JPH0516042B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an extrusion line control method for highly foamed insulated wire, and particularly to a highly foamed insulated wire extrusion line control system where control variables such as the outer diameter and capacitance of the extrusion coated gas foamed insulator are multivariable. It is related to the extrusion line control method for seed wire.

Generally, communication cables are made by extruding and coating a conductor with an insulator having a small capacitance and therefore a small dielectric constant, in order to reduce transmission loss in terms of electrical characteristics. The insulator also needs to be a support for the cable. For this reason, chemically foamed polyethylene (PFE), which is polyethylene mixed with a foaming agent, is often used as an insulator for communication cables. This extrusion method is called a "chemical foaming method" and can achieve a foaming degree of up to about 50%.

However, recently, the transmission band has become wider,
As CATV and CCTV facilities are increasing,
A broadband, low-loss transmission line is required, and therefore a "gas foaming method" that exhibits high foaming, for example, a degree of foaming of about 85%, has been adopted.

This gas foaming extrusion line is shown in Figures 1-2.
In this line 10, the core wire supply drum 10a
The core wire 11 pulled out from the delivery side capstan 1
2 and reaches the preheater 13. The preheater 13 heats the core wire 11 by induction heating, thereby producing uniform foaming and improving the adhesion between the core wire and the foamed insulator.

The core 11 then passes through an incoming temperature sensor 14 to a crosshead 16 of an extruder 15. The incoming temperature measurement sensor 14 is located in California, USA.
TRANS-MET ENGINE- in LA HABLA
The NCT-4500-3 model manufactured by ERING, INC. is capable of continuously measuring the temperature of the core wire 11 in a non-contact manner, and has an accuracy of ±1°C.

The extruder 15 includes a first stage extruder 17 and a resin inlet 20 at a docking part 19 with a discharge port 18 thereof.
and a second stage extruder 21 connected and arranged in series (Figs. 1 to 3). Each extruder 17, 21 is equipped with cylinder heaters 22-26 and 27-30 on the outer periphery of cylinder 17a, 21a, respectively, and screws 17b, 21b extend inside the cylinder. Although not shown, hot water is supplied to the first stage screw 17b and the second stage screw 2
Cold water is flowing back into 1b. Each screw 17
b and 21b are rotationally driven by motors 17c and 21c, respectively.

The crosshead 16 is provided with a crosshead heater (not shown).

Thus, the insulating composition containing the polyolefin resin supplied from the hopper 31 to the extruder 17 is
The heat generated by the kneading of the screw 17b heated by refluxing hot water and the cylinder heaters 22 to 26 generate heat at, for example, 120°C, 110°C, 120°C, 180°C, 200°C.
It melts and softens due to the cylinder temperature. The lightweight pump 3 is pumped from the tank 32 to the softened resin.
Liquefied high pressure gas is injected from the nozzle 34 through the nozzle 34. Note that the injection site may be the point shown in FIG. 3. The resin into which the gas has been injected is maintained at, for example, 200°C in the docking part 19, and
It is fed into a stage extruder 21. This extruder has a temperature of 100° C. and 110° C., for example, due to the temperature of the screw 21b through which cold water flows back, the heat generated as a result of kneading due to the rotation of the screw, and the cylinder heaters 27 to 30.
℃, 110℃, and 130℃, the cylinder temperature can be lowered to a temperature suitable for producing highly expanded polyethylene insulation. In the second stage extruder, the resin and gas are thoroughly mixed to form a foamed insulation composition with a large number of closed cells trapped within the resin. This composition is extruder coated onto the core wire 11 which is continuously fed to the crosshead of the second stage extruder while being kept warm by the crosshead heater. Here, when the foaming gas in the foamed insulation material, which was loaded with high pressure in the extruder 21, is extruded into the atmosphere, it is released from the high pressure and expands in the resin, and the pressure in the foamed foam is reduced to atmospheric pressure. It becomes maximum when it becomes equal to . If the outer periphery of this foamed insulator is cooled by water cooling or other cooling means to form a barrier on the outer periphery, the growth of foam inside can be prevented. For this purpose, the line 10 is provided with a cooler.

