JP2002338257A - Apparatus for manufacturing glass particulate deposit and method for manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an manufacturing apparatus and a manufacturing method capable of efficiently manufacturing a glass particulate deposit of a stable shape by decreasing the fluctuations in the external diameter of the glass particulate deposit by a CVD process. SOLUTION: The apparatus for depositing the glass particulates spouting from a plurality of glass particulate-synthesizing burners adapted to move back and forth relatively with a glass rod which is a target on the outer periphery of the glass rod while clamping the glass rod to a vertical posture and rotating the rod is arranged with a plurality of the glass particulate-synthesizing burners so as to face downward with respect to a horizontal direction, by which the occurrence of a temperature difference above and below within a reaction vessel is averted and the glass particulate deposit can be manufactured without the fluctuation in the external diameter. The manufacturing method uses this apparatus.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus and a method for efficiently producing a glass particle deposit.

[0002]

2. Description of the Related Art As a method for producing glass for use in optical fibers and optical components, a burner contains a glass raw material gas (which may include a carrier gas such as an inert gas), a fuel gas such as hydrogen, and a combustion assisting gas such as oxygen. Further, if necessary, an inert gas is introduced, and glass fine particles generated by performing a flame hydrolysis reaction or an oxidation reaction of the glass raw material gas in a flame formed in the burner are deposited on the outer periphery of the target to form a porous material. There is a method in which a glass particle deposit is formed, and this is sintered and made transparent to form a glass body.

[0003] As a method for producing such a glass fine particle deposit, a round rod-shaped starting material glass rod (hereinafter abbreviated as "glass rod") is rotatably gripped about its longitudinal center axis as a rotation axis to form a glass target. A burner for synthesizing fine particles (hereinafter sometimes abbreviated as “burner”) is disposed so that its jet port faces the glass rod, and the burner is reciprocated relatively along the longitudinal axis direction of the glass rod. External method (OVD method) in which glass fine particles generated in a flame are deposited on the starting material while being traversed (referred to as traverse), and a glass fine particle deposit is formed on the outer periphery of the starting material.
It has been known. This method realizes a complex refractive index structure by using a glass rod having a refractive index distribution that becomes a core or a core and a clad as a starting material glass rod, producing a glass particle deposit on the outer periphery thereof, and then sintering the same. It is widely used as a method for producing an intermediate in the production of a preform for an optical fiber because it can be performed and the diameter ratio between the core and the clad can be increased.

As a specific example of the external method, for example,
JP-A-228845 discloses a method of averaging the surface irregularities of a porous base material by arranging a plurality of burners having the same structure at equal intervals and depositing glass particles while moving and dispersing the start position of the reciprocating motion. Has been described. Japanese Patent Application Laid-Open No. 10-7421 discloses that a single burner or a plurality of burners disposed in parallel with a starting material (a glass rod serving as a target) and facing upward with respect to the starting material is injected into the starting material. A technique has been proposed in which the glass particles are deposited by inclining the burner with respect to the direction of the starting material so that the angle between the application directions is 50 to 85 °, thereby shortening the tapered end of the glass particle deposit. ing.

[0005]

The external method can be carried out regardless of whether the starting material is in a horizontal state or in a vertical state. Is often held vertically.
The reason is that when the glass fine particle deposit is manufactured while being held in the horizontal direction, the glass rod or the glass fine particle deposit may be bent by gravity. As described above, if the center axis of the starting material glass rod is held in a substantially vertical direction and the synthesis is continued for a long time until the size of the glass fine particle deposit increases, the method disclosed in the above-mentioned Japanese Patent Application Laid-Open No. 3-228845 can be used. However, as shown in FIG. 3, there is a problem that the outer diameter of the glass fine particle deposit is large at the lower part and the outer diameter is small at the upper part, and the outer diameter of the base material also fluctuates in the longitudinal direction. An object of the present invention is to solve this problem and to provide a method for improving the outer diameter stability of a glass fine particle deposit in an OVD method using a plurality of burners and efficiently producing the same, and to provide an apparatus therefor. .

