Patent Publication Number: US-10768555-B1

Title: Cleaning device

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is based on and claims priority under 35 USC 119 from Japanese Patent Application No. 2019-028082 filed Feb. 20, 2019. 
     BACKGROUND 
     (i) Technical Field 
     The present disclosure relates to a cleaning device. 
     (ii) Related Art 
     Japanese Unexamined Patent Application Publication No. 2017-126033 describes a transfer device that includes a second-transfer roller. The second-transfer roller includes an elastic layer and a surface layer that is closely attached to the outside of the elastic layer. The second-transfer roller rotates and transfers a toner image from a surface of an intermediate transfer belt to a recording medium. The transfer device further includes a cleaning member and a pressing member. The cleaning member is in contact with the second-transfer roller and scrapes off substances adhering to the surface layer. The pressing member is pressed against the surface layer at a position downstream of a position where the intermediate transfer belt contacts the second-transfer roller and upstream of the cleaning member in the rotation direction of the second-transfer roller. The pressing member rotates in the same direction as the second-transfer roller. 
     Japanese Unexamined Patent Application Publication No. 2018-25643 describes a cleaning device that includes a first cleaning plate and a second cleaning plate. The first cleaning plate performs cleaning by causing a free end thereof to contact an outer peripheral surface of a cylindrical second-transfer rotational body, which has an elastic layer, in such a way that the outer peripheral surface elastically deforms. The second cleaning plate performs cleaning by causing a free end thereof to contact a portion of the outer peripheral surface of the second-transfer rotational body. The portion is located downstream, in the rotation direction of the second-transfer rotational body, of a position where the free end of the first cleaning plate contacts. The portion elastically deforms in such a way that the curvature of a surface thereof becomes smaller than those of other portions due to contact of the free end of the first cleaning plate. 
     SUMMARY 
     A structure including a scraping portion whose edge is pressed against a rotational body to which toner adheres and that scrapes the toner off the rotational body is known. With such a structure, the toner may be melted by frictional heat that is generated between the edge of the scraping portion and the rotational body, and the toner may firmly adhere to the edge of the scraper and the like. 
     Aspects of non-limiting embodiments of the present disclosure relate to reducing firm adhesion of toner to a scraping portion due to generation of frictional heat, compared with a case where a container is tightly closed. 
     Aspects of certain non-limiting embodiments of the present disclosure address the above advantages and/or other advantages not described above. However, aspects of the non-limiting embodiments are not required to address the advantages described above, and aspects of the non-limiting embodiments of the present disclosure may not address advantages described above. 
     According to an aspect of the present disclosure, a cleaning device includes a scraping portion whose edge is pressed against a rotational body to which toner adheres and that scrapes the toner off the rotational body, and a container that contains the toner that has been scraped off the rotational body. The container has a through-hole that opens in a portion of the container facing the scraping portion and that allows a gas to flow from an inside of the container toward the scraping portion. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       An exemplary embodiment of the present disclosure will be described in detail based on the following figures, wherein: 
         FIG. 1  is a schematic view of an image forming apparatus according to the exemplary embodiment; 
         FIG. 2  is a perspective view of a second-transfer device according to the exemplary embodiment; 
         FIG. 3  is a perspective view of a housing body and a housing cover; 
         FIG. 4  is an enlarged sectional view of the second-transfer device, taken along line IV-IV of  FIG. 2 . 
         FIG. 5  illustrates the relationship between a through-hole and a cover tab; 
         FIG. 6  illustrates the flow of a gas in a waste toner container; 
         FIG. 7  illustrates the flow of a gas around a scraper; 
       and 
         FIG. 8  illustrates the flow of a gas at an end portion of the second-transfer roller. 
     
    
    
     DETAILED DESCRIPTION 
     Hereafter, an exemplary embodiment of the present disclosure will be described with reference to the drawings. 
     Image Forming Apparatus  100   
       FIG. 1  is a schematic view of an image forming apparatus  100  according to the present exemplary embodiment. The image forming apparatus  100  illustrated in  FIG. 1  is a tandem color printer. The image forming apparatus  100  includes the following: an image forming section  10  that forms images corresponding to image data items for respective colors; an image scanner  30  that scans an image of a document; a sheet feeder  40  that supplies a sheet S to the image forming section  10 ; a transport section  50  that transports the sheet S when the image forming apparatus  100  performs duplex printing to form images on both sides of the sheet S; and a controller  90  that controls the operation of the entirety of the image forming apparatus  100 . 
