JP5624911B2

JP5624911B2 - Dehydration sintering furnace and dehydration sintering method for vitrifying porous preform for optical fiber

Info

Publication number: JP5624911B2
Application number: JP2011037209A
Authority: JP
Inventors: 祥遠藤; 智宏布目
Original assignee: Fujikura Ltd
Current assignee: Fujikura Ltd
Priority date: 2011-02-23
Filing date: 2011-02-23
Publication date: 2014-11-12
Anticipated expiration: 2031-02-23
Also published as: JP2012171844A

Description

本発明は、石英ガラス系光ファイバで代表される光ファイバの製造工程において、光ファイバ用多孔質母材を透明ガラス体にするための脱水焼結に用いる脱水焼結炉と、その脱水焼結炉を用いた多孔質母材の脱水焼結方法に関するものである。 The present invention relates to a dehydration sintering furnace used for dehydration sintering for forming a porous preform for an optical fiber into a transparent glass body in an optical fiber manufacturing process typified by a silica glass optical fiber, and the dehydration sintering thereof. The present invention relates to a method for dehydrating and sintering a porous base material using a furnace.

石英ガラス系光ファイバは、一般に、ＶＡＤ法やＯＶＤ法などによって作製した多孔質母材に高温加熱処理を施すことにより、透明ガラス体にしたものを線引きすることによって製造される。このような光ファイバの製造工程のうち、高温加熱処理により多孔質母材を透明なガラス体とする工程が、脱水焼結工程である。 Quartz glass optical fibers are generally manufactured by drawing a transparent glass body by subjecting a porous preform produced by a VAD method, an OVD method, or the like to a high temperature heat treatment. Among such optical fiber manufacturing processes, the process of making the porous base material a transparent glass body by high-temperature heat treatment is a dehydration sintering process.

図４には従来、多孔質母材の脱水焼結工程に用いられてきた脱水焼結炉の構造を示す。この脱水焼結炉は、多孔質母材１を脱水焼結するための炉心管２と、炉心管２を加熱するためのヒータ４と、炉心管２内の圧力を測定する内圧計５と、炉心管２と内圧計５を繋ぐ内圧測定用配管１０と、多孔質母材１の脱水焼結に用いるプロセスガス、もしくは脱水焼結後にプロセスガスを炉心管と内圧測定用配管から排出するために用いる不活性ガスを、それぞれのガス供給源から炉心管２に導くためのガス供給管８と、前記プロセスガスもしくは前記不活性ガスをスクラバ等の排ガス処理装置１８へ導くためのガス排出管９と、脱水焼結中の炉心管内圧を制御するための圧力調整装置７を備えている。そして前記炉心管２には、多孔質母材１の炉心管２への挿入時および炉心管２からの抜去時に開閉される開閉部として、開閉可能な蓋１７が装備されている。なお、プロセスガスとしては、塩素やフッ素などを含むハロゲン含有ガスが用いられ、不活性ガスとしては、ヘリウムや窒素、アルゴンが用いられる。 FIG. 4 shows the structure of a dehydration sintering furnace that has been conventionally used in the dehydration sintering process of a porous base material. The dehydration sintering furnace includes a core tube 2 for dehydrating and sintering the porous base material 1, a heater 4 for heating the core tube 2, an internal pressure gauge 5 for measuring the pressure in the core tube 2, In order to exhaust the process gas used for the dehydration sintering of the porous base material 1 or the process gas after the dehydration sintering from the core tube and the internal pressure measurement pipe, connecting the core pipe 2 and the internal pressure gauge 5 A gas supply pipe 8 for introducing the inert gas to be used from each gas supply source to the core tube 2, and a gas discharge pipe 9 for introducing the process gas or the inert gas to the exhaust gas treatment device 18 such as a scrubber; A pressure adjusting device 7 is provided for controlling the pressure inside the furnace tube during dehydration and sintering. The core tube 2 is provided with a lid 17 that can be opened and closed as an opening / closing portion that is opened and closed when the porous base material 1 is inserted into the core tube 2 and removed from the core tube 2. Note that a halogen-containing gas containing chlorine, fluorine, or the like is used as the process gas, and helium, nitrogen, or argon is used as the inert gas.

脱水焼結工程においては、炉心管２内の温度を１５００℃程度にする必要があり、その温度下では炉心管２は軟質化する。そのため、炉心管２の内圧と外圧に大きな差が生じれば、ヒータ４の周囲の炉心管２が変形してしまうから、脱水焼結中は、炉心管２内の圧力を適切に制御する必要がある。そこで、脱水焼結炉には、前述のように内圧測定用配管１０を通して炉心管２の内圧と外圧との差圧を測定する内圧計５が装備されているのが通常である。 In the dehydration sintering process, the temperature in the core tube 2 needs to be about 1500 ° C., and the core tube 2 is softened at that temperature. Therefore, if there is a large difference between the internal pressure and the external pressure of the core tube 2, the core tube 2 around the heater 4 will be deformed. Therefore, it is necessary to appropriately control the pressure in the core tube 2 during dehydration sintering. There is. Therefore, the dehydration sintering furnace is usually equipped with the internal pressure gauge 5 for measuring the differential pressure between the internal pressure and the external pressure of the furnace core tube 2 through the internal pressure measurement pipe 10 as described above.

このような構造を有する従来の多孔質母材の脱水焼結炉としては、炉心管に繋がっているガス排出経路に電磁弁を設置し、電磁弁の開閉に伴い排気ガスの流量を検出し、検出量に合わせてガスの流量を制御する手段を備えた脱水焼結炉（例えば、特許文献１参照）、炉心管内に圧力計を備え、炉心管内の平均圧力と、炉心管内の圧力の標準偏差との所定の関係が成り立つように制御する脱水焼結炉（例えば、特許文献２参照）、炉心管から排出される圧力と加熱炉から排出される圧力をそれぞれ圧力計で検出し、炉心管内圧と加熱炉内とを同じ圧力になるように、常時自動制御を行う脱水焼結炉（例えば、特許文献３参照）などが提案されている。 As a conventional porous matrix dehydration sintering furnace having such a structure, an electromagnetic valve is installed in the gas discharge path connected to the furnace core tube, and the flow rate of the exhaust gas is detected as the electromagnetic valve is opened and closed. Dehydration sintering furnace equipped with means for controlling the gas flow rate according to the detected amount (see, for example, Patent Document 1), a pressure gauge in the furnace core tube, an average pressure in the furnace core tube, and a standard deviation of the pressure in the furnace core tube The dehydration sintering furnace is controlled so that a predetermined relationship is established (for example, see Patent Document 2), the pressure discharged from the core tube and the pressure discharged from the heating furnace are detected by a pressure gauge, respectively, and the pressure in the core tube is detected. A dehydration sintering furnace (see, for example, Patent Document 3) that performs automatic control at all times so that the pressure in the heating furnace and the inside of the heating furnace are the same has been proposed.

ところで図４に示す脱水焼結炉を用いた脱水焼結工程においては、支持棒に支持された多孔質母材１が炉心管２上方から炉心管２内へ挿入され、続いて脱水や不純物の除去のために、炉心管２底部のガス供給管８からプロセスガスが供給される。挿入された多孔質母材１は、回転しながら炉心管２内に向かって降下され、下部から炉心管２のヒータ４で加熱されることにより、下部から上部に向かって脱水され、透明ガラス化される。ここで、脱水焼結中においては、炉心管２内への異物の混入を防ぐため、炉心管２内は陽圧に保たれるのが通常である。そのため、脱水焼結後に多孔質母材１を抜去する際に、直ちに炉心管２上部の蓋１７を開放すれば、脱水焼結炉内に残留していたプロセスガスが大気中に放出されてしまう。プロセスガスは、塩素やフッ素などの有毒なガスからなるものであるため、そのプロセスガスが大気中に放出されれば、安全上の問題が生じるとともに、環境汚染の問題が生じる。このような問題の発生を防止するため、従来一般には、多孔質母材１を炉心管２から抜去するべく蓋１７を開放する前に、炉心管２底部のガス供給管８から炉心管２内に不活性ガスを送り込んで、炉心管２内からプロセスガスを排除（パージ）することが行われている。 Incidentally, in the dehydration and sintering process using the dehydration and sintering furnace shown in FIG. 4, the porous base material 1 supported by the support rod is inserted into the core tube 2 from above the core tube 2, followed by dehydration and impurities. For removal, a process gas is supplied from a gas supply pipe 8 at the bottom of the core tube 2. The inserted porous base material 1 is lowered into the core tube 2 while rotating, and is heated from the lower part by the heater 4 of the core pipe 2, so that it is dehydrated from the lower part to the upper part to form a transparent glass. Is done. Here, during dehydration and sintering, the core tube 2 is usually kept at a positive pressure in order to prevent foreign matter from entering the core tube 2. Therefore, when the porous base material 1 is removed after dehydration sintering, if the lid 17 at the top of the core tube 2 is immediately opened, the process gas remaining in the dehydration sintering furnace will be released into the atmosphere. . Since the process gas is composed of a toxic gas such as chlorine or fluorine, if the process gas is released into the atmosphere, a safety problem occurs and an environmental pollution problem occurs. In order to prevent the occurrence of such a problem, in general, before the lid 17 is opened to remove the porous base material 1 from the core tube 2, the gas supply pipe 8 at the bottom of the core tube 2 is connected to the inside of the core tube 2. An inert gas is fed into the reactor core tube 2 to remove (purge) the process gas from the furnace core tube 2.

