Patent Publication Number: US-2022214641-A1

Title: Foreign substance collection apparatus, process cartridge, and image forming apparatus

Description:
BACKGROUND OF THE INVENTION 
     Field of the Invention 
     The present invention relates to a cartridge such as a photosensitive unit or a developing unit which is mountable to or detachable from an image forming apparatus adopting an electrophotographic system. 
     Description of the Related Art 
     In a laser beam printer or a copier as an image forming apparatus adopting an electrophotographic system, an image is formed on a recording material by forming a toner image on a photosensitive drum and transferring the toner image onto a sheet as the recording material. In laser beam printers, in order to facilitate maintenance, a system is widely adopted in which a part of components of an image forming apparatus is provided in a cartridge and the cartridge is taken out from an apparatus main body to perform maintenance and replacement. Japanese Patent Application Laid-open No. 2016-224221 discloses a process cartridge in which a developing unit that houses toner is attachable to and detachable from a photosensitive unit that has a photosensitive drum. 
     SUMMARY OF THE INVENTION 
     With process cartridges structured such that a developing unit that houses toner is attachable to and detachable from a photosensitive unit that has a photosensitive drum, there is room for improvement in terms of size, cost, accuracy, usability, lifespan, and the like. 
     An object of the present invention is to provide a technique that enables a capability of a process cartridge to house foreign substances to be improved. 
     In order to achieve the object described above, a foreign substance collection apparatus according to the present invention includes: 
     a frame body; 
     an image bearing member which is rotatably supported by the frame body and which bears a developer image; 
     a first collecting member which is rotatably supported by the frame body and which collects foreign substances from a surface of the image bearing member by rotating in a state of being in contact with the surface of the image bearing member; 
     a second collecting member which is rotatably supported by the frame body and which further collects the foreign substances having been collected by the first collecting member from the first collecting member by rotating in a state of being in contact with a surface of the first collecting member; and 
     a scraping member which is provided on the frame body so as to be capable of rubbing against the second collecting member that is rotating and which scrapes off the foreign substances from the second collecting member, 
     wherein the frame body includes a housing portion which forms a housing space for housing foreign substances, 
     wherein the housing portion includes, in a posture during use: 
     a first inner bottom surface which is positioned below the scraping member in a gravity direction; 
     a second inner bottom surface which is positioned further below the first inner bottom surface; and 
     a connecting surface which intersects the first inner bottom surface and the second inner bottom surface and which connects the first inner bottom surface and the second inner bottom surface with each other. 
     In order to achieve the object described above, a foreign substance collection apparatus according to the present invention includes: 
     a frame body; 
     an image bearing member which is rotatably supported by the frame body and which bears a developer image; 
     a first collecting member which is rotatably supported by the frame body and which collects foreign substances from a surface of the image bearing member by rotating in a state of being in contact with the surface of the image bearing member; 
     a second collecting member which is rotatably supported by the frame body and which further collects the foreign substances having been collected by the first collecting member from the first collecting member by rotating in a state of being in contact with a surface of the first collecting member; and 
     a scraping member which is provided on the frame body so as to be capable of rubbing against the second collecting member that is rotating and which scrapes off the foreign substances from the second collecting member, 
     wherein the frame body includes: 
     a housing portion which forms a housing space for housing foreign substances; and 
     a conveying member which conveys foreign substances inside the housing space. 
     In order to achieve the object described above, a foreign substance collection apparatus according to the present invention includes: 
     a frame body; 
     an image bearing member which is rotatably supported by the frame body and which bears a developer image; 
     a first collecting member which is rotatably supported by the frame body and which collects foreign substances from a surface of the image bearing member by rotating in a state of being in contact with the surface of the image bearing member; 
     a second collecting member which is rotatably supported by the frame body and which further collects the foreign substances having been collected by the first collecting member from the first collecting member by rotating in a state of being in contact with a surface of the first collecting member; 
     a scraping member which is provided on the frame body so as to be capable of rubbing against the second collecting member that is rotating and which scrapes off the foreign substances from the second collecting member; and 
     a third collecting member which is capable of coming into contact with the second collecting member, 
     wherein the third collecting member is controlled to come into contact with an outer circumferential surface of the second collecting member during a rotation operation in which the second collecting member rotates. 
     In order to achieve the object described above, a foreign substance collection apparatus according to the present invention includes: 
     a frame body; 
     an image bearing member which is rotatably supported by the frame body and which bears a developer image; 
     a first collecting member which is rotatably supported by the frame body and which collects foreign substances from a surface of the image bearing member by rotating in a state of being in contact with the surface of the image bearing member; and 
     a second collecting member which is rotatably supported by the frame body and which further collects the foreign substances having been collected by the first collecting member from the first collecting member by rotating in a state of being in contact with a surface of the first collecting member, 
     wherein the first collecting member and the second collecting member are rotationally driven so that, in a contact portion where the first collecting member and the second collecting member come into contact with each other, respective surfaces of the first collecting member and the second collecting member move in reverse directions. 
     In order to achieve the object described above, a foreign substance collection apparatus according to the present invention includes: 
     a frame body; 
     an image bearing member which is rotatably supported by the frame body and which bears a developer image; 
     a first collecting member which is rotatably supported by the frame body and which collects foreign substances from a surface of the image bearing member by rotating in a state of being in contact with the surface of the image bearing member; 
     a second collecting member which is rotatably supported by the frame body and which further collects the foreign substances having been collected by the first collecting member from the first collecting member by rotating in a state of being in contact with a surface of the first collecting member; and 
     a scraping member which is provided on the frame body so as to be capable of rubbing against the second collecting member that is rotating and which scrapes off the foreign substances from the second collecting member, 
     wherein the frame body includes a housing portion which forms a housing space for housing foreign substances, 
     wherein the housing portion includes, in a posture during use: 
     a first side surface which is positioned below the frame body in a front-back direction; 
     a second side surface which is positioned further apart from the scraping member than the first side surface; and 
     a connecting surface which intersects the first side surface and the second side surface and which connects the first side surface and the second side surface with each other. 
     According to the present invention, a capability of a process cartridge to house foreign substances can be improved. 
     Further features of the present invention will become apparent from the following description of exemplary embodiments with reference to the attached drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a sectional view of an image forming apparatus according to a first embodiment; 
         FIG. 2  is a sectional view of a developing unit according to the first embodiment; 
         FIG. 3  is a perspective view of the developing unit according to the first embodiment; 
         FIG. 4  is an exploded perspective view of the developing unit according to the first embodiment; 
         FIG. 5  is a sectional view of a process cartridge according to the first embodiment; 
         FIG. 6  is a top view of the developing unit according to the first embodiment; 
         FIG. 7  is a perspective view of the process cartridge according to the first embodiment; 
         FIGS. 8A and 8B  are explanatory diagrams of a detecting member according to the first embodiment; 
         FIG. 9  is a perspective view of the developing unit according to the first embodiment; 
         FIG. 10  is a perspective view of the process cartridge according to the first embodiment; 
         FIGS. 11A and 11B  are partial perspective views of a photosensitive unit according to the first embodiment; 
         FIG. 12  is a perspective view of the developing unit and the photosensitive unit according to the first embodiment; 
         FIG. 13  is a top view of the developing unit and the photosensitive unit according to the first embodiment; 
         FIGS. 14A and 14B  are perspective views of the process cartridge according to the first embodiment; 
         FIG. 15  is a partial perspective view of the developing unit and a lifting member according to the first embodiment; 
         FIGS. 16A and 16B  are diagrams showing a positional relationship of the lifting member and a pressing member according to the first embodiment; 
         FIGS. 17A and 17B  are diagrams showing separation of the developing unit according to the first embodiment; 
         FIG. 18  is a sectional view of the photosensitive unit and a cleaning unit according to the first embodiment; 
         FIG. 19  is a diagram showing sizes of respective portions in a left-right direction according to the first embodiment; 
         FIG. 20  is a diagram showing sizes of respective portions in the left-right direction according to the first embodiment; 
         FIGS. 21A and 21B  are sectional views showing another mode of a foreign substance collecting depressed portion according to the first embodiment; 
         FIG. 22  is a sectional view showing a foreign substance collecting portion and the foreign substance collecting depressed portion according to the first embodiment; 
         FIGS. 23A and 23B  are sectional views of an arrangement of a foreign substance conveying member according to a second embodiment; 
         FIG. 24  is a sectional view of an arrangement of a collection conveying sheet according to a third embodiment; 
         FIG. 25  is a diagram showing rotations of a cleaning roller and a collecting roller according to a fourth embodiment; and 
         FIGS. 26A and 26B  are sectional views showing another mode of a scraping member according to the fourth embodiment. 
     
    
    
     DESCRIPTION OF THE EMBODIMENTS 
     Hereinafter, a description will be given, with reference to the drawings, of embodiments (examples) of the present invention. However, the sizes, materials, shapes, their relative arrangements, or the like of constituents described in the embodiments may be appropriately changed according to the configurations, various conditions, or the like of apparatuses to which the invention is applied. Therefore, the sizes, materials, shapes, their relative arrangements, or the like of the constituents described in the embodiments do not intend to limit the scope of the invention to the following embodiments. 
