Apparatus and method for manufacturing glass preform

Abstract

An apparatus for manufacturing a glass preform according to the present disclosure comprises: a furnace core tube capable of housing a glass fine particle deposit formed by depositing glass fine particles on a support rod; a lid provided on the upper part of the furnace core tube and having a through-hole formed so that the support rod can be displaced in the vertical direction; a heater capable of heating the glass fine particle deposit housed in the furnace core tube; a gas introduction part for introducing gas into the furnace core tube; a gas discharge part for discharging gas from the inside of the furnace core tube; and a plurality of partition plates for dividing and partitioning the space in the furnace core tube between the glass fine particle deposit housed in the furnace core tube and the lid during heating of the glass fine particle deposit.

Description

Glass base material manufacturing apparatus and glass base material manufacturing method

[0001] The present disclosure relates to a glass preform manufacturing apparatus and a glass preform manufacturing method. This application claims priority to Japanese Patent Application No. 2023-123545 filed on July 28, 2023, and incorporates all of the contents of said application by reference.

[0002] Patent Document 1 discloses a manufacturing apparatus for manufacturing a glass base material by sintering a soot glass deposit body. The manufacturing apparatus includes a furnace tube. In the sintering step, an atmospheric gas flows from below to above the soot glass bodies in the furnace tube.

[0003] Japanese Patent Application Publication No. 2000-219519

[0004] In the process of sintering a glass soot deposit while moving it within a furnace tube, it is desirable to make the inside of the furnace tube airtight to prevent impurities from getting mixed in, but it is practically impossible to make the furnace tube completely airtight. Therefore, when the pressure inside the furnace tube is unstable, the outside air of the furnace tube flows into the inside of the furnace tube together with impurities, and the impurities are adsorbed by the glass preform, which can deteriorate the quality of the glass preform.

[0005] An object of the present disclosure is to provide a glass base material manufacturing apparatus and a glass base material manufacturing method that can manufacture glass base materials of stable quality.

[0006] A glass base material manufacturing apparatus according to one embodiment of the present disclosure comprises a furnace tube capable of accommodating a glass soot deposit body formed by depositing glass soot on a support rod; a lid portion provided on top of the furnace tube and having a through hole formed therein so that the support rod can be displaced in an up-and-down direction; a heater capable of heating the glass soot deposit body accommodated in the furnace tube; a gas inlet portion for introducing gas into the interior of the furnace tube; a gas outlet portion for discharging gas from the interior of the furnace tube; and a plurality of partition plates for dividing and partitioning the space within the furnace tube between the glass soot deposit body accommodated inside the furnace tube and the lid portion when the glass soot deposit body is heated.

[0007] According to the present disclosure, it is possible to provide a glass base material manufacturing apparatus and a glass base material manufacturing method that can manufacture glass base materials of stable quality.

[0008] FIG. 1 is a schematic diagram of a glass base material manufacturing apparatus according to the present embodiment. FIG. 2 is a plan view of a partition plate according to the present embodiment. FIG. 3 is a plan view of a partition plate according to a modified example. FIG. 4 is a diagram illustrating the relationship between the number of partition plates and the standard deviation of the pressure in the muffle tube. FIG. 5 is a diagram illustrating the relationship between the number of partition plates and the standard deviation of the pressure in the muffle tube, with and without an insulating section. FIG. 6 is a diagram illustrating the relationship between the ratio of the opening area to the partition plates and the standard deviation of the pressure in the muffle tube. FIG. 7 is a diagram illustrating the transition of the pressure in the muffle tube when one partition plate is installed. FIG. 8 is a diagram illustrating the transition of the pressure in the muffle tube when two partition plates are installed.

[0009] (Explanation of Embodiments of the Present Disclosure) First, embodiments of the present disclosure will be listed and described. (1) A glass base material manufacturing apparatus according to one aspect of the present disclosure includes a muffle tube capable of accommodating a glass soot deposit body formed by depositing glass soot on a support rod; a lid provided on top of the muffle tube and having a through hole formed therein so that the support rod can be displaced vertically; a heater capable of heating the glass soot deposit body accommodated in the muffle tube; a gas inlet for introducing gas into the muffle tube; a gas outlet for discharging gas from the muffle tube; and a plurality of partition plates for dividing and partitioning a space within the muffle tube between the glass soot deposit body accommodated in the muffle tube and the lid when the glass soot deposit body is heated. The manufacturing apparatus includes a plurality of partition plates for dividing and partitioning a space within the muffle tube between the glass soot deposit body accommodated in the muffle tube and the through hole. The space inside the muffle tube is divided into a space farthest from the glass soot deposit and communicating with the outside of the muffle tube via the through-hole, a space located midway between the through-hole and the glass soot deposit, and a space in which the glass soot deposit is accommodated. Therefore, the pressure inside the muffle tube is less likely to fluctuate in the space in which the glass soot deposit is accommodated, and impurities are less likely to be mixed into the muffle tube. Even if impurities are mixed in, they are less likely to reach the space in which the glass soot deposit is accommodated. This allows for the production of glass preforms of consistent quality.

