JP2013169776A - Image recording apparatus, image recording method, program, program recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To allow printing operation which is executed subsequently to reverse conveyance of a recording medium, to be promptly started by shortening a time required for the reverse conveyance.SOLUTION: There is provided an image recording apparatus which ejects a liquid to a recording medium conveyed along a conveyance path and records an image. The image recording apparatus includes: a conveyance part selectively executing a forward conveyance mode for conveying the recording medium in the forward direction of the conveyance path and a backward conveyance mode for conveying the recording medium in the backward direction of the conveyance path which is opposite to the forward direction; an ejection part ejecting the liquid to the recording medium passing through a liquid ejection area; and a control part which controls the conveyance part and the ejection part, executes ejection printing processing for ejecting the liquid from the ejection part, while conveying the recording medium in the forward direction at a speed V1 in the forward conveyance mode, and prints the image on the recording medium. When the ejection printing processing is completed, the control part stops the conveyance of the recording medium in the forward direction and then, moves the recording medium in the backward direction at a speed V2 which is the speed V1 or higher in the backward conveyance mode.

Description

  The present invention relates to a technique for recording an image by ejecting liquid onto a recording medium conveyed along a conveyance path.

  Patent Document 1 discloses a printer that transfers an image obtained by developing a latent image formed on a photosensitive drum with toner onto a recording medium conveyed along a conveyance path, and prints the image on the recording medium. Have been described. In addition, this printer can execute reverse conveyance in which the recording medium is conveyed in the direction opposite to the direction in which the recording medium is conveyed during printing. This reverse conveyance can be executed for various purposes. In particular, the printer disclosed in Patent Document 1 performs reverse conveyance when a predetermined printing operation is completed, so that printing is performed in the next printing operation. The space between the printed image and the printed image (so-called burnt paper) is kept short.

Japanese Patent Laid-Open No. 2005-262738

  Incidentally, for example, printers used for industrial use are required to execute a plurality of printing operations (print jobs) one after another. However, in the case where the above-described reverse conveyance is performed between sequentially executed printing operations, there is a problem that if the reverse conveyance takes a long time, the start of the printing operation after the reverse conveyance is delayed.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a technique capable of shortening the time required for reverse conveyance of a recording medium and promptly starting a subsequent printing operation.

  An image recording apparatus according to the present invention is an image recording apparatus that records an image by discharging a liquid onto a recording medium that is conveyed along a conveyance path. In order to achieve the above object, the image recording apparatus is arranged in the forward direction of the conveyance path. For a transport unit that selectively performs a forward transport mode for transporting a recording medium and a reverse transport mode for transporting a recording medium in the reverse direction of the transport path opposite to the forward direction, and a recording medium that passes through the liquid ejection region A discharge unit that controls a discharge unit that discharges liquid, a transfer unit, and a discharge unit, and discharges liquid from the discharge unit while transferring the recording medium in the forward direction at a speed V1 in the forward transfer mode to print an image on the recording medium. And a control unit that executes a printing process. When the discharge printing process is completed, the control unit stops conveyance of the recording medium in the forward direction, and then moves the recording medium in the reverse direction in the reverse conveyance mode at a speed V1 or higher. Move with V2 It is characterized by a door.

  An image recording method according to the present invention is an image recording method for recording an image by discharging a liquid onto a recording medium conveyed along a conveyance path. In order to achieve the above object, the image recording method is arranged in the forward direction of the conveyance path. A first process of printing an image by ejecting liquid onto a recording medium passing through the liquid ejection area while transporting the recording medium at a speed V1, and when the first process is completed, transporting the recording medium in the forward direction And a second step of moving the recording medium at a speed V2 equal to or higher than the speed V1 in the reverse direction of the transport path opposite to the forward direction.

  A program according to the present invention is a program for causing a computer to execute an image recording method for recording an image by discharging a liquid onto a recording medium transported along a transport path. The first step of printing the image by discharging the liquid onto the recording medium passing through the liquid discharge area while transporting the recording medium at the speed V1 in the forward direction, and when the first step is completed, After the conveyance in the direction is stopped, the computer is caused to execute a second step of moving the recording medium at a speed V2 equal to or higher than the speed V1 in the reverse direction of the transport path opposite to the forward direction.

  A program recording medium according to the present invention is characterized in that the program is recorded.

  In the invention configured as described above (image recording apparatus, image recording method, program, program recording medium), the forward transport mode for transporting the recording medium in the forward direction of the transport path and the transport of the recording medium in the reverse direction of the transport path The reverse conveyance mode can be executed. Then, while the recording medium is conveyed at the speed V1 in the forward direction of the conveyance path in the forward conveyance mode, the liquid is discharged onto the recording medium to execute the ejection printing process. When the ejection printing process is completed, the conveyance is performed in the reverse conveyance mode. The recording medium is conveyed at a speed V2 in the reverse direction of the path (reverse conveyance). At this time, the speed V2 at which the recording medium is conveyed in the reverse direction is set to be equal to or higher than the speed V1 at which the recording medium is conveyed in the ejection printing process. Accordingly, the recording medium can be conveyed at high speed in the reverse direction to shorten the time required for the reverse conveyance of the recording medium, and the subsequent printing operation (discharge printing process) can be started quickly. Become.

  By the way, in an image recording apparatus that discharges a photo-curable liquid from a discharge unit, light is irradiated to a recording medium that passes downstream in the forward direction from the liquid discharge region, and an image printed in the discharge print region is recorded. The image recording apparatus can be configured to further include a light irradiation unit that is fixed to the medium. However, in such an image recording apparatus, when the reverse conveyance mode is executed while the image printed by the ejection printing process is not fixed on the recording medium and the recording medium is conveyed at high speed, the unfixed image may be disturbed. There is a risk that the device parts that have come into contact with the unfixed image are contaminated. Therefore, when the ejection printing process is completed, the control unit continues the forward conveyance mode and fixes the image printed in the ejection printing process before the termination to the recording medium by the irradiation unit, and then forwards the recording medium in the forward direction. You may comprise so that conveyance may be stopped. In such a configuration, when the ejection printing process is completed, the image printed by the ejection printing process is fixed, and then the conveyance of the recording medium in the forward direction is stopped. Therefore, when the reverse conveyance mode is subsequently executed, the image has already been fixed on the recording medium, so that the image is not disturbed or the parts of the apparatus are contaminated even though the recording medium is conveyed at high speed in the reverse conveyance mode. Can be prevented.

  Incidentally, the configuration in which the image is fixed before the reverse conveyance mode is executed in this way is particularly suitable for an image recording apparatus that ends the ejection printing process in error when an error occurs. That is, if an error occurs during the execution of the ejection printing process, the control unit can configure the image recording apparatus to stop the ejection of the liquid from the ejection unit and end the ejection printing process. In such an image recording apparatus, when the reverse conveyance mode is executed as it is when the ejection printing process ends in error, there is a risk that the unfixed image is disturbed or the device parts that are in contact with the unfixed image are contaminated. is there. On the other hand, in the case of having the above-described configuration in which the image is fixed before execution of the reverse conveyance mode, even if the ejection printing process ends in error, the conveyance of the recording medium in the forward conveyance mode is continued and printed before the error ends. After the image is fixed, the conveyance of the recording medium in the forward direction is stopped. Therefore, when the reverse conveyance mode is subsequently executed, the image has already been fixed on the recording medium, so that the image is not disturbed or the parts of the apparatus are contaminated even though the recording medium is conveyed at high speed in the reverse conveyance mode. Can be prevented.

