JP2003025417A - Sheet manufacturing method and sheet thickness control unit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a sheet manufacturing method capable of leveling control input outputted to a thickness adjusting means without changing the thickness distribution of the sheet from a desired distribution to the utmost, and a sheet thickness control unit. SOLUTION: In the sheet manufacturing method, a raw material is extruded using a die equipped with (N) (N: a natural number of 2 or more) thickness adjusting means to be molded to form the sheet and the control inputs outputted to the thickness adjusting means are calculated and the thickness adjusting means are controlled on the basis of the calculated control inputs to control the thickness of the sheet. When the difference with the control input outputted to the approaching thickness adjusting means in the respective continuous (M) (M: a natural number of 2-N) thickness adjusting means among the calculated control input is not less than a predetermined value T, control inputs are outputted to the continuous (M) thickness adjusting means on the basis of a process model showing the relation between the control input to be outputted and sheet thickness having to be obtained on the basis of the operation quantities so that the difference with the control input outputted to the approaching thickness adjusting means becomes small.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a sheet such as a film and a sheet thickness control device.

[0002]

2. Description of the Related Art Conventionally, a sheet such as a plastic film is manufactured by the following process.

FIG. 2 is a diagram showing an overall schematic structure of a general sheet manufacturing facility, and FIG. 3 is an enlarged perspective view of a main part of the die shown in FIG.

The sheet manufacturing equipment is equipped with an extruder 3 for extruding a polymer, a die 4 for extruding the extruded polymer into a sheet, and cooling the extruded polymer (hereinafter referred to as sheet 1). A cooling roll 5, a stretching machine 2 for stretching the sheet 1 in the longitudinal and transverse directions, and a winding machine 6 for winding the stretched sheet 1 are provided. N bases (N: N) arranged in the width direction of the sheet 1 (direction orthogonal to the paper surface of FIG. 2).
A thickness adjusting means 10 having a natural number of 2 or more) and a gap 11 for discharging the polymer are provided. Heat bolts are used as the thickness adjusting means 10, and a heat bolt method of adjusting the gap 11 of the base 4 by changing the temperature of these bolts to thermally expand and contract the bolts, or a lip heater for the thickness adjusting means 10. It is possible to use a lip heater system in which the thickness of the sheet 1 is adjusted by changing the temperature of the polymer and changing the discharge amount of the polymer discharged from the die 4 according to the change in the viscosity of the polymer. . Further, this sheet manufacturing facility is provided with a thickness measuring device 8 for measuring the thickness distribution in the width direction of the sheet, and a control means 9 for controlling the thickness adjusting means 10 based on the thickness distribution. As the thickness measuring device 8, any thickness measuring device such as a β-ray, an X-ray, an ultraviolet ray, a light interference type can be used, and the thickness distribution of the sheet in the width direction can be measured.

The control means (operation amount output means) 9 calculates the operation amount based on the difference value between the thickness distribution in the width direction of the sheet 1 and the target thickness distribution, and the operation amount is adjusted to the thickness adjusting means 10. Output to.

[0006]

By the way, the base 4
In the above, since the integrated lip is provided in the width direction of the sheet, the operation amount applied to each thickness adjusting means 10 also affects the position of the adjacent thickness adjusting means. When the difference in the operation amount between the adjacent thickness adjusting means becomes excessively large, the interference between the thickness adjusting means becomes large, so that the shape of the gap of the die does not follow the operation amount. Therefore, in the die, the gap adjusting ability is reduced, and the sheet thickness control accuracy is reduced.

To solve this problem, if the difference between the adjacent thickness adjusting means becomes excessively large during the control of the sheet thickness, the operation amount output to the thickness adjusting means is corrected to equalize, that is, There is a method of reducing the difference in the operation amount output to the adjacent thickness adjusting means.

In the invention disclosed in Japanese Patent Laid-Open No. 7-329147, the operation amount P _i applied to the i-th (i = 1, 2, ..., N-1) thickness adjusting means and the thickness adjustments on both sides thereof are adjusted. When the difference between the manipulated variables P _i−1 and P _{i + 1} applied to the means exceeds a predetermined upper limit value, the weighted average value of the manipulated variables of the i-th and adjacent thickness adjusting means is set to the i-th thickness adjusting means. The operation amount is output, and the above operation is repeated until the difference between the operation amounts becomes equal to or less than a predetermined upper limit value.

