JP2016164729A - Printing device, and method for controlling web tension - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress the vibration of web tension.SOLUTION: A printing device according to the present invention comprises a tension application unit for applying tension to a web, a detection unit for detecting the tension of the web, and a control unit for executing, on the basis of the result of web tension detected by the detection unit, integral control on the tension applied to the web by the tension application unit, the control unit lowering an integral gain in the integral control when the web tension detected by the detection unit becomes zero.SELECTED DRAWING: Figure 8

Description

  The present invention relates to a technique for controlling web tension.

  Patent Document 1 describes a tension control device that applies a brake torque to the unwinding shaft while pulling out the sheet wound on the unwinding shaft and applies tension to the sheet. The tension control device adjusts the sheet tension to the target tension by feedback-controlling the brake torque based on the detection result of the sheet tension by the detector.

Japanese Patent Laid-Open No. 04-094357

  By the way, even if it is the structure which performs the above feedback control to the tension | tensile_strength of a web, the tension | tensile_strength of a web may not always be stabilized to a target tension, and the tension | tensile_strength of a web may fall to zero. In such a case, as a result of the feedback control operating to recover the web tension lowered to zero, an excessive tension is applied to the web, and the subsequent web tension may vibrate greatly.

  SUMMARY An advantage of some aspects of the invention is to solve at least a part of the problems described above, and the invention can be implemented as the following forms.

  A printing apparatus according to the present invention includes a tension applying unit that applies tension to a web, a detection unit that detects web tension, and a tension applying unit that integrates the tension applied to the web based on the detection result of the web tension. A control unit that executes control, and the control unit lowers the integral gain in the integral control when the tension of the web detected by the detection unit becomes zero.

  The web tension control method according to the present invention includes a step of detecting a web tension, and a step of executing integration control on the tension applied to the web based on the detection result of the web tension. When zero, the integral gain in integral control is lowered.

  In the present invention (printing apparatus, web tension control method) configured as described above, integral control is executed on the web tension based on the detection result of the web tension. Accordingly, it is possible to control the tension of the web while suppressing the steady deviation. However, when the web tension drops to zero, the large integrated value accumulated during that period acts to restore the web tension. As a result, an excessive tension is applied to the web, and the subsequent web tension may vibrate greatly.

  On the other hand, the present invention lowers the integral gain in the integral control when the detection result of the web tension becomes zero. Therefore, the integrated value accumulated during the period when the web tension is reduced to zero can be kept small. Therefore, it is possible to suppress excessive tension on the web and to suppress subsequent vibration of the web tension.

  The control unit also includes a first control mode for lowering the integral gain in the integral control when the web tension detected by the detection unit becomes zero, and an integral gain in the integral control before and after the web tension detected by the detection unit becomes zero. The printing apparatus may be configured so that it can be executed by switching to the second control mode for keeping the constant. This makes it possible to control web tension in various modes.

  The control unit performs integral control on the deviation between the web tension and the web target tension detected by the detection unit, and executes the first control mode when the target tension is less than the threshold value. The printing apparatus may be configured to execute the second control mode when is equal to or greater than the threshold. That is, when the target tension of the web is high, it is not necessary to execute the second control mode because a situation in which the tension of the web is reduced to zero hardly occurs. On the other hand, when the target tension of the web is low, a situation in which the tension of the web is reduced to zero is likely to occur. Therefore, it is preferable to execute the first control mode to suppress the vibration of the web tension.

  In addition, it includes a conveyance unit that conveys the web at a constant speed after accelerating the web over the acceleration period, and the control unit performs integration control with a constant integral gain during the acceleration period, while after the acceleration period elapses The printing apparatus may be configured to start control to lower the integral gain in the integral control when the web tension detected by the detection unit becomes zero. In such a configuration, the tension variation generated on the web can be quickly suppressed with a high integral gain during the web acceleration period. On the other hand, when the web is conveyed at a constant speed, the tension of the web can be suppressed from being vibrated by lowering the integral gain.