[0006]

Means for Solving the Problems The present invention provides the following (1) to
The above problem is solved by the configuration of (7). (1) a mechanism for holding and rotating a glass rod serving as a target for depositing glass particles so that the center axis thereof is substantially vertical, a plurality of burners for synthesizing glass particles,
A driving device for driving one or both of the glass rod and the plurality of burners for synthesizing glass fine particles in the direction of the central axis of the glass rod, and supplying a glass raw material gas, a fuel gas, and an auxiliary gas to the burner for synthesizing glass fine particles. A raw material supply device for supplying, a plurality of burners for synthesizing glass fine particles and a reaction for enclosing the glass rod and depositing the fine glass particles synthesized and ejected in the flame of the burner for synthesizing glass fine particles on the outer periphery of the glass rod. In the apparatus for manufacturing a glass fine particle deposit having a container and a means for exhausting the glass fine particles that have not been deposited from the reaction container, it is preferable that the direction of the ejection port of the burner for synthesizing the glass fine particles is set downward with respect to the horizontal direction. Characteristic glass particle deposit manufacturing equipment. (2) The apparatus for producing a glass particle deposit according to the above (1), wherein the angle between the direction of the ejection port of the glass particle synthesizing burner and the direction of the central axis of the glass rod is 30 to 70 °. (3) A plurality of exhaust ports are provided as a means for exhausting the non-deposited glass fine particles, and at least one of the exhaust ports is attached to a position lower than a top burner of the plurality of burners. The apparatus for producing a glass fine particle deposit according to the above (1) or (2), wherein: (4) The method according to any one of (1) to (3), further comprising a plurality of exhaust means as means for exhausting the glass fine particles that have not been deposited, and having a mechanism for adjusting each exhaust ability. Glass particle deposit manufacturing equipment. (5) A glass raw material gas is introduced into the flame of a glass particle synthesizing burner, and the generated glass particles are sprayed on the outer periphery of a rotating glass rod with its central axis as a rotation axis. In a manufacturing method in which the glass fine particles are deposited on the outer periphery of the glass rod by relatively reciprocating the burner and the burner in parallel with the center axis, using a plurality of the burners for synthesizing the glass fine particles, and from each burner in a horizontal direction. A method for manufacturing a glass fine particle deposit, wherein glass fine particles are ejected downward so as to form a glass fine particle deposit. (6) The glass fine particle deposit body is formed by changing the turning position of the reciprocating motion by changing the fixed value at a fixed value and shifting the turning direction after the shift by the burner interval is completed. ). (7) wherein the glass rod has at least a portion serving as a core of the optical fiber preform (5) or
(6) The method for producing the particulate deposit according to the embodiment described in (6).

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION The present inventors have repeatedly studied the causes of the outer diameter of a glass fine particle deposit as shown in FIG. 3 in a conventional OVD method using a large number of burners. Because the temperature conditions inside are shifted in the longitudinal direction of the base material (composite of glass rod / glass particulates), the outer diameter of the glass particulates is increased in the low temperature part and the same in the high temperature part. Thought it would be thin. That is, as shown in FIG. 4A, in the VAD method, the burner is located below the glass particle deposit to be formed and only heats a part of the glass particle deposit. As shown in (b), when a plurality of or one burner is used to externally extend the burner in a range longer than the burner installation range, only a part of the glass fine particle deposit is heated by the burner. As shown in FIG. 4 (c), when a plurality of burners heat almost the entire glass particle deposit at all times, warm air moves upward, the temperature is higher in the upper part of the reaction vessel, and the temperature is lower in the lower part. Is low. When a difference occurs in the temperature of the reaction vessel, a radiant heat from the reaction causes a temperature difference also on the surface of the glass fine particle deposit, and as a result, the bulk density of the glass fine particle deposit is high in the upper part and low in the lower part. The difference in bulk density gradually increases with the growth of the glass fine particle deposit.
Therefore, the present invention avoids temperature unevenness in the longitudinal direction by fixing a plurality of burners for synthesizing glass fine particles used in the OVD method so as to face downward with respect to the horizontal direction. In other words, if the direction of the central axis of the injection direction of the burner for synthesizing glass fine particles is set downward from the horizontal direction, the heat generated from the burner flame will be supplied more downward, and as a result, the temperature distribution of the reaction vessel will be reduced. There will be no difference between the top and bottom. As a result, a glass particle deposit having a stable shape can be obtained.

