JP2001122635A - Method for manufacturing optical fiber, method for manufacturing preform and apparatus for manufacturing the preform - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a perform which is decreased in variations of outside diameters and an optical fiber. SOLUTION: This method for manufacturing the optical fiber has a setting step of setting heating conditions for heating a glass rod which is a perform of the optical fiber and stretching speed for stretching the same in accordance with the prescribed numerical values changing with the progression of the heating and stretching of the glass rod, a heating and stretching step for forming the perform by heating and stretching the glass in accordance with the set heating conditions and stretching speed rod and a drawing step of forming the optical fiber by further heating the perform and pulling the perform to a fiber form.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical fiber manufacturing method, a preform manufacturing method, and a preform manufacturing apparatus for manufacturing a preform and an optical fiber having small variations in outer diameter.

[0002]

2. Description of the Related Art FIG. 1 shows a conventional glass base material primary stretching apparatus 400. Glass base material 10 serving as base material for optical fiber
2 is a product diameter (φ30 to 80 m) which is usually drawn by the glass base material primary drawing device 400 and is convenient for drawing.
The glass rod 106 is reduced in diameter from 3 mm to 5 mm larger than m). Glass base material primary stretching device 400
Includes a heating furnace 100 for heating the glass base material 102 and a stretching chuck 104 for gripping and stretching the heated glass base material 102. About 2000 ℃
The glass base material 102 is drawn by holding the glass base material 102 with a stretching chuck 104 and continuously pulling the glass base material from below the heating furnace 100 as a glass rod 106.

FIG. 2 shows a configuration of a conventional glass lathe 110. The glass rod 106 reduced in diameter by the glass base material primary stretching apparatus 400 is further subjected to secondary stretching by the glass lathe 110 to be reduced in diameter to a predetermined product diameter to become the preform 107. The glass lathe 110
Chuck 118 and 11 for holding glass rod 106
9 and a tail stock 116 for moving the chuck 119.
And a heating source 122 for heating the glass rod 106. One chuck 1 for holding the glass rod 106
18 is fixed, and the other chuck 119 is movable and a traction force acts. The glass rod 106 held by the chucks 118 and 119 is stretched by moving in a direction in which the tail stock 116 is gradually pulled while being heated by the heating source 122, and is processed into a target outer diameter.

[0004]

When the glass preform 102 is stretched using the conventional glass preform primary stretching apparatus 400, there is a possibility that a bent glass rod 106 may be produced. Further, when the preform 107 is manufactured by stretching the glass rod 106 using the conventional glass lathe 110,
Heating source 1 in the production of each preform 107
The outer diameter of the preform 107 fluctuated due to the difference in the gas amount 22 and the moving speed of the tail stock 116. When the bent glass rod 106 manufactured by the conventional glass base material primary stretching apparatus 400 was secondarily stretched using the glass lathe 110, the outer diameter of the preform 107 further varied. Furthermore, the preform 10 having a varied outer diameter
When the optical fiber is manufactured by drawing the No. 7, the outer diameter of the optical fiber varies, and it has been difficult to manufacture a high quality optical fiber.

Accordingly, an object of the present invention is to provide an optical fiber manufacturing method, a preform manufacturing method, and a preform manufacturing apparatus which can solve the above-mentioned problems. This object is achieved by a combination of features described in the independent claims. The dependent claims define further advantageous embodiments of the present invention.

[0006]

In order to achieve the above object, a method for manufacturing an optical fiber according to the first aspect of the present invention is directed to a method of heating and drawing a glass rod serving as a base material of the optical fiber. A setting step of setting a heating condition for heating the glass rod and a stretching speed based on a predetermined numerical value that changes in accordance therewith; and heating and stretching the glass rod based on the set heating condition and the stretching speed. It is preferable that the method further includes a heating and drawing step for generating a reform, and a drawing step for further heating the preform and drawing the optical fiber in a linear shape.

In the setting step, the heating condition and the stretching speed may be set based on the elapsed time of the heating stretching as a numerical value. The heating and stretching step is a drawing step of reducing the outer diameter of the end of the glass rod. Is preferred. In the setting step, the position of the burner for heating the glass rod and the amount of gas supplied to the burner may be set as the heating condition based on the elapsed time of the heat stretching. Further, in the setting step, the moving speed of the chuck holding the glass rod may be set as the stretching speed based on the elapsed time of the heating stretching.

In the setting step, the heating condition and the stretching speed may be set based on the length of the glass rod stretched by the heating stretching as a numerical value. The heating and stretching step is a drawing step of reducing the outer diameter of the end of the preform. It is preferable to squeeze. In the setting step, the moving amount of the burner for heating the glass rod and the amount of gas supplied to the burner may be set as heating conditions based on the stretched length. Further, in the setting step, the moving speed of the chuck that holds the glass rod may be set as the drawing speed based on the drawn length. In addition, the setting step may use an encoder that measures a rotation angle of a motor provided in a motor that drives the chuck in order to detect an amount of movement of the chuck.

In the setting step, the heating condition and the stretching speed may be set based on the tensile tension generated in the glass rod by the heating and stretching as numerical values. Also,
In the heating and stretching step, a heating source for heating the glass rod moves in the longitudinal direction of the glass rod with the progress of the heating and stretching, and the heating and stretching step performs a tensile tension until the heating source moves a predetermined distance. Is substantially equal to the average of the tensile tensions after the heating source has traveled a predetermined distance.
% Is preferably controlled to be not more than 10%.

Further, the heating and stretching step may include increasing the tensile tension until the heating source travels a predetermined distance from substantially 80% of the average value of the tensile tension after the heating source travels a predetermined distance. It is preferable to control to 110%. Furthermore,
Preferably, the predetermined distance is substantially between 50 mm and 150 mm. In the heating and stretching step, it is preferable to control the speed at which the glass rod is stretched when the heating source moves a predetermined distance to a constant speed. Further, the setting step may set a moving speed of the chuck for gripping the glass rod as a drawing speed based on the tensile tension.

In the setting step, the heating conditions and the drawing speed are set based on the numerical values of the dummy rods welded to both ends of the glass rod and the positions of the marks provided at the joints of the glass rods. You may. The heating and stretching step is a drawing step of reducing the outer diameter of the end of the glass rod. In the heating and drawing step, it is preferable that the end of the glass rod be drawn by heating based on the position of the sign in the drawing step. In the setting step, the heating condition and the stretching speed may be set based on the position of the cut provided at the joint between the glass rod and the dummy bar as the position of the marker. Further, it is preferable that the setting step sets the heating conditions and the stretching speed based on the position of the fluorescent paint applied at the joint between the glass rod and the dummy rod as the position of the marker.

In the setting step, the stretching speed at each position in the axial direction of the glass rod is set based on the numerical value of the outer diameter at each position in the axial direction of the glass rod, and the average value of the outer diameter at each position is set. May be set based on the heating conditions. Further, the end of the glass rod is narrowed, and the setting step is based on the change in the outer diameter at each axial position of the glass rod as a numerical value and the change in the axial length of the glass rod due to heating and stretching. Detecting the position of the constricted portion where the rod is constricted, setting a polishing range for polishing the glass rod with a flame based on the position of the constricted portion, and setting a flame power condition based on the outer diameter of the constricted portion. And a heating and stretching step,
It is preferable that the polishing range of the glass rod is polished by a flame under thermal power conditions.

[0013] A method of manufacturing an optical fiber according to a second aspect of the present invention includes a heating and stretching step of heating and stretching a glass rod serving as a base material of the optical fiber to produce a preform, and further heating the preform. A drawing step of drawing an optical fiber by drawing in a linear form, wherein a heating and drawing step is a preheating step of heating the glass rod until a predetermined part is softened, and further heating and drawing the predetermined part to extend outside the predetermined part. It is preferable to have a drawing step of reducing the outer diameter of the end of the glass rod by a drawing step of reducing the diameter. Further, it is preferable that the drawing step further includes a secondary heating step of heating a region on the center side of the glass rod from the center of the predetermined portion with a flame narrowed down from the flame thickness in the preliminary heating step.

In the first embodiment of the present invention, a method of manufacturing a preform as a preform of an optical fiber is based on a predetermined numerical value which changes with progress of heating and stretching of a glass rod as a preform of a preform. A setting step of setting a heating condition for heating the glass rod and a stretching speed for stretching, and a heating and stretching step for heating and stretching the glass rod to generate a preform based on the set heating condition and the stretching speed. Preferably, it is provided.

In the setting step, the heating condition and the stretching speed may be set based on the elapsed time of the heating stretching as a numerical value. The heating and stretching step is a drawing step of reducing the outer diameter of the end of the glass rod. Is preferred.

In the setting step, the heating conditions and the stretching speed may be set based on the length of the glass rod stretched by the heating stretching as a numerical value. The heating and stretching step is a drawing step of reducing the outer diameter of the end of the preform. It is preferable to squeeze.

Further, in the setting step, the heating conditions and the stretching speed may be set based on the tensile tension generated in the glass rod by the heating and stretching as numerical values. Furthermore,
In the heating and stretching step, a heating source for heating the glass rod moves in the longitudinal direction of the glass rod with the progress of the heating and stretching, and the heating and stretching step performs a tensile tension until the heating source moves a predetermined distance. Is substantially equal to the average of the tensile tensions after the heating source has traveled a predetermined distance.
% Is preferably controlled to be not more than 10%.

Further, the heating and stretching step may include increasing the tensile tension until the heating source travels a predetermined distance from substantially 80% of the average value of the tensile tension after the heating source travels a predetermined distance. It is preferable to control to 110%. Also,
Preferably, the predetermined distance is substantially between 50 mm and 150 mm. Further, it is preferable that the heating and stretching step controls the speed at which the glass rod is stretched when the heating source moves a predetermined distance to a constant speed.

In the setting step, the heating conditions and the drawing speed are set based on the dummy rods welded to both ends of the glass rod as numerical values and the positions of the marks provided at the joints of the glass rods. You may. The heating and stretching step is a drawing step of reducing the outer diameter of the end of the glass rod. In the heating and drawing step, it is preferable that the end of the glass rod be drawn by heating based on the position of the sign in the drawing step.

In the setting step, the stretching speed at each position in the axial direction of the glass rod is set based on the outer diameter at each position in the axial direction of the glass rod as a numerical value, and the average value of the outer diameter at each position is set. May be set based on the heating conditions. Further, the end of the glass rod is narrowed, and the setting step is based on the change in the outer diameter at each axial position of the glass rod as a numerical value and the change in the axial length of the glass rod due to heating and stretching. Detecting the position of the constricted portion where the rod is constricted, setting a polishing range for polishing the glass rod with a flame based on the position of the constricted portion, and setting a flame power condition based on the outer diameter of the constricted portion. And a heating and stretching step,
It is preferable that the polishing range of the glass rod is polished by a flame under thermal power conditions.

According to a second aspect of the present invention, there is provided a method of manufacturing a preform serving as a base material of an optical fiber, comprising: a preheating step of heating a predetermined portion of a glass rod serving as a base material of the preform until it is softened. Preferably, the method further includes a drawing step of further heating and stretching the predetermined portion to reduce the outer diameter of the end portion of the glass rod by a stretching step of reducing the outer diameter of the predetermined portion. It is preferable that the drawing step includes a secondary heating step of heating a region on the center side of the glass rod from the center of the predetermined portion with a flame narrowed down from the thickness of the flame in the preheating step.

An apparatus for manufacturing a preform serving as a preform of an optical fiber according to the first embodiment of the present invention comprises a heating source for heating a glass rod serving as a preform of a preform, and a stretching section for stretching the glass rod. A measuring device that measures a numerical value that changes with the progress of heating and stretching of the glass rod, and a controller that controls a heating condition of a heating source and a stretching speed of a stretching unit based on the numeric value measured by the measuring device. Is preferred.

Further, the measuring device measures the elapsed time of the heat stretching as a numerical value, and the controller controls the heating conditions and the stretching speed based on the elapsed time of the heating stretching measured by the measuring device. Good. Further, the measuring device measures the moving distance of the stretching portion due to the heating stretching as a numerical value, the controller, based on the moving distance of the stretching portion measured by the measuring device,
The heating conditions and the stretching speed may be controlled.

Further, the measuring device measures the tensile tension generated in the glass rod by the heating and drawing as a numerical value, and the controller determines the heating condition and the heating condition based on the tensile tension generated in the glass rod measured by the measuring device. It is preferable to control the stretching speed. Further, the heating source moves in the longitudinal direction of the glass rod as the heating and drawing progresses, and the controller adjusts the tensile tension until the heating source moves a predetermined distance, and the heating source moves the predetermined distance. It is preferable to control the stretching speed so that it is substantially 110% or less of the average value of the tensile tension after the movement.

Further, the control unit may adjust the tensile tension until the heating source travels a predetermined distance from substantially 80% to 110% of the average value of the tensile tension after the heating source travels a predetermined distance. % Is preferably controlled. Further, the predetermined distance is substantially 50 mm to 150 m.
It is preferably between m. Further, the control unit may control the stretching speed to a constant speed when the heating source moves a predetermined distance.

The measuring device measures the position of each of the dummy rods welded to both ends of the glass rod as numerical values and the position of a marker provided at the joint of the glass rods. The heating condition and the stretching speed may be controlled based on the position of the mark.
Further, the measuring device measures the outer diameter at each position in the axial direction of the glass rod as a numerical value, and the controller controls each of the axial directions of the glass rod based on the outer diameter at each position in the axial direction of the glass rod. The heating conditions may be controlled based on the average value of the outer diameter at each position by controlling the stretching speed at each position.

Note that the above summary of the present invention does not list all of the necessary features of the present invention, and sub-combinations of these features may also constitute the present invention.

[0028]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described through embodiments of the present invention. However, the following embodiments do not limit the claimed invention and have the features described in the embodiments. Not all combinations are essential to the solution of the invention.

FIG. 3 shows a system of an optical fiber manufacturing apparatus according to the present invention. The system of the optical fiber manufacturing apparatus of the present invention includes a glass base material generating apparatus 600 for generating a glass base material 102 serving as a base material of an optical fiber, and a glass base material dehydrating and sintering apparatus 700 for dehydrating and sintering the glass base material 102. A glass base material primary stretching apparatus 900 for primary stretching the glass base material 102 to produce a glass rod 106, and a glass rod 106
A glass rod transfer device 380 for transferring the glass rod 106, a glass rod secondary drawing device 111 for forming the preform 107 by secondly drawing the glass rod 106, and a glass rod 10.
And a preform drawing apparatus 500 that draws 6 to produce an optical fiber.

FIG. 4 shows an optical fiber manufacturing method according to the present invention. The glass base material 102 is generated by the glass base material generation device 600 using the VAD method or the like (S200), dehydrated in chlorine gas by the glass base material dehydration and sintering device 700, and sintered in an inert gas ( S202). The diameter of the glass preform 102 is usually φ110 to 200 mm, but the diameter actually used for drawing an optical fiber is
φ30 to 80 mm. Therefore, the glass base material 102 which has been dehydrated and sintered is primarily drawn by the glass base material primary drawing apparatus 900 to reduce the diameter of the product, which is convenient for drawing, from 3 to 80 mm to a diameter larger by 3 to 5 mm. 106 (S204). The glass rod 106 is transported by the glass rod transport device 380 (S205), and the glass rod secondary stretching device 111 is used.
Preform 1
07 (S206). The preform 107 is drawn by being heated and drawn linearly by the preform drawing apparatus 500 to be formed into an optical fiber (S210).

