JP2016056022A - Web winding method and web winding device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress the occurrence of a wrinkle, a slip and a gauge band during winding.SOLUTION: In a web winding method, a web W is wound around a winding core while a winding tension Tw is changed depending on a winding diameter. The distribution of thicknesses in a width direction of the web W is measured. The thickest part in the width direction of the web W is extracted. The winding tension is set on the basis of the thickest part.SELECTED DRAWING: Figure 8

Description

  The present invention relates to a winding technique for winding a long web such as a plastic film.

  In recent years, so-called printed electronics, in which electronic circuits are directly printed on a thin and flexible plastic web substrate, has attracted attention. With advances in printed electronics, for example, high-performance flexible electronic devices have been put into practical use in lithium ion secondary batteries, solar cells, organic EL panels, electronic papers, etc. With the expansion of the market for these industrial products The demand for flexible electronic devices is also increasing.

  As a printing method suitable for mass production, there is a so-called roll-to-roll method in which printing is performed while continuously unwinding a web from an original fabric, and the printed web is wound into a roll. If printing is repeated using the roll-to-roll method, even a flexible electronic device having a complicated electronic circuit can be mass-produced. Therefore, attempts have been made to mass-produce flexible electronic devices by applying the technology of printed electronics to a roll-to-roll printing process.

  However, in the roll-to-roll printing process, various problems that may adversely affect the accuracy of printing and processing may occur during web winding. Suppressing these problems will reduce the mass production of flexible electronic devices. It has become an important issue to realize. The main problems are shown in FIGS.

  FIG. 1 shows a deformation of the web that occurs in the winding direction inside the roll, and is a defect in which wrinkles that wave in the circumferential direction are formed on the end face of the roll (also called wrinkle: star defect). FIG. 2 shows a roll collapse, which is a defect in which a web shift is formed on the end face of the roll in the axial direction (slip: also called a telescope).

  FIG. 3 shows a problem that an annular linear protrusion is formed on the surface of the web (gauge band). The gauge band is generated due to uneven thickness (unevenness) in the width direction of the web. That is, the thickness of the web is not uniform, and even if the tolerance defined by the standard is satisfied, a slight thickness distribution of several μm or nm level exists in the width direction. A gauge band is generated when such thick parts and thin parts overlap each other in multiple layers. Thickness unevenness in the width direction has a problem of increasing not only the gauge band but also the variation in stress distribution inside the roll.

  In order to suppress these problems, it is necessary to wind the web with an appropriate winding tension in accordance with the state of the web, but setting the winding tension is not easy. The wound web not only compresses the inner layer web but also the outer layer web. Therefore, when the number of windings and the winding tension change, the stress applied to the wound web changes accordingly. That is, since the distribution of the internal stress is not fixed unless the winding is finished, it is very difficult to appropriately predict and set the winding tension.

  Conventionally, as one of the winding tension setting methods, a method of reducing the winding tension according to the winding radius (so-called taper tension) is known. However, since the taper tension is based solely on experience, it cannot be said to be appropriate, has a variation in setting, requires time and labor, and has a difficulty in lack of expandability.

  Therefore, a method for analyzing the internal stress of the winding roll using a theoretical model for winding the web and setting an optimum winding tension based on the analysis result has been studied (for example, Patent Document 1, Patent Document). 2, Non-Patent Document 1). In particular, Non-Patent Document 1 discloses a basic technique of a technique for analyzing the internal stress of a winding roll based on a theoretical model, and this technique is also used in the present invention.

  As shown in FIG. 4, it is clarified that the wrinkles and slips are closely related to the radial stress σr and the tangential stress σt acting on the web of each layer inside the roll, as shown in FIG. For example, wrinkles occur when the winding tension is too high and the tangential stress σt becomes a negative value on the web inside the roll and a compressive force acts in the circumferential direction. In addition, slip occurs when the winding tension is too low to generate a radial stress σr sufficient to obtain an appropriate frictional force between the webs.

  Patent Document 1 discloses a method for setting a winding tension using a Hakie model or an extended Hakie model obtained by extending the Hakie model as a theoretical model. In Patent Document 1, under the assumption that the thickness of the web in the width direction is uniform, the internal stress is analyzed using these theoretical models, and the winding tension is optimized along with the load of the nip roller, thereby causing wrinkles and wrinkles. Slip generation is suppressed.

  On the other hand, since the gauge band is generated due to thickness unevenness in the web width direction, it is necessary to consider the thickness unevenness in the web width direction in order to suppress the occurrence of the gauge band. Therefore, in the method of Patent Document 1 in which the thickness unevenness is not taken into consideration, the generation of the gauge band cannot be suppressed.

  On the other hand, in Patent Document 2, the internal stress is analyzed using a theoretical model that assumes a web having uneven thickness in the width direction. Specifically, in Patent Document 2, a plurality of divided models are created by cutting a web roll in the width direction, and analysis is performed for each divided model. Then, a dummy roll for evaluation is produced by actually winding the same web as the web roll to be manufactured, and the defect is determined from the stress for each diameter calculated by each divided model and the diameter at which the defect is generated in the dummy roll. An optimum take-up tension is set by obtaining a failure occurrence stress range that can be generated and recalculating the stress until stress at each diameter is not included in the failure occurrence stress range.

  However, in Cited Reference 2, a specific web having a thick knurl at both ends in the width direction is targeted, and the tension of each divided model is calculated on the basis of the web shape. It is not suitable for suppressing a gauge band generated due to thickness unevenness distributed in the entire direction.

  A web winding device for the purpose of suppressing a gauge band has also been proposed (Patent Document 3). In Patent Document 3, the inside of the pressing roll is partitioned into a plurality of pressure-adjustable chambers so that the outer diameter and the hardness of the outer peripheral surface of the pressing roll (corresponding to a nip roll) can be adjusted at a plurality of positions in the width direction. Yes. And based on the thickness distribution of the web measured in advance, the gauge band is suppressed by changing the outer shape of each part of the pressing roll and the hardness of the outer peripheral surface so as to follow the shape of the web to be wound. .

JP 2012-46261 A JP 2013-180879 A JP 2013-6655 A

Hashimoto, “Basic Web Handling Theory and Applications”, Processing Technology Research Group, April 2008

  The location and number of gauge bands are not uniform. Therefore, in order to suppress the gauge band with high accuracy, it is necessary to subdivide the web in the width direction. However, in the method of Patent Document 3, there is a limit to the subdivision of the chamber of the press roll, and the suppression of the gauge band is required. The accuracy must be low. If the chamber of the press roll is subdivided, the structure of the press roll becomes complicated and the control becomes difficult.

