Patent Publication Number: US-8529053-B2

Title: Seasoning device and image forming apparatus

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is based on and claims priority under 35 USC 119 from Japanese Patent Application No. 2010-179536 filed on Aug. 10, 2010, the disclosure of which is incorporated by reference herein. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a seasoning device and an image forming apparatus. 
     2. Related Art 
     Japanese Patent Application Laid-Open No. 2007-177081 discloses a technique of, by generating micro cracks as fine cracks to a certain extent in image and line portions of a printed medium which is generated by heat-set printing as a kind of offset printing, alleviating the stress inside a dried ink film and reducing wrinkles fixedly formed by the dried film. 
     However, in the related art, the material components of a liquid (ink) used to form an image are limited. 
     SUMMARY OF THE INVENTION 
     The invention is provided to suppress the cockling (ripples) generated in a recording medium (a sheet of paper) having an image formed thereon without depending on the material of a liquid used to form an image. 
     According to a first aspect of the invention, there is provided a seasoning device including: a stack unit on which a recording medium is stacked, the recording medium having an image formed thereon by ejection of liquid droplets and the image being dried; and a spray unit that blows humidified air at the recording medium stacked in the stack unit. 
     According to this configuration, the recording mediums which liquid droplets are ejected to form an image and the formed image is dried are stacked in the stack unit. The spray unit blows the humidified air toward the recording mediums stacked on the stack unit (the humidified air is blown from an end portion of the stacked recording mediums between the recording mediums). Accordingly, an amount of moisture (moisture content) in a non-image-formed portion (a portion in which an image is not formed) of the recording medium increases. 
     In this way, by raising the amount of moisture in the non-image-formed portion of the recording medium, the difference in the amounts of moisture between an image-formed portion (a portion in which an image is formed) and the non-image-formed portion is reduced. Accordingly, it is possible to suppress the cockling (ripples) generated in the recording medium. 
     In this way, in the aspect, the seasoning device is a device that adjusts moisture (humidity) of the recording medium (moisture content in the recording medium) by blowing humidified air at the recording medium stacked in the stack unit. 
     A second aspect of the invention provides the seasoning device according to the first aspect, wherein the spray unit blows non-humidified air in the atmosphere at the recording medium after blowing humidified air at the recording medium. 
     According to this configuration, the spray unit blows non-humidified air in the atmosphere to the recording medium after blowing the humidified air to the recording medium. Accordingly, it is possible to quickly adapt the recording medium to the temperature and humidity of the surrounding atmosphere. 
     A third aspect of the invention provides the seasoning device according to the first or second aspect, wherein the spray unit blows humidified air having a humidity which does not raise a residual amount of moisture contained in an image-formed portion of the recording medium to which the liquid droplets have been ejected to form the image. 
     According to this configuration, the spray unit blows the air with a humidity which does not raise the amount of moisture contained in the image-formed portion to which the liquid droplets are ejected to form the image. Accordingly, it is possible to effectively reduce the difference in the amounts of moisture between the image-formed portion and the non-image-formed portion. 
     A fourth aspect of the invention provides the seasoning device according to any one of the first to third aspects, wherein: the recording medium, on which the image is formed, is discharged from an apparatus main body of an image forming apparatus that forms the image, and the discharged recording medium is stacked in the stack unit, and the spray unit extends in a direction intersecting a discharge direction of the recording medium. 
     According to this configuration, the spray unit extends in the direction intersecting the discharging direction of the recording medium. Accordingly, it is possible to blow the humidified air over the width direction of the recording medium. 
     A fifth aspect of the invention provides the seasoning device according to any one of the first to fourth aspects, wherein the spray unit includes: a water pipe having nozzles from which a mist is sprayed, a water supply device that supplies water to the water pipe, and an air blower that blows humidified air that is humidified by the mist sprayed from the nozzles of the water pipe. 
     According to this configuration, the water supply device supplies water to the water pipe and the mist is sprayed from the nozzles of the water pipe. The air blower blows the air, which is humidified with the mist sprayed from the nozzles of the water pipe, to the recording medium. 
     Accordingly, it is possible to blow the humidified air to the recording medium with a simple structure. 
     A sixth aspect of the invention provides the seasoning device according to the fifth aspect, the device further includes: a humidity detecting section that detects the humidity of a region at which the recording medium is discharged from the apparatus main body; and a controller that controls a volume of water supplied to the water pipe by the water supply device on the basis of a detection signal from the humidity detecting section. 