Hereinafter, the configuration of the apparatus will be specifically described with reference to the schematic diagram of one embodiment of the present invention shown in FIG. In the example of FIG. 1, five burners 1a, 1b to
1e, the burner 1 is fixed and installed in the reaction vessel 2 so that the burner 1 faces downward with respect to the horizontal direction. On the other hand, a glass rod 5 is attached to the tip of the seed rod 4 held by the rotary chuck 3. Each of the burners 1a to 1e is supplied from the gas supply device 6 as a glass raw material gas such as Si.
Cl ₄ , H ₂ as a fuel gas, O ₂ as an auxiliary gas,
Further, Ar is supplied as an inert gas, and the glass raw material gas is subjected to a flame hydrolysis reaction and / or an oxidation reaction in a flame formed at the ejection port of each of the burners 1a to 1e to generate glass fine particles. In the example of FIG. 1, the glass rod is traversed appropriately using the elevator 7, and the glass fine particles generated as described above are deposited on the rotating glass rod 5. In addition, it is preferable that the traverse is performed so that the outer diameter fluctuation of the glass is minimized. For example, it is preferable to traverse as follows. When the burner interval is set to L, the glass rod and the burner are relatively reciprocated in parallel, and the return of the reciprocation is moved in a predetermined direction by a predetermined distance (for example, an integral fraction of the burner interval), and the return is performed. The position is 0.9L-1.
After the movement of 1 L, the turning position is moved in the reverse direction, and this operation is sequentially repeated to sequentially deposit the glass fine particles synthesized by the burner on the surface of the glass rod. At this time, as traverse speed v (mm / min) and rotation speed r (rpm) of the glass rod, A = (r /
v) The value represented by x1 is set to be in a range of 40 ≧ A ≧ 8. During this deposition step, the burners 1a to 1e are fixed and installed downward, so that the escaping flame goes down the reaction vessel 2 and the temperature difference between the upper and lower sides of the reaction vessel 2 becomes small. Variations in the outer diameter of the deposit 10 can be reduced.

FIG. 2 shows the angle .theta. Between the direction of the ejection port of the burner for synthesizing glass fine particles and the central axis of the glass rod in the present invention. It is very advantageous that .theta. It is.

Although glass particles not deposited on the glass rod 5 are exhausted, it is desirable to provide a plurality of exhaust pipes so as to efficiently exhaust them. More preferably, the exhaust pressure of each exhaust pipe can be adjusted.
In the example shown in FIG. 1, three exhaust pipes 8a, 8b and 8c are provided, and each of the exhaust pipes 8a, 8b and 8c is provided with a pressure regulating valve 9a, 9b and 9c. Burners 1a-1e
The glass particles that could not be deposited by setting from the horizontal direction downward flow once downward, but then float upward.
For this reason, at least one of the glass fine particle outlets (portions where the exhaust pipes 8a, 8b and 8c are open in the reaction vessel 2) must be installed at a higher position than the burner 1a located at the highest position. is there. Further, it is necessary to adjust the exhaust balance of the plurality of exhaust pipes and adjust the exhaust state so that exhaust can be performed most efficiently. By doing so, a glass particle deposit having a stable shape can be obtained.

