Patent Publication Number: US-9895906-B2

Title: Recording device and method for controlling recording device

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This is a continuation application of U.S. patent application Ser. No. 14/099,265, filed on Dec. 6, 2013, which is a continuation application of U.S. patent application Ser. No. 13/903,540, filed on May 28, 2013, now U.S. Pat. No. 8,628,162, which is a continuation application of U.S. patent application Ser. No. 13/177,688, filed on Jul. 7, 2011, now U.S. Pat. No. 8,469,478. U.S. patent application Ser. No. 13/177,688 claims foreign priority to Japanese Patent Application No. 2010-163020 filed on Jul. 20, 2010. The entire disclosures of U.S. patent application Ser. Nos. 14/099,265, 13/903,540 and Ser. No. 13/177,688 and Japanese Patent Application No. 2010-163020 are hereby incorporated herein by reference. 
    
    
     BACKGROUND 
     Technical Field 
     The present invention relates to a recording device and a method for controlling a recording device. 
     In an inkjet printer or another recording device, when a recording process is performed on recording paper or another recording medium, the recording medium must be supported by a platen so as to have a certain alignment (parallel) with respect to a recording head. 
     Related Art 
     In conventional practice, a technique for avoiding the inconvenience caused by curling is provided, wherein, as a countermeasure against curling in the recording medium due to any cause, holding members composed of thin, resinous sheets are provided to both sides of the recording medium, and the recording medium is inserted into the gaps formed between the holding members and the medium-supporting surface of the platen (see Japanese Laid-Open Patent Application Publication No. 8-197799, for example). 
     SUMMARY 
     Particularly in cases in which roll paper is used as the recording medium, the ends of the roll paper rise up off the platen due to waviness (curling); therefore, a paper suction part for suctioning the roll paper to the platen is provided in order to keep the paper from rising. 
     In this paper suction part, typically, numerous suction holes are provided to the platen and outside air is drawn through the suction holes by a fan installed on the reverse surface of the platen, whereby the roll paper is held by suction (negative pressure suction) on top of the platen. 
     However, the conveying force is sometimes reduced by the roll paper being suctioned on top of the platen. 
     The present invention was devised in view of the matters described above, and an object thereof is to provide a recording device and a method for controlling a recording device whereby a recording medium can be held satisfactorily and conveyed smoothly. 
     A recording device according to one aspect includes a medium-supporting part having a suction hole, a recording head and a suction part. The recording head is configured and arranged to perform a liquid ejection onto a medium supported on the medium-supporting part. The suction part is connected to the medium-supporting part to suck outside air via the suction hole. A liquid ejection period in which the recording head performs the liquid ejection onto the medium has a first period in which the suction part sucks by a predetermined suction force, and a second period in which the suction part sucks by a suction force which is smaller than the predetermine suction force after the first period. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Referring now to the attached drawings which form a part of this original disclosure; 
         FIG. 1  is a diagram showing the schematic configuration of a printer of the embodiment; 
         FIG. 2  is a plan view of the print area where printing is conducted in the printer; 
         FIG. 3  is a cross-sectional view showing the schematic configuration of the entire printer; 
         FIG. 4  is a plan view showing the schematic configuration of the platen; 
         FIG. 5  is a flowchart showing the process routine pertaining to the conveying process and the printing process; 
         FIG. 6  is a diagram showing the printing process routine; 
         FIG. 7  is a diagram showing the suction sequence caused by the suction fan; 
         FIGS. 8A and 8B  are diagrams showing the depressurized state caused by the suction fan in the negative-pressure chamber; and 
         FIG. 9  is a diagram for describing the scanning action of the carriage. 
     
    
    
     DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS 
     An embodiment of the recording device is described hereinbelow using the drawings. 
     The scope of the present invention is not limited to the following embodiment, and desired modifications are possible within the range of the technological ideals of the present invention. To make the configurations easier to understand in the drawings hereinbelow, the scales, numbers, and other features of the structures are sometimes made to differ from the actual structure. 
       FIG. 1  is a diagram showing the schematic configuration of the printer of the present embodiment.  FIG. 2  is a plan view of the print area where printing is conducted in the printer.  FIG. 3  is a cross-sectional view showing the schematic configuration of the entire printer. 
     A printer (recording device)  11  uses as a printing system an inkjet system for ejecting a liquid from a plurality of recording heads (liquid ejection heads) onto a continuous paper  12 . The printer  11  performs the printing process while sequentially unreeling the long, rectangular continuous paper (the recording medium)  12  wound into a roll shape, and after printing, winds the continuous paper  12  back up into a roll shape. 
     In the present embodiment, there is employed an XYZ orthogonal coordinate system in which the width direction of the continuous paper  12  in a horizontal plane is the X direction, the conveying direction of the continuous paper  12  which is orthogonal to the X direction is the Y direction, and the vertical direction is the Z direction. 
     The printer  11  comprises a main body  14  for executing the printing process, an unreeling part  13  for supplying the continuous paper  12  to the main body  14 , and a winding part  15  for winding up the continuous paper  12  discharged from the main body  14 . 
     The main body  14  comprises a main body case  16 . The unreeling part  13  is placed upstream in the conveying direction (−Y) from the main body case  16 , and the winding part  15  is placed downstream in the conveying direction (+Y) from the main body case  16 . The unreeling part  13  is connected to a medium supply part  16   a  provided to a side wall  16 A on the upstream side in the conveying direction (−Y) of the main body case  16 , while the winding part  15  is connected to a medium discharge part  16   b  provided to a side wall  16 B on the downstream side in the conveying direction (+Y). 
