JP2697928B2 - Heat-melt stretching method for rod-shaped body - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for hot-melt drawing of a rod-shaped body that is melted (including softened) by heating.

2. Description of the Related Art As is well known, a glass rod or the like can be reduced to a required outer diameter by heating and melting the rod.

By the way, when reducing the diameter of the quartz optical fiber preform,
While the optical fiber preform is heated and melted from one end to the other end, the end of the heat-fused optical fiber preform is stretched in the axial direction.

At this time, the outer diameter of the melted portion of the optical fiber preform decreases in the direction in which the optical fiber preform is stretched, and deforms like the tip shape of the spindle.

Therefore, a tapered constricted fusion deformation called a meniscus is generated between the original shape portion of the optical fiber preform and the finish.

When the optical fiber preform is stretched while being heated and melted in this manner, the outer diameter of the melt-deformed portion is measured, and the measured outer diameter is fed back to the optical fiber preform stretching system, and the optical fiber preform is stretched. Control the finish outer diameter of the base material to the target value.

Known documents of such technology include, for example,
-18325.

[Problem to be Solved by the Invention] This kind of conventional technology only shows extremely high-level concepts, including the publicly known documents exemplified above, and lacks practical concreteness.

In particular, when the outer diameter information is to be collected from the melt deformed portion of the optical fiber preform, that is, when the outer diameter measurement position of the melt deformed portion is close to the heat source, the responsiveness and controllability are poor. Although good, the difference between the measured outer diameter of the molten deformed part and the base metal finish is large, and there is a problem that the fluctuation of the outer diameter of the base material original part cannot be absorbed as it is. When it is close to the portion, although the difference between the measured outer diameter of the molten deformed portion and the base material finish is small, the response is poor and hunting causes loss of control.

Therefore, under the present circumstances, it is difficult to finish the finish outer diameter of the base material to the target value based on the outer diameter measurement at an appropriate position with respect to the melt deformed portion, and trial and error has been repeated.

In view of the above technical problems, the present invention, when reducing the diameter of a rod using a combination of the heating and melting means and the stretching means, appropriately set the outer diameter measurement position in the melt deformation portion of the rod, It is an object of the present invention to provide a method capable of obtaining a reduced-diameter rod with high accuracy in outer diameter with good yield by feeding back data obtained from an appropriate measurement position to a stretching system of the rod.

[Means for Solving the Problems] In order to achieve the intended purpose, the present invention sequentially heats and melts the rod from its end, and moves the end of the heated and melted rod in the axial direction thereof. The rod is stretched to form a reduced-diameter finish on the extension end side of the rod, and the outer diameter of the melt-deformed portion from the original part of the rod to the finish is measured at one point, and the measured outer diameter and its melting point are measured. In the method of controlling the finish outer diameter of the rod-like body by feeding back the difference from the target outer diameter in the deformed portion to the rod-like body stretching control system, during the steady stretching operation of the rod-like body under heating and melting, the molten deformed part viscosity and measuring the outside diameter of the portion of finish diameter is ^{6.2 to 107} poise at.

[Operation] As described above, in the method of the present invention, the rod-shaped body is sequentially heated and melted from its end, and the end of the heated and melted rod-like body is stretched in the axial direction.

When the rod-shaped body is heated and melted and stretched in this way, between the original shape portion of the rod-shaped body and the finish of the rod-shaped body generated by the stretching,
Melt deformation (meniscus) is inevitably generated.

For the present invention a method, by paying attention to the viscosity eta at melt deformation portion of the rod-like body, the outer diameter of a portion viscosity eta is in the range of 10 ^6.2 poise ≦ eta ≦ 10 ⁷ poise measured one point, the outer diameter thereof The measured value and the target outer diameter in the melt deformed portion, that is, the difference between the target outer diameter required for the melt deformed portion to finish the finish to the target outer diameter value is fed back to the stretching control diameter of the rod-shaped body. Since the outer diameter of the finish of the rod is controlled, the following is obtained.

As one of them, the measurement site (measurement point) of the melt deformed part whose viscosity is within the above range has a sufficiently high temperature,
In addition, since the viscosity is low, the response at the time of controlling the outer diameter is improved.

As another one, the measurement site of the melt deformed portion whose viscosity is within the above range is close to the solidified finish, and the difference between the measured outer diameter and the outer diameter of the finished portion is small, and the rod-shaped body Is also separated from the original shape portion, the influence (outer diameter variation) of the original shape portion hardly spreads to the finish, and the outer diameter variation of the finish is small.