     The constituent elements of the image forming apparatus  100  are contained in a casing  60 . A stacker  70  is disposed at an upper surface of the casing  60  below the image scanner  30 . Sheets S on which images have been formed by the image forming section  10  are stacked on the stacker  70 . 
     Image Forming Section  10   
     The image forming section  10  includes four image forming units  1 Y,  1 M,  1 C, and  1 K that are arranged side by side at regular intervals. Each of the image forming units  1 Y,  1 M,  1 C, and  1 K forms a toner image by using an electrophotographic method. The image forming units  1 Y,  1 M,  1 C, and  1 K have the same structure, except that toners contained in developing devices  16  (described below) differ from each other. The image forming units  1 Y,  1 M,  1 C, and  1 K respectively form yellow (Y), magenta (M), cyan (C), and black (K) toner images. 
     The image forming section  10  includes an intermediate transfer belt  13  to which the color toner images formed on photoconductor drums  12  of the image forming units  1  are transferred. The image forming section  10  includes first-transfer rollers  17  that successively transfer (first-transfer) the color toner images formed by the image forming units  1  to the intermediate transfer belt  13 . The image forming section  10  further includes a second-transfer device  20  that simultaneously transfers (second-transfers) the color toner images that overlap on the intermediate transfer belt  13  to the sheet S, a fixing device  24  that fixes the second-transferred color toner images to the sheet S, and an output roller  26  that outputs the sheet S. 
     Image Forming Unit  1   
     Each of the image forming units  1  includes the photoconductor drum  12  that holds a toner image, a charging device  14  that charges the photoconductor drum  12 , an exposure device  15  that exposes the surface of the charged photoconductor drum  12  to form an electrostatic latent image, and the developing device  16  that develops the electrostatic latent image on the photoconductor drum  12  to form a toner image. In the developing device  16 , a two-component developer, which includes a magnetic carrier and a toner having a predetermined color, is used. 
     Image Forming Process 
     The image forming apparatus  100  performs an image forming process under the control by the controller  90 . That is, image data is obtained from a PC (not shown) or the image scanner  30 , an image processor (not shown) processes the image data to generate image data items for respective colors, and the image data items are sent to the exposure devices  15  of the image forming units  1 . The exposure devices  15  perform exposure and the developing devices  16  perform development, thereby forming toner images on the photoconductor drums  12 . 
     The first-transfer rollers  17  successively first-transfer the color toner images formed on the photoconductor drums  12  of the image forming units  1  to the intermediate transfer belt  13 , thereby forming an overlapping toner image in which the color toner images overlap. The overlapping toner image is transported toward the second-transfer device  20  as the intermediate transfer belt  13  moves. 
     A sheet S is supplied from the sheet feeder  40  and is transported to the second-transfer device  20  with a timing corresponding to the timing with which the overlapping toner image on the intermediate transfer belt  13  is transported to the second-transfer device  20 . The second-transfer device  20  second-transfers the overlapping toner image from the intermediate transfer belt  13  to the sheet S. The fixing device  24  fixes the overlapping toner image, which has been transferred to the sheet S, to the sheet S. The output roller  26  outputs the sheet S to the stacker  70 . When the image forming apparatus  100  performs duplex printing, the transport section  50  transports the sheet S, on a front surface (first surface) of which a fixed image has been formed through the process described above, again to the second-transfer device  20 , and a fixed image is formed on a back surface (second surface) of the sheet S. 
     The temperature of the second-transfer device  20  easily increases because of the position thereof in the image forming apparatus  100 . To be specific, the temperature of the second-transfer device  20  easily increases, because the fixing device  24  generates heat. In particular, the temperature of the second-transfer device  20  easily increases during duplex printing, because a sheet S whose temperature has been increased due to fixing of an image to the front surface (first surface) thereof is transported again to the second-transfer device  20  via the transport section  50 . Moreover, as described below, the second-transfer device  20  causes a second-transfer roller  21  to form a nip with the intermediate transfer belt  13 , and a cleaning device  22  cleans the second-transfer roller  21 . With such a structure, the distance from a nip point to a region to be cleaned along the outer periphery of the second-transfer roller  21  is short, and the temperature of the second-transfer device  20  easily increases, compared with, for example, a case where the second-transfer roller  21  is composed of a belt (not shown). 