  Further, the control unit may configure the image recording apparatus to move the upstream upstream end of the image printed on the recording medium to the upstream upstream side of the liquid ejection region in the reverse conveyance mode. Such a configuration reduces the waste of the recording medium by shortening the interval between the image printed by the ejection printing process executed following the reverse conveyance mode and the image printed on the recording medium. it can.

  In addition, in the forward conveyance mode for the ejection printing process executed after the reverse conveyance mode, the control unit passes the upstream upstream end of the image printed on the recording medium in the forward upstream end of the liquid ejection area. Until then, the image recording apparatus may be configured such that the distance to which the recording medium is moved in the reverse conveyance mode is set so that the acceleration up to the speed V1 of the recording medium is completed. In such a configuration, when the boundary between the printed image and the unrecorded area (that is, the upstream end in the forward direction of the printed image) reaches the liquid ejection area, the recording medium conveyance speed is the same as that for the ejection printing process. Since the speed V1 is reached, the ejection printing process can be started promptly. As a result, the interval between the image printed by the ejection printing process and the image printed on the recording medium can be shortened, and the waste of the recording medium can be effectively suppressed.

  Incidentally, the control unit may configure the image recording apparatus such that the forward acceleration period for accelerating the conveyance speed of the recording medium to the speed V1 in the forward conveyance mode can be adjusted. Specifically, the control unit can configure the image recording apparatus to adjust the forward acceleration period according to the type of the recording medium. Accordingly, the recording medium can be accelerated over an appropriate forward acceleration period according to the type of the recording medium, and a burden on the recording medium due to the acceleration can be suppressed. Therefore, for example, the control unit may configure the image recording apparatus so as to adjust the forward acceleration period longer as the thickness of the recording medium is thinner. In such a configuration, a thin recording medium can be slowly accelerated over a long forward acceleration period, so that occurrence of damage to the recording medium can be suppressed.

  By the way, when the conveyance of the recording medium in the forward direction is stopped along with the end of the ejection printing process, the conveyance of the recording medium is not immediately stopped, but is stopped after a certain deceleration period. Therefore, during this deceleration period, the recording medium moves (runs idle) in the forward direction without receiving the ejection printing process. At this time, in order to shorten the interval between the image printed by the discharge printing process to be executed next and the image printed on the recording medium, the recording medium can be effectively prevented from being wasted. It is preferable to set a distance for moving the recording medium in the reverse direction in the reverse conveyance mode according to the idle running distance. Therefore, the control unit sets a longer distance for moving the recording medium in the reverse conveyance mode as the forward deceleration period required to decelerate and stop the conveyance speed of the recording medium from the speed V1 in the forward conveyance mode is longer. The image recording apparatus may be configured as described above. As a result, the recording medium is moved in the reverse direction in the reverse conveyance mode by a distance corresponding to the idle running distance of the recording medium after the discharge printing process is completed, so that the occurrence of waste of the recording medium is effectively suppressed. Can do.

  Further, the control unit may configure the image recording apparatus so as to adjust the forward deceleration period according to the type of the recording medium. Accordingly, the recording medium can be decelerated over an appropriate forward deceleration period corresponding to the type of the recording medium, and a burden on the recording medium due to the deceleration can be suppressed. Therefore, for example, the control unit may configure the image recording apparatus so as to adjust the forward deceleration period longer as the recording medium is thinner. In such a configuration, a thin recording medium can be slowly decelerated over a long forward deceleration period, so that the occurrence of damage to the recording medium can be suppressed.

  Further, the image recording apparatus may be configured such that the speed V1 at which the recording medium is conveyed in the forward conveyance mode is equal to the speed V2 at which the recording medium is conveyed in the reverse conveyance mode. In such a configuration, for example, since the control parameter of the motor that provides the driving force for transporting the recording medium can be shared between the forward transport mode and the reverse transport mode, the control system can be shared between the forward transport mode and the reverse transport mode. This has the advantage that the motor control system can be simplified.

FIG. 3 is a diagram schematically illustrating an example of a device configuration included in a printer to which the invention can be applied. FIG. 2 is a diagram schematically showing an electrical configuration for controlling the printer shown in FIG. 1. The flowchart which shows an example of the flow performed in 1st Embodiment. FIG. 4 is a timing chart showing an operation example executed according to the flowchart of FIG. 3. FIG. Operation | movement explanatory drawing which showed the operation example performed according to the flowchart of FIG. The timing chart which shows an example of the operation | movement performed in 2nd Embodiment. Operation | movement explanatory drawing which showed the operation | movement performed according to the timing chart of FIG.

First Embodiment FIG. 1 is a front view schematically showing an example of an apparatus configuration included in a printer to which the present invention can be 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 stretched, and the sheet S is conveyed from the feeding shaft 20 to the winding shaft 40 along the path Pc thus stretched. The printer 1 records an image on the sheet S conveyed along the conveyance path Pc. The type of the sheet S is roughly classified into a paper type and a film type. 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. Schematically, in the printer 1, the feeding unit 2 that feeds the sheet S from the feeding shaft 20, the process unit 3 that records an image on the sheet S that is fed from the feeding unit 2, and an image recorded by the process unit 3. A winding unit 4 for winding the sheet S around the winding shaft 40 is provided. In the following description, of both surfaces of the sheet S, the surface on which an image is recorded is referred to as the front surface, and the opposite surface is referred to as the back surface.

  The feeding unit 2 includes a feeding shaft 20 around which the end of the 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. Incidentally, the sheet S is wound around the feeding shaft 20 via a core tube (not shown) that is detachable from the feeding shaft 20. Therefore, when the sheet S of the feeding shaft 20 is used up, a new core tube around which the roll-shaped sheet S is wound can be mounted on the feeding shaft 20 and the sheet S of the feeding shaft 20 can be replaced. It has become.

  The process unit 3 supports the sheet S fed from the feeding unit 2 by the platen drum 30 and performs processing by the functional units 51, 52, 61, 62, and 63 arranged along the outer peripheral surface of the platen drum 30. An image is recorded 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 platen drum 30, and the sheet S conveyed from the front drive roller 31 to the rear drive roller 32 is supported by the platen 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 winds 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 from the feeding unit 2 to the downstream side of the conveyance path. A nip roller 31n is provided for the front drive roller 31. The nip roller 31 n is in contact with the surface of the sheet S while being urged 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 platen drum 30 is a cylindrical drum that is rotatably supported by a support mechanism (not shown), and winds the sheet S conveyed from the front drive roller 31 to the rear drive roller 32 from the back side. The platen drum 30 supports the sheet S from the back side while receiving the frictional force between the plate S and rotating in the conveyance 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 platen drum 30. Among these, the driven roller 33 wraps the surface of the sheet S between the front driving roller 31 and the platen drum 30 and folds the sheet S. On the other hand, the driven roller 34 wraps the surface of the sheet S between the platen drum 30 and the rear drive roller 32 and folds the sheet S. Thus, by folding the sheet S on the upstream and downstream sides in the transport direction Ds with respect to the platen drum 30, a long winding portion of the sheet S around the platen drum 30 can be secured.

