JP2003221249A - Method and apparatus for manufacturing quartz glass tube - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To easily and stably manufacture a high-precision fused silica tube necessary for a high-grade optical fiber capable of surely preventing the generation of disadvantages such as thickness deflection and eccentricity. <P>SOLUTION: The method for manufacturing the fused silica tube comprises three parts consisting of a heating zone where a piercing tip 17 pierces a fused silica ingot 13, a preheating zone and a postheating zone in the heating area of a heating furnace 19. The heating temperature in the heating zone is controlled within temperatures above the softening temperature of the fused silica ingot 13 and below the working temperature. The heating temperatures in the preheating zone and postheating zone are controlled below the softening temperature. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for manufacturing a quartz glass tube, and more specifically, a punching jig is brought into contact with the quartz glass material in a heating region of the quartz glass material and the punching jig is press-fitted. Thus, the present invention relates to a method and an apparatus for manufacturing a quartz glass tube in which the quartz glass material is gradually formed into a cylindrical quartz glass tube.

[0002]

Demand for quartz glass tubes is rapidly increasing as parts such as furnace core tubes in the field of semiconductor industry and as preforms for optical fibers. As a method for producing such a quartz glass tube, Japanese Patent No. 2798465 and Japanese Patent Application Laid-Open No. 7-1
The piercing method as described in 09135 is popular.

The piercing method is, as shown in FIG. 6, that a quartz glass material 101 is brought into contact with a perforating jig 102, and the perimeter of the abutting portion of the perforating jig 102 is heated by a heating furnace 103 to form the perforating jig 102. In this method, the quartz glass material 101 is pressed into and pressed into the quartz glass material 101 to gradually form the quartz glass material 101 into a cylindrical quartz glass tube 105 from the tip end side.

The heating furnace 103 has a cylindrical heating element 103a that covers the contact area between the quartz glass material 101 and the punching jig 102, and a coil having an appropriate number of turns arranged around the heating element 103a. 103b.
By heating the heating element 103a to a temperature equal to or higher than the softening point of the quartz glass material 101 by induction heating when an alternating current is applied to the coil 103b, the quartz glass material 101 around the contact portion of the punch jig 102 is heated. To do.

Further, the starting end position of the heating region by the heating element 103a is a, the forming start position where the forming is started by press-fitting the punching jig 102 is b, and the forming jig is from the forming start position b.
When the molding completion position at which the molding by the press-fitting of 02 is completed is defined as c and the end position of the heating region is defined as d, conventionally, each position
Since the temperatures at b, c, and d are induction heating by the single coil 103b, as shown by the temperature distribution characteristic line f5 in FIG. 7, at almost any temperature, the temperature is substantially equal to or higher than the softening point of the quartz glass material 101. Becomes

[0006]

By the way, when the quartz glass tube 105 is used as a preform for an optical fiber, a step of internally sooting a glass layer by a MCVD method or a PCVD method, a rod in collapse method, and the like are further performed. After that, high-speed wire drawing is performed in a predetermined heating environment to obtain an optical fiber. At that time, the quartz glass tube 105
The quality characteristics such as uneven thickness, eccentricity, roundness of the cross section, linearity of the axis line, and the amount of adhering and mixing impurities, which have occurred in the above, are inherited as they are, and greatly affect various performances of the optical fiber.
Therefore, in manufacturing the quartz glass tube 105 as a preform for an optical fiber, it is possible to suppress uneven thickness and eccentricity to improve the roundness of the cross section, improve the linearity of the axis line, and adhere impurities.・ An important issue is to prevent contamination.

However, in the above-mentioned conventional manufacturing method,
In the heating region by the heating element 103a, the entire region from the start end position a to the end position d is heated substantially uniformly to a temperature equal to or higher than the softening point. Therefore, if heating is excessively performed in the section from the starting end position a to the forming start position b, the softened quartz glass material 10
1 has a problem in that it is flexibly deformed by its own weight and causes inconveniences such as uneven thickness and eccentricity when punching by the punching jig 102, and it is difficult to achieve high precision required for a high-quality optical fiber.