     The unreeling part  13  comprises a support plate  17  attached to the bottom of the side wall  16 A of the main body case  16 , a winding shaft  18  provided to the support plate  17 , an unreeling stand  19  connected to the medium supply part  16   a  of the main body case  16 , and a relay roller  20  provided to the distal end of the unreeling stand  19 . The continuous paper  12 , which is wound into a roll shape, is rotatably supported on the winding shaft  18 . When unreeled from the roll, the continuous paper  12  is wrapped over the relay roller  20 , shifted to the top surface of the unreeling stand  19 , and conveyed along the top surface of the unreeling stand  19  to the medium supply part  16   a.    
     The winding part  15  comprises a winding frame  41 , and a relay roller  42  and winding drive shaft  43  provided to the winding frame  41 . The continuous paper  12  discharged from the medium-discharging part  16   b  is wrapped over the relay roller  42 , guided to the winding drive shaft  43 , and wound up into a roll shape by the rotatable driving of the winding drive shaft  43 . 
     A plate-shaped base stand  21  is disposed horizontally within the main body case  16  of the main body  14 , and the interior of the main body case is divided into two spaces by the base stand  21 . The space above the base stand  21  is a printing chamber  22  for conducting the printing process on the continuous paper  12 . The printing chamber  22  is provided with a platen (medium-supporting part)  28  fixed in place on the base stand  21 , a recording head (recording processing part)  36  provided above the platen  28 , a carriage  35   a  for supporting the recording head  36 , two guide shafts  35  (see  FIG. 2 ) for supporting the carriage  35   a , and a valve unit  37 . The two guide shafts  35  are arranged parallel to each other along the conveying direction (the Y direction), and are configured so as to enable the carriage  35   a  to move back and forth in the conveying direction. 
     The platen  28  has a box-shaped support stand  28   a  open in the top surface, and a carrying plate  28   b  attached to the opening of the support stand  28   a , as shown in  FIGS. 1 through 3 . The support stand  28   a  is fixed in place on the base stand  21 , and the interior enclosed by the support stand  28   a  and the carrying plate  28   b  constitutes a negative-pressure chamber  31 . The continuous paper  12  is carried on a support surface (medium-supporting surface) PL (the top surface in the drawing) of the carrying plate  28   b.    
     Formed in the carrying plate  28   b  are numerous suction holes  28 A which pass through the thickness direction of the carrying plate  28   b , and formed in one side wall of the support stand  28   a  (the −Y side wall in the present embodiment) is an exhaust port  28 B which passes through this side wall. A suction fan (suction device)  29  is connected to the exhaust port  28 B. The interior of the negative-pressure chamber  31  is suctioned by the suction fan  29 , whereby suction force can be applied to the continuous paper  12  via the numerous suction holes  28 A, and the continuous paper  12  can be suctioned to and kept flat against the support surface PL of the carrying plate  28   b.    
     A pressure detection sensor  32  for detecting the pressure in the negative-pressure chamber  31  is connected to the platen  28 . The pressure detection sensor  32  is arranged on a ventilation line  32   a  which is connected at one end to the bottom of the support stand  28   a  and connected at the other end to a vacuum source  61 , and the pressure detection sensor  32  measures the air pressure in the negative-pressure chamber  31  supplied through the ventilation line  32   a . The detection result thereof is then outputted to a suction fan motor driver (control part)  54  ( FIG. 2 ). 
     A supply conveying system including a plurality of conveying rollers is provided to the upstream side in the conveying direction (−Y) of the platen  28 . The supply conveying system includes a first conveying roller pair  25  provided in the printing chamber  22  near the platen  28 , a relay roller  24  provided in the lower space of the main body case  16 , and a relay roller  23  provided near the medium supply part  16   a.    
     The first conveying roller pair  25  is composed of a first drive roller  25   a  and a first driven roller  25   b . A first conveying motor  26  and a first encoder  26 E are linked to the first drive roller  25   a  as shown in  FIG. 2 . 
     In the supply conveying system, the continuous paper  12  conveyed into the main body case  16  from the unreeling part  13  via the medium supply part  16   a  is wrapped over the first drive roller  25   a  from below via the relay rollers  23 ,  24 , and nipped in the first conveying roller pair  25 . With the rotation of the first drive roller  25   a  driven by the first conveying motor  26 , the continuous paper is unreeled horizontally onto the support surface PL of the platen  28  from the first conveying roller pair  25 . 
     A discharging conveying system including a plurality of conveying rollers is provided on the downstream side in the conveying direction (+Y) of the platen  28 . The discharging conveying system includes a second conveying roller pair  33  provided on the side of the platen  28  opposite the first conveying roller pair  25 , a reversal roller  38  and relay roller  39  provided in the lower space of the main body case  16 , and a feed-out roller  40  provided near the medium-discharging part  16   b.    
     The second conveying roller pair  33  is composed of a second drive roller  33   a  and a second driven roller  33   b . A second conveying motor  34  and a second encoder  34 E are linked to the second drive roller  33   a  as shown in  FIG. 2 . Since the second driven roller  33   b  is placed over the printed surface (the top surface) of the continuous paper  12 , to avoid damage to the printed image, the second driven roller  33   b  may be configured to come in contact only with the widthwise (X direction) end edges of the continuous paper  12 . 
     In the discharging conveying system, the second conveying roller pair  33  nipping the continuous paper  12  conveys the continuous paper  12  off of the platen  28  with the rotation of the second drive roller  33   a  driven by the second conveying motor  34 . The continuous paper  12  unreeled from the second conveying roller pair  33  is conveyed to the feed-out roller  40  via the reversal roller  38  and the relay roller  39 , and is unreeled to the winding part  15  via the medium-discharging part  16   b  by the feed-out roller  40 . 
