Patent Publication Number: US-8977183-B2

Title: Cleaning device, and image carrier unit and image forming apparatus having same

Description:
This application relates to and claims priority from Japanese Patent Application No. 2012-043416, filed on Feb. 29, 2012 in the Japan Patent Office, the entire disclosure of which is incorporated herein by reference. 
     BACKGROUND 
     The present disclosure relates to a cleaning device for cleaning an image carrier which carries a toner image, and an image carrier unit and an image forming apparatus having such a cleaning device. 
     Conventionally, as an image forming apparatus for forming an image on a sheet, known is technology of a sheet passing through a transfer nip part, which is formed between a photoreceptor drum and a transfer roller, in a direction from down to up. A toner image is formed on the photoreceptor drum, and the toner image is transferred to the sheet at the transfer nip part. The image forming apparatus further includes a fixing unit, and the sheet to which the toner image was transferred is subject to fixation processing by the fixing unit, and then discharged. 
     With the foregoing conventional technology, a cleaning device is disposed facing the photoreceptor drum in order to clean the residual toner on the photoreceptor drum after the toner image is transferred at the transfer nip part. As described above, when the sheet passes through the transfer nip part in a direction from down to up, the cleaning device that is disposed on the further downstream side in the rotating direction of the photoreceptor drum than the transfer nip part is often disposed above the photoreceptor drum. 
     When the cleaning member is disposed above the photoreceptor drum, there are cases where the residual toner that was removed from the photoreceptor drum falls from the periphery of the cleaning member. Thus, a toner seal member is disposed to come into contact with the photoreceptor drum around the cleaning member in order to prevent the residual toner from falling. Nevertheless, when a large amount of toner is accumulated above the toner seal member, such toner will press the toner seal member toward the photoreceptor drum. Thus, the contact pressure of the toner seal member against the photoreceptor drum will increase. Meanwhile, when paper dust of the sheet becomes attached to the cylindrical face of the photoreceptor drum at the transfer nip part, there are cases where the paper dust is moved to the leading end of the toner seal member in response to the rotation of the photoreceptor drum. When the contact pressure of the toner seal member against the photoreceptor drum is high as described above, the paper dust becomes a clump between the leading end of the toner seal member and the cylindrical face of the photoreceptor drum. Consequently, there are cases where the leading end of the toner seal member lifts due to the clump of the paper dust, and cause defects such as toner leakage. 
     SUMMARY 
     The cleaning device according to one aspect of the present disclosure is disposed above an image carrier including a rotating axis, and a cylindrical face which rotates in one direction around the rotating axis and carries a toner image, and cleans the cylindrical face. The cleaning device includes a case, a rotating member, a sheet member, and a cover member. The rotating member is provided in the case, includes a peripheral face which comes into contact with the cylindrical face above the rotating axis in a cross section view that is orthogonal to the rotating axis, is rotatively driven in a same direction as the image carrier at a contact position which comes into contact with the cylindrical face, and recovers a toner which has attached on the image carrier. The sheet member is provided in the case, extends, in the cross section view, from a position that is above the rotating axis and separated from the cylindrical face toward a direction approaching a straight line that connects the rotating axis of the image carrier and the contact position of the rotating member, and includes a leading end which comes into contact with the cylindrical face on a side that is further upstream in the rotating direction of the image carrier than the rotating member. The cover member is provided in the case so as to cover an upside of the sheet member, extends from a position that is separated from the cylindrical face in the cross section view toward a direction approaching the straight line, and reaches a position above the leading end of the sheet member. 
     Moreover, the image carrier unit according to another aspect of the present disclosure includes the foregoing cleaning device, and the image carrier. The image carrier is disposed facing the rotating member. 
     Moreover, the image forming apparatus according to another aspect of the present disclosure includes the foregoing cleaning device, the image carrier, and a developing device. The image carrier is disposed facing the rotating member. The developing device supplies a toner to the cylindrical face of the image carrier. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view showing the appearance of the image forming apparatus according to one embodiment of the present disclosure; 
         FIG. 2  is a lateral cross section showing the internal structure of the image forming apparatus according to one embodiment of the present disclosure; 
         FIG. 3  is a lateral cross section showing the internal structure of the image carrier unit according to one embodiment of the present disclosure; 
         FIG. 4  is a lateral cross section showing the internal structure of the image carrier unit to be compared with the present disclosure; 
         FIG. 5  is a schematic diagram explaining a state where the toner is accumulated on the toner seal of  FIG. 4 ; 
         FIG. 6  is a schematic diagram explaining the state where the leading end of the toner seal of  FIG. 4  is lifting due to a clump of paper dust; 
         FIG. 7  is an enlarged cross section of a part of  FIG. 4 ; 
         FIG. 8  is an enlarged cross section of a part of  FIG. 3 ; and 
         FIG. 9  is an enlarged lateral cross section of a part of the image carrier unit according to another embodiment of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     Embodiments of the present disclosure are now explained in detail with reference to the appended drawings.  FIG. 1  is a perspective view showing the appearance of the image forming apparatus  1  according to one embodiment of the present disclosure. Moreover,  FIG. 2  is a lateral cross section showing the internal structure of the image forming apparatus  1  according to one embodiment of the present disclosure. Here, while a black-and-white printer is illustrated as the image forming apparatus  1 , the image forming apparatus may also be a copier, a facsimile machine, or a multi-function product having their functions, or an image forming apparatus which forms color images. 