     In the following description, the up-down direction of the image forming apparatus  100  illustrated in  FIG. 1  (vertical direction) may be simply referred to as the “up-down direction”. The upper side in the up-down direction in  FIG. 1  may be simply referred to as the “upper side”, and the lower side in the up-down direction may be simply referred to as the “lower side”. The left-right direction of the image forming apparatus  100  illustrated in  FIG. 1  may be simply referred to as the “width direction”. The right side along the plane of  FIG. 1  may be simply referred to as the “one side”, and the left side along the plane of  FIG. 1  may be simply referred to as “the other side”. The depth direction of the image forming apparatus  100  with respect to the plane of  FIG. 1  may be simply referred to as the “depth direction”. The proximal side of the plane of  FIG. 1  may be simply referred to as the “proximal side”, and the distal side of the plane of  FIG. 1  may be simply referred to as the “distal side” (see  FIG. 2 ). 
     Second-Transfer Device  20   
       FIG. 2  is a perspective view of the second-transfer device  20  according to the present exemplary embodiment. 
       FIG. 3  is a perspective view of a housing body  33  and a housing cover  35 . In  FIG. 3 , a part of the structure of a housing  31  is simplified for clarity. 
     Next, referring to  FIGS. 1 to 3 , the second-transfer device  20  according to the present exemplary embodiment will be described. 
     As illustrated in  FIG. 2 , the second-transfer device  20  includes the second-transfer roller  21  and the cleaning device  22 . The second-transfer roller  21  rotates while being in contact with the outer peripheral surface of the intermediate transfer belt  13  (see  FIG. 1 ) with a predetermined pressure. The cleaning device  22  cleans the outer peripheral surface of the second-transfer roller  21  by removing unwanted substances, such as toner and paper powder, that remain on and adheres to the outer peripheral surface. 
     The second-transfer roller  21  is a cylindrical member that includes at least an elastic layer and is rotatable in a predetermined direction (see arrow A 1 ). The second-transfer roller  21  illustrated in  FIG. 2  has a structure such that an elastic layer  213  and a surface layer  215  are formed in this order on the outer peripheral surface of an electroconductive roller base  211 , which is made of a metal or the like. The elastic layer  213  is made of, for example, a material that includes an elastic material such as foamed polyurethane and an electroconductive material such as carbon black. The elastic layer  213 , which is elastically deformable, reduces friction with an abutting member such as a scraper  27 . The surface layer  215  is made of, for example, a synthetic resin such as a polyimide resin. The second-transfer roller  21  illustrated in  FIG. 2  is capable of contacting and separating from the outer peripheral surface of the intermediate transfer belt  13  (see  FIG. 1 ). 
     The cleaning device  22  includes a roller seal  23 , a blade  25 , and the scraper  27 , which are located along the outer periphery of the second-transfer roller  21 . The cleaning device  22  includes a housing seal  28 , an auxiliary roller  29 , the housing  31 , and an auger  37 . Hereafter, the constituent elements of the cleaning device  22  will be described. 
     The roller seal  23  is an elongated film-shaped member (plate-shaped member) whose longitudinal direction coincides with the direction in which the rotation shaft of the second-transfer roller  21  extends. One end (base) of the roller seal  23  in a direction (seal width direction) perpendicular to the longitudinal direction is supported by the housing  31 . The other end (edge) of the roller seal  23  in the seal width direction is in contact with the outer peripheral surface of the second-transfer roller  21 . The entirety of the roller seal  23  is disposed in a curved state. The roller seal  23  prevents leakage of unwanted substances, such as toner, collected by the blade  25  and the like, to the outside of the housing  31 . That is, the roller seal  23  functions as a cover member that covers a cleaning opening  32  (described below) of the housing  31 . 
     The blade  25  includes a blade body  251  and a blade holder  253  that holds the blade body  251 . The blade body  251  is an elongated plate-shaped member whose longitudinal direction coincides with the direction in which the rotation shaft of the second-transfer roller  21  extends. One end (base) of the blade body  251  in a direction (blade width direction) perpendicular to the longitudinal direction is supported by the blade holder  253 . The other end (edge) of the blade body  251  in the blade width direction is in contact with the outer peripheral surface of the second-transfer roller  21 . The blade body  251  is in contact with the second-transfer roller  21  at a position on the downstream side of the roller seal  23  in the rotation direction of the second-transfer roller  21  (see arrow A 1 ). The blade body  251  is made of an elastically deformable material such as a rubber or a synthetic resin. The blade holder  253  is made by bending a metal plate, having a substantially rectangular shape in plan view, to have an L-shaped cross section. The blade holder  253  is supported by the housing  31 . 
