Patent Publication Number: US-11383532-B2

Title: Drying device and printing apparatus

Description:
The present application is based on, and claims priority from JP Application Serial Number 2018-243143, filed Dec. 26, 2018, the disclosure of which is hereby incorporated by reference herein in its entirety. 
     BACKGROUND 
     1. Technical Field 
     The present disclosure relates to a drying device that dries a printed medium, and a printing apparatus that performs printing on a medium. 
     2. Related Art 
     For example, as disclosed in JP-A-2005-195897, there is a drying device that blows dry air, which is an example of air, to dry a recording medium, which is an example of a medium. The drying device includes a drying chamber that dries the recording medium, an air flow duct, which is an example of a flow path member that guides dry air to the drying chamber, and a circulation duct that guides the dry air in the drying chamber to the air flow duct. The drying device dries the recording medium using the dry air circulating through the air flow duct, the drying chamber, and the circulation duct. 
     The air flow duct is provided with a heater, which is an example of a heating unit that heats the dry air. When heated dry air is circulated, the drying chamber can be efficiently warmed. However, when the dry air whose humidity has increased after drying the recording medium is circulated, there is a risk that condensation may occur. 
     SUMMARY 
     A drying device that solves the above-described problem includes a support portion configured to support a printed medium, a heating unit provided in a drying chamber for drying the medium supported by the support portion, a flow path member forming an air flow path connecting an inflow port that opens downward in a vertical direction and the drying chamber, an air blowing unit configured to supply air, flowing from the inflow port into the air flow path, to the drying chamber and cause the air to flow out of an outflow portion of the drying chamber, and a control unit configured to control driving of the air blowing unit. The outflow portion is positioned lower than the inflow port in the vertical direction, and the control unit controls the driving of the air blowing unit to change an air flow rate of the air supplied to the drying chamber. 
     A printing apparatus that solves the above-described problem includes a printing unit configured to perform printing on a medium, a support portion configured to support the printed medium, a heating unit provided in a drying chamber for drying the medium supported by the support portion, a flow path member forming an air flow path connecting an inflow port that opens downward in a vertical direction and the drying chamber, and an air blowing unit configured to supply air, flowing from the inflow port into the air flow path, to the drying chamber and cause the air to flow out of an outflow portion of the drying chamber, and a control unit configured to control driving of the air blowing unit. The outflow portion is positioned lower than the inflow port in the vertical direction, and the control unit controls the driving of the air blowing unit to change an air flow rate of the air supplied to the drying chamber. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic cross-sectional view illustrating a first embodiment of a printing apparatus. 
         FIG. 2  is a schematic cross-sectional view of a drying device. 
         FIG. 3  is a flowchart illustrating a warm-up routine. 
         FIG. 4  is a flowchart illustrating a drying routine of a second embodiment. 
         FIG. 5  is a schematic cross-sectional view of the drying device of a modified example. 
     
    
    
     DESCRIPTION OF EXEMPLARY EMBODIMENTS 
     First Embodiment 
     A first embodiment of a drying device and a printing apparatus will be described below with reference to the drawings. The printing apparatus is, for example, an ink jet-type printer that prints an image of characters, photographs, and the like on a medium such as a sheet by ejecting ink, which is an example of a liquid. 
     As illustrated in  FIG. 1 , a printing apparatus  11  is provided with a printing unit  13  that performs printing on a medium  12 , and a drying device  14  that dries the printed medium  12 . The drying device  14  is provided with a support portion  15  including a support face  15   a  that supports the printed medium  12 , a heating device  16  that heats the medium  12  supported by the support portion  15 , and a control unit  17  that controls the drying device  14 . 
     The control unit  17  is configured by a processing circuit and the like including a computer and a memory, for example. The control unit  17  controls various operations executed by the drying device  14  in accordance with a program stored in the memory. The control unit  17  may integrally control driving of each of mechanisms in the printing apparatus  11 . 
     The drying device  14  includes a drying chamber  19 , which is a space for drying the medium  12  supported by the support portion  15 . The drying chamber  19  includes an outflow portion  20 . Air in the drying chamber  19  flows out to the outside from the outflow portion  20 . The outflow portion  20  is an opening formed by the support portion  15  and the heating device  16 . In the present embodiment, the support portion  15  and the heating device  16  form the outflow portion  20  in a state of being separated from each other. In the present embodiment, the medium  12  that has been dried in the drying chamber  19  is discharged from the outflow portion  20 . Note that the support  15  and the heating device  16  may have a configuration in which they are partially in contact with each other and have a predetermined gap therebetween, with the gap functioning as the outflow portion  20 . 
