Patent Publication Number: US-2020276836-A1

Title: Medium conveying device and inkjet printer

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a Continuation of PCT International Application No. PCT/JP2018/041391 filed on Nov. 7, 2018, which claims priority under 35 U.S.C § 119(a) to Japanese Patent Application No. 2017-239620 filed on Dec. 14, 2017. Each of the above application(s) is hereby expressly incorporated by reference, in its entirety, into the present application. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a medium conveying device and an inkjet printer, and particularly relates to a medium conveying device that conveys a medium for printing and an inkjet printer that performs printing on the medium for printing to be conveyed by the medium conveying device by an inkjet method. 
     2. Description of the Related Art 
     In a printer that performs printing while conveying a medium, in a case where the medium is conveyed in an inclined state, a problem such as an image being printed with inclination occurs. For this reason, in the printer that performs printing while conveying the medium, processing of removing an inclination (skew) is performed before the medium is sent to a conveyance mechanism. 
     JP2017-140736A discloses a method in which a medium is made to abut on a pair of stopped conveying rollers to remove an inclination, and then the pair of conveying rollers is rotated to send the medium to a conveyance mechanism. 
     JP2010-221552A discloses a configuration in which a leading end of a medium is made to abut on a front lay to remove an inclination of the medium, and then the medium is delivered by a rotating cylinder. 
     SUMMARY OF THE INVENTION 
     However, the method of JP2017-140736A has a disadvantage that in a case where a diameter of each conveying roller is uneven, an inclination occurs in a case where the medium is sent by the pair of conveying rollers. That is, in a case where the diameter of each conveying roller is uneven, an outer circumferential speed of each conveying roller becomes uneven, and as a result, the medium to be sent is inclined. 
     Further, in a case of the configuration in which the medium is delivered by the rotating cylinder as in JP2010-221552A, there is a disadvantage that a degree of freedom in design is small because a position at which the medium can be delivered is limited. For this reason, in a case of the configuration in which the medium is delivered by the rotating cylinder, there is a disadvantage that, in principle, a conveyance mechanism on a side to which the medium is delivered is also limited to the cylinder. 
     The present invention has been made in view of such circumstances, and an object thereof is to provide a medium conveying device and an inkjet printer that can convey a medium stably. 
     Means for solving the above problems is as follows. 
     (1) A medium conveying device comprising: a posture correction unit that corrects a posture of a medium; a conveying unit that conveys the medium along a plane; and a delivery unit that delivers the medium of which the posture is corrected by the posture correction unit to the conveying unit, in which the delivery unit includes a holding portion that holds a part of the medium of which the posture is corrected by the posture correction unit, and delivers the medium to the conveying unit by moving the holding portion linearly along a conveying direction of the medium by the conveying unit. 
     According to this aspect, after the posture of the medium is corrected by the posture correction unit, the medium is delivered to the conveying unit by the delivery unit. That is, after the posture of the medium is adjusted to a specified posture in the posture correction unit, the medium is delivered to the conveying unit by the delivery unit. For example, in a case of a sheet, after front and rear edges of the sheet are adjusted to a posture orthogonal to the conveying direction by the conveying unit, the sheet is delivered to the conveying unit by the delivery unit. The delivery unit holds a part of the medium of which the posture is corrected by the posture correction unit by the holding portion, and delivers the medium to the conveying unit by moving the holding portion linearly along the conveying direction of the medium by the conveying unit. Accordingly, the medium can be delivered to the conveying unit in a state where the posture is corrected. The conveying unit conveys the medium delivered from the delivery unit along a plane. The delivery unit moves the holding portion linearly along the conveying direction of the medium by the conveying unit, so that the medium can be delivered to the conveying unit at any position. 
     (2) The medium conveying device according to (1), in which the delivery unit accelerates the holding portion to the same speed as a conveying speed of the medium by the conveying unit, and delivers the medium held by the holding portion to the conveying unit. 
     According to this aspect, the holding portion is accelerated to the same speed as the conveying speed of the medium by the conveying unit, and the medium is delivered to the conveying unit. Accordingly, it is possible to prevent the medium from being inclined or shifted in a case where the medium is delivered to the conveying unit from the holding portion. 
     The “same speed” here includes a range recognized as substantially the same speed. That is, a case where the holding portion is accelerated to almost the same speed as the conveying speed of the medium is included. 
     (3) The medium conveying device according to (1), in which the delivery unit accelerates the holding portion to a speed within a range of ±10% of a conveying speed of the medium by the conveying unit, and delivers the medium held by the holding portion to the conveying unit. 
     According to this aspect, the holding portion is accelerated to the speed within the range of ±10% of the conveying speed of the medium by the conveying unit, and the medium is delivered to the conveying unit. That is, the medium is accelerated and delivered such that a speed at which the medium is delivered to the conveying unit is within the range of ±10% of the conveying speed of the medium by the conveying unit. Accordingly, it is possible to prevent the medium from being inclined or shifted in a case where the medium is delivered to the conveying unit from the holding portion. 
     (4) The medium conveying device according to any one of (1) to (3), in which the conveying unit conveys the medium by a belt. 
     According to this aspect, the medium is conveyed by the belt in the conveying unit. That is, the medium is placed on the belt running on a certain path, and the medium is conveyed along the plane. 
     (5) The medium conveying device according to (4), in which the conveying unit conveys the medium by attracting the medium onto the belt. 
     According to this aspect, the medium is conveyed by being attracted onto the belt in the conveying unit. Accordingly, even in a case where the medium is light, the medium can be conveyed stably. A method of using air pressure (negative pressure), a method of using static electricity, or the like can be used for attraction of the medium. In the method of using air pressure, the medium is attracted onto the belt by punching a number of holes in the belt and performing suction from an inside of the belt. In the method of using static electricity, the belt is charged to a high voltage. 