     First Embodiment 
     First, an image forming apparatus and a process cartridge according to a first embodiment of the present invention will be described in detail with reference to the drawings when appropriate.  FIG. 1  is a sectional view of an image forming apparatus  1  that includes a process cartridge  5 . 
     In the following description, directions based on a user who uses the image forming apparatus  1  are defined. Specifically, a front surface side of the image forming apparatus  1  is defined as “front”, a rear surface side is defined as “rear”, an upper surface (top surface) side is defined as “up”, and a lower surface (bottom surface) side is defined as “down”. In addition, a left side of the image forming apparatus  1  when the image forming apparatus  1  is viewed from the front surface side is defined as “left” and a right side is defined as “right”. Directions are also defined with respect to the process cartridge  5  in a similar manner to the image forming apparatus  1  on the assumption that the process cartridge  5  is in the same posture as in a state where the process cartridge  5  is mounted to the image forming apparatus  1 . Each direction in each drawing is defined by an arrow depicted in the drawing. 
     A front-back direction, an up-down direction, and a left-right direction which are depicted by the arrows are directions that are perpendicular to each other. The directions indicate same directions in all of the drawings. The up-down direction is parallel to a vertical direction and the left-right direction and the front-back direction are parallel to a horizontal direction. In addition, the left-right direction is respectively parallel to a rotational axis direction of a photosensitive drum  61  as an image bearing member that bears a developer image and to a rotational axis direction of a developing roller  71 . The front-back direction is perpendicular to both a longitudinal direction of the photosensitive drum  61  and gravity direction. Furthermore, a developing unit  7  being mounted to and integrated with a photosensitive unit  6  is referred to as the process cartridge  5 . The process cartridge  5  is inserted in a direction of an arrow S 1  in  FIG. 1  (a mounting direction) when being mounted to an apparatus main body  2  and is detached in a direction of an arrow S 2  in  FIG. 1 . 
     Overall Configuration of Image Forming Apparatus 
       FIG. 1  is a sectional view of the image forming apparatus  1  to which the process cartridge  5  has been mounted. As shown in  FIG. 1 , the image forming apparatus  1  mainly includes a paper feeding portion  3  for supplying a paper sheet S into the apparatus main body  2 , an exposing apparatus  4 , the process cartridge  5  for transferring a toner image onto the paper sheet S, and a fixing apparatus  8  for thermally fixing the toner image having been transferred onto the paper sheet S. The paper feeding portion  3  is provided in a lower part inside the apparatus main body  2  and mainly includes a paper feeding tray  31  and a paper feeding mechanism  32 . The paper sheet S housed in the paper feeding tray  31  is supplied toward the process cartridge  5  (between the photosensitive drum  61  and a transfer roller  63 ) by the paper feeding mechanism  32 . 
     The exposing apparatus  4  is arranged in an upper part inside the apparatus main body  2  and includes a laser light-emitting portion (not illustrated) and a polygonal mirror, a lens, a mirror reflector, and the like which are shown but are not assigned reference characters. With the exposing apparatus  4 , laser light which is based on image data and which is emitted from the laser light-emitting portion scans a surface of the photosensitive drum  61  at high speed to expose the surface of the photosensitive drum  61 . 
     The process cartridge  5  is arranged below the exposing apparatus  4 . The process cartridge  5  is configured to be inserted in the direction of the arrow S 1  into a housing portion  23  of the apparatus main body  2  from an opening that is created when opening (depicted by a two-dot chain line in  FIG. 1 ) a door (an opening/closing member)  21  provided on the apparatus main body  2 . When detaching the process cartridge  5  from the apparatus main body  2 , the process cartridge  5  is detached by moving the process cartridge  5  in the direction of the arrow S 2 . In this manner, the process cartridge  5  is configured to be attachable to and detachable from the apparatus main body  2  of the image forming apparatus  1 . 
     The process cartridge  5  mainly includes the photosensitive unit  6  and the developing unit  7 . The photosensitive unit  6  mainly includes the photosensitive drum  61 , a charging roller  62 , and the transfer roller  63 . The developing unit  7  is configured to be attachably and detachably mounted to and from the photosensitive unit  6 . The developing unit  7  mainly includes the developing roller  71 , a supplying roller  72 , a layer thickness regulating blade  73 , a toner housing portion (a developer housing portion)  74  that houses toner (a developer), and a first agitator  75 A and a second agitator  75 B provided inside the toner housing portion  74 . 
     Image Forming Process 
     Next, an image forming process using the process cartridge  5  will be described. The photosensitive drum  61  is rotationally driven while the image forming process is being executed. First, a surface of the photosensitive drum  61  is uniformly charged by the charging roller  62  that is a charging member and, subsequently, as the surface of the photosensitive drum  61  is exposed by laser light which corresponds to image data and which is emitted from the exposing apparatus  4 , an electrostatic latent image corresponding to the image data is formed on the photosensitive drum  61 . 
     Meanwhile, after the toner inside the toner housing portion  74  is stirred by the second agitator  75 B and the first agitator  75 A, the toner is supplied to the developing roller  71  via the supplying roller  72 . In addition, the toner supplied to the developing roller  71  penetrates between the developing roller  71  and the layer thickness regulating blade  73  and is borne on the developing roller  71  as a thin layer with a certain thickness. In this manner, the developing roller  71  functions as a developer bearing member that bears the toner that is a developer. 
     The toner borne on the developing roller  71  is supplied to the electrostatic latent image having been formed on the photosensitive drum  61 . Accordingly, toner adheres to the electrostatic latent image and the electrostatic latent image becomes visible, and a toner image is formed on the photosensitive drum  61 . Subsequently, the paper sheet S is conveyed between the photosensitive drum  61  and the transfer roller  63 , and the toner image (the developer image) on the photosensitive drum  61  is transferred onto the paper sheet S by the transfer roller  63  that is a transferring member. At this point, untransferred toner remaining on the photosensitive drum  61  is collected by the developing roller  71  and returned once again to the developing unit  7 . 
     The fixing apparatus  8  is arranged behind the process cartridge  5  and mainly includes a heating roller  92  and a pressure roller  91  which are fixing members. The paper sheet S to which the toner image has been transferred passes through the fixing apparatus  8  and, in doing so, the paper sheet S is heated and pressurized between the heating roller  92  and the pressure roller  91  and the toner image is fixed onto the paper sheet S. The paper sheet S having passed through the fixing apparatus  8  is discharged onto a paper discharge tray  22 . 
     Configuration of Process Cartridge 
     Next, each unit of the process cartridge  5  will be described. As described earlier, the process cartridge  5  includes the photosensitive unit  6  and the developing unit  7  that is attachable to and detachable from the photosensitive unit  6 . 
     Configuration of Developing Unit 
     First, a configuration of the developing unit  7  will be described.  FIG. 2  is a sectional view of the developing unit  7  taken along A-A in  FIG. 3 .  FIG. 3  is a perspective view of the developing unit  7  from above, and  FIG. 7  is a perspective view of the process cartridge  5  from above.  FIG. 4  is an exploded perspective view of the developing unit  7 .  FIG. 5  is a sectional view of the developing unit  7  mounted to the photosensitive unit  6  and a cross section thereof is parallel to the up-down direction and the front-back direction.  FIG. 6  is an upper view of the developing unit  7  showing a state where a top surface of a housing  700  and a side holder  719  have been removed for the purpose of illustration. 
     As shown in  FIG. 2 , the developing unit  7  has a grip portion  701  to be gripped by a user in front of the housing  700  as a developing frame body, and the developing roller  71  is rotatably supported behind the developing unit  7 . Hereinafter, a configuration of the developing unit  7  will be described by referring to the rotational axis direction of the developing roller  71  as an axial direction. 
     As shown in  FIGS. 4 and 6 , the developing roller  71 , the supplying roller  72 , the first agitator (the first stirring member)  75 A, and the second agitator (the second stirring member)  75 B respectively have both ends thereof being rotatably supported by a left-side wall  704  and a right-side wall  705  of the housing  700 . A developing coupling  710 , a developing roller gear  711 , a supplying roller gear  712 , a first agitator gear  713 , a second agitator gear  714 , and idle gears  715 A,  715 B, and  715 C are provided on a left side of the left-side wall  704  of the housing  700 . The developing roller gear  711  is fixed to an end of the developing roller  71 , and the supplying roller gear  712  is fixed to an end of the supplying roller  72 . In addition, the first agitator gear  713  is fixed to an end of a stirring rod  78 A (refer to  FIG. 5 ) of the first agitator  75 A, and the second agitator gear  714  is fixed to an end of a stirring rod  78 B (refer to  FIG. 5 ) of the second agitator  75 B. 
     As shown in  FIG. 3 , the developing unit  7  is provided with a first electrical contact  720 A which is electrically connected to the developing roller  71  and which is supplied with voltage to be applied to the developing roller  71  and a second electrical contact  720 B which is electrically connected to the supplying roller  72  and which is supplied with voltage to be applied to the supplying roller  72 . By bringing the electrical contacts into contact with a power supplying contact (not illustrated) provided in the apparatus main body  2 , power is supplied to the developing roller  71  and the supplying roller  72 . 
