Patent Publication Number: US-11376867-B2

Title: Printing apparatus

Description:
The present application is based on, and claims priority from JP Application Serial Number 2019-116203, filed Jun. 24, 2019, the disclosure of which is hereby incorporated by reference herein in its entirety. 
     BACKGROUND 
     1. Technical Field 
     The disclosure relates to a printing apparatus. 
     2. Related Art 
     In the related art, a configuration of an inkjet printer is known in which a fan is disposed above a platen in such a manner as to overlap the platen in plan view for the purpose of achieving good printing quality while ensuring productivity for ink discharged from a recording unit (printing part) on a recording medium on the platen (e.g., JP-A-2014-156128). 
     In JP-A-2014-156128, air of the fan is uniformly blown to the entire region of the recording medium so as to uniformly dry the ink on the recording medium. However, as a result of the experiment conducted by the inventors, it was confirmed that depending on the conditions, ink may smear in regions of the recording medium that correspond to end regions of the platen in the main scanning direction of a carriage. As such, it has been desired to suppress the occurrence of a smear of ink in the regions of the recording medium that correspond to the end regions of the platen so as to achieve good printing quality. 
     SUMMARY 
     A printing apparatus according to the disclosure includes a support part configured to support a recording medium, a printing part configured to form an image by discharging ink to the recording medium supported by the support part while reciprocating in a main scanning direction, and a drying acceleration part configured to accelerate drying of the ink discharged by the printing part and applied on the recording medium in a state where the recording medium is supported by the support part, wherein a drying capacity of the drying acceleration part is set such that the drying capacity is higher in an end region of the support part than in a central region of the support part in a reciprocation direction of the printing part. 
     In the above-described printing apparatus, the reciprocation direction of the printing part and a transport direction of the recording medium may be parallel to each other. 
     In the above-described printing apparatus, the drying acceleration part may be a plurality of fixed fans disposed above the printing part in such a manner as to face the support part, and an air velocity of the fixed fan that is disposed at a position facing the end region of the support part may be greater than an air velocity of the fixed fan that is disposed at a position facing the central region of the support part. 
     In the above-described printing apparatus, the drying acceleration part may be a heater provided at the support part, and a heating temperature of the heater disposed in the end region of the support part may be higher than a heating temperature of the heater disposed in the central region of the support part. 
     In the above-described printing apparatus, the drying acceleration part may be a carriage fan disposed on both sides of a carriage in the reciprocation direction, the carriage being configured to support a print head and move in the main scanning direction, the print head being configured to discharge the ink, and the carriage fan may be set such that an air velocity in the end region of the support part is greater than an air velocity in the central region of the support part. 
     In the above-described printing apparatus, the drying acceleration part may be a carriage fan disposed on both sides of a carriage in the reciprocation direction, the carriage being configured to support a print head and move in the main scanning direction, the print head being configured to discharge the ink, an air velocity of the carriage fan disposed upstream in a transport direction of the recording medium may be changed such that the air velocity is small in an upstream end region, intermediate in the central region, and large in a downstream end region in the transport direction in the support part, and an air velocity of the carriage fan disposed downstream in the transport direction may be changed such that the air velocity is large in the upstream end region, intermediate in the central region, and small in the downstream end region. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic block view illustrating a configuration of a printing apparatus of an embodiment. 
         FIG. 2  is a schematic front view illustrating a configuration of the printing apparatus of the embodiment. 
         FIG. 3  is a schematic view illustrating raster lines formed in passes in a case of printing in eight passes in a printing operation (pass operation) of a printing unit. 
         FIG. 4  is a diagram illustrating a drying unit. 
         FIG. 5  is a diagram illustrating an air velocity distribution of a fixed blower. 
         FIG. 6  is a diagram illustrating an air velocity distribution of the fixed blower. 
         FIG. 7  is a diagram illustrating a heating temperature distribution of an upper surface of a platen. 
         FIG. 8  is a diagram illustrating a heating temperature distribution of the upper surface of the platen. 
         FIG. 9  is a simplified diagram illustrating magnitudes of air velocities of carriage fans on the front side and the rear side in a travel direction. 
         FIG. 10  is a simplified diagram illustrating magnitudes of air velocities of the carriage fans on the front side and the rear side in the travel direction. 
         FIG. 11  is a simplified diagram illustrating magnitudes of air velocities of the carriage fans on the front side and the rear side in the travel direction. 
         FIG. 12  is a table showing magnitudes of air velocities of the carriage fans in the case where printing is performed in six passes. 
         FIG. 13  is a table showing a suitable combinations of control conditions of a drying unit with respect to printing conditions. 
         FIG. 14  is a schematic view illustrating a degree of a smear in the case where drying of the related art is performed. 
     
    
    
     DESCRIPTION OF EXEMPLARY EMBODIMENTS 
     1. Embodiment 
     An embodiment of a printing apparatus  1  according to an embodiment of the disclosure will be described below with reference to the accompanying drawings. In this embodiment, the printing apparatus  1  is a printing apparatus  1  that transports a base material by a roll-to-roll system. An inkjet printer will be described as an example of the printing apparatus  1 . 
       FIG. 1  is a schematic block view illustrating a configuration of the printing apparatus  1  according to this embodiment.  FIG. 2  is a schematic front view illustrating a configuration of the printing apparatus  1  according to this embodiment. Note that the drawings are not drawn to scale. 
     For the sake of description, an XYZ coordinate system is used on the basis of a case where the printing apparatus  1  is placed on a horizontal surface. Specifically, the front-rear direction of the printing apparatus  1  is set as the X direction, the front direction or front side is set as the +X direction, and the rear direction or the rear side is set as the −X direction. The left-right direction that is orthogonal to the X direction of the printing apparatus  1  in the horizontal plane is set as the Y direction, the left direction or the left side is set as the −Y direction, and the right direction or the right side is set as the +Y direction. The direction that is orthogonal to the X direction and the Y direction of the printing apparatus  1 , or in other words, the direction orthogonal to the horizontal plane is set as the Z-direction, the upper direction or the upper side is set as the +Z direction, and the lower direction (gravity direction) or the lower side is set as the −Z direction. The directions are defined as described above and are appropriately used in the following description. 
     The printing apparatus  1  according to this embodiment prints an image by discharging ink as liquid to a roll sheet (continuous sheet) S as a recording medium. In addition, the printing apparatus  1  is communicably connected to a computer  2 , and the computer  2  creates print data for printing an image at the printing apparatus  1 . Note that the function of the computer  2  may be included in the printing apparatus  1 . 
     As illustrated in  FIG. 1 , the printing apparatus  1  includes a controller  10 , a feeding unit  20 , a transporting unit  30 , a printing unit  40 , a drying unit  50 , a winding unit  60 , and a detector group  70 . In addition, as illustrated in  FIG. 2 , the printing apparatus  1  includes a main body case  110  having a cuboid shape. The main body case  110  is broadly divided into three sections in the left-right direction, and may be sectioned as, from left to right, a feeding region  20 A, a printing region  40 A, and a winding region  60 A. 
     The controller  10  is a control unit configured to control the printing apparatus  1 . An interface  11  is configured to receive and/or transmit data between the computer  2  and the printing apparatus  1 . A CPU  12  is an arithmetic processing unit configured to perform overall control of the printing apparatus  1 . A memory  13  is configured to secure a work area and/or a storage area of a program of the CPU  12 . The CPU  12  controls each unit in accordance with a unit control circuit  14 . Note that the detector group  70  monitors the status inside the printing apparatus  1 , and on the basis of the detection results, the controller  10  controls each unit. 
     The feeding unit  20  is configured to feed the roll sheet S to the transporting unit  30 . As illustrated in  FIG. 2 , the feeding unit  20  includes a rotatably supported winding shaft  21  on which the roll sheet S is wound and a relay roller  22  configured to wind the roll sheet S fed from the winding shaft  21  and guide the roll sheet S to the transporting unit  30 . Note that the feeding unit  20  is located in the feeding region  20 A on the left side in the main body case  110 . 