FIG. 5 shows the configuration of a glass base material primary stretching apparatus 900 according to the present invention. Glass base material primary stretching device 900
Is a primary stretching device 402 for thermally stretching the glass base material 102.
And a glass rod fusing device 370 for fusing the glass rod 106. The primary stretching device 402 includes the heating furnace 100
And a suspension mechanism 134 for feeding the glass preform 102 provided above the drawing furnace 130 into the drawing furnace 130 at a predetermined speed. Primary stretcher 40
Reference numeral 2 further includes a take-off mechanism 140 provided below the drawing furnace 130 for holding the thinned glass rod 106 and drawing the glass rod 106 at a predetermined speed. The hanging mechanism 134 has a base material fixing section 136, and the pulling mechanism 140 has a pulling chuck 142. The glass rod fusing device 370 includes the burner 17
6, rotating table 210, timing belt 214, motor 212, support leg 208, burner stand 216, drawing-in pulling device 206, and fusing pulling chuck 2
18

The glass base material 102 is attached to the base material fixing portion 136, and is fed into the heating furnace 100 at a predetermined speed by the feeder 204. The glass base material 102 heated by the heater of the heating furnace 100 is gripped by the take-off chuck 142, stretched and reduced in diameter, and
06. The glass rod 106 is drawn by the drawing pulling device 206 at a pulling speed corresponding to a target outer diameter and drawn to a desired diameter. At this time, the outer diameter of the glass rod 106 is measured by the outer diameter measuring device 152, and based on this information, the feeder 204, the heating furnace 10
0, the drawing take-off device 206 and the like are controlled, and the drawing is performed so that the outer diameter of the glass rod 106 becomes a desired value.

The glass rod 106 stretched to a predetermined diameter and length has a bubble-free portion or a diameter of 0.3 m.
The portion containing no bubbles of m or more is blown off by the burner 176. As the heating means, an oxygen-hydrogen flame is preferable, and a hydrocarbon gas flame such as a propane oxygen flame may be used.
The burner 176 is installed on the turntable 210 via the support leg 208. The rotating table 21 is driven by a driving device such as a motor 212 via a timing belt 214.
0 rotates. The rotary table 210 has a burner table 216.
It is installed above. While rotating the burner 176, the glass rod 106 is heated and the glass rod 1 is heated.
The glass rod 106 is melted by pulling the sheet No. 06 at a predetermined speed and with a pulling force by the melting chuck 218.

FIG. 6 shows a primary stretching device 402 in which a base material 138 is held by a base material fixing portion 136 to adjust the stretching axis. The suspension mechanism 134 includes a mechanism (not shown) for adjusting the degree of verticality of the base material fixing part 136. A mechanism (not shown) for moving the take-up mechanism 140 in the horizontal plane in the front-rear and left-right directions is also provided.

FIG. 7 shows a detailed flowchart of the glass base material primary stretching step (S204) shown in FIG.
The glass base material primary stretching step (S204) includes a step of adjusting the stretching axis of the primary stretching device 402. First, a rod made of metal or ceramics whose straightness is guaranteed is prepared as a prototype 138. The prototype 138 usually has a length including the glass base material 102 and a dummy rod welded to the glass base material 102, and the linearity of the axis of the prototype 138 is guaranteed over the entire length.

First, as shown in FIG. 6, the prototype 138 is gripped and fixed to the base material fixing portion 136 of the suspension mechanism 134 (S110) so that the orientation of the prototype 138 matches the vertical direction. The inclination A of the suspension mechanism 134 is adjusted (S1).
12). Once the adjustment is completed, once the prototype 138 is
36 (S114).

FIG. 8 shows a state in which the prototype
2 shows the primary stretching device 402 gripped. The prototype 138 is gripped by the pulling chuck 142 of the pulling mechanism 140 (FIG. 7, S116), and the inclination B of the pulling mechanism 140 is adjusted so that the orientation of the gripped prototype 138 matches the vertical direction. It is adjusted (FIG. 7, S118). At this time, it is desirable that take-up chuck 142 grips approximately the center of prototype 138 in the longitudinal direction. Note that the order of adjustment of the suspension mechanism 134 and the take-off mechanism 140 may be reversed. That is, after adjusting the take-off mechanism 140 first, the suspension mechanism 134 may be adjusted.

FIG. 9 shows that the prototype 138 is
1 shows a primary stretching device 402 gripped by a take-off mechanism 140. After each adjustment of the suspension mechanism 134 and the take-off mechanism 140 is completed, the prototype 13 is held in a state where the base material 138 is held by the base material fixing portion 136 of the suspension mechanism 134.
8 with the take-off chuck 142 of the take-off mechanism 140
(FIG. 7, S120). In this state, the prototype 138 is taken off so that the amount of displacement of the prototype 138 from the vertical axis in the horizontal direction, that is, the verticality, is within 0.5 mm per 1 m of length. The horizontal position of the mechanism 140 or the horizontal position C of the suspension mechanism 134 is adjusted (FIG. 7, S12).
2).

Next, the primary stretcher 402 whose verticality has been adjusted
The glass base material 102 is primarily stretched to form a glass rod 106 (FIG. 7, S124). Finally, the glass rod 106 is blown using the glass rod fusing device 370 (S126 in FIG. 7).

FIGS. 10 and 11 show the take-off mechanism 140
In this example, an example in which take-up rollers 144a and 144b are used in place of the take-up chuck 142 will be described. When the take-up rollers 144a and 144b are used, in order to adjust the verticality of the axis connecting the suspension mechanism 134 and the take-up mechanism 140, a step of gripping the prototype 138 with the take-up chuck 142 (FIG. 7, S116).
Is gripped by the take-off rollers 144a and 144b. Next, the step of adjusting the inclination of the take-off mechanism 140 (FIG. 7,
In S118), the take-off rollers 144a, 144
The inclination of the take-off mechanism 140 is adjusted by adjusting the degree of parallelism and the degree of horizontality between the two rotation axes b, so that the prototype 138 can be held vertically.

Next, a step of holding the prototype 138 by the base material fixing portion 136 and the take-off chuck 142 (FIG. 7, S1)
In 20), as shown in FIG.
The base material 138 is gripped by the base material fixing portion 136 of FIG. Next, in the step of adjusting the horizontal position of the hanging mechanism 134 and the pulling mechanism 140 (FIG. 7, S122), the horizontal position of the entire pulling mechanism 140 including the pulling rollers 144a and 144b or the hanging is performed. By adjusting the horizontal position of the mechanism 134, the suspension mechanism 1
The verticality E of the axis connecting the take-up mechanism section 34 and the take-up mechanism section 140 is adjusted.

With the above adjustment method, the suspension mechanism 13
The verticality of the axis connecting the take-off mechanism 4 and the take-off mechanism 140 can be adjusted with high precision. Therefore, not only when the straight glass base material 102 without the misalignment of the dummy bar is stretched,
Even if the glass base material 102 has a slight bend, a glass rod having a reduced diameter within a desired straightness range can be provided if the axis is not shifted when the dummy bar is attached to the glass base material 102. 106 can be obtained.

The primary stretching device 402 can precisely adjust the verticality when the glass base material 102 is gripped by the hanging mechanism 134 and the pulling mechanism 140, and when the glass base material 102 is gripped by both mechanisms. Therefore, the drawn glass base material 10
Due to the weight of 2, the bending moment, which is a cause of the bending generated in the heat-softened portion of the glass base material 102 with the take-up mechanism 140 as a fulcrum, can be reduced. For this reason, since a rod drawn from the glass base material 102 to which a straight dummy bar is attached in advance does not generate an axial deviation during the drawing, the glass base material 102 can be drawn within a desired straightness range.

FIG. 12 shows the glass preform 102 whose degree of bending has been measured. The glass base material 10 was prepared using the primary stretching device 402 whose verticality was adjusted by the above-described adjustment method.
2 was performed. Next, the degree of bending of the glass rod 106 was measured. First, the stretched glass rod 106 is allowed to stand between two horizontal fulcrums 148 and 149 serving as references, and a measuring instrument 1 such as a dial gauge is moved along the glass rod 106.
50 is scanned to measure the maximum or minimum value of the height from the reference plane. Next, the glass rod 106 is rotated 180 degrees, and the maximum or minimum value of the height from the reference plane is measured in the same manner. Further, the maximum value of the difference between the first measured maximum value and the next measured minimum value or the difference between the first measured minimum value and the next measured maximum value is "2h", and h is a fulcrum. Glass rod 1 per unit length divided by distance L1
06 straightness.

Primary stretcher 4 adjusted according to the above method
5, five straight glass preforms 102 with no misalignment of the dummy rods are drawn, and the obtained glass rod 10
The straightness of each sample No. 6 was measured by the method shown in FIG. The straightness of the obtained glass rods 106 was all within h = 0.5 mm. The glass rod 106 drawn by using the primary drawer 402 that has not been adjusted as described above required a rework of the bend by about 90% on average.

FIG. 13 shows a mechanism in which the primary stretching device 402 controls the number of rotations of the rotating rollers 144a and 144b. The primary stretching device 402 includes rotating rollers 144a and 1
Each of the rotation speeds of 44b is individually controlled. The glass base material 102 is suspended from a base material fixing portion 136 of the primary stretching device 402 and sent to a heating furnace (not shown) at a predetermined speed.
The glass rod 106 that has been heated and softened by the heating furnace and stretched has at least a pair of left and right rollers 144.
a, 144b. The center position of the heat-softened portion of the glass base material 102 can be obtained by measuring the outer diameter value of the heat-softened portion of the glass base material 102 using the outer diameter measuring device 152, and simultaneously processing this outer diameter value. . As the outer diameter measuring device 152, a laser light transmission type is used. The laser light is emitted from a window provided below the heater of the heating furnace toward the heated softening portion of the glass base material 102.

The measured outer diameter value is input to an outer diameter control unit 156, and is compared with a target outer diameter value to calculate the outer diameter.
The rotation speed of a is controlled. Further, information on the center position of the heat-softening unit is input to the position control unit 158, and the deviation between the center position of the heat-softening unit and the stretching axis 154 of the primary stretching unit 402 is obtained. The position control unit 158 calculates a correction value of the number of rotations such that the deviation between the center position of the heat-softening unit and the stretching axis 154 becomes substantially zero, and adds the roller 1
44a based on the number of rotations obtained by adding the number of rotations of the roller 44a.
4b.

FIG. 14 shows the relationship between the deviation between the center position of the heat-softened portion of the glass base material 102 and the stretching axis 154 and the bending of the glass rod 106. The larger the deviation between the center position of the heat-softened portion of the glass base material 102 and the stretching axis, that is, the amount of axis deviation, the greater the bending of the glass rod 106. When the axis shift amount is large, the rollers 144a, 1
The heat-resistant member on the surface of 44b is deformed, and rollers 144a,
The shape of 144b is slightly different between left and right. This indicates that the peripheral speeds of the surfaces of the rollers 144a and 144b are different between the left and right. Therefore, the rollers 144a,
Since the deformation of the surface of the 144b contributes to the bending of the glass rod 106, the bending of the glass rod 106 can be controlled by individually controlling the left and right rotation speeds of the rollers 144a and 144b.

The surfaces of the rollers 144a and 144b are formed of a heat-resistant member made of non-asbestos, asbestos, or the like having heat resistance and flexibility so that the high-temperature glass rod 106 can be easily taken off. Therefore, the surfaces of the rollers 144a and 144b that come into contact with the glass rod 106 are gradually deformed due to the high temperature of the glass rod 106 and pinch force or frictional force. Since the deformed state of the rollers 144a and 144b is slightly different between the left and right rollers, the peripheral speed of the surface of the rollers 144a and 144b is different between the left and right.

FIG. 15 shows the deformation of the surfaces of the rollers 144a and 144b. Left roller 144a and right roller 1
The outer peripheral shape is very different from that of 44b. The number of batches is the number of times the glass base material 102 is stretched. As the number of batches increases, rollers 144a and 144b
Deformation and wear progress. For this reason, the roller 144
A difference occurs in the amount of the glass rod 106 to be drawn between the left and right sides a and 144b, and the position of the heat-softened portion of the glass base material 102 fluctuates. As a result, the glass rod 106 is bent.

FIG. 16 shows the number of batches 300 shown in FIG.
4 shows the displacement of the center position of the heat-softened portion of the metal pipe when the metal pipe is pulled using the rollers 144a and 144b of FIG. The vertical axis shows the displacement of the center position of the heat softening part of the metal pipe, and the horizontal axis shows time. Roller 144a,
A curve A showing the variation of the deviation amount in the rotation direction of 144b is
This shows that the rollers 144a and 144b greatly change during one rotation. On the other hand, curve B
Indicates that the fluctuation of the rollers 144a and 144b in the front-back direction or the depth direction is extremely small.

FIG. 17 shows the displacement of the center position of the heating and softening portion by the primary stretching device 402 of this embodiment. The vertical axis shows the displacement of the center position of the heat-softened portion of the glass base material 102, and the horizontal axis shows the time from the start of stretching. About 15 from the start of stretching
After the lapse of 00 seconds, the displacement of the heat-softened portion is slightly suppressed.
By individually controlling the rotation speeds of the left and right rollers 144a and 144b in this manner, the center position of the heat softening portion is maintained substantially constant, and the glass rod 106 having substantially no bending is manufactured.

(Comparative Example) FIG.
4A and 4B show how the center position of the heat-softening portion changes when the rotation speeds of 4a and 144b are controlled at the same rotation speed. The vertical axis is glass preform 1
02 shows the displacement of the center position of the heat-softening part, and the horizontal axis shows the time from the start of stretching. Outer diameter measuring device 1 similar to the embodiment
The outer diameter value of the glass base material 102 at the heat-softened portion is measured using the glass rod 102, and the right and left rollers 144a and 144b are controlled at the same rotation speed to obtain a glass rod 106 having a predetermined diameter.
Was manufactured. When the rotation speeds of the left and right rollers 144a and 144b were the same, the center position of the heat-softened portion fluctuated greatly, and the drawn glass rod 106 was bent to a degree that required correction.

FIG. 19 shows another embodiment of the burner 176 used in the glass rod fusing device 370. The ring-shaped burner 176 has a ring-shaped gas outlet 194 connected to the hydrogen gas supply pipe 190 and the oxygen gas supply pipe 192. The cooling pipe 1 connected to the cooling water supply pipe 198 and the drain pipe 200 is provided around the outer periphery of the ring-shaped burner 176.
96 are arranged. The annular gas outlet 194
May have a single-layer structure in which a mixed gas of hydrogen gas and oxygen gas is jetted out. There may be.

The glass rod 106 is connected to the ring-shaped burner 1
76, and installed in the ring-shaped burner 176.
When hydrogen gas and oxygen gas are supplied and ignited, a flame 178 is generated.
As a result, the surface of the glass rod 106 heated is melted. Since the ring-shaped burner 176 has good heating efficiency and does not require excessive heating of the glass rod 106, opacity of the glass surface which occurs when the glass is heated at a temperature higher than 2000 ° C. is observed in the melted surface. Absent.

According to the above embodiment, the glass rod 106 was blown. The glass base material 102 having a diameter of 120 mm was heated for 10 minutes by the flame of a ring-shaped burner 176 supplied with 300 L / min of hydrogen gas and 120 L / min of oxygen gas. 106 was blown.
The fusion surface of the glass rod 106 was conical and the surface was transparent.

FIG. 20 shows the structure of the glass rod transfer device 380. The glass rod transport device 380 is used to transport the glass rod 106 generated by the primary stretching device 402. The glass rod 106 is attached to the movable gripping member 24 attached to the air cylinder storage box 244.
5 and the fixed-side holding member 246. When an air cylinder (not shown) provided in the air cylinder storage box 244 is driven, the movable gripping member 245 moves toward the fixed gripping member 246, and the glass rod 10 is moved.
6 is gripped.

The movable gripping member 245 is fixed to the fixed gripping member 2.
The force for pushing 46 can be changed by changing the pressure of the air flowing into the air cylinder in the air cylinder storage box 244. The air pressure of the air cylinder can be changed by operating a switch provided in the operation switch box 248 during the transfer operation of the glass rod 106. In the present embodiment, a two-stage pressing force is obtained as a stepwise adjustment method in which the air pressure for pressing the moving-side holding member 245 against the fixed-side holding member 246 can be adjusted in two steps. For example, the weaker first pressing force for pressing the moving side gripping member 245 against the fixed side gripping member 246 is the first pressing force.
The gripping force is used, and the stronger second pressing force is used as the second gripping force. The first gripping force is 0.5 kg and the second gripping force is 80 k
g.