According to this method, the difference between the manipulated variables output to the adjacent thickness adjusting means can be made small, but since the manipulated variable is merely obtained by the weighted average so that the difference becomes small,
The sheet thickness distribution after correction becomes different from the sheet thickness distribution before correction, and there is a problem that the quality of the sheet is impaired.

An object of the present invention is to solve the above-mentioned problems of the prior art, and to make the operation amount output to the thickness adjusting means uniform without changing the thickness distribution of the sheet from the desired distribution as much as possible. Another object of the present invention is to provide a sheet thickness control device.

[0011]

In order to solve the above-mentioned problems, a method for producing a sheet according to the present invention is to extrude a raw material using a die having N (N: a natural number of 2 or more) thickness adjusting means. A sheet manufacturing method for forming a sheet and calculating an operation amount to be output to the thickness adjusting unit and controlling the thickness adjusting unit based on the calculated operation amount to manage the thickness of the sheet. Then, in each of the calculated continuous M thickness adjusting means, when the difference between the operation amount output to the adjacent thickness adjusting means is a predetermined value T or more, the operation amount to be output and the operation amount to be obtained by this Based on the process model showing the relationship with the sheet thickness, the operation amount output to the M continuous thickness adjustment means is corrected so that the difference with the operation amount output to the adjacent thickness adjustment means becomes small. The one in which the features.

As a method of deriving the correction amount, the continuous
Operation amount output to M thickness adjusting means (u₁, U₂・ ・ ・
.., u_M)^TIs a vector U, and when each manipulated variable is output
M sheet thickness measurement values (y
₁, Y₂・ ・ ・ ・ ・ ・ Y_M)^TBe the vector Y, and the process
S model as Y = AU (A is a matrix of size M × M)
When representing, the operation amount vector U before the correction is represented by M of the matrix A.
Eigenvectors v_iMinutes with (i = 1, 2, ..., M)
The coefficient a of each eigenvector when solved _i(I =
1, 2, ..., M) and the fixed values corresponding to the eigenvectors.
Value λ_i(I = 1, 2, ..., M) and a predetermined threshold T
₂(0 <T₁<1) is used to modify the manipulated variable vector
U '= (u₁’, U₂’・ ・ ・ ・ ・ ・ U_M’)^TBy the following formula
It is a preferable form to derive it. Formula (3)

[0013]

[Equation 3]

Further, the manipulated variable vector U before the correction is converted into M eigenvectors v _i (i = 1, 2, ..., Of matrix A).
The coefficient a of each eigenvector when decomposed in M)
_i (i = 1, 2, ..., M) and an eigenvalue λ _i (i = 1, 2, ..., M) corresponding to the eigenvector and a predetermined threshold T ₂ (0 <T ₂ <1) It is also a preferable embodiment of the present invention to derive the corrected manipulated variable vector U ′ = (u ₁ ′, u ₂ ′, ..., U _M ′) ^T by using the following equation. Formula (4)

[0015]

[Equation 4]

Here, A is a vector U representing the manipulated variables (u ₁ , u ₂ , ..., U _M ) output to M successive thickness adjusting means, and each thickness adjustment when each manipulated variable is output. M sheet thickness measurement values (y ₁ , y ₂ , ...,
When y _M is a vector Y, it is a matrix of size M × M that represents the interference of the individual thickness adjusting means and that satisfies the relation of Y = AU, and f _j (j = 1, 2, ...). , M) is a function of the coefficients a _j and λ _j .

In order to solve the above-mentioned problems, the sheet thickness control device of the present invention is based on the measured values of each portion in the width direction measured by the thickness measuring means for measuring the thickness distribution of the sheet in the width direction. N corresponding sheet positions (N:
A control device for giving a manipulated variable to thickness adjusting means of 2 or more natural numbers), which is output to consecutive M (M: a natural number of 2 or more and N or less) thickness adjusting means of the manipulated variables of the thickness adjusting means. The operation amount output to the continuous M thickness adjusting means is corrected based on a process model representing the relationship between the output operation amount and the sheet thickness to be obtained by the operation amount so that the variation in the operation amount to be performed becomes small. It is characterized by having a means for doing so.

