JP2009120451A - Method for producing glass preform, and production apparatus therefor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing a glass preform which can prevent the breakage of a supporting rod by thermal shock in a heating furnace for heating a glass particulate-deposited body, and to provide a production apparatus therefor. <P>SOLUTION: In the method for producing a glass preform where a glass particulate-deposited body 17 connected to a glass rod 18 formed of a quartz glass is heated inside a furnace core pipe 11, so as to be made into a transparent glass, the part of the glass rod 18 at the outside of the furnace core pipe 11 is heated by a heating means 30, and the temperature difference in optional two points at the intervals of 100 mm in the longitudinal direction of the glass rod 18 is controlled to ≤300°C. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a method and an apparatus for manufacturing a glass base material that heats a glass particulate deposit to form a transparent glass.

Glass base material manufacturing method and manufacturing apparatus for heating glass fine particle deposits (porous glass base material) obtained by OVD method, VAD method, MMD method (multi-burner multi-layering method), etc. to make transparent glass Is known (see, for example, Patent Document 1).
The method for producing a glass base material described in Patent Document 1 is a glass fine particle deposit by causing glass raw material gas such as SiCl ₄ and GeCl ₄ to flame hydrolyze to generate glass fine particles, which are deposited on a glass rod. A porous glass base material is manufactured, and then the porous glass base material is sintered to form a transparent glass.

  As shown in FIG. 7, the glass base material manufacturing apparatus 100 described in Patent Document 1 includes a core tube 101. Then, a glass particulate deposit body 106 in which glass particulates are deposited on the glass rod 102 is inserted into the furnace core tube 101 from above, the glass rod 102 is supported upward, and the glass particulate deposit body 106 is suspended around the axis. It is done.

  A gas introduction tube 103 is provided at the lower end of the core tube 101, and chlorine gas, helium gas, etc. used for heat treatment are supplied into the core tube 101. A gas exhaust pipe 104 is provided at the upper end of the core tube 101 to exhaust the inside of the core tube 101. In addition, a heater 105 is provided outside the core tube 101, and the glass particulate deposit 106 suspended in the core tube 101 is heated to become transparent glass. The outside of the core tube 101 is covered and protected by a furnace body 107. The furnace body 107 includes a monitoring window 108 that can monitor the heating state of the core tube 101, and a radiation thermometer that measures the temperature around the core tube 101. 109 is provided.

JP 2006-151715 A

In the heating furnace for heating the glass fine particle deposit as described above, a heating furnace having a furnace core tube made of quartz or high purity carbon is generally used. In this core tube, since the glass particulate deposits have become larger with the progress of manufacturing technology, the inner diameter of the core tube tends to exceed 280 mm.
In such a heating furnace, corrosive gases such as chlorine and fluorine are often used for the dehydration treatment of the glass particulate deposits and the addition of the refractive index adjusting substance. In order to prevent metal impurities from being mixed into the glass base material, a support rod made of quartz (glass rod) is used.

  However, quartz support rods may be damaged by thermal shock when an excessive temperature difference occurs. For example, when the core tube diameter exceeds 280 mm, the radiant heat from the heater that heats the inside of the core tube easily escapes upward in the core tube, and the portion of the support rod that is positioned above the inside of the core tube is likely to be heated. On the other hand, the portion of the support rod exposed to the outside from the core tube is cooled by air cooling and has a low temperature. For this reason, the temperature difference between the inner and outer parts of the core tube becomes large and thermal shock is likely to occur in the support rod. When the support rod is damaged by thermal shock, the glass particulate deposit falls and the core tube is damaged. End up. In that case, replacement of the core tube and long-term shutdown of the equipment are required, which increases the manufacturing cost and adversely affects the manufacturability.

  Accordingly, an object of the present invention is to provide a glass base material manufacturing method and a manufacturing apparatus capable of preventing a support rod from being damaged by thermal shock in a heating furnace for heating a glass particulate deposit.

  A method for producing a glass base material according to the present invention for solving the above-described problem is a glass base material for heating a glass fine particle deposit connected to a support rod made of quartz glass in a furnace tube to form a transparent glass. It is a manufacturing method, Comprising: The temperature difference in two arbitrary points of the 100-mm space | interval in the longitudinal direction of the said support bar shall be 300 degrees C or less.

