JPH05138733A - Frost line control device in inflation molding line - Google Patents

Abstract

PURPOSE:To provide the title device accurately detecting the frost line position of a cylindrical membrane resin on the basis of the change of the surface temp. of the extruded cylindrical membrane resin in the flow direction thereof using fuzzy inference and controlling the amount of the cooling air of a cooler at the accurately detected frost line position so as not to generate the change of the surface temp. of the resin. CONSTITUTION:In an inflation molding line, a spot radiation thermometer 25 measuring the change of the surface temp. of the cylindrical membrane resin 3 extruded from a mold 2 in the flow direction A2 is provided. A position detection part 32 detecting the frost line position of the cylindrical membrane resin 3 on the basis of the change of the surface tap. of the resin measured by the spot radiation thermometer 25 and a control part 30 controlling the amount of the cooling air of a cooler 20 so as to keep the frost line position detected by the position detection part 32 constant are mounted.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a continuous cylindrical thin film resin being extruded upward from a die mounted in front of an extrusion molding machine in the extrusion direction, and extruded in the vicinity of the die. The present invention relates to an inflation molding line provided with a cooling device for cooling a cylindrical thin film resin from the outside, and more specifically, to accurately detect the frost line position of the cylindrical thin film resin extruded from a mold by fuzzy reasoning. Thus, the present invention relates to a frost line control device that performs control for keeping the frost line position constant.

[0002]

2. Description of the Related Art Conventionally, in an inflation molding line, in order to keep the quality of a cylindrical thin film resin extruded from a mold, for example, resin film thickness, strength, etc. There is a method in which the height of the frost line is directly checked and the amount of cooling air of the cooling device is adjusted by volume to adjust the frost line to be constant.

Further, as an automatic device for keeping such a frost line constant, a camera has conventionally been installed in an extruding portion of a die, and a shape pattern of a cylindrical thin film resin inputted through the camera is recognized by an image processing system. However, there is a method in which the recognized shape pattern is compared with a basic pattern stored in a database in advance, and the recognized shape pattern is controlled to match the basic pattern.

Separately from this, by measuring the resin temperature at a certain point of the cylindrical thin film resin with a radiation thermometer and keeping the resin temperature at that point constant, the frost line is indirectly kept constant. The method of doing so can be considered.

[0005]

However, the method using the image processing system described above has a problem that the cost of the entire equipment of the inflation molding line increases because the system itself is expensive. Further, in the image processing system, there is a restriction that a camera for taking a cylindrical thin film resin and the cylindrical thin film resin can be kept at a constant distance, and an object cannot be placed between them, which requires a large installation space. There was also a problem.

On the other hand, the method for keeping the resin temperature at a certain point of the cylindrical thin film resin constant is to indirectly keep the frost line constant by keeping the resin temperature at a certain point constant. Since the frost line position is not directly controlled, there is a problem that the control system falls.

The present invention has been made in view of the above circumstances, and an object thereof is to frost a cylindrical thin film resin by using fuzzy reasoning based on a change in the resin surface temperature in the flow direction of the extruded cylindrical thin film resin. It is an object of the present invention to provide a frost line control device that accurately detects a line position and controls the cooling air volume of the cooling device so that the resin surface temperature does not change at the accurately detected frost line position.

[0008]

In order to solve the above problems, the frost line control device in the inflation molding line of the present invention is a continuous cylindrical thin film resin from a mold attached to the front of the extrusion machine in the extrusion direction. Is extruded upwards, and in the vicinity of the mold, in an inflation molding line provided with a cooling device for cooling the extruded cylindrical thin film resin from the outside, the cylindrical thin film resin extruded from the mold Temperature measuring means for measuring the resin surface temperature change in the flow direction, position detecting means for detecting the frost line position of the cylindrical thin film resin based on the resin surface temperature change measured by this temperature measuring means, and this position The cooling air volume of the cooling device is controlled so that the frost line position detected by the detection means is kept constant. Configuration to which a that control means.