     The blade  25  presses the edge of the blade body  251  against the outer peripheral surface of the second-transfer roller  21  and scrapes off toner that adheres to the second-transfer roller  21 . The term “serape off” refers to removing substances that adhere to a surface of an object (such as the second-transfer roller  21 ) by causing a constituent member (such as the blade body  251 ) to contact the object. The blade  25  illustrated in  FIG. 2  suppresses leakage of unwanted substances, such as collected toner, to the outside of the housing  31 . That is, the blade  25  functions as a member that covers the cleaning opening  32  (described below) of the housing  31 . 
     The scraper  27  includes a scraper body  271  and a scraper holder  273  that holds the scraper body  271 . The scraper body  271  is an elongated plate-shaped member whose longitudinal direction coincides with the direction in which the rotation shaft of the second-transfer roller  21  extends. One end (base) of the scraper body  271  in a direction (scraper width direction) perpendicular to the longitudinal direction is supported by the scraper holder  273 . The other end (edge) of the scraper body  271  in the scraper width direction is in contact with the outer peripheral surface of the second-transfer roller  21 . The scraper body  271  is in contact with the second-transfer roller  21  at a position on the downstream side of the blade body  251  in the rotation direction of the second-transfer roller  21  (see arrow A 1 ). The scraper body  271  is made of a metal or the like and is structured to have higher rigidity than the blade body  251 . The scraper body  271  is made from a member (thin plate) whose thickness (plate thickness) is smaller than that of the blade body  251 . 
     The scraper holder  273  is made by bending a metal plate, having a substantially rectangular shape in plan view, to have an L-shaped cross section. The scraper holder  273  is supported by the housing  31 . The scraper holder  273  and the blade holder  253  are disposed in such a way that the longitudinal directions thereof coincide with the depth direction and the bent portions thereof are separated from the other. That is, the scraper holder  273  and the blade holder  253  are disposed in such a way that a channel R, which is a space interposed therebetween, is large. 
     The scraper  27  presses the edge of the scraper body  271  against the outer peripheral surface of the second-transfer roller  21  and scrapes off toner that adheres to the second-transfer roller  21 . To be more specific, the scraper  27  removes unwanted substances that are not removed by the blade  25 . Toner or the like that adheres to the second-transfer roller  21  may cause so-called “filming”, which is a phenomenon in which the toner or the like forms a film that firmly adheres to the surface of the second-transfer roller  21 . The scraper  27  scrapes the surface of the second-transfer roller  21  with the edge of the scraper body  271  to remove the film of toner formed by filming. The scraper  27  is pressed against the second-transfer roller  21  with a force (for example, a vertical load) that is larger than that of the blade  25 . Because the blade  25  removes unwanted substances in advance, it is possible to reduce a force that presses the scraper  27 , which is located at a position on the downstream side of the blade  25  in the rotation direction of the second-transfer roller  21  (see arrow A 1 ), against the second-transfer roller  21 . 
     The housing seal  28  is an elongated film-shaped member (plate-shaped member) whose longitudinal direction coincides with the direction in which the rotation shaft of the second-transfer roller  21  extends. The housing seal  28  is made of an elastically deformable material such as polyurethane, and seals the channel R that is interposed between the scraper holder  273  and the blade holder  253 . The channel R is a space that is surrounded by the second-transfer roller  21 , the blade  25 , the scraper  27 , the housing seal  28 , and the like and that extends in the depth direction. 
     The housing seal  28  illustrated in  FIG. 2  includes a scraper seal  281 , a blade seal  283 , and a middle seal  285 . The scraper seal  281  is disposed between the scraper holder  273  and the housing body  33  (described below). The blade seal  283  is disposed between the blade holder  253  and the housing body  33 . The middle seal  285  is disposed in a gap (recess) in the housing body  33 . 
     The auxiliary roller  29  includes a plurality of roller pairs that are arranged in the depth direction. The auxiliary roller  29  guides a sheet S, which is supplied from the sheet feeder  40  (see  FIG. 1 ), to a nip between the second-transfer roller  21  and the intermediate transfer belt  13  as the roller pairs rotate. 