特開２０００−１６９１７３号公報JP 2000-169173 A 特開２００６−０５６７７３号公報JP 2006-056773 A 特開２００６−１３１４６３号公報JP 2006-131463 A

しかしながら、上述のように多孔質母材１の抜去前にプロセスガスのパージのために不活性ガスをガス供給管８から炉心管２内に導入しても、炉心管２と内圧計５を繋ぐ内圧測定用配管１０内は脱水焼結炉の外部空間とは遮断されていて、いわゆるメクラ状となっていて、排ガス処理装置１８と直結していないため、その配管１０内のプロセスガスは除去しにくいのが実情である。ここで、脱水焼結においては、プロセスガスとして塩素やフッ素などの酸性ガスを使用するために、炉心管２に繋がっている内圧測定用配管１０やガス供給管８、ガス排出管９にテフロン（登録商標）やポリフッ化ビニル製などの耐酸性のホースやチューブを使用するのが通常であり、また前記各管はスペースの削減や取り扱い性のために、曲げやすいよう蛇腹構造のものが使われることがある。その場合、前記各管の内面にプロセスガスが吸着しやすく、また蛇腹構造の内側の谷となっている部分にプロセスガスが残留しやすくなる。したがって、ガス供給管８からパージ用の不活性ガスを炉心管２内に導入しても、残留ガスを内圧測定用配管１０内から完全に除去するためには著しい長時間が必要となり、その場合、脱水焼結炉の稼働時間が減少して、光ファイバの製造効率が低下するという問題があった。
そして、前述の特許文献１〜３に示されるような脱水焼結炉についての従来の提案でも、上述のような内圧測定用配管内のプロセスガス残留の問題については、特に考慮されておらず、そのため上述の問題を回避し得なかったのが実情である。 However, even if an inert gas is introduced from the gas supply pipe 8 into the core tube 2 for purging the process gas before the porous base material 1 is removed as described above, the core tube 2 and the internal pressure gauge 5 are connected. The internal pressure measurement pipe 10 is cut off from the external space of the dehydration sintering furnace and is in the form of a so-called mekra, and is not directly connected to the exhaust gas treatment device 18, so that the process gas in the pipe 10 is removed. The situation is difficult. Here, in dehydration sintering, an acidic gas such as chlorine or fluorine is used as a process gas, so that the internal pressure measurement pipe 10, the gas supply pipe 8, and the gas discharge pipe 9 connected to the core tube 2 are connected with Teflon ( It is usual to use acid-resistant hoses and tubes such as those made of (registered trademark) and polyvinyl fluoride, and each tube has a bellows structure that is easy to bend to reduce space and handleability. Sometimes. In that case, the process gas tends to be adsorbed on the inner surface of each tube, and the process gas tends to remain in the inner valley of the bellows structure. Therefore, even if an inert gas for purge is introduced from the gas supply pipe 8 into the core tube 2, it takes a very long time to completely remove the residual gas from the internal pressure measurement pipe 10. There has been a problem that the operating time of the dehydration sintering furnace is reduced and the production efficiency of the optical fiber is lowered.
And even in the conventional proposal for the dehydration sintering furnace as shown in the aforementioned Patent Documents 1 to 3, the problem of the process gas remaining in the internal pressure measurement pipe as described above is not particularly considered, Therefore, the actual situation is that the above-mentioned problems could not be avoided.

本発明は、上述の事情を背景としてなされたもので、脱水焼結後に、炉心管内に残留するプロセスガスのみならず、炉心管と内圧計を繋ぐ内圧測定用配管内に残留するプロセスガスをも、短時間で排除し得るようにして、脱水焼結炉の稼働率を上げ、光ファイバの製造効率を高めることを課題とするものである。また本発明は、このような脱水焼結炉を用いた多孔質母材の脱水焼結方法を提供するものである。 The present invention was made against the background described above, and not only the process gas remaining in the core tube after dehydration and sintering, but also the process gas remaining in the internal pressure measurement pipe connecting the core tube and the internal pressure gauge. Therefore, it is an object to increase the operating rate of the dehydration sintering furnace and increase the production efficiency of the optical fiber so that it can be eliminated in a short time. The present invention also provides a method for dehydrating and sintering a porous base material using such a dehydrating and sintering furnace.

上述の課題を解決するため、本発明の脱水焼結炉では、基本的には、炉心管と内圧計とをつなぐ配管（内圧測定用配管）内の残留ガスを除去するための手段を設けることとした。
すなわち、本発明の第１の形態の脱水焼結炉は、石英ガラス系光ファイバ用多孔質母材を脱水焼結するための炉心管と、炉心管内を加熱するためのヒータと、炉心管内にプロセスガスもしくは不活性ガスを供給するためのガス供給管と、炉心管内のガスを排出するためのガス排出管と、炉心管内の圧力を測定する内圧計と、炉心管と内圧計を繋ぐ内圧測定用配管とを備え、かつ前記炉心管には、光ファイバ用多孔質母材の炉心管への挿入および炉心管からの抜去のために開閉される開閉部が設けられてなる脱水焼結炉において、多孔質母材の脱水焼結後に前記内圧測定用配管内に残留するガスを除去するための残留ガス除去手段を有することを特徴とするものである。 In order to solve the above-mentioned problems, in the dehydration sintering furnace of the present invention, basically, means for removing residual gas in a pipe (internal pressure measurement pipe) connecting the core tube and the internal pressure gauge is provided. It was.
That is, the dehydration sintering furnace according to the first aspect of the present invention includes a furnace core tube for dehydrating and sintering a porous preform for a silica glass optical fiber, a heater for heating the inside of the furnace core tube, and a furnace core tube. Gas supply pipe for supplying process gas or inert gas, gas discharge pipe for discharging gas in the reactor core tube, internal pressure gauge for measuring the pressure in the reactor core tube, and internal pressure measurement connecting the reactor core tube and the internal pressure gauge In the dehydration sintering furnace, provided with an open / close portion that is opened and closed for insertion into and removal from the core tube of the optical fiber porous preform. And a residual gas removing means for removing the gas remaining in the internal pressure measurement pipe after dehydration and sintering of the porous base material.

上述の第１の形態の脱水焼結炉による作用は次の通りである。すなわち、炉心管と内圧計を繋ぐ内圧測定用配管に残留ガス除去手段を備えることにより、多孔質母材の脱水焼結後の内圧測定用配管内に残留するプロセスガスを短時間で除去し、多孔質母材の脱水焼結後のプロセスガスパージ時間を短減することができる。またこれにより、脱水焼結炉の稼動時間を増やし、光ファイバの製造効率を上げることができる。 The operation of the dehydration sintering furnace according to the first embodiment is as follows. That is, by providing the residual gas removal means in the internal pressure measurement pipe connecting the core tube and the internal pressure gauge, the process gas remaining in the internal pressure measurement pipe after dehydration sintering of the porous base material is removed in a short time, The process gas purge time after dehydration and sintering of the porous base material can be reduced. Thereby, the operating time of the dehydration sintering furnace can be increased, and the manufacturing efficiency of the optical fiber can be increased.

また、本発明の第２の形態による脱水焼結炉は、前記第１の形態の脱水焼結炉において、前記残留ガス除去手段として、前記内圧測定用配管にガス排出口が設けられており、そのガス排出口が排ガス処理装置に繋がっているものである。 Further, the dehydration sintering furnace according to the second aspect of the present invention is the dehydration sintering furnace of the first aspect, wherein the residual gas removing means is provided with a gas discharge port in the internal pressure measurement pipe, The gas discharge port is connected to the exhaust gas treatment device.

