JP2019142656A - Printer and method for conveying web - Google Patents

Abstract

To suppress occurrence of a tension error in low tension control.SOLUTION: A printer 1 includes a conveyance section 30 that conveys a web S, a first drive section that drives the conveyance section 30, a winding shaft 40 that winds up the web S conveyed by the conveyance section 30, a second drive section that drives the winding shaft 40, and a printer control section 200 that controls a torque output by the second drive section, in which when a specified target tension value is a predetermined value or less, the printer control section 200 sets a target tension value Tct of a winding tension to a first target tension value P1 larger than a specified target tension value P0 according to the maximum speed Vmax of the web S when the web S is conveyed by a specified conveyance distance, then starts conveyance of the web S by the conveyance section 30, and executes control that gradually decreases the target tension value Tct from the first target tension value P1 to the specified target tension value P0 until an acceleration period in the conveyance of the web S ends.SELECTED DRAWING: Figure 17

Description

  The present invention relates to a printing apparatus and a web conveyance method.

  2. Description of the Related Art Conventionally, printing apparatuses that perform printing by an inkjet method while conveying a long web (medium) by a roll-to-roll conveyance method have been known. In such a printing apparatus, it is necessary to convey the web with tension. For example, Patent Document 1 discloses a printing apparatus including a rotation shaft that winds a web on which an image is printed, and a control unit that controls a tension applied to the web. In order to prevent the position of the end of the wound web from being shifted due to a large force applied in the axial direction of the rotating shaft with respect to the web wound around the rotating shaft, The tension (winding tension) applied to the medium wound on the sheet is controlled to be low.

  Patent Document 2 discloses an image recording apparatus (printing apparatus) using a reduction gear as a winding motor. This printing device offsets the target value (target tension value) applied to the web at the start of web conveyance in order to prevent the web from loosening due to tension fluctuation due to mechanical loss of the speed reducer during web conveyance acceleration. Is controlled so as to gradually decrease the offset after the shift to the constant speed conveyance state.

Japanese Unexamined Patent Publication No. 2016-145098 JP, 2015-160708, A

  In the printing apparatus described in Patent Document 1, when a designated target tension value, which is a web winding tension by a rotating shaft, is set to a predetermined value or less, a tension error occurs and conveyance stops. This is considered to be because the torque of the motor for controlling the tension applied to the web is reduced, and the influence of a mechanical torque loss generated in the transport unit is increased.

  Therefore, the inventors of the present invention specify the target tension value of the winding tension at the start of web conveyance in the case of low tension control with a specified target tension value of 10 N or less, as in the printing apparatus described in Patent Document 2. After changing to a first target tension value (specified target tension value + tension offset amount) larger than the value, control to decrease to the specified target tension value was studied. At this time, if the target tension value is decreased in a state in which the conveyance speed becomes a constant designated conveyance speed and printing on the web is started, the web conveyance becomes unstable and the print quality is deteriorated. In addition, when printing is started after the decrease to the designated target tension value is completed and the web conveyance is stabilized in order to avoid a decrease in print quality, a waiting time until the web conveyance is stabilized occurs and the printing efficiency is lowered. Therefore, in order to prevent these, the tension offset amount included in the first target tension value is controlled to decrease stepwise toward the designated target tension value during the constant speed conveyance during the acceleration period of the web.

  However, even in this control, a tension error occurs in the minute conveyance in which the web conveyance speed does not reach the designated conveyance speed, and the conveyance is stopped. Specifically, in a printing apparatus that transports a web in a roll-to-roll system, a print start position is controlled by forming a mark on the web and detecting the mark with a sensor. In this case, in order to appropriately set the mark detection accuracy, detection of the mark by the sensor and adjustment of the detection light amount and detection threshold of the sensor are performed before starting printing. At this time, the web is minutely conveyed and stopped, and then the web is minutely conveyed in the reverse direction and stopped.

  When the low tension control for minute conveyance is performed by the printing apparatus described in Patent Document 1 or Patent Document 2, the tension offset amount of the first target tension value set at the start of web conveyance (at the start of acceleration) is Before the decrease is completed, the deceleration for stopping the web conveyance starts. If the tension offset amount continues to decrease after the web starts to decelerate, the difference between the winding tension generated on the web and the target tension value at that point when the web speed changes from acceleration to deceleration will cause a tension error. There was a problem to do.

  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 or application examples.

  Application Example 1 A printing apparatus according to this application example includes a conveyance unit that conveys a web, a first drive unit that drives the conveyance unit, and a rotation shaft that winds the web conveyed by the conveyance unit; A second driving unit that drives the rotating shaft, and a web winding tension by the rotating shaft while controlling the first driving unit so that the web conveying speed becomes a designated designated conveying speed. A control unit that controls the torque output from the second drive unit so as to approach the designated designated target tension value, and the control unit is configured to perform the operation when the designated target tension value is equal to or less than a predetermined value. The target tension value of the winding tension is set to a first target tension value that is larger than the specified target tension value according to the maximum speed of the web when the web is conveyed by a designated designated conveyance distance. In addition, control for gradually reducing the target tension value from the first target tension value to the designated target tension value until the web conveyance by the conveyance unit is started and the acceleration period in the web conveyance is completed. It is characterized by performing.

  According to this application example, the control unit of the printing apparatus responds to the maximum speed of the web when the web is conveyed by the designated designated conveyance distance in the low tension control in which the designated designated tension value is a predetermined value or less. Thus, the target tension value of the winding tension is set to a first target tension value that is larger than the specified target tension value. Then, the control unit gradually decreases the target tension value from the first target tension value to the designated target tension value by the end of the web acceleration period.

  In other words, when the designated target tension value is equal to or less than a predetermined value that may cause a tension error, the control unit applies a tension offset corresponding to the difference between the first target tension value and the designated target tension value at the start of web conveyance. The amount is set to a value that can be reduced within the acceleration period of the web. This tension offset amount has a correlation with the maximum web speed, and can be determined according to the maximum speed. In this manner, the control unit completes the gradual reduction of the tension offset amount within the web acceleration period. As a result, the web conveyance does not change from acceleration to deceleration until the target tension value reaches the specified target tension value, so that the occurrence of a tension error in the low tension control is suppressed. Therefore, it is possible to provide a printing apparatus that suppresses the occurrence of tension errors in low tension control.

  Application Example 2 In the printing apparatus according to the application example described above, it is preferable that the maximum web speed is determined according to the designated conveyance distance and the designated conveyance speed.

  According to this application example, the maximum web speed during web conveyance is determined according to the designated conveyance distance and the designated conveyance speed. Thereby, the 1st target tension value according to the designated conveyance distance can be set up.

  Application Example 3 In the printing apparatus according to the application example described above, the maximum web speed is determined when the web is transported determined according to the designated transport distance, the designated transport speed, and the designated target tension value. It is preferable to be determined by the web acceleration, which is acceleration, the designated conveyance distance, and the designated conveyance speed.

