JP3901877B2 - Glass base material stretching apparatus and method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a glass base material stretching apparatus and method for stretching a glass base material to a constant outer diameter.
[0002]
[Prior art]
In general, an optical fiber is manufactured by drawing a glass base material obtained by a VAD method, an OVD method, or the like to an outer diameter suitable for drawing, and then drawing to a predetermined outer diameter. In order to stretch the glass base material, a glass base material stretching device including a heating furnace, a take-up machine, or the like is usually used. The glass base material stretching apparatus heats and softens a glass base material sent to a heating furnace with a heating element of the heating furnace, and stretches the glass base material to a desired outer diameter by a take-up machine. When the glass base material is stretched by this glass base material stretching device, as the stretching process proceeds, the heat insulating material in the heating furnace receives the amount of heat from the heating element and the temperature rises, and the unsoftened part of the glass base material is irradiated with radiant heat. While heating, heat is conducted from the heat softened part of the glass base material to the unsoftened part.
Therefore, in the glass base material stretching step, when the temperature of the heating element is kept constant, the temperature of the heat softening portion of the glass base material becomes higher and the viscosity is lower immediately before the end of stretching than immediately after the start of stretching.
[0003]
When the viscosity of the heat softened portion decreases, the take-up force from the take-up machine decreases, and further, the temperature of the heat softened portion rises and the heat softened portion is stretched to a desired outer diameter only by its own weight at the bottom. The take-off machine does not give the take-up force. Further, when the temperature of the heat softening portion rises and the viscosity decreases, the heat softening portion is stretched to a desired outer diameter or less only by its own weight at the bottom, and in this case, the take-up machine is in a pulling direction with respect to the glass base material. Instead of a force, a force in the lifting direction, that is, a compressive force is applied. When a compressive force is applied to the heat softened portion, the glass base material being stretched buckles in the heat softened portion, and as a result, the straightness of the glass base material after stretching is greatly reduced.
Therefore, in order to improve the straightness of the glass base material after stretching, it is necessary to always stretch with a desirable take-up force. For this purpose, it is necessary to lower the temperature of the heating element of the heating furnace as the stretching process proceeds. is there.
[0004]
As a method of improving the straightness of the glass base material by lowering the temperature of the heating element as the stretching process progresses, a heating element temperature change pattern that changes as the stretching process progresses is prepared in advance. There has been a method in which a desired take-up force is applied to the heat softened portion of the glass base material by lowering the temperature of the heating element according to this pattern.
However, the above change pattern occurs for all combinations of the diameter of the glass base material during stretching and the shape of the glass base material, and further considering the amount of heat held by the heating furnace before the start of the stretching process. The number of change patterns that must be set in advance is enormous, and it takes a lot of time and labor to set all the change patterns.
Therefore, in order to solve the problems of the above method, a method of controlling the heating element power by installing a pulling force detector in the pulling machine so that the pulling force detection value of the pulling force detector is suitable is proposed. (JP-A-4-325428).
[0005]
[Problems to be solved by the invention]
However, in the above method, since there is a large effective time delay from the change of the heating element power to the change of the detection value of the pulling force detector, quick and precise heating element power control is difficult. It was.
Then, this invention makes it a subject to provide the glass base material extending | stretching apparatus and method which eliminate the said problem and extend | stretch a glass base material to a fixed outer diameter.
[0006]
[Means for Solving the Problems]
That is, the glass base material stretching apparatus of the present invention includes a heating furnace that heats and softens the glass base material, a take-up machine that applies a take-up force to the glass base material, a take-off force detector that detects the magnitude of the take-up force, and a heating A heating element power supply device for supplying power to a heating element of a furnace, a glass base material heating softening part temperature detector, a heating element temperature detector, and a heating element power controller. The heating element power controller is equipped with a cascade control system composed of a take-off force adjuster and a glass base material heating softening part temperature adjuster , the take-off force detection value of the take-off force detector, and the temperature of the heating element temperature detector. A detection value and a temperature detection value of the glass base material heating softening section temperature detector are input, respectively , and the heating element power supply device is cascade- controlled in accordance with the detection values .
Furthermore, the glass base material stretching method of the present invention uses the glass base material stretching apparatus, controls the heating element power supply device by program control before starting the glass base material stretching, and after starting the glass base material stretching. The heating element power supply device is controlled by cascade control.
[0007]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described in detail with reference to the drawings.
FIG. 1 is a schematic view showing an example of a glass base material stretching apparatus according to the present invention, wherein 1 is a heating furnace, 2 is a heating element of the heating furnace, 3 is a glass base material, 4 is a take-up machine, and 5 is a take-up machine. Alternatively, a take-off force detector disposed in the vicinity thereof, 6 is a heating furnace or a heating element temperature detector disposed in the vicinity thereof, 7 is a heating element power controller, and 8 is a heating element connected to the heating element power controller. The power supply device 9 is a glass base material heating softening portion temperature detector disposed in the heating furnace or in the vicinity thereof.
[0008]
The glass base material 3 is supplied to the heating furnace 1 by a supply machine (not shown), heated and softened by the heating element 2 in the heating furnace 1, and stretched to a desired outer diameter by the take-up machine 4. In this drawing of the glass base material, the take-off force detection value from the take-off force detector 5 and the temperature detection values from the heating element temperature detector 6 and the glass base material heating softening part temperature detector 9 are transferred to the heating element power controller 7. Entered. The heating element power controller 7 controls the heating element power supply device 8 so that the pulling force detection value of the pulling force detector 5 is suitable according to these detection values.