     The transporting unit  30  transports the roll sheet S along a predetermined transport path R with a plurality of transport rollers. As the transport rollers, the transporting unit  30  includes a plurality of relay rollers  31   a  to  31   e , a supply roller  32  disposed upstream of a printing region P, and a discharge roller  33  disposed downstream of the printing region P. The roll sheet S moves through the plurality of transport rollers in sequence, and thus the transport path R for transporting the roll sheet S is formed. Note that the printing region P is a region where the print head  41  performs scanning movement and printing on the upper surface of a platen  48 . 
     The feed roller  32  and the discharge roller  33  are each composed of a pair of rollers. One of the paired rollers is driving rollers  32   a  and  33   a  that are rotated by a motor (not illustrated), and the other roller is driven rollers  32   b  and  33   b  that rotate in conjunction with the driving rollers. The feed roller  32  and the discharge roller  33  transport the roll sheet S by sandwiching the roll sheet S between the paired rollers. 
     The feed roller  32  and the discharge roller  33  transport the roll sheet S and supply the roll sheet S to the printing region P. The feed roller  32  and the discharge roller  33  temporarily stop the transport for a time period during which printing is performed on the portion of the roll sheet S in the printing region P. 
     When printing of an image for the roll sheet S located in the printing region P is completed, the feed roller  32  and the discharge roller  33  transport the portion of the roll sheet S on which the image has been printed from the printing region P to a drying furnace  58 , and supply, to the printing region P, a new portion of the roll sheet S where no image has been printed. In other words, the roll sheet S is intermittently transported in a unit of the printing region P. In the printing apparatus  1  according to this embodiment, the controller  10  (control unit) alternately repeats the operation of transporting roll sheet S of the transporting unit  30  and the image printing operation of the printing unit  40 . 
     The printing unit  40  as a printing part forms (prints) an image by discharging ink to the roll sheet S located in the printing region P while reciprocating in the main scanning direction. The printing unit  40  includes a print head  41  that performs printing by discharging ink in the printing region P, and a carriage  42  that supports the print head  41  and reciprocates in the main scanning direction (Y direction). 
     In addition, the printing unit  40  includes the platen  48  as a support part that supports the roll sheet S from the rear surface side. Note that the platen  48  sucks the roll sheet S to the upper surface of the platen  48  from the rear surface side with a suction mechanism (not illustrated) to thereby hold the roll sheet S on the platen  48  at a predetermined position and secure the printing region P. Note that the printing region P is set to a region within a range from the upstream end (left end) to the downstream end (right end) of the platen  48 , as a region where the print head  41  performs scanning movement. 
     The carriage  42  is configured to reciprocate in the main scanning direction (Y direction) together with the print head  41  along a carriage guide rail  45  (indicated by a two-dot chain line in  FIG. 2 ) extending in the Y direction in the printing region P when the carriage motor (not illustrated) is driven. As such, in this embodiment, the direction of the reciprocating movement (the main scanning direction) and the transport direction D of the roll sheet S are parallel to each other. 
     In addition, a head guide rail (not illustrated) extending in a line direction (X direction: the width direction of the roll sheet S) is provided at the carriage  42 , and the print head  41  is configured to move in the line direction (X direction) along the head guide rail when the carriage motor (not illustrated) is driven. Note that the scanning direction as the line direction is a sub-scanning direction. In this manner, the carriage  42  and the print head  41  can perform printing by reciprocating in the Y direction as the main scanning direction, and can move (to the next line) in the line direction (X direction) as the sub-scanning direction. 
     When performing the image printing operation of the printing unit  40 , the controller  10  temporarily stops the transport of the roll sheet S at the feed roller  32  and the discharge roller  33 . Then, the printing head  41  performs printing for one page by discharging ink to a portion of the stopped roll sheet S in the printing region P while reciprocating in the main scanning direction (Y direction) and moving in the sub-scanning direction (X direction). 
     Note that the method of discharging the ink from the nozzle in the printing operation may be a piezo method in which ink is discharged by applying a voltage to a driving element (piezoelectric element) so as to expand and contract the pressure chamber, or a thermal method in which air bubbles are generated in the nozzle using a heat generating element and ink is discharged using the air bubbles. 
     The drying unit  50  is configured as a drying acceleration part. The drying unit  50  is configured to promote the fixing of the image printed on the roll sheet S. Specifically, the drying unit  50  is configured to accelerate drying of the ink applied on the roll sheet S. In addition, the drying unit  50  (the drying unit  50  in a primary drying step) promotes drying of the ink in the state where the roll sheet S is supported by the platen  48 . The drying unit  50  includes a fixed blower  51  disposed above the printing unit  40  in such a manner as to face the platen  48 , a heater  52  provided at the platen  48 , and a carriage blower  53  provided at the carriage  42 . Note that the drying unit  50  will be described later. 
     The winding unit  60  is configured to wind the roll sheet S sent by the transporting unit  30  after the image printed on the roll sheet S is fixed to the roll sheet S at the drying unit  50 . The winding unit  60  includes relay rollers  61  and  62  that transport in a winding manner the roll sheet S fed from the discharge roller  33 , and a winding drive shaft  63  that winds the roll sheet S. Note that the winding unit  60  is located in the winding region  60 A on the right side in the main body case  110 . 
       FIG. 3  is a schematic view illustrating raster lines formed in passes in the case where printing is performed in eight passes in a printing operation (pass operation) of the printing unit  40 . 
     The operation of the printing unit  40  is further described. 
     The print head  41  is composed of 15 print heads  41   a  in this embodiment. The print head  41   a  includes a plurality of nozzle lines, with nozzles aligned in the line direction (X direction), in the Y direction in accordance with the number of colors. In the print head  41 ,  15  print heads  41   a  are disposed in a staggered form along the X direction. 
     The controller  10  operates such that the nozzle discharges ink while the print head  41  reciprocates in the main scanning direction (Y direction) so as to form a raster line along the main scanning direction (Y direction), and thus printing for one page is performed in the portion of the roll sheet S in the printing region P. Note that, specifically, when the print head  41  reciprocates in the main scanning direction (Y direction), the head is moved in the main scanning direction (+Y direction) on the forward path, and then the head is moved in the sub-scanning direction (X direction) for the movement to the next line, and thereafter, the head is moved in the main scanning direction (−Y direction) on the backward path. Note that the operation of forming a raster line along the main scanning direction (Y direction) by discharging ink from the nozzle while moving the print head  41  back and forth in the main scanning direction (Y direction) is referred to as an image recording pass, or simply, a pass. 
     With reference to  FIG. 3 , operations in the case where printing (bidirectional printing) using a plurality of passes (four passes, six passes, eight passes, or the like) are described. Specifically, in order to increase the resolution of the image in the line direction, printing is performed while moving the position of the print head  41  little by little in the line direction (sub-scanning direction) for each pass. Note that, for example, publicly known interlace (micro weave) printing is performed as the image forming method (printing method). 
     In  FIG. 3 , a nozzle line of the print head  41  (the print head  41   a ) is illustrated on the left side, and raster lines are formed by discharging ink from the nozzles while the print head  41  (the nozzle line) moves in the main scanning direction (Y direction). The position of the nozzles in the line direction of the print head  41   a  (the nozzle line) illustrated in  FIG. 3  is the position in the first pass, and when the print head  41   a  (the nozzle line) moves in the main scanning direction (in this case, the +Y direction) while maintaining this position, printing of the first pass is performed and three raster lines illustrated in the drawing (raster lines L 1  indicated as PASS  1  on the right end) are formed. Note that in  FIG. 3 , straight raster lines with no break are illustrated for the sake of concise illustration, but the raster line breaks when there is no print data. 