     In the drawings, the direction of gravity is indicated by a Z axis while assuming that the printing apparatus  11  is placed on a horizontal surface, and directions along a plane intersecting the Z axis are indicated by an X axis and a Y axis. When the X, Y, and Z axes are orthogonal to each other, the X and Y axes follow the horizontal plane. In the following description, the X axis direction is also referred to as a width direction X of the medium  12 , the Y axis direction as a horizontal direction Y, and the Z axis direction as a vertical direction Z. Of directions along the support face  15   a , a direction in which the medium  12  is transported is also referred to as a transport direction D 1 . A direction perpendicular to a portion of the support face  15   a  configuring the outflow portion  20  is also referred to as a normal direction H. The transport direction D 1  and the normal direction H are orthogonal to the X axis. 
     The printing apparatus  11  may be provided with a guide portion  22  that guides the medium  12  to the drying device  14 . The guide portion  22  guides the medium  12  on which printing is being performed by the printing unit  13 , or the medium  12  before the printing. In the drawings, the medium  12  is illustrated as being separated from the support portion  15  and the guide portion  22 , but the medium  12  is transported in a state of being in contact with and slidably supported by the support portion  15  and the guide  22 . 
     The printing apparatus  11  may be provided with a housing  24  that houses the printing unit  13 , and a transport unit  25  that transports the medium  12  in the transport direction D 1 . The transport unit  25  may be provided with a transport roller  27  that transports the medium  12 , a feeding shaft  28  positioned upstream of the transport roller  27  in the transport direction D 1 , and a winding shaft  29  positioned downstream of the transport roller  27  in the transport direction D 1 . The transport unit  25  may be provided with a plurality of the transport rollers  27 . The feeding shaft  28  and the winding shaft  29  each rotatably support a roll around which the long medium  12  is wound into a cylindrical shape. The feeding shaft  28  feeds the medium  12  while unwinding the wound medium  12 . The transport roller  27  transports the fed medium  12  along the guide portion  22  and the support portion  15 . The winding shaft  29  takes up the transported medium  12 . 
     The printing unit  13  is provided with a liquid ejection head  31  that ejects liquid from a nozzle, a carriage  32  that holds the liquid ejection head  31 , and a guide shaft  33  that guides movement of the carriage  32 . The carriage  32  reciprocates along the guide shaft  33  in the width direction X. While moving together with the carriage  32 , the liquid ejection head  31  ejects the liquid toward the medium  12  positioned in a print position P. Printing is performed on the medium  12  as a result of the liquid being deposited thereon. Note that the printing unit  13  may be a printing unit that ejects the liquid over the width direction X of the medium  12  without moving in the width direction X. 
     The drying device  14  is provided further downstream than the printing unit  13  in the transport direction D 1 . The support portion  15  supports the printed medium  12 , which is transported downstream in the transport direction D 1 , from the print position P at which the printing is performed on the medium  12 . The support portion  15  is inclined from upstream to downstream in the transport direction D 1  and also from an upper to lower side in the vertical direction Z. In other words, the support portion  15  is disposed such that an upstream portion of the support portion  15  in the transport direction D 1  is positioned above a downstream portion thereof in the vertical direction Z. 
     The medium  12  transported by the transport unit  25  passes through the drying chamber  19 . In the drying chamber  19 , the medium  12  on which the printing has been performed by the printing unit  13  is heated and dried. The winding shaft  29  takes up the dried medium  12  that has been dried by passing through the drying chamber  19 . 
     Next, the drying device  14  will be described. 
     As illustrated in  FIG. 2 , the drying device  14  is provided with a heating unit  35  that emits heat, and a cover  36  that covers the heating unit  35 . The drying device  14  is provided with a plurality of the heating units  35 . The heating unit  35  may be, for example, a heater that irradiates infrared rays, or may be an electrically heated wire that generates heat when an electric current is applied. Note that the drying device  14  may be configured to include only one of the heating units  35 . 
     The cover  36  may be provided with an opening  38  that is formed facing the support portion  15  or the medium  12  supported by the support portion  15 . The drying device  14  may be provided with a wire mesh  39  that covers the opening  38 . In a configuration in which the wire mesh  39  is disposed over the opening  38 , the heat from the heating unit  35  is transferred to the medium  12  on the support face  15   a  through the wire mesh  39 . 