As shown in FIG. 1, the cooler may be composed of a moving water tank 35 and a fixed water tank 36. The electric wire, whose foaming is restricted by a cooler, is formed to a predetermined outer diameter D, and has a predetermined capacitance C, passes through an outer diameter measuring device 37, its surface is melted by a heater 38, and the surface is melted by a cooling sizing die 39. After being smoothed, it passes through a capacitance measuring device 40, is taken off at a predetermined line speed at a take-up stand 41, and wound onto a take-up drum 42.

Figure 2 shows a modified example of the cooler system, and the difference from the extrusion line in Figure 1 is that the crosshead 1
6, an outer diameter measuring device 37, a cooling sizing die 39, and a fixed water tank 36 are arranged in this order.

The measuring device 37 is an M503A laser outer diameter measuring device manufactured by Anritsu Electric Co., Ltd., and has an accuracy of ±10 μm.

The measuring device 37 is an M503A laser outer diameter measuring device manufactured by Anritsu Electric Co., Ltd., and has an accuracy of ±10 μm. The measuring device 40 is located in Bucks, High Wycombe, UK.
BETA's KI-700CGA (sensor KG1000) has an accuracy of ±0.2PF/m.

By the way, in manufacturing a foam insulated wire, the outer diameter D and capacitance C of the wire must be uniform in the longitudinal direction of the wire. Therefore, in order to manufacture an electric wire with a uniform outer diameter D and capacitance C, the preheater voltage, each screw rotation speed of the first and second stage extruders, each cylinder temperature, and the rotation speed of the gas injection pump are required. , crosshead heater voltage,
It is necessary to control operating parameters such as the degree of forced cooling of the resin by the cooler and the line speed to predetermined values.

In the above example, the extruder 15 is composed of the first and second stage extruders 17 and 21, but alternatively, these can be composed of a single extruder.

Conventionally, when controlling extrusion of the extrusion line 10 to obtain a predetermined capacitance C and outer diameter D, the extruder 17, 21
The rotational speed of the screws 17b and 21b, the voltage applied to the preheater 13, etc. were controlled.

In addition, the capacitance C is the position of the moving water tank 35 (the first
(Fig. 2) or the position of the cooling sizing die 39 or its temperature (Fig. 2).
The outer diameter D is adjusted manually, and in the case of the extrusion line shown in Fig. 1, the sizing die 3 is finally
9 to smooth the surface of the outer periphery, and in the case of the extrusion line shown in FIG. 2, the outer diameter was finally defined by a sizing die 39.

In either case, the sizing die 39 has the same inner diameter as the desired wire outer diameter D, and the outer diameter of the extruded power source is the same as or slightly larger than the outer diameter D before the sizing die. You need to manually control it. However, even when adjusting the outer diameter manually, the outer diameter has only been adjusted empirically by changing the screw rotation speed of the extruder or the extruder temperature. However, in reality, if you move the moving water tank or sizing die, the capacitance will of course change.
In that case, the outer diameter changes at the same time, so even if the capacitance can be controlled, the outer diameter cannot be controlled, and the outer diameter will fluctuate from the desired value. As a result, it has been extremely difficult to manufacture electric wires of constant high quality by independently controlling the capacitance and outer diameter.

In short, in this type of extruder line, when the extrusion temperature of the extruder is constant, when the screw rotation is slowed down or the line speed is increased, the wire outer diameter decreases, and when the extrusion temperature increases, the foaming rate decreases. On the other hand, as the outer diameter increases and the line speed increases, the time interval from extrusion to cooling and solidification becomes shorter, foaming stops earlier, and the foaming rate decreases.There is a deep relationship between each factor. Therefore, it is necessary to stably control the outer diameter and capacitance (foaming rate) while taking these interrelationships into account.