     Then, when the print head  41   a  (the nozzle line) moves in the sub-scanning direction (+X direction) and the print head  41   a  (the nozzle line) maintaining the position after the movement moves in the main scanning direction (in this case, the −Y direction), printing of the second pass is performed, and two raster lines illustrated in the drawing (raster lines L 2  indicated as PASS  2  on the right end) are formed. Note that since interlace (micro weave) printing is employed, the raster line L 2  adjacent to the raster line L 1  is formed by ink discharged from a nozzle different from the nozzle that discharges the ink for forming the raster line L 1 . Thereafter, the printing of third to eighth passes are performed through similar operations, and the remaining raster lines illustrated in the drawing (raster lines L 3  to L 8  indicated as PASS  3  to PASS  8  on the right end) are formed. 
     Note that in this embodiment, typical so-called bidirectional printing is performed. Bidirectional printing is a printing method in which in reciprocating movement in the main scanning direction, printing is performed on both the forward path and the backward path. In other words, the direction (in this case, the +Y direction as the forward path) in which the print head  41   a  (the nozzle line) moves during the printing of the first, third, fifth, and seventh passes, and the direction (in this case, the −Y direction as the backward path) in which the print head  41   a  (the nozzle line) moves during the printing of the second, fourth, sixth, and eighth passes are opposite to each other. 
     Note that in comparison with bidirectional printing, unidirectional printing is a printing method in which printing is performed only in one direction. Specifically, in unidirectional printing, printing is performed in the +Y direction as the forward path, while idle running is performed without performing the printing in the −Y direction as the backward path, and, such operations are repeated, for example. 
     The drying unit  50  is described. 
     As described above, the drying unit  50  is configured to accelerate drying of the ink applied on the roll sheet S to fix the image, and includes the fixed blower  51 , the heater  52 , and the carriage blower  53 . The drying unit  50  is configured to perform the primary drying step. 
     The primary drying step is a part of a step of fixing an image, and includes an operation of suppressing a smear by evaporating the moisture in the applied ink. The primary drying step is performed on the platen  48 . The primary drying step is performed with the fixed blower  51 , the heater  52 , and the carriage blower  53 . 
     A secondary drying step is a step of evaporating a component, such as a solvent component, other than moisture in the applied ink. The secondary drying step is performed with the drying furnace  58 . Note that since the solvent component has a higher boiling point than water, the solvent component is evaporated through the drying furnace  58  having a high temperature. In addition, there is ink containing a resin for fixing, and in the case where such ink is used, the resin is melted and fixed through the drying furnace  58 . By way of the drying unit  50  and the drying furnace  58 , the rear surface of the roll sheet S can be prevented from being soiled with the ink even when the roll sheet S that has been printed is wound on the winding unit  60 , and thus a high-quality printed material can be provided. 
       FIG. 14  is a schematic view illustrating a degree of a smear that is caused when drying of the related art is performed. Specifically, for the printing, an image for evaluation was arranged over the surface in the printing region P of the roll sheet, and bidirectional printing of four passes was performed. In addition, the result was obtained under printing conditions that are most likely to cause a smear, such as low temperature high humidity and a roll sheet composed of a material that dries slowly. 
     Here, in the printing region P of the roll sheet S, the region on the upstream side in the transport direction D is referred to as an upstream end region SA 1 , a region on the downstream side in the transport direction D is referred to as a downstream end region SA 3 , and a central region sandwiched between the upstream end region SA 1  and the downstream end region SA 3  is referred to as a central region SA 2 . In addition, a region of the platen  48  corresponding to the upstream end region SA 1  of the roll sheet S is referred to as an upstream end region  48 A, a region of the platen  48  corresponding to the central region SA 2  is referred to as a central region  48 B, and a region of the platen  48  corresponding to the downstream end region SA 3  is referred to as a downstream end region  48 C. 
     In  FIG. 14 , a region A where a smear of ink occurred is hatched. In addition, a region B where no smear of ink is recognized is illustrated as a blank. As illustrated in FIG.  14 , it is confirmed that, in the main scanning direction (Y direction) of the carriage  42 , no smear of ink occurred in the central region SA 2  of the roll sheet S, while a smear of ink (region A) occurred in the upstream end region SA 1  and the downstream end region SA 3  of the roll sheet S. 
     In the following description, the regions of the roll sheet S in the main scanning direction (Y direction) of the carriage  42  in the printing region P are described as the upstream end region SA 1 , the central region SA 2 , and the downstream end region SA 3 . 
       FIG. 4  is a diagram illustrating the drying unit  50 . 
     Hereinafter, the configurations and operations of the fixed blower  51 , the heater  52 , and the carriage blower  53  serving as the drying unit  50  serving as the drying acceleration part for performing the primary drying step are described. The drying unit  50  is configured to accelerate drying of the ink discharged by the print head  41  and applied on the roll sheet S in the state where the roll sheet S is supported by the platen  48 . 
     First, the fixed blower  51  is described. 
     As illustrated in  FIG. 4 , the fixed blower  51  is disposed above the platen  48 , the carriage  42  and the print head  41  serving as the printing part in such a manner as to face the platen  48  on the inner surface side of the top surface of the main body case  110 . The fixed blower  51  is composed of a plurality of axial fans. Note that the fixed blower  51  is disposed in such a manner as to cover the printing region P in plan view such that the blowing direction is perpendicular to the roll sheet S on the platen  48  in the state where each rotation axis direction is aligned with the perpendicular direction. The fixed blower  51  sucks the outside air from an opening (not illustrated) that opens at the top surface of the main body case  110  via a filter (not illustrated), and discharges the air in the direction perpendicular to the roll sheet S. 
     Specifically, in plan view, the fixed blower  51  has a configuration of two lows and eight columns (two axial fans arranged in the X direction and eight axial fans arranged in the Y direction), and thus includes a total of 16 axial fans arranged therein. Note that the 16 axial fans have the same specification. The axial fans are controlled by the controller  10  such that, with the two axial fans arranged in the X direction as one unit, the control (the control of the drive voltage) of the eight units of the axial fans arranged in the Y direction are independently performed. The axial fans of eight units are referred to as fixed fans  51   a  to  51   h  in the order from the upstream side in the transport direction D of the roll sheet S. In this embodiment, the fixed fans  51   a  to  51   h  serving as the eight units uniformly cover the printing region P of the roll sheet S in plan view. 
       FIGS. 5 and 6  are diagrams illustrating air velocity distributions of the fixed blower  51 . Specifically,  FIGS. 5 and 6  are diagrams illustrating air velocity distributions that indicate air velocities of the fixed fans  51   a  to  51   h  in the case where the fixed blower  51  is driven for each unit, as sheet-surface air velocities at the roll sheet S. Note that the sheet-surface air velocity refers to the air velocity at or near the sheet surface of the roll sheet S located in the printing region P. In this embodiment, as illustrated in  FIGS. 5 and 6 , the controller  10  controls the air velocity of the fixed blower  51  under air velocity distribution conditions of two types. 
     The air velocity distribution illustrated in  FIG. 5  is a distribution that is controlled such that the sheet-surface air velocities of the fixed fans  51   a  to  51   h  are even sheet-surface air velocities (even airflow rates). Accordingly, during the printing operation of the carriage  42 , the fixed blower  51  blows airflow of even air velocities (even airflow rates) toward the roll sheet S in the printing region P all over the upstream end region SA 1 , the central region SA 2 , and the downstream end region SA 3  in the roll sheet S. Note that this air velocity distribution is the same as that of the related art. 
     Note that the air velocity distribution of the fixed blower  51  illustrated in  FIG. 5  is referred to as an air velocity control condition (1). 
     Through the operation of the fixed blower  51  under the air velocity control condition (1), the moisture in the ink is evaporated with the airflow of the uniform sheet-surface air velocities (uniform airflow rates) in the upstream end region SA 1 , the central region SA 2 , and the downstream end region SA 3  of the printing region P of the roll sheet S. 
