JPH0596608A - Molten resin supply equipment - Google Patents

Abstract

(57) [Summary] [Purpose] To provide a molten resin supply facility capable of coping with disturbance in a cylinder without unnecessarily changing the supply amount of a feeder. [Structure] The input long-term average values of the resin pressure p at the inlet of the gear pump 6 and the screw 4 rotation speed Ns are calculated, the ratios thereof are calculated, and the feed amount q of the raw material resin is calculated from the deviation between this ratio and the initial value of the ratio. The controller 21 is configured to calculate a corrected value of, add it to the theoretical supply amount of the feeder 1 calculated from the input rotation number Ng of the gear pump 6, and output it to the feeder 1 as the supply amount set value q _r of the feeder 1. .. [Effect] The slow fluctuation of the resin pressure p caused by the integration of the difference between the raw material supply amount of the feeder 1 and the discharge amount of the gear pump 6 causes a change in the ratio of the long-term average value of the resin pressure p and the screw rotation speed Ns. Therefore, by correcting the supply amount of the feeder 1, the supply amount of the feeder 1 and the discharge amount of the gear pump 6 can be balanced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention supplies a raw material resin to an extruder with a feeder, melts and kneads the resin with a heater and a screw in a cylinder of the extruder, and supplies the molten resin from its outlet to a die through a gear pump. The present invention relates to a molten resin supply facility.

[0002]

2. Description of the Related Art A conventional molten resin supply facility will be described with reference to the system diagram of FIG. The molten resin supply equipment includes a feeder 1 for supplying a predetermined amount of raw material resin, an extruder 2 for melting and kneading the raw material resin supplied from the feeder 1 and extruding it, and a melter extruded from the extruder 2 driven by a motor 22. Gear pump 6 that supplies resin to die 7 at a stable flow rate
It consists of In order to supply the molten resin to the die 7 at a stable flow rate, the resin pressure at the inlet of the gear pump 6 needs to be constant.

The feeder 1 is a gravimetric feeder, and includes a raw material hopper 14, a belt conveyor 15 that cuts raw material resin from the raw material hopper 14 and supplies it to the extruder 2, and a belt conveyor 15.
Load cell 16 for measuring the weight of raw resin cut out with
And a motor 17 for driving the belt conveyor 15 and this motor
Rotation speed detector 18 connected to 17 to detect motor speed
And the weight signal input from the load cell 16 and the rotation speed signal of the motor, which is input from the rotation speed detector 18 and is proportional to the speed of the belt conveyor 15, are multiplied, and the actual amount of raw material resin supplied to the extruder 2 is supplied. Multiplier 20 that calculates q, and a multiplier
The feed amount q of the raw material resin input from 20 is used as a feedback signal, and the set value q _r input from the ratio setting device 12 described later.
The PI controller 19 controls the number of rotations of the motor 17 (velocity of the belt conveyor 15) by PI to adjust the supply amount q.

The extruder 2 also includes a hopper 4 for receiving the raw material resin supplied from the feeder 1, a cylinder 5 for melting and kneading the raw material resin supplied from the hopper 4 with a screw 4 and a heater 9, and pushing it to a gear pump 6. The screw motor 8 for driving the screw 4, the resin pressure detector 10 for detecting the resin pressure p at the outlet, and the resin pressure p detected by the resin pressure detector 10 are used as feedback signals to set a constant set value p for the resin pressure p. _The PI adjuster 11 that performs PI control of the rotation speed of the screw motor 8 so as to obtain _r , and the screw motor 8
Rotation speed detector 13 for detecting the rotation speed Ns, and a set value q _r of the raw material supply amount of the feeder 1 is calculated according to the rotation speed Ns input from the rotation speed detector 13 and output to the PI controller 19. It is composed of a ratio setter 12.

With the above configuration, the PI adjuster 11
When the resin pressure p changes, the rotation speed Ns of the screw motor 8 is controlled so that the resin pressure p at the outlet of the extruder 2 is controlled to be always constant (set value p _r ). Through this, the molten resin is stably supplied to the die 7. Further, by setting the rotation speed Ns of the screw motor 8 as a result to the set value qr of the supply amount of the feeder 1 by the ratio setter 12, the feeder 1 causes the PI 1 to cause the feeder 1 to move at the speed of the screw motor 8, that is, the extruder 2. The raw material resin corresponding to the extrusion amount of is supplied.

