JPH05294641A - Device for molding optical element of glass - Google Patents

Abstract

PURPOSE:To more uniformly heat a mold and a glass material, to enlarge an aperture, to form a multi-cavity, to reduce power consumption, to increase conversion efficiency and to miniaturize a device in a device for molding glass optical element. CONSTITUTION:Barrel molds 3 and 4 for holding molds 1 and 2 are made up of electrically conductive ceramics or a carbonaceous composite material, heat is generated in the barrel molds themselves by current injection to heat the molds 1 and 2 and the glass material 9.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a glass optical element molding apparatus for directly manufacturing a glass optical element by direct press molding, and more particularly to an electric heating type molding apparatus.

[0002]

2. Description of the Related Art In recent years, a method of manufacturing a lens made of an optical glass is performed by precision pressing a softened glass material using a highly accurate mold, instead of the conventional grinding and polishing manufacturing method. Attention has been drawn to a method of obtaining a glass optical element having a predetermined performance.

A method of heating a die and a glass material (glass material) of an apparatus for press-molding this optical element is disclosed in, for example, Japanese Patent Laid-Open No.
A high frequency induction heating method (RF induction heating method) as disclosed in Japanese Patent Laid-Open No. 3-170228 and Japanese Patent Laid-Open No. 64-45734 is adopted.

In the high frequency induction heating system, the barrel die is made of metal such as tungsten, molybdenum and its alloy, and the barrel die is heated by the high frequency induction heating, and the heat transfer and radiant heat from the heated barrel die are used to form ceramics or the like. The produced mold is heated, and the glass material is heated by these heats. Further, in the thermal radiation heating method as disclosed in Japanese Patent Laid-Open No. 62-59539, a mold or a barrel mold is heated by infrared rays, and heat is transferred from the mold and radiant heat is applied to place the mold inside the mold. The glass material is heated.

On the other hand, FIG. 5 shows an electric heating method in which the mold itself is made of conductive ceramics as shown in Japanese Patent Laid-Open No. 61-266321, and the mold itself is heated by energizing and generating heat. .. In this method, the mold 21,
22 and electrodes 23, 24 between the electrodes 25, 26 and 2
7 and 28 are arranged, and the body dies 23 and 24 are made of non-conductive ceramics, current is passed through the dies 21 and 22 to generate heat, and they are placed in the dies by the heat transfer and radiant heat. The glass material is heated.

[0006]

2. Description of the Related Art As described above, heating by the high-frequency induction heating method causes a problem of high-frequency permeation between the center portion and the peripheral portion of the barrel die, and it is difficult to uniformly heat the barrel die. In particular, when the diameter is increased or a multi-cavity is used, this heating nonuniformity is remarkable. Further, in the high frequency induction heating method, it is impossible to directly perform induction heating on the mold and glass material made of a non-conductor such as ceramic.

In the thermal radiation heating method, it is difficult to make the irradiation amount of infrared rays uniform between the peripheral portion of the body die and the center portion of the die. In particular, when a large diameter or a multi-cavity is used, high frequency induction is applied. As in the case of the heating method, heating non-uniformity appears remarkably, which limits the size of the moldable diameter.

[0008] These heating methods do not directly convert electricity into heat, but secondarily convert it into high frequency or infrared rays, and secondarily convert it into heat, resulting in large power consumption and poor conversion efficiency.

Further, in the energization heating method, which is a method having a high conversion efficiency, in which the mold itself is energized to generate heat from the mold itself, the types of materials constituting the mold are limited, and the electrodes are divided into a mold and a body mold. Since the structure is provided between them, there is a problem that the method of attaching the electrodes and the structures of the mold, the barrel mold and the electrodes are complicated and it is difficult to form a multi-cavity.

Generally, the material forming the glass molding die is required to have strength at high temperature, compactness, and easy workability. There are few types, and it becomes expensive as a mold. Further, when the die is slid and pressed, sliding friction occurs between the die and the inner wall surface of the barrel die, strength and wear resistance at high temperature are required for the electrode, and the electrode attachment method for energization is Have difficulty. Here, in order to prevent the eccentricity error (tilt, decenter) of the press lens, the clearance between the mold and the cylinder must be several μm or less, but consider the expansion coefficient of the mold, the cylinder and the electrode. It is difficult to maintain a clearance of several μm or less at high temperature. Further, in the case of forming a multi-cavity, it is necessary to configure an electrode for each cavity, so that there is a drawback that the method of attaching the electrode and the structure of the mold, the body and the electrode become more complicated than the single cavity. is there.

According to the present invention, since the mold and the glass material can be heated more uniformly, the diameter and the multi-cavity can be easily increased. Moreover, it is an object of the present invention to provide a glass optical element molding apparatus that directly converts electricity into heat, consumes less power, has high conversion efficiency, and can be downsized in terms of apparatus.