     In the present embodiment, a plurality of recording heads  36  are attached to the carriage  35   a  via a head attachment plate  36   a . The head attachment plate  36   a  is configured to be capable of moving over the carriage  35   a  in the medium width direction (the X direction). The position of the head attachment plate  36   a  can be controlled by a head position control part  35   b  connected to the carriage  35   a , and the plurality of recording heads  36  can be integrally moved to a new line by moving the head attachment plate  36   a  in the medium width direction (the X direction). The recording heads  36  are arranged on the head attachment plate  36   a  in alignment at constant intervals in the medium width direction so that adjacent recording heads  36  are in two different levels from each other in the medium conveying direction (the Y direction). 
     The head position control part  35   b  can perform position control of the recording heads  36  in the medium width direction (the X direction) as well as position control of the carriage  35   a  in the medium conveying direction (the Y direction; the head scanning direction), and can place the recording heads  36  in the desired position over the continuous paper  12 . 
     The plurality of recording heads  36  are connected with the valve unit  37  via respective ink supply tubes (not shown). The valve unit  37  is provided to the inner wall of the main body case  16  inside the printing chamber  22  and is connected with an ink tank (ink retention part, not shown). The valve unit  37  supplies ink to the recording heads  36  while temporarily retaining the ink supplied from the ink tank. 
     On the bottom surfaces (nozzle formation surfaces) of the recording heads  36 , numerous ink discharge nozzles are arrayed in the medium width direction (the X direction). The recording heads  36  eject the ink supplied from the valve unit  37  from the ink discharge nozzles onto the continuous paper  12  on the platen  28  and perform printing. 
     The recording heads  36  may also have a plurality of ink discharge nozzle rows. In this case, when four-color or six-color printing is to be performed, if ink is allocated for each color to the respective ink discharge nozzle rows, a plurality of colors of ink can be ejected by a single recording head  36 . 
     The area above the platen  28  in the printing chamber  22  is a printing area R where printing is performed on the continuous paper  12  by the ejection of ink from the ink discharge nozzles. The continuous paper  12  is conveyed intermittently by the supply conveying system and the discharging conveying system described above. Specifically, a length of continuous paper  12  equivalent to the printing area R is loaded onto the platen  28  every time printing is performed, and is fed out to the discharging conveying system after the printing process. 
     The guide shafts  35  extending into the printing chamber  22  extend outward in the medium conveying direction past the printing area R as shown in  FIGS. 1 and 2 . The carriage  35   a  is thereby capable of moving to an area outside of the printing area R. A first maintenance area R 1  is provided to the upstream side in the medium conveying direction (−Y) of the printing area R, and a second maintenance area R 2  is provided to the downstream side in the medium conveying direction (+Y). 
     The first maintenance area R 1  is provided with a maintenance unit  60 . The maintenance unit  60  is configured comprising, for example, cap members and wiping members provided in correspondence to the individual recording heads  36 , and a suction device which is connected to the cap members and which suctions out the interiors of the cap members. 
     The second maintenance area R 2  is not provided with any maintenance units or the like, but is a workspace into which technicians can place their hands and arms. By placing the carriage  35   a  in the second maintenance area R 2 , the nozzle formation surfaces of the recording heads  36  can be exposed in the aforementioned workspace, and the nozzle formation surfaces can be wiped or the recording heads  36  can be replaced by the technicians. 
     After the printing process, the continuous paper  12  is naturally dried while being conveyed through the discharging conveying system, but the configuration may also comprise a heating device for forcefully drying the ink and causing the ink to adhere to the continuous paper  12 . For example, the configuration may provide the platen  28  with a platen heater for heating the carrying plate  28   b , or the configuration may have a heating device provided within the discharging conveying system. 
       FIG. 4  is a plan view showing the schematic configuration of the platen. 
     Suction holes  28 A, composed of numerous through-holes approximately several millimeters in inside diameter, for example, are formed throughout substantially the entire surface of the platen  28  as shown in  FIG. 4 . Specifically, suction holes  28 A having inside diameters of 2 to 3 mm are formed in aligned rows in both the longitudinal direction (the conveying direction of the continuous paper  12 ) and the width direction (the direction orthogonal to the conveying direction) of the platen  28 . 
     The negative-pressure chamber  31  is an airtight space whose ceiling is the platen  28 , and the bottom surface of this chamber is provided with a plurality of suction fans  29 . The suction fans  29  are used to suction out the air in the negative-pressure chamber  31  to create negative pressure. Outside air is thereby suctioned out via the numerous suction holes  28 A formed in the platen  28 , and the continuous paper  12  carried on the surface (the top surface) of the platen  28  is held by suction to the surface of the platen  28 . 
     A curling suppressor  70  holds the side ends  12   a  of the continuous paper  12  carried on the surface of the platen  28  down on the platen  28 , thereby preventing so-called rising in which the side ends  12   a  of the continuous paper  12  curl and separate from the platen  28 . 
     Specifically, the curling suppressor  70  comprises curl-suppressing members  71  composed of a pair of soft and flexible belt-shaped films. The curl-suppressing members  71  each have a thickness of, for example, 0.5 mm or less, and a width of about 30 mm. Polyimide or the like, for example, can be used for the material. 
     The ends of the curl-suppressing members  71  (the ends in the length direction) are linked to curl-suppressing attachment parts  75  fixed in place to a base (not shown) of the printer  11 . The curl-suppressing attachment parts  75  are linked so as to be capable of moving the curl-suppressing members  71  toward and away from each other. Therefore, the side ends  12   a  on both widthwise sides of the continuous paper  12  carried on the top surface of the platen  28  can be held down across the entire length carried on the platen  28 . 
     Next, conveying control and printing control in the printer  11  of the present embodiment will be described with reference to  FIGS. 5 through 9 .  FIG. 5  is a flowchart showing the process routine pertaining to the conveying process and the printing process.  FIG. 6  is a diagram showing the printing process routine.  FIG. 7  is a diagram showing the suction sequence caused by the suction fan.  FIG. 8  is a diagram showing the depressurized state in the negative-pressure chamber caused by the suction fan.  FIG. 9  is a diagram for describing the scanning action of the carriage. 
