JPH1044221A - Extruder and control of rotational speed of screw in extruder - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an extruder capable of changing the kind of a molding with good energy efficiency while preventing a problem from an aspect of quality such as the tearing of a material or the generation of noise and a method controlling the rotational speed of a screw in the extruder. SOLUTION: The rotational speed of a screw 2 controlled corresponding to the change of the quantity of the polymeric material present in the bank part 11 between a material outlet 5 and a roll pair 7, that is, the change of bank quantity is corrected on the basis of the change of the screw current value detected by a screw current detector 14. Therefore, even when a perfect exhausion process is performed for performing the change of a kind, the rotational speed of the screw 2 is kept almost constant.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an extruder for producing a sheet-like molded product by extruding a polymer material such as rubber from a pair of rolls by rotating a screw, and a rotational speed of the screw in the extruder. Related to the method of controlling.

[0002]

2. Description of the Related Art An extruder of this type is known, for example, from Japanese Patent Publication No. 57-26936. In this extruder, a screw is rotatably provided in a housing, and when the screw rotates, a polymer material such as rubber introduced into the housing is extruded from a material outlet of the housing. . A pair of calendar rolls (hereinafter simply referred to as “roll pairs”) are rotatably provided near the material outlet, and the extruded polymer material is formed into a sheet shape via the roll pairs. . Thus, a sheet-like molded product is manufactured by the extruder.

Further, the extruder disclosed in this publication detects a change in the space between the tip of the screw and the pair of rolls, that is, the amount of the polymer material existing in the bank portion (hereinafter referred to as “bank amount”). By controlling the rotation speed of the roll pair or the rotation speed of the screw based on the change in the bank amount, the bank amount is automatically adjusted to an appropriate value. Specifically,

[0004]

(Equation 1)

Where, VS: the rotation speed of the screw, VC: the rotation speed of the roll pair, PS: the rotation speed ratio of the screw and the roll pair in the steady state, ｛= (rotation speed of the screw) / (rotation speed of the roll pair)フ ィ ー ド バ ッ ク, X0: Set bank amount, X: Measured bank amount, KP: Proportional coefficient, TI: Integral coefficient, perform feedback control. For example, regardless of the change in the rotation speed of the roll pair, when the measured bank amount X exceeds the set bank amount X0, the screw rotation speed VS is reduced, while the measured bank amount X is changed to the set bank amount X0.
If it is smaller than this, the screw rotation speed VS is accelerated to adjust the bank amount to a constant value (set bank amount X0). As a control method for keeping the bank amount constant, in addition to the method of controlling the screw rotational speed VS as described above, other than the method of controlling the rotational speed VC of the roll pair, or a method of controlling both rotational speeds VS , VC may be controlled by acceleration / deceleration.

As described above, in the conventional extruder, the rotational speed of the screw and the rotational speed of the pair of rolls are feedback-controlled based on the change in the amount of bank, and the amount of bank is kept uniform, so that the shape of the sheet-like molded product is reduced. We are aiming for uniformity.

In some cases, the control is performed by the bank pressure instead of the bank amount. However, for convenience of explanation, in this specification, the control is limited to the bank amount.

[0008]

However, simply performing feedback control of the screw rotation speed or the like based on the bank amount or bank pressure causes the following problems.

First, there is a case where a plurality of polymer materials are sequentially switched in an extruder to produce different types of sheet-like molded articles. When the type is changed in this way, it is necessary to stop introducing the polymer material into the housing and extrude the polymer material remaining in the housing with a screw. Such processing (“starting out step”)
In the extruder, the rotational speed of the screw is accelerated, and eventually reaches the maximum rotational speed. For this reason, a polymer material, for example, rubber may be cut and a quality problem may occur. In addition, since the screw is rotated at a higher speed than necessary, a loud noise is generated by a drive motor or a speed reducer, etc., which causes a noise problem, or a problem of wasting energy by using extra energy. .