     In conjunction with an operation of closing the door  21  provided on the apparatus main body  2 , a developing drive transmitting member (not illustrated) provided in the apparatus main body  2  moves to a position for engaging with the developing coupling  710 . Conversely, in conjunction with an operation of opening the door  21 , the developing drive transmitting member moves to a position for releasing an engagement with the developing coupling  710 . 
     When the apparatus main body  2  is operated after the door  21  is closed, a driving force is transferred (input) from the developing drive transmitting member to the developing coupling  710  as a driving force receiving member, thereby causing the developing roller  71  to become rotatable via the developing roller gear  711  from a gear provided on a peripheral surface of the developing coupling  710  and the supplying roller  72  to become rotatable via the supplying roller gear  712 . The developing drive transmitting member is configured to be capable of transferring a driving force to the developing coupling  710  while allowing positional deviation of the developing coupling  710  within a prescribed range. Movements in the axial direction of the developing coupling  710 , the developing roller gear  711 , and the supplying roller gear  712  are restricted by the side holder  719  that is attached to the housing  700 . 
     The developing unit  7  adopts two agitators, namely, the first agitator  75 A and the second agitator  75 B, to stir the toner inside the toner housing portion  74 . The first agitator  75 A includes the stirring rod  78 A and a stirring sheet  79 A. The first agitator  75 A is configured to be rotatable by receiving a driving force with the first agitator gear  713  from the developing coupling  710  via the idle gear  715 A. The second agitator  75 B includes the stirring rod  78 B and a stirring sheet  79 B. The second agitator  75 B is configured to be rotatable by receiving a driving force with the second agitator gear  714  from the first agitator gear  713  via the idle gears  715 B and  715 C. 
     The second agitator  75 B supplies the toner inside the toner housing portion  74  to the side of the first agitator  75 A. Toner that is present near the first agitator  75 A inside the toner housing portion  74  is stirred by the first agitator  75 A, supplied to the side of the supplying roller  72 , and further supplied to the developing roller  71  by the supplying roller  72 . 
     In addition, as shown in  FIGS. 4 and 7 , a detecting portion  80  is provided on a left-side end of the developing unit  7 . The detecting portion  80  is provided so as to be capable of detecting a state of an internally-provided detected member  81  with a detecting mechanism (not illustrated) provided in the apparatus main body  2 . A state of the detected member  81  enables a determination to be made as to whether the developing unit  7  is unused or the developing unit  7  has already been used. 
     How the detected member  81  operates will be described with reference to  FIGS. 8A and 8B .  FIGS. 8A and 8B  are diagrams of the developing unit  7  as viewed from a left-side side surface. The side holder  719  has been removed in the diagrams for the purpose of illustration. As shown in  FIG. 8A , the detected member  81  is provided with a detecting protrusion  83  and a detecting gear  82 . As shown in the diagrams, the detecting gear  82  is configured as a partially toothed gear. The detected member  81  receives a driving force to the detecting gear  82  from the second agitator gear  714 . 
       FIG. 8A  shows a state where the developing unit  7  is not in use. The detecting protrusion  83  is positioned on an upper front side of the detected member  81 . In addition, the detecting gear  82  is meshing with the second agitator gear  714 . When the developing unit  7  is used, the second agitator gear  714  rotates in a direction of an arrow R 3  in the drawing due to a driving force that the developing coupling  710  receives from the developing drive transmitting member of the apparatus main body  2 . At this point, since the detecting gear  82  is meshing with the second agitator gear  714 , the detected member  81  rotates in a direction of an arrow R 4  in the drawing. 
       FIG. 8B  represents a state after the detected member  81  has rotated. Since the detecting gear  82  is a partially toothed gear, once the detected member  81  rotates in the direction of the arrow R 4  in the drawing and runs out of gear teeth for meshing with the second agitator gear  714 , the detected member  81  stops rotating. At this point, the detecting protrusion  83  is positioned on an upper rear side of the detected member  81 . Detecting the position of the detecting protrusion  83  of the detected member  81  with a detecting mechanism (not illustrated) provided in the apparatus main body  2  enables a determination to be made as to whether the developing unit  7  is unused or the developing unit  7  has already been used. 
       FIG. 9  is a perspective view of the developing unit  7  from below. As shown in the drawing, a memory  85  and a positioning projection  86  are provided on a bottom surface of the developing unit  7 . The memory  85  includes a memory chip (not illustrated) that stores information related to the developing unit  7  and a memory electrode  85   a  that is conductively connected with the memory chip. The memory electrode  85   a  comes into contact with an electrode (not illustrated) provided in the apparatus main body  2  and enables the memory chip and the apparatus main body  2  to communicate with each other. 
     Configuration of Photosensitive Unit and Support of Developing Unit 
     Next, a detailed configuration of the photosensitive unit  6  will be described.  FIG. 10  is a perspective view of the process cartridge  5 .  FIG. 11A  is a partial perspective view of the photosensitive unit  6  and  FIG. 11B  is a sectional view taken along B-B in  FIG. 11A .  FIG. 12  is a perspective view of the developing unit  7  and the photosensitive unit  6 .  FIG. 13  is an upper view showing an arrangement relationship in the left-right direction of the photosensitive unit  6 , the developing unit  7 , and the developing roller  71 .  FIG. 14A  is a perspective view of the process cartridge  5  from below, and  FIG. 14B  is a perspective view of a positioning portion in the axial direction of the developing unit  7  and the photosensitive drum  61  of the photosensitive unit  6 . For the purpose of illustration, only the positioning projection  86  and the memory  85  of the developing unit  7  are depicted in  FIG. 14B . 
     As shown in  FIG. 10 , the photosensitive unit  6  mainly includes a frame  610  having a left-side wall  611  and a right-side wall  612  which form a pair and the photosensitive drum  61  that is rotatably supported behind the frame  610 . A mounting portion  615  (refer to  FIG. 12 ) to which the developing unit  7  is mountable, a grip portion  617  with which the user grips the photosensitive unit  6 , a pressing member  640  for pressing the developing unit  7 , and a lifting member (a moving member)  642  for lifting the developing unit  7  are provided in front of the frame  610 . The lifting member  642  lifts the developing unit  7  having been mounted to the mounting portion  615 . The toner housing portion  74  of the developing unit  7  having been mounted to the mounting portion  615  is arranged between the left-side wall  611  and the right-side wall  612  in the left-right direction. 
     A first positioning projection  660  that coaxially protrudes with the photosensitive drum  61  from the left-side wall  611  and a first guide rib  662  are provided behind the frame  610 . In a similar manner, a second positioning projection  661  that coaxially protrudes with the photosensitive drum  61  from the right-side wall  612  and a second guide rib  663  are provided (refer to  FIGS. 10 and 13 ). 
     A lifespan of the developing unit  7  which is determined based on a toner amount stored in the developing unit  7  is set shorter than a lifespan of the photosensitive unit  6  which is determined based on a thickness of a photosensitive layer of the photosensitive drum  61 . Therefore, only the developing unit  7  having reached its lifespan must be replaced separately from the photosensitive unit  6 . In this case, the door  21  is opened and the process cartridge  5  is taken out from inside the apparatus main body  2 , the developing unit  7  having reached its lifespan is detached from the photosensitive unit  6 , and another developing unit  7  is mounted to the photosensitive unit  6  as indicated by a mounting direction AD in  FIG. 12 . Subsequently, the photosensitive unit  6  mounted with the developing unit  7  is mounted to the apparatus main body  2  as the process cartridge  5 . 
     As shown in  FIGS. 7, 10, and 12 , a receiving portion  641  that receives rotation bearing members  746 A and  746 B of the developing roller  71  is formed in front of the photosensitive drum  61  on the left-side wall  611  and the right-side wall  612  of the frame  610 . The receiving portion  641  is a depressed portion with an approximate U-shape of which a front side is opened when viewed from a left side and, during the process of mounting the developing unit  7  to the photosensitive unit  6 , a rotating shaft of the developing roller  71  is inserted into the receiving portion  641 . The receiving portion  641  guides movement of the developing unit  7  in the mounting direction AD shown in  FIG. 12  while supporting the developing unit  7  against the photosensitive unit  6 . 
     In addition, as shown in  FIG. 13 , a projected portion  643  that protrudes upward is provided at both ends in the left-right direction of a bottom surface  613  of the frame  610 . The projected portions  643  movably support the developing unit  7  by coming into contact with ribs  718  provided in a bottom portion of the housing  700  of the developing unit  7  shown in  FIG. 9 . 