     Next, referring to  FIGS. 2 and 3 , the housing  31  will be described. The housing  31  is a box-shaped structure whose longitudinal direction coincides with the direction in which the rotation shaft of the second-transfer roller  21  extends and that opens toward the second-transfer roller  21 . To be more specific, the housing  31  has the cleaning opening  32  in a portion thereof that is on the upper side in the up-down direction and on one side in the width direction. The cleaning opening  32  is a rectangular opening that faces the outer peripheral surface of the second-transfer roller  21 . 
     The housing  31  includes the housing body  33 , the housing cover  35  that is fixed to the housing body  33 , and a cover seal  36  that is interposed between the housing body  33  and the housing cover  35 . The housing body  33  and the housing cover  35  constitute a waste toner container (waste toner box)  310 . Toner (waste toner) collected by the blade  25  is accumulated in an inner space of the waste toner container  310 , which is a space interposed between the housing body  33  and the housing cover  35 . 
     As illustrated in  FIG. 3 , the housing body  33  contains the auger  37  and forms an upper space  331  in an upper part of the waste toner container  310 . The housing body  33  has an opening  332  that is in a lower part thereof in the up-down direction and that has a substantially rectangular shape in a front view. The housing body  33  has a seal groove  333  that surrounds the opening  332 . That is, the seal groove  333  is a ring-shaped groove that is formed along the opening  332 . The housing body  33  has a plurality of (four) through-holes  330  that are formed in a body side surface  335  and that allow the inside and the outside of the waste toner container  310  to communicate with each other. Details of the through-holes  330  will be described below. 
     As illustrated in  FIG. 3 , the housing cover  35  includes a cover body  351  that covers the opening  332  of the housing body  33 . The housing cover  35  is a box-shaped member whose side facing the housing body  33  is open. The housing cover  35  forms a lower space  352  (see  FIG. 2 ) in a lower part of the waste toner container  310 . The housing cover  35  includes a cover side surface  353 , which is located on one side in the width direction in a state in which the housing cover  35  is fixed to the housing body  33 , and a plurality of (four) cover tabs  350 , which protrude toward the one side in the width direction from the cover side surface  353 . The cover tabs  350  are inserted into the through-holes  330  of the housing body  33  and determine the position of the housing cover  35  relative to the housing body  33 . The cover tabs  350  illustrated in  FIG. 3  are each a plate-shaped member that is disposed in a direction such that a plate surface thereof intersects the up-down direction. The cover tabs  350  are arranged in the depth direction. Details of the structure of each of the cover tabs  350  will be described below. 
     As illustrated in  FIG. 3 , the cover seal  36  is a ring-shaped member that is made of an elastically deformable material such as polyurethane. The cover seal  36  illustrated in  FIG. 3  is fitted into the seal groove  333 , which has a ring-like shape. The cover seal  36  restricts passing of toner while allowing passing of a gas (air) therethrough. To be more specific, the cover seal  36  is a gas-permeable member that has a large number of small pores smaller than the particle size of toner. The cover seal  36  can be regarded as a mesh member. The cover seal  36  suppresses a flow of waste toner, which is contained in the waste toner container  310 , to the outside. 
     As illustrated in  FIG. 2 , the auger  37  includes a rotation shaft  371  and a screw blade  373  disposed on the outer periphery of the rotation shaft  371 . As the rotation shaft  371  of the auger  37  rotates (see arrow A 2  in  FIG. 2 ) by receiving a driving force from a driving source (not shown), the screw blade  373  transports toner contained in the waste toner container  310  in the depth direction. Thus, the auger  37  levels the waste toner contained in the waste toner container  310 . That is, the auger  37  suppresses piling up of the waste toner in a partial region of the waste toner container  310 . As the auger  37  receives a driving force from the driving source and rotates, the auger  37  accelerates the flow of a gas in the waste toner container  310 . The flow of the gas in the waste toner container  310  will be described below. 
     Through-Hole  330   
       FIG. 4  is an enlarged sectional view of the second-transfer device  20 , taken along line IV-IV in  FIG. 2 . 
       FIG. 5  illustrates the relationship between one of the through-holes  330  and a corresponding one of the cover tabs  350 . 
     Next, referring to  FIGS. 3 to 5 , how the through-holes  330  contribute to cooling of the scraper  27  will be described. 
