Patent Publication Number: US-11390099-B2

Title: Inkjet printing apparatus and cleaning method

Description:
BACKGROUND OF THE INVENTION 
     Field of the Invention 
     The present invention relates to an inkjet printing apparatus and a cleaning method. 
     Description of the Related Art 
     An inkjet printing apparatus prints an image on a printing medium by ejecting ink from a printing head according to image data. During this ejection operation by the printing head, minute droplets may also be generated, which become a mist, floating and adhering to the inside of the apparatus. In particular, adhesion of such a mist to the surface of a platen that supports a printing medium being printed may contaminate a printing medium to be printed next. 
     Japanese Patent Laid-Open No. 2013-35628 discloses a method in which a cleaning sheet having a crease is conveyed in the same convenance path as a printing medium to wipe the surface of a platen with the vertex of the crease of the cleaning sheet and thereby remove ink therefrom. 
     However, there are cases where even the platen cleaning using the method described in Japanese Patent Laid-Open No. 2013-35628 cannot satisfactorily wipe off the ink adhering to the platen. It is possible to repeat the cleaning by conveying a new cleaning sheet until a satisfactory cleaning effect is achieved, but then the cleaning would take a great amount of time. 
     SUMMARY OF THE INVENTION 
     The present invention has been made to solve the above-described problem, and has an object to provide an inkjet printing apparatus capable of wiping off contamination on a platen efficiently. 
     In a first aspect of the present invention, there is provided printing apparatus comprising: a conveyance unit capable of conveying a printing medium in a conveyance direction; a printing head configured to eject ink toward a printing medium that is conveyed by the conveyance unit; a platen having a first region and a second region at different positions in the conveyance direction, facing the printing head and configured to support a printing medium; and a control unit configured to, in a case of cleaning the platen, cause the conveyance unit to move a cleaning sheet in which a first crease and a second crease are formed back and forth in the conveyance direction so that the first crease contacts the first region and the second crease contacts the second region. 
     In a second aspect of the present invention, there is provided a cleaning method for cleaning a platen in an inkjet printing apparatus that includes a conveyance unit capable of conveying a printing medium in a conveyance direction; a printing head configured to eject ink toward a printing medium that is conveyed by the conveyance unit; and a platen having a first region and a second region at different positions in the conveyance direction, facing the printing head and configured to support a printing medium, the cleaning method comprising causing, in a case of cleaning the platen, the conveyance unit to move a cleaning sheet in which a first crease and a second crease are formed back and forth in the conveyance direction so that the first crease contacts the first region and the second crease contacts the second region. 
     Further features of the present invention will become apparent from the following description of exemplary embodiments with reference to the attached drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a diagram showing the outer appearance of an inkjet printing apparatus; 
         FIG. 2  is a diagram showing a schematic configuration of a printing unit; 
         FIG. 3  is a perspective view illustrating the structure of the printing unit of the printing apparatus; 
         FIG. 4  is a block diagram illustrating the control configuration of the printing apparatus; 
         FIGS. 5A and 5B  are diagrams illustrating the configuration of a platen in detail; 
         FIG. 6  is a flowchart illustrating the steps of processing performed in a first embodiment; 
         FIGS. 7A and 7B  are diagrams showing an example of what is displayed on a display panel; 
         FIG. 8  is a diagram illustrating a cleaning sheet of the first embodiment; 
         FIGS. 9A to 9C  are diagrams showing the step of conveying the cleaning sheet according to the first embodiment; 
         FIG. 10  is a flowchart illustrating the steps of processing performed in a second embodiment; 
         FIG. 11  is a diagram illustrating a cleaning sheet of the second embodiment; 
         FIGS. 12A and 12B  are diagrams showing the step of conveying the cleaning sheet according to the second embodiment; and 
         FIG. 13  is a diagram showing a conveyance path in a printing apparatus used in a third embodiment. 
     
    
    
     DESCRIPTION OF THE EMBODIMENTS 
     First Embodiment 
       FIG. 1  is a diagram showing the outer appearance of an inkjet printing apparatus (hereinafter also referred to simply as a printing apparatus)  1  used in a first embodiment. The printing apparatus  1  includes a paper feed unit  2  that feeds a printing medium having no image printed thereon and a paper discharge unit  4  that discharges a printing medium having an image printed thereon. Placed on the front side of the main body of the printing apparatus  1  are a display panel  5  for presenting information to a user and operation keys  6  capable of receiving an instruction from a user. The display panel  5  and the operation keys  6  may be formed integrally as a touch panel. 
