JP2017217848A - Printer and printing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress a transportation speed of a recording medium in a driven rotation member such that it falls within an appropriate range in a printing technique for adjusting liquid discharge timing from a discharge head according to a rotational position of the driven rotation member driven and rotated in association with transportation of the recording medium while controlling the transportation speed of the recording medium by a drive roller.SOLUTION: A printer comprises: a drive roller driving a recording medium by rotating while being brought into contact with the recording medium; a discharge head discharging liquid onto the recording medium; a driven rotation member driven and rotated in association with transportation of the recording medium while being brought into contact with the recording medium; a rotational position detection section detecting a rotational position of the driven rotation member; and a control section adjusting timing when discharging the liquid from the discharge head according to a detection result of the rotational position detection section while transporting the recording medium by rotating the drive roller. The control section adjusts the number of revolutions of the drive roller according to tension of the recording medium at an opposite side to the discharge head of the drive roller.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a technique for executing printing by discharging a liquid onto a recording medium while conveying the recording medium.

  The printing apparatus described in Patent Document 1 prints an image on a recording medium by ejecting liquid from the ejection head onto the recording medium that is transported in a predetermined transport direction. In such a printing apparatus, it is necessary to discharge the liquid from the discharge head at a timing corresponding to the recording medium conveyance speed in the landing range where the liquid discharged from the discharge head lands. Therefore, a driven rotation member is provided corresponding to the landing range, and the liquid discharge timing from the discharge head is controlled based on the detection result of the rotation position of the driven rotation member that rotates following the conveyance of the recording medium. The

JP 2013-220645 A

  By the way, there is a limit to the time interval at which the discharge head can continuously discharge liquid appropriately. For this reason, if the recording medium conveyance speed is too high, it is difficult to appropriately discharge the liquid from the discharge head. Therefore, the printing apparatus of Patent Document 1 adjusts the conveyance speed of the recording medium by controlling the rotation speed of the driving roller that drives the recording medium in the conveyance direction.

  In such a configuration, it was assumed that the peripheral speed of the driven rotation member provided corresponding to the landing range of the liquid basically matches the peripheral speed of the drive roller. However, according to an experiment conducted by the inventors of the present application, it was confirmed that the peripheral speed of the driving roller and the peripheral speed of the driven rotating member do not necessarily match depending on the conditions when the recording medium is conveyed. In particular, it has been found that the peripheral speed of the driven rotating member may be higher than the peripheral speed of the driving roller depending on the conveying conditions such as the tension applied to the recording medium or the configuration of the recording medium. This means that the conveyance speed of the recording medium may become too fast in the landing range provided corresponding to the driven rotation member.

  The present invention has been made in view of the above, and the liquid from the ejection head is controlled according to the rotational position of a driven rotating member that rotates following the conveyance of the recording medium while controlling the conveyance speed of the recording medium by a driving roller. An object of the present invention is to provide a technique capable of suppressing the conveyance speed of a recording medium in a driven rotating member within an appropriate range in a printing technique for adjusting ejection timing.

  A first aspect (printing apparatus) of the present invention includes a driving roller that drives a recording medium by rotating while contacting the recording medium, an ejection head that discharges liquid to the recording medium, and a recording medium that contacts the recording medium. A detection result of the rotation position detection unit while conveying the recording medium by rotating the drive roller, and a rotation position detection unit that detects the rotation position of the driven rotation member. Accordingly, the controller for adjusting the timing of ejecting the liquid from the ejection head, the first tension that is the tension of the recording medium on the ejection head side with respect to the driving roller, and the tension of the recording medium on the opposite side of the ejection head from the driving roller A tension adjusting unit that adjusts the second tension, and the control unit adjusts the rotational speed of the driving roller according to the second tension.

  The second aspect (printing method) of the present invention is a driven rotating member that drives a recording medium by rotating a driving roller that contacts the recording medium, and rotates following the conveyance of the recording medium while contacting the recording medium. And a step of adjusting the timing of discharging the liquid from the discharge head to the recording medium according to the detection result of the rotation position of the driven rotation member. The printing method is adjusted according to the tension of the recording medium on the opposite side of the ejection head.

  That is, in the configuration in which the recording medium is driven by the driving roller, the peripheral speed of the driven rotating member may be higher than the peripheral speed of the driving roller due to the tension of the recording medium on the opposite side of the ejection head from the driving roller. . On the other hand, in the first aspect and the second aspect of the present invention, the rotational speed of the driving roller is adjusted according to the tension of the recording medium on the opposite side of the ejection head from the driving roller. Therefore, the conveyance speed of the recording medium in the driven rotating member can be suppressed to an appropriate range.

  Specifically, the control unit may configure the printing apparatus so as to adjust the rotation speed of the driving roller in accordance with the change in the second tension without depending on the change in the first tension. Alternatively, the control unit may configure the printing apparatus so as to adjust the rotational speed of the driving roller in accordance with a change in the cross-sectional stress of the recording medium caused by the difference between the first tension and the second tension. As a result, the conveyance speed of the recording medium in the driven rotating member can be suppressed to an appropriate range.

  According to a third aspect (printing apparatus) of the present invention, a driving roller that drives a recording medium by rotating while contacting the recording medium, an ejection head that discharges liquid to the recording medium, and a recording medium that contacts the recording medium A detection result of the rotation position detection unit while conveying the recording medium by rotating the drive roller, and a rotation position detection unit that detects the rotation position of the driven rotation member. And a controller that adjusts the timing at which the liquid is ejected from the ejection head, and the controller adjusts the rotational speed of the drive roller according to the configuration of the recording medium.

  A fourth aspect (printing method) of the present invention is a driven rotating member that drives a recording medium by rotating a driving roller that contacts the recording medium, and rotates following the conveyance of the recording medium while contacting the recording medium. And a step of adjusting the timing of ejecting the liquid from the ejection head to the recording medium according to the detection result of the rotational position of the driven rotating member, and the number of rotations of the driving roller is determined by the recording medium. It is adjusted according to the configuration.

  Thus, in the third aspect and the fourth aspect of the present invention, the rotational speed of the drive roller is adjusted according to the configuration of the recording medium. Therefore, the conveyance speed of the recording medium in the driven rotating member can be suppressed to an appropriate range.

  The configuration of the recording medium is a concept including the thickness and width of the recording medium. Here, the thickness of the recording medium corresponds to the dimension of the recording medium in the normal direction of the surface of the recording medium, and the width of the recording medium corresponds to the dimension of the recording medium in the axial direction of the drive roller.

  Specifically, the control unit may configure the printing apparatus so as to adjust the rotational speed of the driving roller according to the thickness of the recording medium. Alternatively, the control unit may configure the printing apparatus so as to adjust the rotational speed of the driving roller according to the width of the recording medium. As a result, the conveyance speed of the recording medium in the driven rotating member can be suppressed within an appropriate range.