Furthermore, if heating is excessively performed in the section from the molding completion position c to the end position d, the softened and molded quartz glass tube 105 is flexibly deformed by its own weight, and the roundness of the cross section is reduced and the axial line There is a problem in that the linearity is reduced, or the quality is reduced, such as the reduction in dimensional accuracy due to the large diameter reduction effect due to surface tension, and it is difficult to achieve the high precision required for high-quality optical fibers. It was

The present invention has been made to solve the above problems, and can reliably prevent the occurrence of inconveniences such as eccentricity and eccentricity, and also reduces the circularity of the cross section and the linearity of the axis. Quartz that suppresses the decrease and prevents the occurrence of a large diameter reduction due to overheating, and can easily and stably manufacture a highly accurate quartz glass tube required for a high-quality optical fiber. An object of the present invention is to provide a glass tube manufacturing method and manufacturing apparatus.

[0010]

A method for manufacturing a quartz glass tube according to claim 1 of the present invention for achieving the above object comprises:
In the method of manufacturing a quartz glass tube, the quartz glass material is gradually formed into a cylindrical quartz glass tube by pressing the punching jig into contact with the quartz glass material in the heating area of the quartz glass material, The area is a pre-heating zone before the molding start position where molding is started by press-fitting the drilling jig, a heat zone from the molding start position to the molding completion position where molding is completed by press-fitting the drilling jig, and the molding completion position The heating temperature in the heat zone is controlled to a temperature range not lower than the working point and not higher than the softening point of the quartz glass material, and the heating temperature in the preheating zone and the postheating zone is the softening point. It is characterized by controlling at the following temperature.

According to the method for producing a quartz glass tube of claim 1, the heating region of the quartz glass material is divided into three regions of a pre-heating zone, a heat zone and a post-heating zone, and the piercing jig is used. In the heat zone for perforation, the heating temperature is controlled above the softening point so that the quartz glass material is softened to a state where it can be easily processed. On the other hand, the heating temperature of each of the pre-heating zone and the post-heating zone located before and after the heat zone is controlled to be equal to or lower than the softening point of the quartz glass material. Therefore, in the pre-heating zone located in front of the heat zone, the quartz glass material does not bend due to softening, so that the perforation can be performed while maintaining the shape of the quartz glass material entering the heat zone. for that reason,
It is possible to reliably prevent the occurrence of inconveniences such as uneven thickness and eccentricity due to the bending of the quartz glass material before perforation. Further, even in the post-heating zone located after the heat zone, the heating temperature is not higher than the softening point, so that the quartz glass tube formed by perforation does not suffer from distortion due to softening.
Therefore, it is possible to suppress a decrease in the roundness of the cross section and a decrease in the linearity of the axis line due to the distortion of the quartz glass tube immediately after molding, and further to prevent the occurrence of a large diameter reduction due to excessive heating. it can.

A method for manufacturing a quartz glass tube according to claim 2 of the present invention for achieving the above object is the method for manufacturing a quartz glass tube according to claim 1, wherein the length of the heat zone is The outer diameter of the quartz glass material is set to 0.5 to 2 times.

According to the manufacturing method of the quartz glass tube of the second aspect, even if the quartz glass materials having different outer diameters are processed into the quartz glass tube, regardless of the skill level of the operator,
The proper heat zone length can be set by simple calculation. Therefore, the processing accuracy of the glass tube can always be kept good.

A method for manufacturing a quartz glass tube according to claim 3 of the present invention for achieving the above object is the method for manufacturing a quartz glass tube according to claim 1 or 2, wherein the boring jig is used. The quartz glass tube formed by press-fitting is forcedly cooled near the end of the heating region.

According to the method for producing a quartz glass tube of claim 3, since the forced air cooling is immediately performed immediately after the heating region, the glass tube after perforation can be cooled quickly, and the bending deformation of the axis line can be achieved. It is possible to prevent the occurrence of inconveniences such as a decrease in the roundness of the cross section and the cross section.

Further, preferably, the forced cooling shown in the method of manufacturing a quartz glass tube according to claim 3 is a method of blowing a gas as described in claim 4, or as described in claim 5. A method of flowing the liquid around the quartz glass tube may be adopted. These cooling methods are
It is possible to easily and flexibly cope with a change in the outer diameter of the formed quartz glass tube.

