JPH05310435A - Apparatus for forming optical element - Google Patents

Abstract

PURPOSE:To enable the molding of a high-precision optical element by accurately controlling a pair of upper and lower molds heated with a high-frequency coil at a prescribed temperature. CONSTITUTION:Assistant heaters 18, 19 are attached via die plates 12, 13 to a pair of upper and lower molds 14, 15 heated with a high-frequency coil 5. The assistant heaters 18, 19 are controlled, separately from the control of the high-frequency coil 5, based on the mold temperature detected by temperature sensors 30a, 31a to control the temperatures of the upper and the lower molds 14, 15 to respective specific levels.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical element molding apparatus for placing a glass material between a pair of upper and lower molds and heating the mold and the glass material by high-frequency heating to perform press molding, and particularly to a pair of upper and lower molds. Regarding the heating of the mold.

[0002]

2. Description of the Related Art Conventionally, an apparatus for placing a glass material between a pair of upper and lower molds facing each other and heating and pressing the mold and the glass material with one high-frequency coil wound around the mold has been known. is there. This type of apparatus generally controls the temperature of a pair of upper and lower molds to a predetermined temperature by detecting the upper or lower mold temperature and controlling the output of the high frequency coil.

This is because if two or more high-frequency coils are arranged close to each other, they interfere with each other and accurate heating cannot be performed. Therefore, the upper and lower molds are heated by one high-frequency coil. Since there is one high-frequency coil, temperature control is performed based on the upper or lower mold temperature, and the temperature balance between the upper and lower molds is the same as the upper and lower molds in the longitudinal direction of the high-frequency coil. This is done by adjusting the relative positional relationship with the high-frequency coil and the density of the coil pitch of the high-frequency coil.

[0004]

By the way, FIG. 5 (a)
As shown in FIG. 5, for example, when the upper die 51 is fixed at a fixed position with respect to the high frequency coil 50 and only the lower die 52 is moved to perform press molding, the lower die 52 is located at a position L1 near the lower end of the high frequency coil 50. When moved from the center position L4 to the center position, the temperature of the lower mold 52 rises as shown by the solid line T2 in FIG. 5B.

This temperature rise is due to the fact that the heating by the high frequency coil 50 is stronger at the center than at the ends. Therefore, when the lower mold 52 is at the L1 position, both molds 51,
If both temperatures of 52 are set to the temperature Tm of FIG. 5 (b), the upper mold 51 is in a closed state where the lower mold 52 is at the L4 position as shown by the broken line T1a of FIG. 5 (b). Since the temperature does not change, the temperature of the lower mold 52 becomes higher than that of the upper mold 51.

Therefore, normally, the temperature of the upper die 51 is set to Tn which is a predetermined high temperature in advance, as shown by the chain line T1b in FIG. 5 (b), and the lower die 52 reaches the L4 position. At that time, the temperatures of the two were made to coincide with each other.

Further, in the apparatus shown in FIG. 5A, when the output of the high frequency coil 50 is controlled so as to keep the temperature of the lower die 52 constant as shown by the solid line T2 'in FIG. 5C, Since the output of the high-frequency coil 50 decreases as the lower mold 52 rises, the temperature of the upper mold 51 is the broken line T1.
As indicated by a'and the chain line T1b ', the lower mold 52 gradually decreases as it moves from the L1 position to the L4 position, and the relative temperature difference between the upper and lower molds 51, 52 is shown in FIG. 5 (b). It is almost the same as the case shown. Therefore, even when the temperature of the lower mold 52 is kept constant as shown in FIG.
As indicated by 1b ', the temperature of the upper mold 51 has been set in advance to be higher by a predetermined amount.

The temperature change shown by the solid line T2 in FIG. 5 (b) can be suppressed by making the length of the high frequency coil 50 sufficiently long or by adjusting the coil pitch. The increase in length is accompanied by various minuses, and the adjustment of the coil pitch is very delicate, and it takes a long time to perform highly accurate adjustment.

It is an object of the present invention to provide an apparatus capable of easily and accurately controlling a pair of upper and lower molds heated by a high frequency coil to a desired temperature and molding an optical element with higher accuracy. I am trying.

[0010]

The present invention for achieving the above object comprises a pair of upper and lower molds facing each other, and a high-frequency coil wound around the molds.
In an optical element molding apparatus in which a glass material is placed between molds and the mold and glass materials are heated by a high-frequency coil and press-molded, an auxiliary heater capable of output control is provided for at least one of a pair of upper and lower molds. It is provided.

