JP2005170759A - Raw material gas jetting apparatus, method of holding center pipe and method of manufacturing glass particle deposited body - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a raw material gas jetting apparatus by which a glass particle deposited body is stably manufactured, a method of holding a center pipe and a method of manufacturing the glass particle deposited body. <P>SOLUTION: The raw material gas jetting apparatus 30 has a glass particle forming burner 31 structured by arranging gas supply pipes 62-68 for supplying a plurality of gases in order to concentrically form flame around the center pipe 61 for supplying the raw material gas in multilayer, a plurality of tubes 71-78 for separately supplying the gas to each pipe of the glass particle forming burner 31 and a holding means 33 for holding the base end part 61a of the the center pipe 61 against the force from the raw material supply tubes 71-78 which works on a direction besides the axial direction of the center pipe 61 in the vicinity of a connection part of the center pipe 61 and the raw material supply tube 71 for supplying the raw material gas. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a raw material gas injection apparatus that generates glass fine particles to be sprayed on a starting material in a manufacturing process of an optical fiber preform, a center pipe holding method, and a glass fine particle deposit manufacturing method.

In general, an optical fiber having a core and a clad is manufactured by heating a porous glass fine particle deposit to make it transparent to produce an optical fiber preform and drawing the optical fiber preform.
Examples of the method for producing a glass fine particle deposit include a VAD method (Vapor Phase Axial Deposition) and an OVD method (Outside Vapor Deposition).
These blow out combustion gas consisting of combustible gas and combustion-supporting gas and glass raw material gas from a burner having a plurality of ports to hydrolyze the glass raw material in the oxyhydrogen flame generated by combustion of the combustion gas. In this method, glass fine particles are deposited on the starting material.

As shown in FIG. 11, when a glass fine particle deposit including a single mode optical fiber core is manufactured by, for example, the VAD method, an oxyhydrogen flame 52 is formed by the core burner 51, and germanium tetrachloride ( Glass raw material gas containing GeCl ₄ ) and silicon tetrachloride (SiCl ₄ ) is blown out to generate glass fine particles by hydrolysis. The generated glass fine particles are deposited below the starting material 55 that rotates about the axis thereof, and a core porous glass body (core soot) 53 is formed.
Similarly, an oxyhydrogen flame 57 is formed by the clad burner 56, and a glass raw material gas made of SiCl ₄ is blown into the oxyhydrogen flame 57 to form a clad porous glass body 58 so as to surround the core soot 53. Is done. As a result, a glass particulate deposit 60 comprising the core soot 53 and the clad porous glass body 58 is manufactured.

  As a burner used when manufacturing this kind of glass fine particle deposit, as shown in FIGS. 12 and 13, multiple pipes 61 to 68 made of quartz having different diameters are arranged concentrically. A multi-tube burner 100 having a tube structure is widely known (see, for example, Patent Documents 1 to 3).

  The multi-tube burner 100 shown in FIGS. 12 and 13 has a central pipe 61 that blows glass raw material gas from its tip on the central axis. And the several gas supply pipes 62-68 which supply the several gas for producing | generating the flame which burns glass raw material gas from a front-end | tip part are arrange | positioned at the multiple concentric form surrounding the outer periphery of the center pipe 61. FIG.

  The central pipe 61 arranged at the center of the multi-tube structure is a straight pipe having both ends opened, and a raw material supply tube 71 for supplying a raw material gas is connected to the opening of the base end portion 61a. The glass raw material gas supplied to is blown out from the opening at the tip. That is, in the center pipe 61, the opening at the base end portion 61a becomes a gas supply connection port 61c for connecting the raw material supply tube 71, and the opening at the tip end portion becomes a gas blowing port 61d.

The gas supply pipes 62 to 68 arranged in multiple layers concentrically with the center pipe 61 as the center have base end portions 62 a to 68 a in the vicinity of the connecting portion between the raw material supply tube 71 and the center pipe 61. The pipe is integrated with the central pipe 61 sequentially by being hermetically welded and fixed to the outer peripheral surface in the vicinity of the base end of the pipe.
Each of the gas supply pipes 62 to 68 has a tube connection pipe port 62b that communicates with the inside of the pipe in a section from the base end portion of the self pipe fixed to the inner pipe to the base end portion of the outer pipe. ˜68b are welded, and the flame source gas supplied from the tubes 72 to 78 connected to the tube connection pipe ports 62b to 68b flows through the gaps between the inner pipes and blows out from the tip.