  The rear drive roller 32 has a plurality of minute protrusions formed by thermal spraying on the outer peripheral surface, and winds the sheet S conveyed from the platen 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. A nip roller 32n is provided for the rear drive roller 32. The nip roller 32 n is in contact with the surface of the sheet S while being urged 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 platen drum 30. In the process unit 3, a plurality of recording heads 51 corresponding to different colors are provided to record a color image on the surface of the sheet S supported by the platen drum 30. 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 platen drum 30 with a slight clearance, and ejects ink of a corresponding color 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 lamps 61 and 62 (light irradiation units) are provided in order 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 lamp 61 is disposed between each of the plurality of recording heads 51. That is, the UV lamp 61 irradiates weak ultraviolet rays to cure (temporarily cure) the ink to such an extent that the shape of the ink does not collapse, and does not completely cure the ink. On the other hand, a UV lamp 62 for main curing is provided on the downstream side in the transport direction Ds with respect to the plurality of recording heads 51. That is, the UV lamp 62 irradiates ultraviolet rays stronger than the UV lamp 61 to completely cure (main cure) the ink. By executing the temporary curing and the main curing in this manner, the color image formed by the plurality of recording heads 51 can be fixed on the surface of the sheet S.

  Further, a recording head 52 is provided downstream of the UV lamp 62 in the transport direction Ds. The recording head 52 is opposed to the surface of the sheet S wound around the platen drum 30 with a slight clearance, and discharges transparent UV ink onto the surface of the sheet S by an ink jet method. That is, the transparent ink is further ejected with respect to the color image formed by the recording heads 51 for four colors. Further, a UV lamp 63 is provided on the downstream side of the recording head 52 in the transport direction Ds. The UV lamp 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, the UV lamps 61, 62, and 63 irradiate the surface of the sheet S that passes through the respective irradiation target areas along the conveyance path Pc with ultraviolet rays. Accordingly, the ink that has landed on the sheet S is irradiated with ultraviolet rays when passing through the irradiation target areas of the UV lamps 61, 62, and 63, and is temporarily or fully cured. In this embodiment, each of the UV lamps 61, 62, and 63 irradiates the surface of the sheet S with ultraviolet rays having an intensity distribution called a top hat type or a flat top type. Each of the UV lamps 61, 62, and 63 is configured to irradiate ultraviolet rays with a region corresponding to the top portion of the top hat type distribution as an irradiation target region.

  As described above, in the process unit 3, the platen drum 30 supports the sheet S around the outer peripheral surface thereof. Then, each of the functional units such as the recording heads 51 and 52 and the UV lamps 61, 62, and 63 is opposed to the winding portion Ra of the platen drum 30 around which the sheet S is wound, and the winding portion Ra is sandwiched therebetween. The ink is appropriately discharged and cured on the surface of the sheet S wound around the sheet. As a result, a color image coated with 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. Incidentally, the sheet S is wound around the winding shaft 40 via a core tube (not shown) that is detachable from the winding shaft 40. Therefore, when the sheet S wound around the winding shaft 40 becomes full, it is possible to remove the sheet S together with the core tube.

  The above is the outline of the device configuration of the printer 1. Subsequently, an electrical configuration for controlling the printer 1 will be described. FIG. 2 is a block diagram schematically showing an electrical configuration for controlling the printer shown in FIG. The operation of the printer 1 described above is controlled by the host computer 10 shown in FIG. 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 is provided with 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 unit of the host computer 10 and controls the operation of the printer 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. Accordingly, the operator operates the operation unit 140 while confirming the monitor 130, thereby opening the print setting screen from the menu screen and setting various print conditions such as the type of print medium, the size of the print medium, and the print quality. Can be set. 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 printer 1 is provided with a printer control unit 200 that controls each unit of the printer 1 in accordance with a command from the host computer 10. Each unit of the recording head, the UV lamp, and the sheet conveyance system is 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 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 E30 that is attached to the rotation shaft of the platen drum 30 and detects the rotation position of the platen drum 30. That is, since the platen drum 30 is driven and rotated 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 platen drum 30. 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 the same function. The ejected ink is landed on the target position of the conveyed sheet S 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 / off the UV lamps 61, 62, and 63 and the amount of irradiation light.

  Further, the printer control unit 200 controls a function of controlling the conveyance of the sheet S described in detail with reference to FIG. That is, motors are connected to 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 200 controls the conveyance of the sheet S by controlling the speed 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 200 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 200 controls the torque of the feeding motor M20 to adjust the tension of the sheet S from the feeding shaft 20 to the front drive roller 31 (feeding tension Ta). That is, a tension sensor S21 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, for example, a load cell that detects a force received from the sheet S. The printer control unit 200 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.

  At this time, the printer control unit 200 feeds the sheet S while adjusting the position of the sheet S supplied from the feeding shaft 20 to the front drive roller 31 in the width direction (direction orthogonal to the paper surface of FIG. 1). That is, the printer 1 is provided with the steering unit 7 that displaces the feeding shaft 20 and the driven roller 21 in the axial direction (in other words, the width direction of the sheet S). Further, an edge sensor Se that detects an end of the sheet S in the width direction is disposed between the driven roller 21 and the front driving roller 31. The edge sensor Se can be constituted by a distance sensor such as an ultrasonic sensor. The printer control unit 200 adjusts the position of the sheet S in the width direction by performing feedback control of the steering unit 7 based on the detection result of the edge sensor Se. As a result, the position of the sheet S in the width direction is optimized, and conveyance failure such as meandering of the sheet S is suppressed.

  Further, 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 sheet S fed from the feeding unit 2 passes through the process unit 3. At this time, torque control is executed for the front drive motor M31, while speed control is executed for the rear drive motor M32. That is, the printer control unit 200 adjusts the rotational speed of the rear drive motor M32 to be constant based on the encoder output of the rear drive motor M32. As a result, the rear drive roller 32 rotates at a constant speed, and the sheet S is conveyed by the rear drive roller 32 at a constant speed.

  On the other hand, the printer control unit 200 controls the torque of the front drive motor M31 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, a tension sensor S33 for detecting the process tension Tb is attached to the driven roller 33 arranged with respect to the transport path Pc between the front drive roller 31 and the platen drum 30. The tension sensor S33 can be constituted by a load cell that detects a force received from the sheet S, for example. Thus, the tension of the sheet S from the front drive roller 31 toward the platen drum 30 is detected by the tension sensor S33. The printer control unit 200 adjusts the process tension Tb of the sheet S by feedback controlling the torque of the front drive motor M31 based on the detection result of the tension sensor S33.

  More specifically, the torque of the front drive motor M31 is controlled so that the front drive roller 31 applies a force opposite to the transport direction of the sheet S to the sheet S conveyed at a constant speed by the rear drive roller 32. The Thus, the sheet S is stretched between the front drive roller 31 and the rear drive roller 32 with a force corresponding to the torque of the front drive motor M31, and the process tension Tb of the sheet S is adjusted to be constant.