[0010] In the glass base material manufacturing apparatus according to (1) above, (2) the furnace tube may include an insulating section provided on the outer periphery of the furnace tube, and at least one partition plate may be provided above the insulating section. The at least one partition plate is provided to define a space together with a wall surface of the lid section including the through hole, and a partitioned space is formed in the lid section, where it is difficult to improve insulation and the internal gas is easily cooled. This space is prone to turbulence, and further, since it is defined including the through hole, it is also prone to impurities being mixed in. However, by dividing this space with a partition plate, the pressure inside the furnace tube is less likely to fluctuate in the space containing the glass soot deposit, and impurities are less likely to be mixed in the furnace tube.

[0011] (3) In the glass base material manufacturing apparatus according to (1) or (2), the partition plate may have openings formed therein to allow the support rods to be displaced in the vertical direction, and the partition plate may be formed so that the opening area of ​​the openings is 0.1% to 25% of the area of ​​the partition plate. This configuration makes it possible to appropriately achieve both the partition plate being less likely to interfere with the support rods and the partition plate being less likely to cause fluctuations in pressure within the furnace tube.

[0012] (4) In the glass base material manufacturing apparatus according to (3), at least one of the partition plates may be placed at a predetermined position on the muffle tube after the start of manufacturing, and the partition plate may be formed so that the opening area is 0.1% to 2.5% of the area of ​​the partition plate. With this configuration, the opening area can be reduced to a level where the inner wall surface of the opening does not interfere with the support rod, making it difficult for the partition plate to cause fluctuations in pressure inside the muffle tube and impurities to adhere to the glass soot deposit and the glass base material.

[0013] (5) In the glass base material manufacturing apparatus according to (3), the partition plate may be movable together with the support rods relative to the muffle tube, and the opening area may be formed so as to be 5% to 25% of the area of ​​the partition plate. This configuration makes it possible to appropriately achieve both the partition plate being less likely to interfere with the support rods and the partition plate being less likely to cause fluctuations in pressure within the muffle tube.

[0014] (6) In the glass base material manufacturing apparatus according to any one of (1) to (5), the through hole may be provided with an airtight ring that keeps the gap between the through hole and the support rod airtight, and the support rod may be inserted into the airtight ring so as to be displaceable in the vertical direction. According to the above configuration, the provision of the airtight ring in the through hole makes it possible to reduce the flow rate of air flowing into the outside of the furnace tube through the through hole.

[0015] (7) In the glass base material manufacturing apparatus according to any one of (1) to (6), the lid may include a buffer gas inlet for introducing an inert gas into a buffer chamber provided in the lid, and the gas outlet, the through-hole, and the airtight ring may be provided in the buffer chamber. According to the above configuration, the introduction of the inert gas into the buffer chamber facilitates maintaining a positive pressure in the buffer chamber. Furthermore, since the airtight ring is formed in the through-hole formed in the buffer chamber, even if the pressure in the buffer chamber becomes negative, air containing impurities from outside the furnace tube is less likely to flow in.

[0016] (8) A manufacturing method for manufacturing a glass base material using the glass base material manufacturing apparatus according to any one of (1) to (7), the manufacturing method including any one of: introducing a gas containing a halide from the gas inlet; dehydrating the glass soot deposit body; and making the glass soot deposit body transparent. According to the above configuration, the addition of halogen, dehydration, and transparency can be performed on the glass soot deposit body in a state where air containing impurities from outside the furnace tube is unlikely to flow in.

[0017] (Details of the embodiment of the present disclosure) Specific examples of the glass preform manufacturing apparatus and the glass preform manufacturing method according to the embodiment of the present disclosure will be described below with reference to the drawings. Note that the present invention is not limited to these examples, but is defined by the claims, and is intended to include all modifications within the meaning and scope equivalent to the claims.