  In addition, it includes a conveyance unit that conveys the web at a constant speed after accelerating the web over an acceleration period, and the control unit performs integration control with a constant integral gain during the acceleration period, while the web detected by the detection unit The printing apparatus may be configured such that when the tension becomes zero, the control for lowering the integral gain in the integral control is started after the acceleration period has elapsed. In such a configuration, the tension variation generated on the web can be quickly suppressed with a high integral gain during the web acceleration period. On the other hand, when the web is conveyed at a constant speed, vibration of the web tension can be suppressed due to the web tension being reduced to zero.

  A plurality of constituent elements of each aspect of the present invention described above are not indispensable, and some or all of the effects described in the present specification are to be solved to solve part or all of the above-described problems. In order to achieve the above, it is possible to appropriately change, delete, replace with another new component, and partially delete the limited contents of some of the plurality of components. In order to solve part or all of the above-described problems or to achieve part or all of the effects described in this specification, technical features included in one embodiment of the present invention described above. A part or all of the technical features included in the other aspects of the present invention described above may be combined to form an independent form of the present invention.

1 is a front view schematically illustrating the configuration of a printer to which the invention is applied. FIG. 2 is a block diagram schematically illustrating an electrical configuration for controlling the printer illustrated in FIG. 1. The block diagram which shows the feedback control with respect to the tension | tensile_strength of a winding part. 6 is a flowchart illustrating an example of a constant gain mode. The flowchart which shows an example of a gain variable mode. The flowchart which shows an example of the control performed with conveyance of a web. The figure which shows typically an example of the operation | movement performed according to the flowchart of FIG. The figure which shows typically the difference in the control result of gain constant mode and variable gain mode.

  FIG. 1 is a front view schematically illustrating the configuration of a printer to which the present invention is applied. As shown in FIG. 1, in the printer 1, a single web S having both ends wound around a feed shaft 20 and a take-up shaft 40 in a roll shape is stretched along a conveyance path. While being transported in the transport direction Ds from the feed shaft 20 toward the take-up shaft 40, image recording is received. The web S is roughly divided into a paper system and a film system. Specific examples include high-quality paper, cast paper, art paper, coated paper, and the like, and film types include synthetic paper, PET (Polyethylene terephthalate) film, and PP (polypropylene) film. Schematically, the printer 1 includes a feeding unit 2 (feeding region) for feeding the web S from the feeding shaft 20, a process unit 3 (process region) for recording an image on the web S fed from the feeding unit 2, and a process. A winding unit 4 (winding region) for winding the web S on which the image is recorded in the unit 3 around the winding shaft 40 is provided. In the following description, of both surfaces of the web S, the surface on which an image is recorded is referred to as the front surface, and the opposite surface is referred to as the back surface.

  The feeding unit 2 includes a feeding shaft 20 around which the end of the web S is wound, and a driven roller 21 around which the web S drawn from the feeding shaft 20 is wound. The feeding shaft 20 supports the end of the web S by winding it with the surface of the web S facing outward. Then, the web S wound around the feed shaft 20 is fed to the process unit 3 via the driven roller 21 as the feed shaft 20 rotates clockwise in FIG. Incidentally, the web S is wound around the feeding shaft 20 via a core tube 22 that can be attached to and detached from the feeding shaft 20. Therefore, when the web S of the feeding shaft 20 is used up, it is possible to replace the web S of the feeding shaft 20 by attaching a new core tube 22 around which the roll-shaped web S is wound to the feeding shaft 20. It has become. Here, as the core tube 22, a flexible core tube 22 such as a paper core tube 22 (paper tube) can be used.

  The process unit 3 performs processing by the functional units 51, 52, 61, 62, and 63 arranged along the outer peripheral surface of the rotating drum 30 while supporting the web S fed from the feeding unit 2 by the rotating drum 30. An image is recorded on the web S as appropriate. In the process unit 3, a front drive roller 31 and a rear drive roller 32 are provided on both sides of the rotary drum 30, and the web S conveyed from the front drive roller 31 to the rear drive roller 32 is supported by the rotary drum 30. And receive an image record.