  Moreover, in the manufacturing method of the glass base material which concerns on this invention, it is preferable that the said temperature difference shall be 300 degrees C or less by heat-retaining or heating the site | part of the said support rod located in the upper end vicinity of the said core tube.

  In addition, a glass base material manufacturing apparatus according to the present invention for solving the above-described problems is a glass base material for heating a glass particulate deposit connected to a support rod made of quartz glass in a vertical furnace core tube. It is a manufacturing apparatus, and has heating means for keeping or heating a portion of the support rod located near the upper end of the core tube.

  Moreover, in the glass base material manufacturing apparatus according to the present invention, even if the inner diameter of the core tube is larger than 280 mm, the support rod is prevented from being damaged by thermal shock by having the heating means. Can do.

  According to the present invention, since the temperature difference at any two points at an interval of 100 mm in the longitudinal direction of the support rod is set to 300 ° C. or less, the temperature gradient in the longitudinal direction of the support rod can be moderately suppressed. It is possible to prevent breakage of the support rod and prevent inconvenience due to dropping of the glass particulate deposit.

Hereinafter, an example of an embodiment of a manufacturing method of a glass base material and a manufacturing device concerning the present invention is explained in detail based on a drawing.
FIG. 1 is a schematic configuration diagram showing a glass base material manufacturing apparatus capable of performing the glass base material manufacturing method of the present embodiment.

The glass fine particle deposit body (porous glass base material) heated in the glass base material manufacturing method and manufacturing apparatus of the present embodiment flame-hydrolyzes a glass raw material gas such as SiCl ₄ or GeCl ₄ to produce SiO ₂ or GeO ₂ glass fine particles are generated and deposited on a starting glass rod or the like.

  As shown in FIG. 1, the glass base material manufacturing apparatus 10 of the present embodiment is a heating furnace having a furnace core tube 11 used for dehydration and sintering of a glass fine particle deposit 17 that is a heated object. The core tube 11 is made of carbon or quartz excellent in heat resistance and corrosion resistance, and consists of two parts, a main body part 12 and an upper lid 13, which are joined together. In the present embodiment, the inner diameter of the core tube 11 is set to exceed 280 mm in consideration of heating the large glass particulate deposits 17. Note that the inner diameter of the core tube 11 may be 280 mm or less, but in that case, thermal shock is unlikely to occur in the support rod. In the present invention, even if the inner diameter of the core tube 11 is 280 mm or more, breakage of the support rod due to thermal shock can be prevented.

  At the upper end of the upper lid 13, there is a hole through which the glass rod 18, which is a support rod extending from the end of the glass particulate deposit body 17, can be rotated. ). The glass rod 18 includes a dummy rod 18a that deposits glass particles to form a glass particle deposit 17 and a support rod 18c that supports the dummy rod 18a via a connecting portion 18b. The connecting portion 18b is also made of quartz glass, and the dummy rod 18a and the support rod 18c are fitted and connected from both sides. A suction device (not shown) is disposed in the vicinity of the hole of the upper lid 13, and gas leaking from the hole is sucked out by this suction device. A plurality of stages of heaters 14 are provided around the main body 12 of the core tube 11 to heat the glass particulate deposits 17 housed in the core tube 11. The heater 14 includes a resistance heating type heater and an induction heating type heater.

  A heat insulating material (not shown) is provided outside the heater 14, and the entire heating unit is covered and protected by a furnace body 19. A gas introduction part 15 is provided in the lower part of the core tube 11 and a gas exhaust part 16 is provided in the upper part, and chlorine gas, helium gas, etc. used for heat treatment are introduced and discharged. Further, the furnace body 19 can be provided with a monitoring window 20 for monitoring the heating state of the core tube 11 and a radiation thermometer 21 for measuring the temperature around the core tube.

  The current or voltage supplied to the heater 14 is adjusted so that the core tube ambient temperature measured by the radiation thermometer 21 has a predetermined value, and the core tube peripheral temperature is set to a predetermined value.

  In the structure in which the glass rod 18 penetrates the upper lid 13 and is exposed to the outside of the core tube 11 as described above, the temperature gradient in the longitudinal direction of the glass rod 18 usually has the inside of the core tube 11 sandwiching the upper lid 13 and the core tube. 11 It is considered that the two points outside are steepest. Alternatively, depending on the structure of the upper lid 13, it may be steepest in the upper lid 13. The temperature gradient in the longitudinal direction of the glass rod 18 is adjusted so that a thermal shock is generated by this steep temperature gradient and the glass rod 18 is not damaged.