[0018] Furthermore, in the description of this embodiment, for convenience of explanation, the "up-down direction," "left-right direction," and "front-rear direction" will be referred to as appropriate. Here, the "up-down direction" is a direction that includes the "upward direction" and the "downward direction." The "left-right direction" is a direction that includes the "leftward direction" and the "rightward direction." The "front-rear direction" is a direction that includes the "forward direction" and the "rearward direction." In the drawings described below, the symbol U indicates the upward direction. The symbol D indicates the downward direction. The symbol L indicates the leftward direction. The symbol R indicates the rightward direction. The symbol F indicates the forward direction. The symbol B indicates the rearward direction.

[0019] 1 is a schematic diagram of a glass base material manufacturing apparatus 1 according to this embodiment. The glass base material manufacturing apparatus 1 is capable of manufacturing a glass base material by sintering a glass soot deposit G formed by depositing glass soot on a support rod 100.

[0020] The manufacturing apparatus 1 includes a furnace tube 10. The furnace tube 10 is capable of accommodating a soot glass deposit G. The furnace tube 10 is formed in a cylindrical shape. The furnace tube 10 is made of, for example, quartz glass, alumina, or carbon.

[0021] The furnace tube 10 may include a heat insulating section 60 provided on the outer periphery of the furnace tube 10. The heat insulating section 60 makes it difficult for the temperature inside the furnace tube 10 to be cooled by the outside air. In this embodiment, the heat insulating section 60 is formed above the heater 30. However, the heat insulating section 60 may also be formed below the heater 30.

[0022] The manufacturing apparatus 1 includes a lid 20. The lid 20 is provided on the top of the furnace tube 10. The lid 20 is made of, for example, quartz glass, alumina, or carbon. A through hole H is formed in the lid 20 so that the support rod 100 can be displaced in the vertical direction.

[0023] In this embodiment, the lid portion 20 is provided with a buffer chamber 21. The buffer chamber 21 is in communication with the internal space of the lid portion 20. A through hole H is formed in the buffer chamber 21. Therefore, when the support rod 100 is not inserted, the buffer chamber 21 is in communication with the external space of the manufacturing apparatus 1.

[0024] The cover 20 includes a buffer gas inlet 22. The buffer gas inlet 22 is capable of introducing an inert gas into the buffer chamber 21. The inert gas is, for example, helium gas.

[0025] An airtight ring 80 is provided in the through hole H. The airtight ring 80 can maintain an airtight state between the through hole H and the support rod 100. The support rod 100 is inserted into the airtight ring 80 so that it can be displaced in the vertical direction. The inner diameter of the airtight ring 80 is, for example, larger than the outer diameter of the support rod 100. For example, the airtight ring 80 has an inner diameter that is larger than the outer diameter of the support rod 100 by 0.02 mm or more and 1.0 mm or less.

[0026] The manufacturing apparatus 1 includes a heater 30. The heater 30 is capable of heating the soot glass deposit G accommodated in the furnace tube 10. The heater 30 generates heat in the sintering step so that the temperature inside the furnace tube 10 reaches a predetermined temperature. The predetermined temperature is, for example, 1500°C.

[0027] The support rod 100 can be displaced in the vertical direction. The support rod 100 may also be displaced downward during the sintering process. For example, as illustrated by the dashed line in FIG. 1 , at the start of sintering, the support rod 100 is positioned so that the lower end of the glass soot deposit G is located above the lower end of the heater 30. However, as illustrated by the solid line in FIG. 1 , at the end of sintering, the support rod 100 is displaced so that the lower end of the glass soot deposit G is located below the lower end of the heater 30.

[0028] The manufacturing apparatus 1 includes a gas inlet 41. In this embodiment, the gas inlet 41 is formed near the lower end of the furnace tube 10. The gas inlet 41 is capable of introducing gas into the furnace tube 10. The gas introduced from the gas inlet 41 is, for example, an inert gas such as nitrogen or a rare gas (helium, neon, argon, etc.), or a reactive gas such as a halide.

[0029] The manufacturing apparatus 1 includes a gas exhaust unit 42. The gas exhaust unit 42 is capable of exhausting gas from the inside of the furnace tube 10. In this embodiment, the gas exhaust unit 42 is formed in the buffer chamber 21.

[0030] The manufacturing apparatus 1 includes a plurality of partition plates. In this embodiment, the manufacturing apparatus 1 includes a first partition plate 51, a second partition plate 52, and a third partition plate 53.

[0031] The first partition plate 51 is disposed at a position closest to the soot glass deposit G during heating of the soot glass deposit G. The second partition plate 52 is disposed above the first partition plate 51. The third partition plate 53 is disposed above the second partition plate 52.