That is, in the case of the gas supply pipes 62 to 68 arranged outside the center pipe 61, the gas supply connections in which the tube connection pipe ports 62b to 68b welded in the vicinity of the base end portions connect the tubes 72 to 78. Ports 62c to 68c are formed, and gaps between the pipes inside the tip end portions are gas blowing ports 62d to 68d.
When a glass particulate deposit is manufactured using this type of multi-tube burner 100, the outer periphery of the gas supply pipe 68 is gripped by the burner bracket 81 so that the tip of the multi-tube burner 100 is The position is positioned at a predetermined position.

JP-A-4-228443 Japanese Patent Laid-Open No. 7-33467 JP-A-7-242434

By the way, in order to improve the transmission characteristics of the optical fiber, it is desirable to make the shape of the refractive index distribution of the core portion stepped as shown in FIG. Furthermore, in order to stabilize the transmission characteristics of the optical fiber, it is desirable to eliminate variations in the refractive index distribution within and between the products.
In order to increase the refractive index, germanium (Ge), which is a dopant, is added to the core porous glass body (core soot), and the refractive index distribution of the optical fiber is determined depending on the distribution of the dopant. Therefore, it is necessary to make the shape of the dopant distribution stepwise to eliminate the variation.

  In order to suppress the occurrence of cracks and deformation in the glass particulate deposit, it is necessary to precisely control the flow rate of the glass raw material gas and the direction of the flame to deposit the glass particulates. If there is a defect in the glass fine particle deposit, the characteristics of the optical fiber manufactured by drawing from the optical fiber preform after the glass fine particle deposit is made transparent are also deteriorated.

  However, when observing the refractive index distribution of an optical fiber manufactured by manufacturing a glass particulate deposit using only the conventional multi-tube burner 100, the core has a smaller diameter than the target value, or FIG. As shown in FIG. 2, there may be a so-called interface horn in which the refractive index protrudes at the interface between the core and the clad. On the contrary, the core has a diameter larger than the target value, or as shown in FIG. 14C, a so-called interdigital state in which the refractive index changes gently at the interface between the core and the clad. is there.

  That is, when a glass particulate deposit is manufactured using only the conventional multi-tube burner 100, the glass particulate may not be stably deposited in a desired state, and there is a variation in the core diameter and refractive index of the optical fiber. As a result, the quality may be degraded.

The present inventor has determined the positioning posture of the central pipe 61 and the gas supply pipes 62 to 68 of the multi-tube burner 100 during the generation processing of the glass fine particles, and the center in order to find out the cause of the glass fine particles not being stably deposited in a desired state. The glass material gas injection form from the pipe 61, the flame form formed by the gas supply pipes 62 to 68, and the like were repeatedly observed and analyzed.
As a result, it was found that there is a cause in the support structure of the burner shown in FIGS.

  That is, as shown in FIGS. 12 and 13, the outer periphery of the intermediate portion of the outermost gas supply pipe 68 is held by the burner bracket 81. The support structure of the burner is such that the gas supply pipes 62 to 67 other than the outermost periphery and the center central pipe 61 are only pipes on the outer peripheral side in the vicinity of the base end portion to which tubes for supplying gas individually are connected. The base end portions 62a to 68a are in a cantilever state fixed by welding.

  Therefore, when the weight of the tube connected to the vicinity of the base end portion of each pipe, the tensile force acting on the tube, etc. act on the center pipe 61 and each gas supply pipe 62-67 as a bending force, the center pipe 61 and each The gas supply pipes 62 to 67 cause a displacement phenomenon centered on the support point on the base end side (welded portion with the outer pipe), and the displacement on the base end side is far from the support point even if slight displacement occurs. The distal ends of the center pipe 61 and the gas supply pipes 62 to 67 are greatly displaced.

  Moreover, since the center pipe 61 and the gas supply pipes 62 to 67 are set by shifting the connection positions of the tubes 71 to 77, the distal ends of the center pipe 61 and the gas supply pipes 62 to 67 have a displacement direction. This results in discontinuity, and this further increases the relative displacement between the center pipe 61 and the gas supply pipes 62 to 68.

  As described above, the positions of the distal ends of the center pipe 61 and the gas supply pipes 62 to 67 are changed to the initial optimum positions by the load acting on the base end side of the center pipe 61 and the gas supply pipes 62 to 67. As a result, there is a difference between the direction of blowing the glass source gas and the direction of the flame, and the generated glass particles cannot be stably deposited in a desired state.

  Accordingly, an object of the present invention is to solve the above-described problems, and provide a raw material gas injection apparatus, a center pipe holding method, and a glass fine particle deposit manufacturing method capable of stably producing a glass fine particle deposit. That is.