  According to this application example, the maximum web speed at the time of web conveyance is the web acceleration, which is the acceleration at the time of web conveyance determined according to the designated conveyance distance, the designated conveyance speed, and the designated target tension value, and the designated conveyance. Since it is determined by the distance and the designated conveyance speed, the first target tension value can be set from the web acceleration, the designated conveyance distance, and the designated conveyance speed.

  Application Example 4 The printing apparatus according to the application example further includes a storage unit that stores a table in which the designated conveyance distance, the designated conveyance speed, the designated target tension value, and the web acceleration are associated with each other. The web acceleration is preferably acquired from the table based on the designated conveyance distance, the designated conveyance speed, and the designated target tension value.

  According to this application example, the web acceleration during web conveyance is acquired from the table stored in the storage unit based on the designated conveyance distance, the designated conveyance speed, and the designated target tension value. By using this web acceleration, the maximum web speed according to the designated transport distance can be obtained.

  Application Example 5 In the printing apparatus according to the application example, the storage unit includes a first table used when the first web is used as the web, and a second table having a different type from the first web as the web. It is preferable to store the second table used when the web is used.

  According to this application example, the storage unit stores a first table corresponding to the first web and a second table for the second web. This allows the printing apparatus to use different types of webs.

  Application Example 6 In the printing apparatus according to the application example described above, it is preferable that a fixed value is used as the designated conveyance speed when the designated conveyance distance is a predetermined value or less.

  According to this application example, the control unit uses a fixed value as the designated conveyance speed when the designated conveyance distance is equal to or less than a predetermined value. Thereby, generation | occurrence | production of a tension error is suppressed and a web can be conveyed suitably.

  Application Example 7 The printing apparatus according to the application example includes a printing unit that performs printing on the web conveyed by the conveyance unit, and the control unit conveys the web at a predetermined constant speed. After reaching the speed, it is preferable that printing by the printing unit is executed, and the designated target tension value is designated as a tension applied to the web on the rotation shaft when printing by the printing unit is performed.

  According to this application example, the designated target tension value is designated as the tension applied to the web at the rotation axis when printing by the printing unit is performed, and the control unit sets the web conveyance speed to a constant speed conveyance speed. Later, printing by the printing unit is executed. Thereby, since the conveyance of the web at the time of printing is stabilized, the print quality is improved.

  Application Example 8 In the printing apparatus according to the application example described above, the web conveyance speed is accelerated to 10% to 80% when the maximum speed of the web that reaches during the acceleration period is 100%. It is preferable to gradually reduce the first target tension value to the designated target tension value.

  According to this application example, the control unit gradually decreases the target tension value from the first target tension value to the designated target tension value during a period in which the web conveyance speed is accelerated to 10% to 80%. Since the web acceleration is stable during the period in which the web conveyance speed is 10% to 80%, a tension error caused by gradually decreasing the target tension value is suppressed.

  Application Example 9 The printing apparatus according to the application example includes a detector that detects a tension applied to the web, and the control unit detects the tension applied to the web to control the tension applied to the web. It is preferable to execute feedback control based on a deviation between the tension and the target tension value.

  According to this application example, since the control unit performs feedback control based on the deviation between the tension detected by the detector and the target tension value, the tension of the web can be suitably adjusted.

  Application Example 10 The printing apparatus according to the application example includes a motor and a reduction gear that receives the torque output from the motor, amplifies the torque, and outputs the amplified torque to the rotating shaft. The reduction ratio is preferably less than 1:10.

  According to this application example, the printing apparatus includes the reduction gear having a reduction ratio of less than 1:10. Since the torque of the motor can be increased by the speed reducer, a small and inexpensive motor can be used.

  Application Example 11 A web conveyance method according to this application example includes a conveyance unit that conveys a web, a first drive unit that drives the conveyance unit, and a rotary shaft that winds the web conveyed by the conveyance unit. And a second drive unit that drives the rotary shaft, and the web drive by the rotary shaft while controlling the first drive unit so that the web transport speed becomes a designated designated transport speed. A web transport method for a printing apparatus, comprising: a control unit that controls a torque output by the second drive unit so that a tension approaches a designated designated target tension value, wherein the designated target tension value is When the web is transported by a designated designated transport distance when the web is below a predetermined value, the target tension value of the winding tension is set to be greater than the designated target tension value according to the maximum speed of the web. A first target tension value setting step for setting a threshold first target tension value; and the conveyance of the web by the conveyance unit is started, and the target tension value is set to the first tension until the acceleration period in the conveyance of the web ends. A tension control step of gradually decreasing from one target tension value to the specified target tension value.

  According to this application example, when the designated designated target tension value is equal to or less than the predetermined value, the web conveyance method is performed according to the maximum speed of the web when the web is conveyed by the designated designated conveyance distance. A first target tension value setting step for setting the target tension value of the take-up tension to a first target tension value that is larger than the specified target tension value, and the target tension value from the first target tension value by the end of the web acceleration period. A tension control step that gradually decreases to a specified target tension value.

  In other words, in the web transport method, in the low tension control in which the specified target tension value is less than a predetermined value that may cause a tension error, the first target tension value is set in the first target tension value setting step and the first target tension value is set. The tension offset amount corresponding to the difference between the tension value and the specified target tension value is set to a value that can be reduced within the web acceleration period. This tension offset amount has a correlation with the maximum web speed, and can be determined according to the maximum speed. In this way, the control unit completes the gradual reduction of the tension offset amount within the web acceleration period in the tension control step. As a result, the web conveyance does not change from acceleration to deceleration until the target tension value reaches the specified target tension value, so that the occurrence of a tension error in the low tension control is suppressed. Therefore, it is possible to provide a web conveying method in which the occurrence of a tension error in the low tension control is suppressed.

1 is a schematic diagram illustrating a schematic overall configuration of a printing apparatus according to an embodiment. FIG. 3 is a block diagram schematically showing an electrical configuration for controlling the printing apparatus. The table | surface which shows the conveyance conditions of the low tension control by a prior art, and its determination result. The figure which shows the relationship between the conveyance speed of a web, conveyance time, and conveyance distance. The figure which shows the relationship between the conveyance speed of a web, conveyance time, and conveyance distance. The figure which shows the relationship between the conveyance speed of a web, conveyance time, and conveyance distance. The figure explaining the target tension value in the low tension control by a prior art. The graph which shows the conveyance speed of the web in case the designated conveyance distance L = 500mm. The graph which shows the winding tension in case the designated conveyance distance L = 500mm. The graph which shows the conveyance speed of the web in case the designated conveyance distance L = 50mm. The graph which shows winding-up tension at the time of the designated conveyance distance L = 50mm. The table | surface which shows the result of the micro conveyance experiment in the low tension control by this embodiment. The table | surface which shows the result of the micro conveyance experiment in the low tension control by this embodiment. The table | surface which shows the result of the micro conveyance experiment in the low tension control by this embodiment. A first table used when the first web is used. A second table used when the second web is used. The figure explaining the target tension value in low tension control. The flowchart figure explaining the conveyance method of a web. The block diagram which shows typically the electric constitution which controls the printing apparatus which concerns on a modification.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
(Embodiment)
<Schematic configuration of printing device>
FIG. 1 is a schematic diagram illustrating a schematic overall configuration of a printing apparatus according to an embodiment. First, a schematic configuration of the printing apparatus 1 according to the present embodiment will be described with reference to FIG. In the present embodiment, a printing apparatus 1 that includes a rotating drum 35 that supports the web S in a cylindrical shape and that transports the web S in a roll-to-roll manner will be described as an example.