  The front driving roller 31 has a plurality of minute protrusions formed by thermal spraying on the outer peripheral surface, and winds the web S fed from the feeding unit 2 from the back side. The front drive roller 31 rotates in the clockwise direction in FIG. 1 to convey the web S fed from the feeding unit 2 to the downstream side of the conveyance path. A nip roller 31 n is provided for the front drive roller 31. The nip roller 31n is in contact with the surface of the web S while being urged toward the front drive roller 31 and sandwiches the web S between the front drive roller 31 and the nip roller 31n. Thereby, the frictional force between the front drive roller 31 and the web S is ensured, and the web S can be reliably conveyed by the front drive roller 31.

  The rotary drum 30 is a cylindrical drum having a diameter of, for example, 400 [mm] supported by a support mechanism (not shown) so as to be rotatable in both the transport direction Ds and the opposite direction. The web S conveyed to the driving roller 32 is wound from the back side. The rotating drum 30 supports the web S from the back side while receiving the frictional force with the web S and rotating in the conveyance direction Ds of the web S. Incidentally, the process unit 3 is provided with driven rollers 33 and 34 for folding the web S on both sides of the winding part around the rotary drum 30. Among these, the driven roller 33 wraps the surface of the web S between the front drive roller 31 and the rotary drum 30 and folds the web S. On the other hand, the driven roller 34 wraps the surface of the web S between the rotating drum 30 and the rear drive roller 32 and folds the web S. As described above, by folding the web S on the upstream and downstream sides in the transport direction Ds with respect to the rotating drum 30, it is possible to secure a long winding portion of the web S around the rotating drum 30.

  The rear driving roller 32 has a plurality of minute protrusions formed by thermal spraying on the outer peripheral surface, and winds the web S conveyed from the rotating drum 30 via the driven roller 34 from the back surface side. Then, the rear driving roller 32 rotates clockwise in FIG. 1 to convey the web S to the winding unit 4. A nip roller 32n is provided for the rear drive roller 32. The nip roller 32 n is in contact with the surface of the web S while being biased toward the rear drive roller 32, and sandwiches the web S with the rear drive roller 32. Thereby, the frictional force between the rear drive roller 32 and the web S is ensured, and the web S can be reliably conveyed by the rear drive roller 32.

  Thus, the web S conveyed from the front drive roller 31 to the rear drive roller 32 is supported on the outer peripheral surface of the rotary drum 30. In the process unit 3, in order to record a color image on the surface of the web S supported by the rotary drum 30, a plurality of recording heads 51 corresponding to different colors are provided. Specifically, four recording heads 51 corresponding to yellow, cyan, magenta, and black are arranged in the transport direction Ds in this color order. Each recording head 51 is opposed to the surface of the web S wound around the rotary drum 30 with a slight clearance, and ejects the corresponding color ink (colored ink) from the nozzles by an ink jet method. Then, each recording head 51 ejects ink onto the web S conveyed in the conveyance direction Ds, whereby a color image is formed on the surface of the web S.

  Incidentally, as the ink, UV (ultraviolet) ink (photo-curable ink) that is cured by irradiating ultraviolet rays (light) is used. Therefore, in the process unit 3, UV irradiators 61 and 62 (irradiation devices) are provided to cure the ink and fix it on the web S. The ink curing is performed in two stages, temporary curing and main curing. A temporary curing UV irradiator 61 is disposed between each of the plurality of recording heads 51. That is, the UV irradiator 61 cures (temporarily cures) the ink to such an extent that the method of wetting and spreading the ink is sufficiently slow compared with the case of not irradiating the ultraviolet ray by irradiating the ultraviolet ray having a weak irradiation intensity. It does not cure the ink. On the other hand, a UV irradiator 62 for main curing is provided downstream of the recording heads 51 in the transport direction Ds. That is, the UV irradiator 62 is cured (mainly cured) by irradiating ultraviolet rays having a stronger irradiation intensity than the UV irradiator 61 so that the wetting and spreading of the ink stops.