     As described above, the scraper  27  is disposed in such a way that the edge of the scraper body  271  is in contact with the outer peripheral surface of the second-transfer roller  21 . In this state, when the second-transfer device  20  operates and the second-transfer roller  21  rotates, the edge of the scraper body  271  rubs against the outer peripheral surface of the second-transfer roller  21  and generates frictional heat. The frictional heat increases the temperature of the scraper body  271  to, for example, 45° C. or higher. If the temperature of the scraper body  271  exceeds the melting temperature of toner, the toner melts and may firmly adhere to the scraper body  271 . In the exemplary embodiment, the through-holes  330  are formed to suppress firm adhesion of toner due to increase in temperature of the scraper body  271 . 
     As illustrated in  FIG. 3 , the through-holes  330 , each of which is an opening having a substantially rectangular shape in a front view, are arranged in the depth direction. As illustrated in  FIG. 4 , each of the through-holes  330  is formed at a position where at least a part of the through-hole  330  faces the scraper  27 . To be more specific, the through-hole  330  opens toward the scraper holder  273  of the scraper  27 . The through-holes  330  allow a flow of a gas from the inside of the waste toner container  310  toward the scraper holder  273  of the scraper  27 . As described below in details, although the internal pressure of the waste toner container  310  increases as the second-transfer roller  21  rotates, increase of the internal pressure of the waste toner container  310  is suppressed because the gas is released from the through-holes  330 . Moreover, the scraper  27  is cooled due to the flow of the gas from the through-holes  330 . To be more specific, it is possible to reduce the temperature of the scraper  27  by forming the through-holes  330  in the waste toner container  310 , compared with a case where the through-holes  330  are not formed and the waste toner container  310  is tightly closed. 
     As illustrated in  FIG. 3 , the through-holes  330  extend through the body side surface  335  in the thickness direction and allow the body side surface  335  side and the inside of the seal groove  333  to communicate with each other. In other words, the through-holes  330  connect the inside and the outside of the body side surface  335 . The cover seal  36  is disposed in the seal groove  333 . A part of the cover seal  36  is exposed toward the inside of the waste toner container  310 . With such a disposition, a gas that flows from the inside of the waste toner container  310  toward the through-holes  330  via the seal groove  333  passes through the cover seal  36 . To be more specific, the gas from the inside of the waste toner container  310  passes through portions  361  of the cover seal  36  that face the through-holes  330 . Thus, a flow of waste toner to the outside from the through-holes  330  is suppressed. 
     As illustrated in  FIG. 4 , each of the cover tabs  350  is inserted into a corresponding one of the through-holes  330  in order to fix the housing cover  35  to the housing body  33 . The through-hole  330  illustrated in  FIG. 4  has dimensions larger than those of the cover tab  350 . Thus, in a state in which the cover tab  350  is inserted, the gas flows out from a gap formed between the cover tab  350  and the through-hole  330 . To be specific, the length L 12  of the through-hole  330  in the depth direction is larger than the length L 11  of the cover tab  350  in the depth direction. Thus, in the state in which the cover tab  350  is inserted into the through-hole  330 , a gap in the depth direction is formed. The length H 12  of the through-hole  330  in the up-down direction is larger than the length H 11  of the cover tab  350  in the up-down direction. Thus, in the state in which the cover tab  350  is inserted into the through-hole  330 , a gap in the up-down direction is formed. Because the cover tab  350  have such dimensions, the gas flows out through a gap formed around the cover tab  350  in a state in which the cover tab  350  is inserted. 
     Flow of Gas 
       FIG. 6  illustrates the flow of a gas in the waste toner container  310 . 
       FIG. 7  illustrates the flow of a gas around the scraper  27 . 
       FIG. 8  illustrates the flow of a gas at an end portion of the second-transfer roller  21 . 
     Next, referring to  FIGS. 6 to 8 , the flow of a gas in the second-transfer device  20  will be described. 
     As illustrated in  FIG. 6 , in a state in which the second-transfer roller  21  is in contact (forms a nip) with the outer peripheral surface of the intermediate transfer belt  13 , the cleaning opening  32  of the waste toner container  310  is covered by the second-transfer roller  21 , the roller seal  23 , and the blade  25 . That is, the waste toner container  310  is a closed space. 
