Sheet warpage suppression device and corrugating machine

Abstract

A sheet warpage suppression device (1) is provided with: adjustment units (6A, 6C) that adjust the moisture content of a back liner (3A) and the moisture content of a front liner (3C); moisture meters (12A, 12C) for measuring the moisture content of the back liner (6A) and the moisture content of the front liner (6C); and a control device (20) for controlling the adjustment units (6A, 6C), the control device (20) calculating a measured difference in moisture content from the moisture content measured by the moisture meters (12A, 12C), determining a correction value for the amount of adjustment in the adjustment units (6A, 6C) on the basis of the measured difference in moisture content and a moisture content difference target value set in advance as the difference between the moisture content of the back liner and the moisture content of the front liner when a corrugated cardboard sheet (3F) reaches a warpage target value defined as a desired warpage amount, and feedback-controlling the adjustment units (6A, 6C) on the basis of the correction value.

Description

Sheet Warpage Suppression Device and Corrugator Machine

[0001] The present disclosure relates to a sheet warpage suppression device and a corrugator machine for suppressing warpage that occurs in corrugated fiberboard sheets.

[0002] A corrugator machine is an apparatus that conveys a belt-shaped corrugated fiberboard sheet formed by laminating a face liner, a corrugating medium, and a back liner, while performing processing such as creasing, slitting, and cutting, to produce a final product, a corrugated fiberboard sheet for box making. This corrugator machine is provided with preheaters (heaters) for preheating the base papers used for the face liner, back liner, and corrugating medium before lamination. Ideally, the manufactured corrugated fiberboard sheet is a flat plate without warpage, but in practice, warpage may occur in the manufactured corrugated fiberboard sheet.

[0003] In conventional corrugator machines, a technique is known for controlling the control values of various control elements, such as the heating amount of the preheater and the gluing amount of the gluing device used for lamination, in order to suppress warpage of corrugated fiberboard sheets. For example, Patent Document 1 discloses that in a corrugator machine, a dataset including production state information, control value information of each control element, and warpage information when the sheet warpage amount is minimized is stored as a set of performance datasets in a history database, the correction amount of the control value is updated based on the accumulated performance datasets, and in a production state similar to a certain performance dataset, a technique is disclosed that performs feedforward control of various control elements using a control value that takes into account the correction amount updated in the relevant performance dataset.

[0004] Further, for example, Patent Document 2 discloses that at the most downstream part of a corrugator machine, the actual warpage state that has occurred in the manufactured corrugated fiberboard sheet is determined by, for example, visual observation by an operator or image processing of an image captured by a CCD camera, and based on a predefined knowledge table of the control values of various control elements, a control value corresponding to the determined warpage state and the operating state of the corrugator machine (such as operating speed and current set values of each control element) is determined, and a technique for performing feedback control on each control element is disclosed.

[0005] Furthermore, for example, Patent Document 3 discloses a control technique for adding moisture to a liner that constitutes a corrugated cardboard sheet in order to suppress warping of the corrugated cardboard sheet, so that the moisture content of the liner is within a predetermined range (10% to 30% by weight). In the technique of Patent Document 3, the moisture content of each liner is set based on the humidity expansion properties of each liner.

[0006] Patent No. 6787835, Patent No. 3905767, Patent No. 7316438

[0007] However, as described in Patent Document 1 above, the technology that feedforward controls various control elements based on performance data accumulated in a historical database uses past performance data and does not directly reflect the current production state. Therefore, if there is a difference between the performance data and the current production state due to environmental errors, there is a risk that the system may not be able to respond appropriately to the occurrence of warping.

[0008] Furthermore, in the technology described in Patent Document 2, which uses feedback control to determine the actual warping state, the structure determines the warping of the corrugated cardboard sheet manufactured at the final stage of the corrugating machine and uses feedback control to control the control elements upstream of the final stage. However, because the corrugating machine is long in the direction of machine flow, there is a considerable distance between the position where the warping state is determined and the position where the control elements are located. As a result, the control response and control cycle become slow, and there is a risk that corrugated cardboard sheets with warping will be produced for a long time due to the delay in feedback convergence. In other words, in the technology described in Patent Document 2, which uses feedback control to determine the actual warping state, it is structurally difficult to ensure real-time feedback control.

[0009] Furthermore, during the production of corrugated cardboard sheets, each liner is laminated, making it difficult to estimate the humidity expansion properties of each liner from the production data of the corrugating machine. Therefore, in technologies that use the humidity expansion properties of each liner, such as in Patent Document 3, it is necessary to calculate and evaluate the humidity expansion properties of each liner through prior testing. However, it is difficult to investigate the humidity expansion properties of all paper types in advance through testing.

[0010] Therefore, conventional technology had room for improvement in suppressing warping in corrugated cardboard sheets. This invention was devised in view of the above-mentioned problems, and one of its objectives is to suppress warping in corrugated cardboard sheets by ensuring real-time feedback control structurally. In addition to this objective, another objective of this invention is to achieve effects and advantages that cannot be obtained by conventional technology, which are derived from the various configurations shown in the embodiments for carrying out the invention described later.

[0011] (1) The sheet warping suppression device in this case is a sheet warping suppression device for suppressing warping of corrugated cardboard sheets, comprising: an adjustment unit for adjusting at least one of the moisture content of the back liner and the front liner used in the manufacture of the corrugated cardboard sheets; a moisture meter including a first moisture meter for measuring the measured value of the moisture content of the back liner and a second moisture meter for measuring the measured value of the moisture content of the front liner; and a control device for controlling the adjustment unit, wherein the moisture content of the back liner measured by the first moisture meter and the moisture content measured by the second moisture meter The device comprises a control device that calculates an actual moisture content difference value based on the difference between the moisture content of the front liner and the back liner, determines a correction value for the adjustment amount in the adjustment unit based on the calculated actual moisture content difference value and a preset moisture content difference target value which is the difference between the moisture content of the back liner and the moisture content of the front liner when the corrugated cardboard sheet reaches a target warp value defined as a desired amount of warp, and provides feedback control of the adjustment unit based on the correction value, wherein the first moisture meter and the second moisture meter are provided downstream of the adjustment unit.

[0012] (2) The corrugated machine in this case is equipped with the sheet warping suppression device described above.

[0013] This sheet warping suppression device focuses on the measured difference in moisture content between the back liner and the front liner, and implements feedback control. Compared to conventional structures that determine warping in corrugated cardboard sheets manufactured at the final stage of the corrugating machine and perform feedback control based on that, this structure allows information for determining warping in corrugated cardboard sheets (measured difference in moisture content) to be acquired upstream in the conveying direction. Therefore, the control cycle of the feedback control can be shortened, and it is easier to ensure the real-time nature of the feedback control structurally.

[0014] The sheet warping suppression device and corrugating machine described in this invention structurally ensure real-time feedback control, thereby suppressing warping that occurs in corrugated cardboard sheets.

[0015] This is an overall configuration diagram of a corrugated machine including a sheet warping suppression device according to one embodiment of this invention. This is an example of the configuration of the target value table used for feedback control. This is a block diagram illustrating the configuration of feedback control by the sheet warping suppression device. This is a block diagram illustrating the configuration of control in which the moisture content difference target value in feedback control is corrected by the amount of warping error. This is an example of the configuration of the moisture content difference error control matrix. This is a table illustrating an example of preheater winding amount, moisture content, and warping shape. This is an example of a table configuration for outputting the correction amount for the moisture content difference target value.

[0016] With reference to the drawings, embodiments of a sheet warping suppression device and a corrugated machine will be described. The embodiments shown below are merely illustrative, and there is no intention to exclude various modifications or applications of techniques not explicitly shown in the embodiments below. Each component of these embodiments can be modified in various ways without departing from their spirit. Furthermore, components can be selected or combined as needed.