     The image forming apparatus  1  includes a body housing  10  which has a substantially rectangular case structure, and a paper feeding unit  20 , an image forming unit  30 , a fixing unit  40  and a toner container  50  which are housed in the body housing  10 . 
     A front cover  11  is provided on a front face side of the body housing  10  and a rear cover  12  is provided on a rear face side of the body housing  10 , respectively. As a result of the front cover  11  being opened, the toner container  50  becomes exposed on the front face side. Consequently, the user can remove the toner container  50  from the front face side of the body housing  10  when the toner is used up. The rear cover  12  is a cover that is opened upon a sheet jam or for maintenance. The image forming unit  30  and the fixing unit  40  can be respectively removed from the rear face side of the body housing  10  as a result of the rear cover  12  being opened. Moreover, a left cover  12 L ( FIG. 1 ) is provided to a side face of the body housing  10  and a right cover  12 R (not shown in  FIG. 1 ) is provided to a side that is opposite to the left cover  12 L, respectively, in a manner of extending in the vertical direction. An inlet  12 La for incorporating air into the body housing  10  is provided to the front side portion of the left cover  12 L. Moreover, the top face of the body housing  10  has a paper discharging unit  13  to which a sheet, after an image is formed thereon, is discharged. Various devices for executing image formation are mounted in an internal space S ( FIG. 2 ) which is demarcated by the front cover  11 , the rear cover  12 , the left cover  12 L, the right cover  12 R, and the paper discharging unit  13 . 
     The paper feeding unit  20  includes a paper feeding cassette  21  for housing the sheets that were subject to the image forming process ( FIG. 2 ). A part of the paper feeding cassette  21  protrudes further forward from the front face of the body housing  10 . Of the paper feeding cassette  21 , the top face of the portion that is housed in the body housing  10  is covered by a paper feeding cassette top panel  21 U. The paper feeding cassette  21  has a sheet housing space where a bundle of sheets is housed, and a lift plate for lifting the bundle of sheets for paper feeding. A sheet supplying unit  21 A is provided to the top part on the rear end side of the paper feeding cassette  21 . The sheet supplying unit  21 A is provided with a paper feed roller  21 B for supplying, one sheet at a time, the uppermost sheet of the sheet bundle in the paper feeding cassette  21 . 
     The image forming unit  30  performs the image forming process of forming a toner image on the sheet that is fed from the paper feeding unit  20 . The image forming unit  30  includes a photoreceptor drum  31  (image carrier), and a charging device  32 , an exposure device (not shown in  FIG. 2 ), a developing device  33 , a transfer roller  34  and a cleaning device  35  which are disposed around the photoreceptor drum  31 . The image forming unit  30  is disposed between the left cover  12 L and the right cover  12 R. 
     The photoreceptor drum  31  includes a rotating axis  31 A, and a cylindrical face  31 B which rotates around the rotating axis  31 A ( FIG. 3 ). An electrostatic latent image is formed on the cylindrical face  31 B, and a toner image according to the electrostatic latent image is carried on the cylindrical face  31 B. As the photoreceptor drum  31 , a photoreceptor drum configured from an amorphous silicon (a-Si)-based material may be used. 
     The charging device  32  is used for uniformly charging the surface of the photoreceptor drum  31 , and includes a charge roller which comes into contact with the photoreceptor drum  31 . 
     The cleaning device  35  includes a cleaning blade and the like. The cleaning device  35  cleans the toner that became attached to the peripheral face of the photoreceptor drum  31  after the transfer of the toner image, and conveys the toner to a recovery device not shown. Moreover, the photoreceptor drum  31 , the charging device  32 , and the cleaning device  35  are configured integrally as a drum unit  31 H (refer to  FIG. 3 ) (image carrier unit). The cleaning device  35  and the drum unit  31 H will be described later in detail. 
     The exposure device includes optical components such as a laser light source, a mirror, and a lens. The exposure device forms an electrostatic latent image on the cylindrical face  31 B of the photoreceptor drum  31  by irradiating a laser beam that was modulated based on the image data provided from an external device such as a personal computer. The developing device  33  supplies a toner to the cylindrical face  31 B of the photoreceptor drum  31  for developing the electrostatic latent image and forming the toner image on the photoreceptor drum  31 . The developing device  33  includes a developing roller  331  for carrying the toner to be supplied to the photoreceptor drum  31 , and a first agitating screw  332  and a second agitating screw  333  for circulating and conveying, while agitating, the developer in a development housing not shown. 
     The transfer roller  34  is a roller for transferring, onto the sheet, the toner image formed on the cylindrical face  31 B of the photoreceptor drum  31 . The transfer roller  34  comes into contact with the cylindrical face  31 B of the photoreceptor drum  31 , and forms a transfer nip part TP ( FIG. 3 ). A transfer bias of reverse polarity to the toner is applied to the transfer roller  34 . 
     The fixing unit  40  performs fixation processing of fixing the transferred toner image onto the sheet. The fixing unit  40  includes a fixing roller  41  internally having a heat source, and a pressure roller  42  pressed against the fixing roller  41  and forms a fixation nip part with the fixing roller  41 . When the sheet to which the toner image was transferred is passed through the fixation nip part, the toner image is fixed onto the sheet based on the heating by the fixing roller  41  and the pressurization by the pressure roller  42 . 