     In the following description, the X direction is the width direction of a printing medium, the Y direction is the direction in which a printing medium is conveyed in a printing unit, and the Z direction is a vertically upward direction. 
       FIG. 2  is a diagram showing a schematic configuration of the printing unit. In the paper feed unit  2 , a printing medium S before printing is placed on a paper feed tray  3  in a stacking manner. A pressure plate  7   a  supports the printing medium S placed on the paper feed tray  3  from the back. To perform a printing operation, the pressure plate  7   a  is raised, bringing the uppermost one of the printing media S placed on the paper feed tray  3  into contact with a paper feed roller  7   b . Then, as the paper feed roller  7   b  rotates, the printing medium S is fed in the direction indicated by the arrow. In this event, the printing media S other than the uppermost one is separated from the uppermost printing medium S by a separation roller  7   c  and brought back to the paper feed tray  3 . 
     An edge sensor  8  is placed on the conveyance path. The edge sensor  8  can detect passage of the leading edge and the tailing edge of the printing medium S as the printing medium S being conveyed comes into contact with and turns the lever of the edge sensor  8 . 
     Downstream of the edge sensor  8  in the conveyance path, there are placed a roller pair formed by an upstream roller  11  and pinch rollers  11   a  and a roller pair formed by a downstream roller  12  and spurs  12   a . Between these two roller pairs, a platen  10  that supports the printing medium S from below is placed. A carriage  9  which is movable in the ±X directions is placed above the platen  10  in the Z direction, facing the platen  10 . The distance from the area of the printing medium S nipped by the two roller pairs and supported on the platen  10  to an ejection port surface  30   a  of a printing head  30  mounted in the carriage  9  is maintained within a certain range. 
       FIG. 3  is a perspective view illustrating the structure of the printing unit of the printing apparatus  1 . The upstream roller  11  and the downstream roller  12  are drive rollers driven by a conveyance motor  13 . The upstream roller  11  rotates by receiving the drive force of the conveyance motor  13  transmitted through a drive motor pully  14 , a timing belt  15 , and a pully gear  16 . The downstream roller  12  rotates by receiving the drive force of the conveyance motor  13  transmitted through the drive motor pully  14 , the timing belt  15 , the pully gear  16 , an idler gear  17 , and a downstream roller gear  18 . The upstream roller  11  and the downstream roller  12  can be rotated reversely by switching of the rotation direction of the conveyance motor  13  which is a DC motor. 
     A cord wheel  19  is placed coaxially with the upstream roller  11 . A plurality of slits are formed in the cord wheel  19  at a predetermined pitch. An encoder sensor  20  provided on a part of the rotating path of the cord wheel  19  detects passage of the slits in the cord wheel  19 , and thereby a controller  205  (see  FIG. 4 ) can detect how much and where the printing medium S has been conveyed. Although the cord wheel  19  is placed coaxially with the upstream roller  11  here, the cord wheel  19  may be attached to a different member driven by the conveyance motor  13 . 
     The carriage  9  equipped with the printing head  30  can move in the ±X directions while being guided and supported by a guide shaft  23 . While the carriage  9  is moving, the printing head  30  ejects ink toward the printing medium S (not shown in  FIG. 3 ) supported on the platen  10  according to ejection data, thereby printing a band of an image on the printing medium S. By alternately repeating this printing scan to print one band of an image and a conveyance operation to convey the printing medium S in the Y direction by a distance corresponding to one band, an image is gradually formed on the printing medium S. 
     In the printing apparatus  1  of the present embodiment, the platen  10  has a groove portion  10   a  extending in the X direction which intersects with the conveying direction. The groove portion  10   a  collects ink that lands outside the leading and tailing edges or the left and right edges of the printing medium S in a “borderless printing” mode. In a region other than the groove portion  10   a , a plurality of ribs  10   b  are placed to keep the printing medium S from waving. A detailed description will be given later for the configuration of the platen  10 . 