第２の形態の脱水焼結炉による作用は次の通りである。すなわち、前記残留ガス除去手段として、内圧測定用配管に、排ガス処理装置に繋がるガス排気口を設けることにより、多孔質母材の脱水焼結後に前記ガス供給管を介して炉心管内にパージ用の不活性ガスを供給すれば、炉心管内のプロセスガスが前記ガス排出管から追い出されるだけではなく、内圧測定用配管内に残留しているガスも、前記ガス排気口を介して、直接的に短時間で排出させることができる。 The operation of the second embodiment of the dehydration sintering furnace is as follows. That is, as the residual gas removing means, a gas exhaust port connected to the exhaust gas treatment device is provided in the internal pressure measurement pipe, so that after the porous base material is dehydrated and sintered, it is purged into the core tube through the gas supply pipe. If the inert gas is supplied, not only the process gas in the core tube is expelled from the gas discharge pipe, but also the gas remaining in the internal pressure measurement pipe is directly reduced through the gas exhaust port. It can be discharged in time.

また、本発明の第３の形態による脱水焼結炉は、前記第１の形態の脱水焼結炉において、前記残留ガス除去手段として、前記内圧測定用配管に不活性ガス供給口が設けられており、そのガス供給口が不活性ガス供給源に繋がっているものである。 The dehydration sintering furnace according to the third aspect of the present invention is the dehydration sintering furnace of the first aspect, wherein the residual gas removing means is provided with an inert gas supply port in the internal pressure measurement pipe. The gas supply port is connected to an inert gas supply source.

第３の形態の脱水焼結炉による作用は次の通りである。すなわち、残留ガス除去手段として、内圧測定用配管に、不活性ガス供給源に繋がる不活性ガス供給口を設けることにより、前記供給口を介して不活性ガスを内圧測定用配管内に導入し、これによって内圧測定用配管内のプロセスガスを炉心管２内に押し出し、さらにガス排出管９へ押し出すため、内圧測定用配管内のプロセスガスを短時間で排除することができる。 The operation of the third embodiment of the dehydration sintering furnace is as follows. That is, as the residual gas removing means, by providing an inert gas supply port connected to the inert gas supply source in the internal pressure measurement pipe, the inert gas is introduced into the internal pressure measurement pipe through the supply port, As a result, the process gas in the internal pressure measurement pipe is pushed out into the reactor core tube 2 and further pushed out to the gas discharge pipe 9, so that the process gas in the internal pressure measurement pipe can be eliminated in a short time.

また、本発明の第４の形態による脱水焼結炉は、前記第１〜第３の形態のうちのいずれかの形態の脱水焼結炉において、前記ガス排出管に、ガス濃度を測定するためのガス検知器を設けたことを特徴とするものである。 A dehydration sintering furnace according to a fourth aspect of the present invention is a dehydration sintering furnace according to any one of the first to third aspects, for measuring a gas concentration in the gas exhaust pipe. The gas detector is provided.

第４の形態の脱水焼結炉による作用は次の通りである。すなわち、脱水焼結炉のガス排出管のガス濃度を測定するためのガス検知器を設けることにより、脱水焼結炉内のプロセスガスのパージ時において、そのプロセスガスの残量もしくは濃度を測定することができる。これにより、正確なガス排気状況とガス残量を把握し、多孔質母材の脱水焼結工程における排気時間を短縮させ、脱水焼結炉の稼動時間を増やして光ファイバの製造効率を上げることができる。 The operation of the fourth embodiment of the dehydration sintering furnace is as follows. That is, by providing a gas detector for measuring the gas concentration in the gas discharge pipe of the dehydration sintering furnace, the remaining amount or concentration of the process gas is measured when purging the process gas in the dehydration sintering furnace. be able to. As a result, it is possible to grasp the exact gas exhaust status and the remaining amount of gas, shorten the exhaust time in the dehydration sintering process of the porous base material, increase the operating time of the dehydration sintering furnace and increase the production efficiency of the optical fiber Can do.

さらに本発明の第５の形態は、前記第１〜第４の形態のうちのいずれかの形態の脱水焼結炉を用いた脱水焼結方法であり、この第５の形態の脱水焼結方法は、炉心管内に光ファイバ用多孔質母材を挿入して炉心管内にプロセスガスを導入するとともに、炉心管内をヒータにより加熱して、光ファイバ用多孔質母材の脱水焼結を行う第１段階と、その第１段階終了後、炉心管の開閉部を開放する前に炉心管内に不活性ガスを導入して、炉心管内の残留ガスを追い出すとともに、前記残留ガス除去手段により前記内圧測定用配管内の残留ガスを排除する第２段階と、その後炉心管の開閉部を開放して多孔質母材を炉心管から取り出す第３段階とを有することを特徴とするものである。 Furthermore, the fifth aspect of the present invention is a dehydration sintering method using the dehydration sintering furnace according to any one of the first to fourth aspects, and the dehydration sintering method according to the fifth aspect. Is a method in which a porous base material for an optical fiber is inserted into the core tube and a process gas is introduced into the core tube, and the inside of the core tube is heated by a heater to dehydrate and sinter the porous base material for the optical fiber. After completion of the first stage and before the opening and closing part of the core tube is opened, an inert gas is introduced into the core tube to expel the residual gas in the core tube, and the residual gas removing means is used for measuring the internal pressure. It has a second stage for removing the residual gas in the pipe, and a third stage for opening the open / close portion of the core tube and then removing the porous base material from the core tube.

第５の形態の脱水焼結方法による作用は次の通りである。すなわち、炉心管の開閉部を開ける前の第２段階において、炉心管内の残留ガスを追い出すばかりでなく、それと同時に内圧測定用配管内の残留ガスをも排除するため、プロセスガスの完全な排除に要する時間を短縮し、これにより脱水焼結炉の稼動時間を増やし、光ファイバの製造効率を上げることができる。 The operation of the fifth embodiment of the dehydration sintering method is as follows. That is, in the second stage before opening the opening and closing part of the core tube, not only the residual gas in the core tube is expelled, but at the same time, the residual gas in the internal pressure measurement pipe is also excluded, so that the process gas can be completely eliminated. This shortens the time required, thereby increasing the operating time of the dehydration sintering furnace and increasing the optical fiber manufacturing efficiency.

本発明の第６の形態は、前記第５の形態の脱水焼結方法において、多孔質母材の脱水焼結工程の第２段階の実施にあたり、第１段階時よりもプロセスガスの排気量および不活性ガスの供給量を増やすことを特徴とするものである。 According to a sixth aspect of the present invention, in the dehydration and sintering method of the fifth aspect, when performing the second stage of the porous base material dehydration and sintering process, the process gas displacement and The supply amount of the inert gas is increased.

第６の形態の脱水焼結方法による作用は次の通りである。すなわち、脱水焼結工程の第２段階において、第１段階時よりもプロセスガスの排気量、および不活性ガスの供給量を増やすことにより、残留ガスが短時間で排ガス処理装置へ押し出され、残留ガス除去速度が上がり、多孔質母材の脱水焼結工程における排気時間を短縮させることができる。さらに、脱水焼結炉の稼動時間を増やして光ファイバの製造効率を上げることができる。 The operation of the sixth embodiment of the dehydration sintering method is as follows. That is, in the second stage of the dehydration and sintering process, by increasing the exhaust amount of the process gas and the supply amount of the inert gas compared to the first stage, the residual gas is pushed out to the exhaust gas treatment device in a short time, and the residual gas The gas removal rate is increased, and the exhaust time in the dehydration sintering process of the porous base material can be shortened. Furthermore, it is possible to increase the operating efficiency of the optical fiber by increasing the operation time of the dehydration sintering furnace.

本発明の第７の形態は、前記第５の形態の脱水焼結方法において、多孔質母材の脱水焼結工程の第２段階の実施にあたり、炉心管内の圧力を所定時間ごとに変化させることを特徴とするものである。 According to a seventh aspect of the present invention, in the dehydration and sintering method of the fifth aspect, the pressure in the furnace core tube is changed every predetermined time in the second stage of the dehydration and sintering process of the porous base material. It is characterized by.

第７の形態の脱水焼結方法による作用は次の通りである。すなわち、脱水焼結工程の第２段階において、炉心管内の圧力を所定時間ごとに変化させることにより、内圧測定用配管が蛇腹部を有していたり、また内圧測定用配管がプロセスガスを吸着しやすい材料からなる場合であっても、その内圧測定用配管から残留ガスを短時間で排除することができ、さらに脱水焼結炉の稼動時間を増やして光ファイバの製造効率を上げることができる。 The operation of the seventh embodiment of the dehydration sintering method is as follows. That is, in the second stage of the dehydration and sintering process, the internal pressure measurement pipe has an accordion portion or the internal pressure measurement pipe adsorbs the process gas by changing the pressure in the core tube every predetermined time. Even if it is made of an easy material, the residual gas can be removed from the internal pressure measurement pipe in a short time, and the operating time of the dehydration sintering furnace can be increased to increase the production efficiency of the optical fiber.