  Note that not all of the plurality of constituent elements included in each aspect of the present invention described above are essential, and in order to solve part or all of the above-described problems or a part of the effects described in the present specification. Or, in order to achieve all of them, it is possible to change, delete, replace with other new components, or delete some of the limited contents of some components of the plurality of components as appropriate. is there. 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 showing an internal configuration of a printer to which the present invention is applied. FIG. 2 is a block diagram illustrating an electrical configuration included in the printer illustrated in FIG. 1. FIG. 4 is a diagram illustrating an example of control for adjusting ink ejection timing of a recording head. The figure which shows an example of the table which shows the relationship between the kind of sheet | seat, and coefficient a, b. The figure which shows the content of the experiment which calculates | requires the coefficients a and b of the primary formula which gives control amount (DELTA) V. The figure regarding the 1st Example which adjusts the rotational speed of a front drive roller. The figure regarding the 1st Example which adjusts the rotational speed of a front drive roller. The figure regarding the 1st Example which adjusts the rotational speed of a front drive roller. The figure regarding 2nd Example which adjusts the rotational speed of a front drive roller. The figure regarding 2nd Example which adjusts the rotational speed of a front drive roller. The figure regarding 2nd Example which adjusts the rotational speed of a front drive roller. The figure regarding 3rd Example which adjusts the rotational speed of a front drive roller. The figure regarding 3rd Example which adjusts the rotational speed of a front drive roller. The figure regarding 3rd Example which adjusts the rotational speed of a front drive roller. The figure regarding 4th Example which adjusts the rotational speed of a front drive roller. The figure regarding 4th Example which adjusts the rotational speed of a front drive roller. The figure regarding 4th Example which adjusts the rotational speed of a front drive roller. The figure which shows the modification of the support mode of a sheet | seat typically. The figure which shows the modification of the support mode of a sheet | seat typically.

  FIG. 1 is a front view schematically showing an example of the internal configuration of a printer to which the present invention is applied. As shown in FIG. 1, in the printer 1, one sheet S (web) whose both ends are wound around the feeding shaft 20 and the winding shaft 40 in a roll shape is interposed between the feeding shaft 20 and the winding shaft 40. The sheet S is conveyed from the feeding shaft 20 to the winding shaft 40. In other words, both ends of the sheet S are wound in a roll shape to form a feeding roll R20 and a winding roll R40. The feeding roll R20 supported on the feeding shaft 20 is pivotally supported on the winding shaft 40. The sheet S is conveyed by a roll-to-roll along the conveyance direction Ds toward the taken-up roll R40.

  In the printer 1, an image is recorded on the sheet S conveyed in the conveyance direction Ds. The material of the sheet S includes paper and film. As specific examples, the paper includes high-quality paper, cast paper, art paper, and coated paper, and the film includes synthetic paper, PET (Polyethylene terephthalate), PP (polypropylene), and the like. In the present specification, the type of the sheet S composed of two stacked papers is represented as “paper + paper”, and the type of the sheet S composed of single-layer paper is represented as “paper single layer”. The type of sheet S composed of laminated film and paper is represented as “F + paper”, the type of sheet S composed of two laminated films is represented as “F + F”, The type of sheet S composed of a film is represented as “film monolayer”. Further, in the following description, of the both surfaces of the sheet S, the surface facing the recording heads 51 and 52 described later is referred to as the front surface, and the opposite surface is referred to as the back surface.

  Schematically, the printer 1 includes a feeding unit 2 (feeding region) that feeds the sheet S from the feeding shaft 20, a process unit 3 (process region) that records an image on the sheet S fed from the feeding unit 2, and a process. A winding unit 4 (winding region) for winding the sheet S on which the image is recorded in the unit 3 around the winding shaft 40 is provided.

  The feeding unit 2 includes a feeding shaft 20 around which the end of the sheet S is wound, and a driven roller 21 around which the sheet S drawn from the feeding shaft 20 is wound. The feeding shaft 20 supports the end of the sheet S by winding the end thereof with the surface of the sheet S facing outward. Then, when the feeding shaft 20 rotates clockwise in FIG. 1, the sheet S wound around the feeding shaft 20 is fed to the process unit 3 via the driven roller 21. Further, the feeding unit 2 is provided with an edge sensor Ss that detects the position of the end of the sheet S in the width direction. Here, the width direction is a direction perpendicular to the normal direction of the transport direction Ds and the sheet S, and is a direction perpendicular to the paper surface of FIG.

  The process unit 3 supports the sheet S fed from the feeding unit 2 by the rotary drum 30 and performs processing by the functional units 51, 52, 61, 62, and 63 arranged along the outer peripheral surface of the rotary drum 30. The image is printed on the sheet 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 sheet 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 drive roller 31 has a plurality of minute protrusions formed by thermal spraying on the outer peripheral surface, and supports the sheet 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 sheet S fed out from the feeding unit 2 to the downstream side in the transport direction Ds. Note that two nip rollers 31 n are provided for the front drive roller 31. These nip rollers 31 n are arranged at intervals in the circumferential direction of the front drive roller 31 and come into contact with the sheet S wound around the circumferential surface of the front drive roller 31. Each nip roller 31 n is biased toward the front drive roller 31 and sandwiches the sheet S between the front drive roller 31. Thereby, the frictional force between the front drive roller 31 and the sheet S is ensured, and the sheet 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] that is rotatably supported by a support mechanism (not shown), and is conveyed from the front drive roller 31 to the rear drive roller 32. Is wound around the peripheral surface from the back side. The rotating drum 30 supports the sheet S from the back side while receiving the frictional force between the rotating sheet 30 and rotating in the conveying direction Ds of the sheet S. Incidentally, the process unit 3 is provided with driven rollers 33 and 34 for folding the sheet S on both sides of the winding part around the rotary drum 30. Among these, the driven roller 33 wraps the surface of the sheet S between the front driving roller 31 and the rotary drum 30 and folds the sheet S. On the other hand, the driven roller 34 wraps the surface of the sheet S between the rotary drum 30 and the rear drive roller 32 and folds the sheet S. In this way, by folding the sheet 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 sheet S around the rotating drum 30. Further, a paper width sensor Sw is provided on the upstream side in the transport direction Ds of the driven roller 33, and the paper width sensor Sw detects the dimension of the sheet S in the width direction, that is, the width W of the sheet S. Further, a temperature sensor S30 is provided so as to face a portion of the peripheral surface of the rotating drum 30 that is exposed without being wound around the sheet S. The temperature sensor S30 is a radiation thermometer, for example, and detects the temperature Tp of the peripheral surface of the rotary drum 30.

  The rear drive roller 32 has a plurality of minute protrusions formed by thermal spraying on the outer peripheral surface, and supports the sheet S conveyed from the rotary drum 30 via the driven roller 34 from the back surface side. Then, the rear drive roller 32 conveys the sheet S to the winding unit 4 by rotating clockwise in FIG. Note that two nip rollers 32 n are provided for the rear drive roller 32. The nip rollers 32 n are arranged at intervals in the circumferential direction of the rear drive roller 32, and come into contact with the sheet S wound around the circumferential surface of the rear drive roller 32. Each nip roller 32 n is biased toward the rear drive roller 32 and sandwiches the sheet S between the rear drive roller 32. Accordingly, a frictional force between the rear drive roller 32 and the sheet S is ensured, and the sheet S can be reliably conveyed by the rear drive roller 32.

  Thus, the sheet 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 sheet 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 sheet S wound around the rotary drum 30 with a slight clearance, and discharges the corresponding color ink (colored ink) from the nozzles by an ink jet method. Then, each recording head 51 ejects ink onto the sheet S conveyed in the conveyance direction Ds, whereby a color image is formed on the surface of the sheet 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 (light irradiating units) are provided to cure the ink and fix it on the sheet 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 shape of the ink does not collapse by irradiating a small amount of accumulated ultraviolet light, and does not completely 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. In other words, the UV irradiator 62 completely cures (mainly cures) the ink by irradiating with a greater amount of accumulated ultraviolet light than the UV irradiator 61.