[0017] In this specification and drawings, for the sake of simplicity of explanation, the three directions MD, CD, and TD will be used as appropriate. The MD direction is the flow direction of the manufacturing process in the corrugating machine, the direction in which the sheets are conveyed in the corrugating machine, and the direction in which the strip-shaped sheets extend. The CD direction is the machine width direction in the corrugating machine, and is also the paper width direction of the sheets conveyed in the corrugating machine and the corrugated cardboard sheets manufactured in the corrugating machine. The TD direction is perpendicular to the MD and CD directions, and is also the vertical direction (height direction) in the corrugating machine, and is also the direction in which the front and back surfaces of the corrugated cardboard sheets face when the manufactured corrugated cardboard sheets are placed on a horizontal surface. In this specification, the terms upstream and downstream refer to the upstream and downstream in the MD direction.

[0018] [1. Configuration] Figure 1 is an overall configuration diagram of a corrugated machine 2 including a sheet warping suppression device 1 according to one embodiment. The sheet warping suppression device 1 in Figure 1 is provided to provide feedback control of various control elements of the corrugated machine 2 so that warping does not occur in the corrugated cardboard sheets manufactured by the corrugated machine 2. In this specification, warping of a corrugated cardboard sheet refers to the surface and back surface of the corrugated cardboard sheet warping upward or downward, for example, both sides in the paper width direction of the corrugated cardboard sheet warping upward or downward. First, the configuration of the production line 2A for manufacturing corrugated cardboard sheets in the corrugated machine 2 will be described with reference to Figure 1.

[0019] The corrugated cardboard machine 2 shown in Figure 1 is a corrugated cardboard sheet manufacturing apparatus that has a production line 2A that manufactures double-sided corrugated cardboard sheets by laminating a front liner and a back liner to both sides of a core, and then processes the double-sided corrugated cardboard sheets by creasing, cutting, and trimming to produce the final product, corrugated cardboard sheets for box making. The strip-shaped base paper (sheets) 3A, 3B, and 3C used for the back liner, core, and front liner, respectively, are supplied to the corrugated cardboard machine 2 from mill roll stands 4A, 4B, and 4C. The mill roll stands 4A, 4B, and 4C are arranged adjacent to each other in this order from the upstream side to the downstream side in the MD direction.

[0020] A single facer 5 is provided downstream of the mill roll stand 4A and adjacent to the upstream of the mill roll stand 4B. A preheater 6A for heating the base paper for the back liner (hereinafter also simply referred to as "back liner") 3A is provided between the mill roll stand 4A and the single facer 5, and a preheater 6B for heating the base paper for the core (hereinafter also simply referred to as "core") 3B is provided between the mill roll stand 4B and the single facer 5.

[0021] The single facer 5 receives a back liner 3A heated by a preheater 6A from the mill roll stand 4A, and a core 3B heated by a preheater 6B from the mill roll stand 4B. The single facer 5 deforms the core 3B into a corrugated shape by creating steps, and then laminates the back liner 3A to the tops of the steps of the corrugated core 3B to form a strip-shaped single-sided corrugated cardboard sheet 3D. A single-sided corrugated cardboard sheet 3D is a corrugated cardboard sheet in which a back liner is laminated to one side of the core.

[0022] A bridge 7 is positioned downstream of the single facer 5 and above the mill roll stands 4B and 4C. The bridge 7 is a bridging transport path for transporting the single-sided corrugated cardboard sheet 3D formed by the single facer 5 to the double facer 9. This bridge 7 functions as a holding area where the single-sided corrugated cardboard sheet 3D is temporarily held to absorb the speed difference between the single facer 5 and the double facer 9.

[0023] Downstream of the mill roll stand 4C, a preheater 6C is provided for heating the base paper for the front liner (hereinafter also simply referred to as "front liner") 3C, and downstream of the bridge 7, a preheater 6D is provided for heating the single-sided corrugated cardboard sheet 3D. Downstream of the preheaters 6C and 6D, a double facer 9 is provided via a glue machine 8.

[0024] The glue machine 8 applies glue to the corrugated surface of the single-sided corrugated cardboard sheet 3D, which has been heated by the preheater 6D, on the side opposite to the side to which the back liner 3A is bonded. The double facer 9 forms a double-sided corrugated cardboard sheet 3E by bonding the front liner 3C to the single-sided corrugated cardboard sheet 3D, and also transports the formed double-sided corrugated cardboard sheet 3E downstream. The double-sided corrugated cardboard sheet 3E is a corrugated cardboard sheet in which liners are bonded to both sides of the core.

[0025] Downstream of the double facer 9, a slitter scorer 10 and a cutoff 11 are arranged adjacent to each other in the MD direction in this order. The slitter scorer 10 and the cutoff 11 each transport the double-sided corrugated cardboard sheet 3E and sequentially perform processing such as scoring, cutting, and trimming on the transported double-sided corrugated cardboard sheet 3E.

[0026] In this way, the final product, corrugated cardboard sheet 3F for box making, is manufactured. The operation of this corrugating machine 2 is automatically controlled by a production control device (not shown). The production control device (not shown) is supplied with information on various manufacturing conditions from a higher-level production control system, such as the sheet transport speed, the type of paper used, basis weight, paper width, and the thickness (flute) of the corrugated cardboard sheet to be manufactured. Based on these manufacturing conditions, the production control device controls various control elements of the production line 2A.

[0027] Furthermore, the corrugated machine 2 in Figure 1 is equipped with various sensors and measuring instruments for monitoring and measuring the condition of sheets 3A to 3F on the production line 2A. Specifically, a moisture meter 12 and a warpage measuring instrument 13 are provided on the production line 2A. The moisture meter 12 is a measuring instrument (sensor) that measures the moisture content, which is the percentage of moisture contained in sheets 3A to 3F. Any well-known and suitable moisture meter can be used as the moisture meter 12. The production line 2A in Figure 1 includes a moisture meter 12A for the back liner (first moisture meter) that measures the moisture content of the back liner 3A (referred to as "back moisture content"), and a moisture meter 12C for the front liner (second moisture meter) that measures the moisture content of the front liner 3C (referred to as "front moisture content"). Note that the moisture content is the percentage that indicates the amount of moisture contained in each liner 3A and 3C. More specifically, the moisture meter 12A for the back liner and the moisture meter 12C for the front liner are installed immediately after the double facer 9 (downstream of the double facer 9). In the manufacturing line 2A, the double-sided corrugated cardboard sheet 3E is transported with the back liner 3A facing upwards and the front liner 3C facing downwards, so the moisture meter 12A for the back liner is positioned above the double-sided corrugated cardboard sheet 3E, and the moisture meter 12C for the front liner is positioned below the double-sided corrugated cardboard sheet 3E. Also, the MD-direction positions of the moisture meter 12A for the back liner and the moisture meter 12C for the front liner are set to approximately the same position. The warp amount measuring instrument 13 is a sensor that measures the amount of warp that occurs in the manufactured corrugated cardboard sheet 3F and outputs the measured value of the warp amount, and consists of, for example, a CCD camera. The CCD camera 13 takes an image of the corrugated cardboard sheet 3F, and the amount of warp of the corrugated cardboard sheet 3F can be measured by image processing. The CCD camera 13 is installed, for example, downstream of the cutoff 11.

[0028] Next, the configuration of the sheet warping suppression device 1 provided in the corrugating machine 2 described above will be explained. This sheet warping suppression device 1 focuses on the difference between the moisture content of the back surface and the moisture content of the front surface as a factor in the warping of the corrugated cardboard sheet 3F manufactured by the corrugating machine 2, and suppresses warping that occurs in the corrugated cardboard sheet manufactured by the corrugating machine 2 by feedback control (moisture content difference feedback control) of the back surface moisture content and the front surface moisture content so that the difference matches the difference in moisture content when the desired amount of warping is defined as the target warping value.

[0029] The sheet warping suppression device 1 shown in Figure 1 comprises a control device 20, adjustment units (here, preheaters 6A and 6C), and a moisture meter 12 including the moisture meter 12A for the back liner and the moisture meter 12C for the front liner. Of the components of the sheet warping suppression device 1, the control device 20 is a computer attached to the corrugated machine 2, and the adjustment units and moisture meter 12 are located on the production line 2A of the corrugated machine 2.