Thus, the finish of the rod-shaped body reduced in diameter by the heat-melting stretching is finished with high accuracy with respect to the outer diameter target value.

"Example" An example of the method of the present invention will be described with reference to figures.

1 and 2 show an embodiment in which the diameter of the large-diameter rod 11 is reduced to a small diameter.

The rod 11 is made of, for example, a quartz-based optical fiber preform and has a core portion and a clad portion.

In FIG. 1 and FIG. 2, one end, that is, a base end of a rod 11 which is rotated while being restricted in axial movement is held by a rotatable stationary chuck (not shown), and moves in the axial direction while rotating. The other end of the rod-shaped body 11, that is, the extended end, is held by a movable chuck (not shown) that is reciprocally movable and rotatable in the axial direction.

In some cases, the base end of the rod 11 is held by a chuck that is rotatable and moves at a low speed in the axial direction, and the extended end of the rod 11 is held by a chuck that is rotatable and moves at a high speed in the axial direction.

Known or well-known chucks are used for these pairs of chucks.

In FIGS. 1 and 2, the burner 21 as a heat source is
The burner 21 is composed of a known or well-known oxyhydrogen flame burner whose burner angle is adjustable, and the burner 21 is arranged at a predetermined position and supported by a movable supporting means (not shown).

The outer diameter measuring device 22 is composed of an optical system having a laser beam irradiation function and a light receiving detection function, and includes a pair of a light irradiator 23 and a light receiving detector 24, and a connecting tool 25 for connecting these two devices. Have.

In the outer diameter measuring device 22, the light irradiator 23 and the light receiving detector 24
Are connected to each other via the connecting tool 25 and face each other.

Further, the outer diameter measuring device 22 is provided with a movement adjusting mechanism 28 mainly including a feed shaft (screw shaft) 26 and a bearing stand 27,
It is supported so that it can move in the horizontal direction.

1 and 2, when a large-diameter rod 11 is processed into a required small diameter, the rod 11 is sequentially heated and melted from one end to the other end via a burner 21, and the rod 11 is processed. Is moved in the direction of the arrow in FIG.

By the heat melting and the stretching, the stretching side of the rod 11 is sequentially reduced to a predetermined outer diameter and solidified.

In this case, a portion from the original shape portion 12 of the rod-shaped body 11 to the finish 14 becomes a melt deformed portion 13 deformed like the tip shape of the spindle.

When the rod-shaped body 11 is reduced in diameter in this way, the outer diameter of the melt-deformed portion 13 is measured at the aforementioned predetermined position.

At this time, a laser beam is irradiated from the light irradiator 23 of the outer diameter measuring device 22 toward the measurement position (measurement point) of the melt deformation portion 13, and the transmitted light is received by the light detector 24 of the outer diameter measuring device 22.
, The outer diameter of the melt-deformed portion 13 is measured.

Thus, the measured outer diameter measurement value of the melt deformed portion 13 is transmitted from the light receiving detector 24 of the outer diameter measuring device 22 to the extension control system of the rod 11, that is, the axis that moves while holding the extension end of the rod. The direction is input to a drive system (not shown), and the stretching speed of the rod 11 is appropriately controlled, so that the finish 14 of the rod 11 is finished with high precision.

The temperature and the viscosity of the melt deformation portion 13 are obtained as follows.

For example, in quartz-based glass (silaka glass), which is a typical material of an optical fiber preform, the balance between viscous force and tension is dominant. Therefore, the following volume flow rate continuous equation [Equation (1)] is used. The equation of momentum [Equation (2)] holds.

D ² v = constant ^{‥‥‥ (1) πD 2/4} × 3η (∂v / ∂Z) = F = constant ‥‥‥ (2) (1) ( 2) wherein, D is the outside of the melt deformation portion Diameter, Z is the axial direction of the rod, v is the velocity of the molten deformed part in the Z-axis direction, F is Z
The axial stretching tension, η, is the viscosity of the melt deformed portion.

Therefore, when determining the viscosity η of the melt-deformed portion, the outer diameter D of the melt-deformed portion is measured, and the measured value of the outer diameter is substituted into the equation (1) to obtain the velocity v. What is necessary is just to substitute in an expression.

Further, the temperature of the melt-deformed portion is obtained from the temperature-viscosity relational expression of the rod-shaped material.