     (6) The medium conveying device according to (5), in which the holding portion attracts and holds a leading end portion of the medium, and the delivery unit delivers the medium to the conveying unit by moving the holding portion to a position where an attraction force by the belt acts. 
     According to this aspect, the leading end portion of the medium is attracted and held by the holding portion. The holding portion moves to the position where the attraction force by the belt acts, and delivers the medium to the conveying unit. Accordingly, the medium can be delivered to the conveying unit with the minimum moving amount. In addition, a feeding speed of the medium can be increased. 
     (7) The medium conveying device according to (6), in which the holding portion attracts and holds the leading end portion of the medium with a plurality of suction holes which can be individually opened and closed, and the suction holes are individually opened and closed according to a size of the medium. 
     According to this aspect, the holding portion comprises the plurality of suction holes, and attracts and holds the leading end portion of the medium by performing suction from the suction holes. Each suction hole can be individually opened and closed, and is individually opened and closed according to the size of the medium. Accordingly, media of different sizes can be stably delivered. 
     (8) The medium conveying device according to any one of (1) to (7), in which the posture correction unit corrects the posture of the medium and positions the medium at a fixed position. 
     According to this aspect, in the posture correction unit, the posture of the medium is corrected, and the medium is positioned at the fixed position. Accordingly, the medium can be conveyed more stably. 
     (9) The medium conveying device according to (8), in which the posture correction unit corrects the posture of the medium and positions the medium at the fixed position by making the medium abut on a first regulating member disposed along a direction orthogonal to a delivery direction of the medium and a second regulating member disposed along the delivery direction of the medium. 
     According to this aspect, the posture of the medium is corrected and the medium is positioned at the fixed position by making the medium abut on a first regulating member disposed along a direction orthogonal to a delivery direction of the medium and a second regulating member disposed along the delivery direction of the medium. Accordingly, the medium can be positioned at the same time as the posture is corrected. 
     (10) The medium conveying device according to any one of (1) to (7), in which the posture correction unit corrects the posture of the medium and positions the medium at a fixed position with respect to a delivery direction of the medium. 
     According to this aspect, in the posture correction unit, the posture of the medium is corrected, and the medium is positioned at the fixed position with respect to the delivery direction of the medium. Accordingly, the medium can be conveyed more stably. 
     (11) The medium conveying device according to (10), in which the posture correction unit corrects the posture of the medium and positions the medium at the fixed position with respect to the delivery direction of the medium by making the medium abut on a regulating member disposed along a direction orthogonal to the delivery direction of the medium. 
     According to this aspect, the posture of the medium is corrected and the medium is positioned at the fixed position with respect to the delivery direction of the medium by making the medium abut on the regulating member disposed along the direction orthogonal to the delivery direction of the medium. Accordingly, the medium can be positioned at the same time as the posture is corrected. 
     (12) The medium conveying device according to any one of (1) to (7), in which the posture correction unit corrects the posture of the medium and positions the medium at a fixed position with respect to a direction orthogonal to a delivery direction of the medium. 
     According to this aspect, in the posture correction unit, the posture of the medium is corrected, and the medium is positioned at the fixed position with respect to the direction orthogonal to the delivery direction of the medium. Accordingly, the medium can be conveyed more stably. 
     (13) The medium conveying device according to (12), in which the posture correction unit corrects the posture of the medium and positions the medium at the fixed position with respect to the direction orthogonal to the delivery direction of the medium by making the medium abut on a regulating member disposed along the delivery direction of the medium. 
     According to this aspect, the posture of the medium is corrected and the medium is positioned at the fixed position with respect to the direction orthogonal to the delivery direction of the medium by making the medium abut on the regulating member disposed along the delivery direction of the medium. Accordingly, the medium can be positioned at the same time as the posture is corrected. 
     (14) The medium conveying device according to any one of (1) to (7), in which the posture correction unit includes a posture detecting portion that detects the posture of the medium, a plurality of conveying rollers disposed along a direction orthogonal to a delivery direction of the medium, and a control unit that individually controls rotation speeds of the conveying rollers based on a detection result of the posture detecting portion and corrects the posture of the medium. 
     According to this aspect, the posture of the medium is corrected by individually controlling the rotation speeds of the plurality of conveying rollers disposed along the direction orthogonal to the delivery direction of the medium. The rotation speed of each conveying roller is set based on the posture of the medium detected by the posture detecting portion. 
     (15) An inkjet printer comprising: the medium conveying device according to any one of (1) to (14); and an inkjet printing unit that performs printing on the medium conveyed by the conveying unit of the medium conveying device by an inkjet method. 
     According to this aspect, in the inkjet printer that performs printing by the inkjet method, the medium is conveyed by using the medium conveying device described in any one of (1) to (14). Accordingly, it is possible to prevent a problem such as an image being printed with inclination from occurring. 
     According to the present invention, a medium can be stably conveyed. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic configuration view showing an embodiment of an inkjet printer to which the present invention is applied. 
         FIG. 2  is a plan view showing a schematic configuration of a posture correction unit. 
         FIG. 3  is a side view showing the schematic configuration of the posture correction unit. 
         FIG. 4  is a plan view showing a schematic configuration of a delivery unit. 
         FIG. 5  is a cross-sectional front view of a paper holding bar. 
         FIG. 6  is a bottom view of the paper holding bar. 
         FIG. 7  is a plan view of a conveying unit and a printing unit. 
         FIG. 8  is a block diagram showing a schematic configuration of a control system of the inkjet printer. 
         FIG. 9  is a plan view showing an example of a posture correction unit in a case where positioning is performed in a direction orthogonal to a conveying direction of a paper. 
         FIG. 10  is a plan view showing an example of a posture correction unit in a case where only a posture of the paper is corrected. 
         FIG. 11  is a table showing results of an experiment. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. 
     [Configuration of Inkjet Printer] 
       FIG. 1  is a schematic configuration view showing an embodiment of an inkjet printer to which the present invention is applied. 