A second problem is that a pulsation occurs in the bank amount signal output from the detector for detecting the bank amount due to the pulsation of the amount of the polymer material depending on the phase of the screw. As a result, feedback control is not performed. In some cases, the quality of the molded product is degraded. Here, in order to solve this problem, it is possible to suppress the influence of pulsation by adjusting control constants (proportional coefficient KP, integral coefficient TI).
The optimum range of these control constants is narrow, and if they are set slightly out of the range, control stability may be lost.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and it is possible to change the type of a molded product with good energy efficiency while preventing quality problems such as material breakage and noise. A first object is to provide an extruder that can be performed and a method for controlling a screw rotation speed in the extruder.

Further, the present invention suppresses the influence of pulsation,
A second object is to provide an extruder capable of producing a high-quality sheet-like molded product and a method for controlling a screw rotation speed in the extruder.

[0013]

According to a first aspect of the present invention, a polymer material is extruded from a material outlet of the housing by rotating a screw provided in the housing, and a pair of rolls provided near the material outlet is provided. An extruder for producing a sheet-like molded product through the apparatus, wherein in order to achieve the first object, an amount or pressure of a polymer material existing between the material outlet and the roll pair is detected. Bank detecting means, a screw detecting means for detecting a current value or an electric power value of a driving portion for rotatingly driving the screw, a change in a detected value detected by the bank detecting means, and the screw detecting means Control means for performing feedback control of the rotation speed of the screw based on a change in the detected value.

According to the first aspect of the present invention, the change in the amount or pressure of the polymer material existing between the material outlet and the roll pair, which is detected by the bank detecting means, is determined by the rotational speed of the screw. Feedback control is performed based on a change in the current value or the power value of the drive unit that rotationally drives the screw detected by the means.

According to a second aspect of the present invention, a screw formed in a housing is rotated to extrude a polymer material from a material outlet of the housing, and a sheet-like molded product is formed through a pair of rolls rotating near the material outlet. An extruder for producing the above, wherein in order to achieve the second object, a bank detecting means for detecting the amount or pressure of the polymer material existing between the material outlet and the roll pair, and the roll Roll detecting means for detecting a current value or a power value of a driving unit for rotating the pair, a change in a detected value detected by the bank detecting means, and a change in a detected value detected by the roll detecting means Control means for performing feedback control of the rotation speed of the screw based on the above.

According to the second aspect of the present invention, the change in the amount or pressure of the polymer material present between the material outlet and the roll pair, which is detected by the bank detecting means, is determined by the rotational speed of the screw. Feedback control is performed based on the change in the current value or the power value of the drive unit that rotationally drives the roll pair detected by the means.

According to a third aspect of the present invention, the control means adjusts the screw rotational speed to be substantially constant by the feedback control.

According to the third aspect of the present invention, the screw rotation speed is substantially constant without being affected by the remaining amount of the polymer material in the housing or pulsation.

According to a fourth aspect of the present invention, a screw provided in a housing is rotated to extrude a polymer material from a material outlet of the housing, and the sheet material is formed through a pair of rolls provided near the material outlet. An apparatus for manufacturing a product, wherein the screw speed is feedback-controlled in accordance with a change in the amount or pressure of the polymer material existing between the material outlet and the pair of rolls so that the amount or the pressure is constant. A screw rotation speed control method for an extruder, wherein the screw rotation speed is corrected based on a change in a current value or an electric power value of a drive unit that rotationally drives the screw in order to achieve the first object. Is added to the feedback control.

According to the fourth aspect of the present invention, the rotational speed of the screw, which is feedback-controlled in accordance with the change in the amount or the pressure of the polymer material existing between the material outlet and the roll pair, drives the screw to rotate. The correction is performed based on a change in the current value or the power value of the unit.

