JP2009107859A - Flame polishing method of glass preform - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a flame polishing method for a glass preform in which the occurrence of cracks can be suppressed. <P>SOLUTION: In the flame polishing method of the glass preform to perform the flame polishing of the glass preform 10 where a glass rod 11 and dummy rods 12, 13 are connected via connection parts 14, 15, a flame polishing step of the glass rod 11 is performed after a strain-removing step to remove strain at the connection parts 14, 15 by heating the connection parts 14, 15 and the neighborhood of the connection parts 14, 15. In the strain-removing step, flame polishing is simultaneously performed from the connection part 14 toward the end part of the glass preform 10 and the flame polishing step starts from the connection part 15. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a flame polishing method for a glass base material.

  Conventionally, in the process of manufacturing a glass base material for optical fibers or the like, a glass raw material is introduced into a flame of a burner, and a glass particle is synthesized by a hydrolysis reaction or an oxidation reaction in the flame, and this is synthesized on the surface of the starting rod. A VAD method (vapor phase shafting method) or the like is known in which a glass fine particle deposition base material is manufactured by depositing on a glass. At this time, if impurities such as dust adhere to the surface of the starting rod, a high-quality glass particulate deposition base material cannot be obtained. For this reason, the surface of the starting rod is cleaned by flame polishing before the glass fine particles are deposited.

  In addition, an optical fiber can be manufactured by heating and drawing an optical fiber glass preform. In the process before the drawing, the surface of the optical fiber glass preform is flame-polished with an oxyhydrogen flame. There is known a flame polishing method for a glass base material (see, for example, Patent Documents 1 and 2).

  As shown in FIG. 3, in the flame polishing apparatus 100 used in the flame polishing method described in Patent Document 1, a glass base material 101 is gripped by a pair of chucks 102 and 103, and the chuck 102 is rotationally driven by a motor 104. Thus, the glass base material 101 is rotated about the axis. Below the glass base material 101, a burner 105 is supported so as to be able to reciprocate along a screw rod 106 rotated by a motor 107, and the rotating glass base material 101 is heated and polished.

  In the flame polishing method described in Patent Document 1, after the non-uniformity of the surface of the base material is removed by the first flame polishing step, the strain remaining in the base material at a temperature lower than that of the first flame polishing step is applied. The second flame polishing step for removing and removing the fogging of the surface of the base material is continuously performed.

  In the flame polishing method described in Patent Document 2, the movement of the flame burner is stopped for a certain time at the start position and the end position of flame polishing, for example, until the internal temperature of the glass base material is heated to 1400 to 1700 ° C. Thus, the internal distortion that occurs at the start and end positions of flame polishing is reduced.

JP 2000-203861 A JP 2004-107176 A

  In general, as shown in FIG. 4, a glass base material 110 as a starting rod is formed by connecting glass dummy bars 112 and 113 to both ends of a glass rod 111 which is an effective portion as a base material. Then, both the dummy bars 112 and 113 are held by the chucks 114 and 115, and the burner 116 is moved from the left end to the right direction, for example, while rotating the glass base material 110, thereby performing flame polishing.

  However, the joints 117 and 118 between the dummy bars 112 and 113 and the glass bar 111 are heated once at the time of joining and remain distorted. Therefore, when the glass base material 110 is heated while moving the burner 116 from left to right, the distortion of the heated portion is removed, but when the central portion of the glass base material 110 is heated and softened, the strain remains. A heavy load was applied to the unheated joint 118, and cracks were likely to occur in this portion. When cracks occur, the glass base material 110 is broken from the cracks, which is a factor for reducing the product yield.

  In addition, when the base material which has a connection part is flame-polished by the method of patent document 1, when performing a 1st flame grinding | polishing process, the distortion of a connection part remains and it is easy to produce a crack in a connection part. In addition, when the base material having the connection portion is flame-polished by the method described in Patent Document 2, it is only the start position of the flame polishing that the distortion is removed when the center portion of the base material is flame-polished. Cracks are likely to occur at the end of the flame polishing connection.

  The objective of this invention is providing the flame polishing method of the glass base material which can suppress generation | occurrence | production of a crack.

  The flame polishing method for a glass base material according to the present invention that can solve the above-described problem is a method for flame polishing a glass base material that flame-polishes a glass base material in which two or more glass rods are connected via a connecting portion. In this case, the flame polishing step is performed after the strain removing step of removing the strain of the connecting portion by heating the connecting portion and the vicinity of the connecting portion.

  In the flame polishing method for a glass base material according to the present invention, it is preferable that the strain removing step also serves as flame polishing.

  Further, in the flame polishing method for a glass base material according to the present invention, the glass base material is obtained by connecting a glass rod as an effective portion and a glass rod as a dummy portion, and the strain removing step includes the connection step. It is preferable that it is performed toward the glass rod as said dummy part from a part and the said connection part vicinity.