Further, a quartz glass tube manufacturing apparatus according to a sixth aspect of the present invention for achieving the above object has a heating furnace for heating a quartz glass material, and the quartz glass material is heated in a heating region of the heating furnace. In a quartz glass tube manufacturing apparatus in which a quartz glass material is gradually formed into a cylindrical quartz glass tube by abutting the punching jig and press-fitting the punching jig, the heating furnace is formed by press-fitting the punching jig. It is divided into a pre-heating zone in front of the molding start position, a heat zone from the molding start position to the molding completion position where the molding is completed by press-fitting the punching jig, and a post-heating zone after the molding completion position. It is characterized in that it has a heating region for heating and that the heating temperature can be controlled for each zone of the heating region.

According to the quartz glass tube manufacturing apparatus of the sixth aspect, the heating region of the quartz glass material is divided into three regions of a pre-heating zone, a heat zone and a post-heating zone, and the heating temperature is divided. It can be controlled for each zone.
Therefore, if the heating temperature of the heat zone is controlled to be equal to or higher than the softening point of the quartz glass material, and the heating temperatures of the pre-heating zone and the post-heating zone are controlled to be equal to or lower than the softening point, the distortion of the quartz glass tube immediately after molding is caused. It is possible to suppress a decrease in the circularity of the cross section and a decrease in the linearity of the axis line, and it is possible to prevent a large diameter reduction due to excessive heating. That is, since the quartz glass material does not bend due to softening in the pre-heating zone located in front of the heat zone, perforation can be performed while maintaining the shape of the quartz glass material entering the heat zone. Therefore, it is possible to reliably prevent the occurrence of inconveniences such as uneven thickness and eccentricity due to the bending of the quartz glass material before perforation. Further, even in the post-heating zone located after the heat zone, distortion due to softening does not occur in the quartz glass tube formed by perforation.

Preferably, the heating furnace shown in the quartz glass tube manufacturing apparatus according to claim 6 is the heating furnace according to claim 7.
As described in, a cylindrical heating element that covers the periphery of the quartz glass material in the heating area, a plurality of sets of coils arranged on the outer circumference of the heating element for each zone of the heating area, and a coil for each zone of the zone. It is preferable that the induction heating furnace includes an electric current control unit capable of controlling an alternating current to be flown, and heats the heating element to a predetermined temperature distribution by induction heating when a high frequency current is passed through each coil.

The apparatus for manufacturing a quartz glass tube according to claim 8 of the present invention for achieving the above object is the apparatus for manufacturing a quartz glass tube according to claim 6 or 7, wherein heating is performed by a heating furnace. A cooling device for forcibly cooling the molded quartz glass tube is provided near the end of the region.

According to the quartz glass tube manufacturing apparatus of the eighth aspect, the forced air cooling is immediately performed immediately after the heating region, so that the glass tube after perforation can be quickly cooled and the bending deformation of the axis line can be achieved. It is possible to prevent the occurrence of inconveniences such as a decrease in the roundness of the cross section and the cross section.

In the above manufacturing method and manufacturing apparatus, as the quartz glass material, specifically, a quartz glass rod, a quartz glass ingot, a quartz glass pipe or the like finished to a predetermined size by an appropriate manufacturing method is used. It can be mentioned.

[0023]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of a method and an apparatus for manufacturing a quartz glass tube according to the present invention will be described below with reference to FIGS. FIG. 1 is a schematic view showing a quartz glass tube manufacturing apparatus of the present invention, and FIG. 2 is a schematic view of the vicinity of the heating furnace shown in FIG. FIG. 3 is a graph showing the temperature distribution of the heating region by the heating furnace shown in FIG. 2, and FIG. 4 is a graph showing the range of the length of the heat zone shown in FIG. Further, FIG. 5 is a schematic diagram showing a modified example of the cooling device shown in FIG.

As shown in FIG. 1, a quartz glass tube manufacturing apparatus 11 of the present embodiment is for manufacturing a quartz glass tube by a so-called piercing method.
A heating furnace 19 for heating the heating furnace 19, an upstream side fixing base 21 arranged upstream of the heating furnace 19, and a downstream side fixing base 27 arranged downstream of the heating furnace 19 are provided.

