JP2003212557A - Method and apparatus for manufacturing glass preform - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method and an apparatus for manufacturing a glass preform, in which a working environment is improved and the quality of the glass preform is stabilized by preventing the flowing-out of a corrosive gas such as a chlorine gas from the apparatus into a room during the heat treatment of a fine glass particle deposit. <P>SOLUTION: The apparatus for manufacturing the glass preform is provided with a furnace tube having a top cover provided with an insert opening to insert a supporting rod to be connected to an elevating device, a heater surrounding the furnace tube, and a furnace body to cover the heater. The tubular sealed chamber is provided on the upper surface of the top cover in a manner covering the lower part of a supporting rod and the insert opening of the supporting rod. The dehydration of the fine glass particle deposit and making of clear glass are carried out while introducing an inert gas to the sealed chamber so as to bring predetermined pressure in the sealed chamber. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for manufacturing a glass base material such as a glass base material for an optical fiber, which heats a glass particle deposit to dehydrate and vitrify it.

[0002]

2. Description of the Related Art Conventionally, glass preforms such as glass preforms for optical fibers are dehydrated and transparent vitrified by heat-treating glass particle deposits (porous glass preforms) produced by the VAD method or OVD method. Manufactured by doing.
In the heat treatment step, the atmosphere gas is selected according to the treatment contents such as dehydration and transparent vitrification. For example, in the method disclosed in JP-A-61-270232, the first heat treatment is performed. He and O _{2 from the} glass particulate deposits
And dehydration gas (chlorine gas, thionyl chloride, fluorinated silane, etc.) are used for dehydration, and in the subsequent second heat treatment, transparent vitrification is performed in an atmosphere containing only He and O ₂ or He.

[0003]

In such a glass base material manufacturing method, in a glass base material manufacturing apparatus for carrying out heat treatment, a glass fine particle deposit supported by a supporting rod is suspended in a furnace core tube, The glass fine particle deposit is dehydrated in a chlorine-based gas (dehydrating agent) atmosphere, and is further made into vitrified glass in an inert gas atmosphere or a mixed atmosphere of an inert gas and a chlorine-based gas or O ₂ , or a chlorine-based material. After dehydration with gas, SiF ₄ for profile (refractive index) adjustment
In general, a method of adding F using a gas such as the above, and then forming a transparent glass in an inert gas atmosphere or in a mixed atmosphere of an inert gas and a chlorine-based gas is performed.

In the case of such a method, corrosive gas (halogen gas such as chlorine gas and fluorine compound gas) leaks from the manufacturing apparatus to corrode metal parts of each apparatus in the room where the manufacturing apparatus is installed, The amount of metal-based dust in the indoor atmosphere may increase. Normally, this type of manufacturing equipment is often installed in the same room as the glass particle deposition apparatus that manufactures glass particle deposits, but if the amount of metal-based dust in the room increases, it will be The metal-based dust in the atmosphere is mixed in the deposition apparatus, and many metal impurities are present in the finally obtained glass base material.

Most of the corrosive gas (halogen-based gas) flowing out from the glass base material manufacturing apparatus into the room flows out from the portion where the support rod of the core upper tube is inserted. As a method for preventing such a corrosive gas from flowing out, there is known a method of providing a seal lid that makes a gas seal between the furnace core tube and the support rod by contacting the flange portion at the upper end of the furnace core tube (Japanese Patent Laid-Open No. HEI-8). −
No. 12365). However, the gas seal of this type alone cannot completely prevent the gas in the core tube from flowing out. The reason is that the gas seal part of this structure has low airtightness, so the pressure in the gas seal part is not stable, and when the pressure in the core tube becomes higher than the pressure in the gas seal section, the gas in the core tube flows out to the outside. The reason is that

The present invention solves the above problems in the prior art and prevents corrosive gas such as halogen gas from flowing out from the glass base material manufacturing apparatus into the room during the heat treatment of the glass particle deposit. However, it is an object of the present invention to provide a glass base material manufacturing method and manufacturing apparatus capable of improving the working environment and stabilizing the quality of the glass base material.