  In this way, the UV irradiator 61 disposed between each of the plurality of recording heads 51 temporarily cures the colored ink ejected to the web S from the recording head 51 on the upstream side in the transport direction Ds. Accordingly, the ink ejected from the one recording head 51 onto the web S is temporarily cured before reaching the recording head 51 adjacent to the one recording head 51 on the downstream side in the transport direction Ds. As a result, the occurrence of color mixing such as mixing of colored inks of different colors is suppressed. In a state in which the color mixture is suppressed in this way, the plurality of recording heads 51 eject colored inks of different colors to form a color image on the web S. Further, a UV irradiator 62 for main curing is provided downstream of the plurality of recording heads 51 in the transport direction Ds. Therefore, the color image formed by the plurality of recording heads 51 is permanently cured by the UV irradiator 62 and fixed on the web S.

  Furthermore, a recording head 52 is provided downstream of the UV irradiator 62 in the transport direction Ds. The recording head 52 is opposed to the surface of the web S wound around the rotary drum 30 with a slight clearance, and discharges transparent UV ink from the nozzles onto the surface of the web S by an inkjet method. That is, the transparent ink is further ejected with respect to the color image formed by the recording heads 51 for four colors. The transparent ink is ejected over the entire surface of the color image, and gives the color image a texture such as a glossy feeling or a matte feeling. A UV irradiator 63 (irradiation device) is provided downstream of the recording head 52 in the transport direction Ds. The UV irradiator 63 irradiates ultraviolet rays stronger than the UV irradiator 61 to fully cure the transparent ink ejected by the recording head 52. Thereby, the transparent ink can be fixed on the surface of the web S.

  As described above, in the process unit 3, ink ejection and curing are appropriately performed on the web S wound around the outer peripheral portion of the rotary drum 30, and a color image coated with the transparent ink is formed. Then, the web S on which the color image is formed is conveyed to the winding unit 4 by the rear drive roller 32.

  The winding unit 4 includes a driven roller 41 that winds the web S from the back side between the winding shaft 40 and the rear drive roller 32 in addition to the winding shaft 40 around which the end of the web S is wound. The winding shaft 40 winds and supports the end of the web S with the surface of the web S facing outward. That is, when the winding shaft 40 rotates clockwise in FIG. 1, the web S conveyed from the rear drive roller 32 is wound around the winding shaft 40 via the driven roller 41. Incidentally, the web S is wound around the winding shaft 40 via a core tube 42 that can be attached to and detached from the winding shaft 40. Therefore, when the web S wound around the winding shaft 40 becomes full, the web S can be removed together with the core tube 42. Here, as the core tube 42, a flexible core tube 42 such as a paper core tube 42 (paper tube) can be used.

  The above is the outline of the device configuration of the printer 1. Subsequently, an electrical configuration for controlling the printer 1 will be described. FIG. 2 is a block diagram schematically illustrating an electrical configuration for controlling the printer illustrated in FIG. 1. In the printer 1, a printer control unit 100 that controls each unit of the printer 1 is provided. The respective units of the recording head, the UV irradiator, and the web conveyance system are controlled by the printer control unit 100. Details of the control of the printer control unit 100 for each part of the apparatus are as follows.

  The printer control unit 100 controls the ink discharge timing of each recording head 51 that forms a color image according to the conveyance of the web S. Specifically, the control of the ink ejection timing is executed based on the output (detection value) of a drum encoder E30 that is attached to the rotating shaft of the rotating drum 30 and detects the rotational position of the rotating drum 30. That is, since the rotating drum 30 is driven and rotated as the web S is conveyed, the conveying position of the web S can be grasped by referring to the output of the drum encoder E30 that detects the rotational position of the rotating drum 30. Therefore, the printer control unit 100 generates a pts (print timing signal) signal from the output of the drum encoder E30, and controls the ink ejection timing of each recording head 51 based on this pts signal, so that each recording head 51 has the same function. The discharged ink is landed on the target position of the web S to be transported to form a color image.

  Similarly, the timing at which the recording head 52 discharges the transparent ink is also controlled by the printer controller 100 based on the output of the drum encoder E30. Thereby, it is possible to accurately eject the transparent ink to the color image formed by the plurality of recording heads 51. Further, the printer controller 100 also controls the timing of turning on / off the UV irradiators 61, 62, and 63 and the amount of irradiation light.