  In the flame polishing method for a glass base material according to the present invention, it is preferable that the flame polishing step is started from the connection portion and the vicinity of the connection portion.

  According to the present invention, when the glass base material is flame polished, the center portion of the glass base material is heated and softened in order to perform the flame polishing step after removing the strain by heating the connecting portion first. However, it is possible to perform the flame polishing by preventing the unheated bonding portion where the strain remains as in the prior art from applying a weight and causing cracks in the vicinity of the bonding portion during the flame polishing.

Hereinafter, an example of an embodiment according to a flame polishing method for a glass base material of the present invention will be described with reference to the drawings.
FIG. 1 is a schematic diagram showing a first embodiment of the glass base material flame polishing method of the present invention, and FIG. 2 is a schematic diagram showing a modification of the first embodiment.

  As shown in FIG. 1, in the apparatus for carrying out the glass base material flame polishing method according to the first embodiment of the present invention, the glass rod 11 as an effective part of the base material is joined to both ends of the glass rod 11. A glass base material 10 formed by joining a pair of glass dummy rods (glass rods 12 and 13 as dummy portions) 12 and 13 via connecting portions 14 and 15 is subjected to flame polishing. Both dummy bars 12 and 13 are gripped by chucks 16 and 17 and rotated by a motor (not shown). The burner 18 that flame polishes the glass base material 10 can be moved in the left-right direction in FIG. 1 by moving means (not shown).

  The glass rod 11 as an effective portion of the base material corresponds to a portion that constitutes an effective portion that is effectively used when glass fine particles are deposited around the base to form an optical fiber base material. For this reason, the glass rod 11 has a portion that becomes the core of the optical fiber, and is a glass rod having a viscosity lower than that of pure quartz glass. The left and right dummy rods 12 and 13 are for supporting the glass rod 11 and are made of pure quartz glass or glass in which a slight amount of impurities are allowed to be mixed with the pure quartz glass. Compared with a glass rod having a higher viscosity.

Next, the flame polishing method for the glass base material of the present embodiment will be described.
First, when the glass base material 10 is flame-polished, a strain removing step of heating the connection portions 14 and 15 is performed. In the strain removing step, the portion including the connecting portions 14 and 15 (the connecting portion and the vicinity of the connecting portion) is heated to remove the strain in the vicinity of the connecting portions 14 and 15. What is necessary is just to heat at temperature lower than flame polishing when removing distortion.

  Further, by moving the burner 18 toward the end portion of the glass base material 10 (that is, toward the dummy rod), it is possible to serve as flame polishing to the connection portions 14 and 15 and the end portion. In the case of flame polishing, the surface temperature of the glass base material 10 is vaporized by heating so that the surface temperature of the glass base material 10 becomes 1600 ° C. or higher. That is, when the strain removal process also serves as flame polishing, the strain removal process is performed at the heating temperature of flame polishing.

  In the strain removal process, as shown in FIG. 1, it is efficient to heat the terminal end 15 in the direction in which the burner 18 is moved in the flame polishing process (that is, the right side in FIG. 1) first. Therefore, in the first heating, the right connecting portion 15 is heated by the burner 18 to remove the distortion of the connecting portion 15, and the burner 18 is directed from the connecting portion 15 toward the end closer to the glass base material 10. The glass base material 10 (that is, the dummy bar 13) on the right side of the connecting portion 15 is subjected to a strain removing process.

Next, the left connection portion 14 is heated to remove the distortion of the connection portion 14, and the burner 18 is moved leftward toward the near end of the glass base material 10, so that the left side of the connection portion 14 is left. The distortion removal process of the glass base material 10 (namely, dummy rod 12) is performed. However, the dummy rod 12 on the left side of the connecting portion 14 is not a portion that becomes an optical fiber product by drawing when the glass fiber is deposited and transparentized to form an optical fiber preform, and a flame polishing process. Then, considering that the burner 18 is moved to the right and the strain is moved to the right, the necessity for flame polishing is low, and it is sufficient that the strain at the connecting portion 14 is removed. For this reason, in consideration of the work efficiency, in the second heating, the heating may be started slightly from the left side of the left connecting portion 14 and the burner 18 may be moved in the right direction.
In this strain removal step, by making the flame temperature of the burner 18 equal to that at the time of flame polishing, it is possible to substantially perform the flame polishing of the connecting portions 14 and 15.

  In addition, after removing the distortion of the connection part 14 by heating the connection part 14, the flame polishing process of the glass rod 11 will be implemented. Therefore, in the flame polishing step, the flame polishing is performed by the burner movement in two steps by performing the flame polishing of the glass rod 11 up to the right connection portion 15 subsequent to the distortion removing step of the connection portion 14. It is possible to improve efficiency.