       FIG. 4  is a block diagram illustrating the control configuration of the inkjet printing apparatus  1 . A CPU  201  causes the controller  205  to perform overall control of the apparatus according to the programs stored in a ROM  202 . The controller  205  controls each mechanism as instructed by the CPU  201 , using a RAM  203  as a work area. An EEPROM  204  holds, in a rewritable manner, parameters needed for the controller  205  to control the printing apparatus  1 . 
     A conveyance motor driver  206  is a driver for driving the conveyance motor  13 . The controller  205  drives the conveyance motor  13  through the conveyance motor driver  206 , thereby controlling the rotation of the upstream roller  11  and the downstream roller  12 , and in turn, the conveyance of the printing medium S. A carriage motor driver  207  is a driver for driving a carriage motor  208 . A head driver  209  is a driver for driving the printing head  30 . 
       FIGS. 5A and 5B  are diagrams illustrating the configuration of the platen  10  in detail.  FIG. 5A  is a top view, and  FIG. 5B  is a sectional view taken along two ribs  10   b  facing each other. Although  FIG. 5A  does not show the printing medium S,  FIG. 5B  shows the printing head  30  printing an image on a leading edge part of the printing medium S. 
     The groove portion  10   a  is a space for collecting ink ejected outside the printing medium S. The width of the groove portion  10   a  in the conveyance direction (the Y direction) is larger than the ejection region of the printing head  30 , so that ink ejected from the printing head  30  can be collected in the groove portion  10   a . Optionally, an absorber for absorbing ink may be placed inside the groove portion  10   a.    
     Each rib  10   b  extends in the Y direction with its tip protruding into the groove portion  10   a , and supports the printing medium S being printed, from the back. The ribs  10   b  facing each other across the groove portion  10   a  form a pair, and such pairs are arranged in the X direction at predetermined intervals. The lengths of the two ribs  10   b  facing each other across the groove portion  10   a  do not have to be the same. 
     In such a configuration, according to the arrangement of the ribs  10   b , small waves are formed in the printing medium S pressed against the platen  10  by being nipped between the upstream roller  11  and the pinch rollers  11   a . The small waves according to the arrangement of the ribs  10   b  are purposely formed in the printing medium S being conveyed, so that the gap between the ejection port surface  30   a  of the printing head  30  and the printing medium S may stay in a predetermined range in order to prevent, for example, a contact between the ejection port surface  30   a  and the printing medium S and disturbance of an image caused by the contact. 
     In “borderless printing”, the printing head  30  prints an image on an area a little larger than the actual size of the printing medium S. For example, to print a leading edge part of the printing medium S as shown in  FIG. 5B , the printing head  30  ejects ink with the leading edge of the printing medium S being included in the ejection region. Then, the ink ejected inside the leading edge of the printing medium S is absorbed by the printing medium S, but the ink ejected outside the leading edge is collected in the groove portion  10   a . Similarly, to print a tailing edge portion of the printing medium S, the ink ejected outside the tailing edge of the printing medium S is collected in the groove portion  10   a , and to print the center portion of the printing medium S, the ink ejected outside the side edges of the printing medium S is collected in the groove portion  10   a.    
     In this way, in the “borderless printing” mode, the ink ejected outside the edge portions of the printing medium S is mostly collected in the groove portion  10   a . However, part of the ink that is not absorbed by the printing medium S may become a mist, floating and adhering to a region other than the groove portion  10   a . Particularly in a case of the platen  10  having the structure of the present embodiment, a large amount of ink is likely to adhere to the ribs  10   b  protruding into the groove portion  10   a . The ink adhering to the ribs  10   b  is absorbed by the back surface of a new printing medium S that is conveyed next, contaminating the printing medium S. In other words, in a case where the printing apparatus  1  has the configuration of the present embodiment, it is necessary to appropriately clean the pairs of the ribs  10   b  that face each other across the groove portion  10   a.    
     A cleaning mode of the present embodiment is described below. 
       FIG. 6  is a flowchart illustrating the steps of processing performed by the controller  205  of the present embodiment in a cleaning mode. The controller  205  performs this processing as instructed by the CPU  201  according to the programs stored in the ROM  202 , using the RAM  203  as a work area. This processing may be started by a user selecting a cleaning mode with the operation keys  6  or may be started through a printer driver of a host apparatus connected externally. 