In the present invention, the number of burners may be two or more and a plurality of burners may be provided. The central axes of the ejection directions are arranged parallel to each other and directed downward to the glass rod, and each of the plurality of burners is independently provided. A driving device is provided so as to be able to reciprocate relatively parallel to the central axis of the glass rod. That is, the glass rod may be reciprocated up and down while being rotated, or a drive device may be provided so that the burner can reciprocate simply by rotating the glass rod. In addition, using a burner array fixed and arranged so that the ejection direction of each of the plurality of burners is downward from the horizontal direction,
A drive device may be provided so that the burner array and the glass rod can traverse relatively.

In the present invention, the traverse pattern of a plurality of burners may be simply reciprocated. Alternatively, for example, as described above, a plurality of burners having the same structure are arranged at equal intervals, and the start position of the reciprocation is determined. A pattern in which glass particles are deposited while moving and dispersing may be adopted. Particularly preferably, a pattern in which the turning position of the reciprocating motion is changed by a fixed value and shifted, and after shifting by the burner interval is completed, the shifting direction is reversed. By reciprocating in such a pattern, a glass particle deposit having a more uniform outer diameter can be obtained.

The glass rod used as a target in the present invention is not particularly limited as long as it is glass produced according to a known technique. However, according to the present invention, a glass fine particle deposit is used as an intermediate for producing an optical fiber preform. When manufactured as a glass rod, a glass rod having a core or having a core and a clad is used. Examples of the glass raw material gas used in the present invention include SiCl ₄ ,
HSiCl ₄ , CH ₃ SiCl ₃ , (CH ₃ ) ₂ SiC
l ₂ , CH ₃ Si (OCH ₃ ) ₃ , Si (OCH ₃ ) ₄
And the like, and a gas of a material for adjusting the refractive index can also be used. As the combustion gas, for example, H ₂ or C
Examples of the auxiliary gas such as hydrocarbons such as H _{4 and the} like are O _{2 and the} like, and if necessary, inert gases such as Ar and N ₂ can be used. In part or all of the process of dehydrating and heating and clarifying the obtained glass particle deposit, for example, Si
An atmosphere containing a fluorine-containing compound gas such as F ₄ , SF ₆ , CF ₄ , C ₂ F ₆ (fluorine compound gas is 100
% If not containing an inert gas such as Ar or He), and finally obtain a fluorine-added glass.

[0014]

EXAMPLES Hereinafter, the present invention will be described specifically with reference to Examples, but the present invention is not limited to these Examples.

(Example 1) Using the apparatus shown in FIG. 1, a glass particle deposit was produced. By changing the angle θ between the burner for glass fine particle synthesis and the rod, the glass rod diameter 2
0 mm, a burner interval of 150 mm, a core length of 500 mm, and a deposit were made until the outer diameter of the upper part of the glass fine particle deposit became 150 mm. Set the return position of the reciprocation of the glass rod to 3
It was manufactured under traverse conditions such that the method of shifting after the burner interval was completed and the shifting method was reversed while changing by 0 mm. Glass particle deposits were obtained by changing the condition of the angle θ between the burner and the rod in increments of 20 ° to 10 °. Under the condition of θ = 20 °, the glass particle deposit was broken from the end of the lowermost portion. The results are shown in Table 1. In Table 1, the rate of change is represented by the following equation. [Variation rate = (lower outer diameter−upper outer diameter) ÷ upper outer diameter] From these results, a variation rate of 5% or less was obtained under the condition of θ = 30 to 70 °, and this range was good. I understand. At 80 ° or more, the variation rate of the base material was large, and the characteristics of the base material were often poor.

[0016]

[Table 1]

[0017]

As described above, according to the present invention, when a large number of burners for synthesizing glass fine particles are used to manufacture a glass fine particle stack by the OVD method in a vertical type, the burners are fixed and disposed downward with respect to the horizontal direction. By using the apparatus described above, even a large-sized glass particle deposit can be manufactured with reduced outer diameter fluctuation. In addition, the method and apparatus of the present invention in which the position of exhaust from the reaction vessel is devised can efficiently produce a glass particle deposit.