Therefore, the raw material gas injection apparatus of the present invention has a central pipe for supplying the raw material gas and a gas supply pipe for supplying a plurality of gases for forming a flame, and the concentrically above the central pipe. A burner having a configuration in which gas supply pipes are arranged in multiple layers;
A plurality of tubes for individually supplying gas to each pipe of the burner;
In the vicinity of the connecting portion between the raw material supply tube for supplying the raw material gas and the central pipe, the raw material supply tube, the central pipe, or the force from the tube acting in a direction other than the axial direction of the central pipe, And holding means for holding one of the pipe joints provided as needed between the raw material supply tube and the central pipe.

  Desirably, the holding means has a holding position adjusting mechanism.

  Preferably, the holding means has a holding block that holds any of the raw material supply tube, the central pipe, and the pipe joint, and the holding position is fixed.

  Preferably, a support substrate is fixed to a burner bracket that supports the burner, and the holding means is fixed to the support substrate.

The center pipe holding method of the present invention includes a center pipe that supplies a raw material gas and a gas supply pipe that supplies a plurality of gases for forming a flame, and is concentrically centered on the center pipe. In a raw material gas injection apparatus having a burner having a configuration in which the gas supply pipes are arranged in multiple layers, and a plurality of tubes for supplying gas individually to each pipe of the burner,
Any of the raw material supply tube, the central pipe, or a pipe joint provided between the raw material supply tube and the central pipe in the vicinity of the connecting portion between the raw material supply tube for supplying the raw material gas and the central pipe. The holding position with respect to the burner is held in an adjustable manner against the force from the tube acting in a direction other than the axial direction of the central pipe.

Further, the method for producing a glass particulate deposit according to the present invention is a method for producing a glass particulate deposit using the raw material gas injection device.
After the holding position of the central pipe with respect to the burner is adjusted and the manufacturing conditions are determined, the glass particulate deposit is manufactured in a state of being held at the holding position.

  According to the raw material gas injection device of the present invention, since the vicinity of the connecting portion between the raw material supply tube for supplying the raw material gas and the central pipe is fixed at the holding position by the holding means, the weight of the tube connected to each pipe or Even if the tensile force acting on the tube acts as a bending force, the holding means receives the bending force, and the tip of each pipe, including the center pipe, rotates on the base end side to which the tube is connected. It does not cause the center wobbling phenomenon.

Therefore, the position of each pipe does not fluctuate, and the position of each pipe is stably maintained at a desired position, and the blowing of the source gas and various gases for the flame is performed. It is possible to control the direction of the above with high accuracy.
Therefore, when producing a glass particulate deposit using the raw material gas injection device, the glass particulates can be stably deposited in a desired state.

Hereinafter, a raw material gas injection apparatus according to an embodiment of the present invention will be described in detail with reference to the accompanying drawings.
In addition, about the structural member of the glass particle generation burner 31 substantially the same as the conventional multiple tube burner 100 already demonstrated in FIG.12 and FIG.13, detailed description is simplified or abbreviate | omitted by attaching | subjecting the same code | symbol in a figure. To do.

FIG. 1 is a schematic configuration diagram of a manufacturing apparatus for manufacturing a glass fine particle deposit by the VAD method.
The glass particle deposit manufacturing apparatus 10 includes a reaction vessel 11. A support rod 14 rotatably supported by an elevating device 13 installed above the reaction vessel 11 is inserted into the reaction vessel 11 from the upper surface side of the reaction vessel 11. A starting material (dummy glass rod) 12 is suspended from the support rod 14. The starting material 12 is lifted and lowered together with the support bar 14 by the lifting device 13, and is configured to be rotatable around its axis together with the support bar 14 by the lifting device 13.

In the reaction vessel 11, a cladding burner 21 and a core burner 22 that spray glass fine particles onto the starting material 12 are installed. The cladding burner 21 and the core burner 22 are installed to be inclined obliquely upward from below with respect to the starting material 12 supported by the support rod 14.
A gas supply device 23 is connected to each of the cladding burner 21 and the core burner 22, and this gas supply device 23 is used to form a glass source gas and a flame on the cladding burner 21 and the core burner 22, respectively. Gas (combustion gas, auxiliary combustion gas, and seal gas) is supplied.