     After this processing is started, first in S 102 , the controller  205  displays on the display panel  5  how to prepare for the cleaning mode. 
       FIGS. 7A and 7B  are diagrams showing how to prepare for the cleaning mode displayed on the display panel  5  in S 102 .  FIG. 7A  shows how to make a cleaning sheet to be used for the cleaning mode.  FIG. 7B  shows how to set the cleaning sheet made.  FIGS. 7A and 7B  may be alternately displayed automatically, or may be switched by a user pressing the operation panel. A user first prepares a cleaning sheet S 1  according to  FIG. 7A . 
       FIG. 8  is a diagram illustrating the cleaning sheet S 1  of the present embodiment. The cleaning sheet S 1  of the present embodiment can be made using an A4-size sheet of plain paper usable for the regular printing operation. While checking on the display of  FIG. 7A , a user makes the cleaning sheet S 1  by folding a A4-size sheet of plain paper so that its short side may be divided into three equal parts and unfolding the sheet. In the cleaning sheet S 1  thus made, two creases CS 1 , CS 2  are formed at an equal interval LS 1 . 
     After making the cleaning sheet S 1 , the user follows the display of  FIG. 7B  and sets the cleaning sheet S 1  into the paper feed tray  3  of the printing apparatus  1 . Specifically, the user sets the cleaning sheet S 1  so that the vertices of the creases CS 1 , CS 2  may extend in the X direction and face the platen  10 . After that, the user instructs to start the cleaning mode using the operation keys  6 . Hereinafter, the crease situated downstream in the conveyance direction (the leading side) is referred to as a first crease CS 1 , and the crease situated upstream in the conveyance direction (the tailing side) is referred to as a second crease CS 2 . 
     Back to  FIG. 6 , upon receipt of a command to start the cleaning mode in S 103 , the controller  205  proceeds to S 104  to start a paper feeding operation in a similar manner to the regular printing operation. Specifically, the controller  205  drives the conveyance motor  13  through the conveyance motor driver  206  to convey the cleaning sheet S 1  set in the paper feed tray  3  in the Y direction. Note that in the following description, conveyance in the same direction as the regular printing operation (the +Y direction) is referred to as forward conveyance, and conveyance in a direction opposite from the regular printing operation (the −Y direction) is referred to as backward conveyance. 
       FIGS. 9A to 9C  are diagrams showing the step of conveying the cleaning sheet according to the present embodiment. In the platen  10  in  FIGS. 9A to 9C , a region which is upstream of the groove portion  10   a  is denoted as a first region CZ 1 , and a region downstream of the groove portion  10   a  is denoted as a second region CZ 2 . In the present embodiment, the first region CZ 1  is defined by the length of the ribs  10   b  placed upstream of the groove portion  10   a , and the second region CZ 2  is defined by the length of the ribs  10   b  placed downstream of the groove portion  10   a.    
       FIG. 9A  shows a state where the leading edge of the cleaning sheet S 1  has reached the edge sensor  8 . The controller  205  can recognize that the cleaning sheet S 1  has reached the edge sensor  8  because the leading edge of the cleaning sheet S 1  comes into contact with and turns the lever of the edge sensor  8 . The forward conveyance of the cleaning sheet S 1  started in S 104  of  FIG. 6  is continued until the leading edge of the cleaning sheet S 1  is detected as in  FIG. 9A . 
     Back to  FIG. 6 , after recognizing the leading edge of the cleaning sheet S 1  in S 105 , in S 106  the controller  205  conveys the cleaning sheet S 1  by a predetermined distance to align the first crease CS 1  with the downstream edge of the first region CZ 1 . With LP 1  being the distance from the edge sensor  8  to the downstream edge of the first region CZ 1  ( FIG. 9A ) and LS 1  being the distance from the leading edge of the cleaning sheet S 1  to the first crease CS 1  (see  FIG. 8 ), both of these distances being known values, the distance of the conveyance in S 106  is LP 1 +LS 1 . At the point the conveyance in S 106  is completed, the first region CZ 1  has been wiped once by the first crease CS 1 . 