  Accordingly, an object of the present invention is to provide a web winding method and a web winding apparatus that are relatively easy to put into practical use and that are particularly effective in suppressing the occurrence of gauge bands.

<First invention>
The first aspect of the present invention is a web winding method for winding a web around a winding core if the winding tension is changed in accordance with the winding diameter. A first step of measuring a thickness distribution in the width direction of the web; a second step of extracting a thickest portion having the largest thickness in the width direction of the web; and the winding based on the thickest portion. And a third step of setting a tension.

  That is, according to the web winding method of the present invention, the thickness distribution in the width direction of the web is measured, and the winding tension is set based on the thickest portion having the largest thickness.

  Gauge bands tend to occur in areas with a large thickness in the width direction of the web. Therefore, before winding up the web, specify the thickest part with the greatest thickness and set the winding tension on the basis of the thickest part. By changing, not only wrinkles and slips, but also gauge bands can be suppressed.

  Further, in the second step, the web is divided into a plurality of web elements in the width direction, an average thickness value is obtained for each web element, and the thickest web element having the largest average thickness value is extracted. In the third step, from the average value of the thickness of the thickest web element, the tangential stress for each winding diameter acting on the thickest web element after winding is analyzed based on a theoretical model, It is preferable to perform the process of setting the winding tension so that the tangential stress does not become a negative value.

  By doing so, the thickest web element can be handled as a roll of a conventional theoretical model, so that the processing load can be greatly reduced. Since the winding tension can be set based on the theory instead of the rule of thumb, the accuracy and expandability can be improved.

  In this case, further, in the third step, the elastic shrinkage amount after winding of the thickest web element is analyzed based on a theoretical model, and the winding tension is corrected based on the elastic shrinkage amount. More preferably.

  In this way, it becomes possible to set the winding tension with higher accuracy in consideration of the amount of elastic shrinkage of the web after winding, so that the accuracy of the winding tension to be set is improved and more stable wrinkles, Slip and gauge band suppression can be realized.

  Examples of the web winding device that winds the web using such a web winding method include a motor that rotationally drives the winding core, a tension adjusting device that adjusts the winding tension, and the tension adjusting device. And a control device that controls the control device, and the control device may include a tension setting unit that executes the processes of the second step and the third step.

  According to this web winding device, since it can be realized simply by adding software to an existing system, it is excellent in versatility.

  Further, the control device includes a tension correction unit that analyzes an elastic shrinkage amount of the thickest web element after winding based on a theoretical model and corrects the winding tension based on the elastic shrinkage amount. It is preferable to make it.

  This makes it possible to set the winding tension with higher accuracy, so that wrinkles, slips, and gauge bands can be more stably suppressed.

<Second invention>
The second aspect of the present invention performs a stress analysis in which a radial stress distribution inside a roll formed by winding a web around a winding core is analyzed using a theoretical model, and a winding tension is calculated based on the analysis result. This is a web winding method for winding a web while changing.

  A tension function setting step for setting a tension function representing the winding tension with respect to the radial position of the roll, and a relational expression for gradually bringing the inter-layer friction force of the web inside the roll to a critical friction force at which slip can occur. An objective function defining step for defining an objective function including: a first constraint defining step for defining a first constraint condition in which the interlayer friction force is greater than or equal to the critical friction force; and a maximum value of the radial stress is a gauge band A second constraint condition defining step for defining a second constraint condition that is less than or equal to a critical radial stress that can occur, and from the predetermined initial tension under the constraint by the first constraint condition and the second constraint condition, A tension function optimizing step for optimizing the tension function by repeating the calculation of the tension function until the objective function is minimized.

  According to this web winding method, first, the objective function including the relational expression for making the interlayer friction force of the web asymptotically approach the critical friction force under the constraint of the first constraint that the interlayer friction force is equal to or greater than the critical friction force is minimized. Since the calculation is repeated until the tension function is optimized, an appropriate lower limit of the radial stress at which slip cannot occur can be specified, and the tension function that can suppress the occurrence of slip can be optimized with high accuracy.

  Furthermore, since the tension function is optimized under the second constraint that the maximum value of the radial stress is equal to or less than the critical radial stress at which the gauge band can be generated, the radial stress at which the gauge band cannot be generated. Can be specified, and the tension function that can suppress the occurrence of gauge bands can be optimized. Therefore, by winding the web while changing the winding tension based on the tension function optimized by such stress analysis, it is possible to wind the web while effectively suppressing the occurrence of gauge bands and slips. It becomes possible.

  Moreover, once the tension function optimized by the stress analysis is acquired, if it is the same type of web, then it can be appropriately wound by using the tension function. Therefore, it is excellent in expandability and convenience. Since it can be realized only by mounting the corresponding software without making a major mechanical change, the existing web winding device can be used, and practical application can be made relatively easily.

  In particular, it is preferable that the tangential stress inside the roll does not become a negative value.

  If it does so, generation | occurrence | production of wrinkles can also be prevented and the main malfunction which generate | occur | produces at the time of winding can be suppressed.

  Specifically, the roll is divided into a plurality of roll elements in the width direction, and a tension distribution that is generated during winding due to thickness unevenness in the width direction of the web is acquired using the plurality of roll elements. The step may be further provided, and the stress analysis may be performed by applying the theoretical model to each of the roll elements as in the first invention.

  As described above, gauge bands are generated due to uneven thickness in the width direction of the web. Therefore, by performing stress analysis in consideration of uneven thickness in the width direction, the generation of gauge bands can be suppressed with higher accuracy. It becomes possible to do. When a roll is divided into a plurality of roll elements and a tension distribution generated during winding due to thickness unevenness is acquired, stress analysis is performed by applying a theoretical model to each of these roll elements. It can be handled as a one-dimensional problem using a model, reducing the analysis burden.

  Further, the objective function may be defined further including a relational expression for minimizing a difference between each maximum value and minimum value of the radial stress obtained for each roll element in the objective function defining step. It may be.

  By doing so, the upper limit of the radial stress at which no gauge band can be generated can be specified more appropriately, and the tension function can be optimized with higher accuracy.

  Further, as in the first invention, the stress analysis may be performed in consideration of the amount of elastic shrinkage of the web wound around the core.