[0030] The adjustment unit is one of the control elements provided in the manufacturing line 2A, and adjusts at least one of the back moisture content and the front moisture content to control the warping of the corrugated cardboard sheet 3F. In Figure 1, a preheater 6A and a preheater 6C are shown as an example of the adjustment unit. As is well known, the preheaters 6A and 6C have a heating roll to which a heat transfer medium (e.g., steam) is supplied, and the back liner 3A or the front liner 3C, which is guided by a guide roll, is wrapped around the circumferential surface of the heating roll to preheat the back liner 3A or the front liner 3C. By driving the guide roll, the amount (wrapping angle) of the back liner 3A or the front liner 3C wrapped around the circumferential surface of the heating roll is adjusted.

[0031] Preheaters 6A and 6C can increase or decrease the heating amount by adjusting the amount of material wrapped around them, thereby adjusting the moisture content on the back and front surfaces, respectively. Specifically, the more material wrapped around the back liner 3A or front liner 3C, the greater the heating amount, which promotes drying and reduces the moisture content. The less material wrapped around the back liner 3A or front liner 3C, the less the heating amount, which promotes drying and increases the moisture content. The other preheaters 6B and 6D installed in the production line 2A are configured in the same way as preheaters 6A and 6C.

[0032] As described above, the moisture meter 12 includes a moisture meter 12A for the back liner and a moisture meter 12C for the front liner, and the control device 20, described later, can obtain the actual moisture difference value from the difference between the moisture content of the back liner and the moisture content of the front liner. The moisture meter 12A for the back liner and the moisture meter 12C for the front liner are installed downstream of the preheaters 6A and 6C. More specifically, they are installed downstream of the double facer 9 and upstream of the last stage of the manufacturing line 2A.

[0033] The control device 20 is a computer (electronic control device) configured as an LSI device or embedded electronic device including a processor 21 and a storage device 22 such as ROM or RAM, and performs the moisture content difference feedback control described above. This control device 20 may be incorporated into a production management system, for example, or it may be a separate computer from the production management system.

[0034] Various sensors and measuring instruments, such as a moisture meter 12 and a CCD camera 13, are connected to the input side of the control device 20, and control elements on the manufacturing line 2A, such as preheaters 6A and 6C, are connected to the output side. The control device 20 is also connected to a learning processing computer 23, which will be described later, in a manner that enables information communication, and can acquire information on manufacturing conditions from a production management device (not shown) and operating data acquired from various sensors, such as the moisture meter 12 and the CCD camera 13, during the operation of the corrugated machine 2.

[0035] The storage device 22 of the control device 20 stores a target value table 22A. The target value table 22A is a data table that stores the moisture content difference target values ​​used in the moisture content difference feedback control described later. The target value table 22A is prepared in advance before the moisture content difference feedback control is implemented.

[0036] The moisture content difference target value stored in the target value table 22A is a value pre-set as the difference between the moisture content of the back liner 3A and the moisture content of the front liner 3C when the manufactured corrugated cardboard sheet reaches the specified target warp value as the desired amount of warp. The difference between the moisture content of the back liner 3A and the front liner 3C is one of the factors that cause warping of the corrugated cardboard sheet 3F. Therefore, it can be said that the amount of warping of the corrugated cardboard sheet 3F manufactured by the corrugating machine 2 can be estimated from the difference between the moisture content of the back liner 3A and the front liner 3C (measured moisture content difference value).

[0037] From the correspondence between the measured difference in moisture content and the amount of warping of the corrugated cardboard sheet 3F, as described above, it can be estimated that if the amount of warping of the corrugated cardboard sheet 3F is a certain value, then the difference between the moisture content of the back liner 3A and the moisture content of the front liner 3C is a certain difference value. Therefore, the storage device 22 (sheet warping suppression device 1) of the control device 20 stores the difference between the moisture content of the back liner 3A and the moisture content of the front liner 3C when the amount of warping of the corrugated cardboard sheet 3F reaches the target warping value as a target value (moisture content difference target value) in the target value table 22A. The state in which the corrugated cardboard sheet reaches the target warping value defined as the desired amount of warping means that the warping is sufficiently suppressed, for example, that the warping is zero, or that the warping is within a small amount of warping that can be considered almost zero. The target warping value is a value (for example, a value in mm) that indicates the amount of warping from a standard, for example, a state of zero warping, and is set in the target value table 22A.

[0038] Figure 2 shows an example of the configuration of the target value table 22A (referred to as the "moisture content difference target value table" in Figure 2). The target value table 22A shown in Figure 2 provides an example of a table configuration in which moisture content difference target values ​​are set according to the sheet transport speed. This target value table 22A is set for a specific paper type and basis weight of a base paper, with moisture content difference target values ​​set according to the transport speed when the target value for warping is reached.

[0039] The moisture content difference target value is a value that indicates the target difference between the moisture content of the back liner 3A and the moisture content of the front liner 3C when the amount of warping of the corrugated cardboard sheet 3F reaches the target warping value, as described above. It is pre-set to adjust the difference in moisture content between the moisture content of the back liner 3A and the moisture content of the front liner 3C so that the amount of warping of the corrugated cardboard sheet 3F reaches the desired amount of warping. For example, the moisture content difference target value can be set by an input entered by the operator using an input means not shown in the diagram. Alternatively, an estimation model can be constructed to estimate the amount of warping of the corrugated cardboard sheet based on the measured moisture content difference values ​​accumulated as operating data history, and the difference between the moisture content of the back liner 3A and the moisture content of the front liner 3C corresponding to the target warping value based on the amount of warping estimated by this estimation model can be set as the moisture content difference target value. Since moisture content is a percentage, the moisture content difference target value is expressed as a percentage (a value in %).

[0040] The conveying speed is the speed at which sheets 3A to 3F are conveyed in the corrugated cardboard machine 2, and can also be called the operating speed of the corrugated cardboard machine 2. The conveying speed is one example of a factor that correlates with the occurrence of warping of corrugated cardboard sheet 3F, other than the difference in moisture content. By setting a target moisture content difference value for each conveying speed, an appropriate target moisture content difference value can be obtained according to the conveying speed.

[0041] In the target value table 22A shown in Figure 2, the moisture content differential target value is set to 0.7% when the conveying speed is 100 [mpm] or less (~100). When the conveying speed is 101 to 150 [mpm] (~150), the moisture content differential target value is set to 0.6%. When the conveying speed is 151 to 200 [mpm] (~200), the moisture content differential target value is set to 0.5%. When the conveying speed is 201 to 250 [mpm] (~250), the moisture content differential target value is set to 0.4%. When the conveying speed is 251 to 300 [mpm] (~300), the moisture content differential target value is set to 0.3%. When the transport speed is 301 to 350 [mpm] (up to 350), the target moisture content difference value is set to 0.2 [%], and when it is 351 [mpm] or higher (351 and above), the target moisture content difference value is also set to 0.2 [%].

[0042] Next, an example of a specific method for creating the target value table 22A will be described. The target value table 22A is created by (1) learning an estimation model that estimates the amount of warp (warp factor) of the corrugated cardboard sheet 3F based on the measured moisture content difference values ​​accumulated as the history of operating data of the corrugated machine 2, and (2) setting moisture content difference target values ​​corresponding to the target warp value from the estimation model. The process of learning the estimation model and creating the target value table 22A as described above (learning process) is carried out, for example, by a learning processing computer 23 that is communicatively connected to the control device 20.

[0043] The learning processing computer 23 receives information on manufacturing conditions from a production management device (not shown) and operating data acquired from various sensors such as a moisture meter 12 and a CCD camera 13 during the operation of the corrugated machine 2, which are supplied from the control device 20 and the corrugated machine 2. This data is stored in a database (not shown) as a history of the operating data. The history of the operating data includes various manufacturing conditions such as the transport speed, the type of paper used, basis weight, paper width, and the thickness (flute) of the corrugated cardboard sheets to be manufactured, as well as the measured difference in moisture content between the back liner 3A and the front liner 3C, and the amount of sheet warping measured by the CCD camera 13.