[0007]

The present invention proposes the following methods and devices (1) to (7) as means for solving the above problems. (1) An upper lid provided with an insertion port for inserting a support rod connected to an elevating device, a furnace core tube for accommodating a glass particulate deposit and heat-treating the inside, a heater surrounding the furnace core tube, and the heater Using a glass base material manufacturing apparatus equipped with a furnace body for covering, the glass particulate deposits supported by the support rods are moved in the vertical direction while being rotated about an axis, and heated to perform dehydration and transparent vitrification. In the method for manufacturing a glass preform, a tubular seal chamber is provided on the upper surface of the upper lid so as to cover the support rod and the support rod insertion port, and the pressure in the seal chamber is higher than the pressure in the core tube. The method for producing a glass base material, which comprises performing dehydration and transparent vitrification while introducing an inert gas so that the pressure becomes equal to. (2) The length of the sealing chamber in the longitudinal direction of the support rod is 50 mm.
It is above, The manufacturing method of the glass base material of said (1) characterized by the above-mentioned. (3) The method for producing a glass preform according to (1) or (2) above, wherein the difference between the inner diameter of the tubular seal chamber and the outer diameter of the support rod is 20 mm or less.

(4) An upper lid provided with an insertion port for inserting a support rod connected to the lifting device, a furnace core tube for accommodating the glass particle deposit and heat-treating the inside, and a heater surrounding the furnace tube. An apparatus for producing a glass base material, comprising: a furnace body that covers the heater; and a glass fine particle deposited body supported by the support rod, which is vertically rotated while being rotated about an axis to be heated, dehydrated, and made into transparent vitrified material. In the above, in the form of covering the support rod and the support rod insertion port on the upper surface of the upper lid, a tubular seal chamber capable of adjusting the internal pressure to a predetermined pressure higher than the pressure in the core tube by adjusting the amount of inert gas introduced is provided. A glass base material manufacturing device characterized by being installed. (5) A measuring device for measuring the pressure in the seal chamber, and a control device for controlling the amount of the inert gas introduced based on the measurement value of the measuring device are provided.
Glass base material manufacturing equipment. (6) The length of the sealing chamber in the longitudinal direction of the support rod is 50 mm.
The glass base material manufacturing apparatus according to the above (4) or (5), which is the above. (7) The difference between the inner diameter of the tubular seal chamber and the outer diameter of the support rod is 20 mm or less, (4) to
An apparatus for manufacturing a glass base material according to any one of (6).

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION A glass base material manufacturing apparatus according to the present invention comprises an upper lid provided with an insertion opening for inserting a supporting rod connected to an elevating device, and a core for accommodating a glass particle deposit and heat-treating it inside. A tube, a heater surrounding the core tube, and a furnace body that covers the heater are main components, and the support rod and the support rod insertion opening are covered on the upper surface of the upper lid by adjusting the amount of inert gas introduced inside. It is configured such that a tubular seal chamber capable of adjusting the pressure of 1 to a predetermined pressure higher than the pressure in the core tube is installed. In this way, a seal chamber is installed which covers the clearance between the upper lid of the glass base material manufacturing apparatus for making the glass particulate deposit body into transparent glass and the support rod for suspending the glass particulate deposit body, and the seal chamber has a higher pressure than the core tube internal pressure. By introducing the inert gas of a predetermined pressure, the airtightness between the atmosphere inside the core tube and the atmosphere outside the apparatus is increased, and the corrosive gas used in the core tube can be prevented from leaking out from the clearance portion of the upper lid.

The present invention will be described in detail below with reference to the drawings. FIG. 1 is a schematic explanatory view showing one embodiment of a glass base material manufacturing apparatus according to the present invention. The apparatus of FIG. 1 includes a furnace core tube 2 having an inlet / outlet for a base material 1 (glass fine particle deposit or glass base material after transparent vitrification) in the upper part, a heater 3 provided around the core tube 2, and a heater 3. An upper lid 5 having a furnace body 4 for covering and a support rod insertion port 7 for sealing the inlet / outlet of the base material above the core tube 2 after the insertion of the base material 1, a lower lid 6 for sealing the lower part of the core tube 2, a mother It is composed of a lifting device 8 for moving the material 1 in the vertical direction.
A seal chamber 9 is installed so as to cover 0 and the support rod insertion port 7. An inert gas introduction port 16 is installed in the seal chamber 9 so that the inert gas can be introduced into the seal chamber 9 so that the seal chamber 9 has a predetermined pressure.

A gas supply line for supplying an inert gas and an exhaust line for exhaust (only an exhaust line 11 connected to the upper lid 5 is shown in the figure) are connected to the core tube 2 and the furnace body 4 as necessary. Has been done. In the figure, 12 is a radiation thermometer for measuring the heater temperature, and 13 is a pressure measuring device for measuring the pressure in the core tube 2.

