JP6066103B2 - Burner for manufacturing porous glass base material - Google Patents

Description

  The present invention relates to a burner for producing a porous glass base material.

Various methods have been proposed for producing optical fiber preforms. Among these methods, glass soot generated in the flame of the burner is reciprocated by the reciprocating motion of the burner or the starting member on the rotating starting member, and deposited and deposited to synthesize soot, which is dehydrated and baked in an electric furnace. The external attachment method (OVD method) is widely used because it can obtain a relatively arbitrary refractive index distribution and can mass-produce a large-diameter optical fiber preform.
Conventionally, a concentric multi-tube burner has been used as a burner for synthesizing a glass particulate deposit. However, a burner having such a structure sufficiently mixes a glass raw material gas, a combustible gas, and an auxiliary combustible gas. As a result, glass fine particles were not sufficiently produced. As a result, the yield was not increased and high-speed synthesis was difficult.

In order to solve this problem, Patent Document 1 proposes a multi-nozzle burner in which a small-diameter auxiliary combustion gas ejection nozzle is disposed in a combustible gas ejection nozzle so as to surround a central raw material gas ejection nozzle. .
Furthermore, in Patent Document 2, if the focal length of the small-diameter supporting gas injection nozzle and L _1, the distance between the tip and the base metal deposition surface of the small-diameter supporting gas injection nozzle was set to L _2, the L ₁ L ₂ A method for improving the deposition efficiency by preventing the flow of the raw material gas from being disturbed has been proposed.

On the other hand, Patent Document 3 proposes a method of increasing the efficiency of gas mixing and improving the deposition efficiency by making L1 smaller than L2.
Further, in Patent Document 4, a plurality of small-diameter gas nozzles are annularly arranged, and the deposition efficiency is improved by adopting a multifocal configuration in which the focal lengths of the outer annular rows are longer than the focal lengths of the inner annular rows. A method for improving the above has been proposed.

Japanese Patent Publication No. 3-9047 Patent No. 3543537 JP2003-226544 JP-A-5-323130

A multi-nozzle burner that improves the gas mixing efficiency by supplying a high-speed auxiliary combustion gas from a focused small-diameter gas injection nozzle and increasing the gas mixing efficiency. If the amount of gas supplied to the small-diameter gas jet nozzle is increased, the auxiliary combustion gas is concentrated too much at one point, the flame is greatly disturbed, and the deposition efficiency is lowered.
On the other hand, avoiding concentration and reducing the number of small-diameter gas ejection nozzles or reducing the amount of gas supplied to the small-diameter gas ejection nozzles will reduce the gas mixing efficiency and diminish the merits of the multi-nozzle type The deposition efficiency is not improved.

Moreover, in the method like patent document 4, although the gas concentration between several rows is avoided, the gas of the same row concentrates. Therefore, when storing the same number of small-diameter gas injection nozzles in the combustible gas injection nozzle, it is necessary to reduce the number of nozzles in the same row and increase the nozzle row. This will increase the amount of flammable gas used.
Therefore, an object of the present invention is to provide a burner for producing a porous glass base material that can suppress the disturbance of the flame and increase the deposition efficiency.

The present invention has been made to solve the above problems, and the porous glass preform manufacturing burner of the present invention is concentrically formed outside the central glass raw material gas injection nozzle with respect to the glass raw material gas injection nozzle. In the glass fine particle synthesis burner having a combustible gas injection nozzle including a small-diameter auxiliary combustion gas injection nozzle arranged in one or a plurality of rows, the small-diameter auxiliary combustion gas injection nozzle arranged on the same row includes In addition, two or more combinations of nozzles having the same focus are included, and the focus of each set is different.
In addition, it is preferable that the small-diameter auxiliary combustible gas ejection nozzles in the same row are arranged so that nozzles having the same focal point are not adjacent to each other. Moreover, it is preferable that the opening diameter of the said small-diameter auxiliary | assistant combustible gas ejection nozzle changes with focus. Furthermore, it is preferable to have a plurality of rows of small-diameter auxiliary gas-injecting nozzles in the combustible gas-injecting nozzles, and the shorter the focal length of the nozzles arranged on the inner side.