  In addition, the printer control unit 200 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 200 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, the tension sensor S41 for detecting the winding tension Tc is attached to the driven roller 41 disposed between the rear drive roller 32 and the winding shaft 40. The tension sensor S41 can be constituted by a load cell that detects a force received from the sheet S, for example. The printer control unit 200 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. Specifically, the printer control unit 200 decreases the winding tension Tc as the diameter of the roll made of the sheet S wound around the winding shaft 40 increases. Thus, the sheet S is controlled so that the pressure of the sheet S near the center of the roll becomes excessive and the sheet S is not damaged as the roll diameter increases.

  In this way, under the control of the printer control unit 200, the sheet S is conveyed from the feeding shaft 20 toward the take-up shaft 40 along the conveyance path Pc. In other words, the printer control unit 200 controls the motors M20, M31, M32, and M40 as described above, so that the sheet S is fed in the forward direction Df from the feeding shaft 20 toward the winding shaft 40 along the transport path Pc. The forward transfer mode for transferring can be executed. The printer control unit 200 can execute an ejection printing process in which an image is printed by ejecting ink from the recording heads 51 and 52 onto the surface of the sheet S while conveying the sheet S in the forward conveyance mode.

  Furthermore, the printer control unit 200 of this embodiment can also execute the reverse conveyance mode in which the sheet S is conveyed in the opposite direction to the normal conveyance mode by controlling the motors M20, M31, M32, and M40. This reverse conveyance mode is a mode in which the sheet S is conveyed in the reverse direction from the take-up shaft 40 toward the feeding shaft 20 along the conveyance path Pc, and is appropriately executed according to various purposes. For example, the reverse conveyance mode is executed when cueing is performed in preparation for the next discharge printing process when one discharge printing process is completed.

  That is, at the time when one discharge printing process (process for printing an image for one job) is completed, the image formed by the one discharge printing process and fixed on the sheet S is the forward direction Df of the transport path Pc. In FIG. Therefore, the image recorded by one ejection printing process and the position at which the recording head 51 starts image recording in the next ejection printing process (a process for printing an image for one job) are greatly separated. Accordingly, when the next discharge printing process is started in this state, a large interval is left between the image printed in one discharge printing process and the image printed in the next discharge printing process. Such an interval results in waste paper on which no image is printed. Therefore, when one ejection printing process is completed, the reverse transport mode is executed, so that the recording head 51 is moved to the upstream side in the forward direction of the transport path Pc from the position where the recording head 51 prints an image. Thus, it is possible to reduce the interval between the image printed in one ejection printing process and the image printed in the next ejection printing process, and to suppress the occurrence of scraped paper. Next, details of the operation of the printer 1 will be described.

  FIG. 3 is a flowchart illustrating an example of a flow executed in the first embodiment. FIG. 4 is a timing chart schematically showing an example of the operation executed according to the flowchart of FIG. FIG. 5 is an operation explanatory diagram schematically showing an example of an operation executed according to the flowchart of FIG. In FIG. 5, symbols R (51) and R (52) indicate regions (ink ejection regions) where the recording heads 51 and 52 eject ink onto the surface of the sheet S, and symbols R (62) and R (63) denote The irradiation target areas of the UV lamps 62 and 63 are shown. As can be seen from FIG. 5, the irradiation target region R (62) of the UV lamp 62 is located downstream of the ink discharge region R (51) of each recording head 51 in the forward direction Df, and the ink discharge region of the recording head 52 The irradiation target region R (63) of the UV lamp 63 is located downstream of the R (52) in the forward direction Df. In FIG. 5, an image I (n) or the like subjected to dot hatching indicates an image fixed on the sheet S, and an image I (n + 1) or the like not subjected to dot hatching is not fixed to the sheet S. The image is shown.

  In the following, after one discharge printing process P1 for sequentially printing n images I (1),..., I (n-1), I (n) on the surface of the sheet S, a predetermined number of images I The operation of restarting the next discharge printing process P2 for printing (n + 1), I (n + 2),... in order on the surface of the sheet S is illustrated. This operation is executed under the control of the printer control unit 200. Specifically, the printer control unit 200 performs the operations shown in FIGS. 3 to 5 while grasping the transport position of the sheet S based on the output of the drum encoder E30 of the platen drum 30 that is driven by the transport of the sheet S. To do.

  In step S101, the type of sheet S (sheet type) is determined. Specifically, the printer control unit 200 determines the sheet type based on the information regarding the sheet type input by the operator from the operation unit 140 and confirms the thickness and material of the sheet S. Subsequently, the strength of the sheet S is determined based on the confirmation result. Specifically, it is determined that a thicker sheet S has higher strength, and a sheet S having a higher Young's modulus has higher strength. The period for accelerating / decelerating the sheet S is set according to the strength of the sheet S thus determined. That is, as the strength of the sheet S is weaker, the forward acceleration period Δfa and the forward deceleration period Δfb are set longer. Here, the forward acceleration period Δfa is a period required to accelerate the transport speed of the sheet S from zero to the forward transport speed Vf in the forward transport mode, and the forward deceleration period Δfb is the sheet S in the forward transport mode. This is the period required to decelerate the transport speed from the forward transport speed Vf to zero. In the operation example shown here, the forward acceleration period Δfa and the forward deceleration period Δfb are set equal (Δfa = Δfb).

  Then, the forward mode is executed at time t1, and the conveyance of the sheet S in the forward direction Df is started (step S102). Specifically, the sheet S is accelerated in the forward direction Df at an acceleration Afa = Vf / Δfa obtained by dividing the forward conveyance speed Vf by the forward acceleration period Δfa. When the forward acceleration period Δfa elapses from time t1 and time t2 is reached, it is determined that the transport speed of the sheet S has reached a predetermined speed (forward transport speed Vf) ("YES" is determined in step S103). ), The acceleration of the sheet S is stopped, and the sheet S is conveyed at a constant conveyance speed Vf. At this time t2, the UV lamps 62 and 63 are turned on (step S104). Further, at this time t2, the ejection printing process is started, ink is ejected from the recording heads 51 and 52 based on the data (image data) of the image to be printed, and an image is printed on the surface of the sheet S ( Step S105).

  Incidentally, in this operation example, in the ejection printing process P1, n images I (1),..., I (n-1), I (n) are lined up at equal intervals Li in the direction of the transport path Pc. They are formed in this order. When it is determined that n images I (1),..., I (n−1), I (n) are printed at time t3 (when “YES” is determined in step S106), Ink ejection from the recording heads 51 and 52 is stopped, and the ejection printing process P1 ends. At this time, even if the discharge printing process P1 is completed, the constant speed conveyance of the sheet S at the forward conveyance speed Vf is performed for n images I (1),..., I (n-1), I (n) The process continues until all of the irradiation target areas R (62) and R (63) pass (steps S107 and S108).