[0006]

In the conventional control system for the molten resin supply equipment, the rotation speed Ns of the screw 4 and the raw material supply amount q of the feeder 1 are operated proportionally to the fluctuation of the resin pressure p due to the disturbance. Although the control target is achieved, the main cause of the disturbance to the resin pressure p is not the fluctuation of the supply amount q of the raw material supplied to the hopper 3, but the state of the molten resin in the cylinder 5 of the extruder 2. That is, the degree of filling, the degree of kneading, the viscosity and the temperature.

From the viewpoint of material balance, since the amount of resin discharged per unit time of the gear pump 6 is constant, the amount of raw material supplied from the feeder 1 per unit time is also constant in the long term. May be.

However, in the above control system, where the resin pressure can be controlled only by the operation of the rotation speed of the screw 4, the feeder 1 is made to perform an unnecessary movement by operating even the supply amount of the raw material. However, there was a risk of causing hunting in the control loop due to the delay in the transportation of the raw material in the cylinder 5.

If the raw material supply amount is controlled to be constant, a slight difference from the discharge amount of the gear pump 6 is integrated,
When operating for a long time, the cylinder 5 is filled with molten resin or becomes empty.

The present invention solves the above problems,
By extracting the difference between the supply amount of the feeder and the discharge amount of the gear pump and feeding it back to the supply amount of the feeder, it is possible to provide a molten resin supply facility that can deal with disturbance in the cylinder without unnecessarily changing the supply amount of the feeder. The purpose is that.

[0011]

In order to solve the above problems, the molten resin supply equipment of the present invention controls the supply amount of the raw material resin as a feedback signal, and supplies the feed material feeder and the resin pressure at the outlet with a feedback signal. As an extruder for controlling the rotation speed of a screw, an extruder for melting and kneading a raw material resin supplied from the raw material feeder with a heater and a screw, and a molten resin including a gear pump for supplying the molten resin extruded from the extruder Supply equipment, a screw rotation speed detector for detecting the rotation speed of the screw, the resin pressure signal and the screw rotation speed signal of the screw rotation speed detector are input, and the long-term average value is calculated respectively. Then, the ratio is calculated, the correction amount of the supply amount of the raw material resin is calculated from the deviation between this ratio and the initial value of the ratio, and It is characterized in that it comprises a control device for outputting the da.

In the molten resin supply equipment of the second invention, in the control device of the first invention, the ratio of the long-term average value of the resin pressure to the screw rotation speed and the deviation of the initial value of the ratio are predetermined values. In the above case, the correction amount of the supply amount of the raw material resin is calculated and output to the feeder.

Furthermore, the molten resin supply equipment of the third invention is
The control device of the first and second inventions is characterized in that the correction value is not changed for a certain period of time after the correction value of the supply amount of the raw material resin is changed.

The molten resin supply equipment of the fourth invention is
A pump rotation speed detector for detecting the rotation speed of the gear pump is provided, and in the control device according to the first aspect of the invention, the rotation speed signal of the gear pump is input from the pump rotation speed detector and the discharge amount of the molten resin is determined from this signal. The calculation is performed, a correction value is added to the discharge amount, and the result is output to the feeder as a supply amount set value.

[0015]

[Function] Assuming that the supply amount of the feeder and the discharge amount of the gear pump are completely the same, and if, for example, the state in the cylinder (resin temperature, etc.) does not change, the resin pressure at the extruder outlet (gear pump inlet) and the screw pressure The rotation speed ratio is constant. Further, the slow fluctuation of the resin pressure is caused by integrating the difference between the supply amount of the raw material supplied from the feeder and the discharge amount of the gear pump. Therefore, the ratio between the resin pressure and the long-term average value of the screw is calculated, and the deviation from the initial value of this ratio that has entered automatic control is obtained, that is, the difference between the supply amount of the raw material supplied from the feeder and the discharge amount of the gear pump. Is calculated, a corrected value of the supply amount of the feeder is calculated and fed back to the set value of the feeder, so that the supply amount of the feeder and the discharge amount of the gear pump are balanced. According to the configuration of the first aspect of the invention, the fluctuation of the resin pressure at the inlet of the gear pump due to the state change generated in the cylinder of the extruder is corrected by controlling the rotation speed of the screw and is supplied from the feeder. The slow fluctuation of the resin pressure caused by the integration of the difference between the feed rate of the raw material and the discharge rate of the gear pump can be grasped from the change in the ratio of the long-term average value of the resin pressure to the screw rotation speed. By correcting the supply amount of the feeder, the difference between the supply amount of the raw material supplied from the feeder and the discharge amount of the gear pump is corrected, and useless operation of the feeder is avoided.