The air pressure of the air cylinder is not limited to the two-stage adjustment system, but may be a multi-stage adjustment system in which the air pressure is changed to three or more stages or a stepless adjustment system. The rotary actuator 250 is connected to the glass rod 106.
Is rotated from the vertical state to the horizontal state, and the gripping members 245 and 246 are rotated via the air cylinder storage box 244. The support frame 252 supports the glass rod transport device by connecting it to the primary stretching device 402. The handle 254 is used to operate the glass rod transfer device 380, and the rotation shaft 256 is used for the air cylinder storage box 244.
To rotate.

FIG. 21 shows the storage container 2 of the primary stretching device 402.
24 is shown. The storage container 224 includes the tray 260, the support 2
62, a pair of support members 2 supporting the glass rod 106
34a and 234b, and a pair of support members 236a and 236b provided below. Support member 234
The shapes of a, 234b, 236a, and 236b have a substantially semicircular shape that is preferable for supporting the glass rod 106 in the storage container 224, and each pair of support members 234 forms a substantially circular support portion. ing. Support members 234a, 23
4b and the support members 236a and 236b are each connected at one end to the support 262 by a pin, and at the other end to a stop pin 257.
Accordingly, the support members 234a and 234b are pin-connected to the support members 234a and 234b by the stopper pin 258, respectively. The height of the support 262 is 1,550 m
m, the inner diameter of the tray 260 is φ300 mm, and the inner diameter of the support portion of the glass rod 106 formed by the pair of support members 234a and 234b and 236a and 236b is φ180 mm.

When the glass rod 106 having an outer diameter of 80 mm is stored in the storage container 224, the inclination angle α of the support 262 with respect to the front-rear direction which the glass rod 106 can take is −
3.7 ° to + 8.1 °, and the inclination angle β of the column 262 with respect to the left-right direction is −5.9 ° to + 5.9 °. The tilt angles α and β described here are only limit values, and in actual work, the glass rod 106 is stored in various positions within these ranges. The glass rod 106 is the storage container 22
There are various postures within 4.

FIG. 22 shows the operation of the glass rod transfer device 380 when the glass rod 106 is transferred. The glass rod 106 in the storage container 224 is
5 and 246 with the first gripping force (b), and the glass rod 106 is held within the restricted range of the support members 234a and 234b.
(C). Since the first gripping force is very weak as described above, the glass rod 106
Is released, the force greater than the first gripping force is applied to the movable gripping member 2.
45, the movable side gripping member 245 is opened. Further, the frictional force acting between the moving-side grip member 245 and the glass rod 106 and between the fixed-side grip member 246 and the glass rod 106
6, the glass rod 106 cannot be lifted even if the glass rod transport device 380 is lifted while holding the glass rod 106 with the first gripping force.

After confirming that the glass rod 106 has become vertical, the gripping force is switched from the first gripping force to the second gripping force (d), the retaining pins 257, 258 are removed, and the support members 234a, 234b and This lower support member 236
a, 236b are opened, and the glass rod 106 is taken out and transported. The glass rod 106 taken out of the storage container 224 is rotated in a horizontal state and arranged in a storage place. When arranging the glass rods 106 horizontally in the storage location, the glass rod transport device 380 is moved up.
By constantly applying air pressure equal to or higher than a certain pressure to the descending air cylinder, the weight of the glass rod transport device 380 is prevented from being applied to the glass rod 106, and the glass rod 106 can be prevented from being broken.

FIG. 23 shows another embodiment of the glass rod transfer device 380. The glass rod transfer device 380 is
It has two rotating mechanisms A and B each provided with a rotary actuator. Specifically, the rotary shaft 250 is rotated by the rotary actuator 250 to rotate the glass rod 106 from a vertical state to a horizontal state, and the rotary shaft 268 is rotated by the rotary actuator 264, and the rotary shaft 268 is Another rotation mechanism B for moving the glass rod 106 up and down or left and right via the connecting shaft 266 is provided. Rotary axis 2
68 is orthogonal to the rotation axis 256 in the horizontal or vertical direction.

FIG. 24 shows the operation when the glass rod transfer device 380 shown in FIG. 23 transfers the glass rod 106. FIG. 24A shows a glass rod transfer device 38.
0 indicates a plane holding the glass rod 106,
FIG. 24B shows a cross section in a state where the glass rod transport device 380 has moved the glass rod 106 to the V block 240. As shown in FIG.
Are vertically rotated by operating the rotary actuator 250 to be rotated from a vertical state to a horizontal state. Next, FIG.
, The rotary actuator 264 is operated to rotate the gripping members 245 and 246 downward.

By operating the rotary actuator 264, the opening / closing direction of the movable gripping member 245 is changed from the vertical direction to the horizontal direction. For this reason, the moving side gripping member 245 is opened, the glass rod 106 is opened, and V
After being placed on the block 240, the grip members 245 and 246 can be retracted upward. Therefore, a rotation mechanism A for rotating the glass rod 106 from vertical to horizontal.
In addition, another rotation axis 2 orthogonal to the rotation axis 256
By providing the rotation mechanism B having the 68, the workability of transporting the glass rod 106 is greatly improved.

FIG. 25 shows the structure of the glass rod secondary stretching apparatus 111 of the present invention. Glass rod secondary stretching device 1
11, a machine base 112, a fixed chuck 118 and a movable chuck 119, a heating source 122, a mass flow controller 278, tail stocks 114 and 116,
The tail drive motor 275, the tail drive encoder 273, the outer diameter measuring device 124, the carriage 120, the slide screw 270, the carriage motor 274, the carriage encoder 272, the chain 276, and the controller 280 Prepare.

Fixed chuck 118 and movable chuck 11
9 holds the glass rod 106 with the dummy rod 108 welded to both ends. The heating source 122 includes the fixed chuck 11
8 and the glass rod 1 held by the movable chuck 119
Heat 06. The mass flow controller 278
The amount of gas supplied to the heating source 122 is adjusted. The tail stock 116 moves the movable chuck 119 to extend the glass rod 106. The tail drive motor 275 is
The tail stock 116 is driven. The tail drive encoder 273 detects the rotation amount of the tail drive motor 275 and controls the speed of the tail drive motor 275. From the rotation amount of the tail drive motor 275 detected by the tail drive encoder 273, the tail stock 116
Can be obtained.

The outer diameter measuring device 124 is provided for the glass rod 106.
Is measured corresponding to the position of the glass rod 106 in the axial direction. The moving table 120 is provided with a heating source 122 and an outer diameter measuring device 124 at an upper portion, and moves the heating source 122 and the outer shape measuring device 124. The movable table 120 is mounted on the machine base 112 movably along a slide screw 270 provided in parallel with an axis connecting the fixed chuck 118 and the movable chuck 119, and is movable via the slide screw 270 and the chain 276. It is driven by a motor 274. The carriage encoder 272 includes a carriage motor 27
4 is controlled. The controller 280 includes a carriage encoder 272, a carriage motor 274, a chain 276,
Heat source 1 through slide screw 270 and moving table 120
22 is controlled. The controller 280 controls the heating source 12 by controlling the mass flow controller 278.
2 is controlled. The controller 280 controls the tail drive encoder 273 to control the rotation speed of the tail drive motor 275, thereby controlling the moving speed of the tail stock 116. Tailstock 11
By controlling the moving speed of 6, the speed at which the glass rod 106 is stretched is controlled.

The tail stocks 114 and 116, the fixed chuck 118, the movable chuck 119, the tail drive motor 275, and the tail drive encoder 273 constitute a stretching unit that extends the glass rod 106.

The data of the outer shape measurement position and outer shape measurement value measured by the outer shape measuring device 124 and the change in the length of the glass rod 106 obtained from the moving amount of the tail stock 116 are as follows.
Input to the controller 280. The controller 280 controls heating conditions such as the amount of movement of the heating source 122 and the amount of gas supplied to the heating source 122 and the stretching speed of the tail stock 116 based on the input data.

FIG. 26 is a detailed flowchart of the glass rod secondary stretching step (S206) shown in FIG. In the glass rod secondary stretching step (S206), first, the fixed chuck 118 and the movable chuck 11
The dummy rod 108 is set in 9, the dummy rod 108 is welded to both ends of the glass rod 106 (S 146), and the glass rod 106 is set in the glass rod secondary stretching device 111. Next, a notch 284 having a depth of 3 mm is provided as a marker around the joint between the glass rod 106 and the dummy bar 108 (S147).

Next, the start position and the end position of the outer diameter measurement of the glass rod 106 and the target diameter are set (S15).
0) Next, the outer diameter of the glass rod 106 before stretching is measured using the outer diameter measuring device 124 in accordance with the axial position of the glass rod 106 (S152). The stretching speed at each position in the axial direction of the glass rod 106 is set based on the measured outer diameter and the measurement position, and the glass rod 106 is set.
The heating conditions including the amount of gas supplied to the heating source 122 and the amount of movement of the heating source 122 are set based on the average value of the outer diameters of (S153). Next, the glass rod 106 is connected to the heating source 12.
While heating under the heating conditions set by using No. 2, the tail stock 116 is moved at the set stretching speed, and the glass rod 106 is sequentially stretched (S154).

Next, the glass rod 106 and the dummy rod 10
The position of the cut 284 provided at the joint of No. 8 is detected by the outer diameter measuring device 124, so that the glass rod 1
A change in the axial length of the glass rod 106 is measured by detecting the position of the effective portion 06 and measuring the amount of movement of the tail stock 116 by the tail drive encoder 273. Further, the outer diameter at a position 50 mm from the cut 284 toward the center of the glass rod 106 is measured (S15).
6). Next, the position of the cut 284 and the glass rod 10
The heating position of the heating source 122 is set based on the change in the axial length of No. 6, and the gas amount of the heating source 122 is set based on the measured outer diameter. Further, the moving speed of the tail stock 116 is set based on the measured outer diameter (S157). Next, the glass rod 106 is heated and stretched under the set heating conditions and stretching speed, and the end of the glass rod 106 is drawn into a shape having a reduced outer diameter (S158).

Next, the outer diameter of the aperture portion and the portion extended by the aperture are measured by using the outer diameter measuring device 124 so as to correspond to the position, the position of the aperture portion is detected, and the tail drive encoder 273 is used. , Glass rod 10 by drawing
The change in the axial length of No. 6 is measured (S160). Next, based on the detected position of the constricted portion and the change in the axial length of the glass rod 106, the start position and the end position of the flame polishing for polishing the glass rod 106 with a flame and the fire power condition of the flame are set ( S161).

Regarding the start position and the end position of the flame polishing, the fogging to be flame-polished occurs near the portion heated strongly by drawing of the glass rod 106.
The locations where fogging occurs are defined as the start and end positions of the flame polishing. Next, using the heating source 122, the glass rod 106 from the set start position to the end position of the flame polishing is set.
Is flame-polished according to the set thermal power condition (S16).
2). After the flame polishing, the finished outer diameter and length of the glass rod 106 are measured to confirm the shape of the glass rod 106 (S164). Next, the dummy rod 108 is removed from the glass rod 106 (S166).
Is subjected to a surface treatment (S168) to obtain a preform 107.

As described above, the stretching step (S15
4) measuring the outer diameter corresponding to the axial position of the glass rod 106 before the start of each of the end drawing step (S158) and the flame polishing step (S162);
By appropriately setting the heating conditions and the stretching speed in the next step, a glass rod 106 having stable quality can be manufactured.

FIG. 27 shows a glass rod secondary stretching apparatus 11.
An example in which a cooling device 330 is provided on one fixed chuck 118 and one movable chuck 119 will be described. The cooling device 330 protects the chucks 118 and 119 from radiant heat of the heating source 122 by circulating cooling water to the chucks 118 and 119. The cooling device 330 uses a gas or liquid cooling medium. By providing the cooling device 330 in the chucks 118 and 119, the temperature rise of the chucks 118 and 119 is controlled, and deformation of the chucks 118 and 119 is suppressed. For this reason, the transmission accuracy of the driving force for rotating the glass rod 106 is not reduced, the heating unevenness of the glass rod 106 is eliminated, and the fluctuation of the outer diameter value of the glass rod 106 is reduced.

(Embodiment) A cooling device 330 shown in FIG.
Chucks 118 and 119 provided with the heat source 12
2 and O ₂ = 15 as a combustion gas to the heating source 122.
0 SLM, H ₂ = 300 SLM was supplied, and the glass rod 106 having an outer diameter of 50 mm and a length of 1000 mm rotating at 15 rpm was flame-polished while the heating source 122 was relatively moved at a speed of about 20 mm / min. .

FIG. 28 shows the results of measuring the temperatures of the chucks 118 and 119 in the example and the following comparative example. The vertical axis shows the temperatures of the chucks 118 and 119, and the horizontal axis shows the processing time of flame polishing. Chuck 118, 11 of the embodiment
9 was maintained at a temperature as low as about 45 ° C. Therefore, the fluctuation of the driving force for rotating the glass rod 106 due to the deformation of the chucks 118 and 119 was small, and the fluctuation range of the outer diameter of the flame-polished glass rod 106 was as small as 0.02%.

(Comparative Example) The chuck 118 shown in FIG.
When the glass rod 106 was processed under the same conditions as in the example except that the cooling device 330 was removed from 119,
The temperature of the chucks 118 and 119 reached almost 100 ° C. as shown in FIG. For this reason, the chucks 118 and 119
Was deformed, the driving force for rotating the glass rod 106 fluctuated, and the fluctuation range of the outer diameter value of the glass rod 106 after flame polishing was 1.0%, which was larger than that of the example.

FIG. 29 shows the heating source 122 and the outer diameter measuring device 12.
4 shows the relationship between the distance from the glass rod 106 and the variation rate of the outer diameter value of the glass rod 106. The variation rate (%) of the outer diameter of the glass rod in FIG. 29 represents (maximum diameter of glass rod−minimum diameter of glass rod) / (average diameter) × 100. The outer diameter measuring device 124 of the glass rod secondary stretching device 111 in FIG. 25 is a fixed distance from the heating source 122, that is, 10 mm to 50 mm.
Since it is installed at a remote position, an accurate measured value of the outer diameter of the glass rod 106 can be obtained, and the outer diameter of the glass rod 106 can be accurately controlled.

When the glass rod 106 is stretched, the heating source 1
22 is moved, so that the glass rod 106 is heated.
Is the highest temperature at that time.
At a position slightly shifted from the position being heated. The stretching speed per unit length becomes maximum at the position where the glass rod 106 has the highest temperature. It is preferable to control the amount of heating by the heating source and the moving speed of the chuck based on the outer diameter and the target value at the position where the stretching speed is the highest. Therefore, the outer diameter of the glass rod 106 is measured at a position where the stretching speed of the glass rod is maximized by providing the outer diameter measuring device 124 at a position away from the heating source 122 by a certain distance, and the outer diameter and the stretching are measured. The moving speed of the chuck 119 is controlled based on the difference from the target diameter.

The position separated from the heating source 122 by a certain distance is a position separated from the position where the heating source 122 is installed by 10 mm to 50 mm in a direction opposite to the moving direction of the heating source 122. That is, the outer diameter measuring device 124 is installed at a position separated from the heating source 122 by 10 mm to 50 mm in a direction opposite to the moving direction of the heating source 122.

When the heating source 122 is an oxyhydrogen burner, the flow rate of hydrogen gas supplied to the heating source 122 is set to 30 liter / min to 500 liter / min, and the flow ratio of hydrogen / oxygen is set to 1.5 to 3.0. The glass rod 106 is heated, and the moving speed of the heating source 122 is changed from 2 mm / min to 65 mm.
/ Min range. When the flow rate of the hydrogen gas is less than 30 liters / minute, the amount of heat is insufficient, and when it exceeds 500 liters / minute, fuel is wasted. On the other hand, if the flow ratio of hydrogen / oxygen is out of the above range, the calorific value becomes insufficient and stretching becomes difficult.