  As shown in FIG. 1, the printing apparatus 1 includes a feeding shaft 20 that unwinds the web S, a conveyance unit 30 that conveys the web S, a winding shaft 40 that serves as a rotation shaft that winds the web S conveyed by the conveyance unit 30, and the like. have. In the printing apparatus 1, a long web S having both ends wound around the feeding shaft 20 and the winding shaft 40 in a roll shape is stretched along the transport path Pc. The web S is subjected to image recording while being transported in the transport direction Ds by the rotating drum 35 provided while going from the feed shaft 20 to the take-up shaft 40. The type of 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 for paper, and synthetic paper, PET (Polyethylene terephthalate), PP (polypropylene) and the like for film-type. Schematically, the printing apparatus 1 includes a feeding area 2 that feeds the web S from the feeding shaft 20, a process area 3 that records an image on the web S that is fed from the feeding area 2, and an image recorded in the process area 3. The web S is composed of three regions including a winding region 4 for winding the web S around the winding shaft 40. 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 area 2 has a feeding shaft 20 around which one 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 one end of the web S by winding the web S with the surface of the web S facing outward. Then, the feeding shaft 20 rotates in the circumferential direction (clockwise in FIG. 1), so that the web S wound around the feeding shaft 20 is fed to the process region 3 via the driven roller 21. The driven roller 21 is in contact with the web S and receives the frictional force between the web S and the web S to be rotated in the web S conveyance direction Ds. 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.

  The process area 3 includes a transport unit 30 and a printing unit 50 that performs printing on a web transported by the transport unit 30. The transport unit 30 includes a front drive roller 31, a rotating drum 35 that supports the web S in a cylindrical shape, and a rear drive roller 32. The printing unit 50 includes recording heads 51 and 52 and UV irradiators 61 and 62. , 63 are provided.

  In the process area 3, the web S fed from the feeding area 2 is supported by the rotating drum 35, and the recording heads 51 and 52 and the UV irradiators 61, 62, and 63 arranged along the outer peripheral surface of the rotating drum 35. Thus, the process for the web S is appropriately performed, and an image is recorded on the web S. A front drive roller 31 that conveys the web S toward the rotating drum 35 is provided on the upstream side of the process area 3, and the web S is conveyed toward the winding shaft 40 on the downstream side of the process area 3. A rear drive roller 32 is provided. The web S conveyed from the front drive roller 31 to the rear drive roller 32 is supported by the rotating drum 35.

  The front drive roller 31 has a cylindrical shape or a columnar shape having a plurality of minute protrusions formed by thermal spraying on the outer peripheral surface, and winds the web S fed from the feeding region 2 from the back surface side. Then, when the front drive roller 31 rotates in the circumferential direction (clockwise in FIG. 1), the web S fed out from the feeding region 2 is transported to the downstream side of the transport path Pc. A nip roller 31n is provided to face the front drive roller 31. The nip roller 31 n abuts on the surface of the web S while being biased toward the front drive roller 31, and sandwiches the web S with the front drive roller 31. 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 rotating drum 35 is a cylindrical drum having a diameter of, for example, 400 mm, which is rotatably supported by a support mechanism (not shown), and the web S conveyed from the front driving roller 31 to the rear driving roller 32. Wrap from the back side. The rotating drum 35 supports the web S from the back side, receives the frictional force with the web S being conveyed, and rotates in accordance with the conveyance direction Ds of the web S. Incidentally, in the process area 3, driven rollers 33 and 34 that change the traveling direction of the web S on both sides in the transport direction Ds of the area in which the web S is wound around the rotating drum 35 are provided. Of these, the driven roller 33 wraps the surface of the web S between the front drive roller 31 and the rotating drum 35 in the transport direction Ds, and turns the traveling direction of the web S in the direction toward the rotating drum 35. On the other hand, the driven roller 34 wraps the surface of the web S between the rotating drum 35 and the rear drive roller 32 in the transport direction Ds, and turns back the traveling direction of the web S. In this way, by folding the web S on the upstream side and the downstream side in the transport direction Ds with respect to the rotating drum 35, a long winding portion of the web S around the rotating drum 35 can be secured.

  The rear drive roller 32 has a cylindrical shape or a columnar shape having a plurality of minute projections formed by thermal spraying on the outer peripheral surface, and the web S conveyed from the rotating drum 35 via the driven roller 34 on the back surface. Wrap from the side. And the web S is conveyed to the winding area | region 4 because the rear drive roller 32 rotates in the circumferential direction (clockwise in FIG. 1). A nip roller 32n is provided to face the rear drive roller 32. The nip roller 32n abuts on 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.

  In this way, 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 rotating drum 35. In the process area 3, a plurality of recording heads 51 corresponding to different colors are provided in order to record a color image on the surface of the web S supported by the rotating drum 35. In the present embodiment, 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 rotating drum 35 with a slight clearance, and ink of a corresponding color (colored ink) is ejected from nozzles of the recording head. Discharge by the 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.

  In the printing apparatus 1 of the present embodiment, UV (ultraviolet) ink (photo-curable ink) that is cured by irradiating ultraviolet rays (light) is used as the ink. Therefore, UV irradiators 61 and 62 are provided in the process region 3 in order to cure the ink and fix it on the web S. 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 irradiates ultraviolet rays having a stronger irradiation intensity than that of the UV irradiator 61, thereby curing the ink (main curing) to such an extent that the wetting and spreading of the ink is stopped.

  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. Therefore, of the two adjacent recording heads 51, the ink ejected from the upstream recording head 51 to the web S is temporarily cured until the downstream recording head 51 is conveyed along with the conveyance of the web S. 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 rotating drum 35 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. Further, a UV irradiator 63 is provided on the downstream side of the recording head 52 in the transport direction Ds. This UV irradiator 63 irradiates ultraviolet rays having a stronger irradiation intensity than that of the UV irradiator 61, thereby permanently curing 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 area 3, ink ejection and curing are appropriately performed on the web S wound around the outer peripheral portion of the rotating drum 35, and a color image having a texture with transparent ink is formed. The Then, the web S on which the color image is formed is conveyed to the winding region 4 by the rear drive roller 32.

  The process area 3 includes a mark detection unit 80 that detects a mark that overlaps the detection area among a plurality of marks provided on the web S in parallel with the transport direction Ds. The mark detection unit 80 is disposed between the front drive roller 31 and the driven roller 33. The plurality of marks are printed together with the image in order to obtain the timing for resuming the temporarily stopped printing, and the mark detection unit 80 detects the mark on the web S that is conveyed to resume printing. To do. The mark is not limited to be printed together with the image, but may be provided on the web S in advance.