  The printer control unit 100 controls a function of controlling the conveyance of the web S described in detail with reference to FIG. That is, motors are connected to each of the feeding shaft 20, the front driving roller 31, the rear driving roller 32, and the winding shaft 40 among members constituting the web conveyance system. The printer control unit 100 controls the conveyance of the web S by controlling the speed and torque of each motor while rotating these motors. The details of the conveyance control of the web S are as follows.

  The printer control unit 100 rotates the feeding motor M <b> 20 that drives the feeding shaft 20, and supplies the web S from the feeding shaft 20 to the front drive roller 31. At this time, the printer control unit 100 controls the torque of the feeding motor M20 to adjust the tension of the web S from the feeding shaft 20 to the front drive roller 31 (feeding tension Ta). That is, a tension sensor S21 for detecting the magnitude of the feeding tension Ta is attached to the driven roller 21 disposed between the feeding shaft 20 and the front drive roller 31. The tension sensor S21 can be constituted by, for example, a load cell that detects the magnitude of the force received from the web S. Then, the printer control unit 100 adjusts the feeding tension Ta of the web S by feedback controlling the torque of the feeding motor M20 based on the detection result (detected value) of the tension sensor S21.

  Further, the printer control unit 100 rotates the front drive motor M31 that drives the front drive roller 31 and the rear drive motor M32 that drives the rear drive roller 32. As a result, the web S fed from the feeding unit 2 passes through the process unit 3. At this time, speed control is executed for the front drive motor M31, while torque control is executed for the rear drive motor M32. That is, the printer control unit 100 adjusts the rotation speed of the front drive motor M31 to be constant based on the encoder output of the front drive motor M31. As a result, the web S is conveyed at a constant speed by the front drive roller 31.

  On the other hand, the printer control unit 100 controls the torque of the rear drive motor M32 to adjust the tension (process tension Tb) of the web S from the front drive roller 31 to the rear drive roller 32. That is, a tension sensor S34 that detects the size of the process tension Tb is attached to the driven roller 34 disposed between the rotary drum 30 and the rear drive roller 32. The tension sensor S34 can be constituted by a load cell that detects the magnitude of the force received from the web S, for example. The printer controller 100 adjusts the process tension Tb of the web S by feedback controlling the torque of the rear drive motor M32 based on the detection result (detection value) of the tension sensor S34.

  Further, the printer control unit 100 rotates the winding motor M <b> 40 that drives the winding shaft 40, and winds the web S conveyed by the rear driving roller 32 around the winding shaft 40. At this time, the printer control unit 100 controls the torque of the winding motor M40 to adjust the tension of the web S from the rear drive roller 32 to the winding shaft 40 (winding tension Tc). That is, the tension sensor S41 for detecting the winding tension Tc is attached to the driven roller 41 disposed between the rear drive roller 32 and the winding shaft 40. The tension sensor S41 can be configured by a load cell that detects a force received from the web S, for example. The printer control unit 100 adjusts the winding tension Tc of the web S by feedback controlling the torque of the winding motor M40 based on the detection result of the tension sensor S41.

  FIG. 3 is a block diagram showing feedback control executed for the winding tension of the winding unit. As shown in the figure, the printer control unit 100 executes feedback control by integral control with respect to the winding tension Tc. Specifically, a deviation Δc between the target value Tct of the winding tension Tc and the detection value Tcd of the tension sensor S41 is obtained, and the value obtained by integrating the deviation Δc of the winding tension Tc with time is multiplied by an integral gain K, An operation amount Vc (voltage signal) is calculated. Then, the operation amount Vc thus obtained is input to the take-up motor M40. Thus, the winding tension Tc is feedback-controlled so that the detection value Tcd of the winding tension Tc approaches the target value Tct (that is, the deviation Δc approaches zero). In particular, in the present embodiment, the printer control unit 100 can selectively execute a constant gain mode for keeping the integral gain K constant and a variable gain mode for dynamically changing the integral gain K.