[0044] The learning processing computer 23 executes a well-known machine learning process using the accumulated history of operation data, so as to learn an estimation model for estimating the warp amount of the corrugated board sheet 3F based on the measured moisture content difference value. The estimation model estimates (predicts) the correspondence relationship between the warp amount of the corrugated board sheet 3F and the measured moisture content difference value calculated by taking the difference between the back moisture content measured by the back liner moisture meter 12A and the front moisture content measured by the front liner moisture meter 12C. Note that well-known techniques such as supervised learning, unsupervised learning, and reinforcement learning can be appropriately applied as the method of the machine learning process.

[0045] Using the learned estimation model, the learning processing computer 23 can estimate (predict) the warp amount of the corrugated board sheet 3F manufactured when the difference in moisture content between the back liner 3A and the front liner 3C is a certain value, and can also estimate (predict) the moisture content difference when the manufactured corrugated board sheet 3F has a certain warp amount. Note that the moisture content difference refers to a value measured at the positions of the moisture meters 12A and 12C. That is, by referring to (back-calculating with) this estimation model, the learning processing computer 23 can estimate the moisture content difference corresponding to a certain target warp value, and can set that moisture content difference as the target moisture content difference value.

[0046] Since the history of operation data used for learning the estimation model includes transport speed information, the transport speed can also be used for learning the estimation model. In that case, the target moisture content difference value can be set according to the transport speed. In addition, the target moisture content difference value corresponding to various manufacturing conditions included in the history of operation data used for learning the estimation model (for example, the paper type of base paper, basis weight, paper width, the thickness of the corrugated board sheet to be manufactured, etc.) can be set in the target value table 22A.

[0047] The learning processing computer 23 periodically executes processing of creating (updating) the target value table 22A. The learning processing computer 23 executes the processing of creating the target value table 22A, for example, at the start of operation on each operation day of the corrugator machine 2. The history of operation data used for learning the estimation model may be a history of operation data of the corrugator machine 2 over a certain past period, or may be a history of operation data of the corrugator machine 2 on the previous day. When the history of operation data of the corrugator machine 2 over a certain past period is used, the accuracy of the estimation model is improved due to the large amount of data. When the history of operation data of the corrugator machine 2 on the previous day is used, the latest contents regarding, for example, the temperature and humidity for each season, the state of the moisture meter 12, and the like are easily reflected, so that the accuracy of the estimation model is improved.

[0048] The processor 21 executes the software program stored in the storage device 22, thereby performing moisture content difference feedback control based on the target value table 22A. The processor 21 includes, as various functions for performing the moisture content difference feedback control, a moisture content difference actual measurement value calculation unit 21A, a moisture content difference target value acquisition unit 21B, a moisture content difference error calculation unit 21C, a correction value determination unit 21D, and an operation amount distribution unit 21E.

[0049] The above functional elements 21A to 21E calculate a moisture content difference actual measurement value by taking the difference between the back moisture content measured by the back liner moisture meter 12A and the front moisture content measured by the front liner moisture meter 12C (moisture content difference actual measurement value calculation unit 21A), determine a correction value for the adjustment amount in the preheaters 6A, 6C (adjustment units) based on the calculated moisture content difference actual measurement value and the moisture content difference target value acquired from the target value table 22A (moisture content difference target value acquisition unit 21B, moisture content difference error calculation unit 21C, correction value determination unit 21D), and perform feedback control on the preheaters 6A, 6C (adjustment units) based on the correction value (operation amount distribution unit 21E).

[0050] However, if the moisture content of the back liner 3A or the front liner 3C is too low or too high, the processor 21 may not be able to properly bond the sheets if it performs feedback control on the preheaters 6A and 6C (adjustment units). In particular, if the moisture content of the front liner 3C is too low, there is a significant tendency for defects in sheet bonding to occur. Therefore, in this embodiment, the processor 21 uses a moisture content determination unit 24 to determine whether the moisture content of the back liner 3A and the front liner 3C is within the range of preset upper and lower limits. If the moisture content of the back liner 3A or the front liner 3C is too low or too high, it does not perform moisture content difference feedback control on the back liner 3A or the front liner 3C (it locks the feedback control).

[0051] The moisture content determination unit 24 determines whether the moisture content of the back liner, measured by the back liner moisture meter 12A, and the moisture content of the front liner, measured by the front liner moisture meter 12C, are within the range of preset upper and lower limits. The upper and lower limits set in the moisture content determination unit 24 are preset as appropriate numerical ranges that allow for proper lamination of the sheets even when feedback control is implemented. Different ranges can be set for the upper and lower limits depending on various manufacturing conditions such as the type of paper, basis weight, paper width of the base paper, and the thickness (flute) of the corrugated cardboard sheet to be manufactured. In this case, the determination by the moisture content determination unit 24 can be performed more appropriately according to various manufacturing conditions. The operator may manually input the upper and lower limits according to the manufacturing conditions using an input means not shown, or the processor 21 may automatically set the upper and lower limits according to the manufacturing conditions based on production data.

[0052] For example, if the moisture content of the back liner 3A or the front liner 3C is greater than the upper limit, the processor 21 does not perform feedback control to increase the moisture content of the back liner 3A or the front liner 3C, and if the moisture content of the back liner 3A or the front liner 3C is less than the lower limit, the processor 21 does not perform feedback control to decrease the moisture content of the back liner 3A or the front liner 3C. However, if the moisture content of the back liner 3A or the front liner 3C is greater than the upper limit, the processor 21 performs feedback control to decrease the moisture content of the back liner 3A or the front liner 3C as usual. Also, if the moisture content of the back liner 3A or the front liner 3C is less than the lower limit, the processor 21 performs feedback control to increase the moisture content of the back liner 3A or the front liner 3C as usual.

[0053] Furthermore, in addition to the functional elements 21A to 21E and 24, the processor 21 has various functions for performing warp amount feedback control, which corrects the moisture content difference target value using the actual warp amount measured by the CCD camera 13. The various functions for performing warp amount feedback control include a warp error calculation unit 21F, a target value correction amount determination unit 21G, and a moisture content difference target value correction unit 21H.

[0054] The above-mentioned functional elements 21F to 21H calculate the warping error, which is the difference between the measured warping amount and the target warping value in the target value table 22A (warping error calculation unit 21F), determine the moisture content difference target value correction amount to correct the moisture content difference target value based on the warping error (target value correction amount determination unit 21G), and correct the moisture content difference target value with the determined moisture content difference target value correction amount (moisture content difference target value correction unit 21H).

[0055] Referring to Figures 3 to 7, specific examples of the moisture content difference feedback control and warpage feedback control performed by the control device 20 will be explained. Figure 3 is a block diagram illustrating an example configuration of the moisture content difference feedback control, and Figure 4 is a block diagram illustrating an example configuration of the warpage feedback control. The warpage feedback control shown in Figure 4 is a local feedback control for correcting the moisture content difference target value used in the moisture content difference feedback control shown in Figure 3. In the moisture content difference feedback control, the implementation of warpage feedback control is not mandatory and is performed as needed. Therefore, in Figure 3, elements related to warpage feedback control are drawn with dashed lines. Note that each functional element shown in the moisture content difference feedback control shown in Figure 3 and the warpage feedback control shown in Figure 4 is realized by the control device 20 executing software program processing using the processor 21 and storage device 22 (hardware resources).