Further, a program for solving the above-mentioned problem is a step of inputting a measured value of a thickness distribution of each portion in the width direction of the sheet, and calculating a difference between the target value of the thickness of each portion and the measured value. And a step of calculating an operation amount to be output to the thickness adjusting means based on the difference between the respective parts, which is a storage medium storing a program for realizing the computer, wherein the step of calculating the operation amount is calculated. When the difference between the operation amount of the M continuous thickness adjusting means and the operation amount output to the adjacent thickness adjusting means is a predetermined value T or more, the difference between the operation amounts becomes small.
Based on a process model that represents the relationship between the output operation amount and the sheet thickness to be obtained thereby, the operation amount output to the M continuous thickness adjusting means is corrected, and each corrected operation amount is calculated as described above. It is characterized by including a step of outputting to each thickness adjusting means.

A computer-readable storage medium storing the program is also a feature of the present invention.

A sheet produced by the method for producing a sheet of the present invention is also a feature of the present invention.

[0021]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described below with reference to the drawings based on an embodiment in which the present invention is applied to the production of a plastic film.

The basic construction of the sheet manufacturing equipment of this embodiment is as shown in FIGS. 2 and 3, and a detailed description thereof is omitted here.

The control means 9, as shown in FIG. 4, is an operation amount calculation means 9a, an operation amount correction means 9b, and an operation amount output means 9c.
Is equipped with. The operation amount calculation means 9a calculates the operation amount by a predetermined control algorithm, and corrects the operation amount when the operation amount correction means 9b needs to correct the operation amount. The operation amount output means actually outputs each corrected amount after correction to the thickness adjusting means 10.
Output to.

In the manipulated variable calculating means 9a, it is preferable to perform conversion processing such as filter processing on the deviation data which is the difference value between the thickness distribution of the sheet 1 and the target thickness distribution. As the filtering process, a moving average in the same direction as the width direction of the sheet, a method of performing a weighted average process with the deviation data before the present time, or the like can be used.

The number of thickness adjusting means 10 arranged in the width direction of the sheet is often smaller than the number of the deviation data. In such a case, data corresponding to each thickness adjusting means is collected from the deviation data that has been filtered. At this time, it is desirable to find the corresponding position of each thickness adjusting means 10 and the deviation data in advance.

Further, the manipulated variable calculating means 9a calculates the manipulated variable for the deviation data in which the number of the thickness adjusting means is adjusted and the number of the thickness adjusting means is calculated, and controls the thickness adjusting means 10. As the control algorithm, PID control or modern control using a mathematical model can be used.

When the sheet thickness is controlled by the above method, as described above, the operation amount output to a certain thickness adjusting means may be excessively larger or smaller than the operation amount output to the adjacent thickness adjusting means. is there. FIG. 5 shows an example of the operation amount 21 output to each thickness adjusting means 10. The horizontal axis represents the position of the thickness adjusting means, and the vertical axis represents the amount of operation.
The magnitude of the manipulated variable can be represented by the ratio of the time for which a constant amount of heat is output to the thickness adjusting means per predetermined time, the amount of heat output to the thickness adjusting means for a predetermined time, and the like. The operation amount of the thickness adjusting means at the positions x and y is excessively larger or smaller than the operation amount output to the thickness adjusting means at the adjacent positions x-1, x + 1 and y-1, y + 1.

A method for leveling the operation amount with respect to such a pattern of the operation amount will be described.

M continuous thickness adjusting means 10 _i (i =
1, 2, ..., M) is the operation amount 21 output to u _i , and the sheet thickness measurement value at the position corresponding to each thickness adjusting means 10 _i when this operation amount is output is y _i (i = 1) 2, ...
, M), the process model is expressed as Y = AU. That is, the static mathematical relationship between u _i and y _i is expressed by Expressions 5 and 6, for example. Formula (5)

[0030]

[Equation 5]

Equation (6)

[0032]

[Equation 6]

The static mathematical relationship refers to the relationship between the sheet thickness and the manipulated variable after a sufficient amount of time has passed since the manipulated variable was added to the thickness adjusting means. Here, A is an interference matrix, which is an M × M size matrix representing the interference between the individual thickness adjusting means.
In Equation 4, α ₁ (≧ 0) is the rate at which the sheet thickness at the position corresponding to the adjacent thickness adjusting means changes when the operation amount is output to a certain thickness adjusting means, and α ₂ (≧ 0) is two apart. The ratio of change in the sheet thickness at the position corresponding to the thickness adjusting means is shown. In the above equation, the rate of change in the sheet thickness at the position corresponding to the thickness adjusting means separated by three or more is set to 0,
It is possible to consider after α ₃ (≧ 0), and α ₁ , α of each row
The values of ₂ can be different.