  As described above, the UV irradiator 61 disposed between each of the plurality of recording heads 51 temporarily cures the colored ink discharged onto the sheet S from the recording head 51 on the upstream side in the transport direction Ds. Therefore, the ink ejected from the one recording head 51 onto the sheet 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 sheet 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 finally cured by the UV irradiator 62 and fixed on the sheet 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 sheet S wound around the rotating drum 30 with a slight clearance, and discharges transparent UV ink from the nozzles onto the surface of the sheet 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. Further, a UV irradiator 63 is provided on the downstream side of the recording head 52 in the transport direction Ds. The UV irradiator 63 irradiates strong ultraviolet rays to completely cure (main cure) the transparent ink ejected by the recording head 52. Thereby, the transparent ink can be fixed on the surface of the sheet S.

  As described above, in the process unit 3, the ink ejected by the recording heads 51 and 52 and the ink effect by the UV irradiators 61 to 63 are applied to the sheet S wound and supported on the circumferential surface of the rotary drum 30. When executed, a color image coated with a transparent ink is formed. Then, the sheet 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 sheet 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 sheet S is wound. The winding shaft 40 winds and supports the end of the sheet S with the surface of the sheet S facing outward. That is, when the winding shaft 40 rotates clockwise in FIG. 1, the sheet S conveyed from the rear drive roller 32 is wound around the winding shaft 40 via the driven roller 41.

  The above is the outline of the device configuration of the printer 1. Next, an electrical configuration for controlling the printer 1 will be described with reference to FIG. FIG. 2 is a block diagram showing an electrical configuration of the printer shown in FIG. The printer 1 includes a printer control unit 100 that comprehensively controls each unit of the apparatus. The printer control unit 100 is a computer composed of a CPU (Central Processing Unit) and a memory.

  The printer 1 includes a UI (User Interface) 9. The UI 9 includes a monitor configured with a liquid crystal display or the like, and an input operation unit configured with a keyboard, a mouse, or the like. A menu screen is displayed on the UI 9 monitor in addition to the image to be printed. Accordingly, the user operates the input operation unit of the UI 9 while confirming the monitor of the UI 9 to open the print setting screen from the menu screen, and various types of printing such as the type of the print medium, the size of the print medium, and the print quality. Conditions can be set. The specific configuration of the UI 9 can be variously modified. For example, a touch panel display may be used as a monitor, and the input operation unit may be configured with the touch panel of the monitor. Then, the printer control unit 100 controls each unit of the recording head, the UV irradiator, and the sheet conveyance system in the following manner in accordance with a command from an external device or an input operation to the UI 9.

  The printer control unit 100 controls the ink ejection timing of each recording head 51 that forms a color image according to the conveyance of the sheet S. Specifically, the control of the ink ejection timing is executed based on the output (detection value) of a drum encoder (rotary encoder) E30 that is attached to the rotating shaft of the rotating drum 30 and detects the rotational position of the rotating drum 30. Is done. That is, since the rotary drum 30 is driven to rotate as the sheet S is conveyed, the conveyance position of the sheet S can be grasped by referring to the output of the drum encoder E30 that detects the rotation position of the rotary drum 30. Therefore, the printer control unit 100 generates a signal referred to as pts (print timing signal) from the output of the drum encoder E30, and controls the ink ejection timing of each recording head 51 based on this pts, whereby each recording The ink ejected by the head 51 is landed on the target position of the conveyed sheet S to form a color image.

  FIG. 3 is a timing chart schematically showing a control example for adjusting the timing at which the recording head ejects ink. As shown in the figure, the printer control unit 100 applies a voltage signal to the nozzles of the recording head 51 in synchronization with pts generated from the output of the drum encoder E30, and the nozzles of the recording head 51 receive the voltage signal and receive ink. Is discharged. According to such control, when the rotational speed of the rotary drum 30 varies, the output interval of pts changes, and the interval at which the voltage signal is applied to the nozzles of the recording head 51 also changes. Accordingly, it is possible to eject ink from the recording head 51 at a timing according to the number of rotations of the rotary drum 30 and land the ink at an appropriate position on the sheet S.

  Returning to FIG. 1 and FIG. 2, the description will be continued. The timing at which the recording head 52 discharges the transparent ink is also controlled by the printer control unit 100 based on the output of the drum encoder E30, similarly to the recording head 51. 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.

  Further, the printer control unit 100 manages a function of controlling the conveyance of the sheet S described in detail with reference to FIG. That is, motors are connected to each of the feeding shaft 20, the front drive roller 31, the rear drive roller 32, and the take-up shaft 40 among members constituting the sheet conveyance system. The printer control unit 100 controls the conveyance of the sheet S by controlling the speed (number of rotations) and torque of each motor while rotating these motors. Details of the conveyance control of the sheet 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 sheet 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 (feeding tension Ta) of the sheet S from the feeding shaft 20 to the front drive roller 31. That is, a tension sensor S <b> 21 for detecting 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 a load cell that detects a force received from the sheet S, for example. The printer control unit 100 adjusts the feeding tension Ta of the sheet S by feedback controlling the torque of the feeding motor M20 based on the detection result of the tension sensor S21. That is, the printer control unit 100 stores the target feeding tension Tat input by the user via the UI 9. Then, the printer control unit 100 feedback-controls the torque of the feeding motor M20 so that the feeding tension Ta detected by the tension sensor S21 approaches the target feeding tension Tat.

  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 sheet S fed from the feeding unit 2 passes through the process unit 3 in the transport direction Ds. At this time, speed control, which will be described in detail later, is executed for the front drive motor M31, while the following torque control is executed for the rear drive motor M32.

  The printer control unit 100 controls the torque of the rear drive motor M32 to adjust the tension (process tension Tb) of the sheet S from the front drive roller 31 to the rear drive roller 32. That is, the tension sensor S34 for detecting 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 configured by a load cell that detects a force received from the sheet S, for example. The printer control unit 100 adjusts the process tension Tb of the sheet S by feedback controlling the torque of the rear drive motor M32 based on the detection result of the tension sensor S34. More specifically, the printer controller 100 stores in advance a table indicating the target process tension Tbt corresponding to the type and width of the sheet S. Then, the printer control unit 100 selects a target process tension Tbt corresponding to the type and width of the sheet S to be conveyed from the table, and the process tension Tb detected by the tension sensor S34 approaches the selected target process tension Tbt. Thus, the torque of the rear drive motor M32 is feedback controlled. Incidentally, the target process tension Tbt is set to a value larger than the target feeding tension Tat.

  Further, the printer control unit 100 rotates the winding motor M <b> 40 that drives the winding shaft 40, and winds the sheet 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 (winding tension Tc) of the sheet S from the rear drive roller 32 to the winding shaft 40. That is, a 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 sheet S, for example. The printer control unit 100 adjusts the winding tension Tc of the sheet S by feedback controlling the torque of the winding motor M40 based on the detection result of the tension sensor S41. That is, the printer control unit 100 stores the target winding tension Tct input by the user via the UI 9. Then, the printer control unit 100 feedback-controls the torque of the winding motor M40 so that the winding tension Tc detected by the tension sensor S41 approaches the target winding tension Tct. At this time, in order to execute a taper tension that changes the winding tension Tc according to the diameter of the winding roll R40, the target winding tension Tct is adjusted according to the diameter of the winding roll R40.