本発明の第８の形態は、前記第７の形態の脱水焼結方法において、多孔質母材の脱水焼結工程の第２段階における炉心管内の圧力を所定時間ごとに変化させる手段として、プロセスガス排気量を変化させることを特徴とするものである。 According to an eighth aspect of the present invention, in the dehydration and sintering method of the seventh aspect, as a means for changing the pressure in the core tube in the second stage of the dehydration and sintering step of the porous base material, a process is performed. The gas exhaust amount is changed.

第８の形態の脱水焼結方法による作用は次の通りである。すなわち、多孔質母材の脱水焼結工程の第２段階において、炉心管内の圧力を所定時間ごとに変化させる手段として、プロセスガス排気量を変化させることにより、排気によるガスの流れから圧力変動が生じ、残留ガスが除去され易くなり、多孔質母材の脱水焼結工程における排気時間を短縮させることができる。さらに、脱水焼結炉の稼動時間を増やして光ファイバの製造効率を上げることができる。 The operation of the eighth embodiment of the dehydration sintering method is as follows. That is, in the second stage of the porous base material dehydration and sintering process, as a means for changing the pressure in the furnace core tube every predetermined time, by changing the process gas exhaust amount, the pressure fluctuation is caused from the gas flow by the exhaust. As a result, the residual gas is easily removed, and the exhaust time in the dehydration sintering process of the porous base material can be shortened. Furthermore, it is possible to increase the operating efficiency of the optical fiber by increasing the operation time of the dehydration sintering furnace.

本発明の第９の形態は、前記第７の形態の脱水焼結方法において、多孔質母材の脱水焼結工程の第２段階における、炉心管内の圧力を所定時間ごとに変化させる手段として、不活性ガス供給量を変化させることを特徴としたものである。 In the dehydration and sintering method of the seventh aspect, the ninth aspect of the present invention is a means for changing the pressure in the furnace core tube every predetermined time in the second stage of the dehydration and sintering process of the porous base material. It is characterized by changing the supply amount of the inert gas.

第９の脱水焼結方法による作用は次の通りである。すなわち、多孔質母材の脱水焼結工程の第２段階における、炉心管内の圧力を所定時間ごとに変化させる手段として、不活性ガス供給量を変化させることにより、供給したガスによる圧力変動が生じて、残留ガスが除去され易くなり、多孔質母材の脱水焼結工程における排気時間を短縮させることができる。さらに、脱水焼結炉の稼動時間を増やして光ファイバの製造効率を上げることができる。 The operation of the ninth dehydration sintering method is as follows. In other words, as a means for changing the pressure in the furnace core tube every predetermined time in the second step of the dehydration and sintering process of the porous base material, pressure fluctuation due to the supplied gas occurs by changing the inert gas supply amount. Thus, the residual gas can be easily removed, and the exhaust time in the dehydration sintering process of the porous base material can be shortened. Furthermore, it is possible to increase the operating efficiency of the optical fiber by increasing the operation time of the dehydration sintering furnace.

本発明の第１０の形態は、前記第５の形態の脱水焼結方法において、多孔質母材の脱水焼結工程の第２段階において、炉心管に供給する不活性ガスとしてヘリウムを使用することを特徴としたものである。 According to a tenth aspect of the present invention, in the dehydration and sintering method of the fifth aspect, helium is used as an inert gas supplied to the core tube in the second stage of the dehydration and sintering process of the porous base material. It is characterized by.

第１０の脱水焼結方法による作用は次の通りである。すなわち、多孔質母材の脱水焼結工程の第２段階において、炉心管に供給する不活性ガスとして粒子の小さなヘリウムを使用することにより、炉心管と内圧測定用配管や、ガス供給管、ガス排出管などを接続するコネクタの隙間などにも、ヘリウムが入り込み、隙間などに残留した残留ガスをも排出し、多孔質母材の脱水焼結工程における排気時間を更に短縮させることができる。さらに、脱水焼結炉の稼動時間を増やして光ファイバの製造効率を上げることができる。 The operation of the tenth dehydration sintering method is as follows. That is, in the second stage of the porous base material dehydration and sintering process, by using helium with small particles as an inert gas supplied to the core tube, the core tube, the internal pressure measurement pipe, the gas supply pipe, the gas Helium also enters the gaps of the connectors connecting the discharge pipes and the like, and the residual gas remaining in the gaps is also discharged, so that the exhaust time in the dehydration sintering process of the porous base material can be further shortened. Furthermore, it is possible to increase the operating efficiency of the optical fiber by increasing the operation time of the dehydration sintering furnace.

本発明の脱水焼結炉、脱水焼結方法によれば、光ファイバ用多孔質母材の脱水焼結後におけるプロセスガスの排気時間を短縮して、稼動効率を高めることができ、これにより光ファイバの製造効率を高めることができる。 According to the dehydration sintering furnace and dehydration sintering method of the present invention, the exhaust time of the process gas after the dehydration sintering of the optical fiber porous preform can be shortened, and the operation efficiency can be increased. The production efficiency of the fiber can be increased.

本発明の第１の実施形態による脱水焼結炉の全体構成を示す略解図である。1 is a schematic diagram illustrating an overall configuration of a dehydration sintering furnace according to a first embodiment of the present invention. 本発明の第２の実施形態による脱水焼結炉の全体構成を示す略解図である。It is a schematic diagram which shows the whole structure of the dehydration sintering furnace by the 2nd Embodiment of this invention. 比較例１および比較例２において用いた脱水焼結炉の全体構成を示す略解図である。3 is a schematic diagram illustrating an overall configuration of a dehydration sintering furnace used in Comparative Examples 1 and 2. FIG. 従来の脱水焼結炉の全体構成を示す略解図である。It is a schematic diagram which shows the whole structure of the conventional dehydration sintering furnace.

以下、本発明の実施の形態を図１、図２を参照して説明する。なお、各図中の矢印はパージ中のガスの流れを示し、破線矢印で図示したガスの流れはプロセスガス検知時のみ発生する。 Hereinafter, an embodiment of the present invention will be described with reference to FIGS. In addition, the arrow in each figure shows the flow of the gas under purge, and the gas flow shown by the broken line arrow is generated only when the process gas is detected.

図１には、本発明の第１の実施形態の脱水焼結炉を示す。この脱水焼結炉は、基本的には、中空円筒上の炉心管２の上端に、脱水焼結対象となる多孔質母材１を挿入、抜去するための開閉部として開閉可能な蓋１７を設け、かつ炉心管２の周囲に、多孔質母材１を加熱するためのヒータ４を設けている。また炉心管２の底部は、ガス供給管８により、図示しないプロセスガス供給源および不活性ガス供給源につながっている。さらに炉心管２の上部には、三方弁１４を介して、炉心管２内の圧力を制御するための圧力調整装置７と、スクラバ等の排ガス処理装置１８およびガス検知器１３に繋がるガス排出管９が設けられている。さらに、炉心管２内の圧力を測定するための内圧計５が、炉心管２の上部と内圧測定用配管１０によって繋がっている。そして、この内圧測定用配管１０には、その中途に分岐管１６が接続され、その分岐管１６はバルブ１５を介してスクラバ等の排ガス処理装置１９に繋がっている。 FIG. 1 shows a dehydration sintering furnace according to a first embodiment of the present invention. This dehydration sintering furnace basically has a lid 17 that can be opened and closed as an opening / closing part for inserting and removing the porous base material 1 to be dehydrated and sintered at the upper end of a furnace core tube 2 on a hollow cylinder. The heater 4 for heating the porous base material 1 is provided around the core tube 2. The bottom of the core tube 2 is connected to a process gas supply source and an inert gas supply source (not shown) by a gas supply tube 8. Further, a pressure adjusting device 7 for controlling the pressure in the core tube 2 and a gas exhaust pipe connected to the exhaust gas processing device 18 such as a scrubber and the gas detector 13 are provided above the core tube 2 through a three-way valve 14. 9 is provided. Further, an internal pressure gauge 5 for measuring the pressure in the core tube 2 is connected to the upper portion of the core tube 2 by an internal pressure measuring pipe 10. A branch pipe 16 is connected to the internal pressure measuring pipe 10 in the middle, and the branch pipe 16 is connected to an exhaust gas treatment device 19 such as a scrubber via a valve 15.

