movement locus of the glass preform held on the arm 25.
The arm 25 is placed in the preform heating device 24 except when the glass preform is received from the preform supply device 22 and when it is transported to the molding chamber 40. The heater temperature of the preform heating device 24 can be about 1100 ° C., and the atmosphere in the furnace, that is, the atmosphere between the upper and lower heaters can be about 700 to 800 ° C. In the present embodiment, the arm 25 is prevented from warping in the vertical direction by providing a temperature difference between the upper and lower heaters.
[0027]
On the other hand, the molding chamber 40 is a region for pressing the glass preform preliminarily heated in the heating chamber 20 to mold a glass optical element of a desired shape. An element carry-out device 42 is installed. Further, a take-out preparation chamber 43 is provided for carrying out the press-molded glass optical element to the outside.
[0028]
The pressing device 41 simultaneously receives six glass preforms conveyed from the heating chamber 20 by the preform conveying device 23 and presses them to obtain a glass optical element having a desired shape. The press device 41 includes a molding die including an upper die and a lower die, and simultaneously presses six glass preforms supplied between them by their molding surfaces. The six glass preforms on the arm 25 of the preform conveying device 23 are dropped onto the lower mold by opening the tip of the arm, and immediately after the arm is retracted from between the molds, the lower mold The glass preform is raised toward the upper mold, thereby pressing the glass preform sandwiched therebetween.
[0029]
Around the mold, induction heating coils 410a and 410b are installed for heating the mold. Prior to pressing the glass preform, the mold is heated by the mold heating device 41a and maintained at a predetermined temperature. The temperature of the mold during pressing may be approximately the same as or lower than the temperature of the preheated glass preform.
[0030]
The carry-out device 42 delivers the glass optical element pressed by the press device 41 to the take-out preparation chamber 43. The carry-out device 42 includes six suction pads 42c at the tip of an arm 42b that is rotatably supported with respect to the drive unit 42a. The suction pad 42c vacuum-sucks the six glass optical elements on the lower mold of the mold so that the suction pad 42c can be transported by the carry-out device 42. The glass optical element adsorbed by the rotation of the arm 42b is transported under the take-out preparation chamber 43 and placed on a lifting means (not shown) installed here. After the arm 42 b is retracted, the elevating means is raised, and the glass optical element is delivered to the take-out preparation chamber 43.
In the present embodiment, the lens mounting surface of the elevating means closes the opening of the extraction preparation chamber 43 that communicates with the molding chamber 40, thereby disabling gas exchange between the extraction preparation chamber 43 and the molding chamber. Become. By opening the upper part of the take-out preparation chamber 43, the glass optical elements inside the robot arm and other carrying-out means are sequentially carried out to the outside. After carrying out the glass optical element, the take-out preparation chamber 43 is sealed and filled with an inert gas.
[0031]
[Pressing equipment]
Next, a press apparatus will be described.
FIG. 2 is a side sectional view showing the main structure of the pressing device of the glass optical element manufacturing apparatus according to the present embodiment. In this press apparatus, a long upper mother die 411a and a lower mother die 411b are attached to an upper main shaft 412a and a lower main shaft 412b, respectively. Six upper molds 413a and 413b are attached to the upper mother mold 411a and the lower mother mold 411b, respectively. In addition, induction heating coils 410a and 410b are provided around the upper mother die 411a and the lower mother die 411b.
Further, a sleeve 414 is provided on the outer periphery of the upper mold 413a to prevent the axial displacement of the upper and lower surfaces of the lens by fitting and sliding with the lower mold 413b with a narrow clearance. A guide pin 415 protrudes from the upper mother die 411a, and a guide hole 416 that engages with the guide pin 415 is formed in the lower mother die 411b.
[0032]
The material of the upper and lower mother dies 411a and 411b uses a heating element that generates heat by induction heating. For example, iron, cobalt, nickel, or the like can be used as the heating element. For the upper and lower molds 413a and 413b, for example, a ceramic such as silicon carbide or silicon nitride, or a cemented carbide can be used.
Here, as the heating elements of the upper and lower mother dies 411a and 411b, it is preferable to use one having a coefficient of thermal expansion close to that of the forming dies 413a and 413b. For example, when ceramic is used as the mold material, it is preferable to use a tungsten alloy or the like as the heating element.