When the heating source 122 is a propane gas burner, the flow rate of propane gas supplied to the heating source 122 is set to 1 liter / min to 15 liter / min, and the propane gas / oxygen flow ratio is set to 0.1 to 0 liter. .3, the glass rod 106 is heated, and the moving speed of the heating source 122 is controlled in the range of 2 mm / min to 65 mm / min. If the propane gas flow rate is less than 1 liter / minute, the calorific value is insufficient,
If it exceeds 15 liters / minute, fuel is wasted. Also,
When the flow ratio of propane gas / oxygen is out of the above range, the calorific value becomes insufficient and stretching becomes difficult. The moving speed of the heating source 122 is preferably controlled in the range of 2 mm / min to 65 mm / min, and if it is less than 2 mm / min, it takes too much time to elongate. And stretching becomes difficult.

(Example 1) Heating source 122 and outer diameter measuring instrument 1
The distance between the glass rod 1 and the glass rod 1 was set to 15 mm.
06 stretching was started. During the elongation of the glass rod 106, the moving speed of the heating source 122 and the tail stock 116 was controlled based on the difference between the measured outer diameter of the glass rod 106 and the target elongation. The combustion conditions of the heating source 122 were such that the hydrogen gas flow rate was 224 liters / minute, the hydrogen / oxygen flow rate ratio was 2.5, and the moving speed of the heating source 122 was 11 mm / minute. The rate of change of the outer diameter of the glass rod 106 after stretching is
0.9%.

(Embodiment 2) Heating source 122 and external shape measuring instrument 1
24 was set to 40 mm. The hydrogen gas flow rate was set to 199 liter / min, the hydrogen / oxygen flow rate ratio was set to 2.5, and the moving speed of the heating source 122 was set to 13 mm / min. The fluctuation rate of the outer diameter of the glass rod 106 after stretching was 0.6%.

(Comparative Example 1) Heating source 122 and external shape measuring instrument 1
24 was set at 5 mm. The hydrogen gas flow rate was set to 209 liters / minute, the hydrogen / oxygen flow rate ratio was set to 2.5, and the moving speed of the heating source 122 was set to 12 mm / minute. Since the distance between the heating source 122 and the outer shape measuring device 124 was too short, the variation rate of the outer diameter of the glass rod 106 after the stretching was:
The value was 3.7%, which was larger than those in Examples 1 and 2.

(Comparative Example 2) Heating source 122 and external shape measuring instrument 1
24 was set at 60 mm. The hydrogen gas flow rate was set to 237 liters / minute, the hydrogen / oxygen flow rate ratio was set to 2.5, and the moving speed of the heating source 122 was set to 10 mm / minute. Since the distance between the heating source 122 and the outer shape measuring device 124 was too large, the variation rate of the outer diameter of the glass rod 106 after stretching was 2.5%, which was larger than that in Examples 1 and 2. Value.

(Comparative Example 3) Heating source 122 and external shape measuring instrument 1
24 was set at 15 mm. The hydrogen gas flow rate was set to 215 liters / minute, the hydrogen / oxygen flow rate ratio was set to 1.0, and the moving speed of the heating source 122 was set to 12 mm / minute. Since the hydrogen / oxygen flow ratio was 1.0, which was smaller than 1.5, the glass rod 106 could not be drawn.

(Comparative Example 4) Heating source 122 and external shape measuring instrument 1
24 was set at 15 mm. The hydrogen gas flow rate was set to 195 liter / min, the hydrogen / oxygen flow rate ratio was set to 4.0, and the moving speed of the heating source 122 was set to 13 mm / min. Since the hydrogen / oxygen flow ratio was 4.0, which was larger than 3.0, the glass rod 106 could not be drawn.

(Comparative Example 5) Heating source 122 and external shape measuring instrument 1
24 was set at 15 mm. The hydrogen gas flow rate was set at 204 liter / min, the hydrogen / oxygen flow rate ratio was set at 2.5, and the moving speed of the heating source 122 was set at 70 mm / min. Since the moving speed of the heating source 122 was 70 mm / min, which was higher than 65 mm / min, stretching could not be performed.

FIG. 30 shows a configuration in which a tensile tension measuring device 282 is provided in the glass rod secondary stretching apparatus 111 of FIG. The glass rod secondary stretching apparatus 111 is provided with a tension measuring device 282 for measuring the tension applied to the glass rod 106 on the movable chuck 119.
The glass rod secondary stretching apparatus 111 can detect the position of the heating source 122 on the moving table 120 by the moving table encoder 272. Tensile tension measuring device 282
Is connected to the controller 280. Until the amount of movement of the heating source 122 reaches a predetermined distance, the controller 280 controls the moving speed of the tail stock 116 based on the value of the tension of the glass rod 106 provided from the tension measuring device 282. .

FIG. 31 is a detailed flowchart of the stretching step (S154) shown in FIG. First, the heating source 1 is used until a predetermined portion of the glass rod 106 is melted and softened.
The glass rod 106 is preheated by 22 to make the glass rod 106 in a stretchable state (S132). Next, the heating source 122 on the moving table 120 is moved by moving the moving table 120. The movement speed of the heating source 122 may be reduced at the initial stage of stretching, as much as possible, in order to suppress the fluctuation of the outer diameter of the glass rod 106, but may be moved at a constant speed. Further, the amount of gas supplied to the heating source 122 may be constant.

Next, the moving speed of the tail stock 116 is adjusted so that the tensile strength of the glass rod 106 measured by the tensile strength measuring device 282 becomes 80% to 110% of the average value of the tensile strength in a steady state described below. Control (S1
36). Therefore, the moving speed of the tail stock 116 set based on the outer diameter at each position in the axial direction of the glass rod 106 is reset based on the tensile tension of the glass rod 106. The glass rod 106 is stretched by the above-mentioned tensile force until the heating source 122 moves from 50 mm to 150 mm (S138).

Further, when the heating source 122 is
When the controller 280 detects the movement of 0 mm by the moving base encoder 272 (S138), the speed of moving the tail stock 116 is switched to the steady state speed described below by controlling the tail drive encoder 273. (S140). The outer diameter of the glass rod 106 is measured by the outer diameter measuring device 124 (S14).
2) Stretch the glass rod 10 to the desired outer diameter and length.
The stretching is completed when the film 6 is stretched (S144).

Here, the speed in a steady state refers to a speed at which the material balance of the glass rod 106 before and after the stretching is matched. For example, when the original diameter of the glass rod 106 before stretching is D ₁ , the target diameter of the glass rod 106 is D ₂ , the moving speed of the heating source 122 is v ₁ , and the speed of stretching the glass rod 106 is v _2. Assuming that stretching does not occur except for the heated portion and the portion to be heated and stretched is extremely small,

[0099] _{^{D 1 2 v 1 = D 2}} 2 (v 1 + v 2) speed drawing the glass rod 106 at the time when the hold v
₂ is the steady state speed. Therefore, the speed at which the glass rod 106 is drawn may be set by adjusting the moving speed of the heating source 122 and the moving speed of the tail stock 116 based on the original diameter and the target diameter of the glass rod 106 to be drawn. The steady tensile tension of the glass rod 106 is the tensile tension when the glass rod 106 is stretched by the moving speed of the tail stock 116 in the steady state.

FIG. 32 shows a process in which the outer diameter fluctuates when the glass rod 106 is extended. Glass rod 106
Has the property of softening when heated.
As shown in (1), there is a case where it is not possible to sufficiently soften until stretching becomes possible only by preheating. In this state, when the movement of the heating source 122 is started, and simultaneously the tail stock 116 is moved at a predetermined speed to start stretching, the tensile tension generated in the glass rod 106 becomes twice to three times the normal value, and FIG. As shown by the shaded area in (2), the preheated portion rapidly expands and becomes smaller in diameter. The elongation of the glass rod 106 at this time is generally absorbed by the preheated portion, and the newly heated portion of the heating source 122 is not stretched so much, and as shown in FIG. Constriction occurs.

The fluctuation of the outer diameter of the glass rod 106 is likely to occur in a region from the place where the stretching of the glass rod 106 is started to about 50 mm. When stretching proceeds from this location, heat is supplied to the glass rod 106 and the glass rod 106
Since the softening speed and the stretching speed of the glass rod 106 are balanced to be in a steady state, the outer diameter of the glass rod 106 does not fluctuate as shown in FIG. Therefore, in the initial stage of the stretching, the glass rod 106 is extended while controlling the moving speed of the tail stock 116 so that the tensile tension of the glass rod 106 is 110% or less of the average value of the tensile tension in a steady state. The balance between the speed of heat supply to the glass rod 106 and the speed of softening of the glass rod 106 and the speed of elongation of the glass rod 106 is controlled to suppress fluctuations in the outer diameter of the glass rod 106 in the initial stage of elongation.

If the tensile tension of the glass rod 106 at the initial stage of stretching is less than 80% of the steady state, the distance required for the outer diameter of the glass rod 106 to reach the target diameter becomes longer, so that a portion that can be used as a product is reduced. The yield decreases and the yield deteriorates. Further, it takes time until the glass rod 106 reaches the target diameter. Therefore, the tensile tension of the glass rod 106 in the initial stage of stretching is preferably set to 80 to 110% of the average value of the tensile tension in a steady state.

FIG. 33 shows a drawing step (S15) in FIG.
Figure 4 shows the glass rod 106 being stretched along 4). First, as shown in FIGS. 33 (1) and (2), the glass rod 1
After the preliminary heating of 06, the heating source 122 is moved, the tail stock 116 is moved, and the stretching of the glass rod 106 is started. Since the tensile tension of the glass rod 106 is controlled to 110% or less of the normal tensile tension, the glass rod 106 is not subjected to an excessive tensile tension, so that the glass rod 106 is suddenly stretched to cause constriction. Absent. Then, if the heating source 122 moves a predetermined distance while maintaining this balanced state, FIG.
As shown in (3), the balance between the speed of the heat supply to the glass rod 106 and the speed of softening the glass rod 106 and the speed of stretching the glass rod 106 from the initial stage to the steady state is maintained. Variation in diameter can be prevented.

However, if the moving speed of the tail stock 116 is controlled based on the tensile tension as it is, the tensile tension of the glass rod 106 changes due to a slight change in the amount of heat received from the heating source 122 or the like. Therefore, the speed at which the tail stock 116 moves in order to control the tensile tension of the glass rod 106 to be constant changes, and the outer diameter of the drawn glass rod 106 changes. Then, after the heating source 122 has moved a predetermined distance from the start of stretching, the moving speed of the tail stock 116 is switched to the speed at the time of steady state, so that the glass rod 106 due to minute fluctuation of the tensile tension is changed.
Can be prevented from changing.

The time at which the moving speed of the tail stock 116 is switched to the normal speed is when the heating source 122 moves from 50 mm to 150 mm. Heat source 12 from stretching start
Since the speed of heat supply to the glass rod 106 and the speed of softening of the glass rod 106 and the speed of stretching the glass rod 106 are not balanced before the movement of the glass rod 106 by 50 mm, the stretching speed is set to the steady speed. , There is a possibility that constriction may occur due to variation in the outer diameter.
Next, until the heating source 122 moves by 50 mm, the tension of the glass rod 106 is controlled to 110% or less of the steady state. On the other hand, it is preferable that the moving speed of the tail stock 116 be switched to the steady state speed before the heating source 122 moves by 150 mm.

(Example) Glass rod secondary stretching apparatus 11
Using No. 1, the glass rod 106 was stretched. A dummy rod 1 having an outer diameter of 60 mmφ and a length of 250 mm was attached to both ends of a glass rod 106 having an outer diameter of 65 mmφ and a length of 980 mm.
08 were welded. Glass rod 106 and dummy rod 108
The number of rotations around the axis at the time of welding was 30 rpm. An oxyhydrogen burner was used as the heating source 122. The oxygen gas supplied to the heating source 122 was 96 L / min, and the hydrogen gas was 240 L / min.

After preheating the glass rod 106, the heating source 122 was moved at a moving speed of 12.4 mm / min to start stretching. Under these conditions, when the glass rod 106 having a diameter of 65 mmφ is stretched to 50 mmφ, the tensile tension in a steady state is about 100 kgf / cm ² , and the moving speed of the tail stock 116 is 8.6 mm / min. Therefore, the heating source 122 is 100 m from the start of stretching.
m, the tensile tension is 110 kgf / cm ²
The moving speed of the tail stock 116 was controlled so as not to exceed. After the heating source 122 moves by 100 mm, the moving speed of the tail stock 116 is a steady speed.
The glass rod 106 was stretched at a control of 6 mm / min.

FIG. 34 shows the tensile tension of the glass rod 106 in the initial stage of elongation in the example. The vertical axis indicates the tensile tension generated in the glass rod 106, and the horizontal axis indicates the moving distance of the heating source 122 from the start of stretching. The tensile strength of the glass rod 106 is 100 mm
110 kgf / cm in the initial stage of stretching before moving
² or less.

FIG. 36 shows the change in the outer diameter of the glass rod 106 after stretching. The vertical axis indicates the radial distance of the glass rod 106, and the horizontal axis indicates the longitudinal distance of the glass rod 106. Glass rod 1 drawn by the method of the embodiment
In 06, there is little fluctuation in diameter such as constriction.
The target diameter could be set at about 0 mm. Further, when the outer diameter of the steady portion of the glass rod 106 stretched by the method of the example was stretched at a steady speed, the accuracy of the outer diameter was almost the same as that of the stretching by the conventional stretching method. .

(Comparative Example) As in the embodiment, the heating source 122
The glass rod 106 having a diameter of 65 mmφ was stretched to a diameter of 50 mmφ under the same moving speed and gas amount. From the start of stretching, stretching was performed while controlling the moving speed of the tail stock 116 to 8.6 mm / min, which is the steady speed.

FIG. 35 shows the fluctuation of the tensile force of the glass rod 106 in the initial stage of stretching in the comparative example. The vertical axis indicates the tensile tension generated in the glass rod 106, and the horizontal axis indicates the moving distance of the heating source 122 from the start of stretching.
The tensile strength of the glass rod 106 is such that
In the initial stage of the stretching until it moved by 00 mm, the tension was 300 kgf / cm ² , which was three times the steady-state tensile tension. FIG.
As shown in FIG. 6, the drawn glass rod 106 of the comparative example has a large constriction at about 100 mm from the start of drawing, and thereafter undulation continues to about 300 mm from the start of drawing, so that this part can be used as a product. The yield was low.

FIG. 37 is a detailed flowchart of the edge drawing step (S158) shown in FIG. First,
The diaphragm position of the glass rod 106 is detected (S16)
9). Next, a predetermined portion of the glass rod 106 is heated to near the softening temperature by the flame of the heating source 122 (S17).
0). Next, by moving the tail stock 116 while heating the predetermined portion of the glass rod 106 with the heating source 122, the predetermined portion of the glass rod 106 is thinly stretched (S172). Next, the heating source 122 is moved from the center of the predetermined portion of the drawn glass rod 106 to a region on the center side of the glass rod 106, and a preheating step (S17) is performed.
The secondary heating is performed by making the thickness of the flame thinner than in (0) (S17).
4). Further, by moving the tail stock 116, a predetermined portion of the glass rod 106 is thinly stretched (S17).
6) A predetermined portion of the glass rod 106 is blown off and blown out by a flame whose thickness is narrower than that of the preheating step (S170) (S178).