     The toner container  50  stores the toner to be supplied to the developing device  33 . The toner container  50  includes a container body  51  which is the main location where the toner is stored, a cylindrical part  52  which protrudes from the bottom part of one side face of the container body  51 , a cover member  53  which covers the other side face of the container body  51 , and a rotating member  54  which conveys the toner housed inside the container. The toner stored in the toner container  50  is supplied inside the developing device  33  from a toner discharge outlet  521  provided to the bottom tip face of the cylindrical part  52  by the rotating member  54  by rotatively driven. Moreover, the container top panel  50 H which covers the upside of the toner container  50  is positioned below the paper discharging unit  13  (refer to  FIG. 2 ). 
     The body housing  10  internally includes a main feeding path  22 F and a reverse feeding path  22 B for feeding the sheets. The main feeding path  22 F extends from the sheet supplying unit  21 A of the paper feeding unit  20  to the paper discharge outlet  14 , which is provided in a manner of facing the top face of the body housing  10 , via the image forming unit  30  and the fixing unit  40 . The reverse feeding path  22 B is a feeding path for returning the sheet subject to one-side printing to the upstream side of the image forming unit  30  in the main feeding path  22 F upon performing both-side printing to the sheet. 
     The main feeding path  22 F (sheet feeding path) is extended in a manner of passing the transfer nip part, which is formed from the photoreceptor drum  31  and the transfer roller  34 , in a direction of down to up. Moreover, a resist roller pair  23  is disposed on a side of the main feeding path  22 F that is further upstream than the transfer nip part TP. The sheet is once stopped by the resist roller pair  23  and the skew correction of the sheet is performed. Subsequently, at a predetermined timing for transferring the image, the sheet is once again fed toward the transfer nip part TP. At the appropriate locations of the main feeding path  22 F and the reverse feeding path  22 B, a plurality of transport rollers for transporting the sheets are disposed and, for example, a paper discharge roller pair  24  is disposed near the paper discharge outlet  14 . 
     The reverse feeding path  22 B is formed between the outer face of the reversal unit  25  and the inner face of the rear cover  12  of the body housing  10 . Note that the transfer roller  34  and one roller of the resist roller pair  23  are mounted on the inner face of the reversal unit  25 . The rear cover  12  and the reversal unit  25  are respectively turnable around the axis of the fulcrum point  121  provided to the lower ends thereof. When a sheet jam occurs in the reverse feeding path  22 B, the rear cover  12  is opened. When a sheet jam occurs in the main feeding path  22 F, or when the units of the photoreceptor drum  31  or the developing device  33  is to be removed outside, the reversal unit  25  is opened in addition to the rear cover  12 . 
     Referring to  FIG. 3  to  FIG. 6 , the configuration of the drum unit  31 H according to this embodiment and conventional problems are explained in detail.  FIG. 3  is an enlarged cross section of the drum unit  31 H according to this embodiment. Moreover,  FIG. 4  is an enlarged cross section of the drum unit  31 HW for comparison with the drum unit  31 H. Note that  FIG. 3  and  FIG. 4  are illustrated as diagrams which invert the left-right direction on the plane of paper (front-back direction of the image forming apparatus  1 ) in  FIG. 2 . 
     Referring to  FIG. 3 , the drum unit  31 H includes a photoreceptor drum  31 , a charging device  32 , and a cleaning device  35 . The drum unit  31 H includes a pair of side plates (supports) not shown at either end in the left-right direction (direction that is orthogonal to the plane of paper of  FIG. 3 ). The photoreceptor drum  31  is rotatably supported by the pair of side plates. Moreover, the charging device  32  and the cleaning device  35  are supported facing the photoreceptor drum  31  by the pair of side plates. The photoreceptor drum  31  is rotatively driven in the arrow DP direction in  FIG. 3 . Moreover, the drum unit  31 H includes a fixing part (not shown) disposed on the side plate. When the drum unit  31 H is mounted on the body housing  10  of the image forming apparatus  1 , the fixing part is fixed to the body housing  10  of the image forming apparatus  1 . Consequently, the position of the drum unit  31 H is fixed in the image forming apparatus  1 . The fixing part is configured from a fastening hole to which a screw is fastened. 
     The charging device  32  is disposed further on the front side than the photoreceptor drum  31 . The charging device  32  includes a charge roller  321 , a cleaning roller  322 , and a charge housing  32 H. The charge housing  32 H has a substantial U-shape in a cross section view that is orthogonal to the rotating axis  31 A of the photoreceptor drum  31 . A charge roller  321  and a cleaning roller  322  are respectively rotatably supported in the charge housing  32 H. 
     The charge roller  321  is a roller member in which the surface thereof is configured from a rubber material. A charged voltage is applied to the charge roller  321  from a bias application part not shown. The charge roller  321  is rotated by following the photoreceptor drum  31  as a result of coming into contact with the cylindrical face  31 B of the photoreceptor drum  31 . The cylindrical face  31 B of the photoreceptor drum  31  is uniformly charged by the charge roller  321  to which a charged voltage was applied. 
     The cleaning roller  322  comes into contact with the charge roller  321 , and rotates together with the charge roller  321  with a linear velocity difference. The cleaning roller  322  is a brush roller formed from conductive nylon fiber. As a result of the charge roller  321  coming into contact with the cylindrical face  31 B of the photoreceptor drum  31 , toner and extraneous matter become attached to the surface of the charge roller  321 . Moreover, as a result of a charged voltage being applied to the charge roller  321  and a discharge occurring at the contact position with the photoreceptor drum  31 , discharge products become attached to the surface of the charge roller  321 . As a result of the cleaning roller  322  rotating with a linear velocity difference while contacting the charge roller  321 , the toner and extraneous matter attached to the surface of the charge roller  321  can be suitably removed. 