  By the way, as described above, speed control is performed on the front drive motor M31 that drives the front drive roller 31. That is, the printer control unit 100 rotates the front drive motor M31 at a predetermined rotation speed V by executing feedback control based on the encoder output of the front drive motor M31. As a result, the sheet S is conveyed in the conveyance direction Ds at the peripheral speed of the front drive roller 31 that rotates at the rotation speed V.

  However, depending on the transport conditions of the sheet S, the transport speed of the sheet S on the peripheral surface of the rotary drum 30 may be faster than the transport speed of the sheet S on the peripheral surface of the front drive roller 31. It was found by experiments by the inventors described later. In such a case, it may be difficult to properly eject ink from the recording heads 51 and 52. That is, as can be seen from FIG. 3, when the conveyance speed of the sheet S on the rotary drum 30 is increased, the time interval between continuously generated pts is shortened and continuously applied to the nozzles of the recording heads 51 and 52. The time interval of the voltage signal is also shortened. On the other hand, each voltage signal changes over a predetermined time. For this reason, if the time interval of the voltage signal becomes too short, the continuous voltage signals overlap each other in time, and ink cannot be appropriately ejected from the recording heads 51 and 52.

Therefore, the printer control unit 100 performs various conveyance conditions such as the target feeding tension Tat [N], the cross-sectional stress [N / mm ² ] of the sheet S, the thickness t [μm] of the sheet S, or the width W [mm] of the sheet S. The rotational speed of the front drive roller 31 is adjusted according to any one of the conveyance conditions C. Specifically, the printer control unit 100 calculates the rotation speed V of the front drive roller 31, in other words, the rotation speed V of the front drive motor M 31 that drives the front drive roller 31 by the following formula: V = (100 [%] − ΔV [%]) × Vr Equation 1
ΔV [%] = a × C + b Equation 2
Determine based on.

  As shown in Expression 2, the printer control unit 100 calculates a control amount ΔV [%] from a linear expression using coefficients a and b as inclination and intercept, and the conveyance condition C as a variable. Further, as shown in Expression 1, the printer control unit 100 calculates the rotation speed V by multiplying the reference rotation speed Vr by a ratio obtained by subtracting the control amount ΔV [%] from 100 [%]. Here, the reference rotational speed Vr is the rotational speed of the front drive motor M31 in an ideal state in which the peripheral speed of the front drive roller 31 and the peripheral speed of the rotary drum 30 match.

  In this way, the printer control unit 100 obtains the rotation speed V before the conveyance of the sheet S is started. When the sheet S is conveyed, the printer control unit 100 rotates the front drive motor M31 at the rotation speed V by performing feedback control of the front drive motor M31 based on the encoder output of the front drive motor M31. As can be seen from Equations 1 and 2, the rotational speed V of the front drive motor M31 varies with the change in the conveyance condition C. That is, the printer control unit 100 adjusts the rotation speed V of the front drive roller 31, in other words, the rotation speed V of the front drive motor M <b> 31 that drives the front drive roller 31 in accordance with the change in the conveyance condition C value. Thereby, the printer control unit 100 appropriately suppresses the peripheral speed of the rotary drum 30.

  Further, the printer control unit 100 stores a table in which the coefficients a and b are determined according to the type of the sheet S. FIG. 4 is a diagram showing an example of a table showing the relationship between the sheet type and the coefficients a and b. As shown in FIG. 4, different combinations of coefficients a and b are used in the calculation of Equation 2 when the sheet S includes paper and when the sheet S does not include paper. That is, the difference between the circumferential speed of the rotating drum 30 and the circumferential speed of the front drive roller 31 may depend on the type of the sheet S. Therefore, the printer control unit 100 controls the rotational speed V of the front drive roller 31 according to the type of the sheet S, in other words, the front drive that drives the front drive roller 31 in order to appropriately suppress the peripheral speed of the rotary drum 30. The rotational speed V of the motor M31 is adjusted. The coefficients a and b shown in the table of FIG. 4 are obtained in advance based on the result of the experiment schematically shown in FIG. 5 and stored in the printer control unit 100.

  FIG. 5 is a diagram schematically showing the content of an experiment for obtaining the coefficients a and b of the linear expression that gives the control amount ΔV. In the figure, the horizontal axis indicates the conveyance condition C, and the vertical axis indicates the conveyance speed offset amount [%]. The conveyance condition C shown on the horizontal axis of the figure is one conveyance condition C selected as a variable of Expression 2 among the target feeding tension Tat, the cross-sectional stress of the sheet S, the thickness t of the sheet S, and the width W of the sheet S. (In other words, the conveyance condition C for which the coefficients a and b are obtained). Further, the conveyance speed offset amount is a percentage obtained by dividing the peripheral speed difference obtained by subtracting the peripheral speed V of the front drive roller 31 from the peripheral speed of the rotary drum 30 by the peripheral speed V of the front drive roller 31. . The peripheral speed of the rotary drum 30 is obtained from the output value of the drum encoder E30 and the diameter of the rotary drum 30, and the peripheral speed of the front drive roller 31 is the encoder output value of the front drive motor M31 and the diameter of the front drive roller 31. It was requested from.

In this experiment, the following conveyance conditions / sheet S thickness t
・ Width W of sheet S
・ Target feeding tension Tat
・ Temperature of rotating drum 30 ・ Rotation speed V of front drive motor M31
The surface (front / rear surface) of the sheet S facing the recording heads 51 and 52
Among them, the conveyance speed offset amount was measured by changing each of the conditions other than the conveyance condition C selected as the variable of the expression 2 within the range of variations under the assumed usage state of the printer 1. In the experiment for obtaining the coefficients a and b for the sheet S including paper, the type of the sheet S (“paper + paper” / “paper single layer” / “F + paper”) is also changed to measure the conveyance speed offset amount. It was done.

  Specifically, as shown in step S101, the conveyance speed offset is changed while changing the other conveyance conditions while the value of the conveyance condition C selected as the variable of the expression 2 is fixed to a predetermined value, for example, the value C1. The quantity is measured and plotted on a graph. And the same measurement is performed about each of different conveyance conditions C2-C5. Subsequently, the approximate straight line Lu of the upper limit value (offset upper limit value Fu) of the transport speed offset amount for each of the different transport conditions C1 to C5 and the lower limit value (offset lower limit value Fl of each of the transport speed offset amounts of the different transport conditions C1 to C5. ) Is calculated (step S102).

  When the upper limit approximate line Lu and the lower limit approximate line Ll are obtained in this way, the above-described linear expression (formula 2) that gives the control amount ΔV is obtained based on these. Specifically, a linear expression of the control amount ΔV is obtained so as to satisfy the restriction condition that the difference [%] between the upper limit approximate straight line Lu and the control amount ΔV is less than the allowable offset amount A (step S103). Here, the allowable offset amount A is a value obtained by adding a predetermined margin to an offset amount at which drive signals continuously output in synchronization with pts start to overlap in time. In the example of FIG. 5, a linear expression of the control amount ΔV is set between the upper limit approximate line Lu and the lower limit approximate line Ll. Then, the slope and intercept of this linear expression are obtained as the coefficients a and b in the table shown in FIG.

  Such an experiment is performed for each of “sheet S including paper”, “F + F”, and “F single layer” shown in FIG. 4 to create the table of FIG. Subsequently, a more specific conveyance condition C, that is, an example in which the target feeding tension Tat, the cross-sectional stress St of the sheet S, the thickness t of the sheet S, or the width W of the sheet S is set as a variable of Expression 2 will be described. .