[0056] As shown in Figure 3, the control device 20 subtracts the surface moisture content measured by the surface moisture content meter 12C from the surface moisture content measured by the surface moisture content meter 12A using the subtraction unit 30, and outputs the measured moisture content difference value (indicated as "moisture content difference" in the figure) (block 31). In other words, the subtraction unit 30 is an example of the measured moisture content difference value calculation unit 21A. The surface moisture content and surface moisture content obtained from the moisture content meters 12A and 12C are smoothed, for example, by moving average processing. The moisture content determination unit 24 determines whether the surface moisture content measured by the surface moisture content meter 12A and the surface moisture content measured by the surface moisture content meter 12C are within the range of preset upper and lower limits, and transmits the determination result information to the subsequent manipulated variable distribution unit 21E. In Figure 3, the transmission line of information from the moisture content determination unit 24 to the manipulated variable distribution unit 21E is drawn with a dashed line.

[0057] The moisture content difference target value acquisition unit (indicated as "moisture content difference error control matrix" in the figure) 21B acquires a moisture content difference target value according to the current transport speed (block 32) based on the target value table 22A. In the warpage amount feedback control described later, the addition unit 33 adds the moisture content difference target value and the moisture content difference target value correction amount, but here, the addition by the addition unit 33 is not performed, and the moisture content difference target value acquired from the target value table 22A is output as the current value of the moisture content difference target value (block 34).

[0058] The moisture content difference error calculation unit 21C calculates the moisture content difference error in the subtraction unit 35 by subtracting the measured moisture content difference value from the current moisture content difference target value (block 36). Since both the current moisture content difference target value and the measured moisture content difference value are expressed as percentages (values ​​in %), the moisture content difference error is expressed as a percentage (value in %).

[0059] The correction value determination unit 21D determines the correction value for the adjustment amount in preheaters 6A and 6C based on the moisture content difference error. The correction value is a correction value for the winding amount (adjustment amount) of each preheater 6A and 6C, and is expressed as a percentage [value in %] of the gain that increases or decreases each winding amount. The winding amounts of preheaters 6A and 6C are basically controlled by the production control device based on various manufacturing conditions as described above, but the winding amount is adjusted based on the moisture content difference error by moisture content difference feedback control. For example, the correction value determination unit 21D determines the total preheater winding correction amount using a predetermined data table (moisture content difference error control matrix) based on the moisture content difference error and the transport speed, and outputs the total preheater winding correction amount (block 37). The total preheater winding correction amount is the total correction amount before distributing the winding amount correction values ​​for each preheater 6A and 6C to each preheater 6A and 6C; more precisely, it can be said to be the total correction amount for the adjustment unit. Since the amount of heating to the liners 3A and 3C changes depending on the correction value when the transport speed is low or high, the moisture content difference error control matrix is ​​configured so that the total preheater winding correction amount can be adjusted according to the transport speed.

[0060] Figure 5 shows an example of the configuration of the moisture content difference error control matrix that determines the total preheater winding correction amount. As shown in Figure 5, the moisture content difference error control matrix defines multiple combination patterns of transport speed and multiple moisture content difference errors, and the total preheater winding correction amount is determined according to the combination pattern of transport speed and moisture content difference error. For example, if the transport speed is in the range of 101 to 150 [mpm] (~150) and the moisture content difference error is in the range of 0.6 to 0.7 [%] (0.6~), the total preheater winding correction amount will be 10 [%]. If the transport speed is in the range of 101 to 150 [mpm] (~150) and the moisture content difference error is in the range of 0.8 to 0.9 [%] (0.8~), the total preheater winding correction amount will be 15 [%]. When the transport speed is in the range of 101 to 150 [mpm] (up to 150) and the moisture content difference error is in the range of 0.4 to 0.5 [%] (0.4 and above), the total preheater winding correction amount is 5 [%].

[0061] The moisture content difference error control matrix shown in Figure 5 specifies only positive values ​​for the moisture content difference error. However, if the moisture content difference error is a negative value, the total preheater winding correction amount should be multiplied by a minus sign (-). For example, if the transport speed is in the range of 101 to 150 [mpm] (~150) and the moisture content difference error is in the range of -0.6 to -0.7 [%] (0.6~), the total preheater winding correction amount will be -10 [%]. Note that the correction value determination unit 21D may determine the correction value using a predetermined calculation formula, not limited to the moisture content difference error control matrix as described above.

[0062] Returning to Figure 3, the manipulated amount distribution unit 21E distributes the manipulated amount for feedback control to each preheater 6A, 6C based on the total preheater winding correction amount determined by the moisture content difference error control matrix (correction value determination unit 21D). In other words, each preheater 6A, 6C is allocated a correction value for its respective winding amount. Here, the manipulated amount for each preheater 6A, 6C can be broadly described as the manipulated amount for feedback control to each adjustment unit. Furthermore, the correction value for the winding amount of each preheater 6A, 6C can also be described as the correction value for the adjustment amount of each adjustment unit.

[0063] This adjusts the winding amount of each preheater 6A and 6C, and feedback control is performed on each preheater 6A and 6C corresponding to the back liner 3A and the front liner 3C. Specifically, the adjustment of the winding amount of each preheater 6A and 6C is carried out by increasing one of the preheaters 6A and 6C and decreasing the other.

[0064] As described above, the manipulated amount distribution unit 21E receives information on the determination result. Based on the determination result transmitted from the moisture content determination unit 24, the manipulated amount distribution unit 21E performs feedback control to each preheater 6A, 6C if the moisture content of the back liner 3A or the front liner 3C is within the range of the upper and lower limits. If the moisture content of the back liner 3A or the front liner 3C exceeds the range of the upper and lower limits, that is, if it is smaller than the lower limit (insufficient) or larger than the upper limit (excessive), the manipulated amount distribution unit 21E does not perform moisture content difference feedback control for that back liner 3A or the front liner 3C.

[0065] Figure 6 is a table illustrating the changes in temperature, moisture content, moisture content difference, warp amount, and warp shape in response to adjustments in the winding amount of each preheater 6A and 6C. In Figure 6, in the left vertical column, "Back +" and "Front -" indicate increasing the winding amount of preheater 6A for the back liner 3A and decreasing the winding amount of preheater 6C for the front liner 3C, while "Back -" and "Front +" indicate decreasing the winding amount of preheater 6A for the back liner 3A and increasing the winding amount of preheater 6C for the front liner 3C. In the temperature column, "+" indicates a temperature rise in the back liner 3A or the front liner 3C, and "-" indicates a temperature drop in the back liner 3A or the front liner 3C.

[0066] In the moisture content column, "+" indicates an increase in the moisture content of the back liner 3A or the front liner 3C, and "-" indicates a decrease in the moisture content of the back liner 3A or the front liner 3C. In the moisture content difference column, "-" indicates a decrease in the moisture content difference between the back liner 3A and the front liner 3C, and "+" indicates an increase in the moisture content difference between the back liner 3A and the front liner 3C. The curvature amount column and curvature shape column define the top and bottom based on the state in which the corrugated cardboard sheet 3F is placed with the back liner 3A on top and the front liner 3C on the bottom. In the curvature amount column, "-" indicates that both ends of the corrugated cardboard sheet 3F in the paper width direction will bend downwards ("downward curvature"), and "+" indicates that both ends of the corrugated cardboard sheet 3F in the paper width direction will bend upwards ("upward curvature"). The "Warping Shape" column schematically depicts the shape of corrugated cardboard sheet 3F when warped. The upper section shows the "downward warping shape," and the lower section shows the "upward warping shape."

[0067] As shown in the table in Figure 6, for example, if the amount of preheater 6A wrapped around the back liner 3A is increased and the amount of preheater 6C wrapped around the front liner 3C is decreased, the temperature of the back liner 3A rises and the temperature of the front liner 3C falls. As a result, compared to before the change in the amount of wrapping, the moisture content of the back liner 3A decreases and the moisture content of the front liner 3C increases, so the difference in moisture content obtained by subtracting the moisture content of the front liner 3C from the moisture content of the back liner 3A decreases. Then the moisture content of the back liner 3A decreases relative to the front liner 3C. After that, the corrugated cardboard sheet 3F is formed by laminating the front liner 3C, the core 3B and the back liner 3A. Here, the back liner 3A, with its reduced moisture content, absorbs more moisture from the air than the front liner 3C after being discharged as a corrugated cardboard sheet 3F. As a result, when the corrugated cardboard sheet 3F is placed with the front liner 3C facing downwards, the back liner 3A, which is located above it, expands. Therefore, the corrugated cardboard sheet 3F is straightened in a direction where both ends in the width direction of the paper curl downwards, that is, in the downward curvature direction.