[0032] Fig. 2 is a plan view of the partition plate according to this embodiment, illustrating the third partition plate 53. As illustrated in Fig. 2, the third partition plate 53 has an opening 53a formed therein so that the support rod 100 can be displaced in the up and down direction.

[0033] Similar openings are formed in the first partition plate 51 and the second partition plate 52, and have the same shape as the third partition plate shown in FIG.

[0034] In the manufacturing apparatus 1 according to this embodiment, when manufacturing starts, the first partition plate 51, the second partition plate 52, and the third partition plate 53 descend together with the soot glass deposit body G. After manufacturing starts, at least one of the partition plates can be placed at a predetermined position in the furnace tube 10. As illustrated in FIG. 1 , convex portions 71, 72, and 73 are formed on the inner wall surface of the furnace tube 10.

[0035] When the support rod 100 is displaced to the lowest position, the first partition plate 51 is placed on the protrusion 71. The second partition plate 52 is placed on the protrusion 72. The third partition plate 53 is placed on the protrusion 73.

[0036] The outer diameters of the first partition plate 51, the second partition plate 52, and the third partition plate 53 increase in the order of first partition plate 51, second partition plate 52, and third partition plate 53. The lengths by which the protrusions 71, 72, and 73 protrude from the inner wall surface of the furnace muffle tube 10 decrease in the order of protrusion 71, protrusion 72, and protrusion 73. Therefore, the first partition plate 51 and the second partition plate 52 do not come into contact with the protrusion 73, and therefore do not rest on the protrusion 73. The first partition plate 51 does not come into contact with the protrusion 72, and therefore does not rest on the protrusion 72.

[0037] 1 , the first partition plate 51, the second partition plate 52, and the third partition plate 53 divide and partition the space within the furnace tube 10 between the soot glass deposit G accommodated inside the furnace tube 10 and the lid portion 20 during heating of the soot glass deposit G. In this embodiment, three partition plates are provided, and therefore the space between the soot glass deposit G and the lid portion 20 is partitioned into four spaces: space A1, space A2, space A3, and space A4.

[0038] Space A1 is a space below the first partition plate 51 and is a space in which the soot glass deposit G is accommodated when the soot glass deposit G is heated. Space A2 is a space partitioned by the first partition plate 51 and the second partition plate 52 and is a space formed above space A1. Space A3 is a space partitioned by the second partition plate 52 and the third partition plate 53 and is a space formed above space A2. Space A4 is a space above the third partition plate 53 and is a space formed above space A3.

[0039] At least one of the partition plates is preferably provided above the heat insulating section 60. In this embodiment, the third partition plate 53, which is the uppermost of the partition plates, is provided above the heat insulating section 60 and defines a space A4 together with the wall surface of the lid section 20. In other words, the space A4 is a space that does not have a heat insulating section provided on its periphery.

[0040] The partitioning of the space between the soot glass deposit G and the lid portion 20 by the first partition plate 51, the second partition plate 52, and the third partition plate 53 will be described.

[0041] The first partition plate 51, the second partition plate 52, and the third partition plate 53 are stacked and arranged (indicated by the two-dot chain line in FIG. 1 ) when the support rod 100 is in its uppermost position at the start of heating the soot glass deposit G. The first partition plate 51 is placed on a protruding portion (not shown) formed on the support rod 100. The second partition plate 52 is placed on the upper surface of the first partition plate 51. The third partition plate 53 is placed on the upper surface of the second partition plate 52.

[0042] When the support rod 100 is displaced downward, all the partition plates are displaced along with the support rod 100. At this time, the first partition plate 51 and the second partition plate 52 do not come into contact with the protrusion 73, but the third partition plate 53 comes into contact with the protrusion 73 and is placed on the protrusion 73. When the third partition plate 53 is placed on the protrusion 73, the space A4 is partitioned.

[0043] When the support rod 100 is displaced downward, the first partition plate 51 and the second partition plate 52 are also displaced together with the support rod 100. At this time, the first partition plate 51 does not come into contact with the protrusion 72, but the second partition plate 52 comes into contact with the protrusion 72 and is placed on the protrusion 72. The second partition plate 52 being placed on the protrusion 72 defines the space A3.

[0044] When the support rod 100 is further displaced downward, the first partition plate 51 is also displaced together with the support rod 100. At this time, the first partition plate 51 comes into contact with the protrusion 71 and is placed on the protrusion 71. By placing the first partition plate 51 on the protrusion 71, the space A1 and the space A2 are separated.

