JP2002220235A - Method and apparatus for producing porous glass base material - Google Patents

Abstract

(57) [Problem] To provide a method of manufacturing a porous glass base material and an apparatus therefor that can reduce a tapered portion formed at an end of a soot body without increasing the number of burners. SOLUTION: A rotating starting rod and a burner for synthesizing glass fine particles are relatively reciprocated in parallel to each other, and glass fine particles (soot) are deposited on the surface of the starting rod while moving the traverse turning position in a certain direction. In the method for manufacturing a porous glass base material, the soot deposition is set so that the interval between the burners located at both ends in the relative movement direction and the adjacent burners is smaller than the interval between the intermediate burners other than the burners at both ends. A method for producing a porous glass base material and an apparatus therefor.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a porous glass base material (glass particle deposit) for depositing glass particles radially on a starting rod while relatively moving a starting rod and a burner for synthesizing glass particles. The present invention relates to a method and an apparatus therefor, and more particularly to a method for manufacturing a porous glass preform capable of obtaining a porous glass preform having a small number of tapered portions formed at both ends of the porous glass preform, and an apparatus therefor.

[0002]

2. Description of the Related Art As a method for manufacturing a large-sized optical fiber preform at a high speed, a plurality of burners 7 for synthesizing glass fine particles are arranged at regular intervals so as to face a starting rod 1 in a container 4 as shown in FIG. The row of the rotating starting rod 1 and the burner 7 are relatively reciprocated (in the figure, an example is shown in which the starting rod 1 is reciprocated up and down), and fine glass particles (soot) are deposited on the surface of the starting rod 1. There is a method of obtaining a glass fine particle deposit (soot body) 6 by depositing in a layer form (multilayer soot attachment).

In such a method of depositing glass particles (soot attachment method), the relative movement distance (traverse distance) between the starting rod and the burner is set to about the burner interval in order to increase the deposition efficiency of the glass particles.
The variation in the outer diameter in the longitudinal direction of the glass particle deposit (soot body) becomes a problem. The variation in the outer diameter of this glass particle deposit is
At the turning position of the relative movement between the starting rod and the burner (the turning position of the traverse, the end of the traverse), there is always a moment when this relative movement stops, so that a substantial amount of glass particles are deposited from the part performing the relative movement at a steady speed. This is due to the longer time and different atmospheres such as how the burner flame hits the glass particle deposit. In particular, when the distance of the relative movement is constant, the turning position always comes to the same position of the starting rod, which promotes the outer diameter fluctuation for the above-described reason. The outer diameter variation increases at an accelerating rate because more deposits accumulate in the portion where is larger.

[0004] In order to obtain an optical fiber preform of good quality, it is important to minimize the variation in the outer diameter of the glass fine particle deposit, and various methods have been proposed. For example, the traverse start position is moved for each traverse, and after moving to a predetermined position, the traverse is moved in the opposite direction to return to the first traverse start position, so that the soothing time is substantially longer. Variations in how the edge or burner flame hits the glass particle deposit are dispersed throughout the glass particle deposit, and the deposition time and atmosphere of the actual glass particles in the entire glass particle deposit are made to coincide with each other on average. A method has been proposed in which the amount of fine particles deposited is made equal in the longitudinal direction to reduce the variation in outer diameter (Japanese Patent Laid-Open No. 3-228845).

Further, as a method for further reducing the variation of the outer diameter, based on the method described in Japanese Patent Application Laid-Open No. 3-288845, a glass particle deposition using a CCD camera and a central information processing device capable of monitoring the entire glass particle deposition body. A method is proposed that measures the outer diameter fluctuation of the whole body and reduces the outer diameter fluctuation by supplementing the deposition of glass particles in the part where the amount of glass particles is small by using an auxiliary burner that can traverse the entire glass particle deposition body by itself (Japanese Patent Application Laid-Open No. H10-158025). When depositing glass particles while moving the start position of the traverse,
There is a method in which clean air is supplied perpendicularly to the longitudinal direction to the entire glass fine particle deposit to reduce the temperature gradient during deposition in the longitudinal direction of the glass fine particle deposit (Japanese Patent Laid-Open No. Hei 4-26).
No. 0618).