On the upstream fixed base 21, there is provided a first moving table 15 which holds one end of a glass ingot 13 made of a glass material and slides in the left-right direction in the drawing. The first moving table 15 can slide at a desired speed, and further, the glass ingot 1
It is possible to rotate the glass ingot 13 about its longitudinal axis by gripping the chuck 3 with the chuck 15a. Further, a supporter 23 that supports the weight of the glass ingot 13 is provided on the upstream-side fixed base 21. The supporter 23 is a gripped glass ingot 1
The height of the glass ingot 13 can be changed according to the height of the glass ingot 3, and can be slid on the upstream side fixed base 21 in the axial direction of the glass ingot 13. In addition, the support portion 23a of the supporter 23
Is a roller that does not restrain the axial rotation of the glass ingot 13.

Further, on the downstream side fixed base 27, one end of the glass dummy pipe 14 is gripped, and the second movement is possible in accordance with the movement of the first movement table 15 so as to be slidable in the horizontal direction in the drawing. A table 29 is provided. The second moving table 29 is capable of rotating the gripped dummy pipe 14 about its longitudinal axis. Further, the rotation is adjusted in accordance with the rotation of the glass ingot 13 by the first moving table 15.

The other end of the glass ingot 13, which is not gripped by the first moving table 15, has the second moving table 2
It is fused with the other end of the dummy pipe 14 gripped by 9. Therefore, the glass ingot 13 and the dummy pipe 14 are gripped by the first moving table 15 and the second moving table 29 in a state where they are integrally introduced in the heating furnace 19 in the axial direction.

Further, a support base 31 is provided on the downstream side fixed base 27, by which the fixed shaft 25 of the punching jig is supported. The punching jig includes a punching piece 17 provided at the tip of the fixed shaft 25. The fixed shaft 25 has the same central axis as the punching piece 17, and is supported by the glass ingot 13 in a state where the central axis coincides. In addition, by the supporter 23 provided on the downstream side fixed base 27,
The weight of the fixed shaft 25 is supported.

As shown in FIG. 2, the heating furnace 1 of the present embodiment.
Reference numeral 9 denotes a high frequency induction heating type furnace, which includes coils 43a to
The heating element 41 generates heat by applying an alternating current to 43f.
The heating element 41 is a cylindrical graphite that covers the periphery of the contact portion between the glass ingot 13 and the punching piece 17, and heats the glass ingot 13 by the heat generated by the heating element 41 to soften it.
The alternating current flowing through the coils 43a to 43f can be controlled by the current control means 45.

Further, in the present embodiment, the heating area by the heating element 41 is a pre-heating zone Z1 for heating an unformed portion of the glass ingot 13 and a heat zone Z2 for heating a material forming section for punching the glass ingot 13. ,
Post-heating zone Z for heating the perforated glass tube 14
It is divided into 3. The pre-heating zone Z1 has a starting end position a.
From the glass ingot 13 by press-fitting the punching piece 17.
This is a section from the molding start position b for drilling to the front.
The heat zone Z2 is a material forming section from the forming start position b to the forming completion position c at which the punching by the press-fitting of the punching piece 17 is completed. The post-heating zone Z3 is a section from the molding completion position c to the end position d of the heating region.

Among the six coils 43a to 43f, the coils 43a and 43b are in the pre-heating zone Z1 of the above heating region, the coils 43c and 43d are in the heat zone Z2 of the above heating region, and the coils 43e and 43f are the same. Are respectively assigned to the post-heating zones Z3 mentioned above. Further, the current control means 45 is capable of controlling the alternating current to be supplied independently for each section of the heating region and further for each coil assigned to each section.

As shown in FIG. 3, the temperature distribution in the heating region is set as shown by the curve f1 by controlling the current supplied to the coils arranged in each section by the current control means 45. That is, the heat zone Z2 (b to c)
The heating temperature is controlled to a temperature range above the softening point of the glass ingot 13 and below the working point. Further, the heating temperature in the pre-heating zone Z1 (ab) is controlled to a temperature equal to or lower than the softening point of the glass ingot 13, and the post-heating zone Z1.
The heating temperature in 3 (c to d) is the glass ingot 1
It is controlled to a temperature range below the softening point of 3 and above the annealing point.

For example, the temperatures of the annealing point, the softening point, and the working point of the silica glass of pure silica produced by the VAD method with few impurities are 1200 ° C., 1700 ° C., and 220 ° C., respectively.
It is about 0 ° C. Such an annealing point, a softening point, and a working point are related to the composition of the glass ingot 13 (impurity content).
It changes depending on, but basically it is defined as follows.