     The drying device  14  may be provided with a reflection plate  41  that reflects the infrared rays emitted by the heating unit  35  toward the support face  15   a . When the reflection plate  41  reflects the infrared rays, the medium  12  can be efficiently heated. A heating chamber  42  is formed between the reflection plate  41  and the cover  36 , and the drying chamber  19  is formed between the reflecting plate  41  and the support portion  15 . 
     The drying device  14  may be provided with a detector  44  that detects the temperature of the drying chamber  19 . The detector  44  may be provided between the reflection plate  41  and the wire mesh  39 , or may be provided between the support portion  15  and the wire mesh  39 . The detector  44  may detect the temperature of the air in the drying chamber  19 , or may detect the temperature of the medium  12 , the support portion  15 , the reflection plate  41 , the wire mesh  39 , and the like, of a member configuring the drying chamber  19 , or of a member provided inside the drying chamber  19 . 
     The heating unit  35  is provided in the drying chamber  19 . The heating unit  35  has a cylindrical shape, for example, and is provided so that the longitudinal direction of the heating unit  35  coincides with the width direction X. When the length of the heating unit  35  is longer than the length of the medium  12  in the width direction X, the heating unit  35  heats the medium  12  over the width direction X. When the plurality of heating units  35  are provided in the normal direction H such that spaces between the heating units  35  and the support portion  15  are the same as each other, uneven heating of the medium  12  can be reduced. 
     The drying device  14  is provided with a flow path member  49  that forms an air flow path  48  connecting an inflow port  46  and an outflow port  47 , and an air blowing unit  50  that is provided in the air flow path  48 . The outflow port  47  opens into the drying chamber  19 . In other words, the air flow path  48  connects the inflow port  46  and the drying chamber  19 . 
     The inflow port  46  opens downward in the vertical direction Z. An inflow upper end  46   a , which is an upper end of an edge of the inflow port  46  in the vertical direction Z, and an inflow lower end  46   b , which is a lower end of the edge of the inflow port  46  in the vertical direction Z, are positioned in different positions with respect to the horizontal direction Y and the vertical direction Z. The inflow lower end  46   b  is positioned closer to the support portion  15  in the horizontal direction Y than the inflow upper end  46   a . In the flow path member  49 , a portion that configures the inflow upper end  46   a  is positioned above the inflow lower end  46   b  in the vertical direction Z. 
     With respect to the inflow port  46 , of directions along a normal line of a virtual plane including the edge of the inflow port  46 , a direction toward an opposite side of the virtual plane from the flow path member  49  includes a component of a downward direction in the vertical direction Z. With respect to the inflow port  46 , on a virtual plane having the width direction X as a normal line thereof, of directions along a straight line orthogonal to a virtual straight line passing through the inflow upper end  46   a  and the inflow lower end  46   b , a direction toward an opposite side of the virtual straight line from the flow path member  49  includes the component of the downward direction in the vertical direction Z. 
     The outflow portion  20  of the drying chamber  19  is positioned lower than the inflow port  46  in the vertical direction Z. The drying device  14  may be provided with an inclined wall  52  positioned between the outflow portion  20  and the inflow port  46 . In the normal direction H, the outflow portion  20  is positioned between the inflow port  46  and the support portion  15 . The outflow portion  20  and the inflow port  46  are at least partially positioned at the same position in the width direction X. The inclined wall  52  connects an outflow upper end  20   a , which is an upper end of the outflow portion  20  in the vertical direction Z, and the inflow lower end  46   b  of the inflow port  46 , and is provided so as to be inclined with respect to the vertical direction Z. The inclined wall  52  has a length in the normal direction H and the width direction X. The inclined wall  52  is an outer surface of the heating device  16  that faces downward in the vertical direction. 
     The flow path member  49  is provided on the outer side of the cover  36 , and forms the air flow path  48  so as to surround the cover  36 . The outflow port  47  is positioned between the heating unit  35  and the printing unit  13  in the transport direction D 1 . A downstream portion of the air flow path  48  including the outflow port  47  extends so as to be inclined with respect to the support face  15   a.    