  In this way, by changing the focal length of the small-diameter auxiliary combustible gas ejection nozzles (hereinafter simply referred to as small-diameter nozzles) in the same row, the focal point of the ejected gas can be dispersed while maintaining the gas mixing efficiency. It is possible to suppress the disturbance of the flame and increase the deposition efficiency. Furthermore, since nozzles having the same focus on the same row are not adjacent to each other, the deposition efficiency can be improved without impairing the straightness of the flame.

It is the schematic which shows an example of the manufacturing apparatus of an optical fiber preform. It is a cross-sectional view which shows an example of the burner for glass fine particle synthesis | combination which has a small diameter nozzle. It is a cross-sectional view of a burner having a conventional small diameter nozzle. FIG. 4 is a vertical cross-section of the small diameter nozzle shown in FIG. 3. It is a cross section which shows an example of the burner which has two sets of small diameter nozzles from which the focus differs in the same row | line | column of this invention. It is a longitudinal cross-section of the small diameter nozzle shown in FIG. It is a cross section which shows the other example of the burner which has two sets of small diameter nozzles from which the focus differs in the same row | line of this invention, and shows the pattern from which the opening size of the small diameter nozzle of each focus differs. It is a longitudinal cross-section of the small diameter nozzle shown in FIG. It is a cross section which shows the example which has three sets of small diameter nozzles from which a focal distance differs of this invention. FIG. 10 is a longitudinal section of the small diameter nozzle shown in FIG. 9. It is a cross section which shows the example which has three sets of small diameter nozzles from which focal distance differs in the same row | line of this invention. 12 is a vertical cross section of the small diameter nozzle shown in FIG.

Hereinafter, the present invention will be described in more detail through embodiments of the present invention. However, the present invention is not limited to the following embodiments, and various modes are possible within the scope of the claims.
Hereinafter, the manufacturing method and apparatus of the optical fiber preform of the present invention will be described in detail with reference to the drawings.

FIG. 1 shows an example of an optical fiber preform manufacturing apparatus.
In FIG. 1, the starting member is formed by welding dummy rods 2 to both ends of the core rod 1, and this starting member is supported by a base material support member (not shown) so as to be rotatable about an axis. A burner 3 that is movable to the left and right is disposed toward the starting member. Here, a fiber raw material, for example, a vapor of SiCl ₄ and a combustion gas (hydrogen gas and oxygen gas) are sprayed from the burner 3 and hydrolyzed in an oxyhydrogen flame to synthesize soot 5 and start. A porous preform for optical fiber is formed by being deposited on the member 1.

Next, a method for manufacturing an optical fiber preform by such an external method (OVD method) will be described. First, while a starting member supported by a base material support (not shown) is rotated around the axis by the rotary motor 4, a flame is injected from the burner 3 toward the starting member to deposit soot on the starting member. . Then, the burner 3 is reciprocated in the longitudinal direction by a burner guide mechanism (not shown) to form a deposited layer, and a porous optical fiber preform is manufactured. The glass fine particles (soot) not deposited are discharged from the exhaust port 6.
An optical fiber preform is obtained by passing the obtained porous glass preform for an optical fiber through a heating furnace composed of a heater and a heat insulating material, followed by dehydration and transparent vitrification.

As the burner, a multi-nozzle type burner having a concentric five-pipe structure as shown in FIG. 2 is used. The burner has eight small-diameter nozzles arranged in a row concentrically with respect to the center tube in the third tube. In addition, as shown in FIG. 3, the symbols are assigned to the nozzles in order from the nozzle A at the 0 o'clock position to H in the clockwise direction.
As shown in FIGS. 3 and 4, the small-bore nozzle has a conventional burner having the same focal length of eight in the same row, and two types of focal lengths as shown in FIGS. Two types of the present invention type burner arranged four by four were prepared. As shown in Table 1, three types each with different focal lengths were prepared, and six types of burners were prepared.