     An inkjet printer  1  is a line printer that performs printing on a sheet by a single pass using a line head, and comprises a paper feeding unit  10 , a posture correction unit  20 , a delivery unit  30 , a conveying unit  40 , an inkjet printing unit  50 , and a paper discharging unit  60 . The posture correction unit  20 , the delivery unit  30 , and the conveying unit  40  form a medium conveying device. After a posture of a paper P supplied from the paper feeding unit  10  is corrected by the posture correction unit  20 , the paper P is delivered to the conveying unit  40  by the delivery unit  30 , is printed by the inkjet printing unit  50 , and is discharged to the paper discharging unit  60 . 
     &lt;&lt;Paper Feeding Unit&gt;&gt; 
     The paper feeding unit  10  supplies the paper P to the posture correction unit  20  one by one. The paper feeding unit  10  is configured by a known paper feeding mechanism, separates the stacked papers P one by one, and supplies the separated paper P to the posture correction unit  20 . A paper feeding direction of the paper feeding unit  10  is the same as a conveying direction of the paper P by the posture correction unit  20 . This direction is a Y direction in  FIG. 1 . 
     &lt;&lt;Posture Correction Unit&gt;&gt; 
       FIG. 2  is a plan view showing a schematic configuration of a posture correction unit.  FIG. 3  is a side view showing the schematic configuration of the posture correction unit. 
     The posture correction unit  20  conveys the paper P to a specified position (a position where the paper P is delivered to the delivery unit  30 ), and corrects a posture of the paper P in the conveyance process. In the present embodiment, the posture of the paper P is corrected so that front and rear edges of the paper P in the conveying direction (Y direction) are set to a posture orthogonal to the conveying direction of the paper P as a specified posture. That is, an inclination (skew) around a Z axis is corrected. 
     The conveying direction of the paper P by the posture correction unit  20  is the same as a direction in which the delivery unit  30  delivers the paper P to the conveying unit  40 . This direction is a Y direction in  FIG. 1 . The posture correction unit  20  comprises a feeder board  21 , a front lay device  22 , a side lay device  23 , and the like. 
     &lt;Feeder Board&gt; 
     The feeder board  21  conveys the paper P supplied from the paper feeding unit  10  toward the front lay device  22 . The feeder board  21  comprises a paper feed roller  24 , a paper feed belt  25 , a paper feed roll  26 , and the like. The paper P supplied from the paper feeding unit  10  is conveyed on the feeder board  21  toward the front lay device  22  by the paper feed roller  24 , the paper feed belt  25 , and the paper feed roll  26 . The paper feed roller  24 , the paper feed belt  25 , and the paper feed roll  26  are driven in synchronization with feeding of the paper P. The paper feed roller  24  and the paper feed roll  26  are moved up and down in synchronization with feeding of the paper P. 
     &lt;Front Lay Device&gt; 
     The front lay device  22  comprises a plurality of front lays  22 A, and corrects the posture of the paper P by making a front edge (edge on a leading end side) of the paper P abut on the front lays  22 A. At the same time, the front lay device  22  positions the paper P at a fixed position with respect to a delivery direction (Y direction). The front lay  22 A is an example of a first regulating member, and is disposed along a direction orthogonal to the conveying direction (Y direction) of the paper P by the feeder board  21 . The front lay  22 A is provided on a front lay shaft  22 B, and is retracted from a conveying path of the paper P by the feeder board  21  by rotating the front lay shaft  22 B. 
     &lt;Side Lay Device&gt; 
     The side lay device  23  comprises a side lay  23 A and a side lay roll  23 B, and corrects the posture of the paper P by making a side edge of the paper P abut on the side lay  23 A. At the same time, the front lay device  22  positions the paper P at a fixed position with respect to a direction (X direction) orthogonal to the delivery direction (Y direction). The side lay  23 A is an example of a second regulating member, and is disposed along the conveying direction (Y direction) of the paper P by the feeder board  21 . The side lay roll  23 B feeds the paper P, which has abutted on the front lay  22 A, in the direction (X direction) orthogonal to the conveying direction (Y direction), so that the side edge of the paper P is made to abut on the side lay  23 A. 
     The posture correction unit  20  is configured as described above. In the posture correction unit  20 , the paper P is first applied to the front lay  22 A, and then to the side lay  23 A. Thus, the posture is corrected and positioning is performed at a fixed position. 
     &lt;&lt;Delivery Unit&gt;&gt; 
       FIG. 4  is a plan view showing a schematic configuration of a delivery unit. 
     The delivery unit  30  delivers the paper P of which the posture is corrected by the posture correction unit  20  and which is positioned at a fixed position to the conveying unit  40 . The delivery direction of the paper P by the delivery unit  30  is the same as the conveying direction of the paper P by the conveying unit  40 . This direction is a Y direction in  FIG. 4 . The delivery unit  30  comprises a paper holding bar  31  that holds the paper P, and a paper holding bar moving mechanism  35  that linearly reciprocates the paper holding bar  31 . 
     &lt;Paper Holding Bar&gt; 
       FIG. 5  is a cross-sectional front view of a paper holding bar.  FIG. 6  is a bottom view of the paper holding bar. 
     The paper holding bar  31  is an example of a holding portion. The paper holding bar  31  has a square bar shape, and is disposed along a direction orthogonal to the delivery direction (Y direction) of the paper P. 
     A bottom surface portion of the paper holding bar  31  serves as an attraction surface  31 A for the paper P. The paper holding bar  31  attracts the paper P onto the attraction surface  31 A, and attracts and holds a leading end portion of the paper P. The attraction surface  31 A is formed of a surface parallel to the paper P to be conveyed by the conveying unit  40 . Specifically, in  FIG. 1 , it is configured on a plane in parallel to an XY plane. 