According to a fifth aspect of the present invention, a screw formed in a housing is rotated to extrude a polymer material from a material outlet of the housing, and a sheet-like molded product is formed through a pair of rolls rotating near the material outlet. An apparatus for manufacturing, wherein the rotational speed of the screw is feedback-controlled in accordance with a change in the amount or pressure of the polymer material existing between the material outlet and the roll pair to keep the amount or pressure constant. A screw rotation speed control method for an extruder, wherein the screw rotation speed is corrected based on a change in a current value or a power value of a drive unit that rotationally drives the roll pair in order to achieve the second object. Is added to the feedback control.

According to the fifth aspect of the present invention, the rotation speed of the screw, which is feedback-controlled in accordance with a change in the amount or pressure of the polymer material existing between the material outlet and the roll pair, drives the roll pair to rotate. The correction is performed based on a change in the current value or the power value of the driving unit.

[0023]

FIG. 1 is a view showing one embodiment of an extruder according to the present invention. In this extruder, as shown in FIG.
Are provided rotatably. A drive motor 3 is connected to the rear end side (the right hand side in the figure) of the screw 2 via a speed reducer, a coupling or the like (not shown), and is driven by an electrically connected screw control device 4. Motor 3
Is controlled so that the screw 2 can be rotated at an arbitrary rotation speed. On the other hand, a material outlet 5 is provided in the housing 1 on the distal end side (the left hand side in FIG. 1) of the screw 2, and the polymer material is supplied to the housing 1 via a hopper 6 attached to the upper side of the side of the housing 1. After the screw 2 is rotated as described above, the polymer material is conveyed to the distal end side of the screw 2 and further extruded through the material outlet 5.

In the vicinity of the material outlet 5, a pair of upper and lower calendar rolls 7, 7 (hereinafter simply referred to as "roll pair 7") are rotatably arranged, and are driven via a speed reducer, a coupling and the like. It is connected to the motor 8. The drive motor 8 is electrically connected to a calendar roll control device 9. The drive of the drive motor 8 is controlled by the calendar roll control device 9 so that the roll pair 7 can be rotated at an arbitrary rotation speed. Has become. Therefore, when the polymer material extruded from the material outlet 5 passes between the pair of rolls 7 rotating as described above, it is formed into a sheet, and moves to the front side (the left-hand side in the figure) as the molded product 10. I will do it.

Between the roll pair 7 and the material outlet 5, there is formed a material reservoir for storing the polymer material, that is, a bank portion 11, and the amount of the polymer material present in the bank portion 11 (the amount of the bank). ), A bank amount detector 12 is provided near the bank unit 11. The bank amount detector 12 is electrically connected to the arithmetic unit 13 and outputs an electric signal corresponding to the actually measured bank amount.
Give to.

The arithmetic unit 13 includes a bank amount detector 1
In addition to 2, the screw current detecting device 14 and the roll current detecting device 15 are electrically connected. The screw current detecting device 14 is electrically connected to the screw control device 4, detects a current value (screw current value) of the screw driving motor 3 based on a signal output from the screw control device 4, and detects the current value. A signal indicating the value is given to the arithmetic unit 13. Further, the roll current detecting device 15 is electrically connected to the calendar roll control device 9, and based on a signal output from the calendar roll control device 9, the current value of the drive motor 8 for the roll pair (calender roll current value). And a signal indicating the detected value is given to the arithmetic unit 13.

The arithmetic unit 13 which has received the actually measured bank amount, screw current value and calendar roll current value in this way gives appropriate control signals to the screw control device 4 and the calendar roll control device 9 based on these information. Feedback control of the entire extruder.

Next, the operation of the extruder configured as described above will be described by dividing it into a steady state (FIG. 2) and a start-out step (FIG. 3). FIG. 2 is a graph showing changes in the calendar roll current, the measured bank amount actually measured by the bank amount detector 12, and the rotation speed of the screw 2 in a steady state. FIG. 3 is a graph showing how the screw current value, the measured bank amount, and the rotation speed of the screw 2 change when the process shifts from the steady state to the start-out process.

