JP2005314209A - Method for manufacturing porous glass preform - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for manufacturing a porous glass preform capable of manufacturing the porous glass preform having the outer diameter uniform in a longitudinal direction and low in variation. <P>SOLUTION: In the method for manufacturing the porous glass preform, glass fine particles are formed by a burner 7 for synthesizing the glass fine particles, and a deposition bar 11 is pulled while axially rotating the bar 11 and the porous glass preform is formed by depositing the glass fine particles on the deposition bar 11. A gas flow rate of the combustion gas supplied to the burner 7 or the glass raw material gas is controlled based on an atmospheric temperature in a reaction vessel 1 or an exhaust gas temperature in an exhaust pipe 15. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method for producing a porous glass base material produced by depositing glass fine particles.

  An optical fiber used for high-speed and large-capacity communication is mainly composed of a core and a clad, and after dewatering and sintering the porous glass base material, which is a deposit of glass particles, into a glass base material, It is manufactured by drawing this glass base material. As a method for producing a porous glass base material for producing an optical fiber, a VAD method (Vapor-phase Axial Deposition method) and an OVD method (Outside Vapor-phase Deposition method) are well known. In this VAD method and OVD method, glass particles are generated in the flame of the burner, and the generated glass particles are deposited around a deposition rod made of quartz or the like to form a cylindrical porous glass base material. Is the method.

  FIG. 6 shows a conventional example of an apparatus for producing a porous glass base material by the VAD method. As shown in FIG. 6, in the manufacturing apparatus 110, a plurality of burners 121, 122, and 123 that generate glass particles are arranged near the lower end of the target bar 112. Burners 121 to 123 are supplied with combustion gas such as hydrogen gas and oxygen gas, and glass source gas such as silicon tetrachloride.

  The burners 121 to 123 generate glass fine particles (silicon dioxide fine particles) by feeding the glass raw material gas into the oxyhydrogen flame, and attach the glass fine particles to the lower end of the target bar 112. The target bar 112 is pulled up while being rotated by the rotary pulling device 113. From the lower end of the target bar 112, a glass particulate deposit (soot preform) 111 grows downward in a cylindrical shape.

Further, the position of the lower end of the glass particulate deposit 111 is detected by the position detector 131. This detection signal is sent to the computer 132, and the pulling speed of the target bar 112 is adjusted so that the lower end position of the glass particulate deposit 111 is always the same. Information regarding the pulling speed of the target rod 112 is sent to the flow rate control device 133, and the flow rate control device 133 controls the flow rate of the gas supplied to the burner 121 according to the pulling speed.
JP 2000-34131 A

  As in Patent Document 1, in the conventional method for producing a porous glass base material, the growth rate of the deposition surface of the glass fine particle deposit formed by the adhesion of the glass fine particles (the adhesion rate of the glass fine particles) is monitored. Based on this position information, the flow rate of gas supplied to the glass particulate deposit is controlled.

However, in the production of the porous glass base material, the production environment of the glass fine particle deposit such as the atmosphere (temperature, humidity, pressure, etc.) in the reaction vessel changes. The temperature of the deposition surface may fluctuate. If the temperature of the deposition surface is not constant, the degree of adhesion of the glass particulates varies, and the bulk density of the glass particulate deposit is not constant.
That is, when the temperature of the deposition surface increases, the bulk density of the deposition surface increases, and when the temperature of the deposition surface decreases, the bulk density of the deposition surface decreases. If the bulk density is not uniform as described above, it is difficult to produce a glass base material having a uniform refractive index in the longitudinal direction when the glass fine particle deposit is stretched and sintered.

Further, if the bulk density of the glass fine particle deposit is not uniform, the growth rate of the deposition surface fluctuates, so that the pulling rate of the deposition rod is not constant.
That is, when the bulk density is high, the deposition surface of the glass particulate deposit becomes dense, and the growth rate of the deposition surface is slow. When the growth speed of the deposition surface is slowed, the pulling speed of the deposition rod is also slowed, and the outer diameter of the glass particulate deposit is increased. On the other hand, when the bulk density is small, the pulling speed of the deposition rod is increased, and the outer diameter of the glass particulate deposit is reduced.

  The objective of this invention is providing the manufacturing method of the porous glass base material which can manufacture the porous glass base material with a uniform bulk density over a longitudinal direction, and little outside-diameter fluctuation | variation.

In order to achieve the above object, the method for producing a porous glass base material according to the present invention supplies a combustion gas and a glass raw material gas to a burner for synthesizing fine glass particles to produce glass fine particles in a reaction vessel. A method for producing a porous glass base material by depositing the glass fine particles on a deposition rod to form a porous glass base material,
The flow rate of at least one of the combustion gas and the glass raw material gas is controlled based on the atmospheric temperature in the reaction vessel or the exhaust temperature in the exhaust pipe of the reaction vessel.

  In the manufacturing method, when the atmospheric temperature or the exhaust temperature is higher than a predetermined temperature, the combustion gas flow rate is decreased, and when the atmospheric temperature or the exhaust temperature is lower than a predetermined temperature, the combustion gas flow rate is reduced. It is preferable to increase.

In order to achieve the above object, the method for producing a porous glass preform according to the present invention supplies a combustion gas and a glass raw material gas to a glass fine particle synthesis burner, and the glass fine particles in a reaction vessel. Producing a porous glass preform by depositing the glass fine particles on a deposition rod to form a porous glass preform,
The flow rate of at least one of the combustion gas and the glass raw material gas is controlled based on the pressure in the reaction vessel or the pressure in the exhaust pipe of the reaction vessel.