     When the second-transfer roller  21  rotates, the edge of the roller seal  23  in the seal width direction may swing, and a gap may be temporarily formed between the roller seal  23  and the second-transfer roller  21 . When a gap is formed, a gas flows into the waste toner container  310  (see arrow B 11  in  FIG. 6 ), and the internal pressure of the waste toner container  310  increases. The gas that has flowed into the waste toner container  310  moves along the blade  25  (see arrow B 12  in  FIG. 6 ), and circulates in the waste toner container  310  (see arrows B 13  to B 16  in  FIG. 6 ). The gas in the waste toner container  310  flows out from the through-holes  330  (see arrow B 17  in  FIG. 6 ). The gas that has flowed out from the through-holes  330  as described above is blown against the scraper  27 . Thus, the scraper  27 , whose temperature has increased due to friction with the second-transfer roller  21 , is cooled. 
     Here, the gas that has flowed out from the through-holes  330  flows into the channel R that is a space disposed among, that is, defined by the blade  25 , the scraper  27 , and the second-transfer roller  21 . Accordingly, the gas that moves in the channel R cools the scraper  27  and the second-transfer roller  21 . 
     As illustrated in  FIG. 7 , because the channel R extends in the depth direction, the gas that flows out from the through-holes  330  flows in the depth direction (see arrows C 11  and C 12  in  FIG. 7 ). In this way, because the gas that flows out from the through-holes  330  moves in the channel R in the depth direction, the gas can cool an area that is large in the depth direction. For example, because the gas flows in the channel R in the depth direction, it is possible to cool an area that is larger than a region where the through-holes  330  are formed (see region W 1  in  FIG. 7 ). 
     Here, in the example illustrated in  FIG. 7 , the gas that moves in the channel R in the depth direction is released to the outside of the second-transfer device  20  from both ends of the channel R in the depth direction. Hereafter, referring to  FIG. 8 , the flow of the gas at both ends of the channel R will be described. 
     First, although description has been omitted, as illustrated in  FIG. 8 , a first drive gear  217  and a second drive gear  218  are disposed at a proximal end portion of the roller base  211  of the second-transfer roller  21  in the depth direction. As the first drive gear  217  and the second drive gear  218  receive a driving force from a driving source (not shown), the second-transfer roller  21  rotates. The housing body  33  has a cutout  338 , in which the roller base  211  is disposed, at a position between the first drive gear  217  and the elastic layer  213  in the depth direction. Moreover, a gap is formed between the cutout  338  and the roller base  211 . The gap is located at a proximal end portion of the channel R in the depth direction. The gas that moves in the channel R in the depth direction is released to the outside of the second-transfer device  20  through the gap (see arrows C 13  and C 14  in  FIG. 8 ). Although detailed description is omitted, a cutout  338  is formed in the housing body  33  also at a distal end portion of the roller base  211  of the second-transfer roller  21  in the depth direction. A gas is released to the outside of the second-transfer device  20  through a gap between the cutout  338  and the roller base  211 . 
     As illustrated in  FIG. 6 , the blade  25  is disposed at a position that covers the cleaning opening  32  of the waste toner container  310 . The scraper  27  is located further toward the outside of the waste toner container  310  (toward the one side in the width direction) than the blade  25 . Accordingly, the blade  25  suppresses a flow of a gas from the inside of the waste toner container  310  toward the scraper  27 . Because the blade  25  covers the opening of the waste toner container  310 , the internal pressure of the waste toner container  310  easily increases. As a result, the amount of gas that flows out from the through-holes  330  increases, and the scraper  27  is more efficiently cooled. As in the example illustrated in  FIG. 6 , by disposing the edge of the blade  25  so as to be in contact with the second-transfer roller  21 , a flow of a gas from a space between the edge of the blade  25  and the second-transfer roller  21  is suppressed, and accordingly the amount of gas that passes through the through-holes  330  is increased. The through-hole  330  illustrated in  FIG. 6  is configured to guide the gas toward the scraper  27  that is located at a position where the gas does not easily flow from the inside of the waste toner container  310 . 
     Although description has been omitted, the housing cover  35  has an inclined surface  355  that is a part of an inner wall of the waste toner container  310  and that is located below the through-holes  330 . The inclined surface  355  is inclined in a direction toward the one side in the width direction and the upper side in the up-down direction. The gas that flows from the other side toward the one side in the width direction (see arrow B 15  in  FIG. 6 ) moves along the inclined surface  355  toward the upper side in the up-down direction. Accordingly, the inclined surface  355  guides the gas flow (gas) toward the through-holes  330 . 