[0012]

According to the present invention, a body for holding a molding die is made of a conductive ceramic or a carbon-based composite material (volume resistivity: 1 × 10 ^{−6 to} 7 × 10 ⁻¹ Ωm). In this structure, an electrode is attached to the barrel die, and an electric current is passed through the barrel die itself to generate heat, and the metal mold and the glass material are heated by heat transfer and radiant heat from the heated barrel die.

[0013]

According to the above construction, since the body itself is heated, by devising the shape of the body and the method of attaching the electrodes, the die can be heated more uniformly and directly, and the power consumption is low and the conversion efficiency is low. Get higher Also, since the temperature of the barrel die that heats up is directly monitored and the amount of electricity that is applied to the barrel die is controlled, it is easy to control the temperature of the barrel die or mold, and a large high-frequency oscillator or infrared lamp unit is not required as a device. Therefore, miniaturization is possible.

[0014]

Embodiments of the present invention will be described with reference to the drawings. Experimental Example 1 FIG. 1 is a configuration diagram of a mold, a barrel mold, and an electrode. The molds 1 and 2 use silicon carbide (SiC) (volume resistivity: 5 × 10 ⁻¹ Ωm) as a mold base material, and a SiC film is formed on the molding surface by the CVD method to a thickness of several 100 μm. The surface of the film is mirror-finished so that Ra = 1 nm or less. The body dies 3 and 4 holding the dies 1 and 2, respectively, are carbon-based composite materials containing silicon carbide (SiC) (volume resistivity: 5 ×
10 ^-4 Ωm), and the electrodes 5, 6 and 7, 8 are made of a metal such as copper, stainless steel, or tungsten. Electrode 5,
6 and 7 and 8 are attached to the body dies 3 and 4 by a method of mechanically pressing them with screws made of metal such as stainless steel, tungsten and molybdenum, and an electric current is applied to the body dies 3 and 4 to generate heat. The metal molds 1 and 2 and the glass material 9 are heated by the heat transfer and heat radiation of the body dies 3 and 4 that generate heat, and after the glass material 9 is softened, the upper and lower molds are closed to perform molding. At this time, mold 1 and body 3
Although there is only a clearance of several μm between the mold 2 and the body mold 4, the mold 1 and the body mold 3 and the mold 2 and the body mold 4 are not electrically connected. That is, by selecting the volume resistivities of the barrel die and the die so that the resistance value between the electrodes of the barrel die is smaller than the resistance value in the electrode direction of the die by three digits or more, the current does not flow even if they contact each other. I try not to flow. Therefore, the clearance between the die and the body die can be maintained at several μm or less, and it becomes easier to heat the die more uniformly, especially when the diameter is increased or the cavity is increased. Here, heating and press molding are performed in a non-oxidizing atmosphere (N ₂ gas or the like) so as not to oxidize.

FIG. 2 is a system diagram for controlling the temperatures of the mold, barrel mold and glass material in press molding. The temperature of the molds 1 and 2 or the body molds 3 and 4 is controlled by the thermocouple 1.
The values 0 and 11 are taken into automatic temperature controllers (ATC) 12 and 13, respectively, and proportional / integral / derivative (PID) control is performed according to the difference from the set temperature. The thyristors 14 and 15 are controlled by the control signals from the ATCs 12 and 13, respectively, and the thyristors 14 and 15 output the voltage or current or the electric energy according to the control signals by the phase control method.

In general, when the barrel type is made of a material having a small temperature coefficient of volume resistivity, the voltage is controlled to be constant with respect to the control signal from the ATC. The body type
When it is made of a material whose volume resistivity changes 4 to 12 times, the current is controlled so as to be constant with respect to the control signal from the ATC. Further, when the barrel mold is made of a material such as silicon carbide whose volume resistivity changes with heat generation temperature and whose volume resistivity changes nearly four times as much as the initial value, the control signal from ATC On the other hand, the amount of electric power is controlled to be constant.

Further, the resistance values of the barrel molds 3 and 4 vary depending on the volume resistivity and shape of the material, and therefore it is necessary to apply a voltage and current corresponding to the resistance values, so that the thyristors 14 and 15 are provided.
After changing the output from the transformers 16 and 17 to an appropriate voltage and current, the electrodes 5, 6 and 7, 8 are passed through the barrel molds 3, 4,
Supply power to.

The body type used in this experiment is silicon carbide (Si
Since the carbon-based composite material containing C) was used, the resistance value between the electrodes was about 0.1Ω at room temperature. Therefore, the above P
The current is controlled to be constant by ID control, and the voltage is MA
The current was X20 V, and the current was heated by heating MAX300A by passing it through a barrel. The temperatures of the upper and lower molds and the body were stable within ± 1 ° C of the set temperature.