  When the web has elasticity, the web inside the roll is elastically deformed by tightening and contraction occurs. Therefore, in such a case, if the stress analysis is performed in consideration of the amount of elastic contraction, the stress analysis can be performed with higher accuracy, so that the optimization of the tension function can be performed with higher accuracy.

  In particular, the average value of the thickness of the web is preferably 140 μm or less.

  The gauge band tends to be generated more easily as the web thickness is thinner and flexible. However, from the verification test results described later, a good result was observed even on a web with a large average thickness of 140 μm. If the web has a thickness less than that and easily generates a gauge band, the generation of a gauge band or the like can be more effectively suppressed.

  A web winding method according to a second aspect of the invention is, for example, a web winding device that winds a web around a winding core while changing a winding tension, and a motor that rotationally drives the winding core, and a rotation speed of the motor. The tension is applied to a web winding device provided with a tension adjusting device that controls the winding tension by controlling the tension, and the tension adjusted by the tension adjusting device is optimized using the web winding method as described above. It may be performed based on a function.

  According to the web winding method of the second invention, since a special mechanical structure is not required, the web winding method can be applied to a web winding device having such a simple structure. Therefore, it can be realized relatively easily without requiring a high cost.

  According to the web winding method and web winding apparatus of the present invention, it is relatively easy to realize, and it is possible to effectively suppress problems such as a gauge band that occurs during winding.

It is the schematic which illustrates the malfunction (wrinkle) which generate | occur | produces at the time of winding of a web. It is the schematic which illustrates the malfunction (strip) which generate | occur | produces at the time of winding of a web. It is the schematic which illustrates the malfunction (gauge band) which generate | occur | produces at the time of winding of a web. It is a figure for demonstrating the stress relationship inside a roll. It is the schematic which shows the web winding apparatus in 1st Embodiment. It is a schematic sectional drawing of the web which a gauge band generate | occur | produces after winding. It is the schematic which shows the web winding apparatus in 2nd Embodiment. It is a figure for demonstrating the pre-process of stress analysis. It is the schematic which shows the web winding apparatus in 3rd Embodiment. It is a flowchart which shows the flow of the method of analyzing the amount of elastic shrinkage after winding of a web. It is a figure for demonstrating the specific process of a relaxation radius. It is a figure for demonstrating the specific process of a relaxation radius. It is a figure for demonstrating the conventional theoretical model. It is a figure for demonstrating the calculation process of the radius after elastic contraction. It is a figure for demonstrating the calculation process of the radius after elastic contraction. It is a graph which shows the verification test result about the stress analysis in 3rd Embodiment. It is a graph which shows the verification test result about the stress analysis in 3rd Embodiment. It is the schematic which shows the web winding apparatus of 4th Embodiment. It is a flowchart of a stress analysis process. It is a flowchart of a winding tension | tensile_strength setting step. It is the schematic which shows an example of a tension function. It is a figure for demonstrating a tension function optimization step. It is a figure for demonstrating a 2nd constraint condition. It is a figure for demonstrating a 1st relational expression. It is a figure for demonstrating a 2nd relational expression. It is a figure which shows the verification test result in 4th Embodiment, and represents the analysis result of the optimized tension | tensile_strength of a thin film web. It is a figure which shows the verification test result in 4th Embodiment, and represents the analysis result of the tension | tensile_strength optimized for the thick film web. It is a figure which shows the verification test result in 4th Embodiment, and represents the analysis result of the thickness distribution and radial direction stress distribution of a thin film web. It is a figure which shows the verification test result in 4th Embodiment, and represents the analysis result of thickness distribution and radial direction stress distribution of a thick film web. It is a figure which shows the verification test result in 4th Embodiment, and represents the analysis result of the tangential direction stress of a thick film web.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. However, the following description is merely illustrative in nature and does not limit the present invention, its application, or its use.

<First Embodiment>
(Web winding device)
In FIG. 5, the outline | summary of 1 A of web winding apparatuses of this embodiment is shown.

  The web winding device 1A is a device that winds a web W which is unwound from a roll mounted on an unillustrated unwinding device and conveyed while being guided by a guide roller or the like into a roll shape.

  The web winding device 1A includes a support shaft 2, a motor 3, a nip roller 4, a load adjusting device 5, a tension adjusting device 6, a control device 7, and the like.

  The support shaft 2 supports the core 8 around which the web W is wound so as to be detachable. The motor 3 is connected to the support shaft 2 and rotationally drives the winding core 8 via the support shaft 2. A tension adjusting device 6 is attached to the motor 3. The tension adjusting device 6 controls the rotational speed of the motor 3 and adjusts the winding tension Tw of the web W wound around the winding core 8. That is, the winding tension Tw of the web W wound around the core 8 is changed by continuously increasing or decreasing the rotation speed of the motor 3 by the tension adjusting device 6.

  The nip roller 4 is configured to advance and retreat toward the core 8 and press-contact with the outer peripheral surface of the roll of web W (also simply referred to as roll R) wound around the core 8. The nip roller 4 is provided with a load adjusting device 5 that adjusts the load pressed against the roll R. The load adjusting device 5 adjusts the load acting between the nip roller 4 and the roll R.

  The control device 7 is a so-called computer system that comprehensively controls the tension adjusting device 6, the load adjusting device 5, and the motor 3. The control device 7 is provided with hardware such as a CPU, a memory, a monitor, and a keyboard, and software such as a control program and various data is mounted.

  The control device 7 includes a tension control unit 7a for controlling the tension adjustment device 6, a load control unit 7b for controlling the load adjustment device 5, a storage unit 7c for storing various data such as mathematical formulas used for calculation, and the like. Yes.

(Web)
The web W is made of an elastic plastic sheet such as PE, PP, and PET. The web W may be a single sheet or a laminate sheet formed by bonding a plurality of sheets. Even when such a web W satisfies a predetermined standard (for example, JISK7130), the width direction is continuous in the winding direction due to deviation of mold ridges or sheet stacking during molding. There is a tendency that unevenness of thickness is easily generated.

  Since the web W is wound around the core 8 with, for example, several hundred turns, if there is such a thickness unevenness, the difference in the total thickness after the end of winding is large between the thick part and the non-thick part. Become. For this reason, in the web W having a thickness unevenness as emphasized in FIG. 6, a gauge band is generated at a portion where the thickness of the web W in the width direction is large.