     Suction for Conveying 
     First, in step S 10 , a controller  44  sets the suction force in the negative-pressure chamber  31  due to the suction fan  29  to F 1  (a first suction force) by setting the rotational speed of the suction fan motor  30 . 
     The controller  44  then sends a control signal to the suction fan motor driver (control part)  54 . Negative pressure (−140 Pa) is thereupon created in the negative-pressure chamber  31  by the suction fan  29  beginning to be rotatably driven along with the rotatable driving of the suction fan motor  30 , and outside air is drawn in from the numerous suction holes  28 A formed in the platen  28  ( FIG. 8A ). As a result, a suction-holding force acts on the continuous paper  12  on the support surface PL of the platen  28  from within the negative-pressure chamber  31  via the suction holes  28 A. In this case, the continuous paper  12  is held by suction on the support surface PL of the platen  28  by a first suction-holding force substantially equal to the suction force F 1  of the suction fan  29  ( FIG. 8B ). 
     Next, in step S 11 , based on the detection signal from the pressure detection sensor (the pressure detection part)  32  connected to the platen  28  (the negative-pressure chamber  31 ), the controller  44  determines whether or not the pressure in the negative-pressure chamber  31  has been reduced to a pressure value substantially equal to the suction force F 1  of the suction fan  29  with the rotatable driving of the suction fan  29 . 
     When the determination result in step S 11  is a positive determination (the pressure of the negative-pressure chamber  31  equals F 1 ), the controller  44  concludes that depressurization by the suction fan  29  of the pressure in the negative-pressure chamber  31  to the desired pressure value is complete, and the process transitions to step S 12 . 
     When the determination result in step S 11  is a negative determination (the pressure of the negative-pressure chamber  31  does not equal F 1 ), the controller  44  concludes that depressurization in the negative-pressure chamber  31  by the suction fan  29  is not complete. The controller  44  continues depressurization in the negative-pressure chamber  31  by the suction fan  29  so that the pressure in the negative-pressure chamber  31  is reduced to the desired pressure value. 
     Conveying Operation 
     Next, in step S 12 , the controller  44  sets the amount the continuous paper  12  will be conveyed by the first drive roller  25   a  by setting the rotation amount of the first conveying motor  26  to C. The rotation amount C of the first conveying motor  26  is set so that when the first drive roller  25   a  is rotatably driven along with the rotatable driving of the first conveying motor  26 , the amount the continuous paper  12  is conveyed by the first drive roller  25   a  is equal to a distance corresponding to the printing area R from the left end to the right end of the platen  28  in the conveying direction. 
     The controller  44  sets the strength of the tensile force applied to the continuous paper  12  from the second drive roller  33   a  by setting the managed torque value of the second conveying motor  34  to T 1 . The managed torque value T 1  of the second conveying motor  34  is set so that the strength of the tensile force applied to the continuous paper  12  on the platen  28 , which is applied by the second drive roller  33   a  based on the torque of the second conveying motor  34 , reaches a strength capable of sufficiently minimizing flapping of the continuous paper  12  during conveying. 
     Next, the controller  44  sends a control signal to the first conveying motor driver  50  and the second conveying motor driver  52 . The first drive roller  25   a  thereupon begins to be rotatably driven along with the rotatable driving of the first conveying motor  26 , and the first drive roller  25   a  thereby conveys the continuous paper  12 . At the same time, the second drive roller  33   a  begins to be rotatably driven along with the rotatable driving of the second conveying motor  34 , and the second drive roller  33   a  thereby applies tensile force to the continuous paper  12 . 
     The continuous paper  12  is sequentially wound up by the winding drive shaft  43  even when pulled downstream in the conveying direction from off of the support surface PL of the platen  28  by the second drive roller  33   a . Therefore, the continuous paper  12  substantially does not warp at the position downstream in the conveying direction from the second drive roller  33   a , and the continuous paper  12  is therefore conveyed in a stable manner along the conveying route by the first drive roller  25   a.    
     While the continuous paper  12  is being conveyed, the controller  44  is constantly observing the rotation amount of the first drive roller  25   a  based on a detection signal from the rotation amount detection sensor  51 , constantly observing the strength of the tensile force applied to the continuous paper  12  from the second drive roller  33   a  based on a detection signal from the torque detection sensor  53 , and also constantly observing the pressure change in the negative-pressure chamber  31  accompanying the rotatable driving of the suction fan  29  based on a detection signal from the pressure detection sensor  32 . 
     The rotational speed of the second drive roller  33   a  is set to be higher than the rotational speed of the first drive roller  25   a . Therefore, the second drive roller  33   a  applies tensile force to the continuous paper  12  while it is being conveyed, and the flatness of the continuous paper  12  on top of the platen  28  is thereby improved. 
     The suction force F 1  of the suction fan  29  is set to a strength that does not cause the continuous paper  12  to stick firmly to the support surface PL of the platen  28 , so as to not impede the conveying of the continuous paper  12  by the first drive roller  25   a . In the present embodiment, this suction force is set to −140 Pa. 
     Therefore, tensile force is reliably applied by the second drive roller  33   a  to the continuous paper  12  on the support surface PL of the platen  28 , and it is therefore possible to adjust with high precision the strength of the tensile force applied to the continuous paper  12  from the second drive roller  33   a . The suction-holding force applied to the continuous paper  12  from the support surface PL of the platen  28  is weak, therefore avoiding excessive drive loads in the first conveying motor  26  and the second conveying motor  34  when the continuous paper  12  is being conveyed. 