     As shown in  FIG. 12 , in the photosensitive unit  6 , a positioning hole  68  that is provided on the frame  610  and a contact opening  69  are provided on a side of one end in the rotational axis direction (the left-right direction) of the photosensitive drum  61 . In this case, the side of one end refers to a same side with respect to a bisector in terms of a length of the photosensitive drum  61  in the left-right direction. When the developing unit  7  is installed in the photosensitive unit  6 , the positioning projection  86  of the developing unit  7  is inserted into the positioning hole  68  of the photosensitive unit  6  as shown in  FIGS. 14A and 14B . The positioning projection  86  and the positioning hole  68  fit each other in the axial direction (the left-right direction) of the photosensitive drum  61  and determine a position of the developing unit  7  in the left-right direction with respect to the photosensitive unit  6 . In addition, the memory  85  of the developing unit  7  is exposed below the process cartridge  5  via the contact opening  69  of the photosensitive unit  6 . 
     In this case, as shown in  FIGS. 11A and 14B , the frame  610  of the photosensitive unit  6  is provided with a box-shaped depressed portion  90 L on a side of one end in the rotational axis direction (the left-right direction) of the photosensitive drum  61 . In addition, the depressed portion  90 L is provided at a position that overlaps with the positioning hole  68  when viewed from the rotational axis direction (the left-right direction) of the photosensitive drum  61 . Due to the depressed portion  90 L, a peripheral position of which strength is reduced by providing the positioning hole  68  is reinforced and the strength thereof is increased. As shown in  FIG. 11B , a depth D 2  of the depressed portion  90 L is set deeper than a depth D 1  of the positioning hole  68  to enhance a reinforcement effect. According to the configuration, the strength around the positioning hole  68  of the photosensitive unit  6  is increased and positioning accuracy in the left-right direction of both the developing unit  7  and the photosensitive unit  6  due to the positioning projection  86  of the developing unit  7  and the positioning hole  68  of the photosensitive unit  6  is increased. As a result, positional accuracy between the memory electrode  85   a  of the memory  85  and the electrode provided in the apparatus main body  2  increases and a reliable contact between electrodes can be achieved. 
     As shown in  FIGS. 11A and 14B , a sheet member  93 L is provided on a side of the photosensitive drum  61  of the depressed portion  90 L. A tip portion  93 LA of the sheet member  93 L is in contact with the photosensitive drum  61 . According to the configuration, image defects are prevented by scraping off unnecessary toner and foreign substances such as paper dust having adhered to the surface of the photosensitive drum  61  during image formation with the tip portion  93 LA. In the present configuration, unnecessary toner and foreign substances such as paper dust having been scraped off are dropped into and collected by the depressed portion  90 L. Therefore, occurrences of contamination of the process cartridge  5  and image defects due to foreign substances dropping onto the paper sheet S which are caused by scattering of the foreign substances can be prevented. Using the depressed portion  90 L for the purposes of structural reinforcement and foreign substance collection as described above eliminates the need to provide a component for foreign substance collection separate from the depressed portion  90 L and enables cartridges to be downsized and configurations to be simplified. 
     As shown in  FIG. 12 , a foreign substance box  90 R including a box-shaped depressed portion is provided on an opposite side in the left-right direction to the positioning hole  68  of the photosensitive unit  6 . A sheet member  93 R is provided on the side of the photosensitive drum  61  of the foreign substance box  90 R. A tip portion  93 RA of the sheet member  93 R is in contact with the photosensitive drum  61 . In a similar manner to the sheet member  93 L described earlier, image defects are prevented by scraping off unnecessary toner and foreign substances such as paper dust having adhered to the surface of the photosensitive drum  61  during image formation with the tip portion  93 RA. Unnecessary toner and foreign substances such as paper dust having been scraped off are dropped into the foreign substance box  90 R and collected inside the box. 
     As shown in  FIG. 12 , a pressing member  640  is provided in front of the frame  610  and at both ends of the frame  610  with respect to the left-right direction. The pressing member  640  is biased in a direction from the front toward the rear by a compression spring  640 A as a biasing member. Therefore, due to a biasing force of the compression spring  640 A, the pressing member  640  presses each of pressed ribs  716 A and  716 B that are provided on the housing  700  of the developing unit  7 . By pressing the developing unit  7  with the pressing member  640 , the developing roller  71  is biased toward the photosensitive drum  61 . 
     As shown in  FIGS. 12 and 7 , a depressed portion  664  is provided on the left-side wall  611  of the photosensitive unit  6  and the detecting portion  80  of the developing unit  7  is positioned in the depressed portion  664 . Since the depressed portion  664  reduces rigidity of the frame  610 , a part of the first guide rib  662  is arranged below the depressed portion  664  so as to overlap with a depressed portion  664 . Since the first guide rib  662  acts as a reinforcing member, a decline in the rigidity of the frame  610  can be reduced. 
     In addition, as shown in  FIG. 11A , a photosensitive member gear (a first gear)  65  and a transfer gear (a second gear)  66  are fixed to a left end of the photosensitive drum  61  and are configured to integrally rotate with the photosensitive drum  61 . When the process cartridge  5  is mounted to the apparatus main body  2 , as a drive gear (not illustrated) of the apparatus main body  2  and the photosensitive member gear  65  mesh with each other, a driving force is transferred to the photosensitive drum  61  and the transfer gear  66  and the photosensitive drum  61  and the transfer gear  66  become rotatable. Furthermore, the transfer gear  66  meshes with a transfer roller gear (a third gear)  67  that is fixed to a left end of the transfer roller  63  and the transfer roller  63  also becomes rotatable. 
     Lifting Mechanism of Developing Unit  7   
       FIG. 15  is a partial perspective view of the developing unit  7  and the lifting member  642 .  FIGS. 16A and 16B  are top views of the photosensitive unit  6  mounted with the developing unit  7  in which  FIG. 16A  shows the photosensitive unit  6  through the lifting member  642  and  FIG. 16B  shows the photosensitive unit  6  without making the lifting member  642  invisible.  FIGS. 17A and 17B  are sectional views of the photosensitive unit  6  and the developing unit  7  and a cross section thereof is parallel to the up-down direction and the front-back direction.  FIG. 17A  represents a state where the developing unit  7  is mounted to the photosensitive unit  6  and  FIG. 17B  represents a state where the developing unit  7  is placed on top of the photosensitive unit  6 . 
     The developing unit  7  having been mounted to the photosensitive unit  6  transitions to a lift-up state by a lifting mechanism and is subsequently detached from the photosensitive unit  6 . The lifting mechanism will be described in detail below. 
     As shown in  FIGS. 15, 17A and 17B , at least a part of the lifting member  642  is arranged on a front side of the housing  700  of the developing unit  7  and rotatably supported by the right-side wall  612  in a state where the lifting member  642  is receiving a force created by a compression spring  650 . In addition, at least a part of the lifting member  642  is arranged so as to overlap with the right-side wall  705  of the housing  700  that houses toner and the pressing member  640  in the front-back direction. A rotational axis  642 X of the lifting member  642  is parallel to the left-right direction (the axial direction of the photosensitive drum  61 ). The lifting member  642  is biased so as to rotate in an R 1  direction by the force created by the compression spring  650 . 
     As the user pushes an operating portion  642 A of the lifting member  642  against the force created by the compression spring  650  and rotates the lifting member  642  in an R 2  direction, the lifting member  642  presses a protruded portion  751  and moves the developing unit  7  in a separating direction LD in which the developing unit  7  separates from the photosensitive unit  6 . Accordingly, the developing unit  7  enters a state where the developing unit  7  can be detached from the photosensitive unit  6 . The operating portion  642 A is arranged on a side of a right end (a side of one end) of the photosensitive unit  6 . 
     As shown in  FIG. 17A , in a mounted state where the developing unit  7  is mounted to the photosensitive unit  6 , due to the housing  700  being pressed by the pressing member  640 , the developing roller  71  is pushed toward the photosensitive drum  61 . In addition, the developing unit  7  is locked by the pressing member  640  so as to prevent the developing unit  7  from separating from the photosensitive unit  6 . As shown in  FIG. 15 , an end of the lifting member  642  causes a contact surface (a contact portion)  751 A of the protruded portion  751  of the housing  700  to move upward. Accordingly, the developing unit  7  can be moved in the separating direction LD from a mounting position where the developing unit  7  is mounted to the mounting portion  615  (refer to  FIG. 12 ) and can be separated from the photosensitive unit  6 . 
     As shown in  FIG. 17B , as a front portion of the developing unit  7  separates from the photosensitive unit  6 , the developing unit  7  is held at a temporary support portion where a supported surface  700 C of the housing  700  is supported by a holding portion  640 B of the pressing member  640 . In addition, the developing unit  7  at the temporary support portion is in a state where the rotation bearing member  746 B ( 746 A) of the developing roller  71  is supported by the receiving portion  641 . This state will be referred to as a lift-up state. At this point, the lock (restraint of the developing unit  7  from being detached from the photosensitive unit  6 ) has been released. In the lift-up state, by gripping the grip portion  701  and lifting up the developing unit  7  as it is, the user can detach the developing unit  7  from the photosensitive unit  6  without having to move the other members. In this manner, the user can detach the developing unit  7  from the photosensitive unit  6  and mount a new developing unit  7  to the photosensitive unit  6 . 
     Next, a characteristic configuration of the photosensitive unit  6  according to the first embodiment will be described in detail with reference to  FIGS. 18 to 22 . 