[0045] The third partition plate 53 is formed so that the opening area of ​​the opening 53a is 0.1% to 25% of the area of ​​the third partition plate 53. The opening area is the area of ​​the opening 53a minus the cross-sectional area of ​​the support rod 100, and is the area of ​​the gap S formed between the support rod 100 and the third partition plate 53 in the sintering process (see FIG. 2). The first partition plate 51 and the second partition plate 52 also have openings formed so that the opening area is 0.1% to 25%.

[0046] That is, all the partition plates may be displaced together with the support rods 100 when the soot glass deposit body G is heated. In this case, the openings are formed so that the opening area is 0.1% or more and 25% or less of the area of ​​the partition plates.

[0047] On the other hand, when at least one partition plate is placed at a predetermined position on the furnace core tube 10 and does not move together with the support rods 100, it is desirable that the opening area of ​​the opening is 0.1% to 2.5% of the area of ​​the partition plate that does not move. A mechanism may be provided that reduces the opening area when the partition plate is placed.

[0048] (Modification of Manufacturing Apparatus) A manufacturing apparatus according to a modification will be described. Fig. 3 is a plan view of a partition plate according to a modification, illustrating the third partition plate 53.

[0049] In this modified example, a protrusion 171 is formed on the support rod 100. The protrusion 171 is a rod that protrudes larger than the openings formed in the first partition plate 51, the second partition plate 52, and the third partition plate 53. The first partition plate 51, the second partition plate 52, and the third partition plate 53 are each placed on the protrusion 171.

[0050] In this state, when the support rod 100 is displaced in the vertical direction, the first partition plate 51, the second partition plate 52, and the third partition plate 53 are also displaced in the vertical direction together with the support rod 100. In this way, the partition plates can move together with the support rod 100 relative to the furnace core tube 10.

[0051] Even in this case, it is desirable that the first partition plate 51, the second partition plate 52, and the third partition plate 53 are formed so that the opening area relative to the area of ​​each partition plate is 5% or more and 25% or less.

[0052] (Manufacturing Method) Next, a manufacturing method for manufacturing a glass base material using the manufacturing apparatus 1 according to this embodiment will be described.

[0053] When the temperature inside the furnace tube 10 reaches a predetermined temperature due to heating by the heater 30, the support rod 100 is displaced downward to start the sintering process for sintering the glass soot deposit G. When the sintering process for the glass soot deposit G is completed, the glass soot deposit G becomes a transparent glass base material.

[0054] During the production of the glass base material, the production method of this embodiment may include any of introducing a gas containing a halide from the gas inlet 41, dehydrating the glass soot deposit G, and making the glass soot deposit G transparent. By introducing a gas containing a halide from the gas inlet 41, halogen is added to the glass soot deposit G, thereby changing the refractive index of the glass base material. The glass soot deposit G is dehydrated by heating the glass soot deposit G for a certain period of time at a temperature lower than the temperature inside the furnace tube 10 during sintering. The glass soot deposit G is made transparent by heating the glass soot deposit G at a temperature higher than the temperature during dehydration, thereby densifying and making the glass soot deposit G transparent.

[0055] Ideally, it is desirable that the through-hole H be completely sealed, so that impurities are less likely to adhere to the inside of the furnace tube 10 and the quality of the glass base material is less likely to deteriorate.

[0056] In reality, it is difficult to completely seal the through-hole H. Therefore, impurities are less likely to enter the furnace core tube 10 by creating a positive pressure inside the furnace core tube 10 relative to the outside air.

[0057] However, because the temperature above the furnace tube is not necessarily constant, the density of the gas inside the furnace tube can become uneven. For example, when the gas inside the furnace tube is heated by a heater, its density decreases and it tends to move upward. However, when the gas in the upper part of the furnace tube is cooled by the outside air, its density increases and it tends to move downward.

[0058] This can cause turbulence in the upper part of the furnace tube, as gases flowing upward mix with gases flowing downward. The turbulence causes pressure fluctuations within the furnace tube, and if the pressure in the space inside the furnace tube becomes negative due to the pressure fluctuations, air from outside the furnace tube can get mixed into the inside of the furnace tube along with impurities.

[0059] Therefore, in order to stabilize the quality of the glass base material, it is essential that the pressure inside the furnace tube does not easily fluctuate, and that even if impurities are mixed in, the impurities do not easily adhere to the glass soot deposit and the glass base material.

[0060] According to the above configuration, the manufacturing apparatus 1 includes a first partition plate 51, a second partition plate 52, and a third partition plate 53, which are multiple partition plates that divide and partition the space inside the furnace tube 10 between the soot glass deposit G accommodated inside the furnace tube 10 and the through hole H. As a result, the space inside the furnace tube is divided into a space A4 that is farthest from the soot glass deposit G and communicates with the outside of the furnace tube 10 via the through hole H, spaces A2 and A3 that are located midway between the through hole H and the soot glass deposit G, and a space A1 in which the soot glass deposit G is accommodated.