Here, a method of correcting the operation amount output to the M continuous thickness adjusting means to equalize the operation amount will be described with reference to FIG.
It will be described based on.

The manipulated variable (u ₁ , u ₂ , ... U _M ) ^T before correction output to each thickness adjusting means 10 _j is defined as a vector U.

First, M pairs of eigenvalues λ _i (i = 1, 2, ...
··, M) and the eigenvectors _{v i (i = 1,2, ···} ,
M) is obtained (step 1). Further, the magnitude of the eigenvector is normalized to 1. At this time, A is an M × M square matrix, and rank (A) = M.

At this time, U can be expressed as a linear combination of eigenvectors v _i as follows.

[0038]

[Equation 7]

A _i is a coefficient indicating how much the eigenvector v _i is included in U, and is calculated by the following equation (step 2).

[0040]

[Equation 8]

At this time, the sheet thickness y _i is v _i , λ _i , a _i
Can be expressed as follows.

[0042]

[Equation 9]

Here, for the component in which the product size | a _i λ _i | of the coefficient a _i and the eigenvalue λ _i is relatively small, the present inventors change the sheet thickness almost, if a _i = 0. It was found that the amount of operation can be leveled without causing it. This is because a component with a small | a _i λ _i | has a large influence on the variation in the manipulated variable and a small influence on the film thickness.

Therefore, | a _i λ _i | is determined by the following equation using a predetermined threshold value T ₁ (0 <T ₁ <1) set in advance,
If | a _i λ _i | <T ₁ , then a _i = 0 (step 3 to
5).

[0045]

[Equation 10]

Where max _j (| a _j λ _j |) is | a _j λ _j
Is the maximum value of | (j = 1, 2, ..., M).

Next, a _i (i =
1, 2, ..., M) are introduced into the following equation to derive a corrected manipulated variable vector U ′ (step 6).

[0048]

[Equation 11]

By correcting the operation amount by the above equation, the operation amount can be leveled while the sheet thickness is hardly changed. When the threshold value T ₁ is increased, many kinds of frequency components can be removed from the manipulated variable vector U, so that the leveling level can be strengthened, but the influence on the film thickness tends to increase. On the other hand, when the threshold value T ₁ is made smaller, the influence on the film thickness becomes smaller, but the leveling level tends to become weaker. The value of the threshold T ₁ is more preferably 0.01 or more and 0.5 or less.

Further, the eigenvector v _i to be removed from the manipulated variable vector U is not changed depending on a _i , but a _i corresponding to the eigenvalue λ _i satisfying the following equation is set to 0, and the above equation 2
The operation amount may be corrected by.

[0051]

[Equation 12]

Here, 0 <T ₂ <1, and 0.01 ≦
T ₂ ≦ 0.5 is more preferable.

Finally, the corrected operation amount is output to the thickness adjusting means (step 7).

In the present invention, the leveling may be performed every control period or intermittently. Further, it is also a preferable mode to execute the processing when a predetermined condition is satisfied. For example, the variance value of the manipulated variables output to M consecutive thickness adjusting means is obtained, and when this value exceeds a predetermined value, the maximum and minimum values of the manipulated variables output to the M thickness adjusting means are calculated. It is also preferable to perform the leveling when the difference between the values exceeds a predetermined value or when the difference between the operation amounts output to the adjacent thickness adjusting means exceeds the predetermined value.

In the present invention, the number M of thickness adjusting means for leveling is 2 or more and N or less. When M = N, that is, M is the number N of all the thickness adjusting means, it is preferable because the operation amounts of all the thickness adjusting means can be leveled collectively. Further, M may be set to any value smaller than N. In this case, the calculation can be simplified by performing the calculation only on the portion that requires leveling.

