JPS63278819A - Temperature controlling apparatus for extruder - Google Patents

Abstract

PURPOSE:To measure precisely a static cooling characteristic and to attempt to make temp. controlling characteristics such as optimization of PID constant and so on to be precise, by setting a switch selecting an electromagnetic valve for cooling base on the signal from either both a sequencer being capable of continuously and automatically operating in an optional and constant on-off pattern and a dual-output type PID controller with a communication functionality or the sequencer. CONSTITUTION:A computer 11 and a dual-output type PID controller 13 with a communication functionality can be communicated by RS232C and the temp. of the barrel 15 of an extruder is sent to the PID controller 13 by means of a temp. sensor 16. A sequencer 17 generates a constant signal being a constant on-off pattern for heating and cooling by an order from the computer 11 and selects whether an output for heating and cooling to the cylinder 15 is carried out by an order from the PID controller 13 or by an order from the computer 11, by means of a switch 18 separately for heating or cooling. The operation of this switch 18 is also done by the order from a computer 11. Even if the switch 18 is on the side of PID controller 13, the measured temp. is transmitted to the computer 11.

Description

[Detailed description of the invention] [Technical fields where inventions succumb] The present invention relates to a temperature control device for an extruder.

[Prior Art] There are several devices and methods for determining an appropriate PID constant for temperature adjustment in the temperature control system of an extruder.

As a conventional method, Ziegler-Ni
There is a transient response method and a limit sensitivity method based on cholS, and recently there are devices and methods such as an expert method using a response waveform of a measured temperature and a fixing signal added to the operation output from a humidity controller.

The plastic material fed into the extruder is transferred to the cylinder by a screw and heated from outside the cylinder.
It is melted by the internal heat generated by the shearing action of the screw. At this time, the calorific value that cannot be completely cooled by natural cooling is forcibly cooled with gas or liquid.When controlling the temperature with a PID controller, a dual type with heating output and cooling output is used. It is used.

The conventional control method using a PII 1mm meter compares the set temperature and the temperature at the control point detected by the temperature sensor at a matching point, and calculates the PID.
The controller calculates the operating output y(t)% as shown in the following formula, and outputs the output to process X for control.

(However, PB: proportional band, Ti (seconds): integral time, Td
(seconds): differential time, e(t): temperature deviation) The above-mentioned PB@Ti@Td is called a PID constant and is appropriately determined by the user according to the operating conditions.

Therefore, if the PID constant is inappropriately set, good control cannot be achieved.

In addition, as mentioned above, the extruder cylinder has heating control and cooling control, and a heater is used for heating control.
The influence of the operation output from the PID controller on the process is linear and it is possible to determine an appropriate PID constant, but cooling control is based on the phase change of the cooling medium (liquid → gas).
Therefore, the influence of the operation output on the process becomes non-linear, making it impossible to determine an appropriate PID constant.

For example, when using a cast aluminum heater with a water cooling pipe as shown in Figure 3 and keeping the temperature of the heater at 200℃,
To explain the static cooling characteristics, which shows the relationship between the ON time of the solenoid valve that passes cooling water and the cooling capacity, when the amount of cooling water is small at the temperature of 100°C to 300°C, where the extruder is generally operated, the cooling pipe Almost all the water in it evaporates, but
As the amount of cooling water increases, the amount of heat absorbed increases, and new cooling water is injected before the inner wall temperature of the cooling pipe has fully recovered, so the temperature difference between the water temperature and the inner wall of the cooling pipe becomes smaller, and the heater that supplies the cooling water It will be understood that the rate of vaporization decreases as the amount of heat decreases, and the cooling effect decreases.

To explain in more detail, the screw speed is low.

In other words, when the amount of heat generated is low and the ON rate of the solenoid valve is low, the amount of cooling water sent to the cooling pipe in the heater is small, the cooling water is easily vaporized, and the amount of cooling heat per solenoid valve ON time, that is, the cooling gain, is growing.

(Region.

On the other hand, when the rotational speed of the screw is high, the solenoid valve ON rate is high and the amount of water supplied increases, resulting in a decrease in cooling effect and a decrease in cooling gain (region ■).

Therefore, there is an inflection point between the area and m, and the cooling gain around this point has a value intermediate between the area and H. (Area ■
).

As mentioned above, the cooling characteristics vary depending on the size of the extruder and the design of the cooling system, but the slope of the characteristics itself varies considerably depending on the valve opening, set temperature, and cooling cycle. Naturally, the PID constant also changes depending on each area.

Conventional devices cannot measure this extremely strong nonlinearity, and therefore cannot determine the optimal PID constant in each region.

[Purpose of the invention] The present invention was made from this point of view, and its purpose is to improve temperature control of an extruder with precise temperature control such as optimization of PID constant by accurately measuring static cooling characteristics. The goal is to provide equipment.