  Specifically, at the time t4 when the image I (n) printed last in the ejection printing process P1 passes through the irradiation handling region R (63) of the UV lamp 63 while being transported in the forward direction Df of the transport path Pc. , N images I (1),..., I (n−1), I (n) are determined to have passed through the irradiation target regions R (62) and R (63) (“ YES ”). Thus, as shown in the column “t4” in FIG. 5, at time t4 when the upstream end of the image I (n) has passed the downstream end of the irradiation target region R (63) in the forward direction Df, the ejection printing process P1. All the printed images I (1),..., I (n−1), I (n) are fixed on the sheet S.

At time t4, the UV lamps 62 and 63 are turned off, and the conveyance speed of the sheet S is started to be reduced (step S109). Specifically, the sheet S is decelerated in the forward direction Df at an acceleration Afb = Vf / Δfb obtained by dividing the forward conveyance speed Vf by the forward deceleration period Δfb. Since the forward acceleration period Δfa and the forward deceleration period Δfb are equal (Δfa = Δfb) as described above, the acceleration Afa during acceleration and the acceleration Afb during deceleration are also equal in the forward direction Df (Afa = Afb). When the forward deceleration period Δfb elapses from time t4 and time t5 is reached, the conveyance of the sheet S is stopped ("YES" is determined in step S110). At this time, as shown in the column of “t5” in FIG. 5, the sheet S is moved by the distance L1 in the forward direction Df during the forward deceleration period Δfb from time t4 to t5. In other words, the sheet S is image I (1). , ..., I (n-1) and I (n) run idle for a distance L1 after time t4 when all of them have settled. The idle travel distance L1 in the forward deceleration period Δfb is expressed by the following equation: L1 = Vf × Δfb / 2 Formula 1
Given in.

Thus, when the conveyance of the sheet S in the forward direction Df is stopped, the reverse conveyance distance L2 for conveying the sheet S in the reverse direction Db is obtained in the subsequent reverse conveyance mode. Here, the reverse conveyance distance L2 is the following equation:
L2 = L1 + L3 + L4 Equation 2
L1: Distance that the sheet S is conveyed during the forward deceleration period Δfb (idle travel distance)
L3: Distance that sheet S is conveyed during forward acceleration period Δfa (running distance)
L4: It is given by the distance from the upstream end of the ink discharge region R (51) of the most upstream recording head 51 in the forward direction Df to the downstream end of the irradiation target region R (63) of the UV lamp 63. Incidentally, the forward deceleration period Δfb and the forward acceleration period Δfa are amounts determined according to the type of the sheet S as described above. Therefore, the distances L1 and L3 are distances set according to the type of the sheet S, and the reverse conveyance distance L2 is also set according to the type of the sheet S. Specifically, the reverse conveyance distance L2 is set longer as the strength of the sheet S is weaker. Thus, in this embodiment, the reverse conveyance distance L2 is determined according to the type of the sheet S (step S111).

Then, the reverse conveyance mode is executed in order to convey the sheet S in the reverse direction Db by the reverse conveyance distance L2 determined in this way. At this time, the acceleration / deceleration period of the sheet S in the reverse conveyance mode is set when the reverse conveyance mode is executed as in the above-described forward conveyance mode. In this embodiment, the reverse conveyance speed Vb for conveying the sheet S in the reverse direction Db is set equal to the forward conveyance speed Va, and the following equation Va = Vb Equation 3
Is established. Further, in this embodiment, the reverse acceleration period Δba and the reverse deceleration period Δbb and the forward acceleration period Δfa and the forward deceleration period Δfb are set to be equal to each other, and the following expression Δba = Δbb = Δfa = Δfb... Formula 4
Is established. Here, the reverse acceleration period Δba is a period required to accelerate the conveyance speed of the sheet S from zero to the reverse conveyance speed Vb in the reverse conveyance mode, and the reverse deceleration period Δbb is the sheet S in the reverse conveyance mode. This is a period required to decelerate the conveyance speed from the reverse conveyance speed Vf to zero.

  When the reverse acceleration period Δba and the reverse deceleration period Δbb are thus set, the reverse conveyance mode is executed at time t6, and the sheet S starts to be conveyed in the reverse direction Db (step S112). Specifically, the sheet S is accelerated in the reverse direction Db at an acceleration Aba = Vb / Δba obtained by dividing the reverse conveyance speed Vb by the reverse acceleration period Δba. When it is determined that the reverse acceleration period Δba has elapsed from time t6 and time t7 has elapsed, and the sheet S conveyance speed has reached a predetermined speed (reverse conveyance speed Vb) ("YES" is determined in step S113). ), The acceleration of the sheet S is stopped, and the sheet S is conveyed at a constant speed at the reverse conveyance speed Vb. Incidentally, since the above equations 3 and 4 are established, the distance that the sheet S moves in the reverse acceleration period Δba is equal to the distance L1, and the position of the sheet S at time t7 is “t4” in FIG. It is the same as that shown in the column.

  Further, the constant speed conveyance of the sheet S at the reverse conveyance speed Vb after time t7 is continued until the sheet S moves by a predetermined distance (= distance L4) in the reverse direction Db (steps S114 and S115). When it is determined that the sheet S has moved by a predetermined distance (= distance L4) after the constant speed conveyance of the sheet S is realized (when “YES” is determined in step S114), the conveyance speed of the sheet S is determined. Is started (step S116). Specifically, the sheet S is decelerated in the reverse direction Db at an acceleration Abb = Vf / Δbb obtained by dividing the reverse conveyance speed Vb by the reverse deceleration period Δbb. At this time, since the reverse acceleration period Δba and the reverse deceleration period Δbb are equal (Δba = Δbb) as described above, the acceleration Aba during acceleration and the acceleration Abb during deceleration are also equal in the reverse direction Db (Aba = Abb). When the reverse deceleration period Δbb elapses from time t8 and time t9 is reached, the conveyance of the sheet S is stopped (determined as “YES” in step S117), and the flowchart of FIG. 3 ends. Incidentally, since the above formulas 3 and 4 are established, the distance that the seat S moves in the reverse deceleration period Δbb is equal to the running distance L3.

  Thus, as shown in the column “t9” in FIG. 5, the sheet S moves by the distance L2 in the reverse direction Db in the reverse conveyance mode executed from time t6 to time t9. As a result, in the forward direction Df, the upstream end of the image I (n) last printed on the sheet S in the discharge printing process P1 is run ahead of the upstream end of the ink discharge region R (51) of the most upstream recording head 51. Located upstream by distance L3.

  Then, when there is an ejection printing process P2 to be executed, the flowchart of FIG. 3 is resumed. That is, as shown in FIGS. 4 and 5, the forward mode is executed at time t10 and the conveyance of the sheet S in the forward direction Df is started. As a result, after the transport speed of the sheet S is accelerated to the forward transport speed Vf over the forward acceleration period Δfa from time t10, the sheet S is transported at a constant speed at the forward transport speed Vf at time t11. During this forward acceleration period Δfa, the seat S moves in the forward direction by the run-up distance L3. Therefore, at time t11 when the forward acceleration period Δfb has elapsed from time t9, the upstream end of the image I (n) printed last on the sheet S in the ejection printing process P1 is the ink ejection area of the most upstream recording head 51. It coincides with the upstream end of R (51) (the column “t11” in FIG. 5).