A release film can be provided on the molding surfaces of the upper and lower molding dies 413a and 413b. As the release film, a film mainly composed of noble metals (Pt, Ir, Rh, etc.) or carbon can be applied. A carbon film is particularly suitable because it is inexpensive and has an excellent release effect.
[0033]
At least one of the upper and lower molds 413a and 413b is provided with a heat conduction adjusting portion. Here, the heat conduction adjusting portion is a portion for adjusting the heat conduction from the surface of the heating element that generates the most heat to the inside and adjusting the heating efficiency in each of the plurality of molds.
FIG. 3 is a schematic partial cross-sectional view showing a state in which the heat conduction adjusting portion is formed on the lower mother die. The heat conduction adjusting portion 417 is formed by drilling a long hole on the outer surface of the lower die 413 of the lower mother die 411b. The size or the position and number of holes constituting the heat conduction adjusting unit 417 are appropriately selected according to the material of the mother die and the forming die, the number of forming dies, the arrangement state of the induction heating coil, and the like. If it does in this way, the temperature dispersion | variation in the molding surface of each shaping | molding die can be made small, and the temperature distribution of each shaping | molding die can be adjusted.
[0034]
The heat conduction adjusting unit 417 is used when lowering or increasing the heating efficiency of an arbitrary mold. For example, when the temperature of any mold is excessively increased, a hole is formed in the mother die that is a heating element in order to reduce the heating efficiency. When a void is formed in the master mold, the part is insulated and the heat conduction path changes, so that the temperature rise of the mold located in the vicinity can be suppressed and the temperature rise of other molds can be promoted. .
When the molding chamber is filled with the atmospheric gas, the atmospheric gas is also filled in the gap as the heat conduction adjusting unit 417. However, the atmospheric gas is usually more heated than the mother die (heating element). Since the conductivity is small, it functions as a heat insulating material. Further, the heating efficiency of the mold may be lowered by embedding a material having a low thermal conductivity in all or part of the gap.
Conversely, in order to increase the heating efficiency of an arbitrary mold, all or part of the gap is filled with a material (for example, metal) having a higher thermal conductivity than the heating element to increase the thermal conductivity.
[0035]
The heat conduction adjusting unit 417 determines the position, number, size, and the like so that the temperature variation between the molding surfaces of each mold is within 10 ° C. If the variation in temperature between the molding surfaces of each mold is within 10 ° C., a plurality of homogeneous glass optical elements can be molded. It is preferable for the temperature variation to be within 8 ° C., since a plurality of glass optical elements can be molded more uniformly.
[0036]
[Estimation of the action of the heat conduction adjuster]
About the effect | action of the heat conduction adjustment part 417 on the mother mold | type (heating element) 411, it can estimate with high accuracy by the finite element method, for example.
The estimation method will be described below. Here, an example using a quarter model of the matrix and the induction heating coil shown in FIG. 4 will be described.
A tungsten alloy having a relative permeability of 22 was used for the matrix heating element, and the molding die was SiC. The induction coil was copper, and the input current and frequency were as shown in Table 1.
[0037]
Under the above conditions, the heating temperature of each mold 150 seconds after the input of current was analyzed. FIG. 5 (a) shows the temperature distribution when using a mother die without a heat conduction adjusting portion, and the temperature difference between the molds (difference between the highest temperature and the lowest temperature) is 25 ° C. .
Next, a gap as shown in FIG. 5B was provided near the outer periphery of the matrix. This void was filled with atmospheric gas, and this atmospheric gas functioned as a heat insulating material. When the heating temperature of each mold was estimated from the temperature distribution when such a heat conduction adjusting portion 417 was formed, the temperature difference between the molds was 10 ° C. If the temperature difference between the molding dies is about 10 ° C., the plurality of glass optical elements to be molded can be within tolerances in both thickness accuracy and surface accuracy.
Next, as shown in FIG. 5C, the temperature distribution when copper 417a is embedded adjacent to one end side of the gap to form the heat conduction adjusting portion 417 (copper thermal conductivity 394 W / K · m). Thus, when the heating temperature of each mold was estimated, the temperature difference was 8 ° C.
As described above, it has been found that when the heat conduction adjusting portion is formed on the mother die, the heating efficiency of each molding die can be adjusted, and soaking can be achieved.
[0038]
[Table 1]