     The air velocity distribution illustrated in  FIG. 6  is controlled such that in the roll sheet S of the printing region P, the sheet-surface air velocity (airflow rate) of the fixed fan  51   a  facing the upstream end region SA 1  is highest (largest) and that the sheet-surface air velocity (airflow rate) gradually decreases in the order of the fixed fans  51   b  and  51   c  toward the fixed fans  51   d  and  51   e  of the central region SA 2 . Further, the air velocity distribution illustrated in  FIG. 6  is controlled such that the sheet-surface air velocity (airflow rate) of the fixed fan  51   h  facing the downstream end region SA 3  is highest (largest) and that the sheet-surface air velocity (airflow rate) gradually decreases in the order of the fixed fans  51   g  and  51   f  toward the fixed fans  51   d  and  51   e  of the central region SA 2 . Note that the sheet-surface air velocity (airflow rate) of the fixed fans  51   d  and  51   e  is equal to the sheet-surface air velocity (airflow rate) of the even sheet-surface air velocities (airflow rates) illustrated in  FIG. 5 . 
     That is, in the air velocity distribution in  FIG. 6 , the air velocities of the fixed fans  51   a  to  51   c  facing the upstream end region SA 1  and the fixed fans  51   f  to  51   h  facing the downstream end region SA 3  are greater than the air velocity of the fixed fans  51   d  and  51   e  facing the central region SA 2  in the roll sheet S of the printing region P. In other words, in the distribution, the air velocities of the fixed fans  51   a  to  51   c  and the fixed fans  51   f  to  51   h  facing the upstream end region  48 A and the downstream end region  48 C of the platen  48  are greater than the air velocity of the fixed fans  51   d  and  51   e  facing the central region  48 B. To put it another way, in the drying unit  50  (fixed blower  51 ) serving as the drying acceleration part, the drying capacities are set such that the drying capacities of the upstream end region  48 A and the downstream end region  48 C serving as the end regions of the platen  48  are higher than that of the central region  48 B of the platen  48 . 
     Note that the air velocity distribution of the fixed blower  51  illustrated in  FIG. 6  is referred to as an air velocity control condition (2). 
     In the upstream end region SA 1  and the downstream end region SA 3 , where a smear of the ink easily occur, of the roll sheet S in the printing region P, the moisture in the ink can be evaporated and dried with the airflow of a sheet-surface air velocity (larger airflow rate) higher than that of the central region SA 2  through the operation of the fixed blower  51  under the air velocity control condition (2) in the upstream end region SA 1  and the downstream end region SA 3 . 
     Next, the heater  52  is described. 
     The platen  48  where the heater  52  is disposed has a rectangular shape, and is composed of a member having a high thermal conductivity such as aluminum having a thickness of 10 mm, for example. As illustrated in  FIG. 4 , the heater  52  is disposed in the lower surface of the platen  48 , and is composed of an upstream heater  52   a  for heating the upstream end region  48 A of the platen  48 , a central heater  52   b  for heating the central region  48 B, and a downstream heater  52   c  for heating the downstream end region  48 C. A nichrome wire may be used as the heater  52 , for example. 
     The platen  48  is provided with a temperature sensor (not illustrated) included in the detector group  70  that respectively detects the temperatures of the upstream heater  52   a , the central heater  52   b , and the downstream heater  52   c . Thus, with the controller  10 , they are independently controlled to respective set temperatures. 
       FIGS. 7 and 8  are diagrams illustrating heating temperature distributions of the upper surface of the platen  48 . Specifically,  FIGS. 7 and 8  are diagrams illustrating the heating temperature distributions of the upper surface of the platen  48  when the three heaters are driven. Note that the heating temperature of the upper surface of the platen  48  can be replaced with the sheet-surface heating temperature of the roll sheet S located on the upper surface. In this embodiment, as illustrated in  FIGS. 7 and 8 , the controller  10  controls the temperature of the heater  52  in the heating temperature distribution of two types. 
     The heating temperature distribution of the upper surface of the platen  48  illustrated in  FIG. 7  is a distribution that is controlled such that the heating temperatures of the three heaters  52  (the upstream heater  52   a , the central heater  52   b , and the downstream heater  52   c ) are all set to a constant heating temperature. Thus, during the printing operation of the carriage  42 , the upstream heater  52   a , the central heater  52   b , and the downstream heater  52   c  heat (warm) the roll sheet S at a constant heating temperature across the upstream end region SA 1 , the central region SA 2 , and the downstream end region SA 3 . Note that this heating temperature distribution is the same as that of the related art. 
     Note that the heating temperature distribution of the heater  52  illustrated in  FIG. 7  is referred to as a heating temperature control condition (1). 
     Through the operation of the heater  52  under the heating temperature control condition (1), the moisture in the ink are evaporated by heating (warming) the roll sheet S at a constant heating temperature in the upstream end region SA 1 , the central region SA 2 , and the downstream end region SA 3  of the roll sheet S in the printing region P. 
     The heating temperature distribution of the upper surface of the platen  48  illustrated in  FIG. 8  is a distribution in which, in the three heaters  52 , the heating temperature of the upstream heater  52   a  and the downstream heater  52   c  is higher than the heating temperature of the central heater  52   b . In other words, the heaters  52  (the upstream heater  52   a  and the downstream heater  52   c ) disposed in the upstream end region  48 A and the downstream end region  48 C serving as the end regions of the platen  48  are set to a heating temperature higher than the heating temperature of the heater  52  (the central heater  52   b ) disposed in the central region  48 B of the platen  48 . To put it another way, in the drying unit  50  (the heater  52 ) serving as the drying acceleration part, the drying capacity in the upstream end region  48 A and the downstream end region  48 C serving as the end regions of the platen  48  is higher than the drying capacity in the central region  48 B of the platen  48 . Note that the heating temperature of the central heater  52   b  in this case is equal to the temperature of the heating temperature control condition (1) illustrated in  FIG. 7 . 
     A heating temperature higher than the heating temperature of the central heater  52   b  is set to the upstream heater  52   a  and the downstream heater  52   c . However, since a temperature gradient results between the upstream end region  48 A and the central region  48 B and between the central region  48 B and the downstream end region  48 C in the platen  48 , a distribution including an inclination of the heating temperature is set as illustrated in  FIG. 8 . 
     Note that the heating temperature distribution of the heater  52  illustrated in  FIG. 8  is referred to as a heating temperature control condition (2). 
     Through the operation of the heater  52  under the heating temperature control condition (2), the heating temperature of the upstream end region SA 1  and the downstream end region SA 3  becomes higher than the heating temperature of the central region SA 2  in the roll sheet S in the printing region P, and thus the moisture in the ink can be evaporated in the upstream end region SA 1  and the downstream end region SA 3  where a smear of the ink easily occurs. 
     Next, the carriage blower  53  is described. 
     As illustrated in  FIG. 4 , the carriage blower  53  is disposed at a position at a center in the X direction on both sides in the Y direction, which is the reciprocating movement direction of the carriage  42 . Regarding the carriage blower  53 , the carriage blower  53  disposed upstream in the transport direction D is referred to as a carriage fan  53   a , and the carriage blower  53  disposed downstream in the transport direction D is referred to as a carriage fan  53   b . The carriage blower  53  is configured using an axial fan. The two carriage fans,  53   a  and  53   b , have the same configuration. 
     The carriage fan  53   a  is disposed such that the carriage fan  53   a  is inclined to face slightly upstream from the upstream end of the carriage  42 , rather than blowing air in the direction perpendicular to the upper surface of the platen  48 . In addition, the carriage fan  53   b  is also disposed such that the blowing direction is inclined to face slightly downstream from the downstream end of the carriage  42 , rather than blowing air in the direction in the direction perpendicular to the upper surface of the platen  48 . 
     In other words, the carriage fans  53   a  and  53   b  are oriented outward in the Y direction of the carriage  42  such that the blowing directions do not affect the application position of the ink of the print head  41  disposed on the inner side of the carriage  42 . Note that in  FIG. 4 , the directions of the air blown from the carriage fans  53   a  and  53   b  are indicated by arrows. 
     The carriage fans  53   a  and  53   b  are disposed in the carriage  42  in the above-mentioned manner, and thus the carriage fans  53   a  and  53   b  are configured to send air toward the roll sheet S supported by the platen  48  while moving along with the movement of the carriage  42  (print head  41 ) in the main scanning direction and the sub-scanning direction. 