[Brief description of the drawings]

FIG. 1 is a schematic diagram illustrating an embodiment of the present invention.

FIG. 2 is a view for explaining the direction of the ejection port of the burner for synthesizing glass fine particles and the angle θ formed by the center axis of the glass rod of the target in the present invention.

FIG. 3 is a schematic diagram illustrating a change in outer diameter of a glass fine particle deposit formed by a conventional method.

FIG. 4 is a diagram schematically illustrating a conventional VAD method, an OVD method, and an OVD method using multiple burners.

[Explanation of symbols]

1a, 1b, 1c, 1d and 1e Burner for synthesizing glass particles 2 Reaction vessel 3 Rotary chuck 4 Seed rod 5 Glass rod 6 Gas supply device 7 Elevator 8a, 8b and 8c Exhaust pipe 9a, 9b and 9c Pressure regulating valve 10 Glass Particle deposit θ The angle between the direction of the outlet of the burner for synthesizing glass particles and the central axis of the glass rod

Claims (7)

[Claims] 1. A mechanism for gripping and rotating a glass rod serving as a target for depositing glass fine particles so that the center axis thereof is substantially vertical, a plurality of burners for synthesizing glass fine particles, the glass rod and the plurality of burners. A driving device for driving one or both of the glass particle synthesizing burners in the direction of the center axis of the glass rod, a raw material supply device for supplying a glass raw material gas, a fuel gas and an auxiliary combustion gas to the glass fine particle synthesizing burner, A reaction vessel for enclosing a plurality of burners for synthesizing glass fine particles and the glass rod and depositing the glass fine particles synthesized and ejected in the flame of the burner for synthesizing glass fine particles on the outer periphery of the glass rod; An apparatus for manufacturing a glass particle deposit body having means for exhausting glass particles from the reaction vessel, wherein the glass particle An apparatus for manufacturing a glass fine particle deposit, characterized in that the nozzles of the nozzles are fixed so as to face downward with respect to the horizontal direction. 2. An angle θ between the direction of the jet port of the burner for synthesizing glass fine particles and the central axis of the glass rod is 30.
The apparatus for producing a glass fine particle deposit according to claim 1, wherein the angle is about 70 °. 3. A plurality of exhaust ports are provided as means for exhausting the non-deposited glass fine particles, and at least one of the exhaust ports is located at a position lower than an uppermost burner of the plurality of burners. The apparatus for producing a glass fine particle deposit according to claim 1, wherein the apparatus is attached to a substrate. 4. The method according to claim 1, further comprising a plurality of exhaust means for exhausting the glass fine particles that have not been deposited, and a mechanism for adjusting each exhaust capacity. Glass particle deposit manufacturing equipment. 5. A method in which a glass raw material gas is introduced into a flame of a burner for synthesizing glass fine particles, and the generated fine glass particles are blown onto the outer periphery of a rotating glass rod around its central axis as a rotation axis. In a manufacturing method of depositing the glass particles on the outer periphery of the glass rod by relatively reciprocating a burner for synthesizing fine particles in parallel with the central axis, a plurality of the burners for synthesizing glass particles are used, and each burner is horizontally moved from each burner. A method for producing a glass fine particle deposit, wherein glass fine particles are ejected so as to face downward in a direction to form a glass fine particle deposit. 6. The method according to claim 1, wherein the turning position of the reciprocating motion is changed by a predetermined value and shifted, and after shifting by the burner interval, the shifting direction is reversed to form the glass fine particle deposit. Item 6. The method for producing a glass fine particle deposit according to Item 5. 7. The method according to claim 5, wherein the glass rod has at least a portion serving as a core of an optical fiber preform.