[0039]
As in this embodiment, when the heat conduction adjusting portion made of a gap is provided in the heating element of the mother die, the heat conduction to the molding die can be adjusted, and at the same time the power consumption is increased by reducing the heat capacity of the heating element. Without this, the temperature of the mold can be increased. Moreover, the temperature of each mold can also be adjusted by selecting the position, size, number, etc., of the heat conduction adjusting portions formed of voids.
[0040]
[Glass optical element manufacturing method]
An embodiment of a method for manufacturing a glass optical element according to the present invention using the glass optical element manufacturing apparatus having the above configuration will be described.
(A) Heating process
Since the upper and lower molds in the state where the previous molding cycle is completed are cooled to a temperature near Tg, it is necessary to heat them to a temperature suitable for press molding. That is, an electric current is passed through the high frequency induction coil wound around the upper mother die and the lower mother die to cause the upper and lower mother dies to generate heat, and the upper and lower molding dies are heated to a predetermined temperature by this heat conduction. At this time, it is important to minimize the variation in temperature among the plurality of molds.
The temperature setting values of the upper and lower molds are usually the same for both the upper and lower molds, but a temperature difference may be provided between the upper and lower molds depending on the shape and diameter of the lens to be molded.
In addition, since the heat capacities of the upper and lower mother molds are different and the heating efficiency is often different, the number of high-frequency coil turns and the output range are determined in consideration of this point.
[0041]
(B) Glass material supply process
The conveyed glass material is supplied between the heated upper and lower molds and placed on the lower mold. The glass material is supplied by using a glass material that has been pre-formed into a predetermined shape with an appropriate weight and softened to a viscosity suitable for molding, or a glass material that is lower than the temperature suitable for molding. May be supplied between the upper and lower molds and further heated in the mold.
When supplying a glass material that has been heated to a temperature higher than the preset temperature of the mold and softened in advance, it is particularly preferable to carry out the present invention because the mold temperature needs to be precisely controlled. In other words, the heat conducted to the plurality of molds is adjusted by the heat conduction adjusting unit in the upper and lower mother molds so that the temperature difference between the molds is small (within about 10 ° C.).
The temperature of the glass material at this time is 10 in terms of viscosity. ⁹ The temperature is less than the equivalent of Poise, preferably 10 ^5.5 -10 ^7.5 Equivalent to Pois.
When the softened glass material is transported and placed on the lower mold, if the glass material comes into contact with the transport member and a defect occurs on the surface, the surface shape of the optical element to be molded is affected, so the glass material is softened. It is preferable to use a jig that conveys the glass material in a state of being floated by gas and drops the glass material onto the lower mold.
[0042]
(C) Pressurization process
When the upper and lower molds and the glass material are each in a predetermined temperature range, and the glass material is heated and softened, the lower base mold is raised and pressed to transfer the molding surface of the upper and lower molds to have a predetermined surface shape. A glass optical element is formed. The lower mold is raised by operating a driving means (for example, a servo motor). When the glass material is supplied in a heated and softened state, pressurization is performed immediately after the supply.
The ascending stroke of the lower mold for pressurization is a value set in advance from the thickness of the optical element to be molded, and is set to an amount that is determined in consideration of heat shrinkage of the glass in the subsequent cooling step. The pressurization schedule can be arbitrarily set according to the shape and size of the optical element to be molded. After initial pressurization, the load is released and then secondary pressurization is performed. A pressurizing method can also be employed.
[0043]
(D) Cooling / mold release process
While maintaining the pressurization or reducing the pressurization, the molded glass optical element and the mold are kept in close contact with each other, and the viscosity of the glass is increased. ¹² After cooling to a temperature equivalent to Poise, release. The mold release temperature is 10 ^12.5 -10 ^13.5 It is preferable to carry out at a Poise equivalent.
[0044]
(E) Removal process
The molded glass optical element is automatically taken out by a take-out arm or the like equipped with a suction member.
[0045]
Next, the result of the example which manufactured the glass optical element using the reference example and the shaping | molding apparatus and manufacturing method of this invention is shown.
[Reference example]
A glass optical element (P ₂ O _Five : 24%, B ₂ O _Three : 4%, Li ₂ O: 20%, Na ₂ O: 13%, K ₂ O: 1%, BaO: 4%, ZnO: 2%, TiO ₂ : 5%, Nb ₂ O _Five : 20%, WO _Three : 7% (mol% display), Tg: 478 ° C. Ts: 527 ° C.) to form a concave meniscus lens having a diameter of 11 mm. A tungsten alloy was used as the mother mold, and a molding surface was formed by precisely processing SiC to form a molding surface, and a carbon film was provided as a release film on the molding surface. The shape of the mother die is as shown in FIG. 5A, and no heat conduction adjusting portion is provided. A control temperature sensor (not shown) was installed near the center of the matrix.
A glass preform preformed into a flat sphere shape in advance in a hot state is heated in a heating chamber 20 at 590 ° C. (10 ⁷ Pre-heated to the equivalent of Poise) and conveyed in a floating state on a floating jig attached to the arm 25, which was simultaneously dropped onto each lower mold forming surface linearly arranged on the lower mother mold and supplied. At this time, the heating time was adjusted using a temperature sensor so that the waveform of the upper and lower molds was 530 ° C. at the center of the mother die.
Immediately, by retracting the arm and raising the lower mother die, the upper and lower molding surfaces are brought closer to each other, and 100 kgf / cm ² And press-molded. With the molding surface kept in close contact with the molded element, it was cooled to the Tg temperature, released from the mold, and the element was taken out. The temperature of each mold at the time of press molding was measured by a thermocouple (not shown) embedded in the mother mold.
As a result, the measurement temperature and the six molded optical elements (glass lenses) were as follows.
[0046]
[Table 2]