[0006]

What is characteristic of the above prior art is that the distance of the reciprocating movement is different between the forward and backward movements in order to disperse the folded position of the traverse over the entire glass fine particle deposit. This focuses on the fact that the outer diameter variation is likely to occur from the turning position of the traverse, and is intended to make the deposition conditions of the glass fine particles equal on average by dispersing this in the longitudinal direction. According to the additional test results, it was confirmed that there was an effect of reducing the outer diameter fluctuation. However, in the case of the above-described method of moving the turning position of the traverse, as shown in FIG. 5 which shows an example of the relative position between the starting rod and the burner and the number of deposited layers (this shape is the most tapered portion in this type of method). Can be reduced), and the deposition shape of the glass fine particles deposited by the burners positioned at both ends of the glass fine particle deposit becomes tapered (the number of deposited layers decreases at the end). In principle, the number of deposited layers is reduced only in the portion where the glass particles are deposited by the burner at the end, but since the glass particles are deposited in a tapered shape, the glass particles by the burner adjacent to it are also likely to flow outward, and the second from the end Many of the portions deposited by the burner located at the end are tapered, resulting in increased ineffectiveness.

FIG. 5 shows how the relative position between the starting rod and the burner changes over time in this method. FIG. 5 shows the outermost burner 2 and the second burner 3 on the outermost side of the burner row (the same applies to the outer burner on the opposite side and the burner on the inner side). The figure shows the number of deposited layers of glass fine particles formed on the starting rod 1 during a series of reciprocating motions until the turning position returns to the initial position. The part below the 18th layer in the figure is 3
Since there is a deposition by the burner after the first, a constant 18 layers are formed except for the lower end.

FIG. 5 shows a state in which the burners are arranged at regular intervals, and the glass particles are deposited until the traverse start position returns to the initial position. Theoretically, this method can make the effective portion the longest and can obtain the effect of reducing the variation in the outer diameter of the glass fine particle deposit. However, when observing the actual phenomenon, since the outer burner is set to form a taper at the end of the glass particle deposit, the glass particles synthesized by the second burner flow in an inclined direction.
The portion where the glass particles are deposited by the second burner is also considerably tapered. As one method of solving this problem, it is conceivable to narrow the burner interval and increase the number of burners accordingly. In this way, the interval between the deposition of the glass particles by the outer burner and the second burner is reduced, and the tapered portion can be reduced.
However, if the burner interval is reduced, it is necessary to increase the number of burners in order to produce a glass particle deposit having an effective portion of the same length. Therefore, the number of gas supply systems is increased, and equipment costs are increased.

The present invention solves such problems in the prior art, and provides a method of manufacturing a porous glass base material capable of reducing the tapered portion formed at the end of the glass fine particle deposit without increasing the number of burners. And an apparatus therefor.

[0010]

According to the present invention, as means for solving the above problems, the following constitutions (1) to (9) are employed. (1) A plurality of burners for synthesizing glass fine particles are arranged in opposition to a rotating starting rod, and the starting rod and the burner for synthesizing glass fine particles are relatively reciprocated in parallel, and the traverse turning position is determined by the burner interval. Is moved in a fixed direction by a fraction of an integer, and when the turning position is moved by the distance of the burner, it is moved in the opposite direction. In the method of manufacturing a porous glass base material by sequentially depositing, the interval between the burners located at both ends in the relative movement direction and the adjacent burners is smaller than the interval between the intermediate burners other than the burners at both ends. A method for producing a porous glass base material, wherein the method is performed by setting so as to be small. (2) The length of a substantially integer fraction of the burner interval, which is the length for moving the turnover position of the traverse, is 5 to 60.
(1) The method for producing a porous glass preform according to (1) above, wherein (3) The production of the porous glass preform according to the above (1) or (2), wherein the supply amount of the glass material to the burners located at both ends is made smaller than the supply amount of the glass material to the intermediate burner. Method. (4) The porous body according to any one of (1) to (3), wherein an interval between the burners located at the both ends and an adjacent burner is set so as not to cause interference of flames of the respective burners. Manufacturing method of glass base material. (5) The method for producing a porous glass preform according to any one of (1) to (4), wherein a burner having a smaller flame spread than an intermediate burner is used as the burners located at both ends. .

(6) A plurality of burners for synthesizing glass fine particles are arranged so as to face the rotating starting rod, and the starting rod and the burner for synthesizing glass fine particles are relatively reciprocated in parallel and synthesized by the burner. An apparatus for manufacturing a porous glass base material by sequentially depositing glass particles to be formed on the surface of a starting rod, wherein the distance between the burners located at both ends in the relative movement direction and the burners adjacent thereto is other than the burners at both ends. An apparatus for manufacturing a porous glass base material, wherein the apparatus is arranged so as to be smaller than an interval between the intermediate burners. (7) The distance between the burners located at both ends and the burners adjacent thereto is 0.2 times or more and less than 1 times the distance between the intermediate burners other than the burners at both ends. Equipment for manufacturing porous glass base material. (8) The burners located at both ends and the burners adjacent thereto can be arbitrarily adjusted within a range of 0.2 times or more and less than 1 times the distance between the intermediate burners other than the burners at both ends. The apparatus for producing a porous glass base material according to the above (6), wherein the apparatus is provided. (9) The apparatus for producing a porous glass preform according to any one of the above (6) to (8), wherein the burners located at both ends are burners having a smaller flame spread than the intermediate burner.

