JPS59131533A - Temperature control in optical glass production - Google Patents

Abstract

PURPOSE:The temperature is measured, when the glass pipe is heated with the heater which is moving forward and the heater is controlled so that the pipe temperature is kept as prescribed, whereby the temperature of the heated glass pipe is stabilized. CONSTITUTION:The gas-phase starting materials are fed from one end of the rotating glass pipe 1 and simultaneously, the heater 2 is allowed to move forward form P to P' to burn H2 and O2 fed from the pipes 6, 7 equipped with flow controllers 4, 5. At the same time, the temperature-measuring device 3 in the temperature control system Tc is allowed to move in the same direction to measure the temperature near the heated part of the pipe 1. The signals of the temperature measurement f are input through the ever-closed relay contact S1 into the temperature controller 8 and compared with the previously prescribed temperature for the pipe 1, the modification signals r are input into the level converter 9 to operate the controllers 4, 5 and adjust the feed rates of H2 and O2 to keep the calorie of the heater in the appropriate level. The signals f are input into the averaging unit 10 where the average value of the signals f is calculated from P to P' and held.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a temperature control method when manufacturing a glass material for an optical system using an MCVD method.

MCVD method G When manufacturing desired optical system glass materials such as optical fiber preforms, image guide preforms, and Rondo lens preforms 2, the method shown in FIG. 1 is generally used.

To briefly explain this, as shown in Fig. 1G, a glass vibrator (1) made of synthesized quartz or the like is held at both ends by chucks (not shown) of a glass lathe, making it rotatable. , inside the glass vibrator (1) (this is from the raw material supply system at one end to the JII air thread at the other end), gaseous glass raw materials (gaseous glass components, gaseous dopant, carrier gas, etc.) are ) is supplied (benevolent).

On the other hand, the heater (2) consisting of an oxyhydrogen flame burner or the like is able to reciprocate in the longitudinal direction of the glass pipe (1) by means of a traverse mechanism (not shown), and is connected to the temperature regulator (3) of the temperature control system. ) is also capable of reciprocating along the longitudinal direction of the crow-pipe together with the heater (2).

When depositing the glass layer in the glass pipe (1) in the above, the pipe (1) contains S.
iC14, 0eC14, 02, etc. are supplied, and the heater (2) heats the glass pipe (1) at a high temperature when moving from the raw material supply side to the IJ1 gas side.

In the heated glass pipe (1), thermal decomposition of the vapor phase glass raw material occurs and white soot (glass oxide powder) is generated, and the soot is further turned into transparent vitrification by high temperature heat (the glass pipe (1)). 1) Inner peripheral surface (1 piece).

Therefore, when the heater (2) moves forward, a glass layer is deposited inside the glass pipe (1), and at this time, the humidity measuring device (3) measures the temperature of the glass pipe (1). , and the feedback control system via the temperature control system stabilizes the heating device (2) at an appropriate temperature for the thermal decomposition and vitrification.

On the other hand, when the heater (2) moves back, the fuel supply system of the heater (2) is cut off or throttled (this causes the heater (2) to be extinguished or in a low flame state (snuffle). Glass pipe + 1) Return to the original position while maintaining the non-heated state.

The following shows the raw material gas supply state (in which the thickness of the glass layer inside the glass pipe (1) increases by reciprocating the heater (2), and a glass layer of a predetermined thickness is deposited inside the glass pipe (1). Then, the same vibrator (1) is collapsed into a glass barrel through a heat treatment in a separate process.

By the way, as mentioned above (when forming a glass layer in the glass pipe (1) by straining, the heater (2) during double action does not heat the glass pipe (1), so the pipe temperature is around room temperature. It suddenly drops to .

Of course, the temperature measuring device (3) and temperature regulator (PI or PID) of the temperature control system are in operation during this time as well.

In this case, when the temperature of the vibrator decreases, the deviation between the vibrator temperature and the temperature set value becomes extremely large. Since the output of is maximum (saturation state),
The heater (2), which shifts from the backward motion state to the forward motion state, is heated by the glass pipe (1) in the maximum combustion state from the temperature regulator ζ.
begins to heat up.

As a result, the temperature of the glass pipe (1) rises rapidly and exceeds the set temperature, and then the combustion state of the heater (2), that is, the glass pipe heating, is determined via the temperature measuring device and temperature regulator. Even if the temperature is stabilized to the set temperature, the rise in the vibrator temperature is large, so the control temperature fluctuates wildly until it is stabilized, and the settling time becomes long.

Moreover, since the pipe heating point of the heater (2) (71 □ 4 degrees 1 rule) and the temperature measurement point of the 71□4 degree 1 rule (3) (71 □ 4 degrees 1 rule) do not match as shown in the diagram, there is a discrepancy in temperature control.
Therefore, the above-mentioned unfavorable tendencies are strongly observed.Of course, if a part of the glass pipe (1) is heated poorly, defects will occur in the core part, and the yield will decrease.