[0009]
There is usually a long effective time delay from when the heating element power controller 7 instructs the heating element power supply device 8 to change the supply power until the take-off force detection value changes. Therefore, as in the prior art, it is difficult to control the heating element power supply device 8 quickly and precisely to make the pulling force detection value suitable by simply providing the pulling force detector 5 and feeding back the detection value.
Therefore, in the present invention, as described above, in addition to the take-off force detector 5, the glass base material heating softening portion temperature detector 9 is provided, and not only the take-off force detection value and the heating element temperature detection value but also the glass base material. The heating softening portion temperature detection value is also input to the heating element power controller 7. By doing this, the effective time delay from when the heating element power controller 7 instructs the heating element power supply device 8 to change the supply power until the glass base material heating softening portion temperature detection value changes is the heating element power. Since the effective time delay from when the controller 7 instructs the heating element power supply device 8 to change the supply power to when the take-off force detection value changes is very short, the heating element power supply device 8 is quickly and accurately adjusted. The feedback force detection value can be made suitable by performing feedback control.
[0010]
As a method for controlling the heating element power supply device 8, for example, a program control system in which the temperature of the heating element 2 is increased according to a predetermined time schedule before starting the drawing of the glass base material 3 is heated. It is provided in the body power controller 7, and the heating element power supply device 8 is controlled by this control method.
And after extending | stretching of the glass base material 3, the heat generating body electric power supply apparatus 8 is controlled not by program control but by cascade control in which quick and precise control is possible.
[0011]
FIG. 2 is a block diagram showing an example of the heating element power controller 7 having a program control system and a cascade control system. As shown in this figure, a take-off force detector 5, a heating element temperature detector 6, and a glass base material heating softening temperature detector 9 are connected to the input section of the heating element power controller 7, and the output section is connected to the output section. A heating element power supply device 8 is connected. Further, the heating element power controller 7 illustrated in FIG. 2 is provided with a take-up force adjuster 10 and a glass base material heating softening portion temperature adjuster 11 constituting a cascade control system. The pulling force adjuster 10 generates a necessary signal based on the target value of the pulling force and the pulling force detector value, and outputs it to the glass base material heating softening part temperature controller 11. In the glass base material heating softening part temperature controller 11, the output from the take-up force controller 10 is added to the output corresponding to the glass base material heating softening part temperature detection value, thereby reducing the execution time delay and the heating element. Power is precisely controlled.
[0012]
As shown in FIG. 2, the heating element power controller 7 includes a temperature pattern holding circuit 14 and a heating element temperature detection value constituting a program control system for heating the heating element 2 in accordance with a preset temperature pattern. It is also possible to provide a heating element temperature controller 13 that receives the input of.
Outputs from the glass base material heating softening section temperature controller 11 and the heating element temperature controller 13 are input to the switching circuit 12, and an output from the switching circuit 12 is sent to the heating element power supply device 8, and as a result, The heating element power is controlled. If the conventional PID controller is used for the take-up force adjuster 10, the glass base material heating softening temperature controller 11, and the heating element temperature controller 13, the control system of the heating element power controller 7 is easy. And it can be designed at low cost.
[0013]
【The invention's effect】
The glass base material stretching apparatus of the present invention can be easily and inexpensively manufactured, and enables rapid and precise heating element power control. Therefore, by using this apparatus, it becomes possible to extend the glass base material to a constant outer diameter at a low cost, and the industrial value is extremely high.
[Brief description of the drawings]
FIG. 1 is a schematic view showing an example of a glass base material stretching apparatus of the present invention.
FIG. 2 is a block diagram showing an example of a heating element power controller.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Heating furnace 2 Heat generating body 3 Glass base material 4 Take-off machine 5 Take-off force detector 6 Heat-generating body temperature detector 7 Heat-generating body power controller 8 Heating body power supply device 9 Glass base material heating softening part temperature detector 10 Take-out force adjustment Unit 11 Glass base material heating softening part temperature controller 12 Switching circuit 13 Heating element temperature controller 14 Temperature pattern holding circuit

Claims (2)

A heating furnace that heats and softens the glass base material, a take-up machine that applies a take-up force to the glass base material, a take-off force detector that detects the magnitude of the take-off force, and a heating element power that supplies power to the heating element of the heating furnace A glass base material stretching device having a supply device, a glass base material heating softening section temperature detector, a heating element temperature detector, and a heating element power controller, wherein the heating element power controller is a take-off power controller And a glass base material heating softening part temperature controller, a take-off force detector take-off force detection value, a heating element temperature detector temperature detection value, a glass base material heating softening part temperature detector The glass base material stretching device is characterized in that the detected temperature values are respectively input, and the heating element power supply device is cascade controlled in accordance with the detected values. A method for stretching a glass base material using the glass base material stretching apparatus according to claim 1, wherein the heating element power supply device is controlled by program control before starting the glass base material stretching, and after the glass base material stretching starts. Is a method for drawing a glass base material, wherein the heating element power supply device is controlled by cascade control.

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