     The cleaning device  35  is disposed above the photoreceptor drum  31 . The cleaning device  35  includes a cleaner housing  35 H, a cleaning blade  351 , a conveying screw  352 , and a polishing roller  353 . Moreover, the cleaning device  35  includes a scraper  354 , a scraper holder  355 , and a top part seal  356 . In addition, the cleaning device  35  includes a first plate  357 , a protective sheet  361 , a second plate  358 , a cover seal  359 , and a toner seal  360 . 
     The cleaner housing  35 H is a case which supports the respective members in the cleaning device  35 . The cleaning device  35  is disposed so as to cover the upside of the photoreceptor drum  31  and the charging device  32 . In particular, the front portion of the cleaner housing  35 H is disposed above the charge roller  321 . Moreover, in a cross section view that is orthogonal to the rotating axis  31 A of the photoreceptor drum  31 , the center portion of the cleaner housing  35 H in the front-back direction has a shape that protrudes cylindrically upward. In addition, the rear portion of the cleaner housing  35 H is demarcated by a housing rear wall  35 H 1  (wall part). The housing rear wall  35 H 1  is a wall part that extends in a vertical direction. The housing rear wall  35 H 1  is disposed to face the polishing roller  353  described later. The lower end of the housing rear wall  35 H 1  is disposed at a given spacing from the cylindrical face  31 B of the photoreceptor drum  31 . Moreover, the lower end of the housing rear wall  35 H 1  is disposed above the toner seal  360  described later at a given spacing and covers the upside of the toner seal  360 . 
     The cleaning blade  351  is disposed in the horizontal direction along the base part of the cleaner housing  35 H. The cleaning blade  351  is a plate-shaped member configured from a rubber material. The cleaning blade  351  is supported by the blade holder  351 H. The blade holder  351 H is an L-shaped metal plate member in the cross section view. The center portion of the blade holder  351 H is fixed to the cleaner housing  35 H by the first fixing screw  351 B. The cleaning blade  351  and the blade holder  351 H are fixed using an adhesive. Consequently, a fixing end of the cleaning blade  351  is formed. Meanwhile, the tip of the cleaning blade  351  is a free end, and comes into contact with the cylindrical face  31 B of the photoreceptor drum  31 . The tip of the cleaning blade  351  comes into contact with the cylindrical face  31 B on a side that is further downstream in the rotating direction (arrow DP direction) of the photoreceptor drum  31  than the polishing roller  353  described later. Consequently, the toner remaining on (attached to) the cylindrical face  31 B of the photoreceptor drum  31  is removed with the tip of the cleaning blade  351 . 
     The conveying screw  352  is rotatably supported by the cleaner housing  35 H above the cleaning blade  351 . The conveying screw  352  includes a shaft, and a spiral fin member disposed around the shaft. The conveying screw  352  conveys, in an axial direction of the rotating axis  31 A of the photoreceptor drum  31 , the recovered toner PT that was wiped by the cleaning blade  351  and accumulated on the cleaning blade  351 . 
     The polishing roller  353  is disposed at the rear of the conveying screw  352 . The polishing roller  353  includes a peripheral face which comes into contact with the cylindrical face  31 B positioned higher than the rotating axis  31 A of the photoreceptor drum  31 . Moreover, the polishing roller  353  comes into contact with the cylindrical face  31 B of the photoreceptor drum  31  from the transfer nip part TP up to a position that is immediately above the rotating axis  31 A of the photoreceptor drum  31 . More specifically, the polishing roller  353  comes into contact with the cylindrical face  31 B immediately above the rotating axis  31 A of the photoreceptor drum  31  or on a side that is slightly further upstream in the rotating direction of the photoreceptor drum  31  than the position that is immediately above the rotating axis  31 A of the photoreceptor drum  31 . The position on the cylindrical face  31 B where the polishing roller  353  comes into contact is defined as the contact position CP. The polishing roller  353  is a rubber roller in which the surface thereof was subject to roughening treatment. The polishing roller  353  rotates by following the photoreceptor drum  31  while coming into contact with the cylindrical face  31 B of the photoreceptor drum  31  (arrow DC). The polishing roller  353  recovers the toner attached to the cylindrical face  31 B of the photoreceptor drum  31 . Moreover, the polishing roller  353  grinds extraneous matter such as discharge products that became attached to the cylindrical face  31 B of the photoreceptor drum  31 . Here, as a result of attaching a predetermined amount of toner to the peripheral face of the polishing roller  353 , removal performance (grind performance) of the discharge products can be improved. 
     The scraper  354  (restricting member) is a plate-shaped member extending in the up-down direction (vertical direction). In this embodiment, the scraper  354  is configured from an SUS plate having a thickness of 0.05 mm. The lower end of the scraper  354  comes into contact with the peripheral face of the polishing roller  353 . The lower end of the scraper  354  comes into contact with the peripheral face of the polishing roller  353  opposite to the rotating direction (arrow DC direction, against direction) of the polishing roller  353 . As a result of the scraper  354  coming into contact with the peripheral face of the polishing roller  353  based on predetermined elastic force, the amount of toner attached to the peripheral face of the polishing roller  353  is restricted. Consequently, the amount of toner that becomes attached to the peripheral face of the polishing roller  353  becomes uniform, and variation in the removal performance of the discharge products by the polishing roller  353  is thereby inhibited. 
     The scraper holder  355  is disposed so as to cover the upside of the polishing roller  353 . The scraper holder  355  is configured from a bent plate member. The center part of the scraper holder  355  extends in the horizontal direction. The front portion of the scraper holder  355  is bent downward, and supports the scraper  354 . Moreover, the rear portion of the scraper holder  355  is bent rearward and downward along the peripheral face of the polishing roller  353 . 