The cladding burner 21 and the core burner 22 blow out the glass raw material gas and the combustion gas supplied from the gas supply device 23 to generate glass particles.
As a result, glass fine particles are deposited on the end portion of the starting material 12, and a glass fine particle deposit 24 is gradually formed.
The reaction vessel 11 is provided with a laser oscillator 25 and a light receiver 26 disposed opposite to the laser oscillator 25 in the vicinity of the lower end thereof. The laser oscillator 25 irradiates the lower end portion of the glass fine particle deposit 24 with laser, and the irradiated laser is received by the light receiver 26. The light receiver 26 is connected to the control device 27 and outputs a light reception signal to the control device 27 based on the intensity of the received laser.

The control device 27 drives and controls the elevating device 13 and the gas supply device 23 so that the output of the light reception signal from the light receiver 26 is constant, and manages the growth rate of the glass particulate deposit 24 to be formed.
Further, the reaction vessel 11 is provided with an exhaust pipe 28, and the gas in the reaction vessel 11 is exhausted from the exhaust pipe 28.

For the clad burner 21 and the core burner 22, a glass fine particle generating burner (burner) 31 according to the raw material gas injection device 30 of the present invention is used.
2 to 6 show a raw material gas injection apparatus 30 according to the first embodiment of the present invention.
The glass fine particle generating burner 31 in the raw material gas injection apparatus 30 has a multi-tube structure in which a plurality of quartz pipes 61 to 68 having different diameters are concentrically arranged, and a glass raw material gas ( A central pipe 61 for blowing out the source gas) from the tip is disposed. And the several gas supply pipes 62-68 which supply several gas for producing | generating the flame which burns glass raw material gas from a front-end | tip part are arrange | positioned concentrically and multilayered centering on the center pipe 61. FIG.

  The central pipe 61 disposed at the center of the multi-tube structure is a straight pipe having both ends opened, and a raw material supply tube 71 is connected to the opening of the base end portion 61a, and glass supplied from the raw material supply tube 71 into the pipe. Source gas is blown out from the opening at the tip. That is, in the center pipe 61, the opening at the base end portion 61a becomes a gas supply connection port 61c for connecting the raw material supply tube 71, and the opening at the tip end portion becomes a gas blowing port 61d.

The gas supply pipes 62 to 68 arranged in multiple layers concentrically with the center pipe 61 as the center have base end portions 62 a to 68 a in the vicinity of the connecting portion between the raw material supply tube 71 and the center pipe 61. The pipe is integrated with the central pipe 61 sequentially by being hermetically welded and fixed to the outer peripheral surface in the vicinity of the base end of the pipe.
Each of the gas supply pipes 62 to 68 has a tube connection pipe port communicating with the inside of the own pipe in a section from the own base end portion fixed to the inner pipe by welding to the base end portion of the outer pipe. 62b-68b is welded, and the flame gas supplied from the tubes 72-78 connected to the tube connection ports 62b-68b flows through the gaps between the inner pipes and blows out from the tip.

  That is, in the case of the gas supply pipes 62 to 68 arranged outside the center pipe 61, the gas supply pipes 62 to 68 are joined to the vicinity of the base end portion where the tubes 72 to 78 for supplying the gas are connected individually. The tube connection pipe ports 62b to 68b thus formed serve as the gas supply connection ports 62c to 68c for connecting the tubes, and the gaps between the pipes inside the tip end portions serve as the gas blowing ports 62d to 68d.

  And the glass particle production | generation burner 31 which concerns on the raw material gas injection apparatus 30 of this embodiment is the burner bracket 81 which grips the intermediate part outer periphery of the gas supply pipe 68 of the outermost periphery, the raw material supply tube 71, and the center pipe 61. The central pipe 61 and the gas supply pipes 62 to 68 in the vicinity of the connecting portion are individually supported and fixed at a predetermined position and orientation by a plurality of holding means 33 for fixing the position near the base end portion to the holding position. ing.

  As shown in FIGS. 2 and 5, the burner bracket 81 includes a bracket body 82 having a V-shaped groove 82a for fitting and positioning the outermost gas supply pipe 68 constituting the glass fine particle generating burner 31; The holding plate 83 is configured to press and fix the outermost gas supply pipe 68 fastened to the upper surface of the bracket body 82 and positioned in the V-shaped groove 82a. The glass particle generating burner 31 is fixed by sandwiching the gas supply pipe 68 on the outer periphery.

  Each holding means 33 is bent by its own weight of the tubes 71 to 78 connected to the central pipe 61 and the gas supply connection ports 61c to 68c of the gas supply pipes 62 to 68, a tensile force acting on the tubes 71 to 78, and the like. The center pipe 61 and the gas supply pipes 62 to 68 are not deformed or displaced by the force and the weight of the center pipe 61 and the gas supply pipes 62 to 68 themselves. ˜67, the raw material supply tube 71 and the central pipe are connected between the support portion fixed by welding and the base end portion, and the outermost gas supply pipe 68 between the support portion by the burner bracket 81 and the base end portion. The gas supply connection ports 61c to 68c, which are in the vicinity of the connection portion with 61, are fixed at the holding position against a load or the like acting on the side.