     Additionally, in the present embodiment, the suction force F 1  of the suction fan  29  and the managed torque value T 1  of the second conveying motor  34  can be modified as desired based on data inputted to the controller  44  from the external input device  48 . Therefore, by setting the suction force F 1  of the suction fan  29  to a lower value, the managed torque value T 1  of the second conveying motor  34  can be set to a lower value within a range in which flapping of the continuous paper  12  during conveying can be minimized. By setting the managed torque value T 1  of the second conveying motor  34  to a lower value, the drive load of the second conveying motor  34  is reduced, the second conveying motor  34  can therefore be prevented from overheating, and energy can be conserved in the entire device. 
     Next, in step S 13 , the controller  44  determines whether or not the rotation amount of the first conveying motor  26  has reached the rotation amount C set in step S 12 , based on a detection signal from the rotation amount detection sensor  51 . 
     When the determination result in step S 13  is a positive determination (the rotation amount of the first conveying motor  26  is equal to C), the controller  44  concludes that the conveying of the continuous paper  12  by the first drive roller  25   a  is complete, the conveyed amount of the continuous paper  12  having reached the desired conveyed amount, and the process transitions to step S 14 . 
     When the determination result in step S 13  is a negative determination (the rotation amount of the first conveying motor  26  does not equal C), the controller  44  concludes that the conveying of the continuous paper  12  by the first drive roller  25   a  is not complete. The controller  44  continues the conveying of the continuous paper  12  by the first drive roller  25   a  until the conveyed amount of the continuous paper  12  by the first drive roller  25   a  reaches the desired conveyed amount. 
     Next, in step S 14 , the controller  44  modifies the suction force generated in the negative-pressure chamber  31  by the suction fan  29  to F 2  (second suction force: −530 Pa), by setting the rotational speed of the suction fan motor  30 . The suction force F 2  of the suction fan  29  is set to a greater value than the suction force F 1  (−140 Pa) of the suction fan  29  set in step S 10 . A predetermined negative pressure can thereby be generated in the negative-pressure chamber  31 . 
     The continuous paper  12  is then held by suction on the support surface PL of the platen  28  by a second suction-holding force, which is substantially equal to the suction force F 2  of the suction fan  29 . Specifically, the suction fan  29  causes the continuous paper  12  to be held to the support surface PL of the platen  28  by the second suction-holding force when the printing process is being executed, and causes the continuous paper  12  to be held to the support surface PL of the platen  28  by the first suction-holding force, which is less than the second suction-holding force, when the conveying process is being executed. 
     The controller  44  transmits a control signal to the suction fan motor driver  54 . The rotational speed of the suction fan motor  30  is thereupon modified so as to decrease, whereby the negative pressure created in the negative-pressure chamber  31  along with the driving of the suction fan  29  changes quickly from −140 Pa to −580 Pa. As a result, the continuous paper  12  on the support surface PL of the platen  28  is held on the support surface PL of the platen  28  by a suction-holding force substantially equal to the suction force F 2  of the suction fan  29 . 
     In this case, a relatively strong suction-holding force acts on the continuous paper  12  which has stopped being conveyed on top of the support surface PL of the platen  28 , therefore eliminating wrinkles and the like in the continuous paper  12  and maintaining flatness on the support surface PL of the platen  28 . Due to the continuous paper  12  being held by suction on the platen  28 , there is virtually no positional misalignment on the support surface PL. 
     Next, in step S 15 , the controller  44  modifies the strength of the tensile force applied to the continuous paper  12  from the second drive roller  33   a  by setting the managed torque value of the second conveying motor  34  to T 2 . The managed torque value T 2  of the second conveying motor  34  is set to a smaller value than the managed torque value T 1  of the second conveying motor  34  set in step S 12 . 
     Next, the controller  44  transmits a control signal to the second conveying motor driver  52 . The strength of the torque transmitted from the second conveying motor  34  to the second drive roller  33   a  is thereupon modified, thereby changing the strength of the tensile force applied to the continuous paper  12  by the second drive roller  33   a . In this case, a relatively small tensile force is applied to the continuous paper  12  from the second drive roller  33   a  while the continuous paper  12  has stopped being conveyed. Therefore, the drive load of the second conveying motor  34  rotatably driving the second drive roller  33   a  is reduced, and energy is conserved in the entire device. 
     In the present embodiment, the controller  44  reduces the managed torque value of the second conveying motor  34  to T 2  in step S 15  after increasing the strength of the suction force of the suction fan  29  to F 2  in step S 14 . Specifically, since the suction force of the suction fan  29  is increased while the strength of the tensile force applied to the continuous paper  12  from the second drive roller  33   a  is relatively large, the continuous paper  12  is held by suction on the support surface PL of the platen  28  while a high degree of flatness is maintained. Therefore, since the continuous paper  12  is held by suction firmly on the support surface PL of the platen  28  even when the strength of the tensile force applied to the continuous paper  12  from the second drive roller  33   a  has been reduced, there is virtually no positional misalignment in the continuous paper  12  on the support surface PL of the platen  28 . 
     Next, in step S 16 , the controller  44  reads the print data relative to the continuous paper  12  from RAM (not shown), and transmits the read print data to a head driver  49 . The head driver  49  thereupon initiates the printing action on the continuous paper  12  by causing ink to be ejected from the ink discharge nozzles of the recording head  36  onto the continuous paper  12  supported on the support surface PL of the platen  28 . Specifically, the recording head  36  is designed to execute the printing process on the continuous paper  12  in between rotating actions of the first drive roller  25   a  caused intermittently by the first conveying motor driver  50 . 
     At this time, the continuous paper  12  positioned on the support surface PL of the platen  28  is reliably suctioned flat across the entire width direction, and the recording head  36  can therefore conduct a high-quality printing process on the continuous paper  12  which is kept flat. 