     The top part seal  356  is fixed on the scraper holder  355 . One end of the top part seal  356  is supported at the center part of the scraper holder  355 , and the other end of the top part seal  356  is disposed to protrude forward from the scraper holder  355 . The top part seal  356  has a function of blocking the toner that becomes airborne upon the toner attached to the peripheral face of the polishing roller  353  being scraped by the scraper  354 . 
     The first plate  357  is disposed facing the housing rear wall  35 H 1  of the cleaner housing  35 H. The first plate  357  is a plate member extending in the up-down direction. The center part of the first plate  357  in the up-down direction is fixed to the housing rear wall  35 H 1  by the second fixing screw  357 B. Moreover, the first plate top part  357 T as the upper side end part of the first plate  357  is bent rearward. In addition, the first plate bottom part  357 S as the lower side end part of the first plate  357  is bent forward. Here, the first plate bottom part  357 S is disposed facing the lower end of the housing rear wall  35 H 1  and so as to be inserted between the lower end of the housing rear wall  35 H 1  and the cylindrical face  31 B of the photoreceptor drum  31 . Moreover, the first plate bottom part  357 S is disposed above the toner seal  360  described later at a given spacing, and covers the toner seal  360 . 
     The protective sheet  361  is configured from a thin plate-shaped elastic material. In this embodiment, the protective sheet  361  is a urethane sheet having a thickness of 100 μm. The protective sheet  361  is disposed on the top face of the bent first plate bottom part  357 S. The protective sheet  361  is configured from a protective base end  361 T that is bonded with and fixed to the top face of the first plate bottom part  357 S, and a protective leading end  361 S which protrudes further forward than the first plate bottom part  357 S. To put it differently, the protective base end  361 T forms the fixing end of the protective sheet  361 , and the protective leading end  361 S forms the free end of the protective sheet  361 . 
     The second plate  358  is disposed facing the first plate  357  at the rear of the first plate  357 . The second plate  358  is a plate member extending in the up-down direction. The second plate top part  358 T as the upper end part of the second plate  358  is bent in the rear direction, and thereafter bent to curve upward. Moreover, the second plate  358  is fixed to the cleaner housing  35 H with a fixing screw not shown outside the paper feeding region. The second plate bottom part  358 S as the lower end part of the second plate  358  is disposed in a manner of bending forward. The second plate bottom part  358 S is disposed parallel to the first plate bottom part  357 S at the rear side of the first plate bottom part  357 S. 
     The cover seal  359  extends in the up-down direction along the second plate  358 . The upper portion of the cover seal  359  is bonded with and fixed to the second plate  358 , and forms the fixing end of the cover seal  359 . Moreover, the lower portion of the cover seal  359  is disposed to protrude downward from the second plate  358 , and forms the free end of the cover seal  359 . The leading end on the lower side of the cover seal  359  is disposed close to cylindrical face  31 B of the photoreceptor drum  31 . 
     The toner seal  360  (sheet member) extends in a horizontal direction along the second plate bottom part  358 S of the second plate  358 . The toner seal  360  is a urethane sheet having a thickness of 100 μm. The rear portion of the toner seal  360  is bonded with and fixed to the second plate bottom part  358 S, and forms the fixing end  360 F of the toner seal  360 . Meanwhile, the leading end  360 S ( FIG. 8 ) of the front portion of the toner seal  360  forms the free end of the toner seal  360  and comes into contact with the cylindrical face  31 B of the photoreceptor drum  31 . The leading end  360 S of the toner seal  360  comes into contact with the cylindrical face  31 B at a position that is higher than the rotating axis  31 A and on a side that is further upstream in the rotating direction of the photoreceptor drum  31  than the polishing roller  353  in a cross section view that is orthogonal to the rotating axis  31 A of the photoreceptor drum  31 . The toner seal  360  comes into contact with the cylindrical face  31 B toward a direction that approaches the reference straight line RL that connects the rotating axis  31 A and the contact position CP of the polishing roller  353  from the second plate bottom part  358 S as the position separated from the cylindrical face  31 B of the photoreceptor drum  31  in a cross section view that is orthogonal to the rotating axis  31 A of the photoreceptor drum  31 . The toner seal  360  has a function of preventing the toner from leaking from the inside of the cleaner housing  35 H. 
     The first plate bottom part  357 S of the first plate  357  and the housing rear wall  35 H 1  are disposed above the front portion of the toner seal  360 . In other words, the first plate bottom part  357 S and the housing rear wall  35 H 1  are disposed above the toner seal  360  such that the toner seal  360  protrudes further toward the front side (polishing roller  353  side) than the fixing end  360 F fixed to the second plate bottom part  358 S. 
     Moreover, the foregoing protective sheet  361  is disposed above the toner seal  360 . The protective sheet  361  is provided to the first plate bottom part  357 S so as to cover the upside of the toner seal  360 . The protective sheet  361  extends, in the cross section view that is orthogonal to the rotating axis  31 A of the photoreceptor drum  31 , from the first plate bottom part  357 S as a position that is separated from the cylindrical face  31 B of the photoreceptor drum  31  toward a direction which approaches the reference straight line RL that connects the rotating axis  31 A and the contact position CP of the polishing roller  353 , until reaching the position  361 M above the leading end  360 S of the front portion of the toner seal  360  ( FIG. 8 ). In addition, the protective sheet  361  extends so as to protrude further toward the direction of approaching the reference straight line RL than the position  361 M above the leading end  360 S. Moreover, the protective sheet  361  extends parallel to the direction that the toner seal  360  extends. 