FIG. 38 shows a notch 284 provided as a marker at the joint between the glass rod and the dummy rod in order to detect the stop position in the stop position detecting step (S169) shown in FIG. A marker is provided at the joint between the glass rod 106 and the dummy rod 108. An apparatus for recognizing a sign is installed in the glass rod secondary stretching apparatus 111, and the position of the sign is detected using the apparatus for recognizing the sign. Based on the position of the detected sign, a position at which the drawing process is started is set, and at the set drawing start position, the stretching process of the glass rod 106 is terminated and the glass rod 1 is set.
Start the end drawing of 06. The method of FIG. 38 is used when the device that recognizes the sign is a device that measures the diameter, such as the outer diameter measuring device 124.

FIG. 39 shows a marking 28 applied to the joint between the glass rod and the dummy rod as another example of the sign.
7 is shown. The method of FIG. 39 is used when the device that recognizes the sign is an image processing device.

FIG. 40 shows the diaphragm position detecting step (S16).
9) shows the glass rod secondary stretching apparatus 111 for detecting the cut 284. Dummy rods 108 are welded to both ends of the glass rod 106, and both ends of the glass rod 106 to which the dummy rods 108 are welded are fixed to chucks (not shown) of the glass rod secondary stretching apparatus 111. Glass rod 1
A notch 284 having a depth of 3 mm is provided on the entire circumference at a welding position serving as a joint between the dummy rod 106 and the dummy rod 108. During the stretching of the glass rod 106, the outer diameter measuring device 124 measures the outer diameter of the glass rod 106. When the outer diameter measuring device 124 detects the position of the cut 284 from the change of the outer diameter, the glass rod secondary stretching device 111 has a bubble-free portion at the center side of the glass rod 106 slightly from the joint between the glass rod 106 and the dummy rod 108 or The squeezing is started at a portion containing no bubbles having a diameter of 0.3 mm or more, and the operation is shifted from drawing to squeezing.

When the mark is the marking 287, a fluorescent paint is applied to the joint between the glass rod 106 and the dummy rod 108. At the position of the outer diameter measuring device 124 of the moving table 120, an imaging unit of an image processing apparatus capable of detecting a fluorescent paint is installed. The imaging unit processes an image of the glass rod 106 while the glass rod 106 is being extended. When the imaging unit detects the fluorescent paint, the glass rod secondary stretching device 111
Starts drawing at a position where the center of the flame hits a bubble-free part or a part that does not contain bubbles with a diameter of 0.3 mm or more on the center side of the preform somewhat from the joint between the glass rod 106 and the dummy rod 108, and from stretching. Move work to aperture.

FIG. 41 shows the operation of the heating source 122 and the tail stock 116 after the drawing position is detected (S169) in the end drawing of the glass rod 106 shown in the flowchart of FIG. In the drawing preheating step (S170), the heating source 122 heats a predetermined portion of the glass rod 106 to near the softening temperature by the flame. In the drawing and drawing step (S172), the heating source 122 heats a predetermined portion of the glass rod 106,
The tail stock 116 moves to move the glass rod 106
Is stretched thinly.

In the secondary heating step (S174), the tail stock 116 stops, and the heating source 122 moves the glass rod 106 from the center of a predetermined position of the glass rod 106.
Is moved to the left side in the figure on the center side of the drawing, and the thickness of the flame is made thinner than in the preliminary heating step (S170) for heating. In the drawing secondary stretching step (S176), the heating source 122 moves further to the left to move the glass rod 106 to the left.
Is heated, the tail stock 116 also moves, and a predetermined portion of the glass rod 106 is elongated thinly. In the drawing fusing step (S178), the heating source 122 heats the glass rod 106 at a position in the drawing secondary stretching step (S176) with a flame whose diameter is smaller than that of the drawing preheating step (S170). The tail stock 116 moves to melt the glass rod 106.

FIG. 42 shows the gas amount and movement amount of the heating source 122 and the movement of the tail stock 116 based on the elapsed time of the end drawing process of the glass rod 106 in the end drawing step (S158) shown in FIG. 4 shows an example of setting of an end drawing method for controlling a speed. In the second heating condition / drawing speed setting step (S157), the glass rod secondary drawing device 111 sets the heating source based on the position of the cut 284, the change in the axial length of the glass rod, and the outer diameter. The amount of gas supplied and the amount of movement supplied to 122 and the movement speed of tail stock 116 are determined by glass rod 1.
The setting is reset based on the elapsed time accompanying the progress of the end drawing process in step 06.

For example, a squeeze preheating step (S17)
In (0), the moving amount of the heating source 122 is 0 mm and the moving speed of the tail stock 116 is 0 mm / 300 seconds.
Min condition, 250c are gas amount of hydrogen, the _{H 2}
c / min, oxygen O at the outlet inside the heating source 122
_The glass rod 106 is heated using the heating source 122 set at 30 cc / min for ₂ (inside) and 100 cc / min for oxygen O ₂ (outside).

Next, in the drawing and drawing step (S172), the gas amount is hydrogen and H ₂ is 25 for 60 seconds.
0 cc / min, oxygen O 2 at the outlet inside heating source 122
₂ (inner) 30 cc / min, oxygen O _{2 at} outer outlet
(Outside) heating source 12 set to 100 cc / min
The glass rod 106 is heated using the heating source 12
2 with the movement amount of 0 mm, and the tail stock 11
6 at a speed of 10 mm / min.
Is stretched.

Next, in the secondary heating step (S174), the moving speed of the tail stock 116 is set to 0 mm / min for 20 seconds, and while the heating source 122 is moved by 15 mm, the gas amounts of hydrogen and H ₂ are reduced. Glass using the heating source 122 set at 130 cc / min, 15 cc / min for oxygen O ₂ (inside) at the outlet inside the heating source 122 and 50 cc / min for oxygen O ₂ (outside) at the outside outlet. The rod 106 is heated.

Next, in the drawing secondary stretching step (S176), the moving amount of the heating source 122 is reduced by 15 for 180 seconds.
from 25 mm to 25 mm while the gas volume is
₂ is set to 130 cc / min, oxygen O ₂ (inside) at the outlet inside the heating source 122 is set to 15 cc / min, and oxygen O ₂ (outside) at the outside outlet is set to 50 cc / min. To heat the glass rod 106 to move the tail stock 116 at a speed of 10 mm / min to stretch the glass rod 106.

Finally, in the squeezing and fusing step (S178), the moving distance of the heating source 122 is set to 25 mm for 30 seconds.
Without moving from the position of the throttle secondarily stretching step (S176), hydrogen gas amount, the _{H 2} is 130 cc / min,
The glass rod 106 is heated using the heating source 122 set to 30 cc / min for oxygen O ₂ (inside) at the outlet inside the heating source 122 and 20 cc / min for oxygen O ₂ (outside) at the outside outlet. Then, tail stock 116
The glass rod 106 is melted by moving at a speed of 20 mm / min.

When a glass rod 106 having an outer diameter of 60 mm was drawn using the glass rod secondary stretching apparatus 111 under the setting conditions shown in FIG. 6 for outer diameter 60mm
It was a good shape with a 1 mm cone. The time required for drawing was 12 minutes.

FIG. 43 shows an end controlling step (S158) for controlling the gas amount and movement amount of the heating source 122 and the movement speed of the tail stock 116 based on the movement amount of the tail stock 116 in the end drawing step (S158) shown in FIG. 4 shows an example of setting of a partial drawing method. Glass rod secondary stretching device 111
Detects the amount of movement of the tail stock 116 and, based on the detected amount of movement of the tail stock 116, determines the position of the cut 284 and the axial length of the glass rod 106 in the second heating condition / stretching speed setting step (S 157). The amount of gas and the amount of movement to be supplied to the heating source 122 and the movement speed of the tail stock 116 are set again based on the change in the height and the outer diameter.

When the glass rod 106 is not sufficiently heated during the end drawing, the tail drive motor 27
In some cases, the amount of movement of the tail stock cannot be measured because the tail stock 116 does not move due to the insufficient force of No. 5. As described above, when the output of the tail drive motor 275 is not sufficiently large, the torque of the output shaft can be detected.
The C servo motor is used to drive the tail stock 116, and a threshold value is set for this torque. When the torque exceeds the threshold value, it is determined that the heating of the glass rod 106 is insufficient, and the driving of the tail stock 116 is temporarily stopped. , Heating source 122
May be controlled such as increasing the amount of gas.

FIG. 43 has the same settings as in FIG. 42, except that the item of the elapsed time has been changed to the item of the moving amount of the tail stock. The edge drawing method of FIG. 43 also includes a drawing preheating step (S170) and a drawing / stretching step (S170).
172), a secondary heating step (S174), a drawing secondary stretching step (S176), and a drawing fusing step (S1).
78). Tailstock 11
For the movement amount of No. 6, the gas amount and the movement amount of the heating source 122 and the movement speed of the tail stock 116 in each step are set.

For example, a squeeze preheating step (S17)
In (0), the moving speed of the tail stock 116 is 0.
mm / min, since the tail stock 116 does not move,
The time from the start of the drawing preheating step is measured for 300 seconds. 300 seconds, with the amount of movement of 0mm state of the heating source 122, the amount of gas is hydrogen, the _{H 2} is 250 cc /
Min, oxygen _{O 2} (in) 30 cc / min for the inner outlet of the heating source 122, a glass rod 106 with a heating source 122 is set to 100 cc / min for the outer oxygen _{O 2} (outside) heating I do. When the elapsed time from the start of the drawing preheating step has reached 300 seconds, the process proceeds to the next step.

Next, in the drawing and drawing step (S172), the moving amount of the tail stock 116 is 0 to 30 mm.
250 while the amount of gas is hydrogen, the _{H 2} to change to
cc / min, oxygen O _{2 at} the outlet inside the heating source 122
(Inner) 30cc / min, oxygen O at outer outlet
₂ (outside) heating source 1 set to 100 cc / min
The glass rod 106 is heated using the heating source 1
22 with the moving amount of the tailstock 22 being 0 mm,
16 at a speed of 10 mm / min.
6 is stretched.

Next, in the secondary heating step (S 174), the moving speed of the tail stock 116 is 0 mm / min, and the moving amount of the tail stock 116 remains unchanged at 30 mm. The gas amount is 130 cc / min for hydrogen and H ₂ , and 15 cc / min for oxygen O ₂ (in) at the outlet inside the heating source 122.
For the oxygen O ₂ (outside) at the outer outlet, the glass rod 106 was heated using a heating source 122 set at 50 cc / min.
Heat. The process proceeds to the next step when the heating source 122 moves by 15 mm.

Next, in the drawing secondary stretching step (S176), while the moving amount of the tail stock 116 increases from 30 mm to 55 mm, the moving amount of the heating source 122 is reduced by one.
The gas amount increased from 5 mm to 25 mm,
Heat source 122 set to 130 cc / min for H ₂ , 15 cc / min for oxygen O ₂ (inside) at outlet inside heating source 122, and 50 cc / min for oxygen O ₂ (outside) at outlet outside Is used to heat the glass rod 106, and the tail stock 116 is moved at a speed of 10 mm / min to stretch the glass rod 106.

Finally, in the squeezing and fusing step (S178), while the moving amount of the tail stock 116 changes from 55 mm to 100 mm, the moving amount of the heating source 122 is reduced by 2 mm.
Without leaving 5mm and position of the secondary stretching step (S176), hydrogen gas amount, the _{H 2} is 130 cc /
The glass rod 106 is heated using the heating source 122 set at 30 cc / min for oxygen O ₂ (inside) at the outlet inside the heating source 122 and 20 cc / min for oxygen O ₂ (outside) at the outside outlet. Heat the tail stock 116
At a speed of 120 mm / min.
Fusing.

(Example 1) A glass rod 106 having an outer diameter of 60 mm was subjected to end drawing based on the set values shown in FIG. Using a 200W AC servomotor for the tail drive motor 275, the tail drive encoder 273
A rotary encoder for detecting the amount of rotation of the tail drive motor 275 was used. The displacement of the tail stock was determined by controlling the rotation speed of the tail drive motor 275 by detecting the output of the tail drive encoder 273 and detecting the rotation amount of the tail drive motor 275. The time required for drawing was 15 minutes. The drawn shape of the processed glass rod 106 was a conical shape in which the length of the drawn portion was 61 mm with respect to the outer diameter of 60 mm, which was a good shape.

(Example 2) A glass rod 106 having an outer diameter of 60 mm was subjected to end drawing based on the set values shown in FIG. Tailstock 116 to tailstock 116
A linear encoder was installed to detect the amount of movement. The gas amount and movement amount of the heating source 122 and the movement speed of the tail stock 116 were controlled based on the movement amount of the tail stock 116 detected by the linear encoder. The drawn shape of the processed glass rod 106 was slightly longer at 65 mm with respect to the outer diameter of 60 mm. The shape of the narrowed portion was a good shape.

FIG. 44 shows the glass rod secondary stretching apparatus 11.
1 shows a configuration of a heating source 122. Outer cylinder 2 of heating source 122
Reference numeral 85 has a closed bottom end and is connected to a flow path 312 for hydrogen gas, which is an example of combustible gas. The heating source 122
The flammable gas flow controller 3 is provided in the flammable gas flow path 312.
It has 14. All the inner pipes 286 are connected to a flow path 308 of an oxygen gas, which is an example of a supporting gas, via a flow dividing device 316. An inert gas pipe 296 is connected in the middle of the oxidizing gas flow path 308, and the oxidizing gas flow controller 310
Are disposed on the oxygen gas inflow side with respect to the inert gas pipe 296. The inert gas pipe 296 includes an on-off valve 300 and an inert gas flow controller 298. The heating source 122 has a control unit 304 that controls the driving of the driving source 306 based on the flow rate data output from the combustible gas flow rate controller 310. The drive source 306 is connected to the on-off valve 300.
The combustible gas flow controller 314 and the combustible gas flow controller 310 control the flow rates of the hydrogen gas H ₂ and the oxygen gas O ₂ described with reference to FIGS. 42 and 43, respectively.

As the on-off valve 300, an electric valve,
An electromagnetic valve or the like is used. A connection tool 302 such as a three-way pipe or a three-way valve is used to connect the inert gas pipe 296 to the supporting gas path 308.

FIG. 45 shows a plane at the tip of the heating source 122. A plurality of inner tubes 286 having an inner diameter of 1 mm and an outer diameter of 3 mm are inserted into an outer cylinder 285 having an inner diameter of 30 mm. Inner tube 28
6 are arranged in a plurality of rows concentrically around the axis of the outer cylinder 285, and the inner tubes 286 are arranged at equal intervals in each row. The interval between the inner tubes 286 in each row is closer to the outer periphery. In addition,
The inner tubes 286 may be arranged at equal density. Inner tube 28
The flammable gas flows into the flammable gas outflow portion 288 inside the tube 6, and the flammable gas flows into the flammable gas outflow portion 290 inside the outer cylinder 285.

The heating source 122 operates as follows.
Hydrogen gas is supplied from a supply source (not shown) to a combustible gas flow path 312.
Through the outer cylinder 285. On the other hand, oxygen gas is supplied from the supply source (not shown) through the combustion supporting gas passage
6 diverges to the inner tube 286. At the tip of the outer cylinder 285, hydrogen gas and oxygen gas are mixed. When the mixture is ignited, a flame 294 is obtained. Glass rod 10
6 according to the purpose of the flame processing of the combustion supporting gas flow controller 3
The amount of hydrogen gas and the amount of oxygen gas are adjusted using 10 and the flammable gas flow controller 314 to obtain an optimal flame state.
At this time, the combustion supporting gas flow rate controller 310 switches to the controller 304.
A signal indicating the flow rate of the oxygen gas is output. If the oxygen gas linear velocity, which is a value obtained by dividing the flow rate by the opening area of the inner pipe 286, is 1.0 m / sec or less, the control unit 304
6 is driven to open the inert gas on-off valve 300. Then, nitrogen gas, which is an inert gas, is supplied to the combustion supporting gas passage 3.
08 flows at a gas linear velocity of 0.5 m / sec and is mixed with oxygen gas. When the oxygen gas linear velocity reaches 1.1 m / sec when the flow rate of oxygen is changed, the control unit 304 drives the drive source 306 to close the on-off valve 300.