次に、第１の実施形態の脱水焼結炉によって多孔質母材の脱水焼結を行う方法について説明する。
前述の脱水焼結炉によって、多孔質母材１の脱水焼結を行うにあたっては、先ず第１段階として、蓋１７を開放して炉心管２内に多孔質母材１を挿入し、その後蓋１７を閉じて、ガス供給管８を介して炉心管２内にプロセスガスを導入するとともに、ヒータ４により炉心管２内を高温にした後、多孔質母材１を下降させ、多孔質母材１を下部から上部に向かって順次脱水焼結する。この脱水焼結段階（第１段階）では、内圧計５によって炉心管２内の圧力が測定される。また、この過程においては、三方弁１４を圧力調整装置７の側に制御し、圧力調整装置７で炉心管２内の圧力を制御する。 Next, a method for performing dehydration sintering of the porous base material in the dehydration sintering furnace of the first embodiment will be described.
In performing the dehydration sintering of the porous base material 1 by the above-described dehydration sintering furnace, first, as a first step, the lid 17 is opened and the porous base material 1 is inserted into the furnace core tube 2, and then the lid 17 is closed, the process gas is introduced into the core tube 2 through the gas supply pipe 8, the interior of the core tube 2 is heated to a high temperature by the heater 4, the porous base material 1 is lowered, and the porous base material 1 is dehydrated and sintered sequentially from the bottom to the top. In this dehydration and sintering stage (first stage), the internal pressure gauge 5 measures the pressure in the core tube 2. Further, in this process, the three-way valve 14 is controlled to the pressure adjusting device 7 side, and the pressure in the furnace core tube 2 is controlled by the pressure adjusting device 7.

次いで第２段階に移行するが、脱水焼結終了後には、直ちには炉心管２の蓋１７を開放せずに、ガス供給管８を介して炉心管２内に不活性ガスを導入し、この不活性ガスによって炉心管２内に残るプロセスガスをパージする。すなわち、ガス排出管９を経て、炉心管２内のプロセスガスを排ガス処理装置１８へ向けて追い出す。同時に、内圧測定用配管１０の分岐管１６に設けられているバルブ１５を開放して、内圧測定用配管１０内に残留しているプロセスガスを排ガス処理装置１９へ向けて追い出す。また、この過程においては、随時三方弁１４をガス検知器１３の側に切り替えて、ガス濃度を検出することができる。 Next, the process proceeds to the second stage. After the dehydration and sintering, the inert gas is introduced into the core tube 2 through the gas supply pipe 8 without opening the lid 17 of the core tube 2 immediately. The process gas remaining in the furnace core tube 2 is purged with the inert gas. That is, the process gas in the core tube 2 is expelled toward the exhaust gas treatment device 18 through the gas discharge pipe 9. At the same time, the valve 15 provided in the branch pipe 16 of the internal pressure measurement pipe 10 is opened to expel the process gas remaining in the internal pressure measurement pipe 10 toward the exhaust gas treatment device 19. In this process, the gas concentration can be detected by switching the three-way valve 14 to the gas detector 13 side at any time.

前述のようにして、炉心管２内、および内圧測定用配管１０内に残留しているプロセスガスを追い出した後、詳しくは前記ガス検知器１３によってプロセスガスが完全に除去されたことを確認した後、第３段階として、蓋１７を開放し、炉心管２内から脱水焼結済みの多孔質母材１を炉心管２内から取り出す。 As described above, after the process gas remaining in the reactor core tube 2 and the internal pressure measurement pipe 10 was expelled, it was confirmed in detail that the process gas was completely removed by the gas detector 13. Thereafter, as a third stage, the lid 17 is opened, and the porous base material 1 that has been subjected to dehydration and sintering is taken out of the core tube 2 from the core tube 2.

上述のように脱水焼結後に不活性ガスの導入により炉心管２内のプロセスガスをパージする段階（第２段階）で、内圧測定用配管１０の分岐管１６のバルブ１５を開放することにより、内圧測定用配管１０内に残留していたプロセスガスも、直ちに排出、除去することができるため、プロセスガスパージ時間をいたずらに長時間取る必要がなくなるのである。 By opening the valve 15 of the branch pipe 16 of the internal pressure measurement pipe 10 at the stage of purging the process gas in the core tube 2 by introducing an inert gas after dehydration and sintering as described above (second stage), Since the process gas remaining in the internal pressure measurement pipe 10 can be immediately discharged and removed, there is no need to take a long process gas purge time.

また、前記第２段階で多孔質母材１を脱水焼結する段階（第１段階）よりも、内圧測定用配管１０の分岐管１６からのプロセスガス排気量を増やすことにより、内圧測定用配管１０内に残留していたプロセスガスを直接的に排出する速度が上がり、プロセスガスパージ時間を短縮することができる。さらに、ガス供給管８およびガス排出管９に、ニードルバルブやマスフローコントローラなどを取り付け、プロセスガス排気量を所定時間ごとに変化させることにより、炉心管２内および内圧測定用配管１０内に圧力変動が生じ、内圧測定用配管１０内の残留ガスが排気し易くなるため、プロセスガスパージ時間を著しく短縮することができる。 Also, the internal pressure measurement pipe is increased by increasing the amount of process gas exhausted from the branch pipe 16 of the internal pressure measurement pipe 10 than in the stage (first stage) of dehydrating and sintering the porous base material 1 in the second stage. The speed at which the process gas remaining in 10 is directly discharged increases, and the process gas purge time can be shortened. Further, a needle valve, a mass flow controller, or the like is attached to the gas supply pipe 8 and the gas discharge pipe 9, and the pressure fluctuations in the reactor core pipe 2 and the internal pressure measurement pipe 10 are made by changing the process gas exhaust amount every predetermined time. And the residual gas in the internal pressure measurement pipe 10 is easily exhausted, so that the process gas purge time can be significantly shortened.

図２には、本発明の第２の実施形態の脱水焼結炉を示す。なお図２において、図１に示した脱水焼結炉と同一の構成の部分については同一の符号を付し、その説明は省略する。図２において、内圧測定用配管１０には、その中途に分岐管１６が接続され、その分岐管１６はバルブ１５を介して図示しない不活性ガス供給源に繋がっている。 FIG. 2 shows a dehydration sintering furnace according to a second embodiment of the present invention. In FIG. 2, the same components as those in the dehydration sintering furnace shown in FIG. In FIG. 2, a branch pipe 16 is connected to the internal pressure measurement pipe 10 in the middle, and the branch pipe 16 is connected to an inert gas supply source (not shown) via a valve 15.

第２の実施形態の脱水焼結炉による多孔質母材１の脱水焼結の過程（第１段階）は第１の実施形態の脱水焼結炉による多孔質母材１の脱水焼結の過程と同一であり、その説明は省略する。 The process of dehydration and sintering of the porous base material 1 by the dehydration sintering furnace of the second embodiment (first stage) is the process of dehydration and sintering of the porous base material 1 by the dehydration sintering furnace of the first embodiment. The description is omitted.

このような脱水焼結炉による多孔質母材１の脱水焼結終了後には、第２段階として、内圧測定用配管１０の分岐管１６に設けられているバルブ１５を開放し、分岐管１６を介して内圧測定用配管１０内に不活性ガスを導入し、この不活性ガスによって内圧測定用配管１０内に残るプロセスガスを炉心管２内に追い出すと同時に、ガス供給管８を介して炉心管２内に不活性ガスを導入し、この不活性ガスによって炉心管２内に残るプロセスガスをガス排出管９の側に追い出す。 After the dehydration sintering of the porous base material 1 in such a dehydration sintering furnace, as a second stage, the valve 15 provided in the branch pipe 16 of the internal pressure measurement pipe 10 is opened, and the branch pipe 16 is opened. An inert gas is introduced into the internal pressure measurement pipe 10 via the internal pressure measurement pipe 10 and the process gas remaining in the internal pressure measurement pipe 10 is expelled into the core pipe 2 by the inert gas and at the same time through the gas supply pipe 8. An inert gas is introduced into 2, and the process gas remaining in the core tube 2 is expelled to the side of the gas discharge pipe 9 by this inert gas.

このようにして、炉心管２内、および内圧測定用配管１０内に残留しているプロセスガスを追い出した後、第３段階として、蓋１７を開放し、炉心管２内から脱水焼結済みの多孔質母材１を炉心管２内から取り出す。 In this manner, after the process gas remaining in the core tube 2 and the internal pressure measurement pipe 10 is expelled, the lid 17 is opened as a third stage, and dehydration and sintering is completed from the core tube 2. The porous base material 1 is taken out from the core tube 2.