In the case of the present embodiment, the holding position that is positioned and fixed by the holding means 33 means that the center axis of the center pipe 61 and the distal ends of the gas supply pipes 62 to 68 arranged in the multi-tube structure coincides with the initial position. This is the position on the base end side of the center pipe 61 and each of the gas supply pipes 62 to 68, which is necessary for maintaining the above state.
However, depending on the manufacturing conditions of the glass particulate deposit, etc., the central pipe 61 and the distal ends of the gas supply pipes 62 to 68 may not be intentionally positioned concentrically. It is not limited to the position which hold | maintains the front-end | tip part of -68 to the concentricity which the center axis line matched.

Further, in the case of the present embodiment, the position held by the holding means 33 is specifically set at a portion to be the base end portion 61a of the center pipe 61 and the gas supply connection ports 61c to 68c of the gas supply pipes 61 to 68. Has been.
That is, in the case of the center pipe 61, the gas supply connection port 61 c of the base end portion 61 a in the vicinity of the connection portion between the raw material supply tube 71 and the center pipe 61 is fixed to the holding position by the holding means 33. In the case of the gas supply pipes 62 to 68, the tube connection pipe ports 62 b to 68 b that become the gas supply connection ports 62 c to 68 c in the vicinity of the connection portion between the raw material supply tube 71 and the center pipe 61 are held by the holding means 33. Fixed to.

  Furthermore, in the case of this embodiment, as shown in FIGS. 2 and 6, the holding unit 33 is configured to connect the center pipe 61 and the tube connection portions of the gas supply pipes 62 to 68 (that is, the base end portion 61 a of the center pipe 61, And a grip block 33a fitted to and attached to the tube connection pipe ports 62b to 68b) provided in the gas supply pipes 62 to 68, a support substrate 33b integrated with the burner bracket 81, and a screw hole 34 of the support substrate 33b. The block position adjusting screw 33c that restricts the position of the gripping block 33a by screwing the tip portion with the gripping block 33a and the block position adjusting screw 33c screwed to the support substrate 33b are prevented from rotating. Thus, a lock nut 33d for fixing the position of the block position adjusting screw 33c is provided.

  Further, the block position adjusting screw 33c of this embodiment can adjust the position of the gripping block 33a along the direction of the center axis of the screw by adjusting the screwing position with respect to the support substrate 33b. The means 33 functions as a holding position adjusting mechanism capable of adjusting the holding positions of the central pipe 61 and the gas supply pipes 62 to 68.

According to the raw material gas injection device 30 of the present embodiment described above, the base end portion 61 a in the vicinity of the connecting portion between the raw material supply tube 71 and the central pipe 61 in the glass fine particle generating burner 31 is held by the holding means 33. Fixed in position.
Therefore, the center pipe 61 is not in a cantilever state that is only supported by the burner bracket 81 via the gas supply pipes 62 to 68 disposed on the outer peripheral side. Even if the weight of each of the tubes 71 to 78 connected to the base end side of the pipes 62 to 68 and the tensile force acting on each of the tubes 71 to 78 act as a bending load on the glass particulate generation burner 31, Since the holding means 33 can receive the load, the distal end portion of each of the gas supply pipes 62 to 68 including the central pipe 61 does not cause a swinging phenomenon with the proximal end side as the rotation center.

  Therefore, the center pipe 61 and the gas supply pipes 62 to 68 do not change in position due to fluctuations, and the positions of the center pipe 61 and the gas supply pipes 62 to 68 are stably held at desired positions so that the glass raw material gas and By blowing out various gases for the flame, it becomes possible to control the blowing direction of the glass raw material gas and the direction of the flame with high accuracy, and the glass fine particles can be stably deposited in a desired state. .

  Furthermore, in the said embodiment, the base end part 61a used as the action point of external loads, such as the weight of each tube 71-78, and the tube connection pipe ports 62b-68b itself are fixed to a holding position by the holding means 33. Therefore, it is possible to prevent the central pipe 61 and part of the gas supply pipes 62 to 68 from being distorted by an external load more reliably, and the distal ends of the center pipe 61 and the gas supply pipes 62 to 68 due to the external load. It is possible to thoroughly prevent the movement of the part.