     As shown in  FIG. 6 , the attraction surface  31 A comprises a plurality of suction holes  32 . The suction holes  32  are disposed at regular intervals along the direction (X direction) orthogonal to the delivery direction (Y direction) of the paper P. Each suction hole  32  comprises a rubber pad  32 A at a portion of a suction port. 
     As shown in  FIG. 5 , each suction hole  32  is communicated with a common space  31 B inside the paper holding bar  31 . Each suction hole  32  comprises a suction hole opening/closing valve  33 . The suction hole opening/closing valve  33  is formed of, for example, an electromagnetic valve, and opening/closing is individually controlled. Thus, each suction hole  32  is configured to be able to be individually opened and closed. 
     A paper holding bar suction pump  34  is connected to the common space  31 B. By driving the paper holding bar suction pump  34 , the common space  31 B is sucked, and suction is performed through the suction hole  32  communicated with the common space  31 B. 
     &lt;Paper Holding Bar Moving Mechanism&gt; 
     The paper holding bar moving mechanism  35  comprises a pair of linear motion guides  36  that guides movement of the paper holding bar  31  and a paper holding bar driving mechanism  37  that moves the paper holding bar  31 . 
     The linear motion guide  36  comprises a base  36 A, a pair of guide rails  36 B disposed on the base  36 A, and a slide table  36 D that slides on the guide rail  36 B via a slider  36 C. The guide rail  36 B is disposed along the delivery direction (Y direction) of the paper P. Therefore, the slide table  36 D slides along the delivery direction (Y direction) of the paper P. 
     The pair of linear motion guides  36  is disposed on both sides of the paper holding bar  31 . Each of both ends of the paper holding bar  31  is fixed to the slide table  36 D of the linear motion guide  36 . Thus, the paper holding bar  31  is supported movably along the delivery direction (Y direction) of the paper P. 
     The paper holding bar driving mechanism  37  is provided on one linear motion guide  36 , and moves the slide table  36 D of the one linear motion guide  36  along the guide rail  36 B. The paper holding bar driving mechanism  37  is configured by a so-called feed screw mechanism, and has a feed screw  37 A, a nut  37 B fastened to the feed screw  37 A, and a feed screw drive motor  37 C that rotates the feed screw  37 A. The feed screw  37 A is disposed between the pair of guide rails  36 B, and is disposed along the guide rail  36 B. The nut  37 B is provided integrally with the slide table  36 D. The feed screw drive motor  37 C is provided on the base  36 A. 
     In a case where the feed screw drive motor  37 C is driven, the feed screw  37 A rotates, and the slide table  36 D moves according to the amount of rotation. Thus, the paper holding bar  31  moves along the delivery direction (Y direction) of the paper P. 
     The delivery unit  30  is configured as described above. In the delivery unit  30 , the paper holding bar  31  moves linearly, and delivers the paper P from the posture correction unit  20  to the conveying unit  40 . A position at which the paper holding bar  31  receives the paper P from the posture correction unit  20  is defined as a receiving position Y 1 , and a position at which the paper holding bar  31  delivers the paper P to the conveying unit  40  is defined as a delivery position Y 2 . The paper holding bar  31  linearly moves from the receiving position Y 1  to the delivery position Y 2 , and delivers the paper P to the conveying unit  40 . 
     In a case where the paper holding bar  31  is located at the receiving position Y 1 , the paper holding bar  31  is disposed with a certain clearance directly above the leading end portion of the paper P of which the posture is corrected by the posture correction unit  20 . Thus, in a case where suction is performed at the receiving position Y 1 , the leading end portion of the paper P can be attracted and held by the paper holding bar  31 . The delivery position Y 2  will be described later. 
     &lt;&lt;Conveying Unit&gt;&gt; 
     The conveying unit  40  receives the paper P from the delivery unit  30 , and conveys the paper P in one direction along a plane. Specifically, in  FIG. 1 , the paper P is conveyed in the Y direction along the XY plane. The conveying unit  40  is configured by a so-called belt conveyance mechanism, and conveys the paper P by attracting the paper P onto a conveying belt  41 . Air pressure (negative pressure) is used for attraction. 
     The conveying belt  41  is an endless belt comprising a large number of suction holes  41 A (see  FIG. 7 ). The conveying belt  41  is wound around a driving roller  42  and a driven roller  43 . 
     The driving roller  42  and the driven roller  43  are disposed along a direction orthogonal to the conveying direction (Y direction) of the paper P, and are disposed on the same plane. Thus, a flat conveyance path is formed by the conveying belt  41 . This conveyance path conveys the paper P in the Y direction along the XY plane. 
     A conveying belt drive motor  44  is connected to the driving roller  42 . By driving the conveying belt drive motor  44 , the driving roller  42  rotates. Thus, the conveying belt  41  runs. 
     The driving roller  42  comprises a rotary encoder  45 . The rotary encoder  45  detects the amount of rotation of the driving roller  42 . A running speed of the conveying belt  41  is detected based on output of the rotary encoder  45 . The running speed of the conveying belt  41  is synonymous with the conveying speed of the paper P. 
     A suction chamber  46  is provided inside the conveying belt  41 . The suction chamber  46  is connected to a conveying belt suction pump  47 . The suction chamber  46  suctions the conveying belt  41  from the inside in an area constituting the conveyance path of the paper P. 
     Here, assuming that a start point of the conveyance path of the paper P is denoted by Y 3  and a start point of suction action by the suction chamber  46  is denoted by Y 4 , the start point Y 4  of suction action is located downstream of the start point Y 3  of the conveyance path due to an installation space of the suction chamber  46 . 
     As described above, the paper P is delivered from the paper holding bar  31  to the conveying belt  41  at the delivery position Y 2 . That is, at the delivery position Y 2 , holding of the paper P by the paper holding bar  31  is released. 