In this extruder, the screw 2 is rotated while continuously or intermittently supplying the polymer material into the housing 1 from the hopper 6 to push out the polymer material from the material outlet 5 and further rotate the roll pair. 7 to produce the sheet-shaped molded product 10 (steady state).
At this time, the measured bank amount detected by the bank amount detector 12 does not completely match the set bank amount (broken line 22 in FIG. 2) as shown by the solid line 21 in FIG. It is larger or smaller, that is, a pulsation is occurring. Here, similarly to the conventional case, when the feedback control is performed based only on the change of the actually measured bank amount detected by the bank amount detector 12,
Due to the pulsation of the measured bank amount, the rotational speed of the screw 2 changes with a relatively large amplitude as shown by the solid line 23, and becomes unstable. As a result, there has been a problem that a high-quality sheet-like molded product cannot be manufactured as described above.

On the other hand, in the extruder according to the present embodiment, not only the feedback control based on the change of the actually measured bank amount (hereinafter referred to as “bank amount feedback control”), but also the Performs a feedback control (hereinafter, referred to as "calendar roll current feedback control") based on a change in the calendar roll current value having a correlation (solid line 24 in FIG. 4).
This calendar roll current feedback control is a feedback control based on a change in the calendar roll current value, that is, a difference between the actually measured calendar roll current value and the calendar roll current value in a steady state, and more specifically, for example, Next formula

[0031]

(Equation 2)

Here, IC0: calendar roll current value in a steady state, IC: measured calendar roll current value, KP2: proportional coefficient in calendar roll current feedback control, TI2: integral coefficient in calendar roll current feedback control, Determine the rotation speed. As described above, when the rotation speed of the screw 2 by the bank amount feedback control is corrected by the feedback control based on the calendar roll current value, as shown by a one-dot chain line 25 in FIG. To reduce wobble. As described above, according to this embodiment, the influence of pulsation can be suppressed, and the sheet-shaped molded product 10 can be stably manufactured with high quality.

Next, a case in which a start-out process is performed to change the type of product will be described. In this case, the introduction of the polymer material from the hopper 6 is stopped. However, when only the bank amount feedback control is performed as in the related art, as shown by a solid line 31 in FIG. The measured bank amount decreases with respect to the set bank amount (broken line 32 in the figure), and the rotation speed of the screw 2 increases accordingly to the maximum speed. For this reason, various problems as described above occur. The solid line 33 in the figure shows how the rotation speed of the screw 2 changes with the execution of the cut-out process.

On the other hand, in the extruder according to this embodiment, the screw current decreases along with the bank amount as the amount of the polymer material in the housing 1 decreases (see the solid lines 31 and 34 in the figure). The rotational speed of the screw 2 is corrected by the bank amount feedback control.
That is, the arithmetic unit 13 performs not only the bank amount feedback control but also feedback control based on a change in the screw current value (hereinafter referred to as “screw current feedback control”). This screw current feedback control is a feedback control based on a change in screw current value, that is, a difference between an actually measured screw current value and a screw current value in a steady state.

[0035]

(Equation 3)

Here, the rotational speed of the screw 2 is determined according to IS0: screw current value in a steady state, IS: measured screw current value, KP3: proportional coefficient in screw current feedback control, TI3: integral coefficient in screw current feedback control. I do. In this way, by performing the feedback control based on the screw current value, as shown by the one-dot chain line 35 in FIG. The speed can be kept almost constant, and quality problems such as material tearing, noise generation and energy waste can be prevented.

In the above-described embodiment, the rotational speed of the screw 2 is determined by different determination methods in the steady state and the start-up process. However, the bank amount feedback control, the calendar roll current feedback control,
The rotation speed of the screw 2 may be determined without discriminating between the steady state and the start-up process by combining all the screw current feedback controls. Specifically, always

[0038]

(Equation 4)

It is also possible to determine the rotational speed of the screw 2 based on the above.

In the above embodiment, the feedback control is performed by detecting the calendar roll current value. However, the calendar roll power value is detected instead of detecting the calendar roll current value or together with the calendar roll current value. Alternatively, feedback control may be performed based on calendar roll current or power. The same can be said for screw current feedback control. That is, instead of detecting the screw current value or together with the screw current value, the screw power value may be detected, and feedback control may be performed based on the screw current or the power.