     According to this configuration, the humidity detecting section detects the humidity of the portion in which the recording medium is discharged from the apparatus main body. The controller controls the volume of water supplied to the water pipe by the water supply device on the basis of the detection signal from the humidity detecting section. 
     Accordingly, it is possible to blow the air humidified in the optimal humidity to the recording medium with a simple structure. 
     A seventh aspect of the invention provides the seasoning device according to the sixth aspect, wherein the controller controls a driving power of the air blower according to a discharge speed of the recording medium. 
     According to this configuration, since the controller controls the driving power of the air blower according to the discharge speed of the recording medium, it is possible to set the amount of air blown to the recording medium to the optimal amount according to the discharging speed of the recording medium. 
     An eighth aspect of the invention provides the seasoning device according to the sixth or seventh aspect, wherein the controller selectively controls opening and closing of the nozzles of the water pipe according to a size of the recording medium. 
     According to this configuration, the controller selectively controls the opening and closing of the nozzles of the water pipe according to the size of the recording medium. Accordingly, it is possible to blow the humidified air to only the recording medium and thus to suppress the humidified air from flying around the recording medium. 
     A ninth aspect of the invention provides the seasoning device according to any one of the first to eighth aspects, wherein the stack unit is vertically movable. 
     According to this configuration, the stack unit is disposed so as to be able to move up and down. By causing the stack unit to move up and down, it is possible to uniformly blow the humidified air between the stacked recording mediums. 
     According to a tenth aspect of the invention, there is provided an image forming apparatus including: a liquid droplet ejecting head that ejects liquid droplets to a recording medium to form an image; and the seasoning device according to any one of the first to ninth aspects in which the recording medium having an image formed thereon is stacked and that blows the humidified air to the stacked recording medium. 
     According to this configuration, since the image forming apparatus includes the seasoning device according to any one of the first to ninth aspects, it is possible to suppress the cockling (ripples) from being generated in the recording medium. 
     According to the aspects of the invention, it is possible to suppress the cockling (ripples) from being generated in a recording medium having an image formed thereon without depending on the material of a liquid used to form the image. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Embodiments of the invention will be described in detail with reference to the following drawings, wherein: 
         FIG. 1  is a perspective view illustrating a seasoning device according to an embodiment of the invention; 
         FIGS. 2A and 2B  are diagrams illustrating an amount of moisture in a sheet of paper when the seasoning device according to the embodiment of the invention is used and an amount of moisture in a sheet of paper according to the related art; and 
         FIG. 3  is a diagram illustrating schematically illustrating the configuration of an image forming apparatus according to an embodiment of the invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     An image forming apparatus  10  according to an embodiment of the invention will be described below with reference to  FIGS. 1 to 3 . Arrow UP in the drawings represents an upside in a vertical direction. 
     Entire Configuration 
     As shown in  FIG. 3 , an image forming apparatus  10  includes a paper feed unit  12  that feeds a sheet of paper P as a recording medium to an apparatus main body  10 A, a process liquid applying unit  14  that applies a process liquid to an image forming surface of the sheet of paper P, an image forming unit  16  that forms an image on the sheet of paper P, a drying unit  18  that reduces the moisture of (dries) the sheet of paper P so as to enhance strength of image layer of an image-formed portion in which an image is formed, a fixing unit  20  that fixes the formed image to the sheet of paper P, and a discharge unit  22  to which the sheet of paper P is discharged. 
     The sheets of paper P are stacked on the paper feed unit  12  and the sheets of paper P are sent out to the apparatus main body  10 A by the paper feed unit  12  sheet by sheet. A feed tray  24  guiding the sheet of paper P sent out from the paper feed unit  12  to the apparatus main body  10 A is disposed downstream side in the transporting direction of the sheet of paper P (hereinafter, simply referred to as “downstream side”) with respect to the paper feed unit  12 . A feed drum  26  rotating and transporting the sheet of paper P along the outer circumferential surface thereof is disposed in the apparatus main body  10 A downstream side with respect to the feed tray  24 . The sheet of paper P is transported to the process liquid applying unit  14  by the feed drum  26 . 