     In a case where the paper holding bar  31  is located at the delivery position Y 2 , the paper holding bar  31  is disposed directly above the conveying belt  41  with a certain clearance. The delivery position Y 2  of the paper P is set on the conveyance path of the paper P by the conveying belt  41  and at least a position where the attraction force acts. Therefore, the delivery position Y 2  is set downstream of the start point Y 4  of suction action. Thus, in a case where holding of the paper P is released, the paper P can be reliably delivered to the conveying belt  41 . In the present embodiment, the delivery position Y 2  is set at a point apart from the start point Y 4  of suction action by the suction chamber  46  by a distance d. By setting the distance d to be short, the amount of movement of the paper holding bar  31  during delivery can be reduced. For example, the delivery position Y 2  is set such that holding of the paper P is released at a time when the suction hole  32  of the paper holding bar  31  passes the start point Y 4  of the suction action. Thus, a moving distance of the paper holding bar  31  can be shortened while preventing a shift or the like. 
     The conveying unit  40  is configured as described above. The paper P is delivered to the running conveying belt  41 , is attracted onto a surface of the conveying belt  41 , and is conveyed at a constant speed along the conveyance path. 
     In a case where the paper P is delivered to the conveying belt  41 , the paper P is accelerated to the same speed as the conveying belt  41 . Thus, it is possible to prevent the paper P from being inclined or shifted during delivery. Here, the same speed includes a range recognized as substantially the same speed. The driving of the paper holding bar  31  is controlled based on information on the running speed of the conveying belt  41  (the conveying speed of the paper P) to be acquired via the rotary encoder  45 . That is, movement of the paper holding bar  31  is controlled such that the speed becomes the same as the running speed of the conveying belt  41  during delivery. 
     &lt;&lt;Inkjet Printing Unit&gt;&gt; 
       FIG. 7  is a plan view of a conveying unit and a printing unit. 
     The inkjet printing unit  50  is disposed on the conveyance path of the paper P by the conveying unit  40 , and drops four colors of ink of cyan (C), magenta (M), yellow (Y), and black (Bk) on the paper P conveyed along the conveyance path to print a color image on the paper P. 
     The inkjet printing unit  50  comprises an inkjet head  51 C that ejects ink droplets of cyan, an inkjet head  51 M that ejects ink droplets of magenta, an inkjet head  51 Y that ejects ink droplets of yellow, and an inkjet head  51 Bk that ejects ink droplets of black. The inkjet heads  51 C,  51 M,  51 Y, and  51 Bk are each configured by a line head corresponding to the maximum paper width, and are disposed along a direction orthogonal to the conveying direction (Y direction) of the paper P. The inkjet heads  51 C,  51 M,  51 Y, and  51 Bk are disposed at equal intervals along the conveying direction (Y direction) of the paper P. 
     Each of the inkjet heads  51 C,  51 M,  51 Y, and  51 Bk is driven in synchronization with the conveyance of the paper P based on data for printing. 
     &lt;&lt;Paper Discharging Unit&gt;&gt; 
     The paper discharging unit  60  collects the printed paper P from the conveying unit  40  and accumulates the paper P on a paper discharge tray. 
     [Control System of Inkjet Printer] 
       FIG. 8  is a block diagram showing a schematic configuration of a control system of the inkjet printer. 
     An overall operation of the inkjet printer  1  is integrally controlled by a control unit  100 . The control unit  100  is configured by a computer, and controls operation of each unit by executing a predetermined control program. A operation unit  101  for operating the inkjet printer  1 , a display unit  102  for displaying various pieces of information, a communication unit  103  for communicating with an external device, and a storage unit  104  for storing programs and various pieces of data necessary for control are connected to the control unit  100 . The image data to be printed is acquired from an external device via the communication unit  103 . The control unit  100  generates data for printing from the acquired image data and executes print processing. 
     [Action of Inkjet Printer] 
     In a case where the image data for printing is input, the control unit  100  generates data for printing. After that, print processing is started according to the print execution instruction. 
     First, the conveying unit  40  is driven, and running of the conveying belt  41  is started. After that, the paper P is supplied from the paper feeding unit  10  to the posture correction unit  20 . The paper P is supplied from the paper feeding unit  10  to the posture correction unit  20  one by one. 
     The paper P supplied to the posture correction unit  20  is conveyed on the feeder board  21  by the paper feed roller  24 , the paper feed belt  25 , and the paper feed roll  26 , and the front edge of the paper P abuts on the front lay  22 A at an end point. Thereby, the posture is corrected. That is, the front and rear edges of the paper P are adjusted to a posture orthogonal to the conveying direction (Y direction) by the conveying unit  40 , and an inclination (skew) is removed. Further, the paper P is positioned at a fixed position with respect to the conveying direction (Y direction) at the same time as the posture is corrected. 
     In a case where the paper P abuts on the front lay  22 A, the paper P is sent by the side lay roll  23 B in the direction (X direction) orthogonal to the conveying direction (Y direction), and one side edge of the paper P abuts on the side lay  23 A. Thus, the paper P is positioned at a fixed position with respect to a direction orthogonal to the conveying direction (Y direction). 
     Through the above processes, the posture of the paper P is corrected, and the paper P is positioned at a fixed position. In a case where the posture of the paper P is corrected by the posture correction unit  20  and the paper P is positioned at a fixed position, the delivery unit  30  delivers the paper P to the conveying unit  40 . 
     First, the paper holding bar  31  moves to the receiving position Y 1 . Thus, the paper holding bar  31  is positioned directly above the leading end portion of the paper P. In this case, the paper holding bar  31  is disposed such that the attraction surface  31 A thereof faces a surface of the paper P with a certain clearance. 