[0068] Conversely, if the amount of preheater 6A wrapped around the back liner 3A is reduced and the amount of preheater 6C wrapped around the front liner 3C is increased, the temperature of the back liner 3A decreases and the temperature of the front liner 3C increases. As a result, compared to before the change in wrapping amount, the moisture content of the back liner 3A increases and the moisture content of the front liner 3C decreases, so the difference in moisture content obtained by subtracting the moisture content of the front liner 3C from the moisture content of the back liner 3A increases. Then, the moisture content of the front liner 3C decreases relative to the back liner 3A. Subsequently, the corrugated cardboard sheet 3F is formed by laminating the front liner 3C, the core 3B, and the back liner 3A. Here, the front liner 3C, with its reduced moisture content, absorbs more moisture from the air than the back liner 3A after being discharged as the corrugated cardboard sheet 3F. As a result, when the corrugated cardboard sheet 3F is placed with the front liner 3C facing downwards, the lower front liner 3C expands. Therefore, the corrugated cardboard sheet 3F is straightened in a direction where both ends in the width direction of the paper curl upward, that is, in the upward curvature direction.

[0069] Next, the warpage feedback control shown in Figure 4 will be explained. This warpage feedback control determines the moisture content difference target value correction amount based on the result of suppressing sheet warpage by the moisture content difference feedback control described above (measured value of sheet warpage) during the operation of the corrugated machine 2. As shown in Figure 4, the control device 20 acquires the warpage amount from the CCD camera (warpage amount measuring instrument) 13 (block 40), and smooths the acquired warpage amount by, for example, moving average processing to obtain the measured value of the warpage amount ("moving average processing" shown in block 41).

[0070] The warp error calculation unit 21F acquires information on the target warp value from the target value table 22A (block 42), subtracts the measured warp amount from the target warp value in the subtraction unit 43, and outputs the warp error (block 44). The warp error is a value (in mm units) that represents the deviation of the measured warp amount from the target warp value.

[0071] The target value correction amount determination unit 21G outputs a provisional value of the moisture content difference target value correction amount corresponding to the warpage error based on the moisture content difference target value correction amount table 45 (block 46). Figure 7 shows an example of the configuration of the table that outputs the correction amount of the moisture content difference target value (indicated as "moisture content difference target value correction amount table" in the figure). As shown in Figure 7, the moisture content difference target value correction amount table has moisture content difference target value correction amounts corresponding to multiple types of warpage errors stored in advance. The provisional value of the moisture content difference target value correction amount is supplied to the error correction unit 47 of the moisture content difference feedback control.

[0072] The error correction unit 47 of the moisture content difference feedback control is supplied with the moisture content difference error calculated in block 36 in the moisture content difference feedback control shown in Figure 3, after the transport delay has been corrected (block 48). This transport delay correction is performed to correct the transport delay caused by the fact that the distance in the MD direction from the CCD camera 13 to the preheaters 6A and 6C is greater than the distance in the MD direction from the moisture meter 12 to the preheaters 6A and 6C.

[0073] Specifically, the moisture content difference error when the corrugated cardboard sheet 3F passes through the moisture meter 12 is stored, and the moisture content difference target value can be corrected by considering both the moisture content difference target value correction amount and the moisture content difference error. For example, if the moisture content difference target value is +1% and the moisture content difference error is 0.3%, the moisture content difference target value correction amount can be set to 0.7%. This is done by correcting the target value considering that the target correction amount will be corrected in the future by the moisture content difference feedback control. In this way, the moisture content difference target value correction amount by the warpage amount feedback control can be determined by considering the transport delay due to the moisture content difference error.

[0074] The error correction unit 47 of the moisture content difference feedback control corrects the error of the moisture content difference feedback control based on the provisional value of the moisture content difference target value correction amount and the moisture content difference error, and outputs the moisture content difference target value correction amount. The moisture content difference target value correction amount is integrated (block 49) and output (block 50). With this control configuration, control interference due to the phase difference between the moisture content difference feedback control and the warp amount feedback control can be avoided. Although not shown in the figures, another example of a method to avoid such control interference is an event-driven control format in which the warp amount feedback control is executed only when the warp amount of the sheet is measured such that the moisture content difference error (the difference between the moisture content difference target value and the measured moisture content difference value) is within a certain range.

[0075] The moisture content difference target value correction amount output in block 50 is added to the moisture content difference target value in the addition unit 33 of Figure 3 and output as the current value of the moisture content difference target value (block 34). This is the operation of the moisture content difference target value correction unit 21H, which makes it possible to correct the moisture content difference target value based on the measured value of the sheet warp.

[0076] [2. Effects] The sheet warping suppression device 1 described above is configured as described above and therefore has the following effects. The sheet warping suppression device 1 is a sheet warping suppression device 1 that suppresses warping of corrugated cardboard sheets 3F and includes adjustment units 6A and 6C that adjust at least one of the moisture content of the back liner 3A and the front liner 3C used in the manufacture of corrugated cardboard sheets 3F, a moisture meter 12 which includes a first moisture meter 12A for measuring the actual moisture content of the back liner 3A and a second moisture meter 12C for measuring the actual moisture content of the front liner 3C, and a control device 20 for controlling the adjustment units 6A and 6C, wherein the first moisture meter 12A and the second moisture meter 12C are provided downstream of the adjustment units 6A and 6C. The control device 20 calculates an actual moisture content difference value based on the difference between the moisture content of the back liner 3A measured by the first moisture meter 12A and the moisture content of the front liner 3C measured by the second moisture meter 12C. Based on the calculated actual moisture content difference value and a preset moisture content difference target value which is the difference between the moisture content of the back liner 3A and the moisture content of the front liner 3C when the manufactured corrugated cardboard sheet has a predetermined target warp value, the control device 20 determines a correction value for the adjustment amount in the adjustment units 6A and 6C, and provides feedback control to the adjustment units 6A and 6C based on the correction value.

[0077] Thus, by focusing on the measured difference in moisture content between the moisture content of the back liner 3A and the front liner 3C, feedback control is implemented. Compared to conventional structures that determine warping in the corrugated cardboard sheet manufactured at the final stage of the corrugated machine and perform feedback control based on that, this structure allows information for determining warping in the corrugated cardboard sheet (measured difference in moisture content) to be acquired upstream in the conveying direction. Therefore, the control cycle of the feedback control can be shortened, and it is easier to ensure the real-time nature of the feedback control structurally.

[0078] Furthermore, the sheet warping suppression device 1 is further equipped with a target value table 22A that stores moisture content difference target values, and the control device 20 obtains the moisture content difference target values ​​from the target value table 22A. By using the target value table 22A, the moisture content difference target values ​​are set automatically, which reduces the amount of work required compared to a configuration in which, for example, an operator manually inputs and sets the moisture content difference target values. The target value table 22A is configured so that the learning processing computer 23 learns an estimation model that estimates the amount of warping of the corrugated cardboard sheet 3F based on the measured moisture content difference values ​​accumulated as the history of operating data, and sets the moisture content difference target values ​​corresponding to the warping target values ​​from the estimation model. In this way, since the estimation model is learned and the target value table 22A is created, the measured moisture content difference values ​​and the amount of warping can be correlated with high accuracy. Therefore, feedback control can be properly implemented.

[0079] Furthermore, the estimation model for creating the target value table 22A is trained periodically, and the target value table 22A is periodically updated by the training processing computer 23 in accordance with the training. This improves the accuracy of the estimation model. The target value table 22A also stores multiple moisture content difference target values ​​according to the manufacturing conditions of the corrugated cardboard sheet. This allows the use of an appropriate moisture content difference target value depending on the manufacturing conditions. In addition, if the operator arbitrarily changes the manufacturing conditions, the moisture content difference target value can be changed to an appropriate value.