       FIG. 18  is a sectional view of a state where a cleaning unit  200  has been mounted to the photosensitive unit  6 .  FIGS. 19 and 20  are diagrams showing sizes of respective portions in a left-right direction of a cleaning unit  200  according to another mode of which details differ from those of the cleaning unit shown in  FIG. 18 .  FIGS. 21A and 21B  are sectional views showing another mode of a foreign substance collecting depressed portion  242 .  FIG. 22  is a sectional view of the frame  610  being provided with a foreign substance collecting portion  620  and a foreign substance collecting depressed portion  621 . 
     As shown in  FIG. 18 , the photosensitive unit  6  includes the photosensitive drum  61  and the cleaning unit  200  to the rear in the front-back direction of the frame  610  that supports the photosensitive drum  61 . In addition, the cleaning unit  200  includes a cleaning roller  210  as an example of a first roller, a collecting roller  220  as an example of a second roller, a scraping member  230 , a case  240 , and the like. Furthermore, the cleaning unit  200  is attached to a unit holding portion  610   a  which is attachably and detachably mounted to the frame  610  of the photosensitive unit  6  and which is enclosed by a bottom wall  610   b  on a lower side in the up-down direction and a side wall  610   c  on a rear side in the front-back direction of the frame  610 . It should be noted that the cleaning unit  200  may be configured to be attachable to and detachable from the apparatus main body  2 . 
     The cleaning roller  210  and the collecting roller  220  are arranged so that respective rotational axes are approximately parallel to the rotational axis of the photosensitive drum  61 . 
     The cleaning roller  210  is arranged so as to oppose the photosensitive drum  61  between the transfer roller  63  and the charging roller  62  in a rotation direction of the photosensitive drum  61 . In addition, the cleaning roller  210  comes into contact with a peripheral surface of the photosensitive drum  61  and rotates at a contact point between the photosensitive drum  61  and the cleaning roller  210  so that a rotation direction of the photosensitive drum  61  and a rotation direction of the cleaning roller  210  become a forward direction. It should be noted that the cleaning roller  210  may be configured to rotate by being driven by the photosensitive drum  61  or configured to rotate by being imparted with a rotative force by a gear or the like. 
     The collecting roller  220  is arranged so as to oppose to the cleaning roller  210 . In addition, the collecting roller  220  comes into contact with a peripheral surface of the cleaning roller  210  and rotates at a contact point between the cleaning roller  210  and the collecting roller  220  so that a rotation direction of the cleaning roller  210  and a rotation direction of the collecting roller  220  become a forward direction. It should be noted that the collecting roller  220  may be configured to rotate by being driven by the cleaning roller  210  or configured to rotate by being imparted with a rotative force by a gear or the like. 
     The scraping member  230  is formed by a material such as foam and is arranged so as to come into slidable contact with a peripheral surface of the collecting roller  220 . In order to improve rubbing performance, a member such as a sheet that is made of a different material may be bonded to a surface of the scraping member  230  on a side that comes into contact with the collecting roller  220 . The case  240  houses the cleaning roller  210  and the collecting roller  220 . In addition, the case  240  has a foreign substance collecting portion  241  on at least a lower side of the collecting roller  220  in the up-down direction and a rear side of the collecting roller  220  in the front-back direction. 
     Next, removal of toner remaining on the photosensitive drum  61  after the toner image on the photosensitive drum  61  has been transferred onto the paper sheet S and foreign substances such as paper dust having adhered to the surface of the photosensitive drum  61  from the paper sheet S will be described. According to the configuration described above, the developing roller  71  is biased toward the photosensitive drum  61  and, in this state, the photosensitive drum  61  and the developing roller  71  are in contact with each other. Accordingly, untransferred toner remaining on the photosensitive drum  61  is collected by the developing roller  71  and returned once again to the developing unit  7 . 
     On the other hand, many of the foreign substances such as paper dust having moved to the surface of the photosensitive drum  61  from the paper sheet S in the transfer process are charged to a same polarity as transfer voltage that is applied to the transfer roller  63 . Therefore, by applying voltage of a reverse polarity to the cleaning roller  210 , the foreign substances are electrostatically moved from the photosensitive drum  61  to the cleaning roller  210 . The foreign substances held by the cleaning roller  210  are collected by the collecting roller  220 . Voltage which has a same polarity as the voltage applied to the cleaning roller  210  and which is larger in terms of absolute values is applied to the collecting roller  220 . Accordingly, the foreign substances on the cleaning roller  210  are electrostatically moved to a surface of the collecting roller  220 . The foreign substances collected on the surface of the collecting roller  220  are physically scraped off by the scraping member  230  in contact with the collecting roller  220 . The foreign substances scraped off by the scraping member  230  are stored in the foreign substance collecting portion  241 . 
     At this point, a rotative force is imparted to the cleaning roller  210  by a gear or the like to provide a velocity difference between the surface of the cleaning roller  210  and the surface of the photosensitive drum  61 . It should be noted that a peripheral velocity of the cleaning roller  210  may be set higher or set lower than a peripheral velocity of the photosensitive drum  61 . In addition, at a contact point between the photosensitive drum  61  and the cleaning roller  210 , the cleaning roller  210  may be rotated so that a rotation direction of the cleaning roller  210  becomes a reverse direction with respect to a rotation direction of the photosensitive drum  61 . According to these configurations, performance of scraping off foreign substances adhered to the photosensitive drum  61  with the cleaning roller  210  can be improved as compared to a case where the cleaning roller  210  is driven by the photosensitive drum  61 . 
     Next, a dimensional relationship among respective parts in the left-right direction will be described with reference to  FIG. 19 . The cleaning roller  210  is provided in the size (or width (the same applies hereinafter)) of the paper sheet S, in a same size (or length (the same applies hereinafter)) of a region (a maximum paper-passing width SL) across which the paper sheet S may come into contact with the photosensitive drum  61  during passage of paper, or in a larger (or longer (the same applies hereinafter)) size than these sizes in consideration of dimensional differences of parts and the like. In addition, the collecting roller  220  is provided in a same size as the cleaning roller  210  or in a larger size than the cleaning roller  210  in consideration of dimensional differences of parts and the like. 
     In addition, the scraping member  230  is provided in a same size as the collecting roller  220  or in a larger size than the collecting roller  220  in consideration of dimensional differences of parts and the like. Alternatively, the scraping member  230  may be provided in at least a same size as the cleaning roller  210  or in a larger size than the cleaning roller  210  in consideration of dimensional differences of parts and the like. 
     Furthermore, the foreign substance collecting portion  241  is provided in a same size as the scraping member  230  or in a larger size than the scraping member  230  in consideration of dimensional differences of parts and the like. Alternatively, the foreign substance collecting portion  241  may be provided in at least a same size as the cleaning roller  210  or in a larger size than the cleaning roller  210  in consideration of dimensional differences of parts and the like. 
     Next, the foreign substance collecting portion  241  will be described in detail with reference to  FIG. 18 . As described earlier, the foreign substance collecting portion  241  is provided on at least the lower side of the collecting roller  220  in the up-down direction and the rear side of the collecting roller  220  in the front-back direction. In the case  240 , a bottom surface that forms a collection space of the foreign substance collecting portion  241  on a bottom wall intersecting a line L 1  drawn downward in the up-down direction from a rotational center of the collecting roller  220  will be defined as a first inner bottom surface  240   a.  In addition, in the case  240 , a side surface that forms the collection space of the foreign substance collecting portion  241  on a side wall intersecting a line L 2  drawn rearward in the front-back direction from the rotational center of the collecting roller  220  will be defined as a first side surface  240   b.    
     The foreign substance collecting portion  241  is a space created by coupling the first inner bottom surface  240   a  and the first side surface  240   b  to each other and is formed by a space including the collecting roller  220 . The first inner bottom surface  240   a  is on an upper side in the up-down direction than the bottom wall  610   b  on the opposing frame  610 , and the first side surface  240   b  is on a front side in the front-back direction than the side wall  610   c  of the opposing frame  610 . 
     In addition, the foreign substance collecting depressed portion  242  is included in a part of the first inner bottom surface  240   a  of the foreign substance collecting portion  241 . The foreign substance collecting depressed portion  242  is provided so as to protrude downward in a vertical direction with respect to the first inner bottom surface  240   a.  In addition, a notched portion  610   d  is provided on the bottom wall  610   b.  Furthermore, the foreign substance collecting depressed portion  242  protrudes downward from the first inner bottom surface  240   a  through the notched portion  610   d  in the up-down direction and protrudes downward to a same height as the bottom wall  610   b  or protrudes lower than the bottom wall  610   b  as shown in  FIG. 18 . Accordingly, a housing capacity for collecting foreign substances can be increased. 
     Configuring an outer bottom surface  242   a  on a lower side in the up-down direction of the foreign substance collecting depressed portion  242  which constitutes a part of an outer wall surface of the foreign substance collecting portion  241  so as to come into contact with the paper sheet S when the side wall surface is being conveyed enables a convey direction of the paper sheet S to be controlled. Accordingly, a part of the outer wall surface of the foreign substance collecting portion  241  can be utilized as a guiding portion of the paper sheet S that is being conveyed. 