     As illustrated in  FIG. 6 , the rotation direction of the auger  37  (see arrow A 2  in  FIG. 6 ) coincides with the direction in which the gas circulates in the waste toner container  310  (see arrows B 13  to B 16  in  FIG. 6 ). In other words, the auger  37  has a function of guiding the gas toward the through-holes  330 . Thus, the amount of gas that flows out from the through-holes  330  is increased, and accordingly the function of cooling the scraper  27  is improved. In addition, because waste toner in the waste toner container  310  is leveled as the auger  37  rotates, overflow of the toner from the through-holes  330  is suppressed. 
     Modifications 
     In the foregoing description of the exemplary embodiment, the through-holes  330  are formed in the cleaning device  22  that cleans the second-transfer roller  21 . However, as long as the cleaning device  22  has a mechanism such that the edge thereof contacts the surface of a rotational body, an object to be cleaned by the cleaning device  22  is not limited to the second-transfer roller  21 . For example, the structure described in the exemplary embodiment may be used in a cleaning device (not shown) that cleans the intermediate transfer belt  13 , the photoconductor drum  12 , or a transfer roller (not shown). 
     In the foregoing description of the exemplary embodiment, the cleaning device  22  includes the blade  25  and the scraper  27 . However, the structure of the cleaning device  22  is not limited to this. For example, a cleaning device that does not have the blade  25  may cool the scraper  27  by using a gas that flows out from the through-holes  330 . A cleaning device that does not have the scraper  27  may cool the blade  25  by using a gas that flows out from the through-holes  330 . 
     In the foregoing description of the exemplary embodiment, the plurality of (four) through-holes  330 , each of which has a substantially rectangular shape in a front view, are arranged in the depth direction. However, the number and the shape of the through-holes are not limited to these. To be more specific, the number and the shape are not limited, as long as the through-holes can guide a gas from the inside of the waste toner container  310  to the scraper  27  or the like. 
     In the foregoing description of the exemplary embodiment, the auger  37  rotates and guides the gas toward the through-hole  330 . However, a member that guides the gas it not limited to an auger. To be more specific, any appropriate rotational body that rotates in the waste toner container  310 , such as a roller or a motor, may be used. 
     In the foregoing description of the exemplary embodiment, the channel R is defined by the blade  25 , the scraper  27 , the second-transfer roller  21 , and the like. However, members that define the channel R are not limited to these. To be more specific, as long as the channel R is a space that is defined by at least one of the blade  25  and the scraper  27 , the space may be defined by both of the blade  25  and the scraper  27 . 
     The cleaning device  22  in the foregoing description is an example of a cleaning device. The blade  25  and the scraper  27  are examples of a scraping portion. The blade  25  is an example of a first scraping member. The scraper  27  is an example of a second scraping member. The waste toner container  310  is an example of a container. The through-hole  330  is an example of a through-hole. The channel R is an example of a space. The cleaning opening  32  is an example of an opening region. The housing seal  28  is an example of a guide portion. The roller base  211  is an example of a rotation shaft. The housing body  33  is an example of a first member. The housing cover  35  is an example of a second member. The cover tab  350  is an example of a positioning tab. The cover seal  36  is an example of a sealing portion. The portion  361  that faces the through-hole  330  is an example of a portion that faces the through-hole. The inclined surface  355  and the auger  37  are examples of an acceleration mechanism. The inclined surface  355  is an example of a guide surface. The auger  37  is an example of another rotational body. The rotation shaft  371  is an example of another rotation shaft. The second-transfer roller  21  is an example of a rotational body. 
     The exemplary embodiment and the modifications described above may be used in combination, as appropriate. 
     The present disclosure is not limited to the exemplary embodiment described above and may be carried out in any forms within the spirit and scope of the present disclosure. 
     The foregoing description of the exemplary embodiment of the present disclosure has been provided for the purposes of illustration and description. It is not intended to be exhaustive or to limit the disclosure to the precise forms disclosed. Obviously, many modifications and variations will be apparent to practitioners skilled in the art. The embodiment was chosen and described in order to best explain the principles of the disclosure and its practical applications, thereby enabling others skilled in the art to understand the disclosure for various embodiments and with the various modifications as are suited to the particular use contemplated. It is intended that the scope of the disclosure be defined by the following claims and their equivalents.