Further, in the above manufacturing method, when the pressure in the reaction vessel or the pressure in the exhaust pipe is larger than a predetermined pressure, the combustion gas flow rate is decreased,
The combustion gas flow rate is preferably increased when the pressure in the reaction vessel or the pressure in the exhaust pipe is smaller than a predetermined pressure.

Furthermore, in order to achieve the above object, the method for producing a porous glass base material according to the present invention supplies a combustion gas and a glass raw material gas to a burner for glass fine particle synthesis, and the glass fine particles in a reaction vessel. Producing a porous glass preform by depositing the glass fine particles on a deposition rod to form a porous glass preform,
The flow rate of at least one of the combustion gas and the glass raw material gas is controlled based on the temperature and pressure in the reaction vessel or the temperature and pressure in the exhaust pipe of the reaction vessel.

Further, in the above manufacturing method, at a location where the glass particulate deposit is not a predetermined outer diameter, at least one of the combustion gas and the glass raw material gas based on the temperature in the reaction vessel or the temperature in the exhaust pipe of the reaction vessel. Control the flow rate of
When the glass fine particle deposit has a predetermined outer diameter, the flow rate of at least one of the combustion gas and the glass raw material gas is controlled based on the pressure in the reaction vessel or the pressure in the exhaust pipe of the reaction vessel. It is preferable.

  Further, in the above manufacturing method, at least one of the combustion gas and the glass raw material gas so that the temperature of the deposition surface of the glass particulate deposit body in which the glass particulates are deposited on the deposition rod becomes a predetermined temperature. It is preferable to control the flow rate.

  According to the method for producing a porous glass base material of the present invention, at least one of a combustion gas and a glass raw material gas supplied to the burner based on the atmospheric temperature in the reaction vessel or the exhaust temperature in the exhaust pipe of the reaction vessel. By controlling the flow rate, it is possible to produce a porous glass base material having a uniform bulk density in the longitudinal direction and little fluctuation in outer diameter.

  Further, since the pressure in the reaction vessel or the pressure in the exhaust pipe of the reaction vessel shows a correlation with the fluctuation of the bulk density of the glass particulate deposit, it is based on the pressure in the reaction vessel or the pressure in the exhaust pipe of the reaction vessel. In addition, by controlling the flow rate of at least one of the combustion gas and glass raw material gas supplied to the burner, a porous glass base material can be produced in which the bulk density is made uniform in the longitudinal direction and the outer diameter fluctuation is small. .

  Further, the combustion gas supplied to the burner based on both the temperature and pressure in the reaction vessel that correlates with the fluctuation of the bulk density of the glass particulate deposit, or both the temperature and pressure in the exhaust pipe of the reaction vessel, and When the flow rate of at least one of the glass raw material gas is controlled, more precise control is possible than when controlling only with respect to either temperature or pressure, and the bulk density is long. The effect of being uniform in the direction is enhanced, and a high-quality porous glass base material with less fluctuation in outer diameter can be produced.

  In addition, fluctuations in the bulk density of the glass particulate deposits are caused by temperature changes on the deposition surface accompanying fluctuations in temperature, pressure, etc. in the reaction vessel and exhaust pipe. In addition, when controlling based on the temperature in the exhaust pipe, the flow rate of the gas supplied to the burner may be controlled so that the temperature of the deposition surface of the glass fine particle deposit body becomes a predetermined temperature. Can be made uniform in the longitudinal direction, and a porous glass base material with little fluctuation in outer diameter can be produced.

Hereinafter, embodiments of a method for producing a porous glass preform according to the present invention will be described with reference to the drawings.
FIG. 1 shows an apparatus for producing a porous glass base material according to this embodiment, wherein (A) is a schematic configuration diagram, and (B) is a view of the inside of the apparatus as viewed from below. As shown in FIGS. 1A and 1B, the porous glass preform manufacturing apparatus 10 has a vertically long reaction vessel 1. A suspending device 13 is installed on the outer upper side of the reaction vessel 1, and the seed rod 12 is suspended by the suspending device 13. A deposition bar 11 is attached to the lower end of the suspended seed bar 12, and the deposition bar 11 is introduced into the reaction vessel 1.

The suspension device 13 can axially move the deposition rod 11 attached to the seed rod 12 and move it in the axial direction. Further, the suspension device 13 can increase the axial movement speed of the deposition rod 11 (the lifting speed of the deposition rod 11). Can be varied.
When glass particles are deposited on the outer periphery of the deposition rod 11, a substantially cylindrical glass particulate deposition body 19 having the deposition rod 11 at the center can be manufactured.

Below the reaction vessel 1, a glass fine particle synthesis burner 7 (hereinafter simply referred to as “burner 7”) for generating glass fine particles is provided. A gas supply tank (not shown) that can supply combustion gas and glass raw material gas is connected to the burner 7 via a gas supply path 17. Here, the combustion gas supplied to the burner 7 is mainly composed of a combustion-supporting gas and a combustion-supporting gas. Hydrogen (H2) is used as the combustion-supporting gas, and oxygen (O2) is used as an example of the combustion-supporting gas. Can be mentioned. An example of the glass raw material gas is silicon tetrachloride (SiCl4).
The burner 7 has a multi-port (multi-tube) structure in which a gas outlet has a plurality of ports, and the combustion gas and the glass raw material gas are blown out from each port, and in the flame generated by the combustion gas, Glass fine particles can be produced by oxidizing or hydrolyzing the glass raw material.

  A gas flow rate control device 6 is installed in the gas supply path 17 connected to the burner 7. The gas flow rate control device 6 can control the flow rate of each gas supplied to the burner 7. The gas flow rate control device 6 is connected to the control unit 4 via the line 23 and is controlled by the control unit 4.