[0080] The adjustment units 6A and 6C adjust the moisture content of the back liner 3A and the front liner 3C, respectively. This allows for individual adjustment of the moisture content of the back liner 3A and the front liner 3C, improving the accuracy of the feedback control. The adjustment units 6A and 6C are preheaters 6A and 6C that include cylindrical heating drums around which at least one of the back liner 3A and the front liner 3C is wound and heated. The control device 20 determines a correction value for the amount of winding of at least one of the back liner 3A and the front liner 3C relative to the preheaters 6A and 6C. This allows for appropriate feedback control of the manipulated amount of the preheaters 6A and 6C.

[0081] The first moisture meter 12A and the second moisture meter 12C are installed downstream of the double facer 9, which is used to laminate the front liner 3C onto the single-sided corrugated cardboard sheet 3D, which is formed by laminating the back liner 3A and the core 3B, in the manufacturing line 2A, and upstream of the last stage of the manufacturing line 2A. This allows the moisture content of the back liner 3A and the front liner 3C to be obtained when the double-sided corrugated cardboard sheet 3E is formed, with the back liner 3A and the front liner 3C laminated to both sides of the core 3B. Therefore, the optimal value of the moisture content difference can be managed to suppress warping in the corrugated cardboard sheet with high accuracy. In addition, the control cycle of the feedback control can be shortened, and the real-time performance of the feedback control can be easily ensured structurally.

[0082] The sheet warping suppression device 1 further includes a moisture content determination unit 24 that determines whether the moisture content of the back liner 3A measured by the first moisture meter 12A and the moisture content of the front liner 3C measured by the second moisture meter 12C are within a preset range from an upper limit to a lower limit. If the control device 20 determines that at least one of the moisture content of the back liner 3A and the front liner 3C exceeds the above range, it will not perform feedback control of the adjustment units 6A and 6C for at least one of the back liner 3A and the front liner 3C that exceeds the range. As a result, if the moisture content of the back liner 3A or the front liner 3C is too low or too high, moisture content difference feedback control will not be performed for that back liner 3A or the front liner 3C (feedback control will be locked). Therefore, the sheets can be properly bonded, and defects in sheet bonding can be suppressed.

[0083] The sheet warping suppression device 1 is further equipped with a warping amount measuring instrument 13 that measures the amount of warping that occurs in the manufactured corrugated cardboard sheet 3F and outputs the measured value of the warping amount. The control device 20 calculates the warping error, which is the difference between the measured value of the warping amount and the target warping value, determines a moisture content difference target value correction amount to correct the moisture content difference target value based on the warping error, and corrects the moisture content difference target value with the determined moisture content difference target value correction amount. Therefore, in addition to feedback control that focuses on the measured value of the moisture content difference, the moisture content difference target value can be further corrected by feedback control based on the measured value of the warping amount. Thus, the accuracy of the feedback control can be further improved. Furthermore, a corrugated machine 2 equipped with the sheet warping suppression device 1 can obtain the same effects as described above.

[0084] [3. Others] The configuration of the sheet warping suppression device 1 in the above-described embodiment is just one example. For example, the adjustment unit is not limited to the preheaters 6A and 6C, but may be a water-adding device that adds water to at least one of the back liner 3A and the front liner 3C. Specifically, the water-adding device may be a glue machine 8 (gluing device) that glues to at least one of the back liner 3A and the front liner 3C. In this case, water is added to the liners 3A and 3C by the water contained in the glue. Alternatively, the water-adding device may be a water-spraying device 14 that sprays water onto at least one of the back liner 3A and the front liner 3C. In this case, the control device 20 determines a correction value for the amount of water added to the back liner 3A and the front liner 3C. Since the water-adding device is feedback controlled, the amount of water added to the front liner 3C and the back liner 3A can be directly controlled. In this case, determining the "total preheater wrapping correction amount" in block 37 of Figure 3 should be interpreted as determining the total correction amount of moisture that the glue machine 8 or water spraying device 14 (hydration device) applies to the back liner 3A and the front liner 3C. Also, the operation amount distribution unit 21E should be interpreted as distributing the operation amount for feedback control to the glue machine 8 or water spraying device 14 (hydration device).

[0085] Furthermore, the first moisture meter 12A and the second moisture meter 12C may be installed downstream of the adjustment unit (preheaters 6A, 6C, glue machine 8, water spraying device 14) and upstream of the double facer 9. This allows the moisture content of the back liner 3A and the front liner 3C, which are not affected by the heating of the double facer 9, to be obtained by the first moisture meter 12A and the second moisture meter 12C. Therefore, the amount of warping can be estimated with high accuracy from the difference in moisture content between the back liner 3A and the front liner 3C, which are not affected by the heating of the double facer 9. In addition, the control cycle of the feedback control can be shortened, and it is structurally easier to ensure the real-time performance of the feedback control.

[0086] Furthermore, the learning processing computer 23 may be incorporated into the control device 20 or the production management device. The configuration of the production line 2A of the corrugated machine 2 is not limited to the example in Figure 1. For example, it may be a configuration capable of producing double flutes. Also, if the moisture content of the liners 3A and 3C to be processed falls below a predetermined moisture content (e.g., 5%), the correction by moisture content difference feedback control for the liners 3A and 3C can be prohibited. This prevents the liners 3A and 3C from changing over time due to excessive drying.

[0087] [4. Addendum] The following addendums are disclosed regarding the embodiments described above.

[0088] (Note 1) A sheet warping suppression device for suppressing warping of a corrugated cardboard sheet, comprising: an adjustment unit for adjusting at least one of the moisture content of the back liner and the front liner used in the manufacture of the corrugated cardboard sheet; a moisture meter including a first moisture meter for measuring the actual moisture content of the back liner and a second moisture meter for measuring the actual moisture content of the front liner; and a control device for controlling the adjustment unit, which calculates an actual moisture content difference value from the difference between the moisture content of the back liner measured by the first moisture meter and the moisture content of the front liner measured by the second moisture meter, determines a correction value for the adjustment amount in the adjustment unit based on the calculated actual moisture content difference value and a preset moisture content difference target value which is the difference between the moisture content of the back liner and the moisture content of the front liner when the corrugated cardboard sheet becomes a warping target value defined as a desired amount of warping, and provides feedback control of the adjustment unit based on the correction value, The first moisture meter and the second moisture meter are sheet warping suppression devices provided downstream of the adjustment unit. (Note 2) The sheet warping suppression device according to Note 1, further comprising a target value table storing the moisture content difference target value, wherein the control device obtains the moisture content difference target value from the target value table. (Note 3) The sheet warping suppression device according to Note 2, wherein the target value table is set from the estimated model, which is learned by a learning processing computer to estimate the amount of warping of the corrugated cardboard sheet based on the measured moisture content difference values ​​accumulated as a history of operating data. (Note 4) The sheet warping suppression device according to Note 3, wherein the learning of the estimated model for creating the target value table is performed periodically, and the target value table is updated periodically by the learning processing computer in accordance with the performance of the learning. (Note 5) The sheet warping suppression device according to any one of Notes 2 to 4, wherein the target value table stores multiple target values ​​for the difference in moisture content according to the manufacturing conditions of the corrugated cardboard sheet. (Note 6) The sheet warping suppression device according to any one of Notes 1 to 5, wherein the adjustment unit adjusts the moisture content of the back liner and the moisture content of the front liner, respectively.(Note 7) The sheet warping suppression device according to any one of Notes 1 to 6, wherein the adjustment unit is a preheater including a cylindrical heating drum that wraps around and heats at least one of the back liner and the front liner, and the control device determines a correction value for the amount of wrapping of at least one of the back liner and the front liner around the preheater as the correction value. (Note 8) The sheet warping suppression device according to any one of Notes 1 to 6, wherein the adjustment unit is a water-adding device that adds water to at least one of the back liner and the front liner, and the control device determines a correction value for the amount of water added to at least one of the back liner and the front liner as the correction value. (Note 9) The sheet warping suppression device according to Note 8, wherein the water-adding device is a gluing device that glues at least one of the back liner and the front liner. (Note 10) The sheet warping suppression device according to Note 8, wherein the water-adding device is a water-spraying device that sprays water onto at least one of the back liner and the front liner. (Note 11) The sheet warping suppression device according to any one of Notes 1 to 10, wherein the first moisture meter and the second moisture meter are installed downstream of the double facer for laminating the front liner to the single-sided corrugated cardboard sheet formed by laminating the back liner and the core, and upstream of the last stage of the manufacturing line. (Note 12) The sheet warping suppression device according to any one of Notes 1 to 10, wherein the first moisture meter and the second moisture meter are installed downstream of the adjustment unit and upstream of the double facer in the manufacturing line. (Note 13) A sheet warping suppression device according to any one of Notes 1 to 12, further comprising a moisture content determination unit that determines whether the moisture content of the back liner measured by the first moisture meter and the moisture content of the front liner measured by the second moisture meter are within a predetermined range from an upper limit to a lower limit, wherein the control device, when the moisture content determination unit determines that at least one of the moisture content of the back liner and the moisture content of the front liner exceeds the range, does not perform feedback control of the adjustment unit for at least one of the back liner and the front liner that exceeds the range.(Note 14) A sheet warping suppression device according to any one of Notes 1 to 13, further comprising a warping amount measuring instrument that measures the amount of warping that occurs in the manufactured corrugated cardboard sheet and outputs the measured value of the warping amount, wherein the control device calculates a warping error which is the difference between the measured value of the warping amount and the target warping value, determines a moisture content difference target value correction amount for correcting the moisture content difference target value based on the warping error, and corrects the moisture content difference target value with the determined moisture content difference target value correction amount. (Note 15) A corrugated machine equipped with a sheet warping suppression device according to any one of Notes 1 to 14.