A plurality of burners for synthesizing glass fine particles are arranged in opposition to the rotating starting rod, and the starting rod and the burner for synthesizing glass fine particles are relatively reciprocated in parallel, and the traverse turning position is determined by the burner interval. Is moved in a fixed direction by a fraction of an integer, and when the turn-back position is moved by the distance of the burner, it is moved in the opposite direction, and this operation is sequentially repeated so that the glass fine particles synthesized by the burner are put on the surface of the starting rod. In the prior art in which a porous glass preform is manufactured by sequentially depositing, the shape of the glass fine particles deposited by the burners located at both ends in the relative movement direction is, as shown in FIG. It changes and becomes tapered. The glass fine particles synthesized by the adjacent burner under the influence flow more toward the burners located at both ends, so that the deposition form of the glass fine particles by the adjacent burner also becomes tapered.

In order to solve this problem, according to the present invention, the distance between the burners (outside burners) located at both ends in the relative movement direction and the burners adjacent thereto is determined by the distance between the burners other than the outer burners (intermediate burners). In addition, a portion where the number of deposited layers per traverse is almost doubled at the boundary between the deposited layer of glass fine particles by the outer burner and the deposited layer of glass particulate by the burner adjacent to the outer burner is formed. In this case, the formation of the tapered portion is suppressed by compensating for the insufficient amount of glass particles.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 schematically shows the relative movement between a starting rod and a burner in a method for manufacturing a porous glass preform according to the present invention and an example of a glass fine particle deposition area for each burner. In this example, four burners A to D are arranged in a row in opposition to the starting rod 1 and relatively vertically reciprocated by the burner interval to produce the glass particulate deposit body 6. The upper figure shows the prior art that is the standard for arranging burners at equal intervals, and the lower figure shows that the distance between the burners at both ends and the burners adjacent to them (intermediate burners) is shorter than the distance between the intermediate burners. According to the method of the present invention.

The upper part of FIG. 1 (the traverse pattern is shown in FIG. 5)
), The intervals between the burners are all equal to a. The glass fine particles formed by the burners A to D accumulate in arrow blade-shaped regions A to D, respectively. In the area A, the movement of the burner A at the upper end is indicated by an arrow. Here, assuming that the interval between the burners A and D at both ends and the intermediate burners B and C adjacent thereto is shorter than the interval a between the intermediate burners B and C, b (a> b) (the moving distance of the relative motion is a 1), overlapping regions E and F occur at the boundaries between the deposition regions A and B and C and D as shown in the lower diagram of FIG. Since the number of deposited layers is doubled in the overlapping regions E and F, it is possible to compensate for a decrease in the amount of deposition caused by the glass fine particles generated by the intermediate burners B and C flowing to the burners A and D at both ends. ,
The tapered portion becomes shorter. The area indicated by the dotted line in the lower part of FIG. 1 is a part corresponding to the deposition area in the upper part.

In the method of the present invention, the turning position of the traverse is moved in a fixed direction by a substantially integral number of the burner interval, and the traverse is moved in the opposite direction when the turning position moves by the burner interval. I try to repeat the operation. Here, “approximately an integral number of the burner interval” means an integral number of “burner interval ± burner thickness”. In addition, it is preferable that the length of a substantially integral number of the burner interval is in the range of 5 to 60 mm, and more preferably in the range of 5 to 40 mm. When the movement interval of the turnover position of the burner is less than 5 mm, the outer diameter fluctuates before the effect of dispersing the turnover position appears, and when it exceeds 60 mm, the effect of dispersing the turnover position decreases.

The distance between the burners at both ends and the burners adjacent to the burners depends on the characteristics of the burners, the deposition conditions of the glass particles, etc., so that the flames of the burners described below do not interfere with each other. What is necessary is just to set suitably as long as the overlap of the deposition layer of the glass fine particles by the adjacent burner does not become too large.
0 for the distance between the intermediate burners other than the burners at both ends.
It is preferably at least 2 times and less than 1 time. In order to prevent flame interference, it is preferable to set the burner interval to 100 mm or more. The adjustment of the burner interval may use a device in which the burner is set at a predetermined interval in advance, but it is convenient to use a device in which the burner is movable and can be set at an arbitrary position.