[Summary of the Invention] The extruder temperature control device of the present invention includes a water cooling system operated by a temperature detection sensor, a heating heater, and a cooling solenoid valve, as well as a dual output type PIDJ meter with a communication function for heating and cooling. The extruder has a sequencer that can automatically operate the cooling solenoid valve continuously with any constant ON-OFF pattern, and a dual output type PID3 with communication function for the cooling solenoid valve! It is characterized by the provision of a selector switch that can be operated by commands from either the J-meter or the sequencer.

[Embodiment 1 of the Invention An embodiment of the present invention will be explained below based on FIG. 1 showing an embodiment of the invention. The computer 11 is equipped with a setting keyboard 12 for setting various conditions.
3 through R5232C, and the temperature of the barrel 15 of the extruder, which has a screw 14 inside, is sent to the PIDr 14 meter 13 by a temperature sensor 16. As a result, the temperature of barrel 15 is
1 and the temperature set on the computer 11 is P
Bidirectional transmission is possible to a total of 13 ID7Afti.

The sequencer 17 generates a fixed signal with a constant ON-OFF pattern for heating and cooling based on commands from the computer 11, and outputs heating and cooling to the cylinder 15 using the cut-off switch 18 based on commands from the PID controller 13.
Alternatively, it is possible to select whether heating or cooling is to be performed based on instructions from the computer 11. This cut-off switch 18 can also be operated by a command from the computer 11, and even if the cut-off switch 18 is located on the PID controller 13 side, the measured temperature can be transmitted to the computer 11. Although FIG. 1 shows one channel, it is also possible to control a plurality of barrels 15 simultaneously. Also!
When the /18 switch 18 is set to the PID controller 13 side for both heating and cooling, normal temperature control is achieved.

An example of determining static cooling characteristics using the temperature control described above will be described below. When the temperature of the barrel 15 is set to the set temperature according to PID investigation section 13 and cooled by the ON time of the cooling solenoid valve 19 that is forcibly measured in the controlled cooling cycle, the temperature decreases, but the output on the heating side by the heater 20 is Controller 1
If the temperature is controlled in step 3, the temperature will be maintained near the set temperature.

At that time, if we calculate the average heating operation output from the PID controller 13 when the difference between the measured temperature and the set temperature is within ±1°C for a certain period of time, we can calculate the average heating operation output from the PID controller 13. Static cooling during ON time The flowchart will now be explained. At 31, the sequencer 17 is commanded to generate a cooling fixed signal of an arbitrary constant ON-OFF pattern set in advance, and at 32, the selector switch 18 is instructed to
PIDJ 0! The 11tl meter 13 instructs the cooling solenoid valve 19 to be controlled on the cooling fixed signal generation side. P at 33
The measured temperature from the ID3Jjlf meter 13 and the heating operation output data are sampled, and the deviation between the sampled measured temperature and the set temperature is calculated at 34. For example, if the deviation is ±1
Determine whether or not it is within 1°C, and if it is within 1, calculate the temperature continuous equilibrium time at 35, and at 36 judge whether the temperature continuous equilibrium time is the preset equilibrium time, and continue from 33 until YES. Repeat step 36. If YES, calculate the average heating operation output in step 37 using all sampled heating operation outputs within the temperature continuous equilibrium time.

Since heating is required to maintain the set temperature in the non-cooling state, by calculating the average heating operation output in the non-cooling state in advance, the cooling capacity during the ON time of any cooling solenoid valve 19 can be determined. It becomes as shown in the following formula.

Cooling capacity = (Average heating operation output during any cooling solenoid valve ON time) - (Average heating operation output without cooling) Here, generally the heating operation output from PID control unit 13 is %
However, since the old proverb about the heater 20 is known, the cooling capacity can be converted to KW.

In this way, by changing the ON time of the cooling solenoid valve 19 and repeating the above steps (this is made possible by the computer 11), the static cooling characteristics at the controlled set temperature and cooling cycle are determined. becomes possible.

[Effects of the Invention] As explained above, the temperature control device for an extruder according to the present invention can accurately measure the static cooling characteristics, so it is possible to improve the precision of temperature control of the extruder, such as by optimizing the PID constant. becomes possible.

[Brief explanation of drawings]

The drawings show an embodiment of the present invention; FIG. 1 is a mechanical diagram, FIG. 2 is a flowchart, and FIG. 3 is a diagram showing static characteristics. 11... Computer, 13... Dual output type PID21 with communication function [1 total, 17... Sequencer, 18... Changeover, switch.

Claims (1)

[Claims] In an extruder that has a water cooling device operated by a temperature detection sensor, a heating heater, and a cooling solenoid valve, and a dual output type PID controller with communication function for heating and cooling,
A sequencer that can continuously and automatically operate the cooling solenoid valve in any fixed ON-OFF pattern, and the cooling solenoid valve is operated by a command from either the dual output type PID controller with communication function or the sequencer. 1. A temperature control device for an extruder, characterized in that it is provided with a changeover switch that allows selection.