上述のように、脱水焼結後にガス供給管８からの不活性ガスの導入により炉心管２内のプロセスガスをパージする段階で、内圧測定用配管１０の分岐管１６に設けられているバルブ１５を開放し、分岐管１６を介して内圧測定用配管１０にも不活性ガスを供給することにより、内圧測定用配管１０内に残留していたプロセスガスは直ちに炉心管２内に追い出され、ガス供給管８から導入される不活性ガスにより、ガス排出管９の側に排出される。 As described above, the valve 15 provided in the branch pipe 16 of the internal pressure measurement pipe 10 at the stage of purging the process gas in the core tube 2 by introducing the inert gas from the gas supply pipe 8 after dehydration and sintering. And the inert gas is supplied also to the internal pressure measurement pipe 10 via the branch pipe 16, so that the process gas remaining in the internal pressure measurement pipe 10 is immediately expelled into the reactor core pipe 2, The inert gas introduced from the supply pipe 8 is discharged to the gas discharge pipe 9 side.

また、前記第２段階で前記第１段階よりも、内圧測定用配管１０の分岐管１６からの不活性ガス供給量を増やすことにより、内圧測定用配管１０内に残留していたプロセスガスを炉心管２内に追い出し、ガス供給管８から炉心管２内に供給される不活性ガスにより、ガス排出管９に押し出す速度が上がるため、プロセスガスパージ時間を短縮することができる。さらに、ガス供給管８およびガス排出管９に、ニードルバルブやマスフローコントローラなどを取り付け、不活性ガス供給量を所定時間ごとに変化させることにより、炉心管２内および内圧測定用配管１０内に圧力変動が生じ、内圧測定用配管１０内の残留ガスが排気し易くなるため、プロセスガスパージ時間を著しく短縮することができる。 Further, by increasing the amount of inert gas supplied from the branch pipe 16 of the internal pressure measurement pipe 10 in the second stage than in the first stage, the process gas remaining in the internal pressure measurement pipe 10 is removed from the core. The inert gas supplied into the furnace core tube 2 from the gas supply tube 8 and expelled into the tube 2 increases the speed of extrusion to the gas discharge tube 9, so that the process gas purge time can be shortened. Further, a needle valve, a mass flow controller, or the like is attached to the gas supply pipe 8 and the gas discharge pipe 9, and the pressure in the reactor core tube 2 and the internal pressure measurement pipe 10 is changed by changing the supply amount of the inert gas every predetermined time. Since the fluctuation occurs and the residual gas in the internal pressure measurement pipe 10 is easily exhausted, the process gas purge time can be remarkably shortened.

実施例１
図１に示す脱水焼結炉による脱水焼結工程の第１段階において、ガス供給管８を介して炉心管２内に、４ＳＬＭのヘリウムガスと、０．１５ＳＬＭのＳｉＦ_４ガスとの混合プロセスガスを供給した。ＳｉＦ_４ガスの供給により、多孔質母材１などに含まれる水分とＳｉＦ_４ガスが反応し、ＳｉＦ_４ガスはＨＦガスとなる。そのため、ガス検知器１３はＨＦ用のものを使用した。また、ガス排出管９に設けた三方弁１４により、ガス排出管９に導入された混合プロセスガスを同ガス排出管９に設けた圧力調整装置７を通して排ガス処理装置１８に押し出すと同時に、圧力調整装置７により炉心管２内の圧力を制御した。この段階では、内圧測定用配管１０に接続された分岐管１６に設けられているバルブ１５は開放されていないため、内圧測定用配管１０内にプロセスガスが存在している。 Example 1
In the first stage of the dehydration sintering process by the dehydration sintering furnace shown in FIG. 1, a mixed process gas of ₄ SLM helium gas and 0.15 SLM SiF ₄ gas is introduced into the furnace core tube 2 through the gas supply pipe 8. Supplied. The supply of SiF ₄ gas, moisture and SiF ₄ gas contained in a porous preform 1 is reacted, SiF ₄ gas becomes HF gas. Therefore, the gas detector 13 for HF was used. In addition, the three-way valve 14 provided in the gas discharge pipe 9 pushes the mixed process gas introduced into the gas discharge pipe 9 to the exhaust gas treatment device 18 through the pressure adjustment device 7 provided in the gas discharge pipe 9 and simultaneously adjusts the pressure. The pressure in the furnace core tube 2 was controlled by the device 7. At this stage, since the valve 15 provided in the branch pipe 16 connected to the internal pressure measurement pipe 10 is not opened, process gas exists in the internal pressure measurement pipe 10.

図１に示す脱水焼結炉による脱水焼結工程の第２段階において、炉心管２および内圧測定用配管１０の内部から残留ガスを一掃するために、ガス供給管８を介して１０ＳＬＭの窒素を炉心管２内に供給し、ガス排出管９を介して、炉心管２内のプロセスガスを排ガス処理装置１８へ向けて追い出すとともに、内圧測定用配管１０に接続された分岐管１６に設けられているバルブ１５を開放することにより、分岐管１６を介して、内圧測定用配管１０内のプロセスガスを排ガス処理装置１９へ向けて追い出した。第２段階におけるプロセスガスの排気開始から３時間経過後に、ガス検知器１３による炉心管２内のフッ素濃度の測定値が０ｐｐｍになったことを確認し、多孔質母材１を炉心管２から抜去した。 In the second stage of the dehydration and sintering process in the dehydration and sintering furnace shown in FIG. 1, 10 SLM of nitrogen is passed through the gas supply pipe 8 in order to sweep out residual gas from the inside of the core tube 2 and the internal pressure measurement pipe 10. The gas is supplied into the core tube 2, and the process gas in the core tube 2 is expelled toward the exhaust gas treatment device 18 through the gas discharge pipe 9, and is provided in the branch pipe 16 connected to the internal pressure measurement pipe 10. By opening the valve 15, the process gas in the internal pressure measurement pipe 10 was expelled toward the exhaust gas treatment device 19 through the branch pipe 16. After 3 hours from the start of exhaust of the process gas in the second stage, it was confirmed that the measured value of the fluorine concentration in the core tube 2 by the gas detector 13 became 0 ppm, and the porous base material 1 was removed from the core tube 2 Extracted.

実施例２
図２に示す脱水焼結炉による脱水焼結工程の第１段階においては、上述の図１に示す脱水焼結炉による脱水焼結工程の第１段階と同一の操作を行ったため、その説明を省略する。この第１段階では、内圧測定用配管１０内には、前記同様にプロセスガスが存在している。 Example 2
In the first stage of the dehydration sintering process by the dehydration sintering furnace shown in FIG. 2, the same operation as the first stage of the dehydration sintering process by the dehydration sintering furnace shown in FIG. Omitted. In the first stage, the process gas exists in the internal pressure measurement pipe 10 as described above.

図２に示す脱水焼結炉による脱水焼結工程の第２段階において、炉心管２および内圧測定用配管１０の内部から残留ガスを一掃するために、ガス供給管８を介して１０ＳＬＭの窒素を炉心管２内に供給し、ガス排出管９を介して、炉心管２内のプロセスガスを排ガス処理装置１８へ向けて追い出すとともに、内圧測定用配管１０に接続された分岐管１６に設けられているバルブ１５を開放し、分岐管１６を介して不活性ガスを内圧測定用配管１０に供給することにより、内圧測定用配管１０内のプロセスガスを炉心管２内へ向けて追い出し、さらに排ガス処理装置１９へ向けて追い出した。第２段階におけるプロセスガスの排気開始から３時間経過後に、ガス検知器１３による炉心管２内のフッ素濃度の測定値が０ｐｐｍになったことを確認し、多孔質母材１を炉心管２から抜去した。 In the second stage of the dehydration and sintering process in the dehydration and sintering furnace shown in FIG. 2, 10 SLM of nitrogen is removed via the gas supply pipe 8 in order to sweep out residual gas from the inside of the core tube 2 and the internal pressure measurement pipe 10. The gas is supplied into the core tube 2, and the process gas in the core tube 2 is expelled toward the exhaust gas treatment device 18 through the gas discharge pipe 9, and is provided in the branch pipe 16 connected to the internal pressure measurement pipe 10. Open the valve 15 and supply the inert gas to the internal pressure measurement pipe 10 via the branch pipe 16, so that the process gas in the internal pressure measurement pipe 10 is expelled into the core tube 2, and the exhaust gas treatment is further performed. Driven towards the device 19. After 3 hours from the start of exhaust of the process gas in the second stage, it was confirmed that the measured value of the fluorine concentration in the core tube 2 by the gas detector 13 became 0 ppm, and the porous base material 1 was removed from the core tube 2 Extracted.