Experimental Example 2 Next, Experimental Example 2 will be described with reference to the drawings. Figure 3
FIG. 3 is a configuration diagram of a mold, a body mold, and an electrode. Mold 1, 2
Uses the same mold as in Experimental Example 1. The mold 1, 2
The cylindrical molds 3 and 4 for holding the respective are made of a carbon-based composite material containing silicon carbide (SiC) (volume resistivity: 1 × 10 ⁻² Ωm), and the electrodes 5, 6 and 7, 8 are made of copper or the like. It is made of metal in an annular shape. The electrodes 5, 6 and 7, 8 are attached to the body dies 3, 4 respectively, and an electric current is applied to the body dies 3, 4 themselves to generate heat.
The metal molds 1 and 2 and the glass material 9 are heated by the heat transfer and heat radiation of the body dies 3 and 4 that generate heat, and after the glass material 9 is softened, the upper and lower molds are closed to perform molding. At this time, the current flows only in the body molds 3 and 4, and no current flows in the molds 1 and 2 themselves. Therefore, the clearance between the mold and the body can be kept at several μm or less, and since the electrodes are attached in the vertical direction, the mold can be heated more uniformly than in Experimental Example 1, and therefore the diameter and the multi-cavity can be increased. This is a very suitable heating method.

FIG. 4 is a system diagram for controlling the temperatures of the mold, barrel and glass material in press molding. The system for controlling the temperature is basically the same as the system of Experimental Example 1. In the case of Experimental Example 2, when the upper and lower dies are closed and press molding is performed in order to attach the electrodes in the vertical direction, the upper die electrode 6 and the lower die electrode 8 are at the same potential so that electrical interference does not occur. Is wired like this.

The same PID control as in Experimental Example 1 was controlled so that the current was constant, the voltage was MAX 30 V, and the current was MA.
The X200A was heated by heating the cylinder mold by energizing it. The temperatures of the upper and lower molds and the barrel mold could be stabilized within ± 1 ° C with respect to the set temperature.

The same effect can be obtained even if the body is made of conductive ceramics such as high-purity SIC or heat-resistant metal.

Experimental Example 3 Next, Experimental Example 3 will be described with reference to the drawings. In FIG. 1, the same experiment as in Experimental Example 1 was performed using high-purity SiC as the material of the barrel molds 3 and 4. Since high-purity SiC (volume resistivity: 6.2 × 10 ⁻² Ωm) was used, the resistance value between the electrodes was about 12.4 Ω at room temperature. Therefore, the power is controlled to be constant by the above-mentioned PID control, the voltage is MAX100V, and the current is MAX8A, which is energized in a barrel shape.
Heated and heated. The temperatures of the molds 1 and 2 and the body molds 3 and 4 could be stabilized within ± 1 ° C with respect to the set temperature.

[0024]

As described above, according to the present invention, since the body for holding the molding die is made of conductive ceramics or carbon-based composite material and a current is passed through the body itself to generate heat. As shown in the examples, the mold and glass material can be heated more efficiently and uniformly by devising the shape of the barrel and the method of attaching the electrodes, and a large diameter and a multi-cavity are positively implemented. Is possible,
Moreover, since electricity is directly converted into heat, power consumption is low and conversion efficiency is high. Moreover, since the temperature of the barrel die to be heated is directly monitored and the amount of electricity supplied to the barrel die is controlled, it is easy to control the temperature of the barrel die or the die, and the apparatus can be downsized.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of a mold, a body, and electrodes in Experimental Example 1 of the present invention.

FIG. 2 is a system diagram of temperature control in Experimental Example 1 of the present invention.

FIG. 3 is a schematic configuration diagram of a mold, a body, and electrodes in Experimental Example 2 of the present invention.

FIG. 4 is a system diagram of temperature control in Experimental Example 2 of the present invention.

FIG. 5 is a schematic configuration diagram of a conventional glass molding die.

[Explanation of symbols]

 1, 2, 21, 22 Mold 3, 4, 23, 24 Body 5, 6, 25, 26, Upper mold electrode 7, 8, 27, 28, Lower mold electrode 9 Glass material (glass material) 10, 11 Thermocouple 12, 13 Automatic Temperature Controller (ATC) 14, 15 Thyristor 16, 17 Transformer

Claims (2)

[Claims] 1. A press molding apparatus for a glass optical element, comprising a molding die and a barrel die for holding the die,
A glass optical element molding apparatus, characterized in that the barrel die is made of a conductive material and the barrel die itself is heated by energization. 2. The glass optical element molding apparatus according to claim 1, wherein the body material is a conductive ceramic or a carbon-based composite material.