[0061] The space in which pressure fluctuations are most likely to occur and in which impurities are most likely to be mixed in is space A4, which is farthest from the soot glass deposit G and which communicates with the outside of the furnace tube 10 via the through-hole H. However, in the example of this embodiment, two spaces A2 and A3 are defined between space A4, in which impurities are most likely to be mixed in, and space A1 in which the soot glass deposit G is accommodated.

[0062] As a result, the pressure inside the furnace tube 10 is less likely to fluctuate in the space containing the soot glass deposit G, and impurities are less likely to be mixed into the furnace tube 10. Even if impurities are mixed in, they are less likely to reach the space A1 containing the soot glass deposit G. Therefore, the manufacturing apparatus 1 of this embodiment can manufacture glass base materials of stable quality.

[0063] According to the above configuration, the manufacturing apparatus 1 includes an insulating section 60 provided on the outer periphery of the furnace core tube 10, and at least one partition, the third partition plate 53, is provided above the insulating section 60. The spaces A2 and A3 covered by the insulating section 60 are spaces in which temperature changes are gradual and turbulence and pressure fluctuations due to density changes are unlikely to occur. However, the space A4 is a space defined by the lid 20.

[0064] Resin or metal parts and the like are likely to be provided in the lid 20. If the temperature of the lid 20 rises excessively, the resin or metal parts and the like may deteriorate, so it is difficult to provide a heat insulating material in the lid 20. Therefore, the space A4 within the lid 20 is a space where temperature changes are likely to occur, and turbulence and pressure fluctuations are also likely to occur.

[0065] However, by dividing the space A4 by the third partition plate 53, the pressure inside the furnace tube 10 in the space A1 containing the glass soot deposit G becomes less likely to fluctuate, and impurities become less likely to be mixed into the furnace tube 10.

[0066] According to the above configuration, the first partition plate 51, the second partition plate 52, and the third partition plate 53 are formed so that the opening area of ​​the opening relative to the area of ​​each partition plate is 0.1% or more and 25% or less.

[0067] If the opening area is too small, the inner wall surface of the opening and the support rod 100 are likely to interfere with each other when the support rod 100 is displaced in the up and down direction. If the opening area is too large, the effect of the partition plate in preventing fluctuations in the pressure inside the furnace core tube 10 is reduced, and impurities are likely to adhere to the glass soot deposit G and the glass base material. If the opening area of ​​the opening relative to the area of ​​the partition plate is 0.1% or more and 25% or less, it is possible to appropriately achieve both the partition plate being less likely to interfere with the support rod 100 and the first partition plate 51, the second partition plate 52, and the third partition plate 53 preventing fluctuations in the pressure inside the furnace core tube 10.

[0068] On the other hand, when at least one partition plate is placed at a predetermined position in the furnace core tube 10 and does not move together with the support rods 100, the first partition plate 51, the second partition plate 52, and the third partition plate 53 that do not move are formed so that the opening area relative to the area of ​​the partition plates is 0.1% to 2.5%. In this case, it is possible to appropriately achieve both the partition plates being less likely to interfere with the support rods 100 and the first partition plate 51, the second partition plate 52, and the third partition plate 53 being less likely to cause fluctuations in the pressure inside the furnace core tube 10.

[0069] According to the above configuration, the airtight ring 80 is provided in the through hole H. This reduces the flow rate of air that flows into the inside of the furnace tube 10 through the through hole H.

[0070] According to the above configuration, the cover 20 includes the buffer chamber 21 having the buffer gas inlet 22 for introducing an inert gas therein, and the gas outlet 42, the through-hole H, and the airtight ring 80 are provided in the buffer chamber 21. By introducing the inert gas into the buffer chamber 21, the pressure inside the buffer chamber 21 is easily maintained at a positive pressure. Furthermore, since the airtight ring 80 is formed in the through-hole H formed in the buffer chamber 21, even if the pressure inside the buffer chamber 21 becomes negative, air containing impurities from outside the furnace core tube 10 is less likely to flow in.

[0071] The above-described method for manufacturing a glass base material uses the glass base material manufacturing apparatus 1. The method for manufacturing a glass base material also includes any one of introducing a gas containing a halide from the gas inlet 41, dehydrating the glass soot deposit G, and making the glass soot deposit G transparent. This allows the addition of halogen, dehydration, and transparency to be performed on the glass soot deposit G in a state where air containing impurities outside the furnace tube 10 is unlikely to flow in.