  FIG. 4 is a flowchart illustrating an example of the constant gain mode. In the constant gain mode, the integral gain K is set to a constant Kc (> 0) in step S101, and when the winding tension Tc is detected by the tension sensor S41 in step S102, the detected value Tcd and the target value Tct are detected in step S103. Deviation Δc is calculated. The manipulated variable Vc is calculated by multiplying the integral gain Kc set in step S101 by the integral value of the deviation Δc (step S104). As described above, in the constant gain mode, the manipulated variable Vc is obtained by multiplying the integral value of the deviation Δc by a constant integral gain K (= Kc) regardless of the detection value Tcd of the winding tension Tc. On the other hand, in the gain variable mode, the integral gain K multiplied by the integral value of the deviation Δc is changed according to the detected value Tcd of the winding tension Tc.

  FIG. 5 is a flowchart illustrating an example of the variable gain mode. In the variable gain mode, when the winding tension Tc is detected by the tension sensor S41 in step S201, it is determined in step S202 whether or not the detected value Tcd of the winding tension Tc is equal to zero. If the detected value Tcd is greater than zero (“NO” in step S202), the value of the integral gain K is set to a constant Kvh (> 0) (step S203). Then, a deviation Δc between the detected value Tcd and the target value Tct is calculated (step S205), and the operation amount Vc is calculated by multiplying the integral gain Kvh set in step S203 by the integral value of the deviation Δc (step S206). On the other hand, when the detected value Tcd is equal to zero (“YES” in step S202), the value of the integral gain K is set to a constant Kvl (≧ 0) smaller than the constant Kvh (step S204). Then, a deviation Δc between the detection value Tcd and the target value Tct is calculated (step S205), and the operation amount Vc is calculated by multiplying the integral gain Kvl set in step S204 by the integral value of the deviation Δc (step S206).

  That is, in the gain variable mode, when the detected value Tcd of the winding tension Tc is larger than zero, the integral control of the winding tension Tc is executed with a relatively large integral gain Kvh. On the other hand, when the detected value Tcd of the winding tension Tc is equal to zero, integral control of the winding tension Tc is executed with a relatively small integral gain Kvl. Therefore, during the feedback control of the winding tension Tc, when the detected value Tcd of the winding tension Tc becomes zero, the integral gain K is lowered to the value Kvl and the integral control of the winding tension Tc is executed. When the detected value Tcd becomes larger than zero, the integral gain K is increased to the value Kvh, and the integral control of the winding tension Tc is executed.

  Various criteria can be considered for selecting a mode to be used from among the constant gain mode and the variable gain mode. Subsequently, an example in which the constant gain mode and the variable gain mode are selectively used in accordance with the conveyance state of the web S will be described.

  FIG. 6 is a flowchart illustrating an example of control executed in accordance with web conveyance. In particular, the flowchart of FIG. 6 illustrates control executed by the printer control unit 100 when the stopped web S is accelerated to a predetermined speed and then conveyed at a constant speed. FIG. 7 is a diagram schematically illustrating an example of an operation executed according to the flowchart of FIG. The upper part of FIG. 7 shows the temporal change in the conveyance speed of the web S, and the lower part of FIG. 7 shows the temporal change of the setting value of the integral gain.

  As shown in FIG. 6, after starting the constant gain mode in step S301, acceleration of the web S is started in step S302. As a result, during the acceleration period (2.5 [s]) in which the web S is accelerated from the stop state to a predetermined speed (15 [m / m]), the integral control in the constant gain mode is performed. Executed at Tc. At this time, the integral gain Kc in the integral control in the constant gain mode is set to a relatively large value (twice).

  When the acceleration period (2.5 [s]) elapses from the acceleration start of the web S (“YES” in step S303), the constant speed conveyance for conveying the web S at a constant predetermined speed (15 [m / m]) is performed. The process is started (step S304). The printer control unit 100 stores the result of experimentally measuring the time required to accelerate the web S from the stopped state to a predetermined speed (15 [m / m]) as an acceleration period. The determination in S303 is executed based on this.

  Subsequently, in step S305, the value of the integral gain K is decreased to an integral gain Kvh (0.1 times) smaller than the integral gain Kc in the constant gain mode. The reduction of the value of the integral gain K is executed over a predetermined period (2.0 [s]). When the reduction of the integral gain K is completed, the gain variable mode is started. Thereby, in the subsequent constant speed conveyance of the web S, the integration control in the gain variable mode is executed on the winding tension Tc of the web S, and the value of the integral gain K changes according to the winding tension Tc. Incidentally, FIG. 7 does not show how the integral gain K changes.