  According to such a flame polishing method for a glass base material of the first embodiment, the glass base material 10 in which two or more glass rods 11, 12, 13 are connected via connection parts 14, 15 is flame-polished. At this time, after removing the strain by heating the connecting portions 14 and 15 first, the flame polishing step of the glass rod 11 as the effective portion of the base material is performed. For this reason, when the central part of the glass base material 10 (corresponding to the central part of the glass rod 11) is heated and softened, a heavy load is applied to the connection parts 14 and 15, but before that, the connection parts 14 and 15 are applied. Since the strain removing process is performed, the flame polishing can be performed without generating cracks in the vicinity of the connecting portions 14 and 15. For example, in the conventional method, the rate of occurrence of cracks in the glass base material 10 was about 0.2%. However, when the flame polishing method for a glass base material of the present embodiment is applied, the rate of occurrence of cracks is about zero%. It became. Thereby, generation | occurrence | production of a crack can be suppressed and the quality glass base material 10 in which impurities, such as dust, have not adhered to the surface can be obtained.

Next, a modification of the glass base material flame polishing method of the first embodiment will be described with reference to FIG. In addition, the same code | symbol is attached | subjected to the site | part which is common in 1st Embodiment mentioned above, and the overlapping description is abbreviate | omitted.
In the first embodiment, the glass base material is formed by connecting the three glass rods of the glass rod 11 and the two dummy rods 12 and 13 by the two connecting portions 14 and 15 as the two or more glass rods. In the case of forming the glass base material 10A, as shown in FIG. 2, the glass base material 10A is formed by connecting the four glass rods 11, 12, 13, 13a by the three connecting portions 14, 15a, 15b. The same applies to the above.

  In order to satisfactorily start the drawing of the effective portion when drawing the optical fiber preform, as shown in FIG. 2, when connecting the low-viscosity glass rod 11 and the higher-viscosity dummy rod 13, In some cases, a low-viscosity dummy rod 13a is provided to reduce the difference in viscosity at the connecting portion 15a. In such a case, first, a strain removing process (first heating) is started from the connecting portion 15a, and the burner 18 is moved toward the right end of the glass base material 10A. Thereby, while removing the distortion in the connection part 15a and the connection part 15b, the flame polishing of the part from the connection part 15a to the right end is performed.

  Next, as in the case of the first embodiment described above, in the second heating, heating is started slightly from the left side of the left connecting portion 14, the burner 18 is moved in the right direction, and the distortion of the connecting portion 14 is started. Is removed, and the glass rod 11 between the connecting portion 14 and the connecting portion 15a is subjected to flame polishing.

  Even if it does in this way, the effect similar to 1st Embodiment mentioned above can be acquired, generation | occurrence | production of a crack can be suppressed, and the quality glass base material 10A with which impurities, such as dust, cannot adhere to the surface can be obtained. .

  In each of the above-described embodiments, as the strain removal process for the connecting portions 14, 15, 15a, after the strain removal of the connecting portion 15 (15a) on the flame polishing end side (that is, the right side) is performed, (I.e., the left side connection portion 14 is strain-removed, and then the flame polishing step is performed. First, the left connection portion 14 is first strain-removed, then the right-side connection portion 15 is subjected to strain removal, and thereafter You may make it implement a flame grinding | polishing process toward the right from the connection part 14 on the left side. However, in this case, as described above, since the flame polishing process cannot be continuously performed following the strain removal of the left connection portion 14, the flame polishing is performed in three processes.

It is a schematic diagram which shows 1st Embodiment which concerns on the flame polishing method of the glass base material of this invention. It is a schematic diagram which shows the modification of 1st Embodiment. It is a schematic diagram which shows the flame polishing method of the conventional glass base material. It is a schematic diagram which shows the flame polishing method of the conventional glass base material.

Explanation of symbols

10, 10A Glass base material 11 Glass rod 12, 13, 13a Dummy rod (glass rod)
14, 15, 15a, 15b Connection 18 Burner

Claims (4)

A glass base flame-polishing method in which two or more glass rods are flame-polished to a glass base material connected via a connecting portion,
A flame polishing method for a glass base material, wherein a flame polishing step is performed after first performing a strain removing step of removing the strain of the connecting portion by heating the connecting portion and the vicinity of the connecting portion.   The method for flame polishing a glass base material according to claim 1, wherein the strain removing step also serves as flame polishing. The glass base material is a glass rod as an effective portion and a glass rod as a dummy portion connected,
The glass base material flame polishing method according to claim 1, wherein the distortion removing step is performed from the connection portion and the vicinity of the connection portion toward a glass rod as the dummy portion.   The flame polishing method for a glass base material according to claim 3, wherein the flame polishing step is started from the connection portion and the vicinity of the connection portion.

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