The burners may be arranged such that the burners 7 are arranged in a line in parallel with the starting rod 1 as shown in FIG. 2 (a) of the arrangement viewed from above in FIG. 2
They may be arranged in a plurality of rows as shown in FIG. 2 (a) is desirable from the viewpoint of exhaust efficiency, but FIG. 2 (b)
With such an arrangement, even if the burner interval is shorter than in the case of arranging in one row, there is no interference of flames with the adjacent burners, so that the burner interval can be shortened, and the starting rod of the same length is often used. Of burners can be used, which is advantageous in terms of improving the deposition rate of glass particles. Note that the burner interval when the burners are not arranged in one row means an interval in a relative position direction as shown in FIG.

The basic concept of the method of the present invention is as follows.
The point is to increase the number of layers deposited on the portion where the amount of glass particles deposited is small, and to adjust the amount of deposition. However, depending on the characteristics of the burner, it may be difficult to adjust the number of deposited layers by adjusting the burner interval. In such a case, the amount of glass material supplied to the outer burner is made smaller than the amount of glass material supplied to the intermediate burner, so that the amount of glass particles deposited can be finely adjusted.

Further, interference with the flame of an adjacent burner causes a reduction in the deposition efficiency of the glass fine particles and a variation in the outer diameter. Therefore, it is desirable to arrange the burners so that no flame interference occurs between the outer burner having the shortest burner interval and the adjacent burner.

As described above, it is desirable to keep the space between the outer burner and the burner adjacent to the outer burner so as not to interfere with the flame. However, without reducing the number of burners, the overlapped area (E, F in FIG. You may want to make it longer. In such a case, a burner having a different design and a small flame spread can be used as the outer burner. All burners may have a small flame spread.However, a burner with a small flame spread has poor deposition efficiency of glass particles, so it is desirable to use a burner with good deposition efficiency as much as possible as an intermediate burner.Only the outer burner is changed. I decided to.

[0022]

EXAMPLES Hereinafter, the method of the present invention will be described more specifically with reference to examples, but the present invention is not limited to these examples. (Comparative Example 1) Eight burners were arranged in a row at an interval of 200 mm in opposition to a starting rod, and glass particles were deposited by a method in which the starting rod was reciprocated up and down. At this time, the starting rod had a structure in which glass rods for grasping were connected to both ends of the glass rod for the core. Using a starting rod having a diameter of 35 mm, the traverse method was the pattern shown in the upper diagram of FIG.
Deposit glass fine particles by setting to shift each time,
When the number of traverse turns became 800 turns (one reciprocating movement of the traverse is defined as one turn), the deposition of glass particles was stopped. The obtained glass particle deposit (porous glass base material) has a total length of 1700 mm and an outer diameter of 240 mm.
The length of the effective portion was 1000 mm, and the length of the tapered portions formed at both ends was 350 mm. The total length of the glass fine particle deposit is a length excluding the portions (each end 50 mm) deposited on the glass rods for gripping both ends from the length of the glass fine particles actually deposited. The length of the effective portion with respect to the entire length was 58.8%.

(Example 1) The traverse method was the same as that of Comparative Example 1 except that the distance between the outer burners at both ends and the adjacent burners was 150 mm. (The moving distance is the same.) Glass fine particles were deposited. The obtained glass particle deposit (porous glass base material) has a total length of 1600 mm and an outer diameter of 24 mm.
At 0 mm, the length of the effective portion was 1200 mm, and the length of the tapered portions formed at both ends was 200 mm. That is, the tapered portion was reduced compared to Comparative Example 1, and the length of the effective portion could be increased by 200 mm.

(Example 2) Glass particles were deposited in the same manner as in Example 1 except that the distance between the outer burners at both ends and the adjacent burners was 120 mm. The obtained glass particle deposited body had a total length of 1540 mm, and the length of the effective portion was 950 mm. In this case, the reason why the effective portion was reduced was not an increase in the tapered portion, but a portion having a large outer diameter due to excessive overlap on both sides of 950 mm, and the effective portion was not formed. The length of the effective portion with respect to the entire length was 61.7%, which was an improvement over Comparative Example 1.