  Therefore, in the web winding device 1A of the present embodiment, before winding the web W, the thickness distribution in the width direction of the web W is measured to identify a portion having a large thickness, and the winding is performed based on the specific portion. By changing the take tension Tw, not only wrinkles and slips but also a gauge band can be suppressed.

(Web winding method)
In this method, first, the thickness distribution in the width direction of the web W is measured (first step). Usually, the thickness of the web W is about several hundreds μm, and the thickness unevenness is 1 μm or less. Therefore, the thickness distribution in the width direction of the web W is continuously or intermittently measured using a measuring instrument capable of measuring the thickness in microns with high accuracy.

  Although the thickness distribution may be measured manually, it is preferable that the thickness distribution is automatically measured using an automatic measuring instrument. For example, an automatic measuring instrument that scans in the width direction of the web W and measures the thickness thereof is electrically connected to the control device 7. Then, it is conceivable that the measured value measured by the automatic measuring instrument is automatically input to the control device 7.

  Then, the thickest part with the largest thickness is extracted from the width direction of the web W (second step). When the thickness distribution is manually measured, the thickness of the thickest part extracted is input to the control device 7. When the measurement is automatically performed using an automatic measuring instrument, the control device 7 may automatically extract the thickest part by comparing the measured values.

  The control device 7 sets the winding tension Tw based on the inputted thickness of the thickest part (third step).

  The storage unit 7c stores data such as a reduction rate of the winding tension Tw set based on an empirical rule. The tension controller 7a and the load controller 7b control the tension adjusting device 6 and the load adjusting device 5 based on these data.

  When the tension control unit 7a and the load control unit 7b control the tension adjusting device 6 and the load adjusting device 5, the web W is applied to the core 8 in a state where the web W is adjusted to the optimum winding tension Tw according to the winding diameter. It is set to be wound up.

  In the web winding device 1A, the winding tension Tw is set based on the inputted thickness of the thickest part. Therefore, since the winding tension Tw at the thickest part where the gauge band is most likely to occur is optimized, wrinkles, slips, and gauge bands at the thickest part can be suppressed.

  Since not only the thickest portion but also the other thick portions, the winding tension Tw is smaller than that of the thickest portion, so that wrinkles, slips, and gauge bands can be suppressed. Therefore, the entire web W can be appropriately wound while suppressing the generation of wrinkles, slips, and gauge bands.

Second Embodiment
In the first embodiment, the winding tension Tw is adjusted based on an empirical rule, which may be insufficient in terms of accuracy and expandability. Therefore, in the present embodiment, the winding tension Tw is adjusted by stress analysis based on a theoretical model so that accuracy and expandability can be improved.

  FIG. 7 shows a web winding device 1B of the present embodiment. In addition to the configuration of the first embodiment, the control device 7 is further provided with a tension setting unit 7d that sets the winding tension Tw based on the theoretical model. Since other configurations are the same as those in the first embodiment, the same reference numerals are used and the description thereof is omitted (the same applies to the third embodiment described later).

  The tension setting unit 7d is mounted with a control program derived based on a conventional theoretical model, and the storage unit 7c stores mathematical formulas and data used in the control program.

  Examples of the conventional theoretical model used here include the Hakiel model and the extended Hakiel model disclosed in Patent Document 1. In the case of the present embodiment, since the nip roller 4 is provided, it is preferable to use an extended Hakiel model in which the weight of the nip roller 4 and air entrainment are taken into consideration. Since these theoretical models are publicly known, a detailed description thereof will be omitted.

  In this embodiment, pre-processing that facilitates stress analysis is performed in the second step.

  Specifically, as shown in FIG. 8, the web W is divided into a plurality of web elements Wa in the width direction. Then, the average value of the thickness is obtained for each web element Wa, and the thickest web element Wa 'having the largest average thickness value is extracted.

  In this way, by dividing the web W in the width direction and extracting the thickest web element Wa ′ having a uniform thickness in the width direction, the thickest web element Wa ′ is handled as the roll R of the conventional theoretical model. Will be able to. Thereby, the conventional theoretical model can be applied as it is in the analysis of the internal stress of the thickest web element Wa '.

  Then, in the third step, from the average value of the thickness of the thickest web element Wa ′, the tangential stress for each winding diameter acting on the thickest web element Wa ′ after winding is calculated based on the conventional theoretical model. The winding tension Tw is set so that the tangential stress does not become a negative value from the start of winding until the end of winding.

  In the case of this embodiment, when analyzing the internal stress requiring complicated processing, the conventional theoretical model can be applied as it is, and only the thickest web element Wa ′ needs to be analyzed, not the entire web W. The processing burden can be greatly reduced.

  Since the winding tension Tw can be set based on the theory instead of the rule of thumb, the accuracy and expandability can be improved.

<Third Embodiment>
Since the web W made of a plastic sheet or the like has elasticity, the inner layer web W wound in a roll R shape is elastically deformed and contracted by the tightening action of the outer layer web W. On the other hand, since the elastic model of the web W is not considered in the theoretical model of the second embodiment, there may be a case where the accuracy is insufficient when a high winding quality is required.

  Therefore, in this case, the present embodiment is configured so that the winding tension Tw can be corrected so that the adjustment can be performed with higher accuracy.

  FIG. 9 shows a web winding device 1C of the present embodiment. In addition to the configuration of the second embodiment, the control device 7 further includes a tension correction unit 7e. The tension correction unit 7e cooperates with the storage unit 7c to analyze the amount of elastic shrinkage after winding the web W based on a theoretical model in the third step, and based on the amount of elastic shrinkage, the thickest web element A process of correcting the winding tension Tw of Wa ′ is executed.

(Analysis of elastic shrinkage)
Next, a method for analyzing the amount of elastic shrinkage after winding the web W will be described in detail.

  As shown in FIG. 10, from the first layer wound around the core 8 to the outermost layer n-th layer, a relaxation radius specifying process (step S100), a radial stress calculation process (step S200), and after elastic contraction Each processing of the radius calculation processing (step S300) is performed for each winding layer.

  In the conventional theoretical model, the roll R is handled as a stack of thin cylinders having an infinite width, and the radial distribution in the width direction of the roll R is not considered. Therefore, in the analysis, in order to consider the radial distribution in the width direction of the roll R, the roll R is divided into a plurality of roll elements Re in the width direction, and the radial stress σr is analyzed for each roll element Re. At that time, the thickness unevenness of the web W does not change in the winding direction but is distributed in the width direction of the roll R. Further, it is assumed that the radius in the width direction of each roll element Re is constant.