     The process liquid applying unit  14  includes a process liquid applying drum  28 , with rotating, receiving the sheet of paper P transported by the feed drum  26  and transporting the sheet of paper P along the outer circumferential surface thereof. Specifically, a holding member  30  holding the end of the sheet of paper P is disposed on the outer circumferential surface of the process liquid applying drum  28 . According to this configuration, the sheet of paper P is transported downstream side by means of the rotation of the process liquid applying drum  28  in the state in which the end of the sheet of paper P is held by the holding member  30 . 
     A process liquid applying device  32  applying the process liquid to the image forming surface of the sheet of paper P transported by the process liquid applying drum  28  is disposed above the process liquid applying drum  28 . The process liquid has an effect of reacting with liquid droplets to be described later to aggregate a coloring material (pigment) and to promote the separation of the coloring material (pigment) from the solvent. 
     A transporting drum  34 , with rotating, receiving the sheet of paper P transported by the process liquid applying drum  28  and transporting the sheet of paper P to the image forming unit  16  is disposed downstream side with respect to the process liquid applying drum  28 . 
     The image forming unit  16  includes an image forming drum  36 , with rotating, receiving the sheet of paper P transported by the transporting drum  34  and transporting the sheet of paper P along the outer circumferential surface thereof. A liquid droplet ejecting head  38  ejecting liquid droplets of ink or the like to the sheet of paper P transported by the image forming drum  36  to form an image on the sheet of paper P is disposed above the image forming drum  36 . The liquid droplet ejecting head  38  is a so-called full-line head having an ink ejecting range corresponding to the maximum width of the sheet of paper P. In this embodiment, the liquid droplet ejecting heads  38  of four colors of Y (Yellow), M (Magenta), C (Cyan), and K (Black) as exemplary basic colors are arranged in the circumferential direction of the image forming drum  36 . 
     A transporting drum  40  receiving the sheet of paper P transported by the image forming drum  36  and transporting the sheet of paper P to the drying unit  18  is disposed downstream side with respect to the image forming drum  36 . 
     The drying unit  18  includes a drying drum  42 , with rotating, receiving the sheet of paper P transported by the transporting drum  40  and transporting the sheet of paper P along the outer circumferential surface thereof. A halogen heater  44  and a warm air nozzle  46  as an example of a drying member are disposed above the drying drum  42 . While the sheet of paper P is being transported by the drying drum  42 , the moisture contained in the sheet of paper P is reduced (dried) by means of the heat from the halogen heater  44  and the warm air from the warm air nozzle  46  so as to enhance strength of image layer of the image-formed portion in which an image is formed. Accordingly, strength of image layer of the image formed on the sheet of paper P is improved. 
     A transporting drum  48  receiving the sheet of paper P transported by the drying drum  42  and transporting the sheet of paper P to the fixing unit  20  is disposed downstream side with respect to the drying drum  42 . 
     The fixing unit  20  includes a fixing drum  50 , with rotating, receiving the sheet of paper P transported by the transporting drum  48  and transporting the sheet of paper P along the outer circumferential surface thereof. A halogen heater  62  for heating (preliminary heating), a fixing roller  64  pressing the sheet of paper P against the fixing drum  50 , and an in-line sensor  66  measuring a check pattern, an amount of moisture, a surface temperature, a gloss level, and the like of the sheet of paper P are disposed to face the outer circumferential surface of the fixing drum  50 . 
     A discharge drum  52 , with rotating, receiving the sheet of paper P transported by the fixing drum  50  and discharging the received sheet of paper P to the outside of the apparatus main body  10 A is disposed downstream side with respect to the fixing drum  50 . 
     A guide plate  54  formed in a curved shape so as to guide the sheet of paper P to the outside of the apparatus main body  10 A is disposed downstream side with respect to the discharge drum  52 . 
     The sheet of paper P discharged to the outside of the apparatus main body  10 A is discharged to a seasoning device  56  disposed in the discharge unit  22  by the discharge drum  52 . The details of the seasoning device  56  will be described later. 
     Main Configuration 
     The seasoning device  56  disposed at the discharge unit  22  will be described below. 
     In the embodiment, the seasoning device  56  is a device that adjusts moisture (humidity) of the sheets of paper P (moisture content in the sheets of paper P) by blowing humidified air at the sheets of paper P stacked in the stack unit  68 . 
     As shown in  FIG. 1 , the seasoning device  56  includes a stack unit  68  in which sheets of paper P having an image formed thereon are stacked and a spray device  70  spraying humidified air to the sheets of paper P stacked in the stack unit  68 . 