The inner wall surface 1A of the reaction vessel 1 is provided with a first thermometer 8a, and the first thermometer 8a measures the atmospheric temperature T1 in the reaction vessel 1 (hereinafter also simply referred to as temperature T1). Here, the atmospheric temperature in the reaction vessel 1 means the temperature of the atmospheric gas (including water vapor, inert gas, undeposited glass fine particles, etc.) filling the reaction vessel 1.
The position where the first thermometer 8a is installed is not particularly limited as long as it is within the reaction vessel 1, but it is preferably provided in the vicinity of the deposition surface 19A of the glass particulate deposit 19.

Further, the inner wall surface 1 </ b> A of the reaction vessel 1 is provided with an exhaust port 9, and the exhaust port 9 communicates with an exhaust pipe 15. Water vapor, inert gas, undeposited glass particles and the like generated in the reaction vessel 1 are discharged from the exhaust pipe 15 to the exhaust gas treatment device through the exhaust port 9.
The inner wall surface 15A of the exhaust pipe 15 is provided with a second thermometer 8b. The second thermometer 8b measures the exhaust temperature T2 (hereinafter also simply referred to as temperature T2) of the gas discharged from the reaction vessel 1 via the exhaust pipe 15.

In addition, although it does not specifically limit as the 1st, 2nd thermometers 8a and 8b, For example, a thermocouple can be used.
The first and second thermometers 8a and 8b are connected to the control unit 4 via lines 21 and 22, respectively. The temperature data T1 and T2 measured by the first and second thermometers 8a and 8b are sent to the control unit 4.

  Outside the reaction vessel 1, a projector 2 is provided toward the deposition surface 19 </ b> A of the glass particulate deposit 19 formed by the burner 7, and the light receiver 3 is located at a position where the laser light 18 emitted from the projector 2 can be received. Is arranged. With the light projector 2 and the light receiver 3, the growth rate of the point P1 on the deposition surface 19A of the glass fine particle deposit 19 can be measured. The light receiver 3 is connected to the suspending device 13 via a line 24 and is configured to vary the lifting speed of the deposition rod 11 based on the position data from the light receiver 3.

Next, a method for manufacturing a porous glass base material using the manufacturing apparatus 10 will be described. First, the deposition rod 11 is attached to the tip of the seed rod 12, and the seed rod 12 is suspended from the suspension device 13. Then, the suspension device 13 is operated to lower the deposition rod 11 so that the distance between the glass particle deposition start point of the deposition rod 11 and the outlet of the burner 7 becomes a desired distance.
On the other hand, supply of the combustion gas (O2 and H2) and the glass raw material gas (SiCl4) to the burner 7 is started. If necessary, an additional gas supply tank may be added to supply an inert gas such as nitrogen, argon or helium, or a refractive index control source gas such as germanium tetrachloride (GeCl4) or POCl3 to the burner 7. .

  The deposition rod 11 is rotated about its axis, and an oxyhydrogen flame is emitted from the burner 7 toward the deposition rod 11. In this oxyhydrogen flame, glass fine particles are generated by an oxidation reaction or hydrolysis reaction of the glass raw material gas. While the generated glass particles are adhered to the outer periphery of the deposition rod 11, the deposition rod 11 is pulled up at a predetermined speed to gradually form and grow the glass particle deposition body 19.

When the glass particulate deposit 19 is grown, the projector 2 and the light receiver 3 always detect the point P1 on the deposition surface 19A of the glass particulate deposit 19 and suspend it based on the position information of this point P1. In the apparatus 13, the pulling speed of the deposition rod 11 is controlled.
Specifically, laser light 18 is emitted from the projector 2 so that the laser light 18 contacts the point P1 on the deposition surface 19A, and the light amount of the laser light 18 is measured by the light receiver 3.

The received light amount data measured by the light receiver 3 is sent to the suspending device 13 every predetermined time. In the suspending device 13, the growth rate at the point P1 is calculated from the received light amount data, and the pulling rate of the deposition rod 11 is controlled based on the growth rate data at the point P1. By controlling the pulling speed in this way, the distance between the deposition surface 19A of the glass fine particle deposit 19 and the burner 7 is always kept constant.
The point P1 is set at an arbitrary position on the deposition surface 19A. Further, instead of the projector 2 and the light receiver 3, a CCD camera or the like can be used to photograph the deposition surface 19A of the glass particulate deposit 19, and the position of the point P1 can be detected by image analysis.

In addition, the atmospheric temperature T1 in the reaction vessel 1 and the exhaust temperature T2 in the exhaust pipe 15 are measured by the first and second thermometers 8a and 8b, respectively. Data of the temperatures T1 and T2 are sent to the control unit 4.
The control unit 4 controls the flow rate of at least one of the combustion gas and the glass material gas supplied to the burner 7 with respect to the gas flow rate control device 6 based on the temperature data T1 and T2.

  When manufacturing the glass particulate deposit 19, the temperature of the deposition surface 19A of the glass particulate deposit 19 may fluctuate due to the influence of the atmosphere in the reaction vessel 1 as described above. If the temperature of the deposition surface 19A is not constant, the degree of adhesion of the glass particulates will fluctuate, so that the bulk density of the glass particulate deposits 19 will not be uniform in the longitudinal direction, resulting in large fluctuations in the outer diameter.