  As described above, in the present embodiment, the integration control is performed on the winding tension Tc of the web S based on the detection result of the winding tension Tc of the web S. Accordingly, it is possible to control the winding tension Tc of the web S while suppressing the steady deviation.

  By the way, when the web S is continuously wound around the winding shaft 40 with a large winding tension Tc, a winding failure such as the web S wound in a roll shape being displaced in the axial direction of the winding shaft 40 occurs. There is a fear. Therefore, it is preferable that the target value Tct of the winding tension Tc applied to the web S after the constant speed conveyance is set relatively low. However, in the control for adjusting the winding tension Tc to the low target value Tc, the winding tension Tc may drop to zero. For this reason, in the configuration in which the integration control is performed on the winding tension Tc, a large integrated value accumulated during the period in which the winding tension Tc falls to zero acts to restore the winding tension Tc. As a result, an excessive winding tension Tc is applied to the web S, and the winding tension Tc of the web S at that time may vibrate greatly.

  On the other hand, in this embodiment, the gain variable mode is executed after the constant speed conveyance of the web S is established. For this reason, when the detection result Tcd of the winding tension Tc of the web S becomes zero, the integral gain K in the integral control decreases. Therefore, the integral value accumulated during the period when the winding tension Tc of the web S is reduced to zero can be suppressed to a small value. Therefore, it is possible to suppress an excessive winding tension Tc from being applied to the web S and to suppress subsequent vibration of the winding tension Tc of the web S. This point will be described using a specific example as follows.

  FIG. 8 is a diagram schematically showing a difference in control results between the constant gain mode and the variable gain mode. The column of “gain constant mode” on the left side of FIG. 8 illustrates a case where control in the constant gain mode is executed on the winding tension Tc after the constant speed conveyance of the web S is established. In the column, the case where the control in the gain variable mode is executed on the winding tension Tc after the constant speed conveyance of the web S is established is illustrated.

  In the “gain constant mode”, the integral gain K is constant at a constant Kvh regardless of whether the winding tension Tc is zero or not. Therefore, even during a period in which the winding tension Tc is zero, the operation value Vc is obtained by multiplying the integral value of the deviation Δc by the large integral gain Kvh. As a result, a large manipulated variable Vc is generated and applied to the winding motor M40, and the winding tension Tc rises to a large peak that greatly exceeds the target value Tct.

  On the other hand, in the “gain variable mode”, when the winding tension Tc becomes zero, the integral gain K in the integral control falls to the value Kvl. Therefore, it is possible to suppress the integral value accumulated during the period in which the winding tension Tc of the web S is reduced to zero and to prevent the excessive operation amount Vc from being applied to the winding motor M40. As a result, the peak indicated by the winding tension Tc exceeding the target value Tct is kept low. That is, the vibration amplitude Av of the winding tension Tc in the gain variable mode is suppressed to be smaller than the vibration amplitude Ac of the winding tension Tc in the constant gain mode. Thus, in the variable gain mode, it is possible to suppress the vibration of the winding tension Tc of the web S.

  Further, the printer control unit 100 can selectively switch between the variable gain mode and the constant gain mode. As a result, the winding tension Tc of the web S can be controlled in various modes.

  Further, the printer control unit 100 conveys the web S at a constant speed after accelerating the web S over an acceleration period. Then, integral control is executed with a constant integral gain K during the acceleration period, and the integral gain K in the integral control is lowered when the acceleration period elapses. With such a configuration, during the acceleration period of the web S, fluctuations in the winding tension Tc generated on the web S can be quickly suppressed with a high integral gain K. On the other hand, when the web S is conveyed at a constant speed, the winding gain Tc of the web S can be suppressed from being vibrated by lowering the integral gain K.

  Thus, in the present embodiment, the printer 1 corresponds to an example of the “printing apparatus” of the present invention, the winding motor M40 corresponds to an example of the “tension applying unit” of the present invention, and the tension sensor S41 corresponds to the present invention. The printer control unit 100 corresponds to an example of the “control unit” of the present invention, and the feeding shaft 20, the front drive roller 31, the rear drive roller 32, and the take-up shaft 40 cooperate. The web S functions as an example of the “web” of the present invention, the winding tension Tc corresponds to an example of the “tension” of the present invention, and the variable gain mode. Corresponds to an example of the “first control mode” of the present invention, and the constant gain mode corresponds to an example of the “second control mode” of the present invention.