[0089] 1 Sheet warping suppression device 2 Corrugated machine 2A Manufacturing line 3A Back liner 3B Core 3C Front liner 3D Single-sided corrugated cardboard sheet 3E Double-sided corrugated cardboard sheet 3F Corrugated cardboard sheet 4A, 4A, 4C Mill roll stand 5 Single facer 6A Preheater (adjustment unit) 6B Preheater 6C Preheater (adjustment unit) 6D Preheater 7 Bridge 8 Glue machine (water addition device) 9 Double facer 10 Slitter scorer 11 Cut-off 12 Moisture meter 12A Moisture meter for back liner (first moisture meter) 12C Moisture meter for front liner (second moisture meter) 13 CCD camera (warping amount measuring device) 14 Water spraying device (water addition device) 20 Control device 21 Processor 21A Moisture content difference actual value calculation unit 21B Moisture content difference target value acquisition unit 21C Moisture content difference error calculation unit 21D Correction value determination unit 21E Manipulated variable distribution unit 21F Warpage error calculation unit 21G Target value correction amount determination unit 21H Moisture content difference target value correction unit 22 Storage device 22A Target value table 23 Learning processing computer 24 Moisture content determination unit 30 Subtraction unit 31 Block 32 Block 33 Addition unit 34 Block 35 Subtraction unit 36 ​​Block 37 Block 40 Moving average processing 41 Block 42 Block 43 Subtraction unit 44 Block 45 Moisture content difference target value correction amount table 46 Block 47 Feedback control error correction unit 48 Block 49 Block 50 Block

Claims

1. A sheet warping suppression device for suppressing warping of a corrugated cardboard sheet, comprising: an adjustment unit for adjusting at least one of the moisture content of the back liner and the front liner used in the manufacture of the corrugated cardboard sheet; a moisture meter including a first moisture meter for measuring the measured value of the moisture content of the back liner and a second moisture meter for measuring the measured value of the moisture content of the front liner; and a control device for controlling the adjustment unit, which calculates a measured moisture content difference value from the difference between the moisture content of the back liner and the moisture content of the front liner measured by the first moisture meter, determines a correction value for the adjustment amount in the adjustment unit based on the calculated measured moisture content difference value and a preset moisture content difference target value which is the difference between the moisture content of the back liner and the moisture content of the front liner when the corrugated cardboard sheet reaches a warping target value defined as a desired amount of warping, and provides feedback control of the adjustment unit based on the correction value, The first moisture meter and the second moisture meter are sheet warping suppression devices provided downstream of the adjustment unit.

2. The sheet warping suppression device according to claim 1, further comprising a target value table storing the moisture content difference target value, wherein the control device obtains the moisture content difference target value from the target value table.

3. The sheet warping suppression device according to claim 2, wherein the target value table is set from the estimated model, which is learned by a learning processing computer to estimate the amount of warping of the corrugated cardboard sheet based on the measured moisture content difference values ​​accumulated as a history of operating data, and the moisture content difference target value corresponding to the warping target value is set from the estimated model.

4. The sheet warping suppression device according to claim 3, wherein the estimation model for creating the target value table is periodically trained, and the target value table is periodically updated by the training processing computer in accordance with the training.

5. The sheet warping suppression device according to any one of claims 2 to 4, wherein the target value table stores multiple target values ​​for the difference in moisture content according to the manufacturing conditions of the corrugated cardboard sheet.

6. The sheet warping suppression device according to any one of claims 1 to 4, wherein the adjustment unit adjusts the moisture content of the back liner and the moisture content of the front liner, respectively.

7. The sheet warping suppression device according to any one of claims 1 to 4, wherein the adjustment unit is a preheater including a cylindrical heating drum that winds and heats at least one of the back liner and the front liner, and the control device determines a correction value for the amount of winding of at least one of the back liner and the front liner with respect to the preheater as the correction value.

8. The sheet warping suppression device according to any one of claims 1 to 4, wherein the adjustment unit is a water-adding device that adds water to at least one of the back liner and the front liner, and the control device determines a correction value for the amount of water added to at least one of the back liner and the front liner as the correction value.

9. The sheet warping suppression device according to claim 8, wherein the watering device is a gluing device that glues to at least one of the back liner and the front liner.

10. The sheet warping suppression device according to claim 8, wherein the water-adding device is a water-spraying device that sprays moisture onto at least one of the back liner and the front liner.

11. The sheet warping suppression device according to any one of claims 1 to 4, wherein the first moisture meter and the second moisture meter are installed downstream of the double facer for laminating the front liner to the single-sided corrugated cardboard sheet formed by laminating the back liner and the core, and upstream of the last stage of the manufacturing line.

12. The sheet warping suppression device according to any one of claims 1 to 4, wherein the first moisture meter and the second moisture meter are installed downstream of the adjustment unit and upstream of the double facer in the manufacturing line.

13. A sheet warping suppression device according to any one of claims 1 to 4, further comprising a moisture content determination unit that determines whether the moisture content of the back liner measured by the first moisture meter and the moisture content of the front liner measured by the second moisture meter are within a preset range from an upper limit to a lower limit, wherein the control device, when the moisture content determination unit determines that at least one of the moisture content of the back liner and the moisture content of the front liner exceeds the range, does not perform feedback control of the adjustment unit for at least one of the back liner and the front liner that exceeds the range.

14. A sheet warp suppression device according to any one of claims 1 to 4, further comprising a warp amount measuring instrument that measures the amount of warp generated in the manufactured corrugated cardboard sheet and outputs the measured value of the warp amount, wherein the control device calculates a warp error which is the difference between the measured value of the warp amount and the target warp value, determines a moisture content difference target value correction amount for correcting the moisture content difference target value based on the warp error, and corrects the moisture content difference target value with the determined moisture content difference target value correction amount.

15. A corrugated machine equipped with a sheet warping suppression device according to any one of claims 1 to 4.

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