[0009]

Function: Above the mold, there is provided a temperature measuring means for measuring a change in the resin surface temperature in the flow direction of the cylindrical thin film resin extruded from the mold. The position detecting means detects the frost line position of the cylindrical thin film resin based on the preset fuzzy rule and membership function based on the resin surface temperature change measured by the temperature measuring means. The control means controls the cooling air volume of the cooling device so that the frost line position detected by the position detection means becomes constant. As a result, the height of the frost line (specifically, the height from the film outlet of the mold) is kept constant, and as a result, the quality of the cylindrical thin film resin can be kept uniform.

Here, the frost line is a milky white annular band formed at the point where the cylindrical thin film resin (inflation film) reaches the final diameter by cooling.

[0011]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a schematic configuration diagram of an inflation molding line equipped with the frost line control device of the present invention.

In the figure, the extrusion direction A of the extrusion molding machine 1
_A mold 2 is connected in front of _{1 and} a cylindrical thin film resin (hereinafter referred to as an inflation film) 3 is formed from the mold 2.
Is pushed upwards. The extrusion molding machine 1 is provided with an extrusion screw (not shown) rotationally driven by an extrusion motor (not shown), and the resin charged into the raw material hopper 12 is sequentially extruded into the mold 2 by this extrusion screw. It is like this.

As a material for the blown film 3, a thermoplastic resin such as polyethylene, polypropylene or polyvinyl chloride is used.

In addition, compressed air is fed from the compressed air source 4 into the inflation film 3 through the mold 2.
By keeping the amount of air in the inside constant, the bulge of a certain shape is maintained.

A cold air blower 20a for cooling the blown inflation film 3 is arranged above the mold 2 so as to surround the inflation film 3. This cold air blower 2
To 0a, cool air is blown from the cooling device 20 so that the air volume can be adjusted. The cooling device 20 adjusts the air volume of the cold air blown out from the cold air blower 20a based on a control signal indicating an air volume setting change instruction from the control unit 30 including a process controller, and although not shown. An inverter motor that can change the air volume according to an air volume setting change instruction from the control unit 30 is provided.
However, the motor is not limited to the inverter motor and may be a motor having a similar function (for example, a DC motor).

A spot radiation thermometer 25 for measuring the resin surface temperature of the extruded inflation film 3 is arranged above the cooling blower 20a. The spot radiation thermometer 25 is provided in the control unit 3
By driving the moving device 33 based on the control signal from 0,
It is provided so as to be vertically movable along the flow direction A ₂ of the inflation film 3. The movement upper limit position U and the movement lower limit position D are set so as to include all the frost line optimum positions when the inflation film 3 is formed into various sizes, and the values are registered in the control unit 30 in advance. Has been done. The temperature change of the resin surface measured by the spot radiation thermometer 25 is converted into digital data and guided to the position detection unit 32.
Further, position data indicating the position of the spot radiation thermometer 25 in the height direction is guided to the position detector 32 from the moving device 33, and the output of the position detector 32 is guided to the controller 30.

The spot radiation thermometer 25 attached to the moving device 33 is moved upward from the film outlet of the mold 2 in the upward direction A ₂ at a constant speed to measure the surface temperature change of the inflation film 3. A temperature change state as shown is obtained. The portion where the temperature change is zero in FIG. 2 corresponds to the portion where the blown film 3 is solidified from the molten state, and this position is called the frost line position.

The position detection unit 32 includes a spot radiation thermometer 2
The temperature data during movement of No. 5 is fetched, and the frost line position is detected based on the fetched temperature change data according to a fuzzy inference rule described later. Therefore, although not shown, the position detection unit 32 includes a condition determination unit for executing fuzzy inference and a fuzzy inference unit.

Further, guide plates 21a and 21b for guiding the inflation film 3 are arranged in a "C" shape above the spot radiation thermometer 25. The guide plates 21a and 21b pass through the guide plates 21a and 21b. The inflation film 3 is folded in two via a take-up machine 22 composed of rollers 22a and 22b driven by a take-up motor 23, and then taken up by a take-up machine (not shown). ..