Using the glass base material manufacturing apparatus having the configuration shown in FIG.
For example, the operation method for producing the glass base material by dehydration and transparent vitrification of the glass particle deposit is as follows. First, a glass particle deposit (base material 1) produced by the VAD method or the OVD method is joined to the lower end of the support rod 10 connected to the elevating device 8, and the start position (usually the uppermost position) in the furnace core tube 2 is joined. Set to.

Next, the glass particulate deposit is heated by the heater 3, and at the same time, Cl ₂ of a predetermined ratio is placed in the furnace tube 2.
And a mixed gas of He are caused to flow. The heater temperature is maintained within a predetermined temperature range, and the base material is lowered from there at an appropriate speed. When the base material 1 arrives at the final position (usually the bottom end) (up to this point is the dehydration step), pulling up of the base material 1 is started,
At the same time, the heater is heated to the clearing temperature and only a mixed gas of Cl ₂ and He in a predetermined ratio or He gas is flown into the furnace core tube.

When the heater temperature reaches the predetermined temperature range, the base material 1 returned to the start position is lowered at an appropriate speed, and when the base material 1 reaches the lowest end, the base material 1 is started to be pulled up, and at the same time, the heater 3 Power off (transparent vitrification process).

The heater temperature (heater outer surface temperature at the central position of the heater 3) during the dehydration step is 1000 to
The temperature is preferably maintained at 1300 ° C, more preferably 1
It is preferable to maintain the temperature in the range of 200 to 1300 ° C. The temperature in the furnace during the transparent vitrification step is 1400 to 16
The temperature is preferably maintained at 00 ° C., more preferably 1520
It is preferable to maintain in the range of ˜1570 ° C.

During the above dehydration and transparent vitrification, the corrosive gas in the core tube 2 may leak out from the support rod insertion port 7 portion of the upper lid 5 (upper lid clearance portion). Is provided with a seal chamber 9 on the upper surface of the upper lid 5 so as to cover the support rod 10 and the support rod insertion port 7. An inert gas is introduced into the seal chamber 9 to adjust the pressure in the seal chamber 9 to the inside of the core tube. Since the inert gas is introduced so as to have a predetermined pressure higher than the pressure, the corrosive gas leaked from the support rod insertion port 7 is sealed at this portion and corroded in the room where the device is installed. It is possible to prevent the volatile gas from leaking out.

The seal chamber 9 is provided with a support rod 10 from the upper surface of the upper lid 5.
It is installed so as to cover (up to about 300 mm from the upper surface of the upper lid 5) and the support rod insertion port 7. However, in order to improve the airtightness of the atmosphere inside the core tube 2 and the outside atmosphere, the seal chamber 9 is supported. The length of the rod 10 in the longitudinal direction is preferably 50 mm or more. For the same reason, it is preferable that the difference between the inner diameter of the tubular seal chamber 9 and the outer diameter of the support rod 10 is 20 mm or less.

The pressure in the seal chamber 9 is adjusted by measuring the pressure in the seal chamber 9 with a pressure measuring device 14 attached to the seal chamber 9 and adjusting the flow rate of the inert gas introduced into the seal chamber 9. Therefore, the method of adjusting the pressure in the seal chamber 9 is preferable. Further, in the pressure adjusting work in the seal chamber 9, the controller 15 and the MF for adjusting the inert gas flow rate based on the measurement value from the pressure measuring device 14 such as a manometer.
By adding C (mass flow controller) 17, it is possible to save labor and reduce costs. By adjusting the flow rate of the inert gas according to the pressure fluctuation, the pressure in the seal chamber 9 and the core tube 2 can be maintained at a predetermined value, and the quality of the product can be maintained. Further, by setting the pressure in the seal chamber 9 higher than the pressure in the furnace core tube 2 (preferably about 10 to 200 Pa), the atmospheric gas in the furnace core tube 2 is less likely to leak from the upper lid clearance portion into the seal chamber 9. As a result, gas leakage to the outside of the device is suppressed more effectively.