  The mark detection unit 80 is a reflective photosensor including a light emitting unit (not shown) that emits light and a light receiving unit (not shown) that receives light. The light emitting part is formed of, for example, a light emitting diode or a tungsten lamp, and the region irradiated with the spot on the web S becomes a detection region for detecting a mark. The light receiving unit is configured by an optical sensor such as a photodiode, for example, receives light emitted from the light emitting unit and reflected by the web S, and outputs a voltage value corresponding to the amount of light received. Thereby, it is possible to detect a mark that has reached the detection area. Further, the mark detection unit 80 has a moving mechanism (not shown) and is configured to be movable in the width direction of the web S that intersects the transport direction Ds.

  The winding region 4 has a driven roller 41 that winds the web S from the back surface side between the winding shaft 40 and the rear drive roller 32 in addition to the winding shaft 40 around which the other end of the web S is wound. Yes. The winding shaft 40 winds and supports the other 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.

  Next, an electrical configuration for controlling the printing apparatus 1 will be described. FIG. 2 is a block diagram schematically showing an electrical configuration for controlling the printing apparatus. The operation of the printing apparatus 1 described above is controlled by the host computer 10 shown in FIG. The host computer 10 may be provided in the printing apparatus 1 or may be provided outside the printing apparatus 1 separately from the printing apparatus 1. In the host computer 10, a host control unit 100 that supervises control operations is configured by a CPU (Central Processing Unit) and a memory. The host computer 10 has a driver 120, and the driver 120 reads the program 124 from the medium 122. Various media such as a CD (Compact Disk), a DVD (Digital Versatile Disk), and a USB (Universal Serial Bus) memory can be used as the medium 122. Then, the host control unit 100 controls each part of the host computer 10 and controls the operation of the printing apparatus 1 based on the program 124 read from the medium 122.

  Further, the host computer 10 is provided with a monitor 130 constituted by a liquid crystal display or the like and an operation unit 140 constituted by a keyboard, a mouse or the like as an interface with an operator. In addition to the image to be printed, a menu screen is displayed on the monitor 130. Therefore, the operator operates the operation unit 140 while checking the monitor 130 to open the print setting screen from the menu screen and set various print conditions such as the web type, web size, and print quality. be able to. The specific configuration of the interface with the worker can be variously modified. For example, a touch panel display may be used as the monitor 130, and the operation unit 140 may be configured with the touch panel of the monitor 130.

  On the other hand, the printing apparatus 1 includes a printer control unit 200 as a control unit that controls each unit of the printing apparatus 1 in response to a command from the host computer 10. The recording heads 51 and 52, the UV irradiators 61, 62 and 63, and each unit of the sheet conveyance system are controlled by the printer control unit 200. Details of the control of the printer control unit 200 for each part of the apparatus are as follows.

  The printer control unit 200 secures a CPU (not shown) for processing input signals from various detectors and controlling each unit of the printing apparatus 1, and an area for storing a CPU program and a work area. The storage unit 210 and the like.

  The printer control unit 200 executes printing by the printing unit 50 after the conveyance speed of the web S reaches a predetermined constant speed conveyance speed. Thereby, since the conveyance of the web S at the time of printing is stabilized, the print quality is improved. Specifically, the printer control unit 200 controls the ink discharge timing of each recording head 51 that forms a color image according to the conveyance of the web S. The control of the ink ejection timing is executed based on the output (detected value) of a drum encoder E30 that is attached to the rotating shaft of the rotating drum 35 and detects the rotational position of the rotating drum 35. That is, since the rotating drum 35 is driven to rotate with the conveyance of the web S, the conveyance speed and conveyance position of the web S can be grasped by referring to the output of the drum encoder E30 that detects the rotation position of the rotation drum 35. be able to. Therefore, the printer control unit 200 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 a function of 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 control unit 200 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 200 also controls the timing of turning on and off the UV irradiators 61, 62 and 63 and the amount of irradiation light.

  The printer control unit 200 controls a function of controlling the conveyance of the web S detailed with reference to FIG. A feeding motor M20 that drives the feeding shaft 20 is connected to the feeding shaft 20. A front drive motor M31 and a rear drive motor M32 as a first drive unit that drives the transport unit 30 are connected to the front drive roller 31 and the rear drive roller 32 that constitute the transport unit 30. A winding motor M40 as a second drive unit that drives the winding shaft 40 is connected to the winding shaft 40. Then, the printer control unit 200 controls the feeding, conveying, and winding 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 200 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 200 controls the driving force (torque) of the feeding motor M20 to adjust the tension of the web S from the feeding shaft 20 to the front driving roller 31 (feeding tension Ta). That is, a tension sensor S21 that detects a feeding tension Ta applied to the web S is attached to the driven roller 21 disposed between the feeding shaft 20 and the front drive roller 31 in the transport direction Ds. The tension sensor S21 can be configured by a load cell that detects a force received from the web S, for example. And the printer control part 200 performs the feedback control of the torque of the feeding motor M20 based on the detection result of the tension sensor S21. Thereby, the feeding tension Ta of the web S is adjusted.

  In addition, the printer control unit 200 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 area 2 passes through the process area 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 200 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 200 controls the torque of the rear drive motor M32 to adjust the tension (process tension Tb) applied to the web S from the front drive roller 31 to the rear drive roller 32. That is, a tension sensor S34 that detects the process tension Tb applied to the web S is attached to the driven roller 34 disposed between the rotating drum 35 and the rear drive roller 32 in the transport direction Ds. The tension sensor S34 can be configured by a load cell that detects a force received from the web S, for example. Then, the printer control unit 200 executes torque feedback control of the rear drive motor M32 based on the detection result of the tension sensor S34. Thereby, the process tension Tb of the web S is adjusted.

  The printing apparatus 1 includes a winding motor M40 as a motor that rotates the winding shaft 40. The printer control unit 200 rotates the winding motor M <b> 40 that drives the winding shaft 40, and winds the web S conveyed by the rear drive roller 32 around the winding shaft 40. At this time, the printer control unit 200 controls the torque of the winding motor M40 to adjust the tension (winding tension Tc) applied to the web S from the rear drive roller 32 to the winding shaft 40. Specifically, the printer control unit 200 controls the front drive motor M31 and the rear drive motor M32 so that the web S conveyance speed becomes the designated conveyance speed V0 (see FIG. 15), and the winding shaft 40 controls the web drive S. The winding motor M40 is controlled so that the winding tension Tc approaches the designated target tension value P0 (see FIG. 15).

  A tension sensor S41 as a detector for detecting a winding tension Tc applied to the web S is attached to the driven roller 41 disposed between the rear drive roller 32 and the winding shaft 40 in the transport direction Ds. The tension sensor S41 can be configured by a load cell that detects a force received from the web S, for example. Then, the printer control unit 200 executes torque feedback control of the winding motor M40 based on the detection result of the tension sensor S41. Thereby, the winding tension Tc of the web S is adjusted.

  In this way, the web S that the transport unit 30 transports toward the winding shaft 40 is wound by the winding shaft 40, whereby the winding tension Tc is applied to the web S. In the printing apparatus 1 of the present embodiment, control for changing the target value of the winding tension Tc, that is, the target tension value Tct, is executed according to the maximum speed of the web S when the web S is conveyed.