Example 3 Glass particles were deposited in the same manner as in Example 2 except that the amount of the raw material supplied to the outer burners at both ends was reduced by 30%. The obtained glass fine particle deposit has a total length of 1540 mm and a length of an effective portion of 1100 mm.
Met. The length of the tapered portions at both ends is 21
0 mm, which indicates that good deposition of glass fine particles having almost no difference from Example 1 was achieved. From this, it can be seen that when the influence of the overlap of the glass particle deposition portion by the outer burner and the adjacent burner is too large, a certain amount of fine adjustment is possible by reducing the amount of the raw material supplied to the outer burner. .

[0026]

According to the present invention, a plurality of glass particle synthesizing burners are arranged opposite to a rotating starting rod, and the starting rod and the glass microparticle synthesizing burner are relatively reciprocated in parallel. The turning position of the traverse is moved in a fixed direction by a fraction of an integer of the burner interval, and the turning position is moved in the reverse direction when the turning position has moved by the burner interval. Solves the problem of increasing the number of tapered portions at both ends of a glass particle deposit body, which occurs in a method of manufacturing a porous glass base material by sequentially depositing glass particles on the surface of a starting rod, and reducing the number of ineffective portions. A method for manufacturing a base material with high deposition efficiency and an apparatus therefor are provided.

[Brief description of the drawings]

FIG. 1 is a view schematically showing a state of a glass particle deposition region for each burner in the method of the present invention.

FIG. 2 is an explanatory view showing an example of the arrangement of burners.

FIG. 3 is a diagram showing a definition of a burner interval when the arrangement is not one-row arrangement.

FIG. 4 is an explanatory view showing an outline of production of a glass particle deposit by a method of depositing multilayer glass particles.

FIG. 5 is an explanatory view showing an example of a state of relative movement between a starting rod and a burner in a conventional method.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Starting rod 2 Outer burner 3 2nd burner 4 Container 5 Exhaust port 6 Glass fine particle deposit
7 Burner

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Yoshio Yokoyama 1-chome, Taya-cho, Sakae-ku, Yokohama-shi, Kanagawa F-term in Sumitomo Electric Industries, Ltd. Yokohama Works 4G014 AH14 4G021 EA03 EB14 EB26

Claims (9)

[Claims] 1. A plurality of burners for synthesizing glass fine particles are arranged in opposition to a rotating starting rod, and the starting rod and the burner for synthesizing glass fine particles are relatively reciprocated in parallel, so that the traverse is turned back. The burner interval is moved in a fixed direction by a substantially integer fraction, and when the turn-back position is moved by the burner interval, it is moved in the opposite direction, and this operation is sequentially repeated to reduce the glass fine particles synthesized by the burner to the starting rod. In the method of manufacturing a porous glass base material by sequentially depositing on the surface, the interval between the burners located at both ends in the relative movement direction and the adjacent burners is determined by the interval between intermediate burners other than the burners at both ends. A method for producing a porous glass base material, wherein the method is performed so as to be smaller than the above. The length of the burner interval, which is a length for moving the traverse turn-back position, is approximately one-fifth of an integer.
The method for producing a porous glass base material according to claim 1, wherein the range is 60 mm. 3. The porous glass base material according to claim 1, wherein a supply amount of the glass raw material to the burners located at both ends is made smaller than a supply amount of the glass raw material to the intermediate burner. Production method. 4. The space between the burners located at both ends and the burners adjacent to the burners is set so as not to cause interference of the flame of each burner.
4. The method for producing a porous glass preform according to any one of the above items 3. 5. The porous glass preform according to claim 1, wherein a burner having a smaller flame spread than an intermediate burner is used as the burners located at both ends. Production method. 6. A plurality of burners for synthesizing glass fine particles are arranged in opposition to a rotating starting rod, and the starting rod and the burner for synthesizing glass fine particles are relatively reciprocated in parallel to be synthesized by the burner. Is a device for manufacturing a porous glass preform by successively depositing glass fine particles on the surface of a starting rod, wherein the distance between the burners located at both ends in the relative movement direction and the adjacent burners is an intermediate point other than the burners at both ends. An apparatus for producing a porous glass base material, wherein the apparatus is arranged so as to be smaller than the interval between burners. 7. A space between the burners located at both ends and a burner adjacent thereto is 0.2 times or more and less than 1 time as a space between intermediate burners other than the burners at both ends. 3. The apparatus for producing a porous glass base material according to claim 1. 8. The distance between the burners located at both ends and the adjacent burners may be arbitrarily adjusted within a range of 0.2 times or more and less than 1 time between the intermediate burners other than the burners at both ends. The apparatus for producing a porous glass base material according to claim 6, wherein the apparatus is provided so as to be capable of being provided. 9. The production of a porous glass preform according to claim 6, wherein the burners located at both ends are burners having a smaller flame spread than an intermediate burner. apparatus.