Further, the deviation of the ratio is caused by the integration of the difference between the supply amount of the feeder and the discharge amount of the gear pump, and changes slowly. Therefore, it is not necessary to immediately respond to the small deviation.
According to the configuration of the second invention, the correction amount of the supply amount of the raw material resin is calculated and output to the feeder only when the deviation is equal to or more than the predetermined value. Therefore, the frequency of changing the set value of the supply amount of the feeder is reduced.

When the set value of the supply amount is changed, the influence of the influence on the resin pressure depends on the distance from the feeder to the position where the molten resin exists at the tip of the cylinder of the extruder. There is delay in transportation, that is, dead time. According to the configuration of the third invention, the deviation of the ratio becomes equal to or more than a predetermined value, and after the modification value is changed, a waiting time of a certain time (dead time) is set, and even if there is deviation during that time, the set value is set. Does not change. Therefore, hunting of the control system is prevented.

According to the structure of the fourth invention, the actual discharge amount of the molten resin is calculated from the rotation speed of the gear pump, and the supply amount set value of the feeder is formed by adding a correction value to this discharge amount. ..

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. The same components as those in FIG. 3 of the conventional example are designated by the same reference numerals and the description thereof will be omitted.

FIG. 1 is a system diagram of molten resin supply equipment showing an embodiment of the present invention. The molten resin supply equipment of the present invention,
The equipment shown in FIG. 3 is connected to a drive motor 22 of the gear pump 6, a rotation speed detector 23 for detecting the rotation speed of the gear pump 6 is added, and instead of the conventional ratio setting device 12, a controller composed of a microcomputer. 21 are provided.

The controller 21 inputs an automatic setting signal as a command signal, and as a sensor signal, the rotation speed detector 13
To screw motor 8 rotation speed Ns, rotation speed detector 23
Input the rotational speed Ng of the gear pump 6 and the resin pressure p at the outlet of the extruder 2 from the resin pressure detector 10, and feed the PI of the feeder 1.
The set value q _r of the raw material supply amount is output to the controller 19.

The configuration of the controller 21 will be described in detail with reference to the block diagram of FIG. Reference numeral 31 is an AUTO relay that operates according to the input automatic setting signal, and its a contact is closed when it is automatic. Further, 32 and 33 are average value calculation units for calculating long-term average values p _A and N _A from the inputted resin pressure p and screw rotation speed Ns, respectively.

The long-term average values p _A and N _A can be obtained, for example, by the difference formula of the following exponential smoothing method. _{p An = α p (p An} -1 -p n) + p n, α p = 1-ΔT / T P N An = α v (N An-1 -N Sn) + N Sn, α v = 1-ΔT / T _v , where T _P , T _v ; time constant ΔT; sampling period n; subscript representing the sampling time point, and 34 is a multiplier, and the multiplier 34 discharges the rotation speed Ng of the gear pump 6 with respect to the feeder 1. Calculate the theoretical supply q _s . This supply q _s
Is calculated by the following formula.

Q _s = K _G N _G where K _G ; coefficient or function The theoretical supply amount q _s is manual (not automatic).
At this time, it is output as the supply amount set value q _r of the feeder 1.

Further, the long-term average value p _A of the resin pressure and the long-term average value N _A of the screw rotation speed Ns obtained by the average value calculation units 32 and 33 are set to the initial value setting unit when manually (not automatically).
36, 37, and is stored as the rotation speed initial value N _Si of the screw motor 8 and the resin pressure initial value p _i at the outlet of the extruder 2, that is, the inlet of the gear pump 6. Further, during automatic operation, the long-term average value p _A of the resin pressure and the long-term average value N _{A of the} screw rotation speed Ns, the resin pressure initial value p _{i at} the inlet of the gear pump 6 and the rotation speed initial value N _si of the screw motor 8 are , Is input to the correction value calculation unit 38 which calculates the correction amount d _q of the supply amount set value q _r of the feeder 1. Correction amount d _q of the feed amount set value q _r of the feeder 1, next the ratio p _A / N _A long term average value p _A and N _A, the ratio p _i / N _Si of the initial value p _i and N _Si It is calculated by the formula.
When the current ratio is higher than the ratio immediately before the automatic switching, the value in the direction of decreasing the supply amount, that is, the correction amount d _q becomes a negative value.