  Therefore, in a period after time t11, an unprinted area where no image is printed passes through the ejection area R (51) in the sheet S. Therefore, at any time after time t11, an image can be printed by ejecting ink to an unprinted area of the sheet S passing through the ejection area R (51). Therefore, in this embodiment, the discharge printing process P2 is started at time t12 slightly delayed from time t11, and the images I (n + 1) and I (n + 2) are sequentially printed on the sheet S. As a result, the images I (n + 1), I (n + 2),... Are adjacent to the image I (n) printed last in the discharge printing process P1 from the upstream side in the forward direction Df. S is printed (in the column “tx” in FIG. 5). The start of the ejection printing process P2 is delayed from the time t11 because the ejection printing process P2 is started after waiting for a period (t1 to t2) during which the sheet S is conveyed by the image forming interval Li. This is because the interval Li is provided between (n) and the image I (n + 1).

  As described above, in this embodiment, the forward conveyance mode in which the sheet S is conveyed in the forward direction Df of the conveyance path Pc and the reverse conveyance mode in which the sheet S is conveyed in the reverse direction Db of the conveyance path Pc can be executed. It is. Then, while the sheet S is transported at the forward transport speed Vf in the forward direction Df of the transport path Pc in the forward transport mode, ink is ejected onto the sheet S to execute the discharge print process P2, while the discharge print process P2 is completed. In the reverse conveyance mode, the sheet S is conveyed at the reverse conveyance speed Vb in the reverse direction Db of the conveyance path Pc (reverse conveyance). At this time, the reverse conveyance speed Vb at which the sheet S is conveyed in the reverse direction Db is set to be equal to or higher than the normal conveyance speed Vf at which the sheet S is conveyed in the discharge printing process. Accordingly, the sheet S can be conveyed at a high speed in the reverse direction Db to shorten the time (= t6 to t9) required for the reverse conveyance of the sheet S, and the discharge printing process P2 to be subsequently executed is immediately started. It becomes possible.

  In particular, it can be said that such a configuration in which the reverse conveyance of the sheet S is performed at high speed is particularly suitable for the printer 1 that prints an image by the recording heads 51 and 52 that are not in contact with the sheet S. In other words, in the configuration in which the toner image formed on the photoconductor is transferred to the recording medium as in Patent Document 1 described above, it is necessary to form a nip between the photoconductor and the recording medium. At this time, when the recording medium is reversely conveyed at a high speed, a large speed difference occurs between the photosensitive member and the transfer medium, and a large frictional force acts between them, and one or both of them may be damaged. Conceivable. Therefore, when the recording medium is reversely conveyed at a high speed, it is necessary to synchronize the rotation of the photosensitive member to some extent with the high-speed conveyance of the recording medium, which may complicate the control for the reverse conveyance. On the other hand, in this embodiment, since the image is printed on the sheet S by the non-contact recording heads 51 and 52, the sheet S can be reversely conveyed at high speed without complicated control. it can.

  By the way, in the printer 1 of this embodiment, an image printed by ejecting UV ink from the recording heads 51 and 52 onto the sheet S is fixed to the sheet S by ultraviolet rays irradiated from the UV lamps 62 and 63. However, in such a printer 1, when the reverse conveyance mode is executed while the image printed by the ejection printing process is not fixed on the sheet S and the sheet S is conveyed at high speed, the unfixed image is disturbed, There is a risk that the device parts coming into contact with the unfixed image may be contaminated. Therefore, in this embodiment, when the discharge printing process P1 is completed, the images I (1),..., I (n−1), I ( After n) is fixed to the sheet S by the UV lamps 62 and 63, the conveyance of the sheet S in the forward direction Df is stopped. Therefore, when the reverse conveyance mode is executed, the images I (1),..., I (n-1), I (n) are already fixed on the sheet S, so that the sheet S is conveyed at high speed in the reverse conveyance mode. Nevertheless, disturbance of the images I (1),..., I (n-1), I (n) and contamination of the device parts can be prevented.

  In this embodiment, in the reverse conveyance mode, the upstream end in the forward direction Df of the images I (1),..., I (n−1), I (n) printed on the sheet S is set to the ink discharge region R ( 51) and R (52) are moved to the upstream side in the forward direction Df. Therefore, the images I (n + 1), I (n + 2),... Printed by the ejection printing process P2 executed following the reverse conveyance mode, and the images I (1),. , I (n-1), I (n) can be shortened to prevent the sheet S from being wasted.

  In this embodiment, in the forward transport mode, the upstream ends of the images I (1),..., I (n−1), I (n) in the forward direction Df are the ink ejection regions R (51), R (52 ), The reverse transport distance L2 for moving the sheet S in the reverse transport mode before the forward transport mode is such that the acceleration up to the forward transport speed Vf of the sheet S is completed before passing the upstream end in the forward direction Df. Is set. In such a configuration, the boundaries between printed images I (1),..., I (n-1), I (n) and unrecorded areas (that is, images I (1),..., I (n-1) ), The upstream end of I (n) in the forward direction) reaches the ink discharge region R (51), and the sheet S transport speed has reached the forward transport speed Vf for discharge printing processing. The discharge printing process P2 can be started. As a result, the images I (n + 1), I (n + 2),... Printed by the discharge printing process P2, and the images I (1),. It is possible to effectively suppress the occurrence of waste of the sheet S by shortening the interval with (n).

  In this embodiment, the forward acceleration period Δfa for accelerating the conveyance speed of the sheet S to the forward speed Vf in the forward conveyance mode can be adjusted. Specifically, the forward acceleration period Δfa can be adjusted according to the type of the sheet S. Accordingly, the sheet S can be accelerated over an appropriate forward acceleration period Δfa according to the type of the sheet S, and a burden on the sheet S accompanying the acceleration can be suppressed. Particularly in this embodiment, the thinner the thickness of the sheet S, the longer the forward acceleration period Δfa is adjusted. In such a configuration, since the thin sheet S can be slowly accelerated over a long forward acceleration period Δfa, the occurrence of breakage of the sheet S and the like can be suppressed.

  By the way, when the conveyance of the sheet S in the forward direction Df is stopped with the end of the ejection printing process P1, the conveyance of the sheet S does not stop immediately but stops after a certain deceleration period Δfb. Therefore, during the deceleration period Δfb, the sheet S moves (runs idle) in the forward direction Df without being subjected to the discharge printing process. At this time, the images I (n + 1), I (n + 2),..., And images I (1),. -1), in order to shorten the interval with I (n) and effectively suppress the occurrence of waste of the sheet S, the sheet S is moved in the reverse conveyance mode according to the idle running distance L1 of the sheet S. It is preferable to set the reverse conveyance distance L2 to be moved in the reverse direction. Therefore, in this embodiment, the reverse conveyance in which the sheet S is moved in the reverse conveyance mode as the forward deceleration period Δfb required to decelerate and stop the conveyance speed of the sheet S from the forward speed Vf in the forward conveyance mode is longer. The distance L2 is set long. As a result, the sheet S is moved in the reverse direction Db in the reverse conveyance mode by a distance corresponding to the idle running distance L1 of the sheet S after the end of the discharge printing process P1, so that the waste of the sheet S is effectively generated. Can be suppressed.

