JP2017218329A - Seal structure of optical fiber drawing furnace and method for manufacturing optical fiber - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide the seal structure of an optical fiber drawing furnace capable of suppressing increase in friction coefficient to excellently maintain the slidability of a blade member, and a method for manufacturing an optical fiber.SOLUTION: The seal structure of an optical fiber drawing furnace for blocking a space between the upper end opening of the optical fiber drawing furnace and an optical fiber glass preform inserted from the upper end opening comprises: blade members 14 and 15 contacting the side surface of the optical fiber glass preform in the circumferential direction; and a housing 11 for housing the blade members and guide members 16 and 17 for slidably supporting the blade members. At least a part or the entire of a sliding surface between the blade member and guide member in the housing is in a space in an atmosphere including at least moisture or oxygen of 0.1% or more.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a sealing structure for an optical fiber drawing furnace and an optical fiber manufacturing method, and more specifically, an upper end opening of an optical fiber drawing furnace and an optical fiber glass base material inserted from the upper end opening. The present invention relates to a sealing structure of an optical fiber drawing furnace for closing a gap between the two, and a method for manufacturing an optical fiber.

  The optical fiber is a glass base material for optical fiber (hereinafter referred to as glass base material) mainly composed of quartz, inserted into the core tube from the upper end opening of an optical fiber drawing furnace (hereinafter referred to as drawing furnace), When the tip of the glass base material is heated and melted to reduce the diameter, the glass base material is drawn from below the drawing furnace. Since the temperature in the drawing furnace at this time is as high as about 2000 ° C., carbon having excellent heat resistance is used for the parts in the drawing furnace.

  In this case, the inside of the drawing furnace is set to a positive pressure to prevent outside air (oxygen) from entering the drawing furnace. However, the gap between the upper end opening of the drawing furnace and the glass base material is well sealed. Otherwise (unsealed), outside air is drawn into the drawing furnace and affects the life of the drawing furnace. For example, Patent Document 1 discloses a technique of a seal structure for closing a gap between an upper end opening of a drawing furnace and a glass base material.

JP 2012-106915 A

  By the way, in the technique of the above-mentioned Patent Document 1, a blade member (sealing element) that contacts the side surface of the glass base material is housed in a housing (chamber). These components are oxidized and deteriorated when oxygen is mixed into the drawing furnace. For this reason, considering that all or part of the gas supplied into the housing leaks into the drawing furnace, the inside of the housing is set to the same inert gas atmosphere as in the drawing furnace. However, when the inside of the housing is in an inert gas atmosphere and carbon, quartz, or metal is used for the blade member or guide member, the friction coefficient of the contact surface of the blade member increases at high temperatures, and the slidability of the blade member decreases. It turns out that there is a case.

  The present invention has been made in view of the above circumstances, and has an optical fiber drawing furnace seal structure that suppresses an increase in the coefficient of friction and maintains good slidability of the blade member, and an optical fiber manufacturing method. The purpose is to provide.

  An optical fiber drawing furnace seal structure according to an aspect of the present invention closes a gap between an upper end opening of an optical fiber drawing furnace and an optical fiber glass preform inserted from the upper end opening. An optical fiber drawing furnace seal structure for a blade member abutting on a circumferential side surface of the optical fiber glass preform, and housing the blade member and slidably supporting the blade member And a space in an atmosphere in which at least a part or all of the sliding surfaces of the blade member and the guide member in the housing contains at least 0.1% of moisture or oxygen. It is in.

  According to the above, it is possible to satisfactorily maintain the slidability of the blade member with respect to the guide member while suppressing an increase in the friction coefficient.

It is a figure explaining the outline of the drawing furnace for optical fibers by one Embodiment of this invention. It is a figure which shows an example of a seal structure. It is a figure explaining the blade member and guide member of FIG. It is AA arrow sectional drawing of FIG. It is a figure which shows an example of the cylindrical slit spring of a seal structure. It is a figure which shows the other example of a blade member.