     An electrostatic latent image is formed on the photoreceptor drum  31  in which its peripheral face was uniformly charged by the charge roller  321  of the charging device  32  by an exposure device not shown on a side that is further downstream in the rotating direction than the charging device  32 . Subsequently, the electrostatic latent image is visualized as a toner image by the developing device  33  ( FIG. 2 ) disposed below the photoreceptor drum  31 . The photoreceptor drum  31  is rotated in a direction of down to up at the transfer nip part TP. In addition, the toner image formed on the photoreceptor drum  31  is transferred on the sheet that is transported in a direction of down to up at the transfer nip part TP. 
     At the transfer nip part TP, a part of the toner image that was transferred to the sheet will remain on the photoreceptor drum  31  as residual toner. The residual toner on the photoreceptor drum  31  is conveyed to the region where the cleaning device  35  faces the photoreceptor drum  31  in a direction of down to up in response to the rotation of the photoreceptor drum  31 . 
     A part of the residual toner that was conveyed to the region facing the cleaning device  35  becomes attached to the peripheral face of the polishing roller  353 . Moreover, the residual toner that did not become attached to the peripheral face of the polishing roller  353  is wiped by the cleaning blade  351 . 
     The problems of a toner seal member (sheet member) provided to the cleaning device  35  are now explained. A part of the toner attached to the peripheral face of the polishing roller  353  is wiped by the scraper  354 . The toner that remains on the peripheral face of the polishing roller  353  as a result of exceeding the leading end of the scraper  354  circles above the polishing roller  353  while passing through the region facing the scraper holder  355  and the housing rear wall  35 H 1 . Here, based on the centrifugal force of the polishing roller  353 , the toner attached to the peripheral face of the polishing roller  353  becomes separate from the polishing roller  353 . The toner separated from the polishing roller  353  is dispersed to a region surrounded by the scraper holder  355 , the housing rear wall  35 H 1  and the peripheral face of the photoreceptor drum  31 . 
       FIG. 4  is a diagram for comparison with the cleaning device  35  according to an embodiment of the present disclosure, and is a cross section of a drum unit  31 HW having a cleaning device  35 W. The cleaning device  35 W includes a toner seal  380 . The toner seal  380  is configured, as with the toner seal  360 , from a urethane sheet disposed in the horizontal direction. The rear portion of the toner seal  380  is fixed and supported by the first plate bottom part  357 S. Moreover, the front portion of the toner seal  380  configures a free end and comes into contact with the peripheral face of the photoreceptor drum  31 . The cleaning device  35 W differs from the foregoing cleaning device  35  in that it does not includes the foregoing protective sheet  361  above the toner seal  380 . 
     The toner dispersed from the peripheral face of the polishing roller  353  accumulates on the toner seal  380  and forms toner residue TN.  FIG. 5  and  FIG. 6  are diagrams showing the state around the toner seal  380  in the foregoing case.  FIG. 7  is an enlarged view of a part of the drum unit  31 HW ( FIG. 4 ) within the portion schematically shown in  FIG. 5  and  FIG. 6 . Referring to  FIG. 5 , the toner residue TN dispersed on the toner seal  380  is accumulated in the form of a mountain shape. Consequently, based on the own weight of the toner residue TN, pressing force as shown with the arrow H is applied to the toner seal  380 . When the toner dispersed on the toner seal  380  is accumulated, the inclined face of the toner residue TN comes into contact with the peripheral face of the polishing roller  353 . Thus, as shown with the arrow G, downward pressing force is applied to the toner residue TN in response to the rotation of the polishing roller  353 . Consequently, the contact pressure that the toner seal  380  applies to the peripheral face of the photoreceptor drum  31  will increase. 
     Meanwhile, there are cases where the paper dust attached to the surface of the sheet P is transferred to the peripheral face of the photoreceptor drum  31  upon the toner image being transferred to the sheet P at the transfer nip part TP. The paper dust attached to the peripheral face of the photoreceptor drum  31  is conveyed toward the tip of the toner seal  380  in response to the rotation of the photoreceptor drum  31 . When toner residue TN is not formed on the toner seal  380 , the tip of the toner seal  380  is in contact with the peripheral face of the photoreceptor drum based on low contact pressure. In the foregoing case, the paper dust conveyed to the photoreceptor drum  31  passes between the tip of the toner seal  380  and the peripheral face of the photoreceptor drum  31 , and is recovered by the polishing roller  353  and the cleaning blade  351 . 
     Nevertheless, in cases where the tip of the toner seal  380  is in strong contact with the peripheral face of the photoreceptor drum  31  due to the toner residue TN accumulated on the toner seal  380 , the paper dust cannot pass between the tip of the toner seal  380  and the peripheral face of the photoreceptor drum  31 . Consequently, as shown in  FIG. 5 , a clump PD of paper dust is formed between the tip of the toner seal  380  and the peripheral face of the photoreceptor drum  31 . 
     Eventually, when the clump PD of paper dust grows, the tip  381  of the toner seal  380  will lift off the peripheral face of the photoreceptor drum  31  in correspondence with the portion where the clump PD exist in the axial direction of the rotating axis  31 A of the photoreceptor drum  31  ( FIG. 6 ). Consequently, the toner TN 1  will begin to leak from the toner residue TN. The toner TN 1  will fall along the peripheral face of the photoreceptor drum  31  according to gravity (arrow DT of  FIG. 6 , arrow D 7  of  FIG. 7 ). In addition, the toner TN 1  that reached the transfer nip part TP becomes attached to the sheet P that was transported to the transfer nip part TP. Consequently, the sheet P is contaminated by the toner. 