[0041]

As described above, according to the first and fourth aspects of the present invention, the rotation of the screw controlled according to the change in the amount or pressure of the polymer material existing between the material outlet and the roll pair. The speed is detected by detecting the current or power value of the drive unit that drives the screw to rotate, and the speed is corrected based on the change in the detected value. It is possible to prevent an increase in speed and to change the type of a molded article with good energy efficiency while preventing quality problems such as material breakage and noise.

According to the second and fifth aspects of the present invention,
The rotational speed of the screw controlled according to the change in the amount or pressure of the polymer material existing between the material outlet and the roll pair, the current value or the electric power value of the drive unit that rotationally drives the roll pair is detected, Since the correction is performed based on the change in the detected value, the influence of the pulsation can be suppressed, and as a result, a sheet-like molded article can be manufactured with excellent quality.

[Brief description of the drawings]

FIG. 1 is a diagram showing one embodiment of an extruder according to the present invention.

FIG. 2 is a graph showing changes in a calendar roll current, an actually measured bank amount measured by a bank amount detector, and a screw rotation speed in a steady state.

FIG. 3 is a graph showing how a screw current value, a measured bank amount, and a screw rotation speed change when the process shifts from a steady state to a start-up process.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 housing 2 screw 5 material outlet 7 roll pair (calender roll) 10 sheet-like molded product 11 bank part 12 bank amount detector (bank detection means) 13 arithmetic unit (control means) 14 screw current detection device (screw detection means) 15) Roll current detection device (roll detection means)

Claims (5)

[Claims] 1. An extrusion in which a screw provided in a housing is rotated to extrude a polymer material from a material outlet of the housing, and a sheet-like molded product is manufactured through a pair of rolls provided near the material outlet. A bank detecting means for detecting an amount or a pressure of a polymer material existing between the material outlet and the roll pair; and a screw for detecting a current value or a power value of a drive unit for rotating and driving the screw. Control means for performing feedback control of the rotation speed of the screw based on a change in the detection value detected by the bank detection means and a change in the detection value detected by the screw detection means. An extruder characterized by comprising: 2. An extruder for rotating a screw provided in a housing to extrude a polymer material from a material outlet of the housing and manufacturing a sheet-like molded product via a pair of rolls rotating near the material outlet. In the above, the bank detecting means for detecting the amount or pressure of the polymer material existing between the material outlet and the roll pair, and the roll for detecting the current value or the electric power value of the drive unit for rotatingly driving the roll pair Control means for performing feedback control of the rotation speed of the screw based on a change in the detection value detected by the bank detection means and a change in the detection value detected by the roll detection means. An extruder characterized by comprising: 3. The extruder according to claim 1, wherein the control means is configured to adjust the screw rotational speed to be substantially constant by the feedback control. 4. An apparatus for rotating a screw provided in a housing, extruding a polymer material from a material outlet of the housing, and manufacturing a sheet-like molded product via a pair of rolls provided near the material outlet. In an extruder that controls the rotation speed of the screw in a feedback manner in accordance with a change in the amount or pressure of the polymer material existing between the material outlet and the roll pair to make the amount or pressure constant. In the screw rotation speed control method, a step of correcting the screw rotation speed based on a change in a current value or a power value of a driving unit that drives the screw to rotate is added to the feedback control. Speed control method. 5. An apparatus for rotating a screw provided in a housing to extrude a polymer material from a material outlet of the housing and manufacturing a sheet-like molded product via a pair of rolls rotating near the material outlet. A screw in an extruder for controlling the rotation speed of the screw in a feedback manner in accordance with a change in the amount or pressure of the polymer material existing between the material outlet and the pair of rolls so as to make the amount or pressure constant. A rotation speed control method, wherein a step of correcting the screw rotation speed based on a change in a current value or a power value of a driving unit that rotationally drives the roll pair is added to the feedback control. Speed control method.