[0047]
[Example 1]
A heat conduction adjusting portion made of a gap having the same shape as that shown in FIG. 5B was formed on upper and lower mother dies made of a tungsten alloy. The space in the heat conduction adjusting portion was filled with the atmospheric gas. Six SiC molds (the same as in Reference Example 1) were placed on the mother mold, and a glass lens was molded in the same procedure as in the Reference Example. The results are shown in Table 3.
[0048]
[Table 3]

[0049]
[Example 2]
Next, as shown in FIG. 5C, the upper and lower matrix cavities used in Example 1 were embedded with copper in an adjacent position on one end side of the cavities to form a heat conduction adjusting portion. Using this matrix, press molding similar to that of the reference example was performed. The results are shown in Table 4.
[0050]
[Table 4]

[0051]
From the above results, it has been found that when the heat conduction adjusting portion is formed on the mother die, the temperature difference between the plurality of molds is reduced, and the optical performance of the manufactured glass optical element is made uniform.
[0052]
【The invention's effect】
As described above, according to the present invention, it is possible to equalize the temperature of the mold supported by the mother die, and in particular, it is possible to manufacture an optical element with uniform performance with high productivity in a plurality of molds using a plurality of molds. .
The present invention is particularly effective in a non-circular matrix in which the heat conduction generated in the matrix is asymmetrical. That is, when a molding die arranged almost linearly on a long base is configured and heated as in the present invention, the coil, the heating element skin (the part that generates the most heat), and the location of the molding die Can be made close to each other, so that heating efficiency can be improved and soaking can be performed.
[Brief description of the drawings]
FIG. 1 is a schematic plan view showing an embodiment of a mold press forming apparatus to which the present invention is applied.
FIG. 2 is a side sectional view showing a first embodiment of a molding apparatus to which the present invention is applied.
FIG. 3 is a ¼ schematic cross-sectional perspective view of a molding apparatus to which the present invention is applied.
FIG. 4 is a ¼ schematic plan view of a molding apparatus that does not form a heat conduction adjusting portion.
FIG. 5 (a) is a ¼ schematic plan view showing a heat distribution state of a molding apparatus in which no heat conduction adjusting portion is formed, and FIG. 5 (b) is a molding device in which a heat conduction adjusting portion including a gap is formed. Is a 1/4 schematic plan view showing the heat distribution state of the forming apparatus in which the heat conduction adjusting portion formed by embedding copper in a part of the gap is formed. It is.
[Explanation of symbols]
10 Optical glass manufacturing equipment
20 Heating chamber
40 Molding chamber
41 Press equipment
410a, 410b high frequency induction coil
411a, 411b Master mold
413a, 413b Mold

Claims (4)

And a pair of upper and lower multiple mold having a machined forming surface in a predetermined shape, and a pair of upper and lower mold for supporting upper and lower molds, respectively, and a high-frequency induction heating coil wound around these mother die A mold press molding apparatus having
The upper and lower mother dies have a heating element that generates heat by high-frequency induction, and further, the heating element of at least one of the upper and lower mother dies has the heating element on the outside of the mold supported by the mother dies. A mold press molding apparatus, characterized in that a heat conduction adjusting portion formed of a gap formed in the surface is formed. Press-molding apparatus according to claim 1 in which a plurality of molds to elongate the matrix are arranged substantially linearly. In a method of manufacturing a glass optical element by press-molding a heat-softened glass material with a plurality of upper and lower molding dies having a molding surface processed into a predetermined shape and heated to a predetermined temperature,
The mother die that supports the molding die is formed of a heating element, and the mother die is provided with a heat conduction adjusting portion that is formed on the outer side of the molding die supported by the mother die and is formed by a gap formed in the heating element. A method of manufacturing a glass optical element, comprising: forming and heating the mold while adjusting heat conduction from a heating element that generates heat by high-frequency induction to the mold by the heat conduction adjusting unit. A plurality of molding dies are arranged on the mother die, and the position and size of the heat conduction adjusting portion are adjusted so that the difference in temperature distribution between the molding surfaces of the plurality of molding dies is within 10 ° C. during press molding. The manufacturing method of the glass optical element of Claim 3 set.

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