     The air blowing unit  50  includes a fan  54  that generates an air flow, and causes the air in the air flow path  48  to flow toward the outflow port  47 . The air blowing unit  50  supplies the air flowing from the inflow port  46  into the air flow path  48  to the drying chamber  19 , and causes the air to flow out of the outflow portion  20 , which is included in the drying chamber  19 . The air blowing unit  50  causes the air in the drying chamber  19  to flow from upstream to downstream in the transport direction D 1 . In other words, the air blowing unit  50  blows the air toward the downstream in the transport direction D 1 , from a position further upstream in the transport direction D 1  than the heating unit  35 . The air in the drying chamber  19  is discharged to the outside of the drying device  14  from the outflow portion  20  positioned further downstream in the transport direction D 1  than the heating unit  35 . 
     Next, a warm-up routine executed by the control unit  17  will be described with reference to a flowchart illustrated in  FIG. 3 . The control unit  17  executes the warm-up routine at a timing at which the drying device  14  is activated. 
     As illustrated in  FIG. 3 , at step S 101 , the control unit  17  drives the air blowing unit  50  so that a rotation speed of the fan  54  per unit time is a first rotation speed, and supplies the air to the drying chamber  19  at a first air flow rate. At step S 102 , the control unit  17  operates the heating unit  35 . 
     At step S 103 , the control unit  17  determines whether or not a detected temperature detected by the detector  44  is equal to or greater than a threshold temperature. When the detected temperature is lower than the threshold temperature, NO is determined at step S 103 , and the control unit  17  drives the air blowing unit  50  at the first rotation speed until the detected temperature reaches the threshold temperature. When the detected temperature becomes equal to or greater than the threshold temperature, YES is determined at step S 103 , and the control unit  17  causes the processing to proceed to step S 104 . 
     At step S 104 , the control unit  17  drives the air blowing unit  50  so that the rotation speed of the fan  54  per unit time is a second rotation speed that is greater than the first rotation speed, and supplies the air to the drying chamber  19  at a second air flow rate. 
     Next, actions of the present embodiment will be described. 
     The control unit  17  controls the driving of the air blowing unit  50  to change the air flow rate of the air supplied to the drying chamber  19 . In other words, when the detected temperature detected by the detector  44  is lower than the threshold temperature, the control unit  17  supplies the air to the drying chamber  19  at the first air flow rate that is less than the second air flow rate. 
     When the air blowing unit  50  supplies the air to the drying chamber  19  from upstream to downstream in the transport direction D 1 , warmed air in the drying chamber  19  flows out of the outflow portion  20  positioned at the downstream end in the transport direction D 1 . The air velocity of the air flowing out of the outflow portion  20  varies depending on the air flow rate of the air flowing into the drying chamber  19 . In other words, when the air is supplied to the drying chamber  19  at the first air flow rate, a first air velocity of the air flowing out of the outflow port  47  is slower than a second air velocity of the air flowing out when the air is supplied to the drying chamber  19  at the second air flow rate. 
     When the air is discharged from the outflow portion  20  at the first air flow rate, the air heated in the drying chamber  19  rises along the inclined wall  52 , and is easily introduced into the air flow path  48  from the inflow port  46 . Thus, the air circulates through the air flow path  48 , the drying chamber  19 , and a space outside the drying device  14 , as indicated by alternate long and short dash line arrows in  FIG. 2 . When the warmed air is circulated, the support portion  15 , the cover  36 , the flow path member  49 , and the like can be efficiently warmed. 
     When the detected temperature detected by the detector  44  becomes equal to or greater than the threshold temperature, the control unit  17  supplies the air to the drying chamber  19  at the second air flow rate that is greater than the first air flow rate. The threshold temperature may be a predetermined value set in accordance with characteristics of the drying device  14 , or may be a value corresponding to a target temperature set in accordance with a type of the medium  12  and a print mode. For example, the threshold temperature for drying the medium  12  that has excellent heat resistance may be higher than the threshold temperature for drying the medium  12  that is easily affected by heat. When printing is performed in which the amount of liquid to be deposited per unit area of the medium  12  is large, the threshold temperature may be higher than the threshold temperature applied when printing is performed in which the amount of liquid to be deposited per unit area is small. 
     After the detected temperature exceeds the threshold temperature, the control unit  17  maintains a state in which the air is supplied to the drying chamber  19  at the second air flow rate. In other words, the control unit  17  maintains the air flow at the second air flow rate even when the detected temperature falls below the threshold temperature. Thus, after the end of the warm-up routine, during a drying period of drying the medium  12 , the air is being supplied to the drying chamber  19  at the second air flow rate. 