     In a case where the paper holding bar  31  moves to the receiving position Y 1 , the suction hole opening/closing valve  33  in an area corresponding to a width of the paper P is opened, and the paper P is sucked through the suction holes  32 . Thus, the leading end portion of the paper P is sucked to the attraction surface  31 A, and the leading end portion of the paper P is held by the paper holding bar  31 . The suction hole opening/closing valve  33  in the area corresponding to the width of the paper P is the suction hole opening/closing valve  33  of the suction hole  32  in an area where the paper P is attracted. By opening only the suction hole opening/closing valve  33  of the suction hole  32  in the area where the paper P is attracted, decrease in the attraction force can be prevented, and the paper P can be stably held. 
     In a case where the paper P is held by the paper holding bar  31 , the feed screw drive motor  37 C is driven, and the paper holding bar  31  moves toward the delivery position Y 2 . In this case, the moving speed of the paper holding bar  31  is controlled such that it becomes the same speed as the conveying belt  41  in a case where the paper holding bar  31  reaches the delivery position Y 2 . That is, movement of the paper holding bar  31  is controlled such that the paper P is delivered while running at the same speed as the conveying belt  41 . 
     In a case where the paper holding bar  31  reaches the delivery position Y 2 , holding of the paper P by the paper holding bar  31  is released. That is, all the suction hole opening/closing valves  33  are closed, and the attraction force on the attraction surface  31 A is released. Thus, the paper P is released from the paper holding bar  31 . In a case where holding of the paper P is released, the paper holding bar  31  stops moving. 
     On the other hand, the paper P released from the paper holding bar  31  is sucked to the surface of the conveying belt  41  by suction from the suction holes  41 A provided in the conveying belt  41 . Thus, the paper P is delivered to the conveying belt  41 . In this case, the paper P is delivered to the conveying belt  41  while moving at the same speed as the conveying belt  41 . Thus, the paper P can be delivered to the conveying belt  41  without causing a shift, an inclination, or the like. 
     The paper P delivered to the conveying belt  41  is conveyed by the conveying belt  41  at a constant speed along a plane in parallel to the XY plane in the Y direction. Then, in the conveyance process, the paper P passes through the inkjet printing unit  50 , and the inkjet heads  51 C,  51 M,  51 Y, and  51 Bk drop four colors of ink of cyan, magenta, yellow, and black to print a color image on the surface of the paper P. 
     The printed paper P is collected by the paper discharging unit  60  at an end point of the conveyance path by the conveying belt  41 , and is accumulated on a paper discharge tray. 
     As described above, according to the inkjet printer  1  of the present embodiment, the paper P is delivered to the conveying belt  41  after the posture is corrected by the posture correction unit  20 . In this case, the leading end portion of the paper P is held by the paper holding bar  31  that moves linearly, and is delivered to the conveying belt  41 . Thus, the paper P can be delivered to the conveying belt  41  while maintaining a specified posture without changing the posture of the paper P after the correction. Accordingly, printing can be performed without causing a position shift, an inclination, or the like. 
     Modification Example 
     &lt;&lt;Modification Example of Posture Correction Unit&gt;&gt; 
     The posture correction unit needs only to be able to correct at least the posture of the medium to a specified posture. As the posture correction unit, a known posture correcting mechanism used in an offset printer or the like can be used. 
     In the above-described embodiment, the paper P is fed using the paper feed roller  24 , the paper feed belt  25 , and the paper feed roll  26  in a case where the paper P abuts on the front lay  22 A. However, the mechanism for feeding the paper P is not limited to this. Other known feed mechanisms can be used. 
     In the side lay device  23 , the paper P is fed using the side lay roll  23 B, but the mechanism for feeding the paper P is not limited to this. Other known feed mechanisms can be used. 
     As described above, the posture correction unit needs only to be able to correct at least the posture of the medium. Therefore, it is not always necessary to perform positioning. 
     In a case where positioning is performed, positioning may be performed only in one direction. For example, a configuration may be adopted in which positioning is performed only in the conveying direction of the paper. Alternatively, a configuration may be adopted in which positioning is performed only in a direction orthogonal to the conveying direction of the paper. For example, in the posture correction unit  20  of the above-described embodiment, in a case where the side lay device  23  is omitted, positioning can be performed only in the conveying direction of the paper. In a case where the front lay device  22  is omitted, positioning can be performed only in a direction orthogonal to the conveying direction of the paper. 
     &lt;Example of Positioning in Direction Orthogonal to Conveying Direction of Paper&gt; 
       FIG. 9  is a plan view showing an example of a posture correction unit in a case where positioning is performed in a direction orthogonal to a conveying direction of a paper. 
     A posture correction unit  120  of the present example comprises a feeder board  121  and a side lay  122 , and corrects the posture of the paper P by making the side edge of the paper P abut on the side lay  122 . At the same time, the paper P is positioned in a direction orthogonal to the conveying direction. 
     The feeder board  121  comprises a plurality of conveying rollers  121 A. Each of the conveying rollers  121 A is disposed to be inclined toward the side lay  122 . Each of the conveying rollers  121 A rotates by being driven by a motor (not shown). The paper P supplied to the feeder board  121  is conveyed obliquely toward the side lay  122  by action of the conveying rollers  121 A disposed to be inclined. 
     The side lay  122  is an example of a regulating member, and is disposed along the delivery direction (Y direction) of the paper P. The side lay  122  is attached so that the position can be adjusted in the X direction. 
     According to the posture correction unit  120  of the present example, the paper P is conveyed obliquely on the feeder board  121  toward the side lay  122 . Then, in the conveyance process, the side edge abuts on the side lay  122 , and the posture is corrected. At the same time, positioning is performed in a direction orthogonal to the conveying direction (delivery direction). In  FIG. 9 , a paper Pa indicated by a dashed line is an initial state paper, a paper Pb indicated by a broken line is an intermediate state paper, and the paper P indicated by a solid line is a final state paper. As shown in the figure, the posture of the paper is corrected in a process of being conveyed on the feeder board  121 , and the paper is positioned in a direction orthogonal to the conveying direction. 
     In the present example, the paper P is fed using the conveying roller  121 A in the oblique direction, but the mechanism for feeding the paper P in the oblique direction is not limited to this. 