[0019]

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples. Example 1 A starting glass rod was produced by welding glass dummy rods to both ends of a core glass rod having a core / clad portion and having a diameter of 20 mm. Glass fine particles were deposited on the outer circumference of this starting rod by the OVD method to prepare a glass fine particle deposit (length: 1000 mm). This glass particulate deposit is used as an apparatus (heater 3
(Length along the longitudinal direction of the furnace core tube 2 of: 400 mm) was used for dehydration and transparent vitrification to produce a glass preform.
The length of the support bar 10 in the longitudinal direction of the seal chamber 9 is 500 mm.
Thus, the difference between the inner diameter of the seal chamber 9 and the outer diameter of the support rod is 5 mm.

The above glass particulate deposit (base material 1) is installed at the start position (uppermost part shown in FIG. 1) in the core tube 2, and the temperature inside the core tube 2 is raised by the heater 3 and at the same time the inside of the core tube 2 is increased. Cl ₂ : ₂ SLM (standard liter /
Min) and He: 20 SLM mixed gas was allowed to flow until the base material 1 reached the lowest end. Heater temperature is 130
The base material 1 was kept at 0 ° C. and lowered from the start position at a speed of 10 mm / min. When the base material 1 reaches the lowermost end of the core tube 2, the temperature rise is started, and Cl ₂ : 2SL is introduced into the core tube 2.
A mixed gas of M and He: 20 SLM was flowed, and at the same time, the base material 1
Started to raise.

After the base material 1 returns to the start position, when the heater temperature reaches 1550 ° C., the base material is lowered at a speed of 3 mm / min, and the base material 1 arrives at the lowermost end of the core tube 2. Then, the heater 3 was turned off, the gas supply was stopped, and the base material 1 was pulled up. As a result, a glass base material of good quality was obtained.

Throughout the above manufacturing period, the inside of the seal chamber 9 is 6
By supplying He of 0 to 70 SLM, the pressure inside the seal chamber 9 was controlled to be +50 Pa due to the chamber pressure difference (pressure difference with the outside of the device). Further, an exhaust line 11 was installed on the upper lid 5, and the pressure measuring device 13 attached to the core tube 2 was controlled so that the chamber pressure difference was −20 Pa.

During the above manufacturing operation, a chlorine gas detector was installed on the upper part of the upper lid 5 of the apparatus, and the leak amount of chlorine gas was confirmed. The measurement position was 1 m above the uppermost part of the upper lid 5 and within the circumference of 1 m in diameter centered on the support rod 10 (the same applies to the following examples and comparative examples). As a result, it was confirmed by the chlorine gas detector that the chlorine leakage amount was 0.01 ppm or less throughout the production period of the glass base material.
Moreover, as a result of measuring the chlorine addition amount (Δ +) of the obtained glass base material (glass refractive index of the target base material−refractive index of SiO ₂ glass), the variation of Δ + in the longitudinal direction was 0.005%. . As a result of repeating this manufacturing operation, foreign substances having a width of 1 mm or more in the glass base material produced by the glass particle deposition apparatus and the sintering apparatus (glass base material production apparatus) installed near the glass base material production apparatus and The number of bubbles remained 0.

(Example 2) Using the same glass particle deposit and glass preform manufacturing apparatus as those used in Example 1, the control conditions of the pressure in the seal chamber 9 and the pressure in the furnace core tube 2 were changed. A glass base material was manufactured in the same manner as in Example 1 except for the above. That is, by supplying 1 to 2 SLM of He into the seal chamber 9 throughout the manufacturing period,
The internal pressure was controlled so that the pressure difference between the chambers was 0 Pa. Further, an exhaust line 11 was installed on the upper lid 5, and the pressure measuring device 13 attached to the core tube 2 was controlled so that the chamber pressure difference was 0 Pa.

During the above manufacturing operation, a chlorine gas detector was installed on the upper lid 5 of the apparatus to check the amount of chlorine gas leaked.
As a result, it was confirmed by the chlorine gas detector that the chlorine leakage amount was 0.02 to 0.03 ppm throughout the production period of the glass base material. Moreover, as a result of measuring the chlorine addition amount (Δ +) of the obtained glass base material, the variation of Δ + in the longitudinal direction was 0.005%. As a result of continuing this manufacturing work, the number of foreign particles and bubbles having a width of 1 mm or more present in the glass base material produced by the glass particle deposition apparatus and the sintering apparatus near this apparatus was determined by this apparatus. Before the start, the number was 0 on average, but two months after the start of production, the number increased to 2 on average.