     When the heating unit  35  heats the printed medium  12 , the liquid deposited on the medium  12  evaporates, and steam is generated. The humidity in the drying chamber  19  increases due to the steam, and the medium  12  becomes less likely to be dried. In this regard, the drying device  14  blows air onto the medium  12  while heating the medium  12  supported by the support face  15   a . The air in the drying chamber  19  flows out of the outflow portion  20  by the amount supplied from the air blowing unit  50 . The steam generated as a result of drying the medium  12  is discharged to the outside of the drying device  14  together with the air in the drying chamber  19 . When the air is supplied to the drying chamber  19  at the second air flow rate, the air in the drying chamber  19  flows out of the outflow portion  20  with significant force compared to when the air is supplied to the drying chamber  19  at the first air flow rate. As illustrated by outlined arrows in  FIG. 2 , the air that has flowed out with the significant force is less likely to return to the inflow port  46 . Thus, the outside air having low humidity readily enters the inflow port  46 , and an increase in humidity in the drying chamber  19  is suppressed. 
     Effects of the present embodiment will now be described. 
     The air supplied to the drying chamber  19  is heated by the heating unit  35 . The inflow port  46  opens downward in the vertical direction Z. The outflow portion  20  is positioned lower than the inflow port  46  in the vertical direction Z. Thus, when the control unit  17  changes the air flow rate of the air supplied to the drying chamber  19 , of the air flowing out from the outflow portion  20 , the amount of air returning to the inflow port  46  can be changed. In other words, when the air flow rate supplied to the drying chamber  19  is small, the air velocity of the air flowing out of the outflow portion  20  is slow, so the amount of air returning to the inflow port  46  increases. Thus, heated air can be circulated to efficiently warm the drying chamber  19 . When the air flow rate of the air supplied to the drying chamber  19  is large, the air velocity of the air flowing out of the outflow portion  20  is fast, so the amount of air returning to the inflow port  46  decreases. Thus, the air having a high humidity can be discharged out of the device. Therefore, by controlling the driving of the air blowing unit  50  in accordance with the case in which the drying chamber  19  is to be heated and the case in which the medium  12  is to be dried, condensation can be reduced while efficiently warming the drying chamber  19 . 
     When the detected temperature is lower than the threshold temperature, the control unit  17  supplies the air at the first air flow rate. The air supplied at the first air flow rate can easily return to the inflow port  46  and efficiently warm the drying chamber  19 . When the detected temperature is equal to or greater than the threshold temperature, the control unit  17  increases the air flow rate and supplies the air at the second air flow rate. The air supplied at the second air flow rate is less likely to return to the inflow port  46 , so the outside air is more likely to flow into the inflow port  46 . Thus, a risk of the temperature of the air passing through the air blowing unit  50  increasing excessively can be reduced. 
     The support portion  15  supports the medium  12  transported downstream in the transport direction D 1  from the print position P. In other words, the medium  12  is transported downstream in the transport direction D 1 , from the print position P positioned further upstream in the transport direction D 1  than the drying device  14 . The air blowing unit  50  causes the air in the drying chamber  19  to flow in the same direction as the direction in which the medium  12  is transported. Thus, compared to a case in which the air in the drying chamber  19  is caused to flow in an opposite direction to the direction in which the medium  12  is transported, a risk of the air flowing out of the drying chamber  19  flowing toward the print position P can be reduced. 
     The air velocity of the air flowing out of the outflow portion  20  can also be varied by changing the shape and size of the outflow portion  20 . Thus, the drying device  14  may change the air velocity of the air flowing out of the outflow portion  20  by including a movable member for changing the shape and size of the outflow portion  20 . However, when the movable member is provided, the configuration becomes complex. In this regard, the air blowing unit  50  changes the rotation speed of the fan  54  to change the air velocity of the air flowing out of the outflow portion  20 . Therefore, the air velocity of the air flowing out of the outflow portion  20  can be changed while preventing the configuration from becoming more complex. 
     When the air blowing unit  50  changes the rotation speed of the fan  54 , the air flow rate of the air flowing in from the inflow port  46  also changes. When the air is supplied to the drying chamber  19  at the second air flow rate that is greater than the first air flow rate, a second inflow amount of the air flowing in from the inflow port  46  is greater than a first inflow amount of the air flowing in from the inflow port  46  when the air is supplied to the drying chamber  19  at the first air flow rate. Thus, when the air blowing unit  50  supplies the air to the drying chamber  19  at the second air flow rate, more air can be taken in than when the air is supplied at the first air flow rate. Thus, the air blowing unit  50  can efficiently exchange air in the drying chamber  19 . 