     In S 107 , the controller  205  performs cleaning processing on the first region CZ 1 . Specifically, the controller  205  repeats the following operations alternately N times (N being an integer of 1 or greater): conveying the cleaning sheet S 1  backward (in the −Y direction) by the distance corresponding to the first region CZ 1  and conveying the cleaning sheet S 1  forward (in the +Y direction) by the same distance. Consequently, the first crease CS 1  of the cleaning sheet S 1  has moved back and forth N times between the downstream edge and the upstream edge of the first region CZ 1 . 
       FIG. 9B  shows how the cleaning processing is performed on the first region CZ 1  in S 107 . The first crease CS 1  of the cleaning sheet S 1  moves back and forth within the first region CZ 1  in the ±Y directions while being in contact with the ribs  10   b . The first crease CS 1  thus acts as a cleaning wiper, wiping off the ink adhering to the ribs  10   b  in the first region CZ 1 . 
     Back to the flowchart in  FIG. 6 , in S 108  the controller  205  starts conveying the cleaning sheet S 1  forward. Then, after recognizing the tailing edge of the cleaning sheet S 1  (S 109 ), the controller  205  proceeds to S 110  to convey the cleaning sheet S 1  further until the second crease CS 2  is located at the downstream edge of the second region CZ 2 . With LP 2  being the distance from the edge sensor  8  to the downstream edge of the second region CZ 2  (see  FIG. 9C ) and LS 1  being the distance from the tailing edge of the cleaning sheet S 1  to the second crease CS 2  (see  FIG. 8 ), the distance of the conveyance in S 110  is LP 2 -LS 1 . At the point the conveyance in S 110  is completed, the second region CZ 2  has been wiped once by the second crease CS 2 . 
     In S 111 , the controller  205  performs cleaning processing on the second region CZ 2 . Specifically, the controller  205  repeats the following operations alternately M times (M being an integer of 1 or greater): conveying the cleaning sheet S 1  backward (in the −Y direction) by the distance corresponding to the second region CZ 2  and conveying the cleaning sheet S 1  forward (in the +Y direction) by the same distance. Consequently, the second crease CS 2  of the cleaning sheet S 1  has moved back and forth M times between the downstream edge and the upstream edge of the second region CZ 2 . 
       FIG. 9C  shows how the cleaning processing is performed on the second region CZ 2  in S 111 . The second crease CS 2  of the cleaning sheet S 1  moves back and forth within the second region CZ 2  in the ±Y directions while being in contact with the ribs  10   b . The second crease CS 2  thus acts as a cleaning wiper, wiping off the ink adhering to the ribs  10   b  in the second region CZ 2 . 
     Back to the flowchart in  FIG. 6 , in S 112  the controller  205  discharges the cleaning sheet S 1  to the paper discharge unit  4 . This processing thus ends. 
     In the flowchart described above, after the cleaning processing on the first region CZ 1  is performed (S 107 ), the cleaning processing on the second region CZ 2  (S 111 ) is performed with the ink-absorbed first crease CS 1  having been moved downstream of the second region CZ 2 . Thus, there are no concerns that the first crease CS 1  which has absorbed ink touches or contaminates the second region CZ 2  which has been cleaned, and therefore the cleaning effect is not harmed. 
     With the cleaning mode of the present embodiment described above, the ribs  10   b  in the first region CZ 1  are wiped by the first crease CS 1  moving back and forth, and the ribs  10   b  in the second region are wiped by the second crease CS 2  moving back and forth. In other words, the two creases formed in the cleaning sheet S 1  are used for the respective corresponding regions. Thus, compared to a conventional configuration in which cleaning processing is performed using the same crease for the entire region of the platen, the configuration according to the present embodiment can make more efficient use of a single cleaning sheet, further enhancing the cleaning effect for the each of the regions. 
     In the above description, the positioning in S 110  between the downstream edge of the second region CZ 2  and the second crease CS 2  is performed based on the tailing edge of the cleaning sheet S 1  detected in S 109 . This is because using the tailing edge of the cleaning sheet S 1  as a reference for the positioning between the second region CZ 2  and the second crease CS 2  makes the conveyance distance from the reference position small, and therefore can make conveyance error small. However, the above positioning can also be performed based on the leading edge of the cleaning sheet S 1  detected in S 103 . In this case, in S 110 , the controller  205  may convey the cleaning sheet S 1  by a distance corresponding to LP 2 +LS 1 +LS 1  from the position at which the leading edge of the cleaning sheet S 1  is detected in S 103 . This approach is effective in a case where, for example, the edge sensor  8  is located more downstream than in the above embodiment and cannot detect the tailing edge of the cleaning sheet S 1  during cleaning processing. This approach is also effective for a configuration where the edge sensor  8  is locked in the backward conveyance of the cleaning sheet S 1  after the cleaning sheet S 1  passes the edge sensor  8 . 