  In addition, in the above-described embodiment, the proximal end portion 61a and the tube connection pipe ports 62b to 68b in the vicinity of the connection portion between the raw material supply tube 71 and the central pipe 61 are moved forward and backward by the block position adjusting screw 33c that is a holding position adjusting mechanism. As a means for finely adjusting the blowing direction of the glass raw material gas and the direction of the flame, it is possible to adjust the positions of the distal ends of the center pipe 61 and the gas supply pipes 62 to 68 by adjusting each of the adjustments. The holding means 33 can also be actively used, and the alignment of the blowing direction of the glass source gas and the direction of the flame becomes easy.

  In the above embodiment, the holding position is fixed by the holding means 33 for each of the central pipe 61 and the gas supply pipes 62 to 68. However, in the case of the multiple tube structure as in the above embodiment, if the vicinity of the connecting portion between the center pipe 61 and the raw material supply tube 71 located at the center of the multiple tube structure is fixed to a predetermined holding position by the holding means 33, Even if the other gas supply pipes 62 to 68 are not fixed by the holding means 33, the entire gas supply pipes 62 to 68 have a double-supported beam-like support structure, so that an external load through the tubes 71 to 78 can be prevented. The effect of suppressing the fluctuation phenomenon of each center pipe 61 and the gas supply pipes 62 to 68 is obtained.

  Accordingly, the position where the holding means 33 is provided may be at least in the vicinity of the base end portion 61a of the center pipe 61. However, like the glass particle generating burner 31 of the above embodiment, the center pipe 61 is concentric. The plurality of gas supply pipes 62 to 68 arranged in multiple layers are also fixed to the holding positions by the holding means 33 at the tube connection pipe ports 62 b to 68 b in the vicinity of the connection portion between the raw material supply tube 71 and the center pipe 61. In this case, the bending load acting on the glass fine particle generating burner 31 can be distributed and received by the plurality of holding means 33, and the load acting on each holding means 33 can be reduced. Therefore, the central pipe 61 and the gas supply pipes 62 to 68 can be fixed to a predetermined holding position more securely.

Moreover, in the said embodiment, the external load which acts on the base end part 61a of each center pipe 61 and the gas supply pipes 62-68 and the tube connection pipe ports 62b-68b is mainly gravity with the dead weight of each tube 71-78. Since the load is in the direction, the block position adjusting screw 33c is mounted upward to restrict the displacement in the gravitational direction.
However, the action direction of the external load acting on the base end portion 61a and the tube connection pipe ports 62b to 68b may be considered to be upward or horizontal depending on the tube routing direction.

  Therefore, the direction to be supported by the block position adjusting screw 33c is not limited to the above embodiment, and is actually supported for each of the central pipe 61 and the gas supply pipes 62 to 68 in consideration of the tube arrangement direction. It is also conceivable to improve the configuration in which the position of the gripping block 33a is regulated from a plurality of directions so that the direction can be changed or the action of loads in a plurality of directions can be withstood.

  Therefore, for example, like the holding means 33 in the raw material gas injection apparatus 40 according to the second embodiment of the present invention shown in FIG. 7, a pair of support substrates 33b extending in parallel with each other with the glass particulate generation burner 31 interposed therebetween, 33b is attached to the burner bracket 81, and the block position adjusting screw 33c is screwed into the screw hole 34 of each support substrate 33b so as to face each other, and the tip portion is brought into contact with the upper and lower surfaces of the gripping block 33a. The position of the gripping block 33a can also be configured so as to be regulated from two directions up and down.

In this case, the gripping blocks 33a fitted and attached to the base end portion 61a supported by the holding means 33 and the tube connection pipe ports 62b to 68b are sandwiched from above and below by the opposing block position adjusting screws 33c and 33c, respectively. Therefore, the vertical displacement is restricted.
Therefore, even when a vertical load is applied to the glass particle generation burner 31 via the tubes 71 to 78 connected to the base end portion 61a and the tube connection pipe ports 62b to 68b, the base end portions 61a and The tube connection pipe ports 62b to 68b can be stably fixed to a predetermined holding position.