     The air flowing out of the outflow portion  20  after drying the medium  12  has a high humidity and temperature. When the air having a high temperature hits the printing unit  13 , there is a risk that so-called nozzle clogging may occur, in which the nozzle is clogged and becomes unable to eject the liquid. The air having a high humidity may cause condensation. In this regard, the outflow portion  20  is positioned in a position further separated from the printing unit  13  than the heating unit  35 , and causes the air to flow out toward the opposite side to the printing portion  13 . Thus, an influence of the air flowing out of the outflow portion  20  on the printing unit  13  can be reduced. 
     Second Embodiment 
     Next, a second embodiment of the printing apparatus will be described with reference to the drawings. Note that control executed by the control unit  17  is different from that of the first embodiment in this second embodiment. Further, since other points are substantially the same as those of the first embodiment, duplicate descriptions of the same configuration will be omitted while assigning the same reference signs to the same components. 
     The control unit  17  of the present embodiment determines whether or not the support portion  15  supports the printed medium  12 . The control unit  17  may determine whether or not the support portion  15  is supporting the printed medium  12  on the basis of the length of a transport path of the medium  12  from the print position P to the drying chamber  19  and the transport speed at which the medium  12  is transported. In other words, the control unit  17  determines that the support portion  15  is supporting the printed medium  12  after a transport time has elapsed, which is a time required to transport a printed portion of the medium  12  to the drying chamber  19  from a time at which the printing unit  13  starts the printing. The control unit  17  determines that the support portion  15  is not supporting the printed medium  12  after the transport time has elapsed from a time at which the printing unit  13  finishes the printing. Note that in the present embodiment, the control unit  17  determines whether or not the support portion  15  is supporting the printed medium  12  on the basis of the elapsed time from the time at which the printing unit  13  starts the printing, but the control unit  17  may use a separately provided image sensor to detect whether or not an image is present on the surface of the medium  12 , and may determine whether or not the support portion  15  is supporting the printed medium  12  on the basis of this detection. 
     Next, a drying routine executed by the control unit  17  will be described with reference to a flowchart illustrated in  FIG. 4 . The control unit  17  executes the drying routine at a timing at which the drying device  14  is activated. 
     As illustrated in  FIG. 4 , at step S 201 , the control unit  17  drives the air blowing unit  50  so that the rotation speed of the fan  54  per unit time is the first rotation speed, and supplies the air to the drying chamber  19  at the first air flow rate. At step S 202 , the control unit  17  operates the heating unit  35 . 
     At step S 203 , the control unit  17  determines whether or not the support portion  15  supports the printed medium  12 . When the support portion  15  supports the printed medium  12 , YES is determined at step S 203 , and the control unit  17  causes the processing to proceed to step S 204 . At step S 204 , the control unit  17  drives the fan  54  at the second rotation speed, and supplies the air to the drying chamber  19  at the second air flow rate. 
     When the support portion  15  does not support the printed medium  12 , NO is determined at step S 203 , and the control unit  17  causes the processing to proceed to step S 205 . At step S 205 , the control unit  17  drives the fan  54  at the first rotation speed, and supplies the air to the drying chamber  19  at the first air flow rate. 
     At step S 206 , the control unit  17  determines whether or not the printing apparatus  11  has finished the printing and the drying device  14  has finished drying the medium  12 . When the drying is not complete, NO is determined at step S 206 , and the control unit  17  causes the processing to proceed to step S 203 . When the drying is complete, YES is determined at step S 206 , and the control unit  17  causes the processing to proceed to step S 207 . At step S 207 , the control unit  17  stops driving the air blowing unit  50 . At step S 208 , the control unit  17  stops operating the heating unit  35 . 
     Next, actions of the present embodiment will be described. 
     When the support portion  15  does not support the printed medium  12 , the control unit  17  supplies the air to the drying chamber  19  at the first air flow rate that is less than at the second air flow rate. When the support portion  15  does not support the printed medium  12 , the humidity inside the drying chamber  19  is less likely to increase. Thus, the warmed air in the drying chamber  19  can be circulated to efficiently warm the support portion  15 , the cover  36 , the flow path member  49 , and the like. 