     In the present embodiment, it is concerned that certain deviations and errors are included in the positions of the creases formed manually by a user and in the ranges in which the creases move relative to the extension ranges of the ribs  10   b . Thus, the sizes of the first region CZ 1  and the second region CZ 2  in the Y direction are preferably set somewhat larger than the extension ranges of the ribs  10   b  in advance. 
     Also, in the present embodiment, the number of times N the first crease CS 1  moves back and forth in the first region CZ 1  and the number of times M the second crease CS 2  moves back and forth in the second region CZ 2  may be variously modified depending on factors such as the length of the ribs  10   b  and the ink absorbing ability of the cleaning sheet S 1 . It goes without saying that N and M may be set to equal values or different values. 
     Second Embodiment 
     Like the first embodiment, a second embodiment uses the printing apparatus  1  described in  FIGS. 1 to 5B . In the first embodiment, cleaning processing on the second region CZ 2  is performed after cleaning processing on the first region CZ 1  is completed. By contrast, in the present embodiment, the cleaning processing on the first region CZ 1  and the cleaning processing on the second region CZ 2  are performed simultaneously in parallel. Thus, in the present embodiment, the lengths of the first region CZ 1  and the second region CZ 2  are defined so that the ribs  10   b  in the first region and the ribs  10   b  in the second region can be satisfactorily wiped by the common movement of two creases. Thus, the regions are set not to sizes defined according to the length of the ribs  10   b  included in the region like in the first embodiment, but to equal sizes so that the longer ribs  10   b  are completely included in the regions. 
       FIG. 10  is a flowchart illustrating the steps of processing performed by the controller  205  of the present embodiment in a cleaning mode of the present embodiment. The controller  205  performs this processing as instructed by the CPU  201  according to the programs stored in the ROM  202 , using the RAM  203  as a work area. This processing may be started by a user selecting a cleaning mode with the operation keys  6  or may be started through a printer driver of a host apparatus connected externally. 
     Once this processing is started, first in S 202 , the controller  205  displays how to prepare for the cleaning mode on the display panel  5 . 
       FIG. 11  is a diagram illustrating a cleaning sheet S 2  used in the present embodiment. In the present embodiment, a third crease CS 3  for cleaning the first region CZ 1  and a fourth crease CS 4  for cleaning the second region CZ 2  are formed with an interval LS 3  interposed therebetween, the interval LS 3  corresponding to the distance between the first region CZ 1  and the second region CZ 2  in the conveyance direction. In  FIG. 11 , the fourth crease CS 4  is formed at a position away from the leading edge by the distance LS 2 , and the third crease CS 3  is formed at a position away from the fourth crease CS 4  by the distance LS 3 . The cleaning sheet S 2  of the present embodiment can be made using plain paper usable for the regular printing operation, as well. 
     After making the cleaning sheet S 2 , the user sets the cleaning sheet S 2  into the paper feed tray  3  of the printing apparatus  1 . Specifically, the user sets the cleaning sheet S 2  so that the vertices of the third and fourth creases CS 3 , CS 4  face the platen  10 . After that, the user instructs to start the cleaning mode using the operation keys  6 . 
     Back to  FIG. 10 , upon receipt of a command to start the cleaning mode in S 203 , the controller  205  proceeds to S 204  to start a paper feeding operation in a similar manner to the regular printing operation. 
       FIGS. 12A and 12B  are diagrams showing the step of conveying the cleaning sheet according to the present embodiment.  FIG. 12A  shows a state where the leading edge of the cleaning sheet S 2  has reached the edge sensor  8 . The controller  205  can know that the cleaning sheet S 2  has reached the edge sensor  8  because the leading edge of the cleaning sheet S 2  comes into contact with and turns the lever of the edge sensor  8 . 