It is to be noted that the difference value between the operation amounts output to the adjacent thickness adjusting means and the position for correcting the operation amount are determined,
The correction amount is preferably calculated using a computer. In this case, it is realized by a program that causes a memory or a CPU of the computer to operate by a subroutine corresponding to each of the above steps. Such a program is distributed via a tangible computer-readable storage medium such as a flexible disk or a CD-ROM, or a transmission medium such as a wired or wireless network.

[0057]

EXAMPLES Now, examples of producing a plastic film by using the present invention will be described.

Using the manufacturing equipment shown in FIGS. 2 and 3,
A heat bolt method is used as the thickness adjusting means 10, and 38
A plastic film was manufactured using the die 4 having individual thickness adjusting means.

In this embodiment, the manipulated variable refers to the ratio of the time during which the heat quantity is applied to the heat bolts per fixed time.

The components of the interference matrix of the equation (6) were set to α ₁ = 0.75 and α ₂ = 0.35 by analyzing the film manufacturing process.

The leveling of the manipulated variable is executed when the standard deviation of the manipulated variables output to the 38 thickness adjusting means is 3% or more. When M = 38 and T ₁ = 0.05 in the equation 1, all 38 manipulated variables were leveled to correct the manipulated variables.

The pattern of the manipulated variable at a certain time during the control of the sheet thickness is as shown in FIG. In FIG.
The vertical axis of the graph represents the magnitude of the operation amount, and here represents the ratio of the time for outputting a constant amount of heat to the heat bolt per predetermined time. At this time, the standard deviation of the manipulated variable is 3.5%
Therefore, the operation amount was leveled. FIG. 7 shows an operation amount pattern given to the thickness adjusting means after leveling. At this time, the standard deviation of the manipulated variable was 2.3%, and the standard deviation of the manipulated variable was reduced by leveling. Further, FIG. 8 shows a sheet thickness shape before leveling, and FIG. 9 shows a sheet thickness shape after leveling. The thickness profile hardly changed before and after leveling.

For comparison, the method described in Japanese Patent Application Laid-Open No. 7-329147 is applied to the pattern of the operation amount similar to that shown in FIG. 6, and the difference between the operation amounts on both sides is 7%. FIG. 10 shows the thickness shape of the sheet when the manipulated variables are sequentially corrected so that the standard deviation of the manipulated variables becomes 2.3%. The thickness and shape of the sheet changed greatly.

Although the heat bolt is used as the thickness adjusting means in the above embodiment, it is not particularly limited as long as it meets the purpose of the present invention. For example, an actuator such as a servo motor or an air motor or a die bolt. It is also possible to use Further, as a factor that changes the operation amount of the thickness adjusting means, conditions other than the energization time and the voltage, for example, the rotation angle of the die bolt and the heater temperature may be used.

[0065]

As described above, in the sheet manufacturing method of the present invention, since the operation amount output to the thickness adjusting means can be leveled without changing the thickness of the sheet, the thickness adjustment can be performed without deteriorating the quality of the sheet. It is possible to prevent the structure of the means and the control accuracy from deteriorating.

[Brief description of drawings]

FIG. 1 is a flowchart of operation amount leveling according to an embodiment of the present invention.

FIG. 2 is a diagram showing an overall schematic configuration of a sheet manufacturing facility according to an embodiment of the present invention.

FIG. 3 is an enlarged perspective view of a main part of the mouthpiece shown in FIG.

FIG. 4 is a diagram showing details of control means.

FIG. 5 is a diagram showing a pattern of an operation amount.

FIG. 6 is a diagram showing a pattern of an operation amount in the embodiment.

FIG. 7 is a diagram showing a result of an example in the present invention.

FIG. 8 is a sheet thickness pattern in FIG.

FIG. 9 is a sheet thickness pattern in FIG.

FIG. 10 is a result of thickness control at the time of manufacturing a sheet by an example of leveling the operation amount by a conventional method.