Next, before describing the control of the winding tension Tc for minute conveyance according to the present invention, the minute conveyance test performed by the inventors of the present invention with the low tension control of the prior art and the determination result will be described.
FIG. 3 is a table showing the transport conditions of low tension control according to the prior art and the determination results. The upper part of FIG. 3 shows the material of the web S and the transport conditions of the web S. A web (first web) S made of a film material was used for both the face surface and the liner surface in the transport test for micro transport. The designated target tension value P0 designated as the winding tension Tc is 5N. Further, the web S is accelerated at a web acceleration a = 50.8 mm / sec ² up to the designated transport speed V0 = 254 mm / sec. The web acceleration a = 50.8 mm / sec ² is 10% acceleration of the maximum acceleration of the web S of the printing apparatus 1 = 508 mm / sec ² .

  In the lower part of FIG. 3, the maximum web speed Vmax reached when the web S is transported by the designated transport distance L with respect to the designated transport distance L for transporting the web S, and at the start of web transport A tension offset amount P added to the designated target tension value P0 as the target tension value Tct and a determination result determined based on the winding tension Tc measured at that time are shown. The designated target tension value P0 is designated as the tension applied to the web S at the winding shaft 40 when printing by the printing unit 50 is executed. In the minute conveyance in which the designated conveyance distance L of the web S is less than 1552 mm, the conveyance speed of the web S changes from acceleration to deceleration before reaching the designated conveyance speed V0 and stops. That is, the maximum speed Vmax of the web S is slower than the designated transport speed V0. In the prior art, in the low tension control with the designated target tension value P0 = 10 N or less, the tension offset amount P is uniformly set to 10 N regardless of the designated conveyance distance L of the web S.

4-6 is a figure which shows the relationship between the conveyance speed of the web S, conveyance time, and conveyance distance. Here, a method for obtaining the maximum speed Vmax of the web S from the designated conveyance distance L, the designated conveyance speed V0 and the web acceleration a will be described.
FIG. 4 shows the relationship between the web S conveyance speed and the conveyance time when the web S is conveyed at the designated conveyance distance L = 1552 mm. When the web S is transported at the designated transport distance L = 1552 mm, the transport speed V of the web S starts decelerating immediately after reaching the designated transport speed V0. The designated transport distance L of the web S coincides with a value (area) obtained by integrating the speed curve shown in FIG. 4 and is L = V0 ² / a * K.
Here, the coefficient K is an S-shaped curve coefficient of a speed curve that changes in an S-shape with the passage of time. In the printing apparatus 1 of the present embodiment, K = 2π / (π + 2) ≈1.222. Note that K varies depending on the characteristics of the S-shaped curve.

  FIG. 5 shows the relationship between the conveyance speed and the conveyance time of the web S when the web S is conveyed at the designated conveyance distance L> 1552 mm. When the web S is transported at a designated transport distance L> 1552 mm, the transport speed V of the web S reaches the designated transport speed V0 and is then transported at a designated transport speed V0 for a predetermined time and starts decelerating. Therefore, as shown in FIGS. 4 and 5, the maximum speed Vmax of the web S in the conveyance in which the designated conveyance distance L is 1552 mm or more becomes the designated conveyance speed V0 and the predetermined constant-speed conveyance speed described above.

FIG. 6 shows the relationship between the web S conveyance speed and the conveyance time when the web S is conveyed at the designated conveyance distance L <1552 mm. When the web S is transported at a designated transport distance L <1552 mm, the transport speed V of the web S starts decelerating before reaching the designated transport speed V0, so the maximum speed Vmax of the web S is greater than the designated transport speed V0. Will also be late. The maximum speed Vmax of the web S at this time is the apex when the similarity is reduced so that the area of the speed curve shown in FIG.
Vmax = √ (L * a / K) (1)

FIG. 7 is a diagram for explaining a target tension value in the low tension control according to the conventional technique. The upper part of FIG. 7 shows the conveyance speed V of the web S, and the lower part shows the target tension value Tct of the winding tension Tc. In the conveyance in which the designated conveyance distance L of the web S is 1552 mm or more, as shown by the broken line in FIG. 7, the target tension value Tct is set to the designated target tension value P0 = 5N and the tension offset amount P = The first target tension value P1 with 10N added is set to 15N. The tension offset amount P of 10N is gradually decreased in a section from T1 to T3 in which the transport speed V of the web S is accelerated from 10% to 80% of the specified transport speed with the specified transport speed of 254 mm / sec being 100%.
In the minute conveyance in which the designated conveyance distance L of the web S is less than 1552 mm, the maximum speed Vmax of the web S does not reach the designated conveyance speed V0. For this reason, as shown by the solid line in FIG. 7, the target tension value Tct gradually decreases to the timing at which the web S switches from acceleration to deceleration, that is, T2 at which the web S reaches the maximum speed Vmax, and the target tension value Tct after T2 is The designated target tension value P0 is changed to 5N.

  Next, the determination result (reference) in FIG. 3 will be described. The determination list of FIG. 3 shows four-level evaluations “A” to “D” depending on the state of the winding tension Tc measured when the web S is conveyed for each designated conveyance distance L. The “order” column of the determination list shows the determination result when the web S is transported in the transport direction Ds, and the “reverse” column of the determination list shows the web S in the direction opposite to the transport direction Ds. A determination result when the sheet is conveyed is shown. The determination result “A” means “Excellent” when the winding tension Tc is 1N or more. The determination result “B” means “Good” when the winding tension Tc is instantaneously reduced to less than 1N. The determination result “C” means “Poor” when the winding tension Tc has decreased to 0 N but no tension error has occurred. The determination result “D” means “No-good” when 0N of the winding tension Tc continues for 1 second or longer, a tension error occurs, and conveyance of the web S stops.

  An example of the determination result “A” is shown. FIG. 8 is a graph showing the web conveyance speed when the designated conveyance distance L = 500 mm. FIG. 9 is a graph showing the winding tension when the designated transport distance L = 500 mm. As shown in FIG. 8, the maximum speed Vmax of the web S when the web S is transported under the transport conditions and the specified transport distance L = 500 mm in FIG. 3 is 144 mm / sec. FIG. 9 shows the winding tension Tc measured by the tension sensor S41. In the case of FIG. 9, since the winding tension Tc of 1 N or more is maintained even before and after T2 when the web S is switched from acceleration to deceleration, the determination is “A”.

  An example of the determination result “D” is shown. FIG. 10 is a graph showing the web conveyance speed when the designated conveyance distance L = 50 mm. FIG. 11 is a graph showing the winding tension when the designated transport distance L = 50 mm. As shown in FIG. 10, the maximum speed Vmax of the web S when the web S is transported under the transport conditions and the specified transport distance L = 50 mm in FIG. 3 is 45 mm / sec. FIG. 11 shows the winding tension Tc measured by the tension sensor S41. In the case of FIG. 11, before and after T2 when the web S switches from acceleration to deceleration, the winding tension Tc of less than 1N continues for 1 sec or more, and therefore “D” determination is made.