In contrast, in the present invention, attention is paid to the fact that the temperature of the deposition surface 19A of the glass particulate deposit 19 has a correlation with the atmosphere temperature T1 in the reaction vessel 1 and the exhaust temperature T2 in the exhaust pipe 15, Based on the temperatures T1 and T2, the flow rate of gas supplied to the burner 7 was controlled to control the temperature of the deposition surface 19A.
In this way, by controlling the gas flow rate supplied to the burner 7 based on the temperatures T1 and T2, the temperature of the deposition surface 19A can be indirectly controlled, and the bulk density of the glass particulate deposits 19 can be controlled in the longitudinal direction. It is possible to produce a glass fine particle deposit 19 that is stabilized and has a small outer diameter variation.
Further, since the temperature of the deposition surface 19A of the glass particulate deposit 19 is not directly measured, the first and second thermometers 8a and 8b do not have to be able to measure a high temperature range. Can be cheap.

As an example, FIG. 3A shows the relationship between the flow rate of hydrogen gas supplied to the burner 7 during the production of the porous glass base material and the temperature of the deposition surface 19A. FIG. 3B shows the relationship between the flow rate of hydrogen gas supplied to the burner 7 during the production of the porous glass base material and the exhaust temperature T2 in the exhaust pipe 15.
3A and 3B, it is understood that the temperature of the deposition surface 19A and the temperature in the exhaust pipe 15 both follow the fluctuation of the hydrogen gas flow rate, and these temperatures are correlated.

In the flow rate control of the combustion gas or the glass raw material gas, any of the gas flow rates of hydrogen gas, oxygen gas, and glass raw material gas may be controlled. In particular, the flame temperature of the burner 7 is easily adjusted. Therefore, it is preferable to control the flow rate of hydrogen gas.
Specifically, when the flow rate of hydrogen gas is controlled, the hydrogen gas flow rate is decreased when the temperature T1 or T2 is higher than a predetermined temperature, and the hydrogen gas flow rate is decreased when the temperature T1 or T2 is lower than the predetermined temperature. Should be increased. The predetermined temperature can be appropriately set depending on the size of the porous glass base material to be manufactured.

That is, when the temperature T1 or T2 is large, the bulk density of the deposition surface 19A of the glass fine particle deposit 19 is increased (densified), so that the growth rate decreases and the outer diameter tends to increase. Therefore, the hydrogen gas flow rate is decreased, the temperature of the deposition surface 19A is lowered, and the bulk density is reduced.
On the contrary, when the temperature T1 or T2 is small, the bulk density of the deposition surface 19A becomes small (becomes dense), so the growth rate tends to increase and the outer diameter tends to decrease. Therefore, the hydrogen gas flow rate is increased, the temperature of the deposition surface 19A is increased, and the bulk density is increased.

When the gas flow rate is varied, a target value of the temperature T1 or T2 is set in advance, and the gas flow rate is controlled so that the measured temperature T1 or T2 approaches the target value.
For example, when the hydrogen gas flow rate is controlled as described above, when the measured temperature T1 or T2 data is larger than the target value, the flow rate of the hydrogen gas supplied to the burner 7 is decreased, and the measured temperature T1 or T2 When the data is smaller than the target value, it is preferable to increase the flow rate of the hydrogen gas supplied to the burner 7.
At this time, the difference between the target value and the measured value of the temperature T1 or T2 is calculated, and the hydrogen gas flow rate may be controlled when the difference between the target value and the measured value falls within a certain range.

In the first embodiment, the method for controlling the hydrogen gas flow rate based on the atmospheric temperature T1 in the reaction vessel 1 or the exhaust temperature T2 in the exhaust pipe 15 has been described. The outer diameter of the glass particulate deposit 19 can be controlled by controlling the gas flow rate of (oxygen gas) or glass raw material gas.
Furthermore, the flow rates of a plurality of gases (two or three selected from hydrogen gas, oxygen gas, and glass raw material gas) may be controlled simultaneously.
For example, when controlling the flow rate of oxygen gas, when the temperature T1 or T2 is high, the flow rate of oxygen gas to the burner 7 is increased and when the temperature T1 or T2 is low, the oxygen gas to the burner 7 is controlled. It is good to control the reduction of the flow rate.

  When controlling the glass raw material gas flow rate based on the temperature T1 or the temperature T2, when the measured value of the temperature T1 or the temperature T2 is large, the flow rate of the glass raw material gas to the burner 7 is controlled to be reduced, and the temperature T1 or When the measured value of the temperature T2 is small, the flow rate of the glass raw material gas to the burner 7 may be increased.

  Moreover, in the said embodiment, although the example which measured the temperature data (T1, T2) of two places was shown, the manufacturing method which concerns on this invention is not limited to this, The atmosphere in reaction container 1 Only one of the temperature T1 and the exhaust temperature T2 in the exhaust pipe 15 may be measured, and the gas flow rate may be controlled based on this temperature data.

  In addition, the manufacturing method of the porous glass base material based on this invention is not limited to embodiment described above, A suitable deformation | transformation, improvement, etc. are possible. For example, in the above-described embodiment, an example in which one burner 7 is used has been described. However, the number of burners is not limited to one, and the present invention can be applied to the case where a plurality of burners are used.

In the first embodiment described above, the manufacturing method of the porous glass base material by the VAD method has been described, but the manufacturing method according to the present invention can be similarly applied to the OVD method. Hereinafter, the manufacturing method (2nd Embodiment) of the porous glass by OVD method is demonstrated.
FIG. 2 shows an embodiment of an apparatus for producing a porous glass base material by the OVD method, (A) is a schematic configuration diagram, and (B) is a sectional view taken along line AA ′ in (A). Yes.