     As described above, the toner seal  380  generates a clump PD of paper dust and the sheet P is contaminated by the toner. In order to resolve the foregoing problem, with the cleaning device of this embodiment, the protective sheet  361  is suitably disposed above the toner seal  360 .  FIG. 8  is an enlarged view of the periphery of the toner seal  360  and the protective sheet  361  in  FIG. 3 . 
     In this embodiment, as shown in  FIG. 8 , the foregoing protective sheet  361  is disposed above the toner seal  360 . The protective sheet  361  is provided to the first plate bottom part  357 S so as to cover the upside of the toner seal  360 . The protective sheet  361  extends, in a cross section view that is orthogonal to the rotating axis  31 A of the photoreceptor drum  31 , from the first plate  357  side to the position  361 M above the leading end  360 S of the toner seal  360  in a direction which approaches the reference straight line RL ( FIG. 3 ) that connects the rotating axis  31 A and the contact position CP of the polishing roller  353 . In addition, the protective sheet  361  extends in a manner of protruding further toward a direction of approaching the reference straight line RL ( FIG. 3 ) than the position  361 M above the leading end  360 S of the toner seal  360 . 
     Consequently, the toner that was dispersed from the polishing roller  353  accumulates on the protective sheet  361  as shown in  FIG. 8 . Thus, it is possible to inhibit the toner from accumulating on the toner seal  360 . The toner accumulated on the protective sheet  361  is guided to the rotating face  31 B side of the photoreceptor drum  31  based on the rotative force of the polishing roller  353 . Here, since the protective sheet  361  is deformable based on elastic force, the toner will not be hardened pressed (rammed down) between the peripheral face of the polishing roller  353  and the protective sheet  361 . Moreover, as a result of the protective leading end  361 S of the protective sheet  361  being deformed downward in accordance with the rotative force of the polishing roller  353 , the transfer of the toner to the photoreceptor drum  31  side is promoted. 
     As described above, with the cleaning device  35  according to this embodiment, the protective sheet  361  effectively inhibits the toner from becoming accumulated on the toner seal  360 . Thus, it is possible to inhibit the increase of the contact pressure of the toner seal  360  against the photoreceptor drum  31  as a result of the toner becoming accumulated on the toner seal  360 . Accordingly, it becomes difficult for a clump of the paper dust PD to be formed between the leading end  360 S of the toner seal  360  and the rotating face  31 B of the photoreceptor drum  31 . Thus, it is possible to inhibit the occurrence of toner leakage as a result of the leading end  360 S of the toner seal  360  lifting off the rotating face  31 B of the photoreceptor drum  31 . Consequently, it is possible to effectively inhibit the sheet P, which is transported to the transfer nip part TP, from becoming contaminated by the toner that falls downward from the leading end  360 S of the toner seal  360 . 
     Particularly, in the foregoing embodiment, the protective sheet  361  is disposed to protrude even further than the upward position  361 M of the leading end  360 S of the toner seal  360 . Thus, it becomes difficult for the toner that was dispersed from the rotating member to reaching the toner seal  360 . 
     In addition, in this embodiment, the first plate bottom part  357 S and the housing rear wall  35 H 1  are disposed above the toner seal  360  to protrude further toward the front side (polishing roller  353  side) than the fixing end  360 F ( FIG. 3 ) in which the toner seal  360  is fixed to the second plate bottom part  358 S. To put it differently, the first plate bottom part  357 S of the first plate  357  is disposed so as to cover the upside of the toner seal  360 . Moreover, the lower end of the housing rear wall  35 H 1  is disposed above the first plate bottom part  357 S. Thus, the upside space of the toner seal  360  is covered by more members, and the accumulation of toner on the toner seal  360  is further inhibited. 
     Moreover, the housing rear wall  35 H 1  is disposed, in a manner of facing the polishing roller  353 , above the leading end  360 S of the toner seal  360  and on the rear side of the peripheral face of the polishing roller  353 . Thus, the toner that is dispersed from the peripheral face of the polishing roller  353  toward the rear in response to the rotation of the polishing roller  353  will collide with the housing rear wall  35 H 1  and fall downward. Accordingly, the housing rear wall  35 H 1  tends to guide the toner onto the protective sheet  361 . 
     Moreover, in the foregoing embodiment, the protective sheet  361  tends to deform due to elastic force. Thus, the protective sheet  361  can be deformed downward based on the own weight of the toner that is accumulated on the protective sheet  361 . Consequently, the toner accumulated on the protective sheet  361  tends to be guided toward the cylindrical face  31 B of the photoreceptor drum  31 . 
     Moreover, according to the foregoing embodiment, in a cross section view that intersects with the rotating axis  31 A of the photoreceptor drum  31 , one end of the toner seal  360  is the fixing end  360 F that is fixed to the cleaner housing  35 H, and the other end of the toner seal  360  is the leading end  360 S configured from a free end. Thus, the leading end  360 S of the toner seal  360  deforms easily as a free end. Consequently, the space between the cleaner housing  35 H and the cylindrical face  31 B of the photoreceptor drum  31  can more easily be blocked by the leading end  360 S of the toner seal  360 . 