As shown in the table of FIG. 3, when the tension offset amount P is fixed to 10 N, it has been found that the tension error of the winding tension Tc occurs as the designated transport distance L of the web S becomes shorter. The present inventors consider that this is because when the designated transport distance L of the web S is short, the target tension value is switched to the designated target tension value P0 while the gradual decrease of the tension offset amount P is insufficient, and the web acceleration a, The experiment was conducted using the designated transport speed V0, the tension offset amount P and the like as parameters. Note that the printing apparatus 1 according to the present embodiment has three modes as the designated transport speed V0: V0 = 254 mm / sec in the normal mode, V0 = 127 mm / sec in the half speed mode, and V0 = 5 mm / sec in the minute feed mode. . Further, the web acceleration a can be changed in units of% with the maximum acceleration 508 mm / sec ² of the web S of the printing apparatus 1 being 100%.

  As a result, when the web S is minutely conveyed with a low tension of 10 N or less, the tension offset amount P is determined according to the maximum speed Vmax of the web S, and the tension offset amount P is decreased during the acceleration period of the web S. It was found that the occurrence of tension errors can be suppressed by performing control.

  12 to 14 are tables showing the results of a micro-transport experiment with low tension control according to the present embodiment. The description format of this table is the same as that in FIG.

The experiment shown in FIG. 12 is different from the conventional low tension control shown in FIG. 3 in that the tension offset amount P is changed according to the maximum speed Vmax of the web S. Since the web acceleration a is the same, the maximum speed Vmax is determined according to the designated transport distance L and the designated transport speed V0. As a result, the tension offset amount P and the first target tension value P1 corresponding to the designated transport distance L can be set. When the web acceleration a = 50.8 mm / sec ² and the designated transport speed V0 = 254 mm / sec, the maximum speed Vmax of the web S having the designated transport distance L of 1552 mm or more is determined by the designated transport speed V0. Further, the maximum speed Vmax of the web S having the designated transport distance L of less than 1552 mm is determined by the equation (1) described with reference to FIG.

  The tension offset amount P is a value proportional to the maximum speed Vmax of the web S calculated according to the specified transport distance L, assuming that the maximum speed Vmax of the web S is 254 mm / sec equal to the specified transport speed V0 and 10N. . Thus, the tension offset amount P can be reduced during the acceleration period of the web S by changing the tension offset amount P according to the maximum speed Vmax of the web S. In the experiment shown in FIG. 12, in the range where the designated transport distance L is 200 mm or more, a determination result of “A” was obtained for both forward and reverse transport.

Experiment shown in Figure 13, that has been changed in accordance with the tension offset amount P to the maximum speed Vmax of the web S, and 3% acceleration of the web acceleration a 15.2mm / sec ² (maximum acceleration = 508 mm / sec ² 3) is different from the conventional low tension control shown in FIG. The maximum speed Vmax and the tension offset amount P of the web S are determined in the same manner as described with reference to FIG. In the experiment shown in FIG. 13, a determination result “A” was obtained for both the forward and reverse transports within the specified transport distance L of 50 mm or more.

The experiment shown in FIG. 14 is different from the conventional low tension control shown in FIG. 3 in that the designated transport speed V0 is changed to 5 mm / sec. When the web acceleration a = 50.8 mm / sec ² and the designated transport speed V0 = 5 mm / sec, the maximum speed Vmax of the web S having the designated transport distance L of 0.6 mm or more is determined by the designated transport speed V0. The tension offset amount P with the designated transport distance L of 0.6 mm or more is determined in the same manner as described with reference to FIG. In addition, when the designated conveyance distance L is less than 0.6 mm, the maximum speed Vmax of the web S is less than 5 mm / sec of the designated conveyance speed V0, and when it is proportional to the maximum speed Vmax of the web S, the tension offset amount P is also 0.2N. However, the tension offset amount P is fixed at 0.2N. In the experiment shown in FIG. 14, a determination result equal to or greater than “B” was obtained in the range of all the designated transport distances L.

  FIG. 15 is a first table used when the first web is used. The first table associates the data of the designated conveyance distance L, the designated conveyance speed V0, the designated target tension value P0, and the web acceleration a on the basis of various kinds of minute conveyance experiment results including the minute conveyance experiments of FIGS. It has been. For example, the experimental results shown in FIG. 12 are reflected in the rows of the designated conveyance speed V0; 254 mm / sec, the designated conveyance distance L; 1552 mm ≦ L, and 200 mm ≦ L <1552 mm. The experimental results shown in FIG. 13 are reflected in a row of designated conveyance speed V0; 254 mm / sec, designated conveyance distance L; 50 mm ≦ L <200 mm. The experimental results shown in FIG. 14 are reflected in the rows of designated conveyance speed V0; 5 mm / sec, designated conveyance distance L; 0.6 mm ≦ L <50 mm, and L <0.6 mm. The first table is stored in the storage unit 210. In addition, although the 1st table shown in FIG. 15 has described the data used at the time of the low tension whose designated target tension value P0 of the winding shaft 40 is 10 N or less, the data used at the time of the high tension exceeding 10 N is also included. Have.

  FIG. 16 is a second table used when the second web is used. The second table is used when a second web different in type from the first web is used. The second web is, for example, a web S using paper for the face surface and a film for the liner surface. The second table is created based on various experimental results using the second web in the same manner as the first web, and is stored in the storage unit 210. Thereby, the printing apparatus 1 can use different types of webs S. In the present embodiment, it has been described that the storage unit 210 of the printing apparatus 1 stores two tables, the first table and the second table, but the storage unit 210 has three or more tables, that is, A table corresponding to three or more types of webs may be stored.

  The web acceleration a, which is the acceleration during the conveyance of the web S, is determined according to the designated conveyance distance L, the designated conveyance speed V0, and the designated target tension value P0. Specifically, the web acceleration a is acquired from the first and second tables based on the designated conveyance distance L, the designated conveyance speed V0, and the designated target tension value P0. Thereby, the maximum speed Vmax of the web S according to the designated conveyance distance L of the web S can be obtained. The maximum speed Vmax of the web S is determined by the web acceleration a, the designated conveyance distance L, and the designated conveyance speed V0. Thereby, the tension offset amount P and the first target tension value P1 can be set from the web acceleration a, the specified transport distance L, and the specified transport speed V0.

  However, when the designated conveyance distance L is equal to or less than a predetermined value (for example, 50 mm or less in the first table), the designated conveyance speed V0 is fixed to a fixed value of 5 mm / sec. Thereby, generation | occurrence | production of a tension error is suppressed and the web S can be conveyed suitably. The tension offset amount P is proportional to the maximum speed Vmax of the web S based on the tension offset amount P = 10 N when the maximum speed Vmax of the web S is 254 mm / sec, except in the region where the designated transport distance L <0.6 mm. It is the value. Note that a fixed value of tension offset amount P = 0.2N is used when a very small amount of conveyance with a designated conveyance distance L <0.6 mm is performed.