[Description of Embodiment of the Present Invention]
First, the contents of the embodiment of the present invention will be listed and described.
An optical fiber drawing furnace seal structure according to an aspect of the present invention includes: (1) an upper end opening of an optical fiber drawing furnace and an optical fiber glass preform inserted from the upper end opening; A sealing structure for an optical fiber drawing furnace for closing a gap, a blade member abutting on a circumferential side surface of the optical fiber glass preform, and housing the blade member, and sliding the blade member A housing that accommodates a freely supporting guide member, and at least a part or all of the sliding surfaces of the blade member and the guide member in the housing contains at least 0.1% or more of moisture or oxygen. It is in a space of atmosphere. By making the inside of the casing into an atmosphere containing moisture or an atmosphere containing oxygen, an increase in the friction coefficient can be suppressed and the slidability of the blade member with respect to the guide member can be maintained well.

(2) The atmosphere containing moisture or oxygen is an air atmosphere. If the inside of the housing is in an air atmosphere (atmosphere made of air with 21% oxygen and a humidity of 0.1 to 80%), an atmosphere containing moisture or a space containing oxygen can be easily formed.
(3) The pressure in the optical fiber drawing furnace is higher than the pressure in the housing. It is possible to prevent the moisture and oxygen in the housing from entering the drawing furnace by making the inside of the drawing furnace more positive than in the housing.

(4) At least one of the blade member or the guide member is formed of carbon. By creating an atmosphere containing moisture or oxygen in the housing, even if carbon is used for any member, the self-lubricating property of carbon will not be lost at high temperatures. Can be suppressed.
(5) At least one of the blade member or the guide member is made of metal. By making the inside of the housing an atmosphere containing moisture or an atmosphere containing oxygen, even if a metal is used for any of the members, an oxide film on the surface can be maintained, so that an increase in the coefficient of friction can be suppressed.
(6) The metal may include any of stainless steel, molybdenum disulfide, fluorine-coated metal, gold-plated metal, chromium nitride-coated metal, and DLC (diamond-like carbon) -coated metal.
(7) At least one of the blade member or the guide member is formed of quartz glass. Even if quartz glass is used for any member, the increase in the coefficient of friction is suppressed by making the inside of the housing an atmosphere containing moisture or oxygen, even if quartz glass is used for any member. it can.

(8) The blade member is made of a plurality of materials. Even if the front part contacts the glass by changing the material of the front part that contacts the glass base material and the material of the rear part that slides against the guide member, the blade member is composed of multiple materials. No material (carbon, quartz glass), and the rear part can be other materials (metal, etc.).
(9) The guide member is water-cooled. By cooling with water, it is possible to suppress deterioration of the carbon and metal used for the guide member due to heat.

(10) In the optical fiber manufacturing method according to an aspect of the present invention, the optical fiber is drawn by using any one of the above-described seal structures of a drawing furnace for an optical fiber. Since the above-described seal structure is used, the airtight ability during drawing can be maintained. Further, it is possible to prevent the glass base material and the seal structure from being damaged when the glass base material is inserted or taken out.

[Details of the embodiment of the present invention]
DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, preferred embodiments of a sealing structure for an optical fiber drawing furnace and an optical fiber manufacturing method according to the invention will be described with reference to the accompanying drawings. In the following, a resistance furnace that heats the core tube with a heater will be described as an example. However, the present invention can also be applied to an induction furnace in which a high-frequency power source is applied to the coil to induction-heat the core tube. Moreover, what is demonstrated below also about the suspension mechanism of a glass base material, the structure of a heat insulating material, etc. is an example, and is not limited to this.

  FIG. 1 is a diagram for explaining the outline of an optical fiber drawing furnace according to an embodiment of the present invention. The drawing furnace 1 includes a furnace casing 2, a furnace core tube 3, a heating source (heater) 4, and a seal structure 10. The furnace housing 2 has an upper end opening 2a and a lower end opening 2b, and is made of, for example, stainless steel. The core tube 3 is formed in a cylindrical shape at the center of the furnace housing 2 and communicates with the upper end opening 2a. The core tube 3 is made of carbon, and the glass base material 5 is inserted into the core tube 3 while being sealed by the seal structure 10 from the upper end opening 2a.