[0026] _{d q = K q (p i} / N Si -p A / N A) , however, K _q; coefficient (positive) Further, the correction amount d _q are respectively + △ Q upper and lower limit - △
It is input to the dead zone 39 designated as Q. Therefore,-△ Q <
When d _q <+ ΔQ, the correction amount d _q becomes zero, the supply amount set value q _r of the feeder 1 is not corrected, and −ΔQ> d _q
Alternatively, when d _q > + ΔQ, the correction amount d _q is output as it is. Furthermore, when this correction amount d _q is output,
After that, in order to prevent the set value q _r from being corrected for a fixed time (dead time T _d ), the dead time calculation unit 40 is provided and the correction amount d _{q is set} to zero during the dead time T _d . This dead time T _d is obtained when the set value q _r of the supply amount is changed,
It is the time until the influence starts to appear in the resin pressure p, that is, the time for compensating the transportation delay due to the distance from the feeder 1 to the position where the molten resin exists at the tip of the cylinder 5 of the extruder 2 from the feeder 1.

Further, the correction amount d _q is integrated by the integrating section 41 and becomes a difference between the supply amount of the feeder 1 and the discharge amount of the gear pump 6, that is, a correction value q _x , which is expressed by the following equation. q _xm = q _{xm -1} + d _q where m is a subscript indicating the processing time point. The corrected value q _x is added to the theoretical supply amount q _s for the feeder 1 by the adder 42, and the supply amount of the feeder 1 is automatically set. It is output as the set value q _r .

Further, the resin pressure p and the screw rotation speed N
_sThe sampling period ΔT of is the frequency of fluctuation due to the disturbance included.
The period is set to 1/2 or less, and the time constant T_pAnd
And T _VIs the resin pressure p and the screw rotation speed N, respectively._s
Set to a time that is sufficiently larger than the fluctuation cycle due to the disturbance of
The dead zone width ΔQ is caused by the disturbance in the cylinder 5.
By setting a value near the fluctuation range of the ratio
Ignoring fluctuations due to disturbances in 5
Only the fluctuation of the resin pressure due to the difference in the discharge amount of the gear pump 6
Supply amount set value q of feeder 1_rIs controlled.

The operation of the above structure will be described below.
First, the fluctuation of the resin pressure p at the inlet of the gear pump 6 due to the state change generated in the cylinder 5 of the extruder 2 is determined by the PI controller.
It is corrected by controlling the rotation speed N _s of the screw motor 8 by 11.

Further, the supply amount of the feeder 1 and the discharge amount of the gear pump 6 are completely the same, for example, the cylinder 5
Assuming that the internal conditions (resin temperature, etc.) do not change,
Resin pressure p at the inlet of the gear pump 6 and screw rotation speed N
The ratio of _s is constant. Further, the slow fluctuation of the resin pressure p is caused by integrating the difference between the supply amount of the raw material supplied from the feeder 1 and the discharge amount of the gear pump 6.
Therefore, the long-term average values p _A and N _A of the resin pressure p and the screw rotational speed N _s are calculated by the average value calculation units 32 and 33, and the ratio p _A / N _A and the initial value of this ratio which is automatically controlled. Value p
The deviation (correction amount d _q ) from _i / N _Si is obtained by the correction value calculation unit 38, and this deviation is integrated by the integration unit 41 to obtain the correction value q _x of the supply amount of the feeder 1 to obtain the theoretical supply amount. By adding to q _s by the adder 42 and feeding back to the set value q _r of the feeder 1, the difference between the supply amount of the feeder 1 and the discharge amount of the gear pump 6 is corrected and balanced.

Further, the deviation of the ratio is caused by the integration of the difference between the supply amount and the discharge amount, and changes slowly. Therefore, it is not necessary to immediately respond to the small deviation. Therefore, the deviation is not less than the width ΔQ of the dead zone 39. Only at this time, the integration section 41 calculates the correction value q _x of the supply amount of the raw material resin and outputs it to the feeder 1, so that the frequency of changing the set value q _r of the supply amount of the feeder 1 is reduced, which is the same as in the conventional case. Useless operation of the feeder 1 can be avoided. Further, by providing the dead time T _d , the transport delay due to the distance from the feeder 1 to the position where the molten resin exists at the tip of the cylinder 5 of the extruder 2 from the feeder 1 is compensated, and hunting of the control system is prevented. be able to.