  FIG. 17 is a diagram for explaining a target tension value in the low tension control. The upper part of FIG. 17 shows the conveyance speed V of the web S, and the lower part shows the target tension value Tct of the winding tension Tc. The printer control unit 200 sets the designated tension value Tct to the first target tension value P1 obtained by adding the tension offset amount P to the designated target tension value P0 before the conveyance of the web S is started. Then, the printer control unit 200 gradually decreases the target tension value Tct from the first target tension value P1 to the designated target tension value P0 until the acceleration period in the conveyance of the web S ends. Note that the gradual decrease from the first target tension value P1 to the designated target tension value P0 is, as shown in FIG. 17, when the maximum speed Vmax of the web S reached during the acceleration period during the web S conveyance is 100%. It is preferable to implement in the period from T1 to T3 when the conveyance speed V of the web S is accelerated to 10% to 80%. During the period from T1 to T3 when the conveyance speed V of the web S is accelerated to 10% to 80%, the web S is stably accelerated at the web acceleration a, so that a tension error caused by gradually decreasing the target tension value Tct is suppressed. Is done.

<Web transport method>
FIG. 18 is a flowchart for explaining a web conveying method. Next, a method for conveying the web S will be described with reference to FIG.

  Step S <b> 1 is a transport condition receiving step for receiving the transport conditions of the web S. The printer control unit 200 receives, from the host computer 10, conveyance conditions including the material of the web S to be used, the designated target tension value P 0 of the winding shaft 40, the designated conveyance speed V 0, and the designated conveyance distance L.

  Step S2 is a first target tension value setting step for setting the first target tension value P1. The printer control unit 200 obtains the tension offset amount P from the table corresponding to the material of the web S. For example, when the designated target tension value P0 is 10N or less as a predetermined value, the target tension of the winding tension Tc is determined according to the maximum speed Vmax of the web S when the web S is conveyed by the designated designated conveyance distance L. The value Tct is set to a first target tension value P1 that is larger than the specified target tension value P0.

  Specifically, if the web S received in step S1 is the first web, the printer control unit 200 refers to the first table stored in the storage unit 210. Then, the web acceleration a is set from the first table based on the designated target tension value P0, the designated conveyance speed V0, and the designated conveyance distance L received in step S1. Next, the printer control unit 200 obtains the maximum speed Vmax of the web S from the set web acceleration a, the designated conveyance speed V0, and the designated conveyance distance L. Specifically, the printer control unit 200 calculates the maximum speed Vmax of the web S from the formula (1), the web acceleration a, and the designated transport distance L. When the calculated maximum speed Vmax of the web S exceeds the designated transport speed V0, the printer control unit 200 sets the designated transport speed V0 as the maximum speed Vmax of the web S.

  The printer control unit 200 calculates a tension offset amount P proportional to the maximum speed Vmax of the web S, assuming that the tension offset amount P when the maximum speed Vmax of the web S is 254 mm / sec is 10N. However, when the designated transport distance L is less than 0.6 mm, the printer control unit 200 sets the tension offset amount P to a fixed value of 0.2N. Then, the printer control unit 200 sets the first target tension value P1 to a value obtained by adding the tension offset amount P to the specified target tension value P0.

  Step S3 is a conveyance start process for starting conveyance of the web S. The printer control unit 200 controls the front drive motor M31 and the rear drive motor M32 of the transport unit 30, and starts transporting the web S.

  Step S4 is a tension control process in which the target tension value Tct is gradually reduced from the first target tension value P1 to the designated target tension value P0. The printer control unit 200 performs control to gradually decrease the target tension value Tct from the first target tension value P1 to the designated target tension value P0 until the acceleration period in the conveyance of the web S ends. The printer controller 200 controls the winding tension Tc applied to the web S based on the deviation between the winding tension Tc detected by the tension sensor S41 and the target tension value Tct that changes with time. The torque feedback control of the take-off motor M40 is executed. Thereby, the winding tension Tc of the web S is suitably adjusted.

  Step S5 is a conveyance stop process for stopping the conveyance of the web S. The printer control unit 200 controls the front drive motor M31 and the rear drive motor M32 of the transport unit 30, stops the transport of the web S, and ends.

  In this way, the printer control unit 200 completes the gradual decrease of the tension offset amount P within the web S acceleration period. As a result, the web S does not turn from acceleration to deceleration until the target tension value Tct reaches the specified target tension value P0, so that occurrence of a tension error in the low tension control is suppressed.

In addition, when performing this conveyance method repeatedly, the printer control part 200 changes the stop time before conveyance provided before conveyance of the web S based on a 1st table in the conveyance start process of step S3. If this stop time before conveyance is not provided, the next conveyance operation is started before the winding tension Tc is stabilized, and the variation of the winding tension Tc may increase.
In the present embodiment, the control of the winding tension Tc has been described. However, the same control may be executed for the feeding tension Ta.

As described above, according to the printing apparatus 1 and the web S transport method according to the present embodiment, the following effects can be obtained.
The printer control unit 200 of the printing apparatus 1 can reduce the tension offset amount P within the acceleration period of the web S in the low tension control in which the designated target tension value P0 is less than a predetermined value that may cause a tension error. Set to. The tension offset amount P has a correlation with the maximum speed Vmax of the web S, and can be obtained according to the maximum speed Vmax of the web S. In this way, the printer control unit 200 completes the gradual decrease of the tension offset amount P within the web S acceleration period. As a result, the web S does not turn from acceleration to deceleration until the target tension value Tct reaches the specified target tension value P0, so that occurrence of a tension error in the low tension control is suppressed. Therefore, it is possible to provide the printing apparatus 1 that suppresses the occurrence of a tension error in the low tension control.

The maximum speed Vmax of the web S during the web conveyance is determined according to the designated conveyance distance L and the designated conveyance speed V0. Thereby, the 1st target tension value P1 according to the designated conveyance distance L can be set.
The maximum speed Vmax of the web S during web conveyance is the web acceleration a which is the acceleration during conveyance of the web S determined according to the designated conveyance distance L, the designated conveyance speed V0, and the designated target tension value P0, and the designated conveyance. Since it is determined by the distance L and the designated conveyance speed V0, the first target tension value P1 can be set from the web acceleration a, the designated conveyance distance L, and the designated conveyance speed V0.

The web acceleration a during web conveyance is acquired from the first and second tables stored in the storage unit 210 based on the designated conveyance distance L, the designated conveyance speed V0, and the designated target tension value P0. By using the web acceleration a, the maximum speed Vmax of the web S corresponding to the designated transport distance L can be obtained.
The storage unit 210 stores a first table corresponding to the first web and a second table for the second web. Thereby, the printing apparatus 1 can use different types of webs S.

The printer control unit 200 uses a fixed value as the designated conveyance speed V0 when the designated conveyance distance L is conveyance of a predetermined value or less. Thereby, generation | occurrence | production of a tension error is suppressed and the web S can be conveyed suitably.
The designated target tension value P0 is designated as the winding tension Tc applied to the web S at the winding shaft 40 when printing by the printing unit 50 is performed, and the printer control unit 200 determines that the conveyance speed V of the web S is constant. After the transport speed is reached, printing by the printing unit 50 is executed. Thereby, since the conveyance of the web S at the time of printing is stabilized, the print quality is improved.