[0011]

The output control of the high frequency coil is carried out in order to keep the upper and lower mold temperatures constant as in the conventional case. The temperature change as shown by T2, T1a'T1b 'in FIG. 5 (b) or (c) at this time is eliminated by controlling the output of the auxiliary heater provided in the lower and / or upper mold. .. In addition,
The temperatures of the upper and lower molds are not always the same, and it is also possible to give a predetermined temperature difference to the two molds by controlling the output of the auxiliary heater to perform more accurate molding.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. In FIG. 1, 1 is a movable plate that can move up and down, and 2 is a fixed plate. A heat-resistant glass tube 3 is attached to the movable plate 1 by an attachment member (not shown) to form a hermetically sealed chamber 4 between the plates 1 and 2. Heat-resistant glass tube 3
A high frequency coil 5 is attached to the outside of the so as to be movable integrally with the heat resistant glass tube 3.

In the chamber 4, a movable plate 1 is vertically movably engaged, and a fixed upper shaft 7 having an inert gas inlet 6 and a fixed plate 2 are vertically movably engaged. And a lower shaft 9 that is vertically moved by a driving device and is given a pressing force and that has an inert gas inlet 8 face each other in the vertical direction.

On both shafts 7 and 9, there are hollow upper and lower heat insulators 1.
0 and 11 are attached respectively to these heat insulators 10,
Die plates 12 and 13 are attached to 11, respectively. Both die plates 12 and 13 have upper and lower dies 1
4, 15 are respectively attached to these molds 14, 1
A plurality of upper and lower cavity dies 16 and 17 are fitted and held in the unit 5.

Both die plates 1 are provided in the heat insulators 10 and 11.
Auxiliary heaters 18 and 19 are attached in close contact with the back surfaces of 2 and 13, respectively. These auxiliary heaters 18, 1
As the heater 9, various known heaters such as a resistance heater embedded in a base material such as metal or ceramics can be used.

A hole 20, is provided at the center of the auxiliary heaters 18, 19.
21 is opened, and pipes 22 and 23 provided in the inert gas inlets 6 and 8 are connected to these holes 20 and 21, respectively. Auxiliary heaters 18, 19 and heat insulators 10, 11
Between the joining surfaces of the die plate 12 and the die plate 13,
A plurality of radial grooves 24, 25 penetrating outward from 21 are provided.

Further, a plurality of inert gas passages 26 and 27 are opened in the body of the heat insulators 10 and 11, and the movable plate 1
The stationary plate 2 has an inert gas inlet port 28 and an exhaust port 2
9 are provided respectively.

Temperature sensors 30a and 31a of the temperature detectors 30 and 31 shown in FIG.
Is attached to take in the temperatures of both molds 14 and 15 to the controller 32 shown in FIG. The control unit 32
The output operation unit (high-frequency oscillator) 33 of the high-frequency coil 5 is operated so that the temperature of the lower mold 15 coincides with the command value, and the temperature changes of the upper and lower molds 14 and 15 are compared to determine the lower mold. Output operation section 34 of the auxiliary heater 18 or 19 of the mold
Alternatively, it is configured to operate 35 to make the temperatures of the two molds 14 and 15 coincide with each other, or to give a temperature difference that is instructed in advance.

Next, the operation of this apparatus will be described. Heat-resistant glass tube 3 and high-frequency coil 5 together with movable plate 1
And chamber 4 is opened. Further, the lower shaft 9 is lowered to open the lower mold 15 with respect to the upper mold 14, and the glass material W is put on the lower cavity die 17. Then, the movable plate 1 is lowered to press the lower end of the heat resistant glass tube 3 against the fixed plate 2 and the chamber 4 is closed.

Next, after the inert gas is supplied through the inert gas inlets 6, 8, 28 and the pipes 22, 23 and exhausted through the exhaust port 29 to replace the air in the chamber 4 with the inert gas. The upper and lower die plates 12 and 13 and the upper and lower molds 14 and 15 are heated at a high frequency by supplying power to the high frequency coil 5, thereby heating the upper and lower cavity dies 16 and 17 and the glass material W.

At this time, the lower mold 15 is at the preheating position shown in FIG. 1, but if there is a temperature difference between the upper and lower molds 14 and 15,
Electric power is supplied to the auxiliary heater 18 or 19 of the mold 14 or 15 having the lower temperature so that the temperatures of both molds 14 and 15 are matched.

When a temperature difference is provided between the upper and lower molds 14, 15, the auxiliary heater 18,
Control 19. That is, when performing temperature control with the temperature of the lower mold 15 as a reference, when it is desired to increase the temperature of the upper mold 14, the upper auxiliary heater 18 is heated to obtain a temperature difference. Further, when it is desired to lower the temperature of the upper mold 14, the temperature of the lower mold 15 is increased by heating the lower auxiliary heater 19, so that the output of the high frequency coil 5 is decreased and the temperature of the upper mold 14 is decreased. The temperature difference can be lowered to obtain a predetermined temperature difference.

In the following description, both molds 14 and 15 will be described.
An example in which the temperatures of 1 and 2 are controlled equally will be described. Both molds 1
4 and 15 are preferably heated with a desired temperature rising gradient to a predetermined press temperature, as shown by points A to B in FIG.