The output of a data setting keyboard 26 for setting control parameters is guided to the control unit 30, and a display 27 for monitoring the control state is connected to the control unit 30.

Although not shown, the control unit 30
The output of the extrusion motor, the output of the take-up motor 23, and the like are guided to the control unit 30, and the control unit 30 sends control signals based on these outputs to the drive units (not shown) of the push-out motor and the take-up motor 23. ) Is sent to.

Next, the frost line detecting operation of the position detecting section 32 in the frost line control device having the above-mentioned structure will be described.

First, the control unit 3 to which a control start instruction is given.
In 0, the inflation molding line is actually operated, extrusion molding of the inflation film 3 is started, and control by the frost line control device is started. However, the cooling device 20 during the operation of the inflation molding line
The air volume is controlled by a preset initial value control amount.

After that, the control unit 30 gives the moving device 33 an instruction to move the spot radiation thermometer 25 up and down. The moving device 33 is driven based on this moving instruction to move the spot radiation thermometer 25 up and down within the range of the moving upper limit position U and the moving lower limit position D. That is, mold 2
The spot radiation thermometer 25 is raised at a constant speed in the upward direction A ₂ from the position of the film blowing port, and the surface temperature of the inflation film 3 is sampled at a constant cycle. Then, the sampling data is used as the position detection unit 32.
Give to. The position detection unit 32 detects the frost line position based on the given sampling data indicating the surface temperature change, according to the fuzzy inference rule described below.

That is, the fuzzy rule for judging in the condition judging unit is the IF-THEN method, and IF temperature change = NB THEN frost line height = PB IF temperature change = NS THEN frost line height = PS IF temperature Change = Z THEN Frost line height = Z IF Temperature change = PS THEN Frost line height = NS IF Temperature change = PB THEN Frost line height = NB

Here, PB is PLUS BIG, PS is PLUS SMALL, Z is ZERO, NS is NEGA.
TIVE SMALL, NB is NEGATIVEBIG
Is represented. As shown in FIG. 3, the membership function is a standard mountain curve such as Sin curve and Cos curve. However, other than this shape, for example, a triangular shape is also possible.

The frost line height position is obtained as follows according to the above rules and membership function.

When the value of the temperature change given from the spot radiation thermometer 25 is zero, (b) in FIG.
(C) and (d) are applied. That is, as shown in FIG.
The points at which the temperature change waveforms of (c) and (d) cross the vertical axis zero (each indicated by a black circle) are extended in the horizontal direction,
The frost line height waveform in each figure is truncated, and the areas (shown with diagonal lines) are overlaid. The superposed state at this time is shown in FIG. Then, the center of gravity is obtained from the superimposed waveform diagrams, and the amount of displacement of the center of gravity from the vertical axis zero is obtained as the fluctuation amount ΔH of the frost line height. Then, the frost line height is obtained from the following formula.

[0030]

## EQU00001 ## Frost line height = H + .DELTA.H where H is an initial value.

In this case, the fact that the temperature change is zero means that the spot radiation thermometer 25 is at the frost line position, and since the center of gravity coincides with the vertical axis zero, the frost line height does not change. It will be. That is, the height position of the spot radiation thermometer 25 at that time is the frost line position.

In this way, the fluctuation amount (ΔH) of the frost line height is obtained as described above from the data of the temperature change sampled at a constant cycle, and the obtained fluctuation amount (ΔH) is obtained last time. By adding to the frost line height, the frost line height when the temperature change is zero is finally obtained.

That is, according to the above rule and membership function, the larger the temperature change toward the negative side, the larger the fluctuation amount (ΔH) of the frost line height becomes. Therefore, the spot radiation thermometer 25 is relatively fast at first. As the temperature rises and the temperature change decreases, the rising speed slows down.

On the other hand, in parallel with the fuzzy inference for detecting the height of the frost line, the control management width of the frost line for use in control is calculated according to the fuzzy inference rule shown below.