     As described above, the cleaning unit  200  that constitutes at least a part of the foreign substance collection apparatus according to the first embodiment which is shown in  FIG. 18  has: the frame  610  as a frame body; the photosensitive drum  61  as an image bearing member that bears a developer image and which is rotatably supported by the frame  610 ; the cleaning roller  210  as a first collecting member that collects foreign substances from a surface of the photosensitive drum  61  by rotating in a state of being in contact with the surface of the photosensitive drum  61  and which is rotatably supported by the frame  610 ; the collecting roller  220  as a second collecting member that further collects, from the cleaning roller  210 , foreign substances having been collected by the cleaning roller  210  by rotating in a state of being in contact with a surface of the cleaning roller  210  and which is rotatably supported by the frame  610 ; and the scraping member  230  which is provided on the frame  610  so as to be capable of rubbing against the collecting roller  220  that is rotating for scraping off foreign substances from the collecting roller  220 . 
     The frame  610  includes the foreign substance collecting portion  241  as a housing portion that forms a housing space for housing foreign substances. The foreign substance collecting portion  241  has, in a posture during use: the first inner bottom surface  240   a  which is positioned below the scraping member  230  in a gravity direction; the outer bottom surface  242   a  as a second inner bottom surface which is positioned further below the first inner bottom surface  240   a;  and a connecting surface  240   c  which intersects the first inner bottom surface  240   a  and the outer bottom surface  242   a  and which connects the first inner bottom surface  240   a  and the outer bottom surface  242   a  with each other. 
     As described above, in the foreign substance collection apparatus according to the first embodiment, since the foreign substance collecting portion  241  that houses foreign substances such as paper dust has, further below the first inner bottom surface  240   a,  the foreign substance collecting depressed portion  242  that is enclosed by the outer bottom surface  242   a  and the connecting surface  240   c,  an improvement in a housing capability of foreign substances or, in other words, an increase in a foreign substance housing space can be achieved. 
     In addition, in a posture during use of the photosensitive unit  6 , when the cleaning roller  210 , the first inner bottom surface  240   a,  and the outer bottom surface  242   a  are projected onto a projection plane in the vertical direction, the cleaning roller  210  is arranged at a position which overlaps with a region of the first inner bottom surface  240   a  but which does not overlap with a region of the outer bottom surface  242   a . Accordingly, since the foreign substance collecting depressed portion  242  that is enclosed by the outer bottom surface  242   a  and the connecting surface  240   c  can be formed at a position that deviates from below the cleaning roller  210 , a space below the cleaning roller  210  can be reduced. As a result, the photosensitive unit  6  can be downsized. 
     Furthermore, the foreign substance collecting portion  241  includes a partition portion  240   e  which is provided so as to protrude upward in the gravity direction from the first inner bottom surface  240   a  and which partitions the housing space. Accordingly, the partition portion  240   e  acts as a rib and the strength of the case  240  that constitutes the foreign substance collecting portion  241  can be increased. In addition, in a posture during use, when the collecting roller  220  and the partition portion  240   e  are projected onto a projection plane in the vertical direction, the partition portion  240   e  is arranged at a position that overlaps with a region of the collecting roller  220 . Accordingly, foreign substances having been scraped off from the collecting roller  220  is less likely to return to the cleaning roller  210  and foreign substances can be housed in an efficient manner. 
     In the foreign substance collecting portion  241 , the outer bottom surface  242   a  is arranged on an opposite side to a side where the photosensitive drum  61  is provided with respect to the partition portion  240   e.  Accordingly, since the outer bottom surface  242   a  is arranged apart from the photosensitive drum  61 , an effect of the presence of the outer bottom surface  242   a  on the strength of the frame  610  that rotatably supports the photosensitive drum  61  can be reduced. 
     Next, modifications of the photosensitive unit  6  and the cleaning unit  200  according to the first embodiment will be described. In the cleaning unit  200  shown in  FIGS. 19 and 20 , the depressed portion of the foreign substance collecting portion  241  is provided on the side surface instead of the bottom surface (refer to  FIGS. 21A and 21B  described below). 
     In the left-right direction shown in  FIG. 19 , a region where a paper feeding pickup roller  32   a  provided in the paper feeding mechanism  32  is arranged is a region where a large amount of foreign substances such as paper dust may be produced from the paper sheet S due to the paper feeding pickup roller  32   a  and the paper sheet S rubbing against each other. Therefore, in order to collect a larger amount of the foreign substances such as paper dust, preferably, as shown in  FIG. 19 , the foreign substance collecting depressed portion  242  is provided so as to be longer than a length D 3  of the paper feeding pickup roller  32   a  in the left-right direction and to overlap with a region where the paper feeding pickup roller  32   a  is arranged. 
     In this manner, the apparatus main body  2  to which the foreign substance collection apparatus is mounted includes the paper feeding pickup roller  32   a  as a conveying roller that conveys the paper sheet S on which an image is recorded. In a longitudinal direction of the paper feeding pickup roller  32   a,  a length of the outer bottom surface  242   a  is longer than the length D 3  of the conveying roller in a similar manner to the foreign substance collecting depressed portion  242 . As described earlier, paper dust that represents an example of a foreign substance is likely to be produced in a contact portion when the paper feeding pickup roller  32   a  conveys the paper sheet S. In consideration thereof, by making the length of the outer bottom surface  242   a  that constitutes a part of the housing space of the foreign substance collecting portion  241  longer than the length D 3  of the paper feeding pickup roller  32   a  in the longitudinal direction, paper dust attributable to the paper sheet S that is conveyed by the paper feeding pickup roller  32   a  can be collected in an efficient manner. 
     In addition, in the left-right direction, a paper width end SE of the paper sheet S is also a region where a large amount of foreign substances such as paper dust may be produced. Therefore, in order to collect a larger amount of the foreign substances such as paper dust, preferably, the foreign substance collecting depressed portion  242  is provided so as to be wider than a maximum paper-passing width (a maximum width of the paper sheet S) SL in the left-right direction and to overlap with a region of the paper width end SE of the paper sheet S. Alternatively, the foreign substance collecting depressed portion  242  is preferably wider in the left-right direction than a minimum width of the paper sheet S that is conveyed by the paper feeding pickup roller  32   a . Alternatively, both ends of the foreign substance collecting depressed portion  242  in the left-right direction are favorably positioned on outer sides of both ends of the paper feeding pickup roller  32   a.  Accordingly, paper dust attributable to the paper sheet S that is conveyed by the paper feeding pickup roller  32   a  can be collected in an efficient manner However, making the foreign substance collecting depressed portion  242  wider than the maximum paper-passing width SL in the left-right direction ends up enlarging, for example, the notched portion  610   d  (or a notched portion  610   e ) of the bottom wall  610   b  shown in  FIG. 18  (or the side wall  610   c  shown in  FIG. 19 ), thereby creating a concern that the rigidity of the frame  610  may decline. 
     In consideration thereof, in order to reduce a decline in the rigidity of the frame  610 , the foreign substance collecting depressed portion  242  may be provided so as to be narrower than the maximum paper-passing width SL in the left-right direction to make the notched portion  610   d  (the notched portion  610   e ) of the bottom wall  610   b  (the side wall  610   c ) smaller. Alternatively, in order to reduce a decline in the rigidity of the frame  610  and to increase a housing capacity for collecting foreign substances, as shown in  FIG. 20 , the foreign substance collecting depressed portion  242  may be provided in plurality in the left-right direction so as to make the notched portion  610   e  of the side wall  610   c  smaller. 
     When providing the foreign substance collecting depressed portion  242  in plurality in the left-right direction, the foreign substance collecting depressed portions  242  are preferably provided at locations where foreign substances such as paper dust are produced in particularly large amounts. In other words, in order to collect a larger amount of the foreign substances such as paper dust, favorably, the foreign substance collecting depressed portions  242  are provided at positions that overlap with the paper feeding pickup roller  32   a  and positions that overlap with the paper width ends SE of the paper sheet S in the left-right direction. 
     The foreign substance collecting depressed portion  242  may be provided so as to protrude rearward in the front-back direction from the first side surface  240   b  as shown in  FIGS. 21A and 21B . In this case, the notched portion  610   e  is provided on the side wall  610   c.  In addition, the foreign substance collecting depressed portion  242  protrudes rearward from the first side surface  240   b  through the notched portion  610   e  in the front-back direction and protrudes rearward to a same position as the side wall  610   c  or protrudes further rearward than the side wall  610   c  as shown in  FIGS. 21A and 21B . Since shapes and arrangements in the left-right direction are similar to those described earlier, a description thereof will be omitted. 
     As described above, the foreign substance collecting portion  241  has, when the front-back direction is a first direction in a posture during use: the first side surface  240   b  is provided in the first direction and is positioned on a side opposite to another side on which the photosensitive drum  61 ; a second side surface  240   f  which is positioned apart from the scraping member  230  than the first side surface  240   b  in the first direction; and a connecting surface  240   g  which intersects the first side surface  240   b  and the second side surface  240   f  and which connects the first side surface  240   b  and the second side surface  240   f  with each other. 
