JP2000313625A - Apparatus for producing porous glass preform - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an apparatus for producing a high-quality porous glass capable of improving the productivity and reducing the amount of a glass raw material or a combustible gas used when depositing glass microparticles and producing the porous glass. SOLUTION: Plural burners 19 blowing glass microparticles on the lateral face of an axially rotated substrate glass rod 2 while repeating the reciprocation in the longitudinal direction of the substrate glass rod 2 are adjacently arranged and an exhaust hood 7 repeating reciprocation synchronously with the burners 19 is arranged above a porous glass preform 1 on which the glass microparticles are blown and successively deposited.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for manufacturing a porous glass preform which is a raw material of an optical fiber.

[0002]

2. Description of the Related Art A porous glass preform is supplied with a glass material gas such as tetrachlorosilane or tetrachlorogermanium to a burner which repeats a reciprocating motion in a longitudinal direction of a rotating base glass rod, and a burner flame is supplied. The glass fine particles produced by the hydrolysis are deposited in layers on the base glass rod.

[0003] When glass particles are deposited using a single burner, productivity is low. Therefore, conventionally, a plurality of burners arranged at sufficient intervals have been used to increase the deposition amount per unit time.

[0004]

However, in this method, the conical deposition portion near the reversal position of the reciprocation of the burner becomes longer, so that the production yield of the porous glass base material is poor. In addition, since the flame tip of the burner is wide, the heating efficiency is low and the amount of glass particles that cannot be deposited is large, so that a large amount of combustible gas and raw material gas are required.

As shown in FIG. 2, as the distance between the burners 24 and 25 is reduced, the conical portion 23 can be shortened, but bubbles remain in the glass when sintered. After examining the cause, the burner flame 2
The vortex 27 generated between the burners due to the interference between 6, 28
It was found that some of the glass fine particles that could not be deposited were entrained and grew into large particles, adhered to the porous glass base material 21 and caused non-uniform density, resulting in bubbles during sintering.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and when producing porous glass by depositing glass fine particles, the productivity is improved and the use of glass raw materials and combustible gas is reduced. It is an object of the present invention to provide an apparatus for producing high quality porous glass.

[0007]

Means for Solving the Problems The apparatus for producing a porous glass base material of the present invention, which has been made to achieve the above object, comprises:
The following is a description with reference to the drawings corresponding to the embodiments.

As shown in FIG. 1, the apparatus for producing a porous glass preform sprays glass fine particles on the side surface of the base glass rod 2 while repeating reciprocating movements in the longitudinal direction of the base glass rod 2 rotating around the axis. An exhaust hood in which a plurality of burners 19 are disposed adjacent to each other, and reciprocating in synchronization with the burners 19 above the porous glass preform 1 on which glass fine particles are sprayed and sequentially deposited. 7 are arranged.

It is preferable that the distance between the centers of the outer tubes of adjacent burners is 1.7 or less with respect to the inner diameter of the outer tube of the burner 19. If wider, the adjacent burner 19
A vortex is generated between them.

Each burner 19 is preferably formed of a stainless steel tube or a quartz glass tube. Each burner 1
9 may be composed of a single outer tube from which a mixed gas of a combustible gas and a supporting gas is ejected, and an inner tube through which the combustible gas flows is inserted into the outer tube through which the supporting gas flows. It may be configured in such a manner. This outer tube has an inner diameter of 20-40.
mm. Adjacent burners may be arranged such that the outer tubes are in contact with each other, or may be arranged with a gap.

Each burner 19 is connected to a supply pipe (not shown) for a combustible gas, a combustion supporting gas, and a raw material gas. By maintaining the supply amounts of these gases constant, glass particles can be uniformly generated from all burners 19.

A pedestal 18 on which a burner 19 is mounted is driven by a burner motor 15 connected to a reciprocating motion control circuit 14.
It can reciprocate in parallel with the base glass rod 2.

The exhaust hood 7 has an exhaust fan 8 for forcibly discharging floating glass particles that cannot be deposited to the outside of the system, and a hood motor 4 connected to a reciprocation control circuit 14. Thereby, the reciprocating motion can be performed in parallel with the burner 19.