That is, a large number of measured quantities (C, D, and the first and second stage extruders 17,
21, the temperature of the crosshead 16 of the second stage extruder, the resin temperature and resin pressure in the crosshead 16, the first
and the pressure of the docking part 19 of the second stage extruder,
The gas injection flow rate or injection pressure, the inlet temperature of the core wire 11, and the temperature of each screw 17b, 21b of the first and second stage extruders) are controlled by a large number of manipulated variables (in the case of this embodiment, each screw 17b, 21b). 21b rotation speed, preheater 1 installed in front of the extruder
3 voltage, heater 2 of each cylinder 17a, 21a
2-30 voltage, crosshead 16 heater voltage, gas injection pump 33 rotation speed, extrusion line 1
In control (multivariable control) where the control variable changes when either the zero speed or the position or temperature from the cooler crosshead is manipulated, each controlled variable is adjusted to the desired value by measuring the measured quantity. It has been extremely difficult in the prior art to simultaneously and automatically control the respective manipulated variables.

Furthermore, due to the correlation between the controlled variable and manipulated variable of multiple variables, a control method that relies only on each pair of controlled variable and manipulated variable has the disadvantage that the stability of the controlled variable is poor and the responsiveness is poor. Ta.

Therefore, the main object of the present invention is to perform multivariable control of a highly foamed or gas-foamed insulated wire extrusion line by detecting elements for measuring measured quantities including the controlled quantities of wire outer diameter and capacitance. The extruder, preheater,
An object of the present invention is to provide a highly foamed insulated wire extrusion line control system that simultaneously and automatically controls the operation amount of a cooler.

Another object of the invention is to provide control means with improved stability and/or reactivity in such systems.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The extrusion line control system for highly foamed insulated wires according to the present invention will be described in detail below with reference to the drawings in an embodiment in which it is applied to an extrusion line shown in FIGS. 1 and 2.

In the control method shown in FIG. 4, the control amount (outer diameter D and capacitance C) of the electric wire extruded from the highly foamed insulated wire extruder line 10, which is the controlled object, Y=Y ₁ Y ₂ and the control state variables that affect the amount (temperature of each cylinder of the first and second stage extruders, temperature of the crosshead of the second stage extruder, resin temperature and resin pressure in the crosshead, first and second
The pressure at the docking part between the stage extruders, the gas injection flow rate or injection pressure, the core wire entry temperature, and the first
and the temperature of each screw of the second stage extruder). However, a plurality of manipulated variables are used as input parameters for varying the control amount (rotational speed of each screw, voltage of a preheater provided in front of the extruder, heater voltage of each cylinder, heater voltage of the crosshead,
gas injection pump rotation speed, extrusion line line speed and cooler crosshead position or temperature) In this case, the manipulated variable is controlled so that the controlled variable is adjusted to its target value Y _R =Y _R1 Y _R2 .

Note that the measured quantities Y ₁ to _{Y 12} and the manipulated quantities U ₁ to _{U 9} shown in FIG. 4 are schematically represented in FIG. 1. These quantities mean the following physical quantities.

Y ₁ ...Outer diameter of the extrusion coated wire D Y ₂ ... Capacitance C Y ₃ ... Temperature of the cylinder of the first stage extruder Y ₄ ... Second stage Y ₅ ... Temperature of the crosshead Y ₆ ... Resin temperature in the crosshead Y ₇ ... Pressure Y ₈ ... Pressure at the docking part of the first and second stage extruders Y ₉ ... Flow rate or injection pressure of the injection gas Y ₁₀ ... Inlet temperature Y ₁₁ ... Temperature of the first stage screw Y ₁₂ ... Temperature of the second stage screw U ₁ ... Rotation speed of the first stage screw U ₂ ... Second stage 〃 U ₃ ... Applied voltage U of the preheater ₄ ...First stage cylinder heater voltage U ₅ ...Second stage U ₆ ...Crosshead heater voltage U ₇ ...Gas injection pump rotation speed U ₈ ...Line speed U ₉ ...Cooler crosshead The _degree of controlled cooling _{of the} resin after extrusion _, such as the position from (Figure) shows the temperature and heater voltage as a representative, and the pressure at the docking part _Y8 is considered to be the resin pressure in the first stage extruder, and as this pressure increases, the gas injection increases.
If other factors, for example the speed of the pump, remain constant, then it will decrease.