     Accordingly, since the foreign substance collecting portion  241  that houses foreign substances such as paper dust has the foreign substance collecting depressed portion  242  that is enclosed by the second side surface  240   f  being positioned further apart from the scraping member  230  than the first side surface  240   b  and the connecting surface  240   g,  an improvement in a housing capability of foreign substances or, in other words, an increase in a foreign substance housing space can be achieved. 
     It should be noted that the foreign substance collecting depressed portion  242  may be provided on both the first inner bottom surface  240   a  and the first side surface  240   b  ( FIG. 21B ) or the foreign substance collecting depressed portion  242  may be provided in plurality on each of the first inner bottom surface  240   a  and the first side surface  240   b.  In addition, the plurality of the foreign substance collecting depressed portions  242  may combine to constitute a part of the foreign substance collecting portion  241 . 
     As described above, by providing the foreign substance collecting depressed portions  242  in a part of the foreign substance collecting portion  241 , a housing capacity for collecting foreign substances such as paper dust can be increased. 
     While the present embodiment has been described using a configuration in which the foreign substance collecting depressed portion  242  is arranged by providing the notched portion  610   d  on the bottom wall  610   b  or the notched portion  610   e  on the side wall  610   c,  this configuration is not restrictive. For example, the bottom wall  610   b  of the frame  610  may be arranged on a lower side in the up-down direction within a range in which the bottom wall  610   b  does not affect the paper convey path and the foreign substance collecting depressed portion  242  may be provided above the bottom wall  610   b  of the frame  610  in the up-down direction. In this case, the bottom wall  610   b  of the frame  610  may be configured so as to control the convey direction of the paper sheet S by coming into contact with the paper sheet S when the paper sheet S is being conveyed. 
     In addition, the side wall  610   c  of the frame  610  may be arranged on a rear side in the front-back direction within a range in which the side wall  610   c  does not interfere with or otherwise affect the apparatus main body  2 , and the foreign substance collecting depressed portion  242  may be provided in the front of the side wall  610   c  of the frame  610  in the front-back direction. According to these configurations, since there is no need to provide the notched portion  610   d  on the bottom wall  610   b  or the notched portion  610   e  on the side wall  610   c  as described earlier, a decline in the rigidity of the frame  610  can be reduced. 
     Furthermore, while the present embodiment has been described using a configuration in which the cleaning unit  200  is attachably and detachably mounted to the frame  610  of the photosensitive unit  6 , this configuration is not restrictive. For example, as shown in  FIG. 22 , the cleaning roller  210 , the collecting roller  220 , and the scraping member  230  may be mounted to the frame  610  of the photosensitive unit  6  and the foreign substance collecting portion  620  may be formed by the bottom wall  610   b  and the side wall  610   c.  In addition, a configuration may be adopted in which the foreign substance collecting depressed portion  621  is provided on the bottom wall  610   b , the side wall  610   c,  or both the bottom wall  610   b  and the side wall  610   c.    
     In addition, while the present embodiment has been described using a configuration in which the cleaning unit  200  that includes the case  240 , the cleaning roller  210 , the collecting roller  220 , the scraping member  230 , and the foreign substance collecting portion  241  is attachably and detachably mounted to the frame  610  of the photosensitive unit  6 , this configuration is not restrictive. For example, a configuration may be adopted in which the case  240  including at least only the foreign substance collecting portion  241  is attachable to and detachable from the photosensitive unit  6 . In other words, for example, a configuration may be adopted in which the case  240  including the foreign substance collecting portion  241  and the scraping member  230  or the case  240  including the foreign substance collecting portion  241 , the collecting roller  220 , and the scraping member  230  are attachable to and detachable from the photosensitive unit  6 . 
     Second Embodiment 
     Next, a second embodiment according to the present invention will be described with reference to  FIGS. 23A and 23B . In the present embodiment, portions that differ from the embodiment described earlier will be described in detail. Since configurations are similar to those of the embodiment described earlier unless particularly noted to the contrary, such portions will be denoted by the same numerals and a detailed description thereof will be omitted. Other embodiments described hereinafter will be treated in a similar manner  FIGS. 23A and 23B  are sectional views of an arrangement of a foreign substance conveying member  250  according to the second embodiment. 
     As shown in  FIG. 23A , the foreign substance conveying member  250  is provided on a lower side of the foreign substance collecting portion  241  in the up-down direction. The foreign substance conveying member  250  is formed by a shaft portion  250   a  and a conveying portion  250   b,  and performs a rotational movement having a rotational axis that extends in the left-right direction due to a driving unit (not illustrated). Alternatively, the foreign substance conveying member  250  may be configured to perform a swinging movement having a rotational axis that extends in the left-right direction. Alternatively, the foreign substance conveying member  250  may be configured to perform a linear reciprocating movement at least in the front-back direction. In other words, as the configuration of the foreign substance conveying member  250 , various configurations may be adopted as long as the foreign substance conveying member  250  is capable of acting on foreign substances such as paper dust housed in the foreign substance collecting portion  241  while moving inside the foreign substance collecting portion  241 . 
     The foreign substances such as paper that are scraped by the scraping member  230  are accumulated above the foreign substance collecting portion  241  in the up-down direction when being housed inside the foreign substance collecting portion  241 . In consideration thereof, by operating the foreign substance conveying member  250 , foreign substances can be moved to the front in the front-back direction with the conveying portion  250   b.  Therefore, an unbiased accumulated state can be formed by leveling the accumulated foreign substances and foreign substances can be housed in the foreign substance collecting portion  241  in an efficient manner. 
     As shown in  FIG. 23B , the foreign substance conveying member  250  may be provided in a configuration in which the foreign substance collecting depressed portion  242  is provided in the foreign substance collecting portion  241 . In addition, the conveying portion  250   b  may be integrally formed with the shaft portion  250   a  or may be formed as a separate body. Furthermore, the conveying portion  250   b  may be formed by a material such as a sheet or may be formed in a gridiron-like flat plate shape or a spiral shape. 
     In addition, in order to house foreign substances such as paper dust in the foreign substance collecting portion  241  in an efficient manner, the conveying portion  250   b  of the foreign substance conveying member  250  may be provided over an entire inside region of the foreign substance collecting portion  241  in the left-right direction. Alternatively, the foreign substance collecting depressed portion  242  may be arranged in the foreign substance collecting portion  241  and, at the same time, the conveying portion  250   b  may be provided at least at a position that opposes the foreign substance collecting depressed portion  242 . 
     As described above, the foreign substance collection apparatus shown in  FIGS. 23A and 23B  has the foreign substance collecting portion  241  that forms a housing space for housing foreign substances and the foreign substance conveying member  250  that conveys foreign substances inside the housing space. In addition, by providing the foreign substance conveying member  250  below the foreign substance collecting portion  241  in the up-down direction, foreign substances such as paper dust can be housed in the foreign substance collecting portion  241  in an efficient manner and moved inside the housing space. In other words, a housing amount of foreign substances can be increased by utilizing the housing space in an efficient manner It should be noted that the foreign substance collecting depressed portion  242  shown in  FIG. 18  may be provided in a lower part of the foreign substance collecting portion  241  shown in  FIGS. 23A and 23B . 
     Third Embodiment 
     Next, a third embodiment according to the present invention will be described with reference to  FIG. 24 .  FIG. 24  is a sectional view of a rotatable collection conveying sheet  260  in a state where the collection conveying sheet  260  is in contact with the collecting roller  220 . 
     As shown in  FIG. 24 , the collection conveying sheet  260  (a third collecting member) is provided inside the foreign substance collecting portion  241 . The collection conveying sheet  260  is formed by a shaft portion  260   a  and a collection conveying portion  260   b  (a sheet portion), the collection conveying portion  260   b  is constituted by a flexible sheet member, and the collection conveying sheet  260  performs a rotational movement having a rotational axis that extends in the left-right direction due to a driving unit (not illustrated). In addition, a tip of the collection conveying portion  260   b,  which is a free end side of the collection conveying portion  260   b,  is opposite to a fixed end side of the collection conveying portion  260   b  where the collection conveying portion  260   b  is attached to the shaft portion  260   a.  When the collection conveying sheet  260  is rotating, the tip of the collection conveying portion  260   b  comes into contact with the collecting roller  220  when approaching the collecting roller  220  and separates from the collecting roller  220  when receding from the collecting roller  220 . 
     Reasons for bringing the collection conveying sheet  260  into contact with the collecting roller  220  (the second collecting member) while the collection conveying sheet  260  rotates as in the present embodiment are: firstly, to remove foreign substances such as paper dust that remain on the collecting roller  220  and convey the foreign substances to the foreign substance collecting portion  241 ; secondly, to extend a lifespan of the scraping member  230 ; and thirdly, to prevent charging polarity of the foreign substances on the collecting roller  220  from becoming reversed. The reasons will be described in detail below. 