実施例３
図２に示す脱水焼結炉による脱水焼結工程の第１段階においては、上述の図１に示す脱水焼結炉による脱水焼結工程の第１段階と同一の操作を行ったため、その説明を省略する。この第１段階では、内圧測定用配管１０内には、前記同様にプロセスガスが残留している。 Example 3
In the first stage of the dehydration sintering process by the dehydration sintering furnace shown in FIG. 2, the same operation as the first stage of the dehydration sintering process by the dehydration sintering furnace shown in FIG. Omitted. In this first stage, the process gas remains in the internal pressure measurement pipe 10 as described above.

図２に示す脱水焼結炉による脱水焼結工程の第２段階において、炉心管２および内圧測定用配管１０の内部から残留ガスを一掃するために、ガス供給管８を介して炉心管２内に、１５分毎に１０ＳＬＭの窒素と４ＳＬＭの窒素とを交互に供給し、ガス排出管９を介して炉心管２内のプロセスガスを排ガス処理装置１８へ向けて追い出すとともに、内圧測定用配管１０に接続された分岐管１６に設けられているバルブ１５を開放し、分岐管１６を介して０．５Ｌの窒素を内圧測定用配管１０に供給することにより、内圧測定用配管１０内のプロセスガスを炉心管２内へ向けて追い出し、さらに排ガス処理装置１９へ向けて追い出した。第２段階におけるプロセスガスの排気開始から３時間経過後に、ガス検知器１３による炉心管２内のフッ素濃度の測定値が０ｐｐｍになったことを確認し、多孔質母材１を炉心管２から抜去した。 In the second stage of the dehydration sintering process by the dehydration sintering furnace shown in FIG. 2, in order to sweep out residual gas from the inside of the core tube 2 and the internal pressure measurement pipe 10, the inside of the core tube 2 is passed through the gas supply pipe 8. In addition, 10 SLM nitrogen and 4 SLM nitrogen are alternately supplied every 15 minutes, and the process gas in the core tube 2 is expelled to the exhaust gas treatment device 18 through the gas discharge pipe 9 and the internal pressure measurement pipe 10 The valve 15 provided in the branch pipe 16 connected to the pipe is opened, and 0.5 L of nitrogen is supplied to the internal pressure measurement pipe 10 via the branch pipe 16, whereby the process gas in the internal pressure measurement pipe 10 is supplied. Was expelled toward the reactor core tube 2 and further expelled toward the exhaust gas treatment device 19. After 3 hours from the start of exhaust of the process gas in the second stage, it was confirmed that the measured value of the fluorine concentration in the core tube 2 by the gas detector 13 became 0 ppm, and the porous base material 1 was removed from the core tube 2 Extracted.

実施例４
図１に示す脱水焼結炉による実施例１に記載されている脱水焼結工程の第１段階終了後、内圧測定用配管１０内にプロセスガスが残留している状態からの同脱水焼結工程の第２段階において、炉心管２および内圧測定用配管１０の内部から残留ガスを一掃するために、ガス供給管８を介して１０ＳＬＭのヘリウムを炉心管２内に供給し、ガス排出管９を介して、炉心管２内のプロセスガスを排ガス処理装置１８へ向けて追い出すとともに、内圧測定用配管１０に接続された分岐管１６に設けられているバルブ１５を開放することにより、分岐管１６を介して、内圧測定用配管１０内のプロセスガスを排ガス処理装置１９へ向けて追い出した。第２段階におけるプロセスガスの排気開始から２．５時間経過後に、ガス検知器１３による炉心管２内のフッ素濃度の測定値が０ｐｐｍになったことを確認し、多孔質母材１を炉心管２から抜去した。 Example 4
After completion of the first stage of the dehydration sintering process described in Example 1 using the dehydration sintering furnace shown in FIG. 1, the dehydration sintering process from the state in which the process gas remains in the internal pressure measurement pipe 10 In the second stage, 10 SLM helium is supplied into the core tube 2 through the gas supply pipe 8 in order to clean out the residual gas from the inside of the core pipe 2 and the internal pressure measurement pipe 10, and the gas discharge pipe 9 is Then, the process gas in the reactor core tube 2 is expelled toward the exhaust gas treatment device 18, and the branch pipe 16 is opened by opening the valve 15 provided in the branch pipe 16 connected to the internal pressure measurement pipe 10. Then, the process gas in the internal pressure measurement pipe 10 was expelled toward the exhaust gas treatment device 19. After 2.5 hours from the start of exhaust of the process gas in the second stage, it was confirmed that the measured value of the fluorine concentration in the core tube 2 by the gas detector 13 became 0 ppm, and the porous base material 1 was removed from the core tube Extracted from 2.

比較例１
以上の各実施例１〜４と比較するため、図３に示す脱水焼結炉を用い、多孔質母材１の脱水焼結を行った。図３に示す脱水焼結炉は、図２に示す本発明の第１の実施形態の脱水焼結炉とは、内圧測定用配管１０に接続された分岐管１６およびその分岐管１６に設けられているバルブ１５が装備されていない点、すなわち内圧測定用配管１０内からの残留ガス除去手段が設けられていない点が異なるものである。 Comparative Example 1
In order to compare with each of the above Examples 1 to 4, the porous base material 1 was dehydrated and sintered using the dehydration sintering furnace shown in FIG. The dehydration sintering furnace shown in FIG. 3 differs from the dehydration sintering furnace of the first embodiment of the present invention shown in FIG. 2 in the branch pipe 16 connected to the internal pressure measurement pipe 10 and the branch pipe 16. The difference is that the valve 15 is not equipped, that is, the means for removing the residual gas from the internal pressure measurement pipe 10 is not provided.

図３に示す脱水焼結炉による脱水焼結工程の第１段階において、ガス供給管８を介して炉心管２内に、４ＳＬＭのヘリウムガスと、０．１５ＳＬＭのＳｉＦ_４ガスとの混合プロセスガスを供給した。ＳｉＦ_４ガスの供給により、多孔質母材１などに含まれる水分とＳｉＦ_４ガスが反応し、ＳｉＦ_４ガスはＨＦガスとなる。また、ガス排出管９に設けた三方弁１４により、ガス排出管９に導入された混合プロセスガスを同ガス排出管９に設けた圧力調整装置７を通して排ガス処理装置１８に押し出すと同時に、圧力調整装置７により炉心管２内の圧力を制御した。このとき、内圧測定用配管１０内にプロセスガスが存在している。 In the first stage of the dehydration sintering process by the dehydration sintering furnace shown in FIG. 3, a mixed process gas of ₄ SLM helium gas and 0.15 SLM SiF ₄ gas is introduced into the furnace core tube 2 through the gas supply pipe 8. Supplied. The supply of SiF ₄ gas, moisture and SiF ₄ gas contained in a porous preform 1 is reacted, SiF ₄ gas becomes HF gas. In addition, the three-way valve 14 provided in the gas discharge pipe 9 pushes the mixed process gas introduced into the gas discharge pipe 9 to the exhaust gas treatment device 18 through the pressure adjustment device 7 provided in the gas discharge pipe 9 and simultaneously adjusts the pressure. The pressure in the furnace core tube 2 was controlled by the device 7. At this time, the process gas exists in the internal pressure measurement pipe 10.

図３に示す脱水焼結炉による脱水焼結工程の第２段階において、炉心管２および内圧測定用配管１０の内部から残留ガスを一掃するために、ガス供給管８を介して１０ＳＬＭの窒素を炉心管２内に供給し、ガス排出管９を介して、炉心管２内のプロセスガスを排ガス処理装置１８へ向けて追い出し、内圧測定用配管１０内のプロセスガスも排ガス処理装置１９へ向けて追い出すことを試みたが、第２段階におけるプロセスガスの排気開始から３時間経過後のガス検知器１３による炉心管２内のフッ素濃度の測定値は１ｐｐｍであり、脱水焼結後の多孔質母材１を炉心管２から抜去することはできず、第２段階におけるプロセスガスの排気開始から６時間経過後に、ガス検知器１３による炉心管２内のフッ素濃度の測定値が０ｐｐｍになったことを確認し、多孔質母材１を炉心管２から抜去した。 In the second stage of the dehydration and sintering process by the dehydration and sintering furnace shown in FIG. 3, 10 SLM of nitrogen is removed via the gas supply pipe 8 in order to sweep out residual gas from the inside of the core tube 2 and the internal pressure measurement pipe 10. The gas is supplied into the core tube 2, and the process gas in the core tube 2 is expelled toward the exhaust gas treatment device 18 through the gas discharge tube 9, and the process gas in the internal pressure measurement pipe 10 is also directed toward the exhaust gas treatment device 19. Attempted to expel, but the measured value of the fluorine concentration in the furnace core tube 2 by the gas detector 13 after 3 hours from the start of exhaust of the process gas in the second stage is 1 ppm, and the porous mother after dehydration sintering The material 1 cannot be removed from the core tube 2, and the measured value of the fluorine concentration in the core tube 2 by the gas detector 13 becomes 0 ppm after 6 hours have passed since the start of exhaust of the process gas in the second stage. Verify was withdrawn porous preform 1 from the core pipe 2.