  In FIG. 2 (A), the manufacturing apparatus 30 can produce a porous glass base material by a multi-layered OVD method, and includes a horizontally long reaction vessel 31 and a control unit 34 that controls each apparatus included in the manufacturing apparatus. Composed. Inside the reaction vessel 31, a support device 33 that holds both ends of the deposition rod 41 and rotates the shaft, a burner 37 that generates glass particles, and a stage 44 that supports the burner 37 at a predetermined distance from the lower end of the glass particle deposit 39. And a traverse device 43 for traversing the stage 44 in the horizontal direction (longitudinal direction of the deposition rod 41).

In the deposition rod 41, dummy rods 41a are welded to both ends of a glass rod 41b having a predetermined length.
The burner 37 has a multiple tube structure like the burner 7 in the first embodiment, and a gas tank (not shown) for supplying combustion (hydrogen gas, oxygen gas) gas and glass raw material gas is a gas supply path 32. Connected through. The glass particulate deposit 39 can be formed on the outer periphery of the deposition rod 41 by traversing the burner 37 in the longitudinal direction of the deposition rod 41 while generating the glass particulates.

A first thermometer 48a is provided on the upper wall surface 31A of the reaction vessel 31, and the atmospheric temperature T1 inside the reaction vessel 31 is measured.
Further, the upper wall surface 31 A of the reaction vessel 31 is provided with an exhaust port 49, and the exhaust port 49 communicates with the exhaust pipe 45. The inner wall surface 45A of the exhaust pipe 45 is provided with a second thermometer 48b, and the exhaust temperature T2 in the exhaust pipe 45 is measured by the second thermometer 48b. Also in the second embodiment, the first and second thermometers 48a and 48b are not particularly limited, and for example, thermocouples can be used.
The first and second thermometers 48a and 48b are connected to the control unit 34 via lines 51 and 52, respectively. The temperature data T1 and T2 measured by the first and second thermometers 48a and 48b are the control unit 34. Sent to.

  Further, a light emitter / receiver 46 is provided outside the reaction vessel 31. The light emitter / receiver 46 is a reflective outer diameter measuring device. The projecting / receiving device 46 can detect an arbitrary point P2 on the surface 39A of the glass particulate deposit 39 to measure the outer diameter of the glass particulate deposit 39.

A method for manufacturing a porous glass base material using the porous glass base material manufacturing apparatus 30 will be described below. Both ends of the deposition rod 41 are held by the support device 33, and the deposition rod 41 is rotated about its axis.
On the other hand, the burner 37 is moved to the deposition start position of the glass fine particles, and the fuel gas and the raw material gas are supplied.
A flame containing glass fine particles is emitted from the burner 37 toward the deposition rod 41 to deposit glass fine particles on the outer periphery of the deposition rod 41, and the stage 44 is traversed horizontally to form a glass fine particle deposit 39. The deposition of the glass particles by the traverse of the burner 37 may be performed one way or reciprocating.

  During the formation of the glass particulate deposit 39, the position of the point P <b> 2 on the surface 39 </ b> A of the glass particulate deposit 39 is detected by the projector / receiver 46, and the outside of the glass particulate deposit 39 formed for each traverse of the burner 37 is detected. Measure the diameter.

In addition, the atmospheric temperature T1 in the reaction vessel 31 and the exhaust temperature T2 in the exhaust pipe 45 are measured by the first and second thermometers 48a and 48b, respectively. The data of the temperatures T1 and T2 are sent to the control unit 34.
The controller 34 controls the flow rate of at least one of the combustion gas and the glass raw material gas supplied to the burner 37 to the gas flow rate control device 36 based on the temperature data T1 and T2.

  Also in the second embodiment, the flow rate of the combustion gas or the glass raw material gas may be any of hydrogen gas, oxygen gas, and glass raw material gas, but it is preferable to control the flow rate of the hydrogen gas. Specifically, when one of the temperatures T1 and T2 is higher than a predetermined temperature, the flow rate of hydrogen gas supplied to the burner 37 is decreased, and when one of the temperatures T1 and T2 is lower than the predetermined temperature, the burner is reduced. The flow rate of hydrogen gas supplied to 37 may be increased.

As described above, the traverse is repeated a plurality of times and finished when the desired outer diameter is reached, and a porous glass base material is manufactured.
Also in the manufacturing method according to the second embodiment described above, by controlling the gas flow rate supplied to the burner 37 based on the atmospheric temperature T1 in the reaction vessel 31 or the exhaust temperature T2 in the exhaust pipe 45, glass fine particle deposition is performed. The temperature of the surface 39A of the body 39 can be controlled, and a porous glass base material having a uniform bulk density and little fluctuation in outer diameter can be produced.

EXAMPLES Hereinafter, although an Example and a comparative example are given and this invention is demonstrated in more detail, this invention is not limited to a following example.
Example 1
1 is used to measure the atmospheric temperature T1 in the reaction vessel 1 and the temperature T2 in the exhaust pipe 15, and increase or decrease the hydrogen gas flow rate based on the temperatures T1 and T2, thereby producing a porous material. A glass preform was produced. The outer diameter of the porous glass base material was 150 mm and the length was 500 mm.

A graph in which the pulling speed at this time is recorded for each elapsed time is shown in FIG. In the graph of FIG. 3C, as indicated by the solid line, the pulling speed of the deposition rod 11, that is, the growth speed at the point P1 of the glass fine particle deposit 19 is within ± 3% from the target value.
The bulk density of the produced porous glass base material was almost uniform in the longitudinal direction. Further, when the outer diameter of the porous glass base material was examined, the longitudinal variation was within 3% of the target value. In addition, when three porous glass base materials were manufactured by the same method as described above, all the porous glass base materials could be manufactured within ± 3% of the growth rate of the target value, and the outer diameter The fluctuation could be within 3%.
In addition, when the porous glass base material was manufactured using the manufacturing apparatus 30 by the OVD method shown in FIG. 2, the bulk density was substantially uniform in the longitudinal direction and the porous with little outside diameter variation was the same as in Example 1 above. A glass base material was obtained.