  As a method for adjusting the temperature gradient of the glass rod 18, there are a method in which a portion where the glass rod 18 is rapidly cooled is heated with a heating gas, or is actively heated using a heater. For example, as shown in FIG. 1, it is preferable to provide a heating means 30 for heating the portion of the glass rod 18 that has come out of the furnace from the upper lid 13. The heating means 30 includes, for example, a heater 31 and an air blowing means 32, and the air sent by the air blowing means 32 can be heated by the heater 31 and blown onto the glass rod 18 to be heated. Alternatively, only the heater 31 may be provided in the vicinity of the upper portion of the upper lid 13, and the glass rod 18 may be heated by the heater 31.

As another method for adjusting the temperature gradient of the glass rod 18, the portion where the glass rod 18 is rapidly cooled may be kept warm with heated gas. For example, as shown in FIG. 2, the upper lid 13a is provided with a plurality of stages of spaces having the gas supply part 16a or the gas discharge part 16b, and heating means 30a for heating the inert gas supplied from the gas supply part 16a. Also good. By supplying the inert gas from the gas supply unit 16a, it is possible to seal the gap between the clearance portion of the upper lid 13a and the glass rod 18, and the heating means 30a, for example, heats the inert gas to 50 degrees or more. By doing so, the glass rod 18 located in the upper lid 13a can be kept warm. As a heating method of the inert gas by the heating means 30a, heating (insulating) the pipe of the gas supply unit 16a by the tape heater 31a can be exemplified.
Moreover, either the heating means 30 shown in FIG. 1 or the heating means 30a shown in FIG. 2 may be installed alone, or both may be installed.

  As another method for adjusting the temperature gradient of the glass rod 18, an inert gas supplied into the upper lid 13a by radiant heat from the main body 12 of the core tube 11 using the configuration of the upper lid 13a shown in FIG. It is also possible to heat the glass rod 18 in the upper lid 13a. In particular, as shown in FIG. 3, the inert gas supplied into the upper lid 13a is temporarily retained by providing circumferential fins 16c in a plurality of spaces partitioned in the upper lid 13a. And can be heated by radiant heat from below.

Next, the examination result regarding the temperature gradient of the glass rod 18 is shown using the glass base material manufacturing apparatus 10.
A glass fine particle deposit having an outer diameter of 250 to 300 mm and a uniform outer diameter of 800 to 1200 mm is manufactured, and this glass fine particle deposit is transparent glass by sintering in a heating furnace having a core tube inner diameter of φ350 mm. Thus, a glass base material having an outer diameter of 110 to 130 mm and a uniform outer diameter of 700 to 1000 mm is manufactured. During this transparent vitrification, the temperature gradient in the longitudinal direction of the support rod is set variously using a heater or a cooler, the temperature is measured at intervals of 100 mm in the longitudinal direction, and the point where the temperature difference is the largest is the maximum temperature difference. . It measures using 100 glass rods about each condition, and calculates the probability that the glass rod will break.
The probability (%) of cracking is calculated by (number of cracks / 100) × 100. The calculation results are shown in Table 1 below. A graph of this is shown in FIG.

  As shown in Table 1 and FIG. 4, when the maximum temperature difference is 10 to 300 ° C., the probability that the support rod breaks is low at 2% at 300 ° C., but rapidly increases to 18% at 320 ° C. above 300 ° C. . From this, it can be understood that the cracking of the support bar can be effectively prevented by setting the temperature difference at any two points at intervals of 100 mm in the longitudinal direction of the support bar to 300 ° C. or less.

Next, the results of studies on the inner diameter of the core tube will be shown.
A glass fine particle deposit having an outer diameter of 210 mm and a uniform outer diameter of 800 to 1200 mm is manufactured. This glass fine particle deposit is converted to transparent glass by changing the inner diameter of the furnace core tube of the heating furnace to produce a glass base material having an outer diameter of φ90 to 95 mm and a uniform outer diameter of 700 to 1000 mm. At the time of this transparent vitrification, the temperature of the support rod is measured at intervals of 100 mm in the longitudinal direction, and the portion having the largest temperature difference is defined as the maximum temperature difference in Table 2. Under each condition, the probability of the support rod breaking is calculated as (number of cracks / 100) × 100 in the same manner as described above. The calculation results are shown in Table 2 below. A graph of this is shown in FIG.