First Example In the first example, the target feeding tension Tat is set as a variable C in Expression 2. 6, 7 and 8 are diagrams relating to the first embodiment in which the rotational speed of the front drive roller is adjusted according to the feeding tension. Specifically, these drawings show changes in the conveyance speed offset amount [%] with respect to changes in the target feeding tension Tat [N]. In particular, FIG. 6 shows data when the sheet S includes paper. 7 shows data when the sheet S is “F + F”, and FIG. 8 shows data when the sheet S is “F single layer”.

In the first embodiment, the printer control unit 100 adjusts the rotational speed V of the front drive roller 31 according to the target feeding tension Tat. Specifically, the printer control unit 100 calculates the rotation speed V of the front drive roller 31, in other words, the rotation speed V of the front drive motor M 31 that drives the front drive roller 31 by the following formula: V = (100 [%] − ΔV [%]) × Vr Equation 11
ΔV = a × Tat + b Equation 12
Determine based on.

  As shown in Expression 12, the printer control unit 100 calculates the control amount ΔV [%] from a linear expression using the coefficients a and b as inclination and intercept, and the target feeding tension Tat as a variable. Furthermore, as shown in Expression 11, the printer control unit 100 calculates the rotation speed V by multiplying the reference rotation speed Vr by a ratio obtained by subtracting the control amount ΔV [%] from 100 [%]. In this way, the printer control unit 100 obtains the rotation speed V before the conveyance of the sheet S is started. When the sheet S is conveyed, the printer control unit 100 rotates the front drive motor M31 at the rotation speed V by performing feedback control of the front drive motor M31 based on the encoder output of the front drive motor M31.

  Incidentally, the coefficients a and b in the linear expression of the control amount ΔV are changed according to the type of the sheet S based on the table shown in FIG. The coefficients a and b are obtained in advance by performing the experiment shown in FIG. 5 and stored in the printer control unit 100. This point will be described using the sheet S including the paper of FIG. 6 as a representative.

In this experiment, the following conveyance conditions and sheet S types ("paper + paper" / "paper single layer" / "F + paper")
・ Thickness t of sheet S
・ Width W of sheet S
・ Temperature of rotating drum 30 ・ Rotation speed V of front drive motor M31
The surface (front / rear surface) of the sheet S facing the recording heads 51 and 52
Each of the above was changed in the range of variations under the assumed usage status of the printer 1, and the conveyance speed offset amount was measured at each of the different target feeding tensions Tat. Thereby, each measurement result is plotted as shown in FIG. As can be seen from the result of FIG. 6, the conveyance speed offset amount is always positive, and the peripheral speed of the rotary drum 30 is always faster than the peripheral speed of the front drive roller 31.

  Subsequently, an approximate straight line (not shown) of the offset upper limit value Fu for each of the different target feed tensions Tat and an approximate straight line (not shown) of the offset lower limit value Fl of each of the different target feed tensions Tat are calculated. When the upper limit approximate line Lu and the lower limit approximate line Ll are obtained in this way, the above-described linear expression (formula 12) that gives the control amount ΔV is obtained based on these. Specifically, a linear expression of the control amount ΔV is obtained so as to satisfy the restriction condition that the difference [%] between the upper limit approximate line Lu and the control amount ΔV is less than the allowable offset amount A. In the example of FIG. 6, a linear expression (y = −0.0008x + 0.4375) of the control amount ΔV is set between the upper limit approximate line Lu and the lower limit approximate line Ll. Here, in the approximate straight line in the figure, the target feeding tension Tat is represented as a variable “x”, and the conveyance speed offset amount is represented as a variable “y”. Then, the slope and intercept of this linear expression are obtained as the coefficients a and b of the “sheet S including paper” in the table shown in FIG.

  The same experiment was performed on the sheets S of “F + F” and “F monolayer”. However, among the conveyance conditions listed above, the type of the sheet S is fixed to the corresponding type. As a result, a linear expression of the control amount ΔV is obtained, and at the same time, coefficients a and b are obtained. Incidentally, for the sheet S of “F + F” in FIG. 7, a linear expression (y = −0.0039x + 0.5489) of the control amount ΔV is set in the middle of the upper limit approximate line Lu and the lower limit approximate line L1 as in FIG. The On the other hand, in the “F single layer” of FIG. 8, the same setting method does not satisfy the above-described limiting condition, and therefore, the maximum end of the target feeding tension Tat of the control amount ΔV is the upper limit approximate line Lu and the lower limit approximation. While the intermediate value of the straight line Ll is set, the minimum end of the target feed tension Tat of the control amount ΔV is set to a value obtained by subtracting the allowable offset amount A from the upper limit approximate straight line Lu. As a result, the linear expression of the control amount ΔV is y = −0.0267x + 1.9967.

  As shown in FIGS. 6 to 8, the conveyance speed offset, that is, the difference between the circumferential speed of the rotary drum 30 and the circumferential speed of the front drive roller 31 is a decrease in the target feeding tension Tat, which is the adjustment target value of the feeding tension Ta. Increases accordingly. Therefore, when the target feeding tension Tat is low, the peripheral speed of the rotary drum 30 may become too fast. On the other hand, in the first embodiment, the rotational speed V of the front drive roller 31 is decreased in accordance with the decrease in the target feeding tension Tat. Thus, the conveyance speed of the sheet S on the rotary drum 30 can be suppressed to an appropriate range.

Second Example In the second example, the cross-sectional stress St (base material cross-sectional stress) generated in the sheet S (base material) at the winding portion around the front driving roller 31, in other words, the feeding tension Ta and the process tension Tb. The cross-sectional stress St generated in the sheet S due to the difference is defined as a variable C in Equation 2. 9, 10 and 11 are diagrams relating to a second embodiment in which the rotational speed of the front drive roller is adjusted according to the cross-sectional stress. Specifically, these drawings show changes in the conveyance speed offset amount [%] with respect to changes in the cross-sectional stress St [N / mm ² ], and in particular, FIG. 9 shows data when the sheet S includes paper. FIG. 10 shows data when the sheet S is “F + F”, and FIG. 11 shows data when the sheet S is “F single layer”.

In the second embodiment, the printer control unit 100 adjusts the rotational speed V of the front drive roller 31 according to the cross-sectional stress St. Specifically, the printer control unit 100 calculates the rotation speed V of the front drive roller 31, in other words, the rotation speed V of the front drive motor M 31 that drives the front drive roller 31 by the following formula: V = (100 [%] − ΔV [%]) × Vr Equation 21
ΔV = a × St + b Equation 22
St = (Tbt−Tat) / (W × t / 1000) Equation 23
Determine based on. Here, the value 1000 for dividing the thickness t in the denominator on the right side of Equation 23 is a value for converting the unit of the thickness t from [μm] to [mm].