(Comparative Example 1)
As in Example 1, a porous glass base material was manufactured using the manufacturing apparatus 10 shown in FIG. However, the gas flow rate was not increased or decreased and kept constant.
As a result, as shown by the broken line in FIG. Moreover, the bulk density and outer diameter of the produced porous glass base material were non-uniform over the longitudinal direction.
Furthermore, when three base materials were manufactured by the same method, not only the growth rate, surface temperature and outer diameter of one base material changed, but also the growth rate, surface temperature and outer diameter of the three base materials. It was scattered.

In the above embodiments and examples, focusing on the temperature in the reaction vessel or the temperature in the exhaust pipe connected to the reaction vessel as a factor that correlates with the fluctuation of the bulk density of the glass particulate deposit, Based on the temperature, the flow rate of at least one of the combustion gas supplied to the burner and the glass raw material gas was controlled.
However, when the exhaust temperature and pressure in the exhaust pipes 15 and 45 are measured during the manufacturing process of the porous glass base material by the manufacturing apparatuses 10 and 30 shown in FIG. 1 and FIG. 2, it is shown in FIG. Thus, it was found that the pressure fluctuated in accordance with the temperature fluctuation, and the exhaust pressure and the exhaust temperature were close.
Therefore, when the correlation between the exhaust gas temperature and the hydrogen gas flow rate in FIG. 3B and the correlation between the hydrogen gas flow rate and the temperature of the deposition surface of the glass particulate deposit in FIG. Even if the flow rate of at least one of the combustion gas and glass raw material gas supplied to the burner is controlled based on the internal pressure, the temperature of the deposition surface of the glass particulate deposit is kept constant, It was found that it is possible to produce a porous glass base material in which the bulk density of the glass fine particle deposit is suppressed, the bulk density is made uniform in the longitudinal direction, and the outer diameter fluctuation is small.

Further, according to experiments by the present inventors, the temperature and pressure in the reaction vessels 1 and 31 of the production apparatuses 10 and 30 shown in FIGS. 1 and 2 are the same as the temperature and pressure in the exhaust pipes 15 and 45. FIG. 3D shows the correlation as shown in FIG.
Therefore, even if the flow rate of at least one of the combustion gas and the glass raw material gas supplied to the burner is controlled based on the pressure in the reaction vessels 1 and 31, the temperature of the deposition surface of the glass particulate deposit is controlled. It is possible to produce a porous glass base material that is kept constant, that is, the bulk density of the glass fine particle deposit is suppressed, the bulk density is made uniform in the longitudinal direction, and the outer diameter fluctuation is small.

The manufacturing apparatus 200 shown in FIG. 4 is based on the above knowledge that the pressure in the reaction vessel or the exhaust pipe is a factor that correlates with the fluctuation of the bulk density of the glass particulate deposit. The apparatus 10 is improved.
The manufacturing apparatus 200 shown in FIG. 4 adds a pressure sensor 208a for detecting the pressure in the reaction vessel 1 and a pressure sensor 208b for detecting the pressure in the exhaust pipe 15 to the manufacturing apparatus 10 shown in FIG. The control unit 4 is replaced with the control unit 204.

  The control unit 204 receives the detection signals of the pressure sensors 208a and 208b via lines (signal transmission paths) 225 and 226, and controls the gas flow rate based on the pressure signal detected by either of the pressure sensors 208a and 208b. The flow rate of at least one of the combustion gas and the glass raw material gas in the apparatus 6 can be controlled.

  The manufacturing apparatus 200 shown in FIG. 4 adds the pressure sensors 208a and 208b as described above, and the combustion gas and the glass raw material gas in the gas flow control device 6 based on the pressure signals detected by these sensors. Except for the point equipped with a control unit 204 capable of controlling at least one of the flow rates, the configuration may be the same as that of the manufacturing apparatus 10 in FIG. Or omitted.

The manufacturing apparatus 300 shown in FIG. 5 is based on the above knowledge that the pressure in the reaction vessel or the exhaust pipe is a factor that correlates with the fluctuation of the bulk density of the glass particulate deposit. The apparatus 30 is improved.
The manufacturing apparatus 300 shown in FIG. 5 adds a pressure sensor 348a for detecting the pressure in the reaction vessel 31 and a pressure sensor 348b for detecting the pressure in the exhaust pipe 45 to the manufacturing apparatus 30 shown in FIG. The control unit 34 is replaced with a control unit 334.

  The control unit 334 receives the detection signals of the pressure sensors 348a and 348b via lines (signal transmission paths) 355 and 356, and controls the gas flow rate based on the pressure signal detected by any of these pressure sensors 348a and 348b. The flow rate of at least one of the combustion gas and the glass raw material gas in the device 36 can be controlled.

  The manufacturing apparatus 300 shown in FIG. 5 adds the pressure sensors 348a and 348b as described above, and the combustion gas and the glass raw material gas in the gas flow control device 36 based on the pressure signals detected by these sensors. Except for the point that a control unit 334 capable of controlling at least one of the flow rates is equipped, the configuration may be the same as that of the manufacturing apparatus 30 in FIG. Or omitted.