  The present invention is not limited to the above-described embodiment, and various modifications can be made to the above-described one without departing from the spirit of the present invention. For example, in the above-described embodiment, the constant gain mode and the variable gain mode are properly used according to the conveyance state of the web S. However, the standard for properly using these modes is not limited to this. Therefore, it may be properly used depending on the winding tension Tc applied to the web S.

  That is, when the target value Tct of the winding tension Tc is less than the threshold value, the variable gain mode is executed, and when the target value Tct of the winding tension Tc is equal to or larger than the threshold value, the constant gain mode may be executed. . That is, when the target value Tct of the winding tension Tc of the web S is high, it is difficult to cause a situation in which the winding tension Tc of the web S is reduced to zero. Therefore, it is sufficient to execute the constant gain mode. On the other hand, when the target value Tct of the winding tension Tc of the web S is low, a situation in which the winding tension Tc of the web S is easily reduced to zero is likely to occur. It is preferable to suppress the vibration of the tension Tc.

  Further, specific values of the integral gains Kc, Kvh, Kvl can be appropriately adjusted and changed. In particular, the integral gain Kvl in the variable gain mode may be zero.

  In the above embodiment, only integral control is performed on the winding tension Tc. However, in the feedback control of the winding tension Tc, at least one of proportional control and differential control may be used in combination.

  Further, in the control of the winding tension Tc, the constant gain mode and the variable gain mode are properly used. However, it may be configured to execute only the gain variable mode without executing the constant gain mode.

  Further, the case where the variable gain mode is executed for the control of the winding tension Tc is illustrated. However, for example, the variable gain mode may be executed for the control of the feeding tension Ta.

  Various changes can be made to the specific configuration of the printer 1. For example, the member that supports the web S to be conveyed is not limited to the cylindrical shape such as the rotating drum 30. Therefore, it is also possible to use a flat platen that supports the web S on a flat surface.

  DESCRIPTION OF SYMBOLS 1 ... Printer, 20 ... Feeding shaft, 31 ... Front drive roller, 32 ... Rear drive roller, 40 ... Winding shaft, 100 ... Printer control part, M40 ... Winding motor, S41 ... Tension sensor, S ... Web, Tc ... Winding tension

Claims (6)

A tension applying section for applying tension to the web;
A detection unit for detecting web tension;
A controller that performs integral control on the tension applied to the web by the tension applying unit based on the detection result of the web tension by the detecting unit;
The control device, wherein the control unit lowers the integral gain in the integral control when the web tension detected by the detection unit becomes zero.   The control unit includes a first control mode for reducing the integral gain in the integral control when the web tension detected by the detection unit becomes zero, and the integration before and after the web tension detected by the detection unit becomes zero. The printing apparatus according to claim 1, wherein the printing apparatus can be executed by switching between a second control mode in which the integral gain in control is constant.   The control unit performs the integration control on the deviation between the web tension detected by the detection unit and the web target tension, and executes the first control mode when the target tension is less than a threshold value. The printing apparatus according to claim 2, wherein the second control mode is executed when the target tension is equal to or greater than a threshold value. It has a transport part that transports at a constant speed after accelerating the web over an acceleration period,
The said control part performs the said integral control with the said integral gain constant during the said acceleration period, and reduces the said integral gain in the said integral control when the said acceleration period passes. The printing apparatus as described. It has a transport part that transports at a constant speed after accelerating the web over an acceleration period,
The control unit executes integration control with a constant integration gain during the acceleration period, and after the acceleration period has elapsed, when the web tension detected by the detection unit becomes zero, the integration in the integration control is performed. The printing apparatus according to claim 1, wherein control for reducing the gain is started. Detecting the tension of the web;
A step of performing integral control on the tension applied to the web based on the detection result of the web tension,
A web tension control method for reducing an integral gain in the integral control when a web tension detection result becomes zero.

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