  In this embodiment, the forward deceleration period Δfb is adjusted according to the type of the sheet S. As a result, the sheet S can be decelerated over an appropriate forward deceleration period Δfb according to the type of the sheet S, and a burden on the sheet S due to the deceleration can be suppressed. Particularly in this embodiment, the thinner the thickness of the sheet S, the longer the forward deceleration period Δfb is adjusted. In such a configuration, since the thin sheet S can be slowly decelerated over a long forward deceleration period Δfb, the occurrence of damage to the sheet S can be suppressed.

  In this embodiment, the forward transport speed Vf at which the sheet S is transported in the forward transport mode is equal to the reverse transport speed Vb at which the sheet S is transported in the reverse transport mode. In such a configuration, for example, the control parameters of the motors M20, M31, M32, and M40 that provide driving force for transporting the sheet S can be made common between the forward transport mode and the reverse transport mode. Therefore, there is an advantage that the control system can be shared and the motor control system can be simplified.

  Specifically, the motor control parameters include a speed command voltage Ev, a speed command pulse frequency Fv, a speed command current Iv, and the like. These are all signals for controlling the speed of the motor. Specifically, the speed command voltage Ev is controlled by the voltage applied to the motor, and the speed command pulse frequency Fv is determined by the pulse frequency applied to the motor. The speed of the motor is controlled, and the speed command current Iv controls the speed of the motor by the current applied to the motor.

  When the motor is controlled by the speed command voltage Ev, the speed command voltage Evf in the forward transport mode and the speed command voltage Evb in the reverse transport mode are set by setting the forward transport speed Vf and the reverse transport speed Vb equal. Can use the same value in common. When the motor is controlled by the speed command pulse frequency Fv, by setting the forward transport speed Vf and the reverse transport speed Vb to be equal, the speed command pulse frequency Fvf in the forward transport mode and the speed command pulse frequency in the reverse transport mode. The same value can be used in common for Fvb. Alternatively, when the motor is controlled by the speed command current Iv, the speed command current Ivf in the forward transport mode and the speed command current Ivb in the reverse transport mode are set by setting the forward transport speed Vf and the reverse transport speed Vb equal. Can use the same value in common.

Second Embodiment Incidentally, there is a case where an error occurs in the operation of the printer 1 during the above-described discharge printing process, and the discharge printing process ends in error (that is, the job may be interrupted). Therefore, in the second embodiment, an example of an operation when the ejection printing process has stopped due to an error will be described. In the following description, the operation characteristic of the second embodiment will be mainly described, and the other parts will be denoted by the same reference numerals as those in the first embodiment, and the description thereof will be omitted as appropriate. However, it goes without saying that the same effect can be achieved in the second embodiment by providing the same configuration as that of the first embodiment.

  FIG. 6 is a timing chart schematically showing an example of the operation executed in the second embodiment. FIG. 7 is an operation explanatory diagram schematically showing an example of the operation executed according to the timing chart of FIG. The notation in FIG. 7 is the same as in FIG. In this embodiment, at time t3, an error occurs in the operation of the printer 1, an error signal is output, and the discharge printing process P1 ends in error. As a result, as indicated by hatching in the column “t3” in FIG. 7, the images I (n−7) to I (n−5) are in the middle of printing with transparent ink, and the image I (n−4) In the state where the printing of the color ink is in progress, the discharge printing process P1 ends. At this time, even if the ejection printing process P1 ends in error, the constant speed conveyance of the sheet S at the forward conveyance speed Vf is performed by the images I (1),. The process continues until all of n-5) and I (n-4) pass through the irradiation target areas R (62) and R (63).

  Specifically, among the images printed in the ejection printing process P1 before the end of the error, the most upstream image I (n-4) in the forward direction Df is transported in the forward direction Df of the transport path Pc, and the UV lamp 63 is used. , I (n-5), I (n-4) are all irradiated target areas R (62), R (63) at time t4 when passing through the irradiation handling area R (63). ). Thus, as shown in the column “t4” in FIG. 7, at the time t4 when the upstream end of the image I (n-4) has passed the downstream end of the irradiation target region R (63) in the forward direction Df, before the end of the error. All the images I (1),..., I (n-5), I (n-4) printed in the discharge printing process P1 are fixed on the sheet S. At time t4, the UV lamps 62 and 63 are turned off, and the conveyance speed of the sheet S is started to be reduced. When the forward deceleration period Δfb elapses from time t4 and time t5 is reached, the conveyance of the sheet S is stopped ("YES" is determined in step S110).

  Subsequently, when the error in the operation of the printer 1 is resolved at time t6 and the error signal is turned off, the reverse conveyance mode is executed, and the sheet S is conveyed by the reverse conveyance distance L2 in the reverse direction Db. As in the first embodiment, the reverse transport speed Vb at this time is set equal to the forward transport speed Vf. When the reverse conveyance mode ends at time t9, the forward conveyance mode is started at time t10, and the sheet S is accelerated in the forward direction Df. Then, after the constant speed conveyance at the forward conveyance speed Vf is established at time t11, the ejection printing process P1 is resumed at time t12. In the discharge printing process P1 after the restart, the images I (n-7) to I (n-6), I (n-5), I, which have not been printed in the discharge printing process P1 before the end of the error. (n-4), ... are printed in order.

  As described above, also in this embodiment, the reverse transport speed Vb at which the sheet S is transported in the reverse direction Db is set to be equal to or higher than the forward transport speed Vf at which the sheet S is transported in the ejection printing process. Therefore, the sheet S can be conveyed at high speed in the reverse direction Db, and the time required for reverse conveyance of the sheet S (= t6 to t9) can be shortened. As a result, it is possible to quickly restart the ejection printing process P1 that has ended in error.

  In this embodiment, even if the discharge printing process P1 ends in error, the conveyance of the sheet S in the forward conveyance mode is continued, and the images I (1),..., I (n− 5) After the fixing of I (n-4), the conveyance of the sheet S in the forward direction is stopped. Therefore, when the reverse conveyance mode is subsequently executed, the images I (1),..., I (n-5), I (n-4) are already fixed on the sheet S. Although S is conveyed at high speed, it is possible to prevent disturbance of the images I (1),..., I (n-5), I (n-4) and contamination of the apparatus parts.

Others As described above, in the above embodiment, the printer 1 corresponds to the “image recording apparatus” of the invention, the sheet S corresponds to the “recording medium” of the invention, and the ink corresponds to the “liquid” of the invention. The feeding shaft 20, the front driving roller 31, the rear driving roller 32, the winding shaft 40, and the motors M20, M31, M32, and M40 that drive these cooperate to function as the “conveying unit” of the present invention. The transport speed Vf corresponds to “speed V1” of the present invention, the reverse transport speed Vb corresponds to “V2” of the present invention, the recording heads 51 and 52 correspond to “discharge section” of the present invention, and the UV lamp 62 , 63 corresponds to the “light irradiating part” of the present invention, ultraviolet light corresponds to the “light” of the present invention, the printer controller corresponds to the “control part” of the present invention, and the ink ejection region R (51), R (52) corresponds to the liquid discharge region of the present invention, and the discharge printing processes P1 and P2 are “ Corresponds to the print processing "out, it corresponds to a" program "of the program 124 by the present invention, media 122 corresponds to the" program recording medium "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 reverse transport speed Vb is set equal to the forward transport speed Va. However, the reverse transport speed Vb may be set faster than the forward transport speed. In short, by setting the reverse transport speed Vb to be equal to or higher than the forward transport speed Vf, the sheet S can be transported at high speed in the reverse direction Db, and the ejection printing process after the reverse transport mode can be started quickly.