[Explanation of symbols]

1: Sheet 2: Drawing machine 3: Extruder 4: Base 5: Cooling roll 6: Winder 7: Transport roll 8: Thickness gauge 9: Control means 9a: operation amount calculation means 9b: Operation amount correcting means 9c: Operation amount output means 10: Thickness adjusting means 11: Gap 21: manipulated variable 40: Corrected operation amount

   ─────────────────────────────────────────────────── ─── Continued front page    F-term (reference) 4F207 AG01 AP11 AR12 KA01 KA17                       KL76 KL84 KM05 KM15

Claims (7)

[Claims] 1. A raw material is extruded using a die equipped with N (N: a natural number of 2 or more) thickness adjusting means, molded into a sheet, and the operation amount output to the thickness adjusting means is controlled. A method for manufacturing a sheet for controlling the thickness of the sheet, wherein the continuous M of the operation amount of the thickness adjusting means is used.
Based on a process model that represents the relationship between the output operation amount and the sheet thickness to be obtained by this so that the variation in the operation amount output to the individual (M: a natural number of 2 or more and N or less) thickness adjusting means is reduced. Then, the sheet manufacturing method is characterized in that the operation amount output to the M continuous thickness adjusting means is corrected. 2. An operation amount (u ₁ , u ₂ , ..., U _M ) ^T output to the continuous M thickness adjusting means is a vector U, and each thickness adjusting means when each operation amount is output. The sheet thickness measurement values (y ₁ , y ₂ , ..., Y _M ) ^T corresponding to M are defined as a vector Y, and the process model is Y = AU (A is M
X M matrix), the operation amount vector U before correction is represented by M eigenvectors v _i of matrix A (i =
, 1, ..., M) when decomposed into eigenvectors a _i (i = 1, 2, ..., M) and eigenvalues λ _i (i = 1, 2, 1) corresponding to the eigenvectors.・ ・ ・
, M) and a predetermined threshold value T ₁ (0 <T ₁ <1), the corrected manipulated variable vector U ′ = (u ₁ ′, u ₂ ′, ...,
The sheet manufacturing method according to claim 1, wherein u _M ') ^T is derived by the following formula. Expression (1) 3. An operation amount (u ₁ , u ₂ , ..., U _M ) ^T output to the M continuous thickness adjusting means is a vector U, and each thickness adjusting means when each operation amount is output. The sheet thickness measurement values (y ₁ , y ₂ , ..., Y _M ) ^T corresponding to M are defined as a vector Y, and the process model is Y = AU (A is M
X M matrix), the operation amount vector U before correction is represented by M eigenvectors v _i of matrix A (i =
, 1, ..., M) when decomposed into eigenvectors a _i (i = 1, 2, ..., M) and eigenvalues λ _i (i = 1, 2, 1) corresponding to the eigenvectors.・ ・ ・
, M) and a predetermined threshold value T ₂ (0 <T ₂ <1), the corrected manipulated variable vector U ′ = (u ₁ ′, u ₂ ′, ...,
The sheet manufacturing method according to claim 1, wherein u _M ') ^T is derived by the following formula. Expression (2) 4. A sheet produced by the method according to claim 1. 5. N (N: a natural number of 2 or more) thicknesses at corresponding positions based on the sheet thickness measurement value of each portion in the width direction measured by the thickness measuring means for measuring the thickness distribution in the width direction of the sheet. A control device for giving an operation amount to an adjusting means, wherein variation in the operation amount output to continuous M (M: a natural number of 2 or more and N or less) thickness adjusting means among the operation amounts of the thickness adjusting means is small. As described above, there is provided a means for correcting the operation amount output to the continuous M thickness adjusting means based on the process model representing the relationship between the output operation amount and the sheet thickness to be obtained thereby. Characteristic sheet thickness control device. 6. A step of inputting a measured value of the thickness of each part in the width direction of the sheet, a step of calculating a difference between the target value of the thickness of each part and the measured value, and N based on the difference of each part. A program for causing a computer to realize a step of calculating an operation amount output to each (N: a natural number of 2 or more) thickness adjusting means, wherein the step of calculating the operation amount is a continuous operation among the calculated operation amounts. A process model that represents the relationship between the output operation amount and the sheet thickness to be obtained by the operation amount so that the variation in the operation amount output to the M (M: a natural number of 2 or more and N or less) thickness adjusting means is reduced. A program including a step of correcting the operation amount based on the above, and outputting each corrected operation amount to each of the thickness adjusting means. 7. A computer-readable storage medium storing the program according to claim 6.