FIG. 8 is an enlarged perspective view of a main part of a glass particle generating burner according to a third embodiment of the present invention, which is supported from the base end part of each gas supply pipe 61 to 68 arranged in a concentric multiple pipe structure. Another mode of the holding means for holding the range up to the portion at a predetermined position is shown.
The holding means 35 shown here includes a support substrate 35a integrated with a burner bracket 81 (see FIG. 2) for gripping and fixing the outer periphery of the intermediate portion of the outermost gas supply pipe 68, and the thickness direction of the support substrate 35a (see FIG. 8 and the adjustment shaft portion 35c fitted and mounted in the through hole 35b of the support substrate 35a, and the central pipe 61 and the gas supply pipe integrally formed at the tip of the adjustment shaft portion 35c. A support ring portion 35d that is externally fitted to the base end portion 61a and the tube connection pipe ports 62b to 68b in 62 to 68, and a set screw 35e that regulates displacement in the plate thickness direction of the adjustment shaft portion 35c. .

The set screw 35e is a screw that is screwed into a screw hole 35f formed in the side surface of the support substrate 35a so as to communicate with the through hole 35b, and is adjusted by pressing the outer peripheral surface of the adjustment shaft portion 35c at the tip portion. By restricting the movement of the shaft portion 35c, a holding position adjusting mechanism that can adjust the holding positions of the center pipe 61 and the gas supply pipes 62 to 68 is configured.
As shown in FIG. 9, the adjustment shaft portion 35c has a chamfered portion 35g obtained by chamfering a part of the peripheral surface. The chamfered portion 35g becomes an engaging surface for preventing rotation, and at the same time, It becomes the contact surface of the screw 35e.

  In the holding means 35 shown in FIG. 8, the center pipe 61 to be supported and the base end portions 61 a of the gas supply pipes 62 to 68 and the tube connection pipe ports 62 b to 68 b other than the direction of the central axis of the support ring portion 35 d. Even in the case where loads in a plurality of directions are applied through the tubes 71 to 78 connected to the base end portion 61a and the tube connection pipe ports 62b to 68b, the center pipe can be controlled in all directions. 61 and gas supply pipes 62 to 68 can be stably held at predetermined positions.

  Furthermore, in the said embodiment, by holding | maintaining the base end part 61a of the center pipe 61 which is the connection part of the raw material supply tube 71 and the center pipe 61 with the holding means 33, it acts other than the axial direction of the center pipe 61. The holding means of the present invention is not limited to this, but for example, the raw material supply tube 71 is directly held, or the raw material supply tube 71 and the central pipe are configured to resist the force from each of the tubes 71 to 78. A pipe joint 90 as shown in FIG.

(Example)
Next, the glass particulate deposit 24 was produced using the glass particulate deposit production apparatus 10 shown in FIG. 1 as an example.
For the dummy glass rod as a starting material, pure quartz glass having a diameter of 20 mm and a length of 300 mm is used. A laser is irradiated from the laser oscillator installed in the lower part of the reaction vessel to the vicinity of the lowermost end of the glass particulate deposit, and the irradiated laser is received by a light receiver. The control device controls the lifting device so that the received light power of the laser detected by the light receiver is constant, and pulls up the glass particulate deposit 24 together with the dummy glass rod.

The clad burner 21 and the core burner 22 are arranged centering on a central pipe 61 having a total length of 600 mm and a cross-sectional area of 28 mm ² (inner diameter 6 mm, outer diameter 8 mm), and are concentrically cut around the central pipe 61. The glass particle generating burner 31 of the raw material gas injection device 30 in which the gas supply pipe 62 having an area of 78 mm ² (inner diameter: 10 mm, outer diameter: 12 mm) is arranged and the gas supply pipes 63 to 68 are sequentially arranged on the outer side is used (FIG. 3). And it installs so that the angle of the center axis | shaft of the glass particle production | generation burner 31 and a floor surface may become 45 degree | times.

The center pipe 61 is held and fixed via a gripping block 33a at a position on the 40 mm raw material supply tube 71 side from the base end portion 62a of the gas supply pipe 62 arranged on the outer peripheral side.
The cladding burner 21 is supplied with germanium tetrachloride (GeCl ₄ ) and silicon tetrachloride (SiCl ₄ ) as source gases, and the core burner 22 is supplied with silicon tetrachloride (SiCl ₄ ). Fine particles and clad glass fine particles are deposited to produce a glass fine particle deposit 24.

Thereafter, the glass particulate deposit 24 is heated to a high temperature to form a transparent glass, thereby producing an optical fiber preform.
Table 1 below shows the intra-lot variation, inter-lot variation, and overall variation of the core refractive index in the optical fiber preform of the above example.
The in-lot variation of the core refractive index is the variation (deviation) of the core refractive index measured at five points in the longitudinal direction of the core having a converted length of 1000 km, and the variation between lots is the average value of the core refractive index of each core. The total variation is the root mean square (standard deviation) of the intra-lot variation and the inter-lot variation of the core refractive index.