     Here, the air velocity of the airflow discharged from the carriage fan  53   a  is referred to as an air velocity Va, and the air velocity of the airflow discharged from the carriage fan  53   b  is referred to as an air velocity Vb. In this embodiment, the controller  10  controls the air velocities Va and Vb under air velocity control conditions of three types described later. 
       FIGS. 9 to 11  are simplified diagrams illustrating magnitudes of the air velocities Va and Vb of the carriage fans  53   a  and  53   b  disposed in the carriage  42 .  FIG. 12  is a table showing magnitudes of the air velocities Va and Vb of the carriage fans  53   a  and  53   b  in the case where printing is performed in six passes. 
     The carriage  42  reciprocates in the Y direction (the main scanning direction). In the reciprocation direction, the travel direction of the carriage  42  in the +Y direction is referred to as a forward direction. The travel direction of the carriage  42  in the −Y direction is referred to as a backward direction. 
       FIG. 9  illustrates a state where the air velocities Va and Vb of the two carriage fans  53   a  and  53   b  disposed in the carriage  42  are both set to an intermediate level regardless of the travel direction. Accordingly, the controller  10  performs control of setting the air velocities Va and Vb of the carriage fans  53   a  and  53   b  to the intermediate level in the forward direction and the backward direction in the reciprocation direction of the carriage  42 . Note that this air velocity control is the same as that of the related art. 
     Note that, the control of the air velocities Va and Vb of the carriage fans  53   a  and  53   b  at the air velocity illustrated in  FIG. 9  is referred to as an air velocity control condition (1). 
     Through the operation of the carriage fans  53   a  and  53   b  under the air velocity control conditions (1), the moisture in the discharged ink is evaporated by setting the air velocities Va and Vb of the carriage fans  53   a  and  53   b  on the front and rear sides of the carriage  42  in the travel direction to the intermediate level. 
       FIGS. 10 and 11  illustrate a state where the air velocity Va or Vb of the carriage fan  53   a  or the carriage fan  53   b  on the rear side in the travel direction is set to a value greater than that of the air velocity Va or Vb of the carriage fan  53   a  or the carriage fan  53   b  on the front side in the travel direction. Specifically,  FIG. 10  illustrates a state where, when the travel direction is the forward direction (+Y direction) in the reciprocation direction of the carriage  42 , the air velocity Va of the carriage fan  53   a  on the rear side in the travel direction is set to a value greater than that of the air velocity Vb of the carriage fan  53   b  on the front side in the travel direction. Accordingly, in the forward direction in the reciprocation direction of the carriage  42 , the controller  10  performs control of setting the air velocity Va of the carriage fan  53   a  on the rear side in the travel direction to a value greater than that of the air velocity Vb of the carriage fan  53   b  on the front side in the travel direction. 
       FIG. 11  illustrates a state where, when the travel direction is in the backward direction (−Y direction) in the reciprocation direction of the carriage  42 , the air velocity Vb of the carriage fan  53   b  on the rear side in the travel direction is set to a value greater than that of the air velocity Va of the carriage fan  53   a  on the front side in the travel direction. Accordingly, in the backward direction in the reciprocation direction of the carriage  42 , the controller  10  performs control of setting the air velocity Vb of the carriage fan  53   b  on the rear side in the travel direction to a value greater than that of the air velocity Va of the carriage fan  53   a  on the front side in the travel direction. In other words, with respect to the carriage fan  53   b  disposed downstream in the transport direction D of the roll sheet S, the carriage fan  53   a  disposed upstream in the transport direction D is set to have a larger air velocity when the travel direction of the carriage  42  is the forward direction (Va&gt;Vb) and have a smaller air velocity when the travel direction is the backward direction (Va&lt;Vb). 
     Note that the control of the air velocities Va and Vb of the carriage fans  53   a  and  53   b  at the air velocities illustrated in  FIGS. 10 and 11  is referred to as an air velocity control condition (2). 
     Through the operation of the carriage fans  53   a  and  53   b  under the air velocity control condition (2), the moisture in the ink can be efficiently evaporated and dried by controlling the air velocity Va or Vb of the carriage fan  53   b  or the carriage fan  53   a  on the rear side in the travel direction to a value greater than that of the air velocity Va or Vb of the carriage fan  53   a  or the carriage fan  53   b  on the front side in the travel direction in the forward direction and the backward direction. In addition, with the difference (large or small) provided between the magnitude of the air velocity of the carriage fan on the rear side in the travel direction and the magnitude of the air velocity of the carriage fan on the front side in the travel direction, it is possible to efficiently evaporate the moisture in the ink at low power consumption. 
       FIG. 12  shows magnitudes of the air velocities Va and Vb in the travel direction of the carriage fans  53   a  and  53   b  in each pass in the case where printing is performed in six passes, for example.  FIG. 12  shows magnitudes of the air velocities Va and Vb in the travel direction of the carriage fans  53   a  and  53   b  in each pass in the case where, among the printing conditions in  FIG. 13  described later, printing is performed in three or more passes in bidirectional printing. 
     As shown in  FIG. 12 , the carriage fans  53   a  and  53   b  change the magnitudes of the air velocities Va and Vb among the upstream end region  48 A, the central region  48 B, and the downstream end region  48 C of the platen  48 . Note that the upstream end region  48 A, the central region  48 B, and the downstream end region  48 C of the platen  48  correspond to the upstream end region SA 1 , the central region SA 2 , and the downstream end region SA 3  in the printing region P of the roll sheet S. 
     As shown in  FIG. 12 , in the first pass, third pass, and fifth pass, the travel direction of the printing is the forward direction (+Y direction) with the carriage fan  53   a  serving as the carriage fan on the rear side in the travel direction and the carriage fan  53   b  serving as the carriage fan on the front side in the travel direction. In addition, as shown in  FIG. 12 , in the second pass, fourth pass, and sixth pass, the travel direction of the printing is the backward direction (−Y direction) with the carriage fan  53   a  serving as the carriage fan on the front side in the travel direction and the carriage fan  53   b  serving as the carriage fan on the rear side in the travel direction. 
     As shown in  FIG. 12 , in the printing of the first pass, the air velocity Va of the carriage fan  53   a  on the rear side in the travel direction is set to “small”, and the air velocity Vb of the carriage fan  53   b  on the front side in the travel direction is set to “stop” in the upstream end region  48 A. In the central region  48 B, the air velocity Va of the carriage fan  53   a  is set to “intermediate”, and the air velocity Vb of the carriage fan  53   b  is set to “stop”. In addition, in the downstream end region  48 C, the air velocity Va of the carriage fan  53   a  is set to “large”, and the air velocity Vb of the carriage fan  53   b  is set to “stop”. 
     In other words, the air velocity of the carriage fan  53   a  of the first pass is changed such that the air velocity is small in the upstream end region  48 A, intermediate in the central region  48 B, and large in the downstream end region  48 C. 
     The reason for setting the air velocity Vb of the carriage fan  53   b  to “stop” all over the platen  48  is that there is no ink droplets in the blowing direction of the carriage fan  53   b  on the front side in the travel direction because of the printing of the first pass. In addition, the reason for changing the air velocity Va of the carriage fan  53   a  on the rear side in the order of “small”, “intermediate”, and “large” is that the time until the ink discharged in the second pass hits on the ink applied in the first pass decreases in the order of the upstream end region  48 A, the central region  48 B, and the downstream end region  48 C. Specifically, in order to prevent occurrence of a smear when the ink discharged in the second pass hits the ink applied in the first pass due to insufficient drying of the ink in the lower layer in the hitting of the ink in the second pass, the ink printed in the first pass is dried such that the drying capacity of the carriage fan  53   a  is changed by changing the air velocity Va of the carriage fan  53   a  in accordance with the time until the ink discharged in the second pass hits. In the upstream end region  48 A, there is a sufficient time until the ink discharged in the second pass hits, and therefore the ink applied in the first pass can be dried until the ink discharged in the second pass hits even with the “small” air velocity of the carriage fans  53   a . In the downstream end region  48 C, the time until the ink discharged in the second pass hits is insufficient, and therefore the air velocity of the carriage fan  53   a  is set to “large” to increase the drying capacity of the carriage fan  53   a  such that the ink applied in the first pass is dried before the ink discharged in the second pass hits so as to prevent occurrence of a smear. 