When the manufacturing apparatuses 200 and 300 described above are used, the following method for manufacturing a porous glass base material can be implemented.
In the reaction vessel 1, 31, the combustion gas and the glass raw material gas are supplied to the glass particle synthesis burners 7, 37 to generate glass particles, and the glass particles are deposited on the deposition rods 11, 41 b to be porous. Is a method for producing a porous glass base material for forming a porous glass base material (glass fine particle deposits) 19, 39, and is a pressure P1 in the reaction vessel 1, 31 detected by the pressure sensors 208a, 208b, 348a, 348b. Alternatively, the porous glass is characterized in that the flow rate of at least one of the combustion gas and the glass raw material gas supplied to the burners 7 and 37 is controlled based on the pressure P2 in the exhaust pipes 15 and 45 of the reaction vessel. It is a manufacturing method of a base material.

  As described above, the pressure P1 in the reaction vessels 1 and 31 or the pressure P2 in the exhaust pipes 15 and 45 connected to the reaction vessel shows a correlation with the fluctuation of the bulk density of the glass particulate deposits 19 and 39. Therefore, by controlling the flow rate of at least one of the combustion gas and the glass raw material gas supplied to the burners 7 and 37 based on the pressure P1 in the reaction vessel or the pressure P2 in the exhaust pipe of the reaction vessel, The temperature of the deposition surface of the fine particle deposits 19 and 39 can be indirectly controlled to be constant. As a result, the fluctuation of the bulk density is suppressed, the bulk density is made uniform in the longitudinal direction, and the outer diameter varies. It is possible to produce a porous glass base material with a small amount.

  The flow rate of hydrogen gas, which is a combustion gas supplied to the burners 7 and 37, is controlled based on the pressure P1 in the reaction vessel or the pressure P2 in the exhaust pipe detected by the pressure sensors 208a, 208b, 348a and 348b. In this case, when the pressure P1 in the reaction vessel or the pressure P2 in the exhaust pipe is larger than a predetermined pressure, the flow rate of hydrogen gas supplied to the burners 7 and 37 is decreased, and the pressure P1 in the reaction vessel or in the exhaust pipe When the pressure P2 is lower than the predetermined pressure, the flow rate of hydrogen gas supplied to the burners 7 and 37 may be increased.

When the flow rate of the gas supplied to the burners 7 and 37 is controlled based on the pressure P1 in the reaction vessel or the pressure P2 in the exhaust pipe, the gas to be controlled includes hydrogen gas or oxygen gas that is a component of the fuel gas, Alternatively, any of the raw material gases can be selected. However, controlling the flow rate of hydrogen gas effective for adjusting the flame temperature is easy to manage and can stabilize the production.
In addition, the predetermined pressure used as the reference | standard which judges the fluctuation | variation of the pressure P1 in the reaction container detected by the pressure sensors 208a, 208b, 348a, 348b or the pressure P2 in the exhaust pipe depends on the size of the porous glass base material to be manufactured. It is good to change the setting appropriately.

  Further, the control units 204 and 334 equipped in the manufacturing apparatuses 200 and 300 have the gas flow rate control device 6 based on the pressure P1 in the reaction vessel or the pressure P2 in the exhaust pipe detected by the pressure sensors 208a, 208b, 348a and 348b. In addition to the function of controlling the gas flow rate of at least one of the combustion gas and the glass raw material gas, the temperature T1 in the reaction vessel or the temperature T2 in the exhaust pipe detected by the thermometers 8a, 8b, 48a, 48b When the gas flow rate control devices 6 and 36 also have a function of controlling the gas flow rate of at least one of the combustion gas and the glass raw material gas, the following method for producing a porous glass base material is carried out. be able to.

  In the reaction vessels 1 and 31, the combustion gas and the glass raw material gas are supplied to the glass fine particle synthesis burners 7 and 37 to generate glass fine particles, and the glass fine particles are deposited on the deposition rods 11 and 41b. A method for producing a porous glass base material for forming glass particulate deposits 19 and 39, wherein both temperature T1 and pressure P1 in reaction vessels 1 and 31, or temperature T2 in exhaust pipes 15 and 45 of the reaction vessel And a flow rate of at least one of the combustion gas and the glass raw material gas supplied to the burners 7 and 37 based on both the pressure P2 and the pressure P2.

  In this way, finer control is possible than in the case where control is performed by focusing on only one of temperature and pressure, the effect of making the bulk density uniform in the longitudinal direction is enhanced, and fluctuations in the outer diameter are increased. Furthermore, a low-quality porous glass base material can be manufactured.

Further, the control of the gas flow rate based on the temperature and the control of the gas flow rate based on the pressure may be switched according to the degree of growth of the outer diameter of the glass particulate deposit.
For example, in a place where a predetermined time elapses after the start of deposition of the glass fine particles and the growth rate fluctuates until the outer diameter of the predetermined glass fine particle deposit is formed, the reaction to the outer diameter of the glass fine particle deposit is good. As the control, the flow rate of at least one of the combustion gas and the glass raw material gas supplied to the burner is controlled based on the temperature in the reaction vessel or the temperature in the exhaust pipe of the reaction vessel.
Then, after the outer diameter of the glass fine particle deposit body becomes a predetermined size and the soot growth rate is stabilized, it continues for 30 to 120 seconds or more within ± 0.5 to 2.0 mm / h of the predetermined growth rate. In the place where the gas enters, the flow rate of at least one of the combustion gas and the glass raw material gas supplied to the burner may be controlled based on the pressure in the reaction vessel or the pressure in the exhaust pipe of the reaction vessel.
As described above, the outer diameter of the glass fine particle deposits 19 and 39 is quickly changed to a desired outer diameter by switching the factor for controlling the gas flow rate from the temperature to the pressure according to the growth of the outer diameter of the glass fine particle deposit. It is possible to grow, and it is possible to efficiently produce a porous glass base material with little fluctuation in outer diameter.