  In order to analyze the distribution of the radial stress σr in the width direction inside the roll R, it is necessary to grasp the distribution of the winding tension Tw generated by the thickness unevenness in the width direction of the web W. Therefore, in the present web winding method, a process of acquiring the distribution of the winding tension Tw in the width direction of the roll R using the divided roll elements Re is performed. Specifically, the distribution of the winding tension Tw for each roll element Re in the width direction of the roll R is acquired by introducing the concept of the relaxation radius into the balance distribution balance equation.

(Identification of relaxation radius)
FIG. 11 illustrates a state in which the roll R is formed by winding the web W having uneven thickness around the core 8. The roll R is divided in the width direction and is divided into M roll elements Re having 1 to M columns. Due to the unevenness in thickness, when the i-th layer web W (Lapi) is wound, a region in contact with the web W (Lapi-1) immediately below and a region in non-contact with each other are generated.

  Therefore, for each roll element Re, a web W that is in contact with the i-th layer web W and a web W that is not in contact with the web W are set. As shown in FIG. 12, the shape of the web W in contact with the web W immediately below follows the shape of the web W of the (i-1) th layer, and the web W not in contact with the web W directly below has a winding diameter. Treat as a constant cylinder. Then, a new concept of relaxation radius is introduced, and the radius of the cylinder is defined as relaxation radius Ro.

  In such a case, assuming that the radius of the roll element Re in the j-th row when the web W is wound up to the i-th layer is r (i, j), it acts on the i-th layer web W in the j-th roll element Re. The tension Tw (i, j) to be expressed is expressed by the following equation (1).

Eθ in Equation (1) represents the Young's modulus of the target web W. Similarly, W is the width of roll R, _{tw. avg} represents the average value of the thickness of the web W, M represents the number of roll elements Re, and ν represents the Poisson's ratio.

  Since the total value Tw (i) of the tensions Tw (i, j) is equal to the winding tension Ta for winding the web W of the i-th layer, the following tension distribution balancing formula (2) is established.

  Ta in Equation (2) is a provisional winding tension, and is set in advance as a calculation condition for each position of the roll R in the radial direction. A relaxation radius Ro that satisfies this equation (2) is obtained. For example, the calculation is repeated while changing the value of the relaxation radius Ro, and the relaxation radius Ro (i) that satisfies Formula (2) within a predetermined error range is specified. By applying the specified relaxation radius Ro (i) to the equation (1), it becomes possible to calculate the tension Tw (i, j), and the roll element Re in the width direction of the roll R. The distribution of the winding tension Tw can be acquired. As a result, the winding tension Tw of the thickest web element Wa 'can be corrected.

(Calculation of radial stress)
Next, the radial stress σr (i, j) of the i-th layer in the thickest web element Wa ′ is calculated based on the conventional theoretical model shown in FIG. Since the calculation method of the radial stress σr is disclosed in Patent Document 1 and Non-Patent Document 1, only the main points are shown here, and the specific description thereof is omitted.

For example, the following equation (3) representing the innermost layer boundary condition and equation (4) representing the outermost layer boundary condition are applied to equation (5), and the incremental dσ of the radial stress in the i-th layer is obtained by successive approximation. _r (i, j) is calculated.

The radial stress σr (i, j) of the i-th layer is obtained by adding the increment dσ _r (i, j) from the i + 1th layer to the n-th layer (outermost layer) using the following equation (6). Desired.

(Calculation of radius after elastic contraction)
By using Hertz's contact theory, the elastic shrinkage of the thickest web element Wa ′ is calculated.

  As shown in FIG. 14, the contact between the first layer web W and the core 8 is assumed to be a contact between a plane and a cylinder, and as shown in FIG. Assume contact between cylinders. It is assumed that the web W does not deform in the width direction.

  In such a case, the contact half width b (i, j) is expressed by the following equations (7) and (8).

  Expression (7) is an expression representing the contact half width b (i, j) of the first layer, and Expression (8) is an expression representing the contact half width b (i, j) of the second layer or more. In these equations, P (i, j) represents the radial load, that is, the radial stress σr, and E represents the radial Young's modulus of the web W.

  When the amount of elastic shrinkage in the radial direction is Δr (i, j), Δr (i, j) is expressed by the following equation (9).

  Using these equations, the elastic shrinkage Δr (i, j) in the radial direction is obtained.

  By applying the obtained elastic shrinkage amount Δr (i, j) to the following equation (10), the provisional radius r (i, j) after elastic shrinkage is obtained.

  That is, the web element Wa contracts by the amount of elastic contraction Δr (i, j) from the roll R used first, and an error occurs in the analysis by that amount.

Therefore, using the obtained temporary radius r (i, j), a new relaxation radius R ₀ (i) is specified, and based on the relaxation radius R ₀ (i), radial stress is calculated and elastic contraction is performed. The amount is calculated. The relaxed radius R ₀ (i), compared with the relaxed identified just before the radius R ₀ (i), for example, 1%, etc., to perform the repetitive operation to converge to within a certain range.

When the relaxation radius R ₀ (i) converges, the temporary radius r (i, j) is specified as the radius r (i, j) after contraction.

Subsequently, the tension is calculated by applying the specified radius r (i, j) after contraction to the equations (1) and (2), and the equations (3), (4), and (5) are calculated. Is applied to the i-th layer radial stress increment dσ _r (i, j), and is applied to the equation (6) to calculate the i-th layer radial stress σr (i, j). .

  By repeating such a series of processes from the first layer to the n-th layer, the radial stress σr (i, j) for each wound layer is calculated. The tangential stress σt (i, j) for each winding layer can be calculated from these radial stresses σr (i, j).

  By performing such stress analysis, it is possible to set the winding tension Tw with higher accuracy in consideration of the elastic shrinkage of the web W after winding.

  In the web winding device 1C of the present embodiment, such calculation processing is executed by the correction control unit 7e, and the winding tension Tw set by the tension setting unit 7d is corrected. As a result, the accuracy of the set winding tension Tw is improved, and more stable wrinkle, slip, and gauge band suppression can be realized.

(Verification test results)
16 and 17 show the test results verified for these stress analyses.

  FIG. 16 is a graph comparing the roll radii (outermost diameter), where the solid line indicates the analysis result after correction processing, the two-dot chain line indicates the actual measurement value, and the broken line indicates the web thickness added for the winding layer. Each roll radius is shown.