     Moreover, according to the foregoing embodiment, the cleaning blade  351  is disposed on a side that is further downstream in the rotating direction of the photoreceptor drum  31  than the polishing roller  353 . Thus, the toner which became attached to the photoreceptor drum  31  can be removed with accuracy. Moreover, even in cases where the toner that accumulated on the protective sheet  361  falls down and becomes attached to the cylindrical face  31 B of the photoreceptor drum  31 , the toner can be recovered by the polishing roller  353  and the cleaning blade  351 . 
     Moreover, according to the foregoing embodiment, the extraneous matter that became attached to the cylindrical face  31 B of the photoreceptor drum  31  is effectively ground by the polishing roller  353 . Moreover, the scraper  354  restricts the amount of toner to become attached to the peripheral face of the polishing roller  353 . Thus, as a result of the toner being interposed between the polishing roller  353  and the cylindrical face  31 B of the photoreceptor drum  31 , variation in the promoted grinding effect can be inhibited by the position on the peripheral face of the polishing roller  353 . 
     Moreover, according to the foregoing embodiment, the polishing roller  353  comes into contact with the cylindrical face  31 B of the photoreceptor drum  31  from the transfer nip part TP to the position immediately above the rotating axis  31 A of the photoreceptor drum  31 . Consequently, the leading end  360 S of the toner seal  360  comes into contact with the cylindrical face  31 B below the position CP where the polishing roller  353  comes into contact with the cylindrical face  31 B and on the upstream side in the rotating direction of the photoreceptor drum  31 . Thus, the toner that was dispersed from the polishing roller  353  tends to fall on the toner seal  360 . Even in the foregoing case, according to the foregoing configuration, the protective sheet  361  is disposed so as to cover the upside of the toner seal  360 . Accordingly, it is possible to prevent the toner from becoming accumulated on the toner seal  360 . Thus, it becomes difficult for the contact pressure of the toner seal  360  against the photoreceptor drum  31  to increase, and it is possible to inhibit the occurrence of toner leakage from the leading end  360 S of the toner seal  360 . In addition, even in cases where the paper dust of sheets becomes attached to the cylindrical face  31 B of the photoreceptor drum  31  at the transfer nip part TP, it is possible to prevent the paper dust that was transferred up to the leading end  360 S of the toner seal  360  in response to the rotation of the photoreceptor drum  31  from growing into a clump between the leading end  360 S of the toner seal  360  and the cylindrical face  31 B of the photoreceptor drum  31 . Consequently, it is possible to prevent the leading end  360 S of the toner seal  360  from lifting due to the clump of the paper dust, and the toner from leaking from a gap between the toner seal  360  and the photoreceptor drum  31 . Accordingly, it is possible to inhibit the toner that leaked downward from contaminating the transported sheet at the transfer nip part TP. 
     The drum unit  31 H and the image forming apparatus  1  including the cleaning device  35  according to an embodiment of the present disclosure were explained above, but the present disclosure is not limited thereto, and may take on, for instance, the modified embodiments described below. 
     (1) In the foregoing embodiment, explained was a mode where the protective sheet  361  extends from the first plate bottom part  357 S parallel to a direction in which the toner seal  360  extends from the second plate bottom part  358 S, but the present disclosure is not limited thereto.  FIG. 9  is an enlarged cross section of the cleaning device  35 V including the protective sheet  362  according to another embodiment of the present disclosure. The protective sheet  362  includes a tip guiding part  361 S 1  at the tip of the protective leading end  362 S. The tip guiding part  361 S 1  is formed as a result of the tip of the protective leading end  362 S being bent downward. The tip guiding part  361 S 1  is disposed to incline toward the cylindrical face  31 B of the photoreceptor drum  31 . As with the protective sheet  361  according to the foregoing embodiment, the toner accumulated on the protective sheet  362  moves to the cylindrical face  31 B of the photoreceptor drum  31  as a result of being guided by the tip guiding part  361 S 1 . Thus, it is possible to inhibit large amounts of toner from being accumulated on the protective sheet  361 , and the function of the protective sheet  362  protecting (covering) the upside of the toner seal  360  is favorably maintained. 
     (2) In the foregoing embodiment, explained was a mode where the polishing roller  353  and the cleaning blade  351  are disposed on a side that is further downstream in the rotating direction of the photoreceptor drum  31  than the toner seal  360 , but the present disclosure is not limited thereto. The polishing roller  353  may also be a cleaning roller which cleans the surface of the photoreceptor drum  31 . In the foregoing case, the cleaning blade  351  may be disposed on a side that is further downstream in the rotating direction of the photoreceptor drum  31  than the cleaning roller, or the mode may be such that the cleaning blade  351  is not provided. 
     (3) In the foregoing embodiment, explained was a mode where the protective sheet  361  as the cover member is configured from a thin plate-shaped elastic member, but the present disclosure is not limited thereto. The protective sheet  361  may also be a part of the member which configures the cleaner housing  35 H. Moreover, the protective sheet  361  (cover member) may also be configured from the first plate bottom part  357 S of the first plate  357 . 
     (4) Moreover, in the foregoing embodiment, explained was a mode where the cleaning device  35  including the toner seal  360  is provided to the drum unit  31 H, but the present disclosure is not limited thereto. The cleaning device  35  including the toner seal  360  may also be mounted on the image forming apparatus  1  individually. 
     Although the present disclosure has been fully described by way of example with reference to the accompanying drawings, it is to be understood that various changes and modifications will be apparent to those skilled in the art. Therefore, unless otherwise such changes and modifications depart from the scope of the present disclosure hereinafter defined, they should be construed as being included therein.