When the flame 294 is reduced by reducing the flow rate of the flammable gas or the supporting gas, the flame 294 is diffused by mixing the inert gas, and the high temperature portion near the tip of the inner flame becomes a heat source. Move away from the tip of 122. Therefore, the surface temperature of the tip of the heating source 122 is controlled to be less than 400 ° C., and the oxidation of the heating source 122 can be prevented. On the other hand, when a strong thermal power is required, mixing the inert gas lowers the combustion temperature, so the inert gas on-off valve 300 is closed. At this time, since the flow rate of the combustible gas or the supporting gas increases and the flame 294 is large, the high temperature portion of the flame 294 is separated from the tip of the heating source 122. Therefore heating source 1
The surface temperature at the tip of No. 22 is less than 400 ° C. On-off valve 3
The gas velocity of the supporting gas at the time of opening and closing of 00 is 1.0
By setting a value different from m / sec or less and 1.1 m / sec or more, generation of a pulsating flow due to opening / closing of the on-off valve 300 can be prevented.

By opening the on-off valve 300, 0.5 to 2 m
It is preferable that an inert gas having an inert gas linear velocity of 1 / sec flows. The inert gas linear velocity is determined by changing the inert gas flow rate to the inner pipe 2
86 is a value obtained by dividing by the opening area of the combustion supporting gas outflow portion 288. When the inert gas linear velocity is 0.5 m / sec or less,
It is difficult to control the temperature at the tip of the heating source 122. on the other hand,
If it is 2 m / sec or more, the combustible gas cannot be completely burned or the flame temperature decreases. Using the heating source 122,
When the glass rod 106 is heat-treated by a flame 294,
Since the temperature at the tip of the heating source 122 can be controlled to 400 ° C. or lower, metal oxide is not easily generated at the tip of the heating source 122. Therefore, a metal oxide does not adhere to the glass rod 106, and a high-quality glass rod 106 can be manufactured.

Heating source 122 for controlling the flow rate of the inert gas
The glass rod 106 having an average diameter of 65 mm was stretched by a glass rod secondary stretching apparatus 111 using the above method. The ratio of the number of adhered foreign substances such as metal oxides to the total number of processed glass rods 106 was as low as 0.2%.
For comparison, the inert gas on-off valve 300 was always closed, and the glass rod 106 was stretched. Glass rod 106
The ratio of the number of foreign substances such as metal oxides adhered to the total number of processed pieces was as high as 15%.

FIG. 46 shows that the heating source 122
The relationship between the linear velocity of the oxygen gas and the temperature at the tip of the heating source 122 for the case where nitrogen gas having a linear velocity of m / sec is always mixed with oxygen gas and the case where nitrogen gas is not always mixed is shown. Show. When nitrogen gas is mixed, the tip temperature of the heating source 122 does not exceed 400 ° C., but when nitrogen gas is not mixed, the tip temperature of the heating source 122 increases when the linear velocity of the oxygen gas is 1 m / sec or less. It has reached 400-700 ° C. Therefore, when the linear velocity of the oxygen gas is 1 m / sec or less, when the nitrogen gas is mixed with the oxygen gas, the surface temperature of the heating source 122 can be controlled.

FIG. 47 is a diagram showing an edge drawing step (S158).
Preform 107 whose outer diameter is narrowed and blown
3 shows the shape of the throttle section. D indicates the diameter of the preform 107, O indicates the place where the diameter of the preform 107 starts to decrease, and P indicates the place where the diameter D of the preform 107 reduces to 99% or less. The both ends of the preform 107 have a tapered shape represented by a formula of 1 / 3D ≦ L ≦ 3D. Here, L represents the length from the point O where the diameter of the preform 107 starts to decrease to the point P where the diameter of the preform 107 decreases to 99% or less.

When drawing the preform 107 into an optical fiber, the time required for the drawing to reach a steady state, that is, the preform 107 is drawn into the preform drawing apparatus 50.
The time from setting to zero until the wire diameter and the wire speed of the drawn optical fiber reach the set values is affected by the initial shape of the preform 107. This effect increases as the diameter of the preform 107 increases, and the time required for the drawing to reach a steady state increases.

The preform 107 having a shape of 1 / 3D ≦ L ≦ 3D can shorten the time required for the drawing to reach a steady state. For L <1 / 3D, the preform 107
The time required for the tip of the optical fiber to sag becomes longer, and the time required for the wire diameter and the wire speed of the optical fiber to reach the set values also becomes longer. In the case of L> 3D, the time until the tip of the preform 107 hangs is reduced, but the preform 10
Since it takes time for the tapered shape of No. 7 to become the shape at the time of the normal drawing, the time until the wire diameter and the wire speed of the optical fiber reach the set values also becomes long. Therefore, preform 1
It is optimal to set the taper shape of L to L = D.

When the preform 107 is locally heated by a flame and melted, distortion remains in the tapered portions at both ends of the preform. If the residual strain is large, preform 1
07 may receive a strong impact or a thermal impact such as welding of a dummy bar to the preform 107 may cause cracks at both ends thereof. Preform 10
It is preferable that the amount of strain at both ends of No. 7 is 40 kgf / cm ² or less. By setting the amount of strain remaining in the preform 107 to 40 kgf / cm ² or less, cracks generated in the preform 107 can be prevented.

(Example) Preform 1 having a diameter of 30 mm
07 was drawn. When the length L was set to 30 mm, the residual strain amount at the tapered portion was 40 kgf / cm ² , and no crack occurred during welding of the dummy bar. When the fiber setting diameter is 125 μm and the drawing speed is 100 mm / min, the time required for the drawing to reach a steady state is determined by the preform 107.
Is set in the preform drawing apparatus 500 until the tip of the preform 107 hangs down.
The time required for the wire diameter and the wire speed of the optical fiber to reach the set values was 10 minutes, which was a total of 20 minutes.

(Comparative Example 1) When the above L was set to 5 mm when drawing a preform 107 having a diameter of 30 mm, the residual strain amount of the tapered portion was 40 kgf / cm ² , and cracks occurred when welding the dummy bar. Did not. When the fiber setting diameter is 125 μm and the drawing speed is 100 mm / min, the time required for the drawing to reach normal is from the time when the preform 107 is set to the preform drawing apparatus 500 until the tip of the preform 107 hangs down. The time was 20 minutes, and the time required for the wire diameter and the wire speed of the optical fiber to reach the set values was 30 minutes, for a total of 50 minutes.

(Comparative Example 2) When the above L was set to 100 mm when drawing a preform 107 having a diameter of 30 mm, the residual strain amount of the tapered portion was 40 kgf / cm.
^In No. ² , no crack occurred when the dummy bar 342 was welded. Fiber setting diameter 125μm, linear velocity 100
The time required for the drawing to reach a steady state at the time of mm / min is as follows.
The time from setting to 0 until the tip of the preform 107 hangs down is 10 minutes, and the time until the optical fiber diameter and speed reach the set values is 30 minutes, a total of 4 minutes.
It was 0 minutes.

(Comparative Example 3) When the above L was set to 30 mm when drawing a preform 107 having a diameter of 30 mm,
The amount of residual strain in the tapered portion was 60 kgf / cm ² , and when the dummy rod was welded to the preform 107, cracks occurred and drawing could not be performed.

As described above, by setting the shape of the tip of the preform 107 to 1 / 3D ≦ L ≦ 3D, the time required for drawing can be reduced.

FIG. 48 shows another form of the shape of the narrowed portion of the preform 107. FIG. Preform 107 in FIG.
Is a fusing portion 332 formed at one end by a flame.
With a flat cut surface 33 machined at the other end
4 The fusing section 332 shown in FIG.
The flame is rapidly blown by the flame, and is blown by the blown portion 332 in FIG.
Is melted while gradually reducing the diameter, and the tapered portion 336 is formed.
Are formed. The fusing portion 332 in FIG. 48C has a tapered portion 336 provided with a small-diameter portion 338 at the tip.

When the preform 107 having the tapered portion 336 is drawn like the fusing portion 332 in FIG. 48 (b), the diameter of the end is reduced.
The time required for the tip of the preform to sag is short, and the amount of the preform 107 sagging is also small. The preform 107 in which the tapered portion 336 and the small diameter portion 338 are formed at the end portion like the fusing portion 332 in FIG. 48C has a tip of the preform 107 that hangs down compared to the preform 107 having the conventional shape. The time required until now can be reduced to less than one third of the conventional case. further,
The loss of the preform 107 due to dripping could be suppressed to a small amount only by the small diameter portion 338.

It is preferable that the small diameter portion 338 has a shape occupying 0.1% by weight to 15% by weight of the fusing portion 332. If the weight of the small-diameter portion 338 is less than 0.1% by weight, the effect of providing the small-diameter portion 338 cannot be obtained, and if it exceeds 15% by weight, the time required for the leading end of the preform 107 to sag during drawing is long. Become and preform 1
07 loss increases. Further, it is preferable that the diameter of the small-diameter portion 338 is か ら to 1/10 of the diameter of the straight body portion of the preform 107. Within this range, the time required for dropping in the initial stage of drawing can be short, and if the length of the small diameter portion 338 is set to about 1 to 5 times this diameter, the loss of the preform 107 is extremely reduced. It can be reduced to a small amount.

FIG. 49 shows the preform 107 which has been damaged before being subjected to the surface treatment in the surface treatment step (S168) shown in FIG. Preform 10 secondarily stretched by glass rod secondary stretching apparatus 111
7 is a preform 107 in which the cladding is chemically cut by hydrofluoric acid etching as a surface treatment, and the core / cladding ratio is set to a predetermined ratio. The hydrofluoric acid etching process is a process for decomposing the Si—O bond of the glass, and chemically cuts the surface of the preform 107 at a room temperature at a speed of about 8 mm per hour. However, if there are scratches or dents on the surface of the preform 107,
The part where the scratches and dents are present due to the hydrofluoric acid treatment is greatly dented due to the progress of chemical cutting from the other parts, and the preform 10
In FIG. 7, a concave portion called hydrofluoric acid is formed. Hydrofluoric acid cleaving causes disconnection when drawing the preform 107 into an optical fiber.

Therefore, the preform 107 having a surface free from hydrofluoric acid can be obtained by polishing and removing the scratches and dents in the preform 107 before the hydrofluoric acid etching treatment. As a polishing method, there is a method of flame polishing the preform 107 at a temperature equal to or higher than the strain point. At the time of flame polishing, the preform 107 is polished so that surface irregularities are within 0.3 mm. Preform 1 by flame polishing before hydrofluoric acid etching
07 is reduced, and a smooth surface without scratches is obtained, thereby preventing hydrofluoric acid cracks. The polishing method is not limited to flame polishing, but may be mechanical polishing.

FIG. 51 shows the frequency of occurrence of hydrofluoric acid cracks of the preform 107 confirmed by visual inspection in the examples and comparative examples, and FIG. 52 shows the preform etched with hydrofluoric acid in the examples and comparative examples. 107 shows the degree of unevenness of the surface of the surface 107. Preprocessing 1 described in FIGS. 51 and 52
In, the preform 107a having a diameter of 60 mm and a length of 1000 mm is lifted at the other end with one end attached to the floor as shown in FIG. 49, and then released at a height of 10 cm.
Another preform 107b of the same shape placed on the floor was hit and scratched. Thus, one preform 107a was scratched at three places at intervals of 20 cm. On the other hand, in the preprocessing 2 shown in FIGS. 51 and 52, the height at which the hand was released was set to 20 cm. In other procedures, the preform 107a was scratched in the same manner as in the pretreatment 1.

In the embodiment shown in FIG. 51 and FIG. 52, each preform
7a with 250 ml / min of hydrogen and 145 ml / m of oxygen
After flame polishing using a burner supplied with an in gas amount, hydrofluoric acid etching treatment was performed at room temperature. The amount of etching of the preform in the radial direction is 0.2 mm, 1.2 mm,
Four stages of 2.2 mm and 3.2 mm were used, and 10 hydrofluoric acid etching treatments were performed for each. After the etching treatment, the presence or absence of hydrofluoric acid cracks was confirmed by visual inspection.

FIG. 50 shows the preform 1 after hydrofluoric acid etching in the embodiment shown in FIGS. 51 and 52.
07 is shown. By measuring the difference between the diameter of the X-marked spot where the impact of the preform 107a was given and the diameter of the non-contacted X-marked spot 10 cm away from the X-mark. The degree of surface irregularities was determined. As the outer diameter of each preform 107a, the average of the outer diameters of three places indicated by a circle was used.

In the comparative examples shown in FIGS. 51 and 52, the preform 107 subjected to the pre-processing 1 or the pre-processing 2 is used.
a was etched with hydrofluoric acid without flame polishing. Confirm the presence or absence of hydrofluoric acid cracks by visual inspection as in the example,
The degree of surface irregularities was determined.

As shown in FIGS. 51 and 52, the pretreatment 2 having a higher dropped height has a greater degree of surface irregularity and a higher incidence of hydrofluoric acid cracking than the pretreatment 1. Also, the greater the hydrofluoric acid etching amount, the greater the degree of surface irregularities and the higher the rate of hydrofluoric acid cracking. The degree of unevenness of the surface of the preform 107a of the example subjected to flame polishing is lower than the degree of unevenness of the surface of the preform 107a of the comparative example not subjected to flame polishing. Further, as shown in FIG. 51, the number of hydrofluoric acid cracks in the example is smaller than that in the comparative example.
Therefore, by performing flame polishing before the hydrofluoric acid etching treatment of the preform 107a, the occurrence rate of hydrofluoric acid cracks is reduced and the preform
7a can be obtained.

FIG. 53 shows a preform 1 subjected to a surface treatment.
07 shows a form in which a handle 340 is provided. A handle 340 made of quartz glass is attached to the cut surface 334 of the preform 107 shown in FIG. 48 (c) by fusion bonding or machining to obtain a preform 107 with a handle 340. Preform 10 with handle 340
7 can be promptly installed in the preform drawing apparatus 500 when drawing. Further, as shown in FIG. 53B, the diameter of the handle 340 attached to the cut surface 334 may be smaller than the diameter of the preform 107.

FIG. 54 shows an ultrasonic cleaning device 404 for cleaning the heating source 122. The ultrasonic cleaning device 404 includes an ultrasonic oscillator 396, and contains a cleaning liquid 398 therein. Cleaning solution 398 contains 10% hydrofluoric acid and 3%
An aqueous solution of nitric acid. Hydrofluoric acid is supplied by heating source 122
The metal oxide on the surface of the outer tube 285 and the inner tube 286 is dissolved. When the material of the outer tube 285 and the inner tube 286 is stainless steel, the oxidation of iron, chromium, and nickel contained in stainless steel by the action of nitric acid forms a passivated thin film on the surface of the stainless steel. Less likely to happen.

The cleaning liquid 398 may contain a water-soluble organic solvent. Water-soluble organic solvents include alcohol, acetone, acetonitrile, and tetrahydrofuran. Further, the heating source 122 is set to the cleaning solution 3 containing hydrofluoric acid.
After immersion in the cleaning solution 98, the substrate may be immersed in another cleaning solution 398 containing nitric acid. The ultrasonic oscillator 396 is 1 W / cm ² to 2 W
/ Cm ² oscillates.

The heating source 122 to be cleaned is made of stainless steel and has a plurality of inner tubes 286 each having an inner diameter of 1 mm and an outer diameter of 3 mm in which an oxygen gas flows, in an outer cylinder 285 having an inner diameter of 30 mm through which hydrogen gas flows. The outer cylinder 285 is connected to the hydrogen gas introduction pipe 3
92, and all the inner tubes 286 are connected to the oxygen gas introduction tube 394.