  As shown in Expression 23, the printer control unit 100 calculates the cross-sectional area of the sheet S as the target tension difference (Tbt−Tat> 0) obtained by subtracting the target feeding tension Tat from the target process tension Tbt [N]. ] (= W × t / 1000). At this time, the value calculated from the detection result of the paper width sensor Sw is used as the width W of the sheet S, and the value input via the UI 9 is used as the thickness t of the sheet S. Then, as shown in Expression 22, the printer control unit 100 calculates the control amount ΔV [%] from a linear expression using the coefficients a and b as the slope and intercept, and the sectional stress St as a variable. Further, as shown in Expression 21, the printer control unit 100 calculates the rotation speed V by multiplying the reference rotation speed Vr by a ratio obtained by subtracting the control amount ΔV [%] from 100 [%]. In this way, the printer control unit 100 obtains the rotation speed V before the conveyance of the sheet S is started. When the sheet S is conveyed, the printer control unit 100 rotates the front drive motor M31 at the rotation speed V by performing feedback control of the front drive motor M31 based on the encoder output of the front drive motor M31.

  Incidentally, the coefficients a and b in the linear expression of the control amount ΔV are changed according to the type of the sheet S based on the table shown in FIG. The coefficients a and b are obtained in advance by performing the experiment shown in FIG. 5 and stored in the printer control unit 100. This point will be described using the sheet S including the paper of FIG. 9 as a representative.

In this experiment, the following conveyance conditions and sheet S types ("paper + paper" / "paper single layer" / "F + paper")
・ Thickness of sheet S ・ Width W of sheet S
・ Target feeding tension Tat
・ Temperature of rotating drum 30 ・ Rotation speed V of front drive motor M31
The surface (front / rear surface) of the sheet S facing the recording heads 51 and 52
Each of the above was changed in the range of variations under the assumed usage status of the printer 1, and the conveyance speed offset amount was measured for each of the different cross-sectional stress St. Thereby, each measurement result is plotted as shown in FIG. As can be seen from the results of FIG. 9, the conveyance speed offset amount is always positive, and the peripheral speed of the rotary drum 30 is always faster than the peripheral speed of the front drive roller 31.

  Subsequently, an approximate straight line (not shown) of the offset upper limit value Fu for each of the different cross-sectional stress St and an approximate straight line (not shown) of the offset lower limit value Fl for each of the different cross-sectional stress St are calculated. When the upper limit approximate line Lu and the lower limit approximate line Ll are obtained in this way, based on these, the above-described linear expression (formula 22) that gives the control amount ΔV is obtained. Specifically, a linear expression of the control amount ΔV is obtained so as to satisfy the restriction condition that the difference [%] between the upper limit approximate line Lu and the control amount ΔV is less than the allowable offset amount A. In the example of FIG. 9, a linear expression (y = 0.039x + 0.3835) of the control amount ΔV is set between the upper limit approximate line Lu and the lower limit approximate line Ll. Here, in the approximate straight line in the drawing, the cross-sectional stress St is represented as a variable “x”, and the conveyance speed offset amount is represented as a variable “y”. Then, the slope and intercept of this linear expression are obtained as the coefficients a and b of the “sheet S including paper” in the table shown in FIG.

  The same experiment was performed on the sheets S of “F + F” and “F monolayer”. However, among the conveyance conditions listed above, the type of the sheet S is fixed to the corresponding type. As a result, a linear expression of the control amount ΔV is obtained, and at the same time, coefficients a and b are obtained. Incidentally, for the sheet S of “F + F” in FIG. 10, a linear expression (y = 0.0289x + 0.259) of the control amount ΔV is set in the middle between the upper limit approximate line Lu and the lower limit approximate line Ll as in FIG. . On the other hand, in the “F single layer” of FIG. 11, the same setting method does not satisfy the above-described restriction condition, and therefore, the minimum end of the cross-sectional stress St of the controlled variable ΔV is the upper limit approximate line Lu and the lower limit approximate line. On the other hand, the maximum end of the sectional stress St of the control amount ΔV is set to a value obtained by subtracting the allowable offset amount A from the upper limit approximate straight line Lu. As a result, the linear expression of the control amount ΔV is y = 0.0926x + 0.3416.

  As shown in FIGS. 9 to 11, the conveyance speed offset, that is, the difference between the circumferential speed of the rotary drum 30 and the circumferential speed of the front drive roller 31 increases as the cross-sectional stress St increases. Therefore, if the cross-sectional stress St is large, the peripheral speed of the rotary drum 30 may become too fast. On the other hand, in the second embodiment, the rotational speed V of the front drive roller 31 is decreased in accordance with the increase in the cross-sectional stress St. Thus, the conveyance speed of the sheet S on the rotary drum 30 can be suppressed to an appropriate range.

Third Example In the third example, the thickness t (base material thickness) of the sheet S (base material) is defined as the variable C in Equation 2. FIGS. 12, 13 and 14 are diagrams relating to a third embodiment in which the rotational speed of the front drive roller is adjusted according to the thickness of the sheet. Specifically, these drawings show changes in the conveyance speed offset amount [%] with respect to changes in the thickness t [μm] of the sheet S. In particular, FIG. 12 shows data when the sheet S includes paper, FIG. 13 shows data when the sheet S is “F + F”, and FIG. 14 shows data when the sheet S is “F single layer”.

In the third embodiment, the printer control unit 100 adjusts the rotational speed V of the front drive roller 31 according to the thickness t of the sheet S. Specifically, the printer control unit 100 calculates the rotation speed V of the front drive roller 31, in other words, the rotation speed V of the front drive motor M 31 that drives the front drive roller 31 by the following formula: V = (100 [%] − ΔV [%]) × Vr Equation 31
ΔV = a × t + b Equation 32
Determine based on.

  As shown in Expression 32, the printer control unit 100 calculates a control amount ΔV [%] from a linear expression using coefficients a and b as inclination and intercept, and thickness t as a variable. At this time, the value input via the UI 9 is used as the thickness t of the sheet S. Further, as shown in Expression 31, the printer control unit 100 calculates the rotation speed V by multiplying the reference rotation speed Vr by a ratio obtained by subtracting the control amount ΔV [%] from 100 [%]. In this way, the printer control unit 100 obtains the rotation speed V before the conveyance of the sheet S is started. When the sheet S is conveyed, the printer control unit 100 rotates the front drive motor M31 at the rotation speed V by performing feedback control of the front drive motor M31 based on the encoder output of the front drive motor M31.

  Incidentally, the coefficients a and b in the linear expression of the control amount ΔV are changed according to the type of the sheet S based on the table shown in FIG. The coefficients a and b are obtained in advance by performing the experiment shown in FIG. 5 and stored in the printer control unit 100. This point will be described using the sheet S including the paper of FIG. 12 as a representative.

In this experiment, the following conveyance conditions and sheet S types ("paper + paper" / "paper single layer" / "F + paper")
・ Width W of sheet S
・ Target feeding tension Tat
・ Temperature of rotating drum 30 ・ Rotation speed V of front drive motor M31
The surface (front / rear surface) of the sheet S facing the recording heads 51 and 52
Each of the above was changed in a range of variations under the assumed usage status of the printer 1, and the conveyance speed offset amount was measured at each of different thicknesses t. Thereby, each measurement result is plotted as shown in FIG. As can be seen from the results of FIG. 12, the conveyance speed offset amount is always positive, and the peripheral speed of the rotary drum 30 is always faster than the peripheral speed of the front drive roller 31.