     In a case of the posture correction unit  120  of the present example, the position of the paper P in the conveying direction (delivery direction) is uncertain, but a shift of the position of the paper P in the conveying direction can be eliminated by individually adjusting the printing position in the inkjet printing unit  50 . That is, by adjusting the printing position to offset a shift, the shift of the position of each paper P in the conveying direction of the paper can be eliminated. The printing position in the conveying direction of the paper can be adjusted by changing a timing at which printing is started. That is, the printing position can be shifted backward by delaying the timing of starting printing. Further, the printing position can be shifted forward by advancing the timing of starting printing. 
     In a case of adjusting the printing position of the paper P, the position of the paper after the posture correction is detected by a sensor, the detection result is given to the control unit  100 , and the printing position in the inkjet printing unit  50  is adjusted. 
     &lt;Example of Correcting Only Posture of Paper&gt; 
       FIG. 10  is a plan view showing an example of a posture correction unit in a case where only a posture of the paper is corrected. 
     A posture correction unit  130  of the present example comprises a feeder board  131  and a posture detection sensor  132 . 
     The feeder board  131  comprises a plurality of conveying rollers  131 A along a direction orthogonal to the conveying direction (delivery direction) of the paper P. In the present example, two rows are provided. Each of the conveying rollers  131 A rotates individually by being driven by a motor (not shown). The driving of each motor is individually controlled by the control unit  100  (see  FIG. 8 ). 
     The posture detection sensor  132  is an example of a posture detecting portion. The posture detection sensor  132  is disposed on an upstream side of the conveying roller  131 A. The posture detection sensor  132  is configured by, for example, a line scanner, and reads the front edge (edge on the leading end side) of the paper P to detect the posture of the paper P. The detected information is output to the control unit  100  (see  FIG. 8 ). 
     The control unit  100  individually drives each conveying roller  131 A based on the detection result of the posture of the paper P by the posture detection sensor  132  to correct the posture of the paper P. That is, by providing a difference in the rotation speed of each conveying roller  131 A, the paper P rotates around the Z axis while being conveyed, and the posture is corrected. 
     In  FIG. 10 , the paper Pa indicated by a dashed line is an initial state paper, the paper Pb indicated by a broken line is an intermediate state paper, and the paper P indicated by a solid line is a final state paper. The front edge of the paper supplied from the paper feeding unit  10  is read in a process of passing through the posture detection sensor  132 , and the posture is detected. Then, the rotation speed of each conveying roller  131 A is individually determined based on the detection result of the posture. That is, the rotation speed of each conveying roller  131 A is individually determined so that the inclination generated on the paper is removed. Then, each conveying roller  131 A is driven at the determined rotation speed, and the paper is conveyed. Thus, the posture of the paper can be corrected. 
     In a case of the posture correction unit  120  of the present example, the position of the paper P is uncertain, but a shift of the position of each paper P can be eliminated by individually adjusting the printing position in the inkjet printing unit  50 . That is, by adjusting the printing position to offset a shift, the shift of the position occurring on each paper can be eliminated. As described above, the printing position in the conveying direction of the paper can be adjusted by changing a timing at which printing is started. On the other hand, the printing position in a direction orthogonal to the conveying direction of the paper can be adjusted by switching an area of a nozzle used for printing in a width direction (X direction). This adjustment is possible in a case where the printing width of an inkjet head (a length of a nozzle row in the X direction) is wider than the width of the paper. 
     In a case of adjusting the printing position of the paper P, the position of the paper after the posture correction is detected by a sensor, the detection result is given to the control unit  100 , and the printing position in the inkjet printing unit  50  is adjusted. 
     &lt;&lt;Modification Example of Delivery Unit&gt;&gt; 
     The delivery unit needs only to be able to hold a part of the medium and convey it linearly. It is preferable that the part to be held is appropriately set according to the medium. For example, in a case of a medium that is hardly deformed, the delivery unit may convey the medium while holding a central portion thereof. 
     In a case where a medium for printing that is thin and easily deformed is delivered, it is preferable to hold the leading end portion as in the above-described embodiment. In this case, it is more preferable to hold a non-printing area. The non-printing area is a so-called margin area, and is an area where printing is not performed. The non-printing area is generally set in a frame shape at a peripheral portion of the paper, and is set as an area that is cut and removed after printing. 
     Further, in the above-described embodiment, the paper as the medium is attracted and held, but a form of holding the paper is not limited to this. For example, a configuration may be adopted in which the leading end portion of the paper is gripped by a gripper. In a case where the paper is attracted and held, the paper may be attracted onto the holding portion using static electricity. In a case where the paper is delivered to the conveyance mechanism for conveying the paper along the plane, such as a conveying belt, the delivery position of the paper can be set randomly by attracting and holding the paper. Thereby, a degree of freedom in design can be improved. 
     In the above-described embodiment, the paper P is delivered to the conveying belt  41  at a time when the suction hole  32  of the paper holding bar  31  passes the start point Y 4  of the suction action. However, the delivery position Y 2  of the paper P is not limited to this. It is preferable the position is appropriately set according to a type of the paper or the like. 
     In the above-described embodiment, each suction hole  32  can be opened and closed individually, but may be opened and closed collectively. For example, in an apparatus that handles a single size paper, a configuration may be adopted in which all suction holes are opened and closed collectively using a common valve. 
     In the above-described embodiment, the paper holding bar is moved using the feed screw mechanism, but the mechanism for moving the paper holding bar is not limited to this. For example, a linear motor may be used as driving means. In addition, it is preferable to use, as a guide mechanism, a mechanism having high reproducibility of the conveying operation position, such as a linear motion guide (also referred to as a linear slider). Thus, position reproducibility for each paper can be secured. 
