JPS6112605B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of manufacturing foamed plastic insulated wire.

Conventionally, when extruding plastic containing a foaming agent onto a conductor using an extruder, in order to control the degree of foaming of the foamed plastic insulator, the capacitance of the foamed plastic insulator, that is, the capacitance between the conductor and the insulator, is measured in a cooling water bath or afterward. The capacitance between the surroundings is detected by an appropriate means, and the deviation of the value from the reference setting value, that is, the capacitance deviation, is used to control the factors that affect the capacitance change as described below. A method is used to converge the deviation to zero.

The objects to be controlled by the above method include the following.

(A) Change the rotation speed of the extruder screw to change the thickness of the insulator.

(B) Change the line speed and change the thickness of the insulator.

(C) Change the degree of foaming of the insulator by changing the extruder cylinder temperature.

(D) Change the degree of foaming of the insulator near the conductor by changing the preheating temperature of the conductor.

(E) The cooling water tank after exiting the extruder is made partially movable and moved closer or further away from the crosshead of the extruder to adjust the foam formation of the foamed plastic insulation immediately after extrusion.

Each of these methods has advantages and disadvantages, and it is not necessarily possible to obtain high-quality foamed plastic insulated wires with just one control.

With method (A) or (B), the thickness of the insulator changes, although it is minute, which is a problem if high quality is required, and method (C) takes time to change the temperature. Therefore, the response speed is slow. Furthermore, although methods (D) and (E) have a fast response speed, the range of change in capacitance that can be changed by this method is small, and it may be difficult to reduce the capacitance deviation to zero using only this method.

The present invention provides a new method that eliminates the drawbacks of these conventional methods.
After being preheated in a conductor preheating machine 2, the plastic containing a foaming agent is extruded and coated in an extruder 3, cooled in a movable water tank 4 and a fixed water tank 5, and passed through a capacitance detector 6 to a take-up machine. Pick up by 7. A capacitance detector may also be installed within the aquarium. The output of this capacitance detector is compared with the capacitance reference setting value, and the difference is taken out as a capacitance deviation and is controlled by moving the movable water tank closer to or away from the crosshead of the extruder via the controller 8. . The distance L between the crosshead of the extruder and the movable water tank and the capacitance C are as follows, assuming that other conditions such as extruder temperature, core wire temperature, and linear speed are constant:
If there is a certain correlation, and the correlation changes as conditions change, but other conditions do not change in a short period of time, the curves shown in FIG. Therefore, by changing L, C can be changed and the capacitance can be brought to the desired value, that is, the reference setting value Co. However, the actual movable range _L of the movable aquarium depends on the aquarium equipment. Since it is limited by the design, if other conditions vary and there is a correlation, the capacitance deviation can be brought to zero by simply moving the movable water tank between L _{and W.} In other words, C can be brought _close to Co, but if other conditions are met to give a correlation such as I can't do it. Therefore, an appropriate point Lo is set between _Lw , the displacement ΔL of the movable water tank from Lo is taken out as an output, and the preheating current of the conductor preheater 2 is changed via the preheating temperature controller 9.

In this case, the preheating temperature changes depending on the preheating current, and the relationship between the capacitance C and the preheating current i is shown in Figure 3. Therefore, while the capacitance deviates from the reference value, the movable water tank moves, and the movable water tank moves. Since the preheating current changes corresponding to the number of minutes, the response speed is faster than when controlling only with a movable water tank. However, since the control range that can be responded to with only a movable water tank and preheating current is limited,
Depending on the deviation Δi of the preheating current i from the standard setting (io) value, the cylinder temperature of the extruder is increased or decreased via the cylinder temperature controller 10. If Δi is positive, the cylinder temperature may be increased, and if Δi is negative, the cylinder temperature may be decreased.

In the above explanation, the movable water tank is controlled based on the capacitance deviation, the preheating current of the conductor preheater is controlled based on the displacement of the movable water tank from the reference point, and the cylinder temperature of the extruder is controlled based on the deviation of the preheating current from the reference value. As mentioned above, the cylinder temperature has a wide response range, that is, a range in which capacitance can be changed, but the response speed is slow, whereas conductor preheating and movable water tanks have a narrow response range but a fast response speed, so the above-mentioned A slight change in the control order controls the preheating current of the conductor preheater based on the capacitance deviation, the movable water tank based on the deviation of the preheating current from the reference value, and the cylinder temperature of the extruder based on the displacement of the movable water tank from the reference point. It is also possible.

In the present invention, the displacement of the movable water tank, the change in the preheating current of the conductor preheater, and the change in the cylinder temperature of the extruder are controlled in combination based on the capacitance deviation. Even if there are drawbacks, by combining them, the control method has a fast response speed and a wide response range, and can be applied to the production of high-quality foamed plastic insulated wires without waste.

[Brief explanation of the drawing]

Fig. 1 is an explanatory diagram of an example of controlling the extrusion coating process of foamed plastic insulation of the present invention, Fig. 2 is a correlation diagram of capacitance, movable water tank, and crosshead distance, and Fig. 3 is a diagram of the relationship between capacitance and conductor preheater. A correlation diagram with preheating current is shown. In the figure, 1 is a conductor, 2 is a conductor preheater, 3 is an extruder, 4 is a movable water tank, 5 is a fixed water tank, 6 is a capacitance detector, 7 is a take-up machine, 8 is a movable water tank position controller, 9 indicates a preheating current controller, and 10 indicates a cylinder temperature controller.

Claims (1)

[Claims] 1. A method of manufacturing a foamed plastic insulated wire by extrusion coating a conductor with foamed plastic, detecting the capacitance of the insulator, and controlling extrusion conditions according to the capacitance deviation from a reference setting value, Depending on the capacitance deviation, either the position of the movable water tank provided between the extruder crosshead and the fixed water tank or the preheating temperature of the conductor preheater can be changed, and the deviation of the movable water tank or preheating temperature from the standard can be further reduced. A method for manufacturing a foamed plastic insulated wire, characterized in that the temperature of a cylinder of an extruder is controlled according to the amount of deviation from the reference value of the later changed value.