[0014] Using the apparatus for manufacturing a porous glass preform,
A vortex is not generated between the plurality of burners 19, glass particles are efficiently deposited, and the conical portion 3 is small. In addition, heat loss due to heat radiation is small and heating efficiency is good.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described in detail. FIG. 1 is a schematic view showing an embodiment of an apparatus for manufacturing a porous glass base material to which the present invention is applied.

As shown in FIG. 1, the apparatus for manufacturing a porous glass preform has an exhaust hood 7 in which a plurality of burners 19 for generating glass particles are arranged adjacent to each other and reciprocate in synchronism with the burners 19. are doing.

Each of the plurality of burners 19 includes a combustible gas supply pipe, a combustible gas supply pipe, and a raw material gas supply pipe (not shown).
It is connected to the. All burners 19 are mounted on a pedestal 18. A screw rod 16 connected to the burner motor 15 connected to the reciprocating motion control circuit 14 is arranged parallel to the base glass rod 2 and screwed to the pedestal 18. Further, a guide rod 17 penetrates the pedestal 18.

The exhaust hood 7 has an exhaust fan 8 and an outlet thereof is connected to a bellows-shaped exhaust pipe 9 communicating outside the system. The screw rod 5 connected to the hood motor 4 connected to the reciprocating motion control circuit 14 is arranged in parallel with the base glass rod 2 and screwed with the exhaust hood 7. Further, a guide rod 6 penetrates the exhaust hood 7.

Both ends of the base glass rod 2 are grippers 12, 13
And one gripping tool 12 is connected to the base material motor 11.

The apparatus for manufacturing a porous glass base material is used as follows. First, the base glass rod 2 made of quartz is gripped by the grippers 12 and 13, and the base material motor 11 is driven to rotate the shaft at a constant speed.

Hydrogen gas, which is a combustible gas, and oxygen gas, which is a supporting gas, are supplied to a plurality of adjacent burners 19, respectively, and a flame 20 is generated when the mixed gas is ignited. When a tetrachlorosilane gas as a raw material gas is supplied to the flame 20 and hydrolyzed, glass fine particles are generated. The exhaust fan 8 is constantly driven to discharge the glass particles that have not been deposited from the exhaust hood 7 to the outside of the system.

In accordance with a command from the reciprocating motion control circuit 14, the screw rod 16 is rotated forward while controlling the drive of the burner motor 15. Then, the pedestal 18 on which the burner 19 is mounted starts moving from the reciprocation start position A to the reciprocation reversal position B. The pedestal 18 is guided by the guide rod 17 and moves parallel to the base glass rod 2. At the same time, the hood motor 4 is driven by the instruction of the reciprocation
, And the exhaust hood 7 is moved in parallel with the burner 19 at the same speed.

After the burner 19 is moved at a constant speed, when the pedestal 18 reaches the reciprocation reversal position B, the drive of the burner motor 15 is stopped according to a command from the reciprocation control circuit 14. Then, the forward rotation of the screw bar 16 stops, and the burner 1
The movement of 9 stops. At the same time, the driving of the hood motor 4 is stopped, and the movement of the exhaust hood 7 is stopped.

Next, when the burner motor 15 and the hood motor 4 are driven in reverse according to a command from the reciprocating motion control circuit 14, the screw rod 16 and the screw rod 5 rotate in reverse. As a result, the burner 19 and the exhaust hood 7 start to move synchronously from the reciprocating reversal position B to the reciprocating start position A, and after moving at a constant speed, reach the reciprocating start position A. The movement is stopped by the command of 14. By repeating this operation, the glass fine particles generated from the burner 19 are sequentially deposited in layers on the base glass rod 2 to form the porous glass preform 1.

The base glass rod may be quartz glass or a core rod having a core and a clad.