That is, the fuzzy rule for making a judgment in the condition judging unit is: IF temperature change = NB THEN Frost line width =
Z IF Temperature change = NS THEN Frost line width =
PS IF Temperature change = Z THEN Frost line width =
PB IF Temperature change = PS THEN Frost line width =
PS IF Temperature change = PB THEN Frost line width =
Z.

As shown in FIG. 5, the membership function is a standard mountain curve such as a Sin curve and a Cos curve. That is, when the temperature change is large on the minus side and the plus side, the frost line width is set to zero,
The rule is that the frost line width is gradually increased as the temperature change becomes smaller, and the frost line width is maximized when the temperature change is zero.

The frost line width is obtained as follows according to the above rules and membership function.

When the value of the temperature change given from the spot radiation thermometer 25 is zero, (b) in FIG.
(C) and (d) are applied. That is, as shown in FIG.
The points at which the temperature change waveforms of (c) and (d) cross the vertical axis zero (each indicated by a black circle) are extended in the horizontal direction,
The frost line height waveform in each figure is truncated, and the areas (shown with diagonal lines) are overlaid. The superposed state at this time is shown in FIG. Then, the center of gravity is obtained from the superimposed waveform diagrams, and the displacement amount of the center of gravity from the vertical axis zero is obtained as the variation ΔW of the frost line width. Then, the frost line width is obtained from the following formula.

[0039]

## EQU00002 ## Frost line width = W + .DELTA.W where W is an initial value.

In this case, the fact that the temperature change is zero means that the spot radiation thermometer 25 is at the frost line position, and the center of gravity is the farthest position from the vertical axis zero, and therefore the frost line width. Can be set large.

In this way, the fluctuation amount (ΔW) of the frost line width is obtained as described above from the data of the temperature change sampled at a constant cycle, and the obtained fluctuation amount (ΔW) is obtained the previous time. By adding to the line width, the frost line width for control management is finally obtained.

The spot radiation thermometer 25 is installed at the frost line height position calculated as described above, and the set temperature and the frost line width calculated above are used to blow out from the cold air blower 20a by a conventional method. The blown film 3 is formed by adjusting the amount of cold air.

[0043]

The frost line control device in the inflation molding line of the present invention comprises a temperature measuring means for measuring the resin surface temperature change in the flow direction of the cylindrical thin film resin extruded from the die, and this temperature measuring means. Position detection means for detecting the frost line position of the cylindrical thin film resin based on the measured resin surface temperature change, and the cooling air volume of the cooling device so as to keep the frost line position detected by this position detection means constant. Since the frost line position is directly controlled, the control accuracy is improved.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of an inflation molding line equipped with a frost line control device of the present invention.

FIG. 2 is a diagram showing a relationship between a height of an inflation film from a die outlet and a surface temperature.

FIG. 3 is a diagram showing a fuzzy inference rule for calculating an inflation height.

FIG. 4 is a diagram illustrating how to determine a center of gravity.

FIG. 5 is a diagram showing a fuzzy inference rule for calculating an inflation width.

FIG. 6 is a diagram illustrating a method of obtaining a center of gravity.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Extruder 3 Cylindrical thin film resin (inflation film) 20 Cooling device 25 Spot radiation thermometer 26 Data setting keyboard 27 Display 30 Control part 32 Position detection part 33 Moving device

Claims (1)

[Claims] 1. A continuous cylindrical thin film resin is extruded upward from a mold attached to the front of the extrusion machine in the extrusion direction, and the extruded cylindrical thin film resin is extruded in the vicinity of the mold. In an inflation molding line provided with a cooling device for cooling from the outside, temperature measuring means for measuring the resin surface temperature change in the flow direction of the cylindrical thin film resin extruded from the mold, and the temperature measuring means were used for measurement. Position detecting means for detecting the frost line position of the cylindrical thin film resin based on a change in resin surface temperature, and controlling the cooling air volume of the cooling device so as to keep the frost line position detected by the position detecting means constant. A frost line control device in an inflation molding line, comprising: a control means.