     In the present embodiment, as described above, printing is conducted on a predetermined area (the printing area R set in correspondence with the size of the platen  28 ) of the continuous paper  12  kept flat on the platen  28 . In practice, as shown in  FIG. 9 , a predetermined printing is conducted on the continuous paper  12  by advancing the plurality of recording heads  36  integrally to the next line while moving the carriage  35   a  in the conveying direction of the continuous paper  12  and also moving the carriage  35   a  in the width direction (the X direction) of the continuous paper  12 . While the carriage  35   a  is advanced a plurality of times (three times) to the next line in the width direction (the X direction) of the continuous paper  12 , the carriage  35   a  is moved back and forth along the conveying direction (the Y direction) of the continuous paper  12  in the following sequence: first scan (1)→second scan (2)→third scan (3)→fourth scan (4). The scans are conducted approximately every two seconds. 
     In this manner is printing conducted on the continuous paper  12  held by suction flat on the platen  28 . 
     In the present embodiment, the pressure inside the negative-pressure chamber  31  is changed while the printing process is being executed. 
     First, the interior of the negative-pressure chamber  31  having reached a predetermined negative pressure (−580 Pa) due to the suction fan  29  being rotatably driven, the carriage  35   a  is repeatedly moved back and forth along the conveying direction of the continuous paper  12  and advanced to the next line in the width direction of the continuous paper  12 , thereby scanning in the sequence first scan (1)→second scan (2)→third scan (3), and conducting printing (step S 20 ). 
     In the fourth scan (4), printing is performed while the carriage  35   a  is moved from the downstream side in the conveying direction of the continuous paper  12  to the upstream side in the conveying direction (step S 21 ). With a predetermined timing during the fourth scan (4), the controller  44  then sets the suction force in the negative-pressure chamber  31  caused by the suction fan  29  to F 1  by setting the rotational speed of the suction fan motor  30  (step S 22 ). The controller  44  then transmits a control signal to the suction fan motor driver  54  and lessens the drive force of the suction fan motor  30  to gradually reduce the rotational speed of the suction fan  29 . The timing in which the drive force of the suction fan motor  30  is lessened is set as appropriate. 
     The controller  44  transmits to the suction fan motor driver  54  a control signal for changing the rotational speed of the suction fan motor  30 . Specifically, a control signal which incrementally reduces the rotational speed of the suction fan motor  30  is transmitted to the suction fan motor driver  54  until the suction force whereby the interior of the negative-pressure chamber  31  is suctioned by the suction fan  29  changes from F 2  to F 1 . The rotational speed of the suction fan motor  30  thereupon gradually decreases, and the pressure in the negative-pressure chamber  31  changes (increases) accordingly. 
     The controller  44  then makes a conclusion as to whether or not the printing process on the predetermined area in the continuous paper  12  has ended (step S 23 ), and when the printing process is concluded to have ended, the process transitions to step S 17 . 
     Next, in step S 17 , the controller  44  makes a conclusion as to whether or not to continue the printing process on the continuous paper  12 . When the controller  44  determines to continue the printing process on the continuous paper  12  in step S 17 , the process returns to step S 11 , and based on a detection signal from the pressure detection sensor  32 , a determination is made as to whether or not the pressure in the negative-pressure chamber  31  has increased to a pressure substantially equal to the suction force F 1  of the suction fan  29  with the reduction in the rotational speed of the suction fan  29 . 
     When the determination result in step S 11  is a positive determination (the pressure in the negative-pressure chamber  31  equals F 1 ), the controller  44  concludes that the pressure in the negative-pressure chamber  31  has increased to a maximum pressure value in the conveying of the continuous paper  12 . The process then transitions to step S 21 , and when it is concluded in step S 21  that printing on the printing area of the continuous paper  12  has ended, the process transitions to step S 17 . 
     When the determination result in step S 22  is a negative determination (the pressure in the negative-pressure chamber  31  does not equal F 1 ), the controller  44  concludes that the pressure in the negative-pressure chamber  31  has not reached the maximum pressure value in the conveying of the continuous paper  12 . The controller  44  then progressively reduces the rotational speed of the suction fan  29  until the pressure in the negative-pressure chamber  31  reaches a pressure substantially equal to the suction force F 1  of the suction fan  29 , and the pressure in the negative-pressure chamber  31  is increased to a predetermined pressure value (about −140 Pa). 
     The controller  44  then observes the pressure in the negative-pressure chamber  31  according to the pressure detection sensor  32  until the determination result in step S 11  is a positive determination. 
     Thus, when the printing process is continued, the process from step S 11  to step S 17  is reflexively executed. 
     When the controller  44  determines not to continue the printing process on the continuous paper  12  in step S 17 , the process routine programs pertaining to the conveying process and the printing process for the continuous paper  12  are ended. 
     As described in detail above, in the printer  11  of the present embodiment, the pressure in the negative-pressure chamber  31  is reduced until it reaches a value substantially equal to the suction force F 2  of the suction fan  29  along with the rotational driving of the suction fan  29 , and the printing process is thereby conducted on the continuous paper  12  after the continuous paper  12  supplied onto the platen  28  is held by suction on the support surface PL of the platen  28 . 
     Since the continuous paper  12  which has been supplied onto the platen  28  and has stopped being conveyed is subjected to a suction-holding force that is relatively greater than that during conveying on the support surface PL of the platen  28 , wrinkles and the like in the continuous paper  12  are eliminated and flatness is maintained on the support surface PL of the platen  28 . Consequently, the recording head  36  can conduct the printing process on the predetermined area of the continuous paper  12  in which flatness is maintained on the platen  28 , making high-quality printing possible. 