     As necessary, the holding portion may comprise an up-and-down mechanism. For example, in the delivery unit  30  of the above-described embodiment, a mechanism for moving the paper holding bar  31  up and down (Z direction) may be provided. Thus, in a case of receiving the paper P, the attraction surface  31 A of the paper holding bar  31  can be brought into close contact with the paper P to receive the paper P. 
     &lt;&lt;Speed of Paper in Case of being Delivered to Conveying Unit&gt;&gt; 
     It is preferable that the speed of the paper in a case where the paper is delivered from the delivery unit to the conveying unit is made to match the conveying speed of the paper by the conveying unit. However, in a case where it is within a range of a certain speed difference, the same effect as a case where the speeds are made to match with each other can be expected. Therefore, an experiment was performed in which the papers were delivered at different speeds, and changes in the postures of the delivered papers were confirmed. 
       FIG. 11  is a table showing results of the experiment. 
     In the table shown in the figure, an item of a speed ratio is a speed ratio with respect to the conveying speed of the paper by the conveying unit (the running speed of the conveying belt). A speed ratio of 85% means that the paper was delivered at a speed of 85% with respect to the conveying speed of the paper by the conveying unit. A speed ratio of 100% is a case where the paper was delivered at the same speed. 
     In addition, evaluation was made in three stages of A, B, and C. A means that there was no change in posture. That is, it means that the paper was delivered while maintaining the posture at the time of correction. B means that a change in posture (inclination (skew) or the like) was recognized, but within an allowable range. C is a case where an unacceptable change in posture occurred. 
     As shown in the table of  FIG. 11 , in a case where the paper is delivered at a speed within a range of ±10% of the conveying speed of the paper by the conveying unit, the paper can be delivered to the conveying unit without changing the posture. 
     &lt;&lt;Modification Example of Conveying Unit&gt;&gt; 
     The conveying unit needs only to have a configuration that can convey the medium along the plane. 
     In the above-described embodiment, the paper as the medium is conveyed along the plane by the so-called belt conveyance mechanism, but the mechanism for conveying the medium along the plane is not limited to this. For example, a conveyance mechanism using a table may be used. The conveyance mechanism using the table places the medium on the table, slides the table along the plane, and conveys the medium along the plane. In this case, the delivery of the medium may be performed with the table stopped, or may be delivered while moving the table. In a case where the medium is delivered to the moving table, it is preferable to accelerate and deliver the paper to the same speed as the table. 
     Further, in the above-described embodiment, the paper as the medium is attracted onto the conveying belt using air pressure, but the mechanism for attracting the medium to the conveying belt is not limited to this. The medium may be attracted onto the conveying belt by using static electricity. In this case, the conveying belt is charged to a high voltage. 
     Further, the medium may be conveyed by being held by holding means other than attraction. For example, the medium may be conveyed by gripping the leading end with a gripper. 
     A mechanism for holding the medium, such as attraction, is not necessarily required in the conveying unit. For example, in the case of a heavy medium, the medium can be stably conveyed without attraction. Therefore, in a case of the medium that can be stably conveyed without attraction or the like, a holding mechanism such as attraction is unnecessary. In this case, the medium is simply placed and conveyed without attraction or the like. 
     In a case where the paper is conveyed by the conveying belt without being attracted, it is preferable to deliver the paper from the delivery unit to the conveying unit at a stage where the entire or almost the entire paper is located on the conveyance path by the conveying belt. 
     Other Modification Examples 
     In the above-described embodiment, the case where the medium conveying device according to the embodiment of the present invention is applied to the conveying device of the inkjet printer has been described as an example, but the application of the medium conveying device according to the embodiment of the present invention is not limited to this. The present invention can be applied to a conveying device of a printer other than the inkjet method. 
     Further, the present invention can be applied to a conveying device that conveys a medium other than the medium for printing. For example, the present invention can be applied to a conveying device that conveys a substrate or the like. 
     In the above-described embodiment, the paper is discharged as it is after printing, but a post-processing process such as drying may be added as necessary. 
     EXPLANATION OF REFERENCES 
     
         
         
           
               1 : inkjet printer 
               10 : paper feeding unit 
               20 : posture correction unit 
               21 : feeder board 
               22 : front lay device 
               22 A: front lay 
               22 B: front lay shaft 
               23 : side lay device 
               23 A: side lay 
               23 B: side lay roll 
               24 : paper feed roller 
               25 : paper feed belt 
               26 : paper feed roll 
               30 : delivery unit 
               31 : paper holding bar 
               31 A attraction surface 
               31 B: common space 
               32 : suction hole 
               32 A: pad 
               33 : suction hole opening/closing valve 
               34 : paper holding bar suction pump 
               35 : paper holding bar moving mechanism 
               36 : linear motion guide 
               36 A: base 
               36 B: guide rail 
               36 C: slider 
               36 D: slide table 
               37 : paper holding bar driving mechanism 
               37 A: feed screw 
               37 B: nut 
               37 C: feed screw drive motor 
               40 : conveying unit 
               41 : conveying belt 
               41 A: suction hole 
               42 : driving roller 
               43 : driven roller 
               44 : conveying belt drive motor 
               45 : rotary encoder 
               46 : suction chamber 
               47 : conveying belt suction pump 
               50 : inkjet printing unit 
               51 C: inkjet head 
               51 M: inkjet head 
               51 Y: inkjet head 
               51 Bk: inkjet head 
               60 : paper discharging unit 
               100 : control unit 
               101 : operation unit 
               102 : display unit 
               103 : communication unit 
               104 : storage unit 
               120 : posture correction unit 
               121 : feeder board 
               121 A: conveying roller 
               122 : side lay 
               130 : posture correction unit 
               131 : feeder board 
               131 A: conveying roller 
               132 : posture detection sensor 
             P: paper 
             Pa: paper 
             Pb: paper 
             Y 1 : receiving position 
             Y 2 : delivery position 
             Y 3 : start point of conveyance path 
             Y 4 : start point of suction action