     When the support portion  15  supports the printed medium  12 , the liquid attached to the heated medium  12  evaporates, and steam is generated, which tends to increase the humidity inside the drying chamber  19 . As a result, the air flowing out of the outflow portion  20  becomes air having high humidity. 
     When the support portion  15  supports the printed medium  12 , the control unit  17  supplies the air to the drying chamber  19  at the second air flow rate that is greater than the first air flow rate. When the air is supplied to the drying chamber  19  at the second air flow rate, the air flowing out of the outflow portion  20  is less likely to return to the inflow port  46  compared to a case in which the air is supplied at the first air flow rate that is less than the second air flow rate. Since the air returning to the inflow port  46  decreases, the outside air having low humidity easily enters the inflow port  46 , and an increase in humidity in the drying chamber  19  is suppressed. 
     Effects of the present embodiment will now be described. 
     (7) When the support portion  15  does not support the printed medium  12 , the control unit  17  supplies the air at the first air flow rate. The air supplied at the first air flow rate can easily return to the inflow port  46  and efficiently warm the drying chamber  19 . When the support portion  15  supports the printed medium  12 , the control unit  17  increases the air flow rate and supplies the air at the second air flow rate. The air supplied at the second air flow rate is less likely to return to the inflow port  46 , so the outside air is more likely to flow into the inflow port  46 . Therefore, the air having an increased humidity as a result of drying the medium  12  can be easily discharged. 
     The present embodiment described above may be modified as follows. The present embodiment and modified examples thereof to be described below may be implemented in combination within a range in which a technical contradiction does not arise.
         As illustrated in  FIG. 5 , the drying device  14  may be provided with an air blower  56  capable of guiding the air flowing out from the outflow portion  20  into the inflow port  46 . The air blower  56  may be provided on the inclined wall  52 . When the control unit  17  drives the air blowing unit  50  to supply the air to the drying chamber  19  at the first air flow rate, the control unit  17  may drive the air blower  56  to guide the air flowing out of the outflow portion  20  to the inflow port  46 . When the control unit  17  drives the air blowing unit  50  to supply the air to the drying chamber  19  at the second air flow rate, the control unit  17  may stop driving the air blower  56 .   The drying chamber  19  may include a discharge portion for discharging the medium  12  separately from the outflow portion  20 .   The medium  12  to be dried by the drying device  14  is not limited to the long medium  12 , and may be a medium of a single sheet. The drying device  14  may include a sensor for detecting the presence or absence of the medium supported by the support portion  15 . Based on the detection result of the sensor, the control unit  17  may supply the air at the first air flow rate when the support portion  15  does not support the medium, and may supply the air at the second air flow rate when the support portion  15  supports the medium.   After the detected temperature exceeds the threshold temperature and the control unit  17  drives the air blowing unit  50  at the second rotation speed, the control unit  17  may control the driving of the air blowing unit  50  depending on whether or not the support portion  15  supports the printed medium  12 . For example, after executing the warm-up routine illustrated in  FIG. 3 , the control unit  17  may execute the drying routine illustrated in  FIG. 4  from step S 203 .   The control unit  17  may switch the air flow rate supplied to the drying chamber  19  in three or more stages. For example, after the detected temperature exceeds the threshold temperature, when the detected temperature falls below the threshold temperature, the control unit  17  may supply the air at a third air flow rate, which is greater than the first air flow rate and less than the second air flow rate.   The air blowing unit  50  may blow the air toward the support face  15   a  in the normal direction H. The air blowing unit  50  may cause the air in the drying chamber  19  to flow in a direction opposite to the transport direction D 1 .   The drying device  14  may be provided separately from the printing apparatus that performs the printing on the medium  12 .   The printing apparatus  11  may be an apparatus that prints an image such as characters, pictures, photographs, and the like by depositing a liquid such as ink on the medium  12 , and may be a serial printer, a lateral printer, a line printer, a page printer, or the like. Further, the printing apparatus may be an offset printing apparatus, a textile printing apparatus, or the like.       

     Hereinafter, technical concepts and effects thereof that are understood from the above-described embodiments and modified examples will be described. 