     Back to  FIG. 10 , after recognizing the leading edge of the cleaning sheet S 2 , in S 206  the controller  205  conveys the cleaning sheet S 2  by a predetermined distance. By this conveyance, the third crease CS 3  is aligned with the downstream edge of the first region CZ 1 , and the fourth crease CS 4  is aligned with the downstream edge of the second region CZ 2 . With LP 1  being the distance from the edge sensor  8  to the downstream edge of the first region CZ 1  (see  FIG. 12A ) and LS 3  being the distance from the downstream edge of the first region CZ 1  and the downstream edge of the second region CZ 2  (see  FIG. 12A ), the distance of the conveyance in S 206  is LP 1 +LS 3 . At the point the conveyance in S 206  is completed, the first region CZ 1  has been wiped once by the third crease CS 3 , and the second region CZ 2  has been wiped once by the fourth crease CS 4 . 
     In S 207 , the controller  205  performs cleaning processing on the first region CZ 1  and cleaning processing on the second region CZ 2  in parallel. Specifically, the controller  205  repeats the following operations alternately K times (K being an integer of 1 or greater): conveying the cleaning sheet S 2  backward (in the −Y direction) by the distance corresponding to each of the first region CZ 1  and the second region CZ 2  and conveying the cleaning sheet S 2  forward (in the +Y direction) by the same distance. Consequently, the third crease CS 3  of the cleaning sheet S 2  has moved back and forth K times between the downstream edge and the upstream edge of the first region CZ 1 , and the fourth crease CS 4  of the cleaning sheet S 2  has moved back and forth K times between the downstream edge and the upstream edge of the second region CZ 2 . 
       FIG. 12B  shows how the cleaning processing is performed on each of the first region CZ 1  and the second region CZ 2  in S 207 . The third crease CS 3  of the cleaning sheet S 2  moves back and forth within the first region CZ 1  while being in contact with the ribs  10   b  in the first region CZ 1 , and the fourth crease CS 4  of the cleaning sheet S 2  moves back and forth within the second region CZ 2  while being in contact with the ribs  10   b  in the second region CZ 2 . Thereby, ink adhering to the ribs  10   b  in the first region CZ 1  and to the ribs  10   b  in the second region CZ 2  are wiped off simultaneously in parallel. The number of times K the third crease CS 3  and the fourth crease CS 4  move back and forth may be variously modified depending on factors such as the length of the ribs  10   b , the ink absorbing ability of the cleaning sheet S 2 , and a period of time since the previous cleaning processing. 
     Back to the flowchart in  FIG. 10 , in S 208  the controller  205  discharges the cleaning sheet S 2  to the paper discharge unit  4 . This processing thus ends. 
     With the cleaning mode of the present embodiment described above, the first region CZ 1  and the second region CZ 2  of the platen  10  are simultaneously wiped by the third crease CS 3  and the fourth crease CS 4 , respectively, moving back and forth in parallel. As a result, the present embodiment achieves a similar cleaning effect to that achieved by the first embodiment, and can also finish the cleaning processing in a shorter period of time than the first embodiment. 
     Third Embodiment 
     The first and second embodiments describe methods for cleaning the platen  10  having the groove portion  10   a , on the assumption that the printing apparatus performs “borderless printing.” By contrast, a third embodiment describes a case of cleaning a flat platen in a printing apparatus that does not perform “borderless printing.” The printing apparatus of the third embodiment has the same outer appearance and control configuration as those of the first and second embodiments depicted in  FIGS. 1 and 4 . 
       FIG. 13  is a diagram showing a conveyance path in the printing apparatus  1  used in the present embodiment. The upstream roller  11 , the pinch rollers  11   a , the downstream roller  12 , the spurs  12   a , and the edge sensor  8  have the same configurations as those in the above embodiments. A flat platen  110  that supports the printing medium S from below is placed between the roller pair formed by the upstream roller  11  and the pinch rollers  11   a  and the roller pair formed by the downstream roller  12  and the spurs  12   a . In the printing apparatus  1  of the present embodiment, the size of the printing region of the printing head and the size of the platen  110  are longer in the Y direction than usual in order to be able to print general documents at high speed. 
     In the present embodiment, an upstream region CZ 3  and a downstream region CZ 4  are set on the flat platen  110  with an overlap region CZ 5  being included. The present embodiment performs the cleaning processing in the same manner as the first and second embodiments by regarding the upstream region CZ 3  as the first region CZ 1  in the above embodiments and the downstream region CZ 4  as the second region CZ 2  in the above embodiments. 