     When printing is performed in the second pass, first, the carriage  42  after completion of the printing of the first pass moves downstream in the forward direction past the downstream end region  48 C of the platen  48 , and then moves in the sub-scanning direction to switch the travel direction to the backward direction, and thereafter, performs printing of the second pass. As shown in  FIG. 12 , in the printing of the second pass, the air velocity Va of the carriage fan  53   a  on the front side in the travel direction is set to “large”, and the air velocity Vb of the carriage fan  53   b  on the rear side in the travel direction is set to “small” in the downstream end region  48 C. In addition, in the central region  48 B, the air velocity Va of the carriage fan  53   a  is set to “intermediate”, and the air velocity Vb of the carriage fan  53   b  is also set to “intermediate”. In addition, in the upstream end region  48 A, the air velocity Va of the carriage fan  53   a  is set to “small” and the air velocity Vb of the carriage fan  53   b  is set to “large”. 
     In other words, the air velocity of the carriage fan  53   a  in the second pass is changed such that the air velocity is small in the upstream end region  48 A, intermediate in the central region  48 B, and large in the downstream end region  48 C. In other words, the air velocity of the carriage fan  53   b  in the second pass is changed such that the air velocity is large in the upstream end region  48 A, intermediate in the central region  48 B, and small in the downstream end region  48 C. 
     When printing is performed by switching the travel direction of the carriage  42  from the first pass to the second pass, the time interval between the printing of the first pass and the printing of the second pass is short, that is, the time interval between the passes is short, in the downstream end region  48 C. As such, depending on the property of the ink, the environmental condition and the printing condition, the moisture in the ink may not sufficiently evaporate within the period until the next pass, and then, a smear of the ink may occur. In view of this, in the first pass, when the carriage  42  switches the travel direction, the air velocity Va of the carriage fan  53   a  on the rear side in the travel direction is set to “large” in order to increase the air velocity of the air sent toward the downstream end region  48 C. In addition, in the second pass, the air velocity Va of the carriage fan  53   a  on the front side in the travel direction is set to “large”. In this manner, the drying capacity of the ink can be improved even in the case where the time interval between the printing of the first pass and the printing of the second pass is short. Note that, in the second pass, the air velocity Va of the carriage fan  53   a  on the front side in the travel direction is set to “large” in the downstream end region  48 C to improve the drying capacity for the ink applied in the first pass. Further, regarding the air velocity Vb of the carriage fan  53   b  that is on the rear side in the travel direction and passes over the ink discharged and applied in the second pass on the ink applied in the first pass, there is a sufficient time until the ink discharged in the third pass hits on the ink applied in the second pass, and therefore the ink can be dried even with a “small” air velocity Vb without causing a smear. Therefore, the power consumption can be reduced by setting the air velocity Vb to “small”. 
     When printing is performed in the third pass, first, the carriage  42  after completion of the printing of the second pass moves upstream in the backward direction past the upstream end region  48 A of the platen  48 , and then moves in the sub-scanning direction to switch the travel direction to the forward direction, and thereafter, performs printing of the third pass. 
     In the printing apparatus  1 , a cleaning unit (not illustrated) for cleaning of the print head  41 , a flushing unit (not illustrated) for performing a flushing operation by discharging ink from the nozzle of each print head  41 , and the like are disposed upstream (−Y direction) of the platen  48 . Then, after the printing of any of the second pass, fourth pass, or sixth pass is performed, the carriage  42  is moved to the above-mentioned units to perform cleaning and flushing of the print head  41 . 
     As shown in  FIG. 12 , in the printing of the third pass, the air velocity Va of the carriage fan  53   a  on the rear side in the travel direction is set to “small”, and the air velocity Vb of the carriage fan  53   b  on the front side in the travel direction is set to “large” in the upstream end region  48 A. In addition, in the central region  48 B, the air velocity Va of the carriage fan  53   a  is set to “intermediate”, and the air velocity Vb of the carriage fan  53   b  is also set to “intermediate”. In addition, in the downstream end region  48 C, the air velocity Va of the carriage fan  53   a  is set to “large” and the air velocity Vb of the carriage fan  53   b  is set to “small”. 
     In other words, the air velocity of the carriage fan  53   a  in the third pass is changed such that the air velocity is small in the upstream end region  48 A, intermediate in the central region  48 B, and large in the downstream end region  48 C. In other words, the air velocity of the carriage fan  53   b  in the third pass is changed such that the air velocity is large in the upstream end region  48 A, intermediate in the central region  48 B, and small in the downstream end region  48 C. 
     When printing is performed by switching the travel direction of the carriage  42  from the second pass to the third pass, the time interval between the printing of the second pass and the printing of the third pass is short, that is, the time interval between the passes is short, in the upstream end region  48 A. As such, depending on the property of the ink, the environmental condition and the printing condition, the moisture in the ink may not sufficiently evaporate within the period until the next pass, and then, a smear of the ink may occur. In view of this, in the second pass, when the carriage  42  switches the travel direction, the air velocity Vb of the carriage fan  53   b  on the rear side in the travel direction is set to “large” in order to increase the air velocity of the air sent toward the upstream end region  48 A. In addition, in the third pass, the air velocity Vb of the carriage fan  53   b  on the front side in the travel direction is set to “large”. In this manner, the drying capacity of the ink can be improved even in the case where the time interval between the printing of the second pass and the printing of the third pass is short. Note that, in the third pass, the air velocity Vb of the carriage fan  53   b  on the front side in the travel direction is set to “large” in the upstream end region  48 A to improve the drying capacity for the ink applied in the second pass. Further, regarding the air velocity Va of the carriage fan  53   a  that is on the rear side in the travel direction and passes over the ink discharged and applied in the third pass on the ink applied in the second pass, there is a sufficient time until the ink discharged in the fourth pass hits on the ink applied in the third pass, and therefore the ink can be dried even with a “small” air velocity Va without causing a smear. Therefore, the power consumption can be reduced by setting the air velocity Va to “small”. 
     When printing is performed in the fourth pass, first, the carriage  42  after completion of the printing of the third pass moves downstream in the forward direction past the downstream end region  48 C of the platen  48 , and then moves in the sub-scanning direction to switch the travel direction to the backward direction, and thereafter, performs printing of the fourth pass. As shown in  FIG. 12 , in the printing of the fourth pass, the air velocity Va of the carriage fan  53   a  on the front side in the travel direction is set to “large”, and the air velocity Vb of the carriage fan  53   b  on the rear side in the travel direction is set to “small” in the downstream end region  48 C. In addition, in the central region  48 B, the air velocity Va of the carriage fan  53   a  is set to “intermediate”, and the air velocity Vb of the carriage fan  53   b  is also set to “intermediate”. In addition, in the upstream end region  48 A, the air velocity Va of the carriage fan  53   a  is set to “small” and the air velocity Vb of the carriage fan  53   b  is set to “large”. This setting is the same as the printing state of the second pass. 
     The air velocity of the carriage fan  53   a  in the fourth pass is the same as that of the second pass, and therefore the description thereof is omitted. In addition, the printing performed in the fifth pass and the sixth pass is the same as the printing in the third pass and the fourth pass, and therefore the description thereof is omitted. 
     Note that the control of the air velocities Va and Vb of the carriage fans  53   a  and  53   b  at the air velocities shown in  FIG. 12  is referred to as an air velocity control condition (3). 