     The spray device  70  includes plural (three in this embodiment) air blowers  72  blowing air to the sheets of paper P and a temperature adjusting member (not shown in the drawing) adjusting the temperature of the air blown to the sheets of paper P by the air blowers  72 . 
     Specifically, the plural air blowers  72  are arranged in the width direction of the sheets of paper P (the direction intersecting the discharging direction of the sheets of paper P) and blow air toward the end portion of the sheets of paper P so that the air is blown between the stacked sheets of paper P (from the end portion of the sheets of paper P). 
     The spray device  70  includes a water pipe  74  disposed between the air blowers  72  and the sheets of paper P, and a water supply device  80  supplying water to the water pipe  58 . Plural nozzles (three in the drawings but not limited to three) spraying flowing water (in the water pipe  74 ) in a spray form (mist) are formed in the outer circumferential surface of the water pipe  58  and the nozzles can be opened and closed. 
     A humidity detecting member  82  (see  FIG. 3 ) detecting the humidity of the portion to which the sheet of paper P is discharged from the apparatus main body  10 A is provided. A controller  84  controlling the volume of water supplied to the water pipe  74  by the water supply device  80  on the basis of the detection signal from the humidity detecting member  82  is further provided. The controller  84  adjusts the driving power of the air blowers  72  depending on the discharging speed of the sheet of paper P. The controller  84  controls the selective opening and closing of the nozzles of the water pipe  74  depending on the size of the sheet of paper P so as to blow the humidified air to only the sheets of paper P. (For example, in a case of the large sheets of paper P, all of the nozzles are made to be opened, and in a case of the small sheets of paper P, for example, in accordance with the size of the sheets of paper P (in a direction intersecting the discharge direction), the nozzles positioned at both end portions in the longitudinal direction of the water pipe  74  are made to be closed.) 
     A driving device  86  driving the stack unit  68  so as to move up and down is disposed in the stack unit  68 . The driving device  86  is actuated to move the stack unit  68  up and down under the control of the controller  84 . 
     In this embodiment, the spray device  70  blows the air humidified in a humidity in a range from 75% RH to 85% RH (aiming at 80% RH) to the sheets of paper P so as not to increase the amount of moisture contained in the image-formed portions formed on the sheets of paper P (humidifying seasoning). In addition, after the humidified air is blown to the sheets of paper P, the controller  84  stops the spraying of water from the water pipe  74  and blows non-humidified air, that is, air in the atmosphere to the sheets of paper P (blowing seasoning). 
     Operation and Effect 
     As shown in  FIG. 6 , the sheet of paper P fed from the paper feed unit  12  is transported along the outer circumferential surfaces of the rotating feed drum  26  and the rotating process liquid applying drum  28 . In the process liquid applying unit  14 , the process liquid applying device  32  applies a process liquid to the image forming surface of the sheet of paper P transported along the outer circumferential surface of the process liquid applying drum  28 . 
     The sheet of paper P to which the process liquid has been applied is sent to the transporting drum  34  and is transported along the outer circumferential surfaces of the rotating transporting drum  34  and the rotating image forming drum  36 . In the image forming unit  16 , the liquid droplet ejecting heads  38  of the respective colors eject the liquid droplets of ink or the like to the image forming surface of the sheet of paper P transported by the image forming drum  36  to form an image on the sheet of paper P. 
     The sheet of paper P having an image formed on the image forming surface thereof is sent to the transporting drum  40  and is transported along the outer circumferential surfaces of the rotating transporting drum  40  and the rotating drying drum  42 . In the drying unit  18 , the sheet of paper P transported by the drying drum  42  is dried by means of the heat from the halogen heater  44  and the warm air blown from the warm air nozzle  46 . That is, the moisture contained in the sheet of paper P is reduced (dried), thereby enhancing strength of image layer of the image-formed portion in which the image has been formed. 
     The sheet of paper P which is made to be to a high temperature by means of the heat from the halogen heater  44  and the warm air blown from the warm air nozzle  46  is sent to the transporting drum  48  and is transported along the outer circumferential surfaces of the rotating transporting drum  48  and the rotating fixing drum  50 . In the fixing unit  20 , the halogen heater  62  disposed to face the fixing drum  50  fixes the image formed on the sheet of paper P onto the sheet of paper P by means of heat. The sheet of paper P transported by the fixing drum  50  is pressed against the fixing drum  50  by the fixing roller  64  and passes through the portion facing the in-line sensor  66 . The in-line sensor  66  measures a check pattern, an amount of moisture, a surface temperature, a gloss level, and the like of the sheet of paper P passing therethrough. 