  As is apparent from FIG. 16, the analysis result approximates the actual measurement value, and it can be seen that advanced prediction can be realized.

  FIG. 17 is a graph comparing the distributions of radial stresses. The plot is an actual measurement value (average value of three measurements), and the broken line is an analysis result when elastic contraction is not taken into consideration (in the second embodiment). The solid line represents the analysis result (corresponding to the third embodiment) when elastic contraction is considered.

  It can be seen that when the elastic contraction is considered, the prediction accuracy of the radial stress is improved as much as the elastic contraction is not considered.

  Therefore, it can be seen that if the winding tension Tw is set in consideration of elastic contraction, highly accurate winding can be performed, and wrinkles, slips, and gauge bands can be more effectively suppressed.

<Fourth embodiment>
The web winding method of this embodiment is a further evolution of the web winding method of the third embodiment. The web winding method includes a stress analysis process for analyzing an optimal tension function using a theoretical model, and the web W while changing the winding tension Tw based on the optimized tension function obtained thereby. And a web winding process for winding.

(Web winding device)
FIG. 4 shows a web winding apparatus 1D that can realize the web winding method. About the structure similar to the web winding apparatus of 2nd Embodiment and 3rd Embodiment, the description is abbreviate | omitted using the same code | symbol.

  In addition to the tension control unit 7a, the load control unit 7b, and the storage unit 7c, the control device 7 includes an optimum tension setting unit 7f instead of the tension setting unit 7d and the tension correction unit 7e. The optimum tension setting unit 7f is a further evolution of the tension setting unit 7d and the tension correction unit 7e, and is an important part for performing stress analysis processing, and will be described in detail later.

  The storage unit 7c stores a tension function set for each web W by the optimum tension setting unit 7f. The tension control unit 7a controls the tension adjusting device 6 using a tension function corresponding to the web W to be wound out of the tension functions stored in the storage unit 7c. The load control unit 7b controls the adjustment load adjusting device 5 so that the pressing load of the nip roller 4 is optimized in conjunction with the control of the tension control unit 7a. Thereby, the tension adjusting device 6 winds the web W around the core 8 while changing the winding tension Tw according to the winding diameter in an optimal state.

  In the web winding device 1, the optimum tension setting unit 7 f is provided in the control device 7, but the optimum tension setting unit 7 f may be provided in a computer system different from the control device 7. Then, advanced stress analysis processing can be quickly performed using another high-performance computer system, and only the tension function of each web W obtained there can be introduced into the control device 7. A high processing capacity is not required, and the control device 7 can be simplified.

  Since the thickness of the portion where the gauge band is generated is relatively large, the radial stress σr is relatively large compared to other portions. If the web W of the same type that satisfies the standard and has the same average thickness and material composition (the same type of web W), the thickness unevenness is less than a predetermined tolerance, and therefore a gauge band is generated. Even if the location and the number of occurrences vary for each web W, the radial stress σr of the occurrence site of the gauge band is considered to be almost the same for the same type of web W.

  Therefore, in this web winding method, a radial test σr (critical radial stress σcr) that can generate a gauge band is obtained for each web W by performing a winding test, and this is used as data for stress analysis processing. I use it.

  As a specific example of the winding test, a sheet-like contact type pressure sensor is prepared, and the pressure sensor is wound between the webs W and wound into a roll R shape. Such a winding test is repeated while changing the conditions such as the winding tension Tw. When the gauge band is generated, the pressure sensor measures the radial stress σr of the site where the gauge band is generated. A critical radial stress σcr is set based on the radial stress σr thus obtained.

  The critical radial direction stress σcr is not necessarily set by a winding test, and can be set arbitrarily. For example, the critical radial stress σcr may be set based on an empirical rule, or the critical radial stress σcr may be set based on a physical property value unique to the web, such as a compressive yield stress.

  In the stress analysis process, the critical friction force Fcr is also used as data in order to suppress the occurrence of slip. The critical frictional force Fcr is the minimum frictional force at which slip can occur, and is set by experiment for each web W of the same type, as with the critical radial stress σcr. The critical frictional force Fcr can also be set arbitrarily, and may be set based on an empirical rule, or may be set based on a physical property value unique to the web.

(Web winding process)
When winding the web W using the web winding device 1D, data specifying the web W to be wound is input to the control device 7 using a keyboard or the like. Accordingly, the web winding device 1D is configured such that the tension control unit 7a reads the tension function corresponding to the web W and the tension adjusting device 6 is controlled using the tension function.

  Then, the web W is set in the web winding device 1D, and winding is started. Then, the control device 7 controls the tension adjusting device 6 and the load adjusting device 5 based on the tension function, and winds the web W around the core 8 while changing the winding tension Tw in an optimum state. Therefore, the web W can be wound up while effectively suppressing the occurrence of slips and gauge bands.

(Stress analysis process)
The stress analysis process is the most important process in the disclosed web winding method, and is executed in the optimum tension setting unit 7f. Specifically, the distribution of the radial stress σr inside the roll R formed by winding the web W around the core 8 so that the occurrence of slip and gauge bands can be effectively suppressed when the web W is wound. Is processed using a theoretical model, and the optimum tension setting unit 7f executes a process of setting an optimum tension function for the roll R.

  Next, details of this stress analysis processing will be described. As shown in FIG. 19, the stress analysis process includes a tension distribution acquisition step S1, a radial stress analysis step S2, an elastic contraction amount calculation step S3, a winding tension setting step S4, and the like. In the stress analysis process, analysis using a theoretical model is performed.

  Specifically, in the web winding method of the present embodiment, as in the third embodiment, the concept of the relaxation radius is introduced into the tension distribution balance equation, so that each roll element Re in the width direction of the roll R is separated. The process of acquiring the distribution of the winding tension Tw at is performed (tension distribution acquisition step S1).

(Identification of relaxation radius)
The method for specifying the relaxation radius is the same as in the third embodiment. That is, as shown in FIG. 11, for each roll element Re, a web W that is in contact with the directly below web W and a web W that is not in contact are set, and the web W that does not contact the directly below web W has a constant winding diameter. Treated as a cylinder, the radius of the cylinder is defined as the relaxation radius Ro.

  Then, the relaxation radius Ro (i) that satisfies the balance distribution equation (2) of the tension distribution is specified, and the specified relaxation radius Ro (i) is applied to the equation (1). As a result, the tension Tw (i, j) can be calculated, and the distribution of the winding tension Tw for each roll element Re in the width direction of the roll R can be acquired.