When the glass rod 106 is heated, the surface of the tip of the heating source 122 is heated to a high temperature of 400 to 700 ° C. by a flame. Are generated, and the metal oxide gradually becomes floating fine particles. Glass rod 106
During the heat treatment, the fine particles of the metal oxide and the heat source 1
When impurity particles such as glass particles attached to the glass particles 22 scatter and adhere to the surface of the glass rod 106, the surface layer must be polished. When the glass rod 106 is polished, the ratio between the clad portion and the core portion of the glass rod 106 changes, and the optical transmission characteristics of the optical fiber deteriorate. Therefore, by cleaning the heating source 122, the metal oxide and the adhered impurity foreign matter at the tip of the heating source 122 are removed.

The heating source 12 using the ultrasonic cleaning device 404
To clean 2, first, the hydrogen gas introduction pipe 392 and the oxygen gas introduction pipe 394 are opened to the outside, and the heating source 122 is attached to the cleaning liquid 398 with the flame port 390 facing down. Outer cylinder 28
5 and the air inside the inner tube 286
2, and the cleaning liquid 398 is removed from the oxygen gas introduction pipe 394.
Is immersed to the level of the water surface. Cleaning is performed by oscillating ultrasonic waves with an ultrasonic oscillator 396. The vibration frequency of the ultrasonic vibration is from 10 kHz to 100 kHz.

The heating source 12 using the ultrasonic cleaning device 404
2 was washed. A metal oxide is attached near the flame port 390 to the stainless steel heating source 122 used for the heat treatment of the glass rod 106. Flame port 3 of this heating source 122
The vicinity of 90 was immersed in a cleaning liquid 398, and ultrasonic waves having a vibration frequency of 10 kHz to 100 kHz were oscillated by a 500 W ultrasonic oscillator 396 for 30 minutes to clean the heating source 122. The heating source 122 was pulled up, the cleaning liquid 398 remaining on the surface was washed away with pure water, and dried. Outer cylinder 285
When the tip of the inner tube 286 was observed, no metal oxides or impure foreign matters were found. When the surface of the glass rod 106 was heat-treated using the cleaned heat source 122, the ratio of the number of the glass rods 106 to which the impure foreign matter adhered to the total number of the processed glass rods 106 was 6%. When the surface of the glass rod 106 is heat-treated using the heating source 122 that has not been subjected to the cleaning treatment for comparison, the ratio of the number of impure foreign matter adhered to the total number of processed glass rods 106 is 15%. Many foreign substances were attached.

As described above, by cleaning the heating source 122 using the ultrasonic cleaning device 404, the heating source 122 is cleaned.
Metal oxides and adhering foreign matter generated at the tip of the substrate can be removed. When the glass rod 106 is heat-treated using the cleaned heating source 122, a high-quality preform 107 can be obtained because foreign matter is little attached.

FIG. 55 shows the configuration of a preform drawing apparatus 500 for drawing the preform 107. The preform drawing apparatus 500 includes a chuck 346 that holds a dummy bar 342 to which the preform 107 is welded, a heating unit 348 that heats the preform 107, and a movable holding unit 34 that supplies the preform 107 to the heating unit 348.
4. Optical fiber 35 from which preform 107 is drawn
Outer diameter measuring device 352 for measuring the outer diameter of 0, optical fiber 35
0, a first curing device 356 for curing the primary-coated optical fiber 350 with ultraviolet light, a second coating device 358 for secondary-coating the optical fiber 350, and a secondary-coated optical fiber. A second curing device 360 for curing 350 with ultraviolet light, and an optical fiber 3
It has a pulling part 362 for winding up 50.

To draw the preform 107 using the preform drawing apparatus 500, first, the dummy bar 342 to which the preform 107 is welded is gripped by the movable holding section 344 of the preform drawing apparatus 500 using the chuck 346. Next, the drawing start end of the preform 107 is set at a predetermined position of the heating means 348 to start heating, and waits for the leading end of the preform 107 to soften and drop. When the tip of the preform 107 hangs down, the tip of the preform 107 is caught and pulled out and passed through the outer diameter measuring device 352. When the optical fiber 350 has a desired wire diameter, it is first coated with a resin through a first coating device 354 and then guided to a first curing device 356 to be cured.
Next, the secondary coating is performed by the second coating device 358, and the coating is cured by the second curing device 360. When the wire diameter and the wire speed of the optical fiber 350 reach the set values, the bobbin (not shown) is passed through the pulling portion 362. To take up.

The glass base material primary stretching apparatus 900 described above
In addition, the glass rod secondary stretching device 111 can produce a high-quality preform 107 with little variation in outer diameter. Therefore, the preform 107 manufactured using the glass base material primary stretching apparatus 900 and the glass rod secondary stretching apparatus 111 is drawn by the preform drawing apparatus 500 to produce a high-quality optical fiber with less variation in outer diameter. Obtainable.

As described above, the present invention has been described using the embodiments. However, the technical scope of the present invention is not limited to the scope described in the above embodiments. It is apparent to those skilled in the art that various changes or improvements can be added to the above embodiment. It is apparent from the description of the appended claims that embodiments with such changes or improvements can be included in the technical scope of the present invention.

[0175]

As is apparent from the above description, according to the present invention, it is possible to manufacture a preform and an optical fiber having a small outer diameter variation.

[Brief description of the drawings]

FIG. 1 shows a conventional glass base material primary stretching apparatus 400.

FIG. 2 shows a configuration of a conventional glass lathe 110.

FIG. 3 shows a system of the optical fiber manufacturing apparatus of the present invention.

FIG. 4 shows an optical fiber manufacturing method of the present invention.

FIG. 5 shows a configuration of a glass base material primary stretching apparatus 900 of the present invention.

FIG. 6 shows a primary stretching device 402 in which a prototype 138 is held by a base material fixing portion 136 to adjust a stretching axis.

FIG. 7 is a drawing step (S) of the glass base material shown in FIG.
204) is a detailed flowchart.

8 shows a primary stretching device 402 in which a prototype 138 is held by a take-off chuck 142. FIG.

9 shows a primary stretching device 402 in which a prototype 138 is held by a suspension mechanism 134 and a take-up mechanism 140. FIG.

FIG. 10 is a schematic view of a prototype 138 with take-off rollers 144a and 1
44b shows the primary stretching device 402 gripped.

11 shows a primary stretching device 402 in which a prototype 138 is gripped by pulling rollers 144a and 144b of a suspending mechanism 134 and a pulling mechanism 140. FIG.

FIG. 12 shows a glass base material 1 whose degree of bending is measured.
02 is shown.

FIG. 13 shows that the primary stretching device 402 is a rotating roller 144.
a shows a mechanism for controlling the number of rotations of a and 144b.

14 shows the relationship between the deviation between the center position of the heat-softened portion of the glass base material 102 and the stretching axis 154 and the bending of the glass rod 106. FIG.

FIG. 15 shows the deformation of the surface of the rotating rollers 144a and 144b.

FIG. 16 shows a roller 1 having a batch number of 300 shown in FIG.
The displacement of the center position of the heating softening part of the metal pipe when the metal pipe is pulled using 44a and 144b is shown.

FIG. 17 shows the displacement of the center position of the heat-softening part by the primary stretching device 402 of the present embodiment.

FIG. 18 shows how the center position of the heating softening portion changes when the left and right rollers 144a and 144b are controlled at the same rotation speed.

FIG. 19 shows another embodiment of the burner 176 used in the glass rod fusing device 370.

FIG. 20 shows a configuration of a glass rod transport device 380.

21 shows a storage container 224 of the primary stretching device 402. FIG.

FIG. 22 shows an operation of the glass rod transport device 380 when transporting the glass rod 106.

FIG. 23 shows another embodiment of the glass rod transport device 380.

FIG. 24 is a diagram illustrating a glass rod transfer device 380 illustrated in FIG. 23;
Shows the operation when the glass rod 106 is transported.

FIG. 25 shows a configuration of a glass rod secondary stretching apparatus 111 of the present invention.

FIG. 26 is a detailed flowchart of a glass rod secondary stretching step (S206) shown in FIG. 4;

FIG. 27 shows an example in which a cooling device 330 is provided on the fixed chuck 118 and the movable chuck 119 of the glass rod secondary stretching device 111.

FIG. 28 shows a chuck 1 in an example and a comparative example described below.
18 and 119 show the results of measuring the temperatures.

29 shows the relationship between the distance between the heating source 122 and the outer diameter measuring device 124 and the rate of change in the outer diameter value of the glass rod 106. FIG.

FIG. 30 shows a configuration in which a tensile tension measuring device 282 is provided in the glass rod secondary stretching device 111 of FIG.

FIG. 31 shows a detailed flowchart of a stretching step (S154) shown in FIG. 26.

FIG. 32 shows a process in which the outer diameter fluctuates when the glass rod 106 is extended.

FIG. 33 shows the glass rod 106 stretched along the stretching step (S154) of FIG.

FIG. 34 shows a glass rod 10 in the initial stage of elongation in an embodiment.
6 shows a tensile tension of 6.

FIG. 35 shows a glass rod 10 in an initial stage of stretching in a comparative example.
6 shows the fluctuation of the tensile tension of No. 6.

FIG. 36 shows the outer diameter fluctuation of the glass rod 106 after stretching.

FIG. 37 is an end drawing step (S15) shown in FIG. 26;
A detailed flowchart of 8) is shown.

FIG. 38: Aperture position detection step (S1) shown in FIG.
69) shows a cut 284 provided at the joint between the glass rod and the dummy rod.

FIG. 39 shows a marking 287 applied to the joint between the glass rod and the dummy rod as another example of the sign.

FIG. 40 shows the glass rod secondary stretching apparatus 111 that detects the cut 284 in the stop position detection step (S169).

41 shows the heating source 122 and the tailstock 11 after the drawing position is detected (S169) in the end drawing of the glass rod 106 shown in the flowchart of FIG. 37.
6 shows the operation.

FIG. 42 is an end drawing step (S15) shown in FIG. 37;
8) shows an example of setting of the end drawing method for controlling the gas amount and the movement amount of the heating source 122 and the moving speed of the tail stock 116 based on the elapsed time of the end drawing.

FIG. 43 is an end drawing step (S15) shown in FIG. 37;
In 8), based on the moving amount of the tail stock 116, the gas amount and moving amount of the heating source 122 and the tail stock 1
16 shows an example of setting of an edge drawing method for controlling the moving speed of No. 16;

FIG. 44: Heating source 1 of glass rod secondary stretching device 111
22 shows the configuration of the second embodiment.

FIG. 45 shows a plane at the tip of the heating source 122.

FIG. 46 shows the relationship between the linear velocity of oxygen gas and the temperature at the tip of the heating source 122.

FIG. 47 shows the shape of the narrowed portion of the preform 107 whose outer diameter has been narrowed and blown by the end narrowing step (S158).

FIG. 48 shows another form of the shape of the narrowed portion of the preform 107.

FIG. 49 shows the surface treatment step (S16) shown in FIG. 26;
8) shows the preform 107 that has been damaged before being surface-treated in 8).

FIG. 50 shows the preform 107 after hydrofluoric acid etching in the embodiment shown in FIGS. 51 and 52.

FIG. 51 shows the frequency of occurrence of hydrofluoric acid cracks of the preform 107 confirmed by visual inspection in Examples and Comparative Examples.

FIG. 52 shows the degree of unevenness of the surface of a preform 107 etched with hydrofluoric acid in Examples and Comparative Examples.

FIG. 53 shows a form in which a handle 340 is provided on a preform 107 subjected to surface treatment.

54 shows an ultrasonic cleaning device 40 for cleaning the heating source 122.
4 is shown.

FIG. 55 shows a configuration of a preform drawing apparatus 500 for drawing a preform 107.

[Explanation of symbols]

100: heating furnace, 102: glass base material, 104
... Stretching chuck, 106 ... Glass rod, 10
7, 107a, 107b ... preform, 108
..Dummy rod, 110 ... conventional glass lathe, 111
... Glass rod secondary stretching device, 112 ... machine stand,
114, 116: tail stock, 118: fixed chuck, 119: movable chuck, 120:
Moving table, 122: heating source, 124: outer diameter measuring instrument, 130: stretching furnace, 134: suspension mechanism,
136: base material fixing part, 138: prototype, 140
..Retrieving mechanism, 142 ... Removing chuck, 1
44a, 144b ... take-off roller, 148, 1
49 ... fulcrum, 150 ... measuring instrument, 152 ... outer diameter measuring instrument, 154 ... stretching axis, 156 ... outer diameter control section, 158 ... position control section, 176 ... Burner, 178: Flame, 190: Hydrogen gas supply pipe,
192: oxygen gas supply pipe, 194: annular gas inlet, 196: cooling pipe, 198: cooling water supply pipe, 200: cooling water drain pipe, 204: feeder, 206 ... Stretching take-off device, 208 ... Support leg, 210 ... Rotating table, 212 ... Motor, 214 ... Timing belt, 216 ... Burner stand, 218 ... Fusing take-off chuck 224
... Storage containers, 234, 234a, 234b, 23
6, 236a, 236b ... support ring, 240 ...
V-block, 244: Air cylinder storage box, 245: Moving side gripping member, 246: Fixed side gripping member, 248: Operation switch box, 250
... Rotary actuator, 252 ... Support frame, 254 ... Handle, 256 ... Rotary axis, 2
57, 258: Locking pin, 260: Receiving tray, 2
62 ... column, 264 ... rotary actuator, 266 ... connection axis, 268 ... rotation axis, 27
0: sliding screw, 272: moving table encoder, 273: tail drive encoder, 274 ...
・ Moving table motor, 275 ・ ・ ・ Tail drive motor,
276: Chain, 278: Mass flow controller, 280: Control device, 282: Tensile tension measuring device, 284: Cut, 285: Outer cylinder, 286 ... Inner pipe, 287 ... Marking, 28
8 ... combustible gas outlet, 290 ... combustible gas outlet, 294 ... flame, 296 ... inert gas flow path, 298 ... inert gas flow controller, 300・ ・
Opening / closing valve, 302 ... Connector, 304 ... Control unit, 3
06 ... Drive source, 308 ... Combustible gas flow path, 31
0: flammable gas flow controller, 312: flammable gas flow path, 314: flammable gas flow controller, 316
..Diversion device, 330 ... cooling device, 332 ... fused portion, 334 ... cut surface, 336 ... tapered portion, 3
38 ... small diameter part, 340 ... handle, 342 ...
.Dummy bar, 344: movable holding section, 346:
Chuck, 348: heating means, 350: optical fiber, 352: outer diameter measuring device, 354: first coating device, 356: first curing device, 358: second coating Device, 360: second curing device, 362: traction unit, 370: glass rod fusing device, 380 ...
Glass rod transfer device, 390 ... Flame port, 392
..Hydrogen introduction pipes, 394 ... Oxygen introduction pipes, 396
・ Ultrasonic oscillator, 398 ・ ・ ・ Cleaning liquid, 400 ・ ・ ・ Conventional glass base material primary stretching device, 402 ・ ・ ・ Primary stretching device, 404 ・ ・ ・ Ultrasonic cleaning device, 500 ・ ・ ・ Preform drawing device, 600: glass base material generation device
700: a glass base material dehydrating and sintering device; 900: a glass base material primary stretching device of the present invention; A: inclination of the suspension mechanism 134; B: inclination of the take-off mechanism 140;
C: horizontal position, D: diameter of preform 107, E: verticality of axis, L1: distance between fulcrums,
L: length from location O to location P, O: location where the diameter of the preform starts to decrease, P: location where the diameter of the preform reduces to 99% or less, S110・
Step of fixing the prototype to the base material fixing section, S112 ...
Step of adjusting the inclination of the suspension mechanism, S114
Removing the prototype from the base material fixing portion, S116
..Step of holding prototype by taking-up chuck, S11
Step 8 for adjusting the inclination of the take-off mechanism, S1
20: Step of gripping the prototype by the base material fixing unit and the take-off chuck, S122: Step of adjusting the horizontal position of the suspension mechanism and the take-up mechanism, S124
..Primary stretching step, S126 ... Primary fusing step, S132 ... Preheating step, S136 ...
Initial stretching step, S138: Step of moving 150 mm from a heating source of 50 mm, S140: Step of stretching at a steady speed, S142: Glass rod outer diameter measuring step, S144: Outside diameter of glass rod And a step of extending the length to a desired outer diameter and length, S146: welding a dummy bar, S
147... Installing a sign, S150.
Setting step of outer diameter measurement position and target diameter, S152
First outer diameter measuring step, S153: first heating condition, stretching speed setting step, S154: stretching step, S156: second outer diameter measuring step, S157
..Second heating conditions.Stretching speed setting step, S158.
..End drawing step, S160: third outer diameter measuring step, S161: thermal power condition setting step, S16
2 ... Flame polishing step, S164 ... Finished diameter measurement step, S166 ... Dummy rod removal step, S168 ... Surface treatment step, S169 ...
Aperture position detection step, S170: preliminary heating step, S172: stretching step, S174: secondary heating step, S176: secondary stretching step, S1
78: fusing step, S200: glass base material generation step, S202: glass base material dehydration sintering step, S204: glass base material primary stretching step, S2
05: glass rod transport step, S206:
Glass rod secondary stretching step, S210 ... Preform drawing step