  In the furnace casing 2, a heater 4 is disposed so as to surround the furnace core tube 3, and a heat insulating material 7 is accommodated so as to cover the outside of the heater 4. The heater 4 heats and melts the glass base material 5 inserted into the core tube 3, and hangs down the optical fiber 5b melted and reduced in diameter from the lower end portion 5a. The glass base material 5 can be moved in a drawing direction (downward direction) by a separately provided moving mechanism, and a support bar 6 for hanging and supporting the glass base material 5 on the upper side of the glass base material 5. Are connected. Further, the drawing furnace 1 is provided with a furnace gas supply mechanism (not shown) using an inert gas or the like, and an inert gas or the like for preventing oxidation or deterioration is provided in the furnace core tube 3 or around the heater 4. It can be supplied.

  Although FIG. 1 shows an example in which the upper end portion of the inner wall of the core tube 3 forms the upper end opening 2a as it is, the present invention is not limited to this. For example, an upper lid that is an upper end opening narrower than the inner diameter d of the core tube 3 may be provided on the upper side of the core tube 3, and in this case, the gap to be sealed is the narrow upper end opening and the glass base material 5. It becomes a gap generated between the two. In addition, the cross-sectional shape of the glass base material 5 is basically generated to aim at a perfect circle, but some non-circles may exist regardless of the accuracy, and the glass base material 5 may have an elliptical shape. May be. The upper end opening 2a may have a circular cross section, but this accuracy does not matter.

  One embodiment of the present invention is directed to a seal structure 10 for closing a gap S between an upper end opening 2a of a drawing furnace 1 and an outer periphery of a glass base material 5 inserted from the upper end opening 2a. In particular, the glass base material 5 in the drawing furnace is heated by the heater 4 while the outside air outside the furnace is not caught by the seal structure 10 provided in the upper end opening 2a.

Hereinafter, an example of the seal structure will be described with reference to FIGS. 2 is a diagram illustrating an example of a seal structure, FIG. 3 is a diagram illustrating the blade member and the guide member in FIG. 2, FIG. 4 is a cross-sectional view taken along the line AA in the housing in FIG. 2, and FIG. It is a figure which shows an example of the cylindrical slit spring of a seal structure.
The seal structure 10 includes a plurality of blade members 14 and 15 having heat resistance, and the blade members 14 and 15 and guide members 16 and 17 for sliding the blade members 14 and 15 linearly. And a body 11. In addition, it is good also as a structure which integrally molded the housing | casing and the guide member so that a part of housing | casing may become a guide member.

  As shown in FIG. 2, the casing 11 is a disk-shaped member having concentric through holes, and an opening for inserting the blade member 15 as shown in FIG. As shown in FIG. 3B and FIG. 3B which is a cross-sectional view deeper than FIG. 3A, the openings 11a for inserting the blade member 14 are alternately formed on the inner peripheral surface of the housing 11, for example. Is provided. The housing 11 is made of, for example, stainless steel, and the blade members 14 and 15 are cooled to 400 ° C. or lower (preferably 300 ° C. or lower in the case of a carbon blade member). It can also have a mechanism (for example, a water cooling system), and can cool a guide member mentioned below by this.

  The blade members 14 and 15 are radially installed with respect to the central axis of the housing 11 and installed in the housing 11. A plurality of blade members 14 are provided at equal intervals along the inner peripheral surface of the housing 11. A plurality of blade members 15 are also provided at equal intervals along the inner peripheral surface of the housing 11. For example, the blade members 14 and 15 have a substantially rectangular parallelepiped shape in which a cross-sectional shape in a plane perpendicular to the moving direction is a substantially rectangular shape, and are arranged alternately in two upper and lower stages.