     Before the end of the printing process on the predetermined area of the continuous paper  12  carried on the platen  28 , the rotational speed of the suction fan  29  is reduced to lower the suction force F 2  of the suction fan  29  to the suction force F 1  during conveying of the continuous paper  12 . After the predetermined printing process has ended, the continuous paper  12  can begin to be conveyed at a faster timing than when the rotational speed of the suction fan  29  is reduced to lower the suction force F 2  of the suction fan  29  to the suction force F 1  during conveying of the continuous paper  12  and the pressure in the negative-pressure chamber  31  is increased to the predetermined pressure value (the pressure value during conveying: −140 Pa). 
     The timing with which the rotational speed of the suction fan  29  is reduced is not limited to the timing described above. When the printing process is being executed, the printer  11  of the present embodiment causes the continuous paper  12  to be held on the support surface PL of the platen  28  by the second suction-holding force (the suction force F 2 ) which is relatively greater than that during the conveying process, and when the conveying process is executed, the printer  11  causes the continuous paper  12  to be held on the support surface PL of the platen  28  by the first suction-holding force (the suction force F 1 ) which is less than the second suction-holding force during the printing process. After the portion of the continuous paper  12  supplied onto the platen  28  has been firmly held by suction and flattened on the support surface PL of the platen  28 , the flatness is thereafter maintained even if the suction-holding force is lessened. Therefore, after the continuous paper  12  is held by the second suction-holding force on the platen  28 , the rotational speed of the suction fan  29  may be incrementally lowered to lessen the suction force at a predetermined timing during any of the first through third scans (1) to (3). 
     It is difficult for outside air to be drawn in from the continuous paper  12  via the suction holes  28 A positioned below the continuous paper  12 , on which ink has been embedded by the printing process. Consequently, the suction holding of the continuous paper  12  onto which ink has been supplied by the printing process involves the gravity of the ink and the suction force applied to the continuous paper  12  via the numerous suction holes  28 A of the platen  28  is increased by the presence of the ink, the result of which is that the flatness of the continuous paper  12  is maintained even when the suction-holding force on the continuous paper  12  is lessened. In other words, because of the abundant moisture after printing, there is less air leakage than in the dry portions (the non-printed portions) and the suction-holding force is greater. 
     Consequently, if the printing process has not yet ended, the rotational speed of the suction fan  29  may be reduced with any timing. 
     After the printing process has ended, when the rotational speed of the suction fan  29  is reduced in order to lessen the depressurized state of the negative-pressure chamber  31 , it takes time for the pressure to reach a predetermined pressure value. When conveying is begun before the pressure of the negative-pressure chamber  31  reaches the predetermined pressure value, the continuous paper  12  undergoes stress and the conveying speed decreases. 
     Therefore, after the printing process has ended, the conveying process is conducted after the pressure in the negative-pressure chamber  31  reaches the predetermined pressure value (the suction force F 1 ). 
     The pressure in the negative-pressure chamber  31  is brought to the predetermined pressure value by reducing the rotational speed of the suction fan  29 , but the suction fan  29  may be stopped before the suction force of the suction fan  29  reaches F 1 . Since it is considered possible that after the suction fan  29  has stopped, outside air could continue to be drawn in via the suction holes  28 A, applying suction-holding force to the continuous paper  12  until the state of depressurization in the negative-pressure chamber  31  is somewhat lessened; the rotational driving of the suction fan  29  may be stopped ahead of the completion of the printing process. 
     No matter what timing during the printing process is used to reduce the rotational speed of the suction fan  29 , if the rotational speed of the suction fan  29  is controlled so that the suction-holding force during conveying (the suction force F 1 ) is reached at the same time that the printing process (the first through fourth scans (1) to (4) of the recording head  36 ) ends, conveying of the continuous paper  12  can be initiated immediately after the printing process ends. 
     Consequently, while flatness on the platen  28  is maintained during the printing process, the continuous paper  12  can be quickly conveyed with a small amount of drive force by lessening the suction-holding force during conveying to reduce the conveying load on the continuous paper  12 . If an attempt is made to convey the continuous paper  12  while it is still being firmly held by suction on the platen  28 , the stress on the continuous paper  12  increases and it becomes difficult to convey the paper quickly. 
     The platen  28  may be provided with an atmosphere opening valve for opening the interior of the negative-pressure chamber  31  to the atmosphere. The degree of depressurization in the negative-pressure chamber  31  can be quickly reduced by using both the atmosphere opening valve and suction force adjustment by the suction fan  29 , and conveying of the continuous paper  12  can be initiated with a faster timing. 
     Instead of the pressure detection sensor  32  according to the embodiment described above, a flow rate detection sensor may be provided for detecting the flow rate of air vented via the suction fan  29 . When the interior of the negative-pressure chamber  31  is vented by the suction fan  29 , the vented air flow rate decreases along with the decrease in pressure, and the pressure in the negative-pressure chamber  31  can therefore be estimated based on the vented air flow rate detected by the flow rate detection sensor. 
     A long, rectangular plastic film or the like may also be used as the recording medium. 
     In the embodiment described above, the recording device was specified as an inkjet printer, but the recording device is not limited thereto and can also be specified as a liquid ejection device which ejects or discharges a liquid other than ink (including liquid substances in which particles of a functional material are dispersed or mixed in a liquid, and fluid substances such as gels). 
     For example, the recording device may be a liquid ejection device which ejects a liquid (a liquid substance) containing an electrode material, a coloring material (pixel material), or another material in the form of a dispersion or a solvent, which is used in the manufacture of liquid crystal displays, electroluminescence (EL) displays, surface-emitting displays, and the like; a liquid ejection device which ejects a biological organic substance used to manufacture biochips; or a liquid ejection device which is used as a precision pipette and which ejects a liquid as a test sample. The recording device may also be a liquid ejection device which ejects lubricating oil at pinpoints onto a watch, a camera, or another precision instrument; a liquid ejection device for ejecting an ultraviolet curing resin or another transparent resin liquid onto a substrate in order to form a microscopic semispherical lens (optical lens) or the like used in an optical communication element or the like; a liquid ejection device for ejecting an acid, an alkali, or another etching liquid in order to etch a substrate or the like; or a liquid ejection device for ejecting a gel (e.g. a physical gel) or another liquid (fluid substance). The present invention can be applied to any of these liquid ejection devices. 