Figure 2 shows the heating situation of the glass pipe (1) in the conventional example above, and as is clear from the figure, when the heater (2) moves forward, the temperature of the glass A large overshoot occurs.0 In order to solve the above problems, the present invention has been developed to stabilize the heating temperature of the glass pipe via the heater in this type of optical glass manufacturing method. The specific method will be explained below with reference to illustrated embodiments.

In the method of the present invention shown in FIG. 3, the glass pipe (1) is fully rotated as described above, and the glass raw material in the gas phase is supplied from one end of the rotating glass pipe (1). When the heater (2), which is reciprocally movable along the longitudinal direction of the pipe outer circumference, moves back and forth, the glass pipe (1) is heated through the heater (2), thereby vitrifying the glass raw material inside the pipe. Glass is attached to the inner circumferential surface of the glass pipe (1), and on the other hand, when the heater (2) is turned back on, the heater (2) is extinguished or set to a low flame and the glass pipe (1) is left unheated. do.

Then, a glass layer is deposited on the inner circumferential surface of the glass pipe (1) by repeating the above-described glass raw material supply and heater reciprocation.

In addition, the heater (2) in forward motion is connected to the glass pipe (1).
), the temperature measuring device of the temperature control system Tc (
3), for example, a glass pipe (1
), and the heater (2) is fully controlled to maintain the pipe temperature at the set temperature. When moving forward from point P' to point P', the fuel supply pipe [6] (71) equipped with a flow regulator +41 (5)
) is supplied with H2,0□, and the mixed gas is combusted.

The heater (2) in the combustion state moves in the direction P' while completely heating the glass pipe (1), but at this time, the temperature measuring device (3) of the temperature control system Tc also moves in the same direction. Place the temperature measuring device (3) near the heated part of the glass pipe (1).
When the temperature measuring device (3) is measuring the temperature of the glass pipe (1), the measured value signal f from the temperature measuring device (3) is sent to the temperature regulator (of the temperature control system Tc) via the normally closed relay contact RsH. 8
), and this temperature adjustment i (8) electrically and electronically compares and calculates the predetermined set temperature of the glass pipe (1) and the above measured value signal f, and generates a correction signal based on this. γ is input to the level converter (9).

Based on the correction signal γ, the level converter (9) operates the flow rate regulator (4) +5], thereby adjusting the supply amount of the H2 gas to the heater (3). )
The heating power of the glass pipe (1) is set to an appropriate level, and the temperature of the glass pipe (1) is maintained at the set temperature f.

These temperature measurements and temperature control based on them are performed using heaters (2
) is carried out until the point P' is reached, during which time the measured value signal f from the temperature measuring device (3) is input to the temperature regulator (8) side, but at this time, the signal average of the temperature control system Tc The measurement value signal f is also input to the conversion device 00), and the device (
10) calculates and holds the average value of the measured value signal f while the heater (2) is moving from point P to point P'.

Mint switch Ls2 when heater (2) reaches point P'
is turned ON, thereby operating the electromagnetic relay R2 in FIG. 4, closing the relay contact Rs 2 and closing the relay contact Rs 1.
At the same time, the fuel supply pipe t6) (7
) are automatically closed by a supply cutoff pulp (not shown).

Therefore, when the heater (2) moves back in the P direction after reaching the P' point, the heater +21 moves back to the glass pipe (1).
(On the other hand, it is in a non-heating state, but in this double-acting special number, relay contact Rs 1 is open and relay contact s is open as described above.
2 is closed, so the temperature regulator (8) is 9! In this case, the heater (2) during double operation does not heat the glass pipe [11], but the temperature regulator (8) 1 is inputted with a fictitious signal f' which is equivalent to heating the glass pipe [11]. The temperature regulator (8) performs a PI operation that does not cause output saturation, and therefore, as will be clear later, no overshoot occurs during the second and subsequent heating.

When the heater (2) in the double-acting state then reaches point P, the limit switch Ls1 is turned on, and the electromagnetic relay R1 is activated (thereby, the relay contact Rs3 is closed and the relay contact Rsl is also closed. It becomes a state of formation,
Furthermore, timer T starts operating.

From this point on, the heater (2) enters the combustion state again, resumes heating the glass pipe (1), and begins to move forward, but since the timer switch Ts is turned on during the switch operation, the relay contact R82 is closed. Therefore, when the heater (2) resumes heating the vibrator, the virtual signal r' is input to the temperature regulator (8) (dark blue), and the heater (2) ( The pipe heating temperature is maintained at the average value at the time of initial heating.

In other words, the temperature of the glass vibrator (1) has decreased (about room temperature)
Since the initial average heating temperature is used as the standard instead, extreme overshoot will not occur.

Thereafter, when a predetermined period of time has elapsed, the timer T turns the timer switch Ts off and opens the relay contact R, s2, so the false signal f' to the temperature regulator (8) is canted, and after that, the relay Due to the closed state of the contact Rs), the measured value signal f is manually applied to the temperature regulator (8), and when the heater (2) reaches the point P', the signal ff is based on the above-mentioned Temperature control is performed.