The controlled quantities Y ₁ to _{Y 2} are drawn out from the drawing point 50 and connected to the subtraction points 51 of the target values Y _R1 to Y _R2 , respectively, and the controlled quantities and the target values are I am getting . These differences ε ₁ and ε ₂ are calculated using the calculation element C
is applied to Element C is In the matrix written as The manipulated variables U'c ₁ ......U'c ₉ are given by linear processing. These manipulated variables are applied to integrators I ₁ to I ₉ , respectively, and an integration operation is performed to obtain the quantity
It is applied to each manipulated variable Uc ₁ to Uc ₉ as Uc ₁ to Uc ₉ .

This quantity Uc is expressed as follows as a result of performing an integral function.

This integral operation includes not only a linear integral function by an integrator but also an operation that includes or is similar to an integral function.

Further, the integral operation may include dynamic compensation.

Note that the calculation element C is Before automatically controlling the highly foamed insulated wire extrusion line 10 as a control object, each element is determined in advance by using the control object as a model and determining optimal control theory and target values.
When giving Y _R1 ~ _{Y R2} , the manipulated variables U′ _C1 ~ U′ _C9 ,
It is determined most appropriately by simulating the behavior of the manipulated variables U ₁ to U ₉ and the controlled variables Y ₁ to _{Y 2} .

Further, the extraction point 50 is the feedback element F
It is connected to the subtraction point 52 via. As a result, a feedback operation is performed on the measured quantities Y ₁ -Y ₁₂ including the controlled quantities Y ₁ -Y ₂ by linear processing, and is subtractively applied to the manipulated quantities U ₁ -U ₉ . This feedback operation may include dynamic compensation. The feedback output U _F is It is.

In addition, Each element is also determined in advance by the aforementioned optimal control theory and simulation.

Furthermore, the extraction point 53 is connected to the summing point 52 via a feed forward element N. As a result, a feedforward operation, that is, a proportional operation is performed on the target values Y _R1 to Y _R2 by linear processing, and is applied additively to the manipulated variables U ₁ to _{U 9} . This feed forward operation may include dynamic compensation. Feedforward output U _N
teeth, It is.

in this case, Each element is also determined in advance by optimal control theory and simulation, as described above.

In this way, as a result of three types of operation inputs being supplied to the manipulated variable U, the manipulated variable U finally becomes as follows.

When the sum output Uc-U _F +U _N supplied to the manipulated variable exceeds a _{predetermined} range, the limiter L ₁ ...L ₉ stops the integral operation at each _operation line. is mediated by.

In Fig. 4, the part surrounded by dotted lines represents the TOSBAC7/40 type CPU made by Tokyo Shibaura Electric Co., Ltd., and the input interface for target values Y _R1 to Y _R2 is the input/output device I/O-1 and the manipulated variable. The output interfaces of U ₁ to _{U 9} have input/output devices I/O for D/A conversion.
O-2, the input interface to the backward path of the measured variables Y ₁ to Y ₁₂ including the controlled variables Y ₁ to Y ₂ is an A/D
An input/output device I/O-3 for conversion is interposed. The multivariable automatic control system configured as described above operates as follows.

First, the extruder line 10 is operated to control the control amount.
The initial value of the integral operation is set according to the measured quantities Y ₁ to _{Y 12} including Y ₁ to _{Y 2} (FIG. 5). Next, the CPU calculates the target values Y _R1 to Y _R2 and the measured quantity Y ₁ including the controlled quantities Y ₁ to _{Y 2} .
~Read data for Y ₁₂ . CPU calculation element C,
The feedback element F and the feedback element N each perform their calculations according to the values expressed by the aforementioned determinant, Calculate.