     Since the collecting roller  220  and the scraping member  230  are constantly in contact with each other, in a process cartridge with a long lifespan, the scraping member may wear down and scraping capability of the scraping member may decline. The scraping member  230  wears down because foreign substances with a large size become sandwiched between the collecting roller  220  and the scraping member  230  and the collecting roller  220  rotates in this state for a long time. When the scraping member  230  wears down, foreign substances slip through in a streak-like manner along the rotation direction of the collecting roller  220 . Charging polarity of a part of the foreign substances having slipped through in a streak-like manner becomes reversed due to the foreign substances rubbing against each other while being entrained by the collecting roller  220 . The foreign substances with reversed charging polarity are electrostatically moved from the collecting roller  220  to the cleaning roller  210  and then moved from the cleaning roller  210  to the photosensitive drum  61  and may cause image defects. 
     In the present embodiment, by bringing the rotatable collection conveying sheet  260  into contact with the collecting roller  220  during rotation, when the collection conveying sheet  260  comes into contact with the collecting roller  220 , large foreign substances on the collecting roller  220  are scraped off by the collection conveying sheet  260  due to a peripheral velocity difference (a relative movement) and are conveyed to the foreign substance collecting portion  241 . In addition, since a contact position of the collection conveying sheet  260  with respect to the collecting roller  220  is on an upstream side of a contact position of the scraping member  230  with respect to a rotation direction of the collecting roller  220 , the collection conveying sheet  260  is less likely to plunge into the scraping member  230  in a state where large foreign substances are adhered onto the collecting roller  220  and, accordingly, the lifespan of the scraping member  230  can be extended. 
     Foreign substances that are not scraped off by the collection conveying sheet  260  and remain on the collecting roller  220  are maintained so that charging polarity is not changed due to the collection conveying portion  260   b  of the collection conveying sheet  260  and the foreign substance rubbing against each other. Therefore, a material capable of maintaining the charging polarity of the foreign substances is favorably used for the collection conveying portion  260   b  of the collection conveying sheet  260 . While Teflon (R) or the like can conceivably be selected when desiring to keep the foreign substances positively charged and nylon or the like can conceivably be selected when desiring to keep the foreign substances negatively charged, materials are not limited thereto as long as the charging polarity of the foreign substances can be maintained. 
     Although an example of a collection conveying sheet  260  having the shaft portion  260   a  and the collection conveying portion  260   b  has been described in the present embodiment, configurations are not limited thereto as long as the functions described earlier can be realized. For example, manifestation of the effect can be expected even with a roller or the like winded with a sponge or a brush in a spiral pattern. In addition, the collection conveying sheet  260  and the collecting roller  220  need not come into uniform contact with each other, and respective rotational axes thereof may or may not be parallel to each other. Furthermore, the rotation direction of the collection conveying sheet  260  with respect to the rotation direction of the collecting roller  220  may be a forward direction or a reverse direction. 
     In other words, the third collecting member may be configured in any way as long as a state of contact with the second collecting member can be created and a peripheral velocity difference (a relative movement) is generated between contact surfaces at a contact portion. For example, when the respective contact surfaces of the second and third collecting members at the contact portion move in a same direction, controlling a movement speed of the contact surface of the third collecting member to be slower than a movement speed of the contact surface of the second collecting member enables adhered substances to be scraped off from the second collecting member. In addition, by controlling the second and third collecting members so that respective contact surfaces move in different directions at the contact portion, adhered substances can be scraped off from the second collecting member. It should be noted that the third collecting member may come into intermittent contact with the second collecting member or may be in constant contact with the second collecting member. 
     Fourth Embodiment 
     Next, a fourth embodiment according to the present invention will be described with reference to  FIGS. 25, 26A and 26B .  FIG. 25  is a sectional view showing rotation directions of the cleaning roller  210  and the collecting roller  220 .  FIGS. 26A and 26B  are sectional views showing another mode of a scraping member  231 . 
     As described earlier, due to the collecting roller  220  rotating while in contact with the surface of the cleaning roller  210 , foreign substances such as paper dust that are held by the cleaning roller  210  are held by the collecting roller  220 . In this case, in order to improve scraping performance with respect to foreign substances adhered to the cleaning roller  210 , an area over which the collecting roller  220  comes into contact with the surface of the cleaning roller  210  may be increased. 
     In addition, a velocity difference may be provided between the surface of the collecting roller  220  and the surface of the cleaning roller  210 , and the surface of the cleaning roller  210  and the surface of the collecting roller  220  may be rubbed against each other. This is realized by imparting a rotative force to the cleaning roller  210  and the collecting roller  220  by a gear or the like. Furthermore, as shown in  FIG. 25 , at the contact point between the cleaning roller  210  and the collecting roller  220 , the collecting roller  220  rotates in a rotation direction that is a reverse direction to a rotation direction of the cleaning roller  210 . 
     In other words, at the contact portion where the cleaning roller  210  and the collecting roller  220  come into contact with each other, the cleaning roller  210  and the collecting roller  220  are rotationally driven so that respective surfaces of the cleaning roller  210  and the collecting roller  220  move in reverse directions. 
     Accordingly, performance of scraping off foreign substances adhered to the cleaning roller  210  can be further improved. Since the collecting roller  220  rotates in a reverse direction with respect to the cleaning roller  210 , there is a concern that rotation load torque may rise. In consideration thereof, using a brush roller, a low repulsion sponge, a low resistance sponge, a roller winded with a sponge in a spiral pattern, or the like as the collecting roller  220  enables a rise in rotation load to be suppressed. 
     Next, a configuration will be described in which foreign substances such as paper dust that are held on the surface of the collecting roller  220  are housed in the foreign substance collecting portion  241  when the collecting roller  220  is rotated so as to move in a reverse direction with respect to the cleaning roller  210  in a contact portion where the cleaning roller  210  and the collecting roller  220  come into contact with each other. 
     As shown in  FIG. 26A , the scraping member  231  is arranged on a downstream side in a rotation direction than a straight line L connecting respective rotational centers of the cleaning roller  210  and the collecting roller  220  in a circumferential direction of the collecting roller  220 . The arrangement is intended to prevent foreign substances housed in the foreign substance collecting portion  241  from adhering to the cleaning roller  210  once again. In addition, the scraping member  231  is formed of a foam-forming material and fixed to a holding portion  240   d  of the scraping member  231  which is provided on the case  240 . 
     In other words, when viewed from a rotational axis direction of the collecting roller  220 , the scraping member  231  is arranged on an opposite side to a side where the photosensitive drum  61  is present with respect to a virtual straight line L that connects the rotational center of the cleaning roller  210  and the rotational center of the collecting roller  220  with each other. Accordingly, foreign substances having been scraped off by the scraping member  231  are more likely to move towards the opposite side to the side where the photosensitive drum  61  is present. 
     The scraping member  231  may be a rubber blade or a metal blade. Adopting such a configuration enables foreign substances having been scraped off from the collecting roller  220  to be housed in the foreign substance collecting portion  241  while being prevented from once again adhering to the cleaning roller  210 . In addition, as shown in  FIG. 26B , the foreign substance collecting depressed portion  242  may be provided in the foreign substance collecting portion  241  and, at the same time, the rotation direction of the collecting roller  220  or the arrangement of the scraping member  231  may be configured as described earlier. 
     As described above, by causing the collecting roller  220  to rotate in a reverse direction to the cleaning roller  210  or exercising ingenuity in arranging the scraping member  231 , foreign substances such as paper dust can be scraped off in an efficient manner from the cleaning roller  210  with the collecting roller  220 . 
     When implementing the present invention, the configurations and arrangements described in the respective embodiments presented above can be appropriately selected and combined with each other as long as no inconsistencies arise. 
     For example, (1) the foreign substance collecting portion  241  shown in  FIG. 18  may be provided with the foreign substance conveying member  250  shown in  FIG. 24A  or  FIG. 24B . 
     Alternatively, (2) the foreign substance collecting portion  241  shown in  FIG. 21A  or  FIG. 21B  may be provided with the foreign substance conveying member  250  shown in  FIG. 24A  or  FIG. 24B . 
     Alternatively, (3) the foreign substance collecting depressed portion  621  shown in  FIG. 22  may be provided with the foreign substance conveying member  250  shown in  FIG. 24A  or FIG,  24 B. 
     Alternatively, (4) the foreign substance collecting portion  241  shown in  FIG. 25  may be provided with the foreign substance conveying member  250  shown in  FIG. 24A  or  FIG. 24B . 
     Alternatively, (5) the foreign substance collecting portion  241  shown in  FIG. 26A  or  FIG. 26B  may be provided with the foreign substance conveying member  250  shown in  FIG. 24A  or  FIG. 24B . 
     Alternatively, (6) the foreign substance collecting depressed portion  242  shown in  FIG. 21A  or  FIG. 21B  may be provided behind the first side surface  240   b  of the foreign substance collecting portion  241  shown in  FIG. 25  or  FIG. 26A . 
     Alternatively, the respective configurations of (1) to (6) above may be combined with each other in plurality. 
     While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. The scope of the following claims is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions. 
     This application claims the benefit of Japanese Patent Application No. 2019-234917, filed on Dec. 25, 2019, and No. 2020-186429, filed on Nov. 9, 2020, which are hereby incorporated by reference herein in its entirety.