     A recording device according to the illustrated embodiment includes a medium-supporting part, a recording processing part, a suction device, and a control part. The medium-supporting part is configured and arranged to support a recording medium on a medium-supporting surface having a plurality of suction holes. The recording processing part is configured to perform recording process for recording on the recording medium supported on the medium-supporting part. The suction device is connected to the medium-supporting part, and configured and arranged to apply a suction force to the recording medium via the suction holes. The control part is configured to control operations of the suction device to set the suction force to a first suction force before the recording medium is supplied to the medium-supporting part, to change the suction force to a second suction force greater than the first suction force after the recording medium is supplied to the medium-supporting part, and to reduce the suction force below the second suction force during the recording process of recording on the recording medium, which has stopped on the medium-supporting surface, so that the suction force is reduced to the first suction force before the recording medium is conveyed. 
     According to this device, wrinkles and the like in the recording medium are eliminated and flatness is ensured in the conveying support surface by causing the suction device to apply a second suction force on the recording medium stopped on the medium-supporting surface, the second suction force being greater than the first suction force used when the recording medium is conveyed. Consequently, the printing process can be performed on a recording medium in which flatness is maintained, therefore making high-quality printing possible. 
     The recording medium can be conveyed smoothly because the recording medium is conveyed after the suction force of the suction device has been reduced from the second suction force to the first suction force after the printing process has ended. In this device, since the suction force of the suction device is reduced from the second suction force before the printing process ends, the recording medium can be conveyed immediately after the printing process ends. 
     In the recording device as described above, the suction device preferably includes a fan, and the control part is preferably configured to reduce a rotational speed of the fan before the recording process ends. 
     According this configuration, setting the suction force is readily accomplished. 
     The recording device as described above preferably further includes a pressure detection part connected to the medium-supporting part, and the control part is preferably configured to confirm that a detection result from the pressure detection part after the recording process has ended is a pressure value substantially equal to the first suction force. 
     According to this configuration, by initiating conveying of the recording medium after the detection result from the pressure detection part after the recording process has ended is confirmed to be a pressure substantially equal to the first suction force, the recording medium can be conveyed quickly without being subjected to any stress. 
     According to the illustrated embodiment, a method is provided for controlling a recording device having a medium-supporting part for supporting a recording medium on a medium-supporting surface having a plurality of suction holes, a recording processing part for performing recording process for recording on the recording medium supported on the medium-supporting part, a suction device for applying a suction force to the recording medium via the suction holes, a pressure detection part connected to the medium-supporting part, and a control part for controlling operations of the suction device based on a detection result from the pressure detection part. The method for controlling a recording device includes: conveying the recording medium using the suction force of the suction device with a first suction force; causing the recording medium supplied to the medium-supporting part to stop on the medium-supporting surface; changing the suction force of the suction device to a second suction force greater than the first suction force, and performing the recording process for recording on the recording medium stopped on the medium-supporting surface; and reducing the suction force of the suction device below the second suction force during the recording process so that the suction force reaches the first suction force, and subsequently conveying the recording medium. 
     According to this method, wrinkles and the like in the recording medium are eliminated and flatness is ensured in the conveying support surface by causing the suction device to apply a second suction force on the recording medium stopped on the medium-supporting surface, the second suction force being greater than the first suction force used when the recording medium is conveyed. Consequently, the printing process can be performed on a recording medium in which flatness is maintained, therefore making high-quality printing possible. 
     The recording medium can be conveyed smoothly because the recording medium is conveyed after the suction force of the suction device has been reduced from the second suction force to the first suction force after the printing process has ended. In this device, since the suction force of the suction device is reduced from the second suction force before the printing process ends, the recording medium can be conveyed immediately after the printing process ends. 
     In the method as described above, the reducing of the suction force during the recording process preferably includes reducing a rotational speed of a fan used as the suction device. 
     According to this method, setting the suction force is easy. 
     The method as described above preferably further includes confirming that the detection result from the pressure detection part is a pressure value substantially equal to the first suction force after the recording process is performed on the recording medium and before the recording medium is conveyed. 
     According to this method, by initiating conveying of the recording medium after the detection result from the pressure detection part is confirmed to be a pressure substantially equal to the first suction force after the recording process has ended, the recording medium can be conveyed quickly while not undergoing any stress. 
     General Interpretation of Terms 
     In understanding the scope of the present invention, the term “comprising” and its derivatives, as used herein, are intended to be open ended terms that specify the presence of the stated features, elements, components, groups, integers, and/or steps, but do not exclude the presence of other unstated features, elements, components, groups, integers and/or steps. The foregoing also applies to words having similar meanings such as the terms, “including”, “having” and their derivatives. Also, the terms “part,” “section,” “portion,” “member” or “element” when used in the singular can have the dual meaning of a single part or a plurality of parts. Finally, terms of degree such as “substantially”, “about” and “approximately” as used herein mean a reasonable amount of deviation of the modified term such that the end result is not significantly changed. For example, these terms can be construed as including a deviation of at least ±5% of the modified term if this deviation would not negate the meaning of the word it modifies. 
     While only selected embodiments have been chosen to illustrate the present invention, it will be apparent to those skilled in the art from this disclosure that various changes and modifications can be made herein without departing from the scope of the invention as defined in the appended claims. Furthermore, the foregoing descriptions of the embodiments according to the present invention are provided for illustration only, and not for the purpose of limiting the invention as defined by the appended claims and their equivalents.