  Further, the reverse conveyance distance L2 for conveying the sheet S in the reverse direction Db in the reverse conveyance mode is not limited to the above, and can be changed as appropriate.

  In the above embodiment, the reverse acceleration period Δba, the reverse deceleration period Δbb, the forward acceleration period Δfa, and the forward deceleration period Δfb are set to be equal to each other. However, the values of the periods Δba, Δbb, Δfa, Δfb can be set independently and do not have to be equal to each other. In the above embodiment, the periods Δba, Δbb, Δfa, and Δfb are set according to the type of the sheet S. However, the above embodiment is modified so that it is set regardless of the type of the sheet S. You can also

  In the above embodiment, when the discharge printing process P1 ends with an error, the images I (1),..., I (n-5) printed before the end of the error are maintained by continuing the forward transport mode for a while. , I (n-4) was fixed. However, when the error ends, the forward conveyance mode is immediately ended, and the images I (1),..., I (n-5), I (n-4) printed before the error end are transferred to the sheet S. It can also be configured not to fix.

  Further, the timing for turning on / off the UV lamps 62 and 63 can be appropriately changed in addition to the above.

  In the above embodiment, the recording head 52 and the UV lamp 63 for transparent ink are provided. However, the present invention can also be applied to a printer 1 that does not include these.

  In the above embodiment, the provisional curing UV lamp 61 is provided, but the printer 1 may be configured by removing these.

  Further, the positions where the recording heads 51 and 52, the UV lamps 61, 62, and 63 are arranged can be changed as appropriate.

  In the above embodiment, the case where the present invention is applied to the printer 1 that forms a color image has been described. However, the present invention can also be applied to the printer 1 that forms a monochrome image.

  In the above embodiment, the sheet S is supported by the cylindrical platen drum 30. However, the specific configuration for supporting the sheet S is not limited to the platen drum 30.

  DESCRIPTION OF SYMBOLS 1 ... Printer, 122 ... Media, 124 ... Program, 200 ... Printer control part, 51 ... Recording head 51, 52 ... Recording head, 61 ... UV lamp, 62 ... UV lamp, 63 ... UV lamp, E30 ... Drum encoder, S ... Sheet, P1 ... Discharge printing process, P2 ... Image recording process

Claims (15)

In an image recording apparatus for recording an image by discharging liquid onto a recording medium conveyed along a conveyance path,
A transport unit that selectively performs a forward transport mode for transporting the recording medium in the forward direction of the transport path and a reverse transport mode for transporting the recording medium in the reverse direction of the transport path opposite to the forward direction;
An ejection unit that ejects liquid to the recording medium passing through the liquid ejection area;
Discharge printing that controls the transport unit and the discharge unit to discharge liquid from the discharge unit and print an image on the recording medium while transporting the recording medium in the forward direction at a speed V1 in the forward transport mode. A control unit for executing processing,
When the discharge printing process is completed, the control unit stops the conveyance of the recording medium in the forward direction, and then moves the recording medium in the reverse direction at the speed V2 equal to or higher than the speed V1 in the reverse conveyance mode. An image recording apparatus. The image recording apparatus according to claim 1, wherein a light curable liquid is discharged from the discharge unit, and the recording medium passing through the downstream side in the forward direction from the liquid discharge region is irradiated with light, A light irradiation unit for fixing the image printed in the ejection printing area to the recording medium;
When the discharge printing process ends, the control unit continues the forward conveyance mode and fixes the image printed in the discharge printing process before the end to the recording medium by the irradiation unit, and then the recording medium. Recording apparatus for stopping the forward conveyance of the image.   The image recording apparatus according to claim 2, wherein when an error occurs during the execution of the ejection printing process, the control unit stops the ejection of liquid from the ejection unit and ends the ejection printing process.   4. The control unit according to claim 1, wherein, in the reverse conveyance mode, the control unit moves the upstream end in the forward direction of the image printed on the recording medium to the upstream side in the forward direction of the liquid ejection region. 5. The image recording apparatus according to one item.   In the forward transport mode for the ejection printing process executed after the reverse transport mode, the control unit is configured such that the upstream end in the forward direction of the image printed on the recording medium is the forward of the liquid ejection area. 5. The image according to claim 4, wherein a distance for moving the recording medium in the reverse conveyance mode is set so that the acceleration of the recording medium to the speed V <b> 1 is completed before passing the upstream end in the direction. Recording device.   The image recording apparatus according to claim 5, wherein the control unit is capable of adjusting a forward acceleration period for accelerating a conveyance speed of the recording medium to the speed V 1 in the forward conveyance mode.   The image recording apparatus according to claim 6, wherein the control unit adjusts the forward acceleration period according to a type of the recording medium.   The image recording apparatus according to claim 7, wherein the control unit adjusts the forward acceleration period longer as the thickness of the recording medium is thinner.   The control unit increases the distance by which the recording medium is moved in the reverse conveyance mode as the forward deceleration period required to decelerate and stop the conveyance speed of the recording medium from the speed V1 in the forward conveyance mode is longer. 9. The image recording apparatus according to claim 4, wherein the image recording apparatus is set to be long.   The image recording apparatus according to claim 9, wherein the control unit adjusts the forward deceleration period according to a type of the recording medium.   The image recording apparatus according to claim 10, wherein the control unit adjusts the forward deceleration period longer as the thickness of the recording medium is thinner.   12. The image recording according to claim 1, wherein the speed V1 at which the recording medium is transported in the forward transport mode and the speed V2 at which the recording medium is transported in the reverse transport mode are equal. apparatus. In an image recording method for recording an image by discharging liquid onto a recording medium conveyed along a conveyance path,
A first step of printing an image by ejecting liquid onto the recording medium passing through a liquid ejection area while conveying the recording medium at a speed V1 in the forward direction of the conveyance path;
When the first step is finished, after the conveyance of the recording medium in the forward direction is stopped, the recording medium is moved at a speed V2 equal to or higher than the speed V1 in the reverse direction of the conveyance path opposite to the forward direction. And an image recording method. In a program for causing a computer to execute an image recording method for recording an image by discharging a liquid onto a recording medium conveyed along a conveyance path,
A first step of printing an image by ejecting liquid onto the recording medium passing through a liquid ejection area while conveying the recording medium at a speed V1 in the forward direction of the conveyance path;
When the first step is finished, after the conveyance of the recording medium in the forward direction is stopped, the recording medium is moved at a speed V2 equal to or higher than the speed V1 in the reverse direction of the conveyance path opposite to the forward direction. And causing the computer to execute a second step.   A program recording medium on which the program according to claim 14 is recorded.

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