This manipulated variable output needs to be controlled and maintained within a predetermined range. Therefore, it is determined whether each manipulated variable output value is within the range, and if it is within the range, an integral operation is performed, and if it exceeds the range, each limiter L ₁ to L ₉ (Figure 4).

In this way, each manipulated variable U′c ₁ ......U′c ₉ is operated by the integrator I ₁ ...I ₉ , and the integral operation is performed. produces an integral output of

If such a function is introduced, even though there is an input operating range as the manipulated variable as in this embodiment, if the integral operation is performed from the start of the operation, the difference between the manipulated variable and the target value will initially be Since _{ε 1 .}

In this way, the integrator repeats the integration operation until the difference between the target value and the controlled variable ε=Y _R1 Y _R2 −Y ₁ Y ₂ becomes zero, and the control loop is activated so that the controlled variable approaches the target value as much as possible. It forms the

Thus, the manipulated variable U U = Uc - U _F + _UN is calculated and output to the extrusion line 10 as the controlled object.

In this case, the feedback output UF of the feedback element _F has the function of stabilizing the inherent characteristics of the control system.

On the other hand, the output U _N of the feedforward element N is
It accelerates the rise of the control amount Y so that it quickly approaches the target value _YR , and has a particularly great effect at the start of operation of the extrusion line. This element N further improves the responsiveness of the control system.

In this way, when the manipulated variable U is output to the controlled object, that is, the extrusion line 10, the next sampling is delayed for a predetermined time and the next operation is repeated again.

In the above embodiment, there are two controlled variables and target values,
We have explained the case where there are 9 manipulated variables and 12 measured quantities, but there are l, n, and m quantities (l, n, and m, respectively).
n, m are positive integers, and even if n, m≧l),
The invention is equally applicable.

As is clear from the above embodiments, according to the present invention, in the gas foaming system as the controlled object and the highly foamed insulated wire extrusion line, the measured quantity including the controlled quantities C and D can be determined by any one of the plurality of manipulated variables. When controlling the manipulated variable so that the controlled variable is adjusted to its target value when the controlled variable also fluctuates due to Since it is applied to the manipulated variable, each manipulated variable performs its function mutually and independently, and the controlled variable is multivariably controlled so that it approaches the target value, resulting in a high-quality product with the desired C and D. Highly foamed insulated wire can be manufactured.

Also, by allowing the control system to perform feedback and/or feedback operations, response is improved and stability is increased.

[Brief explanation of the drawing]

Figures 1 and 2 are explanatory diagrams of an extrusion line for highly foamed insulated wire as a control target, Figure 3 is a partial explanatory diagram of an extruder installed in the line, and Figure 4 is an illustration of the application of the present invention to the control target. FIG. 5 is a block diagram of the automatic control system, and FIG. 5 shows an operational flowchart of the system. 10...Extrusion line, _Y1 - _Y2 ...Controlled amount, _Y1
~ _Y12 ...Measurement amount, _U1 ~ _U9 ...Manipulated amount, Y _R1 ~
Y _R2 ...Target value, _ε1 to _ε2 ...Difference between controlled variable and target value,
U′c ₁ to U′c ₉ ... manipulated variable, 10 ... extrusion line,
11... Cord wire, 13... Preheater, 15... Extruder, 17... First stage extruder, 21... Second stage extruder, 17a, 21a... Cylinder, 17b, 2
1b... Screw, 19... Dotsuking Club, 2
2-30... Cylinder heater, 33... Gas injection pump, 35, 36, 39... Cooler.