The slow cooling point is the temperature at which the viscosity of quartz glass becomes 10 ¹² Pascal seconds (Pa · s), and corresponds to the temperature at which the internal strain generated during glass processing is removed in about 15 minutes.
The softening point is the temperature at which the viscosity of quartz glass is 10 ^6.6 Pascal seconds (Pa · s), and the diameter is 0.55 to 0.7.
1 mm when glass fiber of 5 mm and length of 23 cm is heated
Corresponds to the temperature of elongation at a speed of / min. What is a working point?
It is the temperature at which the viscosity of quartz glass is 10 ³ Pascal seconds (Pa · s), which is the upper limit temperature of the working temperature range.

By the way, the required length of the heat zone Z2 is the outer diameter of the glass ingot 13 and the punching piece 1.
It is necessary to change according to the size and shape of 7. Therefore, if the length of the heat zone Z2 is set depending on the skill of the operator, the length of the heat zone Z2 varies,
It becomes a factor that makes product quality unstable. Therefore, as shown in FIG. 4, in the present embodiment, the length of the heat zone Z2 is set to be a linear function f2, f of the outer diameter of the glass ingot 13.
3, f4. The linear function f2 is for obtaining the reference value of the length of the heat zone, and the linear functions f3, f
4 sets the tolerance from the reference value. The function f2 is Y = X where X is the outer diameter of the ingot and Y is the length of the heat zone. Also, the function f3 is Y = 2X
And the function f4 is Y = 0.5X. Therefore,
The length of the heat zone may be set within a range between the linear function f3 and the linear function f4. For example, when the outer diameter of the ingot is X ₁ , the length of the heat zone is 0.5X ₁ to 2
Set during X ₁ .

Further, the post-heating zone Z3 (c-
In d), the heating temperature is gradually lowered to the annealing point in order to prevent residual strain due to rapid cooling. Then, in the present embodiment, the section Z4 from the end d of the heating region to the position e which is separated by a minute distance is naturally cooled,
Immediately after division Z4 (actually, near the outlet of the heating furnace 19)
In addition, a cooling device 51 for forcibly cooling the molded quartz glass tube to room temperature is provided. Cooling device 51 in the present embodiment is a gas cooling type in which cooling gas 53 is blown onto glass tube 14. As the cooling gas 53, for example, an inert gas such as nitrogen gas, helium gas, or argon gas, or clean air may be used.

In the quartz glass tube manufacturing apparatus 11 described above, the glass ingot 13 fed into the heating furnace 19 is
The glass ingot 13 is gradually molded into a cylindrical quartz glass tube 14 from the tip side by press-fitting the punching piece 17 while heating to the above-mentioned temperature distribution. And the heating furnace 19
The heating temperature in the heat zone Z2 of the three zones of the heating region is controlled to a temperature range above the softening point of the quartz glass material 13 and below the working point, and the heating temperatures in the pre-heating zone Z1 and the post-heating zone Z3 are In both cases, the temperature is controlled to a temperature below the softening point.

Therefore, in the pre-heating zone Z1 located in front of the heat zone Z2, the glass ingot 13 does not bend due to softening, so that the heat zone Z2
Perforation can be performed while maintaining the shape of the entering glass ingot 13. Therefore, it is possible to reliably prevent the occurrence of inconveniences such as uneven thickness and eccentricity due to the bending of the glass ingot 13 before punching. Also, in the post-heating zone Z3 located after the heat zone Z2, the heating temperature is not higher than the softening point, so that the quartz glass tube 14 formed by perforation does not have distortion due to softening.
Therefore, it is possible to suppress a decrease in the roundness of the cross section and a decrease in the linearity of the axis line due to the bending of the glass tube 14 immediately after molding, and further it is possible to prevent the occurrence of a large diameter reduction due to excessive heating. it can. That is, there is no eccentricity or eccentricity,
It is possible to easily and stably manufacture a highly accurate quartz glass tube required for a high-quality optical fiber, such as a circularity of a cross section being high and an axial linearity being excellent.

Further, in the present embodiment, the heat zone Z2
Since the length is set by a linear function of the outer diameter of the glass ingot 13, even when processing glass ingots having different outer diameters into glass tubes, regardless of the skill level of the operator, a simple calculation is performed. Can set an appropriate length of the heat zone, and can stabilize the quality of the glass tube to be manufactured.