As shown in FIG. 3, the blade members 14 and 15 are protruded from the housing 11 and can be brought into contact with the circumferential side surfaces of the glass base material 14a and 15a. As shown in FIG. 11, the outer peripheral surface portions 14 b, 14 c, 14 d, 14 e, 15 b, 15 c, 15 d, 15 e that slide in contact with the guide members 16, 17 are pressed against a blade member, for example, a cylindrical slit spring 18 as described later. The rear end portions 14f and 15f are in contact with each other. The outer peripheral surface portions 14b to 14e and 15b to 15e correspond to the sliding surfaces of the present invention.
When the tip portions 14a and 15a abut on the side surface of the glass base material, it is necessary to make the gap with the glass base material as small as possible. For this reason, it is preferable to make the front-end | tip of the front-end | tip parts 14a and 15a into the circular arc shape which has a curvature suitable for the maximum value (maximum diameter of the glass base material to be used) assumed as the radius of a glass base material.

  When the tip portions 14a and 15a are in contact with the side surfaces of the glass base material, a gap is not generated in the vertical direction between the tip portion 14a and the tip portion 15a, and further, a gap generated in the adjacent tip portion 14a. Is filled with the tip portion 15a, and a gap generated at the adjacent tip portion 15a is filled with the tip portion 14a. Thereby, it is possible to seal the gap S in FIG. 1 so that the outside air is not caught in the furnace.

  The material of the blade members 14 and 15 is preferably carbon. Carbon is not only excellent in heat resistance, but it is a soft material, so there is no worry of damaging the glass base material. In particular, it is preferable to employ soft carbon having a Shore hardness of 100 or less for the blade members 14 and 15 of this example. Carbon is also preferred in that it can be easily molded by press molding or machining.

Further, as a material of the blade members 14 and 15, for example, quartz glass, SiC coated carbon, or the like can be employed in addition to carbon. Even when other hard materials are used, it is possible to prevent the glass base material from being damaged, for example, by using soft carbon only at the tip portion.
The width and the number of the blade members 14 and 15 described above may be appropriately selected according to the outer diameter, the outer diameter fluctuation amount, the bending amount, and the like of the glass base material to be used.

  As shown in FIGS. 3 and 4, the guide members 16 and 17 are formed in a cylindrical shape through which the outer peripheral surface portions 14b to 14e and 15b to 15e of the blade members 14 and 15 are inserted. Has been. Specifically, the guide members 16 and 17 have sliding surfaces 16c to 16e and 17d positioned around the outer peripheral surface portions 14b to 14e of the blade member 14, and the sliding surfaces 16c to 16e and 17d are formed on the blade member 14. It is comprised so that contact | abutting to the outer peripheral surface parts 14b-14e from four directions. Moreover, it has sliding surfaces 16b, 17b, 17c, and 17e positioned around the outer peripheral surface portions 15b to 15e of the blade member 15 at a position lower than the sliding surface 17d, and the sliding surfaces 16b, 17b, 17c, 17e is comprised so that the outer peripheral surface parts 15b-15e of the blade member 15 can contact | abut from four directions. Note that the sliding surfaces 16b to 16e and 17b to 17e of the guide members 16 and 17 also correspond to the sliding surfaces of the present invention.

The material of the guide members 16 and 17 is also preferably carbon, but it is also possible to employ metals such as boron nitride (BN) and, in the case of metals, stainless steel, molybdenum disulfide (MoS ₂ ), and the like. Alternatively, a metal having an oxide film, a metal having various coatings such as a fluorine coat, gold plating, a chromium nitride coat, a DLC (diamond-like carbon) coat, or quartz glass may be employed.

  Next, the cylindrical slit spring 18, which is an example of a mechanism for pressing the blade member, is installed so as to contact the rear end portions 14 c and 15 c of the blade members 14 and 15, and as shown in FIG. The slits 18a from the vertical direction and the slits 18b from the downward direction are alternately formed. The material of the cylindrical slit spring 18 is desirably formed of any one of heat-resistant materials such as carbon, ceramics, carbon-ceramic composite material, and metal material, and has heat resistance of 200 ° C. or higher. Is preferred.