(Embodiment 3) The same control conditions for the pressure in the seal chamber 9 and the pressure in the furnace core tube 2 were changed by using the same glass particle deposit body and glass base material manufacturing apparatus as those used in Embodiment 1. A glass base material was manufactured in the same manner as in Example 1 except for the above. That is, He is supplied to the seal chamber 9 through the manufacturing period for 0 to 50 SLM, and the pressure is positively changed. As a result, the pressure in the seal chamber 9 is 0 to 15 P due to the chamber pressure difference.
It varied in the range of a. Further, the exhaust line 1 is attached to the upper lid 5.
1 was installed and the pressure measuring device 13 attached to the furnace core tube 2 tried to control so that the chamber pressure difference was −10 Pa, but the furnace pressure varied from −15 to −5 Pa.

During the above-mentioned manufacturing work, a chlorine gas detector was installed on the upper lid 5 of the apparatus, and the leak amount of chlorine gas was confirmed.
As a result, it was confirmed by the chlorine gas detector that the chlorine leakage amount was 0.01 to 0.025 ppm throughout the production period of the glass base material. Moreover, the chlorine addition amount (Δ +) of the obtained glass base material was measured, and as a result, Δ
The variation of + was 0.02%. As a result of continuing this manufacturing work, the number of foreign particles and bubbles having a width of 1 mm or more present in the glass base material produced by the glass particle deposition apparatus and the sintering apparatus near this apparatus was determined by this apparatus. Before the start, the number was 0 on average, but after 2 months from the start of production, the number increased to 1 on average.

(Embodiment 4) The construction of the seal chamber 9 is carried out except that the length of the support rod 10 in the longitudinal direction is 500 mm and the difference between the inner diameter of the seal chamber 9 and the support rod outer diameter is 30 mm. A glass base material was manufactured in the same manner as in Example 2. That is, He is allowed to enter the sealing chamber 9 for 1 to 2 S throughout the manufacturing period.
By supplying LM, the pressure in the seal chamber 9 is 0P due to the chamber pressure difference.
It was controlled to be a. Further, the exhaust line 1 is attached to the upper lid 5.
1 is installed and the pressure measuring device 13 is attached to the core tube 2.
It was controlled so that the room pressure difference was 0 Pa.

During the above manufacturing operation, a chlorine gas detector was installed above the upper lid 5 of the apparatus to check the amount of chlorine gas leaked.
As a result, it was confirmed by the chlorine gas detector that the chlorine leakage amount was 0.04 to 0.06 ppm throughout the production period of the glass base material. Moreover, the chlorine addition amount (Δ +) of the obtained glass base material was measured, and as a result, Δ + was measured in the longitudinal direction.
Variation was 0.005%. As a result of continuing this manufacturing work, the number of foreign particles and bubbles having a width of 1 mm or more present in the glass base material produced by the glass particle deposition apparatus and the sintering apparatus near this apparatus was determined by this apparatus. Before the start, the number was 0 on average, but two months after the start of production, the number increased to 5 on average.

(Embodiment 5) The construction of the seal chamber 9 is carried out except that the length of the support rod 10 in the longitudinal direction is 20 mm and the difference between the inner diameter of the seal chamber 9 and the support rod outer diameter is 30 mm. A glass base material was manufactured in the same manner as in Example 2. That is, He is allowed to enter the sealing chamber 9 for 1 to 2 S throughout the manufacturing period.
By supplying LM, the pressure in the seal chamber 9 is 0P due to the chamber pressure difference.
It was controlled to be a. Further, the exhaust line 1 is attached to the upper lid 5.
1 is installed and the pressure measuring device 13 is attached to the core tube 2.
It was controlled so that the room pressure difference was 0 Pa.

During the above manufacturing operation, a chlorine gas detector was installed on the upper lid 5 of the apparatus, and the leak amount of chlorine gas was confirmed.
As a result, it was confirmed by the chlorine gas detector that the chlorine leakage amount was 0.07 to 0.09 ppm throughout the production period of the glass base material. Moreover, the chlorine addition amount (Δ +) of the obtained glass base material was measured, and as a result, Δ + was measured in the longitudinal direction.
Variation was 0.005%. As a result of continuing this manufacturing work, the number of foreign particles and bubbles having a width of 1 mm or more present in the glass base material produced by the glass particle deposition apparatus and the sintering apparatus near this apparatus was determined by this apparatus. The number was 0 on average before the start, but increased to 9 on average 2 months after the start of production.