     In the case where the carriage  42  switches the travel direction through the operation of the carriage fans  53   a  and  53   b  under the air velocity control conditions (3), the air velocity of the carriage fan disposed on the rear side in the travel direction is set to a value larger than that of the carriage fan disposed on the front side in the travel direction in the upstream end region  48 A or the downstream end region  48 C before the switching. In addition, in the upstream end region  48 A or the downstream end region  48 C after the switching, the air velocity of the carriage fan disposed on the front side in the travel direction is set to a value larger than that of the carriage fan disposed on the rear side in the travel direction. In other words, the drying unit  50  (the carriage blower  53 ) as the drying acceleration part is set such that, under the air velocity control condition (3), the drying capacity in the upstream end region  48 A and the downstream end region  48 C that are the end regions of the platen  48  is higher than the drying capacity in the central region  48 B of the platen  48 . 
     Through the operation of the carriage fans  53   a  and  53   b  under the air velocity control condition (3), the moisture in the ink can be efficiently evaporated and dried in the upstream end region  48 A or the downstream end region  48 C before and after the switching of the travel direction. In addition, with the difference (large, intermediate, small) provided between the magnitudes of the air velocities of the carriage fan, it is possible to efficiently evaporate the moisture in the ink at low power consumption. 
       FIG. 13  is a table showing suitable combinations of the control conditions of the drying unit  50  as the drying acceleration part for the printing conditions. Note that in  FIG. 13 , the combinations of control conditions for the printing conditions are described below as combinations A to F. 
     As shown in  FIG. 13 , the printing conditions are divided into unidirectional printing and bidirectional printing. The number of passes in the printing conditions indicates a minimum number of printing for completing the printing in both the unidirectional printing and the bidirectional printing. 
     As described above, the unidirectional printing is a printing method in which printing is performed only in one direction. Specifically, in the unidirectional printing in this embodiment, printing is performed through the movement in the +Y direction as the forward direction of the travel direction, while idle running is performed without performing the printing in the −Y direction as the backward direction. Such operations are repeated in the printing of the second and subsequent passes. 
     The bidirectional printing is a printing method in which printing is performed in both the forward direction and the backward direction of the travel direction by reciprocating in the main scanning direction. 
     As shown in the printing conditions of  FIG. 13 , “unidirectional printing and one pass” means printing that is completed by performing printing in one movement in the +Y direction as the forward direction. In addition, in “unidirectional printing and two or more passes”, the printing of the first pass is performed through the movement in the +Y direction as the forward direction, and it is turned back in the backward direction while performing idle running. Thereafter, the carriage  42  is moved in the sub-scanning direction (X direction). Thereafter, the printing of the second pass is performed through the movement in the +Y direction as the forward direction. Thereafter, in the backward direction, it is turned back while performing idle running. By repeating such operations for two or more passes, the printing is completed. 
     As shown in the printing conditions of  FIG. 13 , “bidirectional printing and two passes” means printing in which the printing of the first pass is performed through the movement in the +Y direction as the forward direction, and then moved in the sub-scanning direction (X direction), and thereafter, the printing is completed by performing the printing of the second pass through the movement in the −Y direction as the backward direction. In addition, “bidirectional printing and three or more passes” means printing in which the printing is completed in three or more passes by continuing the above-described printing of two or more passes. 
     In the combination A, with the printing condition “unidirectional printing and one pass”, the air velocity control condition of the fixed blower  51  is set to (1) or (2), and the heating temperature control condition of the heater  52  is set to (1) or (2). In this case, by selecting (2) in any of the control conditions, the drying capacity in the upstream end region SA 1  and the downstream end region SA 3  of the roll sheet S can be improved, and the time from the end of printing to the end of drying and the start of transport of the roll sheet S can be shortened. In addition, in the combination A, the air velocity control condition of the carriage blower  53  is set to (1) or (2). In this case, drying can be efficiently performed by selecting (2) as the air velocity control condition. 
     In the combination B, with the printing condition “unidirectional printing and two or more passes”, the air velocity control condition of the fixed blower  51  is set to (1), the heating temperature control condition of the heater  52  is set to (1), and the air velocity control condition of the carriage blower  53  is set to (1). In this case, since printing in the backward direction is not performed, the time for drying can be ensured, and drying can be achieved with no problems even when each control condition is set to (1). 
     In the combination C, with the printing condition of “bidirectional printing and two passes”, the air velocity control condition of the fixed blower  51  is set to (1) and the heating temperature control condition of the heater  52  is set to (1). In addition, in the combination C, the air velocity control condition of the carriage blower  53  is set to (2) or (3). In this case, printing in the forward direction and the backward direction is performed once, and therefore, in the downstream end region  48 C of the platen  48 , the time interval between the printing of the first pass and the printing of the second pass as a result of the switching of the travel direction is short, and, sufficient drying cannot be performed. However, since the air velocity control condition is set to (2) or (3), drying can be achieved even with the air velocity control condition set to (1) and the heating temperature control conditions set to (1). While the air velocity control condition may be set to (2), more efficient drying can be performed by selecting (3). In addition, while the amount of ink per unit area is large in the printing performed in two passes, the drying, even in such a case, can be performed by selecting the above-mentioned control conditions. In addition, since the drying can be performed by selecting the efficient control conditions, the consumption of the power for driving the drying unit  50  can be reduced. 
     In the combination D, with the printing condition of “bidirectional printing and two passes”, the air velocity control condition of the fixed blower  51  is set to (1) and the heating temperature control condition of the heater  52  is set to (2). In addition, in the combination D, the air velocity control condition of the carriage blower  53  is set to (2) or (3). In this case, as with the combination C, in the downstream end region  48 C of the platen  48 , the time interval between the printing of the first pass and the printing of the second pass as a result of the switching of the travel direction is short and sufficient drying cannot be performed. However, by setting the air velocity control condition of the carriage blower  53  to (2) or (3) and setting the heating temperature control condition to (2), the drying capacity can be further improved than the combination C. While the air velocity control condition may be set to (2), more efficient drying can be performed by selecting (3). In addition, while the amount of ink per unit area is large in the printing performed in two passes, the drying, even in such a case, can be performed by selecting the above-mentioned control conditions. In addition, since the drying can be performed by selecting the efficient control conditions, the consumption of the power for driving the drying unit  50  can be reduced, although not as much as the combination C. 
     In the combination E, with the printing condition of “bidirectional printing and three or more passes”, the air velocity control condition of the fixed blower  51  is set to (2) and the heating temperature control condition of the heater  52  is set to (1). In addition, in the combination E, the air velocity control condition of the carriage blower  53  is set to (2) or (3). In this case, in the downstream end region  48 C and the upstream end region  48 A of the platen  48 , the time interval between printing in the forward pass and the printing in the backward pass as a result of the switching of the travel direction is short, and sufficient drying cannot be performed. However, by setting the air velocity control condition of the carriage blower  53  to (2) or (3) and setting the air velocity control condition of the fixed blower  51  to (2), the drying capacity can be improved for printing of three or more passes even when the heating temperature control condition is set to (1). While the air velocity control condition may be set to (2), more efficient drying can be performed by selecting (3). In addition, since the drying can be performed by selecting the efficient control conditions, the consumption of the power for driving the drying unit  50  can be reduced for printing of three or more passes. In addition, since efficient drying can be performed, high-speed printing can be achieved. 
     In the combination F, with the printing condition of “bidirectional printing and three or more passes”, the air velocity control condition of the fixed blower  51  is set to (2) and the heating temperature control condition of the heater  52  is set to (2). In addition, in the combination F, the air velocity control condition of the carriage blower  53  is set to (2) or (3). In this case, as with the combination E, in the downstream end region  48 C and the upstream end region  48 A of the platen  48 , the time interval between printing of the forward pass and the printing of the backward pass as a result of the switching of the travel direction is short, and sufficient drying cannot be performed. However, by setting the air velocity control condition of the carriage blower  53  to (2) or (3) and the air velocity control condition of the fixed blower  51  to (2), and, the heating temperature control condition to (2), the drying capacity can be further improved. While the air velocity control condition may be set to (2), more efficient drying can be performed by selecting (3). In addition, since the drying can be performed by selecting the efficient control conditions, the consumption of the power for driving the drying unit  50  can be reduced for three or more passes, although not as much as the combination E. In addition, since efficient drying can be performed, further high-speed printing can be achieved. 