(Radial stress analysis step)
In the radial stress analysis step S2, by applying the conventional theoretical model shown in FIG. 13 to each roll element Re and using the obtained distribution of the winding tension Tw, the i layer in the j-th roll element Re The eye radial stress σr (i, j) is calculated. Since the calculation method is the same as the calculation of the radial stress in the third embodiment, a specific description thereof will be omitted.

(Elastic shrinkage calculation step)
In the case where the web W is made of a plastic sheet or the like, by applying the elastic contraction amount calculating step S3, the stress analysis processing considering the elastic contraction amount of the web W can be performed. The elastic contraction amount calculation method performed in the elastic contraction amount calculation step S3 is the same as the calculation of the radius after elastic contraction in the third embodiment, and a specific description thereof will be omitted.

(Take-up tension setting step)
In the winding tension setting step S4, the optimum winding tension Tw is set using the tension distribution obtained by the series of processes described above and the distribution of the radial stress σr. As shown in FIG. 20, the winding tension setting step S4 includes a tension function setting step S11, an objective function definition step S12, a first constraint condition definition step S13, a second constraint condition definition step S14, a tension function optimization step S15, and the like. It consists of The tension function setting step S11, the objective function definition step S12, the first constraint condition definition step S13, and the second constraint condition definition step S14 may be performed before the tension function optimization step S15, and the order thereof. Can be set arbitrarily.

  In the tension function setting step S11, a tension function used for controlling the winding tension Tw is set. FIG. 21 shows an example of the tension function. In this figure, the vertical axis represents the winding tension Tw, and the horizontal axis represents the dimensionless radial position (r / rc, r is an arbitrary radial position, and rc is the radius of the core) indicating the radial position of the roll R. . The tension function is a function representing the winding tension Tw with respect to the radial position of the roll R, and is set using a cubic spline function. The tension function is optimized in the tension function optimizing step S15, and the optimized tension function is stored in the storage unit 7c in a state associated with the information specifying the web W.

  FIG. 22 is an explanatory diagram of the tension function optimization step S15. As a design condition for optimizing the tension function, in this description, the roll R is equally divided in the radial direction, and nine dimensionless radial positions r1 to r9) are specified. Then, design variables ΔTw1 to ΔTw9 are set for each specified dimensionless radius position as the amount of change from the initial tension (a constant tension that is temporarily set as the initial value of the calculation for optimizing the tension function).

  A smooth continuous tension function is set by performing a cubic spline interpolation process on the tension at each dimensionless radial position obtained by adding the change amount of these design variables to the initial tension. The tension function is optimized by repeating the calculation of the tension function until the objective function converges within a predetermined range from the initial tension to the minimum, under the constraints of the first and second constraints. In this way, each design variable to be converged is specified.

μ：ウエブ層間の有効摩擦係数 The first constraint condition is a constraint condition for suppressing the occurrence of slip, and the interlayer friction force (friction force between each layer of the web W) is defined as a critical friction force Fcr or more (first constraint condition defining step) S13). Here, the inter-layer friction force F (i) of the i-th layer web W is defined as follows.

μ: Effective friction coefficient between web layers

  The critical frictional force Fcr is a frictional force that can cause slip as described above, and the occurrence of slip can be suppressed by satisfying the first constraint that it is greater than that. For example, if the critical frictional force Fcr is 3.5 kN, the first constraint condition can be defined as F (i) ≧ 3.5 (kN).

The second constraint condition is a constraint condition for suppressing the occurrence of a gauge band, and the maximum value of the radial stress σr is defined to be equal to or less than the critical radial stress σcr (second constraint condition definition step S14). For example, FIG. 23 shows the distribution of the radial stress σr and the critical radial stress σcr in the width direction of the web W at a certain dimensionless radial position. As shown in the figure, when the maximum value σr _max of the radial stress σr exceeds the critical radial stress σcr, the stress analysis is repeated so that the value is equal to or less than the critical radial stress σcr as indicated by an arrow. The distribution of the radial stress σr is corrected downward by calculation or the like.

なお、制約関数ｇ（Ｘ）は次の式（１３）で与えられ、これら制約の下、巻取張力Ｔｗの最適化の問題は、次の定式（１４）によって表現される。

These constraints are expressed by the following inequality (12).

The constraint function g (X) is given by the following formula (13). Under these constraints, the problem of optimization of the winding tension Tw is expressed by the following formula (14).

The objective function f (X) of the present embodiment is defined using the first relational expression (front term) and the second relational expression (rear term) as shown in the following formula (15). (Objective function definition step S12).

  As shown by arrows in FIG. 24, the first relational expression indicates that the interlayer friction force F (i) of the web W at each dimensionless radial position inside the roll R is asymptotic to the critical friction force Fcr at which slip can occur. This is a relational expression. However, since a sufficient frictional force cannot be maintained near the outermost layer of the roll R, the first relational expression is calculated within a range of 88% or less of the roll R diameter.

  By making the interlayer frictional force of the web W asymptotically approach the critical frictional force Fcr under the constraint of the first constraint condition, an appropriate lower limit of the radial stress σr at which slip cannot occur is specified, so that the optimal tension function Can be performed with high accuracy.

As shown by arrows in FIG. 25, the second relational expression indicates the difference between the maximum value and the minimum value of the radial stress σr in the width direction of the web W obtained at each dimensionless radial position of each roll element Re. This is a relational expression to be minimized (σ _rave : average value of radial stress σr).

  Under the constraint of the second constraint, by minimizing the difference between the maximum value and the minimum value of the radial stress σr in the width direction of the web W obtained at each dimensionless radial position of each roll element Re, Since an appropriate upper limit of the radial stress σr at which a gauge band cannot be generated is specified, the tension function can be optimized with higher accuracy.

  As described above, in this web winding device 1D, after the distribution of the winding tension Tw and the distribution of the radial stress σr generated by the thickness unevenness in the width direction of the web W are accurately grasped, the occurrence of slips and gauge bands is generated. Since the tension function is optimized by calculation using an objective function and constraint conditions that consider the mechanism, and the web W is wound up while changing the winding tension Tw using the optimized tension function, The web W can be wound while effectively suppressing the occurrence of slip and gauge bands.

  Moreover, if the stress analysis process of the web W to be wound is performed to obtain an optimized tension function, then, if the web W is of the same type, the web winding process can be performed simply by selecting a set tension function. Therefore, extensibility and convenience are excellent. Since it can be realized only by mounting the corresponding software without performing a large mechanical change, the existing web winding device can be used and practical application is relatively easy.