     For example, in a case where the first embodiment is employed, the cleaning processing is performed according to the flowchart depicted in  FIG. 6 . As a result, the upstream region CZ 3  is wiped by the first crease CS 1  moving back and forth. After that, the downstream region CZ 4  is wiped by the second crease CS 2  moving back and forth. 
     In a case where the second embodiment is employed, the cleaning processing is performed according to the flowchart depicted in  FIG. 10 . As a result, the upstream region CZ 3  and the downstream region CZ 4  are simultaneously wiped by the third crease CS 3  and the fourth crease CS 4 , respectively, moving back and forth in parallel. 
     Irrespective of which of the embodiments is employed, the overlap region CZ 5  is wiped doubly by the two creases (CS 1  and CS 2  or CS 3  and CS 4 ). By being provided with such overlap region CZ 5 , the present embodiment can wipe ink adhering to the platen  110  without leaving any, even in a case where, for example, there are deviations in the creases in a cleaning sheet, conveyance error, or error in the detection by the edge sensor  8 . Thus, the overlap region CZ 5  is preferably set to a necessary and sufficient size with the above-described various errors taken into account. 
     Other Embodiments 
     Methods for making the cleaning sheets described in the first and second embodiments are not limited to the ones described in  FIGS. 8 and 11 . The orientations and positions of the creases in a cleaning sheet may be set appropriately according to factors such as the structure and size of the platen in the printing apparatus. To clarify the positions of the creases, a step of printing the positions of creases on a sheet of paper to be used as a cleaning sheet may be performed before the flowchart depicted in  FIG. 6 or 10  is executed. However, there are concerns in this case that the positions of the creases may become unclear in a case where ink on the platen adheres to this sheet of paper. Thus, in such a case, it is preferable to guide the user to make the cleaning sheet so that the printed side will be valley folded. Also, although a user makes a cleaning sheet by folding a sheet of plain paper in the above embodiments, a dedicated cleaning sheet may be prepared in advance. 
     In the above embodiments, the platen is divided into an upstream region and a downstream region, and two creases are formed to correspond to these two regions on a one-to-one basis. Alternatively, there may be more regions in the platen and more creases. For example, an upstream region, a midstream region, and a downstream region may be set as regions of the platen, and a cleaning sheet may be made which has three creases to correspond to these three regions on a one-to-one basis. Also, two or more creases may correspond to each region. In this case, after the first one of the creases moves and wipes a certain region multiple times, the next crease which has yet to absorb any ink moves and wipes the same region multiple times. This way, the wiping effect can be enhanced even more. 
     At any rate, any configuration may be employed as long as a plurality of regions are set on the platen in the conveyance direction, one or more creases are formed to correspond to each of these regions, and a wiping operation is performed using these creases. 
     Embodiment(s) of the present invention can also be realized by a computer of a system or apparatus that reads out and executes computer executable instructions (e.g., one or more programs) printed on a storage medium (which may also be referred to more fully as a ‘non-transitory computer-readable storage medium’) to perform the functions of one or more of the above-described embodiment(s) and/or that includes one or more circuits (e.g., application specific integrated circuit (ASIC)) for performing the functions of one or more of the above-described embodiment(s), and by a method performed by the computer of the system or apparatus by, for example, reading out and executing the computer executable instructions from the storage medium to perform the functions of one or more of the above-described embodiment(s) and/or controlling the one or more circuits to perform the functions of one or more of the above-described embodiment(s). The computer may comprise one or more processors (e.g., central processing unit (CPU), micro processing unit (MPU)) and may include a network of separate computers or separate processors to read out and execute the computer executable instructions. The computer executable instructions may be provided to the computer, for example, from a network or the storage medium. The storage medium may include, for example, one or more of a hard disk, a random-access memory (RAM), a read only memory (ROM), a storage of distributed computing systems, an optical disk (such as a compact disc (CD), digital versatile disc (DVD), or Blu-ray Disc (BD)™), a flash memory device, a memory card, and the like. 
     While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. The scope of the following claims is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions. 
     This application claims the benefit of Japanese Patent Application No. 2020-026161 filed Feb. 19, 2020, which is hereby incorporated by reference wherein in its entirety.