Further, since the forced air cooling is immediately carried out immediately after the heating area, the glass tube after perforation can be quickly cooled, and the inconvenience such as the bending deformation of the axis line and the reduction of the circularity of the cross section is caused. Can be prevented.

Further, since the forced cooling of the present embodiment is gas cooling, it is possible to easily and flexibly deal with the change of the outer diameter of the glass tube to be formed.

The cooling device 51 shown in FIG. 2 may use a water cooling pipe 63 as shown in FIG. 5 instead of gas cooling. As shown in FIG. 5, a quartz glass tube manufacturing apparatus 6
In No. 0, a water cooling pipe 63 for forcibly cooling the molded glass pipe to room temperature is provided near the outlet of the heating furnace 19. The water cooling pipe 63 is formed in a cylindrical shape so as to surround the periphery of the molded glass pipe, and the cooling water supplied to the inside of the pipe is circumferentially flowed and discharged. Since the cooling water is constantly supplied into the tube and the cooling water in the tube is constantly flowing, a stable radiative cooling effect can be obtained for the glass tube. Further, it is possible to easily and flexibly cope with the change of the outer diameter of the glass tube to be formed.

(Examples) Examples of the present invention will be described below. The uneven thickness ratio was compared between the example of the glass tube manufactured according to the above embodiment and the comparative example of the glass tube manufactured with the conventional temperature distribution in the heating area. .

In both the example and the comparative example, the outer diameter was 4
A glass ingot having a length of 6 mm and a length of 1000 mm was perforated using a perforation piece having an outer diameter of 40 mm, and the outer diameter was 10 mm.
A large quartz glass tube having a diameter of 0 mm, an inner diameter of 40 mm and a length of 1000 mm was manufactured. Regarding these Examples and Comparative Examples, the different manufacturing conditions were only the temperature distribution in the above heating region, and the rotation speed of the ingot and other conditions were matched. In the example according to the present invention, the above manufacturing apparatus 11 was used to set the temperature distribution as shown in FIG. here,
The length of the heat zone was set to 45 mm and the maximum heating temperature was set to 1800 ° C. On the other hand, in the comparative example, the manufacturing apparatus 11 was used, but the temperature distribution in the heating region was set to be constant in the longitudinal direction, which is the conventional temperature distribution as shown in FIG. 7. The constant heating temperature was set to 1800 ° C.

With respect to each manufactured glass tube, each glass tube was rotated, and the maximum value t _max and the minimum value t _min of the wall thickness of the tube wall were measured at intervals of 50 mm in the length direction. Then, the uneven thickness ratio H was calculated using the following [Equation 1].

[0046]

[Equation 1]

As a result, in the case of the embodiment according to the present invention,
While the maximum value of the wall thickness deviation over the entire length of the tube was 0.50%, the maximum value of the wall thickness deviation over the entire length of the tube was 3% in the comparative example according to the conventional manufacturing method. From the above results, the uneven thickness ratio can be reduced to about 1/6 by manufacturing according to the temperature distribution of the present embodiment, and the effect obtained by the present invention can be clearly confirmed.

[0048]

As described above, according to the method and apparatus for manufacturing a quartz glass tube of the present invention, the heating area of the quartz glass material is in three areas of the pre-heating zone, the heat zone and the post-heating zone. It is divided and the heating temperature can be controlled for each division zone. Therefore, if the heating temperature of the heat zone is controlled to be equal to or higher than the softening point of the quartz glass material, and the heating temperatures of the pre-heating zone and the post-heating zone are controlled to be equal to or lower than the softening point, the distortion of the quartz glass tube immediately after molding is caused. It is possible to suppress a decrease in the circularity of the cross section and a decrease in the linearity of the axis, and it is possible to prevent the occurrence of a large diameter reduction due to excessive heating. That is, since the quartz glass material does not bend due to softening in the pre-heating zone located in front of the heat zone, perforation can be performed while maintaining the shape of the quartz glass material entering the heat zone. Therefore, it is possible to reliably prevent the occurrence of inconveniences such as uneven thickness and eccentricity due to the bending of the quartz glass material before perforation. Further, even in the post-heating zone located after the heat zone, distortion due to softening does not occur in the quartz glass tube formed by perforation. Therefore, a highly accurate quartz glass tube required for a high-quality optical fiber can be easily and stably manufactured.