<Verification test>
A test was conducted to verify the effect of the optimized tension function. In the test, a web (thin film web) having an average thickness of 3 μm and a web (thick film web) having an average thickness of 140 μm were used for the test, and the tension function was optimized. The distribution of the radial stress σr was analyzed in the case where it was wound up by the above method.

  In the thin film web, a web having an overall diameter of 70 mm was wound around a core having a radius of 7 mm to form a roll having an outer diameter of 12.6 mm. In the thick film web, a roll having an outer diameter of 80 mm was formed by winding a web having a total width of 350 mm around a core having a radius of 45 mm.

  The test results are shown in FIGS. FIG. 26 shows the optimized tension of the thin film web, and FIG. 27 shows the optimized tension of the thick film web. In each case, the solid line indicates the optimized tension, and the broken line indicates the constant tension. The upper part of FIG. 28 shows the thickness distribution of the thin film web, and the lower part of FIG. Similarly, FIG. 29 shows the analysis result of the thickness distribution of the thick film web and the distribution of the radial stress σr. In each lower stage, the solid line shows the analysis result with the optimized tension, and the broken line shows the analysis result with the constant tension.

  As shown in FIGS. 28 and 29, the maximum thickness portion where the radial stress σr is large and the gauge band is likely to occur is about 7 mm in the web width direction position in the thin film web, and in the web width direction position in the thick film web. It was recognized around 50 mm. At these maximum thickness portions, the decreasing rate of the optimized radial radial stress σr with respect to a constant tension tended to be larger than other portions. Therefore, these verification test results also suggest the effectiveness of the optimized tension function for the suppression of the gauge band.

  FIG. 30 shows the analysis result of the tangential stress σt of the thick film web. The solid line is the analysis result with the optimized tension, and the broken line is the analysis result with the constant tension. Since the tangential stress σt maintains a positive value, it is suggested that the generation of wrinkles can be suppressed by using an optimized tension function.

  In addition, the web winding method and web winding apparatus according to the present invention are not limited to the above-described embodiments, and include various other configurations. For example, in the above-described embodiment, the case where the nip roller is installed is illustrated, but the nip roller is not essential. In the stress analysis process, the analysis may be performed using a conventional basic model without considering the thickness unevenness. Further, depending on the web to be wound, it is not necessary to consider the amount of elastic shrinkage. The tension adjusting device and the load adjusting device may be integrated with the control device.

1A, 1B, 1C, 1D Web winding device 2 Support shaft 3 Motor 4 Nip roller 5 Load adjustment device 6 Tension adjustment device 7 Control device 8 Core 7a Tension control unit 7b Load control unit 7c Storage unit 7d Tension setting unit 7f Optimal tension Setting part R Roll Re Roll element W Web Wa Web element

Claims (12)

A web winding method for winding a web around a core while changing the winding tension according to the winding diameter,
A first step of measuring a thickness distribution in the width direction of the web;
A second step of extracting the thickest part of the web in the width direction;
A third step of setting the winding tension based on the thickest portion;
A web winding method including: The web winding method according to claim 1,
In the second step, a process of dividing the web into a plurality of web elements in the width direction, obtaining an average thickness value for each web element, and extracting a thickest web element having the largest average thickness value is performed. I,
In the third step, from the average value of the thickness of the thickest web element, tangential stress for each winding diameter acting on the thickest web element after winding is analyzed based on a theoretical model, and the tangential stress is A web winding method in which the winding tension is set so as not to become negative. The web winding method according to claim 2,
A web winding method in which, in the third step, the elastic shrinkage amount after winding of the thickest web element is analyzed based on a theoretical model, and the winding tension is corrected based on the elastic shrinkage amount. . A web winding device for winding a web using the web winding method according to claim 2,
A motor for rotationally driving the winding core;
A tension adjusting device for adjusting the winding tension;
A control device for controlling the tension adjusting device;
With
The web winding device, wherein the control device includes a tension setting unit that executes the processes of the second step and the third step. In the web winding device according to claim 4,
The web includes a tension correction unit that analyzes the amount of elastic shrinkage of the thickest web element after winding based on a theoretical model and corrects the winding tension based on the amount of elastic shrinkage. Winding device. Perform stress analysis to analyze the distribution of radial stress inside the roll formed by winding the web around the core using a theoretical model, and wind the web while changing the winding tension based on the analysis result A web winding method,
A tension function setting step for setting a tension function representing the winding tension with respect to a radial position of the roll;
An objective function defining step for defining an objective function including a relational expression that makes the inter-layer friction force of the web inside the roll asymptotic to a critical friction force that can cause slipping; and
A first constraint condition defining step for defining a first constraint condition in which the interlayer friction force is greater than or equal to the critical friction force;
A second constraint condition defining step for defining a second constraint condition in which the maximum value of the radial stress is equal to or less than a critical radial stress at which a gauge band can be generated;
A tension that optimizes the tension function by repeating the calculation of the tension function from a predetermined initial tension until the objective function is minimized under the constraints of the first constraint condition and the second constraint condition. A function optimization step;
A web winding method comprising: The web winding method according to claim 6, wherein
A web winding method in which the tangential stress inside the roll does not become a negative value. In the web winding method according to claim 6 or 7,
A tension distribution acquisition step of dividing the roll into a plurality of roll elements in the width direction and acquiring a tension distribution generated during winding due to thickness unevenness in the width direction of the web using the plurality of roll elements; ,
A web winding method in which the stress analysis is performed by applying the theoretical model to each of the roll elements. The web winding method according to claim 8,
The web winding in which the objective function is defined further including a relational expression for minimizing a difference between the maximum value and the minimum value of the radial stress obtained for each roll element in the objective function defining step. Method. In the web winding method according to any one of claims 6 to 9,
A web winding method in which the stress analysis is performed in consideration of an elastic shrinkage amount of the web wound around the winding core. In the web winding method according to any one of claims 6 to 10,
A web winding method wherein the average thickness of the web is 140 μm or less. A web winding device that winds a web around a winding core while changing the winding tension,
A motor for rotationally driving the winding core;
A tension adjusting device for controlling the rotational speed of the motor to change the winding tension;
With
A web winding device in which the tension adjusting device is controlled based on the tension function optimized by using the web winding method according to any one of claims 6 to 11.

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