  Subsequently, an approximate straight line (not shown) for the offset upper limit value Fu for each of the different thicknesses t and an approximate straight line (not shown) for the offset lower limit value Fl for each of the different thicknesses t are calculated. When the upper limit approximate line Lu and the lower limit approximate line Ll are obtained in this way, the above-described linear expression (formula 32) that gives the control amount ΔV is obtained based on these. Specifically, a linear expression of the control amount ΔV is obtained so as to satisfy the restriction condition that the difference [%] between the upper limit approximate line Lu and the control amount ΔV is less than the allowable offset amount A. In the example of FIG. 12, a linear expression (y = 0.014x + 0.1077) of the control amount ΔV is set between the upper limit approximate line Lu and the lower limit approximate line Ll. Here, in the approximate straight line in the figure, the thickness t is represented as a variable “x”, and the conveyance speed offset amount is represented as a variable “y”. Then, the slope and intercept of this linear expression are obtained as the coefficients a and b of the “sheet S including paper” in the table shown in FIG.

  The same experiment was performed on the sheets S of “F + F” and “F monolayer”. However, among the conveyance conditions listed above, the type of the sheet S is fixed to the corresponding type. As a result, a linear expression of the control amount ΔV is obtained, and at the same time, coefficients a and b are obtained. Incidentally, for the sheet S of “F + F” in FIG. 13, a linear expression (y = −0.0017x + 0.6217) of the control amount ΔV is set in the middle of the upper limit approximate line Lu and the lower limit approximate line L1, as in FIG. The On the other hand, in the “F single layer” of FIG. 14, the same setting method does not satisfy the above-described limiting condition, and therefore, the maximum end of the thickness t of the control amount ΔV is the upper limit approximate line Lu and the lower limit approximate line Ll. On the other hand, the minimum end of the thickness t of the control amount ΔV is set to a value obtained by subtracting the allowable offset amount A from the upper limit approximate straight line Lu. As a result, the linear expression of the control amount ΔV is y = −0.0064x + 2.2403.

  When the sheet S including paper is used as shown in FIG. 12, the conveyance speed offset, that is, the difference between the circumferential speed of the rotary drum 30 and the circumferential speed of the front drive roller 31 is in accordance with the increase in the thickness t of the sheet S. Increase. Therefore, if the thickness t of the sheet S is thick, the peripheral speed of the rotary drum 30 may become too fast. On the other hand, in the third embodiment, when the sheet S including paper is used, the rotational speed V of the front drive roller 31 is decreased as the thickness t of the sheet S increases. Thus, the conveyance speed of the sheet S on the rotary drum 30 can be suppressed to an appropriate range.

  13 and 14, when the sheet S not including paper is used, the conveyance speed offset, that is, the difference between the circumferential speed of the rotary drum 30 and the circumferential speed of the front drive roller 31 is the thickness of the sheet S. It increases as t decreases. Therefore, if the thickness t of the sheet S is small, the peripheral speed of the rotary drum 30 may become too fast. On the other hand, in the third embodiment, when the sheet S that does not include paper is used, the rotation speed V of the front drive roller 31 is decreased according to the decrease in the thickness t of the sheet S. Thus, the conveyance speed of the sheet S on the rotary drum 30 can be suppressed to an appropriate range.

Fourth Example In the fourth example, the width W (base material width) of the sheet S (base material) is set as a variable C in Equation 2. FIGS. 15, 16, and 17 are diagrams relating to a fourth embodiment in which the rotational speed of the front drive roller is adjusted according to the width of the sheet. Specifically, these drawings show changes in the conveyance speed offset amount [%] with respect to changes in the width W [mm] of the sheet S. In particular, FIG. 15 shows data when the sheet S includes paper, FIG. 16 shows data when the sheet S is “F + F”, and FIG. 17 shows data when the sheet S is “F single layer”.

In the fourth embodiment, the printer control unit 100 adjusts the rotational speed V of the front drive roller 31 according to the width W of the sheet S. Specifically, the printer control unit 100 calculates the rotation speed V of the front drive roller 31, in other words, the rotation speed V of the front drive motor M 31 that drives the front drive roller 31 by the following formula: V = (100 [%] − ΔV [%]) × Vr Equation 41
ΔV = a × W + b Equation 42
Determine based on.

  As shown in Expression 42, the printer control unit 100 calculates the control amount ΔV [%] from a linear expression using the coefficients a and b as inclination and intercept, and the width W as a variable. At this time, as the width W of the sheet S, a value calculated from the detection result of the paper width sensor Sw is used. Furthermore, as shown in Expression 41, the printer control unit 100 calculates the rotation speed V by multiplying the reference rotation speed Vr by a ratio obtained by subtracting the control amount ΔV [%] from 100 [%]. In this way, the printer control unit 100 obtains the rotation speed V before the conveyance of the sheet S is started. When the sheet S is conveyed, the printer control unit 100 rotates the front drive motor M31 at the rotation speed V by performing feedback control of the front drive motor M31 based on the encoder output of the front drive motor M31.

  Incidentally, the coefficients a and b in the linear expression of the control amount ΔV are changed according to the type of the sheet S based on the table shown in FIG. The coefficients a and b are obtained in advance by performing the experiment shown in FIG. 5 and stored in the printer control unit 100. This point will be described using the sheet S including the paper of FIG. 15 as a representative.

In this experiment, the following conveyance conditions and sheet S types ("paper + paper" / "paper single layer" / "F + paper")
・ Thickness t of sheet S
・ Target feeding tension Tat
・ Temperature of rotating drum 30 ・ Rotation speed V of front drive motor M31
The surface (front / rear surface) of the sheet S facing the recording heads 51 and 52
Each of the above was changed in the range of variations under the assumed usage condition of the printer 1, and the conveyance speed offset amount was measured for each of the different widths W. Thereby, each measurement result is plotted as shown in FIG. As can be seen from the results of FIG. 15, the conveyance speed offset amount is always positive, and the peripheral speed of the rotary drum 30 is always faster than the peripheral speed of the front drive roller 31.

  Subsequently, an approximate straight line (not shown) of the offset upper limit value Fu for each different width W and an approximate straight line (not shown) for the offset lower limit value Fl of each different width W are calculated. When the upper limit approximate line Lu and the lower limit approximate line Ll are obtained in this way, the above-described linear expression (formula 42) that gives the control amount ΔV is obtained based on these. Specifically, a linear expression of the control amount ΔV is obtained so as to satisfy the restriction condition that the difference [%] between the upper limit approximate line Lu and the control amount ΔV is less than the allowable offset amount A. In the example of FIG. 15, a linear expression (y = −0.0001x + 0.4292) of the control amount ΔV is set between the upper limit approximate line Lu and the lower limit approximate line Ll. Here, in the approximate straight line in the figure, the width W is represented as a variable “x”, and the conveyance speed offset amount is represented as a variable “y”. Then, the slope and intercept of this linear expression are obtained as the coefficients a and b of the “sheet S including paper” in the table shown in FIG.

  The same experiment was performed on the sheets S of “F + F” and “F monolayer”. However, among the conveyance conditions listed above, the type of the sheet S is fixed to the corresponding type. As a result, a linear expression of the control amount ΔV is obtained, and at the same time, coefficients a and b are obtained. Incidentally, for the sheet S of “F + F” in FIG. 16, a linear expression (y = −0.0006x + 0.5427) of the control amount ΔV is set in the middle of the upper limit approximate line Lu and the lower limit approximate line L1, as in FIG. The On the other hand, in the “F single layer” of FIG. 17, the same setting method does not satisfy the above-described restriction condition. On the other hand, the minimum end of the width W of the control amount ΔV is set to a value obtained by subtracting the allowable offset amount A from the upper limit approximate straight line Lu. As a result, the linear expression of the control amount ΔV is y = −0.0049x + 2.1192.