[Brief description of drawings]

FIG. 1 is a schematic view showing a quartz glass tube manufacturing apparatus of the present invention, and FIG. 2 is a schematic view of the vicinity of the heating furnace shown in FIG.
FIG. 3 is a graph showing the temperature distribution of the heating region by the heating furnace shown in FIG. 2, and FIG. 4 is a graph showing the range of the length of the heat zone shown in FIG. Further, FIG. 5 is a schematic diagram showing a modified example of the cooling device shown in FIG.

FIG. 1 is a schematic diagram showing a quartz glass tube manufacturing apparatus of the present invention.

FIG. 2 is a schematic diagram near the heating furnace shown in FIG.

3 is a graph showing a temperature distribution in a heating region by the heating furnace shown in FIG.

FIG. 4 is a graph showing a range of length of the heat zone shown in FIG.

5 is a schematic diagram showing a modified example of the cooling device shown in FIG.

FIG. 6 is a schematic view of a main part of a conventional quartz glass tube manufacturing apparatus.

7 is a graph showing a temperature distribution in the heating furnace shown in FIG.

[Explanation of symbols]

11 Quartz glass tube manufacturing equipment 13 Glass ingot (quartz glass material) 14 Quartz glass tube 15 First moving table 17 Punching piece (piercing jig) 19 heating furnace 21 upstream fixed base 25 fixed axis 27 Downstream fixed base 29 Second moving table 41 heating element 43a to 43f coils 45 Current control means 51 Cooling device 60 Quartz glass tube manufacturing equipment 63 Water cooling pipe (cooling device)

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Claims (8)

[Claims] 1. A quartz which gradually forms the quartz glass material into a cylindrical quartz glass tube by abutting a punching jig on the quartz glass material in a heating region of the quartz glass material and press-fitting the punching jig. In the method for manufacturing a glass tube, in the heating region, a pre-heating zone before a molding start position where molding is started by press-fitting the punching jig, and molding by press-fitting the punching jig is completed from the molding start position. A heat zone up to the molding completion position and a post-heating zone after the molding completion position are divided, and the heating temperature in the heat zone is controlled within a temperature range not lower than the working point and not lower than the softening point of the quartz glass material. A method for manufacturing a quartz glass tube, characterized in that the heating temperature in the pre-heating zone and the post-heating zone is controlled to a temperature not higher than the softening point. 2. The method for producing a quartz glass tube according to claim 1, wherein the length of the heat zone is set to 0.5 to 2 times the outer diameter of the quartz glass material. 3. The method for manufacturing a quartz glass tube according to claim 1, wherein the quartz glass tube formed by press-fitting the punching jig is forcibly cooled near the end of the heating region. . 4. The method for manufacturing a quartz glass tube according to claim 3, wherein the forced cooling is performed by blowing a gas. 5. The method for manufacturing a quartz glass tube according to claim 3, wherein the forced cooling is performed by causing a liquid to flow around the quartz glass tube. 6. A quartz furnace having a heating furnace for heating a quartz glass material, wherein the quartz glass material is brought into contact with a punching jig in a heating region of the heating furnace, and the punching jig is press-fitted to obtain the quartz glass. In a quartz glass tube manufacturing apparatus for gradually forming a raw material into a cylindrical quartz glass tube, the heating furnace is a pre-heating zone before a molding start position where molding is started by press-fitting the perforating jig, and the molding start A heating zone from a position to a molding completion position where the molding is completed by press-fitting a piercing jig, and a heating area divided into a post-heating zone after the molding completion position, and each of the above-mentioned heating area division zones An apparatus for manufacturing a quartz glass tube, characterized in that the heating temperature is controllable. 7. The heating furnace comprises: a cylindrical heating element that covers the periphery of the quartz glass material in the heating area; and a plurality of sets of heating elements arranged on the outer periphery of the heating element for each of the section zones of the heating area. A coil and a current control means capable of controlling an alternating current flowing through the coil for each of the section zones,
The apparatus for manufacturing a quartz glass tube according to claim 6, wherein the induction heating furnace heats the heating element to a predetermined temperature distribution by induction heating when a high-frequency current is applied to each of the coils. 8. The quartz glass tube according to claim 6, further comprising a cooling device for forcibly cooling the formed quartz glass tube near the end of the heating region of the heating furnace. Manufacturing equipment.