  The tips of the plurality of blade members 14 and 15 are brought into contact with the side surfaces of the glass base material by the contracting force in the cylindrical radial direction by the cylindrical slit spring 18. Thereby, even if the glass base material 5 descends as shown by an arrow in FIG. 2 due to the progress of drawing, and the outer diameter of the glass base material 5 increases, for example, from φ1 to φ2 (> φ1), the cylindrical slit spring 18 extends outward in a state where the blade members 14 and 15 are tightened uniformly in the circumferential direction. Conversely, when the outer diameter of the glass base material 5 decreases, the cylindrical slit spring 18 can be contracted inward with the blade members 14 and 15 tightened uniformly in the circumferential direction. The cylindrical slit spring 18 is an example of a mechanism that presses the blade member. Besides the slit spring, the blade member may be pushed and pulled by gas supply / exhaust, or a coil spring or an air cylinder may be used.

Incidentally, the housing 11 shown in FIG. 2 is provided with a supply / exhaust port 13 that connects the air reservoir 12 inside the housing 11 to the outside of the housing 11 and introduces air from the outside. The sliding surfaces between the blade members 14 and 15 and the guide members 16 and 17 are disposed in a space having an atmosphere containing at least moisture or oxygen of 0.1% or more.
When a carbon blade member and guide member are used, the bonding between carbons becomes strong in a high-temperature inert gas atmosphere free of moisture and oxygen. The slidability is maintained in a deteriorated state. However, if the inside of the housing is in an atmosphere containing moisture (an atmosphere that is not dry) or an atmosphere containing oxygen, the bonding between the carbons does not become strong, and the slidability of the blade member with respect to the guide member is maintained well. be able to. That is, if the atmosphere contains moisture or oxygen, the self-lubricating property of carbon is not lost, so that an increase in the friction coefficient can be suppressed.
It should be noted that it is preferable not to bring the members into contact with each other in a place where a high-temperature inert gas atmosphere without moisture or oxygen exists, for example, between the casing 11 and the blade members 14 and 15 close to the atmosphere in the drawing furnace. It is preferable to leave a slight gap so as not to contact.

In addition, for example, when a metal having an oxide film is used for the guide member, the oxide film is removed in an inert gas atmosphere, so that the slidability deteriorates. However, outside air (oxygen) is supplied into the housing. If the inside of the casing is in an atmosphere containing oxygen, an increase in the coefficient of friction can be suppressed, so that the slidability of the blade member can be maintained well.
In addition, for example, when a quartz glass blade member and a guide member are used, if the inside of the housing is in an atmosphere containing moisture (non-dry atmosphere), friction that increases in a dry state that has been cleaned and polished by cleaning is increased. Since it does not occur, the slidability of the blade member can be maintained well.
Similarly, when carbon is used for the blade member and materials other than carbon are used for the guide member, the above materials are combined as the respective members. It is difficult for the friction coefficient to increase on the moving surface, and the slidability of the blade member can be maintained well.

And according to the manufacturing method of the optical fiber using the seal structure which suppressed the increase in the coefficient of friction, the airtight capability during drawing can be maintained. In addition, since the slidability of the blade member can be maintained satisfactorily when the glass base material is inserted or taken out, the glass base material or the seal structure can be prevented from being damaged without being caught.
In addition, it is preferable that the pressure in the drawing furnace during drawing is larger than the pressure in the housing. This is because a positive pressure is applied in the drawing furnace to prevent moisture and oxygen in the housing from entering the drawing furnace. Further, the atmospheric pool 12 may be provided with, for example, a humidity sensor or an oxygen sensor, and external air may be supplied from the supply / exhaust port 13 to the atmospheric pool 12 in accordance with an instruction from a controller (not shown).

  For example, when the blade member is pushed and pulled by gas supply / exhaust, the gas in the housing is supplied from the supply / discharge port while the sliding surface between the blade member and the guide member is placed in an atmosphere containing at least moisture or oxygen. (A gas reservoir is formed in the housing) to bring the blade member into contact with the side surface of the glass base material. On the other hand, the gas in the housing can be discharged from the supply / discharge port to separate the blade member from the side surface of the glass base material. It is.