  As shown in FIGS. 15 to 17, the conveyance speed offset, that is, the difference between the circumferential speed of the rotary drum 30 and the circumferential speed of the front drive roller 31 increases as the width W of the sheet S decreases. Therefore, if the width W of the sheet S is narrow, the peripheral speed of the rotary drum 30 may become too fast. On the other hand, in the fourth embodiment, the rotation speed V of the front drive roller 31 is decreased according to the decrease in the width W of the sheet S. Thus, the conveyance speed of the sheet S on the rotary drum 30 can be suppressed to an appropriate range.

  As described above, in the above embodiment, the printer 1 corresponds to an example of the “printing apparatus” of the present invention, the front driving roller 31 corresponds to an example of the “driving roller” of the present invention, and the recording heads 51 and 52 are included. The rotary drum 30 corresponds to an example of the “driven rotation member” of the present invention, the drum encoder E30 corresponds to an example of the “rotational position detection unit” of the present invention, The printer control unit 100 corresponds to an example of the “control unit” and “tension adjustment unit” of the present invention, the process tension Tb corresponds to an example of the “first tension” of the present invention, and the feeding tension Ta corresponds to “ The sheet S corresponds to an example of “second tension”, the sheet S corresponds to an example of “recording medium” of the present invention, and the ink corresponds to an example of “liquid” 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 embodiment, the sheet S is supported by the cylindrical rotary drum 30. However, the support mode of the sheet S is not limited to this. 18 and 19 are diagrams schematically showing modifications of the sheet support mode.

  In the example of FIG. 18, the sheet S is stretched around a plurality of support rollers 71, and a recording head (not shown) faces each support roller 71 with the sheet S interposed therebetween. Thus, the support roller 71 is driven to rotate as the sheet S is conveyed while supporting the sheet S at the portion where the ink ejected from the recording head lands. The ejection timing of each recording head is controlled based on the result of detecting the rotational position of the opposing support roller 71 with an encoder. Even in the printer 1 that supports the sheet S in such a support mode, the present invention can be applied to cope with the peripheral speed difference between the front drive roller 31 and the support roller 71.

  In the example of FIG. 19, the support plate 72 supports the sheet S, and a plurality of recording heads (not shown) face the support plate 72 with the sheet S interposed therebetween. Also, a driven roller 73 that is driven to rotate as the sheet S is conveyed is provided on the downstream side of the support plate 72 in the conveying direction Ds. The ejection timing of each recording head is controlled based on the result of detecting the rotational position of the driven roller 73 with an encoder. Even in the printer 1 that supports the sheet S in such a support mode, the present invention can be applied in order to cope with the peripheral speed difference between the front drive roller 31 and the driven roller 73.

  Further, the width W of the sheet S is obtained based on the detection result of the paper width sensor Sw. However, the width W of the sheet S input by the user via the UI 9 may be used.

  In the first and second embodiments, the target feed tension Tat is used for calculating the control amount ΔV. However, the control amount ΔV may be calculated using a detection value obtained by detecting the feeding tension Ta by the tension sensor S21 instead of the target feeding tension Tat.

  In FIG. 4, for the sheet S that does not include paper, the values of the coefficients a and b are different depending on whether the type of the sheet S is “F + F” or “F single layer”. However, it has been experimentally found that the values of appropriate coefficients a and b differ depending on whether or not PET (polyethylene terephthalate) is contained in the sheet S that does not contain paper. Therefore, for the sheet S not including paper, the values of the coefficients a and b may be varied depending on whether the sheet S includes PET as a material.

  In the above embodiment, the speed control is performed on the front drive motor M31 of the front drive roller 31. However, the present invention may be applied to the printer 1 that executes torque control on the front drive motor M31 of the front drive roller 31 and executes speed control on the rear drive motor M32 of the rear drive roller 32. Absent.

DESCRIPTION OF SYMBOLS 1 ... Printer, 2 ... Feeding part, 20 ... Feeding shaft, R20 ... Feeding roll, 21 ... Driven roller, 3 ... Process part, 30 ... Rotating drum, E30 ... Drum encoder, 31 ... Front drive roller, 31n ... Nip roller, 32: rear drive roller, 32n: nip roller, 33 ... driven roller, 34 ... driven roller, 4 ... winding unit, 40 ... winding shaft, R40 ... winding roller, 41 ... driven roller, 51 ... recording head, 52 ... Recording head, 61 ... UV irradiator, 62 ... UV irradiator, 63 ... UV irradiator, 100 ... Printer control unit, Ta ... Feeding tension, Tb ... Process tension, Tc ... Taking tension, S ... Sheet, Ss ... Edge sensor, Sw ... paper width sensor, S30 ... temperature sensor

Claims (8)

A driving roller for driving the recording medium by rotating while in contact with the recording medium;
An ejection head for ejecting liquid onto the recording medium;
A driven rotating member that rotates following the conveyance of the recording medium while in contact with the recording medium;
A rotational position detector that detects a rotational position of the driven rotational member;
A control unit that adjusts the timing of ejecting the liquid from the ejection head according to the detection result of the rotational position detection unit while conveying the recording medium by rotating the drive roller;
Tension adjustment for adjusting a first tension that is a tension of the recording medium on the ejection head side with respect to the driving roller and a second tension that is a tension of the recording medium on the opposite side of the ejection head with respect to the driving roller With
The said control part is a printing apparatus which adjusts the rotation speed of the said drive roller according to a said 2nd tension.   2. The printing apparatus according to claim 1, wherein the control unit adjusts the number of rotations of the driving roller according to a change in the second tension without depending on a change in the first tension.   The printing apparatus according to claim 1, wherein the control unit adjusts the number of rotations of the driving roller according to a change in cross-sectional stress of the recording medium caused by a difference between the first tension and the second tension. A driving roller for driving the recording medium by rotating while in contact with the recording medium;
An ejection head for ejecting liquid onto the recording medium;
A driven rotating member that rotates following the conveyance of the recording medium while in contact with the recording medium;
A rotational position detector that detects a rotational position of the driven rotational member;
A controller that adjusts the timing of ejecting the liquid from the ejection head according to the detection result of the rotational position detector while conveying the recording medium by rotating the drive roller;
The said control part is a printing apparatus which adjusts the rotation speed of the said driving roller according to the structure of the said recording medium.   The printing apparatus according to claim 4, wherein the control unit adjusts the number of rotations of the driving roller according to the thickness of the recording medium.   The printing apparatus according to claim 4, wherein the control unit adjusts the number of rotations of the driving roller according to a width of the recording medium. Driving the recording medium by rotating a driving roller that contacts the recording medium, and detecting a rotational position of a driven rotating member that rotates following the conveyance of the recording medium while contacting the recording medium;
Adjusting the timing of discharging the liquid from the discharge head to the recording medium according to the detection result of the rotational position of the driven rotation member,
The printing method in which the rotation speed of the driving roller is adjusted according to the tension of the recording medium on the opposite side of the ejection head from the driving roller. Driving the recording medium by rotating a driving roller that contacts the recording medium, and detecting a rotational position of a driven rotating member that rotates following the conveyance of the recording medium while contacting the recording medium;
Adjusting the timing of discharging the liquid from the discharge head to the recording medium according to the detection result of the rotational position of the driven rotation member,
The printing method in which the rotation speed of the driving roller is adjusted according to the configuration of the recording medium.

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