(Comparative Example 1) The same glass particle deposit and glass base material manufacturing apparatus as those used in Example 1 were used, the seal tube 9 was not installed, and the control conditions of the pressure in the core tube 2 were changed. A glass base material was manufactured in the same manner as in Example 1 except that. That is, the exhaust line 11 was installed in the upper lid 5, and the pressure measuring device 13 attached to the core tube 2 was controlled so that the chamber pressure difference was −20 Pa.

During the above manufacturing operation, a chlorine gas detector was installed on the upper part of the upper lid 5 of the apparatus, and the leak amount of chlorine gas was confirmed.
As a result, it was confirmed by the chlorine gas detector that the chlorine leakage amount was 0.2 to 0.3 ppm throughout the production period of the glass base material. As a result of continuing this manufacturing work, the number of foreign particles and bubbles having a width of 1 mm or more present in the glass base material produced by the glass particle deposition apparatus and the sintering apparatus near this apparatus was determined by this apparatus. Before the start, the number was 0 on average, but after 2 months from the start of production, the number increased to 25 on average.

[0034]

According to the present invention, when a glass particulate deposit is heat-treated in a heating furnace for dehydration and transparent vitrification to produce a glass preform, corrosive gas leaks from the furnace core tube into the room. It can be taken out to pollute the environment and suppress the corrosion of metal parts of each apparatus such as the apparatus for manufacturing glass particle deposits installed in the same room. Further, even when the apparatus for producing glass particle deposits is installed in the same room, it is possible to prevent deterioration of the quality of the glass particle deposits due to metal-based dust in the indoor atmosphere being mixed into the deposition apparatus. be able to.

[Brief description of drawings]

FIG. 1 is a schematic explanatory view showing one embodiment of a glass base material manufacturing apparatus according to the present invention.

[Explanation of symbols]

1 Base Material 2 Core Tube 3 Heater 4 Furnace Body 5 Upper Lid 6 Lower Lid 7 Support Rod Loading Port 8 Lifting Device 9
Sealing chamber 10 Support rod 11 Exhaust line 12 Radiation thermometer 13 Pressure measuring instrument 14 Pressure measuring instrument 15 Control device 16 Inert gas introduction port 17 MFC

Claims (7)

[Claims] 1. An upper lid provided with an insertion opening for inserting a support rod connected to an elevating device, a furnace core tube for accommodating a glass particulate deposit and heat-treating the inside, and a heater surrounding the furnace tube. Using a glass base material manufacturing apparatus equipped with a furnace body that covers the heater, the glass particulate deposits supported by the support rods are vertically moved while being rotated about an axis to be heated, dehydrated and transparent. In the method for producing a glass base material to be vitrified, a tubular seal chamber is provided on the upper surface of the upper lid so as to cover the support rod and the support rod insertion port, and the pressure in the seal chamber is higher than the pressure in the core tube. A method for producing a glass base material, comprising performing dehydration and transparent vitrification while introducing an inert gas so as to have a high predetermined pressure. 2. The method for producing a glass preform according to claim 1, wherein the length of the seal chamber in the longitudinal direction of the support rod is 50 mm or more. 3. The difference between the inner diameter of the tubular seal chamber and the outer diameter of the support rod is 20 mm or less.
Or the method for producing a glass base material according to 2. 4. An upper lid provided with an insertion opening for inserting a support rod connected to a lifting device, a furnace core tube for accommodating a glass particulate deposit and heat-treating the inside, and a heater surrounding the furnace core tube. A furnace for covering the heater, comprising: a glass base material manufacturing apparatus for dehydrating and transparent vitrifying by heating and vertically moving a glass particle deposit supported by the support rod while rotating it about an axis. A tubular seal chamber is installed on the upper surface of the upper lid so as to cover the support rod and the support rod insertion port, and the internal pressure can be adjusted to a predetermined pressure higher than the pressure in the core tube by adjusting the amount of inert gas introduced. An apparatus for manufacturing a glass base material, which is characterized in that 5. A measuring device for measuring the pressure in the seal chamber, and a control device for controlling the amount of the inert gas introduced based on the measurement value of the measuring device are provided. The glass base material manufacturing apparatus described. 6. The glass base material manufacturing apparatus according to claim 4, wherein the length of the sealing chamber in the longitudinal direction of the support rod is 50 mm or more. 7. The difference between the inner diameter of the tubular seal chamber and the outer diameter of the support rod is 20 mm or less.
An apparatus for manufacturing a glass base material according to any one of items 1 to 6.