FIG. 3 shows that when the lower mold 15 is in the preheating position as described above, the upper and lower molds 14 and 15 are the high-frequency coil 5.
An example in which the auxiliary heater 18 for the upper die 14 is heated to an equal temperature by only the output is zero as shown in FIG. 3 (c).

As shown by point B in FIG. 3 (a), after the die temperature reaches a predetermined pressing temperature, a predetermined time elapses before reaching point C, and the cavity dies 16, 17 and the glass material W are reached.
When the temperature is stabilized at a predetermined pressing temperature, the lower mold 15 is raised to press the glass material W into a predetermined shape as shown in FIG. 3 (b).

By this press molding, both upper and lower molds 14, 1
5 is closed and thereafter pressurized and held up to point F in FIG. 3 (a) for a predetermined time, but as the lower mold 15 rises, as shown by the dotted line T1a 'in FIG. 5 (c), the upper mold is closed. The temperature of 14 drops. That is, when the lower die 15 is changed from the preheating position to the pressing position, the heating force of the lower die 15 by the high frequency coil 5 is increased, the temperature of the lower die 15 is raised, and the lower die 15 is kept at a predetermined temperature. Then, the output of the high frequency coil 5 is lowered, and the temperature of the upper mold 14 is about to be lowered.

The dotted line t in FIG. 3 (a) shows the temperature drop of the upper mold 14 depending on the position of the lower mold 15 without the time delay.

However, in the present apparatus, when the temperature of the upper mold 14 is about to decrease, this is detected by the temperature detector 30, and the control unit 32 operates the output operation unit 34, so that the temperature shown in FIG.
As shown in (c), power is supplied to the auxiliary heater 18 to prevent the temperature of the upper mold 14 from lowering and keep the upper and lower molds 14 and 15 at a predetermined press temperature. In addition, the output of FIG.
FIG. 3A in which the time delay of the temperature decrease of the lower mold 15 is omitted.
Although it is shown in accordance with the dotted line t, it is needless to say that it actually increases with a certain curve.

After a lapse of a predetermined time from the start of pressing, FIG.
When reaching point D in (a), the temperature of both molds 14 and 15 is gradually cooled to a temperature near the glass transition temperature (point E) with a gentle temperature drop according to a command from the control unit 32.

When the point E is reached, the power supply to the high frequency coil 5 and the auxiliary heaters 18 and 19 is stopped, and the inert gas is introduced from the inert gas inlets 6, 18 and 28 and the pipes 22 and 23 shown in FIG. Increase and decrease the amount of both upper and lower molds 14,15
And so on to a point G where the temperature becomes about 200 ° C.

The mold is opened at a point F, which is a predetermined temperature lower than the point E, and the chamber 4 is opened and the molded optical element is taken out in a natural state after the point G, in which no particular temperature control is performed.

FIG. 4 shows another embodiment of the present invention. Auxiliary heaters 18 'and 19' are interposed between the die plates 12 and 13 and the heat insulators 10 and 11, and the die plates 12 and 13 are formed. Auxiliary heaters 18 ', 1 almost all over the back of the
9'contacted.

The auxiliary heater is not limited to the above embodiment, but may be embedded in the die plates 12 and 13 and the upper and lower molds 14 and 15 and can be variously modified.

[0034]

As described above, according to the present invention, the temperature difference between the upper mold and the lower mold caused by the movement of the mold with respect to the high frequency coil can be easily and accurately removed. In addition, it is possible to remove the temperature difference between the upper and lower dies, which is not caused by the movement of the dies, and positively apply the desired temperature difference to the upper and lower dies, which is extremely useful for forming a highly accurate optical element. Can be obtained.

[Brief description of drawings]

FIG. 1 is a sectional view of an essential part showing an embodiment of the present invention.

FIG. 2 is a block diagram of a control system of the present invention.

FIG. 3 is a diagram showing a relationship among a mold temperature, a lower mold position, and an output of an auxiliary heater during a molding cycle according to the present invention.

FIG. 4 is a cross-sectional view of essential parts showing another embodiment of the present invention.

FIG. 5 is a diagram showing movement of a mold with respect to a high frequency coil and changes in the mold temperature.

[Explanation of symbols]

 1 movable plate 2 fixed plate 3 heat resistant glass tube 5 high frequency coil 7 upper shaft 9 lower shaft 14 upper mold 15 lower mold 16 upper cavity die 17 lower cavity die 18, 18 ', 19, 19' auxiliary heater 30, 31 temperature Detector 32 Control unit 33, 34, 35 Output operation unit

Claims (1)

[Claims] 1. A pair of upper and lower molds facing each other, and a high-frequency coil wound around the mold,
In a molding device of an optical element in which a glass material is placed between the molds and the mold and the glass material are heated and press-molded by the high-frequency coil, output control is possible for at least one of the pair of upper and lower molds. An optical element molding apparatus, which is provided with an auxiliary heater.