     The sheet of paper P having been subjected to the measurement by the in-line sensor  66  is sent to the discharge drum  52 , is transported along the outer circumferential surface of the rotating discharge drum  52 , is guided by the guide plate  54 , and is discharged to the discharge unit  22  outside the apparatus main body  10 A. 
     When the sheet of paper P discharged from the apparatus main body  10 A is left in the stacked state, it is thought the cockling (ripples) are generated due to (depending on) the difference in the amount of moisture between an image-formed portion containing the moisture of the liquid droplets and a non-image-formed portion not containing the moisture of the liquid droplets. 
       FIG. 2B  shows a graph in a case in which a sheet of paper P discharged from the apparatus main body  10 A is left in the stacked state. The vertical axis of the graph represents the amount of moisture and the origin of the vertical axis is set to the amount of moisture originally contained in the sheet of paper P. On the other hand, the horizontal axis represents the time and the origin of the horizontal axis is set to the time at which the sheet of paper P passes through the drying unit  18 . 
     As can be seen from the graph, because of the ejection of the liquid droplets, the amount of moisture in the image-formed portion in which an image is formed on the sheet of paper P is larger than the amount of moisture in the non-image-formed portion in which an image is not formed in the sheet of paper P. 
     In the apparatus main body  10 A, the amounts of moisture in the image-formed portion and the non-image-formed portion are reduced by means of the heat from the halogen heater  44  and the warm air from the warm air nozzle  46 , which are disposed in the drying unit  18 , thereby enhancing strength of image layer of the image-formed portion. Here, the strength of image layer is represented by the vertical axis. 
     When the sheet of paper P is discharged from the apparatus main body  10 A and then is left in the stacked state, the amount of moisture in the image-formed portion is reduced and the amount of moisture in the non-image-formed portion is increased with the lapse of time. Accordingly, the difference in the amounts of moisture between the image-formed portion and the non-image-formed portion (D in  FIG. 2B ) is reduced. However, the amount of moisture in the non-image-formed portion is not returned to the amount of moisture originally contained in the sheet of paper P if the sheet of paper P is merely left undone (uncontrolled) in this way. 
     Since the amount of moisture in the non-image-formed portion is not returned to the amount of moisture originally contained in the sheet of paper P, it is thought that the difference in the amount of moisture between the image-formed portion and the non-image-formed portion is great and thus the cockling (ripples) is generated in the sheet of paper P. 
     As shown in  FIG. 1 , in this embodiment, the sheet of paper P discharged from the apparatus main body  10 A is stacked in the stack unit  68  provided in the seasoning device  56  and humidified air (humidified in 80% RH in this embodiment) is blown thereto by the spray device  70  (humidifying seasoning). 
     The humidified air blown (emitted) from the spray device  70  is blown between the sheets of paper P and supplies moisture to the non-image-formed portions. After blowing the humidified air for 5 minutes, the nozzles of the water pipe  74  are closed and air of the atmosphere, which is not humidified, is blown to the sheets of paper P for 10 minutes under the control of the controller  84  (blowing seasoning). 
       FIG. 2A  shows a graph illustrating the relationship between the amount of moisture and the time in a case where the humidifying seasoning is performed on a sheet of paper P discharged from the apparatus main body  10 A for 5 minutes and the blowing seasoning is performed for 10 minutes after the humidifying seasoning is performed as in this example. 
     As can be seen from this graph, the amount of moisture in the image-formed portion of the sheet of paper P is larger than the amount of moisture in the non-image-formed portion. In the apparatus main body  10 A, the amounts of moisture in the image-formed portion and the non-image-formed portion are reduced by means of the heat from the halogen heater  44  and the warm air from the warm air nozzle  46 , thereby enhancing strength of image layer of the image-formed portion. 
     When a sheet of paper P is discharged from the apparatus main body  10 A and the humidifying seasoning is performed for 5 minutes, the amount of moisture in the non-image-formed portion is returned to the amount of moisture originally contained in the sheet of paper P. The amount of moisture in the image-formed portion is not reduced but is maintained in a constant state. 