[0072] Next, the results of an analysis of the pressure fluctuations in the furnace tube will be explained.

[0073] (Analysis 1: Number of Dividers and Standard Deviation of Pressure in the Muffle Tube) Pressure fluctuations in the muffle tube due to the number of dividers were investigated. Figure 4 illustrates the relationship between the number of dividers and the standard deviation of pressure in the muffle tube. As illustrated in Figure 4, Analysis 1 also investigates the effect on pressure fluctuations in the muffle tube due to differences in the flow rate of gas introduced by the gas inlet. Flow rate L1 is a smaller flow rate than flow rate L2.

[0074] When the number of partition plates is three, it indicates that a first partition plate 51, a second partition plate 52, and a third partition plate 53 are provided, as in the manufacturing apparatus 1 according to the embodiment. When the number of partition plates is two, it indicates that a first partition plate 51 and a third partition plate 53 are provided, and a second partition plate 52 is not provided. When the number of partition plates is one, it indicates that a first partition plate 51 is provided, and a second partition plate 52 and a third partition plate 53 are not provided. When the number of partition plates is zero, it indicates that a first partition plate 51, a second partition plate 52, and a third partition plate 53 are not provided. The pressure measurement point is space A4.

[0075] As shown in Figure 4, the standard deviation of the pressure inside the muffle tube is smaller when two or more partition plates are installed than when zero or one partition plate is installed. The smaller the standard deviation, the less the pressure inside the muffle tube fluctuates. In other words, there is a significant difference in the effect of preventing pressure fluctuations inside the muffle tube when one partition plate is installed compared to when two partition plates are installed.

[0076] For both flow rates L1 and L2, the standard deviation of the pressure inside the muffle tube tends to be smaller when two or more partition plates are provided. This shows that regardless of the flow rate, when two or more partition plates are provided, the pressure inside the muffle tube is less likely to fluctuate.

[0077] (Analysis 2: Presence or absence of thermal insulation and standard deviation of pressure inside the core tube) Next, we investigated whether the presence or absence of thermal insulation changes the trends discovered in Analysis 1. Fig. 5 illustrates the relationship between the number of partition plates and the standard deviation of pressure inside the core tube when thermal insulation is present and when it is not. When thermal insulation is present, it indicates that thermal insulation is provided on the outer periphery of the core tube, as in this embodiment. When thermal insulation is not present, it indicates that thermal insulation is not provided on the outer periphery of the core tube.

[0078] As shown in Figure 5, the standard deviation of the pressure inside the muffle tube tends to be smaller when two or more partition plates are provided, regardless of whether or not an insulating section is provided. However, when an insulating section is provided, the standard deviation of the pressure inside the muffle tube is smaller overall. This shows that the number of partition plates, two or more or one or less, has a dominant effect on preventing fluctuations in the pressure inside the muffle tube, rather than the presence or absence of an insulating section, but that an insulating section can also have the effect of preventing fluctuations in the pressure inside the muffle tube.

[0079] (Analysis 3: Ratio of opening area to partition plate and standard deviation of pressure in the muffle tube) Next, the relationship between the ratio of opening area to partition plate and standard deviation of pressure in the muffle tube was investigated. Figure 6 shows an example of the relationship between the ratio of opening area to partition plate and standard deviation of pressure in the muffle tube. The "opening area ratio" in Figure 6 means the ratio of the opening area to the partition plate (the area of ​​the gap S shown in Figure 2).

[0080] As shown in Figure 6, as the opening area ratio increases, the standard deviation of the pressure inside the muffle tube also increases. Therefore, it is preferable that the opening area ratio be as small as possible to prevent fluctuations in the pressure inside the muffle tube. However, if the opening area ratio is too small, the support rods and the partition plate may interfere with each other, so generally, the opening area ratio is preferably 0.1% to 25%. When the partition plate is placed in a predetermined position, the opening area ratio is preferably 0.1% to 2.5%. When the partition plate is movable relative to the muffle tube together with the support rods, the opening area is preferably 5% to 25%.

[0081] (Analysis 4: Relationship between the number of partition plates and the generation of negative pressure) The relationship between the number of partition plates and the generation of negative pressure was investigated. Figure 7 illustrates the transition of pressure inside the muffle tube when one partition plate is installed. Figure 8 illustrates the transition of pressure inside the muffle tube when two partition plates are installed. In both figures, when the pressure on the vertical axis exceeds 0, it indicates that the pressure inside the muffle tube is positive pressure. When the pressure on the vertical axis is below 0, it indicates that the pressure inside the muffle tube is negative pressure. It is assumed that the pressure inside the muffle tube has the same average value Pm whether there is one partition plate or two partition plates.