FIG. 6 is a diagram illustrating another example of the blade member. An example of the blade member 14 will be described. The blade member 14 is a composite material in which the material of the front portion 14g that comes into contact with the glass base material and the material of the rear portion 14h that slides with respect to the guide member are changed. It may be configured. In this case, the side surface of the rear portion 14h corresponds to the sliding surface of the present invention.
Specifically, the above-described carbon, quartz glass, SiC-coated carbon, or the like is adopted as the material of the front portion 14g, while the material of the rear portion 14h is boron nitride (BN) in addition to the above-described carbon. In the case of metal, a material different from the front portion 14g, such as stainless steel or molybdenum disulfide (MoS ₂ ), can be used. Alternatively, a metal having an oxide film, a metal having various coatings such as a fluorine coat, gold plating, a chromium nitride coat, and a DLC coat, or quartz glass may be employed. By adopting such a configuration, a material that does not have any problem even if it comes into contact with a glass base material such as carbon or quartz is selected as the material that comes into contact with the base material (there is no deterioration in strength or disconnection). From various materials, a material that is less susceptible to friction can be selected.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the meanings described above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

DESCRIPTION OF SYMBOLS 1 ... Optical fiber drawing furnace, 2 ... Furnace housing, 2a ... Upper end opening part, 2b ... Lower end opening part, 3 ... Furnace core tube, 4 ... Heater, 5 ... Optical fiber glass preform, 5a ... Lower end part, 5b: optical fiber, 6: support rod, 7: heat insulating material, 10: seal structure, 11: housing, 11a, 11b ... opening, 12: air reservoir, 13: supply / exhaust port, 14, 15 ... blade member, 14a , 15a ... tip part, 14b, 14c, 14d, 14e, 15b, 15c, 15d, 15e ... outer peripheral surface part, 14f, 15f ... rear end part, 14g ... front part, 14h ... rear part, 16, 17 ... guide member, 16b, 16c, 16d, 16e, 17b, 17c, 17d, 17e ... sliding surface, 18 ... cylindrical slit spring, 18a, 18b ... slit.

Claims (10)

An optical fiber drawing furnace sealing structure for closing a gap between an upper end opening of an optical fiber drawing furnace and an optical fiber glass base material inserted from the upper end opening;
A blade member in contact with a circumferential side surface of the glass preform for optical fiber, and a housing that houses the blade member and a guide member that slidably supports the blade member;
A sealing structure for an optical fiber drawing furnace, wherein at least a part or all of the sliding surfaces of the blade member and the guide member in the housing is in a space having an atmosphere containing at least moisture or oxygen of 0.1% or more. .   The sealing structure for an optical fiber drawing furnace according to claim 1, wherein the atmosphere containing moisture or oxygen is an air atmosphere.   The seal structure of the optical fiber drawing furnace according to claim 1, wherein a pressure in the optical fiber drawing furnace is higher than a pressure in the housing.   The seal structure for an optical fiber drawing furnace according to any one of claims 1 to 3, wherein at least one of the blade member or the guide member is made of carbon.   The seal structure of the drawing furnace for optical fibers according to any one of claims 1 to 3, wherein at least one of the blade member or the guide member is made of metal.   The seal of an optical fiber drawing furnace according to claim 5, wherein the metal includes any of stainless steel, molybdenum disulfide, fluorine-coated metal, gold-plated metal, chromium nitride-coated metal, and DLC (diamond-like carbon) -coated metal. Construction.   The seal structure for an optical fiber drawing furnace according to any one of claims 1 to 3, wherein at least one of the blade member or the guide member is formed of quartz glass.   The said blade member is a seal structure of the drawing furnace for optical fibers according to any one of claims 4 to 7, comprising a plurality of materials.   The seal structure for an optical fiber drawing furnace according to any one of claims 1 to 8, wherein the guide member is water-cooled. The manufacturing method of an optical fiber which draws an optical fiber using the sealing structure of the drawing furnace for optical fibers of any one of Claims 1-9.

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