Of course, while the heater (2) reaches point P' (1), the signal averaging device (10) averages the measured value signal and holds the average value signal as the next pseudo signal f'. , the same signal (/1. Temperature regulator (8) -\manual power is generated) from oNi of limit switch Ls2.

FIG. 5 shows the temperature control state of the glass vibrator (1) described above.

As is clear from this figure), jJ[I When the heating device (2) makes the first forward movement, it is the same as in the conventional example, but from the second time onwards, the false signal f' is different from the heating during the backward movement. Since the temperature regulator (8) is manually applied from the initial stage to the initial stage, there is no large overshoot, and the temperature of the vibrator remains almost constant.

Note that the above fictitious signal f′ is the first overshoot f
This value is averaged including K, but since the edge can be regarded as the average control temperature of the glass vibrator (1), the temperature setting value (
I live in this prefecture.

Furthermore, the fictitious signal f' here is input to the temperature regulator (8) not only during the return operation of the heater (2), but also at the start of each subsequent heating for a period of time t. ,
The time t at this time may be set according to a rule of thumb in consideration of the overshoot situation and its settling time.

As explained above, the present invention supplies a glass raw material in a vapor phase inside a rotating glass vibrator, and when a heater that can reciprocate along the lengthwise direction of the outer periphery of the glass vibrator moves back and forth,
In addition, heating the glass pipe via the heater (by vitrifying the glass raw material inside the glass pipe and causing the glass to adhere to the inner peripheral surface of the glass pipe, and disabling the glass vibrator when the heater returns) In a method for manufacturing an optical glass glass in which a glass layer is deposited on the inner circumferential surface of a glass pipe (by repeating the feeding of the glass raw material and the reciprocating movement of the heater), the heater is reciprocated. When heating the Lanupive with a heater, the temperature measuring device of the heating control system is scanned together with the heating device to measure the glass pipe temperature, and the temperature adjusting device of the heating control system that receives the measured value signal is heated. In the signal averaging device of the temperature control system, the temperature of the glass vibrator is maintained at the set temperature by controlling the temperature measuring device, and further receives the measured value signal from the above-mentioned JLIA degree measuring device.
The measured value signals are averaged and the average value signal is used as a simulated signal, and the simulated signal is used by the temperature adjustment device ( This input is used to control the heater.

Therefore, in the case of the method of the present invention, the first heating of the glass pipe (excluding!), the second and subsequent heating (in this case, a predetermined control based on the artificial signal At the same time, the settling time is shortened, and the heating temperature over the entire glass vibe heating length is stabilized at approximately the same temperature as the set temperature.

Of course, as a result of such temperature control, there are almost no defective parts in the glass material, and high quality products can be obtained at a high yield.

In addition, even if the amount of raw material supplied into the glass vibrator temporarily decreases due to an unforeseen cause, and a sudden overshoot occurs due to this, the fictitious signal (average value signal) Since the temperature adjustment output is reduced at the time of starting heating thereafter, it is possible to automatically take measures against overshoot.

[Brief explanation of the drawings] Fig. 1 is an explanatory diagram of the famous water using the conventional method, Fig. 2 is an explanatory diagram of the controlled temperature situation in the conventional method, Fig. 3 is an explanatory diagram of the famous water of the method of the present invention, The figure is an electrical circuit diagram of the main parts of the device in the same method.
Fig. 5 is an explanatory diagram showing the control temperature situation in the method of the present invention (1)...Glass pipe (2)...Heater (3)...Temperature measurement t4) t5)...Flow regulator +61 t7+...Fuel supply pipe (8) ・
...Temperature regulator (part of temperature regulating device) (9)
...Level converter (part of fjL degree adjustment device) α
0) ...Signal averaging device Tc ...Temperature control system patent applicant representative Patent attorney Makoto Ito

Claims (1)

[Claims] Gas-phase glass raw material is supplied into a rotating glass pipe, and when a heater that can reciprocate along the outer circumferential longitudinal direction of the glass pipe moves back and forth, a glass vibrator is heated through the heater. (Thus, the glass raw material inside the glass pipe is vitrified and the glass is deposited on the inner circumferential surface of the glass pipe, and when the heater returns, the glass vibrator is kept in a non-heating state, and the glass raw material is supplied and the heater (1) is heated. Due to the repeated backward movement and G, the method for manufacturing optical glass materials involves depositing Calanu; ,
The heating control system temperature 6 (U) is scanned together with the heating device to measure the temperature of the glass vibe in the heated state, and the averaging device measures the temperature of the heating control system that receives the measured value signal. The measured value signals are averaged and the average value signal is used as a dummy signal, and when the heater is in a non-heating state (from the return operation to the initial heating start period), the dummy signal is sent to the temperature adjustment device of the temperature control system ( Optical glass material manufacturing method (temperature control method in a heater) that controls the heater by inputting this temperature.