比較例２
図３に示す脱水焼結炉による比較例１に記載されている脱水焼結工程の第１段階終了後、同脱水焼結工程の第２段階において、炉心管２および内圧測定用配管１０の内部から残留ガスを一掃するために、ガス供給管８を介して４ＳＬＭの窒素を炉心管２内に供給し、ガス排出管９を介して、炉心管２内のプロセスガスを排ガス処理装置１８へ向けて追い出し、内圧測定用配管１０内のプロセスガスも排ガス処理装置１９へ向けて追い出すことを試みた。第２段階におけるプロセスガスの排気開始から１２時間経過後に、ガス検知器１３による炉心管２内のフッ素濃度の測定値が０ｐｐｍになったことを確認し、多孔質母材１を炉心管２から抜去した。 Comparative Example 2
After completion of the first stage of the dehydration and sintering process described in Comparative Example 1 using the dehydration and sintering furnace shown in FIG. 3, in the second stage of the dehydration and sintering process, the inside of the core tube 2 and the internal pressure measurement pipe 10 4SLM nitrogen is supplied into the reactor core tube 2 through the gas supply pipe 8 and the process gas in the reactor core tube 2 is directed to the exhaust gas treatment device 18 through the gas discharge pipe 9. Attempts were made to expel the process gas in the internal pressure measurement pipe 10 toward the exhaust gas treatment device 19. After 12 hours from the start of exhaust of the process gas in the second stage, it was confirmed that the measured value of the fluorine concentration in the core tube 2 by the gas detector 13 became 0 ppm, and the porous base material 1 was removed from the core tube 2 Extracted.

実施例１〜４と、比較例１および比較例２とを比較すれば明らかなように、実施例１〜実施例４においては脱水焼結後に必要な排気時間は、比較例１および比較例２で使用した、残留ガス除去手段を持たない脱水焼結炉による多孔質母材の脱水焼結後に必要な排気時間に比べて極めて短いことが確認された。 As is clear when Examples 1 to 4 are compared with Comparative Examples 1 and 2, the exhaust time required after dehydration sintering in Examples 1 to 4 is Comparative Example 1 and Comparative Example 2. It was confirmed that the exhaust time required after dehydration and sintering of the porous base material in the dehydration and sintering furnace having no residual gas removal means used in 1 was extremely short.

１光ファイバ用多孔質母材
２炉心管
４ヒータ
５内圧計
７圧力調整装置
８ガス供給管
９ガス排出管
１０内圧測定用配管
１２分岐管
１３ガス検知器
１４三方弁
１５バルブ
１６分岐管
１７蓋
１８排ガス処理装置
１９排ガス処理装置 DESCRIPTION OF SYMBOLS 1 Porous preform | base_material for optical fibers 2 Reactor core tube 4 Heater 5 Internal pressure gauge 7 Pressure regulator 8 Gas supply pipe 9 Gas exhaust pipe 10 Internal pressure measurement pipe 12 Branch pipe 13 Gas detector 14 Three-way valve 15 Valve 16 Branch pipe 17 Lid 18 Exhaust gas treatment device 19 Exhaust gas treatment device

Claims

A furnace tube for dehydrating and sintering the porous preform for silica glass optical fiber, a heater for heating the inside of the furnace tube, a gas supply tube for supplying process gas or inert gas into the furnace tube, A gas discharge pipe for discharging the gas in the reactor core tube, an internal pressure gauge for measuring the pressure in the reactor core tube, and an internal pressure measurement pipe connecting the reactor core tube and the internal pressure gauge; In a dehydration sintering furnace provided with an opening / closing part that is opened and closed for insertion and removal from the core tube of the base material,
Have a residual gas removal means for removing the gas remaining after the dehydration sintering of the porous preform in the pressure measurement in the pipe,
As the residual gas removing means, an inert gas supply port is provided in the internal pressure measurement pipe, and the gas supply port is connected to an inert gas supply source. Dehydration sintering furnace for vitrification of materials.

In the dehydration sintering furnace according to claim 1 ,
A dehydration sintering furnace for vitrifying a porous preform for optical fibers, comprising a gas detector for measuring a gas concentration in the furnace core tube.

In the dehydration sintering method of the porous preform for optical fiber using the dehydration sintering furnace,
The dehydration and sintering furnace supplies a core tube for dehydrating and sintering a porous preform for a silica glass optical fiber, a heater for heating the inside of the core tube, and supplying process gas or inert gas into the core tube. A gas supply pipe for discharging the gas in the core tube, an internal pressure gauge for measuring the pressure in the core tube, and an internal pressure measuring pipe connecting the core tube and the internal pressure gauge, and the core The pipe is provided with an opening / closing portion that is opened and closed for insertion and removal of the porous preform for the optical fiber from the reactor core tube, and the internal pressure measurement pipe after the porous preform is dehydrated and sintered. A residual gas removing means for removing the gas remaining in the interior;
A first stage in which a porous base material for an optical fiber is inserted into the core tube and a process gas is introduced into the core tube, and the inside of the core tube is heated by a heater to dehydrate and sinter the porous base material for the optical fiber; After the first stage, before opening the opening and closing part of the reactor core tube, an inert gas is introduced into the reactor core tube to expel residual gas in the reactor core tube, and the residual gas removing means possess a second step of removing the residual gas, and a third step of taking out from the core tube followed by opening the opening and closing portion of the core tube porous preform,
In carrying out the second stage, the amount of exhausted process gas and the amount of inert gas supplied are increased compared to those in the first stage, and the dehydration firing for vitrifying the porous optical fiber preform is performed. How to conclude.

In the dehydration sintering method of the porous preform for optical fiber using the dehydration sintering furnace,
The dehydration and sintering furnace supplies a core tube for dehydrating and sintering a porous preform for a silica glass optical fiber, a heater for heating the inside of the core tube, and supplying process gas or inert gas into the core tube. A gas supply pipe for discharging the gas in the core tube, an internal pressure gauge for measuring the pressure in the core tube, and an internal pressure measuring pipe connecting the core tube and the internal pressure gauge, and the core The pipe is provided with an opening / closing portion that is opened and closed for insertion and removal of the porous preform for the optical fiber from the reactor core tube, and the internal pressure measurement pipe after the porous preform is dehydrated and sintered. A residual gas removing means for removing the gas remaining in the interior;
A first stage in which a porous base material for an optical fiber is inserted into the core tube and a process gas is introduced into the core tube, and the inside of the core tube is heated by a heater to dehydrate and sinter the porous base material for the optical fiber; After the first stage, before opening the opening and closing part of the reactor core tube, an inert gas is introduced into the reactor core tube to expel residual gas in the reactor core tube, and the residual gas removing means A second stage for removing the residual gas, and then a third stage for opening the open / close portion of the core tube and removing the porous base material from the core tube,
In carrying out the second stage, the dehydration sintering method for vitrifying the porous optical fiber preform is characterized by changing the pressure in the furnace core tube every predetermined time.

In the dehydration sintering method according to claim 4 ,
In carrying out the second stage, dehydration firing for vitrifying a porous optical fiber preform is characterized in that the process gas displacement is changed as means for changing the pressure in the furnace tube every predetermined time. How to conclude.

In the dehydration sintering method according to claim 4 ,
Dehydration for vitrifying a porous preform for optical fiber, characterized in that the inert gas supply amount is changed as means for changing the pressure in the furnace core tube every predetermined time in carrying out the second stage. Sintering method.

In the dehydration sintering method according to claim 3 ,
In carrying out the second stage, helium is used as an inert gas to be supplied to the core tube, and a dehydration sintering method for vitrifying a porous optical fiber preform.