The printer control unit 200 gradually decreases the target tension value Tct from the first target tension value P1 to the specified target tension value P0 during the period T1 to T3 in which the conveyance speed V of the web S is accelerated to 10% to 80%. During the period from T1 to T3 in which the conveyance speed of the web S is accelerated to 10% to 80%, since the web S is stably accelerated at the web acceleration a, a tension error caused by gradually decreasing the target tension value Tct is suppressed. The
The printer control unit 200 executes torque feedback control of the winding motor M40 based on the deviation between the winding tension Tc detected by the tension sensor S41 and the target tension value Tct. Thereby, the winding tension Tc of the web S is suitably adjusted.

  The web S is transported in a low tension control in which the designated target tension value P0 is less than a predetermined value that may cause a tension error. In the first target tension value setting step, the tension offset amount P is set to the acceleration of the web S. Set to a value that can be reduced within the period. The tension offset amount P has a correlation with the maximum speed Vmax of the web S, and can be obtained according to the maximum speed Vmax of the web S. In this manner, the web S transport method completes the gradual decrease of the tension offset amount P within the acceleration period of the web S in the tension control step. As a result, the web S does not turn from acceleration to deceleration until the target tension value Tct reaches the specified target tension value P0, so that occurrence of a tension error in the low tension control is suppressed. Therefore, it is possible to provide a method for transporting the web S in which the occurrence of a tension error in the low tension control is suppressed.

  Note that the present invention is not limited to the above-described embodiment, and various modifications and improvements can be added to the above-described embodiment. A modification will be described below.

(Modification)
FIG. 19 is a block diagram schematically illustrating an electrical configuration for controlling the printing apparatus according to the modification. Next, a printing apparatus 301 according to a modification will be described with reference to FIG. In addition, about the component same as embodiment, the same number is attached | subjected and the overlapping description is abbreviate | omitted.

  The printing apparatus 301 includes a winding motor M40 that rotates the winding shaft 40, and a reduction gear 43 that receives torque output from the winding motor M40, amplifies the torque, and outputs the amplified torque to the winding shaft 40. . The reduction ratio of the reduction gear 43 is preferably less than 1:10. The speed reducer 43 of less than 1:10 does not affect the low tension control described in the embodiment and can be used in the printing apparatus 301. Further, since the torque of the winding motor M40 is increased by the reduction gear 43, a small and inexpensive motor can be used as the winding motor M40.

  DESCRIPTION OF SYMBOLS 1,301 ... Printing apparatus, 2 ... Delivery area | region, 3 ... Process area | region, 4 ... Winding area | region, 10 ... Host computer, 20 ... Delivery axis | shaft, 30 ... Conveyance part, 31 ... Front drive roller, 32 ... Rear drive roller, 35 ... Rotating drum, 40 ... Winding shaft as rotating shaft, 43 ... Reducer, 50 ... Printing section, 51, 52 ... Recording head, 61, 62, 63 ... UV irradiator, 80 ... Mark detecting section, 200 ... Printer control unit as control unit, 210 ... Storage unit, E30 ... Drum encoder, M20 ... Feeding motor, M31 ... Front drive motor as first drive unit, M32 ... Back drive motor as first drive unit, M40 ... Winding motor as the second drive unit, S21, S34 ... tension sensor, S41 ... tension sensor as detector.

Claims (11)

A transport unit for transporting the web;
A first drive unit for driving the transport unit;
A rotating shaft for winding the web conveyed by the conveying unit;
A second drive unit for driving the rotating shaft;
The web winding tension by the rotating shaft approaches the designated designated target tension value while controlling the first drive unit so that the web carrying speed becomes the designated designated conveyance speed. A control unit for controlling the torque output by the second drive unit;
With
The control unit determines the target tension value of the winding tension according to the maximum speed of the web when the web is conveyed by a designated designated conveyance distance when the designated target tension value is equal to or less than a predetermined value. After setting the first target tension value larger than the specified target tension value, the conveyance of the web by the conveyance unit is started, and the target tension value is set until the acceleration period in the conveyance of the web ends. Executing a control of gradually decreasing from the first target tension value to the designated target tension value;
A printing apparatus characterized by the above. The maximum speed of the web is determined according to the designated conveyance distance and the designated conveyance speed,
The printing apparatus according to claim 1. The maximum speed of the web is the web acceleration, which is the acceleration during the web conveyance determined according to the designated conveyance distance, the designated conveyance speed, and the designated target tension value, the designated conveyance distance, and the designation Depends on the conveyance speed,
The printing apparatus according to claim 1. A storage unit that stores a table in which the designated conveyance distance, the designated conveyance speed, the designated target tension value, and the web acceleration are associated;
The web acceleration is acquired from the table based on the designated transport distance, the designated transport speed, and the designated target tension value;
The printing apparatus according to claim 3. The storage unit
A first table used when the first web is used as the web;
Storing a second table to be used when a second web having a different type from the first web is used as the web;
The printing apparatus according to claim 4. When the designated transport distance is equal to or less than a predetermined value, a fixed value is used as the designated transport speed;
The printing apparatus according to any one of claims 1 to 5, wherein: A printing unit that performs printing on the web conveyed by the conveyance unit;
The control unit executes printing by the printing unit after the web conveyance speed reaches a predetermined constant conveyance speed,
The designated target tension value is designated as a tension applied to the web at the rotation shaft when printing by the printing unit is performed;
The printing apparatus according to any one of claims 1 to 6, wherein: When the maximum speed of the web reached during the acceleration period is 100%, the web target speed gradually decreases from the first target tension value to the designated target tension value during the period in which the web conveyance speed is accelerated to 10% to 80%. Carrying out
The printing apparatus according to any one of claims 1 to 7, wherein: A detector for detecting the tension applied to the web;
The controller performs feedback control based on a deviation between the tension detected by the detector and the target tension value in order to control the tension applied to the web;
The printing apparatus according to any one of claims 1 to 8, wherein: A motor,
A reduction gear that receives the torque output from the motor, amplifies the torque, and outputs the amplified torque to the rotary shaft;
The reduction ratio of the reducer is less than 1:10;
The printing apparatus according to any one of claims 1 to 9, wherein: A transport unit that transports the web; a first drive unit that drives the transport unit; a rotary shaft that winds the web transported by the transport unit; a second drive unit that drives the rotary shaft; and the web The first drive unit is controlled such that the conveyance speed of the web becomes the designated designated conveyance speed, and the web winding tension by the rotating shaft approaches the designated designated target tension value. A control unit for controlling the torque output by the two drive units, and a web transport method for a printing apparatus comprising:
When the designated target tension value is equal to or less than a predetermined value, the target tension value of the winding tension is set to the designated target tension value according to the maximum speed of the web when the web is conveyed by the designated designated conveyance distance. A first target tension value setting step for setting a first target tension value larger than the first target tension value;
A tension control step of gradually reducing the target tension value from the first target tension value to the designated target tension value until the acceleration period in the conveyance of the web is completed while starting conveyance of the web by the conveyance unit; Including
A web conveying method characterized by the above.

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