As described above, since the supply amount of the feeder 1 does not needlessly change and the screw rotation speed only needs to respond to the disturbance in the cylinder 5, a totally stable operation is realized. be able to.

[0033]

As described above, according to the structure of the first invention, the fluctuation of the resin pressure at the inlet of the gear pump due to the state change generated in the cylinder of the extruder can be corrected by controlling the rotation speed of the screw. At the same time, the slow fluctuation of the resin pressure caused by the integration of the difference between the supply amount of the raw material supplied from the feeder and the discharge amount of the gear pump was calculated from the change in the ratio of the long-term average value of the resin pressure to the screw rotation speed. By grasping and correcting the supply amount of the feeder, the supply amount of the feeder and the discharge amount of the gear pump can be balanced.

Further, according to the structure of the second invention, the deviation of the ratio is caused by the integration of the difference between the feed amount of the feeder and the discharge amount of the gear pump, and changes slowly. Therefore, it is necessary to immediately respond to the small deviation. Therefore, only when the deviation is equal to or greater than the predetermined value, the correction amount of the feed amount of the raw material resin is calculated and output to the feeder, so that the frequency of changing the set value of the feed amount of the feeder can be reduced, thus reducing the waste of the feeder. It is possible to avoid movement, and to realize stable operation overall.

Further, according to the structure of the third invention, after the deviation of the ratio becomes a predetermined value or more and the correction value is changed,
By setting a waiting time of a certain time (dead time) and not changing the set value even if there is a deviation during that time, when the set value of the supply amount is changed, the effect until it begins to appear in the resin pressure. It is possible to compensate for the time, that is, the transportation delay time due to the distance from the feeder to the position where the molten resin exists at the tip of the cylinder of the extruder from the feeder, and it is possible to prevent hunting of the control system.

According to the structure of the fourth invention, the actual discharge amount of the molten resin is calculated from the rotation speed of the gear pump,
By adding a correction value to this discharge amount, the feeder supply amount set value can be formed.

[Brief description of drawings]

FIG. 1 is a system diagram of molten resin supply equipment showing an embodiment of the present invention.

FIG. 2 is a block diagram of a controller of the molten resin supply equipment.

FIG. 3 is a system diagram of a conventional molten resin supply facility.

[Explanation of symbols]

 1 Feeder 2 Extruder 3 Hopper 4 Screw 5 Cylinder 6 Gear pump 7 Die 8 Screw motor 10 Resin pressure detector 11 Controller 13 Rotation speed detector 14 Raw material hopper 15 Belt conveyor 16 Load cell 17 Conveyor drive motor 18 Rotation speed detector 19 Adjustment Total 21 Controller 22 Gear pump drive motor 23 Rotation speed detector

Claims (4)

[Claims] 1. A raw material resin supplied from said raw material feeder is controlled by controlling the supply amount of the raw material resin as a feedback signal, and by controlling the screw rotation speed by using a feed signal of the raw material resin as a feedback signal. An extruder for melting and kneading and extruding by a heater and a screw, and a molten resin supply facility including a gear pump for supplying the molten resin extruded from the extruder, and a screw rotation speed detector for detecting the rotation speed of the screw. The resin pressure signal and the screw rotation speed signal of the screw rotation speed detector are input, the long-term average value is calculated, the ratio is calculated, and the deviation is calculated from the deviation between this ratio and the initial value of the ratio. A molten resin supply facility comprising a control device for calculating a correction value of a supply amount of a raw material resin and outputting it to the feeder. 2. The control device calculates a corrected value of the supply amount of the raw material resin when the ratio of the long-term average value of the resin pressure and the screw rotation speed and the deviation of the initial value of the ratio are equal to or more than a predetermined value,
The molten resin supply equipment according to claim 1, wherein the molten resin is output to a feeder. 3. The molten resin supply equipment according to claim 1, wherein the control device does not change the correction value for a certain period of time after changing the correction value of the supply amount of the raw material resin. 4. A pump rotation speed detector for detecting the rotation speed of the gear pump, wherein the control device inputs a rotation speed signal of the gear pump from the pump rotation speed detector and calculates the discharge amount of the molten resin from this signal. 2. The molten resin supply equipment according to claim 1, wherein a correction value is added to this discharge amount and the result is output to the feeder as a supply amount set value.