The gas introduced into the burner is glass raw material gas SiCl ₄ and auxiliary combustion gas O ₂ in the first gas injection nozzle 7, seal gas N _{2 in} the second gas injection nozzle 8, and combustible gas H _{2 in} the third gas injection nozzle 10. The fourth gas injection nozzle 11 was supplied with the seal gas N ₂ , the fifth gas injection nozzle 12 was supplied with the auxiliary combustion gas O ₂ , and the small diameter nozzle 9 was supplied with the auxiliary combustion gas O ₂ .
Here, three burners of the same type were arranged side by side, and 100 kg of porous glass fine particles were deposited on the starting member in which a dummy rod having an outer diameter of 60 mm was welded to both ends of a core rod having an outer diameter of 60 mm and a length of 1500 mm. .
As a result, as shown in Table 1, the deposition efficiency of each burner was obtained.

From Table 1, the conventional type with the focal length set to 150 mm showed the highest deposition efficiency of 63.7%.
On the other hand, the burner according to the present invention in which two kinds of focal lengths are alternately arranged has a high gas mixing efficiency and a stable flame effect, and the deposition efficiency is 67.4 to 68.3%. did. In particular, the deposition efficiency of the burner of the invention 3 having the focal length set around the focal length of 150 mm, which had the highest deposition efficiency in the conventional type, was the highest.

Furthermore, various aspects are possible for the burner for porous glass preform | base_material manufacture of this invention, For example, the following examples are given.
7 and 8 are cross sections showing another example of a burner having two sets of small diameter nozzles with different focal points, and show patterns in which the opening sizes of the small diameter nozzles at the respective focal points are different. In the figure, small diameter nozzle, large opening diameter, and the group of A, C, E, G, which has a focal length _{L 2,} smaller and more opening diameter, B having a focal length _{L 1,} D, F, H- It consists of a group.

9 and 10 show examples having three sets of small diameter nozzles having different focal lengths. Outer rows of small diameter nozzles, a group of A, C, E, G, which has a focal length L _3, B having a focal length L _2, becomes D, F, from the group of H, the small diameter nozzle inner column has a shortest focal length L _1.

The example shown in FIGS. 11 and 12 shows an example having three sets of small diameter nozzles having different focal lengths in the same row. Small diameter nozzle groups of this embodiment, C having a group A, D, G, J having a focal length _{L 3,} B having a focal length _{L 1,} E, H, and the group of K, the focal length _{L 2} , F, I, and L.

  As described above, in the burner shown in this embodiment, the small-aperture nozzles arranged on the same row include two or more combinations of nozzles having the same focus, and the focus of each set is different. Therefore, it is possible to suppress the disturbance of the flame by dispersing the focus of the injected gas while maintaining the gas mixing efficiency, and the nozzles having the same focus on the same row are adjacent to each other. In this case, the deposition efficiency could be improved without impairing the straightness of the flame.

  As mentioned above, although this invention was demonstrated using embodiment, the technical scope of this invention is not limited to the range as described in the said embodiment, A various change or improvement can also be added to the said embodiment. It is clear that we can do it.

1 core rod,
2 dummy rod,
3 Burner,
4 Rotating motor,
5 Soot,
6 Exhaust port,
7 First gas ejection nozzle,
8 Second gas ejection nozzle,
9 Small diameter nozzle,
10 Third gas ejection nozzle,
11 Fourth gas ejection nozzle,
12 Fifth gas ejection nozzle.

Claims (4)

Fine glass particles provided with a combustible gas jet nozzle containing a small-diameter auxiliary combustion gas jet nozzle arranged in one or more rows concentrically with the glass raw material gas jet nozzle outside the central glass source gas jet nozzle In the synthesis burner, the small-aperture auxiliary gas ejection nozzles arranged on the same row include two or more combinations of nozzles having the same focus, and the focus of each set is different. Burner for manufacturing porous glass base material. 2. The burner for producing a porous glass base material according to claim 1, wherein the small-diameter auxiliary combustion gas ejection nozzles in the same row are arranged such that nozzles having the same focal point are not adjacent to each other. The burner for manufacturing a porous glass base material according to claim 1 or 2, wherein an opening diameter of the small-diameter auxiliary combustible gas ejection nozzle varies depending on a focal point. The porous body according to any one of claims 1 to 3, wherein a plurality of rows of small-diameter auxiliary gas-injecting nozzles are provided in the combustible gas-injecting nozzles, and the focal length is shorter as the nozzles are arranged more inside. Burner for the production of quality glass base material.

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