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Tadakatsu Shimada 2-3-1-1, Isobe, Annaka-shi, Gunma Shin-Etsu Chemical Industry Co., Ltd. Precision Functional Materials Laboratory (72) Inventor Hideo Hirasawa Isobe, Annaka-shi, Gunma 2-13-1 Shin-Etsu Kagaku Kogyo Co., Ltd.Precision Functional Materials Research Laboratory (72) Inventor Takaaki Nagao 2-13-1 Isobe, Annaka-shi, Gunma Prefecture Shin-Etsu Kagaku Kogyo Co., Ltd. Precision Functional Materials Research Laboratory (72) Inventor Mitsukuni Sakashita 2-3-1 Isobe, Annaka-shi, Gunma Prefecture Shin-Etsu Chemical Industry Co., Ltd.Precision Functional Materials Research Laboratory (72) Inventor Kazuichi Yamamura 2-3-1-1, Isobe, Annaka-shi, Gunma Prefecture Shin-Etsu Chemical (72) Inventor Masataka Watanabe 2-13-1, Isobe, Annaka-shi, Gunma Shin-Etsu Chemical Industry Co., Ltd. (72) Inventor Shinji Suzuki 2- 13-1, Isobe, Annaka-shi, Gunma Prefecture Shin-Etsu Chemical Industry Co., Ltd.Precision Functional Materials Research Laboratories (72) Inventor Minoru Taya 2-3-1, Isobe, Annaka-shi, Gunma Prefecture Shin-Etsu Kagaku Kogyo Co., Ltd. Precision Functional Materials Research Laboratory (72) Inventor Kazuhisa Hatayama 2-13-1, Isobe, Annaka-shi, Gunma Shin-Etsu Kagaku Kogyo Co., Ltd. Precision Functional Materials Research Laboratory F-term (reference) 4G021 BA00

Claims (50)

[Claims] 1. A method for manufacturing an optical fiber, comprising: heating conditions for heating the glass rod based on a predetermined numerical value that changes with progress of heating and stretching of a glass rod serving as a base material of the optical fiber. And a setting step of setting a stretching speed for stretching, based on the set heating conditions and the stretching speed,
An optical fiber, comprising: a heat stretching step of heating and stretching the glass rod to generate a preform; and a drawing step of further heating the preform and drawing the fiber in a linear shape. Production method. 2. The optical fiber manufacturing method according to claim 1, wherein the setting step sets the heating conditions and the stretching speed based on the elapsed time of the heating stretching as the numerical value. 3. The heating and stretching step includes a drawing step of reducing an outer diameter of an end of the glass rod, and the drawing step includes the step of reducing an end of the glass rod based on an elapsed time of the drawing step. 3. The method according to claim 2, wherein the fiber is drawn by heating. 4. The method according to claim 1, wherein in the setting step, a position of a burner for heating the glass rod and an amount of gas supplied to the burner are set as the heating condition based on an elapsed time of the heating and stretching. Item 3. An optical fiber manufacturing method according to Item 2. 5. The optical fiber according to claim 2, wherein the setting step sets a moving speed of a chuck for gripping the glass rod as the stretching speed based on an elapsed time of the heating stretching. Production method. 6. The method according to claim 1, wherein the setting step sets the heating condition and the stretching speed based on a length of the glass rod stretched by the heating stretching as the numerical value. An optical fiber manufacturing method as described in the above. 7. The heating and drawing step includes a drawing step of reducing an outer diameter of an end of the preform, and the drawing step includes the step of drawing the glass rod based on a length of the drawn glass rod. The optical fiber manufacturing method according to claim 6, wherein the end portion is drawn by heating. 8. The method according to claim 1, wherein the setting step sets a moving amount of a burner for heating the glass rod and an amount of gas supplied to the burner as the heating condition based on the stretched length. Item 7. An optical fiber manufacturing method according to Item 6. 9. The optical fiber manufacturing according to claim 6, wherein the setting step sets a moving speed of a chuck for gripping the glass rod as the drawing speed based on the drawn length. Method. 10. The method according to claim 1, wherein the setting step uses an encoder for measuring a rotation angle of the motor provided on a motor driving the chuck to detect an amount of movement of the chuck. 10. The method for manufacturing an optical fiber according to item 9. 11. The method according to claim 1, wherein the setting step sets the heating condition and the stretching speed based on a tensile tension generated in the glass rod by the heating stretching as the numerical value. Optical fiber manufacturing method. 12. In the heating and stretching step, a heating source for heating the glass rod moves in a longitudinal direction of the glass rod with the progress of the heating and stretching, and the heating and stretching step includes a step of: The stretching speed is controlled such that the tensile tension until the heating source moves the predetermined distance is substantially 110% or less of the average value of the tensile tension after the heating source has moved the predetermined distance. The method of manufacturing an optical fiber according to claim 11, wherein: 13. The heating / stretching step may include determining the tensile tension until the heating source travels the predetermined distance, and calculating an average value of the tensile tension after the heating source travels the predetermined distance. 13. The method according to claim 12, wherein the optical fiber is controlled to substantially 80% to 110%. 14. The predetermined distance is substantially 50 mm.
13. The distance between the object and the object.
3. The method for producing an optical fiber according to item 1. 15. The optical fiber according to claim 12, wherein the heating and drawing step controls a speed at which the glass rod is drawn at a constant speed when the heating source moves the predetermined distance. Production method. 16. The optical fiber manufacturing method according to claim 11, wherein the setting step sets a moving speed of a chuck for gripping the glass rod as the stretching speed based on the tensile tension. 17. The method according to claim 17, wherein the setting step is performed based on each of the dummy rods welded to both ends of the glass rod as the numerical values and a position of a mark provided at a joint of the glass rods. The method according to claim 1, wherein the stretching speed is set. 18. The heating and stretching step includes a drawing step of reducing an outer diameter of an end of the glass rod, and the drawing step heats the end of the glass rod based on a position of the marker. The optical fiber manufacturing method according to claim 17, wherein the optical fiber is drawn and drawn. 19. The heating step and the stretching speed are set based on a position of a cut provided at a joint between the glass rod and the dummy rod as a position of the marker. The optical fiber manufacturing method according to claim 17, wherein 20. The method according to claim 20, wherein the setting step sets the heating condition and the stretching speed based on a position of the fluorescent paint applied at a joint between the glass rod and the dummy rod as a position of the marker. The method for manufacturing an optical fiber according to claim 17, wherein: 21. The setting step sets the stretching speed at each position in the axial direction of the glass rod based on the outer diameter at each position in the axial direction of the glass rod as the numerical value. The optical fiber manufacturing method according to claim 1, wherein the heating condition is set based on an average value of the outer diameter in (1). 22. An end portion of the glass rod is narrowed, and the setting step includes: an outer diameter at each position in the axial direction of the glass rod as the numerical value; Detecting a position of a narrowed portion where the glass rod is narrowed based on a change in length; and setting a polishing range for polishing the glass rod with a flame based on the position of the narrowed portion, and setting the polishing range. Setting the heat condition of the flame based on the outer diameter of the flame, wherein the heating and stretching step polishes the polishing range of the glass rod with the flame under the heat condition. 2. The method for producing an optical fiber according to item 1. 23. A method for manufacturing an optical fiber, comprising: a heating and stretching step of heating and stretching a glass rod serving as a base material of the optical fiber to produce a preform; A drawing step of drawing an optical fiber by pulling the glass rod, wherein the heating and drawing step is a preheating step of heating the glass rod until a predetermined part is softened, and further heating and drawing the predetermined part to extend the predetermined part. An optical fiber manufacturing method, comprising: a drawing step of reducing the outer diameter of the end of the glass rod by a drawing step of reducing the outer diameter of the glass rod. 24. The drawing step, further comprising a secondary heating step of heating a region on the center side of the glass rod from the center of the predetermined portion with a flame narrower than the flame thickness in the preheating step. The optical fiber manufacturing method according to claim 23, wherein 25. A method of manufacturing a preform which is a base material of an optical fiber, comprising: a step of: A setting step of setting a heating condition for heating the glass rod and a stretching speed for stretching, based on the set heating condition and the stretching speed,
A step of heating and stretching the glass rod to form a preform. 26. The method according to claim 2, wherein the setting step sets the heating conditions and the stretching speed based on the elapsed time of the heating stretching as the numerical value.
6. The method for producing a preform according to 5. 27. The heating and stretching step includes a drawing step of reducing an outer diameter of an end of the glass rod, and the drawing step adjusts an end of the glass rod based on an elapsed time of the drawing step. The method for producing a preform according to claim 26, wherein the preform is heated and drawn. 28. The method according to claim 25, wherein the setting step sets the heating conditions and the stretching speed based on a length of the glass rod stretched by the heating stretching as the numerical value. The preform manufacturing method according to the above. 29. The heating and stretching step includes a drawing step of reducing an outer diameter of an end of the preform, and the drawing step includes the step of drawing the glass rod based on a length of the drawn glass rod. The method for producing a preform according to claim 28, wherein the end portion is drawn by heating. 30. The method according to claim 25, wherein the setting step sets the heating condition and the stretching speed based on a tensile tension generated in the glass rod by the heating and stretching as the numerical value. Preform manufacturing method. 31. In the heating and stretching step, a heating source for heating the glass rod moves in a longitudinal direction of the glass rod with the progress of the heating and stretching, and the heating and stretching step includes the step of: The stretching speed is controlled such that the tensile tension until the heating source moves the predetermined distance is substantially 110% or less of the average value of the tensile tension after the heating source has moved the predetermined distance. The method for producing a preform according to claim 30, wherein: 32. The heating and stretching step, wherein the tensile force until the heating source travels the predetermined distance, the average value of the tensile tension after the heating source travels the predetermined distance. The preform manufacturing method according to claim 31, wherein the preform is controlled substantially from 80% to 110%. 33. The predetermined distance is substantially 50 mm
32. The method according to claim 31, wherein the distance is between 150 and 150 mm.
The method for producing a preform according to item 1. 34. The preform according to claim 31, wherein the heating and stretching step controls a speed at which the glass rod is stretched when the heating source moves by the predetermined distance to a constant speed. Production method. 35. The heating step according to claim 35, wherein the setting step is performed based on each of the dummy rods welded to both ends of the glass rod as the numerical values and a position of a mark provided at a joint of the glass rods. The method for producing a preform according to claim 25, wherein the stretching speed is set. 36. The heating and stretching step includes a drawing step of reducing an outer diameter of an end of the glass rod, and the drawing step heats the end of the glass rod based on a position of the marker. The method for producing a preform according to claim 35, wherein the preform is stretched and squeezed. 37. The setting step sets the stretching speed at each position in the axial direction of the glass rod based on the outer diameter at each position in the axial direction of the glass rod as the numerical value. The preform manufacturing method according to claim 25, wherein the heating condition is set based on an average value of the outer diameters in (1). 38. An end portion of the glass rod is narrowed, and the setting step includes: an outer diameter at each position in the axial direction of the glass rod as the numerical value; Detecting a position of a narrowed portion where the glass rod is narrowed based on a change in length; and setting a polishing range for polishing the glass rod with a flame based on the position of the narrowed portion, and setting the polishing range. Setting the heat condition of the flame based on the outer diameter of the flame, wherein the heating and stretching step polishes the polishing range of the glass rod with the flame under the heat condition. 26. The preform manufacturing method according to 25. 39. A method of manufacturing a preform that is a base material of an optical fiber, comprising: a preheating step of heating a predetermined portion of the glass rod that is a base material of the preform until the glass rod is softened; And a drawing step of reducing the outer diameter of the end portion of the glass rod by a drawing step of further heating and drawing to reduce the outer diameter of the predetermined portion. 40. The method according to claim 30, wherein the drawing step includes a secondary heating step of heating a region on the center side of the glass rod from the center of the predetermined location with a flame narrowed down from the flame thickness in the preheating step. Claim 3
10. The method for producing a preform according to item 9. 41. An apparatus for producing a preform serving as a preform of an optical fiber, comprising: a heating source for heating a glass rod serving as a preform of the preform; a stretching section for stretching the glass rod; A measuring device that measures a numerical value that changes with the progress of heating and stretching of the glass rod; and a controller that controls heating conditions of the heating source and a stretching speed of the stretching unit based on the numeric value measured by the measuring device. A preform manufacturing apparatus comprising: 42. The measuring device measures the elapsed time of the heating stretching as the numerical value, and the controller controls the heating condition and the heating condition based on the elapsed time of the heating stretching measured by the measuring device. The preform manufacturing apparatus according to claim 41, wherein the stretching speed is controlled. 43. The measuring device measures a moving distance of the stretching portion accompanying the heating stretching as the numerical value, and the controller determines a moving distance of the stretching portion measured by the measuring device. The preform manufacturing apparatus according to claim 41, wherein the heating condition and the stretching speed are controlled. 44. The measuring device measures a tensile force generated in the glass rod by the heating and stretching as the numerical value, and the controller controls the tensile force generated in the glass rod measured by the measuring device. 42. The preform manufacturing apparatus according to claim 41, wherein the heating condition and the stretching speed are controlled based on: 45. The heating source moves in the longitudinal direction of the glass rod as the heating and drawing progresses, and the controller controls the tensile tension until the heating source moves a predetermined distance. Is substantially equal to the average of the tensile tensions after the heating source has moved the predetermined distance.
The preform manufacturing apparatus according to claim 44, wherein the stretching speed is controlled so as to be 0% or less. 46. The controller, wherein the controller controls the tensile force until the heating source travels the predetermined distance, and calculates an average value of the tensile tension after the heating source travels the predetermined distance. The preform manufacturing apparatus according to claim 45, wherein the stretching speed is controlled to be substantially 80% to 110%. 47. The preform manufacturing apparatus according to claim 45, wherein the predetermined distance is substantially between 50 mm and 150 mm. 48. The optical fiber manufacturing method according to claim 45, wherein the control unit controls the drawing speed to a constant speed when the heating source moves the predetermined distance. 49. The measuring device measures each of the dummy rods welded to both ends of the glass rod as the numerical values and a position of a marker provided at a joint of the glass rods. The preform manufacturing apparatus according to claim 41, wherein the heating condition and the stretching speed are controlled based on a position of the marker measured by the measuring device. 50. The measuring device measures an outer diameter at each axial position of the glass rod as the numerical value, and the controller determines the outer diameter at each axial position of the glass rod based on the outer diameter at each axial position. The preform according to claim 41, wherein the stretching speed is controlled at each position in the axial direction of the glass rod, and the heating condition is controlled based on an average value of the outer diameter at each position. manufacturing device.