In addition, the temperature of the melt deformation portion can be measured by an infrared radiation thermometer.

Next, a more specific example of the method of the present invention will be described.

As the rod-shaped body 11, a quartz-based external optical fiber preform having an outer diameter of 23.5 mmφ of the original form part 12 is used,
It was decided to finish.

Further, the moving velocity V _B of the burner 21 was 10 mm / min.

FIG. 3 shows the actual measured value of the outer diameter of the rod 11 in this specific example, and the measured position of the outer diameter of the molten deformation portion 13 (reference point 0 = burner 21).
FIG. 4 shows the relationship between the temperature distribution of the melt deformation portion 13 and the outer diameter measurement position.

Measurement positions P ₁ , P ₂ and P _{3 in} FIG. ₃ and measurement positions in FIG.
P ₁ , P ₂ , and P ₃ correspond to each other.

In FIG. 3, the measurement position is set to P ₂ in the melt deformation portion 13,
When the predetermined outer diameter control is performed based on the measurement data obtained from the measurement position, the outer diameter of the finish 14 (the target value is 13.0 mm
φ) was finished to 13.0 ± 0.05 mmφ.

FIG. 3 and FIG. 4 summarize the contents of the measurement positions of the melt deformation portion 13 as shown in the following table.

As apparent from the above table, by setting the measuring points of the melt deformation portion 13 at the viscosity ^{6.2 to 107} poise (temperature range 1700 to 1800 ° C.) to measure the outside diameter of the melt deformation portion 13, the When the difference between the measured outer diameter and the target outer diameter in the melt-deformed portion is fed back to the stretching control system of the rod 11 to control the outer diameter of the finish 14, the finish 14 having a small outer diameter variation is controlled. Is obtained.

In contrast, if the viscosity was measured point at less than 10 ^6.2 poise, for example, the measurement point is Figure 3, when the P ₁ shown in FIG. 4, the finish and an outer size measurements of melt deformable portion 13 14
Large difference between the outer diameter, can not absorb the outside diameter variation of the original section 12, further, when the viscosity was measured point where more than 10 ⁷ poise, for example, the measurement point is Figure 3,
When P ₃ shown in Figure 4, the response in external diameter control is poor, leading to loss of control by the hunting.

Therefore, when the rod-shaped body 11 is heated and melted and stretched, it is technically effective to measure the outer diameter D of the melt-deformed portion 13 with the viscosity of ^106.2 to 10 ⁷ poise as a measurement point. Was demonstrated by the above example.

[Effects of the Invention] As described above, when the method of the present invention heat-melts and stretches a rod-shaped body to form a reduced-diameter finish on the stretched end side of the rod-shaped body, the melt-deformed portion is measured at a viscosity of 10 ^6.2 ~ 10 ⁷ poises to measure the outer diameter of the molten deformed part, and feedback control based on the measurement data to control the finishing outer diameter of the rod, so that the reduced diameter rod with high finishing accuracy Is obtained stably.

[Brief description of the drawings]

1 and 2 are a front view and a longitudinal sectional side view of a main part schematically showing an embodiment of the method of the present invention, and FIG. 3 shows a relationship between an outer diameter measured value and an outer diameter measurement point of a rod-shaped body. FIG. 4 is a diagram showing the relationship between the temperature gradient of the melt deformed portion and the outer diameter measurement point. 11 ... rod-shaped body 12 ... original part of rod-shaped body 13 ... molten-deformed part of rod-shaped body 14 ... finish of rod-shaped body 21 ... burner 22 ... outer diameter measuring device 23 ... light of outer diameter measuring device Irradiator 24 …… Receiver detector of outer diameter measuring device

Claims (1)

(57) [Claims] 1. A finish whose diameter is reduced toward the extending end of the rod-shaped body while the rod-shaped body is sequentially heated and melted from its end, and the end of the heated and melted rod is stretched in the axial direction thereof. And at one point the outer diameter of the melt-deformed portion from the original part of the rod to the finish, and the difference between the measured outer diameter and the target outer diameter in the melt-deformed part is sent to the rod-elongation control system. and feedback, in the method of controlling the finish outside diameter of the rod-like body, the steady operation stretching of the rod-shaped body under heating and melting, the viscosity at the melt deformation part is finish sites diameter is ^{6.2 to 107} poises A method for heating and melting a rod-shaped body, comprising measuring an outer diameter.