  As shown in Table 2 and FIG. 5, when the inner diameter of the core tube exceeds 280 mm, the radiant heat from the heater that heats the core tube increases, so the maximum temperature difference in the support rod also increases, and the probability of the support rod breaking rapidly increases. To do. From this, particularly when the inner diameter of the core tube exceeds 280 mm, cracking of the support rod can be more effectively prevented by setting the temperature difference at any two points at 100 mm intervals in the longitudinal direction of the support rod to 300 ° C. or less. You can see that

According to the manufacturing method and the manufacturing apparatus 10 of the glass base material described above, the temperature difference is set to 300 ° C. or less at any two points with a distance of 100 mm in the longitudinal direction of the glass rod 18. The temperature gradient in the direction can be suppressed relatively gently, and the glass rod 18 can be prevented from being damaged by thermal shock. Therefore, even when the core tube 11 having an inner diameter of more than 280 mm is used and the portion of the glass rod located above the core tube 11 is easily heated by the radiant heat from the heater 14 that heats the inside of the core tube 11, the glass The thermal shock of the rod 18 can be prevented to prevent the glass particulate deposit 17 from falling, and it is possible to prevent the core tube 11 from being replaced and the manufacturing apparatus 10 from being forced to stop for a long time. Cost reduction and manufacturability can be improved.
Moreover, since the site | part of the glass rod 18 in the outer side of the core tube 11 is heated by the heating means 30, the temperature gradient of the glass rod 18 can be made small efficiently.

  As shown in FIG. 6, in addition to the configuration of the manufacturing apparatus 10 shown in FIG. 1, thermometers 22 a and 22 b that measure temperatures at two points with a distance L of 100 mm in the glass rod 18 are provided. Based on the measurement signals from the totals 22a and 22b, a control unit 40 may be provided that controls the heater 31 and the air blowing means 32 as the heating means 30 so that the temperature difference between the two points is 300 ° C. or less.

  With the configuration shown in FIG. 6, the temperature difference between the two points can always be suppressed to 300 ° C. or less. It is also possible to perform temperature measurement by moving the position of the two points while keeping the distance between the two points where the temperature is measured by the thermometers 22a and 22b at 100 mm, and search for the position where the temperature difference is the largest. it can.

It is a schematic block diagram which shows the manufacturing apparatus of the glass base material which can implement the manufacturing method of the glass base material of this invention. It is sectional drawing which shows another example of embodiment of the manufacturing apparatus of the glass base material of this invention. It is an enlarged view of the upper cover shown in FIG. It is a graph which shows the examination result regarding the temperature gradient of a glass rod. It is a graph which shows the examination result regarding a core tube inner diameter. It is sectional drawing which shows another example of embodiment of the manufacturing apparatus of the glass base material of this invention. It is sectional drawing which shows the example of the manufacturing apparatus of the conventional glass base material.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Glass base material manufacturing apparatus 11 Core tube 17 Glass particulate deposit 18 Glass rod (support rod)
30, 30a Heating means

Claims (4)

A method for producing a glass base material in which a glass particulate deposit connected to a support rod made of quartz glass is heated in a furnace core tube to become transparent glass,
A method for producing a glass base material, characterized in that a temperature difference between two arbitrary points at an interval of 100 mm in the longitudinal direction of the support rod is 300 ° C. or less. It is a manufacturing method of the glass base material of Claim 1,
A method for producing a glass base material, characterized in that the temperature difference is set to 300 ° C. or less by keeping or heating a portion of the support rod located in the vicinity of the upper end of the furnace tube. A glass base material manufacturing apparatus for heating a glass particulate deposit connected to a support rod made of quartz glass in a vertical furnace core tube,
An apparatus for producing a glass base material, comprising heating means for keeping or heating a portion of the support rod located near the upper end of the furnace core tube. The glass base material manufacturing apparatus according to claim 3,
An apparatus for producing a glass base material, wherein the inner diameter of the furnace core tube is larger than 280 mm.

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