(Comparative example)
On the other hand, an optical fiber preform of a comparative example is produced under the same conditions as in the above example except that the glass fine particle generating burner 100 (see FIG. 12) is used as the cladding burner 21 and the core burner 22.
Table 1 below shows the intra-lot variation, inter-lot variation, and overall variation of the core refractive index in the optical fiber preform of the comparative example.

  As apparent from Table 1 above, the variation in the core refractive index in the optical fiber preform of the example is smaller than the variation in the core refractive index in the optical fiber preform of the comparative example, and the base end of the center pipe 61 It was found that the glass particulate deposit 24 can be stably manufactured by using the glass particulate generation burner 31 in which the portion 61a is held and fixed via the gripping block 33a.

It is the schematic which shows the manufacturing apparatus of the glass particle deposit body using the burner for glass particle production | generation which concerns on one Embodiment of this invention. It is a perspective view of the burner for glass particle production concerning a 1st embodiment of the present invention. FIG. 3 is a partially broken plan view of the glass fine particle generating burner shown in FIG. 2. It is a side view of the burner for glass fine particle production | generation shown in FIG. It is a front view of the burner for glass fine particle production | generation shown in FIG. It is a disassembled perspective view of the holding means shown in FIG. It is a side view of the glass microparticle production | generation burner which concerns on the 2nd Embodiment of this invention. It is a principal part expansion perspective view of the holding means in the burner for glass fine particle production | generation concerning the 3rd Embodiment of this invention. It is sectional drawing of the axial part for adjustment shown in FIG. It is a top view of the pipe joint provided between the raw material supply tube and the center pipe. It is the schematic at the time of manufacturing a glass particulate deposit. It is a partially broken top view of the conventional glass particle production | generation burner used for manufacture of a glass particle deposit. It is a side view of the burner for glass fine particle production | generation shown in FIG. It is an example of the refractive index distribution in an optical fiber, (a) shows the case where the refractive index distribution from a core part to a clad part is a step shape, (b) shows locally on the outer peripheral part of a core part. The case where there is a portion where the refractive index is increased is shown, and (c) is a diagram showing the case where there is a refractive index gradient from the core portion to the cladding portion.

Explanation of symbols

30 Raw material gas injection device 31 Burner for glass fine particle generation (burner)
33 Holding means 33a Holding block 33b Support substrate 33c Block position adjusting screw 33d Lock nut 61 Center pipe 61c Gas supply connection port 62 to 68 Gas supply pipe 62c to 68c Gas supply connection port 71 Raw material supply tube 72 to 78 Tube 81 Burner bracket

Claims (6)

It has a configuration in which a central pipe that supplies a raw material gas and a gas supply pipe that supplies a plurality of gases for forming a flame are arranged in multiple layers concentrically around the central pipe With a burner,
A plurality of tubes for individually supplying gas to each pipe of the burner;
In the vicinity of the connecting portion between the raw material supply tube for supplying the raw material gas and the central pipe, the raw material supply tube, the central pipe, or the force from the tube acting in a direction other than the axial direction of the central pipe, A raw material gas injection apparatus comprising: holding means for holding one of pipe joints provided as necessary between the raw material supply tube and the central pipe. The raw material gas injection apparatus according to claim 1, wherein the holding unit includes a holding position adjusting mechanism. 2. The raw material according to claim 1, wherein the holding unit includes a holding block that holds one of the raw material supply tube, the center pipe, and the pipe joint, and the holding position is fixed. Gas injection device. The raw material gas injection device according to claim 1, wherein a support substrate is fixed to a burner bracket that supports the burner, and the holding means is fixed to the support substrate. It has a configuration in which a central pipe for supplying a raw material gas and a gas supply pipe for supplying a plurality of gases for forming a flame are provided, and the gas supply pipes are arranged in multiple layers concentrically around the central pipe. In the raw material gas injection apparatus having a burner and a plurality of tubes for individually supplying gas to each pipe of the burner, the raw material supply in the vicinity of a connecting portion between the raw material supply tube for supplying the raw material gas and the central pipe Either the tube, the center pipe, or a pipe joint provided between the raw material supply tube and the center pipe, against the force from the tube acting in a direction other than the axial direction of the center pipe, A holding method of the center pipe, wherein the holding position with respect to the burner is held in an adjustable manner. In the method for producing a glass particulate deposit using the raw material gas injection device according to claim 1,
After the holding position of the central pipe with respect to the burner is adjusted and the manufacturing conditions are determined, the glass particle deposit is manufactured in a state of being held at the holding position.

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