[0082] 7 and 8, the pressure in the muffle tube when one partition plate is provided fluctuates more than the pressure in the muffle tube when two partition plates are provided. For example, pressure P1, when the pressure in the muffle tube when one partition plate is provided and the pressure deviates most from the average value Pm, deviates more from the average value Pm than pressure P2, when the pressure in the muffle tube when two partition plates are provided and the pressure deviates most from the average value Pm.

[0083] Furthermore, the number of times the pressure on the vertical axis falls below 0 is greater when one partition plate is installed than when two partition plates are installed. This shows that when there is one partition plate, negative pressure occurs more frequently than when there are two partition plates, and the turbulence intensity when negative pressure occurs is also stronger.

[0084] Although the present disclosure has been described in detail and with reference to specific embodiments, it will be apparent to those skilled in the art that various changes and modifications can be made without departing from the spirit and scope of the present disclosure. Furthermore, the number, position, shape, etc. of the components described above are not limited to the above embodiments, and can be changed to the number, position, shape, etc. that are suitable for implementing the present disclosure.

[0085] In the manufacturing apparatus 1 according to this embodiment, a gas inlet 41 is formed near the lower end of the furnace muffle tube 10, and a gas outlet 42 is formed above the furnace muffle tube 10. However, the manufacturing apparatus may also have a gas inlet formed above the furnace muffle tube, and a gas outlet formed near the lower end of the furnace muffle tube.

[0086] REFERENCE SIGNS LIST 1 Manufacturing apparatus 10 Furnace tube 20 Lid 21 Buffer chamber 22 Buffer gas inlet 30 Heater 41 Gas inlet 42 Gas outlet 51 First partition plate 52 Second partition plate 53 Third partition plate 53a Opening 60 Heat insulating portion 71, 72, 73 Convex portion 80 Airtight ring 100 Support rod 171 Protruding portion A1, A2, A3, A4 Space G Soil glass deposit H Through hole S Gap

Claims

1. An apparatus for manufacturing a glass base material comprising: a core tube capable of accommodating a glass soot deposit formed by depositing glass soot on a support rod; a lid provided on an upper portion of the core tube and having a through hole formed therein to allow the support rod to be displaced in an up-down direction; a heater capable of heating the glass soot deposit accommodated in the core tube; a gas inlet portion for introducing gas into the interior of the core tube; a gas outlet portion for discharging gas from the interior of the core tube; and a plurality of partition plates for dividing and partitioning a space within the core tube between the glass soot deposit accommodated inside the core tube and the lid portion when the glass soot deposit is heated.

2. The glass base material manufacturing apparatus according to claim 1, wherein the furnace tube has an insulating section provided on the outer periphery of the furnace tube, and at least one partition plate is provided above the insulating section.

3. A glass base material manufacturing apparatus as described in claim 1 or claim 2, wherein an opening is formed in the partition plate so that the support rod can be displaced in the vertical direction, and the partition plate is formed so that the opening area of ​​the opening is 0.1% or more and 25% or less of the area of ​​the partition plate.

4. The glass base material manufacturing apparatus according to claim 3, wherein at least one of the partition plates is placed at a predetermined position on the furnace tube after production begins, and the partition plate is formed so that the opening area relative to the area of ​​the partition plate is 0.1% or more and 2.5% or less.

5. The glass base material manufacturing apparatus according to claim 3, wherein the partition plate is movable together with the support rod relative to the furnace tube, and the opening area is formed so as to be 5% or more and 25% or less of the area of ​​the partition plate.

6. A glass base material manufacturing apparatus as described in any one of claims 1 to 5, wherein an airtight ring is provided in the through hole to maintain an airtight state between the through hole and the support rod, and the support rod is inserted into the airtight ring so as to be displaceable in the vertical direction.

7. The glass base material manufacturing apparatus according to claim 6, wherein the lid portion is provided with a buffer gas inlet portion for introducing an inert gas into the inside of a buffer chamber provided in the lid portion, and the gas exhaust portion, the through hole and the airtight ring are provided in the buffer chamber.

8. A method for producing a glass base material using the glass base material manufacturing apparatus described in any one of claims 1 to 7, the method including any one of the following: introducing a gas containing a halide from the gas inlet; dehydrating the glass soot deposit body; and making the glass soot deposit body transparent.

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