According to the above-described embodiment, a porous glass base material was produced as a trial. Twelve burners made of quartz and having an inner diameter of the outer tube of 30 mm and an outer diameter of 34 mm are arranged side by side at an interval of 45 mm between the centers of the outer tubes of the burners, and each burner is supplied with 100 L / min of hydrogen gas. 35 L / min of oxygen gas and 20 L / min of 25% tetrachlorosilane gas diluted with oxygen gas were supplied. The moving speed of the burner at a constant speed was 270 mm / min, and the burner was reciprocated between 1000 mm to form a porous glass preform having a diameter of 120 mm. The time required for the trial production was 8 hours, and the molar ratio of the deposited glass fine particles to the supplied tetrachlorosilane, that is, the Si yield was 75%.
Met. The number of bubbles generated was 4 pieces / piece.

For comparison, four burners each having an inner diameter of the outer tube of 30 mm and an outer diameter of 34 mm are arranged side by side at a distance of 150 mm between the centers of the outer tubes of the burners, and each burner is supplied with 150 L / min of hydrogen gas. Then, 53 L / min of oxygen gas and 20 L / min of 25% tetrachlorosilane gas diluted with oxygen gas were supplied to produce a porous glass base material as a trial. When the burner was moved at a constant speed of 90 mm / min and reciprocated between 1000 mm to form a porous glass base material having a diameter of 120 mm, the time required for trial production was 27 hours, and the Si yield was 65%. And the number of bubbles generated was 5 pieces / piece. Production efficiency,
Both the amount of gas used and the quality of the porous glass base material were inferior.

[0028]

As described above in detail, when the apparatus for manufacturing a porous glass base material of the present invention is used, since a plurality of burners are adjacent to each other, the tip of the flame of the burner does not diffuse and the porous glass is not diffused. No swirl is generated toward the base material. Further, since the heat loss due to heat radiation is small and the heating efficiency is good, the amount of combustible gas or combustible gas used can be suppressed. As a result, the glass particles are efficiently deposited and the conical portion is reduced, so that the consumption of the glass raw material gas can be reduced. Therefore, the productivity of the porous glass base material is high.

[Brief description of the drawings]

FIG. 1 is a schematic view showing an embodiment of a manufacturing apparatus of a porous glass base material to which the present invention is applied.

FIG. 2 is a view showing a main part of a manufacturing apparatus of a porous glass base material to which the present invention is not applied.

[Explanation of symbols]

1 is a porous glass base material, 2 is a base glass rod, 3 is a conical portion, 4 is a motor for hood, 5 is a screw rod, 6 is a guide rod, 7 is an exhaust hood, 8 is an exhaust fan, and 9 is an exhaust fan. Exhaust pipe, 11 is a base material motor, 12 and 13 are grippers, 14 is a reciprocating motion control circuit, 15 is a burner motor, 16 is a screw bar, 17 is a guide bar, 18 is a pedestal, 19 is a burner, 20 Is a flame, 21
Is a porous glass base material, 22 is a base glass rod, 23 is a conical portion, 24 is a burner, 25 is a burner, 26 and 28 are a flame,
7 is a vortex, A is a reciprocation start position, and B is a reciprocation reversal position.

 ────────────────────────────────────────────────── ─── Continuing from the front page (72) Inventor Hideo Hirasawa 2-13-1, Isobe, Annaka-shi, Gunma Shin-Etsu Kagaku Kogyo Co., Ltd. Precision Functional Materials Laboratory F-term (reference) 4G014 AH16 AH19 4G021 EA03 EB11 EB14

Claims (2)

[Claims] 1. A plurality of burners for spraying glass fine particles on the side surface of a base glass rod while repeating reciprocating movement in the longitudinal direction of the base glass rod rotating in an axial direction, are disposed adjacent to each other. An apparatus for manufacturing a porous glass base material, wherein an exhaust hood that repeats reciprocating motion in synchronization with the burner is disposed above the porous glass base material on which fine particles are sprayed and sequentially deposited. 2. The porous glass mother according to claim 1, wherein the distance between the centers of the outer tubes of adjacent burners is 1.7 or less with respect to the inner diameter of the outer tube of the burner. Material manufacturing equipment.