     Note that, the present disclosure is not limited to the embodiments described above, and various modifications and improvements can be added to the above-described embodiments. Modifications are described below. 
     2. Modifications 
     In  FIGS. 10 and 11 , as the air velocity control condition (2), the air velocity Va or Vb of the carriage fan  53   a  or the carriage fan  53   b  on the rear side in the travel direction is controlled to a value greater than the air velocity Va or Vb of the carriage fan  53   a  or the carriage fan  53   b  on the front side in the travel direction, in the forward direction and the backward direction. In other words, in the forward direction and the backward direction, the air velocity of the carriage fan on the rear side in the travel direction is controlled to a value greater than that of the air velocity of the carriage fan on the front side in the travel direction. 
     However, this is not a limitation, and it is also possible to set the air velocity of the upstream end region  48 A and the downstream end region  48 C as the end regions of the platen  48  to a value greater than the air velocity of the central region  48 B. Specifically, the air velocities Va and Vb of the carriage fans  53   a  and  53   b  may be set to “large” in the upstream end region  48 A and the downstream end region  48 C, and may be set to “intermediate” or “small” in the central region  48 B in both the forward direction and the backward direction. In addition, the control of the air velocities Va and Vb of the carriage fans  53   a  and  53   b  as described in this modification may be set as a new air velocity control condition. 
     According to this modification, the drying capacity of the carriage blower  53  may be set to be greater in the upstream end region  48 A and the downstream end region  48 C of the platen  48  than in the central region  48 B of the platen  48  in the reciprocation direction of movement of the carriage  42 . 
     Contents derived from the above-mentioned embodiments and modification are described below. 
     A printing apparatus includes a support part configured to support a recording medium, a printing part configured to form an image by discharging ink to the recording medium supported by the support part while reciprocating in a main scanning direction, and a drying acceleration part configured to accelerate drying of the ink discharged by the printing part and applied on the recording medium in a state where the recording medium is supported by the support part, wherein a drying capacity of the drying acceleration part is set such that the drying capacity is higher in an end region of the support part than in a central region of the support part in a reciprocation direction of the printing part. 
     With this configuration, since the drying capacity of the drying acceleration part is set such that the drying capacity is higher in the end region of the support part than in the central region of the support part in the reciprocation direction of the printing part, the drying capacity in the end region of the recording medium that corresponds to the end region of the support part can be set to a value greater than that of the drying capacity in the central region of the recording medium. Thus, an occurrence of a smear in the end region of the recording medium can be suppressed. In addition, since it suffices to increase the drying capacity only in the region where a smear occurs, and it is not necessary to uniformly increase the drying capacity in the entire region, the power consumption for the drying can be reduced. 
     Preferably, in the above-described printing apparatus, the reciprocation direction of the printing part and a transport direction of the recording medium are parallel to each other. 
     With this configuration, the reciprocation direction of the printing part and the transport direction of the recording medium are parallel to each other, and thus, in printing of a recording medium that is an elongated medium such as roll sheet, enhanced efficiency of the printing can be achieved, and the size reduction can be achieved in the arrangement of the drying acceleration part, for example. 
     Preferably, in the above-described printing apparatus, the drying acceleration part is a plurality of fixed fans disposed above the printing part in such a manner as to face the support part, and an air velocity of the fixed fan that is disposed at a position facing the end region of the support part is greater than an air velocity of the fixed fan that is disposed at a position facing the central region of the support part. 
     With this configuration, since the drying acceleration part is the plurality of fixed fans disposed above the printing part in such a manner as to face the support part, and the air velocity of the fixed fan that is disposed at a position facing the end region of the support part is greater than the air velocity of the fixed fan that is disposed at a position facing the central region of the support part, the drying capacity in the end region of the recording medium that corresponds to the end region of the support part can be set to a value greater than that of the drying capacity in the central region of the recording medium. Thus, an occurrence of a smear in the end region of the recording medium can be suppressed. In addition, since it suffices to increase the air velocity only in the region where a smear occurs, and it is not necessary to uniformly increase the air velocity in the entire region, the power consumption for the drying can be reduced. 
     Preferably, in the above-described printing apparatus, the drying acceleration part is a heater provided at the support part, and a heating temperature of the heater disposed in the end region of the support part is higher than a heating temperature of the heater disposed in the central region of the support part. 
     With this configuration, since the drying acceleration part is the heater provided at the support part, and the heating temperature of the heater disposed in the end region of the support part is higher than the heating temperature of the heater disposed in the central region of the support part, the drying capacity in the end region of the recording medium that corresponds to the end region of the support part can be set to a value greater than that of the drying capacity in the central region of the recording medium. Thus, an occurrence of a smear in the end region of the recording medium can be suppressed. In addition, since it suffices to increase the heating temperature only in the region where a smear occurs, and it is not necessary to uniformly increase the heating temperature in the entire region, the power consumption for the drying can be reduced. 
     Preferably, in the above-described printing apparatus, the drying acceleration part is a carriage fan disposed on both sides of a carriage in the reciprocation direction, the carriage being configured to support a print head and move in the main scanning direction, the print head being configured to discharge the ink, and the carriage fan is set such that an air velocity in the end region of the support part is greater than an air velocity in the central region of the support part. 
     With this configuration, the drying acceleration part includes the carriage fan disposed on both sides in the reciprocation direction of the carriage configured to support the print head and move in the main scanning direction. The print head is configured to discharge ink. Further, the air velocity in the end region of the support part is set to a value greater than that of the air velocity in the central region of the support part. In this manner, the drying capacity in the upstream end region and the downstream end region of the support part can be set to a value greater than that of the drying capacity in the central region of the support part. Thus, an occurrence of a smear in the end region of the recording medium can be suppressed. In addition, since it suffices to increase the magnitude of the air velocity only in the region where a smear occurs, and it is not necessary to uniformly increase the magnitude of the air velocity in the entire region, the power consumption for the drying can be reduced. 
     Preferably, in the above-described printing apparatus, the drying acceleration part is a carriage fan disposed on both sides of a carriage in the reciprocation direction, the carriage being configured to support a print head and move in the main scanning direction, the print head being configured to discharge the ink, an air velocity of the carriage fan disposed upstream in a transport direction of the recording medium is changed such that the air velocity is small in an upstream end region, intermediate in the central region, and large in a downstream end region in the transport direction in the support part, and an air velocity of the carriage fan disposed downstream in the transport direction is changed such that the air velocity is large in the upstream end region, intermediate in the central region, and small in the downstream end region. 
     With this configuration, the drying acceleration part includes the carriage fan disposed on both sides in the reciprocation direction of the carriage Further, the air velocity of the carriage fan disposed upstream in the transport direction of the recording medium is changed such that the air velocity is small in the upstream end region, intermediate in the central region, and large in the downstream end region in the transport direction in the support part. In addition, the air velocity of the carriage fan disposed downstream in the transport direction is changed such that the air velocity is large in the upstream end region, intermediate in the central region, and small in the downstream end region. In this manner, when the carriage switches the travel direction, the carriage fan disposed on the rear side in the travel direction has a larger air velocity than the carriage fan disposed on the front side in the travel direction in the end region before the switching. In addition, in the end region after the switching, the carriage fan disposed on the front side in the travel direction has a larger air velocity than the carriage fan disposed on the rear side in the travel direction. In this manner, the drying capacity in the end region of the recording medium corresponding to the end region of the support part can be increased together with the drying capacity in the central region of the recording medium. Thus, an occurrence of a smear in the end region of the recording medium can be suppressed. In addition, since it suffices to increase the magnitude of the air velocity only in the region where a smear easily occurs, and it is not necessary to increase the magnitude of the air velocity in the entire region, the power consumption for the drying can be reduced.