  It should be noted that the predetermined time after starting the deposition of the glass fine particles and the outer diameter of the reference glass fine particle deposit when reaching the predetermined shape differ depending on the size of the porous glass base material to be manufactured, etc. Needless to say, it can be appropriately set according to the size of the porous glass base material to be produced.

Further, the gas flow rate control based on the pressure P1 in the reaction vessel or the pressure P2 in the exhaust pipe described above, or the gas flow rate control based on the temperature T1 in the reaction vessel or the temperature T2 in the exhaust pipe, This is to make the bulk density uniform by preventing fluctuation of the surface temperature.
Therefore, in other words, the method for producing the porous glass preform of the present invention can be applied to the deposition rods 11 and 41b even when the flow rate of the gas supplied to the burner is controlled based on the temperature in the reaction vessel and the exhaust pipe. The flow rate of at least one of the combustion gas and the glass raw material gas supplied to the burners 7 and 37 is controlled so that the temperature of the deposition surface of the glass particulate deposits 19 and 39 on which the glass particulates are deposited becomes a predetermined temperature. As a result, it is possible to produce a porous glass base material in which the bulk density is uniform in the longitudinal direction and the outer diameter fluctuation is small.

BRIEF DESCRIPTION OF THE DRAWINGS It is a schematic block diagram of one Embodiment (1st Embodiment of this invention) of the manufacturing apparatus of the porous glass base material by VAD method. It is a schematic block diagram of one Embodiment (2nd Embodiment of this invention) of the manufacturing apparatus of the porous glass base material by OVD method. (A) is a graph showing the relationship between the hydrogen gas flow rate and the deposition surface temperature, (B) is a graph showing the relationship between the hydrogen gas flow rate and the exhaust temperature T2, and (C) is a comparison between Example 1 and the comparison. It is a graph which shows the change of the raising speed in Example 1, (D) is a graph which shows the relationship between the pressure in the exhaust pipe connected to the reaction container, and temperature. It is a schematic block diagram of one Embodiment (3rd Embodiment of this invention) of the manufacturing apparatus of the porous glass base material by VAD method. It is a schematic block diagram of form of one Embodiment (4th Embodiment of this invention) of the manufacturing apparatus of the porous glass base material by OVD method. An example of the manufacturing apparatus of the porous glass base material by the conventional VAD method is shown.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1,31 Reaction vessel 4,34 Control part 7,37 Burner 8a, 48a for glass fine particle synthesis | combination 1st thermometer 8b, 48b 2nd thermometer 10,30 Manufacturing apparatus 11,41 Deposition rod 15,45 Exhaust pipe 21 , 51 line 22, 52 line 200, 300 Manufacturing device 204, 334 Control unit 208a, 348a Pressure sensor 208b, 348b Pressure sensor 225, 355 line (signal transmission path)
226,356 lines (signal transmission line)

Claims (7)

A porous material in which a combustion gas and a gas for glass raw material are supplied to a burner for glass fine particle synthesis, glass fine particles are generated in a reaction vessel, and the glass fine particles are deposited on a deposition rod to form a porous glass base material A method for producing a glass base material,
A porous glass base material, wherein the flow rate of at least one of the combustion gas and the glass raw material gas is controlled based on an atmospheric temperature in the reaction vessel or an exhaust temperature in an exhaust pipe of the reaction vessel. Manufacturing method. When the ambient temperature or the exhaust temperature is higher than a predetermined temperature, the combustion gas flow rate is decreased,
2. The method for producing a porous glass base material according to claim 1, wherein the combustion gas flow rate is increased when the ambient temperature or the exhaust temperature is lower than a predetermined temperature. A porous material in which a combustion gas and a gas for glass raw material are supplied to a burner for glass fine particle synthesis, glass fine particles are generated in a reaction vessel, and the glass fine particles are deposited on a deposition rod to form a porous glass base material A method for producing a glass base material,
Production of a porous glass base material, wherein the flow rate of at least one of the combustion gas and the glass raw material gas is controlled based on the pressure in the reaction vessel or the pressure in the exhaust pipe of the reaction vessel Method. When the pressure in the reaction vessel or the pressure in the exhaust pipe is greater than a predetermined pressure, the combustion gas flow rate is decreased,
The method for producing a porous glass base material according to claim 3, wherein when the pressure in the reaction vessel or the pressure in the exhaust pipe is smaller than a predetermined pressure, the combustion gas flow rate is increased. A porous material in which a combustion gas and a gas for glass raw material are supplied to a burner for glass fine particle synthesis, glass fine particles are generated in a reaction vessel, and the glass fine particles are deposited on a deposition rod to form a porous glass base material A method for producing a glass base material,
A porous material characterized by controlling the flow rate of at least one of the combustion gas and the glass raw material gas based on the temperature and pressure in the reaction vessel or the temperature and pressure in the exhaust pipe of the reaction vessel. Manufacturing method of glass base material. At a location where the glass particulate deposit is not a predetermined outer diameter, based on the temperature in the reaction vessel or the temperature in the exhaust pipe of the reaction vessel, control the flow rate of at least one of the combustion gas and the glass raw material gas,
When the glass fine particle deposit has a predetermined outer diameter, the flow rate of at least one of the combustion gas and the glass raw material gas is controlled based on the pressure in the reaction vessel or the pressure in the exhaust pipe of the reaction vessel. The manufacturing method of the porous glass base material of Claim 5 characterized by the above-mentioned.   Controlling the flow rate of at least one of the combustion gas and the glass raw material gas so that the temperature of the deposition surface of the glass particulate deposit body obtained by depositing the glass particulates on the deposition rod becomes a predetermined temperature. The manufacturing method of the porous glass base material as described in any one of Claim 1 or 2 characterized by the above-mentioned.

Images