Claims (1)

[Claims] 1. High pressure gas is injected into the softened polyolefin resin in the first stage extruder, and the resin and gas are mixed in the second stage extruder connected in series to the first stage extruder. Forming a foamed insulation composition with a large number of closed cells trapped in the resin, which is extrusion coated onto a core wire that is continuously fed to a second stage extruder and then passed through a cooler. In the extrusion line control method for highly foamed insulated wire, which controls the outer diameter and capacitance of the foamed insulator to predetermined values,
A plurality of control variables such as the outer diameter and capacitance Y=Y ₁ 〓 Yl, the temperature of each cylinder of the first and second stage extruders, the temperature of the crosshead of the second stage extruder, and the temperature of the resin at the crosshead. and the pressure of the resin, the pressure of the docking part between the first and second stage extruders,
A plurality of measured quantities Y ₁ 〓 consisting of state variables that influence said controlled variables, such as the injection flow rate or injection pressure of the gas, the inlet temperature of the core, and the temperature of each screw of the first and second stage extruders. Ym is the rotational speed of each screw, the voltage of the preheater provided in front of the extruder, the heater voltage of each cylinder, the heater voltage of the crosshead, the rotational speed of the gas injection pump, the line speed of the extrusion line, and the cooling A plurality of manipulated variables as input parameters that vary the controlled variable, such as the position or temperature from the crosshead of the device U=U ₁ 〓 Un (However, l, n, and m are positive integers of 2 or more, and n,
In controlling the manipulated variable so that the controlled variable is adjusted to its target value YR=YR ₁ 〓 YRl, the controlled variable and the target difference in value is a calculation element predetermined by a simulation evaluation of the behavior of the manipulated variable and the controlled variable when giving the target value. Manipulated variable U′c = Uc ₁ 〓 Output obtained by performing integral operation on each of Ucn = Uc ₁ 〓 Ucn is each manipulated variable, and multiple measured quantities including the above-mentioned controlled variable Y ₁ 〓 The output UF=UF ₁ 〓 UFn obtained by performing the feedback operation on Ym is applied to each of the manipulated variables, and the output Uc- is supplied to each of the manipulated variables, respectively.
A highly foamed insulated wire extrusion line control method, characterized in that each of the integral operations is stopped when the sum of the outputs UF exceeds a predetermined value. 2. High pressure gas is injected into the softened polyolefin resin in the extruder, and the resin and gas are mixed to form a foamed insulation composition in which a large number of closed cells are trapped in the resin, and this is fed into the extruder. In an extrusion line control system for highly foamed insulated wire, in which the outer diameter and capacitance of the foamed insulator are controlled to predetermined values by extrusion coating the continuously fed core wire and then passing it through a cooler. , a plurality of control variables such as the outer diameter and capacitance Y=Y ₁ 〓 Yl, the temperature of each cylinder of the extruder, the temperature of the crosshead of the extruder, the temperature and pressure of the resin at the crosshead, and the injection of gas. A plurality of measured quantities Y ₁ 〓 Ym is defined by a plurality of measured quantities Y 1 〓 Ym consisting of state variables that influence said controlled variables, such as flow rate or injection pressure, core wire entry temperature, and temperature of each screw of the extruder. , the voltage of the preheater provided in front of the extruder, the heater voltage of each cylinder, the heater voltage of the crosshead, the rotation speed of the gas injection pump, the line speed of the extrusion line, and the position or temperature of the cooler from the crosshead. A plurality of manipulated variables as input parameters for varying the controlled variable U=U ₁ 〓 Un (However, l, n, m are positive integers of 2 or more, and n,
m≧l), the controlled variable is adjusted to its target value YR=YR ₁ 〓 YRl. difference in value is a calculation element predetermined by a simulation evaluation of the behavior of the manipulated variable and the controlled variable when giving the target value. Manipulated variable U′c = Uc ₁ 〓 Output obtained by performing integral operation on each of Ucn = Uc ₁ 〓 Ucn is each manipulated variable, and multiple measured quantities including the above-mentioned controlled variable Y ₁ 〓 The output UF=UF ₁ 〓 UFn obtained by performing the feedback operation on Ym is applied to each of the manipulated variables, and the output Uc- is supplied to each of the manipulated variables, respectively.
A highly foamed insulated wire extrusion line control method, characterized in that each of the integral operations is stopped when the sum of the outputs UF exceeds a predetermined value.