     After performing of the 5 minutes of humidifying seasoning is finished, the blowing seasoning is performed for 10 minutes. By this, the image-formed portion is adapted to the atmosphere and the amount of moisture in the image-formed portion is thus reduced. Specifically, by performing the blowing seasoning, the amount of moisture (F shown in  FIG. 2A ) in the image-formed portion becomes substantially equal to the amount of moisture (G shown in  FIG. 2B ) in the image-formed portion in a case where the sheet of paper P discharged from the apparatus main body  10 A is left undone. 
     Accordingly, the difference in the amounts of moisture (J shown in  FIG. 2A ) between the image-formed portion and the non-image-formed portion decreases. Since the amount of moisture in the non-image-formed portion is returned to the amount of moisture originally contained in the sheet of paper P unlike the case in which the sheet of paper P is left undone, the difference in the amounts of moisture (J shown in  FIG. 2A ) between the image-formed portion and the non-image-formed portion is smaller than the difference in the amounts of moisture (D shown in  FIG. 2B ) between the image-formed portion and the non-image-formed portion in the case in which the sheet of paper P is merely left undone. 
     In this way, by performing the humidifying seasoning, it is possible to reduce the difference in the amounts of moisture between the image-formed portion and the non-image-formed portion. 
     Since the difference in the amounts of moisture between the image-formed portion and the non-image-formed portion is reduced, it is possible to suppress the cockling (ripples) from being generated in the sheet of paper P. 
     By performing the blowing seasoning, it is possible to effectively adapt the image-formed portion to the ambience and reduce the amount of moisture in the image-formed portion. 
     By setting the air blown to the sheets of paper P to a humidity of 75% RH to 85% RH (aiming at 80% RH) at the time of performing the humidifying seasoning, it is possible to suppress the amount of moisture contained in the image-formed portion from increasing. 
     By suppressing the amount of moisture contained in the image-formed portion from increasing, it is possible to suppress the difference in the amounts of moisture between the image-formed portion and the non-image-formed portion from increasing. 
     The spray device  70  extends in the direction intersecting the discharging direction of the sheet of paper P. Accordingly, it is possible to uniformly blow the humidified air all over the width direction of the sheet of paper P. 
     Although a specific embodiment of the invention has been described in detail, it will be apparent to those skilled in the art that the invention is not particularly limited to the embodiment but may be modified in various forms within the scope of the invention. For example, it has been described in the embodiment that the air with a humidity of 75% RH to 85% RH (aiming at 80% RH) is blown to the sheet of paper P at the time of performing the humidifying seasoning. However, the invention is not limited to this configuration, but the humidity may be set to such a humidity to promote the increase in the amount of moisture in the non-image-formed portion and to suppress the increase in the amount of moisture in the image-formed portion. 
     Although not specifically described in the embodiment, a sheet bundle of the sheets of paper P stacked in the stack unit  68  may be moved to a particular different place after the humidifying seasoning and the blowing seasoning are ended. In this case, it is possible to efficiently perform the humidifying seasoning and the blowing seasoning to the sheets of paper P stacked in the stack unit  68  after the moving. 
     Although not specifically described in the embodiment, the driving device  86  may be actuated to move up and down the stack unit  68  under the control of the controller  84  at the time of performing the humidifying seasoning or the blowing seasoning. In this way, by moving up and down the stack unit  68 , the sheets of paper P are moved up and down with respect to the spray device  70 , thereby effectively blowing the humidified air between the sheets of paper P. 
     Although not specifically described in the embodiment, the controller  84  may adjust the volume of water supplied to the water pipe  74  by the water supply device  80  on the basis of the detection signal from the humidity detecting member  82 . In this case, it is possible to adjust the humidity of the humidified air corresponding to (on the basis of) the humidity of the portion in which the sheets of paper P are discharged, with a simple structure. 
     Although not specifically described in the embodiment, the controller  84  may adjust the driving power of the air blowers  72  corresponding to (on the basis of) the discharging speed of the sheets of paper P. In this case, it is possible to set the volume of air blown to the sheets of paper P to the optimal volume corresponding to the discharging speed of the sheets of paper P. 
     In a case where the controller  84  is selectively open and close the nozzles of the water pipe  74  depending on the size of the sheet of paper P, it is possible to blow the humidified air to only the sheets of paper P and thus to suppress the humidified air from flying around the sheets of paper P.