     A drying device includes a support portion configured to support a printed medium, a heating unit provided in a drying chamber for drying the medium supported by the support portion, a flow path member forming an air flow path connecting an inflow port that opens downward in a vertical direction and the drying chamber, an air blowing unit configured to supply air, flowing from the inflow port into the air flow path, to the drying chamber and cause the air to flow out of an outflow portion of the drying chamber, and a control unit configured to control driving of the air blowing unit. The outflow portion is positioned lower than the inflow port in the vertical direction, and the control unit controls the driving of the air blowing unit to change an air flow rate of the air supplied to the drying chamber. 
     According to this configuration, the air supplied to the drying chamber is heated by the heating unit. The inflow port opens downward in the vertical direction. The outflow portion is positioned lower than the inflow port in the vertical direction. Thus, when the control unit changes the air flow rate of the air supplied to the drying chamber, of the air flowing out of the outflow portion, the amount of air returning to the inflow port can be changed. In other words, when the air flow rate of the air supplied to the drying chamber is small, the air velocity of the air flowing out from the outflow portion is slow, so the amount of air returning to the inflow port increases. Thus, heated air can be circulated to efficiently warm the drying chamber. When the air flow rate of the air supplied to the drying chamber is large, the air velocity of the air flowing out of the outflow portion is fast, so the amount of air returning to the inflow port decreases. Thus, air having a high humidity can be discharged out of the device. Therefore, by controlling the driving of the air blowing unit in accordance with the case in which the drying chamber is to be warmed and the case in which the medium is to be dried, condensation can be reduced while efficiently warming the drying chamber. 
     The drying device may further include a detector configured to detect a temperature of the drying chamber. When a detected temperature detected by the detector is lower than a threshold temperature, the control unit may supply the air to the drying chamber at a first air flow rate, and when the detected temperature is equal to or greater than the threshold temperature, the control unit may supply the air to the drying chamber at a second air flow rate that is greater than the first air flow rate. 
     According to this configuration, when the detection temperature is lower than the threshold temperature, the control unit supplies the air at the first air flow rate. The air supplied at the first air flow rate can easily return to the inflow port and efficiently warm the drying chamber. When the detection temperature is equal to or greater than the threshold temperature, the control unit increases the air flow rate and supplies the air at the second air flow rate. The air supplied at the second air flow rate is less likely to return to the inflow port, so the outside air easily flows into the inflow port. Thus, the risk of the temperature of the air passing through the air blowing unit excessively increasing can be reduced. 
     In the drying device, when the support portion does not support the printed medium, the control unit may supply the air to the drying chamber at a first air flow rate, and when the support portion supports the printed medium, the control unit may supply the air to the drying chamber at a second air flow rate that is greater than the first air flow rate. 
     According to this configuration, when the support portion does not support the printed medium, the control unit supplies the air at the first air flow rate. The air supplied at the first air flow rate can easily return to the inflow port and efficiently warm the drying chamber. When the support portion supports the printed medium, the control unit increases the air flow rate and supplies the air at the second air flow rate. The air supplied at the second air flow rate is less likely to return to the inflow port, so the outside air easily flows into the inflow port. Therefore, air having an increased humidity as a result of drying the medium can be easily discharged. 
     In the drying device, the support portion may support the medium transported downstream in a transport direction from a print position at which printing is performed, and the air blowing unit may cause the air in the drying chamber to flow from upstream to downstream in the transport direction. 
     According to this configuration, the support portion supports the medium transported downstream in the transport direction from the print position. In other words, the medium is transported downstream in the transport direction, from the print position positioned further upstream in the transport direction than the drying device. The air blowing unit causes the air in the drying chamber to flow in the same direction as the direction in which the medium is transported. Thus, compared to a case in which the air in the drying chamber is caused to flow in the direction opposite to the direction in which the medium is transported, the risk of the air flowing out from the drying chamber flowing toward the print position can be reduced. 
     A printing apparatus includes a printing unit configured to perform printing on a medium, a support portion configured to support the printed medium, a heating unit provided in a drying chamber for drying the medium supported by the support portion, a flow path member forming an air flow path connecting an inflow port that opens downward in a vertical direction and the drying chamber, an air blowing unit configured to supply air, flowing from the inflow port into the air flow path, to the drying chamber and cause the air to flow out of an outflow portion of the drying chamber, and a control unit configured to control driving of the air blowing unit. The outflow portion is positioned lower than the inflow port in the vertical direction, and the control unit controls the driving of the air blowing unit to change an air flow rate of the air supplied to the drying chamber. 
     According to this configuration, the same effect as the drying device described above can be obtained.